JP2006278023A - Semiconductor particulate paste and its manufacturing method as well as photoelectric conversion element - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a semiconductor particulate paste with semiconductor particulate of a specific size dispersed in it, especially one with high dispersion, and its manufacturing method. <P>SOLUTION: The manufacturing method of the semiconductor particulate paste is used for forming a semiconductor layer of a photoelectric conversion element, and includes a process (a) of dispersing semiconductor particulate in a solvent, a process (b) of centrifuging semiconductor particulate slurry obtained in the process (a) and extracting semiconductor particulate slurry containing semiconductor particulate of a specific size, and a process (c) of forming the semiconductor particulate paste from the semiconductor particulate slurry obtained in the process (b). <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a semiconductor fine particle paste, a method for producing the same, and a photoelectric conversion element using the semiconductor fine particle paste.

  In recent years, as a battery that does not rely on fossil fuels, there is a great interest in photoelectric conversion elements using solar energy, so-called solar cells. Among them, the dye-sensitized solar cell (also referred to as “Gretzel cell”) proposed by Gretzer et al. Performs photoelectric conversion by injecting excited electrons generated by the absorption of light by the sensitizing dye into the semiconductor. It is a solar cell that exhibits higher energy conversion efficiency than conventional solar cells (see, for example, Non-Patent Document 1).

  In general, a Gretzel cell is manufactured by forming a semiconductor layer carrying a sensitizing dye in contact with an electrode, and then laminating the electrode and the counter electrode with a sealing material between the semiconductor layer and the counter electrode. It is filled with electrolyte. Conventionally, as shown in FIG. 2, a semiconductor layer is conventionally manufactured by dispersing semiconductor fine particles in a solvent to form a semiconductor fine particle slurry in which the aggregation of the semiconductor fine particles is loosened, and then adjusting the viscosity. A fine particle paste is formed, and then this semiconductor fine particle paste is applied onto a substrate and baked (see, for example, Patent Document 1).

  On the other hand, in order to further improve the energy conversion efficiency of the Gretzel cell, it is desirable to contribute as much light incident on the semiconductor layer as possible to the photoelectric conversion. For this purpose, it is important to suppress reflection loss in which light is reflected by the light-receiving surface of the semiconductor layer and light transmission loss in which light is transmitted through the semiconductor layer, in other words, to suppress the reflectance and transmittance of the semiconductor layer. It is. Therefore, a structure is known in which the light-receiving surface side of the semiconductor layer is a semiconductor layer having a low light scattering property, and the electrolyte layer side of the semiconductor layer is a semiconductor layer having a high light scattering property (see, for example, Patent Document 2).

  Further, the state of aggregation of the semiconductor fine particles in the semiconductor fine particle slurry is greatly related to the light scattering property of the semiconductor layer. That is, a highly dispersed semiconductor fine particle slurry in which aggregation of semiconductor fine particles is well loosened becomes a low light scattering semiconductor layer, and a low dispersion semiconductor fine particle slurry in which aggregation is not loosely loosened becomes a highly light scattering semiconductor layer. It is known to be. This is thought to be because the semiconductor fine particles that are not loosened, that is, have a large particle size, act as light confusion points.

The state of aggregation of the semiconductor fine particles can be evaluated from, for example, an average primary particle diameter and an average secondary particle diameter by a laser scattering method, and the light scattering property of the semiconductor layer can be evaluated from, for example, a haze ratio.
Gratzel, 1 other, “Nature” (UK), Oct. 24, 1991, volume 353, p. 737-740 JP 2000-36330 A JP-A-10-255863

  However, it is possible to obtain a semiconductor fine particle slurry in which semiconductor fine particles having a desired particle size are dispersed by a conventional method, in particular, a highly dispersed semiconductor fine particle slurry having a small particle size is obtained by dispersing the semiconductor fine particles in a solvent. For example, it is difficult to sufficiently agglomerate the particles, and it is difficult to produce a highly dispersed semiconductor fine particle paste.

  In order to solve the above-mentioned problems, the present invention provides a semiconductor fine particle paste in which semiconductor fine particles having a specific particle diameter are dispersed, particularly a highly dispersed semiconductor fine particle paste, a method for producing the same, and a photoelectric conversion element.

  The method for producing a semiconductor fine particle paste of the present invention is a method for producing a semiconductor fine particle paste used for forming a semiconductor layer of a photoelectric conversion element, comprising: (a) a step of dispersing semiconductor fine particles in a solvent; and (b) the step ( centrifuge the semiconductor fine particle slurry obtained in a), collect a semiconductor fine particle slurry containing semiconductor fine particles of a specific particle size, and (c) use the semiconductor fine particle slurry obtained in the step (b). And a step of forming a semiconductor fine particle paste.

  The semiconductor fine particle paste of the present invention is a semiconductor fine particle paste used for forming a semiconductor layer of a photoelectric conversion element, and is obtained in (a) a step of dispersing the semiconductor fine particles in a solvent, and (b) the step (a). Centrifuge the obtained semiconductor fine particle slurry to collect a semiconductor fine particle slurry containing semiconductor fine particles having a specific particle diameter, and (c) a semiconductor fine particle paste using the semiconductor fine particle slurry obtained in the step (b). A semiconductor fine particle having an average primary particle diameter of 5 nm to 50 nm.

  Furthermore, the photoelectric conversion element of the present invention includes an electrode, a semiconductor layer disposed in contact with one main surface of the electrode, a counter electrode disposed to face the semiconductor layer, the electrode, and the counter electrode. And an electrolyte layer disposed between the semiconductor layer and the semiconductor layer, wherein the semiconductor layer includes the semiconductor fine particle paste of the present invention and a sensitizing dye.

  According to the method for producing a semiconductor fine particle paste of the present invention, it is possible to produce a particularly highly dispersed semiconductor fine particle paste in which semiconductor fine particles having a specific particle diameter are dispersed.

  Moreover, according to the semiconductor fine particle paste of the present invention, a semiconductor layer containing highly dispersed semiconductor fine particles and having a low light scattering property can be formed.

  In addition, according to the photoelectric conversion element of the present invention, it is possible to provide a photoelectric conversion element having a semiconductor layer with low light scattering properties and good energy conversion efficiency.

  An example of a method for producing a semiconductor fine particle paste used for forming a semiconductor layer of the photoelectric conversion element of the present invention includes a step (a) of dispersing semiconductor fine particles in a solvent, and centrifuging the semiconductor fine particle slurry obtained in step (a). And (b) collecting a semiconductor fine particle slurry containing semiconductor fine particles having a specific particle diameter, and (c) forming a semiconductor fine particle paste using the semiconductor fine particle slurry obtained in the step (b). Is included. By using this manufacturing method, a semiconductor fine particle paste in which semiconductor fine particles having a specific particle diameter are dispersed can be obtained.

  Moreover, it is preferable that the centrifugation of the said process (b) is performed with a centrifugal acceleration of 100 xg or more and 13000 xg or less. In particular, the centrifugal acceleration is more preferably 800 × g or more and 7000 × g or less, and further preferably 1000 × g or more and 4000 × g or less. By setting the centrifugal acceleration within the above range, the semiconductor fine particles can be more clearly classified according to the size of the particle diameter, and a semiconductor fine particle slurry containing semiconductor fine particles having a more uniform particle diameter can be collected. Moreover, since the semiconductor fine particle slurry which was not extract | collected, especially the semiconductor particle slurry of low dispersion | distribution can be used according to the objective, material can be utilized effectively.

  The centrifugal acceleration is a value defined by the following formula.

(Equation 1)
G = (2πN / 60) ² r / 980 = 1.13379 × 10 ⁻⁶ π ² rN ²

  However, G is a centrifugal acceleration (xg), r is a radius (cm), N is the number of rotations per minute (rpm).

  The average secondary particle size of the semiconductor fine particles contained in the semiconductor fine particle slurry obtained in the step (b) is preferably 5 nm to 500 nm, and more preferably 5 nm to 200 nm. Thereby, a highly dispersed semiconductor fine particle paste can be obtained. Moreover, the average secondary particle diameter of the semiconductor fine particles contained in the semiconductor fine particle slurry obtained in the step (b) can be larger than 500 nm. Thereby, a semiconductor particle paste with lower dispersion can be obtained.

  The step (c) may be a step including at least adjusting the viscosity of the semiconductor fine particle slurry.

  The average primary particle size of the semiconductor fine particles contained in the semiconductor fine particle paste is preferably 5 nm to 50 nm, and more preferably 5 nm to 30 nm. Thereby, a highly dispersed semiconductor fine particle paste can be obtained.

  On the other hand, an example of the semiconductor fine particle paste used for forming the semiconductor layer of the photoelectric conversion element of the present invention includes a step (a) of dispersing the semiconductor fine particles in a solvent, and a centrifugal separation of the semiconductor fine particle slurry obtained in the step (a). A step (b) of collecting a semiconductor fine particle slurry containing semiconductor fine particles having a specific particle diameter, and a step (c) of forming a semiconductor fine particle paste using the semiconductor fine particle slurry obtained in the step (b). The semiconductor fine particles manufactured by the method and having an average primary particle diameter of 5 nm to 50 nm are included. With such a structure, a highly dispersed semiconductor fine particle paste containing semiconductor fine particles with little variation in particle diameter can be obtained, and a semiconductor layer of a photoelectric conversion element with low light scattering property can be formed.

  The average secondary particle size of the semiconductor fine particles contained in the semiconductor fine particle paste is more preferably 5 nm or more and 500 nm or less. By obtaining a highly dispersed semiconductor fine particle paste, a semiconductor layer of a photoelectric conversion element having a lower light scattering property can be formed.

  Furthermore, an example of the photoelectric conversion element of the present invention includes an electrode, a semiconductor layer disposed in contact with one main surface of the electrode, a counter electrode disposed to face the semiconductor layer, and an electrode and a counter electrode. The semiconductor layer includes the above-described semiconductor fine particle paste and a sensitizing dye. With such a structure, a photoelectric conversion element having a semiconductor layer with low light scattering properties and excellent energy conversion efficiency is obtained.

  The haze ratio of the semiconductor layer is preferably 10% or less, more preferably 8% or less. Thereby, it becomes a semiconductor layer with lower light scattering property.

  The haze ratio is a value defined in JIS K7105.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

<Embodiment of semiconductor fine particle paste>
FIG. 1 is a schematic diagram showing an example of a manufacturing process of a semiconductor fine particle paste used for a semiconductor layer of a photoelectric conversion element in the present invention.

  In FIG. 1, first, semiconductor fine particles are dispersed in a solvent (step (a)). For example, the semiconductor fine particles may be dispersed by applying mechanical force from the outside to the semiconductor fine particles and the solvent using a high-speed rotary shear type device, a mill dispersing device, a high-pressure jet type device, an ultrasonic device, or the like. At this time, you may add a dispersing agent etc. as needed.

If the said semiconductor fine particle is a semiconductor material generally used for the semiconductor layer of a photoelectric conversion element, it will not specifically limit. For example, oxides of metals such as Cd, Zn, In, Pb, Mo, W, Sb, Bi, Cu, Hg, Ti, Ag, Mn, Fe, V, Sn, Zr, Sr, Ga, Si, Cr, SrTiO _3, CaTiO ₃ or the like of the _{perovskite, CdS, ZnS, in 2 S} 3, PbS, Mo 2 S, WS 2, Sb 2 S 3, Bi 2 S 3, ZnCdS 2, Cu 2 sulfides S such, CdSe, Metal chalcogenides such as In ₂ Se ₃ , WSe ₂ , HgSe, PbSe, and CdTe, and other GaAs, Si, Se, Cd ₃ P ₂ , Zn ₃ P ₂ , InP, AgBr, PbI ₂ , HgI ₂ , BiI _3, etc. are used. be able to. In addition, a composite containing at least one selected from the above semiconductor materials, for example, CdS / TiO ₂ , CdS / AgI, Ag ₂ S / AgI, CdS / ZnO, CdS / HgS, CdS / PbS, ZnO / ZnS, ZnO / ZnSe, CdS / HgS, ZnS / CdSe, ZnSe / CdSe, CdS / ZnS, TiO ₂ / Cd ₃ P ₂ , CdS / HgS / CdS, and the like can also be used. In particular, it is more preferable to use TiO ₂ , ZnO or SnO ₂ because the photoelectric conversion efficiency is particularly high.

  The solvent is not particularly limited as long as the semiconductor fine particles can be dispersed. For example, water, ethanol, isopropyl alcohol, ionic liquid, or the like can be used. This ionic liquid is a liquid in which ionic crystals are melted at least at room temperature.

  Next, the semiconductor fine particle slurry obtained in the step (a) is centrifuged to collect a semiconductor fine particle slurry containing semiconductor fine particles having a specific particle size (step (b)).

  The centrifugation may be performed using a general method so that the semiconductor fine particles can be classified. At this time, the centrifugal acceleration may be appropriately selected depending on the semiconductor fine particles and the solvent to be used.

  The semiconductor particle slurry is collected by selecting a semiconductor fine particle slurry containing semiconductor fine particles having a specific particle diameter from the semiconductor fine particle slurry classified by centrifugation. For example, an upper layer portion (supernatant portion) of the classified semiconductor fine particle slurry can be collected to obtain a semiconductor fine particle slurry containing semiconductor fine particles having a small particle diameter, or a lower layer portion (precipitation portion) can be collected to obtain particles. A semiconductor fine particle slurry containing semiconductor fine particles having a large diameter can also be obtained.

  Finally, the viscosity of the semiconductor fine particle slurry obtained in the step (b) is adjusted to form a semiconductor fine particle paste (step (c)). For example, by adding an organic material having a high thickening effect such as ethyl cellulose or ethylene glycol, or by replacing it with a solvent having a high viscosity such as terpineol, the semiconductor fine particle slurry is necessary for a semiconductor fine particle paste used for a semiconductor layer. What is necessary is just to adjust to a viscosity.

  By the production method having the above steps, a semiconductor fine particle paste in which semiconductor fine particles having a specific particle diameter are dispersed can be obtained.

  In the centrifugation in the step (b), the centrifugal acceleration is preferably 100 × g or more and 13000 × g or less. In particular, it is more preferably 800 × g or more and 7000 × g or less, and further preferably 1000 × g or more and 4000 × g or less. By making the centrifugal acceleration within the above range, the semiconductor fine particles can be classified more clearly according to the size of the particle diameter, and the semiconductor fine particle paste in which the semiconductor fine particles having a more uniform particle diameter are dispersed, especially the higher dispersion. A semiconductor fine particle paste can be obtained. Moreover, since the semiconductor fine particle slurry that has not been collected, particularly the low-dispersion semiconductor fine particle slurry, can be used as a semiconductor fine particle paste according to the purpose, a material such as a semiconductor can be effectively used.

  The average secondary particle size of the semiconductor fine particles contained in the semiconductor fine particle slurry obtained in the step (b) is preferably 5 nm to 500 nm, and more preferably 5 nm to 200 nm. Moreover, the average secondary particle diameter of the semiconductor fine particles contained in the semiconductor fine particle slurry obtained in the step (b) can be larger than 500 nm.

  The semiconductor fine particle paste obtained by the manufacturing method described above preferably has an average primary particle size of the semiconductor fine particles contained in the paste of 5 nm to 50 nm. With such a configuration, a highly dispersed semiconductor fine particle paste containing semiconductor fine particles with little variation in particle diameter can be formed, and a semiconductor layer with low light scattering property can be formed. Furthermore, the average secondary particle diameter of the semiconductor fine particles is more preferably 5 nm or more and 500 nm or less. A semiconductor layer having a lower light scattering property can be formed by forming a highly dispersed semiconductor fine particle paste containing semiconductor fine particles having a uniform particle diameter.

<Embodiment of photoelectric conversion element>
An example of the photoelectric conversion element of the present invention includes an electrode, a semiconductor layer disposed in contact with one main surface of the electrode, a counter electrode disposed to face the semiconductor layer, and an electrode and a counter electrode. And an electrolyte layer disposed therebetween. The semiconductor layer is formed by fixing the semiconductor fine particle paste described in the embodiment of the semiconductor fine particle paste and supporting a sensitizing dye.

  FIG. 3 is a partial cross-sectional view showing an example of the photoelectric conversion element of the present invention. In FIG. 3, the photoelectric conversion element 1 includes an electrode 4 to which a semiconductor layer 5 carrying a sensitizing dye is attached, a counter electrode 6 disposed opposite to the semiconductor layer 5, and an electrolyte layer 7. They are stacked via the material 8. The electrode 4 is attached to the surface of the substrate 2 and the counter electrode 6 is attached to the surface of the substrate 3.

  In the present embodiment, as long as the semiconductor layer 5 is formed using the semiconductor fine particle paste, the material of other members is not particularly limited. Moreover, the magnitude | size of each member used for this embodiment is not specifically limited.

  The semiconductor layer 5 is formed using at least the semiconductor fine particle paste. The semiconductor layer 5 can be manufactured by a conventionally known method. For example, on the electrode 4 formed on the surface of the substrate 2, the semiconductor fine particle paste is selected from 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. It can be produced by applying using a method and then applying pressure or heating. By repeating the application and pressurization or heating, the semiconductor layer 5 having a specific thickness can be produced. For the pressurization, a press using a flat plate, a roll press, a calendar, or the like can be used. For this heating, heating using a hot plate, a muffle furnace and a conveyor furnace, infrared heating, microwave heating, or the like can be used.

  The thickness of the semiconductor layer 5 is preferably 0.1 μm or more and 100 μm or less. In particular, the thickness of the semiconductor layer 5 is more preferably 1 μm or more and 50 μm or less, and even more preferably 5 μm or more and 30 μm or less. By controlling the thickness of the semiconductor layer 5, the roughness factor (the ratio of the actual area inside the porous to the substrate area) can be determined. The roughness factor is more preferably 20 or more, and even more preferably 150 or more. If the roughness factor is 20 or more, the carrying amount of the sensitizing dye is sufficient, and the photoelectric conversion characteristics can be improved. The upper limit of the roughness factor is generally about 5000. If the semiconductor layer 5 is thick, the roughness factor is large and the surface area of the semiconductor is widened, so an increase in the amount of sensitizing dye supported can be expected. However, if the semiconductor layer 5 is too thick, the light transmittance and resistance loss of the semiconductor layer 5 are affected. If the porosity is high, the roughness factor can be increased even if the semiconductor layer 5 is not thick. However, if the porosity is too high, the contact area between the semiconductor fine particles decreases, so the influence of resistance loss must be taken into account. Accordingly, the porosity of the semiconductor layer is preferably 50% or more, and the upper limit is generally about 80%. This porosity can be calculated from the measurement result of the adsorption-desorption isotherm curve of nitrogen gas or krypton gas under liquid nitrogen temperature.

  The semiconductor layer 5 has a low light scattering semiconductor layer using a highly dispersed semiconductor fine particle paste disposed on the light receiving surface side (electrode 4 side), and the light scattering property using a low dispersed semiconductor fine particle paste. It is more preferable that the high semiconductor layer has at least a two-layer structure in which the high semiconductor layer is disposed on the electrolyte layer 7 side. For example, for this highly dispersed semiconductor fine particle paste, a semiconductor fine particle paste formed from a semiconductor fine particle slurry obtained by collecting the upper layer portion of the semiconductor fine particle slurry classified in the above-mentioned step (b) is used. The semiconductor fine particle paste formed from the semiconductor fine particle slurry obtained by collecting the lower layer portion may be used. Particularly, in the highly dispersed semiconductor fine particle paste, the average primary particle diameter of the semiconductor fine particles contained in the paste is preferably 5 nm to 50 nm, and the average secondary particle diameter is more preferably 5 nm to 500 nm. preferable.

The sensitizing dye supported on the semiconductor layer 5 is not particularly limited as long as it is a dye generally used for photoelectric conversion elements, and may be an inorganic dye or an organic dye. Examples of the inorganic dye include a RuL ₂ (H ₂ O) ₂ type ruthenium-cis-diaqua-bipyridyl complex, or ruthenium-tris (RuL ₃ ), ruthenium-bis (RuL ₂ ), and osmium-tris (OsL ₃ ). And a transition metal complex of a type such as osnium-bis (OsL ₂ ), or a dye such as zinc-tetra (4-carboxyphenyl) porphyrin, iron-hexocyanide complex, phthalocyanine, or the like can be used. However, L in the above chemical formula represents 4,4′-dicarboxyl-2,2′-bipyridine. Examples of organic dyes include 9-phenylxanthene dyes, coumarin dyes, acridine dyes, triphenylmethane dyes, tetraphenylmethane dyes, quinone dyes, azo dyes, indigo dyes, cyanine dyes, Merocyanine dyes, xanthene dyes, and the like can be used. In particular, a ruthenium-bis (RuL ₂ ) derivative is more preferable because it has a high light absorption capability and is chemically stable.

The amount of the sensitizing dye supported on the semiconductor layer 5 is preferably 1 × 10 ⁻⁸ mol / cm ² or more and 1 × 10 ⁻⁶ mol / cm ² or less, particularly 1.0 × 10 ⁻⁸ mol / cm ² or more. 9.0 × 10 ⁻⁷ mol / cm ² or less is more preferable. If the carrying amount is within this range, sufficient photoelectric conversion efficiency can be obtained, and wasteful sensitizing dyes are eliminated, which is economical.

  As a method of supporting the sensitizing dye on the semiconductor layer 5, for example, a method of immersing the substrate 2 on which the semiconductor layer 5 is adhered in a solution in which the sensitizing dye is dissolved can be used. At this time, a method in which the solution is heated to reflux or immersed while applying ultrasonic waves is effective. The solvent of the solution is not particularly limited as long as it can dissolve the sensitizing dye, and for example, water, alcohol, toluene, dimethylformamide and the like can be used.

  As the substrate 2 and the substrate 3, transparent glass, plastic, or the like can be used. In particular, since plastic has flexibility, it is suitable for applications that require flexibility.

  The counter electrode 6 functions as a positive electrode of the photoelectric conversion element 1, and the material thereof is platinum, graphite, carbon nanotube, polypyrrole, polyaniline, poly (3,4-ethylenedioxide) having a catalytic action to give electrons to the electrolyte reductant. Conductive polymers such as oxythiophene (PEDOT) are preferred. Further, a conductive film made of a material different from that of the counter electrode 6 may be provided between the counter electrode 6 and the substrate 3.

  The electrolyte of the electrolyte layer 7 is not particularly limited as long as a pair of redox constituents composed of an oxidant and a reductant is contained in the solvent, and the oxidant and the reductant have the same charge. It is more preferable if it is a redox component. In the present invention, the redox-system constituent substances refer to a pair of substances that reversibly exist in the form of an oxidant and a reductant in an oxidation-reduction reaction.

  Examples of the redox constituents of the electrolyte layer 7 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) Manganate ion-permanganate ion, ferricyanide-ferrocyanide, quinone-hydroquinone, fumaric acid-succinic acid and the like can be used. In particular, an iodine compound-iodine is preferably used. 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, iodine It is more preferable to use a diimidazolium iodide compound such as dimethylpropylimidazolium iodide.

  The type of the solvent for the electrolyte layer 7 is not particularly limited as long as it can dissolve the redox constituents, and is more preferably a solvent having excellent ion conductivity. Moreover, although any solvent of an aqueous solvent and an organic solvent can be used, in order to stabilize the said oxidation-reduction type | system | group constituent material more, it is preferable to use an organic solvent. Examples of the organic 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, and 1,2-dimethoxy. Ether compounds such as ethane, 1,3-dioxosilane, tetrahydrofuran, 2-methyl-tetrahydrofuran, heterocyclic compounds such as 3-methyl-2-oxazozirinone, 2-methylpyrrolidone, acetonitrile, methoxyacetonitrile, propionitrile, 3-methoxy Nitrile compounds such as propionitrile, aprotic polar compounds such as sulfolane, didimethyl sulfoxide, dimethylformamide, N, N, N ′, N′-tetramethyl Le urea, di dimethyl sulfoxide, dimethylformamide, formamide, N- methylformamide, N- methylacetamide, a N- methylpropionamide and the like can be used. An ionic liquid having low volatility can also be used. These solvents can be used alone or in combination of two or more. Especially, as a solvent used for an electrolyte layer, it is preferable that an electrolyte layer is comprised with a solvent whose boiling point is 100 degreeC or more. When a solvent having a boiling point lower than 100 ° C. is used, when the photoelectric conversion element is stored in a high temperature environment, sealing failure is easily caused by an increase in internal pressure, which significantly reduces the photoelectric conversion efficiency. On the other hand, when the electrolyte layer is composed of a solvent having a boiling point of 100 ° C. or higher, it is possible to provide a photoelectric conversion element that hardly causes sealing failure and has excellent long-term stability. Furthermore, a nitrile solvent has a feature that an electrolyte layer having a low viscosity and excellent ion conductivity can be constructed. Examples of the nitrile solvent having a boiling point of 100 ° C. or higher include 3-methoxypropionitrile, succinonitrile, butyronitrile, isobutyronitrile, valeronitrile, benzonitrile, α-tolunitrile and the like. In particular, 3-methoxypropionitrile can provide a photoelectric conversion element with high conversion efficiency and excellent long-term stability. Moreover, as a solvent which comprises an electrolyte layer, room temperature molten salts, such as an imidazolium salt, can be used preferably. Among them, 1-methyl-3-propylimidazolium iodide is preferable because it has a low viscosity, and thus high photoelectric conversion efficiency can be obtained. Further, the room temperature molten salt and the organic solvent can be mixed and used.

  The sealing material 8 is not particularly limited as long as it has translucency. For example, epoxy resin, silicone resin, polyolefin, butyl rubber, ethylene-vinyl acetate copolymer, ethylene / α-olefin copolymer, ethylene -In addition to methyl acrylate copolymer, ethylene-ethyl acrylate copolymer, ethylene-acrylic acid copolymer, ethylene-methacrylic acid copolymer, low density polyethylene, acrylic resin, silicone resin, ionomer resin, Polystyrene-based, polyolefin-based, polydiene-based, polyester-based, polyurethane-based, fluororesin-based, polyamide-based elastomers, and the like can be used.

  The haze ratio of the semiconductor layer is preferably 10% or less, and particularly preferably 8% or less, because it becomes a semiconductor layer having a lower light scattering property, which is more preferable.

  In addition, it can also be set as a photoelectric conversion module by arrange | positioning the photoelectric conversion element of this embodiment in two or more planar shape or curved surface shape. Thereby, a relatively large neutral density filter can be provided.

  Hereinafter, the present invention will be described more specifically with reference to examples. In addition, this invention is not limited to a following example.

<Preparation of semiconductor fine particle paste>
Example 1
First, 7.5 parts by weight of titanium oxide powder (manufactured by Nippon Aerosil Co., Ltd., average primary particle size of about 21 nm), 0.5 parts by weight of acetylacetone and 22.5 parts by weight of ethanol are used at 360 rpm for 2 hours using a planetary ball mill. Distributed processing. Next, the semiconductor fine particle slurry is diluted 2 times with ethanol, and centrifuged at a centrifugal acceleration of 2800 × g (5000 rpm) for 30 minutes using a centrifuge (manufactured by Kokusan Co., Ltd., cooled high-speed centrifuge <H-9R>). did. The supernatant of the centrifuged slurry was collected to obtain a semiconductor fine particle slurry 1. Next, the semiconductor fine particle slurry 1 was diluted with ethanol to adjust the titanium oxide content to 1 wt%. To 100 parts by weight of this collected and diluted slurry, 0.55 parts by weight of ethyl cellulose and 3 parts by weight of terpineol were added, stirred at 50 ° C. for 12 hours, and then concentrated by an evaporator to obtain a semiconductor fine particle paste 1 of this example.

  Moreover, the sedimentation part of the centrifuged slurry was extract | collected, ethanol was added so that a titanium oxide content rate might be 20 wt%, and it disperse-processed for 30 minutes at 360 rpm using the planetary ball mill, and obtained the semiconductor fine particle slurry 2. Next, the semiconductor fine particle slurry 2 was diluted with ethanol to adjust the titanium oxide content rate to 10 wt%. To 10 parts by weight of the collected and diluted slurry, 0.55 parts by weight of ethyl cellulose and 3 parts by weight of terpineol were added, stirred at 50 ° C. for 12 hours, and then concentrated by an evaporator to obtain a semiconductor fine particle paste 2 of this example.

(Example 2)
The semiconductor fine particle slurry 3 and the semiconductor fine particle paste 3 of this example are obtained in the same manner as the semiconductor fine particle slurry 1 and the semiconductor fine particle paste 1 except that the centrifugal separation is performed at a centrifugal acceleration of 99 × g (2000 rpm) for 30 minutes. It was.

(Comparative Example 1)
First, 7.5 parts by weight of titanium oxide powder (manufactured by Nippon Aerosil Co., Ltd., average primary particle size of about 21 nm), 0.5 parts by weight of acetylacetone and 22.5 parts by weight of ethanol are used at 360 rpm for 2 hours using a planetary ball mill. Dispersion treatment was performed to obtain a semiconductor fine particle slurry 4. Next, the semiconductor fine particle slurry 4 was diluted with ethanol to adjust the titanium oxide content to 10 wt%. To 10 parts by weight of the diluted slurry, 0.55 parts by weight of ethyl cellulose and 3 parts by weight of terpineol were added, stirred at 50 ° C. for 12 hours, and then concentrated by an evaporator to obtain a semiconductor fine particle paste 4 of this comparative example. That is, the semiconductor fine particle paste 4 is a semiconductor fine particle paste produced without performing the centrifugation step applied to the semiconductor fine particle pastes 1 to 3.

(Comparative Example 2)
First, 3.5 parts by weight of titanium oxide powder (manufactured by Nippon Aerosil Co., Ltd., average primary particle diameter of about 21 nm), 4 parts by weight of titanium oxide powder (manufactured by Catalyst Chemical Industry Co., Ltd., average primary particle diameter of about 400 nm), 0. 5 parts by weight and 22.5 parts by weight of ethanol were dispersed at 360 rpm for 2 hours using a planetary ball mill to obtain a semiconductor fine particle slurry 5. Next, the semiconductor fine particle slurry 5 was diluted with ethanol to adjust the titanium oxide content to 20 wt%. To 5 parts by weight of the diluted slurry, 0.55 parts by weight of ethyl cellulose and 3 parts by weight of terpineol were added, stirred at 50 ° C. for 12 hours, and then concentrated by an evaporator to obtain a semiconductor fine particle paste 5 of this comparative example. That is, the semiconductor fine particle paste 5 is a semiconductor fine particle paste conventionally used for forming a semiconductor layer of a photoelectric conversion element.

  By the way, the dispersion state of the semiconductor fine particle paste can be evaluated by measuring the particle size distribution of the semiconductor fine particles. For example, the smaller the average primary particle diameter and the average secondary particle diameter of the semiconductor fine particles, the higher the dispersion of the semiconductor fine particle paste. Moreover, the smaller the haze ratio of the semiconductor layer formed using the semiconductor fine particle paste, the higher the dispersion of the semiconductor fine particle paste.

  Then, the average secondary particle diameter of the semiconductor fine particles contained in the semiconductor fine particle pastes 1 to 5 was measured by a laser confusion method, and the dispersion state of the semiconductor fine particle paste was evaluated. In this measurement, the semiconductor fine particle slurries 1 to 5 before adjusting the viscosity were diluted 40 times with ethanol, and measured using a laser diffraction / scattering particle size analyzer “Microtrac UPA 9340 type” manufactured by Nikkiso Co., Ltd. did.

  In order to evaluate the dispersion state from the particle size, it is necessary to compare the value of (average secondary particle size) / (average primary particle size). However, in this example and the comparative example, the average primary particle diameters of the semiconductor fine particle slurries 1 to 4 are all equal, and the average primary particle diameter of the semiconductor fine particle paste 5 is obviously larger than the other pastes. The dispersion state was evaluated by comparing only the particle size.

  Furthermore, the haze rate of the semiconductor layer sample formed using the said semiconductor fine particle pastes 1-5 was measured, and the dispersion state of the semiconductor fine particle paste was evaluated. This sample was coated with a semiconductor fine particle paste on a 1 mm thick conductive glass substrate (manufactured by Asahi Glass Co., Ltd., surface resistance 15 Ω / □), dried, and then fired at 450 ° C. for 30 minutes to a thickness of 4 μm. The haze ratio was measured using a spectrophotometer “V-570” (trade name) manufactured by JASCO Corporation.

  Table 1 shows the average secondary particle diameter of the semiconductor fine particle slurries 1 to 5 and the haze ratio of the semiconductor layer sample formed using the semiconductor fine particle pastes 1 to 5.

  From Table 1, it can be seen that the semiconductor fine particle pastes 1 to 3 of this example are remarkably highly dispersed semiconductor fine particle pastes compared to the conventional semiconductor fine particle paste 5 used in the semiconductor layer of the photoelectric conversion element. . Furthermore, it can be seen that the semiconductor fine particle pastes 1 and 3 are more highly dispersed semiconductor fine particle pastes than the semiconductor fine particle paste 4. That is, it can be seen that by using the production method of the present invention, a semiconductor fine particle paste in which semiconductor fine particles having a uniform particle diameter are dispersed can be obtained. In particular, it can be seen that a highly dispersed semiconductor fine particle paste can be obtained when formed from a semiconductor fine particle slurry obtained by collecting the centrifuged supernatant.

<Production of photoelectric conversion element>
(Example 3)
First, the semiconductor fine particle paste 1 was applied on a 1 mm thick conductive glass substrate (manufactured by Asahi Glass Co., Ltd., surface resistance 15 Ω / □), dried, and then baked at 450 ° C. for 30 minutes to obtain a thickness of 8 μm. A first semiconductor layer was produced. Next, the semiconductor fine particle paste 5 was applied onto the first semiconductor layer, dried, and then baked at 450 ° C. for 30 minutes, thereby producing a second semiconductor layer having a thickness of 4 μm. The substrate provided with this semiconductor layer is immersed in a solution containing a sensitizing dye represented by [Ru (4,4′-dicarboxyl-2,2′-bipyridine) _2- (NCS) ₂ ], and 20 The sensitizing dye was adsorbed on the semiconductor layer by allowing to stand at 24 ° C. for 24 hours. The sensitizing dye was dissolved in a mixed solvent in which acetonitrile and tert-butanol were mixed at a volume ratio of 50:50 so that the concentration was 3 × 10 ⁻⁴ mol / dm ³ . The solution was used.

Further, a solution containing H ₂ PtCl ₆ is applied to a glass substrate with a transparent electrode having a thickness of 20 nm (manufactured by Asahi Glass Co., Ltd., surface resistance: 15 Ω / □) on one main surface by sputtering with 5 × 10 ⁻⁶ dm ³ / After coating at a rate of cm ² , baking was performed at 450 ° C. for 15 minutes to produce a counter electrode. As this solution, a solution in which H ₂ PtCl ₆ was dissolved in isopropyl alcohol so as to have a concentration of 5 × 10 ⁻³ mol / dm ³ was used.

A substrate having a semiconductor layer carrying a sensitizing dye and a substrate having a counter electrode are formed by using a sealing material “bynel” (trade name) manufactured by DuPont having a thickness of 50 μm, and the semiconductor layer and the counter electrode. They were pasted so that they faced each other. This bonding was performed at 230 ° C. for 30 seconds. Next, an electrolytic solution was injected from a 1 mm diameter injection port provided in the counter electrode using a reduced pressure injection method, and a 500 μm thick cover glass was fixed with the “bynel” to seal the injection port. The electrolyte solution is γ-butyrolactone, iodine at a concentration of 0.005 mol / dm ³ , LiI at a concentration of 0.01 mol / dm ³ , tert-butylpyridine at a concentration of 0.5 mol / dm ³ , and methyltripropylammonium iodide. Each solution dissolved so as to have a concentration of 0.5 mol / dm ³ was used.

  Finally, a silicone filler “Buscoke” (trade name) manufactured by Cemedine Co., Ltd. was applied to the periphery of the sealing material to obtain a photoelectric conversion element of this example.

  Note that all the reagents used in this example were dried, and the assembling work was performed in a dry room, so that attention was paid as much as possible to prevent moisture from being mixed into the photoelectric conversion element during assembly.

Example 4
A photoelectric conversion element of this example was obtained in the same manner as in Example 3 except that the semiconductor fine particle paste 3 was used in place of the semiconductor fine particle paste 1.

(Example 5)
A photoelectric conversion element of this example was obtained in the same manner as in Example 3 except that the semiconductor fine particle paste 2 was used instead of the semiconductor fine particle paste 5. That is, the photoelectric conversion element of this example is formed using the semiconductor fine particle paste obtained by collecting the supernatant in the centrifugation step of Example 1 and the semiconductor fine particle paste obtained by collecting the precipitate.

(Comparative Example 3)
A photoelectric conversion element of this comparative example was obtained in the same manner as in Example 3 except that the semiconductor fine particle paste 4 was used in place of the semiconductor fine particle paste 1. That is, the photoelectric conversion element of this comparative example can be compared with the photoelectric conversion elements of Examples 3 and 4 as conventional photoelectric conversion elements.

  The photoelectric conversion elements of Examples 3 to 5 and Comparative Example 3 were irradiated with light from a fluorescent lamp having an illuminance of 200 lx, and the open circuit voltage, short circuit current density, form factor, and output were measured. Table 2 shows the measurement results.

  From the above, it can be seen that Examples 3 to 5 are photoelectric conversion elements having better energy conversion efficiency than Comparative Example 3. In particular, the effect of Example 3 using the semiconductor fine particle paste 1 centrifuged at a centrifugal acceleration of 100 × g or more is great. Further, it can be seen that Example 5 can sufficiently obtain the effects of the present invention while effectively using materials such as semiconductor fine particles.

  As described above, according to the method for producing a semiconductor fine particle paste of the present invention, it is possible to produce a particularly highly dispersed semiconductor fine particle paste in which semiconductor fine particles having a specific particle diameter are dispersed.

  Moreover, according to the semiconductor fine particle paste of the present invention, a semiconductor layer containing highly dispersed semiconductor fine particles and having a low light scattering property can be formed.

  In addition, according to the photoelectric conversion element of the present invention, it is possible to provide a photoelectric conversion element having a semiconductor layer with low light scattering properties and good energy conversion efficiency.

It is a schematic diagram which shows an example of the manufacturing process of the semiconductor fine particle paste used for the semiconductor layer of the photoelectric conversion element of this invention. It is a schematic diagram which shows the manufacturing process of the conventional semiconductor fine particle paste. It is a fragmentary sectional view which shows an example of the photoelectric conversion element of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Photoelectric conversion element 2, 3 Substrate 4 Electrode 5 Semiconductor layer 6 Counter electrode 7 Electrolyte layer 8 Sealing material

Claims (10)

A method for producing a semiconductor fine particle paste used for forming a semiconductor layer of a photoelectric conversion element,
(A) dispersing the semiconductor fine particles in a solvent;
(B) centrifuging the semiconductor fine particle slurry obtained in the step (a), and collecting a semiconductor fine particle slurry containing semiconductor fine particles having a specific particle diameter;
(C) forming a semiconductor fine particle paste using the semiconductor fine particle slurry obtained in the step (b), and a method for producing a semiconductor fine particle paste.   The method for producing a semiconductor fine particle paste according to claim 1, wherein the centrifugal separation in the step (b) is performed at a centrifugal acceleration of 100 × g to 13000 × g.   2. The method for producing a semiconductor fine particle paste according to claim 1, wherein an average secondary particle diameter of the semiconductor fine particles contained in the semiconductor fine particle slurry obtained in the step (b) is 5 nm or more and 500 nm or less.   The method for producing a semiconductor fine particle paste according to claim 1, wherein the average secondary particle diameter of the semiconductor fine particles contained in the semiconductor fine particle slurry obtained in the step (b) is larger than 500 nm.   The method for producing a semiconductor fine particle paste according to claim 1, wherein the step (c) is a step including at least a viscosity adjustment of the semiconductor fine particle slurry.   2. The method for producing a semiconductor fine particle paste according to claim 1, wherein an average primary particle diameter of the semiconductor fine particles contained in the semiconductor fine particle paste is 5 nm or more and 50 nm or less. A semiconductor fine particle paste used for forming a semiconductor layer of a photoelectric conversion element,
(A) dispersing the semiconductor fine particles in a solvent;
(B) centrifuging the semiconductor fine particle slurry obtained in the step (a), and collecting a semiconductor fine particle slurry containing semiconductor fine particles having a specific particle diameter;
(C) using the semiconductor fine particle slurry obtained in the step (b), and a step of forming a semiconductor fine particle paste,
A semiconductor fine particle paste comprising semiconductor fine particles having an average primary particle size of 5 nm to 50 nm.   The semiconductor fine particle paste according to claim 7, wherein an average secondary particle diameter of the semiconductor fine particles contained in the semiconductor fine particle paste is 5 nm or more and 500 nm or less. An electrode, a semiconductor layer disposed in contact with one main surface of the electrode, a counter electrode disposed opposite to the semiconductor layer, and an electrolyte layer disposed between the electrode and the counter electrode A photoelectric conversion element comprising:
The said semiconductor layer contains the semiconductor fine particle paste described in Claim 7 or 8, and a sensitizing dye, The photoelectric conversion element characterized by the above-mentioned.   The photoelectric conversion element according to claim 9, wherein the semiconductor layer has a haze ratio of 10% or less.

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