Autonomous Control of Ion Migration at α‐FAPbI3 Heterointerfaces via Interfacial‐Self‐Assembled 2D Perovskite

Abstract Harmonizing homogeneity in charge distribution within metal halide perovskite solar cells is essential for maintaining device quality. The adsorption of ions from perovskites onto the electron transport layer leads to the creation of redistributed space‐charge regions (SCR), which facilitate halide segregation and ionic migration, resulting in charge imbalances and diminished extraction capability at the interface. The research examines the intricate interplay between SCRs affecting iodide oxidation and their impact on photovoltaics, uncovering a previously overlooked aspect that the influence of ionic accumulation on electronic charge uniformity. A paradox is identified that electronic charge accumulation at interfaces improves initial open‐circuit voltage, however, compromises stability with a collapsed charge distribution. To address this issue, ion conduction is regulated by utilizing a self‐assembled 2D perovskite resulting from cationic exchange with a low migration barrier at the buried interface, thereby mitigating halide segregation and charge inhomogeneity. This approach exhibits a power conversion efficiency (PCE) of 24.38% with a fill‐factor of 84% and maintains 91.87% of the initial PCE for a duration of 2070 h.