Dresden 2009 – wissenschaftliches Programm

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CPP: Fachverband Chemische Physik und Polymerphysik

CPP 26: Organic Photovoltaics I

CPP 26.2: Vortrag

Mittwoch, 25. März 2009, 14:15–14:30, ZEU 222

Stability of organic electronics - P3HT as model to study general mechanistic effects. — •Holger Hintz¹, Hans-Joachim Egelhaaf^1,2,3, Christoph Brabec³, 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, Altenbergerstaße 69, A-4040 Linz — ³Konarka Austria GmbH, Altenbergerstaße 69, A-4040 Linz

The stability of Polythiophene (P3HT) is still unsatisfactory and the degradation mechanism has not yet been fully understood. Photo-oxidation of thin P3HT layers was performed under ambient conditions and under varying partial pressures of oxygen, water and ozone using Xenon light. The kinetics were monitored by FTIR and UV/VIS spectroscopy and can be described by the laws of photo-oxidation of layer systems, considering the blue-shift of the absorption spectra of formed P3HT fragments. A sublinear dependence of the degradation rate on oxygen partial pressure is monitored, probably due to the formation of singlet oxygen via a long-lived triplet excited state of P3HT. This is supported by strongly reduced degradation rates upon addition of PCBM, due to the quenching of the polymer excited state. Further support comes from the comparison of the temperature dependences of photo degradation and oxygen diffusion. Photo-oxidation at different humidity levels showed enhanced degradation rates in the presence of water. As water in the absence of oxygen does not cause any degradation, this is due to either a solvent effect or a catalytic mechanism.