Influence of ZnCl2 concentration on the structural and optical properties of electrochemically deposited nanostructured ZnO

These works present the electrochemical deposition of ZnO nanostructured thin films on glass substrates covered by SnO2 thin films. Nanostructured ZnO films are obtained by an electrochemical process using a three-electrode system with a saturated calomel electrode as reference electrode, in aqueous solution containing ZnCl2 and KCl. The influence of ZnCl2 concentration on the structural properties of the obtained ZnO layers is investigated by X-ray Diffraction (XRD), Scanning Electron Microscopy (SEM) and optical profilometry. The SEM micrographs show that the ZnO films consist of nanograins at lower ZnCl2 concentrations that transform in a shape of walls at the highest one. The XRD spectra demonstrate the polycrystalline nature of the films at all studied concentrations with the presence of (1 0 0), (0 0 2), (1 0 1), (1 0 2), (1 1 0) and (1 0 3) characteristic reflexes of the ZnO. The influence of the ZnCl2 concentration on the transmittance and reflectance spectra and haze ratio of ZnO thin films is presented and discussed. The ZnO nanostructured layers exhibit high values of the diffuse transmission and reflection in the 400-900 nm spectral range; they can be applied as rear contacts of thin films solar cells thus increasing the light trapping.