Cyclopentadithiophene-cored non-fullerene acceptors for efficient polymer solar cells with superior stability

摘要

The past few years has witnessed rapid progresses in the power conversion efficiencies (PCEs) of organic solar cells based on non-fullerene acceptors. However, most high-performance non-fullerene acceptors are synthesized by using complicated ring-fused aromatics which have relatively high synthetic cost. In this work, we report on the design and synthesis of two small molecule acceptors (SSBR and SSBRC) by using a simple cyclopentadithiophene central core franked by 3-ethylrhodanine or 2-(1,1-dicyanomethylene)-3-ethylrhodanine units with two benzothiadiazole bridges. The terminal electron-withdrawing groups have an important effect on physical, electronic and photovoltaic properties of the non-fullerene acceptors. Inverted polymer solar cells based on PTB7-Th:SSBRC showed an inferior PCE of 3.35%. In contrast, devices based on PTB7-Th:SSBR afforded an initial PCE of 7.82%, and an increased PCE of 8.16% after 88 days storage. Furthermore, the best performance device can retain about 98% of its initial PCE after more than 6 months storage demonstrating its superior stability.