Dye-sensitized solid-state photovoltaic cells: Suppression of electron-hole recombination by deposition of the dye on a thin insulating film in contact with a semiconductor

The heterojunction n-SnO2/Ru-dye/p-CuI prepared by deposition of the ruthen ium bipyridyl dye on a meso-porous film of SnO2 followed by deposition of p -CuI was found to be inactive with respect to visible light photoresponse a nd dark current rectification. However, n-SnO2/Al2O3/Ru-dye/p-CuI where the dye is coated on a thin film of Al2O3 first deposited on SnO2, delivered a short-circuit current density of similar to1.7 mAcm(-2) and an open-circui t voltage of similar to 350 mV, behaving as a dye-sensitized solid-state ph otovoltaic cell. This result is explained as a transfer of energetic electr ons released by excitation of the dye molecules to the conduction band of S nO2 via tunneling across the thin layer of Al2O3. The implications of the r esult on suppression of recombination in dye-sensitized photovoltaic cells are discussed.