The possibility of using conjugated polymers (CP) as thermoelectric materials has been widely explored over the last two decades, giving rewarding results 1 . Such materials are particularly attractive for room temperature application and flexible devices, but their low efficiencies in comparison with the inorganic benchmark still represent a main drawback. For this reason, several different paths have been pursued to maximise their performances 2–4 , by enhancing CP thermoelectric power factor (PF=α 2 σ, where α is the Seebeck coefficient and σ is the electrical conductivity). An appealing strategy to address this aim is focused on the increase of the polymeric crystallinity level, since it causes elevated σ and only marginally affects α value 5 . In order to obtain an highly conductive CP with a good crystallinity level, vapor phase polymerization (VPP) appears to be the best technique 6 . This communication reports on a study on poly(3,4-ethylenedioxythiophene) (PEDOT) prepared through VPP with trifluoromethansulfonate iron salt (FeTf 3 ) as oxidative agent, which has been proven to be particularly beneficial to the final material properties 5 . Thanks to the optimization of the recipe and post- treatment procedure, a remarkable σ value of 3095 Ω -1 cm -1 has been reached, while an optimized PF value of 69 µWK -2 m -1 has been obtained thanks to a slight reduction of the polymer, i.e. dedoping. Furthermore, the progressive reduction performed on the material allowed to monitor the modification of σ and α values at different oxidation levels, giving a deeper insight on the material transport properties. The overall thermoelectric study done on this novel material will be presented, including stability investigation and dedoping performed in different conditions. The results obtained will be discussed emphasizing the synthetic and post-treatment parameters that allowed the optimization of VPP PEDOT:Tf thermoelectric features
Galliani, D., Brooke, R., Ail, U., Ullah Khan, Z., Crispin, X. (2017). Thermoelectric properties of vapour phase polymerized poly(3,4- ethylenedioxythiophene)-trifluoromethanesulfonate (VPP PEDOT:Tf): a study on a highly performing conductive polymer. Intervento presentato a: International Workshop "Thermoelectric materials: From theoretical design to industrial application", Cork, Irlanda.
Thermoelectric properties of vapour phase polymerized poly(3,4- ethylenedioxythiophene)-trifluoromethanesulfonate (VPP PEDOT:Tf): a study on a highly performing conductive polymer
GALLIANI, DANIELAPrimo
;
2017
Abstract
The possibility of using conjugated polymers (CP) as thermoelectric materials has been widely explored over the last two decades, giving rewarding results 1 . Such materials are particularly attractive for room temperature application and flexible devices, but their low efficiencies in comparison with the inorganic benchmark still represent a main drawback. For this reason, several different paths have been pursued to maximise their performances 2–4 , by enhancing CP thermoelectric power factor (PF=α 2 σ, where α is the Seebeck coefficient and σ is the electrical conductivity). An appealing strategy to address this aim is focused on the increase of the polymeric crystallinity level, since it causes elevated σ and only marginally affects α value 5 . In order to obtain an highly conductive CP with a good crystallinity level, vapor phase polymerization (VPP) appears to be the best technique 6 . This communication reports on a study on poly(3,4-ethylenedioxythiophene) (PEDOT) prepared through VPP with trifluoromethansulfonate iron salt (FeTf 3 ) as oxidative agent, which has been proven to be particularly beneficial to the final material properties 5 . Thanks to the optimization of the recipe and post- treatment procedure, a remarkable σ value of 3095 Ω -1 cm -1 has been reached, while an optimized PF value of 69 µWK -2 m -1 has been obtained thanks to a slight reduction of the polymer, i.e. dedoping. Furthermore, the progressive reduction performed on the material allowed to monitor the modification of σ and α values at different oxidation levels, giving a deeper insight on the material transport properties. The overall thermoelectric study done on this novel material will be presented, including stability investigation and dedoping performed in different conditions. The results obtained will be discussed emphasizing the synthetic and post-treatment parameters that allowed the optimization of VPP PEDOT:Tf thermoelectric features
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