(Invited) Completely Organic Carbon Nanostructured Thermoelectric Thin Films with Power Factors Exceeding Bismuth Telluride

Abstract

Low electrical conductivity (s) and thermopower (S) have long excluded polymers from thermoelectric applications. Adding carbon nanotubes produces polymer nanocomposites that exhibit thermoelectric behavior (i.e., generate electricity via a thermal gradient). These nanocomposites exhibit electrical conductivity as high as 200,000 S/m, with a reasonable S (35 – 70 mV/K).1,2 This high electrical conductivity is paired with low thermal conductivity (k ~ 0.3 W m-1 K-1). Power factors (PF = S2s) are as high as 500 mW m-1 K-2) for these composites, containing carbon nanotubes stabilized by porphines and poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate), making them competitive with inorganic semiconductors (e.g., lead telluride) in terms of conversion efficiency. These composites are lightweight and relatively flexible when compared with traditional semiconductor thermoelectrics (e.g., bismuth telluride). Very recent work using layer-by-layer (LbL) assembly will also be described. Sequential layering of PANi, graphene, and double walled carbon nanotubes (DWNT) produces films with increased carrier mobility, originating from strong π-π interactions between PANi and DWNT and the higher electrical conductivity of graphene. In this investigation of the thermoelectric behavior of an LbL-assembled film, the resulting multilayer thin films exhibit a remarkable power factor (1825 mW m-1 K-2) that exceeds lead telluride and is more than half the value of bulk bismuth telluride.3 Additionally, these water-based systems can be applied like ink or paint, which should further improve their usefulness in harnessing waste heat from a variety of sources (e.g., exhaust manifolds or the human body through clothing). For more information about the Polymer Nanocomposites Lab visit: http://nanocomposites.tamu.edu.