Tailoring Precursor Chemistry Enabled Room Temperature‐Processed Perovskite Films in Ambient Air for Efficient and Stable Solar Cells with Improved Reproducibility

Abstract The perovskite solar cells (PSCs) are promising for commercialization and practical application. However, high‐quality perovskite films are normally fabricated in inert gas‐filled glovebox, followed by thermal annealing, which is energy‐consuming and thus not cost‐effective. In this study, a simple manufacturing strategy is demonstrated to fabricate the highly‐crystalline perovskite films in ambient air (a relative humidity of over ≈50%) at room temperature via blade‐coating without the subsequent thermal–annealing. The perovskite precursor chemistry is tailored by solvent engineering via employing 2‐methoxyethanol, which can strongly coordinate with ammonium halide species, thus forming highly uniform small‐sized colloids and facilitating the homogeneous nucleation and rapid crystallization of perovskite films even at room temperature. The resultant PSCs fabricated with ambient‐processed, annealing‐free MAPbI 3 perovskite films exhibit a champion efficiency up to 19.16% with negligible hysteresis and improved reproducibility, which is on par with the high‐temperature annealed counterparts fabricated in N 2 , and represented one of the highest reported efficiencies for the room‐temperature processed PSCs in ambient air. The unencapsulated devices show extended lifespan over 1000 h with nearly no efficiency loss.