Supplement Information for Publication

See the supplementary material for information about photovoltaic parameter statistics of perovskite devices deposited on ZnO/SnO2 treated with different concentrations (Fig. S1), visual phenomenon of perovskite film deposited directly on SnO2 or ZnO (Fig. S2), transmittance and absorption spectra of different ETLs, AFM images of the different ETLs (Fig. S3), AFM images of the different ETLs (Fig. S4), XPS spectra of perovskite films on ETL with ZnO/SnO2 substrate (Fig. S5), the absorption spectra of perovskite films deposited on different ETLs (Fig. S6), the cross-sectional SEM images of perovskite layer at ITO/SnO2 interface modified by ZnO (Fig. S7), the J-V curves of FAPbI3 PSCs prepared by two-step sequential deposited perovskite films based on optimized ZnO/SnO2 bilayer ETLs and the monolayer SnO2 ETL (Fig. S8), the contribution of ZnO and SnO2 as ETL in the field of PSCs in recent years is summarized (Table S1), the summary of the detailed photovoltaic parameters of freshly prepared perovskite devices with different ETLs and the hysteresis factor (Table S2), the summary of the detailed photovoltaic parameters of unpackaged devices with different ETLs stored in N2 environment for different days (Table S3).