Mechanism of Tunable Band Gap of Halide Cubic Perovskite CsPbBr3−xIx

Abstract

In recent years, CsPbBr3−xIx has garnered significant attention in the field of optoelectronics due to its tunable bandgap and excellent photovoltaic properties. In this theoretical study, the structural, electronic, and optical properties of CsPbBr3−xIx through density functional theory calculations are investigated. The calculations reveal that the substitution of Br with I leads to a significant reduction in the bandgap of CsPbBr3−xIx, resulting in improved light absorption properties. The band gap can be tuned by using the ratios of Br and I ions in the structure. One of the important results obtained in this study is that when Br and I ions are added to the system, two energy levels close to each other are formed in conduction band minimum (CBM). These two close energy levels may have the effect of increasing the efficiency of CsPbBr3 in harvesting light. Another finding is that the energy level of the conduction band minimum (CBM) and valence band maximum (VBM) can be adjusted using the ratio of the I ion in CsPbBr3−xIx. This is important for the efficiency of perovskite-based solar cells with a layered structure.