Alkylammonium Salt as Additives to Expand the Processing Window of Wide-Bandgap Perovskite Solar Cells Made in Ambient Air

Abstract

Wide-bandgap (WBG) perovskites are critical for advancing tandem solar cell technology, yet their fabrication remains constrained by narrow processing windows and environmental instability. A synergistic alkylammonium salt additive strategy coupled with a mild gas-flow-assisted crystallization method is presented to produce ambient-air-processed WBG perovskite solar cells (PSCs) with improved reproducibility and scalability. Co-utilizing long-chain alkylammonium chlorides (xACls) and methylammonium chloride (MACl) reduced gas-flow speed requirements while expanding the crystallization kinetics window, suppressing non-radiative recombination and defects, which are verified by fluorescence lifetime imaging microscopy (FLIM), in situ UV–vis spectroscopy, and XRD. High-quality Cs_0.2FA_0.8PbI_2.3Br_0.7 films are successfully prepared under a low gas flow speed (≈2.7 m s⁻¹), which is much lower than the traditional gas quenching method (>26 m s⁻¹). Cs_0.2FA_0.8PbI_2.3Br_0.7 solar cells made by using 12ACl/MACl additives yielded a champion power conversion efficiency (PCE) of 19.72% (V_oc: 1.238 V), which is among the highest efficiency for WBG PSCs made in ambient air. This method has the advantages of high humidity tolerance (PCE >19% for cells made under 20–65% RH), compatibility with cost-effective fan drying, elimination of anti-solvents, and >70% inert gas-flow intensity reduction, establishing an eco-friendly scalable protocol that bridges lab-to-industry translation for high-performance WBG PSCs.