Impurity clustering and impurity-induced bands in PbTe-, SnTe-, and GeTe-based bulk thermoelectrics

Abstract

Complex multicomponent systems based on PbTe, SnTe, and GeTe are of great interest for infrared devices and high-temperature thermoelectric applications. A deeper understanding of the atomic and electronic structure of these materials is crucial for explaining, predicting, and optimizing their properties, and to suggest new materials for better performance. In this work, we present our first-principles studies of the energy bands associated with various monovalent (Na, K, and Ag) and trivalent (Sb and Bi) impurities and impurity clusters in PbTe, SnTe, and GeTe using supercell models. We find that monovalent and trivalent impurity atoms tend to come close to one another and form impurity-rich clusters, and the electronic structure of the host materials is strongly perturbed by the impurities. There are impurity-induced bands associated with the trivalent impurities that split off from the conduction-band bottom with large shifts towards the valence-band top. This is due to the interaction between the $p$ states of the trivalent impurity cation and the divalent anion which tends to drive the systems towards metallicity. The introduction of monovalent impurities (in the presence of trivalent impurities) significantly reduces (in PbTe and GeTe) or slightly enhances (in SnTe) the effect of the trivalent impurities. One, therefore, can tailor the band gap and band structure near the band gap (hence transport properties) by choosing the type of impurity and its concentration or tuning the monovalent/trivalent ratio. Based on the calculated band structures, we are able to explain qualitatively the measured transport properties of the whole class of PbTe-, SnTe-, and GeTe-based bulk thermoelectrics.

37 pages, 13 figures, 2 tables; added new figures and paragraphs; to appear in Phys. Rev. B

References in corpus (4)

• Resonant States in the Electronic Structure of the High Performance Thermoelectrics AgPb${}_{m}SbTe$_{2+m}$ ; The Role of Ag-Sb Microstructures
• Ab initio studies of electronic structure of defects in PbTe
• Thermal conductivity of the A_xBO_2 type layered oxides Na_0.77MnO_2 and LiCoO_2
• Charge ordering and self-assembled nanostructures in a fcc Coulomb lattice gas

Cited by in corpus (7)

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• Review of Nanolayered Post-transition Metal Monochalcogenides: Synthesis, Properties, and Applications
• Defects responsible for abnormal n-type conductivity in Ag-excess doped PbTe thermoelectrics
• Fermi surface evolution of Na-doped PbTe studied through density functional theory calculations and Shubnikov-de Haas measurements
• Persistence of symmetry-protected Dirac points at the surface of the topological crystalline insulator SnTe upon impurity doping
• Bonding Hierarchy and Coordination Interaction Leading to High Thermoelectricity in Wide Bandgap TlAgI2
• Lattice dynamical origin of peak thermoelectric performance in AgPbmSbTe2+m observed by inelastic neutron scattering