Berlin 2005 – wissenschaftliches Programm
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O: Oberflächenphysik
O 15: Postersitzung (Adsorption an Oberfl
ächen, Epitaxie und Wachstum, Organische Dünnschichten, Oxide und Isolatoren, Rastersondentechniken, Zeitaufgelöste Spektroskopie, Methoden)
O 15.9: Poster
Freitag, 4. März 2005, 17:00–20:00, Poster TU D
Adsorption properties of pyridine molecules on TiO2 surfaces — •M. Dürr, A. Yasuda und G. Nelles — Materials Science Laboratories, Sony Int. (Europe) GmbH, D - 70327 Stuttgart
Photochemical solar cells based on nano-crystalline TiO2 which is sensitized by organic dye molecules (dye-sensitized solar cells) have been shown to exhibit a strongly increased open circuit voltage and thus improved power conversion efficiency upon the addition of tert-butylpyridine to the electrolyte. This improvement of the cell performance was earlier attributed to a suppression of electron transfer between the TiO2 conduction band and the redox couple in the electrolyte.
For a better understanding of the underlying mechanisms, the adsorption of pyridine molecules on TiO2 was investigated by means of quartz crystal microbalance techniques and ultraviolett photoemission spectroscopy (UPS). A clear correlation between pyridine adsorption and the increase of open circuit voltage was observed. Moreover, it could be shown that only a small fraction of the total surface area is covered by the pyridine molecules at saturation coverage. The results are interpreted in terms of adsorption at defect sites and are correlated to adsorption-induced changes in the electronic structure as observed by means of UPS.