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

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You are here: Home Events Prof. Dr. Carsten Deibel "Charge Generation and Recombination in Organic Solar Cells"

Prof. Dr. Carsten Deibel "Charge Generation and Recombination in Organic Solar Cells"

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Institut für Physik, Technische Universität Chemnitz, 09126 Chemnitz, Germany

What
  • Seminar
When Apr 27, 2016
from 02:15 PM to 03:00 PM
Where Seminarraum A, FMF, Stefan-Meier-Str. 21, Freiburg
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Organic semiconductors offer interesting physical properties for a range of optoelectronic applications, including photovoltaics. For the optimisation of organic solar cells — made of a blend of two organic semiconductors, one acting as donor and one as acceptor — a deeper understanding of the physical processes from light absorption to charge extraction is required. I will show two related examples of our work, the first concerning the photogeneration of charge carriers. As the screening of charges in organic semiconductors is only weak, the exciton binding energies are much higher than the thermal energy at room temperature, and also photogenerated charge carriers are initially bound. I will discuss why their separation is still very efficient in polymer-fullerene blends, based on time resolved charge extraction experiments. The second example is on the recombination of already separated charge carriers. The corresponding loss rate is often described by the so called reduced Langevin recombination, which is reduced by orders of magnitude compared to the original theory. Based on simulations, I will present two likely candidates explaining the reduced recombination rate: by charge carrier concentration gradients in the device and the donor-acceptor phase separation. I discuss these limiting factors of photogeneration and recombination in organic solar cells in view of the attainable power conversion efficiencies.

 

invited by Michael Sommer

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