Cesium Moderation and Structural Transformation on α-CsPbI2Br Perovskite Durability via Cation Retarding Migration: A Combined Simulation and Experimental Study

Abstract

Preliminary density functional theory studies suggest that cesium-ion (Cs+) migration possesses a low energy barrier at defective surfaces, which potentially induces lattice distortion of α-CsPbI2Br perovskites. Herein, we introduced surface design via mixed-cation and mixed-halide methods to enhance the durability and functionality of all-inorganic CsPbI2Br solar cells. The adsorption and adhesion energies indicate that formamidinium bromide (FABr) passivation creates a nonbonding surface with resistance to water molecules and induces lattice reconstruction at the surface into a cubic-like structure. Experimental validation in solar cell applications reveals that nonencapsulated formamidinium bromide − based devices can retain 84 % of the initial efficiency (13.29 %) after 336 h of use with 40 %–43 % of relative humidity, outperforming the reference cell that retained 20 % of the original efficiency (10.31 %) after 144 h. This findings highlight the dual role of FABr passivation in stabilizing the surface and reorganizing the lattice structure, contributing to significantly enhanced durability and performance CsPbI2Br solar cells.