Thermoelectric conversion module and method for manufacturing the same

Abstract

This thermoelectric conversion module comprises: a substrate that has a first main surface and a second main surface; a thermoelectric conversion part that is located on the first main surface; and a first thermal conduction part and a second thermal conduction part that are located on the second main surface. The thermoelectric conversion part has a p-type thermoelectric conversion element and an n-type thermoelectric conversion element side-by-side along a first direction, a first end part of the p-type thermoelectric conversion element contacts a first end part of the n-type thermoelectric conversion element, the first thermal conduction part overlaps a second end part of the p-type thermoelectric conversion element, the second thermal conduction part overlaps a second end part of the n-type thermoelectric conversion element, the thicknesses of the n-type thermoelectric conversion element and the p-type thermoelectric conversion element are both 3-30 µm, the p-type thermoelectric conversion element and the n-type thermoelectric conversion element both include carbon nanotubes and a conductive resin, and the mass ratio of the carbon nanotubes to the total mass of each thermoelectric conversion part is 30-70%.

Description

[Technical Field]

[0001] This disclosure relates to a thermoelectric conversion module and a method for manufacturing the same. [Background technology]

[0002] Thermoelectric elements are sometimes used to generate electricity using geothermal energy or waste heat from factories. Patent Document 1 discloses an embodiment in which a flexible substrate having a pattern layer consisting 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 Patent Document 1, the metal layer in one flexible substrate overlaps one electrode in the thermoelectric conversion module, and the metal layer in the other flexible substrate overlaps the other electrode in the thermoelectric conversion module. In the above embodiment, by setting one flexible substrate to a high temperature state and the other flexible substrate to a low temperature state, a temperature difference is created in the planar 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 [Overview of the project] [Problems that the invention aims to solve]

[0004] To improve the output of a thermoelectric conversion module as described in Patent Document 1, for example, one could increase the thermoelectric conversion efficiency by widening the temperature difference. In Patent Document 1, one way to widen the temperature difference is to make the P-type thermoelectric element material and the N-type thermoelectric element material thinner. In this case, the thinner each thermoelectric element material becomes, the higher the electrical resistance of each thermoelectric element material becomes, which may actually worsen the thermoelectric conversion efficiency. For this reason, there is a need for a method that can reliably improve the output of a thermoelectric conversion module per unit area.

[0005] One aspect of this disclosure is to provide a thermoelectric conversion module capable of improving output per unit area and a method for manufacturing the same. [Means for solving the problem]

[0006] A thermoelectric conversion module and a method for manufacturing the same relating to one aspect of this disclosure are as follows. [1] A substrate having a first main surface and a second main surface located opposite the first main surface, a thermoelectric conversion section located on the first main surface, and a first heat conduction section and a second heat conduction section located on the second main surface and adjacent to each other along a first direction perpendicular to the thickness direction of the substrate, wherein the thermoelectric conversion section has a p-type thermoelectric conversion element and an n-type thermoelectric conversion element arranged along the first direction, the first end of the p-type thermoelectric conversion element in the first direction is in contact with the first end of the n-type thermoelectric conversion element in the first direction, the first heat conduction section overlaps with the second end of the p-type thermoelectric conversion element in the first direction in the thickness direction, and the second heat conduction section A thermoelectric conversion module in which the second end of the n-type thermoelectric conversion element overlaps the p-type thermoelectric conversion element in the first direction, the thickness of the p-type thermoelectric conversion element and the n-type thermoelectric conversion element are 3 μm or more and 30 μm or less, the distance between the first heat conduction part and the second heat conduction part in the first direction is greater than the length of the p-type thermoelectric conversion element and the length of the n-type thermoelectric conversion element in the first direction, the p-type thermoelectric conversion element and the n-type thermoelectric conversion element each contain carbon nanotubes and conductive resin, and the mass ratio of carbon nanotubes to the total mass of the thermoelectric conversion part is 30% or more and 70% or less. [2] The thermoelectric conversion module as described in [1], wherein the mass ratio of carbon nanotubes to the total mass of the thermoelectric conversion section is 40% or more and 60% or less. [3] The thermoelectric conversion module according to [1] or [2], wherein the mass ratio of carbon nanotubes to the total mass of the p-type thermoelectric conversion element is 30% or more and 70% or less, and the mass ratio of carbon nanotubes to the total mass of the n-type thermoelectric conversion element is 30% or more and 70% or less. [4] The thermoelectric conversion module according to any one of [1] to [3], wherein the distance between the first heat conduction part and the second heat conduction part in the first direction is 3 mm or more and 15 mm or less. [5] A thermoelectric conversion module according to any one of [1] to [4], wherein the thickness of each of the p-type thermoelectric conversion element and the n-type thermoelectric conversion element is 5 μm or more and 25 μm or less, and the distance between the first heat conduction part and the second heat conduction part in the first direction is 3 mm or more and less than 12 mm. [6] Further comprising: a first thermoelectric conversion group located on a first main surface and having a thermoelectric conversion section; and a second thermoelectric conversion group located on the first main surface and adjacent to the first thermoelectric conversion group along a second direction perpendicular to the thickness direction and the first direction, wherein the second thermoelectric conversion group has a second thermoelectric conversion section located adjacent to the thermoelectric conversion section along the second direction, and the second thermoelectric conversion section has a second p-type thermoelectric conversion element and a second n-type thermoelectric conversion element arranged along the first direction, and the first of the second p-type thermoelectric conversion elements in the first direction The end of the thermoelectric conversion module according to any one of [1] to [5], wherein the end is in contact with the first end of the second n-type thermoelectric conversion element in the first direction, and each of the first and second heat conduction portions extends along the second direction, and in the thickness direction, the first heat conduction portion overlaps with the second end of the second n-type thermoelectric conversion element included in the second thermoelectric conversion portion in the first direction, and in the thickness direction, the second heat conduction portion overlaps with the second end of the second p-type thermoelectric conversion element included in the second thermoelectric conversion portion in the first direction. [7] The thermoelectric conversion module according to [6], further comprising: a first conductive portion located on a first main surface and connected to one end of a first thermoelectric conversion group in a first direction; and a second conductive portion located on the first main surface and connected to the other end of the first thermoelectric conversion group in a first direction and to one end of a second thermoelectric conversion group in a first direction, wherein the conductivity types of the first conductive portion and the second conductive portion are the same. [8] The thermoelectric conversion module according to any one of [1] to [7], wherein the width of the first heat conduction section and the second heat conduction section along the first direction is 0.5 mm or more and 2.0 mm or less. [9] A thermoelectric conversion module according to any one of [1] to [8], wherein the substrate, the first thermoelectric conversion unit, the second thermoelectric conversion unit, the first heat conduction unit, and the second heat conduction unit each exhibit flexibility.

[10] A method for manufacturing a thermoelectric conversion module according to any one of [1] to [9], comprising: a first step of forming a mask on a first main surface of a substrate; a second step of forming a first layer containing a p-type thermoelectric conversion material on the first main surface; a third step of forming a thermoelectric conversion layer extending in a first direction by immersing the substrate in an organic solvent after removing the mask; a fourth step of forming a plurality of heat conduction parts on a second main surface of the substrate after the third step; and a fifth step of forming an n-type thermoelectric conversion element in a part of the thermoelectric conversion layer by dropping a dopant solution onto the part after the fourth step. [Effects of the Invention]

[0007] According to one aspect of this disclosure, it is possible to provide a thermoelectric conversion module capable of improving output per unit area and a method for manufacturing the same. [Brief explanation of the drawing]

[0008] [Figure 1] Figure 1(a) is a schematic plan view showing a thermoelectric conversion module according to the embodiment, and Figure 1(b) is a schematic bottom view showing a thermoelectric conversion module according to the embodiment. [Figure 2] Figure 2(a) is an enlarged view of a portion of Figure 1(a) (the area enclosed by the dashed line), and Figure 2(b) is a cross-sectional view along the line IIb-IIb in Figure 2(a). [Figure 3] Figures 3(a) to 3(c) illustrate the manufacturing method of the thermoelectric conversion module according to the embodiment. [Figure 4] Figures 4(a) and 4(b) illustrate the manufacturing method of the thermoelectric conversion module according to the embodiment. [Figure 5] Figures 5(a) and 5(b) illustrate the manufacturing method of the thermoelectric conversion module according to the embodiment. [Figure 6] Figure 6 is a graph showing the power factors of the thermoelectric conversion sections in Examples 1-5 and Comparative Examples 1 and 2. [Figure 7] Figure 7 is a graph showing the temperature difference of the thermoelectric conversion section in Examples 1-5 and Comparative Examples 1 and 2. [Figure 8] FIG. 8 is a graph showing the maximum output density of the thermoelectric conversion modules of Examples 1 to 5 and Comparative Examples 1 and 2.

DETAILED DESCRIPTION OF THE INVENTION

[0009] Hereinafter, embodiments of the present disclosure will be described in detail with reference to the accompanying drawings. In the following description, the same reference numerals will be used for the same elements or elements having the same function, and redundant descriptions will be omitted. The terms "identical" and similar words in this specification are not limited to "exactly identical".

[0010] First, the configuration of the thermoelectric conversion module according to this embodiment will be described while referring to FIGS. 1 and 2. FIG. 1(a) is a schematic plan view showing the thermoelectric conversion module according to this embodiment, and FIG. 1(b) is a schematic bottom view showing the thermoelectric conversion module according to this embodiment. FIG. 2(a) is an enlarged view of a part (region surrounded by a dashed line) of FIG. 1(a). FIG. 2(b) is a cross-sectional view taken along line IIb-IIb of FIG. 2(a).

[0011] The thermoelectric conversion module 1 shown in FIGS. 1(a) and 1(b) is a device that can generate electricity by receiving heat from the outside. The thermoelectric conversion module 1 is a so-called in-plane type device. Therefore, the thermoelectric conversion module 1 tends to be more excellent in processability and flexibility than, for example, a π-type element (cross-plane type element). Thus, the thermoelectric conversion module 1 can be provided along the side surface of, for example, a cylindrical pipe used for recovering factory waste heat. That is, the thermoelectric conversion module 1 can be easily arranged at various locations. Therefore, the thermoelectric conversion module 1 is used, for example, as a power source for a plant sensor that utilizes waste heat. In addition, the contact resistance between the thermoelectric conversion material and the electrode included in the thermoelectric conversion module 1 also tends to be lower than that of a π-type module. Hereinafter, the temperatures of each component of the thermoelectric conversion module 1 are assumed to be measured under natural convection conditions of air.

[0012] The thermoelectric conversion module 1 includes a substrate 2, a plurality of thermoelectric conversion groups 3, a plurality of conductive parts 4, and a plurality of heat conduction parts 5. At least one of the substrate 2, the plurality of thermoelectric conversion groups 3, the plurality of conductive parts 4, and the plurality of heat conduction parts 5 exhibits flexibility.

[0013] The substrate 2 is a resin sheet member exhibiting heat resistance and flexibility, and for example, has a substantially flat plate shape. The resin constituting the substrate 2 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 2 is, for example, 5 μm or more and 50 μm or less. The thermal conductivity of the substrate 2 is, for example, 0.1 W / mK (corresponding to 0.1 watt per meter per kelvin, and 0.1 W×m -1 ×K -1 and the like) or more and 0.3 W / mK or less. When the thermal conductivity of the substrate 2 is 0.3 W / mK or less, a temperature difference can occur inside the thermoelectric conversion group 3. The thermal conductivity of the substrate 2 is measured by a steady-state method or a non-steady-state method.

[0014] The substrate 2 has a first main surface 2a and a second main surface 2b located on the opposite side of the first main surface 2a. The first main surface 2a and the second main surface 2b are surfaces that intersect with respect to the direction along the thickness of the substrate 2. The shapes of the first main surface 2a and the second main surface 2b are not particularly limited, and are, for example, polygonal, circular, elliptical, or the like. Hereinafter, the direction along the thickness of the substrate 2 is simply referred to as the thickness direction D1. Looking from the thickness direction D1 corresponds to a plan view. Also, the directions orthogonal to the thickness direction D1 are defined as the first direction D2 and the second direction D3.

[0015] On the first main surface 2a, a thermoelectric conversion region R1 and two conductive regions R2 are defined. Multiple thermoelectric conversion groups 3 are provided in the thermoelectric conversion region R1. Multiple conductive parts 4 are provided in each conductive region R2. The thermoelectric conversion region R1 is located between the two conductive regions R2 in the first direction D2. The larger the proportion of the first main surface 2a occupied by the thermoelectric conversion region R1, the higher the output of the thermoelectric conversion module 1 tends to be. In a plan view, the proportion of the area occupied by the thermoelectric conversion region R1 on the first main surface 2a is, for example, 50% to 90%. Also, in a plan view, the proportion of the area occupied by the two conductive regions R2 on the first main surface 2a is, for example, 5% to 30%. In this case, the thermoelectric conversion module 1 can exhibit good output while reliably forming conductive paths connecting the thermoelectric conversion groups 3.

[0016] Each of the multiple thermoelectric conversion groups 3 is a part that can generate electricity by being supplied with heat from the outside, and is located on the first main surface 2a. The multiple thermoelectric conversion groups 3 extend along the first direction D2 and are arranged along the second direction D3. Each of the multiple thermoelectric conversion groups 3 has a strip shape when viewed from the thickness direction D1. Each thermoelectric conversion group 3 is spaced apart from each other, but is electrically connected to each other in series. In the first direction D2, one end of each thermoelectric conversion group 3 is connected to one of the multiple conductive parts 4 included in one conductive region R2, and the other end of each thermoelectric conversion group 3 is connected to one of the multiple conductive parts 4 included in the other conductive region R2. Each of the multiple thermoelectric conversion groups 3 has multiple thermoelectric conversion parts 11. In this embodiment, each thermoelectric conversion group 3 has 10 thermoelectric conversion parts 11, but is not limited to this. In each thermoelectric conversion group 3, the multiple thermoelectric conversion parts 11 are arranged along the first direction D2. Two adjacent thermoelectric conversion units 11 in the first direction D2 are in contact with each other and are connected in series.

[0017] In the following, of the two thermoelectric conversion groups 3 shown in Figure 2(a), one thermoelectric conversion group 3 will be referred to as the first thermoelectric conversion group 3a, and the other thermoelectric conversion group 3 located next to the first thermoelectric conversion group 3a along the second direction D3 will be referred to as the second thermoelectric conversion group 3b. Furthermore, the thermoelectric conversion unit 11 included in the first thermoelectric conversion group 3a will be referred to as the first thermoelectric conversion unit 11a, and the thermoelectric conversion unit 11 included in the second thermoelectric conversion group 3b will be referred to as the second thermoelectric conversion unit 11b. The multiple first thermoelectric conversion units 11a included in the first thermoelectric conversion group 3a are arranged sequentially along the first direction D2, and the multiple second thermoelectric conversion units 11b included in the second thermoelectric conversion group 3b are arranged sequentially along the first direction D2. The first thermoelectric conversion units 11a and the second thermoelectric conversion units 11b are adjacent to each other along the second direction D3.

[0018] Each of the multiple thermoelectric conversion sections 11 is a part in the thermoelectric conversion module 1 where thermoelectric conversion is performed, and is flexible. The shape of the thermoelectric conversion section 11 in plan view is not particularly limited, but can be polygonal, circular, elliptical, etc. The p-type thermoelectric conversion element 21 and the n-type thermoelectric conversion element 22 have the same shape, but are not limited to this. Each thermoelectric conversion section 11 has a p-type thermoelectric conversion element 21 and an n-type thermoelectric conversion element 22 arranged along the first direction D2. In each thermoelectric conversion section 11, the first end 21a of the p-type thermoelectric conversion element 21 and the first end 22a of the n-type thermoelectric conversion element 22 in the first direction D2 are in contact with each other. In each thermoelectric conversion unit 11, the second end 21b of the p-type thermoelectric conversion element 21 in the first direction D2 is located at one end of the corresponding thermoelectric conversion unit 11, and the second end 22b of the n-type thermoelectric conversion element 22 in the first direction D2 is located at the other end of the corresponding thermoelectric conversion unit 11. In two adjacent thermoelectric conversion units 11 in the first direction D2, the second end 21b of the p-type thermoelectric conversion element 21 included in one thermoelectric conversion unit 11 and the second end 22b of the n-type thermoelectric conversion element 22 included in the other thermoelectric conversion unit 11 are in contact with each other.

[0019] In each of the multiple thermoelectric conversion groups 3, the p-type thermoelectric conversion elements 21 and the n-type thermoelectric conversion elements 22 are arranged alternately in the first direction D2. As shown in Figure 2(a), in this embodiment, the p-type thermoelectric conversion element 21 of the first thermoelectric conversion unit 11a is located next to the n-type thermoelectric conversion element 22 (second n-type thermoelectric conversion element) of the second thermoelectric conversion unit 11b in the second direction D3, and the n-type thermoelectric conversion element 22 of the first thermoelectric conversion unit 11a is located next to the p-type thermoelectric conversion element 21 (second p-type thermoelectric conversion element) of the second thermoelectric conversion unit 11b in the second direction D3.

[0020] The p-type thermoelectric element 21 is provided on the first main surface 2a of the substrate 2 and is in contact with the n-type thermoelectric element 22. The thickness T1 of the p-type thermoelectric element 21 is, for example, 3 μm or more and 30 μm or less. By having a thickness T1 of 3 μm or more, the electrical resistance of the p-type thermoelectric element 21 can be reduced effectively. By having a thickness T1 of 30 μm or less, a temperature gradient can be easily formed inside the p-type thermoelectric element 21. The thickness T1 may be 5 μm or more, 8 μm or more, 10 μm or more, 25 μm or less, 20 μm or less, or 15 μm or less. The length L1 of the p-type thermoelectric element 21 in the first direction D2 is, for example, 2 mm or more and 10 mm or less. In this case, a temperature gradient can be easily formed inside the p-type thermoelectric element 21. The length of the p-type thermoelectric element 21 in the second direction D3 is, for example, 5 mm or more and 30 mm or less. In this case, a sufficient number of thermoelectric conversion sections 11 can be formed on the first main surface 2a. The thermal conductivity of the p-type thermoelectric element 21 in the in-plane direction is, for example, 20.0 W / mK or more and 35.0 W / mK or less. This thermal conductivity may be 22.0 W / mK or more, 23.0 W / mK or more, 25.0 W / mK or more, 32.0 W / mK or less, 30.0 W / mK or less, or 28.0 W / mK or less. The thermal conductivity of the p-type thermoelectric element 21 in the in-plane direction is measured, for example, by the optical AC method or the 3-omega method. The p-type thermoelectric element 21 is formed, for example, by various dry or wet methods. Wet methods include, for example, the doctor blade method, dip coating method, spray coating method, spin coating method, and inkjet method.

[0021] The p-type thermoelectric element 21 is, for example, a p-type semiconductor layer. The p-type thermoelectric element 21 includes, for example, carbon nanotubes (CNTs) and a conductive resin different from the carbon nanotubes. The carbon nanotubes are p-type. The carbon nanotubes may be single-layer, double-layer, or multi-layer. From the viewpoint of the electrical conductivity of the p-type thermoelectric element 21, single-walled carbon nanotubes (SWCNTs) may be used. The ratio of single-walled carbon nanotubes to the total amount of carbon nanotubes may be 25% by mass or more, 50% by mass or more, or 100% by mass. The diameter of the single-walled carbon nanotubes is not particularly limited, but for example, it may be 20 nm or less, 10 nm or less, or 3 nm or less. The lower limit of the diameter of the single-walled carbon nanotubes is also not particularly limited, but may be 0.4 nm or more, or 0.5 nm or more. The thermal conductivity of the carbon nanotubes is, for example, 30 W / mK or more and 40 W / mK or less.

[0022] In this specification, the diameter of single-walled carbon nanotubes is defined as 100-300 cm² by Raman spectroscopy. -1 The wavenumber of the peak that appears (ω(cm) -1 From this, the diameter can be calculated using the formula "diameter (nm) = 248 / ω". The G / D ratio in laser Raman spectroscopy is known as a method for evaluating single-walled carbon nanotubes. In this embodiment, the single-walled carbon nanotube may have a G / D ratio of 10 or more, or 20 or more, in laser Raman spectroscopy at a wavelength of 532 nm. Using such a single-walled carbon nanotube tends to yield a p-type thermoelectric conversion element 21 with even better electrical conductivity. The upper limit of the above G / D ratio is not particularly limited and may be 500 or less, or 300 or less.

[0023] The conductive resin in this embodiment is not particularly limited, and any known conductive resin can be used without any particular restriction. Examples of conductive resins include polyaniline-based conductive resins, polythiophene-based conductive resins, polypyrrole-based conductive resins, polyacetylene-based conductive resins, polyphenylene-based conductive resins, and polyphenylene-vinylene-based conductive resins. An example of a polythiophene-based conductive resin is poly(3,4-ethylenedioxythiophene) (PEDOT). In this embodiment, the conductive resin includes PEDOT and an electron acceptor. In this case, the electrical conductivity of the p-type thermoelectric conversion element 21 tends to be higher. Examples of electron acceptors include polystyrene sulfonic acid, polyvinyl sulfonic acid, poly(meth)acrylic acid, polyvinyl sulfonic acid, toluene sulfonic acid, dodecylbenzene sulfonic acid, camphor sulfonic acid, bis(2-ethylhexyl) sulfosuccinate, chlorine, bromine, iodine, phosphorus pentafluoride, arsenic pentafluoride, boron trifluoride, hydrogen chloride, sulfuric acid, nitric acid, tetrafluoroboric acid, perchloric acid, iron(III) chloride, and tetracyanoquinodimethane. From the viewpoint of the electrical conductivity of the p-type thermoelectric element 21, polystyrene sulfonic acid (PSS) may also be used as the electron acceptor. The thermal conductivity of conductive resins is significantly lower than that of carbon nanotubes, for example, 1 W / mK or less.

[0024] In the p-type thermoelectric element 21, carbon nanotubes and conductive resin may be aggregated. The p-type thermoelectric element 21 may also include a porous structure in which the conductive resin binds carbon nanotubes together.

[0025] The n-type thermoelectric element 22 is provided on the first main surface 2a of the substrate 2 and is in contact with the p-type thermoelectric element 21. The thickness of the n-type thermoelectric element 22 is the same as or substantially the same as the thickness T1 of the p-type thermoelectric element 21. The length of the n-type thermoelectric element 22 in the first direction D2 is the same as or substantially the same as the length L1 of the p-type thermoelectric element 21. The length of the n-type thermoelectric element 22 in the second direction D3 is, for example, 2 mm or more and 10 mm or less. In this case, a sufficient number of thermoelectric conversion sections 11 can be formed on the first main surface 2a. The thermal conductivity of the n-type thermoelectric element 22 in the in-plane direction is, for example, 25.0 W / mK or more and 37.0 W / mK or less. The thermal conductivity may be 26.0 W / mK or higher, 28.0 W / mK or higher, 30.0 W / mK or higher, 35.0 W / mK or lower, or 32.0 W / mK or lower. The thermal conductivity of the n-type thermoelectric element 22 in the in-plane direction is measured, for example, by the optical AC method or the 3-omega method. The n-type thermoelectric element 22 is formed, like the p-type thermoelectric element 21, by, for example, various dry or wet methods.

[0026] The n-type thermoelectric element 22 is, for example, an n-type semiconductor layer. The n-type thermoelectric element 22 includes, for example, a composite of multiple organic materials, or a composite of inorganic and organic materials. In this embodiment, the n-type thermoelectric element 22 is the portion that exhibits n-type properties due to the inclusion of a dopant compared to the p-type thermoelectric element 21. Therefore, the n-type thermoelectric element 22 includes carbon nanotubes, a conductive resin, and a dopant. In this embodiment, the dopant is intended to be a substance that changes the Seebeck coefficient of the portion to which the dopant is applied. "Changing the Seebeck coefficient" means decreasing the value of the Seebeck coefficient, or changing the value of the Seebeck coefficient from a positive value to a negative value. A thermoelectric material exhibiting a positive Seebeck coefficient has p-type conductivity, and a thermoelectric material exhibiting a negative Seebeck coefficient has n-type properties.

[0027] The dopant of this embodiment contains, for example, a coordination compound that can dissociate into an anion (hereinafter also simply referred to as "anion") and an alkali metal cation (hereinafter also simply referred to as "cation"), and a cation scavenger (hereinafter also simply referred to as "scavenger"). Within the n-type thermoelectric element 22, at least a portion of the coordination compound may be dissociated into the anion and the cation. In this case, the cation may be captured by the scavenger. The dopant may contain multiple types of at least one of the coordination compound and the scavenger. In the portion of the p-type thermoelectric element 21 containing the dopant, the Seebeck coefficient changes. As a result, an n-type thermoelectric element 22 is formed in that portion.

[0028] The reasons for the above-mentioned effects are not particularly limited, but one possible reason is that the scavenging agent contained in the dopant captures the cation, causing the anion to dissociate, and this anion then changes the carrier of the carbon nanotube from holes to electrons. In this embodiment, since the anion is a complex ion with a metal atom at its center, it is thought that the interaction between the metal atom and the carbon nanotube causes it to become significantly n-type. Furthermore, because the complex ion has a large ion size, its good dissociation from the cation captured by the scavenging agent is also thought to be one of the reasons for the above-mentioned effects. In the dopant of this embodiment, the anion is a complex ion. Therefore, the n-type thermoelectric element 22 contains metal atoms derived from the complex ion. For this reason, in this embodiment, the metal atoms remaining in the n-type thermoelectric element 22 can function as antioxidants.

[0029] The complex ion (anion) obtained by the dissociation of the coordination compound may be selected from the group consisting of ferrocyanide ions, ferricyanide ions, tetrachloroferrate(III) ions, tetrachloroferrate(II) ions, tetracyanonicticate(II) ions, tetrachloronicticate(II) ions, tetracyanocobalt(II) ions, tetrachlorocobalt(II) ions, tetracyanocopper(I) ions, tetrachlorocopper(II) ions, hexacyanochrome(III) ions, tetrahydroxyzinc(II) ions, and tetrahydroxyaluminin(III) ions. The above anion may also be a ferrocyanide ion. If the above anion is a ferrocyanide ion, a material with better properties can be obtained. Furthermore, if the anion is a ferrocyanide ion, the iron atoms remaining in the n-type thermoelectric conversion element 22 function suitably as antioxidants, the change in physical properties over time is further suppressed, and the storage stability tends to be further improved.

[0030] The above anion may contain an iron atom. That is, the coordination compound may contain an iron atom. In this case, the anion may be selected from the group consisting of, for example, ferrocyanide ions, ferricyanide ions, tetrachloroferrate(III) ions, and tetrachloroferrate(II) ions. From the viewpoint of the characteristics of the n-type thermoelectric element 22, the above anion containing an iron atom may also be a ferrocyanide ion. From the viewpoint of antioxidant effect, the iron atom content in the n-type thermoelectric element 22 may be 0.001% by mass or more and 15% by mass or less, 0.005% by mass or more and 12% by mass, or 0.01% by mass or more and 10% by mass. The iron atom content in the n-type thermoelectric element 22 is, for example, the value measured by ICP emission spectrometry.

[0031] The coordination compound may also be a complex salt. Examples of complex salts include potassium ferrocyanide, sodium ferrocyanide, potassium ferricyanide, sodium ferricyanide, potassium tetrachloroferrate(III), sodium tetrachloroferrate(III), potassium tetrachloroferrate(II), and sodium tetrachloroferrate(II). The complex salt may also be a hydrate.

[0032] Alkali metal cations obtained by the dissociation of the coordination compound include sodium ions, potassium ions, and lithium ions. The coordination compound may contain at least one of a ferrocyanine compound and a ferricyanine compound.

[0033] The cation scavenger is not particularly limited as long as it is a substance that has the ability to take in cations. Examples of cation scavengers include crown ether compounds, cyclodextrins, calixarenes, ethylenediaminetetraacetic acid, porphyrins, phthalocyanines, and their derivatives. In this embodiment, the cation scavenger is a crown ether compound. Examples of crown ether compounds include 15-crown-5-ether, 18-crown-6-ether, 12-crown-4-ether, benzo-18-crown-6-ether, benzo-15-crown-5-ether, and benzo-12-crown-4-ether. The crown ether used as a scavenger should have a ring size that matches the size of the metal ion to be taken in. For example, if the metal ion is a potassium ion, the crown ether compound may be an 18-membered ring crown ether. If the metal ion is a sodium ion, the crown ether compound may be a 15-membered ring crown ether. If the metal ion is a lithium ion, the crown ether compound may be a 12-membered ring crown ether.

[0034] Crown ether compounds may contain a benzene ring. In this case, the stability of the crown ether compound may be improved. Examples of crown ether compounds containing a benzene ring include benzo-18-crown-6-ether, benzo-15-crown-5-ether, and benzo-12-crown-4-ether.

[0035] The molar ratio of the scavenging agent content C2 to the cation content C1 (C2 / C1) may be between 0.1 and 5, between 0.3 and 3, or between 0.5 and 2.

[0036] In each of the multiple thermoelectric conversion units 11, the mass ratio of carbon nanotubes to the total mass of the thermoelectric conversion unit 11 is, for example, 30% to 70%. By having a mass ratio of 30% or more, the thermoelectric conversion unit 11 can have good electrical conductivity. By having a mass ratio of 70% or less, the temperature difference within the thermoelectric conversion unit 11 tends to be large. The mass ratio may also be 35% or more, 40% or more, 45% or more, or 50% or more. The mass ratio may also be 65% or less, 60% or less, or 55% or less. The mass ratio of carbon nanotubes to the total mass of the p-type thermoelectric conversion element 21 may be 30% to 70%, and the mass ratio of carbon nanotubes to the total mass of the n-type thermoelectric conversion element 22 may be 30% to 70%. In each of the multiple thermoelectric conversion groups 3, the mass ratio of carbon nanotubes to the total mass of the thermoelectric conversion group 3 may be 30% to 70% or 40% to 60%. The internal temperature difference of the thermoelectric conversion section 11, etc., is measured, for example, using thermography.

[0037] Each of the multiple conductive parts 4 is a conductive portion located on the first main surface 2a and is connected to the corresponding thermoelectric conversion group 3. Each conductive part 4 may be a semiconductor instead of a conductor. The thickness of each conductive part 4 is the same as or substantially the same as the thickness T1 of the p-type thermoelectric conversion element 21. The conductivity of each conductive part 4 should be equal to or greater than that of the p-type thermoelectric conversion element 21. The thermal conductivity of each conductive part 4 should be equal to or greater than that of the p-type thermoelectric conversion element 21. At least a portion of the multiple conductive parts 4 may have a single-layer structure or a laminated structure. For example, at least a portion of the multiple conductive parts 4 may have an organic conductive layer and a metal conductive layer located on the organic conductive layer. In this embodiment, the multiple conductive parts 4 are formed from the same material as the p-type thermoelectric conversion element 21. Therefore, each conductive part 4 has the same conductivity type (p-type).

[0038] Each of the multiple conductive parts 4 has a first conductive part 4a that functions as a terminal for connecting to the external device, and a second conductive part 4b that functions as a conductive path connecting adjacent thermoelectric conversion groups 3. Each of the multiple conductive parts 4 has two first conductive parts 4a, and these two first conductive parts 4a are located within one conductive region R2. Only the second conductive part 4b is provided in the other conductive region R2. The multiple thermoelectric conversion groups 3 are connected in series with each other via the multiple second conductive parts 4b. Therefore, when the thermoelectric conversion module 1 is performing thermoelectric conversion, current can flow in series from one first conductive part 4a to the other first conductive part 4a. For example, one first conductive part 4a located within one conductive region R2 is connected to one end of the first thermoelectric conversion group 3a in the first direction D2, and one second conductive part 4b located within the other conductive region R2 is connected to the other end of the first thermoelectric conversion group 3a and one end of the second thermoelectric conversion group 3b in the first direction D2.

[0039] The multiple heat conduction sections 5 are portions that exhibit a higher thermal conductivity than the substrate 2 and are located on the second main surface 2b. At least a portion of the multiple heat conduction sections 5 overlaps the thermoelectric conversion group 3 (i.e., the thermoelectric conversion section 11) in the thickness direction D1. More specifically, at least a portion of the multiple heat conduction sections 5 overlaps the edges of the thermoelectric conversion section 11. On the other hand, each heat conduction section 5 does not overlap the center of the thermoelectric conversion section 11. This allows for a good temperature gradient to be generated inside the thermoelectric conversion section 11 along the first direction D2. The multiple heat conduction sections 5 are spaced apart from each other along the first direction D2 and have a strip shape that extends along the second direction in a plan view. The shape of each heat conduction section 5 in a plan view is not particularly limited, but can be a polygon, a circle, an ellipse, etc. Each heat conduction section 5 includes, for example, metals (silver, copper, aluminum, etc.), carbon, resins (e.g., silicone resin, epoxy resin, (meth)acrylic resin), etc. Each heat conduction section 5 may contain ceramics such as boron nitride or aluminum nitride, which exhibit high thermal conductivity. From the viewpoint of manufacturing efficiency, each heat conduction section 5 may also contain the above-mentioned resin. In this case, the heat conduction section 5 may be formed using the resin or a solution containing the resin. The thermal conductivity of each heat conduction section 5 is, for example, 1 W / mK or more and 400 W / mK or less. As a result, when the thermoelectric conversion module 1 is heated, heat is transferred well to the thermoelectric conversion section 11 via the multiple heat conduction sections 5. The thermal conductivity of each heat conduction section 5 is measured by a steady-state method or a transient method.

[0040] The length T2 of each heat conduction section 5 along the thickness direction D1 is, for example, 50 μm or more and 2000 μm or less. The width L2 of each heat conduction section 5 along the first direction D2 is, for example, 0.5 mm or more and 2.0 mm or less. In these cases, the heat conduction function of each heat conduction section 5 can be effectively performed. Between two adjacent heat conduction sections 5, the spacing S along the first direction D2 is greater than the length L1 of the p-type thermoelectric conversion element 21 and the length of the n-type thermoelectric conversion element 22 in the first direction D2. The spacing S is 3 mm or more and 15 mm or less. The spacing S may be 4 mm or more, 5 mm or more, or 6 mm or more. The spacing S may be 12 mm or less, 10 mm or less, or 8 mm or less. Alternatively, the spacing S may be less than 12 mm or less than 10 mm.

[0041] In the following, of the two heat conduction sections 5 shown in Figure 2(b), one heat conduction section 5 may be referred to as the first heat conduction section 5a, and the other heat conduction section 5 located next to the first heat conduction section 5a along the first direction D2 may be referred to as the second heat conduction section 5b. In this case, in the thickness direction D1, the first heat conduction section 5a overlaps with one end of the first thermoelectric conversion section 11a in the first direction D2. Also, in the thickness direction D1, the second heat conduction section 5b overlaps with the other end of the first thermoelectric conversion section 11a in the first direction D2. More specifically, in the thickness direction D1, the first heat conduction section 5a overlaps with the second end 22b of the n-type thermoelectric conversion element 22 included in the first thermoelectric conversion section 11a, and the second heat conduction section 5b overlaps with the second end 21b of the p-type thermoelectric conversion element 21 included in the first thermoelectric conversion section 11a. Furthermore, as shown in Figure 2(a), in the thickness direction D1, the first heat conduction portion 5a overlaps with the second end portion 21b of the p-type thermoelectric conversion element 21 included in the second thermoelectric conversion portion 11b, and the second heat conduction portion 5b overlaps with the second end portion 22b of the n-type thermoelectric conversion element 22 included in the second thermoelectric conversion portion 11b.

[0042] The thermoelectric conversion module 1 may further include configurations other than those described above. For example, the thermoelectric conversion module 1 may include wiring for electrically connecting to other thermoelectric conversion modules, wiring for drawing power to an external circuit, and so on.

[0043] Next, an example of a method for manufacturing the thermoelectric conversion module 1 according to this embodiment will be described with reference to Figures 3 to 5. Figures 3(a) to 3(c), 4(a) and 4(b), and 5(a) and 5(b) are diagrams illustrating the method for manufacturing the thermoelectric conversion module according to this embodiment.

[0044] First, as shown in Figure 3(a), a mask 31 is formed on the first main surface 2a of the substrate 2 that has been prepared in advance (first step). In the first step, the mask 31 is formed in a predetermined area of ​​the first main surface 2a. The mask 31 is a resist mask, masking tape, etc. In the former case, the mask 31 is formed by a known patterning. In the latter case, the tape is fixed to the predetermined area.

[0045] Next, as shown in Figure 3(b), a first layer 41 is formed on the first main surface 2a (second step). In the second step, first, a dispersion is dropped onto the first main surface 2a by known methods such as the inkjet method, dispensing method, doctor blade method, screen printing method, casting method, dip coating method, or spray coating method. Subsequently, the first layer 41 is formed by drying the dispersion. For example, the substrate 2 is heated by placing it on a hot plate set to 25°C or higher and 90°C or lower for 10 minutes or more and 21,600 minutes or less. This dries the dispersion and forms the first layer 41. In the second step, instead of placing the substrate 2 on a hot plate, the dispersion may be dried by placing the substrate 2 in a forced-air dryer for 10 minutes or more and 21,600 minutes or less.

[0046] The dispersion used in the second step is, for example, a liquid in which a p-type thermoelectric conversion material is dispersed. In this embodiment, the dispersion is a liquid in which carbon nanotubes and a conductive resin are dispersed. The carbon nanotube content in the dispersion is, for example, 25% by mass or more, 30% by mass or more, 35% by mass or more, or 40% by mass or more, and 80% by mass or less, 75% by mass or less, 70% by mass or less, or 60% by mass or less, based on the total amount of conductive resin and carbon nanotubes. In this case, a temperature difference is more likely to occur in the first layer 41, and the electrical conductivity of the first layer 41 tends to increase. Furthermore, in each of the multiple thermoelectric conversion units 11 described later, the mass ratio of carbon nanotubes to the total mass of the thermoelectric conversion unit 11 can be easily adjusted to 30% to 70%. The total mass concentration of carbon nanotubes and conductive resin in the dispersion is, for example, 0.05% by mass or more, 0.06% by mass or more, 0.07% by mass or more, 0.10% by mass or more, 0.12% by mass or more, or 0.15% by mass or more. The total mass concentration of carbon nanotubes and conductive resin in the dispersion may be 10% by mass or less, or 2% by mass or less. The dispersion used in the second step is, for example, a mixture formed by mixing a first liquid containing carbon nanotubes and a second liquid containing conductive resin. The carbon nanotube content in the dispersion, based on the total amount of conductive resin and carbon nanotubes, is substantially equal to the mass ratio of carbon nanotubes to the total mass of the thermoelectric conversion unit 11. Therefore, in this specification, the carbon nanotube content in the dispersion, based on the total amount of conductive resin and carbon nanotubes, can be considered as the mass ratio of carbon nanotubes to the total mass of the thermoelectric conversion unit 11.

[0047] The first liquid comprises, for example, carbon nanotubes and a first solvent. The concentration of carbon nanotubes in the first liquid is, for example, 0.01% by mass or more and 10% by mass or less. The first solvent may be any solvent capable of dispersing carbon nanotubes, such as a polar liquid or an aqueous solvent. The aqueous solvent may be water or a mixed solvent of water and an organic solvent. The first solvent may be a protic solvent or an aprotic solvent. Specific examples of the first solvent include, for example, water, alcohols (methanol, ethanol, etc.), amides (N,N-dimethylformamide, N,N-dimethylacetamide, N-methylpyrrolidone, etc.), ketones (acetone, methyl ethyl ketone, etc.), glycols (ethylene glycol, diethylene glycol, etc.), dimethyl sulfoxide, acetonitrile, etc. The first solvent may contain one or more of the group consisting of water, methanol, ethanol, N-methylpyrrolidone, and dimethyl sulfoxide, and may also contain water. The first liquid may further contain additives such as surfactants and organic binders.

[0048] The second liquid comprises, for example, a conductive resin (PEDOT / PSS) consisting of PEDOT and PSS, and a second solvent. In PEDOT / PSS, the content ratio of PEDOT and PSS is not particularly limited. The ratio (mass ratio) of PSS to PEDOT is, for example, 1 or more, 1.25 or more, or 1.5 or more, and 30 or less, or 20 or less. The second solvent may be any solvent capable of dispersing PEDOT / PSS, such as a polar liquid or an aqueous solvent. The second solvent may be a protic solvent or an aprotic solvent. Specific examples of the second solvent are the same as those of the first solvent. The second solvent may contain one or more substances from the group consisting of water, methanol, and ethanol, or it may contain water. In one embodiment, the second liquid may be an aqueous dispersion of PEDOT / PSS. The second solvent may be used alone or mixed with two or more substances. The second liquid may further contain various additives.

[0049] Next, as shown in Figure 3(c), the p-type thermoelectric conversion layer 42 is formed by immersing the substrate 2 in an organic solvent after removing the mask 31 (third step). For example, if the mask 31 is a resist mask, the mask 31 is removed by light, a solvent, etc. In this case, a solvent that does not affect the dispersion is used as the organic solvent. For example, if the mask 31 is masking tape, the mask 31 is physically peeled off from the substrate 2. In this embodiment, after patterning the first layer 41, the entire substrate 2 is immersed in dimethyl sulfoxide (DMSO), which is the organic solvent (immersion treatment). For example, the entire substrate 2 is immersed in dimethyl sulfoxide set to room temperature for 1 minute to 7200 minutes. After the immersion treatment, the substrate 2 may be heated from the second main surface 2b side. For example, the substrate 2 is heated by placing it on a hot plate set to 25°C to 90°C for 10 minutes to 21600 minutes. This completes the formation of a patterned p-type thermoelectric conversion layer 42. A portion of the p-type thermoelectric conversion layer 42 will later become an n-type thermoelectric conversion element 22. Another portion of the p-type thermoelectric conversion layer 42 will later become a p-type thermoelectric conversion element 21. Yet another portion of the p-type thermoelectric conversion layer 42 will later become a conductive portion 4.

[0050] Next, as shown in Figures 4(a) and 4(b), after the third step, a plurality of heat conduction parts 5 are formed on the second main surface 2b of the substrate 2 (fourth step). In the fourth step, a high thermal conductivity material is coated by known methods such as the inkjet method, the dispensing method, the doctor blade method, or the screen printing method. Subsequently, the plurality of heat conduction parts 5 are formed by curing the high thermal conductivity material by heating.

[0051] Next, as shown in Figure 5(a), after the fourth step, a dopant-containing solution (dopant solution 51) is dropped onto a portion 42a of the p-type thermoelectric conversion layer 42. This forms an n-type thermoelectric conversion element 22 on the portion 42a (fifth step). In the fifth step, the dopant solution 51 is impregnated into a portion 42a of the p-type thermoelectric conversion layer 42 by a known method such as an inkjet method or a dispensing method. In this embodiment, the p-type thermoelectric conversion layer 42 is provided with alternating areas where the dopant solution 51 has been dropped and areas where the dopant solution 51 has not been dropped. Subsequently, the portion 42a is transformed into an n-type thermoelectric conversion element 22 by drying the dopant solution 51. For example, the substrate 2 is heated by placing it on a hot plate set to 25°C to 100°C or 25°C to 90°C for 10 minutes to 21600 minutes. This dries the dopant solution 51. The solvents contained in the dopant solution 51 include, for example, water, acetonitrile, ethanol, ethylene glycol, dimethyl sulfoxide (DMSO), N-methylpyrrolidone, N,N-dimethylformamide, and N,N-dimethylacetamide. Furthermore, the portion of the p-type thermoelectric conversion layer 42 where the dopant solution 51 was not dropped becomes a p-type thermoelectric conversion element 21 or a conductive part 4, as shown in Figure 5(b). Thus, a thermoelectric conversion module 1 in which multiple thermoelectric conversion parts 11 are formed is created.

[0052] Next, we will explain the effects and benefits of the thermoelectric conversion module 1 formed by the manufacturing method according to the embodiment described above.

[0053] The thermoelectric conversion module 1 according to this embodiment has a first heat conduction section 5a and a second heat conduction section 5b. In the thickness direction D1, the first heat conduction section 5a overlaps with the second end 22b of the n-type thermoelectric conversion element 22 included in the first thermoelectric conversion section 11a, and in the thickness direction D1, the second heat conduction section 5b overlaps with the second end 22b of the p-type thermoelectric conversion element 21 included in the first thermoelectric conversion section 11a. In addition, the distance S between the first heat conduction section 5a and the second heat conduction section 5b in the first direction D2 is greater than the length L1 of the p-type thermoelectric conversion element 21 and the length of the n-type thermoelectric conversion element 22 in the first direction D2. As a result, the first heat conduction section 5a and the second heat conduction section 5b overlap both ends of the first thermoelectric conversion section 11a in the thickness direction D1, but do not overlap the center of the first thermoelectric conversion section 11a. Therefore, by heating, for example, the first heat conduction section 5a and the second heat conduction section 5b, an internal temperature difference can be created in the p-type thermoelectric conversion element 21 and the n-type thermoelectric conversion element 22, respectively. Here, the thickness T1 of the p-type thermoelectric conversion element 21 (and the thickness of the n-type thermoelectric conversion element 22) is 3 μm or more and 30 μm or less. By having the thickness T1 within the above range, it is possible to suppress the increase in the number of elements per unit area and the internal resistance of the elements. In addition, each of the p-type thermoelectric conversion element 21 and the n-type thermoelectric conversion element 22 included in the thermoelectric conversion section 11 contains carbon nanotubes and conductive resin, and in each of the multiple thermoelectric conversion sections 11, the mass ratio of carbon nanotubes to the total mass of the thermoelectric conversion section 11 is, for example, 30% or more and 70% or less. This makes it easy to widen the temperature difference within each thermoelectric conversion section 11 while ensuring the electrical conductivity of each thermoelectric conversion section 11. Therefore, by adopting the thermoelectric conversion module 1 according to this embodiment, it is possible to improve the output per unit area.

[0054] In this embodiment, the mass ratio of carbon nanotubes to the total mass of the thermoelectric conversion unit 11 may be 40% or more and 60% or less. In this case, it is easier to further widen the temperature difference within each thermoelectric conversion unit 11.

[0055] In this embodiment, the mass ratio of carbon nanotubes to the total mass of the p-type thermoelectric element 21 is 30% to 70%, and the mass ratio of carbon nanotubes to the total mass of the n-type thermoelectric element 22 may also be 30% to 70%. In this case, the temperature difference can be easily widened in both the p-type thermoelectric element 21 and the n-type thermoelectric element 22, making it possible to achieve further improvements in output per unit area.

[0056] In this embodiment, the distance S between the first heat conduction section 5a and the second heat conduction section 5b in the first direction D2 may be 3 mm or more and 15 mm or less. In this case, a further increase in the temperature difference within each thermoelectric conversion section 11 can be achieved by the first heat conduction section 5a and the second heat conduction section 5b.

[0057] In this embodiment, the thickness T1 of the p-type thermoelectric conversion element 21 may be 5 μm or more and 25 μm or less. The spacing S may be 3 mm or more and less than 12 mm. In these cases, it is possible to achieve further improvement in output per unit area of ​​the thermoelectric conversion module 1.

[0058] In this embodiment, the width L2 of each heat conduction part 5 along the first direction D2 may be 0.5 mm or more and 2.0 mm or less. In this case, the heat transfer performance of each heat conduction part 5 can be effectively demonstrated, and the internal temperature difference of the thermoelectric conversion part 11 can be increased.

[0059] In this embodiment, the substrate 2, the thermoelectric conversion unit 11, and the heat conduction unit 5 may each exhibit flexibility. In this case, for example, the thermoelectric conversion module 1 can be easily mounted along the surface of a cylindrical pipe. That is, the limitations on the mounting location of the thermoelectric conversion module 1 can be relaxed.

[0060] In this embodiment, a dopant solution 51 is dropped onto a portion 42a of the p-type thermoelectric conversion layer 42, thereby converting that portion 42a into an n-type thermoelectric conversion element 22. In this case, the contact resistance between the p-type thermoelectric conversion element 21 and the n-type thermoelectric conversion element 22 can be effectively reduced. Furthermore, the dropping of the dopant solution 51 is performed after the formation of the heat conduction section 5. This makes the material contained in the dopant solution 51 less susceptible to deterioration due to heating or other factors.

[0061] The thermoelectric conversion module and its manufacturing method described herein are not limited to the above embodiments and can be modified in various ways. For example, in the above embodiments, the thermoelectric conversion elements are exposed on the first main surface, but this is not the case. For example, the thermoelectric conversion elements may be covered with a resin sealing layer or the like. In addition, an insulator may be provided between two adjacent thermoelectric conversion groups. In this case, the thermal conductivity of the insulator may be low from the viewpoint of maintaining the internal temperature difference of the thermoelectric conversion section.

[0062] In the above embodiment, a space exists between two adjacent heat conduction sections, but this is not limited to this. For example, an insulator may be provided between two adjacent heat conduction sections. In this case, the thermal conductivity of the insulator may be low from the viewpoint of maintaining the internal temperature difference of the thermoelectric conversion section. [Examples]

[0063] One aspect of this disclosure will be further described in detail by the following examples, but this aspect of the disclosure is not limited to these examples.

[0064] (Example 1) <Dispersion> 80 g of a carbon nanotube dispersion (concentration: 0.2 mass%, G / D ratio: 41, aqueous dispersion, single-walled carbon nanotubes, diameter 0.9-1.7 nm) was concentrated by vacuum until the carbon nanotube concentration reached 0.4 mass%. Next, 5.7 g of a PEDOT / PSS aqueous dispersion (Heraeus K.K. "Clevious® PH1000", solid content concentration: 1.2 mass%) and the concentrated carbon nanotube dispersion were thoroughly mixed using a three-way motor (AS ONE Corporation "PM203" model) (mixing time: 30 minutes). Then, the mixed liquid was thoroughly degassed using a rotation-orbit mixer (Thinky Co., Ltd. "Awatori Rentaro ARE-310" model) (processing time: 3 minutes). This prepared a dispersion with a carbon nanotube (CNT) content of 70 mass% relative to the total amount of PEDOT / PSS and carbon nanotubes. Shear rate: 0.01 s -1The viscosity of the dispersion was 1,070,000 mPa·sec. The viscosity of the dispersion was measured using a rheometer (Anton Paar "MCR302" (product name)). The measurement conditions were: temperature: 25°C, plate: φ25 mm parallel plate, gap: 1 mm.

[0065] <Dopant Solution> A dopant solution was prepared by dissolving 0.32 g of potassium ferrocyanide trihydrate and 0.94 g of benzo-18-crown-6-ether in 15 mL of ultrapure water. In the dopant solution, the concentrations of potassium ions and benzo-18-crown-6-ether were both 0.2 M. The molar ratio (C2 / C1) was 1.

[0066] <Circuit board> Double-sided tape (Nichiban Co., Ltd., Nicetack weak adhesive type) was attached to all four sides of a 100mm square glass plate. Spray adhesive (3M Japan Limited, Regular Series S / N 55) was then applied to the glass plate. A 100mm square polyimide film (Toray DuPont Co., Ltd., Kapton H type, 25μm film thickness, 0.16W / mK thermal conductivity) was prepared as a substrate. Next, the protective sheet from the double-sided tape attached to the glass plate was removed, and the polyimide film was then attached to the glass plate. The polyimide film was then cleaned with acetone. Next, masking tape (Eyes Project Co., Ltd., Micron Masking Tape, 1mm width) was applied to predetermined positions on the polyimide film. Polyimide tape was also used to attach the polyimide film to the periphery of the glass plate. This formed a laminate of the polyimide film and glass plate that functions as a substrate.

[0067] <Thermoelectric Conversion Module> After dropping the above dispersion onto the polyimide film, coating was performed using a doctor blade with a gap of 2.8 mm. Subsequently, the laminate coated with the dispersion was placed in a forced-air dryer set to 60°C for 3 hours. This formed a composite film with a thickness of 62 μm on the polyimide film. The composite film is present in both the thermoelectric conversion region on the polyimide film where a thermoelectric conversion element will later be installed, and the conductive region on the polyimide film where a conductive part will later be installed. Then, the masking tape was removed. This resulted in patterning the composite film. In the thermoelectric conversion region, the composite film was patterned in a stripe pattern.

[0068] A high-precision digital micrometer (MDH-25MB, manufactured by Mitutoyo Corporation) was used to measure the thickness of the composite film. Specifically, the thickness of the area where the composite film was applied and the thickness of the area where the composite film was not applied (the area with only polyimide film) were measured separately, and the difference between the two was defined as the thickness of the composite film.

[0069] Next, the entire laminate was immersed in DMSO (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) at room temperature for 30 minutes. Subsequently, the laminate removed from the DMSO was placed on a hot plate set to 60°C for 120 minutes. After that, the polyimide film was separated from the glass plate by removing the polyimide tape at the edges. This formed a p-type thermoelectric conversion layer on the first main surface of the polyimide film. In Example 1, the thickness of the p-type thermoelectric conversion layer was 10.5 μm.

[0070] Next, the polyimide film was fixed onto the glass plate with the p-type thermoelectric conversion layer facing the glass plate. Subsequently, a high thermal conductivity material (Shin-Etsu Chemical Co., Ltd., G-789, silicone resin) was coated onto the second main surface of the polyimide film using an Iwashita Engineering dispenser "AD3000C" and a desktop robot "EzROBO-5GX". At this time, the spacing between the nozzle positions from which the high thermal conductivity material was discharged was set to 11 mm, and the coating was performed while moving the nozzle along the second direction. As a result, multiple strip-shaped high thermal conductivity materials were coated onto the second main surface. After coating, the substrate was placed on a hot plate set to 120°C for 60 minutes. This formed multiple heat conduction sections (thermal conductivity: 3.0 W / mK). The length T2 of the heat conduction section was 1 mm, the width L2 of the heat conduction section was 1 mm, and the spacing S between the heat conduction sections in the second direction perpendicular to the first direction was 10 mm. Furthermore, the direction in which each heat conduction section extends is perpendicular to the direction in which the p-type thermoelectric conversion layer provided in the thermoelectric conversion region extends.

[0071] Next, the polyimide film was fixed onto the glass plate with the heat-conducting portion facing the glass plate. Subsequently, the glass plate was placed on a hot plate set to 60°C. Then, a dopant solution was dropped onto a portion of the p-type thermoelectric conversion layer that functions as a thermoelectric conversion element. In Example 1, first, the dopant solution was dropped onto an area 10 mm wide and 5.5 mm long. Subsequently, the dopant solution was dropped onto an area 10 mm wide and 5.5 mm long at intervals of 5.5 mm. By repeating this dropping operation, areas with and without dopant solution were arranged alternately. As a result, 48 p-type thermoelectric conversion elements and 48 n-type thermoelectric conversion elements were formed on the polyimide film. In other words, a total of 96 thermoelectric conversion elements were formed on the polyimide film. Thus, a total of 48 thermoelectric conversion sections, each containing one p-type thermoelectric conversion element and one n-type thermoelectric conversion element, were formed. Here, the thickness of the n-type thermoelectric element was substantially the same as that of the p-type thermoelectric element. The edges of each thermoelectric conversion section overlapped the heat conduction section, while at least the center of each thermoelectric conversion section did not overlap the heat conduction section. Furthermore, the area occupied by the thermoelectric conversion element on the polyimide film was 52.8 cm². 2 The area occupied by the two conductive regions R2 on the polyimide film was 17.4 cm². 2 The iron atom content in the n-type thermoelectric element was between 0.01% by mass and 10% by mass.

[0072] Next, the thermoelectric element polyimide film was left on the hot plate and dried for 30 minutes. Subsequently, the polyimide film was placed in a forced-air dryer set to 100°C for 60 minutes. Through the above process, a thermoelectric conversion module was fabricated in which p-type thermoelectric elements and n-type thermoelectric elements were alternately arranged in series. The thermal conductivity of the p-type thermoelectric element in the in-plane direction in Example 1 is the standard value when the thermal conductivity of the p-type thermoelectric element in the in-plane direction in Comparative Example 1, described later, is set to 100, and is shown in Table 1 below. Similarly, the thermal conductivity of the n-type thermoelectric element in the in-plane direction in Example 1 is the standard value when the thermal conductivity of the n-type thermoelectric element in the in-plane direction in Comparative Example 1, described later, is set to 100, and is shown in Table 1 below.

[0073] The thermal conductivity of a thermoelectric element is expressed as (density) × (specific heat) × (thermal diffusivity). The density of the thermoelectric element was calculated from its shape and mass. The specific heat of the thermoelectric element was calculated using the literature value for the specific heat of PEDOT / PSS and the literature value for the specific heat of graphite as the specific heat of carbon nanotubes. At this time, the specific heat of the thermoelectric element was calculated assuming that additivity holds with respect to the mixing ratio of PEDOT / PSS and carbon nanotubes. The thermal diffusivity of the thermoelectric element was measured in the in-plane direction of the thermoelectric element using the optical AC method with a thermal diffusivity measuring device (ULVAC, Inc., product name: LaserPIT). The details of the thermal diffusivity measurement method are as follows: First, alternating current heat of a certain frequency is applied to the sample surface by light irradiation. Periodic temperature changes occur in the sample, and a temperature wave is formed. The AC temperature amplitude and phase are measured at the heating position and at a position other than the heating position. The thermal diffusivity is calculated from the measured AC temperature amplitude and phase according to the principle of the measurement method.

[0074] (Example 2) A thermoelectric conversion module was formed in the same manner as in Example 1, except that a dispersion was used in which the carbon nanotube content relative to the total amount of PEDOT / PSS and carbon nanotubes was 60% by mass. The parameters in Example 2 are shown in Table 1 below.

[0075] (Example 3) A thermoelectric conversion module was formed in the same manner as in Example 1, except that a dispersion was used in which the carbon nanotube content was 50% by mass relative to the total amount of PEDOT / PSS and carbon nanotubes. The parameters in Example 3 are shown in Table 1 below.

[0076] (Example 4) A thermoelectric conversion module was formed in the same manner as in Example 1, except that a dispersion was used in which the carbon nanotube content relative to the total amount of PEDOT / PSS and carbon nanotubes was 40% by mass. The parameters in Example 4 are shown in Table 1 below.

[0077] (Example 5) A thermoelectric conversion module was formed in the same manner as in Example 1, except that a dispersion was used in which the carbon nanotube content relative to the total amount of PEDOT / PSS and carbon nanotubes was 30% by mass. The parameters in Example 5 are shown in Table 1 below.

[0078] (Comparative Example 1) A thermoelectric conversion module was formed in the same manner as in Example 1, except that a dispersion was used in which the carbon nanotube content relative to the total amount of PEDOT / PSS and carbon nanotubes was 75% by mass. The parameters in Comparative Example 1 are shown in Table 1 below.

[0079] (Comparative Example 2) A thermoelectric conversion module was formed in the same manner as in Example 1, except that a dispersion was used in which the carbon nanotube content relative to the total amount of PEDOT / PSS and carbon nanotubes was 25% by mass. The parameters in Comparative Example 2 are shown in Table 1 below.

[0080] (Reference example 1) A thermoelectric conversion module was formed in the same manner as in Comparative Example 1, except that the spacing between the heat conduction parts was set to 6.0 mm and the dopant solution dropping area was set to a width of 10 mm and a length of 3.5 mm (i.e., the lengths of the p-type thermoelectric conversion element and the n-type thermoelectric conversion element were set to 3.5 mm). The parameters in Reference Example 1 are shown in Table 2 below.

[0081] (Reference example 2) The thermoelectric conversion module was formed in the same manner as in Reference Example 1, except that the gap in the doctor blade was set to 4.0 mm. The parameters in Reference Example 2 are shown in Table 2 below.

[0082] (Reference example 3) A thermoelectric conversion module was formed in the same manner as in Reference Example 1, except that the gap in the doctor blade was set to 2.0 mm. The parameters in Reference Example 3 are shown in Table 2 below.

[0083] (Reference example 4) The thermoelectric conversion module was formed in the same manner as in Reference Example 1, except that the gap in the doctor blade was set to 1.1 mm. The parameters in Reference Example 4 are shown in Table 2 below.

[0084] (Reference example 5) A thermoelectric conversion module was formed in the same manner as in Reference Example 1, except that the nozzle spacing was set to 5 mm, the dopant solution dropping area was set to a width of 10 mm and a length of 2.5 mm (i.e., the lengths of the p-type and n-type thermoelectric conversion elements were set to 2.5 mm), and the number of thermoelectric conversion elements on the polyimide film was set to 224. The parameters for Reference Example 5 are shown in Table 2 below.

[0085] (Reference example 6) A thermoelectric conversion module was formed in the same manner as in Reference Example 1, except that the nozzle spacing was set to 11 mm, the dopant solution dropping area was set to a width of 10 mm and a length of 5.5 mm (i.e., the lengths of the p-type and n-type thermoelectric conversion elements were set to 5.5 mm), and the number of thermoelectric conversion elements on the polyimide film was set to 96. The parameters for Reference Example 6 are shown in Table 2 below.

[0086] (Reference example 7) A thermoelectric conversion module was formed in the same manner as in Reference Example 1, except that the nozzle spacing was set to 17 mm, the dopant solution dropping area was set to a width of 10 mm and a length of 8.5 mm (i.e., the lengths of the p-type and n-type thermoelectric conversion elements were set to 8.5 mm), and the number of thermoelectric conversion elements on the polyimide film was set to 64. The parameters for Reference Example 7 are shown in Table 2 below.

[0087] [Table 1]

[0088] [Table 2]

[0089] (Power Generation Evaluation of Thermoelectric Conversion Module) The heat conduction parts of the thermoelectric conversion modules of Examples 1 to 5, Comparative Examples 1 and 2, and Reference Examples 1 to 7 were brought into contact with a hot plate at 100°C. As a result, a temperature difference was generated in each thermoelectric conversion part. Then, the resistance value, open-circuit voltage, short-circuit current, maximum output, and maximum output density per unit area of the thermoelectric conversion element of each thermoelectric conversion module were evaluated using a source meter (Keithley 2612B manufactured by Tektronix). Further, the temperature difference in the thermoelectric conversion part was measured by thermography (InfRec R550Pro manufactured by Nippon Avionics Co., Ltd.). When each of the resistance value, open-circuit voltage, short-circuit current, maximum output, and maximum output density per unit area of the thermoelectric conversion module of Comparative Example 1 was set to 100, the evaluation results of Examples 1 to 5 and Comparative Examples 1 and 2 are shown in Table 3 below. Also, when each of the resistance value, open-circuit voltage, short-circuit current, maximum output, and maximum output density per unit area of the thermoelectric conversion module of Reference Example 7 was set to 100, the evaluation results of Reference Examples 1 to 6 are shown in Table 4 below.

[0090] FIG. 6 is a graph showing the power factors of the thermoelectric conversion parts of Examples 1 to 5 and Comparative Examples 1 and 2. In FIG. 6, the horizontal axis represents the mass ratio of carbon nanotubes, and the vertical axis represents the power factor. Here, the power factor is one of the indexes for evaluating the performance of the thermoelectric conversion part and corresponds to σS 2 . σ is the electrical conductivity of the thermoelectric conversion part, and S is the Seebeck coefficient of the thermoelectric conversion part. Also, in FIG. 6, plots 61 to 65 represent Examples 1 to 5, respectively, and plots 66 and 67 represent Comparative Examples 1 and 2, respectively. From FIG. 6, the σS 2 of Examples 1 and 2 and Comparative Example 1 are almost the same values. On the other hand, the σS 2 of Examples 3 to 5 is the σS of Comparative Example 12 It was clearly lower than that. Furthermore, when the power factor of the thermoelectric conversion section of Comparative Example 1 is set to 100, the power factors of Examples 1-5 and Comparative Examples 1 and 2 are shown in Table 3 below.

[0091] Figure 7 is a graph showing the temperature difference in the thermoelectric conversion section of Examples 1-5 and Comparative Examples 1 and 2. In Figure 7, the horizontal axis represents the mass percentage of carbon nanotubes, and the vertical axis represents the temperature difference. In Figure 7, plots 71-75 show the temperature differences of Examples 1-5, respectively, and plots 76 and 77 show the temperature differences of Comparative Examples 1 and 2, respectively. From Figure 7, it can be seen that the temperature difference tends to increase as the mass percentage of carbon nanotubes decreases. When the temperature difference of the thermoelectric conversion section of Comparative Example 1 is set to 100, the temperature differences of Examples 1-5 and Comparative Examples 1 and 2 are shown in Table 3 below.

[0092] [Table 3]

[0093] [Table 4]

[0094] Figure 8 is a graph showing the maximum power density of thermoelectric conversion modules for Examples 1-5 and Comparative Examples 1 and 2. In Figure 8, the horizontal axis represents the mass percentage of carbon nanotubes, and the vertical axis represents the maximum power density (normalized value). In Figure 8, plots 81-85 show the maximum power densities for Examples 1-5, respectively, and plots 86 and 87 show the maximum power densities for Comparative Examples 1 and 2, respectively. As shown in Figure 8, the maximum power densities for Examples 1-5 were all higher than those of Comparative Example 1. In particular, the maximum power densities for Examples 2-4 were all more than 1.5 times that of Comparative Example 1. Also, the maximum power density of Comparative Example 2 was lower than that of Comparative Example 1.

[0095] In addition, as shown in Table 3, the resistance values ​​of Examples 1, 3-5 are all higher than those of Comparative Example 1. On the other hand, the open-circuit voltage and maximum output of Examples 1-5 are all higher than those of Comparative Example 1. Furthermore, as mentioned above, the maximum power density of Examples 1-5 is higher than that of Comparative Example 1. In particular, the maximum power density of Examples 2-4 is more than 1.5 times that of Comparative Example 1. Also, the maximum power density of Comparative Example 2 is lower than that of Comparative Example 1. From the above, it can be seen that Examples 1-5 (especially Examples 2-4) are more practical as power supplies than Comparative Examples 1 and 2.

[0096] As shown in Table 4, the open-circuit voltages of Reference Examples 1 to 6 were all higher than those of Reference Example 7. Furthermore, the short-circuit currents of Reference Examples 1 to 6 were all higher than those of Reference Example 7. The maximum output and maximum power density of Reference Examples 1 to 6 were all higher than those of Reference Example 1. These results indicate that further performance improvements of thermoelectric conversion modules can be achieved by appropriately adjusting the spacing between heat conduction parts, the thickness of thermoelectric conversion elements, and other factors. [Explanation of symbols]

[0097] 1... Thermoelectric conversion module, 2... Substrate, 2a... First main surface, 2b... Second main surface, 3... Thermoelectric conversion group, 3a... First thermoelectric conversion group, 3b... Second thermoelectric conversion group, 4... Conductive part, 5... Heat conduction part, 5a... First heat conduction part, 5b... Second heat conduction part, 11... Thermoelectric conversion part, 11a... First thermoelectric conversion part, 11b... Second thermoelectric conversion part, 21... p-type thermoelectric conversion element, 21a... First end, 21b... Second end, 22... n-type thermoelectric conversion element, 22a... First end, 22b... Second end, D1... Thickness direction, D2... First direction, D3... Second direction, L1... Length, L2... Width, S... Spacing, R1... Thermoelectric conversion area, R2... Conductive area, T1... Thickness, T2... Length.

Claims

1. A substrate having a first main surface and a second main surface located on the opposite side of the first main surface, A thermoelectric conversion unit located on the first main surface, A first heat conduction portion and a second heat conduction portion located on the second main surface and adjacent to each other along a first direction perpendicular to the thickness direction of the substrate, A first thermoelectric conversion group located on the first main surface and having the thermoelectric conversion unit, A second thermoelectric conversion group is located on the first main surface and adjacent to the first thermoelectric conversion group along a second direction perpendicular to the thickness direction and the first direction, A first conductive portion located on the first main surface and connected to one end of the first thermoelectric conversion group in the first direction, A second conductive portion located on the first main surface and connected to the other end of the first thermoelectric conversion group in the first direction and to one end of the second thermoelectric conversion group in the first direction, Equipped with, The thermoelectric conversion unit has p-type thermoelectric conversion elements and n-type thermoelectric conversion elements arranged along the first direction. The first end of the p-type thermoelectric element in the first direction is in contact with the first end of the n-type thermoelectric element in the first direction. In the thickness direction, the first heat conduction portion overlaps the second end of the p-type thermoelectric conversion element in the first direction. In the thickness direction, the second heat conduction portion overlaps the second end of the n-type thermoelectric conversion element in the first direction. The thickness of the p-type thermoelectric element and the n-type thermoelectric element are 3 μm or more and 30 μm or less. The distance between the first heat conduction part and the second heat conduction part in the first direction is greater than the length of the p-type thermoelectric conversion element and the length of the n-type thermoelectric conversion element in the first direction. Each of the p-type thermoelectric element and the n-type thermoelectric element comprises a carbon nanotube and a conductive resin. The mass ratio of the carbon nanotubes to the total mass of the thermoelectric conversion section is 40% or more and 60% or less. The second thermoelectric conversion group has a second thermoelectric conversion unit located adjacent to the thermoelectric conversion unit along the second direction, The second thermoelectric conversion unit has a second p-type thermoelectric conversion element and a second n-type thermoelectric conversion element arranged along the first direction, The first end of the second p-type thermoelectric element in the first direction is in contact with the first end of the second n-type thermoelectric element in the first direction. Each of the first heat conduction portion and the second heat conduction portion extends along the second direction, In the thickness direction, the first heat conduction portion overlaps with the second end of the second n-type thermoelectric conversion element included in the second thermoelectric conversion portion in the first direction. In the thickness direction, the second heat conduction portion overlaps with the second end of the second p-type thermoelectric conversion element included in the second thermoelectric conversion portion in the first direction. The conductivity types of the first conductive part and the second conductive part are the same. Thermoelectric conversion module.

2. The mass ratio of carbon nanotubes to the total mass of the p-type thermoelectric conversion element is 40% or more and 60% or less. The thermoelectric conversion module according to claim 1, wherein the mass ratio of carbon nanotubes to the total mass of the n-type thermoelectric conversion elements is 40% or more and 60% or less.

3. The thermoelectric conversion module according to claim 1 or 2, wherein the distance between the first heat conduction part and the second heat conduction part in the first direction is 3 mm or more and 15 mm or less.

4. The thickness of the p-type thermoelectric element and the n-type thermoelectric element are 5 μm or more and 25 μm or less. The thermoelectric conversion module according to claim 1 or 2, wherein the distance between the first heat conduction part and the second heat conduction part in the first direction is 3 mm or more and less than 12 mm.

5. The thermoelectric conversion module according to claim 1 or 2, wherein the width of the first heat conduction portion and the second heat conduction portion along the first direction is 0.5 mm or more and 2.0 mm or less.

6. The thermoelectric conversion module according to claim 1 or 2, wherein each of the substrate, the thermoelectric conversion unit, the first heat conduction unit, and the second heat conduction unit exhibits flexibility.

7. A method for manufacturing a thermoelectric conversion module according to claim 1 or 2, comprising a first step of forming a mask on the first main surface of the substrate, A second step is to form a first layer containing a p-type thermoelectric conversion material on the first main surface, A third step involves removing the mask and then immersing the substrate in an organic solvent to form a p-type thermoelectric conversion layer. A fourth step is to form the first heat conduction portion and the second heat conduction portion on the second main surface of the substrate after the third step, A method for manufacturing a thermoelectric conversion module, comprising: a fifth step of dropping a dopant solution onto a portion of the p-type thermoelectric conversion layer after the fourth step, thereby forming the n-type thermoelectric conversion element on the portion thereof.

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