Boosting Thermoelectric Performance of Bi₂Te₃ Material by Microstructure Engineering

Due to the intrinsic contradiction of electrical conductivity and Seebeck coefficient in thermoelectric materials, the enhancement for the power factor (PF) is limited. Since the PF decides the output power, strategies to the enhancement of PF are of paramount importance. In this work, Bi2Te3/Sb and Bi2Te3/W multilayer films are proposed to enhance the thermoelectric properties. Both systems possess extremely high conductivity of approximate to 5.6 x 10(5) S m(-1). Moreover, the electrical conductivity and Seebeck coefficient simultaneously increase as temperature rising, showing the overcome of the intrinsic contradiction. This results in ultrahigh PFs of 1785 mu Wm(-1) K-2 for Bi2Te3/W and of 1566 mu Wm(-1) K-2 for Bi2Te3/Sb at 600 K. Thermal heating of the Bi2Te3/Sb multilayer system shows compositional changes with subsequent formation of Bi-Te-Sb phases, Sb-rich Bi-Te precipitates, and cavities. Contrary, the multilayer structure of the Bi2Te3/W films is maintained, while Bi2Te3 grains of high-crystalline quality are confined between the W layers. In addition, bilayer defects in Bi2Te3 and smaller cavities at the interface to W layers are also observed. Thus, compositional and confinement effects as well as structural defects result in the ultrahigh PF. Overall, this work demonstrates the strategies on how to obtain ultrahigh PFs of commercial Bi2Te3 material by microstructure engineering using multilayer structures.