JP2012204324A - Dye-sensitized solar cell photoelectrode - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a dye-sensitized solar cell photoelectrode which can achieve high photoelectric conversion efficiency and a method for manufacturing the dye-sensitized solar cell photoelectrode.SOLUTION: The dye-sensitized solar cell photoelectrode includes a porous metal oxide semiconductor layer and a sensitization dye adsorbed in the porous metal oxide semiconductor layer. The porous metal oxide semiconductor layer has a porosity of 40-90% by volume and an average short diameter of holes of 100-3000 nm, where a percentage of holes forming contiguous holes adjacent to one another relative to all holes is 10% or less.

Description

The present invention relates to a dye-sensitized solar cell photoelectrode capable of realizing high photoelectric exchange efficiency and a method for producing the dye-sensitized solar cell photoelectrode.

In recent years, solar cells capable of converting light energy into electric energy have attracted attention from the viewpoint of environmental problems. The mainstream of solar cells currently in practical use is silicon-based solar cells composed of single crystal, polycrystalline and amorphous silicon, but these are high material costs and energy costs in the manufacturing process, and are a major obstacle to the widespread use of solar cells. It was.
On the other hand, dye-sensitized solar cells are particularly attracting attention because the manufacturing cost can be kept low. Dye-sensitized solar cells are also excellent in that they have added value that is difficult to realize with existing silicon solar cells, such as colorfulness, lightweight flexibility, and see-through properties, in addition to low manufacturing cost and low environmental impact. ing.

A dye-sensitized solar cell includes a photoelectrode having an oxide semiconductor layer carrying a sensitizing dye and a transparent conductive layer, a counter electrode, and an electrolyte layer sandwiched between these electrodes. When the electrode is irradiated with light, the sensitizing dye is excited to emit electrons, and the electrons reach the transparent electrode layer through the oxide semiconductor layer, whereby electric energy is extracted.

On the other hand, although the production cost of the dye-sensitized solar cell is low, the low photoelectric conversion efficiency is an obstacle to practical use. On the other hand, the light receiving area of the dye-sensitized solar cell has been increased to increase the output of the battery, but simply increasing the area results in a loss of power due to an increase in the internal resistance of the battery. As a result, there is a problem that the conversion efficiency is lowered and the shape factor (fill factor (FF)) is reduced.

In the dye-sensitized solar cell, the photoelectric conversion efficiency varies depending on the amount of the sensitizing dye adsorbed and the charge mobility in the electrolyte. Therefore, in order to increase the photoelectric conversion efficiency, it is necessary to increase the porosity of the oxide semiconductor layer to increase the surface area and make it easier to move the electrolytic solution.
However, in recent years, high-viscosity electrolytes such as ionic liquids are often used as the electrolyte, and in such cases, the mobility of the electrolyte is particularly poor.

On the other hand, in Patent Document 1, as a method for producing a porous structure used for a dye-sensitized solar cell or the like, porous structure-forming particles, thickeners, additives (resin particles, etc.) and A method of forming pores by preparing a mixture containing a solvent and the like and then depositing the mixture on a substrate and removing the thickener and additives is disclosed. In Patent Document 1, the shape and size of the pores can be controlled by appropriately selecting the shape and size of the additive.
However, in the method of Patent Document 1, a new problem arises that the pores of the resulting porous structure become non-uniform due to the aggregation of the additive. If the pores are non-uniform, there is a problem that stress is applied to the porous structure to cause cracks or the like, an efficient light confinement effect cannot be obtained, and the photoelectric conversion efficiency is lowered.

JP 2006-324011 A

The present invention relates to a dye-sensitized solar cell photoelectrode capable of obtaining a dye-sensitized solar cell having high conversion efficiency without causing defects such as cracks, and a method for producing the dye-sensitized solar cell photoelectrode The purpose is to provide.

The present invention is a photoelectrode for a dye-sensitized solar cell having a porous metal oxide semiconductor layer and a sensitizing dye adsorbed on the porous metal oxide semiconductor layer, the porous metal oxide semiconductor layer comprising: The dye sensitization has a porosity of 40 to 90% by volume, an average minor axis of pores of 100 to 3000 nm, and a ratio of adjacent pores forming continuous pores of 10% or less of all pores. It is a photoelectrode for a solar cell.
The present invention is described in detail below.

As a result of intensive studies, the present inventors have determined that the porosity of the porous metal oxide semiconductor layer and the average minor axis of the pores are within a predetermined range in the dye-sensitized solar cell photoelectrode, and adjacent to each other. By reducing the proportion of pores that form continuous pores, the strength of the porous metal oxide semiconductor layer can be improved, cracks can be prevented, and high photoelectric conversion is achieved by controlling the shape of the pores. It discovered that the photoelectrode for dye-sensitized solar cells which can manufacture the dye-sensitized solar cell which has efficiency was obtained, and came to complete this invention.

In the porous metal oxide semiconductor layer, the lower limit of the porosity is 40% by volume, and the upper limit is 90% by volume. When the porosity is less than 40% by volume, the adsorption amount of the sensitizing dye is decreased, and the metal oxide semiconductor layer may be too dense and the strength may be weakened. In addition to the decrease in conductivity of the porous metal oxide semiconductor layer, the metal oxide semiconductor layer may become too sparse and weak in strength. A preferred lower limit is 55% by volume, and a preferred upper limit is 80% by volume.
In this specification, the porosity is a percentage (%) of the volume of the hollow portion occupied in the entire volume of the porous metal oxide semiconductor layer. For example, the gas adsorption method pore distribution measuring device Asap 2020 (Manufactured by Shimadzu Corporation) can be measured under conditions of an enclosed nitrogen pressure of 0 to 760 mmHg.

In the porous metal oxide semiconductor layer, the lower limit of the average minor axis of pores is 100 nm, and the upper limit is 3000 nm.
By setting the average minor axis within the above range, the retention amount of the porous metal oxide semiconductor layer is improved while maintaining the strength of the porous metal oxide semiconductor layer and the light diffusing effect, and becomes a path for injecting the sensitizing dye and electrolyte. As a result, the resulting dye-sensitized solar cell can achieve high photoelectric exchange efficiency. If the average minor axis of the vacancies is less than 100 nm, sufficient strength and light diffusion effect may not be obtained, and if it exceeds 3000 nm, stress may be concentrated and the strength may be lowered. A preferred lower limit is 150 nm and a preferred upper limit is 1500 nm.
Note that the average minor axis of the pores is, for example, an image analysis of a SEM photograph obtained by photographing a cut surface in the thickness direction of the porous metal oxide semiconductor layer. After measuring a diameter, it can measure by calculating | requiring the average value.

In the porous metal oxide semiconductor layer, the preferable upper limit of the Cv value of the minor axis of the pores is 30%. When the Cv value of the short diameter exceeds 30%, the pores of the porous metal oxide semiconductor layer are not uniform, and the intended light diffusion effect cannot be obtained, so that the photoelectric conversion efficiency of the dye-sensitized solar cell decreases. There are things to do. A more preferable upper limit of the Cv value of the minor axis is 25%.
The Cv value of the minor axis can be calculated from the average minor axis m and the standard deviation σ by the following formula (1).
Cv = σ / m × 100 (%) (1)

In the porous metal oxide semiconductor layer constituting the photoelectrode for dye-sensitized solar cell of the present invention, the proportion of pores that form adjacent pores is 10% or less of the total pores.
By using such vacancies, vacancies that can promote optical scattering can be formed, and higher photoelectric conversion efficiency can be realized by promoting the light confinement effect and ion diffusion.
In addition, by forming a large number of independent pores with uniformly distributed pores, the porous metal oxide semiconductor layer forms a honeycomb structure and relaxes internal stress and strain to give flexibility and strength to the porous material. be able to. As a result, the semiconductor layer can be formed without cracks even if thick coating is performed. On the other hand, when there are many adjacent continuous holes, the whole hole becomes enormous, and stress may concentrate and cause cracks.
When the ratio of the void | hole which forms the said continuous hole exceeds 10%, in addition to a photoelectric conversion efficiency falling, the intensity | strength of a porous metal oxide semiconductor layer may fall and a crack may enter.
The upper limit with the preferable ratio of the void | hole which forms the said continuous hole is 5%.
In the present application, “a hole that forms a continuous hole adjacent to each other” refers to a hole in which two or more independent holes are connected, and a part of adjacent holes penetrate each other. It means the state that is.
In addition, the “ratio of vacancies that form continuous pores” is, for example, an arbitrary number of randomly extracted SEM photographs obtained by photographing SEM photographs taken in the thickness direction of the porous metal oxide semiconductor layer. About a void | hole, it can measure by counting the ratio of the void | hole which forms the continuous hole.

The pores of the porous metal oxide semiconductor layer are preferably obtained by the disappearance of the heat extinguishing resin particles. Such holes are preferable because it is easy to control the average minor axis of the holes, the shape of the holes, and the dispersion state of the holes.
In addition, since the porous metal oxide semiconductor layer is obtained in this way, in addition to the gap between the metal oxide particles produced by sintering, the average minor axis due to the disappearance of the heat extinguishing resin particles is obtained. It will have many holes of 100 nm or more. Thereby, a porosity can be made high compared with the conventional porous metal oxide semiconductor layer.

The preferable lower limit of the thickness of the porous metal oxide semiconductor layer is 1 μm, and the preferable upper limit is 50 μm. If the thickness is less than 1 μm, the amount of semiconductor is small and photoelectric conversion is insufficient, and if it exceeds 50 μm, the dye-sensitized solar cell itself may be cracked.

The porous metal oxide semiconductor layer is made of silicon oxide, titanium oxide, tin oxide, zinc oxide, zirconium oxide, strontium oxide, niobium oxide, cerium oxide, tungsten oxide, aluminum oxide, indium oxide, gallium oxide and yttrium oxide. It is preferably made of at least one metal oxide selected from the group, or a complex oxide containing the metal oxide. Of these, titanium oxide, zinc oxide, and the like are preferred because they have a wide band gap and are relatively abundant in resources.

The porous metal oxide semiconductor layer may be made of metal oxide semiconductor particles. In particular, when the metal oxide semiconductor particles are titanium oxide particles, for example, normal rutile type titanium oxide particles, anatase type titanium oxide particles, brookite type titanium oxide particles, and titanium oxide modified with these crystalline titanium oxides. Particles or the like can be used.

A sensitizing dye is adsorbed on the porous metal oxide semiconductor layer.
Examples of the sensitizing dye include ruthenium-tris, ruthenium-bis type ruthenium dyes, and organic dyes such as phthalocyanine, porphyrin, cyanidin dye, merocyanine dye, rhodamine dye, xanthene dye, and triphenylmethane dye.

In the photoelectrode for dye-sensitized solar cell of the present invention, conventionally known members can be used for members such as the porous metal oxide semiconductor layer and the transparent substrate other than the sensitizing dye and the transparent conductive layer.

Although it will not specifically limit as said transparent substrate if it is a transparent substrate, Glass substrates, such as silicate glass, etc. are mentioned. The glass substrate may be chemically and thermally strengthened. Furthermore, various plastic substrates or the like may be used as long as light transmittance can be secured.
The thickness of the transparent substrate is preferably 0.1 to 10 mm, and more preferably 0.3 to 5 mm.

Examples of the transparent conductive layer include a layer made of a conductive metal oxide such as In ₂ O ₃ or SnO ₂ and a layer made of a conductive material such as a metal. Examples of the conductive metal oxide include In ₂ O ₃ : Sn (ITO), SnO ₂ : Sb, SnO ₂ : F, ZnO: Al, ZnO: F, and CdSnO ₄ .

The photoelectrode for dye-sensitized solar cell of the present invention includes, for example, a step of preparing a metal oxide semiconductor paste containing metal oxide semiconductor particles, heat extinguishing resin particles and an organic solvent, and applying the metal oxide semiconductor paste. A step of forming a porous metal oxide semiconductor layer by drying and baking the metal oxide semiconductor paste, and a step of adsorbing a sensitizing dye to the porous metal oxide semiconductor layer The metal oxide semiconductor particles have a primary crystal particle diameter of 100 nm or less, and the heat extinguishing resin particles have a zeta value measured in a solvent having an SP value of 9 (cal / cm) ^1/2 or more. The absolute value of the potential is 20 mV or more, the average particle diameter is 100 to 3000 nm, and the addition amount of the heat extinguishing resin particles to the metal oxide semiconductor particles is 5 to 100 times It can be produced by a method which is in%. Such a method for producing a dye-sensitized solar cell photoelectrode is also one aspect of the present invention.

The manufacturing method of the photoelectrode for dye-sensitized solar cells of this invention has the process of preparing the metal oxide semiconductor paste containing a metal oxide semiconductor particle, a heat extinction resin particle, and an organic solvent.

The metal oxide semiconductor particles include silicon oxide, titanium oxide, tin oxide, zinc oxide, zirconium oxide, strontium oxide, niobium oxide, cerium oxide, tungsten oxide, aluminum oxide, indium oxide, gallium oxide, and yttrium oxide. It is preferable to use at least one metal oxide selected from the above or a composite oxide containing the metal oxide.

As the particle diameter of the metal oxide semiconductor particles, the upper limit of the primary crystal particle diameter is 100 nm. By setting it within the above range, the surface area on which the sensitizing dye is adsorbed can be increased, and the light energy absorption capability can be enhanced. A preferred lower limit is 3 nm and a preferred upper limit is 50 nm. In addition, two or more kinds of fine particles having different particle size distributions may be mixed. For the purpose of improving the light capture rate by scattering incident light, a metal oxide having a large particle size, for example, a primary crystal particle size of about 400 nm is used. Solid semiconductor particles may be mixed. The primary crystal particle diameter can be measured by SEM.

The heat extinguishing resin particle is not particularly limited as long as it is a particle composed of a polymer resin that decomposes and disappears at a temperature lower than 500 ° C. at which a metal oxide semiconductor such as titanium oxide begins to sinter. For example, polystyrene Examples thereof include particles containing resin, poly (meth) acrylate resin, polyethylene resin, polypropylene resin, polyurethane resin, vinyl chloride resin, polyoxyalkylene resin, poly (meth) acrylonitrile resin, and the like. Among these, particles made of a resin containing oxygen atoms are preferable, and particles containing a polyoxyalkylene resin are particularly preferable.
Resins containing oxygen atoms, such as poly (meth) acrylate resins, decompose and disappear with a combustion reaction when given heat is applied, and exhibit excellent heat extinction properties.
In addition, the above polyoxyalkylene resin is decomposed into low molecular weight hydrocarbons, ethers, etc. by heating to a predetermined temperature, and then disappears due to phase change such as combustion reaction or evaporation. Demonstrate.

Although it does not specifically limit as said polyoxyalkylene resin, It is preferable to contain polyoxypropylene, polyoxyethylene, or polyoxytetramethylene. When these polyoxyalkylene resins are not contained, predetermined heat extinction properties and particle strength may not be obtained. Of these, polyoxypropylene is more preferable. In order to obtain moderate heat extinction properties and particle strength, it is preferable that 5% by weight or more of the polyoxyalkylene resin contained in the heat extinction resin particles is polyoxypropylene. Moreover, polyoxyethylene shall contain ethylene glycol.

Examples of commercially available polyoxyalkylene resins include MS polymers S-203, S-303, S-903 (manufactured by Kaneka), Silyl SAT-200, MA-403, and MA-447. (Above, manufactured by Kaneka Corporation), Epion EP103S, EP303S, EP505S (above, manufactured by Kaneka Corporation), Exester ESS-2410, ESS-2420, ESS-3630 (above, manufactured by Asahi Glass Co., Ltd.) and the like.

The number average molecular weight of the polyoxyalkylene resin is not particularly limited, but the preferred lower limit of the number average molecular weight is 300, and the preferred upper limit is 1,000,000. When the number average molecular weight is less than 300, high heat extinction properties may not be realized, and when it exceeds 1,000,000, high particle strength may not be realized.

In the heat extinguishing resin particles, the preferred lower limit of the content of the polyoxyalkylene resin is 5% by weight. If it is less than 5% by weight, the heat extinction property may not be sufficiently realized.

The heat extinguishing resin particles preferably contain a polymer obtained by polymerizing a polymerizable monomer containing a crosslinkable monomer.
By containing the crosslinkable monomer, the compressive strength of the heat extinguishing resin particles can be improved. Further, by containing the crosslinkable monomer, the heat extinguishing resin particles can be prevented from swelling in the organic solvent.
The crosslinkable monomer is not particularly limited, and examples thereof include acrylic polyfunctional monomers such as trimethylolpropane tri (meth) acrylate and ethylene glycol di (meth) acrylate, divinylbenzene, and two or more functional groups described below. For example, macromonomers.

The content of the crosslinkable monomer in the polymerizable monomer containing the crosslinkable monomer is preferably 0.5% by weight or more. Thereby, the swelling property to an organic solvent can further be reduced. More preferably, it is 1 to 30% by weight.

The heat extinguishing resin particles preferably further contain an acrylic monomer polymer. The acrylic monomer polymer is easy to depolymerize and is excellent in thermal decomposability. Particularly, the coexistence with the polyoxyalkylene resin can further improve the decomposability.

The acrylic monomer polymer is not particularly limited. For example, ethyl acrylate, propyl acrylate, n-butyl acrylate, cyclohexyl acrylate, 2-ethylhexyl acrylate, ethyl methacrylate, butyl methacrylate, methyl methacrylate, butyl methacrylate, isobutyl methacrylate. And the like.
A polymer of an acrylic polyfunctional monomer such as trimethylolpropane tri (meth) acrylate is preferably used.

The heat extinguishing resin particles have an absolute value of zeta potential of 20 mV or more measured in a solvent having an SP value of 9 (cal / cm) ^1/2 or more. By mixing the metal oxide semiconductor particles and the organic solvent in a state where the absolute value of the zeta potential is 20 mV or more, and preparing the metal oxide semiconductor paste, the metal oxide semiconductor particles and the heat extinguishing resin particles are Alternatively, the heat extinguishing resin particles repel each other in an organic solvent, and the heat extinguishing resin particles can be maintained in a dispersed state without agglomerating in the metal oxide semiconductor paste. By sintering the metal oxide semiconductor paste in which the dispersibility of the heat extinguishing resin particles is maintained, a porous metal oxide semiconductor layer having independent pores in which pores are uniformly distributed can be obtained. It is the feature.

The method of forming pores in the porous metal oxide semiconductor layer using resin particles has been reported so far, but when using metal oxide semiconductor particles having a primary crystal particle diameter of 100 nm or less, the specific surface area is extremely high. Therefore, if resin particles in a dry powder state that is electrically neutral are used, the metal oxide semiconductor particles and the resin particles, or the resin particles are aggregated in the metal oxide semiconductor paste, and are baked. Even when bonded, it was not possible to obtain a porous metal oxide semiconductor layer having independent pores in which pores were uniformly distributed.
When the absolute value of the zeta potential of the heat extinguishing resin particles is less than 20 mV, the repulsive force between the particles is small, and the agglomeration of the heat extinguishing resin particles occurs in the paste as in the case of adding the dry powder. . The absolute value of the zeta potential is more preferably 30 mV or more.
Further, in order for the metal oxide semiconductor particles and the heat extinguishing resin particles to be electrically repelled, both potentials need to have the same positive / negative potential.
The zeta potential can be measured with a zeta potentiometer or a dynamic light scattering photometer.

Examples of the solvent having an SP value of 9 (cal / cm) ^1/2 or more include, for example, water (SP value = 23.4 (cal / cm) ^1/2 , source: Polymer Handbook 3rd edition), methanol ( 14.5), ethanol (12.7), propanol (11.5), butanol (11.4), dimethylformamide (12.1), dimethyl sulfoxide (14.5), methyl ethyl ketone (9.3) , Acetone (9.9) and the like are used.

The degree of swelling of the heat-extinguishing resin particles is 1.5 times or less when immersed in the organic solvent for 24 hours. By setting the swelling degree to 1.5 times or less, the particle strength in the paste is maintained, and the function of forming pores is exhibited.
When the degree of swelling exceeds 1.5 times, the resin particle strength in the paste is reduced, and when mixed with the metal oxide semiconductor particles, the resin particles may be destroyed by shearing.
The swelling degree is preferably 1.2 times or less.
The degree of swelling is measured by adding a weighed sample to a predetermined organic solvent, allowing to stand for 24 hours, and then calculating the ratio of the weight of the organic solvent taken into the sample to the weight of the sample added first. can do.
Moreover, the said organic solvent means the organic solvent used when producing a metal oxide semiconductor paste.

It is preferable that 90% by weight or more of the heat extinguishing resin particles disappear within one hour by heating to a predetermined temperature of 100 to 350 ° C.
The heat extinguishing resin particles exhibit extremely excellent decomposability even in a low temperature region. When the time required for disappearance of 90% by weight or more exceeds 1 hour, the production efficiency of the porous resin film may be lowered when used for the production of the porous resin film. If the portion that disappears within 1 hour is less than 90% by weight, the amount of heat generation may be reduced, and the effect of suppressing deformation may be insufficient.

The lower limit of the average particle diameter of the heat extinguishing resin particles is 100 nm and the upper limit is 3000 nm. If the average particle size is less than 100 nm, the optical confinement effect of the porous metal oxide semiconductor layer may not be obtained and the conversion efficiency may be reduced, or the honeycomb structure may not be formed and the strength may be reduced. If it exceeds 1, the strength of the resulting porous metal oxide semiconductor layer may decrease. A preferred lower limit is 150 nm and a preferred upper limit is 1500 nm.

The lower limit of the addition amount of the heat extinguishing resin particles in the metal oxide semiconductor paste is 5% by weight and the upper limit is 100% by weight with respect to the metal oxide semiconductor particles. If the addition amount is less than 5% by weight, the light confinement effect cannot be obtained and the conversion efficiency is lowered, or the honeycomb structure cannot be formed and the strength is lowered. When it exceeds 100% by weight, the strength of the obtained porous metal oxide semiconductor layer is lowered. A preferred lower limit is 10% by weight and a preferred upper limit is 60% by weight.

The method for producing the heat extinguishing resin particles is not particularly limited, and for example, using a conventionally known polymerization method such as a suspension polymerization method, an emulsion polymerization method, a dispersion polymerization method, a soap-free polymerization method, a mini-emulsion polymerization method or the like. The method of superposing | polymerizing etc. is mentioned.
Especially, as a manufacturing method of the particle | grains containing polyoxyalkylene resin, the method which has the process of superposing | polymerizing the mixed monomer of a polyoxyalkylene macromonomer or a polyoxyalkylene macromonomer, and another polymerizable monomer is preferable. In the present specification, the macromonomer refers to a high molecular weight linear molecule having a polymerizable functional group such as a vinyl group at the molecular end, and the polyoxyalkylene macromonomer is a polymer having a linear portion having a poly moiety. A macromonomer composed of oxyalkylene.
Moreover, when superposing | polymerizing the said heat extinction resin particle, a decomposition accelerator may be added to a monomer.

The metal oxide semiconductor paste usually contains a binder resin. Examples of the binder resin include cellulose compounds such as ethyl cellulose, polyvinyl alcohol (PVA), polyvinyl butyral (PVB), polyethylene glycol, polystyrene, acrylic resin, and polylactic acid.

The metal oxide semiconductor paste contains an organic solvent. The organic solvent preferably has a high polarity. For example, terpene solvents such as α-terpineol and γ-terpineol, alcohol solvents such as ethanol and isopropyl alcohol, mixed solvents such as alcohol solvents / hydrocarbons, dimethyl Examples include heteroamides such as formamide, dimethyl sulfoxide and tetrahydrofuran, and water.

Examples of the method for preparing the metal oxide semiconductor paste include the metal oxide semiconductor particles, the heat extinguishing resin particles, the binder resin, and the organic solvent, such as a two-roll mill, a three-roll mill, a bead mill, a ball mill, a disper, and a planetar. Examples of the method include mixing using a Lee mixer, a rotation and revolution type stirring device, a kneader, an extruder, a mix rotor, a stirrer, and the like.

In the step of preparing the metal oxide semiconductor paste, the heat extinguishing resin particles are preferably added in a state of being dispersed in a solvent having an SP value of 9 (cal / cm) ^1/2 value or more. Thus, by preliminarily dispersing in a highly polar solvent, the heat extinguishing resin particles and the metal oxide semiconductor particles can be easily mixed uniformly. Such an effect is attributed to the fact that the metal oxide semiconductor particles are stably dispersed in a solvent having a large SP value.

The manufacturing method of the photoelectrode for dye-sensitized solar cells of this invention has the process of applying a metal oxide semiconductor paste.
Although it does not specifically limit as a method to apply the said metal oxide semiconductor paste, It is preferable to use the screen-printing method from being able to apply, maintaining the shape of the said heat extinction resin particle.

The step of applying the metal oxide semiconductor paste is generally performed by applying on the transparent conductive layer of the transparent substrate on which the transparent conductive layer is formed.

The size of the screen plate opening, the squeegee tack angle, the squeegee speed, the squeegee pressing force, and the like in the screen printing step are preferably set as appropriate.

The manufacturing method of the photoelectrode for dye-sensitized solar cells of this invention has the process of forming a porous metal oxide semiconductor layer by drying and baking a metal oxide semiconductor paste.

Drying and baking of the metal oxide semiconductor paste can be appropriately adjusted in temperature, time, atmosphere, and the like depending on the type of substrate to be coated. For example, it is preferable to carry out for about 10 seconds to 12 hours in the range of about 50 to 800 ° C. in the air or in an inert gas atmosphere. The drying and firing may be performed once at a single temperature or twice or more by changing the temperature.

The manufacturing method of the photoelectrode for dye-sensitized solar cells of this invention performs the process which makes a sensitizing dye adsorb | suck to the said porous metal oxide semiconductor layer.
Examples of the method for adsorbing the sensitizing dye include a method of immersing the substrate on which the porous metal oxide semiconductor layer is formed in an alcohol solution containing the sensitizing dye, and then drying and removing the alcohol. .

The dye-sensitized solar cell photoelectrode thus obtained is placed facing the counter electrode, and an electrolyte layer is formed between these electrodes to produce a dye-sensitized solar cell. Can do. The dye-sensitized solar cell thus obtained can achieve high photoelectric conversion efficiency.

ADVANTAGE OF THE INVENTION According to this invention, the manufacturing method of the photoelectrode for dye-sensitized solar cells which can implement | achieve high photoelectric exchange efficiency, and this photoelectrode for dye-sensitized solar cells can be provided.

2 is an SEM photograph obtained by photographing a cut surface in a thickness direction of a porous metal oxide semiconductor layer of a photoelectrode for dye-sensitized solar cell obtained in Example 1. FIG. It is the SEM photograph which image | photographed the cut surface of the thickness direction of the porous metal oxide semiconductor layer of the photoelectrode for dye-sensitized solar cells obtained by the comparative example 1. FIG.

Hereinafter, the present invention will be described in more detail with reference to examples. However, the present invention is not limited to these examples.

Example 1
(Preparation of heat extinguishing resin particles)
As monomer components, 20 g of polyoxypropylene dimethacrylate (the number of polyoxypropylene units = about 4) and 80 g of isobutyl methacrylate were mixed with stirring to prepare a monomer solution. The total amount of the monomer solution obtained was added to 100 g of an aqueous solution containing 1% by weight of polyoxyethylene alkyl ether as an emulsifier, and the mixture was stirred using a stirring and dispersing device to obtain an emulsified suspension.

Next, after charging 800 g of ion exchange water into a 2 liter polymerization vessel equipped with a stirrer, jacket, reflux condenser and thermometer, the inside of the polymerization vessel was depressurized and deoxygenated in the vessel, and then nitrogen gas Thus, the pressure was returned to atmospheric pressure, and the inside of the polymerization vessel was set to a nitrogen atmosphere. After confirming that the temperature of the polymerization vessel was constant at 60 ° C., 1 g of ammonium persulfate was added as a polymerization initiator and stirred for 15 minutes. Into this polymerization vessel, 2% by weight (4 g) of the emulsified suspension was charged all at once, and polymerization of seed particles was started. After confirming that the polymerization of the seed particles was completed in about 15 minutes, the remaining emulsified suspension was added dropwise over 2 hours, followed by further aging for 1 hour to complete the polymerization. The polymerization vessel was cooled to room temperature to obtain an emulsion of heat extinguishing resin particles.

It was 485 nm when the average particle diameter of the obtained heat extinction resin particle was measured. The average particle diameter (volume average particle diameter) of the heat extinguishing resin particles was measured by using a dynamic light scattering photometer (manufactured by Particle Sizing Systems, “NICOMP model 380 ZLS-S”).
Moreover, when the obtained heat extinction resin particle emulsion was diluted with ethanol and the zeta potential was measured with the same dynamic light scatterometer, it was -41 mV.
Further, after the resin particles were settled using a centrifugal separator, the obtained heat extinguishing resin particle emulsion was substituted with methyl ethyl ketone, and a methyl ethyl ketone (MEK) dispersion (resin solid content) of the heat extinguishing resin particles. A concentration of 20% by weight) was obtained. In addition, when the swelling degree in MEK of the heat extinguishing resin particle was measured by the following method, it was 1.05 times.

[Swelling degree measurement]
Weigh 1 g of heat extinguishing resin particles into a centrifuge tube and add 30 g of MEK. After standing for 24 hours, the particles were settled by centrifugation and the supernatant solvent was discarded. The weight of the swollen heat extinguishing resin particles was weighed, and the degree of swelling was determined by the following formula (2).
Swelling degree (times) = (weight of swollen heat extinguishing resin particle / weight of heat extinguishing resin particle added first) (2)

(Preparation of dye-sensitized solar cell photoelectrode)
MEK dispersion of 20 parts by weight of titanium oxide powder (primary crystal particle diameter 15 nm), 10 parts by weight of ethyl cellulose (manufactured by Wako Pure Chemical Industries, EC100), 70 parts by weight of terpineol, and the resulting heat extinguishing resin particles ( After mixing 15 parts by weight of a resin solid content concentration of 20% by weight, the pressure was reduced to evaporate MEK. Furthermore, the titanium oxide paste was prepared by mixing uniformly using 3 rolls.

Thereafter, the obtained titanium oxide paste was applied to a glass substrate laminated with FTO by a screen printing method. Subsequently, after drying at 150 degreeC for 30 minutes, the porous metal oxide semiconductor layer which consists of titanium oxide was produced by baking at 500 degreeC for 30 minutes (film thickness: 5 micrometers). Furthermore, by immersing the glass substrate on which the porous metal oxide semiconductor layer is formed in a 0.3 mM ruthenium dye solution at 25 ° C. for 1 day, the sensitizing dye is adsorbed, washed, and dried. A photoelectrode for a dye-sensitized solar cell was produced.

(Example 2)
(Preparation of heat extinguishing resin particles)
As a monomer component, 5 g of trimethylpropane trimethacrylate, 95 g of methyl methacrylate and 1 g of isobutyronitrile as a polymerization initiator were stirred and mixed to prepare a monomer solution. The total amount of the monomer solution obtained was added to 900 parts by weight of an aqueous solution of 1% by weight of polyvinyl alcohol (PVA) and 0.02% by weight of sodium nitrite, and stirred for 1 minute at 10,000 rpm using a homogenizer, emulsified suspension A liquid was obtained.

Next, using a 2 liter polymerization vessel equipped with a stirrer, jacket, reflux condenser and thermometer, the inside of the polymerization vessel was depressurized, the vessel was deoxygenated, and then the pressure was returned to atmospheric pressure with nitrogen gas. The inside of the polymerization vessel was set to a nitrogen atmosphere. The entire amount of the resulting emulsified suspension was charged all at once into the polymerization vessel, and the polymerization was started by raising the temperature of the polymerization vessel to 60 ° C. After polymerization for 4 hours, the polymerization vessel was cooled to room temperature to obtain an emulsion of heat extinguishing resin particles.

It was 1340 nm when the average particle diameter of the obtained heat extinction resin particle was measured. Moreover, when the obtained heat extinction resin particle emulsion was diluted with ethanol and the zeta potential was measured, it was -28 mV.
Furthermore, after the resin particles were settled by using a centrifugal separator, the obtained heat extinguishing resin particle emulsion was replaced with ethanol, and an ethanol dispersion of the heat extinguishing resin particles (resin solid content concentration 20 wt. %). In addition, when the swelling degree (in ethanol) of the heat extinguishing resin particles was measured, it was 1.06 times.

(Preparation of dye-sensitized solar cell photoelectrode)
A porous metal oxide semiconductor layer (film thickness: 5 μm) and dye sensitization were obtained in the same manner as in Example 1 except that the obtained ethanol dispersion of the heat extinguishing resin particles (resin solid content concentration 20% by weight) was used. A photoelectrode for a solar cell was produced.

(Example 3)
In Example 1 (preparation of photoelectrode for dye-sensitized solar cell), 20 parts by weight of titanium oxide powder (primary crystal particle diameter: 15 nm), 10 parts by weight of ethyl cellulose (Wako Pure Chemical Industries, EC100), terpineol 70 The porous metal oxide semiconductor layer (film) was the same as in Example 1 except that 80 parts by weight of MEK dispersion of heat extinguishing resin particles (resin solid concentration 20% by weight) was added to parts by weight. (Thickness: 5 μm) and a dye-sensitized solar cell photoelectrode.

Example 4
In Example 1 (preparation of photoelectrode for dye-sensitized solar cell), 20 parts by weight of titanium oxide powder (primary crystal particle diameter: 15 nm), 10 parts by weight of ethyl cellulose (Wako Pure Chemical Industries, EC100), terpineol 70 The porous metal oxide semiconductor layer (film) was the same as in Example 1 except that 8 parts by weight of MEK dispersion (resin solid content concentration 20% by weight) of heat extinguishing resin particles was added to parts by weight. (Thickness: 5 μm) and a dye-sensitized solar cell photoelectrode.

(Example 5)
In Example 1 (Preparation of photoelectrode for dye-sensitized solar cell), 20 parts by weight of zinc oxide powder (primary crystal particle diameter 12 nm) instead of 20 parts by weight of titanium oxide powder (primary crystal particle diameter 15 nm) A porous metal oxide semiconductor layer (film thickness: 7 μm) and a dye-sensitized solar cell photoelectrode were prepared in the same manner as in Example 1 except that was used.

(Comparative Example 1)
Polystyrene powder was used as the heat extinguishing resin particles.
With respect to this polystyrene powder, 100 randomly extracted particle diameters were measured, and the average particle diameter was determined to be 510 nm. Moreover, when this polystyrene powder was diluted with ethanol, a part of the polystyrene powder remained agglomerated. Furthermore, when the zeta potential of the ethanol suspension of this polystyrene powder was measured using a dynamic light scatterometer, it was -1 mV.

(Preparation of dye-sensitized solar cell photoelectrode)
After mixing 20 parts by weight of titanium oxide powder (primary crystal particle diameter 15 nm), 10 parts by weight of ethyl cellulose (Wako Pure Chemical Industries, EC100), 70 parts by weight of terpineol, and 3 parts by weight of polystyrene powder while defoaming. Further, a titanium oxide paste was prepared by uniformly mixing using three rolls. Thereafter, a porous metal oxide semiconductor layer (film thickness: 6 μm) and a dye-sensitized solar cell photoelectrode were prepared in the same procedure as in Example 1.

(Comparative Example 2)
A porous metal oxide semiconductor was prepared in the same manner as in Comparative Example 1 except that the amount of polystyrene powder added was changed from 3 parts by weight to 6 parts by weight in (preparation of dye-sensitized solar cell photoelectrode) in Comparative Example 1. A layer (film thickness: 6 μm) and a dye-sensitized solar cell photoelectrode were prepared.

(Comparative Example 3)
(Preparation of heat extinguishing resin particles)
In Example 2 (Preparation of heat-extinguishing resin particles), the heat-extinguishing resin particles were prepared in the same manner as in Example 2 except that the number of rotations of the homogenizer when preparing the emulsion suspension was changed from 10,000 rpm to 1000 rpm. Produced.
In addition, it was 5660 nm when the average particle diameter of the obtained heat extinction resin particle was measured. Moreover, when the obtained heat extinction resin particle emulsion was diluted with ethanol and the zeta potential was measured, it was -29 mV.
Furthermore, after the resin particles were settled by using a centrifugal separator, the obtained heat extinguishing resin particle emulsion was replaced with ethanol, and an ethanol dispersion of the heat extinguishing resin particles (resin solid content concentration 20 wt. %). In addition, when the swelling degree (in MEK) of the heat extinguishing resin particle was measured, it was 1.05 times.

(Preparation of dye-sensitized solar cell photoelectrode)
A porous metal oxide semiconductor layer (film thickness: 5 μm) and dye-sensitized solar were obtained in the same manner as in Example 1 using the obtained ethanol dispersion of the heat extinguishing resin particles (resin solid concentration 20 wt%). A photoelectrode for a battery was produced.

(Comparative Example 4)
In Example 1 (preparation of photoelectrode for dye-sensitized solar cell), the amount of addition of MEK dispersion (resin solid content concentration 20% by weight) of the heat extinguishing resin particles obtained was 15 to 200 parts by weight. A porous metal oxide semiconductor layer (film thickness: 5 μm) and a photoelectrode for dye-sensitized solar cell were prepared in the same manner as in Example 1 except for changing to

(Comparative Example 5)
In Example 1 (Preparation of photoelectrode for dye-sensitized solar cell), except that 15 parts by weight of MEK dispersion (resin solid content concentration: 20% by weight) of the obtained heat extinguishing resin particles was not added. In the same manner as in Example 1, a porous metal oxide semiconductor layer (film thickness: 5 μm) and a dye-sensitized solar cell photoelectrode were prepared.

(Comparative Example 6)
In Example 5 (Preparation of photoelectrode for dye-sensitized solar cell), except that 15 parts by weight of MEK dispersion (resin solid content concentration: 20% by weight) of the obtained heat extinguishing resin particles was not added. In the same manner as in Example 1, a porous metal oxide semiconductor layer (film thickness: 7 μm) and a dye-sensitized solar cell photoelectrode were prepared.

<Evaluation>
The following evaluation was performed about the porous metal oxide semiconductor layer and dye-sensitized solar cell photoelectrode obtained in Examples and Comparative Examples. The results are shown in Table 1.

(1) Porosity, average short diameter of pores, ratio measurement of pores forming continuous pores (1-1) Porosity After peeling the obtained porous metal oxide semiconductor layer from the substrate, pores The porosity was measured using a distribution measuring device (manufactured by Shimadzu Corporation, “ASAP 2020”).

(1-2) Average short diameter of pores and Cv value With respect to the obtained porous metal oxide semiconductor layer, a cut surface in the thickness direction was photographed using SEM, and 100 pores were obtained from the obtained photograph. Were extracted at random, the minor axis of the pores was measured, and the average value was taken as the average minor axis of the pores. Further, the Cv value was calculated from the average minor axis and the standard deviation by the above formula (1).
In addition, the SEM photograph which image | photographed the cut surface of the thickness direction of the porous metal oxide semiconductor layer of the photoelectrode for dye-sensitized solar cells obtained in Example 1 is shown in FIG. The SEM photograph which image | photographed the cut surface of the thickness direction of the porous metal oxide semiconductor layer of the photoelectrode for solar sensitive cells was shown in FIG.

(1-3) Percentage of pores forming continuous pores With respect to the obtained porous metal oxide semiconductor layer, a cut surface in the thickness direction was photographed using SEM, and 100 pores were obtained from the obtained photograph. Are extracted at random, and the number of holes in which two or more of the holes are connected to form a continuous hole is examined, and the number of holes related to the connection is counted. ) To calculate the “ratio of holes forming continuous holes”.
Percentage of pores forming continuous pores (%) = (number of pores involved in connection / 100) × 100 (3)

(2) Residual carbon amount The obtained porous metal oxide semiconductor layer was held at 400 ° C. for 120 minutes under a flow of 100 ml / min of air by a thermogravimetry apparatus (TG), and the weight reduction rate (%) was measured. . The weight reduction rate due to combustion oxidation was defined as the residual carbon amount.

(3) Strength (presence / absence of cracks)
About the surface of the obtained porous metal oxide semiconductor layer, it image | photographed using SEM and observed the acquired photograph, and it was confirmed whether the crack has generate | occur | produced in arbitrary 1000 micrometers square area | regions.

(4) Light confinement effect The total light transmittance of the porous metal oxide semiconductor layer prepared on the glass substrate was measured, and the value (absorbance) subtracted from 100% was defined as the light confinement effect.

(5) Evaluation of dye-sensitized solar cell Photoelectrode for dye-sensitized solar cell from which an electrolyte comprising 0.4 M TPAI (tetrapropylammonium iodide), 0.05 M I ₂ and methoxypropionitrile was obtained The porous metal oxide semiconductor layer was formed. Furthermore, after fixing an opposing electrode so that it might overlap with the photoelectrode for dye-sensitized solar cells through electrolyte, the side surface was sealed with the epoxy-type adhesive agent, and the dye-sensitized solar cell was produced.

About the obtained dye-sensitized solar cell, the current-voltage characteristic was measured. Specifically, A.I. Using pseudo sunlight of M1.5 and 100 mW / cm ² , open circuit voltage (Voc), short circuit current (Jsc), fill factor (FF), and photoelectric conversion efficiency (Eff) were measured.
In addition, about the dye-sensitized solar cell photoelectrode obtained by the comparative example 2 and the comparative example 4, the crack which arose in the electrode was large and the electric current value was not measured.

ADVANTAGE OF THE INVENTION According to this invention, the manufacturing method of the photoelectrode for dye-sensitized solar cells which can implement | achieve high photoelectric exchange efficiency, and this photoelectrode for dye-sensitized solar cells can be provided.

Claims (6)

A photoelectrode for a dye-sensitized solar cell having a porous metal oxide semiconductor layer and a sensitizing dye adsorbed on the porous metal oxide semiconductor layer,
The porous metal oxide semiconductor layer has a porosity of 40 to 90% by volume, an average minor axis of pores of 100 to 3000 nm, and a ratio of pores adjacently forming continuous pores. A photoelectrode for a dye-sensitized solar cell, wherein the photoelectrode is 10% or less. 2. The dye-sensitized solar cell photoelectrode according to claim 1, wherein the pores of the porous metal oxide semiconductor layer are obtained by the disappearance of the heat extinguishing resin particles. 3. The dye-sensitized solar cell photoelectrode according to claim 1, wherein the pores of the porous metal oxide semiconductor layer have a minor axis Cv value of 30% or less. The porous metal oxide semiconductor layer is made of silicon oxide, titanium oxide, tin oxide, zinc oxide, zirconium oxide, strontium oxide, niobium oxide, cerium oxide, tungsten oxide, aluminum oxide, indium oxide, gallium oxide and yttrium oxide. 4. The dye-sensitized solar cell photoelectrode according to claim 1, wherein the photoelectrode is made of at least one kind of metal oxide selected from the above or a composite oxide containing the metal oxide. A method for producing a photoelectrode for a dye-sensitized solar cell according to claim 1, 2, 3, or 4,
Preparing a metal oxide semiconductor paste containing metal oxide semiconductor particles, heat extinguishing resin particles and an organic solvent;
Applying the metal oxide semiconductor paste;
Forming the porous metal oxide semiconductor layer by drying and baking the metal oxide semiconductor paste; and
Having a step of adsorbing a sensitizing dye to the porous metal oxide semiconductor layer,
The metal oxide semiconductor particles have a primary crystal particle size of 100 nm or less,
The heat extinguishing resin particles have an absolute value of zeta potential measured in a solvent having an SP value of 9 (cal / cm) ^1/2 or more, an average particle diameter of 100 to 3000 nm, and The method for producing a dye-sensitized solar cell photoelectrode, wherein an amount of the heat extinguishing resin particles added to the metal oxide semiconductor particles is 5 to 100% by weight. 6. The step of preparing a metal oxide semiconductor paste, wherein the heat extinguishing resin particles are added in a state of being dispersed in a solvent having an SP value of 9 (cal / cm) ^1/2 or more. A method for producing a photoelectrode for a dye-sensitized solar cell.