Realizing high-efficiency thermoelectric module by suppressing donor-like effect and improving preferred orientation in n-type Bi2(Te, Se)3

Abstract

Thermoelectric materials have a wide range of application because they can be directly used in refrigeration and power generation. And the Bi₂Te₃ stand out because of its excellent thermoelectric performance and are used in commercial thermoelectric devices. However, n-type Bi₂Te₃ has seriously hindered the development of Bi₂Te₃-based thermoelectric devices due to its weak mechanical properties and inferior thermoelectric performance. Therefore, it is urgent to develop a high-performance n-type Bi₂Te₃ polycrystalline. In this work, we employed interstitial Cu and the hot deformation process to optimize the thermoelectric properties of Bi₂Te_2.7Se_0.3, and a high-performance thermoelectric module was fabricated based on this material. Our combined theoretical and experimental effort indicates that the interstitial Cu reduce the defect density in the matrix and suppresses the donor-like effect, leading to a lattice plainification effect in the material. In addition, the two-step hot deformation process significantly improves the preferred orientation of the material and boosts the mobility. As a result, a maximum ZT of 1.27 at 373 K and a remarkable high ZT_ave of 1.22 across the temperature range of 300-425 K are obtained. The thermoelectric generator (TEG, 7-pair) and thermoelectric cooling (TEC, 127-pair) modules were fabricated with our n-type textured Cu_0.01Bi₂Te_2.7Se_0.3 coupled with commercial p-type Bi₂Te₃. The TEC module demonstrates superior cooling efficiency compared with the commercial Bi₂Te₃ device, achieving a ΔT of 65 and 83.4 K when the hot end temperature at 300 and 350 K, respectively. In addition, the TEG module attains an impressive conversion efficiency of 6.5% at a ΔT of 225 K, which is almost the highest value among the reported Bi₂Te₃-based TEG modules.

Keywords: Bi(2)Te(3); Donor-like effect; TEC; TEG; Texture engineering.