Enhanced thermoelectric performance of a quintuple layer of Bi2Te3

J Zhang and HJ Liu and L Cheng and J Wei and J Shi and XF Tang and C Uher, JOURNAL OF APPLIED PHYSICS, 116, 023706 (2014).

DOI: 10.1063/1.4889921

The electronic structure of a quintuple layer (QL) of Bi2Te3 is calculated using the first-principles pseudopotential method. It is found that the band gap of an isolated QL is considerably larger than that of bulk Bi2Te3. The electronic transport of the QL is, then, evaluated using the semiclassical Boltzmann theory within the relaxation time approximation. By fitting the energy surface from first-principles calculations, a suitable Morse potential is constructed and used to predicate the lattice thermal conductivity via equilibrium molecular dynamics simulations. By optimizing the carrier concentration of the system, the ZT of Bi2Te3 QL can be enhanced to a relatively high value. Moreover, the ZT value exhibits strong temperature dependence and can reach as high as 2.0 at 800 K. This value can be further increased to 2.2 by the substitution of Bi atoms with Sb atoms, giving nominal formula of (Bi0.25Sb0.75)(2)Te-3. The significantly enhanced ZT value makes QL a very appealing candidate for thermoelectric applications. (C) 2014 AIP Publishing LLC.

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