Ultrahigh Conductivity Carbon Nanotube Fibers with Ultrahigh Thermoelectric Power Factors

Thermoelectric generators (TEGs), which convert thermal energy into electricity, have emerged as a recharge-free and safe power source for flexible and wearable devices. Macroscopic, neat assemblies of carbon nanotubes (CNTs) are strong candidates for TEGs with high power factor due to their superb electrical, mechanical properties and large Seebeck coefficient derived from the one-dimensionality of CNTs. Here, we studied the thermoelectric properties of CNT fibers with an ultrahigh electrical conductivity (>10⁷ Sm^-1) by varying the Fermi energy. When the Fermi energy was near the first van Hove singularity in the electronic density of states, the conductivity and Seebeck coefficient were enhanced simultaneously, resulting in an ultrahigh thermoelectric power factor at room temperature of 14±5 mWm^-1K^-2. The unique properties of CNT fibers, such as flexibility, mechanical strength, and high-temperature resilience, combined with the excellent power factor, allowed us to fabricate a textileTEG with enough output power to drive a light-emitting diode. Our findings provide a route for powerful, mechanically robust, refractory, and flexible TEGs.