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Center for Excitonics Seminar Series
Thursday, Nov. 29, 2012
3:00 - 4:00 PM
RLE HAUS and ALLEN rooms: 36-428
Excitons in highly efficient organic devices
Karl Leo, Institute of Applied Photophysics, Dresden University of Technology
Abstract:
Organic semiconductors with conjugated electron system are currently intensively
investigated for optoelectronic applications. This interest is spurred by novel devices
such as organic light-emitting diodes (OLED), and organic solar cells. For both devices,
high efficiency is a key parameter for many applications. In this talk, I will discuss
some of the recent progress on highly efficient OLED and solar cells. In both classes of
devices, excitons play crucial roles: in OLED, efficient radiative recombination is key,
in solar cells, exciton separation is the key process. Specifically, I will briefly
discuss results on white OLED where triplet harvesting allows to achieve high quantum
efficiencies despite using fluorescent blue emitters. Even richer are the exciton
phenomena in organic solar cells. I will discuss results of exciton separation dependence
on energetic alignment and the influence of triplet generation in bulk heterojunction
devices.
Bio
Karl Leo obtained the Diplomphysiker degree from the University of Freiburg in 1985,
working with Adolf Goetzberger at the Fraunhofer-Institut für Solare Energiesysteme. In
1988, he obtained the PhD degree from the University of Stuttgart for a PhD thesis
performed at the Max-Planck-Institut für Festkörperforschung in Stuttgart under
supervision of Hans Queisser. From 1989 to 1991, he was postdoc at AT&T Bell
Laboratories in Holmdel, NJ, U.S.A. From 1991 to 1993, he was with the
Rheinisch-Westfälische Technische Hochschule (RWTH) in Aachen, Germany. He became Full
Professor of Optoelectronics at the Technische Universität Dresden in 1993. Since 2002,
he has worked at the Fraunhofer-Institution for Organics, Materials and Electronic Devices
COMEDD and currently serves as director. His main interests are novel semiconductor
systems like semiconducting organic thin films; with special emphasis to understand basics
device principles and the optical response. His work was recognized by the following
awards: Otto-Hahn-Medaille (1989), Bennigsen-Förder-Preis (1991), Leibniz-Award (2002),
award of the Berlin-Brandenburg Academy (2002), Manfred-von-Ardenne-Preis (2006), and
Zukunftspreis of the German president (2011). He is cofounder of several companies,
including Novaled AG and Heliatek GmbH.
Light refreshments will be provided
The Center for Excitonics is an Energy Frontier Research Center funded by the U.S.
Department of Energy, Office of Science and Office of Basic Energy Sciences
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