Systematic investigation of the mechanical, electronic structure and optical properties of halide double perovskite Cs2BSbBr6 (B = Li, Na, K, Rb) with first-principles method

Halide double perovskite Cs 2 BMX 6 possesses excellent photoelectronic properties. The material properties would have been markedly influenced by the variant electronic structures if the chemical elements of B, M and X had been changed. In this paper, we have a systematic investigation on the mechanical, electronic structure and optical properties of Cs 2 BSbBr 6 (B[Formula: see text][Formula: see text][Formula: see text]Li, Na, K, Rb) using first-principles method. The results show that Cs 2 LiSbBr 6 and Cs 2 NaSbBr 6 are indirect band gap semiconductors, while Cs 2 KSbBr 6 and Cs 2 RbSbBr 6 are direct band gap semiconductors. The band gap values of Cs 2 BSbBr 6 (B = Li, Na, K, Rb) are 2.81, 2.96, 3.37 and 3.36[Formula: see text]eV, respectively. It is worth noting that the band gap value of Cs 2 BSbBr 6 increases with the increased atomic number of B (Li–Na–K–Rb) atoms. Due to the inter-band transition of electrons, the strong absorption spectrum occurs in the visible region. These physical and electronic properties of Cs 2 BSbBr 6 provide references for the potential applications.