Berlin 2008 – scientific programme

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DS: Fachverband Dünne Schichten

DS 5: Organic Thin Films

DS 5.6: Talk

Monday, February 25, 2008, 19:00–19:15, H 2013

Improved understanding of polythiophene photo-oxidation mechanism and the role of PMMA layers as diffusion barriers — •Holger Hintz¹, Hans Joachim Egelhaaf², Ulf Dettinger¹, Umut Aygül¹, Heiko Peisert¹, and Thomas Chassé¹ — ¹University of Tübingen, Institute for Theoretical and Physical Chemistry, Auf der Morgenstelle 8, D-72076 Tübingen — ²Christian-Doppler Labor für oberflächenoptische Methoden, Johannes-Kepler University & Konarka Austria GmbH, Altenbergerstaße 69, A-4040 Linz

Polythiophene (P3HT) plays an important role in organic electronic devices. The stability of this material is still unsatisfactory and the degradation mechanism has not yet been fully understood. Investigations of the photo-oxidation of thin P3HT layers were performed under ambient conditions and under varying partial pressures of oxygen and water using Xenon light. The degradation kinetics were investigated using UV/VIS spectroscopy. A linear decrease of absorbance was observed under all experimental conditions. In the presence of water, the oxidation rate increased significantly. The deposition of thin PMMA films on top of the P3HT layers clearly lowered the degradation rate under ambient conditions. In order to understand this stabilizing effect, oxygen diffusion coefficients through the PMMA top layer were determined by monitoring the quenching kinetics of the fluorescence of the P3HT layer. It was attempted to rationalize the experimental results by numerical simulations of the degradation kinetics.