High-Performance Flexible Perovskite Solar Cells with a Metal Sulfide Electron Transport Layer of SnS₂ by Room-Temperature Vacuum Deposition

In this work, high mobility n-type SnS2 semiconductor films have been fabricated by vacuum deposition at room temperature and employed as the electron transport layer of flexible perovskite solar cells for the first time. The deposited SnS2 film exhibits homogeneous microstructure and good energy-level matching and presents a fast charge mobility and collection rate. By introducing SnS2 layer as an electron transport layer in fabricating flexible PKSC devices, a high cell performance with negligible hysteresis and an improved stability have been achieved. Because ZnO can be damaged by MAPbI3, the introduction of SnS2 buffer layer seems to be useful for improving the stability. By optimizing the SnS2 film thickness, a maximum power conversion efficiency of 13.2% with negligible hysteresis effect has been achieved in the device with a 60 nm SnS2 electron transport layer due to the optimal coverage, electron extraction, and large charge recombination resistance. This work demonstrates an encouraging prospect of SnS2 for high-performance flexible perovskite solar cells and also provides a new vision to the research and development of flexible perovskite photovoltaic devices for future applications.