| Investigation on degraded thermoelectric performance of SnSe2 polycrystalline alloys by Bi doping |
Okmin Park1, TaeWan Kim2, Ui Chan Song1, Seungchan Seon1, BeomSoo Kim1, Weon Ho Shin3, Sang-il Kim1
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1Department of Materials Science and Engineering, University of Seoul, Seoul, 02504, South Korea
2School of Advanced Fusion Studies, University of Seoul, Seoul, 02504, South Korea
3Department of Electronic Materials Engineering, Kwangwoon University, Seoul, 01897, South Korea |
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Received: August 6, 2024; Revised: November 19, 2024 Accepted: December 1, 2024. Published online: December 16, 2024.
*Okmin Park and TaeWan Kim contributed equally to this work. |
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| ABSTRACT |
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SnSe2 layered alloys can be considered promising thermoelectric materials with enhancement in their electrical transport properties. Several studies have shown that electron doping via anion doping could effectively enhance the thermoelectric properties of SnSe2 polycrystalline alloys. In this study, the influence of Bi doping, which is cation doping, on the electric and thermoelectric transport properties of SnSe2 polycrystalline alloys was investigated systematically by synthesizing a series of Sn1-xBixSe2 (x = 0.02, 0.04, 0.06, and 0.08) compositions. It was shown that Bi ion in SnSe2 exhibited an oxidation state of + 3 by X-ray photoelectron spectroscopy and Bi behaved as an acceptor in the Sn4+ site of SnSe2, thereby greatly decreasing the electron concentration of SnSe2 from 2.2 × 1019 to 2.3 × 1015 cm-3 at x = 0.02. Therefore, a significant decrease in electrical conductivity was observed, and the Seebeck coefficient was also decreased owing to the severe decrease in the density of state effective mass, resulting in severe power factor decrease by the Bi doping. Total and lattice thermal conductivity did not show decrease with the Bi doping. Consequently, the maximum thermoelectric figure of merit zT for the doped samples decreased to ~ 0.01 from 0.10 for pristine SnSe2. Additionally, analysis of the thermoelectric performance was performed based on single parabolic band model, suggesting that increasing carrier concentration to ~ 1020 cm-3 could maximize the zT value of SnSe2. |
| Key words:
SnSe2 · Thermoelectric · Cation doping |
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