KR101065385B1 - Electrode substrate, manufacturing method thereof and photoelectric conversion element comprising the same - Google Patents

Abstract

Provided is an electrode substrate for a photoelectric conversion element including a current collecting electrode provided on a transparent conductive substrate and a coating layer covering a surface of the current collecting electrode. The coating layer is formed by coating and baking a glass paste composition on the surface of the current collecting electrode, and when the thickness of the coating layer is a μm and the maximum length of pores generated in the coating layer by the firing is b μm, b ≦ 0.5a is satisfied.

Description

Electrode substrate, manufacturing method thereof, and photoelectric conversion element including the same TECHNICAL FIELD [0001] AND PHOTOELECTRIC CONVERSION DEVICE INCLUDING THE SAME}

The present disclosure relates to an electrode substrate, a method of manufacturing the same, and a photoelectric conversion element including the same.

In recent years, research and development of photoelectric conversion elements, such as solar cells which convert light energy into electrical energy, have been actively performed as clean energy having a small environmental load.

Examples of the solar cell include silicon-based solar cells such as monocrystalline silicon solar cells, polycrystalline silicon solar cells, and amorphous silicon solar cells, and compound semiconductor solar cells using compound semiconductors such as cadmium telluride or indium copper selenide instead of silicon. It is targeted for research and development.

However, in order to spread such solar cells, it is necessary to overcome problems such as high production costs, difficulty in securing raw materials, and long energy recovery time.

On the other hand, many solar cells using organic materials aiming at large area and low price of devices have been proposed so far, but there is a problem of low conversion efficiency and low durability.

In such a situation, the dye-sensitized solar cell using the semiconductor porous body sensitized with the dye is developed (for example, refer nonpatent literature 1, patent document 1).

As a dye-sensitized solar cell, what is currently the subject of research and development is what is called a grazel cell which fixed the pigment | dye on the surface of the porous titanium oxide thin film.

A grachel battery is a dye-sensitized photoelectric conversion battery in which a porous titanium oxide thin film layer spectrally sensitized with a ruthenium complex dye is used as a working electrode, and an electrolyte layer and a counter electrode mainly composed of urea are stacked thereon.

The first advantage of the Gratzel battery is that it is possible to provide an inexpensive photoelectric conversion element because of the use of an inexpensive oxide semiconductor such as titanium oxide, and the second advantage is that the ruthenium complex dyes available can absorb a wide range of visible light. In other words, relatively high conversion efficiency can be obtained.

In addition, in such a dye-sensitized solar cell, conversion efficiency exceeding 12% has also been reported recently, and sufficient practicality is ensured even when compared with a silicon-based solar cell.

In general, however, when a large area of a photoelectric conversion element such as a solar cell is increased, the generated current is converted into Joule heat in a relatively low-conductivity substrate such as a transparent electrode, thereby reducing the photoelectric conversion efficiency. Occurs.

In order to solve this problem, attempts have been made in various solar cells to reduce the loss of electrical energy by forming a highly conductive metal wiring such as silver or copper in a grid and having a collecting electrode (grid electrode). have.

However, when such a collector electrode is provided in a dye-sensitized solar cell, it is necessary to prevent the formed collector electrode from being corroded by the electrolyte solution containing urea.

From such a viewpoint, after forming a collector electrode, the technique of covering or protecting the circumference | surroundings of a collector electrode with the glass material of low melting point is proposed (for example, refer patent document 2 and patent document 3).

Further, a plurality of coating layers covering the current collecting electrodes may be configured (for example, refer to Patent Document 4), or the current collecting electrodes themselves may be made of a material having excellent electrolyte resistance without forming a coating layer (for example, Patent Document 5). A technique is also proposed.

Moreover, the technique which prevents a crack from generate | occur | producing in a coating layer is proposed by using the material with which the difference of the linear expansion coefficient with a board | substrate is small as a glass material which forms the coating layer which coats a collector electrode (for example, patent) See Document 6).

However, in the technique of patent documents 2 and 3, sufficient electrolyte resistance may not be obtained in some cases.

In the technique described in Patent Literature 4, there was a problem in which the structure of the solar cell became complicated. In the technique described in Patent Literature 5, the material having excellent electrolyte resistance had a high resistance, which caused a problem of deteriorating the characteristics of the solar cell.

Moreover, in the technique of patent document 6, the stress may generate | occur | produce in a coating layer after baking of the glass material used for a coating layer, and the crack may generate | occur | produce.

As described above, the conventional technique could not effectively prevent the occurrence of cracks in the coating layer.

Patent Document 1: US Patent No. 4927721

Patent Document 2: Japanese Patent Laid-Open No. 2004-164970

Patent Document 3: Japanese Patent Laid-Open No. 2006-261090

Patent Document 4: Japanese Unexamined Patent Publication No. 2006-261089

Patent Document 5: Japanese Unexamined Patent Publication No. 2008-117782

Patent Document 6: Japanese Unexamined Patent Publication No. 2008-177022

[Non-Patent Document 1] Michael Gratzel et al., Nature, No. 353, pp. 737-740, 1991

Provided is an electrode substrate for a photoelectric conversion element which can prevent the occurrence of cracks in a coating layer covering a current collecting electrode and ensure sufficient electrolyte resistance.

Provided is a photoelectric conversion element including the electrode substrate for the photoelectric conversion element.

It provides a method for producing the electrode substrate.

MEANS TO SOLVE THE PROBLEM As a result of repeating research in order to solve the said subject, when a glass material is used for formation of a coating layer, not only the difference of the linear expansion coefficient of a glass material and a base material but also a glass material arises in the generation of the crack (glass splitting). It was found that the pores generated in the coating layer greatly influenced upon firing.

In other words, depending on the size of the pores present in the coating layer after firing of the glass material, cracks may occur in the coating layer during the production of photoelectric conversion elements such as solar cells starting from such pores.

As a result of this study, the present inventors found that by controlling the size of pores generated in the coating layer at the time of firing the glass material, it is possible to prevent the occurrence of cracks in the coating layer, thus completing the present invention.

According to an aspect of the present invention there is provided an electrode substrate for a photoelectric conversion element comprising a current collecting electrode provided on a transparent conductive substrate and a coating layer covering the surface of the current collecting electrode, the coating layer is a glass paste composition on the surface of the current collecting electrode It is formed by coating and firing. When the thickness of the coating layer is a µm and the maximum length of pores generated in the coating layer by the firing is b µm, b≤0.5a is satisfied.

According to another aspect of the invention there is provided an electrode substrate for a photoelectric conversion element having a current collector electrode provided on the transparent conductive substrate and a coating layer covering the surface of the current collector electrode, the coating layer is a glass paste composition on the surface of the current collector electrode Is formed by coating and firing, and the maximum length of pores generated in the coating layer by the firing is 10 µm or less.

According to another aspect of the invention provides a photoelectric conversion element comprising the electrode substrate.

The photoelectric conversion element may be a dye-sensitized solar cell.

According to another aspect of the invention after applying a glass paste composition comprising a glass frit, a binder resin and an organic solvent on the surface of the current collecting electrode provided on a transparent conductive substrate, the glass paste composition is a softening point of the glass frit ( Softening temperature (Ts) ℃ It provides a method for producing an electrode substrate comprising the step of baking at a temperature of less than the softening point + 40 (Ts + 40) ℃ to cover the surface of the current collecting electrode.

In the method of manufacturing the electrode substrate, before reaching the firing temperature, the method may further include maintaining at least 5 minutes at the temperature of the disappearance temperature (° C) of the binder resin or more below the softening point (Ts) ° C of the glass frit. have.

Other aspects of the present invention are included in the following detailed description.

According to an embodiment of the present invention, in the photoelectric conversion element electrode substrate including a current collecting electrode, a method of manufacturing the same, and the photoelectric conversion element including the photoelectric conversion element electrode substrate, the coating layer by firing the glass paste composition By setting the maximum length of the pores to be less than or equal to half of the thickness of the coating layer or 10 μm or less, it is possible to prevent the occurrence of cracking of the coating layer covering the current collecting electrode and to secure sufficient electrolyte resistance.

Accordingly, high efficiency and long life of the photoelectric conversion element including the electrode substrate can be achieved.

1 is an explanatory view showing the overall configuration of a photoelectric conversion element according to an embodiment of the present invention.
2 is an explanatory diagram schematically showing a state in which a dye is connected to an inorganic metal oxide semiconductor.
3 is an explanatory diagram showing a structure of an electrode substrate according to an embodiment of the present invention.
4A and 4B are explanatory views showing the structure of the coating layer formed on the electrode substrate shown in FIG.
5 is a graph showing the firing profile of the glass paste composition according to an embodiment of the present invention.
6A is a micrograph showing an example of the state of the coating layer after firing.
6B is a micrograph showing an example of the state of the coating layer after firing.
6C is a micrograph showing an example of the state of the coating layer after firing.
6D is a micrograph showing an example of the state of the coating layer after firing.
6E is a micrograph showing an example of the state of the coating layer after firing.
6F is a micrograph showing an example of the state of the coating layer after firing.
Fig. 7A is a micrograph showing an example of the state of the coating layer after firing when no pretreatment step is added.
7B is a micrograph showing an example of the state of the coating layer after firing when a pretreatment step is added.
8A is a micrograph showing an example of a state in which corrosion occurs in the current collecting electrode.
8B is a micrograph showing an example of a state in which corrosion occurs in the current collecting electrode.
9 is a graph showing the relationship between the conversion efficiency η and time of the photoelectric conversion cells according to the Examples and Comparative Examples of the present invention.

EMBODIMENT OF THE INVENTION Hereinafter, preferred embodiment of this invention is described in detail, referring an accompanying drawing.

In addition, in this specification and drawing, the same code | symbol is attached | subjected about the component which has a substantially same functional structure, and duplication description is abbreviate | omitted.

[First Embodiment]

(Overall Configuration of Photoelectric Conversion Element)

First, referring to Figures 1 and 2, the overall configuration of a photoelectric conversion device according to an embodiment of the present invention will be described.

1 is an explanatory diagram showing an overall configuration of a photoelectric conversion element 1 according to an embodiment of the present invention.

2 is an explanatory diagram schematically showing a state in which a dye is connected to an inorganic metal oxide semiconductor.

In addition, below, the dye-sensitized solar cell containing the grachel cell as shown in FIG. 1 as a photoelectric conversion element 1 is demonstrated as an example.

As shown in FIG. 1, a photoelectric conversion element 1 according to an exemplary embodiment of the present invention includes two substrates 2, two electrode substrates 10, a photoelectrode 3, a counter electrode 4, Electrolyte solution 5, spacer 6, and lead wire 7;

<About board>

The two substrates 2 are arranged to face each other at predetermined intervals.

The material of the substrate 2 is not particularly limited as long as it is a transparent material having a low light absorption from the visible light region of the light (sunlight, etc.) outside the photoelectric conversion element 1 to the near infrared region.

As a material of the said board | substrate 2, For example, glass base materials, such as quartz, ordinary glass, BK7, and lead glass, polyethylene terephthalate, polyethylene naphthalate, polyimide, polyester, polyethylene, polycarbonate, polyvinyl butyrate Resin substrates such as polypropylene, tetraacetyl cellulose, syndiotactic polystyrene, polyphenylene sulfide, polyarylate, polysulfone, polyester sulfone, polyetherimide, cyclic polyolefin, brominated phenoxy, vinyl chloride, and the like. have.

<About electrode substrate>

The electrode substrate 10 (10A, 10B) is formed on the surface of the board | substrate 2A of the two board | substrates 2 on which the light from the outside at least enters, for example, a transparent conductive oxide (transparent conductive oxide) oxide, TCO) to have a transparent electrode formed into a film. Details of the transparent electrode will be described later.

In order to improve the photoelectric conversion efficiency, the sheet resistance (surface resistance) of the electrode substrate 10 is preferably as low as possible, and specifically, it is preferable that it is 20 kW / cm ² (kW / sq.) Or less.

However, of the two substrates 2, the electrode substrate 10B provided on the surface of the substrate 2B facing the substrate 2A does not necessarily need to be installed, and is transparent even when the electrode substrate 10B is provided. It is not necessary to do (i.e., light absorption is small from the visible light region to the near infrared region of the light outside the photoelectric conversion element 1).

On the other hand, a detailed description of the electrode substrate according to an embodiment of the present invention will be described later.

<About Photoelectrode>

In the photoelectric conversion element 1, the photoelectrode 3 is used as an inorganic metal oxide semiconductor film having a photoelectric conversion function, and is formed of a porous film.

More specifically, as shown in FIG. 1, the photoelectrode 3 has a plurality of fine particles 31 of an inorganic metal oxide semiconductor such as TiO ₂ on the surface of the electrode substrate 10 (hereinafter referred to as “metal oxide fine particles”). (31) &quot;) is a porous body (nanoporous film) including pores in nanometer units in the layer of the metal oxide fine particles 31 thus laminated.

Since the photoelectrode 3 is formed of a porous body including a plurality of small pores as described above, the surface area of the photoelectrode 3 can be increased, and a large amount of sensitizing dye 33 is formed on the metal oxide fine particles 31. It can be connected to the surface, thereby the photoelectric conversion element 1 can have a high photoelectric conversion efficiency.

Here, as shown in FIG. 2, in the photoelectrode 3, the sensitizing dye 33 is connected to the surface of the metal oxide fine particles 31 via the connector 35 so that the inorganic metal oxide semiconductor is sensitized. The electrode 3 is obtained.

On the other hand, the term "connection" as used herein means that the inorganic metal oxide semiconductor and the sensitizing dye are chemically bonded or physically bonded (for example, bonded by adsorption or the like).

Therefore, the "linking group" as used herein includes not only chemical functional groups but also anchor groups and adsorber groups.

Although FIG. 2 shows a state in which only one sensitizing dye 33 is connected to the surface of the metal oxide fine particles 31, FIG. 2 is merely shown schematically. In order to improve the electrical output of the photoelectric conversion element 1, The number of sensitizing dyes 33 connected to the surface of the oxide fine particles 31 is as large as possible, and it is preferable that a number of sensitizing dyes 33 cover a wide range of the surface of the metal oxide fine particles 31 as much as possible. Do.

However, when the number of the sensitizing dyes 33 to be coated increases, excitated electrons may recombine due to interaction between adjacent sensitizing dyes 33 and may not be taken out by electric energy. In this case, a co-adsorption material such as deoxycholic acid may be used so that the sensitizing dye 33 can be coated while maintaining a proper distance.

The photoelectrode 3 may be formed by stacking a plurality of metal oxide fine particles 31 having a size of about 20 nm to about 100 nm as the number average particle diameter of the primary particles.

The film thickness of the photoelectrode 3 is preferably in the order of several micrometers (preferably 10 micrometers or less).

When the film thickness of the photoelectrode 3 is thinner than several micrometers, the light which permeate | transmits the photoelectrode 3 increases, the photoexcitation of the sensitizing dye 33 becomes inadequate, and an effective photoelectric conversion efficiency cannot be obtained. have.

On the other hand, if the film thickness of the photoelectrode 3 is thicker than several micrometers, the surface of the photoelectrode 3 (the surface of the side in contact with the electrolyte solution 5) and the electrically conductive surface (photoelectrode 3 and the electrode substrate) Since the distance from the interface (10) is increased, it is difficult for the generated exciton electrons to be effectively transmitted to the electrically conductive surface, so that a good conversion efficiency may not be obtained.

Next, the metal oxide fine particles 31 and the sensitizing dye 33 that can be used for the photoelectrode 3 according to the embodiment of the present invention will be described in detail.

<Metal Oxide Fine Particles>

In general, the inorganic metal oxide semiconductor possesses a photoelectric conversion function with respect to light in a portion of the wavelength region, but by connecting the sensitizing dye 33 to the surface of the metal oxide fine particles 31, the inorganic metal oxide semiconductor has a structure in the range from visible to near infrared rays. Photoelectric conversion is possible with respect to light.

The compound which can be used as the metal oxide fine particles 31 is not particularly limited as long as the photoelectric conversion function is increased or decreased by connecting the sensitizing dye 33, but for example, titanium oxide, tin oxide, tungsten oxide, and oxidation Zinc, indium oxide, niobium oxide, iron oxide, nickel oxide, cobalt oxide, strontium oxide, tantalum oxide, antimony oxide, lanthanum oxide element, yttrium oxide, vanadium oxide and the like.

Here, since the surface of the metal oxide fine particles 31 is sensitized by the sensitizing dye 33, it is preferable that the conduction band of the inorganic metal oxide is present at a position to receive electrons from the photoexcitation trap of the sensitizing dye 33. Do.

As such a compound, titanium oxide, tin oxide, zinc oxide, niobium oxide, or the like is preferable as the compound used as the metal oxide fine particles 31.

Moreover, titanium oxide is more preferable from a viewpoint of price, environmental hygiene, etc.

In addition, in one embodiment of the present invention, as the metal oxide fine particles 31, one of the above-described inorganic metal oxides may be used alone, or a plurality of species may be used in combination.

<About dark blue dye>

The sensitizing dye 33 is not particularly limited as long as the metal oxide fine particles 31 have a photoelectric conversion function with respect to light in a region in which the metal oxide fine particles 31 do not have a photoelectric conversion function (for example, the region from visible light to near infrared light). Examples include azo dyes, quinacridone dyes, diketopyrrolopyrrole dyes, squarylium dyes, cyanine dyes, merocyanine dyes, triphenylmethane dyes, xanthene dyes and porphyrin dyes. Dyes, chlorophyll dyes, ruthenium complex dyes, indigo dyes, perylene dyes, dioxadine dyes, anthraquinone dyes, phthalocyanine dyes, naphthalocyanine dyes and derivatives thereof.

The sensitizing dye 33 includes a functional group capable of connecting to the surface of the metal oxide fine particles 31 as the linking group 35 in its structure so that the excited electrons of the photoexcited dye can be quickly transferred to the conduction band of the inorganic metal oxide. It is desirable to do it.

The functional group is not particularly limited as long as it is a substituent having a function of connecting the sensitizing dye 33 to the surface of the metal oxide fine particles 31 and rapidly transferring excitation electrons of the dye to the conduction band of the inorganic metal oxide. , Carboxyl group, hydroxy group, hydroxamic acid group, sulfonic acid group, phosphonic acid group, phosphinic acid group and the like.

<About the electrode>

The counter electrode 4 functions as an anode of the photoelectric conversion element 1, and an electrode substrate is formed on the surface of the substrate 2 facing the substrate 2 on which the electrode substrate 10 is provided, of the two substrates 2. It is formed opposite to 10 and is formed of a film.

In other words, in the region surrounded by the two electrode substrates 10 and the spacers 6, the counter electrode 4 is provided on the surface of the electrode substrate 10 so as to face the photoelectrode 3.

On the surface of the counter electrode 4 (the side opposite to the photoelectrode 3), a metal catalyst layer possessing conductivity is provided.

Examples of the conductive material that can be used for the metal catalyst layer of the counter electrode 4 include metals (platinum, gold, silver, copper, aluminum, rhodium, indium, etc.), metal oxides (indium tin oxide (ITO), and oxidation). Tin (including those doped with fluorine, etc.), zinc oxide, and the like), conductive carbon materials or conductive organic materials, and the like.

On the other hand, the film thickness of the counter electrode 4 is not particularly limited, but is preferably about 5 nm to about 10 mu m, for example.

On the other hand, the lead conductor 7 is connected to the electrode substrate 10A and the counter electrode 4 on the side where the photoelectrode 3 is provided, so that the lead conductor 7 from the electrode substrate 10A is opposite to the lead conductor 7. The lead wire 7 from the electrode 4 is connected outside the photoelectric conversion element 1 to form a current circuit.

In addition, the electrode substrate 10A and the counter electrode 4 can be separated by the spacer 6 at predetermined intervals.

The spacer 6 is formed along the outer edges of the electrode substrate 10A and the counter electrode 4, and may serve to seal a space between the electrode substrate 10A and the counter electrode 4.

It is preferable to use resin with high sealing property and corrosion resistance as said spacer 6, For example, the thermoplastic resin, photocurable resin, ionomer resin, glass frit, etc. which were formed in the film form can be used.

As ionomer resin, Himiran (brand name) made from Mitsui Dupont Polychemical, etc. are mentioned, for example.

<About electrolyte solution>

In addition, the electrolyte solution 5 is put in the space between the electrode substrate 10A and the counter electrode 4 and sealed by the spacer 6.

The electrolyte solution 5 contains, for example, an electrolyte, a medium and an additive.

Here, the electrolyte as I ₃ ^- / I ^- based, Br ₃ ^- / Br ^- can be used for such a redox electrolyte such as type, specific examples, I ₂ and iodide (LiI, NaI, KI, CsI, MgI ₂ , CaI ₂ , CuI, tetraalkylammonium iodide, pyridinium iodide, imidazolium iodide, etc.), mixture of Br ₂ and bromide (LiBr, etc.), organic molten salt compounds, and the like. Although it can use, it is not limited to this.

Here, the organic molten salt compound is a compound composed of an organic cation and an inorganic or organic anion, and means that the melting point is room temperature or less.

Specific examples of the organic cation constituting the organic molten salt compound include aromatic cations such as N-methyl-N'-ethylimidazolium cation and N-methyl-N'-n-propylimidazolium cation. N-alkyl-N'-alkylimidazolium cations such as N-methyl-N'-n-hexyl imidazolium cation; N-alkylpyridinium cations, such as an N-hexyl pyridinium cation and an N-butylpyridinium cation, etc. are mentioned.

As the aliphatic cations, aliphatic cations such as N, N, N-trimethyl-N-propylammonium cation; Cyclic aliphatic cations, such as N, N-methyl pyrrolidinium, etc. are mentioned.

On the other hand, examples of the inorganic or organic anion constituting the organic molten salt compound include halide ions such as chloride ions, bromide ions, and iodide ions; Inorganic anions such as phosphorus hexafluoride ion, boron tetrafluoride ion, trifluoromethane sulfonate salt, perchlorate ion, hypochlorite ion, chlorate ion, sulfate ion and phosphate ion; Amide anions such as bis (trifluoromethylsulfonyl) imide or imide anions.

In addition, as the organic molten salt compound, known compounds such as Inorganic Chemistry, Vol. 35, pages 1168 to 1178, and those described in 1996 can be used.

The above-mentioned iodide, bromide, etc. can be used individually or in combination of multiple types.

Among these, an electrolyte in which a combination of I ₂ and iodide (for example, I ₂ and LiI), pyridinium iodide, imidazolium iodide, and the like is preferably used, is not limited thereto.

The concentration of the electrolyte solution 5 is an I ₂ from about 0.01 M to about 0.5 M, either one or both of iodide and bromide such as (in the case of a plurality of types are a mixture of them) is about 0.1 M to about the medium It is preferable that it is 15M.

As a medium which can be used for the electrolyte solution 5, it is preferable that it is a compound which can express favorable ion conductivity.

Examples of the liquid phase of these media include ether compounds such as dioxane and diethyl ether; Chain ethers such as ethylene glycol dialkyl ether, propylene glycol dialkyl ether, polyethylene glycol dialkyl ether and polypropylene glycol dialkyl ether; Alcohols such as methanol, ethanol, ethylene glycol monoalkyl ether, propylene glycol monoalkyl ether, polyethylene glycol monoalkyl ether and polypropylene glycol monoalkyl ether; Polyhydric alcohols such as ethylene glycol, propylene glycol, polyethylene glycol, polypropylene glycol and glycerin; Nitrile compounds such as acetonitrile, glutarodinitrile, methoxy acetonitrile, propionitrile and benzonitrile; Carbonate compounds such as ethylene carbonate and propylene carbonate; Heterocyclic ring compounds such as 3-methyl-2-oxazolidinone; Aprotic polar substances such as dimethyl sulfoxide and sulfolane; Water and the like can be used.

These may be used independently or may be used in combination of multiple types.

In order to use the medium of a solid form (including gel type), a polymer may be put in a liquid medium.

In this case, a polymer such as polyacrylonitrile or polyvinylidene fluoride may be added to the liquid medium, or the polyfunctional monomer containing an ethylenically unsaturated group may be polymerized in the liquid medium to use the medium as a solid.

As a medium usable in the electrolyte solution 5, an organic-inorganic ion band (also referred to as an "ionic liquid") that becomes a liquid at room temperature may be used.

When an ionic liquid is used as the medium used for the electrolyte solution 5, evaporation of the electrolyte solution 5 can be suppressed, so that the durability of the photoelectric conversion element 1 can be improved.

On the other hand, as the electrolyte solution 5, CuI, CuSCN (these compounds are p-type semiconductors that do not require a liquid medium and act as an electrolyte) or the like, and Nature, 395, pages 583 to 585 (1998). October 8,） hole transport materials such as 2,2 ', 7,7'-tetrakis (N, N-di-p-methoxyphenylamine) -9,9'-spirobifluorene You can also use

Various additives may be further added to the electrolyte solution 5 in order to improve durability and electrical output of the photoelectric conversion element 1.

For example, inorganic salts, such as magnesium iodide, can be added for durability improvement, and amines, such as t-butyl pyridine, 2-picolin, 2,6- lutidine, for an electric output improvement; Steroids such as deoxycholic acid; Monosaccharides such as glucose, glucosamine and glucuronic acid, and sugar alcohols thereof; Disaccharides such as maltose; Linear oligosaccharides such as raffinose; Cyclic oligosaccharides such as cyclodextrin; Hydrolyzed oligosaccharides, such as lacto oligosaccharide, etc. can also be added.

Moreover, the thickness of the layer in which the electrolyte solution 5 is enclosed and sealed is not specifically limited, It is preferable to set it as the thickness which does not directly contact the counter electrode 4 and the photoelectrode 3 which the pigment | dye adsorb | sucked. Do.

Specifically, the thickness is preferably about 0.1 μm to about 100 μm.

<Working principle of photoelectric conversion element>

In the photoelectrode 3 including the metal oxide fine particles 31 and the sensitizing dye 33 connected to the surface of the metal oxide fine particles 31 via a connector 35, as shown in FIG. When light comes into contact with the sensitizing dye 33 connected to the surface of the oxide fine particles 31, the sensitizing dye 33 is brought into an excited state, and the sensitizing dye 33 emits photoexcited excitation electrons.

The released excitation electrons are transferred to the conduction band of the metal oxide fine particles 31 through the connector 35.

The excitation electrons that reach the metal oxide fine particles 31 are transferred to the other metal oxide fine particles 31 to reach the electrode substrate 10, and flow out to the outside of the photoelectric conversion element 1 through the lead conductor 7.

On the other hand, the sensitizing dye 33 which emits excitation electrons and becomes in an electron deficient state receives electrons supplied from the counter electrode 4 through an electrolyte such as I ⁻ / I ₃ ^{− in the} electrolyte solution 5, Return to the electrically neutral state.

(About the structure of the electrode substrate 10)

As mentioned above, although the whole structure of the photoelectric conversion element 1 which concerns on one Embodiment of this invention was demonstrated, next, referring to FIG. 3, FIG. 4A and FIG. 4B, the electrode substrate 10 which concerns on one Embodiment of this invention. The configuration of will be described in detail.

3 is an explanatory view showing the structure of an electrode substrate 10 according to an embodiment of the present invention.

4A and 4B are explanatory views showing the structure of the coating layer provided on the electrode substrate 10 shown in FIG.

As shown in FIG. 3, an electrode substrate 10 according to an embodiment of the present invention may be a transparent electrode 110, a current collecting electrode 120, and an example of the transparent conductive substrate according to an embodiment of the present invention. The coating layer 130 is included.

The transparent electrode 110 is formed of a film using, for example, a transparent conductive oxide (TCO).

The transparent conductive oxide is not particularly limited as long as it is a conductive material having low light absorption from the visible light region of the light outside the photoelectric conversion element 1 to the near infrared region, but is indium tin oxide (ITO) or tin oxide (SnO). ₂ ), metal oxides having good conductivity such as tin oxide (FTO) doped with fluorine or the like, antimony-containing tin oxide (ITO / ATO), zinc oxide (ZnO ₂ ), and the like are preferable.

The collecting electrode 120 transfers the excitation electrons reaching the electrode substrate 10 through the metal oxide fine particles 31 to the lead conductor 7, and thus, the metal wiring installed on the surface of the electrode substrate 10. to be.

The current collecting electrode 120 generally has a high sheet resistance of the electrode substrate 10 (about 10? / Sq or more), and thus the generated current is converted into joule heat among relatively low conductivity substrates such as the transparent electrode 110. In order to prevent the phenomenon that the photoelectric conversion efficiency is lowered, it is provided.

In this respect, since the current collecting electrode 120 is electrically connected to the electrode substrate 10, the material for forming the current collecting electrode 120 may be Ag, Ag / Pd, Cu, Au, Ni, Ti, Co, Cr, Highly conductive metals or alloys such as Al are preferred.

The wiring pattern of the current collecting electrode 120 is not particularly limited as long as it can reduce the loss of electrical energy. The wiring pattern can be formed in any shape such as a lattice shape, a stripe shape, a rectangle, and a comb shape.

Here, since the current collecting electrode 120 is formed of a metal such as Ag, Ag / Pd, Cu, Au, Ni, Ti, Co, Cr, Al, or the like, iodine (I ⁻ / I ₃ ⁻⁾ And the like may be corroded by the electrolyte solution 5 containing the same).

For this reason, the photoelectric conversion element 1 according to the embodiment of the present invention includes the coating layer 130 described below.

The coating layer 130 serves to prevent or suppress corrosion by the electrolyte solution 5 of the current collecting electrode 120. The coating layer 130 covers the periphery of the current collecting electrode 120 to cover the current collecting electrode 120 with the electrolyte solution 5. It is a layer which protects from corrosion by), and is obtained by apply | coating and baking a low melting glass paste composition on the surface of the collector electrode 120.

The glass paste composition which can be used for the said coating layer 130 is a paste-type composition containing glass frit, binder resin, a solvent, an additive, etc.

Hereinafter, each component of a glass paste composition is demonstrated.

As the glass frit used in the glass paste composition according to the embodiment of the present invention, other metal oxides are basically used in the SiO ₂ skeleton, the B ₂ O ₃ skeleton, or the P ₂ O ₅ skeleton for control of melting point and chemical stability. Those contained can be used, for example, SiO ₂ -Bi ₂ O ₃ -MO _X system, B ₂ O ₃ -Bi ₂ O ₃ -MO _X system, SiO ₂ -CaO-Na (K) ₂ O-MO based, P ₂ O ₅ -MgO-based _X MO (M is at least one metal element) can be used in combination of a low melting point glass alone or in combination of two or more of such.

As a binder resin used for the glass paste composition which concerns on one Embodiment of this invention, what burns completely at 600 degrees C or less and does not leave a residue can be used, A specific example is ethyl cellulose (EC) resin.

Moreover, as another example of the binder resin used for a glass paste composition, polyvinyl alcohol, polyethyleneglycol, an acrylic resin, methacryl resin, etc. are mentioned.

The solvent used for the glass paste composition which concerns on one Embodiment of this invention is not specifically limited.

However, when considering the manufacturing process of the photoelectric conversion element 1, when drying speed is too fast, it will not dry because it will dry during manufacture, precipitation of solid content, etc. will not be preferable.

From this point of view, as the solvent used in the glass paste composition according to the embodiment of the present invention, a solvent having a boiling point of about 150 ° C. or higher, more preferably about 180 ° C. or higher is preferable, and as such a solvent, for example, a terpene-based A solvent (terpineol etc.), a galbitol type solvent (butyl carbitol, butyl carbitol acetate), etc. can be used.

In the glass paste composition according to the embodiment of the present invention, additives may be added as necessary to improve the dispersibility of the glass frit or resin, or to adjust the rheology.

Such additives include, for example, polymers added for adjustment of a viscosity suitable for a process such as screen printing or improvement of dispersibility of glass frit, thickeners added for rheology adjustment, and production of a glass paste composition having good dispersibility. The dispersing agent etc. which are added are mentioned.

As a polymer, polyvinyl alcohol, polyethylene glycol, ethyl cellulose (EC), an acrylic resin, methacryl resin, etc. are mentioned, for example.

As a thickener, cellulose resins, such as ethyl cellulose, polyoxyalkylene resins, such as polyethylene glycol, etc. are mentioned, for example.

Examples of the dispersant include acids such as nitric acid, acetyl acetone, polyethylene glycol, Triton X-100, and the like.

Meanwhile, as in the electrode substrate 10 according to the exemplary embodiment of the present invention, when the coating layer 130 covering the current collecting electrode 120 is formed by firing the low melting glass paste composition, the glass layer may be formed in the glass paste composition upon firing. The binder resin remains, and the remaining binder resin is burned at the time of firing to become a gas in the coating layer 130, and as shown in Figs. 4A and 4B, this gas forms the coating layer (the pores 131). 130)

As the pores 131, as shown in Fig. 4A, pores 131a having a large size as a result of the generation of gas having a large volume, pores 131b having a plurality of pores of a small size aggregated to a large size, and small There exist various sizes and shapes, such as size pores 131c.

As a result of the present inventors examining the relationship between the structure of the coating layer 130 and the electrolyte resistance, it has been found that the size of the pores 131 existing in the coating layer 130 after firing greatly affects the electrolyte resistance. .

In other words, as shown in FIG. 4A, when large size pores (131a, 13lb, etc.) exist in the coating layer 130, cracks may occur in the coating layer 130 starting from the pores (131a, 13lb, etc.). It has been found that the electrolyte solution 5 is easily brought into contact with the current collecting electrode 120 through the pores 131a, 13lb, and the like, and as a result, the current collecting electrode 120 is corroded.

Therefore, in the photoelectric conversion element 1 according to the exemplary embodiment of the present invention, as shown in FIG. 4B, the thickness of the coating layer 130 is a μm and the maximum length of the pores 131 existing in the coating layer 130. If b is µm, control is performed to satisfy b≤0.5a.

When b μm, the maximum length of the pores 131, is b> 0.5a, cracks tend to occur in the coating layer 130, or the electrolyte solution 5 collects the electrode 120 through the pores 131a, 13lb, and the like. May corrode.

From the viewpoint of more effectively preventing the occurrence of cracks and intrusion from the pores (131a, 13lb, etc.) of the electrolyte solution 5, it is more preferable that the maximum length of the pores 131 satisfies b ≦ 0.3a. Do.

On the other hand, the maximum length of the pore 131 is smaller than the thickness of the coating layer 130, so the lower limit value of the maximum length of the pore 131 is not particularly necessary, but can be controlled in practice. As a lower limit of b micrometer which is the maximum length of the pore 131, it becomes about b≥0.01a.

Here, the maximum length of the pores 131 in the embodiment of the present invention is a cross section of the pores 131 when the coating layer 130 is cut in a plane parallel or perpendicular to the transparent electrode 110. The length of the largest part of the length, that is, the maximum length of the line segment connecting any two points of the main phase of the cross section of the pore 131 (for example, the diameter when the cross section of the pore 131 is the cause) , When the cross section of the pore 131 is an ellipse, long diameter).

For b, which is the maximum length of the pores 131, it is necessary that all the pores 131 present in the coating layer 130 satisfy b≤0.5a.

For example, even if the average value of b, which is the maximum length of the pores 131 present in the coating layer 130, is 0.5a or less, when one or more pores 131 having b> 0.5a exist, such pores 131 are formed. This is because cracks may occur in the coating layer 130 as a starting point.

However, in reality, since it is difficult to measure b, which is the maximum length of all the pores 131 in the coating layer 130, in one embodiment of the present invention, the above conditions are within the range of about 0.2% of the total cross-sectional area of the coating layer. It should be good if we are satisfied.

About b which is the maximum length of the above-mentioned pore 131, it can measure by the following method.

First, the pores 131 are photographed with a metal microscope, and the shape and size of the pores 131 part are observed by displaying an image as an easy-to-observe image such as the shape and size of the pores. An example of a method of displaying the image of the pore shape and the size that is easily observed is to set a specific criterion, and to display in black when the observation target is larger than the criterion, and to display in white when the observation object is smaller than the criterion. It may be, but is not limited thereto. This makes it possible to easily grasp the distribution, shape, size and number of the pores.

On the other hand, the shape and size of the pore 131 portion is automatically measured by using image analysis software such as "GRADING ANALYSIS" manufactured by KEYENCE, thereby observing the shape and size of the pore portion. Easy image can be obtained.

By using such image analysis software, in an image in which the shape and size of the pore portion can be easily observed, the number of pores 131 portions, b, which is the maximum length, and the average value thereof can be measured.

In addition, the thickness of the coating layer 130 can be measured using a surface shape measuring instrument (for example, Dektak150 by Veeco).

The maximum length of the pores 131 as described above can be controlled by firing the glass paste composition applied to the surface of the current collecting electrode 120 under predetermined conditions.

Detailed description of the firing conditions will be described later.

(About the manufacturing method of a photoelectric conversion element)

In the above, the structure of the photoelectric conversion element 1 which concerns on one Embodiment of this invention was demonstrated in detail.

Next, the manufacturing method of the photoelectric conversion element 1 which concerns on one Embodiment of this invention which has the above-mentioned structure is demonstrated in detail.

<Production of Anode>

First, tin oxide (FTO) doped with indium tin oxide (ITO), tin oxide (SnO ₂ ), fluorine, etc., antimony-containing tin oxide (ITO / ATO), zinc oxide (ZnO ₂₎ Transparent conductive oxide (TCO), such as), is applied by a sputtering method or the like to form a transparent electrode 110.

Subsequently, the paste composition including highly conductive metals such as Ag, Ag / Pd, Cu, Au, Ni, Ti, Co, Cr, Al, alloys, resins, solvents, and the like on the transparent electrode 110 may have a photoelectric conversion efficiency. The coating is performed so as to have the best structure (for example, a comb shape).

It does not specifically limit as a coating method of the said metal or alloy, For example, screen printing, application | coating by a dispenser, inkjet printing, a metal mask method, etc. are mentioned.

The dried paste composition is dried at a temperature at which the solvent disappears (about 80 ° C to about 200 ° C), and then the resin is lost and calcined at a temperature at which the metal is sintered (about 400 ° C to about 600 ° C), whereby the current collecting electrode Form 120.

Next, a coating layer 130 covering the surface of the current collecting electrode 120 is formed.

Specifically, the glass frit mentioned above, the binder resin which binds this, and the additive added as needed are disperse | distributed in water or a suitable solvent, and a glass paste composition is manufactured.

Next, the manufactured glass paste composition is apply | coated so that the whole collection electrode 120 may be covered except for the part (drawing part) to which the drawing lead 7 was connected.

As a coating method of the said glass paste composition, screen printing, application | coating by a dispenser, inkjet printing etc. are mentioned, for example.

However, since the coating layer 130 is formed of a material having low conductivity, the glass paste composition may be formed so that the coating layer 130 covers the current collecting electrode 120 sufficiently and at the same time the coating area is as small as possible in order to improve the photoelectric conversion efficiency. It is preferable to apply.

Subsequently, after drying the apply | coated glass paste composition at the temperature (about 80 degreeC-about 200 degreeC) which a solvent lose | disappears, after binder resin disappears and glass frit sinters more than the glass softening point temperature (Ts) of glass frit By firing at a temperature) to form the coating layer 130.

Here, with reference to FIG. 5, the baking method of the glass paste composition in one Embodiment of this invention is demonstrated in detail.

5 is a graph showing an example of a firing profile of the glass paste composition according to the embodiment of the present invention.

As shown in FIG. 5, in the method of manufacturing the photoelectric conversion element 1 according to the exemplary embodiment of the present invention, as described above, b, which is the maximum length of the pores 131, corresponds to the thickness a of the coating layer 130. In order to control so that b <= 0.5a, it is necessary to bake a glass paste composition, raising temperature from room temperature (RT) to the temperature of Ts or more of glass frit, and maintaining temperature below Ts + 40 degreeC.

When the firing temperature of the glass paste composition is Ts + 40 ° C. or more, since the size of the bubbles of the gas generated by the burning of the binder resin becomes too large, it cannot be controlled to satisfy b ≦ 0.5a, and thus the coating layer 130 Cracking may easily occur, or the electrolyte solution 5 may corrode the current collecting electrode 120 through the pores 131.

Moreover, since it is necessary to bake a glass paste composition more than the temperature which glass frit sinters, it is necessary to bake at the temperature more than Ts of a glass frit.

In other words, the firing temperature of the glass paste composition in one embodiment of the present invention is required to be equal to or higher than the softening point (Ts) (° C) of the glass frit and below Ts + 40 ° C.

In addition, the time which keeps a baking temperature at the temperature of the softening point (Ts) (degreeC) of glass frit more than Ts + 40 degreeC is not specifically limited as long as binder resin disappears and the glass frit sinters, but baking The temperature may be, for example, about 5 minutes to about 60 minutes.

In the manufacturing method of the photoelectric conversion element 1 which concerns on one Embodiment of this invention, as shown in FIG. 5, before reaching the baking temperature mentioned above, the disappearance temperature (degreeC) of binder resin or more and below Ts (degreeC). It is preferable to keep at least about 5 minutes at a temperature of.

In this case, the "holding / supporting" does not need to be a constant temperature if the temperature within the above range is maintained for about 5 minutes or more when the temperature within the range of the dissipation temperature (° C) or more and Ts (° C) or less of the binder resin is used. There may be a temperature change.

As such, before reaching the firing temperature, by maintaining / supporting at least about 5 minutes at the temperature of disappearance temperature (° C) or higher than Ts (° C) of the binder resin, before the firing temperature of the glass paste composition is reached, that is, glass Before the frit softens and melts, the binder resin and other organic substances contained in the glass paste composition can be removed by gasifying.

Therefore, when baking a glass paste composition, since the binder resin and other organic substance hardly remain in a glass paste composition, generation | occurrence | production of the big pore 131 which is the largest length b can be suppressed.

On the other hand, the "disappearance temperature of the binder (° C)" used herein means a temperature at which 95% or more of weight is lost when performing thermogravimetry-diffrential thermal analysis (TG-DTA) in air. do.

After the coating layer 130 is formed as described above, the effective area (the area of the photoelectric conversion region) of the surface of the electrode substrate 10 is entirely formed of metal (platinum, gold, silver, copper, aluminum, rhodium, indium, etc.), A counter electrode by treating a metal oxide (indium tin oxide (ITO), tin oxide (including those doped with fluorine, etc.), zinc oxide, etc.), a conductive carbon material or a conductive organic material by a known method such as sputtering (4) is formed.

A positive electrode can be produced as mentioned above.

<Production of Cathode>

As for the cathode, first, in the same manner as in the case of the anode, an electrode substrate 10 including a transparent electrode 110, a collecting electrode 120, and a coating layer 130 is formed on the surface of the substrate 2.

Subsequently, a paste composition is prepared by dispersing metal oxide fine particles 31 such as TiO ₂ (preferably having a particle size in nanometers) and an organic binder for binding them in water or a suitable organic solvent.

Subsequently, the prepared paste composition is applied to the entire surface of the electrode substrate 10 in an effective area (area of a region capable of photoelectric conversion).

As a coating method of the said paste composition, screen printing, application | coating by a dispenser, spin coating, application | coating using a squeegee, dip coating, application | coating by spraying, die coating, inkjet printing, etc. are mentioned, for example.

Subsequently, after the applied paste composition is dried at a temperature at which the solvent disappears (about 80 ° C. to about 200 ° C.), a temperature at which the binder resin disappears and the metal oxide fine particles 31 are sintered (about 400 ° C. to about 600) By firing at), a metal oxide semiconductor film is formed.

The substrate 2 and the electrode substrate 10 on which the metal oxide semiconductor film is formed are immersed in a solution in which the sensitizing dye 33 is dissolved (for example, an ethanol solution of a ruthenium complex dye) for several hours. The sensitizing dye 33 is bonded to the surface of the metal oxide fine particles 31 by using the affinity between the surface of the 31 and the connector 35 of the sensitizing dye 33.

Subsequently, at a temperature at which the solvent disappears (about 40 ° C. to about 100 ° C.), the metal oxide semiconductor film to which the sensitizing dye 33 is bonded is dried to form the photoelectrode 3.

On the other hand, the method of bonding the sensitizing dye 33 to the surface of the metal oxide fine particles 31 is not limited to the above method.

A negative electrode can be manufactured as mentioned above.

<Junction of anode and cathode>

The positive electrode and the negative electrode which were produced as described above are faced to each other, and the spacer 6 (for example, ionomer resin such as Himiran (trade name) made by Mitsui DuPont Poly Chemical) is formed at the peripheral connection portion of each substrate 2. And heat-bond the positive electrode and the negative electrode at a temperature of about 120 ° C.

Then, it is possible to obtain an electrolyte solution, the photoelectric conversion element (1) by injecting into the inlet of the (e. G., The LiI and I ₂ is dissolved in acetonitrile electrolyte solution), the electrolyte of the battery so as to widely spread in total.

In addition, the photoelectric conversion element 1 may combine and connect several photoelectric conversion element 1 as needed.

For example, by combining a plurality of photoelectric conversion elements 1 in series, the overall generated voltage can be increased.

Second Embodiment

The photoelectric conversion element according to another embodiment of the present invention has the same configuration as the photoelectric conversion element according to the embodiment of the present invention described above, but the maximum length of pores present in the coating layer is not related to the thickness of the coating layer. The maximum length of the pores is defined by itself.

Specifically, the maximum length of the pores according to another embodiment of the present invention needs to be 10 μm or less.

When the maximum length of the pores exceeds 10 µm, cracks tend to occur in the coating layer, or the electrolyte solution may corrode the current collecting electrode through the pores.

Moreover, also in order to improve the conversion efficiency of a photoelectric conversion element, it is necessary to make the maximum length of a pore be 10 micrometers or less.

In general, in the photoelectric conversion element, if the gap of the cell, that is, the gap between the anode and the cathode is made too large, the conversion efficiency of the photoelectric conversion element is lowered.

Here, one example of the relationship between the gap of the cell and the conversion efficiency confirmed by the present inventors will be described.

The present inventors manufactured the photoelectric conversion cell by the method similar to an Example using the coating layer (refer Table 4) shown in the Example mentioned later.

At this time, the gap of the cell was changed and the conversion efficiency of the photoelectric conversion cell in each cell gap was measured by the method similar to an Example.

The measurement results are shown in Table 1 below.

Cell gap (μm) Conversion efficiency (%) 30 7.23 60 7.16 90 6.67 120 6.02 150 5.29

As shown in Table 1, the larger the cell gap, the lower the conversion efficiency.

In another embodiment of the present invention, if the thickness of the coating layer is thick, the gap of the cell must also be large, so that the thickness of the coating layer is preferably as small as possible.

In addition, when the maximum length of the pores is too large compared to the thickness of the coating layer, cracks tend to occur in the coating layer.

Therefore, in order to improve the conversion efficiency, it is desirable to make the maximum length of the pores as small as possible (in another embodiment of the present invention, about 10 μm or less).

On the other hand, the smaller the maximum length of the pores, the better. Therefore, the lower limit of the maximum length of the pores does not need to be specifically defined, but the lower limit of the maximum length of the pores that can be actually controlled is about 0.2 μm.

On the other hand, the definition of the maximum length of the pores, the measuring method and the control method are the same as described in the first embodiment of the present invention.

Since the structure of the other photoelectric conversion element and the manufacturing method of the photoelectric conversion element are the same as those described in the first embodiment of the present invention, detailed descriptions thereof will be omitted.

Example

Hereinafter, this invention is demonstrated concretely using an Example.

In the present Example, evaluation of the durability (electrolyte resistance) with respect to the electrolyte solution of the coating layer and the performance (photoelectric conversion efficiency) of the dye-sensitized solar cell were performed.

(Evaluation of Durability for Electrolyte Solution)

First, durability of the electrolyte solution of the coating layer was evaluated.

<Formation of collecting electrode>

Screen printing method to form Ag paste (MH1085, manufactured by Tanaka Precious Metals Co., Ltd., MH1085) on a glass substrate having a fluorine-doped tin oxide layer (transparent electrode layer) to a stripe shape having a thickness of 10 μm and a width of 500 μm. Patterning was performed to form a current collecting electrode.

<Production of Glass Paste Composition>

5 g of ethyl cellulose resin (loss temperature 400 ° C), 60 g of glass frit (B ₂ O ₃ -SiO ₂ -Bi ₂ O ₃ system, glass softening point (Ts) 475 ° C), terpineol (manufactured by Kanto Chemical) Was mixed with 30 g and 5 g of butyl carbitol acetate (manufactured by Kanto Chemical Co., Ltd.), and then sufficiently dispersed in a three-roll mixer to obtain a glass paste composition.

<Formation of coating layer>

Using the glass paste composition prepared above, a pattern was formed by screen printing so as to form a stripe having a width of 1000 µm while completely covering the current collecting electrode.

Subsequently, after drying and removing the solvent in a glass paste composition in 150 degreeC oven, it bakes for 30 minutes in air atmosphere, the binder resin component was lost, and the coating layer was formed.

Firing of the glass paste composition was carried out at the respective temperatures (490 ° C., 500 ° C., 510 ° C., 520 ° C.) shown in Table 2 below.

In addition, the total number of pores which exist in the formed coating layer, the maximum value in b which is the maximum length of a pore, and the number average value of b which is the maximum length of a pore were measured.

As the value of the maximum length of pores, b is automatically measured using image analysis software GRADING ANALYSIS, and the maximum length of pores is 160 μm × 120 μm on the screen of the device. It measured in five places.

In Table 2 below, the firing temperature of each of the formed coating layers, the heating rate up to the firing temperature, the maximum value of b as the maximum length of the pores, the total number of pores, and the number average value of b as the maximum length of all the pores are shown.

In addition, the thickness of the coating layer was 20 micrometers in all the examples.

In this embodiment, the firing temperature refers to the highest achieved temperature of the glass paste composition upon firing, and the rate of temperature increase is when the temperature of the glass paste composition reaches the glass softening point temperature of the glass frit and then the temperature is raised to the firing temperature. It means the rate of temperature rise.

Firing temperature
(℃) Pore number
(dog) the maximum value of b
(Μm) mean value of b
(Μm) 490 1932 10.0 0.99 500 1750 9.4 1.0 510 1567 9.9 0.99 520 1337 12.3 0.93

* The temperature increase rate in Table 2 is 10 ° C / min.

As shown in Table 2 above, when the conditions of the firing temperature specified in the present invention (more than the softening point (Ts) of the glass frit or less than Ts + 40 ° C) are satisfied (the firing temperature is 490 ° C, 500 ° C or 510 ° C). Example: Example) It turns out that the maximum value of b which is the maximum length of a pore becomes 10 micrometers or less, and satisfy | fills the conditions of b which is the maximum length of the pore prescribed | regulated by this invention.

On the other hand, when the firing temperature exceeds Ts + 40 ° C. (an example of firing temperature of 520 ° C .: comparative example), the maximum value of b, which is the maximum length of the pores, exceeds 10 μm, and the maximum of the pores defined in the present invention. It can be seen that the condition of length b is not satisfied.

<Production of Evaluation Cell>

The glass substrate and the FTO glass substrate on which the collecting electrode obtained as described above were formed were thermo-compressed using a high melt (120 탆) hot melt resin, and the electrolyte solution was injected into the previously opened electrolyte inlet. The cell for evaluation was produced by sealing using Himiran and a glass cover.

<Evaluation of electrolyte resistance>

After leaving the produced evaluation cell at 1000C for 1000 hours, the state / shape of the current collector electrode and the coating layer was observed.

As a result, no damage was observed visually in the cell of the example.

Effect of firing temperature on the generation of pores

The influence which baking temperature gives on generation | occurrence | production of the pore to a coating layer was investigated.

In other words, the glass paste composition obtained as described above is applied to a glass substrate (type U-TCO, manufactured by Asahi Glass Co., Ltd.) having a fluorine-doped tin oxide layer (transparent electrode layer), and the glass paste composition is The solvent was dried and then fired in an air atmosphere.

At this time, about baking conditions, as shown to FIGS. 6A-6F, baking temperature is changed to Ts + 15 degreeC-Ts + 75 degreeC, and a temperature increase rate is 10 degreeC / min (5 degreeC only in the case of FIG. 6F). / Min), and the firing time was 20 minutes.

6A to 6F are micrographs showing an example of the state of the coating layer after firing.

As a result, in the examples of FIGS. 6A to 6C satisfying the conditions of the firing temperature (less than Ts + 40 ° C.) in the method of manufacturing the photoelectric conversion element according to the embodiment of the present invention, pores (black portions in the photograph) It can be seen that the size of) is small and the number is small.

On the other hand, about the example of FIGS. 6D-6F whose baking temperature is Ts + 40 degreeC or more, it turns out that a pore size is large.

Effect of pretreatment on the generation of pores

The influence which the pretreatment process (temperature holding / supporting process before baking) has on the generation | occurrence | production of the pore to a coating layer was investigated.

In other words, the glass paste composition obtained as described above is applied to a glass substrate (type U-TCO, manufactured by Asahi Glass Co., Ltd.) having a fluorine-doped tin oxide layer (transparent electrode layer), and the glass paste composition is The solvent was dried and then fired in an air atmosphere.

The firing conditions set the baking temperature of 500 degreeC, the holding / supporting time of the said baking temperature for 20 minutes, and the temperature increase rate to 10 degreeC / min.

At this time, for one of the two types of samples fired under the same conditions, a pretreatment step of maintaining at 420 ° C. for 30 minutes before firing was added, and the other pretreatment step was not added.

The results are shown in Figs. 7A and 7B.

7A is a micrograph showing an example of the state of the coating layer after firing when no pretreatment step is added.

7B is a micrograph showing an example of the state of the coating layer after firing when a pretreatment step is added.

Pretreatment Process Pore number
(dog) the maximum value of b
(Μm) mean value of b
(Μm) radish 1783 9.5 1.19 U 1688 9.4 1.08

As a result, it can be seen that the example shown in FIG. 7B in which the pretreatment step is added has a smaller size and smaller number of pores (black portion in the photo) than the example shown in FIG. 7A in which the pretreatment step is not added.

In other words, in the example shown in FIG. 7B, by adding a pretreatment step, the number of pores itself is reduced, and at the same time, generation of pores with a large value of b, which is the maximum length, is suppressed, and as a result, shown in Table 3 As such, it is assumed that the average value of the maximum length of the pores is significantly smaller in the example shown in FIG. 7B in which the pretreatment step is added.

<Example of the corrosion of current collector electrodes caused by pores>

8A and 8B show examples of the case where the size of pores present in the coating layer is too large, causing cracks in the coating layer and corrosion of the current collecting electrode.

8A and 8B are micrographs showing an example of a state where corrosion occurs in the current collecting electrode.

As shown in Figs. 8A and 8B, when b, the maximum length of pores with respect to the film thickness a of the coating layer, is b> 0.5a, the current collecting electrode is the electrolyte solution due to the large pores present in the center of the coating layer. It can be seen that it is corroded and disappears (the transparent part in Figs. 8A and 8B is the part where the current collecting electrode disappears).

(Performance evaluation of dye-sensitized solar cell)

Subsequently, performance evaluation as a dye-sensitized solar cell was performed.

<Transparent electrode>

In all the examples and comparative examples, a glass substrate (type U-TCO manufactured by Asahi Glass Co., Ltd.) having a fluorine-doped tin oxide layer (transparent electrode layer) was used as the transparent electrode.

<Formation of collecting electrode>

Ag paste (MH1085, manufactured by Tanaka Precious Metals Co., Ltd.) was patterned on the glass substrate by screen printing to form a stripe having a thickness of 10 μm and a width of 500 μm, thereby forming a current collecting electrode.

At this time, the pitch between collector electrodes was 7,000 micrometers.

<Formation of coating layer>

5 g of ethyl cellulose resin (loss temperature 400 ° C), 60 g of glass frit (B ₂ O ₃ -SiO ₂ -Bi ₂ O ₃ system, glass softening point (Ts) 480 ° C), terpineol (manufactured by Kanto Chemical) After mixing 30 g of this and 5 g of butyl carbitol acetate (manufactured by Kanto Chemical Co., Ltd.), the mixture was sufficiently dispersed in a three-roll mixer to obtain a glass paste composition.

Using the obtained glass paste composition, the electrode substrate with a coating layer by the Example and comparative example of this invention was produced on the following baking conditions.

In the firing conditions of the examples, after the pretreatment step of maintaining at 420 ° C. for 30 minutes, the firing temperature was 500 ° C. and the firing temperature holding / supporting time was 20 minutes.

The baking conditions of the comparative example did not add a pretreatment process, and made baking temperature 550 degreeC and baking temperature holding / supporting time for 20 minutes.

The coating layer was formed so that the film thickness might be 20 micrometers in both the Example and the comparative example.

About the coating layer obtained as mentioned above, the comparison (b / a) of the thickness a of a coating layer and b which is the maximum length of a pore, and the number of pores of the range of each (b / a) were measured.

As the measured value of b, the maximum length of the pores, a value automatically measured using GRADING ANALYSIS (manufactured by Giens), which is an image analysis software, was used.

On the other hand, b, the maximum length of the pores, was measured in one region of 10 mm x 50 mm on the screen of the device.

The above measurement results are shown in Table 4 (Examples) and Table 5 (Comparative Examples).

On the other hand, the "number of error points" in Table 4 and Table 5 means the number of places where the current collector electrode was damaged in the coating layer by the crack caused by the large pores of b which is the maximum length.

b / a Pore number
(dog) The number of error points
(dog) 0.1 or less 872930 0 0.1 or more and 0.2 or less 985 0 0.2 or more and 0.3 or less 219 0 0.3 or more and 0.4 or less 38 0 0.4 or more and 0.5 or less 4 0 More than 0.5 less than 0.6 0 - 0.6 or more 0.7 or less 0 - 0.7 or more and 0.8 or less 0 - 0.8 or more and 0.9 or less 0 - Greater than 0.9 and less than 1.0 0 -

b / a Pore number
(dog) The number of error points
(dog) 0.1 or less 604965 0 0.1 or more and 0.2 or less 5406 0 0.2 or more and 0.3 or less 1395 0 0.3 or more and 0.4 or less 476 0 0.4 or more and 0.5 or less 158 0 More than 0.5 less than 0.6 35 7 0.6 or more 0.7 or less 11 6 0.7 or more and 0.8 or less 3 3 0.8 or more and 0.9 or less One One Greater than 0.9 and less than 1.0 0 -

As shown in Table 4 and Table 5, in the coating layer according to the example, b / a ≦ 0.5 (b ≦ 0.5a) was satisfied for all the pores within the measurement range, and no error point occurred.

On the other hand, in the coating layer by a comparative example, many large pores of the maximum length b of b / a> 0.5 generate | occur | produced, and it turns out that many error places generate | occur | produce according to such large pores.

<Relative electrode>

In both Examples and Comparative Examples, after forming a current collecting electrode and a coating layer on the electrically conductive layer of a glass substrate (type U-TCO, manufactured by Asahi Glass Co., Ltd.) having a fluorine-doped tin oxide layer as a counter electrode, platinum was formed by sputtering. What laminated | stacked the layer (platinum electrode layer) (thickness 150 nm) was used.

In addition, the formation method of a collector electrode and a coating layer is as above-mentioned.

<Production of Paste Composition for Photoelectrode (titanium oxide electrode)>

Next, the paste composition for photoelectrodes was manufactured.

Specifically, in all the examples and the comparative examples, 3 g of titanium oxide fine particles (manufactured by Japan Aerosol Co., P-25), 0.2 g of acetyl acetone, and surfactant (wako pure chemicals, polyoxyethylene octylphenyl ether) 0.3 g was dispersed with 7.0 g of terpineol for 12 hours by a beads mill treatment.

1.0 g of ethyl cellulose resin was added as a binder resin to the obtained dispersion liquid, and the paste composition was produced.

The viscosity at the shear rate of 10 sec ⁻¹ of the paste composition was, for example, to have a viscosity sufficient for screen printing.

<Production of Titanium Oxide Electrode>

Next, a titanium oxide electrode containing titanium oxide fine particles was produced.

Specifically, in each of the Examples and Comparative Examples, the paste composition prepared as described above was formed into a film by screen printing on the electrically conductive surface of the electrode substrate on which the coating layer was formed, and then sintered in an oven at 450 ° C. for 1 hour. A titanium oxide electrode having a titanium oxide porous membrane having a thickness of 10 μm and an effective area of 100 cm ² was obtained.

<Adsorption of dark dyes>

Subsequently, the titanium oxide electrode obtained as mentioned above was made to adsorb | suck a sensitizing dye as follows.

A dye solution was prepared by dissolving photosensitive conversion dye N719 (manufactured by Solaronix) in ethanol (concentration 0.6 mmol / L), and after immersing the titanium oxide electrode in the dye solution, it was allowed to stand at room temperature for 24 hours.

The surface of the colored titanium oxide electrode was washed with ethanol, and then immersed in a 2 mol% alcohol solution of 4-t-butyl pyridine for 30 minutes, dried at room temperature, and included a titanium oxide porous membrane adsorbed with sensitizing dyes. An electrode was obtained.

Preparation of Electrolyte Solution

Next, an electrolyte solution of the following composition was prepared.

As the solvent for dissolving the electrolyte, methoxy acetonitrile was used.

LiI: 0.1 M

I ₂ : 0.05 M

4-t-butyl pyridine: 0.5 M

1-propyl-2,3-dimethylimidazolium iodide: 0.6 M

<Assembly of Photoelectric Conversion Battery>

Then, the test sample of the photoelectric conversion battery (photoelectric conversion element) as shown in FIG. 1 was assembled using the photoelectrode and counter electrode produced as mentioned above.

In other words, the photoelectrode fabricated as described above and the counter electrode fabricated as described above were sandwiched between a resin film spacer (made by Mitsui DuPont Poly Chemicals and a Himir film (120 µm thick)). It fixed, and the electrolyte solution was inject | poured into the space | gap, and the electrolyte solution layer was formed.

The conductive wire for measurement of conversion efficiency was connected to the glass substrate, respectively.

<Measurement of Conversion Efficiency>

The conversion efficiency was measured by the following method about the photoelectric conversion battery in each Example and comparative example produced as mentioned above.

In other words, a solar simulator manufactured by ORIEL is combined with an air mass filter, and adjusted to an amount of light of 100 mW / cm ^{2 on} a photometer to be a light source for measurement, which is then irradiated with a test sample of the photoelectric conversion battery. The IV curve characteristics were measured using a KEITHLEY MODEL 2400 source meter.

The conversion efficiency (η,%) was calculated by Equation 1 which calculates the following conversion efficiency using the open voltage Voc, the short circuit current Isc, and the filling factor ff obtained from the I-V curve characteristic measurement.

The state / shape of the change with time of the value of the obtained conversion efficiency is shown in FIG.

9 is a graph showing the relationship between the conversion efficiency (η) and time of the photoelectric conversion battery according to the Examples and Comparative Examples of the present invention.

[Equation 1]

As shown in Fig. 9, in both the photoelectric conversion cells of the examples and the comparative examples, a high conversion efficiency of more than 6% was obtained for the initial photoelectric conversion efficiency (for example, the photoelectric conversion cell of the example at the elapsed time 0). Conversion efficiency is 6.67%, and the conversion efficiency of the photoelectric conversion cell of the comparative example is 6.75%).

However, it was found that the photoelectric conversion battery of the comparative example significantly lowers the conversion efficiency with time, whereas the photoelectric conversion battery of the example can maintain high conversion efficiency even with time.

Since the photoelectric conversion battery of the comparative example has a large number of pores with a large maximum length, as a result of cracks in the coating layer, the current collecting electrode is corroded by the electrolyte solution, and it is considered that the conversion efficiency is lowered.

On the other hand, in the photoelectric conversion battery of the embodiment, since the maximum length of all the pores present in the coating layer is within 0.5 times the thickness of the coating layer, generation of cracks in the coating layer is suppressed, and corrosion of the current collecting electrode hardly occurs, resulting in conversion efficiency. It seems to be sustainable.

As can be seen from the above results, when the coating layer covering the current collecting electrode formed under the conditions within the scope of the present invention is formed, the size of pores present in the coating layer also falls within the scope of the present invention.

As a result, cracking (cracking) of the coating layer can be prevented, and since the current collecting electrode does not contact the electrolyte solution, corrosion of the current collecting electrode can be prevented.

Therefore, a photoelectric conversion element such as a dye-sensitized solar cell manufactured using such an electrode substrate can have high efficiency, long life and high durability.

As mentioned above, although this invention was demonstrated about preferred embodiment, referring an accompanying drawing, this invention is not limited to this.

Anyone possessing ordinary knowledge in the technical field to which the present invention belongs can clearly reach various modifications or modifications within the scope of the technical idea described in the claims, and these are naturally also the present invention. It is understood to belong to the technical scope of the.

For example, in the above-described embodiment of the present invention, the inorganic semiconductor fine particles having a photoelectric conversion function and sensitized by being connected to a sensitizing dye on the surface thereof have been described with the metal oxide fine particles 31 as an example, but the inorganic semiconductor according to the present invention. The fine particles are not limited to the metal oxide fine particles 31 and may be, for example, inorganic semiconductor fine particles other than metal oxides.

Examples of the compound that can be used as the inorganic semiconductor fine particles other than such metal oxides include silicon, germanium, group III-V type semiconductors, and metal chalcogenides.

1: photoelectric conversion element, 2: substrate,
3: photoelectrode, 4: counter electrode,
5: electrolyte solution, 6: spacer,
7: lead wire, 10: electrode substrate,
31: metal oxide fine particles, 33: sensitizing dye,
110: transparent electrode, 120: current collecting electrode,
130: coating layer, 131: pores

Claims (6)

An electrode substrate for a photoelectric conversion element comprising a current collecting electrode provided on a transparent conductive substrate and a coating layer covering a surface of the current collecting electrode.
The coating layer is formed by coating and baking a glass paste composition on the surface of the current collecting electrode,
The thickness of the said coating layer is a micrometer, and when the largest length of the pore which generate | occur | produces in the said coating layer by the said baking is b micrometer, it will satisfy b <= 0.5a.
An electrode substrate for a photoelectric conversion element having a current collecting electrode provided on a transparent conductive substrate and a coating layer covering the surface of the current collecting electrode,
The coating layer is formed by coating and baking a glass paste composition on the surface of the current collecting electrode,
And the maximum length of pores generated in the coating layer by the firing is 10 m or less.
A photoelectric conversion element comprising the electrode substrate according to claim 1.
The method of claim 3,
The photoelectric conversion element is a dye-sensitized solar cell.
After applying a glass paste composition comprising a glass frit, a binder resin, and an organic solvent on the surface of the current collecting electrode provided on the transparent conductive substrate, the glass paste composition is softened to a softening temperature (Ts) ° C or higher of the glass frit. Baking at a temperature below 40 (Ts + 40) ° C. to form a coating layer covering the surface of the current collecting electrode.
The method of claim 5,
The method of manufacturing an electrode substrate further comprising the step of maintaining at least the temperature of disappearance (℃) of the binder resin above the softening point (Ts) ℃ of the glass frit before reaching the firing temperature.

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