This work derived the relationship between the concentrations of Pb²⁺ and I⁻ vacancies, along with MA⁺ vacancies, in MAPbI₃ crystals and their effect on the short-circuit current of MAPbI₃-based solar photovoltaic devices. First principles calculations revealed that Pb²⁺ and I⁻ vacancies introduce shallow defect levels near the Fermi level, acting as non-radiative recombination centers, which significantly influence the short-circuit current and open-circuit voltage. In contrast, MA⁺ vacancies have a negligible effect on the optoelectronic properties of MAPbI₃. Based on this correlation, we successfully elucidated the declining trend of the short-circuit current (J_sc) in MAPbI₃-based devices with increasing Pb²⁺/I⁻ vacancy concentrations, while uncovering the microscopic mechanism responsible for the minor performance impact of MA⁺ vacancies.

In this study, we investigate the influence of the halogen elements bromine (Br) and chlorine (Cl) on iodine defect properties primarily in FAPbI₃ through first-principles calculations, aiming to understand the effect of high defect densities on the efficiency of organic–inorganic hybrid perovskite cells. The results indicate that Br and Cl interstitials minimally alter the overall band structure of FAPbI₃ but significantly modify the defect energy levels. Br and Cl interstitials, with defect states closer to the valence band and lower formation energies, effectively convert deep-level traps induced by iodine interstitials (I_i) into shallow-level traps. This conversion enhances carrier transport by reducing non-radiative recombination while preserving light absorption efficiency. Excess Br/Cl co-doping in FAPbI₃ synthesis thereby suppresses non-radiative recombination and mitigates the detrimental effects of iodide-related defects.