High near-room temperature figure of merit of n-type Bi2GeTe4-based thermoelectric materials via a stepwise optimization of carrier concentration

Liang Cao Yin, Wei Di Liu, Xiao Lei Shi, Han Gao, Meng Li, De Zhuang Wang, Hao Wu, Liangzhi Kou, Haizhong Guo, Yifeng Wang, Qingfeng Liu, Zhi Gang Chen

Research output: Contribution to journalArticlepeer-review

29 Scopus citations

Abstract

Bi2GeTe4 is a promising near room-temperature thermoelectric candidate with a low lattice thermal conductivity. Carrier concentration of intrinsic Bi2GeTe4 changes dramatically with tiny Ge content adjustment, leading to a challenge in carrier concentration optimization. To overcome this challenge, we firstly introduce excessive Ge into Bi2GeTe4 to shift the Fermi level deep into the conduction band and transfer Bi2GeTe4 into a highly degenerate n-type semiconductor. Secondly, the embedded p-type Bi2Ge2Te5 secondary phase induces further optimization of the Fermi level and carrier concentration. Finally, the power factor of the as-synthesized Bi2GeTe4-based material is significantly increased from ∼ 0.08 μW cm−1 K−2 to ∼ 4.2 μW cm−1 K−2 at 423 K when increasing the nominal Ge content (x) of Bi2GexTe4 from 1 to 1.45. Correspondingly, a high figure-of-merit of ∼ 0.22 at 423 K is achieved in Bi2GeTe4-based thermoelectric materials. This result indicates our viable stepwise strategy can be used to optimize carrier concentration and achieve high thermoelectric performance of the n-type Bi2GeTe4.

Original languageEnglish
Article number133775
JournalChemical Engineering Journal
Volume433
DOIs
StatePublished - 1 Apr 2022

Keywords

  • BiGeTe
  • Carrier concentration
  • Optimization
  • Thermoelectric
  • zT

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