JP5519179B2 - Semiconductor electrode, solar cell using semiconductor electrode, and method of manufacturing semiconductor electrode - Google Patents

Description

  The present invention relates to a semiconductor electrode that converts light energy into electric energy, a solar cell using the semiconductor electrode, and a method for manufacturing the semiconductor electrode.

  Conventionally, in a solar cell, a substrate made of crystalline silicon (Si), amorphous silicon or the like is used as a photoelectric conversion element (see Patent Document 1). Some conventional solar cells use an oxide semiconductor sensitized with an organic dye instead of silicon as a photoelectric conversion element (see Patent Document 2). The photoelectric conversion element converts light energy into electrical energy.

JP-A 61-54275 Japanese Patent No. 2955646

  However, for example, in the solar cell disclosed in Patent Document 1, there is a problem of supply of silicon as a raw material, energy and power generation capacity for a process of forming a substrate such as bulk or thin film crystalline silicon, amorphous silicon, and the like. There are many issues to be solved, such as the problem of energy balance. Further, in the dye-sensitized solar cell disclosed in Patent Document 2, improvement in durability, improvement in power generation efficiency, and the like are problems.

  Therefore, in the field of solar cells, development of a new solar cell different from the conventional solar cell is desired together with the improvement of the conventional solar cell described above.

  Then, an object of this invention is to provide the manufacturing method of the new semiconductor electrode which can be utilized as an electrode used for a solar cell, the solar cell using a semiconductor electrode, and a semiconductor electrode.

  In order to solve the above-described problems, the present invention has the following features. First, the first feature of the present invention is that a transparent electrode disposed on a surface of a light-transmitting substrate is provided, and a metal oxide layer is provided on the opposite surface of the substrate on which the transparent electrode is disposed. And the metal oxide layer includes silicon fine particles that absorb a specific wavelength among light wavelengths transmitted through the substrate, and metal oxide fine particles, and the silicon fine particles are formed of the silicon fine particles. The mixed powder containing is formed into a predetermined particle size by being etched with an etching solution containing hydrofluoric acid and an oxidizing agent, and the silicon fine particles are disposed between the metal oxide fine particles. It is a summary.

  In the feature of the present invention, the silicon fine particles disposed in the metal oxide layer absorbs a specific wavelength that is different for each particle size out of the wavelengths of light transmitted through the substrate, and emits electrons. Therefore, the semiconductor electrode can extract light energy of a specific wavelength among the wavelengths of light transmitted through the substrate as electric energy.

  The second feature of the present invention relates to the first feature of the present invention, and is summarized in that the silicon fine particles having a plurality of types of particle diameters are mixed and used.

  According to the second feature of the present invention, the wavelength to be absorbed is different for each particle size. By using silicon fine particles having a plurality of particle sizes, it is possible to cope with a wide range of wavelengths of light in the visible light region.

  The third feature of the present invention is that the semiconductor electrode has a light-transmitting and incident surface on which light is incident, a counter electrode disposed to face the semiconductor electrode, and the semiconductor electrode and the counter An electrolyte disposed in a space between the electrodes and a sealing material that seals the electrolyte disposed in the space, and the light energy of the light incident on the semiconductor electrode is converted into electrical energy. A solar cell for conversion, wherein the semiconductor electrode has a transparent electrode disposed on a surface of a substrate having optical transparency, and a metal oxide is formed on the opposite surface of the substrate on which the transparent electrode is disposed. A physical layer is provided, and the metal oxide layer includes silicon fine particles that absorb a specific wavelength among wavelengths of light transmitted through the substrate, and metal oxide fine particles, Mixing powder containing silicon fine particles with hydrofluoric acid and It is formed to a predetermined particle size by being etched by the etching solution containing the agent, wherein the silicon particles is summarized in that disposed between the fine particles of the metal oxide.

  In the feature of the present invention, the silicon fine particles disposed in the metal oxide layer absorb a specific wavelength among the wavelengths of light transmitted through the substrate and emit electrons. Therefore, the solar cell can extract light energy of a specific wavelength among the wavelengths of light transmitted through the substrate as electric energy.

  A fourth feature of the present invention relates to the third feature of the present invention, and is summarized in that the silicon fine particles having a plurality of types of particle diameters are mixed and used.

  A fifth feature of the present invention relates to the third feature of the present invention, and has a plurality of transparent electrodes, and each of the transparent electrodes has the metal oxide layer disposed on the opposite surface. The plurality of transparent electrodes are stacked between the substrate and the counter electrode, and each transparent electrode is sealed with the sealing material while being filled with the electrolyte. The gist is that

  The sixth feature of the present invention is related to the fifth feature of the present invention and is summarized in that silicon fine particles having different particle diameters are disposed for each of the plurality of transparent electrodes.

  The seventh feature of the present invention is a step of firing a mixture containing a silicon source and a carbon source in an inert atmosphere, and a step of extracting a product gas from the inert atmosphere and rapidly cooling to obtain a mixed powder containing silicon fine particles And the step of immersing and etching the mixed powder in an etching solution containing hydrofluoric acid and an oxidizing agent, and the transparent electrode on the surface of the transparent electrode formed on the surface. The gist of the invention is to include a step of disposing a metal oxide layer on the opposite surface of the surface to be provided and a step of adsorbing the mixed powder to the metal oxide layer.

  The eighth feature of the present invention relates to the seventh feature of the present invention, and is summarized in that the silicon source is ethyl silicate.

  A ninth feature of the present invention relates to the seventh feature of the present invention, and is summarized in that the carbon source is a phenol resin.

  ADVANTAGE OF THE INVENTION According to this invention, the manufacturing method of the new semiconductor electrode which can be used for the new semiconductor electrode which can be used as an electrode used for a solar cell, the solar cell using a semiconductor electrode, and a solar cell can be provided.

FIG. 1 is a configuration diagram of a single-layer solar cell according to an embodiment of the present invention. FIG. 2 is a configuration diagram of a tandem solar cell according to an embodiment of the present invention. FIG. 3 is a configuration diagram illustrating an intermediate electrode according to an embodiment of the present invention. FIG. 4 is a flowchart illustrating a mixed powder containing silicon fine particles. FIG. 5 is a flowchart illustrating a method for manufacturing a semiconductor electrode. FIG. 6 is a schematic view of a manufacturing apparatus used for manufacturing silicon fine particles.

  Embodiments of a semiconductor electrode and a solar cell according to the present invention will be described with reference to the drawings. Specifically, (1) structure of solar cell, (2) method for producing silicon fine particles and semiconductor electrode, (3) silicon source and carbon source, (4) action / effect, and (5) other embodiments explain.

  In the following description of the drawings, the same or similar parts are denoted by the same or similar reference numerals. However, it should be noted that the drawings are schematic and ratios of dimensions and the like are different from actual ones.

  Accordingly, specific dimensions and the like should be determined in consideration of the following description. Moreover, it is a matter of course that portions having different dimensional relationships and ratios are included between the drawings.

(1) Structure of Solar Cell (1-1) Single Layer Type FIG. 1 is a configuration diagram of a single layer type solar cell according to the present invention. The solar cell 1 includes a semiconductor electrode 10, a counter electrode 20, an electrolyte 30, and a sealing material 40. The semiconductor electrode 10 is light transmissive and has an incident surface 11a on which light is incident. The counter electrode 20 is disposed to face the semiconductor electrode 10. The electrolyte 30 is disposed in a space between the semiconductor electrode 10 and the counter electrode 20. The sealing material 40 seals the electrolyte 30 disposed in the space. The transparent electrode 12 and the counter electrode 20 are electrically connected by a terminal and an electric wire (not shown).

  The semiconductor electrode 10 has a transparent electrode 12. The transparent electrode 12 is disposed on the surface opposite to the incident surface 11a in the substrate 11 having light transmittance and having the incident surface 11a.

  The transparent electrode 12 has a metal oxide layer 13 disposed on the opposite surface to the surface to which the substrate 11 is bonded. The metal oxide layer 13 includes metal oxide fine particles 14 and silicon fine particles 15.

  The substrate 11 is a substrate having optical transparency. For example, silicate glass and a plastic substrate are mentioned. Various plastic substrates may be bonded together. As a material for the plastic substrate, a resin having a glass transition temperature of 50 ° C. or higher is preferable.

  For example, polyester resins such as polyethylene terephthalate, polycyclohexylene terephthalate, polyethylene naphthalate, polyamide resins such as nylon 46, modified nylon 6T, nylon MXD6, polyphthalamide, and ketone resins such as polyphenylene sulfide and polythioethersulfine Main components are organic resins such as sulfone resins such as polysulfone and polyethersulfone, polyether nitrile, polyarylate, polyetherimide, polyamideimide, polycarbonate, polymethyl methacrylate, triacetyl cellulose, polystyrene, and polyvinyl chloride. A transparent resin substrate can be used. Among these, polycarbonate, polymethyl methacrylate, polyvinyl chloride, polystyrene, and polyethylene terephthalate are excellent in transparency. Also, the birefringence value is good.

The transparent electrode 12 is a thin film of conductive metal oxide containing In ₂ O ₃ and SnO ₂ . Examples of conductive metal oxides include In ₂ O ₃ : Sn (ITO), SnO ₂ : Sb (ATO), SnO ₂ : F (FTO), ZnO: Al (AZO), ZnO: F, CdSnO ₄ can be mentioned.

  As the metal oxide fine particles 14, one or more of known semiconductors such as titanium oxide, zinc oxide, tungsten oxide, antimony oxide, niobium oxide, indium oxide, barium titanate, strontium titanate, and cadmium sulfide are used. Can be used. From the viewpoint of stability, it is preferable to use titanium oxide. Examples of titanium oxide include various types of titanium oxide such as anatase type titanium oxide, rutile type titanium oxide, amorphous titanium oxide, metatitanic acid, orthotitanic acid, titanium hydroxide, and hydrous titanium oxide.

  The silicon fine particles 15 have a characteristic of absorbing a specific wavelength corresponding to the particle diameter among wavelengths of light transmitted through the substrate 11. That is, the silicon fine particles 15 are excited by light having a specific wavelength and emit electrons. The silicon fine particles 15 are disposed between the metal oxide fine particles 14. The silicon fine particles 15 are used by mixing a plurality of types of silicon fine particles. The particle size of the silicon fine particles 15 is included in a predetermined size range.

  In the present embodiment, the silicon fine particles 15 are generated by immersing a mixed powder of silicon dioxide and silicon in an etching solution. In particular, it is determined by the etching time in the etching process.

  The metal oxide fine particles 14 and the silicon fine particles 15 may be dispersed in a binder and applied to the transparent electrode 12. The binder only needs to disperse the metal oxide fine particles 14 and the silicon fine particles 15. In general, polymers are used. For example, polyalkylene glycol (for example, polyethylene glycol), acrylic resin, polyester, polyurethane, epoxy resin, silicon resin, fluorine resin, polyvinyl acetate, polyvinyl alcohol, polyacetal, polybutyral, petroleum resin, polystyrene, fiber resin, etc. Can be mentioned.

The electrolyte 30 is, for example, a redox electrolyte. Examples thereof include I ⁻ / I ₃ ⁻ system, Br ⁻ / Br ₃ ⁻ system, and quinone / hydroquinone system. I ^- / I ₃ ^- system electrolyte can be obtained by mixing an ammonium salt of iodine and iodine. The electrolyte 30 may be a liquid or a solid. For example, a liquid electrolyte or a solid polymer electrolyte containing a liquid electrolyte in a polymer substance.

  As the solvent for the liquid electrolyte, an electrochemically inert electrolyte can be used. As the liquid electrolyte, for example, acetonitrile, propylene carbonate, ethylene carbonate, or the like can be used.

The solvent for the liquid electrolyte may have conductivity. It is preferable to use one having a catalytic ability that allows a reduction reaction of oxidized redox ions such as I ₃ -ion to be performed at a sufficient speed. As an example, a platinum electrode, a surface of a conductive material subjected to platinum plating or platinum deposition, rhodium metal, ruthenium metal, ruthenium oxide, carbon, and the like can be given.

The solar cell 1 is produced using each structure mentioned above. A metal oxide layer 13 is formed on the substrate 11 on which the transparent electrode 12 is formed. Specifically, a dispersion liquid in which a binder is added to the metal oxide fine particles 14 as necessary is prepared and applied onto the substrate 11 to form the metal oxide layer 13. If necessary, after heating, pressurizing, etc., it is immersed in a silicon fine particle dispersion to adsorb the silicon fine particles on the surface of the oxide fine particles. Heating or the like may be added to strengthen the chemical bond.
The counter electrode 20 uses a substrate in which a transparent base material and a catalyst transparent electrode (for example, a platinum electrode produced by vacuum deposition) are disposed on the incident surface side surface of the transparent base material. The counter electrode 20 is bonded to the substrate 11 on which the metal oxide layer 13 is disposed via the sealing material 40. An electrolyte 30 is sealed in a space between the substrate 11 and the counter electrode 20.

In the solar cell 1 described above, the silicon fine particles 15 arranged around the metal oxide fine particles 14 absorb a specific wavelength corresponding to the particle diameter among wavelengths of light transmitted through the substrate 11. That is, the silicon fine particles 15 are excited by light having a specific wavelength and emit electrons. The emitted electrons are delivered to the transparent electrode 12 through the metal oxide fine particles 14. The holes remaining in the silicon fine particles 15 oxidize the electrolyte 30. For example, I ^{− is changed} to I ₃ ⁻ or Br ⁻ is changed to Br ₃ ⁻ . The oxidized iodide ion or bromide ion receives electrons again at the counter electrode 20 and is reduced. Thus, a solar cell is comprised by an electron cycling between both poles.

(1-2) Multijunction Type FIG. 2 is a configuration diagram of a tandem solar cell according to the present invention. The solar cell 2 includes a plurality of transparent electrodes. That is, the solar cell 2 includes a substrate 101, a plurality of intermediate electrodes 110, 120, 130, 140, 150, a counter electrode 102, an electrolyte 103, and a sealing material 104. The substrate 101 is light transmissive and has an incident surface 101a. An intermediate electrode 110 is disposed on the surface of the substrate 101 opposite to the incident surface 101a.

  The configuration of the intermediate electrodes 110, 120, 130, 140, 150 is shown in FIG. The intermediate electrode is disposed on the transparent substrate 501, the transparent electrode 502 disposed on the incident surface side of the transparent substrate 501, and the catalyst electrode 503 formed on the surface opposite to the incident surface of the transparent substrate 501. Transparent electrode 504. The intermediate electrode 110 is disposed on the surface of the substrate 101 opposite to the incident surface 101a.

  A metal oxide layer 111 is disposed on the intermediate electrode 110. In the metal oxide layer 111, metal oxide fine particles on which silicon fine particles are supported are arranged. A metal oxide layer 121 is disposed on the transparent electrode 120. The metal oxide layer 121 includes metal oxide fine particles 211 and silicon fine particles 212. A metal oxide layer 131 is disposed on the intermediate electrode 130. The metal oxide layer 131 includes metal oxide fine particles 221 and silicon fine particles 222. A metal oxide layer 141 is disposed on the intermediate electrode 140. The metal oxide layer 141 includes metal oxide fine particles 231 and silicon fine particles 232. A metal oxide layer 151 is disposed on the intermediate electrode 150. The metal oxide layer 151 includes metal oxide fine particles 241 and silicon fine particles 242.

  The silicon fine particles 202, the silicon fine particles 212, the silicon fine particles 222, the silicon fine particles 232, and the silicon fine particles 242 are so-called silicon nanodots. The particle diameters of the silicon fine particles 202, the silicon fine particles 212, the silicon fine particles 222, the silicon fine particles 232, and the silicon fine particles 242 are different.

  The silicon microparticles 202, the silicon microparticles 212, the silicon microparticles 222, the silicon microparticles 232, and the silicon microparticles 242 absorb different specific wavelengths among the wavelengths of light transmitted through the substrate 101.

  For example, the absorption wavelength of the silicon fine particles 202 is 500 nm. The absorption wavelength of the silicon fine particles 212 is 600 nm. The absorption wavelength of the silicon fine particles 222 is 700 nm. The absorption wavelength of the silicon fine particles 232 is 900 nm. The absorption wavelength of the silicon fine particles 242 is 1100 nm.

  The electrolyte 103 is disposed in a space between the intermediate electrode 110 and the intermediate electrode 120. The electrolyte 103 is disposed in a space between the intermediate electrode 120 and the intermediate electrode 130. The electrolyte 103 is disposed in a space between the intermediate electrode 130 and the intermediate electrode 140. The electrolyte 103 is disposed in a space between the intermediate electrode 140 and the intermediate electrode 150. The electrolyte 103 is disposed in a space between the intermediate electrode 150 and the counter electrode 102. The sealing material 40 seals the electrolyte 103 in the space.

  A material that can be used for the substrate 11 described above can be used as the substrate 101. Moreover, the material applicable to the transparent electrode 12 mentioned above can be used as the intermediate electrode 110, the intermediate electrode 120, the intermediate electrode 130, the intermediate electrode 140, and the intermediate electrode 150. Materials usable as the metal oxide fine particles 14 can be used as the metal oxide fine particles 201, the metal oxide fine particles 211, the metal oxide fine particles 221, the metal oxide fine particles 231, and the metal oxide fine particles 241. . Similarly, materials applicable to the silicon fine particles 15, the electrolyte 30, and the sealing material 40 can be used as the silicon fine particles 202, the silicon fine particles 212, the silicon fine particles 222, the silicon fine particles 232 and the silicon fine particles 242, the electrolyte 103, and the sealing material 104. .

(2) Production of Silicon Fine Particles (2-1) Silicon Fine Particles A production process for producing the above-described silicon fine particles 15, silicon fine particles 202, silicon fine particles 212, silicon fine particles 222, silicon fine particles 232, and silicon fine particles 242 will be described.

  In the process of manufacturing the silicon carbide sintered body, a powder (silicon carbide powder) used to form the silicon carbide sintered body is manufactured. As an example of a method for producing silicon carbide powder, there is a method of firing a high-purity silicon carbide precursor (referred to as a high-purity precursor). The high purity precursor is a mixture obtained by homogeneously mixing a silicon source, a carbon source, and a polymerization or crosslinking catalyst.

  The silicon fine particles used in the present embodiment are separated from the gas produced as a by-product in the step of firing the high purity precursor. In the process of producing silicon carbide powder from a high-purity precursor, after mixing a silicon source and a carbon source, when the mixture is heated at a temperature of 1600 ° C. or higher in a non-oxidizing atmosphere, silicon carbide (SiC) is converted into a powder. It is taken out.

  That is, in the process of producing silicon carbide powder from a high-purity precursor, silicon monoxide (SiO) gas is generated by a chemical reaction represented by the following formulas (1) and (2) in an inert atmosphere (non-oxidizing atmosphere). Via, silicon carbide is produced. According to this method, silicon carbide is extracted as a powder.

SiO ₂ + C → SiO + CO (1)
SiO + 2C → SiC + CO (2)

When the present invention rapidly cools the gas extracted from the inert atmosphere after silicon carbide is generated to a temperature of less than 1600 ° C., a chemical reaction represented by the following formula (3) occurs, thereby causing silicon (Si ) And silicon dioxide (SiO ₂ ) was found to be obtained. The silicon fine particles used in the present embodiment are included in the mixed powder formed by the formula (3).

2SiO → Si + SiO ₂ (3)
As described above, the mixed powder containing silicon fine particles shown as an embodiment of the present invention is to separate silicon fine particles from the gas generated as a by-product in the step of firing a high purity precursor.

(2-2) Method for Producing Silicon Fine Particles FIG. 4 is a flowchart for explaining a mixed powder containing silicon fine particles. As shown in FIG. 1, the mixed powder containing silicon fine particles has a firing step S1, a rapid cooling step S2, and a step S3 of immersing and etching the mixed powder in an etching solution containing hydrofluoric acid and an oxidizing agent. .

  The firing step S1 is a mixture (referred to as a high-purity precursor) in which a silicon source containing at least one silicon compound, a carbon source containing at least one organic compound that generates carbon by heating, and a polymerization or crosslinking catalyst are mixed. ) In an inert atmosphere. The silicon source is, for example, ethyl silicate. The carbon source is, for example, a phenol resin. Details of the silicon source and the carbon source will be described later.

  In the firing step S1, first, a mixture of ethyl silicate as a silicon source, a phenol resin as a carbon source, and maleic acid as a polymerization catalyst is heated at about 150 ° C. to be cured. The Si / C ratio is preferably 0.5 to 3.0. Next, the cured product is heated at 800 to 1200 ° C. in a nitrogen or argon atmosphere for 0.5 to 2 hours. Then, it heats at 1500-2000 degreeC by nitrogen or argon atmosphere.

  The rapid cooling step S2 is a step in which the gas generated when the high-purity precursor is fired in the firing step is extracted from the inert atmosphere and rapidly cooled. That is, a gas which is a by-product of the reaction for generating silicon carbide by firing a high-purity precursor is taken out and cooled. When the gas as a by-product is cooled under the above conditions, a mixed powder containing silicon fine particles is obtained.

In the rapid cooling step S2, the product gas is extracted by placing it in an argon gas stream. The product gas is quenched to room temperature. A mixed powder composed of silicon (Si) and silica (SiO ₂ ) is obtained from the generated gas.

  The etching step S3 is a step of etching by immersing the mixed powder in an etching solution containing hydrofluoric acid and an oxidizing agent. Silicon is extracted from the mixed powder obtained in the quenching step S2 by the etching step S3. Thereafter, if necessary, silicon is extracted from the silicon solution and dried. Thereby, silicon fine particles having a desired particle diameter are obtained.

Specifically, in the etching step S3, the mixed powder is immersed in an etching solution containing hydrofluoric acid and an oxidizing agent. Examples of the oxidizing agent include nitric acid (HNO ₃ ) and hydrogen peroxide (H ₂ O ₂ ). Further, a hydrophobic solvent such as cyclohexane or a slightly polar solvent such as 2-propanol may be mixed in the etching solution in order to facilitate the collection of silicon fine particles. The etching time is adjusted so that a desired emission peak is obtained. As the etching time becomes longer, the emission peak tends to shift to the shorter wavelength side. When etching progresses to such an extent that a desired emission peak is obtained, the silicon fine particle illuminant is taken out of the etching solution and subjected to a surface termination reaction or appropriately dried to obtain silicon fine particles having a desired extinction coefficient.

(2-3) Manufacturing Method of Semiconductor Electrode FIG. 5 is a flowchart for explaining a manufacturing method of the semiconductor electrode 10 according to this embodiment. In the method for manufacturing the semiconductor electrode 10 according to the present embodiment, the transparent electrode 12 is disposed on the surface of the light-transmitting substrate 11 and the surface opposite to the surface of the transparent electrode 12 that is bonded to the substrate 11 is used. Step S12 in which the metal oxide layer 13 is disposed, Step S13 for supporting or adsorbing the silicon fine particle dispersion obtained through the baking step S1, the quenching step S2, and the extraction step S3 described above on the metal oxide layer 11; Have

  The order of the step of disposing the metal oxide layer 13 on the substrate 11 on which the transparent electrode 12 is disposed and the above-described firing step S1, quenching step S2, and etching step S3 are limited to the order shown in FIG. Not. That is, after the metal oxide layer 13 is provided on the substrate 11 on which the transparent electrode 12 is provided, the step of producing the silicon fine particles 15 may be performed, or after the silicon fine particles 15 are produced, The step of disposing the metal oxide layer 13 on the substrate 11 on which is disposed may be performed.

(3) Silicon source and carbon source (3-1) Silicon source The silicon source containing the silicon compound is at least one selected from the group comprising a liquid silicon compound and a silicon solid synthesized from a hydrolyzable silicon compound. A seed containing silicon. A liquid silicon source and a solid silicon source can be used in combination. When a plurality of types of silicon sources are used, at least one type is liquid.

  The liquid silicon source is a polymer of alkoxysilane (mono-, di-, tri-, tetra-) and tetraalkoxysilane. Among the alkoxysilanes, tetraalkoxysilane is preferably used. Specific examples include methoxysilane, ethoxysilane, propoxysilane, butoxysilane and the like. In view of easy handling of the raw material, ethoxysilane is preferably used.

  Examples of the tetraalkoxysilane polymer include a low molecular weight polymer (oligomer) having a polymerization degree of about 2 to 15 and a silicate polymer having a high polymerization degree and exhibiting a liquid state. Examples of the solid silicon source that can be used in combination with these include silicon oxide.

  Silicon oxide includes SiO, silica gel (colloidal ultrafine silica-containing liquid, hydroxyl group, alkoxyl group, etc. inside), silicon dioxide (fine silica, quartz powder, etc.) and the like.

  In addition, as a silicon-containing raw material, a group of polymers obtained by trimethylation of a hydrolyzable silicic acid compound, an ester of a hydrolyzable silicon compound and a monovalent or polyhydric alcohol (for example, diol, triol) (for example, four Ethyl silicate synthesized by the reaction of silicon chloride and ethanol), reaction products other than esters obtained by the reaction of hydrolyzable silicon compounds and organic compounds (for example, tetramethylsilane, dimethyldiphenylsilane, polydimethylsilane) ) And the like.

  The silicon solid synthesized from the hydrolyzable silicon compound may be any substance that reacts with carbon to form silicon carbide in a high-temperature non-oxidizing atmosphere (in an inert atmosphere). A preferred example of the siliceous solid is amorphous silica fine powder obtained by hydrolysis of silicon tetrachloride.

  A silicon source may be used independently and may be used together 2 or more types. Among these silicon sources, from the viewpoint of good homogeneity and handling properties, it is preferable to use a tetraethoxysilane oligomer or a mixture of tetraethoxysilane oligomer and fine powder silica.

  The silicon source is preferably a substance containing silicon with high purity. Here, high purity indicates that the impurity content of the silicon compound before the formation of the mixture is 20 ppm or less. More preferably, the impurity content is 5 ppm or less.

  The silicon source is preferably one that generates silicon monoxide by heating. Specifically, it is preferable to use ethyl silicate as the silicon source.

(3-2) Carbon source The carbon-containing raw material used as the carbon source is preferably a high-purity organic compound containing oxygen in the molecule and carbon remaining by heating. The carbon source is a monomer, oligomer, or polymer composed of any one or two or more organic compounds that can be polymerized or crosslinked by heat, a catalyst, or a crosslinking agent.

  Preferable specific examples of the carbon source include phenol resins, furan resins, urea resins, epoxy resins, unsaturated polyester resins, curable resins such as polyimide resins and polyurethane resins, phenoxy resins, monosaccharides such as glucose, sucrose, etc. And various saccharides such as polysaccharides such as cellulose and starch. In particular, a resol type or novolac type phenol resin having a high residual carbon ratio and excellent workability is preferable.

  The resol type phenolic resin useful in the present embodiment includes monovalent or divalent phenols such as phenol, cresol, xylenol, resorcin, and bisphenol A in the presence of a catalyst (specifically, ammonia or organic amine). It is produced by reacting aldehydes such as formaldehyde, acetaldehyde and benzaldehyde.

  The carbon source is liquid at room temperature. The carbon source has solubility in a solvent. The carbon source has thermoplasticity or heat melting property and becomes soft or liquid by heating. Thus, the liquid or softening carbon source can be homogeneously mixed with the silicon source. A resol type phenol resin, a novolac type phenol resin, or the like can be suitably used as a carbon source. In particular, a resol type phenol resin is preferably used.

(3-3) Catalyst The polymerization and crosslinking catalyst used for the production of high-purity silicon carbide powder can be appropriately selected depending on the carbon source. For example, when the carbon source is a phenol resin or a furan resin, acids such as maleic acid, toluenesulfonic acid, toluenecarboxylic acid, acetic acid, oxalic acid, sulfuric acid and the like can be mentioned. Among these, toluenesulfonic acid is preferably used.

(4) Silicon Fine Particle Manufacturing Device (4-1) Configuration of Manufacturing Device FIG. 6 shows a schematic diagram of a manufacturing device 301 used for manufacturing silicon fine particles. The manufacturing apparatus 301 includes a heating container 302 and a stage 308 that holds the heating container 302. The heating container 302 contains a mixture (high purity precursor) W in which a silicon source, a carbon source, and a polymerization or crosslinking catalyst are mixed.

  The manufacturing apparatus 301 includes heating elements 310a and 310b. The heating elements 310 a and 310 b heat the mixture W inside the heating container 302. The manufacturing apparatus 301 includes a heat insulating material 312 that covers the heating container 302 and the heating elements 310a and 10b.

  The manufacturing apparatus 301 includes a suction pipe 321 and a dust collector 322. The suction tube 321 is connected to the inside of the heating container 302. The suction pipe 321 sucks the gas generated when the mixture W is baked from the inside of the heating container 302 and guides it to the dust collector 322. The dust collector 322 collects the mixed powder obtained from the sucked gas.

  The manufacturing apparatus 301 includes a blower 323 and a supply pipe 324 connected to the heating container 302. The blower 323 supplies argon gas to the supply pipe 324. The supply pipe 324 supplies argon gas into the heating container 302. That is, the argon gas circulates in the order of the supply pipe 324, the heating container 302, and the suction pipe 321 of the manufacturing apparatus 301. The gas generated from the mixture W is collected by the dust collector 322 on an argon gas stream.

  The manufacturing apparatus 301 has a solenoid valve 325. The electromagnetic valve 325 is provided in the suction pipe 321, and the electromagnetic valve 325 is automatically opened and closed according to the pressure set as the internal pressure of the heating container 302.

(4-2) Operation of Manufacturing Apparatus The manufacturing apparatus 301 generates heat from the heating elements 310a and 310b and heats the heating container 302 under a predetermined temperature condition. At this time, the inside of the heating container 302 is maintained in a nitrogen atmosphere or an argon atmosphere. The above corresponds to the firing step S1.

Subsequently, the manufacturing apparatus 301 operates the blower 323. At this time, when the blower 323 is activated, the gas generated from the mixture W is extracted from the inside of the heating container 302 to the dust collector 322 via the suction pipe 321 along the air flow of the argon gas supplied from the blower 323. Since the outside of the heat insulating material 312 is at room temperature, the gas guided to the outside of the heating container 302 by riding on an argon gas stream is rapidly cooled to room temperature. At this time, a composite of silicon (Si) and silicon dioxide (SiO ₂ ) is obtained from the gas. The obtained composite is collected by a dust collector 322. The above corresponds to the rapid cooling step S2.

The composite powder (referred to as mixed powder) collected by the dust collector 322 is etched by being immersed in an etching solution containing hydrofluoric acid and an oxidizing agent (corresponding to the etching step S3). The silicon dioxide (SiO ₂ ) covering the periphery of the silicon fine particles 15 is removed by etching. Furthermore, the particle size of silicon (Si) is adjusted.

(5) Action / Effect The semiconductor electrode 10 has a transparent electrode 12 disposed on the surface of the substrate 11 having optical transparency, and metal oxide is formed on the surface of the substrate 11 opposite to the surface on which the transparent electrode 12 is disposed. The physical layer 13 is disposed, and the metal oxide layer 13 includes silicon fine particles 15 that absorb a specific wavelength among light wavelengths transmitted through the substrate 11 and metal oxide fine particles 14. The silicon fine particles 15 are etched by immersing the obtained composite powder of silicon (Si) and silicon dioxide (SiO ₂ ) (referred to as mixed powder) in an etching solution containing hydrofluoric acid and an oxidizing agent. The silicon dioxide (SiO ₂ ) covering the periphery of the silicon fine particles 15 is removed by etching. Furthermore, the particle size of silicon (Si) is adjusted. The etched silicon fine particles 15 are disposed between the metal oxide fine particles 14.

  In the solar cell 1, the silicon fine particles 15 disposed on the metal oxide layer 13 absorb a specific wavelength among the wavelengths of light transmitted through the substrate 11 and emit electrons. Therefore, the semiconductor electrode 10 can extract light energy of a specific wavelength among the wavelengths of light transmitted through the substrate 11 as electric energy.

  The solar cell 2 shown as this embodiment has a plurality of intermediate electrodes 110 to 150, and each of the intermediate electrodes 110 to 150 has a metal oxide layer 111 and a metal oxide layer on the surface opposite to the light incident surface. A physical layer 121, a metal oxide layer 131, a metal oxide layer 141, and a metal oxide layer 151 are provided. The plurality of intermediate electrodes 110 to 150 uses the intermediate electrode described in FIG.

  In each of the metal oxide layer 111, the metal oxide layer 121, the metal oxide layer 131, the metal oxide layer 141, and the metal oxide layer 151, silicon fine particles having different particle diameters are disposed. Therefore, it is possible to absorb a specific wavelength different for each of the plurality of transparent electrodes.

  As described above, the semiconductor electrode 10 according to this embodiment can be used as an electrode used in a solar cell.

(6) Other Embodiments As described above, the present invention has been described according to the embodiment. However, it should not be understood that the description and drawings constituting a part of this disclosure limit the present invention. From this disclosure, various alternative embodiments, examples and operational techniques will be apparent to those skilled in the art. It goes without saying that the present invention includes various embodiments not described herein. Therefore, the technical scope of the present invention is defined only by the invention specifying matters according to the scope of claims reasonable from the above description.

  DESCRIPTION OF SYMBOLS 1 ... Solar cell, 2 ... Solar cell, 10 ... Semiconductor electrode, 11 ... Substrate, 11a ... Incident surface, 12 ... Transparent electrode, 13 ... Metal oxide layer, 14 ... Fine particle, 15 ... Silicon fine particle, 20 ... Counter electrode, DESCRIPTION OF SYMBOLS 30 ... Electrolyte 40 ... Sealing material 101 ... Substrate 101a ... Incident surface 102 ... Counter electrode 103 ... Electrolyte 104 ... Sealing material 110-150 ... Transparent electrode 111 ... Metal oxide layer 121 ... Metal oxide layer, 131 ... Metal oxide layer, 141 ... Metal oxide layer, 151 ... Metal oxide layer, 201 ... Fine particles, 202 ... Silicon fine particles, 211 ... Fine particles, 212 ... Silicon fine particles, 221 ... Fine particles, 222 ... Silicon fine particles, 231 ... fine particles, 232 ... silicon fine particles, 241 ... fine particles, 242 ... silicon fine particles, S1 ... firing step, S2 ... sudden Process, S3 ... etching process

Claims (10)

A substrate having light permeability and having a first main surface provided on the light incident side and a second main surface provided on the opposite side of the first main surface;
A transparent electrode disposed on the second main surface of the substrate and having a first main surface provided on the light incident side and a second main surface provided on the opposite side of the first main surface;
A metal oxide layer disposed on the second main surface of the transparent electrode,
The metal oxide layer has silicon fine particles that absorb a specific wavelength among light wavelengths transmitted through the substrate, and metal oxide fine particles,
The silicon fine particles are formed to have a predetermined particle size by etching the mixed powder containing the silicon fine particles with an etching solution containing hydrofluoric acid and an oxidizing agent,
The silicon fine particles are semiconductor electrodes disposed between the metal oxide fine particles.   The semiconductor electrode according to claim 1, wherein the silicon fine particles having a plurality of types of particle diameters are mixed and used. A semiconductor electrode having optical transparency and having an incident surface on which light is incident;
A counter electrode disposed to face the semiconductor electrode;
An electrolyte disposed in a space between the semiconductor electrode and the counter electrode;
A sealing material for sealing the electrolyte disposed in the space,
A solar cell that converts light energy of light incident on the semiconductor electrode into electrical energy,
The semiconductor electrode is
A substrate having light permeability and having a first main surface provided on the light incident side and a second main surface provided on the opposite side of the first main surface;
A transparent electrode disposed on the second main surface of the substrate and having a first main surface provided on the light incident side and a second main surface provided on the opposite side of the first main surface;
A metal oxide layer disposed on the second main surface of the transparent electrode,
The metal oxide layer has silicon fine particles that absorb a specific wavelength among light wavelengths transmitted through the substrate, and metal oxide fine particles,
The silicon fine particles are formed to have a predetermined particle size by etching the mixed powder containing the silicon fine particles with an etching solution containing hydrofluoric acid and an oxidizing agent,
The silicon fine particles are solar cells disposed between the metal oxide fine particles.   The solar cell according to claim 3, wherein the silicon fine particles having a plurality of types of particle sizes are mixed and used. Comprising a plurality of transparent electrodes laminated between the semiconductor electrode and the counter electrode;
Each of the plurality of transparent electrodes has light transparency, and has a first principal surface provided on the light incident side and a second principal surface provided on the opposite side of the first principal surface. A material, a first transparent electrode provided on the first main surface, and a second transparent electrode provided on the second main surface,
The metal oxide layer is disposed on the side opposite to the light incident side of the second transparent electrode ,
The pair of transparent electrodes adjacent to each other in the stacking direction of the plurality of transparent electrodes among the plurality of transparent electrodes are sealed with the sealing material while being filled with the electrolyte. Solar cell.   The solar cell according to claim 5, wherein each of the plurality of transparent electrodes is provided with silicon fine particles having different particle sizes. A substrate having light transmission and having a first main surface provided on the light incident side and a second main surface provided on the opposite side of the first main surface; and the second main surface of the substrate They are arranged in a first main surface provided on the light incident side, a manufacturing method of a semiconductor electrode and a transparent electrode and a second main surface provided on the opposite side of the first main surface ,
Firing a mixture containing a silicon source and a carbon source under an inert atmosphere;
Extracting the product gas from the inert atmosphere and rapidly cooling to obtain a mixed powder containing silicon fine particles; and
Etching by immersing the mixed powder in an etching solution containing hydrofluoric acid and an oxidizing agent;
A step of disposing a metal oxide layer on the second main surface of the transparent electrode;
And a step of adsorbing silicon fine particles extracted from the mixed powder by the etching to the metal oxide layer.   The method of manufacturing a semiconductor electrode according to claim 7, wherein in the etching step, the particle size of the silicon fine particles is controlled by adjusting an etching time.   The method for producing a semiconductor electrode according to claim 7, wherein the silicon source is ethyl silicate.   The method for producing a semiconductor electrode according to claim 7, wherein the carbon source is a phenol resin.

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