Flexible layer-structured Bi₂Te₃ thermoelectric on a carbon nanotube scaffold

Inorganic chalcogenides are traditional high-performance thermoelectric materials. However, they suffer from intrinsic brittleness and it is very difficult to obtain materials with both high thermoelectric ability and good flexibility. Here, we report a flexible thermoelectric material comprising highly ordered Bi₂Te₃ nanocrystals anchored on a single-walled carbon nanotube (SWCNT) network, where a crystallographic relationship exists between the Bi₂Te₃ <[Formula: see text]> orientation and SWCNT bundle axis. This material has a power factor of ~1,600 μW m^-1 K^-2 at room temperature, decreasing to 1,100 μW m^-1 K^-2 at 473 K. With a low in-plane lattice thermal conductivity of 0.26 ± 0.03 W m^-1 K^-1, a maximum thermoelectric figure of merit (ZT) of 0.89 at room temperature is achieved, originating from a strong phonon scattering effect. The origin of the excellent flexibility and thermoelectric performance of the Bi₂Te₃-SWCNT material is attributed, by experimental and computational evidence, to its crystal orientation, interface and nanopore structure. Our results provide insight into the design and fabrication of high-performance flexible thermoelectric materials.