Co-reporter:Xiaojun Wang, Xinrui Miao, Lei Ying, Wenli Deng, and Yong Cao
The Journal of Physical Chemistry C September 7, 2017 Volume 121(Issue 35) pp:19305-19305
Publication Date(Web):August 16, 2017
DOI:10.1021/acs.jpcc.7b06511
We reported the synthesis, characterization, and self-assembly of two new regioisomeric π-conjugated chromophores (p-DBPy and d-DBPy) based on pyridyl-flanked diketopyrrolopyrrole (DPP), where the nitrogen atom in the pyridyl was proximal or distal to the central DPP unit. Their solid powders and solutions displayed different colors, especially for p-DBPy, which could be attributed to the conversion of molecular conformation and different intermolecular aggregations. UV–vis spectra demonstrated that the possible intermolecular hydrogen bonding existed in the solution of p-DBPy. Of particular interest is that the morphology of solid powders and thin films for each molecule investigated by SEM and AFM, respectively, were dramatically different owing to different intermolecular interactions and different crystal growth speed. Their spectroscopic and electrochemical properties turned out to be strongly dependent on the orientation of the pyridyl group. DFT calculations were performed to determine the optimized molecular conformation and molecular 3D charge density. At the liquid–solid interface, as visualized by STM, d-DBPy formed a 2D fishbone-like adlayer with linear molecular conformation by the molecule–substrate van der Waals force; however, p-DBPy self-assembled into a fish-scale-like pattern with flexed molecular conformation resulting from intra- and intermolecular hydrogen bonds. Compared with the 2D adlayers, the π–π stacking is another important driving force to determine the morphology of the films. The results demonstrated that understanding the effect of pyridyl orientation along the conjugated core on the molecular conformation and self-assembly is of critical importance for fabricating desired films with special morphology for high-performance organic electronic devices.
Co-reporter:Wenkai Zhong, Baobing Fan, Jing Cui, Lei Ying, Feng Liu, Junbiao Peng, Fei Huang, Yong Cao, and Guillermo C. Bazan
ACS Applied Materials & Interfaces October 25, 2017 Volume 9(Issue 42) pp:37087-37087
Publication Date(Web):October 6, 2017
DOI:10.1021/acsami.7b12902
We designed and synthesized two isomeric nonfullerene acceptors, IFBR-p and IFBR-d. These molecular semiconductors contain indacenodithiophene (IDT) as the central unit, adjacent asymmetric 5-fluorobenzo[c][1,2,5]thiadiazole units, and are flanked with rhodanine as the peripheral units. The orientation of the two fluorine atoms (proximal, p, or distal, d), relative to IDT impacts most severely the film morphologies when blended with the electron-donating polymer PTzBI. Polymer solar cells based on PTzBI:IFBR-p give rise to a power conversion efficiency (7.3 ± 0.2%) that is higher than what is achieved with PTzBI:IFBR-d (5.2 ± 0.1%). This difference is attributed to the lower tendency for (over)crystallization by IFBR-p and the resulting more favorable morphology of the photoactive layer. These results highlight the subtle impact of substitution regiochemistry on the properties of nonfullerene acceptors through modulation of their self-assembly tendencies.Keywords: acceptor; fluorobenzo[c][1,2,5]thiadiazole; nonfullerene; polymer solar cells; regiochemistry;
Co-reporter:Wenkai Zhong, Kang Li, Jing Cui, Tianyi Gu, Lei Ying, Fei Huang, and Yong Cao
Macromolecules October 24, 2017 Volume 50(Issue 20) pp:8149-8149
Publication Date(Web):October 5, 2017
DOI:10.1021/acs.macromol.7b01432
We developed a novel wide-bandgap conjugated polymer PTzBI-O based on an alkoxylated electron-deficient monomer 4,8-di(thiophen-2-yl)-[1,2,3]triazolo[4,5-f]isoindole-5,7(2H,6H)-dione (TzBI-O). Regarding that of alkyl-substituted imide-functionalized benzotriazole (TzBI) unit, the incorporation of oxygen atom into the substitution of TzBI-O increased the electronegativity. The resulting polymer PTzBI-O exhibited an absorption onset of 708 nm, corresponding to a bandgap of 1.75 eV. The PTzBI-O:N2200 blend exhibited strong aggregation in toluene solution, resulting in the enhanced absorptivity in thin film compared to those of equivalent films processed with chlorinated solvents. The fabricated all-polymer solar cell based on PTzBI-O:N2200 blend film processed with toluene exhibited an impressive power conversion efficiency of 7.91%. The higher efficiency of the toluene-processed device than those based on films processed with chlorinated solvents can be attributed to more effective charge dissociation, trivial bimolecular recombination, greater charge transportation, and more favorable thin film morphology of the toluene-cast blend film. These findings indicated that the resulting copolymer has great potential for the construction of high-performance all-polymer solar cells.
Co-reporter:Wenkai Zhong, Jing Cui, Baobing Fan, Lei Ying, Yu Wang, Xue Wang, Guichuan Zhang, Xiao-Fang Jiang, Fei Huang, and Yong Cao
Chemistry of Materials October 10, 2017 Volume 29(Issue 19) pp:8177-8177
Publication Date(Web):September 12, 2017
DOI:10.1021/acs.chemmater.7b02228
We developed a novel nonfullerene electron acceptor, IffBR, that consists of electron-rich indaceno[1,2-b:5,6-b′]dithiophene as the central unit and an electron-deficient 5,6-difluorobenzo[c][1,2,5]thiadiazole unit flanked with rhodanine as the peripheral group. IffBR exhibits peak UV–vis absorbance at 658 nm, which is complementary with the absorption profiles of the wide-bandgap conjugated polymers poly[4,8-bis(4,5-dihexylthiophen-2-yl)benzo[1,2-b:4,5-b′]-dithiophene-alt-2-(2-butyloctyl)-5,6-difluoro-4,7-di(thiophen-2-yl)-2H-benzo[d][1,2,3]triazole] (PBTA-BO) and the fullerene acceptor [6,6]-phenyl-C71-butyric acid methyl ester (PC71BM). The ternary device constructed with PBTA-BO/PC71BM/IffBR as the light-absorption layer exhibited significantly better photovoltaic performance than those obtained from devices based on a bulk-heterojunction layer comprised of binary components. This improvement was attributed to the broadened absorbance, formation of cascade charge-transfer pathways, reduced nongeminate recombination, enhanced charge extraction, and more favorable morphologies of the bulk-heterojunction films. The optimized ternary device exhibited a power conversion efficiency of 9.06%, which is significantly higher than those of binary devices based on either PBTA-BO/IffBR (6.24%) or PBTA-BO/PC71BM (4.73%). These results indicate that IffBR is an outstanding electron acceptor, suitable for the fabrication of nonfullerene or multicomponent-blend polymer solar cells.
Co-reporter:Wenkai Zhong, Sheng Sun, Lei YingFeng Liu, Linfeng Lan, Fei Huang, Yong Cao
ACS Applied Materials & Interfaces 2017 Volume 9(Issue 8) pp:
Publication Date(Web):January 31, 2017
DOI:10.1021/acsami.6b13673
In this study, we developed a ternary conjugated polymer, IFBT-TT, consisting of centrosymmetric indaceno[1,2-b:5,6-b′]dithiophene and thieno[3,2-b]thiophene as the electron-donating units and an asymmetric 5-fluorobenzo[c][1,2,5]thiadiazole as the electron-accepting unit. The target copolymer was synthesized using an acceptor–donor–acceptor (A–D–A) type of macromonomer, which gave the target copolymer a precisely defined D1–A–D2–A architecture. Theoretical simulation revealed that the IFBT-TT features C–H···N and F···S nonbonding interactions, leading to a highly rigid and planar molecular backbone. Although the spin-cast IFBT-TT films exhibited an amorphous morphology lacking in ordered structures, the fabricated field-effect transistors presented remarkable p-type transport properties with high mobility of up to 5.0 cm2 V–1 s–1 and excellent ambient stability. These observations highlight that the integration of a three-component D1–A–D2–A-type backbone framework is an effective molecular design strategy for high-mobility conjugated polymers.Keywords: donor−acceptor-type polymers; high mobility; organic field-effect transistors; regioregular polymers; ternary conjugated polymers;
Co-reporter:Yunping Huang;Nannan Zheng;Zhenfeng Wang;Fei Huang;Yong Cao
Chemical Communications 2017 vol. 53(Issue 12) pp:1997-2000
Publication Date(Web):2017/02/07
DOI:10.1039/C6CC09317E
Regioregular polymers based on an asymmetric dithieno[3,2-b:2′,3′-d]pyridin-5(4H)-one (TN) unit that consists of a lactam moiety were synthesized via palladium-catalyzed direct heteroarylation polymerization. The random orientation of the lactam moiety can be prevented by carefully designing the monomers with tailored molecular structures. It is noted that connecting the TN unit in different fashions generates substructures in the polymer backbone with different electronic structures. Compared to the random counterparts, the regioregular homopolymers exhibit dramatically discrepant optical properties and electronic structures, while the variations in the copolymers are less distinguished.
Co-reporter:Feng Peng;Na Li;Wenkai Zhong;Ting Guo;Jing Cui;Wei Yang;Yong Cao
Journal of Materials Chemistry C 2017 vol. 5(Issue 37) pp:9680-9686
Publication Date(Web):2017/09/28
DOI:10.1039/C7TC02515G
We developed a series of high-performance blue light-emitting polymers that contain hole-transport moieties comprising carbazole or triphenylamine substituents in the side chains of random copolymer poly(fluorene-co-dibenzothiophene-S,S-dioxide) (PFSO). The incorporation of these hole-transport species had negligible effects on the optical properties of the polymers but obviously facilitated hole injection from the anode, leading to significant improvements in hole/electron flux in the emissive layer. Interestingly, the copolymers that comprised either carbazole or triphenylamine substituents exhibited dramatically enhanced luminous efficiencies compared with the original copolymer. A PFSO-T5-based device yielded an excellent luminous efficiency of 7.04 cd A−1 at a brightness of 1000 cd m−2 with CIE coordinates of (0.16, 0.18), the highest efficiency reported so far for blue light-emitting polymers based on single-layer devices. The electroluminescent spectra of the PFSO-T5-based device exhibited excellent stability, as evidenced by a lack of change as the driving voltage increased from 4 to 8 V. These results indicate that the introduction of a hole-transporting group in the side chain is a very promising strategy for the development of highly efficient blue polymers for single-layer devices.
Co-reporter:Junfei Liang;Zhenji Zhong;Shuang Li;Xiao-Fang Jiang;Wei Yang;Junbiao Peng;Yong Cao
Journal of Materials Chemistry C 2017 vol. 5(Issue 9) pp:2397-2403
Publication Date(Web):2017/03/02
DOI:10.1039/C6TC05264A
Efficient white polymer light-emitting diodes were developed based on exciplex electroluminescence from a single polymer PFTS that consists of an electron-donating side chain and an electron-withdrawing backbone. It is noted that the device performances can be dramatically improved by incorporating a certain amount of high triplet energy level poly(9-vinylcarbazole) (PVK) into the emissive layer, which can lead to a more balanced charge carrier and decrease the exciton back transfer from the formed exciplex to the backbone of poly(fluorene-co-dibenzothiophene-5,5-dioxide). The luminous efficiency can be further improved by utilizing PVK as the hole transport layer, which can achieve greenish white emission with a luminous efficiency of 9.12 cd A−1 and CIE coordinates of (0.25, 0.37). Of particular interest is that the emission of PFTS can be modified by varying the thickness of the emissive layer by virtue of micro-cavity effects, where the optimized device exhibits a remarkable luminous efficiency of 7.37 cd A−1 with CIE coordinates of (0.30, 0.43). These observations demonstrated the great promise of utilizing the single polymer with the exciplex emission for the construction of efficient white polymer light-emitting devices.
Co-reporter:Baobing Fan;Wenkai Zhong;Xiao-Fang Jiang;Qingwu Yin;Fei Huang;Yong Cao
Advanced Energy Materials 2017 Volume 7(Issue 11) pp:
Publication Date(Web):2017/06/01
DOI:10.1002/aenm.201602127
Efficient ternary polymer solar cells are constructed by incorporating an electron-deficient chromophore (5Z,5′Z)-5,5′-((7,7′-(4,4,9,9-tetrakis(4-hexylphenyl)-4,9-dihydro-s-indaceno[1,2-b:5,6-b′]dithiophene-2,7-diyl)bis(6-fluorobenzo[c][1,2,5]thiadiazole-7,4-diyl))bis(methanylylidene))bis(3-ethyl-2-thioxothiazolidin-4-one) (IFBR) as an additional component into the bulk-heterojunction film that consists of a wide-bandgap conjugated benzodithiophene-alt-difluorobenzo[1,2,3]triazole based copolymer and a fullerene acceptor. With respect to the binary blend films, the incorporation of a certain amount of IFBR leads to simultaneously enhanced absorption coefficient, obviously extended absorption band, and improved open-circuit voltage. Of particular interest is that devices based on ternary blend film exhibit much higher short-circuit current densities than the binary counterparts, which can be attributed to the extended absorption profiles, enhanced absorption coefficient, favorable film morphology, as well as formation of cascade energy level alignment that is favorable for charge transfer. Further investigation indicates that the ternary blend device exhibits much shorter charge carrier extraction time, obviously reduced trap density and suppressed trap-assisted recombination, which is favorable for achieving high short-circuit current. The combination of these beneficial aspects leads to a significantly improved power conversion efficiency of 8.11% for the ternary device, which is much higher than those obtained from the binary counterparts. These findings demonstrate that IFBR can be a promising electron-accepting material for the construction of ternary blend films toward high-performance polymer solar cells.
Co-reporter:Baobing Fan;Peng Zhu;Feilong Pan;Feng Liu;Junwu Chen;Fei Huang;Yong Cao
Advanced Materials 2017 Volume 29(Issue 47) pp:
Publication Date(Web):2017/12/01
DOI:10.1002/adma.201703906
AbstractA novel wide-bandgap conjugated copolymer based on an imide-functionalized benzotriazole building block containing a siloxane-terminated side-chain is developed. This copolymer is successfully used to fabricate highly efficient all-polymer solar cells (all-PSCs) processed at room temperature with the green-solvent 2-methyl-tetrahydrofuran. When paired with a naphthalene diimide-based polymer electron-acceptor, the all-PSC exhibits a maximum power conversion efficiency (PCE) of 10.1%, which is the highest value so far reported for an all-PSC. Of particular interest is that the PCE remains 9.4% after thermal annealing at 80 °C for 24 h. The resulting high efficiency is attributed to a combination of high and balanced bulky charge carrier mobility, favorable face-on orientation, and high crystallinity. These observations indicate that the resulting copolymer can be a promising candidate toward high-performance all-PSCs for practical applications.
Co-reporter:Feng Peng, Ting Guo, Lei Ying, Wei Yang, Junbiao Peng, Yong Cao
Organic Electronics 2017 Volume 48(Volume 48) pp:
Publication Date(Web):1 September 2017
DOI:10.1016/j.orgel.2017.05.037
•An efficient end-capping strategy was utilized to synthesize PFSO derivatives.•The end-capped copolymers exhibit enhanced luminous efficiency (LE).•Blue PLED based on the end-capped PFSO-TF16 shows a maximum LE of 4.45 cd/A.In this manuscript, we introduced an effective strategy to improve the electroluminescent performance of poly[(fluorene)-co-dibenzothiophene-S,S-dioxide]s (PFSO) derivatives by end-capping, which was carried out by introducing N-([1,1'-biphenyl]-4-yl)-N-(4-phenyl)-9,9-dimethyl-9H-fluoren-2-amine moiety (TF) at the end of the polymerisation. Compared with the pristine copolymer PFSO that end-capped by phenyl unit, the TF-end-capped copolymers exhibit improved highest occupied molecular orbital levels, which can facilitate hole injection and thus lead to more balanced charge carrier transport in the emissive layer. Of particular importance is that the resulting copolymers can be used to fabricate single-layer devices without hole transport layer, which dramatically reduced driving voltage and obviously increased luminous efficiency relative to device fabricated from the copolymer PFSO that end-capped by phenyl unit. The best performance is obtained from device based on PFSO-TF16, which exhibits an unprecedented turn-on voltage of 2.7 V and a maximum luminous efficiency of 4.45 cd A−1, with CIE coordinates of (0.15, 0.13). These results demonstrate that our end-capping strategy has great potential for the development of highly efficient blue light-emitting polymers for single-layer light-emitting devices.Download high-res image (240KB)Download full-size image
Co-reporter:Zhiming Zhong;Xiaojun Wang;Sen Zhao;Feng Peng;Jian Wang;Wei Yang;Junbiao Peng;Yong Cao
Journal of Materials Chemistry C 2017 vol. 5(Issue 25) pp:6163-6168
Publication Date(Web):2017/06/29
DOI:10.1039/C7TC01280B
The effects of the component distribution of a red light-emitting random copolymer poly(9,9-dioctylfluorene-co-(4,7-dithienyl-benzothiadiazole)) (DOF : DBT = 9 : 1 mol/mol, PFO-DBT10) on its optoelectronic properties are systematically investigated. The PFO-DBT10 copolymers with various molecular weights (MWs) have identical absorption spectra and energy levels. However, as the molecular weight increases, so does the photoluminescence intensity ratio of DBT to DOF segments. For polymer light-emitting diodes, PFO-DBT10 with a large MW shows an enhanced charge trapping effect, leading to increased operation voltage under any given current density, worse luminous efficiency, and more saturated red emission, compared to the one with a small MW. The experiments are performed within the framework of the component's molar ratio dispersion of random copolymer chains induced by the MW using the binomial distribution formula. According to the formula, the high MW random copolymer is analogous to the ideal PFO-DBT10 in terms of the uniformly distributed units. The low MW random copolymer is more likely to be a mixture of pure PFO and PFO-DBTx, in which the molar ratio x varies, due to its dispersive component distribution. This work offers a new approach to study the opto-electronic properties of random copolymers in the light of component distribution.
Co-reporter:Renlong Li;Gongchu Liu;Manjun Xiao;Xiye Yang;Xiang Liu;Zhenfeng Wang;Fei Huang;Yong Cao
Journal of Materials Chemistry A 2017 vol. 5(Issue 45) pp:23926-23936
Publication Date(Web):2017/11/21
DOI:10.1039/C7TA06631G
We designed and synthesized two novel non-fullerene small molecule acceptors (IDT-N and IDT-T-N) that consist of indacenodithiophene (IDT) as the electron-donating core and 2-(3-oxo-2,3-dihydro-1H-cyclopenta[b]naphthalen-1-ylidene)malononitrile (N) as a novel electron-withdrawing end group. IDT-N and IDT-T-N consisting of the naphthyl-based N group exhibited an expanded plane compared to phenyl-based indanone (INCN), which strengthened the intramolecular push–pull effect between the core donor unit and the terminal acceptor units. This strengthened effect resulted in a reduced bandgap that was beneficial for solar photon collection and increased short-circuit current density of the resulting devices. IDT-N and IDT-T-N exhibited red-shifted absorptions and smaller optical bandgaps than the corresponding phenyl-fused indanone end-capped chromophores. Both acceptors exhibited broad absorptions and energy levels that were well-matched with the donor materials. Polymer solar cells based on IDT-N and IDT-T-N and two representative polymer donors (PTB7-Th and PBDB-T) exhibited impressive photovoltaic performances. The devices based on the PBDB-T:IDT-N system exhibited a power conversion efficiency of up to 9.0%, with a short-circuit current density of 15.88 mA cm−2 and a fill factor of 71.91%. These results demonstrate that IDT-N and IDT-T-N are promising electron acceptors for use in polymer solar cells.
Co-reporter:Baobing Fan;Zhenfeng Wang;Baitian He;Xiao-Fang Jiang;Fei Huang;Yong Cao
Energy & Environmental Science (2008-Present) 2017 vol. 10(Issue 5) pp:1243-1251
Publication Date(Web):2017/05/17
DOI:10.1039/C7EE00619E
Increasing interest has been devoted to developing high-performance all-polymer solar cells (all-PSCs) owing to their specific advantages in light absorption and long-term stability. In this work, we systematically investigated the synergistic effects of processing solvents and molecular weight on the photovoltaic performance of all-PSCs, which consist of an n-type polymer N2200 and a p-type wide bandgap polymer PTzBI that are made up of benzodithiophene and imide-functionalized benzotriazole units. It is noted that increasing the molecular weight of N2200 can simultaneously enhance exciton generation and dissociation, reduce bimolecular recombination, and facilitate charge extraction. The films processed with the environmentally-friendly solvent 2-methyl-tetrahydrofuran (MeTHF) exhibit a more favourable film morphology than those processed with commonly used halogenated solvents. The all-PSC consisting of the high molecular weight N2200 and PTzBI processed with the environmentally friendly solvent MeTHF presents a remarkable power conversion efficiency of 9.16%, which is the highest value so far observed for all-PSCs. Of particular interest is that the PCE remains 6.37% with the active layer thickness of 230 nm. These observations imply the great promise of the developed all-PSCs for practical applications toward high-throughput roll-to-roll technology.
Co-reporter:Baobing Fan;Kai Zhang;Xiao-Fang Jiang;Fei Huang;Yong Cao
Advanced Materials 2017 Volume 29(Issue 21) pp:
Publication Date(Web):2017/06/01
DOI:10.1002/adma.201606396
High-performance nonfullerene polymer solar cells (PSCs) are developed by integrating the nonfullerene electron-accepting material 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′]dithiophne) (ITIC) with a wide-bandgap electron-donating polymer PTzBI or PTzBI-DT, which consists of an imide functionalized benzotriazole (TzBI) building block. Detailed investigations reveal that the extension of conjugation can affect the optical and electronic properties, molecular aggregation properties, charge separation in the bulk-heterojunction films, and thus the overall photovoltaic performances. Single-junction PSCs based on PTzBI:ITIC and PTzBI-DT:ITIC exhibit remarkable power conversion efficiencies (PCEs) of 10.24% and 9.43%, respectively. To our knowledge, these PCEs are the highest efficiency values obtained based on electron-donating conjugated polymers consisting of imide-functionalized electron-withdrawing building blocks. Of particular interest is that the resulting device based on PTzBI exhibits remarkable PCE of 7% with the thickness of active layer of 300 nm, which is among the highest values of nonfullerene PSCs utilizing thick photoactive layer. Additionally, the device based on PTzBI:ITIC exhibits prominent stability, for which the PCE remains as 9.34% after thermal annealing at 130 °C for 120 min. These findings demonstrate the great promise of using this series of wide-bandgap conjugated polymers as electron-donating materials for high-performance nonfullerene solar cells toward high-throughput roll-to-roll processing technology.
Co-reporter:Junfei Liang, Jing Cui, Ting Guo, Feng Peng, Yingcheng Li, Lei Ying, Wei Yang, Junbiao Peng, Yong Cao
Organic Electronics 2017 Volume 51(Volume 51) pp:
Publication Date(Web):1 December 2017
DOI:10.1016/j.orgel.2017.09.013
•The utilization of the hole transport layer of PVK:BCFN improves LE of PFO.•A maximum LE of 4.31 cd A−1 CIE coordinates of (0.17, 0.13) was obtained.•The LE remains as 4.27 cd A−1 at a luminance of 1000 cd m−2.•The electroluminescent spectra shows excellent stability under applied voltage of 5–11 V.Efficient blue polyfluorenes have been generated by incorporating the hole transport material N-([1,1′-biphenyl]-4-yl)-9,9-dimethyl-N-(4-(9-phenyl-9H-carbazol-3-yl)- phenyl)-9H-fluoren-2-amine (BCFN) into poly(9,9-dioctylfluorene) (PFO) as an emissive layer. BCFN has an appropriate highest occupied molecular orbital (HOMO) energy level and high hole transport/electron barrier properties, which can effectively reduce the hole injection barrier and improve the charge carrier injection and transport. These properties resulted in a significant improvement in the electroluminescent (EL) performance of PFO. To further improve the EL performance of PFO, the blend hole transport layer, PVK [Poly(N-vinylcarbazole)]:BCFN with weight ratio of 3:7, was inserted between the PEDOT:PSS and the emissive layer. The blend hole transport layer effectively reduced exciton quenching and markedly decreased the hole injected barrier. A maximum luminous efficiency (LEmax) of 4.31 cd A−1 was obtained with the CIE coordinates of (0.17, 0.13). The device maintained a LEmax of 4.27 cd A−1 at a luminance of 1000 cd m−2. In addition, stable EL spectra were obtained and were nearly identical when the applied voltage was increased from 5 to 11 V. These results indicate that blending the appropriate hole transport material can be an efficient method to improve device performance based on the large band gap of blue-lighting materials.Download high-res image (243KB)Download full-size image
Co-reporter:Huan Chang, Zhiming Chen, Xiye Yang, Qingwu Yin, Jie Zhang, Lei Ying, Xiao-Fang Jiang, Baomin Xu, Fei Huang, Yong Cao
Organic Electronics 2017 Volume 45(Volume 45) pp:
Publication Date(Web):1 June 2017
DOI:10.1016/j.orgel.2017.03.022
•Two PDI-based n-type copolymers containing the ethynyl unit were developed.•These copolymers can be used as electron-accepting materials for all-PSCs.•The power conversion efficiency over 5% was achieved based on PPDI-F.We designed and synthesised two n-type donor-acceptor copolymers based on perylenediimide (PDI). These copolymers contained an ethynyl moiety as the π-bridge between PDI and the electron-donating unit of either benzodithiophene (BDT) or fluorine (F), with the corresponding polymers denoted as PPDI-BDT and PPDI-F, respectively. The molecular geometry and the optical and electrochemical properties of the polymers were affected by the electron-donating unit. Both copolymers exhibited relatively broad light-absorption profiles and deep lowest unoccupied molecular orbital energy levels of about −3.8 eV. All-polymer solar cells (all-PSCs) were fabricated using these copolymers as the electron-accepting material and a medium-bandgap conjugated polymer, PBDB-T, as the electron-donating material. The resulting all-PSC based on PPDI-F exhibited a power conversion efficiency of 5.09%, which is significantly higher than that of the device fabricated using PPDI-BDT (2.73%). This improvement was attributed to the higher open-circuit voltage, greater charge carrier mobility and more effective charge transfer of the PBDB-T:PPDI-F blend film. These results suggest that the developed n-type PDI-based copolymers are promising candidates as electron-accepting materials for the construction of high-performance all-polymer solar cells.Download high-res image (278KB)Download full-size image
Co-reporter:Jing Wang;Kai Lin;Kai Zhang;Xiao-Fang Jiang;Khalid Mahmood;Fei Huang;Yong Cao
Advanced Energy Materials 2016 Volume 6( Issue 11) pp:
Publication Date(Web):
DOI:10.1002/aenm.201502563
A novel crosslinkable aminoalkyl-functionalized polymer, poly[9,9-bis(6-(N,N-diethylamino)propyl)fluorene-alt-9,9-bis(hex-5-en-1-yl)-fluorene] (PFN-V), is designed and synthesized. The resulting polymer can be rapidly crosslinked by UV-curing within 5 s in a nearly quantitative yield based on the “click” chemistry of alkyene end-groups of the PFN-V side chains and the addition of 1,8-octanedithiol. The crosslinked PFN-V film exhibits excellent solvent resistance property and can act as effective cathode interlayer to modify the indium tin oxide (ITO) electrode, which can thus facilitate the formation of Ohmic contact between cathode and active layer. The surface energy of PFN-V is quite comparable to that of PC71BM, which is favorable for the formation of vertical phase separation in the bulk heterojunction film that can facilitate extraction of charges as verified by transient photocurrent measurements. Based on the resulting PFN-V as the cathode interlayer, the fabricated polymer solar cells with inverted device structure show a remarkable enhancement of power conversion efficiency from 3.11% for the control device to 9.18% for PFN-V based device. These observations indicate that the synthesized PFN-V can be a promising crosslinked copolymer as the cathode interlayer for high performance polymer solar cells.
Co-reporter:Wenkai Zhong, Jingyang Xiao, Sheng Sun, Xiao-Fang Jiang, Linfeng Lan, Lei Ying, Wei Yang, Hin-Lap Yip, Fei Huang and Yong Cao
Journal of Materials Chemistry A 2016 vol. 4(Issue 21) pp:4719-4727
Publication Date(Web):11 Apr 2016
DOI:10.1039/C6TC00271D
Two wide bandgap donor–acceptor type π-conjugated polymers based on dithienobenzodithiophene as the donor unit and difluorobenzotriazole or difluorobenzothiadiazole as the acceptor unit were designed and synthesized. The copolymer based on difluorobenzothiadiazole exhibited more pronounced aggregations in chlorobenzene solutions than that of the copolymer based on difluorobenzotriazole. Both copolymers exhibited relatively wide bandgaps with deep highest occupied molecular orbitals, leading to high open circuit voltages of over 0.95 V for the fabricated polymer solar cells. These copolymers exhibited quite analogous hole mobility of about 0.1 cm2 V−1 s−1 as measured by organic field effect transistors. Bulk heterojunction polymer solar cells based on these copolymers as the electron-donating materials and PC71BM as the electron-accepting material exhibited relatively high performance, with the best power conversion efficiency of 7.45% attained for the copolymer based on the difluorobenzothiadiazole unit. These results demonstrated that the constructed wide bandgap π-conjugated polymers can be promising candidates for the fabrication of high performance solar cells with multi-junction architectures.
Co-reporter:Jing Yue, Sheng Sun, Junfei Liang, Wenkai Zhong, Linfeng Lan, Lei Ying, Fei Huang, Wei Yang and Yong Cao
Journal of Materials Chemistry A 2016 vol. 4(Issue 13) pp:2470-2479
Publication Date(Web):15 Feb 2016
DOI:10.1039/C6TC00051G
Two novel regio-isomeric π-conjugated polymers consisting of the pyridyl unit flanked by diketopyrrolopyrrole as the electron-accepting unit and 2,5-bis(3-hexylthiophen-2-yl)thieno[3,2-b]thiophene as the electron-donating unit were designed and synthesized. The comparison of the optical and electrochemical properties indicated that the copolymer based on the nitrogen atom proximal to the central diketopyrrolopyrrole unit (p-PDBPy) exhibited bathochromic shifted absorption spectra and narrower bandgaps than the counterpart copolymer (d-PDBPy) with the distally oriented nitrogen atom, which can be correlated with the stronger intermolecular aggregation of the former as a result of the different intrinsic molecular geometry of the polymer backbone. Of particular interest is that the copolymer p-PDBPy exhibited a moderate hole mobility of 0.35 cm2 V−1 s−1, which is about three orders of magnitude higher than the hole mobility of 3.2 × 10−4 cm2 V−1 s−1 obtained based on the counterpart copolymer d-PDBPy, as measured using organic field-effect transistors. These results demonstrated that the delicate control of the pyridyl orientations along the polymer backbone is of vital importance for the molecular design of π-conjugated polymers for high-performance organic electronic devices.
Co-reporter:Zhiming Zhong, Sen Zhao, Jian Pei, Jian Wang, Lei Ying, Junbiao Peng, and Yong Cao
ACS Applied Materials & Interfaces 2016 Volume 8(Issue 31) pp:20237
Publication Date(Web):July 20, 2016
DOI:10.1021/acsami.6b05172
Polymer light-emitting diodes (PLEDs) have attracted broad interest due to their solution-processable properties. It is well-known that to achieve better performance, organic light-emitting diodes require multilayer device structures. However, it is difficult to realize multilayer device structures by solution processing for PLEDs. Because most semiconducting polymers have similar solubility in common organic solvents, such as toluene, xylene, chloroform, and chlorobenzene, the deposition of multilayers can cause layers to mix together and damage each layer. Herein, a novel semiorthogonal solubility relationship was developed and demonstrated. For the first time, an alkane-soluble dendrimer is utilized as the electron-transport layer (ETL) in PLEDs via a solution-based process. With the dendrimer ETL, the external quantum efficiency increases more than threefold. This improvement in the device performance is attributed to better exciton confinement, improved exciton energy transfer, and better charge carrier balance. The semiorthogonal solubility provided by alkane offers another process dimension in PLEDs. By combining them with water/alcohol-soluble polyelectrolytes, more exquisite multilayer devices can be fabricated to achieve high device performance, and new device structures can be designed and realized.Keywords: alkane soluble; electron transport; multilayer device; polymer light-emitting diodes; solution process
Co-reporter:Junfei Liang, Sen Zhao, Xiao-Fang Jiang, Ting Guo, Hin-Lap Yip, Lei Ying, Fei Huang, Wei Yang, and Yong Cao
ACS Applied Materials & Interfaces 2016 Volume 8(Issue 9) pp:6164
Publication Date(Web):February 17, 2016
DOI:10.1021/acsami.5b11926
In this Article, we designed and synthesized a series of polyfluorene derivatives, which consist of the electron-rich 4,4′-(9-alkyl-carbazole-3,6-diyl)bis(N,N-diphenylaniline) (TPA-Cz) in the side chain and the electron-deficient dibenzothiophene-5,5-dioxide (SO) unit in the main chain. The resulting copolymer PF-T25 that did not comprise the SO unit exhibited blue light-emission with the Commission Internationale de L’Eclairage coordinates of (0.16, 0.10). However, by physically blending PF-T25 with a blue light-emitting SO-based oligomer, a novel low-energy emission correlated to exciplex emerged due to the appropriate energy level alignment of TPA-Cz and the SO-based oligomers, which showed extended exciton lifetime as confirmed by time-resolved photoluminescent spectroscopy. The low-energy emission was also identified in copolymers consisting of SO unit in the main chain, which can effectively compensate for the high-energy emission to produce binary white light-emission. Polymer light-emitting diodes based on the exciplex-type single greenish-white polymer exhibit the peak luminous efficiency of 2.34 cd A–1 and the maximum brightness of 12 410 cd m–2, with Commission Internationale de L’Eclairage color coordinates (0.27, 0.39). The device based on such polymer showed much better electroluminescent stability than those based on blending films. These observations indicated that developing a single polymer with the generated exciplex emission can be a novel and effective molecular design strategy toward highly stable and efficient white polymer light-emitting diodes.Keywords: exciplex; highly stable electroluminescence; polymer light-emitting diodes; solution process; white light-emitting;
Co-reporter:Chunchen Liu, Wenzhan Xu, Qifan Xue, Ping Cai, Lei Ying, Fei Huang, Yong Cao
Dyes and Pigments 2016 Volume 125() pp:54-63
Publication Date(Web):February 2016
DOI:10.1016/j.dyepig.2015.10.003
•Indigo and isoindigo-based molecules with removable substituents were developed.•The substituents can be thermally removed at about 190 °C.•Molecular coplanarity can be significantly improved after removal of substituents.•One-dimensional nanowires were obtained via hydrogen bond assisted self-assembly.•These nanowires exhibited impressive charge transport property.In this manuscript, indigo and isoindigo-based π-conjugated molecules with thermal removable tert-butoxycarbonyl (t-Boc) side groups were designed and synthesized. It was noted that the t-Boc side groups can be eliminated in nearly quantitative yields after thermal treatment at 200 °C for 15 min, as confirmed by thermogravimetric analysis and Fourier transform infrared spectroscopy. From the thermal treated solution of isoindigo-based molecule DTIIC8C12 in the co-solvent of 1,2-dichlorobenzene/pyridine with volume ratio of 10/90, one-dimensional nanowires can be formed due to the hydrogen bonding assisted self-assembly. The afforded nanowires exhibited a moderate hole mobility of 1.3 × 10−3 cm2 V−1 s−1, as estimated from the organic field effect transistors. These observations illustrated that the utilization of thermal removable side chain functionalized conjugated polymers can be an effective strategy for developing conjugated polymers with impressive charge carrier transport.
Co-reporter:Sen Zhao, Junfei Liang, Ting Guo, Yu Wang, Xuan Chen, Denghao Fu, Junbin Xiong, Lei Ying, Wei Yang, Junbiao Peng, Yong Cao
Organic Electronics 2016 Volume 38() pp:130-138
Publication Date(Web):November 2016
DOI:10.1016/j.orgel.2016.08.007
•Two blue light-emitting polymers with aromatic unit in side chain are synthesized.•The incorporated aromatic units can induce the formation of PFO β-phase.•Both luminous efficiency and color purity can be simultaneously improved.•A peak luminous efficiency of 2.25 cd A−1 was obtained for PFO-SO.Two novel polyfluorene-based blue-light emitting copolymers consisting of aromatic carbazole or dibenzothiophene-S,S-dioxide (SO) moiety in side chain are designed and synthesized based on a palladium-catalyzed Suzuki polymerization. The UV–vis absorption, photoluminescence characteristics and wide-angle X-ray diffraction measurements of the resulting copolymers demonstrate that the incorporation of such aromatic units can induce the formation of the β-phase. The resulting copolymers consisting of aromatic units exhibit improved electroluminescence properties relative to the pristine PFO film. A maximum luminous efficiency of 2.25 cd A−1 with Commission Internationale de l’Eclairage coordinates of (0.17, 0.09) is obtained from the light-emitting device based on the copolymer consisting of SO unit (PFO-SO). Device based on copolymer PFO-SO also exhibits stable electroluminescent spectra and relatively low roll-off of luminous efficiency at high current densities. These observations indicate that the incorporation of aromatic moiety in side chain is a promising strategy to obtain stable blue-light-emitting polyfluorenes with enhanced efficiency.
Co-reporter:Ting Guo, Wenkai Zhong, Anqi Zhang, Jianhua Zou, Lei Ying, Wei Yang and Junbiao Peng
New Journal of Chemistry 2016 vol. 40(Issue 1) pp:179-186
Publication Date(Web):21 Oct 2015
DOI:10.1039/C5NJ02185E
A series of electrophosphorescent copolymers were synthesized by Suzuki polymerization. A diketone-ended alkyl chain which is grafted in the N-position of the carbazole unit is used as a ligand to form a pendant cyclometalated Ir complex with 1-(9,9-dioctyl-9H-fluoren-2-yl)isoquinoline and 1-(N,N-diphenyl-benzenamine-4-yl)isoquinoline. The electroluminescence from the backbone of the copolymers is completely quenched by tethered iridium complexes even though with the content of iridium complexes being as low as 1 mol%. Saturated red light-emitting diodes were fabricated on the basis of these two series of copolymers. The best device performance with a maximum external quantum efficiency of 7.8% on the basis of copolymer PF-IrNiq1 was achieved, which was among the highest efficiencies of the reported electrophosphorescent red light-emitting polymers comprising iridium ligands.
Co-reporter:Ruihao Xie, Zhiming Chen, Wenkai Zhong, Guichuan Zhang, Yunping Huang, Lei Ying, Fei Huang and Yong Cao
New Journal of Chemistry 2016 vol. 40(Issue 5) pp:4727-4734
Publication Date(Web):15 Mar 2016
DOI:10.1039/C5NJ03174E
A series of novel electron-donating building blocks of alkyltriazolyl substituted benzodithiophene were synthesized on the basis of Cu(I)-catalyzed azide–alkyne cycloaddition. The alternating donor–acceptor type of π-conjugated copolymers by using such alkyltriazolyl substituted benzodithiophene as donor units and diketopyrrolopyrrole as acceptor units were synthesized via Suzuki polymerization. The resultant copolymers exhibited good thermal properties and can be easily dissolved in various organic solvents. All copolymers show quite comparable absorption profiles in the range of 300–850 nm with the absorption onset at about 1.4 eV, where the copolymer with longer side chains exhibited a slightly enhanced absorption coefficient. The cyclic voltammetry measurements indicated the highest occupied molecular orbitals and the lowest unoccupied molecular orbitals located at about −5.40 and −3.40 eV, respectively, which were nearly independent of the size of alkyl side chains. Polymer solar cells based on the resultant copolymers as electron-donating materials and PC71BM as the electron-accepting material exhibited moderate photovoltaic performances.
Co-reporter:Chen Song, Zhiming Zhong, Zhanhao Hu, Juanhong Wang, Lei Wang, Lei Ying, Jian Wang, Yong Cao
Organic Electronics 2016 Volume 28() pp:252-256
Publication Date(Web):January 2016
DOI:10.1016/j.orgel.2015.10.039
•Low conductive PEDOT:PSS 8000 OLED device has severe efficiency roll-off.•The insulating PSS on PEDOT:PSS 8000 surface prevents efficient hole injection.•Methanol treatment removes the redundant PSS.•Without PSS, 8000 device performance is better than high conductive 4083 device.In order to achieve high device efficiency in blue-emitting polymer light-emitting diodes (PLED) and white-emitting PLED, low-conductive PEDOT:PSS Clevios™ P CH 8000 (8000) has been used to replace widely adopted high-conductive PEDOT:PSS Clevios™ P Al 4083 (4083). In a blue PLED with poly (dibenzothiophene-S,S-dioxide-co-9,9-dioctyl-2,7-fluorene) (PF-FSO) as the emission layer, though the 8000 device has a higher efficiency and a lower turn-on voltage than the 4083 device, the 8000 device exhibits low peak luminance, sharp efficiency roll-off, and permanent degradation of the emission material. By analyzing the hole-only device and the X-ray photoelectron spectroscopy spectra, it's revealed that the insulating PSS layer on 8000 surface is responsible for the inefficient hole injection. A simple methanol treatment on the 8000 surface effectively removes the redundant PSS. Without the insulating PSS layer, the hole injection becomes efficient which extends the recombination zone. As the result, the methanol-treated 8000 device not only retains low turn-on voltage and the high device efficiency of the untreated 8000 device, but also achieves the peak luminance, mild efficiency roll-off, and device stability of the 4083 device.
Co-reporter:Wenkai Zhong, Junfei Liang, Shuzhi Hu, Xiao-Fang Jiang, Lei Ying, Fei Huang, Wei Yang, and Yong Cao
Macromolecules 2016 Volume 49(Issue 16) pp:5806-5816
Publication Date(Web):August 2, 2016
DOI:10.1021/acs.macromol.6b00185
The effects of fluorine substitutions on the molecular geometry and optoelectronic properties were investigated based on the conjugated molecular framework consisting of the mono-fluorinated benzo[c][1,2,5]thiadiazole unit. The two-dimensional nuclear magnetic resonance spectroscopy of model compounds indicated that the fluorine substitution can significantly change the chemical environment of the adjacent hydrogen atoms, which was in consistence with the changed molecular geometry as indicated by single crystal diffractions and theoretical calculations. Based on an AB type of monomer, the regioregular conjugated polymer with specifically oriented fluorine along the vector of the polymer backbone was constructed. The UV–vis absorption, photoluminescent, and electroluminescent spectra demonstrated the slightly hypsochromic shift of the copolymer comprising the fluorine substitution relative to the non-fluorinated counterpart. Of particular interest is that the copolymer based on the fluorinated benzothiadiazole unit exhibited electron-dominant charge transportation, for which the electron mobility is about 1 order of magnitude higher than that of hole mobility.
Co-reporter:Yunping Huang;Wenzhan Xu;Cheng Zhou;Wenkai Zhong;Ruihao Xie;Xiong Gong;Fei Huang;Yong Cao
Journal of Polymer Science Part A: Polymer Chemistry 2016 Volume 54( Issue 14) pp:2119-2127
Publication Date(Web):
DOI:10.1002/pola.28079
ABSTRACT
Two novel dibromo monomers consisting of the isomers of 5-alkylphenanthridin-6(5H)-one (PN) and 6-alkoxylphenanthridine (PO) were synthesized through alkylation of the precursor 3,8-dibromophenanthrindi-6(5H)-one, where the molecular structures were confirmed by NMR spectroscopy. The medium bandgap conjugated polymers PDBTPN and PDBTPO were constructed by utilizing such two isomers PN and PO as the electron-donating units and dithiophenebenzo[2,1,3]diathiazole as the electron-accepting unit. The resulting polymers exhibited analogous absorption profiles with optical bandgap of 1.90 eV, while PDBTPO showed slightly higher absorption coefficiency. Cyclic voltammetry measurements revealed that these polymers had relatively deep highest occupied molecular orbital levels of about −5.70 eV. Polymer solar cells based on such two polymers showed relatively high open-circuit voltage of about 0.90 V. All devices exhibited moderate performances with the best power conversion efficiency of 3.77% achieved based on PDBTPO. Devices based on PDBTPO showed slightly higher power conversion efficiency than those based on PDBTPN, which can be ascribed to higher hole mobility and more favorable film morphology of the former. © 2016 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2016, 54, 2119–2127
Co-reporter:Chunchen Liu, Sheng Dong, Ping Cai, Peng Liu, Shengjian Liu, Junwu Chen, Feng Liu, Lei Ying, Thomas P. Russell, Fei Huang, and Yong Cao
ACS Applied Materials & Interfaces 2015 Volume 7(Issue 17) pp:9038
Publication Date(Web):April 13, 2015
DOI:10.1021/am5089956
A series of donor–acceptor type of π-conjugated copolymers based on tert-butoxycarbonyl (t-Boc) substituted indigo, isoindigo or diketopyrrolopyrrole as the acceptor unit and a benzodithiophene derivative as the donor unit was designed and synthesized. These copolymers can be readily dissolved in organic solvents and can produce uniform films by solution deposition. Thermal treatment of copolymer films at 200 °C for 10 min resulted in elimination of t-Boc side groups in nearly quantitative yield as suggested by thermogravimetric analysis and Fourier transform infrared spectroscopy. The elimination of the bulky t-Boc side groups resulted in the emergence of N–H···O═C hydrogen bonding interactions by virtue of the lactam structures of the indigo, isoindigo and diketopyrrolopyrrole units. Of particular interests is the distinctly increased field-effect mobility of these copolymers after thermal treatment, which may arise from the enhanced coplanarity and intermolecular ordering of the indigo, isoindigo or diketopyrrolopyrrole units after elimination of the bulky t-Boc side groups. These results demonstrate that the incorporation of latent side groups provides a viable strategy to construct conjugated polymers that can attain more ordered intermolecular stacking by simple thermal treatments. On the other hand, despite the thermal cleavage of t-Boc groups can also lead to increased ordering of polymer chains when blending with [6,6]-phenyl C71 butyric acid methyl ester, the photovoltaic performances of the resulting bulk heterojunction solar cells did not obviously increase due to the serious phase separation and coarsening of the film morphology.Keywords: conjugated polymers; hydrogen bonding; intermolecular ordering; organic field-effect transistor; polymer solar cell; thermal cleavage;
Co-reporter:Liuyuan Lan, Zhiming Chen, Yunchuan Li, Lei Ying, Fei Huang and Yong Cao
Polymer Chemistry 2015 vol. 6(Issue 43) pp:7558-7569
Publication Date(Web):31 Aug 2015
DOI:10.1039/C5PY01235J
A series of donor–acceptor type of conjugated polymers were designed and synthesized via palladium catalyzed Stille copolymerization. These copolymers consisted of the electron-donating benzodithiophene or indacenodithiophene units and the electron-deficient cyclic imide substituted quinoxaline derivatives. It was noted that all copolymers exhibited typical dual-absorption characteristics in both solution and as thin films with an optical band gap in the range of 1.61–1.72 eV. In comparison with the copolymers based on the electron-deficient unit of 5,9-di(thien-2-yl)-2,3-diphenyl-7-octyl-6H-pyrrolo[3,4-g]quinoxaline-6,8(7H)-dione (TPQD) as the electron-accepting unit, the resultant copolymers based on the enlarged coplanar N-octyl-10,13-di(thien-2-yl)-2,7-dioctyldibenzo[a,c]phenazine-11,12-dicarboxylic imide (TBPDI) unit exhibited an obviously enhanced absorption coefficiency. All polymers showed relatively deep highest occupied molecular orbital energy levels ranging from −5.40 to −5.52 eV. It was also realized that the hole mobility of copolymers based on TBPDI is much higher than those based on the TPQD unit as measured by the space charge limited current method. Polymer solar cells with a device architecture of ITO/PEDOT:PSS/polymer:PC71BM/Ca/Al demonstrated that TBPDI-based copolymers exhibited higher performances than TPQD-based copolymers. The best device performance with a power conversion efficiency of 4.60% was achieved by using the indacenodithiophene-alt-TBPDI copolymer as the photoactive layer. Further optimization of devices by introducing a cathode interfacial layer and solvent vapor annealing in chloroform led to an impressive power conversion efficiency of 5.58%. These observations indicated that the developed TBPDI unit that has enlarged coplanarity can be a promising building block for the construction of highly efficient conjugated polymers for solar cell applications.
Co-reporter:Xuelong Huang, Guichuan Zhang, Cheng Zhou, Liqian Liu, Yaocheng Jin, Shengjian Liu, Lei Ying, Fei Huang and Yong Cao
Polymer Chemistry 2015 vol. 6(Issue 22) pp:4154-4161
Publication Date(Web):27 Apr 2015
DOI:10.1039/C5PY00201J
A series of narrow band gap conjugated copolymers comprising two electron-rich (donor, D) and one electron-deficient (acceptor, A) moieties regularly alternating along the polymer backbone were designed and synthesized. The ternary copolymers with the repeating unit in a D1–A–D2–A manner were constructed by copolymerizing a bisstannyled-D1 (D1 = cyclopentadithiophene or benzodithiophene-derivatives) and a dibromo-monomer (Br–A–D2–A–Br, D2 = dithienosilole, A = benzothiadiazole) through a palladium-catalyzed Stille polymerization. It was recognized that the optical properties, frontier molecular orbital energy levels and the photovoltaic performance of the resulting copolymers can be influenced by modifying the copolymerized D1 moiety. By carefully optimizing the electron-donating behaviours and substitutions of the D1 unit, bulk-heterojunction solar cells with a power conversion efficiency of 4.11% were achieved based on an inverted device configuration of ITO/PFN-OX/PBDT-O-ADA:PC71BM/MoO3/Al. These results demonstrated that the construction of regularly alternating narrow band gap conjugated ternary copolymers can be an effective strategy for the development of electron-donating materials for polymer solar cells.
Co-reporter:Wei Li, Qingduan Li, Chunhui Duan, Shengjian Liu, Lei Ying, Fei Huang, Yong Cao
Dyes and Pigments 2015 Volume 113() pp:1-7
Publication Date(Web):February 2015
DOI:10.1016/j.dyepig.2014.07.034
•A series of star-shaped π-conjugated molecules with triphenylamine as the core were prepared.•Symmetric and asymmetric star-shaped architectures bearing peripheral electron-withdrawing groups both were reported.•The electronic structures and absorption characteristics varied with the electron-withdrawing ability of the end groups.•The current work presents an effective molecular design strategy to broaden the absorption profiles.A series of star-shaped π-conjugated molecules with triphenylamine as the core and a thiophene unit as the π-bridge were designed and synthesized based on a donor-π-bridge-acceptor type of molecular framework. Various peripheral electron-deficient groups including octyl-2-cyanoacrylate, octyl-2,3-dicyanoacrylate and 1,3-diethyl-2-thiobarbituric were incorporated as electron-withdrawing moieties. By altering the terminal groups, star-shaped molecules with symmetric and asymmetric architectures were obtained. It was worth noting that the asymmetric molecules exhibited well-extended absorbance with the combination of absorption features of different donor-acceptor species. Electrochemical investigation indicated that the frontier molecular orbital energy levels can be modified by the terminal electron-withdrawing groups. Despite the fabricated organic photovoltaic devices based on the new molecules as electron-donating materials exhibited less pronounced performances, we surmise the current work illustrated an effective molecular design strategy for the realization of broad absorbance that was beneficial for the utilization of solar photon flux.
Co-reporter:Ting Guo, Lei Yu, Yong Yang, Yanhu Li, Yun Tao, Qiong Hou, Lei Ying, Wei Yang, Hongbin Wu, Yong Cao
Journal of Luminescence 2015 Volume 167() pp:179-185
Publication Date(Web):November 2015
DOI:10.1016/j.jlumin.2015.06.026
•Hyperbranched red light-emitting polymers are synthesized.•Red light-emitting iridium complex is used as the branched core unit.•Hyperbranched polymers based on PFCz exhibit higher luminescence.•The highest luminous efficiency of 5.33 cd A−1 is attained.A series of hyperbranched π-conjugated light-emitting polymers containing an iridium complex as the branched core unit and polyfluorene or poly(fluorene-alt-carbazole) as the branched segments were synthesized via a palladium catalyzed Suzuki polymerization. Apparent Förster energy transfer in the photoluminescent spectra as thin films was observed, while no discernible characteristic absorbance and photoluminescence of the iridium complex can be realized in dilute solutions. Copolymers based on poly(fluorene-alt-carbazole) as the branched segments demonstrated enhanced highest occupied molecular orbital energy levels relative to those based on polyfluorene. The electroluminescent spectra of these copolymers exclusively showed the characteristic emission of the iridium complex, with corresponding CIE coordinates of (0.67±0.01, 0.31). All devices exhibited relatively slow roll-off of efficiency, and the best device performance with the maximum luminous efficiency of 5.33 cd A−1 was attained by using PFCzTiqIr3 as the emissive layer. These results indicated that the hyperbranched conjugated architectures can be a promising molecular design strategy for efficient electrophosphorescent light-emitting polymers.
Co-reporter:Xuelong Huang, Guichuan Zhang, Cheng Zhou, Shengjian Liu, Jie Zhang, Lei Ying, Fei Huang and Yong Cao
New Journal of Chemistry 2015 vol. 39(Issue 5) pp:3658-3664
Publication Date(Web):16 Feb 2015
DOI:10.1039/C4NJ02350A
A series of donor–acceptor type of π-conjugated oligomers based on dithieno[3,2-b;2′,3′-d]silole as the electron donor and 2,1,3-benzothiadiazole as the electron acceptor were designed and synthesized. It was found that the elongation of the molecular lengths of the chromophores can significantly influence the thermal properties, UV-vis absorption, electrochemical properties, and photovoltaic performances of fabricated organic solar cells. The higher molecular weight chromophore exhibited a narrower band gap compared to lower molecular weight counterparts. Solution processed bulk-heterojunction organic solar cells were fabricated with the inverted device structure of ITO/PFN-OX/oligomer:PCBM/MoO3/Al, in which the best device performance was achieved with a power conversion efficiency of 1.12%. These results indicated that the elongation of the molecular length of π-conjugated small-molecules can be an effective strategy for improving the organic photovoltaic performance of narrow band-gap chromophores.
Co-reporter:Wenkai Zhong, Jin Xu, Sheng Sun, Junfei Liang, Bin Zhang, Ruifeng He, Linfeng Lan, Fei Huang, Lei Ying, Wei Yang, Junbiao Peng, Yong Cao
Organic Electronics 2015 Volume 23() pp:17-27
Publication Date(Web):August 2015
DOI:10.1016/j.orgel.2015.04.005
•Two novel donor-π-acceptor type of conjugated polymers were synthesized.•Selenophene copolymer showed higher absorptivity and intermolecular ordering.•Device performances improved obviously after replacing thiophene with selenophene.Two novel donor-π-acceptor type of conjugated polymers with thiophene or selenophene as the π-bridge between the electron-donating indolocarbazole and electron-accepting difluorobenzotriazole unit, were designed and synthesized through a palladium catalyzed Suzuki polymerization. The replacement of the thiophene bridge by selenophene shows negligible effects on the geometries of molecular chain, as indicated by theoretical calculation on the basis of density of functional theory. However, obvious bathochromic shift along with the increased intensity in the UV–vis absorption profile of selenophene based copolymers relative to their thiophene based counterparts are realized, as can be attributed to the more pronounced heavy atom effects of the selenium than the sulfur atom. Compared to the thiophene based copolymer, the selenophene based copolymer exhibited about one order of magnitude increase in hole mobility, from 0.0014 to 0.01 cm2 V−1 s−1, and about two times of magnitude increase in power conversion efficiency, from 1.01% to 2.39%, as evaluated by field effect transistors and bulk heterojunction polymer solar cells, respectively. These results indicated that the selection of appropriate π-bridge by is crucial for the improvement of performance of π-conjugated polymers.
Co-reporter:Junfei Liang, Wenkai Zhong, Lei Ying, Wei Yang, Junbiao Peng, Yong Cao
Organic Electronics 2015 Volume 27() pp:1-6
Publication Date(Web):December 2015
DOI:10.1016/j.orgel.2015.08.024
•The performance of blue polymer light-emitting diodes can be improved by solvent vapor annealing.•The good solvents of chloroform and toluene for polymer PFSO were used.•The β-phase can be induced by solvent vapor annealing.•Stable electroluminescent spectra were attained after solvent vapor annealing.In this manuscript, we reported the effects of solvent vapor annealing on performances of blue polymer light-emitting diodes, where the blue light-emitting poly(dibenzothiophene-S,S-dioxide-co-dioctyl-2,7-fluorene) that comprising dibenzothiophene-S,S-dioxide with molar ratio of 10% was used as the emissive layer, and toluene or chloroform was use as the annealing solvents. It was noted that the performances of PLED in terms of both luminous efficiency and brightness were obviously enhanced by solvent vapor annealing treatment, which can be correlated to the improved film morphology. The formation of β-phase lead to more balanced electron and hole flux as evaluated by single carrier devices. The best device performance with luminous efficiency of 4.8 cd/A was realized, which increased about 70% relative to that of 2.77 cd/A for the pristine device. These observations demonstrated that the solvent vapor annealing approach can be an effective strategy to improve performances of polymer light-emitting diodes.
Co-reporter:Ting Guo, Wenkai Zhong, Jianhua Zou, Lei Ying, Wei Yang and Junbiao Peng
RSC Advances 2015 vol. 5(Issue 109) pp:89888-89894
Publication Date(Web):15 Oct 2015
DOI:10.1039/C5RA16717E
Efficient binary white-light-emitting electrophosphorescent copolymers were designed and synthesized via Suzuki polymerization. These copolymers were constructed by grafting a small amount of fluorinated iridium complexes as the side chain of the poly(fluorene-co-2,3-bisphenyl-6-fluoroquinoxaline) backbone. Efficient white-light emission was obtained simultaneously from the fluorescent blue light-emitting backbone and the tethered phosphorescent yellow light-emitting iridium species. A peak luminous efficiency of 7.20 cd A−1 with the Commission Internationale de l'Eclairage coordinates of (0.32, 0.38) were obtained based on copolymer PFQ-IrFppy. The white-light emission of devices from the copolymer is stable over the whole white-light region at various applied voltages, and the luminous efficiencies decline slightly with increasing current density. These observations highlighted that the strategy of utilizing both the blue fluorescence from the backbone and yellow phosphorescence from the side chains can be an encouraging approach to realize efficient binary white light-emission.
Co-reporter:Liuyuan Lan, Guichuan Zhang, Yang Dong, Lei Ying, Fei Huang, Yong Cao
Polymer 2015 Volume 67() pp:40-46
Publication Date(Web):12 June 2015
DOI:10.1016/j.polymer.2015.04.061
•Two new medium band gap conjugated copolymers containing naphtha[1,2-c:5,6-c]bis(2-octyl-[1,2,3]triazole) were synthesized.•The resulted copolymers showed medium band gap of about 1.8 eV.•Bulk-heterojunction polymer solar cells based on copolymer P1 exhibited a moderate power conversion efficiency of 2.58%.Two new donor–acceptor type of conjugated polymers derived from naphtho[1,2-c:5,6-c]bis(2-octyl-[1,2,3]triazole) and dithieno[3,2-b:2′,3′-d]silole were prepared by Stille polymerization. The thermal, electrochemical and photophysical properties of these copolymers were studied. Both polymers have excellent thermal stability with decomposition temperature up to 430 °C. The copolymers show medium band gap of ∼1.8 eV. Inverted bulk heterojunction solar cells in which these copolymers are used as electron donors in combination with PC61BM as the electron acceptor were fabricated. Under AM 1.5 G illumination at 100 mW/cm2, device based on P1:PC61BM as the photoactive layer displays a moderate power conversion efficiency of 2.58% with an open-circuit voltage of 0.83 V, a short circuit current of 5.53 mA/cm2, and a fill factor of 56.13%. Our work indicates that naphtho[1,2-c:5,6-c]bis(2-octyl-[1,2,3]triazole) can be a promising electron-deficient building block for designing donor–acceptor type of polymeric materials.
Co-reporter:Wei Li;Qingduan Li;Shengjian Liu;Chunhui Duan
Science China Chemistry 2015 Volume 58( Issue 2) pp:257-266
Publication Date(Web):2015 February
DOI:10.1007/s11426-014-5275-8
Four new 2D donor-acceptor conjugated polymers were designed and synthesized. These new polymers comprised fluorene-alt-triphenylamine or carbazole-alt-triphenylamine as the backbones, and pendants with 2,1,3-benzothiadiazole (BT) or naphtho[ 1,2-c:5,6-c]bis[1,2,5]thiadiazole (NT) in a triphenylamine unit as the side groups. By changing the acceptor BT for a stronger electron-withdrawing unit of NT moiety in the side chain, the energy levels, absorption spectra, band gaps, and charge-transport abilities of the resultant polymers could be effectively tuned. Bulk heterojunction solar cells with these polymers as the electron donors and (6,6)-phenyl-C71-butyric acid methyl ester as the electron acceptor exhibited high open-circuit voltage (more than 0.8 eV). The power conversion efficiency can be improved from 1.37% to 3.52% by replacing the BT with an NT moiety, which indicates that introducing NT as the side-chain building block can be an effective strategy to construct efficient 2D conjugated polymers for PSCs.
Co-reporter:Ting Guo;Lei Yu;Baofeng Zhao;Hongbin Wu;Wei Yang ;Yong Cao
Journal of Polymer Science Part A: Polymer Chemistry 2015 Volume 53( Issue 8) pp:1043-1051
Publication Date(Web):
DOI:10.1002/pola.27532
ABSTRACT
A series of blue light-emitting hyperbranched polymers comprising poly(fluorene-co-dibenzothiophene-S,S-dioxide) as the branch and benzene, triphenylamine, or triphenyltriazine as the core were synthesized by an “A2 + A2' + B3” approach of Suzuki polymerization, respectively. All resulted copolymers exhibited quite comparable thermal properties with the glass transition temperatures in the range of 59–68 °C and relatively high decomposition temperatures over 420 °C. Photoluminescent spectra exhibited slight variation with the molar ratio of the dibenzothiophene-S,S-dioxide unit and the size of the core units. Polymer light-emitting devices demonstrated blue emission with excellent stability of electroluminescence. Copolymers based on smaller core units of benzene and triphenylamine exhibited enhanced device performances regarding to that of triphenyltriazine. With the device configuration of ITO/PEDOT:PSS/polymer/CsF/Al, a maximum luminous efficiency of 4.5 cd A−1 was obtained with Commission Internationale de L'.Eclairage (CIE) coordinates of (0.16, 0.19) for the copolymer PFSO15B. These results indicated that hyperbranched structure can be a promising strategy to attain spectrally stable blue-light-emitting polymers with high efficiency. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2015, 53, 1043–1051
Co-reporter:Shengjian Liu, Chengmei Zhong, Sheng Dong, Jie Zhang, Xuelong Huang, Cheng Zhou, Junming Lu, Lei Ying, Lei Wang, Fei Huang, Yong Cao
Organic Electronics 2014 Volume 15(Issue 4) pp:850-857
Publication Date(Web):April 2014
DOI:10.1016/j.orgel.2014.01.016
•A family of aminoalkyl-functionalized blue-, green- and red-emitting polyfluorene derivatives were synthesized.•The aminoalkyl-functionalized copolymers exhibited dual functions of efficient light emission and electron injection.•Device performances can be optimized by varying the molar ratios of the incorporated aminoalkyl side groups.A family of aminoalkyl functionalized blue-, green- and red-emitting polyfluorene based copolymers were synthesized by Suzuki copolymerization. Dibenzothiophene-S,S-dioxide-3,7-diyl (FSO), 2,1,3-benzothiadiazole (BT) and 4,7-di-2-thienyl-2,1,3-benzothiadiazole (DTBT) were incorporated into the backbone of copolymers as blue, green and red chromophores, respectively. It was realized that for all these aminoalkyl functionalized copolymers, the thermal stabilities, UV–vis absorption and electrochemical properties are not affected by molar ratio of aminoalkyl side groups. However, the increased amino-groups content can induce the formation of excimer in FSO based blue-emitting copolymer, which in turn leaded to broadened photoluminescence and electroluminescence spectra along with decreased emission efficiency. In contrast, device based on green and red-emitting copolymers exhibited stable emission, and device performance improved progressively with the enhanced content of aminoalkyl co-monomers. Comparing to the copolymers without aminoalkyl side chains, aminoalkyl functioned materials exhibited distinctly improved device performances for the application as emissive layer in light emitting diodes using high work-function Al as cathode due to the formation of interfacial dipoles that can facilitate electron injection. The maximum luminous efficiency of 3.28, 7.31 and 0.79 cd A−1 was achieved based on copolymers BFN1, GFN15 and RFN15, respectively with device architecture of ITO/PEDOT:PSS/PVK/copolymer/Al. These results indicate that aminoalkyl functionalized copolymers can have great potential for the application as efficient light-emitting layer with high work-function/air-stable cathode.Graphical abstract
Co-reporter:Yong Yang, Lei Yu, Yong Xue, Qinghua Zou, Bin Zhang, Lei Ying, Wei Yang, Junbiao Peng, Yong Cao
Polymer 2014 Volume 55(Issue 7) pp:1698-1706
Publication Date(Web):1 April 2014
DOI:10.1016/j.polymer.2014.02.032
A series of efficient and spectrally stable blue light-emitting polyfluorene derivatives containing 3,7-dibenzothiophene-S,S-dioxide (SO) unit in main chain and oxadiazole (OXD) moiety in the side chain were synthesized via Suzuki copolymerization. It was realized that the glass transition temperatures of the resulted copolymers PFSO-OXD increased gradually with the content of OXD, while the UV-vis absorption, photoluminescence spectra, as well as electrochemical properties were not significantly influenced by the molar ratio of OXD unit. Apparent solvatochromism of copolymers PFSO-OXD can be realized by varying polarity of solvents from toluene to dichloromethane. Light-emitting devices based on PFSO-OXD exhibited superior performances to those of PFSO and PF-OXD20 due to the more balanced charge carrier mobility of the devices. The electroluminescence spectra of all copolymers are independent with the current densities and thermal annealing. The best device performance was achieved based on PFSO-OXD20 with a maximal luminous efficiency of 4.9 cd A−1 with the Commission Internationale de L'Eclairage (CIE) coordinates of (0.16, 0.12). The results indicated that the strategy of concurrently incorporating SO and OXD unit into the main chain and side chain of polyfluorenes, respectively has great potential to achieve efficient blue light-emitting polymers.
Co-reporter:Ruifeng He, Lei Yu, Ping Cai, Feng Peng, Jin Xu, Lei Ying, Junwu Chen, Wei Yang, and Yong Cao
Macromolecules 2014 Volume 47(Issue 9) pp:2921-2928
Publication Date(Web):April 17, 2014
DOI:10.1021/ma500333r
A series of new 2,7-dioctyl-substituted dibenzo[a,c]phenazine (BPz) derivatives were designed and synthesized as electron-deficient units, which were copolymerized with an electron-rich indacenodithiophene (IDT) to construct narrow-band-gap copolymers PIDT–OHBPz, PIDT–OFBPz, and PIDT–OBPQ via Stille polycondensation. The 2,7-dioctyl substituents enhanced solubility and offered a new approach for developing various BPz derivatives. All copolymers showed high hole mobilities above 0.01 cm2 V–1 s–1 as measured by field effect transistors. The best performance of polymer solar cell was achieved based on PIDT–OFBPz with inverted device structure of ITO/ZnO/PFN/polymer:PC61BM/MoO3/Al, which showed an open-circuit voltage (Voc) of 0.97 V, a short-circuit current (Jsc) of 8.96 mA/cm2, and a fill factor (FF) of 58.99%, leading to a high power conversion efficiency (PCE) of 5.13%. These results indicate that 2,7-alkyl-substituted BPz derivatives can be used as an excellent electron-deficient building block for the construction of high-performance organic electronic materials.
Co-reporter:Yang Dong, Wanzhu Cai, Ming Wang, Qingduan Li, Lei Ying, Fei Huang, Yong Cao
Organic Electronics 2013 Volume 14(Issue 10) pp:2459-2467
Publication Date(Web):October 2013
DOI:10.1016/j.orgel.2013.06.002
•Three novel narrow band gap conjugated copolymers containing [1,2,5]thiadiazolo[3,4-f]benzotriazole were synthesized.•The copolymers exhibited comparatively narrow band gap of ca. 1 eV.•Broad photocurrent response up to 1.1 μm was realized.Three novel donor–acceptor type of narrow band gap conjugated copolymers were synthesized through a palladium-catalyzed Stille copolymerization based on [1,2,5]thiadiazolo[3,4-f]benzotriazole (TBZ) derivatives as acceptor and 4,8-di(2,3-didecylthiophen-5-yl)-benzo[1,2-b:4,5-b′]dithiophene (BDT) as donor. All resulted copolymers exhibited absorbance up to near-infrared region along with relatively narrow band gap in the range of 0.96–1.10 eV. Cyclic voltammetry measurements illustrated that the highest occupied molecular orbital energy levels of copolymers lay in the range of −5.04 to −5.13 eV, and lowest unoccupied molecular orbital (LUMO) energy levels were in the range of −4.03 to −4.16 eV. Photovoltaic performances were evaluated based on the resulted copolymers as donor and [6,6]-phenyl-C60 butyric acid methyl ester (PC61BM) as acceptor with optimized weight ratio of 1:2. All devices displayed comparatively low power conversion efficiencies in the range of 0.1–0.4% due to the low-lying LUMO energy levels. Broad photocurrent response up to near infrared region of 1.1 μm was realized for copolymer P2 that containing thiophene unit as the bridge between BDT and TBZ moieties, indicating that it can be potentially applied for near infrared photodetectors.Graphical abstract
Co-reporter:Wenkai Zhong, Jingyang Xiao, Sheng Sun, Xiao-Fang Jiang, Linfeng Lan, Lei Ying, Wei Yang, Hin-Lap Yip, Fei Huang and Yong Cao
Journal of Materials Chemistry A 2016 - vol. 4(Issue 21) pp:NaN4727-4727
Publication Date(Web):2016/04/11
DOI:10.1039/C6TC00271D
Two wide bandgap donor–acceptor type π-conjugated polymers based on dithienobenzodithiophene as the donor unit and difluorobenzotriazole or difluorobenzothiadiazole as the acceptor unit were designed and synthesized. The copolymer based on difluorobenzothiadiazole exhibited more pronounced aggregations in chlorobenzene solutions than that of the copolymer based on difluorobenzotriazole. Both copolymers exhibited relatively wide bandgaps with deep highest occupied molecular orbitals, leading to high open circuit voltages of over 0.95 V for the fabricated polymer solar cells. These copolymers exhibited quite analogous hole mobility of about 0.1 cm2 V−1 s−1 as measured by organic field effect transistors. Bulk heterojunction polymer solar cells based on these copolymers as the electron-donating materials and PC71BM as the electron-accepting material exhibited relatively high performance, with the best power conversion efficiency of 7.45% attained for the copolymer based on the difluorobenzothiadiazole unit. These results demonstrated that the constructed wide bandgap π-conjugated polymers can be promising candidates for the fabrication of high performance solar cells with multi-junction architectures.
Co-reporter:Jing Yue, Sheng Sun, Junfei Liang, Wenkai Zhong, Linfeng Lan, Lei Ying, Fei Huang, Wei Yang and Yong Cao
Journal of Materials Chemistry A 2016 - vol. 4(Issue 13) pp:NaN2479-2479
Publication Date(Web):2016/02/15
DOI:10.1039/C6TC00051G
Two novel regio-isomeric π-conjugated polymers consisting of the pyridyl unit flanked by diketopyrrolopyrrole as the electron-accepting unit and 2,5-bis(3-hexylthiophen-2-yl)thieno[3,2-b]thiophene as the electron-donating unit were designed and synthesized. The comparison of the optical and electrochemical properties indicated that the copolymer based on the nitrogen atom proximal to the central diketopyrrolopyrrole unit (p-PDBPy) exhibited bathochromic shifted absorption spectra and narrower bandgaps than the counterpart copolymer (d-PDBPy) with the distally oriented nitrogen atom, which can be correlated with the stronger intermolecular aggregation of the former as a result of the different intrinsic molecular geometry of the polymer backbone. Of particular interest is that the copolymer p-PDBPy exhibited a moderate hole mobility of 0.35 cm2 V−1 s−1, which is about three orders of magnitude higher than the hole mobility of 3.2 × 10−4 cm2 V−1 s−1 obtained based on the counterpart copolymer d-PDBPy, as measured using organic field-effect transistors. These results demonstrated that the delicate control of the pyridyl orientations along the polymer backbone is of vital importance for the molecular design of π-conjugated polymers for high-performance organic electronic devices.
Co-reporter:Yunping Huang, Nannan Zheng, Zhenfeng Wang, Lei Ying, Fei Huang and Yong Cao
Chemical Communications 2017 - vol. 53(Issue 12) pp:NaN2000-2000
Publication Date(Web):2017/01/18
DOI:10.1039/C6CC09317E
Regioregular polymers based on an asymmetric dithieno[3,2-b:2′,3′-d]pyridin-5(4H)-one (TN) unit that consists of a lactam moiety were synthesized via palladium-catalyzed direct heteroarylation polymerization. The random orientation of the lactam moiety can be prevented by carefully designing the monomers with tailored molecular structures. It is noted that connecting the TN unit in different fashions generates substructures in the polymer backbone with different electronic structures. Compared to the random counterparts, the regioregular homopolymers exhibit dramatically discrepant optical properties and electronic structures, while the variations in the copolymers are less distinguished.
Co-reporter:Zhiming Zhong, Xiaojun Wang, Sen Zhao, Feng Peng, Jian Wang, Lei Ying, Wei Yang, Junbiao Peng and Yong Cao
Journal of Materials Chemistry A 2017 - vol. 5(Issue 25) pp:NaN6168-6168
Publication Date(Web):2017/05/15
DOI:10.1039/C7TC01280B
The effects of the component distribution of a red light-emitting random copolymer poly(9,9-dioctylfluorene-co-(4,7-dithienyl-benzothiadiazole)) (DOF:DBT = 9:1 mol/mol, PFO-DBT10) on its optoelectronic properties are systematically investigated. The PFO-DBT10 copolymers with various molecular weights (MWs) have identical absorption spectra and energy levels. However, as the molecular weight increases, so does the photoluminescence intensity ratio of DBT to DOF segments. For polymer light-emitting diodes, PFO-DBT10 with a large MW shows an enhanced charge trapping effect, leading to increased operation voltage under any given current density, worse luminous efficiency, and more saturated red emission, compared to the one with a small MW. The experiments are performed within the framework of the component's molar ratio dispersion of random copolymer chains induced by the MW using the binomial distribution formula. According to the formula, the high MW random copolymer is analogous to the ideal PFO-DBT10 in terms of the uniformly distributed units. The low MW random copolymer is more likely to be a mixture of pure PFO and PFO-DBTx, in which the molar ratio x varies, due to its dispersive component distribution. This work offers a new approach to study the opto-electronic properties of random copolymers in the light of component distribution.
Co-reporter:Junfei Liang, Zhenji Zhong, Shuang Li, Xiao-Fang Jiang, Lei Ying, Wei Yang, Junbiao Peng and Yong Cao
Journal of Materials Chemistry A 2017 - vol. 5(Issue 9) pp:NaN2403-2403
Publication Date(Web):2017/01/31
DOI:10.1039/C6TC05264A
Efficient white polymer light-emitting diodes were developed based on exciplex electroluminescence from a single polymer PFTS that consists of an electron-donating side chain and an electron-withdrawing backbone. It is noted that the device performances can be dramatically improved by incorporating a certain amount of high triplet energy level poly(9-vinylcarbazole) (PVK) into the emissive layer, which can lead to a more balanced charge carrier and decrease the exciton back transfer from the formed exciplex to the backbone of poly(fluorene-co-dibenzothiophene-5,5-dioxide). The luminous efficiency can be further improved by utilizing PVK as the hole transport layer, which can achieve greenish white emission with a luminous efficiency of 9.12 cd A−1 and CIE coordinates of (0.25, 0.37). Of particular interest is that the emission of PFTS can be modified by varying the thickness of the emissive layer by virtue of micro-cavity effects, where the optimized device exhibits a remarkable luminous efficiency of 7.37 cd A−1 with CIE coordinates of (0.30, 0.43). These observations demonstrated the great promise of utilizing the single polymer with the exciplex emission for the construction of efficient white polymer light-emitting devices.
![Pyrrolo[3,4-c]pyrrole-1,4-dione, 3,6-bis(5-bromo-2-thienyl)-2,5-dihydro-2,5-bis(2-octyldodecyl)-](/data/chemimg/139000/1260685-63-9.png)
![Pyrrolo[3,4-c]pyrrole-1,4-dione, 3,6-bis(5-bromo-2-thienyl)-2,5-dihydro-2,5-bis(2-octyldodecyl)-](/data/chemimg/139000/1260685-63-9_b.png)
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![Poly[[2,3,5,6-tetrahydro-2,5-bis(2-octyldodecyl)-3,6-dioxopyrrolo[3,4-c]pyrrole-1,4-diyl]-2,5-thiophenediyl[4,8-bis[1-(2-hexyldecyl)-1H-1,2,3-triazol-4-yl]benzo[1,2-b:4,5-b']dithiophene-2,6-diyl]-2,5-thiophenediyl]](/data/chemimg/3722600/1793071-16-5_b.png)
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![2,5-Bis(trimethylstannyl)thieno[3,2-b]thiophene](http://img.cochemist.com/ccimg/470000/469912-82-1_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)
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