Effects of Grain Size on the UV‐Photoresponse of Zinc Oxide Thin Films Grown by Spray‐Pyrolysis

Zinc oxide films with different average grain size are deposited on glass substrates by spray‐pyrolysis at 425 °C. Samples are characterized by XRD, UV–Vis transmittance, FE‐SEM, and electrical properties measurements. The increase in conductivity observed under 365 nm wavelength illumination is evaluated in terms of grain size. Films with small grains (120 nm) show higher response with respect to films with larger grains (230 and 300 nm). A model considering resistivity and grain size for the prediction of the response of films in terms of UV‐to‐dark conductivity ratio is proposed and validated with experimental results.