JP2001338700A - Pigment sensitizing solar cell - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a solar cell with macromolecular solid electrolyte which has excellent liquid preserving property and mechanical strength. SOLUTION: The pigment sensitization type solar cell installs a macromolecular solid electrolyte of which, electrolyte is stably preserved in a macromolecular compound with three dimensional bridge bond. The electrolyte is preserved in the macromolecular compound composed of unit constituent monomers shown by the formula (I), (where; R1 and R2, which can be either same with or different from each other, are hydrogen atom or methyl group, and A is a bonding position or a group with two valence derived from (poly) oxyalkylene group, and n is an integer of 0-2).

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention relates to a dye-sensitized solar cell using a solid polymer electrolyte. More specifically,
The present invention relates to a dye-sensitized solar cell using a three-dimensionally crosslinked polymer compound containing a structural unit formed from a monomer having a specific structure.

[0002]

2. Description of the Related Art Dye-sensitized solar cells (hereinafter referred to as "solar cells") have received widespread attention because of their high conversion efficiency among organic solar cells. A solar cell is composed of an electrolyte layer sandwiched between a semiconductor electrode and a counter electrode.When light is irradiated on the semiconductor electrode, electrons are excited on the electrode side, and the excited electrons form an electric circuit. Then, the electrons move to the counter electrode, and the electrons that have moved to the counter electrode move as ions in the electrolyte and return to the semiconductor electrode, and electric energy is extracted by repeating such a cycle.

As a semiconductor electrode used as a photoelectric conversion material of a solar cell, a semiconductor electrode having a spectral sensitizing dye having absorption in a visible light region adsorbed on a semiconductor surface is used.
As such a solar cell, for example, a solar cell using a metal oxide semiconductor in which a spectral sensitizing dye composed of a transition metal complex is adsorbed on a semiconductor surface (Japanese Patent No. 2664194)
), A solar cell having a spectral sensitizing dye layer such as a transition metal complex on the surface of a titanium oxide semiconductor doped with metal ions (Japanese Patent Publication No. 8-15097), and heating and refluxing an ethanol solution of a spectral sensitizer on the semiconductor surface Cell using the semiconductor for a photoelectric conversion material obtained by the
249790).

FIG. 2 is a schematic sectional view of a main part showing a layer structure of a conventional solar cell using an oxidation-reduction electrolyte. This solar cell is manufactured by the following procedure. First, a semiconductor electrode 23 such as titanium oxide is formed on a transparent conductor 22 formed on the surface of a transparent support 21, and a dye is adsorbed on the semiconductor electrode 23. The counter electrode 25 is coated with a catalyst such as platinum 26, and the transparent support 21 and the counter electrode 25 are overlapped so that the semiconductor electrode 23 and the platinum 26 face each other.
In the meantime, the electrolyte 24 is injected and the transparent support 21 and the counter electrode 2
5 is sealed with an epoxy resin 27 or the like.

Japanese Patent Application Laid-Open Nos. 8-236165 and 9-27352 disclose a general formula (III) in order to prevent electrolyte leakage.

[0006]

Embedded image

Wherein R ⁴ and R ⁵ are the same or different and each is a hydrogen atom or a methyl group, R ⁶ is a hydrogen atom or a lower alkyl group, m is an integer of 1 or more, and 1 is 0
A solar cell in which a layer of an electrolytic solution is solidified with a polymer compound containing a structural unit formed from a monomer represented by the following formula (1 / m is a range of 0 to 5): I have.

However, in the solar cell described in the above-mentioned publication, the ability to hold the electrolyte and the electrolytic solution with respect to the polymer compound and the mechanical strength of the polymer compound were not sufficient.

[0009]

SUMMARY OF THE INVENTION An object of the present invention is to provide a solar cell provided with a polymer solid electrolyte having excellent liquid holding power and mechanical strength.

[0010]

Means for Solving the Problems The inventors of the present invention have conducted intensive studies to solve the above-mentioned problems, and as a result, a three-dimensionally crosslinked polymer compound obtained by polymerizing a specific monomer has been found to be an electrolyte. The present invention has been found to exhibit excellent holding power and mechanical strength with respect to the present invention, and has completed the present invention.

Thus, according to the present invention, in a solar cell having a porous semiconductor layer in which a dye is adsorbed and an electrolyte between a transparent conductive film formed on the surface of the transparent substrate and the conductive substrate, the electrolyte is General formula (I):

[0012]

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Wherein R ¹ and R ² are the same or different and each is a hydrogen atom or a methyl group, A is a bond or a divalent group derived from a (poly) alkyleneoxy group, and n is (It is an integer of 0 to 2) provided by a polymer compound including a structural unit formed from a monomer represented by the formula (1):

[0014]

BEST MODE FOR CARRYING OUT THE INVENTION The polymer compound of the present invention has a three-dimensional cross-linking structure, and has excellent liquid holding power and mechanical strength for an electrolyte of a solar cell. Or a monomer represented by the general formula (I) and another methacrylic acid-based monomer and / or an acrylic acid-based monomer (hereinafter, referred to as “(meth) acrylic acid-based monomer”) Is obtained by (co) polymerization. When n in the general formula (I) is 0, it represents a bond.

Examples of the monomer in which A of the general formula (I) is a bond include glycyl methacrylate, tetrahydrofurfuryl acrylate (tetrahydrofurfuryl acrylate), tetrahydrofurfuryl methacrylate and the like.

A monomer wherein A in the general formula (I) is a divalent group derived from a (poly) alkyleneoxy group;
In particular, formula (II) wherein A is derived from (poly) ethyleneoxy and (poly) propyleneoxy groups:

[0017]

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(Wherein a and b are the same or different and are 0 or a positive integer, and R ³ is a hydrogen atom or a methyl group). In the general formula (I), R ¹ is a methyl group, R ² is a hydrogen atom, A is a divalent group derived from eight ethyleneoxy groups and two propyleneoxy groups (a in the formula (II) is 8, b is 2) and n is 1.

The monomer represented by the general formula (I) is preferable because it has a good affinity for propylene carbonate or ethylene carbonate which is a typical solvent used for the electrolytic solution. Further, a polymer compound obtained by polymerizing such a monomer is preferable since it has excellent ability to retain an electrolyte.

As the (meth) acrylic acid-based monomer to be copolymerized with the monomer of the general formula (I), any commercially available monomer can be used. Specifically, methyl methacrylate, ethyl methacrylate, n-butyl methacrylate, isobutyl methacrylate, 2-ethylhexyl methacrylate, lauryl methacrylate, benzyl methacrylate, tridecyl methacrylate, stearyl methacrylate, cyclohexyl methacrylate and the like Methacrylic acid monomers, isobornyl acrylate, dimethylaminoethyl acrylate, isobutyl acrylate, cetyl acrylate (hexadecyl acrylate), 4-hydroxybutyl acrylate, t-butyl acrylate, 2-methoxyethyl acrylate, Acrylic monomers such as 3-methoxybutyl acrylate and lauryl acrylate are exemplified.

Of these, methyl methacrylate, ethyl methacrylate, lauryl methacrylate, stearyl methacrylate, isobutyl acrylate, cetyl acrylate, 3-methoxybutyl acrylate, and lauryl acrylate are particularly preferred.

The ratio of the monomer of the general formula (I) to the (meth) acrylic acid-based monomer varies depending on the type of each monomer and the combination thereof, and is appropriately determined according to the crosslinking properties of the polymer compound and the performance required for the solar cell. do it. Usually, the (meth) acrylic acid-based monomer (Y) is used in an amount of 50 to 98 mol based on the monomer (X) of the general formula (I).
%, That is, the molar ratio of X: Y is about 1: 1 to 49.

The solid polymer electrolyte is mainly composed of a polymer compound and an electrolyte injected into the polymer compound. The electrolyte is not particularly limited as long as it is an electrolyte that can be generally used in batteries and solar cells. Further, the electrolyte in the electrolyte is preferably an oxidation-reduction electrolyte, which is not particularly limited as long as it can be generally used in batteries and solar cells.
A combination of a metal iodide such as I and CaI ₂ with iodine, and a combination of a metal bromide such as LiBr, NaBr, KBr, and CaBr ₂ with bromine are preferred. Among these, a combination of a metal iodide and iodine is preferred.

The concentration of the electrolyte may be in the range of 0.1 to 1.5 mol / liter.
0.7 mol / l is preferred. Examples of the solvent for the electrolyte include carbonate compounds such as propylene carbonate, nitrile compounds such as acetonitrile, alcohols such as ethanol, and other substances such as water and aprotic polar substances. Among these, carbonate compounds and nitrile compounds Is preferred.

To inject the electrolyte into the polymer compound,
The polymer compound may be immersed in an electrolyte solution in which the electrolyte is dissolved in a solvent such as polycarbonate, and the electrolyte solution may be permeated into the polymer compound. The permeation time is about 2 hours, but it is preferable to set the permeation temperature high because the electrolyte solution is activated and the permeation speed is increased, and the time required for producing the polymer solid electrolyte can be shortened. The infiltration temperature needs to be suppressed to such an extent that a radical reaction does not occur.
It is about 5 ° C.

In a solar cell, the conversion efficiency is deteriorated unless the solid polymer electrolyte is sufficiently injected into the porous semiconductor. For this reason, the porous semiconductor is usually impregnated with a liquid monomer, and in some cases, a monomer dissolved in a ketone-based solvent, a carbonate-based solvent, or the like, and then subjected to radical polymerization.

As the polymerization method, photopolymerization or thermal polymerization is applied. In solar cells, titanium oxide is often used for a porous semiconductor. Titanium oxide is a substance that causes a photocatalytic reaction in the ultraviolet region, so if ultraviolet light is irradiated during photopolymerization, a photocatalytic reaction occurs, which may cause problems such as decomposition of the dye adsorbed on the porous semiconductor. Therefore, the polymerization is preferably performed by thermal polymerization.

Usually, thermal polymerization is carried out by heating using a polymerization initiator, and the concentration of the polymerization initiator and the heating temperature are appropriately determined depending on the monomer used. Generally, the polymerization rate in radical polymerization is proportional to the 0.5th power of the concentration of the polymerization initiator, so that when the concentration of the polymerization initiator is low, the polymerization time becomes extremely long. Therefore, the concentration of the polymerization initiator is preferably about 0.5 to 10% by weight based on the monomer.

Examples of the porous semiconductor constituting the porous semiconductor layer include known semiconductors such as titanium oxide, zinc oxide, tungsten oxide, barium titanate, strontium titanate, and cadmium sulfide. These porous semiconductors can be used as a mixture of two or more kinds. Among them, titanium oxide is particularly preferred from the viewpoint of conversion efficiency, stability and safety. As such a titanium oxide,
Various titanium oxides such as anatase-type titanium oxide, rutile-type titanium oxide, amorphous titanium oxide, metatitanic acid, and orthotitanic acid, and a titanium-oxide-containing composite are exemplified, and any of these may be used.

As the porous semiconductor, various forms such as a particle form and a film form can be used, but a film form porous semiconductor formed on a substrate is preferable. As a substrate when forming a film-shaped porous semiconductor, for example, a glass substrate,
A plastic substrate and the like can be mentioned, and among them, a highly transparent substrate (transparent substrate) is particularly preferable.

As a method for forming a film-like porous semiconductor on a substrate, various known methods can be used. Specifically, a method of applying a suspension containing semiconductor particles on a substrate, followed by drying and baking, and a method of forming a semiconductor film on a substrate by a CVD method or a MOCVD method using a desired source gas. , And P using raw material solids
Examples include a method of forming a semiconductor film by a VD method, an evaporation method, a sputtering method, a sol-gel method, or the like.

Although the thickness of the porous semiconductor is not particularly limited, it may be from the viewpoint of transparency, conversion efficiency, and the like.
It is preferably about 5 to 20 μm. Further, in order to improve the conversion efficiency, it is necessary to make the film-shaped porous semiconductor adsorb a larger amount of the dye described below. For this reason, the film-like porous semiconductor preferably has a large specific surface area,
Specifically, it is preferably about 10 to 200 m ² / g.

Examples of the semiconductor particles include commercially available particles having a suitable average particle diameter, for example, particles of a single or compound semiconductor having a diameter of about 1 nm to 500 nm. Examples of the solvent used for suspending the semiconductor particles include grime solvents such as ethylene glycol monomethyl ether, alcohol solvents such as isopropyl alcohol, mixed solvents such as isopropyl alcohol / toluene, and water. .

Drying and baking of the porous semiconductor in the method for forming a film-like porous semiconductor are performed by appropriately adjusting conditions such as temperature, time and atmosphere depending on the type of substrate and semiconductor particles used. For example, in the range of about 50 to 800 ° C. in the atmosphere or in an inert gas atmosphere, for 10 seconds to 1 hour.
It can be performed for about 2 hours. The drying and baking can be performed once at a single temperature or twice or more at different temperatures.

The transparent conductive film that can be used as an electrode is not particularly limited.
A transparent conductive film such as SnO ₂ is preferred. The manufacturing method, the film thickness, and the like of these electrodes can be appropriately selected.

A dye functioning as a photosensitizer (hereinafter referred to as "dye") is adsorbed on the porous semiconductor. As the method, for example, there is a method of immersing a porous semiconductor film formed on a substrate in a solution in which a dye is dissolved.

The dye used has an absorption in various visible light regions and infrared light regions, and a carboxyl group or a carboxyl group is contained in the dye molecule in order to strongly adsorb the semiconductor layer.
Those having an interlock group such as an alkoxy group, a hydroxyl group, a hydroxyalkyl group, a sulfonic acid group, an ester group, a mercapto group and a phosphonyl group are preferred.

The interlocking group provides an electrical bond that facilitates electron transfer between the dye in the excited state and the conduction band of the semiconductor. Examples of dyes containing these interlock groups include, for example, ruthenium bipyridine dyes, azo dyes, quinone dyes, quinone imine dyes,
Quinacridone dyes, squarylium dyes, cyanine dyes, merocyanine dyes, triphenylmethane dyes, xanthene dyes, porphyrin dyes, phthalocyanine dyes, berylen dyes, indigo dyes, naphthalocyanine dyes, and the like. .

The solvent for dissolving the dye is not particularly limited as long as it can dissolve the dye, and examples thereof include alcohols such as ethanol, ketones such as acetone, ethers such as diethyl ether and tetrahydrofuran, and nitrogen such as acetonitrile. Compounds, halogenated aliphatic hydrocarbons such as chloroform, aliphatic hydrocarbons such as hexane,
Examples include aromatic hydrocarbons such as benzene and toluene, esters such as ethyl acetate, and water. These solvents can be used as a mixture of two or more kinds.

The concentration of the dye in the solution can be appropriately adjusted depending on the types of the dye and the solvent to be used, but it is preferable that the concentration is as high as possible in order to improve the adsorption function. The dye concentration may be, for example, 5 × 10 ⁻⁵ mol / liter or more.

The conditions for immersing the solution in which the dye is dissolved in the semiconductor, such as the solution temperature, the ambient temperature and the pressure, are not particularly limited, and include, for example, about room temperature and atmospheric pressure. The immersion time can be appropriately adjusted depending on the type of the dye and the solvent to be used, the concentration of the solution, and the like. In order to effectively perform the immersion, the immersion may be performed under heating at or below the boiling point of the solvent used. This is preferable because the dye is easily adsorbed on the porous semiconductor.

[0042]

EXAMPLES The present invention will be described more specifically with reference to examples, but the present invention is not limited by these examples.

Example 1 A solar cell using a solid polymer electrolyte was manufactured by the manufacturing procedure shown in FIGS. 1 (a) to 1 (e). In FIG. 1, 1 is a transparent substrate, 2 is a transparent conductive film, 3 is a titanium oxide film, 4 is a separator, and 5 is PET.
Film, 6 a press plate, 7 a polymer monomer, 8 a polymer compound, 9 an electrolyte, 10 a container, 11 a sealant,
Reference numeral 12 denotes a platinum film, and 13 denotes a conductive substrate.

First, a coating liquid for preparing a titanium oxide film 3 as a porous semiconductor layer was prepared. That is, commercially available titanium oxide particles (manufactured by Teica Co., Ltd., trade name: AMT-6)
00, anatase type crystal, average particle size 30 nm, specific surface area 50 m ^{2 /} g) 4.0 g and diethylene glycol monomethyl ether 20 ml were dispersed in glass paint for 6 hours using a paint shaker to obtain a titanium oxide suspension. Was prepared.

An SnO ₂ film was formed as a transparent conductive film 2 on a glass substrate as a transparent substrate 1 (FIG. 1A).
Next, the prepared titanium oxide suspension was applied to the transparent conductive film 2 side of the transparent substrate 1 with a doctor blade, and the film thickness was 10 μm.
m, and a coating film having an area of about 10 mm × 10 mm was obtained. The coating film was pre-dried at 100 ° C. for 30 minutes, and baked at 460 ° C. for 40 minutes in an oxygen atmosphere to obtain a titanium oxide film 3 having a thickness of about 8 μm.

Next, a ruthenium dye (Solaroni)
x, trade name: Ruthenium 535) was dissolved in anhydrous ethanol to prepare a dye solution for adsorption having a dye concentration of 4 × 10 ⁻⁴ mol / l. The transparent substrate 1 provided with the transparent conductive film 2 and the titanium oxide film 3 was immersed in the prepared dye solution for adsorption for about 4 hours, so that the dye was adsorbed on the titanium oxide film 3. Thereafter, the transparent substrate 1 was washed several times with anhydrous ethanol and dried at about 60 ° C. for about 20 minutes (FIG. 1).
(B)).

Next, R ^{1 in the} general formula (I) is a methyl group, R ²
Is a hydrogen atom, and A is a divalent group derived from eight ethyleneoxy groups and two propyleneoxy groups (a in the formula (II)
Is dissolved in propylene carbonate (hereinafter referred to as “PC”) so that the monomer concentration becomes 20 wt%, and azobisisobuty is used as a thermal polymerization initiator. Ronitrile (AIBN) was added and dissolved to a concentration of 1 wt% with respect to the monomer to prepare a monomer solution.

The titanium oxide film 3 was impregnated with the obtained monomer solution in the following procedure. A beaker was set in a vacuum vessel, and the transparent substrate 1 provided with the transparent conductive film 2 and the titanium oxide film 3 was put therein, and evacuated by a rotary pump for about 10 minutes. The monomer solution is poured into a beaker while maintaining the vacuum state in the vacuum vessel, and is maintained for about 15 minutes.
The monomer solution was sufficiently impregnated therein. A separator 4 made of polyethylene, a PET (polyethylene terephthalate) film 5 and a holding plate 6 were placed on the transparent substrate 1 and fixed with a jig. Next, the monomer was thermally polymerized by heating the transparent substrate 1 at about 85 ° C. for 30 minutes to obtain a polymer compound 8 insoluble in an organic solvent (FIG. 1C).

Next, an electrolytic solution 9 for impregnating the polymer compound 8 was prepared. That is, when lithium iodide has a concentration of 0.5
Mol / liter and iodine at a concentration of 0.0
Lithium iodide and iodine were dissolved in PC so as to be 5 mol / l.

The transparent substrate 1 on which the polymer compound 8 was formed was immersed in the obtained electrolytic solution 9 at an infiltration temperature of 50 ° C. for 1 hour.
The electrolyte solution 9 was sufficiently impregnated into the polymer compound 8 to prepare a polymer solid electrolyte (FIG. 1D).

Next, the side of the titanium oxide film 3 of the transparent substrate 1 on which the polymer solid electrolyte was prepared and the side of the platinum film 12 of the conductive substrate 13 provided with the platinum film 12 were put together, and the surroundings were sealed with an epoxy sealant 11. Was sealed (FIG. 1 (e)).

As described above, a solar cell using the solid polymer electrolyte of the present invention was obtained. When the performance of the obtained solar cell was measured under the measurement conditions: AM-1.5, the short-circuit current was 17.6 [mA / cm ² ], the open-circuit voltage was 0.6 [V],
Fill factor 0.68, conversion efficiency 7.3 [%]
Met. These performances were equivalent to a solar cell in which the electrolyte was not solidified.

From the above, the solar cell of the present invention has the same performance as the conventional solar cell, and has a liquid holding power superior to that of the conventional solar cell using the solid polymer electrolyte, due to the structure of the monomer used. High mechanical strength can be expected.

(Examples 2 to 4) A solar cell was produced and its conversion efficiency was measured in the same manner as in Example 1 except that the monomers of the general formula (I) were changed to those shown in Table 1. The results are shown in Table 1 together with the monomer of the general formula (I).

[0055]

[Table 1]

From the results in Table 1, it can be seen that the conversion efficiency of the solar cell is changed by replacing the monomer, and that the monomer has a three-membered ring of glycyl methacrylate (when n in the general formula (I) is 0). Also, it can be seen that tetrahydrofurfuryl (meth) acrylate in which the monomer has a 5-membered ring (when n in the general formula (I) is 2) can obtain higher conversion efficiency. This is thought to be because the size of the ring has an effect on the conversion efficiency of the solar cell because the monomer having a ring opens during polymerization.

Examples 5 to 12 As polymer compounds,
A solar cell was prepared and the conversion efficiency was measured in the same manner as in Example 1, except that a copolymer of the monomer of the general formula (I) and the (meth) acrylic acid-based monomer shown in Table 2 was used. The results are shown in Table 2 together with the monomer of the general formula (I) and the (meth) acrylic acid-based monomer.

[0058]

[Table 2]

From the results shown in Table 2, it can be seen that the longer the side chain of the (meth) acrylic acid monomer copolymerized with the monomer of the general formula (I), the higher the conversion efficiency can be obtained. This is considered to be related to the fact that the longer the side chain of the monomer, the higher the swelling property of the solid polymer electrolyte.

[0060]

The solar cell of the present invention has a solid polymer electrolyte having the same level of ionic conductivity as an electrolyte in which a large amount of the electrolyte is stably retained in a three-dimensionally crosslinked polymer compound. . Therefore, the present invention can provide a solar cell having the same performance as a solar cell using an electrolytic solution and having excellent mechanical strength.

[Brief description of the drawings]

FIG. 1 is a schematic cross-sectional view of a solar cell according to a manufacturing procedure of the solar cell of the present invention.

FIG. 2 is a schematic sectional view of a main part showing a layer structure of a conventional solar cell.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Transparent substrate 2 Transparent conductive film 3 Titanium oxide film 4 Separator 5 PET film 6 Press plate 7 Polymer monomer 8 Polymer compound 9, 24 Electrolyte 10 Container 11 Sealant 12 Platinum film 13 Conductive substrate 21 Transparent support 22 Transparent conductor 23 Semiconductor electrode 25 Counter electrode 26 Platinum 27 Epoxy resin

 ────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Kazuhiro Enomoto 22-22, Nagaikecho, Abeno-ku, Osaka-shi, Osaka F-term (reference) 4J100 AL03Q AL04Q AL05Q AL08P AL08Q AL09Q BA05Q BA08P BA09P BC54P CA04 FA03 5F051 AA11 AA14 FA02 FA06 5H032 AA06 AS16 CC17 EE04 EE08 EE16

Claims (5)

[Claims] 1. A dye-sensitized solar cell having a porous semiconductor layer in which a dye is adsorbed and an electrolyte between a conductive film and a transparent conductive film formed on the surface of the transparent substrate, wherein the electrolyte has a general formula (I): Wherein R ¹ and R ² are the same or different and are a hydrogen atom or a methyl group, A is a bond or a divalent group derived from a (poly) alkyleneoxy group, and n is 0
A dye-sensitized solar cell, which is held by a polymer compound containing a structural unit formed from a monomer represented by the following formula: 2. A of the general formula (I) is represented by the formula (II): (Where a and b are the same or different and are 0 or a positive integer, and R ³ is a hydrogen atom or a methyl group)
The dye-sensitized solar cell according to claim 1, which is a divalent group represented by the formula: 3. The dye sensitizer according to claim 1, wherein the polymer compound is a copolymer of a monomer represented by the general formula (I) and a methacrylic acid-based monomer and / or an acrylic acid-based monomer. Sensitive solar cell. 4. The dye-sensitized solar cell according to claim 1, wherein the porous semiconductor layer is made of titanium oxide. 5. The dye-sensitized solar cell according to claim 1, wherein the electrolyte comprises iodine and an iodine compound.