Functionalization of fullerene materials toward applications in perovskite solar cells†
Fullerene materials exhibit high electron affinity, high electron mobility and small reorganization energy, thus they have been widely utilized as electron transport layers, cathode interfacial layers and trap passivators in constructing efficient organic–inorganic hybrid halide perovskite solar cells (PSCs). Herein, we summarize the recent progress of functionalized fullerene materials (i.e., fullerene derivatives) which have been applied in PSCs, focusing on chemical functionalization strategies. We provide exhaustive lists of all reported fullerene derivatives applied in PSCs, and categorize them based on the types of addend groups and addition patterns. In particular, we manage to unveil the correlation between the chemical structures of fullerene derivatives, especially the addend groups, and their performance in improving the PSC device efficiency and stability. Finally, we propose an outlook on the future development of fullerene derivatives in realizing high-performance PSC devices.