JP6947349B2 - Thermoelectric generator - Google Patents

Description

The present invention relates to a thermoelectric power generation device.

A thermoelectric power generator is a device that uses renewable energy to generate electrical energy from the temperature difference in the environment. The thermoelectric power generation device can increase the output by forming a large temperature gradient in the thermoelectric conversion element. In order to form a temperature gradient, it was considered advantageous to increase the length of the thermoelectric conversion element in order to make the parasitic thermal resistance other than the thermoelectric conversion element relatively small.

As a thermoelectric power generation device, for example, Patent Document 1 is disclosed. The thermoelectric power generation device of Patent Document 1 includes a plurality of thermoelectric conversion elements and an electric wiring board connected to the upper and lower ends of the thermoelectric conversion element, and the electric wiring board at the upper end is heated and the electric wiring board at the lower end is cooled. Has been done. The thermoelectric conversion element of Patent Document 1 has a temperature gradient in the height direction.

Japanese Unexamined Patent Publication No. 2016-9779

FIG. 7 shows the result of obtaining the scaling law in the conventional thermoelectric power generation device 100. The thermoelectric power generation device 100 includes a P-type thermoelectric conversion unit 108 and an N-type thermoelectric conversion unit 110 having a long length in the height direction. The P-type thermoelectric conversion unit 108 and the N-type thermoelectric conversion unit 110 are electrically connected to the electrode 106 at the lower end and to the electrode 112 at the upper end. Assuming that the width of the P-type thermoelectric conversion unit 108 and the height of the N-type thermoelectric conversion unit 110 are L and the height is H, the maximum output P when the parasitic thermal resistance is negligible is P = (S ^{2 HσΔT 2} ) / (32H). ² ). Here, S and σ represent the Seebeck coefficient and the electric conductivity of the thermoelectric converter, respectively. ΔT is the temperature difference between both ends of the thermoelectric conversion unit. Therefore, in the case of the conventional thermoelectric power generation device 100, it is not possible to increase the output even if the width L is reduced. That is, the conventional thermoelectric power generation device 100 has a problem that a high output cannot be obtained even if it is miniaturized.

An object of the present invention is to provide a thermoelectric power generation device that can be miniaturized to obtain a high output.

The thermoelectric power generation device according to the present invention includes a substrate, a thermoelectric conversion element on the surface of the substrate, and a heat conductive portion thermally connected to the thermoelectric conversion element, and the thermoelectric conversion element includes at least a pair of thermoelectric conversion elements. It has a P-type thermoelectric conversion unit and an N-type thermoelectric conversion unit, and the heat conduction unit is thermally connected to one end side of the P-type thermoelectric conversion unit and the N-type thermoelectric conversion unit in a direction parallel to the substrate surface. It is characterized by being connected.

According to the present invention, the length and width of the thermoelectric conversion element can be minimized and miniaturized to increase the output.

It is a front view which shows the use state of the thermoelectric power generation apparatus which concerns on this embodiment. It is a top view which shows the structure of the thermoelectric power generation apparatus which concerns on this embodiment. It is a vertical cross-sectional view which shows the manufacturing method of the thermoelectric power generation apparatus which concerns on this embodiment stepwise, FIG. 3C is the stage where the pattern is formed on the oxide film, FIG. 3D is the stage where the metal film is formed, FIG. 3E is the stage where the metal film and the pattern are removed, and FIG. 3F is the stage where the heat conductive portion is formed. FIG. 4A is a diagram showing the results of simulation, and FIG. 4B is a diagram showing the results of contouring the temperature distribution of FIG. 4A. It is a graph which shows the relationship between the position and temperature of a thermoelectric conversion element. It is a perspective view which provides the explanation of the scaling law in the thermoelectric power generation apparatus which concerns on this embodiment. It is a perspective view which provides the explanation of the scaling law in the conventional thermoelectric power generation apparatus.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. The thermoelectric power generation device 10 shown in FIG. 1 includes a substrate 12, a thermoelectric conversion element 14 on the surface of the substrate 12, and a heat conductive portion 16 thermally connected to the thermoelectric conversion element 14. The thermoelectric power generation device 10 is thermally connected to the heat source through the heat conductive portion 16.

_{The substrate 12 has a SiO 2} layer 17 as an insulating layer on its surface. A Si substrate can be used as the substrate 12. A diamond substrate can also be used for the substrate 12, and in this case, the insulating layer 17 becomes unnecessary. In the case of the present embodiment, the substrate 12 has a Si layer 15 and a SiO ₂ layer 17 on the Si layer 15.

The thermoelectric conversion element 14 has one or more (two in the case of this figure) a pair of P-type thermoelectric conversion units 18 and an N-type thermoelectric conversion unit 20. The materials of the P-type thermoelectric conversion unit 18 and the N-type thermoelectric conversion unit 20 are Si, Ge, SiGe, CrSi ₂ , FeSi ₂ , MnSi, Mg ₂ Si, Mg ₂ Ge, CoSb ₃ , AgSbTe ₂ , SnTe, PbTe, BiSe. ₃ , Sb ₂ Te ₃ , Bi ₂ Te _{3 are} selected. For microfabrication, the materials of the P-type thermoelectric conversion unit 18 and the N-type thermoelectric conversion unit 20 are preferably Si, Ge or SiGe. When Si is used in the thermoelectric conversion unit, the P-type dopant is B, Al, Ga, and the N-type dopant is P, As, Sb.

The P-type thermoelectric conversion unit 18 and the N-type thermoelectric conversion unit 20 can obtain a sufficient temperature gradient if the length L from one end to the other end in the direction parallel to the surface of the substrate 12 is 500 nm. The length L of the P-type thermoelectric conversion unit 18 and the N-type thermoelectric conversion unit 20 is more preferably 200 nm or less. The lower limit of the length L of the P-type thermoelectric conversion unit 18 and the N-type thermoelectric conversion unit 20 is not particularly limited, but is about 10 nm at the time of filing the present patent application from the viewpoint of workability. The height H of the P-type thermoelectric conversion unit 18 and the N-type thermoelectric conversion unit 20 is preferably a length L or more.

The thermoelectric conversion element 14 has an electric conduction unit 26 between the P-type thermoelectric conversion unit 18 and the N-type thermoelectric conversion unit 20. The material of the electrical conduction portion 26 is _{selected from NiSi, NiSi 2} , CoSi, TiSi ₂ , and ErSi.

In the case of the present embodiment, the thermoelectric conversion element 14 has two sets of the P-type thermoelectric conversion unit 18 and the N-type thermoelectric conversion unit 20 with the electric conduction unit 26 sandwiched between them, and the two sets of the P-type thermoelectric conversion unit 18. It has an electrical conduction unit 26 sandwiched between N-type thermoelectric conversion units 20 and electrodes 32 and 34 arranged on both sides of the substrate 12. The electrode 32 is electrically connected to the adjacent N-type thermoelectric conversion unit 20, and the electrode 34 is electrically connected to the adjacent P-type thermoelectric conversion unit 18.

Material of the heat conducting portion 16, an insulating material which has a thermal conductivity, for example, selected AlN, BN, BeO, from _Si 2 _{N 3.} A plurality of (three in the case of this figure) thermoelectric conversion elements 16 are provided on the thermoelectric conversion element 14 including the thermoelectric conversion element 14, the electric conduction unit 26, and the electrodes 32 and 34. In the case of the present embodiment, the space 30 between the heat conductive portions 16 contains the same gas such as the atmosphere as the surroundings of the thermoelectric power generation device 10.

The central heat conductive portion 16A is arranged on the central electric conductive portion 26A. One end of the heat conductive portion 16A in the length direction is attached to one end 24 of the P-type thermoelectric conversion unit 18A arranged on one side of the electric conductive portion 26A and one end 22 of the N-type thermoelectric conversion unit 20A arranged on the other side. Each is thermally connected. An electric conduction portion 26A is arranged between one end 24 of the P-type thermoelectric conversion unit 18A and one end 22 of the N-type thermoelectric conversion unit 20A.

The heat conductive portion 16B on one side (left side in the drawing) of the surface of the substrate 12 is arranged on the electrode 32. One end of the heat conductive portion 16B in the length direction is thermally connected to one end 22 of the N-type thermoelectric conversion unit 20 electrically connected to the electrode 32.

The heat conductive portion 16C on the other side (right side in the drawing) of the surface of the substrate 12 is arranged on the electrode 34. One end of the heat conductive portion 16C in the length direction is thermally connected to one end 24 of the P-type thermoelectric conversion unit 18 electrically connected to the electrode 34.

As described above, the heat conductive portion 16 is thermally connected to one end 24 of the P-type thermoelectric conversion unit 18 and one end 22 of the N-type thermoelectric conversion unit 20 in a direction parallel to the surface of the substrate 12. .. An electrical conduction portion 26B is arranged between the other end 25 of the P-type thermoelectric conversion unit 18A and the other end 23 of the N-type thermoelectric conversion unit 20B. An electric conduction portion 26C is arranged between the other end 25 of the P-type thermoelectric conversion unit 18B and the other end 23 of the N-type thermoelectric conversion unit 20A.

In the P-type thermoelectric conversion unit 18, one end 24 that is thermally connected to the heat conductive unit 16 is a high temperature part, and the other end 25 is a low temperature part. In the N-type thermoelectric conversion unit 20, one end 22 thermally connected to the heat conductive unit 16 is a high temperature part, and the other end 23 is a low temperature part. In the P-type thermoelectric conversion unit 18 and the N-type thermoelectric conversion unit 20, a temperature gradient is generated between the high temperature portion and the low temperature portion.

The other end of the heat conductive portion 16 is thermally connected to the heat bath 28. The heat bath 28 can be, for example, Cu, Au, Ag, BN, or diamond.

As shown in FIG. 2, the thermoelectric conversion element 14 may have the same width D as the length L. The thermoelectric conversion element has a nanowire shape extending linearly from the electrode 32 to the electrode 34, and a plurality of (8 in the case of this figure) are arranged in parallel and connected to the electrodes 32 and 34.

Next, a method of manufacturing the thermoelectric power generation device 10 will be described with reference to FIG. _{First, the Si layer on the SiO 2} layer 17 as an insulating layer is subjected to N-type doping to form an N-type thermoelectric conversion layer (n—Si layer) 40 (FIG. 3A). Next, after the photoresist mask 44 is selectively formed, the N-type thermoelectric conversion layer at the opening of the photoresist mask is subjected to P-type doping to form a P-type thermoelectric conversion unit (p—Si unit) 18 (FIG. 3B).

Then, the photoresist mask 44 is removed using an organic solvent. Next, an oxide film 46 is formed by using a chemical vapor deposition (CVD) method. A photoresist mask 48 is selectively formed on the oxide film 46 (FIG. 3C).

The oxide film at the opening of the photoresist mask 48 is removed by etching to form the oxide mask 47. Then, the photoresist mask is removed using an organic solvent. Then, for example, a Ni film 50 is formed as a metal film by using a sputtering method (FIG. 3D). Then, annealing treatment is performed under the conditions of 400 to 600 ° C. By the annealing treatment, a part of the N-type heat conduction conversion layer (n—Si layer 15) 40 not covered with the oxide film mask 47 is alloyed (NiSi). After the annealing treatment, the metal film and the oxide mask are removed and flattened by chemical mechanical polishing (CMP) (FIG. 3E). In this way, the thermoelectric conversion element 14 is formed on the substrate 12.

Next, after selectively forming the photoresist mask, an AlN layer as a heat conductive material layer is formed. By removing the photoresist mask using an organic solvent, the heat conductive material layer formed on the photoresist mask is also removed by lift-off, and the heat conductive portion 16 is formed on the thermoelectric conversion element 14 (FIG. 3F). .. As described above, the thermoelectric power generation device 10 can be manufactured.

The thermoelectric power generation device 10 of the present embodiment is used by thermally connecting the other end of the heat conductive portion 16 to the heat bath 28. The heat of the heat bath 28 is transferred from the other end of the heat conductive portion 16 to one end, and heats the one end 24 side of the P-type thermoelectric conversion unit 18 and the one end 22 side of the N-type thermoelectric conversion unit 20.

Since only one end 24 of the P-type thermoelectric conversion unit 18 is thermally connected to the heat conductive unit 16, a temperature difference occurs between the one end 24 and the other end 25. That is, the P-type thermoelectric conversion unit 18 has a temperature gradient in which the temperature decreases from one end 24 to the other end 25. Since only one end 22 of the N-type thermoelectric conversion unit 20 is thermally connected to the heat conductive unit 16, a temperature difference occurs between the one end 22 and the other end 23. That is, the N-type thermoelectric conversion unit 20 has a temperature gradient in which the temperature decreases from one end 22 to the other end 23. Due to this temperature gradient, the holes in the P-type thermoelectric conversion unit 18 move from one end 24 to the other end 25, and the electrons in the N-type thermoelectric conversion unit 20 move from one end 22 to the other end 23. In this way, the holes in the P-type thermoelectric conversion unit 18 and the electrons in the N-type thermoelectric conversion unit 20 recombine through the electrical conduction unit 26 to generate a voltage. This voltage is output to the outside from the electrodes 32 and 34 at both ends.

The thermoelectric power generation device 10 of the present embodiment utilizes a temperature gradient generated by heat conducted from the heat conductive portion 16 in a region of several hundred nm in a direction parallel to the surface of the substrate 12 in the thermoelectric conversion element 14.

The figures shown in FIGS. 4A and 4B show the results of simulating temperature changes in a thermoelectric power generation device similar to the thermoelectric power generation device 10 of the present embodiment. The thermoelectric power generation device in this figure _{has a plurality of wire-shaped heat conversion elements 56 on the SiO 2} layer 54, and a heat conduction portion 52 on the heat conversion element 56. The material of the thermoelectric conversion element 56 was Si, and the material of the heat conductive portion 52 was AlN. In this figure, it is shown that the temperature is highest in white and decreases as the color becomes darker. It was confirmed that the temperature of the heat conductive portion 52 was the highest, and the temperature gradually decreased toward the periphery of the heat conductive portion 16.

From the results of FIGS. 4 and 4B, FIG. 5 shows the results of examining the relationship between the distance from the heat conductive portion 52 of the thermoelectric conversion element 56 and the temperature according to the length of the thermoelectric conversion element 14. In FIG. 5, the horizontal axis represents the position (μm) of the thermoelectric conversion element, and the vertical axis represents the temperature (K). The length of the thermoelectric conversion element 56 was 10, 50, 100, 500 nm.

From this figure, it was confirmed that even when the length of the thermoelectric conversion element 56 is 500 nm, a temperature gradient of about 50 K is generated, and that the shorter the length, the steeper the temperature gradient can be obtained, especially at 200 nm or less. rice field.

FIG. 6 shows the result of obtaining the scaling law in the thermoelectric power generation device 10 according to the present embodiment. Assuming that the length and width of the thermoelectric conversion element 14 are L and the height is H, the output P is P = (S ^{2 HσΔT 2} ) / (32L ² ). That is, in the case of the thermoelectric power generation device 10 of the present embodiment, the length and width L of the thermoelectric conversion element 14 can be minimized and miniaturized to increase the output.

The present invention is not limited to the above embodiment, and can be appropriately modified within the scope of the gist of the present invention.

For example, in the case of the above embodiment, the case where the electric conduction unit 26 is provided between the P-type thermoelectric conversion unit 18 and the N-type thermoelectric conversion unit 20 has been described, but the present invention is not limited to this, and electricity is not limited to this. The conduction portion 26 may be omitted.

The case where the thermoelectric conversion element 14 has two sets of the P-type thermoelectric conversion unit 18 and the N-type conversion element with the electric conduction unit 26 sandwiched between them has been described, but the present invention is not limited to this, and one set or three sets or more. May be.

Although the case where the thermoelectric power generation device 10 includes eight thermoelectric conversion elements 14 has been described, the present invention is not limited to this, and the number may be 7 or less or 9 or more.

The case where the space 30 between the heat conductive portions 16 has the same gas such as the atmosphere around the thermoelectric power generation device 10 has been described, but the present invention is not limited to this, and the present invention is not limited to this, and the material has low heat conductivity and is insulating. For example, the space 30 may be filled with a perylene-based or epoxy-based resin or porous silica. The space 30 may be evacuated. The space 30 can be evacuated by arranging the non-evaporative getter material inside the space 30 and adsorbing the active gas in the space 30 to the non-evaporative getter material. The non-evaporative getter material is selected from Ti, Zr, Nb, Ta, V, Hf and a mixture thereof.

The thermoelectric power generation device 10 operates even when the temperature of the heat bath 28 is lower than that of the substrate 12. In this case, the polarities of the electromotive forces generated in the electrodes 32 and 34 are reversed.

The thermoelectric power generation device 10 also operates as a Perche cooler. By passing an electric current between the electrodes 32 and 34, a temperature difference can be provided between the heat bath 28 and the substrate 12.

10 Thermoelectric power generation device 12 Substrate 14 Thermoelectric conversion element 15 Si layer 16 Heat conduction part 16A, 16B, 16C Heat conduction part 16B Heat conduction part 16C Heat conduction part 17 SiO ₂ layers 18 P type thermoelectric conversion part 20 N type thermoelectric conversion part 22 One end 24 One end 26 Electric conduction part 26A, 26B, 26C Electric conduction part

Claims (3)

With the board
A thermoelectric conversion element provided on the surface of the substrate and
It is provided with a heat conductive portion provided on the thermoelectric conversion element.
The thermoelectric conversion element includes a P-type thermoelectric conversion unit, an N-type thermoelectric conversion unit, and a first electrode or first electricity arranged on one end side of the P-type thermoelectric conversion unit in a direction parallel to the substrate surface. A conduction portion, a second electrode or a second electrical conduction portion arranged on one end side in a direction parallel to the substrate surface of the N-type thermoelectric conversion portion, and a parallel to the substrate surface of the P-type thermoelectric conversion portion. It has a third electrical conduction portion sandwiched between the other end side in the above direction and the other end side in the direction parallel to the substrate surface of the N-type thermoelectric conversion unit.
The length from the one end to the other end of the P-type thermoelectric conversion unit and the length from the one end to the other end of the N-type thermoelectric conversion unit are 500 nm or less.
The thermoelectric conversion element has a nanowire shape and has a nanowire shape.
The heat conductive portion is thermally connected to the heat bath and has a first heat conductive portion and a second heat conductive portion.
The first heat conductive portion is provided on the first electrode or the first electric conductive portion, and is thermally connected to the one end side of the P-type thermoelectric conversion unit.
The second heat conductive portion is provided on the second electrode or the second electric conductive portion, and is thermally connected to the one end side of the N-type thermoelectric conversion unit.
The substrate is a Si substrate or a diamond substrate having a surface layer of _{SiO 2} , and does not have a through hole penetrating the substrate.
The heat bath is heated to a high temperature with respect to the substrate .
The P-type thermoelectric conversion unit and the N-type thermoelectric conversion unit are thermoelectric power generation devices in which a temperature gradient is generated between one end and the other end in a direction parallel to the surface of the substrate. The thermoelectric conversion element, a thermoelectric power generating device according to claim 1, characterized in that it contains at least one Si and Ge. The thermoelectric power generation device according to claim 1 or 2 , wherein the thermoelectric conversion element is a nanowire having a plane length of the substrate of 200 nm or less.

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