JP2006331791A - Separator for dye-sensitized solar cell, and its utilization - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a separator composed of a thin insulating porous film optimum as the separator of a film made dye-sensitized solar cell in particular, and to provide a counter-electrode and a semiconductor electrode for a dye-sensitized solar cell in which this separator is integrated. <P>SOLUTION: This is the separator for the dye-sensitized solar cell composed of the insulating porous film formed by an electro-spinning method. The counter electrode 10A and the semiconductor electrode 10B for a separator integrated dye-sensitized solar cell in which these separators 13A, 13B are formed on the surface. By depositing insulating polymer compounds in a fiber state by the electro-spinning method, the thin insulating porous film which is porous enough for an electrolytic solution to pass freely, which has sufficient insulation property to prevent short-circuit between the electrodes effectively, and which does not damage thin-wall forming property of a film-type solar cell can be formed easily. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention comprises a dye-sensitized semiconductor electrode, a counter electrode provided facing the dye-sensitized semiconductor electrode, and an electrolyte disposed between the dye-sensitized semiconductor electrode and the counter electrode. In a dye-sensitized solar cell having a separator, a separator disposed between a semiconductor electrode and a counter electrode to prevent an electrical short circuit between the two electrodes, and a counter electrode for a separator provided with this separator integrally And a semiconductor electrode and a dye-sensitized solar cell including such a separator, a counter electrode, or a semiconductor electrode.

  It is already known that a solar cell is configured using an oxide semiconductor adsorbed with a sensitizing dye as an electrode. FIG. 3 is a sectional view showing a general structure of such a dye-sensitized solar cell. As shown in FIG. 3, a transparent conductive film 2 such as FTO (fluorine-doped tin oxide) or ITO (indium tin oxide) is provided on a substrate 1 such as a glass substrate, and a spectral sensitizing dye is formed on the transparent conductive film 2. As a result, the dye-sensitized semiconductor electrode 4 is formed. A counter electrode 5 is disposed opposite to the dye-adsorbing semiconductor film 3 with a space therebetween, and an electrolyte 7 is sealed between the dye-sensitized semiconductor electrode and the counter electrode 5 by a sealing material 6.

  The dye-adsorbing semiconductor film 3 is usually composed of a titanium oxide thin film to which a dye is adsorbed, and this titanium oxide film is formed by a sol-gel method. The dye adsorbed on the titanium oxide thin film is excited by visible light, and power is generated by passing the generated electrons to the titanium oxide fine particles.

  The counter electrode 5 has a transparent conductive film such as ITO or FTO formed on a substrate such as glass or plastic, and promotes the transfer of electrons between the transparent conductive film and the sensitizing dye on the transparent conductive film. The platinum film as the catalyst is formed to a thickness that does not decrease the transmittance.

As the electrolyte 7, redox substances, for example, LiI, NaI, KI, combinations of metal iodides and iodine, such as CaI _2, LiBr, NaBr, KBr, the metal bromide and bromine, such as CaBr ₂ combination, preferably Uses an electrolytic solution obtained by dissolving a redox substance composed of a combination of metal iodide and iodine in a solvent such as a carbonate compound such as propylene carbonate and a nitrile compound such as acetonitrile.

  In such a dye-sensitized solar cell, when the semiconductor electrode and the counter electrode are in electrical contact with each other, they are short-circuited inside and do not function as a solar cell. In particular, in recent years, for the purpose of reducing the thickness, size, and weight of solar cells, film-type solar cells using resin films have been developed as substrates for semiconductor electrodes and counter electrodes of dye-sensitized solar cells. In the case of such a film type solar cell, a short circuit between the electrodes tends to occur due to deformation of the film. Therefore, a separator for preventing electrical conduction is required between the semiconductor electrode and the counter electrode. This separator is required to have sufficient insulating properties and porosity that allows the electrolytic solution to pass through freely. Further, the separator is required to be thin enough not to impair the thinness of the film type solar cell.

  However, with the conventional technology, it has been extremely difficult to form an insulating thin film while maintaining sufficient porosity. In addition, in a film independent as a separator, it is necessary to combine at least three members of a semiconductor electrode, a counter electrode, and a separator at the time of assembling a solar cell, and there is a problem that the assembling work becomes complicated.

  The present invention solves the above-mentioned conventional problems, and in particular, a separator comprising a thin insulating porous film suitable as a separator for a film-type dye-sensitized solar cell, and a dye-sensitized solar cell in which this separator is integrated It is an object to provide a counter electrode for a separator and a semiconductor electrode, and a dye-sensitized solar cell using the separator, the counter electrode, or the semiconductor electrode.

  The separator for a dye-sensitized solar cell of the present invention (invention 1) is characterized by having an insulating porous film formed by an electrospinning method.

  The separator for a dye-sensitized solar cell according to claim 2 is the separator according to claim 1, wherein the insulating material constituting the insulating porous film is a polyolefin polymer compound, a polyester polymer compound, an acrylic polymer compound, It is characterized by being one or more transparent polymer materials selected from the group consisting of nylon polymer compounds and fluorine polymer compounds.

The separator for a dye-sensitized solar cell according to claim 3 is characterized in that the basis weight is 0.5 to 50 mg / cm ² in claim 1 or 2.

  The counter electrode for a separator-integrated dye-sensitized solar cell of the present invention (Claim 4) is a counter electrode disposed facing the dye-sensitized semiconductor electrode via an electrolyte in the dye-sensitized solar cell. The separator according to any one of claims 1 to 3 is provided on a surface facing the semiconductor electrode.

  The separator-integrated dye-sensitized solar cell semiconductor electrode according to claim 5 is a semiconductor electrode of a dye-sensitized solar cell, and the semiconductor film surface of the semiconductor electrode is any one of claims 1 to 3. It is characterized by providing the separator of description.

  The dye-sensitized solar cell of the present invention (invention 6) includes a dye-sensitized semiconductor electrode, a counter electrode provided facing the dye-sensitized semiconductor electrode, and the dye-sensitized semiconductor electrode. In the dye-sensitized solar cell having an electrolyte disposed between the counter electrode and the counter electrode, the separator for the dye-sensitized solar cell of the present invention is disposed between the counter electrode and the semiconductor electrode. It is characterized by.

  The dye-sensitized solar cell of the present invention (invention 7) includes a dye-sensitized semiconductor electrode, a counter electrode provided facing the dye-sensitized semiconductor electrode, the dye-sensitized semiconductor electrode, A dye-sensitized solar cell having an electrolyte disposed between the counter electrode and the counter electrode is characterized in that the counter electrode is the counter electrode for a separator-integrated dye-sensitized solar cell of the present invention.

  The dye-sensitized solar cell of the present invention (invention 8) includes a dye-sensitized semiconductor electrode, a counter electrode provided facing the dye-sensitized semiconductor electrode, and the dye-sensitized semiconductor electrode. A dye-sensitized solar cell having an electrolyte disposed between the counter electrode and the counter electrode, wherein the semiconductor electrode is the semiconductor electrode for a separator-integrated dye-sensitized solar cell according to the present invention.

  According to the present invention, a separator made of a thin insulating porous film particularly suitable as a separator for a film-type dye-sensitized solar cell, a counter electrode for a dye-sensitized solar cell separator integrated with the separator, and A dye-sensitized solar cell using a semiconductor electrode and these separators, a counter electrode, or a semiconductor electrode is provided.

  That is, by depositing an insulating polymer compound in a fibrous form by electrospinning, it is porous enough to allow the electrolyte to pass freely, and can effectively prevent a short circuit between the electrodes. Therefore, it is possible to easily form a thin insulating porous film that has sufficient insulation and does not impair the thinness of the film-type solar cell. Thus, the fiber diameter, film thickness, porosity (weight per unit area), etc. can be freely controlled by appropriately designing the conditions for depositing the polymer compound in the fibrous form by electrospinning. In addition, it is possible to easily produce an optimum separator adapted to the viscosity of the electrolytic solution and the electrode configuration.

  It is also easy to directly form such a fibrous insulating polymer compound deposition layer on the surface of the counter electrode or the semiconductor electrode. In this case, as the separator integrated counter electrode or the separator integrated semiconductor electrode, It is possible to reduce the number of assembly members during battery assembly and simplify the solar cell assembly process.

  Therefore, according to the present invention, an unprecedented thin insulating porous membrane separator effectively prevents a short circuit between electrodes in a dye-sensitized solar cell, particularly a film-type solar cell, and provides a highly reliable dye. In addition to providing a sensitized solar cell, it is possible to increase productivity by simplifying the solar cell manufacturing process when such a separator is used.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
FIG. 1A is a schematic cross-sectional view showing an embodiment of a counter electrode for a separator-integrated dye-sensitized solar cell of the present invention, and FIG. 1B is a separator-integrated dye-sensitized method of the present invention. It is typical sectional drawing which shows embodiment of the semiconductor electrode for type | mold solar cells. FIG. 2 is a configuration diagram illustrating a general electrospinning apparatus.

  In the separator-integrated counter electrode 10A of FIG. 1A, a transparent conductive film 12A is formed on a substrate 11A, and a catalyst film (not shown) such as a platinum thin film is formed on the transparent conductive film 12A. Further thereon, a separator layer 13A made of a deposited layer of fibrous insulating transparent polymer material is formed.

  In the separator-integrated semiconductor electrode 10B of FIG. 1B, a transparent conductive film 12B is formed on a base material 11B, and a semiconductor film 14 on which a spectral sensitizing dye is adsorbed is formed on the transparent conductive film 12B. A separator layer 13B made of a deposited layer of a fibrous insulating transparent polymer material is formed on the dye-adsorbing semiconductor film 14.

  As the base materials 11A and 11B of the separator-integrated counter electrode 10A and the separator-integrated semiconductor electrode B, glass or plastic such as PET, PEN, PES, polyimide, fluororesin is usually used, and the thickness is 20 μm to Although it is about 5 mm, the present invention is particularly effective for a film-type solar cell in which a plastic film having a thickness of about 50 to 200 μm is used as an electrode base material for the reasons described above.

As the transparent conductive films 12A and 12B, conductive metal oxide thin films of In ₂ O ₃ or SnO ₂ or conductive thin films such as metals are used. Preferable examples of the conductive metal oxide include In ₂ O ₃ : Sn (ITO), SnO ₂ : Sb, SnO ₂ : F (FTO), ZnO: Al, ZnO: F, CdSnO _{4 and the} like. . In addition, as a transparent conductive film, you may laminate | stack these 2 or more types of transparent conductive films, and may mix and use 2 or more types of materials.

  There is no restriction | limiting in particular in the formation method of transparent conductive film 12A, 12B, Sputtering method, a laser vapor deposition method, CVD method etc. are employ | adopted. The transparent conductive films 12A and 12B are usually formed to a thickness of about 100 to 1000 nm.

  A platinum thin film (not shown) formed on the transparent conductive film 12A of the separator-integrated counter electrode 10A is usually formed to a thickness of about 0.2 to 10 nm so as not to impair the transparency. A carbon thin film may be formed instead of the platinum thin film.

  In the separator-integrated semiconductor electrode 10B, a metal oxide semiconductor film is usually used as the semiconductor film of the dye-adsorbing semiconductor film 14, and the metal oxide includes titanium oxide, zinc oxide, tungsten oxide, antimony oxide, and oxide. One or more known metal oxide semiconductors such as niobium, tungsten oxide, and indium oxide can be used. In particular, titanium oxide is preferable from the viewpoint of stability and safety.

  There is no restriction | limiting in particular in the formation method of such a metal semiconductor film, Sputtering method, laser vapor deposition method, CVD method etc. are employ | adopted. The semiconductor film is usually formed to a thickness of about 0.1 to 10 μm.

  The organic dye (spectral sensitizing dye) adsorbed on the metal oxide semiconductor film has absorption in the visible light region and / or infrared light region, and one or two of various metal complexes and organic dyes. More than seeds can be used. Those having a functional group such as a carboxyl group, a hydroxyalkyl group, a hydroxyl group, a sulfone group, and a carboxyalkyl group in the molecule of the spectral sensitizing dye are preferable because adsorption onto a semiconductor is fast. Moreover, since it is excellent in the effect of spectral sensitization and durability, a metal complex is preferable. As a metal complex, a metal phthalocyanine such as copper phthalocyanine or titanyl phthalocyanine, a complex of chlorophyll, hemin, ruthenium, osmium, iron or zinc described in JP-A-1-220380 and JP-A-5-504023 Can do. As the organic dye, metal-free phthalocyanine, cyanine dye, merocyanine dye, xanthene dye, and triphenylmethane dye can be used. Specific examples of cyanine dyes include NK1194 and NK3422 (both manufactured by Nippon Sensitive Dye Research Co., Ltd.). Specific examples of merocyanine dyes include NK2426 and NK2501 (both manufactured by Nippon Sensitive Dye Research Laboratories). Specific examples of xanthene dyes include uranin, eosin, rose bengal, rhodamine B, and dibromofluorescein. Specific examples of the triphenylmethane dye include malachite green and crystal violet.

  In order to adsorb the organic dye (spectral sensitizing dye) to the semiconductor film, the metal oxide semiconductor film is attached to the substrate at room temperature or under heating in an organic dye solution prepared by dissolving the organic dye in an organic solvent. What is necessary is just to immerse. The solvent of the solution is not particularly limited as long as it can dissolve the spectral sensitizing dye to be used. Specifically, water, alcohol, toluene, and dimethylformamide can be used.

In the present invention, the separator layers 13A and 13B are formed by an electrospinning method.
The electrospinning method is a well-known method for forming fibers using electric force. As shown in FIG. 2, the substrate to be treated (in the case of the separator-integrated counter electrode 10A, a transparent conductive material is formed on the substrate 11A. A rotating drum in which a film 12A and a platinum film (not shown) are formed, or in the case of the separator-integrated semiconductor electrode 10B, a transparent conductive film 12B and a dye-adsorbing semiconductor film 14 are formed on a base material 11B. When a DC voltage is applied from the power source 20 between the container 21 and the container 22 with a capillary (needle) 22 </ b> A that holds the spray raw material, the spray raw material is released toward the substrate on the rotating drum 21. Although the spray raw material is discharged as a droplet from the capillary 22A due to its surface tension, electric charges collect on the surface of the droplet and repel each other. When the repulsive force of this charge exceeds the surface tension, the droplet breaks up and becomes a jet. During this time, the solvent in the sprayed raw material is volatilized, so that the repulsive force of the charge is further increased, and the jet is further split into a fine jet 23. In this jet 23, the polymer compound chains in the spraying raw material are oriented, become elongated fibers, reach the substrate, and aggregate in this state, thereby depositing the polymer compound nanofibers on the substrate. A layer is formed.

  In this electrospinning method, by appropriately adjusting the applied voltage, the distance between the capillary and the base material, the discharge port diameter of the capillary, the spray raw material composition, etc., the nanofibers of the polymer compound having a desired average diameter and average length are deposited. A layer can be formed.

  In the present invention, the applied voltage in the electrospinning method is preferably about 10 to 30 kV. If the applied voltage is lower than this range, sufficient fiberization cannot be achieved. If the applied voltage is high, there is no problem in the formation of nanofibers, but it is dangerous for the device and the human body.

  Further, the distance between the capillary tip and the substrate is preferably about 5 to 15 cm, although it varies depending on the applied voltage, the viscosity of the spraying raw material, the conductivity, and the like. If this distance is too close or too far away, good nanofibers cannot be formed. Moreover, the discharge port diameter of a capillary is about 300-500 micrometers normally. If the discharge port diameter of this capillary is too large or too small, good nanofibers cannot be formed.

  Further, the spray raw material is preferably a solution obtained by dissolving the polymer compound for forming the polymer compound chain in a solvent.

  Here, the polymer compound is one or more selected from the group consisting of polyolefin polymer compounds, polyester polymer compounds, acrylic polymer compounds, nylon polymer compounds, and fluorine polymer compounds. The transparent insulating polymer compound is preferable, and its molecular weight is preferably about 100,000 to 500,000.

  The solvent is not particularly limited as long as it dissolves the above-described polymer compound and does not react with them, and is not particularly limited, but N, N-dimethylformamide (DMF), formamide, dioxane, methanol, ethanol 1 type, or 2 or more types, such as alcohols, such as benzene, tetrahydrofuran (THF), etc. are mentioned.

  If the concentration of the polymer compound in the spray raw material is too low or too high, good nanofibers cannot be formed, and depending on the type of polymer compound used, it is about 10 to 30% by weight. preferable.

  It is sufficient as a separator that the nanofibers of the polymer compound formed on the base material by the electrospinning method using such spray raw materials have an average diameter of about 50 to 500 nm and an average length of about 1 mm or more. It is preferable for securing sufficient porosity for mechanical strength and circulation of the electrolyte.

If the amount of the polymer compound nanofibers in the separator layers 13A and 13B formed of the polymer compound nanofiber deposition layer thus formed is too small, sufficient short-circuit prevention performance as a separator cannot be obtained. If the amount is too large, the production cost is increased, the thin film property is impaired, and the flowability of the electrolyte solution may be impaired. weight per unit area) is 0.5 to 50 mg / cm ^2, it is preferable preferably 1-10 mg / cm ² or so.

  The separator of the present invention is not limited to the one formed integrally with the counter electrode or the semiconductor electrode in this way. For example, an aluminum foil having a thickness of about 3 to 30 μm is used as the base material, and this base material is used. On the top, a separator layer made of a polymer compound nanofiber deposition layer is formed in the same manner as described above, and the separator layer is mechanically deformed to be peeled off from the base material, whereby an electrode is formed. It can also be a separate separate separator.

  In any case, it is preferable that the separator layer formed of the polymer compound nanofiber deposition layer has the above-described fiber diameter and fiber length in the range of the above-mentioned basis weight.

  In addition, in the separator-integrated counter electrode and the separator-integrated semiconductor electrode, the counter electrode or the semiconductor electrode serving as a substrate on which the separator is integrally formed is not limited to the above-described configuration. The electrode may be platinum or other metal electrode.

  The dye-sensitized solar cell of the present invention uses such a separator of the present invention, a separator-integrated counter electrode or a separator-integrated semiconductor electrode, and a separator is interposed between the semiconductor electrode and the counter electrode according to a conventional method. Thus, the same structure as that of the dye-sensitized solar cell shown in FIG. 3 is manufactured.

  In this case, particularly when the separator-integrated counter electrode or the separator-integrated semiconductor electrode of the present invention is used, a step of interposing a separator between these electrodes separately from the counter electrode and the semiconductor electrode is not required. Is advantageous. When the separator-integrated counter electrode of the present invention is used, the semiconductor electrode combined with this does not need to be the separator-integrated semiconductor electrode of the present invention, but the separator-integrated counter electrode of the present invention and the separator-integrated type Needless to say, a semiconductor electrode may be combined.

  Hereinafter, the present invention will be described more specifically with reference to examples.

Example 1
A spray raw material having the following composition was prepared.
[Spray raw material composition]
6 nylon: 20g
Formic acid: 80 g

A glass substrate in which an FTO film (thickness 300 nm) and a platinum film (thickness 30 nm) are formed on the FTO film by the electrospinning method shown in FIG. A deposited layer of nylon nanofibers was formed on a platinum film having a thickness of 1.1 mm.
[Electrospinning conditions]
Applied voltage: 15 kV
Distance between capillary tip and substrate: 15 cm

As a result of SEM observation, it was confirmed that nylon nanofibers having a diameter of 80 to 300 nm and a length of 1 mm or more were formed on the platinum film at a rate of 5 mg / cm ² .

  A dye-sensitized solar cell was assembled using the separator-integrated counter electrode thus manufactured.

On a glass substrate (thickness: 2 mm), a titanium oxide layer having a titanium oxide deposition amount of 1.2 mg / cm ² and a thickness of about 10 μm was formed by a doctor blade method.

As a spectral sensitizing dye, cis-di (thiocyanato) -N, N′-bis (2,2′-bipyridyl-4,4′-dicarboxylate ruthenium (II) dihydrate in ethanol solution is 3 × 10 ⁻⁴ mol. The substrate on which the titanium oxide layer was formed was placed in the solution dissolved at / L, and immersed for 18 hours at room temperature to obtain a dye-sensitized semiconductor electrode. The surface area was 10 μg per 1 cm ² .

  Separately, a liquid electrolyte is prepared by mixing 0.3 mol / L of lithium iodide and 0.03 mol / L of iodine in a mixed solvent of acetonitrile: 3-methyl-2-oxazolidinone = 50: 50 (weight ratio). did.

  On the dye-sensitized semiconductor electrode, a liquid flow prevention tape was attached to provide a weir, and a liquid electrolyte was applied. The separator-integrated counter electrode was laminated on the electrolyte membrane surface, and the side surfaces were sealed with resin, and then lead wires were attached to fabricate a dye-sensitized solar cell.

  This dye-sensitized solar cell was able to generate power stably without a problem of short circuit of electrodes.

Example 2
In Example 1, a dye-sensitized solar cell was assembled in the same manner except that the separator layer formed by the electrospinning method was formed on the dye-adsorbing semiconductor film of the semiconductor electrode instead of the counter electrode. This dye-sensitized solar cell was also able to generate power stably without the problem of electrode short-circuiting.

FIG. 1A is a schematic cross-sectional view showing an embodiment of a counter electrode for a separator-integrated dye-sensitized solar cell of the present invention, and FIG. 1B is a separator-integrated dye-sensitized method of the present invention. It is typical sectional drawing which shows embodiment of the semiconductor electrode for type | mold solar cells. It is a block diagram which shows a general electrospinning apparatus. It is sectional drawing which shows the structure of a dye-sensitized solar cell.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Substrate 2 Transparent conductive film 3 Dye adsorption semiconductor film 4 Dye sensitized semiconductor electrode 5 Counter electrode 6 Sealing material 7 Electrolyte 10A Separator integrated counter electrode 10B Separator integrated semiconductor electrode 11A, 11B Base material 12A, 12B Transparent conductive film 13A, 13B Separator layer 14 Dye adsorption semiconductor film 14 Platinum

Claims (8)

  A separator for a dye-sensitized solar cell, comprising an insulating porous film formed by an electrospinning method.   2. The group according to claim 1, wherein the insulating material constituting the insulating porous film is a polyolefin polymer compound, a polyester polymer compound, an acrylic polymer compound, a nylon polymer compound, and a fluorine polymer compound. A dye-sensitized solar cell separator, characterized by being one or more transparent polymer materials selected from: According to claim 1 or 2, dye-sensitized solar cell separator, wherein the basis weight is 0.5 to 50 mg / cm ^2.   4. The dye-sensitized solar cell according to claim 1, wherein the counter electrode is disposed to face the dye-sensitized semiconductor electrode via an electrolyte, and is disposed on a surface facing the semiconductor electrode. 5. A separator-integrated dye-sensitized solar cell counter electrode, wherein a separator is provided.   A semiconductor electrode of a dye-sensitized solar cell, wherein the separator according to any one of claims 1 to 3 is provided on a semiconductor film surface of the semiconductor electrode. Semiconductor electrode for sensitized solar cell.   Dye sensitizing comprising a dye sensitized semiconductor electrode, a counter electrode provided facing the dye sensitized semiconductor electrode, and an electrolyte disposed between the dye sensitized semiconductor electrode and the counter electrode A dye-sensitized solar cell according to any one of claims 1 to 3, wherein the dye-sensitized solar cell separator is disposed between the counter electrode and the semiconductor electrode. Type solar cell.   Dye sensitizing comprising a dye sensitized semiconductor electrode, a counter electrode provided facing the dye sensitized semiconductor electrode, and an electrolyte disposed between the dye sensitized semiconductor electrode and the counter electrode A dye-sensitized solar cell, wherein the counter electrode is the counter electrode for a separator-integrated dye-sensitized solar cell according to claim 4.   Dye sensitizing comprising a dye sensitized semiconductor electrode, a counter electrode provided facing the dye sensitized semiconductor electrode, and an electrolyte disposed between the dye sensitized semiconductor electrode and the counter electrode A dye-sensitized solar cell, wherein the semiconductor electrode is the separator-integrated dye-sensitized solar cell semiconductor electrode according to claim 5.

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