Recent Progress of Benzodifuran-Based Polymer Donors for High-Performance Organic Photovoltaics

At present, a variety of benzo[1,2-b:4,5-b′]dithiophene (BDT)-based polymer donors are designed and synthesized, which have made great progress toward achieving high power conversion efficiencies (PCEs) of polymer solar cells (PSCs). Despite many advantages of benzo[1,2-b:4,5-b′]difuran (BDF) compared with BDT unit, the overall performance of BDF polymer-based PSCs lags far behind that of the counterpart BDT-based polymers. Recently, great advances have been achieved in BDF polymer-based PSCs with the highest PCEs over 16%, suggesting that BDF-based polymers have the significant potential to catch up or even surpass the performance of BDT-based polymers. In this review, the recent advances of BDF polymers in PSCs are first summarized and then the design strategies and the chemical structure–performance relationships of BDF polymers are discussed. Finally, perspectives on the future development of BDF polymers for high-efficiency PSCs are provided.