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Thermal conductivity of benzothieno-benzothiophene derivatives at the nanoscale

Abstract : We study by scanning thermal microscopy the nanoscale thermal conductance of films (40-400 nm thick) of [1]benzothieno[3,2-b][1]benzothiophene (BTBT) and 2,7-dioctyl[1]benzothieno[3,2-b][1]benzothiophene (C8-BTBT-C8). We demonstrate that the out-of-plane thermal conductivity is significant along the interlayer direction, larger for BTBT (0.63 ± 0.12 W m-1 K-1) compared to C8-BTBT-C8 (0.25 ± 0.13 W m-1 K-1). These results are supported by molecular dynamics calculations (Approach to Equilibrium Molecular Dynamics method) performed on the corresponding molecular crystals. The calculations point to significant thermal conductivity (3D-like) values along the 3 crystalline directions, with anisotropy factors between the crystalline directions below 1.8 for BTBT and below 2.8 for C8-BTBT-C8, in deep contrast with the charge transport properties featuring a two-dimensional character for these materials. In agreement with the experiments, the calculations yield larger values in BTBT compared to C8-BTBT-C8 (0.6-1.3 W m-1 K-1 versus 0.3-0.7 W m-1 K-1, respectively). The weak thickness dependence of the nanoscale thermal resistance is in agreement with a simple analytical model.
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https://hal.archives-ouvertes.fr/hal-03135025
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Submitted on : Wednesday, February 10, 2021 - 11:52:58 AM
Last modification on : Saturday, June 19, 2021 - 11:42:01 PM
Long-term archiving on: : Tuesday, May 11, 2021 - 6:30:14 PM

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Magatte Gueye, Alexandre Vercouter, Rémy Jouclas, David Guérin, Vincent Lemaur, et al.. Thermal conductivity of benzothieno-benzothiophene derivatives at the nanoscale. Nanoscale, Royal Society of Chemistry, 2021, 13 (6), pp.3800-3807. ⟨10.1039/D0NR08619C⟩. ⟨hal-03135025⟩

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