We have investigated the effect of ultraviolet (UV) light irradiation during the deposition of nominally undoped ZnO thin films using metalorganic chemical vapor deposition (MOCVD) and/or in situ hydrogen post-treatment. Due to the desorption of oxygen and incorporation of hydrogen as a shallow donor at the surface, the ZnO film prepared by the photo-MOCVD and in situ hydrogen post-treatment shows the highest film quality as a transparent conductive electrode for thin-film solar cells. (C) 2004 Elsevier B.V. All rights reserved.