INVESTIGATIONS ON THE ELECTRICAL PROPERTIES OF ZnO NANORODS AND COMPOSITES FOR PHOTOVOLTAIC AND ELECTROCHEMICAL APPLICATIONS

ZnO nanorods grown by hydrothermal technique on glass, Zinc, and Indium tin oxide (ITO) substrates exhibit both open and closed hexagonal structures. On the nanoscale, closed ZnO nanostructures exhibit two types of ion conduction regions as revealed by AC-impedance spectra collected through the tip of an atomic force microscope (AFM). One region has higher impedance values (apparent values of approximately 10(7) ohms) with two semicircles. Two semicircles are indicative of a ZnO structure composed of bulk and grain boundary conduction. Other regions were found to have impedance values that were two orders of magnitude lower (apparent values of 10(5) ohms). This indicates that these ZnO films have two conduction pathways. The polyethylene oxide (PEO)-ZnO nanorod composite was made by spin-coating the ZnO rods growing from the ITO substrate with PEO. In the PEO-ZnO composite film, only the AC impedance values of 10(5) ohms were observed. This is higher than PEO electrolyte without ZnO nanorods. Since regions of higher impedance were not seen in the PEO-ZnO nanorod composites, the polymer electrolyte either dominated the conduction of the system or suppressed the first pathway of higher impedance in the ZnO rods.