Insight into the Interface Engineering of a SnO2/FAPbI3 Perovskite Using Lead Halide as an Interlayer: A First-Principles Study.

The interfacial properties of the perovskite photovoltaic layer and electron transport layer (ETL) are critical to minimize energy losses of perovskite solar cells (PSCs) induced by interfacial recombination. Herein, the interface engineering of the SnO2/FAPbI3 perovskite using PbX2 (X = Cl, Br, or I) as an interlayer is extensively studied using first-principles calculations. The results reveal that the thickness of the PbI2 interlayer needs to be finely controlled, which may limit charge transport if there is a large amount of PbI2 precipitation at the interface. The high lattice mismatch of the PbBr2 with the SnO2/FAPbI3 interface makes PbBr2 an unfavorable passivation material. Due to the strong coupling of the PbCl2 with both SnO2 and FAPbI3, an efficient electron transport pathway could be built after applying PbCl2 as an interlayer. Meanwhile, the PbCl2 interlayer could also effectively passivate interface defects, therefore lowering the energy losses of PSCs.