title: Experimental evidence of a UV light-induced long-range electric field in nanostructured TiO2 thin films in contact with aqueous electrolytes.
abstract: Nanostructured TiO(2) thin-film electrodes of controlled thickness were obtained by immobilization of TiO(2) powder (Degussa P25) on SnO(2):F (FTO)-coated glasses by electrophoresis. The photocurrent-potential characteristics of the electrodes in contact with an indifferent aqueous electrolyte, for both front--and backside UV illumination, show the existence of a macroscopic electric field in the electrode region near the FTO substrate. This electric field, which is only photoinduced in the presence of water (it does not appear in TiO(2) dye-sensitized solar cells under visible illumination), apparently disappears when an efficient hole scavenger, like methanol, is added to the aqueous electrolyte. It is attributed to a nonhomogeneous spatial accumulation of photogenerated holes at surface-bound OH radicals resulting from the photooxidation of chemisorbed water molecules. The influence of film thickness and UV illumination mode (front- and backside) on the photoinduced electric field is analyzed by solving the transport equations for diffusion and drift of electrons.
authors.affiliation: Instituto de Catalisis y Petroleoquímica, CSIC, Madrid, Spain, Departament de Ciències Experimentals, Universitat Jaume I, 12080 Castelló, Spain.
authors.forename: T
authors.initials: T
authors.lastname: Lana-Villarreal
authors.forename: J
authors.initials: J
authors.lastname: Bisquert
authors.forename: I
authors.initials: I
authors.lastname: Mora-Seró
authors.forename: P
authors.initials: P
authors.lastname: Salvador