JP2014022207A - Method of manufacturing dye-sensitized solar cell - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method of manufacturing a dye-sensitized solar cell having a high photoelectric conversion efficiency.SOLUTION: A method of manufacturing a dye-sensitized solar cell includes: a first step of forming a porous semiconductor layer 2 on a transparent conductive substrate 1; a second step of pressing a fine rugged sheet 3 having fine ruggedness against the porous semiconductor layer 2 to unify the porous semiconductor 2 and the fine rugged sheet 3, and thereby, produce a transparent electrode precursor α; and a third step of baking the transparent electrode precursor α to sinter the porous semiconductor layer 2, and ashing the fine rugged sheet 3 to remove the fine rugged sheet 3 from the transparent electrode precursor α.

Description

  The present invention relates to a method for producing a dye-sensitized solar cell, and more particularly to a method for producing a dye-sensitized solar cell with high power generation efficiency.

  Against the backdrop of environmental issues and resource issues, solar cells as clean energy are attracting attention. However, conventional silicon-based solar cells still have problems such as high manufacturing costs and insufficient raw material supply, and have not yet been widely spread. In addition, although compound solar cells such as CIS have excellent characteristics such as extremely high photoelectric conversion efficiency, problems such as cost and environmental load are still an obstacle to widespread use.

  On the other hand, dye-sensitized solar cells are attracting attention as solar cells that are inexpensive and can obtain high photoelectric conversion efficiency. As a general structure of this dye-sensitized solar cell, a porous semiconductor layer using oxide semiconductor nanoparticles such as titanium dioxide is formed on a transparent conductive substrate, and a sensitizing dye is supported on this layer. In combination with a counter electrode such as a conductive glass obtained by sputtering with platinum, an organic electrolyte containing an oxidizing / reducing species such as iodine / iodide ions between the electrodes can be used as a charge transfer layer. .

  In order to further increase the photoelectric conversion efficiency of the dye-sensitized solar cell, it is known that fine irregularities are formed on the surface of the porous semiconductor layer to increase the surface area of the porous semiconductor layer. (For example, patent document 1). Patent Document 1 discloses a method of forming fine irregularities on the surface of a porous semiconductor layer using nanoimprint technology. However, in the above method, when the mold is pulled out from the porous semiconductor layer after firing, a part of the porous semiconductor layer is also pulled out together with the mold. Therefore, it becomes difficult to form fine irregularities on the surface of the porous semiconductor layer, and a porous semiconductor layer having a large surface area cannot be created. As a result, there has been a problem that it is difficult to produce a dye-sensitized solar cell having high photoelectric conversion efficiency.

JP 2009-193854 A

  Accordingly, an object of the present invention is to provide a method for producing a dye-sensitized solar cell having high photoelectric conversion efficiency.

  In order to achieve the above object, the present invention is configured as follows.

  According to the present invention, the porous semiconductor layer formed on the transparent conductive substrate is a method for producing a dye-sensitized solar cell having fine irregularities, and the porous semiconductor layer is formed on the transparent conductive substrate. A second step of pressing the fine uneven sheet having fine unevenness on the porous semiconductor layer, integrating the porous semiconductor and the fine uneven sheet, and creating a transparent electrode precursor; A dye comprising at least a third step of firing the transparent electrode precursor, baking the porous semiconductor layer, and ashing the fine uneven sheet to remove the fine uneven sheet from the transparent electrode precursor A method for producing a sensitized solar cell is provided.

  According to a second aspect of the present invention, there is provided a method for producing a dye-sensitized solar cell, comprising a fourth step of adsorbing a sensitizing dye to the porous semiconductor layer after completion of the third step.

  According to the 3rd aspect of this invention, the manufacturing method of the dye-sensitized solar cell whose depth of the recessed part of the fine unevenness | corrugation of the said fine uneven | corrugated sheet is 0.5 micrometer-5 micrometers is provided.

  According to the 4th aspect of this invention, the manufacturing method of the dye-sensitized solar cell whose aspect-ratio of the fine unevenness | corrugation of the said fine uneven | corrugated sheet is 1: 1-1: 5 is provided.

  According to the 5th aspect of this invention, the manufacturing method of the dye-sensitized solar cell whose thickness of the said fine uneven | corrugated sheet is 50 micrometers-250 micrometers is provided.

  According to the 6th aspect of this invention, the manufacturing method of the dye-sensitized solar cell whose material of the said fine uneven | corrugated sheet is a PET film or a PEN film is provided.

  According to a seventh aspect of the present invention, there is provided a method for producing a dye-sensitized solar cell, wherein the porous semiconductor layer has a thickness of 1 μm to 20 μm.

  ADVANTAGE OF THE INVENTION According to this invention, the manufacturing method of the dye-sensitized solar cell which has high photoelectric conversion efficiency can be provided.

It is sectional drawing which concerns on the manufacturing process of the dye-sensitized solar cell of this invention. It is sectional drawing which concerns on the manufacturing process of a fine uneven | corrugated sheet.

  Hereinafter, embodiments according to the present invention will be described in more detail with reference to the drawings. It should be noted that the dimensions, materials, shapes, relative positions, etc. of the parts and portions described in the embodiments of the present invention are not intended to limit the scope of the present invention only to those unless otherwise specified. This is just an illustrative example.

<Method for producing dye-sensitized solar cell>
Below, the manufacturing method of the dye-sensitized solar cell of this invention is demonstrated. The method for obtaining a dye-sensitized solar cell includes the following steps.

  FIG. 1 is a cross-sectional view of a process for producing a dye-sensitized solar cell. As shown in FIG. 1A, in the first step of the present invention, a porous semiconductor layer 2 is formed on a transparent conductive substrate 1.

<Transparent conductive substrate>
The transparent conductive substrate has a configuration in which a transparent conductive film layer is formed on a transparent substrate.

  The transparent substrate is made of a transparent glass plate or plastic plate. The thickness of the transparent substrate is about 0.1 to 5 mm.

  Note that the transparent conductive film layer is made of an organic material or an inorganic material. As the organic material, a conductive polymer material can be used. Among the conductive polymer materials, it is preferable to use a water-dispersed polythiophene derivative (PEDOT: PSS) prepared using polystyrene sulfonic acid (PSS) and 3,4-ethylenedioxythiophene (EDOT). The water-dispersed polythiophene derivative (PEDOT: PSS) has high transparency and high conductivity. Therefore, by using a water-dispersed polythiophene derivative (PEDOT: PSS) for the transparent conductive film layer, it is possible to efficiently incorporate external light into the dye-sensitized solar cell and to generate electrons generated from the dye sensitization. Can be efficiently transported to the electrode extraction portion. As a result, a dye-sensitized solar cell with high energy efficiency is obtained. In addition to the above, since the water-dispersed polythiophene derivative (PEDOT: PSS) is water-soluble, it has an advantage that a transparent conductive film layer can be easily formed on the translucent substrate. In this case, the transparent conductive film layer is formed by a printing method such as gravure printing.

  As the inorganic material, an inorganic oxide such as fluorine-doped tin oxide, indium tin oxide, gallium-doped zinc oxide, aluminum-doped zinc oxide, or niobium-doped titanium oxide can be used. In addition, as for the thickness of a transparent conductive film layer, about 0.3-2 micrometers is preferable. When the thickness is less than 0.3 μm, the sheet resistance increases, and the series resistance of the dye-sensitized solar cell increases, so that the fill factor characteristic tends to be deteriorated. In this case, the transparent conductive film layer is formed by a CVD method, a sputtering method, a spray method, or the like.

  Furthermore, the transparent conductive film layer may be composed of a binder resin such as acrylic, polyester, polyurethane, and polyvinyl chloride, and conductive nanofibers. In this case, the transparent conductive film layer can be provided by a method such as painting or inkjet, and the thickness of the transparent conductive film layer can be appropriately set in the range of several tens of nm to several hundreds of nm. When the thickness is less than several tens of nm, the strength as a layer is insufficient, and when the thickness is greater than several hundred nm, the flexibility as the layer is lost and processing becomes difficult. In addition to carbon nanofibers, conductive nanofibers can be made continuously by applying an applied voltage or current from the tip of the probe to the surface of a precursor carrying metal ions such as gold, silver, platinum, copper, and palladium. Gold particles are added to metal nanowires that are created by pulling them out, or nanofibers that are formed by self-organizing graphite nanofibers, peptides, or their derivatives, which are produced by introducing a source gas onto a transparent substrate and using the CVD method. And peptide nanofibers. In this case, the transparent conductive film layer is formed by a printing method such as gravure printing.

<Porous semiconductor layer>
As a material constituting the porous semiconductor layer, titanium oxide (TiO2) is optimal, and as other materials, titanium (Ti), zinc (Zn), tin (Sn), niobium (Nb), indium (In ), Yttrium (Y), lanthanum (La), zirconium (Zr), tantalum (Ta), hafnium (Hf), strontium (Sr), barium (Ba), calcium (Ca), vanadium (V), tungsten (W) And at least one metal oxide semiconductor of a metal element such as TiO2, WO3, ZnO, Nb2O5, Ta2O5, or SrTiO3. Moreover, you may contain 1 or more types of nonmetallic elements, such as nitrogen (N), carbon (C), fluorine (F), sulfur (S), chlorine (Cl), phosphorus (P). Titanium oxide or the like is preferable because it has an electron energy band gap in the range of 2 to 5 eV, which is larger than the energy of visible light.

  The thickness of the porous semiconductor layer is preferably 1 μm to 20 μm. If the thickness of the porous semiconductor layer is less than 1 μm, there arises a problem that the dye cannot be adsorbed in the sensitizing dye adsorption process. On the other hand, if the thickness exceeds 20 μm, the porous semiconductor is cracked and peeled off, causing a problem that the film cannot be formed.

  Examples of the method for forming the porous semiconductor layer on the transparent conductive substrate include a method of printing and sintering a paste in which an oxide semiconductor is dispersed in a polymer and a solvent. For example, when the porous semiconductor layer is made of titanium oxide, it is formed as follows. First, acetic acid is added to a TiO 2 anatase powder, and then kneaded with deionized water and ethanol to prepare a titanium oxide paste stabilized with a solvent and a polymer. The prepared paste is applied onto the transparent conductive film layer at a constant speed by a printing method such as a screen printing method or a doctor blade method, and heated in the atmosphere at 400 to 600 ° C. for 10 to 60 minutes, preferably 20 to 40 minutes. By processing, a porous semiconductor layer is obtained.

  As shown in FIG. 1 (b), in the second step of the present invention, a fine uneven sheet 3 is installed on the porous semiconductor layer 2. The fine uneven sheet 3 is installed by pressing the fine uneven surface of the fine uneven sheet 3 on the uncured porous semiconductor layer 2.

<Fine uneven sheet>
The shape of the unevenness of the fine unevenness sheet is not particularly limited, but is preferably a slit shape or a dot shape. The length of the fine irregularities in the major axis direction is preferably 0.5 μm to 5 μm. If the length in the major axis direction is less than 0.5 μm, there arises a problem that the fine uneven sheet cannot be easily processed. On the other hand, if the thickness exceeds 5 μm, the film thickness of the porous semiconductor is reduced, so that the amount of adsorption of the sensitizing dye is reduced, resulting in a problem that the power generation amount cannot be secured. The length of the fine irregularities in the minor axis direction is preferably 0.5 μm to 5 μm. If the length in the minor axis direction is less than 0.5 μm, there arises a problem that processing into a fine uneven sheet cannot be easily performed. On the other hand, when the thickness exceeds 5 μm, the film thickness of the porous semiconductor is reduced, so that the amount of adsorption of the sensitizing dye is reduced, resulting in a problem that the power generation amount cannot be secured.

  The aspect ratio of the fine irregularities (ratio between the minor axis direction and the height direction of the fine irregularities) is preferably 1: 1 to 1: 5. If the aspect ratio of the fine irregularities is less than 1: 1, the fine processing into the porous semiconductor is insufficient, so that there is a problem that high photoelectric conversion efficiency cannot be achieved. On the contrary, when exceeding 1: 5, when pressing a fine uneven | corrugated sheet to a porous semiconductor, the convex part of a fine uneven | corrugated sheet breaks and the problem that an unevenness | corrugation cannot be formed arises.

    FIG. 2 is a cross-sectional view according to the manufacturing process of the fine uneven sheet. As shown in FIGS. 2A to 2C, the fine uneven sheet 3 is obtained by forming fine uneven parts on the surface of the base sheet 20 using a stamper S. Examples of the base sheet 20 include resin sheets such as polypropylene resin, polyethylene resin, polyamide resin, polyester resin, acrylic resin, and polyvinyl chloride resin.

  In addition, it is preferable that a base sheet is comprised from a PET film or a PEN film. This is because it is low in cost, and has high strength and dimensional stability, and is excellent in workability.

  Further, the thickness of the base sheet is preferably in the range of 50 μm to 250 μm. When the thickness is less than 50 μm, when forming fine irregularities on the surface of the base sheet, it becomes difficult to process wrinkles on the base sheet. Disappear.

  As shown in FIG. 1 (c), in the third step of the present invention, a transparent electrode precursor α in which the transparent conductive substrate 1, the porous semiconductor layer 2, and the fine uneven sheet 3 are integrated is placed in a firing furnace. After that, the porous semiconductor layer 2 is fired, the fine uneven sheet 3 is ashed, and the fine uneven sheet 3 is removed from the porous semiconductor layer 2.

  If comprised in this way, when the baking of the porous semiconductor layer 2 is completed, since the fine uneven | corrugated sheet 3 is incinerated, even if it does not pull out the fine uneven | corrugated sheet 3 from the baked porous semiconductor layer 2, the porous semiconductor layer 2 Can be removed. As a result, there is no problem that a part of the porous semiconductor layer 2 is removed when the fine uneven sheet 3 is removed from the porous semiconductor layer 2. Therefore, since the dye-sensitized solar cell 20 having the porous semiconductor layer 3 having fine irregularities on the surface can be produced, the dye-sensitized solar cell having high photoelectric conversion efficiency is obtained through the first to third steps. 20 can be manufactured.

  In addition, in order to bake a porous semiconductor and incinerate a fine uneven | corrugated sheet, it is preferable to heat a transparent electrode precursor for 30 minutes-60 minutes at the temperature of 450 to 550 degreeC.

  As shown in FIGS. 1D and 1E, in the fourth step of the present invention, after the sensitizing dye 2a is adsorbed to the porous semiconductor layer 2, the opposing substrate made of the conductive substrate 5 and the catalyst layer 6 is used. The electrode 4 is opposed to the transparent conductive substrate 1, and the periphery of the transparent conductive substrate 1 and the counter electrode 4 is bonded with a sealing material 7. In addition, since the fine unevenness | corrugation is formed in the porous semiconductor layer 2 at the 3rd process, the sensitizing dye 2a is easy to adsorb | suck to the porous semiconductor layer 2. FIG. Therefore, the dye-sensitized solar cell 20 having high photoelectric conversion efficiency can be obtained by sufficiently adsorbing the sensitizing dye 2a to the porous semiconductor layer 2 in the fourth step.

<Sensitizing dye>
As the sensitizing dye, an organic dye or a metal complex dye can be used. Examples of the organic dye include an acridine dye, an azo dye, an indigo dye, a quinone dye, a coumarin dye, a merocyanine dye, and a phenylxanthene dye. As the metal complex dye, a ruthenium dye is preferable, and a ruthenium bipyridine dye and a ruthenium terpyridine dye, which are ruthenium complexes, are particularly preferable. For example, visible light (wavelength of about 400 to 800 nm) can hardly be absorbed with only an oxide semiconductor film, but by supporting a ruthenium complex, visible light can be significantly taken in and photoelectrically converted.

  In order to efficiently adsorb the sensitizing dye to the porous semiconductor layer, at least one carboxyl group, sulfonyl group, hydroxamic acid group, alkoxy group, aryl group, phosphoryl group, etc. are substituted on the sensitizing dye. It is effective to have it as a group. This is because these substituents can firmly chemisorb the first sensitizing dye itself to the porous semiconductor layer and can easily transfer charges from the excited sensitizing dye to the porous semiconductor layer.

  As a method for adsorbing a sensitizing dye, a method in which a porous semiconductor layer is impregnated with a solution in which a sensitizing dye is dissolved is preferable. Solvents for dissolving the sensitizing dye when adsorbing the sensitizing dye to the porous semiconductor layer include alcohols such as ethanol, ketones such as acetone, ethers such as diethyl ether, nitrogen compounds such as acetonitrile, etc. May be one or a mixture of two or more. The concentration of the sensitizing dye in the solution is preferably about 5 × 10 −5 to 2 × 10 −3 mol / l (l (liter): 1000 cm 3).

  When adsorbing the sensitizing dye to the porous semiconductor layer, the temperature conditions of the solution and the atmosphere are not particularly limited, and examples thereof include conditions under atmospheric pressure or in vacuum, room temperature, or substrate heating. The time required for adsorption of the first sensitizing dye can be appropriately adjusted depending on the kind of the sensitizing dye and the solution, the concentration of the solution, the circulation amount of the solution of the sensitizing dye, and the like. Thereby, a sensitizing dye can be made to adsorb | suck to a porous semiconductor layer.

<Counter electrode>
As shown in FIG. 1D, the counter electrode 4 has a configuration in which a catalyst layer 6 is formed on a conductive substrate 5, and the conductive substrate 5 has a configuration in which a conductive layer is formed on the substrate. .
<Conductive substrate>

  A board | substrate consists of a glass plate, a plastic plate, etc., and thickness is about 0.5-20 mm.

  Examples of the material for the conductive layer include fluorine-doped tin oxide (FTO), tin-doped indium (ITO), aluminum-doped zinc (AZO), gallium-doped zinc (GZO), and niobium-doped titanium oxide (NTO). Among the above, it is preferable to use fluorine-doped tin oxide (FTO). By using fluorine-doped tin oxide (FTO), the conversion efficiency of the dye-sensitized solar cell is improved.

  The thickness of the conductive layer is preferably 0.1 to 10 μm. If it is less than 0.1 μm, high conductivity cannot be obtained. If it exceeds 10 μm, the dye-sensitized solar cell cannot transmit light. The conductive layer is formed on the substrate by a method such as chemical vapor deposition (CVD), spray pyrolysis (SPD), or sputtering.

<Catalyst layer>
Examples of the material for the catalyst layer include platinum, carbon, and polythiophene derivatives. Among the above, it is preferable to use platinum. By using platinum, conversion efficiency and transparency are improved. The thickness of the catalyst layer is preferably 0.1 to 100 nm. If the thickness is less than 0.1 μm, the material constituting the charge transport layer cannot be reduced. If it exceeds 100 μm, the cost is too high. Furthermore, a dye-sensitized solar cell that transmits light cannot be produced. The catalyst layer is formed on the conductive layer by a method such as doctor blade, screen printing, spray coating, or ink jet.

<Encapsulant>
Examples of the material for the sealing material include resin adhesives such as polyethylene, polypropylene, epoxy resin, fluororesin or silicone resin, acrylic UV resins, or inorganic adhesives such as glass frit and ceramics.

  The height of the sealing material is preferably 0.5 to 500 μm. If the thickness is less than 0.5 μm, the thickness of the porous semiconductor layer becomes 0.5 μm or less, and the dye cannot sufficiently absorb light. When the thickness exceeds 500 μm, the charge transport layer becomes close to 500 μm and the internal resistance increases. The sealing material is formed by a method such as hot pressing or UV curing.

  As shown in FIG. 1 (f), in the fifth step of the present invention, the charge transport layer 8 is formed in the space formed by the transparent conductive substrate 1, the conductive substrate 5 and the sealing material 7.

<Charge transport layer>
As a material for the charge transport layer, a liquid electrolyte or a gel electrolyte is preferably used. Photoelectric conversion efficiency is improved by using a liquid electrolyte or a gel electrolyte excellent in charge transport characteristics. The charge transport layer is composed of a solid electrolyte such as a polymer electrolyte, a conductive polymer such as polythiophene / polypyrrole or polyphenylene vinylene, or an organic molecular electron transport agent such as a fullerene derivative, a pentacene derivative, a perylene derivative, or a triphenyldiamine derivative. There may be.

  The charge transport layer contains iodine / iodide salt, bromine / bromide salt, cobalt complex, potassium ferrocyanide and the like.

  The thickness of the charge transport layer is preferably 1 to 500 μm. If it exceeds 500 μm, the resistance increases during charge transport, and the efficiency of the dye-sensitized solar cell cannot be increased.

  The charge transport layer is formed by forming a hole in the transparent conductive substrate or the conductive substrate and injecting an electrolyte solution constituting the charge transport layer into the solar cell from the hole.

1: Transparent conductive substrate 2: Porous semiconductor layer 2a: Sensitizing dye 3: Fine uneven sheet 4: Counter electrode 5: Conductive substrate 6: Catalyst layer 7: Sealing material 8: Charge transport layer 10: Dye sensitized Type solar cell 20: base sheet α: transparent electrode precursor S: stamper

Claims (7)

A method for producing a dye-sensitized solar cell in which a porous semiconductor layer formed on a transparent conductive substrate has fine irregularities,
A first step of forming a porous semiconductor layer on the transparent conductive substrate;
Pressing the fine uneven surface of the fine uneven surface having a fine uneven surface on the porous semiconductor layer, and integrating the porous semiconductor and the fine uneven sheet to create a transparent electrode precursor;
A third step of firing the transparent electrode precursor, baking the porous semiconductor layer, ashing the fine uneven sheet, and removing the fine uneven sheet from the transparent electrode precursor;
A method for producing a dye-sensitized solar cell comprising at least   The manufacturing method of the dye-sensitized solar cell of Claim 1 including the 4th process of adsorb | sucking a sensitizing dye to the said porous semiconductor layer after completion | finish of said 3rd process.   The method for producing a dye-sensitized solar cell according to claim 1 or 2, wherein the depth of the concave portion of the fine unevenness of the fine unevenness sheet is 0.5 µm to 5 µm.   The method for producing a dye-sensitized solar cell according to claim 1, wherein an aspect ratio of the fine unevenness of the fine unevenness sheet is 1: 1 to 1: 5.   The method for producing a dye-sensitized solar cell according to claim 1, wherein the fine uneven sheet has a thickness of 50 μm to 250 μm.   The method for producing a dye-sensitized solar cell according to claim 1, wherein a material of the fine uneven sheet is a PET film or a PEN film.   The method for producing a dye-sensitized solar cell according to claim 1, wherein the porous semiconductor layer has a thickness of 1 μm to 20 μm.

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