Impedance spectroscopy of nanostructured ZnO morphologies

In this study, four nanostructured ZnO morphologies, nanoribbons, nanorods, nanoparticles, and nanoshuttles, were synthesized at annealing temperatures of 300 °C, 500 °C, and 700 °C. Structural properties were studied by Scanning Electron Microscopy (SEM), Transmission Electron Microscopy (TEM), X-ray Diffraction Spectroscopy (XRD), and Differential Scanning Calorimetry (DSC). Optical properties were analyzed by UV–Visible Spectroscopy and Photoluminescence (PL). Electrical transport properties were studied by the Cole–Cole plot technique and electrical resistivity. From the impedance spectroscopy analysis, we extracted the carrier lifetime, the RC time constant, and grain and grain boundary parameters in each morphology. We observed that resistance decreased with increasing temperature in all samples in general, while nanorods, nanoshuttles, and nanoribbons showed well-defined semicircle profiles due to grain and grain boundaries at higher temperatures. From wettability studies, we obtained that surface with ZnO nanoparticles has hydrophobic properties, while nanorods, nanoribbons, and nanoshuttles resulted in a superhydrophobic surface. The optimum ZnO nanomorphology based on impedance studies can be used for developing electrodes for dye-sensitized solar cells.