Elemental tellurium as a chiralp-type thermoelectric material

Abstract

The thermoelectric transport properties of elemental tellurium are investigated by density functional theory combined with the Boltzmann transport equation in the rigid band approximation. We find that the thermoelectric transport properties parallel and perpendicular to the helical chains are highly asymmetric (almost symmetric) for p-(n-) type doped tellurium due to the anisotropic (isotropic) hole (electron) pockets of the Fermi surface. The electronic band structure shows that the lone-pair derived uppermost heavy-hole and extremely light-hole lower valence bands offer the opportunity to obtain both a high Seebeck coefficient and electrical conductivity along the chains through Sb or Bi doping. Furthermore, the stairlike density of states yields a large asymmetry for the transport distribution function relative to the Fermi energy which leads to large thermopower. The calculations reveal that tellurium has the potential to be a good p-type thermoelectric material with an optimum figure of merit zT of 0.31 (0.56) at room temperature (500 K) at a hole concentration around 1 × 10 19 cm −3 . Exploiting the rich chemistry of lone pairs in chiral solids may have important implications for the discovery of high-zT polychalcogenide-based thermoelectric materials.

High‐Performance Thermoelectric Paper Based on Double Carrier‐Filtering Processes at Nanowire Heterojunctions

“…Bulk Te forms a degenerate semiconductor with a narrow bandgap of 0.33 eV, in which the Fermi level is positioned close to the valence band. [ 27 ] The work function of the TeNWs is assumed to be the same as that of bulk Te. [ 28 ] The work functions of PEDOT:PSS and rGO were measured using ultraviolet photoelectron spectroscopy (UPS), Figure S11).…”

Radial Spin Texture in Elemental Tellurium with Chiral Crystal Structure

“…1a,b. To the best of our knowledge, the band structure of tellurium has been established before the 1970s by theoretical [20][21][22][23][24][25] and experimental 18,26,27 studies, which identified a gap size of 0.32 eV 18,19 and the valence band maxima (VBM) located slightly off the H-and H'-point (Fig. 1f).…”

Electronic and thermoelectric properties of van der Waals materials with ring-shaped valence bands

“…Another qualitative change that occurs in a number of 2D materials is the inversion of the parabolic dispersion at a band extremum into a 'Mexican hat' dispersion. [2][3][4] Mexican hat dispersions are also referred to as a Lifshiftz transition 3,5,6 , an electronic topological transition 7 or a camel-back dispersion 8,9 .…”