Enhancement of Thermoelectric Performance by Doping to Reduce Degeneracy

• Published in: Physica status solidi. PSS-RRL. Rapid research letters 2024-01, Vol.18 (1), p.n/a
• Main Authors: Shi, Yunji, Wan, Rundong, Zhang, Zhengfu, Tian, Guocai
• Format: Article
• Language: English
• Subjects: band engineering; Carrier density; Doping; Electronegativity; first principle; half-Heusler; Reduction; Seebeck effect; thermoelectric; Thermoelectric materials; Valence band; Zirconium
• ISSN: 1862-6254; 1862-6270
• DOI: 10.1002/pssr.202300133

Increasing valley degeneracy via doping is one approach to enhance thermoelectric performance. Herein, it is shown that reducing degeneracy can also have a positive impact on performance, particularly for materials with high degeneracy around their undoped band edges. Specifically, doping NbFeSb with Zr or Hf atoms split the valence band edge, resulting in a 1.33 reduction in hole concentration, compared with the experimental carrier concentrations. The reduction increases Seebeck coefficients and overall thermoelectric performance to better agreement with the experimental ones. Notably, for potentially effective thermoelectric materials with high degeneracy, if the doped atom has significantly lower (higher) electronegativity, it is expected to produce a high‐performance p‐type (n‐type) thermoelectric material. In this work, it is shown that reducing degeneracy can also have a positive impact on performance, particularly for materials with high degeneracy around their undoped band edges. Doping NbFeSb with Zr or Hf atoms splits the valence band edge, resulting in a 1.33 reduction in hole concentration and corresponding increases in Seebeck coefficients and overall thermoelectric performance.