Boosting Thermoelectric Performance of Bi<sub>2</sub>Te<sub>3</sub> Material by Microstructure Engineering: Fid-Bau Portal

Boosting Thermoelectric Performance of Bi₂Te₃ Material by Microstructure Engineering

Wang, Guoxiang / Meng, Fanzheng / Chen, Yingqi / Lotnyk, Andriy / Shen, Xiang

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 ≈5.6 × 10⁵ 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 µWm⁻¹ K⁻² for Bi₂Te₃/W and of 1566 µWm⁻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.