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Range and energetics of charge hopping in organic semiconductors

Hassan Abdalla, Guangzheng Zuo, and Martijn Kemerink
Phys. Rev. B 96, 241202(R) – Published 22 December 2017
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Abstract

The recent upswing in attention for the thermoelectric properties of organic semiconductors (OSCs) adds urgency to the need for a quantitative description of the range and energetics of hopping transport in organic semiconductors under relevant circumstances, i.e., around room temperature (RT). In particular, the degree to which hops beyond the nearest neighbor must be accounted for at RT is still largely unknown. Here, measurements of charge and energy transport in doped OSCs are combined with analytical modeling to reach the univocal conclusion that variable-range hopping is the proper description in a large class of disordered OSC at RT. To obtain quantitative agreement with experiment, one needs to account for the modification of the density of states by ionized dopants. These Coulomb interactions give rise to a deep tail of trap states that is independent of the material's initial energetic disorder. Insertion of this effect into a classical Mott-type variable-range hopping model allows one to give a quantitative description of temperature-dependent conductivity and thermopower measurements on a wide range of disordered OSCs. In particular, the model explains the commonly observed quasiuniversal power-law relation between the Seebeck coefficient and the conductivity.

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  • Received 21 September 2017
  • Revised 1 November 2017

DOI:https://doi.org/10.1103/PhysRevB.96.241202

©2017 American Physical Society

Physics Subject Headings (PhySH)

Condensed Matter, Materials & Applied PhysicsPolymers & Soft Matter

Authors & Affiliations

Hassan Abdalla, Guangzheng Zuo, and Martijn Kemerink*

  • Complex Materials and Devices, Department of Physics, Chemistry and Biology (IFM), Linköping University, SE-581 83 Linköping, Sweden

  • *Corresponding author: martijn.kemerink@liu.se

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Issue

Vol. 96, Iss. 24 — 15 December 2017

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