Improvement of the Thermoelectric Properties in CNT/Bi₂Te₃ Composite Films Due to Evolution of the Depletion Layer and Point Defects under the Pulse Current Field

A carbon nanotube (CNT) composite is an effective method to improve the thermoelectricity of materials. However, the depletion layer between the CNT and thermoelectric (TE) material always decreases the contribution of CNT to the conductivity of the TE material. It is important to eliminate the depletion layer for improving the TE properties. Pulsed-electric-field (PEF) treatment was used to eliminate the depletion layer based on the atomic short-range diffusion on the interface of CNT and Bi₂Te₃. When the pulse current density is 30 A·dm^-2, the CNT composite Bi₂Te₃ film has high mobility, a high carrier concentration, and a high effective mass due to no depletion layer and a low density of point defects. Both the resistivity and Seebeck coefficient improve in the CNT composite Bi₂Te₃ films by PEF treatment of 30 A·dm^-2. The power density is 1.36 W·m^-2 when the hot side temperature is 373 K. The maximum ZT value of this film is 1.66 at 513 K. Thus, the PEF is an effective way to achieve TE property enhancement in the composite films.