Thermal conductivity of benzothieno-benzothiophene derivatives at the nanoscale

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...

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Authors: Gueye, Magatte Niang|||0000-0003-4337-4179; Vercouter, Alexandre|||0000-0003-0682-0176; Jouclas, Rémy|||0000-0002-1346-6817; Guerin, David|||0000-0002-4338-1742; Lemaur, Vincent|||0000-0001-8601-286X; Schweicher, Guillaume|||0000-0002-6501-0790; Lenfant, Stephane|||0000-0002-6857-8752; Antidormi, Aleandro|||0000-0002-5266-8147; Geerts, Yves Henri|||0000-0002-2660-5767; Melis, Claudio|||0000-0002-5768-8403; Cornil, Jerome|||0000-0002-5479-4227; Vuillaume, Dominique|||0000-0002-3362-1669
Format: Article
Publication date:2021
Country:España
Institution:Universitat Autònoma de Barcelona
Repository:Dipòsit Digital de Documents de la UAB
Language:English
OAI Identifier:oai:ddd.uab.cat:241023
Online Access:https://ddd.uab.cat/record/241023
https://dx.doi.org/urn:doi:10.1039/d0nr08619c
Access Level:Open access
Keyword:Anisotropy factor
Approach to equilibrium
Benzothiophene derivatives
Crystalline directions
Molecular dynamics calculation
Scanning thermal microscopy
Thermal conductance
Thickness dependence
Summary: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-1versus 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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