Interfacial engineering toward the perovskite layer/electron transporting layer (ETL) interface has been demonstrated to be critical for achieving highly efficient perovskite solar cells (PSCs). In this work, PSCs with ETL/perovskite interfacial modification by benzoic acid derivatives are fabricated. No obvious influence of this interfacial modification on optical properties, crystal structure and surface morphology of perovskite films are found. Enhancement of the charge extracting ability of treated TiO 2 and passivation toward trap states of the TiO 2 surface are confirmed from transient PL spectra and EIS measurements. Besides, the effect of different groups on the para -position is also investigated. A PCE as high as 18.43% with a maximal steady-state output PCE of 17.19% has been achieved for the PSCs treated with para -Cl substituted benzoic acid. Enhanced performance of a perovskite solar cell via simple interfacial modification onto a mesoporous TiO 2 layer.