Regensburg 2013 – scientific programme
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DS: Fachverband Dünne Schichten
DS 16: Organic Thin Films I
DS 16.4: Talk
Tuesday, March 12, 2013, 15:30–15:45, H32
Changes in glassy polymers induced by light — •Ioan Botiz1,2, Paul Freyberg1, Natalie Stingelin3, Arnold Chang-Mou Yang4, and Günter Reiter1,2 — 1Institute of Physics, University of Freiburg, Freiburg, Germany — 2Freiburg Institute for Advanced Studies, Freiburg, Germany — 3Imperial College London, London, UK — 4National Tsing Hua University, Hsinchu, Taiwan
We have experimentally compared the photoluminescence (PL) emission from a thin film of conjugated poly[2-methoxy-5-((2'-ethylhexyl)oxy)-1,4-phenylenvinylene] (MEH-PPV) embedded in a polystyrene (PS) inert matrix, with and without exposure to light. A systematic variation of temperature, conjugated polymer content in the PS inert matrix and film thickness revealed an increase of PL of up to 30% for films exposed to light of wavelength shorter than 700 nm. The increase in PL was higher for thinner films containing 100% MEH-PPV and kept at 35 °C (at this temperature both MEH-PPV and PS are glassy) during 1 hour of illumination. All experiments were performed under nitrogen atmosphere. We tentatively propose that this enhancement of PL is due to changes in conformation induced even in the glassy state of conjugated molecules trough photoexcitations. Deformation of conjugated molecules by light might lead to a reduced phonon-exciton coupling of these polymer chains, i.e. to better PL emission.