Possible Charge Density Wave and Enhancement of Thermoelectric Properties at Mild-Temperature Range in n-Type CuI-Doped Bi2Te2.1Se0.9 Compounds

Hyunyong Cho, Jae Hyun Yun, Jin Hee Kim, Song Yi Back, Ho Seong Lee, Sung Jin Kim, Seokyeong Byeon, Hyungyu Jin, Jong Soo Rhyee

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25 Scopus citations


Bi2Te3-based compounds have long been studied as thermoelectric materials in cooling applications near room temperature. Here, we investigated the thermoelectric properties of CuI-doped Bi2Te2.1Se0.9 compounds. The Cu/I codoping induces the lattice distortion partially in the matrix. We report that the charge density wave caused by the local lattice distortion affects the electrical and thermal transport properties. From the high-temperature specific heat, we found a first-order phase transitions near 490 and 575 K for CuI-doped compounds (CuI)xBi2Te2.1Se0.9 (x = 0.3 and 0.6%), respectively. It is not a structural phase transition, confirming from the high-temperature X-ray diffraction. The temperature-dependent electrical resistivity shows a typical behavior of charge density wave transition, which is consistent with the temperature-dependent Seebeck coefficient and thermal conductivity. The transmission electron microscopy and electron diffraction show a local lattice distortion, driven by the charge density wave transition. The charge density wave formation in the Bi2Te3-based compounds are exceptional because of the possibility of coexistence of charge density wave and topological surface states. From the Kubo formula and Boltzmann transport calculations, the formation of charge density wave enhances the power factor. The lattice modulation and charge density wave decrease lattice thermal conductivity, resulting in the enhancement of thermoelectric performance simultaneously in CuI-doped samples. Consequently, an enhancement of thermoelectric performance ZT over 1.0 is achieved at 448 K in the (CuI)0.003Bi2Te2.1Se0.9 sample. The enhancement of ZT at high temperature gives rise to a superior average ZTavg (1.0) value than those of previously reported ones.

Original languageEnglish
Pages (from-to)925-933
Number of pages9
JournalACS Applied Materials and Interfaces
Issue number1
StatePublished - 8 Jan 2020

Bibliographical note

Publisher Copyright:
© 2019 American Chemical Society.


  • BiTe
  • charge density wave
  • codoping
  • lattice modulation
  • phase transition
  • thermoelectric


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