Efficient charge transfer process in Coumarin 153–nanotubolar TiO2 hybrid system

In this Letter the optical properties of a new hybrid electrode based on Coumarin 153 adsorbed on nanotubular TiO2 arrays are presented. The absorbance measurements show an enlargement in the visible spectral range and the photocurrent response is sensibly increased with respect to pure TiO2 nanostructure; moreover, the analysis of the luminescence spectra suggests the formation of Coumarin aggregates on TiO2 surface. The mechanism of the fast injection of photoexcited electrons from the Coumarin excited levels to the TiO2 conduction band was studied and, based on absorption, emission and photocurrent data, a strong coupling between the two components is proposed.