Defect management by a cesium fluoride-modified electron transport layer promotes perovskite solar cells.

SnO is a candidate material for electron transport layers (ETLs) in perovskite solar cells (PSCs). However, a large number of defects at the SnO/perovskite interface lead to notable non-radiative interfacial recombination. Moreover, the energy level arrangement between SnO/perovskite does not match well. In this study, a SnO/CsF-SnO double-layer ETL was prepared by doping CsF into SnO, effectively passivating the defects of the SnO ETL and SnO/perovskite interface. The formation of a good energy level arrangement with the perovskite layer reduces the interface non-radiative recombination and improves the performance of the interface charge extraction. The photoelectric conversion efficiency of the optimal CsF-modified PSC reached 22.18%, owing to the significant increase in the open-circuit voltage to 1.180 V.