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

Abstract High temperatures facilitate the formation of stable, high‐crystallinity α‐FAPbI 3 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‐FAPbI 3 film without any dopants. High temperature can promote the transformation of δ‐FAPbI 3 to α‐FAPbI 3 , 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‐FAPbI 3 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.