JP2013196948A - Cathode separator integrated electrode and photoelectric conversion element - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an integrated electrode allowing the manufacture of a photoelectric conversion element whose photoelectric conversion efficiency and maintenance rate are not reduced when a spacer is used in order to easily manufacture the photoelectric conversion element.SOLUTION: In the integrated electrode in which a cathode and a separator are integrated together, the separator is made of a porous material containing titanium oxide. It is preferable that the integrated electrode contains an electrolyte particularly in a porous structure of the separator.

Description

  The present invention relates to a positive electrode separator integrated electrode and a photoelectric conversion element.

  Dye-sensitized solar cells are attracting attention as solar cells following silicon-based solar cells because they can be manufactured by a low-cost process that does not require vacuum equipment, and the constituent materials are also low-cost. Unlike the silicon-based solar cell, the structure is usually a structure in which an electrolytic solution is interposed between the opposing negative electrode and positive electrode. The electrolytic solution plays a role of transporting charges between the positive electrode and the negative electrode, and high ion mobility is required. At the same time, it is necessary to prevent a short circuit between the positive electrode and the negative electrode. For this reason, a cell having a spacer structure is required so that ions in the electrolytic solution easily move.

  As the spacer, a hollow film having a shape that can secure a space is generally used (Non-Patent Document 1). It has been proposed to use a porous material such as a nonwoven fabric as a spacer (Patent Document 1).

  Further, a quasi-solid gel electrolyte may be used instead of the electrolytic solution without using the spacer (Non-patent Document 2).

JP 2006-040828 A Japanese Patent No. 3513738 Japanese Patent No. 3983533 Japanese Patent No. 4633179 International Publication No. 00/40509 Pamphlet Japanese Patent No. 3355442 JP 2002-338220 A Japanese Patent No. 3569806 Patent No. 2546114

Thin Solid Films 516, 4613-4619 (2008) Fujikura Technical Review, 107, 73-78 (2004)

  As in Patent Document 1, when a conventional porous layer is formed on the positive electrode as a spacer, a uniform electrode distance can be secured. In addition, although the device manufacturing process can be simplified, the pore size is limited and the current density is reduced. Therefore, when applied to a cell that requires a high current density such as a dye-sensitized solar cell, a sufficient current cannot be obtained and the conversion efficiency is lowered. Also, as in Non-Patent Document 2, even if the electrolyte is a gel electrolyte, the gel electrolyte is indefinite and soft, so when producing a foldable battery, the gel electrolyte alone is not suitable. Since it is difficult to maintain a certain distance between the electrodes, a spacer was eventually required, and this was not a radical solution. An object of this invention is to provide the integrated electrode which can solve such a trade-off. That is, an object is to provide an integrated electrode capable of manufacturing a photoelectric conversion element that does not decrease the photoelectric conversion efficiency and the maintenance rate when a spacer is used to easily manufacture the photoelectric conversion element.

As a result of intensive studies, the present inventors have integrally formed a porous layer of titania nanoparticles (especially a porous layer made of a sintered body) on the positive electrode of the dye-sensitized solar cell. I found that it can be solved. The present invention has been completed by further research based on such knowledge. That is, the present invention includes the following configurations.
Item 1. An integrated electrode in which a positive electrode and a separator are integrated,
The separator is made of a porous body containing titanium oxide.
Integrated electrode.
Item 2. Item 2. The integrated electrode according to Item 1, wherein the separator is made of a porous sintered body containing titanium oxide.
Item 3. Item 3. The integrated electrode according to Item 2, wherein the separator has a thickness of 0.1 to 5 µm.
Item 4. Item 4. The integrated electrode according to any one of Items 1 to 3, wherein the porous body has a specific surface area of 3 to 150 m ² / g.
Item 5. Item 5. The integrated electrode according to any one of Items 1 to 4, wherein the titanium oxide contains titania nanotubes.
Item 6. Item 6. The integrated electrode according to any one of Items 1 to 5, wherein the positive electrode includes a conductive substrate.
Item 7. Item 6. The integrated electrode according to any one of Items 1 to 5, wherein the positive electrode has a conductive layer containing a conductive material formed on a substrate.
Item 8. Item 8. The integrated electrode according to any one of Items 1 to 7, wherein the positive electrode has a conductive layer containing a conductive material formed on a conductive substrate.
Item 9. Item 9. The integrated electrode according to Item 7 or 8, wherein the conductive layer further contains a binder.
Item 10. Item 10. The integrated electrode according to Item 9, wherein the binder is an inorganic oxide.
Item 11. Item 11. The integrated electrode according to Item 10, wherein the inorganic oxide is at least one oxide selected from the group consisting of tin oxide, titanium oxide, and zinc oxide.
Item 12. Item 12. The integrated electrode according to any one of Items 1 to 11, wherein the integrated electrode contains an electrolytic solution.
Item 13. Item 13. The integrated electrode according to Item 12, wherein the electrolytic solution is present in pores of the porous body.
Item 14. Item 14. The integrated electrode according to Item 12 or 13, wherein the electrolytic solution contains an ionic liquid.
Item 15. Item 15. The integrated electrode according to Item 14, wherein the ionic liquid is 1-ethyl-3-methylimidazolium bisfluorosulfonylimide.
Item 16. The electrolytic solution contains an electrolyte containing iodide including iodine and 1,3-dialkylimidazolium iodide, and
(1) The 1,3-dialkylimidazolium iodide includes 1-ethyl-3-methylimidazolium iodide and 1,3-dimethylimidazolium iodide.
(2) The electrolytic solution contains 3.0 mol / liter or more of the 1,3-dialkylimidazolium iodide.
(3) The integrated electrode according to any one of Items 12 to 15, wherein the 1,3-dialkylimidazolium iodide satisfies at least one of containing 1-methyl-3-propylimidazolium iodide.
Item 17. The electrolyte is
(1) The integral electrode according to item 16, wherein the 1,3-dialkylimidazolium iodide satisfies 1-ethyl-3-methylimidazolium iodide and 1,3-dimethylimidazolium iodide.
Item 18. Item 18. The integrated electrode according to Item 17, wherein the electrolytic solution contains 3.0 mol or more of the 1,3-dialkylimidazolium iodide with respect to 1 liter of solvent.
Item 19. The 1,3-dialkylimidazolium iodide further includes 1-methyl-3-propylimidazolium iodide and / or 1-butyl-3-methylimidazolium iodide.
Item 19. The integrated electrode according to Item 17 or 18.
Item 20. Item 20. The method for producing an integral electrode according to any one of Items 1 to 19,
A manufacturing method provided with the process of apply | coating and sintering the composition for separator formation containing a titanium oxide or a titanium oxide precursor on a positive electrode.
Item 21. Item 20. A photoelectric conversion element comprising the integrated electrode according to any one of Items 1 to 19.
Item 22. Item 22. The photoelectric conversion element according to Item 21, further comprising a negative electrode.
Item 23. A method for producing a photoelectric conversion element comprising a negative electrode and the integral electrode according to any one of Items 1 to 19,
A manufacturing method comprising a step of sealing after directly bonding the integrated electrode to the negative electrode.
Item 24. Item 23. A dye-sensitized solar cell comprising the photoelectric conversion element according to Item 21 or 22.

  If the integral electrode of the present invention is used, a porous body containing titanium oxide (especially a porous sintered body) is used as a spacer, and it is possible to include an electrolytic solution in the holes of this spacer. A photoelectric conversion element can be easily manufactured only by pasting together with a negative electrode.

  Further, unlike the conventional case, the integrated electrode of the present invention does not have a decrease in current density despite the use of a porous spacer, and an excellent photoelectric conversion efficiency can be obtained.

  Furthermore, since the space | interval of a positive electrode and a negative electrode can be made uniform, the output characteristic when incorporating in a dye-sensitized solar cell module is stabilized, and photoelectric conversion efficiency can be maintained.

It is an electron microscope (SEM) photograph which shows the surface shape of the tubular aggregate | assembly of a titania nanoparticle. It is an electron microscope (TEM) photograph of one iron-carbon complex which comprises the carbonaceous material obtained in Example 1 of patent document 7. It is an electron microscope (TEM) photograph which shows the presence state of the iron-carbon composite in the carbonaceous material obtained in Example 1 of patent document 7. It is the electron microscope (TEM) photograph which made one iron-carbon composite_body | complex obtained in Example 1 of patent document 7 into the shape of a ring. In addition, the black triangle ((triangle | delta)) shown in the photograph of FIG. 4 has shown the EDX measurement point for composition analysis. The schematic diagram of the TEM image of a carbon tube is shown, (a-1) is a schematic diagram of the TEM image of a cylindrical nano flake carbon tube, (a-2) is the TEM image of the multi-layer carbon nanotube of a nested structure FIG.

1. Integrated electrode The integrated electrode of the present invention is an electrode in which a positive electrode and a separator are integrated.

(1) Positive electrode The positive electrode may have a single-layer structure made of a conductive substrate, or a multilayer structure in which a conductive layer is formed on a substrate (which may be a conductive substrate or a non-conductive substrate).

  The substrate is not particularly limited, and the material, thickness, dimensions, shape, and the like can be appropriately selected according to the purpose. For example, metal, colorless or colored glass, meshed glass, glass block, etc. are used. A resin substrate may be used.

  As the metal, it is preferable to employ a metal such as platinum, gold, nickel, titanium, aluminum, copper, silver, or tungsten.

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

  When a conductive substrate is employed as the substrate, it is preferable to use, for example, a metal, a conductive carbon material, a conductive organic substance, or the like.

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

  As the conductive material constituting the conductive layer, 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), gallium In addition to a doped zinc oxide film (GZO film), a material having a small specific resistance such as a metal such as platinum, gold, nickel, titanium, aluminum, copper, silver, and tungsten, a carbon material, and a conductive organic material is preferably used. it can.

  The conductive layer may contain a binder. A stronger conductive layer can be formed by fixing the conductive material with a binder. As such a binder, inorganic oxides (particularly tin oxide, titanium oxide, zinc oxide, etc.) are preferable.

  The thickness of these conductive layers is preferably about 0.02 to 10 μm.

  A metal lead may be used for the purpose of reducing the resistance of the positive 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.

(2) Separator In the present invention, the separator is preferably made of a porous body containing titanium oxide, particularly preferably a porous sintered body.

[Titanium oxide]
In the present invention, “titanium oxide” or “titania” does not only refer to titanium dioxide (TiO ₂ ) but also titanium dioxide (Ti ₂ O ₃ ); titanium monoxide (TiO); Ti ₄ O _7. It is a concept including a composition in which oxygen is deficient from titanium dioxide represented by 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.

In the present invention, the titanium oxide constituting the separator is not particularly limited as long as the finally obtained separator is a porous body (particularly a porous sintered body), and various forms of titanium oxide can be employed. In particular,
(A) Known or commercially available titania nanoparticles (B) Amorphous titania nanotubes (C) Tube-like aggregates of titania nanoparticles (titania nanotubes composed of continuous titania nanoparticles)
Etc.

(A) Titania nanoparticle As titania nanoparticle, a commercially available or well-known titania nanoparticle may be used, for example, you may synthesize | combine 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 in this case include titanium alkoxides such as titanium tetraisopropoxide, titanium dioxide, titanium hydroxide, titanium chloride, and titanium sulfate.

  The crystal structure of the titania nanoparticle 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, due to electron leakage It is more preferable that anatase type titanium oxide is included from the point of an internal short circuit. The crystal structure of the titania nanoparticle (A) can be measured by, for example, an X-ray diffraction method, Raman spectroscopic analysis, or the like.

  The average particle diameter of the titania nanoparticles is preferably 10 to 1000 nm, more preferably 20 to 500 nm, from the viewpoint that ions easily pass through and the incident light can be effectively used from the negative electrode. In addition, an average particle diameter can be measured by electron microscope (SEM) observation etc., for example.

(B) Amorphous Titania Nanotube As the amorphous titania nanotube, a known or commercially available titania nanotube can be adopted. Examples thereof include titania nanotubes described in Patent Documents 2 to 3 and the like. As described above, when titania nanotubes are used, ions move in the space in the tube, so that it is possible to secure a space in which ions move while ensuring film forming properties. As a result, conversion efficiency can be improved.

(C) Titania nanotubular aggregate (titania nanotubes composed of continuous titania nanoparticles)
As the tube-like aggregate of titania nanoparticles, the material described in Patent Document 4 can be used. Specifically, it is as follows.

  The tube-like aggregate of titania nanoparticles is composed of continuous titania nanoparticles. In the present invention, “consecutively” means that the titania nanoparticles are in close contact with the adjacent titania nanoparticles while maintaining the shape of the particles. That is, it differs from amorphous titania nanotubes.

  The tube-like aggregate of titania nanoparticles is formed by connecting titania nanoparticles so as to form a tube. Thereby, as shown in FIG. 1, the fine unevenness | corrugation exists in the surface of the tube-shaped aggregate of a titania nanoparticle. This not only secures a space for ions to move, but also makes it easier for ions to enter the polarity, surface state, etc. of the internal space. As a result, the conversion efficiency can be improved compared to the case where amorphous titania nanotubes are used.

  The crystal structure of the titania nanoparticle 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. It is more preferable to contain anatase type titanium oxide from the point which suppresses a short circuit and has a low baking temperature and excellent workability. In addition, it is preferable to select a material that can further promote ion movement while further suppressing electron conduction with the electrode. The crystal structure of titania nanoparticles can be measured by, for example, X-ray diffraction, Raman spectroscopic analysis, or the like. In addition to the anatase-type titanium oxide, rutile-type titanium oxide and brookite-type titanium oxide, the titania nanoparticles further include a divalent titanium oxide, a trivalent titanium oxide and a tetravalent titanium oxide. It may contain at least one selected from

In addition to the above, titania nanoparticles preferably 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 titania nanoparticles is preferably 10 to 1000 nm, more preferably 20 to 500 nm, from the viewpoint that ions easily pass through and the incident light can be effectively utilized from the negative electrode. In addition, an average particle diameter can be measured by electron microscope (SEM or TEM) observation etc., for example.

The tubular aggregate of titania 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-like aggregate of titania nanoparticles has a route through which ions can move, so that the average inner diameter orthogonal to the long axis is 5 to 500 nm (particularly 10 to 100 nm), and the long axis has an average length of 0.1 to 0.1. 50 μm (1 to 10 μm) is preferable. Moreover, the average internal diameter and average length of the tubular aggregate of titania nanoparticles can be measured, for example, by observation with an electron microscope (SEM).

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

The tubular aggregate of titania nanoparticles is, for example,
(I) A step of forming a titanium oxide-coated nanoscale carbon by forming a coating layer composed of titania nanoparticles on the surface of a rod-like or fibrous nanoscale carbon by precipitation reaction from a titanium fluoro complex, and (II) ) It is obtained by a method comprising a step of eliminating nanoscale carbon present in titanium oxide-coated nanoscale carbon.

  In the step (I), a coating layer composed of continuous titania nanoparticles is formed on the surface of a rod-like or fibrous nanoscale carbon by a precipitation reaction from a titanium fluoro complex, thereby producing a titanium oxide-coated nanoscale carbon.

  Specifically, for example, rod-like or fibrous nanoscale carbon is treated with an acid such as nitric acid, sulfuric acid, hydrochloric acid, etc., and then dispersed in a solvent containing a dispersant. In this method, titania nanoparticles are precipitated by adding a fluoride ion scavenger such as aluminum.

  Here, the titanium fluoro complex is not particularly limited, and examples thereof include ammonium hexafluorotitanate, hexafluorotitanic acid, and potassium hexafluorotitanate.

  Although it does not restrict | limit especially as said solvent, For example, the solvent etc. which a titanium fluoro complex melt | dissolves, such as water, the mixed solvent of water and alcohol, etc. are mentioned.

  In addition, as the dispersant, anionic dispersion such as sodium naphthalenesulfonate formalin condensate-based dispersant, polycarboxylate-based dispersant, maleic acid α-olefin copolymer salt-based dispersant, anionic surfactant, etc. Agents; Cationic dispersants such as quaternary ammonium salt dispersants and alkylamine salts; Nonionic dispersants such as cellulose dispersants, polyvinyl alcohol dispersants, polyether dispersants; amphoteric surfactants, etc. Other dispersants and the like. Among these, nonionic dispersants are preferable, and polyether dispersants are more preferable.

  The nanoscale carbon that can be used in the step (I) will be described in detail below.

Nanoscale carbon Although there is no restriction | limiting in particular as rod-like or fibrous nanoscale carbon used by this invention, It is preferable to use a nanoscale carbon tube. The nanoscale carbon tube is preferably formed of a conductive material.

  In addition, this rod-like or fibrous nanoscale carbon is preferably dispersed in the solution in a straight shape from the point that titania is deposited on the nanoscale as a template, and the average diameter orthogonal to the major axis is 1 to 1. About 100 nm (especially 1 to 50 nm), the average length of the major axis is about 0.1 to 1000 μm (particularly 1 to 50 μm), and the average aspect ratio is about 5 to 1,000,000 (particularly 5 to 10,000, more preferably about 10 to 10,000). . In addition, the average diameter orthogonal to the long axis, the average length of the long axis, and the average aspect ratio can be measured, for example, by observation with an electron microscope (SEM or TEM).

Nanoscale carbon tube The nanoscale carbon tube refers to a carbon tube having a nano-sized diameter, and iron or the like may be included in the inner space of the carbon tube.

As such a nanoscale carbon tube,
(1) single-walled carbon nanotubes or multi-walled carbon nanotubes,
(2) Amorphous nanoscale carbon tube developed by the applicant,
(3) Nano flake carbon tube,
(4) (a) a carbon tube selected from the group consisting of nano-flake carbon tubes and nested multi-walled carbon nanotubes, and (b) iron carbide or iron, and 10 of the space in the tube of the carbon tube (a). An iron-carbon composite filled with iron carbide or iron of (b) in a range of -90%;
(5) A mixture of two or more of these can be exemplified.

< Carbon nanotube >
A carbon nanotube is a hollow carbon material in which a graphite sheet (that is, a carbon atom plane or graphene sheet of a graphite structure) is closed like a tube, its diameter is nanometer scale, and the wall structure has a graphite structure. . Among the carbon nanotubes, one with a single graphite sheet whose wall structure is closed in a tube shape is called a single-walled carbon nanotube, and a plurality of graphite sheets are each closed in a tube shape and are nested. It is called a multi-walled carbon nanotube with a nested structure. In the present invention, both of these single-walled carbon nanotubes and nested multi-walled carbon nanotubes can be used.

  The single-walled carbon nanotube has an average diameter orthogonal to the major axis of about 1 to 10 nm (especially 1 to 5 nm, more preferably 1 to 2 nm), and an average length of the major axis of 0.1 to 500 μm (particularly 1 to 100 μm, The average aspect ratio is preferably about 10 to 500,000 (especially 10 to 50,000, more preferably 15 to 30000, especially 20 to 20000).

  In addition, the multi-walled carbon nanotube having a nested structure has an average diameter orthogonal to the major axis of about 1 to 100 nm (particularly 1 to 50 nm, further 1 to 40 nm), and an average length of the major axis of about 0.1 to 500 μm (particularly The average aspect ratio is preferably about 1 to 500,000 (especially 5 to 10,000, more preferably 10 to 10,000).

< Amorphous nanoscale carbon tube >
Amorphous nanoscale carbon tubes are described in Patent Documents 5 to 6, have a main skeleton made of carbon, have a diameter of 0.1 to 1000 nm, have an amorphous structure, and are linear. In the X-ray diffraction method (incident X-ray: CuKα), the plane interval (d002) of the carbon network plane (002) measured by the diffractometer method is 3.54 mm or more, particularly 3.7 mm. The diffraction angle (2θ) is 25.1 degrees or less, particularly 24.1 degrees or less, and the full width at half maximum of the 2θ band is 3.2 degrees or more, particularly 7.0 degrees or more. .

  The amorphous nanoscale carbon tube is a thermally decomposable resin having a decomposition temperature of 200 to 900 ° C. in the presence of a catalyst made of at least one metal chloride such as magnesium, iron, cobalt, nickel, etc. It can be obtained by subjecting tetrafluoroethylene, polyvinylidene chloride, polyvinylidene fluoride, polyvinyl alcohol or the like to excitation treatment.

  The shape of the thermally decomposable resin as a starting material may be any shape such as a film shape, a sheet shape, a powder shape, or a lump shape. For example, when obtaining a carbon material in which a thin amorphous nanoscale carbon tube is formed on a substrate, excitation treatment under appropriate conditions can be performed with a thermally decomposable resin applied or placed on the substrate. preferable.

  As the excitation treatment, for example, heating is performed in an inert atmosphere, preferably in a temperature range of about 450 to 1800 ° C. and at a temperature equal to or higher than the thermal decomposition temperature of the raw material, and in a temperature range of about room temperature to 3000 ° C. The process of plasma processing etc. can be illustrated by the above.

  Amorphous nanoscale carbon tubes are nanoscale carbon nanotubes having an amorphous structure (amorphous structure), are hollow linear, and have highly controlled pores. The shape is mainly a cylinder, a quadrangular prism, etc., and at least one of the tips often has no cap (open). When the tip is closed, the shape is often flat.

  The amorphous nanoscale carbon tube has an average outer diameter of about 1 to 100 nm (particularly 1 to 50 nm), an average length of about 0.1 to 1,000 μm (particularly 1 to 50 μm), and an average aspect ratio of 1 to 1,000,000 (particularly 5 to 10,000, more preferably about 10 to 10,000).

  Here, “amorphous structure” means a carbonaceous structure consisting of an irregular carbon network plane, not a graphite structure consisting of a continuous carbon layer of regularly arranged carbon atoms. The graphene sheets are irregularly arranged. From an image obtained by a transmission electron microscope, which is a typical analysis technique, in the nanoscale carbon tube having an amorphous structure that can be used in the present invention, the spread in the plane direction of the carbon network plane is 1 of the diameter of the amorphous nanoscale carbon tube. Less than double. As described above, the amorphous nanoscale carbon tube has an amorphous structure in which a large number of fine graphene sheets (carbon network surface) are irregularly distributed instead of a graphite structure, so that the outermost layer is formed. The carbon mesh surface is not continuous over the entire length in the tube longitudinal direction but is discontinuous. In particular, the length of the carbon network surface constituting the outermost layer is less than 20 nm, particularly less than 5 nm.

Amorphous carbon generally does not exhibit X-ray diffraction, but exhibits broad reflection. In the graphitic structure, the carbon mesh planes are regularly stacked, so the carbon mesh plane spacing (d ₀₀₂ ) is narrowed, and the broad reflection shifts to the high angle side (2θ) and becomes gradually sharper (in the 2θ band). The full width at half maximum becomes narrower), and it can be observed as a d ₀₀₂ diffraction line (d ₀₀₂ = 3.354 mm when regularly stacked due to the graphite positional relationship).

In contrast, an amorphous structure generally does not exhibit X-ray diffraction as described above, but partially exhibits very weak coherent scattering. In the X-ray diffraction method (incident X-ray = CuKα), the theoretical crystallographic characteristics of the amorphous nanoscale carbon tube measured by the diffractometer method are defined as follows: carbon network plane spacing (d ₀₀₂ ) is 3.54 mm or more, more preferably 3.7 mm or more; the diffraction angle (2θ) is 25.1 degrees or less, more preferably 24.1 degrees or less; the 2θ band The full width at half maximum is 3.2 degrees or more, more preferably 7.0 degrees or more.

Typically, an amorphous nanoscale carbon tube has a diffraction angle (2θ) by X-ray diffraction in the range of 18.9 to 22.6 degrees, and a carbon network plane spacing (d ₀₀₂ ) of 3.9 to 4 The half-width of the 2θ band is in the range of 7.6 to 8.2 degrees.

The term “linear”, which is one term representing the shape of the amorphous nanoscale carbon tube, is defined as follows. That is, the length of the amorphous nanoscale carbon tubes image by a transmission electron microscope is L, the length of time that extended the amorphous nanoscale carbon tubes in the case of the L _0, L / L ₀ is 0.9 or more It shall mean the shape characteristic that becomes.

  The tube wall portion of such an amorphous nanoscale carbon tube has an amorphous structure composed of a plurality of fine carbon network planes (graphene sheets) oriented in all directions, and the active point is determined by the carbon plane spacing of these carbon network planes. It has the advantage that it is excellent in affinity with resin because it has.

< Iron-carbon composite >
The iron-carbon composite (IV) is described in Patent Documents 7 to 8, and (a) a carbon tube selected from the group consisting of a nanoflake carbon tube and a multi-walled carbon nanotube with a nested structure; and (b) carbonization. It consists of iron or iron, and the iron carbide or iron of (b) is filled in the range of 10 to 90% of the space in the tube of the carbon tube (a). That is, 100% of the space in the tube is not completely filled, and the iron carbide or iron is filled in the range of 10 to 90% of the space in the tube (that is, partially). It is characterized in that it is filled in). The wall portion is a patchwork-like or machete-like (so-called paper match-like) nanoflake carbon tube.

  In this specification, the “nano flake carbon tube” is a graphite sheet composed of a plurality of (usually many) flake-like graphite sheets assembled in a patchwork shape or a papier-like shape. It refers to a carbon tube made of aggregate.

Such an iron-carbon composite is obtained according to the method described in Patent Document 7.
(1) Ratio when the pressure is adjusted to 10 ⁻⁵ Pa to 200 kPa in an inert gas atmosphere, the oxygen concentration in the reactor is A (liter), and the oxygen amount is B (Ncc). A step of heating the iron halide to 600 to 900 ° C. in a reaction furnace adjusted to a concentration at which B / A is 1 × 10 ⁻¹⁰ to 1 × 10 ⁻¹ ; and (2) an inert gas in the reaction furnace. And a heat decomposable carbon source is introduced at a pressure of 10 ⁻⁵ Pa to 200 kPa and a heat treatment is performed at 600 to 900 ° C.

  Here, “Ncc”, which is a unit of the oxygen amount B, means a volume (cc) when converted to a standard state of gas at 25 ° C.

  The iron-carbon composite is composed of (a) a carbon tube selected from the group consisting of nano flake carbon tubes and nested multi-walled carbon nanotubes, and (b) iron carbide or iron, The space portion (that is, the space surrounded by the tube wall) is not completely filled, but a part of the space portion, more specifically, about 10 to 90%, particularly about 30 to 80%. Preferably, about 40 to 70% is filled with iron carbide or iron.

  In the iron-carbon composite, as described in Patent Document 7, the carbon portion becomes a nano flake carbon tube when cooled at a specific rate after performing the production steps (1) and (2). After performing steps (1) and (2), heat treatment is performed in an inert gas, and cooling is performed at a specific cooling rate, thereby forming a multi-walled carbon nanotube having a nested structure.

<(A-1) Nano flake carbon tube>
The iron-carbon composite composed of the nano flake carbon tube (a-1) and iron carbide or iron (b) is typically cylindrical, but such a cylindrical iron-carbon composite (Patent Literature). 7 is a transmission electron microscope (TEM) photograph of a cross-section substantially perpendicular to the longitudinal direction of FIG. 4, and a side TEM photograph is shown in FIG.

  Moreover, the schematic diagram of the TEM image of such a cylindrical nano flake carbon tube is shown to (a-1) of FIG. In (a-1) of FIG. 5, 100 schematically shows a TEM image in the longitudinal direction of the nanoflakes carbon tube, and 200 shows a TEM image in a cross section substantially perpendicular to the longitudinal direction of the nanoflakes carbon tube. This is shown schematically.

  The nano flake carbon tube (a-1) constituting the iron-carbon composite typically has a hollow cylindrical shape, and when the cross section is observed with a TEM, arc-shaped graphene sheet images are concentrically assembled. Each graphene sheet image forms a discontinuous ring. When the longitudinal direction of the graphene sheet is observed with a TEM, the substantially linear graphene sheet images are arranged in multiple layers substantially parallel to the longitudinal direction. The individual graphene sheet images are not continuous over the entire length in the longitudinal direction, but are discontinuous.

  More specifically, the nanoflake carbon tube (a-1) constituting the iron-carbon composite is perpendicular to the longitudinal direction, as is apparent from 200 of FIGS. 4 and 5 (a-1). When the cross-section is observed by TEM, a large number of arc-shaped graphene sheet images are concentrically (multi-layered tube shape), but each graphene sheet image is completely closed as shown in 210 and 214, for example. It does not form a continuous ring, but forms a discontinuous ring that is interrupted. Some graphene sheet images may be branched as indicated by 211. At the discontinuity point, the plurality of arc-shaped TEM images constituting one discontinuous ring may have a partially disturbed layer structure as indicated by 222 in FIG. As shown in 223, there may be a gap between adjacent graphene sheet images, but a large number of arc-shaped graphene sheet images observed by TEM form a multilayer tube structure as a whole. Yes.

  Further, as apparent from 100 of FIGS. 2 and 5 (a-1), when the longitudinal direction of the nanoflake carbon tube (a-1) is observed with a TEM, a large number of substantially linear graphene sheet images are obtained. Although it is arranged in multiple layers substantially parallel to the longitudinal direction of the iron-carbon composite, the individual graphene sheet images 110 are not continuous over the entire length in the longitudinal direction of the iron-carbon composite, and are discontinuous in the middle. It has become. Some graphene sheet images may be branched as indicated by reference numeral 111 in FIG. Further, at the discontinuous point, among the TEM images arranged in a layered manner, the TEM image of one discontinuous layer is at least partly adjacent to the adjacent graphene sheet image as indicated by 112 in FIG. In some cases, they may overlap each other or may be slightly separated from adjacent graphene sheet images as indicated by 113, but a large number of substantially linear TEM images form a multilayer structure as a whole.

  The structure of the nano flake carbon tube (a-1) is greatly different from the conventional multi-walled carbon nanotube. That is, as indicated by reference numeral 400 in FIG. 5A-2, the multi-walled carbon nanotube (a-2) having a nested structure substantially has a cross-sectional TEM image perpendicular to the longitudinal direction as indicated by reference numeral 410. A straight graphene sheet image 310 or the like that is a concentric tube that is a complete circular TEM image, and is continuous over the entire length in the longitudinal direction, as indicated by 300 in FIG. It is a structure arranged in parallel (concentric cylindrical or nested structure).

  Although the details have not been fully elucidated yet, the nano-flake carbon tube (a-1) constituting the iron-carbon composite has a large number of flake-like graphene sheets overlapped in a patchwork or tension form. It seems to form a tube as a whole.

  Such an nano-flake carbon tube (a-1) and an iron-carbon composite made of iron carbide or iron (b) contained in the inner space of the tube have a nested structure as described in Patent Document 9. The structure of the carbon tube is greatly different from that of the composite in which the metal is included in the inner space of the multi-walled carbon nanotube (a-2).

  When the nano-flake carbon tube (a-1) constituting the iron-carbon composite is observed with a TEM, each graphene sheet image is related to a number of substantially straight graphene sheet images oriented in the longitudinal direction. The length is usually about 2 to 500 nm, particularly about 10 to 100 nm. That is, as indicated by 100 in (a-1) of FIG. 5, a large number of TEM images of the substantially linear graphene sheet indicated by 110 are collected, and a TEM image of the wall portion of the nano flake carbon tube (a-1). The length of each substantially linear graphene sheet image is usually about 2 to 500 nm, particularly about 10 to 100 nm.

  Thus, in the iron-carbon composite, the outermost layer of the nano flake carbon tube (a-1) constituting the wall portion is formed from discontinuous graphene sheets that are not continuous over the entire length in the tube longitudinal direction. The length of the outermost carbon network surface is usually about 2 to 500 nm, particularly about 10 to 100 nm.

The carbon portion of the wall portion of the nano-flake carbon tube (a-1) constituting the iron-carbon composite has a tube shape as a whole with a large number of flake-like graphene sheets oriented in the longitudinal direction as described above. However, when measured by the X-ray diffraction method, the carbon fiber has an average distance (d ₀₀₂ ) having a graphite structure of 0.34 nm or less.

  Moreover, the thickness of the wall part which consists of an iron-carbon composite nano flake carbon tube (a-1) is 49 nm or less, Especially about 0.1-20 nm, Preferably it is about 1-10 nm, Comprising: And substantially uniform.

<(A-2) Nested multi-walled carbon nanotube>
As described above, the carbon tube constituting the iron-carbon composite obtained by performing the specific heating step after performing the steps (1) and (2) is a multi-walled carbon nanotube (a- 2).

  In the nested multi-walled carbon nanotube (a-2) thus obtained, a TEM image of a cross section perpendicular to the longitudinal direction forms a substantially perfect circle as indicated by 400 in FIG. 5 (a-2). And a graphene sheet image that is continuous over the entire length in the longitudinal direction thereof is arranged in parallel (a concentric cylindrical or nested structure).

The carbon portion of the wall portion of the multi-walled carbon nanotube (a-2) having a nested structure constituting the iron-carbon composite has an average distance (d ₀₀₂ ) between the carbon network surfaces of 0 when measured by X-ray diffraction. It has a graphite structure of .34 nm or less.

  Further, the thickness of the wall portion composed of the multi-walled carbon nanotubes (a-2) of the iron-carbon composite nested structure is 49 nm or less, particularly about 0.1 to 20 nm, preferably about 1 to 10 nm. Substantially uniform.

<(B) Iron carbide or iron contained>
In the present specification, the filling ratio of the space portion in the carbon tube selected from the group consisting of the nano flake carbon tube (a-1) and the multi-layer carbon nanotube (a-2) with a nested structure by iron carbide or iron (b) ( 10 to 90%) observes the iron-carbon composite with a transmission electron microscope, and the iron carbide or the area of the image of the space portion of each carbon tube (that is, the space surrounded by the tube wall of the carbon tube) It is the ratio of the area of the image of the part filled with iron (b).

  As for the filling form of iron carbide or iron (b), there are a form in which the space in the carbon tube is continuously filled, a form in which the space in the carbon tube is intermittently filled, etc. Filled intermittently. Therefore, the iron-carbon composite that can be used in the present invention should also be referred to as a metal-encapsulated carbon composite, an iron compound-encapsulated carbon composite, iron carbide, or an iron-encapsulated carbon composite.

  Moreover, the iron carbide or iron (b) included in the iron-carbon composite is oriented in the longitudinal direction of the carbon tube, has high crystallinity, and is filled with the iron carbide or iron (b). The ratio of the area of the TEM image of crystalline iron carbide or iron (b) to the area of the TEM image (hereinafter referred to as “crystallization rate”) is generally about 90 to 100%, particularly about 95 to 100%. .

  The high crystallinity of the iron carbide or iron (b) contained is apparent from the fact that the TEM images of the inclusions are arranged in a lattice pattern when observed from the side of the iron-carbon composite. It is also clear from the fact that a clear diffraction pattern is obtained in electron beam diffraction.

  Further, the inclusion of iron carbide or iron (b) in the iron-carbon composite can be easily confirmed by an electron microscope and EDX (energy dispersive X-ray detector).

<Overall shape of iron-carbon composite>
The iron-carbon composite has a small shape, is linear, and has a uniform thickness over the entire length because the wall portion has a substantially uniform thickness. Yes. The shape is columnar and mainly cylindrical.

  The iron-carbon composite has an average outer diameter of about 1 to 100 nm (particularly 1 to 50 nm), an average length of about 0.1 to 1,000 μm (particularly 1 to 400 μm), and an average aspect ratio of 1 to 1,000,000 (particularly 5 to 10,000, more preferably about 10 to 10,000).

  The term “linear”, which is one term representing the shape of the iron-carbon composite, is defined as follows. That is, a carbonaceous material containing an iron-carbon composite is observed in the range of 200 to 2000 nm by a transmission electron microscope, the length of the image is W, and the length when the image is linearly extended is Wo. In this case, the shape characteristic means that the ratio W / Wo is 0.8 or more, particularly 0.9 or more.

  The iron-carbon composite has the following properties when viewed as a bulk material. That is, in the present invention, iron is contained in a range of 10 to 90% of the space in the tube of the carbon tube selected from the nano flake carbon tube (a-1) and the multi-walled carbon nanotube (a-2) having the nested structure as described above. Alternatively, the iron-carbon composite filled with iron carbide (b) is not a trace amount that can be barely observed by microscopic observation, but is a bulk material containing a large number of the iron-carbon composite, It is obtained in a large amount in the form of a carbonaceous material containing a body, or a material to be called iron carbide or an iron-containing carbonaceous material.

  The electron micrograph of the carbonaceous material which can be used by this invention which consists of the nano flake carbon tube (a-1) manufactured in Example 1 of patent document 7, and the iron carbide (b) with which the space part in the tube was filled. As shown in FIG.

  As can be seen from FIG. 3, in a carbonaceous material containing an iron-carbon composite, basically, in almost all (particularly 99% or more) carbon tubes, the space (that is, the tube of the carbon tube). Usually, iron carbide or iron (b) is filled in a range of 10 to 90% of the space surrounded by the wall, and there is usually substantially no carbon tube filled with the space. However, in some cases, a small amount of carbon tubes not filled with iron carbide or iron (b) may be present.

  Further, in the carbonaceous material, an iron-carbon composite in which iron or iron carbide (b) is filled in 10 to 90% of the space in the carbon tube as described above is a main component. In addition to the carbonaceous composite, soot may be contained. In such a case, components other than the iron-carbonaceous complex are removed to improve the purity of the iron-carbonaceous complex in the carbonaceous material, and the carbonaceous material substantially consisting of only the iron-carbon complex. You can also get

  In addition, unlike materials that can only be confirmed in microscopic amounts by conventional microscopic observation, a carbonaceous material containing an iron-carbon composite can be synthesized in a large amount, so that its weight can easily be set to 1 mg or more.

The carbonaceous material is attributed to iron or iron carbide (b) contained in powder X-ray diffraction measurement in which X-rays of CuKα are irradiated with an irradiation area of 25 mm ² or more with respect to 1 mg of the carbonaceous material. Of the peaks at 40 ° <2θ <50 °, the peak showing the strongest integrated intensity is Ia, and 26 ° <2θ <27 attributed to the average distance (d ₀₀₂ ) between the carbon network surfaces of the carbon tubes. In the case of the integrated intensity Ib of the peak at °, the ratio R (= Ia / Ib) of Ia to Ib is preferably about 0.35 to 5, particularly about 0.5 to 4, more preferably 1 It is about ~ 3.

In this specification, the ratio of Ia / Ib is referred to as an R value. As for this R value, when a carbonaceous material containing an iron-carbon composite is observed in an X-ray diffraction area with an X-ray irradiation area of 25 mm ² or more, a peak intensity is observed as an average value of the entire carbonaceous material. Therefore, iron carbide or iron (b) filling as a whole carbonaceous material that is an aggregate of iron-carbon composites, not the inclusion rate or filling rate in one iron-carbon composite that can be measured by TEM analysis It shows the average value of rate or inclusion rate.

  In addition, the average filling rate as the whole carbonaceous material containing many iron-carbon composites observes a several visual field with TEM, and the iron carbide or iron in several iron-carbon composites observed in each visual field ( It can also be obtained by measuring the average filling rate of b) and calculating the average value of the average filling rates of a plurality of visual fields. When measured by such a method, the average filling rate of iron carbide or iron (b) as a whole carbonaceous material composed of an iron-carbon composite is about 10 to 90%, particularly about 40 to 70%.

< Nano flake carbon tube >
The iron or iron carbide (b) contained in the nano-flake carbon tube (a-1) is partially encapsulated in the inner space of the nano-flake carbon tube (a-1) by acid treatment. b) is dissolved and removed, and a hollow nanoflake carbon tube in which iron or iron carbide (b) is not present in the space in the tube can be obtained.

  Examples of the acid used for the acid treatment include hydrochloric acid, sulfuric acid, nitric acid, hydrofluoric acid, and the like, and the concentration is preferably about 0.1 to 2N. As an acid treatment method, various methods can be used. For example, 1 g of iron-encapsulated nanoflake carbon tube is dispersed in 100 ml of 1N hydrochloric acid, and stirred at room temperature for 6 hours, followed by filtration and separation. After that, a hollow nanoflake carbon tube can be obtained by performing the same treatment twice with 100 ml of 1N hydrochloric acid twice.

  The basic structure of the nano flake carbon tube is not particularly changed by this acid treatment. Therefore, even in the hollow nanoflakes carbon tube in which iron or iron carbide (b) does not exist in the space in the tube, the length of the carbon network surface constituting the outermost surface is 500 nm or less, particularly 2 to 500 nm, In particular, it is 10 to 100 nm.

Titanium oxide-coated nanoscale carbon Titanium oxide-coated nanoscale carbon obtained in this way has a titanium oxide coverage on the surface of rod-like or fibrous nanoscale carbon from the viewpoint of obtaining titania nanotubes composed of continuous titania nanoparticles. 70 to 100%, and particularly preferably 85 to 100%. The surface element ratio of carbon / titanium is preferably 0/100 to 70/30 (atomic ratio), more preferably 0/100 to 50/50 (atomic ratio). In addition, the surface coverage (ratio of the portion covered with the coating layer formed by continuous particulate titanium oxide on the surface of the carbon) can be determined by, for example, observation with an electron microscope (SEM or TEM) or the carbon / The surface element ratio of titanium can be measured by, for example, X-ray photoelectron spectroscopy.

  In the step (II), the nanoscale carbon existing in the titanium oxide-coated nanoscale carbon obtained in the step (I) is eliminated, and a tubular aggregate of titania nanoparticles is produced. Thereby, there is an advantage that the titanium oxide has an anatase type crystal structure and adhesion is increased. In step (II), the nanoscale carbon may be eliminated, and the method is not particularly limited, but it is easy to eliminate the oxidation. For example, in the case of heating in air to cause oxidation to disappear, the heating temperature is preferably 450 ° C. or higher, more preferably 550 ° C. or higher, further preferably 600 to 750 ° C., particularly preferably 600 to 700 ° C. .

[shape]
In the present invention, the separator is made of the above-described porous titanium oxide, and preferably made of a porous sintered body.

  By making the separator have a porous structure, it becomes possible to contain an electrolyte in the porous structure (especially pores) of the separator later. In the conventional separator structure, the electrolyte is injected later in the process. It was necessary to re-enclose, but when the electrolyte solution is included in advance, it can be sealed as it is after being soaked in the electrolyte solution, which not only simplifies the process but also eliminates the need for re-sealing. The stopping performance is also improved. In addition, when injecting a highly viscous electrolytic solution or gel electrolyte, it was difficult to inject it later, but by impregnating the porous separator with the electrolytic solution or gel electrolyte in advance, it is simple and sealable. High structure.

Specifically, the specific surface area of the porous material constituting the separator, 3～150M ² / g approximately, in particular 5~80m about ² / g are preferred.

  Moreover, the thickness of the separator is preferably about 0.1 to 5 μm, particularly preferably about 0.5 to 3 μm. By setting the thickness of the separator to this level, it is possible to more effectively suppress a short circuit without increasing the internal resistance. When a conventional nonwoven fabric or the like is used as a separator, a thickness greater than 5 μm (especially 10 μm or more) is required, but in the present invention, as described above, a short-circuit is sufficiently suppressed at about 0.1 to 5 μm. can do. For this reason, an increase in internal resistance can be further suppressed.

[Formation method]
There is no restriction | limiting in particular in the method of forming a separator on a board | substrate. For example, it is preferable to apply and dry a separator-forming composition containing titanium oxide or a titanium oxide precursor on the positive electrode. At this time, when a conductive layer is formed on the positive electrode, the separator-forming composition is preferably formed on the conductive layer.

  Specific examples of the titanium oxide precursor include titanium alkoxides such as titanium isopropoxide, titanium dioxide, titanium hydroxide, titanium chloride, and titanium sulfate.

  At this time, water, an organic solvent, or the like can be used as a solvent for the composition.

  The organic solvent is not particularly limited as long as it can disperse the above titanium oxide or titanium oxide precursor. For example, alcohols such as ethanol, methanol, and terpineol; glycols such as ethylene glycol, polyethylene glycol, propylene glycol, and polypropylene glycol can be used. These solvents are usually mixed and used in consideration of dispersibility, volatility, and viscosity. The proportion of the solvent in the composition is 50 to 90% by weight, particularly 60 to 90% in terms of providing fluidity during coating, maintaining the thickness after coating, and forming porous titanium oxide. 75% by weight is preferred.

  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. Among these, alkyl cellulose, particularly ethyl cellulose can be preferably used.

  The proportion of the thickener in the paste is preferably 2 to 20% by weight, particularly 3 to 15% by weight from the viewpoint of balancing the fluidity during coating and the thickness after coating.

  The ratio of the solid content in the paste is preferably 5 to 50% by weight, particularly 10 to 30% by weight, from the viewpoint of the balance between the fluidity at the time of coating and the thickness after coating, as described above.

(3) Electrolytic Solution The integrated electrode of the present invention preferably contains an electrolytic solution. Specifically, the integral electrode of the present invention preferably contains an electrolytic solution in a porous structure (especially pores) present in the separator (porous body). As described above, by including the electrolytic solution in the integrated electrode of the present invention, it is possible to easily produce a photoelectric conversion element only by pasting it together with the negative electrode. In particular, ionic liquids and high-boiling solvents with excellent durability are generally highly viscous, and when such highly durable solvents are introduced by conventional methods, it is difficult to inject them into the cell later. Had to re-seal, which had a negative effect. However, a highly viscous ionic liquid, a high boiling point solvent, or a gel electrolyte is impregnated with an electrolytic solution in advance, whereby a photoelectric conversion element can be easily produced simply by bonding them together. In addition, since the separator is not in the form of surrounding the element but in contact with both electrodes, the electrolyte can be injected from the gap between the positive electrode and the negative electrode even after the cells are bonded together. High durability sealing becomes possible.

  In addition, there is no restriction | limiting in particular in the method of including electrolyte solution in the integral electrode of this invention (especially in the porous structure which exists in a separator), for example, impregnating the integral electrode of this invention in the electrolyte solution produced beforehand It is preferable.

  The electrolyte is not particularly limited, but it can be expected to be more durable at high temperatures due to its vapor pressure is almost zero, high chemical stability, high thermal stability, etc. It is preferable to use an ionic liquid as the solvent.

Thus, when an ionic liquid is used as a solvent, the viscosity is higher than that of a normal solvent. Therefore, iodide ions (I ⁻ ) and triiodide ions (I ₃ ^-) diffusion tends to be late. Therefore, in the case of using an ionic liquid, the charge transfer is carried out by containing a large amount of electrolyte so that the viscosity is not excessively increased and by causing a large number of exchange reactions between the redox couples I ⁻ and I ₃ ^−. More preferably.

From this point of view, the electrolytic solution contains an electrolyte containing iodide including iodine and 1,3-dialkylimidazolium iodide, and
(1) The 1,3-dialkylimidazolium iodide includes 1-ethyl-3-methylimidazolium iodide and 1,3-dimethylimidazolium iodide.
(2) The electrolytic solution contains 3.0 mol / liter or more of the 1,3-dialkylimidazolium iodide.
(3) The 1,3-dialkylimidazolium iodide preferably satisfies at least one of 1-methyl-3-propylimidazolium iodide.

<First aspect>
The electrolyte solution in the first aspect is
An electrolytic solution containing iodine, an iodide containing 1,3-dialkylimidazolium iodide and a solvent,
The 1,3-dialkylimidazolium iodide preferably includes 1-ethyl-3-methylimidazolium iodide and 1,3-dimethylimidazolium iodide.

The electrolyte solution preferably contains iodine as an electrolyte and 1-ethyl-3-methylimidazolium iodide and 1,3-dimethylimidazolium iodide as 1,3-dialkylimidazolium iodide. .

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 that the titania conduction band is lowered to further improve the electron injection rate from the dye to titania. In addition, there is an effect of further promoting the transport of electrons injected into titania. Thereby, a short circuit current density can be improved more and, as a result, a photoelectric conversion efficiency can be improved more.

In the present invention, as described later, it is preferable to use 1-ethyl-3-methylimidazolium bisfluorosulfonylimide as the ionic liquid. As will be described later, 1-ethyl-3-methylimidazolium bisfluorosulfonylimide has high polarity and hydrophobicity, and has a function of further suppressing deterioration due to moisture ingress. Further, 1-ethyl-3-methylimidazolium bisfluorosulfonylimide has a viscosity at 25 ° C. of about 19 mPa · s and is higher than that of an organic solvent (for example, the viscosity at 25 ° C. is 0.378 mPa · s). About 50 times that of acetonitrile). For this reason, the moving speed of iodide ion (I ⁻ ) and triiodide ion (I ₃ ⁻ ) is slower than the electrolytic solution using an organic solvent as a solvent. Thus, iodide ion (I ^-) and triiodide (I 3 ^_-) than the physical diffusion, iodide ion charge transfer by exchange reaction (I ^- _-) and triiodide (I ³⁾ In order to perform mainly, it is preferable to set the density | concentration of an iodine and an iodide high compared with the electrolyte solution which used the organic solvent as a solvent.

In this case, the concentration of 1-ethyl-3-methylimidazolium iodide and 1,3-dimethylimidazolium iodide used as an iodide ion (I ⁻ ) source is not simply increased. It is preferable to set the concentration high and suppress the amount of iodine added to further suppress the amount of light absorption and increase the ionic conductivity.

  From such a viewpoint, the concentration of iodine in the electrolytic solution is preferably about 0.1 to 10 mol / liter (particularly 0.2 to 5 mol / liter).

  The concentration of 1,3-dialkylimidazolium iodide in the electrolytic solution is preferably about 3.0 mol or more (particularly 5 to 20 mol, more preferably 7 to 15 mol) with respect to 1 liter of solvent. By making it within this range, the conversion efficiency can be further improved.

  The concentrations of 1-ethyl-3-methylimidazolium iodide and 1,3-dimethylimidazolium iodide present in the electrolyte as 1,3-dialkylimidazolium iodide may be the same or different. Although not particularly limited, 1-ethyl-3-methylimidazolium iodide is about 1.5 mol / liter or more (especially 2.5 to 10 mol / liter), and 1,3-dimethylimidazolium iodide is 1 It is preferably about 5 mol / liter or more (particularly 2.5 to 10 mol / liter).

  Further, the concentration ratio of 1-ethyl-3-methylimidazolium iodide to 1,3-dimethylimidazolium iodide is not particularly limited, but it is difficult to dissolve 3 mol / liter or more alone. However, since it becomes easy to melt | dissolve in a polar solvent by making it coexist, 1: 9-9: 1 (molar ratio), Especially 4: 6-6: 4 (molar ratio) are preferable.

  It should be noted that 1-ethyl-3-methylimidazolium iodide and 1,3-dimethylimidazolium iodide are solid at room temperature, and both are independent of 1-ethyl-3-methylimidazolium bissulfonylimide. Dissolves only up to about 3M at room temperature. However, if it is heated to about 70 ° C. in the presence of coexistence, it can be dissolved even in an amount larger than 3M (for example, about 30M). Further, it is possible to continue to dissolve in a large amount without precipitation even after cooling to room temperature.

Thus, iodide ion (I ^-) and triiodide (I 3 ^_-) by exchange reaction if ask performed primarily charge transfer, iodide ion (I ^-) and triiodide (I ₃ ^-) The apparent diffusion rate can be further improved as compared with the electrolytic solution using an organic solvent, and as a result, the photoelectric conversion efficiency can be further improved.

  In the present invention, as 1,3-dialkylimidazolium iodide, in addition to 1-ethyl-3-methylimidazolium iodide and 1,3-dimethylimidazolium iodide, 1-methyl-3 iodide Other iodides such as 1-butylimidazolium iodide, 1-butyl-3-methylimidazolium iodide, 1-methyl-3-hexylimidazolium iodide (preferably 1-methyl-3-propylimidazolium iodide, etc.) 1,3-dialkylimidazolium may be included.

  Under the present circumstances, the density | concentration of other 1, 3- dialkyl imidazolium iodide should just be a grade which does not impair the effect of this invention.

  In the present invention, lithium iodide may be included as the iodide.

Also by using this lithium iodide, I ⁻ / I ₃ ⁻ which is a redox pair can be formed with iodine, so that the titania conduction band is further lowered and the electron injection rate from the dye to titania is increased. Can be further improved. It also has the effect of further promoting the transport of electrons injected into titania. Thereby, a short circuit current density can be improved more and a photoelectric conversion efficiency can be improved further.

  In addition, it is thought that the lithium ion produced | generated by addition of lithium iodide adsorb | sucks to the porous titania used for the titania negative electrode etc. of a dye-sensitized solar cell.

Further, from the viewpoint of sufficiently maintaining the open-circuit voltage of the dye-sensitized solar cell and obtaining sufficient photoelectric conversion efficiency, 1,3-dialkylimidazolium iodide (particularly iodine) is used as a main source of iodide ion I ^−. 1-ethyl-3-methylimidazolium iodide and 1,3-dimethylimidazolium iodide). Therefore, the concentration of lithium iodide may be reduced as compared to 1,3-dialkylimidazolium iodide (particularly 1-ethyl-3-methylimidazolium iodide and 1,3-dimethylimidazolium iodide). preferable.

  From this viewpoint, the concentration of lithium iodide is preferably 0.05 to 0.3 mol / liter (particularly 0.1 to 0.2 mol / liter). The concentration ratio of lithium iodide to 1,3-dialkylimidazolium iodide is 1:30 to 1: 300 (molar ratio), particularly 1:60 to 1: 200 (molar ratio), and further 1:70. ˜1: 120 (molar ratio) is preferred.

Ionic liquids Ionic liquids generally have high water absorption, and even if they are gelled, the affinity for moisture greatly depends on the characteristics of the original ionic liquid. From the viewpoint of improvement, 1-ethyl-3-methylimidazolium bissulfonylimide is preferable as the ionic liquid used as the solvent. 1-ethyl-3-methylimidazolium bissulfonylimide has a melting point of −14 ° C. and a viscosity at 25 ° C. of 19 mPa · s, and is hydrophobic.

This 1-ethyl-3-methylimidazolium bissulfonylimide has a low viscosity at 25 ° C. among ionic liquids having a 1-ethyl-3-methylimidazolium cation. Than ethyl-3-methylimidazolium thiocyanate (23.1 mPa · S; melting point −50 ° C.), 1-ethyl-3-methylimidazolium bistrifluoromethanesulfonylimide (28 mPa · S; melting point −16 ° C.), etc. This is a low value, and is advantageous in that iodide ions (I ⁻ ) and triiodide ions (I ₃ ⁻ ) are easily diffused.

1-methyl-3-imidazolium tetracyanoborate has a viscosity at 25 ° C. of 20 mPa · S and approximately the same as 1-ethyl-3-methylimidazolium bissulfonylimide, but has a melting point of 13 ° C. In low temperature environments such as winter, 1-ethyl-3-methylimidazolium bistrifluoromethanesulfonylimide is more preferable. Furthermore, since the tetracyanoborate anion (B (CN) ₄ ⁻ ) may inhibit the movement of iodide ions (I ⁻ ) and triiodide ions (I ₃ ⁻ ), the short circuit current density (Jsc) From the viewpoint of conversion efficiency and high temperature durability, 1-ethyl-3-methylimidazolium bistrifluoromethanesulfonylimide is more preferable.

  Moreover, since 1-ethyl-3-methylimidazolium bisfluorosulfonylimide has hydrophobicity, performance deterioration due to moisture ingress can be more efficiently suppressed.

  As a solvent, it is also conceivable to use a mixed solvent of 1-ethyl-3-methylimidazolium bissulfonylimide and an organic solvent or other ionic liquid. However, considering high temperature durability and stability, it can be a mixed solvent with an organic solvent having a vapor pressure, or a mixed solvent with other ionic liquids that will increase the types of cations and anions, etc. It is preferable to use 1-ethyl-3-methylimidazolium bissulfonylimide alone.

In addition to the above-described components, the other component electrolyte solution may contain a basic substance such as 4-tertiarybutylpyridine, N-methylbenzimidazole, and the like. When these basic substances are contained, when the photoelectric conversion element is produced, it is adsorbed on the titania surface of the titania electrode, can prevent reverse electron transfer from the titania electrode, and further improve the open-circuit voltage, Photoelectric conversion efficiency can be further improved.

  Further, in order not to desorb the sensitizing dye adsorbed on titania, the addition amount of the basic substance in the electrolytic solution is preferably about 0.01 to 1 mol / liter. In particular, when a metal complex dye is used, it is preferably about 0.1 to 1.0 mol / liter, particularly about 0.3 to 0.8 mol / liter. 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, is added to the electrolytic solution used in the present invention, as in the case of the above-described lithium iodide. be able to. In this case, the addition amount of these may be about 0.1 to 1.0 mol / liter.

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

<Second aspect>
The electrolyte solution in the second aspect used in the present invention is:
An electrolytic solution containing iodine, an iodide containing 1,3-dialkylimidazolium iodide and a solvent,
It is preferable to contain 3.0 mol / liter or more of the 1,3-dialkylimidazolium iodide.

The electrolyte solution preferably contains iodine and 1,3-dialkylimidazolium iodide as an 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 that the titania conduction band is lowered to further improve the electron injection rate from the dye to titania. In addition, there is an effect of further promoting the transport of electrons injected into titania. 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 1,3-dialkylimidazolium iodide include 1-ethyl-3-methylimidazolium iodide, 1,3-dimethylimidazolium iodide, 1-methyl-3-propylimidazolium iodide, and 1-iodide iodide. Butyl-3-methylimidazolium, 1-butyl-3-methylimidazolium iodide, 1-methyl-3-hexylimidazolium iodide and the like are preferable.

  Among these, 1-ethyl-3-methylimidazolium iodide and 1,3-dimethylimidazolium iodide are preferable from the viewpoint of high temperature durability.

  However, 1-ethyl-3-methylimidazolium iodide and 1,3-dimethylimidazolium iodide are solid at room temperature, and both are independent of 1-ethyl-3-methylimidazolium bissulfonylimide. Dissolves only up to about 3M at room temperature. However, if it is heated to about 70 ° C., it can be dissolved even in an amount larger than 3M (for example, about 30M). Further, it is possible to continue to dissolve in a large amount without precipitation even after cooling to room temperature.

  On the other hand, 1-methyl-3-propylimidazolium iodide is liquid at room temperature, and can be contained in a large amount in the electrolytic solution as it is. For this reason, 1-methyl-3-propylimidazolium iodide may be employed as the 1,3-dialkylimidazolium iodide. Of course, 1-methyl-3-propylimidazolium iodide may be used in combination with 1-ethyl-3-methylimidazolium iodide and 1,3-dimethylimidazolium iodide.

In the present invention, as described later, it is preferable to use 1-ethyl-3-methylimidazolium bisfluorosulfonylimide as the ionic liquid. As will be described later, 1-ethyl-3-methylimidazolium bisfluorosulfonylimide has high polarity and hydrophobicity, and has a function of further suppressing deterioration due to moisture ingress. Further, 1-ethyl-3-methylimidazolium bisfluorosulfonylimide has a viscosity at 25 ° C. of about 19 mPa · s and is higher than that of an organic solvent (for example, the viscosity at 25 ° C. is 0.378 mPa · s). About 50 times that of acetonitrile). In the electrolyte gel of the present invention, since it is gelled, the viscosity is further increased. For this reason, the moving speed of iodide ion (I ⁻ ) and triiodide ion (I ₃ ⁻ ) is slower than the electrolytic solution using an organic solvent as a solvent. Thus, iodide ion (I ^-) and triiodide (I 3 ^_-) than the physical diffusion, iodide ion charge transfer by exchange reaction (I ^- _-) and triiodide (I ³⁾ In order to perform mainly, it is preferable to set the density | concentration of an iodine and an iodide high compared with the electrolyte solution which used the organic solvent as a solvent.

At this time, the concentration of 1,3-dialkylimidazolium iodide used as an iodide ion (I ⁻ ) source is set high to suppress the amount of iodine added, rather than simply increasing the concentration of the electrolyte. Thus, the amount of light absorption can be further suppressed, and the ionic conductivity can be further increased.

  From such a viewpoint, the concentration of iodine is preferably about 0.1 to 10 mol / liter (particularly 0.2 to 5 mol / liter).

  The concentration of 1,3-dialkylimidazolium iodide is preferably about 3.0 mol (especially 5 to 20 mol, more preferably 7 to 15 mol) with respect to 1 liter of solvent. By making it within this range, the conversion efficiency can be further improved.

  When 1-ethyl-3-methylimidazolium iodide and 1,3-dimethylimidazolium iodide are used as 1,3-dialkylimidazolium iodide, 1-ethyl iodide iodide present in the electrolytic solution is used. The concentrations of 3-methylimidazolium and 1,3-dimethylimidazolium iodide may be the same or different, and are not particularly limited. However, 1-ethyl-3-methylimidazolium iodide is 1.5 mol / mol. It is preferably about 1 liter or more (especially about 2.5 to 10 mol / liter) and 1,3-dimethylimidazolium iodide is about 1.5 mol / liter or more (particularly about 2.5 to 10 mol / liter).

  Further, when 1-ethyl-3-methylimidazolium iodide and 1,3-dimethylimidazolium iodide are used, the ratio of the concentrations is not particularly limited, but both of them are dissolved alone at 3 mol / liter or more. However, it is preferably 1: 9 to 9: 1 (molar ratio), particularly 4: 6 to 6: 4 (molar ratio) because it is easily dissolved in a polar solvent by coexistence.

  When 1-methyl-3-propylimidazolium iodide is used in combination with the aforementioned 1-ethyl-3-methylimidazolium iodide and 1,3-dimethylimidazolium iodide, a total of 1,3 iodide What is necessary is just to set so that the density | concentration of dialkyl imidazolium may be about 3 mol / liter or more (especially 5-20 mol / liter) grade. However, from the viewpoint of maintaining high-temperature durability, the addition amount of 1-methyl-3-propylimidazolium iodide should be about 0.1 to 5 mol / liter (particularly 0.1 to 3 mol / liter). Is preferred.

  In the present invention, lithium iodide may be included as the iodide.

Also by using this lithium iodide, I ⁻ / I ₃ ⁻ which is a redox pair can be formed with iodine, so that the titania conduction band is further lowered and the electron injection rate from the dye to titania is increased. Can be further improved. It also has the effect of further promoting the transport of electrons injected into titania. Thereby, a short circuit current density can be improved more and a photoelectric conversion efficiency can be improved further.

  In addition, it is thought that the lithium ion produced | generated by addition of lithium iodide adsorb | sucks to the porous titania used for the titania negative electrode etc. of a dye-sensitized solar cell.

Further, from the viewpoint of obtaining sufficient photoelectric conversion efficiency by sufficiently maintaining the open-circuit voltage of the dye-sensitized solar cell, 1,3-dialkylimidazolium iodide is used as the main source of iodide ion I ⁻ . Is preferred. Therefore, it is preferable to reduce the concentration of lithium iodide as compared with 1,3-dialkylimidazolium iodide.

  From this viewpoint, the concentration of lithium iodide is preferably 0.05 to 0.3 mol / liter (particularly 0.1 to 0.2 mol / liter). The concentration ratio of lithium iodide to 1,3-dialkylimidazolium iodide is 1:30 to 1: 300 (molar ratio), particularly 1:60 to 1: 200 (molar ratio), and further 1:70. ˜1: 120 (molar ratio) is preferred.

Ionic liquids Ionic liquids generally have high water absorption, and even if they are gelled, the affinity for moisture greatly depends on the characteristics of the original ionic liquid. From the viewpoint of improvement, it is preferable to use 1-ethyl-3-methylimidazolium bissulfonylimide as the ionic liquid used as the solvent. 1-ethyl-3-methylimidazolium bissulfonylimide has a melting point of −14 ° C. and a viscosity at 25 ° C. of 19 mPa · s, and is hydrophobic.

This 1-ethyl-3-methylimidazolium bissulfonylimide has a low viscosity at 25 ° C. among ionic liquids having a 1-ethyl-3-methylimidazolium cation. Than ethyl-3-methylimidazolium thiocyanate (23.1 mPa · S; melting point −50 ° C.), 1-ethyl-3-methylimidazolium bistrifluoromethanesulfonylimide (28 mPa · S; melting point −16 ° C.), etc. This is a low value, and is advantageous in that iodide ions (I ⁻ ) and triiodide ions (I ₃ ⁻ ) are easily diffused.

1-methyl-3-imidazolium tetracyanoborate has a viscosity at 25 ° C. of 20 mPa · S and approximately the same as 1-ethyl-3-methylimidazolium bissulfonylimide, but has a melting point of 13 ° C. In low temperature environments such as winter, 1-ethyl-3-methylimidazolium bistrifluoromethanesulfonylimide is more preferable. Furthermore, since the tetracyanoborate anion (B (CN) ₄ ⁻ ) may inhibit the movement of iodide ions (I ⁻ ) and triiodide ions (I ₃ ⁻ ), the short circuit current density (Jsc) From the viewpoint of conversion efficiency and high temperature durability, 1-ethyl-3-methylimidazolium bistrifluoromethanesulfonylimide is more preferable.

  Moreover, since 1-ethyl-3-methylimidazolium bisfluorosulfonylimide has hydrophobicity, performance deterioration due to moisture ingress can be more efficiently suppressed.

  As a solvent, it is also conceivable to use a mixed solvent of 1-ethyl-3-methylimidazolium bissulfonylimide and an organic solvent or other ionic liquid. However, considering high temperature durability and stability, it can be a mixed solvent with an organic solvent having a vapor pressure, or a mixed solvent with other ionic liquids that will increase the types of cations and anions, etc. It is preferable to use 1-ethyl-3-methylimidazolium bissulfonylimide alone.

Other Components In addition to the components described above, the electrolytic solution used in the present invention may contain a basic substance such as 4-tertbutylpyridine, N-methylbenzimidazole and the like. When these basic substances are contained, when the photoelectric conversion element is produced, it is adsorbed on the titania surface of the titania electrode, can prevent reverse electron transfer from the titania electrode, and further improve the open-circuit voltage, Photoelectric conversion efficiency can be further improved.

  Further, in order not to desorb the sensitizing dye adsorbed on titania, the addition amount of the basic substance in the electrolytic solution is preferably about 0.01 to 1 mol / liter. In particular, when a metal complex dye is used, it is preferably about 0.1 to 1.0 mol / liter, particularly about 0.3 to 0.8 mol / liter. 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, is added to the electrolytic solution used in the present invention, as in the case of the above-described lithium iodide. be able to. In this case, the addition amount of these may be about 0.1 to 1.0 mol / liter.

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

<Third Aspect>
The electrolyte solution in the third aspect used in the present invention is:
An electrolytic solution containing iodine, an iodide containing 1,3-dialkylimidazolium iodide and a solvent,
The 1,3-dialkylimidazolium iodide preferably includes 1-methyl-3-propylimidazolium iodide.

The electrolyte solution contains iodine as an electrolyte and 1-methyl-3-propylimidazolium iodide as 1,3-dialkylimidazolium iodide.

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 that the titania conduction band is lowered to further improve the electron injection rate from the dye to titania. In addition, there is an effect of further promoting the transport of electrons injected into titania. Thereby, a short circuit current density can be improved more and, as a result, a photoelectric conversion efficiency can be improved more.

In the present invention, as described later, it is preferable to use 1-ethyl-3-methylimidazolium bisfluorosulfonylimide as the ionic liquid. As will be described later, 1-ethyl-3-methylimidazolium bisfluorosulfonylimide has high polarity and hydrophobicity, and has a function of further suppressing deterioration due to moisture ingress. Further, 1-ethyl-3-methylimidazolium bisfluorosulfonylimide has a viscosity at 25 ° C. of about 19 mPa · s and is higher than that of an organic solvent (for example, the viscosity at 25 ° C. is 0.378 mPa · s). About 50 times that of acetonitrile). Therefore, than the electrolytic solution using an organic solvent as a solvent, iodide ion than the physical diffusion, iodide ion (I ^- _-) and triiodide (I ³⁾ (I ^-) and triiodide In order to mainly perform charge transfer by the exchange reaction of (I ₃ ⁻ ), it is preferable to set the concentrations of iodine and iodide higher than the electrolytic solution using an organic solvent as a solvent.

At this time, the concentration of 1-methyl-3-propylimidazolium iodide used as an iodide ion (I ⁻ ) source is set high and the amount of iodine added is not simply increased. By suppressing, it is preferable to further suppress the amount of light absorption and further increase the ionic conductivity.

  From such a viewpoint, the concentration of iodine in the electrolytic solution is preferably about 0.1 to 10 mol / liter (particularly 0.2 to 5 mol / liter).

  Further, 1,3-dialkylimidazolium iodide to be added (especially 1-ethyl-3-methylimidazolium iodide and 1,3-dimethylimidazolium iodide to 1-methyl-3-propylimidazolium iodide) The concentration of 1-methyl-3-propylimidazolium iodide itself is 6M with respect to 1 liter of 1-methyl-3-propylimidazolium iodide). (Especially 3-9 mol / liter) is preferable. By making it within this range, the conversion efficiency can be further improved.

  Since 1-methyl-3-propylimidazolium iodide is a liquid at room temperature, it can be contained in a large amount in the electrolyte as it is.

  In the present invention, as 1,3-dialkylimidazolium iodide, besides 1-methyl-3-propylimidazolium iodide, 1-ethyl-3-methylimidazolium iodide, 1,3 iodide -Dimethylimidazolium, 1-butyl-3-methylimidazolium iodide, 1-butyl-3-methylimidazolium iodide, 1-butyl-3-methylimidazolium iodide, 1-methyl-3-hexyl iodide Other 1,3-dialkylimidazolium iodides such as imidazolium (preferably 1-ethyl-3-methylimidazolium iodide and 1,3-dimethylimidazolium iodide) may be included.

  However, 1-ethyl-3-methylimidazolium iodide and 1,3-dimethylimidazolium iodide are solid at room temperature, and both are independent of 1-ethyl-3-methylimidazolium bissulfonylimide. Dissolves only up to about 3M at room temperature. However, if it is heated to about 70 ° C., it can be dissolved even in an amount larger than 3M (for example, about 30M). Further, it is possible to continue to dissolve in a large amount without precipitation even after cooling to room temperature.

  At this time, the concentration of other 1,3-dialkylimidazolium iodide was the same as that of 1-methyl-3-propylimidazolium iodide, and the concentration of 1,3-dialkylimidazolium iodide was 3 mol / It is preferable to set so as to be about liter or more (particularly 5 to 20 mol / liter). However, from the viewpoint of maintaining high temperature durability, the amount of other 1,3-dialkylimidazolium iodide added should be about 0.1 to 5 mol / liter (particularly 0.1 to 3 mol / liter). Is preferred.

  In the present invention, lithium iodide may be included as the iodide.

Also by using this lithium iodide, I ⁻ / I ₃ ⁻ which is a redox pair can be formed with iodine, so that the titania conduction band is further lowered and the electron injection rate from the dye to titania is increased. Can be further improved. It also has the effect of further promoting the transport of electrons injected into titania. Thereby, a short circuit current density can be improved more and a photoelectric conversion efficiency can be improved further.

  In addition, it is thought that the lithium ion produced | generated by addition of lithium iodide adsorb | sucks to the porous titania used for the titania negative electrode etc. of a dye-sensitized solar cell.

Further, from the viewpoint of sufficiently maintaining the open-circuit voltage of the dye-sensitized solar cell and obtaining sufficient photoelectric conversion efficiency, 1,3-dialkylimidazolium iodide (particularly iodine) is used as a main source of iodide ion I ^−. 1-methyl-3-propylimidazolium). Therefore, it is preferable to reduce the concentration of lithium iodide as compared with 1,3-dialkylimidazolium iodide (particularly 1-methyl-3-propylimidazolium iodide).

  From this viewpoint, the concentration of lithium iodide is preferably 0.05 to 0.3 mol / liter (particularly 0.1 to 0.2 mol / liter). The concentration ratio of lithium iodide to 1,3-dialkylimidazolium iodide is 1:30 to 1: 300 (molar ratio), particularly 1:60 to 1: 200 (molar ratio), and further 1:70. ˜1: 120 (molar ratio) is preferred.

Ionic liquids Ionic liquids generally have high water absorption, and even if they are gelled, the affinity for moisture greatly depends on the characteristics of the original ionic liquid. From the viewpoint of improvement, it is preferable to use 1-ethyl-3-methylimidazolium bissulfonylimide as the ionic liquid used as the solvent. 1-ethyl-3-methylimidazolium bissulfonylimide has a melting point of −14 ° C. and a viscosity at 25 ° C. of 19 mPa · s, and is hydrophobic.

This 1-ethyl-3-methylimidazolium bissulfonylimide has a low viscosity at 25 ° C. among ionic liquids having a 1-ethyl-3-methylimidazolium cation. Than ethyl-3-methylimidazolium thiocyanate (23.1 mPa · S; melting point −50 ° C.), 1-ethyl-3-methylimidazolium bistrifluoromethanesulfonylimide (28 mPa · S; melting point −16 ° C.), etc. This is a low value, and is advantageous in that iodide ions (I ⁻ ) and triiodide ions (I ₃ ⁻ ) are easily diffused.

1-methyl-3-imidazolium tetracyanoborate has a viscosity at 25 ° C. of 20 mPa · S and approximately the same as 1-ethyl-3-methylimidazolium bissulfonylimide, but has a melting point of 13 ° C. In an environment where the temperature is low, such as in winter, 1-ethyl-3-methylimidazolium bissulfonylimide is more preferable. Furthermore, since the tetracyanoborate anion (B (CN) ₄ ⁻ ) may inhibit the migration of iodide ions (I ⁻ ) and triiodide ions (I ₃ ⁻ ), the short-circuit current density and conversion efficiency From the viewpoint of high temperature durability, 1-ethyl-3-methylimidazolium bissulfonylimide is more preferable.

  Moreover, since 1-ethyl-3-methylimidazolium bisfluorosulfonylimide has hydrophobicity, performance deterioration due to moisture ingress can be more efficiently suppressed.

  As a solvent, it is also conceivable to use a mixed solvent of 1-ethyl-3-methylimidazolium bissulfonylimide and an organic solvent or other ionic liquid. However, considering high temperature durability and stability, it can be a mixed solvent with an organic solvent having a vapor pressure, or a mixed solvent with other ionic liquids that will increase the types of cations and anions, etc. It is preferable to use 1-ethyl-3-methylimidazolium bissulfonylimide alone.

Other Components In addition to the components described above, the electrolytic solution used in the present invention may contain a basic substance such as 4-tertbutylpyridine, N-methylbenzimidazole and the like. When these basic substances are contained, when the photoelectric conversion element is produced, it is adsorbed on the titania surface of the titania electrode, can prevent reverse electron transfer from the titania electrode, and further improve the open-circuit voltage, Photoelectric conversion efficiency can be further improved.

  Further, in order not to desorb the sensitizing dye adsorbed on titania, the addition amount of the basic substance in the electrolytic solution is preferably about 0.01 to 1 mol / liter. In particular, when a metal complex dye is used, it is preferably about 0.1 to 1.0 mol / liter, particularly about 0.3 to 0.8 mol / liter. 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, is added to the electrolytic solution used in the present invention, as in the case of the above-described lithium iodide. be able to. In this case, the addition amount of these may be 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.

2. Photoelectric Conversion Element and Dye-Sensitized Solar Cell The photoelectric conversion element of the present invention comprises at least a conductive substrate (negative electrode substrate), a semiconductor layer, and an integrated electrode (positive electrode) of the present invention.

  The conductive substrate (negative electrode substrate) usually has a conductive film on the substrate. The substrate is not particularly limited, and the material, thickness, dimensions, shape, and the like can be appropriately selected according to the purpose. For example, metal, colorless or colored glass, meshed glass, glass block, etc. are used. Colorless or colored 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. In addition, the board | substrate in this invention has a smooth surface at normal temperature, The surface may be a plane or a curved surface, and may deform | transform by stress.

The material of the conductive film that acts as an electrode is not particularly limited, and examples thereof include a metal such as gold, silver, chromium, copper, tungsten, and titanium, a metal thin film, and a conductive film made of a metal oxide. As the metal oxide, for example, Indium Tin Oxide (ITO (In ₂ O ₃ : Sn)), or Fluorine doped Tin Oxide (FTO (SnO ₂ )) obtained by doping a metal oxide such as tin or zinc with a small amount of another metal element. : F)), Aluminum doped Zinc Oxide (AZO (ZnO: Al)), Antimony doped Tin Oxide (ATO (SnO ₂ : Sb)), and the like are preferably used.

  The film thickness of the conductive film is usually 100 to 10,000 nm, preferably 300 to 2000 nm. The surface resistance (resistivity) is appropriately selected, but is usually 0.5 to 500 Ω / sq, preferably 1 to 50 Ω / sq.

  The method for forming the conductive film is not particularly limited, and a known method can be appropriately employed depending on the type of metal or metal oxide used. Usually, a vacuum deposition method, an ion plating method, a CVD method, a sputtering method, or the like is used. In either case, it is desirable that the substrate temperature be formed within a range of 20 to 700 ° C.

  As the semiconductor layer, a titanium oxide material is used. For example, known or commercially available titania nanoparticles, amorphous titania nanotubes (Patent Documents 2 to 3 and the like), tubular aggregates of titania nanoparticles (Patent Document 4) and the like can be used alone or in combination.

  The method for forming the semiconductor layer on the conductive substrate (negative electrode substrate) is not particularly limited. For example, a paste containing the above titanium oxide material is prepared, applied onto the conductive substrate (negative electrode substrate), and fired. And the like. At this time, water, an organic solvent, or the like can be used as a solvent for the paste.

  The organic solvent is not particularly limited as long as it can disperse the titanium oxide material. For example, alcohols such as ethanol, methanol, and terpineol; glycols such as ethylene glycol, polyethylene glycol, propylene glycol, and polypropylene glycol can be used. These solvents are usually mixed and used in consideration of dispersibility, volatility, and viscosity. The proportion of the solvent in the paste is 50 to 90% by weight, particularly 60 to 75%, from the viewpoint of imparting fluidity during coating, maintaining the thickness after coating, and forming porous titanium oxide. % By weight is preferred.

  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. Among these, alkyl cellulose, particularly ethyl cellulose can be preferably used.

  The proportion of the thickener in the paste is preferably 2 to 20% by weight, particularly 3 to 15% by weight from the viewpoint of balancing the fluidity during coating and the thickness after coating.

  The ratio of the solid content in the paste is preferably 10 to 50% by weight, particularly preferably 10 to 30% by weight, from the viewpoint of the balance between the fluidity at the time of coating and the thickness after coating, as described above.

  In the photoelectric conversion element of the present invention, a semiconductor layer having a dye supported (adsorbed, contained, etc.) on the semiconductor layer is used for the purpose of improving the light absorption efficiency of the semiconductor layer.

  The dye is not particularly limited as long as it has absorption characteristics in the visible region and near infrared region, and improves (sensitizes) the light absorption efficiency of the semiconductor layer. However, metal complex dyes, organic dyes, natural dyes, semiconductors, etc. Is preferred. In addition, in order to impart adsorptivity to the semiconductor layer, a functional group such as a carboxyl group, a hydroxyl group, a sulfonyl group, a phosphonyl group, a carboxylalkyl group, a hydroxyalkyl group, a sulfonylalkyl group, or a phosphonylalkyl group is included in the dye molecule. Those having a group are preferably used.

  As the metal complex dye, for example, a ruthenium, osmium, iron, cobalt, zinc, mercury complex (for example, mellicle chromium), 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, or a fine particle semiconductor that exhibits a quantum size effect and efficiently absorbs visible light is 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.

  As a method for adsorbing the dye to the semiconductor layer, for example, a solution in which the dye is dissolved in a solvent is applied on the semiconductor layer by spray coating, spin coating, or the like, and then dried. In this case, the substrate may be heated to an appropriate temperature. Alternatively, a method in which the semiconductor layer is immersed in a solution and adsorbed can 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 20 hours. Moreover, you may heat a solvent and a board | substrate when immersing as needed. The concentration of the dye in the case of forming a solution is about 1 to 1000 mmol / L, preferably about 10 to 500 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, a semiconductor using an amine, a quaternary ammonium salt, a ureido compound having at least one ureido group, a silyl compound having at least one silyl group, an alkali metal salt, an alkaline earth metal salt, etc. The surface of the 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.

  Thus, after forming a semiconductor layer on a negative electrode substrate and producing a negative electrode, the separator and the semiconductor layer are bonded together so that the integrated electrode and the negative electrode containing the electrolyte solution are in contact as described above. The photoelectric conversion element of the present invention can be easily produced. Alternatively, the electrolyte solution may be injected after the integrated electrode and the negative electrode are bonded together so that the separator and the semiconductor layer are in contact with each other.

  The dye-sensitized solar cell of the present invention can be manufactured by modularizing the photoelectric conversion element of the present invention 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.

Example 1
[Production of separator-forming composition containing titania]
Acetic acid 0.05 mol was added to titanium isopropoxide 0.05 mol and stirred for 15 minutes. Distilled water 73 ml was added and stirred for 1 hour. Further, 1 ml of concentrated nitric acid was added, and the mixture was heated and stirred at 80 ° C. for 75 minutes. Distilled water was added to make a total volume of 93 ml to obtain an aqueous titania sol solution. 40 mL of this aqueous titania sol solution was placed in a pressure reaction vessel with an internal volume of 125 ml and heated at 250 ° C. for 12 hours. The obtained white precipitate (titania) was subjected to solvent substitution with ethanol, and then made into a 100 ml ethanol dispersion. To this, 7 g of α-terpineol and 8.65 g of a 10 wt% ethanol solution of ethyl cellulose were added and stirred. After sufficiently stirring, ethanol was distilled off using an evaporator to obtain 10 g of a film forming composition containing titania.

[Production of integrated electrode]
Including the titania produced above using a polyester screen printing plate (225 mesh) on a substrate obtained by sputtering 50 nm of platinum on glass with fluorine-doped tin oxide (FTO) film (manufactured by Nippon Sheet Glass Co., Ltd .; 4 mm thickness) The film-forming composition was screen-printed once in a size of 5 mm square. Furthermore, the porous titanium oxide layer (separator) having a film thickness of 1.5 μm, a specific surface area of 71 m ² / g, and a thickness of 1.1 μm was integrated with the negative electrode by firing in an electric furnace at 500 ° C. for 1 hour. An electrode was obtained.

[Production of titania negative electrode]
A film-forming composition containing titania prepared as described above was prepared using a polyester screen printing plate (225 mesh) on a glass with fluorine-doped tin oxide (FTO) film (manufactured by Nippon Sheet Glass Co., Ltd .; 4 mm thickness). Screen printing was repeatedly performed until the film thickness was 14 μm in the size of millimeter square. Furthermore, it put into the electric furnace and baked at 500 degreeC for 1 hour.

[Immobilization of sensitizing dye]
A titania negative electrode calcined at 500 ° C. in a solution obtained by dissolving N-719 dye manufactured by Daisol in a mixed solvent of tertiary butyl alcohol and acetonitrile at a volume ratio of 1: 1 at a concentration of 0.5 mmol / liter was used at 25 ° C. The pigment was fixed by immersion for 20 hours.

[Assembly of small cells]
By impregnating the integral electrode in the electrolyte, the electrolyte is included in the porous structure of the separator of the integral electrode, and bonded to the titania negative electrode to which the dye is fixed, and the periphery is sealed using an ultraviolet effect resin. A photoelectric conversion element (small cell) was produced. Using this small cell, the performance was evaluated as described later. The results are shown in Table 1.

  The composition of the electrolytic solution was as follows.

<Electrolyte>
Iodine (I ₂ ): 0.2M
Lithium iodide (LiI): 0.1M
4-tert-butylpyridine (TBP): 0.5M
1-methyl-3-propylmidazolium iodide (MPImI): 6M

[Performance evaluation of small cells]
The produced small cell was irradiated with light having an intensity of 100 mW / cm ² under the condition of AM1.5 (JISC8912A rank) with a solar simulator manufactured by Mitsunaga Electric Co., Ltd., and the photoelectric conversion characteristic of the small cell was measured at 25 ° C. Evaluated.

[85 ° C durability evaluation of small cells]
The produced small cell was put into a 85 degreeC drying furnace, and was hold | maintained for 1000 hours. After holding for 1000 hours, the photoelectric conversion characteristics of the small cells were evaluated in the same manner as the above performance evaluation.

Comparative Example 1
Glass with fluorine-doped tin oxide (FTO) film sputtered with platinum using a low-density polyethylene film (Bunel manufactured by DuPont) with a thickness of 50 μm as a spacer / sealant on the above-mentioned titania negative electrode fixed with a dye (Pilkinton Co., Ltd.) ; 2.2 mm thickness). That is, a porous body containing titanium oxide was not used as the separator. Thereafter, the electrolytic solution used in Example 1 was injected and sealed to produce a photoelectric conversion element. The results are shown in Table 1.

Example 2
According to the method described in Example 1 of Patent Document 4, a tubular aggregate of titania nanoparticles having an outer diameter of 100 nm, an inner diameter of 30 nm, and a length of about 2000 nm and an average particle diameter of about 10 nm was produced. A small cell was prepared and evaluated in the same manner as in Example 1 except that 5% by weight of the tubular assembly of titania nanoparticles prepared in the separator-forming composition containing titania was mixed. At this time, the film thickness of the separator was 1.5 μm, and the specific surface area was 75 m ² / g. The results are shown in Table 1.

Example 3
By mixing 4.8 g of 50% SnO ₂ methanol dispersion and 3.6 g of Ketjen Black, adding 30 g of ethanol solution of 10% ethylcellulose, sonicating, adding 32 g of terpineol, and distilling ethanol off, A film forming composition was obtained. This film-forming composition was applied to a titanium metal plate by screen printing at 1.5 μm to produce a positive electrode made of a carbon material. This positive electrode was used in place of the platinum sputter substrate used in Example 1, and a separator composition containing titania was screen printed and baked in the same manner as in Example 1 to produce a small cell and evaluated. . The results are shown in Table 1.

Example 4
A small cell was prepared and evaluated in the same manner as in Example 1 except that the composition of the electrolytic solution was as follows. The results are shown in Table 2.

<Electrolyte>
Iodine (I ₂ ): 0.2M
Lithium iodide (LiI): 0.1M
4-tert-butylpyridine (TBP): 0.5M
1-ethyl-3-methylimidazolium iodide (EMImI): 2.0M
1,3-dimethylimidazolium iodide (DMImI): 2.0M
As the ionic liquid, 1-methyl-3-ethylimidazolium bisfluorosulfonylimide (EMIm-FSI) was used.

Example 5
A small cell was prepared and evaluated in the same manner as in Example 1 except that the composition of the electrolytic solution was as follows. The results are shown in Table 2.

<Electrolyte>
Iodine (I ₂ ): 0.2M
Lithium iodide (LiI): 0.1M
4-tert-butylpyridine (TBP): 0.5M
1-ethyl-3-methylimidazolium iodide (EMImI): 5.0M
1,3-dimethylimidazolium iodide (DMImI): 5.0M
As the ionic liquid, 1-methyl-3-ethylimidazolium bisfluorosulfonylimide (EMIm-FSI) was used.

Example 6
A small cell was prepared and evaluated in the same manner as in Example 1 except that the composition of the electrolytic solution was as follows. The results are shown in Table 2.

<Electrolyte>
Iodine (I ₂ ): 0.2M
Lithium iodide (LiI): 0.1M
4-tert-butylpyridine (TBP): 0.5M
1-ethyl-3-methylimidazolium iodide (EMImI): 10.0M
1,3-dimethylimidazolium iodide (DMImI): 10.0M
As the ionic liquid, 1-methyl-3-ethylimidazolium bisfluorosulfonylimide (EMIm-FSI) was used.

Example 7
In the production of the integrated electrode, a small cell was produced and evaluated in the same manner as in Example 6 except that PST400C manufactured by JGC Catalysts & Chemicals Co., Ltd. was used as the film forming composition containing titania. At this time, the specific surface area of the separator was 5 m ² / g and the thickness was 3 μm. The results are shown in Table 2.

Claims (24)

An integrated electrode in which a positive electrode and a separator are integrated,
The separator is made of a porous body containing titanium oxide.
Integrated electrode. The integrated electrode according to claim 1, wherein the separator is made of a porous sintered body containing titanium oxide. The integrated electrode according to claim 2, wherein the separator has a thickness of 0.1 to 5 μm. The integrated electrode according to claim 1, wherein the porous body has a specific surface area of 3 to 150 m ² / g. The integrated electrode according to claim 1, wherein the titanium oxide contains titania nanotubes. The integrated electrode according to claim 1, wherein the positive electrode includes a conductive substrate. The integrated electrode according to claim 1, wherein the positive electrode has a conductive layer containing a conductive material formed on a substrate. The integrated electrode according to claim 1, wherein the positive electrode has a conductive layer containing a conductive material formed on a conductive substrate. The integrated electrode according to claim 7 or 8, wherein the conductive layer further contains a binder. The integrated electrode according to claim 9, wherein the binder is an inorganic oxide. The integrated electrode according to claim 10, wherein the inorganic oxide is at least one oxide selected from the group consisting of tin oxide, titanium oxide, and zinc oxide. The integrated electrode according to claim 1, wherein the integrated electrode contains an electrolytic solution. The integrated electrode according to claim 12, wherein the electrolytic solution is present in pores of the porous body. The integrated electrode according to claim 12 or 13, wherein the electrolytic solution includes an ionic liquid. The integrated electrode according to claim 14, wherein the ionic liquid is 1-ethyl-3-methylimidazolium bisfluorosulfonylimide. The electrolytic solution contains an electrolyte containing iodide including iodine and 1,3-dialkylimidazolium iodide, and
(1) The 1,3-dialkylimidazolium iodide includes 1-ethyl-3-methylimidazolium iodide and 1,3-dimethylimidazolium iodide.
(2) The electrolytic solution contains 3.0 mol / liter or more of the 1,3-dialkylimidazolium iodide.
(3) The integrated electrode according to any one of claims 12 to 15, wherein the 1,3-dialkylimidazolium iodide satisfies at least one of containing 1-methyl-3-propylimidazolium iodide. The electrolyte is
(1) The integrated electrode according to claim 16, wherein the 1,3-dialkylimidazolium iodide satisfies a condition including 1-ethyl-3-methylimidazolium iodide and 1,3-dimethylimidazolium iodide. The integrated electrode according to claim 17, wherein the electrolytic solution contains 3.0 mol or more of the 1,3-dialkylimidazolium iodide with respect to 1 liter of a solvent. The 1,3-dialkylimidazolium iodide further includes 1-methyl-3-propylimidazolium iodide and / or 1-butyl-3-methylimidazolium iodide.
The integral electrode according to claim 17 or 18. A method for producing an integral electrode according to any one of claims 1 to 19,
A manufacturing method provided with the process of apply | coating and sintering the composition for separator formation containing a titanium oxide or a titanium oxide precursor on a positive electrode. A photoelectric conversion element comprising the integrated electrode according to claim 1. Furthermore, the photoelectric conversion element of Claim 21 provided with a negative electrode. It is a manufacturing method of a photoelectric conversion element provided with the negative electrode and the integrated electrode in any one of Claims 1-19,
A manufacturing method comprising a step of sealing after directly bonding the integrated electrode to the negative electrode. A dye-sensitized solar cell comprising the photoelectric conversion element according to claim 21 or 22.

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