A Single‐Step Cleaning Process for Simultaneous Removal of Surface Impurities and Passivation of Sub‐Surface Defects in Perovskite Solar Cells

Abstract Perovskite solar cells (PSCs) suffer from the presence of non‐active and metastable species on the surface of solution‐processed perovskite films, and their adverse effects on charge extraction and long‐term stability cannot be fully addressed by conventional surface passivation strategies. In this study, a novel concept is proposed to achieve both precise removal of surface impurities and effective passivation of sub‐surface defects in a single step, utilizing a functional polymer‐based cleaning strategy. The moderate intermolecular force provided by the functional polymer and their inherent robust interchain interactions enable effective surface cleaning without disturbing the active crystal lattice. Following surface cleaning, the electron‐donating groups (C═O) in the polymer passivate the uncoordinated Pb 2+ defects at the sub‐surface level. This synergistic effect of surface cleaning and sub‐surface defect passivation leads to a drastic reduction in interfacial non‐radiative recombination, elimination of ion migration pathways, and prevention of triggers for photodegradation. As a result, the power conversion efficiency (PCE) significantly improved from 22.84% to 25.51%, accompanied by a remarkable enhancement in operational stability. Moreover, the operability and effectiveness of this approach make it highly suitable for scaling up perovskite solar modules in the future.