Effects of silver particles on the photovoltaic properties of dye-sensitized TiO2 thin films

To evaluate the possibility of using the plasmon resonance effect to enhance the efficiency of photochemical cells, cis-(SCN)₂Bis(2,2′-bipyridyl-4,4′-dicarboxylate) ruthenium (II) dye-sensitized cells were used to measure the photoresponse of TiO₂ film electrodes before and after deposition of Ag particles. The deposited Ag particles created a film with Ag islands. We found that the photoresponse in the visible region increased as the mass-equivalent Ag-island film thickness, t_Ag, increased to 3.3 nm, but decreased when t_Ag was further increased to 6 nm. On the other hand, compared with bare TiO₂ films, the photoresponse in the UV region decreased for any level of Ag islands. These results suggest that under proper conditions, enhancement of the optical absorption of the dye by the Ag plasmon resonance effect contributes to the photocurrent, and indicates the possibility of improving the energy conversion efficiency of photoelectrochemical cells with Ag-island films.