Multifunctional Buffer Layer for Bolstering the Stability and Photovoltaic Performance of Perovskite Solar Cells

ABSTRACT Despite the impressive power conversion efficiency (PCE) of perovskite solar cells (PSCs), their long‐term operational stability remains compromised by endogenous ion migration and interfacial recombination. Herein, we report a robust strategy by introducing a novel multifunctional cathode buffer layer based on 4,4′‐((1,10‐Phenanthroline‐3,8‐diyl)bis(ethyne‐2,1‐diyl))dianiline (BAE‐Phen), which exhibits excellent thermal stability. Theoretical simulations and experimental characterizations reveal that BAE‐Phen operates through synergistic mechanisms: its phenanthroline core strongly coordinates with metal ions to decelerate detrimental electrode corrosion, while its extended π‐conjugated backbone enhances π–π stacking with the [6,6]‐phenyl‐C 61 ‐butyric acid methyl ester (PCBM) electron transport layer, facilitating efficient charge transfer. Consequently, the optimized BAE‐Phen‐based devices achieve a champion PCE of 27.07% (certified 26.85%). Notably, unencapsulated devices retained 90.5% of their initial PCE after 2000 h of thermal aging at 85°C. Furthermore, encapsulated devices maintain nearly 100% of their initial performance after 2200 h of continuous maximum power point tracking under 1‐sun illumination, demonstrating exceptional thermal and operational stability. This work presents a strategic interface engineering approach using a multifunctional molecular buffer, providing pivotal insights into the synergistic optimization of charge transmission and ionic to electronic stability for next‐generation photovoltaics.