Achievement of incident photon to electric current conversion yields exceeding 80% in the spectral sensitization of titanium dioxide by coumarin

Abstract

We have discovered that the laser dye coumarin 343 sensitizes the visible light induced injection of electrons in the conduction band of TiO 2 films with a very high yield. The incident photon to current conversion efficiency (IPCE) exceeds 70% in the entire wavelength domain between 400 and 500 nm. It is as high as 83.5% around the absorption maximum of the dye, i.e. 440 nm. These unprecedentedly high current yields arise from efficient light collection by the dye attached to the surface of the TiO 2 film and practically unit quantum yield for charge injection. Factors contributing to the unusually high visible light harvesting efficiency of the dye-coated TiO 2 films, which is related to their specific surface texture, are scrutinized.