Reduced Bipolar Conduction in Bandgap-Engineered n -Type Cu 0.008 Bi 2 (Te,Se) 3 by Sulfur Doping

Weon Ho Shin, Hyun-Sik Kim, Se Yun Kim, Sung-sil Choo, Seok-won Hong, Yeseong Oh, Yerim Yang, Yoona Kim, Hee Jung Park and Sang-il Kim
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Weon Ho Shin: Department of Electronic Materials Engineering, Kwangwoon University, Seoul 01897, Korea
Hyun-Sik Kim: Department of Materials Science and Engineering, Hongik University, Seoul 04066, Korea
Se Yun Kim: Samsung Electronics, Suwon 16678, Korea
Sung-sil Choo: Department of Materials Science and Engineering, University of Seoul, Seoul 02504, Korea
Seok-won Hong: Department of Materials Science and Engineering, University of Seoul, Seoul 02504, Korea
Yeseong Oh: Department of Materials Science and Engineering, University of Seoul, Seoul 02504, Korea
Yerim Yang: Department of Materials Science and Engineering, University of Seoul, Seoul 02504, Korea
Yoona Kim: Department of Materials Science and Engineering, University of Seoul, Seoul 02504, Korea
Hee Jung Park: Department of Materials Science and Engineering, Dankook University, Cheonan 31116, Korea
Sang-il Kim: Department of Materials Science and Engineering, University of Seoul, Seoul 02504, Korea

Energies, 2020, vol. 13, issue 2, 1-8

Abstract: Significant bipolar conduction of the carriers in Bi 2 Te 3 -based alloys occurs at high temperatures due to their narrow bandgaps. Therefore, at high temperatures, their Seebeck coefficients decrease, the bipolar thermal conductivities rapidly increase, and the thermoelectric figure of merit, zT , rapidly decreases. In this study, band modification of n -type Cu 0.008 Bi 2 (Te,Se) 3 alloys by sulfur (S) doping, which could widen the bandgap, is investigated regarding carrier transport properties and bipolar thermal conductivity. The increase in bandgap by S doping is demonstrated by the Goldsmid–Sharp estimation. The bipolar conduction reduction is shown in the carrier transport characteristics and thermal conductivity. In addition, S doping induces an additional point-defect scattering of phonons, which decreases the lattice thermal conductivity. Thus, the total thermal conductivity of the S-doped sample is reduced. Despite the reduced power factor due to the unfavorable change in the conduction band, zT at high temperatures is increased by S doping with simultaneous reductions in bipolar and lattice thermal conductivity.

Keywords: thermoelectric; bipolar conduction; S doping; bandgap; point defect (search for similar items in EconPapers)
JEL-codes: Q Q0 Q4 Q40 Q41 Q42 Q43 Q47 Q48 Q49 (search for similar items in EconPapers)
Date: 2020
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