Effect of UV illumination treatment on surface photovoltaic properties of TiO2 films

TiO2 films and N-doped TiO2 films were prepared by magnetron sputtering methodology. The films were illuminated at 365 nm for 5-20 min followed by the measurement of contact angles and surface photovoltage spectroscopy. The results show that for n-type TiO2 film, UV illumination treatment can increase the photovoltage, while for p-type TiO2 film, such treatment can decreases the photovoltage. The photovoltaic changing was explained by Ti-OH group increasing due to photo-induced hydrophility. For n-type TiO2 film, Ti-OH groups can increase the photo-induced charge separation and thus iucrease the photovoltage; for p-type TiO2 film, Ti-OH groups decrease the photo-induced charge separation and thus decrease the photovoltage.