Mesostructured Fullerene Electrodes for Highly Efficient n–i–p Perovskite Solar Cells

Electron-transporting layers in today’s state-of-the-art n–i–p organohalide perovskite solar cells are almost exclusively made of metal oxides. Here, we demonstrate a novel mesostructured fullerene-based electron-transporting material (ETM) that is crystalline, hydrophobic, and cross-linked, rendering it solvent- and heat-resistant for subsequent perovskite solar cell fabrication. The fullerene ETM is shown to enhance the structural and electronic properties of the CH₃NH₃PbI₃ layer grown atop, reducing its Urbach energy from ∼26 to 21 meV, while also increasing crystallite size and improving texture. The resulting mesostructured n–i–p solar cells achieve reduced recombination, improved device-to-device variation, reduced hysteresis, and a power conversion efficiency above 15%, surpassing the performance of similar devices prepared using mesoporous TiO₂ and well above the performance of planar heterojunction devices on amorphous or crystalline [6,6]-phenyl-C₆₁-butyric acid methyl ester (PCBM). This work is the first demonstration of a viable, hydrophobic, and high-performance mesostructured electron-accepting contact to work effectively in n–i–p perovskite solar cells