Chemical Vapor Deposition of Transparent Conducting Oxide Nanostructures on Various Substrates for Solar Cell Applications

Nanostructured wide band gap transparent conducting oxides are important in the optoelectronic industry. Chemical vapor deposition (CVD) is a simple and effective method for synthesizing high-quality nanostructures from bulk materials. Three areas were investigated during this research: the effects of a ZnO seed layer on ZnO nanowires grown on transparent substrates by CVD, the vapor-liquid-solid synthesis of nanostructures by CVD using graphite to reduce Ga2O3, and a preliminary study of dye-sensitized solar cell design and testing. The ZnO seed layer was shown to improve the vertical alignment and distribution of the synthesized ZnO nanowires on mica, fused quartz, and c-plane sapphire substrates. Scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS), X-ray diffraction (XRD), and room temperature photoluminescence were used to characterize the ZnO nanostructures. Nanoparticles and nanowires were synthesized on Si(100) substrates with a 10-nm catalytic gold layer by varying the reaction conditions. However, these experiments were not always reproducible. The products were analyzed by SEM and EDS to determine the morphology and average chemical composition of the structures, but the small amount of deposition prohibited proper analysis of the crystal phase of the nanostructures by XRD and room temperature photoluminescence with the available instrumentation. Rudimentary dye-sensitized solar cells were fabricated using conductive glass, bulk TiO2, N3 dye (cis-bis(isothiocyanato)bis(2,2′-bipyridyl-4,4′-dicarboxylato)ruthenium(II), and an I-/I3- redox couple electrolyte. These cells produced voltage measurements comparable to literature values for similarly constructed cells, but the measured current was significantly lower than expected