Stabilizer-assisted growth of formamdinium-based perovskites for highly efficient and stable planar solar cells with over 22% efficiency

The best reported state-of-the-art perovskite solar cells (PSCs) show record power conversion efficiency (PCE) over 23%, where sequentially deposited formamidinium (FA)-dominated perovskites were adopted. Here, we develop a stabilizer-assisted growth method involving two stabilizers (MAPbBr3 and MACl) to fabricate phase-pure formamidinium lead iodide (α-FAPbI3) perovskite and substantially improve its opto-electronic properties. The high crystalline and large crystal grains within the α-FAPbI3 perovskite film as well as the reduced defects contribute to the enhanced PCE up to 22.51% in planar PSCs. More importantly, the stability of phase-stabilized FAPbI3 PSC is also significantly improved and the corresponding device exhibits an impressive 97% retention after 2600 h storage under ambient conditions. This work paves a way to further improve the photovoltaic performance and stability of FA-based planar PSCs.