Preparation and Properties of MA0.9FA0.1PbI3 Perovskite Solar Cells by Br- doping

In this study, under fixed cation stoichiometry, the effects of Br⁻ doping with varying ratios on the structural and optoelectronic properties of perovskite films and corresponding device performance were systematically investigated. The substitution of Br⁻ for partial I⁻ in the perovskite lattice demonstrated significant morphological refinement and enhanced crystallographic quality, as evidenced by reduced defect density and grain boundary formation. The optimized composition, MA₀.₉FA₀.₁PbI₂.₈₅Br₀.₁₅, exhibited superior film uniformity and crystallinity, which translated into improved photovoltaic parameters in carbon-electrode-based perovskite solar cells (PSCs). The champion device achieved a power conversion efficiency (PCE) of 9.33%, outperforming the undoped MA₀.₉FA₀.₁PbI₃ counterpart. Environmental stability assessments revealed that unencapsulated Br⁻-doped devices maintained 92% of their initial PCE after 60 days in ambient atmosphere (25°C, 40–60% RH), demonstrating markedly enhanced operational durability compared to the undoped control group. This work highlights halogen engineering as an effective strategy for simultaneously optimizing phase stability and defect passivation in mixed-halide perovskite systems.