Suppression of Iodide Ion Migration via Sb₂S₃ Interfacial Modification for Stable Inorganic Perovskite Solar Cells

In mixed halide perovskite, the halide phase segregation is commonly observed due to halide ion migration, which causes severe stability issues in perovskite devices. Here, we directly revealed the iodide-migration process via potentiostatic treatment in CsPbIBr₂ perovskite. The absence of iodide ions was reduced significantly via a Sb₂S₃ interfacial modification. We further employed the density functional theory (DFT) calculation to optimize the geometry positions at the perovskite interface and radial distribution functions (RDF) to analyze the atom perturbation. The simulation yielded a slight distortion of the perovskite lattice at the Sb₂S₃-CsPbIBr₂ interface and iodide ion fluctuation was reduced due to the decrease of halide vacancies. In addition, the thermally stimulated current was calculated to evaluate the defect density in the modified perovskite device. Due to the Sb₂S₃ interaction with perovskite, the device became stable against humidity and maintained its photoactivity over 400 h. The champion efficiency of 9.31% with 26.31% improvement was obtained in modified CsPbIBr₂ perovskite solar cells.