Stable δ-FA(Cs)PbI₃ intermediate enables fabrication of large-area perovskite solar modules in ambient air

Fabrication of large-area perovskite solar modules under ambient air conditions remains a critical challenge due to air sensitivity of perovskite intermediate phases during crystallization. Here, we introduce 2-iodoimidazole (IIZ) into the perovskite precursor, enabling the formation of an air-stable pure δ-phase intermediate, which, upon annealing, fully transforms into a highly oriented α-phase perovskite film with reduced defects and variability. Leveraging this approach, we achieve a stabilized power conversion efficiency of 20.9% for 927.5 cm2 perovskite solar modules with high reproducibility. The encapsulated modules meet stringent international photovoltaic testing standards (IEC61215:2021), demonstrating excellent stability under continuous operation, thermal cycling (−40 to 85 °C) and damp heat (85 °C and 85% relative humidity).