Improvement in the thermoelectric performance of highly reproducible n-type (Bi,Sb)Se alloys by Cl-doping

• Published in: RSC advances 2020-06, Vol.1 (41), p.24663-24668
• Main Authors: Nasir, Nadra, Lee, Kyu Hyoung, Kim, Sang-il, Kim, Hyun-Sik, Lim, Jae-Hong, Fu, Liangwei, Kim, Sung Wng
• Format: Article
• Language: English
• ISSN: 2046-2069
• DOI: 10.1039/d0ra04065g

(Bi,Sb) 2 Se 3 alloys are promising alternatives to commercial n-type Bi 2 (Te,Se) 3 ingots for low-mid temperature thermoelectric power generation due to their high thermoelectric conversion efficiency at elevated temperatures. Herein, we report the enhanced high-temperature thermoelectric performance of the polycrystalline Cl-doped Bi 2− x Sb x Se 3 ( x = 0.8, 1.0) bulks and their sustainable thermal stability. Significant role of Cl substitution, characterized to enhance the power factor and reduce the thermal conductivity synergetically, is clearly elucidated. Cl-doping at Se-site of both Bi 1.2 Sb 0.8 Se 3 and BiSbSe 3 results in a high power factor by carrier generation and Hall mobility improvement while maintaining converged electronic band valleys. Furthermore, point defect phonon scattering originated from mass fluctuations formed at Cl-substituted Se-sites reduces the lattice thermal conductivity. Most importantly, spark plasma sintered Cl-doped Bi 2− x Sb x Se 3 bulks are thermally stable up to 700 K, and show a reproducible maximum thermoelectric figure of merit, zT , of 0.68 at 700 K. Cl-doped Bi 2− x Sb x Se 3 bulks are thermally stable at below 700 K showing a reproducible maximum zT of ∼0.68 at 700 K.