Composite films of poly(3-hexylthiophene) and single- as well as multi-walled carbon nanotubes are demonstrated to offer a competitive thermoelectric performance. The power factor significantly exceeds values obtained with either constituent alone provided that the conjugated polymer is sufficiently p-doped. The use of single-walled carbon nanotubes consistently results in a higher electrical conductivity with a maximum value above 10³ S cm⁻¹ and thus gives rise to a power factor of 25 ± 6 μW m⁻¹ K⁻² for a filler content of only 8 wt% and a maximum 95 ± 12 μW m⁻¹ K⁻² for 42–81 wt%. Moreover, a carbon nanotube content of 8–10 wt% does not compromise the low bulk thermal conductivity of the polymer matrix, which promises a high figure of merit of at least ZT > 10⁻² at room-temperature. All samples are cast on plastic substrates, emphasising their suitability for large-area, flexible thermoelectric applications.

The behavior of mixtures of polymers with carbon nanotubes are reviewed. The use of polymers as dispersing agents of individual CNT is described in detail. Two groups of polymer–CNT systems are presented. One corresponds to the case in which the polymer–CNT interactions modify the electronic properties of the tubes. The second case corresponds to the polymers end-tethered to the tubes. This case results in changing the inter-tube interactions from strongly attractive to repulsive, through the entropic (steric) polymer induced repulsions. It is shown that the shape and dimensionality of the tubes determines the strength, range and type of inter-tube van der Waals attractions and polymer induced repulsions. The experimental verification of these ideas, and their implications for tube dispersions and separation are discussed