Boosting Thermoelectric Performance of Bi<sub>2</sub>Te<sub>3</sub> Material by Microstructure Engineering
Guoxiang Wang, Fanzheng Meng, Yingqi Chen, Andriy Lotnyk, Xiang Shen
Abstract
Abstract 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, Bi 2 Te 3 /Sb and Bi 2 Te 3 /W multilayer films are proposed to enhance the thermoelectric properties. Both systems possess extremely high conductivity of ≈5.6 × 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 PF s of 1785 µWm −1 K −2 for Bi 2 Te 3 /W and of 1566 µWm −1 K −2 for Bi 2 Te 3 /Sb at 600 K. Thermal heating of the Bi 2 Te 3 /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 Bi 2 Te 3 /W films is maintained, while Bi 2 Te 3 grains of high‐crystalline quality are confined between the W layers. In addition, bilayer defects in Bi 2 Te 3 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 PF s of commercial Bi 2 Te 3 material by microstructure engineering using multilayer structures.