JP5191647B2 - Titanium oxide film, titanium oxide film electrode film structure, and dye-sensitized solar cell - Google Patents

Description

  The present invention relates to a titanium oxide film that bears the power generation function of a dye-sensitized solar cell, and is capable of increasing its photoelectric conversion efficiency.

Japanese Patent Application Laid-Open No. 2002-141115 discloses a titanium oxide film that has a power generation function of a dye-sensitized solar cell, which is composed of acicular crystalline titanium oxide. It is said that a structure with attached is preferable. This acicular crystalline titanium oxide is formed on a glass substrate by an electrodeposition method.
In this prior invention, by using acicular crystal titanium oxide, the movement of generated charges to the transparent conductive film on the glass substrate is improved, and the photoelectric conversion efficiency is improved.

However, also in this prior invention, the photoelectric conversion efficiency of the dye-sensitized solar cell is not high at all, and further improvement is required for practical use. Moreover, since acicular crystal titanium oxide is formed on a glass substrate by an electrodeposition method, there is a problem that it takes time and costs increase.
JP 2002-141115 A

  Therefore, an object of the present invention is to achieve a higher photoelectric conversion efficiency in a titanium oxide film constituting a dye-sensitized solar cell, and to make it easy and inexpensive.

To solve this problem,
The invention according to claim 1 is a titanium oxide film provided on a substrate,
The titanium oxide film is a porous film containing a rutile crystal needle-like titanium oxide having a diameter of 30 to 200 nm and a length of 0.5 to 20 μm, and an anatase crystal granular titanium oxide having a diameter of 5 to 400 nm. A titanium oxide film.

The invention according to claim 2 is characterized in that a weight ratio of the rutile crystal needle-like titanium oxide and the anatase crystal granular titanium oxide is 0.1: 1 to 2: 1 . It is a titanium oxide film.

The invention according to claim 3 is the titanium oxide film according to claim 1 or 2 formed by a screen printing method.
The invention according to claim 4 is a dye-sensitized solar cell comprising the titanium oxide film according to any one of claims 1 to 3.

The invention according to claim 5 is a three-layered titanium oxide film electrode film structure,
4. The titanium oxide according to claim 1, wherein the base layer in contact with the transparent conductive film on the transparent substrate is composed of a titanium oxide film made of fine anatase type crystalline granular titanium oxide having a diameter of 5 to 10 nm. The titanium oxide film electrode film structure is characterized in that it is composed of a film, and the uppermost layer is composed of a titanium oxide film made of anatase-type crystalline granular titanium oxide having a diameter of 20 to 400 nm.

The invention according to claim 6 is the titanium oxide film electrode film structure according to claim 5, wherein the uppermost layer, the intermediate layer, and the underlayer are formed by a screen printing method.
The invention according to claim 7 is a dye-sensitized solar cell comprising the titanium oxide film electrode film structure according to claim 5 or 6.

  According to the present invention, the intermediate layer of the titanium oxide film is composed of a porous film containing rutile crystal needle-like titanium oxide and anatase crystal granular titanium oxide, and therefore a dye using this titanium oxide film In the sensitized solar cell, the photoelectric conversion efficiency is high.

That is, in the case of a titanium oxide film composed only of rutile crystal needle-like titanium oxide, the photoelectric conversion efficiency is low, but it is the present inventor that the photoelectric conversion efficiency is remarkably improved by mixing anatase type crystalline granular titanium oxide with this. Obtained from the study.
Further, since this intermediate layer can be formed by a coating method such as a screen printing method, it can be manufactured at low cost.

  Furthermore, by providing a base layer, effects such as suppression of reverse electron transfer from the transparent conductive film and improvement of conductivity between the transparent conductive film and the porous electrode film can be obtained, and by providing the uppermost layer By reflecting the transmitted light from the porous electrode film, effects such as light confinement can be obtained.

[Titanium oxide film electrode structure]
FIG. 1 schematically shows an example of a titanium oxide film electrode film structure of the present invention. In the figure, reference numeral 1 denotes a glass substrate as a transparent substrate. As the transparent substrate, a transparent plastic substrate such as polycarbonate (PC), polyethylene terephthalate (PET), polyethylene (PE), polyvinyl chloride (PVC), and fluororesin can be used in addition to the glass substrate.
On the glass substrate 1, a transparent conductive film 2 made of ITO, FTO or the like and having a sheet resistance of 100Ω or less, preferably 30Ω or less and a thickness of 100 nm or more is formed.

Further, a titanium oxide film electrode film structure 3 is formed on the transparent conductive film 2. The titanium oxide film 3 in this example has a three-layer structure, and is composed of an underlayer 31, an intermediate layer 32, and an uppermost layer 33 from the glass substrate 1 side.
In the formation of the electrode film, when the electrode film is formed while repeating the process of applying and firing the slurry and paste constituting each layer constituting the electrode film, and at the stage where each layer is applied and the fluidity is lost In some cases, an electrode film is formed by applying a slurry or paste to be a layer and firing at once.

[Underlayer]
A base layer 31 is formed immediately above the transparent conductive film 2.
The underlayer 31 is a solid titanium oxide layer having a thickness of 0.1 to 10 μm made of anatase type crystalline granular titanium oxide having a diameter of 5 to 10 nm.
The underlayer 31 is formed by applying a slurry or paste of titanium oxide particles having a rutile crystal structure by screen printing or spraying to form a coating film having a thickness of 0.1 μm or more. When the transparent substrate is a soda lime glass substrate, it is baked at 350 to 550 ° C. to form the base layer 31 made of a dense titanium oxide film.

As a method of forming this titanium oxide dense film, titanium alkoxide, for example, tetraethoxy titanium Ti (C ₂ H ₅ O) ₄ is dissolved in ethanol, and this is sprayed and fired to form a titanium oxide film. Alternatively, the base layer 31 may be formed by applying and baking a sol solution prepared by adding water to an alcohol solution in which a titanium alkoxide is diluted and spraying.

Alternatively, the base layer 31 may be formed by mixing organometallic titanium and rutile-type crystalline titanium oxide particles, and applying and baking by screen printing or spraying.
The titanium oxide layer that forms the underlayer 31 does not need to be titanium oxide having an anatase type crystal structure in particular because it may prevent reverse electron transfer from the transparent conductive film 2 to the electrolytic solution. From the viewpoint of conversion, the base layer 31 is preferably made of titanium oxide having a rutile or anatase crystal structure.

[Middle layer]
An intermediate layer 32 is formed on the base layer 31.
The intermediate layer 32 is a porous film containing rutile crystal needle-like titanium oxide having a diameter of 30 to 200 nm and a length of 0.5 to 20 μm and anatase crystal granular titanium oxide having a diameter of 5 to 400 nm.

The acicular titanium oxide particles having a rutile crystal structure constituting the intermediate layer 32 have a diameter of 30 to 200 nm, a length of 0.5 to 20 μm and an aspect ratio of 5 or more .
The aspect ratio here is a value obtained by dividing the average length of the acicular particles by the acicular average diameter. The specific surface area is 5 to 30 m ² / g.
This rutile crystal needle-like titanium oxide is mixed with anatase crystal grain titanium oxide powder and applied as a slurry or paste to form rutile needle-like crystal particles on a porous body made of titanium oxide having an anatase crystal structure. The porous electrode layer produced by immobilization is the intermediate layer 32 in the present invention.

  The anatase-type titanium oxide particles forming the intermediate layer 32 preferably have a diameter of 5 nm to 400 nm, and the anatase-type titanium oxide has a rutile structure-type crystal structure. In some cases, it may be mixed as particles having a rutile crystal structure.

Regarding the method for forming the intermediate layer 32, a slurry of rutile crystal acicular titanium oxide mixed with anatase crystal granular titanium oxide powder and organometallic titanium, for example, tetraethoxy titanium Ti (C ₂ H ₅ O) ₄ described above. The same effect can be obtained even if the intermediate layer 32 is formed by using a paste. Similarly, a titanium oxide sol solution mixed with rutile crystal needle-like titanium oxide and anatase crystal granular titanium oxide powder may be used.

In the intermediate layer 32, an oxide such as zinc oxide, magnesium oxide, silicon oxide, aluminum oxide or the like having a particle size of 0.2 to 5 μm is mixed to improve the photoelectric conversion efficiency as a diffuse reflection component of transmitted light. Is possible.
Further, a photoelectric conversion efficiency is obtained as a diffuse reflection component of transmitted light by laminating an oxide such as titanium oxide, zinc oxide, magnesium oxide, silicon oxide, and aluminum oxide with a particle size of 0.2 to 5 μm on the intermediate layer 32. It is also possible to improve.

[Top layer]
An uppermost layer 33 is provided on the intermediate layer 32. The uppermost layer 33 is a porous film having a thickness of 0.1 to 10 μm made of anatase type crystalline granular titanium oxide having a diameter of 20 to 400 nm.
As a method for forming the uppermost layer 33, for example, a paste or slurry is applied on the intermediate layer by screen printing or spraying, and then dried and fired at 400 to 600 ° C., preferably 450 to 550 ° C. The uppermost layer 33 is not particularly limited to titanium oxide, and may be made of an oxide such as zinc oxide, magnesium oxide, silicon oxide, or aluminum oxide.

  In addition, before and after the dye is adsorbed on the titanium oxide film electrode film structure 3, for example, ketone, carboxylic acid, ether, etc., metal alkoxide, metal complex, metal salt, etc. are used for reverse electron transfer. The photoelectric conversion efficiency may be improved by forming a high resistance film or adsorption layer on the surface with a thickness of 5 nm or less.

  In the above description, the production method of the titanium oxide film electrode film structure 3 in the case of using a transparent substrate excellent in heat resistance such as soda lime glass has been described. However, PC, PE, and PET having insufficient heat resistance. In the following, description will be made on the case of using a transparent substrate made of an organic material such as PVC, fluororesin film or the like.

Basically, the transparent conductive film 2 is formed on a PC substrate, for example, by a film forming method such as sputtering, vapor deposition, or CVD. At this time, if a pinhole is generated in the film to be formed on the film surface, the resin substrate is swollen or dissolved by the solvent of the electrolytic solution, and the film is formed in a clean room in order to cause peeling of the film. Of the film formation methods, from the viewpoint of management and mass productivity, the sputtering method is usually good, and film formation by continuous sputtering is desirable in the chamber.
As a film-forming material for the transparent conductive film 2, ITO is easy to manage because ITO is not affected by the atmosphere. By such a film forming process, the transparent conductive film 2 is made conductive so that the sheet resistance becomes 100Ω or less.

After this transparent conductive film 2 is formed, a titanium alkoxide, a metal salt, or a titanium sol solution is mixed with an anatase crystal structure titanium oxide powder, applied, and dried at about 100 ° C. to form an underlayer 31. . This temperature is performed below the heat resistant temperature of the film material.
At this time, using a metal alkoxide or titanium sol solution, the titanium oxide powder of anatase type crystal structure is mixed and applied by screen printing or spraying, and fixed by gelation reaction at room temperature to about 50 ° C., Peeling due to thermal expansion of the substrate and thermal damage to the substrate can be reduced.

A porous titanium oxide electrode film is formed on the underlayer 31 by mixing the titanium oxide particles having an anatase type crystal structure to be the intermediate layer 32 with acicular titanium oxide having a rutile type crystal structure.
The intermediate layer 32 is preferably formed by mixing a titanium oxide particle having anatase type crystal structure with a titanium oxide having a needle-like form having a rutile type crystal structure and a titanium alkoxide and crosslinking the mixture by a hydrolysis reaction. Alternatively, without using titanium alkoxide, a method may be used in which the substrate surface is brought into contact with the high-frequency plasma and only the surface is heated to cool the back side of the substrate.

  Further, an intermediate layer 32 composed of a porous titanium oxide electrode film obtained by mixing a titanium oxide particle having a rutile crystal structure with titanium oxide particles having an anatase crystal structure directly on the transparent conductive film 2 is formed as a titanium alkoxide. The intermediate layer 32 may be formed by using a high-frequency plasma without using titanium alkoxide.

  As the film formation method of the uppermost layer 33, for example, a paste or slurry is applied on the intermediate layer by screen printing or spraying, and then dried, and only the surface is brought into high temperature so that the substrate surface is in contact with the high frequency plasma and necked. To form a film. Or you may make it discharge-sinter after drying of a coating film.

In the case of producing a cell using PC, PE, PET, PVC, or a fluororesin film, the transparent conductive film 2 is formed on the base of the titanium oxide film electrode film structure 3. In order to improve the durability, it is also easy to form a film, and to form a film of aluminum oxide, silicon oxide or the like in order to improve barrier properties against oxygen and moisture. The same applies to the positive electrode side of the counter electrode.
For example, the positive electrode is formed by forming a barrier film against oxygen or moisture on a PC film, forming a transparent conductive film thereon, and further depositing Pt to 10 nm or more by sputtering or the like.

[Dye-sensitized solar cell]
The dye-sensitized solar cell of the present invention uses a transparent substrate on which the titanium oxide film or the titanium oxide film electrode film structure 3 constituting the intermediate layer 32 described above is used as a negative electrode. Adsorb the dye for use.
Examples of the dye to be adsorbed on the titanium oxide film include ruthenium bipyridine dye, azo dye, quinone dye, quinone imine dye, quinacridone dye, squarylium dye, cyanine dye, merocyanine dye, triphenylmethane dye, Xanthene dyes, porphyrin dyes, phthalocyanine dyes, berylene dyes, indigo dyes, naphthalocyanine dyes and the like can be mentioned.

Examples of the dye adsorption method include a method in which the titanium oxide film 3 formed on the substrate is immersed in a solution in which the dye is dissolved (dye adsorption solution).
The solvent for dissolving the dye may be any solvent that dissolves the dye. Specifically, alcohols such as ethanol, ketones such as acetone, ethers such as diethyl ether and tetrahydrofuran, and nitrogen compounds such as acetonitrile. , Halogenated aliphatic hydrocarbons such as chloroform, aliphatic hydrocarbons such as hexane, aromatic hydrocarbons such as benzene, and esters such as ethyl acetate. Two or more of these solvents can be used in combination.

The concentration of the dye in the solution can be adjusted as appropriate depending on the type of dye and solvent to be used, but it is preferable that the concentration be as high as possible in order to improve the adsorption function. Therefore, a low concentration is preferable, and it may be 3 × 10 ⁻⁴ mol / liter or more.

Examples of the redox couple constituting the electrolyte include redox electrolytes such as an I ₃ ⁻ / I ⁻ system electrolyte and a Br ₃ ⁻ / Br ⁻ system electrolyte, and the oxidant constituting the redox pair is I _3. ^And an electrolyte of I ₃ ⁻ / I ⁻ system in which the reductant constituting the redox pair is I ⁻ is preferable, and metal iodides such as LiI, NaI, KI, CsI, and CaI ₂ , and tetra Combinations of iodides such as iodine salts of quaternary ammonium compounds such as alkylammonium iodide, pyridinium iodide, imidazolium iodide, and I ₂ can be mentioned. When an electrolyte made of such an iodine redox solution is used in such an electrolytic solution, the positive electrode side is preferably made of platinum or a conductive carbon material, and the catalyst particles are preferably made of platinum or a conductive carbon material.

  Solvents constituting the electrolyte include carbonate compounds such as ethylene carbonate and propylene carbonate; heterocyclic compounds such as 3-methyl-2-oxazolidinone; ether compounds such as dioxane and diethyl ether; ethylene glycol dialkyl ether and propylene glycol dialkyl ether , Polyethylene glycol dialkyl ether, polypropylene glycol dialkyl ether, ethylene glycol monoalkyl ether, propylene glycol monoalkyl ether, ethers such as polyethylene glycol monoalkyl ether, polypropylene glycol monoalkyl ether; alcohols such as methanol and ethanol; ethylene glycol, Propylene glycol, polyethylene glycol, polypropylene Glycol, polyhydric alcohols such as glycerin; acetonitrile, glutarodinitrile, methoxy acetonitrile, propionitrile, nitrile compounds such as benzonitrile; dimethyl sulfoxide, and the like aprotic polar substances such as sulfolane.

  The electrolyte concentration may be appropriately set depending on the type of electrolyte and solvent, and is, for example, 0.01 to 1.5 mol / liter, preferably 0.01 to 0.7 mol / liter. As an example of a specific electrolytic solution, lithium iodide is dissolved in acetonitrile so as to have concentrations of 0.06 mol / liter, iodine 0.06 mol / liter, and tertiary butylpyridine 0.3 mol / liter. Can be mentioned.

  As a method for bonding substrates, a substrate on which a dye-adsorbed titanium oxide film is formed and a substrate on which platinum is supported on a transparent conductive film are faced to each other and thermally fixed using an organic material such as an ionomer for sealing and fixing. Furthermore, a method of sealing the outer peripheral portion with a gas barrier material can be used.

Below, the characteristic and preparation conditions of the dye-sensitized solar cell of this invention are demonstrated.
Example 1
A glass plate made by cutting a glass plate (manufactured by Nippon Sheet Glass) having a transparent conductive film formed on a soda lime glass plate to a thickness of 3 mm 5 cm square was used as the glass substrate.
An ITO transparent conductive film having a thickness of 1 micron was formed on this glass plate by a spray method, and baked at 450 ° C. for 1 hour in the air. One glass substrate on which this transparent conductive film was formed was formed into a Pt film with a thickness of 200 nm by a sputtering method, and holes with a diameter of 1 mmΦ were formed at two opposite ends in a diagonal direction by a drill.

On a glass substrate on which another transparent conductive film was formed, a titanium oxide paste (SOLARONIX product name: Nanoxide HT) was applied to a thickness of 10 μm by screen printing. The applied film was baked at 450 ° C. for 1 hour to form a base layer.
An intermediate layer was formed thereon. Titanium oxide paste was applied in a thickness of 20 μm by screen printing. The titanium oxide paste used was 45% by weight as the amount of titanium oxide, and the others consisted of an ethylcellulose-based binder and a terpione solvent. The viscosity measured using a Brookfield rotational viscometer was 120 Pa · s under the conditions of a spindle No. 14 at 10 rpm and 25 ° C.

  Titanium oxide includes titanium oxide having an anatase type crystal structure with a particle size of 25 nm (trade name: “P25” manufactured by Degussa) and acicular titanium oxide having a rutile type crystal structure (product name: FTL-100). The mixed powder was used. The length and aspect ratio of the long axis of the powder vary depending on the mixing and grinding conditions of the powder. In this experiment, the acicular titanium oxide used from SEM observation has a diameter of 0.13 μm, a minimum length of 0.5 μm, and a maximum length of 4.0 μm. The average length was 1.7 μm. The aspect ratio was 4. Samples were made by changing the mixing ratio of the mixed powder. After applying the paste, baking was performed at 450 ° C. for 1 hour in the air.

Thereafter, a ruthenium complex-based dye ruthenium 535 (SOLARAONIX product name: ruthenium 535) was immersed in an ethanol solution having a concentration of 5 × 10 ⁻⁴ mol / liter and held for 8 hours. And it was immersed in absolute ethanol, the excess pigment | dye was removed, and it dried at 100 degreeC. When the electrode film is formed, printing is performed so that the titanium oxide paste is not attached to a portion 3 mm from the peripheral edge of the glass substrate. The peripheral edge of the glass substrate has a thickness of 60 μm from the outside to the inside. An ionomer (spacer S (trade name: “HIMILAN”) manufactured by Mitsui DuPont Polychemical Co., Ltd.) was attached with a width of 3 mm, and a load of 50 gf / cm ² was applied. In this state, heat fusion was performed at 120 ° C. with an ionomer.

Acetonitrile electrolyte solution to produce the cells were dissolved LiI and I ₂ were placed from the inlet, and injected to be uniform throughout the cell. The structure of the porous layer of this sample was observed with FE-SEM, and then the photoelectric conversion characteristics were examined.
As a comparative example, a cell was fabricated using a cell that did not contain acicular titanium oxide and a mixed ratio of titanium oxide with anatase-type crystal structure and acicular titanium oxide with a rutile-type crystal structure, and the photoelectric conversion efficiency was evaluated. did.

The produced titanium oxide film was observed with FE-SEM. The result of photographing the cross section of the titanium oxide film at a high magnification is shown in FIG. From this result, it can be seen that acicular titanium oxide is present in a dispersed state in the porous electrode layer of titanium oxide.
The result of photographing at a low magnification is shown in FIG. From this figure, it can be seen that a porous electrode layer is formed on the titanium oxide layer as the underlying layer on the transparent conductive film.
Further, when the ratio of acicular titanium oxide to titanium oxide having an anatase type crystal structure is 1:10, the titanium oxide needle as shown in FIG. 4 is observed by FE-SEM from the upper surface of the porous electrode layer. It was confirmed that there are cases where the shaped particles are oriented.

Next, the short-circuit current density (Jsc), open-circuit voltage (Voc), fill factor (FF), and energy conversion efficiency (η (%)) of the prepared cell and the dye-sensitized solar cell of the comparative example were measured. did.
The energy conversion efficiency (η (%)) of the dye-sensitized solar cell is represented by the following formula (A). Here, in the following formula (A), P ₀ is the incident light intensity [mWcm ⁻² ], Voc is the open circuit voltage [V], Jsc is the short circuit current density [mA · cm ⁻² ], F.I. F. Indicates a fill factor.
η = 100 × (Voc × Jsc × FF) / P ₀ (A)

The battery characteristic evaluation test uses a solar simulator (manufactured by Yamashita Denso, trade name: “YS-100H type”), and the irradiation condition of pseudo sunlight from a xenon lamp light source through an AM filter (AM1.5) is 100 mW. / Cm ² (so-called “1Sun” irradiation condition). Table 1 shows the results of photoelectric conversion efficiency.
From this result, the weight ratio of acicular titanium oxide to titanium oxide of anatase type crystal structure (value obtained by dividing the weight of acicular titanium oxide by the weight of titanium oxide of anatase type crystal structure) is in the range of 0.1 to 2. I found it good.

  The aspect ratio of the acicular particles used varies depending on the pulverization conditions at the time of mixing the powder, but the above-mentioned tendency is not changed as long as it is at least 6 or more.

( Test example )
Next, a description will be given of the results of a similar evaluation performed by changing the size of the anatase-type titanium oxide constituting the intermediate layer.
The production conditions of the dye-sensitized solar cell were the same. As the titanium oxide, a mixed powder of titanium oxide having an anatase type crystal structure (SOLARONIX product name: Nanoxide HT) and acicular titanium oxide having a rutile type crystal structure (product name: FTL-300) having a particle size of 9 nm was used.
Samples were made by changing the mixing ratio of the mixed powder.
The acicular titanium oxide used had a diameter of 0.22 μm, a minimum length of 1.0 μm, a maximum length of 15.0 μm and an average length of 5.3 μm. The aspect ratio was 24.

The short-circuit current density (Jsc), open-circuit voltage (Voc), fill factor (FF), and energy conversion efficiency (η (%)) of the produced cell and the dye-sensitized solar cell of the comparative example were measured. The measurement conditions for the photoelectric conversion efficiency were the same as described above.
The results of photoelectric conversion efficiency are shown in Table 2. From this result, as in Example 1, the weight ratio of acicular titanium oxide to titanium oxide having an anatase type crystal structure (value obtained by dividing the weight of acicular titanium oxide by the weight of titanium oxide having an anatase type crystal structure) was 0. A range of 1 to 2 was found to be good.

  The aspect ratio of the acicular particles used varies depending on the pulverization conditions at the time of mixing the powder, but the above-mentioned tendency was not changed as long as it is at least 5 or more.

(Example 3)
Next, the result in the case where the intermediate layer is formed directly without forming the underlying titanium oxide film on the transparent conductive film is shown. Sample preparation conditions are as follows.
The glass substrate used was a glass plate obtained by cutting a glass plate (Japanese plate glass product name :) having a transparent conductive film formed on a soda lime glass plate to a thickness of 3 mm and 5 cm square. One glass substrate was formed into a Pt film with a thickness of 100 nm by a sputtering method, and holes with a diameter of 1 mmΦ were formed at both ends in a diagonal direction by a drill.

In another glass substrate, an intermediate layer was formed on the transparent conductive film of the glass substrate. Titanium oxide paste was applied in a thickness of 20 μm by screen printing.
The titanium oxide paste used was 38% by weight as the amount of titanium oxide, and the others consisted of an ethylcellulose-based binder and a terpione solvent. The viscosity measured using a Brookfield rotational viscometer was 135 Pa · s under the conditions of No. 14 spindle, 10 rpm and 25 ° C. As the titanium oxide, a mixed powder of anatase type crystal structure titanium oxide (SOLARONIX product name: Nanoxide HT) having a particle size of 25 nm and a rutile type crystal structure of acicular titanium oxide ( manufactured by Ishihara Sangyo ) was used. Samples were made by changing the mixing ratio of the mixed powder. After applying the paste, baking was performed at 450 ° C. for 1 hour in the air.

Thereafter, a ruthenium complex-based dye ruthenium 535 (SOLARAONIX product name: ruthenium 535) was immersed in an ethanol solution having a concentration of 5 × 10 ⁻⁴ mol / liter and held for 8 hours. And it was immersed in absolute ethanol, the excess pigment | dye was removed, and it dried at 100 degreeC. When the electrode film is formed, printing is performed so that the titanium oxide paste is not attached to a portion 3 mm from the peripheral edge of the glass plate. The peripheral edge of the glass plate has a thickness of 60 μm from the outside to the inside. An ionomer (spacer S (trade name: “HIMILAN”) manufactured by Mitsui DuPont Polychemical Co., Ltd.) was adhered at a width of 3 mm, and a load of 50 gf / cm ² was applied. In this state, heat fusion was performed at 120 ° C. with an ionomer.

The short-circuit current density (Jsc), open-circuit voltage (Voc), fill factor (FF), and energy conversion efficiency (η (%)) of the produced cell and the dye-sensitized solar cell of the comparative example were measured. The measurement conditions for the photoelectric conversion efficiency were the same as described above.
The results of photoelectric conversion efficiency are shown in Table 3. From this result, the weight ratio of acicular titanium oxide to titanium oxide (value obtained by dividing the weight of acicular titanium oxide by the weight of titanium oxide) is preferably in the range of 0.1 to 2 as in Example 1 and the test example. I understood that.

In Example 3, the effect on the photoelectric conversion efficiency was examined by using a reflection film layer formed on the intermediate layer. As the reflective film, a titanium oxide having a particle size of 400 nm and a film having a size of 20 nm were used, and each of them was used alone to form a reflective layer.
The reflective film at this time was observed with an FE-SEM and shown in FIGS. From this result, it was confirmed that the titanium oxide size of the reflective film was made from 20 to 400 nm.
Next, Table 4 shows the results of evaluation assuming that the photoelectric conversion efficiency measurement conditions were the same as in Example 3. From this result, the photoelectric conversion efficiency was improved by forming the reflective film layer as the uppermost layer, and the result that the size of 400 nm was improved more than 20 nm was obtained.

It is the schematic sectional drawing which showed typically the example of the titanium oxide film electrode film structure of this invention. It is the photograph which image | photographed the cross section of the titanium oxide film electrode film structure of this invention at high magnification. It is the photograph which image | photographed the cross section of the titanium oxide film electrode film structure of this invention at low magnification. It is a photograph which shows the state in which the acicular particle | grains of the titanium oxide of this invention are orientating. It is the photograph which image | photographed the uppermost reflective film at low magnification at the time of forming a reflective film layer using a 20-nm titanium oxide particle for the intermediate | middle layer in this invention. It is the photograph which image | photographed the uppermost reflection film at low magnification at the time of forming a reflection film layer using a 400-nm titanium oxide particle for the intermediate layer in this invention.

Explanation of symbols

1 .... Glass substrate 2 .... Transparent conductive film 3 .... Titanium oxide film electrode film structure 31 ... Under layer 32 ... Intermediate layer 33 ... Top layer

Claims (7)

A titanium oxide film provided on a substrate,
The titanium oxide film is a porous film containing a rutile crystal needle-like titanium oxide having a diameter of 30 to 200 nm and a length of 0.5 to 20 μm, and an anatase crystal granular titanium oxide having a diameter of 5 to 400 nm. Titanium oxide film. The titanium oxide film according to claim 1 , wherein a weight ratio of the rutile crystal needle-like titanium oxide and the anatase crystal granular titanium oxide is 0.1: 1 to 2: 1 .   The titanium oxide film according to claim 1 or 2 formed by a screen printing method.   A dye-sensitized solar cell comprising the titanium oxide film according to any one of claims 1 to 3. A three-layer titanium oxide film electrode film structure,
4. The titanium oxide according to claim 1, wherein the base layer in contact with the transparent conductive film on the transparent substrate is composed of a titanium oxide film made of fine anatase type crystalline granular titanium oxide having a diameter of 5 to 10 nm. A titanium oxide film electrode film structure characterized in that it is composed of a film, and the uppermost layer is composed of a titanium oxide film made of anatase-type crystalline granular titanium oxide having a diameter of 20 to 400 nm.   6. The titanium oxide film electrode film structure according to claim 5, wherein the uppermost layer, the intermediate layer, and the underlayer are formed by a screen printing method.   A dye-sensitized solar cell comprising the titanium oxide film electrode film structure according to claim 5 or 6.

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