WO2015002029A1 - Thermoelectric conversion element - Google Patents

Abstract

　The present invention addresses the problem of providing a thermoelectric conversion element having excellent thermoelectric properties and an excellent conversion efficiency. A thermoelectric conversion element having: a thermoelectric conversion layer containing a dopant; and a pair of electrodes provided on the thermoelectric conversion layer. The average of the doping ratio in a first region, which is a region corresponding to half of the thermoelectric conversion layer on the side of one of the electrodes, is greater than the average of the doping ratio in a second region, which is a region corresponding to half of the thermoelectric conversion layer on the side of the other electrode.

Description

Thermoelectric conversion element

The present invention relates to a thermoelectric conversion element.

Thermoelectric conversion materials that can mutually convert thermal energy and electrical energy are used in thermoelectric conversion elements such as thermoelectric power generation elements and Peltier elements.
Thermoelectric power generation using such thermoelectric conversion materials and thermoelectric conversion elements can directly convert heat energy into electric power, does not require moving parts, operates at body temperature, power supplies for remote areas, power supplies for space, etc. It is used for.
Further, the figure of merit Z of the thermoelectric conversion element is represented by the following formula (A), and improvement of the thermoelectromotive force S and conductivity σ is important for improving the performance. In general, since the conductivity σ and the thermoelectromotive force S bring a contradictory effect, the power factor PF represented by S ² · σ is used for performance evaluation of the thermoelectric conversion element.
<Performance index>
Figure of merit ZT = S ² · σ · T / κ (A)
S (V / K): Thermoelectromotive force (Seebeck coefficient)
σ (S / m): conductivity κ (W / mK): thermal conductivity T (K): absolute temperature

In such a thermoelectric conversion element, a dopant is contained in the thermoelectric conversion layer in order to improve performance.
For example, Patent Document 1 describes “Thermoelectric semiconductor element characterized in that a Ge-rich region is formed at the junction between the Si-based thermoelectric semiconductor and the carbon electrode.”
Patent Document 2 describes “(A) a carbon nanotube, (B) a conductive polymer, and (C) a conductive composition containing an onium salt compound.”
Patent Document 3 discloses “(A) a carbon nanotube, (B) a conductive polymer, and (C) a conductive composition containing a compound that generates radicals upon irradiation with active energy rays or application of heat”. Is described.

JP 2007-243010 A International Publication No. 2012/133314 JP 2013-095821 A

However, when the inventor studied improvement of the thermoelectric conversion materials and the like described in Patent Documents 1 to 3, the thermoelectromotive force S and the power factor PF (hereinafter also referred to as “thermoelectric characteristics”) are further increased. Clarified that there is room for improvement.

Therefore, an object of the present invention is to provide a thermoelectric conversion element having excellent thermoelectric characteristics and excellent conversion efficiency.

As a result of diligent studies to solve the above problems, the present inventors have found that a thermoelectric conversion element excellent in thermoelectric characteristics can be produced by varying the amount of dopant on one electrode side and the other electrode side, The present invention has been completed.
That is, the present inventor has found that the above problem can be solved by the following configuration.

(1) 1st area | region which has a thermoelectric conversion layer containing a thermoelectric conversion material and a dopant, and a pair of electrodes provided on a thermoelectric conversion layer, and is a half area | region of the thermoelectric conversion layer used as one electrode side The thermoelectric conversion element in which the average doping rate of the dopant is larger than the average doping rate of the dopant in the second region, which is a half region of the thermoelectric conversion layer on the other electrode side.
(2) The thermoelectric conversion element according to (1), wherein the doping ratio in the first region is 3 to 10 mol%.
(3) The thermoelectric conversion element according to (1) or (2), wherein the thermoelectric conversion material of the thermoelectric conversion layer is an organic material.
(4) The thermoelectric conversion element according to any one of (1) to (3), wherein the dopant is an acid compound.
(5) The thermoelectric conversion element according to (4), wherein the acid compound is generated by irradiating the onium salt compound with heat or active energy rays.
(6) The thermoelectric conversion element according to any one of (1) to (5), wherein the doping rate of the thermoelectric conversion layer gradually increases from the other electrode side toward the one electrode side.
(7) The thermoelectric conversion element according to any one of (1) to (6), wherein a doping rate in a region in contact with one electrode is larger than a doping rate in a region in contact with the other electrode.
(8) The thermoelectric conversion element according to any one of (1) to (7), which has a junction with a heat source on the first region side of the thermoelectric conversion layer.

As shown below, according to the present invention, a thermoelectric conversion element having excellent thermoelectric characteristics and excellent conversion efficiency can be provided.

It is sectional drawing which shows typically an example of the thermoelectric conversion element of this invention. The arrows in FIG. 1 indicate the direction of the temperature difference applied when the element is used. It is sectional drawing which shows typically another example of the thermoelectric conversion element of this invention. The arrows in FIG. 2 indicate the direction of the temperature difference applied when the element is used. It is sectional drawing which shows typically another example of the thermoelectric conversion element of this invention. It is sectional drawing which shows typically the module using another example of the thermoelectric conversion element of this invention.

[Thermoelectric conversion element]
In the thermoelectric conversion element of the present invention, the dopant doping average in the first region which is a half region of the thermoelectric conversion layer on one electrode side is half the region of the thermoelectric conversion layer on the other electrode side. It is characterized by being larger than the average dopant doping rate in a certain second region. That is, the present invention is characterized in that the average density of the number of dopants in the first region, that is, the number density is larger than the average density of the dopants in the second region, and the amount of dopant in the first region is increased. More than the amount of dopant in the second region.
In the present invention, the layer structure of the thermoelectric conversion element is such a configuration, and one electrode side is a high temperature part, and the other electrode side is a low temperature part, thereby increasing the number of carriers on the high temperature part side. The number of carriers on the part side decreases, and the difference in the number of carriers between the high temperature part side and the low temperature part side increases. Due to the large difference in the number of carriers, the thermoelectromotive force S is increased, the power factor PF is increased, and the conversion efficiency is improved.
Hereinafter, the configuration of the thermoelectric conversion element of the present invention will be described in detail with reference to FIGS.

FIG. 1 is a schematic cross-sectional view schematically showing an example of the thermoelectric conversion element of the present invention.
The thermoelectric conversion element 10 shown in FIG. 1 includes a base material 12, a first electrode 14 and a second electrode 16 that are a pair of electrodes, and a thermoelectric conversion layer 18.

As shown in FIG. 1, the thermoelectric conversion element 10 includes a first electrode 14 and a second electrode 16 that are laminated at spaced positions on the substrate 12, and further, the first electrode 14 and the second electrode 16. A thermoelectric conversion layer 18 is laminated on the substrate 12 so as to cover the electrode 16.
The first electrode 14 and the second electrode 16 constitute an electrode pair.
Here, the thermoelectric conversion layer 18 has two regions, the first region 18a and the second region 18b, having different doping rates, that is, dopant densities, in the direction from the first electrode 14 to the second electrode 16. Do it. The first region 18a and the second region 18b are substantially the same size. That is, the amount of dopant in the first region 18a on the first electrode 14 side is larger than the amount of dopant in the second region 18b on the second electrode 16 side.
Note that, in the first region 18a and the second region 18b, the dopant is dispersed substantially uniformly.

Further, the thermoelectric conversion element 10 shown in FIG. 1 is a mode in which an electromotive force, that is, a voltage is obtained using a temperature difference in a direction indicated by an arrow, and is in contact with the heat source 50 on the first electrode 14 side. That is, in FIG. 1, one surface on the first electrode 14 side corresponds to the contact portion.

Here, the thermoelectric conversion element generates a temperature difference between the electrode pairs, thereby causing a difference in the number of carriers, that is, the density between one electrode side and the other electrode side, thereby generating a potential difference between the electrode pairs. Is.

In the present invention, as described above, in the direction from the first electrode 14 toward the second electrode 16, which is the direction in which the temperature difference is generated, the thermoelectric conversion layer 18 has two different dopant contents, that is, doping rates. By having a structure having a region, the first electrode 14 side, i.e., the first region 18a side, having a high dopant content is set as the high temperature portion side, and the second electrode 16 side, i.e., the first electrode, having a low dopant content. 2 side 18b side can be made into the low temperature part side.
This increases the number of carriers on the high-temperature part side, increases the difference in the number of carriers with the low-temperature part side, and can increase the difference more than the difference in the number of carriers due to the temperature. By increasing the potential difference, the thermoelectromotive force can be improved. Therefore, thermoelectric characteristics can be improved and conversion efficiency can be improved.

The thermoelectric conversion element 10 shown in FIG. 1 may have other layers such as a protective layer and a second substrate that are laminated on the surface of the thermoelectric conversion layer 18 opposite to the substrate 12.
Moreover, the thermoelectric conversion layer 18 should just contain the dopant in the 1st area | region 18a at least, and the structure which does not contain a dopant in the 2nd area | region 18b may be sufficient as it.

Here, in the embodiment shown in FIG. 1, the thermoelectric conversion layer 18 has two regions in which the doping rate, that is, the average density of the dopant is different, in the direction parallel to the base material 12. It is good also as a structure which has the area | region where dope rate, ie, the average density of a dopant, differs in the direction perpendicular | vertical to a base material.

FIG. 2 is a schematic cross-sectional view schematically showing another example of the thermoelectric conversion element of the present invention.
The thermoelectric conversion element 20 shown in FIG. 2 is an element having a base material 22, a first electrode 24, a thermoelectric conversion layer 28, and a second electrode 26 in this order.
Here, in the direction from the first electrode 24 to the second electrode 16, that is, in the direction perpendicular to the main surface of the base material 22, the thermoelectric conversion layer 28 has two regions having different doping rates, that is, average dopant densities, The first region 28a and the second region 28b are provided. The first region 28a and the second region 28b have substantially the same size. Further, the amount of dopant in the first region 28a on the first electrode 24 side is larger than the amount of dopant in the second region 28b on the second electrode 26 side. In addition, the dopant is dispersed substantially uniformly in each of the first region 28a and the second region 28b.

Further, the thermoelectric conversion element 20 shown in FIG. 2 is a mode in which an electromotive force, that is, a voltage is obtained by using a temperature difference in the direction indicated by the arrow, and the first electrode 24 side through the heat source 50 and the base material 22. Touched with. That is, in FIG. 2, the lower surface of the base material 22 that is the surface opposite to the surface on which the first electrode 24 is laminated corresponds to the contact portion.

As described above, even when the electrode pair and the thermoelectric conversion layer 28 are sequentially stacked in the direction perpendicular to the base material 22, the first region 28 a side, which is the first electrode 24 side, has a large dopant content. Can be the high temperature portion side, and the second region 28b side, which is the second electrode 26 side with a low dopant content, can be the low temperature portion side. This increases the number of carriers on the high-temperature part side, increases the difference in the number of carriers with the low-temperature part side, and can increase the difference more than the difference in the number of carriers due to the temperature. By increasing the potential difference, the thermoelectromotive force can be improved. Therefore, thermoelectric characteristics can be improved and conversion efficiency can be improved.

Moreover, in the aspect shown in FIG. 1, although the thermoelectric conversion layer was set as the structure which has two area | regions with different dope rates, this invention is not limited to this, 3 or more with different dope rates It may have a region. At that time, it is preferable that the doping rate gradually decreases from one electrode to the other electrode.

FIG. 3 is a schematic cross-sectional view schematically showing another example of the thermoelectric conversion element of the present invention.
The thermoelectric conversion element 40 shown in FIG. 3 includes a base material 42, a first electrode 44, a second electrode 46, and a thermoelectric conversion layer 48.
As shown in FIG. 3, the thermoelectric conversion element 40 includes a first electrode 44 and a second electrode 46 that are laminated at spaced positions on the base material 42, and further, the first electrode 44 and the second electrode 46. A thermoelectric conversion layer 48 is laminated on the base material 42 so as to cover the electrode 46.

Here, the thermoelectric conversion layer 48 includes five regions 49a to 49e having different doping rates in the direction from the first electrode 44 to the second electrode. Each region 49a to 49e has substantially the same size. Further, the doping rate in the region 49a on the first electrode 44 side is the highest, the doping rate is lower in the region on the second electrode 46 side, and the doping rate in the region 49e on the second electrode 46 side is the lowest. .
Therefore, in the thermoelectric conversion element 40, the average doping ratio in the first region 48a, which is the half region of the thermoelectric conversion layer 48, which includes the regions 49a, 49b, and 49c, is approximately half that of the region 49c. And an average doping ratio in the second region 48b, which is a half region of the thermoelectric conversion layer 48, including the region 49d and the region 49e.

Moreover, the thermoelectric conversion element 40 shown in FIG. 3 is an aspect which obtains an electromotive force, ie, voltage, using the temperature difference of the direction shown by the arrow.

Thus, even in the case of a configuration having three or more regions having different doping rates, the first region 48a side, which is the first electrode 44 side, which has a high dopant content, is the high temperature part side, and the dopant content The second region 48b side, which is the second electrode 46 side with a small amount, can be the low temperature part side. This increases the number of carriers on the high-temperature part side, increases the difference in the number of carriers with the low-temperature part side, and can increase the difference more than the difference in the number of carriers due to the temperature. By increasing the potential difference, the thermoelectromotive force can be improved. Therefore, thermoelectric characteristics can be improved and conversion efficiency can be improved.

Here, in the thermoelectric conversion element 40 shown in FIG. 3, the doping rate in the thermoelectric conversion layer 48 is configured to gradually decrease from the first electrode 44 toward the second electrode 46, but this is not limitative. If the constitution is such that the doping rate in the first region 48a, which is a half region of the thermoelectric conversion layer 48, is larger than the doping rate in the second region 48b, which is a half region of the thermoelectric conversion layer 48, The relationship between the average densities of the regions 49a to 49e is not particularly limited. However, it is preferable to gradually reduce the size from one electrode side to the other electrode side.
Further, the thermoelectric conversion layer 48 may have a region that does not contain a dopant as long as the dopant is contained in at least the region 49 a on the first electrode 44 side.

In the thermoelectric conversion element 40 shown in FIG. 3, the regions 49a to 49e have substantially the same size, but the present invention is not limited to this, and the sizes of the regions may be different.
Moreover, it is preferable that the dope rate in the area | region which contact | connects one electrode, ie, the average density of a dopant, is larger than the dope rate in the area | region which touches the other electrode, ie, the average density of a dopant. That is, in the example shown in FIG. 3, the doping rate in the region 49 a in contact with the first electrode 44 is preferably larger than the doping rate in the region 49 e in contact with the second electrode 46.

In the present invention, as shown in FIG. 4, a base material 31 common to the thermoelectric conversion elements 30 adjacent to each other is used, and the second electrode 33 in one thermoelectric conversion element 30 and other thermoelectric elements adjacent to the second electrode 33 are used. It is good also as the module 300 which connected each thermoelectric conversion element 30 in series by electrically connecting with the 1st electrode 32 of the conversion element 30. FIG.
The thermoelectric conversion element 30 shown in FIG. 4 is similar to the thermoelectric conversion element 20 shown in FIG. 2 in that the first electrode 32 and the second electrode that are electrode pairs in the direction perpendicular to the main surface of the substrate 31. 33 are stacked so as to sandwich the thermoelectric conversion layer 34, the thermoelectric conversion layer 34 has two regions with different doping rates, the first region 34 a and the first region 34 in the direction perpendicular to the main surface of the base material 31. 2 regions 34b. In addition, the doping rate in the first region 34a on the first electrode 32 side, that is, the amount of dopant is larger than the doping rate in the second region 34b on the second electrode 33 side, that is, the amount of dopant.

Next, each layer such as a base material, an electrode, and a thermoelectric conversion layer constituting the thermoelectric conversion element of the present invention will be described in detail.

<Base material>
Although the base material which the thermoelectric conversion element of this invention has is not specifically limited, It is preferable to select the base material which is hard to be influenced at the time of formation of an electrode or the formation of a thermoelectric conversion layer.
Examples of such a substrate include glass, transparent ceramics, metal, and plastic film. Among these, a plastic film is preferable from the viewpoint of cost and flexibility.
Specific examples of the plastic film include polyethylene terephthalate, polyethylene isophthalate, polyethylene naphthalate, polybutylene terephthalate, poly (1,4-cyclohexylenedimethylene terephthalate), polyethylene-2,6-phthalenedicarboxylate, and bisphenol A. Polyester film such as polyester film with iso and terephthalic acid; polycycloolefin film such as ZEONOR film (manufactured by ZEON Corporation), ARTON film (manufactured by JSR Corporation), Sumilite FS1700 (manufactured by Sumitomo Bakelite Corporation); Kapton ( Polyimide films such as Toray DuPont Co., Ltd., Apical (Kaneka Co., Ltd.), Ubilex (Ube Industries Co., Ltd.), Pomilan (Arakawa Chemical Industries Co., Ltd.), etc. Rum; Polycarbonate films such as Pure Ace (manufactured by Teijin Chemicals Ltd.) and Elmec (manufactured by Kaneka Corporation); Polyether ether ketone films such as Sumilite FS1100 (manufactured by Sumitomo Bakelite Co., Ltd.); Polyphenyl sulfide film; and the like.
Of these, commercially available polyethylene terephthalate, polyethylene naphthalate, various polyimides, polycarbonate films, and the like are preferable from the viewpoints of availability, heat resistance of 100 ° C. or higher, economy, and effects.

In the present invention, the thickness of the substrate can be appropriately selected according to the purpose of use. For example, when a plastic film is used, it is generally preferable to use a substrate having a thickness of 5 to 500 μm. .

<Electrode>
Although the electrode which the thermoelectric conversion element of this invention has is not specifically limited, As a material, specifically, transparent electrodes, such as ITO and ZnO; Metal electrodes, such as silver, copper, gold | metal | money, aluminum; CNT, graphene Carbon materials such as: organic materials such as PEDOT / PSS; conductive paste in which conductive fine particles such as silver and carbon black are dispersed; conductive paste containing metal nanowires such as silver, copper and aluminum.

<Thermoelectric conversion layer>
The thermoelectric conversion layer which the thermoelectric conversion element of this invention has will not be specifically limited if a dopant is contained.
The thermoelectric conversion layer contains at least a thermoelectric conversion material and a dopant. The thermoelectric conversion layer may contain a polymer material or an inorganic material.

(Thermoelectric conversion material)
The thermoelectric conversion material contained in the thermoelectric conversion layer used in the thermoelectric conversion element of the present invention is not particularly limited, and conventionally known organic materials such as conductive polymers and conductive nanocarbon materials, or nanometallic materials. Thermoelectric conversion materials such as (metal-containing conductive nanomaterials) and inorganic materials such as inorganic oxide semiconductors can be used. In the present invention, it is preferable to use an organic material such as a conductive polymer or a conductive nanocarbon material as the thermoelectric conversion material, and it is particularly preferable to use a conductive polymer. Moreover, these may be used individually by 1 type and may use 2 or more types together.

(Conductive polymer)
In the present invention, the conductive polymer used as the thermoelectric conversion material is not particularly limited, and a conventionally known conductive polymer can be used.
For example, as the conductive polymer, a polymer compound having a conjugated molecular structure can be used. Here, the polymer having a conjugated molecular structure is a polymer having a structure in which a single bond and a double bond are alternately connected in a carbon-carbon bond on the main chain of the polymer. Further, the conductive polymer used in the present invention is not necessarily a high molecular weight compound, and may be an oligomer compound.

Such conjugated polymers include thiophene compounds, pyrrole compounds, aniline compounds, acetylene compounds, p-phenylene compounds, p-phenylene vinylene compounds, p-phenylene ethynylene compounds, p-full Olenylene vinylene compound, polyacene compound, polyphenanthrene compound, metal phthalocyanine compound, p-xylylene compound, vinylene sulfide compound, m-phenylene compound, naphthalene vinylene compound, p-phenylene oxide compound, phenylene Sulfuric compounds, furan compounds, selenophene compounds, azo compounds, metal complex compounds, and derivatives having substituents introduced into these compounds as monomers, and conjugated compounds having repeating units derived from the monomers Min And the like.

As such a conductive polymer, for example, those described in paragraphs [0011] to [0040] of JP2013-084947A can be appropriately employed.

(Conductive nanocarbon material)
In the present invention, the conductive nanocarbon material used as the thermoelectric conversion material is not particularly limited, and a conventionally known nanocarbon material (carbon-containing conductive nanomaterial) can be used.
In addition, the size of the conductive nanomaterial is not particularly limited as long as it is a nanosize of less than 1 μm. For example, for carbon nanotubes and carbon nanofibers described later, the average minor axis is nanosized, for example, the average minor axis is What is necessary is just 500 nm or less.

Specific examples of the conductive nanocarbon material include carbon nanotubes (hereinafter also referred to as “CNT”), carbon nanofibers, graphite, graphene, carbon nanoparticles, and the like. Or two or more of them may be used in combination.
Of these, CNT is preferred because of its better thermoelectric properties.
Examples of the CNT include, for example, paragraphs [0017] to [0021] of International Publication No. 2012/133314 (Patent Document 1) and [0018] to [0022] of JP2013-095820 (Patent Document 2). ] Those described in the paragraph can be adopted as appropriate.
The solid content of the thermoelectric conversion material composition is preferably 0.01 to 10%, more preferably 0.05 to 5%.

(Nano metal material)
In this invention, the nano metal material utilized as a thermoelectric conversion material is not specifically limited, Conventionally well-known nano metal materials, such as metal nanowire, can be used.

(Inorganic oxide semiconductor)
In the present invention, the inorganic oxide semiconductor used as the thermoelectric conversion material is not particularly limited, and a conventionally known inorganic oxide semiconductor such as an inorganic oxide semiconductor containing indium can be used.
As such an inorganic oxide semiconductor, for example, those described in paragraph [0044] of JP2013-102155A can be appropriately employed.

(Dopant)
The dopant contained in the thermoelectric conversion layer used in the thermoelectric conversion element of the present invention is not particularly limited and includes conventionally known acid compounds, oxidizing agents, acidic compounds, electron acceptor compounds, transition metal compounds, and the like. 1 type may be used independently and 2 or more types may be used together.

As the acid compound used as the dopant, for example, a sulfonic acid compound, a carboxylic acid compound, a phosphoric acid compound, or the like can be used. Alternatively, an acid compound generated by irradiating a photoacid generator such as an onium salt compound with heat or active energy rays can be used.

Examples of the onium salt compound that generates an acid compound upon application of energy such as irradiation of active energy rays such as radiation or electromagnetic waves or application of heat include sulfonium salts, iodonium salts, ammonium salts, carbonium salts, phosphonium salts, and the like. Of these, sulfonium salts, iodonium salts, ammonium salts, and carbonium salts are preferable, and sulfonium salts, iodonium salts, and carbonium salts are more preferable. Examples of the anion moiety constituting the salt include a strong acid counter anion.

As such onium salt compounds, for example, those described in paragraphs [0044] to [0068] of JP-A-2013-089798 can be appropriately employed.

Examples of the oxidizing agent, acidic compound, electron acceptor compound, and transition metal compound that can be used as a dopant include those described in paragraphs [0069] to [0083] of JP2013-089798A. It can be adopted as appropriate.

In the present invention, it is preferable to use an acid compound as a dopant because it can be efficiently doped without causing a side reaction, and the thermoelectric characteristics are improved. In particular, it is preferable to use an acid compound generated by energy application such as irradiation of active energy rays or application of heat to the onium salt compound in terms of easy adjustment of the dopant density and easy production.

In the present invention, when the molar ratio between the material to be doped and the dopant in the thermoelectric conversion material is a doping ratio, the average value of the doping ratio in the first region of the thermoelectric conversion layer satisfies 3 mol% to 10 mol%. It is preferable. As a result, the number of carriers on the high temperature side can be increased to increase the potential difference generated between the electrode pairs, thereby improving the thermoelectromotive force.
In the present specification, a numerical range represented by using “to” means a range including numerical values described before and after “to” as a lower limit value and an upper limit value.

Further, the difference between the doping rate in the first region and the doping rate in the second region of the thermoelectric conversion layer is preferably 3 mol% to 10 mol%. Thereby, the difference in the number of carriers between the high temperature part side and the low sound part side can be increased to increase the potential difference generated between the electrode pairs, thereby improving the thermoelectromotive force.

In addition, when using an acid compound generated by irradiating an onium salt compound with heat or active energy rays as a dopant, when a substance serving as a dopant is not added directly, that is, when the amount of dopant cannot be measured directly The molar ratio between a dopant such as an onium salt compound and a doping object is regarded as a doping rate.

(Other ingredients)
The thermoelectric conversion layer of the present invention may contain other components in addition to the thermoelectric conversion material and the dopant.
For example, you may contain antioxidant, a light stabilizer, a heat stabilizer, a plasticizer, etc. suitably. The content of these components is preferably 5% by mass or less based on the total mass of the material.
As antioxidants, Irganox 1010 (manufactured by Nippon Ciga-Beegie Co., Ltd.), Sumilizer GA-80 (manufactured by Sumitomo Chemical Co., Ltd.), Sumilizer GS (manufactured by Sumitomo Chemical Co., Ltd.), Sumilizer GM (manufactured by Sumitomo Chemical Co., Ltd.) ) And the like.
Examples of the light resistance stabilizer include TINUVIN 234 (manufactured by BASF), CHIMASSORB 81 (manufactured by BASF), and Siasorb UV-3853 (manufactured by Sun Chemical Co., Ltd.).
Examples of the heat stabilizer include IRGANOX 1726 (manufactured by BASF).
Examples of the plasticizer include Adeka Sizer RS (manufactured by Adeka Corporation).

(solvent)
In preparing the thermoelectric conversion layer, a solvent can be appropriately used.
The solvent should just be able to disperse | distribute or melt | dissolve the composition of thermoelectric conversion layers, such as a thermoelectric conversion material and a dopant favorably, and can use water, an organic solvent, and these mixed solvents. Preferred are organic solvents, halogen solvents such as alcohol and chloroform, polar organic solvents such as DMF, NMP, and DMSO, and aromatic solvents such as chlorobenzene, dichlorobenzene, benzene, toluene, xylene, pyridine, tetrahydronaphthalene, and mesitylene Solvents, ketone solvents such as cyclohexanone, acetone and methyl ethyl ketone, and ether solvents such as diethyl ether, THF, t-butyl methyl ether, dimethoxyethane and diglyme are preferably used.

The solvent is preferably degassed in advance. The dissolved oxygen concentration in the solvent is preferably 10 ppm or less. Examples of the degassing method include a method of irradiating ultrasonic waves under reduced pressure, a method of bubbling an inert gas such as argon, and the like.
Similarly, the solvent is preferably dehydrated in advance. The amount of water in the solvent is preferably 1000 ppm or less, and more preferably 100 ppm or less. As a dehydration method, a known method such as a method using molecular sieve or distillation can be used.
The solvent may be used in an appropriate amount depending on the kind of the material, but is preferably 90 to 99.99% by mass, more preferably 95 to 99.95% by mass with respect to the total mass of the solution. 98 to 99.9% by mass is more preferable.

(Method for forming thermoelectric conversion layer)
The method for forming the thermoelectric conversion layer of the thermoelectric conversion element of the present invention is not particularly limited, but a solution in which the composition of the thermoelectric conversion layer is dispersed or dissolved in a solvent, that is, a composition for forming a thermoelectric conversion layer is applied on a substrate. And a thermoelectric conversion layer can be formed by forming into a film. In addition, when a dopant is not added directly to a solution but a dopant is added, a thermoelectric conversion layer can be formed by irradiating with heat or active energy rays after film formation. it can.

The preparation method of the composition for forming a thermoelectric conversion layer is not particularly limited, and may be prepared by mixing a thermoelectric conversion material, a dopant or a dopant, and other components as required. You may use a solvent suitably. The preparation can be carried out at ordinary temperature and pressure using an ordinary mixing apparatus or the like. For example, each component may be prepared by dissolving or dispersing in a solvent by stirring and shaking. Sonication may be performed to promote dissolution and dispersion.

The film forming method is not particularly limited. For example, known coating methods such as spin coating, extrusion die coating, blade coating, bar coating, screen printing, stencil printing, roll coating, curtain coating, spray coating, dip coating, and inkjet method. Can be used.
Moreover, after application | coating, a drying process is performed as needed. For example, the solvent can be volatilized and dried by blowing hot air.

In the present invention, the thickness of the thermoelectric conversion layer is preferably 0.1 μm to 1000 μm, more preferably 1 μm to 100 μm, from the viewpoint of imparting a temperature difference.

When the composition for forming a thermoelectric conversion layer contains a photoacid generator such as an onium salt compound as a dopant, heating or irradiation with active energy rays is performed for doping after film formation. By this treatment, an acid compound is generated from the onium salt compound. For example, the acid compound protonates the conductive polymer, so that the conductive polymer is doped with a positive charge.
Active energy rays include radiation and electromagnetic waves, and radiation includes particle beams (high-speed particle beams) and electromagnetic radiation. As particle beams, alpha rays (α rays), beta rays (β rays), proton beams, electron beams that accelerate electrons with an accelerator regardless of nuclear decay, deuteron charged particles, and uncharged particles A certain neutron beam, a cosmic ray, etc. are mentioned, As an electromagnetic radiation, a gamma ray (gamma ray) and an X ray (X ray, soft X ray) are mentioned. Examples of electromagnetic waves include radio waves, infrared rays, visible rays, near ultraviolet rays, far ultraviolet rays, extreme ultraviolet rays, X-rays, and gamma rays. The line type used in the present invention is not particularly limited, and for example, an electromagnetic wave having a wavelength near the maximum absorption wavelength of the onium salt compound to be used may be appropriately selected.
Of these active energy rays, ultraviolet rays, visible rays, and infrared rays are preferable from the viewpoint of doping effect and safety, and ultraviolet rays are more preferable. Specifically, the light beam has a maximum absorption at 240 to 1100 nm, preferably 300 to 850 nm, more preferably 350 to 670 nm.

Here, as described above, in the present invention, the thermoelectric conversion layer is formed so that the doping rate, that is, the density of the dopant is different for each region.
As a method of forming a thermoelectric conversion layer having a different doping rate, that is, a dopant density, a region having a different dopant density in a direction parallel to the main surface of the substrate is used, as in the thermoelectric conversion element shown in FIGS. In the case of having a thermoelectric conversion layer, a thermoelectric conversion layer having regions with different dopant densities is formed by forming a composition for forming a thermoelectric conversion layer having a different dopant content in each desired region by masking. be able to.
Alternatively, when a photoacid generator such as an onium salt compound is contained and doping is performed by irradiation with heat or active energy rays, a desired composition is formed after forming the thermoelectric conversion layer forming composition containing the dopant. By performing doping by irradiating only the region with heat or active energy rays, a thermoelectric conversion layer having regions with different dopant densities can be formed.

Moreover, when forming the thermoelectric conversion layer which has an area | region where dope rates differ in the direction perpendicular | vertical to a base material like the thermoelectric conversion element shown in FIG. 2, the composition for thermoelectric conversion layer formation from which the content rate of a dopant differs The thermoelectric conversion layers having regions with different doping rates can be formed by sequentially laminating and forming films. Alternatively, when a doping agent is included, layers having different doping rates may be formed by performing irradiation by irradiating heat or active energy rays from one surface.

Hereinafter, although an Example demonstrates this invention further in detail, this invention is not limited to these.

[Example 1]
<Production of thermoelectric conversion element>
As Example 1, a thermoelectric conversion element having the form shown in FIG.
As a thermoelectric conversion material, a conductive polymer [poly-3-hexylthiophene (molecular weight: Mw 20000, manufactured by Aldrich)] was used, and 10 mg (0.059 mol in terms of monomer) of this conductive polymer, and single-walled CNT [ 4 mg of KH Chemical lot number: HM-100208] was added to 20 ml of orthodichlorobenzene and stirred for 20 minutes with a mechanical stirring device. Thereafter, a dispersion A was prepared by ultrasonic dispersion at 30 ° C. for 40 minutes using an ultrasonic cleaner (US-150, manufactured by AS ONE Corporation).
Next, 4 mg (0.0039 mol) of the compound represented by [Chemical Formula 1] which is an onium salt compound as a dopant is added to the prepared dispersion A at room temperature to prepare dispersion B which is a composition for forming a thermoelectric conversion layer. did.
Here, the molar ratio, that is, the doping ratio, between the conductive polymer as the doping target and the onium salt compound as the doping agent was 6.6 mol%.

On the other hand, a glass substrate having a thickness of 1.1 mm and a size of 40 mm × 50 mm was used as the base material. This substrate was ultrasonically cleaned in acetone and then subjected to UV-ozone treatment for 10 minutes.
Thereafter, gold having a size of 30 mm × 5 mm and a thickness of 10 nm was formed as a first electrode and a second electrode on both ends of the substrate.

The prepared chloroform solution of dispersion B is affixed with a Teflon (registered trademark) frame on the substrate on which the electrodes are formed, and the solution is poured into the frame and dried on a hot plate at 60 ° C. for 1 hour. After drying, the frame was removed, and a conductive film having a thickness of about 1.1 μm was formed.
After that, half of the film formed using an ultraviolet irradiation machine (ECS-401GX manufactured by Eye Graphics Co., Ltd.) is irradiated with ultraviolet light at a light amount of 200 mJ / cm ² , so that only the half region, ie, the first region is doped. The thermoelectric conversion layer was formed and the thermoelectric conversion element of this invention shown by FIG. 1 was produced.

[Example 2]
Dispersion C, which is a composition for forming a thermoelectric conversion layer, was prepared in the same manner as in Example 1 except that 1.4 mg (0.0055 mol) of iodine was used in place of the onium salt compound as a dopant.
Here, the doping rate in the first region was 9.3 mol%.
Further, a dispersion similar to the dispersion C, that is, the dispersion A was prepared except that no iodine was contained.

Next, first, a portion to be the first region, that is, a region other than the first electrode side is masked, and the dispersion C is applied and dried on the base material to form the first region of the thermoelectric conversion layer. A film was formed. Thereafter, the second region, that is, the region other than the second electrode side is masked, and the dispersion A is applied to the substrate and dried to form the second region of the thermoelectric conversion layer. The thermoelectric conversion layer of Example 2 was produced by forming a thermoelectric conversion layer.
In addition, the used base material is the same as that of Example 1, and the first electrode and the second electrode are formed in advance.

Example 3
A thermoelectric conversion element was produced in the same manner as in Example 2 except that 0.73 mg (0.0045 mol) of iron (III) chloride was used instead of iodine as a dopant.
Here, the doping rate in the first region was 7.6 mol%.

Example 4
A thermoelectric conversion element was produced in the same manner as in Example 2, except that 0.7 mg (0.003 mol) of camphorsulfonic acid was used as the dopant instead of iodine.
Here, the doping rate in the first region was 5.1 mol%.

Example 5
A thermoelectric conversion element was produced in the same manner as in Example 1 except that the amount of the onium salt compound in the dispersion B was changed so that the doping rate of the first region was 2 mol%.

Example 6
A thermoelectric conversion element was produced in the same manner as in Example 1 except that the amount of the onium salt compound in the dispersion B was changed so that the doping rate in the first region was 3 mol%.

Example 7
A thermoelectric conversion element was produced in the same manner as in Example 1 except that the amount of the onium salt compound in the dispersion B was changed so that the doping ratio of the first region was 10 mol%.

Example 8
A thermoelectric conversion element was produced in the same manner as in Example 1 except that the amount of the onium salt compound in the dispersion B was changed and the doping rate of the first region was changed to 12 mol%.

[Comparative Example 1]
A thermoelectric conversion element was produced in the same manner as in Example 1 except that the entire surface was doped by ultraviolet irradiation.

[Comparative Example 2]
A thermoelectric conversion element was produced in the same manner as in Example 2 except that the conductive film containing the dopant was formed on the entire surface of the substrate.

[Comparative Example 3]
A thermoelectric conversion element was produced in the same manner as in Example 3 except that the conductive film containing the dopant was formed on the entire surface of the substrate.

[Comparative Example 4]
A thermoelectric conversion element was produced in the same manner as in Example 4 except that the conductive film containing the dopant was formed on the entire surface of the substrate.

The power factor of each manufactured thermoelectric conversion element was evaluated by the following method.

[Measurement of conductivity]
Measure the surface resistivity (Ω / □) of the thermoelectric conversion layer using a low resistivity meter (Loresta GP manufactured by Mitsubishi Chemical Analytech Co., Ltd.), and measure the film thickness (cm) using a stylus type film thickness meter. The electrical conductivity σ (S / cm) was calculated from the following formula (1).
(Conductivity σ) = 1 / ((surface resistivity) × (film thickness)) Formula (1)

[Measurement of thermoelectromotive force (Seebeck coefficient)]
Using a thermoelectric property measuring apparatus (MODEL RZ2001i manufactured by Ozawa Scientific Co., Ltd.), the first region side, that is, the first electrode side is installed on the high temperature side, and measurement is performed in an air atmosphere at a temperature of 100 ° C. The power S and Seebeck coefficient (μV / K) were measured.

[Calculation of power factor]
From the measured electrical conductivity σ and thermoelectromotive force S, the power factor PF (μW / mK ² ) was calculated from the following formula (2).
Power factor PF = S ² · σ Equation (2)
Table 1 shows the calculated power factor PF.

From the results shown in Table 1, the doping rate in the first region on the first electrode side of the thermoelectric conversion layer, that is, the dopant density, the doping rate in the second region on the second electrode side, that is, the dopant Examples 1 to 8, which are the thermoelectric conversion elements of the present invention having a density higher than the density, have a higher power factor PF than the comparative examples 1 to 4 in which the entire thermoelectric conversion layer contains the dopant uniformly, and have thermoelectric characteristics. It can be seen that the efficiency of thermoelectric conversion is improved.
From the comparison of Examples 1 to 4, when an acid compound is used as a dopant, the thermoelectric characteristics are improved, and furthermore, when an acid compound generated by irradiating the onium salt compound with heat or active energy rays is used. In addition, it can be seen that the thermoelectric characteristics become better.
Further, it can be seen from the comparison between Examples 1 and 5 to 8 that the thermoelectric characteristics are better when the doping rate is 3 to 10 mol%.
The effects of the present invention are clear from the above results.

10, 20, 30, 40 Thermoelectric conversion element 12, 22, 31, 42 Base material 14, 24, 32, 44 First electrode 16, 26, 33, 46 Second electrode 18, 28, 34, 48 Thermoelectric conversion Layer 18a, 28a, 34a, 48a First region 18b, 28b, 34b, 48b Second region 49a-49e Region 50 Heat source 300 Module

Claims (8)

A thermoelectric conversion layer containing a thermoelectric conversion material and a dopant, and a pair of electrodes provided on the thermoelectric conversion layer,
The second region in which the average doping ratio of the dopant in the first region which is a half region of the thermoelectric conversion layer on one electrode side is a half region of the thermoelectric conversion layer on the other electrode side The thermoelectric conversion element characterized by being larger than the average of the doping rate of the said dopant in. The thermoelectric conversion element according to claim 1, wherein the doping ratio in the first region is 3 to 10 mol%. The thermoelectric conversion element according to claim 1 or 2, wherein the thermoelectric conversion material of the thermoelectric conversion layer is an organic material. The thermoelectric conversion element according to any one of claims 1 to 3, wherein the dopant is an acid compound. The thermoelectric conversion element according to claim 4, wherein the acid compound is generated by irradiating the onium salt compound with heat or active energy rays. The thermoelectric conversion element according to any one of claims 1 to 5, wherein the doping rate of the thermoelectric conversion layer gradually increases from the other electrode side toward the one electrode side. The thermoelectric conversion element according to any one of claims 1 to 6, wherein the doping rate in a region in contact with the one electrode is larger than the doping rate in a region in contact with the other electrode. The thermoelectric conversion element according to any one of claims 1 to 7, further comprising a contact portion with a heat source on the first region side of the thermoelectric conversion layer.

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