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Research output: Contribution to Journal/Magazine › Journal article › peer-review
Research output: Contribution to Journal/Magazine › Journal article › peer-review
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TY - JOUR
T1 - Thermoelectric properties of organic thin films enhanced by π-π stacking
AU - Wang, Xintai
AU - Sangtarash, Sara
AU - Lamantia, Angelo
AU - Dekkiche, Hervé
AU - Forcieri, Leonardo
AU - Kolosov, Oleg
AU - Jarvis, Samuel
AU - Bryce, Martin R.
AU - Lambert, Colin
AU - Sadeghi, Hatef
AU - Robinson, Benjamin
PY - 2022/4/30
Y1 - 2022/4/30
N2 - Thin films comprising synthetically robust, scalable molecules have been shown to have major potential for thermoelectric en-ergy harvesting. Previous studies of molecular thin-films have tended to focus on massively parallel arrays of discrete but iden-tical conjugated molecular wires assembled as a monolayer perpendicular to the electrode surface and anchored via a covalent bond, know as self-assembled monolayers. In these studies, to optimise the thermoelectric properties of the thin-film there has been a trade-off between synthetic complexity of the molecular components and the film performance, limiting the opportuni-ties for materials integration into practical thermoelectric devices. In this work, we demonstrate an alternative strategy for en-hancing the thermoelectric performance of molecular thin-films. We have built up a series of films, of controlled thickness, where the basic units – here zinc tetraphenylporphyrin – lie parallel to the electrodes and are linked via π-π stacking. We have compared three commonly used fabrications routes and characterised the resulting films with scanning probe and computation-al techniques. Using a Langmuir-Blodgett fabrication technique, we successfully enhanced the thermopower perpendicular to the plane of the ZnTPP multilayer film by a factor of 10, relative to the monolayer, achieving a Seebeck coefficient of -65 μV/K. Furthermore, the electronic transport of the system, perpendicular to the plane of the films, was observed to follow the tunnel-ling regime for multi-layered films, and the transport efficiency was comparable with most conjugated systems. Furthermore, scanning thermal microscopy characterisation shows a factor of 7 decrease in thermal conductance with increasing film thick-ness from monolayer to multilayer, indicating enhanced thermoelectric performance in a π-π stacked junction.
AB - Thin films comprising synthetically robust, scalable molecules have been shown to have major potential for thermoelectric en-ergy harvesting. Previous studies of molecular thin-films have tended to focus on massively parallel arrays of discrete but iden-tical conjugated molecular wires assembled as a monolayer perpendicular to the electrode surface and anchored via a covalent bond, know as self-assembled monolayers. In these studies, to optimise the thermoelectric properties of the thin-film there has been a trade-off between synthetic complexity of the molecular components and the film performance, limiting the opportuni-ties for materials integration into practical thermoelectric devices. In this work, we demonstrate an alternative strategy for en-hancing the thermoelectric performance of molecular thin-films. We have built up a series of films, of controlled thickness, where the basic units – here zinc tetraphenylporphyrin – lie parallel to the electrodes and are linked via π-π stacking. We have compared three commonly used fabrications routes and characterised the resulting films with scanning probe and computation-al techniques. Using a Langmuir-Blodgett fabrication technique, we successfully enhanced the thermopower perpendicular to the plane of the ZnTPP multilayer film by a factor of 10, relative to the monolayer, achieving a Seebeck coefficient of -65 μV/K. Furthermore, the electronic transport of the system, perpendicular to the plane of the films, was observed to follow the tunnel-ling regime for multi-layered films, and the transport efficiency was comparable with most conjugated systems. Furthermore, scanning thermal microscopy characterisation shows a factor of 7 decrease in thermal conductance with increasing film thick-ness from monolayer to multilayer, indicating enhanced thermoelectric performance in a π-π stacked junction.
U2 - 10.1088/2515-7655/ac55a3
DO - 10.1088/2515-7655/ac55a3
M3 - Journal article
VL - 4
JO - J. Phy. Energy
JF - J. Phy. Energy
SN - 2515-7655
IS - 2
M1 - 024002
ER -