Al-doped ZnO (AZO) nanocrystalline thin films are prepared by a sol-gel technique. Effects of the Al-doped concentration on microstructural, electrical and optical properties of the AZO thin films are studied and discussed. Results indicate that the AZO crystalline thin film with a highly preferred c-axis orientation perpendicular to the substrate is grown, and the AZO thin film with a small crystal grain size of 30-40 nm, high transmittance of above 90% in visible region, and low resistivity of 1.9 x 10(-2) Omega cm can be obtained when the Al-doped concentration is up to 1 at%. Furthermore, ZnO nanowire (ZnO NW) arrays with a large surface area are grown on the sol-gel derived AZO thin film, which acts as a seed layer, by using a hydrothermal method. Optical properties of the grown ZnO NW arrays reveal that a high transmittance in visible region can be obtained, and only a strong UV emission at about 380 nm is observed in the room-temperature photoluminescence spectra, which implies that few crystal defects exist inside the as-assembled ZnO NW arrays. (C) 2010 Elsevier B.V. All rights reserved.