Synergistic Passivation Strategies for Enhancing Efficiency and Stability of Perovskite Solar Cells

Perovskite solar cells (PSCs) are celebrated for their potential in clean and renewable energy applications. However, their performance and longevity are often compromised by surface and grain boundary defects. Herein, a posttreatment strategy using 4‐hydroxy‐4′‐biphenylcarboxylic acid ethyl ester (EHBC) is introduced to passivate these defects in perovskite films, thereby enhancing the performance of PSCs. As a Lewis base, the carbonyl group of EHBC interacts with uncoordinated lead ions to passivate lead vacancy defects, while the hydroxyl group forms hydrogen bonds with iodide ions, reducing their migration. Additionally, the hydrophobic biphenyl groups of EHBC enhance the resistance to moisture. The study demonstrates that PSCs treated with EHBC retain 69% of their initial performance after 700 h under 30% relative humidity, achieving a maximum power conversion efficiency (PCE) of 24.48%, a significant improvement over the untreated control PSCs (PCE = 23.04%). This synergistic passivation strategy offers an effective approach for fabricating high‐efficiency and stable PSCs.