Relation of Ru(II) dye desorption from TiO₂ film during illumination with photocurrent decrease of dye-sensitized solar cells

The initial decrease in the short-circuit photocurrent density (J_sc) of a Ru(II)-bipyridine dye-sensitized solar cell (DSSC) during illumination is correlated with the decrease in the amount of remaining dye adsorbed on the TiO₂ film monitored by UV-vis absorption spectroscopy. The analyses reveal that the illumination causes the N719 dye molecules to desorb from the TiO₂ film into the electrolytic solution. The amount of dye remaining adsorbed on the TiO₂ film is influenced by the viscosity and donor number of the electrolytic solution. More dye molecules remain adsorbed on the TiO₂ film in the solution of 3-methoxypropionitrile than in the less viscous solution of acetonitrile. The addition of water and Triton X-100 to the 3-methoxypropionitrile solution results in the enhancement of the dye desorption, partly due to the increase in the donor number.