π-type thermoelectric conversion module

Abstract

This invention provides a π-type thermoelectric conversion module with excellent cooling performance that suppresses heat backflow. [Solution] A π-type thermoelectric conversion module is provided, in which a thermoelectric conversion member A including a thermoelectric conversion element M and a thermal backflow suppression member B including a thermoelectric conversion element K are alternately spaced apart between a pair of opposing first substrates having a first electrode and a second substrate having a second electrode, and the thermoelectric conversion member A and the thermal backflow suppression member B are electrically connected in series via the first electrode on the first substrate and the second electrode on the second substrate, wherein the carriers of the thermoelectric conversion element M and the thermoelectric conversion element K are different from each other, one being a hole and the other being an electron, and the total area S of the surface side of the thermoelectric conversion member A that is in contact with the first electrode and the second electrode. A (m 2 ) is the sum of the areas S of the surfaces of the thermal backflow suppression member B that are in contact with the first electrode and the second electrode. B (m 2 A π-type thermoelectric conversion module, larger than ).

Description

[Technical Field]

[0001] This invention relates to a π-type thermoelectric conversion module. [Background technology]

[0002] Conventionally, as one means of efficiently utilizing energy, there are devices that directly convert thermal energy and electrical energy into each other using thermoelectric conversion modules that have thermoelectric effects such as the Seebeck effect and the Peltier effect.

[0003] As the aforementioned thermoelectric conversion module, the use of a so-called π-type thermoelectric conversion element is known. A π-type thermoelectric element has a basic configuration in which a pair of electrodes spaced apart from each other are provided on a substrate, for example, the lower surface of a P-type thermoelectric element is placed on one electrode and the lower surface of an N-type thermoelectric element is placed on the other electrode, also spaced apart from each other, and the upper surfaces of both types of thermoelectric elements are connected to the opposing electrodes on the substrate. Typically, multiple such basic units are configured within both substrates, electrically connected in series and thermally connected in parallel. In recent years, as products using π-type thermoelectric conversion modules, including such π-type thermoelectric conversion elements, are being put into full-scale practical use, there are various demands for further improvement in the thermoelectric performance of π-type thermoelectric conversion modules, increased density, and reduction in constituent materials. There can be a significant difference in thermoelectric performance between P-type and N-type thermoelectric elements. For example, if it were possible to construct a thermoelectric conversion module using only P-type thermoelectric elements, a significant performance improvement could be expected. In such cases, it has been devised to construct a thermoelectric conversion module using only P-type thermoelectric elements by using a conductive material instead of an N-type thermoelectric element (this is called a Unireg-type thermoelectric conversion module). However, in a Unireg-type thermoelectric conversion module, since an N-type thermoelectric element is not used, heat transfer occurs in the conductive material, and there is a problem that the heat transferred from the P-type thermoelectric element flows back into the P-type thermoelectric element. Patent Document 1 discloses a configuration that combines a P-type thermoelectric element as a P-type thermoelectric conversion member and a laminate of an N-type thermoelectric element and a conductive member as an N-type thermoelectric conversion member, as shown in Figure 3 of Patent Document 1. [Prior art documents] [Patent Documents]

[0004] [Patent Document 1] Japanese Patent Publication No. 2018-157136 [Overview of the project] [Problems that the invention aims to solve]

[0005] However, the thermoelectric conversion module described in Patent Document 1 merely uses the above configuration to suppress the generation of thermal stress due to the difference in thermal expansion and contraction between the P-type thermoelectric conversion member and the N-type thermoelectric conversion member in the operating environment (100°C, 300°C, 500°C). Furthermore, there is no description or suggestion whatsoever regarding how the difference in area of ​​the upper and lower surfaces of the P-type and N-type thermoelectric conversion members that are joined to the electrodes affects the thermoelectric performance.

[0006] This invention has been made in view of the above circumstances, and aims to provide a π-type thermoelectric conversion module that has excellent cooling performance with suppressed heat backflow. [Means for solving the problem]

[0007] As a result of diligent research to solve the above problems, the present inventors have found a π-type thermoelectric conversion module configuration in which a thermoelectric conversion member A including a thermoelectric conversion element M and a heat backflow suppression member B including a thermoelectric conversion element K are arranged alternately at intervals, wherein the carriers of the thermoelectric conversion elements M and K are different from each other, and the total area S of the surfaces of the thermoelectric conversion member A that are in contact with the first electrode and the second electrode. A (m 2 ) is the sum of the areas S of the surfaces of the thermal backflow suppression member B that are in contact with the first electrode and the second electrode. B (m2 ) By making it larger, it was found that the reverse flow of heat between the thermoelectric conversion element M and the thermoelectric conversion element K is suppressed and it has excellent cooling performance, and the present invention was completed. That is, the present invention provides the following [1] to [4]. [1] A thermoelectric conversion member A including a thermoelectric conversion element M and a heat reverse flow suppression member B including a thermoelectric conversion element K are alternately spaced apart and arranged between a pair of opposed first substrates having a first electrode and second substrates having a second electrode, and the thermoelectric conversion member A and the heat reverse flow suppression member B are electrically connected in series via the first electrode on the first substrate and the second electrode on the second substrate. A π-type thermoelectric conversion module, wherein the carriers of each of the thermoelectric conversion element M and the thermoelectric conversion element K are different from each other, one is a hole and the other is an electron, the total area S A (m 2 ) of the surface side of the thermoelectric conversion member A that joins the first electrode and the second electrode B (m 2 ) is larger than the total area S (m A ) of the surface side of the heat reverse flow suppression member B that joins the first electrode and the second electrode, B A π-type thermoelectric conversion module. [2] The ratio R [= S A / (S A + S A )] of the total area S B of the surface side of the thermoelectric conversion member A that joins the first electrode and the second electrode to the sum of the total area S of the surface side of the heat reverse flow suppression member B that joins the first electrode and the second electrode is 0.55 or more and less than 0.95. The π-type thermoelectric conversion module according to [1] above. [4] The π-type thermoelectric conversion module according to [3] above, wherein the height of the thermoelectric conversion element M in the thickness direction of the thermoelectric conversion member A is higher than the height of the thermoelectric conversion element K in the thickness direction of the heat backflow prevention member B having the conductive member. [Effects of the Invention]

[0008] According to the present invention, it is possible to provide a π-type thermoelectric conversion module that has excellent cooling performance with suppressed heat backflow. [Brief explanation of the drawing]

[0009] [Figure 1] This is a cross-sectional view showing an embodiment (configuration A) of the π-type thermoelectric conversion module of the present invention. [Figure 2] This is a cross-sectional view showing an embodiment (configuration B) of the π-type thermoelectric conversion module of the present invention. [Figure 3] This is a cross-sectional view showing an embodiment (configuration C) of a conventional thermoelectric conversion module. [Figure 4] This is a cross-sectional diagram showing an embodiment (configuration D) of a conventional π-type thermoelectric conversion module. [Modes for carrying out the invention]

[0010] [Thermoelectric Conversion Module] The π-type thermoelectric conversion module of the present invention is a π-type thermoelectric conversion module in which a thermoelectric conversion member A including a thermoelectric conversion element M and a thermal backflow suppression member B including a thermoelectric conversion element K are alternately spaced apart between a pair of opposing first substrates having a first electrode and a second substrate having a second electrode, and the thermoelectric conversion member A and the thermal backflow suppression member B are electrically connected in series via the first electrode on the first substrate and the second electrode on the second substrate. The carriers in the thermoelectric conversion element M and the thermoelectric conversion element K are different from each other; one is a hole and the other is an electron. The sum of the areas S of the surfaces of the thermoelectric conversion member A that are in contact with the first electrode and the second electrode. A (m 2) is the sum of the areas S of the surfaces of the thermal backflow suppression member B that are in contact with the first electrode and the second electrode. B (m 2 It is characterized by being larger than ). In the present invention, in a π-type thermoelectric conversion module configuration in which a thermoelectric conversion member A including a thermoelectric conversion element M and a thermal backflow suppression member B including a thermoelectric conversion element K are arranged alternately at intervals, the carriers (holes, electrons) of each thermoelectric conversion element M and thermoelectric conversion element K are made to be different combinations. For example, by making the thermoelectric conversion element M a P-type thermoelectric conversion element whose carrier is holes, and the thermoelectric conversion element K a N-type thermoelectric conversion element whose carrier is electrons, thermal backflow from the thermal backflow suppression member B to the thermoelectric conversion member A can be suppressed compared to a combination of a thermoelectric conversion element with one type of carrier and a conductive member (the so-called Unireg type). Furthermore, the total area S of the surface side of the thermoelectric conversion member A that is in contact with the first electrode and the second electrode. A (m 2 ) is the sum of the areas S of the surfaces of the thermal backflow suppression member B that are in contact with the first electrode and the second electrode. B (m 2 This makes it larger than ). As a result, a thermoelectric conversion member A having a thermoelectric conversion element M with superior thermoelectric performance can be used over a relatively large area, and a π-type thermoelectric conversion module with superior cooling performance can be obtained.

[0011] In this specification, thermoelectric elements M and K may be simply referred to as "thermoelectric elements." The first substrate and the second substrate may be simply referred to as "substrates." Furthermore, the first electrode and the second electrode may be simply referred to as "electrodes."

[0012] In this specification, any provision deemed preferable can be selected at will, and any combination of preferred provisions is considered more preferable. In this specification, the notation "XX~YY" means "XX or greater and YY or less". In this specification, the lower and upper limits described in steps for a preferred numerical range (e.g., range of content, etc.) can be combined independently. For example, from the description "preferably 10 to 90, more preferably 30 to 60", the "preferred lower limit (10)" and the "more preferred upper limit (60)" can be combined to arrive at "10 to 60".

[0013] Thermoelectric conversion member A includes a thermoelectric conversion element M. Furthermore, the heat backflow suppression member B includes a thermoelectric conversion element K. Details of thermoelectric elements M and K will be described later.

[0014] The π-type thermoelectric conversion module of the present invention will be described below with reference to the figures.

[0015] Figure 1 is a cross-sectional view showing an embodiment (configuration A) of the π-type thermoelectric conversion module of the present invention. The π-type thermoelectric conversion module 1 is configured such that a thermoelectric conversion member A4a including a thermoelectric conversion element M4a1 and a thermal backflow suppression member B4b including a thermoelectric conversion element K4b1 are alternately spaced apart between a pair of opposing first substrates 2a having a first electrode 3a and a second substrate 2b having a second electrode 3b, and the thermoelectric conversion member A4a and the thermal backflow suppression member B4b are electrically connected in series via the first electrode 3a on the first substrate 2a and the second electrode 3b on the second substrate 2b. Here, for example, the area of ​​the upper and lower surfaces (not shown) of the thermoelectric conversion member A4a, which includes the thermoelectric conversion element M4a1, that are joined to the first electrode 3a side or the second electrode 3b side is larger than the area of ​​the upper and lower surfaces (not shown) of the heat backflow suppression member B4b, which includes the thermoelectric conversion element K4b1, that are joined to the first electrode 3a side or the second electrode 3b side.

[0016] The total area S of the surfaces of the thermoelectric conversion member A that are in contact with the first electrode and the second electrode. A The total area S of the surfaces of the thermal backflow suppression member B that are in contact with the first electrode and the second electrode. B The sum of the areas S of the surfaces of the thermoelectric conversion member A that are in contact with the first electrode and the second electrode, and the sum of the areas S of the surfaces that are in contact with the first electrode and the second electrode. AThe ratio R[=S A / (S A +S B The value of ) is preferably 0.55 or more and less than 0.95, more preferably 0.65 or more and less than 0.95, even more preferably 0.75 to 0.93, and particularly preferably 0.80 to 0.90. A ratio R of 0.55 or higher makes it easier to increase the amount of heat absorbed per unit area of ​​the thermoelectric element M contained in the thermoelectric conversion member A. Since the ratio R is less than 0.95, it is easier to suppress heat backflow from the heat backflow suppression member B to the thermoelectric conversion member A, and the amount of heat absorbed per unit area of ​​the thermoelectric conversion element K included in the heat backflow suppression member B can be kept high.

[0017] The thermal backflow suppression member B includes a thermoelectric conversion element K and a conductive member, and it is preferable that the thermoelectric conversion element K and the conductive member are stacked in a direction facing each other between the first substrate and the second substrate.

[0018] Figure 2 is a cross-sectional view showing an embodiment (configuration B) of the π-type thermoelectric conversion module of the present invention. The π-type thermoelectric conversion module 11 is configured such that a thermoelectric conversion member A4a, which includes a thermoelectric conversion element M4a1, and a thermal backflow suppression member B4b, which includes a configuration in which a thermoelectric conversion element K4b1 and a conductive member 4b2 are stacked, are alternately spaced apart between a pair of opposing first substrates 2a having a first electrode 3a and a second substrate 2b having a second electrode 3b, and the thermoelectric conversion member A4a and the thermal backflow suppression member B4b are electrically connected in series via the first electrode 3a on the first substrate 2a and the second electrode 3b on the second substrate 2b. Here, for example, the area of ​​the upper and lower surfaces (not shown) of the thermoelectric conversion member A4a, which includes the thermoelectric conversion element M4a1, that are joined to the first electrode 3a side or the second electrode 3b side is larger than the area of ​​the upper and lower surfaces (not shown) of the thermal backflow suppression member B4b, which includes a configuration in which the thermoelectric conversion element K4b1 and the conductive member 4b2 are stacked, that are joined to the first electrode 3a side or the second electrode 3b side.

[0019] <Conductive material> The conductive member used in the present invention is preferably used in a laminated form with the thermoelectric conversion element K. The laminate may be, for example, a single-layer configuration of the conductive member and the thermoelectric conversion element K, a three-layer configuration in which the conductive member is sandwiched between the thermoelectric conversion elements K, or a configuration in which multiple layers are alternately laminated. The conductive member may be made of a conductive material as described later, or it may be a thin film made of a composition containing such materials.

[0020] Examples of conductive materials that make up conductive components include metallic materials such as copper, silver, gold, platinum, nickel, aluminum, constantan, chromium, indium, iron, or alloys thereof, as well as indium tin oxide (ITO) and zinc oxide (ZnO). Among these, from the viewpoint of thermoelectric performance, it is preferable to use a conductive material that has low electrical resistance and is easy to increase thermal resistance.

[0021] There are no particular limitations on the method for forming the conductive member or laminating it on the thermoelectric conversion element K, but examples include PVD (physical vapor deposition) such as vacuum deposition, sputtering, and ion plating, or dry processes such as CVD (chemical vapor deposition) such as thermal CVD and atomic layer deposition (ALD), or known methods such as screen printing, flexographic printing, gravure printing, spin coating, dip coating, die coating, spray coating, bar coating, and doctor blade methods, and there are no particular limitations. When forming a coating film of the composition in a pattern, screen printing or slot die coating methods that allow for easy pattern formation using a screen plate with the desired pattern are preferably used. Furthermore, the patterning of conductive materials can be carried out by known physical or chemical treatments, primarily photolithography, or by a combination of these methods.

[0022] It is preferable that the height of the thermoelectric element M in the thickness direction of the thermoelectric conversion member A is higher than the height of the thermoelectric element K in the thickness direction of the heat backflow prevention member B having a conductive member. By making the height of the thermoelectric conversion element M greater than the height of the thermoelectric conversion element K, the electrical resistance of the thermoelectric conversion element K can be kept low, and a sufficient amount of current can be secured even if the surface area of ​​the surface facing the electrodes of the thermoelectric conversion element K is small. As a result, the effect of ensuring current flow while preventing backflow of heat transfer by the thermoelectric conversion member A through the thermoelectric conversion element K becomes more pronounced. From this perspective, there are no particular restrictions on the thickness of the conductive member, but it is adjusted as appropriate depending on the thickness of the thermoelectric conversion element K. For example, when the thermal backflow suppression member B is composed of a single layer of the conductive member and the thermoelectric conversion element K, the ratio of the thickness of the thermoelectric conversion element K to the thickness of the conductive member is preferably 1:9 to 9:1, more preferably 2:8 to 8:2, and even more preferably 2:8 to 4:6.

[0023] The total area S of the surfaces of the thermoelectric conversion member A that are in contact with the first electrode and the second electrode. A The total area S of the surfaces of the thermal backflow suppression member B that are in contact with the first electrode and the second electrode. B The sum of the areas S of the surfaces of the thermoelectric conversion member A that are in contact with the first electrode and the second electrode, and the sum of the areas S of the surfaces that are in contact with the first electrode and the second electrode. A The ratio R[=S A / (S A +S B Regarding ), it is as previously stated.

[0024] The total area S of the surface of the thermoelectric conversion member A that is in contact with the first electrode. A1 And the total area S of the surface of the heat backflow suppression member B that is in contact with the first electrode. B1 and, the sum of S A1B1 And the total area S of the surface of the thermoelectric conversion member A that is in contact with the second electrode. A2 And the total area S of the surface of the heat backflow suppression member B that is in contact with the second electrode. B2 and, the sum of S A2B2 These may be the same or different, but from the viewpoint of uniformity of the heat-absorbing surface, it is preferable that they be the same.

[0025] The total area S of the surface of the thermoelectric conversion member A that is in contact with the first electrode. A1 And the total area S of the surface of the thermoelectric conversion member A that is in contact with the second electrode.A2 These may be the same or different, but it is preferable that they be the same. The total area S of the surface of the thermal backflow suppression member B that is in contact with the first electrode. B1 And the total area S of the surface of the heat backflow suppression member B that is in contact with the second electrode. B2 They may be the same or different, but it is preferable that they be the same.

[0026] Figure 3 is a cross-sectional view showing an embodiment (configuration C) of a conventional thermoelectric conversion module. The thermoelectric conversion module 21 is a so-called Unireg type thermoelectric conversion module, in which a thermoelectric conversion member A4a including a thermoelectric conversion element M4a1 and a conductive member 4b2 are alternately spaced apart between a pair of opposing first substrates 2a having a first electrode 3a and a second substrate 2b having a second electrode 3b, and the thermoelectric conversion member A4a and the conductive member 4b2 are electrically connected in series via the first electrode 3a on the first substrate 2a and the second electrode 3b on the second substrate 2b. Here, for example, the area of ​​the upper and lower surfaces (not shown) of the thermoelectric conversion member A4a, which includes the thermoelectric conversion element M4a1, that are joined to the first electrode 3a side or the second electrode 3b side is larger than the area of ​​the upper and lower surfaces (not shown) of the conductive member 4b2 that are joined to the first electrode 3a side or the second electrode 3b side.

[0027] Figure 4 is a cross-sectional view showing an embodiment (configuration D) of a conventional π-type thermoelectric conversion module. In the π-type thermoelectric conversion module 31, a thermoelectric conversion member A4a including a thermoelectric conversion element M4a1 and a thermoelectric conversion element K4b1 are arranged alternately spaced apart between a pair of opposing first substrates 2a having a first electrode 3a and second substrate 2b having a second electrode 3b. In addition, the thermoelectric conversion member A4a including the thermoelectric conversion element M4a1 and the thermoelectric conversion element K4b1 are electrically connected in series via the first electrode 3a on the first substrate 2a and the second electrode 3b on the second substrate 2b. Here, for example, the area of ​​the upper and lower surfaces (not shown) of the thermoelectric conversion member A4a, which includes the thermoelectric conversion element M4a1, that are joined to the first electrode 3a side or the second electrode 3b side is configured to be approximately the same size as the area of ​​the upper and lower surfaces (not shown) of the thermoelectric conversion element K4b1 that are joined to the first electrode 3a side or the second electrode 3b side.

[0028] [Amount of heat absorbed] The amount of heat absorbed was calculated using the thermal simulation shown below.

[0029] (a) Heat absorption of P-type thermoelectric elements and N-type thermoelectric elements The heat absorption Qc of a P-type thermoelectric element and an N-type thermoelectric element can be calculated from the following formula (1). Q c =SeT c I-(λS / L)ΔT-(1 / 2)RI 2 (1) Q c : Heat absorption of thermoelectric conversion element (W / m 2 ) Se: Seebeck coefficient (V / K) I: Current value (A) of thermoelectric conversion module T c : Temperature (K) of the heat-absorbing surface of the thermoelectric conversion module T h : Temperature (K) of the heat dissipation surface of the thermoelectric conversion module ΔT: Temperature difference (T h -T c )(K) R: Electrical resistance value (Ω) of the thermoelectric conversion module λ: Thermal conductivity of the thermoelectric element [W / (m·K)] L: Height of the thermoelectric element (m) S: Area (m²) of the heat-absorbing surface that is in contact with the first and second electrodes of the thermoelectric conversion element. 2 ) Note that the maximum heat absorption Q CMAX (W) can be calculated in equation (1) above by setting the current value (A) of the thermoelectric conversion module to the maximum current value (A) and setting ΔT to 0.

[0030] (b) Amount of heat transfer of conductive member Heat transfer amount Q of conductive material A This can be calculated from the following formula (2). Q A =-(λS / L)ΔT (2) Q A :Heat transfer amount (W / m 2 ) ΔT: Temperature difference (T h -T c )(K) λ: Thermal conductivity of conductive material [W / (m·K)] L: Height L of the conductive material (m) S: Area of ​​the heat-absorbing surface side of the conductive member that is in contact with the first electrode and the second electrode (m²) 2 )

[0031] (c) Total heat absorption amount Total heat absorption Q F This can be calculated from the following formula (3). Q F =Q c +Q A (3)

[0032] <Thermoelectric conversion element> The thermoelectric conversion element M in the thermoelectric conversion member A and the thermoelectric conversion element K in the heat backflow suppression member B used in the present invention are not particularly limited as long as different carriers are used in combination, and may be made of a thermoelectric semiconductor material or a thin film made of a thermoelectric semiconductor composition. From the viewpoint of flexibility, thinness, and thermoelectric performance, it is preferable that the thin film be made of a thermoelectric semiconductor composition containing one or both of a thermoelectric semiconductor material (hereinafter sometimes referred to as "thermoelectric semiconductor particles"), a resin, an ionic liquid, and an inorganic ionic compound.

[0033] (Thermoelectric semiconductor materials) The thermoelectric semiconductor material used in the thermoelectric conversion element M and the thermoelectric conversion element K is preferably pulverized to a predetermined size using, for example, a fine pulverization device, and used as thermoelectric semiconductor particles. The particle size of the thermoelectric semiconductor particles is preferably 10 nm to 100 μm. The average particle size of the thermoelectric semiconductor particles is obtained by measuring it with a laser diffraction particle size analyzer (Malvern Mastersizer 3000) and is taken as the median value of the particle size distribution.

[0034] In the thermoelectric conversion elements M and K used in the present invention, the thermoelectric semiconductor materials constituting the P-type thermoelectric conversion element and the N-type thermoelectric conversion element are, for example, bismuth-tellurium-based thermoelectric semiconductor materials such as P-type bismuth telluride and N-type bismuth telluride; telluride-based thermoelectric semiconductor materials such as GeTe and PbTe; antimony-tellurium-based thermoelectric semiconductor materials; ZnSb and Zn3Sb. 2、 Zinc-antimony thermoelectric semiconductor materials such as Zn4Sb3; silicon-germanium thermoelectric semiconductor materials such as SiGe; bismuth selenide thermoelectric semiconductor materials such as Bi2Se3; β-FeSi2, CrSi2, MnSi 1.73 Silicide-based thermoelectric semiconductor materials such as Mg2Si; oxide-based thermoelectric semiconductor materials; Heusler materials such as FeVAl, FeVAlSi, and FeVTiAl; and sulfide-based thermoelectric semiconductor materials such as TiS2 are used.

[0035] The content of thermoelectric semiconductor particles in the thermoelectric semiconductor composition is preferably 30 to 99% by mass. When the content of thermoelectric semiconductor particles is within the above range, the Seebeck coefficient (absolute value of the Peltier coefficient) is large, the decrease in electrical conductivity is suppressed, and only the thermal conductivity decreases, resulting in a film that exhibits high thermoelectric performance, as well as sufficient film strength and flexibility, which is preferable.

[0036] Furthermore, it is preferable that the thermoelectric semiconductor particles are annealed (hereinafter sometimes referred to as "annealing treatment A"). By performing annealing treatment A, the crystallinity of the thermoelectric semiconductor particles is improved, and the surface oxide film of the thermoelectric semiconductor particles is removed, thereby increasing the Seebeck coefficient (absolute value of the Peltier coefficient) of the thermoelectric conversion element and further improving the thermoelectric figure of merit.

[0037] (resin) The resin used in this invention has the effect of physically bonding thermoelectric semiconductor materials (thermoelectric semiconductor particles), which can improve the flexibility of the thermoelectric conversion module and facilitate the formation of thin films by coating or other means. As the resin, a heat-resistant resin or a binder resin is preferred.

[0038] When a heat-resistant resin is subjected to crystalline growth of thermoelectric semiconductor particles in a thin film made of a thermoelectric semiconductor composition through annealing or other processes, its various physical properties, such as mechanical strength and thermal conductivity, are maintained without being impaired. The heat-resistant resin is preferably polyamide resin, polyamide-imide resin, polyimide resin, or epoxy resin because it has higher heat resistance and does not adversely affect the crystal growth of thermoelectric semiconductor particles in the thin film, and more preferably polyamide resin, polyamide-imide resin, or polyimide resin because it has excellent flexibility.

[0039] The heat-resistant resin preferably has a decomposition temperature of 300°C or higher. If the decomposition temperature is within the above range, as will be described later, even when a thin film made of a thermoelectric semiconductor composition is annealed, the binder function is not lost and flexibility can be maintained.

[0040] The content of the heat-resistant resin in the thermoelectric semiconductor composition is 0.1 to 40% by mass. When the content of the heat-resistant resin is within this range, it functions as a binder for the thermoelectric semiconductor material, making it easier to form a thin film.

[0041] The binder resin also facilitates the removal of the thermoelectric conversion material chips from substrates such as glass, alumina, and silicon after the annealing process (corresponding to "Annealing Process B" described later, and the same applies hereafter).

[0042] The binder resin refers to a resin that decomposes by 90% or more by mass at the annealing temperature. In other words, by using a resin that decomposes at a lower temperature than the heat-resistant resin mentioned above, the binder resin decomposes during firing. This reduces the amount of binder resin, which is an insulating component in the fired body, and promotes the crystal growth of thermoelectric semiconductor particles in the thermoelectric semiconductor composition. As a result, the voids in the thermoelectric conversion material layer can be reduced, and the packing density can be improved. Furthermore, whether or not a resin decomposes at a predetermined value (for example, 90% by mass) or more at the annealing temperature is determined by measuring the mass loss rate at the annealing temperature (the value obtained by dividing the mass after decomposition by the mass before decomposition) using thermogravimetric analysis (TG).

[0043] Examples of such binder resins include thermoplastic resins and curable resins. Examples of thermoplastic resins include polyolefin resins such as polyethylene, polypropylene, polyisobutylene, and polymethylpentene; polycarbonate; thermoplastic polyester resins such as polyethylene terephthalate and polyethylene naphthalate; polyvinyl polymers such as polystyrene, acrylonitrile-styrene copolymer, polyvinyl acetate, ethylene-vinyl acetate copolymer, vinyl chloride, polyvinylpyridine, polyvinyl alcohol, and polyvinylpyrrolidone; polyurethane; and cellulose derivatives such as ethylcellulose. Examples of curable resins include thermosetting resins and photocurable resins. Examples of thermosetting resins include epoxy resins and phenolic resins. Examples of photocurable resins include photocurable acrylic resins, photocurable urethane resins, and photocurable epoxy resins. These may be used individually or in combination of two or more.

[0044] The content of the binder resin in the thermoelectric semiconductor composition is 0.1 to 40% by mass.

[0045] (Ionic liquid) The ionic liquid that can be included in the thermoelectric semiconductor composition is a molten salt formed by combining a cation and an anion, and refers to a salt that can exist as a liquid in any temperature range from -50°C or higher to less than 400°C. The ionic liquid has characteristics such as an extremely low vapor pressure and being non-volatile, having excellent thermal stability and electrochemical stability, having a low viscosity, and having a high ionic conductivity. Therefore, as a conductive auxiliary agent, it can effectively suppress the reduction of the electrical conductivity between thermoelectric semiconductor materials.

[0046] Known or commercially available ionic liquids can be used. For example, nitrogen-containing cyclic cation compounds such as pyridinium, pyrimidinium, pyrazolium, pyrrolidinium, piperidinium, imidazolium and their derivatives; tetraalkylammonium-based amine cations and their derivatives; phosphine-based cations such as phosphonium, trialkylsulfonium, tetraalkylphosphonium and their derivatives; cation components such as lithium cation and its derivatives, and Cl - , Br - , I - , AlCl4 - , Al2Cl7 - , BF4 - , PF6 - , ClO4 - , NO3 - , CH3COO - , CF3COO - , CH3SO3 - , CF3SO3 - , (FSO2)2N - , (CF3SO2)2N - , (CF3SO2)3C - , AsF6 - , SbF6 - , NbF6 - , TaF6 - , F(HF) n - , (CN)2N - , C4F9SO3 - , (C2F5SO2)2N - , C3F7COO - , (CF3SO2)(CF3CO)N -Examples include those composed of anionic components such as the following.

[0047] The content of the ionic liquid in the thermoelectric semiconductor composition is preferably 0.01 to 50% by mass. When the ionic liquid content is within the above range, the decrease in electrical conductivity is effectively suppressed, and a film with high thermoelectric performance can be obtained.

[0048] (Method for preparing thermoelectric semiconductor compositions) There are no particular limitations on the method for preparing the thermoelectric semiconductor composition. For example, the thermoelectric semiconductor particles, the ionic liquid, the resin, and optionally the other additives and a solvent may be mixed and dispersed using known methods such as an ultrasonic homogenizer, spiral mixer, planetary mixer, disperser, or hybrid mixer to prepare the thermoelectric semiconductor composition. Examples of the aforementioned solvents include toluene, ethyl acetate, methyl ethyl ketone, alcohol, tetrahydrofuran, methylpyrrolidone, and ethyl cellosolve. These solvents may be used individually or in mixtures of two or more. The solid content concentration of the thermoelectric semiconductor composition is not particularly limited, as long as the composition has a viscosity suitable for coating.

[0049] The thermoelectric conversion element made of the thermoelectric semiconductor composition is not particularly limited, but for example, it can be formed by coating the thermoelectric semiconductor composition onto a substrate such as glass, alumina, silicon, or a resin film, or onto a substrate on which a sacrificial layer (described later) has been formed, obtaining a coating film, drying it, and then separating it from the substrate as appropriate. By forming it in this way, a large number of thermoelectric conversion elements can be obtained simply and at low cost. As the resin film, one with heat resistance is preferable, and a film made of polyamide resin, polyamide-imide resin, or polyimide resin is preferred. Methods for applying a thermoelectric semiconductor composition to obtain a thermoelectric conversion element include, but are not limited to, known methods such as screen printing, flexographic printing, gravure printing, spin coating, dip coating, die coating, spray coating, bar coating, and doctor blade coating. When forming a coating film in a pattern, screen printing or slot die coating methods, which allow for easy pattern formation using a screen plate with the desired pattern, are preferably used. Next, the obtained coating film is dried to form a thermoelectric conversion element. Conventional drying methods such as hot air drying, hot roll drying, and infrared irradiation can be used. The heating temperature is usually 80 to 150°C, and the heating time varies depending on the heating method, but is usually several seconds to several tens of minutes. Furthermore, when a solvent is used in the preparation of a thermoelectric semiconductor composition, there are no particular restrictions on the heating temperature, as long as it is within a temperature range that allows the solvent to be dried.

[0050] The thickness of the thermoelectric conversion element is preferably thin, typically 2000 μm or less, because this keeps the electrical resistance of the thermoelectric conversion element low, making it easier for the current flowing through the thermoelectric conversion element to increase, and thus leading to an increase in the heat absorbed by the thermoelectric conversion module. The thickness of the thermoelectric conversion element is preferably 10 to 1600 μm, more preferably 50 to 1400 μm, even more preferably 100 to 1200 μm, and particularly preferably 400 to 1000 μm. By having a thickness of the thermoelectric conversion element equal to or greater than the lower limit, it is possible to suppress the increase in heat generation in the electrodes, solder material layer, etc., that constitute the π-type thermoelectric conversion module, and to increase the heat absorption of the thermoelectric conversion module.

[0051] The electrical resistance value per thermoelectric conversion element M is preferably 30 (mΩ) or less. By being 30 (mΩ) or less, the current value per unit area of the thermoelectric conversion element increases, making it easier to increase the heat absorption amount to a desired range. Also, the lower limit value of the electrical resistance value is not particularly restricted, but from the perspective of ease of manufacturing, it is about 0.01 (mΩ). From such a perspective, it is preferably 0.01 to 30 (mΩ), more preferably 0.1 to 20 (mΩ), still more preferably 1.0 to 17 (mΩ), and particularly preferably 6 to 13 (mΩ). The electrical resistance value per thermoelectric conversion element K is preferably 100 (mΩ) or less. By being 100 (mΩ) or less, the current value per unit area of the thermoelectric conversion element increases, making it easier to increase the heat absorption amount to a desired range. Also, the lower limit value of the electrical resistance value is not particularly restricted, but from the perspective of ease of manufacturing, it is about 0.1 (mΩ). From such a perspective, it is preferably 0.1 to 100 (mΩ), more preferably 1 to 60 (mΩ), still more preferably 10 to 50 (mΩ), and particularly preferably 30 to 45 (mΩ).

[0052] The areas of the upper and lower surfaces of the thermoelectric conversion element M are each independently preferably 0.04 to 30 (mm 2 ), more preferably 0.30 to 10 (mm 2 ), still more preferably 0.5 to 4 (mm 2 ), and particularly preferably 0.7 to 2 (mm 2 ). On the other hand, the areas of the upper and lower surfaces of the thermoelectric conversion element K are each independently preferably 0.01 to 2 (mm 2 ), more preferably 0.04 to 1 (mm 2 ), still more preferably 0.06 to 0.9 (mm 2 ), and particularly preferably 0.1 to 0.6 (mm 2 ). The ratio of the area of the upper surface to the area of the lower surface of each of the thermoelectric conversion elements M and K is each independently preferably 0.80 to 1.20, more preferably 0.90 to 1.10, and still more preferably 0.99 to 1.01. When the area of ​​the top and bottom surfaces of the thermoelectric element chip, and the ratio of the top surface area to the bottom surface area of ​​the thermoelectric element, are within this range, the electrical resistance is kept low, and the amount of heat absorbed is easily increased.

[0053] When the upper and lower surfaces of the thermoelectric conversion elements M and K are rectangular (the overall shape is a rectangular parallelepiped or cube), the length of one side is preferably 0.2 to 10 mm, more preferably 0.5 to 5 mm, and even more preferably 0.8 to 2 mm. However, the length of at least one side on the upper and lower surfaces of the thermoelectric conversion element K is shorter than the length of the equivalent part of the thermoelectric conversion element M. For example, the length of at least one side is preferably 1 to 90%, more preferably 5 to 60%, and particularly preferably 10 to 30% of the length of the equivalent part of the thermoelectric conversion element M. By ensuring that the length of one side of the upper and lower surfaces of the thermoelectric conversion elements M and K, and the ratio of the lengths of their respective sides, fall within the above-mentioned range, it becomes possible to manufacture a π-type thermoelectric conversion module with high accuracy and high heat absorption capacity.

[0054] It is preferable to further anneal the thermoelectric conversion element, which is a thin film made of a thermoelectric semiconductor composition, (hereinafter sometimes referred to as "annealing treatment B"). By performing annealing treatment B, the thermoelectric performance can be stabilized and the thermoelectric semiconductor particles in the thin film can be grown crystal-like, thereby further improving the thermoelectric performance. Annealing treatment B is not particularly limited, but is usually performed under an inert gas atmosphere such as nitrogen or argon, a reducing gas atmosphere, or under vacuum conditions with controlled gas flow rates, and is performed at 100 to 700°C for several minutes to several tens of hours, depending on the heat resistance temperature of the resin and ionic compound used. Furthermore, in annealing treatment B, the thermoelectric semiconductor composition may be pressed to improve the density of the thermoelectric semiconductor composition.

[0055] As the sacrificial layer, a resin such as polymethyl methacrylate or polystyrene, or a release agent such as a fluorine-based release agent or a silicone-based release agent can be used. By using a sacrificial layer, the thermoelectric conversion element formed on a substrate such as glass can be easily peeled off from the glass after annealing treatment B. The formation of the sacrificial layer is not particularly restricted and can be carried out by known methods such as flexographic printing and spin coating.

[0056] <Circuit board> As the substrate for the π-type thermoelectric conversion module of the present invention, specifically the first and second substrates, it is preferable to use a plastic film, ceramic substrate, or the like that does not affect the decrease in electrical conductivity or increase in thermal conductivity of the thermoelectric conversion element. Even when the thermoelectric conversion element is annealed, the substrate does not undergo thermal deformation, maintaining the performance of the π-type thermoelectric conversion module. From the standpoint of high heat resistance and dimensional stability, polyimide film, polyamide film, polyetherimide film, polyaramid film, polyamideimide film, and glass epoxy sheet are preferred as plastic films.

[0057] The thickness of the plastic film used in the substrate is preferably 1 to 1000 μm, more preferably 10 to 500 μm, and even more preferably 20 to 100 μm, from the viewpoint of flexibility, heat resistance, and dimensional stability. On the other hand, the thickness of the ceramic substrate is preferably 100 μm to 30 mm, more preferably 500 μm to 10 mm, and particularly preferably 1 to 5 mm.

[0058] <Electrode> The metal material used as the electrode for the π-type thermoelectric conversion module of the present invention is not particularly limited, but examples of metal materials for the first electrode and the second electrode include gold, nickel, aluminum, rhodium, platinum, chromium, palladium, stainless steel, molybdenum, or alloys containing any of these metals. Furthermore, the product may be formed using a paste material containing a solvent or resin component in addition to the metal material. When using a paste material, it is preferable to remove the solvent or resin component by firing or other means. Silver paste and aluminum paste are preferred as paste materials. The thickness of the electrode layer is preferably 10 nm to 200 μm. If the thickness of the electrode layer is within the above range, the electrical conductivity will be high and the resistance low, and sufficient strength as an electrode can be obtained.

[0059] Methods for forming electrodes include known physical or chemical treatments, primarily photolithography, or a combination thereof, to process the electrodes into a predetermined pattern shape; or methods for forming electrode patterns using screen printing, stencil printing, inkjet printing, etc. Methods for forming electrodes without a pattern include PVD (Physical Vapor Deposition) such as vacuum deposition, sputtering, and ion plating; vacuum deposition methods such as CVD (Chemical Vapor Deposition) such as thermal CVD and atomic layer deposition (ALD); various coatings such as dip coating, spin coating, spray coating, gravure coating, die coating, and doctor blade methods; wet processes such as electrodeposition; silver salt methods; electrolytic plating; electroless plating; and lamination of metal foils, which are selected appropriately depending on the metal material.

[0060] <Solder material layer> The solder material layer is used to join the thermoelectric conversion element and the electrode. Known materials that make up the solder layer include Sn, Sn / Pb alloy, Sn / Ag alloy, Sn / Cu alloy, Sn / Sb alloy, Sn / In alloy, Sn / Zn alloy, Sn / In / Bi alloy, Sn / In / Bi / Zn alloy, Sn / Bi / Pb / Cd alloy, Sn / Bi / Pb alloy, Sn / Bi / Cd alloy, Bi / Pb alloy, Sn / Bi / Zn alloy, Sn / Bi alloy, Sn / Bi / Pb alloy, Sn / Pb / Cd alloy, and Sn / Cd alloy. Examples of commercially available soldering materials include: for example, 42Sn / 58Bi alloy (manufactured by Tamura Corporation, product name: SAM10-401-27), 41Sn / 58Bi / Ag alloy (manufactured by Nihon Handa Co., Ltd., product name: PF141-LT7HO), and 96.5Sn3Ag0.5Cu alloy (manufactured by Nihon Handa Co., Ltd., product name: PF305-207BTO).

[0061] The thickness of the solder material layer (after heating and cooling) is preferably 10 to 200 μm. Having the solder material layer thickness within this range facilitates good adhesion between the thermoelectric conversion element and the electrodes.

[0062] Methods for applying solder material to a circuit board include stencil printing, screen printing, and D Known methods such as the spencening method can be used. The heating temperature varies depending on the solder material, resin film, etc. used, but is usually 150-280°C for 3-20 minutes.

[0063] <Heat dissipation layer> In the π-type thermoelectric conversion module of the present invention, from the viewpoint of thermoelectric performance, it is preferable to further provide a heat dissipation layer on at least one surface of the aforementioned substrate. The material used for the heat dissipation layer is not particularly limited, and known materials can be used. Preferably, it is selected from gold, silver, copper, nickel, tin, iron, chromium, platinum, palladium, rhodium, iridium, ruthenium, osmium, indium, zinc, molybdenum, manganese, titanium, aluminum, stainless steel, and brass.

[0064] There are no particular limitations on the method for laminating the heat dissipation layer, but examples include PVD (Physical Vapor Deposition) such as vacuum deposition, sputtering, and ion plating; dry processes such as thermal CVD and atomic layer deposition (ALD); wet processes such as dip coating, spin coating, spray coating, gravure coating, die coating, and doctor blade coating; and electrodeposition; as well as silver salt methods, electrolytic plating, and electroless plating. Furthermore, the heat dissipation layer patterning can be carried out by known physical or chemical treatments, primarily photolithography, or by a combination of these methods. The thermal conductivity of each heat dissipation layer is preferably 5 to 500 W / (m·K).

[0065] The thickness of the heat dissipation layer is determined appropriately from the viewpoint of thermoelectric performance, but is preferably 1 to 550 μm. Furthermore, the calculated heat absorption per unit area of ​​one unit (a pair consisting of thermoelectric conversion element A and heat backflow suppression element B) that constitutes a thermoelectric conversion module is 1 to 30 W / cm². 2 Preferably, the voltage is 2.5 to 10 W / cm². 2 It is more preferable that the current level is 3.5-5.0 W / cm². 2 It is particularly preferable that this is the case. If it is within this range, it is easier to obtain a thermoelectric conversion module that is thin and has a high heat absorption capacity.

[0066] The total thickness of the π-type thermoelectric conversion module is preferably 300 μm to 20 mm. When the total thickness of a π-type thermoelectric conversion module falls within this range, the module resistance of the thermoelectric conversion module is easily suppressed, resulting in a thin π-type thermoelectric conversion module with high cooling performance.

[0067] The π-type thermoelectric conversion module of the present invention has excellent cooling performance with suppressed heat backflow. [Examples]

[0068] Next, the present invention will be described in more detail with reference to examples, but the present invention is not limited in any way by these examples.

[0069] The heat absorption amounts for the π-type thermoelectric conversion module with the configuration of the present invention, the conventional π-type thermoelectric conversion module, and the Unireg-type thermoelectric conversion module were evaluated using the following method.

[0070] (a) Evaluation of heat absorption For the thermoelectric conversion modules of Examples 1 and 2, and Comparative Examples 1 and 2, the cooling performance (heat absorption per unit area) per unit (one pair of thermoelectric conversion member A and reverse heat flow suppression member B) was evaluated using the thermal simulation described above.

[0071] (Example 1) A thermal simulation was performed on the π-type thermoelectric conversion module of the embodiment (Configuration A) shown in Figure 1 to evaluate the amount of heat absorbed per unit area. First, the cooling surface (heat absorption surface) temperature was set to 50°C, and the heat dissipation surface temperature was set to 70°C. Furthermore, the physical properties of the thermoelectric conversion component A, the physical properties of the reverse heat flow suppression component B, the current value of the thermoelectric conversion module, and the electrical resistance value of the thermoelectric conversion module were set as follows. (Thermoelectric conversion component A) Thermoelectric conversion element M [P-type (BiSbTe system)] Size: A rectangular prism with top and bottom surfaces measuring 1mm vertically x 1mm horizontally and 1mm thick. Se: Seebeck coefficient [183 × 10 -6 (V / K)] I: Current value of thermoelectric conversion module [1(A)] T c :Temperature of the heat-absorbing surface of the thermoelectric conversion module [273.15 + 50 (K)] T h Temperature of the heat dissipation surface of the thermoelectric conversion module [273.15 + 70 (K)] ΔT: Temperature difference (T h -T c )[20(K)] R: Electrical resistance value of one thermoelectric element M [10.5 (mΩ)] λ: Thermal conductivity of thermoelectric element M [1.02 [W / (m·K)]] L: Height (thickness) of thermoelectric element M [1 × 10 -3 (m)] S: Area of ​​the surface of the thermoelectric conversion element M that is in contact with the first electrode and the second electrode [1 × 10 -6 (m 2 )]

[0072] (Thermal backflow suppression member B) Thermoelectric conversion element K [N-type (BiTe system)] Size: A rectangular prism with top and bottom surfaces measuring 1mm vertically x 0.2mm horizontally and 1mm thick. Se: Seebeck coefficient [-132 × 10 -6 (V / K)] I: Current value of the thermoelectric conversion module [1(A)]. T c :Temperature of the heat-absorbing surface of the thermoelectric conversion module [273.15 + 50 (K)] T hTemperature of the heat dissipation surface of the thermoelectric conversion module [273.15 + 70 (K)] ΔT: Temperature difference (T h -T c )[20(K)] R: Electrical resistance value of one thermoelectric element K [44.7 (mΩ)] λ: Thermal conductivity of thermoelectric element K [1.02 [W / (m·K)]] L: Height (thickness) of thermoelectric element K [1 × 10 -3 (m)] S: Area of ​​the surface of the thermoelectric conversion element K that is in contact with the first electrode and the second electrode [0.2 × 10 -6 (m 2 )] Conductive material: None Distance between thermoelectric elements M and K: 0.1 mm Therefore, the unit area including the thermoelectric element M, the thermoelectric element K, and the distance between them is 1.3 mm². 2 This is the result.

[0073] (Example 2) In Example 1, the π-type thermoelectric conversion module was modified to the embodiment (configuration B) shown in Figure 2. The thickness of the thermoelectric conversion element K [N-type (BiTe-based)] in the heat backflow suppression member B was set to 0.2 mm. Additionally, copper with the following size and thermal conductivity was used as a conductive material. Otherwise, the thermal simulation was performed in the same manner as in Example 1, and the amount of heat absorbed per unit area was evaluated. Size: A rectangular prism with top and bottom surfaces measuring 1mm vertically x 0.2mm horizontally and 0.8mm thick. λ: Thermal conductivity [398[W / (m·K)]] (However, the electrical resistance of the conductive material was assumed to be 0 mΩ for the calculation.) R: Electrical resistance value of one thermoelectric element K [8.9 (mΩ)]

[0074] (Comparative Example 1) In Example 1, the thermoelectric conversion module (Unireg type) was changed to the embodiment (configuration C) shown in Figure 3, and in the heat backflow suppression member B, copper with the following size and thermal conductivity was used as a conductive member instead of the thermoelectric conversion element K [N type (BiTe system)]. Otherwise, a thermal simulation was performed in the same manner as in Example 1, and the amount of heat absorbed per unit area was evaluated. Size: A rectangular prism with top and bottom surfaces measuring 1mm vertically x 0.2mm horizontally and a thickness of 1.0mm. λ: Thermal conductivity [398[W / (m·K)]]

[0075] (Comparative Example 2) In Example 1, the conventional π-type thermoelectric conversion module of the embodiment (configuration D) shown in Figure 4 was replaced, and the size of the thermoelectric conversion element K [N-type (BiTe system)] in the heat backflow suppression member B was set as follows. Otherwise, a thermal simulation was performed in the same manner as in Example 1, and the amount of heat absorbed per unit area was evaluated. Size: A rectangular prism with top and bottom surfaces measuring 1mm vertically x 1.0mm horizontally and 1.0mm thick.

[0076] Table 1 shows the simulation results of the heat absorption of the thermoelectric conversion modules obtained in Examples 1-2 (π type) and Comparative Examples 1 (Unireg type)-2 (π type).

[0077] [Table 1]

[0078] Table 1 shows that the π-type thermoelectric conversion modules of Examples 1 and 2, which satisfy the provisions of the present invention, can obtain a higher heat absorption amount compared to the conventional Unireg-type thermoelectric conversion module of Comparative Example 1 and the conventional π-type thermoelectric conversion module of Comparative Example 2, which do not satisfy the provisions of the present invention. [Industrial applicability]

[0079] The π-type thermoelectric conversion module of the present invention has excellent cooling performance with suppressed heat backflow, and is therefore considered applicable to cooling applications in the field of electronic equipment, such as temperature control of CPUs (Central Processing Units) used in smartphones and various computers, as well as image sensors such as CMOS (Complementary Metal Oxide Semiconductor Image Sensors) and CCDs (Charge Coupled Devices), and various sensors such as MEMS (Micro Electro Mechanical Systems) and other light-receiving elements. [Explanation of Symbols]

[0080] 1: π-type thermoelectric conversion module 11: π-type thermoelectric conversion module 21: Thermoelectric conversion module (Unireg type) 31: π-type thermoelectric conversion module (conventional type) 2a: 1st board 2b: 2nd board 3a: 1st electrode 3b: 2nd electrode 4a: Thermoelectric conversion element A 4a1: Thermoelectric conversion element M 4b: Thermal backflow suppression member B 4b1: Thermoelectric conversion element K 4b2: Conductive material

Claims

1. A π-type thermoelectric conversion module is provided, in which a thermoelectric conversion member A including a thermoelectric conversion element M and a thermal backflow suppression member B including a thermoelectric conversion element K are alternately spaced apart between a pair of opposing first substrates having a first electrode and a second substrate having a second electrode, and the thermoelectric conversion member A and the thermal backflow suppression member B are electrically connected in series via the first electrode on the first substrate and the second electrode on the second substrate, The carriers of the thermoelectric conversion element M and the thermoelectric conversion element K are different from each other; one is a hole and the other is an electron. The sum of the surface areas S of the thermoelectric conversion member A that are in contact with the first electrode and the second electrode. Ａ (m ２ ) is the sum of the areas S of the surfaces of the thermal backflow suppression member B that are in contact with the first electrode and the second electrode. Ｂ (m ２ A π-type thermoelectric conversion module, larger than ).

2. The sum of the surface areas S of the thermoelectric conversion member A that are in contact with the first electrode and the second electrode. Ａ The total area S of the surface of the heat backflow suppression member B that is in contact with the first electrode and the second electrode. Ｂ For the sum of and The total area S of the surface side of the thermoelectric conversion member A that joins to the first electrode and the second electrode Ａ The ratio R [= S Ａ / (S Ａ + S Ｂ ) is 0.55 or more and less than 0.

95. The π-type thermoelectric conversion module according to claim 1.

3. The π-type thermoelectric conversion module according to claim 1 or 2, wherein the thermal backflow suppression member B includes the thermoelectric conversion element K and a conductive member, and the thermoelectric conversion element K and the conductive member are stacked in a direction facing the first substrate and the second substrate.

4. The π-type thermoelectric conversion module according to claim 3, wherein the height of the thermoelectric conversion element M in the thickness direction of the thermoelectric conversion member A is higher than the height of the thermoelectric conversion element K in the thickness direction of the heat backflow prevention member B having the conductive member.

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