Stabilizing initial phase for efficient and stable FAPbI3 perovskite solar cells

Formamidinium lead triiodide (FAPbI3) perovskite stands at the forefront of efficiency in perovskite solar cells (PSCs), yet the thermodynamically unstable alpha-phase poses a challenge to device long-term stability. While thermal annealing is essential for producing high-quality polycrystalline films that stabilize the alpha-FAPbI3 phase, it also induces partial decomposition of FAPbI3 into PbI2, leading to extra phase instability of FAPbI3 films. Here, we develop a zero dimensional (0D) perovskite-decorated strategy to enhance the intrinsic stability of FAPbI3 film by stabilization of the initially formed alpha-FAPbI3 phase. This is achieved by reducing the defect density and forming mixed 0D/3D perovskites, which effectively slow down perovskite decomposition during thermal annealing and decrease the amount of residual PbI2 in the final film. The reduced trap density in 0D perovskitetreated PSCs suppresses Shockley-Read-Hall nonradiative recombination and improves charge collection efficiency. Consequently, the 0D perovskite-decorated PSCs endow significant enhancements in both power conversion efficiency (from 22.23% to 24.56%) and device stability. This novel 0D perovskite-decorated strategy offers a promising path toward more robust PSCs.