To improve the power conversion efficiency (PCE) and stability of inverted perovskite solar cells (PSCs) prepared in humid air (RH = 55%), a new zinc oxide (ZnO):TIPD composite film is inserted between PCBM layer and Ag electrode for the first time. Compared to the single PCBM layer, the formed PCBM/ZnO:TIPD electron transport layer (ETL) has better coverage on the perovskite layer and more effective charge extraction ability from the perovskite layer. The insertion of ZnO:TIPD film effectively suppress the charge recombination at perovskite/ETL interface. Besides, the PCBM/ZnO:TIPD layer has better ability to prevent moisture from penetrating into the perovskite layer than single PCBM film. For these reasons, the PCE and stability of the PSCs with the PCBM/ZnO:TIPD are significantly improved compared to the PSCs with single PCBM (or ZnO:TIPD) layer. The highest efficiency of the cell with PCBM/ZnO:TIPD ETL reaches (13.7 +/- 0.4)% in ambient atmosphere, which is 1.20 times that of the PSCs with PCBM only.