Co-reporter:Fei Chen;Ligong Yang;Renjia Zhou;Minmin Shi;Mang Wang;Hongzheng Chen;Gang Wu
The Journal of Physical Chemistry C September 4, 2008 Volume 112(Issue 35) pp:13457-13462
Publication Date(Web):2017-2-22
DOI:10.1021/jp802745b
Well-defined hexangularly faced CdS nanorod arrays were fabricated via a facile one-step and nontemplate hydrothermal approach in large scale by using biomolecules of glutathione as capping agents. Structural and morphological evolutions of CdS nanorod arrays were studied by scanning electron microscopy, transmission electron microscopy, and X-ray diffraction. A formation mechanism of CdS nanorod arrays via this one-step synthesis was tentatively studied by investigating the effects of synthesis parameters on the nanorod arrays. The growth process of CdS nanorod arrays was discussed further from the absorption spectra of CdS nanorod arrays obtained at different reaction times.
Co-reporter:Jing-Qi Xu;Wenqing Liu;Shi-Yong Liu;Jun Ling;Jiangquan Mai
Science China Chemistry 2017 Volume 60( Issue 4) pp:561-569
Publication Date(Web):2017 April
DOI:10.1007/s11426-016-9003-9
Three new electron donating small molecules (SMs), Pyr(EH-DPP)2, Pyr(HD-DPP)2 and PyrA(EH-DPP)2, are designed and synthesized through coupling electron rich pyrene core with electron deficient diketopyrrolopyrrole (DPP) terminals, of which the derived organic solar cells (OSCs) exhibit interesting structure-performance correlation. It shows that the tune of their solubilizing side chains and π-bridge for the acceptor-donor-acceptor (A-D-A) SMs can significantly alter the resultant short-circuit current density and power conversion efficiency (PCE) in OSCs. The Pyr(EH-DPP)2 with short side chains displays broader absorption and higher hole mobility than the Pyr(HD-DPP)2 with long side chains. Although showing planar structure, the acetylene bridge-incorporated PyrA(EH-DPP)2 adapts an undesired edge-on packing and strong aggregation in film, leading to non-ideal morphology and poor miscibility with fullerene acceptors. As a result, the PCE of the solar cell based on Pyr(EH-DPP)2 is several times higher than those based on Pyr(HD-DPP)2 and PyrA(EH-DPP)2, indicating the A-D-A combination of polyaromatics with DPP would be the promising skeleton for developing photovoltaic semiconductors.
Co-reporter:Cuixia Yuan, Wenqing Liu, Minmin Shi, Shuixing Li, Yuzhou Wang, Huanle Chen, Chang-Zhi Li, Hongzheng Chen
Dyes and Pigments 2017 Volume 143(Volume 143) pp:
Publication Date(Web):1 August 2017
DOI:10.1016/j.dyepig.2017.04.045
•A non-fullerene electron acceptor, SF(DPPFB)4, is designed and synthesized.•SF(DPPFB)4 has four fluorine atoms as the terminal groups.•The introduction of fluorine atoms decreases the energy levels of SF(DPPFB)4.•The fluorination also enhances the electron mobility of SF(DPPFB)4.•The OSCs with SF(DPPFB)4 as the electron acceptor show the improved currents.In this paper, a non-fullerene electron acceptor, SF(DPPFB)4, which owns a spirobifluorene core and four diketopyrrolopyrrole (DPP) arms end capped by 4-fluorobenzene, is designed and synthesized for solution-processable organic solar cells (OSCs). SF(DPPFB)4 shows similar absorption bands as those of its non-fluorinated parent compound, SF(DPPB)4. However, the terminal fluorine atoms reduce the energy levels of SF(DPPFB)4, especially, its lowest unoccupied molecular orbital level decreases by 0.04 eV than that of SF(DPPB)4, which enlarges the energy offset between the electron donor and acceptor, favorable for the dissociation of excitons in OSCs. Moreover, the fluorination improves the electron mobility of SF(DPPFB)4. Thus, the OSCs with poly(3-hexylthiophene) as the electron donor and SF(DPPFB)4 as the electron acceptor can provide a maximum power conversion efficiency of 4.42%, with a lifted short-circuit current (Jsc) of 8.48 mA cm−2.
Co-reporter:Tang Liu, Wenqing Liu, Yuting Zhu, Shengping Wang, Gang Wu, Hongzheng Chen
Solar Energy Materials and Solar Cells 2017 Volume 171(Volume 171) pp:
Publication Date(Web):1 November 2017
DOI:10.1016/j.solmat.2017.06.025
•Chemical inert Au shell is coated outside of Ag NWs (Ag@Au NWs).•All solution processed perovskite solar cells with Ag@Au NWs as electrode are fabricated.•Stable perovskite solar cells with Ag@Au NWs as top electrode are demonstrated.In this paper, solution-processed Au-coated Ag nanowires (Ag@Au NWs) was successfully fabricated as top electrode by spray deposition in planar perovskite solar cells (PVSCs) with structure ITO/PTAA:F4-TCNQ/MAPbI3/PC61BM/Ag@Au NWs, which shows favorable bandgap alignment. Sheet resistance of electrode and series resistance of solar cells over time as well as the stability of PVSCs were measured. The results indicate that the Au shell which serves as a physical separation layer sandwiched in between the perovskite/hole transporting layer (HTL) and the halide-reactive silver nanowires (Ag NWs) can significantly enhance the stability of PVSCs. The efficiency of solar cells employing Ag NWs as top electrode decreases rapidly within 10 min while the efficiency of solar cells employing Ag@Au NWs still remains 85% of its original efficiency even after one week in air. The as-fabricated PVSCs exhibit a power conversion efficiency of 11.0% with an open-circuit voltage of 0.99 V, a short-circuit current density of 18.5 mA/cm2, and a fill factor of 64.3%. This work paves a way for realizing low cost, stable, all solution processable PVSCs.
Co-reporter:Bo Wang;Wenqing Liu;Huanbin Li;Jiangquan Mai;Shiyong Liu;Xinhui Lu;Hanying Li;Minmin Shi;Chang-Zhi Li;Hongzheng Chen
Journal of Materials Chemistry A 2017 vol. 5(Issue 19) pp:9396-9401
Publication Date(Web):2017/05/16
DOI:10.1039/C7TA02582C
In this work, we present two new electron acceptors, TriPDI and Fused-TriPDI, in which three perylene diimide (PDI) moieties are tethered to a benzotrithiophene (BTT) core via either single bonds (TriPDI) or ring-fusion (Fused-TriPDI). TriPDI connects three PDIs to BTT via carbon–carbon single bonds, resulting in a rotatable and highly twisted skeleton. Instead, Fused-TriPDI, made through oxidative ring-fusion of TriPDI, exhibits good structural rigidity and planarity, as well as effective conjugation between PDI and BTT. As a result, the fused molecule shows up-shifted energy levels, and enhanced absorption and charge mobility over the unfused one. The polymer solar cells (PSCs) with a PTB7-Th:Fused-TriPDI blend show the best power conversion efficiency of 6.19%, which is around three times higher than that with PTB7-Th:TriPDI.
Co-reporter:Zhongqiang Zhang;Wenqing Liu;Tahir Rehman;Huan-Xin Ju;Jiangquan Mai;Xinhui Lu;Minmin Shi;Junfa Zhu;Chang-Zhi Li;Hongzheng Chen
Journal of Materials Chemistry A 2017 vol. 5(Issue 20) pp:9649-9654
Publication Date(Web):2017/05/23
DOI:10.1039/C7TA01554B
Efficient fullerene-free polymer solar cells (PSCs) are fabricated with a polymer donor PBDB-T1 and a non-fullerene acceptor ITTIC. With the incorporation of one thiophene bridge between the indacenodithienothiophene (IDTT) core and 2-(3-oxo-2,3-dihydroinden-1-ylidene)malononitrile (IC) terminal, the new acceptor ITTIC exhibits a higher lying lowest unoccupied molecular orbital (LUMO), and a narrower bandgap than the pristine ITIC acceptor. The resultant PSCs with PBDB-T1:ITTIC blends exhibit a power conversion efficiency of 9.12%, with an increased open circuit voltage (VOC) and broader photoresponse, compared with the PBDB-T1:ITIC based devices. Interestingly, it is shown that the charge transfer remains effective at a diminished highest occupied molecular orbital (HOMO) difference of 0.02 eV between PBDB-T1 and ITTIC, leading to a mitigated energy loss of 0.54 eV in PBDB-T1:ITTIC based devices. Overall, this work provides new insights into further improvement of fullerene-free PSCs.
Co-reporter:Lijian Zuo;Shuhua Zhang;Minmin Shi;Hanying Li;Hongzheng Chen
Materials Chemistry Frontiers 2017 vol. 1(Issue 2) pp:304-309
Publication Date(Web):2017/02/16
DOI:10.1039/C6QM00043F
Successfully transferring the device efficiency of small area organic solar cells (SA-OSCs) to a large scale area is a tough challenge. The charge collecting and transporting grids are demonstrated to be effective at addressing this issue, and are widely used in commercial silicon solar cells. However, appreciable shadow loss (5–10%) can be caused with these grids. Thus, a rational design of the grid structure to reduce this significant shadow loss is highly desired. Here, we show that the significant energy loss on scaling up the OSC area stems from the accumulated current density along the charge transport direction. Accordingly, a rational pattern of shorter and triangular Ag grids is designed to accommodate the accumulated current density, leading to a high efficiency of 6.93% for up-scaled OSCs of 4 cm2.
Co-reporter:Jie-huan Chen;Shi-da Yang;Wen-qing Liu;Wei-fei Fu
Chinese Journal of Polymer Science 2017 Volume 35( Issue 2) pp:309-316
Publication Date(Web):2017 February
DOI:10.1007/s10118-017-1891-z
The strategy of sequentially spin-coating a perovskite film from the perovskite precursor and an electron transporting layer of [6,6]-phenyl-C71-butyric acid methyl ester (PC71BM) is developed to simplify the fabrication procedure of perovskite solar cells. X-ray diffraction and scanning electron microscopy indicate that PC71BM film on perovskite layer can retard the evaporation of dimethyl sulfoxide (DMSO) efficiently, thus prolonging the transformation of intermediate phase to perovskite crystals, leading to a high quality perovskite thin film. The solar cells with the structure of indium tin oxides (ITO)/poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS)/CH3NH3PbI3/PC71BM/bathocuproine (BCP)/Ag made from this simplified method exhibit a higher efficiency (12.68%) than those from the conventional one-step method (9.49%).
Co-reporter:
Journal of Polymer Science Part A: Polymer Chemistry 2017 Volume 55(Issue 4) pp:747-753
Publication Date(Web):2017/02/15
DOI:10.1002/pola.28427
ABSTRACTA green and facile method has been developed for the room temperature and aqueous solution preparation of NiOx film as anode buffer layers for polymer solar cells (PSCs). The NiOx buffer layer is prepared simply by spin-coating nickel acetylacetonate precursor-based aqueous solution onto ITO substrate at room temperature in air. UV-ozone post-treatment promotes the formation of dipolar NiOOH species on the film surface, resulting in the anode buffer layer with suitable work function. PSCs have been fabricated with the device structure of ITO/NiOx/photoactive layer/PFN/Al. The power conversion efficiencies of the PSCs based on PTB7:PC71BM blends (8.43%) and P3HT:PC71BM blends (3.04%) with NiOx anode buffer layer are comparable to those with the commonly used PEDOT:PSS anode buffer layer. In addition, the devices made with NiOx buffer layer exhibit much better air stability than those with PEDOT:PSS. These results indicate that the water solution processed NiOx film at room temperature in air is a promising anode buffer layer for efficient and stable PSCs. © 2016 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2017, 55, 747–753
Co-reporter:Huanle Chen;Weifei Fu;Chuyi Huang;Zhongqiang Zhang;Shuixing Li;Feizhi Ding;Minmin Shi;Chang-Zhi Li;Alex K.-Y. Jen;Hongzheng Chen
Advanced Energy Materials 2017 Volume 7(Issue 18) pp:
Publication Date(Web):2017/09/01
DOI:10.1002/aenm.201700012
Two hole-extraction materials (HEMs), TPP-OMeTAD and TPP-SMeTAD, have been developed to facilitate the fabrication of efficient p-i-n perovskite solar cells (PVSCs). By replacing the oxygen atom on HEM with sulfur (from TPP-OMeTAD to TPP-SMeTAD), it effectively lowers the highest occupied molecular orbital of the molecule and provides stronger PbS interaction with perovskites, leading to efficient charge extraction and surface traps passivation. The TPP-SMeTAD-based PVSCs exhibit both improved photovoltaic performance and reduced hysteresis in p-i-n PVSCs over those based on TPP-OMeTAD. This work not only provides new insights on creating perovskite-HEM heterojunction but also helps in designing new HEM to enable efficient organic–inorganic hybrid PVSCs.
Co-reporter:Shuixing Li;Zhongqiang Zhang;Minmin Shi;Chang-Zhi Li;Hongzheng Chen
Physical Chemistry Chemical Physics 2017 vol. 19(Issue 5) pp:3440-3458
Publication Date(Web):2017/02/01
DOI:10.1039/C6CP07465K
Nowadays, organic solar cells (OSCs) with efficiencies over 10% have been achieved through the elaborate design of electron donors and fullerene acceptors. However, the drawbacks of fullerene acceptors, like poor absorption, limited chemical and energetic tunabilities, high-cost purification and morphological instability, have become the bottlenecks for the further improvement of OSCs. To overcome the mentioned shortages from fullerene, research studies on non-fullerene electron acceptors have boomed. To date, the highest efficiency of fullerene-free OSCs has been pushed to be 12%, which surpasses that of fullerene-based OSCs. In this perspective, we focus on summarizing the development of small molecule electron acceptors designed to replace the fullerene derivatives. Since it has been revealed that the search for matched donor:acceptor pairs is important for accomplishing high efficiencies, we therefore divide electron acceptors into several categories according to the donors used in fullerene-free OSCs. After the introduction of these acceptors, we outline the designing rules as well as perspectives for the development of non-fullerene acceptors. We believe that the development of non-fullerene electron acceptors will make organic photovoltaics closer to practical applications.
Co-reporter:Shuixing Li, Wenqing Liu, Minmin Shi, Jiangquan Mai, Tsz-Ki Lau, Junhua Wan, Xinhui Lu, Chang-Zhi Li and Hongzheng Chen
Energy & Environmental Science 2016 vol. 9(Issue 2) pp:604-610
Publication Date(Web):03 Dec 2015
DOI:10.1039/C5EE03481G
In this study, we design and synthesize a new non-fullerene electron acceptor, SF(DPPB)4, in which a spirobifluorene (SF) core is installed with four benzene endcapped diketopyrrolopyrrole (DPP) arms. SF(DPPB)4 exhibits energy levels matching perfectly with those of the commonly used poly(3-hexyl thiophene) (P3HT) donor in polymer solar cells (PSCs). Furthermore, a designed cross-shaped molecular geometry helps in suppressing strong intermolecular aggregation in the P3HT:SF(DPPB)4 blend, leading to efficient non-fullerene PSCs. The resultant devices give a maximum power conversion efficiency (PCE) of 5.16% with an extremely high open-circuit voltage (Voc) of 1.14 V. In contrast, the devices based on P3HT:PC61BM blends provide a PCE of 3.18% with a Voc of 0.62 V. Finally, we observe that the P3HT:SF(DPPB)4 devices exhibit significantly improved thermal stability from that of the P3HT:PC61BM devices; upon thermal treatment at 150 °C for 3 h, the PCEs of P3HT:SF(DPPB)4 devices remain unchanged, whereas those of the P3HT:PC61BM devices drop drastically to below 1%. The abovementioned results demonstrate that the new design strategy of employing a high-performance non-fullerene acceptor, SF(DPPB)4, is promising for the future practical application of PSCs.
Co-reporter:Chuyi Huang; Weifei Fu; Chang-Zhi Li; Zhongqiang Zhang; Weiming Qiu; Minmin Shi; Paul Heremans; Alex K.-Y. Jen;Hongzheng Chen
Journal of the American Chemical Society 2016 Volume 138(Issue 8) pp:2528-2531
Publication Date(Web):February 15, 2016
DOI:10.1021/jacs.6b00039
Herein we present a new structural design of hole-transporting material, Trux-OMeTAD, which consists of a C3h Truxene-core with arylamine terminals and hexyl side-chains. This planar, rigid, and fully conjugated molecule exhibits excellent hole mobility and desired surface energy to the perovskite uplayer. Perovskite solar cells fabricated using the p-i-n architecture with Trux-OMeTAD as the p-layer, show a high PCE of 18.6% with minimal hysteresis.
Co-reporter:Shuixing Li, Wenqing Liu, Chang-Zhi Li, Feng Liu, Yingzhu Zhang, Minmin Shi, Hongzheng Chen and Thomas P. Russell
Journal of Materials Chemistry A 2016 vol. 4(Issue 27) pp:10659-10665
Publication Date(Web):14 Jun 2016
DOI:10.1039/C6TA04232E
Perylene diimide (PDI), which features intense absorption, a low-lying energy level, and high electron mobility, is a promising building block for electron acceptors in organic solar cells (OSCs). However, this planar molecule has a strong tendency to form large aggregates during film formation which strongly limits its OSC performance. Herein, we report a new and simple PDI derivative, B(PDI)3, in which a central benzene unit is employed to connect three PDI arms. This compact arrangement of sterically bulky PDI moieties leads to a twisted molecular geometry of the resultant structure. This suppresses the strong crystallization tendency of PDI chromophores, owing to the broken molecular coplanarity and symmetry. Therefore, B(PDI)3 is applied as a non-fullerene acceptor in OSCs, providing a good power conversion efficiency of 5.65% when blended with the PTB7-Th donor.
Co-reporter:Tao Ye, Weifei Fu, Jiake Wu, Zhikai Yu, Xinyi Jin, Hongzheng Chen and Hanying Li
Journal of Materials Chemistry A 2016 vol. 4(Issue 4) pp:1214-1217
Publication Date(Web):22 Dec 2015
DOI:10.1039/C5TA10155G
We have successfully grown single-crystalline lead halide perovskite arrays on a poly(3,4-ethylene dioxythiophene):polystyrenesulfonic acid (PEDOT:PSS) coated ITO substrate by the droplet-pinned crystallization (DPC) method and, for the first time, single-crystalline perovskite solar cells have been fabricated with a power conversion efficiency of 1.73%.
Co-reporter:Shuhua Zhang, Lijian Zuo, Jiehuan Chen, Zhongqiang Zhang, Jiangquan Mai, Tsz-Ki Lau, Xinhui Lu, Minmin Shi and Hongzheng Chen
Journal of Materials Chemistry A 2016 vol. 4(Issue 5) pp:1702-1707
Publication Date(Web):05 Jan 2016
DOI:10.1039/C5TA09727D
Incorporating two polymer donors with different bandgaps to compose a ternary blend bulk heterojunction (BHJ) is proved to be an effective approach to improve the device performance of BHJ polymer solar cells (PSCs). Here, we demonstrate an efficient ternary PSC consisting of a polythieno[3,4-b]-thiophene/benzodithiophene (PTB7):[6,6]-phenyl C71 butyric acid methyl ester (PC71BM) host blend sensitized by a low band gap (LBG) polymer poly[2,7-(5,5-bis-(3,7-dimethyloctyl)-5H-dithieno[3,2-b:20,30-d]pyran)-alt-4,7-(5,6-difluoro-2,1,3-benzothiadiazole)] (PDTP-DFBT). The addition of the PDTP-DFBT sensitizer remarkably extended the PSC photon to electron response from 750 to 900 nm, which increased the Jsc from 15.12 to 16.27 mA cm−2, and the device performance from 8.08% to 8.63%. A study on the morphology involving the atomic force microscopy mapping and grazing incident X-ray diffraction showed that the incorporation of PDTP-DFBT improved the crystallinity of the PTB7 film with most of the sensitizers associated with the PTB7 domains when blending with a PC71BM film. This observation, together with the unchanged Voc of the ternary PSC, implies a sensitizing mechanism with addition of PDTP-DFBT. After further interfacial modification with a capronic acid self-assembling monolayer (C3-SAM), a higher PCE of 9.06% was achieved, which is among the highest values of efficient ternary PSCs. Our work suggests that a sensitizing mechanism of ternary blends compensates for the light absorbing limitation of binary blend PSCs for high device performance.
Co-reporter:Lijian Zuo, Chih-Yu Chang, Chu-Chen Chueh, Yunxiang Xu, Hongzheng Chen and Alex K.-Y. Jen
Journal of Materials Chemistry A 2016 vol. 4(Issue 3) pp:961-968
Publication Date(Web):07 Dec 2015
DOI:10.1039/C5TA09247G
Series-connected tandem organic photovoltaic devices (SCTOPVs) have been shown to provide higher power conversion efficiencies (PCEs) than the single junction devices due to the improved light harvesting. To achieve the optimal device performance of SCTOPVs, balancing the photocurrents generated from the sub-cells is critical according to the Kirchhoff law. In this work, we demonstrate that the out-of-cell capping layer of an ITO-free microcavity SCTOPV plays an important role in manipulating the optical field distribution in the constituent sub-cells for achieving balanced photocurrents and optimal photovoltaic performance. Two mirror-like electrodes, a semi-transparent ultrathin Ag capped with a dielectric TeO2 layer and a thick Ag electrode were used to construct an ITO-free top-illuminated microcavity configuration, in which certain frequencies of solar irradiance can resonate between the reflective surfaces. As a result, a top-illuminated ITO-free SCTOPV with a comparable performance (7.4%) to the ITO-based counterpart (7.5%) was demonstrated despite the inferior transmittance of the ultra-thin Ag relative to ITO.
Co-reporter:Shida Yang, Wenqing Liu, Lijian Zuo, Xinqian Zhang, Tao Ye, Jiehuan Chen, Chang-Zhi Li, Gang Wu and Hongzheng Chen
Journal of Materials Chemistry A 2016 vol. 4(Issue 24) pp:9430-9436
Publication Date(Web):17 May 2016
DOI:10.1039/C6TA02999J
Thiocyanate ammonium (NH4SCN) is introduced into the fabrication of formamidinium lead triiodide (FAPbI3) films through one-step spin-coating. The promoted formation of black trigonal phase α-FAPbI3 with better crystallinity has been observed after the addition of NH4SCN, together with the supression of the formation of yellow hexagonal phase δ-FAPbI3. Planar perovskite solar cells (PVSCs) based on NH4SCN-assisted formed α-FAPbI3 films with high quality present a highest power conversion efficiency of 11.44% when 30 mol% NH4SCN is applied. Notably, the addition of NH4SCN is found to enhance the moisture stability of the perovskite. As a result, the planar PVSCs with 30 mol% NH4SCN additive show improved stability under ambient conditions (RH: 30–40%) over those based on pristine FAPbI3. NH4SCN simultaneously enhances the efficiency and moisture stability of FAPbI3 based PVSCs through a single one-step solution method, facilitating their commercial fabrication and application.
Co-reporter:Shuixing Li, Jielin Yan, Chang-Zhi Li, Feng Liu, Minmin Shi, Hongzheng Chen and Thomas P. Russell
Journal of Materials Chemistry A 2016 vol. 4(Issue 10) pp:3777-3783
Publication Date(Web):04 Feb 2016
DOI:10.1039/C6TA00056H
Effective electron acceptor materials usually have a deep lowest unoccupied molecular orbital (LUMO) energy level that can split excitons and generate current. A non-fullerene electron acceptor (F8-DPPTCN) was developed, using fluorene as the core with arms of diketopyrrolopyrrole (DPP) having thiophene-2-carbonitrile as the terminal units. The new molecule had a LUMO of −3.65 eV and a narrow bandgap (Eg) of 1.66 eV, owing to the electronegativity of the thiophene-2-carbonitrile group and its conjugation with DPP units. Organic solar cells (OSCs) with F8-DPPTCN as the acceptor and poly(3-hexylthiophene) (P3HT) as the donor were fabricated. A power conversion efficiency (PCE) of 2.37% was obtained with an open-circuit voltage (Voc) of 0.97 V, a short-circuit current (Jsc) of 6.25 mA cm−2, and a fill factor (FF) of 0.39. Structural characterization showed that P3HT and F8-DPPTCN were kinetically trapped in a weakly separated state whereas thermal annealing led to the crystallization of P3HT and the formation of a network structure with a mesh-size of several hundred nanometers. When a solvent additive, diiodooctane, was used and the mixture was thermally annealed, both P3HT and F8-DPPTCN crystallized and a multi-length scale network was formed. Though the PCEs were low, the changes in the PCE could be correlated with the morphological changes, opening pathways to increase performance further.
Co-reporter:Zhikai Yu, Wenqing Liu, Weifei Fu, Zhongqiang Zhang, Weitao Yang, Shengping Wang, Hongfei Li, Mingsheng Xu and Hongzheng Chen
Journal of Materials Chemistry A 2016 vol. 4(Issue 14) pp:5130-5136
Publication Date(Web):07 Mar 2016
DOI:10.1039/C6TA00909C
A facile and green method has been developed for the aqueous solution preparation of CuOX as an anode buffer layer for organic solar cells (OSCs). The CuOX buffer layer is prepared simply by spin-coating a copper acetylacetonate precursor based aqueous solution onto an ITO substrate at room temperature in ambient air. Hydrogen peroxide (H2O2) is used to modify the precursor aqueous solution and can greatly increase the work function of the CuOX film to improve the hole collection efficiency and the charge transport efficiency. UV-ozone post-treatment of the CuOX film leads to the fully oxidized state of copper oxide, which significantly improves the performance of OSCs. Through H2O2 modification and UV-ozone post-treatment on the CuOX anode buffer layer, the highest power conversion efficiency of the OSCs based on PTB7:PC71BM blends reaches 8.68%, which is 10% higher than that of the standard PEDOT:PSS anode buffer layer based OSCs. In addition, the devices with the CuOX buffer layer show much better air stability than those with PEDOT:PSS. Our results indicate that the aqueous solution processed CuOX with low cost and green solvents is a promising anode buffer layer material for efficient and stable OSCs.
Co-reporter:Shabi Thankaraj Salammal, Zhongqiang Zhang, Jiehuan Chen, Basab Chattopadhyay, Jiake Wu, Lei Fu, Congcheng Fan, and Hongzheng Chen
ACS Applied Materials & Interfaces 2016 Volume 8(Issue 32) pp:20916
Publication Date(Web):July 19, 2016
DOI:10.1021/acsami.6b05084
Four different polymorphic conformations of diethyl 5,5′-[5,5′-[2,5-bis(2-ethylhexyl)-3,6-dioxo-2,3,5,6-tetrahydropyrrolo[3,4-c]pyrrole-1,4-diyl]bis(thiophene-5,2-diyl)]difuran-2-carboxylate (DPP-(CF)2), namely, DPP-(CF)2-α, DPP-(CF)2-β, DPP-(CF)2-γ, and DPP-(CF)2-ω, were identified from X-ray diffraction analysis conducted on their thin films and single crystals. Highly crystalline and well-textured thin films of these four polymorphs were successfully prepared via postgrowth solvent vapor and thermal annealing treatments to investigate the polymorphic phase-dependent optical and electrical properties of DPP-(CF)2. Interestingly, during the phase transition from DPP-(CF)2-α to DPP-(CF)2-ω, the optical band gap decreases from 1.75 to 1.5 eV because of the enhanced π–π interaction between the neighboring molecules. Except for DPP-(CF)2-γ, the other three phases show ambipolar charge transport. Although DPP-(CF)2-β and DPP-(CF)2-γ exhibit a similar way of packing, a small increment in the π–π-stacking distance (0.006 Å) and twist conformation of the grafted electron-donating moieties of DPP-(CF)2-γ are found to reduce its hole mobility.Keywords: diketopyrrolopyrrole; optical and electrical properties; organic electronics; polymorphism; π−π stacking
Co-reporter:Wenqing Liu, Tao Liang, Qi Chen, Zhikai Yu, Yingying Zhang, Yujing Liu, Weifei Fu, Feng Tang, Liwei Chen, and Hongzheng Chen
ACS Applied Materials & Interfaces 2016 Volume 8(Issue 14) pp:9254
Publication Date(Web):March 25, 2016
DOI:10.1021/acsami.6b00327
Solution-processed 8-hydroxyquinolinatolithium (s-Liq) was successfully applied as an efficient cathode interlayer in bulk heterojunction polymer solar cells (PSCs), giving rise to enhancement in device performance. The ultraviolet photoelectron spectra results revealed that the presence of s-Liq could lower work function of Al cathode, allowing for the ohmic contacts with the fullerene acceptor for better electron extraction and also a larger work function difference between the two electrodes, which leads to an increase in open-circuit voltage (Voc). Scanning Kelvin probe microscopy study on the surface potential of active layers suggested that an interfacial dipole was formed in the s-Liq interlayer between the active layer and the Al cathode, which enhanced the intrinsic built-in potential in the device for better charge transportation and extraction. Consequently, the Voc, fill factor, and current density of the device can be improved by the introduction of s-Liq interlayer, leading to a power conversion efficiency (PCE) improvement. With PTB7 (or PTB7-Th) as the donor and PC71BM as the acceptor, the s-Liq-based PSC devices exhibited a PCE of 8.37% (or 9.04%), much higher than those of devices with the evaporated Liq (7.62%) or commonly used PFN (8.14%) as the cathode interlayer. Moreover, the s-Liq-based devices showed good stability, maintaining 75% (in N2) and 45% (in air) of the initial PCE after 7 days, respectively. These results suggest the great potential of s-Liq as cathode interlayer material for high-performance solar cells application.Keywords: cathode interlayer; Liq; PCE; PSC; stability; work function
Co-reporter:Weifei Fu, Jielin Yan, Zhongqiang Zhang, Tao Ye, Yujing Liu, Jiake Wu, Jizhong Yao, Chang-Zhi Li, Hanying Li, Hongzheng Chen
Solar Energy Materials and Solar Cells 2016 Volume 155() pp:331-340
Publication Date(Web):October 2016
DOI:10.1016/j.solmat.2016.06.037
•Two PbI2(X) complexes with different coordination strength of ligand X are synthesized.•Correlations between morphology, carrier lifetime and photovoltaic performance are investigated with various PbI2(X).•Highly efficient inverted planar perovskite solar cells with power conversion efficiency up to 17.0% are achieved.Lead halide complexes are efficient precursors to obtain high quality perovskite films and high performance solar cells. However, how the lead halide complex affects the crystallization kinetics and thus the film quality of perovskite has not been systematically studied. Herein, two PbI2(X) complexes with different coordination strength of ligand X in complexation with PbI2 (PbI2(DMF) and PbI2(DMSO)) are synthesized. The correlation between the morphology, evolution of the perovskite formation, defects state, carrier lifetime and the subsequent photovoltaic performance are investigated in details via a two-step coating method with various PbI2(X) complexes. We find that PbI2(DMSO) derived perovskite film shows larger grains and vertically oriented grain boundaries as well as enhanced photoluminescence intensity and longer carrier lifetime. As a result, highly efficient inverted planar perovskite solar cells with a power conversion efficiency up to 17.0% are achieved from PbI2(DMSO) complex under 1 sun illumination. This research could open up a new pathway to further improve the performance of perovskite solar cells through the control of perovskite crystallization kinetics by choosing proper PbI2(X) complex precursors.
Co-reporter:Jiachi Huang, Zhuowei Gu, Lijian Zuo, Tao Ye, Hongzheng Chen
Solar Energy 2016 Volume 133() pp:331-338
Publication Date(Web):August 2016
DOI:10.1016/j.solener.2016.04.017
•FPDI was used as novel electron transport material in perovskite solar cells.•Morphology control is critical to achieve high efficiency perovskite solar cells.•The morphology of ETL layer could be controlled by convenient solvent treatments.•The morphology of perovskite layer could be optimized by ETL layer.•The fill factor increased significantly for solar cells with better morphology.Morphology control is critical to achieve high efficiency CH3NH3PbI3 perovskite solar cells (PSC). In this paper, fluorinated perylene diimide (FPDI) was used as novel organic electron transport material in planar heterojunction perovskite solar cells. The perovskite film was fabricated by sequential vacuum vapor deposition, and the film morphology could be controlled by optimizing the FPDI film morphology with short time solvent spin-coating or solvent vapor annealing (SVA). Dense and uniform perovskite film with high substrate coverage could be obtained when the FPDI film was treated by chloroform SVA for half an hour, and the fill factor (FF) of the perovskite solar cell increased from 30.44% to 55.20%, enhancing the power conversion efficiency (PCE) from 3.23% to 7.44%. The PCE of the best device reached 7.93%, which was comparable to that (8.25%) of the conventional ZnO electron transport layer based perovskite device prepared by the same method.Fluorinated perylene diimide (FPDI) was used as novel organic electron transport material in planar heterojunction perovskite solar cells. The PCE of the best device reached 7.93% after optimizing the perovskite film morphology via controlling the FPDI film morphology with short time solvent vapor annealing.
Co-reporter:Shi-Yong Liu, Wen-Qing Liu, Cui-Xia Yuan, Ai-Guo Zhong, Deman Han, Bo Wang, Muhammad Naeem Shah, Min-Min Shi, Hongzheng Chen
Dyes and Pigments 2016 Volume 134() pp:139-147
Publication Date(Web):November 2016
DOI:10.1016/j.dyepig.2016.07.007
•Sequential activation of CH bonds for accessing complicate multi-DPP-based oligomers.•The integration of easily accessible acceptors with economical donor for fullerene-free OPVs.•High VOC of fullerene-free OPVs using P3HT as donor.•Accessing renewable solar energy via sustainable chemistry.Exploring sustainable chemistry for renewable energy plays a key role in meeting the ever increasing energy demand without sacrificing the environment. In this study, two novel diketopyrrolopyrrol(DPP)-based π-conjugated oligomers (named as TPE-DPP4 and BP-DPP4) have been readily synthesized via a ligand-free Pd-catalyzed sequential activation of CH bond in two steps with good yields starting from simple building blocks. Poly(3-hexylthiophene) is employed as an electron donor to blend with the new DPP-derived electron acceptors for the fullerene-free bulk heterojunction organic photovoltaics. The power conversion efficiency of 2.49% has been achieved, corresponding with an open-circuit voltage of 1.16 V, which is among the highest open-circuit voltages for the single-junction organic photovoltaics. The facilely accessible electron acceptors blended with cost-effective poly(3-hexylthiophene) donor for fullerene-free organic photovoltaics opens a new pathway to access renewable solar energy via sustainable chemistry.
Co-reporter:Bing Guo, Gang Wu, Hong-Zheng Chen, Mang Wang
Organic Electronics 2016 Volume 29() pp:13-21
Publication Date(Web):February 2016
DOI:10.1016/j.orgel.2015.11.018
•Devices with structure of ITO/PEDOT:PSS/TmPyPB/Py-NaTaO3/Al were fabricated.•Device presented selective sensitivity to wavelength shorter than 317 nm UV light.•The device showed ultraviolet signal-to-noise ratio of about 3 orders of magnitude.Wide bandgap NaTaO3 nanocrystals (NaTaO3 NCs) were synthesized by a two-step hydrothermal method. The hybrid film based on the pyridine modified NaTaO3 NCs and 1, 3, 5-tri(m-pyrid-3-yl-phenyl) benzene (TmPyPB) was prepared by solution processing at room temperature. Photodetector based on the hybrid film presented selective sensitivity to UV signals with wavelength shorter than 317 nm because the bandgap wider than 4.0 eV. Under 5 mW/cm2 280 nm illumination through the semi-transparent Al cathode, a high ultraviolet signal-to-noise ratio of 3 orders of magnitude with response time about 200–300 ms can be achieved for the device in the case of −3 V bias.
Co-reporter:Shasha Wu, Shuixing Li, Chang-Zhi Li, Minmin Shi, Hongzheng Chen
Tetrahedron Letters 2016 Volume 57(Issue 25) pp:2797-2799
Publication Date(Web):22 June 2016
DOI:10.1016/j.tetlet.2016.05.049
•An AlQ3 derivative Al(4CAQ)3 is designed and synthesized in 6-step reactions.•Al(4CAQ)3 has three 2-ethylhexyl cyanoacrylate groups at C-4 of the quinoline ring.•Al(4CAQ)3 owns an appropriate LUMO of −3.7 eV to pair with donors in OSCs.•Al(4CAQ)3 shows excellent solubility and good UV–visible absorptions.•Al(4CAQ)3 would be a promising non-fullerene acceptor for solution-processed OSCs.In this Letter, a new AlQ3 derivative is designed and synthesized through introducing 2-ethylhexyl cyanoacrylate at C-4 of the quinoline ring. The obtained Al(4CAQ)3 shows excellent solubility (>50 mg/ml) in common solvents. Furthermore, the LUMO energy level of Al(4CAQ)3 is greatly lowered to −3.70 eV, which matches those of donors used in organic solar cells (OSCs). Together with its octahedral molecular geometry and good UV–visible absorptions, Al(4CAQ)3 would be a promising solution-processed electron acceptor for OSCs.
Co-reporter:Zhongqiang Zhang, Wenqing Liu, Jielin Yan, Minmin Shi, Hongzheng Chen
Synthetic Metals 2016 Volume 222(Part B) pp:211-218
Publication Date(Web):December 2016
DOI:10.1016/j.synthmet.2016.10.022
•Molecule DPP(C2T)2 end-capped with thiophene-2,3-dicarboxylate was synthesized.•Introducing ester groups to both α and β-position of thiophene ring was achieved.•Energy levels were manipulated by introducing of extra ester groups.•DPP(C2T)2 can serve as both donor and acceptor in OSCs.It is a primary strategy to manipulate the energy levels of organic semiconductor molecules for getting better performances in organic photovoltaic devices. In this paper, we designed and synthesized a diketopyrrolopyrrole (DPP)-based small molecule, 3,6-bis(5-[(diethyl thiophene-2,3-dicarboxylate)-2-yl]thiophene-2-yl)- 2,5-bis(2-ethylhexyl)pyrrolo[3,4-c]pyrrole-1,4-dione (DPP(C2T)2), by introducing ester groups to both α and β-position of the end-capped thiophene ring. Due to the electron-withdrawing effect of ester groups, the resulting molecule exhibits low-lying the highest occupied molecular orbital (HOMO) energy level of −5.37 eV and the lowest unoccupied molecular orbital (LUMO) energy level of −3.78 eV. Therefore, DPP(C2T)2 can be used as either electron donor or acceptor for solution processed organic solar cells and shows a power conversion efficiency (PCE) of 1.66% when blended with [6,6]-phenyl-C71-butyric acid methyl ester (PC71BM) and 1.08% with poly(3-hexylthiophene) (P3HT). The crystallinity, carrier mobilities and film morphology are systematically investigated and discussed, in order to study the influence of extra ester group on the properties of the resulting molecule.
Co-reporter:Xinqian Zhang;Gang Wu;Zhuowei Gu;Bing Guo;Wenqing Liu;Shida Yang
Nano Research 2016 Volume 9( Issue 10) pp:2921-2930
Publication Date(Web):2016 October
DOI:10.1007/s12274-016-1177-8
We systematically investigated the development of film morphology and crystallinity of methyl-ammonium bismuth (III) iodide (MA3Bi2I9) through onestep spin-coating on TiO2-deposited indium tin oxide (ITO)/glass. The precursor solution concentration and substrate structure have been demonstrated to be critically important in the active-layer evolution of the MA3Bi2I9-based solar cell. This work successfully improved the cell efficiency to 0.42% (average: 0.38%) with the mesoscopic architecture of ITO/compact-TiO2/mesoscopic-TiO2 (meso-TiO2)/MA3Bi2I9/2,2′,7,7′-tetrakis(N,N-di-4-methoxyphenylamino)-9,9′spiro-bifluorene (spiro-MeOTAD)/MoO3/Ag under a precursor concentration of 0.45 M, which provided the probability of further improving the efficiency of the Bi3+-based lead-free organic–inorganic hybrid solar cells.
Co-reporter:Lijian Zuo, Chih-Yu Chang, Chu-Chen Chueh, Shuhua Zhang, Hanying Li, Alex K.-Y. Jen and Hongzheng Chen
Energy & Environmental Science 2015 vol. 8(Issue 6) pp:1712-1718
Publication Date(Web):05 May 2015
DOI:10.1039/C5EE00633C
A versatile interconnecting layer (ICL) based on reflective ultra-thin Ag (8–14 nm) was developed to enable the fabrication of a series-connected micro-cavity tandem polymer solar cell. This novel ICL can manipulate the optical field distribution between the constituent sub-cells to address the challenge of current matching. As a result, a very high power conversion efficiency (∼11%) and high summed external quantum efficiency of >90% were demonstrated.
Co-reporter:Lijian Zuo;Shuhua Zhang;Hanying Li ;Hongzheng Chen
Advanced Materials 2015 Volume 27( Issue 43) pp:6983-6989
Publication Date(Web):
DOI:10.1002/adma.201502827
Co-reporter:Lijian Zuo; Zhuowei Gu; Tao Ye; Weifei Fu; Gang Wu; Hanying Li;Hongzheng Chen
Journal of the American Chemical Society 2015 Volume 137(Issue 7) pp:2674-2679
Publication Date(Web):February 4, 2015
DOI:10.1021/ja512518r
Morphology control is critical to achieve high efficiency CH3NH3PbI3 perovskite solar cells (PSC). The surface properties of the substrates on which crystalline perovskite thin films form are expected to affect greatly the crystallization and, thus, the resulting morphology. However, this topic is seldom examined in PSC. Here we developed a facile but efficient method of modifying the ZnO-coated substrates with 3-aminopropanioc acid (C3-SAM) to direct the crystalline evolution and achieve the optimal morphology of CH3NH3PbI3 perovskite film. With incorporation of the C3-SAM, highly crystalline CH3NH3PbI3 films were formed with reduced pin-holes and trap states density. In addition, the work function of the cathode was better aligned with the conduction band minimum of perovskite for efficient charge extraction and electronic coupling. As a result, the PSC performance remarkably increased from 9.81(±0.99)% (best 11.96%) to 14.25(±0.61)% (best 15.67%). We stress the importance of morphology control through substrate surface modification to obtain the optimal morphology and device performance of PSC, which should generate an impact on developing highly efficient PSC and future commercialization.
Co-reporter:Xiao-Feng Wu;Wei-Fei Fu;Zheng Xu;Minmin Shi;Feng Liu;Jun-Hua Wan;Thomas P. Russell
Advanced Functional Materials 2015 Volume 25( Issue 37) pp:5954-5966
Publication Date(Web):
DOI:10.1002/adfm.201502413
This work focuses on developing diketopyrrolopyrrole (DPP)-based small molecular nonfullerene acceptors for bulk heterojunction (BHJ) organic solar cells. The materials, SF-DPPs, have an X-shaped geometry arising from four DPP units attached to a spirobifluorene (SF) center. The spiro-dimer of DPP-fluorene-DPP is highly twisted, which suppresses strong intermolecular aggregation. Branched 2-ethylhexyl (EH), linear n-octyl (C8), and n-dodecyl (C12) alkyl sides are chosen as substituents to functionalize the N,N-positions of the DPP moiety to tune molecular interactions. SF-DPPEH, the best candidate in SF-DPPs family, when blended with poly(3-hexylthiophene) (P3HT) showed a moderate crystallinity and gives a Jsc of 6.96 mA cm−2, Voc of 1.10 V, a fill factor of 47.5%, and a power conversion efficiency of 3.63%. However, SF-DPPC8 and SF-DPPC12 exhibit lower crystallinity in their BHJ blends, which is responsible for their reduced Jsc. Coupling DPP units with SF using an acetylene bridge yields SF-A-DPP molecules. Such a small modification leads to drastically different morphological features and far inferior device performance. These observations demonstrate a solid structure–property relationship by topology control and material design. This work offers a new molecular design approach to develop efficient small molecule nonfullerene acceptors.
Co-reporter:Shi-Yong Liu, Jae Woong Jung, Chang-Zhi Li, Jiang Huang, Jianyuan Zhang, Hongzheng Chen and Alex K.-Y. Jen
Journal of Materials Chemistry A 2015 vol. 3(Issue 44) pp:22162-22169
Publication Date(Web):15 Sep 2015
DOI:10.1039/C5TA06639E
Non-fullerene acceptor based organic photovoltaic devices (OPVs) reported so far are inferior to those derived from fullerenes. This increases the speculation on whether donors need to be tailored for advancing non-fullerene OPVs. We explored herein two direct arylation-derived diketopyrrolopyrrole (DPP)-based three-dimensional (3D) donors that can deliver respectable power conversion efficiencies (PCEs) of 4.64% and 4.02% with polymeric acceptor N2200 blends, surpassing those obtained from PC71BM (3.56% and 3.22%, respectively). It is found that these 3D-shaped molecular donors can yield improved photo-to-current conversion and balanced charge transport when blending with the linear N2200 polymer. This finding suggests that engineering molecular geometry can be a promising approach for developing high-performance materials.
Co-reporter:Bing Guo, Gang Wu, Hongzheng Chen and Mang Wang
Journal of Materials Chemistry A 2015 vol. 3(Issue 36) pp:9346-9352
Publication Date(Web):10 Aug 2015
DOI:10.1039/C5TC02334C
A convenient two-step hydrothermal method was developed to synthesize water dispersible NaTaO3 nanoparticles. The growth of the NaTaO3 nanoparticles was retarded with the aid of a water soluble complex agent in the first step, such as citric acid, bicine, triacetin, and EDTA 2Na, which formed complexes with Ta5+. The sizes of the NaTaO3 nanoparticles, ranging from 5 nm to 30 nm, could be tuned by adjusting the reaction time as well as the complexing agent. An ultraviolet photodetector was fabricated with the solution processed NaTaO3 film as the active layer, which presented a sensitive response to 280 nm deep UV illumination with a light to dark current ratio of about 160 and a response time of about 50 ms.
Co-reporter:Zhuowei Gu, Lijian Zuo, Thue T. Larsen-Olsen, Tao Ye, Gang Wu, Frederik C. Krebs and Hongzheng Chen
Journal of Materials Chemistry A 2015 vol. 3(Issue 48) pp:24254-24260
Publication Date(Web):2015/10/06
DOI:10.1039/C5TA07008B
The morphologies of the perovskite (e.g. CH3NH3PbI3) layer are demonstrated to be critically important for highly efficient perovskite solar cells. This work applies 3-aminopropanoic acid as a self-assembled monolayer (C3-SAM) on a poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) hole transport layer (HTL) to modify the crystallinity and coverage of the CH3NH3PbI3−xClx film, resulting in a much smoother perovskite surface morphology together with a PCE increase from 9.7% to 11.6%. Since all fabrication steps of these inverted structure devices are carried out under low temperature conditions (processing temperature < 120 °C), it is possible to employ this method on flexible polymer substrates using roll-coating for the layer deposition. The roll-coated perovskite film on C3-SAM modified PEDOT:PSS presents a similar trend of improvement and results in enhanced PCE from 3.7% to 5.1%. The successful application of the facile HTL modification indicates a common strategy for SAM material design and selection for efficiency enhancement in perovskite photovoltaic devices.
Co-reporter:Hangqi Shi, Weifei Fu, Minmin Shi, Jun Ling and Hongzheng Chen
Journal of Materials Chemistry A 2015 vol. 3(Issue 5) pp:1902-1905
Publication Date(Web):16 Dec 2014
DOI:10.1039/C4TA06035K
A new diketopyrrolopyrrole derivative with appropriate energy levels and bipolar charge-transport properties is designed and synthesized. When this molecule is used as either electron donor or acceptor, the resulting organic solar cells both give the power conversion efficiencies over 3%.
Co-reporter:Shi-Yong Liu;Chen-Hao Wu;Chang-Zhi Li;Sheng-Qiang Liu;Kung-Hwa Wei;Alex K.-Y. Jen
Advanced Science 2015 Volume 2( Issue 4) pp:
Publication Date(Web):
DOI:10.1002/advs.201500014
Co-reporter:Yingying Zhang, Shuang Liu, Wenqing Liu, Tao Liang, Xi Yang, Mingsheng Xu and Hongzheng Chen
Physical Chemistry Chemical Physics 2015 vol. 17(Issue 41) pp:27565-27572
Publication Date(Web):17 Sep 2015
DOI:10.1039/C5CP05011A
Nanoscale morphology is of significance to the electronic properties of semiconducting polymers. Solution-processed poly-3-hexylthiophene (P3HT) has been demonstrated as a promising active-layer material in organic thin film transistors (OTFTs) and solar cells. Controlling the crystallinity of P3HT chains is critical for gaining high-performance devices. Here we demonstrated the immediate crystallization of P3HT induced by two-dimensional MoS2 nanosheets under ultrasonication. The resulting aggregation was attributed to the presence of interaction between the MoS2 nanosheets and P3HT, which could enhance the inter-chain ordering and association of P3HT. The crystallization of P3HT contributed to the 38-fold enhancement in the hole mobility of the thin film as compared to the non-crystallized thin films because of the absence of MoS2. Our approach of using 2D MoS2 nanosheets to induce immediate aggregation of P3HT provides a facile process to control the crystallization of conjugated polymers for the development of high-performance organic electronics.
Co-reporter:Lijian Zuo, Shuhua Zhang, Shuai Dai and Hongzheng Chen
RSC Advances 2015 vol. 5(Issue 61) pp:49369-49375
Publication Date(Web):28 May 2015
DOI:10.1039/C5RA08441E
In this work, a Cs doped sol–gel ZnO film (ZnO:Cs) as an efficient and robust electron transporting layer (ETL) in versatile systems of organic solar cells (OSCs) is developed, which can be simply formulated by blending the Cs2CO3 with the Zn(Ac)2 precursor in solutions. The Cs doping significantly increased the ZnO film conductivity and lowered its work function, as unveiled by the conductive atomic force microscope and the ultra-violet photoelectron spectroscopy. Decent device performance enhancements of OSCs with versatile photovoltaic materials, e.g. P3HT:PC61BM, P3HT:ICBA, and PTB7:PC71BM, were observed with the doped ZnO:Cs as the ETL compared with the pristine ZnO ETL. The enhanced device performance was also found in the tandem solar cells. Moreover, the device performance shows little drop with the thickness of the doped ZnO:Cs ETL ranging from 40 to 520 nm, indicating the less thickness dependence for the doped ZnO:Cs ETL. The current work verifies the potential of the Cs doped ZnO as a high performance ETL material for printable OSCs.
Co-reporter:Wenqing Liu, Hangqi Shi, Thomas R. Andersen, Natalia K. Zawacka, Pei Cheng, Eva Bundgaard, Minmin Shi, Xiaowei Zhan, Frederik C. Krebs and Hongzheng Chen
RSC Advances 2015 vol. 5(Issue 45) pp:36001-36006
Publication Date(Web):09 Apr 2015
DOI:10.1039/C5RA04336K
We report organic solar cells (OSCs) with non-fullerene small molecule acceptors (SMAs) prepared in large area via a roll coating process. We employ all solution-processed indium tin oxide (ITO)-free flexible substrates for inverted solar cells with a new SMA of F(DPP)2B2. By utilizing poly(3-hexylthiophene) as donor blended with F(DPP)2B2 as acceptor, ITO-free large-area flexible SMA based OSCs were produced under ambient conditions with the use of slot-die coating and flexographic printing methods on a lab-scale compact roll-coater that is readily transferrable to roll-to-roll processing. The effect of different processing solvents on the device performance was investigated, and the best performance with a power conversion efficiency of 0.65%, an open circuit voltage of 0.85 V, a short-circuit current density of 2.19 mA cm−2, and a fill factor of 35% was obtained.
Co-reporter:Wenqing Liu, Hangqi Shi, Weifei Fu, Lijian Zuo, Ling Wang, Hongzheng Chen
Organic Electronics 2015 Volume 25() pp:219-224
Publication Date(Web):October 2015
DOI:10.1016/j.orgel.2015.06.043
•A bipolar small molecule (F(DPP)2B2) was incorporated into P3HT:PC61BM blend to fabricate ternary PSCs.•F(DPP)2B2 can act as an efficient cascade material for the ternary PSCs.•An enhanced light absorption from 550 to 700 nm is achieved.•The optimized ternary PSC delivered an 23% improvement of PCE as compared to the binary PSC.We present a ternary strategy to enhance the power conversion efficiency (PCE) of bulk heterojunction polymer solar cells (PSCs) with a bipolar small molecule as cascade material. A bipolar diketopyrrolopyrrole small molecule (F(DPP)2B2), as the second electron acceptor, was incorporated into poly(3-hexylthiophene) (P3HT): [6,6]-phenyl-C61-butyric-acidmethyl-ester (PC61BM) blend to fabricate ternary blend PSCs. The introduction of the bipolar compound F(DPP)2B2 can not only broaden the light absorption of the active layer because of its absorption in near infrared region but also play a bridging role between P3HT and PC61BM due to the cascaded energy level structure, thus improving the charge separation and transportation. The optimized ternary PSC with 5 wt% F(DPP)2B2 content delivered a high PCE of 3.92% with a short-circuit current density (Jsc) of 9.63 mA cm−2, an open-circuit voltage (Voc) of 0.62 V and a fill factor (FF) of 64.90%, showing an 23% improvement of PCE as compared to the binary systems based on P3HT:PC61BM (3.18%) or P3HT:F(DPP)2B2 (3.17%). The results indicate that the ternary PSCs with a bipolar compound have the potential to surpass high-performance binary PSCs after carefully device optimization.Graphical abstract
Co-reporter:Tang Liu, Lijian Zuo, Tao Ye, Jiake Wu, Guobiao Xue, Weifei Fu and Hongzheng Chen
RSC Advances 2015 vol. 5(Issue 115) pp:94752-94758
Publication Date(Web):30 Oct 2015
DOI:10.1039/C5RA20125J
Perovskite solar cells (PSCs) have been considered as a promising photovoltaic technology due to their attractive power conversion efficiency (PCE) exceeding 20% and ease of processability at low temperature. However, there have been a few reports on low temperature processed ITO-free PSCs. In this work, highly transparent and conductive poly(3,4-ethylenedioxythiophene):polystyrene sulfonate (HC-PEDOT:PSS, PH1000) was employed as electrode as an alternative material to ITO. PSCs built on three different electrodes (PH1000-5%, PH1000-10% and PH1000-H) with or without a hole transport layer (HTL) were fabricated. The factors that influence the performance of PSCs such as conductivity, morphology, work function and wettability of the electrode, morphology of perovskite films and different electrode treatments were investigated. A comparison of different electrodes as well as their corresponding impact on the device performance were also presented. The optimized average PCE of 7.95% with the highest PCE up to 9.65% for PSCs built on the PH1000-10% electrode without HTL were achieved. When a layer of PEDOT:PSS was spin coated on PH1000-H to prevent perovskite from decomposing, the optimized PCE of 6.98% with the highest up to 9.31% was achieved. Our results indicate that PH-1000 is a promising material to replace both ITO electrode and HTL, providing a much simpler architecture for flexible PSC applications.
Co-reporter:Shabi Thankaraj Salammal;Jiehuan Chen
Journal of Inorganic and Organometallic Polymers and Materials 2015 Volume 25( Issue 1) pp:12-26
Publication Date(Web):2015 January
DOI:10.1007/s10904-014-0107-z
The fast-growing organic electronics field has received the attention of a lot of researchers because of its wide applicability in the consumer electronics, photovoltaics and biotechnology. Since the charge transport, absorption of electromagnetic radiations and exciton migration in the organic semiconductors is direction dependent, it is mandatory to control the morphology and orientation of the active layer with respect to the applications. So, in this review we have briefly discussed the role of thin film morphology on the organic solar cell and organic field-effect transistor performance. And the efforts have been taken by the researchers to control the morphology of thin films through the active layer engineering and molecular engineering are summarized.
Co-reporter:Xi Yang;Wenqing Liu;Hongzheng Chen
Science China Chemistry 2015 Volume 58( Issue 2) pp:210-220
Publication Date(Web):2015 February
DOI:10.1007/s11426-014-5219-3
Light trapping based on the localized surface-plasmon resonance (LSPR) effect of metallic nanostructures is a promising strategy to improve the device performance of organic solar cells (OSCs). We review recent advances in plasmonic-enhanced OPVs with solution-processed metallic nanoparticles (NPs). The different types of metallic NPs (sizes, shapes, and hybrids), incorporation positions, and NPs with tunable resonance wavelengths toward broadband enhancement are systematically summarized to give a guideline for the realization of highly efficient plasmonic photovoltaics.
Co-reporter: Hanying Li;Congcheng Fan;Weifei Fu;Dr. Huolin L. Xin; Hongzheng Chen
Angewandte Chemie International Edition 2015 Volume 54( Issue 3) pp:956-960
Publication Date(Web):
DOI:10.1002/anie.201408882
Abstract
Organic single crystals are ideal candidates for high-performance photovoltaics due to their high charge mobility and long exciton diffusion length; however, they have not been largely considered for photovoltaics due to the practical difficulty in making a heterojunction between donor and acceptor single crystals. Here, we demonstrate that extended single-crystalline heterojunctions with a consistent donor-top and acceptor-bottom structure throughout the substrate can be simply obtained from a mixed solution of C60 (acceptor) and 3,6-bis(5-(4-n-butylphenyl)thiophene-2-yl)-2,5-bis(2-ethylhexyl)pyrrolo[3,4-c]pyrrole-1,4-dione (donor). 46 photovoltaic devices were studied with the power conversion efficiency of (0.255±0.095) % under 1 sun, which is significantly higher than the previously reported value for a vapor-grown organic single-crystalline donor–acceptor heterojunction (0.007 %). As such, this work opens a practical avenue for the study of organic photovoltaics based on single crystals.
Co-reporter:Lijian Zuo;Chu-Chen Chueh;Yun-Xiang Xu;Kung-Shih Chen;Yue Zang;Chang-Zhi Li;Hongzheng Chen;Alex K.-Y. Jen
Advanced Materials 2014 Volume 26( Issue 39) pp:6778-6784
Publication Date(Web):
DOI:10.1002/adma.201402782
Co-reporter:Chih-Yu Chang;Lijian Zuo;Hin-Lap Yip;Chang-Zhi Li;Yongxi Li;Chain-Shu Hsu;Yen-Ju Cheng;Hongzheng Chen;Alex K-Y. Jen
Advanced Energy Materials 2014 Volume 4( Issue 7) pp:
Publication Date(Web):
DOI:10.1002/aenm.201301645
Highly efficient tandem and semitransparent (ST) polymer solar cells utilizing the same donor polymer blended with [6,6]-phenyl-C61-butyric acid methyl ester (PC61BM) and [6,6]-phenyl-C71-butyric acid methyl ester (PC71BM) as active layers are demonstrated. A high power conversion efficiency (PCE) of 8.5% and a record high open-circuit voltage of 1.71 V are achieved for a tandem cell based on a medium bandgap polymer poly(indacenodithiophene-co-phananthrene-quinoxaline) (PIDT-phanQ). In addition, this approach can also be applied to a low bandgap polymer poly[2,6-(4,4-bis(2-ethylhexyl)-4H-cyclopenta[2,1-b;3,4-b′]dithiophene)-alt-4,7-(5-fluoro-2,1,3-benzothia-diazole)] (PCPDTFBT), and PCEs up to 7.9% are achieved. Due to the very thin total active layer thickness, a highly efficient ST tandem cell based on PIDT-phanQ exhibits a high PCE of 7.4%, which is the highest value reported to date for a ST solar cell. The ST device also possesses a desirable average visible transmittance (≈40%) and an excellent color rendering index (≈100), permitting its use in power-generating window applications.
Co-reporter:Lei Fu, Weifei Fu, Pei Cheng, Zhixin Xie, Congcheng Fan, Minmin Shi, Jun Ling, Jianhui Hou, Xiaowei Zhan and Hongzheng Chen
Journal of Materials Chemistry A 2014 vol. 2(Issue 18) pp:6589-6597
Publication Date(Web):19 Feb 2014
DOI:10.1039/C3TA13534A
We designed and synthesized a diketopyrrolopyrrole (DPP) molecule with a fully-planar molecular geometry, 3,6-bis{5-[(ethylfuran-2-carboxylate)-2-yl]thiophene-2-yl}-2,5-bis(2-ethylhexyl)pyrrolo[3,4-c]pyrrole-1,4-dione (DPP(CF)2), for solution-processable organic solar cells (OSCs). It is theoretically calculated that the dihedral angles between the two furan-2-carboxylate end-groups and the DPP core are both only 0.56°. Due to this negligible steric distortion, the molecular conformation of DPP(CF)2 can be considered fully coplanar, leading to a higher crystallinity for the DPP(CF)2 film. As a result, the hole mobility of DPP(CF)2 is one order of magnitude higher than that of the DPP derivative with thiophene-2-carboxylate as the end-group (DPP(CT)2). DPP(CF)2 exhibits both a low optical band gap (Eg) of 1.60 eV and a low-lying highest occupied molecular orbital (HOMO) energy level of −5.33 eV, implying that DPP(CF)2 is a promising electron donor for OSCs. OSCs with DPP(CF)2 or DPP(CT)2 as the electron donor and [6,6]-phenyl-C71-butyric acid methyl ester (PC71BM) as the electron acceptor were fabricated. It is found that the DPP(CF)2-based devices exhibit much better photovoltaic performance than the DPP(CT)2-based devices, with the highest power conversion efficiency of 5.37% and a short-circuit current density of 11.4 mA cm−2. This phenomenon can be ascribed to the superior charge-transporting ability of DPP(CF)2 due to its fully-planar molecular geometry.
Co-reporter:Xi Yang, Weifei Fu, Wenqing Liu, Jinghua Hong, Yu Cai, Chuanhong Jin, Mingsheng Xu, Haibo Wang, Deren Yang and Hongzheng Chen
Journal of Materials Chemistry A 2014 vol. 2(Issue 21) pp:7727-7733
Publication Date(Web):25 Mar 2014
DOI:10.1039/C4TA01336K
The effects of different local crystalline structures on two-dimensional (2D) MoS2 sheets are studied to provide new insights into how the local characteristics affect the performance of organic solar cells (OSCs) and how to tailor the local characteristics towards high-performance devices. UV–ozone post-treatment of 2D MoS2 sheets led to incorporation of oxygen atoms into the lattice of the sheets. The incorporated oxygen in 2D MoS2 sheets significantly improved the performance of OSCs, where 2D MoS2 sheets were used as hole transport layers.
Co-reporter:Weifei Fu, Ling Wang, Jun Ling, Hanying Li, Minmin Shi, Jiangeng Xue and Hongzheng Chen
Nanoscale 2014 vol. 6(Issue 18) pp:10545-10550
Publication Date(Web):25 Jul 2014
DOI:10.1039/C4NR02339K
Effects of molecular dipole at the conjugated polymer–nanocrystal interface on the energy level alignment, the exciton dissociation process, and consequently the photovoltaic performance of poly[2,6-(4,4-bis-(2-ethylhexyl)-4H-cyclopenta[2,1-b;3,4-b′]-dithiophene)-alt-4,7-(2,1,3-benzothiadiazole)] (PCPDTBT):CdSe quantum dot bulk heterojunction hybrid solar cells are systemically studied. Power conversion efficiency up to 4.0% is achieved when 4-fluorobenzenethiol is used for ligand exchange.
Co-reporter:Xi Yang, Jie Li, Tao Liang, Chunyan Ma, Yingying Zhang, Hongzheng Chen, Nobutaka Hanagata, Huanxing Su and Mingsheng Xu
Nanoscale 2014 vol. 6(Issue 17) pp:10126-10133
Publication Date(Web):19 Jun 2014
DOI:10.1039/C4NR01965B
Graphene-like two-dimensional materials (2DMats) show application potential in optoelectronics and biomedicine due to their unique properties. However, environmental and biological influences of these 2DMats remain to be unveiled. Here we reported the antibacterial activity of two-dimensional (2D) chemically exfoliated MoS2 (ce-MoS2) sheets. We found that the antibacterial activity of ce-MoS2 sheets was much more potent than that of the raw MoS2 powders used for the synthesis of ce-MoS2 sheets possibly due to the 2D planar structure (high specific surface area) and higher conductivity of the ce-MoS2. We investigated the antibacterial mechanisms of the ce-MoS2 sheets and proposed their antibacterial pathways. We found that the ce-MoS2 sheets could produce reactive oxygen species (ROS), different from a previous report on graphene-based materials. Particularly, the oxidation capacity of the ce-MoS2 sheets toward glutathione oxidation showed a time and concentration dependent trend, which is fully consistent with the antibacterial behaviour of the ce-MoS2 sheets. The results suggest that antimicrobial behaviors were attributable to both membrane and oxidation stress. The antibacterial pathways include MoS2–bacteria contact induced membrane stress, superoxide anion (O2˙−) induced ROS production by the ce-MoS2, and the ensuing superoxide anion-independent oxidation. Our study thus indicates that the tailoring of the dimension of nanomaterials and their electronic properties would manipulate antibacterial activity.
Co-reporter:Ling Wang, Weifei Fu, Zhuowei Gu, Congcheng Fan, Xi Yang, Hanying Li and Hongzheng Chen
Journal of Materials Chemistry A 2014 vol. 2(Issue 43) pp:9087-9090
Publication Date(Web):19 Sep 2014
DOI:10.1039/C4TC01875C
A cadmium selenide (CdSe) nanocrystal was used as an electron transport/extraction layer for perovskite solar cells due to its high electron mobility and solution-processability at low temperatures. Power conversion efficiency (PCE) up to 11.7% was achieved under standard AM1.5G conditions in air.
Co-reporter:Hanying Li, Congcheng Fan, Michael Vosgueritchian, Benjamin C.-K. Tee and Hongzheng Chen
Journal of Materials Chemistry A 2014 vol. 2(Issue 18) pp:3617-3624
Publication Date(Web):25 Feb 2014
DOI:10.1039/C3TC32431A
Single crystals of C60 have been widely prepared previously. However, their electronic properties are much less frequently studied, although C60 is known as an outstanding electronic material. Also, the reported electron mobility values (∼10−2 cm2 V−1 s−1) of C60 single-crystals are unexpectedly low possibly due to the difficulties in the fabrication of single-crystal devices. We have recently reported a droplet receding method for the solution-grown C60 single-crystals with mobilities above 1 cm2 V−1 s−1. In this work, we systematically investigate the effects of solvent and surface properties of the substrate on the growth of C60 single-crystals. Well-aligned C60 needle-like and ribbon-like single-crystals were grown from suitable solvents (m-xylene or a mixed solvent of m-xylene and carbon tetrachloride) conformally on the field-effect transistor (FET) substrates that were wet well by the receding droplet. Based on the ribbon-like single-crystals, an average electron mobility of 2.0 ± 0.61 cm2 V−1 s−1, Ion/Ioff > 106, and a VT between 36 and 85 V were achieved from 60 field-effect transistors. Insights provided by this work may help accelerate the development of solution-grown single-crystals of organic semiconductors.
Co-reporter:Xi Yang, Wenqing Liu, Min Xiong, Yingying Zhang, Tao Liang, Jingting Yang, Mingsheng Xu, Jian Ye and Hongzheng Chen
Journal of Materials Chemistry A 2014 vol. 2(Issue 36) pp:14798-14806
Publication Date(Web):16 Jul 2014
DOI:10.1039/C4TA03178D
A novel hole transport layer (HTL) composed of ultrathin two-dimensional, molybdenum disulfide (MoS2) sheets decorated with 20 nm gold nanoparticles (NPs) (MoS2@Au) was developed to make use of plasmonics for organic solar cells (OSCs). Both experimental and theoretical simulations revealed that the device with the MoS2@Au composite as the HTL exhibited enhanced short-circuit photocurrent density (Jsc) and efficiency compared to that with MoS2 alone as the HTL.
Co-reporter:Wenqing Liu, Shiyong Liu, Natalia K. Zawacka, Thomas R. Andersen, Pei Cheng, Lei Fu, Meirong Chen, Weifei Fu, Eva Bundgaard, Mikkel Jørgensen, Xiaowei Zhan, Frederik C. Krebs and Hongzheng Chen
Journal of Materials Chemistry A 2014 vol. 2(Issue 46) pp:19809-19814
Publication Date(Web):25 Sep 2014
DOI:10.1039/C4TA04733H
All solution-processed flexible large area small molecule bulk heterojunction solar cells were fabricated via roll-coating technology. Our devices were produced from slot-die coating on a lab-scale mini roll-coater under ambient conditions without the use of spin-coating or vacuum evaporation methods. Four diketopyrrolopyrrole based small molecules (SMs 1–4) were utilized as electron donors with (6,6)-phenyl-C61-butyric acid methyl ester as an acceptor and their photovoltaic performances based on roll-coated devices were investigated. The best power conversion efficiency (PCE) of 1.01%, combined with an open circuit voltage of 0.73 V, a short-circuit current density of 3.13 mA cm−2 and a fill factor of 44% were obtained for the device with SM1, which was the first example reported for efficient roll-coating fabrication of flexible large area small molecule solar cells with PCE exceeding 1%. In addition, roll-coated devices based on SMs 2–4 also showed good performances with PCEs of 0.41%, 0.54%, and 0.31%, respectively. Our results prove that small molecules have the potential for use in industries for large scale production of efficient organic solar cells.
Co-reporter:Shi-Yong Liu, Wen-Qing Liu, Jing-Qi Xu, Cong-Cheng Fan, Wei-Fei Fu, Jun Ling, Jun-Yong Wu, Min-Min Shi, Alex K.-Y. Jen, and Hong-Zheng Chen
ACS Applied Materials & Interfaces 2014 Volume 6(Issue 9) pp:6765
Publication Date(Web):April 10, 2014
DOI:10.1021/am500522x
In this report, an atom efficient and facile synthetic strategy for accessing multi-diketopyrrolopyrrole (DPP)-based oligomers used in solution-processed organic field effect transistors (OFETs) and organic solar cells (OSCs) has been developed. The DPP units were successfully installed onto benzene and pyrene cores via palladium-catalyzed dehydrohalogenative coupling of mono-capped DPPs with multi-bromo-benzene or -pyrene (direct arylation), affording four oligomer small molecules (SMs 1–4) containing bis-, tri-, tri-, and tetra-DPP, respectively, in high yields of 78–96%. All the designed linear or branched DPP-based oligomers exhibit broad light absorptions, narrow band-gaps (1.60–1.73 eV), deep highest occupied molecular orbital (HOMO) levels (−5.26 ∼ −5.18 eV), and good thermal stability (Td = 390–401 °C). OFETs based on SMs 1–4 showed hole mobilities of 0.0033, 0.0056, 0.0005, and 0.0026 cm2 V–1 s–1, respectively. OSCs based on SMs 1–4 under one sun achieved power conversion efficiencies of 3.00%, 3.71%, 2.47%, and 1.86% accordingly, along with high open-circuit voltages of 0.86–0.94 V. For OSC devices of SM 1, SM 3, and SM 4, the solvent CHCl3 was solely employed to the formation of active layers; neither high boiling point additives nor annealing post-treatment was needed. Such a simple process benefits the large-scale production of OSCs via roll to roll technology.Keywords: diketopyrrolopyrrole; direct arylation; organic field effect transistors; organic solar cells; pyrene; solution-processed small molecules;
Co-reporter:Weifei Fu, Ling Wang, Yanfang Zhang, Ruisong Ma, Lijian Zuo, Jiangquan Mai, Tsz-Ki Lau, Shixuan Du, Xinhui Lu, Minmin Shi, Hanying Li, and Hongzheng Chen
ACS Applied Materials & Interfaces 2014 Volume 6(Issue 21) pp:19154
Publication Date(Web):October 22, 2014
DOI:10.1021/am505130a
Achieving superior solar cell performance based on the colloidal nanocrystals remains challenging due to their complex surface composition. Much attention has been devoted to the development of effective surface modification strategies to enhance electronic coupling between the nanocrystals to promote charge carrier transport. Herein, we aim to attach benzenedithiol ligands onto the surface of CdSe nanocrystals in the “face-on” geometry to minimize the nanocrystal–nanocrystal or polymer–nanocrystal distance. Furthermore, the “electroactive” π-orbitals of the benzenedithiol are expected to further enhance the electronic coupling, which facilitates charge carrier dissociation and transport. The electron mobility of CdSe QD films was improved 20 times by tuning the ligand orientation, and high performance poly[2,6-(4,4-bis(2-ethylhexyl)-4H-cyclopenta[2,1-b;3,4-b′]-dithiophene)-alt-4,7-(2,1,3-benzothiadiazole)] (PCPDTBT):CdSe nanocrystal hybrid solar cells were also achieved, showing a highest power conversion efficiency of 4.18%. This research could open up a new pathway to improve further the performance of colloidal nanocrystal based solar cells.Keywords: charge transport; electronic coupling; exciton dissociation; hybrid solar cell; ligand orientation
Co-reporter:Lijian Zuo, Jizhong Yao, Hanying Li, Hongzheng Chen
Solar Energy Materials and Solar Cells 2014 Volume 122() pp:88-93
Publication Date(Web):March 2014
DOI:10.1016/j.solmat.2013.11.018
•We propose an improved equivalent circuit model to interpret the origin of S shape curve.•The improved equivalent circuit model involves a rectifying junction connected with the D:A junction in series.•The validity of this model is confirmed by good reproduction of the experimental results.•Effect of the formation of S shape curve on device parameters is analyzed through the equivalent model.•Detailed effect of the rectifying junction on the I–V curve of organic solar cells is simulated.Formation of S-shaped I–V curve or the so-called kink has been shown detrimental to organic solar cells (OSC) performance. Previous researches have indicated that a variety of reasons could count for the origin of the S-shaped I–V curve. However, its origin is still not clear. In this contribution, we investigated the origin of S-shaped I–V curve from the view of an equivalent circuit model (ECM) in OSCs. The proposed ECM involves a rectifying junction connected with a donor/accepter (D/A) junction in series. OSCs with and without a Schottky barrier that was a rectifying junction were fabricated to verify the modeled results. And the good reproduction of experimental results confirmed the validity of our model. The results indicate that the origin of S-shaped I–V curve in OSCs is associated with the rectifying junction. With this model, the effects of the rectifying junction on the shape of I–V characteristic and its effect on device parameters are analyzed: fill factor (FF) dropped, short circuit current density decreased, open circuit voltage however, remained. Also, from simulation, we varied the parameters of the rectifying junction to study their influence on the device performance.In this work, we study the origin of S shape curve through an improved equivalent circuit model (ECM). The improved ECM involves a D:A junction as well as a rectifying junction to interpret the bias-dependent-recombination.
Co-reporter:Wenqing Liu, Xi Yang, Yingying Zhang, Mingsheng Xu and Hongzheng Chen
RSC Advances 2014 vol. 4(Issue 62) pp:32744-32748
Publication Date(Web):22 Jul 2014
DOI:10.1039/C4RA04116J
A simple and effective procedure was developed to modify chemically exfoliated MoS2 surfaces with a hydrophilic surfactant through electrostatic interaction. The modified ce-MoS2 colloidal solution shows ultra long-term stability, making it a storable solution ready for highly efficient organic solar cells.
Co-reporter:Min-Min Shi, Vincent C. Tung, Jing-Jing Nie, Hong-Zheng Chen, Yang Yang
Organic Electronics 2014 Volume 15(Issue 1) pp:281-285
Publication Date(Web):January 2014
DOI:10.1016/j.orgel.2013.11.011
•A perylene diimide derivative with bulky rigid substituents was synthesized.•This compound owns both high electron mobility and high fluorescence quantum yield.•The above phenomenon can be ascribed to its unique crystal structure.In this paper, we report that a kind of perylene diimide derivative with bulky rigid substituents, 1,7-bis(p-tert-butylphenoxy)-N,N′-dicyclohexyl-perylene-3,4,9,10-tetracarboxylic diimide (TBPCHPDI) possesses both high electron mobility (1.8 cm2 V−1s−1) and high fluorescence quantum yield (0.32) in the solid state. Through X-ray diffraction (XRD), UV–Vis absorption and fluorescence spectra, and differential scanning calorimetry (DSC) measurements, it is demonstrated that the above phenomenon can be ascribed to the unique crystal structure of TBPCHPDI: due to steric hindrance of bulky rigid substituents, the intermolecular π–π actions are neglectable, providing high luminescence efficiency; in the mean time, the spacing between perylene chromophores is still very short (3.47 Å), which is favorable for the hopping transportation of charge carrier from one molecule to neighboring molecule. Therefore, our finding would help design and synthesize novel organic semiconductive materials with potential applications in electrically pumped lasers which require high emission efficiency when large current density is applied.Graphical abstract
Co-reporter:Mei-Rong Chen, Cong-Cheng Fan, Thomas R. Andersen, Henrik F. Dam, Wei-Fei Fu, Yu-Ze Lin, Eva Bundgaard, Frederik C. Krebs, Xiao-Wei Zhan, Hong-Zheng Chen
Synthetic Metals 2014 Volume 195() pp:299-305
Publication Date(Web):September 2014
DOI:10.1016/j.synthmet.2014.06.023
•Diketopyrrolopyrrole derivative with cross-linkable azide groups was designed and synthesized.•A solvent-resistant molecule was emerged after cross-linking.•Solar cells employing the target molecule as either electron donor or acceptor were fabricated by roll coating.•This was the first report of small molecule solar cells with large area by roll-to-roll processing.A novel cross-linkable azide-functionalized diketopyrrolopyrrole based compound DPP(BT-N3)2 was designed and synthesized via Stille coupling. Cross-linking of such molecule could help us fabricate insoluble film which could be used to fabricate heterostructures through solution processing, without dissolving the pre-patterned layers. In order to investigate the photovoltaic performances of the newly synthesized compound, large area solar cells were produced by roll coating technique. Two set of devices were fabricated by employing DPP(BT-N3)2 as either an electron donor or acceptor. A best power conversion efficiency of 0.067%, combined with an open circuit voltage of 0.53 V, and a fill factor of 37.6% were obtained for the device with DPP(BT-N3)2 as an electron acceptor. In addition, we could prove that the large area small molecule based organic solar cells could be fabricated using roll coating, which could be used in the industries for large-scale of production.
Co-reporter:Jiachi Huang;Hanying Li;Xiong Mo;Minmin Shi
Chemical Research in Chinese Universities 2014 Volume 30( Issue 1) pp:63-67
Publication Date(Web):2014 February
DOI:10.1007/s40242-013-3294-1
One-dimensional crystals of fluorinated perylene diimides were achieved by the self-assembly of them via solvent-nonsolvent exchanging. The π-conjugated fluorinated perylene diimides were assembled into highly-ordered nanostructures of well-defined morphologies in organic solvents due to the π-π interaction between the aromatic cores. It was found that with more introduced F atoms, perylene diimides showed remarkably improved solubility and thus were much easier to grow into crystals, due to the increased polarity induced by the strong electron-withdrawing F group. More importantly, single crystal of N,N′-diperfluorophenyl-3,4,9,10-perylenetetracarboxylic diimide(DPFPP) was obtained, and the unit cell-dimensions of triclinic structure were determined by the selected area electron diffraction( SAED) patterns to be a=0.712 nm, b=1.072 nm, c=2.914 nm, α=97.0°, β=89.6°, γ=93.4°. Owing to most of the longest c-axis orienting nearly vertically to the long axis of the needle crystal, the molecular planes are expected to be vertical to the needle axis.
Co-reporter:Quan-xiang Yan;Zhuo-wei Gu;Qi Li;Wei-fei Fu
Chinese Journal of Polymer Science 2014 Volume 32( Issue 4) pp:395-401
Publication Date(Web):2014 April
DOI:10.1007/s10118-014-1415-z
Stable aqueous amino-grafted silicon nanoparticles (SiNPs-NH2) were prepared via one-pot solution method. By grafting amino groups on the particle surface, the dispersion of SiNPs in water became very stable and clear aqueous solutions could be obtained. By incorporating SiNPs-NH2 into the hole transport layer of poly(3,4-ethylenedioxythiophene)/polystyrene sulfonic acid (PEDOT:PSS), the performance of polymer solar cells composed of poly[2-methoxy,5-(2′-ethylhexyloxy)-1,4-phenylene vinylene] (MEH-PPV):[6,6]-phenyl-C61-butyric acid methyl ester (PCBM) as active layer can be improved. SiNPs-NH2 are dispersed uniformly in the PEDOT:PSS solution and help form morphologies with small-sized domains in the PEDOT:PSS film. SiNPs-NH2 serve as screens between conducting polymer PEDOT and ionomer PSS to improve the phase separation and charge transport of the hole transport layer. As a result, the sheet resistance of PEDOT:PSS thin films is decreased from (93 ± 5) × 105 to (13 ± 3) × 105 Ω/□. The power conversion efficiency (PCE) of polymer solar cells was thus improved by 9.8% for devices fabricated with PEDOT:PSS containing 1 wt% of SiNPs-NH2, compared with the devices fabricated by original PEDOT:PSS.
Co-reporter:Congcheng Fan;Arjan P. Zoombelt;Hao Jiang;Weifei Fu;Jiake Wu;Wentao Yuan;Yong Wang;Hanying Li;Hongzheng Chen;Zhenan Bao
Advanced Materials 2013 Volume 25( Issue 40) pp:5762-5766
Publication Date(Web):
DOI:10.1002/adma.201302605
Co-reporter:Xi Yang;Chu-Chen Chueh;Chang-Zhi Li;Hin-Lap Yip;Peipei Yin;Hongzheng Chen;Wen-Chang Chen;Alex K-Y. Jen
Advanced Energy Materials 2013 Volume 3( Issue 5) pp:666-673
Publication Date(Web):
DOI:10.1002/aenm.201200726
Abstract
Significantly increased power conversion efficiency (PCE) of polymer solar cells (PSCs) is achieved by applying a plasmonic enhanced light trapping strategy to a low bandgap conjugated polymer, poly(indacenodithiophene- co-phananthrene-quinoxaline) (PIDT-PhanQ) and [6,6]-phenyl-C71-butyric acid methyl ester (PC71BM) based bulk-heterojunction (BHJ) system. By doping both the rear and front charge-selecting interfacial layers of the device with different sizes of Au NPs, the PCE of the devices is improved from 6.65% to 7.50% (13% enhancement). A detailed study of processing, characterization, microscopy, and device fabrication is conducted to understand the underlying mechanism for the enhanced device performance. The success of this work provides a simple and generally applicable approach to enhance light harnessing of low bandgap polymers in PSCs.
Co-reporter:Chih-Yu Chang;Lijian Zuo;Hin-Lap Yip;Yongxi Li;Chang-Zhi Li;Chain-Shu Hsu;Yen-Ju Cheng;Hongzheng Chen;Alex K.-Y. Jen
Advanced Functional Materials 2013 Volume 23( Issue 40) pp:5084-5090
Publication Date(Web):
DOI:10.1002/adfm201301557
The versatility of a fluoro-containing low band-gap polymer, poly[2,6-(4,4-bis(2-ethylhexyl)-4H-cyclopenta[2,1-b;3,4-b’]dithiophene)-alt-4,7-(5-fluoro-2,1,3-benzothia-diazole)] (PCPDTFBT) in organic photovoltaics (OPVs) applications is demonstrated. High boiling point 1,3,5-trichlorobenzene (TCB) is used as a solvent to manipulate PCPDTFBT:[6,6]-phenyl-C71-butyric acid methyl ester (PC71BM) active layer morphology to obtain high-performance single-junction devices. It promotes the crystallization of PCPDTFBT polymer, thus improving the charge-transport properties of the active layer. By combining the morphological manipulation with interfacial optimization and device engineering, the single-junction device exhibits both good air stability and high power-conversion efficiency (PCE, of 6.6%). This represents one of the highest PCE values for cyclopenta[2,1-b;3,4-b’]dithiophene (CPDT)-based OPVs. This polymer is also utilized for constructing semitransparent solar cells and double-junction tandem solar cells to demonstrate high PCEs of 5.0% and 8.2%, respectively.
Co-reporter:Shi-Yong Liu, Min-Min Shi, Jia-Chi Huang, Zheng-Neng Jin, Xiao-Lian Hu, Jun-Ying Pan, Han-Ying Li, Alex K.-Y. Jen and Hong-Zheng Chen
Journal of Materials Chemistry A 2013 vol. 1(Issue 8) pp:2795-2805
Publication Date(Web):21 Dec 2012
DOI:10.1039/C2TA01318E
Diketopyrrolopyrrole (DPP) derivatives are an important class of high-performance pigment used in inks, paints, plastics, and organic electronics. Until now, DPP derivatives containing sophisticated aryl units at the DPP core have usually been obtained via Suzuki, Stille, or Negishi cross-coupling reactions, which require organometallic precursors. In this work, a series of DPP-based π-conjugated molecules bearing diverse aryl substituents on the thiophene- or benzene-DPPs were facilely synthesized in moderate to excellent yields through the Pd-catalyzed direct arylation of C–H bonds. The synthetic procedures feature advantages over traditional C–C cross-coupling reactions such as: (1) avoidance of the use of organometallic reagents in the starting materials leading to simpler byproducts and higher atom economy, (2) fewer synthetic steps, (3) higher yields, (4) better compatibility with chemically sensitive functional groups, and (5) simpler catalytic systems free of phosphine ligands. These advantages make the present protocol an ideal and versatile strategy for the synthesis of DPP derivatives, especially for structurally complicated DPPs that may possess chemically sensitive functionalities. The optical and electrochemical properties of the synthesized DPPs (17 compounds) were systematically investigated using UV-vis spectroscopy, steady-state fluorescence spectroscopy, and cyclic voltammetry (CV).
Co-reporter:Meirong Chen, Weifei Fu, Minmin Shi, Xiaolian Hu, Junying Pan, Jun Ling, Hangying Li and Hongzheng Chen
Journal of Materials Chemistry A 2013 vol. 1(Issue 1) pp:105-111
Publication Date(Web):27 Sep 2012
DOI:10.1039/C2TA00148A
For highly efficient organic solar cells (OSCs), the electron donor should possess not only a narrow band gap (Eg) but also a low highest occupied molecular orbital (HOMO) energy level. To achieve it, in this paper, we designed and synthesized a diketopyrrolopyrrole (DPP) derivative end capped with an ethyl thiophene-2-carboxylate moiety, 3,6-bis{5-[(ethyl thiophene-2-carboxylate)-2-yl]thiophene-2-yl}-2,5-bis(2-ethylhexyl)pyrrolo[3,4-c]pyrrole-1,4-dione (DPP(CT)2). Through UV-vis absorption and cyclic voltammetry (CV) measurements, we demonstrated that the resulting molecule exhibits both a low optical Eg of 1.65 eV and a lower-lying HOMO energy level of −5.33 eV owing to the electronegativity of the ester group and the conjugation effect of the thiophene ring. Therefore, when DPP(CT)2 is used as the electron donor to blend with [6,6]-phenyl-C71-butyric acid methyl ester (PC71BM) for solution processable OSCs, a power conversion efficiency (PCE) of 4.02% combined with an open-circuit voltage (VOC) as high as 0.94 V and a broad photovoltaic response range extending to around 750 nm is obtained.
Co-reporter:Peipei Yin, Gang Wu, Wenlong Qin, Xiaoqiang Chen, Mang Wang and Hongzheng Chen
Journal of Materials Chemistry A 2013 vol. 1(Issue 4) pp:843-849
Publication Date(Web):29 Nov 2012
DOI:10.1039/C2TC00344A
Chromatic organic pigment–SiO2 composite particles with six different colors (CYM and RGB) were prepared by a modified sol–gel method. With the aid of a cationic polyelectrolyte, poly(diallyldimethylammoniumchloride), amorphous silica was coated onto the surface of organic pigments which was revealed by the variation of the zeta potential and average particle size, together with TEM images and EDX and XPS results. Because of the fine scattering properties of silica to visible light, the intensity of the reflectance peak increased significantly, which makes the composite particles more vivid than the organic pigments. The chromatic electrophoretic suspension was prepared by mixing Span 85 and the composite particles anchored with a self-made block copolymer PLMA-b-PDMAEMA in tetrachloroethylene. All the colored ink particles have similar zeta potentials and mobility of about 30 mV and 4–5 × 10−10 m2 V−1 s−1, respectively. White/color (CYM and RGB) dual-particle electronic ink containing PLMA-b-PDMAEMA treated pigment–SiO2 composite particles and TiO2 grafted with a polymer present excellent performance and quick response under an applied DC field of 0.15 V μm−1.
Co-reporter:Wei-Fei Fu, Ye Shi, Ling Wang, Min-Min Shi, Han-Ying Li, Hong-Zheng Chen
Solar Energy Materials and Solar Cells 2013 Volume 117() pp:329-335
Publication Date(Web):October 2013
DOI:10.1016/j.solmat.2013.06.042
•A ligand exchange process by acetic acid in the hybrid film of P3HT: CdSe QDs was achieved.•Hybrid solar cells with PCE of nearly 2% at low annealing temperature (120 °C) after ligand exchange were achieved.•The mechanism of performance enhancement was investigated.•Acetic acid shows its advantages of environmental friendliness, non-toxicity and mild odors, comparing to the thiols that are widely used in hybrid solar cells.We utilize an adsorption/desorption process between the excess acetic acid in solution and the bound oleate ions on the surface of CdSe quantum dots to achieve ligand exchange process in the hybrid film of poly (3-hexylthione) (P3HT): CdSe quantum dots (QDs). By this post-deposition ligand exchange method, we achieved hybrid solar cells with power conversion efficiency of nearly 2% at low annealing temperature (120 °C). Compared to the thiols that are widely used in hybrid solar cells, acetic acid shows its advantages of environmental friendliness, non-toxicity and mild odors. As such, our method is attractive for future hybrid solar cell applications.
Co-reporter:Xiaoqiang Chen, Lijian Zuo, Weifei Fu, Quanxiang Yan, Congcheng Fan, Hongzheng Chen
Solar Energy Materials and Solar Cells 2013 Volume 111() pp:1-8
Publication Date(Web):April 2013
DOI:10.1016/j.solmat.2012.12.016
Photovoltaic performances of polymer bulk-heterojunction solar cells (PSCs) with various sized (20, 35, 50, and 75 nm) Au nanoparticles (NPs) incorporated on indium tin oxide (ITO)-coated glass substrates are investigated in detail, wherein poly(3-hexylthiophene):phenyl-C61-butyric acid methyl ester (P3HT:PCBM) blend serves as active layer and poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) as anode buffer layer on ITO. The optical and electrical properties of these devices incorporated with Au NPs with different space distributions in the interface of PEDOT:PSS buffer layer and P3HT:PCBM active layer are investigated. We find that, the optical property is improved as the Au NPs are large enough to penetrate into the active layer, while the performance of PSCs with small Au NPs can only benefit from the improved hole collection efficiency. Meanwhile, the exciton dissociation efficiency reduces remarkably as increasing the size of Au NPs. Finally, we demonstrated a maximum power conversion efficiency (PCE) improvement of ∼23% in the PSCs by incorporating 35 nm Au NPs.Highlights► Various sized Au NPs were spin-coated between ITO/anodic buffer layer. ► We explored optical and electrical properties of PSCs with various sized Au NPs. ► The mechanism of PCE enhancement of PSCs with Au NPs was revealed. ► A maximum PCE improvement of ∼23% was achieved.
Co-reporter:Wei-Fei Fu, Xiaoqiang Chen, Xi Yang, Ling Wang, Ye Shi, Minmin Shi, Han-Ying Li, Alex K.-Y. Jen, Jun-Wu Chen, Yong Cao and Hong-Zheng Chen
Physical Chemistry Chemical Physics 2013 vol. 15(Issue 40) pp:17105-17111
Publication Date(Web):01 Aug 2013
DOI:10.1039/C3CP52723A
Plasmonics have been proven to be an effective way to harness more incident light to achieve high efficiency in photovoltaic devices. Herein, we explore the possibility that plasmonics can be utilized to enhance light trapping and power conversion efficiency (PCE) for polymer–quantum dot (QD) hybrid solar cells (HSCs). Based on a low band-gap polymer poly[2,6-(4,4-bis-(2-ethylhexyl)-4H-cyclopenta[2,1-b;3,4-b′]-dithiophene)-alt-4,7-(2,1,3-benzothiadiazole)] (PCPDTBT) and a CdSe QD bulk-heterojunction (BHJ) system, gold nanoparticles were doped at different locations of the devices. Successfully, an improved PCE of 3.20 ± 0.22% and 3.16 ± 0.15% was achieved by doping the hole transporting layer and the active layer, respectively, which are among the highest values reported for CdSe QD based HSCs. A detailed study of processing, characterization, microscopy, and device fabrication is conducted to understand the underlying mechanism for the enhanced device performance. The success of this work provides a simple and generally applicable approach to enhance light harnessing of polymer–QD hybrid solar cells.
Co-reporter:Lei Fu, Hongbin Pan, Thue T. Larsen-Olsen, Thomas R. Andersen, Eva Bundgaard, Frederik C. Krebs, Hong-Zheng Chen
Dyes and Pigments 2013 Volume 97(Issue 1) pp:141-147
Publication Date(Web):April 2013
DOI:10.1016/j.dyepig.2012.12.009
New conjugated small molecules 5,5′-bis{5-Octyl-2-(2,2′-bithiophen-5-yl)-4H-thieno[2,3-c]pyrrole-4,6-dione}-3,3′-di-octylsilylene-2,2′-bithiophene DTS(BTTPD)2 and 5,5′-bis{5-Octyl-2-(2,5-thiophenyl)-4H-thieno[2,3-c]pyrrole-4,6-dione}-3,3′-di-octylsilylene-2,2′-bithiophene DTS(TTPD)2 of the acceptor–π–donor–π–acceptor type end-capped with thieno[2,3-c]pyrrole-4,6-dione (TPD) units for small molecule solar cells have been prepared through coupling of dithienosilole and TPD units bridged with thienylene and bithienylene. They are soluble in common organic solvents and show an interesting absorption. These small molecules have very similar optical band gaps (1.87 eV and 1.92 eV) and fairly close highest occupied molecular orbital energy levels (−5.52 to −5.55 eV). The best solar cells using DTS(TTPD)2 as an electron donor and [6,6]-phenyl-C61-butyric acid methyl ester (PC61BM) as an electron acceptor demonstrated efficient performance with an obviously high open-circuit voltage (VOC) of 0.97 V and a power conversion efficiency of 1.20% after annealing and using MoO3 as electron-blocking layer. The solar cells based on DTS(BTTPD)2 and PC61BM blend also exhibited a high VOC of 0.97 V under optimized conditions.Graphical abstractHighlights► A new electron-withdrawing moiety TPD was applied in organic solar cells. ► Two new conjugated small molecules end-capped with TPD were synthesized. ► DTS(BTTPD)2 and DTS(TTPD)2 are soluble with a low band gap and crystallinity in solid state. ► Solar cells under different optimized conditions were fabricated and tested in air.
Co-reporter:Hongbin Pan, Lijian Zuo, Weifei Fu, Congcheng Fan, Birgitta Andreasen, Xiaoqing Jiang, Kion Norrman, Frederik C. Krebs, Hongzheng Chen
Organic Electronics 2013 Volume 14(Issue 3) pp:797-803
Publication Date(Web):March 2013
DOI:10.1016/j.orgel.2012.12.020
Efficient and stable polymer bulk-heterojunction solar cells based on regioregular poly(3-hexylthiophene):[6,6]-phenyl-C61-butyric acid methyl ester (P3HT:PC61BM) blend active layer have been fabricated with a MoO3–Au co-evaporation composite film as the anode interfacial layer (AIL). The optical and electrical properties of the composite MoO3–Au film can be tuned by altering the concentration of Au. A composite film with 30% (weight ratio) Au was used as the AIL and showed a better performance than both pure MoO3 and PEDOT:PSS as AIL. The surface morphology of the MoO3–Au composite film was investigated by atomic force microscopy (AFM) and showed that the originally rough ITO substrate became smooth after depositing the composite film, with the root mean square roughness (RMS) decreased from 4.08 nm to 1.81 nm. The smooth surface reduced the bias-dependent carrier recombination, resulting in a large shunt resistance and thus improving the fill factor and efficiency of the devices. Additionally, the air stability of devices with different AILs (MoO3–Au composite, MoO3 and PEDOT:PSS) were studied and it was found that the MoO3–Au composite layer remarkably improved the stability of the solar cells with shelf life-time enhanced by more than 3 and 40 times compared with pure MoO3 layer and PEDOT:PSS layer, respectively. We argue that the stability improvement might be related with the defect states in MoO3 component.Graphical abstract.Highlights► A novel composite MoO3–Au film for anode interface modification was developed. ► A smoother, more uniform anode interface was achieved. ► Life time of the devices under ambient condition was prolonged significantly.
Co-reporter:Quanxiang Yan;Lijian Zuo;Zhuowei Gu;Ligong Yang;Rong Wang;Mang Wang ;Hongzheng Chen
Chinese Journal of Chemistry 2013 Volume 31( Issue 11) pp:1380-1384
Publication Date(Web):
DOI:10.1002/cjoc.201300303
Abstract
We have studied the effect of silicon nanocrystals (SiNCs) as a third component on performance of organic bulk heterojunction solar cells composed of poly[2-methoxy,5-(2′-ethylhexyloxy)-1,4-phenylene vinylene] (MEH-PPV):[6,6]-phenyl-C61-butyric acid methyl ester (PCBM) blend film. By adding suitable amounts of SiNCs into MEH-PPV:PCBM blend, the device performance such as external quantum efficiency, short circuit current density (JSC), and power conversion efficiency (PCE) improved. Incorporation of 2.5% SiNCs in the blend led to 13.6% improvement of JSC, which in turn resulted in 18% improvement of PCE up to 2.28%. The improved performance was mainly due to the improvements both in the charge generation from the interface of MEH-PPV/SiNCs and the charge collection at the cathode.
Co-reporter:Xiaoqiang Chen, Xi Yang, Weifei Fu, Mingsheng Xu, Hongzheng Chen
Materials Science and Engineering: B 2013 Volume 178(Issue 1) pp:53-59
Publication Date(Web):1 January 2013
DOI:10.1016/j.mseb.2012.10.024
We reported the enhanced performance of polymer solar cells with the blend of poly (2-methoxy-5(2′-ethylhexyloxy)-1,4-phenylene-vinylene) (MEH-PPV) and [6,6]-phenyl C61 butyric acid methyl ester (PCBM) as active layer by incorporation of an assembled gold nanoparticle (Au NP) monolayer. The dense Au NP monolayer has been fabricated by Langmuir–Blodgett (LB) assembly and positioned between the transparent electrode ITO and the anode-modification PEDOT:PSS [poly (3,4-ethylenedioxythiophene):poly(styrene sulfonate)] layer, resulting in the device architecture of ITO/Au/PEDOT:PSS/MEH-PPV:PCBM/Al. We attribute the performance improvement to the localized surface plasmon resonance (LSPR) effect of Au NP films, which could lead to the increased absorption of the active layer. The parameters (nanoparticle size and interparticle distance) that govern this SPR effect have been optimized by selecting various sizes of Au NPs and controlling the LB assembly conditions. We observed ∼10–20% enhancement in power conversion efficiency for all the devices with the Au NP monolayer.Graphical abstractHighlights► Au NP monolayers are incorporated into ITO/anodic buffer layer by LB method. ► Au NP monolayers are surface oxidized by UV/O3 treatment. ► The effects of packing density and particle size on device performance were investigated. ► Both short-circuit current and open-circuit voltage are improved with Au NP layer.
Co-reporter:Ya-xiong Nan;Jun-jie Li;Wei-fei Fu;Wei-ming Qiu
Chinese Journal of Polymer Science 2013 Volume 31( Issue 6) pp:879-884
Publication Date(Web):2013 June
DOI:10.1007/s10118-013-1274-z
Improved hybrid solar cells consisting of vertical aligned cadmium sulfide (CdS) nanorod arrays and interpenetrating polythiophene (P3HT) have been achieved via modification of CdS nanorod surface by using conjugated N719 dye. The complete infiltration of P3HT between CdS nanorods interspacing was verified by scanning electron microscopy. By employing absorption and photoluminescence spectra, and current-voltage characterization the interaction between N719 molecules and CdS nanorods/P3HT interface was explored, and the role of N719 dye on the improvement of device performance was discussed.
Co-reporter:Xiaolian Hu, Lijian Zuo, Weifei Fu, Thue T. Larsen-Olsen, Martin Helgesen, Eva Bundgaard, Ole Hagemann, Minmin Shi, Frederik C. Krebs and Hongzheng Chen
Journal of Materials Chemistry A 2012 vol. 22(Issue 31) pp:15710-15716
Publication Date(Web):14 Jun 2012
DOI:10.1039/C2JM31700A
To increase the open circuit voltage (VOC) of polymer solar cells based on diketopyrrolopyrrole (DPP) containing polymers, the weakly electron-withdrawing thiophene-3,4-dicarboxylate unit was introduced into the polymer backbone. Two ester group functionalized DPP containing polymers, PCTDPP with a random structure and PDCTDPP with a regular structure, were designed and synthesized by the Stille coupling reaction. The resulting copolymers exhibit broad and strong absorption bands from 350 to 1000 nm with low optical band gaps below 1.40 eV. Through cyclic voltammetry measurements, it is found that regular PDCTDPP's HOMO energy level is 0.18 V lower than that of the corresponding random PCTDPP (−5.14 eV for PCTDPP and −5.32 eV for PDCTDPP). Preliminary photovoltaic properties of the copolymers blended with [6,6]-phenyl-C61-butyric acid methyl ester (PCBM) as an electron acceptor were investigated. The PSC based on a PCTDPP:PCBM blend shows a power conversion efficiency (PCE) up to 3.52%, with a VOC of 0.66 V, a short circuit current (ISC) of 8.53 mA cm−2, and a fill factor (FF) of 0.63. For the PDCTDPP:PCBM blend, the highest VOC reaches a value of 0.84 V, and a final PCE (0.92%) is limited by the poor hole mobility of the active layer.
Co-reporter:Ye Shi, Hanying Li, Ling Wang, Wei Shen, and Hongzheng Chen
ACS Applied Materials & Interfaces 2012 Volume 4(Issue 9) pp:4800
Publication Date(Web):August 15, 2012
DOI:10.1021/am3011516
Various semiconductors have been studied as photocatalysts for photocatalytic degradation of pollutants in aqueous solutions. As one of the promising visible-light-driven semiconductor photocatalysts, α-Fe2O3 has advantages of low cost and stability. However, its application is inhibited by the poor separation of photogenerated electron-hole pair. In this work, hybrid structures were prepared to improve the performance of α-Fe2O3. CdS nanoparticles were overgrown on the preformed single-crystalline α-Fe2O3 nanorods by a simple and mild one-step wet-chemical method, resulting in α-Fe2O3/CdS cornlike nanocomposites. X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and Raman spectroscopy showed the α-Fe2O3/CdS core/shell heterostructure of the nanocomposite with high crystallinity. Furthermore, the cornlike nanocomposites exhibited superior photocatalytic performances under visible light irradiation over the pure α-Fe2O3 nanorods and CdS nanoparticles. The photocatalytic activity of the composites is superior to the previously-reported pure α-Fe2O3 nanomaterials, and the performance is comparable to both the commercial TiO2 (P25) which is used under UV irradiation and the newly developed α-Fe2O3/SnO2 photocatalyst under visible light irradiation. The enhanced performance is associated with the larger surface area of the cornlike structure, the crystalline nature of the materials and the synergy in light absorption and charge separation between α-Fe2O3 and CdS. As such, our α-Fe2O3/CdS cornlike nanocomposites may be promising to be used as visible-light-driven high-performance photocatalyst.Keywords: CdS; hybrid materials; photocatalyst; semiconductors; visible-light-driven; α-Fe2O3;
Co-reporter:Weifei Fu, Ye Shi, Weiming Qiu, Ling Wang, Yaxiong Nan, Minmin Shi, Hanying Li and Hongzheng Chen
Physical Chemistry Chemical Physics 2012 vol. 14(Issue 35) pp:12094-12098
Publication Date(Web):24 Jul 2012
DOI:10.1039/C2CP42487H
High-performance hybrid solar cells (HSCs) based on P3HT:CdSe QD blends are achieved through post-deposition ligand exchange by n-butanethiol (n-BT) with a high power conversion efficiency of 3.09%. The mechanism by which n-BT modifies the surface structures of CdSe QDs and thus improves the HSCs performance is investigated.
Co-reporter:Minmin Shi, Feng Hao, Lijian Zuo, Yi Chen, Yaxiong Nan, Hongzheng Chen
Dyes and Pigments 2012 Volume 95(Issue 2) pp:377-383
Publication Date(Web):November 2012
DOI:10.1016/j.dyepig.2012.05.003
In this paper, three violanthrone derivatives with different substituents, 16,17-bis(2-ethylhexyloxy)-anthra[9,1,2-cde-]benzo[rst]pentaphene-5,10-dione (3), 16,17-bis(octyloxy)-anthra[9,1,2-cde-]benzo[rst]pentaphene-5,10-dione (4), 16,17-bis(hexyloxy)-anthra[9,1,2-cde-]benzo[rst]pentaphene-5,10-dione (5), are synthesized. It is found that the substituent has a great effect on the aggregate structures of violanthrone derivatives: the shorter the side chain is, the stronger the intermolecular π–π actions in the solid state is. Because all compounds are p-type semiconductive materials with the relatively low-lying highest occupied molecular orbital (HOMO) energy levels (∼−5.1 eV) and low band gaps (∼1.8 eV), their photovoltaic properties are evaluated when the blends of violanthrone derivatives and 6 and 6-phenyl-C61-butyric acid methyl ester (PCBM) (1:1, w/w) are used as the active layers of organic solar cells. Among three violanthrone derivatives, compound 5 exhibits the best photovoltaic performance with the power conversion efficiency (PCE) of 0.54% since the aggregate structure of compound 5 is in favor of charge transport.Highlights► Three soluble violanthrone derivatives with different alkyloxy substituents are synthesized. ► All violanthrone derivatives are potential electron donors in organic solar cells. ► The violanthrone derivative with the shortest linear substituent shows the highest hole mobility. ► The violanthrone derivative with the shortest linear substituent also exhibits the best photovoltaic performance.
Co-reporter:Xiao-Lian Hu, Li-Jian Zuo, Ya-Xiong Nan, Martin Helgesen, Ole Hagemann, Eva Bundgaard, Min-Min Shi, Frederik C. Krebs, Hong-Zheng Chen
Synthetic Metals 2012 Volume 162(Issue 23) pp:2005-2009
Publication Date(Web):December 2012
DOI:10.1016/j.synthmet.2012.10.001
To lower the HOMO (highest occupied molecular orbital) energy level of polythieno[3,4-b]thiophene (∼−4.5 eV), a series of ester-functionalized polythieno[3,4-b]thiophene derivatives (P1–P3) were designed and synthesized by Stille cross coupling reaction. The resulting copolymers exhibited broad and strong absorption bands from visible to near infrared region with low optical band gaps of 1.23–1.42 eV. Through cyclic voltammetry measurements, it was found that the HOMO energy levels of the copolymers gradually decreased with increasing the content of the thiophene-3,4-dicarboxylate moiety, i.e. −4.91 eV for P1, −5.00 eV for P2, and −5.11 eV for P3. Preliminary photovoltaic properties of the copolymers blended with [6,6]-phenyl-C61-butyric acid methyl ester (PCBM) as electron acceptor were investigated. Among the three copolymers, P1 exhibited the best photovoltaic performance with an open circuit voltage (Voc) of 0.54 V, a short circuit current density (Isc) of 3.3 mA/cm2, a fill factor (FF) of 0.57, and a power conversion efficiency (PCE) of 1.02%. A high Voc up to 0.71 V was achieved in the solar cell based on a P3:PCBM blend.Graphical abstractHighlights► We introduce thiophene-3,4-dicarboxylate into polythieno[3,4-b]thiophene's backbone. ► The HOMO gradually decreased with increasing the content of thiophene-3,4-dicarboxylate. ► Photovoltaic properties of copolymers were investigated. ► A relatively high Voc of 0.71 V was achieved.
Co-reporter:Lin Chen, Yunlong Zou, Weiming Qiu, Fei Chen, Mingsheng Xu, Minmin Shi, Hongzheng Chen
Thin Solid Films 2012 Volume 520(Issue 16) pp:5249-5253
Publication Date(Web):1 June 2012
DOI:10.1016/j.tsf.2012.03.085
We report the synthesis of Cu2S nanocrystalline thin film directly on indium tin oxide (ITO) substrate by a facile hydrothermal method using glutathione as the capping agent. The morphology and the phase composition of the obtained Cu2S nanostructure film are characterized by X-ray diffraction and field emission scanning electron microscopy. A capping agent directed two-step growth mechanism is proposed based on investigation of the reaction condition dependent product morphology. Optical study shows that Cu2S crystalline film has a broad spectrum response over visible and near-infrared region. The current–voltage results from ITO/Cu2S/Al devices indicate that Cu2S film with larger crystal size has better conduction capacity.Highlights► We use a hydrothermal process to synthesize Cu2S nanocrystalline films. ► Glutathione content and reaction time have great effects on film morphologies. ► The Cu2S films show broad spectrum response in the near-infrared region. ► Morphology influences both optical and electrical properties of the thin films.
Co-reporter:Minmin Shi;Lei Fu;Xiaolian Hu;Lijian Zuo;Dan Deng;Jian Chen
Polymer Bulletin 2012 Volume 68( Issue 7) pp:1867-1877
Publication Date(Web):2012 April
DOI:10.1007/s00289-011-0662-1
In this article, a simple and common electron-withdrawing moiety, carbonyl group, is applied in the molecular design of conjugated polymers for high-performance polymer solar cells (PSCs). Two series of donor–acceptor (D–A) copolymers are synthesized through alternating copolymerization of the electron-donating (D) benzodithiophene and dithienopyrrole with various electron-accepting (A) units containing carbonyl groups. The absorption range and the band gap of copolymers can be tuned by changing the molecular structure of A unit and the number of carbonyl groups. Moreover, by introducing the carbonyl group, the highest occupied molecular orbital energy level of the copolymer is lowered efficiently, leading to the improvement of the open-circuit voltage (VOC) of PSCs. The best photovoltaic performance is obtained while poly(benzodithiophene-alt-thiophene-3-carboxylate) is functioned as the electron donor and [6,6]-phenyl-C61-butyric acid methyl ester as electron acceptor in a bulk heterojunction solar cell with a power conversion efficiency of 4.13%, a VOC of 0.80 V, a short-circuit current of 8.19 mA/cm2, and a fill factor of 63.2%.
Co-reporter:MingSheng Xu;Yan Gao;Xi Yang;HongZheng Chen
Science Bulletin 2012 Volume 57( Issue 23) pp:3000-3009
Publication Date(Web):2012 August
DOI:10.1007/s11434-012-5128-9
Graphene has unique physical properties, and a variety of proof-of-concept devices based on graphene have been demonstated. A prerequisite for the application of graphene is its production in a controlled manner because the number of graphene layers and the defects in these layers significantly influence transport properties. In this paper, we briefly review our recent work on the controlled synthesis of graphene and graphene-based composites, the development of methods to characterize graphene layers, and the use of graphene in clean energy applications and for rapid DNA sequencing. For example, we have used Auger electron spectroscopy to characterize the number and structure of graphene layers, produced single-layer graphene over a whole Ni film substrate, synthesized well-dispersed reduced graphene oxide that was uniformly grafted with unique gold nanodots, and fabricated graphene nanoscrolls. We have also explored applications of graphene in organic solar cells and direct, ultrafast DNA sequencing. Finally, we address the challenges that graphene still face in its synthesis and clean energy and biological sensing applications.
Co-reporter:Li-Jian Zuo, Xiao-Lian Hu, Tao Ye, Thomas R. Andersen, Han-Ying Li, Min-Min Shi, Mingsheng Xu, Jun Ling, Qiang Zheng, Jun-Ting Xu, Eva Bundgaard, Frederik C. Krebs, and Hong-Zheng Chen
The Journal of Physical Chemistry C 2012 Volume 116(Issue 32) pp:16893-16900
Publication Date(Web):July 24, 2012
DOI:10.1021/jp3049444
This paper reports how the morphology of a polymer–fullerene derivative blend is tuned via the different aggregate states of the polymer in solutions. Based on a copolymer with benzodiothiophene and thiophene-3-carboxylate as alternating units (PBDTCT), we explored the polymer aggregation (i.e., organo-gels) behavior as a function of steric hindrance of aromatic solvents imposed by substituents. We showed that the size of organo-gels decreased as the substituents of solvents got larger. Also, the phase separation and domain size of the subsequent spin-coated films increased monotonically with that of the organo-gels in solution. Through this knowledge, we eventually achieve controlled morphology and optimized organic solar cells (OSCs) performance. Our results present a significant step forward for understanding the self-assembly behavior of conjugated polymers, control of their morphology and optimization of OSC performance.
Co-reporter:Shi-Yong Liu, Han-Ying Li, Min-Min Shi, Hao Jiang, Xiao-Lian Hu, Wang-Qiu Li, Lei Fu, and Hong-Zheng Chen
Macromolecules 2012 Volume 45(Issue 22) pp:9004-9009
Publication Date(Web):November 5, 2012
DOI:10.1021/ma3019238
Conjugated polymers are the primary blocks for organic electronics. Traditionally, conjugated polymers synthesized via Suzuki, Heck, and Stille couplings are catalyzed by soluble homogeneous ligated palladiums, which suffer the contaminations of residual nano-palladium and phosphine impurity resulting from side reaction of aryl–aryl exchange. To overcome these drawbacks, a commercially available, clean, and ligand-free heterogeneous catalyst Pd/C for the C–C coupling polymerizations was developed in this work. The Pd/C catalyst showed increases in catalytic activity for Suzuki and Heck polymerizations, as compared with the classical homogeneous catalyst Pd(PPh3)4. Furthermore, the Pd/C catalyst exhibited advantage of much less Pd residue in the resulting polymers, leading to better charge transport properties as demonstrated by field effect transistors.
Co-reporter:Yan Gao;Hin-Lap Yip;Kung-Shih Chen;Kevin M. O’Malley;Orb Acton;Ying Sun;Guy Ting;Hongzheng Chen;Alex K.-Y. Jen
Advanced Materials 2011 Volume 23( Issue 16) pp:1903-1908
Publication Date(Web):
DOI:10.1002/adma.201100065
Co-reporter:Weiming Qiu, Mingsheng Xu, Xi Yang, Fei Chen, Yaxiong Nan, Jinglin Zhang, Hideo Iwai and Hongzheng Chen
Journal of Materials Chemistry A 2011 vol. 21(Issue 35) pp:13327-13333
Publication Date(Web):03 Aug 2011
DOI:10.1039/C1JM11616A
We report the synthesis and formation mechanism of In2S3 porous films composed of ultrathin curved nanoflakes by a simple and environment-friendly biomolecule-assisted hydrothermal process. We find that concentrations of the pH conditioner and the biomolecule glutathione significantly affect the morphology and structure of In2S3 films. The as-synthesized In2S3 porous films exhibit strong absorption in the ultraviolet region and the early visible region of the UV-Vis spectrum, with the absorption threshold around 501 nm. As compared with its dense film, the In2S3 porous film shows enhanced photocatalytic properties for the degradation of methyl orange due to its porous and curved nanostructures.
Co-reporter:Xi Yang, Mingsheng Xu, Weiming Qiu, Xiaoqiang Chen, Meng Deng, Jinglin Zhang, Hideo Iwai, Eiichiro Watanabe and Hongzheng Chen
Journal of Materials Chemistry A 2011 vol. 21(Issue 22) pp:8096-8103
Publication Date(Web):20 Apr 2011
DOI:10.1039/C1JM10697J
Graphene sheets decorated with metal nanoparticles are emerging novel graphene-based hybrids for tuning the intrinsic properties of both components for fundamental research and technological applications. Here we report a new wet-chemistry strategy to efficiently and uniformly decorate reduced graphene oxide (RGO) with unique gold nanodots (GNDs). Non-covalent self-assembly of a perylene thiol derivative (ETPTCDI) on the basal plane of GO forms graphene by reducing the dispersed GO and serves as an excellent two-dimensional template in solution for in situ nucleation and growth of gold nanodots via thiol-Au bonding. We characterized the resulting RGO-ETPTCDI-GND in detail and confirm that the Au nanodots with unique size (∼2 nm) decorate the RGO-ETPTCDI sheets uniformly due to the self-assembly of ETPTCDI molecules on the basal plane of graphene. We demonstrate that our RGO-ETPTCDI-GND sheets have astonishing dispersibility, reliability, and processibility. The uniform decoration of the ∼2 nm GNDs on the graphene surface makes it possible to use the nanodots as a contrast enhancement agent for easily revealing the fine structure of the graphene surface. The electrochemical activity of our RGO-ETPTCDI-GND modified glassy carbon electrode showed significant improvement, suggesting RGO-ETPTCDI-GND as an attractive robust and advanced hybrid electrode material with great promise for electrochemical sensors and energy conversion.
Co-reporter:Xi Yang, Minmin Shi, Renjia Zhou, Xiaoqiang Chen and Hongzheng Chen
Nanoscale 2011 vol. 3(Issue 6) pp:2596-2601
Publication Date(Web):12 May 2011
DOI:10.1039/C1NR10287G
Water-soluble, monodispersed, and bluish green-emitting Au10 nanoclusters were synthesized through a simple reaction, in which histidine served as both a reducing agent and a protecting ligand. UV-visible absorption, photoluminescence, electrospray ionization (ESI) mass spectrometry, and X-ray photoelectron spectroscopy (XPS) were carried out to demonstrate the chemical composition and optical properties of the Au10 clusters. The mechanism of this proposed reaction was explored and the reducing ability of histidine was proved from its imidazole group. Finally, the fluorescence of Au NCs at different reaction times, pH value, and temperature was measured in situ. Then a synthetic strategy was proposed for gold nanoclusters with a defined chemical composition, and the resulting Au10 clusters stabilized by histidine are biocompatible with bioorganisms, showing a great potential for applications such as biological labeling and biosensors.
Co-reporter:Yunan Cheng, Tim Stakenborg, Pol Van Dorpe, Liesbet Lagae, Mang Wang, Hongzheng Chen, and Gustaaf Borghs
Analytical Chemistry 2011 Volume 83(Issue 4) pp:1307
Publication Date(Web):January 24, 2011
DOI:10.1021/ac102463c
We investigated fluorescence quenching and enhancement near gold nanoparticles (GNP) of various sizes using fluorescently labeled hairpin DNA probes of different lengths. A closed hairpin caused intimate contact between the fluorophore and the gold, resulting in an efficient energy transfer (quenching). Upon hybridization with complementary DNA, the DNA probes were stretched yielding a strong increase in fluorescence signal. By carefully quantifying the amount of bound fluorescent probes and the GNP concentrations, we were able to determine the quenching and enhancement efficiencies. We also studied the size and distance dependence theoretically, using both FDTD simulations and the Gersten−Nitzan model and obtained a good agreement between experiments and theory. On the basis of experimental and theoretical studies, we report over 96.8% quenching efficiency for all particle sizes tested and a maximal signal increase of 1.23 after DNA hybridization. The described results also demonstrate the potential of gold nanoparticles for label free DNA sensing.
Co-reporter:Xiaolian Hu;Minmin Shi;Jian Chen;Lijian Zuo;Lei Fu;Yujing Liu ;Hongzheng Chen
Macromolecular Rapid Communications 2011 Volume 32( Issue 6) pp:506-511
Publication Date(Web):
DOI:10.1002/marc.201000711
Co-reporter:Fei Chen, Weiming Qiu, Xiaoqiang Chen, Ligong Yang, Xiaoxia Jiang, Mang Wang, Hongzheng Chen
Solar Energy 2011 Volume 85(Issue 9) pp:2122-2129
Publication Date(Web):September 2011
DOI:10.1016/j.solener.2011.05.020
This paper reported the fabrication of CdS nanorod arrays on transparent conductive tin-doped In2O3 (ITO) glass substrate by combining electrodeposition and hydrothermal processes. One thin layer of CdS particles on substrates was prepared by electrodeposition as seeds, upon which well-aligned nanorod arrays were hydrothermally grown in large scale. The morphology, structure and phase composition of CdS nanorod arrays were examined by X-ray diffraction, field-emission scanning electron microscopy, energy-dispersive X-ray spectroscopy, transmission electron microscopy (TEM), and high-resolution TEM. The optical absorption spectra and the temperature-dependent photoluminescence of CdS nanorod arrays were also studied. An organic/inorganic hybrid solar cell prototype device was fabricated based on the as-prepared CdS nanoarrays grown on the transparent ITO electrode (ITO/CdS arrays/poly[2-methoxy-5-(20-ethylhexyloxy)-1,4-phenylene-vinylene]/Au). The power conversion efficiency was 0.06%, showing an obvious photovoltaic effect.Highlights► We fabricated Highly-ordered CdS nanorod arrays on transparent conductive substrates. ► The process we used was electrodeposition combined with hydrothermal method. ► The device based on this CdS nanorod array shows obvious photovoltaic phenomenon.
Co-reporter:Weiming Qiu, Mingsheng Xu, Fei Chen, Xi Yang, Yaxiong Nan and Hongzheng Chen
CrystEngComm 2011 vol. 13(Issue 14) pp:4689-4694
Publication Date(Web):24 May 2011
DOI:10.1039/C1CE05225J
We report the detailed roadmap of the morphology evolution of semiconductor PbS crystals synthesized by a green route. Without using any surfactant in our electrochemical deposition process, we obtained rich morphologies of PbS crystals in a bulk amount with uniform size, showing continuous shape change from octahedral to star-like, then to football-like, and finally to cubic morphology, by simple control over the PbCl2 precursor concentration. We discuss such a morphology evolution in detail on the basis of the relative contributions of branching growth and capping effects of the Cl− ions.
Co-reporter:Minmin Shi, Xiaowei Pan, Weiming Qiu, Dingxiang Zheng, Mingsheng Xu, Hongzheng Chen
International Journal of Hydrogen Energy 2011 Volume 36(Issue 23) pp:15153-15159
Publication Date(Web):November 2011
DOI:10.1016/j.ijhydene.2011.07.145
n-Type Si nanowire (NW) arrays coated with a thin layer of ZnO were fabricated via a two-step route combined with metal-assisted chemical etching and sol-gel processes. Scanning electron microscopy, transmission electron microscopy and X-ray diffraction were utilized to characterize the core/shell structure. The obtained Si/ZnO core/shell NW arrays exhibit about 8% optical reflectance in visible region, implying good optical absorption. Water splitting performance of Si/ZnO NW arrays was studied. The photoconversion efficiency for Si/ZnO NW arrays reaches 0.38% upon exposure to the illumination with a light intensity of 10 mW/cm2, which is higher than those of the planar bilayer structure of Si/ZnO (0.19%) and the pure planar ZnO (0.09%). The relationship between the illumination intensity and the photoconversion efficiency of Si/ZnO NW arrays was also discussed.Highlights► Si/ZnO core–shell nanowire (NW) arrays were fabricated via a two-step route. ► Si/ZnO core/shell NW arrays exhibit about 8% optical reflectance in visible region. ► The efficiency of Si/ZnO NW arrays for water splitting reaches 0.38%.
Co-reporter:Weiming Qiu, Mingsheng Xu, Xi Yang, Fei Chen, Yaxiong Nan, Hongzheng Chen
Journal of Alloys and Compounds 2011 Volume 509(Issue 33) pp:8413-8420
Publication Date(Web):18 August 2011
DOI:10.1016/j.jallcom.2011.05.103
We report the synthesis of CdS crystals with novel dendritic structures by a simple amino acid mediated hydrothermal process, in which various amino acids were used as capping agents. We elaborated that a slight change of the side group of amino acids can significantly influence the type and the structure of CdS crystals. We found that the reaction temperature and the time also have effects on the formation of CdS crystals. The resulting different-shaped CdS crystals exhibited different UV–vis absorption characteristics. Our results suggest that the biomolecule-assisted hydrothermal route using amino acids as capping agents provides an effective and green approach to produce hierarchical CdS crystals with rich morphologies.Highlights► We use an amino acid mediated hydrothermal process to synthesize CdS crystals. ► Various CdS crystals with novel dendritic structures are synthesized. ► Amino acid, reaction temperature and time have great effects on morphologies. ► These CdS crystals show morphology-related UV–vis absorptions.
Co-reporter:Yunan Cheng, Mang Wang, Gustaaf Borghs, and Hongzheng Chen
Langmuir 2011 Volume 27(Issue 12) pp:7884-7891
Publication Date(Web):May 16, 2011
DOI:10.1021/la200840m
In this study, gold nanoparticles (GNP) were stabilized for the first time as dimers by a conducting polymer (CP). The morphology of kissing particles was examined by high-resolution transmission electronic microscopy (HRTEM). The broad-band localized surface plasmon resonance (LSPR) tunable by solvent variation and molecular binding was demonstrated by UV–vis measurement. The sensitivity of the longitudinal LSPR to the surrounding media or the binding of a biomolecule was 6 times higher than that of the transversal LSPR. A homogeneous bioassay was directly developed from the highly stable GNP-CP dimers with LSPR as prober, and protein sensing with detection limit well below 100 ng/mL was achieved.
Co-reporter:Lin Chen ; Dan Deng ; Yaxiong Nan ; Minmin Shi ; Paddy K. L. Chan ;Hongzheng Chen
The Journal of Physical Chemistry C 2011 Volume 115(Issue 22) pp:11282-11292
Publication Date(Web):May 17, 2011
DOI:10.1021/jp201104s
Two diketo-pyrrolo-pyrrole-based donor–acceptor copolymers, PCPDT–PDPP and PDTP–PDPP, were synthesized and applied as p-type component for bulk heterojunction solar cells. Using a facile molecular engineering of the main chain linking bridge, we have successfully tuned the band gap of the materials from low to medium level, which results in an improved balance between the device open circuit voltage and short circuit current. The power conversion efficiencies of the polymer/PC70BM combinations achieve 2.03% (PCPDT–PDPP) and 1.32% (PDTP–PDPP) without any interface engineering or post-treatment. A totally different composition-dependent photovoltaic behavior was also discovered for each of the two materials, although they share similar donor–acceptor (D–A) structure. Morphological and photophysical studies reveal a phase structure dominated, light harvesting subordinated mechanism, in which some nonkernel molecular level factors, such as the branch chain density and the molecular weight, are found to play important roles.
Co-reporter:Min-Min Shi, Yi Chen, Ya-Xiong Nan, Jun Ling, Li-Jian Zuo, Wei-Ming Qiu, Mang Wang, and Hong-Zheng Chen
The Journal of Physical Chemistry B 2011 Volume 115(Issue 4) pp:618-623
Publication Date(Web):December 13, 2010
DOI:10.1021/jp109683h
To investigate the relationship between π−π stacking and charge transport property of organic semiconductors, a highly soluble violanthrone derivative, 16,17-bis(2-ethylhexyloxy)anthra[9,1,2-cde-]benzo[rst]pentaphene-5,10-dione (3), is designed and synthesized. The π−π stacking behavior and the aggregation of compound 3 in both solution and thin film were studied in detail by 1H nuclear magnetic resonance (NMR) spectroscopy, ultraviolet−visible (UV−vis) absorption, X-ray diffraction (XRD), and atomic force microscopy (AFM). When 1H NMR spectroscopy and theoretical modeling results were combined, the arrangements of compound 3 molecules in the aggregates are demonstrated, where the dipole moments of the two adjacent molecules are nearly reversed to achieve efficient intermolecular π−π overlapping. Furthermore, it is interesting to find that the π−π stacking of compound 3, in both solution and thin films, can be enhanced by introducing a poor solvent n-hexane into the dilute chloroform solution. The resulting film exhibits more red-shifted absorption and higher crystallinity than the film made from pure chloroform solvent, suggesting that π−π interactions in the solid state are intensified by the poor solvent. Organic field-effect transistors (OFETs) with compound 3 film as the transportation layer were fabricated. It is disclosed that the compound 3 film obtained from the chloroform/n-hexane mixed solvents exhibits 1 order of magnitude higher hole mobility than that from the pure chloroform solvent because of the enhanced π−π interactions and the higher crystallinity in the former film. This work provided us valuable information in the improvement of electronic and optoelectronic performances of organic semiconductors by tuning their aggregate structures.
Co-reporter:Min-Min Shi;Dan Deng;Lin Chen;Jun Ling;Lei Fu;Xiao-Lian Hu
Journal of Polymer Science Part A: Polymer Chemistry 2011 Volume 49( Issue 6) pp:1453-1461
Publication Date(Web):
DOI:10.1002/pola.24567
Abstract
A strategy of the fine-tuning of the degree of intrachain charge transfer and aromaticity of polymer backbone was adopted to design and synthesize new polymers applicable in photovoltaics. Three conjugated polymers P1, P2, and P3 were synthesized by alternating the electron-donating dithieno[3,2-b:2′3′-d]pyrrole (D) and three different electron-accepting (A) segments (P1: N-(2-ethylhexyl)phthalimide; P2: 1,4-diketo-3,6-diphenylpyrrolo[3,4-c]pyrrole; and P3: thiophene-3-hexyl formate) in the polymer main chain. Among the three polymers, P2 possessed the broadest absorption band ranging from 300 to 760 nm, the lowest bandgap (1.63 eV), and enough low HOMO energy level (−5.27 eV) because of the strong intrachain charge transfer from D to A units and the appropriate extent of quinoid state in the main chain of P2, which was convinced by the theoretical simulation of molecular geometry and front orbits. Photovoltaic study of solar cells based on the blends of P1–P3 and [6,6]-phenyl-C61-butyric acid methyl ester (PCBM) demonstrated that P2:PCBM exhibited the best performance: a power conversion efficiency of 1.22% with a high open-circuit voltage (VOC) of 0.70 V and a large short-circuit current (ISC) of 5.02 mA/cm2 were achieved. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011
Co-reporter:Meng Deng, Xi Yang, Musa Silke, Weiming Qiu, Mingsheng Xu, Gustaaf Borghs, Hongzheng Chen
Sensors and Actuators B: Chemical 2011 Volume 158(Issue 1) pp:176-184
Publication Date(Web):15 November 2011
DOI:10.1016/j.snb.2011.05.062
By exploiting the electrostatic interaction between positively charged pyrrole cation radicals and negatively charged graphene oxide (GO) sheets, we prepared polypyrrole/graphene oxide (PPy/GO) composite films by a one-step electrochemical process. We studied the effects of the polymerization current density and the GO content in electrolyte on the formation of PPy/GO coatings onto platinum neural microelectrode sites. As compared with pure PPy film, PPy/GO coatings show a rougher surface feature with micrometer-scale bulges. The impedance of the PPy/GO coated Pt electrode is only about 10% of the bare Pt electrode at the biological relevant 1 kHz, while the charge capacity density is more than two orders of the magnitude of the bare Pt electrode. Moreover, the PPy/GO coated Pt electrodes show higher performance than the PPy coated electrodes for the application of neural probe.Highlights► Polypyrrole and graphene oxide are electrochemically co-deposited. ► This composite is applied on neural microelectrodes. ► Impedance of the modified microelectrode is largely decreased. ► Charge capacity density is more than two orders of magnitude of the bare electrode. ► Higher performance of neural probe is anticipated.
Co-reporter:Ya-Xiong Nan, Fei Chen, Li-Gong Yang, Xiao-Xia Jiang, Li-Jian Zuo, Jing-Lin Zhang, Quan-Xiang Yan, Min-Min Shi, Hong-Zheng Chen
Solar Energy Materials and Solar Cells 2011 95(12) pp: 3233-3240
Publication Date(Web):
DOI:10.1016/j.solmat.2011.07.014
Co-reporter:Lijian Zuo, Xiaoxia Jiang, Mingsheng Xu, Ligong Yang, Yaxiong Nan, Quanxiang Yan, Hongzheng Chen
Solar Energy Materials and Solar Cells 2011 95(9) pp: 2664-2669
Publication Date(Web):
DOI:10.1016/j.solmat.2011.05.038
Co-reporter:Runying Dai;Gang Wu;Hongzheng Chen
Colloid and Polymer Science 2011 Volume 289( Issue 4) pp:401-407
Publication Date(Web):2011 February
DOI:10.1007/s00396-011-2375-2
The performance of electrophoretic displays is strongly dependent on the stability of the electrophoretic suspension in the device. In this manuscript, to obtain the stable electrophoretic suspension, the titanium dioxide grafted with poly [N-(p-vinyl benzyl) phthalimide] (TiO2-g-PVBP) composite particles were prepared via radical polymerization. The obtained TiO2-g-PVBP composite particles were fully characterized. The results showed that PVBP was grafted onto TiO2 surface by chemical bonding. The composite particles with the effective diameter of 300 nm can monodisperse stably in tetrachloroethylene due to the long-chain polymer PVBP, which can provide each TiO2 particle with steric stabilization. The zeta potential and electrophoretic mobility of the composite particles were 30.3 mV and 4.69 × 10−6 cm2/Vs, respectively, without charge control agent. With the stable electrophoretic suspension containing the prepared composite particles, the matrix electrophoretic display prototype with good performance operated at 9 V was demonstrated.
Co-reporter:LiGong Yang;Hao Xu;GuoQiang Zhang;Mang Wang;Yang Li
Science China Chemistry 2011 Volume 54( Issue 4) pp:636-640
Publication Date(Web):2011 April
DOI:10.1007/s11426-011-4240-z
Remarkable and repeatable negative differential resistance (NDR) phenomenon was observed in a metal-polymer-metal structure diode based on bishexyloxy-divinyl-benzene-alt-diketopyrrolopyrrole (C6DPPPPV), a type of donor-acceptor (D-A) conjugated copolymer. Thickness dependence of the devices implied that the observed NDR characteristics were bulk-controlled. The device performance was considered to depend on the slow trapping and releasing processes related to the local deep states, which was enhanced by the growth and thermal rupture of conducting filaments through the organic layer. The results suggest that the D-A conjugated copolymer is a promising memory material based on NDR effect.
Co-reporter:Yan Gao, Xiaoqiang Chen, Hao Xu, Yunlong Zou, Renpeng Gu, Mingsheng Xu, Alex K.-Y. Jen, Hongzheng Chen
Carbon 2010 Volume 48(Issue 15) pp:4475-4482
Publication Date(Web):December 2010
DOI:10.1016/j.carbon.2010.08.007
We report a Langmuir–Blodgett (LB) approach for highly-efficient fabrication of nanoscrolls from functionalized graphene oxide single sheets. Transmission electron microscope study reveals that the scroll has a tubular structure without caps at its ends. The scrolls align parallel to the moving barriers of the LB equipment and exhibit a loose-dense pattern during the LB compression process. We find that specific solvents can unwind the scrolled structures. Electrical characterization of the well-aligned scrolls was also performed. The method demonstrated here opens up a new avenue for high-yield fabrication of carbon nanoscrolls using functionalized graphene oxide as the building blocks.Graphical abstractHighly-efficient fabrication of carbon nanoscrolls (CNSs) from functionalized graphene oxide by Langmuir–Blodgett method: (a) Scattered sheets float on the water surface. (b) Close-packed monolayer of sheets forms. (c) CNSs begin to form. (d) Scrolling proceeds. (e) CNS monolayer collapses and bundles form. (f) Loose (individual CNSs) – dense (bundle) pattern forms.Research highlights► Carbon nanoscrolls (CNSs) are fabricated by Langmuir-Blodgett (LB) method. ► Loose-dense pattern of CNSs is formed during the LB compression process. ► Specific solvents can cause unwinding of the scrolled structures.
Co-reporter:Dan Deng, Minmin Shi, Fei Chen, Lin Chen, Xiaoxia Jiang, Hongzheng Chen
Solar Energy 2010 Volume 84(Issue 5) pp:771-776
Publication Date(Web):May 2010
DOI:10.1016/j.solener.2010.01.028
We report the synthesis of 3D structural CdS nanocrystals by a simple biomolecule-assisted hydrothermal process. The CdS nanocrystals are composed of many branched nanorods with the diameter of about 50 nm, and the length of about 250 nm. The phase and crystallographic properties are characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), and X-ray diffractometry (XRD). The composites based on CdS nanocrystals and poly[2-methoxy-5-(2-ethylhexyloxy-p-phenylenevinylene)] (MEH-PPV) have been prepared by spin-coating of the mixture in the common solvent. The optical properties of the composites are investigated using ultraviolet–visible (UV–Vis) absorption and photoluminescence (PL) spectroscopies. A significant fluorescence quenching of MEH-PPV in the composites is observed at high CdS nanocrystals/MEH-PPV ratios, indicating that the photo-induced charge transfer occurred due to the energy level offset between the donor MEH-PPV and the acceptor CdS nanocrystals. The obvious photovoltaic behavior of the solar cell made from this composite further demonstrates the mentioned photo-induced charge transfer process.
Co-reporter:Fei Chen, Weiming Qiu, Xiaoqiang Chen, Mang Wang and Hongzheng Chen
CrystEngComm 2010 vol. 12(Issue 6) pp:1893-1898
Publication Date(Web):17 Feb 2010
DOI:10.1039/B922261H
Octahedra and truncated octahedra PbS microcrystals were synthesized via a facile electrochemical process without any templates or surfactants. PbS microcrystals with a Maya-pyramid structure were prepared by employing octahedra PbS as seeds through a hydrothermal process. The reaction conditions influencing the synthesis of these PbS microcrystals, such as reaction time, electrodeposition current density, and initial precursors' concentrations were studied. The morphology, structure and phase composition of the obtained PbS microcrystals were examined by X-ray diffraction, field-emission scanning electron microscopy, energy-dispersive X-ray spectroscopy, transmission electron microscopy (TEM), and high-resolution TEM. The mechanism of the octahedra, truncated octahedra PbS microcrystals and PbS crystals with Maya-pyramid structure formation is also discussed.
Co-reporter:Chao-Hua Xue, Ren-Jia Zhou, Min-Min Shi, Gang Wu, Xiao-Bin Zhang, Mang Wang, Hong-Zheng Chen
Journal of Electroanalytical Chemistry 2010 Volume 642(Issue 1) pp:92-97
Publication Date(Web):1 April 2010
DOI:10.1016/j.jelechem.2010.02.010
In this paper we have described that multi-walled carbon nanotubes (MWNTs) can be homogeneously dispersed and solubilized in water using non-covalent functionalization. These soluble MWNTs were then used for the immobilization of glucose oxidase (GOx) on glassy carbon electrode. Scanning electron microscopy is used to investigate the nanoscale structure of the film formed by the functionalized MWNTs. Electrochemical measurements were conducted to reveal the electroactivity of the GOx on the MWNT modified electrode. The functionalized MWNTs served as a network carrier for GOx as well as a conductor, enhancing greatly the response current. The GOx immobilized in this way retained its bioelectrocatalytic activity for the oxidation of glucose.
Co-reporter:Wei Shen, Minmin Shi, Mang Wang, Hongzheng Chen
Materials Chemistry and Physics 2010 Volume 122(2–3) pp:588-594
Publication Date(Web):1 August 2010
DOI:10.1016/j.matchemphys.2010.03.051
Magnetite Fe3O4 nanocrystal clusters (50–60 nm in diameter) with good dispersibility in aqueous medium were prepared by modified co-precipitation method in the presence of surfactants including sodium dodecylsulfate (SDS), trisodium citrate dehydrate (TSCD), and polyacrylic acid sodium salt (PAASS). The influence of surfactant on the formation of Fe3O4 nanocrystal clusters was studied. It was found that Fe3O4 nanocrystal clusters exhibited almost a super-paramagnetic behavior with very small coercivity and a high magnetization (Ms = 44–56 emu g−1). Magnetite (Fe3O4) nanocrystal clusters–polyaniline (PANI) composites were further synthesized via a self-assembly process in the presence of Fe3O4 nanoclusters containing SDS as the dopant. It was also noted that the morphology, the magnetic, and the electrical properties of Fe3O4–PANI composites could be adjusted by altering the contents of Fe3O4 and SDS.
Co-reporter:Qiaozhen Yu, Mang Wang, Hongzheng Chen
Materials Letters 2010 Volume 64(Issue 3) pp:428-430
Publication Date(Web):15 February 2010
DOI:10.1016/j.matlet.2009.11.039
TiO2 has wide applications in chemical industry. In this manuscript we describe the ordered TiO2 nanoribbon arrays fabricated by electrospinning. A modified collector with a pair of split electrodes was employed to collect the TiO2 nanoribbon arrays during the electrospinning. The morphology and the structure of the resulting arrays were analyzed by scanning electron micrograph. It was found that the morphology of the aligned TiO2 ribbon arrays could be controlled by the spinneret geometry and the applied voltage. The ordered degree of the aligned TiO2 nanoribbon arrays could also be controlled by the environmental relative humidity.
Co-reporter:Hai-guo Li, Gang Wu, Min-min Shi, Hong-Zheng Chen, Mang Wang
Synthetic Metals 2010 Volume 160(15–16) pp:1648-1653
Publication Date(Web):August 2010
DOI:10.1016/j.synthmet.2010.05.035
Two new solution processable organic molecules based on carbazole and triphenylamine (TPA) substituted fluorene were synthesized by Suzuki coupling reaction. The bandgap of the molecules can be controlled by the 3,6-linkage of the carbazole. The propeller-shaped TPA moieties endow the molecules with good thermal stability and perfect solution processability. Smooth films of both molecules could be readily obtained by spin-coating and n-type ZnO nanoparticles were further incorporated to construct bulk-heterojunction. Under the excitation of 1 mW/cm2 ultraviolet light at 365 nm, devices with those hybrid films as active layers show a relative quick response with photo-to-dark current ratio of about three orders of magnitude. The current decay time (decay to 1% of the value before removing of the light) is less than 200 ms. Moreover, the spectral response of the devices covers 300–400 nm and can be well tuned by the conjugation length of the organic molecules. Those results indicate that the synthesized molecules might be candidates for solution processable low cost UV photodetectors.
Co-reporter:Xiaojie Zhang Dr.;Xiaoxia Jiang Dr.;Jing Luo Dr.;Chunyan Chi Dr.;Hongzheng Chen ;Jishan Wu
Chemistry - A European Journal 2010 Volume 16( Issue 2) pp:464-468
Publication Date(Web):
DOI:10.1002/chem.200902675
Co-reporter:Xiaojie Zhang Dr.;Xiaoxia Jiang Dr.;Jing Luo Dr.;Chunyan Chi Dr.;Hongzheng Chen ;Jishan Wu
Chemistry - A European Journal 2010 Volume 16( Issue 11) pp:
Publication Date(Web):
DOI:10.1002/chem.201090047
No abstract is available for this article.
Co-reporter:Runying Dai, Gang Wu, Weigang Li, Qiang Zhou, Xihua Li, Hongzheng Chen
Colloids and Surfaces A: Physicochemical and Engineering Aspects 2010 Volume 362(1–3) pp:84-89
Publication Date(Web):5 June 2010
DOI:10.1016/j.colsurfa.2010.03.041
We have described the microcapsules containing electrophoretic fluid as core material, prepared from gelatin, sodium carboxymethylcellulose (NaCMC) and dioctyl sulfosuccinate sodium (DSS) by complex coacervation method. The gelatin/NaCMC/DSS microcapsules are characterized by optical microscopy (OM), scanning electron microscopy (SEM), particle size analysis and thermogravimetric analysis (TGA). It is found that DSS plays an important role in the formation of the microcapsule wall and the concentration of DSS deeply affects the yield of microcapsules by enhancing the interaction between gelatin and NaCMC. The microcapsules prepared with DSS content of 0.6 mM show compact capsule wall which endows the capsules with good barrier property and high thermal stability. These microcapsules are applied successfully to prepare a 4-in. clock display panel controlled by single-chip microprocessor (SCM) operated at a low direct current (DC) voltage of 3 V, demonstrating that these microcapsules are potential for the applications in the area of electrophoretic displays.
Co-reporter:Xiaoxia Jiang, Fei Chen, Hao Xu, Ligong Yang, Weiming Qiu, Minmin Shi, Mang Wang, Hongzheng Chen
Solar Energy Materials and Solar Cells 2010 94(2) pp: 338-344
Publication Date(Web):
DOI:10.1016/j.solmat.2009.10.010
Co-reporter:Ya-Xiong Nan, Fei Chen, Li-Gong Yang and Hong-Zheng Chen
The Journal of Physical Chemistry C 2010 Volume 114(Issue 27) pp:11911-11917
Publication Date(Web):June 22, 2010
DOI:10.1021/jp103085n
Well-defined intersectional CdS nanocrystalline thin films with a conifer-like morphology were synthesized by a facile electrochemical process. The morphology, structure, and phase composition of CdS nanostructures were examined by X-ray diffraction, field emission scanning electron microscopy, atomic force microscopy, and energy-dispersive X-ray spectroscopy. The electrochemical deposition conditions influencing the synthesis of these conifer-like CdS nanocrystals, such as deposition temperature, deposition time, current density, and concentrations of the precursors, were studied systematically. The orientation-transformation mechanism of the growth of conifer-like CdS nanocrystals was proposed based on the results, which is beneficial for the shape-controlled synthesis of other shaped nanostructures. The charge transport properties of these thin films before and after annealing treatment were also studied via the space-charge-limited conduction model, from which the total density of trapping states and the electron mobility in CdS nanocrystalline thin films were estimated.
Co-reporter:Yangang Han, Gang Wu, Mang Wang, Hongzheng Chen
Polymer 2010 Volume 51(Issue 16) pp:3736-3743
Publication Date(Web):22 July 2010
DOI:10.1016/j.polymer.2010.05.057
Monodispersed ligand-capped TiO2 nanocrystals are synthesized by a low temperature solvothermal method using oleic acid (OA) as the capping agent. The single layer hybrid films based on the OA-capped TiO2 nanocrystals and poly(9,9-dihexylfluorene) (PFH) are prepared by solution processing at room temperature and characterized by atomic force microscopy, UV–vis absorption and photoluminescence spectra. The hybrid film is applied in the fabrication of nanostructured UV-A photodetector (320–420 nm) by sandwiching it between two electrodes to form bulk heterojunction. The high ultraviolet signal-to-noise ratio of 3 orders of magnitude with short response time less than 200 ms can be achieved for the device. Furthermore, the device shows drastic changes in current under a wide range of UV irradiation with a linear relationship between them. The thermal behavior of the device is also discussed. The high photosensitivity in the UV-A range and the low-cost endow them with potential for environmental and biological uses.
Co-reporter:Lin Chen, Ligong Yang, Minmin Shi, Hongzheng Chen
Solar Energy Materials and Solar Cells 2010 94(12) pp: 2244-2250
Publication Date(Web):
DOI:10.1016/j.solmat.2010.07.019
Co-reporter:Xiaoxia Jiang, Fei Chen, Qiu Weiming, Quanxiang Yan, Yaxiong Nan, Hao Xu, Ligong Yang, Hongzheng Chen
Solar Energy Materials and Solar Cells 2010 94(12) pp: 2223-2229
Publication Date(Web):
DOI:10.1016/j.solmat.2010.07.016
Co-reporter:Jian Chen, Min-Min Shi, Xiao-Lian Hu, Mang Wang, Hong-Zheng Chen
Polymer 2010 Volume 51(Issue 13) pp:2897-2902
Publication Date(Web):7 June 2010
DOI:10.1016/j.polymer.2010.04.035
Three novel conjugated polymers have been designed and synthesized via the alternative copolymerization of the electron-donating monomer benzodithiophene (BDT) and three different electron-accepting monomers: perylene diimide (PDI), naphthalene diimide (NDI), and phthalimide (PhI). All obtained copolymers show good solubility in common organic solvents as well as broader absorptions in visible region and narrower optical band gaps compared to homopolymers from BDT units. It is found that the absorptions of the copolymers are red-shifted with increasing the electron-withdrawing ability of the co-monomer. In particular, the absorption edge of P(BDT-NDI) film extends to 760 nm, whereas that of P(BDT-PhI) film is only at 577 nm. Cyclic voltammograms of the three polymers disclose that P(BDT-PDI) and P(BDT-NDI) are typical n-type materials because PDI and NDI are strong electron-accepting groups, while P(BDT-PhI) is a stable p-type material where the weak electron-withdrawing monomer (PhI) is introduced. The results suggest that the absorption range and the electrochemical properties of the conjugated polymers can be tuned by appropriate molecule-tailoring, which will help exploring ideal conducting polymers for potential applications in polymer optoelectronics, especially in polymer solar cells.
Co-reporter:Xiao-Wei Pan, Min-Min Shi, Ding-Xiang Zheng, Nan Liu, Gang Wu, Mang Wang, Hong-Zheng Chen
Materials Chemistry and Physics 2009 Volume 117(2–3) pp:517-521
Publication Date(Web):15 October 2009
DOI:10.1016/j.matchemphys.2009.06.037
We report a new solution route for the preparation of SiO2-capped silicon nanocrystals (Si NCs). The Si NCs terminated with SiO2 are fully characterized by transmission electron microscopy, X-ray diffraction, UV–vis absorption, photoluminescence decay and Fourier transform infrared spectra. The photoluminescence spectra reveal that the Si NCs solution emits green luminescence at 535 and 578 nm excited at 490 nm. The origin of the green luminescence of Si NCs is studied. Our theoretical calculations reveal that the green emission is due to the surface related localized states of self-trapped excitons rather than the purely quantum-confined states, which agrees well with the experimental results. A self-trapped exciton model is proposed to take into account the stepwise localization of electron and hole at the Si–SiO2 interface. From the localization energies the effective Bohr radii of the localized electrons and holes are estimated to be about 1.71 and 1.57 nm, respectively.
Co-reporter:Li-Gong Yang, Peng Wu, Xu Liu, Pei-Fu Gu, Mang Wang, Hong-Zheng Chen
Materials Chemistry and Physics 2009 Volume 114(2–3) pp:660-664
Publication Date(Web):15 April 2009
DOI:10.1016/j.matchemphys.2008.10.033
The electroluminescence (EL) from tetramethyl ester of perylene-3,4,9,10-tetracarboxylic acid (TMEP)-doped poly(vinylcarbazole) (PVK) light-emitting diodes and their current-voltage characteristics were investigated. The results indicated that field-emission tunneling injection predominated in the ITO/TMEP:PVK/Al diodes at high applied voltages. With increasing the TMEP dopant density, the injection barrier for holes was slightly reduced. Under injection-limited conditions, the possible kinetic processes were discussed in view of the field evolution of the EL spectra and the energy level alignment in the diode configuration. With increasing the field intensity, different emission components varying their intensities in EL spectra indicates that both charge transfer and energy transfer occurred in TMEP-doped PVK layer. These transfer processes are influenced by varying the concentration of TMEP dopants as electron traps. The results indicate that the dynamic equilibrium among carrier recombination, charge transfer and energy transfer, can be adjusted by dopant concentration and external bias. This information helps to establish a design framework for host–dopant systems.
Co-reporter:Min-Min Shi, Jia-Jun Lin, Yue-Wen Shi, Mi Ouyang, Mang Wang, Hong-Zheng Chen
Materials Chemistry and Physics 2009 Volume 115(2–3) pp:841-845
Publication Date(Web):15 June 2009
DOI:10.1016/j.matchemphys.2009.02.046
A novel blue-emissive Alq3 derivative, tris-(4-methyl-6-fluoro-8-hydroxyquinoline) aluminum (6), has been designed and prepared. Because the strong electronegative F atom at 6-position lowers the HOMO significantly and the weak electron-donating methyl group at 4-position retains the drop of the LUMO, the band gap of 6 is broadened, and a blue-shift by 53 nm of the emission peak (λem) with substantially enhanced intensity is demonstrated when compared to that of Alq3. It is also found that 6 possesses good thermal stability and solubility in common solvents. Through theoretical simulations of the frontier orbitals, it is disclosed that 6's λem can be blue-shifted further if methyl is replaced with a stronger electron-donating substituent, such as methoxy or N,N′-dimethylamino group.
Co-reporter:Gang Wu, Siyuan Cheng, Meng Deng, Yingying Zheng, Hongzheng Chen, Mang Wang
Synthetic Metals 2009 Volume 159(23–24) pp:2425-2429
Publication Date(Web):December 2009
DOI:10.1016/j.synthmet.2009.06.010
The organic–inorganic hybrid compound ((C6H4)2N(CH2)6NH3)2PbCl4 (N6AHMC–PbCl4) and ((C6H4)2N(CH2)6NH3)2PbCl2I2 (N6AHMC–PbCl2I2) were synthesized by treating N-6-aminohexamethylcarbazole chloride (N6AHMC–HCl) with stoichiometric amount of PbX2 (X = Cl, I) at room temperature using dimethylformamide (DMF) as solution. High order diffraction peaks corresponding to (0 0 l) (l = 2, 4, 6, …) were observed in the X-ray diffraction profile of N6AHMC–PbCl4 and N6AHMC–PbCl2I2, indicating the formation of hybrid crystal with layered perovskite structure. N6AHMC–PbCl4 presented characteristic absorptions of PbCl-based layered perovskite centered at about 329 nm. Similar to the PL spectrum of N6AHMC–HCl, the film of N6AHMC–PbCl4 showed three strong emission peaks, indicating that the exciton emission of the N6AHMC–PbCl4 film comes from the organic layer of the hybrids. Owing to the partially replacement of Cl− with I−, the fluorescence quenched N6AHMC–PbCl2I2 showed broad absorption at about 400 nm, which is assigned to the transition from the hybrid orbital hybridized by Cl 3p and I 5p valence states to Pb 6p conduction bands. For the reason of the variation of the energy band structure, from type I quantum well structure to type II heterojunction, the photoconductivity of N6AHMC–PbCl2I2 is higher than that of N6AHMC–PbCl4.
Co-reporter:Lin Chen, Ligong Yang, Zhisheng Yang, Minmin Shi, Mang Wang, Hongzheng Chen, Wenhua Zhang and Faqiang Xu
The Journal of Physical Chemistry C 2009 Volume 113(Issue 39) pp:17160-17169
Publication Date(Web):September 2, 2009
DOI:10.1021/jp903381n
P-doping of zinc phthalocyanine (ZnPc) with a perylene derivative of N,N′-di-(2,4-difluorophenyl)-3,4,9,10-perylenetetracarboxylic diimide (D24DFPP) is investigated for wide range of doping ratios. I−V measurements in air for the three-layered devices [Au(40 nm)/organic(400 nm)/Au(35 nm)] show a 4 orders of magnitude increment in current density after doping. Ultraviolet and X-ray photoemission spectroscopy (XPS and UPS) studies confirm that the efficient host-to-dopant electron transfer is the primary reason for this increment. Carrier transport is found to be more efficient in the lightly doped film than in the heavily doped film for our D24DFPP-doped ZnPc system. Morphology study and the detailed modeling analysis attribute this to both bulk conductivity and interfacial injection effect. The lower injection barrier and better energy level alignment with the electrode in the lightly doped ZnPc film facilitate the field-emission tunneling process, leading to a more efficient carrier injection compared with the heavily doped film. For the heavily doped film, the inferior transporting performance is also correlated with its disrupted crystalline structure and more severe phase separation.
Co-reporter:Weigang Li, Gang Wu, Hongzheng Chen, Mang Wang
Colloids and Surfaces A: Physicochemical and Engineering Aspects 2009 Volume 333(1–3) pp:133-137
Publication Date(Web):5 February 2009
DOI:10.1016/j.colsurfa.2008.09.046
Stable, elastic and optical transparent microcapsules containing tetrachloroethylene as core material were prepared from gelatin, sodium dodecyl sulfate (SDS) and sodium carboxymethylcellulose (NaCMC) by complex coacervation method for electrophoretic display. Microcapsules were characterized by scanning electron microscopy, optical microscopy, and thermogravimetric analysis. It is suggested that SDS plays an important role during the process of microencapsulation, i.e. the existence of SDS increases the interaction between gelatin and NaCMC and facilitates the progress of complex coacervation. Because of the compact structure of the capsule wall, the microcapsules represent high thermal stability and good barrier property, both of which prevent core materials from penetrating outside the capsules.
Co-reporter:Ru Bai, Minmin Shi, Mi Ouyang, Yunan Cheng, Hanbo Zhou, Ligong Yang, Mang Wang, Hongzheng Chen
Thin Solid Films 2009 Volume 517(Issue 6) pp:2099-2105
Publication Date(Web):30 January 2009
DOI:10.1016/j.tsf.2008.10.020
Erbium bisphthalocyanine (HErPc2) films comprised of one-dimensional (1D) organic nanowires were obtained by the electrophoretic deposition method from the mixed solutions of chloroform and trifluoroacetic acid containing the protonated HErPc2. Effects of the deposition voltage (Vd) and the deposition time (td) on the morphology of the films were studied by X-ray diffraction, UV–vis absorption and scanning electron microscope. The results revealed that the growth of 1D organic nanostructure could be conveniently controlled by tuning the deposition parameters of Vd and td. The influences of the annealing time and the annealing temperature were also investigated and the effect of time–temperature correspondence principle was found. The film growth mechanism was discussed for both stages of the electrophoretic deposition and the annealing process. Furthermore, the as-deposited HErPc2 films showed interesting photoresponse in the near infrared (NIR) region, indicating the possibility for NIR photodetection application.
Co-reporter:Renjia Zhou;Minmin Shi Dr.;Xiaoqiang Chen;Mang Wang ;Hongzheng Chen
Chemistry - A European Journal 2009 Volume 15( Issue 19) pp:4944-4951
Publication Date(Web):
DOI:10.1002/chem.200802743
Co-reporter:Xiaoxia Jiang, Hao Xu, Ligong Yang, Minmin Shi, Mang Wang, Hongzheng Chen
Solar Energy Materials and Solar Cells 2009 93(5) pp: 650-653
Publication Date(Web):
DOI:10.1016/j.solmat.2009.01.005
Co-reporter:Ru Bai, Mi Ouyang, Zhi-Zhuo Li, Li-Gong Yang, Min-Min Shi, Gang Wu, Mang Wang and Hong-Zheng Chen
Journal of Materials Chemistry A 2008 vol. 18(Issue 36) pp:4318-4323
Publication Date(Web):01 Aug 2008
DOI:10.1039/B804958K
Highly-ordered and well-aligned fullerene nanofibre arrays were fabricated via a nanotemplate preparation method and surface-wetting technique. The as-prepared fullerene nanofibre arrays were characterized by field-emission scanning electron microscopy, transmission electron microscopy, ultraviolet-visible absorption spectra and X-ray diffraction analysis. The dual-layered photoreceptors containing the fullerene nanofibre arrays or bulk fullerene films as the charge-generation layer (CGL) were fabricated. The photosensitivity of photoreceptors with fullerene nanoarrays as CGL was improved by one order of magnitude compared to that of their bulk films. The effect of the diameter and the length of the fullerene nanofibres on the photosensitivity of the photoreceptors was also investigated.
Co-reporter:Yangang Han;Gang Wu;Hongzheng Chen;Mang Wang
Journal of Applied Polymer Science 2008 Volume 109( Issue 2) pp:882-888
Publication Date(Web):
DOI:10.1002/app.28110
Abstract
A functional organic–inorganic composite containing carbazole moieties (electron donors) and TiO2 (electron acceptors) in different molar ratios, TiO2-modified poly(N-vinylcarbazole) (PVK–TiO2), was synthesized through a nucleophilic reaction. The molecular and electronic structure of the PVK–TiO2 composite was characterized with Fourier transform infrared, ultraviolet–visible absorption, cyclic voltammetry, and so forth. The highest occupied molecular orbital and lowest unoccupied molecular orbital energy levels of the PVK–TiO2 composite were higher than those of pristine poly(N-vinylcarbazole). The PVK–TiO2 composite exhibited an enhanced glass-transition temperature and improved thermal stability. The photoinduced charge transfer observed in photofluorescence and photoconductivity measurements makes applications in the field of photodetectors possible. The PVK–TiO2 composite containing carbazole moieties and TiO2 in a molar ratio of about 58 :1 was found to have the best photosensitivity. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008
Co-reporter:Lan Ying Yang, Min Min Shi, Mang Wang, Hong Zheng Chen
Chinese Chemical Letters 2008 Volume 19(Issue 10) pp:1260-1263
Publication Date(Web):October 2008
DOI:10.1016/j.cclet.2008.07.008
An asymmetrical perylene diimide 3, N-(4-methoxyphenyl)-N′-(4-nitrophenyl)-perylene-3,4,9,10-tetracarboxylic diimide, was synthesized, and its self-assembly and dissociation behaviors in chloroform was studied in detail by UV–vis and fluorescence spectroscopies. The resulting unique helical nanostructures from 3 were proposed to be self-assembled via the cooperative actions of π–π stacking, steric hindrance and electrophile–nucleophile type pairing.
Co-reporter:Qiao Zhen Yu, Ying Li, Mang Wang, Hong Zheng Chen
Chinese Chemical Letters 2008 Volume 19(Issue 2) pp:223-226
Publication Date(Web):February 2008
DOI:10.1016/j.cclet.2007.12.005
Nanobelts, flower-like and rhizoid-like nanostructures of pure polyaniline (PANI) doped with sulfuric acid or hydrochloric acid were prepared via electrospinning by using a coagulation bath as the collector after optimizing the fabrication parameters. The morphologies of these nanostructures were characterized by scanning electron microscope (SEM). The possible formation mechanisms were discussed.
Co-reporter:Bo Liu;MinMin Shi;LiGong Yang;HongZheng Chen
Science China Chemistry 2008 Volume 51( Issue 2) pp:152-157
Publication Date(Web):2008 February
DOI:10.1007/s11426-007-0099-4
A novel organic electron acceptor, N,N′-dipyrimidinyl-3,4,9,10-perylene-tetracarboxylic diimide (DMP), was designed and synthesized. The molecular structure was characterized by FTIR spectrum and elemental analysis. By cyclic voltammetry measurements, DMP was found to possess a lower LUMO energy level than N,N′-diphenyl-3,4,9,10-perylene-tetracarboxylic diimide due to the stronger electron-withdrawing pyrimidinyl group than the phenyl group. Fluorescence quenching is observed in a dual-layer film consisting of a DMP layer and a C60 layer and was attributed to the charge transfer at the interface due to the energy level offset between DMP and C60.
Co-reporter:Nan Liu, Min-Min Shi, Xiao-Wei Pan, Wei-Ming Qiu, Jian-Hui Zhu, Hai-Ping He, Hong-Zheng Chen and Mang Wang
The Journal of Physical Chemistry C 2008 Volume 112(Issue 40) pp:15865-15869
Publication Date(Web):2017-2-22
DOI:10.1021/jp802385g
An inorganic−organic hybrid composite was prepared from a soluble N-dodecyl-N′-phenyl-3,4,9,10-perylenetetracarboxylic diimide (DOPP) and silicon nanoparticles (NPs). The silicon NPs were synthesized by a solution-phase method. Remarkable photoluminescence (PL) quenching was observed in the composite dispersed in a polymethyl methacrylate matrix. On the basis of the analysis of the PL quenching mechanism, it was demonstrated that a photoinduced electron transfer from silicon NPs to DOPP could occur in the composite. The photoconductivity of the composite was studied, and the photosensitivity enhancement of the composite was realized due to the photoinduced electron transfer between silicon NPs and DOPP.
Co-reporter:Mi Ouyang, Ru Bai, Lin Chen, Ligong Yang, Mang Wang and Hongzheng Chen
The Journal of Physical Chemistry C 2008 Volume 112(Issue 30) pp:11250-11256
Publication Date(Web):June 26, 2008
DOI:10.1021/jp802522y
Based on an anodic aluminum oxide template, a sol−gel dip-coating technique and electrophoretic deposition processes were combined to fabricate TiO 2 nanowire arrays, copper phthalocyanine (CuPc) nanowire arrays, and CuPc-coated TiO 2 nanowire (CuPc/TiO 2 NW) arrays. The resulting nanostructures were characterized by field-emission scanning electron microscope, energy dispersive X-ray microanalysis system, X-ray diffraction patterns, and time-resolved fluorescence spectra. A series of dual-layered photoreceptors containing the above three kinds of nanowire arrays as the charge generation layer (CGL) were designed and fabricated. Their photoconductivities under illumination of visible light were investigated using a photoinduced xerographic discharge technique. It was found that the photoreceptor based on CuPc/TiO 2 NW arrays as CGL exhibited 1 order of magnitude higher photoconductivity than that of pristine TiO 2 or CuPc nanowire arrays due to the large donor−acceptor (CuPc-TiO 2) contact area and the directional alignment of TiO 2 nanowires.
Co-reporter:Qiao-Zhen Yu, Min-Min Shi, Meng Deng, Mang Wang, Hong-Zheng Chen
Materials Science and Engineering: B 2008 Volume 150(Issue 1) pp:70-76
Publication Date(Web):25 April 2008
DOI:10.1016/j.mseb.2008.02.008
Sub-micron fibers of pure polyaniline (PANI) doped with sulfuric acid or hydrochloric acid were prepared by electrospinning PANI with suitable molecular weight dissolved in hot sulfuric acid. A modified electrospinning setup was employed with a coagulation bath as a collector, where dilute sulfuric acid was used as coagulation bath. The factors influencing the morphology and conductivity of the synthesized PANI fibers were investigated, including the concentration of dilute H2SO4 solution in the coagulation bath, the doped PANI concentration in H2SO4 solution, the type of doping acid and the voltage applied to the solution. The morphologies of doped PANI fibers were characterized by scanning electron microscope (SEM). The structure of the resulting fibers was analyzed by Fourier transform infrared spectroscopy and UV–vis spectrometer. The conductivity of PANI fibers were characterized by I–V characteristics. Homogeneous PANI fibers with a diameter of 370 nm and a high conductivity of 52.9 S/cm were prepared. The possible mechanisms of different morphology formation and conductivity of PANI fibers were also discussed.
Co-reporter:Meng Deng, Gang Wu, Si-Yuan Cheng, Mang Wang, Gustaaf Borghs, Hong-Zheng Chen
Materials Science and Engineering: B 2008 Volume 147(Issue 1) pp:90-94
Publication Date(Web):25 January 2008
DOI:10.1016/j.mseb.2007.11.024
PbCl2-based thin films of perovskite structure with hole-transporting carbazole derivatives as the organic layer were successfully prepared by spin-coating from dimethylformamide solution containing stoichiometric amounts of organic and inorganic moieties. The crystal structure and optical property of the hybrid perovskite were characterized by Fourier transform infrared (FT-IR) spectrum, X-ray diffraction (XRD), UV–vis absorption and photoluminescence (PL). FT-IR spectra confirmed the formation of organic–inorganic hybrid perovskite structure. UV–vis spectra of hybrid perovskite thin films exhibited a wide absorption band in ultraviolet region as well as a sharp peak at 330 nm characteristic of PbCl2-based layered perovskite. X-ray diffraction profiles indicated that the layered structure was oriented parallel to the silica glass slide plane. Meanwhile, double-layer photoreceptors of the hybrid perovskite were also fabricated, which showed the enhancement of photoconductivity by carbazole chromophore.
Co-reporter:Li-Gong Yang, Hong-Zheng Chen, Mang Wang
Thin Solid Films 2008 Volume 516(Issue 21) pp:7701-7707
Publication Date(Web):1 September 2008
DOI:10.1016/j.tsf.2008.03.027
Exciton diffusion in organic materials is crucial for designing and optimizing organic photovoltaic devices. This paper addresses the important complication of the choice of film thickness affecting measurement accuracy in the method of measuring exciton diffusion length from thickness-dependent photocurrent response in organic bilayer heterostructures. Based on the photocurrent model integrated with optical interference effect, the correlation between the exciton diffusion length and the optimal thickness of organic layer is analytically solved. It shows that the intrinsic nonlinearity of the correlation causes prominent uncertainty of estimated diffusion length. Two approaches were proposed to improve the measurement accuracy: (1) the thickness effect of each layer in this heterostructure on photocurrent response is asymmetric so that certain thickness combination can be chosen to reduce the uncertainty; (2) on account of the limited accuracy of the optimal thickness determined by photocurrent spectra, estimated diffusion length should be verified by spectrum fitting. Taking these improvements into account, the exciton diffusion length in copper phthalocyanine film is determined as 20 ± 5 nm from curve fitting by this method.
Co-reporter:Nan Liu, Hong-Zheng Chen, Mang Wang
Thin Solid Films 2008 Volume 516(Issue 12) pp:4272-4276
Publication Date(Web):30 April 2008
DOI:10.1016/j.tsf.2008.01.002
Organic–inorganic hybrid heterojunctions were fabricated from porous silicon (PS) and N,N′-diphenyl-3,4,9,10-perylenetetracarboxylic diimide (DPP). PS was prepared by electrochemical anodization of p-type Si wafers and DPP was embedded into PS by electrodeposition to form DPP/PS composites. Photoluminescence and surface photovoltaic spectra demonstrated a charge transfer process taking place in the composites, resulting in a higher exciton dissociation efficiency for the composites than pristine PS. The exciton dissociation efficiency could also be adjusted by the PS etching time, because the interface area in the composites varied with the PS etching time.
Co-reporter:Hong-Zheng Chen;Ru Bai;Lei Cao;Hua-Bing Xu
Research on Chemical Intermediates 2008 Volume 34( Issue 2-3) pp:115-125
Publication Date(Web):2008 February
DOI:10.1163/156856708783623528
This paper focuses on the fabrication of organic-inorganic composite materials with optoelectronic functionality based on carbon nanotubes (CNTs) by chemical and physical modifications. The one-dimensionally (1D) ordered composites of rare earth phthalocyanine compounds (RePc2) encapsulated by MWCNTs were obtained using a simple capillary filling method. The CNT-templated assembly of RePc2 nanowires was performed by a phase-separation method. Two other kinds of organic-inorganic 1D-ordered optoelectronic composites were prepared using the template method: coating MWCNTs with a fluorescent poly(tripheny lamine) related co-polymer can be realized via a facile phase-separation strategy: 1D hy brid of bamboo-shaped CNTs covalently bound to RePc2. The relationship between the microstructure of the obtained 1D-ordered composites and optoelectronic properties was studied, and it was found that these ordered composites exhibited enhanced photoconductivity due to the charge transfer between the composite components.
Co-reporter:Gang Wu, Hui-Ying Yang, Hong-Zheng Chen, Fang Yuan, Li-Gong Yang, Mang Wang, Ren-Jun Fu
Materials Chemistry and Physics 2007 Volume 104(2–3) pp:284-287
Publication Date(Web):15 August 2007
DOI:10.1016/j.matchemphys.2007.03.013
High porous poly(hydroxyethyl acrylate-co-acrylonitrile) [P(HEA-AN)] membranes were prepared by a phase inversion method. Porous polymer electrolytes are prepared by soaking the porous membranes in the electrolyte solution. The ionic conductivity of the porous polymer electrolytes was found to be as high as 3.66 × 10−3 S cm−1. The membrane structure changed with the different processing conditions. With increasing mole ratio of AN in the copolymer, the cross-sectional structure of the membrane changes from finger-like to honeycomb-like and ionic conductivity of porous polymer electrolytes is improved. As the polymer concentration increases, the pore diameter of porous membrane decreases and ionic conductivity of porous polymer electrolyte is improved obviously.
Co-reporter:Yue-Wen Shi, Min-Min Shi, Jia-Chi Huang, Hong-Zheng Chen, Mang Wang, Xiao-Dong Liu, Yu-Guang Ma, Hai Xu and Bing Yang
Chemical Communications 2006 (Issue 18) pp:1941-1943
Publication Date(Web):30 Mar 2006
DOI:10.1039/B516757D
This communication reports that not only the emission colour but also the photoluminescence quantum yield of Alq3 can be tuned by introducing fluorine atoms at different positions; with fluorination at C-5 the emission is red-shifted with a tremendously decreased intensity, fluorination at C-6 causes a blue-shift with a significantly increased intensity, and fluorination at C-7 has a minor effect on both the colour and intensity of Alq3's emission.
Co-reporter:Gang Wu;Hui-Ying Yang;Hongzheng Chen;Fang Yuan;Mang Wang;Ren-Jun Fu
Journal of Applied Polymer Science 2006 Volume 101(Issue 1) pp:461-464
Publication Date(Web):25 APR 2006
DOI:10.1002/app.23291
The transparent and flexible solid polymer electrolytes (SPEs) were fabricated from polyacrylonitrile-polyethylene oxide (PAN-PEO) copolymer which was synthesized by methacrylate-headed PEO macromonomer and acrylonitrile. The formation of copolymer is confirmed by Fourier-transform infrared spectroscopy (FTIR) measurements. The ionic conductivity was measured by alternating current (AC) impedance spectroscopy. Ionic conductivity of PAN-PEO-LiClO4 complexes was investigated with various salt concentration, temperatures and molecular weight of PEO (Mn). And the maximum ionic conductivity at room temperature was measured to be 3.54 × 10−4 S/cm with an [Li+]/[EO] mole ratio of about 0.1. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 461–464, 2006
Co-reporter:Ying-Ying Zheng, Gang Wu, Meng Deng, Hong-Zheng Chen, Mang Wang, Ben-Zhong Tang
Thin Solid Films 2006 Volume 514(1–2) pp:127-131
Publication Date(Web):30 August 2006
DOI:10.1016/j.tsf.2006.02.082
The organic–inorganic hybrid compound (C8NH6–CH2CH2NH3)2CuCl4 (AEI–CuCl4) was synthesized from ethanol solution containing copper chloride and 3-2-(aminoethyl) indole hydrochloride (AEI–HCl). High order diffraction peaks corresponding to (0 0 l; l = 2, 4, 6, …) observed in the X-ray diffraction profile of AEI–CuCl4 indicated the formation of hybrid crystal with layered perovskite structure. The organic–inorganic hybrid crystal thin film can be easily prepared by spin-coating method from the ethanol solution of the AEI–CuCl4 perovskite and it showed characteristic absorptions of CuCl-based layered perovskite centered at 288 and 388 nm, as well as the photoluminescence peak at around 420 nm. The unaided-eye-detectable blue fluorescence emission comes from the cooperation of AEI–HCl and AEI–CuCl4 perovskite, in which protonized aminoethyl indole dominates the shape of the spectrum and the enhancement of emission intensity is due to the formation of the perovskite structure. The thermal analysis presented that the AEI–CuCl4 perovskite started to melt at 182 °C, together with the beginning of the decomposition of the hybrids. Compared with the organic–inorganic perovskite hybrids reported previously, the AEI–CuCl4 perovskite shows a novel stepwise decomposition behavior.
Co-reporter:Zheng-Long Yang, Hong-Zheng Chen, Min-Min Shi, Chao Pan, Mang Wang
Materials Science and Engineering: B 2005 Volume 122(Issue 3) pp:211-217
Publication Date(Web):25 September 2005
DOI:10.1016/j.mseb.2005.06.016
An organic single-layered photoreceptor (SLPR), where 2,5-bis(1″-azo-2″-hydroxy-3″-naphthoyl-o-chloroanide) oxazole/oxititanium phthalocyanine composite (O-bisazo/TiOPc composite) was used as the charge generation material (CGM) and N,N′-diethyl-4-aminobenzaldehyde-1-phenyl-1′-(α-naphthyl)-hydrazone (DENPH) as the charge transportation material (CTM), was prepared by the dip coating method and its photoconductivity was studied under the exposure of various wavelengths. It was found that such obtained SLPR showed much better photoconductivity than those from pristine O-bisazo or TiOPc and also better than the double-layered photoreceptor (DLPR) from the same composite. With the aid of UV–vis SEM, surface photovoltaic spectroscopy (SPS) and field-induced surface photovoltaic spectroscopy (FISPS) measurements, the enhanced photoconductivity was attributed to the formation of the charge transfer complex between O-bisazo and TiOPc as well as the much larger interfacial areas between CGM and CTM in the SLPR than those in the DLPR.
Co-reporter:Ze-Long Xiao, Hong-Zheng Chen, Min-Min Shi, Gang Wu, Ren-Jia Zhou, Zhi-Sheng Yang, Mang Wang, Ben-Zhong Tang
Materials Science and Engineering: B 2005 Volume 117(Issue 3) pp:313-316
Publication Date(Web):25 March 2005
DOI:10.1016/j.mseb.2004.12.052
Organic–inorganic hybrid perovskite (C4H9NH3)2CuCl4 was prepared via the reaction between copper chloride and butylammonium chloride. Its chemical structure was characterized by FT–IR and elemental analysis. Its thin film was obtained by spin-coating, and X-ray diffraction (XRD) measurements indicated the formation of two-dimensional layered perovskites structure, with the c-axis perpendicular to the substrate surface. The electronic structure, thermal properties and electrical properties of the hybrid perovskite (C4H9NH3)2CuCl4 were also studied by UV–vis, photoluminescience (PL), TGA, DSC, and Hall measurement.
Co-reporter:Yong Wang, Hong-Zheng Chen, Han-Ying Li, Mang Wang
Materials Science and Engineering: B 2005 Volume 117(Issue 3) pp:296-301
Publication Date(Web):25 March 2005
DOI:10.1016/j.mseb.2004.12.007
Modified multiwalled carbon nanotubes (MWCNTs) bonded dodecyl chain and copper-tetra(4-dodecoxy-carboxyl)phthalocyanine (CuPcdc) were prepared respectively, resulting in improved solubility in organic solvents, good compatibility between these two compounds and film-forming characteristic. The novel composite of the modified MWCNTs/CuPcdc was prepared by the solution-blending method. Transmission electron microscope (TEM) showed the good compatibility between the modified MWCNTs and CuPcdc due to a stronger interaction between these two compounds, which is demonstrated by X-ray photoelectron spectroscopy (XPS) of the composite and by comparing the UV–vis absorption spectrum of the composite with that of modified MWCNTs/copper phthalocyanine (CuPc)/polyvinylbutyral (PVB). The stronger interaction is favoring to the photoinduced charge transfer as demonstrated via the study of the photoconductivity of modified MWCNTs/CuPcdc composites.
Co-reporter:Zhenglong Yang, Hongzheng Chen, Lei Cao, Hanying Li, Mang Wang
Materials Letters 2004 Volume 58(17–18) pp:2238-2242
Publication Date(Web):1 July 2004
DOI:10.1016/j.matlet.2004.01.036
Nanoscale azo pigment immobilized on the outer shell of multiwalled carbon nanotubes (MWCNT–AZO) were prepared by modified liquid phase reprecipitation method, and the MWCNT–AZO hybrid was characterized by means of TEM, X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and UV–VIS absorption. The photoconductivity of single-layered photoreceptors, where MWCNT–AZO served as the charge generation material (CGM), was studied by the xerographic photoinduced discharge method. The results indicated that the MWCNT–AZO nano hybrid showed broader and enhanced photosensitivity than MWCNT/bulk azo pigments (AZO) blend or the bulk AZO did, which was interpreted in terms of nanometer size effect of MWCNT–AZO hybrid and charge transfer from AZO nanoparticles to MWCNT.
Co-reporter:Hong-Zheng Chen, Zhong-Yang Li, Hong-Wei Ye, Mang Wang
Materials Science and Engineering: B 2004 Volume 111(2–3) pp:242-246
Publication Date(Web):25 August 2004
DOI:10.1016/j.mseb.2004.05.001
The effect of poly(4-vinyl-pyridine) (PVP) on the adsorption behavior of cis-Cl2 bis(2,2′-bipyridyl) ruthenium(II) (RuL2Cl2), lack of carboxyl groups, on nanocrystalline TiO2 film was investigated. It is found that the maximum amount of RuL2Cl2 adsorbed by TiO2 with PVP, 5 × 10−10 mol/cm2, is 30 times higher than that of RuL2Cl2 adsorbed by TiO2 without PVP. The interaction between PVP and RuL2Cl2 was characterized by IR and UV–vis. The effect of adsorption time on the amount of RuL2Cl2 with PVP was also investigated. The role of PVP in the adsorption of RuL2Cl2 was explained and the structure of RuL2Cl2 and PVP on nanocrystalline TiO2 film surface was supposed.
Co-reporter:L. Cao;H.-Z. Chen;H.-B. Zhou;L. Zhu;J.-Z. Sun;X.-B. Zhang;J.-M. Xu;M. Wang
Advanced Materials 2003 Volume 15(Issue 11) pp:
Publication Date(Web):2 JUN 2003
DOI:10.1002/adma.200304637
Co-reporter:Min-Min Shi, Hong-Zheng Chen, Jing-Zhi Sun, Jian Ye and Mang Wang
Chemical Communications 2003 (Issue 14) pp:1710-1711
Publication Date(Web):13 Jun 2003
DOI:10.1039/B304141G
A novel soluble and air-stable electron acceptor was reported: due to the fluorination, N,N′-diperfluorophenyl-3,4,9,10-perylenetetracarboxylic diimide (1) possessed not only good solubility but also much lower LUMO energy level: −4.37 eV. Furthermore, the photoinduced charge transfer between 1 and PVK was also studied.
Co-reporter:Lei Cao, Hong-Zheng Chen, Li Zhu, Xiao-Bin Zhang, Mang Wang
Materials Letters 2003 Volume 57(26–27) pp:4309-4314
Publication Date(Web):September 2003
DOI:10.1016/S0167-577X(03)00308-2
Erbium biphthalocyanine (HErPc2) thin films are prepared by vacuum deposition at various substrate temperatures. The effects of substrate temperature and film thickness on film morphology, crystalline structure, and optical absorption are studied. The HErPc2 films exhibit fine-grain morphology and small degree of crystallization at low substrate temperature. The size of the crystallites is enlarged when the film thickness increases. If the substrate temperature is elevated to 100 °C, the HErPc2 films exhibit a high crystallization, and fibre-like clusters are observed, with orientation mainly parallel to the substrate. The high photoresponse of the HErPc2 films in the near-infrared (NIR) region presents potential application of rare earth biphthalocyanines as NIR photodetectors.
Co-reporter:Jian Ye, Hong-Zheng Chen, Mang Wang
Materials Chemistry and Physics 2003 Volume 82(Issue 1) pp:210-215
Publication Date(Web):28 September 2003
DOI:10.1016/S0254-0584(03)00198-6
The organic single-layered photoreceptors (SLPRs) consisting of polycarbonate (PC) matrix containing dispersed N,N′-diethyl-4-aminobenzaldehyde-1-phenyl-1′-(α-naphthyl)-hydrazone (BAH) and 2,4,7-trinitrylfluorenone (TNF) as bipolar charge (hole and electron) transport materials, as well as oxotitanium phthalocyanine (TiOPc) as charge generation materials (CGMs), were prepared. The influence of organic electron transport material (ETM) on the photosensitivity in the photoreceptors was investigated. It was found that small amount of TNF (TNF/BAH ≤0.005) could improve the photosensitivity of photoreceptors greatly, i.e. the enhanced photoconductive effect, but the further increase of TNF concentration would lead to the decline of the photosensitivity. Differential scanning calorimeter (DSC), UV-Vis and cyclic voltammograms (CV) study showed that the enhanced photoconductivity might be resulted from the improvement of the separation efficiency of electron–hole pairs, and the decline of photosensitivity was due to the formation of the charge transfer complex (CTC) of TNF–BAH.
Co-reporter:Dan Deng, Minmin Shi, Fei Chen, Lin Chen, Xiaoxia Jiang, Hongzheng Chen
Solar Energy (May 2010) Volume 84(Issue 5) pp:771-776
Publication Date(Web):1 May 2010
DOI:10.1016/j.solener.2010.01.028
We report the synthesis of 3D structural CdS nanocrystals by a simple biomolecule-assisted hydrothermal process. The CdS nanocrystals are composed of many branched nanorods with the diameter of about 50 nm, and the length of about 250 nm. The phase and crystallographic properties are characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), and X-ray diffractometry (XRD). The composites based on CdS nanocrystals and poly[2-methoxy-5-(2-ethylhexyloxy-p-phenylenevinylene)] (MEH-PPV) have been prepared by spin-coating of the mixture in the common solvent. The optical properties of the composites are investigated using ultraviolet–visible (UV–Vis) absorption and photoluminescence (PL) spectroscopies. A significant fluorescence quenching of MEH-PPV in the composites is observed at high CdS nanocrystals/MEH-PPV ratios, indicating that the photo-induced charge transfer occurred due to the energy level offset between the donor MEH-PPV and the acceptor CdS nanocrystals. The obvious photovoltaic behavior of the solar cell made from this composite further demonstrates the mentioned photo-induced charge transfer process.
Co-reporter:Lijian Zuo, Jizhong Yao, Hanying Li, Hongzheng Chen
Solar Energy Materials and Solar Cells (March 2014) Volume 122() pp:88-93
Publication Date(Web):1 March 2014
DOI:10.1016/j.solmat.2013.11.018
•We propose an improved equivalent circuit model to interpret the origin of S shape curve.•The improved equivalent circuit model involves a rectifying junction connected with the D:A junction in series.•The validity of this model is confirmed by good reproduction of the experimental results.•Effect of the formation of S shape curve on device parameters is analyzed through the equivalent model.•Detailed effect of the rectifying junction on the I–V curve of organic solar cells is simulated.Formation of S-shaped I–V curve or the so-called kink has been shown detrimental to organic solar cells (OSC) performance. Previous researches have indicated that a variety of reasons could count for the origin of the S-shaped I–V curve. However, its origin is still not clear. In this contribution, we investigated the origin of S-shaped I–V curve from the view of an equivalent circuit model (ECM) in OSCs. The proposed ECM involves a rectifying junction connected with a donor/accepter (D/A) junction in series. OSCs with and without a Schottky barrier that was a rectifying junction were fabricated to verify the modeled results. And the good reproduction of experimental results confirmed the validity of our model. The results indicate that the origin of S-shaped I–V curve in OSCs is associated with the rectifying junction. With this model, the effects of the rectifying junction on the shape of I–V characteristic and its effect on device parameters are analyzed: fill factor (FF) dropped, short circuit current density decreased, open circuit voltage however, remained. Also, from simulation, we varied the parameters of the rectifying junction to study their influence on the device performance.In this work, we study the origin of S shape curve through an improved equivalent circuit model (ECM). The improved ECM involves a D:A junction as well as a rectifying junction to interpret the bias-dependent-recombination.Download full-size image
Co-reporter:Zhi-Kai Yu, Wei-Fei Fu, Wen-Qing Liu, Zhong-Qiang Zhang, Yu-Jing Liu, Jie-Lin Yan, Tao Ye, Wei-Tao Yang, Han-Ying Li, Hong-Zheng Chen
Chinese Chemical Letters (January 2017) Volume 28(Issue 1) pp:
Publication Date(Web):January 2017
DOI:10.1016/j.cclet.2016.06.021
A solution-processed CuOx film has been successfully integrated as the hole-transporting layer (HTL) for inverted planar heterojunction perovskite solar cells (PVSCs). The CuOx layer is fabricated by simply spin-coating a copper acetylacetonate (Cu(acac)2) chloroform solution onto ITO glass with high transparency in the visible range. The compact and pinhole-free perovskite film with large grain domains is grown on the CuOx film. The inverted PVSCs with the structure of ITO/CuOx/MAPbI3/PC61BM/ZnO/Al are fabricated and show a best PCE of 17.43% under standard AM 1.5G simulated solar irradiation with a VOC of 1.03 V, a JSC of 22.42 mA cm−2, and a fill factor of 0.76, which is significantly higher and more stable than that fabricated from the often used hole-transporting material PEDOT:PSS (11.98%) under the same experimental conditions. The enhanced performance is attributed to the efficient hole extraction through the CuOx layer as well as the high-quality CH3NH3PbI3 films grown on the CuOx. Our results indicate that low-cost and solution-processed CuOx film is a promising HTL for high performance PVSCs with better stability.A high power conversion efficiency of 17.43% is achieved by integrating a solution-processed CuOx film as the hole-transporting layer for inverted planar heterojunction perovskite solar cells.
Co-reporter:Xiaoqiang Chen, Lijian Zuo, Weifei Fu, Quanxiang Yan, Congcheng Fan, Hongzheng Chen
Solar Energy Materials and Solar Cells (April 2013) Volume 111() pp:1-8
Publication Date(Web):1 April 2013
DOI:10.1016/j.solmat.2012.12.016
Photovoltaic performances of polymer bulk-heterojunction solar cells (PSCs) with various sized (20, 35, 50, and 75 nm) Au nanoparticles (NPs) incorporated on indium tin oxide (ITO)-coated glass substrates are investigated in detail, wherein poly(3-hexylthiophene):phenyl-C61-butyric acid methyl ester (P3HT:PCBM) blend serves as active layer and poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) as anode buffer layer on ITO. The optical and electrical properties of these devices incorporated with Au NPs with different space distributions in the interface of PEDOT:PSS buffer layer and P3HT:PCBM active layer are investigated. We find that, the optical property is improved as the Au NPs are large enough to penetrate into the active layer, while the performance of PSCs with small Au NPs can only benefit from the improved hole collection efficiency. Meanwhile, the exciton dissociation efficiency reduces remarkably as increasing the size of Au NPs. Finally, we demonstrated a maximum power conversion efficiency (PCE) improvement of ∼23% in the PSCs by incorporating 35 nm Au NPs.Highlights► Various sized Au NPs were spin-coated between ITO/anodic buffer layer. ► We explored optical and electrical properties of PSCs with various sized Au NPs. ► The mechanism of PCE enhancement of PSCs with Au NPs was revealed. ► A maximum PCE improvement of ∼23% was achieved.
Co-reporter:Bo Ding, Minmin Shi, Fei Chen, Renjia Zhou, Meng Deng, Mang Wang, Hongzheng Chen
Journal of Crystal Growth (1 March 2009) Volume 311(Issue 6) pp:1533-1538
Publication Date(Web):1 March 2009
DOI:10.1016/j.jcrysgro.2009.01.086
Large-scale PbS crystals in sub-micrometer/nanometer dimensions with various morphologies, such as cubes, dendrites, stars, and wires, were synthesized via a facile hydrothermal method. Pb(NO3)2, thiourea, and capping agents like hexamethylenetetramine (HMT) and cetyltrimethylammonium bromide (CTAB), were used as precursors for the syntheses. The morphology, structure, and phase composition of PbS submicro-/nano-structures were determined by X-ray diffraction (XRD), scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS), and transmission electron microscopy (TEM). The influence of different capping agents on the growth of these PbS crystals was investigated and optimized. The formation mechanisms of these PbS crystals were proposed, which could give a proper explanation on the evolution of the crystal growth and may also pave the way to shape-controlled synthesis of other inorganic crystals with versatile complex structures via this facile hydrothermal method.
Co-reporter:Weiming Qiu, Mingsheng Xu, Xi Yang, Fei Chen, Yaxiong Nan, Jinglin Zhang, Hideo Iwai and Hongzheng Chen
Journal of Materials Chemistry A 2011 - vol. 21(Issue 35) pp:NaN13333-13333
Publication Date(Web):2011/08/03
DOI:10.1039/C1JM11616A
We report the synthesis and formation mechanism of In2S3 porous films composed of ultrathin curved nanoflakes by a simple and environment-friendly biomolecule-assisted hydrothermal process. We find that concentrations of the pH conditioner and the biomolecule glutathione significantly affect the morphology and structure of In2S3 films. The as-synthesized In2S3 porous films exhibit strong absorption in the ultraviolet region and the early visible region of the UV-Vis spectrum, with the absorption threshold around 501 nm. As compared with its dense film, the In2S3 porous film shows enhanced photocatalytic properties for the degradation of methyl orange due to its porous and curved nanostructures.
Co-reporter:Shuixing Li, Jielin Yan, Chang-Zhi Li, Feng Liu, Minmin Shi, Hongzheng Chen and Thomas P. Russell
Journal of Materials Chemistry A 2016 - vol. 4(Issue 10) pp:NaN3783-3783
Publication Date(Web):2016/02/04
DOI:10.1039/C6TA00056H
Effective electron acceptor materials usually have a deep lowest unoccupied molecular orbital (LUMO) energy level that can split excitons and generate current. A non-fullerene electron acceptor (F8-DPPTCN) was developed, using fluorene as the core with arms of diketopyrrolopyrrole (DPP) having thiophene-2-carbonitrile as the terminal units. The new molecule had a LUMO of −3.65 eV and a narrow bandgap (Eg) of 1.66 eV, owing to the electronegativity of the thiophene-2-carbonitrile group and its conjugation with DPP units. Organic solar cells (OSCs) with F8-DPPTCN as the acceptor and poly(3-hexylthiophene) (P3HT) as the donor were fabricated. A power conversion efficiency (PCE) of 2.37% was obtained with an open-circuit voltage (Voc) of 0.97 V, a short-circuit current (Jsc) of 6.25 mA cm−2, and a fill factor (FF) of 0.39. Structural characterization showed that P3HT and F8-DPPTCN were kinetically trapped in a weakly separated state whereas thermal annealing led to the crystallization of P3HT and the formation of a network structure with a mesh-size of several hundred nanometers. When a solvent additive, diiodooctane, was used and the mixture was thermally annealed, both P3HT and F8-DPPTCN crystallized and a multi-length scale network was formed. Though the PCEs were low, the changes in the PCE could be correlated with the morphological changes, opening pathways to increase performance further.
Co-reporter:Shida Yang, Wenqing Liu, Lijian Zuo, Xinqian Zhang, Tao Ye, Jiehuan Chen, Chang-Zhi Li, Gang Wu and Hongzheng Chen
Journal of Materials Chemistry A 2016 - vol. 4(Issue 24) pp:NaN9436-9436
Publication Date(Web):2016/05/17
DOI:10.1039/C6TA02999J
Thiocyanate ammonium (NH4SCN) is introduced into the fabrication of formamidinium lead triiodide (FAPbI3) films through one-step spin-coating. The promoted formation of black trigonal phase α-FAPbI3 with better crystallinity has been observed after the addition of NH4SCN, together with the supression of the formation of yellow hexagonal phase δ-FAPbI3. Planar perovskite solar cells (PVSCs) based on NH4SCN-assisted formed α-FAPbI3 films with high quality present a highest power conversion efficiency of 11.44% when 30 mol% NH4SCN is applied. Notably, the addition of NH4SCN is found to enhance the moisture stability of the perovskite. As a result, the planar PVSCs with 30 mol% NH4SCN additive show improved stability under ambient conditions (RH: 30–40%) over those based on pristine FAPbI3. NH4SCN simultaneously enhances the efficiency and moisture stability of FAPbI3 based PVSCs through a single one-step solution method, facilitating their commercial fabrication and application.
Co-reporter:Meirong Chen, Weifei Fu, Minmin Shi, Xiaolian Hu, Junying Pan, Jun Ling, Hangying Li and Hongzheng Chen
Journal of Materials Chemistry A 2013 - vol. 1(Issue 1) pp:NaN111-111
Publication Date(Web):2012/09/27
DOI:10.1039/C2TA00148A
For highly efficient organic solar cells (OSCs), the electron donor should possess not only a narrow band gap (Eg) but also a low highest occupied molecular orbital (HOMO) energy level. To achieve it, in this paper, we designed and synthesized a diketopyrrolopyrrole (DPP) derivative end capped with an ethyl thiophene-2-carboxylate moiety, 3,6-bis{5-[(ethyl thiophene-2-carboxylate)-2-yl]thiophene-2-yl}-2,5-bis(2-ethylhexyl)pyrrolo[3,4-c]pyrrole-1,4-dione (DPP(CT)2). Through UV-vis absorption and cyclic voltammetry (CV) measurements, we demonstrated that the resulting molecule exhibits both a low optical Eg of 1.65 eV and a lower-lying HOMO energy level of −5.33 eV owing to the electronegativity of the ester group and the conjugation effect of the thiophene ring. Therefore, when DPP(CT)2 is used as the electron donor to blend with [6,6]-phenyl-C71-butyric acid methyl ester (PC71BM) for solution processable OSCs, a power conversion efficiency (PCE) of 4.02% combined with an open-circuit voltage (VOC) as high as 0.94 V and a broad photovoltaic response range extending to around 750 nm is obtained.
Co-reporter:Weifei Fu, Ye Shi, Weiming Qiu, Ling Wang, Yaxiong Nan, Minmin Shi, Hanying Li and Hongzheng Chen
Physical Chemistry Chemical Physics 2012 - vol. 14(Issue 35) pp:NaN12098-12098
Publication Date(Web):2012/07/24
DOI:10.1039/C2CP42487H
High-performance hybrid solar cells (HSCs) based on P3HT:CdSe QD blends are achieved through post-deposition ligand exchange by n-butanethiol (n-BT) with a high power conversion efficiency of 3.09%. The mechanism by which n-BT modifies the surface structures of CdSe QDs and thus improves the HSCs performance is investigated.
Co-reporter:Wenqing Liu, Shiyong Liu, Natalia K. Zawacka, Thomas R. Andersen, Pei Cheng, Lei Fu, Meirong Chen, Weifei Fu, Eva Bundgaard, Mikkel Jørgensen, Xiaowei Zhan, Frederik C. Krebs and Hongzheng Chen
Journal of Materials Chemistry A 2014 - vol. 2(Issue 46) pp:NaN19814-19814
Publication Date(Web):2014/09/25
DOI:10.1039/C4TA04733H
All solution-processed flexible large area small molecule bulk heterojunction solar cells were fabricated via roll-coating technology. Our devices were produced from slot-die coating on a lab-scale mini roll-coater under ambient conditions without the use of spin-coating or vacuum evaporation methods. Four diketopyrrolopyrrole based small molecules (SMs 1–4) were utilized as electron donors with (6,6)-phenyl-C61-butyric acid methyl ester as an acceptor and their photovoltaic performances based on roll-coated devices were investigated. The best power conversion efficiency (PCE) of 1.01%, combined with an open circuit voltage of 0.73 V, a short-circuit current density of 3.13 mA cm−2 and a fill factor of 44% were obtained for the device with SM1, which was the first example reported for efficient roll-coating fabrication of flexible large area small molecule solar cells with PCE exceeding 1%. In addition, roll-coated devices based on SMs 2–4 also showed good performances with PCEs of 0.41%, 0.54%, and 0.31%, respectively. Our results prove that small molecules have the potential for use in industries for large scale production of efficient organic solar cells.
Co-reporter:Xi Yang, Mingsheng Xu, Weiming Qiu, Xiaoqiang Chen, Meng Deng, Jinglin Zhang, Hideo Iwai, Eiichiro Watanabe and Hongzheng Chen
Journal of Materials Chemistry A 2011 - vol. 21(Issue 22) pp:NaN8103-8103
Publication Date(Web):2011/04/20
DOI:10.1039/C1JM10697J
Graphene sheets decorated with metal nanoparticles are emerging novel graphene-based hybrids for tuning the intrinsic properties of both components for fundamental research and technological applications. Here we report a new wet-chemistry strategy to efficiently and uniformly decorate reduced graphene oxide (RGO) with unique gold nanodots (GNDs). Non-covalent self-assembly of a perylene thiol derivative (ETPTCDI) on the basal plane of GO forms graphene by reducing the dispersed GO and serves as an excellent two-dimensional template in solution for in situ nucleation and growth of gold nanodots via thiol-Au bonding. We characterized the resulting RGO-ETPTCDI-GND in detail and confirm that the Au nanodots with unique size (∼2 nm) decorate the RGO-ETPTCDI sheets uniformly due to the self-assembly of ETPTCDI molecules on the basal plane of graphene. We demonstrate that our RGO-ETPTCDI-GND sheets have astonishing dispersibility, reliability, and processibility. The uniform decoration of the ∼2 nm GNDs on the graphene surface makes it possible to use the nanodots as a contrast enhancement agent for easily revealing the fine structure of the graphene surface. The electrochemical activity of our RGO-ETPTCDI-GND modified glassy carbon electrode showed significant improvement, suggesting RGO-ETPTCDI-GND as an attractive robust and advanced hybrid electrode material with great promise for electrochemical sensors and energy conversion.
Co-reporter:Wei-Fei Fu, Xiaoqiang Chen, Xi Yang, Ling Wang, Ye Shi, Minmin Shi, Han-Ying Li, Alex K.-Y. Jen, Jun-Wu Chen, Yong Cao and Hong-Zheng Chen
Physical Chemistry Chemical Physics 2013 - vol. 15(Issue 40) pp:NaN17111-17111
Publication Date(Web):2013/08/01
DOI:10.1039/C3CP52723A
Plasmonics have been proven to be an effective way to harness more incident light to achieve high efficiency in photovoltaic devices. Herein, we explore the possibility that plasmonics can be utilized to enhance light trapping and power conversion efficiency (PCE) for polymer–quantum dot (QD) hybrid solar cells (HSCs). Based on a low band-gap polymer poly[2,6-(4,4-bis-(2-ethylhexyl)-4H-cyclopenta[2,1-b;3,4-b′]-dithiophene)-alt-4,7-(2,1,3-benzothiadiazole)] (PCPDTBT) and a CdSe QD bulk-heterojunction (BHJ) system, gold nanoparticles were doped at different locations of the devices. Successfully, an improved PCE of 3.20 ± 0.22% and 3.16 ± 0.15% was achieved by doping the hole transporting layer and the active layer, respectively, which are among the highest values reported for CdSe QD based HSCs. A detailed study of processing, characterization, microscopy, and device fabrication is conducted to understand the underlying mechanism for the enhanced device performance. The success of this work provides a simple and generally applicable approach to enhance light harnessing of polymer–QD hybrid solar cells.
Co-reporter:Yingying Zhang, Shuang Liu, Wenqing Liu, Tao Liang, Xi Yang, Mingsheng Xu and Hongzheng Chen
Physical Chemistry Chemical Physics 2015 - vol. 17(Issue 41) pp:NaN27572-27572
Publication Date(Web):2015/09/17
DOI:10.1039/C5CP05011A
Nanoscale morphology is of significance to the electronic properties of semiconducting polymers. Solution-processed poly-3-hexylthiophene (P3HT) has been demonstrated as a promising active-layer material in organic thin film transistors (OTFTs) and solar cells. Controlling the crystallinity of P3HT chains is critical for gaining high-performance devices. Here we demonstrated the immediate crystallization of P3HT induced by two-dimensional MoS2 nanosheets under ultrasonication. The resulting aggregation was attributed to the presence of interaction between the MoS2 nanosheets and P3HT, which could enhance the inter-chain ordering and association of P3HT. The crystallization of P3HT contributed to the 38-fold enhancement in the hole mobility of the thin film as compared to the non-crystallized thin films because of the absence of MoS2. Our approach of using 2D MoS2 nanosheets to induce immediate aggregation of P3HT provides a facile process to control the crystallization of conjugated polymers for the development of high-performance organic electronics.
Co-reporter:Bing Guo, Gang Wu, Hongzheng Chen and Mang Wang
Journal of Materials Chemistry A 2015 - vol. 3(Issue 36) pp:NaN9352-9352
Publication Date(Web):2015/08/10
DOI:10.1039/C5TC02334C
A convenient two-step hydrothermal method was developed to synthesize water dispersible NaTaO3 nanoparticles. The growth of the NaTaO3 nanoparticles was retarded with the aid of a water soluble complex agent in the first step, such as citric acid, bicine, triacetin, and EDTA 2Na, which formed complexes with Ta5+. The sizes of the NaTaO3 nanoparticles, ranging from 5 nm to 30 nm, could be tuned by adjusting the reaction time as well as the complexing agent. An ultraviolet photodetector was fabricated with the solution processed NaTaO3 film as the active layer, which presented a sensitive response to 280 nm deep UV illumination with a light to dark current ratio of about 160 and a response time of about 50 ms.
Co-reporter:Hanying Li, Congcheng Fan, Michael Vosgueritchian, Benjamin C.-K. Tee and Hongzheng Chen
Journal of Materials Chemistry A 2014 - vol. 2(Issue 18) pp:NaN3624-3624
Publication Date(Web):2014/02/25
DOI:10.1039/C3TC32431A
Single crystals of C60 have been widely prepared previously. However, their electronic properties are much less frequently studied, although C60 is known as an outstanding electronic material. Also, the reported electron mobility values (∼10−2 cm2 V−1 s−1) of C60 single-crystals are unexpectedly low possibly due to the difficulties in the fabrication of single-crystal devices. We have recently reported a droplet receding method for the solution-grown C60 single-crystals with mobilities above 1 cm2 V−1 s−1. In this work, we systematically investigate the effects of solvent and surface properties of the substrate on the growth of C60 single-crystals. Well-aligned C60 needle-like and ribbon-like single-crystals were grown from suitable solvents (m-xylene or a mixed solvent of m-xylene and carbon tetrachloride) conformally on the field-effect transistor (FET) substrates that were wet well by the receding droplet. Based on the ribbon-like single-crystals, an average electron mobility of 2.0 ± 0.61 cm2 V−1 s−1, Ion/Ioff > 106, and a VT between 36 and 85 V were achieved from 60 field-effect transistors. Insights provided by this work may help accelerate the development of solution-grown single-crystals of organic semiconductors.
Co-reporter:Shi-Yong Liu, Min-Min Shi, Jia-Chi Huang, Zheng-Neng Jin, Xiao-Lian Hu, Jun-Ying Pan, Han-Ying Li, Alex K.-Y. Jen and Hong-Zheng Chen
Journal of Materials Chemistry A 2013 - vol. 1(Issue 8) pp:NaN2805-2805
Publication Date(Web):2012/12/21
DOI:10.1039/C2TA01318E
Diketopyrrolopyrrole (DPP) derivatives are an important class of high-performance pigment used in inks, paints, plastics, and organic electronics. Until now, DPP derivatives containing sophisticated aryl units at the DPP core have usually been obtained via Suzuki, Stille, or Negishi cross-coupling reactions, which require organometallic precursors. In this work, a series of DPP-based π-conjugated molecules bearing diverse aryl substituents on the thiophene- or benzene-DPPs were facilely synthesized in moderate to excellent yields through the Pd-catalyzed direct arylation of C–H bonds. The synthetic procedures feature advantages over traditional C–C cross-coupling reactions such as: (1) avoidance of the use of organometallic reagents in the starting materials leading to simpler byproducts and higher atom economy, (2) fewer synthetic steps, (3) higher yields, (4) better compatibility with chemically sensitive functional groups, and (5) simpler catalytic systems free of phosphine ligands. These advantages make the present protocol an ideal and versatile strategy for the synthesis of DPP derivatives, especially for structurally complicated DPPs that may possess chemically sensitive functionalities. The optical and electrochemical properties of the synthesized DPPs (17 compounds) were systematically investigated using UV-vis spectroscopy, steady-state fluorescence spectroscopy, and cyclic voltammetry (CV).
Co-reporter:Peipei Yin, Gang Wu, Wenlong Qin, Xiaoqiang Chen, Mang Wang and Hongzheng Chen
Journal of Materials Chemistry A 2013 - vol. 1(Issue 4) pp:NaN849-849
Publication Date(Web):2012/11/29
DOI:10.1039/C2TC00344A
Chromatic organic pigment–SiO2 composite particles with six different colors (CYM and RGB) were prepared by a modified sol–gel method. With the aid of a cationic polyelectrolyte, poly(diallyldimethylammoniumchloride), amorphous silica was coated onto the surface of organic pigments which was revealed by the variation of the zeta potential and average particle size, together with TEM images and EDX and XPS results. Because of the fine scattering properties of silica to visible light, the intensity of the reflectance peak increased significantly, which makes the composite particles more vivid than the organic pigments. The chromatic electrophoretic suspension was prepared by mixing Span 85 and the composite particles anchored with a self-made block copolymer PLMA-b-PDMAEMA in tetrachloroethylene. All the colored ink particles have similar zeta potentials and mobility of about 30 mV and 4–5 × 10−10 m2 V−1 s−1, respectively. White/color (CYM and RGB) dual-particle electronic ink containing PLMA-b-PDMAEMA treated pigment–SiO2 composite particles and TiO2 grafted with a polymer present excellent performance and quick response under an applied DC field of 0.15 V μm−1.
Co-reporter:Ling Wang, Weifei Fu, Zhuowei Gu, Congcheng Fan, Xi Yang, Hanying Li and Hongzheng Chen
Journal of Materials Chemistry A 2014 - vol. 2(Issue 43) pp:NaN9090-9090
Publication Date(Web):2014/09/19
DOI:10.1039/C4TC01875C
A cadmium selenide (CdSe) nanocrystal was used as an electron transport/extraction layer for perovskite solar cells due to its high electron mobility and solution-processability at low temperatures. Power conversion efficiency (PCE) up to 11.7% was achieved under standard AM1.5G conditions in air.
Co-reporter:Bo Wang, Wenqing Liu, Huanbin Li, Jiangquan Mai, Shiyong Liu, Xinhui Lu, Hanying Li, Minmin Shi, Chang-Zhi Li and Hongzheng Chen
Journal of Materials Chemistry A 2017 - vol. 5(Issue 19) pp:NaN9401-9401
Publication Date(Web):2017/04/14
DOI:10.1039/C7TA02582C
In this work, we present two new electron acceptors, TriPDI and Fused-TriPDI, in which three perylene diimide (PDI) moieties are tethered to a benzotrithiophene (BTT) core via either single bonds (TriPDI) or ring-fusion (Fused-TriPDI). TriPDI connects three PDIs to BTT via carbon–carbon single bonds, resulting in a rotatable and highly twisted skeleton. Instead, Fused-TriPDI, made through oxidative ring-fusion of TriPDI, exhibits good structural rigidity and planarity, as well as effective conjugation between PDI and BTT. As a result, the fused molecule shows up-shifted energy levels, and enhanced absorption and charge mobility over the unfused one. The polymer solar cells (PSCs) with a PTB7-Th:Fused-TriPDI blend show the best power conversion efficiency of 6.19%, which is around three times higher than that with PTB7-Th:TriPDI.
Co-reporter:Lijian Zuo, Shuhua Zhang, Minmin Shi, Hanying Li and Hongzheng Chen
Inorganic Chemistry Frontiers 2017 - vol. 1(Issue 2) pp:NaN309-309
Publication Date(Web):2016/08/08
DOI:10.1039/C6QM00043F
Successfully transferring the device efficiency of small area organic solar cells (SA-OSCs) to a large scale area is a tough challenge. The charge collecting and transporting grids are demonstrated to be effective at addressing this issue, and are widely used in commercial silicon solar cells. However, appreciable shadow loss (5–10%) can be caused with these grids. Thus, a rational design of the grid structure to reduce this significant shadow loss is highly desired. Here, we show that the significant energy loss on scaling up the OSC area stems from the accumulated current density along the charge transport direction. Accordingly, a rational pattern of shorter and triangular Ag grids is designed to accommodate the accumulated current density, leading to a high efficiency of 6.93% for up-scaled OSCs of 4 cm2.
Co-reporter:Zhuowei Gu, Lijian Zuo, Thue T. Larsen-Olsen, Tao Ye, Gang Wu, Frederik C. Krebs and Hongzheng Chen
Journal of Materials Chemistry A 2015 - vol. 3(Issue 48) pp:NaN24260-24260
Publication Date(Web):2015/10/06
DOI:10.1039/C5TA07008B
The morphologies of the perovskite (e.g. CH3NH3PbI3) layer are demonstrated to be critically important for highly efficient perovskite solar cells. This work applies 3-aminopropanoic acid as a self-assembled monolayer (C3-SAM) on a poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) hole transport layer (HTL) to modify the crystallinity and coverage of the CH3NH3PbI3−xClx film, resulting in a much smoother perovskite surface morphology together with a PCE increase from 9.7% to 11.6%. Since all fabrication steps of these inverted structure devices are carried out under low temperature conditions (processing temperature < 120 °C), it is possible to employ this method on flexible polymer substrates using roll-coating for the layer deposition. The roll-coated perovskite film on C3-SAM modified PEDOT:PSS presents a similar trend of improvement and results in enhanced PCE from 3.7% to 5.1%. The successful application of the facile HTL modification indicates a common strategy for SAM material design and selection for efficiency enhancement in perovskite photovoltaic devices.
Co-reporter:Zhongqiang Zhang, Wenqing Liu, Tahir Rehman, Huan-Xin Ju, Jiangquan Mai, Xinhui Lu, Minmin Shi, Junfa Zhu, Chang-Zhi Li and Hongzheng Chen
Journal of Materials Chemistry A 2017 - vol. 5(Issue 20) pp:NaN9654-9654
Publication Date(Web):2017/04/12
DOI:10.1039/C7TA01554B
Efficient fullerene-free polymer solar cells (PSCs) are fabricated with a polymer donor PBDB-T1 and a non-fullerene acceptor ITTIC. With the incorporation of one thiophene bridge between the indacenodithienothiophene (IDTT) core and 2-(3-oxo-2,3-dihydroinden-1-ylidene)malononitrile (IC) terminal, the new acceptor ITTIC exhibits a higher lying lowest unoccupied molecular orbital (LUMO), and a narrower bandgap than the pristine ITIC acceptor. The resultant PSCs with PBDB-T1:ITTIC blends exhibit a power conversion efficiency of 9.12%, with an increased open circuit voltage (VOC) and broader photoresponse, compared with the PBDB-T1:ITIC based devices. Interestingly, it is shown that the charge transfer remains effective at a diminished highest occupied molecular orbital (HOMO) difference of 0.02 eV between PBDB-T1 and ITTIC, leading to a mitigated energy loss of 0.54 eV in PBDB-T1:ITTIC based devices. Overall, this work provides new insights into further improvement of fullerene-free PSCs.
Co-reporter:Xi Yang, Weifei Fu, Wenqing Liu, Jinghua Hong, Yu Cai, Chuanhong Jin, Mingsheng Xu, Haibo Wang, Deren Yang and Hongzheng Chen
Journal of Materials Chemistry A 2014 - vol. 2(Issue 21) pp:NaN7733-7733
Publication Date(Web):2014/03/25
DOI:10.1039/C4TA01336K
The effects of different local crystalline structures on two-dimensional (2D) MoS2 sheets are studied to provide new insights into how the local characteristics affect the performance of organic solar cells (OSCs) and how to tailor the local characteristics towards high-performance devices. UV–ozone post-treatment of 2D MoS2 sheets led to incorporation of oxygen atoms into the lattice of the sheets. The incorporated oxygen in 2D MoS2 sheets significantly improved the performance of OSCs, where 2D MoS2 sheets were used as hole transport layers.
Co-reporter:Shi-Yong Liu, Jae Woong Jung, Chang-Zhi Li, Jiang Huang, Jianyuan Zhang, Hongzheng Chen and Alex K.-Y. Jen
Journal of Materials Chemistry A 2015 - vol. 3(Issue 44) pp:NaN22169-22169
Publication Date(Web):2015/09/15
DOI:10.1039/C5TA06639E
Non-fullerene acceptor based organic photovoltaic devices (OPVs) reported so far are inferior to those derived from fullerenes. This increases the speculation on whether donors need to be tailored for advancing non-fullerene OPVs. We explored herein two direct arylation-derived diketopyrrolopyrrole (DPP)-based three-dimensional (3D) donors that can deliver respectable power conversion efficiencies (PCEs) of 4.64% and 4.02% with polymeric acceptor N2200 blends, surpassing those obtained from PC71BM (3.56% and 3.22%, respectively). It is found that these 3D-shaped molecular donors can yield improved photo-to-current conversion and balanced charge transport when blending with the linear N2200 polymer. This finding suggests that engineering molecular geometry can be a promising approach for developing high-performance materials.
Co-reporter:Shuhua Zhang, Lijian Zuo, Jiehuan Chen, Zhongqiang Zhang, Jiangquan Mai, Tsz-Ki Lau, Xinhui Lu, Minmin Shi and Hongzheng Chen
Journal of Materials Chemistry A 2016 - vol. 4(Issue 5) pp:NaN1707-1707
Publication Date(Web):2016/01/05
DOI:10.1039/C5TA09727D
Incorporating two polymer donors with different bandgaps to compose a ternary blend bulk heterojunction (BHJ) is proved to be an effective approach to improve the device performance of BHJ polymer solar cells (PSCs). Here, we demonstrate an efficient ternary PSC consisting of a polythieno[3,4-b]-thiophene/benzodithiophene (PTB7):[6,6]-phenyl C71 butyric acid methyl ester (PC71BM) host blend sensitized by a low band gap (LBG) polymer poly[2,7-(5,5-bis-(3,7-dimethyloctyl)-5H-dithieno[3,2-b:20,30-d]pyran)-alt-4,7-(5,6-difluoro-2,1,3-benzothiadiazole)] (PDTP-DFBT). The addition of the PDTP-DFBT sensitizer remarkably extended the PSC photon to electron response from 750 to 900 nm, which increased the Jsc from 15.12 to 16.27 mA cm−2, and the device performance from 8.08% to 8.63%. A study on the morphology involving the atomic force microscopy mapping and grazing incident X-ray diffraction showed that the incorporation of PDTP-DFBT improved the crystallinity of the PTB7 film with most of the sensitizers associated with the PTB7 domains when blending with a PC71BM film. This observation, together with the unchanged Voc of the ternary PSC, implies a sensitizing mechanism with addition of PDTP-DFBT. After further interfacial modification with a capronic acid self-assembling monolayer (C3-SAM), a higher PCE of 9.06% was achieved, which is among the highest values of efficient ternary PSCs. Our work suggests that a sensitizing mechanism of ternary blends compensates for the light absorbing limitation of binary blend PSCs for high device performance.
Co-reporter:Zhikai Yu, Wenqing Liu, Weifei Fu, Zhongqiang Zhang, Weitao Yang, Shengping Wang, Hongfei Li, Mingsheng Xu and Hongzheng Chen
Journal of Materials Chemistry A 2016 - vol. 4(Issue 14) pp:NaN5136-5136
Publication Date(Web):2016/03/07
DOI:10.1039/C6TA00909C
A facile and green method has been developed for the aqueous solution preparation of CuOX as an anode buffer layer for organic solar cells (OSCs). The CuOX buffer layer is prepared simply by spin-coating a copper acetylacetonate precursor based aqueous solution onto an ITO substrate at room temperature in ambient air. Hydrogen peroxide (H2O2) is used to modify the precursor aqueous solution and can greatly increase the work function of the CuOX film to improve the hole collection efficiency and the charge transport efficiency. UV-ozone post-treatment of the CuOX film leads to the fully oxidized state of copper oxide, which significantly improves the performance of OSCs. Through H2O2 modification and UV-ozone post-treatment on the CuOX anode buffer layer, the highest power conversion efficiency of the OSCs based on PTB7:PC71BM blends reaches 8.68%, which is 10% higher than that of the standard PEDOT:PSS anode buffer layer based OSCs. In addition, the devices with the CuOX buffer layer show much better air stability than those with PEDOT:PSS. Our results indicate that the aqueous solution processed CuOX with low cost and green solvents is a promising anode buffer layer material for efficient and stable OSCs.
Co-reporter:Ru Bai, Mi Ouyang, Zhi-Zhuo Li, Li-Gong Yang, Min-Min Shi, Gang Wu, Mang Wang and Hong-Zheng Chen
Journal of Materials Chemistry A 2008 - vol. 18(Issue 36) pp:NaN4323-4323
Publication Date(Web):2008/08/01
DOI:10.1039/B804958K
Highly-ordered and well-aligned fullerene nanofibre arrays were fabricated via a nanotemplate preparation method and surface-wetting technique. The as-prepared fullerene nanofibre arrays were characterized by field-emission scanning electron microscopy, transmission electron microscopy, ultraviolet-visible absorption spectra and X-ray diffraction analysis. The dual-layered photoreceptors containing the fullerene nanofibre arrays or bulk fullerene films as the charge-generation layer (CGL) were fabricated. The photosensitivity of photoreceptors with fullerene nanoarrays as CGL was improved by one order of magnitude compared to that of their bulk films. The effect of the diameter and the length of the fullerene nanofibres on the photosensitivity of the photoreceptors was also investigated.
Co-reporter:Hangqi Shi, Weifei Fu, Minmin Shi, Jun Ling and Hongzheng Chen
Journal of Materials Chemistry A 2015 - vol. 3(Issue 5) pp:NaN1905-1905
Publication Date(Web):2014/12/16
DOI:10.1039/C4TA06035K
A new diketopyrrolopyrrole derivative with appropriate energy levels and bipolar charge-transport properties is designed and synthesized. When this molecule is used as either electron donor or acceptor, the resulting organic solar cells both give the power conversion efficiencies over 3%.
Co-reporter:Lijian Zuo, Chih-Yu Chang, Chu-Chen Chueh, Yunxiang Xu, Hongzheng Chen and Alex K.-Y. Jen
Journal of Materials Chemistry A 2016 - vol. 4(Issue 3) pp:NaN968-968
Publication Date(Web):2015/12/07
DOI:10.1039/C5TA09247G
Series-connected tandem organic photovoltaic devices (SCTOPVs) have been shown to provide higher power conversion efficiencies (PCEs) than the single junction devices due to the improved light harvesting. To achieve the optimal device performance of SCTOPVs, balancing the photocurrents generated from the sub-cells is critical according to the Kirchhoff law. In this work, we demonstrate that the out-of-cell capping layer of an ITO-free microcavity SCTOPV plays an important role in manipulating the optical field distribution in the constituent sub-cells for achieving balanced photocurrents and optimal photovoltaic performance. Two mirror-like electrodes, a semi-transparent ultrathin Ag capped with a dielectric TeO2 layer and a thick Ag electrode were used to construct an ITO-free top-illuminated microcavity configuration, in which certain frequencies of solar irradiance can resonate between the reflective surfaces. As a result, a top-illuminated ITO-free SCTOPV with a comparable performance (7.4%) to the ITO-based counterpart (7.5%) was demonstrated despite the inferior transmittance of the ultra-thin Ag relative to ITO.
Co-reporter:Xiaolian Hu, Lijian Zuo, Weifei Fu, Thue T. Larsen-Olsen, Martin Helgesen, Eva Bundgaard, Ole Hagemann, Minmin Shi, Frederik C. Krebs and Hongzheng Chen
Journal of Materials Chemistry A 2012 - vol. 22(Issue 31) pp:
Publication Date(Web):
DOI:10.1039/C2JM31700A
Co-reporter:Xi Yang, Wenqing Liu, Min Xiong, Yingying Zhang, Tao Liang, Jingting Yang, Mingsheng Xu, Jian Ye and Hongzheng Chen
Journal of Materials Chemistry A 2014 - vol. 2(Issue 36) pp:NaN14806-14806
Publication Date(Web):2014/07/16
DOI:10.1039/C4TA03178D
A novel hole transport layer (HTL) composed of ultrathin two-dimensional, molybdenum disulfide (MoS2) sheets decorated with 20 nm gold nanoparticles (NPs) (MoS2@Au) was developed to make use of plasmonics for organic solar cells (OSCs). Both experimental and theoretical simulations revealed that the device with the MoS2@Au composite as the HTL exhibited enhanced short-circuit photocurrent density (Jsc) and efficiency compared to that with MoS2 alone as the HTL.
Co-reporter:Lei Fu, Weifei Fu, Pei Cheng, Zhixin Xie, Congcheng Fan, Minmin Shi, Jun Ling, Jianhui Hou, Xiaowei Zhan and Hongzheng Chen
Journal of Materials Chemistry A 2014 - vol. 2(Issue 18) pp:NaN6597-6597
Publication Date(Web):2014/02/19
DOI:10.1039/C3TA13534A
We designed and synthesized a diketopyrrolopyrrole (DPP) molecule with a fully-planar molecular geometry, 3,6-bis{5-[(ethylfuran-2-carboxylate)-2-yl]thiophene-2-yl}-2,5-bis(2-ethylhexyl)pyrrolo[3,4-c]pyrrole-1,4-dione (DPP(CF)2), for solution-processable organic solar cells (OSCs). It is theoretically calculated that the dihedral angles between the two furan-2-carboxylate end-groups and the DPP core are both only 0.56°. Due to this negligible steric distortion, the molecular conformation of DPP(CF)2 can be considered fully coplanar, leading to a higher crystallinity for the DPP(CF)2 film. As a result, the hole mobility of DPP(CF)2 is one order of magnitude higher than that of the DPP derivative with thiophene-2-carboxylate as the end-group (DPP(CT)2). DPP(CF)2 exhibits both a low optical band gap (Eg) of 1.60 eV and a low-lying highest occupied molecular orbital (HOMO) energy level of −5.33 eV, implying that DPP(CF)2 is a promising electron donor for OSCs. OSCs with DPP(CF)2 or DPP(CT)2 as the electron donor and [6,6]-phenyl-C71-butyric acid methyl ester (PC71BM) as the electron acceptor were fabricated. It is found that the DPP(CF)2-based devices exhibit much better photovoltaic performance than the DPP(CT)2-based devices, with the highest power conversion efficiency of 5.37% and a short-circuit current density of 11.4 mA cm−2. This phenomenon can be ascribed to the superior charge-transporting ability of DPP(CF)2 due to its fully-planar molecular geometry.
Co-reporter:Tao Ye, Weifei Fu, Jiake Wu, Zhikai Yu, Xinyi Jin, Hongzheng Chen and Hanying Li
Journal of Materials Chemistry A 2016 - vol. 4(Issue 4) pp:NaN1217-1217
Publication Date(Web):2015/12/22
DOI:10.1039/C5TA10155G
We have successfully grown single-crystalline lead halide perovskite arrays on a poly(3,4-ethylene dioxythiophene):polystyrenesulfonic acid (PEDOT:PSS) coated ITO substrate by the droplet-pinned crystallization (DPC) method and, for the first time, single-crystalline perovskite solar cells have been fabricated with a power conversion efficiency of 1.73%.
Co-reporter:Shuixing Li, Wenqing Liu, Chang-Zhi Li, Feng Liu, Yingzhu Zhang, Minmin Shi, Hongzheng Chen and Thomas P. Russell
Journal of Materials Chemistry A 2016 - vol. 4(Issue 27) pp:NaN10665-10665
Publication Date(Web):2016/06/14
DOI:10.1039/C6TA04232E
Perylene diimide (PDI), which features intense absorption, a low-lying energy level, and high electron mobility, is a promising building block for electron acceptors in organic solar cells (OSCs). However, this planar molecule has a strong tendency to form large aggregates during film formation which strongly limits its OSC performance. Herein, we report a new and simple PDI derivative, B(PDI)3, in which a central benzene unit is employed to connect three PDI arms. This compact arrangement of sterically bulky PDI moieties leads to a twisted molecular geometry of the resultant structure. This suppresses the strong crystallization tendency of PDI chromophores, owing to the broken molecular coplanarity and symmetry. Therefore, B(PDI)3 is applied as a non-fullerene acceptor in OSCs, providing a good power conversion efficiency of 5.65% when blended with the PTB7-Th donor.
Co-reporter:Shuixing Li, Zhongqiang Zhang, Minmin Shi, Chang-Zhi Li and Hongzheng Chen
Physical Chemistry Chemical Physics 2017 - vol. 19(Issue 5) pp:NaN3458-3458
Publication Date(Web):2016/12/20
DOI:10.1039/C6CP07465K
Nowadays, organic solar cells (OSCs) with efficiencies over 10% have been achieved through the elaborate design of electron donors and fullerene acceptors. However, the drawbacks of fullerene acceptors, like poor absorption, limited chemical and energetic tunabilities, high-cost purification and morphological instability, have become the bottlenecks for the further improvement of OSCs. To overcome the mentioned shortages from fullerene, research studies on non-fullerene electron acceptors have boomed. To date, the highest efficiency of fullerene-free OSCs has been pushed to be 12%, which surpasses that of fullerene-based OSCs. In this perspective, we focus on summarizing the development of small molecule electron acceptors designed to replace the fullerene derivatives. Since it has been revealed that the search for matched donor:acceptor pairs is important for accomplishing high efficiencies, we therefore divide electron acceptors into several categories according to the donors used in fullerene-free OSCs. After the introduction of these acceptors, we outline the designing rules as well as perspectives for the development of non-fullerene acceptors. We believe that the development of non-fullerene electron acceptors will make organic photovoltaics closer to practical applications.
![Anthra[2,1,9-def:6,5,10-d'e'f']diisoquinoline-1,3,8,10(2H,9H)-tetrone, 5-bromo-2,9-bis(1-pentylhexyl)-](/data/chemimg/3731700/1309387-42-5.png)
![Anthra[2,1,9-def:6,5,10-d'e'f']diisoquinoline-1,3,8,10(2H,9H)-tetrone, 5-bromo-2,9-bis(1-pentylhexyl)-](/data/chemimg/3731700/1309387-42-5_b.png)
![4H,8H-Benzo[1,2-c:4,5-c']dithiophene-4,8-dione, 1,3-bis(5-bromo-2-thienyl)-5,7-bis(2-ethylhexyl)-](/data/chemimg/3730500/1415929-78-0.png)
![4H,8H-Benzo[1,2-c:4,5-c']dithiophene-4,8-dione, 1,3-bis(5-bromo-2-thienyl)-5,7-bis(2-ethylhexyl)-](/data/chemimg/3730500/1415929-78-0_b.png)
![Dithieno[2,3-d:2',3'-d']-s-indaceno[1,2-b:5,6-b']dithiophene, 6,6,12,12-tetrakis(4-hexylphenyl)-6,12-dihydro-](/data/chemimg/3782000/1420071-64-2.png)
![Dithieno[2,3-d:2',3'-d']-s-indaceno[1,2-b:5,6-b']dithiophene, 6,6,12,12-tetrakis(4-hexylphenyl)-6,12-dihydro-](/data/chemimg/3782000/1420071-64-2_b.png)
![Pyrrolo[3,4-c]pyrrole-1,4-dione, 3,3'-(1,4-phenylenedi-5,2-thiophenediyl)bis[2,5-bis(2-ethylhexyl)-2,5-dihydro-6-(2-thienyl)-](/data/chemimg/3782000/1469884-52-3.png)
![Pyrrolo[3,4-c]pyrrole-1,4-dione, 3,3'-(1,4-phenylenedi-5,2-thiophenediyl)bis[2,5-bis(2-ethylhexyl)-2,5-dihydro-6-(2-thienyl)-](/data/chemimg/3782000/1469884-52-3_b.png)
![[2,2'-Bithiophene]-5-carboxylic acid, 5',5'''-[2,5-bis(2-ethylhexyl)-2,3,5,6-tetrahydro-3,6-dioxopyrrolo[3,4-c]pyrrole-1,4-diyl]bis-, 5,5''-diethyl ester](/data/chemimg/3782000/1416418-07-9.png)
![[2,2'-Bithiophene]-5-carboxylic acid, 5',5'''-[2,5-bis(2-ethylhexyl)-2,3,5,6-tetrahydro-3,6-dioxopyrrolo[3,4-c]pyrrole-1,4-diyl]bis-, 5,5''-diethyl ester](/data/chemimg/3782000/1416418-07-9_b.png)
![Pyrrolo[3,4-c]pyrrole-1,4-dione, 2,5-bis(2-ethylhexyl)-3-[5-(4-fluorophenyl)-2-thienyl]-2,5-dihydro-6-(2-thienyl)-](/data/chemimg/3782000/1421711-95-6.png)
![Pyrrolo[3,4-c]pyrrole-1,4-dione, 2,5-bis(2-ethylhexyl)-3-[5-(4-fluorophenyl)-2-thienyl]-2,5-dihydro-6-(2-thienyl)-](/data/chemimg/3782000/1421711-95-6_b.png)
![Pyrrolo[3,4-c]pyrrole-1,4-dione, 3-(5-bromo-2-thienyl)-2,5-bis(2-ethylhexyl)-2,5-dihydro-6-(5-phenyl-2-thienyl)-](/data/chemimg/3777600/1421711-97-8.png)
![Pyrrolo[3,4-c]pyrrole-1,4-dione, 3-(5-bromo-2-thienyl)-2,5-bis(2-ethylhexyl)-2,5-dihydro-6-(5-phenyl-2-thienyl)-](/data/chemimg/3777600/1421711-97-8_b.png)
![Pyrrolo[3,4-c]pyrrole-1,4-dione, 3,6-bis[5-(4-butylphenyl)-2-thienyl]-2,5-bis(2-ethylhexyl)-2,5-dihydro-](/data/chemimg/3777600/1558577-91-5.png)
![Pyrrolo[3,4-c]pyrrole-1,4-dione, 3,6-bis[5-(4-butylphenyl)-2-thienyl]-2,5-bis(2-ethylhexyl)-2,5-dihydro-](/data/chemimg/3777600/1558577-91-5_b.png)
![5H-Tribenzo[a,f,k]trindene-2,7,13-triamine, 5,5,10,10,15,15-hexahexyl-10,15-dihydro-N2,N2,N7,N7,N13,N13-hexakis(4-methoxyphenyl)-](/data/chemimg/3782000/1879983-76-2.png)
![5H-Tribenzo[a,f,k]trindene-2,7,13-triamine, 5,5,10,10,15,15-hexahexyl-10,15-dihydro-N2,N2,N7,N7,N13,N13-hexakis(4-methoxyphenyl)-](/data/chemimg/3782000/1879983-76-2_b.png)
![[2,2'-Bithiophene]-5-carbonitrile, 5'-[2,5-bis(2-ethylhexyl)-2,3,5,6-tetrahydro-3,6-dioxo-4-(2-thienyl)pyrrolo[3,4-c]pyrrol-1-yl]-](/data/chemimg/3782000/1883603-57-3.png)
![[2,2'-Bithiophene]-5-carbonitrile, 5'-[2,5-bis(2-ethylhexyl)-2,3,5,6-tetrahydro-3,6-dioxo-4-(2-thienyl)pyrrolo[3,4-c]pyrrol-1-yl]-](/data/chemimg/3782000/1883603-57-3_b.png)
![[2,2'-Bithiophene]-5-carbonitrile, 5'-[4-(5-bromo-2-thienyl)-2,5-bis(2-ethylhexyl)-2,3,5,6-tetrahydro-3,6-dioxopyrrolo[3,4-c]pyrrol-1-yl]-](/data/chemimg/3782000/1883603-58-4.png)
![[2,2'-Bithiophene]-5-carbonitrile, 5'-[4-(5-bromo-2-thienyl)-2,5-bis(2-ethylhexyl)-2,3,5,6-tetrahydro-3,6-dioxopyrrolo[3,4-c]pyrrol-1-yl]-](/data/chemimg/3782000/1883603-58-4_b.png)
![5H-Tribenzo[a,f,k]trindene-2,7,12-triamine, 5,5,10,10,15,15-hexahexyl-10,15-dihydro-N2,N2,N7,N7,N12,N12-hexakis(4-methoxyphenyl)-](/data/chemimg/3782000/1922933-11-6.png)
![5H-Tribenzo[a,f,k]trindene-2,7,12-triamine, 5,5,10,10,15,15-hexahexyl-10,15-dihydro-N2,N2,N7,N7,N12,N12-hexakis(4-methoxyphenyl)-](/data/chemimg/3782000/1922933-11-6_b.png)
![5H-Tribenzo[a,f,k]trindene-2,7,12-triamine, 5,5,10,10,15,15-hexahexyl-10,15-dihydro-N2,N2,N7,N7,N12,N12-hexakis(5-methoxy-2-thienyl)-](/data/chemimg/3782000/1922933-12-7.png)
![5H-Tribenzo[a,f,k]trindene-2,7,12-triamine, 5,5,10,10,15,15-hexahexyl-10,15-dihydro-N2,N2,N7,N7,N12,N12-hexakis(5-methoxy-2-thienyl)-](/data/chemimg/3782000/1922933-12-7_b.png)
![5H-Tribenzo[a,f,k]trindene-2,7,12-triamine, 5,5,10,10,15,15-hexahexyl-10,15-dihydro-N2,N2,N7,N7,N12,N12-hexakis[4-(methylthio)phenyl]-](/data/chemimg/3782000/1922933-13-8.png)
![5H-Tribenzo[a,f,k]trindene-2,7,12-triamine, 5,5,10,10,15,15-hexahexyl-10,15-dihydro-N2,N2,N7,N7,N12,N12-hexakis[4-(methylthio)phenyl]-](/data/chemimg/3782000/1922933-13-8_b.png)
![[2,2'-Bithiophene]-4,5-dicarboxylic acid, 5'-[4-[4',5'-bis(ethoxycarbonyl)[2,2'-bithiophen]-5-yl]-2,5-bis(2-ethylhexyl)-2,3,5,6-tetrahydro-3,6-dioxopyrrolo[3,4-c]pyrrol-1-yl]-, 4,5-diethyl ester](/data/chemimg/3777600/2077861-99-3.png)
![[2,2'-Bithiophene]-4,5-dicarboxylic acid, 5'-[4-[4',5'-bis(ethoxycarbonyl)[2,2'-bithiophen]-5-yl]-2,5-bis(2-ethylhexyl)-2,3,5,6-tetrahydro-3,6-dioxopyrrolo[3,4-c]pyrrol-1-yl]-, 4,5-diethyl ester](/data/chemimg/3777600/2077861-99-3_b.png)
![5H-Tribenzo[a,f,k]trindene, 5,5,10,10,15,15-hexahexyl-10,15-dihydro-](http://img.cochemist.com/ccimg/600200/600172-85-8.png)
![5H-Tribenzo[a,f,k]trindene, 5,5,10,10,15,15-hexahexyl-10,15-dihydro-](http://img.cochemist.com/ccimg/600200/600172-85-8_b.png)
![[1]benzothieno[3,2-b][1]benzothiophene, 2,7-dioctyl-](http://img.cochemist.com/ccimg/583100/583050-70-8.png)
![[1]benzothieno[3,2-b][1]benzothiophene, 2,7-dioctyl-](http://img.cochemist.com/ccimg/583100/583050-70-8_b.png)
![Poly[2,7-(9,9-di-octyl-fluorene)-alt-4,7-bis(thiophen-2-yl)benzo-2,1,3-thiadiazole]](/data/chemimg/133300/782469-77-6.png)
![Poly[2,7-(9,9-di-octyl-fluorene)-alt-4,7-bis(thiophen-2-yl)benzo-2,1,3-thiadiazole]](/data/chemimg/133300/782469-77-6_b.png)
![3'H-Cyclopropa[1,2][5,6]fullerene-C60-Ih-3'-butanoic acid, 3'-phenyl-, methyl ester](/data/chemimg/102800/824404-45-7.png)
![3'H-Cyclopropa[1,2][5,6]fullerene-C60-Ih-3'-butanoic acid, 3'-phenyl-, methyl ester](/data/chemimg/102800/824404-45-7_b.png)
![Pyrrolo[3,4-c]pyrrole-1,4-dione, 3-(5-bromo-2-thienyl)-2,5-bis(2-ethylhexyl)-2,5-dihydro-6-(2-thienyl)-](/data/chemimg/139400/1308671-90-0.png)
![Pyrrolo[3,4-c]pyrrole-1,4-dione, 3-(5-bromo-2-thienyl)-2,5-bis(2-ethylhexyl)-2,5-dihydro-6-(2-thienyl)-](/data/chemimg/139400/1308671-90-0_b.png)
![2,5-Bis(2-ethylhexyl)-3,6-di(thiophen-2-yl)pyrrolo[3,4-c]pyrrole-1,4(2H,5H)-dione](http://img.cochemist.com/ccimg/1185900/1185885-86-2.png)
![2,5-Bis(2-ethylhexyl)-3,6-di(thiophen-2-yl)pyrrolo[3,4-c]pyrrole-1,4(2H,5H)-dione](http://img.cochemist.com/ccimg/1185900/1185885-86-2_b.png)
![Pyrrolo[3,4-c]pyrrole-1,4-dione, 3,6-bis(5-bromo-2-thienyl)-2,5-bis(2-ethylhexyl)-2,5-dihydro-](/data/chemimg/139400/1000623-95-9.png)
![Pyrrolo[3,4-c]pyrrole-1,4-dione, 3,6-bis(5-bromo-2-thienyl)-2,5-bis(2-ethylhexyl)-2,5-dihydro-](/data/chemimg/139400/1000623-95-9_b.png)
![Poly[(9,9-dioctylfluorenyl-2,7-diyl)-alt-(benzo[2,1,3]thiadiazol-4,7-diyl)]](/data/chemimg/107700/210347-52-7.png)
![Poly[(9,9-dioctylfluorenyl-2,7-diyl)-alt-(benzo[2,1,3]thiadiazol-4,7-diyl)]](/data/chemimg/107700/210347-52-7_b.png)
![Poly[2,6-(4,4-bis-(2-ethylhexyl)-4H-cyclopenta[2,1-b;3,4-b']dithiophene)-alt-4,7(2,1,3-benzothiadiazole)]](/data/chemimg/102300/920515-34-0.png)
![Poly[2,6-(4,4-bis-(2-ethylhexyl)-4H-cyclopenta[2,1-b;3,4-b']dithiophene)-alt-4,7(2,1,3-benzothiadiazole)]](/data/chemimg/102300/920515-34-0_b.png)
![N2,N2,N2',N2',N7,N7,N7',N7'-Octakis(4-methoxyphenyl)-9,9'-spirobi[fluorene]-2,2',7,7'-tetraamine](http://img.cochemist.com/ccimg/207800/207739-72-8.png)
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