Hamburg 2001 – scientific programme

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SYOF: Organische Festkörper

SYOF 5: Poster Session

SYOF 5.25: Poster

Tuesday, March 27, 2001, 17:00–19:00, Aula S3

Ultrafast relaxation of free excitons in quasi-1D organic molecular crystals — •T.W. Canzler, T. Hasche und K. Leo — Institut für Angewandte Photophysik, Technische Universität Dresden, 01062 Dresden

Quasi-1D organic crystals are attractive for device applications, because generation and transport of free carriers are favored due to strong inter-molecular interactions. The absorption spectra of these materials have recently been described using a model based on free Frenkel and charge-transfer excitons. Still, the energy relaxation is rather puzzling: Typical fluorescence quantum yields are very low, preventing application in emission devices. Therefore, a detailed investigation of the initial exciton relaxation is needed.

Here, we use pump-probe spectroscopy with 35 fs temporal resolution to study the energy relaxation of excitons in the model 1D-system MePTCDI (N-N’- dimethylperylene -3,4,9,10-dicarboximide). We observe several signal contributions on distinct time scales. The mechanisms underlying the ultrafast transients will be discussed in terms of exciton intraband relaxation, phonon relaxation and exciton self-trapping.