In this work, we introduced a novel Ni-4 mercaptophenol (Ni4MP) as an interfacial layer in Sb2S3 -sensitized mesoporous TiO2 solar cells. Ni4MP thin films with controllable thickness were prepared by an integrated approach via atomic/molecular layer deposition techniques and were systematically characterized. Introduction of the Ni4MP interlayer significantly enhanced the photovoltaic performance and the interfacial charge transfer kinetics of Sb2S3-sensitized solar cells. The augmentation of open circuit voltage and short circuit density due to the insertion of a Ni4MP interlayer enhanced the power conversion efficiency of the solar cells from 2.07% to 2.79%, corresponding to a 35% increase in efficiency. This improvement in device performance was discussed based on the energy band diagram. We found that the Ni4MP interlayer can effectively extract the photo-generated holes from the Sb2S3 sensitizer due to the excellent band matching and hole scavenging characteristics, thus enhancing the charge transport and suppressing the recombination.