Water-Enhanced Mixed-Alkylammonium Chloride Perovskite Inks for Humidity-Tolerant Fabrication of Solar Modules

Ambient-air fabrication of perovskite solar cells (PSCs) remains challenging due to humidity-induced defects. Here, we develop a humidity-tolerant fabrication of formamidinium lead iodide (FAPbI3) incorporating methylammonium chloride (MACl) and propylammonium chloride (PACl), optimized through compositionally graded films (CGFs). We identify FAPbI3 ink containing MACl/PACl at 5/25 mol.% (relative to FAPbI3) and 5 vol.% water (relative to final solution) as optimal to yield high-quality perovskite films across a broad range of relative humidity conditions. Nuclear magnetic resonance (NMR) and pH analyses reveal PACl’s role in moderating water interactions and suppressing acid-induced degradation pathways. Films made from this humidity-tolerant ink exhibit improved crystallinity, reduced defect density, and phase-pure α-FAPbI3. PSCs fabricated with this ink achieve a power conversion efficiency of 22.7% (0.049 cm²), while 10.23 cm² minimodules achieve 17.5% efficiency. The PSCs retain ~80% initial efficiency after 400 hours of maximum power point tracking under illumination and 330 hours of thermal aging. This work advances scalable, climate-resilient perovskite photovoltaics.