Raising the thermoelectric performance of p-type Pbs with endotaxial nanostructuring and valence-band offset engineering using CdS and ZnS

Li Dong Zhao, Jiaqing He, Shiqiang Hao, Chun I. Wu, Timothy P. Hogan, C. Wolverton, Vinayak P. Dravid, Mercouri G. Kanatzidis

Research output: Contribution to journalArticle

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Abstract

We have investigated in detail the effect of CdS and ZnS as second phases on the thermoelectric properties of p-type PbS. We report a ZT of ∼1.3 at 923 K for 2.5 at.% Na-doped p-type PbS with endotaxially nanostructured 3.0 at.% CdS. We attribute the high ZT to the combination of broad-based phonon scattering on multiple length scales to reduce (lattice) thermal conductivity and favorable charge transport through coherent interfaces between the PbS matrix and metal sulfide nanophase precipitates, which maintains the requisite high carrier conductivity and the associated power factor. Similar to large ionically bonded metal sulfides (ZnS, CaS, and SrS), the covalently bonded CdS can also effectively reduce the lattice thermal conductivity in p-type PbS. The presence of ubiquitous nanostructuring was confirmed by transmission electron microscopy. Valence and conduction band energy levels of the NaCl-type metal sulfides, MS (M = Pb, Cd, Zn, Ca, and Sr) were calculated from density functional theory to gain insight into the band alignment between PbS and the second phases in these materials. The hole transport is controlled by band offset minimization through the alignment of valence bands between the host PbS and the embedded second phases, MS (M = Cd, Zn, Ca, and Sr). The smallest valence band offset of about 0.13 eV at 0 K was found between PbS and CdS which is diminished further by thermal band broadening at elevated temperature. This allows carrier transport between the endotaxially aligned components (i.e., matrix and nanostructure), thus minimizing significant deterioration of the hole mobility and power factor. We conclude the thermoelectric performance of the PbS system and, by extension, other systems can be enhanced by means of a closely coupled phonon-blocking/electron-transmitting approach through embedding endotaxially nanostructured second phases.

Original languageEnglish
Pages (from-to)16327-16336
Number of pages10
JournalJournal of the American Chemical Society
Volume134
Issue number39
DOIs
Publication statusPublished - Oct 3 2012

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Sulfides
Valence bands
Phonons
Thermal Conductivity
Metals
Thermal conductivity
Phonon scattering
Hole mobility
Carrier transport
Nanostructures
Conduction bands
Transmission Electron Microscopy
Cell Division
Electron energy levels
Density functional theory
Deterioration
Charge transfer
Precipitates
Hot Temperature
Electrons

ASJC Scopus subject areas

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

Cite this

Raising the thermoelectric performance of p-type Pbs with endotaxial nanostructuring and valence-band offset engineering using CdS and ZnS. / Zhao, Li Dong; He, Jiaqing; Hao, Shiqiang; Wu, Chun I.; Hogan, Timothy P.; Wolverton, C.; Dravid, Vinayak P.; Kanatzidis, Mercouri G.

In: Journal of the American Chemical Society, Vol. 134, No. 39, 03.10.2012, p. 16327-16336.

Research output: Contribution to journalArticle

Zhao, Li Dong ; He, Jiaqing ; Hao, Shiqiang ; Wu, Chun I. ; Hogan, Timothy P. ; Wolverton, C. ; Dravid, Vinayak P. ; Kanatzidis, Mercouri G. / Raising the thermoelectric performance of p-type Pbs with endotaxial nanostructuring and valence-band offset engineering using CdS and ZnS. In: Journal of the American Chemical Society. 2012 ; Vol. 134, No. 39. pp. 16327-16336.
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AU - Wu, Chun I.

AU - Hogan, Timothy P.

AU - Wolverton, C.

AU - Dravid, Vinayak P.

AU - Kanatzidis, Mercouri G.

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