Construction of Efficient and Stable FAPbI3 Perovskite Solar Cells through Bifunctional Ionic Liquid‐Assisted Crystallization and Defect Passivation

FAPbI 3 is considered one of the most ideal perovskite materials to construct highly efficient perovskite solar cell (PSC), but the poor phase stability and film‐forming properties hinder further performance improvements. Herein, an ionic liquid 3‐(2‐amino‐2‐oxoethyl)‐1‐methyl‐1H‐imidazol‐3‐ium chloride (AOMCl) with multifunctional cations and Cl anion to assist crystallization, reduce defects, and stabilize α‐FAPbI 3 is reported. Results show that the perovskite film's nonradiative recombination and phase transition are suppressed after AOMCl treatment. The PSCs with AOMCl treatment obtain a power conversion efficiency (PCE) up to 22.01% with negligible hysteresis. In addition, the large‐area (1 cm 2 ) device achieves a PCE of 17.11%. The AOMCl‐treated unencapsulated device exhibits impressive stability, maintaining an initial efficiency of over 94% after 1600 h in air environment. This work provides a strategy for designing FAPbI 3 additive ideally.