| 초록 |
Dye-sensitized solar cell (DSC) has attracted great attention with their low production cost of electricity and relatively high energy conversion efficiency. One of the key elements in DSC is the design of the porous photoelectrode, and typically TiO2 nanoparticles are utilized for this purpose to obtain high surface area and to generate nanopore structure. Herein, several submicron-sized monodispersed TiO2 spheres were synthesized by the controlled hydrolysis of titanium tetraisopropoxide (TTIP) and subsequent hydrothermal treatment at 230oC. The diameters of the TiO2 spheres were selectively controlled in the range of 250800 nm, by adjusting the ratio of TTIP to water (r-factor). The sizes of sphere were inversely proportional to the r-factor in the hydrolysis reaction. The prepared TiO2 spheres, in the pure anatase phase with a crystallite size of ~15 nm, were highly porous structures with the surface areas of 105115 m2g-1. First, the deformed TiO2 microspheres with the size of 250 nm were synthesized, and were applied to the main electrode layer of DSC. The achieved conversion efficiency was remarkably higher than that of the cells derived from the commercial TiO2 pastes. The advantages and disadvantages of the nanoporous TiO2 microspheres were fully analyzed and discussed in the work. Second, several TiO2 spheres in different sizes were applied as the scattering layer of the dye-sensitized solar cell (DSC) for the efficient utilization of sun light, and the size-dependent scattering effects for those TiO2 spheres were investigated. It was found that the 450-nm-sized sphere provides the highest scattering efficiency among the spheres in the range of 250800 nm, and its high scattering efficiency seemed to be caused by a significant photonic reflection at 650-700 nm. As a result, the photovoltaic conversion efficiency () of DSC was increased from 6.8 to 8.9% by introducing the 450-nm-sized spheres as scattering layer. Third, it has been found that spherical TiO2 can be successfully applied for the formation of flexible DSC. Herein, the 300-nm-sized spherical TiO2 structure was mixed with the 25-nm-sized nanoparticle (Degussa P25) to form the TiO2 layer. Blending of the large TiO2 sphere significantly increased the surface area, improved the electron transport properties, and enhanced the quantum efficiency in the long wavelength region. As a result, the photovoltaic conversion efficiency of DSC processed at 140oC was enhanced from 4.4% to 6.3%. |
