Potential Thermoelectric Performance from Optimization of Hole-DopedBi2Se3

Abstract

We present an analysis of the potential thermoelectric performance of hole-doped Bi 2 Se 3 , which is commonly considered to show inferior room temperature performance when compared to (2008).]) the material may show optimized ZT values of unity or more in the 300-500 K temperature range and thus be suitable for cooling and moderate temperature waste heat recovery and thermoelectric solar cell applications. Central to this conclusion are the larger band gap and the relatively heavier valence bands of Bi 2 Se 3 .

Experimental study of the valence band ofBi2Se3

“…This paper further concludes by presenting a rationale for the discrepancy in calculated properties 11 and the experimental measurements, and then suggest a more fundamental explanation related to the presence of Van der Waals interlayer bonds in Bi 2 Se 3 material. The density functional theory used in Ref [11] is less accurate in solids with such weak bonding, and in fact the development of new Van der Waals energy functionals is an active and ongoing area of research. 14 This second conclusion is likely to have implications for band structure calculations of many of today's bulk 2-dimensional-like solids.…”

“…The valence band mass is only about 20% heavier than the conduction band mass,3 , 4 and significantly smaller than predicted by the calculations. 11 A first conclusion of this paper is that p-type Bi 2 Se 3 is not likely to be a significantly better thermoelectric semiconductor than any n-type variant of this material. This paper further concludes by presenting a rationale for the discrepancy in calculated properties 11 and the experimental measurements, and then suggest a more fundamental explanation related to the presence of Van der Waals interlayer bonds in Bi 2 Se 3 material.…”

“…11 The existence of high-mobility p-type near the band gap and the Fermi level, whereas Bi 2 Se 3 has only one in the center (Γ point) of the Brillouin zone. Higher band degeneracy improves zT because it increases density of states effective mass, which allows the material to have a higher carrier concentration and therefore better electrical conductivity without affecting the thermopower.…”

“…The valence band, however, is more complex. 11 We show in Fig. 1 the hole Fermi surface (generated from data in Ref [11] using code in Ref [12]) for hole concentrations of 6x10 18 cm -3 and 4x10 19 cm -3 respectively.…”

“…11 A first conclusion of this paper is that p-type Bi 2 Se 3 is not likely to be a significantly better thermoelectric semiconductor than any n-type variant of this material. This paper further concludes by presenting a rationale for the discrepancy in calculated properties 11 and the experimental measurements, and then suggest a more fundamental explanation related to the presence of Van der Waals interlayer bonds in Bi 2 Se 3 material. The density functional theory used in Ref [11] is less accurate in solids with such weak bonding, and in fact the development of new Van der Waals energy functionals is an active and ongoing area of research.…”