Preprints of Annual Meeting of The Ceramic Society of Japan<br> Preprints of Fall Meeting of The Ceramic Society of Japan

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ZnO is a candidate for the photoelectrode materials in dye-sensitized solar cells (DSSCs). Oxide photoelectrodes in these cells act as a support for dye adsorption and also a route for electron transportation. The essential requirements for the semiconductor layer are as follows: (1) high crystallinity permitting high efficiency of electron mobility; (2) large surface areas enabling to increase dye adsorption; (3) good adherence to the substrate; (4) appropriate thicknesses; and (5) flat surfaces. In this research, we tried to purposely arrange the ZnO crystals of optimized morphologies with specific orientations on the substrate through a solution-based bio-inspired route, which is one of attractive research field for preparation of better ceramics through chemistry. We have obtained various ZnO nanostructures from nanorods, nanoplates to complex architectures on both polymer and glass substrates pre-coated with transparent conductive oxide layers. We have assembled DSSCs using these films, and an overall conversion efficiency of about 0.7% has been obtained. Present study is focused on improving the cell performance by detailed control of morphology and improving the adherence of the film to substrate along with the conductivity. We hope that the effort we are making in this study may contribute to develop a low-cost, simple process for the fabrication of dye-sensitized solar cells.

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The preparation methods of TiO2 and ZrO2 fine particles by hydrolysis from concentrated slurries at temperatures below 100 C were investigated. For Ti-system rutile fine particles were formed and high bulk densities were obtained by firing at temperatures below 1000 C after forming the powder. For Zr-system high bulk densities were obtained by firing at 1150 C. The special merits of this method will be discussed.

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ZnO₂ thin films were deposited on glass substrates from aqueous solutions containing Zn salts, hydrogen peroxide and ammonia. By heat-treating the ZnO₂ films, ZnO thin films were prepared. Factors affecting visual transparency and microstructure of the ZnO₂ thin films were investigated including the composition of the starting solution and the deposition temperature. Zinc sulfate was the most suitable starting material, and an optimum concentration was found to be approximately 10mM. An optimum deposition temperature was 333K. The film thickness after a one-hour deposition was approximately 400nm.

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Nano-sized Fe3O4 particles were synthesized using a semipermiable membrane. The resultant particles were paramagnetic and approximately 15nm in diameter. The composite of the particles and a microbe (Sphaerotilis natans) were applicable to adsorber of heavy-metal ions including Pb²⁺, Cu²⁺, and Cr⁶⁺. Characteristics of the nano-particles and conditions affecting meavy-metal adsorption were investigated.

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