Photoelectronic processes in transition-element doped n-type TiO 2 electrodes

Abstract

Photoelectronic properties of n-TiO 2 anodes doped with first row transition elements and giving an absorption in the visible region, have been investigated. The photocurrent has been measured vs wavelength for a given electrode potential and vs time at different anode potentials. Significant photocurrents resulting from visible light excitation are observed for n-type TiO 2 anodes doped with large amounts of trivalent chromium. When other transition elements (V 3+ or Mn 2+) are considered, such a long wavelength photoresponse was not observed. Co 2+ and Ni 2+ ions could not be introduced into n-TiO 2 anodes because of the reduction into Co or Ni metal. The experimental data have been discussed on the basis of a model involving hole tunneling from Cr 4+ ions to the valence band.