Theoretical study on the effect of the optical properties and electronic structure for the Bi-doped CsPbBr₃

Metal doping, including Bi, Yb, Eu, Sb and so on, are important means to improve the photoelectric properties and stability of metal halide perovskite materials. Among these works, Bi-doped CsPbBr₃ especially has attracted much attention for both experimental and theoretical investigation. But there are still some arguments to be solved. One view thinks that Bi doping in CsPbBr₃ not only influences the band structure, but also improves the charge transfer (Raihana et al 2017 J. Am. Chem. Soc. 139 731-7). The other supported the points that there are no changes in the valence band structure of Bi-doped CsPbBr₃ and the concept of the band-gap engineering in Bi-doped CsPbBr₃ halide perovskite is not valid (Olga et al 2018 J. Phys. Chem. Lett. 9 5408-11). They also have different opinions for the reason of the red-shift phenomenon caused by Bi-doped CsPbBr₃. In this work, the density functional theory (DFT) based first-principles methods is adopted to investigate the effect of the optical properties and electronic structure for Bi doping CsPbBr₃. The calculated results clarify that the red-shift phenomenon is caused by the slight reduction of band gap and the transition levels of Bi_i and Bi_Pb defects. The values of red-shift also were estimated about 150 meV for Bi_i defects, which is close the experimental value of about 140 meV. Moreover, our studies also show that the Bi doping does not affect the valence bands, but Bi_i defects change the electron distribution of the conduction band. Our work and experimental results support and confirm each other, which provides a useful reference for the study of Sb-doped CsPbBr₃, Eu-doped CsPbBr₃ and so on.