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Rate-determining processes in photoelectrochromic devices

: Georg, A.; Georg, A.; Krasovec, U.O.; Wittwer, V.

Journal of new materials for electrochemical systems 8 (2005), Nr.4, S.329-340
ISSN: 1480-2422
Fraunhofer ISE ()

Photoelectrochromic windows are a combination of a dye solar cell and an electrochromic material, usually WO3. They change their transmittance on illumination. We prepared a particularly advantageous configuration, which can be coloured and bleached under illumination, and bleached in the dark,. In this paper we discuss variations of the light intensity, the ion concentrations in the electrolyte and of the solvent. With this approach, we define the rate-determining processes of the device. The rate of the colouring process with an open circuit is determined by the electron excitation at the dye by the incident light. The electron transfer from the WO3 to the I-3(-) in the electrolyte is the dominating loss reaction and the phase change of the WO3 during the charge injection is also of importance. Transport processes in the TiO2 or WO3 and loss reactions at the TiO2 are less significant.