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Enhanced thermoelectric efficiency of porous silicene nanoribbons.

Sadeghi H, Sangtarash S, Lambert CJ - Sci Rep (2015)

Bottom Line: Including the effect of phonons yields a value for the full figure of merit of ZT = 3.5.As a method of tuning the Fermi energy, we analyse the effect of doping the silicene with either a strong electron donor (TTF) or a strong electron acceptor (TCNQ) and demonstrate that adsorbed layers of the former increases ZTe to a value of 3.1, which is insensitive to temperature over the range 100 K - 400 K.This combination of a high, temperature-insensitive ZTe, and the ability to choose the sign of the thermopower identifies nanoporous silicene as an ideal thermoelectric material with the potential for unprecedented performance.

View Article: PubMed Central - PubMed

Affiliation: Quantum Technology Centre, Lancaster University, LA1 4YB Lancaster, UK.

ABSTRACT
There is a critical need to attain new sustainable materials for direct upgrade of waste heat to electrical energy via the thermoelectric effect. Here we demonstrate that the thermoelectric performance of silicene nanoribbons can be improved dramatically by introducing nanopores and tuning the Fermi energy. We predict that values of electronic thermoelectric figure of merit ZTe up to 160 are achievable, provided the Fermi energy is located approximately 100 meV above the charge neutrality point. Including the effect of phonons yields a value for the full figure of merit of ZT = 3.5. Furthermore the sign of the thermopower S can be varied with achievable values as high as S = +/- 500 μV/K. As a method of tuning the Fermi energy, we analyse the effect of doping the silicene with either a strong electron donor (TTF) or a strong electron acceptor (TCNQ) and demonstrate that adsorbed layers of the former increases ZTe to a value of 3.1, which is insensitive to temperature over the range 100 K - 400 K. This combination of a high, temperature-insensitive ZTe, and the ability to choose the sign of the thermopower identifies nanoporous silicene as an ideal thermoelectric material with the potential for unprecedented performance.

No MeSH data available.


Related in: MedlinePlus

Sketch of the molecular structure of the Silicene and its alloys.(a) silicene molecular structure, (b) a TTF (top) and TCNQ (bottom) doped silicene ribbon with two layers of dopant, (c) silicene monolayer ribbon with hydrogen terminated edges (ZSiNR-H), (d) silicene monolayer containing a nanopore (ZSiNR-P). All edges are terminated with hydrogen. (e) silicene monolayer ribbon with an oxygen terminated scattering region and hydrogen terminated electrodes (ZSiNR-HO), (f) silicene monolayer ribbon with oxygen terminated edges (ZSiNR-O), (g) as for (d), but with adsorbed Tetracyanoquinodimethane (TCNQ) and (h) as for (d), but with adsorbed Tetrathiafulvalene (TTF).
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f1: Sketch of the molecular structure of the Silicene and its alloys.(a) silicene molecular structure, (b) a TTF (top) and TCNQ (bottom) doped silicene ribbon with two layers of dopant, (c) silicene monolayer ribbon with hydrogen terminated edges (ZSiNR-H), (d) silicene monolayer containing a nanopore (ZSiNR-P). All edges are terminated with hydrogen. (e) silicene monolayer ribbon with an oxygen terminated scattering region and hydrogen terminated electrodes (ZSiNR-HO), (f) silicene monolayer ribbon with oxygen terminated edges (ZSiNR-O), (g) as for (d), but with adsorbed Tetracyanoquinodimethane (TCNQ) and (h) as for (d), but with adsorbed Tetrathiafulvalene (TTF).

Mentions: We have calculated the electronic contribution to the thermal conductance, the Seebeck and Peltier coefficients and ZTe for the structures shown in Figure 1c–h. The optimized lattice constant (a0) and buckling (d) of the silicene nanoribbon shown in Figure 1a are found to be 3.6 Å and 0.53 Å, respectively, similar to that reported elsewhere103247. The engineered silicene nanoribbons shown in Figure 1 include: a zigzag monolayer silicene nanoribbon with hydrogen terminated edges (ZSiNR-H, Figure 1c), a zigzag monolayer silicene nanoribbon containing a nanopore with all edges terminated by hydrogen (ZSiNR-P, Figure 1d), a zigzag monolayer silicene nanoribbon with a central region containing oxygen terminated edges, connected to hydrogen-terminated leads (ZSiNR-HO, Figure 1e), and a zigzag monolayer silicene nanoribbon with oxygen terminated edges (ZSiNR-O, Figure 1f). The nanoribbons length and width in all cases are almost equal (L ≈ 6 nm (scattering region ≈ 3.48 nm), W ≈ 3 nm) and the pore diameter is ≈1.3 nm. We shall find that a key strategy for improving the thermoelectric performance of these structures involves tuning the Fermi energy (EF). As an example of how this could be achieved, we investigated the effect of introducing adsorbates onto the surface of the ZSiNR-P hydrogen-terminated nanoribbon, as shown in Figures 1f and 1g. The latter show examples of such functionalised ribbons containing adsorbed TTF (a strong electron donor) and TCNQ (a strong electron acceptor), which form charge-transfer complexes with the silicene.


Enhanced thermoelectric efficiency of porous silicene nanoribbons.

Sadeghi H, Sangtarash S, Lambert CJ - Sci Rep (2015)

Sketch of the molecular structure of the Silicene and its alloys.(a) silicene molecular structure, (b) a TTF (top) and TCNQ (bottom) doped silicene ribbon with two layers of dopant, (c) silicene monolayer ribbon with hydrogen terminated edges (ZSiNR-H), (d) silicene monolayer containing a nanopore (ZSiNR-P). All edges are terminated with hydrogen. (e) silicene monolayer ribbon with an oxygen terminated scattering region and hydrogen terminated electrodes (ZSiNR-HO), (f) silicene monolayer ribbon with oxygen terminated edges (ZSiNR-O), (g) as for (d), but with adsorbed Tetracyanoquinodimethane (TCNQ) and (h) as for (d), but with adsorbed Tetrathiafulvalene (TTF).
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4377624&req=5

f1: Sketch of the molecular structure of the Silicene and its alloys.(a) silicene molecular structure, (b) a TTF (top) and TCNQ (bottom) doped silicene ribbon with two layers of dopant, (c) silicene monolayer ribbon with hydrogen terminated edges (ZSiNR-H), (d) silicene monolayer containing a nanopore (ZSiNR-P). All edges are terminated with hydrogen. (e) silicene monolayer ribbon with an oxygen terminated scattering region and hydrogen terminated electrodes (ZSiNR-HO), (f) silicene monolayer ribbon with oxygen terminated edges (ZSiNR-O), (g) as for (d), but with adsorbed Tetracyanoquinodimethane (TCNQ) and (h) as for (d), but with adsorbed Tetrathiafulvalene (TTF).
Mentions: We have calculated the electronic contribution to the thermal conductance, the Seebeck and Peltier coefficients and ZTe for the structures shown in Figure 1c–h. The optimized lattice constant (a0) and buckling (d) of the silicene nanoribbon shown in Figure 1a are found to be 3.6 Å and 0.53 Å, respectively, similar to that reported elsewhere103247. The engineered silicene nanoribbons shown in Figure 1 include: a zigzag monolayer silicene nanoribbon with hydrogen terminated edges (ZSiNR-H, Figure 1c), a zigzag monolayer silicene nanoribbon containing a nanopore with all edges terminated by hydrogen (ZSiNR-P, Figure 1d), a zigzag monolayer silicene nanoribbon with a central region containing oxygen terminated edges, connected to hydrogen-terminated leads (ZSiNR-HO, Figure 1e), and a zigzag monolayer silicene nanoribbon with oxygen terminated edges (ZSiNR-O, Figure 1f). The nanoribbons length and width in all cases are almost equal (L ≈ 6 nm (scattering region ≈ 3.48 nm), W ≈ 3 nm) and the pore diameter is ≈1.3 nm. We shall find that a key strategy for improving the thermoelectric performance of these structures involves tuning the Fermi energy (EF). As an example of how this could be achieved, we investigated the effect of introducing adsorbates onto the surface of the ZSiNR-P hydrogen-terminated nanoribbon, as shown in Figures 1f and 1g. The latter show examples of such functionalised ribbons containing adsorbed TTF (a strong electron donor) and TCNQ (a strong electron acceptor), which form charge-transfer complexes with the silicene.

Bottom Line: Including the effect of phonons yields a value for the full figure of merit of ZT = 3.5.As a method of tuning the Fermi energy, we analyse the effect of doping the silicene with either a strong electron donor (TTF) or a strong electron acceptor (TCNQ) and demonstrate that adsorbed layers of the former increases ZTe to a value of 3.1, which is insensitive to temperature over the range 100 K - 400 K.This combination of a high, temperature-insensitive ZTe, and the ability to choose the sign of the thermopower identifies nanoporous silicene as an ideal thermoelectric material with the potential for unprecedented performance.

View Article: PubMed Central - PubMed

Affiliation: Quantum Technology Centre, Lancaster University, LA1 4YB Lancaster, UK.

ABSTRACT
There is a critical need to attain new sustainable materials for direct upgrade of waste heat to electrical energy via the thermoelectric effect. Here we demonstrate that the thermoelectric performance of silicene nanoribbons can be improved dramatically by introducing nanopores and tuning the Fermi energy. We predict that values of electronic thermoelectric figure of merit ZTe up to 160 are achievable, provided the Fermi energy is located approximately 100 meV above the charge neutrality point. Including the effect of phonons yields a value for the full figure of merit of ZT = 3.5. Furthermore the sign of the thermopower S can be varied with achievable values as high as S = +/- 500 μV/K. As a method of tuning the Fermi energy, we analyse the effect of doping the silicene with either a strong electron donor (TTF) or a strong electron acceptor (TCNQ) and demonstrate that adsorbed layers of the former increases ZTe to a value of 3.1, which is insensitive to temperature over the range 100 K - 400 K. This combination of a high, temperature-insensitive ZTe, and the ability to choose the sign of the thermopower identifies nanoporous silicene as an ideal thermoelectric material with the potential for unprecedented performance.

No MeSH data available.


Related in: MedlinePlus