Fullerene Derivative-Modified SnO Electron Transport Layer for Highly Efficient Perovskite Solar Cells with Efficiency over 21.

Tin dioxide (SnO) has been widely applied as an electron transport layer (ETL) for the n-i-p-type perovskite solar cells (Pero-SCs). However, the existence of defects at the surface of SnO and the hysteresis behavior of the devices with SnO ETL limit its application in the Pero-SCs. In this study, a fullerene derivative pyrrolidinofullerene C-substituted phenol (NPC-OH) was synthesized and applied to modify the SnO ETL in Pero-SCs for the first time. The systematic and comparative characterizations demonstrated that, after the introduction of an NPC-OH modification layer on the SnO ETL, the perovskite films in the corresponding device showed enlarged grain size and these devices presented enhanced electron transport and decreased charge recombination velocity. Besides, the NPC-OH layer could significantly reduce the trap-state density in the perovskite film. As a result, a champion power conversion efficiency (PCE) of 21.39% was achieved for the SnO/NPC-OH-based Pero-SCs, with suppressed hysteresis and improved stability, while the control devices with pristine SnO ETL showed a lower PCE of 19.04%.