Medium-Bandgap Conjugated Polymer Donors for Organic Photovoltaics

Recently, an increasing number of researchers have begun to focus on developing nonfullerene acceptors, so it is very important to synthesize new polymers that are compatible with nonfullerene acceptors. Besides, wide- or medium-bandgap polymer donors could be better to match narrow nonfullerene acceptors. The design of medium-bandgap (MBG) polymer donors and their application in organic photovoltaics (OPVs) play an important part in the improvement of OPV device performance. This review summarizes the photovoltaic performance of MBG polymers that have been reported during the last decade. Furthermore, their structure–property relationships and device performance are discussed. On the basis of analyzing many polymer structures, guidance toward the design of novel photovoltaic materials might be helpful to understand the basic OPV mechanism and the path towards commercialization.