Double‐Side Interface Engineering Synergistically Boosts the Efficiency of Inorganic CsPbIBr₂ Perovskite Solar Cells Over 12%

Abstract All‐inorganic CsPbIBr₂ perovskite solar cells (PSCs) have aroused the worldwide interest because of their excellent thermal stability. However, the bottom and upper surfaces of CsPbIBr₂ films are vulnerable to surface defects, corroding the carrier dynamic in PSCs. Meanwhile, the band alignment mismatch also affects the interfacial carrier transport. Therefore, this work systematically investigates the passivation effect and band alignment of rubidium acetate (RbAc) interface layer at electron transport layer (ETL)/perovskite and perovskite/hole transport layer (HTL), respectively. When RbAc is introduced to ETL/perovskite interface, the improved morphology quality of CsPbIBr₂ films and the elevated conductive band minimum of SnO₂ leads to effective electron extraction and band alignment. Furthermore, once RbAc is introduced to perovskite/HTL interface, it passivates grain boundary defects and reduces the roughness of CsPbIBr₂ films, contributing to reduced nonradiative recombination. In addition, the raised valence band maximum of CsPbIBr₂ also accelerates the hole transfer. It is found that each single‐side interface modification contributes to improved photovoltaic performance and air stability. Consequently, a synergy effect of double‐side interface modification is investigated for improving the device efficiency. Accordingly, the modified PSCs achieve a champion efficiency of 12.11%, which is increased by 30.78% compared to that of the pristine devices.