Low-bandgap polymers with quinoid unit as π bridge for high-performance solar cells  

作　　者：Bilal Shahid Xiyue Yuan Qian Wang Di Zhou Ergang Wang Xichang Bao Dangqiang Zhu Renqiang Yang 

机构地区：[1]Qingdao Institute of Bioenergy and Bioprocess Technology,Chinese Academy of Sciences,Qingdao 266101,Shandong,China [2]Center of Materials Science and Optoelectronics Engineering,University of Chinese Academy of Sciences,Beijing 100049,China [3]Department of Chemistry and Chemical Engineering/Applied Chemistry,Chalmers University of Technology,Gothenburg SE-41296,Sweden

出　　处：《Journal of Energy Chemistry》2020年第1期180-187,I0007,共9页能源化学（英文版）

基　　金：the National Natural Science Foundation of China (21604092, 51573205 and 51773220);China Postdoctoral Science Foundation (2017M610453;the Youth Innovation Promotion Association CAS (2016194) for financial support;the CAS-TWAS President’s Fellowship Program for Ph.D

摘　　要：To construct efficient low band gap polymers,increasing the Quinone structure of the polymer backbone could be one desirable strategy.In this work,two D–Q–A–Q polymers P1 and P2 were designed and synthesized with thiophenopyrrole diketone(TPD)and benzothiadiazole(BT)unit as the core and ester linked thieno[3,4-b]thiophene(TT)segment as π-bridging,and the main focus is to make a comparative analysis of different cores in the influence of the optical,electrochemical,photochemical and morphological properties.Compared with the reported PBDTTEH–TBTTHD-i,P1 exhibited the decreased HOMO energy level of-5.38 e V and lower bandgap of 1.48 e V.Furthermore,when replaced with BT core,P2 showed a red-shifted absorption profile of polymer but with up-shifted HOMO energy level.When fabricated the photovoltaic devices in conventional structure,just as expected,the introduction of ester substituent made an obvious increase of VOC from 0.63 to 0.74 V for P1.Besides,due to the deep HOMO energy level,higher hole mobility and excellent phase separation with PC71 BM,a superior photovoltaic performance(PCE=7.13%)was obtained with a short-circuit current density(JSC)of 14.9 m A/cm^2,significantly higher than that of P2(PCE=2.23%).Generally,this study highlights that the strategy of inserting quinoid moieties into D–A polymers could be optional in LBG-polymers design and presents the importance and comparison of potentially competent core groups.To construct efficient low band gap polymers, increasing the Quinone structure of the polymer backbone could be one desirable strategy. In this work, two D–Q–A–Q polymers P1 and P2 were designed and synthesized with thiophenopyrrole diketone（TPD） and benzothiadiazole（BT） unit as the core and ester linked thieno[3,4-b]thiophene（TT） segment as π-bridging, and the main focus is to make a comparative analysis of different cores in the influence of the optical, electrochemical, photochemical and morphological properties. Compared with the reported PBDTTEH–TBTTHD-i, P1 exhibited the decreased HOMO energy level of-5.38 e V and lower bandgap of 1.48 e V. Furthermore, when replaced with BT core, P2 showed a red-shifted absorption profile of polymer but with up-shifted HOMO energy level. When fabricated the photovoltaic devices in conventional structure, just as expected, the introduction of ester substituent made an obvious increase of VOC from 0.63 to 0.74 V for P1. Besides, due to the deep HOMO energy level,higher hole mobility and excellent phase separation with PC71 BM, a superior photovoltaic performance（PCE = 7.13%） was obtained with a short-circuit current density(JSC) of 14.9 m A/cm2, significantly higher than that of P2（PCE = 2.23%）. Generally, this study highlights that the strategy of inserting quinoid moieties into D–A polymers could be optional in LBG-polymers design and presents the importance and comparison of potentially competent core groups.

关 键 词：Low bandgap polymer Side-chain engineering Quinone structure π-bridging 

分 类 号：TQ317[化学工程—高聚物工业] TM914.4[电气工程—电力电子与电力传动]