Thermoelectric Switching of Single-Walled Carbon Nanotubes due to Encapsulation of Iodine Atomic Chain

We report significant enhancement of the Seebeck coefficient of an experimentally realized metallic single-walled carbon nanotube encapsulated by iodine chain. Our nonequilibrium Green’s function-based density functional theory study on a 18.76 A long (6, 6) nanotube having diameter 8.14 A showed a robust increase in the Seebeck coefficient up to 240% and a concomitant 10³% increase in the thermoelectric figure of merit (ZT) due to incorporation of the iodine chain in the nanocavity. Interestingly, pristine carbon nanotube that is reported to be an n-type thermoelectric material with a negative Seebeck coefficient changes its sign and becomes p-type when the chain of iodine atoms is present inside. Our in silico study reveals that the charge transfer from the nanotube to the iodine chain is mainly attributed to the switching behavior of the Seebeck coefficient of the studied material and this has been thoroughly justified from the analysis of the density of states, electron density, and the slope of the transmission coefficient at the Fermi level.