Simultaneous Solvent and Interface Engineering of Electron Transport Layer for Efficient and Stable Perovskite Solar Cells.

Despite the high electron mobility and favorable interfacial properties, [6,6]-phenyl-C61-butyric acid methyl ester (PCBM) electron transport layers (ETLs) in perovskite solar cells often suffer from molecular aggregation, resulting in inhomogeneous films, insufficient defect passivation, and suboptimal energy-level alignment. Here, we introduce acetyl cyanide (AC) as a processing additive into the PCBM precursor solution. Through van der Waals interactions, AC disrupts π-π stacking between PCBM molecules, thereby improving dispersion and enhancing film homogeneity. This strategy significantly improves the conductivity and charge extraction capability of the PCBM ETL, while also optimizing energy-level alignment and strengthening interfacial passivation. Consequently, AC-modified devices achieve an efficiency of 25.75%, along with excellent operational stability, retaining over 80% of their initial performance after 1400 h under both ambient conditions and 85 °C thermal stress in nitrogen. This work offers a scalable and effective strategy to mitigate PCBM aggregation, facilitating more efficient and stable perovskite photovoltaics.