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

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-C₆₁-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.