Regensburg 2002 – wissenschaftliches Programm

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SYOH: Organische Halbleiter

SYOH 7: Poster

SYOH 7.46: Poster

Montag, 11. März 2002, 18:00–21:00, C

Optical Investigation of Interchain Interactions in Ultra-Thin PPV Polymer Films — •Stefan Forero Lenger, Jürgen Gmeiner, and Wolfgang Brütting — Experimentalphysik II and Bayreuther Institut für Makromolekülforschung (BIMF), Universität Bayreuth, 95440 Bayreuth, Germany

The evolution of optical spectra during the conversion of precursor route PPV has been assigned to an increase in effective conjugation length. However we show by vibrational studies that in PPV interchain aggregation influences significantly the vibrational characteristics. To separate intrachain and interchain effects we carried out UV-Vis spectroscopy on ultra thin PPV films with a thickness of 0.5 to 20nm. In this way it was possible to vary the interchain distance in fully converted PPV. We interprete our results on the basis of an exciton model for molecular aggregates. Whereas the thinnest films show the characteristics of single polymer chains, the thicker ones exhibit solid state properties upon polymer chain stacking and aggregation. The single polymer chain is interpreted as an array of stilbene like chromophores where lowering of polymer chain distance significantly influences the Franck-Condon overlap and thus the intensity of the vibronic bands.