Benzodifuran-based polymer donors for binary all-polymer solar cells with nearly 18% efficiency
Kang Xiao, Jianxiao Wang, Xin Jing, Zhengkun Du, Hongxiang Li, Fuzhen Bi, Mingliang Sun, Xichang Bao, Junhao Chu
Abstract
Owing to the strong intermolecular interactions and high energy levels of benzodifuran (BDF)-based copolymers, their photovoltaic performance has progressed slowly. Herein, a "strong donor–weak acceptor" design strategy is proposed that can effectively optimize the strong intermolecular interactions of BDF-based polymers by using the steric effect of long alkyl side chains to weaken the dithiophene quinoxaline-based acceptor unit. Two new high-performance polymer donors, PQR16-BFCl and PQR16-BFF, were prepared via copolymerization with BDF unit. The binary all-polymer solar cells fabricated by combining PQR16-BFCl and PQR16-BFF with PY-IT achieved power conversion efficiencies of 17.91% and 17.26%, respectively, along with high fill factors exceeding 75%. Notably, PQR16-BFCl:PY-IT set a new record efficiency for BDF-based all-polymer solar cell binary devices. This study showed that the strong interaction advantage of BDF can be utilized in a weak acceptor unit system, showing prominent advantages in stabilizing the orientation of polymer molecules, alleviating steric hindrance, and reducing aggregation. This study demonstrates the application of BDF-based donor units and will undoubtedly accelerate the development of BDF-based polymer solar cells. • Developed a novel high-performance benzofuran-based polymer donor. • “Strong donor & weak acceptor” design strategy is proposed. • A nearly 18% efficiency was obtained, one of the highest values reported so far for benzofuran-based APSCs. • Long alkyl side chains effectively optimize intermolecular interaction.