Non‐Equivalent Donor‐Acceptor Type Polymers as Dopant‐Free Hole‐Transporting Materials for Perovskite Solar Cells

Abstract

Electron donor (D)‐electron acceptor (A) type conjugated polymers present bright prospects as dopant‐free hole‐transporting materials (HTMs) for perovskite solar cells (PVSCs). Most of the reported D‐A polymeric HTMs contain equivalent amounts of D and A units, while the appropriate excess proportion of D units could optimize the aggregation state of polymer chains and improve the hole transport properties of the polymers. Herein, a non‐equivalent D‐A copolymerization strategy was utilized to develop three indacenodithiophene‐benzotriazole‐based polymeric HTMs for PVSCs, named as F‐10, F‐15, and F‐20, and the equivalent D‐A polymer F‐00 was studied in parallel. Effects of D : A ratio on the hole transport properties of these D‐A type polymeric HTMs, including energy level, molecular stacking, hole mobility, and surface morphology, were investigated by theoretical simulation and test analysis. F‐15 performed best due to the appropriate D : A ratio, endowing the PVSCs a champion power conversion efficiency of 20.37 % with high stability, which confirms the fine‐tuning D : A ratio via non‐equivalent D‐A copolymerization strategy is very helpful to construct D‐A type polymeric HTMs for high‐performance PVSCs.