Thermoelectric conversion element

Abstract

This thermoelectric conversion element comprises: a substrate having a first main surface and a second main surface; a first electrode, an n-type thermoelectric conversion layer, a p-type thermoelectric conversion layer, and a second electrode which are provided on the first main surface; a sealing layer which is provided on the first main surface and covers the first electrode, the n-type thermoelectric conversion layer, the p-type thermoelectric conversion layer, and the second electrode; and a first high-heat conduction part, a second high-heat conduction part, and a low-heat conduction part which are provided on the second main surface. The first electrode, the n-type thermoelectric conversion layer, the p-type thermoelectric conversion layer, and the second electrode are arranged in order along an arrangement direction perpendicular to the thickness direction of the substrate, the first electrode overlaps the first high-heat conduction part in the thickness direction, the second electrode overlaps the second high-heat conduction part in the thickness direction, a contact part between the n-type thermoelectric conversion layer and the p-type thermoelectric conversion layer overlaps the low-heat conduction part in the thickness direction, and the sealing layer constitutes the outermost layer located on the first main surface.

Description

[Technical field]

[0001] The present disclosure relates to a thermoelectric conversion element. [Background technology]

[0002] Thermoelectric conversion elements are sometimes used to generate electricity using geothermal energy or waste heat from factories. The following Patent Document 1 discloses an embodiment in which a flexible substrate having a pattern layer made of a resin layer and a metal layer is provided on both sides of a thermoelectric conversion module having a P-type thermoelectric element material and an N-type thermoelectric element material. In the following Patent Document 1, the metal layer included in one flexible substrate overlaps one electrode included in the thermoelectric conversion module, and the metal layer included in the other flexible substrate overlaps the other electrode included in the thermoelectric conversion module. In the above embodiment, one flexible substrate is in a high temperature state and the other flexible substrate is in a low temperature state, thereby generating a temperature difference in the surface direction of the thermoelectric conversion module. This generates an electromotive force in the thermoelectric conversion module. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent No. 4895293 Summary of the Invention [Problem to be solved by the invention]

[0004] In the thermoelectric conversion element as described above, further improvement in thermoelectric conversion efficiency is required. Therefore, an object of one aspect of the present disclosure is to provide a thermoelectric conversion element capable of improving the thermoelectric conversion efficiency. [Means for solving the problem]

[0005] A thermoelectric conversion element according to one aspect of the present disclosure is as follows. [1] A substrate having a first main surface and a second main surface located opposite to the first main surface, a first electrode provided on the first main surface, an n-type thermoelectric conversion layer electrically connected to the first electrode, a p-type thermoelectric conversion layer in contact with the n-type thermoelectric conversion layer, and a second electrode electrically connected to the p-type thermoelectric conversion layer, a sealing layer provided on the first main surface and covering the first electrode, the n-type thermoelectric conversion layer, the p-type thermoelectric conversion layer, and the second electrode, and a first high thermal conductivity portion, a second high thermal conductivity portion, and a low thermal conductivity portion provided on the second main surface. a first electrode, an n-type thermoelectric conversion layer, a p-type thermoelectric conversion layer, and a second electrode are arranged in order along an arrangement direction perpendicular to the thickness direction of the substrate, the first electrode overlaps a first high thermal conductivity portion in the thickness direction, the second electrode overlaps a second high thermal conductivity portion in the thickness direction, a contact portion between the n-type thermoelectric conversion layer and the p-type thermoelectric conversion layer overlaps a low thermal conductivity portion in the thickness direction, and a sealing layer constitutes an outermost layer located on the first principal surface. [2] The thermoelectric conversion element according to [1], wherein the low thermal conductivity portion has a thermal conductivity of 0.2 W / mK or less. [3] The thermoelectric conversion element according to [1] or [2], wherein the thermal conductivity of the low thermal conductive portion is 0.08 W / mK or less. [4] The thermoelectric conversion element according to any one of [1] to [3], wherein the first high thermal conductivity section and the second high thermal conductivity section have a thermal conductivity of 5 W / mK or more. [5] The thermoelectric conversion element according to any one of [1] to [4], wherein the first electrode and the second electrode have a thermal conductivity of 5 W / mK or more. [6] The thermoelectric conversion element according to any one of [1] to [5], wherein the substrate exhibits flexibility. [7] A thermoelectric conversion element according to any of [1] to [6], wherein a distance from the first high thermal conductivity portion to the contact portion along the arrangement direction is at least five times the length of the first high thermal conductivity portion along the thickness direction, and a distance from the second high thermal conductivity portion to the contact portion along the arrangement direction is at least five times the length of the second high thermal conductivity portion along the thickness direction. Effect of the Invention

[0006] According to one aspect of the present disclosure, it is possible to provide a thermoelectric conversion element capable of improving thermoelectric conversion efficiency. [Brief description of the drawings]

[0007] [Figure 1] FIG. 1 is a schematic cross-sectional view showing a thermoelectric conversion element according to this embodiment. [Diagram 2] FIG. 2 is a schematic cross-sectional view showing the first simulation condition. [Diagram 3] FIGS. 3(a) and 3(b) are graphs showing the results of the first simulation. [Figure 4] FIG. 4 is a schematic cross-sectional view showing the second simulation conditions. [Diagram 5] FIG. 5 is a graph showing the results of the second simulation. [Figure 6] FIG. 6 is a schematic cross-sectional view showing the third simulation condition. [Figure 7] FIG. 7 is a graph showing the results of the third simulation. [Figure 8] (a) of Figure 8 is a schematic cross-sectional view of a thermoelectric conversion element according to a first reference example, (b) of Figure 8 is a schematic cross-sectional view of a thermoelectric conversion element according to a second reference example, and (c) of Figure 8 is a schematic cross-sectional view of a thermoelectric conversion element according to a third reference example. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0008] Hereinafter, the embodiments of the present disclosure will be described in detail with reference to the accompanying drawings. In the following description, the same elements or elements having the same functions will be designated by the same reference numerals, and duplicated descriptions will be omitted. In this specification, the term "same" and similar words are not limited to "completely same".

[0009] First, the configuration of the thermoelectric conversion element according to the present embodiment will be described with reference to FIG. 1. FIG. 1 is a schematic cross-sectional view showing the thermoelectric conversion element according to the present embodiment. The thermoelectric conversion element 1 shown in FIG. 1 is an element capable of generating electricity by supplying heat from the outside. The thermoelectric conversion element 1 is, for example, an element that converts heat into electricity by utilizing the temperature difference inside the element. The thermoelectric conversion element 1 is a so-called in-plane type element. For this reason, the thermoelectric conversion element 1 tends to be more excellent in processability and flexibility than, for example, a π-type element (cross-plane type element). Therefore, the thermoelectric conversion element 1 can be provided along the side of, for example, a cylindrical pipe used for recovering factory exhaust heat. That is, the thermoelectric conversion element 1 can be easily arranged in various places. Therefore, the thermoelectric conversion element 1 is used, for example, as a power source for a plant sensor that utilizes exhaust heat. In addition, the contact resistance between the thermoelectric conversion material and the electrodes contained in the thermoelectric conversion element 1 also tends to be lower than that of a π-type module. In the following, the temperature of each component of the thermoelectric conversion element 1 is measured under natural convection conditions of air.

[0010] The thermoelectric conversion element 1 includes a thermoelectric conversion module 2 and a sheet member 3. The thermoelectric conversion module 2 is a thermoelectric conversion section in the thermoelectric conversion element 1, and includes a substrate 11, a first electrode 12, a second electrode 13, an element section 14, and a sealing layer 15.

[0011] The substrate 11 is, for example, a sheet member made of a resin exhibiting heat resistance and flexibility, and has a substantially flat plate shape. The resin constituting the substrate 11 is, for example, a (meth)acrylic resin, a (meth)acrylonitrile resin, a polyamide resin, a polycarbonate resin, a polyether resin, a polyester resin, an epoxy resin, an organosiloxane resin, a polyimide resin, a polysulfone resin, or the like. The thickness of the substrate 11 is, for example, 5 μm or more and 50 μm or less. The thermal conductivity of the substrate 11 is, for example, 0.1 W / mK (0.1 watts per meter per Kelvin, and 0.1 W×m -1 ×K -1The thermal conductivity of the substrate 11 is 0.3 W / mK or less. When the thermal conductivity of the substrate 11 is 0.3 W / mK or less, a temperature difference may occur inside the element portion 14. The substrate 11 has a first main surface 11a and a second main surface 11b located on the opposite side of the first main surface 11a. The first main surface 11a and the second main surface 11b are surfaces that intersect with the direction along the thickness of the substrate 11. The shapes of the first main surface 11a and the second main surface 11b are not particularly limited, and may be, for example, a polygonal shape, a circular shape, an elliptical shape, or the like. Hereinafter, the direction along the thickness of the substrate 11 is simply referred to as a thickness direction D1. Viewing from the thickness direction D1 corresponds to a planar view.

[0012] The first electrode 12 is a member constituting a terminal included in the thermoelectric conversion module 2, and is a conductor provided on the first main surface 11a of the substrate 11. The first electrode 12 is, for example, a conductor made of metal, alloy, or conductive resin. When the first electrode 12 is made of metal or alloy, the first electrode 12 is formed on the substrate 11 by, for example, various dry methods. The dry method is, for example, a physical vapor deposition method (PVD method), patterning of a metal foil or alloy foil, etc. The first electrode 12 may be formed using a nanopaste in which metal particles are dispersed, etc. The shape of the first electrode 12 in a plan view is not particularly limited, and may be, for example, a polygonal shape, a circular shape, an elliptical shape, etc. The thickness of the first electrode 12 is, for example, 6 μm or more and 70 μm or less. The thermal conductivity of the first electrode 12 is, for example, 5 W / mK or more. In this case, the first electrode 12 tends to be easily heated from the outside. The thermal conductivity of the first electrode 12 may be, for example, 30 W / mK or more.

[0013] The second electrode 13, like the first electrode 12, is a member constituting a terminal included in the thermoelectric conversion module 2, and is a conductor provided on the first main surface 11a of the substrate 11. The second electrode 13 is separated from the first electrode 12. The second electrode 13 is formed at the same time as the first electrode 12. Therefore, the second electrode 13 is made of the same material as the first electrode 12. The shape of the second electrode 13 in a plan view is not particularly limited, and may be, for example, a polygonal shape, a circular shape, an elliptical shape, or the like. The thermal conductivity of the second electrode 13 is, like the first electrode 12, for example, 5 W / mK or more. The thermal conductivity of the second electrode 13 may be, for example, 30 W / mK or more.

[0014] The element section 14 is a member where thermoelectric conversion is performed in the thermoelectric conversion module 2. The shape of the element section 14 in a plan view is not particularly limited, and may be, for example, a polygonal shape, a circular shape, an elliptical shape, or the like. The element section 14 has an n-type thermoelectric conversion layer 14a and a p-type thermoelectric conversion layer 14b. In this embodiment, the n-type thermoelectric conversion layer 14a and the p-type thermoelectric conversion layer 14b have the same shape, but are not limited to this.

[0015] The n-type thermoelectric conversion layer 14a is provided on the first main surface 11a of the substrate 11 and is electrically connected to the first electrode 12. In this embodiment, the n-type thermoelectric conversion layer 14a is located between the first electrode 12 and the second electrode 13 and is in contact with the first electrode 12. The n-type thermoelectric conversion layer 14a covers a part of the first electrode 12. The n-type thermoelectric conversion layer 14a is, for example, an n-type semiconductor layer. The n-type thermoelectric conversion layer 14a includes, for example, a composite of an inorganic substance and an organic substance, or a composite of a plurality of organic substances. Examples of the inorganic substance include titanium disulfide (TiS2), bismuth tellurium (Bi2Te3), skutterudite, nickel (Ni), etc. Examples of the organic substance include n-type single-walled carbon nanotubes (SWCNT), tetrathiafulvalene-tetracyanoquinodimethane (TTF-TCNQ), etc. The n-type thermoelectric conversion layer 14a is formed by, for example, various dry or wet methods. Examples of the wet methods include a doctor blade method, a dip coating method, a spray coating method, a spin coating method, and an inkjet method. The thickness of the n-type thermoelectric conversion layer 14a is, for example, 9 μm or more and 200 μm or less. The thermal conductivity of the n-type thermoelectric conversion layer 14a is, for example, 0.01 W / mK or more and 0.5 W / mK or less. In this case, a temperature gradient can be easily formed inside the n-type thermoelectric conversion layer 14a. The thickness of the n-type thermoelectric conversion layer 14a corresponds to the thickness of the portion not overlapping with the first electrode 12 in the thickness direction D1.

[0016] The p-type thermoelectric conversion layer 14b is provided on the first main surface 11a of the substrate 11 and is in contact with the n-type thermoelectric conversion layer 14a. In this embodiment, the p-type thermoelectric conversion layer 14b is located between the first electrode 12 and the second electrode 13, and is located on the opposite side of the first electrode 12 with the n-type thermoelectric conversion layer 14a sandwiched therebetween. The p-type thermoelectric conversion layer 14b covers a part of the second electrode 13 and is in contact with the part. The p-type thermoelectric conversion layer 14b is, for example, a p-type semiconductor layer. The p-type thermoelectric conversion layer 14b includes, for example, carbon nanotubes and a conductive polymer different from the carbon nanotubes. The carbon nanotubes are, for example, p-type SWCNTs. The conductive polymer is, for example, poly(3,4-ethylenedioxythiophene) (PEDOT), polystyrene sulfonic acid (PSS), or the like. In the p-type thermoelectric conversion layer 14b, the carbon nanotubes and the conductive polymer may be aggregated. The p-type thermoelectric conversion layer 14b may include a porous structure in which carbon nanotubes are bonded to each other by a conductive polymer.

[0017] The p-type thermoelectric conversion layer 14b is formed by, for example, various dry or wet methods, similar to the n-type thermoelectric conversion layer 14a. The thickness of the p-type thermoelectric conversion layer 14b is, for example, 9 μm or more and 200 μm or less. The thermal conductivity of the p-type thermoelectric conversion layer 14b is, for example, 0.01 W / mK or more and 0.5 W / mK or less. In this case, a temperature gradient can be easily formed inside the p-type thermoelectric conversion layer 14b. The thickness of the p-type thermoelectric conversion layer 14b corresponds to the thickness of the portion not overlapping with the second electrode 13 in the thickness direction D1.

[0018] The sealing layer 15 is a resin layer that protects the first electrode 12, the second electrode 13, the n-type thermoelectric conversion layer 14a, and the p-type thermoelectric conversion layer 14b, and constitutes the outermost layer of the thermoelectric conversion element 1 located on the first main surface 11a. In this embodiment, the outermost layer is composed of only the sealing layer 15. The sealing layer 15 is provided on the first main surface 11a and covers the first electrode 12, the second electrode 13, the n-type thermoelectric conversion layer 14a, and the p-type thermoelectric conversion layer 14b. The resin that constitutes the sealing layer 15 is, for example, a (meth)acrylic resin, a (meth)acrylonitrile resin, a polyamide resin, a polycarbonate resin, a polyether resin, a polyester resin, an epoxy resin, an organosiloxane resin, a polyimide resin, a polysulfone resin, or the like. The thickness of the sealing layer 15 is, for example, 50 μm or more and 200 μm or less, which is smaller than the intervals S1 and S2 described below. The thermal conductivity of the sealing layer 15 is, for example, 0.01 W / mK or more and 0.5 W / mK or less.

[0019] The first electrode 12, the n-type thermoelectric conversion layer 14a, the p-type thermoelectric conversion layer 14b, and the second electrode 13 are arranged in order along an arrangement direction D2 perpendicular to the thickness direction D1. For example, the first electrode 12 is located at one end of the thermoelectric conversion module 2 in the arrangement direction D2, and the second electrode 13 is located at the other end of the thermoelectric conversion module 2 in the arrangement direction D2. In consideration of the difference in thermal conductivity of each component of the thermoelectric conversion module 2, for example, when the thermoelectric conversion module 2 is heated from the substrate 11 side, the temperature of the n-type thermoelectric conversion layer 14a tends to be the highest at a portion in contact with the first electrode 12, and the temperature of the p-type thermoelectric conversion layer 14b tends to be the highest at a portion in contact with the second electrode 13. The temperature of the contact portion CP between the n-type thermoelectric conversion layer 14a and the p-type thermoelectric conversion layer 14b tends to be the lowest. For this reason, a temperature gradient may occur along the arrangement direction D2 in each of the n-type thermoelectric conversion layer 14a and the p-type thermoelectric conversion layer 14b. In plan view, the contact portion CP extends, for example, along a direction intersecting both the thickness direction D1 and the arrangement direction D2. In plan view, the contact portion CP may be linear, wavy, or arc-shaped.

[0020] The length of the n-type thermoelectric conversion layer 14a along the arrangement direction D2 is longer than the length of the sealing layer 15 along the thickness direction D1. The length of the n-type thermoelectric conversion layer 14a along the arrangement direction D2 is, for example, 5 times or more or 10 times or more the length of the sealing layer 15 along the thickness direction D1. As described above, the thermal conductivity of the sealing layer 15 is, for example, 0.1 W / mK or more and 0.5 W / mK or less. For this reason, for example, heat conducted from the first electrode 12 to the sealing layer 15 is more likely to reach the upper surface 15a of the sealing layer 15 than the contact portion CP. In other words, the contact portion CP is less likely to be heat-transferred through the sealing layer 15. Rather, the heat of the contact portion CP tends to be released to the outside through the sealing layer 15.

[0021] The sheet member 3 is a member disposed between the thermoelectric conversion module 2 and the heat source, and is provided on the second main surface 11b of the substrate 11. Therefore, heat generated from the heat source is conducted to the thermoelectric conversion module 2 via the sheet member 3. The sheet member 3 has a first high thermal conductivity section 21, a second high thermal conductivity section 22, and a low thermal conductivity section 23.

[0022] The first highly thermally conductive portion 21 and the second highly thermally conductive portion 22 are portions that exhibit a higher thermal conductivity than the low thermally conductive portion 23, and are spaced apart from each other. The first highly thermally conductive portion 21 overlaps the first electrode 12 in the thickness direction D1, and the second highly thermally conductive portion 22 overlaps the second electrode 13 in the thickness direction D1. The shapes of the first highly thermally conductive portion 21 and the second highly thermally conductive portion 22 in a plan view are not particularly limited, and may be, for example, polygonal, circular, or elliptical. In a plan view, the shape of the first highly thermally conductive portion 21 and the shape of the first electrode 12 may be the same as each other or may be different from each other. Similarly, in a plan view, the shape of the second highly thermally conductive portion 22 and the shape of the second electrode 13 may be the same as each other or may be different from each other. Each of the first highly thermally conductive portion 21 and the second highly thermally conductive portion 22 includes, for example, a metal (silver, copper, aluminum, etc.), carbon, etc. Each of the first highly thermally conductive portion 21 and the second highly thermally conductive portion 22 may contain a ceramic such as boron nitride or aluminum nitride that exhibits high thermal conductivity. The thermal conductivity of each of the first highly thermally conductive portion 21 and the second highly thermally conductive portion 22 is, for example, 5 W / mK or more and 400 W / mK or less. Thereby, when the sheet member 3 is heated, heat is transferred satisfactorily to the first electrode 12 and the second electrode 13 via the first highly thermally conductive portion 21 and the second highly thermally conductive portion 22, respectively.

[0023] From the viewpoint of increasing the efficiency of heat transfer from the first highly thermally conductive portion 21 to the first electrode 12, the first electrode 12 may be located inside the edge of the first highly thermally conductive portion 21 in a plan view, or the edge of the first electrode 12 and the edge of the first highly thermally conductive portion 21 may completely overlap each other. Similarly, from the viewpoint of widening the temperature gradient along the arrangement direction D2 inside the n-type thermoelectric conversion layer 14a, the first highly thermally conductive portion 21 may be located closer to one end in the arrangement direction D2 than the first electrode 12. That is, from the viewpoint of increasing the heat transfer efficiency from the first highly thermally conductive portion 21 to the first electrode 12 in a plan view, the edge of the first highly thermally conductive portion 21 on the one end side may be located outside the edge of the first electrode 12 on the one end side. Similarly, the second highly thermally conductive portion 22 may be located closer to the other end in the arrangement direction D2 than the second electrode 13.

[0024] The length T1 of the first high thermal conductivity portion 21 along the thickness direction D1 is, for example, 50 μm or more and 500 μm or less. In a plan view, the interval S1 from the first high thermal conductivity portion 21 (contact portion between the first high thermal conductivity portion 21 and the low thermal conductivity portion 23) along the arrangement direction D2 to the contact portion CP is, for example, 5 times or more or 10 times or more the length T1 of the first high thermal conductivity portion 21. In this case, a temperature gradient can be favorably generated inside the n-type thermoelectric conversion layer 14a along the arrangement direction D2. Similarly, the length T2 of the second high thermal conductivity portion 22 along the thickness direction D1 is, for example, 50 μm or more and 500 μm or less. In a plan view, the interval S2 from the second high thermal conductivity portion 22 (contact portion between the second high thermal conductivity portion 22 and the low thermal conductivity portion 23) along the arrangement direction D2 to the contact portion CP is, for example, 5 times or more or 10 times or more the length T2 of the second high thermal conductivity portion 22. In this case, a temperature gradient can be favorably generated inside the p-type thermoelectric conversion layer 14b along the arrangement direction D2. Depending on the length T1 of the first high thermal conductivity portion 21, the interval S1 may be 5 times or more, 10 times or more, or 20 times or less than the length T1. Similarly, the interval S2 may be 5 times or more, 10 times or more, or 20 times or less than the length T2. For example, when the length T1 is 100 μm or more and 200 μm or less, the interval S1 is preferably 5 times or more, and more preferably 10 times or more, of the length T1.

[0025] The low thermal conductive portion 23 is a portion exhibiting a lower thermal conductivity than the first high thermal conductive portion 21 and the second high thermal conductive portion 22, and is a main portion of the sheet member 3. The low thermal conductive portion 23 overlaps at least the contact portion CP in the thickness direction D1, and covers most of the second main surface 11b. In this embodiment, the low thermal conductive portion 23 overlaps most of the n-type thermoelectric conversion layer 14a and the p-type thermoelectric conversion layer 14b in addition to the contact portion CP in the thickness direction D1. The low thermal conductive portion 23 fills the gap between the first high thermal conductive portion 21 and the second high thermal conductive portion 22 in the arrangement direction D2. The low thermal conductive portion 23 includes, for example, cellulose nanofiber (CNF), silica aerogel, or the like. The low thermal conductive portion 23 may be a foam.

[0026] The thermal conductivity of the low thermal conductive portion 23 is significantly lower than the thermal conductivity of the first high thermal conductive portion 21 and the second high thermal conductive portion 22, and is, for example, 0.01 W / mK or more and 0.2 W / mK or less. As a result, when the sheet member 3 is heated, the portion of the thermoelectric conversion module 2 that is located on the first main surface 11a and overlaps with the low thermal conductive portion 23 is less likely to be heated. Therefore, since the contact portion CP and its vicinity are less likely to be heated, the temperature gradient inside the n-type thermoelectric conversion layer 14a along the arrangement direction D2 and the temperature gradient inside the p-type thermoelectric conversion layer 14b can each be generated well. From the viewpoint of generating the above temperature gradient better, the thermal conductivity of the low thermal conductive portion 23 may be 0.08 W / mK or less.

[0027] The sheet member 3 is formed directly on the second main surface 11b, for example. In this case, the first high thermal conductive portion 21, the second high thermal conductive portion 22, and the low thermal conductive portion 23 are each formed by various dry or wet methods. Alternatively, the sheet member 3 may be attached to the second main surface 11b by an adhesive (not shown). The adhesive may be, for example, a (meth)acrylic resin, a (meth)acrylonitrile resin, a polyamide resin, a polycarbonate resin, a polyether resin, a polyester resin, an epoxy resin, an organosiloxane resin, a polyimide resin, a polysulfone resin, or the like. The thermal conductivity of the adhesive is, for example, approximately the same as the thermal conductivity of the substrate 11.

[0028] The thermoelectric conversion element 1 may further include configurations other than those described above. For example, the thermoelectric conversion element 1 may include wiring for electrically connecting other thermoelectric conversion elements, wiring for extracting electric power to an external circuit, and the like.

[0029] In the thermoelectric conversion element 1 according to the present embodiment described above, the first electrode 12 overlaps the first high thermal conductivity portion 21 in the thickness direction D1, the second electrode 13 overlaps the second high thermal conductivity portion 22 in the thickness direction D1, and the contact portion CP between the n-type thermoelectric conversion layer 14a and the p-type thermoelectric conversion layer 14b overlaps the low thermal conductivity portion 23 in the thickness direction D1. As a result, when the thermoelectric conversion module 2 is heated from the sheet member 3 side, the temperature of the contact portion CP tends to be the lowest in the n-type thermoelectric conversion layer 14a, and the temperature of the portion closest to the first electrode 12 tends to be the highest. Similarly, the temperature of the contact portion CP tends to be the lowest in the p-type thermoelectric conversion layer 14b, and the temperature of the portion closest to the second electrode 13 tends to be the highest. In this case, for example, the temperature gradient of the n-type thermoelectric conversion layer 14a in the arrangement direction D2 and the temperature gradient of the p-type thermoelectric conversion layer 14b in the arrangement direction D2 tend to be larger than when one electrode side is in a high temperature state and the other electrode side is in a low temperature state in the arrangement direction D2. In other words, the temperature difference between both ends of the n-type thermoelectric conversion layer 14a in the arrangement direction D2 and the temperature difference between both ends of the p-type thermoelectric conversion layer 14b in the arrangement direction tend to be larger than when one electrode side is in a high temperature state and the other electrode side is in a low temperature state in the arrangement direction D2. In addition, the sealing layer 15 constitutes the outermost layer located on the first main surface 11a, so that the above temperature gradient tends to be maintained. Therefore, according to the thermoelectric conversion element 1 according to this embodiment, it is possible to improve the thermoelectric conversion efficiency.

[0030] In this embodiment, the thermal conductivity of the low thermal conductive portion 23 may be 0.2 W / mK or less. In this case, the temperature difference between both ends of the n-type thermoelectric conversion layer 14a and the p-type thermoelectric conversion layer 14b in the arrangement direction D2 can be effectively increased. If the thermal conductivity of the low thermal conductive portion 23 is 0.08 W / mK or less, the temperature difference can be effectively increased.

[0031] In this embodiment, the thermal conductivity of the first high thermal conductivity section 21 and the second high thermal conductivity section 22 may be 5 W / mK or more. In this case, the temperature difference between both ends of each of the n-type thermoelectric conversion layer 14a and the p-type thermoelectric conversion layer 14b in the arrangement direction D2 can be satisfactorily increased.

[0032] In this embodiment, the thermal conductivity of the first electrode 12 and the second electrode 13 may be 5 W / mK or more. In this case, the temperature difference between both ends of the n-type thermoelectric conversion layer 14a and the p-type thermoelectric conversion layer 14b in the arrangement direction D2 can be effectively increased.

[0033] In this embodiment, the substrate 11 exhibits flexibility. Therefore, the thermoelectric conversion element 1 can exhibit flexibility. Therefore, the thermoelectric conversion element 1 can be easily provided along the surface of, for example, a cylindrical pipe. In other words, restrictions on the location where the thermoelectric conversion element 1 can be attached can be alleviated.

[0034] In this embodiment, the distance S1 from the first highly thermally conductive portion 21 to the contact portion CP along the arrangement direction D2 is 5 or more times or 10 or more times the length T1 of the first highly thermally conductive portion 21 along the thickness direction D1, and the distance S2 from the second highly thermally conductive portion 22 to the contact portion CP along the arrangement direction D2 is 5 or more times or 10 or more times the length T2 of the second highly thermally conductive portion 22 along the thickness direction D1. Therefore, the temperature difference between both ends of the n-type thermoelectric conversion layer 14a and the p-type thermoelectric conversion layer 14b in the arrangement direction D2 can be effectively widened.

[0035] Below, we explain the results of simulating the temperature change inside a thermoelectric conversion element when the position or characteristics of the components included in the element are changed. In each of the following simulations, a two-dimensional model is set up. In carrying out the following simulations, an Excel model was used in which the fundamental differential equation for two-dimensional heat conduction is applied to differentiation. The finite volume method was applied as the differentiation method.

[0036] FIG. 2 is a schematic cross-sectional view showing the first simulation conditions. As shown in FIG. 2, the model 30 in the first simulation includes high thermal conductivity parts 31, 32 and a low thermal conductivity part 33, similar to the sheet member 3 of the above embodiment. The high thermal conductivity part 31 is exposed on one side in the thickness direction D1 and is located at one end of the model 30 in the arrangement direction D2. The high thermal conductivity part 32 is exposed on the other side in the thickness direction D1 and is located at the other end of the model 30 in the arrangement direction D2. In the model 30, the dimensions of the high thermal conductivity parts 31, 32 along the thickness direction D1 were set to be the same. The low thermal conductivity part 33 was set to have a sheet shape with a thickness of 1 mm and to be integrated with the high thermal conductivity parts 31, 32. The thermal conductivity of the high thermal conductivity parts 31, 32 was set to 398 W / mK, and the thermal conductivity of the low thermal conductivity part 33 was set to 0.3 W / mK.

[0037] In model 30, the distance between highly thermally conductive portions 31, 32 in arrangement direction D2 is distance X (mm), and the distance between highly thermally conductive portions 31, 32 in thickness direction D1 is distance Y (mm) (distance Y is less than 1). When distance X is 0 mm, edge 31a on the center side of highly thermally conductive portion 31 in arrangement direction D2 overlaps with edge 32a on the center side of highly thermally conductive portion 32 in arrangement direction D2 in thickness direction D1. When distance Y is 0 mm, edge 31b on the center side of highly thermally conductive portion 31 in thickness direction D1 overlaps with edge 32b on the center side of highly thermally conductive portion 32 in thickness direction D1 in arrangement direction D2.

[0038] Two temperature evaluation points 34, 35 are set in the model 30. The temperature evaluation point 34 is located on the edge 31a on the center side of the high thermal conductivity section 31 in the thickness direction D1, and at the center of the interval Y. Therefore, when the interval Y is 0 mm, the temperature evaluation point 34 overlaps with the intersection of the edges 31a, 31b. The temperature evaluation point 35 is located on the edge 32a on the center side of the high thermal conductivity section 32 in the thickness direction D1, and at the center of the interval Y. Therefore, when the interval Y is 0 mm, the temperature evaluation point 35 overlaps with the intersection of the edges 32a, 32b.

[0039] In the thickness direction D1, one side of the model 30 is set as the heat source side, and the other side of the model 30 is set as the air side. In the first simulation, the temperature on the heat source side is set to 70° C., and the air side is set to room temperature (23° C.). In the first simulation, it is assumed that the surface 30b of the model 30 located on the heat source side in the thickness direction D1 is heated by natural convection, and the surface 30a of the model 30 located on the air side in the thickness direction D1 is cooled by natural convection.

[0040] 3(a) and (b) are graphs showing the first simulation results. FIG. 3(a) is a graph showing the change in temperature difference between the temperature evaluation points 34 and 35 when the interval X is changed. In FIG. 3(a), the horizontal axis shows the interval X, and the vertical axis shows the temperature difference between the temperature evaluation points 34 and 35. Plot 41 shows the simulation result when the interval Y is 0 mm, plot 42 shows the simulation result when the interval Y is 0.1 mm, plot 43 shows the simulation result when the interval Y is 0.2 mm, plot 44 shows the simulation result when the interval Y is 0.3 mm, plot 45 shows the simulation result when the interval Y is 0.4 mm, and plot 46 shows the simulation result when the interval Y is 0.5 mm. As shown in FIG. 3(a), under the condition that the interval X is 1 mm or less, the temperature difference between the temperature evaluation points 34 and 35 increases as the interval X increases, regardless of the value of the interval Y. When the interval X was 1 mm or more and less than 2 mm, the temperature difference did not increase easily even if the interval X was increased. When the interval X was 2 mm or more, the temperature difference did not change much even if the interval X was increased, regardless of the value of the interval Y. This suggests that, for example, in the sheet member 3 of the above embodiment, when the interval between the first high thermal conductivity portion 21 and the second high thermal conductivity portion 22 in the arrangement direction D2 is set to 2 mm or more, it is not necessary to consider the interval between the first high thermal conductivity portion 21 and the second high thermal conductivity portion 22 in the thickness direction D1.

[0041] FIG. 3B is a graph showing the change in temperature difference between the temperature evaluation points 34 and 35 when the distance Y is changed. In FIG. 3B, the horizontal axis shows the distance Y, and the vertical axis shows the temperature difference between the temperature evaluation points 34 and 35. Plot 47 shows the simulation result when the distance X is 0 mm, and plot 48 shows the simulation result when the distance X is 10 mm. As shown in FIG. 3B, regardless of the value of the distance X, the shorter the distance Y, the larger the temperature difference between the temperature evaluation points 34 and 35. This suggests that, for example, in model 30, the shorter the distance Y between the high thermal conductivity parts 31 and 32 in the thickness direction D1, the larger the temperature difference.

[0042] FIG. 4 is a schematic cross-sectional view showing the second simulation conditions. As shown in FIG. 4, the model 50 in the second simulation includes high thermal conductivity parts 51, 52 and low thermal conductivity part 53, similar to the model 30. The positions where the high thermal conductivity parts 51, 52 and the low thermal conductivity part 53 are provided in the model 50 and their thermal conductivities are the same as those of the model 30. In the model 50, the interval between the high thermal conductivity parts 51, 52 along the arrangement direction D2 is set to 2 mm. The length of the high thermal conductivity part 51 along the thickness direction D1 is set to Z mm, and the length of the high thermal conductivity part 52 along the thickness direction D1 is set to 1-Z mm. The temperature conditions around the model 50 are the same as those of the first simulation.

[0043] Two temperature evaluation points 54, 55 are set in model 50. Temperature evaluation point 54 is located at the intersection of center side edge 51a of highly thermally conductive portion 51 along arrangement direction D2 and center side edge 51b of highly thermally conductive portion 51 along thickness direction D1. Temperature evaluation point 55 is located at the intersection of center side edge 52a of highly thermally conductive portion 52 along arrangement direction D2 and center side edge 52b of highly thermally conductive portion 52 along thickness direction D1.

[0044] FIG. 5 is a graph showing the results of the second simulation, showing the change in temperature difference between the temperature evaluation points 54, 55 when the length of the high thermal conductivity portion 51 along the thickness direction D1 is changed. In FIG. 5, the horizontal axis indicates the length Z, and the vertical axis indicates the temperature difference between the temperature evaluation points 54, 55. As shown in FIG. 5, the temperature difference increases as the length along the thickness direction D1 of the high thermal conductivity portion 51 located on the heat source side in the thickness direction D1 increases. This result suggests that in order to increase the temperature difference between the temperature evaluation points 54, 55 along the arrangement direction D2 in the model 50, it is effective to make the thickness of the high thermal conductivity portion located on the heat source side as large as possible.

[0045] FIG. 6 is a schematic cross-sectional view showing the third simulation conditions. Based on the results of the first and second simulations, the model used in the third simulation is structured such that the largest temperature difference is estimated to occur in the arrangement direction D2. Specifically, as shown in FIG. 6, the model 60 in the third simulation includes a high thermal conductivity section 61 and a low thermal conductivity section 62. The high thermal conductivity section 61 and the low thermal conductivity section 62 are sequentially arranged along the arrangement direction D2 and are integrated with each other. The dimension of the high thermal conductivity section 61 and the low thermal conductivity section 62 along the thickness direction D1 is 1 mm. The thermal conductivity of the high thermal conductivity section 61 is set to 398 W / mK.

[0046] In the thickness direction D1, one side of the model 60 is set as the heat source side, and the other side of the model 60 is set as the air side. In the third simulation, unlike the first simulation, the temperature on the heat source side is set to 100° C. On the other hand, the air side has the same conditions as the first simulation.

[0047] A temperature evaluation point 63 is set on the model 60, located on the surface 60a of the model 60. The temperature evaluation point 63 is located on the low thermal conductive portion 62, 2 mm away from the contact portion 64 between the high thermal conductive portion 61 and the low thermal conductive portion 62 along the arrangement direction D2. Therefore, the temperature of the temperature evaluation point 63 indicates the temperature of the surface 60a when the model 60 is heated (more specifically, the temperature of the surface 60a constituted by the low thermal conductive portion 62).

[0048] FIG. 7 is a graph showing the results of the third simulation, showing the temperature change of the temperature evaluation point 63 when the thermal conductivity of the low thermal conductive portion 62 is changed. In FIG. 7, the horizontal axis shows the thermal conductivity of the low thermal conductive portion 62, and the vertical axis shows the temperature of the temperature evaluation point 63. As shown in FIG. 7, the smaller the thermal conductivity of the low thermal conductive portion 62, the lower the temperature of the temperature evaluation point 63. When the thermal conductivity of the low thermal conductive portion 62 is 0.2 W / mK, the temperature difference between the heat source and the temperature evaluation point 63 is about 8° C. When the thermal conductivity of the low thermal conductive portion 62 is 0.08 W / mK, the temperature difference between the heat source and the temperature evaluation point 63 is about 15° C. On the other hand, when the thermal conductivity of the low thermal conductive portion 62 is 30 W / mK or more, the temperature difference between the heat source and the temperature evaluation point 63 is almost 0. This suggests that, for example, when the thermal conductivity of the low thermal conductive portion 23 contained in the sheet member 3 is 0.2 W / mK or less, the low thermal conductive portion 23 tends to exhibit good insulation properties, and that when the thermal conductivity of the low thermal conductive portion 23 is 0.08 W / mK or less, the low thermal conductive portion 23 tends to exhibit even better insulation properties.

[0049] Next, a simulation result of the maximum temperature difference in the element portion when the configuration of the thermoelectric conversion element is changed will be described. Fig. 8(a) is a schematic cross-sectional view of a thermoelectric conversion element according to a first reference example, Fig. 8(b) is a schematic cross-sectional view of a thermoelectric conversion element according to a second reference example, and Fig. 8(c) is a schematic cross-sectional view of a thermoelectric conversion element according to a third reference example.

[0050] The thermoelectric conversion element 101 shown in FIG. 8(a) includes, in addition to each of the constituent elements of the thermoelectric conversion element 1, a high thermal conductivity portion 110 and a low thermal conductivity portion 120 provided on the sealing layer 15. The high thermal conductivity portion 110 is provided to improve the heat dissipation of the n-type thermoelectric conversion layer 14a and the p-type thermoelectric conversion layer 14b, and overlaps the contact portion CP in the thickness direction D1. The center of the high thermal conductivity portion 110 in the arrangement direction D2 overlaps the contact portion CP in the thickness direction D1. The low thermal conductivity portion 120 is a sheet member provided to reduce the heat dissipation of the first electrode 12, the second electrode 13, and the surroundings thereof. The low thermal conductivity portion 120 surrounds the high thermal conductivity portion 110 in a direction perpendicular to the thickness direction D1, and overlaps the first electrode 12, the second electrode 13, the first high thermal conductivity portion 21, and the second high thermal conductivity portion 22 in the thickness direction D1. The high thermal conductive portion 110 and the low thermal conductive portion 120 have the same length in the thickness direction D1.

[0051] 8(b) includes, in addition to the respective constituent elements of the thermoelectric conversion element 1, a low thermally conductive section 220 provided on the sealing layer 15. The low thermally conductive section 220 is a sheet member that covers the upper surface of the sealing layer 15. The length of the low thermally conductive section 220 along the thickness direction D1 is the same as the length along the thickness direction D1 of the high thermally conductive section 110 and the low thermally conductive section 120 shown in FIG. 8(a).

[0052] 8(c) includes, in addition to the respective constituent elements of the thermoelectric conversion element 1, a highly thermally conductive portion 310 provided on the sealing layer 15. The highly thermally conductive portion 310 is a sheet member that covers the upper surface of the sealing layer 15. The length of the highly thermally conductive portion 310 in the thickness direction D1 is the same as the length of the highly thermally conductive portion 110 and the low thermally conductive portion 120 in the thickness direction D1 shown in FIG. 8(a).

[0053] In this simulation, in the thermoelectric conversion elements 1, 101, 201, and 301, the length of the thermoelectric conversion module 2 along the thickness direction D1 was set to 0.6 mm, the length of the substrate 11 along the thickness direction D1 was set to 50 μm, the length of the sheet member 3 along the thickness direction D1 was set to 400 μm, and the lengths of the thermoelectric conversion module 2 and the sheet member 3 along the arrangement direction D2 were set to 15 mm. The length of the thermoelectric conversion module 2 along the thickness direction D1 does not include the length of the high thermal conductivity parts 110 and 310 along the thickness direction D1 and the length of the low thermal conductivity parts 120 and 220 along the thickness direction D1. The length of the first electrode 12 and the second electrode 13 along the thickness direction D1 was set to 25 μm, the length of the n-type thermoelectric conversion layer 14a and the p-type thermoelectric conversion layer 14b along the thickness direction D1 was set to 100 μm, the maximum length of the sealing layer 15 along the thickness direction D1 was set to 150 μm, the lengths of the first high thermal conductive portion 21, the second high thermal conductive portion 22 and the low thermal conductive portion 23 along the thickness direction D1 were set to 400 μm, the length of the first electrode 12 and the second electrode 13 along the arrangement direction D2 was set to 3 mm, the length of the n-type thermoelectric conversion layer 14a and the p-type thermoelectric conversion layer 14b along the arrangement direction D2 was set to 2.5 mm, and the length of the first high thermal conductive portion 21 and the second high thermal conductive portion 22 along the arrangement direction D2 was set to 3 mm. In addition, the length of the highly thermally conductive portion 110 along the thickness direction D1 was set to 400 μm, and the length of the highly thermally conductive portion 110 along the arrangement direction D2 was set to 3 mm.

[0054] In this simulation, in the thermoelectric conversion elements 1, 101, 201, and 301, the thermal conductivity of the substrate 11 and the sealing layer 15 was set to 0.3 W / mK, the thermal conductivity of the first electrode 12 and the second electrode 13 was set to 398 W / mK, the thermal conductivity of the n-type thermoelectric conversion layer 14a and the p-type thermoelectric conversion layer 14b was set to 0.5 W / mK, the thermal conductivity of the first high thermal conductive portion 21 and the second high thermal conductive portion 22 was set to 5.0 W / mK, and the thermal conductivity of the low thermal conductive portion 23 was set to 0.05 W / mK. The thermal conductivity of the high thermal conductive portions 110 and 310 was set to 5.0 W / mK, the thermal conductivity of the low thermal conductive portion 120 was set to 0.05 W / mK, and the thermal conductivity of the low thermal conductive portion 220 was set to 0.1 W / mK.

[0055] In the thermoelectric conversion elements 1, 101, 201, and 301, the temperature on the heat source side is set to 100° C., and the air side is set to room temperature (23° C.) in the same manner as in the third simulation described above. The temperature of the exposed surface of the sheet member 3 intersecting the thickness direction D1 was also set to 100° C.

[0056] The maximum temperature difference of the element portion 14 was simulated in the thermoelectric conversion elements 1, 101, 201, and 301 set under the above-mentioned conditions. As a result, the maximum temperature difference of the element portion 14 of the thermoelectric conversion element 1 was 5.259°C, the maximum temperature difference of the element portion 14 of the thermoelectric conversion element 101 was 4.909°C, the maximum temperature difference of the element portion 14 of the thermoelectric conversion element 201 was 4.785°C, and the maximum temperature difference of the element portion 14 of the thermoelectric conversion element 301 was 1.577°C. When the maximum temperature difference of the element portion 14 of the thermoelectric conversion element 101 was taken as the reference (100%), the maximum temperature difference of the element portion 14 of the thermoelectric conversion element 1 was 107%, the maximum temperature difference of the element portion 14 of the thermoelectric conversion element 201 was 87%, and the maximum temperature difference of the element portion 14 of the thermoelectric conversion element 301 was 32%. The above results suggest that in a configuration including a thermoelectric conversion element 1, the thermoelectric conversion efficiency tends to be highest when the outermost layer located on the first main surface 11a of the substrate 11 is composed of a sealing layer 15.

[0057] The thermoelectric conversion element according to the present disclosure is not limited to the above embodiment, and various other modifications are possible. For example, in the above embodiment, the outermost layer located on the first main surface is composed of only a sealing layer, but this is not limited thereto. For example, the outermost layer may be composed of the sealing layer and a member different from the sealing layer.

[0058] In the above embodiment, one thermoelectric conversion module is provided on the first main surface, but this is not limited thereto. For example, a plurality of thermoelectric conversion modules may be provided on the first main surface. In this case, the plurality of thermoelectric conversion modules may be electrically connected to each other. In at least some of the thermoelectric conversion modules, the first electrode or the second electrode may be common. When a plurality of thermoelectric conversion modules are provided on the first main surface, the sheet member may include a high thermal conductivity portion other than the first and second high thermal conductivity portions.

[0059] In the above embodiment, the first electrode and the second electrode are formed at the same time, but this is not limited to the above. The first electrode and the second electrode may be formed from different materials. [Explanation of symbols]

[0060] 1,101,201,301...thermoelectric conversion element, 2...thermoelectric conversion module, 3...sheet member, 11...substrate, 11a...first main surface, 11b...second main surface, 12...first electrode, 13...second electrode, 14...element portion, 14a...n-type thermoelectric conversion layer, 14b...p-type thermoelectric conversion layer, 15...sealing layer, 21...first high thermal conductivity portion, 22...second high thermal conductivity portion, 23...low thermal conductivity portion, 110,310...high thermal conductivity portion, 120,220...low thermal conductivity portion, CP...contact portion, S1,S2...spacing, T1...length of first high thermal conductivity portion, T2...length of second high thermal conductivity portion.

Claims

1. a substrate having a first major surface and a second major surface opposite the first major surface; a first electrode provided on the first main surface, an n-type thermoelectric conversion layer electrically connected to the first electrode and covering a part of an upper surface of the first electrode, a p-type thermoelectric conversion layer in contact with the n-type thermoelectric conversion layer, and a second electrode electrically connected to the p-type thermoelectric conversion layer; a sealing layer provided on the first principal surface and covering the first electrode, the n-type thermoelectric conversion layer, the p-type thermoelectric conversion layer, and the second electrode; a first high thermal conductivity section, a second high thermal conductivity section, and a low thermal conductivity section (excluding the low thermal conductivity section having adhesive properties) provided on the second main surface; the first electrode, the n-type thermoelectric conversion layer, the p-type thermoelectric conversion layer, and the second electrode are sequentially arranged along an arrangement direction perpendicular to a thickness direction of the substrate, the first electrode overlaps the first high thermal conductivity portion in the thickness direction, the second electrode overlaps the second high thermal conductivity portion in the thickness direction, and a contact portion between the n-type thermoelectric conversion layer and the p-type thermoelectric conversion layer overlaps the low thermal conductivity portion in the thickness direction, the sealing layer constitutes an outermost layer located on the first main surface, the first high thermal conductivity portion, the second high thermal conductivity portion, and the low thermal conductivity portion are located only on the second main surface of the substrate and are in direct contact with the second main surface; Thermoelectric conversion element.

2. The thermoelectric conversion element according to claim 1 , wherein the thermal conductivity of the low thermal conductive portion is equal to or higher than 0.01 W / mK and equal to or lower than 0.2 W / mK.

3. The thermoelectric conversion element according to claim 1 , wherein the low thermal conductivity portion has a thermal conductivity of 0.01 W / mK or more and 0.08 W / mK or less.

4. The thermoelectric conversion element according to any one of claims 1 to 3, wherein the thermal conductivity of the first high thermal conductivity portion and the second high thermal conductivity portion is 5 W / mK or more and 400 W / mK or less.

5. The thermoelectric conversion element according to any one of claims 1 to 4, wherein the substrate is flexible.

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