Perovskite Solar Cells (PSCs) have attracted considerable attention because of their unique features and high efficiency. However, the stability of perovskite solar cells remains to be improved. In this study, we modified the TiO ${}_{\mathrm{2}}$ Electron Transport Layer (ETL) interface with PbCl ${}_{\mathrm{2}}$. The efficiency of the perovskite solar cells with carbon electrodes increased from 11.28% to 13.34%, and their stability obviously improved. The addition of PbCl ${}_{\mathrm{2}}$ had no effect on the morphology, crystal structure, and absorption property of the perovskite absorber layer. However, it affected the band energy level alignment of the solar cells and accelerated the electron extraction and transfer at the interface between the perovskite layer and the ETL, thus enhancing the overall photovoltaic performance. The interfacial modification of ETL with PbCl ${}_{\mathrm{2}}$ is a promising way for the potential commercialization of low-cost carbon electrode-based perovskite solar cells.