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Nat Mater. 2019 Mar;18(3):242-248. doi: 10.1038/s41563-018-0277-0. Epub 2019 Jan 28.

Molecular parameters responsible for thermally activated transport in doped organic semiconductors.

Author information

1
Dresden Integrated Center for Applied Physics and Photonic Materials, Technische Universität Dresden, Dresden, Germany. martin.schwarze1@tu-dresden.de.
2
Center for Advancing Electronics Dresden and Dresden Center for Computational Materials Science, Technische Universität Dresden, Dresden, Germany.
3
Dresden Integrated Center for Applied Physics and Photonic Materials, Technische Universität Dresden, Dresden, Germany.
4
Institute for Molecular Science, Department of Photo-Molecular Science, Myodaiji, Okazaki, Aichi, Japan.
5
Department of Chemical Engineering, Stanford University, Stanford, CA, USA.
6
Institute for Materials Research (IMO), Hasselt University, Diepenbeek, Belgium.
7
Heliatek GmbH, Dresden, Germany.
8
Graduate School of Advanced Integration Science, Chiba University, Chiba, Japan.
9
Center for Advancing Electronics Dresden and Dresden Center for Computational Materials Science, Technische Universität Dresden, Dresden, Germany. frank.ortmann@tu-dresden.de.
10
Dresden Integrated Center for Applied Physics and Photonic Materials, Technische Universität Dresden, Dresden, Germany. karl.leo@iapp.de.

Abstract

Doped organic semiconductors typically exhibit a thermal activation of their electrical conductivity, whose physical origin is still under scientific debate. In this study, we disclose relationships between molecular parameters and the thermal activation energy (EA) of the conductivity, revealing that charge transport is controlled by the properties of host-dopant integer charge transfer complexes (ICTCs) in efficiently doped organic semiconductors. At low doping concentrations, charge transport is limited by the Coulomb binding energy of ICTCs, which can be minimized by systematic modification of the charge distribution on the individual ions. The investigation of a wide variety of material systems reveals that static energetic disorder induced by ICTC dipole moments sets a general lower limit for EA at large doping concentrations. The impact of disorder can be reduced by adjusting the ICTC density and the intramolecular relaxation energy of host ions, allowing an increase of conductivity by many orders of magnitude.

PMID:
30692647
DOI:
10.1038/s41563-018-0277-0

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