Enhanced thermoelectric performance of nanostructured topological insulator Bi2Se3

Abstract

To enhance thermoelectric performance by utilizing topological properties of topological insulators has attracted increasing attention. Here, we show that as grain size decreases from microns to ∼80 nm in thickness, the electron mobility μ increases steeply from 12–15 cm2 V−1 s−1 to ∼600 cm2 V−1 s−1, owing to the contribution of increased topologically protected conducting surfaces. Simultaneously, its lattice thermal conductivity is lowered by ∼30%–50% due to enhanced phonon scattering from the increased grain boundaries. As a result, thermoelectric figure of merit, ZT, of all the fine-grained samples is improved. Specifically, a maximum value of ZT = ∼0.63 is achieved for Bi2Se3 at T = ∼570 K.

The surface-to-volume ratio: a key parameter in the thermoelectric transport of topological insulator Bi2Se3nanowires

“…[29][30][31] As a result, the TE coefficients of TIs are no longer intrinsic material properties, rather they are significantly influenced by metallic surface states. [29][30][31] Nonetheless, the role of TISS in TE transport still remains controversial, because some researchers reported enhanced ZT values due to the existence of TISS 14,32,33 while other claim the TISS could degrade TE properties, especially when the surface-to-volume ratio (s/v) is very large. 30,31 In this study, we performed a systematic investigation of the influence of TISS on the TE properties by varying the s/v of Bi 2 Se 3 NWs.…”

Topological insulators for thermoelectrics

“…However, they are mostly attributed to suppression of phonon transportation or filtering of low-energy electrons. 7,87 Sun et al 88 found some evidence of the surface contributions through a series of measurements and analysis. The electron mobility µ in Bi 2 Se 3 nanocomposites produced by milling and sintering is found to increase by 50 times at 300 K, when the grain size decreases from microns to~80 nm in thickness.…”

Thermoelectric Properties of Topological Insulators

“…However, the improvement of their properties was achieved due to a decrease of the lattice thermal conductivity. Some papers report an increase in the power factor in nanograined Bi 2 Se 3 or nanosheets of Bi 2 Se 3 . But the effect, observed in nanograined Bi 2 Se 3 hardly has a topological nature, since, for a formation of topological surface states, a grain of TI should be in direct contact with sufficiently thick layer of a trivial insulator, however, no phase other than Bi 2 Se 3 was present in the samples of ref.…”

“…But the effect, observed in nanograined Bi 2 Se 3 hardly has a topological nature, since, for a formation of topological surface states, a grain of TI should be in direct contact with sufficiently thick layer of a trivial insulator, however, no phase other than Bi 2 Se 3 was present in the samples of ref. . The power factor of the Bi 2 Se 3 nanosheets in principle can increase due to contribution of the surface states, however, the authors of ref.…”

“…There are several experimental studies of TIs, in which the possible contribution of nontrivial surface states to the power factor and the thermoelectric efficiency of these materials is discussed. Obtained results are ambiguous.…”