ZnO xerogel powders for photovoltaic applications

ZnO nanoparticles were prepared by a sol–gel technique and drying in supercritical ethanol, and evaluated for light energy conversion in a photoelectrochemical cell. They were characterized by SEM, XRD, XPS, UV–Vis absorption and photoluminescence analyses. Thermal treatment caused changes in the crystallinity (zincite), particle size and defect population. The oxide semiconductor produced significant photocurrents upon illumination in the ultraviolet region and exhibited a maximum photon-to-electron conversion efficiency at wavelength 350 nm. The quantum efficiency was remarkably improved after addition of methanol to the wet-type cell. In this work, oxygen vacancies in the bulk ZnO or oxygen species in the electrolyte solution influenced the photocurrent yield and photopotential growth. Results demonstrate the feasibility of ZnO xerogel powders for use in solar cells.