Anharmonicity-Driven Modulation of Carrier Lifetime and Mobility in BF ₄ -Doped All-Inorganic CsPbX ₃ (X = I, Br) Perovskites

Pseudohalide (such as BF₄^-) doping has emerged as a crucial strategy for enhancing the photovoltaic performance of all-inorganic halide perovskite CsPbX₃ (X = I, Br) solar cells. Here, we employ density functional theory and <i>ab initio</i> nonadiabatic molecular dynamics to elucidate how BF₄^- doping modulates carrier dynamics through anharmonicity-driven mechanisms. We demonstrate that BF₄^- incorporation substantially enhances intrinsic anharmonicity (∼4.5-fold in CsPbI₃, >10-fold in CsPbBr₃), amplifying dynamic disorder that induces charge localization and reduces electron-phonon coupling. This mechanism extends nonradiative recombination lifetimes by 131% in CsPbI₃ and 47% in CsPbBr₃. Critically, we reveal a nonmonotonic relationship between anharmonicity and carrier transport: whereas moderate anharmonicity enhancement improves electron mobility by 35% in CsPbI₃, excessive enhancement induces mobility degradation in CsPbBr₃ due to charge overlocalization. Our work establishes fundamental design principles connecting lattice anharmonicity to carrier lifetime and mobility, providing atomic-level insights for optimizing pseudohalide-doped perovskite optoelectronics.