A wide bandgap conjugated polymer donor based on alkoxyl-fluorophenyl substituted benzodithiophene for high performance nonfullerene polymer solar cells
Wanbin Li‡a, Guangda Li‡a, Huan Guo a, Xia Guo a, Bing Guo a, Qinglian Zhu b, Qunping Fan a, Wei Ma b, Maojie Zhang *a（张茂杰） and Yongfang Li ac
a Laboratory of Advanced Optoelectronic Materials, College of Chemistry, Chemical Engineering and Materials Science, Soochow University, Suzhou 215123, China.
b State Key Laboratory for Mechanical Behavior of Materials, Xi'an Jiaotong University, Xi'an 710049, China
c CAS Research/Education Center for Excellence in Molecular Sciences, CAS Key Laboratory of Organic Solids, Institute of Chemistry, Chinese Academy of Sciences, Beijing 100190, China
‡ W. Li & G. Li contributed equally to this work.
J. Mater. Chem. A, 2019, 7, 1307--1314
A new wide bandgap (WBG) conjugated polymer PFOPB based on a fluorinated-alkoxyphenyl benzodithiophene donor unit and a benzodithiophene-4,8-dione acceptor unit was designed and synthesized for application as a donor in non-fullerene (NF) polymer solar cells (PSCs). In order to investigate the effect of side chain fluorination on the photovoltaic performance, a corresponding non-fluorinated polymer POPB was also synthesized as a comparison material. Compared to POPB with a bandgap of 1.81 eV, a highest occupied molecular orbital (HOMO) energy level of −5.38 eV, an extinction coefficient of 5.31 × 104 cm−1 at 577 nm and a hole mobility of 3.96 × 10−4 cm2 V−1 s−1, the fluorinated polymer PFOPB possesses a wider bandgap of 1.86 eV, a deeper HOMO level of −5.50 eV, a higher extinction coefficient of 8.45 × 104 cm−1 at 612 nm and a higher hole mobility of 1.51 × 10−3 cm2 V−1 s−1. The PFOPB:IT-4F-based PSCs exhibit a much higher power conversion efficiency (PCE) of 11.7% than POPB:IT-4F-based devices (6.2%). These results suggest that side-chain fluorination is an effective strategy to improve the optoelectronic properties of WBG polymers in NF-PSCs.