Strong Suppression of Thermal Conductivity in the Presence of Long Terminal Alkyl Chains in Low-Disorder Molecular Semiconductors

Ekaterina Selezneva, Alexandre Vercouter, Guillaume Schweicher, Vincent Lemaur, Katharina Broch, Aleandro Antidormi, Kazuo Takimiya, Veaceslav Coropceanu, Jean Luc Brédas, Claudio Melis, Jérôme Cornil, Henning Sirringhaus

Research output: Contribution to journalArticlepeer-review

1 Citation (Scopus)

Abstract

While the charge transport properties of organic semiconductors have been extensively studied over the recent years, the field of organics-based thermoelectrics is still limited by a lack of experimental data on thermal transport and of understanding of the associated structure–property relationships. To fill this gap, a comprehensive experimental and theoretical investigation of the lattice thermal conductivity in polycrystalline thin films of dinaphtho[2,3-b:2′,3′-f]thieno[3,2-b]thiophene (Cn-DNTT-Cn with n = 0, 8) semiconductors is reported. Strikingly, thermal conductivity appears to be much more isotropic than charge transport, which is confined to the 2D molecular layers. A direct comparison between experimental measurements (3ω–Völklein method) and theoretical estimations (approach-to-equilibrium molecular dynamics (AEMD) method) indicates that the in-plane thermal conductivity is strongly reduced in the presence of the long terminal alkyl chains. This evolution can be rationalized by the strong localization of the intermolecular vibrational modes in C8-DNTT-C8 in comparison to unsubstituted DNTT cores, as evidenced by a vibrational mode analysis. Combined with the enhanced charge transport properties of alkylated DNTT systems, this opens the possibility to decouple electron and phonon transport in these materials, which provides great potential for enhancing the thermoelectric figure of merit ZT.

Original languageEnglish
Article number2008708
JournalAdvanced Materials
Volume33
Issue number37
DOIs
Publication statusPublished - 2021 Sep 16
Externally publishedYes

Keywords

  • molecular dynamics
  • organic semiconductors
  • thermal conductivity
  • thermoelectrics

ASJC Scopus subject areas

  • Materials Science(all)
  • Mechanics of Materials
  • Mechanical Engineering

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