Reliable perovskite solar cells

A simple route is developed to synthesize oxidized open-cage fullerene derivatives that are then incorporated as electrontransporting materials in perovskite solar cells. The obtained devices provide competitive power conversion efficiencies, open-circuit voltage values and good stability. These good figures arise from the high perovskite passivation ability of the open-cage fullerenes, and a good overlap between the highest occupied molecular orbital/lowest unoccupied molecular orbital levels of our derivatives and the conduction band of the perovskite.