Improved Performance of Planar Perovskite Solar Cells Using an Amino-Terminated Multifunctional Fullerene Derivative as the Passivation Layer

Organic–inorganic metal-halide perovskite solar cells (PSCs) have been revolutionizing the photovoltaic (PV) community in the past decade. However, the trap states in TiO2 as the electron-transport layer seriously affect the device PV performance and stability. Here, we design and synthesize a fullerene derivative C60NH2 featuring an amino-terminated group. We use C60NH2 as a passivation layer between TiO2 and perovskite in planar PSCs with a standard configuration to improve the quality of the obtained perovskite film as well as the electron-transfer efficiency, resulting in an obvious increment of PV performance and stability of the devices. The champion power conversion efficiency of 18.34% is achieved under 100 mW cm–2 illumination utilizing C60NH2 as the passivation layer with much less hysteresis. Planar PSCs demonstrate superior stability under natural sunlight and 40–50% relative humidity after C60NH2 passivation. This work enriches the choices of materials for interface engineering toward fabrication of planar PSCs with high performance.