Organic-inorganic hybrid perovskite solar cell devices have received wide attention because of their high efficiency, and interface problem is one of the key problems in the preparation of perovskite solar cells. An efficient double-layered ethylene diamine tetraacetic acid (EDTA)/SnO₂ composite structure, the ultrathin EDTA layer in contact with ITO electrode and an SnO₂ layer interfaced with the perovskite, is developed as an electron-transport layer (ETL) in the preparation of perovskite solar cells. It is interesting that the surface morphology of the top SnO₂ side of the composite ETL can be finely adjusted by tuning the underneath EDTA layer. These control the nucleation process in crystallization of the perovskite layer and adjust carrier extraction process between the electron transport and perovskite layers. High performance perovskite solar cells having a certified power conversion efficiency of 20.2% with negligible hysteresis are achieved.