Asymmetric Fused-ring Photovoltaic Electron Acceptors

Benefiting from the development of fused-ring electron acceptors (FREAs), power conversion efficiencies of organic solar cells have rapidly increased from 12% for the fullerene era to 20% for the non-fullerene era. The asymmetric molecular design strategy plays an important role in the enhancement of photovoltaic performance. In this paper, we review the research progress of asymmetric FREAs according to the following three kinds of molecular design strategies:the asymmetric fused-ring backbone, asymmetric end groups and asymmetric side chains, discuss the structure-property relationship, and finally provide an outlook on the future development of asymmetric FREAs.