Synthesis and physical properties of TiO2 microparticles coated by a sol–gel method and their application to dye-sensitized solar cells

This paper reports the synthesis and physical properties of TiO2 microparticles coated with SiO2, Al2O3, and ZnO nanoparticles using a modified sol–gel method. The concentration and pH of mixed solutions of the TiO2 microparticles and oxide nanoparticles were changed to determine their effects on the characteristics of the TiO2 microparticles. The surface morphology of the TiO2 microparticles was strongly related to the electrostatic interactions between the TiO2 microparticles and colloid oxide nanoparticles. This can be explained by the opposite polarity between the two particles based on the zeta potential distribution as a function of pH. The optimal adsorption conditions for the electrostatic interactions of oxide nanoparticles estimated from the zeta potential–pH relationships and the isoelectric point were applied to the surface modification of light scattering TiO2 microparticles used in dye-sensitized solar cell. The dye-sensitized solar cell with high reflectance showed high quantum efficiency and photocurrent density, resulting in high energy conversion efficiency.