Comparative investigation of structural, electronic, mechanical and optical responses of CsPbI3-PbSe and CsPbI3 with Mg-doped for optoelectronic applications: A first-principles study

A and B-site doping has been viewed as a very effective approach to stabilise the desired perovskite cube phase of pure and doped hetero-structure CsPbI₃-Pb_1-xMg_xSe and the simple system CsPb_1-xMgxI₃. In this analysis, the effect of (Mg²⁺) on the crystal structure, electronic, mechanical, and optical responses of hetero-structure CsPbI₃-Pb_1-xMg_xSe and CsPb_1-xMgxI₃ were thoroughly investigated, by employing first-principles computations. A theoretical study of target responses of the metal-halide CsPbI₃ is presented with a plane wave ultra-soft pseudopotential approach as personified in the CASTP code. The computed results show that the band gap of CsPbI₃-Pb_1-xMg_xSe can be changed from '1.809eV' to '1.75eV' when the concentration range (x = 0 to 0.25) is changed. A valuable band gap of '0.48eV' and '1.28eV' of doped CsPbI₃-Pb_1-xMg_xSe can be achieved under concentrations changed from (x = 0.25 to '0.75eV') and as shown in direct (Γ - Γ) nature and become optically active. The density of states shows that Cs-6p, I-4p, and Pb-6p states contribute to the valence band maximum, whereas the main involvement conduction band minimum by Mg-5p and Cs-6p states in the CsPbI₃-Pb_1-xMg_xSe system. Elastic properties designate the flexibility and softness of target materials. The computed elastic parameters further indicate that this hetero-structure material is stable under the doping concentration condition. Replacing the Pb²⁺ site with Mg²⁺ has red-shifted the maximum absorption edges and changed the optical characteristics to be anisotropic. Their ability of these two materials with their Mg²⁺ based mixed halide perovskite nature for optoelectronic applications.