Enhancement of Dye Adsorption on TiO2Surface through Hydroxylation Process for Dye-sensitized Solar Cells

Abstract

To enhance the power conversion efficiency of dye-sensitized solar cell (DSSC), the surface of titanium dioxide (<TEX>$TiO_2$</TEX>) photoelectrode was modified by hydroxylation treatment with <TEX>$NH_4OH$</TEX> solution at <TEX>$70^{\circ}C$</TEX> for 6 h. The <TEX>$NH_4OH$</TEX> solutions of various concentrations were used to introduce the hydroxyl groups on <TEX>$TiO_2$</TEX> surface. As the concentration of <TEX>$NH_4OH$</TEX> was increased, the short-circuit current density (<TEX>$J_{SC}$</TEX>) value and conversion efficiency of solar cells were increased because the amount of adsorbed dye molecules on <TEX>$TiO_2$</TEX> surface was increased. As a result of the surface modification to introduce hydroxyl groups, the concentration of adsorbed dye on the <TEX>$TiO_2$</TEX> 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 <TEX>$TiO_2$</TEX> surface were characterized by using FE-SEM, <TEX>$N_2$</TEX> 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.