Tailored Polymer Hole‐Transporting Materials with Multisite Passivation Functions for Effective Buried‐Interface Engineering of Inverted Quasi‐2D Perovskite Solar Cells

Abstract Although quasi‐2D Ruddlesden‒Popper (RP) perovskite exhibits advantages in stability, their photovoltaic performance are still inferior to 3D counterparts. Optimizing the buried interface of RP perovskite and suppress energetic losses can be a promising approach for enhancing efficiency and stability of inverted quasi‐2D RP perovskite solar cells (PSCs). Among which, constructing polymer hole‐transporting materials (HTMs) with defect passivation functions is of great significance for buried‐interface engineering of inverted quasi‐2D RP PSCs. Herein, by employing side‐chain tailoring strategy to extend the π‐conjugation and regulate functionality of side‐chain groups, target polymer HTMs (PVCz‐ThSMeTPA and PVCz‐ThOMeTPA) with high mobility and multisite passivation functions are achieved. The presence of more sulfur atom‐containing groups in side‐chain endows PVCz‐ThSMeTPA with increased intra/intermolecular interaction, appropriate energy level, and enhanced buried interfacial interactions with quasi‐2D RP perovskite. The hole mobility of PVCz‐ThSMeTPA is up to 9.20 × 10 −4 cm 2 V −1 S −1 . Furthermore, PVCz‐ThSMeTPA as multifunctional polymer HTM with multiple chemical anchor sites for buried‐interface engineering of quasi‐2D PSCs can enable effective charge extraction, defects passivation, and perovskite crystallization modulation. Eventually, the PVCz‐ThSMeTPA‐based inverted quasi‐2D PSC achieves a champion power conversion efficiency of 22.37%, which represents one of the highest power conversion efficiencies reported to date for quasi‐2D RP PSCs.