Improvement in the thermoelectric performance of highly reproducible n-type (Bi,Sb)2Se3 alloys by Cl-doping

Nadra Nasir; Kyu Hyoung Lee; Sang-Il Kim; Hyun-Sik Kim; Jae-Hong Lim; Liangwei Fu; Sung Wng Kim

doi:10.1039/d0ra04065g

Improvement in the thermoelectric performance of highly reproducible n-type (Bi,Sb)₂Se₃ alloys by Cl-doping

RSC Adv. 2020 Jun 29;10(41):24663-24668. doi: 10.1039/d0ra04065g. eCollection 2020 Jun 24.

Authors

Nadra Nasir¹, Kyu Hyoung Lee², Sang-Il Kim³, Hyun-Sik Kim⁴, Jae-Hong Lim⁵, Liangwei Fu¹, Sung Wng Kim^{1

6}

Affiliations

¹ Department of Energy Science, Sungkyunkwan University Suwon 16419 South Korea fulw@skku.edu kimsungwng@skku.edu.
² Department of Materials Science and Engineering, Yonsei University Seoul 03722 South Korea.
³ Department of Materials Science and Engineering, University of Seoul Seoul 02504 South Korea.
⁴ Department of Materials Science and Engineering, Hongik University Seoul 04066 South Korea.
⁵ Department of Materials Science and Engineering, Gachon University Seongnam 13120 South Korea.
⁶ Center for Integrated Nanostructure Physics, Institute of Basic Science Suwon 16419 South Korea.

Abstract

(Bi,Sb)₂Se₃ alloys are promising alternatives to commercial n-type Bi₂(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 Se₃ (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_1.2Sb_0.8Se₃ and BiSbSe₃ 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 Se₃ bulks are thermally stable up to 700 K, and show a reproducible maximum thermoelectric figure of merit, zT, of 0.68 at 700 K.