Dopant‐Free Squaraine‐Based Polymeric Hole‐Transporting Materials with Comprehensive Passivation Effects for Efficient All‐Inorganic Perovskite Solar Cells

Abstract

Development of high performance dopant‐free hole transporting materials (HTMs) with comprehensive passivation effect is highly desirable for all‐inorganic perovskite solar cells (PVSCs). Squaraines (SQs) could be one of ideal material candidates of dopant‐free HTMs as they are natural passivators for perovskites. One major limitation for SQs to be efficient dopant‐free HTMs is their relatively low hole mobilities. Herein we demonstrate that polymerizing SQs into pseudo two dimensional (2D) p‐π conjugated polymers is a feasible solution to overcome this challenge. By rationally using N,N‐diarylanilinosquaraines as the comonomers, the resulting polysquaraine HTMs not only exhibit suitable energy levels and efficient passivation effects, but also achieve very high hole mobility close to 0.01 cm‐2V‐1s‐1. Thus as the dopant‐free HTMs for α‐CsPbI2Br‐based all‐inorganic PVSCs, the best PCE can reach 15.5% from PSQ2, outperforming those of the doped‐Spiro‐OMeTAD (14.4%) based control devices and also among the best for all‐inorganic PVSCs reported so far.