Efficiencies of Electron Injection from Excited N3 Dye into Nanocrystalline Semiconductor (ZrO2, TiO2, ZnO, Nb2O5, SnO2, In2O3) Films

The efficiency of electron injection from excited N3 dye ( cis -bis-(4,4‘-dicarboxy-2,2‘-bipyridine) dithiocyanato ruthenium(II), Ru(dcbpy) 2 (NCS) 2 ), into various nanocrystalline semiconductor (ZrO 2, TiO 2, ZnO, Nb 2 O 5, SnO 2, In 2 O 3 ) films was studied by transient absorption spectroscopy. For TiO 2, ZnO, Nb 2 O 5, SnO 2, or In 2 O 3 films, injection efficiencies were found to be very high; for ZrO 2 film, the efficiency was very low. These findings indicate that electron injection occurs efficiently if the LUMO level of N3 dye is located sufficiently far above the bottom of the conduction band of the semiconductor film. On the basis of the results, we discuss the reason TiO 2 exhibits higher solar cell performance than other materials.