Dresden 2011 – wissenschaftliches Programm

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CPP: Fachverband Chemische Physik und Polymerphysik

CPP 32: Transport and Spectroscopy in Molecular Nanostructures I (related to SYMN, jointly with MO)

CPP 32.6: Vortrag

Mittwoch, 16. März 2011, 15:15–15:30, ZEU 160

Size-dependent Excitonic Properties of Perylene Bisimide Aggregates — •Steffen Wolter, Franziska Fennel, Henning Marciniak, and Stefan Lochbrunner — Universität Rostock, Institut für Physik, Universitätsplatz 3, 18055 Rostock

The excitonic properties of J-aggregates made from substituted Perylene Bisimides are investigated by stationary and femtosecond spectroscopy. The high quantum yield of 82 % [1] and the recently shown long exciton diffusion length [2] make these aggregates promising candidates for applications like organic solar cells or optoelectronic switches. Here we focus on the excitonic properties in dependence of the aggregat size. Upon heating, a smooth transition from the J-aggregat to the monomer is observed in the absorption spectra. However, the emission shows a distinct minimum of the quantum yield at intermediate temperatures, indicating the existence of a weakly emitting species. Further information on this species is obtained by femtosecond pump probe and fluorescence lifetime measurements. For J-aggregates, pronounced annihilation is observed, indicating that the excitons are highly mobile. In contrast, almost no remaining annihilation dynamic remains and the fluorescence life time rises abruptly for the weakly emitting state. We discuss the possibility, that the weakly emitting state might be a short H-type aggregate.

[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., submitted to J. Phys. Chem.