Phase transition, electronic and optical properties of A2PdBr4I2 (A = Rib, Cs): A theoretical study

Abstract Through first-principles calculations, we have discussed the structural, electronic and optical properties of A2PdBr6 and A2PdBr4I2 (A = Rb, Cs). The phase transition is confirmed from A2PdBr6 to A2PdBr4I2 by combining with the theoretical calculations and experimental results. A2PdBr6 has a cubic structure at room temperature, while A2PdBr4I2 adopts a tetragonal structure. The electronic structures and optical properties of four compounds are calculated by the HSE06 functional. These compounds have tunable band gaps from 1.29 to 1.72 eV. The results suggest that Rb2PdBr4I2 and Cs2PdBr4I2 show wider and higher optical absorption coefficients than those of Rb2PdBr6 and Cs2PdBr6 in the entire visible spectrum. This work reveals that the optical absorption can be greatly improved by adjusting the band gap of Pd-based double perovskites . Rb 2PdBr4I2 and Cs2PdBr4I2 are proposed to be promising candidates for solar cells.