Thermoelectric Properties of Ultrasmall Single-Wall Carbon Nanotubes

The electronic transport of three kinds of ultrasmall single-wall carbon nanotubes are studied by using nonequilibrium Green’s function method. It is found that the transmission function displays a clear stepwise structure that gives the number of electron channels. The calculated power factor of these nanotubes can be optimized to much higher values in a wide temperature range. Using nonequilibrium molecule dynamics simulations, the lattice thermal conductivity of these nanotubes are predicated with quantum correction. Our calculations indicate that the (4,2) tube has relatively higher room temperature figure of merit (ZT value) compared with those of the (5,0) and (3,3) tubes. Moreover, the thermoelectric performance of these nanotubes can be greatly enhanced by surface design, formation of bundles, increasing the tube length, and so on, which significantly reduce the phonon and electron-derived thermal conductance.