VECTORIAL ELECTRON INJECTION INTO TRANSPARENT SEMICONDUCTOR MEMBRANES AND ELECTRIC-FIELD EFFECTS ON THE DYNAMICS OF LIGHT-INDUCED CHARGE SEPARATION

Transparent titanium dioxide membranes (thickness 2.7 μm) were prepared by sintering of 8-nm colloidal anatase particles on a conducting glass support. The dynamics of charge recombination following electron injection from the excited state of RuL3 (L = 2,2′-bipyridine-4,4′-dicarboxylic acid) into the conduction band of the semiconductor were examined under potentiostatic control of the electric field within the space charge layer of the membrane. Biasing the Fermi level of the TiO2 positive of the flat-band potential sharply reduced the recombination rate, a 1000-fold decrease being associated with a potential change of only 300 mV. Photoelectrochemical experiments performed with the same RuL3-loaded membrane in Nal-containing water show the onset of anodic photocurrent to occur in the same potential domain. Forward biasing of the membrane potential impairs photosensitized charge injection turning on the photoluminescence of the adsorbed sensitizer. © 1990 American Chemical Society.