Enhancement of Dye Adsorption on TiO2 Surface through Hydroxylation Process for Dye-sensitized Solar Cells

To enhance the power conversion efficiency of dye-sensitized solar cell (DSSC), the surface of titanium dioxide (TiO2) photoelectrode was modified by hydroxylation treatment with NH4OH solution at 70 degrees C for 6 h. The NH4OH solutions of various concentrations were used to introduce the hydroxyl groups on TiO2 surface. As the concentration of NH4OH was increased, the short-circuit current density (J(SC)) value and conversion efficiency of solar cells were increased because the amount of adsorbed dye molecules on TiO2 surface was increased. As a result of the surface modification to introduce hydroxyl groups, the concentration of adsorbed dye on the TiO2 surface could be improved up to 32.61% without the changes of morphology, surface area and pore volume of particles. The morphology, the specific surface area, the pore volume and the chemical states of TiO2 surface were characterized by using FE-SEM, N-2 adsorption-desorption isotherms and XPS measurements. The amount of adsorbed dye and the performance of fabricated cells were analyzed by using UV-Vis absorption spectroscopy and solar simulator.