Preparation Of Titanium Oxide Nanocrystalline And Aggregates And Their Application In Dye Sensitiezed Solar Cells

Dye-sensitized solar cells （DSCs） have attracted much attention for their easyfabrication, low production cost, low price and very high photo-to-currentconversion efficiency （PCCE）. Photoanode, one of the heart parts of DSCs, are usedfor loading dyes, transporting electron and improving light scattering property.Nanocrystalline titanium oxide is widely used as the photoanode. Recently, a newTiO₂nanocrystallite aggregates have been reported and are instantly regarded as themost promising photoanode materials and can surpass the current cells performancefor their huge surface area, good light scattering performance. This paper willsynthetize nanocrystalline titanium oxide and TiO₂nanocrystallite aggregatesemploying hydrothermal method and sol-gel-hydrothermal method, respectively,and study performance of various nanofilms thickness of photoanode and ofhierarchical structure made from nanocrystalline TiO₂and TiO₂nanocrystalliteaggregates.Main contents as follows:（1）9～40nm nanocrystalline titanium oxide has been successfully obtainedthrough adjusting reaction temperature, reaction time and amount of ethyleneglycol（EG）. No EG was added in the system, average pore size would be heavilydepended on average particle size; when EG exists, the hydrolysis rate of titaniumsource would be reduced dramatically and therefore promote growth ofnanoparticles. But when less EG was added, average pore size would be alsodepended on average particle size, when more EG was added, average pore sizewould be reduced as the growth of nanoparticles. Then, above synthesizednanoparticles are employed to prepare various thickness of DSCs. Test shows thatabsorbed percentage of Uv-vis light can be augmented dramatically as photoanodethickness increases. When the thickness reached19.2μm, light absorbptionpercentage of Uv-vis light approaches the maximum in low wavelength region, butcan improve in red wavelength region. As photoanode thickness aggrandizes,short-circuit current density raises quickly and then goes up slowly, open-circuitvoltage goes down all the time, and PCCE increases and then reduces as thethickness increases. The highest PCCE can be acquired when the thickness goes to8.6μm, and the PCCE reduced a little as the thickness becomes19.2μm.（2）Adopting sol-gel-hydrothermal method, TiO₂nanocrystallite aggregateshave been successfully obtained size range from200nm to600nm, and their size andmorphology could be adjusted by the amount of octadecylamine and H2O, keepingtime, hydrothermal time and hydrothermal temperature. Houwver, Ammonia canonly affects the morphology of nanometer-sized crystallites and roughness of TiO₂ nanocrystallite aggregates, but if ammonia is excess, hierarchical nanoporous TiO₂spheres would be damaged. Tests indicate that hierarchical photoanodes combinednanocrystalline titanium oxide and TiO₂nanocrystallite aggregates shows high lightabsorbption percentage during Uv-vis region, and wide light absorbption range. Also,short-circuit current density and PCCE of DSCs assembled by hierarchicalphotoanodes display nearly twice as much as that of only nanocrystalline titaniumoxide, and open-circuit voltage increases as well.