©　2018　The　Author(s).　It　is　well　known　that　electron　transport　layer　(ETL)　plays　an　indispensable　role　in　the　planar　heterojunction　perovskite　solar　cells　(PSCs).　TiO2　is　widely　used　as　an　ETL　material　due　to　its　excellent　transport　properties,　however,　the　presence　of　defects　in　the　TiO2　layer　diminishes　the　power　conversion　efficiency　(PCE)　of　the　devices.　Herein,　we　introduce　a　method　of　low-temperature　TiCl4　treatment　to　deposit　a　TiOx　layer　on　the　surface　of　TiO2　film,　which　can　effectively　passivate　trap　states　at　the　TiO2　surface.　Moreover,　the　treating　process　is　optimized　to　be　30min　using　a　40mM　TiCl4　aqueous　solution.　Benefiting　from　this,　we　obtain　the　champion　device　with　the　highest　PCE　of　18.47%,　which　is　mainly　due　to　the　reduction　of　surface　defects　and　the　deposition　of　the　well-crystallized　perovskite　films.　Besides,　the　modified　PSCs　exhibit　an　average　PCE　of　17.59%,　which　is　much　better　than　the　control　devices.