Chemical Coordination of Acetic Acid to Improve Photovoltaic Performance and Long‐Term Stability of Sn−Pb Perovskite Solar Cells

Abstract Mixed Tin‐Lead perovskite solar cells (Sn−Pb PSCs) with a narrow band gap (NBG) are significant for single‐junction and all‐perovskite tandem solar cells due to their low toxicity and ideal band gap. Nevertheless, the performance and stability of the device are adversely affected by the uncontrollable crystallization and ion migration processes. Acetic acid (HAc) is introduced into the perovskite precursor solution as a multifunctional additive to enhance the film crystallization process and restrain ion migration in the device. The study shows that the introduction of HAc modulates the crystallization rates of Sn−Pb perovskite, significantly improving the crystal quality of the film and suppressing the oxidation of Sn 2+ , thereby reducing the generation of defects. Additionally, the polar hydroxyl groups (−OH) in HAc form hydrogen bonds with I − , inhibiting I − ion migration and effectively protecting the Ag electrode from corrosion. Consequently, the optimized Sn−Pb PSCs containing HAc achieved a power conversion efficiency (PCE) of 21.42 % (1 sun, AM1.5). Simultaneously, the unencapsulated devices treated with HAc exhibited excellent long‐term stability, maintaining a certain percentage of their initial efficiency after aging for 1000 hours in an N₂ atmosphere.