Thermoelectric Performance of the 2D Bi2Si2Te6Semiconductor

Yubo Luo, Zheng Ma, Shiqiang Hao, Songting Cai, Zhong Zhen Luo, Christopher Wolverton, Vinayak P. Dravid, Junyou Yang*, Qingyu Yan, Mercouri G. Kanatzidis

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

1 Scopus citations

Abstract

Bi2Si2Te6, a 2D compound, is a direct band gap semiconductor with an optical band gap of ∼0.25 eV, and is a promising thermoelectric material. Single-phase Bi2Si2Te6 is prepared by a scalable ball-milling and annealing process, and the highly densified polycrystalline samples are prepared by spark plasma sintering. Bi2Si2Te6 shows a p-type semiconductor transport behavior and exhibits an intrinsically low lattice thermal conductivity of ∼0.48 W m-1 K-1 (cross-plane) at 573 K. The first-principles density functional theory calculations indicate that such low lattice thermal conductivity is derived from the interactions between acoustic phonons and low-lying optical phonons, local vibrations of Bi, the low Debye temperature, and strong anharmonicity result from the unique 2D crystal structure and metavalent bonding of Bi2Si2Te6. The Bi2Si2Te6 exhibits an optimal figure of merit ZT of ∼0.51 at 623 K, which can be further enhanced by the substitution of Bi with Pb. Pb doping leads to a large increase in power factor S2σ, from ∼3.9 μW cm-1 K-2 of Bi2Si2Te6 to ∼8.0 μW cm-1 K-2 of Bi1.98Pb0.02Si2Te6 at 773 K, owing to the increase in carrier concentration. Moreover, Pb doping induces a further reduction in the lattice thermal conductivity to ∼0.38 W m-1 K-1 (cross-plane) at 623 K in Bi1.98Pb0.02Si2Te6, due to strengthened point defect (PbBi′) scattering. The simultaneous optimization of the power factor and lattice thermal conductivity achieves a peak ZT of ∼0.90 at 723 K and a high average ZT of ∼0.66 at 400-773 K in Bi1.98Pb0.02Si2Te6.

Original languageEnglish (US)
Pages (from-to)1445-1454
Number of pages10
JournalJournal of the American Chemical Society
Volume144
Issue number3
DOIs
StatePublished - Jan 26 2022

ASJC Scopus subject areas

  • Catalysis
  • Chemistry(all)
  • Biochemistry
  • Colloid and Surface Chemistry

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