Light‐Driven Dynamic Defect‐Passivation for Efficient Inorganic Perovskite Solar Cells

Abstract Due to its soft lattice characteristics, all‐inorganic cesium lead halide (CsPbI_3‐xBr_x) perovskite is vulnerable to external environmental stress such as moisture, polar solvent, illumination. resulting in structural defects (V_I, I_i, etc.) and ion mobility. However, most of the prior arts focus on short‐term and static passivation, which has a negligible effect on defects formed during solar cell operation. Herein, a photoisomerizable molecule, 1,3,3‐trimethylindolino‐8′‐methoxybenzopyrylospiran (OMe‐SP), exhibiting light‐driven pre‐isomeric (SP) and post‐isomeric (PMC) configurations, is employed as an interfacial protective layer on top of CsPbI_3‐xBr_x. The present strategy not only effectively suppresses migration of halogen ions, but also enables sustainable passivation of defects, thereby significantly reducing interfacial charge recombination and retarding perovskite degradation. Consequently, the OMe‐SP‐modified perovskite solar cells (PSCs) exhibit superior stability, maintaining 91% of their initial efficiency after aging 1032 h under maximum power point (MPP) tracking and continuous one sun illumination. Meanwhile, the OMe‐SP‐modified cell also achieves an impressive power conversion efficiency of 22.20%, which stands as the highest among all‐inorganic perovskite solar cells. Overall, the implementation of this robust strategy provides sustainable defect passivation and continuous suppression of ion migration for achieving both high PCE and stable inorganic perovskite.