Due to the capacity to directly and reversibly convert heat into electricity, thermoelectric (TE) material has potential applications in solid-state heat pumping and exhaust heat recuperation, thus attracting the worldwide attention. Bi 2 Te 3 stands out for its excellent thermoelectric properties and has been used in commercial thermoelectric devices. However, the development of Bi 2 Te 3 -based thermoelectric devices is seriously hindered by the weak mechanical properties and low TE properties of n-type Bi 2 (Te, Se) 3 . Therefore, it is important to develop a high-performance n-type Bi 2 Te 3 polycrystalline material.
To address this issue, in this study, extra Cu is introduced into the classical n-type Bi 2 Te 2.7 Se 0.3 to optimize its local defect state, and a two-step hot deformation process was employed to construct the high textured polycrystalline Bi 2 Te 2.7 Se 0.3 material. This research reveals that the extra Cu is able to enter the van der Waals gaps between the Te (1) -Te (1) layers in Bi 2 Te 2.7 Se 0.3 matrix, suppressing the formation of the anionic vacancies. This reduction in defect density contributes to lattice plainification in Cu 0.01 Bi 2 Te 2.7 Se 0.3 , improving the carrier mobility of Bi 2 Te 2.7 Se 0.3 from 174 cm 2 V –1 s –1 to 226 cm 2 V –1 s –1 with the 1% additional Cu, resulting in a maximum ZT of 1.10 at 348 K. Subsequently, the SPS-sintered Cu 0.01 Bi 2 Te 2.7 Se 0.3 bulk material underwent a two-step hot deformation process. Since the interstitial Cu can stabilize the lattice and effectively suppress the donor-like effect. The carrier concentration of hot deformation sample remains almost unchanged, while its grain orientation and grain size have significantly increased, which dramatically boosts the carrier mobility, from the initial 174 cm 2 V –1 s –1 to 333 cm 2 V –1 s –1 , representing a 91% increase after the hot deformation process. This significant improvement in electronic properties contributes to a substantial enhancement in ZT for hot deformation sample. The ZT max of the textured Cu 0.01 Bi 2 Te 2.7 Se 0.3 reaches 1.27 at 373 K, and its average ZT value is 1.22 in the range of 300-425 K, nearly twice as much as the initial Bi 2 Te 2.7 Se 0.3 . Furthermore, a 127-pair thermoelectric cooling device (TEC) was fabricated by using the textured Cu 0.01 Bi 2 Te 2.7 Se 0.3 sample coupled with commercial p-type BST. The TEC module achieved cooling temperature differentials of 65 K and 83.4 K at hot-end temperatures ( T h ) of 300 K and 350 K, respectively, which is superior to the commercial Bi 2 Te 3 -based TEC modules. And a 7-pair thermoelectric generator module (TEG) was constructed by using the same materials. The TEG module demonstrated a significantly high conversion efficiency of 6.5% at a temperature different of 225 K, which is comparable to other state-of-the-art Bi 2 Te 3 -based TEG modules.
Yichen Li, Shulin Bai, Yi Wen, Zhe Zhao, Lei Wang, Shibo Liu, Junqing Zheng, Siqi Wang, Shan Liu, Dezheng Gao, Dongrui Liu, Yingcai Zhu, Qian Cao, Xiang Gao, Hongyao Xie, Li-Dong Zhao. Realizing high-efficiency thermoelectric module by suppressing donor-like effect and improving preferred orientation in n-type Bi2(Te, Se)3. Science Bulletin 2024;69(11): doi: 10.1016/j.scib.2024.04.034
Science Bulletin