Hybrid photovoltaics made of ZnO nanorods, which were deposited by solution process, and a polymer layer showed poor properties probably because the surface of ZnO nanorods was contaminated by organic materials used for the deposition. We tried to remove the organic contaminants remaining on the surface of ZnO nanorods by using the photocatalytic activity of ZnO under UV light before depositing a polymer layer. We found that the UV-treatment carried out at room temperature is effective to remove the organic contaminants and to improve the solar cell properties. The removal of organic materials was confirmed by X-ray photoelectron spectroscopy. In addition, we found that photoluminescence from poly(3-hexylthiophene-2,5-diyl) (P3HT) was quenched more by a ZnO substrate after the UV-treatment, suggesting that excitons of P3HT were dissociated into carriers more efficiently on the UV-treated ZnO substrate.