Density Functional Study of Structural, Electronic and Optical Properties of Bromine-Doped CsPbI3 with the Tetragonal Symmetry

Abstract Herein, the structural, electronic and optical properties of CsPbI3 perovskite with the tetragonal symmetry (β-CsPbI3) and its Br-doped structures are investigated. All calculations are performed by the first-principles method based on Density Functional Theory (DFT). The mixed perovskite CsPb(I1-xBrx)3 are constructed by substituting I- ion with Br- ion in the crystal cell, which the replacement ratios is 1/6, 1/3, 1/2, 2/3, 5/6, and 1. The calculated structural parameters show that crystal volumes of CsPb(I1-xBrx)3 decrease and their structural stabilities are improved with the increasing of Br content. The electronic structures indicate that these crystals are direct-bandgap semiconductors and the bandgap increases by increasing Br content. Partial density of state reveals that electronic properties are mainly associated with [PbI6]4- octahedron. By analyzing optical properties of CsPb(I1-xBrx)3, they are concluded to possess similar properties. Moreover, absorption coefficients heighten (2.0×105 - 2.5×105cm-1) with an increasing range of Br content. Therefore, Br doping can adjust the band gap and improve the structural stability, which is expected to be useful for applications in the optoelectronics industry.