Dye-sensitized anodic TiO2 nanotubes

In this work, we report on dye-sensitization of self-organized TiO2 nanotubes and the photoelectrochemical response of this system. The tubes were grown by Ti anodization in fluoride containing electrolytes in two different forms as “long” tube (tube lengths ∼ 2.5 μm) and “short” tubes (tube lengths ∼ 500 nm). Both the tube types have a tube diameter of approximately 100 nm and a wall thickness of 15 nm. After annealing the tubes to anatase they were sensitized with Ru-dye (N3) in different concentrations. The results show that apart from the dye concentration also the tube length affects the magnitude of the photocurrent response. For the “long” tubes an IPCEmax (at 540 nm) of 3.3% and for the “short tubes” of 1.6% (at 530 nm) are obtained. These results show that self-organized TiO2 nanotubes can be dye-sensitized in the visible range and a considerable light conversion efficiency can be achieved.