Aromatic Cage Mediated Surfacial Passivation for Photovoltaic Perovskites

ABSTRACT The chemical imperative of surface passivation for perovskite solar cells (PSCs) is hindered by the non‐complementary mechanisms employed by current aliphatic and aromatic ammonium halides. Even the widely used aromatic passivator 2‑(4‑fluorophenyl)ethylammonium iodide (FPEAI) faces efficiency limitations due to residual lead defects and interfacial charge‑transport barriers. Through mechanistic analysis of the functional moieties in FPEAI, we designed and synthesized novel passivation molecules, elucidating the respective roles of lead‑chelation, π‑conjugation, and steric hindrance in defect suppression. The optimized molecule 2‐(methylthio)ethoxy‐p‐phenylene ethylammonium iodide (OSPEAI) forms a coordinative cage‑like architecture around Pb 2 + sites via synergistic aliphatic‑chain and benzene‑ring interactions, effectively passivating lead‑related defects and inhibiting non‑radiative recombination. As a result, OSPEAI‑modified PSCs achieved a power conversion efficiency of 26.35% with enhanced operational stability, offering innovative molecular‑design insights for chemical passivation in perovskite photovoltaics.