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. [ABSTRACT FROM AUTHOR]