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TU Dresden » Faculty of Mechanical Science and Engineering » Institute for Materials Science » Chair of Materials Science and Nanotechnology



Thursday, 15 July 2010
(at 13:00 in room 115, Hallwachsstr. 3)
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Charge Transport in Organic Crystals

Karsten Hannewald

Institute for Solid State Theory and Solid State Opics
University of Jena
  Germany  






Organic semiconductors are promising materials for low-cost and easy-to-process electronic and optoelectronic devices. Besides conjugated polymers, an important class of organic semiconductors are molecular crystals of high purity. Due to their high degree of structural order, such crystals are ideal candidates for the investigation of the intrinsic excitations and charge-carrier transport phenomena in organic solids. A particularly important and challenging topic is the understanding of the charge-carrier mobilities in these crystals, as the mobility is a fundamental material property and a central quantity for the optimization of device performance. The description of charge transport in organic crystals is a nontrivial task due to the strong coupling of electronic and vibronic degrees of freedom. In my talk, I will present a theory for charge transport in organic crystals which generalizes Holstein's small polaron model to polarons of arbitrary size and and allows to calculate the carrier mobility from density-functional theory (DFT). The generalized mobility expression treats coherent band transport and thermally induced hopping on equal footing and reproduces the results of previous theories in the respective limits. As a prototypical example, the theory is applied to herringbone-stacked crystals where the temperature dependence of the mobilities is simulated and compared to experimental data. Finally, the mobility anisotropy is analyzed by a novel 3D visualization technique for the relevant transport channels.

Brief Bio:

Karsten Hannewald obtained his PhD in 2001 at the University of Jena (Germany) where he modelled the femtosecond dynamics of optically excited semiconductors. He then moved for 3 years as a post-doc to the University of Technology in Eindhoven (Netherlands) where he started his research on organic crystals. After a brief stay as a guest researcher at the University of Arizona in Tucson (USA), he returned to Jena in 2004 where he is currently working on his Habilitation thesis.



slides (pdf)

Invited by G. Cuniberti

last modified: 2018.10.24 Mi
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