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

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 cm² 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.