U.S. patent application number 12/457173 was filed with the patent office on 2009-11-05 for glass composition for dye-sensitized solar cell and material for dye-sensitized solar cell.
Invention is credited to Kouji AMANO, Masaaki HAYASHI, Masahiro SAWADA, Tomoko YAMADA.
Application Number | 20090275461 12/457173 |
Document ID | / |
Family ID | 41199140 |
Filed Date | 2009-11-05 |
United States Patent
Application |
20090275461 |
Kind Code |
A1 |
SAWADA; Masahiro ; et
al. |
November 5, 2009 |
Glass composition for dye-sensitized solar cell and material for
dye-sensitized solar cell
Abstract
A dye-sensitized solar cell having high long-term reliability is
provided by inventing a glass composition, which is hardly eroded
by an iodine electrolyte solution and has a low-melting point
property, and a material using the glass composition. The glass
composition for a dye-sensitized solar cell of the present
invention is characterized by including as a glass composition, in
terms of mass %, to 70% of V.sub.2O.sub.5 and 10 to 50% of
P.sub.2O.sub.5.
Inventors: |
SAWADA; Masahiro; (Otsu-shi,
JP) ; HAYASHI; Masaaki; (Otsu-shi, JP) ;
AMANO; Kouji; (Otsu-shi, JP) ; YAMADA; Tomoko;
(Otsu-shi, JP) |
Correspondence
Address: |
WENDEROTH, LIND & PONACK, L.L.P.
1030 15th Street, N.W.,, Suite 400 East
Washington
DC
20005-1503
US
|
Family ID: |
41199140 |
Appl. No.: |
12/457173 |
Filed: |
June 3, 2009 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
PCT/JP2009/057519 |
Apr 14, 2009 |
|
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12457173 |
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Current U.S.
Class: |
501/46 |
Current CPC
Class: |
C03C 8/08 20130101; H01M
14/005 20130101; C03C 3/21 20130101; Y02E 10/542 20130101; Y02E
60/10 20130101; H01G 9/2031 20130101; C03C 17/04 20130101; H01G
9/2059 20130101; H01M 50/183 20210101 |
Class at
Publication: |
501/46 |
International
Class: |
C03C 3/21 20060101
C03C003/21 |
Foreign Application Data
Date |
Code |
Application Number |
Apr 18, 2008 |
JP |
2008-108766 |
Claims
1. A glass composition for a dye-sensitized solar cell, comprising
as a glass composition, in terms of mass %, 20 to 70% of
V.sub.2O.sub.5 and 10 to 50% of P.sub.2O.sub.5.
2. A glass composition for a dye-sensitized solar cell according to
claim 1, further comprising as a glass composition, in terms of
mass %, 10 to 55% of ZnO+SrO+BaO+CuO.
3. A glass composition for a dye-sensitized solar cell according to
claim 2, comprising, in terms of mass %, 0 to 30% of ZnO, 0 to 20%
of SrO, 0 to 45% of BaO, and 0 to 15% of CuO.
4. A glass composition for a dye-sensitized solar cell according to
claim 1, which has a mass reduction of 0.1 mg/cm.sup.2 or less
after being immersed in an iodine electrolyte solution at
25.degree. C. for 2 weeks.
5. A glass composition for a dye-sensitized solar cell according to
claim 1, which has a thermal expansion coefficient of 65 to
120.times.10.sup.-7/.degree. C.
6. A material for a dye-sensitized solar cell, comprising: 50 to
100 vol % of a glass powder formed of the glass composition for a
dye-sensitized solar cell according to any one of claims 1 to 5;
and to 50 vol % of a refractory filler powder.
7. A material for a dye-sensitized solar cell according to claim 6,
which has a softening point of 550.degree. C. or lower.
8. A material for a dye-sensitized solar cell according to claim 6,
which is used for sealing.
9. A material for a dye-sensitized solar cell according to claim 8,
which is used for sealing by a laser beam.
10. A material for a dye-sensitized solar cell according to claim
6, which is used for overcoating a collector electrode.
Description
CROSS-REFERENCE TO RELATED APPLICATION
[0001] This is a continuation application of international
application PCT/JP2009/057519 filed Apr. 14, 2009, and claiming the
priority of Japanese application 2008-108766 filed Apr. 18,
2008.
TECHNICAL FIELD
[0002] The present invention relates to a glass composition for a
dye-sensitized solar cell and a material for a dye-sensitized solar
cell, and more specifically to a glass composition for a
dye-sensitized solar cell and a material for a dye-sensitized solar
cell which are suitable for sealing a transparent electrode
substrate and a counter electrode substrate of a dye-sensitized
solar cell, forming a partition wall for dividing cells, and
overcoating a collector electrode.
[0003] 1. Background Art
[0004] The dye-sensitized solar cell which was developed by Gratzel
et al. is low in cost compared with solar cells each using a
silicon semiconductor, and there are abundant raw materials needed
for the production of the dye-sensitized solar cell, and hence, the
dye-sensitized solar cell is expected as a next-generation solar
cell.
[0005] The dye-sensitized solar cell includes: a transparent
electrode substrate having a transparent conductive film; a porous
oxide semiconductor electrode including a porous oxide
semiconductor layer (mainly a TiO.sub.2 layer), which is formed on
the transparent electrode substrate; a dye such as a Ru-dye, which
is adsorbed to the porous oxide semiconductor electrode; an iodine
electrolyte solution containing iodine; a counter electrode
substrate on which a catalyst film and a transparent conductive
film are formed; and the like.
[0006] There are used a glass substrate, a plastic substrate, and
the like for the transparent electrode substrate and the counter
electrode substrate. When the plastic substrate is used for the
transparent electrode substrate, the resistivity of a transparent
electrode film becomes large and the photoelectric conversion
efficiency of the dye-sensitized solar cell lowers. On the other
hand, when the glass substrate is used for the transparent
electrode substrate, the resistivity of the transparent electrode
film hardly increases, and hence, the photoelectric conversion
efficiency of the dye-sensitized solar cell can be maintained.
Therefore, in recent years, the glass substrate has been used as
the transparent electrode substrate.
[0007] In the dye-sensitized solar cell, the iodine electrolyte
solution is filled between the transparent electrode substrate and
the counter electrode substrate. In order to prevent the leakage of
the iodine electrolyte solution from the dye-sensitized solar cell,
the peripheries of the transparent electrode substrate and the
counter electrode substrate need to be sealed. Further, in order to
effectively extract the generated electrons, a collector electrode
(e.g., Ag or the like is used therefor) may be formed on the
transparent electrode substrate. In this case, there is a need to
overcoat the collector electrode and prevent a situation that the
collector electrode is eroded by the iodine electrolyte solution.
In addition, in the case of forming a cell circuit on one sheet of
glass substrate, a partition wall may be formed between the
transparent electrode substrate and the counter electrode
substrate.
[0008] 2. Prior Art Documents
[0009] Patent Document 1: JP 1-220380 A
[0010] Patent Document 2: JP 2002-75472 A
[0011] Patent Document 3: JP 2004-292247 A
SUMMARY OF THE INVENTION
Problems to be Solved by the Invention
[0012] In a dye-sensitized solar cell, it is the improvement in
long-term durability that is an object for practical application.
One of the reasons for which the long-term durability is impaired
is, for example, as follows. Solar cell members (sealing material,
collector electrode, and the like) react with an iodine electrolyte
solution, and the solar cell members and the iodine electrolyte
solution are degraded. In particular, the tendency is remarkable
when a resin is used for the sealing material and an organic
solvent such as acetonitrile is used for the iodine electrolyte
solution. In this case, the resin is eroded by the iodine
electrolyte solution, and hence, the iodine electrolyte solution is
leaked from the solar cell, whereby cell performances remarkably
deteriorate. In the case where a resin is used for forming a
partition wall or for coating a collector electrode in the similar
way, the resin is also eroded by the iodine electrolyte solution,
and hence, there occurs deterioration of the collector electrode,
tearing of the partition wall, or the like.
[0013] In view of the above circumstances, there are proposed
methods in which a resin is not used for a sealing material. For
example, in Patent Document 1, it is described that the peripheries
of a transparent electrode substrate and a counter electrode
substrate are sealed using glass. Further, in each of Patent
Documents 2 and 3, it is described that the peripheries of a
transparent electrode substrate and a counter electrode substrate
are sealed using a lead glass.
[0014] However, even in the case where the lead glass is used for
the sealing material, a component of the lead glass is eluted into
an iodine electrolyte solution due to long-term use, because the
lead glass is easily eroded by the iodine electrolyte solution. As
a result, the iodine electrolyte solution is degraded, and the cell
performances deteriorate. Further, even in the case where the lead
glass is used for overcoating a collector electrode or for forming
a partition wall, there occurs deterioration of the collector
electrode or tearing of the partition wall due to long-term use.
Those phenomena are also caused by the erosion of the lead glass by
the iodine electrolyte solution.
[0015] Further, when the softening point of the sealing material is
higher than the strain point of a glass substrate, the glass
substrate is deformed during a sealing process. Therefore, it is
required that the sealing material (glass to be used for the
sealing material) have a low-melting point property, e.g., a
softening point of preferably 550.degree. C. or lower or more
preferably 500.degree. C. or lower.
[0016] Accordingly, the present invention has a technical object to
provide a dye-sensitized solar cell having high long-term
reliability, by inventing a glass composition, which is hardly
eroded by an iodine electrolyte solution and has a low-melting
point property, and a material using the glass composition.
Means for Solving the Problems
[0017] The inventors of the present invention have conducted
various studies and as a result, they have found that the above
technical object can be solved by introducing V.sub.2O.sub.5 and
P.sub.2O.sub.5 as essential components into a glass composition,
and have proposed the finding as the present invention. That is, a
glass composition for a dye-sensitized solar cell of the present
invention is characterized by including as a glass composition, in
terms of mass %, 20 to 70% of V.sub.2O.sub.5 and 10 to 50% of
P.sub.2O.sub.5. It should be noted that the mechanism in which it
becomes less likely that a glass is eroded by the iodine
electrolyte solution when V.sub.2O.sub.5 and P.sub.2O.sub.5 are
introduced into the glass composition is not clear at the present
time, and is currently under intensive investigation.
[0018] When the content of V.sub.2O.sub.5 is regulated to 20 to
70%, it becomes less likely that the glass is eroded by the iodine
electrolyte solution while the thermal stability of the glass is
improved, and in addition, the melting point of the glass can be
lowered.
[0019] When the content of P.sub.2O.sub.5 is regulated to 10 to
50%, it becomes less likely that the glass is eroded by the iodine
electrolyte solution while the thermal stability of the glass is
improved, and in addition, the melting point of the glass can be
lowered.
[0020] Second, the glass composition for a dye-sensitized solar
cell of the present invention is characterized by further including
as a glass composition, in terms of mass %, 10 to 55% of
ZnO+SrO+BaO+CuO (a total amount of ZnO, SrO, BaO, and/or CuO).
[0021] Third, the glass composition for a dye-sensitized solar cell
of the present invention is characterized by including as a glass
composition, in terms of mass %, 0 to 30% of ZnO, 0 to 20% of SrO,
0 to 45% of BaO, and 0 to 15% of CuO.
[0022] Fourth, the glass composition for a dye-sensitized solar
cell of the present invention is characterized by having a mass
reduction of 0.1 mg/cm.sup.2 or less after being immersed in an
iodine electrolyte solution at 25.degree. C. for 2 weeks. Here, as
the iodine electrolyte solution used for calculating the mass
reduction, there is used a solution in which 0.1 M lithium iodide,
0.05 M iodine, 0.5 M tert-butylpyridine, and 0.6 M
1,2-dimethyl-3-propyl imidazolium iodide are dissolved in
acetonitrile. Further, "mass reduction" is calculated by: immersing
a glass substrate on which glass powder formed of the glass
composition is densely baked (glass substrate having a baked film)
in the iodine electrolyte solution inside a closed container; and
dividing a value obtained by subtracting a mass after the elapse of
2 weeks from a mass before the immersion by an area of the baked
film which is in contact with the iodine electrolyte solution. It
should be noted that a glass substrate which is not eroded by the
iodine electrolyte solution is used as the glass substrate.
[0023] In general, the iodine electrolyte solution refers to a
solution in which iodine compounds such as iodine, an alkali metal
iodide, an imidazolium iodide, or a quaternary ammonium salt is
dissolved in an organic solvent, but also refers to a solution in
which compounds other than the iodine compound are also dissolved,
such as tert-butylpyridine and 1-methoxybenzoimidazole. As the
solvent, there is used a nitrile-based solvent such as
acetonitrile, methoxyacetonitrile, or propionitrile; a
carbonate-based solvent such as ethylene carbonate or propylene
carbonate; a lactone-based solvent; or the like. Regarding the
iodine electrolyte solutions composed of those compounds and
solvents, however, the above-mentioned problem that the glass is
eroded by the iodine electrolyte solution may occur. Therefore, it
is preferred that the glass composition for a dye-sensitized solar
cell of the present invention have a mass reduction of 0.1
mg/cm.sup.2 or less after being immersed in any one of those iodine
electrolyte solutions at 25.degree. C. for 2 weeks.
[0024] Fifth, the glass composition for a dye-sensitized solar cell
of the present invention is characterized by having a thermal
expansion coefficient of 65 to 120.times.10.sup.-7/.degree. C.
Here, the "thermal expansion coefficient" refers to a value
measured by a push-rod type thermal expansion coefficient measuring
apparatus (TMA) in a temperature range of 30 to 300.degree. C.
[0025] Sixth, a material for a dye-sensitized solar cell of the
present invention is characterized by including 50 to 100 vol % of
a glass powder formed of the glass composition for a dye-sensitized
solar cell and 0 to 50 vol % of a refractory filler powder. It
should be noted that the material for a dye-sensitized solar cell
of the present invention includes an aspect in which the material
is formed only of the glass powder formed of the glass composition.
Further, in the material for a dye-sensitized solar cell of the
present invention, the content of the refractory filler powder is,
from the viewpoint of fluidity, preferably 10 vol % or less or 5
vol % or less, and particularly preferably 1 vol % or less, and it
is more preferred that the material be substantially free of the
refractory filler powder (to be specific, the content of the
refractory filler powder is 0.5 vol % or less). Particularly in the
case where the material is used for the sealing, the gap between
the transparent electrode substrate and the counter electrode
substrate can be easily made small and uniform when the content of
the refractory filler powder is reduced.
[0026] Seventh, the material for a dye-sensitized solar cell of the
present invention is characterized by having a softening point of
550.degree. C. or lower. Here, the "softening point" refers to a
value measured by a macro-type differential thermal analysis (DTA)
apparatus. DTA initiates measurement from room temperature and has
a rate of temperature rise of 10.degree. C./min. It should be noted
that the softening point measured by the macro-type DTA apparatus
is represented by a temperature (Ts) at the fourth inflection point
illustrated in FIG. 1.
[0027] Eighth, the material for a dye-sensitized solar cell of the
present invention is characterized by being used for sealing. Here,
the sealing includes sealing of a glass tube or the like in
addition to sealing of the transparent electrode substrate and the
counter electrode substrate. It should be noted that there is a
case where multiple openings are provided on the transparent
electrode substrate, the counter electrode substrate, and the like,
and glass tubes are sealed to the respective multiple openings, and
after that, a liquid containing a pigment or the like is circulated
inside the dye-sensitized solar cell via the glass tubes, whereby
the pigment is adsorbed to a porous oxide semiconductor. In this
case, it becomes less likely that the leakage of the liquid or the
like, etc. occur when the glass tubes are sealed using the material
for a dye-sensitized solar cell of the present invention.
[0028] Ninth, the material for a dye-sensitized solar cell of the
present invention is characterized by being used for sealing by a
laser beam.
[0029] Tenth, the material for a dye-sensitized solar cell of the
present invention is characterized by being used for overcoating a
collector electrode.
EFFECTS OF THE INVENTION
[0030] In the glass composition for a dye-sensitized solar cell of
the present invention, when V.sub.2O.sub.5 and P.sub.2O.sub.5 are
introduced as essential components into a glass composition, the
erosion by the iodine electrolyte solution hardly occurs, and the
mass reduction of the glass composition for a dye-sensitized solar
cell after being immersed in the iodine electrolyte solution at
25.degree. C. for 2 weeks can be set to 0.1 mg/cm.sup.2 or less. As
a result, a sealed part, a partition wall, and a overcoated part
are hardly eroded by the iodine electrolyte solution, and the
degradation of the iodine electrolyte solution or the cell
performances can be prevented for a long period of time.
BEST MODE FOR CARRYING OUT THE INVENTION
[0031] In a glass composition for a dye-sensitized solar cell of
the present invention, the reason for limiting the range of a glass
composition to the above range is described below. It should be
noted that, unless otherwise mentioned, "%" used below means "mass
%".
[0032] V.sub.2O.sub.5 is, as well as being a glass-forming oxide, a
component which makes it less likely that the erosion by the iodine
electrolyte solution occurs, and is also a component which lowers
the melting point of glass. The content thereof is 20 to 70%, more
preferably 30 to 60%, and still more preferably 45 to 55%. When the
content of V.sub.2O.sub.5 is less than 20%, the viscosity of the
glass becomes high and the baking temperature becomes high.
Further, when the content of V.sub.2O.sub.5 is set to 45% or more,
the fluidity of the glass improves, and a high airtightness can be
obtained. On the other hand, when the content of V.sub.2O.sub.5 is
more than 70%, the glass composition may be vitrified, but the
devitrification resistance of the glass is easily lowered. Further,
when the content of V.sub.2O.sub.5 is more than 70%, the glass
becomes easily foamed at the time of baking. Further, when the
content of V.sub.2O.sub.5 is 55% or less, the devitrification
resistance can be improved and the thermal stability of the glass
improves.
[0033] P.sub.2O.sub.5 is, as well as being a glass-forming oxide, a
component which makes it less likely that the erosion by the iodine
electrolyte solution occurs, and is also a component which lowers
the melting point of the glass. The content thereof is 10 to 50%,
more preferably 15 to 35%, and still more preferably 20 to 30%.
When the content of P.sub.2O.sub.5 is less than 10%, the thermal
stability of the glass is easily lowered. On the other hand, when
the content of P.sub.2O.sub.5 is more than 60%, the moisture
resistance of the glass is easily deteriorated.
[0034] The glass composition for a dye-sensitized solar cell of the
present invention can contain, apart from the above components, the
following components in a glass composition.
[0035] ZnO+SrO+BaO+CuO is a network-modifier oxide which stabilizes
the glass. The content thereof is 10 to 55% and more preferably 14
to 30%. When the content of ZnO+SrO+BaO+CuO is less than 10%, the
effect of stabilizing the glass is poor, and when the content of
ZnO+SrO+BaO+CuO is more than 55%, the balance between the
components of the glass composition is disturbed, and the other way
around, the glass becomes unstable and is easily devitrified at the
time of forming a molten glass into the glass.
[0036] ZnO is a component which stabilizes the glass. On the other
hand, ZnO has a tendency of promoting the erosion of the glass by
the iodine electrolyte solution. Therefore, the content thereof is
0 to 30%, more preferably 0 to 20%, still more preferably 0 to 15%,
and particularly preferably 0 to 10%. When the content of ZnO is
more than 30%, the devitrification resistance of the glass is
easily lowered.
[0037] SrO is, as well as being a component which improves the
thermal stability of the glass and suppresses the devitrification
of the glass, a component which lowers the viscosity of the glass.
The content thereof is 0 to 20% and preferably 0 to 15%. When the
content of SrO is more than 20%, the balance between the components
of the glass composition is disturbed, and the other way around,
the thermal stability of the glass is easily lowered.
[0038] BaO is, as well as being a component which improves the
thermal stability of the glass and suppresses the devitrification
of the glass, a component which lowers the viscosity of the glass.
The content thereof is 0 to 45% and more preferably 3 to 22%. When
the content of BaO is more than 45%, the balance between the
components of the glass composition is disturbed, and the other way
around, the thermal stability of the glass is easily lowered.
[0039] CuO is, as well as being a component which improves the
thermal stability of the glass and suppresses the devitrification
of the glass, a component which improves the weatherability of the
glass. The content thereof is 0 to 15% and preferably 0 to 10%.
When the content of CuO is more than 15%, the viscosity of the
glass becomes too high, and the sealing temperature is easily
increased.
[0040] Further, in the glass composition for a dye-sensitized solar
cell of the present invention, there can be introduced into a glass
composition, in addition to the above components, up to 20% of CaO,
MgO, TeO.sub.2, B.sub.2O.sub.3, Fe.sub.2O.sub.3, Al.sub.2O.sub.3,
SiO.sub.2, and the like. It should be noted that, from the
environmental viewpoint and the viewpoint of preventing the erosion
by an iodine electrolyte solution, it is preferred that the glass
composition for a dye-sensitized solar cell of the present
invention be substantially free of PbO. Here, the phrase "be
substantially free of PbO" refers to the case where the content of
PbO in the glass composition is 1,000 ppm or less.
[0041] In the glass composition for a dye-sensitized solar cell of
the present invention, the mass reduction after being immersed in
an iodine electrolyte solution at 25.degree. C. for 2 weeks is 0.1
mg/cm.sup.2 or less and preferably 0.05 mg/cm.sup.2 or less, and it
is still more preferred that there be substantially no mass
reduction. When the mass reduction is 0.1 mg/cm.sup.2 or less, the
degradation of the iodine electrolyte solution or the cell
performances can be prevented for a long period of time. Here, "be
substantially no mass reduction" refers to the case where the mass
reduction is 0.01 mg/cm.sup.2 or less.
[0042] In the glass composition for a dye-sensitized solar cell of
the present invention, the thermal expansion coefficient is
preferably 65 to 120.times.10.sup.-7/.degree. C. and more
preferably 80 to 110.times.10.sup.-7/.degree. C. When the
difference between the thermal expansion coefficient of the glass
composition for a dye-sensitized solar cell of the present
invention and the thermal expansion coefficient of a glass
substrate (e.g., soda glass substrate) used for the transparent
electrode substrate or the like is too large, there remains, unless
a refractory filler powder is added thereto, undue stress on the
glass substrate, a sealed part, or the like after baking, and
hence, it becomes more likely that a crack is generated on the
glass substrate, the sealed part, or the like, or peeling occurs at
the sealed part.
[0043] The material for a dye-sensitized solar cell of the present
invention is preferably formed only of a glass powder formed of the
glass composition for a dye-sensitized solar cell. In such a
manner, the cell gap of the solar cell can be easily made small and
uniform, and also, a mixing process or the like of the refractory
filler powder, etc. becomes unnecessary. Therefore, the production
cost of the material for a dye-sensitized solar cell can be
reduced.
[0044] The material for a dye-sensitized solar cell of the present
invention may contain a refractory filler powder in order to
improve the mechanical strength or to decrease the thermal
expansion coefficient. On the other hand, if the addition amount of
the refractory filler powder is decreased, the fluidity, or in
particular, the sealing property, of the material for a
dye-sensitized solar cell can be enhanced. Accordingly, the mixing
ratio is 50 to 100 vol % of the glass powder to 0 to 50 vol % of
the refractory filler powder, preferably 65 to 100 vol % of the
glass powder to 0 to 35 vol % of the refractory filler powder, and
more preferably 95 to 100 vol % of the glass powder to 0 to 5 vol %
of the refractory filler powder, and it is desired that, from the
reasons stated above, the material be substantially free of the
refractory filler powder. When the content of the refractory filler
powder is more than 50 vol %, the ratio of the glass powder
relatively becomes too low, and hence, it becomes difficult to
obtain the desired fluidity.
[0045] In general, the cell gap of the dye-sensitized solar cell is
50 .mu.m or less, which is extremely small. Therefore, when the
particle size of the refractory filler powder is too large, a
protrusion is generated locally at the sealed part, and hence, it
becomes difficult to make the cell gap uniform. In order to prevent
such situation, the maximum particle size of the refractory filler
powder is preferably 25 .mu.m or less and more preferably 15 .mu.m
or less. Here, the "maximum particle size" refers to the particle
size of a particle in which, in a cumulative particle size
distribution curve on a volumetric basis when measured by a laser
diffraction method, the integrated quantity thereof is 99% when
accumulated in the order starting from the particle having the
smallest particle size.
[0046] The material of the refractory filler powder is not
particularly limited, and is preferably a material which hardly
reacts with the glass powder formed of the glass composition for a
dye-sensitized solar cell of the present invention and the iodine
electrolyte solution. Specifically, as the refractory filler
powder, there can be used zircon, zirconia, tin oxide, aluminum
titanate, quartz, .beta.-spodumene, mullite, titania, quartz glass,
.beta.-eucryptite, .beta.-quartz, zirconium phosphate, zirconium
phosphotungstate, zirconium tungstate, willemite, a compound having
[AB.sub.2(MO.sub.4).sub.3] as a basic structure where A represents
Li, Na, K, Mg, Ca, Sr, Ba, Zn, Cu, Ni, Mn, or the like, B
represents Zr, Ti, Sn, Nb, Al, Sc, Y, or the like, and M represents
P, Si, W, Mo, or the like, and a solid solution thereof.
[0047] In the material for a dye-sensitized solar cell of the
present invention, the softening point is preferably 550.degree. C.
or lower and more preferably 500.degree. C. or lower. When the
softening point is higher than 500.degree. C., the viscosity of the
glass becomes too high and the sealing temperature is unduly
increased, and hence, the glass substrate is easily deformed.
Further, in the case where the material for a dye-sensitized solar
cell and a porous oxide semiconductor layer are baked
simultaneously, the fusion of oxide semiconductor particles may
proceed too much when the sealing temperature is too high. In such
a case, the surface area of the porous oxide semiconductor layer
decreases, which makes it less likely that a pigment is adsorbed
thereto.
[0048] In the material for a dye-sensitized solar cell of the
present invention, the mass reduction after being immersed in an
iodine electrolyte solution at 25.degree. C. for 2 weeks is 0.1
mg/cm.sup.2 or less and preferably 0.05 mg/cm.sup.2 or less, and it
is desired that there be substantially no mass reduction. When the
mass reduction is 0.1 mg/cm.sup.2 or less, the deterioration of the
iodine electrolyte solution or the cell performances can be
prevented for a long period of time.
[0049] The material for a dye-sensitized solar cell of the present
invention in a powder form may be used as it is, and when the
material is kneaded homogeneously with a vehicle and processed into
a paste, it becomes easier to handle. The vehicle is mainly
composed of a solvent and a resin, and the resin is added thereto
for adjusting the viscosity of the paste. Further, a surfactant, a
thickener, or the like may also be added thereto, if required. The
produced paste is subjected to coating by using a coating machine
such as a dispenser or a screen printing machine.
[0050] As the resin, there can be used an acrylate (acrylic resin),
ethylcellulose, a polyethylene glycol derivative, nitrocellulose,
polymethylstyrene, polyethylene carbonate, a methacrylate, and the
like. In particular, an acrylate and nitrocellulose are preferred
because of having good thermolytic property.
[0051] As the solvent, N,N'-dimethyl formamide (DMF), there can be
used .alpha.-terpineol, a higher alcohol, .gamma.-butyrolactone
(.gamma.-BL), tetralin, butylcarbitol acetate, ethyl acetate,
isoamyl acetate, diethylene glycolmonoethyl ether, diethylene
glycolmonoethyl ether acetate, benzyl alcohol, toluene,
3-methoxy-3-methylbutanol, triethylene glycol monomethyl ether,
triethylene glycol dimethyl ether, dipropylene glycol monomethyl
ether, dipropylene glycol monobutyl ether, tripropylene
glycolmonomethyl ether, tripropylene glycol monobutyl ether,
propylene carbonate, dimethyl sulfoxide (DMSO),
N-methyl-2-pyrrolidone, and the like. In particular,
.alpha.-terpineol is preferred because of having high viscosity and
good solubility of a resin and the like.
[0052] The material for a dye-sensitized solar cell of the present
invention is preferably used for a sealing purpose, and
particularly preferably used for sealing a transparent electrode
substrate and a counter electrode substrate. The material for a
dye-sensitized solar cell of the present invention has low-melting
point property and is hardly eroded by the iodine electrolyte
solution, and hence, the iodine electrolyte solution hardly leaks
during long-term use and the prolonged lifetime of the solar cell
can be expected. Further, in the case where the material is used
for sealing the transparent electrode substrate and the counter
electrode substrate, a spacer such as a glass bead may be added to
the material for a dye-sensitized solar cell of the present
invention in order to make the cell gap of the solar cell
uniform.
[0053] The material for a dye-sensitized solar cell of the present
invention contains 20% or more of V.sub.2O.sub.5 in a glass
composition, and hence, the material can be subjected to a sealing
treatment by a laser beam. When the laser beam is used, the
material for a dye-sensitized solar cell can be locally heated.
Therefore, the transparent electrode substrate and the counter
electrode substrate can be sealed while preventing the heat
deterioration of a constituent member such as the iodine
electrolyte solution. In the case where the transparent electrode
substrate and the counter electrode substrate are sealed by using
the laser beam, the material for a dye-sensitized solar cell of the
present invention contains preferably 30% or more or 40% or more,
or particularly preferably 45% or more of V.sub.2O.sub.5 in a glass
composition. When the content of V.sub.2O.sub.5 is thus regulated,
light energy of the laser beam can be effectively converted into
heat energy, in other words, the laser beam can be absorbed to the
glass accurately, and hence, only the parts to be sealed can be
locally heated accurately. On the other hand, when the content of
V.sub.2O.sub.5 is regulated to 70% or less, and particularly to 60%
or less, a situation that the glass is devitrified at the time of
irradiating the laser beam can be prevented. Here, various laser
beams can be used as the laser beam, and in particular, a
semiconductor laser, a YAG laser, a CO.sub.2 laser, an excimer
laser, an infrared laser, and the like are suitable, because they
are easy to handle. Further, in order to allow the glass to absorb
the laser beam accurately, the laser beam preferably has an
emission center wavelength of 500 to 1,600 nm and preferably 750 to
1,300 nm.
[0054] The material for a dye-sensitized solar cell of the present
invention is preferably used for overcoating a collector electrode.
In general, there is used Ag for the collector electrode, but Ag is
easily eroded by the iodine electrolyte solution. Accordingly, in
the case where Ag is used for the collector electrode, the
collector electrode needs to be protected. The material for a
dye-sensitized solar cell of the present invention has low-melting
point property, and hence, a dense coating layer can be formed at
low temperature. In addition, the material is hardly eroded by the
iodine electrolyte solution, and hence can protect the collector
electrode for a long period of time.
[0055] The material for a dye-sensitized solar cell of the present
invention can be used for forming a partition wall. In general, in
the case where the partition wall is formed in the dye-sensitized
solar cell, inside the cell is filled with the iodine electrolyte
solution. The material for a dye-sensitized solar cell of the
present invention has low-melting point property, and hence, a
dense partition wall can be formed at low temperature. In addition,
the material is hardly eroded by the iodine electrolyte solution,
and hence can prevent tearing of the partition wall for a long
period of time.
EXAMPLES
[0056] The present invention is described in detail based on
examples. Table 1 shows Examples (Sample Nos. 1 to 5) and
Comparative Examples (Sample No. 6) of the present invention.
TABLE-US-00001 TABLE 1 Comparative Example Example 1 2 3 4 5 6
Glass V.sub.2O.sub.5 50.0 46.0 47.5 55.0 50.0 -- composition
P.sub.2O.sub.5 25.0 29.0 25.0 28.0 25.0 -- (mass %) ZnO 7.5 12.5 --
2.0 7.5 -- BaO 14.0 12.5 20.0 14.0 3.0 -- SrO 3.5 -- -- 1.0 14.5 --
CuO -- -- 7.5 -- -- -- PbO -- -- -- -- -- 85.3 B.sub.2O.sub.3 -- --
-- -- -- 12.7 SiO.sub.2 -- -- -- -- -- 1.0 Al.sub.2O.sub.3 -- -- --
-- -- 1.0 Refractory filler Absent Absent Absent Absent Absent
PbTiO.sub.3 powder (vol %) 37 Thermal expansion 93 86 98 99 94 73
coefficient (10.sup.-7/.degree. C.) Softening point (.degree. C.)
420 437 449 438 431 390 Mass reduction 0.00 0.00 0.00 0.00 0.00
0.32 (mg/cm.sup.2)
[0057] Each of the samples described in the table was prepared as
follows. First, a glass batch in which raw materials such as
various oxides and carbonates were mixed so as to have a glass
composition shown in the table was prepared, and was then loaded
into a platinum crucible and melted at 1,000 to 1,200.degree. C.
for 1 to hours. Next, a part of the molten glass, which serves as a
sample for measuring a thermal expansion coefficient, was poured
into a die made of stainless steel, and the remaining molten glass
was formed into a flaky shape by a water cooled roller. The sample
for measuring a thermal expansion coefficient was subjected to a
predetermined annealing treatment. Finally, the flaky glass was
pulverized by a ball mill and then allowed to pass through a sieve
having a mesh of 75 .mu.m, whereby each glass powder having an
average particle size of about 10 .mu.m was obtained. It should be
noted that Sample No. 6 is a sample which is obtained by adding the
refractory filler powder (lead titanate, average particle size of
10 .mu.m) shown in the table to the glass composition at the ratio
shown in the table and mixing the resultant.
[0058] Next, each glass powder (mixed powder in the case of Sample
No. 6) and a vehicle (which was obtained by dissolving
ethylcellulose in .alpha.-terpineol) were kneaded into a paste. The
paste was screen printed on a soda glass substrate (thermal
expansion coefficient: 100.times.10.sup.-7/.degree. C.) so as to
have a diameter of 40 mm and a thickness of 40 to 80 .mu.m,
followed by drying at 120.degree. C. for 10 minutes and then baking
at 500.degree. C. for 30 minutes in an electric furnace, whereby a
sample for evaluating mass reduction was obtained.
[0059] The above samples were used, and the thermal expansion
coefficient, the softening point, and the mass reduction with
respect to an iodine electrolyte solution were evaluated. The
results are shown in Table 1.
[0060] The thermal expansion coefficient was measured by a TMA
measuring apparatus. The thermal expansion coefficient was measured
at a temperature range of 30 to 300.degree. C. It should be noted
that Sample No. 6 was processed to have a predetermined shape by
densely sintering the mixed powder, and then was used as a
measurement sample.
[0061] The softening point was determined by a DTA apparatus. The
measurement was performed in air and the rate of temperature rise
was set to 10.degree. C./min.
[0062] The mass reduction was calculated as follows. First, the
mass of the sample for evaluating mass reduction and the surface
area of the baked film which is in contact with the iodine
electrolyte solution were measured. Next, the sample was immersed
in the iodine electrolyte solution inside a closed container made
of glass, and then the closed container made of glass was left
standing still in a thermostat at 25.degree. C. The mass reduction
was calculated by dividing a value obtained by subtracting the mass
of the sample after the elapse of 2 weeks from the mass of the
sample before the immersion by the surface area of the baked film.
As the iodine electrolyte solution used for the evaluation of the
mass reduction, there was used a solution in which 0.1 M lithium
iodide, 0.05 M iodine, 0.5 M tert-butylpyridine, and 0.6 M
1,2-dimethyl-3-propyl imidazolium iodide were added to
acetonitrile.
[0063] As is clear from Table 1, Sample Nos. 1 to 5 each had a
thermal expansion coefficient of 86 to 99.times.10.sup.-7/.degree.
C. and a softening point of 420 to 449.degree. C. Further, in each
sample for measuring mass reduction, the baked film satisfactorily
adhered to the glass substrate without causing peeling. In
addition, the mass reduction could not be confirmed in each of
Sample Nos. 1 to 5, so Sample Nos. 1 to 5 were hardly eroded by the
iodine electrolyte solution. On the other hand, Sample No. 6 had a
mass reduction of 0.32 mg/cm.sup.2, because Sample No. 6 used lead
glass, so Sample No. 6 was eroded by the iodine electrolyte
solution.
INDUSTRIAL APPLICABILITY
[0064] The glass composition for a dye-sensitized solar cell and
the material for a dye-sensitized solar cell of the present
invention are suitable for sealing the transparent electrode
substrate and the counter electrode substrate of a dye-sensitized
solar cell, forming the partition wall for dividing cells, and
overcoating the collector electrode.
BRIEF DESCRIPTION OF THE DRAWING
[0065] FIG. 1 is a schematic diagram illustrating a softening point
of glass measured by a macro-type DTA apparatus.
* * * * *