WO2013005770A1 - Dye sensitization type photoelectric conversion element and dye sensitization type solar cell module - Google Patents

Abstract

[Problem] To provide a dye sensitization type solar cell module with high photoelectric conversion efficiency in a range spreading from low illumination (500 lux) to high illumination (100,000 lux), even when the photoelectric conversion element has a small power generation area (300 mm² to 600 mm²). [Solution] A dye sensitization type photoelectric conversion element that has a transparent base material, a transparent electrode layer, a porous oxide semiconductor layer that includes a photosensitized dye, an electrolyte layer, an opposing electrode and a transparent base material laminated in this order and that is characterized in that the planar shape of the porous oxide semiconductor layer that includes a photosensitized dye is a rectangle, and the area (S) of the rectangle is 300 mm² to 600 mm², and the ratio (L) of the long side to the short side of the rectangle is included in a region that satisfies formulas (1) and (2).

Description

[Name of invention determined by ISA based on Rule 37.2] Dye-sensitized photoelectric conversion element and dye-sensitized solar cell module

The present invention relates to a dye-sensitized solar cell module having high photoelectric conversion efficiency over a wide range from low illuminance (500 lux) to high illuminance (100,000 lux) and a method for producing the same.

In recent years, solid pn junction solar cells have been actively studied as photoelectric conversion elements that convert solar energy into electric power. The solid junction solar cell uses a silicon crystal, an amorphous silicon thin film, or a multilayer thin film of a non-silicon compound semiconductor.
However, since these solar cells are manufactured at a high temperature or under vacuum, there are disadvantages that the cost of the plant is high and the energy payback time is long.

As a next-generation solar cell that replaces these conventional solar cells, development of an organic solar cell that can be manufactured at a lower temperature and at a lower cost is expected.
Of particular interest is a dye-sensitized solar cell that can be mass-produced at low cost in the atmosphere, and a highly efficient photoelectric conversion method using a dye-sensitized porous semiconductor film has been proposed ( Patent Document 1). A dye-sensitized solar cell is a wet solar cell that employs a solid (semiconductor) -liquid (electrolyte) junction instead of a solid (semiconductor) -solid (semiconductor) junction in a solid junction solar cell.

A dye-sensitized solar cell is a photo-active electrode substrate (light-sensitive substrate) in which a sensitizing dye is supported on a porous semiconductor fine particle layer made of metal oxide semiconductor nanoparticles typified by titanium dioxide nanoparticles formed on a transparent conductive substrate. Electrode) and a counter electrode substrate (counter electrode) in which a platinum or carbon counter electrode layer is formed on a conductive substrate, are arranged to face each other, the electrolyte solution is filled between the substrates, and the electrolyte solution is sealed Consists of.

When this dye-sensitized solar cell is irradiated with light from the transparent electrode side, the sensitizing dye absorbs light and generates electrons, and the generated electrons move from the photoelectrode to the counter electrode through an external electric circuit. Then, the moved electrons are carried by the ions in the electrolytic solution and return to the photoelectrode. Energy can be continuously extracted from the dye-sensitized solar cell by repeating such a series of electron transfer.

By the way, the current obtained from one dye-sensitized solar cell unit (hereinafter referred to as “dye-sensitized photoelectric conversion element” in the present invention) is the area of the porous semiconductor fine particle layer carrying the sensitizing dye. (Hereinafter referred to as “power generation area” in the present invention). On the other hand, by increasing the power generation area, the in-plane resistance of the transparent electrode increases, and the internal series resistance also increases proportionally. As a result, the fill factor (FF: fill factor) in the current-voltage characteristics at the time of photoelectric conversion, and further the short-circuit current are reduced, and the photoelectric conversion efficiency is lowered.

As a means for increasing the photoelectric conversion efficiency of the dye-sensitized photoelectric conversion element, it has been proposed to mix scattering particles with a porous semiconductor fine particle layer in order to effectively utilize incident external light (Patent Document 2). , 3). Further, in order to reduce the electrical resistance of the current collecting electrode in the photoelectrode, a current collector made of a conductive porous film is provided in the porous semiconductor fine particle layer (Patent Document 4), and from a fine wire mesh provided on the transparent substrate. It has been proposed to form a porous semiconductor fine particle layer on a current collector (Patent Document 5).

US Pat. No. 4,927,721 JP 2002-289274 A JP 2005-322445 A JP 2003-187883 A JP 2010-73416 A

However, the above-described technique is based on the premise of increasing the size and area of the dye-sensitized solar cell. Dye-sensitized solar cells, especially film-type dye-sensitized solar cells that have been reduced in weight for portable purposes, are expected to be used on the assumption that they are used indoors at low illuminance (500 lux) or outdoors at high illuminance (100,000 lux). It is necessary to consider the conversion efficiency. In this case, in a miniaturized dye-sensitized solar cell, it has not been clarified how the planar shape of the power generation area is designed to improve the photoelectric conversion efficiency from low illuminance to high illuminance. Therefore, it is necessary to develop a dye-sensitized solar cell that maintains stable photoelectric conversion efficiency over a wide range from indoors with low illuminance to outdoors with high illuminance. In addition, a solar cell module in which a plurality of dye-sensitized photoelectric conversion elements are integrated in series or in parallel (hereinafter referred to as “dye-sensitized solar cell module” in the present invention) can be provided. Practical voltage and battery life can be realized. The present invention has been made to solve such a problem.

The present invention can be implemented in the following aspects (1) to (3).

(Aspect 1) A transparent substrate, a transparent electrode layer formed on the transparent substrate, an undercoat layer formed on the transparent electrode layer, and a sensitizing dye formed on the undercoat layer are supported. The porous semiconductor fine particle layer, the base material facing the porous semiconductor fine particle layer, the electrode layer formed on the surface of the opposing base material on the porous semiconductor fine particle layer side, and formed on the electrode layer A dye-sensitized photoelectric conversion element having a formed catalyst layer, an electrolyte layer provided between the porous semiconductor fine particle layer and the catalyst layer, and a sealing layer provided around the electrolyte layer In
The planar shape of the porous semiconductor fine particle layer carrying the sensitizing dye is rectangular,
The area (S) of the rectangle is 300 mm ² to 600 mm ² , and the ratio (L) of the length of the long side to the short side of the rectangle is included in the region satisfying the following expressions (1) and (2). This is a dye-sensitized photoelectric conversion element characterized by the above.

In the formulas (1) and (2), S is a rectangular area (mm ² ) of the porous oxide semiconductor layer containing the sensitizing dye, and L is a rectangular shape of the porous oxide semiconductor layer containing the sensitizing dye. The ratio of the length of the long side to the short side.
By setting the planar shape and the power generation area of the porous semiconductor fine particle layer carrying the sensitizing dye within this range, the internal resistance per unit area of the dye-sensitized photoelectric conversion element can be minimized, This is because the conversion efficiency can be maximized.

(Aspect 2) A base material facing the porous semiconductor fine particle layer, an electrode layer formed on the surface of the opposing base material on the porous semiconductor fine particle layer side, and a catalyst layer formed on the electrode layer Any of these are formed from a transparent material, The dye-sensitized photoelectric conversion device according to (Aspect 1).
This is because the photoelectric conversion efficiency is increased by setting the light receiving surfaces to both the photoelectrode side and the counter electrode side.

(Aspect 3) The above (Aspect 1) or (Aspect 3), wherein the electrolytic solution constituting the electrolytic solution layer does not contain a redox pair (I ⁻ / I ₃ ⁻ ) composed of a combination of iodine and iodide. It is a dye-sensitized photoelectric conversion element as described in aspect 2).
By not including an oxidation-reduction pair that traps electrons in the electrolyte, the sensitizing dye emits light when light is irradiated from the transparent electrode side to the dye-sensitized photoelectric conversion element even at low illumination. A series of repeated electron movements in which electrons are absorbed to generate electrons, the generated electrons move from the photoelectrode through the external electrical circuit to the counter electrode, and the moved electrons are transported by the ions in the electrolyte and return to the photoelectrode. This is because energy can be continuously extracted from the dye-sensitized photoelectric conversion element. In addition, when iodine is used, the electrolytic solution is colored by the formation of triiodide ions (I3 ⁻ ), the light energy conversion efficiency is lowered, and the battery is further deteriorated by the oxidation corrosion reaction of iodine.

(Aspect 4) A dye-sensitized solar cell module comprising the dye-sensitized photoelectric conversion elements described in (Aspect 1) to (Aspect 3) connected in parallel or in series.
This is because a practical voltage and battery life can be realized by providing various integrated modules using the dye-sensitized photoelectric conversion element of the present invention.
(Aspect 5) The dye-sensitized solar cell module in which the dye-sensitized photoelectric conversion elements are connected in series is connected in series with the dye-sensitized photoelectric change element through an electrode connection portion made of a current collector and conductive fine particles. The dye-sensitized solar cell module according to (Aspect 4), which is connected to
This is because the thickness of the dye-sensitized solar cell module can be controlled by using the conductive fine particles, and the current collection effect is enhanced by overlapping with the current collector.

According to the present invention, even in a photoelectric conversion element having a small power generation area (300 mm ² to 600 mm ² ), a dye-sensitized solar with high photoelectric conversion efficiency over a wide range from low illuminance (500 lux) to high illuminance (100,000 lux). A battery module is obtained.

It is sectional drawing which shows the structure of one example of the dye-sensitized photoelectric conversion element of this invention. It is the top view (upper stage) and sectional drawing (lower stage) which show an example which bonded the mask film to the transparent conductive substrate in order to form the semiconductor fine particle layer of the dye-sensitized photoelectric conversion element of this invention. It is sectional drawing (upper stage) and top view (lower stage) which show an example of the dye-sensitized solar cell module of this invention. It is a top view which shows another example of the dye-sensitized solar cell module of this invention. It is a graph which shows the relationship between the area (S) of the porous oxide semiconductor layer containing a photosensitizing dye, and ratio (L) of the length of the long side with respect to a short side.

Hereinafter, the dye-sensitized photoelectric conversion element and the dye-sensitized solar cell module of the present invention will be described.

1. Structure of Dye-Sensitized Photoelectric Conversion Device FIG. 1 is a cross-sectional view showing a structural example of the dye-sensitized photoelectric conversion device of the present invention. The dye-sensitized photoelectric conversion element 1 includes a transparent electrode 11 having a transparent conductive layer 12, an undercoat layer 13, and a porous semiconductor fine particle layer 14 carrying a sensitizing dye laminated on a transparent substrate 11 in this order, and a transparent substrate. 11, a transparent conductive layer 12 and a catalyst layer 17 laminated in this order, a counter electrode layer 18, an electrolyte layer 16 provided between the photoelectrode layer 15 and the counter electrode layer 18, and a sealing surrounding the electrolyte layer It is composed of a layer 19, a collector line 20, and terminals 21.
Hereinafter, the photoelectrode layer 15, the electrolytic solution layer 16, the counter electrode layer 18, and the sealing layer 19 will be described in this order.

[1] Photoelectrode layer (1) Plastic substrate The plastic substrate material used in the present invention is a material that is uncolored, highly transparent, highly heat resistant, excellent in chemical resistance and gas barrier properties, and low in cost. Preferably selected. From this viewpoint, preferable materials include, for example, polyethylene terephthalate (PET), polyethylene naphthalate (PEN), syndiotactic polystyrene (SPS), polyphenylene sulfide (PPS), polycarbonate (PC), polyarylate (PAr), polysulfone ( PSF), polyester sulfone (PES), polyetherimide (PEI), transparent polyimide (PI) and the like are used. Among these, polyethylene terephthalate (PET) and polyethylene naphthalate (PEN) are particularly preferable in terms of chemical stability and cost, and most preferable is polyethylene naphthalate (PEN).

(2) Transparent conductive layer The transparent conductive layer used in the present invention includes metals (eg, platinum, gold, silver, copper, aluminum, indium, titanium), carbon, conductive metal oxides (eg, tin oxide, zinc oxide). ) Or composite metal oxides (eg, indium-tin oxide, indium-zinc oxide). Of these, conductive metal oxides are preferable in view of high optical transparency, and indium-tin composite oxide (ITO), zinc oxide, and indium-zinc oxide (IZO) are particularly preferable. Most preferred are indium-tin composite oxide (ITO) and indium-zinc oxide (IZO), which are excellent in heat resistance and chemical stability.
The surface resistance value of the transparent conductive layer is preferably 100Ω / □ or less, more preferably 50Ω / □ or less, further preferably 30Ω / □ or less, still more preferably 10Ω / □ or less, and most preferably 5Ω / □ or less. The light transmittance (measurement wavelength: 500 nm) of the photoelectrode substrate provided with a transparent electrode layer on the transparent substrate is preferably 60% or more, more preferably 75% or more, and most preferably 80% or more.

In order to achieve a low surface resistance value, it is preferable to use a metal, but the problem of being not transparent can be solved by forming a transparent conductive layer having a metal mesh structure. In this case, an auxiliary lead for current collection can be placed on this conductive layer by patterning, etc., and it is made of a low-resistance metal material (eg, copper, silver, aluminum, platinum, gold, titanium, nickel). Is done. The resistance value of the surface including the auxiliary lead is preferably controlled to 1Ω / □ or less. Such an auxiliary lead pattern is preferably formed on a transparent substrate by vapor deposition, sputtering or the like, and a transparent conductive layer made of tin oxide, ITO film, IZO film or the like is further provided thereon.

(3) Undercoat layer When the electrolyte layer is a liquid, the undercoat layer has a structure in which the electrolyte layer is in contact with the transparent conductive layer. Therefore, reverse electron transfer in which electrons leak from the transparent conductive layer to the electrolyte layer. The internal short-circuit phenomenon called the occurrence of reverse current unrelated to light irradiation and the prevention of the decrease in photoelectric conversion efficiency, and the adhesion of the porous semiconductor fine particle layer to the conductive substrate is improved It has a role.

The material for the undercoat layer is not particularly limited as long as it is a high resistance semiconductor and insulating material. For example, there are titanium oxide, niobium oxide, tungsten oxide, and the like. In addition, as a method of forming the undercoat layer, a method of directly sputtering the material on the transparent conductive layer, a solution in which the material is dissolved in a solvent, a solution in which a metal hydroxide that is a precursor of a metal oxide is dissolved, Alternatively, there is a method in which a solution containing a metal hydroxide obtained by dissolving an organometallic compound in a mixed solvent containing water is applied onto a conductive substrate composed of a substrate and a conductive layer, dried, and sintered as necessary.

The undercoat layer of the present invention is preferably formed of an organic titanium oligomer and a hydrolysis product thereof. The organic titanium oligomer used in the present invention is a compound having a multimeric structure (—Ti—O—Ti—) in the molecule by condensing a titanium alkoxide (Ti—OR) compound or a titanium chelate compound. By oligomerizing titanium, a surface structure having a multimeric structure (—Ti—O—Ti—) in the molecule can be formed, so that the surface of the transparent conductive substrate can be densely formed without gaps.
The present invention is not limited to organic titanium oligomers, and the same effect can be obtained as long as it is an organometallic oligomer (M is a metal) having a multimeric structure (-MOMM) in the molecule. It is done.

When the undercoat layer is formed on a conductive substrate, a good undercoat layer can be formed even under conditions in which cracking occurs in film formation with a titanium monomer.
Further, metal alkoxides conventionally used for undercoat layers are highly reactive and easily hydrolyzed, making it difficult to control the properties of the coating film surface. However, the organotitanium oligomer used in the present invention has a slow hydrolysis rate, a stable coating surface property, and a coating layer surface property of the undercoat layer when a semiconductor porous layer made of a metal oxide is overlaid. Has the advantage of being stable over a long period of time.

The organotitanium oligomer used in the present invention is produced by a method of hydrolysis by adding water or a mixture of water and a water-soluble solvent without substantially diluting tetraalkoxytitanium with a solvent (special feature). Open 2008-156280).
In addition, the organic titanium oligomer used in the present invention is a silicon compound having one or more alkoxy groups in the molecule with respect to the titanium compound oligomer in order to improve the coating film formability and coating film adhesion (adhesiveness). Alternatively, it may be a composite compound (Japanese Patent Laid-Open No. 2008-143990) having a structure obtained by reacting or a mixture.

In order to form the undercoat layer on the conductive substrate, it is preferable to use a sol-gel method in which an organic titanium oligomer solution is applied on the conductive substrate, dried and baked by heating to form a film. The solvent is preferably an alcohol such as butanol, a hydrocarbon such as hexane or toluene, or a mixture thereof having a boiling point of about 100 ° C. from the viewpoint of drying speed.

Examples of the coating method include a gravure coating method, a bar coating method, a printing method, a spray method, a spin coating method, a dip method, and a die coating method.

In the photoelectrode manufacturing method of the present invention, in order to prevent adhesion between the undercoat layer and the metal oxide porous semiconductor layer, which will be described later, in particular, peeling in the electrolytic solution, the wetting tension on the surface of the undercoat layer is less than 50 mN / m. The metal oxide semiconductor fine particles are overlaid. When the undercoat layer is formed from an organotitanium oligomer as in the present invention, the change in the wetting tension of the coating surface over time is slower than when formed from a metal alkoxide monomer. It becomes easy to layer the layers sequentially or continuously.

(4) Metal oxide semiconductor nanoparticles The metal oxide semiconductor nanoparticles contained in the metal oxide semiconductor nanoparticle dispersion of the present invention can be produced using a known method. As a production method, for example, the sol-gel method described in “Science of Sol-Gel Process”, Agne Jofu Co., Ltd. (1998), or metal chloride is converted to an oxide by high-temperature hydrolysis in an inorganic oxyhydrogen salt. It can be prepared by a production method, a vapor-phase spray pyrolysis method in which a metal compound is thermally decomposed at a high temperature in a gas phase to form ultrafine particles. The ultrafine particles and nanoparticles of titanium dioxide (TiO2) produced by these methods are explained in “Particle Engineering System Vol. 2 (Applied Technology)” supervised by Hiroaki Yanagida (2002). Examples of the metal oxide semiconductor material include oxides of titanium, tin, zinc, iron, tungsten, zirconium, strontium, indium, cerium, vanadium, niobium, tantalum, cadmium, lead, antimony, and bismuth. As the semiconductor material, there is an n-type inorganic semiconductor material. Specifically, TiO2, ZnO, Nb2O3, SnO2, WO3, Si, CdS, CdSe, V2O5, ZnS, ZnSe, KTaO3, FeS2, PbS, etc. are preferable, TiO2, ZnO, Nb2O3, SnO2, and WO3 are more preferable, and dioxide dioxide. Titanium (TiO2) is particularly preferred.

As a method for producing titanium dioxide, there are a liquid phase method in which titanium tetrachloride and titanyl sulfate are hydrolyzed and a gas phase method in which titanium tetrachloride and oxygen or an oxygen-containing gas are mixed and burned. In the liquid phase method, anatase can be obtained as the main phase, but it becomes a sol or slurry, and drying is necessary to use it as a powder, but there is a problem that aggregation (secondary particle formation) proceeds by drying. . On the other hand, the vapor phase method is characterized by excellent dispersibility, high temperature during synthesis, and excellent crystallinity compared to the liquid phase method because no solvent is used.
By the way, there are anatase type, brookite type and rutile type in the crystal form of titanium dioxide nanoparticles. When titanium oxide is produced by a vapor phase method, titanium oxide that is stable at the lowest temperature is anatase type, and is converted into a brookite type or a rutile type as heat treatment is applied. The crystal structure can be determined by measuring a diffraction pattern by an X-ray diffraction method or detecting a crystal lattice image by observation with a transmission electron microscope. Moreover, the average particle diameter of the titanium dioxide nanoparticles can be calculated from a particle size distribution measurement by a light correlation method using a laser light scattering method or a scanning electron microscope observation method.

The crystalline titanium dioxide nanoparticles having an average primary particle size of 40 to 70 nm used in the present invention are those obtained by a gas phase method, and are a mixture of rutile type crystals and anatase type crystals. % Or less. This is because when the rutile ratio exceeds 40%, the function as a photocatalyst is lowered and the photovoltaic power is lowered, so that sufficient performance as a dye-sensitized solar cell cannot be obtained. The form of the titanium dioxide nanoparticles may be various forms such as amorphous, spherical, polyhedral, fibrous, and nanotube-like, but a polyhedral or nanotube-like form is preferable, and a polyhedral form is more preferable. From the viewpoint of dispersion stability, the solid content concentration contained in the metal oxide semiconductor nanoparticle dispersion is 0.1 to 25 wt%, preferably 0.5 to 20 wt%, and more preferably 0.5 to 15 wt%.

On the other hand, metal oxide semiconductor nanoparticles having an average primary particle size of 10 to 30 nm used in the present invention are prepared as an acidic sol aqueous solution in which titanium dioxide nanoparticles containing brookite crystals obtained by a liquid phase method are dispersed. Yes. This is because brookite-type titanium oxide is excellent in binding property to a dye and can provide higher photoelectric conversion efficiency than rutile or anatase-type titanium oxide. Brookite-type titanium oxide produced by a liquid phase method, particularly brookite-type titanium oxide produced by hydrolysis of titanium tetrachloride or titanium trichloride is preferred. This is because it is used as a metal oxide semiconductor nanoparticle dispersion for forming a porous semiconductor fine particle layer, so that there is no problem in the state of the dispersion sol, the dispersion state is stable, and the coating property is excellent. In order to enhance dispersibility, the aqueous medium is adjusted to be acidic, and the pH is 1 to 6, preferably 3 to 5. From the viewpoint of dispersion stability, the solid content concentration contained in the metal oxide semiconductor nanoparticle dispersion is 1 to 15 wt%, preferably 2 to 12 wt%, and more preferably 2 to 10 wt%.

(5) Metal Oxide Semiconductor Nanoparticle Dispersion The present invention is a dye-sensitized photoelectric conversion in which a metal oxide semiconductor nanoparticle dispersion is applied on a conductive substrate and heat-treated to form a porous semiconductor fine particle layer. The present invention relates to a device photoelectrode. In the present invention using a plastic substrate, since a low-temperature film forming method is adopted, a dispersion composition not containing a binder material such as resin or latex added for the purpose of improving the film forming property and leveling property of the dispersion is preferable. . The metal oxide semiconductor nanoparticle dispersion of the present invention is a viscous milky white liquid in which metal oxide semiconductor nanoparticles are dispersed in a solvent composed of a mixture of water and an alcohol having 5 or less carbon atoms.

The solvent used for the metal oxide semiconductor nanoparticle dispersion of the present invention is a mixed solvent of water and a hydrophilic organic solvent mainly composed of ethanol. As the hydrophilic solvent, other alcohols having 3 to 5 carbon atoms can be selected, and t-butanol, 2-butanol and the like can be added. In the metal oxide semiconductor nanoparticle dispersion of the present invention, water is used as a dispersion solvent in addition to the alcohol. This is added for the purpose of maintaining the dispersion stability of the metal oxide semiconductor nanoparticles and maintaining the viscosity of the dispersion at an appropriate level.

According to the present invention, the dispersion includes both metal oxide semiconductor nanoparticles having an average primary particle diameter of 10 to 30 nm and metal oxide semiconductor nanoparticles having an average primary particle diameter of 40 to 70 nm. It is a feature. By simply mixing metal oxide semiconductor nanoparticles that do not overlap in the average particle size range of the primary particles, the specific surface area is large and the amount of sensitizing dye supported is large, and the electrolyte that forms the electrolyte layer is a porous semiconductor. A porous semiconductor fine particle layer having a porous structure capable of diffusing to details of the fine particle layer can be easily produced. Therefore, a metal oxide semiconductor nanoparticle dispersion containing metal oxide semiconductor nanoparticles and a solvent as essential components as proposed in Japanese Patent Application Laid-Open No. 2002-324591 is obtained by changing the composition of the dispersion continuously or discontinuously. There is no need to spray. Moreover, the volume shrinkage distortion at the time of drying can be relieve | moderated by mixing the particle | grains from which an average particle diameter differs greatly. Furthermore, the structure of the porous semiconductor fine particle layer formed after drying is solidified by dehydration condensation of the metal oxide semiconductor nanoparticles having an average primary particle size of 10 to 30 nm.
In the method of dispersing metal oxide semiconductor nanoparticles having an average primary particle size of 40 to 70 nm in the present invention in a solvent, a paint conditioner, a homogenizer, an ultrasonic stirring device, or the like is used. A conditioner is preferably used. After the metal oxide semiconductor nanoparticles having an average primary particle size of 40 to 70 nm are dispersed in a solvent, an aqueous acidic sol solution in which metal oxide semiconductor nanoparticles having an average primary particle size of 10 to 30 nm are dispersed is added. Then, a metal oxide semiconductor nanoparticle dispersion is prepared. From the viewpoint of dispersion stability and coating film formability, the solid content concentration of the entire metal oxide semiconductor nanoparticles contained in the dispersion is 5 to 30 wt%, preferably 8 to 25 wt%, more preferably 8 to 20 wt%.

(6) Porous semiconductor fine particle layer The upper part of FIG. 2 is a plan view of the transparent conductive substrate 2 to which the mask film of the present invention is bonded, and the lower part of FIG. 2 is the transparent conductive substrate 2 to which the mask film of the present invention is bonded. FIG. FIG. 2 shows an embodiment in which the dye-sensitized photoelectric conversion elements of the present invention are manufactured in 6 rows.
As shown in FIG. 2, the porous semiconductor fine particle layer of the present invention is obtained by laminating a mask film 22 on a transparent conductive substrate 21 on which an undercoat layer is formed, and on an open portion 23 of the bonded mask film. It forms by apply | coating a metal oxide semiconductor nanoparticle dispersion liquid. The open part of the mask film serves as a model of the semiconductor fine particle layer of the present invention. The planar shape of the open portion 23 of the mask film is a rectangle having four rounded corners, and its size is determined by the planar shape of the porous semiconductor fine particle layer to be formed.

The mask film of the present invention has an open portion serving as a template for the semiconductor fine particle layer of the present invention, and at the same time can be easily attached to a transparent conductive substrate on which an undercoat layer is formed. There is no particular limitation as long as it is an adhesive film having an adhesive layer that can be easily peeled off after the particle dispersion is applied. Specifically, it is a laminated film in which a slightly adhesive layer and a release film are provided on one side of a base film, and an antistatic layer and an antifouling layer are provided on the other side. It is a laminated adhesive film used for a surface protective film of a phase difference film. A peeling film is peeled at the time of use, and a mask film is bonded to the transparent conductive substrate in which the undercoat layer was formed.
However, since it is necessary to heat and dry the coated metal oxide semiconductor nanoparticle dispersion to form the semiconductor fine particle layer, the base film is of the same level as the transparent conductive substrate on which the undercoat layer is formed. It must be heat shrinkage. Specifically, the thermal contraction rate (MD · TD) under heating conditions (150 ° C., 30 min) is 0.5% or less, more preferably 0.2% or less.

The mask film of the present invention can be used by laminating a plurality of mask films having different adhesive forces. This is because, after the porous semiconductor fine particle layer is formed, the uppermost layer is peeled off, and the mask film can be peeled off after protecting the transparent conductive substrate on which the undercoat layer is formed at the time of dye adsorption.

The planar shape of the porous semiconductor fine particle layer is a rectangle, the area (S) of the rectangle is 300 mm ² to 600 mm ² , and the ratio (L) of the length of the long side to the short side of the rectangle is It is included in the region satisfying the expressions (1) and (2). By setting the planar shape of the porous semiconductor fine particle layer within this range, the internal resistance per unit area of the dye-sensitized photoelectric conversion element can be minimized, and the conversion efficiency can be maximized. is there.

In the formulas (1) and (2), S is a rectangular area (mm ² ) of the porous oxide semiconductor layer containing the sensitizing dye, and L is a rectangular shape of the porous oxide semiconductor layer containing the sensitizing dye. The ratio of the length of the long side to the short side.

As a coating method of the metal oxide semiconductor nanoparticle dispersion liquid, a known method such as a screen printing method, a drop casting method, a spin coating method, an air spray method, or the like can be used. From the viewpoint of the uniformity of the formed porous semiconductor fine particle layer, an air spray method using a spray device is preferred.

The spraying apparatus used for spraying the metal oxide semiconductor nanoparticle dispersion of the present invention can form the metal oxide semiconductor nanoparticle dispersion in a mist of 200 μm or less, more preferably 50 μm or less, and even more preferably 30 μm or less. Use the device. For example, there are an air spray device, an inkjet device, and an ultrasonic spray device.
Here, the air spray device refers to a device that scatters liquid in a certain direction using a pressure difference generated by expansion of compressed air. From the viewpoint of uniformly forming a coating film having a certain width, it is preferable to use a two-fluid slit nozzle. An ink jet device refers to a device that discharges liquid as fine particles by volume shrinking or increasing the temperature of a fine nozzle filled with a liquid to be sprayed. The ultrasonic spray device refers to a device that scatters liquid in a mist form by irradiating the liquid with ultrasonic waves. These apparatuses can be arbitrarily selected depending on the size of the porous semiconductor fine particle layer to be produced, in other words, the size of the photoelectrode or the solid content concentration of the dispersion.

The thickness of the porous semiconductor fine particle layer formed by spraying the metal oxide semiconductor nanoparticle dispersion on the transparent conductive substrate is preferably less than 30 μm and more preferably less than 20 μm in consideration of absorption loss of transmitted light. This is because if the thickness of the porous semiconductor fine particle layer is smaller than the above range, a layer having a uniform thickness cannot be formed, and if it is larger than this range, the resistance of the porous semiconductor fine particle layer becomes high. The porosity of the formed porous semiconductor fine particle layer (ratio of the volume occupied by the pores in the film) is preferably 50 to 85%, more preferably 65 to 85%.
The heat treatment temperature is within the range of heat resistance of the conductive substrate. For example, when the transparent conductive substrate is a plastic substrate, the porous semiconductor is formed by a low temperature film formation method (eg, 200 ° C. or lower, preferably 150 ° C. or lower). A fine particle layer can be formed.

(7) As a dye molecule used for sensitization of the sensitizing dye porous semiconductor fine particle layer, various organic and metal complexes conventionally used for spectral sensitization of semiconductor electrodes using dye molecules in the field of electrochemistry are used. Systematic sensitizing materials are used. Also, in order to make the wavelength range of photoelectric conversion as wide as possible and increase the conversion efficiency, two or more kinds of dyes may be used in combination, and the dyes to be mixed in accordance with the wavelength range and intensity distribution of the light source The mixing ratio may be selected.
Sensitizing dyes include organic dyes (eg, cyanine dyes, merocyanine dyes, oxonol dyes, xanthene dyes, squarylium dyes, polymethine dyes, coumarin dyes, riboflavin dyes, perylene dyes) and metal complex dyes (eg, phthalocyanine complexes, porphyrin complexes) including. Examples of the metal constituting the metal complex dye include ruthenium and magnesium. In addition, synthetic dyes and natural dyes described in “Functional Materials”, June 2003, pages 5 to 18, “Journal of Physical Chemistry”, B.I. An organic dye mainly composed of coumarin described in Vol. 107, page 597 (2003) can also be used.

(8) Adsorption of the dye to the porous semiconductor fine particle layer As a method of adsorbing the dye to the porous semiconductor fine particle layer, a method of immersing a conductive substrate having a well-dried porous semiconductor fine particle layer in a dye solution, Alternatively, a method of applying a dye solution to the porous semiconductor fine particle layer can be used. In the case of the immersion method, the dye may be adsorbed at room temperature, or may be carried out by heating and refluxing as described in JP-A-7-249790. As the coating method, a coating method such as a wire bar method, a slide hopper method, an extrusion method, a curtain method, a spin method, or a spray method, or a printing method such as letterpress, offset, gravure, or screen printing can be used.

The solvent used for the dye solution can be appropriately selected according to the solubility of the dye. For example, alcohols (methanol, ethanol, t-butanol, benzyl alcohol, etc.), nitriles (acetonitrile, propionitrile, 3-methoxypropionitrile, etc.), nitromethane, halogenated hydrocarbons (dichloromethane, dichloroethane, chloroform, chlorobenzene, etc.) ), Ethers (diethyl ether, tetrahydrofuran, etc.), dimethyl sulfoxide, amides (N, N-dimethylformamide, N, N-dimethylacetamide, etc.), N-methylpyrrolidone, 1,3-dimethylimidazolidinone, 3-methyloxazolidinone, esters (ethyl acetate, butyl acetate, etc.), carbonates (diethyl carbonate, ethylene carbonate, propylene carbonate, etc.), ketones (acetone, 2-butanone, cyclohexanone, etc.), hydrocarbons ( Hexane, petroleum ether, benzene, toluene, etc.), a mixture of these solvents can be used.

The dye adsorption method may be appropriately selected according to the viscosity of the dye solution, the coating amount, the material of the transparent conductive substrate, the coating speed, and the like. From the viewpoint of mass production, it is preferable to shorten the time required for dye adsorption after coating as much as possible. The total amount of the dye used is preferably 0.01 to 100 mmol per unit surface area (1 m ² ) of the transparent conductive substrate. If the amount of dye adsorbed is too small, the sensitizing effect will be insufficient, and if the amount of dye adsorbed is too large, the dye not adhering to the porous semiconductor fine particle layer will float, reducing the sensitizing effect. In order to increase the amount of dye adsorbed, the porous semiconductor fine particle layer is preferably heat-treated before adsorption. Also, in order to avoid water adsorption on the surface of the porous semiconductor fine particle layer after the heat treatment, the dye is quickly adsorbed at a temperature of 40 ° C. to 80 ° C. without returning to the normal temperature after the heat treatment. Is preferred. The unadsorbed dye is preferably removed by washing immediately after adsorption. The washing is preferably performed using an organic solvent such as acetonitrile or an alcohol solvent.

For the purpose of reducing the interaction between dyes such as association, a colorless compound having properties as a surfactant may be added to the dye solution and co-adsorbed on the porous semiconductor fine particle layer. Examples of the coadsorbing compound include steroid compounds having a carboxyl group (eg, cholic acid, chenodeoxycholic acid). Moreover, you may use a ultraviolet absorber together. Further, for the purpose of promoting the removal of excess dye, the surface of the porous semiconductor fine particle layer may be treated with amines after adsorbing the dye. Examples of amines include pyridine, 4-t-butylpyridine, and polyvinylpyridine. When these are liquids, they may be used as they are, or may be used after being dissolved in an organic solvent.

[2] Electrolytic Solution Layer The electrolytic solution constituting the electrolytic solution layer of the present invention is characterized by not containing an oxidation-reduction pair (I ⁻ / I ₃ ⁻ ) composed of a combination of iodine and iodide. Specifically, basically, an inorganic salt and an iodide salt which is an ionic liquid (for example, an imidazolium salt, a tetraalkylammonium salt, a salt of a compound having a quaternary nitrogen atom as a spiro atom) or a mixture thereof. Is a solute, and one or both of glycol ether and 5-membered cyclic ether is used as a solvent. Hereinafter, typical electrolyte components will be described.

(1) Solute As the solute of the electrolytic solution of the present invention, a mixture of an inorganic salt represented by the general formula (1) and an imidazolium salt represented by the general formula (2) can be used.

(1)
In the formula (1), M is an alkali metal, an alkaline earth metal, or ammonium, and X is Cl, Br, or I.

(2)
In the formula, R ²¹ , R ²² and R ²³ are hydrogen or an alkyl group having 1 to 8 carbon atoms, and X is Cl, Br, or I.

As the inorganic salt used in the present invention, an alkali metal halide, alkaline earth metal halide, or ammonium halide represented by the general formula (1) is preferably used. As the halogen of the halide, chlorine, bromine and iodine are preferably used, bromine and iodine are particularly preferred, and iodine is most preferred.

Specific examples of inorganic salts used in the present invention include alkali metal halides (eg, lithium iodide, sodium iodide, potassium iodide, lithium bromide, sodium bromide, potassium bromide, lithium chloride, sodium chloride, etc.). , Alkaline earth metal halides (eg, magnesium iodide, calcium iodide, magnesium bromide, calcium bromide, magnesium chloride, calcium chloride, etc.), ammonium halides (eg, ammonium iodide, ammonium bromide, ammonium chloride) and so on.

As the halide of the present invention, a halide having a solubility in water of 90 to 220 g / 100 g water (25 ° C.) is preferable because of its excellent solubility in the solvents of the following general formulas (3) and (4), Among these, iodine compounds (eg, potassium iodide, sodium iodide, lithium iodide, magnesium iodide, calcium iodide, ammonium iodide, etc.) are particularly preferable because of high photoelectric conversion efficiency.

The addition concentration of the halide of the present invention is preferably 0.01 to 3.0 mol / L, more preferably 0.05 to 2.0 mol / L.

As the ionic liquid used in the present invention, a so-called room temperature molten salt that becomes liquid near room temperature (25 ° C.) can be used. In the present invention, it is preferable to use the halide salt of alkyl imidazolium represented by the general formula (2). It is more preferable to use an iodide salt of an alkyl imidazolium.
Specific examples of the alkyl imidazolium iodide salt of the present invention include iodide salts of dimethyl imidazolium, methyl propyl imidazolium, methyl butyl imidazolium, and methyl hexyl imidazolium.
The concentration of the ionic liquid used in the present invention is preferably 0.01 to 5.0 mol / L, and preferably 0.05 to 2.0 mol / L in view of high energy conversion efficiency.

(2) Solvent As the solvent of the electrolytic solution of the present invention, it has a low viscosity and a high ion mobility, a high dielectric constant and an effective carrier concentration can be increased, or both. What can express is preferable. This is because the dye-sensitized semiconductor thin film layer obtained by adsorbing the dye to the porous semiconductor fine particle layer is used as a photoelectrode, so that the permeability to the porous semiconductor fine particle layer is necessary for improving the photoelectric conversion efficiency. Moreover, it is preferable that it is a high boiling point, especially a boiling point is 200 degreeC or more in order to hold | maintain the amount of electrolyte solution. Furthermore, from the viewpoint of solubility of a mixture of an inorganic salt used as a solute and an imidazolium salt that is an ionic liquid, an aprotic polar solvent is also preferable.

As the solvent of the present invention, glycol ethers represented by the following general formula (3) are preferable, and dialkyl glycol ethers are more preferable in terms of high energy conversion efficiency.

(3)
In the formula (3), R ³¹ and R ³² are hydrogen or an alkyl group having 1 to 8 carbon atoms, and n is an integer of 1 to 10.

Specific examples of such solvents include glycols (eg, ethylene glycol, diethylene glycol, triethylene glycol, polyethylene glycol, etc.), monoalkyl glycol ethers (eg, ethylene glycol monobutyl ether, ethylene glycol monopentyl ether, ethylene glycol). Monohexyl ether, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, diethylene glycol monopropyl ether, diethylene glycol monobutyl ether, diethylene glycol monopentyl ether, diethylene glycol monohexyl ether, diethylene glycol monooctyl ether, triethylene glycol monomethyl ether, triethylene glycol monoethyl ether Ter, triethylene glycol monopropyl ether, triethylene glycol monobutyl ether, triethylene glycol monopentyl ether, etc.), dialkyl glycol ethers (eg, diethylene glycol dimethyl ether, diethylene glycol diethyl ether, diethylene glycol dibutyl ether, triethylene glycol dimethyl ether, triethylene glycol) Diethyl ether, triethylene glycol dibutyl ether, tetraethylene glycol dimethyl ether, polyethylene glycol diethyl ether, etc.). Two or more of these glycol ethers may be used in combination.

As the solvent of the present invention, it is preferable to use a 5-membered cyclic ether represented by the general formula (4). Specific examples of the 5-membered cyclic ester (γ-lactone) include γ-butyrolactone.

(4)
In the formula (4), R ⁴¹ , R ⁴² and R ⁴³ are each independently a hydrogen atom or an alkyl group having 1 to 20 carbon atoms.

(3) Redox versus electrolyte of the present invention is not included unless the triiodide ion (I ₃ ⁻ ) concentration is 0 mol / L (mixed as an impurity in the ionic liquid).

In the electrolytic solution of the present invention, a small amount of a reducing agent may be added to the electrolytic solution in order to remove a trace amount of iodine compound ions (I ₃ ⁻ ) in the electrolytic solution. Examples of the reducing agent include inorganic compounds such as sodium thiosulfate and sodium sulfite, and organic compounds such as thiosalicylic acid, ascorbic acid, hydroquinone, phenidone, and paramethylaminophenol sulfate.

(4) Others The electrolytic solution can further contain other components. Examples of other components include benzimidazole compounds represented by the following general formula (5), (iso) thiocyanate ions, and guanidinium ions represented by the general formula (6) described later. In particular, a benzimidazole compound is preferably used in combination because the conversion efficiency is further improved.

(5)
In the formula (5), R ⁵¹ is an aliphatic group having 1 to 20 carbon atoms, and R ⁵² is a hydrogen atom or an aliphatic group having 1 to 6 carbon atoms.

When the benzimidazole compound represented by the general formula (5) is added to the electrolytic solution, the concentration of the benzimidazole compound in the electrolytic solution is preferably 0.01 to 1M, more preferably 0.02 to 0.8M. Most preferred is 0.05 to 0.6M.

Specific examples of the benzimidazole compound include N-methylbenzimidazole, N-ethylbenzimidazole, 1,2-dimethylbenzimidazole, N-butylbenzimidazole, N-hexylbenzimidazole, N-pentylbenzimidazole, N-isopropyl. Benzimidazole, N-isobutylbenzimidazole, N-benzylbenzimidazole, N- (2-methoxyethyl) benzimidazole, N- (3-methylbutyl) benzimidazole, 1-butyl-2-methylbenzimidazole, N- (2 -Ethoxyethyl) benzimidazole, N- (2-isopropoxyethyl) benzimidazole and the like.

When thiocyanate ions (S ⁻ —C≡N) or isothiocyanate ions (N ⁻ = C═S) are added to the electrolyte, the total concentration of thiocyanate ions and isothiocyanate ions in the electrolyte is 0.00. 01 to 1M is preferable, 0.02 to 0.5M is more preferable, and 0.05 to 0.2M is most preferable.
In preparing the electrolytic solution, it is preferable to add the isothiocyanate ion as a salt. The counter ion of the salt is preferably a guanidinium ion described later.

When guanidinium ions represented by the following general formula (6) are added to the electrolytic solution, the concentration of guanidinium ions in the electrolytic solution is preferably 0.01 to 1M, more preferably 0.02 to 0.5M. Preferably, 0.05 to 0.2M is most preferable.

(6)
In the formula (6), R ⁶¹ , R ⁶² and R ⁶³ are each independently a hydrogen atom or an aliphatic group having 1 to 20 carbon atoms.

The number of carbon atoms in the aliphatic group is preferably 1 to 12, more preferably 1 to 6, and most preferably 1 to 3. A hydrogen atom is preferred over an aliphatic group. That is, unsubstituted guanidinium ions are most preferred.
In preparing the electrolytic solution, guanidinium ions are preferably added as a salt. The counter ion of the salt is preferably an iodide ion or an isothiocyanate ion, and more preferably an isothiocyanate ion.

If necessary, an anionic surfactant, a cationic surfactant, a nonionic surfactant, and an amphoteric surfactant may be added to the electrolytic solution.

The electrolytic solution layer is a layer made of an electrolytic solution having a function of replenishing electrons to the oxidant of the dye. The photoelectrode layer preferably has pores in its porous structure filled with an electrolytic solution. Specifically, the ratio of the pores of the photoelectrode layer filled with the electrolyte is preferably 20% by volume or more, and more preferably 50% by volume or more. The thickness of the electrolytic solution layer can be adjusted by, for example, the size of the spacer provided between the photoelectrode layer and the counter electrode layer. The thickness of the portion where the electrolytic solution exists alone outside the photoelectrode is preferably 1 μm to 50 μm, more preferably 1 μm to 30 μm, still more preferably 1 μm to 20 μm, and most preferably 1 μm to 15 μm.
The light transmittance of the electrolyte layer is preferably 70% or more (in the optical path length of 30 μm) when the thickness of the electrolyte layer is 30 μm at a measurement wavelength of 400 nm, and preferably 80% or more. Is more preferable, and 90% or more is most preferable. The light transmittance preferably has the above-described transmittance in the entire wavelength region of 350 nm to 900 nm. In order to form the electrolytic solution layer of the present invention, a method of applying an electrolytic solution on the photoelectrode layer by a casting method, a coating method, a dipping method, etc. For example, a method of injecting a liquid may be used.

When an electrolyte layer is formed by a coating method, an additive such as a coating property improver (leveling agent, etc.) is added to the electrolyte containing a molten salt, and this is applied to a spin coating method, a dip coating method, an air knife coating. It may be applied by a method such as a coating method, a curtain coating method, a roller coating method, a wire bar coating method, a gravure coating method, an extrusion coating method using a hopper, or a multilayer simultaneous coating method, and then heated as necessary. The heating temperature for heating may be appropriately selected depending on the heat resistant temperature of the dye, etc., but is usually preferably 10 ° C. to 150 ° C., more preferably 10 ° C. to 100 ° C. Although the heating time depends on the heating temperature and the like, it is preferably about 5 minutes to 72 hours.
According to a preferred embodiment, since the electrolyte solution is applied in an amount larger than the amount that completely fills the voids in the photoelectrode layer, the obtained electrolyte solution layer is opposed from the boundary of the photoelectrode layer with the transparent conductive layer. It exists between the boundary of the electrode layer and the transparent conductive layer. Here, the thickness of the electrolyte layer (excluding the semiconductor particle layer) is preferably 0.001 μm to 200 μm, more preferably 0.1 μm to 100 μm, and more preferably 0.1 to 50 μm. Particularly preferred. The thickness of the electrolyte layer (the thickness of the layer substantially containing the electrolyte) is preferably 0.1 μm to 300 μm, more preferably 1 μm to 130 μm, and 2 μm to 75 μm. Particularly preferred.

[3] The counter electrode layer The counter electrode functions as a positive electrode when the photoelectric conversion element is a photochemical battery. The counter electrode is preferably composed of a transparent substrate and a transparent conductive layer. The details of the transparent substrate and the transparent conductive layer are the same as those of the transparent substrate and the transparent conductive layer of the photoelectrode layer.

(1) Catalyst layer The catalyst layer of the counter electrode is preferably noble metal particles having a catalytic action. A preferred counter electrode with a catalyst layer can be produced by providing a catalyst layer on the conductive film of the counter electrode. The noble metal particles are not particularly limited as long as they have a catalytic action, but are preferably composed of at least one of metal platinum, metal palladium and metal ruthenium having a relatively high catalytic action. The method for applying the catalyst layer is not particularly limited. For example, these metals may be applied by a vapor deposition method or a sputtering method, and a dispersion obtained by dispersing the metal fine particles in a solvent may be coated or sprayed. The electrode may also be placed on the conductive layer. When installing by a dispersion method, the dispersion liquid may further contain a binder, and a conductive polymer is preferably used. The conductive polymer is not particularly limited as long as it has conductivity and can disperse the noble metal particles, but higher conductivity is preferable.

Examples of such highly conductive polymers include Poly (thiophene-2,5-diyl), Poly (3-butylthiophene-2,5-diyl),
Polythiophene such as Poly (3-hexylthiophene-2,5-diyl), poly (2,3-dihydrothieno- [3,4-b] -1,4-dioxin), polyacetylene and its derivatives, polyaniline and its derivatives, polypyrrole And its derivatives, Poly (p-xylenetrahythrophenium
choride), Poly [(2-methoxy-5- (2'ethylhexyloxy))-1,4-phenylvinylene]], Poly [(2-methoxy-5- (3 ', 7'-dimethyloxy))-1,4-phenylenevine. )], Poly [2-2 ′, 5′-bis (2 ″ -ethylhexyloxy) phenyl] -1,4-phenylenevinylene] and the like can be used. Among these, a particularly preferable conductive polymer is Poly (2,3-dihydrothieno- [3,4-b] -1,4-dioxin) / Poly (styrenesulfate).
(PEDOT / PSS).

Moreover, the catalyst layer can contain another binder from the viewpoint of improving the adhesion to the conductive layer. The binder may be an organic resin or an inorganic material. Examples of organic resins include polyvinyl alcohol, polyvinyl pyrrolidone, polyethylene glycol, polypropylene glycol, polyacrylic acid, acrylic resin, polyester resin, polyurethane resin, polyolefin resin, polystyrene resin, cellulose and derivatives, butyral resin, alkyd resin, and vinyl chloride resin. Thermosetting or thermoplastic organic polymer compounds, ultraviolet (UV) curable organic polymer compounds, electron beam (EB) curable organic polymer compounds, inorganic polymer compounds such as polysiloxane, etc., alone or in combination Can be used.

Examples of the inorganic substance include silica sol, silicate such as M2O.nSiO2 (M: Li, Na, K), phosphate, silicon oxide, zirconium oxide, titanium oxide, aluminum oxide particle colloid, silicon, zirconium Further, metal alkoxides of titanium and aluminum, partial hydrolysis-condensation polymers thereof, molten frit, water glass, etc. can be used alone or in combination.

In addition to the binder described above, for the purpose of further improving the film adhesion strength, conductivity, etc. of the catalyst layer, for example, silicon, aluminum, zirconium, cerium, titanium, yttrium, zinc, magnesium, indium, Conductive oxide particles such as oxide or composite oxide particles such as tin, antimony, gallium, and ruthenium, tin oxide, fluorine-doped tin oxide, and tin-doped indium oxide can also be included. The thickness of the catalyst layer is preferably 100 nm to 1 μm, more preferably 50 nm to 5 μm, and particularly preferably 30 nm to 5 μm.

[4] A functional layer such as a protective layer or an antireflection layer may be provided on one or both of the photoelectrode layer and the counter electrode layer that act as other layer electrodes. When such a functional layer is formed in multiple layers, a simultaneous multilayer coating method or a sequential coating method can be used. In addition to the above basic layer configuration, the film type photovoltaic cell of the present invention can be further provided with various layers as desired. For example, a dense semiconductor thin film layer can be provided as an undercoat layer between the conductive plastic support and the porous semiconductor layer. A metal oxide is preferable as the undercoat layer, and examples thereof include TiO2, SnO2, Fe2O3, WO3, ZnO, and Nb2O5. The undercoat layer is, for example, Electrochim. In addition to the spray pyrolysis method described in Acta 40, 643-652 (1995), it can be applied by sputtering. The preferred thickness of the undercoat layer is 5 to 100 nm.

[5] Sealing layer The sealing layer of the present invention is provided around the electrolyte layer and has a function of sealing the electrolyte layer. The sealing layer is a spacer for forming an electrolyte layer by adjusting a necessary gap between the photoelectrode substrate and the counter electrode substrate, and a sealing material for bonding the photoelectrode substrate and the counter electrode substrate. It is comprised by.

(1) Sealing material The sealing material of the present invention is not particularly limited as long as it can adhere the photoelectrode substrate and the counter electrode substrate and seal the electrolyte layer. It is preferable that it is excellent in the adhesiveness between board | substrates, the tolerance (chemical resistance) with respect to electrolyte solution, and high temperature, high humidity durability (moisture heat resistance). This is because, in order to effectively and continuously suppress the leakage of the electrolytic solution, it is necessary to have excellent chemical resistance and wet heat resistance in addition to adhesiveness.

Examples of the sealing material excellent in adhesiveness, chemical resistance, and wet heat resistance include thermoplastic resins, thermosetting resins, and active radiation (light, electron beam) curable resins. Examples of the material include an acrylic resin, a fluorine resin, a silicone resin, an olefin resin, and a polyamide resin. From the viewpoint of excellent handleability, a photocurable acrylic resin is preferable.

(2) Spacer The spacer of the present invention is not particularly limited as long as a necessary gap can be adjusted within a desired range between the photoelectrode substrate and the counter electrode substrate. Usually, spherical resin particles, inorganic particles, glass beads and the like can be appropriately selected.
In the present invention, it is preferable to use perfect circle resin particles. The particle size is preferably 1 μm to 100 μm, more preferably 1 μm to 50 μm, and particularly preferably 1 μm to 20 μm. This is because the photoelectrode substrate and the counter electrode substrate are not in contact with each other, and the shorter gap is kept uniform, thereby reducing the electrolyte resistance and improving the photoelectric conversion efficiency.

It is preferable that the thickness of the sealing layer of the present invention is substantially the same as the thickness of the porous semiconductor fine particle layer. This is to maintain stable power generation efficiency by keeping the gap between the photoelectrode substrate and the counter electrode substrate uniform.
Further, the width (thickness) of the sealing layer of the present invention is not particularly limited, but is preferably in the range of 0.5 mm to 5 mm, and more preferably in the range of 0.8 mm to 3 mm. If the width of the sealing layer is too small, sufficient durability against the electrolyte may not be exhibited. If the width of the sealing layer is too large, the element area contributing to power generation in the dye-sensitized solar cell element This is because the effective area with respect to the module area decreases and the effective power generation efficiency may decrease.

[6] Current Collection In the present invention, the surface resistivity of the transparent transmissive electrode made of a transparent conductive film is lowered by disposing a current collection line made of metal (good conductor) on the transparent conductive film. The current collector is preferably provided outside the dye-sensitized photoelectric conversion element composed of a photoelectrode layer, an electrolytic solution layer, and a counter electrode layer separated by a sealing layer. This is to protect the collecting electrode from corrosion by the electrolytic solution.
The material of the current collector is not particularly limited as long as it has conductivity, but at least one selected from metal materials having a relatively low resistivity, for example, silver, copper, aluminum, tungsten, nickel, and chromium. It is preferably made of the above metals or alloys thereof, and silver is more preferable from the viewpoint of low resistivity and easy formation as a line. The current collector may be formed in a lattice shape on the transparent conductive layer. As a method for forming the current collector, sputtering, vapor deposition, plating, screen printing, or the like is used.
The width of the current collector is 0.5 mm to 5 mm, more preferably 0.7 mm to 3 mm, and the thickness of the current collector is 5 μm to 50 μm, more preferably 6 μm to 20 μm. In addition to ensuring a sufficient electric conductivity per line cross-sectional area, and an appropriate width for securing a necessary gap between the photoelectrode substrate and the counter electrode substrate in combination with conductive fine particles described later. This is because a thickness is required.

[7] Extraction Electrode In the present invention, the photoelectric conversion element includes a pair of extraction electrodes. When the photoelectric conversion element is covered with an exterior or barrier package described later, a lead material can be attached to the extraction electrode.
The material of the extraction electrode is not particularly limited as long as it has conductivity. It is preferably made of a metal material having a relatively low resistivity, for example, at least one metal selected from gold, platinum, silver, copper, aluminum, nickel, zinc, titanium, and chromium, or an alloy thereof.
The thickness of the extraction electrode is preferably 50 nm to 100 μm. This is because it is necessary that the thickness of the extraction electrode is not too thin so that the yield of the dye-sensitized photoelectric conversion element does not decrease due to disconnection, and it is not necessary to increase the thickness excessively from the viewpoint of cost. The shape of the extraction electrode is not particularly limited. For example, any of metal foil, a metal tape, plate shape, and string shape may be sufficient. A metal tape is preferable from the viewpoint of workability.

[8] Dye-sensitized solar cell module Since the electromotive force obtained by a single dye-sensitized photoelectric conversion element is limited, a plurality of dye-sensitized photoelectric conversion elements are connected in series to extract a practical voltage. Or it is necessary to connect in parallel. The upper part of FIG. 3 is a sectional view of the dye-sensitized solar cell module 3 of the present invention in which six dye-sensitized photoelectric conversion elements of the present invention are connected in series at predetermined intervals, and the lower part of FIG. 3 is a plan view of the sensitive solar cell module 3. FIG. This is an example of the embodiment, and the present invention is not limited to this.
As shown in the upper part of FIG. 3, the individual dye-sensitized photoelectric conversion elements 31 are connected in series by an electrode connection portion 34 including a current collecting line 32 and conductive fine particles 33. Further, the electrode connecting portion 34 is partitioned by a non-conductive sealing layer 35. The sealing layer 35 plays a role of sealing the electrolyte solution layer 16 of each dye-sensitized photoelectric conversion element 31. In addition, extraction electrodes 36 are provided on the current collector 32 at both ends of the dye-sensitized solar cell module 3. A lead wire is joined to the extraction electrode and connected to a desired electrical device to be used as a power generation source.
FIG. 4 shows the series connection module 3 shown in the upper part of FIG. 3 connected in parallel by sharing the electrode 35.

Here, the conductive fine particles 33 are conductive fine particles having elasticity obtained by performing gold plating on plastic fine particles having a sharp particle size distribution. Excellent elasticity with the current collector because of its elasticity. Further, the thickness of the electrolyte layer can be controlled by selecting conductive fine particles having a particle size 1 to 1.5 times, preferably 1.1 to 1.3 times the spacer.
In the present invention, the electrode connection portion is a combination of the current collector and the conductive fine particles. Specifically, after the current collector is formed, the conductive fine particles including the sealing material are laminated on the current collector, so that the transparent conductive This is to ensure the conductivity between the photoelectrode and the counter electrode due to the formation of the undercoat layer on the conductive layer.

FIG. 4 shows two dye-sensitized solar cell modules connected in parallel. By connecting in parallel, there is an advantage that the output current can be controlled sufficiently and sufficiently while maintaining the output voltage.

[9] Exterior, barrier package In the present invention, the substrate is designed to reduce its permeability to water vapor and gas, but there is a possibility that output degradation may be seen due to severe environmental conditions. In particular, it is important to provide durability under high temperature and high humidity environmental conditions. These improvement methods can be achieved by making the substrate a substrate having a barrier property against gas or water vapor, or enclosing the dye-sensitized photoelectric conversion element of the present invention in a package having a barrier property. Hereinafter, the barrier film preferably used in the present invention, particularly the water vapor barrier property will be described below.

As described above, the dye-sensitized photoelectric conversion element of the invention preferably has a layer having a barrier property against gas and water vapor outside the substrate. Furthermore, it is preferable that it is packaged or wrapped with a packaging material having a water vapor barrier property. At that time, there may be a space between the dye-sensitized photoelectric conversion element of the present invention and the high barrier packaging material, or the dye-sensitized photoelectric conversion element may be bonded with an adhesive. Furthermore, the dye-sensitized photoelectric conversion element is packaged in a packaging material using a liquid or solid (eg, liquid or gel paraffin, silicon, phosphate ester, aliphatic ester, etc.) that is difficult to pass water vapor or gas. May be.

The preferable water vapor permeability of the substrate or packaging material having a barrier property preferably used in the present invention is 0.1 g / m 2 / day or less in an environment of 40 ° C. and a relative humidity of 90% (90% RH), more preferably. Is 0.01 g / m 2 / day or less, more preferably 0.0005 g / m 2 / day or less, and particularly preferably 0.00001 g / m 2 / day or less. Further, even when the environmental temperature is 60 ° C. and 90% RH, the water vapor permeability of the substrate or packaging material having a barrier property is more preferably 0.01 g / m 2 / day or less, and still more preferably. 0.0005 g / m 2 / day or less, particularly preferably 0.00001 g / m 2 / day or less. The oxygen permeability of the substrate or packaging material having a barrier property is preferably about 0.001 g / m 2 / day or less, more preferably 0.00001 g / m 2 / day in an environment of 25 ° C. and 0% RH. preferable.

Although there is no particular limitation on imparting via properties to water vapor or gas to the substrate or packaging material having barrier properties for the dye-sensitized solar cell of the present invention, it is necessary not to interfere with the amount of light necessary for the solar cell. Therefore, it is a substrate or packaging material that is permeable and has a barrier property, and its transmittance is preferably 50% or more, more preferably 70% or more, still more preferably 85% or more, and particularly preferably. 90% or more. The board | substrate or packaging material which has the said characteristic with a barrier property is not specifically limited in the structure and material, If it has this characteristic, it will not specifically limit.

A preferred substrate or packaging material having a barrier film of the present invention is preferably a film in which a barrier layer having low water vapor and gas permeability is provided on a plastic support. Examples of the gas barrier film include those obtained by vapor-depositing silicon oxide and aluminum oxide (Japanese Patent Publication No. Sho 53-12953, Japanese Patent Laid-Open Publication No. 58-217344), and those having an organic-inorganic hybrid coating layer (Japanese Patent Laid-Open Publication No. 2000-323273, Japanese Patent Laid-Open Publication No. 2004). 25732), those having an inorganic layered compound (Japanese Patent Laid-Open No. 2001-205743), those obtained by laminating inorganic materials (Japanese Patent Laid-Open No. 2003-206361, Japanese Patent Laid-Open No. 2006-263389), those obtained by alternately laminating organic layers and inorganic layers (special features) No. 2007-30387, US Pat. No. 6413645, Affinito et al., Thin Solid Films 1996, pages 290-291), and organic layers and inorganic layers laminated continuously (US Pat. No. 2004-46497).

Next, Table 1 and Table 2 show the embodiments that achieve the effects of the present invention as examples and the embodiments that do not exhibit the effects of the present invention as comparative examples, respectively. Further, FIG. 5 shows the relationship between the area (S) of the porous oxide semiconductor layer containing a photosensitizing dye (having a rectangular shape) and the ratio of the length of the long side to the short side of the rectangle (L).

[1] Example 1
(1) Preparation of electrolytic solution [Electrolytic solution formulation 1]
Add 2.6 g of N-methylbenzimidazole, 3.3 g of potassium iodide, and 6.6 g of 1,3-butylmethylimidazolium iodide into a 50 mL volumetric flask, and add γ-butyrolactone to a total volume of 50 mL. It was. Electrolyte formulation containing no redox couple (I ⁻ / I ₃ ⁻ ) consisting of a combination of iodine and iodide after stirring for 1 hour by vibration with an ultrasonic cleaner and then standing in the dark for at least 24 hours 1 was prepared.
[Electrolyte formulation 2]
By further adding 0.5 g of iodine to the composition of the electrolyte formulation 1, an electrolyte solution containing an oxidation-reduction pair (I ⁻ / I ₃ ⁻ ) composed of a combination of iodine and iodide is prepared. 2.

(2) Preparation of dye solution 72 mg of ruthenium complex dye (N719, manufactured by Solaronics) was placed in a 200 mL volumetric flask. 190 mL of dehydrated ethanol was mixed and stirred. After stoppering the volumetric flask, the mixture was stirred for 60 minutes by vibration with an ultrasonic cleaner. After keeping the solution at room temperature, dehydrated ethanol was added to adjust the total amount to 200 mL to prepare a dye solution.

(3) Production of photoelectrode layer A screen on a transparent conductive substrate (sheet resistance 13 ohm / sq) coated with a transparent conductive layer (indium tin oxide (ITO)) on a transparent substrate (polyethylene naphthalate film, thickness 200 μm) A conductive silver paste (K3105, manufactured by Pernox Co., Ltd.) was printed and applied at intervals according to the photoelectrode cell width by a printing method, and heat-dried in a hot air circulation oven at 150 degrees for 15 minutes to produce a current collector. .
The undercoat layer was set on a coating coater with the current collector forming surface of the transparent conductive substrate facing up, and an organic PC-600 solution (manufactured by Matsumoto Fine Chemical) diluted to 1.6% was swept with a wire bar (10 mm). / Second), dried at room temperature for 10 minutes, and further dried by heating at 150 ° C. for 10 minutes.
On the undercoat layer forming surface of the transparent conductive substrate on which the undercoat layer was formed, laser treatment was performed at intervals according to the photoelectrode cell width to form insulating lines.
A mask film (bottom: PC-542PA, manufactured by Fujimori Kogyo Co., Ltd., top: NBO-0424, manufactured by Fujimori Kogyo Co., Ltd.) with a protective film coated with an adhesive layer on a polyester film is used to form a porous semiconductor fine particle layer. A part (length: 60 mm, width 5 mm) was punched out. The processed mask film was bonded to the current collector forming surface of the transparent conductive substrate on which the undercoat layer was formed so that air bubbles would not enter.
A high-pressure mercury lamp (rated lamp power: 400 W) is placed at a distance of 10 cm from the mask bonding surface, and immediately after irradiation with electromagnetic waves for 1 minute, a binder-free titanium oxide paste that does not contain polymer components (PECC-C01-06, Pexel Technologies) Co., Ltd.) was applied with a Baker type applicator. After the paste is dried at room temperature for 10 minutes, the protective film on the upper side of the mask film (NBO-0424, manufactured by Fujimori Kogyo Co., Ltd.) is peeled off and dried in a hot air circulation oven at 150 ° C. for 5 minutes. A fine particle layer (length: 60 mm, width 5 mm) was formed.
Thereafter, the transparent conductive substrate on which the porous semiconductor fine particle layer (length: 60 mm, width 5 mm) was formed was immersed in the prepared dye solution (40 ° C.), and the dye was adsorbed while gently stirring. After 90 minutes, the dye-adsorbed titanium oxide film was taken out from the dye-adsorption container, washed with ethanol and dried, and the remaining mask film was peeled and removed to produce a photoelectrode.

(4) Preparation of counter electrode layer On the conductive surface of a transparent conductive substrate (sheet resistance 13 ohm / sq) coated with a transparent conductive layer (indium tin oxide (ITO)) on a transparent substrate (polyethylene naphthalate film, thickness 200 μm) A metal mask with punched openings (length: 60 mm, width: 5 mm) is overlaid, and a platinum film pattern (catalyst layer) is formed by sputtering, and the catalyst layer forming portion has a light transmittance of about 72%. A counter electrode layer was obtained. At this time, when the photoelectrode layer and the counter electrode layer are overlapped with their conductive surfaces facing each other, the titanium oxide pattern (porous semiconductor fine particle layer forming portion) and the platinum pattern (catalyst layer forming portion) are Matched structure.

(5) Preparation of dye-sensitized photoelectric conversion element The surface of the counter electrode layer that is the catalyst layer forming surface is fixed on an aluminum adsorption plate using a vacuum pump, and a liquid photo-curing sealant (Three Bond Co., Ltd.) Was applied to the outer periphery of the platinum film pattern by an automatic application robot. Then, a predetermined amount of the electrolyte solution (electrolyte formulation 1) prepared as described above is applied to the platinum film pattern portion, and a rectangular platinum pattern and a titanium oxide pattern of the same type face each other using an automatic bonding apparatus. Then, they were superposed in a reduced pressure environment, irradiated with light from the photoelectrode side with a metal halide lamp, and then irradiated with light from the platinum electrode side. After that, a plurality of photoelectric conversion elements arranged in the substrate after bonding are cut out, and a dye is increased by sticking a conductive copper anchor tape (CU7636D, manufactured by Sony Chemical & Information Device Co., Ltd.) to the extraction electrode part. A photoelectric conversion element was produced.

(6) Evaluation of dye-sensitized solar cell element As a light source, a pseudo solar light source (PEC-L11 type, manufactured by Pexel Technologies Co., Ltd.) in which an AM1.5G filter was attached to a 150 W xenon lamp light source device was used. The amount of light was adjusted to 1 sun (approximately 100,000 lux AM1.5G, 100 mWcm-2 (JIS C 8912 class A)). The produced dye-sensitized solar cell element was connected to a source meter (type 2400 source meter, manufactured by Keithley). For the current-voltage characteristics, the output current was measured while changing the bias voltage from 0 V to 0.8 V in units of 0.01 V under 1 sun light irradiation. Similarly, the bias voltage was measured by stepping in the reverse direction from 0.8 V to 0 V, and the conversion efficiency of each rectangular cell was obtained using the average value of the forward and reverse measurements as photocurrent data. Next, after adding an ND filter to the pseudo solar light source to adjust the light amount to 500 lux, the conversion efficiency at 500 lux was obtained by the same measurement method as described above.

[2] Examples 2 to 10, Comparative Examples 1 to 25
The same procedure as in Example 1 was performed except that the size of the opening of the mask film was changed.
Table 1 shows the conversion efficiencies of the rectangular cells obtained in 100,000 lux and 500 lux. Further, the planar shape of the porous semiconductor fine particle layer supporting the sensitizing dye constituting the photoelectrode, specifically, the relationship between the area (mm2) and the long side (length) with respect to the short side (width) is compared with the examples. A comparative example is shown in FIG.

[3] Comparative Examples 26 and 27
The same procedure as in Examples 2 and 6 was conducted except that the electrolyte solution was changed to the electrolyte solution formulation 2.
Table 2 shows the conversion efficiencies of the rectangular cells obtained in 100,000 lux and 500 lux.
From the results of Tables 1 and 2 and FIG. 5, the following is clear.

(1) The conversion efficiency of the dye-sensitized photoelectric conversion element varies depending on the light amount (500 lux and 100,000 lux) and the shape of the porous semiconductor fine particle layer constituting the photoelectrode. When the shape of the porous semiconductor fine particle layer constituting the photoelectrode is a specific condition (relationship between the area and the long side ratio to the short side), the conversion efficiency is low light amount (500 lux) and high light amount (100,000 LUX). It becomes high in any. This is a dye-sensitized photoelectric conversion element that has a small dependency on the photoelectric conversion efficiency of the light amount change, in other words, the conversion efficiency is constant and the conversion efficiency is high even if the light amount change greatly changes. It shows (contrast with an Example and a comparative example).
(2) Further, the dye-sensitized photoelectric conversion element having a small dependency of the change in the light amount on the conversion efficiency has a redox pair (I ^{−) in} which the electrolytic solution constituting the electrolytic solution layer is a combination of iodine and iodide. / I ₃ ⁻ ) can be achieved (contrast between Examples 2 and 6 and Comparative Examples 26 and 27).

In the dye-sensitized photoelectric conversion element according to the present invention, high photoelectric conversion efficiency is obtained in a wide range from low illuminance (500 lux) to high illuminance (100,000 lux), and the change in photoelectric change efficiency is small.

DESCRIPTION OF SYMBOLS 1 Dye-sensitized photoelectric conversion element 11 Transparent substrate 12 Transparent conductive layer 13 Undercoat layer 14 Porous semiconductor fine particle layer 15 carrying sensitizing dye 15 Photoelectrode layer 16 Electrolyte layer 17 Catalyst layer 18 Counter electrode layer 19 Sealing layer 20 Current collector 21 Extraction electrode 2 Transparent conductive substrate 22 bonded with mask film Mask film 23 Open portion 3 of mask film Series-connected dye-sensitized solar cell module 31 Dye-sensitized photoelectric conversion element 32 Current collector 33 Conductive fine particles 34 Electrode connection portion 35 Sealing layer 36 Extraction electrode

Claims (4)

1. A transparent substrate, a transparent electrode layer formed on the transparent substrate, a porous oxide semiconductor layer formed on the transparent electrode layer and containing a photosensitizing dye, and facing the oxide semiconductor layer A substrate, a counter electrode layer formed on the surface of the counter substrate on the oxide semiconductor side, an electrolyte layer provided between the transparent electrode layer and the counter electrode layer, and the electrolyte layer In the dye-sensitized photoelectric conversion element that is provided around the element and has an element seal portion that seals the electrolyte layer,
   The planar shape of the porous oxide semiconductor layer containing the photosensitizing dye is rectangular,
   The area (S) of the rectangle is 300 mm ² to 600 mm ² , and the ratio (L) of the length of the long side to the short side of the rectangle is included in the region satisfying the following expressions (1) and (2). The dye-sensitized photoelectric conversion element characterized by the above-mentioned.
   

   

   In the formulas (1) and (2), S is a rectangular area (mm ² ) of the porous oxide semiconductor layer containing the sensitizing dye, and L is a rectangular shape of the porous oxide semiconductor layer containing the sensitizing dye. The ratio of the length of the long side to the short side.
2. 2. The dye-sensitized photoelectric film according to claim 1, wherein the electrolyte solution constituting the electrolyte solution layer does not contain a redox pair (I ⁻ / I ₃ ⁻ ) composed of a combination of iodine and iodide. Conversion element.
3. A dye-sensitized solar cell module, wherein the dye-sensitized photoelectric conversion elements according to claim 1 or 2 are connected in parallel or in series.
4. A dye-sensitized solar cell module in which the dye-sensitized photoelectric change elements are connected in series, and the dye-sensitized photoelectric change elements are connected in series via an electrode connection portion made of a current collector and conductive fine particles. The dye-sensitized solar cell module according to claim 4, wherein

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