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1.
A donor-acceptor (D-A) conjugated copolymer PSBT-FTT, incorporating alkylthiophenylthienyl (SBT) side chains on benzo[1,2-b:4,5-b']dithiophene units (BDT), was designed and synthesized. Compared to the analogical polymer PSB-FTT with alkylthiophenyl (SB) side chains, PSBT-FTT exhibits stronger interchain π-π interaction, more redshifted absorption spectrum, stronger absorption coefficient, better compatibility with (7,7)-phenyl-C71-butyric acid methyl ester (PC71BM), more effective exciton dissociation and higher hole mobility. Therefore, the PSBT-FTT-based bulk heterojunction polymer solar cells (PSCs) achieved a PCE value of 7.06% that is almost 50% higher than 4.83% of the PSB-FTT based PSCs. The result indicates that the introducing SBT side chains is an excellent strategy for designing high performance photovoltaic polymers. 相似文献
2.
Kun Lu Jin Fang Zai Yu Han Yan Xiangwei Zhu Yajie Zhang Chang He Zhixiang Wei 《Organic Electronics》2012,13(12):3234-3243
Two donor–acceptor (D–A) type conjugated polymers using dodecyl- and ethylhexyl-thiophene substituted benzo[1,2-b:4,5-b′]dithiophene (BDT-DDT and BDT-EHT, respectively) as donors and n-alkylthieno[3,4-c]pyrrole-4,6-dione (TPD) as acceptor were synthesized and characterized. The thiophene substituted BDT unit was recognized as a two-dimensional (2D) π-extended segment with high carrier mobility and TPD unit was a relatively strong electron-drawing acceptor, which could lead to deep-lying highest occupied molecular orbital (HOMO) levels of the polymers. The optical properties, electrochemical behavior, and charge carrier properties of the polymers were compared in parallel. The results indicated that ethylhexyl-substitution could optimize the polymer structures and properties. The bulk-heterojunction polymer solar cells (PSCs) based on the two polymers were fabricated and characterized. The devices based on ethylhexyl-substituted polymer showed better performance than that of dodecyl-substituted one. Further analysis proved that the improvement was mainly ascribed to the formation of well-defined nanostructures by using branched ethylhexyl side chains, which facilitated charge separation and transport in the bicontinous active layer. This study suggests that obtaining appropriate film morphology and phase separation by altering alkyl side chains is extraordinary important for high performance PSCs based on D–A type polymers. 相似文献
3.
Zhao Li Sai‐Wing Tsang Xiaomei Du Ludmila Scoles Gilles Robertson Yanguang Zhang Floyd Toll Ye Tao Jianping Lu Jianfu Ding 《Advanced functional materials》2011,21(17):3331-3336
A series of alternating copolymers of cyclopenta[2,1‐b;3,4‐b′]dithiophene (CPDT) and thieno[3,4‐c]pyrrole‐4,6‐dione (TPD) have been prepared and characterized for polymer solar cell (PSC) applications. Different alkyl side chains, including butyl (Bu), hexyl (He), octyl (Oc), and 2‐ethylhexyl (EH), are introduced to the TPD unit in order to adjust the packing of the polymer chain in the solid state, while the hexyl side chain on the CPDT unit remains unchanged to simplify discussion. The polymers in this series have a simple main chain structure and can be synthesized easily, have a narrow band gap and a broad light absorption. The different alkyl chains on the TPD unit not only significantly influence the solubility and chain packing, but also fine tune the energy levels of the polymers. The polymers with Oc or EH group have lower HOMO (highest occupied molecular orbital) and LUMO (lowest unoccupied molecular orbital) energy levels, resulting higher open circuit voltages (Voc) of the PSC devices. Power conversion efficiencies (PCEs) up to 5.5% and 6.4% are obtained from the devices of the Oc substituted polymer (PCPDTTPD‐Oc) with PC61BM and PC71BM, respectively. This side chain effect on the PSC performance is related to the formation of a fine bulk heterojunction structure of polymer and PCBM domains, as observed with atomic force microscopy. 相似文献
4.
Dongfeng Dang Manjun Xiao Pei Zhou Junwei Shi Qiang Tao Hua Tan Yafei Wang Xichang Bao Yu Liu Ergang Wang Renqiang Yang Weiguo Zhu 《Organic Electronics》2014,15(11):2876-2884
A class of low band-gap two-dimensional conjugated polymers of PBDTT-FQ, PBDTT-TQ, PBDTT-BTQ and PBDTT-TTQ was designed and synthesized, which contains the same di(alkylthiophene)-substituted benzo[1,2-b:4,5-b′]dithiophene (BDTT) and 6,7-difluoroquinoxaline (Q) units, as well as various conjugated spacers of furan, thiophene, bithiophene and thieno[3,2-b]thiophene in the main chain. Significant effect of the varied spacers between the BDTT and Q units on the thermal, optical, electrochemical and photovoltaic properties was investigated and observed for these two-dimensional copolymers in the polymer solar cells. The maximum power conversion efficiency of 5.9% with a short circuit current of 13.7 mA/cm2 and a fill factor of 0.56 was obtained for the PBDTT-TQ with thiophene spacer in the bulk hetero-junction PSCs using [6,6]-phenyl-C71-butyric acid methyl ester as acceptor. 相似文献
5.
Qunping Fan Yu Liu Manjun Xiao Hua Tan Yafei Wang Wenyan Su Delong Yu Renqiang Yang Weiguo Zhu 《Organic Electronics》2014,15(11):3375-3383
Two novel donor–acceptor (D–A)-type conjugated polymers of PTTPPz-BDT and PTTPPz-BDTT were successfully synthesized by Stille coupling polymerization, in which 7,8-dialkoxy benzo[1,2-b:4,5-b′]dithiophene (BDT) and 7,8-bithienyl benzo[1,2-b:4,5-b′]dithiophene (BDTT) were used as donor units, thiophene and pyrene-fused phenazine (PPz) were employed as π-bridges and acceptor units, respectively. High carrier mobilities, broad absorption spectra, narrow optical band gaps, and low HOMO energy levels were observed for both polymers. Furthermore, high-efficiency photovoltaic performance with power conversion efficiency (PCE) over 4.25% was exhibited in their polymer solar cells (PSCs) using [6,6]-phenyl-C71-butyric-acid-methyl-ester (PC71BM) as acceptor. The maximum PCE of 4.86% with short-circuit current density of 11.10 mA cm−2 and fill factor of 62.5% was obtained in the PTTPPz-BDTT based cell. These results indicate that incorporating large planar PPz moiety into D–A-type copolymer is an efficient approach to improve photovoltaic performance for PSCs. 相似文献
6.
Combinatorial Study of Temperature‐Dependent Nanostructure and Electrical Conduction of Polymer Semiconductors: Even Bimodal Orientation Can Enhance 3D Charge Transport
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Sangsik Park Moo Hyung Lee Kwang Seok Ahn Hyun Ho Choi Jihye Shin Jie Xu Jianguo Mei Kilwon Cho Zhenan Bao Dong Ryeol Lee Moon Sung Kang Do Hwan Kim 《Advanced functional materials》2016,26(26):4627-4634
Temperature‐dependent (80–350 K) charge transport in polymer semiconductor thin films is studied in parallel with in situ X‐ray structural characterization at equivalent temperatures. The study is conducted on a pair of isoindigo‐based polymers containing the same π‐conjugated backbone with different side chains: one with siloxane‐terminated side chains (PII2T‐Si) and the other with branched alkyl‐terminated side chains (PII2T‐Ref). The different chemical moiety in the side chain results in a completely different film morphology. PII2T‐Si films show domains of both edge‐on and face‐on orientations (bimodal orientation) while PII2T‐Ref films show domains of edge‐on orientation (unimodal orientation). Electrical transport properties of this pair of polymers are also distinctive, especially at high temperatures (>230 K). Smaller activation energy (E A) and larger pre‐exponential factor (μ 0) in the mobility‐temperature Arrhenius relation are obtained for PII2T‐Si films when compared to those for PII2T‐Ref films. The results indicate that the more effective transport pathway is formed for PII2T‐Si films than for the other, despite the bimodally oriented film structure. The closer π–π packing distance, the longer coherence length of the molecular ordering, and the smaller disorder of the transport energy states for PII2T‐Si films altogether support the conduction to occur more effectively through a system with both edge‐on and face on orientations of the conjugated molecules. Reminding the 3D nature of conduction in polymer semiconductor, our results suggest that the engineering rules for advanced polymer semiconductors should not simply focus on obtaining films with conjugated backbone in edge‐on orientation only. Instead, the engineering should also encounter the contribution of the inevitable off‐directional transport process to attain effective transport from polymer thin films. 相似文献
7.
Effect of annealing-induced oxidation of molybdenum oxide on organic photovoltaic device performance
Molybdenum oxide (MoOx) has been widely used as a hole transport layer in organic photovoltaic cells (OPVs), whose performance can be improved by inserting a MoOx layer between an organic active layer and a transparent anode because of efficient carrier dissociation. In this study, the influence of thermally annealed MoOx on the photovoltaic performance of OPVs was first investigated using low-bandgap polymer and [6,6]-phenyl C71-butyric acid methyl ester (PC71BM) blend films as the active layer. We used three low-bandgap polymers: poly[2,6-(4,4-bis-(2-ethylhexyl)-4H-cyclopenta[2,1-b;3,4-b′]dithiophene)-alt-4,7(2,1,3-benzothiadiazole)] (PCPDTBT), poly(4,8-bis[(2-ethylhexyl)oxy]benzo[1,2-b:4,5-b′]dithiophene-2,6-diyl3-fluoro-2-[(2-ethylhexyl)carbonyl]thieno[3,4-b]thiophenediyl) (PTB7), and poly([2,6′-4,8-di(5-ethylhexylthienyl)benzo[1,2-b,3,3-b]dithiophene]3-fluoro-2[(2-ethylhexyl)carbonyl]thieno[3,4-b]thiophenediyl) (PTB7-Th). Power conversion efficiencies were drastically increased for all investigated polymers when the as-deposited MoOx layer was annealed at 160 °C for 5 min. In particular, a high efficiency of 6.57% was achieved when PTB7 was used; for comparison, the efficiency of a reference device with an as-deposited MoOx layer (not subjected to annealing) was 1.40%. Specifically, the short-circuit current density and fill factor were remarkably improved after annealing, which means that efficient carrier dissociation was achieved in the active layer. We evaluated optical absorption and surface morphology to elucidate reasons behind the improved photovoltaic performance, and these parameters only slightly changed after annealing. In contrast, angle-dependent X-ray photoelectron spectroscopy revealed that the MoOx layer was oxidized after annealing. In general, the oxygen vacancies of MoOx act as carrier traps; a reduction in the number of carrier traps causes high hole mobility in the organic layer, which, in turn, results in an improved photovoltaic performance. Therefore, our results indicate that the annealing-induced oxidation of MoOx is useful for achieving high photovoltaic performance. 相似文献
8.
Kun Lu Jin Fang Han Yan Xiangwei Zhu Yuanping Yi Zhixiang Wei 《Organic Electronics》2013,14(10):2652-2661
Two novel donor–acceptor (D–A) type conjugated polymers using thiophene and hexyl-thiophene spacers between two-dimensional alkyl-thiophene substituted benzo[1,2-b:4,5-b′]dithiophene (BDT-RT) and alkylthieno[3,4-c]pyrrole-4,6-dione (TPD) units are synthesized and characterized. The effects of incorporation of alkyl-thiophene spacers in the polymer backbone on the optical, electrochemical, charge transport and photovoltaic properties are studied. The bulk-heterojunction (BHJ) polymer solar cells (PSCs) based on the polymer with hexyl-thiophene spacers show much better performance (with power conversion efficiency up to 6.08%) than that of polymer without spacers, which is very distinct from alkyl-thiophene spacer effect of other BDT-TPD structured polymers reported previously. The experimental results and theoretical calculations show that a subtle tuning of chemical structure can significantly influence the absorption coefficient by inserting alkyl-thiophene spacers in the polymer backbone. This provides an important route for designing new materials to obtain higher current density (Jsc) and fill factors (FF). 相似文献
9.
High‐Performance All‐Polymer Photoresponse Devices Based on Acceptor–Acceptor Conjugated Polymers
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Xiaofen Wang Lei Lv Lingliang Li Yusheng Chen Kai Zhang Haoran Chen Huanli Dong Jinsong Huang Guozhen Shen Zhou Yang Hui Huang 《Advanced functional materials》2016,26(34):6306-6315
Three acceptor–acceptor (A–A) type conjugated polymers based on isoindigo and naphthalene diimide/perylene diimide are designed and synthesized to study the effects of building blocks and alkyl chains on the polymer properties and performance of all‐polymer photoresponse devices. Variation of the building blocks and alkyl chains can influence the thermal, optical, and electrochemical properties of the polymers, as indicated by thermogravimetric analysis, differential scanning calorimetry, UV–vis, cyclic voltammetry, and density functional theory calculations. Based on the A–A type conjugated polymers, the most efficient all‐polymer photovoltaic cells are achieved with an efficiency of 2.68%, and the first all‐polymer photodetectors are constructed with high responsivity (0.12 A W?1) and detectivity (1.2 × 1012 Jones), comparable to those of the best fullerene based organic photodetectors and inorganic photodetectors. Photoluminescence spectra, charge transport properties, and morphology of blend films are investigated to elucidate the influence of polymeric structures on device performances. This contribution demonstrates a strategy of systematically tuning the polymeric structures to achieve high performance all‐polymer photoresponse devices. 相似文献
10.
Ta‐Ya Chu Jianping Lu Serge Beaupré Yanguang Zhang Jean‐Rémi Pouliot Jiayun Zhou Ahmed Najari Mario Leclerc Ye Tao 《Advanced functional materials》2012,22(11):2345-2351
A series of low‐bandgap alternating copolymers of dithienosilole and thienopyrrolodione (PDTSTPDs) are prepared to investigate the effects of the polymer molecular weight and the alkyl chain length of the thienopyrrole‐4,6‐dione (TPD) unit on the photovoltaic performance. High‐molecular‐weight PDTSTPD leads to a higher hole mobility, lower device series resistance, a larger fill factor, and a higher photocurrent in PDTSTPD:[6,6]‐phenyl C71 butyric acid methyl ester (PC71BM) bulk‐heterojunction solar cells. Different side‐chain lengths show a significant impact on the interchain packing between polymers and affect the blend film morphology due to different solubilities. A high power conversion efficiency of 7.5% is achieved for a solar cell with a 1.0 cm2 active area, along with a maximum external quantum efficiency (EQE) of 63% in the red region. 相似文献
11.
Two new conjugated D–A polymers P3 (PBTT-d-BTT) and P4 (PBTT-d-TPD) based on same benzo[1,2-b:3,4-b′:6,5-b″] trithiophene (BTT) donor and different acceptors monomers 5,8-dibromo-2-dodecanoylbenzo[1,2-b:3,4-b′:6,5-b″] trithiophene (d-BTT), and 1,3-dibromo-5-(2-ethylhexyl)thieno[3,4]pyrrol-4,6-dione (d-TPD) respectively, were synthesized by Stille cross-coupling reaction and characterized by gel permeation chromatography (GPC), 1H NMR, UV–Vis absorption, thermal analysis and electrochemical cyclic voltammetry (CV) tests. Photovoltaic properties of the polymers were studied by using the polymers as donor and PC71BM as acceptor with a weight ratio of polymer:PC71BM 1:1, 1:2 and 1:2.5. The optimized photovoltaic device was fabricated with an active layer of a blend P3:PC71BM and P4:PC71BM with a blend ratio of 1:2 showed PCE 3.16% and 2.42%, respectively under illumination of AM 1.5 at 100 mW/cm2 with solar simulator. The PCE of the device based on P3:PC71BM processed with DIO/o-DCB has been further improved up to 4.64% with Jsc of 10.52 mA/cm2 and FF of 0.58 attributed to the increase in crystalline nature of active layer and more balanced charge transport in the device, induced by DIO additive. 相似文献
12.
Improved Morphology and Efficiency of Polymer Solar Cells by Processing Donor–Acceptor Copolymer Additives
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Baobing Fan Chen Sun Xiao‐Fang Jiang Guichuan Zhang Zhiming Chen Lei Ying Fei Huang Yong Cao 《Advanced functional materials》2016,26(35):6479-6488
A novel wide‐bandgap conjugated polymer PBTA‐FPh based on benzodithiophene‐alt‐benzo[1,2,3]triazole as the main chain and a polar pentafluorothiophenyl (FPh) group in the side chain has been designed and synthesized. In comparison to the pristine polymer PBTA‐BO that consists of nonpolar alkyl side chains, the resulting PBTA‐FPh exhibits less pronounced aggregation while possessing analogous optical and electrochemical bandgaps. Contact angle measurements demonstrate that the surface energy can be enhanced by incorporating FPh moiety, leading to a better miscibility of PBTA‐BO with PC71BM in the presence of a certain amount of PBTA‐FPh. The photoactive layer of PBTA‐BO:PC71BM:PBTA‐FPh with weight ratio of 1:1.2:0.02% exhibits a percolated network with the fibrous features, as revealed by transmission electron microscopy measurements. Of particular interest is the significantly improved photovoltaic performances of polymer solar cell devices for which the power conversion efficiency is enhanced from 6.46% for the control device to 7.91% for device processed with PBTA‐FPh as the polymeric additive. These observations indicate that introducing donor–acceptor type of polymeric additive comprising of polar groups in the side chain can be a promising strategy for the fabrication of high‐performance polymer solar cells. 相似文献
13.
Optimization and Analysis of Conjugated Polymer Side Chains for High‐Performance Organic Photovoltaic Cells
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Ji‐Hoon Kim Sebastian Wood Jong Baek Park Jessica Wade Myungkwan Song Sung Cheol Yoon In Hwan Jung Ji‐Seon Kim Do‐Hoon Hwang 《Advanced functional materials》2016,26(10):1517-1525
Optimization and analysis of conjugated polymer side chains for high‐performance organic photovoltaic cells (OPVs) reveal a critical relationship between the chemical structure of the side chains and photovoltaic properties of polymer‐based bulk heterojunction OPVs. In particular, the impact of the alkyl side chain length on the π‐bridging (thienothiophene, TT) unit is considered by designing and synthesizing a series of benzodithiophene derivatives (BDT(T)) and thieno[3,2‐b]thiophene‐π‐bridged thieno[3,4‐c]pyrrole‐4,6(5H)‐dione (ttTPD) alternating copolymers, PBDT(T)‐(R2)ttTPD, with alkyl chains of varying length on the TT unit. Using a combination of 2D X‐ray diffraction, Raman spectroscopy, and electrical device characterization, it is elucidated in detail how these subtle changes to the chemical structure affect the molecular conformation, thin film molecular packing, blend film morphology, optoelectronic properties, and hence overall photovoltaic performance. For copolymers employing both the alkoxy or alkylthienyl‐substituted BDT motifs, it is found that octyl side chains on TT unit yield the maximum degree of molecular backbone coplanarity and result in the highest quality of molecular packing and optimized hole mobility. Inverted devices fabricated using this PBDTT‐8ttTPD: polymer/[6,6]‐phenyl‐C71‐butylic acid methyl ester active layer show a maximum power conversion efficiency (PCE) of 8.7% with large area cells (0.64 cm2) maintaining a PCE of 7.5%. 相似文献
14.
Young‐Jae Jin Jung‐Eun Bae Kwang‐Soo Cho Wang‐Eun Lee Dong‐Yeon Hwang Giseop Kwak 《Advanced functional materials》2014,24(13):1928-1937
High molecular weight poly(diphenylacetylene) [PDPA] derivatives are introduced as fluorescent, soft conjugated polymers that exist in the gum state at room temperature. The gum‐like behavior of the polymers is easily modified according to the side alkyl chain length and substitution position. Long alkyl chain‐coupled PDPA derivatives provide soft and sticky gums at room temperature. Manual kneading of gum polymers produce soft films with very smooth surfaces. The gum polymers show an endothermic transition due to the melting of long alkyl chains. The X‐ray diffraction of gum polymers reveals a new signal due to the molten aliphatic chains. The gum polymers show significant viscoelastic relaxation at the melting temperature of the alkyl side chains. The dynamic thermo‐mechanical analysis (DTMA) of gum polymers at room temperature suggest that the meta‐substituted polymer is softer and stickier than para‐polymer. Rheological analysis suggests that the meta‐polymer has less entanglement than para‐polymer. The fluorescence emission of gum polymer is quite intense in the film and solution. The gum polymer film is readily stretched to produce a uniaxually oriented film. Stretching and subsequent relaxation of elastomer‐supported gum polymer film generate buckles perpendicular to the axis of strain. The gum polymer film accommodates the large strain without cracking and delamination. 相似文献
15.
The impact of alkyl chain length of different additives, such as 1,4-diiodobutane (DIB), 1,6-diiodohexane (DIH), 1,8-diiodooctane (DIO) and 1,10-diiododecane (DID), on the PC71BM distribution in PTB7:PC71BM-based polymer solar cells, is systematically investigated, for the first time. Among these additives, DIO is found to have the optimum alkyl chain length that maximizes the performance of PTB7:PC71BM based polymer solar cells, attaining a power conversion efficiency as high as 8.84%, which is almost four times higher than that without any additives. For DID additives (longer alkyl chain length than DIO), a drop in efficiency to 7.91% was observed. Experimental investigations show that the microstructure of the bulk and the surface layer as well as the surface morphology of the PTB7:PC71BM polymer film can be controlled simultaneously by varying the alkyl chain length of additives. Results also show that the substantial improvement in performance is attributed to the improved 1) phase segregation, 2) PC71BM distribution uniformity in the bulk of the PTB7:PC71BM film, 3) surface smoothness and 4) high PTB7 content at the interface between the active layer and the top electrode. 相似文献
16.
The electron–donor polymers containing dibenzo[a,c]phenazine (BPz) derivatives with 2,7-alkyl and 11,12-alkoxy substituted, PBDT-BPzC and PBDT-OBPz, respectively, were synthesized to investigate the photovoltaic effect of different side chain substitutions. The polymers exhibit similar physical properties, except the HOMO and LUMO of PBDT-BPzC are 0.18 and 0.15 eV deeper than PBDT-OBPz, resulting in the Voc of polymer solar cells (PSCs) based on PBDT-BPzC are above 0.1 V higher than that of PBDT-OBPz. With the contribution of the superior Voc, polymer PBDT-BPzC showed preferable photovoltaic performances, and the PCE reached 4.44%, which is 0.49% higher than PBDT-OBPz. This research reveals a preferred side chain substituted way to modify BPz unit, and gives an optimally developing the dibenzo[a,c]phenazine derivatives based electron–donor polymers. 相似文献
17.
Structure Tuning of Crown Ether Grafted Conjugated Polymers as the Electron Transport Layer in Bulk‐Heterojunction Polymer Solar Cells for High Performance
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Yi‐Lun Li Yu‐Shan Cheng Po‐Nan Yeh Sih‐Hao Liao Show‐An Chen 《Advanced functional materials》2014,24(43):6811-6817
A series of novel electron transport (ET) polymers composed of different conjugated main chains (fluorene, thiophene, and 2,7‐carbazole) and crown ether side chain (crown ether, aza‐crown ether and amine) is presented for bulk‐heterojunction polymer solar cells with poly(3‐hexylthiophene) (P3HT) or poly[[4,8‐bis[(2‐ethylhexyl)oxy]benzo [1,2‐b:4,5‐b′] dithiophene‐2,6‐diyl][3‐fluoro‐2‐[(2‐ethylhexyl)carbonyl]thieno[3,4‐b]thiophenediyl]](PTB7) as the active polymer and aluminum metal as the cathode. Unexpectedly, it is found that the main chain of ET polymers has a greater effect on the interfacial dipole than the side chain, even when attaching a high polarity group. The electron‐rich bridge atom of the main chain may also contribute appreciably to the interfacial dipole. When used as the ET layer, all of these polymers can generate an optical interference effect for redistribution of the optical electric field as an optical spacer and, therefore, allow more light to be absorbed by the active layer, thus leading to an increase in short‐circuit current density. They can also block hole diffusion to the cathode and prevent electron–hole recombination during the ET process. Among the five ET polymers investigated, PCCn6 is the most effective one, providing a remarkable improvement in the power conversion efficiency (measured in air) of the device to 8.13% compared to 5.20% for PTB7:[6,6]‐phenyl‐C71‐butyric acid methyl ester (PC71BM). 相似文献
18.
In previous studies, PSCs based on polymers with an inward alkyl positioned DTBT unit showed poor power conversion efficiency mainly due to the greatly distorted polymer backbone structure caused by severe steric hindrance between the alkyl groups on the flanking thiophene of DTBT and the BT unit. In this study, PSCs based on polymers with an inward alkyl positioned DTBT unit are markedly improved by controlling the molecular weight and alkyl chain length. Two BDT-DTBTs and one BDT-BT polymers were synthesized by engineering alkylthienyl chains on BDT and by installing these with a short alkyl chain on the inward alkyl positioned DTBT. Extraordinary bathochromic shifts in the absorption maxima at 146 nm for PA and 165 nm for PB were observed going from solution to a solid film state, suggesting great differences in the polymer structures of the two states. Optical and electrochemical measurements were taken, and the HOMO levels of PA, PB, and PC were determined to be −5.76, −5.66, and −5.71 eV, respectively, indicating very low-lying HOMO energy levels. The optimized PSCs based on PA, PB, and PC exhibit power conversion efficiencies (PCEs) of 3.75%, 2.42%, and 2.30%, respectively, with Voc (0.77–0.86 V), Jsc (6.9–8.7 mA/cm2), and FF (38–52%). We believe that the highest PCE for the PSCs based on PA may be attributed to the high molecular weight and improved processability relative to those of PB and PC. A theoretical study suggests that the polymer backbones of PA and PB are highly distorted between the donor unit and the acceptor unit, by as much as 49°, possibly by the steric hindrance between BT and the inward positioned methyl group on the flanking thiophene. Therefore, the conjugations for the HOMO p-orbitals of PA and PB are highly localized throughout the backbone while the conjugations for the HOMO p-orbitals of PC are well delocalized. The AFM study revealed that DIO additive greatly changed the morphology of the polymer blend from an amorphous state into distinct nanoscale phase separated states, leading to a great improvement in PCEs. The XRD study revealed that all polymers are amorphous. 相似文献
19.
Effect of Spacer Length of Siloxane‐Terminated Side Chains on Charge Transport in Isoindigo‐Based Polymer Semiconductor Thin Films
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Jianguo Mei Hung‐Chin Wu Ying Diao Anthony Appleton Hong Wang Yan Zhou Wen‐Ya Lee Tadanori Kurosawa Wen‐Chang Chen Zhenan Bao 《Advanced functional materials》2015,25(23):3455-3462
A series of isoindigo‐based conjugated polymers (PII2F‐CmSi, m = 3–11) with alkyl siloxane‐terminated side chains are prepared, in which the branching point is systematically “moved away” from the conjugated backbone by one carbon atom. To investigate the structure–property relationship, the polymer thin film is subsequently tested in top‐contact field‐effect transistors, and further characterized by both grazing incidence X‐ray diffraction and atomic force microscopy. Hole mobilities over 1 cm2 V?1 s?1 is exhibited for all soluble PII2F‐CmSi (m = 5–11) polymers, which is 10 times higher than the reference polymer with same polymer backbone. PII2F‐C9Si shows the highest mobility of 4.8 cm2 V?1 s?1, even though PII2F‐C11Si exhibits the smallest π–π stacking distance at 3.379 Å. In specific, when the branching point is at, or beyond, the third carbon atoms, the contribution to charge transport arising from π–π stacking distance shortening becomes less significant. Other factors, such as thin‐film microstructure, crystallinity, domain size, become more important in affecting the resulting device's charge transport. 相似文献
20.
Optimization of Solubility,Film Morphology and Photodetector Performance by Molecular Side‐Chain Engineering of Low‐Bandgap Thienothiadiazole‐Based Polymers
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Ji Qi Xiaokang Zhou Dezhi Yang Wenqiang Qiao Dongge Ma Zhi Yuan Wang 《Advanced functional materials》2014,24(48):7605-7612
A series of donor–acceptor (D‐A) type low‐bandgap polymers containing the terthiophene and thieno[3,4‐b]thiadiazole units in the main chain but different numbers of identical side chains are designed and synthesized in order to study the effect of side chain on the polymer properties and optimize the performance of polymer photodetectors. Variation in the side chain content can influence the polymer solubility, molecular packing, and film morphology, which in turn affects the photodetector performance, particularly with regard to the photoresponsivity and dark current. X‐ray diffraction patterns indicate that molecular ordering increases with more side chains. Atomic force microscopy shows that appropriate morphology of the active layer in the polymer photodetector is necessary for high photocurrent and low dark current. Using BCP as a hole blocking layer (10 nm), the photodetector based on P4 exhibits the optimized performance with specific detectivity of 1.4 × 1012 Jones at 800 nm, which is among the best reported values for polymer photodetectors and even comparable to that of a silicon photodetector. 相似文献