U.S. patent application number 15/451073 was filed with the patent office on 2017-07-06 for thermoelectric conversion material, thermoelectric conversion element, article for thermoelectric power generation and power supply for sensor.
This patent application is currently assigned to FUJIFILM Corporation. The applicant listed for this patent is FUJIFILM Corporation. Invention is credited to Ryo HAMASAKI, Yoichi MARUYAMA, Ryo NISHIO, Kimiatsu NOMURA.
Application Number | 20170194547 15/451073 |
Document ID | / |
Family ID | 51623699 |
Filed Date | 2017-07-06 |
United States Patent
Application |
20170194547 |
Kind Code |
A1 |
NISHIO; Ryo ; et
al. |
July 6, 2017 |
THERMOELECTRIC CONVERSION MATERIAL, THERMOELECTRIC CONVERSION
ELEMENT, ARTICLE FOR THERMOELECTRIC POWER GENERATION AND POWER
SUPPLY FOR SENSOR
Abstract
A thermoelectric conversion element (1) having, on a substrate
(12), a first electrode (13), a thermoelectric conversion layer
(14), and a second electrode (15), wherein a nano conductive
material and a low band gap material are contained in the
thermoelectric conversion layer (14); an article for thermoelectric
power generation and a power supply for a sensor using the
thermoelectric conversion element (1); and a thermoelectric
conversion material containing the nano conductive material and the
low band gap material.
Inventors: |
NISHIO; Ryo;
(Ashigarakami-gun, JP) ; HAMASAKI; Ryo;
(Ashigarakami-gun, JP) ; NOMURA; Kimiatsu;
(Ashigarakami-gun, JP) ; MARUYAMA; Yoichi;
(Ashigarakami-gun, JP) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
FUJIFILM Corporation |
Tokyo |
|
JP |
|
|
Assignee: |
FUJIFILM Corporation
Tokyo
JP
|
Family ID: |
51623699 |
Appl. No.: |
15/451073 |
Filed: |
March 6, 2017 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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14862264 |
Sep 23, 2015 |
9660166 |
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15451073 |
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PCT/JP2014/056869 |
Mar 14, 2014 |
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14862264 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
H01L 35/14 20130101;
C08G 2261/3243 20130101; C08G 2261/1426 20130101; C08G 2261/55
20130101; H01L 35/32 20130101; C08G 2261/3244 20130101; C08G
2261/228 20130101; H01L 35/24 20130101; C08G 2261/3223 20130101;
C08G 2261/148 20130101; C08G 61/124 20130101; C08G 2261/3162
20130101; C08G 61/12 20130101; H01L 35/20 20130101; C08G 2261/312
20130101; C08G 2261/124 20130101; C08G 61/126 20130101; C08G
2261/1412 20130101; C08G 2261/1428 20130101; C08G 2261/3221
20130101; C08G 2261/11 20130101; C08G 2261/1424 20130101; C08G
2261/3142 20130101 |
International
Class: |
H01L 35/24 20060101
H01L035/24; C08G 61/12 20060101 C08G061/12 |
Foreign Application Data
Date |
Code |
Application Number |
Mar 29, 2013 |
JP |
2013-072148 |
Jul 31, 2013 |
JP |
2013-159268 |
Claims
1. A thermoelectric conversion element comprising, on a substrate,
a first electrode, a thermoelectric conversion layer, and a second
electrode, wherein a nano conductive material and a low band gap
material are contained in the thermoelectric conversion layer, and
an optical band gap of the low band gap material is 0.1 eV or more
and 1.1 eV or less, and the low band gap material is a
non-polymeric metal complex compound represented by Formula (3B):
##STR00047## wherein, in Formula (3B), M is a metal atom selected
from the group consisting of Ni, Fe, Cu and Sn, or a metal ion
thereof; when M is a metal ion, the compound represented by Formula
(3B) may have an arbitrary counter ion; X.sup.a11 and X.sup.a12
each independently represent a hetero atom; at least one of
X.sup.a11 and X.sup.a12 is a sulfur atom or an oxygen atom; nx
represents an integer of 0 or more; R.sup.a11 to R.sup.a14,
R.sup.b11 and Rb.sup.12 each independently represent a substituent
selected from the group consisting of an alkyl group, a cycloalkyl
group, an alkenyl group, an alkynyl group, an aromatic hydrocarbon
ring group, an aromatic heterocyclic group, an oxazolyl group, a
benzoxazolyl group, a thiazolyl group, an isoxazolyl group, an
isothiazolyl group, a furazanyl group, a thienyl group, a quinolyl
group, a benzofuryl group, a dibenzofuryl group, a benzothienyl
group, a dibenzothienyl group, an indolyl group, a carbazolyl
group, a carbolinyl group, a diazacarbazolyl group, a quinoxalinyl
group, a pyridazinyl group, a triazinyl group, a quinazolinyl
group, a phthalazinyl group, a borole group, and an azaborine
group, a heterocyclic group, an alkoxy group, a cycloalkoxy group,
an aryloxy group, an alkylthio group, a cycloalkylthio group, an
arylthio group, an alkoxycarbonyl group, an aryloxycarbonyl group,
a sulfamoyl group, an acyl group, an acyloxy group, an amide group,
a carbamoyl group, an ureido group, a sulfinyl group, an
alkylsulfonyl group, an arylsulfonyl group or a heteroarylsulfonyl
group, an amino group, a cyano group, a nitro group, a hydroxyl
group, a mercapto group, and a silyl group.
2. The thermoelectric conversion element according to claim 1,
wherein the thermoelectric conversion layer further contains at
least one polymer in addition to the nano conductive material and
the low band gap material selected from the group consisting of a
conjugated polymer and a non-conjugated polymer.
3. The thermoelectric conversion element according to claim 1,
wherein the nano conductive material is at least one kind of
material selected from the group consisting of a carbon nanotube, a
carbon nanofiber, graphite, graphene, carbon nanoparticles and a
metal nanowire.
4. The thermoelectric conversion element according to claim 1,
wherein the nano conductive material is a carbon nanotube.
5. The thermoelectric conversion element according to claim 1,
wherein the first electrode and the second electrode each
independently are formed by aluminum, gold, silver, or copper.
6. An article for thermoelectric power generation using the
thermoelectric conversion element according to claim 1.
7. A power supply for a sensor using the thermoelectric conversion
element according to claim 1.
8. A thermoelectric conversion material for forming a
thermoelectric conversion layer of a thermoelectric conversion
element, the material comprising a nano conductive material and a
low band gap material, wherein an optical band gap of the low band
gap material is 0.1 eV or more and 1.1 eV or less, and the low band
gap material is a non-polymeric metal complex compound represented
by Formula (3B): ##STR00048## wherein, in Formula (3B), M is a
metal atom selected from the group consisting of Ni, Fe, Cu and Sn,
or a metal ion thereof; when M is a metal ion, the compound
represented by Formula (3B) may have an arbitrary counter ion;
X.sup.a11 and X.sup.a12 each independently represent a hetero atom;
at least one of X.sup.a11 and X.sup.a12 is a sulfur atom or an
oxygen atom; nx represents an integer of 0 or more; R.sup.a11 to
R.sup.a14, R.sup.b11 and R.sup.b12 each independently represent a
substituent selected from the group consisting of an alkyl group, a
cycloalkyl group, an alkenyl group, an alkynyl group, an aromatic
hydrocarbon ring group, an aromatic heterocyclic group, an oxazolyl
group, a benzoxazolyl group, a thiazolyl group, an isoxazolyl
group, an isothiazolyl group, a furazanyl group, a thienyl group, a
quinolyl group, a benzofuryl group, a dibenzofuryl group, a
benzothienyl group, a dibenzothienyl group, an indolyl group, a
carbazolyl group, a carbolinyl group, a diazacarbazolyl group, a
quinoxalinyl group, a pyridazinyl group, a triazinyl group, a
quinazolinyl group, a phthalazinyl group, a borole group, and an
azaborine group, a heterocyclic group, an alkoxy group, a
cycloalkoxy group, an aryloxy group, an alkylthio group, a
cycloalkylthio group, an arylthio group, an alkoxycarbonyl group,
an aryloxycarbonyl group, a sulfamoyl group, an acyl group, an
acyloxy group, an amide group, a carbamoyl group, an ureido group,
a sulfinyl group, an alkylsulfonyl group, an arylsulfonyl group or
a heteroarylsulfonyl group, an amino group, a cyano group, a nitro
group, a hydroxyl group, a mercapto group, and a silyl group.
9. The thermoelectric conversion material according to claim 8,
further comprising at least one polymer in addition to the nano
conductive material and the low band gap material selected from the
group consisting of a conjugated polymer and a non-conjugated
polymer.
10. The thermoelectric conversion element according to claim 1,
wherein the non-polymeric metal complex compound has a metal ion
and a counter ion.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application is a Rule 53(b) Continuation Application of
U.S. application Ser. No. 14/862,264 filed Sep. 23, 2015, which is
a Continuation of PCT International Application No.
PCT/JP2014/056869 filed on Mar. 14, 2014, which claims priority
under 35 U.S.C. .sctn.119 (a) to Japanese Patent Application No.
2013-072148 filed in Japan on Mar. 29, 2013, and Patent Application
No. 2013-159268 filed in Japan on Jul. 31, 2013. Each of the above
applications is hereby expressly incorporated by reference, in its
entirety, into the present application.
TECHNICAL FIELD
[0002] The present invention relates to a thermoelectric conversion
material and a thermoelectric conversion element, and an article
for thermoelectric power generation and a power supply for a sensor
using the same.
BACKGROUND ART
[0003] A thermoelectric conversion material that allows mutual
conversion between heat energy and electric energy is used for a
thermoelectric conversion element such as a thermoelectric
generation device and a Peltier device. In thermoelectric
generation to which the thermoelectric conversion material or the
thermoelectric conversion element applies, heat energy can be
directly converted into electric power, and a movable part is not
required. Thus, the thermoelectric generation is used for a wrist
watch operated by body temperature, a power supply for remote
districts, a space power supply or the like.
[0004] As one indication for evaluating the thermoelectric
conversion performance of the thermoelectric conversion element,
there is a dimensionless figure of merit ZT (hereinafter, simply
referred to as a figure of merit ZT in some cases). This figure of
merit ZT is represented by the following Equation (A), and for
enhancement of the thermoelectric conversion performance, it is
required to increase a thermopower per absolute temperature of 1 K
(hereinafter, referred to as a thermopower in some cases) S and an
electrical conductivity .sigma., and to decrease a thermal
conductivity .kappa..
Figure of merit ZT=S.sup.2.sigma.T/.kappa. (A)
[0005] In Equation (A), S(V/K): thermopower per absolute
temperature of 1 K (Seebeck coefficient) [0006] .sigma. (S/m):
Electrical conductivity [0007] .kappa. (W/mK): Thermal conductivity
[0008] T(K): Absolute temperature
[0009] Preferable thermoelectric conversion performance is required
for the thermoelectric conversion material, and thus a material
which is mainly put into practical use at the present day is an
inorganic material. However, the inorganic material needs a
complicated processing process for using in the thermoelectric
conversion element, is expensive, and contains harmful substances
in some cases.
[0010] On the other hand, an organic thermoelectric conversion
element can be produced at a relatively low price and facilitated
to process for forming a film or the like. For these reasons,
recently, researches have actively been carried out, and eventually
an organic thermoelectric conversion material and a thermoelectric
conversion element using the same have been reported. In order to
increase the figure of merit ZT for thermoelectric conversion, an
organic material having high Seebeck coefficient and electrical
conductivity and low thermal conductivity is demanded. For example,
a thermoelectric conversion element, which includes a carrier
transportation layer formed by an organic semiconductor material
such as pentacene and a carrier generation layer of
tetrafluorotetracyanoquinodimethane or the like, is proposed (see
Patent Literature 1). In addition, a conductive polymer or a
charge-transfer complex is proposed as an organic compound in a
thermoelectric material including an organic compound and a dopant
(see Patent Literature 2). Moreover, phthalocyanine is proposed as
a thermoelectric conversion material (see Patent Literature 3). A
metal phthalocyanine is proposed as a p-type semiconductor material
to be used in a thermoelectric conversion element (see Patent
Literature 4).
CITATION LIST
Patent Literatures
[0011] Patent Literature 1: JP-A-2011-243809 ("JP-A" means
unexamined published Japanese patent application) [0012] Patent
Literature 2: JP-A-2006-128444 [0013] Patent Literature 3:
JP-A-2008-305831 [0014] Patent Literature 4: JP-A-2010-199276
SUMMARY OF INVENTION
Technical Problem
[0015] As a conductive organic material, a nano conductive material
(nanometer-sized conductive material) such as a carbon nanotube is
known. However, when a nano conductive material is used alone, it
is difficult to obtain desired performance as the thermoelectric
conversion material.
[0016] An object of the present invention is to provide a
thermoelectric conversion material and a thermoelectric conversion
element which exhibit excellent thermoelectric conversion
performance and an article for thermoelectric power generation and
a power supply for a sensor which use the same.
Solution to Problem
[0017] The present inventors examined a material in which high
thermoelectric conversion performance can be realized when a nano
conductive material is co-existed in a thermoelectric conversion
layer of the thermoelectric conversion element, in view of the
above-described problems. As a result, they found that, when an
organic material having a specific optical band gap is co-existed
with a nano conductive material, excellent thermoelectric
conversion performance is exerted in the thermoelectric conversion
element. The present invention has been made based on these
findings.
[0018] According to the present invention, there is provided the
following means:
<1> A thermoelectric conversion element comprising, on a
substrate, a first electrode, a thermoelectric conversion layer,
and a second electrode,
[0019] wherein a nano conductive material and a low band gap
material are contained in the thermoelectric conversion layer, and
an optical band gap of the low band gap material is 0.1 eV or more
and 1.1 eV or less.
<2> The thermoelectric conversion element according to item
<1>, wherein the low band gap material is a charge-transfer
complex composed of an organic electron donor and an organic
electron acceptor. <3> The thermoelectric conversion element
according to item <2>, wherein the organic electron donor is
a compound having an aromatic ring structure. <4> The
thermoelectric conversion element according to item <2> or
<3>, wherein the organic electron donor is a compound having
a condensed ring structure with three or more rings, and the
condensed ring has an aromatic ring structure. <5> The
thermoelectric conversion element according to any one of items
<2> to <4>, wherein the organic electron donor is a
compound having a carbazole structure or a fluorene structure.
<6> The thermoelectric conversion element according to any
one of items <2> to <5>, wherein the organic electron
donor is a compound represented by Formula (2):
X EWG).sub.na Formula (2) [0020] wherein, in Formula (2), X
represents a na-valent organic group; EWG represents an
electron-withdrawing group; and na represents an integer of 1 or
more. <7> The thermoelectric conversion element according to
item <1>, wherein the low band gap material is a metal
complex. <8> The thermoelectric conversion element according
to item <7>, wherein, in the metal complex, at least one of
atoms that coordinate to the central metal is a sulfur atom or an
oxygen atom. <9> The thermoelectric conversion element
according to item <7> or <8>, wherein the central metal
of the metal complex is a metal atom selected from the group
consisting of Ni, Fe, Cu and Sn, or a metal ion thereof. <10>
The thermoelectric conversion element according to any one of items
<7> to <9>, wherein the metal complex is a compound
represented by Formula (3):
##STR00001##
[0021] wherein, in Formula (3), M is a metal atom selected from the
group consisting of Ni, Fe, Cu and Sn, or a metal ion thereof; when
M is a metal ion, the compound represented by Formula (3) may have
an arbitrary counter ion; X.sup.11, X.sup.12, X.sup.13 and X.sup.14
each independently represent a hetero atom; at least one of
X.sup.11 to X.sup.14 is a sulfur atom or an oxygen atom; R.sup.11,
R.sup.12, R.sup.13 and R.sup.14 each independently represent a
substituent; R.sup.11 and R.sup.12 may be bonded to each other; and
R.sup.13 and R.sup.14 may be bonded to each other.
<11> The thermoelectric conversion element according to item
<1>, wherein the low band gap material is an arylamine
compound. <12> The thermoelectric conversion element
according to item <11>, wherein the arylamine compound is a
compound represented by Formula (5), or a one- or two-electron
oxidized derivative of the compound represented by Formula (5):
##STR00002##
[0022] wherein, in Formula (5), Ar.sup.51 to Ar.sup.55 each
independently represent an aromatic hydrocarbon ring, an aromatic
heterocycle, a single bond, or an alkylene group, proviso that at
least one of Ar.sup.51 and Ar.sup.52 is an aromatic hydrocarbon
ring and at least one of Ar.sup.53 and Ar.sup.54 is an aromatic
hydrocarbon ring; R.sup.51 to R.sup.55 each independently represent
a substituent; n.sub.51 to n.sub.55 each independently represent an
integer of 0 to 3; and ml represents 0 or 1.
<13> The thermoelectric conversion element according to item
<12>, wherein, in Formula (5), R.sup.51 to R.sup.55 each
independently represent a dialkylamino group, a diarylamino group,
or an alkoxy group. <14> The thermoelectric conversion
element according to any one of items <1> to <13>,
wherein the thermoelectric conversion layer contains at least one
polymer selected from a conjugated polymer and a non-conjugated
polymer. <15> The thermoelectric conversion element according
to item <14>, wherein the conjugated polymer has, as a
repeating unit, a constituent derived from at least one compound
selected from the group consisting of a thiophene compound, a
pyrrole compound, an acetylene compound, a p-phenylene compound, a
p-phenylenevinylene compound, a p-phenylene ethynylene compound, a
fluorene compound, and an arylamine compound. <16> The
thermoelectric conversion element according to item <14>,
wherein the non-conjugated polymer has, as a repeating unit, a
constituent derived from at least one compound selected from the
group consisting of a vinyl compound, a (meth)acrylate compound, a
carbonate compound, an ester compound, an amide compound, an imide
compound, and a siloxane compound. <17> The thermoelectric
conversion element according to any one of items <14> to
<16>, wherein the thermoelectric conversion layer contains a
conjugated polymer and a non-conjugated polymer. <18> The
thermoelectric conversion element according to any one of items
<1> to <17>, wherein the nano conductive material is a
nano carbon material or a nano metal material. <19> The
thermoelectric conversion element according to any one of items
<1> to <18>, wherein the nano conductive material is at
least one kind of material selected from the group consisting of a
carbon nanotube, a carbon nanofiber, graphite, graphene, carbon
nanoparticles and a metal nanowire. <20> The thermoelectric
conversion element according to any one of items <1> to
<19>, wherein the nano conductive material is a carbon
nanotube. <21> The thermoelectric conversion element
according to any one of items <1> to <20>, wherein the
thermoelectric conversion layer contains a dopant. <22> The
thermoelectric conversion element according to any one of items
<1> to <21>, wherein the substrate has flexibility.
<23> The thermoelectric conversion element according to any
one of items <1> to <22>, wherein the first electrode
and the second electrode each independently are formed by aluminum,
gold, silver, or copper. <24> An article for thermoelectric
power generation using the thermoelectric conversion element
according to any one of items <1> to <23>. <25> A
power supply for a sensor using the thermoelectric conversion
element according to any one of items <1> to <23>.
<26> A thermoelectric conversion material for forming a
thermoelectric conversion layer of a thermoelectric conversion
element, the material comprising a nano conductive material and a
low band gap material, wherein an optical band gap of the low band
gap material is 0.1 eV or more and 1.1 eV or less. <27> The
thermoelectric conversion material according to item <26>,
comprising at least one polymer selected from a conjugated polymer
and a non-conjugated polymer. <28> The thermoelectric
conversion material according to item <26> or <27>,
comprising an organic solvent. <29> The thermoelectric
conversion material according to item <28>, wherein the nano
conductive material is dispersed in the organic solvent.
[0023] In the present invention, a numerical value range indicated
using "to" means a range including the numerical values described
before and after "to" as the lower limit and the upper limit.
[0024] In the present invention, when a substituent is described as
an xxx group, the xxx group may have an arbitrary substituent.
Also, when there are a number of groups represented by the same
reference symbol, the groups may be identical with or different
from each other.
[0025] A repeating unit represented by each formula includes
different repeating units when they are within the range
represented by the each formula, but they are not nonetheless
completely identical repeating units. For example, in the case that
the repeating unit has an alkyl group, the repeating unit
represented by the each formula may be composed only of a repeating
unit having a methyl group, or may include a repeating unit having
another alkyl group, e.g. an ethyl group, in addition to the
repeating unit having a methyl group.
Advantageous Effects of Invention
[0026] The thermoelectric conversion material and the
thermoelectric conversion element of the present invention exhibit
excellent thermoelectric conversion performance. Further, the
article for thermoelectric power generation, the power supply for a
sensor, and the like of the present invention using the
thermoelectric conversion element of the present invention exhibit
excellent thermoelectric conversion performance.
[0027] Other and further features and advantages of the invention
will appear more fully from the following description,
appropriately referring to the accompanying drawings.
BRIEF DESCRIPTION OF DRAWINGS
[0028] FIG. 1 schematically shows a cross-sectional view for one
example of the thermoelectric conversion element of the present
invention. An arrow in FIG. 1 shows a direction of temperature
difference to be imparted during using the element.
[0029] FIG. 2 schematically shows a cross-sectional view for
another example of the thermoelectric conversion element of the
present invention. An arrow in FIG. 2 shows a direction of
temperature difference to be imparted during using the element.
DESCRIPTION OF EMBODIMENTS
[0030] A thermoelectric conversion element of the present invention
includes a first electrode, a thermoelectric conversion layer, and
a second electrode on a substrate. The thermoelectric conversion
layer contains a nano conductive material and a low band gap
material. This thermoelectric conversion layer is formed on the
substrate by a thermoelectric conversion material of the present
invention containing a nano conductive material and a low band gap
material.
[0031] Thermoelectric conversion performance of the thermoelectric
conversion element of the present invention may be defined in
figure of merit ZT represented by Equation (A).
Figure of merit ZT=S.sup.2.sigma.T/.kappa. (A)
[0032] In Equation (A), S(V/K): thermopower per absolute
temperature of 1 K (Seebeck coefficient) [0033] .sigma. (S/m):
Electrical conductivity [0034] .kappa. (W/mK): Thermal conductivity
[0035] T(K): Absolute temperature
[0036] As is apparent from the above Equation (A), for enhancement
of the thermoelectric conversion performance, it is required to
increase thermopower S and electrical conductivity .sigma., and to
decrease the thermal conductivity .kappa.. As such, the
thermoelectric conversion performance is largely affected by
factors other than electrical conductivity .sigma.. Therefore, even
for a material which is generally considered to have high
electrical conductivity .sigma., it is still unknown whether the
material would function effectively as a thermoelectric conversion
material in actual applications.
[0037] Furthermore, a thermoelectric conversion element works under
the condition of keeping a temperature difference in the direction
of the thickness and the plane of a thermoelectric conversion
layer, so as to transfer the temperature in the direction of the
thickness and the plane. Thus, it is necessary to form a
thermoelectric conversion layer by forming a thermoelectric
conversion material into a shape having a certain thickness.
Therefore, in the case of forming a film shape of the
thermoelectric conversion layer by coating, a thermoelectric
conversion material is required to have satisfactory coating
property or film-forming property. The thermoelectric conversion
material of the present invention has satisfactory dispersibility
of a nano conductive material and excellent coating property or
film-forming property, so that the thermoelectric conversion
material is suitable to be molded and processed into a
thermoelectric conversion layer.
[0038] Hereinafter, thermoelectric conversion material of the
present invention and, next, thermoelectric conversion element of
the present invention will be explained.
[Thermoelectric Conversion Material]
[0039] The thermoelectric conversion material of the present
invention is a thermoelectric conversion composition for forming a
thermoelectric conversion layer of a thermoelectric conversion
element and contains a nano conductive material and a low band gap
material.
[0040] First, each component to be used in the thermoelectric
conversion material of the present invention will be explained
<Nano Conductive Material>
[0041] A nano conductive material to be used in the present
invention may be a material having a nanometer size and having
electrical conductivity. As such a nano conductive material, a
carbon material having electrical conductivity and a nanometer size
(hereinafter, referred to as the nanocarbon material in some
cases), a metal material having a nanometer size (hereinafter,
referred to as the nano-metal material in some cases), or the like
is exemplified.
[0042] Among the nanocarbon materials and the nano-metal materials,
as the nano conductive material used in the present invention,
nanocarbon materials such as a carbon nanotube (hereinafter, also
referred to as CNT), a carbon nanofiber, fullerene, graphite,
graphene, and carbon nanoparticles, and metal nanowires, which will
be respectively described below, are preferable, and a carbon
nanotube is particularly preferable from the viewpoint of improving
electrical conductivity and the dispersibility in the dispersion
medium.
[0043] The content of the nano conductive material in the
thermoelectric conversion material is, from the viewpoint of
thermoelectric conversion performance, in the total solid content
of the thermoelectric conversion material, i.e. in the
thermoelectric conversion layer, preferably 2 to 60% by mass, more
preferably 5 to 55% by mass, and particularly preferably 10 to 50%
by mass.
[0044] One kind of the nano conductive materials may be used alone,
or two or more kinds thereof may be used in combination. When two
or more kinds are used in combination as the nano conductive
material, at least one kind of nanocarbon materials and at least
one kind of nano-metal materials may be used in combination, or two
kinds of respective nanocarbon materials or nano-metal materials
may be used in combination
1. Nanocarbon Material
[0045] The nanocarbon material is, as described above, a carbon
material having nanometer size and electrical conductivity. The
nanocarbon material, for example, includes the nanometer-sized
conductive material obtained by the chemical bonding of carbon
atoms by means of a carbon-carbon bond formed at sp.sup.2 hybrid
orbital of a carbon atom. Specific examples thereof include
fullerene (including metal-containing fullerene and onion-shaped
fullerene), a carbon nanotube (including peapods), a carbon
nanohorn having a shape in which one end of a carbon nanotube is
blocked, a carbon nanofiber, a carbon nanowall, a carbon
nanofilament, a carbon nanocoil, vapor grown carbon (VGCF),
graphite, graphene, carbon nanoparticles, and a cup-shaped
nanocarbon substance in which a hole is formed on the top portion
of a carbon nanotube. In addition, various carbon blacks having a
graphite crystalline structure and electrical conductivity can be
used as the nanocarbon material, and examples thereof include
Ketjen Black and acetylene black. Specifically, carbon blacks such
as "Vulcan" manufactured by Cabot are exemplified.
[0046] These nanocarbon materials can be produced by a production
method of the related art. Specifically, examples thereof include
catalytic hydrogen reduction of carbon dioxide, an arc discharge
method, a laser vaporization method, a CVD method, a vapor-phase
epitaxial method, a vapor-phase flow method, a HiPco method in
which carbon monoxide is allowed to react together with an iron
catalyst under high temperature and high pressure to grow carbon in
a gas phase, and an oil furnace method. The nanocarbon material
produced in this way can be used as it is, or a nanocarbon material
subjected to purification by cleaning, centrifugal separation,
filtration, oxidation, chromatograph, or the like can also be used.
Further, a nanocarbon material subjected to pulverization, as
necessary, by using ball type kneading apparatuses such as a ball
mill, a vibration mill, a sand mill and a roll mill, or a
nanocarbon material subjected to cutting to have a short length by
a chemical or physical treatment can also be used.
[0047] The size of the nano conductive material to be used in the
present invention is not particularly limited as long as it is
nanometer-sized. When the nano conductive material is a carbon
nanotube, a carbon nanohorn, a carbon nanofiber, a carbon
nanofilament, a carbon nanocoil, vapor grown carbon fiber (VGCF), a
cup-shaped nanocarbon substance, or the like, particularly, when
the nano conductive material is the CNT, an average length is not
particularly limited, but is preferably 0.01 to 1,000 .mu.m and
more preferably 0.1 to 100 .mu.m from the viewpoint of ease of
production, film-forming property, and electrical conductivity.
Further, an average diameter of the CNT used in the present
invention is not particularly limited, but from viewpoints of
durability, transparency, film-forming property, electrical
conductivity, or the like, the average diameter is preferably 0.4
nm or more to 100 nm or less, more preferably 50 nm or less, and
further preferably 15 nm or less.
[0048] Among the nanocarbon materials described above, a carbon
nanotube, a carbon nanofiber, graphite, graphene, and carbon
nanoparticles are preferable, and a carbon nanotube is particularly
preferable.
[0049] Hereinafter, explanation will be made as to the carbon
nanotube. The CNT includes a single-walled CNT in which one sheet
of carbon film (graphene sheet) is cylindrically wound, a
double-walled CNT in which two graphene sheets are concentrically
wound, and a multi-walled CNT in which a plurality of graphene
sheets are concentrically wound. In the present invention, the
single-walled CNT, the double-walled CNT, and the multi-walled CNT
may be used alone, or in combination with two or more kinds. A
single-walled CNT and a double-walled CNT have excellent properties
in the electrical conductivity and the semiconductor
characteristics, and therefore a single-walled CNT and a
double-walled CNT are preferably used, and a single-walled CNT is
more preferably used.
[0050] For a single-walled CNT, the symmetry of the spiral
structure based on the direction of hexagon of graphene of a
graphene sheet is referred to as axial chirality, and a
two-dimensional lattice vector from a reference point of a
6-membered ring on graphene is referred to as a chiral vector. (n,
m) obtained by the indexation of this chiral vector is referred to
as a chiral index, and metallic CNT and semiconductive CNT can be
classified by this chiral index. Specifically, the CNT that has n-m
of a multiple of 3 is metallic, while the CNT that does not have
n-m of a multiple of 3 is semiconductive.
[0051] The single-walled CNT to be used in the present invention
may be used in the form of a semiconductive one or a metallic one,
or both in combination with the semiconductive one and the metallic
one. Moreover, the CNT may include a metal therein, or one
including a molecule of fullerene or the like therein (particularly
the one including fullerene is referred to as peapod) may also be
used.
[0052] The CNT can be produced by an arc discharge process, a
chemical vapor deposition process (hereinafter, referred to as a
CVD process), a laser ablation process, or the like. The CNT used
in the present invention may be obtained by any method, but
preferably by the arc discharge process and the CVD process.
[0053] Upon producing the CNT, fullerene, graphite, or amorphous
carbon is simultaneously formed as a by-product. In order to remove
these impurities, purification is preferably performed. A method of
purification of the CNT is not particularly limited, but acid
treatment by nitric acid, sulfuric acid, or the like, or
ultrasonication is effective in removal of the impurities. In
addition thereto, separation and removal using a filter is also
preferably performed from the viewpoint of an improvement of
purity.
[0054] After purification, the CNT obtained can also be directly
used. Moreover, the CNT is generally produced in the form of
strings, and therefore may be cut into a desired length according
to a use. The CNT can be cut in the form of short fibers by acid
treatment by nitric acid or sulfuric acid, ultrasonication, a
freeze mill process, or the like. Moreover, in addition thereto,
separation using the filter is also preferred from the viewpoint of
an improvement of purity.
[0055] In the present invention, not only a cut CNT, but also a CNT
previously prepared in the form of short fibers can be used. Such a
CNT in the form of short fibers can be obtained, for example, by
forming on a substrate a catalyst metal such as iron and cobalt,
and according to the CVD method, allowing on the surface thereof
vapor deposition of the CNT by thermally decomposing a carbon
compound at 700 to 900.degree. C., thereby obtaining the CNT in the
shape of alignment on a substrate surface in a vertical direction.
The thus prepared CNT in the form of short fibers can be taken out
from the substrate by a method of stripping off the CNT, or the
like. Moreover, the CNT in the form of short fibers can also be
obtained by supporting a catalyst metal on a porous support such as
porous silicon or on an anodized film of alumina to allow on a
surface thereof vapor deposition of a CNT according to the CVD
process. The CNT in the form of aligned short fibers can also be
prepared according to a method in which a molecule such as iron
phthalocyanine containing a catalyst metal in the molecule is used
as a raw material, and a CNT is prepared on a substrate by
performing CVD in a gas flow of argon/hydrogen. Furthermore, the
CNT in the form of aligned short fibers can also be obtained on a
SiC single crystal surface according to an epitaxial growth
process.
2. Nano-Metal Material
[0056] The nano-metal material is, for example, a fibrous or
particulate metal material having a nano-meter size, and specific
examples thereof include a fibrous metal material (also referred to
as a metal fiber) and a particulate metal material (also referred
to as metal nanoparticles). As the nano-metal material, metal
nanowires to be described later are preferable.
[0057] The metal fiber is preferably in the form of solid fibers or
hollow fibers. A metal fiber having a solid structure which has an
average short axis length of 1 to 1,000 nm and an average long axis
length of 1 to 100 .mu.m is referred to as a metal nanowire. A
metal fiber having a hollow structure which has an average short
axis length of 1 to 1,000 nm and an average long axis length of 0.1
to 1,000 .mu.m is referred to as a metal nanotube.
[0058] The material of the metal fiber may be a metal having
electrical conductivity, and can be appropriately selected
depending on the purposes. For example, as the material, at least
one metal element selected from the group consisting of the metals
of the 4th period, the 5th period and the 6th period of the Long
Periodic Table (IUPAC 1991) is preferred; at least one metal
element selected from the group consisting of Group 2 to Group 14
is more preferred; and at least one metal element selected from the
group consisting of Group 2, Group 8, Group 9, Group 10, Group 11,
Group 12, Group 13 and Group 14 is further preferred.
[0059] Specific examples of the metal include copper, silver, gold,
platinum, palladium, nickel, tin, cobalt, rhodium, iridium, iron,
ruthenium, osmium, manganese, molybdenum, tungsten, niobium,
tantalum, titanium, bismuth, antimony, lead, and alloys thereof.
Among these, silver or an alloy containing silver is preferred from
the viewpoint of being excellent in electrical conductivity.
Examples of a metal to be used for alloy containing silver include
platinum, osmium, palladium, and iridium. One kind thereof may be
used alone or two or more kinds thereof may be used in
combination.
[0060] The shape of the metal nanowires is not particularly limited
as long as the metal nanowires are formed by the above-described
metal and have a hollow structure, and the shape thereof can be
appropriately selected depending on the purposes. For example, it
is possible to take an arbitrary shape such as a cylindrical shape,
a rectangular parallelepiped shape, or a columnar shape with a
polygonal cross-section. However, a cylindrical shape or a
cross-sectional shape with a polygonal cross-section with rounded
corners is preferred from the viewpoint of increasing transparency
of the thermoelectric conversion layer. The cross-sectional shape
of the metal nanowires can be examined by observing the
cross-section using a transmission electron microscope (TEM).
[0061] The average short axis length (referred to as "an average
short axis diameter" or "an average diameter" in some cases) of the
metal nanowires is preferably 50 nm or less, more preferably 1 to
50 nm, even more preferably 10 to 40 nm, and particularly
preferably 15 to 35 nm, from the same viewpoint as in the nano
conductive material described above. The average short axis length
is determined from the average value of measured short axis lengths
obtained by observing 300 metal nanowires with a transmission
electron microscope (TEM; JEM-2000FX manufactured by JEOL Ltd.). In
cases where the short axis of the metal nanowires is not circular,
the maximum length is used as the short axis length.
[0062] Similarly, the average long axis length (referred to as an
average length in some cases) of the metal nanowires is preferably
1 .mu.m or more, more preferably 1 to 40 .mu.m, even more
preferably 3 to 35 .mu.m, and particularly preferably 5 to 30
.mu.m. The average long axis length of the metal nanowires is, for
example, determined from the average value of measured long axis
lengths obtained by observing 300 metal nanowires with a
transmission electron microscope (TEM; JEM-2000FX manufactured by
JEOL Ltd.). When a metal nanowire is curved, a circle having the
arc of the metal nanowire is taken into account and the value
calculated from the radius and the curvature of the circle is used
as the long axis length.
[0063] The metal nanowire may be produced by any method. The metal
nanowire is preferably produced by reducing metal ions while
heating in a solvent in which a halogen compound and a dispersing
additive are dissolved, as described in JP-A-2012-230881. Detailed
description of the halogen compound, the dispersing additive, the
solvent, heating conditions, or the like is described in
JP-A-2012-230881. In addition to the above-described production
methods, the methods described in JP-A-2009-215594,
JP-A-2009-242880, JP-A-2009-299162, JP-A-2010-84173,
JP-A-2010-86714 or the like may be used to manufacture the metal
nanowires.
[0064] The shape of the metal nanotubes is not particularly limited
as long as the metal nanotubes are formed by the above-described
metal and have a hollow structure. The metal nanotubes may have a
single-walled structure or a multi-walled structure. From the
viewpoint having excellent electrical conductivity and thermal
conductivity, the metal nanotubes preferably have a single-walled
structure.
[0065] The thickness (difference between the outer diameter and the
inner diameter) of the metal nanotube is preferably from 3 nm to 80
nm, and more preferably from 3 nm to 30 nm, from the viewpoint of
durability, transparency, film-forming properties, and electrical
conductivity. The average long axis length of the metal nanotubes
is preferably 1 to 40 .mu.m, more preferably 3 to 35 .mu.m, and
even more preferably 5 to 30 .mu.m, from the same viewpoint as in
the nano conductive material described above. It is preferable that
the average short axis length of the metal nanotubes be the same as
the average short axis length of the metal nanowires.
[0066] The metal nanotubes may be produced by any method. For
example, the method described in US 2005/0056118 or the like can be
used to produce the metal nanotubes.
[0067] The metal nanoparticles may be metal fine particles having a
particulate shape or a powder shape which are formed by the
above-described metal, may also be metal fine particles or metal
fine particles of which surfaces are covered with a protection
agent, or may also be those obtained by dispersing, in a dispersion
medium body, the metal fine particles of which surfaces are covered
with a protection agent. As a metal to be used in metal
nanoparticles, among the above-described metals, silver, copper,
gold, palladium, nickel, or rhodium is preferably exemplified. In
addition, an alloy made of at least two or more kinds of these or
an alloy made of iron and at least one kind of these can also be
used. Examples of the alloy made of two kinds include a
platinum-gold alloy, a platinum-palladium alloy, a gold-silver
alloy, a silver-palladium alloy, a palladium-gold alloy, a
platinum-gold alloy, a rhodium-palladium alloy, a silver-rhodium
alloy, a copper-palladium alloy, and a nickel-palladium alloy.
Further, examples of the alloy with iron include an iron-platinum
alloy, an iron-platinum-copper alloy, an iron-platinum-tin alloy,
an iron-platinum-bismuth alloy, and an iron-platinum-lead alloy.
These metals or alloys can be used alone or two or more kinds
thereof can be used in combination.
[0068] The average particle diameter (dynamic light scattering
method) of the metal nanoparticles is preferably 1 to 150 nm from
the viewpoint of excellent electrical conductivity.
[0069] As the protecting agent of the metal fine particles, for
example, a protecting agent described in JP-A-2012-222055 is
preferably exemplified. Moreover, a protecting agent having a
linear or branched alkyl chain with 10 to 20 carbon atoms,
particularly, aliphatic acids or aliphatic amines, aliphatic thiols
or aliphatic alcohols, and the like are further exemplified
preferably. Here, when the number of carbon atoms is 10 to 20,
storage stability of metal nanoparticles is high and electrical
conductivity is also excellent. Aliphatic acids, aliphatic amines,
aliphatic thiols, and aliphatic alcohols described in
JP-A-2012-222055 are preferable.
[0070] The metal nanoparticles may be produced by any production
method, and examples of the production method include an in-gas
evaporation method, a sputtering method, a metal vapor synthesis
method, a colloid method, an alkoxide method, a co-precipitation
method, a homogeneous precipitation method, a thermal decomposition
method, a chemical reduction method, an amine reduction method, and
a solvent evaporation method. These production methods each have
idiosyncratic features, but particularly, for the purpose of mass
production, a chemical reduction method and an amine reduction
method are preferably used. When these production methods are
performed, as well as selecting and using the above-described
protecting agent as necessary, a well-known reducing agent or the
like can be appropriately used.
<Low Band Gap Material>
[0071] The thermoelectric conversion material of the present
invention contains a low band gap material together with the nano
conductive material described above. The low band gap material in
the present invention indicates a material having an optical band
gap of 0.1 eV or more and 1.1 eV or less.
[0072] Here, the band gap indicates a forbidden band and is an
energy level and an energy difference from the top of the valence
band (the highest energy band occupied with electrons in the band
structure) to the bottom of the conduction band (the lowest energy
band with no electrons).
[0073] The optical band gap in the present invention is defined by
an absorption end at the long wavelength side in the absorption
spectrum of the material, and specifically, is obtained by the
following Equation (B).
Optical band gap (eV)=1240/absorption long wavelength end (nm)
Equation (B)
[0074] In Equation (B), the absorption long wavelength end
indicates a wavelength (nm) of the absorption end at the long
wavelength side in the absorption spectrum of the material. The
absorption spectrum of the material can be measured by a
spectrophotometer.
[0075] Specifically, the material is dissolved in a soluble organic
solvent and is applied onto a quartz substrate to form a film. The
absorption spectrum of this coating film is measured by a
spectrophotometer. The wavelength .lamda.5 (unit: nm) of the
absorption end at the long wavelength side in which the absorbance
becomes 5% relative to the maximum value (.lamda.max) of the
absorbance is obtained. The obtained .lamda.5 is set as the
absorption long wavelength end and then the optical band gap (unit:
eV) is calculated by Equation (B). As the spectrophotometer, an
ultraviolet visible near infrared (UV-Vis-NIR) spectrophotometer or
the like can be used.
[0076] The low band gap material for use in the present invention
has an optical band gap of preferably 0.1 eV or more and 1.0 eV or
less, more preferably 0.1 eV or more and 0.9 eV or less.
[0077] When such a low band gap material is used together with the
nano conductive material in the thermoelectric conversion material,
the thermoelectric conversion performance is enhanced.
[0078] For the enhancement of the thermoelectric conversion
performance, it is effective to enhance the thermal excitation
probability and to increase the generation amount of the thermal
exciton. However, since heat energy to be used in thermoelectric
conversion is smaller than light energy, the generation amount of
thermal exciton is not sufficient in some cases. It is speculated
that, since a material having a small band gap is used in the
thermoelectric conversion material of the present invention, the
thermal excitation probability is enhanced, and as a result, the
generation amount of thermal exciton at a high temperature side of
the thermoelectric conversion element is increased, the thermopower
(Seebeck coefficient of the material) is increased, and thus the
thermoelectric conversion performance is enhanced.
[0079] In addition, the carrier transportation path is formed in
the material by the nano conductive material and thus the
electrical conductivity is also improved. It is considered that,
when the low band gap material is used together with the nano
conductive material, the thermopower and the electrical
conductivity are enhanced, and as a result, the thermoelectric
conversion performance is further enhanced.
[0080] The content of the low band gap material in the
thermoelectric conversion material is preferably 5 to 500 parts by
mass and more preferably 20 to 200 parts by mass relative to 100
parts by mass of the nano conductive material, in terms of the
thermoelectric conversion performance.
[0081] In the thermoelectric conversion material of the present
invention, one kind of the low band gap material may be used alone
or two or more kinds thereof may be used in combination.
[0082] As the low band gap material, preferably, the following
charge-transfer complex, metal complex, and arylamine compound are
exemplified.
1. Charge-Transfer Complex
[0083] A charge-transfer complex is exemplified as a first low band
gap material.
[0084] The charge-transfer complex in the present invention is an
intermolecular compound composed of an electron-donating molecule
(electron donor) and an electron-withdrawing molecule (electron
acceptor) and has charge-transfer interaction.
[0085] The charge-transfer theory based on the molecular orbital
theory is defined by R. S. Mulliken. When the charge-transfer
amount of complexes D.cndot..cndot. A consisting of the electron
donor D (electron donor) and the electron acceptor A (electron
acceptor) is denoted as .delta., the following equation is
established and a new absorption band (charge-transfer absorption
band), which does not appear in the case of only one of the
electron donor and the electron acceptor, appears at the long
wavelength side. Further, as the electron affinity of the electron
acceptor increases, the absorption maximum wavelength is shifted
toward the long wavelength side.
D+A.fwdarw.D.sup.+.delta..cndot..cndot.A.sup.-.delta.0.ltoreq..delta..lt-
oreq.1
[0086] The charge-transfer complex to be used in the present
invention is an organic charge-transfer complex composed of an
organic electron donor and an organic electron acceptor. Both of
the organic electron donor and the organic electron acceptor are
not ionized or not partially ionized before the complex is formed,
and are a neutral compound. If the organic electron donor and the
organic electron acceptor are mixed with each other so that
molecules thereof come into close contact with each other, the
charge transfer only occurs so as to form the complex.
[0087] Further, in the charge-transfer complex in the present
invention, it is preferable that a covalent bond in the molecules
(any covalent bond in the electron donor D or any covalent bond in
the electron acceptor A) be not broken, that is, be not decomposed
even in the case of irradiation of an active energy ray (for
example, light or heat). Here, the state where the covalent bond in
the molecules is not broken means the state where the absorption
maximum value of the absorption spectrum (absorption maximum of
charge-transfer absorption band) is not changed in the case of
irradiation of an active energy ray of 0.5 J/cm.sup.2 or more and
3.0 J/cm.sup.2 or less, or the state where, even if the absorption
maximum value is changed, the changed value reversibly returns to
the original value due to other external stimulus (for example,
changes without the breakage of the covalent bond, such as
cis-trans sterical isomerization, phase transition, or pair salt
exchange).
[0088] An onium salt compound as one example of dopants to be
described later is different from the charge-transfer complex in
that both of the electron donor and the electron acceptor are
ionized before a salt is formed, and are charged. Further,
regarding the onium salt, the covalent bond in the molecules is
irreversibly broken by irradiation of an active energy ray and this
is associated with chemical decomposition. For example, regarding a
sulfonium salt, the covalent bond between a sulfur atom and a
carbon atom constituting a sulfonium cation is broken by
irradiation of light, and radical is generated. The state where the
covalent bond in the molecules is irreversibly broken means the
state where the absorption maximum value of the absorption spectrum
is irreversibly changed in the case of irradiation of an active
energy ray of 0.5 J/cm.sup.2 or more and 3.0 J/cm.sup.2 or less,
and the changed value does not return to the original value.
[0089] Since the charge-transfer complex to be used in the present
invention has a specific optical band gap, when the charge-transfer
complex is used together with the nano conductive material as
described above, the performance of the thermoelectric conversion
element can be enhanced. In addition, it is speculated that the
configuration unique to the charge-transfer complex is also
contributed to the performance enhancement of the thermoelectric
conversion element.
[0090] In order to realize high thermoelectric conversion
performance, it is desired to smoothly perform charge transfer
between nano conductive materials in the thermoelectric conversion
material. When a charge-transfer complex is used as the low band
gap material, electronic interaction (.pi.-.pi. interaction or
cation-n interaction) occurs on the surfaces of the charge-transfer
complex and the nano conductive material, and the charge-transfer
complex is electronically adsorbed to the surface of the nano
conductive material. The charge-transfer complex adsorbed to the
surface of the nano conductive material and another charge-transfer
complex or nano conductive material are stacked in layers by
further electronic interaction, and a carrier path can be
established between the molecules of the nano conductive material.
It is considered that the charge transfer between the molecules of
the nano conductive material is assisted by this carrier path, the
charge diffusion is accelerated, and as a result, the
thermoelectric conversion performance is enhanced. Further, it is
also considered that the generation amount of thermal excitation
carrier is increased due to physical properties unique to the
charge-transfer complex, that is, physical properties in which the
charge-transfer complex is stable to heat and has ionicity, and
thus the temperature gradient in the carrier distribution is
increased, thereby achieving the enhancement of the thermoelectric
conversion performance.
[0091] Further, when a charge-transfer complex is used as the low
band gap material, it is possible to obtain a thermoelectric
conversion element with excellent temporal stability.
[0092] Since the thermoelectric conversion element is used in a
power supply for a wrist watch, a power supply for remote
districts, a space power supply, or the like as described above, it
is assumed that the thermoelectric conversion element is used under
the condition at high temperature and high humidity over a long
period of time. For this reason, the thermoelectric conversion
element has excellent thermoelectric conversion performance at the
initial stage, and in addition thereto, it is desirable that the
thermoelectric conversion performance at the initial stage can be
maintained over a long period of time even under high temperature
and high humidity. When the charge-transfer complex is used
together with the nano conductive material, it is possible to
obtain an element with excellent temporal stability under high
temperature and high humidity as well as high thermoelectric
conversion performance. The mechanism thereof has not been
completely elucidated, but is speculated as follows.
[0093] Since the electronic interaction between the charge-transfer
complex and the nano conductive material is strong, this electronic
bonding state is less likely to be broken even under high
temperature and high humidity. Further, the bonding in the
molecules of the charge-transfer complex itself is also less likely
to be broken. For these reasons, when the thermoelectric conversion
element is used, it is possible to suppress cracks occurring in the
thermoelectric conversion layer or incorporation of impurities in
air into the thermoelectric conversion layer. As a result, the
thermoelectric conversion element, which can maintain the
thermoelectric conversion performance at the initial stage and is
excellent in the temporal stability even when the thermoelectric
conversion element is used under high temperature and high humidity
over a long period of time, is obtained.
[0094] Incidentally, high temperature and high humidity in the
present invention indicate, for example, a temperature of 50 to
200.degree. C. and a relative humidity of 70 to 100%.
[0095] The content of the charge-transfer complex in the
thermoelectric conversion element is, from the viewpoint of
thermoelectric conversion performance, relative to 100 parts by
mass of the nano conductive material, preferably 5 to 500 parts by
mass, more preferably 20 to 200 parts by mass. In the
thermoelectric conversion material of the present invention, the
charge-transfer complex may be used in one kind alone, or two kinds
or more of the charge-transfer complex may be used in
combination.
[0096] The charge-transfer complex and the electron donor and
electron acceptor constituting the complex to be used in the
present invention may be any one of a low-molecular compound and a
polymer compound, and is preferably a low-molecular compound. The
weight average molecular weight of the charge-transfer complex is
preferably 250 to 100,000 and more preferably 450 to 50,000.
Further, the weight average molecular weight of the electron donor
is preferably 150 to 100,000 and more preferably 250 to 50,000. The
weight average molecular weight of the electron acceptor is
preferably 100 to 1,200 and more preferably 120 to 800.
[0097] A weight average molecular weight can be measured by Gel
Permeation Chromatography (GPC). For example, the average molecular
weight can be obtained by performing the GPC under the
configurations and conditions of Apparatus: "Alliance GPC2000
(manufactured by Waters), Column: TSKgel GMH6-HT.times.2+TSKgel
GMH6-HTL.times.2 (all manufactured by Tosoh Corporation, 7.5 mm
I.D..times.30 cm), Column temperature: 140.degree. C., Detector:
Differential refractive index detector, Mobile phase: Solvent (for
example, o-dichlorobenzene) and using standard polystyrene as the
molecular weight configuration.
[0098] The electron donor constituting the charge-transfer complex
of the present invention is an electron-donating organic compound
and does not contain a metal atom.
[0099] The organic electron donor is preferably a compound having
an aromatic ring structure. The aromatic ring structure may be an
aromatic hydrocarbon ring or an aromatic heterocycle, and is
preferably an aromatic heterocycle.
[0100] Here, a monocyclic heterocycle having aromaticity may be
used as the aromatic hydrocarbon ring, but as a basic ring thereof,
a benzene ring is exemplified.
[0101] The aromatic heterocycle is not particularly limited as long
as it is a monocyclic heterocycle having aromaticity, but a
5-membered aromatic heterocycle or a 6-membered aromatic
heterocycle is preferably exemplified. Examples of the hetero atom
for forming the heterocycle include a sulfur atom, a nitrogen atom,
an oxygen atom, a silicon atom, and a selenium atom. Among these, a
sulfur atom and a nitrogen atom are preferred, and a sulfur atom is
more preferred. Examples of the 5-membered aromatic heterocycle
include a thiophene ring, a furan ring, a pyrrole ring, a
selenophene ring, a silole ring, an imidazole ring, a pyrazole
ring, an oxazole ring, an isoxazole ring, a thiazole ring, an
isothiazole ring, and a triazole ring. Examples of the 6-membered
aromatic heterocycle include a pyridine ring, a pyrimidine ring, a
pyridazine ring, a pyrazine ring, and a triazine ring. Among them,
in terms of the thermoelectric conversion performance, a 5-membered
aromatic heterocycle is more preferred, a thiophene ring, a furan
ring, or a pyrrole ring is further preferred, and a thiophene ring
is particularly preferred.
[0102] The organic electron donor preferably contains a condensed
ring structure. A ring forming the condensed ring may be an
aliphatic ring or an aromatic ring, or may be a hydrocarbon ring or
a heterocycle. Among these, a condensed ring having an aromatic
ring structure is preferred, a condensed ring having an aromatic
heterocyclic structure is more preferred, and a condensed ring of
an aromatic heterocycle or a condensed ring of an aromatic
hydrocarbon ring and an aromatic heterocycle is further preferred.
Examples of the aromatic hydrocarbon ring and the aromatic
heterocycle forming the condensed ring include the aromatic ring
and the aromatic heterocycle described above and a preferable range
thereof is also the same.
[0103] The condensed ring has preferably a condensed polycyclic
structure in which three or more rings are condensed, more
preferably a structure in which three or more rings including an
aromatic ring are condensed, and further preferably a structure in
which three or more rings selected from aromatic hydrocarbon rings
and aromatic heterocycles are condensed.
[0104] A carbazole structure or a fluorene structure is more
preferable as the condensed ring structure.
[0105] The ring structure included in the electron donor described
above may have a substituent. Examples of the substituent include
an alkyl group, an alkenyl group, an alkynyl group, an alkoxy
group, an alkylthio group, and an amino group (including an
alkylamino group and an arylamino). Among these, an alkyl group or
an alkoxy group is preferred.
[0106] The alkyl group may be linear, branched, or cyclic, and a
linear alkyl group is preferred. The number of carbon atoms of the
alkyl group is preferably 1 to 20 and more preferably 1 to 10.
[0107] The alkyl part of the alkoxy group has the same meaning as
the above-described alkyl group, and a preferable range thereof is
also the same.
[0108] The alkyl part of the alkylthio group has the same meaning
as the above-described alkyl group, and a preferable range thereof
is also the same.
[0109] The amino group is preferably a mono- or di-alkylamino
group. The alkyl part of the alkylamino group has the same meaning
as the above-described alkyl group, and a preferable range thereof
is also the same.
[0110] The organic electron donor that can be used in the present
invention is preferably a compound having a structure represented
by Formula (1A) or (1B).
##STR00003##
[0111] In Formulas (1A) and (1B), the ring A represents an aromatic
ring; and the ring B represents an aromatic ring, a non-aromatic
heterocycle, or a non-aromatic hydrocarbon ring. The ring C and the
ring D each represent a non-aromatic heterocycle or a non-aromatic
hydrocarbon ring. Ry represents a substituent, and n represents an
integer of 0 or more.
[0112] The rings A to D may be further condensed with an aromatic
ring, a non-aromatic heterocycle, or a non-aromatic hydrocarbon
ring.
[0113] The aromatic rings in the rings A and B have the same
meaning as the aromatic ring (the aromatic hydrocarbon ring and the
aromatic heterocycle) described above, and preferable ranges
thereof are also the same.
[0114] The non-aromatic heterocycles in the rings B to D are
preferably a 5- to 7-membered ring. Further, the hetero atom for
forming the ring is preferably a sulfur atom, a nitrogen atom, an
oxygen atom, a silicon atom, or a selenium atom and may be a
saturated ring or an unsaturated ring (but is not an aromatic
ring).
[0115] The non-aromatic hydrocarbon rings in the rings B to D are
preferably a 5- to 7-membered ring, and may be a saturated ring or
an unsaturated ring (but is not an aromatic ring).
[0116] The rings A to D are preferably a heterocycle or a ring in
which a heterocycle is condensed.
[0117] When there is a plurality of Rys, the plurality of Rys may
be identical with or different from each other.
[0118] Ry is preferably an aromatic group (e.g., an aromatic
hydrocarbon ring group, and an aromatic heterocyclic group), an
alkyl group, an alkenyl group, an alkynyl group, an alkoxy group,
an alkylthio group, or an amino group (including an alkylamino
group and an arylamino). The aromatic group represented by Ry may
be further substituted with an alkyl group, an alkenyl group, an
alkynyl group, an alkoxy group, an alkylthio group, or an amino
group (including an alkylamino group and an arylamino).
[0119] The structure represented by Formula (1B) is further
preferably a structure represented by Formula (1B-1) or (1B-2).
##STR00004##
[0120] In Formulas (1B-1) and (1B-2), G.sup.1 to G.sup.4 each
independently represent --S-- or --Se--; and G.sup.5 and G.sup.6
each independently represent --S--, --N(Rx)--, or --CH.dbd.CH--. Rx
represents a hydrogen atom or a substituent. Examples of the
substituent include an alkyl group, an alkenyl group, an alkynyl
group, and an alkoxy group. Rx is preferably a hydrogen atom.
[0121] In Formulas (1B-1) and (1B-2), Ry and n each have the same
meaning as Ry and n in Formulas (1A) and (1B), and preferable
ranges thereof are also the same.
[0122] Specific examples of the organic electron donor that can be
used in the present invention are shown below, but the present
invention is not limited thereto. Meanwhile, in the following
specific examples, symbol * represents a linking site of the
repeating unit.
##STR00005## ##STR00006## ##STR00007## ##STR00008## ##STR00009##
##STR00010## ##STR00011## ##STR00012## ##STR00013##
##STR00014##
[0123] The electron acceptor constituting the charge-transfer
complex of the present invention is an electron-withdrawing organic
compound and does not contain a metal atom.
[0124] It is preferable that the organic electron acceptor be a
compound having at least one electron-withdrawing group.
[0125] The electron-withdrawing group in the present invention
means a substituent having a Hammett substituent constant
.sigma..sub.p value of more than 0.
[0126] The expression "Hammett substituent constant .sigma..sub.p
value" used herein will be described. The Hammett's Rule is an
empirical rule proposed by L. P. Hammett in 1935 to discuss
quantitatively the influence of substituents on the reaction or
equilibrium of benzene derivatives, and its validity is approved
widely nowadays. The substituent constant determined with the
Hammett's Rule includes .sigma..sub.p value and .sigma..sub.m
value, and these values can be found in many general literatures
and books. For example, such values are described in detail in
"Lange's Handbook of Chemistry", 12th edition (1979), edited by J.
A. Dean (McGraw-Hill); and "Kagaku No Ryoiki" ("Region of
Chemistry"), extra edition, No. 122, pp. 96-103 (1979) (Nankodo).
Meanwhile, in the present specification, various substituents will
be defined or described based on the Hammett substituent constant
.sigma..sub.p; however, this does not imply that the substituents
are limited only to the substituents having values that exist in
the literature, which are found in the textbooks described above.
It is needless to say that the substituents include those
substituents having constant values such that even if the values
are not known in the literature, the values will be included in the
range when measured based on Hammett's Rule. The organic electron
acceptor that can be used in the present invention include a
compound which is not a benzene derivative, but, as a scale for
indicating the electron effect of the substituent, the
.sigma..sub.p value is used irrespective of the substitution
position. In the present invention, the .sigma..sub.p value will be
used as the aforementioned meaning.
[0127] Examples of the electron-withdrawing group having the
Hammett substituent constant .sigma..sub.p value of 0.60 or more
include a cyano group, a nitro group, an alkylsulfonyl group (e.g.,
a methanesulphonyl group), and an arylsulfonyl group (e.g., a
benzenesulphonyl group).
[0128] Examples of the electron-withdrawing group having the
Hammett substituent constant .sigma..sub.p value of 0.45 or more
include, in addition to the above-described electron-withdrawing
group, an acyl group (e.g., an acetyl group), an alkoxycarbonyl
group (e.g., a dodecyloxycarbonyl group), an aryloxycarbonyl group
(e.g., a m-chlorophenoxycarbonyl group), an alkylsulfinyl group
(e.g., a n-propylsulfinyl group), an arylsulfinyl group (e.g., a
phenylsulfinyl group), a sulfamoyl group (e.g., a N-ethylsulfamoyl
group, and a N,N-dimethylsulfamoyl group), an alkyl halide group
(e.g., a trifluoromethyl group), an ester group, a carbonyl group,
and an amide group.
[0129] Examples of the electron-withdrawing group having the
Hammett substituent constant .sigma..sub.p value of 0.30 or more
include, in addition to the above-described electron-withdrawing
group, an acyloxy group (e.g., an acetoxy group), a carbamoyl group
(e.g., a N-ethylcarbamoyl group, and N,N-dibutylcarbamoyl group),
an alkoxy halide group (e.g., a trifluoromethyloxy group), an
aryloxy halide group (e.g., a pentafluorophenyloxy group), a
sulfonyloxy group (e.g., a methylsulfonyloxy group), an alkylthio
halide group (e.g., a difluoromethylthio group), an aryl group
substituted with two or more electron-withdrawing groups having the
Hammett substituent constant .sigma..sub.p value of 0.15 or more
(e.g., a 2,4-dinitrophenyl group, a pentachlorophenyl group), and a
heterocyclic group (e.g., a 2-benzoxazoyl group, a 2-benzothiazolyl
group, and a 1-phenyl-2-benzimidazolyl group).
[0130] Examples of the electron-withdrawing group having the
Hammett substituent constant .sigma..sub.p value of 0.20 or more
include, in addition to the above-described electron-withdrawing
group, a halogen atom and the like.
[0131] In the present invention, the electron-withdrawing group is
preferably an electron-withdrawing group having the Hammett
substituent constant .sigma..sub.p value of 0.20 or more. Among
these, a cyano group, a nitro group, an alkylsulfonyl group, an
arylsulfonyl group, an acyl group, an alkylsulfinyl group, an
arylsulfinyl group, a sulfamoyl group, an alkyl halide group, an
alkoxycarbonyl group, an aryloxycarbonyl group, a halogen atom, and
an amide group are preferred; and a cyano group, a nitro group, an
alkylsulfonyl group, an arylsulfonyl group, an acyl group, an alkyl
halide group, an alkoxycarbonyl group, a halogen atom, and an amide
group are more preferred.
[0132] The organic electron acceptor is preferably a compound
represented by Formula (2). Incidentally, when the electron
acceptor is a polymer compound, a polymer having, as a repeating
unit, a constituent corresponding to a compound represented by the
following Formula (2) is preferred.
X EWG).sub.na Formula (2)
[0133] In Formula (2), X represents a na-valent organic group. EWG
represents an electron-withdrawing group. na represents an integer
of 1 or more.
[0134] In Formula (2), the electron-withdrawing group of EWG has
the same meaning as the above-described electron-withdrawing group,
and a preferable range thereof is also the same.
[0135] In Formula (2), X is preferably a na-valent group
corresponding to a conjugated aliphatic group having two or more
carbon atoms, aromatic group, or a combination group thereof.
[0136] The conjugated aliphatic group is an aliphatic group having
a conjugated structure formed by an unsaturated bond, and may be
linear, branched, or cyclic. Further, the conjugated aliphatic
group may have a hetero atom. Specific examples of the aliphatic
group include aliphatic groups corresponding to ethylene,
butadiene, benzoquinone, cyclohexadiene, quinodimethane,
cyclohexene, and the like. Aliphatic groups corresponding to
benzoquinone, cyclohexadiene, and quinodimethane are preferred.
[0137] The aromatic group may be an aromatic hydrocarbon ring group
or an aromatic heterocyclic group.
[0138] The aromatic hydrocarbon ring group may be a monocyclic
hydrocarbon ring group having aromaticity, but as a basic ring
thereof, benzene ring is exemplified.
[0139] The aromatic heterocyclic group is not particularly limited
as long as it is a monocyclic heterocycle having aromaticity, but
5-membered aromatic heterocycle or 6-membered heterocycle is
preferably exemplified. Examples of the hetero atom for forming the
heterocycle include a sulfur atom, a nitrogen atom, and an oxygen
atom. Among these, a sulfur atom and a nitrogen atom are preferred.
Examples of the 5-membered aromatic heterocycle include a thiophene
ring, a furan ring, a pyrrole ring, an imidazole ring, a pyrazole
ring, an oxazole ring, an isoxazole ring, a thiazole ring, an
isothiazole ring, a triazole ring, and a thiadiazole ring. Examples
of the 6-membered aromatic heterocycle include a pyridine ring, a
pyrimidine ring, a pyridazine ring, a pyrazine ring, and a triazine
ring. Among these, a 5-membered aromatic heterocycle is more
preferred; and a thiophene ring, a pyrrole ring, a thiazole ring,
and a thiadiazole ring are further preferred.
[0140] These aliphatic groups or aromatic groups may have a
substituent other than the electron-withdrawing group EWG described
above, but it is preferable that these groups do not have the
substituent.
[0141] na represents an integer of 1 or more, preferably an integer
of 4 or more.
[0142] The organic electron acceptor that can be used in the
present invention is preferably a compound having a structure
represented by any one of Formulas (2A) to (2C).
##STR00015##
[0143] In Formulas (2A) to (2C), Rz represents a substituent.
Plural Rzs may be the same as or different from each other. Y
represents an oxygen atom, or a carbon atom substituted with two
electron-withdrawing groups. n represents an integer of 0 or more.
Two Rzs adjacent to each other may be bonded to each other to form
a ring.
[0144] The substituent in Rz is preferably an electron-withdrawing
group except for a group as a pendant to be incorporated into a
polymer. Incidentally, as the electron-withdrawing group, the
above-described electron-withdrawing group is exemplified, and a
preferable range is the same.
[0145] In Formula (2A), Rz is preferably a cyano group. In Formula
(2B), Rz is preferably a halogen atom, or a cyano group; more
preferably a halogen atom. In Formula (2C), Rz is preferably a
halogen atom, an alkyl group, an alkenyl group, an alkynyl group,
an alkoxycarbonyl group, an acyl group, a carbamoyl group, a
sulfamoyl group, an alkyl- or aryl-sulfonyl group, a perfluoroalkyl
group, a cyano group, or a nitro group.
[0146] In a case where Y is a carbon atom substituted with two
electron-withdrawing groups, the electron-withdrawing group is
preferably a cyano group or an acyl group.
[0147] The ring E is preferably a 5- or 6-membered ring, and more
preferably a 6-membered ring. Further, a saturated hydrocarbon ring
or an unsaturated hydrocarbon ring is preferred, and an aromatic
ring, a non-aromatic heterocycle, or a non-aromatic hydrocarbon
ring may be condensed to these rings. The aromatic ring, the
non-aromatic heterocycle, or the non-aromatic hydrocarbon ring is
preferably rings exemplified in the above Formulas (1A) and
(1B).
[0148] The ring E is preferably a 6-membered ring of a quinoid
structure (2,5-cyclopentadienyl-1,4-diylidene).
[0149] The rings F and G are preferably a 5- or 6-membered ring,
and may be an aromatic ring, a non-aromatic heterocycle, or a
non-aromatic hydrocarbon ring. The aromatic ring, the non-aromatic
heterocycle, or the non-aromatic hydrocarbon ring is preferably
rings exemplified in the above Formulas (1A) and (1B). Further, the
aromatic ring, the non-aromatic heterocycle, or the non-aromatic
hydrocarbon ring may be condensed.
[0150] The rings F and G each are preferably a ring selected from
the group consisting of a benzene ring, a naphthalene ring, a
pyridine ring, a thiophene ring, a thiadiazole ring, an
imidazolidinone ring, a thiazole ring, a 2H-imidazole ring, a
pyrazolone ring, a pyrrolidinedione ring, and a cyclopentadienone
ring.
[0151] Specific examples of the organic electron acceptor that can
be used in the present invention are shown below, but the present
invention is not limited thereto. Meanwhile, in the following
specific examples, symbol * represents a linking site of the
repeating unit.
##STR00016## ##STR00017## ##STR00018## ##STR00019##
[0152] Commercially available products can also be used as the
charge-transfer complex to be used in the present invention, and
the charge-transfer complex may be appropriately synthesized as in
Examples described later.
2. Metal Complex
[0153] A metal complex is exemplified as a second low band gap
material. Since the metal complex to be used in the present
invention has a specific optical band gap, when the metal complex
is used together with the nano conductive material as described
above, it is possible to enhance the performance of the
thermoelectric conversion element.
[0154] The content of the metal complex in the thermoelectric
conversion material is preferably 5 to 500 parts by mass and more
preferably 20 to 200 parts by mass relative to 100 parts by mass of
the nano conductive material, in terms of the thermoelectric
conversion performance.
[0155] In the thermoelectric conversion material of the present
invention, one kind of the metal complex may be used alone or two
or more kinds thereof may be used in combination.
[0156] The central metal of the metal complex is preferably a metal
atom selected from the group consisting of Ni, Fe, Cu and Sn, or a
metal ion thereof.
[0157] The atom that coordinates to the central metal is preferably
a hetero atom, and more preferably a sulfur atom, an oxygen atom,
or a nitrogen atom. Further, among the atoms that coordinate to the
central metal, at least one atom is preferably a sulfur atom or an
oxygen atom.
[0158] The metal complex that can be used in the present invention
is preferably metal complex represented by Formula (3).
##STR00020##
[0159] In Formula (3), M represents a metal atom selected from the
group consisting of Ni, Fe, Cu and Sn, or a metal ion thereof. When
M is a metal ion, the compound represented by Formula (3) may have
an arbitrary counter ion. X.sup.11, X.sup.12, X.sub.13 and X.sup.14
each independently represent a hetero atom; and at least one of
X.sup.11 to X.sup.14 is a sulfur atom or an oxygen atom. R.sup.11,
R.sup.12, R.sup.13 and R.sup.14 each independently represent a
substituent. R.sup.11 and R.sup.12 may be bonded to each other, and
R.sup.13 and R.sup.14 may be bonded to each other.
[0160] The hetero atom represented by X.sup.11 to X.sup.14 is
preferably a sulfur atom, an oxygen atom, or a nitrogen atom.
[0161] Examples of the substituent represented by R.sup.11 to
R.sup.14 include an alkyl group (e.g., a methyl group, an ethyl
group, a propyl group, an isopropyl group, a tert-butyl group, a
pentyl group, a hexyl group, an octyl group, a dodecyl group, a
tridecyl group, a tetradecyl group, and a pentadecyl group), a
cycloalkyl group (e.g., a cyclopentyl group, and a cyclohexyl
group), an alkenyl group (e.g., a vinyl group, and an allyl group),
an alkynyl group (e.g., an ethinyl group, and a propargyl group),
an aromatic hydrocarbon ring group (also referred to as "aromatic
carbon ring group" or "aryl group", e.g., a phenyl group, a
p-chlorophenyl group, a mesityl group, a tolyl group, a xylyl
group, a naphthyl group, an anthryl group, an azulenyl group, an
acenaphthenyl group, a fluorenyl group, a phenanthryl group, an
indenyl group, a pyrenyl group, and a biphenylyl group), an
aromatic heterocyclic group (preferably a 5- or 6-membered aromatic
heterocyclic group, and the hetero atom for forming the ring being
preferably a sulfur atom, a nitrogen atom, an oxygen atom, a
silicon atom, a boron atom, and a selenium atom, e.g., a pyridyl
group, a pyrimidinyl group, a furyl group, a pyrrolyl group, an
imidazolyl group, a benzimidazolyl group, a pyrazolyl group, a
pyrazinyl group, a triazolyl group (e.g., a 1,2,4-triazole-1-yl
group, and a 1,2,3-triazole-1-yl group), an oxazolyl group, a
benzoxazolyl group, a thiazolyl group, an isoxazolyl group, an
isothiazolyl group, a furazanyl group, a thienyl group, a quinolyl
group, a benzofuryl group, a dibenzofuryl group, a benzothienyl
group, a dibenzothienyl group, an indolyl group, a carbazolyl
group, a carbolinyl group, a diazacarbazolyl group (which is a
group in which one carbon atom for forming the carboline ring of
the above-described carbolinyl group is substituted with a nitrogen
atom), a quinoxalinyl group, a pyridazinyl group, a triazinyl
group, a quinazolinyl group, a phthalazinyl group, a borole group,
and an azaborine group), a heterocyclic group (which is an
non-aromatic heterocyclic group and may be a saturated ring or
unsaturated ring, preferably a 5- or 6-membered heterocyclic group,
and the hetero atom for forming the ring being preferably a sulfur
atom, a nitrogen atom, an oxygen atom, a silicon atom, and a
selenium atom, e.g., a pyrrolidyl group, an imidazolidyl group, a
morpholy group, and an oxazolyl group), an alkoxy group (e.g., a
methoxy group, an ethoxy group, a propyloxy group, a pentyloxy
group, a hexyloxy group, an octyloxy group, and a dodecyloxy
group), a cycloalkoxy group (e.g., a cyclopentyloxy group, and a
cyclohexyloxy group), an aryloxy group (e.g., a phenoxy group, and
a naphthyloxy group), an alkylthio group (e.g., a methylthio group,
an ethylthio group, a propylthio group, a pentylthio group, a
hexylthio group, an octylthio group, and a dodecylthio group), a
cycloalkylthio group (e.g., a cyclopentylthio group, and a
cyclohexylthio group), an arylthio group (e.g., a phenylthio group,
and a naphthylthio group), an alkoxycarbonyl group (e.g., a
methyloxycarbonyl group, an ethyloxycarbonyl group, a
butyloxycarbonyl group, an octyloxycarbonyl group, and a
dodecyloxycarbonyl group), an aryloxycarbonyl group (e.g., a
phenyloxycarbonyl group, and a naphthyloxycarbonyl group), a
sulfamoyl group (e.g., an aminosulfonyl group, a
methylaminosulfonyl group, a dimethylaminosulfonyl group, a
butylaminosulfonyl group, a hexylaminosulfonyl group, a
cyclohexylaminosulfonyl group, an octylaminosulfonyl group, a
dodecylaminosulfonyl group, a phenylaminosulfonyl group, a
naphthylaminosulfonyl group, and a 2-pyridylaminosulfonyl
group),
[0162] An acyl group (e.g., an acetyl group, an ethylcarbonyl
group, a propylcarbonyl group, a pentylcarbonyl group, a
cyclohexylcarbonyl group, an octylcarbonyl group, a
2-ethylhexylcarbonyl group, a dodecylcarbonyl group, an acryloyl
group, a methacryloyl group, a pheynylcarbonyl group, a
naphthylcarbonyl group, and a pyridylcarbonyl group), an acyloxy
group (e.g., an acetyloxy group, an ethylcarbonyloxy group, a
butylcarbonyloxy group, an octyl carbonyloxy group, a dodecyl
carbonyloxy group, and a phenylcarbonyloxy group), an amide group
(e.g., a methylcarbonylamino group, an ethylcarbonylamino group, a
dimethylcarbonylamino group, a propylcarbonylamino group, a
pentylcarbonylamino group, a cyclohexylcarbonylamino group, a
2-ethylhexylcarbonylamino group, an octylcarbonylamino group, a
dodecylcarbonylamino group, a phenylcarbonylamino group, and a
naphthylcarbonylamino group), a carbamoyl group (e.g., an
aminocarbonyl group, a methylaminocarbonyl group, a
dimethylaminocarbonyl group, a propylaminocarbonyl group, a
pentylaminocarbonyl group, a cyclohexylaminocarbonyl group, an
octylaminocarbonyl group, a 2-ethylhexylaminocarbonyl group, a
dodecylaminocarbonyl group, a phenylaminocarbonyl group, a
naphthylaminocarbonyl group, and a 2-pyridylaminocarbonyl group),
an ureido group (e.g., a methylureido group, an ethylureido group,
a pentylureido group, a cyclohexylureido group, an octylureido
group, a dodecylureido group, a phenylureido group, a
naphthylureido group, and a 2-pyridylaminoureido group), a sulfinyl
group (e.g., a methylsulfinyl group, an ethylsulfinyl group, a
butylsulfinyl group, a cyclohexylsulfinyl group,
2-ethylhexylsulfinyl group, a dodecylsulfinyl group, a
phenylsulfinyl group, a naphthylsulfinyl group, and a
2-pyridylsulfinyl group), an alkylsulfonyl group (e.g., a
methylsulfonyl group, an ethylsulfonyl group, a butylsulfonyl
group, a cyclohexylsulfonyl group, a 2-ethylhexylsulfonyl group,
and a dodecylsulfonyl group), an arylsulfonyl group or a
heteroarylsulfonyl group (e.g., a phenylsulfonyl group, a
naphthylsulfonyl group, and a 2-pyridylsulfonyl group), an amino
group (including an amino group, an alkylamino group, an arylamino
group and a heterocyclic amino group, e.g., an amino group, an
ethylamino group, a dimethylamino group, a butylamino group, a
cyclopentylamino group, a 2-ethylhexylamino group, a dodecylamino
group, an anilino group, a naphthylamino group, and a
2-pyridylamino group), a cyano group, a nitro group, a hydroxyl
group, a mercapto group, and a silyl group (e.g., a trimethylsilyl
group, a triisopropylsilyl group, a triphenylsilyl group, a
phenyldiethylsilyl group).
[0163] Among these, preferred examples thereof include an aromatic
hydrocarbon ring group, an aromatic heterocyclic group, a
heterocyclic group, an aryloxy group, an arylthio group, an
aryloxycarbonyl group, a sulfamoyl group, an acyl group, an acyloxy
group, an amide group, and a carbamoyl group.
[0164] The metal complex represented by Formula (3) is preferably a
metal complex represented by any one of Formulas (3A) to (3D).
##STR00021##
[0165] In Formulas (3A) to (3D), M has the same meaning as M in
Formula (3), and a preferable range thereof is also the same. When
M is a metal ion, the compound represented by any one of Formulas
(3A) to (3D) may have an arbitrary counter ion. X.sup.a11 to
X.sup.a14 each independently represent --S-- or --O--. R.sup.a11 to
R.sup.a14, R.sup.b11 and R.sup.b12 each independently represent a
hydrogen atom or a substituent. R.sup.c11 to R.sup.c14 each
independently represent a substituent. In R.sup.a11 to R.sup.a14,
R.sup.b11, R.sup.b12, and R.sup.c11 to R.sub.c14, two groups
adjacent to each other may be bonded to each other to form a ring.
nx represents an integer of 0 or more.
[0166] Examples of the substituent represented by R.sup.a11 to
R.sup.a14, R.sup.b11, R.sup.b12 and R.sup.c11 to R.sup.c14 include
the substituent exemplified as R.sup.11 to R.sup.14 described
above. R.sup.b11 and R.sup.b12 each are preferably a hydrogen atom,
an alkyl group or an aryl group.
[0167] Specific examples of the metal complex are shown below, but
the present invention is not limited thereto.
##STR00022## ##STR00023## ##STR00024##
[0168] Commercially available products can also be used as the
metal complex to be used in the present invention and the metal
complex may be chemically synthesized.
3. Arylamine Compound
[0169] An arylamine compound is exemplified as a third low band gap
material. Since the arylamine compound to be used in the present
invention has a specific optical band gap, when the arylamine
compound is used together with the nano conductive material as
described above, it is possible to enhance the performance of the
thermoelectric conversion element.
[0170] The content of the arylamine compound in the thermoelectric
conversion material is preferably 5 to 500 parts by mass and more
preferably 20 to 200 parts by mass relative to 100 parts by mass of
the nano conductive material, in terms of the thermoelectric
conversion performance.
[0171] In the thermoelectric conversion material of the present
invention, one kind of the arylamine compound may be used alone or
two or more kinds thereof may be used in combination.
[0172] The arylamine compound that can be used in the present
invention is preferably a one-electron oxidized derivative of an
arylamine compound represented by Formula (4A), or a two-electron
oxidized derivative of an arylamine compound represented by Formula
(4B).
##STR00025##
[0173] In Formula (4A), La represents an arylene group, a
heteroarylene group, or a combination group thereof. Ar.sup.41
represents an aromatic hydrocarbon ring group or an aromatic
heterocyclic group. R.sup.41 to R.sup.43 each independently
represent an aromatic hydrocarbon ring group, an aromatic
heterocyclic group, an alkyl group, an aryl group, or a cycloalkyl
group. Y represents an arbitrary counter anion. n of n.sup.-
represents an integer of 1 or more.
[0174] Here, when n is 2 or more, any one of Ar.sup.41 and R.sup.41
to R.sup.43 has a cationic substituent or a partial structure
(preferably radical cation of another nitrogen atom), but does not
have a nitrogen atom subjected to one-electron oxidation at a
position where .pi.-conjugation with the nitrogen atom subjected to
one-electron oxidation is carried out. It is necessary to break the
conjugation in an alkylene group or the like. If a nitrogen atom
subjected to one-electron oxidation is present at the conjugated
position, a quinoid structure is adopted.
[0175] The oxidation state of a two or more electron oxidized
derivative is unstable and n is preferably 2.
[0176] The arylene group in La is preferably a phenylene group. The
heterocycle of the heteroarylene group in La is preferably a 5- or
6-membered ring, or a benzene ring and a heterocycle may be
condensed. For example, a thiophene ring, a thiazole ring, a
pyridine ring, or the like is exemplified. Specific examples
thereof include thiophene-2,5-diyl and
benzo[1,2-b:4,5-b]dithiophene-2,6-diyl. Further, as the combination
group thereof, a biphenylene group is exemplified.
[0177] The one-electron oxidized derivative of the arylamine
compound represented by Formula (4A) is preferably a one-electron
oxidized derivative represented by Formula (4A-1).
##STR00026##
[0178] In Formula (4A-1), Ar.sup.41, R.sup.41 to R.sup.43, Y and
n.sup.- each have the same meaning as Ar.sup.41, R.sup.41 to
R.sup.43, Y and n.sup.- in Formula (4A), and preferable ranges
thereof are also the same. R.sup.4a represents a substituent.
n.sub.4a represents an integer of 0 to 4.
[0179] The substituent represented by R.sup.4a is preferably an
alkyl group or a halogen atom.
[0180] On the other hand, the two-electron oxidized derivative has
a quinoid structure (quinonediimine structure).
##STR00027##
[0181] In Formula (4B), Lb represents a group having a quinoid
structure of an aromatic hydrocarbon ring, a group having a quinoid
structure of an aromatic heterocycle, or a combination group
thereof. Ar.sup.41, R.sup.41 to R.sup.43, Y and n.sup.- each have
the same meaning as Ar.sup.41, R.sup.41 to R.sup.43, Y and n.sup.-
in Formula (4A), and preferable ranges thereof are also the same.
"n" in n.sup.- represents an integer of 2 or more.
[0182] Here, when n is 3 or more, that is, in the case where any
one of Ar.sup.41 and R.sup.41 to R.sup.43 has a cationic
substituent or a partial structure, oxidation state of two or more
electron oxidized derivative is unstable, and thus n is preferably
2.
[0183] The group having a quinoid structure of an aromatic
hydrocarbon ring in Lb is preferably a group having a quinoid
structure of a benzene ring (2,5-cyclohexadienyl-1,4-diylidene).
The aromatic heterocycle in the group having the quinoid structure
of the aromatic heterocycle in Lb is preferably a 5- or 6-membered
ring, a benzene ring and a heterocycle may be condensed, and for
example, a thiophene ring, a thiazole ring, a pyridine ring, or the
like is exemplified. Specific examples thereof include
thiophenyl-2,5-diylidene and
benzo[1,2-b:4,5-b]dithiophenyl-2,6-diylidene. Further, as the
combination group thereof, a group having a quinoid structure of a
biphenylene group is exemplified.
[0184] The two-electron oxidized derivative of the arylamine
compound represented by Formula (4B) is preferably a two-electron
oxidized derivative represented by Formula (4B-1).
##STR00028##
[0185] In Formula (4B-1), Ar.sup.41, R.sup.41 to R.sup.43, Y and
n.sup.- each have the same meaning as Ar.sup.41, R.sup.41 to
R.sup.43, Y and n.sup.- in Formula (4B), and preferable ranges
thereof are also the same. R.sup.4b represents a substituent.
n.sub.4b represents an integer of 0 to 4.
[0186] The substituent represented by R.sup.4b is preferably an
alkyl group or a halogen atom.
[0187] The arylamine compound that can be used in the present
invention is preferably a compound represented by Formula (5), or a
one- or two-electron oxidized derivative of the compound
represented by Formula (5). The one- or two-electron oxidized
derivative of the arylamine compound represented by Formula (5) may
have an arbitrary counter anion.
##STR00029##
[0188] In Formula (5), Ar.sup.51 to Ar.sup.55 each independently
represent an aromatic hydrocarbon ring, an aromatic heterocycle, a
single bond, or an alkylene group, proviso that at least one of
Ar.sup.51 and Ar.sup.52 is an aromatic hydrocarbon ring and at
least one of Ar.sup.53 and Ar.sup.54 is an aromatic hydrocarbon
ring. R.sup.51 to R.sup.55 each independently represent a
substituent. n.sub.51 to n.sub.55 each independently represent an
integer of 0 to 3. ml represents 0 or 1.
[0189] Examples of the aromatic hydrocarbon ring represented by
Ar.sup.51 to Ar.sup.55 include a benzene ring and a naphthalene
ring. Among these, a benzene ring is preferred.
[0190] Examples of the aromatic heterocycle represented by
Ar.sup.51 to Ar.sup.55 include a pyrrole ring, a thiophene ring, a
furan ring, an imidazole ring, a pyrazole ring, an oxazole ring, an
isoxazole ring, a thiazole ring, an isothiazole ring, a silole
ring, a selenophene ring, a tellurophene ring, a benzoquinone ring,
a cyclopentadiene ring, a pyridine ring, a pyridone-2-one ring, a
pyrimidine ring, a pyridazine ring, a pyrazine ring, and a triazine
ring. Among these, a thiophene ring, a furan ring and a pyridine
ring are preferred.
[0191] As the alkylene group of Ar.sup.51 to Ar.sup.55, an alkylene
group having 2 to 14 carbon atoms is exemplified, and an alkylene
group having 2 to 8 carbon atoms is preferred.
[0192] Examples of the substituent represented by R.sup.51 to
R.sup.55 include an alkyl group, an alkenyl group, an alkynyl
group, an amino group, a dialkylamino group, a diarylamino group,
N-alkyl-N-arylamino group, an alkoxy group, an aryloxy group, an
alkylthio group, an arylthio group, and a halogen atom. These
groups may be further substituted. For example, an aryl part of a
diarylamino group may be further substituted with a dialkylamino
group or a diarylamino group. Further, a hydrogen atom in an alkyl
part of these groups may be substituted with a halogen atom.
R.sup.51 to R.sup.55 each are preferably a dialkylamino group, a
diarylamino group, or an alkoxy group; and more preferably an
alkylamino group.
[0193] The one-electron oxidized derivative of the compound
represented by Formula (5) is a derivative in which a nitrogen atom
(>N--) with which at least one aromatic ring included in the
above Formula (5) is substituted becomes a radical cation
(>N.sup..+--).
[0194] Incidentally, in the present specification, the one-electron
oxidized derivative means an oxidation state on one nitrogen atom,
and includes a derivative in which another nitrogen atom present at
a position at which a quinoid structure cannot be formed is
subjected to one-electron oxidation so as to have two or more
radical cationic nitrogen atoms in total.
[0195] Specific examples of the arylamine compound that can be used
in the present invention are shown below, but the present invention
is not limited thereto. Further, these compounds may have an
arbitrary counter anion.
##STR00030## ##STR00031## ##STR00032## ##STR00033##
##STR00034##
[0196] Commercially available products can also be used as the
arylamine compound to be used in the present invention and the
arylamine compound may be chemically synthesized.
<Polymer Compound>
[0197] The thermoelectric conversion material of the present
invention preferably contains a polymer compound in addition to the
nano conductive material and the low band gap material. When the
thermoelectric conversion material contains the polymer compound,
the thermoelectric conversion performance of the thermoelectric
conversion element can be further enhanced.
[0198] Examples of the polymer compound include a conjugated
polymer and a non-conjugated polymer. The thermoelectric conversion
material of the present invention preferably contains at least one
of the conjugated polymer and the non-conjugated polymer and more
preferably contains both of the conjugated polymer and the
non-conjugated polymer. Further, two or more conjugated polymers or
non-conjugated polymers may be contained. When the thermoelectric
conversion material contains both of the conjugated polymer and the
non-conjugated polymer, still further enhancement of the
thermoelectric conversion performance can be realized.
[0199] The polymer compound may be a homopolymer or a copolymer.
When the polymer compound is a copolymer, the polymer compound may
be a block copolymer, a random copolymer, or an alternate
copolymer. Moreover, the polymer compound may also be a graft
copolymer or the like.
[0200] The content of the polymer compound in the thermoelectric
conversion material is not particularly limited, but in terms of
the thermoelectric conversion performance, is preferably 10 to 80%
by mass, more preferably 20 to 70% by mass, and further preferably
30 to 60% by mass in the total solid content of the thermoelectric
conversion material, that is, in the thermoelectric conversion
layer.
[0201] The content of the conjugated polymer compound in the
thermoelectric conversion material is not particularly limited, but
in terms of the thermoelectric conversion performance, within the
range that suffices the above-described content of the polymer
compound, is preferably 15 to 70% by mass, more preferably 25 to
60% by mass, and further preferably 30 to 50% by mass in the total
solid content of the thermoelectric conversion material, that is,
in the thermoelectric conversion layer.
[0202] Similarly, the content of the non-conjugated polymer
compound in the thermoelectric conversion material is not
particularly limited, but in terms of the thermoelectric conversion
performance, within the range that suffices the above-described
content of the polymer compound, is preferably 20 to 70% by mass,
more preferably 30 to 65% by mass, and further preferably 35 to 60%
by mass in the total solid content of the thermoelectric conversion
material, that is, in the thermoelectric conversion layer.
1. Conjugated Polymer
[0203] The conjugated polymer is not particularly limited as long
as it is a compound having a main chain with a structure which is
conjugated by .pi. electrons or lone-pair electrons (a lone pair).
As such a conjugated structure, for example, a structure in which a
single bond and a double bond are alternately connected in a
carbon-to-carbon bond on a main chain is exemplified.
[0204] Examples of such a conjugated polymer include conjugated
polymers having, as a repeating unit, a constituent derived from at
least one compound selected from the group consisting of a
thiophene-based compound, a pyrrole-based compound, an
acetylene-based compound, a p-arylene-based compound, a
p-arylenevinylene-based compound, a p-aryleneethynylene-based
compound, a p-fluorenylenevinylene-based compound, a fluorene-based
compound, an aromatic polyamine-based compound (also referred to as
an arylamine-based compound), a polyacene-based compound, a
polyphenanthrene-based compound, a metal-phthalocyanine-based
compound, a p-xylylene-based compound, a vinylenesulfide-based
compound, a m-phenylene-based compound, a naphthalenevinylene-based
compound, a p-phenyleneoxide-based compound, a
phenylenesulfide-based compound, a furan-based compound, a
selenophene-based compound, an azo-based compound, and a metal
complex-based compound.
[0205] Among these, from the viewpoint of thermoelectric conversion
performance, a conjugated polymer having, as a repeating unit, a
constituent derived from at least one compound selected from the
group consisting of a thiophene-based compound, a pyrrole-based
compound, an acetylene-based compound, a p-phenylene-based
compound, a p-phenylenevinylene-based compound, a
p-phenyleneethynylene-based compound, a fluorene-based compound,
and an arylamine-based compound.
[0206] A substituent to be introduced into the compounds described
above is not particularly limited, but it is preferable to
appropriately select and introduce a substituent which can improve
the dispersibility of the conjugated polymer in the dispersion
medium, in consideration of compatibility with other components,
types of dispersion mediums to be used, and the like.
[0207] As an example of the substituent, when an organic solvent is
used as the dispersion medium, a linear, branched, or cyclic alkyl
group, alkenyl group, alkynyl group, alkoxy group, or thioalkyl
group, and also alkoxyalkyleneoxy group, alkoxyalkyleneoxyalkyl
group, crown ether group, or aryl group can be preferably used.
These groups may further have a substituent. In addition, the
number of carbon atoms of the substituent is not particularly
limited, but is preferably 1 to 12 and more preferably 4 to 12. A
long-chain alkyl group, alkoxy group, thioalkyl group,
alkoxyalkyleneoxy group, or alkoxyalkyleneoxyalkyl group having 6
to 12 carbon atoms is particularly preferred.
[0208] On the other hand, when an aqueous medium is used as the
dispersion medium, a hydrophilic group such as a carboxylic acid
group, a sulfonate group, a hydroxyl group, or a phosphate group is
preferably further introduced into each monomer terminal or the
above-described substituent. In addition thereto, a dialkylamino
group, a monoalkylamino group, an amino group, a carboxyl group, an
ester group, an amide group, a carbamate group, a nitro group, a
cyano group, an isocyanate group, an isocyano group, a halogen
atom, a perfluoroalkyl group, a perfluoroalkoxy group, or the like
can be introduced as the substituent, and such introduction is
preferred.
[0209] The number of substituents that can be introduced is not
particularly limited, but in consideration of the dispersibility,
the compatibility, and the electrical conductivity of the
conjugated polymer, one or a plurality of substituents can be
introduced as appropriate.
[0210] As the conjugated polymer, specifically, a conductive
polymer described in JP-A-2012-251132 can be preferably used.
[0211] The molecular weight of the conjugated polymer is preferably
3,000 to 200,000 and more preferably 5,000 to 100,000. A weight
average molecular weight can be measured by Gel Permeation
Chromatography (GPC). The specific measurement method is the same
as in the case of the charge-transfer complex.
2. Non-Conjugated Polymer
[0212] The non-conjugated polymer is a polymer compound which does
not exhibit electric conductivity in the conjugated structure of
the polymer main chain. Specifically, the non-conjugated polymer is
a polymer other than a polymer having a polymer main chain
consisting of a ring, a group, or an atom selected from an aromatic
ring (carbocyclic aromatic ring or heteroaromatic ring), an
ethylene bond, an ethenylene bond, and a hetero atom having
lone-pair electrons.
[0213] Such a non-conjugated polymer is not particularly limited,
and generally known non-conjugated polymer may be used. From the
viewpoint of the thermoelectric conversion performance, a
non-conjugated polymer having, as a repeating unit, a constituent
derived from at least one compound selected from the group
consisting of a vinyl compound, a (meth)acrylate compound, a
carbonate compound, an ester compound, an amide compound, an imide
compound, and a siloxane compound. These compounds may have a
substituent, and as the substituent, the same substituent as that
of the conjugated polymer is exemplified.
[0214] In the present invention, the term "(meth)acrylate" means
both or either of acrylate and methacrylate, and a mixture of
these.
[0215] Specific examples of the vinyl compound that forms
polyvinyl-based polymer include a vinylarylamines such as styrene,
vinylpyrrolidone, vinylcarbazole, vinylpyridine, vinylnaphthalene,
vinylphenol, vinyl acetate, styrenesulfonic acid,
vinyltriphenylamine; and vinyltrialkylamines such as
vinyltributylamine.
[0216] Specific examples of the (meth)acrylate compound that forms
the poly(meth)acrylate include acrylate monomers including
hydrophobic acrylic alkyl esters such as methyl acrylate, ethyl
acrylate, propyl acrylate, and butyl acrylate; acrylic hydroxyalkyl
esters such as 2-hydroxyethyl acrylate, 1-hydroxyethyl acrylate,
2-hydroxypropyl acrylate, 3-hydroxypropyl acrylate, 1-hydroxypropyl
acrylate, 4-hydroxybutyl acrylate, 3-hydroxybutyl acrylate,
2-hydroxybutyl acrylate, and 1-hydroxybutyl acrylate; and
methacrylate monomers in which the acryloyl groups of these
monomers are changed to methacryloyl groups.
[0217] Specific examples of the polycarbonate include
general-purpose polycarbonates formed from bisphenol A and
phosgene, IUPIZETA (trade name, manufactured by MITSUBISHI GAS
CHEMICAL CO., INC.), and PANLITE (trade name, manufactured b TEIJIN
LIMITED).
[0218] As the compound for forming the polyester, polyalcohol, and
a hydroxy acid such as polycarboxylic acid and lactic acid can be
exemplified. Specific examples of the polyester include VYLON
(trade name, manufactured by TOYOBO CO., LTD.).
[0219] Specific examples of the polyamide include PA-100 (trade
name, manufactured by T&K TOKA CO., LTD).
[0220] Specific examples of the polyimide include SOLPIT 6,6-PI
(trade name, manufactured by Solpit Industries, Ltd.).
[0221] Specific examples of the polysiloxane include
polydiphenylsiloxane and polyphenylmethylsiloxane.
[0222] The molecular weight of the non-conjugated polymer is
preferably 5,000 to 300,000 and more preferably 10,000 to 150,000.
A weight average molecular weight can be measured by Gel Permeation
Chromatography (GPC). The specific measurement method is the same
as in the case of the charge-transfer complex.
<Dispersion Medium>
[0223] The thermoelectric conversion material of the present
invention contains a dispersion medium, and a nano conductive
material is dispersed in this dispersion medium.
[0224] The dispersion medium may disperse the nano conductive
material, and water, an organic solvent, and mixed solvents thereof
can be used. The solvent is preferably an organic solvent, and
preferred examples include alcohols; aliphatic halogen-based
solvents such as chloroform; aprotic polar solvents such as DMF,
NMP and DMSO; aromatic solvents such as chlorobenzene,
dichlorobenzene, benzene, toluene, xylene, mesitylene, tetralin,
tetramethylbenzene, and pyridine; ketone-based solvents such as
cyclohexanone, acetone, and methyl ethyl ketone; and ether-based
solvents such as diethyl ether, THF, t-butyl methyl ether,
dimethoxyethane, and diglyme, and more preferred examples include
halogen-based solvents such as chloroform, aprotic polar solvents
such as DMF and NMP; aromatic solvents such as dichlorobenzene,
xylene, tetralin, and tetramethylbenzene; and ether-based solvents
such as THF.
[0225] For the thermoelectric conversion material of the present
invention, one kind of the dispersion medium may be used alone or
two or more kinds thereof may be used in combination.
[0226] Furthermore, it is preferable to have the dispersion medium
degassed in advance and to adjust the dissolved oxygen
concentration in the dispersion medium to 10 ppm or less. Examples
of the method of degassing include a method of irradiating
ultrasonic waves under reduced pressure; and a method of bubbling
an inert gas such as argon.
[0227] Furthermore, it is preferable to have the dispersion medium
dehydrated in advance. It is preferable to adjust the amount of
water in the dispersion medium to 1,000 ppm or less, and more
preferably to 100 ppm or less. Regarding the method of dehydration
of the dispersion medium, known methods such as a method of using a
molecular sieve, and distillation, can be used.
[0228] The amount of the dispersion medium in the thermoelectric
conversion material is preferably 25 to 99.99% by mass, more
preferably 30 to 99.95% by mass, and further preferably 30 to 99.9%
by mass, relative to the total amount of the thermoelectric
conversion material.
<Dopant >
[0229] When the thermoelectric conversion material of the present
invention contains the conjugated polymer described above, it is
preferable to further contain a dopant in terms of the fact that
the electrical conductivity of the thermoelectric conversion layer
can be enhanced due to an increase in carrier concentration.
[0230] The dopant is a compound that is doped into the
above-described conjugated polymer, and may be any compound capable
of doping the conjugated polymer to have a positive charge (p-type
doping) by protonizing the conjugated polymer or eliminating
electrons from the .pi.-conjugated system of the conjugated
polymer. Specifically, an onium salt compound, an oxidizing agent,
an acidic compound, an electron acceptor compound and the like as
described below can be used.
1. Onium Salt Compound
[0231] The onium salt compound to be used as the dopant preferably
includes a compound (an acid generator, acid precursor) that
generates acid by providing energy such as irradiation of active
energy rays (such as radiation and electromagnetic waves). Specific
examples of such onium salt compounds include a sulfonium salt, an
iodonium salt, an ammonium salt, a carbonium salt, and a
phosphonium salt. Among these, a sulfonium salt, an iodonium salt,
an ammonium salt, or a carbonium salt is preferred, a sulfonium
salt, an iodonium salt, or a carbonium salt is more preferred, a
sulfonium salt, an iodonium salt is particularly preferred.
Specific examples of an anion part constituting such a salt include
counter anions of strong acid.
[0232] As the onium salt compound, specifically, an onium salt
compound described in JP-A-2012-251132 can be preferably used.
2. Oxidizing agent, acidic compound, and electron acceptor
compound
[0233] Specific examples of the oxidizing agent to be used as the
dopant in the present invention include halogen (Cl.sub.2,
Br.sub.2, I.sub.2, ICl, ICl.sub.3, IBr, IF), Lewis acid (PF.sub.5,
AsF.sub.5, SbF.sub.5, BF.sub.3, BCl.sub.3, BBr.sub.3, SO.sub.3), a
transition metal compound (FeCl.sub.3, FeOCl, TiCl.sub.4,
ZrCl.sub.4, HfCl.sub.4, NbF.sub.5, NbCl.sub.5, TaCl.sub.5,
MoF.sub.5, MoCl.sub.5, WF.sub.6, WCl.sub.6, UF.sub.6, LnCl.sub.3
(Ln=lanthanoid such as La, Ce, Pr, Nd and Sm), and also O.sub.2,
O.sub.3, XeOF.sub.4, (NO.sub.2.sup.+)(SbF.sub.6.sup.-),
(NO.sub.2.sup.+)(SbCl.sub.6.sup.-,
(NO.sub.2.sup.+)(BF.sub.4.sup.-), FSO.sub.2OOSO.sub.2F,
AgClO.sub.4, H.sub.2IrCl.sub.6 and
La(NO.sub.3).sub.3.6H.sub.2O.
[0234] As the acidic compound, polyphosphoric acid(diphosphoric
acid, pyrophosphoric acid, triphosphoric acid, tetraphosphoric
acid, metaphosphoric acid, and the like), hydroxy compound, carboxy
compound, or sulfonic acid compound, proton acid (HF, HCl,
HNO.sub.3, H.sub.2SO.sub.4, HClO.sub.4, FSO.sub.3H, CISO.sub.3H,
CF.sub.3SO.sub.3H, various organic acids, amino acids and the like)
are exemplified.
[0235] Examples of the electron acceptor compound include TCNQ
(tetracyanoquinodimethane), tetrafluorotetracyanoquinodimethane,
halogenated tetracyanoquinodimethane, 1,1-dicyanovinylene,
1,1,2-tricyanovinylene, benzoquinone, pentafluorophenol,
dicyanofluorenone, cyano-fluoroalkylsulfonyl-fluorenone, pyridine,
pyrazine, triazine, tetrazine, pyridopyrazine, benzothiadiazole,
heterocyclic thiadiazole, porphyrin, phthalocyanine, boron
quinolate-based compounds, boron diketonate-based compounds, boron
diisoindomethene-based compounds, carborane-based compounds, other
boron atom-containing compounds, and the electron acceptor
compounds described in Chemistry Letter, 1991, pp. 1707-1710.
[0236] In the present invention, it is not essential to use these
dopants, but it is preferable that further enhancement of the
thermoelectric conversion property be expected by the improvement
of the electrical conductivity when the dopant is used. In case of
using the dopant, one kind thereof may be used alone or two or more
kinds thereof may be used in combination. Regarding the used amount
of the dopant, from the viewpoint of controlling the optimum
carrier concentration, the dopant is used preferably in a ratio of
more than 0 part by mass but 80 parts by mass or less, more
preferably in a ratio of more than 0 part by mass but 60 parts by
mass or less, further preferably in a ratio of 2 to 50 parts by
mass, and still more preferably 5 to 40 parts by mass, relative to
100 parts by mass of the polymer compound described above.
[0237] Among the dopants described above, an onium salt compound is
preferably used from the viewpoint of improving the dispersibility
and the film-forming property of the thermoelectric conversion
material. The onium salt compound is neutral before acid release,
and generates an acid by being decomposed when energy such as light
or heat is imparted, and this acid causes doping effect to be
developed. Therefore, after the thermoelectric conversion material
is formed and processed into a desired shape, the doping is carried
out by light irradiation or the like and thus the doping effect can
be exerted. Further, since the onium salt compound is neutral
before acid release, each component such as the conjugated polymer
or the nano conductive material is uniformly dissolved or dispersed
in the thermoelectric conversion material without the aggregation
or precipitation of the above-described conjugated polymer. Due to
this uniform solubility or dispersibility of the thermoelectric
conversion material, excellent electrical conductivity can be
exerted after doping. Further, since favorable coating property or
film-forming property can be achieved, the formation or processing
of the thermoelectric conversion layer and the like is also
excellent.
<Metal Element>
[0238] In the thermoelectric conversion material of the present
invention, a metal element is preferably contained as a simple
substance, an ion, or the like, in terms of further improving
thermoelectric conversion performance. One kind of the metal
elements can be used alone or two or more kinds thereof can be used
in combination.
[0239] In the case where the thermoelectric conversion material
contains the metal element, electron transportation in the
thermoelectric conversion layer to be formed is promoted by the
metal element, and thus thermoelectric conversion performance are
considered to be improved. The metal element is not particularly
limited, but a metal element having an atomic weight of 45 to 200
is preferable, a transition metal element is more preferable, and
zinc, iron, palladium, nickel, cobalt, molybdenum, platinum, and
tin are particularly preferable, in terms of thermoelectric
conversion performance. Regarding the added amount of the metal
element, as the added amount is too small, the effect of enhancing
the thermoelectric conversion characteristics is not sufficiently
exerted; on the other hand, as the added amount is too large, the
physical strength of the thermoelectric conversion layer is
decreased and the thermoelectric conversion characteristics is
decreased due to the occurrence of cracks in some cases.
[0240] The mixing rate of the metal element is preferably 50 to
30,000 ppm, more preferably 100 to 10,000 ppm, and further
preferably 200 to 5,000 ppm in the total solid content of the
preliminary mixture in terms of the thermoelectric conversion
characteristics of the thermoelectric conversion layer. The
concentration of the metal element in the dispersion can be
measured by a well-known method using, for example, an ICP mass
spectrometer (for example, ICPM-8500 (trade name, manufactured by
Shimadzu Corporation)), or an energy dispersive X-ray fluorescence
spectrometer (for example, EDX-720 (trade name, manufactured by
Shimadzu Corporation)).
[0241] The mixing rate of other components is preferably 5% by mass
or less and more preferably 0 to 2% by mass in the total solid
content of the preliminary mixture.
<Other Component>
[0242] In addition to the above-described component, the
thermoelectric conversion material of the present invention may
contain an antioxidant, a light-resistant stabilizer, a
heat-resistant stabilizer and a plasticizer.
[0243] Specific examples of the antioxidant include IRGANOX 1010
(manufactured by Nihon Ciba-Geigy K.K.), SUMILIZER GA-80
(manufactured by Sumitomo Chemical Co., Ltd.), SUMILIZER GS
(manufactured by Sumitomo Chemical Co., Ltd.) and SUMILIZER GM
(manufactured by Sumitomo Chemical Co., Ltd.). Specific examples of
the light-resistant stabilizer include TINUVIN 234 (manufactured by
BASF), CHIMASSORB 81 (manufactured by BASF) and CYASORB UV-3853
(manufactured by Sun Chemical Corporation). Specific examples of
the heat-resistant stabilizer include IRGANOX 1726 (manufactured by
BASF). Specific examples of the plasticizer include ADK CIZER RS
(manufactured by ADEKA Corporation).
[0244] The mixing rate of other components is preferably 5% by mass
or less and more preferably 0 to 2% by mass in the total solid
content of the preliminary mixture.
<Preparation of Thermoelectric Conversion Material>
[0245] The thermoelectric conversion material of the present
invention can be prepared by mixing the various components
described above. Preferably, the thermoelectric conversion material
is prepared by mixing a nano conductive material, a low band gap
material, each component as demanded in a dispersion medium, and
dissolving or dispersing the components. At this time, regarding
each component in the thermoelectric conversion material, it is
preferable that the nano conductive material be in a dispersed
state, while other components such as the low band gap material and
a polymer are in a dispersed or dissolved state; and more
preferable that the components other than the nano conductive
material be in a dissolved state. When the components other than
the nano conductive material are in a dissolved state, it is
preferable because an effect of suppressing a decrease in the
electrical conductivity by grain boundaries may be obtained.
Meanwhile, the dispersed state as described above refers to a state
of molecular aggregation having a particle size to the extent that
even though the material is stored for a long time (as a rough
indication, for one month or more), sedimentation does not occur in
the solvent, and the dissolved state refers to a state in which the
component is solvated in the state of individual molecules in the
solvent.
[0246] There are no particular limitations on the method for
preparing a thermoelectric conversion material, and the material
can be prepared at normal temperature and normal pressure using a
conventional mixing apparatus or the like. For example, the
material may be prepared by dissolving or dispersing various
components in a solvent by stirring, shaking, or kneading. An
ultrasonication treatment may also be carried out in order to
accelerate dissolution or dispersion.
[0247] In the above dispersion process, dispersibility of the nano
conductive material can be increased by heating the solvent to a
temperature higher than or equal to room temperature and lower than
or equal to the boiling point, by prolonging the dispersion time,
or by increasing the application intensity of stirring,
infiltration, kneading, ultrasonic waves and the like.
[Thermoelectric Conversion Element]
[0248] The thermoelectric conversion element of the present
invention includes the first electrode, the thermoelectric
conversion layer, and the second electrode on the substrate. The
thermoelectric conversion layer contains the nano conductive
material and the low band gap material.
[0249] The thermoelectric conversion element of the present
invention may be a thermoelectric conversion element including the
first electrode, the thermoelectric conversion layer, and the
second electrode on the substrate. The other configurations such as
the positional relationship between the first and second electrodes
and the thermoelectric conversion layer are not particularly
limited. In the thermoelectric conversion element of the present
invention, the thermoelectric conversion layer may be disposed such
that at least one surface thereof comes into contact with the first
electrode and the second electrode. For example, the thermoelectric
conversion element may have an aspect in which the thermoelectric
conversion layer is interposed between the first electrode and the
second electrode, that is, the thermoelectric conversion element of
the present invention may have an aspect in which the first
electrode, the thermoelectric conversion layer, and the second
electrode are provided in this order on a substrate. Moreover, the
thermoelectric conversion element may have an aspect in which one
surface of the thermoelectric conversion layer is disposed to come
into contact with both of the first electrode and the second
electrode, that is, the thermoelectric conversion element of the
present invention may have an aspect in which the thermoelectric
conversion layer is laminated on both of the first electrode and
the second electrode, the electrodes being separately formed each
other on the substrate.
[0250] As an example of the structure of the thermoelectric
conversion element of the present invention, the structures of the
elements illustrated in FIG. 1 and FIG. 2 are exemplified. In FIG.
1 and FIG. 2, the arrows indicate a direction of temperature
difference at the use of the thermoelectric conversion element.
[0251] Thermoelectric conversion element 1 illustrated in FIG. 1
includes, on first substrate 12, a pair of electrodes of first
electrode 13 and second electrode 15, and thermoelectric conversion
layer 14 formed by the thermoelectric conversion material of the
present invention provided between electrodes 13 and 15. Second
substrate 16 is disposed on the other surface of second electrode
15, and metal plates 11 and 17 are disposed at the outsides of
first substrate 12 and second substrate 16 to face each other.
[0252] In the thermoelectric conversion element of the present
invention, the thermoelectric conversion layer is preferably formed
in the shape of a film (membrane) on the substrate with the
electrodes interposed therebetween by using the thermoelectric
conversion material of the present invention. For thermoelectric
conversion element 1, it is preferable that first electrode 13 or
second electrode 15 be provided on the surface (formed surface of
thermoelectric conversion layer 14) of two substrates 12 and 16,
and the structure have the thermoelectric conversion layer 14 which
is formed by the thermoelectric conversion material of the present
invention being provided between these electrodes 13 and 15.
[0253] In thermoelectric conversion element 2 illustrated in FIG.
2, first electrode 23 and second electrode 25 are disposed on first
substrate 22, and thermoelectric conversion layer 24 is formed
thereon which is formed by the thermoelectric conversion material
of the present invention.
[0254] In thermoelectric conversion layer 14 of thermoelectric
conversion element 1, One surface thereof is covered with first
substrate 12 with first electrode 13 interposed therebetween. From
the viewpoint of the protection of thermoelectric conversion layer
14, it is preferable that other surface of thermoelectric
conversion layer 14 also come into press contact with second
substrate 16. At this time, it is preferable that second electrode
15 be interposed between thermoelectric conversion layer 14 and
substrate 16. In addition, in thermoelectric conversion layer 24 of
thermoelectric conversion element 2, on surface thereof is covered
with first electrode 23, second electrode 25, and first substrate
22. From the viewpoint of the protection of thermoelectric
conversion layer 24, it is preferable that other surface of
thermoelectric conversion layer 24 also come into press contact
with second substrate 26. That is, it is preferable that second
electrode 15 be formed in advance on the surface of second
substrate 16 (a compression bonding surface of thermoelectric
conversion layer 14) to be used in thermoelectric conversion
element 1. Further, in thermoelectric conversion elements 1 and 2,
press contact of the electrode and the thermoelectric conversion
layer is preferably carried out with heating to approximately
100.degree. C. to 200.degree. C., from the viewpoint of enhancing
adhesion.
[0255] For the substrate of the thermoelectric conversion element
of the present invention, first substrate 12 and second substrate
16 of thermoelectric conversion element 1, a substrate material
such as glass, transparent ceramics, a metal, or a plastic film can
be used. In the thermoelectric conversion element of the present
invention, a substrate having flexibility is preferred.
Specifically, it is preferable to use a substrate having
flexibility in which the number of cycles on folding endurance test
MIT by the measurement method according to ASTM D2176 is 10,000 or
more. Such a substrate having flexibility is preferably a plastic
film, and preferred examples of the plastic film include a
polyester film such as a polyethylene terephthalate, a polyethylene
isophthalate, a polyethylene naphthalate, a polybutylene
terephthalate, a poly(1,4-cyclohexylene dimethylene terephthalate),
a polyethylene-2,6-phthalenedicarboxylate, and a polyester film of
bisphenol A and isophthalic acid and terephthalic acid; a
polycycloolefin film such as Zeonor Film (trade name, manufactured
by Zeon Corporation), Arton Film (trade name, manufactured by JSR
Corporation) and SUMILITE FS1700 (trade name, manufactured by
SUMITOMO BAKELITE CO., LTD.); a polyimide film Kapton (trade name,
manufactured by DU PONT-TORAY CO., LTD.), APICAL (trade name,
manufactured by Kaneka Corporation), Upilex (trade name, Ube
Industries, Ltd.) and POMIRAN (trade name, manufactured by Arakawa
Chemical Industries, Ltd.); a polycarbonate film such as PURE ACE
(trade name, manufactured by Teijin Chemicals Ltd.) and ELMEC
(trade name, manufactured by Kaneka Corporation); a polyether ether
ketone film such as SUMILITE FS1100 (trade name, manufactured by
SUMITOMO BAKELITE CO., LTD.); and a polyphenylsulfide film such as
TORELINA (trade name, manufactured by Toray Industries, Inc.).
Appropriate selection is allowed depending on using conditions and
an environment, but from viewpoints of easy availability, heat
resistance, preferably, of 100.degree. C. or higher, profitability
and an effect, a commercially available polyethylene terephthalate
film, polyethylene naphthalate film, various kinds of polyimide
films, polycarbonate film, and the like are preferred.
[0256] In particular, it is preferably to use a substrate provided
with an electrode material which is arranged on a compression
bonding surface with the thermoelectric conversion layer. As the
electrode material for which the first electrode and the second
electrode are provided on this substrate, such a material can be
used as a transparent electrode such as ITO and ZnO, a metal
electrode such as silver, copper, gold and aluminum, a carbon
material such as CNT and graphene, an organic material such as
PEDOT/PSS, conductive paste into which conductive particulates such
as silver and carbon are dispersed, and conductive paste containing
a metal nanowire of silver, copper and aluminum. Among these,
aluminum, gold, silver, or copper is preferable. At this time, in
thermoelectric conversion element 1, substrate 11, first electrode
13, thermoelectric conversion layer 14, and second electrode 15 are
configured in this order. Outside of second electrode 15, second
substrate 16 may be adjacent thereto, or second electrode 15 may be
exposed to the air as an outermost surface without providing second
substrate 16. Further, in thermoelectric conversion element 2,
substrate 22, first electrode 23, and second electrode 25,
thermoelectric conversion layer 24 are configured in this order.
Outside of thermoelectric conversion layer 24, second substrate 26
may be adjacent thereto, or thermoelectric conversion layer 24 may
be exposed to the air as an outermost surface without providing
second substrate 26.
[0257] In view of handling properties, durability or the like,
thickness of the substrate is preferably 30 to 3,000 .mu.m, more
preferably, 50 to 1,000 .mu.m, further preferably, 100 to 1,000
.mu.m, and particularly preferably, 200 to 800 .mu.m. When the
thickness of the substrate is set within the range, the thermal
conductivity is not decreased and the damage of the film (the
thermoelectric conversion layer) due to external impact is also
less likely to occur.
[0258] It is preferable that the thermoelectric conversion layer of
the thermoelectric conversion element of the present invention be
formed by the thermoelectric conversion material of the present
invention and, in addition thereto, contain the polymer described
above, and the dopant or a decomposed substance thereof, the metal
element, and other components may be contained. The components and
the content thereof in the thermoelectric conversion layer are as
described above.
[0259] In the thermoelectric conversion element of the present
invention, the carrier concentration of the thermoelectric
conversion layer is preferably 1.times.10.sup.23 to
1.times.10.sup.26/m.sup.3 and more preferably 1.times.10.sup.24 to
5.times.10.sup.25/m.sup.3. The carrier concentration of the
material is generally known to have an influence on the
thermoelectric conversion performance thereof, and when the carrier
concentration of the thermoelectric conversion layer is within the
above range, it is possible to achieve satisfactory thermoelectric
conversion performance, which is preferred. When the thermoelectric
conversion layer is formed using the thermoelectric conversion
material of the present invention, the above-described carrier
concentration can be achieved.
[0260] The carrier concentration of the thermoelectric conversion
layer can be measured using an electron spin resonance (ESR)
analysis. In the ESR measurement, for example, BRUKER ESR EMXplus
type apparatus (manufactured by Hitachi High-Tech Science
Corporation) or the like can be used.
[0261] Film thickness of the thermoelectric conversion layer is
preferably 0.1 .mu.m to 1,000 .mu.m, and more preferably, 1 .mu.m
to 100 .mu.m. When the film thickness is set within the range, the
temperature difference is easily imparted and an increase in
resistance in the film can be prevented.
[0262] In general, the thermoelectric conversion element, in
comparison with a photoelectric conversion element such as an
element for an organic thin film solar cell, the element can be
simply produced. In particular, when the thermoelectric conversion
material of the present invention is used, film thickness can be
increased by 100 times to 1,000 times, since it is not necessary to
consider optical absorption efficiency, in comparison with the
element for the organic thin film solar cell, and chemical
stability to oxygen or moisture in air is improved.
[0263] The method of forming a thermoelectric conversion layer is
not particularly limited, and known coating methods, such as spin
coating, extrusion die coating, blade coating, bar coating, screen
printing, stencil printing, roll coating, curtain coating, spray
coating, and dip coating, can be used. Among them, screen printing
is particularly preferable, from the viewpoint of the adhesion
property of the thermoelectric conversion layer to the
electrodes.
[0264] After the coating process, as necessary, a drying process is
performed. For example, a solvent can be vaporized or dried by
heating drying or blowing hot air.
(Doping by Energy Application)
[0265] When the thermoelectric conversion material contains the
onium salt compound as a dopant, it is preferable to enhance
electrical conductivity by subjecting, after film forming, the
relevant film to irradiation with active energy ray or heating to
perform a doping treatment. This treatment causes generation of
acid from the onium salt compound, and when this acid protonates
the conjugated polymer, the conjugated polymer is doped with a
positive charge (p-type doping).
[0266] The active energy rays include radiation and electromagnetic
waves, and the radiation includes particle beams (high-speed
particle beams) and electromagnetic radiation. Specific examples of
the particle beams include charged particle beams such as alpha
rays (.alpha.-rays), beta rays (.beta.-rays), proton beams,
electron beams (meaning ones accelerating an electron by means of
an accelerator without depending on nuclear decay), and deuteron
beams; non-charged particle beams such as neutron beams; and cosmic
rays. Specific examples of the electromagnetic radiation include
gamma rays (.gamma.-rays) and X-rays (X-rays and soft X-rays).
Specific examples of the electromagnetic waves include radio waves,
infrared rays, visible rays, ultraviolet rays (near-ultraviolet
rays, far-ultraviolet rays, and extreme ultraviolet rays), X-rays,
and gamma rays. Types of active energy rays used in the present
invention are not particularly limited. For example,
electromagnetic waves having a wavelength near a maximum absorption
wavelength of the onium salt compound may be selected as
appropriate.
[0267] Among these active energy rays, from viewpoints of the
doping effect and safety, ultraviolet rays, visible rays, or
infrared rays are preferred. Specifically, the active energy rays
include rays having a maximum emission wavelength in the range of
240 to 1,100 nm, preferably in the range of 240 to 850 nm, and more
preferably in the range of 240 to 670 nm.
[0268] For irradiation with active energy rays, radiation equipment
or electromagnetic wave irradiation equipment is used. A wavelength
of radiation or electromagnetic waves for irradiation is not
particularly limited, and one allowing radiation or electromagnetic
waves in a wavelength region corresponding to a response wavelength
of the onium salt compound may be selected.
[0269] Specific examples of the equipment allowing radiation or
irradiation with electromagnetic waves include exposure equipment
using as a light source an LED lamp, a mercury lamp such as a
high-pressure mercury lamp, an ultra-high pressure mercury lamp, a
Deep UV lamp, and a low-pressure UV lamp, a halide lamp, a xenon
flash lamp, a metal halide lamp, an excimer lamp such as an ArF
excimer lamp and a KrF excimer lamp, an extreme ultraviolet ray
lamp, electron beams, and an X-ray lamp. Irradiation with
ultraviolet rays can be applied using ordinary ultraviolet ray
irradiation equipment such as commercially available ultraviolet
ray irradiation equipment for curing/bonding/exposure use (for
example, SP9-250UB, USHIO INC.).
[0270] Exposure time and an amount of light may be selected as
appropriate in consideration of a kind of onium salt compound to be
used and the doping effect. Specific examples of the amount of
light include 10 mJ/cm.sup.2 to 10 J/cm.sup.2, and preferably 50
mJ/cm.sup.2 to 5 J/cm.sup.2.
[0271] When doping is carried out by heating, a formed
thermoelectric conversion layer may be heated to a temperature
higher than or equal to the temperature at which the onium salt
compound generates acid. A heating temperature is preferably
50.degree. C. to 200.degree. C., and more preferably 70.degree. C.
to 150.degree. C. Heating time is preferably 1 minute to 60
minutes, and more preferably 3 minutes to 30 minutes.
[0272] The timing of the doping treatment is not particularly
limited, but it is preferable to perform the doping treatment after
processing the thermoelectric conversion material of the present
invention by film forming or the like.
[0273] The thermoelectric conversion layer (also referred to as the
thermoelectric conversion film) formed by the thermoelectric
conversion material of the present invention and the thermoelectric
conversion element of the present invention exhibit excellent
thermoelectric conversion performance. Further, the thermoelectric
conversion element in which the charge-transfer complex is used as
the low band gap material has also satisfactory temporal stability
of the thermoelectric conversion performance, and the
thermoelectric conversion performance at the initial stage can be
maintained for a long period of time even under the extreme
environment such as high temperature and high humidity
environment.
[0274] The thermoelectric conversion element of the present
invention can be suitably used as a power generation device for an
article for thermoelectric generation. Specifically, as the power
generation device, a generator of hot spring thermal power
generation, solar thermal electric conversion, waste heat electric
conversion, or a power supply for a wrist watch, a semiconductor
drive power supply, a power supply for a (small sized) sensor, or
the like is exemplified.
[0275] Further, the thermoelectric conversion material of the
present invention and the thermoelectric conversion layer formed by
the thermoelectric conversion material of the present invention are
suitably used as the thermoelectric conversion element of the
present invention, a material for a thermoelectric generation
device, a film for thermoelectric generation, or various conductive
film, and specifically, are suitably used as the thermoelectric
conversion material for the power generation device described
above, a film for thermoelectric generation, or the like.
EXAMPLES
[0276] The present invention will be described in more detail based
on the following examples, but the invention is not intended to be
limited thereto.
[0277] The low band gap material, the nano conductive material, the
polymer compound, and the dopant used in Examples are described
below.
[Low Band Gap Material]
1. Charge-Transfer Complex
[0278] The following charge-transfer complexes 1 to 8 were
used.
TABLE-US-00001 TABLE 1 Low band gap Optical Electron Electron
material band gap donor acceptor Charge-transfer 0.8 eV Electron
Electron complex 1 donor 1 acceptor 1 Charge-transfer About 1.1 eV
Electron Electron complex 2 donor 2 acceptor 2 Charge-transfer 0.9
eV Electron Electron complex 3 donor 3 acceptor 3 Charge-transfer
About 1.1 eV Electron Electron complex 4 donor 4 acceptor 4
Charge-transfer About 1.0 eV Electron Electron complex 5 donor 5
acceptor 5 Charge-transfer About 1.0 eV Electron Electron complex 6
donor 6 acceptor 6 Charge-transfer About 1.0 eV Electron Electron
complex 7 donor 7 acceptor 7 Charge-transfer About 1.0 eV Electron
Electron complex 8 donor 8 acceptor 8
##STR00035## ##STR00036## ##STR00037## ##STR00038##
[0279] In the repeating units the electron donor and the electron
acceptor described above, symbol * represents a linking site of the
repeating unit.
2. Metal Complex
[0280] The following metal complexes 1 to 8 were used.
[0281] The optical band gaps of metal complexes 1 to 8 are shown
below. [0282] Metal complex 1: Optical band gap=0.7 eV [0283] Metal
complex 2: Optical band gap=0.9 eV [0284] Metal complex 3: Optical
band gap=0.8 eV [0285] Metal complex 4: Optical band gap=1.0 eV
[0286] Metal complex 5: Optical band gap=0.8 eV [0287] Metal
complex 6: Optical band gap=0.8 eV [0288] Metal complex 7: Optical
band gap=1.0 eV [0289] Metal complex 8: Optical band gap=1.1 eV
##STR00039## ##STR00040##
[0289] 3. Arylamine Compound
[0290] The following arylamine compounds 1 to 4 were used.
[0291] The optical band gaps of arylamine compounds 1 to 4 are
shown below. [0292] Arylamine compound 1: Optical band gap=1.1 eV
[0293] Arylamine compound 2: Optical band gap=0.8 eV [0294]
Arylamine compound 3: Optical band gap=1.1 eV [0295] Arylamine
compound 4: Optical band gap=0.9 eV
##STR00041##
[0295] <Synthesis of Arylamine Compound 1>
[0296] 5 g of N,N,N-tri(4-aminophenyl)-amine, 14 mL of
1-iodobutane, 17 g of potassium carbonate, and 100 mL of DMF were
mixed and then stirred at 110.degree. C. for 3 hours. Thereafter,
ethyl acetate was added thereto, and the resultant mixture was
washed with water and dried, thereby obtaining intermediate A.
[0297] 2 g of intermediate A was dissolved in acetone and heated at
50.degree. C. An acetone solution containing 540 mg of silver
nitrate and 1.2 g of potassium hexafluorophosphate was added
thereto and reacted for 2 hours. Thereafter, the resultant mixture
was cooled to room temperature, filtered through a filter, dried,
and purified, thereby obtaining 1.7 g of arylamine compound 1. Mass
spectrum of the obtained compound was measured and a result of
m/z=771 was obtained. As a result, the obtained compound was
confirmed to be arylamine compound 1.
##STR00042##
<Synthesis of Arylamine Compound 2>
[0298] Arylamine compound 2 was synthesized in the same manner as
in the synthesis of arylamine compound 1 described above, except
that N,N,N',N'-tetrakis(4-aminophenyl)-p-phenylenediamine was used
instead of N,N,N-tri(4-aminophenyl)-amine,
1,1,1-trifluoro-4-iodobutane was used instead of 1-iodobutane, and
sodium perchlorate was used instead of potassium
hexafluorophosphate. Mass spectrum of the obtained compound was
measured and a result of m/z=1452 was obtained. As a result, the
obtained compound was confirmed to be arylamine compound 2.
4. Comparative Compounds
[0299] As comparative compounds, the following comparative
compounds 101 and 102 were used. The optical band gaps of these
compounds are shown below. [0300] Compound 101: Optical band gap
<0.1 eV [0301] Compound 102: Optical band gap >1.2 eV
##STR00043##
[0302] The optical band gaps of the low band gap material and the
comparative compound were calculated by the following method.
<Measurement of Optical Band Gap>
[0303] The low band gap material was dissolved in a soluble organic
solvent and was applied onto a quartz substrate (size: 15
mm.times.15 mm, thickness: 1.1 mm) which had been subjected to the
UV ozone treatment by a spin coat method. The coating film was
dried under the vacuum condition for 1 hour to distill off the
remaining organic solvent. Thereafter, the absorption spectrum was
measured by an ultraviolet visible near infrared (UV-Vis-NIR)
spectrophotometer (manufactured by Shimadzu Corporation, trade
name: UV-3600). The wavelength .lamda.5 (unit: nm) of the
absorption end at the long wavelength side in which the absorbance
becomes 5% relative to the maximum value (.lamda.max) of the
absorbance was obtained, and the unit of .lamda.5 was converted to
calculate the optical band gap (unit: eV).
[Nano Conductive Material]
[0304] Nano conductive materials other than CNT were used as
follows: [0305] Graphite: AGB-5 (trade name, manufactured by Ito
Graphite Co., Ltd) [0306] Carbon nanofiber: VGCF-X (trade name,
manufactured by Showa Denko K.K.) [0307] Graphene: F-GF1205-AB
(trade name, manufactured by SPI Supplies) [0308] Carbon black:
KETJENBLACK EC600JD (trade name, manufactured by Lion Corporation)
[0309] Carbon nanoparticles: Nano diamond PL-D-G (trade name,
manufactured by PlasmaChem) [0310] Silver nanowire: prepared based
on the description in Production Method 2 of JP-A-2012-230881
[0311] Nickel nanotube: prepared based on the description in
Example 1 of JP-B-4374439 [0312] Gold nanoparticle: 636347 (product
number, manufactured by Sigma-Aldrich Co. LLC.) [0313] Fullerene:
nanom purple ST (trade name, manufactured by Frontier Carbon
Corporation.)
[Polymer Compound]
1. Conjugated Polymer
[0314] The following polymer compounds 1 to 6 and PEDOT:PPS were
used as the conjugated polymer.
##STR00044## ##STR00045##
[0315] In the repeating units of Polymer compounds 1 to 6 and
PEDOT:PPS described above, symbol * represents a linking site of
the repeating unit.
[0316] Molecular weights of polymer compounds 1 to 6 were as
follows. The molecular weights were measured by gel-permeation
chromatography (GPC). [0317] Polymer compound 1: Weight average
molecular weight=53,000 [0318] Polymer compound 2: Weight average
molecular weight=20,000 [0319] Polymer compound 3: Weight average
molecular weight=19,000 [0320] Polymer compound 4: Weight average
molecular weight=41,000 [0321] Polymer compound 5: Weight average
molecular weight=34,000 [0322] Polymer compound 6: Weight average
molecular weight=26,000 [0323] PEDOT:PSS:
poly(3,4-ethylenedioxythiophene) and poly(styrenesulfonate),
manufactured by H. C. Starck GmbH, trade name "Baytron P",
PEDOT/PSS about 1.3% by mass of water dispersion), EDOT/PSS (mass
ratio)=1/2.5
[0324] The above-described polymer compound 2 was synthesized as
shown below.
Synthesis Example of Polymer Compound 2
[0325] Into a 200 mL flask,
9-(2-ethylhexyl)-9-(2-ethylpentyl)-2,7-bis(trimethylstannyl)-9H-fluorene
(3.08 g, 4.38 mmol), methyl 3-(bis(4-bromophenyl)amino)benzoate
(2.02 g, 4.38 mmol), and tetrakis triphenylphosphine palladium (253
mg, 0.219 mmol) were introduced and the inside of the vessel was
replaced by nitrogen. In the vessel, toluene (35 mL) and
N,N-dimethylformamide (9 mL) as a solvent were added using a
syringe, and then the resultant mixture was reacted in an oil bath
at 120.degree. C. under a nitrogen atmosphere by heating under
stirring for 24 hours. The reaction solution was cooled to room
temperature, and then the solution was filtered through Celite to
remove insoluble components. The obtained filtrate was added
dropwise into methanol little by little, solids were precipitated,
and then the solids were separated by filtration. The solids were
heated and washed using an acetone solvent for 10 hours by using a
Soxhlet extractor to remove impurities. Finally, the solids were
dried in a vacuum for 10 hours, thereby obtaining target polymer
compound 2 (production amount: 2.21 g, yield: 73%).
[0326] The weight average molecular weight of the obtained polymer
compound 2 was measured by the method described above.
2. Non-Conjugated Polymer
[0327] As the non-conjugated polymer, the following polymers were
used. [0328] Polystyrene: 430102 (product number, manufactured by
Sigma-Aldrich, Weight average molecular weight=192,000) [0329]
Polymethyl methacrylate: manufactured by Wako Pure Chemical
Industries, Ltd. [0330] Polyvinyl acetate: manufactured by Wako
Pure Chemical Industries, Ltd. [0331] Polylactic acid: PLA-0015
(trade name, manufactured by Wako Pure Chemical Industries, Ltd.)
[0332] Polyvinylpyrrolidone: manufactured by Wako Pure Chemical
Industries, Ltd. [0333] Polyimide compound: SOLPIT 6,6-PI (trade
name, manufactured by Solpit Industries, Ltd.) [0334] Polycarbonate
compound: lupizeta PCZ-300 (trade name, manufactured by MITSUBISHI
GAS CHEMICAL COMPANY, INC.)
[Dopant]
[0335] The following polymer compounds 1 to 4 were used as the
dopant.
##STR00046##
Example 1
[0336] 2 mg of the charge-transfer complex 1, 4 mg of single-walled
CNT (ASP-100F, manufactured by Hanwha Nanotech Corporation,
dispersion (CNT concentration: 60% by mass), an average length of
CNT: about 5 to 20 .mu.m, an average diameter: about 1.0 to 1.2
nm), and 4 mg of polymer compound 1 were added in 4.0 ml of
ortho-dichlorobenzene, and the mixture was dispersed in an
ultrasonic bath for 70 minutes. This dispersion liquid was applied
on the surface of the electrode 12 of the glass substrate 11
(thickness: 0.8 mm) having gold as the first electrode 13
(thickness: 20 nm, width: 5 mm) on one side of the surface thereof
by a screen printing method, and was heated at 80.degree. C. for 45
minutes to remove the solvent. Thereafter, the drying was carried
out at room temperature in a vacuum for 10 hours, thereby forming
the thermoelectric conversion layer 14 having a film thickness of
2.2 .mu.m and a size of 8 mm.times.8 mm. Then, the glass substrate
16 having gold deposited thereon as the second electrode 15
(thickness of the electrode 15: 20 nm, width of the electrode 15: 5
mm, thickness of the glass substrate 16: 0.8 mm) was superimposed
on the top of the thermoelectric conversion layer 14 at 80.degree.
C. such that the second electrode 15 faced the thermoelectric
conversion layer 14. Thus, a thermoelectric conversion element 101
of the present invention as the thermoelectric conversion element 1
illustrated in FIG. 1 was produced.
[0337] Thermoelectric conversion elements 102 to 114 of the present
invention and comparative thermoelectric conversion elements c101
to c107 were produced in the same manner as in the thermoelectric
conversion element 101, except that the charge-transfer complex,
the polymer compound, the CNT, and the electrode material were
changed as shown in the following Table 2.
[0338] Regarding each of the thermoelectric conversion elements,
the thermoelectric characteristic value (thermopower S) and the
temporal stability of the thermoelectric performance relative to
temperature and humidity were evaluated by the following methods.
The results thereof are shown in Table 2.
[Measurement of Thermoelectric Characteristic Value (Thermopower
S)]
[0339] The first electrode 13 of each thermoelectric conversion
element was disposed on a hot plate maintaining constant
temperature, and a Peltier device for controlling temperature was
disposed on the second electrode 15. When the temperature of the
Peltier device was decreased while the temperature of the hot plate
was maintained constantly (100.degree. C.), the temperature
difference (a range of more than 0 K but 4 K or less) was imparted
between both electrodes. At this time, when the thermopower (.mu.V)
generated between both electrodes was divided by a specific
temperature difference (K) generated between both electrodes, the
thermopower S (.mu.V/K) per unit temperature difference was
calculated and this value was designated as the thermoelectric
characteristic value of the thermoelectric conversion element. The
calculated thermoelectric characteristic value is designated as a
relative value to the calculated value of the comparative
thermoelectric conversion element c101 and is shown in Table 2.
[Evaluation on Temporal Stability of Thermoelectric
Performance]
[0340] A Seebeck coefficient S (unit: .mu.V/K) at 100.degree. C.
and electrical conductivity .sigma. (unit: S/cm) of the
thermoelectric conversion layer 14 formed by the film-forming and
drying processes were measured by using a thermoelectric
characteristic measuring apparatus (RZ2001i manufactured by OZAWA
SCIENCE CO., LTD.). Then, the thermal conductivity .kappa. (unit:
W/mK) was measured by using a thermal conductivity measuring
apparatus (HC-074 manufactured by EKO Instruments Co., Ltd.). The
figure of merit (ZT value) at the initial stage at 100.degree. C.
was calculated according to the following Equation (A) using these
values.
Figure of merit ZT=S.sup.2.sigma.T/.kappa. Equation (A) [0341] S
(.mu.V/K): thermopower per absolute temperature of 1 K (Seebeck
coefficient) [0342] .sigma. (S/m): Electrical conductivity [0343]
.kappa. (W/mK): Thermal conductivity [0344] T(K): Absolute
temperature
[0345] Subsequently, the thermoelectric conversion layer 14 was
stored in a thermostatic bath of a temperature of 85.degree. C. and
a humidity of 85% RH in the air, and after a predetermined time
interval has elapsed, the figure of merit (ZT value) was calculated
in the same manner as in the figure of merit at the initial stage.
The cycle consisting of the storing for the predetermined time
interval and the calculation of the figure of merit was repeated,
and a period of time required when the figure of merit (ZT value)
after starting storage was decreased to 80% of the figure of merit
(ZT value) at the initial stage was designated as an indication for
the temporal stability of the thermoelectric performance. The
results thereof are shown in Table 2.
[0346] As the period of time required when the figure of merit (ZT
value) after starting storage was decreased to 80% of the figure of
merit (ZT value) at the initial stage is long, the temporal
stability relative to temperature and humidity is excellent.
TABLE-US-00002 TABLE 2 Thermoelectric Charge-transfer Polymer
Electrode Temporal Thermopower conversion element complex compound
CNT material stability (hrs) (Relative value) Remarks 101 1 1
Present Gold 201 197 Ex 102 1 None Present Gold 186 185 Ex 103 2 6
Present Gold 244 238 Ex 104 3 3 Present Gold 257 297 Ex 105 3 None
Present Gold 213 235 Ex 106 3 Polystyrene Present Gold 269 283 Ex
107 3 Polylactic acid Present Copper 261 280 Ex 108 4 PEDOT:PSS
Present Silver 235 266 Ex 109 5 4 Present Gold 232 257 Ex 110 5
None Present Aluminum 183 218 Ex 111 6 Polyvinyl acetate Present
Aluminum 263 248 Ex 112 6 5 Present Silver 255 239 Ex 113 7
Polymethyl Present Copper 248 261 Ex methacrylate 114 8 2 Present
Silver 231 267 Ex c101 None Polystyrene Present Gold 93 100
(standard) C Ex c102 Electron donor 3 only None Present Gold 22 126
C Ex c103 Electron acceptor 3 only Polystyrene Present Gold 35 114
C Ex c104 None PEDOT:PSS Present Gold 15 180 C Ex c105 1 None None
Gold Unmeasurable Below detectable C Ex limit c106 None 2 None Gold
Unmeasurable Below detectable C Ex limit c107 4 3 None Gold
Unmeasurable Below detectable C Ex limit "Ex" means Example
according to the present invention, and "C Ex" means Comparative
Example.
[0347] As clearly seen from Table 2, all of the thermoelectric
conversion elements 101 to 114 of the present invention containing
the charge-transfer complex having an optical band gap of 0.1 eV or
more and 1.1 eV or less and the CNT as the nano conductive material
had excellent temporal stability as well as high thermopower.
[0348] On the other hand, comparative thermoelectric conversion
elements c101 to c107 not containing the low band gap material or
the CNT had low thermopower and inferior temporal stability as
compared to thermoelectric conversion elements 101 to 107 of the
present invention.
Example 2
[0349] Thermoelectric conversion element 201 of the present
invention was produced in the same manner as in thermoelectric
conversion element 101, except that the types of the polymer
compound and the nano conductive material were changed as shown in
Table 3. The thermopower (the relative value to the calculated
value of thermoelectric conversion element c101) and the temporal
stability were evaluated in the same manner as in Example 1.
[0350] Subsequently, thermoelectric conversion elements 202 to 209
and comparative thermoelectric conversion element c201 were
produced in the same manner as in thermoelectric conversion element
201, except that the types of the charge-transfer complex and the
nano conductive material were changed as shown in Table 3. The
evaluation was performed in the same manner as in the
thermoelectric conversion element 201.
[0351] The results thereof are shown in Table 3.
TABLE-US-00003 TABLE 3 Thermoelectric Charge-transfer Polymer Nano
conductive Temporal Thermopower conversion element complex compound
material stability (hrs) (Relative value) Remarks 201 1 Polystyrene
Graphite 248 202 Ex 202 2 Polystyrene Carbon nanofiber 230 248 Ex
203 3 Polystyrene Graphene 225 215 Ex 204 3 Polystyrene Carbon
black 251 233 Ex 205 4 Polystyrene Carbon nanoparticles 253 247 Ex
206 5 Polystyrene Silver nanowire 237 228 Ex 207 6 Polystyrene
Nickel nanotube 201 189 Ex 208 7 Polystyrene Gold nanoparticles 217
171 Ex 209 8 Polystyrene Fullerene 255 197 Ex C201 None Polystyrene
Carbon nanofiber 240 139 C Ex "Ex" means Example according to the
present invention, and "C Ex" means Comparative Example.
[0352] As apparent from Table 3, as to thermoelectric conversion
elements 201 to 209 of the present invention, which contain a nano
conductive material and a charge-transfer complex of which band gap
is of 0.1 eV or more and 1.1 eV or less, all of them had
thermopower higher than thermoelectric conversion element c101, and
had excellent thermoelectric conversion performance.
Example 3
[0353] 2 mg of charge-transfer complex 1, 2 mg of CNT (ASP-100F,
manufactured by Hanwha Nanotech Corporation), 2 mg of dopant 1, and
2.5 mg of polystyrene (Aldrich 430102) as a polymer compound, and
2.5 mg of polymer compound 1 were added in 5 ml of
ortho-dichlorobenzene, and the mixture was dispersed in an
ultrasonic bath for 70 minutes. After the thermoelectric conversion
layer was formed using this dispersion liquid in the same manner as
in Example 1, the thermoelectric conversion layer was subjected to
ultraviolet irradiation (amount of light: 1.06 J/cm.sup.2) using an
ultraviolet irradiator (ECS-401GX manufactured by EYE GRAPHICS Co.,
Ltd.) and doping was carried out. Thereafter, the second electrode
was superimposed in the same manner as in Example 1, thereby
producing thermoelectric conversion element 301 of the present
invention.
[0354] Thermoelectric conversion elements 302 to 310 of the present
invention and comparative thermoelectric conversion element c301
were produced in the same manner as in thermoelectric conversion
element 301, except that the charge-transfer complex, the dopant,
and the polymer compound were changed as shown in the following
Table 4. Incidentally, in thermoelectric conversion elements 302,
304, and 307, the doping treatment by ultraviolet irradiation was
not performed.
[0355] Regarding each of the thermoelectric conversion elements,
the thermoelectric characteristic value (thermopower S) and the
temporal stability were evaluated in the same manner as in Example
1. The results thereof are shown in Table 4. Incidentally, the
thermopower shown in Table 4 is a relative value to the calculated
value of the comparative thermoelectric conversion element c101
produced in Example 1.
TABLE-US-00004 TABLE 4 Thermoelectric Charge-transfer Polymer
Temporal Thermopower conversion element complex CNT Dopant compound
stability (hrs) (Relative value) Remarks 301 1 Present 1 Polymer
compound 1 201 348 Ex Polystyrene 302 2 Present FeCl.sub.3 Polymer
compound 2 208 394 Ex Polymethyl methacrylate 303 3 Present 2
Polymer compound 3 322 413 Ex Polyvinyl acetate 304 3 Present 3
Polymer compound 4 237 371 Ex 305 4 Present Sulfuric acid Polymer
compound 5 277 349 Ex Polylactic acid 306 5 Present 4 Polymer
compound 6 248 338 Ex Polyvinylpyrrolidone 307 5 Present 2 Polymer
compound 2 241 407 Ex Polyimide compound 308 5 Present 3 Polymer
compound 3 208 346 Ex 309 6 Present 2 Polymer compound 4 246 348 Ex
Polystyrene 310 7 Present Pyrophosphoric Polymer compound 3 255 341
Ex acid Polycarbonate compound c301 None Present 3 Polystyrene 128
103 C Ex "Ex" means Example according to the present invention, and
"C Ex" means Comparative Example.
[0356] As clearly seen from Table 4, all of thermoelectric
conversion elements 301 to 310 of the present invention containing
the polymer compound and the dopant in addition to the CNT and the
charge-transfer complex having an optical band gap of 0.1 eV or
more and 1.1 eV or less exhibited further excellent thermopower and
temporal stability.
[0357] On the other hand, comparative thermoelectric conversion
element c301 not containing the low band gap material was inferior
in both of the thermopower and the temporal stability.
Example 4
[0358] Thermoelectric conversion element 401 of the present
invention as the thermoelectric conversion element 1 was produced
in the same manner as in thermoelectric conversion element 101 of
Example 1, except that the second substrate (made of glass) 16
having the second electrode 15 in which a polyethylene
terephthalate film (thickness: 125 .mu.m) having flexibility (the
number of cycles on folding endurance test MIT measured by the
measurement method according to ASTM D2176 being 50,000 cycles or
more) was formed by a copper paste (trade name: ACP-080,
manufactured by Asahi Chemical Research Laboratory Co., Ltd.)
instead of glass, was used as the first substrate 12 having the
first electrode 13. When the temperature difference of 3.degree. C.
was imparted between the first substrate (polyethylene
terephthalate film) 12 having the first electrode 13 and the second
electrode 15 with the second substrate 16 interposed therebetween,
it was confirmed by a voltmeter that the thermopower of 248 .mu.V
was generated between both electrodes.
[0359] Comparative thermoelectric conversion element c401 was
produced in the same manner as in the thermoelectric conversion
element 401, except that the thermoelectric conversion material
produced in the thermoelectric conversion element c101 of Example 1
was used as the thermoelectric conversion material. When the
temperature difference of 3.degree. C. was imparted between the
first substrate having the first electrode and the second electrode
with the second substrate interposed therebetween, it was confirmed
by a voltmeter that the thermopower of 101 .mu.V was generated
between both electrodes.
[0360] As clearly seen from the above results, in the
thermoelectric conversion element 401 containing the CNT and the
charge-transfer complex, the generated thermopower was large as
compared to the comparative thermoelectric conversion element c401
not containing the charge-transfer complex.
Example 5
[0361] Thermoelectric conversion elements 501 to 504 of the present
invention were produced in the same manner as in the thermoelectric
conversion element 101, except that a metal salt shown in Table 5
was added in an added amount shown in Table 5 to the
charge-transfer complex 3 and the single-walled CNT, and the
thermopower (the relative value to the calculated value of the
thermoelectric conversion element c101) and the temporal stability
were evaluated in the same manner as in Example 1. The results
thereof are shown in Table 5.
TABLE-US-00005 TABLE 5 Addition amount Temporal Thermoelectric
Charge-transfer Polymer of metal salt stability Thermopower
conversion element complex CNT compound Metal salt (ppm) (hrs)
(Relative value) Remarks 501 3 Present 3 Cobalt bromide 50 247 304
Ex 502 3 Present 3 Palladium chloride 630 301 361 Ex 503 3 Present
3 Nickel chloride 7500 248 348 Ex 504 3 Present 3 Molybdenum boride
15000 197 260 Ex "Ex" means Example according to the present
invention.
[0362] As clearly seen from Table 5, all of thermoelectric
conversion elements 501 to 504 of the present invention containing
the metal element in addition to the CNT and the charge-transfer
complex having an optical band gap of 0.1 eV or more and 1.1 eV or
less exhibited excellent thermopower and temporal stability.
Example 6
[0363] 2 mg of the metal complex 1, 4 mg of single-walled CNT
(ASP-100F, manufactured by Hanwha Nanotech Corporation, dispersion
(CNT concentration: 60% by mass), an average length of CNT: about 5
to 20 .mu.m, an average diameter: about 1.0 to 1.2 nm, a volume
average diameter (D50): 50 nm), and 4 mg of the polymer compound 1
were added in 4.0 ml of ortho-dichlorobenzene, and the mixture was
dispersed in an ultrasonic bath for 70 minutes. This dispersion
liquid was applied on the surface of the electrode of the glass
substrate (thickness: 0.8 mm) having gold as the first electrode
(thickness: 20 nm, width: 5 mm) on one side of the surface thereof
by a screen printing method, and was heated at 80.degree. C. for 60
minutes to remove the solvent. Thereafter, the drying was carried
out at room temperature in a vacuum for 10 hours, thereby forming
the thermoelectric conversion layer having a film thickness of 2.1
.mu.m and a size of 15 mm.times.15 mm. Then, the glass substrate
having gold deposited thereon as the second electrode (thickness of
the electrode: 20 nm, width of the electrode: 5 mm, thickness of
the glass substrate: 0.8 mm) was superimposed on the top of the
thermoelectric conversion layer at 80.degree. C. such that the
second electrode faced the thermoelectric conversion layer. Thus,
thermoelectric conversion element 601 was produced.
[0364] Thermoelectric conversion elements 602 to 627 and
comparative thermoelectric conversion elements c601 to c608 were
produced in the same manner as in thermoelectric conversion element
601, except that the metal complex, the polymer compound, the nano
conductive material, and the electrode material were changed as
shown in the following Table 6-1 and Table 6-2. Incidentally, when
two kinds of the polymer compounds were used, each of the polymer
compounds was added in an amount of 2.0 mg.
[0365] The thermoelectric characteristic values (thermopower and
thermoelectric output) of each thermoelectric conversion element
were evaluated by the following method. The results thereof are
shown in Table 6-1 and Table 6-2.
[Measurement of Thermopower and Thermoelectric Output]
[0366] The first electrode 13 of each thermoelectric conversion
element was disposed on a hot plate maintaining constant
temperature, and a Peltier device for controlling temperature was
disposed on the second electrode 15. When the temperature of the
Peltier device was decreased while the temperature of the hot plate
was maintained constantly (100.degree. C.), the temperature
difference (a range of more than 0 K but 4 K or less) was imparted
between both electrodes. At this time, when the voltage generated
between both electrodes was designated as the thermopower V (unit:
V) and the current was designated as the I (unit: A), the
thermoelectric output calculated by the product of the thermopower
V and the current I (thermopower V.times.current I, unit: W) was
calculated. The obtained values of the thermopower and the
thermoelectric output each are shown in Table 6-1 and Table 6-2 as
the relative values to the calculated values of comparative
thermoelectric conversion element c601.
TABLE-US-00006 TABLE 6-1 Thermoelectric Thermoelectric Metal
Polymer Nano conductive Electrode Thermopower output conversion
element complex compound material material (Relative value)
(Relative value) Remarks 601 1 1 CNT Gold 250 348 Ex 602 1 5 CNT
Aluminum 310 470 Ex Polystyrene 603 1 Polystyrene CNT Gold 286 309
Ex 604 2 4 CNT Gold 281 362 Ex 605 3 6 CNT Gold 266 340 Ex 606 4
None CNT Gold 256 287 Ex 607 3 5 CNT Gold 304 467 Ex
Polyvinylcarbazole 608 3 1 CNT Aluminum 287 410 Ex 4 609 4 2 CNT
Silver 299 407 Ex 5 610 4 3 CNT ITO 302 435 Ex Polylactic acid 611
5 2 CNT Gold 398 388 Ex 612 5 Polystyrene CNT Gold 296 324 Ex 613 5
Polylactic acid CNT Aluminum 252 309 Ex 614 6 PEDOT:PSS CNT Copper
248 266 Ex 615 6 3 CNT Aluminum 296 452 Ex Polyvinyl acetate 616 7
Polymethyl methacrylate CNT Gold 335 320 Ex 617 8 1 CNT Silver 277
391 Ex 618 1 3 Carbon black Gold 294 383 Ex Polystyrene 619 2 None
Graphite Gold 269 294 Ex 620 2 3 Graphite Gold 301 428 Ex
Polystyrene 621 3 3 Graphene Gold 327 469 Ex Polystyrene 622 3 3
Carbon nanofiber Gold 289 446 Ex Polystyrene 623 4 3 Nickel
nanotube Gold 307 386 Ex Polystyrene 624 5 3 Silver nanowire Gold
369 403 Ex Polystyrene 625 6 3 Carbon nanoparticles Gold 290 362 Ex
Polystyrene 626 7 3 Fullerene Gold 264 352 Ex Polystyrene 627 8 3
Gold nanoparticles Gold 286 366 Ex Polystyrene "Ex" means Example
according to the present invention.
TABLE-US-00007 TABLE 6-2 Thermoelectric Thermoelectric Metal
Polymer Nano conductive Electrode Thermopower output conversion
element complex compound material material (Relative value)
(Relative value) Remarks c601 101 1 CNT Gold 100 (standard) 100
(standard) C Ex c602 102 3 CNT Gold 116 138 C Ex Polylactic acid
c603 None Polystyrene CNT Gold 104 86 C Ex c604 None 1 CNT Aluminum
93 114 C Ex Polystyrene c605 None 3 Carbon nanofiber Gold 87 187 C
Ex Polystyrene c606 5 None None Gold Undetectable Undetectable C Ex
c607 None 2 None Gold Undetectable Undetectable C Ex c608 4 3 None
Gold Undetectable Undetectable C Ex "C Ex" means Comparative
Example.
[0367] As apparent from Table 6-1, Table 6-2, all of the
thermoelectric conversion elements of the present invention,
containing the metal complex having the optical band gap of 0.1 eV
or more and 1.1 eV or less and nano conductive material, exhibited
excellent thermopower and thermoelectric output.
[0368] On the other hand, Comparative Examples c601 and c602 using
the metal complex having an optical band gap of less than 0.1 eV or
more than 1.1 eV and Comparative Examples c603 to c605 not using
the low band gap material had low thermopower and low
thermoelectric output. Further, Comparative Examples c606 to c608
not containing the nano conductive material had the thermopower and
the thermoelectric output which were equal to or less than the
detection limit.
Example 7
[0369] 2 mg of the arylamine compound 1, 4 mg of single-walled CNT
(ASP-100F, manufactured by Hanwha Nanotech Corporation, dispersion
(CNT concentration: 60% by mass), an average length of CNT: about 5
to 20 .mu.m, an average diameter: about 1.0 to 1.2 nm, a volume
average diameter (D50): 50 nm), and 4 mg of the polymer compound 1
were added in 4.0 ml of ortho-dichlorobenzene, and the mixture was
dispersed in an ultrasonic bath for 70 minutes. This dispersion
liquid was applied on the surface of the electrode of the glass
substrate (thickness: 0.8 mm) having gold as the first electrode
(thickness: 20 nm, width: 5 mm) on one side of the surface thereof
by a screen printing method, and was heated at 80.degree. C. for 60
minutes to remove the solvent. Thereafter, the drying was carried
out at room temperature in a vacuum for 10 hours, thereby forming
the thermoelectric conversion layer having a film thickness of 2.1
.mu.m and a size of 15 mm.times.15 mm. Then, the glass substrate
having gold deposited thereon as the second electrode (thickness of
the electrode: 20 nm, width of the electrode: 5 mm, thickness of
the glass substrate: 0.8 mm) was superimposed on the top of the
thermoelectric conversion layer at 80.degree. C. such that the
second electrode faced the thermoelectric conversion layer. Thus,
thermoelectric conversion element 701 was produced.
[0370] Thermoelectric conversion elements 702 to 713 were produced
in the same manner as in thermoelectric conversion element 701,
except that the arylamine compound, the polymer compound, the nano
conductive material, and the electrode material were changed as
shown in the following Table 7. Incidentally, when two kinds of the
polymer compounds were used, each of the polymer compounds was
added in an amount of 2.0 mg.
[0371] The thermopower and the thermoelectric output of each
thermoelectric conversion element were evaluated in the same manner
as in Example 6. The results thereof are shown in Table 7. The
thermopower and the thermoelectric output are represented as the
relative values of comparative thermoelectric conversion element
c601 of Example 6. Further, in Table 7, comparative thermoelectric
conversion elements c603 to c605, and c607 produced in Example 6
are shown together.
TABLE-US-00008 TABLE 7 Thermoelectric Thermoelectric Arylamine
Polymer Nano conductive Electrode Thermopower output conversion
element compound compound material material (Relative value)
(Relative value) Remarks 701 2 None CNT Gold 340 289 Ex 702 1 1 CNT
Aluminum 297 356 Ex 703 2 3 CNT Copper 275 395 Ex 704 3 3 CNT Gold
253 330 Ex 705 4 4 CNT ITO 240 377 Ex 706 1 2 CNT Gold 307 403 Ex
Polylactic acid 707 4 3 CNT Gold 336 425 Ex Polystyrene 708 4
PEDOT:PSS CNT Gold 268 288 Ex 709 1 2 Graphite Gold 280 376 Ex
Polystyrene 710 2 2 Carbon nanofiber Gold 301 402 Ex Polystyrene
711 3 5 Graphene Gold 277 329 Ex Polystyrene 712 4 2 Nanowire of
silver Gold 311 353 Ex Polystyrene 713 1 3 Carbon black Gold 318
390 Ex Polylactic acid c603 None Polystyrene CNT Gold 104 86 C Ex
c604 None 1 CNT Aluminum 93 114 C Ex Polystyrene c605 None 3 Carbon
nanofiber Gold 87 187 C Ex Polystyrene c607 None 2 None Gold
Undetectable Undetectable C Ex "Ex" means Example according to the
present invention, and "C Ex" means Comparative Example.
[0372] As apparent from Table 7, all of the thermoelectric
conversion elements of the present invention, containing the
arylamine compound and nano conductive material, exhibited
excellent thermopower and thermoelectric output.
[0373] On the other hand, Comparative Examples c603 and c605 not
using the low band gap material had low thermopower and low
thermoelectric output. Further, Comparative Examples c607 not
containing the nano conductive material had the thermopower and the
thermoelectric output which were equal to or less than the
detection limit.
[0374] Having described our invention as related to the present
embodiments, it is our intention that the invention not be limited
by any of the details of the description, unless otherwise
specified, but rather be construed broadly within its spirit and
scope as set out in the accompanying claims.
REFERENCE SIGNS LIST
[0375] 1, 2 Thermoelectric conversion element [0376] 11, 17 Metal
plate [0377] 12, 22 First substrate [0378] 13, 23 First electrode
[0379] 14, 24 Thermoelectric conversion layer [0380] 15, 25 Second
electrode [0381] 16, 26 Second substrate
* * * * *