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

Author

Listed:
  • Weon Ho Shin

    (Department of Electronic Materials Engineering, Kwangwoon University, Seoul 01897, Korea
    These authors equally contributed to this study.)

  • Hyun-Sik Kim

    (Department of Materials Science and Engineering, Hongik University, Seoul 04066, Korea
    These authors equally contributed to this study.)

  • 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)

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.

Suggested Citation

  • Weon Ho Shin & Hyun-Sik Kim & Se Yun Kim & Sung-sil Choo & Seok-won Hong & Yeseong Oh & Yerim Yang & Yoona Kim & Hee Jung Park & Sang-il Kim, 2020. "Reduced Bipolar Conduction in Bandgap-Engineered n -Type Cu 0.008 Bi 2 (Te,Se) 3 by Sulfur Doping," Energies, MDPI, vol. 13(2), pages 1-8, January.
    • Handle: RePEc:gam:jeners:v:13:y:2020:i:2:p:337-:d:307203
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