Optoelectronic Evolution in Halogen-Doped Organic-Inorganic Halide Perovskites: A First-Principles Analysis

Cl, Br, and I are elements in the halogen family, and are often used as dopants in semiconductors. When employed as dopants, these halogens can significantly modify the optoelectronic properties of materials. From the perspective of halogen doping, we have successfully achieved the stabilization of crystal structures in CH₃NH₃PbX₃, CH₃NH₃PbI_3-xCl_x, CH₃NH₃PbI_3-xBr_x, and CH₃NH₃PbBr_3-xCl_x, which are organic-inorganic hybrid perovskites. Utilizing first-principles density functional theory calculations with the CASTEP module, we investigated the optoelectronic properties of these structures by simulations. According to the calculations, a smaller difference in electronegativity between different halogens in doped structures can result in smoother energy bands, especially in CH₃NH₃PbI_3-xBr_x and CH₃NH₃PbBr_3-xCl_x. The PDOS of the Cl-3p orbitals undergoes a shift along the energy axis as a result of variances in electronegativity levels. The optoelectronic performance, carrier mobility, and structural stability of the CH₃NH₃PbBr_3-xCl_x system are superior to other systems like CH₃NH₃PbX₃. Among many materials considered, CH₃NH₃PbBr₂Cl exhibits higher carrier mobility and a relatively narrower bandgap, making it a more suitable material for the absorption layer in solar cells. This study provides valuable insights into the methodology employed for the selection of specific types, quantities, and positions of halogens for further research on halogen doping.