U.S. patent application number 14/695549 was filed with the patent office on 2015-08-20 for dye-sensitized solar cell.
The applicant listed for this patent is DAI NIPPON PRINTING CO., LTD.. Invention is credited to Ryo FUJIWARA, Naohiro OBONAI.
Application Number | 20150235774 14/695549 |
Document ID | / |
Family ID | 43991450 |
Filed Date | 2015-08-20 |
United States Patent
Application |
20150235774 |
Kind Code |
A1 |
OBONAI; Naohiro ; et
al. |
August 20, 2015 |
DYE-SENSITIZED SOLAR CELL
Abstract
A dye-sensitized solar cell includes a base material that
functions as an electrode, has flexibility, and has a porous layer,
containing a dye-sensitizer-supported fine particle of a metal
oxide semiconductor on one surface thereof. A counter electrode
base material is arranged to oppose the base material for dye
sensitized solar cell, functions as an electrode, and has
flexibility. A solid electrolyte layer is provided between the base
material for dye-sensitized solar cell and the counter electrode
base material and contacts the porous layer. Among the base
materials, at least one has transparency; and at least one has an
insulating layer provided on a surface thereof. The insulating
layer is provided in a region a region where the porous layer is
formed, and where the base materials are opposed to each other. The
insulating layer has an external communication portion that leads
from an inside of the porous layer-forming region to outside.
Inventors: |
OBONAI; Naohiro; (Tokyo-to,
JP) ; FUJIWARA; Ryo; (Tokyo-to, JP) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
DAI NIPPON PRINTING CO., LTD. |
Tokyo-to |
|
JP |
|
|
Family ID: |
43991450 |
Appl. No.: |
14/695549 |
Filed: |
April 24, 2015 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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13389887 |
Feb 10, 2012 |
9064637 |
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PCT/JP2010/061488 |
Jul 6, 2010 |
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14695549 |
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Current U.S.
Class: |
136/256 ;
438/98 |
Current CPC
Class: |
H01G 9/2095 20130101;
H01G 9/2009 20130101; H01G 9/2027 20130101; H01G 9/2077 20130101;
Y02E 10/542 20130101; H01G 9/2022 20130101; H01G 9/2031 20130101;
H01G 9/2059 20130101 |
International
Class: |
H01G 9/20 20060101
H01G009/20 |
Foreign Application Data
Date |
Code |
Application Number |
Nov 16, 2009 |
JP |
2009-261158 |
Claims
1. A dye-sensitized solar cell comprising: a base material for
dye-sensitized solar cell that functions as an electrode, has
flexibility, and has a porous layer, containing a
dye-sensitizer-supported fine particle of a metal oxide
semiconductor, provided on one surface of the base material for
dye-sensitized solar cell; a counter electrode base material that
is arranged so as to oppose to the base material for dye sensitized
solar cell, functions as an electrode, and has flexibility; and a
solid electrolyte layer that is provided between the base material
for dye-sensitized solar cell and the counter electrode base
material so as to come into contact with the porous layer, wherein
at least one of the base material for dye-sensitized solar cell and
the counter electrode base material has transparency; at least one
of the base material for dye-sensitized solar cell and the counter
electrode base material has an insulating layer provided on a
surface thereof; the insulating layer is provided in a region which
surrounds a porous layer-forming region where the porous layer is
formed, and which is where the base material for dye-sensitized
solar cell and the counter electrode base material are opposed to
each other; and the insulating layer has an external communication
portion that leads from an inside of the porous layer-forming
region to outside.
2. The dye-sensitized solar cell according to claim 1, wherein the
external communication portion is a void space where the insulating
layer is not provided in part of a region which surrounds the
porous layer-forming region and which is where the base material
for dye-sensitized solar cell and the counter electrode base
material are opposed to each other.
3. The dye-sensitized solar cell according to claim 1, wherein the
base material for dye-sensitized solar cell is composed of a metal
foil and the counter electrode base material has transparency.
4. The dye-sensitized solar cell according to claim 1, wherein the
insulating layer has tackiness.
5. A dye-sensitized solar cell module comprising the two or more
dye-sensitized solar cells according to claim 1 connected
together.
6. A method for producing a dye-sensitized solar cell comprising
the steps of: first preparing a base material for dye-sensitized
solar cell that functions as an electrode, has flexibility, and has
a porous layer, containing a dye-sensitizer-supported fine particle
of a metal oxide semiconductor, provided on one surface of the base
material for dye-sensitized solar cell, and a counter electrode
base material that is arranged so as to oppose to the base material
for dye-sensitized solar cell, functions as an electrode, and has
flexibility; then forming the porous layer on the base material for
dye-sensitized solar cell; forming a solid electrolyte layer so as
to come into contact with the porous layer; forming an insulating
layer on a surface of at least one of the base material for
dye-sensitized solar cell and the counter electrode base material
in a region which surrounds a region corresponding to a porous
layer-forming region, where the porous layer is formed, and which
is where the base material for dye-sensitized solar cell and the
counter electrode base material are opposed to each other when they
are bonded together; and then bonding together the base material
for dye-sensitized solar cell and the counter electrode base
material opposed to each other with the porous layer and the solid
electrolyte layer being interposed therebetween, wherein at least
one of the base material for dye-sensitized solar cell and the
counter electrode base material has transparency, and the porous
layer-forming step, the solid electrolyte layer-forming step, and
the insulating layer-forming step are performed in no particular
order.
7. The method for producing a dye-sensitized solar cell according
to claim 6, wherein a metal foil is used as the base material for
dye-sensitized solar cell, a base material having transparency is
used as the counter electrode base material, and in the porous
layer-forming step, the porous layer is formed by burning.
8. The method for producing a dye-sensitized solar cell according
to claim 6, wherein in the insulating layer-forming step, the
insulating layer is formed by applying a composition for forming an
insulating layer in a pattern onto at least one of the base
material for dye-sensitized solar cell and the counter electrode
base material or by using a tape having insulating properties.
9. The method for producing a dye-sensitized solar cell according
to claim 6, wherein: the porous layer is formed by applying a
composition for forming a porous layer in a pattern onto the base
material for dye-sensitized solar cell in the porous layer-forming
step; the solid electrolyte layer is formed by applying a
composition for forming a solid electrolyte layer in a pattern onto
the porous layer in the solid electrolyte layer-forming step; and
the insulating layer is formed by applying a composition for
forming an insulating layer in a pattern onto at least one of the
base material for dye-sensitized solar cell and the counter
electrode base material in the insulating layer-forming step.
Description
TECHNICAL FIELD
[0001] The present invention relates to a dye-sensitized solar cell
that has flexibility and is free from problems such as a short
circuit.
BACKGROUND ART
[0002] In recent years, environmental issues such as global warming
believed to be caused by an increase in carbon dioxide have become
serious, and therefore measures against such environmental issues
have been taken on a global basis. Above all, solar cells utilizing
the energy of sunlight have been actively researched and developed
as environmentally-friendly clean energy sources. As such solar
cells, monocrystal silicon solar cells, polycrystal silicon solar
cells, amorphous silicon solar cells, and compound-semiconductor
solar cells have already been practically used, but these solar
cells have problems such as high production cost etc. For this
reason, dye-sensitized solar cells have received attention as solar
cells that are environmentally friendly and can be produced at
lower cost, and research and development of such dye-sensitized
solar cells have been promoted.
[0003] An example of the general structure of a dye-sensitized
solar cell is shown in FIG. 11. As shown in FIG. 11, a general
dye-sensitized solar cell 100 has a structure comprising: a base
material for dye-sensitized solar cell 110 having a base material
111 and a first electrode layer 112 laminated on the base material
111, and a counter electrode base material 120 that functions as an
electrode, and a porous layer 102 containing dye
sensitizer-supported fine particles of a metal oxide semiconductor
and an electrolyte layer 101 provided inside a sealant 103 and
interposed between the base material for dye-sensitized solar cell
110 and the counter electrode base material 120. Therefore, the dye
sensitizer adsorbed to the surface of the metal oxide semiconductor
fine particles contained in the porous layer 102 is excited by
receiving sunlight from the base material 111 side, and excited
electrons are transferred to the first electrode layer and then
transferred to the counter electrode base material through an
external circuit. Then, the electrons are returned to the ground
state of the dye sensitizer by a redox couple so that electricity
is generated.
[0004] Such a dye-sensitized solar cell conventionally uses a glass
substrate as a base material. However, in recent years, there has
been a demand for flexible dye-sensitized solar cells, and
therefore the use of a flexible substrate as a base material has
been contemplated. However, when a flexible base material is used,
there is a problem that the base material is bent and therefore an
internal short circuit is caused by electrical contact between the
first electrode layer and the counter electrode base material.
[0005] In order to solve such a problem, for example, Patent
Literatures 1 and 2 disclose that a separator, such as an
insulating porous film, is provided between a counter electrode
layer and a power-generating layer composed of a porous layer and
an electrolyte layer to prevent a short circuit. Further, Patent
Literature 3 discloses that a spacer is provided on a counter
electrode layer to prevent a short circuit. All the electrolytes
used in Patent Literatures 1 to 3 are liquid.
[0006] However, a dye-sensitized solar cell having an electrolyte
layer using such a liquid electrolyte has the problem of high
production cost because the electrolyte layer usually needs to be
sealed with an expensive sealant having high resistance to iodine
contained in the electrolyte, and further has a problem that, even
when the electrolyte layer is sealed with such a sealant, there is
a possibility that liquid leakage from the electrolyte layer
occurs. Further, as described above, since the production of such a
dye-sensitized solar cell having an electrolyte layer using a
liquid electrolyte requires sealing with a sealant, alignment
between a base material for dye-sensitized solar cell and a counter
electrode base material for bonding requires high accuracy.
Further, in such a dye-sensitized solar cell, the sealant needs to
be provided outside a region where a porous layer is provided, and
therefore adjustment of the formation position of each of the
members of the dye-sensitized solar cell also requires high
accuracy. Therefore, such a dye-sensitized solar cell has a problem
that its production process is complicated.
[0007] In order to solve such problems, a dye-sensitized solar cell
having a solid electrolyte layer using a solid electrolyte instead
of such a liquid electrolyte as described above has been studied.
Such a dye-sensitized solar cell having a solid electrolyte layer
uses a solid electrolyte having no fluidity, and therefore can be
produced at low cost without sealing the solid electrolyte layer
with such an expensive sealant as described above. The use of such
a solid electrolyte also makes it possible to solve the problem of
liquid leakage from an electrolyte layer. Further, as described
above, since it is not necessary to perform sealing with a sealant,
alignment between a base material for dye-sensitized solar cell and
a counter electrode base material for bonding and adjustment of the
formation position of each of the members of the dye-sensitized
solar cell do not require high accuracy. This eliminates the
above-described complications associated with the production of a
dye-sensitized solar cell using a liquid electrolyte and makes it
easy to produce a dye-sensitized solar cell.
[0008] Such a dye-sensitized solar cell using a solid electrolyte
layer is also required to use a flexible base material.
[0009] When such a dye-sensitized solar cell using a solid
electrolyte layer uses a flexible base material, a base material
for dye-sensitized solar cell and a counter electrode base material
can be separated from each other by a laminated body composed of
the solid electrolyte layer and a porous layer, which is
advantageous in that the necessity to use a member such as the
above-described separator or spacer can be eliminated.
[0010] However, such a dye-sensitized solar cell using a solid
electrolyte layer has a problem that there is a possibility that an
internal short circuit occurs due to contact between the base
material for dye-sensitized solar cell and the counter electrode
base material in a region surrounding the porous layer. In order to
solve such a problem, for example as shown in FIG. 12, a
dye-sensitized solar cell in which a base material for
dye-sensitized solar cell 1 and a counter electrode base material 2
are not opposed to each other around a porous layer 4 has also been
studied. However, in this case, there is a problem that alignment
between the base material for dye-sensitized solar cell and the
counter electrode base material for bonding requires high accuracy,
which complicates the production process of the dye-sensitized
solar cell. It is to be noted that a detailed description of FIG.
12 will be made later.
CITATION LIST
Patent Literature
Patent Literature 1: Japanese Patent Application Laid-Open (JP-A)
No. 2005-243388
Patent Literature 2: JP-A No. 2006-331791
Patent Literature 3: JP-A No. 2004-296203
SUMMARY OF INVENTION
Technical Problem
[0011] It is a major object of the present invention to provide a
dye-sensitized solar cell that does not cause problems such as a
short circuit even when a flexible base material is used and a
dye-sensitized solar cell production method that is capable of
easily producing such a dye-sensitized solar cell at low cost.
Solution to Problem
[0012] In order to achieve the above object, the present invention
provides a dye-sensitized solar cell comprising: a base material
for dye-sensitized solar cell that functions as an electrode, has
flexibility, and has a porous layer, containing a
dye-sensitizer-supported fine particle of a metal oxide
semiconductor, provided on one surface of the base material for
dye-sensitized solar cell; a counter electrode base material that
is arranged so as to oppose to the base material for dye-sensitized
solar cell, functions as an electrode, and has flexibility; and a
solid electrolyte layer that is provided between the base material
for dye-sensitized solar cell and the counter electrode base
material so as to come into contact with the porous layer, wherein
at least one of the base material for dye-sensitized solar cell and
the counter electrode base material has transparency; at least one
of the base material for dye-sensitized solar cell and the counter
electrode base material has an insulating layer provided on a
surface thereof; the insulating layer is provided in a region which
surrounds a porous layer-forming region where the porous layer is
formed, and which is where the base material for dye-sensitized
solar cell and the counter electrode base material are opposed to
each other; and the insulating layer has an external communication
portion that leads from an inside of the porous layer-forming
region to outside.
[0013] According to the present invention, by providing the
insulating layer, it is possible to prevent contact between the
base material for dye-sensitized solar cell and the counter
electrode base material in a region which surrounds the porous
layer-forming region and where both the base materials are opposed
to each other. This makes it possible to prevent the occurrence of
a short circuit in the dye-sensitized solar cell.
[0014] Further, according to the present invention, by providing
the solid electrolyte layer using an electrolyte having no
fluidity, it is possible to eliminate the necessity to seal the
solid electrolyte layer with an expensive sealant having high
resistance to iodine. This allows the dye-sensitized solar cell to
be produced at low cost.
[0015] Further, according to the present invention, since the solid
electrolyte layer and the insulating layer are provided, adjustment
of the formation position of each of the members and alignment
between the base material for dye-sensitized solar cell and the
counter electrode base material for bonding during the production
of the dye-sensitized solar cell do not require high accuracy. This
allows the dye-sensitized solar cell to be easily produced.
[0016] Further, according to the present invention, by providing
the external communication portion in a region surrounding the
porous layer, it is possible to discharge air in the dye-sensitized
solar cell through the external communication portion when the base
material for dye-sensitized solar cell and the counter electrode
base material are bonded together in the step of bonding them
together during the production of the dye-sensitized solar cell.
This allows the dye-sensitized solar cell to be easily
produced.
[0017] According to the present invention, it is preferred that the
base material for dye-sensitized solar cell is composed of a metal
foil and the counter electrode base material has transparency. When
the base material for dye-sensitized solar cell is composed of a
metal foil, the porous layer can be directly formed on the base
material for dye-sensitized solar cell by burning. This allows the
dye-sensitized solar cell to achieve good adhesion between the base
material for dye-sensitized solar cell and the porous layer.
[0018] Further, when the dye-sensitized solar cell has a structure
in which the base material for dye-sensitized solar cell is
composed of a metal foil and the counter electrode base material
has transparency (hereinafter, sometimes referred to as an
"inverted structure"), light enters the porous layer through the
solid electrolyte layer, and therefore there is a concern about the
loss of light in the solid electrolyte layer. Therefore, the
thickness of the solid electrolyte layer is preferably reduced, but
a reduction in the thickness of the solid electrolyte layer narrows
the gap between the two base materials, which increases the risk of
a short circuit between the electrodes. For this reason, in the
case of such an inverted-structure dye-sensitized solar cell, the
use of the insulating layer used in the present invention is
preferred.
[0019] According to the present invention, it is also preferred
that the insulating layer has tackiness. This makes it possible to
previously perform, for example, temporal bonding between the base
material for dye-sensitized solar cell and the counter electrode
base material by using the insulating layer so that a desired
positional relationship between the base material for
dye-sensitized solar cell and the counter electrode base material
can be achieved when they are bonded together. This allows the
dye-sensitized solar cell to achieve high quality.
[0020] According to the present invention, it is also preferred
that the porous layer-forming region is quadrilateral and the
insulating layer is provided along the two opposite sides of the
porous layer-forming region.
[0021] Such a shape of the dye-sensitized solar cell is suitable
for mass production, and mass production of the dye-sensitized
solar cell can be achieved by, for example, a Roll-to-Roll
method.
[0022] The present invention is also directed to a dye-sensitized
solar cell module comprising the above-described two or more
dye-sensitized solar cells connected together.
[0023] According to the present invention, the use of the
above-described dye-sensitized solar cells makes it possible to
prevent the occurrence of an internal short circuit in the
dye-sensitized solar cell module.
[0024] The present invention also provides a method for producing a
dye-sensitized solar cell comprising the steps of: first preparing
a base material for dye-sensitized solar cell that functions as an
electrode, has flexibility, and has a porous layer, containing a
dye-sensitizer-supported fine particle of a metal oxide
semiconductor, provided on one surface of the base material for
dye-sensitized solar cell, and a counter electrode base material
that is arranged so as to oppose to the base material for
dye-sensitized solar cell, functions as an electrode, and has
flexibility; then forming the porous layer on the base material for
dye-sensitized solar cell; forming a solid electrolyte layer so as
to come into contact with the porous layer; forming an insulating
layer on a surface of at least one of the base material for
dye-sensitized solar cell and the counter electrode base material
in a region which surrounds a region corresponding to a porous
layer-forming region where the porous layer is formed, and which is
where the base material for dye-sensitized solar cell and the
counter electrode base material are opposed to each other when they
are bonded together; and then bonding together the base material
for dye-sensitized solar cell and the counter electrode base
material opposed to each other with the porous layer and the solid
electrolyte layer being interposed therebetween, wherein at least
one of the base material for dye-sensitized solar cell and the
counter electrode base material has transparency and the porous
layer-forming step, the solid electrolyte layer-forming step, and
the insulating layer-forming step are performed in no particular
order.
[0025] According to the present invention, it is possible to easily
produce a dye-sensitized solar cell that does not cause an internal
short circuit.
[0026] Further, according to the present invention, since a solid
electrolyte layer and an insulating layer are formed in the solid
electrolyte layer-forming step and the insulating layer-forming
step, alignment between the base material for dye-sensitized solar
cell and the counter electrode base material for bonding in the
bonding step does not require high accuracy. This makes it easy to
produce a dye-sensitized solar cell.
[0027] Further, the method according to the present invention does
not include the step of sealing an electrolyte layer with a
sealant. This makes it easy to produce a dye-sensitized solar cell
as compared to a conventional method for producing a dye-sensitized
solar cell in which a base material for dye-sensitized solar cell
having a porous layer provided thereon and a counter electrode base
material are sealed with a sealant and then an electrolyte layer is
formed by injecting an electrolyte.
[0028] According to the present invention, it is preferred that a
metal foil is used as the base material for dye-sensitized solar
cell, a base material having transparency is used as the counter
electrode base material, and in the porous layer-forming step, the
porous layer is formed by burning. This is because good adhesion
between the base material for dye-sensitized solar cell and the
porous layer can be achieved and, in the case of an
inverted-structure dye-sensitized solar cell using a metal foil as
a base material for dye-sensitized solar cell, an insulating layer
formed in the insulating layer-forming step can effectively perform
its function and have a great effect.
[0029] Further, according to the present invention, it is also
preferred that, in the insulating layer-forming step, the
insulating layer is formed by applying a composition for forming an
insulating layer in a pattern onto at least one of the base
material for dye-sensitized solar cell and the counter electrode
base material or by using a tape having insulating properties. This
allows the insulating layer to be easily formed on at least one of
the base material for dye-sensitized solar cell and the counter
electrode base material.
[0030] Further, according to the present invention, it is also
preferred that: the porous layer is formed by applying a
composition for forming a porous layer in a pattern onto the base
material for dye-sensitized solar cell in the porous layer-forming
step; the solid electrolyte layer is formed by applying a
composition for forming a solid electrolyte layer in a pattern onto
the porous layer in the solid electrolyte layer-forming step; and
the insulating layer is formed by applying a composition for
forming an insulating layer in a pattern onto at least one of the
base material for dye-sensitized solar cell and the counter
electrode base material in the insulating layer-forming step. By
performing all the porous layer-forming step, the solid electrolyte
layer-forming step, and the insulating layer-forming step by an
application method in such a manner as described above, it is
possible to produce a dye-sensitized solar cell on a single
production line and therefore to improve production efficiency.
Further, both the base material for dye-sensitized solar cell and
the counter electrode base material used in the present invention
have flexibility, and therefore by performing all these steps by an
application method, it is possible to reduce loads applied to the
base material for dye-sensitized solar cell and the counter
electrode base material as compared to a case where a tape or the
like is used and therefore to prevent a reduction in processing
accuracy.
Advantageous Effects of Invention
[0031] The dye-sensitized solar cell according to the present
invention comprises the insulating layer, and therefore contact
between the base material for dye-sensitized solar cell and the
counter electrode base material can be prevented even when flexible
base materials are used as these base materials. This makes it
possible to prevent the occurrence of a short circuit in the
dye-sensitized solar cell.
[0032] Further, the dye-sensitized solar cell according to the
present invention comprises the insulating layer and the solid
electrolyte layer, and therefore adjustment of the formation
position of each of the members of the dye-sensitized solar cell
and alignment between the base material for dye-sensitized solar
cell and the counter electrode base material for bonding do not
require high accuracy. This allows the dye-sensitized solar cell to
be easily produced.
BRIEF DESCRIPTION OF DRAWINGS
[0033] FIGS. 1A and 1B are each a schematic view of one example of
a dye-sensitized solar cell according to the present invention.
[0034] FIGS. 2A and 2B are each a schematic view of another example
of the dye-sensitized solar cell according to the present
invention.
[0035] FIG. 3 is a schematic view of one example of a multifaceted
member that allows the dye-sensitized solar cells according to the
present invention to be obtained.
[0036] FIG. 4 is a schematic view of another example of the
multifaceted member that allows the dye-sensitized solar cells
according to the present invention to be obtained.
[0037] FIG. 5 is a schematic view of yet another example of the
multifaceted member that allows the dye-sensitized solar cells
according to the present invention to be obtained.
[0038] FIG. 6 is a schematic view of another example of the
dye-sensitized solar cell according to the present invention.
[0039] FIGS. 7A and 7B are each a schematic view of yet another
example of the dye-sensitized solar cell according to the present
invention.
[0040] FIG. 8 is a schematic sectional view of one example of a
dye-sensitized solar cell module according to the present
invention.
[0041] FIGS. 9A to 9E is a flow chart of one example of a method
for producing a dye-sensitized solar cell according to the present
invention.
[0042] FIGS. 10A to 10D is a flow chart of another example of the
method for producing a dye-sensitized solar cell according to the
present invention.
[0043] FIG. 11 is a schematic view of one example of a general
dye-sensitized solar cell.
[0044] FIG. 12 is a schematic view of one example of a
dye-sensitized solar cell.
DESCRIPTION OF EMBODIMENTS
[0045] Hereinbelow, a dye-sensitized solar cell according to the
present invention, a solar cell module using the dye-sensitized
solar cells according to the present invention, and a method for
producing the dye-sensitized solar cell according to the present
invention will be described in detail.
[0046] A. Dye-Sensitized Solar Cell
[0047] The dye-sensitized solar cell according to the present
invention comprises: a base material for dye-sensitized solar cell
that functions as an electrode, has flexibility, and has a porous
layer, containing a dye-sensitizer-supported fine particle of a
metal oxide semiconductor, provided on one surface of the base
material for dye-sensitized solar cell; a counter electrode base
material that is arranged so as to oppose to the base material for
dye-sensitized solar cell, functions as an electrode, and has
flexibility; and a solid electrolyte layer that is provided between
the base material for dye-sensitized solar cell and the counter
electrode base material so as to come into contact with the porous
layer, wherein at least one of the base material for dye-sensitized
solar cell and the counter electrode base material has
transparency; at least one of the base material for dye-sensitized
solar cell and the counter electrode base material has an
insulating layer provided on a surface thereof; the insulating
layer is provided in a region which surrounds a porous
layer-forming region where the porous layer is formed, and which is
where the base material for dye-sensitized solar cell and the
counter electrode base material are opposed to each other; and the
insulating layer has an external communication portion that leads
from an inside of the porous layer-forming region to outside.
[0048] In the present invention, the phrase "the insulating layer
has an external communication portion that leads from an inside of
the porous layer-forming region to outside" means that the
insulating layer is provided in such a manner that the porous
layer-forming region is not hermetically sealed, and refers to, for
example, a state where there is a portion where the base material
for dye-sensitized solar cell and the counter electrode base
material are not opposed to each other and the insulating layer is
not provided in a region surrounding the porous layer or a state
where, when the insulating layer is provided so as to surround the
entire porous layer, the insulating layer has a void space in at
least part thereof.
[0049] Further, the phrase "the insulating layer has a void space"
refers to a state where the insulating layer is provided so as not
to come into contact with one of the base material for
dye-sensitized solar cell and the counter electrode base material
or a state where the insulating layer is partially absent.
[0050] Further, in the present invention, the term "solid
electrolyte layer" refers to one having no fluidity.
[0051] The dye-sensitized solar cell according to the present
invention will be described with reference to the accompanying
drawings. FIG. 1A is a schematic view of one example of the
dye-sensitized solar cell according to the present invention, and
FIG. 1B is a sectional view of the dye-sensitized solar cell
according to the present invention taken along the A-A line in FIG.
1A. As shown in FIG. 1B, a dye-sensitized solar cell 10 according
to the present invention comprises: a base material for
dye-sensitized solar cell 1 that has a base material 1a, a first
electrode layer 1b, and a porous layer 4 provided on the first
electrode layer 1b and containing dye-sensitizer-supported fine
particles of a metal oxide semiconductor; a counter electrode base
material 2 that is arranged so as to oppose to the base material
for dye-sensitized solar cell 1 and functions as an electrode; a
solid electrolyte layer 3 provided between the base material for
dye-sensitized solar cell 1 and the counter electrode base material
2 so as to come into contact with the porous layer 4; and an
insulating layer 5 provided on the surface of the base material for
dye-sensitized solar cell 1 and the surface of the counter
electrode base material 2. It is to be noted that in FIG. 1B, the
insulating layer 5 is provided on the surface of the base material
for dye-sensitized solar cell 1 and the surface of the counter
electrode base material 2, but may be provided on the surface of at
least one of the base material for dye-sensitized solar cell 1 and
the counter electrode base material 2. Further, as shown in FIG.
1A, the insulating layer 5 is provided in a region which surrounds
a porous layer-forming region T where the porous layer 4 is formed,
and which is where the base material for dye-sensitized solar cell
1 and the counter electrode base material 2 are opposed to each
other. The dye-sensitized solar cell 10 according to the present
invention has, in a region surrounding the porous layer 4, a
portion where the base material for dye-sensitized solar cell 1 and
the counter electrode base material 2 are not opposed to each other
and the insulating layer 5 is not provided as an external
communication portion 5a that leads from the porous layer-forming
region T to the outside of the dye-sensitized solar cell 10. It is
to be noted that in FIG. 1A, the base material 1a and the porous
layer 4 are omitted for illustrative clarity.
[0052] FIGS. 2A and 2B are each a schematic view of another example
of the dye-sensitized solar cell according to the present
invention. The dye-sensitized solar cell shown in each of FIGS. 2A
and 2B is one in which the insulating layer 5 is provided so as to
surround the porous layer-forming region T. FIG. 2B is a schematic
sectional view of the dye-sensitized solar cell according to the
present invention taken along the A-A line in FIG. 2A. As shown in
FIG. 2A, when the insulating layer 5 is provided so as to surround
the porous layer-forming region T, as shown in FIG. 2B, the
external communicating portion 5a is provided in a region
surrounding the porous layer 4 by providing a void space in the
thickness direction of the insulating layer, that is, by providing
the insulating layer 5 on the surface of only one of the base
material for dye-sensitized solar cell 1 and the counter electrode
base material 2. In FIG. 2B, the insulating layer 5 is provided not
on the counter electrode base material 2 but on the base material
for dye-sensitized solar cell 1, but may be provided not on the
base material for dye-sensitized solar cell 1 but on the counter
electrode base material 2. It is to be noted that reference signs
shown in FIGS. 2A and 2B but not described here are the same as
those shown in FIGS. 1A and 1B, and therefore a description thereof
is omitted here.
[0053] According to the present invention, by providing the
insulating layer, it is possible to prevent contact between the
base material for dye-sensitized solar cell and the counter
electrode base material in a region which surrounds the porous
layer-forming region and which is where both the base materials are
opposed to each other. This makes it possible to prevent the
occurrence of a short circuit in the dye-sensitized solar cell.
[0054] Further, according to the present invention, by providing
the solid electrolyte layer using an electrolyte having no
fluidity, it is possible to eliminate the necessity to seal the
solid electrolyte layer with an expensive sealant having high
resistance to iodine. This allows the dye-sensitized solar cell to
be produced at low cost. Further, as described above, since the
solid electrolyte layer does not need to be sealed with a sealant,
adjustment of the formation position of each of the members and
alignment between the base material for dye-sensitized solar cell
and the counter electrode base material for bonding during the
production of the dye-sensitized solar cell do not require high
accuracy. This allows the dye-sensitized solar cell to be easily
produced.
[0055] In the case of a dye-sensitized solar cell using a solid
electrolyte layer, it can be considered that, for example as shown
in FIG. 12, the occurrence of a short circuit in the dye-sensitized
solar cell can be prevented not by providing the insulating layer 5
but by not providing, around the porous layer-forming region T
where the porous layer 4 is formed, a region where the base
material for dye-sensitized solar cell 1 and the counter electrode
base material 2 are opposed to each other. However, the production
of such a dye-sensitized solar cell involves a possible problem
that alignment between the base material for dye-sensitized solar
cell and the counter electrode base material for bonding requires
high accuracy, resulting in a complicated production process. It is
to be noted that reference signs shown in FIG. 12 but not described
here are the same as those shown in FIGS. 1A and 1B.
[0056] However, according to the present invention, since the
insulating layer is provided, alignment between the base material
for dye-sensitized solar cell and the counter electrode base
material for bonding during the production of the dye-sensitized
solar cell does not require high accuracy. This allows the
dye-sensitized solar cell to be easily produced.
[0057] Further, according to the present invention, by providing
the external communication portion in a region surrounding the
porous layer, it is possible to discharge air in the dye-sensitized
solar cell through the external communication portion when the base
material for dye-sensitized solar cell and the counter electrode
base material are bonded together in the step of bonding them
together during the production of the dye-sensitized solar cell.
This allows the dye-sensitized solar cell to be easily
produced.
[0058] Further, since the dye-sensitized solar cell according to
the present invention uses the solid electrolyte layer, a
multifaceted member that allows the two or more dye-sensitized
solar cells to be obtained can be previously prepared, and the
plural dye-sensitized solar cells can be obtained by cutting the
multifaceted member into predetermined sizes. This makes it
possible to mass-produce the dye-sensitized solar cell at low cost
by preparing such a multifaceted member by, for example, a
Roll-to-Roll method and cutting it into predetermined sizes.
[0059] The multifaceted member prepared to mass-produce the
dye-sensitized solar cell according to the present invention will
be described with reference to the drawings. FIGS. 3 to 5 are
schematic views of examples of the multifaceted member that allows
the dye-sensitized solar cells according to the present invention
to be obtained. As shown in FIGS. 3 to 5, a multifaceted member 20
used in the present invention includes plural dye-sensitized solar
cells 10 produced in advance. The mass production of the
dye-sensitized solar cell 10 can be achieved by cutting the
multifaceted member 20 at cutting positions. It is to be noted that
when the multifaceted member shown in FIG. 3 or 4 is used, such two
or more dye-sensitized solar cells as shown in FIGS. 1A and 1B
whose porous layer-forming region is rectangle and insulating layer
is provided along the two opposite sides of the porous
layer-forming region can be produced by cutting the multifaceted
member at cutting positions.
[0060] On the other hand, when the multifaceted member shown in
FIG. 5 is used, such two or more dye-sensitized solar cells as
shown in FIGS. 2A and 2B whose insulating layer is provided so as
to surround the porous layer-forming region can be produced by
cutting the multifaceted member at cutting positions.
[0061] It is to be noted that reference signs shown in FIGS. 3 and
4 but not described here are the same as those shown in FIGS. 1A-1B
and reference signs shown in FIG. 5 but not described here are the
same as those shown in FIGS. 2A-2B, and therefore a description
thereof is omitted here.
[0062] Hereinbelow, each of the members used in the present
invention will be described.
[0063] 1. Insulating Layer
[0064] The insulating layer used in the present invention is
provided on the surface of at last one of the base material for
dye-sensitized solar cell (which will be described later) and the
counter electrode base material (which will be described later) in
a region which surrounds the porous layer-forming region where the
porous layer (which will be described later) is formed, and which
is where the base material for dye-sensitized solar cell and the
counter electrode base material are opposed to each other.
[0065] In the dye-sensitized solar cell according to the present
invention, the insulating layer provided in a region surrounding
the porous layer (which will be described later) has the external
communication portion that leads from the porous layer-forming
region to the outside of the dye-sensitized solar cell. As
described above, the external communication portion refers to a
portion which is provided in a region surrounding the porous layer
and where the insulating layer is not provided and the base
material for dye-sensitized solar cell and the counter electrode
base material are not opposed to each other or a void space
provided in the insulating layer provided so as to surround the
porous layer.
[0066] The dye-sensitized solar cell according to the present
invention is not particularly limited as long as the insulating
layer is formed so as to have, as the external communication
portion, at least one of the following two types of external
communication portions: a portion which is provided in a region
surrounding the porous layer and where the insulating layer is not
provided and the base material for dye-sensitized solar cell and
the counter electrode base material are not opposed to each other;
and a void space provided in the insulating layer provided so as to
surround the porous layer. The insulating layer may be formed so as
to have both the types of external communication portions.
[0067] Therefore, the insulating layer used in the present
invention is not particularly limited as long as it is formed such
that the dye-sensitized solar cell according to the present
invention can have the external communication portion in a region
surrounding the porous layer and electrical contact between the
base material for dye-sensitized solar cell and the counter
electrode base material in a region surrounding the porous layer
can be prevented.
[0068] When the external communication portion is of a type
provided, in a region surrounding the porous layer, as a portion
where the base material for dye-sensitized solar cell and the
counter electrode base material are not opposed to each other and
the insulating layer is not provided and the porous layer is, for
example, polygonal, the insulating layer used in the present
invention is not particularly limited as long as it is formed in
such a manner that at least one of the sides of the polygonal
porous layer-forming region serves as the external communication
portion.
[0069] Further, according to the present invention, it is preferred
that the porous layer-forming region is quadrilateral and the
insulating layer is provided along the two opposite sides of the
porous layer-forming region as shown in FIGS. 1A and 1B. By forming
the insulating layer in such a manner as described above, the
dye-sensitized solar cell can be easily produced and can achieve
high quality even by mass production.
[0070] It is to be noted that when the external communication
portion is of the type described above, the insulating layer may be
formed so as to come into close contact with the base material for
dye-sensitized solar cell and the counter electrode base
material.
[0071] On the other hand, when the external communication portion
is of a type provided as a void space in the insulating layer
provided so as to surround the porous layer, the insulating layer
is not particularly limited as long as it is formed so as to have
at least one of: a void space where the insulating layer is not in
contact with one of the base material for dye-sensitized solar cell
and the counter electrode base material, and a void space where the
insulating layer is not provided and which is provided in part of a
region which surrounds the porous layer-forming region where the
porous layer is formed, and which is where the base material for
dye-sensitized solar cell and the counter electrode base material
are opposed to each other. The insulating layer may have both the
void spaces. It is to be noted that the void space where the
insulating layer is not provided is preferably formed in such a
manner that the base material for dye-sensitized solar cell (which
will be described later) and the counter electrode base material
(which will be described later) do not come into contact with each
other.
[0072] Examples of the insulating layer having, as the external
communication portion, a void space where the insulating layer is
not in contact with one of the base material for dye-sensitized
solar cell and the counter electrode base material include: one
obtained by forming an insulating layer on only one of the base
material for dye-sensitized solar cell and the counter electrode
base material so as not to come into contact with the other base
material, and one obtained by forming an insulating layer on both
the surface of the base material for dye-sensitized solar cell and
the surface of the counter electrode base material in such a manner
that the insulating layers are not come into contact with each
other.
[0073] On the other hand, when having, as the external
communication portion, a void space where the insulating layer is
not provided and which is provided in part of a region which
surrounds the porous layer-forming region where the porous layer is
formed, and which is where the base material for dye-sensitized
solar cell and the counter electrode base material are opposed to
each other, the insulating layer may be formed so as to come into
close contact with both the base material for dye-sensitized solar
cell and the counter electrode base material.
[0074] It is to be noted that in the dye-sensitized solar cells
shown in FIGS. 1 to 5, the insulating layer 5 is formed in a
continuous stripe shape, but as shown in FIG. 6, the insulating
layer 5 may be composed of islands spaced apart from one another in
such a manner that the base material for dye-sensitized solar cell
1 and the counter electrode base material 2 do not come into
contact with each other. It is to be noted that reference signs
shown in FIG. 6 but not described here are the same as those shown
in FIGS. 2A and 2B.
[0075] According to the present invention, the insulating layer is
not particularly limited as long as it is formed so as to prevent
electrical contact between the base material for dye-sensitized
solar cell (which will be described later) and the counter
electrode base material (which will be described later). For
example, as shown in FIG. 7A, the porous layer 4 and the solid
electrolyte layer 3 may be formed on part of the insulating layer
5, or as shown in FIG. 7B, a gap may be formed between the
insulating layer 5 and a laminated body composed of the porous
layer 4 and the solid electrolyte layer 3. Therefore, according to
the present invention, adjustment of the formation position of each
of the members of the dye-sensitized solar cell does not require
high accuracy, which allows the dye-sensitized solar cell to be
easily produced. It is to be noted that reference signs shown in
FIGS. 7A and 7B but not described here are the same as those shown
in FIGS. 2A and 2B.
[0076] The width of the insulating layer is not particularly
limited as long as the insulating layer can prevent electrical
contact between the base material for dye-sensitized solar cell and
the counter electrode base material. When the width of the
insulating layer is larger, the degree of accuracy required for
alignment between the base material for dye-sensitized solar cell
and the counter electrode base material for bonding is lower, that
is, when the width of the insulating layer is smaller, the degree
of accuracy required for such alignment for bonding is higher.
Therefore, the width of the insulating layer is preferably
determined in consideration of the power generating area of the
dye-sensitized solar cell and the degree of accuracy required for
alignment for bonding. More specifically, the width of the
insulating layer is preferably in the range of 0.5 mm to 50 mm. If
the width of the insulating layer is less than 0.5 mm, it is
difficult to reliably prevent the occurrence of a short circuit in
a region which surrounds the porous layer-forming region where the
porous layer (which will be described later) is formed, and which
is where the base material for dye-sensitized solar cell and the
counter electrode base material are opposed to each other. On the
other hand, if the width of the insulating layer exceeds 50 mm, the
part of the dye-sensitized solar cell that does not contribute to
power generation increases.
[0077] The material of the insulating layer used in the present
invention is not particularly limited as long as it has insulating
properties and can form the insulating layer on at least one of the
base material for dye-sensitized solar cell and the counter
electrode base material. The material of the insulating layer may
be either one having transparency or one not having
transparency.
[0078] Such a material of the insulating layer may be either
inorganic or organic. Examples of the inorganic material include
insulating materials such as SiO.sub.2. Examples of the organic
material include an elastomer such as natural rubber and nitrile
rubber, an epoxy resin, an acrylic resin, a polyester resin, a
urethane resin, an ionomer resin, and an ethylene-acrylic acid
copolymer.
[0079] The film thickness of the insulating layer used in the
present invention is not particularly limited as long as the
insulating layer can prevent electrical contact between the base
material for dye-sensitized solar cell and the counter electrode
base material. The thickness of the insulating layer may be either
larger or smaller than that of a laminated body composed of the
porous layer (which will be described later) and the solid
electrolyte layer (which will be described later).
[0080] More specifically, the difference in thickness between the
insulating layer and a laminated body composed of the porous layer
and the solid electrolyte layer is preferably about .+-.20 .mu.m,
more preferably about .+-.10 .mu.m, and particularly preferably
about .+-.5 .mu.m.
[0081] When the difference in thickness between the insulating
layer and a laminated body composed of the porous layer and the
solid electrolyte layer is small, the dye-sensitized solar cell
according to the present invention can have a uniform thickness at
its ends.
[0082] According to the present invention, the insulating layer
preferably has tackiness. When the insulating layer has tackiness,
the base material for dye-sensitized solar cell and the counter
electrode base material can be temporarily bonded together in
advance to perform alignment between them or can be firmly bonded
together using the insulating layer in the step of bonding together
the base material for dye-sensitized solar cell and the counter
electrode base material during the production of the dye-sensitized
solar cell. It is to be noted that when the base material for
dye-sensitized solar cell and the counter electrode base material
are firmly bonded together, the insulating layer has a region where
the insulating layer is in contact with only one of the base
material for dye-sensitized solar cell and the counter electrode
base material and is not in contact with the other or a region
where the insulating layer is partially absent.
[0083] Further, in a case where the base material for
dye-sensitized solar cell and the counter electrode base material
are temporarily or firmly bonded together using the insulating
layer having tackiness, even when the thickness of the insulating
layer is smaller or larger than that of a laminated body composed
of the porous layer and the solid electrolyte layer, the base
material for dye-sensitized solar cell and the counter electrode
base material can be temporarily or firmly bonded together by
pressure bonding. Therefore, also in a case where the insulating
layer has tackiness, the film thickness of the insulating layer may
be either larger or smaller than that of a laminated body composed
of the porous layer (which will be described later) and the solid
electrolyte layer (which will be described later).
[0084] The tackiness of the insulating layer is not particularly
limited as long as the base material for dye-sensitized solar cell
and the counter electrode base material opposed to each other can
be temporarily bonded together by the insulating layer having
tackiness by pressure bonding. More specifically, the tackiness of
the insulating layer is particularly preferably 100 mN/25 mm or
larger. It is to be noted that the tackiness of the insulating
layer can be determined by measuring a force required to peel off
each of the base materials (peel force) with the use of a measuring
instrument such as TENSILON.TM. manufactured by A&D Co.,
Ltd.
[0085] Examples of the material of such an insulating layer include
some of the above-mentioned materials of the insulating layer that
are solvent-based or polymerizable and have adhesiveness. Specific
examples of such a material include various adhesives such as
UV-curable adhesives, emulsion-type adhesives, heat-melt adhesives,
dry lamination adhesives, and heat-sealable adhesives. Examples of
the materials of such adhesives include various materials such as
natural rubber-based materials, nitrile rubber-based materials,
epoxy resin-based materials, vinyl acetate emulsion-based
materials, acrylic materials, acrylic acid ester copolymer-based
materials, polyvinyl alcohol-based materials, phenol resin-based
materials, urethane resins, and ionomer resins.
[0086] 2. Solid Electrolyte Layer
[0087] The solid electrolyte layer used in the present invention is
provided between the base material for dye-sensitized solar cell
(which will be described later) and the counter electrode base
material (which will be described later) so as to come into contact
with the porous layer. Further, the solid electrolyte layer is
located between the porous layer (which will be described later)
and the counter electrode base material to transport electrical
charge when electrical charge transferred from the porous layer is
imported into the porous layer through the base material for
dye-sensitized solar cell and the counter electrode base
material.
[0088] As described above, the solid electrolyte layer used in the
present invention has no fluidity during the production and use of
the dye-sensitized solar cell according to the present invention.
Examples of such a solid electrolyte layer include one obtained by
solidifying a redox couple electrolyte by a polymer component and
one obtained by lowering the fluidity of an electrolyte solution
used in a general solar cell by adding titanium oxide particles or
silica particles thereto. However, the solid electrolyte layer used
in the present invention is preferably one obtained by solidifying
a redox couple electrolyte by a polymer component. This is because
such a solid electrolyte layer can be easily formed and is less
likely to be degraded with time.
[0089] Preferred examples of the polymer component used for forming
the solid electrolyte layer include polymers having, as a main
chain, polyether, polymethacrylic acid, polyacrylic alkyl ester,
polymethacrylic alkyl ester, polycaprolactone, polyhexamethylene
carbonate, polysiloxane, polyethylene oxide, polypropylene oxide,
polyacrylnitrile, polyvinylidene fluoride, polyvinyl fluoride,
polyhexafluoropropylene, polyfluoroethylene, polyethylene,
polypropylene, or polyacrylonitrile and copolymers of two or more
of these monomer components.
[0090] Alternatively, the polymer component used for forming the
solid electrolyte layer may be a cellulose-based resin. A
cellulose-based resin has high heat resistance, and therefore an
electrolyte layer solidified by a cellulose-based resin does not
cause liquid leakage even at high temperature and has high heat
stability. Specific examples of such a cellulose-based resin
include: cellulose; cellulose acetates (CA) such as cellulose
acetate, cellulose diacetate, and cellulose triacetate; cellulose
esters such as cellulose acetate butylate (CAB), cellulose acetate
propionate (CAP), cellulose acetate phthalate, and cellulose
nitrate; and cellulose ethers such as methyl cellulose, ethyl
cellulose, benzyl cellulose, cyanoethyl cellulose, hydroxymethyl
cellulose, hydroxyethyl cellulose, hydroxypropyl cellulose,
hydroxypropylmethyl cellulose, and carboxymethyl cellulose. These
cellulose-based resins may be used singly or in combination of two
or more of them. Among these cellulose-based resins, cationic
cellulose derivatives are particularly preferably used from the
viewpoint of compatibility with an electrolyte solution. The
cationic cellulose derivative refers to one obtained by cationizing
cellulose or its derivative by reacting OH groups thereof with a
cationization agent. By allowing an electrolyte solution to contain
such a cationic cellulose derivative, it is possible to obtain a
solid electrolyte that is excellent in the ability to hold the
electrolyte solution, does not cause leakage of the electrolyte
solution even at high temperature or even by application of
pressure, and has excellent heat stability.
[0091] The molecular weight of such a cellulose-based resin varies
depending on the type of cellulose-based resin used and is not
particularly limited. However, the weight-average molecular weight
of the cellulose-based resin is preferably 10,000 or more
(polystyrene standard), and particularly preferably in the range of
100,000 to 200,000 from the viewpoint of achieving excellent film
forming properties for forming the electrolyte layer. For example,
when ethyl cellulose is used as the cellulose-based resin, the
ethyl cellulose preferably has a molecular weight such that a 2 wt
% aqueous solution thereof has a viscosity of 10 mPas to 1000 mPas,
and particularly 5 mPas to 500 mPas at 30.degree. C.
[0092] The glass transition temperature of the cellulose-based
resin is preferably in the range of 80 to 150.degree. C. to allow
the electrolyte layer to have sufficiency heat stability.
[0093] The polymer component content of the solid electrolyte layer
is not particularly limited as long as the solid electrolyte layer
can be formed. However, if the concentration of the polymer
component in the solid electrolyte layer is too low, the heat
stability of the solid electrolyte layer is reduced. On the other
hand, if the concentration of the polymer component in the solid
electrolyte layer is too high, the photoelectric conversion
efficiency of the solar cell is reduced. Therefore, the
concentration of the polymer component in the solid electrolyte
layer is appropriately determined in consideration of such factors.
More specifically, the concentration of the polymer component in
the solid electrolyte layer is preferably 5 wt % to 60 wt %. If the
concentration of the polymer component in the solid electrolyte
layer is lower than the above lower limit, there is a case where
adequate adhesion between the solid electrolyte layer and the
porous layer (which will be described later) cannot be achieved,
and there is also a case where the mechanical strength of the solid
electrolyte layer itself is reduced. On the other hand, if the
concentration of the polymer component in the solid electrolyte
layer exceeds the above upper limit, there is a fear that the
function of transporting electrical charge is inhibited because the
polymer component having insulating properties is present in a
large amount.
[0094] The redox couple electrolyte contained in the solid
electrolyte layer used in the present invention is not particularly
limited as long as it is generally used in solid electrolyte
layers. More specifically, a combination of iodine and iodide and a
combination of bromine and bromide are preferred. Examples of the
combination of iodine and iodide include combinations of I.sub.2
and a metal iodide such as LiI, NaI, KI, or CaI.sub.2. Examples of
the combination of bromine and bromide include combinations of
Br.sub.2 and a metal bromide such as LiBr, NaBr, KBr, or
CaBr.sub.2.
[0095] The redox couple electrolyte content of the solid
electrolyte layer is not particularly limited as long as the solid
electrolyte layer can be formed. More specifically, the redox
couple electrolyte content of the solid electrolyte layer is
preferably in the range of 1 wt % to 50 wt %, and particularly
preferably in the range of 5 wt % to 35 wt %. By setting the redox
couple electrolyte content to a value within the above range, it is
possible for the solid electrolyte layer to sufficiently perform
the function of transporting electrical charge from a second
electrode layer to an oxide semiconductor layer.
[0096] If necessary, the solid electrolyte layer used in the
present invention may appropriately contain a component other than
the polymer component and the redox couple electrolyte. An example
of such a component is an ionic liquid.
[0097] The ionic liquid is used to reduce the viscosity of the
electrolyte and to improve ionic conductivity to thereby enhance
photoelectric conversion efficiency. The ionic liquid has a very
low vapor pressure, and virtually hardly evaporates at room
temperature. Therefore, unlike conventional organic solvents, the
ionic liquid is free from the risk of volatilization or ignition,
thereby preventing the deterioration of cell characteristics caused
by volatilization. Examples of the ionic liquid include: ionic
liquids containing cations (positive ions) such as
imidazolium-based cations (e.g., 1-methyl-3-methylimidazolium,
1-ethyl-3-methylimidazolium, 1-propyl-3-methylimidazolium,
1-butyl-3-methylimidazolium, 1-hexyl-3-methylimidazolium,
1-octyl-3-methylimidazolium, 1-octadecyl-3-methylimidazolium,
1-methyl-2,3-dimethylimidazolium, 1-butyl-2,3-dimethylimidazolium,
1-hexyl-2,3-dimethylimidazolium, 1-octyl-2,3-dimethylimidazolium,
and 1-octadecyl-2,3-dimethylimidazolium), pyridium-based cations
(e.g., 1-methyl-pyridium, 1-butyl-pyridium, and 1-hexyl-pyridium),
alicyclic amine-based cations, aliphatic amine-based cations; and
ionic liquid containing anions (negative ions) such as an iodine
ion, a bromine ion, a chlorine ion, fluorine-based anions (e.g.,
tetrafluoroborate, hexafluoroborate, trifluoromethane sulfonate,
and trifluoroacetate), cyanate-based anions, and thiocyanate-based
anions. These materials may be used singly or in combination of two
or more of them.
[0098] When an iodide-based ionic liquid containing iodine as an
anion is used, it functions not only as a source of iodine ions and
but also as the redox couple described above. Specific examples of
such an iodide-based ionic liquid include
1,2-dimethyl-3-n-propylimidazolium iodide,
1-methyl-3-n-propylimidazolium iodide, 1-propyl-3-methylimidazolium
iodide, 1-butyl-2,3-dimethylimidazolium iodide, and
1-hexyl-3-methylimidazolium iodide. It is to be noted that when the
electrolyte layer contains an ionic liquid that also functions as a
redox couple such as an iodide-based ionic liquid, such an ionic
liquid is regarded not as an ionic liquid but as a redox couple to
determine the concentration of a redox couple and the concentration
of an ionic liquid in the electrolyte layer.
[0099] The ionic liquid content of the solid electrolyte layer used
in the present invention varies depending on the type of ionic
liquid used. However, as the ratio between redox couple/ionic
liquid/resin of the solid electrolyte layer, the resin content of
the solid electrolyte layer is preferably 5 wt % to 60 wt % and
particularly preferably 5 wt % to 40 wt %, the ionic liquid content
of the solid electrolyte layer is preferably 0 wt % to 80 wt % and
particularly preferably 10 wt % to 70 wt %, and the redox couple
(including PMIm-I) content of the solid electrolyte layer is
preferably 3 wt % to 95 wt % and particularly preferably 10 wt % to
85 wt %.
[0100] The film thickness of the solid electrolyte layer is not
particularly limited as long as it is commonly used for solid
electrolyte layers, but is preferably in the range of 0.5 .mu.m to
100 .mu.m and particularly preferably in the range of 2 .mu.m to 50
.mu.m.
[0101] 3. Porous Layer
[0102] Hereinbelow, the porous layer used in the present invention
will be described. The porous layer used in the present invention
contains dye-sensitizer-supported fine particles of a metal oxide
semiconductor provided on the base material for dye-sensitized
solar cell (which will be described later), and is in contact with
the solid electrolyte layer.
[0103] The shape of the porous layer used in the present invention
is not particularly limited as long as the porous layer can be
formed on the base material for dye-sensitized solar cell (which
will be described later), and examples thereof include polygons.
Among polygons, the shape of the porous layer used in the present
invention is preferably a quadrilateral. This makes it easy to form
the porous layer. Further, when the shape of the porous layer is a
quadrilateral, the insulating layer can also be easily formed in a
region surrounding the porous layer.
[0104] Here, the phrase "the shape of the porous layer is a
quadrilateral" means that the porous layer is a rectangle, a
parallelogram, a rhombus, or the like. It is to be noted that the
term "quadrilateral" also includes rectangles, parallelograms,
rhombuses, and the like whose corners only are rounded.
[0105] The porous layer-forming region, in which the porous layer
used in the present invention is formed, is not particularly
limited as long as it is located on the base material for
dye-sensitized solar cell (which will be described later) and is
not hermetically sealed with the insulating layer. For example, as
shown in FIGS. 2A and 2B, the porous layer may be formed so that
the insulating layer can be formed all around the porous layer.
Alternatively, as shown in FIGS. 1A and 1B, the porous layer may be
formed so that there is a portion where the base material for
dye-sensitized solar cell and the counter electrode base material
are not opposed to each other and the insulating layer is not
provided in a region surrounding the porous layer.
[0106] The positional relationship between the porous layer and the
above-mentioned insulating layer used in the present invention is
not particularly limited as long as the porous layer-forming region
is not hermetically sealed with the insulating layer and the
insulating layer can prevent the occurrence of an internal short
circuit in a region surrounding the porous layer. For example, as
shown in FIG. 2B, the porous layer may be provided inside the
insulating layer, or as shown in FIG. 7A, the porous layer may be
provided on part of the surface of the insulating layer.
[0107] The metal oxide semiconductor fine particles and the dye
sensitizer used for forming the porous layer will be described
below.
[0108] (1) Metal Oxide Semiconductor Fine Particles
[0109] The metal oxide semiconductor fine particles used in the
present invention are not particularly limited as long as they are
made of a metal oxide having semiconductor characteristics.
Examples of such a metal oxide constituting the metal oxide
semiconductor fine particles used in the present invention include
TiO.sub.2, ZnO, SnP.sub.2, ITO, ZrO.sub.2, MgO, Al.sub.2O.sub.3,
CeO.sub.2, Bi.sub.2O.sub.3, Mn.sub.3O.sub.4, Y.sub.2O.sub.3,
WO.sub.3, Ta.sub.2O.sub.5, Nb.sub.2O.sub.5, and La.sub.2O.sub.3.
The metal oxide semiconductor fine particles made of such a metal
oxide are suitable for forming the porous layer, and are therefore
preferably used in the present invention to improve energy
conversion efficiency and achieve cost reduction.
[0110] The metal oxide semiconductor fine particles used in the
present invention may be made of the same metal oxide or two or
more different metal oxides. The metal oxide semiconductor fine
particles used in the present invention may have a core-shell
structure in which a core fine particle made of one metal oxide
semiconductor is coated with a shell made of another metal oxide
semiconductor.
[0111] Among others, metal oxide semiconductor fine particles made
of TIO.sub.2 are most preferably used in the present invention.
This is because TIO.sub.2 is particularly excellent in
semiconductor characteristics.
[0112] The average particle size of the metal oxide semiconductor
fine particles used in the present invention are not particularly
limited as long as the porous layer can have a specific surface
area within a desired range, but is usually preferably in the range
of 1 nm to 10 .mu.m and particularly preferably in the range of 10
nm to 1000 nm. If the average particle size is less than the above
lower limit, there is a case where the individual metal oxide
semiconductor fine particles agglomerate to form secondary
particles. On the other hand, if the average particle size exceeds
the above upper limit, there is a possibility that not only an
increase in the thickness of the porous layer but also a reduction
in the porosity, that is, specific surface area, of the porous
layer occurs. If the specific surface area of the porous layer is
reduced, for example, there is a case where it is difficult for the
porous layer to support a dye sensitizer in an amount sufficient to
achieve photoelectric conversion.
[0113] It is to be noted that the average particle size of the
metal oxide semiconductor fine particles refers to an average
primary particle size.
[0114] The metal oxide semiconductor fine particles used in the
present invention may be metal oxide semiconductor fine particles
having the same average particle size or two or more types of metal
oxide semiconductor fine particles having different average
particle sizes. The use of a combination of two or more types of
metal oxide semiconductor fine particles having different average
particle sizes has the advantage that light scattering effect in
the porous layer can be enhanced and therefore the dye-sensitized
solar cell according to the present invention has higher power
generation efficiency.
[0115] When two or more types of metal oxide semiconductor fine
particles having different average particle sizes are used in the
present invention, an example of a combination of different
particle sizes is a combination of metal oxide semiconductor fine
particles having an average particle size of 10 nm to 50 nm and
metal oxide semiconductor fine particles having an average particle
size of 50 nm to 800 nm.
[0116] (2) Dye Sensitizer
[0117] The dye sensitizer used in the present invention is not
particularly limited as long as it can absorb light to generate
electromotive force. Examples of such a dye sensitizer include
organic pigments and metal complex pigments. Examples of the
organic pigments include acridine-based pigments, azo-based
pigments, indigo-based pigments, quinone-based pigments,
coumarine-based pigments, merocyanine-based pigments,
phenylxanthene, indoline, and carbazole-based pigments. Among these
organic pigments, coumarine-based pigments are preferably used in
the present invention. On the other hand, as the metal complex
pigments, ruthenium-based pigments are preferably used. Among them,
ruthenium bipyridine pigments and ruthenium terpyridine pigments,
which are ruthenium complexes, are particularly preferably used.
This is because such ruthenium complexes have wide light absorption
wavelength ranges and therefore the wavelength range of light that
can be converted into electricity can be significantly
broadened.
[0118] (3) Optional Component
[0119] The porous layer used in the present invention may contain
an optional component other than the metal oxide semiconductor fine
particles. Examples of such an optional component used in the
present invention include binder resins. By allowing the porous
layer to contain a binder resin, it is possible to improve the
brittleness of the porous layer used in the present invention.
[0120] The binder resin that can be used for the porous layer in
the present invention is not particularly limited as long as the
brittleness of the porous layer can be improved to a desired level.
However, according to the present invention, since the porous layer
is provided so as to come into contact with the electrolyte layer,
the binder resin to be used for the porous layer needs to have
resistance to the electrolyte layer. Examples of such a binder
resin include polyvinyl pyrrolidone, ethyl cellulose, and
caprolactam.
[0121] It is to be noted that the binder resins that can be used in
the present invention may be used singly or in combination of two
or more of them.
[0122] (4) Others
[0123] The thickness of the porous layer used in the present
invention is not particularly limited, and can be appropriately
determined depending on the intended use of the dye-sensitized
solar cell according to the present invention. However, the
thickness of the porous layer used in the present invention is
usually preferably in the range of 1 .mu.m to 100 .mu.m and
particularly preferably in the range of 3 .mu.m to 30 .mu.m. If the
thickness of the porous layer exceeds the above upper limit, there
is a case where cohesive failure of the porous layer itself is
likely to occur, which is likely to result in membrane resistance.
On the other hand, if the thickness of the porous layer is less
than the above lower limit, there is a possibility that it is
difficult to form the porous layer so as to have a uniform
thickness or the porous layer cannot sufficiently absorb sunlight
due to a reduction in the amount of the supporting dye sensitizer
and therefore performance failure occurs.
[0124] The porous layer used in the present invention may have a
structure composed of a single layer or a structure in which two or
more layers are laminated. As such a structure of the porous layer
in which two or more layers are laminated, any structure can be
appropriately selected and used depending on, for example, a method
for forming the base material for dye-sensitized solar cell used in
the present invention. For example, the porous layer may have a
two-layer structure composed of an oxide semiconductor layer that
is in contact with the base material for dye-sensitized solar cell
and an intermediate layer that is provided on the oxide
semiconductor layer and has a porosity higher than that of the
oxide semiconductor layer. This is because by allowing the porous
layer to have such a two-layer structure composed of an oxide
semiconductor layer and an intermediate layer, it is possible to
easily form the porous layer used in the present invention by a
so-called transfer method. More specifically, the porous layer used
in the present invention can be formed by a method in which the
porous layer and the first electrode layer are formed on a
heat-resistant substrate by burning and are then transferred onto
the base material for dye-sensitized solar cell. Therefore, by
allowing the porous layer used in the present invention to have
such a two-layer structure composed of an oxide semiconductor layer
and an intermediate layer, it is possible to reduce the adhesive
force between the heat-resistant substrate and the porous layer
without degrading the performance of the porous layer, which makes
it easy to form the base material for dye-sensitized solar cell
used in the present invention by a transfer method.
[0125] In a case where the porous layer has a two-layer structure
composed of the oxide semiconductor layer and the intermediate
layer, the ratio of the thickness of the oxide semiconductor layer
to the thickness of the intermediate layer is not particularly
limited, but is preferably in the range of 10:0.1 to 10:5, and more
preferably in the range of 10:0.1 to 10:3.
[0126] The porosity of the oxide semiconductor layer is preferably
in the range of 10 to 60%, and particularly preferably in the range
of 20 to 50%. If the porosity of the oxide semiconductor layer is
less than the above lower limit, for example, there is a
possibility that the porous layer cannot effectively absorb
sunlight. On the other hand, if the porosity of the oxide
semiconductor layer exceeds the above upper limit, there is a
possibility that the porous layer cannot contain a desired amount
of dye sensitizer for support.
[0127] The porosity of the intermediate layer is not particularly
limited as long as it is larger than that of the oxide
semiconductor layer, but is usually preferably in the range of 25
to 65%, and particularly preferably in the range of 30 to 60%.
[0128] It is to be noted that in the present invention, the
porosity refers to the percentage of volume not occupied by the
metal oxide semiconductor fine particles per unit volume. The
porosity can be determined by measuring a pore volume by a gas
sorption analyzer (Autosorb-1MP.TM. manufactured by Quantachrome
Instruments) and then calculating the ratio of the pore volume to a
volume per unit area. The porosity of the intermediate layer can be
determined by measuring the porosity of the porous layer, in which
the oxide semiconductor layer and the intermediate layer are
laminated, and then performing calculation using a value obtained
by measurement of only the oxide semiconductor layer.
[0129] 4. Base Material for Dye-Sensitized Solar Cell
[0130] The base material for dye-sensitized solar cell used in the
present invention functions as an electrode, has flexibility, and
has a porous layer, containing dye-sensitizer-supported fine
particles of a metal oxide semiconductor, provided on one surface
of the base material for dye-sensitized solar cell.
[0131] Here, the flexibility of the base material for
dye-sensitized solar cell refers to the ability to bend when a
force of 5 KN is applied to the base material for dye-sensitized
solar cell in accordance with a bending test method for fine
ceramics specified in JIS R1601 or a bending test method for metal
materials specified in JIS Z 2248.
[0132] The base material for dye-sensitized solar cell has two
embodiments, one having a base material and a first electrode layer
provided on the base material (hereinafter, referred to as a "first
embodiment") and the other being composed of a metal foil
(hereinafter, referred to as a "second embodiment"). Each of the
embodiments will be described below. It is to be noted that when
the first embodiment of the base material for dye-sensitized solar
cell is used, the porous layer is provided on the first electrode
layer.
(1) First Embodiment
[0133] The first embodiment of the base material for dye-sensitized
solar cell includes a base material and a first electrode layer
provided on the base material. The base material and the first
electrode layer will be described below.
[0134] (a) Base Material
[0135] First, the base material used in this embodiment will be
described. The base material used in this embodiment is not
particularly limited as long as it has flexibility and has
self-supporting properties so as to be able to support the first
electrode layer used in this embodiment and the porous layer.
[0136] It is to be noted that the definition of the flexibility of
the base material is the same as that described above with
reference to the base material for dye-sensitized solar cell, and
therefore a description thereof is omitted here.
[0137] The base material is not particularly limited as long as it
has flexibility, and specific examples thereof include a thin glass
base material and a resin base material. Among them, a resin base
material is preferred because it is light, has excellent
workability, and contributes to lower production costs.
[0138] The base material used in this embodiment is not
particularly limited as long as a first electrode layer can be
formed thereon. Further, the base material used in this embodiment
may be either one having transparency or one not having
transparency, but is preferably one having transparency. This is
because it is possible to form a transparent base material for
dye-sensitized solar cell composed of a base material having
transparency and a first electrode layer having sunlight
transmission.
[0139] Examples of the resin base material include base materials
made of resin such as an ethylene-tetrafluoroethylene copolymer
film, a biaxially-drawn polyethylene terephthalate film, a
polyether sulfone (PES) film, a polyether ether ketone (PEEK) film,
a polyether imide (PEI) film, a polyimide (PI) film, a polyester
naphthalate (PEN) film, and a polycarbonate (PC) film. Among them,
a biaxially-drawn polyethylene terephthalate (PET) film, a
polyester naphthalate (PEN) film, and a polycarbonate (PC) film are
preferably used in this embodiment.
[0140] The thickness of the base material used in this embodiment
can be appropriately selected depending on, for example, the
intended use of the dye-sensitized solar cell, but is usually
preferably in the range of 10 .mu.m to 2000 .mu.m, particularly
preferably in the range of 50 pinto 1800 .mu.m, and more preferably
in the range of 100 .mu.m to 1500 .mu.m.
[0141] The base material used in this embodiment preferably has
excellent heat resistance, weather resistance, and gas barrier
properties against water vapor and other gases. By allowing the
base material to have gas barrier properties, for example, it is
possible to improve the temporal stability of the dye-sensitized
solar cell according the present invention. Particularly, the base
material used in this embodiment preferably has gas barrier
properties such that oxygen permeability is 1 cc/m.sup.2/dayatm or
less under conditions of a temperature of 23.degree. C. and a
humidity of 90% and water vapor permeability is 1 g/m.sup.2/day or
less under conditions of a temperature of 37.8.degree. C. and a
humidity of 100%. According to this embodiment, any gas barrier
layer may be provided on the base material to achieve such gas
barrier properties.
[0142] (b) First Electrode Layer
[0143] The first electrode layer used in this embodiment will be
described below. The first electrode layer used in this embodiment
is provided on the base material.
[0144] The material of the first electrode layer used in this
embodiment is not particularly limited as long as it has desired
conductivity, and a conductive polymer material, a metal oxide, or
the like can be used.
[0145] The metal oxide is not particularly limited as long as it
has desired conductivity, but the metal oxide used in this
embodiment preferably has sunlight transmission. Examples of such a
metal oxide having sunlight transmission include SnO.sub.2, ITO,
IZO, and ZnO. According to this embodiment, any of these metal
oxides can be preferably used, but fluorine-doped SnO.sub.2
(hereinafter, referred to as "FTO") or ITO is particularly
preferably used. This is because FTO and ITO are excellent in both
conductivity and sunlight transmission.
[0146] On the other hand, examples of the conductive polymer
material include polythiophene, polyethylenesulfonic acid (PSS),
polyaniline (PA), polypyrrole, and polyestyrene dioxythiophene
(PEDOT). These conductive polymer materials may be used in
combination of two or more of them.
[0147] The first electrode layer used in this embodiment may have a
structure composed of a single layer or a structure in which two or
more layers are laminated. Examples of such a structure in which
two or more layers are laminated include one in which two or more
layers made of materials different in work function from each other
are laminated and one in which two or more layers made of metal
oxides different from each other are laminated.
[0148] The thickness of the first electrode layer used in this
embodiment is not particularly limited as long as the first
electrode layer can have desired conductivity that depends on, for
example, the intended use of the dye-sensitized solar cell.
However, the thickness of the first electrode layer used in this
embodiment is usually preferably in the range of 5 nm to 2000 nm,
and particularly preferably in the range of 10 nm to 1000 nm. If
the thickness of the first electrode layer exceeds the above upper
limit, there is a case where it is difficult to make the first
electrode layer uniform or it is difficult to achieve high
photoelectric conversion efficiency due to a reduction in total
light transmittance. On the other hand, if the thickness of the
first electrode layer is less than the above lower limit, there is
a possibility that the first electrode layer is poor in
conductivity.
[0149] It is to be noted that, when the first electrode layer is
composed of two or more layers, the thickness refers to the total
thickness of all the layers.
[0150] A method for forming the first electrode layer on the base
material is the same as a general method for forming an electrode
layer, and therefore a description thereof is omitted here.
[0151] (c) Optional Component
[0152] The base material for dye-sensitized solar cell according to
this embodiment comprises at least the base material and the first
electrode layer, but if necessary, may include another optional
component. An example of such an optional component used in this
embodiment is an auxiliary electrode made of a conductive material
and provided so as to come into contact with the first electrode
layer. By providing such an auxiliary electrode, it is possible,
when the first electrode layer is poor in conductivity, to
compensate for the lack of conductivity. This is advantageous in
that the dye-sensitized solar cell according to the present
invention can have higher power generation efficiency.
(2) Second Embodiment
[0153] The second embodiment of the base material for
dye-sensitized solar cell is composed of a metal foil.
[0154] In the case of the base material for dye-sensitized solar
cell according to this embodiment, the metal foil itself functions
as an electrode. Therefore, the base material for dye-sensitized
solar cell according to this embodiment does not always need to
have another component. The metal foil used as the base material
for dye-sensitized solar cell is not particularly limited as long
as it has flexibility. Examples of the material of the metal foil
include copper, aluminum, titanium, chromium, tungsten, molybdenum,
platinum, tantalum, niobium, zirconium, zinc, various stainless
steels, and alloys of two or more of them. Among them, titanium,
chromium, tungsten, various stainless steels, and alloys of two or
more of them are preferred. When the base material for
dye-sensitized solar cell composed of a metal foil is used, the
thickness of the metal foil is not particularly limited as long as
the metal foil has flexibility and can impart self-supporting
properties to the base material for dye-sensitized solar cell so
that the porous layer can be formed on the base material for
dye-sensitized solar cell. However, the thickness of the metal foil
is usually preferably in the range of 5 .mu.m to 1000 .mu.m, more
preferably in the range of 10 .mu.m to 500 .mu.m, and even more
preferably in the range of 20 .mu.m to 200 .mu.m.
[0155] 5. Counter Electrode Base Material
[0156] Hereinbelow, the counter electrode base material used in the
present invention will be described. The counter electrode base
material used in the present invention is arranged so as to oppose
to the base material for dye-sensitized solar cell, functions as an
electrode, and has flexibility.
[0157] The definition of the flexibility of the counter electrode
base material used in the present invention is the same as that
described above with reference to the base material for
dye-sensitized solar cell, and therefore a description thereof is
omitted here.
[0158] The counter electrode base material used in the present
invention is not particularly limited as long as it functions as an
electrode. Examples of such a counter electrode base material
include one composed of a metal foil and one having a structure in
which a second electrode layer is provided on a counter base
material.
[0159] When the counter electrode base material used in the present
invention is composed of a metal foil, it is the same as that
described above in the section "(2) Second Embodiment" in the
paragraph "4. Base Material for Dye-Sensitized Solar Cell", and
therefore a description thereof is omitted here.
[0160] On the other hand, when the counter electrode base material
used has a structure in which a second electrode layer is provided
on a counter base material, the second electrode layer is not
particularly limited as long as it is made of a conductive material
having desired conductivity, and may be made of a conductive
polymer material, a metal oxide, or the like. Examples of the
conductive polymer material and the metal oxide include those
mentioned above as materials for forming the first electrode
layer.
[0161] The second electrode layer used in the present invention may
have a structure composed of a single layer or a structure in which
two or more layers are laminated. Examples of such a structure in
which two or more layers are laminated include one in which two or
more layers made of materials different in work function from each
other are laminated and one in which two or more layers made of
metal oxides different from each other are laminated. The thickness
of the second electrode layer used in the present invention is
usually preferably in the range of 5 nm to 2000 nm, and
particularly preferably in the range of 10 nm to 1000 nm.
[0162] The counter base material used in the present invention is
the same as the base material used in the base material for
dye-sensitized solar cell, and therefore a description thereof is
omitted here.
[0163] If necessary, the counter electrode base material used in
the present invention may have a catalyst layer. By providing a
catalyst layer in the counter electrode base material, it is
possible to further enhance the power generation efficiency of the
dye-sensitized solar cell according to the present invention.
Examples of such a catalyst layer include, but are not limited to,
one formed on the second electrode layer by vapor deposition of Pt
and one made of polyethylene dioxythiophene (PEDOT),
polystyrenesulfonic acid (PSS), polyaniline (PA),
paratoluenesulfonic acid (PTS), or a mixture of two or more of
them. It is to be noted that when the counter electrode base
material used has the counter base material and the second
electrode layer, the catalyst layer is provided on the second
electrode layer.
[0164] 6. Combination of Base Material for Dye-Sensitized Solar
Cell and Counter Electrode Base Material
[0165] The dye-sensitized solar cell according to the present
invention acts when the dye sensitizer adsorbed to the porous layer
receives sunlight and is excited. Therefore, at least one of the
base material for dye-sensitized solar cell and the counter
electrode base material needs to have transparency. For this
reason, according to the present invention, the base material for
dye-sensitized solar cell and the counter electrode base material
are appropriately selected so that at least one of them has
transparency. According to the present invention, both the base
material for dye-sensitized solar cell and the counter electrode
base material may have transparency or one of the base material for
dye-sensitized solar cell and the counter electrode base material
may be composed of a metal foil while the other has
transparency.
[0166] According to the present invention, it is more preferred
that the base material for dye-sensitized solar cell is composed of
a metal foil and the counter electrode base material has
transparency. This is because when the base material for
dye-sensitized solar cell is composed of a metal foil, the porous
layer can be directly formed on the base material for
dye-sensitized solar cell by burning, which makes it possible to
achieve good adhesion between the base material for dye-sensitized
solar cell and the porous layer.
[0167] Further, when the dye-sensitized solar cell has such an
inverted structure, light enters the porous layer through the solid
electrolyte layer, and therefore there is a concern about the loss
of light in the solid electrolyte layer. Therefore, the thickness
of the solid electrolyte layer is preferably reduced, but a
reduction in the thickness of the solid electrolyte layer narrows
the gap between the two base materials, which increases the risk of
a short circuit between the electrodes. For this reason, in the
case of such an inverted-structure dye-sensitized solar cell, the
use of the insulating layer used in the present invention is
preferred because the insulating layer effectively performs its
function and has a great effect.
[0168] Further, according to the present invention, it is also
preferred that the base material for dye-sensitized solar cell has
transparency and the counter electrode base material is composed of
a metal foil. When the dye-sensitized solar cell has such a
structure, the occurrence of a short circuit in the dye-sensitized
solar cell can be more effectively prevented by providing the
insulating layer described above.
[0169] 7. Other Members
[0170] The dye-sensitized solar cell according to the present
invention is not particularly limited as long as it comprises the
above-described insulating layer, solid electrolyte layer, porous
layer, base material for dye-sensitized solar cell, and counter
electrode base material, and if necessary, another member may be
provided. An example of such a member is a fixing member that is
provided outside the base material for dye-sensitized solar cell
and the counter electrode base material to fix these base materials
when the base material for dye-sensitized solar cell and the
counter electrode base material opposed to each other are bonded
together.
[0171] Such a fixing member is not particularly limited as long as
it can fix the base material for dye-sensitized solar cell and the
counter electrode base material to prevent, for example,
misalignment between them bonded together, and a fixing member
usually used to bond base materials together can be used. Examples
of the material of such a fixing member include low-density
polyethylene (LDPE), straight (linear) low-density polyethylene (a
polymer obtained by polymerization using a multi-site catalyst,
LLDPE), an ethylene/.alpha.-olefin copolymer obtained by
polymerization using a metallocene catalyst (single-site catalyst),
middle-density polyethylene (MDPE), high-density polyethylene
(HDPE), a polypropylene-based resin, an ethylene-vinyl acetate
copolymer, an ionomer resin, an ethylene-acrylic acid copolymer, a
thermoplastic polyester-based resin, a thermoplastic
polyamide-based resin, and other thermoplastic resin. These
materials may be used singly or in combination of two or more of
them.
[0172] B. Dye-Sensitized Solar Cell Module
[0173] A dye-sensitized solar cell module according to the present
invention comprises the two or more dye-sensitized solar cells
described above in the paragraph "A. Dye-Sensitized Solar Cell"
connected together.
[0174] The dye-sensitized solar cell module according to the
present invention will be described with reference to FIG. 8. FIG.
8 is a schematic sectional view of one example of the
dye-sensitized solar cell module according to the present
invention. A dye-sensitized solar cell module 30 according to the
present invention comprises the two or more dye-sensitized solar
cells 10 connected together in parallel, the dye-sensitized solar
cells 10 each comprises: the base material for dye-sensitized solar
cell 1 having: the base material 1a, the first electrode layer 1b,
and the porous layer 4 provided on the first electrode layer 1b and
containing dye-sensitizer-supported fine particles of a metal oxide
semiconductor; the counter electrode base material 2 that is
arranged so as to oppose to the base material for dye-sensitized
solar cell 1 and functions as an electrode; the solid electrolyte
layer 3 provided between the base material for dye-sensitized solar
cell 1 and the counter electrode base material 2 so as to come into
contact with the porous layer 4; and the insulating layer 5
provided on the surface of the base material for dye-sensitized
solar cell 1 and the surface of the counter electrode base material
2.
[0175] It is to be noted that, although not shown, the
dye-sensitized solar cells constituting the dye-sensitized solar
cell module according to the present invention may be connected
together in series.
[0176] According to the present invention, by connecting together
the two or more dye-sensitized solar cells described above, it is
possible to provide a dye-sensitized solar cell module in which the
occurrence of an internal short circuit is suppressed.
[0177] The dye-sensitized solar cells used in the dye-sensitized
solar cell module according to the present invention may be the
same as that described above in the paragraph "A. Dye-Sensitized
Solar Cell", and therefore a description thereof is omitted
here.
[0178] The dye-sensitized solar cell module according to the
present invention in which the two or more dye-sensitized solar
cells are connected together is not particularly limited as long as
it can generate a desired electromotive force, and the individual
dye-sensitized solar cells may be connected together either in
series or in parallel.
[0179] C. Method for Producing Dye-Sensitized Solar Cell
[0180] A method for producing a dye-sensitized solar cell according
to the present invention comprises the steps of: first preparing a
base material for dye-sensitized solar cell that functions as an
electrode, has flexibility, and has a porous layer, containing
dye-sensitizer-supported fine particles of a metal oxide
semiconductor, provided on one surface of the base material for
dye-sensitized solar cell, and a counter electrode base material
that is arranged so as to oppose to the base material for
dye-sensitized solar cell, functions as an electrode, and has
flexibility; then forming the porous layer on the base material for
dye-sensitized solar cell; forming a solid electrolyte layer so as
to come into contact with the porous layer; forming an insulating
layer on a surface of at least one of the base material for
dye-sensitized solar cell and the counter electrode base material
in a region which surrounds a region corresponding to a porous
layer-forming region where the porous layer is formed, and which is
where the base material for dye-sensitized solar cell and the
counter electrode base material are opposed to each other when they
are bonded together; and then bonding together the base material
for dye-sensitized solar cell and the counter electrode base
material opposed to each other with the porous layer and the solid
electrolyte layer being interposed therebetween, wherein at least
one of the base material for dye-sensitized solar cell and the
counter electrode base material has transparency; and the porous
layer-forming step, the solid electrolyte layer-forming step, and
the insulating layer-forming step are performed in no particular
order.
[0181] In the method for producing a dye-sensitized solar cell
according to the present invention, the porous layer-forming step,
the solid electrolyte layer-forming step, and the insulating
layer-forming step can be performed in no particular order. This
makes it possible to determine the order of these steps depending
on the form of a dye-sensitized solar cell to be produced. The
method for producing a dye-sensitized solar cell according to the
present invention will be described below with reference to
drawings.
[0182] FIGS. 9A to 9E is a flow chart of one example of the method
for producing a dye-sensitized solar cell according to the present
invention. As shown in FIGS. 9A to 9E, the method for producing a
dye-sensitized solar cell according to the present invention
comprises the steps of: first preparing the base material for
dye-sensitized solar cell 1 composed of a metal foil and the
counter electrode base material 2 that is arranged so as to oppose
to the base material for dye-sensitized solar cell 1 and has a
counter base material 2a and a second electrode layer 2b (FIG. 9A);
then forming, on the base material for dye-sensitized solar cell 1,
the porous layer 4 containing dye-sensitizer-supported fine
particles of a metal oxide semiconductor (FIG. 9B); forming the
solid electrolyte layer 3 on the porous layer 4 (FIG. 9C); forming
the insulating layer 5 on the base material for dye-sensitized
solar cell 1 in a region which surrounds the porous layer-forming
region T where the porous layer 4 is formed, and which is where the
base material for dye-sensitized solar cell 1 and the counter
electrode base material 2 are opposed to each other when they are
bonded together (FIG. 9D); and then bonding together the base
material for dye-sensitized solar cell 1 and the counter electrode
base material 2 so that the second electrode layer 2b of the
counter electrode base material 2 and the base material for
dye-sensitized solar cell 1 are opposed to each other with the
porous layer 4 and the solid electrolyte layer 3 being interposed
therebetween (FIG. 9E).
[0183] FIGS. 10A to 10D is a flow chart of another example of the
method for producing a dye-sensitized solar cell according to the
present invention. As shown in FIGS. 10A to 10D, the method for
producing a dye-sensitized solar cell according to the present
invention comprises the steps of: first preparing the base material
for dye-sensitized solar cell 1 composed of a metal foil and the
counter electrode base material 2 that is arranged so as to oppose
to the base material for dye-sensitized solar cell 1 and has a
counter base material 2a and a second electrode layer 2b (FIG.
10A); then forming the insulating layer 5 on the second electrode
layer 2b of the counter electrode base material 2 in a region which
surrounds a region corresponding to the porous layer-forming region
T where the porous layer 4 is formed, and which is where the base
material for dye-sensitized solar cell 1 and the counter electrode
base material 2 are opposed to each other when they are bonded
together (FIG. 10B); forming, on the base material for
dye-sensitized solar cell 1, the porous layer 4 containing
dye-sensitizer-supported fine particles of a metal oxide
semiconductor (FIG. 10B); forming the solid electrolyte layer 3 on
the porous layer 4 (FIG. 10C); and then bonding together the base
material for dye-sensitized solar cell 1 and the counter electrode
base material 2 so that the second electrode layer 2b of the
counter electrode base material 2 and the base material for
dye-sensitized solar cell 1 are opposed to each other with the
porous layer 4 and the solid electrolyte layer 3 being interposed
therebetween (FIG. 10D).
[0184] Although not shown, according to the present invention, the
insulating layer may be formed on the base material for
dye-sensitized solar cell before the porous layer-forming step and
the solid electrolyte layer-forming step. FIGS. 9 and 10 illustrate
cases where a metal foil is used as the base material for
dye-sensitized solar cell, but the base material for dye-sensitized
solar cell used may be one having a base material and a first
electrode layer provided on the base material. When the base
material for dye-sensitized solar cell has transparency, the
counter electrode base material used may be one composed of a metal
foil or one having a counter base material and a second electrode
layer.
[0185] According to the present invention, it is possible to easily
produce a dye-sensitized solar cell that does not cause an internal
short circuit. Further, according to the present invention, since a
solid electrolyte layer and an insulating layer are formed in the
solid electrolyte layer-forming step and the insulating
layer-forming step, alignment between the base material for
dye-sensitized solar cell and the counter electrode base material
for bonding in the bonding step does not require high accuracy,
which makes it easy to produce a dye-sensitized solar cell.
[0186] Further, the method for producing a dye-sensitized solar
cell according to the present invention does not include the step
of sealing an electrolyte layer with a sealant, which makes it
easier to produce a dye-sensitized solar cell as compared to a
conventional method for producing a dye-sensitized solar cell in
which a base material for dye-sensitized solar cell having a porous
layer provided thereon and a counter electrode base material are
sealed with a sealant and then an electrolyte layer is formed by
injecting an electrolyte.
[0187] The base material for dye-sensitized solar cell and the
counter electrode base material used in the method according to the
present invention and a combination of the base material for
dye-sensitized solar cell and the counter electrode base material
are the same as those described above in the paragraph "A.
Dye-Sensitized Solar Cell", and therefore a description thereof is
omitted here.
[0188] The porous layer-forming step, the solid electrolyte
layer-forming step, the insulating layer-forming step, and the
bonding step of the method according to the present invention will
be described below.
[0189] 1. Porous Layer-Forming Step
[0190] This step is a step of forming a porous layer on the base
material for dye-sensitized solar cell.
[0191] A method for forming a porous layer used in this step is not
particularly limited as long as a desired porous layer can be
formed on the base material for dye-sensitized solar cell. Specific
examples of such a method include the following three methods: a
method in which a porous layer is formed on a metal foil used as
the base material for dye-sensitized solar cell by burning
(hereinafter, referred to as a "third embodiment"); a method in
which a porous layer is formed by applying a composition for
forming a porous layer in a pattern onto the base material for
dye-sensitized solar cell (hereinafter, referred to as a "fourth
embodiment"); and a method in which a porous layer is formed on a
heat-resistant substrate, placed on the base material for
dye-sensitized solar cell, and then the heat-resistant substrate is
removed (transfer method) (hereinafter, referred to as a "fifth
embodiment"). Each of the embodiments will be described below.
(1) Third Embodiment
[0192] This embodiment of the porous layer forming method is a
method in which a porous layer is formed on a metal foil used as
the base material for dye-sensitized solar cell by burning.
[0193] The metal foil used in this embodiment is not particularly
limited as long as it has heat resistance to withstand a burning
temperature during formation of a porous layer by burning.
[0194] In this embodiment, since a metal foil is used as the base
material for dye-sensitized solar cell, a transparent base material
is prepared as the counter electrode base material.
[0195] As described above in the paragraph "A. Dye-Sensitized Solar
Cell", when the dye-sensitized solar cell has an inverted
structure, there is a concern about the loss of light in the solid
electrolyte layer because light enters the porous layer through the
solid electrolyte layer. Therefore, the thickness of the solid
electrolyte layer is preferably reduced, but a reduction in the
thickness of the solid electrolyte layer narrows the gap between
the two base materials, which increases the risk of a short circuit
between the electrodes. For this reason, when the dye-sensitized
solar cell has an inverted structure, the insulating layer formed
in the insulating layer-forming step (which will be described
later) effectively performs its function and has a great effect.
Therefore, the method of this embodiment in which a porous layer is
formed on a metal foil used as the base material for dye-sensitized
solar cell is preferred.
[0196] Further, a metal foil has a high upper temperature limit,
and therefore the method of this embodiment has advantages such as
a wider choice of materials used for forming a porous layer and
good adhesion between the metal foil and the porous layer.
[0197] In the porous layer forming method of this embodiment, a
coating liquid for forming a porous layer composed of metal oxide
semiconductor fine particles, a binder resin, and a solvent is
first prepared. Then, the prepared coating liquid for forming a
porous layer is applied onto a metal foil to a desired film
thickness to form a coating film for forming a porous layer, and
then the coating film for forming a porous layer is burned to
decompose the binder resin to form a layer for forming a porous
layer. Then, a dye sensitizer is adhered to the surface of the
layer for forming a porous layer to form a porous layer.
[0198] The metal oxide semiconductor fine particles used in this
embodiment may be the same as those described above in the
paragraph "A. Dye-Sensitized Solar Cell", and therefore a
description thereof is omitted here.
[0199] The binder resin used in the coating liquid for forming a
porous layer is not particularly limited as long as it is
decomposed by burning. Examples of such a binder rein include a
cellulose-based resin, a polyester-based resin, a polyamide-based
resin, a polyacrylic acid ester-based resin, a polyacrylic resin, a
polycarbonate resin, a polyurethane resin, a polyolefin-based
resin, a polyvinyl acetal-based resin, a fluorine-based resin, a
polyimide resin, and polyhydric alcohols such as polyethylene
glycol.
[0200] The solvent used in the coating liquid for forming a porous
layer is not particularly limited as long as it can dissolve or
disperse a desired amount of the binder resin. Examples of such a
solvent include water and various solvents such as methanol,
ethanol, isopropyl alcohol, propylene glycol monomethyl ether,
terpineol, dichloromethane, acetone, acetonitrile, ethyl acetate,
and tert-butyl alcohol.
[0201] A method for applying the coating liquid for forming a
porous layer is not particularly limited as long as the coating
liquid for forming a porous layer can be uniformly applied in a
pattern onto a metal foil to a desired film thickness, and may be
the same as a general coating method. Examples of such a
conventional coating method include die coating, gravure coating,
gravure reverse coating, roll coating, reverse roll coating, bar
coating, blade coating, knife coating, air-knife coating, slot die
coating, slide die coating, dip coating, microbar coating, microbar
reverse coating, offset coating, and screen printing (rotary
type).
[0202] In this embodiment, the film thickness of the coating film
for forming a porous layer formed on a metal foil is not
particularly limited as long as a porous layer having a desired
film thickness can be formed, but is preferably in the range of 0.5
.mu.m to 50 .mu.m, more preferably in the range of 2 .mu.m to 30
.mu.m, and particularly preferably in the range of 5 .mu.m to 20
.mu.m. If the film thickness of the coating film for forming a
porous layer is less than the above lower limit or exceeds the
above upper limit, it is difficult to form a porous layer having a
desired film thickness.
[0203] In this embodiment, the coating film for forming a porous
layer may be pressurized before it is burned. This is because by
pressurizing the coating film for forming a porous layer, it is
possible to enhance the adhesion between the resulting porous layer
and the base material for dye-sensitized solar cell. A method for
pressurizing the coating film for forming a porous layer may be the
same as that used for producing a conventional dye-sensitized solar
cell, and therefore a description thereof is omitted here.
[0204] In this embodiment, a method for burning the coating film
for forming a porous layer is not particularly limited as long as
the coating film for forming a porous layer can be evenly burned
without uneven heating, and a well-known burning method can be
used.
[0205] In this embodiment, the temperature of burning is not
particularly limited as long as the binder rein contained in the
coating film for forming a porous layer can be thermally
decomposed, and is appropriately determined depending on the
pyrolysis temperature of the binder resin used. However, the
temperature of burning is preferably in the range of 250 to
550.degree. C., more preferably in the range of 350 to 550.degree.
C., and particularly preferably in the range of 400 to 550.degree.
C.
[0206] A method for adhering the dye sensitizer used in this
embodiment to the surface of the layer for forming a porous layer
is not particularly limited as long as the dye sensitizer can
receive sunlight in a dye-sensitized solar cell produced using a
porous layer formed by the porous layer forming method of this
embodiment, and may be the same as that used for producing a
general dye-sensitized solar cell.
[0207] The dye sensitizer used in this embodiment may be the same
as that described above in the paragraph "A. Dye-Sensitized Solar
Cell", and therefore a description thereof is omitted here.
(2) Fourth Embodiment
[0208] This embodiment of the porous layer forming method is a
method in which a porous layer is formed by applying a composition
for forming a porous layer in a pattern onto the base material for
dye-sensitized solar cell. In this embodiment, heat treatment may
be performed at a temperature equal to or lower than the upper
temperature limit of heat resisting temperature of the base
material for dye-sensitized solar cell (hereinafter, sometimes
simply referred to as "heat treatment").
[0209] The base material for dye-sensitized solar cell used in this
embodiment may be either one composed of a metal foil or one
composed of a base material and a first electrode layer provided on
the base material. Examples of the base material include a thin
glass base material and a resin film.
[0210] The counter electrode base material to be prepared may be
either one having transparency or one not having transparency as
long as at least one of the base material for dye-sensitized solar
cell and the counter electrode base material has transparency.
[0211] In the porous layer forming method of this embodiment, a
layer for forming a porous layer is first formed by applying and
drying a composition for forming a porous layer containing metal
oxide semiconductor fine particles and a solvent, and then a dye
sensitizer is adhered to the layer for forming a porous layer to
form a porous layer.
[0212] The metal oxide semiconductor fine particles used in the
composition for forming a porous layer may be the same as those
described above in the paragraph "A. Dye-Sensitized Solar Cell",
and therefore a description thereof is omitted here.
[0213] The solvent is not particularly limited as long as it can
disperse the metal oxide semiconductor fine particles, can dissolve
or disperse a resin component, and can be removed by natural drying
or heat treatment. Examples of such a solvent include, but not
limited to, water, ethanol, isopropyl alcohol, ethyl acetate,
methyl ethyl ketone, cyclohexanone, toluene, and xylene. These
solvents may be used in combination of two or more of them. From
the viewpoint of the effects of volatile matter on the environment
after film formation, water or an alcohol-based solvent is more
preferably used.
[0214] A method for applying the composition for forming a porous
layer and the film thickness of a coating film obtained by applying
the composition for forming a porous layer are not particularly
limited as long as a porous layer having a desired film thickness
can be uniformly formed on the base material for dye-sensitized
solar cell, and may be the same as the method for applying a
coating liquid for forming a porous layer and the film thickness of
a coating film for forming a porous layer described above in the
section "(1) Third Embodiment", and therefore a description thereof
is omitted here.
[0215] The dye sensitizer used in this embodiment and a method for
adhering the dye sensitizer onto the layer for forming a porous
layer may be the same as those described above in the section "(1)
Third Embodiment", and therefore a description thereof is omitted
here.
(3) Fifth Embodiment
[0216] This embodiment of the porous layer forming method is a
method (transfer method) in which a porous layer is formed on a
heat-resistant substrate by burning, is then placed on the base
material for dye-sensitized solar cell, and then the heat-resistant
substrate is removed.
[0217] The porous layer forming method of this embodiment is not
particularly limited as long as a porous layer can be formed on a
heat-resistant substrate by burning and placed on the base material
for dyes-sensitized solar cell. However, it is preferred that the
heat-resistant substrate is removed after a first electrode layer
is formed on the porous layer and a base material is bonded to the
first electrode layer. This makes it possible to produce a
dye-sensitized solar cell excellent in adhesion between the porous
layer and the base material for dye-sensitized solar cell.
[0218] From the above viewpoint, the base material for
dye-sensitized solar cell used in this embodiment is preferably
composed of a base material and a first electrode layer provided on
the base material. The counter electrode base material to be
prepared may be either one having transparency or one not having
transparency as long as at least one of the base material for
dye-sensitized solar cell and the counter electrode base material
has transparency.
[0219] The heat-resistant substrate used in this embodiment is not
particularly limited as long as it has desired heat resistance.
However, high-temperature burning treatment is commonly performed
when a porous layer is formed on the heat-resistant substrate, and
therefore the heat-resistant substrate used in this embodiment
preferably has heat resistance to withstand a heating temperature
during such burning treatment for forming a porous layer. Such a
heat-resistant substrate may be the same as that used for producing
a general dye-sensitized solar cell, and therefore a description
thereof is omitted here.
[0220] A method for forming a porous layer on the heat-resistant
substrate may be the same as that used in the section "(1) Third
Embodiment" for forming a porous layer on a metal foil, and
therefore a description thereof is omitted here.
[0221] In this embodiment, a method for forming a first electrode
layer on the porous layer is not particularly limited as long as a
first electrode layer having a desired film thickness can be
uniformly formed on the porous layer, and may be the same as a
general method for forming an electrode layer, and therefore a
description thereof is omitted here. The material of the first
electrode layer used in this embodiment may be the same as that
described above in the paragraph "A. Dye-Sensitized Solar Cell",
and therefore a description thereof is omitted here.
[0222] In this embodiment, a method for bonding a base material
onto the first electrode layer is not particularly limited as long
as a desired adhesive force between the base material and the first
electrode layer bonded together can be achieved. Usually, the base
material and the first electrode layer are bonded together with an
adhesive layer provided therebetween.
[0223] The adhesive layer may be the same as that used for
producing a general dye-sensitized solar cell, and therefore a
description thereof is omitted here.
[0224] A method for removing the heat-resistant substrate is not
particularly limited as long as the heat-resistant substrate can be
removed without damaging the porous layer, and a conventional
removal method can be used. In this step, the heat-resistant
substrate may be removed by mechanical polishing or chemical
removal such as etching.
(4) Others
[0225] When this step is performed after the insulating
layer-forming step (which will be described later), for example as
shown in FIG. 7A, the porous layer may be provided on part of the
insulating layer. The insulating layer (which will be described
later) is not particularly limited as long as it is formed so as to
prevent electrical contact between the base material for
dye-sensitized solar cell and the counter electrode base material
in a dye-sensitized solar cell produced by the production method
according to the present invention. Therefore, formation of the
porous layer on the porous layer-forming region where the
insulating layer is not provided does not require high positional
accuracy, and therefore the porous layer can be easily formed.
[0226] 2. Solid Electrolyte Layer-Forming Step
[0227] This step is a step of forming a solid electrolyte layer so
as to come into contact with the porous layer.
[0228] In this step, a method for forming a solid electrolyte layer
is not particularly limited as long as a solid electrolyte layer
having a desired film thickness can be formed on the porous layer
so as to come into contact with the porous layer. Examples of such
a method include: one in which a composition for forming a solid
electrolyte layer is prepared by dispersing or dissolving a polymer
component, a redox couple electrolyte, and an additive such as a
cross-linking agent or a photopolymerization initiator in an
appropriate solvent, applied onto the porous layer in a pattern,
and cured by irradiation with active light rays; one in which a
solid electrolyte layer is separately formed as a solid polymer
film and then placed on the porous layer; and one in which a solid
electrolyte layer is formed on the counter electrode base material
and then the counter electrode base material and the base material
for dye-sensitized solar cell having a porous layer provided
thereon are bonded together such that the solid electrolyte layer
comes into contact with the porous layer.
[0229] In this step, a solid electrolyte layer is particularly
preferably formed by applying the composition for forming a solid
electrolyte layer onto the porous layer in a pattern. This makes it
easier to form a solid electrolyte layer as compared to a method in
which a base material for dye-sensitized solar cell and a counter
electrode base material are sealed with a sealant and then a solid
electrolyte layer is formed by injecting a solid electrolyte layer
material.
[0230] The polymer component and the redox couple electrolyte may
be the same as those described above in the paragraph "A.
Dye-Sensitized Solar Cell", and therefore a description thereof is
omitted here. Further, other components used in the composition for
forming a solid electrolyte layer may be the same as those used for
forming a general solid electrolyte layer, and therefore a
description thereof is omitted here.
[0231] Others relating to the solid electrolyte layer may be the
same as those described above in the paragraph "A. Dye-Sensitized
Solar Cell", and therefore a description thereof is omitted
here.
[0232] 3. Insulating Layer-Forming Step
[0233] This step is a step of forming an insulating layer on the
surface of at least one of the base material for dye-sensitized
solar cell and the counter electrode base material in a region
which surrounds a region corresponding to the porous layer-forming
region where the porous layer is formed and which is where the base
material for dye-sensitized solar cell and the counter electrode
base material are opposed to each other when they are bonded
together.
[0234] In this step, a method for forming an insulating layer is
not particularly limited as long as an insulating layer can be
formed so as to prevent the occurrence of an internal short circuit
in a dye-sensitized solar cell produced by the dye-sensitized solar
cell production method according to the present invention. Examples
of such an insulating layer forming method include: one in which an
insulating layer is formed by applying a composition for forming an
insulating layer in a pattern on at least one of the base material
for dye-sensitized solar cell and the counter electrode base
material; one in which an insulating layer is formed by adhering a
tape having insulating properties to at least one of the base
material for dye-sensitized solar cell and the counter electrode
base material; one in which an insulating layer is formed by
interposing an insulating layer material (e.g., a polymer film)
between the base material for dye-sensitized solar cell having a
porous layer provided thereon and the counter electrode base
material having a solid electrolyte layer provided thereon, which
are opposed to each other so that the porous layer and the solid
electrolyte layer are interposed therebetween, and then bonding
together the base material for dye-sensitized solar cell and the
counter electrode base material by pressure bonding; and one in
which an insulating layer is formed by forming a vapor-deposited
insulating film, such as SiO.sub.2, on at least one of the base
material for dye-sensitized solar cell and the counter electrode
base material by vapor deposition, sputtering, CVD, or the
like.
[0235] In this step, an insulating layer is preferably formed by
applying the composition for forming an insulating layer in a
pattern on at least one of the base material for dye-sensitized
solar cell and the counter electrode base material or by using a
tape having insulating properties. This makes it easy to form an
insulating layer.
[0236] It is to be noted that the composition for forming an
insulating layer contains the material of an insulating layer
described above in the paragraph "A. Dye-Sensitized Solar cell",
and the tape having insulating properties contains the material of
an insulating layer described above in the paragraph "A.
Dye-Sensitized Solar Cell" and has desired width and thickness.
[0237] The insulating material (polymer film) may be either one
containing the material of an insulating layer described above in
the paragraph "A. Dye-Sensitized Solar Cell" and having or not
having heat sealability or one containing the material of an
insulating layer described above in the paragraph "A.
Dye-Sensitized Solar Cell" and having or not having tackiness.
[0238] A method for applying the composition for forming an
insulating layer in a pattern may be the same as a general pattern
application method, and is particularly preferably a printing
method, an inkjet method, a dispenser method, die coating, gravure
coating, gravure reverse coating, offset coating, or screen
printing (rotary type).
[0239] The method for forming an insulating layer by using a tape
having insulating properties is not particularly limited as long as
the tape can be adhered to a predetermined position on the base
material for dye-sensitized solar cell or the counter electrode
base material, and may be the same as a general tape adhering
method, and therefore a description thereof is omitted here.
[0240] The insulating layer formed in this step is not particularly
limited as long as it can prevent electrical contact between the
base material for dye-sensitized solar cell and the counter
electrode base material in a region surrounding the porous layer in
a dye-sensitized solar cell produced by the production method
according to the present invention. However, the insulating layer
formed in this step is more preferably formed such that a
dye-sensitized solar cell produced by the production method
according to the present invention can have an external
communication portion that leads from the porous layer-forming
region where the porous layer is formed, to the outside of the
dye-sensitized solar cell. This is because in the bonding step
(which will be described later), air in the dye-sensitized solar
cell can be discharged through the external communication portion
when the base material for dye-sensitized solar cell and the
counter electrode base material are bonded together, which allows
the dye-sensitized solar cell to be easily produced.
[0241] It is to be noted that the external communication portion
may be the same as that described above in the paragraph "A.
Dye-Sensitized Solar Cell", and therefore a description thereof is
omitted here.
[0242] In this step, as shown in FIGS. 1A and 1B, the insulating
layer may be continuously formed, or as shown in FIG. 6, the
insulating layer may be composed of islands spaced apart from one
another without causing an internal short circuit in a
dye-sensitized solar cell produced by the dye-sensitized solar cell
production method according to the present invention.
[0243] Matters relating to the insulating layer formed in this step
are the same as those described above in the paragraph "A.
Dye-Sensitized Solar Cell", and therefore a description thereof is
omitted here.
[0244] 4. Bonding Step
[0245] This step is a step of bonding together the base material
for dye-sensitized solar cell and the counter electrode base
material opposed to each other with the porous layer and the solid
electrolyte layer being interposed therebetween.
[0246] In this step, the base material for dye-sensitized solar
cell and the counter electrode base material opposed to each other
are bonded together with the porous layer and the solid electrolyte
layer being interposed therebetween after the porous layer-forming
step, the solid electrolyte layer-forming step, and the insulating
layer-forming step. This makes it possible to produce a
dye-sensitized solar cell on a single production line and therefore
to improve production efficiency.
[0247] A method for bonding together the base material for
dye-sensitized solar cell and the counter electrode base material
used in this step is not particularly limited as long as the base
material for dye-sensitized solar cell and the counter electrode
base material opposed to each other can be bonded together with the
porous layer and the solid electrolyte layer being interposed
therebetween, and may be the same as that used in a method for
producing a general dye-sensitized solar cell.
[0248] 5. Other Steps
[0249] The dye-sensitized solar cell production method according to
the present invention is not particularly limited as long as it
includes the above-described bonding step, but if necessary, may
include another step. An example of such another step is a step of
cutting a dye-sensitized solar cell fabricated in the bonding step
into desired sizes. According to the present invention, a solid
electrolyte is used, and therefore the fabricated dye-sensitized
solar cell can be cut into desired sizes.
[0250] The dye-sensitized solar cell production method according to
the present invention may include, for example, a catalyst layer
forming step for forming a catalyst layer on the counter electrode
base material. A method for forming the catalyst layer may be the
same as that used for producing a general dye-sensitized solar
cell, and therefore a description thereof is omitted here.
[0251] 6. Others
[0252] According to the present invention, it is preferred that:
the porous layer is formed by applying a composition for forming a
porous layer in a pattern onto the base material for dye-sensitized
solar cell in the porous layer-forming step; the solid electrolyte
layer is formed by applying a composition for forming a solid
electrolyte layer in a pattern onto the porous layer in the solid
electrolyte layer-forming step; and the insulating layer is formed
by applying a composition for forming an insulating layer in a
pattern onto at least one of the base material for dye-sensitized
solar cell and the counter electrode base material in the
insulating layer-forming step. This makes it possible to produce
the dye-sensitized solar cell according to the present invention on
a single production line, thereby improving production efficiency.
Further, since both the base material for dye-sensitized solar cell
and the counter electrode base material used in the present
invention have flexibility, by performing all these steps by an
application method, it is possible to reduce loads applied to the
base material for dye-sensitized solar cell and the counter
electrode base material as compared to a case where these members
are formed using a tape or the like, thereby preventing a reduction
in processing accuracy.
[0253] Further, the dye-sensitized solar cell production method
according to the present invention also makes it possible to
mass-produce a dye-sensitized solar cell by using a multifaceted
member, such as one shown in FIG. 3, 4, or 5, having two or more
dye-sensitized solar cells formed.
[0254] An example of such a method for producing a dye-sensitized
solar cell by using a multifaceted member includes one in which,
two or more each of the members necessary to produce two or more
dye-sensitized solar cells are formed in the above-mentioned porous
layer-forming step, solid electrolyte layer-forming layer, and
insulating layer-forming step, and then the base material for
dye-sensitized solar cell and the counter electrode base material
having these members formed thereon are bonded together in the
above-mentioned the bonding step to prepare a multifaceted member
having two or more dye-sensitized solar cells formed, and then the
multifaceted member is cut at predetermined cutting positions.
[0255] The porous layer-forming step, the solid electrolyte
layer-forming step, and the insulating layer-forming step used in
the method for producing two or more dye-sensitized solar cells by
using a multifaceted member are not particularly limited as long as
a multifaceted member having two or more desired dye-sensitized
solar cells produced can be prepared. However, as described above,
all the porous layer-forming step, the solid electrolyte
layer-forming step, and the insulating layer-forming step are
preferably performed by a pattern application method. This makes it
possible to perform these steps and the bonding step on a single
production line to prepare a multifaceted member, which makes it
possible to improve production efficiency and to prevent a
reduction in processing accuracy as compared to a case where each
of the members is formed using a tape or the like.
[0256] Further, the mass-production of a dye-sensitized solar cell
can be achieved by preparing a multifaceted member by, for example,
a Roll-to-Roll method and cutting the multifaceted member, which
makes it possible to produce a dye-sensitized solar cell at low
cost.
[0257] It is to be noted that the present invention is not limited
to the above embodiments. The above embodiments are merely
illustrative, and those that have substantially the same structure
as the technical concept described in the claims of the present
invention and demonstrate the same functions and effects are all
included in the technical scope of the present invention.
EXAMPLES
[0258] Hereinbelow, the present invention will be more specifically
described with reference to the following examples.
Example 1
[0259] A titanium foil was prepared as a base material for
dye-sensitized solar cell. A transparent conductive film obtained
by forming an ITO film on a PEN film was prepared as a counter base
material, and a counter electrode base material was prepared by
laminating platinum with a thickness of 13 .ANG. (transmittance
72%) on the ITO film.
[0260] (Porous Layer-Forming Step)
[0261] A coating liquid for forming a porous layer was prepared by
adding 5% (solid ratio) of ethyl cellulose (ST-100.TM. manufactured
by Nissin Kasei Kogyo Co., Ltd.) as a polymer component to a
dispersion liquid obtained by dispersing P25.TM. (manufactured by
Nippon Aerosil Co., Ltd.) in ethanol. The coating liquid for
forming a porous layer was applied with a doctor blade onto the
titanium foil in an area of 10 mm.times.10 mm and dried at
120.degree. C. to obtain a 6 .mu.m-thick coating film for forming a
porous layer. A pressure of 0.1 t/cm was applied onto the coating
film for forming a porous layer with a pressing machine. The reason
for adding the polymer component is to prevent the coating film for
forming a porous layer from clinging to a roll during pressing.
After the completion of pressing, the coating film for forming a
porous layer was burned at 500.degree. C. to obtain a layer for
forming a porous layer. Then, the layer for forming a porous layer
was immersed for 20 hours in a dye solution obtained by dissolving
a ruthenium complex (RuL.sub.2(NCS).sub.2 manufactured by Solaronix
SA) in anhydrous ethanol to achieve a concentration of
3.0.times.10.sup.-4 mol/L. After the completion of immersion, the
layer for forming a porous layer was pulled out of the dye
solution, washed with acetonitrile to remove the dye solution
adhered thereto, and air-dried. In this way, a
dye-sensitizer-supported porous layer was obtained.
[0262] (Solid Electrolyte Layer-Forming Step)
[0263] 10.0 g of PMIm-I and 0.24 g of I.sub.2 were added to and
dissolved in 3.64 g of EMIm-B(CN).sub.4 with stirring to obtain a
solution. Then, 28 g of a 5 wt % [[w %]] methanol solution of
cationic hydroxyl cellulose (Jellner QH-200.TM. manufactured by
Daicel Corporation) was added to the solution with stirring to
prepare a coatable composition for forming a solid electrolyte
layer.
[0264] Then, the composition for forming a solid electrolyte layer
was applied with a doctor blade onto the same region as a region
where the porous layer of the base material for dye-sensitized
solar cell was formed, and was then dried at 100.degree. C. to
provide a 4 .mu.m-thick solid electrolyte layer.
[0265] (Insulating Layer-Forming Step and Bonding Step)
[0266] Then, a 12 .mu.m-thick PET film (Lumirror T-25.TM.
manufactured by Toyobo Co., Ltd.) was provided as an insulating
layer so as to be interposed between the base material for
dye-sensitized solar cell and the counter electrode base material
in a region where the porous layer was not formed and the base
material for dye-sensitized solar cell and the counter electrode
base material overlapped one another (in the region of the
insulating layer 5 shown in FIG. 1A), and then the base material
for dye-sensitized solar cell and the counter electrode base
material were arranged so as to oppose to each other. Then, the
base material for dye-sensitized solar cell and the counter
electrode base material were pressure-bonded by heat sealing at
120.degree. C. using a 40 .mu.m-thick OPP film (P3162.TM.
manufactured by Toyobo Co., Ltd.) externally attached thereto. In
this way, a dye-sensitized solar cell was obtained
Example 2
[0267] A dye-sensitized solar cell was obtained in the same manner
as in Example 1 except that a 15 .mu.m-thick double-faced tape
(400P15.TM. manufactured by KGK Kyodo Giken Chemical Co., Ltd.) was
used in the insulating layer-forming step.
Example 3
[0268] A dye-sensitized solar cell was obtained in the same manner
as in Example 1 except that the area of the base material for
dye-sensitized solar cell was 10 mm.times.40 mm and the insulating
layer was provided at the position of the insulating layer 5 shown
in FIG. 3. Then, as shown in FIG. 3, 10 mm.times.10 mm
dye-sensitized solar cells were obtained by cutting the
dye-sensitized solar cell at cutting positions on the insulting
layer.
Example 4
[0269] A dye-sensitized solar cell was obtained in the same manner
as in Example 1 except that the porous layer was formed by applying
the coating liquid for forming a porous layer in a pattern onto a
30 mm.times.30 mm titanium foil in four 10 mm.times.10 mm areas and
the insulating layer was provided at the position of the insulating
layer 5 shown in FIG. 5. Then, as shown in FIG. 5, 10 mm.times.10
mm dye-sensitized solar cells were obtained by cutting the
dye-sensitized solar cell at cutting positions on the insulating
layer.
Example 5
[0270] A transparent conductive film obtained by forming an ITO
film on a PEN film was prepared as a base material for
dye-sensitized solar cell. The base material for dye-sensitized
solar cell had an area of 10 mm.times.40 mm. A counter electrode
base material was prepared by laminating platinum with a thickness
of 13 .ANG. (transmittance 72%) on a titanium foil used as a
counter base material.
[0271] The above-described coating liquid for forming a porous
layer was applied by a doctor blade method onto the surface of the
ITO film of the base material for dye-sensitized solar cell, and
was then dried at 120.degree. C. for 5 minutes to obtain a 4
.mu.m-thick coating film for forming a porous layer. Then, the
layer for forming a porous layer (coating liquid for forming a
porous layer) was immersed for 20 hours in a dye solution obtained
by dissolving a ruthenium complex (RuL.sub.2(NCS).sub.2
manufactured by Solaronix SA) in anhydrous ethanol to achieve a
concentration of 3.0.times.10.sup.-4 mol/L. After the completion of
immersion, the layer for forming a porous layer was pulled out of
the dye solution, washed with acetonitrile to remove the dye
solution adhered thereto, and air-dried. In this way, a
dye-sensitizer-supported porous layer was obtained.
[0272] Then, the above-described composition for forming a solid
electrolyte layer was applied with a doctor blade onto the same
region as a region where the porous layer of the base material for
dye-sensitized solar cell was formed, and was then dried at
100.degree. C. to provide a 4 .mu.m-thick solid electrolyte
layer.
[0273] Then, a dry lamination adhesive (manufactured by Toyo Ink
Group, adhesive AD-76PI.TM./curing agent CAT-RT85.TM.=100/7) was
applied with a doctor blade onto a region where the porous layer
was not provided and the base material for dye-sensitized solar
cell and the counter electrode base material overlapped one another
(onto the region of the insulating layer 5 shown in FIG. 3) and
dried at 100.degree. C. to provide a 8 .mu.m-thick insulating
layer. The base material for dye-sensitized solar cell and the
counter electrode base material were arranged so as to oppose to
each other and bonded together, and were then subjected to aging at
50.degree. C. for 7 days.
[0274] Then, similarly to Example 3, the thus obtained
dye-sensitized solar cell was cut at cutting positions shown in
FIG. 3 to obtain 10 mm.times.10 mm dye-sensitized solar cells.
Comparative Example 1
[0275] A dye-sensitized solar cell was produced in the same manner
as in Example 1 except that the insulating layer was omitted.
Comparative Example 2
[0276] Dye-sensitized solar cells were produced in the same manner
as in Example 4 except that the insulating layer was omitted.
[0277] [Evaluation]
[0278] The current-voltage characteristics of each of the
dye-sensitized solar cells produced in Examples 1 to 5 and
Comparative Examples 1 and 2 were measured by application of a
voltage with the use of AM 1.5 artificial sunlight (intensity of
incident light: 100 mW/cm.sup.2) as a light source and a source
measure unit (Keithley 2400 type).
[0279] The dye-sensitized solar cells produced in Examples 1 to 5
did not cause a short circuit and generated electric power without
problems. On the other hand, all the dye-sensitized solar cells
produced in Comparative Examples 1 and 2 caused a short
circuit.
REFERENCE SIGNS LIST
[0280] 1 Base material for dye-sensitized solar cell [0281] 1a Base
material [0282] 1b First electrode layer [0283] 2 Counter electrode
base material [0284] 2a Counter base material [0285] 2b Second
electrode layer [0286] 3 Solid electrolyte layer [0287] 4 Porous
layer [0288] 5 Insulating layer [0289] 10 Dye-sensitized solar cell
[0290] 20 Multifaceted member [0291] 30 Dye-sensitized solar cell
module
* * * * *