Qunping Fan a, Wenyan Su a, Xia Guo *a（国霞）,Yan Wang a, Juan Chen a,Chennan Ye a,Maojie Zhang *a（张茂杰）and Yongfang Li ab
aState and Local Joint Engineering Laboratory for Novel Functional Polymeric Materials, Laboratory of Advanced Optoelectronic Materials, College of Chemistry, Chemical Engineering and Materials Science, Soochow University, Suzhou 215123, China.
bBeijing National Laboratory for Molecular Sciences, CAS Key Laboratory of Organic Solids, Institute of Chemistry, Chinese Academy of Sciences, Beijing 100190, China
J. Mater. Chem. A, 2017, 5, 9204--9209
In this work, a new wide-bandgap polymer, PSBZ, based on thienyl substituted benzodithiophene (BDTT) as the donor unit and difluorobenzotriazole (BTz-2F) as the acceptor unit was synthesized for photovoltaic applications. Compared to the analogous polymer J61 with linear dodecylthio side chains in the BDTT unit and a long 2-hexyldecyl side chain in BTz-2F, PSBZ possesses branched 2-butyloctyl side chains to increase steric hindrance of the BDTT unit and a short 2-butyloctyl side chain to decrease steric hindrance of the BTz-2F unit for more efficient charge separation and transport in the devices. As a result, PSBZ exhibited stronger π–π interaction and smaller stacking spacing leading to a higher extinction coefficient of 1.48 × 105 cm−1 and a high hole mobility of 8.56 × 10−3 cm2 V−1 s−1. Compared to the analogous polymer J61 with a power conversion efficiency (PCE) of 9.53% and a short-circuit current density (Jsc) of 17.43 mA cm−2, the PSBZ:ITIC-based polymer solar cells yielded a higher PCE of 10.5% with a higher Jsc of 19.0 mA cm−2. The results show that our design strategy is successful for improving photovoltaic performance by side chain engineering.
链接：http://pubs.rsc.org/en/content/articlehtml/2017/TA/C7TA02075A
