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

Abstract

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 ≈3µm (with grains up to 10µm) and demonstrates excellent damp-heat stability, showing no significant change after 20s 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 1000h at 85°C and 85% relative humidity.