Pseudohalide BF₄^-doping in metal halide perovskites: a first-principles perspective

Over the past decade, metal halide perovskite solar cells have achieved remarkable progress with power conversion efficiency increasing from 3.8% to over 27%. However, the inherent instability of perovskites under thermal, moisture, light, and interfacial stress remains a critical limitation for commercialization. Pseudohalide BF₄^-doping has emerged as a promising strategy to enhance both efficiency and stability. In this Perspective, we systematically review recent progress in BF₄^--doped perovskites by integrating experimental observations with first-principles theoretical understanding. We highlight how BF₄^-doping influences structural properties, optoelectronic performance, and multidimensional stability through hydrogen bonding network reconstruction, lattice anharmonicity suppression, and defect passivation. Importantly, we identify the lattice anharmonicity suppression as fundamental mechanism underlying these multifaceted improvements, establishing a general design principle that extends beyond BF₄^-to other pseudohalides. This comprehensive analysis provides both fundamental insights into perovskite physics and practical guidance for developing next-generation high-efficiency, stable perovskite photovoltaic devices with commercial viability.