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 ruthenium 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 and 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-circuit voltage of similar to 350 mV, behaving as a dye-sensitized solid-state photovoltaic cell. This result is explained as a transfer of energetic electrons released by excitation of the dye molecules to the conduction band of SnO2 via tunneling across the thin layer of Al2O3. The implications of the result on suppression of recombination in dye-sensitized photovoltaic cells are discussed.