Tunneling-Limited Thermoelectric Transport in Carbon Nanotube Networks Embedded in Poly(dimethylsiloxane) Elastomer

As an emerging flexible thermoelectric material, polymer composites with embedded carbon nanotube (CNT) networks have shown promising properties, but their thermoelectric transport has not been fully understood. Herein, we embedded CNT networks in poly(dimethylsiloxane) (PDMS) elastomers and analyzed their thermoelectric properties using Landauer theory. We find that the simultaneous increase in Seebeck coefficient and electrical conductivity with increasing CNT content up to similar to 40% can be attributed to the tunneling transport at CNT junctions with the gap distance decreasing with increasing CNT content. Beyond 40% CNTs, both properties are reduced and saturated due to the reduced PDMS content and increased material nonuniformity, which effectively replaced the PDMS gap with an air gap at the junction with a higher barrier to reduce the properties. Our results and analysis provide important insights into the material optimization of hybrid thermoelectric composites based on CNT networks and many other nanoscale fillers.