| As a multifunctional material, ZnO possesses remarkable and unique properties and has attracted much research interest for use in a variety of applications. Especially, it has been regarded as a leading material for flexible and transparent electronics, which is a promising emerging technology in electronics. This dissertation studies doping behavior of Ga in ZnO for transparent electrode applications and presents new approaches to ZnO nanostructures for next-generation flexible and transparent electronics. These approaches include developing techniques that enable multiple stacked ZnO nanoflowers and thermal treatment processes at high temperature.;Transparent conductive oxides have been extensively studied for the use as a transparent electrode, which is one of the most fundamental and essential parts in transparent electronic devices. In this study, Ga-doped ZnO nanorods were grown on glass substrates, and the effects of Ga doping concentration on the physical properties of ZnO nanorods were investigated using various characterization tools.;ZnO nanoflower is a highly preferred nanostructure for solar cells, sensors, and photodetectors due to its high surface area to volume ratio. To-date, ZnO nanoflowers have mostly been synthesized in the form of nanopowders without a substrate, and ZnO nanoflowers grown on substrates have only been single-stacks. Atmospheric pressure plasma jet treatment was used to increase the surface area to volume ratio of ZnO nanoflowers. The plasma treatment induced a significant increase in the height and density of the ZnO nanoflowers/nanorods because the plasma effectively increased the surface energy and roughness of the seed layers while barely affecting the crystal shape and phase of the ZnO nanoflowers/nanorods.;Flexible and transparent mica substrates were used for the growth of vertically well-aligned ZnO nanorods. The adoption of mica as a substrate material permitted high temperature annealing processes, which improved the structural and optical properties of ZnO nanorods with uniform surface coverage and excellent adhesion. A practical application for the synthesized ZnO nanorods is also presented in this dissertation. ZnO nanorod-based flexible and transparent dye-sensitized solar cells (DSSCs) and piezoelectric nanogenerators (NGs) were fabricated and the device performances were investigated. Although only two kinds of energy-harvesting devices (DSSCs and NGs) are presented as examples of applications in this dissertation, it is expected that this new approach will provide a breakthrough for overcoming the limited process temperature on plastic and cellulose nanopaper substrates because mica can be extensively used as a flexible and transparent substrate material for electronics, optoelectronics, energy/environmental, and biomedical applications where high temperature processes are required. |
