JP2009283429A - Porous semiconductor electrode, dye-sensitized solar cell using the same, and cell structure thereof - Google Patents

Abstract

A cell structure of a dye-sensitized solar cell is provided.
A porous semiconductor electrode is tungsten oxide or a composite material of tungsten oxide having high visible light response. When tungsten oxide or tungsten oxide composite was measured by X-ray diffraction method, (1) peak A (2θ = 22.8-23.4 °), peak B (2θ = 23.4-23.8 °), peak C (2θ = 24.0-24.25) °), of the intensity ratio of peak D (2θ = 24.25 to 24.5 °), A / D ratio and B / D ratio range of 0.5 to 2.0, C / D ratio range of 0.04 to 2.5, (2) peak E (2θ = 33.85 to 34.05 °) and peak F (2θ = 34.05 to 34.25 °) intensity ratio (E / F) in the range of 0.1 to 2.0, (3) Peak G (2θ = 49.1 to 49.7 °) and peak The intensity ratio (G / H) of H (2θ = 49.7 to 50.3 °) is in the range of 0.04 to 2.0, and the average particle diameter (D50) is 1 to 548 nm.
[Selection] Figure 6

Description

The present invention relates to a porous semiconductor electrode, a dye-sensitized solar cell using the same, and a cell structure thereof.

As a general dye-sensitized solar cell, an electrode (semiconductor electrode) composed of a semiconductor layer made of fine metal oxide particles having a dye supported thereon, and a transparent electrode (conductive layer) facing the electrode And a liquid carrier transfer layer (electrolyte layer) interposed between two electrodes are known (see Patent Document 1).

This dye-sensitized solar cell operates through the following process. That is, light incident on the semiconductor electrode reaches a metal complex such as ruthenium or an organic dye supported on the surface of the semiconductor electrode and excites the dye. The excited dye quickly passes electrons to the semiconductor electrode. On the other hand, the positively charged dye by losing electrons is electrically neutralized by receiving electrons from ions diffused from the electrolyte layer. The ions that have passed the electrons diffuse to the transparent electrode and receive the electrons. The solar cell is operated by using the semiconductor electrode and the transparent electrode facing the semiconductor electrode as a negative electrode and a positive electrode, respectively.

As this semiconductor electrode, a semiconductor electrode using an oxide semiconductor such as porous titanium dioxide or zinc oxide made of nanocrystals is known. In addition, an oxide semiconductor electrode having a porous structure has been reported in order to increase the amount of dye supported in order to improve efficiency. On the other hand, in order to further improve the efficiency of the solar cell, it is expected to use visible light as excitation light, and although a technique using a semiconductor having visible light response has been proposed, visible light irradiation As a result, a material showing an efficient reaction has not been obtained yet.

On the other hand, for dye-sensitized solar cells, in order to improve the light conversion efficiency, the area is increased,
Moreover, the thing of the structure which gave the flexibility to the shape of the solar cell is known. However, in the cell structure of a solar battery, the gap between the electrodes is preferably small from the viewpoint of relaying charge transport. In the case of a structure having a large area as described above or a structure having flexibility, a slight addition is required. There is a problem that the semiconductor electrode and the counter electrode are in contact with each other due to the pressure and short-circuited.
JP 2002-289268 A

An object of the present invention is to provide a porous semiconductor electrode for use in a dye-sensitized solar cell, a porous semiconductor electrode comprising tungsten oxide or a tungsten oxide composite having high visible light response, and a dye-sensitized solar using the same. To provide a battery.
Furthermore, the present invention provides a cell structure of a dye-sensitized solar cell in which a semiconductor electrode and a counter electrode in the dye-sensitized solar cell are not brought into contact with each other by an external pressure and short-circuited.

A porous semiconductor electrode according to one embodiment of the present invention is a porous semiconductor electrode comprising tungsten oxide or a tungsten oxide composite, and when the tungsten oxide or tungsten oxide composite is measured by an X-ray diffraction method,
(1) A peak having A, 2 and 3 with 2θ in the range of 22.5 to 25 ° and 2θ in the range of 22.8 to 23.4 ° is A and 2θ is 23. .4 to 23.8 °
When the peak existing in the range of B, 2θ is in the range of 24.0 to 24.25 °, C is the peak in the range of 2θ to 24.25 to 24.5 °, and D is the peak Intensity ratio (A / D) of the peak A to the peak D, and the peak B to the peak D
Intensity ratio (B / D) of each of these is in the range of 0.5 to 2.0, and the intensity ratio of peak C to peak D (C / D) is in the range of 0.04 to 2.5. (2) 2θ is 33
. When the peak existing in the range of 85 to 34.05 ° is E and the peak existing in the range of 24.0 is 34.05 to 34.25 ° is F, the intensity ratio of the peak E to the peak F (E
/ F) is in the range of 0.1 to 2.0, and (3) G 2θ is in the range of 49.7 to 50.3 °, and 2θ is in the range of 49.1 to 49.7 °. When the peak existing in H is H,
The intensity ratio (G / H) of the peak G to the peak H is in the range of 0.04 to 2.0, and the average particle diameter (D50) by image analysis is in the range of 1 to 548 nm. Yes.

The dye-sensitized solar cell of the present invention includes the porous semiconductor electrode according to the aspect of the present invention.

The cell structure of the dye-sensitized solar cell of the present invention includes an n-type semiconductor electrode in which a transparent electrode layer and a porous semiconductor layer are sequentially laminated on at least a transparent substrate, and the dye is adsorbed on the semiconductor, and at least on the transparent substrate A transparent electrode layer, a counter electrode having a conductive catalyst layer, an n-type semiconductor electrode, and an electrolyte composition layer between the counter electrode, and a polymer on the conductive film of the counter electrode. It comprises the pillar which becomes.

According to the porous semiconductor electrode according to the aspect of the present invention, the visible light responsiveness can be improved and stabilized based on the crystal structure and the average particle diameter of the tungsten oxide or the tungsten oxide composite material. Therefore, by using such a porous semiconductor electrode, it is possible to provide a dye-sensitized solar cell excellent in visible light responsiveness.
Furthermore, according to the cell structure of the dye-sensitized solar cell according to the present invention, it is possible to prevent a short circuit between the n-type semiconductor electrode and the counter electrode.

Hereinafter, modes for carrying out the present invention will be described. A porous semiconductor electrode according to an embodiment of the present invention includes tungsten oxide or a tungsten oxide composite. The tungsten oxide or the tungsten oxide composite constituting the porous semiconductor electrode satisfies the following conditions (1) to (3) when measured by the X-ray diffraction method, and the average particle diameter (D50) by image analysis:
Is in the range of 1 to 548 nm.

(1) In the X-ray diffraction chart, the first peak (diffraction peak having the highest intensity among all peaks) and the second peak (diffraction peak having the second highest intensity) in the range of 2θ of 22.5 to 25 °
And a third peak (diffraction peak with the third highest intensity). Furthermore, 2θ is 22
. A peak that exists in the range of 8 to 23.4 ° is A, a peak that is in the range of 23.4 to 23.8 ° is B, and a peak that is in the range of 24.0 to 24.25 ° is B 2θ. , Where C and 2θ are in the range of 24.25 to 24.5 °, where D is the intensity ratio of peak A to peak D (A / D) and the intensity ratio of peak B to peak D (B / D) is in the range of 0.5 to 2.0, and the intensity ratio of peak C to peak D (C / D) is 0.
. It is in the range of 04 to 2.5.

(2) In the X-ray diffraction chart, when the peak existing in the range of 33.85 to 34.05 ° is E and the peak existing in the range of 24.0 to 34.05 to 34.25 ° is F, the peak F The intensity ratio (E / F) of the peak E with respect to is in the range of 0.1 to 2.0.

(3) In the X-ray diffraction chart, the peak existing in the range of 49.1 to 49.7 ° is represented by G
When the peak of 2θ in the range of 49.7 to 50.3 ° is H, the intensity ratio (G / H) of the peak G to the peak H is in the range of 0.04 to 2.0.

The measurement and analysis of X-ray diffraction will be described. X-ray diffraction measurement is performed using a Cu target and Ni filter, and only the smoothing process and background removal are performed so that the analysis is not affected by the difference in processing conditions, and the peak intensity is removed without performing Kα2 removal. Measurement shall be performed. Here, how to read the peak intensity within each 2θ range of the X-ray diffraction chart is:
When the mountain is clear, the peak of the mountain within the range is taken as the peak, and the height is read. When the mountain is not clear but there is a shoulder, the shoulder portion is regarded as a peak within the range, and the height of the shoulder portion is read. When the slope has no peaks or shoulders, the height in the middle of the range is read and regarded as the peak intensity within the range.

FIG. 1 shows an example of an X-ray diffraction result of tungsten oxide or a tungsten oxide composite material.
The X-ray-diffraction chart of the tungsten oxide powder of the comparative example 1 mentioned later is shown. 2 shows 2θ
Is an enlarged view of the range of 22.5 to 25 °, showing examples of peaks A to D. FIG. 3 shows an example of the peaks E to F. FIG. 4 shows an example of peaks GH. 5 is shown in FIG.
2 is an enlarged view of the range of 2θ to 22.5 to 25 °, and shows how to read peak C in the case of a pattern different from FIG.

In the tungsten oxide or tungsten oxide composite material that satisfies the above conditions (1) to (3), the tungsten oxide is tungsten trioxide, and at least one selected from monoclinic and triclinic crystals and orthorhombic crystals, It is estimated that it is a mixed crystal containing. A monoclinic crystal, a triclinic crystal, or a mixed crystal of a monoclinic crystal and a triclinic crystal is mainly present, and it is presumed that an orthorhombic crystal is included in the mixed crystal. The tungsten oxide or the tungsten oxide composite material having such a crystal structure can stably exhibit excellent visible light responsiveness. Although it is difficult to identify the abundance ratio of each crystal phase, when the conditions (1) to (3) are satisfied, the visible light responsiveness of the tungsten oxide or the tungsten oxide composite can be improved, and Such performance can be exhibited stably.

2θ range (22.5 to 25 °) of the first, second and third peaks in condition (1),
The intensity ratio of the peaks (peak A, peak B, peak C, peak D) existing in each 2θ range is a premise that the above-described mixed crystal is generated. 1st, 2nd and 3rd peaks are 2
When it deviates from the 2θ range of 2.5 to 25 °, it means that a heterogeneous phase appears, and the mixed crystal state described above cannot be obtained.

When the A / D ratio and B / D ratio are less than 0.5 or more than 2.0, the balance between at least one selected from monoclinic crystals and triclinic crystals and orthorhombic crystals is lowered, and sufficient Visible light response cannot be obtained. The A / D ratio and B / D ratio are each preferably in the range of 0.7 to 2.0, and more preferably in the range of 0.7 to 1.5. The A / D ratio and the B / D ratio are each preferably in the range of 0.7 to 1.3.

Peak C, peak D and C / D ratio in condition (1), peak E in condition (2)
, Peak F and E / F ratio, peak G, peak H and G / H ratio in condition (3) are
In any case, the crystal structure of tungsten oxide or tungsten oxide composite is at least one selected from monoclinic and triclinic crystals, or a mixed crystal in which orthorhombic crystals are mixed. Show. When the C / D ratio is less than 0.04, when the E / F ratio is less than 0.1, when the G / H ratio is less than 0.04, there is a single phase, or orthorhombic crystals Presumed not to appear. When the C / D ratio exceeds 2.5, when the E / F ratio exceeds 2.0, when the G / H ratio exceeds 2.0, it is a single phase or the amount of orthorhombic crystals Is estimated to be excessive. In any case, sufficient visible light responsiveness cannot be obtained.

The C / D ratio in condition (1) is preferably in the range of 0.5 to 2.5, more preferably in the range of 0.5 to 1.5. The C / D ratio is preferably in the range of 0.7 to 1.1. The E / F ratio in the condition (2) is preferably in the range of 0.5 to 2.0, more preferably in the range of 0.5 to 1.5. The E / F ratio is preferably in the range of 0.7 to 1.1. The G / H ratio in condition (3) is preferably in the range of 0.2 to 2.0, more preferably in the range of 0.2 to 1.5. The G / H ratio is desirably in the range of 0.4 to 1.1. By satisfying such a condition, the visible light response of the tungsten oxide or the tungsten oxide composite can be improved with high reproducibility.

The visible light responsiveness of the tungsten oxide or the tungsten oxide composite of this embodiment cannot be improved only by the above-described crystal structure. That is, conditions (1) to (3)
And a porous semiconductor electrode having excellent visible light responsiveness can be obtained by using tungsten oxide or a tungsten oxide composite material having an average particle diameter in the range of 1 to 548 nm. Here, the average particle diameter is determined from the average particle diameter (D50) of n = 50 or more from image analysis of photographs such as SEM and TEM.

The photoresponsiveness of the porous semiconductor is higher when the specific surface area is larger, that is, when the particle size is smaller. Moreover, when using for a dye-sensitized solar cell etc., a pigment | dye is made to adhere. The greater the amount of attached dye, the higher the photoreactivity. Therefore, if the specific surface area of the porous semiconductor is large, the amount of adhesion can be increased and high performance can be obtained. Therefore, when the average particle diameter exceeds 548 nm, sufficient visible light responsiveness cannot be obtained even if the tungsten oxide or the tungsten oxide composite satisfies the conditions (1) to (3). When the average particle size of the tungsten oxide or the tungsten oxide composite is less than 1 nm, it means that the average particle size of the raw material powder is too small, and the practicality is lowered because the handleability as a powder is inferior.

Average particle size by image analysis of tungsten oxide or tungsten oxide composite is 2.5-
It is preferably in the range of 75 nm, more preferably in the range of 5.5 to 51 nm. The BET specific surface area is preferably in the range of 1.5 to 820 m ² / g.
More preferably, it is in the range of 300 m 2 / g. More preferably 16 to 150 m ² /
The range of g.

In the case of applying tungsten oxide or a tungsten oxide composite as a porous semiconductor, fine particles of tungsten oxide or a tungsten oxide composite are dispersed in a solvent and applied as a slurry to an electrode substrate. The substrate of the electrode base material of the present invention is not particularly limited, but a glass substrate,
A transparent substrate such as a plastic substrate is used. For plastic substrates, plastic films such as polymethyl methacrylate, polycarbonate, polystyrene, polyethylene sulfide, polyethersulfone, polyolefin, polyethylene terephthalate, polyethylene naphthalate, triacetylcellulose, etc. can be used, but insulation and transparency Those having the following are preferred. Considering direct contact with sunlight, a material having light resistance and heat resistance is preferable from the viewpoint of environment and life. In order to efficiently use incident light, an antireflection film or the like may be formed on the side where the electrode layer is not laminated.

The electrode layer is provided on the light receiving surface side through the transparent conductive film provided on the transparent substrate described above. As the transparent conductive film, one having little absorption in the visible light region and having conductivity is preferable. As such a transparent conductive film, it is preferable to use a tin oxide film or a zinc oxide film doped with fluorine or indium. A porous semiconductor electrode layer comprising tungsten oxide or a tungsten oxide composite material according to the present invention is provided on the transparent conductive film. The method for forming the porous semiconductor electrode layer is not particularly limited, but a method of applying a slurry or paste comprising tungsten oxide or a tungsten oxide composite according to the present invention, a method by printing such as screen printing, or an oxidation according to the present invention. A method such as attaching a film including tungsten or a tungsten oxide composite is used.

When manufacturing the above-described slurry, paste, film, etc., if the particle size of the tungsten oxide fine particles or the tungsten oxide composite is too small, the dispersibility of the particles decreases, so that the uniform slurry, paste with stable dispersibility It becomes difficult to produce a coating solution or a film. In order to improve such a point, it is preferable to use tungsten oxide fine particles or tungsten oxide composites having an average particle diameter of 8.2 nm or more. Also,
From the viewpoint of controlling the amount of the dye adsorbed on the surface after the formation of the porous semiconductor, the particle size of the tungsten oxide or tungsten oxide composite in the slurry, paste, or film is made appropriate, and at the same time, the content (concentration) Are also appropriately controlled.

As described above, the porous semiconductor electrode according to this embodiment has the crystal structure represented by the conditions (1) to (3) based on the X-ray diffraction results and the average particle diameter (D50) in the range of 1 to 548 nm. It has a tungsten oxide or a tungsten oxide composite material. By using tungsten oxide or a tungsten oxide composite material that satisfies such conditions, it is possible to provide a porous semiconductor electrode with improved visible light responsiveness.

The tungsten oxide or the tungsten oxide composite material constituting the porous semiconductor electrode may contain a metal element as a trace amount of impurities. The content of the metal element as the impurity element is preferably 10% by mass or less. Furthermore, in order to suppress a change in color tone of tungsten oxide or a tungsten oxide composite material, the content of the impurity metal element is desirably 2% by mass or less. Examples of the impurity metal element include elements generally contained in tungsten ore and contaminating elements mixed when producing a tungsten compound used as a raw material. For example, Fe, Mo, Mn, Cu, Ti, Al, Ca, Ni, Cr, Mg, etc. are mentioned.

In the porous semiconductor electrode according to this embodiment, the porous semiconductor preferably comprises 1% by mass or more and 100% by mass or less of the tungsten oxide or the tungsten oxide composite material.

According to the porous semiconductor electrode according to this embodiment, in addition to the controlled crystal structure of the tungsten oxide or tungsten oxide composite material, the average particle size is small and the specific surface area is large. In addition to high performance, when a dye is adsorbed, a large amount of dye can be adsorbed, and higher visible light responsiveness can be obtained.

The tungsten oxide or the tungsten oxide composite material according to this embodiment is excellent in visible light responsiveness. Here, visible light refers to light having a wavelength range of 380 to 830 nm. As a light source for irradiating the tungsten oxide or the tungsten oxide composite material of this embodiment, sunlight,
Examples include general illumination such as fluorescent lamps, white LEDs, light bulbs, halogen lamps, and xenon lamps, and light sources such as blue light emitting diodes and blue lasers.

The tungsten oxide or the tungsten oxide composite material that constitutes the porous semiconductor electrode of the above-described embodiment is produced, for example, as follows. Tungsten oxide or a tungsten oxide composite material is manufactured by applying a sublimation process. It is also effective to combine a heat treatment process with a sublimation process. According to the fine particles of tungsten oxide or tungsten oxide composite material produced by applying a sublimation process or a combination of a sublimation process and a heat treatment process, the above-described crystal structure and average particle diameter can be stably realized.

Examples of the method for sublimating the tungsten raw material in the oxygen atmosphere in the sublimation process include at least one treatment selected from inductively coupled plasma treatment, arc discharge treatment, laser treatment, electron beam treatment, and gas burner treatment. Among these, in laser processing or electron beam processing, a sublimation process is performed by irradiating a laser or electron beam. Lasers and electron beams have a small irradiation spot diameter, so it takes time to process a large amount of raw materials at once, but there is an advantage that it is not necessary to strictly control the stability of the raw material particle size and supply amount. .

Inductively coupled plasma treatment and arc discharge treatment require adjustment of the plasma and arc discharge generation region, but a large amount of raw material powder can be oxidized at a time in an oxygen atmosphere. In addition, the amount of raw material that can be processed at one time can be controlled. Although the gas burner treatment is relatively inexpensive, it is difficult to treat a large amount of raw material powder or raw material solution. For this reason, the gas burner treatment is inferior in terms of productivity. The gas burner treatment is not particularly limited as long as it has sufficient energy for sublimation. A propane gas burner or an acetylene gas burner is used.

On the other hand, the tungsten oxide composite material according to the embodiment of the present invention is a composite of tungsten oxide fine particles produced by the above-described manufacturing method and another element alone or a compound of another element, and other elements. It exists in a form in which a compound such as an oxide is formed. In the manufacturing method described above, by treating tungsten oxide simultaneously with another element, fine particles of a composite material in which a compound such as a composite oxide of tungsten oxide and another element is formed can be formed.

The tungsten oxide or the tungsten oxide composite material may contain a transition metal element in order to improve visible light response. The transition metal element content is preferably 0.01% by mass or more and 50% by mass or less. When the content of the transition metal element exceeds 50% by mass, the visible light response may be lowered. The content of the transition metal element is preferably 10% by mass or less, and more preferably 2% by mass or less. Transition metal elements are atomic numbers 21-29, 39-
47, 57-79, 89-109, and among these, Ti, Fe, Cu, Z
It is preferable to use at least one selected from r, Ag and Pt. Transition metal elements are contained in the form of metal, oxide, composite oxide, compound, etc., and may be mixed or supported. Further, a compound with tungsten may be formed.

The tungsten oxide or tungsten oxide composite material of this embodiment may be used as it is as a porous semiconductor, or a powder (or a substance in a form other than powder) obtained by mixing, carrying, impregnating with other materials. ) Can also be used as a porous semiconductor. The porous semiconductor electrode of this embodiment contains tungsten oxide or a tungsten oxide composite in the range of 1 to 100% by mass. The content of tungsten oxide or tungsten oxide composite is appropriately selected according to the desired characteristics, but if it is less than 1% by mass, sufficient performance as an electrode cannot be obtained. The porous semiconductor electrode may comprise titanium dioxide together with tungsten oxide or a tungsten oxide composite.

After the porous semiconductor electrode according to this embodiment is formed as a porous semiconductor layer on the transparent substrate on which the above-described tungsten oxide or tungsten oxide composite material is formed,
It is obtained by adsorbing the dye on the surface. Examples of the dye to be adsorbed include a ruthenium tris type transition metal complex, a ruthenium-bis type transition metal complex, and an osmium-
A tris type transition metal complex, an osmium-bis type transition metal complex, a ruthenium-cis-diaqua-bipyridyl complex, a phthalocyanine, a porphyrin, and the like can be given.

Since the porous semiconductor electrode according to this embodiment has a small average particle diameter and a large specific surface area, it can adsorb a large amount of dye. Further, the surface of the dye adsorbed on a single molecule on the surface of tungsten oxide or a tungsten oxide complex can be formed into a fractal shape having self-similarity like a resinous structure, and the amount of adsorption can be further increased.

The dye-sensitized solar cell according to this embodiment includes the above-described porous semiconductor electrode, a counter substrate disposed on the surface of the semiconductor electrode so as to be spaced apart from the semiconductor electrode, the porous semiconductor electrode, and the conductive film. And an electrolyte composition that relays charge transport therebetween.

It is preferable that the counter substrate has little absorption in the visible light region and has conductivity. In particular, it is preferable to use a tin oxide film, a tin oxide film doped with fluorine, a zinc oxide film, or the like. It is preferable that platinum or carbon is attached to the counter substrate. Platinum is
It can be attached to the counter substrate by electrochemical or sputtering. The conductive film provided on the surface of the counter substrate can be formed of, for example, a metal such as platinum, gold, and silver, or carbon. In view of durability against the electrolytic solution, platinum is particularly preferable.

The electrolyte composition is sandwiched between the above-described porous semiconductor electrode and the conductive film of the counter substrate. The injected electrolyte composition is held in the pores in the n-type semiconductor electrode and is interposed between the n-type semiconductor electrode and the counter electrode. In the dye-sensitized solar cell, when light is incident from the glass substrate side, the dye adsorbed on the surface of the n-type semiconductor electrode is first excited by absorbing the incident light, and the excited dye enters the n-type semiconductor electrode. Photoelectric conversion is performed by passing electrons and passing holes to the electrolyte composition.

The electrolyte composition preferably includes a reversible redox couple. The reversible redox _couple can be supplied from, for example, a mixture of iodine (I ₂ ) and iodide, iodide, bromide, hydroquinone, TCNQ complex, and the like. In particular, a redox pair consisting of I ⁻ and I ₃ ⁻ supplied from a mixture of iodine and iodide is preferable.

The redox couple as described above desirably exhibits a redox potential that is 0.1 to 0.6 V smaller than the oxidation potential of the dye described later. In the redox pair showing a redox potential 0.1 to 0.6 V lower than the oxidation potential of the dye, for example, a reducing species such as I ⁻ can receive holes from the oxidized dye. By including such a redox couple in the electrolyte, n
The speed of charge transport between the type semiconductor electrode and the conductive film can be increased, and the open-circuit voltage can be increased.

The electrolyte composition further contains iodide. Examples of iodides include alkali metal iodides, iodides of organic compounds, and molten salts of iodides. The molten salt of iodide includes imidazolium salt, pyridinium salt, quaternary ammonium salt,
Iodides of heterocyclic nitrogen-containing compounds such as pyrrolidinium salts, pyrazolidium salts, isothiazolidinium salts, and isoxazolidinium salts can be used.

Examples of the molten salt of iodide include 1,1-dimethylimidazolium iodide, 1-methyl-3-ethylimidazolium iodide, 1-methyl-3-pentylimidazolium iodide, and 1-methyl-3. -Isopentylimidazolium iodide,
1-methyl-3-hexylimidazolium iodide, 1-methyl-3-isohexyl
(Branched) imidazolium iodide, 1-methyl-3-ethylimidazolium iodide, 1,2-dimethyl-3-propylimidazole iodide, 1-ethyl-3-isopropylimidazolium iodide, 1-propyl-3 -Propyl imidazolium iodide, pyrrolidinium iodide, etc. can be mentioned.

Such a molten salt of iodide can be used alone or in combination of two or more. Moreover, it is preferable that the content is about 0.005 mol / L or more and 7 mol / L or less in electrolyte solution. In the case of less than 0.005 mol / L, it is difficult to obtain sufficient effects. On the other hand, if it exceeds 7 mol / L, the viscosity is high and the ionic conductivity may be significantly reduced.

Furthermore, the electrolyte composition in the present invention contains iodine in an amount of 0.01 mol / L to 3 mol / L.
It is preferable to contain in the range below L. Iodine is mixed with iodide in the electrolyte composition of the present invention and acts as a reversible redox pair. Therefore, when the content of iodine is less than 0.01 mol / L, the oxidized form of the redox couple is insufficient and it becomes difficult to sufficiently transport charges. On the other hand, when it exceeds 3 mol / L, the light absorption of the solution increases, and there is a possibility that light cannot be efficiently applied to the tungsten oxide or the tungsten oxide composite material. The iodine content is more preferably 0.03 mol / L or more and 1.0 mol / L or less.

The electrolyte composition in the present invention may be either liquid or gel and can contain an organic solvent. By containing the organic solvent, the viscosity of the electrolyte composition can be further reduced, so that it can easily penetrate into the semiconductor electrode. Examples of the organic solvent that can be used include cyclic carbonates such as ethylene carbonate (EC) and propylene carbonate (PC); chain carbonates such as dimethyl carbonate, methyl ethyl carbonate, and diethyl carbonate; _γ -butyrolactone, acetonitrile, Examples include methyl propionate and ethyl propionate. Furthermore, cyclic ethers such as tetrahydrofuran and 2-methyltetrahydrofuran; chain ethers such as dimethoxyethane and diethoxyethane; Can be mentioned.

These organic solvents can be used alone or as a mixture of two or more. The content of the organic solvent is not particularly limited, but is preferably 80% by weight or less, and more preferably 0% by weight or more and 30% by weight or less in the electrolyte composition.

In the cell structure of the dye-sensitized solar cell according to this embodiment, a polymer column is provided on the conductive film of the counter electrode. The polymer column functions as a spacer that prevents a short circuit between the porous semiconductor electrode and the counter electrode. The polymer is not particularly limited as long as it is a polymer resistant to an electrolytic solution, and an epoxy resin, an acrylic resin, or the like is used. Columns made of polymer are wet-coated with a photosensitive resin, and after drying, pattern exposure, development,
It can be formed through a drying process. Moreover, after mixing a two-component epoxy resin, it can also form by printing using a screen mask. A one-component epoxy resin may be used for curing by heating after printing.

The formed polymer column is preferably a quadrangular shape having a side length of 10 to 100 μm and a height of 10 to 100 μm in cross-sectional shape. By forming the column made of the polymer at an arbitrary position on the conductive film of the counter electrode, it becomes a spacer between the n-type semiconductor electrode and the counter electrode, and has a function of preventing a short circuit between the two electrodes. The cell structure including the polymer column can effectively prevent a short circuit between the electrodes even when the dye-sensitized solar cell has a flexible structure.

When the spacer is made of silica or the like, if the dye-sensitized solar cell is bent, the position of the spacer may move, creating a part that does not have a spacer locally, causing a short circuit at that part. was there. On the other hand, if the spacer is formed using a column made of a polymer, the position does not move, so that a short circuit between the electrodes can be effectively prevented.

It is preferable to place the polymer column on the conductive film of the counter electrode so as to be arranged above the metal current collector wiring of the n-type semiconductor electrode, because the light can be efficiently absorbed by the light receiving portion.
In addition, it is possible to appropriately set a place for the placement using a mask or the like.

Since the dye-sensitized solar cell according to this embodiment includes a tungsten oxide or a tungsten oxide composite material having high visible light responsiveness in the porous semiconductor electrode, when visible light is used as excitation light, Demonstrate high energy conversion efficiency.
Furthermore, since a polymer column is provided between the semiconductor electrode and the counter electrode, even when an external force is applied, a short circuit between the electrodes can be effectively prevented.

Next, specific examples of the present invention and evaluation results thereof will be described. In the following examples, inductively coupled plasma processing is applied to the sublimation process, but the present invention is not limited to this.

Example 1
First, a tungsten oxide powder having an average particle size of 0.5 μm was prepared as a raw material powder. This raw material powder was sprayed onto RF plasma together with a carrier gas (Ar), and argon was flowed as a reaction gas at a flow rate of 40 L / min and oxygen at a flow rate of 100 L / min. In this way
Tungsten oxide fine particles were produced through a sublimation process in which the raw material powder was subjected to an oxidation reaction while sublimating. Further, the tungsten oxide fine particles were heat-treated in the atmosphere at 700 ° C. × 1 h.

The obtained tungsten oxide fine particles were subjected to X-ray diffraction. X-ray diffraction was performed using a Rigaku X-ray diffractometer RINT-2000, Cu target, Ni filter, graphite (0
02) Performed using a monochromator. Measurement conditions are tube voltage: 40 kV, tube current:
40 mA, divergent slit: 1/2 °, scattering slit: automatic, light receiving slit: 0.15 mm
,
2θ measurement range: 20 to 70 °, scanning speed: 0.5 ° / min, sampling width: 0.00
4 °. In measuring the peak intensity, Kα2 removal was not performed, but only smoothing and background removal processes were performed. The smoothing was performed using Savizky-Golay (least square method), and filter points 11 were set. Background removal is a linear fit within the measurement range,
The threshold value σ3.0 was used. Table 1 shows the X-ray diffraction results.

Moreover, the average particle diameter by the image analysis of the TEM photograph of the obtained tungsten oxide microparticles | fine-particles was measured. For TEM observation, H-7100FA manufactured by Hitachi, Ltd. was used, and an enlarged photograph was subjected to image analysis to extract 50 or more particles, and a volume-based integrated diameter was obtained to calculate D50. The measurement results of the average particle diameter are shown in Table 1.

Next, a paste was prepared using the obtained tungsten oxide fine particles to produce a porous semiconductor electrode. A fluorine-doped SnO ₂ transparent electrode (6Ω / □) was provided on a glass substrate, and the prepared paste was printed thereon by a screen printing method, followed by heat treatment at a temperature of 450 ° C. Further, by repeating this screen printing and heat treatment a plurality of times, an n-type semiconductor electrode made of tungsten oxide fine particles was formed.

On the other hand, cis-bis (thiocyanato) -N, N-bis (2,2′-dipyridyl-4,4 ′
-Dicarboxylic acid) -ruthenium (II) dihydrate) in dry ethanol
A -4M dry ethanol solution was prepared. The porous semiconductor electrode described above was immersed in this solution (temperature of about 80 ° C.) for 4 hours, and then pulled up in an argon stream. Thus, an n-type semiconductor electrode having a ruthenium complex as a dye supported on the surface of the porous semiconductor was produced.

In addition, a fluorine-doped tin oxide conductive film was formed on a glass substrate having platinum attached to the surface, to produce a counter electrode. On this, a one-component epoxy adhesive was printed through a screen mask and allowed to stand for 12 hours, thereby forming a column made of a polymer having a size of 50 μm square and a height of 50 μm as a spacer. On the substrate on which the n-type semiconductor electrode described above was fabricated, a counter electrode on which a spacer was formed was placed. Furthermore, the periphery of the electrolyte composition was left and the periphery was fixed with an epoxy resin and fixed to obtain a photoelectric conversion unit.

The electrolyte composition was prepared as follows. First, in 100 ml of acetonitrile, 0.5 mol / L of lithium iodide, 0.3 mmol of methylhexylimidazolium iodide
1 / L, t-butylpyridine 0.5 mol / L, and iodine 0.05 mol / L were dissolved to prepare an electrolyte composition.
Next, the electrolyte composition was injected into the opening of the photoelectric conversion unit from the injection port. The electrolyte composition penetrated into the n-type semiconductor electrode and was also injected between the n-type semiconductor electrode and the counter electrode.
Thereafter, the opening of the photoelectric conversion unit was sealed with an epoxy resin, and then heated on a hot plate at 60 ° C. for 30 minutes to produce a dye-sensitized solar cell.

For this dye-sensitized solar cell, white fluorescent lamp (FL20SS · W manufactured by Toshiba Lighting & Technology Corp.)
As a light source, an ultraviolet cut filter (manufactured by Nitto Jushi Kogyo Co., Ltd., Clarex N-16
9), the wavelength of less than 380 nm was cut, and visible light was irradiated with an illuminance of 6000 lx. The energy conversion efficiency and FF at that time are determined, and the results are summarized in Table 2.

(Example 2)
Tungsten oxide fine particles were produced through the same sublimation process as in Example 1 except that oxygen was flowed as a reaction gas at a flow rate of 80 L / min. However, no heat treatment was applied. The tungsten oxide fine particles thus obtained were measured and evaluated in the same manner as in Example 1. Tables 1 and 2 show the measurement and evaluation results of the tungsten oxide fine particles. Example 1 and Example 2
It was confirmed that the dye-sensitized solar cell including the porous semiconductor electrode formed by the tungsten oxide fine particles by the above has excellent energy conversion efficiency in visible light irradiation.

(Comparative Example 1)
Using commercially available tungsten oxide powder (made by Rare Metallic) as a reagent,
A dye-sensitized solar cell was produced in the same manner as in Example 1 and evaluated. Tables 1 and 2 show the measurement evaluation results. Moreover, the X-ray-diffraction result of the tungsten oxide powder of the comparative example 1 is shown in FIG. When the peak intensity ratio was determined from the X-ray diffraction results, the A / D ratio was 0.96, the B / D ratio was 0.96, the C / D ratio was 0.03, and the E / F ratio was 0.15. The G / H ratio was 0.03. The average particle size was 1210. It was confirmed that the peak intensity ratio and the average particle diameter based on the X-ray diffraction results did not reach the values specified in the present invention, and sufficient energy conversion efficiency could not be obtained due to low visible light responsiveness.

(Comparative Example 2)
Using a commercially available paste (manufactured by Solaronix, Switzerland) containing high-purity titanium oxide (anatase) powder having an average primary diameter of about 10 to 20 nm, a dye-sensitized solar cell was produced in the same manner as in Example 1, Evaluation was performed. The evaluation results are shown in Table 2.

(Comparative Example 3)
A dye-sensitized solar cell was fabricated using the same process as in Example 1 except that no polymer column was formed on the counter electrode.
When the cell center part of the produced dye-sensitized solar cell was pressed with a finger, the cell was short-circuited.

It is a figure which shows the X-ray-diffraction result of the tungsten oxide powder by the comparative example 1. It is a figure which shows an example of the peaks AD in the X-ray-diffraction result of the tungsten oxide in this invention. It is a figure which shows an example of the peaks EF in the X-ray-diffraction result of the tungsten oxide in this invention. It is a figure which shows an example of the peaks GH in the X-ray-diffraction result of the tungsten oxide in this invention. It is a figure which shows the other example of the peaks AD in the X-ray-diffraction result of the tungsten oxide in this invention. FIG. 3 is a diagram showing an X-ray diffraction result of tungsten oxide according to Example 1. It is an example of the dye-sensitized solar cell by this invention. It is a figure which shows the middle of the manufacturing process of the dye-sensitized solar cell created in the Example of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Glass substrate 2 Transparent electrically conductive film 3 Tungsten oxide particle 4 Porous semiconductor electrode 5 Conductive film 6 Counter electrode 7 Spacer column 8, 11 Epoxy resin 9 Inlet 10 Electrolyte composition

Claims (8)

A porous semiconductor electrode comprising tungsten oxide or a tungsten oxide composite,
When the tungsten oxide or the tungsten oxide composite is measured by an X-ray diffraction method,
(1) A peak having A, 2 and 3 with 2θ in the range of 22.5 to 25 ° and 2θ in the range of 22.8 to 23.4 ° is A and 2θ is 23. A peak existing in the range of 4 to 23.8 ° is B, and a peak of 2θ is in the range of 24.0 to 24.25 ° is C 2
When the peak existing in the range of θ of 24.25 to 24.5 ° is D, the intensity ratio (A / D) of the peak A to the peak D and the intensity ratio of the peak B to the peak D ( B / D) is in the range of 0.5 to 2.0, and the intensity ratio (C / D) of the peak C to the peak D is in the range of 0.04 to 2.5.
(2) A peak where 2θ is in the range of 33.85 to 34.05 ° is E and 2θ is 34.05.
When the peak existing in the range of ˜34.25 ° is F, the intensity ratio (E / F) of the peak E to the peak F is in the range of 0.1 to 2.0,
(3) A peak having 2θ in the range of 49.1 ° to 49.7 ° is G, and 2θ is 49.7 to 50.
. When the peak existing in the range of 3 ° is H, the intensity ratio (G / H) of the peak G to the peak H is in the range of 0.04 to 2.0,
And the average particle diameter (D50) by image analysis is the range of 1-548 nm, The porous semiconductor electrode characterized by the above-mentioned. The porous semiconductor electrode according to claim 1,
A material for forming a porous semiconductor comprises 1% by mass or more and 100% by mass of the tungsten oxide or the tungsten oxide composite material. In the porous semiconductor electrode according to claim 1 or 2,
A porous semiconductor electrode comprising 0.01% by mass to 50% by mass of a transition metal element. In the porous semiconductor electrode according to any one of claims 1 to 3,
A porous semiconductor electrode comprising titanium dioxide. The porous semiconductor electrode according to claim 1, wherein the porous semiconductor electrode is a visible light responsive type. In the porous semiconductor electrode according to any one of claims 1 to 5,
A porous semiconductor electrode, wherein the porous semiconductor adsorbs a dye. A dye-sensitized solar cell comprising the porous semiconductor electrode according to any one of claims 1 to 6. In the cell structure of the dye-sensitized solar cell according to claim 7,
An n-type semiconductor electrode formed by laminating at least a transparent electrode layer and a porous semiconductor layer in order on a transparent substrate, and adsorbing a dye to the semiconductor;
A counter electrode comprising at least a transparent electrode layer and a conductive catalyst layer on a transparent substrate;
Comprising an electrolyte composition layer between the n-type semiconductor electrode and the counter electrode;
A cell structure of a dye-sensitized solar cell, comprising a column made of a polymer on the conductive film of the counter electrode.

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