WO-2026093700-A1 - THERMOELECTRIC MATERIAL WITH LARGE POWER FACTOR

Abstract

A structure for use in a thermoelectric generator, comprising a matrix comprising an arrangement of cavities, wherein the matrix is a semi-conductor. A dopant substance is disposed within the cavities and configured to modify the potential energy band profile of the matrix, such that, the potential energy band profile becomes non-uniform along a transport direction of the structure. The transport direction is the direction which, in use, current is configured to flow through the structure. The spacing between cavities along the transport direction is substantially consistent throughout the matrix.

Assignees

• THE UNIVERSITY OF WARWICK

Dates

Publication Date

20260507

Application Date

20250908

Priority Date

20241104

Claims (16)

1. 1. A structure for use in a thermoelectric generator, comprising: a matrix formed of, or comprising, a semi-conductor material, wherein the matrix comprises an arrangement of cavities; and a dopant substance disposed within the cavities and configured to modify the potential energy band profile of the matrix, such that, the potential energy band profile becomes non-uniform along a transport direction of the structure; wherein the transport direction is the direction which, in use, current is configured to flow through the structure; and wherein the spacing between cavities along the transport direction is substantially consistent throughout the matrix.
2. 2. The structure of claim 1, wherein the cavities extend through the matrix in a direction substantially perpendicular to the transport direction.
3. 3. The structure of claim 1 or claim 2, wherein the dopant substance is configured to modify the shape of the conduction band energy profile of the matrix by lowering the conduction band energy profile proximate the cavities.
4. 4. The structure of claim 3, wherein the dopant substance is configured to modify the shape of the conduction band energy profile of the matrix by: lowering the conduction band energy profile proximate the cavities below the Fermi energy of the matrix; and keeping the conduction band energy profile energy within 0-5kflT of the Fermi energy of the matrix in regions distal from the cavities.
5. 5. The structure of claim 1 or claim 2, wherein the dopant substance is configured to modify the shape of the valence band energy profile of the matrix by increasing the valence band energy profile proximate the cavities.
6. 6. The structure of claim 5, wherein the dopant substance is configured to modify the shape of the valence band energy profile of the matrix by: increasing the valence band energy profile proximate the cavities above the Fermi energy of the matrix; and keeping the valence band energy profile within 0-5kflT of the Fermi energy of the matrix in regions distal from the cavities.
7. 7. The structure of any preceding claim, wherein the average distance between adjacent cavities along the transport direction is less than three times the energy relaxation mean-free-path of the semi-conductor material.
8. 8. The structure of any preceding claim, wherein the average distance between adjacent cavities along the transport direction is less than 2 times the energy relaxation mean-free-path of the semi-conductor material.
9. 9. The structure of any preceding claim, wherein the average distance between adjacent cavities along the transport direction is between 5-200nm.
10. 10. The structure of any preceding claim, wherein the average distance between adjacent cavities along the transport direction is between 5-150nm.
11. 11. The structure of any preceding claim, wherein the average distance between adjacent cavities along the transport direction is between 50-150nm.
12. 12. The structure of any preceding claim, wherein the dopant substance is: (i) an electrolyte, wherein the redox level of the electrolyte differs from the Fermi energy of the semi-conductor material; (ii) a conductor, wherein the workfunction of the conductor differs from the Fermi energy of the semi-conductor material; or (iii) a semiconductor, wherein the Fermi energy of the semiconductor differs from the Fermi energy of the semi-conductor material.
13. 13. The structure of any preceding claim, wherein the porosity of the matrix is between 10-60% by volume.
14. 14. The structure of claim 11, wherein the porosity of the matrix is between 20-50% by volume; and, optionally or preferably, wherein the porosity of the matrix is between 20-40% by volume.
15. 15. The structure of any preceding claim, wherein the matrix is a crystalline, or semi-crystalline, semi-conductor.
16. 16. A thermoelectric generator comprising the thermoelectric structure of any preceding claim.

Description

THERMOELECTRIC MATERIAL WITH LARGE POWER FACTOR The invention relates generally to a thermoelectric material. More particularly, but not exclusively, the invention relates to a thermoelectric material comprising a plurality of cavities filled with a dopant substance. Background Thermoelectric generators (TEGs) convert temperature gradients across a material directly into electricity, and vice versa. They can play a major role in the search for sustainable paths for energy harvesting and cooling in a variety of applications. However, large scale exploitation of TEGs has been limited by the high prices, toxicity, scarcity, and the low efficiencies of the prominent thermoelectric (TE) materials. Thermoelectric performance is quantified by the figure of merit ZT = r>S2T (Ke Ki,). where a is the electrical conductivity, S is the Seebeck coefficient, T is the absolute temperature, and Ke and KL are the electronic and lattice parts of the thermal conductivity, respectively. The product aS2 is called the power factor (PF). Over the last two decades, progress on thermoelectric materials has been rapidly expanding with the synthesis of a myriad of new materials and their alloys, while ZTs increased by more than two-fold reaching values close to ZT ~ 3 in some cases. Most of this increase is a result of thermal conductivity reduction through nano structuring and defect engineering, which increases phonon scattering. However, progress relating to reductions to thermal conductivity via nano structuring is slowing down. It is becoming increasingly clear that any further benefits to ZT must now come from power factor ( .S'2) improvements, which has not experienced similar progress thus far. The lack of progress in the power factor is attributed to the adverse interdependence of the electrical conductivity ( ) and Seebeck coefficient (.S') via charge carrier density, which proves very difficult to overcome. Nano structuring techniques have been proposed to target improvements in o without strong reductions in S, and vice versa, to improve the power factor. For improvements in . material designs that take advantage of modulation doping and gating have been proposed. These designs attempt to create dopant-free material channels with high mobility and conductivity. Modulation doping refers to the addition of a donor material to a base material which donates charge carriers to the base material such that the charge carriers are spatially separated from the donor material. Having the charge carriers move away from the donor reduces carrier-donor scattering, so modulation-doped semiconductors have very high charge carrier mobilities. For the improvements in S, energy filtering of charge carriers is implemented by introducing potential barriers along the transport path of the charge carriers. The addition of a potential barrier favours the transport of hot, high energy charge carriers over cold, low energy charge carriers, thereby leading to increasing the energy of the current flow, and therefore the Seebeck coefficient and Seebeck voltage. Energy filtering has been attempted in nanocomposites and superlattices, where the grain/grain- boundary system in a variety of materials can allow for energy filtering. The approaches described above have been used to achieve marginal increases in power factors. However, the aforementioned interdependence of the electrical conductivity ( ) and Seebeck coefficient (.S') via the carrier density prevents either of these approaches from providing higher power factors. The present invention was devised with the foregoing in mind. Summary of Invention According to a first aspect of the invention, there is provided a structure for use in a thermoelectric generator. The structure may comprise a matrix formed of, or comprising, a semi-conductor material, wherein the matrix comprises an arrangement of cavities. The matrix being formed of a semi-conductor may refer to the matrix itself being a semi-conductor. The matrix may be a crystalline semi-conductor. The matrix be a semi-conductor which is at least partly crystalline (e.g., semi-crystalline). The presence of cavities may enable the insertion of dopant substances at regular intervals without substantially increasing the number of impurities in the structure of the matrix. The semi-conductor material may comprise dopant atoms. The semi-conductor material may be positively doped. The semi-conductor material may be negatively doped. The semi-conductor material may be undoped. The cavities may be a plurality of holes extending at least partially through the matrix. The cavities may be a plurality of holes extending at least partially through the matrix substantially perpendicular to the transport direction. The cavities may be a plurality of holes extending through the matrix between an upper and lower surface of the matrix. The cavities may be cylindrical, or substantially cylindrical, holes. The cavities may be holes which are cylindrical but wi