JP6032915B2 - Porous oxide semiconductor layer for photoelectric conversion element and method for producing the same - Google Patents

Description

  The present invention relates to a porous oxide semiconductor layer used for a photoelectric conversion element such as a dye-sensitized solar cell and a method for producing the same.

  Solar cells are attracting attention as environmentally friendly power generation devices, and silicon-based semiconductors using pn junctions are widely known. However, silicon-based solar cells require a high vacuum and a high temperature during production, and it is difficult to reduce the cost, which has hindered their spread.

  While development of a lower cost solar cell is awaited, a dye-sensitized solar cell using a titanium dioxide modified with a dye as an active electrode has been reported by Gretzel et al. (See Patent Document 1). Dye-sensitized solar cells are attracting attention as solar cells that can be easily manufactured at low cost.

  As the negative electrode for the dye-sensitized solar cell, a negative electrode made of an oxide semiconductor is used, and the light absorption amount of the oxide semiconductor is increased by using gold nanoparticles, silver nanoparticles, etc. Attempts have been made to increase the density (see Patent Document 2 and Non-Patent Document 1).

Japanese Patent Publication No. 8-15097 JP 2007-265694 A Japanese Patent No. 3513738 Japanese Patent No. 3983533 Japanese Patent No. 4633179

Keiji ISHIKAWA, Ching-Ju Wen, et al, Journal of Chemical Engineering. 2004, 37, 645-649

  However, if metal nanoparticles such as gold nanoparticles or silver nanoparticles are supported on an oxide semiconductor, the amount of light absorption increases, but the metal nanoparticles become a current leakage source, which can improve photoelectric conversion efficiency. could not. In particular, when the amount of metal nanoparticles was increased, the photoelectric conversion efficiency deteriorated.

  As described above, in the present invention, it is possible to suppress the metal nanoparticles from becoming a leak source while increasing the light absorption amount by the metal nanoparticles, and to improve the photoelectric conversion efficiency when the photoelectric conversion element is manufactured. An object of the present invention is to provide a porous oxide semiconductor layer that can be used.

As a result of intensive studies in view of the above object, a porous oxide semiconductor layer that has solved the above problems by forming a thin film made of an oxide semiconductor after supporting metal nanoparticles on the porous oxide semiconductor film is provided. It was found that it can be obtained. The present invention has been completed by further research based on such knowledge. That is, the present invention includes the following configurations.
Item 1. A porous oxide semiconductor layer for a photoelectric conversion element, wherein a thin film made of an oxide semiconductor is formed on a porous oxide semiconductor film on which metal nanoparticles are supported.
Item 2. Furthermore, the porous oxide semiconductor layer for photoelectric conversion elements of claim | item 1 with which the pigment | dye is carry | supported.
Item 3. Item 3. The porous oxide semiconductor layer for a photoelectric conversion element according to Item 1 or 2, wherein the metal nanoparticles include platinum nanoparticles.
Item 4. Item 4. The porous oxide semiconductor layer for a photoelectric conversion element according to any one of Items 1 to 3, wherein the oxide semiconductor constituting the thin film contains titanium oxide.
Item 5. Item 5. The porous oxide semiconductor layer for a photoelectric conversion element according to any one of Items 1 to 4, wherein the oxide semiconductor constituting the porous oxide semiconductor film contains titanium oxide.
Item 6. It is a manufacturing method of the porous oxide semiconductor layer for photoelectric conversion elements in any one of claim | item 1-5,
(1) A step of applying a paste composition containing titanium oxide and metal nanoparticles on a substrate to obtain a porous oxide semiconductor film carrying metal nanoparticles, and (2) obtained in step (1) above. And a step of immersing the porous oxide semiconductor film carrying the metal nanoparticles in a solution containing a precursor of the oxide semiconductor.
Item 7. further,
(3) The manufacturing method of claim | item 6 provided with the process which makes a porous oxide semiconductor layer for photoelectric conversion elements obtained at process (2) carry | support a pigment | dye.
Item 8. Item 8. The production method according to Item 6 or 7, wherein in the step (1), the content of the metal nanoparticles in the paste composition containing the metal nanoparticles is 0.1 to 10% by weight in the solid content.
Item 9. Item 9. The manufacturing method according to any one of Items 6 to 8, wherein in the step (1), the paste composition containing metal nanoparticles further contains an oxide semiconductor.
Item 10. Item 10. The production method according to any one of Items 6 to 9, wherein in the step (2), the immersion time is 1 to 120 minutes.
Item 11. Item 6. A negative electrode for a photoelectric conversion element, comprising the porous oxide semiconductor layer for a photoelectric conversion element according to any one of Items 1 to 5 on a substrate.
Item 12. Item 12. A photoelectric conversion device comprising the negative electrode for photoelectric conversion device according to Item 11.
Item 13. Item 13. A dye-sensitized solar cell comprising the photoelectric conversion element according to Item 12.

  ADVANTAGE OF THE INVENTION According to this invention, it can suppress that a metal nanoparticle becomes a leak source, increasing the light absorption amount by a metal nanoparticle, and improves photoelectric conversion efficiency when manufacturing a photoelectric conversion element. It is possible to provide a porous oxide semiconductor layer that can be used. This effect becomes more prominent if the amount of the metal nanoparticles used for supporting the metal nanoparticles is adjusted.

It is a graph which compares the open circuit voltage of an Example and a comparative example.

1. Porous oxide semiconductor layer In the porous oxide semiconductor layer of the present invention, a thin film made of an oxide semiconductor is formed on a porous oxide semiconductor film on which metal nanoparticles are supported.

<Porous oxide semiconductor film>
Although there is no restriction | limiting in particular as an oxide semiconductor which a porous oxide semiconductor film has, The titanium oxide etc. which are normally used for a photoelectric conversion element are used suitably.

In the present invention, “titanium oxide” or “titania” does not mean only titanium dioxide (TiO ₂ ), but dititanium trioxide (Ti ₂ O ₃ ); titanium monoxide (TiO); Ti ₄ It is a concept including a composition having oxygen deficiency from titanium dioxide represented by O ₇ , Ti ₅ O _{9 and the} like. Further, as represented by the terminal OH group, a group other than Ti—O—Ti resulting from the synthesis of titanium oxide may be included.

  When the porous oxide semiconductor film contains titanium oxide, the shape of the titanium oxide is not particularly limited as long as it is a material capable of forming a porous film. Examples thereof include titanium oxide nanoparticles, titanium oxide nanotubes, and tubular aggregates of titanium oxide nanoparticles (titanium oxide nanotubes in which titanium oxide nanoparticles are linked). Similarly, various shapes of materials can be used for other oxide semiconductors.

  As the titanium oxide nanoparticles, commercially available or known titania nanoparticles may be used, and for example, they may be synthesized by a sol-gel reaction using a titanium oxide precursor. Considering the conversion efficiency, it is preferable to synthesize by a sol-gel reaction using a titanium oxide precursor. Examples of the titanium oxide precursor that can be used at this time include titanium alkoxides such as titanium tetraisopropoxide, titanium hydroxide, titanium chloride, and titanium sulfate.

  The crystal structure of the titanium oxide nanoparticles is not particularly limited, but preferably contains at least one selected from the group consisting of anatase-type titanium oxide, rutile-type titanium oxide and brookite-type titanium oxide, and is active against light. From the viewpoint of high, it is more preferable to contain anatase type titanium oxide (particularly 70% by weight or more). Moreover, the crystal structure of the titanium oxide nanoparticles is not necessarily only one type, and two or more types of titanium oxide nanoparticles having different crystal structures may be mixed. When mixing two or more types of titanium oxide nanoparticles having different crystal structures, it is preferable to mix anatase-type titanium oxide and rutile-type titanium oxide and / or brookite-type titanium oxide. It is preferable to contain 70 to 95% by weight (particularly 90 to 95% by weight) of titanium oxide. The crystal structure of the titanium oxide nanoparticles can be measured by, for example, an X-ray diffraction method, Raman spectroscopic analysis, or the like.

  The average particle diameter of the titanium oxide nanoparticles is preferably 1 to 500 nm, more preferably 3 to 100 nm, from the viewpoint that more dye can be adsorbed and light can be absorbed. Moreover, as a titanium oxide nanoparticle, you may mix 2 or more types of titanium oxide nanoparticles from which an average particle diameter differs. In particular, from the viewpoint of the light confinement effect inside the battery, titanium oxide nanoparticles having a large average particle diameter (about 100 to 500 nm) and a large light scattering are used together with titanium oxide nanoparticles having a small average particle diameter (about 1 to 100 nm). May be. In addition, an average particle diameter can be measured by electron microscope (SEM) observation etc., for example.

  As the titanium oxide nanotubes, known or commercially available titanium oxide nanotubes can be adopted. For example, the titanium oxide nanotube etc. which are described in patent documents 3-4 etc. are mentioned.

  As the tubular aggregate of titanium oxide nanoparticles, the material described in Patent Document 5 can be used. Specifically, it is as follows.

  The tube-like aggregate of titanium oxide nanoparticles consists of a series of titanium oxide nanoparticles. In the present invention, “being connected” means that the titanium oxide nanoparticles are in close contact with the adjacent titanium oxide nanoparticles while maintaining the shape of the particles. In other words, it is different from amorphous titanium oxide nanotubes.

  The tubular aggregate of titanium oxide nanoparticles is formed such that the titanium oxide nanoparticles are continuously formed so as to form a tube. Thereby, the fine unevenness | corrugation exists in the surface of the tubular aggregate | assembly of a titanium oxide nanoparticle. By having fine irregularities on the surface, a large amount of dye can be supported and incident light can be efficiently absorbed. Since electrons are generated efficiently and adjacent titanium oxides are in close contact with each other, the electrons can be efficiently transferred to the transparent electrode through the adjacent titanium oxide.

  The crystal structure of the titanium oxide nanoparticles is not particularly limited, but preferably contains at least one selected from the group consisting of anatase-type titanium oxide, rutile-type titanium oxide and brookite-type titanium oxide, and is active against light. From the point of being high, it is more preferable that anatase type titanium oxide is included. The crystal structure of the titanium oxide nanoparticles can be measured by, for example, X-ray diffraction method, Raman spectroscopic analysis or the like. In addition to anatase-type titanium oxide, rutile-type titanium oxide and brookite-type titanium oxide, the titanium oxide nanoparticles further comprise a bivalent titanium oxide, a trivalent titanium oxide and a tetravalent titanium oxide. It may contain at least one selected from the group.

In addition to the titanium oxide nanoparticles, it is preferable to include titanium oxide having a crystal form of a Magneli phase structure. Although the specific structure of the titanium oxide having the crystal form of the magnetic phase structure is not clear, it is represented by the composition formula: Ti _n O _2n-1 (n: 4 to 10) and has the same conductivity as the metal. It is titanium oxide which has this. By containing a small amount of titanium oxide having a crystal form of this magnetic phase structure, it becomes possible to avoid electrical contact with the electrode and promote ion migration, and exhibits excellent characteristics. The content is 3% by weight or less, preferably 1% by weight or less.

  The average particle diameter of the titanium oxide nanoparticles is preferably 1 to 200 nm, more preferably 1 to 50 nm, from the point that light can be absorbed. In addition, an average particle diameter can be measured by electron microscope (SEM or TEM) observation etc., for example.

The tubular aggregate of titanium oxide nanoparticles preferably has a specific surface area of 20 m ² / g or more, more preferably 70 m ² / g or more, and still more preferably 80 m ² / g or more. The specific surface area is preferably larger, and the upper limit is not particularly limited, but is about 3000 m ² / g. The specific surface area can be measured by the BET method or the like.

  The tube-shaped aggregate of titanium oxide nanoparticles has a sufficient surface area and efficiently transmits electrons, so that the average inner diameter orthogonal to the major axis is 5 to 500 nm (especially 7 to 300 nm), and the average length of the major axis. 0.1 to 1000 μm (especially 1 to 50 μm) and an average aspect ratio (average length of long axis / average diameter perpendicular to the long axis) of 3 to 200000 (particularly 3 to 5000, more preferably 10 to 1000) are preferable. . In addition, a diameter means an outer diameter. The average inner diameter and average length of the tubular aggregate of titanium oxide nanoparticles can be measured, for example, by observation with an electron microscope (SEM).

  The thickness of the tubular aggregate of titanium oxide nanoparticles is not particularly limited, but is preferably about 2 to 500 nm and more preferably about 5 to 50 nm from the viewpoint of film formability. Moreover, the thickness of the tube-like aggregate of titanium oxide nanoparticles can be measured, for example, by observation with an electron microscope (SEM or TEM).

  The tubular aggregate of titanium oxide nanoparticles can be produced by the method described in Patent Document 5.

  The thickness of the porous oxide semiconductor film is not particularly limited. From the viewpoint of absorbing more incident light, the point of penetration of the electrolyte to the deep part of the electrode film, the point of ensuring uniform and good film formability, and the like. About 30 μm is preferable, and about 2-18 μm is more preferable.

<Metal nanoparticles>
In the present invention, the metal nanoparticles do not necessarily have to be coated with the porous oxide semiconductor film as long as they are supported (attached).

  As will be described later, when a dye is supported, electrons are difficult to conduct even if the metal nanoparticles and the dye are adjacent to each other. For this reason, it is preferable to interpose an oxide semiconductor between the metal nanoparticles and the dye. From this point of view, when supporting the metal nanoparticles, it is preferable to support the oxide semiconductor at the same time. As the oxide semiconductor at this time, those described above can be used.

  There is no restriction | limiting in particular as a metal which comprises a metal nanoparticle, Platinum, gold | metal | money, silver, etc. are mentioned. These are preferably made of at least one selected from the group consisting of platinum, gold, and silver because the wavelength at which plasmons are generated by the metal nanoparticles overlaps with the light absorption wavelength of the dye. Among these, platinum is preferable because it is a metal that does not dissolve by reacting with the electrolytic solution.

  3-30 nm is preferable and, as for the average particle diameter of a metal nanoparticle, 5-15 nm is more preferable. By setting the average particle diameter of the metal nanoparticles within the above range, plasmons are likely to be generated in a region near 30 to 800 nm. In addition, an average particle diameter can be measured by electron microscope (SEM or TEM) observation etc., for example.

  The supported amount of the metal nanoparticles is preferably about 0.01 to 10% by weight from the viewpoint of increasing the light absorption amount and suppressing the leakage current to improve the photoelectric conversion efficiency. A weight percentage is more preferred.

<Thin film made of oxide semiconductor>
In the present invention, a thin film made of an oxide is formed on a porous oxide semiconductor film on which metal nanoparticles are supported. More preferably, the porous oxide semiconductor film carrying the metal nanoparticles is covered with a thin film made of an oxide. Thereby, even if it is a case where a metal nanoparticle is not completely covered, a leak current can be suppressed effectively and photoelectric conversion efficiency can be improved.

  As will be described later, when a dye is supported, electrons are difficult to conduct even if the metal nanoparticles and the dye are adjacent to each other. For this reason, it is preferable to form the thin film which consists of an oxide semiconductor, and to interpose the thin film which consists of an oxide semiconductor between a metal nanoparticle and a pigment | dye.

  The oxide semiconductor constituting the thin film made of this oxide semiconductor can be as described above, and examples include titanium oxide. Further, preferable characteristics and the like are the same.

  The thickness of the thin film made of the oxide semiconductor is preferably about 1 to 20 μm, and more preferably 2 to 14 μm. By setting the thickness of the thin film made of an oxide semiconductor within this range, the electrolyte can easily penetrate to the deep part of the negative electrode, and the light use efficiency can be sufficient.

  The porous oxide semiconductor layer of the present invention may further carry a dye.

  The dye is not particularly limited as long as the dye has absorption characteristics in the visible region and the near infrared region, and improves (sensitizes) the light absorption efficiency of the porous oxide semiconductor layer. Dyes, semiconductors and the like are preferable. In addition, in order to impart adsorptivity to the porous oxide semiconductor layer, a carboxyl group, hydroxyl group, sulfonyl group, phosphonyl group, carboxylalkyl group, hydroxyalkyl group, sulfonylalkyl group, phosphonylalkyl group in the dye molecule Those having a functional group such as a group are preferred.

  As the metal complex dye, for example, a ruthenium, osmium, iron, cobalt, zinc, mercury complex, metal phthalocyanine, chlorophyll, or the like can be used. Examples of organic dyes include, but are not limited to, cyanine dyes, hemicyanine dyes, merocyanine dyes, xanthene dyes, triphenylmethane dyes, metal-free phthalocyanine dyes, and the like. As a semiconductor that can be used as a dye, an amorphous semiconductor having a large i-type light absorption coefficient, a direct transition semiconductor, a fine particle semiconductor that exhibits a quantum size effect and efficiently absorbs visible light, and the like are preferable. Usually, one of various semiconductors, metal complex dyes and organic dyes, or two or more kinds of dyes can be mixed in order to make the wavelength range of photoelectric conversion as wide as possible and increase the conversion efficiency. Moreover, the pigment | dye to mix and its ratio can be selected so that it may match with the wavelength range and intensity distribution of the target light source.

2. Method for producing porous oxide semiconductor layer The method for producing a porous oxide semiconductor layer of the present invention comprises:
(1) Applying a paste composition containing an oxide semiconductor and metal nanoparticles on a substrate to obtain a porous oxide semiconductor film carrying metal nanoparticles, and (2) In the step (1) A step of immersing the obtained porous oxide semiconductor film carrying metal nanoparticles in a solution containing an oxide semiconductor precursor is provided.

<Step (1)>
The oxide semiconductor and metal nanoparticles contained in the paste composition containing the oxide semiconductor and metal nanoparticles are those described above.

  In the paste composition containing an oxide semiconductor and metal nanoparticles, the content of the oxide semiconductor and metal nanoparticles in the solid content is preferably 90 to 99.9% by weight of the oxide semiconductor, respectively, and 95 to 99. 8% by weight is more preferable, and 96 to 99.7% by weight is more preferable. Moreover, 0.1-10 weight% is preferable, as for content of a metal nanoparticle, 0.2-5 weight% is more preferable, and 0.3-4 weight% is further more preferable. By making content of an oxide semiconductor and a metal nanoparticle in the said range, while increasing light absorption amount, a leak current can be suppressed effectively and photoelectric conversion efficiency can be improved.

  In the paste composition containing the oxide semiconductor and the metal nanoparticles, the solid content concentration is 5 to 5 in terms of balancing the fluidity at the time of coating and the thickness after coating, and controlling the pore size of the porous oxide semiconductor film. 40% by weight, particularly 8 to 20% by weight, is preferred.

  Moreover, water, an organic solvent, etc. can be used as a solvent of the paste composition containing a metal nanoparticle.

  The organic solvent is not particularly limited as long as it can disperse the metal nanoparticles and the oxide semiconductor. For example, alcohols such as ethanol, methanol and terpineol (particularly α-terpineol); glycols such as ethylene glycol, polyethylene glycol, propylene glycol and polypropylene glycol can be used. These solvents may be used alone or in combination of two or more in consideration of dispersibility, volatility and viscosity. A preferred example is terpineol (particularly α-terpineol). The proportion of the solvent in the paste composition containing the metal nanoparticles is preferably 30 to 80% by weight, particularly 60 to 75% by weight, because fluidity is imparted during coating.

  As a component of the dispersion liquid, a thickener or the like may be included in addition to the above solvent.

  Examples of the thickener include alkyl celluloses such as methyl cellulose and ethyl cellulose. Of these, ethyl cellulose can be preferably used.

  The proportion of the thickener in the paste composition for forming a porous oxide semiconductor film is preferably 5 to 20% by weight, particularly preferably 6 to 15% by weight, from the viewpoint of fluidity during application.

  There is no restriction | limiting in particular as a board | substrate, It has a smooth surface at normal temperature, The surface may be either a plane and a curved surface, and may deform | transform by stress. Specific examples of the substrate that can be used include various glasses, and transparent resins such as PET (polyethylene terephthalate) and PEN (polyethylene naphthalate) that have a transparent conductive function. However, when baking at a high temperature of 300 ° C. or higher, it is preferable to use a glass substrate.

  The coating method is not particularly limited, and conventional methods such as screen printing, doctor blade, dip coating, spray coating, spin coating, and squeegee method may be adopted. Screen printing is preferably employed because the throughput can be realized.

  It is preferable to dry after coating. The drying conditions are not particularly limited, but are preferably 25 to 250 ° C., preferably 50 to 150 ° C. for 1 to 120 minutes, preferably 5 to 15 minutes.

  By this step, a porous oxide semiconductor film carrying metal nanoparticles can be obtained.

<Step (2)>
The solution in which the porous oxide semiconductor film carrying the metal nanoparticles obtained in the step (1) is immersed contains an oxide semiconductor precursor. As such an oxide semiconductor precursor, an oxide semiconductor can be formed by, for example, heating after immersing the porous oxide semiconductor film carrying the metal nanoparticles obtained in step (1). Although there is no particular limitation as long as it is present, for example, titanium hydroxide, titanium halide (titanium tetrachloride, etc.), titanium alkoxide (tetraisopropoxy titanium, tetraethoxy titanium, etc.), titanium metal and the like can be mentioned. Of these, titanium halides, particularly titanium tetrachloride, are preferred from the viewpoint that a uniform titanium oxide film can be obtained at low cost and is easy to handle.

  In addition, the solvent of the solution in which the porous oxide semiconductor film carrying the metal nanoparticles obtained in the step (1) is immersed is not particularly limited as long as it can dissolve the oxide semiconductor precursor, In order to synthesize titanium oxide by hydrolysis, an aqueous solvent such as water is preferred.

  The concentration of the oxide semiconductor precursor in the solution is not particularly limited, but is preferably 0.1 to 100 mmol / L from the viewpoint that coating can be performed in a short time and titanium oxide does not precipitate in the solution. ˜50 mmol / L is more preferable.

  The time for immersing the porous oxide semiconductor film on which the metal nanoparticles obtained in step (1) are supported is not particularly limited, but is preferably 1 to 120 minutes, preferably 5 to 60 minutes.

  It is preferable to further heat after immersion. The heating condition is 100 to 750 ° C., preferably 350 to 550 ° C. for 10 to 180 minutes, particularly preferably 15 to 30 minutes.

<Step (3)>
In the present invention, after the step (2),
(3) You may give the process which carry | supports a pigment | dye to the porous oxide semiconductor layer for photoelectric conversion elements obtained at the process (2).

  The dye is as described above.

  As a method of adsorbing the dye to the porous oxide semiconductor layer, for example, a method in which a solution in which the dye is dissolved in a solvent is applied on the porous titanium oxide coating film by spray coating or spin coating and then dried. Can be formed. In this case, the substrate may be heated to an appropriate temperature. Moreover, the method of immersing a porous oxide semiconductor layer in the said pigment | dye solution and adsorb | sucking can also be used. The immersion time is not particularly limited as long as the dye is sufficiently adsorbed, but is preferably 10 minutes to 30 hours, more preferably 1 to 25 hours. In addition, it is preferable to adjust the time immersed in a pigment | dye solution with the pigment | dye to be used. For example, when D908 (ruthenium dye) manufactured by EverSolar is used, it is preferably about 15 to 25 hours, and when MK-2 (organic dye) manufactured by Sigma-Aldrich is used, it is preferably about 1 to 5 hours. Moreover, you may heat when immersing as needed. The concentration of the dye in the solution is preferably about 0.01 to 100 mmol / L, and more preferably about 0.1 to 10 mmol / L.

  The solvent to be used is not particularly limited, but water and an organic solvent are preferably used. Examples of the organic solvent include alcohols such as methanol, ethanol, 1-propanol, 2-propanol, 1-butanol, 2-butanol, and t-butanol; acetonitrile, propionitrile, methoxypropionitrile, glutaronitrile, and the like. Nitriles; aromatic hydrocarbons such as benzene, toluene, o-xylene, m-xylene, p-xylene; aliphatic hydrocarbons such as pentane, hexane, heptane; alicyclic hydrocarbons such as cyclohexane; acetone, methyl ethyl ketone Ketones such as diethyl ketone and 2-butanone; ethers such as diethyl ether and tetrahydrofuran; ethylene carbonate, propylene carbonate, nitromethane, dimethylformamide, dimethyl sulfoxide, hexamethylphosphoamide, dimethoxy Ethane, γ-butyrolactone, γ-valerolactone, sulfolane, dimethoxyethane, adiponitrile, methoxyacetonitrile, dimethylacetamide, methylpyrrolidinone, dimethylsulfoxide, dioxolane, sulfolane, trimethyl phosphate, triethyl phosphate, tripropyl phosphate, ethyl phosphate Dimethyl, tributyl phosphate, tripentyl phosphate, trihexyl phosphate, triheptyl phosphate, trioctyl phosphate, trinonyl phosphate, tridecyl phosphate, tris phosphate (trifluoromethyl), tris phosphate (pentafluoroethyl), Examples thereof include triphenyl polyethylene glycol phosphate and polyethylene glycol.

  In order to reduce the interaction such as aggregation between the dyes, a colorless compound having properties as a surfactant may be added to the dye adsorption liquid and co-adsorbed to the semiconductor layer. Examples of such colorless compounds include steroid compounds such as cholic acid having a carboxyl group or sulfo group, deoxycholic acid, chenodeoxycholic acid, taurodeoxycholic acid, sulfonates, and the like.

  It is preferable to remove the unadsorbed dye by washing immediately after the adsorption step. Washing is preferably performed using acetonitrile, an alcohol solvent or the like in a wet washing tank.

  After adsorbing the dye, oxidation with amines, quaternary ammonium salts, ureido compounds having at least one ureido group, silyl compounds having at least one silyl group, alkali metal salts, alkaline earth metal salts, etc. The surface of the titanium layer may be treated. Examples of preferred amines include pyridine, 4-t-butylpyridine, polyvinylpyridine and the like. Examples of preferred quaternary ammonium salts include tetrabutylammonium iodide, tetrahexylammonium iodide and the like. These may be used by dissolving in an organic solvent, or may be used as they are in the case of a liquid.

3. The substrate anode above described porous oxide semiconductor layer is formed may be a negative electrode of the present invention.

  As described above, the substrate used here is preferably a resin substrate or a glass substrate (in particular, a transparent substrate made of a resin substrate or a glass substrate). However, when baking at a temperature of 300 ° C. or higher, it is preferable to use a glass substrate.

  The resin substrate is not particularly limited as long as it is transparent. For example, polyester such as polyethylene naphthalate resin substrate (PEN resin substrate) and polyethylene terephthalate resin substrate (PET resin substrate); polyamide; polysulfone; polyethersulfone; Examples include ether ether ketone, polyphenylene sulfide, polycarbonate, polyimide, polymethyl methacrylate, polystyrene, cellulose triacetate, and polymethylpentene.

  There is no restriction | limiting in particular also as a glass substrate, What is necessary is just to use a well-known or commercially available thing, and any of colorless or colored glass, meshed glass, a glass block etc. may be sufficient.

  The resin substrate or glass substrate preferably has a thickness of about 0.05 to 10 mm.

  In the present invention, the porous oxide semiconductor layer may be directly formed on the surface of the resin substrate or the glass substrate, but may be formed through a transparent conductive film.

  Examples of the transparent conductive film include a tin-doped indium oxide film (ITO film), a fluorine-doped tin oxide film (FTO film), an antimony-doped tin oxide film (ATO film), an aluminum-doped zinc oxide film (AZO film), and a gallium-doped zinc oxide. Examples include a film (GZO film). By passing through these transparent conductive films, in the case of a structure for collecting current from the resin substrate or glass substrate side (front contact), it becomes easy to take out the generated current to the outside. The film thickness of these transparent conductive films is preferably about 0.02 to 10 μm.

  The method for forming the porous oxide semiconductor layer on the resin substrate or the glass substrate is the method described in the above “1. Porous oxide semiconductor layer” and “2. Method for producing porous oxide semiconductor layer”. Can be adopted.

4). Photoelectric Conversion Element and Dye-Sensitized Solar Cell The photoelectric conversion element of the present invention can be produced, for example, by forming a counter electrode (counter electrode) on the negative electrode of the present invention and filling between these electrodes with an electrolytic solution.

  The counter electrode may have a single layer structure made of a conductive material, or may be composed of a conductive layer and a substrate. The substrate is not particularly limited, and the material, thickness, dimensions, shape, and the like can be appropriately selected according to the purpose. Resin may be used. Examples of such resins include polyesters such as polyethylene terephthalate, polyamide, polysulfone, polyether sulfone, polyether ether ketone, polyphenylene sulfide, polycarbonate, polyimide, polymethyl methacrylate, polystyrene, cellulose triacetate, and polymethylpentene. Alternatively, a counter electrode may be formed by directly applying, plating, or vapor-depositing (PVD, CVD) a conductive material on the charge transport layer.

  As the conductive material, a metal having a small specific resistance, such as a metal such as platinum, gold, nickel, titanium, aluminum, copper, silver, or tungsten; a carbon material; or a conductive organic material is used.

  A metal lead may be used for the purpose of reducing the resistance of the counter electrode. The metal lead is preferably made of a metal such as platinum, gold, nickel, titanium, aluminum, copper, silver or tungsten, and particularly preferably made of aluminum or silver.

  The electrolytic solution is not particularly limited.

In the electrolyte solution, it is preferable to use iodine and iodide as the electrolyte.

Iodine and iodide form I ⁻ / I ₃ ⁻ which is a redox _couple in the electrolytic solution of the present invention (I ₃ ⁻ is produced by adding I ₂ in the presence of I ⁻ ).

  As a result, there is an effect of improving the electron injection rate from the dye to the titanium oxide by lowering the titanium oxide conduction band. It also has an effect of promoting the transport of electrons injected into titanium oxide. Thereby, a short circuit current density can be improved more and, as a result, a photoelectric conversion efficiency can be improved more.

  Examples of the iodide as the electrolyte include lithium iodide, 1-ethyl-3-methylimidazolium iodide, 1,3-dimethylimidazolium iodide, 1-methyl-3-propylimidazolium iodide, Examples thereof include 1-butyl-3-methylimidazolium iodide, imidazolium salt of 1-methyl-3-hexylimidazolium iodide, and the like. In the present invention, 1-methyl-3-propylimidazolium iodide which can also be used as a solvent is preferable.

  Concentrations of electrolytes are 0.05 to 0.6 mol / liter (preferably 0.1 to 0.5 mol / liter) for iodine, and 0.05 to 20 mol / liter for lithium iodide or imidazolium salt, respectively. About (preferably 0.1-10 mol / liter) is preferable.

  As described above, 1-methyl-3-propylimidazolium iodide may be used as a solvent, and ionic liquid 1-ethyl-3-methylimidazolium bissulfonylimide or the like may be used as a solvent.

  In addition to the above-described components, the electrolytic solution may contain a basic substance such as 4-tertiarybutylpyridine and N-methylbenzimidazole. If these basic substances are contained, when a photoelectric conversion element is produced, it is adsorbed on the surface of the titanium oxide of the negative electrode and can prevent reverse electron transfer from the negative electrode, further improving the open-circuit voltage, Conversion efficiency can be further improved.

  Further, in order not to desorb the dye, the basic substance is added in an amount of about 0.1 to 1.0 mol / liter, particularly about 0.3 to 0.8 mol / liter when a metal complex dye is used. Is preferred. Moreover, when using an organic pigment | dye, about 0.01-0.1 mol / liter, especially about 0.03-0.08 mol / liter are preferable.

  In addition, guanidine thiocyanate, which has the effect of lowering the titania conduction band and improving the electron injection rate from the dye to titania, can be added to the electrolytic solution as in the case of lithium iodide described above. In this case, the amount of addition is preferably about 0.1 to 1.0 mol / liter.

  In addition, in the electrolytic solution, in addition to the above components, a viscosity modifier (polyethylene glycol, etc.), a dehydrating agent (zeolite, silica gel, etc.) and the like can be included within a range that does not impair the effects of the present invention.

  The dye-sensitized solar cell of the present invention can be manufactured by modularizing the photoelectric conversion element and providing predetermined electrical wiring.

  The present invention will be specifically described based on examples, but the present invention is not limited to these examples.

Comparative Example 1
Using a polyester screen printing plate (225 mesh) on a glass with an FTO film, a commercially available titanium oxide paste PST18NRD made by JGC Catalysts & Chemicals Co., Ltd. is 5 mm square and 4 μm thick. Screen printing was repeated until Furthermore, it put into the electric furnace and baked at 550 degreeC for 1 hour.

  The obtained titanium oxide layer was added to a solution prepared by using 0.3 mMol / L ruthenium dye (D708) as a solvent prepared with acetonitrile and tertiary butyl alcohol at a volume ratio of 1: 1 at 25 ° C. (room temperature) for 20 hours. After dipping, the film was dried and a dye was supported thereon to produce a negative electrode of Comparative Example 1.

  Next, a platinum-plated counter electrode was bonded to a transparent glass substrate with a transparent electrode through a spacer, and 0.15 mol / L iodine, 0.1 mol / L guanidine thiocyanate, 0.5 mol / L was used as an electrolytic solution therebetween. A 1-methyl-3-propylimidazolium iodide solution containing L n-methylbenzimidazole was injected to produce a photoelectric conversion element.

Comparative Example 2
As a commercially available titanium oxide paste, 99% by weight of PST18NRD made by JGC Catalysts & Chemicals Co., Ltd., and as a commercially available platinum paste, 1% by weight of T / SP made by SOLALONIX was mixed and stirred to paste platinum for carrying platinum. A composition was obtained.

  Using the polyester screen printing plate (225 mesh) on the FTO film-coated glass, the above-prepared platinum-supporting paste composition was repeatedly screen-printed to a size of 5 mm square and a film thickness of 4 μm. It was. Furthermore, it put into the electric furnace and baked at 550 degreeC for 1 hour, and obtained the platinum carrying | support titanium oxide layer. The supported amount is approximately the same as the platinum / titanium oxide ratio in the platinum supporting paste composition.

  The obtained platinum-supported titanium oxide layer was added to a solution prepared by using 0.3 mmol / L of a ruthenium dye (D708) as a solvent in which acetonitrile and tertiary butyl alcohol were prepared at a volume ratio of 1: 1 at 25 ° C. (room temperature). After being immersed for 20 hours, it was dried and a dye was supported thereon to produce a negative electrode of Comparative Example 2.

  Next, a platinum-plated counter electrode was bonded to a transparent glass substrate with a transparent electrode through a spacer, and 0.15 mol / L iodine, 0.1 mol / L guanidine thiocyanate, 0.5 mol / L was used as an electrolytic solution therebetween. A 1-methyl-3-propylimidazolium iodide solution containing L n-methylbenzimidazole was injected to produce a photoelectric conversion element.

Example 1
As a commercially available titanium oxide paste, 99% by weight of PST18NRD manufactured by JGC Catalysts & Chemicals Co., Ltd., and as a commercially available platinum paste, 1% by weight of T / SP manufactured by SOLARONIX was mixed and stirred to mix with platinum. A composition was obtained.

  Using the polyester screen printing plate (225 mesh) on the FTO film-coated glass, the produced platinum-supporting paste composition was repeatedly screen-printed to a size of 5 mm square and a film thickness of 4 μm. . Furthermore, it put into the electric furnace and baked at 550 degreeC for 1 hour, and obtained the platinum carrying | support titanium oxide layer.

  Next, coating was performed by immersing PST18NRD made by JGC Catalysts & Chemicals Co., Ltd., a commercially available titanium oxide paste on a platinum-supported titanium oxide layer for 10 minutes in a titanium tetrachloride aqueous solution having a concentration of 40 mmol / L. . Furthermore, it put into the electric furnace and baked for 30 minutes at 500 degreeC.

  The obtained titanium oxide layer was added to a solution prepared by using 0.3 mMol / L ruthenium dye (D708) as a solvent prepared with acetonitrile and tertiary butyl alcohol at a volume ratio of 1: 1 at 25 ° C. (room temperature) for 20 hours. After being immersed, it was dried and a dye was supported thereon to produce the negative electrode of Example 1.

  Next, a platinum-plated counter electrode was bonded to a transparent glass substrate with a transparent electrode through a spacer, and 0.15 mol / L iodine, 0.1 mol / L guanidine thiocyanate, 0.5 mol / L was used as an electrolytic solution therebetween. A 1-methyl-3-propylimidazolium iodide solution containing L n-methylbenzimidazole was injected to produce a photoelectric conversion element.

Example 2
The negative electrode and photoelectric conversion inhibition of Example 2 were obtained in the same manner as in Example 1 except that the time of immersion in the aqueous titanium tetrachloride solution was 30 minutes instead of 10 minutes.

Comparative Example 3
The paste composition for supporting platinum is not a paste composition containing 99% by weight of PST18NRD made by JGC Catalysts Chemical Co., Ltd. and 1% by weight of T / SP made by SOLARONIX, but 95 of PST18NRD made by JGC Catalysts Chemical Co., Ltd. A negative electrode and a photoelectric conversion element of Comparative Example 3 were obtained in the same manner as Comparative Example 2 except that a paste composition containing 5% by weight of T / SP made by SOLARONIX was used.

Example 3
The paste composition for supporting platinum is not a paste composition containing 99% by weight of PST18NRD made by JGC Catalysts Chemical Co., Ltd. and 1% by weight of T / SP made by SOLARONIX, but 95 of PST18NRD made by JGC Catalysts Chemical Co., Ltd. Example 1 except that a paste composition containing 5% by weight of T / SP made by SOLARONIX is used, and the coating time for coating the titanium oxide paste after carrying platinum is 30 minutes instead of 10 minutes. Similarly, the negative electrode and photoelectric conversion inhibition of Example 3 were obtained.

Experimental Example Light having an intensity of 100 mW / cm ² under the conditions of AM1.5 (JISC8912A rank) was applied to the photoelectric conversion elements produced in Examples 1 to 3 and Comparative Examples 1 to 3 using a solar simulator manufactured by Yamashita Denso Co., Ltd. The photoelectric conversion characteristics were evaluated.

  The results of the experimental examples are shown in Table 1 and FIG. 1 for each example and comparative example.

Claims (10)

Metal nanoparticles supported porous oxide semiconductor film, the porous oxide semiconductor layer and the metal nanoparticles Ri Do from the oxide semiconductor is coated with a thin film which is not supported further dye is supported and has a porous oxide semiconductor layer for a photoelectric conversion element, photoelectric the thin film and the metal nanoparticle Ri do from the oxide semiconductor between said metal nanoparticle dyes is not carried is interposed A porous oxide semiconductor layer for a conversion element. The porous oxide semiconductor layer for a photoelectric conversion element according to claim 1, wherein the metal nanoparticles include platinum nanoparticles. The porous oxide semiconductor layer for photoelectric conversion elements according to claim 1 or 2, wherein the oxide semiconductor constituting the thin film contains titanium oxide. The porous oxide semiconductor layer for photoelectric conversion elements according to claim 1, wherein the oxide semiconductor constituting the porous oxide semiconductor film contains titanium oxide. It is a manufacturing method of the porous oxide semiconductor layer for photoelectric conversion elements in any one of Claims 1-4,
(1) A step of applying a paste composition containing titanium oxide and metal nanoparticles on a substrate to obtain a porous oxide semiconductor film carrying metal nanoparticles,
(2) A step of heating the porous oxide semiconductor film carrying the metal nanoparticles obtained in the step (1) after being immersed in a solution containing a precursor of an oxide semiconductor, and a step (3). Porous oxide semiconductor for photoelectric conversion element , wherein the porous oxide semiconductor film carrying the metal nanoparticles obtained in (2) is covered with a thin film made of an oxide semiconductor and not carrying the metal nanoparticles A production method comprising a step of supporting a dye on a layer. The manufacturing method according to claim 5, wherein in the step (1), the content of the metal nanoparticles in the paste composition containing the metal nanoparticles is 0.1 to 10% by weight in the solid content. The manufacturing method of Claim 5 or 6 whose immersion time is 1-120 minutes in the said process (2). The negative electrode for photoelectric conversion elements provided with the porous oxide semiconductor layer for photoelectric conversion elements in any one of Claims 1-4 on a board | substrate. A photoelectric conversion element provided with the negative electrode for photoelectric conversion elements of Claim 8. A dye-sensitized solar cell comprising the photoelectric conversion element according to claim 9.

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