Co-reporter:Xiaoyu Liu, Jialin Wang, Jiajun Peng, and Ziqi Liang
Macromolecules September 12, 2017 Volume 50(Issue 17) pp:6954-6954
Publication Date(Web):August 23, 2017
DOI:10.1021/acs.macromol.7b01509
Recently, the ternary blend method has been successfully applied to nonfullerene organic solar cells (OSCs) and enhanced the device performance by utilizing complementary optical absorption. Here we demonstrate the two polymer donors and one small-molecule acceptor (i.e., 2D/1A) strategy to finely regulate the blend film morphology in fullerene-free OSCs. One crystalline polymer donor, PffBT4T–2OD, can act as an effective morphology regulator for a benchmark blend of PTB7–Th and ITIC, leading to appropriate phase-separated morphology, suppressed charge recombination, efficient charge transport and high carrier mobility. The resulting solvent additive- and annealing-free fabricated bulk-heterojunction OSCs show the best power conversion efficiency (PCE) of 8.22% with a significant increase of fill factor compared to their binary counterparts. Importantly, such ternary OSCs when processed under ambient condition retain excellent device performance with a PCE of 7.57%, indicative of good air-stability.
Co-reporter:Jialin Wang, Jiajun Peng, Xiaoyu Liu, and Ziqi Liang
ACS Applied Materials & Interfaces June 21, 2017 Volume 9(Issue 24) pp:20704-20704
Publication Date(Web):June 1, 2017
DOI:10.1021/acsami.7b03757
Planar perylene diimides (PDIs), when used as nonfullerene acceptors for organic photovoltaics, are constrained by their large π-aggregation in solid state. To tackle this issue, another planar nonfullerene acceptor 3,9-bis(2-methylene-(3-(1,1-dicyanomethylene)-indanone)-5,5,11,11-tetrakis(4-hexylphenyl)-dithieno[2,3-d:2′,3′-d′]-s-indaceno[1,2-b:5,6-b′]dithiophene (ITIC) with weak crystallinity and near-infrared light absorption is introduced into the PTB7-Th:PDI binary blend to fabricate efficient and stable ternary solar cells. We have finely tuned the PDI/ITIC weight ratio to investigate the influences of individual ITIC and PDI on the optical, electronic, and morphological properties of the PTB7-Th:ITIC:PDI ternary blend. Compared to the binary blend, complementary optical absorption is achieved in all ternary blends. More importantly, it is found that ITIC plays a critical role on largely suppressing the PDI aggregates in the PTB7-Th:PDI blend, while PDI aids to form an interpenetrating network morphology to facilitate charge transport in the PTB7-Th:ITIC blend. Consequently, when the PDI/ITIC ratio is 3:7 (w/w), the PTB7-Th:ITIC:PDI based inverted solar cells exhibit the highest power conversion efficiency of 8.64% due to their favorable out-of-plane π–π stacking, finest phase-separation morphology, and highest charge mobility. Remarkably, the optimal cells that are solution-processed in air show the promising efficiency of 7.09%, suggesting good ambient stability of such ternary solar cells.Keywords: aggregation; air stability; phase miscibility; planar perylene diimide; ternary organic solar cells;
Co-reporter:Yijing Sun, Dongsheng Chen, Ziqi Liang
Materials Today Energy 2017 Volume 5(Volume 5) pp:
Publication Date(Web):1 September 2017
DOI:10.1016/j.mtener.2017.04.008
•Solution chemistry and structural characterization methods for MXenes.•MXene-based electrodes for batteries and supercapacitors.•Potential thermoelectric applications of semiconducting MXenes.An emerging family of layered early transition metal carbides and/or nitrides—MXenes—has been intensively investigated by both theoretical calculations and experimental research to explore their unique properties and potential applications. The two-dimensional film morphology coupled with a fascinating combination of metallic conductivity and the hydrophilic nature of their functionalized surface render them as promising candidates for a wide range of utilizations. This article reviews recent advances on MXenes and their composites with either polymers or small molecules. Their wet chemistry and structural characterization are first described. Then we discuss in detail their numerous applications of energy storage and conversion including supercapacitors, batteries and thermoelectric devices. In particular, their electrochemical and thermoelectric properties, performances and mechanisms are presented with regard to their respective structures, compositions and fabrication methods. Finally, a conclusion of recent progress on MXenes is made with a perspective for their possible future directions.
Co-reporter:Minhong He;Xinfang Gao;Bin Liu;Jun Zhou
RSC Advances (2011-Present) 2017 vol. 7(Issue 70) pp:44254-44258
Publication Date(Web):2017/09/11
DOI:10.1039/C7RA07714A
Herein we report the solution fabrication of highly conductive and bendable conductors based on Ag nanowires (NWs) embedded within a polyvinylidene fluoride matrix. A typical percolation behavior of electrical conductivity is observed due to the formation of a conductive network. The highest conductivity, 1.77 × 104 S cm−1, is achieved at 80 wt% Ag NWs and it remains nearly unchanged after 1000 bending events.
Co-reporter:Jiajun Peng;Yani Chen;Kaibo Zheng;Tõnu Pullerits
Chemical Society Reviews 2017 vol. 46(Issue 19) pp:5714-5729
Publication Date(Web):2017/10/02
DOI:10.1039/C6CS00942E
Organo-metal halide perovskites have recently obtained world-wide attention as promising solar cell materials. They have broad and strong light absorption along with excellent carrier transport properties which partially explain their record power conversion efficiencies above 22%. However, the basic understanding of the underlying physical mechanisms is still limited and there remain large discrepancies among reported transport characteristics of perovskite materials. Notably, the carrier mobility of perovskite samples either in thin films or within solar cells obtained using different techniques can vary by up to 7–8 orders of magnitude. This tutorial review aims to offer insights into the scope, advantages, limitations and latest developments of the techniques that have been applied for studying charge carrier dynamics in perovskites. We summarize a comprehensive set of measurements including (1) time-resolved laser spectroscopies (transient absorption, time-resolved photoluminescence, terahertz spectroscopy and microwave conductivity); (2) electrical transient techniques (charge extraction by linearly increasing voltage and time-of-flight); and (3) steady-state methods (field-effect transistor, Hall effect and space charge limited current). Firstly, the basics of the above measurements are described. We then comparatively summarize the charge carrier characteristics of perovskite-based neat films, bilayer films and solar cells. Finally, we compare the different approaches in evaluating the key parameters of transport dynamics and unravel the reasons for the large discrepancies among these methods. We anticipate that this tutorial review will serve as the entry point for understanding the experimental results from the above techniques and provide insights into charge carrier dynamics in perovskite materials and devices.
Co-reporter:Yani Chen;Yong Sun;Jiajun Peng;Wei Zhang;Xiaojun Su;Kaibo Zheng;Tõnu Pullerits
Advanced Energy Materials 2017 Volume 7(Issue 18) pp:
Publication Date(Web):2017/09/01
DOI:10.1002/aenm.201700162
2D perovskites have recently been shown to exhibit significantly improved environmental stability. Derived from their 3D analogues, 2D perovskites are formed by inserting bulky alkylammonium cations in-between the anionic layers. However, these insulating organic spacer cations also hinder charge transport. Herein, such a 2D perovskite, (iso-BA)2(MA)3Pb4I13, that contains short branched-chain spacer cations (iso-BA+) and shows a remarkable increase of optical absorption and crystallinity in comparison to the conventional linear one, n-BA+, is designed. After applying the hot-casting (HC) technique, all these properties are further improved. The HC (iso-BA)2(MA)3Pb4I13 sample exhibits the best ambient stability by maintaining its initial optical absorption after storage of 840 h in an environmental chamber at 20 °C with a relative humidity of 60% without encapsulation. More importantly, the out-of-plane crystal orientation of (iso-BA)2(MA)3Pb4I13 film is notably enhanced, which increases cross-plane charge mobility. As a result, the highest power conversion efficiencies (PCEs) measured from for current density versus voltage curves afford 8.82% and 10.63% for room-temperature and HC-processed 2D perovskites based planar solar cells, respectively. However, the corresponding steady-state PCEs are remarkably lower, which is presumably due to the significant hysteresis phenomena caused by low charge extraction efficiency at interfaces of C60/2D perovskites.
Co-reporter:Jingwei Sun;Yani Chen
Advanced Functional Materials 2016 Volume 26( Issue 17) pp:2783-2799
Publication Date(Web):
DOI:10.1002/adfm.201505013
Modulation of luminescent color or intensity by varying external stimuli, such as temperature, light, ion concentration, etc., has received increasing attention recently because of numerous applications such as sensors, bioanalysis, optical imaging and memories. For instance, electrically induced luminescent switching — electroluminochromism (ELC) — is one of the most powerful and promising approaches to implement controllable emission due to its facile and precise operation. Recent years have witnessed significant advances in ELC research in the context of materials development and device optimizations. This feature article reviews the fundamentals and recent progress in this emerging field, focusing on working mechanisms, materials, devices and performance improvements. Perspectives for future ELCs are also outlined.
Co-reporter:Jingwei Sun and Ziqi Liang
ACS Applied Materials & Interfaces 2016 Volume 8(Issue 28) pp:18301-18308
Publication Date(Web):June 27, 2016
DOI:10.1021/acsami.6b05661
Electrofluorochromic (EFC) materials, which exhibit electrochemically controllable fluorescence, hold great promise in optoelectronic devices and biological analysis. Here we design such donor–acceptor (D−A) conjugated polymers—P(TPACO) and P(TCEC)—that contain the same electron-rich and oxidizable polytriphenylamine (PTPA) as π-backbone, yet with different electron-deficient ketone and cyano units as pendant groups, respectively. They both exhibit solvatochromic effects due to intrinsic characteristics of intramolecular charge transfer (ICT). Compared to P(TPACO), P(TCEC) shows stronger ICT, which leads to higher electrochemical oxidation potential and lower ion diffusion coefficient. Moreover, both polymers present simultaneous electrochromic (EC) and EFC behaviors with multistate display and remarkably rapid fluorescence response. The response time of P(TPACO) is as short as 0.19 s, nearly 4-fold faster than that of P(TCEC) (0.92 s). Such rapid response is found to be determined by the ion diffusion coefficient which is associated with the ICT nature. Finally, the EFC display device based on P(TPACO) is successfully demonstrated, which shows green fluorescence ON/OFF switching upon applied potentials. This work has successfully demonstrated that swift EFCs can be achieved by rational modulation of the ICT effect in such D–A conjugated polymers.
Co-reporter:Jialin Wang and Ziqi Liang
ACS Applied Materials & Interfaces 2016 Volume 8(Issue 34) pp:22418
Publication Date(Web):August 11, 2016
DOI:10.1021/acsami.6b08284
Solvent additive has proven as a useful protocol for improving the film nanomorphology of polymer donor (D): fullerene acceptor (A) blends in bulk heterojunction (BHJ) photovoltaic cells. By contrast, the effect of such solvent additive on nonfullerene BHJ cells based on perylene diimide acceptor, for instance, is less effective because of their highly planar structure and strong π-aggregation in solid state. Here we choose N,N′-bis(1-ethylpropyl)-perylene-3,4,9,10-tetracarboxylic diimide (PDI) and thieno[3,4-b]thiophene-alt-benzodithiophene (PTB7) as a model D:A blend system to investigate how solvent engineering strategy synergistically impacts the blend film nanomorphology. Based on the differences of solvent volatility and solubility, various host solvents—chloroform (CF) and chlorobenzene (CB) and solvent additives—chloronaphthalene (CN) and 1,8-diiodooctane (DIO) are selected for comparative studies. It is found that the π-aggregation of PDIs can be largely suppressed by using low-boiling point (Tb) CF solvent, yet enlarged by using high-Tb CB. Moreover, CN additive provides good solubility of PDI molecules and hence reduces large PDI aggregates in CB system, while DIO exhibiting poor solubility works oppositely. By contrast, DIO that presents larger Tb difference with CF prolongs the film-forming, which assists in optimizing the PDI aggregation and increases the intermixed PTB7:PDI phases more significantly than CN in CF system, yielding the finest phase-separation morphology and balanced charge mobility. Consequently, the inverted BHJ cells based on CF-processed PTB7:PDI blend film with 0.4 vol % DIO exhibit the highest PCE of 3.55% with a fill factor of 56%, both of which are among the best performance for such a paradigm PTB7:PDI blend-based BHJ cells.Keywords: aggregation; nonfullerene; organic photovoltaics; perylene diimide; solvent engineering
Co-reporter:Yani Chen;Minhong He;Jiajun Peng;Yong Sun
Advanced Science 2016 Volume 3( Issue 4) pp:
Publication Date(Web):
DOI:10.1002/advs.201500392
Recently, organic–inorganic halide perovskites have sparked tremendous research interest because of their ground-breaking photovoltaic performance. The crystallization process and crystal shape of perovskites have striking impacts on their optoelectronic properties. Polycrystalline films and single crystals are two main forms of perovskites. Currently, perovskite thin films have been under intensive investigation while studies of perovskite single crystals are just in their infancy. This review article is concentrated upon the control of perovskite structures and growth, which are intimately correlated for improvements of not only solar cells but also light-emitting diodes, lasers, and photodetectors. We begin with the survey of the film formation process of perovskites including deposition methods and morphological optimization avenues. Strategies such as the use of additives, thermal annealing, solvent annealing, atmospheric control, and solvent engineering have been successfully employed to yield high-quality perovskite films. Next, we turn to summarize the shape evolution of perovskites single crystals from three-dimensional large sized single crystals, two-dimensional nanoplates, one-dimensional nanowires, to zero-dimensional quantum dots. Siginificant functions of perovskites single crystals are highlighted, which benefit fundamental studies of intrinsic photophysics. Then, the growth mechanisms of the previously mentioned perovskite crystals are unveiled. Lastly, perspectives for structure and growth control of perovskites are outlined towards high-performance (opto)electronic devices.
Co-reporter:Jiajun Peng;Yani Chen;Xianfeng Zhang;Angang Dong
Advanced Science 2016 Volume 3( Issue 6) pp:
Publication Date(Web):
DOI:10.1002/advs.201500432
Co-reporter:Jialin Wang;Lingqiang Kong
Macromolecular Chemistry and Physics 2016 Volume 217( Issue 13) pp:1513-1520
Publication Date(Web):
DOI:10.1002/macp.201600072
Co-reporter:Jiajun Peng, Yong Sun, Yani Chen, Yao Yao, and Ziqi Liang
ACS Energy Letters 2016 Volume 1(Issue 5) pp:1000
Publication Date(Web):October 18, 2016
DOI:10.1021/acsenergylett.6b00393
Pre-exposure of perovskite solar cells to light or heat can greatly improve their performance, yet the underlying physical mechanisms are still obscure. Herein we systematically investigate the influences of light soaking and thermal phase transition on charge transport dynamics in two-step fabricated CH3NH3PbI3 perovskite solar cells. By applying the time-of-flight (TOF) measurement under various light illumination times, we not only confirm the existence of nondispersive charge transport in perovskite solar cells but also directly observe a shallow trap filling process and thus increased charge mobility upon light soaking. We further employ the delay-time-dependent charge extraction by linearly increasing voltage (CELIV) technique to reveal that dispersive bimolecular recombination is also largely inhibited. On the other hand, we conduct temperature-dependent TOF and electrical conductivity studies and surprisingly find a rapid change of both hole and electron mobilities during phase transition from tetragonal to cubic crystalline structures at around 310–330 K until reaching a balance of charge transport.
Co-reporter:Jiajun Peng;Xiaoqing Chen;Yani Chen;Oskar J. Sberg;Ronald Österbacka
Advanced Electronic Materials 2016 Volume 2( Issue 3) pp:
Publication Date(Web):
DOI:10.1002/aelm.201500333
We have utilized the metal–insulator–semiconductor charge extraction by linearly increasing voltage (MIS-CELIV) technique to clarify the hole- and electron-transport properties in benchmark poly(3-hexylthiophene) (P3HT) and its blend with phenyl-C61-butyric acid methyl ester (PCBM) by using a thick lithium fluoride (LiF) as the charge-blocking layer. Both dark and light MIS-CELIV are employed to comparatively investigate the differences in the recombination process and charge mobilities in neat P3HT and P3HT:PCBM blends. Our studies quantitatively show that balanced hole and electron transport can be achieved in the P3HT:PCBM blend under light illumination, leading to a high efficiency in the photovoltaic cell. Furthermore, light MIS-CELIV can be employed as a novel method to directly evaluate the capability of photoelectric conversion of organic photovoltaic materials.
Co-reporter:Dongsheng Chen;Yan Zhao;Yani Chen;Tingyu Lu;Yuanyuan Wang;Jun Zhou
Advanced Electronic Materials 2016 Volume 2( Issue 6) pp:
Publication Date(Web):
DOI:10.1002/aelm.201500473
Co-reporter:Yani Chen, Yan Zhao and Ziqi Liang
Energy & Environmental Science 2015 vol. 8(Issue 2) pp:401-422
Publication Date(Web):07 Nov 2014
DOI:10.1039/C4EE03297G
Organic semiconductor materials have advantages of low cost, light weight, mechanical flexibility and low-temperature solution processability over large areas, enabling the development of personal, portable, and flexible thermal modules. This review article summarizes the recent progress made in the area of organic thermoelectrics (TEs), including organic molecular structures, devices, characterization methods, and approaches to improve the performance. We begin with the discussion of each TE parameter and particularly their correlations in organic TEs. Then the TE applications of molecular organic semiconductors, poly(3,4-ethylenedioxythiophene), polymer nanostructures and molecular junctions are reviewed. Next we turn to highlight the nanocomposites of polymers and carbon nanotubes or nanocrystals, which lead to enhanced TEs. Interestingly, the merging of TEs and photovoltaics offers a new direction towards a great capability of electric energy output. Critical challenges of organic TE materials include stability, sample preparation and measurement techniques, which are also discussed. Finally, the relationships among organic semiconductor structures, hybrid composites, doping states, film morphology and TE performance are revealed, and a viable avenue is envisioned for synergistic optimization of organic TEs.
Co-reporter:Yani Chen, Yixin Zhao, and Ziqi Liang
Chemistry of Materials 2015 Volume 27(Issue 5) pp:1448
Publication Date(Web):February 19, 2015
DOI:10.1021/acs.chemmater.5b00041
Co-reporter:Yani Chen, Yixin Zhao and Ziqi Liang
Journal of Materials Chemistry A 2015 vol. 3(Issue 17) pp:9137-9140
Publication Date(Web):13 Mar 2015
DOI:10.1039/C5TA01198A
We demonstrate that nonvolatile CaCl2 additives can significantly improve the film morphology of CH3NH3PbI3. Unlike those volatile chlorinated additives, a small portion of Cl anions from CaCl2 seem to enter into the CH3NH3PbI3 crystal, yet most insulating CaCl2 remains within the perovskite film, which is detrimental to perovskite solar cells.
Co-reporter:Minhong He, Yani Chen, Hui Liu, Jialin Wang, Xiaosheng Fang and Ziqi Liang
Chemical Communications 2015 vol. 51(Issue 47) pp:9659-9661
Publication Date(Web):11 May 2015
DOI:10.1039/C5CC02282G
A facile in situ solution method was developed for chemical decoration of CH3NH3PbI3 perovskites with reduced graphene oxides (rGOs) to significantly improve the photodetector performance. Such CH3NH3PbI3/rGO molecular hybrids show a 6 times higher ON/OFF ratio and notably faster response speed than neat CH3NH3PbI3.
Co-reporter:Yin Zhang, Juan Du, Xiaohan Wu, Guoqian Zhang, Yingli Chu, Dapeng Liu, Yixin Zhao, Ziqi Liang, and Jia Huang
ACS Applied Materials & Interfaces 2015 Volume 7(Issue 39) pp:21634
Publication Date(Web):September 21, 2015
DOI:10.1021/acsami.5b05221
CH3NH3PbI3 perovskite-based optoelectronics have attracted intense research interests recently because of their easy fabrication process and high power conversion efficiency. Herein, we report a novel photodetector based on unique CH3NH3PbI3 perovskite films with island-structured morphology. The light-induced electronic properties of the photodetectors were investigated and compared to those devices based on conventional compact CH3NH3PbI3 films. The island-structured CH3NH3PbI3 photodetectors exhibited a rapid response speed (<50 ms), good stability at a temperature of up to 100 °C, a large photocurrent to dark current ratio (Ilight/Idark > 1 × 104 under an incident light of ∼6.59 mW/cm2, and Ilight/Idark > 1 × 102 under low incident light ∼0.018 mW/cm2), and excellent reproducibility. Especially, the performance of the island-structured devices markedly exceed that of the conventional compact CH3NH3PbI3 thin-film devices. These excellent performances render the island-structured device to be potentially applicable for a wide range of optoelectronics.Keywords: CH3NH3PbI3 perovskites; high sensitivity; island-structured thin film, sensor; photodetector
Co-reporter:Jiajun Peng, Yani Chen, Xiaohan Wu, Qian Zhang, Bin Kan, Xiaoqing Chen, Yongsheng Chen, Jia Huang, and Ziqi Liang
ACS Applied Materials & Interfaces 2015 Volume 7(Issue 24) pp:13137
Publication Date(Web):June 11, 2015
DOI:10.1021/acsami.5b03073
Efficient charge transport is a key step toward high efficiency in small-molecule organic photovoltaics. Here we applied time-of-flight and organic field-effect transistor to complementarily study the influences of molecular structure, trap states, and molecular orientation on charge transport of small-molecule DRCN7T (D1) and its analogue DERHD7T (D2). It is revealed that, despite the subtle difference of the chemical structures, D1 exhibits higher charge mobility, the absence of shallow traps, and better photosensitivity than D2. Moreover, charge transport is favored in the out-of-plane structure within D1-based organic solar cells, while D2 prefers in-plane charge transport.Keywords: charge mobility; organic field-effect transistor; organic photovoltaics; time-of-flight; transport dynamics; π-conjugated small molecules;
Co-reporter:Dongsheng Chen, Yan Zhao, Yani Chen, Biao Wang, Yuanyuan Wang, Jun Zhou, and Ziqi Liang
ACS Applied Materials & Interfaces 2015 Volume 7(Issue 44) pp:24403
Publication Date(Web):October 25, 2015
DOI:10.1021/acsami.5b08011
As a new class of potential midrange temperature thermoelectric materials, quaternary chalcogenides like Cu2ZnSnS4 (CZTS) and Cu2ZnSnSe4 (CZTSe) suffer from low electrical conductivity due to insufficient doping. In this work, Cu-doped CZTSe nanocrystals consisting of polygon-like nanoparticles are synthesized with sufficient Cu doping contents. The hot-injection synthetic method, rather than the traditional one-pot method, in combination with the hot-pressing method is employed to produce the CZTSe nanocrystals. In Cu-doped CZTSe nanocrystals, the electrical conductivity is enhanced by substitution of Zn2+ with Cu+, which introduces additional holes as charge carriers. Meanwhile, the existence of boundaries between nanoparticles in as-synthesized CZTSe nanocrystals collectively results in intensive phonon-boundary scatterings, which remarkably reduce the lattice thermal conductivity. As a result, an average thermoelectric figure of merit of 0.70 is obtained at 450 °C, which is significantly larger than that of the state-of-the-art quaternary chalcogenides thermoelectric materials. The theoretical calculations from the Boltzmann transport equations and the modified effective medium approximation are in good agreement with the experimental data.Keywords: Cu2ZnSnSe4; figure of merit; hot-injection; nanocrystals; thermoelectric materials
Co-reporter:Dongsheng Chen, Yan Zhao, Yani Chen, Biao Wang, Haiyan Chen, Jun Zhou, and Ziqi Liang
ACS Applied Materials & Interfaces 2015 Volume 7(Issue 5) pp:3224
Publication Date(Web):January 21, 2015
DOI:10.1021/am507882f
ZnO as high-temperature thermoelectric material suffers from high lattice thermal conductivity and poor electrical conductivity. Al is often used to n-dope ZnO to form Zn1–xAlxO (AZO). Owing to very limited Al solubility (less than 2 atom %) in AZO, however, electrical conductivity is difficult to improve further. Moreover, such a low concentration of Al dopants can hardly reduce the thermal conductivity. Here, we propose slightly adding chemically reduced graphene oxides (rGOs) to AZO in various contents to modulate the carrier concentration and simultaneously optimize the electrical and thermal conductivities. Such nanocomposites with rGO embedded in AZO matrix are formed on the molecular level by one-step solution chemistry method. No obvious changes are found in crystalline structures of AZO after introducing rGOs. The rGO inclusions are shown to uniformly mix the AZO matrix that consists of compacted nanoparticles. In such AZO/rGO hybrids, Zn2+ is captured by the rGO, releasing extra electrons and thus increasing electron density, as confirmed by Hall measurements. The phonon-boundary scattering at the interface between AZO and rGO remarkably reduces the lattice thermal conductivity. Therefore, a respectable thermoelectric figure of merit of 0.28 at 900 °C is obtained in these nanocomposites at the rGO content of 1.5 wt %, which is 8 times larger than that of pure ZnO and 60% larger than that of alloyed AZO. This work demonstrates a facile wet chemistry route to produce nanostructured thermoelectric composites in which electrical conductivity can be greatly increased while largely lowering thermal conductivity, collectively enhancing the thermoelectric performance.Keywords: Al-doped ZnO; hybrids/nanocomposites; reduced graphene oxide; solution processing; thermoelectric materials
Co-reporter:Yani Chen, Jiajun Peng, Diqing Su, Xiaoqing Chen, and Ziqi Liang
ACS Applied Materials & Interfaces 2015 Volume 7(Issue 8) pp:4471
Publication Date(Web):February 19, 2015
DOI:10.1021/acsami.5b00077
Hybrid organic–inorganic perovskites have emerged as novel photovoltaic materials and hold great promise for realization of high-efficiency thin film solar modules. In this study, we unveil the ambipolar characteristics of perovskites by employing the transport measurement techniques of charge extraction by linearly increasing voltage (CELIV) and time-of-flight (TOF). These two complementary methods are combined to quantitatively determine the mobilities of hole and electron of CH3NH3PbI3 perovskite while revealing the recombination process and trap states. It is revealed that efficient and balanced transport is achieved in both CH3NH3PbI3 neat film and CH3NH3PbI3/PC61BM bilayer solar cells. Moreover, with the insertion of PC61BM, both hole and electron mobilities of CH3NH3PbI3 are doubled. This study offers a dynamic understanding of the operation of perovskite solar cells.Keywords: ambipolar; CELIV; charge mobility; charge transport; perovskite; TOF
Co-reporter:Yani Chen, Bobo Li, Wei Huang, Deqing Gao and Ziqi Liang
Chemical Communications 2015 vol. 51(Issue 60) pp:11997-11999
Publication Date(Web):19 Jun 2015
DOI:10.1039/C5CC03615A
We report the addition of a small amount of Pb(SCN)2 into PbI2 in a two-step solution method. The resulting CH3NH3PbI3−x(SCN)x perovskite films present larger-sized crystals and fewer traps than CH3NH3PbI3. Their planar solar cells exhibit a maximum power conversion efficiency of 11.07% with remarkably high reproducibility and good stability.
Co-reporter:Xiaoqing Chen
The Journal of Physical Chemistry C 2015 Volume 119(Issue 13) pp:7039-7046
Publication Date(Web):March 13, 2015
DOI:10.1021/acs.jpcc.5b00679
Understanding of the dynamic optoelectronic processes at the organic/metal electrode interface is crucial to the interface engineering of organic electronics. Here we present the systematic studies of exciton dissociation of p-type organic semiconductor at the organic/Ag interface. The interfacial dissociation of photogenerated excitons at the N,N′-di(1-naphthyl)-N,N′-diphenyl-(1,1′-biphenyl)-4,4′-diamine (NPB)/Ag interface was systematically investigated using the transient photovoltage technique as a proof-of-concept. The results indicate that two types of exciton dissociation—transfer of either electrons or holes to the metal electrode—coexist at the organic/metal electrode interface. This conclusion is further confirmed by two additional experiments—the current response of the NPB/Ag interface to light illumination under constant biases and the successive light current–voltage measurements under constant illumination. Moreover, the proportion of two types of dissociations was found to be tunable upon the oxidation of the silver electrode or the insertion of a lithium fluoride interlayer to the NPB/Ag interface. These results may be useful for interface engineering of organic photovoltaic cells.
Co-reporter:Yani Chen, Bobo Li, Wei Huang, Deqing Gao and Ziqi Liang
Chemical Communications 2015 - vol. 51(Issue 60) pp:NaN11999-11999
Publication Date(Web):2015/06/19
DOI:10.1039/C5CC03615A
We report the addition of a small amount of Pb(SCN)2 into PbI2 in a two-step solution method. The resulting CH3NH3PbI3−x(SCN)x perovskite films present larger-sized crystals and fewer traps than CH3NH3PbI3. Their planar solar cells exhibit a maximum power conversion efficiency of 11.07% with remarkably high reproducibility and good stability.
Co-reporter:Yani Chen, Yixin Zhao and Ziqi Liang
Journal of Materials Chemistry A 2015 - vol. 3(Issue 17) pp:NaN9140-9140
Publication Date(Web):2015/03/13
DOI:10.1039/C5TA01198A
We demonstrate that nonvolatile CaCl2 additives can significantly improve the film morphology of CH3NH3PbI3. Unlike those volatile chlorinated additives, a small portion of Cl anions from CaCl2 seem to enter into the CH3NH3PbI3 crystal, yet most insulating CaCl2 remains within the perovskite film, which is detrimental to perovskite solar cells.
Co-reporter:Minhong He, Yani Chen, Hui Liu, Jialin Wang, Xiaosheng Fang and Ziqi Liang
Chemical Communications 2015 - vol. 51(Issue 47) pp:NaN9661-9661
Publication Date(Web):2015/05/11
DOI:10.1039/C5CC02282G
A facile in situ solution method was developed for chemical decoration of CH3NH3PbI3 perovskites with reduced graphene oxides (rGOs) to significantly improve the photodetector performance. Such CH3NH3PbI3/rGO molecular hybrids show a 6 times higher ON/OFF ratio and notably faster response speed than neat CH3NH3PbI3.
