An Ag modified bathocuproine:ZnO nanoparticles (BCP:ZnO NPs) thin film was used as the buffer layer of inverted-type perovskite solar cells, which increased the bifacial power conversion efficiency from 6.82% to 15.50%. The surface-enhanced Raman scattering and absorbance spectra show that the Ag modified BCP small molecules can effectively passivate the surface oxygen defects of ZnO NPs and thereby increasing the crystallinity, which simultaneously increases the short-circuit current density (JSC) and fill factor. It is noted that a high incident photon-to-electron conversion efficiency (IPCE) of 92% is achieved at the wavelength of 587 nm due to the constructive interference effect in the multilayer structure, which can be used to explain the high photocurrent generation in a semi-transparent solar cell. In addition, the light intensity-dependent experimental results of the bifacial perovskite solar demonstrates that the hole transportation is better than the electron transportation in the perovskite thin film. This concept can be readily used in the optimization of high-efficiency bifacial perovskite solar cells.