Efficient Polymer Solar Cells With High Fill Factor Enabled by A Furo[3,4-c]pyrrole-4,6-dione-Based Copolymer

Non-fullerene polymer solar cells (NF-PSCs) have achieved tremendous progress in power conversion efficiency (PCE), which is mainly attributed to the well absorption complementation and the admirable energy-level alignment between donor polymers and fullerene-free acceptors. However, the development of efficient donor polymers pairing with fullerene-free acceptors relatively lags behind that of fullerene-free acceptors in terms of number and diversity for fabricating NF-PSCs. In this work, a two-dimensional medium bandgap copolymer (PBDFFPD) based on benzo[1,2-b:3,4-b′]difuran (BDF) and furo[3,4-c]pyrrole-4,6-dione (FPD), is firstly designed and synthesized. The as-prepared polymer possesses a large conjugated plane with negligible torsion, strong intermolecular and intramolecular interaction, and deep highest occupied molecular orbital (HOMO) energy level. The optimized photovoltaic device based on PBDFFPD:ITIC wins a remarkable PCE of 9.58% with a large FF of 70.1%, the highest values ever reported for FPD-based polymers. In addition, the statistical data from different batches of devices shows that PSCs based on PBDFFPD:ITIC at optimized conditions depict an excellent reproducibility of PCE with a deviation of 2.29%. The results demonstrate that PBDFFPD possesses great potential for constructing highly efficient NF-PSCs.