Here, phenyl-C61-butyric acid (PCBA) is presented as a generic passivation coating for metal oxide electron transport layers used in planar n-i-p configuration of perovskite solar cells. PCBA shows better adhesion to tin and zinc oxides due to strong acid-base interactions as compared to the conventionally used phenyl-C61-butyric acid methyl ether (PCBM). Therefore, depositing a compact PCBA passivation coating can be achieved in a much more economical way using 100 times less concentrated precursor solution. In addition, PCBA coating delivers higher power conversion efficiencies (up to 20.3%) as compared to the pristine oxide layers with or without PCBM coating. Finally, the fabricated solar cells using PCBA coating are more stable in comparison with the reference cells with conventional PCBM passivation and preserved 70% of the initial efficiency after 1500 h of continuous 30 mW/cm2 white light illumination at 50 °C.