Abstract: The surface of Perovskite films fabricated via solution processing exhibit a significantly higher defect density compared to their bulk phase. Furthermore, when fabricated under ambient air conditions, such surface defects tend to interact with water molecules, inducing film degradation and thereby reducing the power conversion efficiency (PCE) of devices. In this work, a novel surface passivation material, 2-Phenoxyethanamidine hydrochloride (POECl), is employed to modulate these surface defects. The results reveal that POECl achieves defects passivation by complexing with PbI₂ on the perovskite film surface and forming a 2D perovskite phase. Concurrently, the Ostwald ripening effect during passivation significantly enhances the crystallinity of the perovskite film. Perovskite solar cell (PSC) passivated with POECl demonstrate an increase in PCE from 23.06% (control PSC) to 24.59%. Moreover, the POECl-passivated PSC exhibits superior operational stability, retaining 81% of its initial efficiency after 600 h of maximum power point tracking inside an argon glovebox.