Dye-sensitization of the TiO2 rutile (110) surface by perylene dyes:: Quantum-chemical periodic B3LYP computations

The adsorption of perylene derivatives on the rutile TiO2(110) surface was studied by quantum-chemical periodic calculations employing the hybrid HF-DFT functional B3LYP. The perylene molecule, which is a possible constituent of dyes in dye-sensitized solar cells, was functionalized by attachment of phosphonic acid or carboxylic acid groups to permit anchoring to the metal oxide surface. The anchor groups were bound to the molecule directly or via different spacer groups, namely --CH2-, -CH2-CH2-, and -CH = CH-. The effects of the anchor and spacer groups on the adsorption geometry and energy, on the electronic structure of the dye-TiO2 interface, and on the electron transfer rates were investigated. The phosphonic acid anchor group was found to bind the perylene derivatives much more strongly to the surface than the carboxylic acid anchor group. The spacer groups were capable of significantly altering electron transfer rates across the dye-metal oxide interface, where the unsaturated groups permitted injection times in the low femtosecond regime.