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 (FAPbI 3 ) incorporating methylammonium chloride (MACl) and propylammonium chloride (PACl), optimized through compositionally graded films. We identify FAPbI 3 ink containing MACl/PACl at 5/25 mol.% (relative to FAPbI 3 ) 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 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-FAPbI 3 . PSCs fabricated with this ink achieve a power conversion efficiency of 22.7% (0.049 cm 2 ), while 10.23 cm 2 minimodules achieve 17.5% efficiency. The PSCs retain ∼80% initial efficiency after 400 h of maximum power point tracking under illumination and 330 h of thermal aging. This work advances scalable, climate-resilient perovskite photovoltaics.