Kilogram-scale one-pot synthesis of multicomponent fullerene composites for efficient inverted perovskite solar cells

The high cost and detrimental self-aggregation of conventional single-component fullerenes such as C60 and PCBM constitute a major obstacle to the commercialization of inverted perovskite solar cells (IPSCs). We report a kilogram-scale, one-pot synthesis of a multi-component fullerene composite (FC), comprising C60, a bis((3-methyloxetan-3-yl)methyl) malonate-C60 mono-adduct (BCM), and its bis-adduct (BCB). FC is obtained in 96% yields without complex column chromatography, significantly reducing production costs. Upon thermal annealing, BCM and BCB undergo cross-linking to form a robust encapsulation network that homogeneously incorporates C60, enhancing film stability and electron mobility. IPSCs incorporating cross-linked fullerene composite (CFC) demonstrate an impressive efficiency of 26.55%, surpassing that of PCBM-based devices (24.82%). Additionally, CFC-based devices maintain 96.0% and 95.1% of their initial efficiency after 1000 hours under ISOS-L-1 and ISOS-D-2 protocols, respectively. Notably, CFC demonstrates excellent performance across a range of device configurations, including wide-bandgap (1.68 eV and 1.77 eV) cells, large-area devices (1 cm2), and mini-modules (14.4 cm2). High cost and aggregation of single-component fullerenes hinder inverted perovskite solar cell development. The authors synthesize a fullerene composite in high yield that cross-links during annealing, improving stability and efficiency while maintaining performance in various device formats.