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arXiv · 2102.05377

Thermal conductivity of benzothieno-benzothiophene derivatives at the nanoscale

Magatte N. Gueye·Alexandre Vercouter·Rémy Jouclas·David Guérin·Vincent Lemaur·Guillaume Schweicher·Stéphane Lenfant·Aleandro Antidormi·Yves Geerts·Claudio Melis·Jérôme Cornil·Dominique Vuillaume
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Abstract

We study by scanning thermal microscopy the nanoscale thermal conductance of films (40 to 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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Magatte N. Gueye, Alexandre Vercouter, Rémy Jouclas, David Guérin, Vincent Lemaur, Guillaume Schweicher, Stéphane Lenfant, Aleandro Antidormi, Yves Geerts, Claudio Melis, Jérôme Cornil, Dominique Vuillaume. 2021-02-10. Thermal conductivity of benzothieno-benzothiophene derivatives at the nanoscale. https://doi.org/10.1039/d0nr08619c

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