JP4887664B2 - Method for producing porous structure and method for producing photoelectric conversion element - Google Patents

Description

  The present invention relates to a method for producing a porous structure and a method for producing a photoelectric conversion element such as a solar cell.

  Conventionally, as a method for producing a microporous structure, particles for forming a porous structure, a thickening agent such as a polymer organic substance, and a solvent are mixed to form a paste, ink or A method in which a porous structure is obtained by preparing a clay-like mixture, applying or molding the mixture on a substrate, and then removing the thickener by a treatment such as baking is widely used.

JP 2001-196104 A (page 4, column 5, line 47 to column 6, line 27)

  However, in the manufacturing method according to the conventional example, it is difficult to control the size of the pores in the porous structure. Further, in order to increase the porosity, it is necessary to increase the amount of the thickening agent, and the control range of the porosity is limited to a level that does not make the operation during coating or molding difficult.

  For example, when a semiconductor layer is formed by attaching a sensitizing dye to a porous structure made of semiconductor particles, and a dye-sensitized solar cell is manufactured using this semiconductor layer, the manufacturing method according to the conventional example uses a thickening method. Since the porosity, size, and shape are limited by the molecular weight and concentration of the polymer organic material as the agent, and the concentration is also limited to a range that does not impair the coating property, it is difficult to obtain desired pores.

  In addition, it is difficult to uniformly disperse the thickener, and it tends to be unevenly distributed in the mixture. Therefore, it is practically difficult to control the size of the pores obtained by removing the thickener. For example, Japanese Patent Application Laid-Open No. 2004-207205 states that it is difficult to control the size of holes by a conventional method.

Moreover, in the dye-sensitized solar cell, by increasing the porosity, the electrolyte can be smoothly supplied to the inside of the semiconductor layer, thereby improving the photoelectric conversion characteristics.

  However, in the method according to the conventional example in which the thickening agent is removed to increase the porosity, if the concentration of the thickening agent is increased to increase the porosity, the viscosity of the mixture becomes too high. Such a forming method becomes difficult. Therefore, it is difficult to obtain a smooth semiconductor layer, and it is difficult to realize good photoelectric conversion characteristics. In such a case, a method using a polymer having a smaller average molecular weight is used, but even by this, a desired porosity cannot always be obtained.

  The present invention has been made to solve the above-described problems, and its object is to produce a porous structure capable of controlling the shape and size of the pores and the degree of porosity. And it is providing the manufacturing method of a photoelectric conversion element.

  That is, the present invention includes a step of preparing a mixture containing particles for forming a porous structure, a thickener, an additive other than the thickener, and a solvent, and the mixture on a substrate. And a step of forming pores by removing the additive together with the thickener, and a method for producing a porous structure.

In the method of manufacturing a photoelectric conversion element including a first electrode, a second electrode, and a semiconductor layer and an electrolyte layer sandwiched between these electrodes,
A step of preparing a mixture containing semiconductor particles for forming a porous structure, a thickener, an additive other than the thickener, and a solvent; and a substrate provided with the first electrode. The present invention relates to a method for producing a photoelectric conversion element, comprising a step of attaching the mixture and a step of forming pores by removing the additive together with the thickener.

  According to the present invention, the mixture containing the particles (or the semiconductor particles) for forming a porous structure, the thickener, the additive, and the solvent is attached on the substrate. The pores are formed by removing the additive together with the thickener, and the shape and size of the pores are controlled by appropriately selecting the shape and size of the additives. Can do.

  Moreover, since the porosity can be controlled by appropriately selecting the amount of the additive added, a desired porosity can be realized.

  That is, the method for manufacturing a photoelectric conversion element of the present invention can control the shape, size, and porosity of the vacancies in the semiconductor layer, so that the charge transfer from the electrolyte layer is the smoothest. It is possible to form an electrochemical interface that can produce high photoelectric conversion characteristics.

  In the present invention, it is desirable to add non-thickening particles having no thickening as the additive. Thereby, without considering the viscosity of the mixture in particular, for example, the concentration of the non-thickening particles can be increased and the porosity can be increased.

  Moreover, it is preferable to use fine particles having a glass transition point or a melting point of 50 ° C. or more as the non-thickening particles. This effectively prevents loss of the shape of the non-thickening particles due to heat generation expected when mixing with the thickener or the like, or heating when removing the solvent. it can.

  The shape of the non-thickening particles may be any structure such as a spherical shape, a needle shape, or a cylindrical shape. Further, the pores may be connected to each other or separated from each other, and can be appropriately selected depending on the method of using the porous structure according to the present invention. The shape of the holes can be controlled by the shape of the non-thickening particles.

  Moreover, it is preferable that the non-thickening particles have a particle size or a minor axis of 500 nm or less and 10 nm or more. More preferably, they are 500 nm or less and 50 nm or more, More preferably, they are 300 nm or less and 100 nm or more. When it exceeds 500 nm, the pores become too large, and the effect of reducing the surface area becomes dominant. When the thickness is less than 10 nm, the size of the pores obtained is not so different from that obtained by removing the thickener, and thus the above-described effects of the present invention may not be obtained. Further, when the non-thickening particles have a cylindrical shape or a needle-like shape, they may have a length of 500 nm or more (for example, several μm) in the longitudinal direction.

  Specifically, it is preferable to use fine particles made of a polymer or a carbon material as the non-thickening particles.

  The polymer is not particularly limited, but for example, at least one selected from the group consisting of polystyrene fine particles, polyethylene fine particles, polyester fine particles, polyurethane fine particles, polypropylene fine particles and polymethyl methacrylate fine particles is preferably used. Moreover, polymers other than these can also be used.

  As the carbon material, it is preferable to use multi-wall carbon nanotubes or graphite. The diameter of the carbon nanotube is, for example, 20 to 30 nm. The graphite is vapor-grown carbon and is a fibrous or acicular carbon material having a diameter of several tens to several hundreds of nanometers.

In addition, an oxide semiconductor material is preferably used as the particle or the semiconductor particle. Examples of the oxide semiconductor material include metal oxides such as TiO ₂ , MgO, ZnO, SnO ₂ , WO ₃ , Nb ₂ O ₅ , and TiSrO ₃ , and those doped with N or S. However, the present invention is not limited to these, and it is also possible to use an element other than the above two kinds, or a mixture or combination of two or more kinds of metal oxides.

  The non-thickening particles are preferably added in an amount of 1 to 100%, more preferably 15 to 50%, and still more preferably about 30% with respect to the oxide semiconductor material. Thereby, in the said photoelectric conversion element, formation of the electrochemical interface which can make the charge transfer from the said electrolyte layer the smoothest is enabled, and a higher photoelectric conversion characteristic is realizable.

  Moreover, after apply | coating the said mixture on the said base | substrate, it is preferable to heat-process and to remove the said additives, such as the said solvent, the said thickener, and the said non-thickening particle.

  The method for removing the non-thickening particles is not particularly limited, but a method of elution with an organic solvent or a method of electrochemical dissolution may be used in addition to the method by firing. In the case of firing, the temperature is preferably 700 ° C. or lower, and if it exceeds 700 ° C., the substrate may not withstand. The lower limit is, for example, 250 ° C., and it is desirable to appropriately select a temperature at which the non-thickening particles can be effectively removed.

  Furthermore, it is preferable to perform ultraviolet irradiation, ozone treatment or plasma treatment after the heat treatment. Thereby, a trace amount residue can be removed completely. For example, ultraviolet irradiation may be performed by using UV irradiation apparatus TOSURE 401 manufactured by Toshiba Corporation for 30 minutes. The ozone treatment may be performed for 30 minutes using an eye ozone cleaning device manufactured by Eye Graphics Co., Ltd. This treatment method is not limited to the above method as long as it does not impair the properties required for the target porous structure.

  In the method for producing a photoelectric conversion element according to the present invention, after attaching a sensitizing dye to the semiconductor layer having the holes, the electrolyte layer is disposed between the semiconductor layer and the second electrode, and the dye is increased. It is preferable to manufacture a sensitive solar cell.

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

  FIG. 1 is a schematic cross-sectional view of an example of a dye-sensitized wet solar cell produced by the method for producing a photoelectric conversion element according to the present invention.

  The dye-sensitized solar cell 1 includes a transparent substrate 3 provided with a transparent conductive film (transparent electrode) 2, and a substrate 6 having a conductive film (counter electrode) 4 and a current collector 5 that constitute a counter electrode of the transparent electrode 2. In addition, a semiconductor layer 7 and an electrolyte layer 8 are provided. The semiconductor layer 7 includes, for example, the oxide semiconductor material as the semiconductor particles and the sensitizing dye. Further, the transparent conductive film 2 and the conductive film 4 are connected by a conductive wire, and a current circuit 10 having an ammeter (ammeter) 9 is formed.

  And the sealing material 11 is provided in the end surface of the semiconductor layer 7 and the electrolyte layer 8, and the semiconductor layer 7 and the electrolyte layer 8 are sealed.

  In this dye-sensitized solar cell 1, light is irradiated from the transparent electrode 2 side. The current collector 5 may be omitted, or a layer made of Cr or the like may be provided to improve the adhesion between the counter electrode 4 and the current collector 5 or the substrate 6. Moreover, the conductive film 4 and the current collector 5 may be integrated.

  In the semiconductor layer 7, the oxide semiconductor material is sintered on the transparent electrode 2, and the sensitizing dye is supported on the oxide semiconductor material. The oxide semiconductor material is sensitized by the sensitizing dye.

  Hereinafter, an example of the manufacturing method of the semiconductor layer 7 by the manufacturing method based on this invention is demonstrated with reference to FIG.

  First, the mixture containing the semiconductor particles such as an oxide semiconductor material, the thickener, the additive other than the thickener, and the solvent is prepared.

  The additive is desirably the non-thickening particles that do not have thickening. This makes it possible to increase the porosity by increasing the concentration of the non-thickening particles without particularly considering the viscosity of the mixture.

  Moreover, it is preferable to use fine particles having a glass transition point or a melting point of 50 ° C. or more as the non-thickening particles. This effectively prevents loss of the shape of the non-thickening particles due to heat generation expected when mixing with the thickener or the like, or heating when removing the solvent. it can.

  The shape of the non-thickening particles may be any structure such as a spherical shape, a needle shape, or a cylindrical shape. Further, the pores may be connected to each other or separated from each other, and can be appropriately selected depending on the method of using the porous structure according to the present invention. The shape of the holes can be controlled by the shape of the non-thickening particles.

  Moreover, it is preferable that the non-thickening particles have a particle size or a minor axis of 500 nm or less and 10 nm or more. More preferably, they are 500 nm or less and 50 nm or more, More preferably, they are 300 nm or less and 100 nm or more. When it exceeds 500 nm, the pores become too large, and the effect of reducing the surface area becomes dominant. When the thickness is less than 10 nm, the size of the pores obtained is not so different from that obtained by removing the thickener, and thus the above-described effects of the present invention may not be obtained. Further, when the non-thickening particles have a cylindrical shape or a needle-like shape, they may have a length of 500 nm or more (for example, several μm) in the longitudinal direction.

  Specifically, it is preferable to use fine particles made of a polymer or a carbon material as the non-thickening particles.

  The polymer is not particularly limited, but for example, at least one selected from the group consisting of polystyrene fine particles, polyethylene fine particles, polyester fine particles, polyurethane fine particles, polypropylene fine particles and polymethyl methacrylate fine particles is preferably used. Moreover, polymers other than these can also be used.

  As the carbon material, it is preferable to use multi-wall carbon nanotubes or graphite. The diameter of the carbon nanotube is, for example, 20 to 30 nm. The graphite is vapor-grown carbon and is a fibrous or acicular carbon material having a diameter of several tens to several hundreds of nanometers.

Examples of the oxide semiconductor material include metal oxides such as TiO ₂ , MgO, ZnO, SnO ₂ , WO ₃ , Nb ₂ O ₅ , and TiSrO ₃ , and those doped with N or S. . However, the present invention is not limited to these, and it is also possible to use an element other than the above two kinds, or a mixture or combination of two or more kinds of metal oxides. For example, titanium oxide nanoparticles having an average particle diameter of 25 nm can be used. The mixing amount of the semiconductor particles such as the oxide semiconductor material can be appropriately selected.

  Moreover, it is preferable to add the non-thickening particles in a volume ratio of 1 to 100% with respect to the oxide semiconductor material. More preferably, it is 15 to 50%, and further preferably about 30%. Thereby, it is possible to form an electrochemical interface that can make charge transfer from the electrolyte layer 8 the smoothest, and to realize higher photoelectric conversion characteristics.

  As the thickener, polyethylene oxide (PEO), polyethylene glycol (PEG) or the like can be used. The mixing ratio is preferably, for example, 5 to 50% by volume with respect to the oxide semiconductor material.

  Next, the mixture prepared as described above is applied onto the transparent electrode 2 by a doctor blade method or the like.

  Next, the oxide semiconductor material such as titanium oxide is sintered, and the non-thickening particles, the thickening agent, and the solvent are removed by baking. Here, the method for removing the non-thickening particles is not particularly limited, and a method of elution with an organic solvent or a method of electrochemical dissolution may be used in addition to the method by firing. In the case of firing, the temperature is preferably 700 ° C. or lower, and if it exceeds 700 ° C., the substrate may not withstand. The lower limit is, for example, 250 ° C., and it is desirable to appropriately select a temperature at which the non-thickening particles can be effectively removed.

  Moreover, it is preferable to perform ultraviolet irradiation, ozone treatment, or plasma treatment after the heat treatment. Thereby, a trace amount residue can be removed completely. For example, ultraviolet irradiation may be performed by using UV irradiation apparatus TOSURE 401 manufactured by Toshiba Corporation for 30 minutes. The ozone treatment may be performed for 30 minutes using an eye ozone cleaning device manufactured by Eye Graphics Co., Ltd. This treatment method is not limited to the above method as long as it does not impair the properties required for the target porous structure.

  Next, the sensitizing dye is attached to the porous structure produced as described above. Any sensitizing dye may be used as long as it provides a sensitizing action. For example, bipyridine, phenanthrine derivatives, xanthene dyes, cyanine dyes, basic dyes, porphyrin compounds, azo compounds can be used. Examples include dyes, phthalocyanine compounds, anthraquinone dyes, and polycyclic quinone dyes. Moreover, these may form a complex with a metal such as ruthenium, zinc, platinum or palladium.

  As described above, the semiconductor layer 7 can be manufactured.

  According to the production method based on the present invention, the mixture containing the semiconductor particles, the thickener, the additive such as the non-thickening particles, and the solvent is adhered onto the transparent electrode 2, Since the pores are formed by removing the non-thickening particles together with the thickener, the shape and size of the pores can be easily adjusted by controlling the shape and size of the non-thickening particles. Can be controlled.

  Moreover, since the porosity can be controlled by appropriately selecting the addition amount of the non-thickening particles, a desired porosity can be realized without particularly considering the viscosity of the mixture.

  That is, since the shape and size of the vacancies in the semiconductor layer 7 and the degree of vacancies can be controlled, it is possible to form an electrochemical interface that can most smoothly perform charge transfer from the electrolyte layer 8. High photoelectric conversion characteristics can be realized.

  In the dye-sensitized solar cell 1 as shown in FIG. 1, as the transparent substrate 3 and the substrate 6, for example, a glass substrate, a transparent plastic substrate, or the like is suitable.

  The transparent electrode 2 is made of a transparent conductive material. As the transparent conductive material, ITO is most widely known. However, even if it is an ITO single film or a material doped with elements such as Zr, Hf, Te, and F, other transparent conductive materials can be used. It may be formed by forming a laminated structure with a functional material. As a laminated structure, for example, a structure in which a metal such as Au, Ag, or Cu is laminated between ITO layers, or a structure in which a nitride layer is laminated between oxide layers is known, but it is not limited thereto.

  The electrolyte layer 8 is formed by dissolving at least one material system (redox system) that reversibly changes the state of oxidation / reduction in the electrolyte.

  As solvents, nitriles such as acetonitrile, carbonates such as propylene carbonate and ethylene carbonate, gamma butyrolactone, pyridine, dimethylacetamide, other polar solvents, room temperature molten salts such as methylpropylimidazolium-iodine, or mixtures thereof can be used. It is.

Examples of the oxidation-reduction system include halogens such as I ⁻ / I ³⁻ and Br ⁻ / Br ₂ , pseudohalogens such as quinone / hydroquinone and SCN ⁻ / (SCN) ₂ , iron (II) ions / iron (III). Examples thereof include, but are not limited to, ions, copper (I) ions / copper (II) ions, and the like.

  A supporting electrolyte may be added to the electrolyte. Examples of the supporting electrolyte include inorganic salts such as lithium iodide and sodium iodide, and organic salts such as imidazolium salts and quaternary ammonium salts.

  The electrolyte may be a liquid electrolyte, or may be a gel electrolyte polymer solid electrolyte or an inorganic solid electrolyte containing this in a polymer material.

  The conductive film 4 is a good conductor and has a small overvoltage for the oxidation / reduction reaction of a chemically and electrochemically stable redox couple, such as platinum, platinum black, palladium, rhodium, ruthenium, or a metal such as carbon, or a compound thereof. A conductive polymer, a carbon material, a mixture thereof, or a transparent conductive glass carrying them is preferable.

  The current collector 5 is generally made of glass, transparent conductive glass, metal, polymer film or the like, but is not limited thereto. However, in the case where pinholes exist in the conductive film 4, it is desirable that they do not react even when they come into contact with the electrolyte. In addition, a layer made of Cr or the like can be provided between the conductive film 4 in order to improve adhesion to the conductive film 4.

  In the dye-sensitized solar cell 1 as shown in FIG. 1, it is preferable that each element is housed in a case and sealed, or the whole is resin-sealed. In this case, the semiconductor layer 4 has a structure in which light strikes from the transparent substrate 2 side.

  The operation mechanism of the dye-sensitized solar cell 1 is that light received by the light-receiving surface 12 of the transparent substrate 2 excites the sensitizing dye carried on the surface of the semiconductor layer 7, and the sensitizing dye is transferred to the semiconductor layer 7 as an electron. Pass on promptly. On the other hand, the sensitizing dye that has lost electrons receives electrons from the ions of the electrolyte layer 8 that is the carrier transfer layer. The molecule that has passed the electron receives the electron from the counter electrode 4 again. In this way, a current flows between both electrodes 2 and 4.

  According to the manufacturing method based on the present invention, the shape, size, and porosity of the semiconductor layer 7 are arbitrarily controlled by appropriately selecting the shape, size, and addition amount of the non-thickening particles. be able to. Therefore, since the produced dye-sensitized solar cell 1 has an electrochemical interface that can make charge transfer from the electrolyte layer 8 most smooth, high photoelectric conversion characteristics can be realized.

  Hereinafter, although the specific Example of this invention is described, this invention is not limited to this Example.

Example 1
Preparation of the TiO ₂ paste was performed with reference to “the latest technology of dye-sensitized solar cells (CMC)”. And the dye-sensitized solar cell as shown in FIG. 1 was produced.

First, 125 ml of titanium isopropoxide was slowly added dropwise to 750 ml of 0.1 M nitric acid aqueous solution with stirring at room temperature. When the dropping was completed, the mixture was transferred to a constant temperature bath at 80 ° C. and stirred for 8 hours to obtain a cloudy translucent sol solution. The sol solution was allowed to cool to room temperature, filtered through a glass filter, and then made up to 700 ml. The obtained sol solution was transferred to an autoclave, hydrothermally treated at 220 ° C. for 12 hours, and then subjected to dispersion treatment by ultrasonic treatment for 1 hour. Next, this solution was concentrated by an evaporator at 40 ° C. so that the content of TiO ₂ was 11% by mass. PEO (polyethylene oxide) having a molecular weight of 500,000 was added to the concentrated sol solution at a volume ratio of 15% with respect to TiO ₂ and mixed uniformly by a planetary ball mill.

Here, polystyrene fine particles having an average particle diameter of 200 nm (the non-thickening particles) were added so as to be 30% by volume with respect to TiO ₂ , and further mixed and thickened using a shaker until uniform. A TiO ₂ paste was obtained. The viscosity of the thus prepared TiO ₂ paste was measured and found to be 3.2 × 10 ³ cp.

In addition, an FTO (fluorine-doped ITO (indium tin oxide)) substrate is used as a transparent electrode, and the TiO ₂ paste produced as described above is 0.7 cm × 0.7 cm in size by screen printing on the FTO substrate. After coating, the substrate was held at 450 ° C. for 60 minutes in a nitrogen atmosphere, and nanoporous TiO ₂ was sintered on an FTO substrate (15Ω / cm ² ).

Furthermore, 1 h UV light was irradiated with an ultraviolet irradiation device (TOSURE 401, manufactured by TOSHIBA) to obtain a TiO ₂ semiconductor layer.

  Then 0.5 mM cis-bis (isothiocyanate) -N, N-bis (2,2′-dipyridyl-4,4′-dicarboxylic acid) -ruthenium (II) dihydrate and 20 mM deoxychol It was immersed in a dehydrated ethanol solution in which acid was dissolved for 12 hours to adsorb the dye. This semiconductor layer was washed with an ethanol solution of 4-tert-butylpyridine and dehydrated ethanol in this order, and dried in the dark.

  Pt sputtered glass was used as the counter electrode.

Further, 2 g of lithium iodide (LiI), 5 g of 1-propyl-2,3-dimethylimidazolium iodide, 0.5 g of iodine (I ₂ ), and ₂ g of 4-tert-butylpyridine were dissolved in 30.5 g of acetonitrile. An electrolyte solution was prepared.

  The electrolytic solution produced as described above was dropped on the semiconductor layer and joined to the counter electrode via a silicon rubber spacer (30 μm), and a dye-sensitized solar cell as shown in FIG. 1 was produced. Here, FIG. 3 and FIG. 4 show SEM photographs of a cross section of the semiconductor layer manufactured as described above. As shown in FIGS. 3 and 4, pores corresponding to a particle size of 200 nm of polystyrene fine particles as the non-thickening particles could be obtained.

Example 2
Porous titanium oxide and a dye-sensitized solar cell were produced in the same manner as in Example 1 except that the average particle diameter of polystyrene fine particles introduced into the titanium oxide paste was 500 nm. The viscosity of the prepared TiO ₂ paste was measured and found to be 2.9 × 10 ³ cp.

Example 3
Porous titanium oxide and a dye-sensitized solar cell were produced in the same manner as in Example 1 except that the average particle diameter of polystyrene fine particles introduced into the titanium oxide paste was 100 nm. The viscosity of the prepared TiO ₂ paste was measured and found to be 3.0 × 10 ³ cp.

Example 4
Porous titanium oxide and a dye-sensitized solar cell were produced in the same manner as in Example 1 except that the average particle diameter of polystyrene fine particles introduced into the titanium oxide paste was 1000 nm. The viscosity of the prepared TiO ₂ paste was measured and found to be 2.8 × 10 ³ cp.

Example 5
Porous titanium oxide and a dye-sensitized solar cell were produced in the same manner as in Example 1 except that the TiO ₂ ratio of polystyrene fine particles introduced into the titanium oxide paste was 2%. The viscosity of the prepared TiO ₂ paste was measured and found to be 3.0 × 10 ³ cp.

Example 6
Porous titanium oxide and a dye-sensitized solar cell were produced in the same manner as in Example 1 except that the TiO ₂ ratio of the polystyrene fine particles introduced into the titanium oxide paste was 5%. The viscosity of the prepared TiO ₂ paste was measured and found to be 3.1 × 10 ³ cp.

Example 7
Porous titanium oxide and a dye-sensitized solar cell were prepared in the same manner as in Example 1 except that the TiO ₂ ratio of the polystyrene fine particles introduced into the titanium oxide paste was 15%. The viscosity of the prepared TiO ₂ paste was measured and found to be 3.1 × 10 ³ cp.

Example 8
Porous titanium oxide and a dye-sensitized solar cell were produced in the same manner as in Example 1 except that the TiO ₂ ratio of the polystyrene fine particles introduced into the titanium oxide paste was 50%. The viscosity of the prepared TiO ₂ paste was measured and found to be 2.8 × 10 ³ cp.

Example 9
Porous titanium oxide and a dye-sensitized solar cell were produced in the same manner as in Example 1 except that the TiO ₂ ratio of the polystyrene fine particles introduced into the titanium oxide paste was 100%. The viscosity of the prepared TiO ₂ paste was measured and found to be 2.8 × 10 ³ cp.

Example 10
Porous titanium oxide and a dye-sensitized solar cell were prepared in the same manner as in Example 1 except that carbon nanotubes (average particle size 50 nm) were used as the fine particles to be introduced into the titanium oxide paste and firing was performed while O ₂ was flowed. . The viscosity of the prepared TiO ₂ paste was measured and found to be 2.9 × 10 ³ cp.

Example 11 (comparative example)
Porous titanium oxide and a dye-sensitized solar cell were produced in the same manner as in Example 1 except that polystyrene fine particles were not added to the titanium oxide paste. The viscosity of the prepared TiO ₂ paste was measured and found to be 3.0 × 10 ³ cp.

About each dye-sensitized solar cell produced as mentioned above, the photoelectric conversion characteristic was evaluated. Photoelectric conversion efficiency is generated by connecting a crocodile clip to the fluorine-doped conductive glass substrate and the counter electrode on the transparent electrode side of each dye-sensitized solar cell and irradiating the dye-sensitized solar cell with light. The measured current was measured with a current-voltage measuring device. The ratio between the maximum output obtained by this measurement and the light irradiation intensity was defined as the photoelectric conversion efficiency. In the light irradiation, a xenon lamp was used as a light source, and the light intensity on the dye-sensitized solar cell was set to 100 mW / cm ² . The results are shown in Table 1, FIG. 5 and FIG.

As apparent from Table 1 above, according to the production method based on the present invention, TiO ₂ particles as the particles (the semiconductor particles) for forming a porous structure, PEO as the thickener, The mixture containing polystyrene fine particles (or carbon nanotubes) as the non-thickening particles and the solvent is adhered onto the FTO substrate as the substrate, and the non-thickening particles are removed together with the thickening agent. Thus, the pores were formed, and the size of the pores could be easily controlled by controlling the size of the non-thickening particles.

  In addition, by appropriately selecting the amount of polystyrene fine particles added as the non-thickening particles, the porosity can be controlled, and a desired porosity can be realized.

  Further, as is clear from Table 1 and FIG. 5, it is preferable that the average particle diameter of the polystyrene fine particles as the non-thickening particles is 500 nm or less. The effect of lowering becomes dominant. The lower limit is preferably 10 nm or more, for example, and when it is less than 10 nm, the size of the pores is not much different from that obtained by removing the thickener, and thus the effects of the present invention as described above. May not be obtained.

Further, as apparent from Table 1 and FIG. 6, when a dye-sensitized solar cell is produced as the photoelectric conversion element, polystyrene fine particles as the non-thickening particles are used as TiO ₂ as the oxide semiconductor material. It is preferable to add 1 to 100% by volume with respect to the particles. More preferably, it is 15 to 50%, and further preferably about 30%. As a result, it was possible to form an electrochemical interface capable of making the charge transfer from the electrolyte layer the smoothest, and to realize higher photoelectric conversion characteristics. When it exceeds 100%, the photoelectric conversion efficiency decreases due to a decrease in the electrode surface area.

  That is, according to the manufacturing method according to the present invention, the shape, size, and porosity of the holes in the semiconductor layer are controlled by appropriately selecting the shape, size, and addition amount of the non-thickening particles. Therefore, it is possible to form an electrochemical interface that can make the charge transfer from the electrolyte layer the smoothest, thereby realizing high photoelectric conversion characteristics.

  While the present invention has been described with reference to the embodiments and examples, the above examples can be variously modified based on the technical idea of the present invention.

  For example, it goes without saying that the form, structure, materials used, and the like of the dye-sensitized photoelectric conversion device can be appropriately selected without departing from the gist of the present invention.

  In addition, although an example of a single solar battery cell has been described with reference to FIG. 1, a plurality of solar battery cells may be arranged in parallel to form a stack structure.

  Furthermore, although the dye-sensitized solar cell has been described as an example of the photoelectric conversion element, the present invention can also be applied to solar cells other than the dye-sensitized type and photoelectric conversion elements other than the solar cell.

It is a schematic sectional drawing of an example of the dye-sensitized solar cell produced by the manufacturing method based on this invention by embodiment of this invention. It is a process flow figure of an example of the manufacturing method based on this invention equally. It is a SEM photograph of the cross section of the semiconductor layer produced in Example 1 by the Example of this invention. 3 is an SEM photograph of a cross section of the semiconductor layer manufactured in Example 1; It is a graph which shows the relationship between the average particle diameter of the polystyrene fine particle as said non-thickening particle | grains, and photoelectric conversion efficiency. It is a graph which shows the relationship between the addition amount of the polystyrene microparticles | fine-particles as said non-thickening particle | grains, and photoelectric conversion efficiency similarly.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Dye-sensitized solar cell, 2 ... Transparent electrically conductive film (transparent electrode), 3 ... Transparent substrate,
4 ... conductive film (counter electrode), 5 ... current collector, 6 ... substrate, 7 ... semiconductor layer, 8 ... electrolyte layer,
9 ... Ammeter (ammeter), 10 ... Current circuit, 11 ... Sealing material, 12 ... Light receiving surface

Claims (17)

And particles to form a porous structure, a thickener, and an additive comprising a non-thickening particles having no thickening, preparing a mixture containing a solvent, the substrate with said mixture The manufacturing method of a porous structure which has the process made to adhere | attach and the process of forming a void | hole by removing the said additive with the said thickener. Examples non-thickening particles, the glass transition point or melting point used 50 ° C. or more particles, the production method of the porous structure of claim 1. As the non-thickening particles, fine particles made of a polymer or a carbon material are used, and the polymer is at least one selected from the group consisting of polystyrene fine particles, polyethylene fine particles, polyester fine particles, polyurethane fine particles, polypropylene fine particles and polymethyl methacrylate fine particles. the use, as the carbon material, use of carbon nanotubes or graphite, manufacturing method of the porous structure of claim 1. 2. The method for producing a porous structure according to claim 1 , wherein the non-thickening particles have a particle diameter or a minor axis of 500 nm or less and 10 nm or more.   The method for producing a porous structure according to claim 1, wherein an oxide semiconductor material is used as the particles. The method for producing a porous structure according to claim 5 , wherein the additive is added in an amount of 1 to 100% by volume with respect to the oxide semiconductor material.   The method for producing a porous structure according to claim 1, wherein after applying the mixture onto the substrate, the solvent, the thickener, and the additive are removed by heat treatment. The method for producing a porous structure according to claim 7 , wherein ultraviolet irradiation, ozone treatment, or plasma treatment is performed after the heat treatment. In the method of manufacturing a photoelectric conversion element including a first electrode, a second electrode, and a semiconductor layer and an electrolyte layer sandwiched between these electrodes,
And semiconductor particles to form a porous structure, a thickener, and an additive comprising a non-thickening particles having no thickening, preparing a mixture containing a solvent, wherein the first A method for producing a photoelectric conversion element, comprising: adhering the mixture on a substrate provided with an electrode; and forming pores by removing the additive together with the thickener. . The method for producing a photoelectric conversion element according to claim 9 , wherein fine particles having a glass transition point or a melting point of 50 ° C. or higher are used as the non-thickening particles. As the non-thickening particles, fine particles made of a polymer or a carbon material are used, and the polymer is at least one selected from the group consisting of polystyrene fine particles, polyethylene fine particles, polyester fine particles, polyurethane fine particles, polypropylene fine particles and polymethyl methacrylate fine particles. The method for producing a photoelectric conversion element according to claim 9 , wherein carbon nanotubes or graphite are used as the carbon material . The method for producing a photoelectric conversion element according to claim 9 , wherein the non-thickening particles have a particle diameter or a minor axis of 500 nm or less and 10 nm or more. The method for manufacturing a photoelectric conversion element according to claim 9 , wherein an oxide semiconductor material is used as the semiconductor particles. The manufacturing method of the photoelectric conversion element according to claim 13 , wherein the additive is added in an amount of 1 to 100% by volume with respect to the oxide semiconductor material. The method for producing a photoelectric conversion element according to claim 9 , wherein after applying the mixture onto the substrate, the solvent, the thickener, and the additive are removed by heat treatment. The method for manufacturing a photoelectric conversion element according to claim 15 , wherein ultraviolet irradiation, ozone treatment, or plasma treatment is performed after the heat treatment. After depositing a sensitizing dye to the semiconductor layer having the holes, the disposed the electrolyte layer between the semiconductor layer and the second electrode, to produce a dye-sensitized solar cell, to claim 9 The manufacturing method of the described photoelectric conversion element.

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