Erlangen 2018 – wissenschaftliches Programm
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MO: Fachverband Molekülphysik
MO 21: Advanced Time-Resolved Spectroscopy
MO 21.3: Vortrag
Donnerstag, 8. März 2018, 14:30–14:45, PA 2.150
Exciton diffusion in molecular aggregates characterized by exciton-exciton interaction spectroscopy — •Jakub Dostál1, Franziska Fennel2, Federico Koch1, Stefanie Herbst2, Frank Würthner2, and Tobias Brixner1 — 1Institut für Physikalische und Theoretische Chemie, Universität Würzburg, Am Hubland, 97074 Würzburg — 2Institut für Organische Chemie, Universität Würzburg, Am Hubland, 97074 Würzburg
An essential part of natural and artificial light harvesting is the efficient transport of excitation energy. In molecular aggregates it often proceeds as random diffusion of excitons delocalized over several aggregate sites. Random encounters of two excitons lead to a rapid annihilation of one of them due to internal conversion. Tracking the number of such events as a function of population time and excitation intensity can provide valuable information on the timescale of exciton diffusion.
In our contribution we study exciton diffusion in one-dimensional J-aggregates of a perylene bisimide (PBI) dye by means of exciton-exciton interaction 2D spectroscopy (EEI2D). This recently developed spectroscopic technique is able to single out the signal specific to interactions between exciton pairs. We observed that the EEI2D signal of the studied PBI aggregates consists of the diffusion-enabled exciton annihilation and the direct excitation of the two exciton states. Theoretical modeling of time evolution of the EEI2D signal allowed us to determine the exciton diffusion constant and estimate the exciton delocalization length.