JP2008243623A - Manufacturing method of photoelectric conversion element, and photoelectric conversion element - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a manufacturing method of a highly reliable photoelectric conversion element provided with high photoelectric conversion efficiency, high durability, and particularly high temperature retaining characteristics. <P>SOLUTION: This is the manufacturing method of the photoelectric conversion element equipped with a first substrate 3 equipped with a first electrode 6 having a semiconductor layer 7 carrying sensitized dye, a second substrate 9 equipped with a second electrode 11 opposingly facing the semiconductor layer 7 of the first electrode 6, a charge transport layer 13 formed between the first electrode 6 and the second electrode 11, and a sealing part 15 which is formed at the surrounding of the charge transport layer 13 and which retains the charge transport layer 13 between the first electrode 6 and the second electrode 11. This includes a step of sealing the charge transport layer 13 with the sealing part 15 in an atmosphere of lower pressure than the atmosphere by 0.02 MPa or more. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a method for producing a photoelectric conversion element suitable for use in a dye-sensitized solar cell and the like, and a photoelectric conversion element.

  For example, photoelectric conversion elements such as solar cells are highly expected as clean energy sources, and pn junction solar cells using silicon semiconductor pn junctions have already been put into practical use. However, such a silicon-based solar cell uses a high-purity material as a raw material, or requires a high-temperature process or a vacuum process of about 1000 ° C., so that a reduction in manufacturing cost has been a major issue.

  Under such circumstances, in recent years, wet solar cells that perform charge separation by a potential gradient generated at a solid-liquid interface without relatively requiring high-purity materials and high-energy processes have been attracting attention. In particular, by absorbing a light-absorbing dye on the surface of the semiconductor electrode and absorbing the visible light having a wavelength longer than the band gap of the semiconductor electrode with the dye, how much of the irradiated light energy is converted into electrical energy. Research on so-called dye-sensitized photoelectric conversion elements that aim to improve the photoelectric conversion efficiency is actively conducted.

  The dye-sensitized solar cell proposed by Gretzell et al. In 1991 has been attracting attention because it operates by a mechanism different from a pn junction of a silicon semiconductor and exhibits high photoelectric conversion efficiency. The dye-sensitized solar cell realizes photoelectric conversion by injecting excited electrons generated by a dye that collects light into a semiconductor. Therefore, it is important to support a large amount of a sensitizing dye on a semiconductor in order to increase the light collecting ability, and to inject electrons from the sensitizing dye into the semiconductor as soon as possible. This new dye-sensitized solar cell, also referred to as a Gretzel cell, solves this problem by supporting a Ru film that is a sensitizing dye on a porous film made of ultrafine titanium oxide (for example, a non-colored cell). (See Patent Document 1).

A porous film made of titanium oxide can be produced by a sol-gel method. The porosity of the membrane is about 50%, and a nanoporous structure having a very large internal surface area is formed. For example, if the film thickness is 8 μm, the roughness factor (ratio of the actual area inside the porous to the substrate area) reaches about 720. When this surface is geometrically calculated, the amount of sensitizing dye supported reaches 1.2 × 10 ⁻⁷ mol / cm ³ , and about 98% of incident light is actually absorbed at the maximum absorption wavelength. Become.

As a Ru complex, Gretzell et al. Developed a bis (bipyridyl) Ru (II) complex. The Ru complex has a structure of the general formula cis-X ₂ bis (2,2′-bipyridyl-4,4′-dicarboxylate) Ru (II). X is Cl-, CN-, SCN- or the like. These have been systematically studied for fluorescence, visible light absorption, electrochemical and photoredox behavior, and of these, cis- (diisocyanate) -bis (2,2′-bipyridyl-4,4). '-Dicarboxylate) Ru (II) has been shown to have significantly better performance as a solar absorber and dye sensitizer.

  The visible light absorption of this Ru complex is a charge transfer transition from Ru as a metal atom to a carboxyl group as a ligand. In addition, the carboxyl group is directly coordinated to the Ti atom of titanium oxide on which the Ru complex is supported, thereby forming an intimate electronic contact between the dye sensitizer and the titanium oxide. Due to this electronic contact, electron injection from the Ru complex into the conduction band of titanium oxide occurred at an extremely fast rate of 1 picosecond or less, and was injected into the conduction band of titanium oxide by the oxidized Ru complex in the opposite direction. Electron recapture is thought to occur on the order of microseconds. This speed difference creates the directionality of the photoexcited electrons and performs charge separation with extremely high efficiency. This is a difference from a pn-junction type solar cell that performs charge separation by the potential gradient of the pn junction surface, and is an essential feature of a Gretzel cell.

By the way, the structure of a dye-sensitized photoelectric conversion element is a so-called sandwich structure in which a substance such as an electrolyte solution is sandwiched between two electrodes, and in that sense, is similar to the structure of a liquid crystal element. As a method for producing a dye-sensitized photoelectric conversion element, generally, semiconductor fine particles such as titanium oxide are applied and baked on a substrate such as glass on which a transparent conductive layer is formed, and a sensitizing dye is applied to the surface of the fine particles. A first electrode is formed by supporting the first electrode and a second electrode in which platinum or carbon is fixed on a substrate such as glass on which a transparent conductive layer is similarly formed. Examples of the method include bonding with a resin or a UV curable resin, injecting an electrolyte solution between the electrodes, and finally closing the injection port. Therefore, the dye-sensitized photoelectric conversion element can be manufactured with a simple apparatus.
Gratzel, 1 other, “Nature” (UK), Oct. 24, 1991, volume 353, p. 737-740

  However, although the conversion efficiency that shows how much of the irradiated light energy is converted into electrical energy has improved dramatically, most of the methods for manufacturing photoelectric conversion elements that combine high photoelectric conversion efficiency and high durability have been developed. Is not progressing.

  The present invention has been made in view of the above problems, and an object of the present invention is to provide a method for producing a highly reliable photoelectric conversion element having both high photoelectric conversion efficiency and high durability, particularly high temperature holding characteristics. To do.

  In order to solve the above problems, a method for producing a photoelectric conversion device according to claim 1 includes a first substrate including a first electrode having a semiconductor layer carrying a sensitizing dye, and a first electrode. A second substrate having a second electrode facing the semiconductor layer; a charge transport layer formed between the first electrode and the second electrode; and formed around the charge transport layer, And a sealing portion that holds the charge transport layer between the second electrode and the second electrode, wherein the charge transport layer is at a pressure atmosphere lower than the atmospheric pressure by 0.02 MPa or more. And the step of sealing with a sealing portion.

  According to a second aspect of the present invention, in the method for manufacturing a photoelectric conversion element according to the first aspect, the sealing is performed in a room temperature atmosphere.

  The photoelectric conversion element according to claim 3 includes a first substrate including a first electrode having a semiconductor layer carrying a sensitizing dye, and a second electrode facing the semiconductor layer of the first electrode. A second substrate, a charge transport layer formed between the first electrode and the second electrode, and formed around the charge transport layer, between the first electrode and the second electrode. And a sealing portion that holds the charge transport layer, wherein a pressure of a portion where the charge transport layer is held is 0.02 MPa or more lower than an external pressure.

  The invention according to claim 4 is characterized in that, in the invention according to claim 3, the pressure of the portion where the charge transport layer is held is 0.02 MPa or more lower than the external pressure in the room temperature atmosphere. .

  ADVANTAGE OF THE INVENTION According to this invention, the manufacturing method of the highly reliable photoelectric conversion element which combined high photoelectric conversion efficiency and high durability, especially a high temperature holding characteristic can be provided.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. In the following description, the present invention may be described with specific examples, but the present invention is not limited to the following specific examples.

  FIG. 1 is a schematic cross-sectional view illustrating an example of a photoelectric conversion element. As shown in FIG. 1, the photoelectric conversion element 1 was formed on a substrate 3 (referred to as a first substrate), an electrode 5 formed on one surface of the substrate 3, and a substrate 3. A semiconductor layer 7 formed on the electrode 5 and carrying a sensitizing dye (the electrode 6 composed of the electrode 5 and the semiconductor layer 7 is a first electrode) and a substrate 9 facing the semiconductor layer 7 ( A second substrate), a counter electrode 11 (formed as a second electrode) formed on one surface of the substrate 9, and a charge transport layer 13 formed between the electrode 6 and the counter electrode 11. And a sealing portion 15 formed between the electrode 6 and the counter electrode 11 and around the charge transport layer 13 is a basic configuration.

  Hereinafter, each component requirement is explained in full detail.

  The substrate 3 is often made of glass from the viewpoint of durability, but a resin film may be used as long as the difference between the pressure inside and outside the photoelectric conversion element 1 can be maintained. it can. Transparent films include recycled cellulose film, diacetate cellulose film, triacetate cellulose film, tetraacetyl cellulose film, polyethylene film, polypropylene film, polyvinyl chloride film, polyvinylidene chloride film, polyvinyl alcohol film, polyethylene terephthalate film, polycarbonate film Polyethylene naphthalate film, polyethersulfone film, polyetheretherketone film, polysulfone film, polyetherimide film, polyimide film, polyarylate film, cycloolefin polymer film, norbornene resin film, polystyrene film, hydrochloric acid rubber film, Nylon film, polyacryle Tofirumu, polyvinyl fluoride film, and the like polytetrafluoroethylene film. Among these, a polyethylene terephthalate film, a polyethylene naphthalate film, a polyether sulfone film, a polyimide film, a polyarylate film, a cycloolefin polymer film, and a norbornene resin film are particularly preferable because they are tough and excellent in heat resistance. If the substrate 9 is to function as a light incident substrate, a metal foil such as nickel, zinc, or titanium can be used as the film of the substrate 3.

  The electrode 5 functions as the negative electrode of the photoelectric conversion element 1.

  The electrode 5 is formed of a metal itself or is formed by laminating a conductive material layer on a film. Preferred conductive materials include metals such as platinum, gold, silver, copper, aluminum, rhodium, indium, etc., or carbon or conductive metal oxides such as indium-tin composite oxide, tin oxide doped with antimony , Fluorine-doped tin oxide or the like, or a composite of the above compound or a material obtained by coating silicon oxide, tin oxide, titanium oxide, zirconium oxide, aluminum oxide or the like on the above compound.

  The electrode 5 is better as the surface resistance is lower. The surface resistance is preferably 200Ω / □ or less, and more preferably 50Ω / □ or less. The lower limit is not particularly limited, but is usually 0.1Ω / □.

  The electrode 5 is better as the light transmittance is higher. A preferable light transmittance range is 50% or more, and more preferably 80% or more.

  The film thickness of the electrode 5 is preferably 0.1 to 10 μm. This is because within this range, an electrode film having a uniform thickness can be formed, and light transmittance is not lowered, and sufficient light can be incident on the semiconductor layer 7. When the transparent electrode 5 is used, light is preferably incident from the electrode 5 on the side where the semiconductor layer 7 carrying the sensitizing dye is deposited.

  The semiconductor layer 7 is formed by applying a mixed solution of semiconductor particles and a binder to the electrode 5 by a known and conventional method, for example, a coating method using a doctor blade or a bar coater, a spray method, a dip coating method, a screen printing method, a spin coating method, or the like. If it is a glass substrate, it can be heated and fired at around 500 ° C., and if it is a film substrate, it can be formed by applying pressure with a press.

Semiconductor materials include metal elements such as Cd, Zn, In, Pb, Mo, W, Sb, Bi, Cu, Hg, Ti, Ag, Mn, Fe, V, Sn, Zr, Sr, Ga, Si, and Cr. oxides, SrTiO _3, perovskites such as _{CaTiO 3, CdS, ZnS, in} 2 S 3, PbS, Mo 2 S, sulfides such as _{WS 2, Sb 2 S 3,} Bi 2 S 3, ZnCdS 2, Cu 2 S Metal, chalcogenides such as CdSe, In ₂ Se ₃ , WSe ₂ , HgS, PbSe, CdTe, GaAs, Si, Se, Cd ₂ P ₃ , Zn ₂ P ₃ , InP, AgBr, PbI ₂ , HgI ₂ , BiI ₃ A semiconductor material such as CdS / TiO ₂ , CdS / AgI, Ag ₂ S / AgI, CdS / ZnO, CdS / HgS, CdS / PbS, ZnO / ZnS, ZnO / ZnSe, CdS / HgS, CdS x / CdSe 1 - x, CdS x / Te 1 - x, CdSe x / Te 1 - x, ZnS / CdSe, ZnSe / CdSe, CdS / ZnS, TiO ₂ / Cd ₃ P ₂ , CdS / CdSeCd _y Zn _{1 -y} S, CdS / HgS / CdS and the like can be mentioned. Among these, in the Gretzel cell, titanium oxide is preferable in that it avoids photodissolution in the charge transport layer 13 and exhibits high photoelectric conversion characteristics.

  In general, the particle diameter of the semiconductor particles in the semiconductor layer 7 is preferably 5 to 1000 nm. Within this range, the pore diameter of the semiconductor layer 7 becomes an appropriate pore diameter, and the electrolyte constituting the charge transport layer 13 can sufficiently penetrate into the semiconductor layer 7 to obtain excellent photoelectric conversion characteristics. Because. The particle size of the semiconductor particles is particularly preferably 10 to 100 nm.

  The film thickness of the semiconductor layer 7 is preferably 0.1 to 100 μm. This is because, within this range, a sufficient photoelectric conversion effect can be obtained, and the transparency to visible light and near infrared light is not deteriorated. The film thickness of the semiconductor layer 7 is more preferably 1 to 50 μm, particularly preferably 5 to 30 μm, and most preferably 10 to 20 μm.

As the sensitizing dye, any dye that is commonly used in conventional dye-sensitized photoelectric conversion elements can be used. Such dyes are, for example, RuL ₂ (H ₂ O) ₂ type ruthenium-cis-diaqua-bipyridyl complexes, or ruthenium-tris (RuL ₃ ), ruthenium-bis (RuL ₂ ), osnium-tris (OsL _3). ), Osnium-bis (OsL ₂ ) type transition metal complexes, or zinc-tetra (4-carboxyphenyl) porphyrin, iron-hexocyanide complex, phthalocyanine, and the like. Also, 9-phenylxanthene dyes, coumarin dyes, acridine dyes, triphenylmethane dyes, tetraphenylmethane dyes, quinone dyes, azo dyes, indigo dyes, cyanine dyes, merocyanine dyes, xanthenes Organic dyes such as system dyes can also be suitably used. Among these, ruthenium-bis (RuL ₂ ) derivatives are particularly preferable because they have a wide absorption spectrum in the visible light region.

  Examples of the method of supporting the sensitizing dye on the semiconductor layer 7 include a method of immersing the substrate 3 including the electrode 5 on which the semiconductor layer 7 is deposited in a solution in which the sensitizing dye is dissolved. Any solvent can be used as the solvent for the solution as long as it can dissolve the sensitizing dye, such as water, alcohol, toluene, and dimethylformamide. Further, when the substrate 3 provided with the electrode 5 having the semiconductor layer 7 deposited on the sensitizing dye solution is immersed for a certain period of time, it can be heated and refluxed or an ultrasonic wave can be applied. After the sensitizing dye is supported on the semiconductor layer 7, the sensitizing dye remaining on the semiconductor layer 7 without being supported is preferably removed by washing with alcohol or heating under reflux.

The amount of the sensitizing dye supported on the semiconductor particles may be 1 × 10 ⁻⁸ to 1 × 10 ⁻⁶ mol / cm ² , and particularly 0.1 × 10 ^{−7 to} 9.0 × 10 ⁻⁷ mol / cm ^2. it is preferable that the cm ^2. Within this range, the effect of improving the photoelectric conversion efficiency can be obtained economically and sufficiently.

  The substrate 9 can be made of the same material as the substrate 3. The translucency of the substrate 9 may be either transparent or opaque, but is preferably transparent in that light can be incident from the substrates on both sides. When a metal foil is used as the film of the substrate 3, it is preferable to use a light-transmitting material for the substrate 9.

  The counter electrode 11 functions as a positive electrode of the photoelectric conversion element 1 and can be formed in the same manner as the electrode 5 on the side where the semiconductor layer 7 carrying the sensitizing dye is deposited.

  As the counter electrode 11, it is preferable to use a material having a catalytic action to give electrons to the electrolyte reductant in order to efficiently act as the positive electrode of the photoelectric conversion element 1. Such materials include, for example, metals such as platinum, gold, silver, copper, aluminum, rhodium, and indium, or carbon materials such as graphite, carbon nanotubes, and carbon carrying platinum, or indium-tin composite oxide and antimony. Conductive metal oxides such as doped tin oxide and fluorine-doped tin oxide, or conductive polymers such as polyethylenedioxythiophene, polypyrrole, and polyaniline. Of these, platinum, graphite, polyethylenedioxythiophene and the like are particularly preferable. The substrate 9 on the side on which the counter electrode 11 is arranged can also have a transparent conductive film (not shown) on the surface to which the counter electrode 11 is attached. For example, the transparent conductive film can be formed from the same material as the electrode 5. In this case, it is preferable that the counter electrode 11 is also transparent. If the counter electrode 11 is also transparent, light may be irradiated from the counter electrode 11 side or from both sides. Such a configuration is effective when light irradiation from both the front and back surfaces of the photoelectric conversion element 1 is expected due to the influence of reflected light and the like.

  The charge transport layer 13 is formed by supplying a charge transport material, and the charge transport material is obtained by dissolving an electrolyte in a solvent as necessary.

  The electrolyte is not particularly limited as long as it is a pair of redox constituents composed of an oxidant and a reductant, but a redox constituent that has the same charge as the oxidant and the reductant is preferable. The redox-system constituent material in this specification means a pair of substances that reversibly exist in the form of an oxidant and a reductant in a redox reaction. Examples of such a redox-based constituent material include chlorine compound-chlorine, iodine compound-iodine, bromine compound-bromine, thallium ion (III) -thallium ion (I), mercury ion (II) -mercury ion (I ), Ruthenium ion (III) -ruthenium ion (II), copper ion (II) -copper ion (I), iron ion (III) -iron ion (II), vanadium ion (III) -vanadium ion (II), Examples thereof include, but are not limited to, manganate ion-permanganate ion, ferricyanide-ferrocyanide, quinone-hydroquinone, fumaric acid-succinic acid, and the like. Among these, an iodine compound-iodine is preferable. Examples of the iodine compound include metal iodides such as lithium iodide and potassium iodide, quaternary ammonium iodide compounds such as tetraalkylammonium iodide and pyridinium iodide, and iodide. Particularly preferred are imidazolium iodide compounds such as dimethylpropylimidazolium.

  The solvent used for dissolving the electrolyte is preferably a compound that dissolves the redox constituents and has excellent ion conductivity. As the solvent, either an aqueous solvent or an organic solvent can be used, but it is preferable to use an organic solvent in order to further stabilize the redox constituent. Examples of organic compounds include carbonate compounds such as dimethyl carbonate, diethyl carbonate, methyl ethyl carbonate, ethylene carbonate, and propylene carbonate, ester compounds such as methyl acetate, methyl propionate, and γ-butyrolactone, diethyl ether, and 1,2-dimethoxyethane. , Ether compounds such as 1,3-dioxosilane, tetrahydrofuran, 2-methyl-tetrahydrofuran, heterocyclic compounds such as 3-methyl-2-oxazodilinone, 2-methylpyrrolidone, nitrile compounds such as acetonitrile, methoxyacetonitrile, propionitrile, Examples include aprotic polar compounds such as sulfolane, didimethyl sulfoxide, and dimethylformamide. These can be used alone or in combination of two or more. Among these, from the viewpoint of improving the output characteristics of solar cells, carbonate compounds such as ethylene carbonate and propylene carbonate, heterocyclic compounds such as γ-butyrolactone, 3-methyl-2-oxazozirinone and 2-methylpyrrolidone, acetonitrile, methoxyacetonitrile Nitrile compounds such as propionitrile, 3-methoxypropionitrile and valeric nitrile are preferred. On the other hand, when a device is produced under a reduced pressure environment, a device having a low vapor pressure such as γ-butyrolactone is preferable from the viewpoint of solvent volatilization.

  It can also be said that using an ionic liquid is effective from the viewpoint of non-volatility and flame retardancy. In that case, all known ionic liquids can be used. For example, imidazolium-based, pyridine-based, alicyclic amine-based, aliphatic amine-based, azonium amine-based ionic liquid or EP-716288, WO95 / 18456, Electrochemical Vol. 65, No. 11, page 923 (1997), J. MoI. Electrochem. Soc. 143, 10, 3099 (1996), Inorg. Chem. 35, 1168 (1996).

  Furthermore, when an electrolyte is used as the charge transport material, a gelled electrolyte or a polymer electrolyte can also be used. Examples of the gelling agent include a gelling agent obtained by a polymer, a polymer crosslinking reaction, a gelling agent based on a polyfunctional monomer that can be polymerized, and an oil gelling agent. Generally used gelling electrolytes and polymer electrolytes can be used, but vinylidene fluoride polymers such as polyvinylidene fluoride, acrylic acid polymers such as polyacrylic acid, and acrylonitrile such as polyacrylonitrile. It is preferable to use a polymer having a amide structure in the structure or a polyether polymer such as polyethylene oxide.

  Further, as the charge transport material, a conductive polymer or a hole transport material may be used. In this case, materials generally used for dye-sensitized photoelectric conversion elements, organic solar cells, organic EL elements, and the like can be used.

  In addition, when a liquid such as an organic solvent or an ionic liquid is included in a part of the charge transport material, a material that can be impregnated with a liquid, such as a nonwoven fabric or a porous material, may be used for the charge transport layer 13.

  Further, the charge transport material may be a solid type, and its form is not limited.

  The sealing unit 15 holds the charge transport layer 13 between the electrode 6 and the counter electrode 11.

  As a material of the sealing portion 15, a generally used material can be applied as long as the charge transport layer 13 can be sealed. A thermoplastic resin may be used, or a reactive resin such as an epoxy resin may be used. The reactive resin may be a resin that reacts with heat or a resin that reacts with light such as ultraviolet rays. In addition, an inorganic resin such as glass frit may be used.

  Here, the pressure inside the photoelectric conversion element 1 is lower than the external pressure at the temperature of the use environment (for example, room temperature). In particular, the difference is preferably 0.02 MPa or more. By adopting such a configuration, the photoelectric conversion element 1 has excellent photoelectric conversion efficiency even when exposed to a high temperature environment of 80 ° C. or higher.

  Next, the manufacturing method of the photoelectric conversion element 1 is demonstrated.

  The manufacturing method of the photoelectric conversion element 1 includes a first substrate 3 including a first electrode 6 having a semiconductor layer 7 carrying a sensitizing dye, and a second substrate facing the semiconductor layer 7 of the first electrode 6. A second substrate 9 provided with an electrode 11, a charge transport layer 13 formed between the first electrode 6 and the second electrode 11, and a first electrode formed around the charge transport layer 13. 6 and a second electrode 11, and a sealing part 15 that holds the charge transport layer 13. A photoelectric conversion element manufacturing method comprising: a charge transport layer 13 of 0.02 MPa or more than atmospheric pressure Sealing with a seal in a low pressure atmosphere.

  Here, the pressure of the atmosphere when sealing the charge transport layer 13 becomes the pressure inside the photoelectric conversion element 1 at the temperature at that time. That is, if the temperature of the atmosphere when sealing the charge transport layer 13 is room temperature and the pressure is 0.02 MPa or more lower than atmospheric pressure, the pressure inside the obtained photoelectric conversion element 1 is lower than atmospheric pressure at room temperature. It becomes 0.02 MPa or more lower. Here, when sealing the charge transport layer 13, not only the pressure but also the temperature management is very important. When the charge transport layer 13 is sealed at a temperature lower than the temperature of the usage environment of the photoelectric conversion element 1, the pressure inside the photoelectric conversion element 1 does not become lower than the atmospheric pressure by 0.02 MPa or more under the temperature of the usage environment. There is a case. Therefore, by making the temperature at which the charge transport layer 13 is sealed higher than the temperature of the usage environment of the photoelectric conversion element 1, the pressure inside the photoelectric conversion element 1 is made lower than the atmospheric pressure under the temperature of the usage environment. May be.

  Note that the step of bonding the first electrode 6 with the substrate 3 and the second electrode 11 with the substrate 9 and the step of forming the charge transport layer 13 may be performed before or after or simultaneously.

Hereinafter, the present invention will be described more specifically with reference to examples. The present invention is not limited to the following examples.
Example 1
First, a high-purity titanium oxide powder having an average primary particle diameter of 20 nm was dispersed in ethyl cellulose to prepare a screen printing paste. This was used as the first paste. Further, a high-purity titanium oxide powder having an average primary particle size of 20 nm and an average primary particle size of 400 nm was dispersed in ethyl cellulose to prepare a screen printing paste. This was used as the second paste.

Next, the first paste is applied onto a conductive glass substrate with a transparent electrode (manufactured by Asahi Glass Co., Ltd., fluorine-doped SnO ₂ , thickness 1 mm, surface resistance 10 Ω / □) and dried. The porous titanium oxide film having a thickness of 10 μm was formed on the transparent electrode by firing in air at 30 ° C. for 30 minutes. Then, the second paste is applied on the formed porous titanium oxide film and dried, and the obtained dried product is baked in the air at 500 ° C. for 30 minutes, on the porous titanium oxide film having a thickness of 10 μm. Further, a 4 μm porous titanium oxide film was formed. Thereafter, the substrate on which the porous titanium oxide film is formed is immersed in a sensitizing dye solution represented by [Ru (4,4′-dicarboxyl-2,2′-bipyridine) 2- (NCS) 2]. Then, it was left to stand at room temperature in a dark place for 24 hours, and a dye adsorption treatment was performed to produce a transparent electrode with a glass substrate.

Moreover, platinum was formed on the upper surface of a conductive glass substrate with a transparent electrode (manufactured by Asahi Glass Co., Ltd., fluorine-doped SnO ₂ , surface resistance 10Ω / □) to produce a counter electrode with a glass substrate.

Then, on the counter electrode, a frame-shaped sealing portion surrounding the porous titanium oxide film in the transparent electrode is formed with a hot-melt adhesive, and the frame-shaped sealing portion and the counter electrode are formed. A nonwoven fabric sheet impregnated with an electrolytic solution as a charge transport material was placed on the bottom surface of the recessed portion. Here, the electrolytic solution was 0.5 mol / dm ³ methyltripropylammonium iodide, 0.01 mol / dm ³ lithium iodide, 0.005 mol / dm ³ iodine, 0.5 mol / dm ³ 4- It was prepared by dissolving tert-butylpyridine with γ-butyrolactone.

  Thereafter, the transparent electrode and the counter electrode are bonded together so that the sealing portion is sandwiched in an atmosphere reduced to 0.01 MPa by a vacuum pump at room temperature, and only the sealing portion is heated, and the photoelectric conversion element Was made. Here, the pressure inside the device was at least 0.03 MPa or less at room temperature from the pressure and temperature at the time of bonding and the change in thickness before and after heating the sealing portion.

Results of investigating the relative value to the initial value of the solar cell output after holding the solar cell output when irradiated with 0.1 mW / cm ² light with a xenon lamp for 500 hours in a high temperature environment of 85 ° C. 0.97.
(Example 2)
Except that the pressure at the time of element production was 0.075 MPa, a photoelectric conversion element was produced by the same method as in Example 1, and the solar cell output before and after being held under the same conditions as in Example 1 was examined. The relative value with respect to the initial value after holding was 0.93. The pressure inside the device at this time was approximately 0.1 MPa at room temperature.
(Comparative example)
Except that the pressure at the time of device fabrication was atmospheric pressure, a photoelectric conversion device was fabricated by the same method as in Example 1, and the solar cell output before and after being held under the same conditions as in Example 1 was checked. The relative value to the later initial value was 0.84.

  In the high temperature holding test, the relative value with respect to the initial value is desirably at least 0.9, and in the comparative examples, excellent high temperature holding characteristics were not obtained, whereas in Examples 1 and 2, an excellent high temperature was obtained. Retention characteristics were obtained.

It is a schematic sectional drawing which shows an example of a photoelectric conversion element.

Explanation of symbols

1 photoelectric conversion element 3 substrate (first substrate)
5 electrode 6 electrode (first electrode)
7 Semiconductor layer 9 Substrate (second substrate)
11 Counter electrode (second electrode)
13 Charge transport layer 15 Sealing part

Claims (4)

A first substrate comprising a first electrode having a semiconductor layer carrying a sensitizing dye;
A second substrate comprising a second electrode facing the semiconductor layer of the first electrode;
A charge transport layer formed between the first electrode and the second electrode;
A sealing portion formed around the charge transport layer and holding the charge transport layer between the first electrode and the second electrode;
A method for producing a photoelectric conversion element comprising:
A method for producing a photoelectric conversion element, comprising: sealing the charge transport layer with the sealing portion in a pressure atmosphere lower than atmospheric pressure by 0.02 MPa or more.   The method for producing a photoelectric conversion element according to claim 1, wherein the sealing is performed in a room temperature atmosphere. A first substrate comprising a first electrode having a semiconductor layer carrying a sensitizing dye;
A second substrate comprising a second electrode facing the semiconductor layer of the first electrode;
A charge transport layer formed between the first electrode and the second electrode;
A sealing portion formed around the charge transport layer and holding the charge transport layer between the first electrode and the second electrode;
A photoelectric conversion element comprising:
The photoelectric conversion element, wherein a pressure of a portion where the charge transport layer is held is 0.02 MPa or more lower than an external pressure.   The photoelectric conversion element according to claim 3, wherein the pressure of the portion where the charge transport layer is held is 0.02 MPa or more lower than the external pressure in a room temperature atmosphere.

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