Light-Weight Flexible Carbon Nanotube Based Organic Composites with Large Thermoelectric Power Factors

Abstract

Typical organic materials have low thermal conductivities that are best suited to thermoelectrics, but their poor electrical properties with strong adverse correlations have prevented them from being feasible candidates. Our composites, containing single-wall carbon nanotubes, poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) and/or polyvinyl acetate, show thermopowers weakly correlated with electrical conductivities, resulting in large thermoelectric power factors in the in-plane direction of the composites, ∼160 μW/m 3 K 2 at room temperature, which are orders of magnitude larger than those of typical polymer composites. Furthermore, their high electrical conductivities, ∼10 5 S/m at room temperature, make our composites very promising for various electronic applications. The optimum nanotube concentrations for better power factors were identified to be 60 wt % with 40 wt % polymers. It was noticed that high nanotube concentrations above 60 wt % decreased the electrical conductivity of the composites due to less effective nanotube dispersions. The thermal conductivities of our 60 wt % nanotube composites in the out-of-plane direction were measured to be 0.2À0.4 W/m 3 K at room temperature. The in-plane thermal conductivity and thermal contact conductance between nanotubes were also theoretically estimated.

Photoinduced p‐ to n‐type Switching in Thermoelectric Polymer‐Carbon Nanotube Composites

“…[ 12,13 ] Interestingly, the thermal conductivity of bulk polymers as well as conjugated macromolecules can be tuned by controlling molecular orientation. [14][15][16] In order to increase the modest electrical conductivity of polymers, a number of strategies have been proposed, including careful doping, [ 4,11,[17][18][19][20][21] making composites of polymers with conductive fi llers such as CNTs, [22][23][24] or fabricating multilayer composite A broad range of organic electronic applications rely on the availability of both p-and n-type organic semiconductors, and the possibility to deposit them as sequential layers or to form spatial patterns. Examples include transport layers in diodes (OLEDs, photovoltaics, etc.…”

Highly anisotropic P3HT films with enhanced thermoelectric performance via organic small molecule epitaxy

“…Previous studies on the TE properties of conducting polymers and their composites revealed that the use of template induction with inorganic nanoparticles (for example, carbon nanotubes, graphene, metal nanowires) increased the degree of ordering of polymer molecular arrangements and therefore improved σ and S, [11][12][13][14][15][16] but a clear explanation for the intrinsic effect of the molecular structure on electron transport is still lacking. The electron transport in a conducting polymer composite containing an inorganic dispersion phase is complex because multiple factors may influence the transport process in diverse ways.…”

SWNT Composites with Compositionally Tunable Prussian Blue Nanoparticles for Thermoelectric Coordination Programming Materials

“…Thermoelectric materials based on single-walled carbon nanotubes (SWNTs) are the most striking candidates for future flexible power generators. 13 Their degree of energy conversion is usually expressed as a dimensionless figure of merit, ZT = ¡ 2 ·T/¬, where ¡ is the Seebeck coefficient, · is electrical conductivity, T is temperature, and ¬ is thermal conductivity. SWNTs possess high electrical conductivity and structural flexibility but have the disadvantages of a small Seebeck coefficient and high thermal conductivity.…”

“…In most cases, conducting polymers serve as efficient electrical conductors, and insulating polymers are useful for low thermal conductivity, which thus enhance ZT. 13,14 On the other hand, a rational approach for improving the Seebeck coefficient of SWNTs is still a challenging subject. Because of the trade-off relationship between conductivity and the Seebeck coefficient, the Seebeck coefficient was usually sacrificed for increased electrical conductivity.…”