Preparation And Performance Of Novel TiO₂ Film Electrode For Dye-sensitized Solar Cell

Over the past decades dye-sensitised nanocrystalline solar cells have been the subject of intense research and development efforts. These systems provide a technically and economically credible alternative to classical p-n junction solar cells.The nanocrystalline TiO₂ electrode plays an important role in dye-sensitized solar cells. In this thesis, the TiO₂ electrode modified by ZnO and the TiO₂ electrode containing large regular spherical nanovoids were made, and the properties of the two new TiC₂ electrodes as well as the performance of assembled solar cell were also studied.The anatase nanocrystalline TiC₂ was prepared by sol-gel method. Dye-sensitized solar cell was assembled using the EC/PC solution as electrolyte. The influence mechanism of the content of I₂ and KI on the photoelectric properties of the solar cell was explored through the measurement of some parameters of the electrolytes such as absorbance, impedance and dark current.ZnO modified TiO₂ electrode was obtained by adding Zn(CH₃COO)₂·2H₂O during the preparing process of TiO₂ colloid. The conversion efficiency of 5.89% was achieved in the electrolyte- (EC:PC=1:1, V/V) +0.5mol L^-1 KI+0.05mol L^-1 I₂+0.05mol L^-1 LiI, which was much higher than the conversion efficiency of 4.98% obtained by the pure anocrystalline TiO₂ electrode. Some experiments, such as darck current, transient photocurrent, impedance and flat band potential, were carried out to explore the causes for the enhancement of conversion efficiency.Polyacrylonitrile was added into the electrolyte-(EC:PC=1:1, V/V) +0.5mol L^-1 KI+0.05mol L^-1 I₂ to prepare quasi-solid state electrolyte. Quasi-solid state dye-sensitized solar cell was assembled and the photoelectric properties and ion diffusion performance were investigated. With the increasing of the viscosity of electrolyte, the diffusion coefficient of I₃ ion decreased rapidly to be a new controlling step in the quasi-solid state dye-sensitized solar cell. This consequence was confirmed by the studying of effect of TiO₂ film thickness and the content of I₂ on the diffusion process of I₃ ion and the photovoltaic performance.Monodispersed polystyrene microspheres with uniform diameter and regular shape were obtained through seed emulsion polymerization. The polystyrene microspheres were used as pore former to prepare nanocrystalline TiO₂ film with regular spherical nanovoids. The presence of regular spherical nanovoids improved the light scattering property of the nanocrystalline TiO₂ electrode. More important thing was that the pore structure of nanocrystalline TiO₂ electrode had great effect on the I₃ ion diffusion properties in the solar cells and this effect was greater in the electrolyte with higher viscosity. The I₃ ion could diffuse more rapidly in the TiO₂ film with regular spherical nanovoids than the TiO₂ film with randomly packed pore structure and in the nanocrystalline TiO₂ film electrode with 200nm regular spherical nanovoids, I₃ ion had the highest diffusion velocity. The nanocrystalline TiO₂ electrode with 200nm regular spherical nanovoids was used in quasi-solid state dye-sensitized solar cells. It was found that the effect of I₃ ion diffusion performance on the photovoltaic properties was reduced and the short circuit current under high light intensity was improved.