Thermoelectric conversion module and method for manufacturing thermoelectric conversion module

Abstract

To provide thermoelectric conversion modules which are compact and lightened in weight, and also to provide methods of manufacturing such thermoelectric conversion modules.SOLUTION: There is provided, a photoelectric conversion module 100 in which a metal layer 2 and a conductive polymer layer 1 with a thickness of 40 μm or less are alternately stacked without gaps therebetween; an insulating layer 3 and an electrode layer 4, and an insulating layer 3 and an electrode layer 5 are laminated on both faces of the conductive polymer layer 1, respectively; the electrode layers 4, 5 are located respectively on a first end side of a first face of the conductive polymer layer 1 and a second end side of a second face on an opposing side of the first end side; and the conductive polymer layer 1 and the metal layer 2 are electrically connected via the electrode layer 4 or the electrode layer 5. In addition, provided is a method of manufacturing a thermoelectric conversion module 100, in which electrode layers 4, 5 are formed in a metal layer 2 or a conductive polymer layer 1, and the metal layer 2 and the conductive polymer layer 1 with a thickness of 40 μm or less are laminated alternately without gaps such that the conductive polymer layer 1 and the metal layer 2 are electrically connected via the electrode layer 4 or the electrode layer 5 with an insulating layer 3 interposed therebetween.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to a thermoelectric conversion module and a method for manufacturing the same, and more specifically to a thermoelectric conversion module using a conductive polymer as a thermoelectric material and a method for manufacturing the same. [Background technology]

[0002] Thermoelectric conversion is a technology that directly converts thermal energy into electrical energy and vice versa using a solid-state thermoelectric conversion module. The technology that converts thermal energy into electrical energy is called thermoelectric generation, and is based on the Seebeck effect, which is one of the thermoelectric effects. In thermoelectric generation, the temperature difference between both ends of the thermoelectric conversion module is directly converted into electrical energy.

[0003] Thermoelectric conversion using organic materials has attracted attention as an energy harvesting technology that recovers low-temperature waste heat due to its light weight and simple manufacturing method. Conductive polymers, in particular, have the advantages of being lightweight, flexible, non-toxic, and inexpensive. Furthermore, their manufacturing process offers advantages such as mass production, large-area production, low cost, and low manufacturing energy requirements, making them promising materials for use in electrical and electronic components.

[0004] For example, Patent Documents 1 and 2 below disclose thermoelectric conversion modules in which multiple layers of PEDOT / PSS (poly(3,4-ethylenedioxythiophene) doped with poly(4-styrenesulfonic acid)), a conductive polymer film, insulating films, metal films, etc. are stacked. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Patent Publication No. 2021-27061 [Patent Document 2] Patent No. 6781982 Summary of the Invention [Problem to be solved by the invention]

[0006] In recent years, such thermoelectric conversion modules have been required to be used in a variety of environments, and in response to modern demands, there is a demand for them to be even smaller and lighter in weight as well as have higher performance.

[0007] Therefore, an object of the present invention is to provide a small and lightweight thermoelectric conversion module and to provide a method for manufacturing such a thermoelectric conversion module. [Means for solving the problem]

[0008] In a thermoelectric conversion module, it is preferable that the internal electrical resistance is low. However, if an attempt is made to thin the film thickness of the conductive polymer that constitutes the thermoelectric conversion module in order to produce a small and lightweight thermoelectric conversion module, the electrical resistance of the entire module will increase. However, the present inventors have found that reducing the thickness of the conductive polymer film increases the electrical conductivity, that is, has the effect of suppressing an increase in electrical resistance, and have thus completed the present invention.

[0009] One embodiment of the present invention is a thermoelectric conversion module in which metal layers and conductive polymer layers having a thickness of 40 μm or less are alternately stacked without any gaps, insulating layers and electrode layers are bonded to both sides of the conductive polymer layer, the electrode layers are located at a first end side of a first surface of the conductive polymer layer and at a second end side of a second surface opposite to the first end side, and the conductive polymer layers and the metal layers are electrically connected via the electrode layers.

[0010] Furthermore, one embodiment of the present invention is a method for manufacturing a thermoelectric conversion module by stacking a metal layer, an insulating layer, and a conductive polymer layer, the method comprising the steps of: forming electrode layers on both sides of the metal layer so that, when stacked, the electrode layers are located at a first end side of a first surface of the conductive polymer layer and at a second end side of a second surface opposite the first end side; or forming electrode layers on the first end side of the first surface of the conductive polymer layer and at a second end side of the second surface opposite the first end side; and stacking the conductive polymer layer and the metal layer alternately and without gaps, with the insulating layer sandwiched between them, so that the conductive polymer layer and the metal layer are electrically connected via the electrode layer; and using a conductive polymer layer having a thickness of 40 μm or less as the conductive polymer layer. [Effects of the Invention]

[0011] According to the present invention, it is possible to provide a small and lightweight thermoelectric conversion module and a method for manufacturing such a thermoelectric conversion module. [Brief explanation of the drawings]

[0012] [Figure 1] 1 is a schematic diagram illustrating a configuration of a thermoelectric conversion module according to an embodiment of the present invention. [Figure 2] 1A and 1B are a side view and a plan view showing the configuration of a thermoelectric conversion module according to one embodiment of the present invention. [Figure 3] FIG. 2 is a plan view of each component of the thermoelectric conversion module. [Figure 4] FIG. 1 is an explanatory diagram of a method for measuring electrical conductivity. [Figure 5] FIG. 1 is a diagram showing the relationship between the film thickness and electrical conductivity of a conductive polymer film. [Figure 6] 10A and 10B are a side view and a plan view showing the configuration of another embodiment of a thermoelectric conversion module. [Figure 7] 10 is another example showing the configuration of a thermoelectric conversion module. [Figure 8] 1 is a photograph of a thermoelectric conversion module. [Figure 9]10 is another example showing the configuration of a thermoelectric conversion module. [Figure 10] 1 is a photograph of the fabricated thermoelectric conversion module. [Figure 11] FIG. 4 is a diagram showing the relationship between voltage and output at each temperature of a thermoelectric conversion module. [Figure 12] FIG. 10 is a graph showing the relationship between the thickness of the PEDOT / PSS film and the power density of the module. DETAILED DESCRIPTION OF THE INVENTION

[0013] (Embodiment 1) FIG. 1 shows the configuration of a thermoelectric conversion module according to one embodiment of the present invention. FIG. 2 shows a side view and a plan view of a thermoelectric conversion module according to one embodiment of the present invention. The right view of FIG. 2(A) corresponds to a view of the thermoelectric conversion module of FIG. 1(c) rotated 90 degrees. FIG. 3 shows a plan view of each component of the thermoelectric conversion module. The thermoelectric conversion module 100 of this embodiment has a structure in which conductive polymer layers 1 and metal layers 2 are alternately stacked. The conductive polymer layers 1 are arranged at both ends of the module. The ends of the module may be insulating layers other than conductive polymer layers (electrode layers on one end side) or metal layers. When a numerical range is indicated in this specification, it is intended to include both upper and lower limits.

[0014] The conductive polymer layer 1 is made of a material with thermoelectric properties and has a rectangular surface. The metal layer 2 is made of a metal for electrical connection. Therefore, the thermoelectric conversion module of one embodiment of the present invention has a configuration in which thermoelectric materials (conductive polymer layers) and electrical connection materials (metal layers) are alternately stacked.

[0015] FIG. 1(b) shows details of the region enclosed by the ellipse in FIG. 1(a), i.e., the configuration 10 including the metal layer 2 between the two conductive polymer layers 1. As shown in this figure, an insulating layer 3 and electrode layers 4 and 5 are bonded to both sides of the metal layer 2. In this specification, these may be collectively referred to as bonding layer 12. Electrode layer 4 is located at one end of the front surface of the metal layer 2, and electrode layer 5 is located at the other end of the back surface opposite to the one end.

[0016] In FIG. 1(b), there is a space between the insulating layer 3 and the electrode layers 4 and 5 and the conductive polymer layer 1. However, this space is provided to make the configuration easier to understand. In reality, the bonding layer 12, which is composed of the insulating layer 3 and the electrode layers 4 and 5, is also bonded to the adjacent conductive polymer layer 1. This is common to all embodiments. Therefore, when viewed from the inner surface of the two conductive polymer layers 1 in FIG. 1(b), the electrode layer 4 is located at one end of the surface of one conductive polymer layer 1, and the electrode layer 5 is located at the other end of the surface of the other conductive polymer layer 1, opposite to the one end. As a result, the conductive polymer layer 1 and the metal layer 2 are electrically connected in series via the electrode layers 4 and 5.

[0017] 1(c) is an image diagram showing how a thermoelectric conversion module 100 in which multiple configurations of (b) are joined generates power through thermoelectric conversion. In this thermoelectric conversion module 100, conductive polymer layers 1 are arranged on both ends (outsides) of the thermoelectric conversion module 100, and bonding layers 12 and conductive polymer layers 1 are arranged alternately between them.

[0018] As mentioned above, the overall electrical resistance of such a thermoelectric conversion module increases as the thickness of the conductive polymer layer decreases. To increase the output power of a conventional thermoelectric conversion module with the same area, it is possible to increase the voltage by increasing the number of thin conductive polymer layers per unit area. However, this would increase the number of layers connected in series, further increasing the overall electrical resistance. Because conductive polymers have significantly higher electrical resistance than metal components, a thicker conductive polymer layer is preferable. On the other hand, the insulating layer, which is an insulating material, has almost no effect on the characteristics of such modules. Therefore, considering the need to reduce the overall thickness of the module, it is preferable to make it as thin as possible. Furthermore, because the electrical resistance of metal layers (metal components) is significantly lower than that of conductive polymers, even when they are thin, they are preferably as thin as possible in terms of thermal resistance.

[0019] Therefore, in conventional thermoelectric conversion modules, the conductive polymer film thickness is limited to a certain thickness (for example, when the temperature difference is 50 K and the power density is several tens of μW / cm) to avoid an increase in electrical resistance. 2 A thermoelectric conversion module of this size requires a thickness of generally 50 μm or more, and thinner thicknesses were not anticipated. On the other hand, for example, a PEDOT / PSS film has a structure in which short conductive PEDOT molecules are dispersed and attached to both sides or within the layers of a layered PSS film (insulating film) that serves as a framework. Electrical conductivity is achieved by connecting adjacent PEDOT molecules. It was thought that thinning or compressing the PEDOT / PSS film would facilitate the connection of adjacent PEDOT molecules, thereby improving electrical conductivity. Since electrical conductivity is the reciprocal of resistivity, an increase in electrical conductivity suppresses an increase in electrical resistance. Therefore, samples of conductive polymer films with different thicknesses were prepared and the electrical conductivity of each sample was measured. The measurement conditions were as follows:

[0020] The following amounts of PEDOT / PSS (containing 3% by weight of ethylene glycol) were placed in a container with a base area of ​​194 mm x 104 mm (ABS non-charged square case type 10, manufactured by AS ONE Corporation) according to the film thickness, and the water was evaporated (40°C, 24 hours) to produce samples A to E. Sample A had a thickness of 61.8 μm (liquid volume: 91 mL; the same applies below), Sample B had a thickness of 40.3 μm (liquid volume: 72.8 mL), Sample C had a thickness of 30.9 μm (liquid volume: 54.6 mL), Sample D had a thickness of 18.9 μm (liquid volume: 36.4 mL), and Sample E had a thickness of 5.8 μm (liquid volume: 18.2 mL). Each sample was punched out to 22 mm × 22 mm and then cut (approximately 20 mm × 5 mm) to prepare measurement specimens. Samples C and E were compressed using a heat press (AH-1T, manufactured by AS ONE Corporation) at 50 °C and 50 kgf for 30 minutes. The thickness of Sample C was 26.0 μm, and that of Sample E was 4.8 μm.

[0021] Figure 4 shows an explanatory diagram of the electrical conductivity measurement method. Four wires are connected to the sample 9. The outer two wires 8 serve as current input terminals, and the inner two wires 7 serve as voltage measurement terminals. The sample 9 is placed on the four wires, and a cover (not shown) is placed over the sample 9 to hold it in contact. A predetermined current (e.g., 5 mA) is passed between the wires 8 and 8, and the electrical conductivity (the reciprocal of electrical resistance) is evaluated from the voltage measured between the wires 7 and 7. Note that the electrical conductivity δ is expressed as δ = (I·l) / (V·w·t), where t is the thickness of the rectangular PEDOT / PSS film, l (the length between the wires 7) × w (the width), I is the current, and V is the measured voltage. Figure 5 shows the results. In Figure 5, open circles represent the case without compression, and filled circles represent the case with compression. Measurements were performed using a voltage-current generator (Yokogawa Electric Corporation, GS820) to apply a current (5 mA) and measure the voltage.

[0022] Electrical conductivity is a per-unit value inherent to the material and generally does not change with film thickness. On the other hand, electrical resistance increases as the thickness of the conductive polymer film decreases and the number of conductive polymer films increases. On the other hand, electromotive force increases as the number of conductive polymer films increases, since the number of series also increases. Figure 5 shows that electrical conductivity, which should be an inherent value per unit of material, increases with thinner film thickness in the case of conductive polymers. An increase in electrical conductivity suppresses the increase in electrical resistance, meaning that thinning the conductive polymer film does not increase the electrical resistance of the entire module. Figure 5 also shows that electrical conductivity increases further when the conductive polymer is compressed.

[0023] The reason for the increased electrical conductivity of these conductive polymers due to thinning or compression is thought to be that PEDOT molecules become more easily bonded to each other, as mentioned above. For example, adding ethylene glycol (EG) during the deposition of PEDOT / PSS films helps the PSS film and PEDOT molecules align neatly (increasing anisotropy). Similarly, thinning or compressing conductive polymer films increases the anisotropy of the organic film structure, which is thought to contribute greatly to improved electrical conductivity. This also applies to conductive polymers such as polyaniline and carbon nanotubes (CNTs) in addition to PEDOT / PSS films. Each component is explained in detail below.

[0024] (Conductive polymer layer) The conductive polymer layer 1 is made of, for example, a PEDOT / PSS film. Polyaniline, carbon nanotubes (CNTs), etc. may also be used. PEDOT / PSS is a charge transfer complex composed of poly(3,4-ethylenedioxythiophen) (PEDOT) and poly(styrenesulfonate) (PSS). PEDOT / PSS has p-type thermoelectric properties. In PEDOT / PSS, PSS, which acts as a dopant, supplies carriers to PEDOT, resulting in good conductivity of PEDOT. Furthermore, as mentioned above, adding ethylene glycol (EG) during the deposition of the PEDOT / PSS film aligns the crystal orientation, improving the electrical conductivity of the deposited PEDOT / PSS film.

[0025] Specifically, when the conductive polymer layer 1 is a PEDOT / PSS film, it can be fabricated by the following method. A suitable amount of EG (several percent) is mixed with the raw material reagent, placed in a mold, and heated (e.g., at 40°C) on a heater for a predetermined time (e.g., 24 hours) to evaporate the water. The film thickness can be adjusted by controlling the amount of EG added based on the mold's base area. To achieve high performance and compactness in the thermoelectric conversion module, the film thickness should be 40 μm or less. While there is no lower limit to the film thickness as long as it is feasible and maintains strength, a thin film of 5-30 μm or 10-30 μm is preferable. This level of film thickness meets the demand for compact thermoelectric conversion modules, facilitates fabrication of the thermoelectric conversion module, and ensures sufficient strength. The film thickness can also be adjusted to the above range by compressing the film.

[0026] (metal layer) The metal layer 2 is made of, for example, a nickel (Ni) film. Other metals are not particularly limited, and examples include aluminum, iron, copper, etc. Alloys are also acceptable, and examples of metal materials with large thermoelectric power include copper-nickel alloys and aluminum-nickel alloys. Since most metals have n-type thermoelectric properties, it is desirable for the metal layer 2 to be a metal with strong n-type thermoelectric properties, such as Ni, in addition to providing electrical connections for module construction. The metal layer 2 may be rectangular like the conductive polymer layer 1, but preferably has an I-shaped surface (Figure 3). The reason for making the metal layer 2 I-shaped is that, since the metal layer 2 has the best thermal conductivity, it is necessary to keep the contact electrical resistance between the metal layer 2 and the conductive polymer layer 1 low while simultaneously keeping thermal conduction low to increase the temperature difference ΔT in the left-right direction (Figure 2). The film thickness should be 5-10 μm to minimize thermal conduction.

[0027] (insulating layer and electrode layer) For example, an insulating polymer can be used as the insulating layer 3. For example, an insulating polyimide film can be used as the insulating polymer. Other examples include fluororesin film, acetate film, PET film, and epoxy film, but polyimide film is preferable because it is thin, strong, and heat-resistant. The electrode layers 4 and 5 can be made of gold (Au), platinum (Pt), silver (Ag), graphite (C), or copper (Cu). More preferably, Au or Pt, which have low contact resistance and are resistant to oxidation, can be used for the electrode layers 4 and 5. The thinner the insulating layer 3, the better, with a thickness of 5-10 μm being preferred. For example, insulating polyimide films with a thickness of 5 μm are commercially available and easy to obtain. The electrode layers 4 and 5 may be made to any thickness that ensures conductivity. However, in the case of gold vapor deposition, a thickness of approximately 20 nm is recommended to ensure uniform surface coverage.

[0028] (Method of manufacturing thermoelectric conversion module) An outline of a method for manufacturing the thermoelectric conversion module 100 according to one embodiment of the present invention shown in Fig. 1-2 will be described below. In the following method, an example will be described in which a PEDOT / PSS film is used as the conductive polymer layer 1, an I-type Ni film is used as the metal layer 2, an insulating polyimide film is used as the insulating layer 3, and gold (Au) is used as the electrode layers 4 and 5. (a) Prepare a PEDOT / PSS film of a predetermined size, an insulating polyimide film (shortened in length by the size of the Au), and an I-type Ni film. The thickness of the PEDOT / PSS film can be adjusted using the method described above. That is, the film thickness can be adjusted during film formation, or by compressing the film after formation. (b) Au is applied to predetermined locations (edges) on both the front and back of the I-type Ni film to reduce contact resistance (this can be done by vacuum deposition or by applying a paste or the like). (c) A predetermined number of the components prepared in (a) and (b) are stacked and placed into the recesses of a dedicated jig (not shown) containing a metal plate with a recess and a metal plate with a protrusion. The stacking order is as shown in Figure 2. The polyimide films are stacked alternately so that the PEDOT / PSS and Ni come into contact via the Au. (d) The two metal plates of the special jig are aligned so that the convex parts are inserted into the concave parts, and the laminate is heated and pressurized to set the shape (50°C, 50 kgf, approximately 60 minutes). (e) The two metal plates of the dedicated jig are separated, and the laminate is removed from the recess. Conductive wires are connected to the edges of the upper and lower PEDOT / PSS films using a conductive adhesive or by crimping, and power is extracted. In this specification, the laminate is also referred to as a thermoelectric conversion module. In step (b), Au was applied to the Ni film, but Au may also be applied to both sides of the PEDOT / PSS film.

[0029] In the example of thermoelectric conversion module 100 shown in FIG. 2, both ends of the thermoelectric conversion module are made of conductive polymer layers 1, so the conductive polymer layer 1 is first placed, and then the required number of insulating layers 3, metal layers 2, insulating layers 3, and conductive polymer layers 1 are laminated on top of that in this order. On the other hand, if the arrangement of components differs from that of thermoelectric conversion module 100 shown in FIG. 2, such as when both ends of the thermoelectric conversion module do not have conductive polymer layers 1 or when only one end of the thermoelectric conversion module has conductive polymer layers 1, the order in which these components are laminated can be changed. Although not shown in the thermoelectric conversion module 100 shown in FIG. 2, conductive wires can be connected to the edges of the upper and lower conductive polymer layers 1 as shown in FIG. 1 to serve as a power source for the device.

[0030] As shown in Figure 1, the thermoelectric conversion module 100 is heated by a heat source on its lower side. Current generated within the module by the Seebeck effect flows sequentially as indicated by arrow 6, is output to an external circuit, and heat is dissipated from the upper side. The upper side of the module is not specifically cooled, allowing heat to be dissipated naturally. Within the module, current generated within the conductive polymer layer 1 flows upward through the connecting electrode layer 4 to the adjacent metal layer 2. Current then flows downward within the metal layer 2 and then through the connecting electrode layer 5 to the adjacent conductive polymer layer 1. A similar current flow 6 is repeated, enabling the module to be used as a power source for Bluetooth signals, various sensors used in mobile devices such as automobiles, or various IoT applications, such as health monitors and location information transmitters for humans and animals. Heat sources include factory waste heat, equipment waste heat, exhaust pipes, drainage pipes, household waste heat, the human body, animals, geothermal heat, and solar heat.

[0031] (Embodiment 2) FIG. 6 is a side view and a plan view showing the configuration of another embodiment of a thermoelectric conversion module. Although not shown in FIG. 6, conductive wires can be connected to the edges of the upper and lower conductive polymer layers 1 using a conductive adhesive (not shown) or the like to serve as a power source for the device. This thermoelectric conversion module 101 is formed by stacking conductive polymer layers 1, insulating layers 3, metal layers 2, and the like in a stepped manner, offset along a line connecting one end of the conductive polymer layer 1 where the electrode layers 4 and 5 are located to the other end. First, the conductive polymer layer 1 is placed, and then a required number of units 11 each consisting of an insulating layer 3, a metal layer 2, an insulating layer 3, and a conductive polymer layer 1 are stacked in a stepped manner on top of it. This reduces the height and creates a compact thermoelectric conversion module. Since the entire rectangular surface of the conductive polymer layer 1 is conductive, electrical loss can be reduced by stacking the members placed on the conductive polymer layer 1 in a stepped manner with offsetting.

[0032] As in the first embodiment, this embodiment also includes various structures, such as a case where both ends of the thermoelectric conversion module are not provided with the conductive polymer layer 1, or a case where only one end of the thermoelectric conversion module is provided with the conductive polymer layer 1. As an example of stacking in steps, each layer, a plurality of layers, or a combination of these may be stacked in steps. Furthermore, units each composed of a plurality of layers and single layers may be alternately, regularly, or randomly stacked in a stepped manner, as long as these layers are stacked in a stepped manner overall.

[0033] In the illustrated example, a single unit is formed by laminating an insulating layer 3 (electrode layer 4 or electrode layer 5), a metal layer 2, an insulating layer 3, and a conductive polymer layer 1, but there are various other combinations of layers that form a unit, such as a single unit formed by laminating an insulating layer 3, a metal layer 2, and an insulating layer 3 (bonding layer 12) or a single unit formed by laminating an insulating layer 3 and a conductive polymer layer 1. For example, when electrode layers 4 and 5 are vapor-deposited on metal layer 2, it is preferable to form bonding layer 12 as a single unit, as this facilitates fabrication.

[0034] Other examples of thermoelectric conversion modules are shown in Fig. 7. Fig. 7(A) shows an example in which units 13 and single-layer metal layers 2 are alternately stacked, and Fig. 7(B) shows an example in which units 15 are stacked. Such a unit structure is easy to fabricate and is preferable when the electrode layers 4 and 5 are vapor-deposited on the conductive polymer layer 1. Furthermore, compared to when each layer (each component) is shifted slightly, the flexibility of the entire module is not affected even if only a few layers (several sheets) are stacked, and from the viewpoint of workability, it is preferable to shift each unit as shown in Figures 6 and 7. In either case, it is sufficient that the conductive polymer layer 1 and the metal layer 2 are electrically connected in series via the electrode layers 4 and 5. Also in this embodiment, a current flows in the direction of arrow 6 due to the temperature difference ΔT (FIG. 6) between the ends on the electrode layer 4 and 5 side, and thus, similar to the first embodiment, it can be used as various power sources.

[0035] According to this embodiment, the layers constituting the thermoelectric conversion module are stacked in a stepped manner, resulting in a longer planar length, enabling power generation from a heat source with a wider surface area. Furthermore, the thin thermoelectric conversion module can be adapted to curved surfaces. Figure 8 shows a photograph of a thermoelectric conversion module stacked in a stepped manner, as shown in Figure 6. In particular, when flexible materials such as thin films are used as components of the thermoelectric conversion module, they can easily fit curved surfaces and generate power efficiently. Note that flexibility refers to the property of easily deforming when external force is applied, for example, with a finger. By using flexible films such as a PEDOT / PSS film on the order of 10 microns as the conductive polymer layer 1, an insulating film on the order of several microns to several 10 microns as the insulating layer 3, or a metal film on the order of several microns to several 10 microns as the metal layer 2, the thermoelectric conversion module can be wrapped around a person's arm, a pipe, or the like.

[0036] The manufacturing method of the thermoelectric conversion module of this embodiment is generally the same as that of the thermoelectric conversion module 100 of embodiment 1, except that the units 11 are stacked on the conductive polymer layer 1 with a staggered offset of a length W1. Increasing this length W1 reduces the stack height and increases flexibility, but shortens the length W2 required to create an effective temperature difference (e.g., approximately 5 K), thereby reducing the available temperature difference ΔT and resulting in reduced output. Therefore, the offset length W1 should be set to a length sufficient to maintain an effective temperature difference sufficient to obtain a certain level of output. The offset lengths of the individual layers may be different lengths. While FIG. 6B shows a plan view of the thermoelectric conversion module 101, the stacking is not limited to a straight horizontal offset, and the modules may also be stacked with a diagonal offset, as shown in FIG. 9. This offset facilitates spiral wrapping, particularly around a human arm or a pipe. Needless to say, flexible materials may be used as constituent materials of the thermoelectric conversion module 100 of the first embodiment. [Example]

[0037] An example of embodiment 1 (FIG. 2) is shown. A PEDOT / PSS film was formed by mixing a few percent of EG (Fujifilm Wako Chemical Co., Ltd.) with the raw material reagent (Heraeus Clevios-PH1000). The mixture was placed in a mold (AS ONE Corporation, ABS non-charged rectangular case-10 type) and heated on a heater at 40°C for 24 hours to evaporate the water. The film thickness was adjusted to 20 μm by controlling the amount of material added based on the bottom area of ​​the mold. Furthermore, Ni foil (Nilaco Corporation, NI-313133, 5 μm (thickness) × 100 × 300 mm) was used as the I-type Ni film. Au (Tanaka Kikinzoku Kogyo Co., Ltd., Au particles, sapling-shaped, purity 99.99% or higher) was deposited on both the front and back edges of the I-type Ni film using a vapor deposition system (Vacuum Device Co., Ltd., VE-2012) at a vacuum level of 5 × 10°C. -3 The deposition was carried out at 100 Pa for 5 minutes. The current value at that time was approximately 12-14 A. The deposited Au film thickness was approximately 20 nm. Furthermore, a roll of film (Toray Industries, Inc., Kapton (registered trademark), 20EN, 5 μm (thickness) × 508 mm × 20 m) was used as the insulating polyimide film. The PEDOT / PSS film, Ni foil, and insulating polyimide film were formed into a predetermined size using a die-cutting punch. The PEDOT / PSS film and Ni foil were formed into a 22 mm × 22 mm rectangle, and the Ni foil was cut into an I-shape.

[0038] These components were stacked in the same shape as shown in Figure 2 (50 PEDOT / PSS films, 49 Ni foils, and 98 insulating polyimide films), and the stack was heated and pressurized (50°C, 50 kgf, 60 minutes) using a dedicated metal jig to adjust the shape, and the stack was removed from the dedicated jig to produce a thermoelectric conversion module 100. The thermoelectric conversion module 100 measured 0.175 cm (thickness) x 2.2 cm x 2.2 cm, weighed 1.27 g, and had a resistance of 66 Ω (1.32 Ω per sheet) at room temperature and 68 Ω at 100°C.

[0039] FIG. 10 shows a photograph of the fabricated thermoelectric conversion module. FIG. 11 shows the relationship between voltage and output at each temperature (heat source) of the thermoelectric conversion module 100 fabricated according to this example. A hot plate was used as the heat source to adjust the temperature at one end of the thermoelectric conversion module 100, and the other end was allowed to naturally dissipate heat. Output was measured by directly contacting the PEDOT / PSS films at both ends with external conductive wires connected to a measuring device (Keithley Instruments, Inc., SourceMeter (registered trademark) 2400). The measurement time was 1 minute at each temperature.

[0040] From the results in Figure 11, it can be seen that an output of 30 μW was obtained when placed on a 100°C heat source (the temperature difference with natural heat dissipation is 46 K). When placed on a 50°C heat source, the temperature difference with natural heat dissipation was 19 K. With this level of output (30 μW), it can be used as a temperature and humidity sensor via various boost circuits, and it is also possible to wirelessly transmit temperature information to a mobile device. The open circuit voltage also reaches 90 mV. The output (30 μW) can be calculated by dividing the output (30 μW) by the heat source contact area (0.175 (thickness) x 2.2 cm (width) = 0.385 cm 2 ), the power density is 78 μW / cm 2 This is what happened.

[0041] As a comparative example, a thermoelectric conversion module was fabricated using a 50 μm-thick PEDOT / PSS film. The raw material reagents, I-type Ni film material, insulating polyimide film, and electrode layer used were the same as in Example 1. The thickness of the PEDOT / PSS film was adjusted to 50 μm by controlling the amount of liquid added based on the base area of ​​the mold during film formation. These components were then stacked as shown in Figure 2 (300 PEDOT / PSS films, 299 Ni foils, and 598 insulating polyimide films). The stack was heated and pressurized (50°C, 50 kgf, 60 minutes) using a dedicated jig to shape it. The stack was then removed from the dedicated jig to fabricate a comparative thermoelectric conversion module. The dimensions of the comparative thermoelectric conversion module were 2.0 cm (thickness) × 2.2 cm × 2.2 cm, and the weight was 5.0 g. The overall module resistance was 186 Ω (0.62 Ω per film) at room temperature and 219 Ω at 100°C.

[0042] As in Example 1, the temperature of one end of the thermoelectric conversion module was adjusted to 100°C using a hot plate as a heat source, and the other end was allowed to naturally dissipate heat (temperature difference: 50K, or 21K when the temperature of one end was 50°C). The output was measured, and the output density was 40 μW / cm 2 Therefore, when the thickness of the PEDOT / PSS film is 20 μm (the output density is 78 μW / cm 2 ) resulted in approximately double the power density compared to when the thickness was 50 μm. This means that even if the thickness of the thermoelectric conversion module was halved, the same power output as that of a conventional module could be obtained.

[0043] 12 shows the relationship between the thickness of the PEDOT / PSS film and the output density in Example 1 (film thickness 20 μm) and Comparative Example (film thickness 50 μm) with black circles. In addition to Example 1 and Comparative Example, calculated values ​​for other film thicknesses (film thicknesses 10 μm, 30 μm, and 40 μm) are also shown with white circles. As described above, the power density (black circles) for Example 1 and the Comparative Example was measured using a measuring instrument (Keithley Instruments, Inc., SourceMeter® 2400). The calculated values ​​(white circles) were calculated using the following method. The high-temperature side was set to 100°C, and the low-temperature side was set to room temperature (25°C, natural cooling). The temperature difference (ΔT) was calculated from the thermal resistance of the materials of the three components (PEDOT / PSS, nickel, polyimide), and the thermoelectric power was calculated from the temperature difference. The output power was then calculated from the voltage (thermoelectric power) and electrical resistance (calculated from the electrical conductivity and size of each component; for conductive polymers, the electrical conductivity was set based on the film thickness), and the power density was calculated by dividing the calculated power by the contact area with the heat source.

[0044] As can be seen from Figure 12, the thinner the conductive polymer film, the higher the output density. This indicates that the thinner the conductive polymer film, the higher the electrical conductivity. When the film thickness is 40 μm or less, the output density is 50 μW / cm 2 That is, the output density is 1.25 times or more when the film thickness is 50 μm, and 60 μW / cm when the film thickness is 30 μm or less.2 Above 20μm, 70μW / cm 2 In particular, when the film thickness is 30 μm or less, the power density is about twice as high as that of 50 μm, and when the film thickness is 20 μm or less, the power density is about twice as high. Therefore, the thermoelectric conversion module of this embodiment can achieve both high performance and compact size.

[0045] On the other hand, considering that the thinning and compression of the conductive polymer film limits the ease with which PEDOT molecules can connect structurally, the thinner the film, the greater the electrical conductivity does not necessarily become. Also, considering that thinning the conductive polymer film can affect the metal layer, which has good thermal conductivity, making it difficult to create a usable temperature difference, a lower limit of about 5 μm is preferable. Furthermore, considering ease of fabrication and strength, a lower limit of about 10 μm is even more preferable. Therefore, from these results, it can be said that a PEDOT / PSS film having a thickness of 5-30 μm is preferable, and a thin film having a thickness of 10-30 μm is more preferable. As described above, the thermoelectric conversion module of this embodiment can be made even smaller and lighter in weight as well as offering higher performance. [Industrial Applicability]

[0046] The thermoelectric conversion module according to the present invention can be used as a power source for various IoT applications, such as a power source for Bluetooth signals, a power source for various sensors used in mobile objects such as automobiles, or a power source for health monitors and location information transmitters for humans and animals. [Explanation of symbols]

[0047] 1 Conductive polymer layer 2 metal layers 3. Insulation layer 4, 5 electrode layer 6 Arrow indicating the direction of current 7, 8 wire 9 Samples 11, 13, 15 units 12 Bonding layer 100, 101 Thermoelectric conversion module

Claims

1. Metal layers and conductive polymer layers having a thickness of 40 μm or less are alternately laminated without any gaps, an insulating layer and an electrode layer are bonded to both surfaces of the conductive polymer layer; the electrode layer is located on a first end side of a first surface of the conductive polymer layer and on a second end side of a second surface opposite to the first end side, and the conductive polymer layer and the metal layer are electrically connected in a stacking direction via the electrode layer, the conductive polymer layer includes a PEDOT / PSS film; the metal layer, the conductive polymer layer, the insulating layer, and the electrode layer are laminated without any gaps and are laminated in a stepped manner overall; Thermoelectric conversion module.

2. 2. The thermoelectric conversion module according to claim 1, wherein the conductive polymer layer has a thickness of 5 to 30 μm.

3. The thermoelectric conversion module according to claim 1 or 2, wherein the conductive polymer layer is compressed.

4. The thermoelectric conversion module according to claim 1 , wherein the metal layer, the conductive polymer layer, and the insulating layer are flexible.

5. A method for manufacturing a thermoelectric conversion module, comprising laminating a metal layer, an insulating layer, and a conductive polymer layer to manufacture a thermoelectric conversion module, the method comprising: a step of forming electrode layers on both surfaces of the metal layer so as to be located at a first end side of the first surface of the conductive polymer layer and at a second end side of the second surface opposite to the first end side when laminated, or a step of forming electrode layers on the first end side of the first surface of the conductive polymer layer and at a second end side of the second surface opposite to the first end side; and stacking the conductive polymer layers and the metal layers alternately and without gaps, with the insulating layer sandwiched therebetween, so that the conductive polymer layers and the metal layers are electrically connected in a stacking direction via the electrode layer, As the conductive polymer layer, a PEDOT / PSS film having a thickness of 40 μm or less is used, In the step of stacking, the metal layer, the insulating layer, and the conductive polymer layer are stacked without any gaps and so as to form a stepped structure overall.

6. 6. The method for manufacturing a thermoelectric conversion module according to claim 5, wherein a PEDOT / PSS film having a thickness of 5 to 30 μm is used as the conductive polymer layer.

7. The method for manufacturing a thermoelectric conversion module according to claim 5 or 6, wherein a PEDOT / PSS film compressed to the thickness is used as the conductive polymer layer.

8. The method for manufacturing a thermoelectric conversion module according to claim 5 , wherein flexible materials are used as the metal layer, the insulating layer, and the conductive polymer layer.

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