Hamburg 2001 – scientific programme

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SYOF: Organische Festkörper

SYOF 4: Optical Properties

SYOF 4.1: Talk

Tuesday, March 27, 2001, 15:10–15:25, S6

Coherent Phonon Dynamics in Organic Molecular Crystals — •T. Hasche¹, T.W. Canzler¹, R. Scholz² und K. Leo¹ — ¹Institut für Angewandte Photophysik, Technische Universität Dresden, 01062 Dresden — ²Institut für Physik, Technische Universität Chemnitz, 09107 Chemnitz

Organic films with semiconducting properties are interesting for device applications such as charge transport layers, organic LED, and solar cells. This holds especially for quasi-one-dimensional organic molecular crystals due to the strong intermolecular coupling in one direction. However, the coupling of phonon modes to electronic excitations is only little understood. Since self-trapping might be critical for the realization of emission devices, a detailed investigation of the phonon properties is required.

We have directly time resolved coherent phonon oscillations in MePTCDI employed as a model system for quasi-one-dimensional organic molecular crystals. The measurements are carried out using a pump-probe technique with a time resolution of 35 fs. The observed phonons with energies between 30 cm⁻¹ and 600 cm⁻¹ can be assigned to both intramolecular and lattice modes. We compare our results with calculations and literature data. Furthermore we discuss the damping times of the various modes and show that, for the lattice modes, the damping time decreases with energy.