Improved the long-term air stability of ZnO-based perovskite solar cells prepared under ambient conditions via surface modification of the electron transport layer using an ionic liquid

Poor long-term stability of perovskite solar cells (PSCs) in ambient air has hindered the PSC commercialization. In this work, we introduce an ionic liquid (IL) of 1-ethyl-3-methylimidazolium hexafluorophosphate ([EMIM]PF 6 ) as an inter-layer between the ZnO and perovskite layers. The devices are fabricated in air without any atmosphere controlling. Solar cell with a power conversion efficiency of 13.50% is obtained, and a small J-V hysteresis is accomplished. More importantly, after 90 days (>2000 h) storage in air, our device without encapsulation retains 88.17% of its initial efficiency. Our work provides a simple valid strategy to develop air-processed, stable and efficient PSCs for future applications.