Regensburg 2013 – wissenschaftliches Programm

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O: Fachverband Oberflächenphysik

O 58: Poster Session III (Solid-liquid interfaces; Scanning probe and other methods; Electronic structure theory; Spin-orbit interaction)

O 58.82: Poster

Mittwoch, 13. März 2013, 18:15–21:45, Poster B1

Impedance Spectroscopy performed to measure and modify the oxide thickness on aluminum wires in an aqueous solution — •Felix Fiehler and Derck Schlettwein — Institute of Applied Physics, Justus-Liebig-University Giessen, Germany

Metal wires are of interest as electrode materials in different applications also, e.g., in solar cells like dye-sensitized solar cells (DSC). Electron back transfer from the metal collector electrode to the iodine electrolyte or, even worse, corrosion of the metal can be a major problem. Some metals (including aluminum) are covered with a thin oxide layer, which is formed in contact with air providing a thin tunneling barrier, protecting the electrode from further corrosion by the electrolyte. This oxide layer, however, also can present a barrier in the electrodeposition of an active semiconductor and, in the DSC, an injection barrier for charge injection from the semiconductor to the metal. The thickness of the oxide therefore has to be controlled in detail for a successful application of aluminum wires in DSC. It is well known that electrochemical impedance spectroscopy (EIS) offers such a possibility to determine the thickness of the passivating oxide layer in situ during different applied potentials. The latter are of interest since the oxide thickness can be tuned by applying different positive or negative potentials relative to the standard electrode potential. Impedance spectra were measured for planar sheets and for wires of aluminum under variation of the applied DC potentials. The experimental results in the different potential ranges were discussed by use of established equivalent circuits.