P-type material for thermoelectric conversion, manufacturing method thereof, and thermoelectric conversion element

Abstract

To provide a novel p-type material for thermoelectric conversion having excellent thermoelectric conversion performance.SOLUTION: In a p-type material for thermoelectric conversion which is obtained by doping a conductive material with a dopant, the conductive material contains carbon nanotubes and the dopant contains a salt of a nitrosonium ion and an anion.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present disclosure relates to a p-type material for thermoelectric conversion, a method for producing the same, and a thermoelectric conversion element. [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] In recent years, as the applications of thermoelectric conversion modules have expanded, there has been a demand for the development of new materials with excellent thermoelectric conversion performance.

[0006] The present disclosure aims to provide a novel p-type material for thermoelectric conversion that has excellent electrical conductivity, a method for producing the p-type material for thermoelectric conversion, and a thermoelectric conversion element containing the p-type material for thermoelectric conversion. [Means for solving the problem]

[0007] The present disclosure relates to, for example, the following [1] to [5]. [1] A p-type material for thermoelectric conversion, which is obtained by doping a conductive material with a dopant, the conductive material contains carbon nanotubes; The p-type material for thermoelectric conversion, wherein the dopant contains a salt of a nitrosonium ion and an anion. [2] The p-type material for thermoelectric conversion according to [1], wherein the anion is selected from the group consisting of a hexafluorophosphate ion, a hexafluoroantimonate ion, and a tetrafluoroborate ion. [3] an impregnation step of impregnating at least a portion of a conductive film containing a conductive material with a dopant liquid containing a dopant and a liquid medium; a removing step of removing at least a portion of the liquid medium from the conductive film; Including, the conductive material contains carbon nanotubes; The method for producing a p-type material for thermoelectric conversion, wherein the dopant contains a salt of a nitrosonium ion and an anion. [4] The method for producing a p-type material for thermoelectric conversion according to [3], wherein the anion is selected from the group consisting of a hexafluorophosphate ion, a hexafluoroantimonate ion, and a tetrafluoroborate ion. [5] A thermoelectric conversion element comprising the p-type material for thermoelectric conversion according to [1] or [2]. [Effects of the Invention]

[0008] The present disclosure provides a novel p-type material for thermoelectric conversion having excellent electrical conductivity, a method for producing the p-type material for thermoelectric conversion, and a thermoelectric conversion element containing the p-type material for thermoelectric conversion. DETAILED DESCRIPTION OF THE INVENTION

[0009] Preferred embodiments of the present disclosure will be described in detail below.

[0010] In this specification, a numerical range indicated using "to" indicates a range that includes the numerical values ​​before and after "to" as the minimum and maximum values, respectively. In numerical ranges described in stages in this specification, the upper or lower limit value described in one numerical range may be replaced with the upper or lower limit value of another numerical range described in stages. In numerical ranges described in this specification, the upper or lower limit value of that numerical range may be replaced with a value shown in the examples.

[0011] In this specification, unless otherwise specified, the materials exemplified below may be used alone or in combination of two or more within the range that meets the conditions. When multiple substances corresponding to each component are present, the content of each component means the total amount of the multiple substances unless otherwise specified.

[0012] In this specification, whether a thermoelectric conversion material exhibits p-type conductivity or n-type conductivity can be determined by the positive or negative value of the Seebeck coefficient. When the Seebeck coefficient is positive, the thermoelectric conversion material exhibits p-type conductivity, and a material having such properties is called a p-type material for thermoelectric conversion. When the Seebeck coefficient is negative, the thermoelectric conversion material exhibits n-type conductivity, and a material having such properties is called an n-type material for thermoelectric conversion. The Seebeck coefficient can be measured, for example, by the measurement method in the Examples described below, and the polarity of the thermoelectric conversion material can be determined from the positive or negative value of the measured value.

[0013] <P-type materials for thermoelectric conversion> The p-type material for thermoelectric conversion of this embodiment is obtained by doping a conductive material with a dopant. The conductive material contains carbon nanotubes, and the dopant contains a salt of a nitrosonium ion and an anion.

[0014] The p-type material for thermoelectric conversion of this embodiment achieves excellent thermoelectric conversion performance (particularly, excellent electrical conductivity) by doping a specific conductive material with a specific dopant. The reason for this effect is not entirely clear, but is thought to be as follows. In this embodiment, carbon nanotubes in the conductive material are oxidized by nitrosonium ions in the dopant, increasing the number of holes in the carbon nanotubes. At this time, the nitrosonium ions that supplied the holes are discharged to the outside of the system as NO gas, and it is therefore believed that no insulating residues derived from the dopant cations are present in the p-type material for thermoelectric conversion. Therefore, in this embodiment, the adverse effects of residues derived from the dopant are suppressed, and a p-type material for thermoelectric conversion with excellent thermoelectric conversion performance (particularly, excellent electrical conductivity) is obtained.

[0015] In this embodiment, the p-type material for thermoelectric conversion has high electrical conductivity, so that even if the thickness of the thermoelectric conversion film varies to some extent, the variation in electrical resistance can be suppressed. Therefore, the p-type material for thermoelectric conversion of this embodiment also has the effect of making it easier to obtain thermoelectric conversion elements of stable quality.

[0016] The carbon nanotubes may be single-walled, double-walled, or multi-walled (three or more walls), and are preferably single-walled from the viewpoint of further improving the electrical conductivity and power factor of the p-type material for thermoelectric conversion.

[0017] The carbon nanotubes preferably include single-walled carbon nanotubes. The content of single-walled carbon nanotubes relative to the total amount of carbon nanotubes is preferably 25% by mass or more, more preferably 50% by mass or more, and may be, for example, 100% by mass.

[0018] The diameter of the single-walled carbon nanotube is not particularly limited, but may be, for example, 20 nm or less, preferably 10 nm or less, and more preferably 3 nm or less. The lower limit of the diameter of the single-walled carbon nanotube may be, for example, 0.4 nm or more, or 0.5 nm or more.

[0019] In this specification, the diameter of a single-walled carbon nanotube is determined by Raman spectroscopy to be 100 to 300 cm -1 The wave number of the peak that appears in -1 )) can be calculated using the formula diameter (nm) = 248 / ω.

[0020] The G / D ratio in laser Raman spectroscopy is known as a method for evaluating single-walled carbon nanotubes. In this embodiment, the G / D ratio of single-walled carbon nanotubes in laser Raman spectroscopy at a wavelength of 532 nm is preferably 10 or more, more preferably 20 or more. By using such single-walled carbon nanotubes, a thermoelectric conversion material with even better electrical conductivity tends to be obtained. The upper limit of the G / D ratio is not particularly limited, and may be, for example, 500 or less, or 300 or less.

[0021] The conductive material may be primarily composed of carbon nanotubes, and the content of carbon nanotubes in the conductive material may be, for example, 50% by mass or more, 70% by mass or more, 90% by mass or more, 95% by mass or more, 97% by mass or more, 99% by mass or more, or even 100% by mass based on the total amount of the conductive material.

[0022] The conductive material may contain carbon nanotubes and a conductive resin. In this case, the content of carbon nanotubes in the conductive material may be, for example, 20% by mass or more, 30% by mass or more, 40% by mass or more, 50% by mass or more, or 60% by mass or more, based on the total amount of the conductive material. Furthermore, the content of carbon nanotubes in the conductive material may be, for example, 99% by mass or less, 97% by mass or less, 95% by mass or less, or 90% by mass or less, based on the total amount of the conductive material.

[0023] When the conductive material contains carbon nanotubes and a conductive resin, the content of the conductive resin in the conductive material may be, for example, 1% by mass or more, 3% by mass or more, 5% by mass or more, or 10% by mass or more, based on the total amount of the conductive material. Furthermore, when the conductive material contains carbon nanotubes and a conductive resin, the content of the conductive resin in the conductive material may be, for example, 80% by mass or less, 70% by mass or less, 60% by mass or less, 50% by mass or less, or 40% by mass or less, based on the total amount of the conductive material.

[0024] In the conductive material, the total content of the carbon nanotubes and the conductive resin may be, for example, 50 mass% or more, 70 mass% or more, 90 mass% or more, 95 mass% or more, 97 mass% or more, or 99 mass% or more, or may be 100 mass% based on the total amount of the conductive material.

[0025] The conductive resin is not particularly limited, and known conductive resins used in thermoelectric conversion materials (especially p-type materials for thermoelectric conversion) can be used. Examples of conductive resins include polyaniline-based conductive polymers, polythiophene-based conductive polymers, polyoligothiophene-based conductive polymers, polypyrrole-based conductive polymers, polyacetylene-based conductive polymers, polyphenylene-based conductive polymers, and polyphenylene vinylene-based conductive polymers. Examples of polythiophene-based conductive polymers include poly(3,4-ethylenedioxythiophene), and examples of polyoligothiophene-based conductive polymers include poly(3-ethylhexyloxyoligothiophene) and copolymers of dodecyl octyl dioxythiophene and ethylenedioxythiophene.

[0026] The conductive resin may be poly(3,4-ethylenedioxythiophene) (hereinafter sometimes referred to as "PEDOT"), poly(4,4"-bis(3-ethylhexyloxy)-2,2':5',2"-terthiophene) (hereinafter sometimes referred to as "P3EH3T"), or a conductive resin composed of a copolymer of 3,4-bis(2-octyldodecyloxy)thiophene and 3,4-ethylenedioxythiophene (hereinafter sometimes referred to as "P(DROT-co-EDOT)") and an electron acceptor. Use of such a conductive resin tends to increase the electrical conductivity of the thermoelectric conversion material.

[0027] Examples of the electron acceptor include polystyrene sulfonic acid, polyvinyl sulfonic acid, poly(meth)acrylic acid, polyvinyl sulfonic acid, toluenesulfonic acid, dodecylbenzenesulfonic acid, camphorsulfonic acid, bis(2-ethylhexyl) sulfosuccinate, chlorine, bromine, iodine, phosphorus pentafluoride, arsenic pentafluoride, boron trifluoride, hydrogen chloride, sulfuric acid, nitric acid, tetrafluoroboric acid, perchloric acid, iron(III) chloride, tetracyanoquinodimethane, etc. From the viewpoint of further improving the electrical conductivity of the thermoelectric conversion material, the electron acceptor may be polystyrene sulfonic acid (hereinafter sometimes referred to as "PSS").

[0028] In this specification, the dopant refers to a substance that changes the thermoelectric conversion performance, such as the Seebeck coefficient, electrical conductivity, and power factor, of the material to which the dopant is doped.

[0029] The dopant is a nitrosonium ion (NO + The dopant may be a salt containing a nitrosonium ion and an anion.

[0030] It is believed that the anions in the dopant reside in the vicinity of the carbon nanotubes in the p-type thermoelectric material to maintain charge balance.

[0031] Since the anion remains in the p-type thermoelectric conversion material, it is desirable that the anion be stable in the environment in which the thermoelectric conversion element is used. From this viewpoint, the anion may be, for example, a halide ion (e.g., a fluoride ion (F - ), chloride ions (Cl - ), bromide ion (Br - ), iodide ion (I - )), hexafluorophosphate ion (PF6 - ), hexafluoroantimonate ion (SbF6 - ), tetrafluoroborate ion (BF4 - ), trifluoromethanesulfonate ion (CF3SO3 - ), trifluoroacetate ion (CF3CO2 - ) etc. are preferred.

[0032] The anion is preferably an anion selected from the group consisting of hexafluorophosphate ion, hexafluoroantimonate ion, and tetrafluoroborate ion. These anions are preferred because they have weak interactions with cations, making doping with nitrosonium ions more efficient, and because they are highly stable as anions, allowing them to stably exist near carbon nanotubes in the p-type thermoelectric conversion material. From this perspective, the hexafluorophosphate ion is even more preferred as the anion.

[0033] The p-type material for thermoelectric conversion of this embodiment may be formed by, for example, doping at least a part of a conductive film containing a conductive material with a dopant.

[0034] The method for doping the conductive material with the dopant is not particularly limited, but examples thereof include a method in which a dopant liquid containing the dopant and a liquid medium is impregnated into the conductive material (e.g., at least a part of a conductive film containing the conductive material), and then the liquid medium is removed.

[0035] That is, the p-type material for thermoelectric conversion of this embodiment may be produced by a production method including, for example, an impregnation step of impregnating a conductive material with a dopant liquid containing a dopant and a liquid medium, and a removal step of removing at least a part of the liquid medium.

[0036] The dopant solution can be obtained by mixing a dopant and a liquid medium. The liquid medium may be any liquid medium capable of dissolving or uniformly dispersing the dopant. Examples of liquid media include water, acetonitrile, acetone, methanol, ethanol, 1-propanol, 2-propanol, ethylene glycol, dimethyl sulfoxide (DMSO), N-methylpyrrolidone, N,N-dimethylformamide, and N,N-dimethylacetamide. Among these, acetonitrile is preferred.

[0037] The concentration of the dopant in the dopant solution is not particularly limited, and may be, for example, 0.05 mmol / L or more, 0.1 mmol / L or more, or 0.5 mmol / L or more. The concentration of the dopant in the dopant solution may be, for example, 10 mmol / L or less, 5 mmol / L or less, or 1 mmol / L or less.

[0038] The dopant liquid may contain other components in addition to the dopant and the liquid medium, as long as the above-mentioned effects are not impaired. Examples of other components include a binder resin, an antioxidant, a thickener, and a surfactant.

[0039] The total amount of the dopant and the liquid medium in the dopant liquid may be, for example, 50% by mass or more, 70% by mass or more, 90% by mass or more, 95% by mass or more, 97% by mass or more, or 99% by mass or more, or may be 100% by mass, based on the total amount of the dopant liquid.

[0040] The method for impregnating the conductive material with the dopant liquid is not particularly limited, and examples thereof include a method of immersing the conductive material in the dopant liquid, and a method of dropping or coating the dopant liquid onto the conductive material.

[0041] The impregnation step may be, for example, a step of impregnating at least a portion of a conductive film containing a conductive material with a dopant liquid.

[0042] The conductive film may be mainly composed of a conductive material. The content of the conductive material in the conductive film may be, for example, 50 mass % or more, 70 mass % or more, 90 mass % or more, 95 mass % or more, 97 mass % or more, or 99 mass % or more, or even 100 mass %, based on the total mass of the conductive film.

[0043] The conductive film may be formed on a support.

[0044] The thickness of the conductive film may be, for example, 1 μm or more, 5 μm or more, or 8 μm or more, and may be, for example, 80 μm or less, 60 μm or less, or 40 μm or less.

[0045] The time for impregnating the conductive material with the dopant liquid may be, for example, 1 hour or more, or 2 hours or more.

[0046] The temperature when the conductive material is impregnated with the dopant liquid may be, for example, 10° C. or higher and 50° C. or lower, or may be room temperature (for example, 23° C.).

[0047] In the removing step, at least a portion of the liquid medium is removed from the conductive material that has been impregnated with the dopant liquid in the impregnation step.

[0048] The removing step may be, for example, a step of drying the conductive material impregnated with the dopant liquid. Alternatively, the removing step may be, for example, a step of washing the conductive material impregnated with the dopant liquid with a washing liquid and then removing (drying) the washing liquid.

[0049] The cleaning liquid is not particularly limited, and may be, for example, the liquid medium exemplified as the liquid medium in the dopant liquid.

[0050] The drying method is not particularly limited, and may be natural drying or drying under heat and / or reduced pressure. The drying conditions are not particularly limited, and may be appropriately selected depending on the boiling point of the liquid medium, etc.

[0051] The shape of the p-type material for thermoelectric conversion of this embodiment is not particularly limited and may be, for example, a film. The thickness of the p-type material for thermoelectric conversion may be, for example, 0.1 μm or more, 1 μm or more, or 5 μm or more. For example, it may be 80 μm or less, 60 μm or less, or 40 μm or less.

[0052] In this embodiment, the thickness of the p-type thermoelectric conversion material may be thinner than the thickness of the conductive material. The ratio (T1 / T0) of the thickness T1 of the p-type thermoelectric conversion material to the conductive material T0 may be, for example, 0.01 or more, or 0.05 or more. Furthermore, the ratio (T1 / T0) may be, for example, 1 or less, or 0.8 or less.

[0053] The p-type material for thermoelectric conversion of this embodiment has a positive Seebeck coefficient. In this embodiment, the Seebeck coefficient of the p-type material for thermoelectric conversion may be, for example, 1 μV / K or more, or may be 10 μV / K or more. Alternatively, the Seebeck coefficient of the p-type material for thermoelectric conversion may be, for example, 200 μV / K or less, or 50 μV / K or less.

[0054] In this embodiment, the Seebeck coefficient of the p-type thermoelectric material may be lower than that of the conductive material. In this embodiment, the p-type thermoelectric material has significantly improved electrical conductivity due to doping with a dopant, and therefore, even if the Seebeck coefficient is reduced, the power factor may be improved.

[0055] The p-type material for thermoelectric conversion of this embodiment can be suitably used as a p-type material for thermoelectric conversion elements, and can also be suitably used for applications such as Peltier elements and temperature sensors.

[0056] <Thermoelectric conversion element> The thermoelectric conversion element of this embodiment includes the above-described p-type material for thermoelectric conversion.

[0057] The thermoelectric conversion element of this embodiment may include, for example, two conductive substrates and a thermoelectric conversion film disposed between the conductive substrates and containing the p-type material for thermoelectric conversion.

[0058] The conductive substrate may be any of various known conductive substrates, and may contain at least one conductive material selected from the group consisting of tin-doped indium oxide (ITO), fluorine-doped tin oxide (FTO), and stainless steel, since these materials are resistant to corrosion and elution.

[0059] The two conductive substrates can also be referred to as a first electrode and a second electrode, respectively.

[0060] The thermoelectric conversion element of this embodiment can be manufactured, for example, by a method including a lamination step of arranging a thermoelectric conversion film containing a p-type material for thermoelectric conversion between conductive substrates.

[0061] The thermoelectric conversion element of this embodiment can be manufactured by a method including, for example, a first lamination step of arranging a conductive film containing a conductive material on one conductive substrate, an impregnation step of impregnating the conductive film with a dopant liquid, a removal step of removing at least a portion of the liquid medium from the conductive film to obtain a thermoelectric conversion film containing a p-type material for thermoelectric conversion, and a second lamination step of laminating the other conductive substrate on the thermoelectric conversion film.

[0062] The thermoelectric conversion element may further include components other than those described above. For example, the thermoelectric conversion element may further include a sealant for sealing the thermoelectric conversion film, wiring for electrically connecting the thermoelectric conversion elements 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 element, etc.

[0063] Although the preferred embodiments of the present disclosure have been described above, the present disclosure is not limited to the above embodiments. [Example]

[0064] The present disclosure will be described in more detail below with reference to examples, but the present disclosure is not limited to these examples.

[0065] (Comparative Example 1) <Preparation of conductive film> 12.4 mg of carbon nanotubes (single-walled carbon nanotubes, manufactured by Meijo Nanocarbon Co., Ltd., MEIJO eDIPS EC1.5-P) were weighed into a sample bottle, and 6 mL of o-dichlorobenzene was added. The mixture was dispersed using an ultrasonic irradiator (manufactured by Hielscher, UP200St) to obtain a dispersion. 2 mL of the obtained dispersion was suction filtered through a membrane filter, and the filter and the mixture were sandwiched between filter paper and dried under vacuum. After vacuum drying, the conductive film made of carbon nanotubes was peeled off to obtain a conductive film (thermoelectric conversion film of Comparative Example 1).

[0066] Example 1 <Preparation of p-type materials for thermoelectric conversion> 4.81 mg of nitrosonium hexafluorophosphate (manufactured by Acros, purity 95%) was weighed and diluted with acetonitrile in a 50 mL measuring flask to obtain a dopant solution with a concentration of 0.55 mmol / L. 2 mL of the dopant solution was placed in a flat petri dish (outer diameter 32 mm, inner diameter 27 mm), and the conductive film of Comparative Example 1 was immersed in the dopant solution and allowed to stand at room temperature for 2 hours. The conductive film was removed and placed in another flat petri dish containing 2 mL of acetonitrile for washing. After washing, the film was sandwiched between filter paper and vacuum dried for 24 hours to obtain a thermoelectric conversion film made of a p-type material for thermoelectric conversion.

[0067] Example 2 <Preparation of conductive film> 12.4 mg of carbon nanotubes (single-walled carbon nanotubes, Meijo Nanocarbon Co., Ltd., MEIJO eDIPS EC1.5-P) were weighed into sample bottle (1), 6 mL of o-dichlorobenzene was added, and the mixture was dispersed using an ultrasonic irradiator (Hielscher, UP200St) to obtain a dispersion. In another sample bottle (2), o-dichlorobenzene (1 mL) was added to P3EH3T (7.8 mg) and the mixture was stirred at room temperature overnight. The contents of sample bottle (1) and sample bottle (2) were mixed and stirred at room temperature overnight. Then, 2 mL of the mixed dispersion was suction filtered through a membrane filter, sandwiched between filter paper, and vacuum dried. After vacuum drying, the conductive film (2) was peeled off from the filter.

[0068] <Preparation of p-type materials for thermoelectric conversion> A thermoelectric conversion film was obtained in the same manner as in Example 1, except that the conductive film (2) obtained above was used.

[0069] Example 3 <Preparation of conductive film> 12.4 mg of carbon nanotubes (single-walled carbon nanotubes, Meijo Nanocarbon Co., Ltd., MEIJO eDIPS EC1.5-P) were weighed into sample bottle (1), 6 mL of o-dichlorobenzene was added, and the mixture was dispersed using an ultrasonicator (Hielscher, UP200St) to obtain a dispersion. In another sample bottle (2), o-dichlorobenzene (1 mL) was added to P(DROT-co-EDOT) (7.8 mg) and the mixture was stirred overnight at room temperature. The contents of sample bottle (1) and sample bottle (2) were mixed and stirred overnight at room temperature. Then, 2 mL of the mixed dispersion was suction-filtered through a membrane filter, sandwiched between filter paper, and vacuum-dried. After vacuum drying, the conductive film (3) was peeled off from the filter, and the conductive film composed of carbon nanotubes was peeled off.

[0070] <Creating p-type materials for thermoelectric conversion> A thermoelectric conversion film was obtained in the same manner as in Example 1, except that the conductive film (3) obtained above was used.

[0071] Example 4 <Preparation of p-type materials for thermoelectric conversion> 4.6 mg of nitrosonium tetrafluoroborate (manufactured by Angene International, purity 97% or higher) was weighed out and diluted with acetonitrile in a 50 mL measuring flask to obtain a dopant solution with a concentration of 0.55 mmol / L. 2 mL of the dopant solution was placed in a flat petri dish (outer diameter 32 mm, inner diameter 27 mm), and the conductive film of Comparative Example 1 was immersed in the solution and allowed to stand at room temperature for 2 hours. The conductive film was removed and placed in another flat petri dish containing 2 mL of acetonitrile for washing. After washing, the film was sandwiched between filter paper and vacuum dried for 24 hours to obtain a thermoelectric conversion film made of a p-type material for thermoelectric conversion.

[0072] Example 5 <Preparation of p-type materials for thermoelectric conversion> 4.3 mg of nitrosonium hexafluoroantimonate (manufactured by Angene International, purity 90% or higher) was weighed out and diluted with acetonitrile in a 50 mL measuring flask to obtain a dopant solution with a concentration of 0.55 mmol / L. 2 mL of the dopant solution was placed in a flat petri dish (outer diameter 32 mm, inner diameter 27 mm), and the conductive film of Comparative Example 1 was immersed in the solution and allowed to stand at room temperature for 2 hours. The conductive film was removed and placed in another flat petri dish containing 2 mL of acetonitrile for washing. After washing, the film was sandwiched between filter paper and vacuum dried for 24 hours to obtain a thermoelectric conversion film made of a p-type material for thermoelectric conversion.

[0073] (Evaluation of thermoelectric conversion films (i)) The electrical conductivity of the thermoelectric conversion films obtained in Comparative Example 1 and Examples 1 to 5 was measured by the following method. The results are shown in Table 1.

[0074] <Measurement of electrical conductivity> The sheet resistance of the thermoelectric conversion film (R s) and film thickness (t) were measured using a low resistivity meter (Loresta-GP, MCP-T610, QPP probe) manufactured by Nitto Seiko Analytech Co., Ltd. (formerly Mitsubishi Chemical Corporation) and a high-precision Digimatic Micrometer (MDH-25MB) manufactured by Mitutoyo Corporation, respectively, and the electrical conductivity (σ = 1 / (R s × t)) was calculated.

[0075] [Table 1]

[0076] (Evaluation of thermoelectric conversion films (ii)) The Seebeck coefficient was measured and the power factor was calculated by the following methods for the thermoelectric conversion films obtained in Comparative Example 1 and Examples 1 to 4. The results are shown in Table 2.

[0077] <Seebeck coefficient measurement> One end of a test piece (15 mm in diameter) was heated by a Peltier element, while the other end was kept at room temperature. The temperatures at both ends were measured using a Keysight data logger (DAQ973A) via an alumel-chromel thermocouple, and the potential difference between the two ends was measured using a Keysight nanovoltmeter (34420A). The voltage applied to the Peltier element was controlled using a Matsuda DC power supply (PK-80). The Seebeck coefficient was calculated from the slope of the temperature difference versus voltage within a temperature difference range of 2°C.

[0078] <Calculating the 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))

[0079] [Table 2]

Claims

1. A p-type material for thermoelectric conversion, which is obtained by doping a conductive material with a dopant, the conductive material contains carbon nanotubes; The p-type material for thermoelectric conversion, wherein the dopant contains a salt of a nitrosonium ion and an anion.

2. 2. The p-type material for thermoelectric conversion according to claim 1, wherein the anion is selected from the group consisting of a hexafluorophosphate ion, a hexafluoroantimonate ion, and a tetrafluoroborate ion.

3. an impregnation step of impregnating at least a portion of a conductive film containing a conductive material with a dopant liquid containing a dopant and a liquid medium; a removing step of removing at least a portion of the liquid medium from the conductive film; Including, the conductive material contains carbon nanotubes; The method for producing a p-type material for thermoelectric conversion, wherein the dopant contains a salt of a nitrosonium ion and an anion.

4. 2. The method for producing a p-type material for thermoelectric conversion according to claim 1, wherein the anion is selected from the group consisting of a hexafluorophosphate ion, a hexafluoroantimonate ion, and a tetrafluoroborate ion.

5. A thermoelectric conversion element comprising the p-type thermoelectric conversion material according to claim 1 or 2.

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