Density functional theory study of Br doped CsPbI₃ perovskite for photovoltaic and optoelectronic applications

First-principle calculations were used to investigate the structural, optoelectronic, elastic and thermodynamic properties of Br-doped CsPbI₃ perovskite material using GGA-PBE, SCAN, and LDA functionals. The computed lattice parameters are consistent with the experimental and theoretical calculations, reported in the literature. The band structure along with the electronic density of states indicated that CsPbI_3−xBr_x (x = 0, 1, 2, 3) materials are semiconductors with direct band gaps, as projected using the three functionals. The energy band gap of CsPbI₃ was tuned by replacing I ions with Br ions, resulting in CsPbI₂Br, CsPbBr₂I, and CsPbBr₃ materials. These perovskite materials were found to be mechanically stable, ductile in nature and elastically anisotropic. The results of optical parameters such as absorption coefficients, refractive index, optical conductivity, optical reflectivity, electron energy loss, and extinction coefficients were calculated and analysed. The thermodynamic parameters including heat capacity, and Debye temperature were calculated. The direct band gap and energy-dependent optical parameters especially the absorption coefficient in the infrared and visible region of these perovskite materials suggest that they might be candidates for potential use in photovoltaic solar cells and optoelectronic applications.