Efficiency enhancement of dopant-free perovskite solar cells by employing fluoro-substituted electron donor–electron acceptor type polymeric hole-transporting materials

Abstract

For the conventional n–i–p perovskite solar cells (PVSCs), dopant-free hole-transporting polymers can be employed to achieve high device performances. Herein, two electron donor–electron acceptor (D–A) type conjugated polymers PBCz-BTz and PBCz-FBTz were developed, in which benzodithiophene served as the D unit, and benzotriazole without or with fluoro-substituents was used as the A unit. PBCz-FBTz with fluoro-substituents exhibits a better π–π stacking effect, suitable energy levels, higher backbone planarity and hole mobility to PBCz-BTz. Thus, the champion device based on PBCz-FBTz exhibits an outstanding power conversion efficiency of 20.71% and retains over 90% of its original PCE after being stored under ambient conditions for 30 days. Our work confirms that developing novel polymeric HTMs with fluoro-substituents is a promising molecular design strategy for highly efficient PVSCs.