Observation of photocurrent generation in electrodeposited zinc oxide layers

Wurtzite zinc oxide (ZnO) films with band gap energy of about 3.3 eV were deposited onto conductive substrates by electrodeposition from a simple aqueous zinc nitrate solution at 335 K. The films showed optical transmission around 70% in the visible light region. The electrical resistance showed a strong dependence on cathodic potential. The decrease in electrical resistance could be observed with light irradiation irrespective of the cathodic potential and was attributed to the excitation of electrons from valence band to conduction band by light with wavelength below 375 nm. A photocurrent of about 0.10 mu A was generated for a cell composed of Ag electrode/Au/ZnO/NESA glass substrate under conditions of irradiation by sunlight.