High-Temperature Driven Recrystallization for Stable Dopant-Free α-FAPbI₃ Perovskite Solar Cells

High temperatures facilitate the formation of stable, high-crystallinity α-FAPbI₃ films but can lead to the volatilization of organic components in perovskites. Here, a 300 °C hot-press-assisted recrystallization strategy is reported to grow stable phase-pure α-FAPbI₃ film without any dopants. High temperature can promote the transformation of δ-FAPbI₃ to α-FAPbI₃, and induces recrystallization to relieve strain. The applied pressure creates a confined space that effectively prevents the volatilization of organic components in perovskite. The α-FAPbI₃ film prepared by hot-press at 300 °C achieves an average grain size of ≈3 µm (with grains up to 10 µm) and demonstrates excellent damp-heat stability, showing no significant change after 20 s in deionized water. The result solar cell delivers a power conversion efficiency as high as 24.06% and retains >70% of their initial efficiency value after 1000 h at 85 °C and 85% relative humidity.