High-Stability Cesium Lead Iodide Perovskite Solar Cells Enabled by Buried Interface Regulation

Cesium lead iodide perovskite (CsPbI₃) is a class of promising photovoltaic materials while prone to undergo spontaneous transformation from the photoactive black phase to the nonphotoactive yellow phase under ambient conditions, posing a significant challenge to the long-term applications. Herein, a buried interface regulation strategy is reported, where the crystalline seeds containing bromide ions are formed on the substrates through a treatment with cesium bromide prior to the growth of CsPbI₃. This results in the initial construction of a thin CsPbI_3-<i>x</i>Br_<i>x</i> perovskite layer with high lattice matching at the buried interface, which enables the subsequent growth of highly oriented CsPbI₃ perovskites that effectively enhances their phase stability. Furthermore, the modified substrate reveals greater wettability, leading to accelerated crystallization kinetics, reduced defect density, and favorable interfacial charge transfer. Consequently, the corresponding device exhibits simultaneous promotion in both photoelectric performance and operational stability.