Regensburg 2007 – scientific programme

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DS: Fachverband Dünne Schichten

DS 26: Oxides

DS 26.10: Talk

Thursday, March 29, 2007, 17:15–17:30, H34

Light-induced processes on electrochromic WO₃ layers — •Thomas Leichtweiß¹, Bruno K. Meyer¹, Angelika Polity¹, Thomas Löwenstein², Derck Schlettwein², Jeremy Matthews³, and Dirk Jödicke³ — ¹Justus- Liebig- Universität Gießen, I. Physikalisches Institut, Heinrich-Buff-Ring 16, 35392 Gießen — ²Justus- Liebig- Universität Gießen, Institut für Angewandte Physik, Heinrich-Buff-Ring 16, 35392 Gießen — ³EControl-Glas GmbH & Co. KG, 93437 Furth im Wald

Electrochromic materials such as tungsten oxide in contact with a suitable electrolyte change their transmission upon the application of a potential. Technical applications include switchable mirrors and smart windows. The latter are made up of thin-film layers containing at least one electrochromic active material and make it possible to control the light- and energy-input of a building.

This work concerns the influence of UV-A and UV-B light on tungsten oxide layers. WO₃ films have been irradiated in an electrochemical cell containing different electrolytes and in atmosphere. Transmission spectra and the open circuit potential have been recorded. All layers show a photochromic behavior, they colour blue upon UV-irradiation due to partial reduction of tungsten atoms without application of an external potential. The films have been bleached electrochemically in order to determine the photogenerated charge and the colouration efficiency of the photochromic process. The reactions taking place place in irradiated films and their influence on the electrochromical switching behaviour of smart windows will be discussed.