Diastereomeric Fullerene Composite Engineering for Enhanced Perovskite Solar Cells

Achieving high performance and long-term stability in perovskite solar cells (PSCs) typically requires the use of surface passivation layers to suppress the interfacial defects. However, these additional passivation agents often introduce chemical and structural instabilities, limiting the device lifetime. Here, we present a molecular engineering strategy utilizing a chiral series of C₆₀-Furan-Sugar (CFS) fullerene derivatives blended with [6,6]-phenyl-C₆₁-butyric acid methyl ester (PCBM) to modify the electron transport layer (ETL). The incorporation of CFSs significantly enhances the electron mobility and dielectric constant of the ETL, while their intrinsic passivation functionality effectively passivates perovskite surface defects. As a result, PSCs employing PCBM:CFS-RS blends achieve a power conversion efficiency (PCE) of 25.81% without the use of additional passivation layers and retain 95% of their initial performance after 1000 h of aging. Notably, CFS-RS is a chiral molecule bearing a side chain with R/S configurational isomers, which facilitates interfacial compatibility and contributes to the enhanced device performance. This work demonstrates that tuning the orientation of polar substituents in fullerene side chains can effectively influence the optoelectronic properties of the blended films, thereby simultaneously enhancing both efficiency and stability in PSCs.