Investigation of the structure, stability and physical properties of CH₃NH₃PbI_3−xBr_x

In this study, the Castep module is used to construct and calculate eight configurations of the orthorhombic structure CH₃NH₃PbI_3−xBr_x (x = 0.00, 0.25, 3.00) as new energy materials. The Perdew, Burke and Ernzerhof version of the generalized gradient approximation functional is used to investigate the physical properties of the eight configurations. When x = 0.25, the most stable structure is determined by comparing the final energies of CH₃NH₃PbI_2.75Br_0.25 with those of different replaced positions. The CH₃NH₃PbBr₃ structure exhibits the most stable structural frameworks among x = 0.00, 0.25 and 3.00. The energy band structure, density of states and optical absorption properties are calculated and plotted; these indicate that all materials are direct semiconductors with bandgaps ranging from 1.726 to 2.274 eV, and the bandgap increases as x increases. Furthermore, the substitutions at different sites change the intrinsic properties of the material and enhance the stability of the material, which provides a new viewpoint in materials technology.