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Freiburger Materialforschungszentrum
Stefan-Meier-Str. 21
79104 Freiburg, Germany

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You are here: Home Events Dr. Richard Hildner "Tailoring the Photophysics of Supramolecular Nanostructures"

Dr. Richard Hildner "Tailoring the Photophysics of Supramolecular Nanostructures"

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Experimentalphysik IV, Universität Bayreuth, 95440 Bayreuth, Germany

What
  • Seminar
When Dec 14, 2016
from 02:15 PM to 03:00 PM
Where Seminarraum A, FMF, Stefan-Meier-Str. 21, Freiburg
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Efficient long-range transport of excitation energy through supramolecular aggregates is a key process in light-harvesting systems as well as in molecular electronics [1]. However, in disordered organic materials the exciton diffusion length is typically in the order of ~ 10 nm largely determined by the probability laws of incoherent hopping [2]. Here I will discuss our recent efforts in tailoring the supramolecular assembly of organic molecules to promote energy transport. To this end we used carbonyl-bridged triarylamines [3] as building blocks to optimise the electronic and geometric structure of supramolecular nanofibres, to support efficient long-range transport of excitation energy over more than 4 µm at room temperature. Our data suggest that this remarkable long-range transport is predominantly coherent, i.e. governed by a strong coherent delocalisation of excitation energy, which is achieved by one-dimensional self-assembly into well-defined H-aggregates with substantial electronic interactions between the building blocks [4]. The high efficiency of this energy transport is further demonstrated by time-resolved measurements as a function of excitation fluence. The excited state lifetime is substantially quenched by exciton-exciton annihilation for only few (2 - 3) excitons per µm-long nanofibre.

For applications of such nanostructures an important issue is their controlled growth from a defined starting point. Using a supramolecular nucleating agent, we demonstrate the formation of highly oriented nanofibers based on the prototypical conjugated polymer poly(3-hexylthiophene), P3HT, with a Shish-Kebab-like superstructure [5]. Employing confocal imaging and spectroscopy, we resolve the variation of the structural and electronic order along those P3HT nanofibers. Moreover, we show that this order can be controlled by applying proper processing protocols.

[1] F. Laquai et al., Macromol. Rapid Commun. 33, 1203 (2009)
[2] Lin et al., Mater. Horiz. 1, 280 (2014)
[3] A. T. Haedler, S. R. Beyer, N. Hammer, R. Hildner, M. Kivala, J. Köhler, H.-W. Schmidt, Chem. Eur. J. 20, 11708 (2014)
[4] A. T. Haedler, K. Kreger, A. Issac, B. Wittmann, M. Kivala, N. Hammer, J. Köhler, H.-W. Schmidt, R. Hildner, Nature 523, 196 (2015)
[5] M. Brinkmann et al., Adv. Funct. Mater. 19, 2759 (2009)

 

invited by Günter Reiter

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