Ambient-compatible precursor engineering for efficient perovskite photovoltaics

Achieving high-efficiency perovskite solar cells (PSCs) under ambient conditions remains a critical bottleneck for commercialization, primarily owing to the strong susceptibility of perovskite precursors and film formation processes to moisture and oxygen. Here, we develop a robust air-processing strategy for inverted PSCs by incorporating 1-butyl-3-methylimidazolium trifluoroacetate (BMIT) into precursor solutions, resulting in enhanced environmental tolerance of perovskite precursors by inhibiting iodide oxidation and facilitating stable film formation across a wide humidity range (20–60%). Moreover, the balanced ionic coordination suppresses Pb-I aggregation, mitigates colloidal clustering, and modulates nucleation kinetics, resulting in dense, highly crystalline perovskite films with excellent reproducibility. Consequently, we demonstrate high-efficiency devices across varied bandgaps (1.51, 1.54, and 1.68 eV), including a certified power conversion efficiency (PCE) of 26.48% with a fill factor of up to 85.00% for the 1.54-eV cell. Our device retains 96% of its initial PCE after 1,400 h of continuous 1-sun operation in ambient air. Perovskite solar cells face efficiency losses in ambient air because their precursors are highly moisture- and oxygen-sensitive. Liu et al. use an ionic-liquid additive to stabilize precursor chemistry, enabling robust processing and high-performance devices.