JP2009057544A - Paste for forming semiconductor porous layer - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a paste for forming a semiconductor porous layer, with which a coating layer having a uniform thickness can be stably formed without causing sagging even if it is applied on a part having a large surface area and which can be suitably used, in particular, in screen printing. <P>SOLUTION: The paste contains 5-60 wt.% of titanium oxide fine particles, 10-90 wt.% of terpineol, and 5-60 wt.% in total of two kinds of ethylcellulose exhibiting different viscosities when they are dissolved in a solvent. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a paste used for forming a semiconductor porous layer, and more particularly to a paste for forming a semiconductor porous layer provided on a negative electrode of a dye-sensitized solar cell.

  Currently, there is great expectation for photovoltaic power generation from the viewpoint of global environmental problems and fossil energy resource depletion problems, and single crystal and polycrystalline silicon photoelectric conversion elements are put into practical use as solar cells. However, this type of solar cell is expensive and has a problem of supply of silicon raw materials, and the practical application of solar cells using materials other than silicon is desired.

  From the above viewpoint, recently, a dye-sensitized solar cell has attracted attention as a solar cell using a material other than silicon. A typical example of such a dye-sensitized solar cell is one having the structure shown in FIG.

That is, this battery has a transparent electrode substrate (positive electrode substrate) 1 and a metal electrode substrate (negative electrode substrate) 10.
In the transparent electrode substrate 1, a transparent conductive film 5 (for example, an ITO film) is formed on a transparent substrate 3 such as transparent glass or a transparent resin film, and a vapor deposition film such as platinum or platinum is further provided on the transparent conductive film 5 if necessary. The conductive layer 7 is formed. On the other hand, the metal electrode substrate 10 has a metal substrate 11, and a dye-sensitized semiconductor porous layer 13 is formed on the metal substrate 11 with a reverse electron prevention layer 15 formed as necessary. ing. The transparent electrode substrate 1 and the metal electrode substrate 10 have a structure facing each other with the electrolyte layer 20 interposed therebetween, and the peripheral portion between the transparent electrode substrate 1 and the metal electrode substrate 10 is the electrolyte layer 20. Is sealed with a sealing material 30 so as not to leak. That is, the region where the metal electrode substrate 10 and the transparent electrode substrate 1 face each other with the dye-sensitized semiconductor porous layer 13 and the electrolyte layer 20 interposed therebetween is the power generation region X. A sealed region is a sealed region Y.

  In the dye-sensitized solar cell having such a structure, when visible light is irradiated from the transparent electrode substrate 1 side, the dye in the dye-sensitized semiconductor porous layer 13 is excited and transitions from the ground state to the excited state. The dye electrons thus injected are injected into the conduction band in the porous layer 13 and move to the transparent electrode substrate 1 through an external circuit (not shown). The electrons that have moved to the transparent electrode substrate 1 are carried by the ions in the electrolyte layer 20 and return to the pigment. Electric energy is extracted by repeating such a process. The power generation mechanism of such a dye-sensitized solar cell is different from a pn junction photoelectric conversion element, in which light capture and electronic conduction are performed in different places, and is very similar to a plant photoelectric conversion process. Yes.

  In the dye-sensitized solar cell having the above-described structure, the semiconductor porous layer 13 carrying the dye can be directly formed on the low-resistance metal substrate 11, thereby avoiding a decrease in conversion efficiency. Further, there is an advantage that an increase in internal resistance (curvature factor; FF) when the cell is enlarged can be suppressed.

  A dye-sensitized solar cell having a structure opposite to the above is also known. Specifically, the dye-sensitized semiconductor porous layer 13 in FIG. It is formed on the electron reduction layer 7), and has a structure in which the metal electrode substrate 10 is opposed to each other with the electrolyte layer 20 interposed therebetween. In this type, the transparent electrode substrate 1 becomes a negative electrode substrate, and the metal electrode substrate 10 (metal substrate 11) becomes a positive electrode substrate, and power is generated by light irradiation from the negative electrode substrate side.

  By the way, the semiconductor porous layer 13 provided on the negative electrode substrate of the dye-sensitized solar cell as described above is formed of semiconductor particles such as titanium oxide on the negative electrode substrate (the metal electrode substrate 10 in the structure of FIG. 1). A paste in which is dispersed is applied and baked to form a semiconductor porous layer 3 made of titanium oxide, a dye solution is applied thereon, and the dye is adsorbed on the porous layer 13. It is manufactured by removing the solvent (see Patent Document 1).

  As means for applying the semiconductor fine particle paste, spin coating, die coating, screen printing, and the like are generally used, but screen printing is the most suitable in terms of large area. Is widely used.

  The above paste for screen printing (hereinafter sometimes simply referred to as “semiconductor paste”) is a resin in which a resin as a binder is dispersed in an organic solvent together with semiconductor fine particles. For example, the resin does not aggregate the semiconductor fine particles. In addition, ethyl cellulose is used because the semiconductor fine particles can be stably bonded and held even when the paste coating layer is dried, and can be reliably removed by firing, and the solvent is inert to the semiconductor fine particles. From the viewpoint that it can be uniformly dispersed without impairing the characteristics of the semiconductor fine particles, terpineol is used (Patent Documents 2 and 3).

JP 2002-298646 A JP 2004-153030 A JP 2007-26994 A

  However, since the semiconductor paste as described above is usually applied to a large area portion, it should be capable of forming a coating layer having a uniform thickness without causing any particular sagging. If this thickness becomes non-uniform, unevenness occurs in the thickness of the finally obtained semiconductor porous layer, making it difficult to obtain stable characteristics. For example, a semiconductor paste using a binder component such as ethyl cellulose or an organic solvent such as terpineol does not cause much problem when it is coated on a relatively small area portion. In the case of coating, the thickness tends to be non-uniform due to sagging or the like, and an improvement thereof is demanded.

  Accordingly, the object of the present invention is to prevent the occurrence of sagging and to stably form a coating layer having a uniform thickness even when applied to a large area, and is particularly suitable for screen printing. Another object of the present invention is to provide a paste for forming a semiconductor porous layer.

  As a result of intensive studies on the above problems, the present inventors have achieved excellent coating properties by using two types of ethyl cellulose having different viscosities as the binder component, and a uniform coating layer even when applied to a large area. The present inventors have found that a semiconductor paste capable of forming a film can be obtained, and have completed the present invention.

  According to the present invention, 5 to 60% by weight of titanium oxide fine particles and 10 to 90% by weight of terpineol are included, and two types of ethyl cellulose having different viscosities when dissolved in a solvent are added in a total amount of 5 to 60% by weight. Thus, a semiconductor porous layer forming paste is provided.

In the paste (semiconductor paste) of the present invention,
(1) As the ethyl cellulose, a low-viscosity ethyl cellulose having a viscosity (25 ° C.) of 5 to 15 cP and a high-viscosity ethyl cellulose having a viscosity (25 ° C.) of 30 to 50 cP in a 10% solid ethyl cellulose concentration solution using toluene as a solvent Containing
(2) containing the low-viscosity ethyl cellulose (ES ¹ ) and the high-viscosity ethyl cellulose (ES ² ) in a weight ratio of ES ¹ / ES ² = 51/49 to 80/20,
Is preferred.

  The semiconductor paste of the present invention is characterized by the fact that it contains two types of ethyl cellulose having different viscosities when dissolved in a solvent as a binder component. Even when the area is coated by screen printing, a coating layer having a uniform thickness can be formed, and a semiconductor porous layer having a uniform thickness can be formed on the electrode.

  That is, ethyl cellulose is used as a binder in conventionally known semiconductor pastes. However, low-viscosity ethyl cellulose suitable for screen printing and other applications has a low viscosity, so when coated over a large area, sagging occurs, the coating layer thickness becomes unstable, and finally formed As a result, the thickness of the semiconductor porous layer formed becomes uneven, making it difficult to exhibit stable characteristics.

  However, according to the present invention, since high-viscosity ethyl cellulose is combined with low-viscosity ethyl cellulose, the coating layer having a large area is obtained without impairing the binder properties of ethyl cellulose and without reducing the dispersibility in the solvent. In this case, sagging can be effectively prevented and a coating layer having a uniform thickness can be formed.

<Semiconductor paste>
The semiconductor paste of the present invention uses titanium dioxide fine particles as semiconductor fine particles, which are dispersed in an organic solvent together with a binder.

  As titanium dioxide, anatase type, brookite type and rutile type are known, and in the present invention, any type of titanium dioxide can be used, but the semiconductor porous layer has high conversion efficiency. From the viewpoint of obtaining, anatase type or brookite type titanium dioxide is most preferable.

  Further, the fine particles of titanium dioxide generally need to be fine with a particle size of 500 nm or less. That is, when coarse particles are used, the light permeability to the semiconductor porous layer is likely to vary, and it may be difficult to exhibit stable characteristics as a solar cell.

  In the semiconductor paste of the present invention, the titanium dioxide fine particles should be contained in an amount of 5 to 60% by weight, particularly 10 to 30% by weight. That is, if the amount of titanium dioxide fine particles is less than the above range, it is necessary to coat the semiconductor paste more than necessary when forming a semiconductor porous layer having a certain thickness. It becomes easy to produce. Further, there is a disadvantage that the basis weight of the formed semiconductor porous layer is reduced. Furthermore, when the titanium dioxide fine particles are contained in a larger amount than the above range, there arises a disadvantage that the coating property of the paste is lowered.

  In the present invention, it is most preferable to use spherical particles and irregularly shaped particles having a finer particle diameter than the spherical particles as the titanium dioxide fine particles described above. Spherical particles are particles having no corners that form a surface in an observation using an electron microscope such as SEM or TEM. Unless the corners are observed, not only true spherical particles but also elliptical cross sections are used. It means particles having a large diameter and not more than 10 times the short diameter, including shaped particles. In addition, the irregularly shaped particles cannot recognize a specific shape in the electron microscope observation as described above, but ridges or corners indicating the boundary between the surfaces are observed. It is a ball-shaped particle having a shape, and means a particle having a large diameter of 10 times or less of a short diameter, like a spherical particle. In spherical particles and irregularly shaped particles, the particle size (grain diameter) means the maximum diameter.

  That is, FIGS. 2 and 3 show a partially enlarged semiconductor porous layer 50 (corresponding to the semiconductor porous layer 13 of FIG. 1) formed using the semiconductor paste of the present invention. As shown in FIG. 2, when the titanium dioxide fine particles A having a constant particle diameter are used, the titanium dioxide fine particles become a densely bonded layer, and the sensitizing dye 55 carried on the surface of these particles. Is distributed only on the surface portion of the semiconductor porous layer 50 and has a structure that is difficult to distribute inside (particularly on the electrode substrate 51 side). On the other hand, as shown in FIG. 3, when spherical particles A and irregularly shaped particles B having a particle diameter smaller than the spherical particles are used, the sensitizing dye 53 permeates. A large number of macropores of easy size are formed, the porosity is increased (for example, 60% or more), and the surface area is increased. As a result, the dye 55 penetrates uniformly not only to the surface layer portion of the semiconductor porous layer 50 but also to the inside. In addition, the light irradiated for power generation due to the large gap spreads throughout the semiconductor porous layer 50 due to scattering, and it is possible to ensure high conversion efficiency. is there.

Therefore, in the present invention, in order to express the above characteristics, the spherical particle A has a particle diameter larger than that of the irregularly-shaped titanium dioxide particles B. The diameter of the polyhedral fine particles B should be in the range of 5 to 100 nm, especially 15 to 60 nm, and the diameter of the polyhedral fine particles B should be in the range of 1 to 80 nm, particularly 5 to 30 nm. The diameter is desirably 10 nm or more larger than the particle diameter of the irregularly shaped particles B. That is, the larger the difference in grain diameter between the two, the easier it is to form a structure having macropores as shown in FIG.
The particle diameter of the particles can be determined by an electron microscope after performing sputtering such as platinum sputtering.

  Further, the abundance ratio (A / B) between the spherical titanium dioxide particles A and the irregularly shaped titanium dioxide particles B is not particularly limited, but in general, A / B (weight ratio) = 10. / 90 to 90/10, particularly 30/70 to 70/30.

  The spherical particles A of titanium dioxide and the irregularly shaped titanium dioxide particles B as described above are known per se. For example, the spherical titanium dioxide particles A are commercially available as ST series products from Ishihara Sangyo Co., Ltd. In addition, the irregularly shaped titanium dioxide particles B are commercially available as products of the AMT series from Teika Corporation. In order to adjust the particle size distribution of each particle to the above-described range of the particle diameter, for example, it is performed by an electroforming sieve or the like.

In the present invention, terpineol is used as a solvent for dispersing the above-described titanium dioxide fine particles. Terpineol (C ₁₀ H ₁₈ O) is an unsaturated alcohol produced by dehydrating one molecule of water from 1,8-terbin, and three types of α, β and γ are known. In general, α-terpineol (Bp: 219 to 221 ° C.) or a mixture containing α-terpineol as a main component and other types such as β-terpineol mixed (generally commercially available) Are preferably mixtures).

  That is, the above-mentioned terpineol is a relatively viscous liquid, the above-described titanium dioxide fine particles can be easily and uniformly dispersed, and without adversely affecting the semiconductor properties of the titanium dioxide fine particles by heating, It can be easily stripped.

  In the semiconductor paste of the present invention, this terpineol is contained in the semiconductor paste in an amount of 10 to 90% by weight, particularly 40 to 80% by weight. If this amount is out of the range, the balance between the titanium dioxide fine particles and the binder component described later is lost, and it becomes difficult to uniformly disperse the titanium dioxide fine particles, and the coating property is deteriorated. Cause inconvenience.

  Furthermore, the semiconductor paste of the present invention contains two types of ethyl cellulose, low viscosity ethyl cellulose and high viscosity ethyl cellulose, as binder components. That is, ethyl cellulose is a substance that is inactive with respect to the titanium dioxide fine particles and can be decomposed and removed without adversely affecting the semiconductor characteristics and particle shape of the titanium dioxide fine particles by firing. Conventionally known semiconductor pastes use one type of ethyl cellulose as a binder component. For this reason, when coating is performed on a large area, sagging occurs and the thickness of the coating layer becomes non-uniform. As described above, it is reflected in the formed semiconductor porous layer, adversely affecting the battery characteristics and making it difficult to develop stable characteristics. However, in the present invention, by using two types of ethyl cellulose as described above, it is possible to effectively prevent sagging without lowering the binder performance, and even when coating is performed in a large area, A coating layer having a uniform thickness can be formed. As a result, the thickness of the semiconductor porous layer can be made uniform, and stable battery characteristics can be expressed.

  In the present invention, among the above-mentioned ethylcellulose, low-viscosity ethylcellulose particularly exhibits a binder function, and the viscosity (25 ° C.) in the case of a 10% solid content ethylcellulose concentration solution using toluene as a solvent is in the range of 5 to 15 cP. is there. That is, by blending such low-viscosity ethyl cellulose, the above-mentioned titanium dioxide fine particles are maintained in a uniformly dispersed state without agglomerating in the semiconductor paste, and the solvent (terpineol) is coated after the semiconductor paste is coated. Even after being removed by heating and drying, the layered state in which the titanium dioxide fine particles are stacked is stably maintained.

  On the other hand, high-viscosity ethylcellulose has a binder function as described above to some extent, but is particularly used for rheology modification. In the case of a 10% solid content ethylcellulose concentration solution using toluene as a solvent. The viscosity (25 ° C.) is in the range of 30-50 cP. That is, since the semiconductor paste of the present invention contains such high-viscosity ethyl cellulose, dripping can be effectively prevented without impairing the binder function of low-viscosity ethyl cellulose, and the semiconductor paste can be coated over a large area. Even in this case, the variation in the thickness of the coating layer is suppressed, and the thickness of the coating layer can be kept uniform.

  In the present invention, the low-viscosity ethyl cellulose and the high-viscosity ethyl cellulose are required to be contained in the semiconductor paste in a total amount of 5 to 60% by weight, particularly 5 to 30% by weight. That is, when the total amount is outside the above range, the balance with the titanium dioxide fine particles and terpineol described above is lost, the dispersion state of the titanium dioxide fine particles becomes unstable, or the coating property is impaired. This causes inconveniences such as adversely affecting the film characteristics of the semiconductor porous layer.

Further, the low viscosity ethyl cellulose (ES ¹ ) and the high viscosity ethyl cellulose (ES ² ) are blended in a weight ratio of ES ¹ / ES ² = 51/49 to 80/20, particularly 55/45 to 70/30. This is suitable for effectively expressing the binder function of low-viscosity ethyl cellulose and the rheology modification function of high-viscosity ethyl cellulose. That is, if low-viscosity ethyl cellulose is used in a larger amount than the above range, the sagging prevention effect is reduced, and if high-viscosity ethyl cellulose is used in a larger amount than the above range, the binder function is impaired and the titanium dioxide fine particles are aggregated. Or when the solvent is removed from the coating layer of the semiconductor paste, the layered structure of the titanium dioxide fine particles tends to be damaged, and it may be difficult to form a semiconductor porous layer having a certain thickness. .

  Various additives such as leveling agents, surfactants, thickeners and the like are added to the semiconductor paste of the present invention in appropriate amounts as long as they do not adversely affect the sagging prevention ability and the semiconductor properties of the titanium dioxide fine particles. May be.

  Further, the semiconductor paste of the present invention is prepared by mixing the above-mentioned components, and there is no limitation on the order of addition of the components, but the viscosity (25 ° C.) of the paste is in the range of about 15 to 50 cP. Thus, it is preferable to set the usage amount of each component within the range of the amount ratio described above.

<Formation of dye-sensitized porous semiconductor layer>
The above-described semiconductor paste of the present invention is coated on an electrode substrate 51 (for example, the metal electrode substrate 10 in FIG. 1), and this coating layer is dried and baked. A porous layer 50 is formed. The thickness of the semiconductor porous layer 50 is usually about 5 to 20 μm, and the oxide semiconductor weight (total weight of the particles A and B) is suitably about 0.001 to 0.005 g / cm ^2. It is.

  As the coating means, known means such as screen printing, spray coating, die coating and the like can be adopted. However, since the semiconductor paste of the present invention described above does not sag even when coated in a large area, screen printing. Is suitably applied to form a coating layer having a uniform thickness, thereby forming a dye-sensitized semiconductor porous layer 50 having no variation in thickness and exhibiting stable characteristics.

  The semiconductor paste coating layer is dried and baked at a temperature that does not deteriorate the semiconductor characteristics and layer structure of the oxide semiconductor fine particles such as titanium dioxide fine particles, for example, at 350 to 550 ° C. for about 30 to 60 minutes. As a result, the solvent is volatilized, and the oxide semiconductor fine particles are sintered to form a semiconductor porous layer.

  The sensitizing dye 53 is supported by bringing the dye solution into contact with the semiconductor porous layer, whereby the semiconductor porous layer 50 sensitized with the dye 53 as shown in FIGS. It is formed on the substrate 51. In particular, when a semiconductor paste containing spherical titanium dioxide particles A and irregularly shaped titanium dioxide particles B is used, as shown in FIG. 3, the sensitizing dye 53 is deep and penetrates inside and is carried. The formed semiconductor porous layer 50 is formed, and particularly high conversion efficiency can be obtained.

  The contact of the dye solution is usually performed by dipping, and the adsorption treatment time (immersion time) is usually about 30 minutes to 24 hours, and after adsorption, the solvent of the dye solution is removed by drying, Sensitizing dye 53 can penetrate and be supported.

As the sensitizing dye to be used, those known per se having a bonding group such as a carboxylate group, a cyano group, a phosphate group, an oxime group, a dioxime group, a hydroxyquinoline group, a salicylate group, an α-keto-enol group are used. Those described in Patent Documents 1 to 3 described above, for example, ruthenium complexes, osmium complexes, iron complexes, and the like can be used without any limitation. Ruthenium-tris (2,2′-bispyridyl-4,4′-dicarboxylate), ruthenium-cis-diaqua-bis (2,2′-bispyridyl-4,4) in that it has a particularly broad absorption band. Ruthenium-based complexes such as' -dicarboxylate) are preferred. Such a dye solution of a sensitizing dye is prepared using an alcohol-based organic solvent such as ethanol or butanol as a solvent, and the dye concentration is about 3 × 10 ^{−4 to} 5 × 10 ⁻⁴ mol / l. .

  The electrode substrate 51 having the dye-sensitized semiconductor porous layer 50 formed on the surface as described above is used as a negative electrode substrate by facing the counter electrode (positive electrode substrate) with the electrolyte layer interposed therebetween. Used as a dye-sensitized solar cell.

<Dye-sensitized solar cell>
As already described, the semiconductor paste of the present invention does not cause sagging and the like, and is therefore suitable for forming a coating layer by screen printing, and is therefore particularly suitable for forming a semiconductor porous layer on a large-area electrode substrate. Is preferred. Accordingly, the electrode substrate 51 on which the semiconductor porous layer 50 as described above is formed is particularly suitable as the negative electrode substrate (metal electrode substrate) 10 having the structure shown in FIG. Such a negative electrode substrate 10 is used as a dye-sensitized solar cell by facing the positive electrode substrate (transparent electrode substrate) 1 with the electrolyte layer 20 interposed therebetween. That is, in the negative electrode substrate 10, the porous semiconductor layer 50 having the above-described structure (in FIG. 1, this semiconductor porous layer is formed on the metal substrate 11 via a reverse electron prevention layer 15 formed as necessary. 13) is formed.

In the dye-sensitized solar cell having such a structure, the metal substrate 11 is not particularly limited as long as it is formed from a metal material having a low electrical resistance, but generally 6 × 10 ⁻⁶ Ω · m. A metal or alloy having the following specific resistance, for example, aluminum, iron (steel), stainless steel, copper, nickel, or the like is used. Further, the thickness of the metal substrate 11 is not particularly limited as long as it has a thickness enough to maintain an appropriate mechanical strength. If productivity is not taken into consideration, the metal substrate 11 may be formed on a resin film or the like, for example, by vapor deposition. Of course, the substrate such as the resin film does not need to be transparent.

  In the metal substrate 11 as described above, the dye-sensitized semiconductor porous layer 50 (13) described above is formed in a portion that becomes the power generation region X, and the periphery thereof is a sealing region Y that does not participate in power generation. That is why.

  The reverse electron prevention layer 15 appropriately formed on the surface of the metal substrate 11 functions as a rectifying barrier and is formed to suppress a reverse current from the metal substrate 11 to the dye-sensitized semiconductor porous layer 50 (13). For example, it is formed from a metal or metal oxide (for example, titanium dioxide) having a higher resistance than the metal substrate 11 or a chemical conversion treatment film disclosed in Japanese Patent Application Laid-Open No. 2008-53165. Is generally about 5 to 500 nm.

  According to the present invention, a transparent electrode substrate (positive electrode substrate) 1 used as a counter electrode of a negative electrode substrate 10 on which a semiconductor porous layer 50 (13) sensitized with a dye is formed is transparent on a transparent substrate 3. A conductive film 5 is formed.

  As said transparent substrate 3, a transparent glass plate and a transparent resin film are used. As the transparent resin film, any film can be used as long as it is transparent. For example, low-density polyethylene, high-density polyethylene, polypropylene, poly-1-butene, poly-4-methyl-1-pentene, or ethylene, propylene, Polyolefin resins such as random or block copolymers of α-olefins such as 1-butene and 4-methyl-1-pentene; ethylene-vinyl acetate copolymer, ethylene-vinyl alcohol copolymer, ethylene-vinyl chloride Ethylene-vinyl compound copolymer resins such as copolymers; styrene resins such as polystyrene, acrylonitrile-styrene copolymers, ABS, α-methylstyrene-styrene copolymers; polyvinyl alcohol, polyvinyl pyrrolidone, polyvinyl chloride, Polyvinylidene chloride, vinyl chloride-vinyl chloride Vinyl resins such as den copolymers, polyacrylic acid, polymethacrylic acid, polymethyl acrylate and polymethyl methacrylate; polyamide resins such as nylon 6, nylon 6-6, nylon 6-10, nylon 11 and nylon 12 Polyester resins such as polyethylene terephthalate and polybutylene terephthalate; polycarbonates; polyphenylene oxide; cellulose derivatives such as carboxymethyl cellulose and hydroxyethyl cellulose; starches such as oxidized starch, etherified starch and dextrin; and resins composed of a mixture thereof. A film can be used. In general, a polyethylene terephthalate film is preferably used from the viewpoint of strength and heat resistance. Moreover, the thickness and size of the transparent substrate 3 are not particularly limited, and are appropriately determined according to the use of the dye-sensitized solar cell to be finally used.

  The transparent conductive film 5 is typically a film made of an indium oxide-tin oxide alloy (ITO film) or a film in which tin oxide is doped with fluorine (FTO film). Is preferred. These are formed on the transparent substrate 3 by vapor deposition, and the thickness is usually about 0.5 to 0.7 μm.

  An electron reduction conductive layer 7 is appropriately formed on the surface of the transparent conductive film 5. The electron-reducing conductive layer 7 is generally made of a thin platinum layer and has a function of quickly transferring electrons flowing into the transparent conductive film 5 to the electrolyte layer 20. Such an electron reduction conductive layer 20 is thinly formed by vapor deposition so that the average thickness thereof is about 0.1 to 1.5 nm so as not to impair the light transmittance.

  The negative electrode substrate 10 and the transparent electrode substrate (positive electrode substrate) 1 formed as described above are opposed to each other with the electrolyte layer 20 interposed therebetween, and the dye-sensitized semiconductor porous layer 50 (13) having the structure described above and the electrolyte are opposed to each other. The power generation region X is formed by the layer 20.

  The electrolyte layer 20 is formed of various electrolyte solutions containing cations such as lithium ions and anions such as chlorine ions as in the known solar cell. Further, it is preferable that an oxidation-reduction pair capable of reversibly taking an oxidized structure and a reduced structure is present in the electrolyte 20. Examples of such an oxidized-reduced pair include iodine-iodine compounds, bromine- Examples thereof include bromine compounds and quinone-hydroquinone.

  The electrolyte layer 20 is sealed by the sealing material 30 provided in the sealing region Y located at the periphery of the power generation region X, and liquid leakage from between the electrodes is prevented. In general, the thickness of the electrolyte layer 20 is generally about 10 to 50 μm, although it varies depending on the size of the battery finally formed.

  As the sealing material 30, various heat-sealable thermoplastic resins or thermoplastic elastomers such as low-density polyethylene, high-density polyethylene, polypropylene, poly-1-butene, poly-4-methyl-1-pentene, or ethylene, Polyolefin resins such as random or block copolymers of α-olefins such as propylene, 1-butene and 4-methyl-1-pentene; ethylene-vinyl acetate copolymer, ethylene-vinyl alcohol copolymer, ethylene- Ethylene-vinyl compound copolymer resin such as vinyl chloride copolymer; Styrenic resin such as polystyrene, acrylonitrile-styrene copolymer, ABS, α-methylstyrene-styrene copolymer; polyvinyl alcohol, polyvinyl pyrrolidone, polychlorinated Vinyl, polyvinylidene chloride, vinyl chloride Nyl-vinylidene chloride copolymer, vinyl resins such as polyacrylic acid, polymethacrylic acid, polymethyl acrylate, polymethyl methacrylate; nylon 6, nylon 6-6, nylon 6-10, nylon 11, nylon 12, etc. Polyamide resin; Polyester resin such as polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate; Polycarbonate; Polyphenylene oxide; Cellulose derivatives such as carboxymethyl cellulose and hydroxyethyl cellulose; Starch such as oxidized starch, etherified starch, dextrin; and mixtures thereof A resin comprising, for example, is used.

  That is, the sealing material 30 is obtained by molding into a ring shape having a width corresponding to the sealing region Y, for example, by extrusion molding, injection molding, or the like using the above-described thermoplastic resin. By heat sealing (thermocompression bonding) in a state where the material 30 is sandwiched between the negative electrode substrate 10 and the transparent electrode substrate 1 arranged to face each other, the negative electrode substrate 10 and the transparent electrode substrate 1 are joined. Next, an injection tube is inserted into the sealing material 30, and an electrolyte solution for forming the electrolyte layer 20 is injected into the space between the two electrode substrates through the injection tube, whereby the structure shown in FIG. The dye-sensitized solar cell having the electrode substrate having the dye-sensitized semiconductor porous layer 50 (13) and having the structure shown in FIG. 1 can be obtained.

  When a transparent resin film or the like is used as the transparent substrate 3, for example, the negative electrode substrate 10 and the transparent electrode substrate 1 are sealed with a sealing agent 30, and then filled with an electrolyte solution from an unsealed opening, Finally, the dye-sensitized solar cell having the structure shown in FIG. 1 can also be produced by completely sealing the opening with the sealant 30.

  In the dye-sensitized solar cell thus formed, as described above, the dye-sensitized semiconductor porous material formed on the negative electrode substrate 10 by irradiating visible light from the transparent electrode substrate 1 side. The dye in the layer 50 (13) is excited and transitions from the ground state to the excited state, and electrons of the excited dye are injected into the conduction band in the porous layer 50 (13), and the metal electrode substrate 10 ( It moves to the transparent electrode substrate 1 through an external circuit (not shown) through the metal substrate 11). The electrons that have moved to the transparent electrode substrate 1 are carried by the ions in the electrolyte layer 20 and return to the pigment. By repeating such a process, electric energy is extracted and electric power is generated. In the present invention, the sensitizing dye 5 is not only deeply and evenly distributed to the inside and adsorbed and supported on the semiconductor porous layer 50 (13), but also has a large porosity due to scattering. ) Shows high conversion efficiency. Furthermore, even when the power generation region X has a large area, the thickness of the semiconductor porous layer 50 (13) does not vary and has a uniform thickness, so that stable characteristics can be exhibited.

  In addition, although the example which used the electrode substrate 51 in which the semiconductor porous layer 50 was formed according to this invention as the negative electrode substrate 10 of the dye-sensitized solar cell of the structure shown in FIG. 1 was demonstrated, such an electrode substrate was demonstrated. Is not limited to the example of FIG. 1, for example, dye sensitization on the transparent conductive film 5 (or the electron-reduction conductive layer 7) in the dye-sensitized solar cell having the structure shown in FIG. It is of course possible to use the electrode substrate of the present invention as the negative electrode substrate on which the semiconductor porous layer 50 is formed and disposed on the side irradiated with light. In this case, the metal electrode substrate 10 or the transparent electrode substrate provided with the transparent conductive film is the positive electrode substrate.

The superior effect of the present invention is illustrated in the following example.
(Example 1)
The following two types of titanium dioxide fine particles and two types of binder agents (low viscosity ethyl cellulose and high viscosity ethyl cellulose) were prepared as oxide semiconductor fine particles. The viscosity of ethyl cellulose as a binder is a value measured with a B-type viscometer at 25 ° C. using a 10 wt% ethyl cellulose solid content toluene solution.
Spherical titanium dioxide fine particles (A);
Showa Titanium Co., Ltd. F Series Particle size: 30nm
Amorphous titanium dioxide fine particles (B);
AMT series manufactured by Teika Co., Ltd. Particle size 7nm
Low viscosity ethyl cellulose (ES ¹ );
Viscosity: 5-15 cP
Highly viscous ethylcellulose (ES ² );
Viscosity: 30-50 cP

Using the above oxide semiconductor fine particles and ethyl cellulose, terpioneel was used as an organic solvent, and a semiconductor paste having the following composition was prepared.
Composition of semiconductor paste;
Spherical titanium dioxide fine particles A: 15% by weight
Amorphous titanium dioxide fine particle B: 5% by weight
(A / B = 3)
Low viscosity ethyl cellulose (ES ¹ ): 4.4% by weight
Highly viscous ethyl cellulose (ES ² ): 5.6% by weight
^{(ES 1 / ES 2 = 11} /14)
Terpioneer: 70% by weight

  Next, a phosphoric acid chromate treated aluminum plate (thickness 0.3 mm) is prepared as a metal substrate, and the paste prepared above is applied onto this aluminum plate and baked at 450 ° C. for 30 minutes. A 10 μm semiconductor porous layer was formed. In this coating, no one is produced at all, and when the film thickness distribution of the obtained semiconductor layer is measured in a 1 cm square area, a film thickness error range of ± 0.2 μm can be formed with a substantially uniform film thickness. I found out.

  As a result of carrying out nitrogen adsorption / desorption type BET measurement for this semiconductor porous layer, the maximum peak of the pore volume was confirmed at a portion having a pore diameter of about 50 nm. The porosity in the layer was 69% according to the calculated value.

Furthermore, the semiconductor porous layer is immersed in a dye solution composed of a ruthenium complex dye dispersed in ethanol having a purity of 99.5% for 24 hours, and then dried, whereby the semiconductor porous material sensitized with the dye is obtained. A negative electrode substrate having a porous layer was obtained. The ruthenium complex dye used is represented by the following formula.
[Ru (dcbpy) ₂ (NCS) ₂ ] · 2H ₂ O

On the other hand, a counter electrode (positive electrode) substrate composed of an ITO / PEN film deposited with platinum was prepared.
A dye-sensitized solar cell having the structure shown in FIG. 1 was produced by sandwiching an electrolyte solution between the counter electrode substrate and the negative electrode structure produced above. The thickness of the electrolyte solution layer at this time was 5 μm.
As the electrolyte _solution, used was added 4-tert-butylpyridine LiI / I 2 a (0.5 mol / 0.025 mol) to those dissolved in methoxypropionitrile.

When the conversion efficiency of the obtained battery was measured, it was as follows with a measurement area of 1 cm ² , and high conversion efficiency was obtained.
Conversion efficiency: 5.08%
FF (internal resistance): 0.57
J _SC (short circuit current density): 12.9 mA / cm ²
V _OC (open voltage): 0.69V

(Comparative Example 1)
Only spherical titanium dioxide fine particles A are used as oxide semiconductor fine particles, amorphous titanium dioxide fine particles B are not used, and only low-viscosity ethyl cellulose (ES ¹ ) is used as a binder, and high-viscosity ethyl cellulose ( A TiO ₂ paste was prepared in the same manner as in Example 1 except that ES ² ) was not used, and a semiconductor porous layer having a thickness of about 10 μm was formed using this paste in the same manner as in Example 1. did. When the film thickness distribution of the semiconductor porous layer was measured in a 1 cm square area, it was found that the film thickness error range is ± 1 μm, and the film cannot be said to be uniform.

  Next, using the aluminum plate having the above-described semiconductor porous layer on the surface, the dye was supported in exactly the same manner as in Example 1, and then this was used as the negative electrode substrate, and the dye sensitization having the structure shown in FIG. Type solar cells were produced.

When the conversion efficiency of the obtained battery was measured, the measurement area was 1 cm ^{2 and} was as follows. Compared to Example 1, the conversion efficiency was low.
Conversion efficiency: 3.20%
FF (internal resistance): 0.61
J _SC (short circuit current density): 7.64 mA / cm ²
V _OC (open voltage): 0.69V

The figure which shows schematic structure of a dye-sensitized solar cell. The partial expanded sectional view which shows the structure of a semiconductor porous layer. The partial expanded sectional view which shows the structure of the especially suitable semiconductor porous layer.

Explanation of symbols

1: Transparent electrode substrate 3: Transparent substrate 7: Electron reduction conductive layer 10: Negative electrode substrate (metal electrode substrate)
11: Metal substrate 13: Dye-sensitized semiconductor porous layer 15: Reverse electron blocking layer 20: Electrolyte layer 50: Dye-sensitized semiconductor porous layer 51: Electrode substrate 53: Sensitizing dye

Claims (3)

  It contains 5 to 60% by weight of titanium oxide fine particles and 10 to 90% by weight of terpineol, and further contains two types of ethyl cellulose having different viscosities when dissolved in a solvent in a total amount of 5 to 60% by weight. A paste for forming a porous semiconductor layer.   The ethyl cellulose contains low-viscosity ethyl cellulose having a viscosity (25 ° C.) of 5 to 15 cP and a high-viscosity ethyl cellulose having a viscosity (25 ° C.) of 30 to 50 cP in the case of a 10% solid ethyl cellulose concentration solution using toluene as a solvent. The paste for forming a semiconductor porous layer according to claim 1. The semiconductor porous layer according to claim 2, wherein the low-viscosity ethyl cellulose (ES ¹ ) and the high-viscosity ethyl cellulose (ES ² ) are contained at a weight ratio of ES ¹ / ES ² = 51/49 to 80/20. Forming paste.

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