Thermoelectric conversion element

Abstract

A first thermoelectric conversion module of this thermoelectric conversion element comprises: a first substrate having a first major surface and a second major surface; a first electrode, a first n-type thermoelectric conversion layer, a first p-type thermoelectric conversion layer in contact with the first n-type thermoelectric conversion layer, and a second electrode which are provided on the first major surface; and a sealing layer provided on the first major surface. Each of a pair of sheet members of the thermoelectric conversion element is provided with a first high-heat transfer portion, a second high-heat transfer portion, and a low-heat transfer portion. The first electrode, the first n-type thermoelectric conversion layer, the first p-type thermoelectric conversion layer, and the second electrode are disposed in order along an arrangement direction. The first electrode overlaps the first high-heat transfer portion of the sheet member. The second electrode overlaps the second high-heat transfer portion of the sheet member. A first contact portion between the first n-type thermoelectric conversion layer and the first p-type thermoelectric conversion layer overlaps the low-heat transfer portion of the sheet member.

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 thermoelectric conversion element including a first thermoelectric conversion module and a pair of sheet members sandwiching the first thermoelectric conversion module, the first thermoelectric conversion module including a first 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, a first n-type thermoelectric conversion layer electrically connected to the first electrode, a first p-type thermoelectric conversion layer in contact with the first n-type thermoelectric conversion layer, and a second electrode electrically connected to the first p-type thermoelectric conversion layer, and a sealing layer provided on the first main surface and covering the first electrode, the first n-type thermoelectric conversion layer, the first p-type thermoelectric conversion layer, and the second electrode, and the pair of sheet members a first electrode, a first n-type thermoelectric conversion layer, a first p-type thermoelectric conversion layer, and a second electrode arranged in order along an arrangement direction perpendicular to the thickness direction of the first substrate, the first electrode overlapping the first high thermal conductivity portion of each of the pair of sheet members in the thickness direction, the second electrode overlapping the second high thermal conductivity portion of each of the pair of sheet members in the thickness direction, and a first contact portion between the first n-type thermoelectric conversion layer and the first p-type thermoelectric conversion layer overlapping the low thermal conductivity portion of each of the pair of sheet members in the thickness direction. [2] The thermoelectric conversion element according to [1], further comprising a second thermoelectric conversion module located on the opposite side of the first thermoelectric conversion module in the thickness direction, with one of a pair of sheet members being sandwiched between them. The second thermoelectric conversion module comprises: a second substrate having a third main surface located on the first thermoelectric conversion module side in the thickness direction and a fourth main surface located opposite the third main surface; a third electrode provided on the fourth main surface, a second n-type thermoelectric conversion layer electrically connected to the third electrode, a second p-type thermoelectric conversion layer in contact with the second n-type thermoelectric conversion layer, and a fourth electrode electrically connected to the second p-type thermoelectric conversion layer; and a second sealing layer provided on the fourth main surface and covering the third electrode, the second n-type thermoelectric conversion layer, the second p-type thermoelectric conversion layer, and the fourth electrode. [3] A thermoelectric conversion element described in [2], wherein the third electrode overlaps the first high thermal conductivity portion of each of the pair of sheet members and the first electrode in the thickness direction, the fourth electrode overlaps the second high thermal conductivity portion of each of the pair of sheet members and the second electrode in the thickness direction, and a second contact portion between the second n-type thermoelectric conversion layer and the second p-type thermoelectric conversion layer overlaps the low thermal conductivity portion of each of the pair of sheet members in the thickness direction. [4] The thermoelectric conversion element described in [2], wherein the third electrode overlaps the second high thermal conductivity portion of each of the pair of sheet members and the second electrode in the thickness direction, the fourth electrode overlaps the first high thermal conductivity portion of each of the pair of sheet members and the first electrode in the thickness direction, and a second contact portion between the second n-type thermoelectric conversion layer and the second p-type thermoelectric conversion layer overlaps the low thermal conductivity portion of each of the pair of sheet members in the thickness direction. [5] The thermoelectric conversion element according to any one of [2] to [4], wherein the second thermoelectric conversion module is electrically connected to the first thermoelectric conversion module. [6] The thermoelectric conversion element according to any one of [2] to [5], wherein the second sealing layer constitutes an outermost surface located on the fourth main surface. [7] A thermoelectric conversion element according to any one of [2] to [5], further comprising a sheet member other than the pair of sheet members, the other sheet member being located on the opposite side of the first thermoelectric conversion module in the thickness direction, sandwiching the second thermoelectric conversion module therebetween. [8] The thermoelectric conversion element according to any one of [1] to [7], wherein the low thermal conductive portion has a thermal conductivity of 0.2 W / mK or less. [9] The thermoelectric conversion element according to [8], wherein the thermal conductivity of the low thermal conductive portion is 0.08 W / mK or less.

[10] The thermoelectric conversion element according to any one of [1] to [9], wherein the first high thermal conductivity section and the second high thermal conductivity section have a thermal conductivity of 5 W / mK or more.

[11] The thermoelectric conversion element according to any one of [1] to

[10] , wherein the first electrode and the second electrode have a thermal conductivity of 5 W / mK or more.

[12] The thermoelectric conversion element according to any one of [1] to

[11] , wherein the substrate is flexible.

[13] A thermoelectric conversion element according to any of [1] to

[12] , wherein the distance from the first high thermal conductivity portion to the first 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 the distance from the second high thermal conductivity portion to the first 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 diagram in which a part of FIG. 1 is extracted. [Diagram 3] FIG. 3 is a schematic cross-sectional view showing a thermoelectric conversion element according to a first modified example. [Figure 4] FIG. 4 is a schematic cross-sectional view showing a thermoelectric conversion element according to a second modified example. [Diagram 5] FIG. 5 is a schematic cross-sectional view showing the first simulation condition. [Figure 6] FIGS. 6(a) and 6(b) are graphs showing the results of the first simulation. [Figure 7] FIG. 7 is a schematic cross-sectional view showing the second simulation conditions. [Figure 8] FIG. 8 is a graph showing the results of the second simulation. [Figure 9] FIG. 9 is a schematic cross-sectional view showing the third simulation condition. [Figure 10] FIG. 10 is a graph showing the results of the third simulation. [Figure 11] FIG. 11(a) is a schematic cross-sectional view of a thermoelectric conversion element according to a first reference example, and FIG. 11(b) is a schematic cross-sectional view of a thermoelectric conversion element according to a second reference example. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0008] Hereinafter, an embodiment according to one aspect 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 and FIG. 2. FIG. 1 is a schematic cross-sectional view showing the thermoelectric conversion element according to the present embodiment. FIG. 2 is a diagram of a part of FIG. 1. The thermoelectric conversion element 1 shown in FIG. 1 is an element capable of generating electricity by heat being supplied 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 electrode contained in the thermoelectric conversion element 1 also tends to be lower than that of a π-type module. In the following, it is assumed that 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 thermoelectric conversion modules 2A, 2B and sheet members 3A, 3B. The thermoelectric conversion modules 2A, 2B and the sheet members 3A, 3B are alternately stacked. In this embodiment, the sheet member 3A, the thermoelectric conversion module 2A (first thermoelectric conversion module), the sheet member 3B, and the thermoelectric conversion module 2B (second thermoelectric conversion module) are arranged in this order. The thermoelectric conversion modules 2A, 2B have the same shape as each other, and the sheet members 3A, 3B have the same shape as each other. That is, the thermoelectric conversion modules 2A, 2B have the same configuration requirements as each other, and the sheet members 3A, 3B have the same configuration requirements as each other. The direction in which the thermoelectric conversion modules 2A, 2B and the sheet members 3A, 3B are stacked corresponds to the direction along the thickness of the thermoelectric conversion modules 2A, 2B and the sheet members 3A, 3B. Hereinafter, the direction along the thickness of the thermoelectric conversion modules 2A, 2B and the sheet members 3A, 3B is simply referred to as the thickness direction D1. Viewing from the thickness direction D1 corresponds to a plan view. Fig. 2 shows a thermoelectric conversion module 2A and a pair of sheet members 3A and 3B sandwiching the thermoelectric conversion module 2A. A thermoelectric conversion element according to one aspect of the present disclosure may have a structure shown in Fig. 2.

[0011] The thermoelectric conversion module 2A is a thermoelectric conversion section in the thermoelectric conversion element 1, and has a substrate 11 (first substrate), electrodes 12, 13 (first and second electrodes), an element section 14, and a sealing layer 15 (first sealing layer).

[0012] 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 -1(corresponding to 0.3 W / mK) or more and 0.3 W / mK or less. When the thermal conductivity of the substrate 11 is 0.3 W / mK or less, a temperature difference can occur inside the element portion 14. The substrate 11 has a main surface 11a (first main surface) and a main surface 11b (second main surface) located opposite the main surface 11a. The main surfaces 11a and 11b are surfaces that intersect with the direction along the thickness of the substrate 11. The shape of the main surfaces 11a and 11b is not particularly limited, and may be, for example, a polygonal shape, a circular shape, an elliptical shape, or the like.

[0013] The electrode 12 is a member constituting a terminal included in the thermoelectric conversion element 1, and is a conductor provided on the main surface 11a of the substrate 11. The electrode 12 is, for example, a conductor made of metal, alloy, or conductive resin. When the electrode 12 is made of metal or alloy, the 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 electrode 12 may be formed using a nanopaste in which metal particles are dispersed, etc. The shape of the 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 electrode 12 is, for example, 6 μm or more and 70 μm or less. The thermal conductivity of the electrode 12 is, for example, 5 W / mK or more. In this case, the electrode 12 tends to be easily heated from the outside. The thermal conductivity of the electrode 12 may be, for example, 30 W / mK or more.

[0014] Like electrode 12, electrode 13 is a member constituting a terminal included in thermoelectric conversion element 1, and is a conductor provided on main surface 11a of substrate 11. Electrode 13 is spaced apart from electrode 12. Electrode 13 is formed at the same time as electrode 12. Therefore, electrode 13 is made of the same material as electrode 12. The shape of 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. Like electrode 12, electrode 13 has a thermal conductivity of, for example, 5 W / mK or more. The thermal conductivity of electrode 13 may be, for example, 30 W / mK or more.

[0015] The element portion 14 is a member where thermoelectric conversion is performed in the thermoelectric conversion element 1. The shape of the element portion 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 portion 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.

[0016] The n-type thermoelectric conversion layer 14a is provided on the main surface 11a of the substrate 11 and is electrically connected to the electrode 12. In this embodiment, the n-type thermoelectric conversion layer 14a is located between the electrodes 12 and 13 and is in contact with the electrode 12. The n-type thermoelectric conversion layer 14a covers a part of the electrode 12. The n-type thermoelectric conversion layer 14a is, for example, an n-type semiconductor layer. The n-type thermoelectric conversion layer 14a contains, for example, a composite of an inorganic substance and an organic substance, or a composite of multiple organic substances. The inorganic substance is, for example, titanium sulfide (TiS 2 ), Bismuth tellurium (Bi 2 Te 3 ), skutterudite, nickel (Ni), etc. The organic matter is, for example, 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. The wet method is, for example, a doctor blade method, a dip coating method, a spray coating method, a spin coating method, an inkjet method, etc. 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 electrode 12 in the thickness direction D1.

[0017] The p-type thermoelectric conversion layer 14b is provided on the 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 electrodes 12 and 13, and is located on the opposite side of the electrode 12 with the n-type thermoelectric conversion layer 14a sandwiched therebetween. The p-type thermoelectric conversion layer 14b covers a part of the 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.

[0018] 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 electrode 13 in the thickness direction D1.

[0019] The sealing layer 15 is a resin layer that protects the electrodes 12 and 13, the n-type thermoelectric conversion layer 14a, and the p-type thermoelectric conversion layer 14b. The sealing layer 15 is provided on the main surface 11a and covers the electrodes 12 and 13, the n-type thermoelectric conversion layer 14a, and the p-type thermoelectric conversion layer 14b. The resin constituting 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, and is smaller than the intervals S1 and S2 described later. The thermal conductivity of the sealing layer 15 is, for example, 0.1 W / mK or more and 0.5 W / mK or less.

[0020] The electrode 12, the n-type thermoelectric conversion layer 14a, the p-type thermoelectric conversion layer 14b, and the electrode 13 are arranged in order along the arrangement direction D2 perpendicular to the thickness direction D1. Therefore, the electrode 12 is located at one end of the thermoelectric conversion element 1 in the arrangement direction D2, and the electrode 13 is located at the other end of the thermoelectric conversion element 1 in the arrangement direction D2. Therefore, in consideration of the difference in thermal conductivity of each component of the thermoelectric conversion element 1, for example, when the thermoelectric conversion element 1 is heated from the substrate 11 side, the temperature of the part of the n-type thermoelectric conversion layer 14a that contacts the electrode 12 tends to be the highest, and the temperature of the part of the p-type thermoelectric conversion layer 14b that contacts the electrode 13 tends to be the highest. The temperature of the contact part CP between the n-type thermoelectric conversion layer 14a and the p-type thermoelectric conversion layer 14b tends to be the lowest. Therefore, 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.

[0021] 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 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.

[0022] Similar to the thermoelectric conversion module 2A, the thermoelectric conversion module 2B is a thermoelectric conversion section in the thermoelectric conversion element 1. As described above, the thermoelectric conversion modules 2A and 2B have the same configuration requirements, and therefore the thermoelectric conversion module 2B also has a substrate 11 (second substrate), an electrode 12 (third electrode), an electrode 13 (fourth electrode), an element section 14, and a sealing layer 15 (second sealing layer). In the thermoelectric conversion element 1, the sealing layer 15 constitutes the outermost surface located on the main surface 11a (on the fourth main surface) of the substrate 11. In this embodiment, the outermost layer is composed of only the sealing layer 15.

[0023] In the thermoelectric conversion modules 2A and 2B, the electrodes 12 overlap each other in the thickness direction D1, the electrodes 13 overlap each other in the thickness direction D1, the n-type thermoelectric conversion layers 14a overlap each other in the thickness direction D1, and the p-type thermoelectric conversion layers 14b overlap each other in the thickness direction D1. In this embodiment, the thermoelectric conversion module 2A is electrically connected to the thermoelectric conversion module 2B, but this is not limited to this. When the thermoelectric conversion module 2A is electrically connected to the thermoelectric conversion module 2B, the thermoelectric conversion modules 2A and 2B may be connected in series or in parallel.

[0024] The sheet member 3A is a member disposed between the thermoelectric conversion module 2A and the heat source, and is provided on the main surface 11b of the substrate 11. Therefore, heat generated from the heat source is conducted to the thermoelectric conversion module 2A via the sheet member 3A. The sheet member 3A has a first high thermal conductivity section 21, a second high thermal conductivity section 22, and a low thermal conductivity section 23.

[0025] 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 electrode 12 in the thickness direction D1, and the second highly thermally conductive portion 22 overlaps the 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 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 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 3A is heated, heat is transferred satisfactorily to the electrodes 12 and 13 via the first highly thermally conductive portion 21 and the second highly thermally conductive portion 22, respectively.

[0026] From the viewpoint of increasing the efficiency of heat transfer from the first highly thermally conductive portion 21 to the electrode 12, the 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 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 electrode 12. That is, from the viewpoint of increasing the heat transfer efficiency from the first highly thermally conductive portion 21 to the 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 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 electrode 13.

[0027] 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 section 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.

[0028] 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 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.

[0029] 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 3A is heated, the portion of the thermoelectric conversion module 2A located on the main surface 11a and overlapping 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 be generated well. From the viewpoint of generating the temperature gradient better, the thermal conductivity of the low thermal conductive portion 23 may be 0.08 W / mK or less.

[0030] The sheet member 3A is formed, for example, directly on the main surface 11b. 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 3A may be attached to the main surface 11b with 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.

[0031] The sheet member 3B is a member disposed between the thermoelectric conversion modules 2A, 2B in the thickness direction D1. The sheet member 3B is provided on the sealing layer 15 of the thermoelectric conversion module 2A, on the main surface 11b (on the third main surface) of the substrate 11 of the thermoelectric conversion module 2B. The sheet member 3B is formed, for example, directly on the main surface 11b of the substrate 11 of the thermoelectric conversion module 2B. In this case, the sheet member 3B is attached to the sealing layer 15 of the thermoelectric conversion module 2A with an adhesive (not shown). Alternatively, the sheet member 3B is attached to both of the thermoelectric conversion modules 2A, 2B with an adhesive (not shown).

[0032] As described above, the sheet members 3A and 3B have the same configuration requirements, and therefore the sheet member 3B also has a first highly thermally conductive portion 21, a second highly thermally conductive portion 22, and a low thermally conductive portion 23. The first highly thermally conductive portion 21 of the sheet member 3B is located between the electrodes 12 of the thermoelectric conversion modules 2A and 2B in the thickness direction D1, and the second highly thermally conductive portion 22 of the sheet member 3B is located between the electrodes 13 of the thermoelectric conversion modules 2A and 2B in the thickness direction D1. Therefore, when the sheet member 3A is heated, heat is transferred well from the electrodes 12 of the thermoelectric conversion module 2A to the electrodes 12 of the thermoelectric conversion module 2B via the first highly thermally conductive portion 21 of the sheet member 3B. When the sheet member 3A is heated, heat is transferred well from the electrodes 13 of the thermoelectric conversion module 2A to the electrodes 13 of the thermoelectric conversion module 2B via the second highly thermally conductive portion 22 of the sheet member 3B.

[0033] On the other hand, the low thermal conductive portion 23 of the sheet member 3B is located at least between the contact portions CP of the element portions 14 of the thermoelectric conversion modules 2A and 2B in the thickness direction D1. Therefore, when the sheet member 3A is heated, the low thermal conductive portion 23 of the sheet member 3B effectively suppresses heat transfer from the element portion 14 of the thermoelectric conversion module 2A to the element portion 14 of the thermoelectric conversion module 2B.

[0034] To summarize the above description, in the thermoelectric conversion element 1, the electrodes 12 of the thermoelectric conversion modules 2A and 2B overlap the first high thermal conductivity portions 21 of the sheet members 3A and 3B in the thickness direction D1, and the electrodes 13 of the thermoelectric conversion modules 2A and 2B overlap the second high thermal conductivity portions 22 of the sheet members 3A and 3B in the thickness direction D1. A contact portion CP (first contact portion) between the n-type thermoelectric conversion layer 14a (first n-type thermoelectric conversion layer) and the p-type thermoelectric conversion layer 14b (first p-type thermoelectric conversion layer) in the thermoelectric conversion module 2A, and a contact portion CP (second contact portion) between the n-type thermoelectric conversion layer 14a (second n-type thermoelectric conversion layer) and the p-type thermoelectric conversion layer 14b (second p-type thermoelectric conversion layer) in the thermoelectric conversion module 2B overlap the low thermal conductivity portions 23 of the sheet members 3A and 3B in the thickness direction D1.

[0035] 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 the thermoelectric conversion modules 2A and 2B, wiring for electrically connecting other thermoelectric conversion elements, wiring for extracting electric power to an external circuit, and the like.

[0036] In the thermoelectric conversion module 2A of the thermoelectric conversion element 1 according to the present embodiment described above, the electrode 12 overlaps the first high thermal conductivity portion 21 in the thickness direction D1, the 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 2A is heated from the sheet member 3A 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 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 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. Therefore, according to the thermoelectric conversion element 1 of this embodiment, it is possible to improve the thermoelectric conversion efficiency.

[0037] In addition, in this embodiment, in each of the thermoelectric conversion modules 2A and 2B, the electrode 12 overlaps the first high thermal conductive portion 21 of the sheet members 3A and 3B in the thickness direction D1, the electrode 13 overlaps the second high thermal conductive portion 22 of the sheet members 3A and 3B in the thickness direction D1, and the contact portion CP overlaps the low thermal conductive portion 23 of the sheet members 3A and 3B in the thickness direction D1. As a result, in the thermoelectric conversion module 2B, 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 electrode 12 tends to be the highest. In the p-type thermoelectric conversion layer 14b, the temperature of the contact portion CP tends to be the lowest, and the temperature of the portion closest to the electrode 13 tends to be the highest. As a result, in each of the thermoelectric conversion modules 2A and 2B stacked along the thickness direction D1, the temperature gradient in the element portion 14 tends to widen. Therefore, according to the thermoelectric conversion element 1 according to this embodiment, it is possible to achieve both a further improvement in the thermoelectric conversion efficiency of the thermoelectric conversion element 1 and a reduction in size in plan view.

[0038] In this embodiment, the thermoelectric conversion module 2A may be electrically connected to the thermoelectric conversion module 2B. In this case, the electromotive force or current capacity of the thermoelectric conversion element 1 can be increased.

[0039] In this embodiment, the sealing layer 15 of the thermoelectric conversion module 2B constitutes the outermost surface located on the main surface 11a. In this case, the temperature gradient of the element portion 14 in the thermoelectric conversion module 2B tends to be maintained.

[0040] 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.

[0041] 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.

[0042] In this embodiment, the thermal conductivity of the electrodes 12, 13 may be equal to or greater than 5 W / mK. 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 effectively increased.

[0043] 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.

[0044] 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.

[0045] A modification of the above embodiment will be described below with reference to FIGS.

[0046] Fig. 3 is a schematic cross-sectional view of a thermoelectric conversion element according to a first modified example. As shown in Fig. 3, the thermoelectric conversion element 1A according to the first modified example includes, in addition to the configuration of the thermoelectric conversion element 1, a sheet member 3C that is separate from the sheet members 3A and 3B. The sheet member 3C is located on the opposite side of the thermoelectric conversion module 2A in the thickness direction D1, sandwiching the thermoelectric conversion module 2B therebetween. Therefore, the thermoelectric conversion module 2B is sandwiched between the sheet members 3B and 3C in the thickness direction D1. The sheet member 3C is configured as a part of the outermost layer of the thermoelectric conversion element 1A.

[0047] The sheet member 3C has the same configuration as the sheet members 3A and 3B. That is, the sheet member 3C has a first high thermal conductivity portion 21, a second high thermal conductivity portion 22, and a low thermal conductivity portion 23. The first high thermal conductivity portion 21 of the sheet member 3C overlaps with the electrodes 12 of the thermoelectric conversion modules 2A and 2B and the first high thermal conductivity portion 21 of the sheet members 3A and 3B in the thickness direction D1. The second high thermal conductivity portion 22 of the sheet member 3C overlaps with the electrodes 13 of the thermoelectric conversion modules 2A and 2B and the second high thermal conductivity portion 22 of the sheet members 3A and 3B in the thickness direction D1.

[0048] The first modified example described above also provides the same advantageous effects as the above embodiment.

[0049] Fig. 4 is a schematic cross-sectional view of a thermoelectric conversion element according to a second modified example. As shown in Fig. 4, a thermoelectric conversion element 1B according to the second modified example includes thermoelectric conversion modules 2C to 2E and sheet members 3D to 3F. In the second modified example, the thermoelectric conversion modules 2C to 2E are electrically connected to each other, but this is not limited to the above.

[0050] Each of the thermoelectric conversion modules 2C to 2E has a substrate 11, a plurality of element units 14, a sealing layer 15, and a plurality of electrodes 16. The element units 14 and the electrodes 16 provided on the substrate 11 and covered with the sealing layer 15 are alternately arranged in the arrangement direction D2. Therefore, some of the plurality of electrodes 16 are in contact with both the n-type thermoelectric conversion layer 14a and the p-type thermoelectric conversion layer 14b. In the thermoelectric conversion element 1B, the n-type thermoelectric conversion layer 14a and the p-type thermoelectric conversion layer 14b are alternately stacked along the thickness direction D1. Therefore, for example, the electrodes 16 in contact only with the n-type thermoelectric conversion layer 14a and the electrodes 16 in contact only with the p-type thermoelectric conversion layer 14b are alternately stacked along the thickness direction D1. The electrodes 16 are conductors corresponding to the electrodes 12 or 13 in the above embodiment.

[0051] The sheet member 3D is located on one side of the thermoelectric conversion module 2C in the thickness direction D1. The sheet member 3E is located on the other side of the thermoelectric conversion module 2C (and one side of the thermoelectric conversion module 2D) in the thickness direction D1, and is located between the thermoelectric conversion modules 2C and 2D. The sheet member 3F is located on the other side of the thermoelectric conversion module 2D (and one side of the thermoelectric conversion module 2E) in the thickness direction D1, and is located between the thermoelectric conversion modules 2D and 2E. The sheet members 3D to 3F include a low thermal conductive portion 23 and a high thermal conductive portion 24. The high thermal conductive portion 24 is a portion that overlaps the electrode 16 in the thickness direction D1. The high thermal conductive portion 24 corresponds to the first high thermal conductive portion 21 or the second high thermal conductive portion 22 in the above embodiment.

[0052] From the viewpoint of increasing the efficiency of heat transfer from the highly thermally conductive portion 24 to the electrode 16, the electrode 16 may be located inside the edge of the highly thermally conductive portion 24 in a planar view, or the edge of the electrode 16 may completely overlap the edge of the highly thermally conductive portion 24. From the viewpoint of widening the temperature gradient along the arrangement direction D2 inside each element portion 14, the highly thermally conductive portion 24 may be located inside the edge of the electrode 16 that contacts both the n-type thermoelectric conversion layer 14a and the p-type thermoelectric conversion layer 14b in a planar view.

[0053] The second modified example described above also provides the same advantageous effects as the above embodiment and the above first modified example.

[0054] 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.

[0055] FIG. 5 is a schematic cross-sectional view showing the first simulation conditions. As shown in FIG. 5, 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.

[0056] 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.

[0057] 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.

[0058] 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.

[0059] 6(a) and 6(b) are graphs showing the first simulation results. FIG. 6(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. 6(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. 6(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.

[0060] FIG. 6B 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. 6B, 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. 6B, 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.

[0061] FIG. 7 is a schematic cross-sectional view showing the second simulation conditions. As shown in FIG. 7, 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.

[0062] 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.

[0063] FIG. 8 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. 8, the horizontal axis shows the length Z, and the vertical axis shows the temperature difference between the temperature evaluation points 54, 55. As shown in FIG. 8, 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.

[0064] FIG. 9 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. 9, 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.

[0065] 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.

[0066] 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).

[0067] FIG. 10 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. 10, 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. 10, 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.

[0068] 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. 11(a) is a schematic cross-sectional view of a thermoelectric conversion element according to a first reference example, and Fig. 11(b) is a schematic cross-sectional view of a thermoelectric conversion element according to a second reference example.

[0069] The thermoelectric conversion element 101 shown in FIG. 11(a) includes a thermoelectric conversion module 2A and sheet members 3A-1 and 103-1. The sheet member 3A-1 is a member having a shape similar to that of the sheet member 3, and includes a first highly thermally conductive portion 21-1, a second highly thermally conductive portion 22-1, and a low thermally conductive portion 23-1. The thicknesses (lengths along the thickness direction D1) of the sheet members 3A and 3A-1 may be different from each other. The sheet member 103-1 includes a highly thermally conductive portion 110-1 and a low thermally conductive portion 120-1 provided on the sealing layer 15 of the thermoelectric conversion module 2A. The highly thermally conductive portion 110-1 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 110-1 in the arrangement direction D2 overlaps with the contact portion CP in the thickness direction D1. The low thermal conductivity portion 120-1 is a sheet member provided to reduce heat dissipation of the electrodes 12, 13 and their surroundings. The low thermal conductivity portion 120-1 surrounds the high thermal conductivity portion 110-1 in a direction perpendicular to the thickness direction D1, and overlaps with the electrodes 12, 13, the first highly thermal conductive portion 21-1, and the second highly thermal conductive portion 22-1 in the thickness direction D1. The high thermal conductivity portion 110-1 and the low thermal conductivity portion 120-1 have the same length in the thickness direction D1.

[0070] The thermoelectric conversion element 201 shown in FIG. 11(b) includes thermoelectric conversion modules 2A and 202, and sheet members 3A-2, 3B-2, and 103-2. In the thermoelectric conversion element 201, the sheet member 3A-2, the thermoelectric conversion module 2A, the sheet member 103-2, the thermoelectric conversion module 202, and the sheet member 3B-2 are laminated in this order. The sheet members 3A-2 and 3B-2 are members having the same shape as the sheet members 3A and 3A-1, and include a first high thermal conductive portion 21-2, a second high thermal conductive portion 22-2, and a low thermal conductive portion 23-2. That is, the sheet members 3A-2 and 3B-2 have the same shape or substantially the same shape as each other. The thicknesses (lengths along the thickness direction D1) of the sheet members 3A-2 and 3B-2 and the thicknesses (lengths along the thickness direction D1) of the sheet members 3A and 3A-1 may be different from each other. The sheet member 103-2 has a similar shape to the sheet member 103-1, and includes a high thermal conductive portion 110-2 and a low thermal conductive portion 120-2. The sheet members 103-1 and 103-2 may have different thicknesses (lengths along the thickness direction D1).

[0071] The thermoelectric conversion module 202 includes a substrate 11, an electrode 212, an n-type thermoelectric conversion layer 14a, a p-type thermoelectric conversion layer 14b, and a sealing layer 15. The electrode 212 overlaps the contact portion CP of the thermoelectric conversion module 2A and the high thermal conductivity portion 110-2 of the sheet member 103-2 in the thickness direction D1. Therefore, when the thermoelectric conversion element 201 is heated from the sheet member 3A-2 side in the thickness direction D1, the electrode 212 is mainly heated by heat transferred through the element portion 14 of the thermoelectric conversion module 2A and the high thermal conductivity portion 110-2. In the arrangement direction D2, the n-type thermoelectric conversion layer 14a is provided on one end side of the electrode 212, and the p-type thermoelectric conversion layer 14b is provided on the other end side of the electrode 212. In the thermoelectric conversion module 202, the n-type thermoelectric conversion layer 14a and the p-type thermoelectric conversion layer 14b are spaced apart from each other.

[0072] In this simulation, in the thermoelectric conversion elements 1, 101, 201, the length of the substrate 11 along the thickness direction D1 was set to 50 μm, the length of the sheet members 3A, 3B along the thickness direction D1 was set to 300 μm, the length of the sheet members 3A-1, 103-1 along the thickness direction D1 was set to 400 μm, and the length of the sheet members 3A-2, 3B-2, 103-2 along the thickness direction D1 was set to 200 μm. The length of the electrodes 12, 13, 212 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 300 μm, the lengths of the first high thermal conductive portion 21-1, the second high thermal conductive portion 22-1 and the low thermal conductive portion 23-1 along the thickness direction D1 were set to 400 μm, and the lengths of the first high thermal conductive portion 21-2, the second high thermal conductive portion 22-2 and the low thermal conductive portion 23-2 along the thickness direction D1 were set to 200 μm. Furthermore, the length of high thermal conductivity portion 110-1 and low thermal conductivity portion 120-1 along thickness direction D1 was set to 400 μm, and the length of high thermal conductivity portion 110-2 and low thermal conductivity portion 120-2 along thickness direction D1 was set to 300 μm.

[0073] In addition, the lengths of the thermoelectric conversion modules 2A, 2B, 202 and the sheet members 3A, 3A-1, 3A-2, 3B, 3B-2, 103-1, 103-2 along the arrangement direction D2 were set to 15 mm, the lengths of the electrodes 12, 13, 212 along the arrangement direction D2 were set to 3 mm, the lengths of the n-type thermoelectric conversion layer 14a and the p-type thermoelectric conversion layer 14b along the arrangement direction D2 were set to 2.5 mm, and the lengths of the first high thermal conductivity portions 21, 21-1, 21-2 and the second high thermal conductivity portions 22, 22-1, 22-2 along the arrangement direction D2 were set to 3 mm. Furthermore, the lengths of the high thermal conductivity portions 110-1, 110-2 along the arrangement direction D2 were set to 3 mm.

[0074] In this simulation, in the thermoelectric conversion elements 1, 101, 201, the thermal conductivity of the substrate 11 and the sealing layer 15 was set to 0.3 W / mK, the thermal conductivity of the electrodes 12, 13, 212 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 conductivity portions 21, 21-1, 21-2 and the second high thermal conductivity portions 22, 22-1, 22-2 was set to 5 W / mK, and the thermal conductivity of the low thermal conductivity portions 23, 23-1, 23-2 was set to 0.05 W / mK. The thermal conductivity of high thermal conductive portions 110-1 and 110-2 was set to 5 W / mK, and the thermal conductivity of low thermal conductive portions 120-1 and 120-2 was set to 0.05 W / mK.

[0075] In the thermoelectric conversion elements 1, 101, and 201, 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 temperatures of the exposed surfaces of the sheet members 3A, 3A-1, and 3A-2 intersecting the thickness direction D1 were also set to 100° C.

[0076] In the thermoelectric conversion elements 1, 101, and 201 set under the above-mentioned conditions, the maximum temperature difference of the element portion 14 was simulated. In the thermoelectric conversion element 201, the maximum temperature difference of one of the n-type thermoelectric conversion layer 14a and the p-type thermoelectric conversion layer 14b was simulated. As a result, in the thermoelectric conversion element 1, the maximum temperature difference of the element portion 14 of the thermoelectric conversion module 2A was 3.193°C, and the maximum temperature difference of the element portion 14 of the thermoelectric conversion module 2B was 6.628°C. The maximum temperature difference of the element portion 14 of the thermoelectric conversion element 101 was 4.909°C. In the thermoelectric conversion element 201, the maximum temperature difference of the element portion 14 of the thermoelectric conversion module 2A was 2.793°C, and the maximum temperature difference of the thermoelectric conversion module 202 was 1.168°C. From this, the total temperature difference of the thermoelectric conversion element 1 was 9.821°C, and the total temperature difference of the thermoelectric conversion element 201 was 3.961°C.

[0077] The above results suggest that a configuration including the thermoelectric conversion element 101 and in which a plurality of thermoelectric conversion modules are stacked along the thickness direction (for example, thermoelectric conversion element 201) tends to have a lower thermoelectric conversion efficiency than the configuration of thermoelectric conversion element 1. In other words, it is suggested that a configuration including the thermoelectric conversion element 101 and in which a plurality of thermoelectric conversion modules are stacked along the thickness direction (for example, thermoelectric conversion element 201) tends to have a lower power generation capacity per unit area than the configuration of thermoelectric conversion element 1.

[0078] The thermoelectric conversion element according to the present disclosure is not limited to the above embodiment and the above modification, and various other modifications are possible. For example, the above embodiment and the above second modification may be appropriately combined to provide a plurality of element parts along the arrangement direction on the substrate. The above first modification and the above second modification may be appropriately combined.

[0079] In the above embodiment and the second modified example, the outermost layer is composed of only the sealing layer, but is not limited thereto. For example, the outermost layer may be composed of the sealing layer and a member different from the sealing layer. Alternatively, the outermost layer may be composed of another sheet member made of a low thermal conductive portion.

[0080] In the above embodiment and modified example, the electrodes are formed simultaneously, but this is not limiting. [Explanation of symbols]

[0081] 1, 1A, 1B, 101, 201... thermoelectric conversion element, 2A to 2E, 202... thermoelectric conversion module, 3A to 3F, 3A-1, 3A-2, 3B-2, 103-1, 103-2... sheet member, 11... substrate, 11a, 11b... main surface, 12, 13, 16, 212... electrode, 14... element portion, 14a... n-type thermoelectric conversion layer, 14b... p-type thermoelectric conversion layer, 15... sealing Layer, 21, 21-1, 21-2...first high thermal conductivity section, 22, 22-1, 22-2...second high thermal conductivity section, 23, 23-1, 23-2...low thermal conductivity section, 24...high thermal conductivity section, 110-1, 110-2...high thermal conductivity section, 120-1, 120-2...low thermal conductivity section, CP...contact section, S1, S2...spacing, T1...length of first high thermal conductivity section, T2...length of second high thermal conductivity section.

Claims

1. A thermoelectric conversion element including a first thermoelectric conversion module and a pair of sheet members sandwiching the first thermoelectric conversion module, The first thermoelectric conversion module is a first 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, a first n-type thermoelectric conversion layer electrically connected to the first electrode, a first p-type thermoelectric conversion layer in contact with the first n-type thermoelectric conversion layer, and a second electrode electrically connected to the first p-type thermoelectric conversion layer; a sealing layer provided on the first principal surface and covering the first electrode, the first n-type thermoelectric conversion layer, the first p-type thermoelectric conversion layer, and the second electrode; each of the pair of sheet members includes a first high thermal conductive portion, a second high thermal conductive portion, and a low thermal conductive portion (excluding the low thermal conductive portion having adhesive properties); the first electrode, the first n-type thermoelectric conversion layer, the first p-type thermoelectric conversion layer, and the second electrode are sequentially arranged along an arrangement direction perpendicular to a thickness direction of the first substrate, the first electrode overlaps the first high thermal conductive portion of each of the pair of sheet members in the thickness direction, the second electrode overlaps the second high thermal conductive portion of each of the pair of sheet members in the thickness direction, a first contact portion between the first n-type thermoelectric conversion layer and the first p-type thermoelectric conversion layer overlaps with the low thermal conductivity portion of each of the pair of sheet members in the thickness direction; each of the first high thermal conductivity portion, the second high thermal conductivity portion, and the low thermal conductivity portion included in one of the pair of sheet members directly contacts the second main surface of the first substrate; Thermoelectric conversion element.

2. a second thermoelectric conversion module located on the opposite side of the first thermoelectric conversion module in the thickness direction, with the other of the pair of sheet members being sandwiched therebetween; The second thermoelectric conversion module is a second substrate having a third main surface located on the first thermoelectric conversion module side in the thickness direction and a fourth main surface located on an opposite side to the third main surface; a third electrode provided on the fourth principal surface, a second n-type thermoelectric conversion layer electrically connected to the third electrode, a second p-type thermoelectric conversion layer in contact with the second n-type thermoelectric conversion layer, and a fourth electrode electrically connected to the second p-type thermoelectric conversion layer; 2. The thermoelectric conversion element according to claim 1, further comprising: a second sealing layer provided on the fourth principal surface and covering the third electrode, the second n-type thermoelectric conversion layer, the second p-type thermoelectric conversion layer, and the fourth electrode.

3. the third electrode overlaps with the first high thermal conductive portion and the first electrode of each of the pair of sheet members in the thickness direction, the fourth electrode overlaps with the second high thermal conductive portion and the second electrode of each of the pair of sheet members in the thickness direction, The thermoelectric conversion element according to claim 2 , wherein a second contact portion between the second n-type thermoelectric conversion layer and the second p-type thermoelectric conversion layer overlaps the low thermal conductivity portion of each of the pair of sheet members in the thickness direction.

4. the third electrode overlaps with the second high thermal conductive portion and the second electrode of each of the pair of sheet members in the thickness direction, the fourth electrode overlaps with the first high thermal conductive portion and the first electrode of each of the pair of sheet members in the thickness direction, The thermoelectric conversion element according to claim 2 , wherein a second contact portion between the second n-type thermoelectric conversion layer and the second p-type thermoelectric conversion layer overlaps the low thermal conductivity portion of each of the pair of sheet members in the thickness direction.

5. The thermoelectric conversion element according to any one of claims 2 to 4, wherein the second thermoelectric conversion module is electrically connected to the first thermoelectric conversion module.

6. The thermoelectric conversion element according to any one of claims 2 to 5, wherein the second sealing layer constitutes an outermost surface located on the fourth main surface.

7. Further comprising a sheet member other than the pair of sheet members, The thermoelectric conversion element according to any one of claims 2 to 5, wherein the other sheet member is located on the opposite side of the first thermoelectric conversion module in the thickness direction, sandwiching the second thermoelectric conversion module therebetween.

8. The thermoelectric conversion element according to any one of claims 1 to 7, wherein the thermal conductivity of the low thermal conductive portion is 0.01 W / mK or more and 0.2 W / mK or less.

9. The thermoelectric conversion element according to claim 8 , 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 0.08 W / mK.

10. The thermoelectric conversion element according to any one of claims 1 to 9, 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.

11. The thermoelectric conversion element according to any one of claims 1 to 10, wherein the first substrate is flexible.

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