Zinc oxide (ZnO) thin films were fabricated by ultrasonic spray pyrolysis using aqueous zinc acetate solutions. Acetic acidwas added as a stabilizing agent in the concentration range of 0.1 to 10 vol.% and its effects on themorphology and electrical and optical properties of the thin films were investigated. The increase of acetic acid in the solution led to more (001)-textured films and influenced the grain size and roughness. While this did not result in a significant difference in the optical transmission characteristics, a strong dependence in the electrical properties of the films could be observed. After illumination under a sun simulator with an AM 1.5G spectrum, the films presented a resistivity in the range of 0.2-9 Omega cm, with the lowest resistivity obtained for acetic acid concentration of 2 vol.%. The deposited films showed average optical transmittance higher than 80% (including the glass substrate) for wavelengths between 400 and 1000 nm. (C) 2015 Elsevier B.V. All rights reserved.