Al-Sn co-doped ZnO (ATZO) nanocrystals were successfully synthesized onto glass substrates by the sol-gel processing. The structure and morphology of the films are characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and high resolution transmission electron microscopy (HRTEM). The results indicated that co-doped ZnO films showed a preferred orientation toward the c-axis and the full width at half maximum (FWHM) of the (0 0 2) plane increased first and then decreased, reaching a minimum of about 0.213 with Sn concentration of 2%. The effects of various Sn concentrations on electrical and optical properties were also investigated by 4-point probe device and ultraviolet-visible (UV-vis) spectroscopy, respectively. The X-ray photoelectron spectroscopy (XPS) study showed Sn-O and Al-O bonding in the synthesized co-doped ZnO thin films, which confirmed the substitution of Zn2+ by Sn and Al ions. Room temperature photoluminescence (PL) was observed for pure and co-doped ZnO thin films and the origin of these emissions was discussed. (C) 2012 Elsevier B.V. All rights reserved.