Dye-sensitization of magnesium-oxide-coated cadmium sulfide

Nanocrystalline films of cadmium sulfide sensitized with ruthenium N3 dye show only a feeble photoresponse either in the absorption region of the dye or the band gap excitation of cadmium sulfide. However, when an ultrathin outer shell of magnesium oxide is deposited on the cadmium sulfide crystallites in the film, the photoresponse in both the above regions of the spectrum are greatly enhanced. The result is explained as electron injection from excited dye molecules on the outer magnesium oxide shell to the conduction band of cadmium sulfide and suppression of the leakage of the relaxed electrons to the interface by the magnesium oxide barrier, where they undergo recombinations. Possible applications of this effect in dye-sensitized solar cells are discussed.