TY - JOUR
T1 - Strong Suppression of Thermal Conductivity in the Presence of Long Terminal Alkyl Chains in Low-Disorder Molecular Semiconductors
AU - Selezneva, Ekaterina
AU - Vercouter, Alexandre
AU - Schweicher, Guillaume
AU - Lemaur, Vincent
AU - Broch, Katharina
AU - Antidormi, Aleandro
AU - Takimiya, Kazuo
AU - Coropceanu, Veaceslav
AU - Brédas, Jean Luc
AU - Melis, Claudio
AU - Cornil, Jérôme
AU - Sirringhaus, Henning
N1 - Publisher Copyright: © 2021 The Authors. Advanced Materials published by Wiley-VCH GmbH
PY - 2021/9/16
Y1 - 2021/9/16
N2 - 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.
AB - 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.
KW - molecular dynamics
KW - organic semiconductors
KW - thermal conductivity
KW - thermoelectrics
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U2 - 10.1002/adma.202008708
DO - 10.1002/adma.202008708
M3 - Article
C2 - 34342927
SN - 0935-9648
VL - 33
JO - Advanced Materials
JF - Advanced Materials
IS - 37
M1 - 2008708
ER -