Thermoelectric conversion film and manufacturing method thereof, thermoelectric conversion module, and thermoelectric conversion material

Abstract

To provide a thermoelectric conversion film having excellent thermoelectric conversion properties and excellent mechanical properties, and a manufacturing method thereof.SOLUTION: A thermoelectric conversion film includes a complex containing a poly(3,4-ethylenedioxythiophene) cation, and a polystyrene sulfonate anion and a tetracyanoborate anion, a peak area derived from the poly(3,4-ethylenedioxythiophene) cation is A(PEDOT) and a peak area derived from the polystyrene sulfonate anion is A(PSS), measured by X-ray photoelectron spectroscopy, A(PEDOT) and A(PSS) satisfy the following formula (1). 0.50≤A(PEDOT) / A(PSS)≤0.90 (1).SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a thermoelectric conversion film and a method for producing the same, a thermoelectric conversion module, and a thermoelectric conversion material. [Background technology]

[0002] Thermoelectric conversion is a technology that uses the Seebeck effect to directly convert heat into electricity, and is attracting attention as an energy recovery technology that converts waste heat generated when using fossil fuels into electricity.

[0003] Conventionally, inorganic materials have been mainly studied as thermoelectric conversion materials. However, due to problems such as difficulty in installation on curved surfaces, the use of rare or toxic elements, and unsuitability for installation over large areas, organic materials have attracted attention as thermoelectric conversion materials, and thermoelectric conversion modules equipped with thermoelectric conversion films made of organic materials are being studied (e.g., Patent Documents 1 to 3). [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2003-332638 [Patent Document 2] Japanese Patent Application Laid-Open No. 2000-323758 [Patent Document 3] Japanese Patent Application Laid-Open No. 2017-041540 Summary of the Invention [Problem to be solved by the invention]

[0005] However, conventional thermoelectric conversion films made of organic materials are insufficient in terms of thermoelectric conversion properties and mechanical properties, and there is still room for improvement.

[0006] Therefore, a main object of the present invention is to provide a thermoelectric conversion film that is excellent in both thermoelectric conversion characteristics and mechanical properties, and a method for producing the same. [Means for solving the problem]

[0007] The present inventors have conducted extensive research to solve the above-mentioned problems and have found that a thermoelectric conversion film containing a composite obtained by substituting a portion of polystyrene sulfonate anions with tetracyanoborate anions in a conductive polymer made of poly(3,4-ethylenedioxythiophene) and polystyrene sulfonic acid has excellent thermoelectric conversion properties as well as excellent mechanical properties, which led to the completion of the present invention.

[0008] That is, the present invention provides a method for producing a thermoelectric conversion film according to any one of [1] to [4], a thermoelectric conversion film according to [5], a thermoelectric conversion module according to [6], and a thermoelectric conversion material according to [7]. [1] A method for producing a thermoelectric conversion film, comprising the steps of: mixing a first dispersion containing a conductive polymer made of poly(3,4-ethylenedioxythiophene) and polystyrenesulfonic acid and a first solvent with a second dispersion containing 1-ethyl-3-methylimidazolium tetracyanoborate and a second solvent to obtain a mixed solution; applying the mixed solution to a substrate and removing the first solvent and the second solvent to form a coating film; and washing the coating film with the second solvent to obtain a thermoelectric conversion film containing a complex containing poly(3,4-ethylenedioxythiophene) cations, polystyrenesulfonate anions, and tetracyanoborate anions, wherein, in the thermoelectric conversion film, when measured by X-ray photoelectron spectroscopy, the peak area derived from the poly(3,4-ethylenedioxythiophene) cations is defined as A(PEDOT), and the peak area derived from the polystyrenesulfonate anions is defined as A(PSS), the values ​​of A(PEDOT) and A(PSS) satisfy the following formula (1): 0.50≦A(PEDOT) / A(PSS)≦0.90 (1) [2] The method for producing a thermoelectric conversion film according to [1], wherein the amount of 1-ethyl-3-methylimidazolium tetracyanoborate added is 0.5 to 5.5 μmol per 1 mg of the conductive polymer. [3] The method for producing a thermoelectric conversion film according to [1] or [2], wherein the thermoelectric conversion film has a thickness of 0.5 μm or more. [4] The method for producing a thermoelectric conversion film according to any one of [1] to [3], wherein the thermoelectric conversion film has an electrical conductivity of 500 S / cm or more. [5] A thermoelectric conversion film containing a complex containing a poly(3,4-ethylenedioxythiophene) cation, a polystyrenesulfonate anion, and a tetracyanoborate anion, wherein, when measured by X-ray photoelectron spectroscopy, the peak area derived from the poly(3,4-ethylenedioxythiophene) cation is defined as A(PEDOT), and the peak area derived from the polystyrenesulfonate anion is defined as A(PSS), A(PEDOT) and A(PSS) satisfy the following formula (1): 0.50≦A(PEDOT) / A(PSS)≦0.90 (1) [6] A thermoelectric conversion module comprising the thermoelectric conversion film according to [5]. [7] A thermoelectric conversion material containing a complex containing a poly(3,4-ethylenedioxythiophene) cation, a polystyrenesulfonate anion, and a tetracyanoborate anion, wherein, when measured by X-ray photoelectron spectroscopy, the peak area derived from the poly(3,4-ethylenedioxythiophene) cation is defined as A(PEDOT), and the peak area derived from the polystyrenesulfonate anion is defined as A(PSS), A(PEDOT) and A(PSS) satisfy the following formula (1): 0.50≦A(PEDOT) / A(PSS)≦0.90 (1) [Effects of the Invention]

[0009] According to the present invention, a thermoelectric conversion film having excellent thermoelectric conversion characteristics and excellent mechanical properties and a method for producing the same are provided. Also, according to the present invention, a thermoelectric conversion module using the thermoelectric conversion film is provided. Furthermore, according to the present invention, a thermoelectric conversion material capable of forming a thermoelectric conversion film having excellent thermoelectric conversion characteristics and mechanical properties is provided. DETAILED DESCRIPTION OF THE INVENTION

[0010] Hereinafter, embodiments of the present invention will be described, but the present invention is not limited to the following embodiments.

[0011] [Thermoelectric conversion film and its manufacturing method] The thermoelectric conversion film of one embodiment contains a complex (hereinafter sometimes referred to as "PEDOT / (PSS+TCB)") containing poly(3,4-ethylenedioxythiophene) cation (hereinafter sometimes referred to as "PEDOT"), polystyrene sulfonate anion (hereinafter sometimes referred to as "PSS"), and tetracyanoborate anion (hereinafter sometimes referred to as "TCB"), and when the peak area derived from PEDOT measured by X-ray photoelectron spectroscopy is A(PEDOT) and the peak area derived from PSS is A(PSS), A(PEDOT) and A(PSS) satisfy the following formula (1): 0.50≦A(PEDOT) / A(PSS)≦0.90 (1)

[0012] PEDOT / (PSS+TCB) can be said to be a polyion complex composed of PEDOT, PSS, and TCB.

[0013] The thermoelectric conversion film of this embodiment can be produced by a method including, for example, a step of mixing a first dispersion containing a conductive polymer made of poly(3,4-ethylenedioxythiophene) and polystyrene sulfonic acid (the conductive polymer can be referred to as a polyion complex composed of poly(3,4-ethylenedioxythiophene) cation (PEDOT) and polystyrene sulfonate anion (PSS); hereinafter, the conductive polymer may be referred to as "PEDOT / PSS") and a first solvent with a second dispersion containing 1-ethyl-3-methylimidazolium tetracyanoborate (hereinafter, sometimes referred to as "EMIM / TCB") and a second solvent to obtain a mixed liquid (hereinafter, sometimes referred to as the "first step"); a step of applying the mixed liquid to a substrate and removing the first solvent and the second solvent to form a coating film (hereinafter, sometimes referred to as the "second step"); and a step of washing the coating film with the second solvent to obtain a thermoelectric conversion film containing PEDOT / (PSS+TCB) (hereinafter, sometimes referred to as the "third step").

[0014] (First step) This step involves mixing a first dispersion containing PEDOT / PSS and a first solvent with a second dispersion containing EMIM / TCB and a second solvent to obtain a mixed solution. PEDOT / PSS can also be called PEDOT doped with PSS.

[0015] In PEDOT / PSS, when the peak area derived from PEDOT is A0(PEDOT) and the peak area derived from PSS is A0(PSS) as measured by X-ray photoelectron spectroscopy, A0(PEDOT) / A0(PSS) may be, for example, less than 0.50, preferably 0.45 or less. A0(PEDOT) / A0(PSS) may be, for example, 0.10 or more, preferably 0.20 or more, more preferably 0.30 or more.

[0016] In this specification, "A(PEDOT) / A(PSS)" and "A(PEDOT) / A(PSS)" described below can be determined, for example, by measuring the photoelectron spectrum (S2p spectrum) of sulfur atoms of PEDOT / PSS or a thermoelectric conversion film (thermoelectric conversion material) using an X-ray photoelectron spectrometer, separating the peaks of components derived from PEDOT and components derived from PSS, and calculating the area of ​​each peak.

[0017] The content of PEDOT / PSS in the first dispersion is not particularly limited. The content of PEDOT / PSS may be, for example, 0.1% by mass or more, preferably 0.5% by mass or more, based on the total amount of the first dispersion. The content of PEDOT / PSS may be, for example, 5% by mass or less, preferably 2.5% by mass or less, based on the total amount of the first dispersion. When the content of PEDOT / PSS is within this range, the dispersibility of PEDOT / PSS tends to be improved.

[0018] The first solvent is not particularly limited as long as it is a solvent capable of dispersing or dissolving PEDOT / PSS. The first solvent may be, for example, a polar solvent or an aqueous solvent. The aqueous solvent means water or a mixed solvent of water and an organic solvent. The first solvent may be a protic solvent or an aprotic solvent, but is preferably a protic solvent.

[0019] When the first solvent is a polar solvent, the relative dielectric constant (20°C) of the polar solvent may be, for example, 10 or more, preferably 15 or more, and more preferably 20 or more. For example, the relative dielectric constant (20°C) of water is 80. By using such a polar solvent as the first solvent, the dispersibility of PEDOT / PSS improves, and a thermoelectric conversion film with a denser structure tends to be more easily obtained.

[0020] From the viewpoint of facilitating removal of the solvent when forming the thermoelectric conversion film, the boiling point of the first solvent is preferably 250° C. or lower, more preferably 200° C. or lower. Moreover, from the viewpoints of ease of handling and operational safety, the boiling point of the first solvent is preferably 50° C. or higher, more preferably 60° C. or higher.

[0021] Examples of the first solvent include water, alcohols (methanol, ethanol, etc.), amides (N,N-dimethylformamide, N,N-dimethylacetamide, N-methylpyrrolidone, etc.), ketones (acetone, methyl ethyl ketone, etc.), glycols (ethylene glycol, diethylene glycol, etc.), dimethyl sulfoxide, and acetonitrile. The first solvent may be used singly or in combination of two or more. Among these, the first solvent is preferably at least one selected from the group consisting of water, methanol, and ethanol, and more preferably water. In a preferred embodiment, the first dispersion may be an aqueous dispersion (aqueous solution) containing PEDOT / PSS and water.

[0022] The first dispersion may further contain components other than PEDOT / PSS and the first solvent, such as a carbon-based conductive material, an inorganic conductive material, an inorganic thermoelectric material, a binder resin, a surfactant, an antifoaming agent, a coupling agent, an antioxidant, an ultraviolet absorber, a viscosity modifier, and a leveling agent.

[0023] EMIM / TCB is an ionic liquid composed of 1-ethyl-3-methylimidazolium cation and tetracyanoborate anion. EMIM / TCB can be obtained by reacting 1-ethyl-3-methylimidazolium chloride with potassium tetracyanoborate. Commercially available EMIM / TCB can also be used.

[0024] The content of EMIM / TCB in the second dispersion is not particularly limited. The content of EMIM / TCB may be, for example, 0.1% by mass or more, and preferably 0.5% by mass or more, based on the total amount of the second dispersion. The content of EMIM / TCB may be, for example, 5% by mass or less, and preferably 2.5% by mass or less, based on the total amount of the first dispersion. When the content of EMIM / TCB is within this range, the dispersibility of EMIM / TCB tends to be improved.

[0025] The second solvent is not particularly limited as long as it is a solvent capable of dispersing or dissolving EMIM / TCB, but is preferably a solvent that is compatible with the first solvent. The second solvent may be, for example, a polar solvent or an aqueous solvent. The second solvent may be either a protic solvent or an aprotic solvent, but is preferably a protic solvent. The relative dielectric constant (20°C) of the polar solvent in the second solvent may be the same as the relative dielectric constant (20°C) of the polar solvent in the first solvent, and the boiling point of the second solvent may be the same as the boiling point of the first solvent.

[0026] The first solvent may be the same as the second solvent. The second solvent is preferably at least one selected from the group consisting of water, methanol, and ethanol, and more preferably water. In a preferred embodiment, the second dispersion may be an aqueous dispersion (aqueous solution) containing EMIM / TCB and water.

[0027] The second dispersion may further contain components other than EMIM / TCB and the second solvent, such as a carbon-based conductive material, an inorganic conductive material, an inorganic thermoelectric material, a binder resin, a surfactant, an antifoaming agent, a coupling agent, an antioxidant, an ultraviolet absorber, a viscosity modifier, and a leveling agent.

[0028] When the first dispersion and the second dispersion are mixed, the amount of EMIM / TCB added to the second dispersion may be 0.5 to 5.5 μmol per 1 mg of PEDOT / PSS in the first dispersion. When the amount of EMIM / TCB added is 0.5 μmol or more, the thermoelectric conversion properties of the thermoelectric conversion film tend to be better. When the amount of EMIM / TCB added is 5.5 μmol or less, the mechanical properties of the thermoelectric conversion film tend to be better. The amount of EMIM / TCB added may be 1.0 μmol or more, 1.5 μmol or more, 2.0 μmol or more, 2.5 μmol or more, 3.0 μmol or more, 3.5 μmol or more, or 4.0 μmol or more, or 5.2 μmol or less, 5.0 μmol or less, 4.8 μmol or less, or 4.5 μmol or less, per 1 mg of PEDOT / PSS.

[0029] The method for mixing the first dispersion liquid and the second dispersion liquid is not particularly limited, and for example, the second dispersion liquid may be added to the first dispersion liquid, the first dispersion liquid may be added to the second dispersion liquid, or the first dispersion liquid and the second dispersion liquid may be simultaneously charged into another container and mixed.

[0030] In the first step, the first dispersion and the second dispersion are preferably mixed and then stirred for a predetermined time. The stirring method is not particularly limited, and can be carried out using, for example, a magnetic stirrer, a planetary mixer, or the like. The stirring time may be, for example, 1 minute or more, preferably 2 minutes or more, and more preferably 5 minutes or more. There is no particular upper limit to the stirring time, but it may be, for example, 24 hours or less, or 20 hours or less. By performing such a stirring operation, the desired composite tends to be more easily obtained.

[0031] The temperature, pressure, atmosphere, etc. during mixing and stirring in the first step are not particularly limited, and may be any conditions that allow PEDOT / PSS and EMIM / TCB to be thoroughly mixed in the mixture.

[0032] The mixing in the first step can produce a complex containing PEDOT, PSS, and TCB (PEDOT / (PSS+TCB)), in which part of the PSS derived from PEDOT / PSS has been replaced with TCB derived from EMIM / TCB, and a complex containing EMIM derived from EMIM / TCB and PSS derived from PEDOT / PSS (hereinafter sometimes referred to as "EMIM / PSS"). That is, the mixed solution obtained in the first step can contain EMIM / PSS in addition to PEDOT / (PSS+TCB).

[0033] (Second step) This step involves applying the mixed solution onto a substrate and removing the first solvent and the second solvent (at least a portion of the first solvent and the second solvent) to form a coating film. The coating film contains PEDOT / (PSS+TCB) and may also contain EMIM / PSS.

[0034] The method for applying the mixed solution onto the substrate is not particularly limited, and various methods can be used, such as a doctor blade method, a casting method, a dip coating method, a spray coating method, a spin coating method, a dispenser method, and a metal mask printing method.

[0035] The substrate is not particularly limited, and examples thereof include a glass substrate, a resin substrate, and a conductive substrate. The substrate may be a conductive substrate from the viewpoint of facilitating use in a thermoelectric conversion module. The conductive substrate is a substrate having a conductive portion that can be used as an electrode, and may be, for example, a substrate that can be used as an electrode for a thermoelectric conversion module.

[0036] As the conductive substrate, various known conductive substrates can be used. From the viewpoint of being less susceptible to corrosion or elution, the conductive substrate is preferably a substrate containing at least one conductive material selected from the group consisting of tin-doped indium oxide (ITO), fluorine-doped tin oxide (FTO), and stainless steel, more preferably a substrate containing at least one conductive material selected from the group consisting of FTO and stainless steel. The conductive substrate may be a substrate made of the above conductive material.

[0037] The method for removing the first solvent and the second solvent is not particularly limited as long as at least a portion of the first solvent and the second solvent is removed. The method for removing the solvent may be, for example, a method for removing the solvent by natural drying, or a method for removing the solvent by carrying out a heat treatment, a reduced pressure treatment, or the like.

[0038] The temperature of the heat treatment is not particularly limited and may be, for example, 40° C. or higher, preferably 50° C. or higher, and more preferably 60° C. or higher. The temperature of the heat treatment may be, for example, 200° C. or lower, preferably 150° C. or lower, and more preferably 130° C. or lower.

[0039] The time for the heat treatment is not particularly limited and may be, for example, 1 minute or more, preferably 10 minutes or more, and may be 6 hours or less, preferably 3 hours or less.

[0040] The thickness of the coating film can be adjusted as desired to match the desired thickness of the thermoelectric conversion film to be finally obtained. The thickness of the coating film may be, for example, 0.5 μm or more, preferably 1 μm or more, more preferably 3 μm or more, and even more preferably 5 μm or more. The upper limit of the thickness of the coating film may be, for example, 1000 μm or less, or may be 500 μm or less.

[0041] (Third step) In this step, the coating film is washed with a second solvent to obtain a thermoelectric conversion film containing PEDOT / (PSS+TCB). By washing the coating film with the second solvent, at least a portion of EMIM / PSS can be removed.

[0042] The method for washing the coating film with the second solvent is not particularly limited, and examples thereof include a method of immersing the coating film in the second solvent, a method of applying the second solvent to the coating film, etc. Among these, the method of immersing the coating film in the second solvent is preferred, from the viewpoint that the coating film can be easily exposed to the second solvent while maintaining its shape.

[0043] After washing the coating film with the second solvent, the solvent may be removed, if necessary. Examples of the method for removing the solvent include the same method as the method for removing the first solvent and the second solvent in the second step.

[0044] In the thermoelectric conversion film, when the peak area derived from PEDOT measured by X-ray photoelectron spectroscopy is defined as A(PEDOT) and the peak area derived from PSS is defined as A(PSS), A(PEDOT) / A(PSS) satisfies the following formula (1): 0.50≦A(PEDOT) / A(PSS)≦0.90 (1)

[0045] When A(PEDOT) / A(PSS) is 0.50 or more, the thermoelectric conversion film tends to have excellent thermoelectric conversion properties. When A(PEDOT) / A(PSS) is 0.90 or less, the thermoelectric conversion film tends to have excellent mechanical properties. A(PEDOT) / A(PSS) may be 0.55 or more, 0.60 or more, 0.65 or more, 0.70 or more, 0.75 or more, or 0.80 or more, or may be 0.88 or less, or 0.85 or less.

[0046] The thermoelectric conversion film of this embodiment has excellent mechanical properties, making it possible to form a thin thermoelectric conversion film. The thickness of the thermoelectric conversion film may be, for example, 0.5 μm or more, preferably 1 μm or more, more preferably 3 μm or more, and even more preferably 5 μm or more. The upper limit of the thickness of the thermoelectric conversion film may be, for example, 1000 μm or less, or may be 500 μm or less.

[0047] From the viewpoint of improving the output of the thermoelectric conversion module, the electrical conductivity of the thermoelectric conversion film may be, for example, 500 S / cm or more, preferably 700 S / cm or more, more preferably 900 S / cm or more, and even more preferably 1000 S / cm or more. The upper limit of the electrical conductivity of the thermoelectric conversion film is not particularly limited, but may be, for example, 5000 S / cm or less.

[0048] From the viewpoint of improving the output of the thermoelectric conversion module, the Seebeck coefficient of the thermoelectric conversion film may be, for example, 10 μV / K or more, preferably 12 μV / K or more, and more preferably 14 μV / K or more. The Seebeck coefficient means, for example, the magnitude of the electromotive force per 1°C of temperature difference when a temperature difference is applied to the thermoelectric conversion film. There is no particular upper limit to the Seebeck coefficient of the thermoelectric conversion film, but it may be, for example, 50 μV / K or less.

[0049] From the perspective of improving the output of the thermoelectric conversion module, the power factor of the thermoelectric conversion film is, for example, 5 μW / m K. 2 or more, preferably 10 μW / m K 2 More than 15μW / m K is preferable. 2 More than 20 μW / m K is preferable.2 The power factor is an index of the power generated by the thermoelectric conversion film. There is no particular upper limit to the power factor of the thermoelectric conversion film, but it is generally set to, for example, 50 μW / m K. 2 It may be the following:

[0050] The thermoelectric conversion film of this embodiment can be suitably used for a thermoelectric conversion module. The thermoelectric conversion film of this embodiment can also be suitably used for applications such as a Peltier element and a temperature sensor.

[0051] [Thermoelectric conversion module] A thermoelectric conversion module according to one embodiment includes the thermoelectric conversion film. More specifically, the thermoelectric conversion module includes two conductive substrates and the thermoelectric conversion film disposed between the conductive substrates. Such a thermoelectric conversion module has excellent thermoelectric conversion characteristics due to the use of the thermoelectric conversion film.

[0052] The two conductive substrates can also be referred to as a first electrode and a second electrode, respectively.

[0053] The thermoelectric conversion module of this embodiment may be manufactured by a manufacturing method including a step of disposing a thermoelectric conversion film between two conductive substrates, for example.

[0054] The above step may be, for example, a step of forming a thermoelectric conversion film (thermoelectric conversion layer) on one conductive substrate and laminating the other conductive substrate on the formed thermoelectric conversion film. Alternatively, the above step may be, for example, a step of attaching two conductive substrates to both sides of the thermoelectric conversion film.

[0055] The thermoelectric conversion module may further include components other than those described above. For example, the thermoelectric conversion module may further include a sealing material for sealing the thermoelectric conversion film, wiring for electrically connecting the thermoelectric conversion modules to each other or for extracting power to an external circuit, a heat insulating material or a thermally conductive material for controlling the thermal conductivity of the thermoelectric conversion module, etc.

[0056] [Thermoelectric materials] A thermoelectric conversion material according to one embodiment contains the composite (PEDOT / (PSS+TCB)). The thermoelectric conversion material containing PEDOT / (PSS+TCB) can form a thermoelectric conversion film having excellent thermoelectric conversion properties and mechanical properties.

[0057] The thermoelectric conversion material may further contain components other than PEDOT / (PSS+TCB), such as a carbon-based conductive material, an inorganic conductive material, an inorganic thermoelectric material, a binder resin, a surfactant, an antifoaming agent, a coupling agent, an antioxidant, an ultraviolet absorber, a viscosity modifier, and a leveling agent. [Example]

[0058] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to these examples.

[0059] [Example 1] (Preparation of Second Dispersion) To 0.5 g of deionized water, 10.2 mg of 1-ethyl-3-methylimidazolium tetracyanoborate (EMIM / TCB) was added, and the mixture was stirred with a magnetic stirrer for 10 minutes to obtain a second dispersion.

[0060] (Preparation of mixed solution) The second dispersion was added to 1 g of Heraeus' "Clevious PH1000" (PEDOT / PSS aqueous dispersion, solids concentration: 1% by mass) as the first dispersion, and the mixture was stirred for 15 hours with a magnetic stirrer to obtain a mixed solution. The amount of EMIM / TCB added was 4.5 μmol per mg of PEDOT / PSS. The mixed solution may contain a complex containing PEDOT, PSS, and TCB (PEDOT / (PSS+TCB)), and a complex containing EMIM and PSS (EMIM / PSS).

[0061] (Formation of coating film) The resulting mixture was drop-cast onto a glass substrate measuring 5 mm x 5 mm (for X-ray photoelectron spectroscopy measurement) or 7 mm x 7 mm (for thermoelectric conversion property measurement) and dried at 60°C for 60 minutes to obtain a coating film.

[0062] (Preparation of thermoelectric conversion film) The resulting coating film was washed with deionized water to remove the EMIM / PSS, and then dried at 60° C. for 60 minutes to obtain a thermoelectric conversion film containing PEDOT / (PSS+TCB) of Example 1.

[0063] (X-ray photoelectron spectroscopy measurements) The photoelectron spectrum of sulfur atoms was measured using an X-ray photoelectron spectrometer (Shimadzu ESCA-3400), and the peaks of the components derived from PEDOT and the components derived from PSS were separated and their respective peak areas were calculated. In the thermoelectric conversion film of Example 1, when the peak area derived from PEDOT was designated A(PEDOT) and the peak area derived from PSS was designated A(PSS), the area ratio of A(PEDOT) to A(PSS) (A(PEDOT) / A(PSS)) was 0.85.

[0064] (Film thickness measurement) The thermoelectric conversion film on the 7 mm x 7 mm glass substrate was peeled off from the glass substrate, and the film thickness was measured using a color 3D laser microscope (VK-9700 manufactured by Keyence Corporation). The film thickness of the thermoelectric conversion film in Example 1 was 5 μm.

[0065] (Measurement of thermoelectric conversion properties) The electrical conductivity (σ), Seebeck coefficient (S), and power factor (PF) of the obtained thermoelectric conversion film were measured by the following methods. The electrical conductivity of the thermoelectric conversion film of Example 1 was 1143 S / cm, the Seebeck coefficient was 14.7 μV / K, and the power factor was 24.7 μW / m K. 2 It was.

[0066] Electrical conductivity The electrical conductivity was measured by the four-probe method (using a resistivity meter Loresta MCP-T610 manufactured by Mitsubishi Chemical Analytech Co., Ltd., probe: QPP). Seebeck coefficient The Seebeck coefficient was calculated using a PTM3 manufactured by Wuhan Joule Yacht. Power Factor The power factor (PF) was calculated using the following formula: PF=S 2 σ (S: Seebeck coefficient (V / K), σ: electrical conductivity (S / m))

[0067] [Example 2] The thermoelectric conversion film of Example 2 was obtained in the same manner as in Example 1, except that the amount of EMIM / TCB in the second dispersion was changed from 10.2 mg to 6.8 mg so that the amount of EMIM / TCB added was 3.0 μmol per 1 mg of PEDOT / PSS. The A(PEDOT) / A(PSS) ratio was determined in the same manner as above, and was found to be 0.72 for the thermoelectric conversion film of Example 2. Furthermore, a thermoelectric conversion film with a thickness of 5 μm was prepared for measuring thermoelectric conversion properties, and the electrical conductivity (σ), Seebeck coefficient (S), and power factor (PF) were determined in the same manner as above. The thermoelectric conversion film of Example 2 had an electrical conductivity of 756 S / cm, a Seebeck coefficient of 13.6 μV / K, and a power factor of 14.0 μW / m K. 2 It was.

[0068] [Example 3] The thermoelectric conversion film of Example 3 was obtained in the same manner as in Example 1, except that the amount of EMIM / TCB in the second dispersion was changed from 10.2 mg to 3.4 mg so that the amount of EMIM / TCB added was 1.5 μmol per 1 mg of PEDOT / PSS. The A(PEDOT) / A(PSS) ratio was determined in the same manner as above, and was found to be 0.61 for the thermoelectric conversion film of Example 3. Furthermore, a thermoelectric conversion film with a thickness of 5 μm was prepared for measuring thermoelectric conversion properties, and the electrical conductivity (σ), Seebeck coefficient (S), and power factor (PF) were determined in the same manner as above. The thermoelectric conversion film of Example 3 had an electrical conductivity of 532 S / cm, a Seebeck coefficient of 14.6 μV / K, and a power factor of 11.3 μW / m K. 2 It was.

[0069] [Comparative Example 1] The thermoelectric conversion film of Comparative Example 1 was obtained in the same manner as in Example 1, except that the amount of EMIM / TCB in the second dispersion was changed from 10.2 mg to 13.6 mg so that the amount of EMIM / TCB added was 6.0 μmol per 1 mg of PEDOT / PSS. The A(PEDOT) / A(PSS) ratio was determined in the same manner as above, and was found to be 0.92 for the thermoelectric conversion film of Comparative Example 1. On the other hand, when a thermoelectric conversion film with a thickness of 5 μm was prepared for measuring thermoelectric conversion properties, it broke when peeled off from the glass substrate, and the electrical conductivity (σ), Seebeck coefficient (S), and power factor (PF) could not be determined.

[0070] Comparative Example 2 A thermoelectric conversion film of Comparative Example 2 was obtained in the same manner as in Example 1, except that the second dispersion liquid was not added, i.e., EMIM / TCB was not added. When A(PEDOT) / A(PSS) was determined in the same manner as above, the A(PEDOT) / A(PSS) ratio for the thermoelectric conversion film of Comparative Example 2 was 0.43. Furthermore, a thermoelectric conversion film with a thickness of 5 μm was prepared for measuring thermoelectric conversion properties, and the electrical conductivity (σ), Seebeck coefficient (S), and power factor (PF) were determined in the same manner as above. The electrical conductivity of the thermoelectric conversion film of Comparative Example 2 was 1.04 S / cm, the Seebeck coefficient was 15.2 μV / K, and the power factor was 0.02 μW / m K. 2 It was.

[0071] [Table 1]

[0072] As shown in Table 1, the thermoelectric conversion films of Examples 1 to 3, which satisfy formula (1), not only had excellent thermoelectric conversion properties, but also had excellent mechanical properties, with no breakage occurring when the thermoelectric conversion film was peeled off from the glass substrate. In contrast, the thermoelectric conversion film of Comparative Example 1, in which A(PEDOT) / A(PSS) exceeded 0.90, broke when the thermoelectric conversion film was peeled off from the glass substrate, and had insufficient mechanical properties. Furthermore, the thermoelectric conversion film of Comparative Example 2, in which A(PEDOT) / A(PSS) was less than 0.50, had insufficient thermoelectric conversion properties. From the above, it was confirmed that the thermoelectric conversion film of the present invention has excellent thermoelectric conversion properties as well as excellent mechanical properties.

Claims

1. a step of mixing a first dispersion containing a conductive polymer made of poly(3,4-ethylenedioxythiophene) and polystyrene sulfonic acid and a first solvent with a second dispersion containing 1-ethyl-3-methylimidazolium tetracyanoborate and a second solvent to obtain a mixed solution; applying the mixed solution onto a substrate and removing the first solvent and the second solvent to form a coating film; a step of washing the coating film with the second solvent to obtain a thermoelectric conversion film containing a complex including poly(3,4-ethylenedioxythiophene) cations, polystyrenesulfonate anions, and tetracyanoborate anions; Equipped with In the thermoelectric conversion film, when a peak area derived from the poly(3,4-ethylenedioxythiophene) cation is defined as A(PEDOT) and a peak area derived from the polystyrene sulfonate anion is defined as A(PSS), as measured by X-ray photoelectron spectroscopy, A(PEDOT) and A(PSS) satisfy the following formula (1): 0.61≦A(PEDOT) / A(PSS)≦0.85 (1)

2. 2. The method for producing a thermoelectric conversion film according to claim 1, wherein the amount of 1-ethyl-3-methylimidazolium tetracyanoborate added is 1.5 to 4.5 μmol per 1 mg of the conductive polymer.

3. The method for producing a thermoelectric conversion film according to claim 1 or 2, wherein the thermoelectric conversion film has a thickness of 0.5 μm or more.

4. The method for producing a thermoelectric conversion film according to any one of claims 1 to 3, wherein the thermoelectric conversion film has an electrical conductivity of 500 S / cm or more.

5. The present invention relates to a composite material containing a poly(3,4-ethylenedioxythiophene) cation, a polystyrene sulfonate anion, and a tetracyanoborate anion. A thermoelectric conversion film, in which, when measured by X-ray photoelectron spectroscopy, a peak area derived from the poly(3,4-ethylenedioxythiophene) cation is defined as A(PEDOT), and a peak area derived from the polystyrene sulfonate anion is defined as A(PSS), A(PEDOT) and A(PSS) satisfy the following formula (1): 0.61≦A(PEDOT) / A(PSS)≦0.85 (1)

6. A thermoelectric conversion module comprising the thermoelectric conversion film according to claim 5 .

7. The present invention relates to a composite material containing a poly(3,4-ethylenedioxythiophene) cation, a polystyrene sulfonate anion, and a tetracyanoborate anion. A thermoelectric conversion material, in which, when measured by X-ray photoelectron spectroscopy, a peak area derived from the poly(3,4-ethylenedioxythiophene) cation is defined as A(PEDOT), and a peak area derived from the polystyrene sulfonate anion is defined as A(PSS), A(PEDOT) and A(PSS) satisfy the following formula (1): 0.61≦A(PEDOT) / A(PSS)≦0.85 (1)

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