Regulated Aggregation of Phenyl-C61-Butyric Acid Methyl Ester (PCBM) Electron-Transporting Layer via Solvent Engineering for Performance Improvement in Perovskite Solar Cells

Fullerene derivatives, particularly phenyl-C61-butyric acid methyl ester (PCBM), are widely used as electron transport layers (ETLs) in inverted perovskite solar cells due to their excellent electron extraction capabilities. However, the relatively weak solvent-solute interactions in conventional chlorobenzene solvents often lead to intrinsic PCBM aggregation, resulting in interfacial charge accumulation and reduced device performance. In this study, an asymmetrical solvent, 2-chlorothiophene (2Cl-Th), is introduced to effectively regulate PCBM agglomeration by enhancing electrostatic interactions, which can efficiently regulate the molecular dispersion and boost the uniformity of PCBM molecules. The optimized morphology can coherently suppress interfacial charge recombination and promote the carrier extraction capability, leading to a champion power conversion efficiency of 23.22% with elevated operational stability.