Enhancement of thermoelectric properties of carbon nanotube composites by inserting biomolecules at nanotube junctions

Carbon nanotubes (CNTs) are an attractive material for flexible thermoelectric devices because of their mechanical strength, lightness, and high conductivity. However, their thermoelectric performance is restricted by their large thermal conductivity. In this letter, a novel material design for improving the performance of CNTs by inserting biobased molecules at CNT/CNT junctions is proposed. We demonstrate that the thermal conductivity is markedly suppressed, but the electrical conductivity is increased by the addition of cage-shaped proteins with semiconducting cores. The Seebeck coefficient also increases by selecting the appropriate core material. By improving the three above-mentioned important parameters, the ZT value is increased over 1000-fold. (C) 2014 The Japan Society of Applied Physics