The electron fluence was varied by adjusting the irradiation time. PCBM/TiO2 electrodes were irradiated by 1, 2, and 4 h which correspond to electron fluence of 3.6 × 1016, 7.2 × 1016, and 1.44 × 1017 cm-2, respectively. Diffuse reflectance UV-visible (VIS) spectra of electron-irradiated PCBM/TiO2 powders were measured on a spectrometer by scratching the nanoparticle film off the FTO glass substrate.