Dresden 2011 – scientific programme

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MO: Fachverband Molekülphysik

MO 4: Femtosecond Spectroscopy I

MO 4.5: Talk

Monday, March 14, 2011, 15:30–15:45, TOE 317

Exciton Diffusion in thin Organic Films influenced by Inhomogeneous Broadening — •Franziska Fennel and Stefan Lochbrunner — Institut für Physik, Universität Rostock, Universitätsplatz 3, 18055 Rostock

We investigate a disordered material system which has the potential for long exciton diffusion lengths in combination with a high versatility. The perylene bisimide dye Perylene Red is incorporated in a polymer matrix with a high concentration. Excitons can be efficiently exchanged between the dye molecules by Förster resonance energy transfer (FRET). The dye molecules represent active sites with a narrow energy distribution for the electronically excited state, which reduces the trapping probability. The mobility of the excitons and their diffusion length is measured by the energy transfer to an acceptor. An exciton diffusion length of 30 nm is found for a Perylene Red concentration of 0.1 M [1]. This demonstrates that long distance energy transfer is possible in the disordered material system. However, the observed diffusion constant is about two times smaller than the theoretical predicted one. The relevant mechanism limiting the exciton diffusion distance might be inhomogeneous broadening of the transition energy of Perylene Red in the system. The amount of inhomogeneous broadening is quantified by femtosecond spectroscopy and its influence on the energy transfer is described by energy dependent migration models. [1] F. Fennel and S. Lochbrunner, PCCP, 2010, DOI: 10.1039/c0cp01211d.