Restructuring of Dye Layers in Dye Sensitized Solar Cells: Cooperative Adsorption of N719 and Chenodeoxycholic Acid on Titania

The effect of the co-adsorbent chenodeoxycholic acid (CDCA) up to a concentration of 20 mM on the adsorption of the dye N719 onto titania has been investigated using neutral impact collision ion scattering spectroscopy. It is shown that the co-adsorption of CDCA changes the adsorption mode of N719 from multilayer toward monolayer. FT-IR spectroscopy shows that the adsorption of CDCA increases with increasing CDCA concentration. In contrast, the amount of N719 adsorbed onto titania shows a minimum at 10 mM CDCA, and the relationship between the amount of CDCA and of N719 adsorbed onto titania depends nonmonotonically on the CDCA concentration. The co-adsorption of CDCA and N719 can be described as cooperative. The effect is observed for both low and high N719 concentrations.