Stuttgart 2012 – wissenschaftliches Programm

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MO: Fachverband Molekülphysik

MO 9: Femtosecond Spectroscopy II

MO 9.3: Vortrag

Dienstag, 13. März 2012, 11:15–11:30, V38.03

Impact of High Excitation Densities upon Excitons in Perylene Bisimide Aggregates — •Marcus Seidel, Steffen Wolter, and Stefan Lochbrunner — Universität Rostock, Institut für Physik, Universitätsplatz 3, 18055 Rostock

Transient absorption measurements are performed on substituted Perylene Bisimide Aggregates with intense pump pulses that clearly saturate the ground state absorption of the molecules. The investigated Perylene Bisimides form J-aggregates at room temperature if solved in a nonpolar solvent with sufficiently high concentration [1]. Since the fluorescence quantum yield and the exciton diffusion length of these aggregates are high [1,2], they might be very suitable components for optoelectronic devices such as organic solar cells. Exciton-Exciton-Annihilation has been observed as the dominating interaction at moderately high excitation densities [2]. Although the interaction itself is not known in detail, it is assumed that two- and multi-excitonic states, resp. play an important role in the light induced dynamics of the quasi-particles. In a first approach to detect these multi-excitonic states in fs-pump-probe measurements, intense laser pulses are utilized to generate high excitation densities. The corresponding transient absorption spectra reveal a fast decaying component, which is considered as a multi-excitonic state signature.

[1] Li X.-Q., Zhang X., Ghosh S., Würthner F., Chem. Eur. J. 14, p.8074 - p.8078 (2008)

[2] Marciniak H., Li X.-Q., Würthner F., Lochbrunner S., J. Phys. Chem. 115, p.648 - p.654 (2011)