| Influence of band gap enlargement on thermoelectric properties of Bi2Se3 by solid-solution alloying with In2Se3 |
Hyungyu Cho1, Hyunjin Park1, Seungchan Seon1, BeomSoo Kim1, Okmin Park1, TaeWan Kim2, Hyun-Sik Kim1, 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 |
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Received: July 17, 2024; Revised: September 24, 2024 Accepted: October 19, 2024. Published online: November 25, 2024. |
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| ABSTRACT |
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Bi2Se3 alloys are considered promising thermoelectric materials for application at ambient to moderately high temperatures. However, because of the narrow band gap (Eg) of Bi2Se3-based materials, bipolar conduction dominates and impairs their thermoelectric performance at elevated temperatures. In this study, we investigated the electrical and thermal transport properties of Bi2Se3 alloyed with indium (In) by incorporating as much as 50% In in the ((Bi1-xInx)2Se3, where x = 0, 0.125, 0.25, 0.375, and 0.5) compositions, which widen the Eg of the Bi2Se3. Analysis of the activation energy, the Goldsmid−Sharp Eg, and optical Eg revealed that Eg might gradually become wider with increasing In content. This gradual widening of Eg led to a corresponding gradual decrease in the carrier concentration. However, the heaving doping of In induces an exponential decrease in the mobility, which resulted in an significant decrease in the electrical conductivity and power factor. The lattice thermal conductivity decreased significantly owing to strong phonon scattering by the heavy In doping and the bipolar thermal conductivity appeared to be reduced. Overall, a thermoelectric figure of merit is significantly reduced for the heavily In-doped Bi2Se3 mainly due to significant reduction of the mobility. Although the significant reduction in klatt and kbp was observed. Therefore, further theoretical analysis based on a two-band model was performed to further investigate the estimated correlation on the electrical and thermal transport properties of Bi2Se3 and its Eg. |
| Key words:
Thermoelectric · Bi2Se3 · In2Se3 · Solid-solution alloying · Band gap · Bipolar conduction |
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