JP2008235104A - Photoelectric conversion element and manufacturing method thereof - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a photoelectric conversion element that can be manufactured by a simple manufacturing process and exhibits superior durability and reliability under a high-temperature condition, and to provide a manufacturing method for such a photoelectric conversion element. <P>SOLUTION: A photoelectric conversion element 1 has a structure of a charge transport layer 4 being held between a substrate 2 and a substrate 3, wherein the outer circumferential portion of the charge transport layer 4 is sealed with a sealing member 5. Further, on the photoelectric conversion element 1, a cladding part 6 is arranged to straddle between the substrate 2 and the substrate 3 at the outer circumferential portion of the sealing member 5. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a photoelectric conversion element such as a dye-sensitized solar cell and a method for producing the same.

  A photoelectric conversion element typified by a solar cell is expected as a clean energy source, and a silicon-based pn junction solar cell has already been put into practical use. However, since silicon-based solar cells use high-purity materials as raw materials or require high-energy processes such as a high-temperature process of about 1000 ° C. or a vacuum process at the time of manufacture, manufacturing costs can be reduced. It has become a big issue.

  Against this background, in recent years, wet solar cells, which do not require high-purity materials or high-energy processes and perform charge separation using a potential gradient generated at a solid-liquid interface, have attracted attention. In particular, a so-called dye that aims to improve conversion efficiency by adsorbing a sensitizing dye that absorbs light on the surface of the semiconductor electrode and absorbing visible light having a wavelength longer than the band gap width of the semiconductor electrode with the sensitizing dye. Research on sensitized photoelectric conversion elements has been actively conducted (see Patent Documents 1 and 2 and Non-Patent Document 1).

In general, a dye-sensitized photoelectric conversion element includes a first glass substrate having a first electrode on which a semiconductor carrying a sensitizing dye is attached, and a second glass having a second electrode disposed opposite to the semiconductor. A glass substrate, and a charge transport layer disposed between the first electrode and the second electrode. In addition, in order to prevent the electrolyte solution constituting the charge transport layer from leaking to the outside or foreign substances from entering the electrolyte solution, the first glass substrate and the second glass substrate are epoxy resin or the like at the periphery thereof. It is joined and sealed with a sealing material made of a resin.
Japanese Patent No. 2664194 JP 2005-93313 A Abstracts of Annual Meeting of the Electrochemical Society of Japan 2002, 141, 2E27

  However, in the conventional dye-sensitized photoelectric conversion element, since the sealing material is formed of a resin that is an organic material, there is a problem in durability and reliability in a high temperature state. In order to solve such a problem, a method of replacing an organic material with an inorganic material can be considered. However, according to this method, it is necessary to heat the entire element to about 400 ° C. in order to melt the inorganic material, and the sensitizing dye is thermally deteriorated when heated. Therefore, when using this method, in order to prevent thermal deterioration of the sensitizing dye, a hole must be formed in the substrate before sealing, and the dye solution must be introduced through the hole after sealing, The manufacturing process is complicated, and the characteristics of the photoelectric conversion element are deteriorated due to insufficient loading of the sensitizing dye.

  The present invention has been made to solve the above-described problems, and an object of the present invention is to provide a photoelectric conversion element that can be manufactured by a simple manufacturing process and has excellent durability and reliability in a high temperature state and a method for manufacturing the photoelectric conversion element. It is to provide.

  The photoelectric conversion element according to the present invention includes a first substrate having a first electrode to which a semiconductor carrying a sensitizing dye is attached, a second substrate having a second electrode disposed opposite to the semiconductor, In a photoelectric conversion element including a charge transport layer disposed between a first electrode and a second electrode and a sealing portion disposed on an outer peripheral portion of the charge transport layer, at least an outer surface of the sealing portion is covered. And a coating portion made of a metal oxide.

  A method for producing a photoelectric conversion element according to the present invention includes a first substrate having a first electrode on which a semiconductor carrying a sensitizing dye is attached, and a second substrate having a second electrode disposed opposite to the semiconductor. In a method for manufacturing a photoelectric conversion element comprising a substrate, a charge transport layer disposed between a first electrode and a second electrode, and a sealing portion disposed on an outer periphery of the charge transport layer, the charge transport layer includes: A step of forming a sealing portion leaving a through-hole portion communicating with a region to be formed, and a material for forming a charge transport layer between the first electrode and the second electrode are supplied through the through-hole portion. And a step of forming a covering portion made of a metal oxide that covers at least the outer surface of the sealing portion after sealing the through-hole portion with a resin-based adhesive.

  According to the photoelectric conversion element and the manufacturing method thereof according to the present invention, since the outer peripheral portion of the sealing portion is covered with the metal oxide, it can be manufactured by a simple manufacturing process, and can be manufactured at a high temperature. It is possible to provide an excellent photoelectric conversion element.

  Hereinafter, with reference to drawings, the manufacturing method of the photoelectric conversion element used as embodiment of this invention is demonstrated.

  As shown in FIG. 1, a photoelectric conversion element 1 according to an embodiment of the present invention has a configuration in which a charge transport layer 4 is sandwiched between a substrate 2 (first substrate) and a substrate 3 (second substrate). The outer peripheral portion of the charge transport layer 4 is sealed with a sealing material 5. Further, in the photoelectric conversion element 1, the covering portion 6 is disposed on the outer peripheral portion of the sealing material 5 so as to straddle between the substrate 2 and the substrate 3. The substrate 2 includes a base material 7, an electrode layer 8 (first electrode) formed on the surface of the base material 7, and a porous semiconductor layer 9 formed on the surface of the electrode layer 8. The semiconductor layer 9 faces the substrate 3. The substrate 3 includes a base material 10 and an electrode layer 11 (second electrode, counter electrode) formed on the surface of the base material 10 and faces the substrate 2 on the electrode layer 11 side. In this embodiment, the covering portion 6 is arranged so as to cover only the outer peripheral portion of the sealing material 5, but as shown in FIG. 2, it is arranged so as to cover the outer peripheral portion of the substrates 2 and 3 as well. May be.

  In the photoelectric conversion element 1 having such a configuration, photoelectric conversion is performed by the following operation mechanism. That is, incident light is absorbed by the sensitizing dye carried on the semiconductor layer 9 via the base material 7 and the electrode layer 8. Excited electrons are generated in the sensitizing dye that has absorbed light, and the excited electrons move to the semiconductor layer 9 and pass between the semiconductor particles and reach the electrode layer 8. Further, the electrons move to the electrode layer 11 through a conducting wire (not shown). The sensitizing dye that has lost the excited electrons receives electrons from the reductant contained in the charge transport layer 4 and returns to the sensitizing dye in the ground state. The oxidized reductant receives electrons from the electrode layer 11 and returns to its original state. The semiconductor layer 9 transports electrons emitted from the sensitizing dye to the electrode layer 8.

  As a method for preparing the charge transport layer 4, a known method can be employed. The charge transport layer 4 can be prepared, for example, by dissolving iodide and iodine in the following solvent or the like. Examples of iodides include tetraalkylammonium iodides such as tetrapropylammonium iodide, asymmetric alkylammonium iodides such as methyltripropylammonium iodide and diethyldibutylammonium iodide, and pyridinium iodides. Examples include quaternary ammonium salt compounds, lithium iodide, 1,2-dimethyl-3-propyl-imidazolium iodide, and the like.

  Examples of the solvent 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, 1,2-dimethoxyethane, Ether compounds such as 1,3-dioxosilane, tetrahydrofuran and 2-methyl-tetrahydrofuran, heterocyclic compounds such as 3-methyl-2-oxazodilinone and 2-methylpyrrolidone, nitrile compounds such as acetonitrile, methoxyacetonitrile and propionitrile, sulfolane And aprotic polar compounds such as didimethyl sulfoxide and dimethylformamide. Further, an ionic liquid (room temperature molten salt) may be used instead of these organic solvents. The ionic liquid is effective from the viewpoint of non-volatility, flame retardancy, and the like, and examples thereof include imidazolium salts, pyridine salts, ammonium salts, alicyclic amines, aliphatic amines, and azonium amines. it can.

  As the sealing material 5, it is preferable to use an organic material such as an epoxy resin, an olefin resin, or an ultraviolet curable resin, or a low-melting-point inorganic material, but it is not limited thereto. In order to inject the charge transport layer 4 inside the base material 7 or the base material 10 after sealing, it is necessary to provide an injection hole. The injection hole needs to be closed with an ultraviolet curable resin after the charge transport layer 4 is injected. Further, a hole may be formed in the sealing material 5 instead of the base material 7 or the base material 10.

  As the covering portion 6, it is important to use a metal oxide, thereby providing a photoelectric conversion element that can be manufactured by a simple manufacturing process and is excellent in durability and reliability in a high temperature state. . As this metal oxide, organosiloxanes such as tetraethoxysilane, tetramethoxysilane, and methyltriethoxysilane, and partial hydrolysates thereof can be used. In a reaction solution composed of water and an organic solvent, boron is used. Solution obtained by hydrolyzing and dehydrating and condensing hydrolyzable organometallic compounds while adjusting the pH value within the range of 4.5 to 5.0 using halide ions as catalysts in the presence of ions It is preferable to use a metal oxide obtained by applying vitrification to the outer peripheral portion of the sealing material 5 and then vitrifying it at a temperature of 200 ° C. or lower. Examples of the method for applying the precursor for forming the metal oxide include a dipping method.

  The material of the base material 7 is not particularly limited as long as the base material 7 side is the light incident side as long as it is a material excellent in translucency, weather resistance, and gas barrier properties. Specifically, a glass plate or a resin film transparent to visible light (wavelength 400 to 800 nm) can be exemplified. Resin film materials include regenerated cellulose, diacetate cellulose, triacetate cellulose, tetraacetyl cellulose, polyethylene, polypropylene, polyvinyl chloride, polyvinylidene chloride, polyvinyl alcohol, polyethylene terephthalate, polycarbonate, polyethylene naphthalate, and polyethersulfone. , Polyetherketone, polysulfone, polyetherimide, polyimide, polyarylate, cycloolefin polymer, norbornene resin, polystyrene, hydrochloric acid rubber, nylon, polyacrylate, polyvinyl fluoride, and polytetrafluoroethylene film 1 or 2 or more types selected from can be used.

  In addition, when the base material 10 side is a light incident side, the base material 7 may be a metal foil such as nickel, zinc, or titanium. Moreover, there is no restriction | limiting in particular in the thickness of the base material 7, but when the base material 7 is a glass plate, it is suitable that the thickness is 0.1-5 mm, especially about 0.7-2 mm. Is preferred. Moreover, when the base material 7 is a resin film, it is suitable that the thickness is 0.01-5 mm, and about 0.07-1 mm is especially preferable.

  The electrode layer 8 functions as the negative electrode of the photoelectric conversion element 1. The electrode layer 8 is preferably made of a material having high conductivity and translucency, zinc oxide, indium-tin composite oxide, a laminate composed of an indium-tin composite oxide layer and a silver layer, and doped with antimony. Examples thereof include tin oxide, tin oxide doped with fluorine, and the like. Among these, tin oxide doped with fluorine and having particularly high conductivity and translucency is preferable. The thickness of the electrode layer 8 is preferably in the range of 0.1 to 10 μm. If the thickness of the electrode layer 8 is within this range, the electrode layer 8 having a uniform thickness can be produced. Further, when the thickness of the electrode layer 8 is within this range, the electrode layer 8 has a sufficient light-transmitting property, and light can be sufficiently incident on the semiconductor layer 9. The surface resistance of the electrode layer 8 is preferably as low as possible, but is preferably 200Ω / □ or less, more preferably 50Ω / □ or less. The lower limit is not particularly limited, but is usually 0.1Ω / □.

  The thickness of the semiconductor layer 9 is preferably in the range of 0.1 to 100 μm. If the thickness of the semiconductor layer 9 is within this range, a sufficient photoelectric conversion effect can be obtained and sufficient transparency to visible light and near infrared light can be secured. The thickness of the semiconductor layer 9 is more preferably 1 to 50 μm, and particularly preferably 3 to 20 μm. The semiconductor layer 9 can be formed by a known method. The porous transparent conductive layer of the semiconductor layer 9 can be formed by, for example, a coating method in which a paste containing semiconductor fine particles and a binder is applied to the electrode layer 8 using a doctor blade, a bar coater, or the like. The paste may be attached to the surface of the electrode layer 8 by spraying, dip coating, screen printing, spin coating, electrodeposition, or the like. When the substrate 6 is a glass substrate, the paste on the surface of the electrode layer 8 is baked at around 400 ° C. to become a porous transparent conductive layer. Further, the semiconductor layer 9 can be formed by immersing the porous material in a metal chloride solution, a metal alkoxide solution, or the like and firing the same. Materials used for the porous transparent conductive layer include nanoparticles such as fluorine-doped tin oxide (FTO), tin-doped indium oxide (ITO), antimony-doped tin oxide, and aluminum-doped zinc oxide. As an example, it is desirable to use FTO nanoparticles because of their high heat resistance and translucency.

As the semiconductor layer formed on the surface of the porous transparent conductive layer, Cd, Zn, In, Pb, Mo, W, Sb, Bi, Cu, Hg, Ti, Ag, Mn, Fe, V, Sn, Zr , Sr, Ga, Si, Cr and other metal oxides, SrTiO ₃ , CaTiO _{3 and} other perovskite oxides, CdS, ZnS, In ₂ S ₃ , PbS, Mo ₂ S, WS ₂ , Sb ₂ S ₃ , Sulfides such as 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, and BiI but ₃ may be exemplified complexes comprising one or more selected from the group consisting of a, the optically dissolved into the electrolyte solution Ku, it is preferable to use TiO ₂ having excellent photoelectric conversion characteristics. As the above-mentioned _{complex, 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 / CdSe / Cd _y Zn _{1- y} S, CdS / HgS / Cds and the like can be exemplified.

The sensitizing dye carried by the semiconductor layer 9 may be the same as that used in conventional dye-sensitized photoelectric conversion elements, and may be either an inorganic dye or an organic dye. Examples of inorganic dyes include ruthenium-cis-diaqua-bipyridyl complexes represented by the composition formula RuL ₂ (H ₂ O) ₂ (L represents 4,4′-dicarboxyl-2,2′-bipyridine), ruthenium- Transition metal complex represented by tris (RuL ₃ ), ruthenium-bis (RuL ₂ ), osmium-tris (OsL ₃ ), composition formula osnium-bis (OsL ₂ ), zinc-tetra (4-carboxyphenyl) porphyrin, Illustrative examples include iron-hexocyanide complexes and phthalocyanines. Examples of organic dyes include 9-phenylxanthene dyes, coumarin dyes, acridine dyes, triphenylmethane dyes, tetraphenylmethane dyes, quinone dyes, azo dyes, indigo dyes, cyanine dyes, Examples include merocyanine dyes and xanthene dyes. Among these, it is preferable to use a ruthenium-bis (RuL ₂ ) derivative having a wide absorption spectrum in the visible light region.

Examples of the method for supporting the sensitizing dye on the semiconductor layer 9 include a method in which the semiconductor layer 9 is immersed in a solution in which the sensitizing dye is dissolved in a solvent to adsorb the sensitizing dye. As the solvent of this solution, any solvent that can dissolve the sensitizing dye, such as water, alcohol, toluene, dimethylformamide, and the like can be used. As the immersion method, while the semiconductor layer 9 is immersed in the solution, the solution is heated and refluxed, or ultrasonic waves are applied to the solution. May be promoted. Further, after the sensitizing dye is adsorbed to the semiconductor layer 9, the sensitizing dye that is not adsorbed and remains in the semiconductor layer 9 is preferably removed from the semiconductor layer 9 by alcohol washing or heating reflux. The amount of the sensitizing dye supported on the semiconductor layer 9 is desirably in the range of 1 × 10 ⁻⁸ to 1 × 10 ⁻⁶ mol / cm ² . Within this range, economical and sufficient photoelectric conversion efficiency can be realized.

  The base material 10 can use the same material as the base material 7. When the base material 7 is transparent, the base material 10 does not necessarily need to be transparent. If both the base materials 7 and 10 are transparent, it is preferable at the point which can inject light from the both base material side.

  The electrode layer 11 functions as the positive electrode of the photoelectric conversion element 1. As the material of the electrode layer 11, the same material as that of the electrode layer 8 can be used, but it is preferable that a material having a catalytic action to give electrons to the reductant is included. Materials having catalytic action include metals such as platinum, gold, silver, copper, aluminum, rhodium, and indium, graphite, carbon carrying platinum, indium-tin composite oxide, tin oxide doped with antimony, and fluorine. Examples thereof include conductive metal oxides such as tin oxide. Of these, platinum, graphite and the like are preferably used. A transparent conductive film may be provided between the base material 10 and the electrode layer 11, and this transparent conductive film can be formed of the same material as the electrode layer 8. In this case, it is desirable that the electrode layer 11 is also transparent. If the electrode layer 11 is transparent, light can be received from the substrate 10 side or the substrate 7 and the substrate 10 side.

  Next, the photoelectric conversion element according to the present invention will be specifically described based on examples.

[Example 1]
In Example 1, first, TiO ₂ nanoparticles having an average primary particle size of 20 nm were dispersed in alcohol to prepare a screen printing paste. Next, this paste is applied onto a 1 mm thick conductive glass substrate (manufactured by Asahi Glass, one surface coated with fluorine-doped tin oxide, F-SnO ₂ , sheet resistance 10 Ω / □). Dried. The obtained dried product was immersed in an aqueous TiCl ₄ solution at 80 ° C. for 1 hour, washed with pure water and air-dried. Next, this was baked in air at 500 ° C. for 30 minutes using an electric furnace to form a semiconductor layer having a thickness of 10 μm on the substrate. Next, after immersing the semiconductor layer in a solution obtained by adding the sensitizing dye bis-tetrabutylammonium [Ru (4,4′-dicarboxyl-2,2′-pipyridine) _2- (NCS) ₂ ] to ethanol, The semiconductor layer was taken out from the solution and allowed to stand in the dark at room temperature for 24 hours to adsorb the sensitizing dye to the semiconductor layer. On the other hand, a platinum layer was formed on one surface of the conductive glass substrate by sputtering. Subsequently, a hole was made with a diamond drill so as to penetrate the conductive glass substrate and the platinum layer. Note that the tin oxide and the platinum layer coated on the conductive glass substrate are the counter electrode. Next, an olefin resin-based hot-melt sealing material is placed between the conductive glass substrate on which the semiconductor layer is formed and the counter electrode so as to surround the semiconductor layer, and these are pressed in the thickness direction while heating them. Then, the glass substrate and the counter electrode were joined through the sealing material. Subsequently, an electrolyte was injected between the conductive glass substrate and the counter electrode from the hole to form a charge transport layer, and then the hole was closed. Next, the metal alkoxide is hydrolyzed in the main agent consisting of water and ethanol while adjusting the pH value within the range of 4.5 to 5.0 using ammonium acid fluoride as a catalyst in the presence of the metal compound boron ion. The outer periphery of the sealing material was immersed in a solution obtained by decomposition and dehydration condensation (manufactured by Micro Giken Co., Ltd., Siragusital B4373). And the said solution was vitrified by applying the temperature of 80 degreeC to the outer peripheral part of a semiconductor layer for 48 hours, and the coating | coated part was formed. Thus, a photoelectric conversion element having a light receiving area of 1 cm ² was obtained.

[Example 1]
In Comparative Example 1, a photoelectric conversion element having a light receiving area of 1 cm ² was obtained by performing the same process as in Example 1 except that the covering portion was not formed.

[Evaluation]
After the photoelectric conversion elements of Example 1 and Comparative Example 1 were stored in a high temperature (80 ° C.) environment for 300 hours, the battery output was measured. The measurement results are shown in Table 1 below as relative values to the initial battery output. For measurement, a photoelectric conversion element was connected to an ammeter (KEYTHLEY236 model), and a solar simulator (manufactured by Yamashita Denso) having an intensity of 100 mW / cm ² was used.

  As is clear from Table 1, the relative value of the photoelectric conversion element of Example 1 is maintained higher than the relative value of the photoelectric conversion element of Comparative Example 1. From this, it was found that a photoelectric conversion element having higher durability over a long time can be obtained by forming the covering portion. Since the covering portion can be formed at a relatively low temperature, the sensitizing dye hardly desorbs or deteriorates when forming the covering portion, and the output is not lowered.

  As mentioned above, although the embodiment to which the invention made by the present inventor is applied has been described, the present invention is not limited by the description and the drawings that form part of the disclosure of the present invention according to this embodiment. That is, it should be added that other embodiments, examples, operation techniques, and the like made by those skilled in the art based on the above embodiments are all included in the scope of the present invention.

It is sectional drawing which shows the structure of the photoelectric conversion element used as embodiment of this invention. It is sectional drawing which shows the structure of the application example of the photoelectric conversion element used as embodiment of this invention.

Explanation of symbols

1: Photoelectric conversion element 2, 3: Substrate 4: Charge transport layer 5: Sealing material 6: Covering portion 7, 10: Base material 8, 11: Electrode layer 9: Semiconductor layer

Claims (4)

  A first substrate having a first electrode to which a semiconductor carrying a sensitizing dye is attached; a second substrate having a second electrode disposed opposite to the semiconductor; the first electrode; In a photoelectric conversion element comprising a charge transport layer disposed between two electrodes and a sealing portion disposed on an outer peripheral portion of the charge transport layer, a metal oxide covering at least the outer surface of the sealing portion A photoelectric conversion element comprising a covering portion.   2. The photoelectric conversion element according to claim 1, wherein the covering portion has a pH value of 4.5 or more and 5.0 in a reaction solution composed of water and an organic solvent using a halide ion in the presence of boron ions as a catalyst. A solution obtained by hydrolyzing and dehydrating and condensing a hydrolyzable organometallic compound while being adjusted within the following range is obtained by vitrifying at a temperature of 200 ° C. or lower. A characteristic photoelectric conversion element.   A first substrate having a first electrode to which a semiconductor carrying a sensitizing dye is attached; a second substrate having a second electrode disposed opposite to the semiconductor; the first electrode; In a method for manufacturing a photoelectric conversion element comprising a charge transport layer disposed between two electrodes and a sealing portion disposed on an outer peripheral portion of the charge transport layer, the device communicates with a region where the charge transport layer is formed. Forming the sealing portion leaving a through-hole portion, supplying a material for forming the charge transport layer between the first electrode and the second electrode via the through-hole portion; And a step of forming a covering portion made of a metal oxide covering at least the outer surface of the sealing portion after sealing the through-hole portion with a resin-based adhesive. Device manufacturing method.   In the manufacturing method of the photoelectric conversion element of Claim 3, the said coating | coated part is pH 4.5 or more in the reaction liquid which consists of water and an organic solvent by making a halide ion into a catalyst in presence of a boron ion. It was obtained by vitrifying a solution obtained by hydrolyzing and dehydrating and condensing a hydrolyzable organometallic compound while adjusting it within a range of 5.0 or less. A method for producing a photoelectric conversion element, comprising:

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