27 Jul
2016
27 Jul
'16
9:17 a.m.
TODAY
Please post and forward to your groups
----------------
The William Tisdale Group Presents:
Oleg V. Koslov, University of Groningen, The Netherlands
“Watching molecular excitons move”
Wednesday, July 27, 2016
Room 66-144, 2:00 – 3:00pm
Oleg V. Kozlov1, Foppe de Haan1, Ross A. Kerner,2 Barry P. Rand2, David Cheyns3 and Maxim
S. Pshenichnikov1
1 Zernike Institute for Advanced Materials, University of Groningen, The Netherlands
2 Department of Electrical Engineering and Andlinger Center for Energy and the
Environment, Princeton University, Princeton, NJ, USA
3 imec, Leuven, Belgium
o.kozlov@rug.nl<mailto:o.kozlov@rug.nl>
Organic electronic devices are based on organic semiconductors, which combine attractive
properties of organic materials with semiconducting behavior. The elementary excitation in
these materials is a so-called “Frenkel exciton” – a strongly bound pair of negative
(electron) and positive (hole) charges. As a result, organic electronics essentially rely
on exciton diffusive dynamics that have to be controlled and observed to ensure the
development of high-efficient organic devices.
Here we watch the exciton diffusion process in real time with a new technique based on
ultrafast photoinduced absorption spectroscopy with ~100 fs time resolution. Using
vacuum-deposited C70 layers as a model system, we demonstrate an extremely high diffusion
coefficient of D ≈ 3.5·10‑3 cm2/s that originates from surprisingly low energetic disorder
of <5 meV. The experimental results are well-described by the analytical model and
supported by extensive Monte-Carlo simulations. The proposed technique is deemed as a
powerful tool for further development of organic opto-electronic components, such as
simple layered solar cells, light-emitting diodes, and electrically pumped lasers.
Oleg V. (Viktorovich) Kozlov received his Masters in Physics degree from Moscow State
University, Faculty of Physics, in 2013. In 2009, he joined the research group of
Professor Dmitry Paraschuk at Moscow State University, where he worked on device physics
of organic solar cells and light emitting diodes. In 2012, he started a collaboration with
Dr. Maxim Pshenichnikov (Zernike Institute for Advanced Materials, University of
Groningen, the Netherlands) on ultrafast spectroscopy of novel organic molecules. In 2013,
he moved to the same group as a PhD candidate, where he studies ultrafast charge and
exciton dynamics (charge generation and recombination, exciton diffusion,
singlet-to-triplet conversion, etc) in organic solids.