Controlled Synthesis Of Semiconductor Selenide Nanocrystals And Their Application In Photovoltaic Field

Fluorescent semiconductor materials have attracted much attention due to their unique optical and electrical properties which makes them have potential application in light-emitting diodes (LED), biological labeling and solar cells. Preparation of nanomaterials with special-defined size, morphology, surface construction and diversity through simple and environmental friendly synthetic methods and the investigation of their growth mechanisms should be a crucial step to understand the relations between their structures and physical and chemical properties. In this dissertation, some explorations have been carried out on new simple and chemical green manipulated synthetic strategies for the II-VI group fluorescent semiconductor nanostructures, and their growth mechanisms and unique properties. And also, some research in solar cell field has been done for these prepared semiconductor nanomaterials.By utilizing the stability diversity of the Na₂SeSO₃ in different PH environment, Se power has been transformed to monodisperse amorphous Se (a-Se) spheres through the synthesis and dismutation of the Na₂SeSO₃. And the size of the a-Se can be adjusted by changing the pH value of the solution. Meanwhile, selenium nanowires are obtained through a"solid-solution-solid"process by dispersing the prepared Se spheres in ethanol solvent.A room temperature injection technique has been developed to synthesize the CdSe nanocrystal. The CdSe seed clusters are prepared at room temperature, and the CdSe nanocrystals with different sizes are obtained by a subsequent crystal growth process at different temperature after the injection. CdSe nanocrystals with fluorescent from green to red region can be adjusted by changing the growth temperature. The activity of the surfactant is found to be the crucial factor to control the growth rate of the nanocrystals. An effective oxidation route has been developed to etch the small size CdSe nanocrystals. By etching the CdSe nanocrystals, the fluorescent of the CdSe nanocrystals can be adjusted in blue-violet region. Zinc blende CdSe nanocrystals with different shape have been synthesized in octadecene solution by reacting Se powder and Cd(Ac)₂, the reaction temperature is found to be the key factor to control the final shape of the CdSe nanocrystal products as the temperature will affect the activity of the surfactant, and the thermodynamic property of the CdSe crystal is also one of the reason to affect the shape of the final products. By controlling the reaction temperature, CdSe nanocrystals with cube, sphere, tetrahedron and branched shape have been obtained. The shape controlled process here can give useful information to guide the control synthesis of other zinc blende structure nanocrystals.By using an emulsion-based bottom-up self-assembly method, CdSe/TiO₂ hybrid colloidal spheres have been synthesized and use as photoanode for photoelectrochemical (PEC) application. The PEC results show that the photoanode made from CdSe/TiO₂ hybrid colloidal spheres perform more active in PEC cells than the narmal CdSe-link-TiO₂ photoanode as the CdSe/TiO₂ hybrid colloidal spheres provide a better connection between the CdSe and TiO₂. This study illustrates the importance of fundamental structural control in influencing PEC properties of hybrid assembled nanostructures.