Optimizing the Nanostructural Characteristics of Chemical Bath Deposition Derived ZnO Nanorods by Post-Hydrothermal Treatments

Abstract

Zinc oxide (ZnO) is an inorganic semiconductor material which has been widely studied due to its various potential applications. Over the past decades, one-dimensional (1-D) nanostructures such as nanowires and nanorods have stimulated significant scientific interests because of their unique properties in comparison to bulk materials. For the application of dye sensitized solar cell (DSSC), 1-D ZnO nanostructures are more desired than the spherical nanoparticles since the former provides ballistic effect leading to faster electron transfer which in turn can increase the device performance. Motivated by this consideration, in the current study ZnO nanorods were deposited on ITO glass substrate via chemical bath deposition (CBD) process where the seeding solution was prepared at 0°C. In order to increase their crystallinity and optical properties, the as-deposited ZnO nanorods were subjected to post-hydrothermal treatment at 150°C for 3, 6 and 9 hours. The scanning electron microscope (SEM) analysis revealed that the ZnO nanorods were successfully grown as vertically-aligned hexagonal structure, while the X-ray diffraction (XRD) study showed that the intensity of (002) crystal plane is the highest peak for all nanorod samples. The optical study by UV-Vis spectroscopy showed that the absorption edge of the as-deposited sample was slightly red-shifted to visible region after post-hydrothermal treatment. The ZnO nanorods sample derived from post-hydrothermal treatment for 6 hours provided the optimum nanostructural characteristics with an average diameter of 228 nm, crystallite size of 27.97 nm and the band gap energy, Eg, of 3.12 eV.