JP2014177695A - Manufacturing method of composite film, composite film, optical electrode, and dye-sensitized solar cell - Google Patents

Abstract

Provided is a method for efficiently producing a composite film containing an inorganic semiconductor and a conductive additive in a large amount.
[1] A method for producing a composite film comprising an inorganic semiconductor and a conductive additive, wherein the inorganic semiconductor and the conductive additive are physically sprayed on a substrate to form a film. . [2] The composite film formed by spraying is further contacted with a solution containing a compound having a lower electron conduction band energy or a precursor of the compound than the conductive auxiliary agent. The manufacturing method. [3] The film is formed by spraying composite fine particles containing the inorganic semiconductor and the conductive assistant on a base material using a conductive assistant composed of a material that generates a thermal oxidation reaction when heated in the presence of oxygen. Production method. [4] The production method, wherein the composite fine particles are a mixed powder obtained by mixing fine particles made of the inorganic semiconductor and fine particles made of the conductive auxiliary material. [5] The said manufacturing method whose carbon content rate of the said conductive support agent is 50 mass% or more.
[Selection figure] None

Description

  The present invention relates to a method for producing a composite film that does not require a baking treatment, a composite film produced by the production method, a photoelectrode using the composite film, and a dye-sensitized solar cell using the photoelectrode.

  In order to improve the photoelectric conversion efficiency of the dye-sensitized solar cell, a technique for improving the electronic conduction of the semiconductor layer on which the dye is adsorbed can be considered. Conventionally, an attempt has been made to combine a conductive additive (a material that assists or promotes electronic conduction) in a semiconductor layer. For example, a nanocomposite in which carbon nanotubes are combined with a titanium oxide layer has been proposed (Patent Document 1). It has been reported that by using this nanocomposite as a semiconductor layer constituting a photoelectrode, the photoelectric conversion efficiency is improved by 7.6% at the maximum as compared with the case of a semiconductor layer made of only titanium oxide.

  However, a semiconductor layer made of titanium oxide that constitutes a commonly used photoelectrode needs to be baked at 450 to 600 ° C. for several hours in order to sinter titanium oxide particles in the manufacturing process. is there. In order to apply this firing treatment to the formation of a semiconductor layer containing a conductive aid such as carbon nanotubes, it is necessary to control the atmosphere during firing. This is because if the firing is performed in an air atmosphere containing oxygen, the conductive aid may be decomposed or deteriorated by a thermal oxidation reaction. For example, an example of producing a composite film of titanium oxide and carbon nanotubes by firing in an inert gas argon atmosphere has been reported (Non-Patent Document 1). Although such atmosphere control at the time of firing can be applied at the laboratory level, the manufacturing process becomes complicated, and therefore, it is required to efficiently manufacture a large number of semiconductor layers containing a conductive assistant that is easily thermally oxidized. Not necessarily suitable for industrial use.

Special table 2012-515132 gazette

Nature nanotechnology 2011, 6, 377-384

  This invention is made | formed in view of the said situation, and makes it a subject to provide the method of manufacturing efficiently the composite film containing an inorganic semiconductor and a conductive support agent in large quantities.

[1] A method for producing a composite film comprising an inorganic semiconductor and a conductive additive, wherein the inorganic semiconductor and the conductive additive are physically sprayed onto a substrate to form a composite film. Method.
[2] The composite film formed by spraying is further subjected to a treatment in which a solution containing a compound having a lower electron conduction band energy than the conductive auxiliary agent or a precursor of the compound is contacted. The method for producing a composite film as described in [1] above.
[3] As the conductive assistant, a conductive assistant composed of a material that causes a thermal oxidation reaction when heated in the presence of oxygen is used, and the composite fine particles containing the inorganic semiconductor and the conductive assistant are used as a base material. The method for producing a composite film according to [1] or [2], wherein the film is formed by spraying.
[4] Any of [1] to [3], wherein the composite fine particles are a mixed powder obtained by mixing fine particles made of the inorganic semiconductor and fine particles made of a material constituting the conductive auxiliary agent. A method for producing the composite film according to claim 1.
[5] The method for producing a composite film according to any one of [1] to [4], wherein the conductive auxiliary agent has a carbon content of 50% by mass or more.
[6] The method for producing a composite film according to any one of [1] to [5], wherein the conductive additive is graphite, carbon nanotube, graphene, or fullerene.
[7] The content of the conductive additive with respect to the mass of the composite fine particles is 0.01 to 0.5% by mass, according to any one of [1] to [6], A method for producing a composite membrane.
[8] The method for producing a composite film according to any one of [1] to [7], wherein the conductive additive is a semiconductor or a conductor of the same type as the inorganic semiconductor.
[9] A composite film formed by the production method according to any one of [1] to [8].
[10] A photoelectrode comprising the composite film according to [9].
[11] A dye-sensitized solar cell comprising the photoelectrode according to [10].

According to the method for producing a composite film according to the present invention, since the film can be formed without firing, even when a conductive assistant that is easily thermally oxidized is used, the deterioration is suppressed, and the characteristic inherent to the conductive assistant. A composite membrane utilizing the above can be formed.
Since the composite film, the photoelectrode and the dye-sensitized solar cell according to the present invention do not require firing in the production process, the characteristics inherent to the conductive auxiliary agent are sufficiently reflected as the properties of the composite film. .

It is a schematic block diagram of the film forming apparatus applicable to the manufacturing method of the composite film concerning this invention.

  Hereinafter, the present invention will be described with reference to the drawings based on preferred embodiments, but the present invention is not limited to such embodiments.

<Production method of composite membrane>
The manufacturing method of the composite film of 1st embodiment of this invention is a method of physically spraying an inorganic semiconductor and a conductive support agent on a base material, and forming the composite film containing the said inorganic semiconductor and the said conductive support agent It is. For example, a composite film including an inorganic semiconductor and a conductive additive that generates a thermal oxidation reaction when heated in the presence of oxygen (a conductive auxiliary that is easily thermally oxidized) can be manufactured. Here, the conductive additive is a material different from the inorganic semiconductor.
The composite film can be obtained by physically spraying composite fine particles containing the inorganic semiconductor and the conductive auxiliary agent on a substrate to form a film.

  The kind in particular of the said inorganic semiconductor is not restrict | limited, A conventionally well-known inorganic semiconductor is applicable, The inorganic semiconductor which can be shape | molded into the microparticles | fine-particles which have a particle size (particle diameter) about 10 nm-100 micrometers is preferable. Examples of such an inorganic semiconductor include an oxide semiconductor that constitutes a photoelectrode of a conventionally known dye-sensitized solar cell. Specific examples include titanium oxide and zinc oxide. As the inorganic semiconductor, one kind of inorganic semiconductor may be used, or two or more kinds of inorganic semiconductors may be used in combination.

  In the present specification and claims, the “thermal oxidation reaction” refers to a reaction in which the conductive auxiliary agent is oxidized by oxygen when the conductive auxiliary agent is heated. Usually, the inherent property of the conductive auxiliary agent is changed by the thermal oxidation reaction, and its electrical conductivity is lowered. For this reason, when the purpose of incorporating the conductive assistant into the inorganic semiconductor is to improve the conductivity of the thin film made of the inorganic semiconductor, the thermal oxidation reaction is a reaction that should be avoided as much as possible.

  The temperature at which the conductive auxiliary agent is substantially oxidized in the presence of oxygen, that is, the temperature at which the conductivity of the composite film or the composite fine particles is greatly changed by the oxidation depends on the type of the conductive auxiliary agent. It is about 700 ° C.

  More specifically, examples of the conductive assistant include a carbon-based material (a material in which 50% by weight or more of the total weight of the material is carbon). By using these conductive assistants, the conductivity of the composite film according to the present invention can be further improved. However, the dye used for the dye-sensitized solar cell described later (sensitizing dye) is excluded from the conductive auxiliary agent.

  The carbon-based material is preferably graphite, carbon nanotube, graphene, or fullerene. By using a conductive additive having a carbon content of 100% by mass, the conductivity of the composite film according to the present invention can be further improved. In addition, these carbon-based materials are easily subjected to a thermal oxidation reaction, and the electrical conductivity of the carbon-based material is greatly reduced when firing is performed. However, the firing method is unnecessary in the manufacturing method of the present embodiment. A composite film can be produced without impairing the electrical conductivity inherent to the carbon-based material.

  In order to improve the conductivity of the composite film obtained by the manufacturing method of the present embodiment, the content of the conductive auxiliary agent with respect to the total mass of the composite film is 0.01 to 0.5% by mass. Preferably, 0.02-0.4 mass% is more preferable, and 0.05-0.3 mass% is still more preferable. Within these ranges, conductivity suitable for using the composite film as a semiconductor layer of the photoelectrode can be imparted to the composite film. In addition, the inorganic semiconductor constitutes the remainder obtained by removing the conductive additive from the constituent material of the composite film, thereby producing a composite film having high structural strength that reflects the physical strength of the inorganic semiconductor. Can be membrane.

In order to improve the conductivity of the composite film obtained by the manufacturing method of the present embodiment, the conductive additive may be a semiconductor or a conductor of the same type as the inorganic semiconductor, It may be a different type of semiconductor or conductor. The conductive additive is preferably a semiconductor or a conductor of the same type as the inorganic semiconductor. For example, when the inorganic semiconductor is an N type in which free electrons are used as carriers for carrying charges, the conductive additive is preferably an N type semiconductor. On the contrary, when the inorganic semiconductor is a P-type semiconductor in which holes are used as carriers for carrying charges, it is preferable that the conductive additive is also a P-type semiconductor. Thus, by compounding a semiconductor of the same type as the inorganic semiconductor constituting the composite film, excellent photoelectric conversion efficiency can be obtained when the composite film is used as a semiconductor layer of a photoelectrode.
The carbon nanotubes are generally known as a metal type and a semiconductor type. The conductor includes the metal-type carbon nanotube.

Examples of the conductive auxiliary that is the N-type semiconductor include oxide semiconductors such as SnO and ZnO, compound semiconductors such as Si, Cd, and ZnS doped with pentavalent elements, and carbon-based materials such as fullerenes and carbon nanotubes. An organic semiconductor containing
Examples of the conductive assistant that is the P-type semiconductor include an oxide semiconductor such as NiO and Si doped with a trivalent element.

  The composite fine particles in the film forming method of the present embodiment are fine particles containing the inorganic semiconductor and the conductive additive. Examples of such fine particles include fine particles obtained by adhering the conductive additive to fine particles made of the inorganic semiconductor. Conversely, fine particles obtained by attaching the inorganic semiconductor to fine particles made of the conductive auxiliary agent may be used. Further, mixed fine particles (mixed powder) obtained by mixing the fine particles made of the conductive assistant and the fine particles made of the inorganic semiconductor may be used as the composite fine particles. When the composite film according to the present invention is used as the semiconductor layer constituting the photoelectrode, it is preferable to use composite fine particles obtained by adhering the conductive additive to the fine particles made of the inorganic semiconductor. In this case, the content of the conductive additive with respect to the total mass of the composite fine particles is preferably 0.01 to 0.5% by mass, more preferably 0.02 to 0.4% by mass, -0.3 mass% is still more preferable. Within these ranges, conductivity suitable for using the composite film as a semiconductor layer of the photoelectrode can be imparted to the composite film.

  The average particle diameter (average of the major axis) of the composite fine particles sprayed on the substrate is not particularly limited. 005 μm to 100 μm is preferable, 0.01 μm to 10 μm is more preferable, and 0.01 μm to 2.0 μm is particularly preferable.

  When the average particle diameter of the composite fine particles is 0.005 μm or more, a structurally strong porous composite film different from the green compact can be easily obtained. That is, a sufficient film forming effect can be easily obtained. When the composite fine particles have an average particle size of 2.0 μm or less, a sufficient specific surface area can be obtained while forming a structurally strong porous composite film. When the average particle size of the composite fine particles is larger than 100 μm, in addition to the effect of increasing the thickness of the composite film by spraying, the blasting effect of scraping the already formed film may become prominent.

When the composite fine particles are the mixed fine particles, the average particle size of the fine particles comprising the conductive auxiliary agent is preferably 0.01 μm to 10 μm, and more preferably 0.1 μm to 2 μm.
When the average particle diameter is 0.01 μm or more, sufficient energy can be obtained for hitting the particles against the substrate in spraying during film formation. When the average particle diameter is 10 μm or less, a porous composite film having a specific surface area sufficient for adsorbing the dye can be obtained.
When the composite fine particles are the mixed fine particles, the average particle size of the fine particles made of the inorganic semiconductor is preferably the average particle size described as the average particle size of the composite fine particles.

  As a method for obtaining the average particle size of the composite fine particles, for example, a method of determining as a peak value of a volume average particle size distribution obtained by measurement with a laser diffraction particle size distribution measuring device or a long diameter of a plurality of composite fine particles by SEM observation. The method of measuring and averaging is mentioned. The larger the number of measurements when calculating the average, the better. However, for example, a method of calculating the average value by measuring the major axis of 30 to 100 composite fine particles can be mentioned. The primary particle diameter of the composite fine particles is preferably measured by the SEM observation.

The said inorganic semiconductor may be used individually by 1 type, and may use 2 or more types together.
The said conductive support agent may be used individually by 1 type, and may use 2 or more types together.

<Film formation by AD method>
Hereinafter, an example of an embodiment of the present invention will be described with reference to FIG. The drawings used in the following description are schematic, and the length, width, thickness ratio, and the like are not necessarily the same as the actual ones, and can be changed as appropriate.

  FIG. 1 is a configuration diagram of a film forming apparatus 60 applicable to the present embodiment. However, the film forming apparatus used in the film forming method of the present embodiment is not limited to the configuration shown in FIG. 1 as long as the apparatus can spray the composite fine particles, which are raw materials of the composite film, onto the base material.

<Film forming device>
The film forming apparatus 60 includes a gas cylinder 55, a transfer pipe 56, a nozzle 52, a base 63, and a film forming chamber 51.
The gas cylinder 55 is filled with a gas (hereinafter referred to as carrier gas) for accelerating the composite fine particles 54 and spraying the composite fine particles 54 onto the base material 53.
One end of a transfer pipe 56 is connected to the gas cylinder 55. The carrier gas supplied from the gas cylinder 55 is supplied to the carrier pipe 56.

  The transport pipe 56 is provided with a mass flow controller 57, an aerosol generator 58, and a disintegrator 59 and a classifier 61 that can appropriately adjust the dispersion degree of the composite fine particles 54 in the transport gas in order from the front side. ing. By the crusher 59, the state in which the composite fine particles 54 adhere to each other due to moisture or the like can be solved. Further, even if there are composite fine particles that have passed through the crusher 59 in the attached state, the particles can be removed by the classifier 61.

  The mass flow controller 57 can adjust the flow rate of the carrier gas supplied from the gas cylinder 55 to the carrier pipe 56. The aerosol generator 58 is loaded with composite fine particles 54. In the case of manufacturing a semiconductor layer constituting a photoelectrode for a dye-sensitized solar cell, a sensitizing dye may be adsorbed in advance on the composite fine particles 54 before spraying. The composite fine particles 54 are dispersed in the carrier gas supplied from the mass flow controller 57 and conveyed to the crusher 59 and the classifier 61.

  The nozzle 52 is disposed such that an opening (not shown) faces the base material 53 on the base 63. The other end of the transport pipe 56 is connected to the nozzle 52. The carrier gas containing the composite fine particles 54 is injected to the base material 53 from the opening of the nozzle 52.

  The base material 53 is placed on the upper surface 72 of the base 63 so that one surface 73 of the base material 53 comes into contact therewith. Further, the other surface 71 (film forming surface) of the substrate 53 faces the opening of the nozzle 52. The composite fine particles 54 injected together with the carrier gas from the nozzle 52 collide with the film forming surface, and a composite film composed of the composite fine particles 54 is formed.

  The members constituting the base 63 of the film forming apparatus 60 are the collision energy between the composite fine particles 54 and the substrate 53 on the film forming surface 71 and the composite fine particles according to the average particle diameter, hardness, and spraying speed of the composite fine particles 54. It is preferable that the collision energy between 54 is made of a material that is appropriately controlled. With such a member, the adhesion of the composite fine particles 54 to the film-forming surface 71 is enhanced, and the composite fine particles 54 to be deposited are easily joined together, so that a highly porous composite film can be easily formed. can do.

  The base material 53 is preferably made of a material that allows the sprayed composite fine particles 54 to bite into the film-forming surface 71 and adhere to the composite fine particles 54 without penetrating. Examples of such a substrate 53 include a resin film (resin sheet). Since the film can be formed at room temperature according to the AD method, the substrate 53 is not required to have high heat resistance. More specific selection of the base material 53 may be appropriately performed according to the material of the composite fine particles 54, film forming conditions such as spraying speed, and the use of the composite film.

The film forming chamber 51 is provided for film formation in a reduced pressure atmosphere. A vacuum pump 62 is connected to the film forming chamber 51, and the inside of the film forming chamber 51 is depressurized as necessary.
The film forming chamber 51 is provided with a base exchange means (not shown).

<Blowing method>
Hereinafter, an example of a method for spraying the composite fine particles 54 will be described.
First, the vacuum pump 62 is operated to depressurize the film forming chamber 51. The pressure in the film forming chamber 51 is not particularly limited, but is preferably set to 5 to 1000 Pa. By reducing the pressure to this extent, convection in the film forming chamber 51 is suppressed, and it becomes easy to spray the composite fine particles 54 onto a predetermined portion of the film forming surface 71.

Next, the carrier gas is supplied from the gas cylinder 55 to the carrier pipe 56, and the flow rate and flow rate of the carrier gas are adjusted by the mass flow controller 57. As the carrier gas, for example, a general gas such as O ₂ , N ₂ , Ar, He, or air can be used.
The flow rate and flow rate of the carrier gas may be set as appropriate according to the material, average particle size, flow rate and flow rate of the composite fine particles 54 sprayed from the nozzle 52.

  The composite fine particles 54 are loaded into the aerosol generator 58, and the composite fine particles 54 are dispersed in the carrier gas flowing in the carrier pipe 56 and accelerated. The composite fine particles 54 are ejected from the opening of the nozzle 52 at a subsonic to supersonic speed and are laminated on the film forming surface 71 of the substrate 53. At this time, the spraying speed of the composite fine particles 54 onto the film forming surface 71 can be set to 10 to 1000 m / s, for example. However, this speed is not particularly limited, and may be set as appropriate according to the material of the base material 53.

  By continuing to spray the composite fine particles 54, the composite fine particles 54 collide one after another with the composite fine particles 54 that have digged into the film-forming surface 71 of the base material 53. A new surface is formed on the surface, and the composite fine particles 54 are joined to each other on the new surface. When the composite fine particles 54 collide with each other, a temperature rise that melts the entire composite fine particles 54 does not occur, so that a grain boundary layer made of glass is hardly formed on the new surface.

When the composite film composed of the composite fine particles 54 reaches a predetermined film thickness (for example, 1 μm to 100 μm), the spraying of the composite fine particles 54 is stopped.
Through the above steps, a composite film having a predetermined film thickness composed of the composite fine particles 54 is formed on the film forming surface 71 of the substrate 53.

  Although the film formation method by AD method was illustrated above, the film formation method of this invention is not limited to AD method. A composite film may be formed by spraying the composite fine particles onto a substrate using a spray method, a cold spray method, an electrostatic spray method, or the like, which is a conventionally known powder spraying method.

<Processing after film formation>
In the method for producing a composite film of the present embodiment, the composite film formed by spraying further contains a compound having a lower electron conduction band energy than the conductive auxiliary agent or a precursor of the compound. It is preferable to perform a treatment (post treatment) for bringing the solution into contact.

  In the composite film before the post-treatment, the portions where the conductive auxiliary agent is exposed on the surface are scattered. When this composite film is used as a photoelectrode for a dye-sensitized solar cell and the composite film is brought into contact with the electrolytic solution, the exposed conductive aid and the electrolytic solution are in direct contact with each other. A recombination reaction with ions in the liquid can occur. This recombination reaction may hinder the improvement of battery characteristics such as photoelectric conversion efficiency. In order to prevent this, the exposed conductive aid is coated with the above compound to reduce the area where the conductive aid and the electrolytic solution are in direct contact, and the recombination reaction between the conductive aid and the ions in the electrolytic solution. And the improvement of battery characteristics such as photoelectric conversion efficiency by the conductive assistant can be further promoted.

  Coating of the composite film with the compound may be performed on the entire composite film or a part thereof. Moreover, you may give with respect to the inorganic semiconductor which comprises not only the conductive support agent exposed on the surface of a composite film but the surface of a composite film.

  One of the reasons for using a compound having a lower electron conduction band energy than the conductive assistant or a precursor thereof as the compound for coating the conductive assistant is that the compound oxidizes the conductive assistant (electron In order to prevent the recombination reaction. Here, “a compound having an electron conduction band energy lower than that of the conductive auxiliary agent” means a compound having a standard reduction potential lower than that of the conductive auxiliary agent.

  From the viewpoint of maintaining or improving the conductivity of the composite film, the compound or a precursor thereof is preferably a compound containing an inorganic substance constituting the inorganic semiconductor or a precursor thereof. Here, the precursor of the compound is a compound that can be changed to the compound in a solution containing the precursor or a solution containing the precursor that is changed to the compound after contacting the composite membrane. Meaning a compound.

Examples of the compound or a precursor thereof include titanium alkoxide such as titanium tetrachloride (TiCl ₄ ), peroxotitanic acid (PTA), titanium ethoxide, and titanium isopropoxide (TTIP). These compounds or precursors thereof are particularly suitable when titanium oxide is used as the inorganic semiconductor and the carbon-based material is used as the conductive aid.

  In addition to titanium alkoxide, metal alkoxides such as zinc alkoxide, alkoxysilane, and zirconium alkoxide can be used as the compound or precursor thereof. When these metal alkoxides are used to coat a conductive additive exposed on the surface of the composite film, a known sol-gel method can be applied. In the case of heating the composite film in this sol-gel method, it is preferable to heat at a low temperature, for example, 120 ° C. or less, at which the conductive additive is not thermally degraded.

  As a specific method of the post-treatment, for example, a solution containing the compound or its precursor at a desired concentration is prepared, and the composite film is immersed in the solution at a temperature higher than room temperature, and a desired time elapses. A method of lifting the composite film later, washing the excess solution with an alcohol solution, and drying at a temperature at which the conductive additive does not deteriorate can be mentioned. The temperature at which the composite film is immersed in the solution is not particularly limited, and may be performed at room temperature or higher, or may be performed at a temperature lower than room temperature.

Examples of the concentration, immersion temperature, and immersion time of the solution containing titanium tetrachloride include immersion conditions of 10 to 100 mM, 50 to 90 ° C., and 10 to 60 minutes.
Examples of the concentration, immersion temperature, and immersion time of the solution containing PTA include immersion conditions of 1 to 5% by mass, 40 to 80 ° C., and 10 to 60 minutes.
Examples of the concentration, immersion temperature, and immersion time of the solution containing TTIP include immersion conditions of 1 to 5% by mass, 20 to 40 ° C., and 10 to 60 minutes.

  The solvent of the solution is not particularly limited as long as it can dissolve the compound or its precursor, and examples thereof include water and alcohol. The pH of the solution may be adjusted to acidic or alkaline as appropriate according to the reaction required for coating.

Examples of the drying conditions include 100 to 130 ° C. and about 10 to 40 minutes.
The atmosphere in the drying is not particularly limited, and may be an air atmosphere or an inert gas atmosphere. Moreover, you may apply the vacuum drying method dried while reducing pressure.

<Composite membrane>
The composite membrane of the second embodiment of the present invention is a composite membrane formed on a substrate by the composite membrane production method of the first embodiment. In addition, since the baking treatment is unnecessary in the manufacturing process of the composite film, the characteristics inherent to the conductive auxiliary agent are sufficiently reflected as the properties of the composite film. By using a material that improves the conductivity of the inorganic semiconductor included in the composite film as the conductive aid, a composite film having excellent conductivity can be obtained. By using such a composite film as the semiconductor layer of the photoelectrode, the photoelectrode and the dye-sensitized solar cell provided with the composite film of the present invention have excellent photoelectric conversion efficiency.

  The use of the composite film of the second embodiment is not limited to the photoelectrode, but can be widely applied to uses utilizing the physical characteristics or chemical characteristics of the inorganic semiconductor and the conductive additive.

<< Photoelectrode >>
The photoelectrode of the third embodiment of the present invention is a photoelectrode in which a sensitizing dye is adsorbed on the composite film of the second embodiment. The kind of sensitizing dye is not particularly limited, and conventionally known dyes can be applied. That is, the photoelectrode of the third embodiment can be produced by adding a step of adsorbing the dye to the composite film to each step of the production method of the first embodiment. In the third embodiment, the composite film is preferably formed on a transparent conductive substrate.
Examples of the method of adsorbing the dye on the composite film include a method of immersing the formed composite film in a dye solution and a method of spraying the composite fine particles on which the dye has been adsorbed in advance onto a substrate.

  The photoelectrode of the third embodiment can be produced by a conventional method except that the composite film of the second embodiment is used. For example, the photoelectrode of the third embodiment is formed by forming a composite film on which the dye is adsorbed on the base material and electrically connecting the lead-out wiring to the composite film as necessary by the step of adsorbing the dye. Can be produced.

《Dye-sensitized solar cell》
The dye-sensitized solar cell according to the fourth embodiment of the present invention includes the photoelectrode according to the third embodiment, a counter electrode, and an electrolytic solution or an electrolyte layer. The electrolytic solution is preferably sealed with a sealing material between the photoelectrode and the counter electrode.

As the substrate on which the composite film constituting the photoelectrode is formed, a resin film or a resin sheet having a transparent conductive film formed on the surface can be used. As the resin (plastic), those having visible light permeability are preferable, and examples thereof include polyacryl, polycarbonate, polyester, polyimide, polystyrene, polyvinyl chloride, and polyamide.
Among these, polyester, particularly polyethylene terephthalate (PET), is produced and used in large quantities as a transparent heat-resistant film. By using such a resin substrate, a thin and light flexible dye-sensitized solar cell can be manufactured.

  As the electrolytic solution, an electrolytic solution used in a conventionally known dye-sensitized solar cell can be applied. A redox couple (electrolyte) is dissolved in the electrolytic solution. The electrolyte solution may contain other additives such as fillers and thickeners without departing from the spirit of the present invention.

  Further, an electrolyte layer (solid electrolyte layer) may be applied instead of the electrolytic solution. The electrolyte layer has a function similar to that of the electrolytic solution, and is in a gel or solid state. As the electrolyte layer, for example, a solution obtained by gelling or solidifying the electrolyte solution by adding a gelling agent or a thickener to the electrolyte solution and removing the solvent as necessary can be applied. By using the gel or solid electrolyte layer, there is no possibility of the electrolyte solution leaking from the dye-sensitized solar cell.

  The sealing material is preferably a member that can hold the electrolytic solution inside the battery cell. As such a sealing material, synthetic resins, such as a conventionally well-known thermoplastic resin and a thermosetting resin, are applicable, for example.

  The dye-sensitized solar cell of the fourth embodiment can be manufactured by a conventional method except that the photoelectrode of the third embodiment is used. For example, the electrolyte solution or the electrolyte is disposed between the photoelectrode and the counter electrode and sealed, and if necessary, the lead-out wiring is electrically connected to the photoelectrode and / or the counter electrode. The dye-sensitized solar cell of the embodiment can be manufactured.

  As the counter electrode, for example, an ITO film or an FTO film that imparts conductivity is formed on the surface of a resin substrate or glass substrate such as PEN or PET that can also be used as a base material of the photoelectrode, and further thereon And a counter electrode having a structure in which a catalyst layer of platinum or the like is formed.

  EXAMPLES Next, although an Example demonstrates this invention further in detail, this invention is not limited by these examples.

[Examples 1-8, Comparative Examples 1-3]
As fine particles comprising an inorganic semiconductor, anatase TiO ₂ particles having an average particle diameter of about 20 nm (manufactured by Nippon Aerosil Co., Ltd .; trade name: P25) were used. As shown in Table 1, powder of each conductive additive (carbon-based material) was added to the TiO ₂ particles, and mixed powder was obtained by stirring and mixing. The content ratio of each conductive additive to the total mass of each mixed powder was adjusted to 0.2% by mass.
In Comparative Example 1, a conductive auxiliary agent was not used and a powder of only the TiO ₂ particles was used for film formation.

As a base material for spraying the powder, an ITO-PEN substrate in which ITO (tin-doped tin oxide) was previously formed on a PEN substrate was used, and a composite film was formed using the film forming apparatus 60 shown in FIG. .
Specifically, in the film forming chamber 51, the mixed powders of the respective examples and comparative examples are individually applied to the ITO-PEN substrate from the nozzle 52 having a rectangular opening of 10 mm × 0.5 mm. Sprayed the material. O ₂ or N ₂ , which is a carrier gas, was supplied from the cylinder 55 to the carrier pipe 56, and the flow rate was adjusted by the mass flow controller 57. The composite fine particles for spraying (the mixed powder) were loaded into the aerosol generator 58, dispersed in the carrier gas, conveyed to the crusher 59 and the classifier 61, and sprayed from the nozzle 52 onto the substrate 53. A vacuum pump 62 is connected to the film forming chamber 51, and the film forming chamber is set to a negative pressure. The conveyance speed in the nozzle 52 was 5 mm / sec.

The atmosphere shown in Table 1 is the atmosphere in the film forming chamber. The atmosphere in the film forming chamber is maintained by the carrier gas. The temperature shown in Table 1 is the temperature in the film forming chamber or the firing temperature. The “printing and firing” of the film forming method shown in Table 1 is performed by using a commercially available paste (manufactured by Solaronics, trade name: T / SP paste) containing 11% by weight of TiO ₂ particles and carbon nanotubes containing all TiO ₂ particles. A paste added in an amount of 0.2% by weight (ie, 0.2 parts by weight) with respect to the weight (100 parts by weight) is prepared, and the paste is formed on the substrate so that the paste has a predetermined film thickness. After the coating, the porous composite film is formed by baking at the temperature shown in Table 1 for 30 minutes.

All the conductive assistants shown in Table 1 are carbon-based materials, and the carbon content thereof is about 100%. Carbon nanotubes, graphite, fullerene, and graphene shown in Table 1 are all N-type semiconductors, and TiO ₂ particles are also N-type semiconductors.

  The post-treatment shown in Table 1 indicates the presence or absence of post-treatment in which the composite film (film-formed body) obtained by spraying the powder is immersed in a solution containing the compound shown in Table 1.

In Example 6, the substrate on which the composite film of Example 2 was formed was immersed in a 50 mM aqueous solution of titanium tetrachloride (TiCl ₄ ) at 70 ° C. for 30 minutes, and then the substrate was washed with ethanol and then washed at 120 ° C. The post-process which dried for 30 minutes was performed.

  In Example 7, the substrate on which the composite film of Example 2 was formed was immersed in a 1.8 mass% peroxotitanic acid (PTA) aqueous solution at 60 ° C. for 30 minutes, and then the substrate was washed with ethanol. The post-process which dried at 120 degreeC for 30 minutes was performed.

  In Example 8, the substrate on which the composite film of Example 2 was formed was immersed in a 1.8% by mass titanium isopropoxide (TTIP) ethanol solution at 30 ° C. for 30 minutes, and then the substrate was washed with ethanol. Then, post-treatment was performed by drying at 120 ° C. for 30 minutes.

The appearance of the porous composite film obtained by film formation in this way was evaluated by visual observation. The results are shown in Table 2. The composite films of Examples 1 to 8 and Comparative Example 1 were well formed without being damaged such as deformation of the substrate (◯). On the other hand, in the composite films of Comparative Examples 2 and 3, the substrate was greatly deformed by firing, and the state of the composite film was poor (×).
Table 2 shows the film thickness (unit: μm) of each composite film obtained by film formation.

A dye-sensitized solar cell using each composite film as a photoelectrode was produced as follows.
Each composite membrane (area: 0.4 cm x 0.4 cm) formed in a dye solution prepared by dissolving sensitizing dye N719 at a concentration of 0.3 mM in a 1: 1 mixture of acetonitrile and tert-butanol The substrate was immersed for 20 hours, and a dye was adsorbed to each composite film to obtain a photoelectrode.

  The photoelectrode manufactured by the above method and the platinum counter electrode are overlapped and clipped via a 30 μm thick resin gasket (separator) (trade name: High Milan), and an electrolyte is injected between both electrodes. As a result, a dye-sensitized solar cell was assembled. The counter electrode has a structure in which platinum is coated on the surface of a polyethylene naphthalate (PEN) substrate.

  As an electrolytic solution, an electrolytic solution obtained by dissolving 0.05M iodine, 0.6M dimethylpropylimidazolium iodide, 0.1M lithium iodide, and 0.5M t-butylpyridine in acetonitrile as a solvent. Using.

  Photoelectric conversion efficiency η, short circuit current Isc, open circuit voltage Voc, and fill factor FF, which are the power generation performance of the produced cell, were evaluated by a solar simulator (AM1.5). The results are shown in Table 2.

  From the above results, the dye-sensitized solar cell using the composite film of Examples 1 to 5 was superior in photoelectric conversion efficiency to the dye-sensitized solar cell using the composite film of Comparative Example 1.

  Furthermore, the dye-sensitized solar cells using the composite films of Examples 6 to 8 that were subjected to the post-treatment were superior to Examples 1 to 5 in electrical characteristics such as photoelectric conversion efficiency. As a reason for this, in the composite film that has been subjected to post-processing, the area where the conductive additive and the electrolytic solution are in direct contact is reduced, so that the recombination reaction between the conductive aid and the ions in the electrolytic solution is suppressed, It is presumed that the effect of the conductive additive could be further promoted.

  According to the method for producing a composite film of the present invention, even when oxygen gas is used as a carrier gas, the conductive auxiliary agent to be sprayed does not undergo oxidative deterioration. Therefore, it is clear that an inert gas atmosphere is not required to prevent the oxidative deterioration of the conductive additive, and that the film can be formed without causing the oxidative deterioration of the conductive additive even in a normal air atmosphere. Therefore, it is easy to use a material (thermal decomposition material) that easily undergoes oxidative degradation as a conductive additive.

  In addition, since the method for producing a composite film of the present invention can be formed at room temperature, it can be formed even on a substrate having low heat resistance, which could not be used in a film forming method that requires a conventional baking process. can do. For example, when a resin sheet is used as a base material, mass production by a roll-to-roll method is also possible.

  The configurations and combinations thereof in the embodiments described above are examples, and the addition, omission, replacement, and other modifications of the configurations can be made without departing from the spirit of the present invention. Further, the present invention is not limited by each embodiment, and is limited only by the scope of the claims.

  The method for producing a composite film according to the present invention, the composite film, the photoelectrode provided with the composite film, and the dye-sensitized solar cell using the photoelectrode are widely applicable in the field of solar cells.

DESCRIPTION OF SYMBOLS 51 ... Film forming chamber, 52 ... Nozzle, 53 ... Base material, 54 ... Composite fine particle, 55 ... Cylinder, 56 ... Transfer pipe, 57 Mass flow controller, 58 ... Aerosol generator, 59 ... Crusher, 60 ... Film forming 61: Classifier 62: Vacuum pump 63: Base, 71: Film-forming surface, 72: Mounting surface (upper surface) of the base, 73: Surface opposite to the film-forming surface

Claims (11)

  A method for producing a composite film comprising an inorganic semiconductor and a conductive additive, wherein the inorganic semiconductor and the conductive additive are physically sprayed on a substrate to form a film.   The composite film formed by spraying is further subjected to a treatment in which a solution containing a compound having a lower electron conduction band energy than the conductive assistant or a precursor of the compound is contacted. The method for producing a composite membrane according to claim 1.   As the conductive auxiliary agent, a conductive auxiliary agent composed of a material that causes a thermal oxidation reaction when heated in the presence of oxygen is used, and composite fine particles containing the inorganic semiconductor and the conductive auxiliary agent are sprayed onto a substrate. The method for producing a composite membrane according to claim 1, wherein the membrane is formed.   4. The composite powder according to claim 1, wherein the composite fine particles are a mixed powder in which fine particles made of the inorganic semiconductor and fine particles made of a material constituting the conductive auxiliary agent are mixed. 5. A method for producing a composite membrane.   The method for producing a composite film according to any one of claims 1 to 4, wherein the conductive auxiliary agent has a carbon content of 50 mass% or more.   The method for producing a composite film according to claim 1, wherein the conductive additive is graphite, carbon nanotube, graphene, or fullerene.   The content rate of the said conductive support agent with respect to the mass of the said composite fine particle is 0.01-0.5 mass%, The manufacturing method of the composite film as described in any one of Claims 1-6 characterized by the above-mentioned.   The method for producing a composite film according to claim 1, wherein the conductive additive is a semiconductor or a conductor of the same type as the inorganic semiconductor.   The composite film formed by the manufacturing method as described in any one of Claims 1-8.   A photoelectrode comprising the composite film according to claim 9.   A dye-sensitized solar cell comprising the photoelectrode according to claim 10.

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