摘要： In mixed halide perovskite, the halide phase segregation is commonly observed due to halide ions 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 Sb2S3 interfacial modification. We further employed the 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 perovskite lattice at the interface of Sb2S3-CsPbIBr2 and iodide ions fluctuation was reduced due to the decrease of halide vacancies. In addition, the thermally stimulated current was calculated to evaluate the defects density in the modified perovskite device. Due to the Sb2S3 interaction with perovskite, the device became stable against humidity and maintained photoactive over 400 h. The champion efficiency of 9.31% with 26.31% improvement was obtained in modified CsPbIBr2 perovskite solar cells.