Scalable fabrication of high-efficiency FAPbI₃ perovskite solar modules in humid air via intermediate-phase engineering

Stable fabrication of perovskite modules in ambient air is critical for commercialization. However, the efficiency of perovskite solar cells (PSCs) fabricated in humid air remains suboptimal—especially for large-area modules. Here, we demonstrate that under high humidity, the conventional PbI₂·DMSO intermediate readily hydrates to form PbI₂·DMSO--H₂O, which promotes the undesired formation of δ-FAPbI₃. To mitigate this, we introduce 2-chlorobenzamidine acetate (CBAc) to form a stable PbI₂·DMSO--CBAc intermediate, effectively preventing water incorporation and enabling the phase-pure formation of α-FAPbI₃. Small-sized n-i-p and p-i-n PSCs, fabricated by spin-coating in air, achieved efficiencies of 26.06% and 26.52% (certified 26.29%), respectively, and a mini-module attained 22.36%. The encapsulated small-area devices retained 95.1% of its initial efficiency after 1,550 h of continuous maximum power point tracking in ambient air. Furthermore, this strategy shows great potential for commercial manufacturing, with modules fabricated via slot-die coating in air, achieving 21.10% efficiency on a 100.8 cm² aperture area.