Synthesis Of ZnO Micro-Nanostructure And Photoelectrochemical Properties

In this thesis, Thermal evaporation and hydrothermal methods were utilized tofabricate ZnO miro-nano structures of various morphologies, including nanoparticles,nanocombs, and nanowires grown on Zn membranes, flower-like miro-nano structures onFTO, composited nanostructures via a combined method of hydrothermal and screenprinting. Characterizations were performed on the morphologies, component, andluminescence properties of these structures. The results were analyzed to explain thegrowth mechanisms. The structures were applied to the photoanode materials ofdye-sensitized solar cells (DSSCs). The photo-electrochemical properties of these DSSCswere also investigated.1. Zn membrane on FTO glass: The effect of the thickness on the growth of ZnOnanostructures and the application on DSSCs.Zn membranes of different thickness were electrodeposited on the FTO glass wouldaffect ZnO nanostructures which were fabricated via thermal evaporation method on theas-grown Zn membranes. For thin Zn membrane, nanoparticles of a patterned surfacewill grow, and nanowires grow between them. For mid-thickness of Zn membrane,nanocombes will grow. Nanorods mixed with nanoshells and Zn impurity will formusing thin Zn membranes.2. The composite structure of spherical ZnO nanoparticles and uniform nano-arrays:Synthesis and photo-electrochemical propertiesThe comparative analysis of the composite structure and pure nano-arrays revealed thatthe former had a sharp XRD diffraction peak. Room temperature photoluminescencespectrum showed that the emission spectrum of composite structure had a UVemission(388nm) and a green emission peak(510nm). The composite structure had aenhanced dye-adsorption rate, which increased the photoelectric conversion efficiency of DSSCs pure nano-arrays revealed that the former had a enhanced dye-adsorption rate,which increased the photoelectric conversion efficiency of DSSCs.3. ZnO spherical flower-Like micro-nano hierarchical structure: Fabrication andphotoelectrical propertiesa spherical flower-like ZnO micro-nano hierarchical structure weresuccessfully grown via thermal evaporation method on F-doped SnO2(FTO)conductive glass coated with Zn. The morphology, composition andluminescence properties of spherical micro-nano hierarchical structure werecharacterized by field emission scanning electron microscopy (SEM), X-raydiffraction(XRD) and photoluminescence spectroscopy (PL), respectively.The results reveal that the spherical flower-like wurtzite ZnO micro-nanohierarchical structure are of porous surface with a high surface area. The PLmeasurement exhibited that the as-synthesized products have three emissionpeaks (402nm,460nm and500nm) due to near band edge emission and deeplevel defects. dye-sensitized solar cells(DSSC) were assembled using thestructure as anode material. A conversion efficiency η=0.67%was obtained,which was higher than cells of nanorods, nanobranches and nanocombs basedanode materials. The deep level defects and porous surface were consideredas factors determining the final conversion efficiency.