We have investigated the effect of mixing an alcohol-soluble C₆₀ derivative into a self-assembled monolayer (SAM), which consisted of a redox-active Ru-complex with multipoint anchoring groups, on an indium tin oxide surface. Angle-resolved X-ray photoelectron spectroscopy of the mixed SAM revealed that the C₆₀ derivative was well incorporated into the redox-active Ru-complex SAM. In addition, some of the C₆₀ derivatives were present on the mixed SAM surface. In the presence of a sacrificial reagent, the action spectra of the mixed molecular layer exhibited a broad spectral response due to the presence of the C₆₀ derivative, whereas a sharp response was observed for the monocomponent Ru-complex SAM. We propose that an efficient charge separation arising from the combination of the C₆₀ derivative and the Ru-complex enhanced the spectral response of the mixed SAM.