JP2015191985A - Dye-sensitized solar cell and method for producing dye-sensitized solar cell - Google Patents

Abstract

Disclosed is a dye-sensitized solar cell that can improve battery characteristics even when an electrode is made of a thermoplastic resin, and a method of manufacturing the dye-sensitized solar cell. A transparent electrode 1 made of a thermoplastic resin, a counter electrode 2 having a substrate 21, an electrolyte 3 disposed between the two electrodes 1, 2 between the two electrodes, and the transparent electrode 1 side. The photocatalyst film 4 is a dye-sensitized solar cell comprising a photocatalyst film 4 and a photosensitizer dye adsorbed on an oxide semiconductor film comprising a plurality of oxide semiconductor layers. Yes, the oxide semiconductor layer is formed by sintering a porous film infiltrated with a solution of metal oxide fine particles before being disposed on the transparent electrode, and the oxide semiconductor film is disposed on the transparent electrode. Before stacking, the stacked oxide semiconductor layers are sintered. [Selection] Figure 1

Description

  The present invention relates to a dye-sensitized solar cell and a method for producing a dye-sensitized solar cell.

In general, a dye-sensitized solar cell includes, as its elements, a transparent electrode in which a transparent conductive film is formed on a transparent substrate such as a glass plate, a counter electrode, an electrolyte disposed between these electrodes, It is comprised from the photocatalyst film | membrane arrange | positioned on the surface of the said transparent electrode between electrodes. As the photocatalyst film, a film in which an oxide semiconductor film made of titanium oxide (TiO ₂ ) or the like is formed and then a photosensitizing dye such as ruthenium is adsorbed is known.

  Since the oxide semiconductor film is an aggregate of fine particles (metal oxide), the photocatalyst film in which the photosensitizing dye is adsorbed is also flexible. In order to make use of this characteristic, by adopting a flexible material such as plastic (an example of a thermoplastic resin) for the substrates of both electrodes, there is an advantage that the entire dye-sensitized solar cell becomes flexible.

  The dye-sensitized solar cell has the above-described advantages, but also has a defect that the battery performance is low. In order to improve battery performance, it is necessary to increase the photosensitizing dye adsorbed on the oxide semiconductor film. For this purpose, it is effective to make the photocatalyst film porous and thick.

  As a conventional technique, a porous film (for example, non-woven fabric) immersed in a solution of metal oxide fine particles is sintered to form an oxide semiconductor film, and a photocatalytic film in which a photosensitizing dye is adsorbed on the oxide semiconductor film Has been proposed (see, for example, Patent Document 1). Since this photocatalyst film is made porous by the porous film (nonwoven fabric), the photosensitizing dye to be adsorbed increases.

Japanese Patent No. 5021914

  By the way, the dye-sensitized solar cell described in Patent Document 1 is applied to a transparent electrode (transparent conductive layer in Patent Document 1) in the manufacturing process as described in paragraph [0083] of Patent Document 1. A porous film (a metal oxide nonwoven fabric in Patent Document 1) is disposed and then heat-treated, whereby an oxide semiconductor film (a porous metal oxide film in Patent Document 1) is formed.

  For this reason, the dye-sensitized solar cell described in Patent Document 1 is weak against heat because the transparent electrode is made of plastic (thermoplastic resin), and the temperature of the heat treatment in the manufacturing process must be lowered. If the temperature of the heat treatment is low, the bond between metal oxides (particularly between layers) becomes weak, so that the oxide semiconductor film cannot be multilayered as a means for thickening the photocatalytic film. On the other hand, as a means for increasing the thickness of the photocatalytic film, it is conceivable to increase the thickness of the oxide semiconductor film itself by using a thick porous film. However, if a thick porous film is used, the metal oxide fine particle solution is difficult to dry up to the inside of the porous film, so that the photocatalytic film is prevented from being made porous. As is clear from these results, the photocatalyst film does not adsorb many photosensitizing dyes. Therefore, the dye-sensitized solar cell provided with the photocatalyst film, that is, the dye-sensitized solar cell described in Patent Document 1 has insufficient battery performance.

  Then, an object of this invention is to provide the manufacturing method of the dye-sensitized solar cell which can improve a battery characteristic even if an electrode is a product made from a thermoplastic resin, and a dye-sensitized solar cell.

In order to solve the above problems, a dye-sensitized solar cell of the present invention according to claim 1 includes a transparent electrode made of a thermoplastic resin, a counter electrode having a substrate, an electrolyte disposed between these electrodes, A dye-sensitized solar cell comprising a photocatalytic film disposed between the electrodes and on the transparent electrode side,
The photocatalytic film is obtained by adsorbing a photosensitizing dye to an oxide semiconductor film composed of a plurality of oxide semiconductor layers,
Before the oxide semiconductor layer is disposed on the transparent electrode, the porous film into which the solution of metal oxide fine particles has permeated is sintered.
Before the oxide semiconductor film is disposed on the transparent electrode, the stacked oxide semiconductor layers are sintered.

Further, in the dye-sensitized solar cell of the present invention according to claim 2, the photocatalytic film according to claim 1 has a larger particle size of the metal oxide fine particles contained in the porous film closer to the counter electrode It is.
Furthermore, in the dye-sensitized solar cell of the present invention according to claim 3, the photocatalyst film in the dye-sensitized solar cell according to claim 1 or 2 contains a conductive material.

The method for producing a dye-sensitized solar cell of the present invention according to claim 4 includes a transparent electrode made of a thermoplastic resin, a counter electrode having a substrate, an electrolyte disposed between these electrodes, and a gap between both electrodes. And a method for producing a dye-sensitized solar cell comprising a photocatalytic film disposed on the transparent electrode side,
A process of forming an oxide semiconductor layer by infiltrating a solution of metal oxide fine particles into the porous film and sintering the porous film;
Stacking the oxide semiconductor layer and sintering the stacked oxide semiconductor layer to form an oxide semiconductor film; and
A step of disposing the oxide semiconductor film on the transparent electrode and adsorbing a photosensitizing dye to the oxide semiconductor film to form a photocatalytic film;
A step of disposing an electrolyte and a counter electrode on the transparent electrode on which the photocatalytic film is formed;
Is provided.

  According to the said dye-sensitized solar cell and the manufacturing method of a dye-sensitized solar cell, even if an electrode is a product made from a thermoplastic resin, a battery characteristic can be improved.

It is sectional drawing which shows schematic structure of the dye-sensitized solar cell (element) which concerns on embodiment of this invention. It is sectional drawing which shows schematic structure of the same dye-sensitized solar cell (module).

  Hereinafter, a dye-sensitized solar cell and a manufacturing method thereof according to an embodiment of the present invention will be described with reference to the drawings. In addition, the dye-sensitized solar cell which concerns on this Embodiment points out the element, as shown in FIG.

  As shown in FIG. 1, the dye-sensitized solar cell includes a transparent electrode 1 made of a thermoplastic resin as a negative electrode, a counter electrode 2 as a positive electrode, and an electrolyte 3 disposed between the two electrodes 1 and 2. A photocatalyst film 4 disposed between the electrodes 1 and 2 and on the transparent electrode 1 side, and a sealing portion 5 disposed around the electrolyte 3 between the electrodes 1 and 2 are provided.

  The photocatalyst film 4 which is the gist of the present invention is composed of two photocatalyst layers (specifically, a first photocatalyst layer 41 and a second photocatalyst layer 42). The photocatalyst film 4 is obtained by adsorbing a photosensitizing dye on an oxide semiconductor film composed of two oxide semiconductor layers (the same number as the photocatalyst layers 41 and 42). The oxide semiconductor layer is obtained by sintering a porous film infiltrated with a solution of metal oxide fine particles before being placed on the transparent electrode 1. The oxide semiconductor film is formed by sintering the stacked oxide semiconductor layers before being disposed on the transparent electrode 1. That is, the sintering is not performed by involving other constituent members (component members other than the photocatalyst film 4, for example, the transparent electrode 1 made of thermoplastic resin). For this reason, the temperature of the said sintering is not restrict | limited to the heat-resistant temperature of said other structural member. Therefore, since the bonding between the oxide semiconductor layers in the oxide semiconductor film is strengthened by increasing the sintering temperature, the photocatalyst film 4 becomes a single thick film.

  The photocatalytic film 4 has a larger particle size of the metal oxide fine particles contained in the photocatalyst layer 42 closer to the counter electrode 2, in other words, the metal oxide contained in the photocatalyst layer 41 closer to the transparent electrode 1. The particle size of the product fine particles is reduced. For this reason, the photocatalyst film 4 composed of such photocatalyst layers 41 and 42 has a light confinement effect.

Further, the photocatalytic film 4 contains a conductive material. For this reason, since the photocatalyst film 4 has conductivity, its electric resistance is reduced.
As the porous membrane, a porous membrane having an electrolytic solution resistance such as glass paper (thickness 30 μm, weighing 4.0 to 12.0 g / m ² ), paper, non-woven fabric, etc. is used. In addition, as the conductive material, a carbon material, a metal material, or the like is used. Examples of the carbon material include carbon nanotubes, carbon nanocoils, and carbon black. The conductive material has a particle size equal to or less than the thickness of the porous film, preferably less than half the thickness of the porous film (in this case, 15 μm or less).

  The transparent electrode 1 includes a transparent substrate 11 and a transparent conductive film 12 formed (arranged) on the surface of the transparent substrate 11. The counter electrode 2 includes a transparent substrate 21 and a transparent conductive film 22 formed (arranged) on the surface of the transparent substrate 21. In addition, this transparent conductive film 22 forms the material which has catalytic property.

  As each of the transparent substrates 11 and 21, a synthetic resin plate, a glass plate, or the like is appropriately used, but a film made of a thermoplastic resin is preferable in terms of weight reduction, price reduction, and safety (hard to break). . Examples of the thermoplastic resin include polyester resins such as polyethylene naphthalate (PEN) and polyethylene terephthalate (PET), polycarbonate resins, and resins such as polyolefins.

Further, the transparent conductive films 12 and 22 are not particularly limited, but include tin-added indium oxide (ITO), tin oxide (SnO ₂ ), indium zinc oxide (IZO), zinc oxide (ZnO), and the like. Although a thin film containing a conductive metal oxide is used, a thin film containing fluorine-added tin oxide (FTO) is preferable. This is because fluorine-added tin oxide (FTO) has high strength as a material, so that the applied voltage at the time of aging can be increased. As a result, in the photocatalyst film 4 of the dye-sensitized solar cell to be manufactured, This is because the adsorption between the sensitizing dye and the oxide semiconductor film can be strengthened.

  By the way, the counter electrode 2 is not limited to the transparent substrate 21 and the transparent conductive film 22 formed with a material having catalytic properties, as described above. As the counter electrode 2, a material such as platinum or carbon having catalytic properties may be formed on a metal sheet such as aluminum, copper or tin or a mesh electrode. Examples of the method for forming the material having catalytic properties include sputtering and immersing the counter electrode 2 in a platinum nanocolloid solution. Further, the counter electrode 2 has a conductive adhesive layer formed on the surface of the transparent substrate 21 on the electrolyte 3 side, and a separately generated vertically aligned carbon nanotube group was transferred to the conductive adhesive layer. It may be a thing.

  As the electrolyte solution of the electrolyte 3, a liquid electrolyte solution or a gel electrolyte solution is used. Examples of liquid electrolytes include iodine-based electrolytes, which are electrolyte components such as iodine, iodide ions, and tertiary butyl pyridine dissolved in organic solvents such as ethylene carbonate and methoxyacetonitrile. is there. Examples of the gel electrolyte include dimethylpropylimidazolium iodide (DMPImI), metal iodide (lithium iodide, sodium iodide, potassium iodide, cesium iodide, calcium iodide), tetraalkylammonium iodide. Combinations of iodide and iodine such as iodine salts of quaternary ammonium compounds such as id, metal bromides (lithium bromide, sodium bromide, potassium bromide, cesium bromide, calcium bromide), tetraalkylammonium bromide, etc. And combinations of bromides such as bromine salts of quaternary ammonium compounds with bromine.

  By the way, as described above, the photocatalyst film 4 is composed of a plurality of photocatalyst layers 41 and 42, and light is applied to an oxide semiconductor film composed of a plurality of layers (the same number of layers as the photocatalyst layers 41 and 42). A sensitizing dye is adsorbed. For this reason, the photocatalyst layers 41 and 42 are obtained by adsorbing the photosensitizing dye to the oxide semiconductor layer. In forming the oxide semiconductor layer, a solution of metal oxide fine particles (a paste containing an oxide semiconductor) is infiltrated into the porous film, and the porous film is sintered. In forming the oxide semiconductor film, the plurality of formed oxide semiconductor layers are stacked, and the stacked oxide semiconductor layers are sintered. As an example of a method for adsorbing a photosensitizing dye to an oxide semiconductor film, a transparent electrode 1 in which the oxide semiconductor film is disposed in a dye solution obtained by dissolving a photosensitizing dye in an organic solvent is predetermined. Examples include soaking for a time (about 10 minutes to 24 hours).

As the oxide semiconductor, fine particles of a photocatalytic substance such as titanium oxide (TiO ₂ ), tin oxide (SnO ₂ ), tungsten oxide (WO ₃ ), zinc oxide (ZnO), niobium oxide (Nb ₂ O ₅ ), and the like. (Metal oxide fine particles) are used. The particle size of these fine particles is not particularly limited, but is preferably about 5 to 100 μm. Examples of photosensitizing dyes include ruthenium complexes and iron complexes having ligands containing a bipyridine structure or a terpyridine structure, porphyrin-based or phthalocyanine-based metal complexes, or organic dyes such as eosin, rhodamine, merocyanine, and coumarin. used. In particular, a ruthenium complex is preferably used from the viewpoint of versatility (battery performance and durability), and an organic dye is preferably used from the viewpoint of design. As an organic solvent for dissolving the photosensitizing dye, alcohol such as ethanol, acetonitrile, or the like is used. When titanium oxide (TiO ₂ ) was used as the oxide semiconductor, it was obtained by dissolving titanium (IV) isopropoxide (TTIP) in propanol for the purpose of strengthening the bond of titanium oxide. A solution (which is a photocatalyst precursor solution) may be mixed with the dye solution.

  Further, the sealing part 5 is not particularly limited, but an acrylic resin sealant, a fluorine resin sealant, a silicone resin sealant, an epoxy resin sealant, and an olefin resin. Sealants, silane-modified resin-containing sealants, hot-melt sealants, photocurable resin sealants, and the like are used.

Next, the manufacturing method of the said dye-sensitized solar cell is demonstrated.
[Transparent electrode 1 and photocatalyst film 4]
Titanium (IV) isopropoxide (TTIP) and a conductive material are mixed in a solvent such as alcohol, and a TTIP solution (the concentration of titanium oxide is about 0.01 to 1% and the concentration of the conductive material is 0.1 to 0.1%). A few percent). Next, the porous film is immersed in a TTIP solution, so that the porous film contains a conductive material and a small amount of titanium oxide fine particles.

  On the other hand, metal oxide (oxide semiconductor) fine particles are mixed with an organic solvent and water and stirred to produce a paste-like oxide solution (also referred to as a solution of metal oxide fine particles). In addition, alcohol, acetone, hexane, etc. are used for this organic solvent. Next, the oxide solution penetrates into the porous membrane by immersing the porous membrane in the oxide solution. The oxide semiconductor layer is formed by sintering the porous film infiltrated with the oxide solution at 150 ° C. or higher. These oxide semiconductor layers are stacked and sintered at 500 ° C. or higher (usually 450 to 550 ° C., but may be 550 ° C. or higher), thereby forming an oxide semiconductor composed of a plurality of oxide semiconductor layers. A film (becomes the photocatalyst film 4 by adsorbing the photosensitizing dye) is formed.

  The oxide semiconductor film thus formed is arranged on the transparent conductive film 12 side of the transparent electrode 1. In addition, immediately before disposing the oxide semiconductor film on the transparent electrode 1, the TTIP solution is spray-coated on the transparent conductive film 12 side of the transparent electrode 1, and after disposing the oxide semiconductor film on the transparent electrode 1, the transparent electrode 1 is sintered below its heat-resistant temperature. Here, a diluted solution obtained by diluting a solution of metal oxide fine particles (a paste containing an oxide semiconductor) may be added to the TTIP solution. When the diluted solution is sintered, the solvent passes through the oxide semiconductor film and volatilizes, thereby bonding the transparent electrode 1 and the oxide semiconductor film more firmly.

Next, the photocatalytic film 4 which is a negative electrode is obtained by adsorbing the photosensitizing dye to the oxide semiconductor film by the method of immersing the transparent electrode 1 in the dye solution described above. Here, the content of the photosensitizing dye in the dye solution is not particularly limited, but is preferably 0.2 × 10 ^{−3 to} 1.0 × 10 ⁻³ [mol / L], More preferably, it is 0.3 × 10 ^{−3 to} 0.6 × 10 ⁻³ [mol / L]. Because, when the content is less than 0.2 × 10 ⁻³ [mol / L], a sufficient amount of the photosensitizing dye cannot be adsorbed to the oxide semiconductor film, and as a result, the produced dye It is because the battery characteristic of a sensitized solar cell falls. Further, when the content exceeds 1.0 × 10 ⁻³ [mol / L], the photosensitizing dye does not completely dissolve in the dye solution, or the photosensitizing dye is adsorbed unevenly on the oxide semiconductor film. There is a problem that occurs. In this case, the photosensitizing dye adsorbed on the oxide semiconductor film becomes excessive, so that the photosensitizing dyes are bonded to each other, so that the flow of electrons from the photosensitizing dye to the oxide semiconductor film is inhibited, As a result, the battery characteristics of the produced dye-sensitized solar cell are deteriorated.

[Electrolyte 3, counter electrode 2 and sealing part 5]
Thereafter, the transparent electrode 1 (negative electrode) and the counter electrode 2 (positive electrode) are arranged to face each other, and the electrolyte 3 is arranged between the electrodes 1 and 2. The specific method of arranging the electrolyte 3 differs depending on whether the electrolyte 3 is a liquid electrolyte solution or a gel electrolyte solution.

  When the electrolyte 3 is a liquid electrolyte, holes are formed in the transparent electrode 1 and / or the counter electrode 2 in advance, and the transparent electrode 1 and the counter electrode 2 are arranged to face each other. Then, the sealing part 5 is arrange | positioned facing the outer peripheral side of the photocatalyst film | membrane 4 (that is, it seals). Next, the electrolyte 3 is injected from the hole, and the electrolyte 3 is filled inside the sealing portion 5, thereby forming the electrolyte 3.

  When the electrolyte 3 is a gel electrolyte, the transparent electrode 1 and the counter electrode 2 are arranged to face each other after the electrolyte 3 is stacked on the photocatalyst film 4. Then, the sealing part 5 is arrange | positioned facing the outer peripheral side of the photocatalyst film | membrane 4 (that is, it seals). In addition, heat bonding is mentioned as an example of the sealing method mentioned above. This heat bonding may be bonding using a mold, or may be performed by a method of irradiating plasma, an energy beam such as visible light having a wavelength of 600 nm or more, infrared light, or microwave. Here, the adhesion using the mold means that the applied material (sealing agent) for the sealing portion 5 is pressed and heated to be cured by using the die, thereby sealing the portion 5. It is what. Moreover, the method of irradiating the energy beam is to form the sealing portion 5 by irradiating the applied sealant with the energy beam and curing the sealant.

  As described above, according to the dye-sensitized solar cell and the manufacturing method thereof according to the above embodiment, the photosensitizing dye adsorbed on the photocatalyst film 4 is increased by making the photocatalyst film 4 porous and thick. Battery performance can be improved.

Moreover, since the photocatalyst film 4 has a light confinement effect, the battery performance can be further improved.
Furthermore, since the photocatalytic film 4 containing a conductive material reduces electric resistance, the battery performance can be further improved.

Hereinafter, a dye-sensitized solar cell according to an example that more specifically shows the above embodiment and a dye-sensitized solar cell according to a comparative example will be described. In the following examples and comparative examples, the following conditions were all satisfied.
(1) The transparent electrode 1 was a PEN-ITO film (manufactured by Pexel Technologies) having a thickness of 188 μm.
(2) The porous membrane was glass paper. Moreover, the oxide solution made the metal oxide fine particle into the titanium oxide nanoparticle (Nippon Aerosil make, P-25, average particle diameter of 20 nm), and made the solvent into alcohol (propanol etc.). Furthermore, the conductive material was a single-walled carbon nanotube.
(3) The photosensitizing dye was N719 (Dyesol) which is a ruthenium metal complex dye. This was dissolved at a concentration of 0.3 m [mol / L] in a solution in which acetonitrile and t-butyl alcohol were mixed at a ratio of 1: 1 and used as a dye solution. Further, the immersion of the oxide semiconductor film in the dye solution was performed in an atmosphere of 40 ° C. for 90 minutes.
(4) The distance between the transparent electrode 1 and the counter electrode 2 was 40 μm.

  The photocatalyst film 4 was composed of three photocatalyst layers. Of these three layers, glass paper having a thickness of 10 μm was used for each of the two layers, and glass paper having a thickness of 5 μm was used for the other layer.

According to the dye-sensitized solar cell according to this example, the short-circuit current was 2.15 mA / cm ² , the open-circuit voltage was 4.56 V, the fill factor was 0.54, and the conversion efficiency was 5.28%.
[Comparative example]
The titanium oxide film (oxide semiconductor film) is formed by sintering a low temperature titanium oxide paste (PECC-C01-06, manufactured by Pexel Technologies) having a particle size of 50 to 60 μm without using a porous film. The thickness was 6 to 7 μm.

According to the dye-sensitized solar cell according to this comparative example, the short-circuit current was 1.22 mA / cm ² , the open-circuit voltage was 4.53 V, the fill factor was 0.58, and the conversion efficiency was 3.21%.
Thus, it is clear that the dye-sensitized solar cells according to the above examples and comparative examples are compared, but according to the dye-sensitized solar cell according to the above examples, the battery characteristics could be improved.

  By the way, in the said embodiment and Example, although the element of the dye-sensitized solar cell was demonstrated, the module of a dye-sensitized solar cell as shown in FIG. 2 may be sufficient. As shown in FIG. 2, the dye-sensitized solar cell (module) has the elements of the dye-sensitized solar cell described in the above embodiment and Example 1 connected in series, and transparent elements 11 and 21 are connected to each element. Are common. The dye-sensitized solar cell includes an interconnector 7 disposed between the elements, and a current collector 8 disposed on one end side of the transparent substrate 11 and the other end side of the transparent substrate 21. ing. The interconnector 7 connects the transparent conductive film 12 in one element and the transparent conductive film 22 in the other element, and connects adjacent elements in series.

DESCRIPTION OF SYMBOLS 1 Transparent electrode 2 Counter electrode 3 Electrolyte 4 Photocatalyst film 5 Sealing part 41 1st photocatalyst layer 42 2nd photocatalyst layer

Claims (4)

Dye-sensitized solar cell comprising a transparent electrode made of thermoplastic resin, a counter electrode having a substrate, an electrolyte disposed between both electrodes, and a photocatalyst film disposed between both electrodes and on the transparent electrode side Because
The photocatalytic film is obtained by adsorbing a photosensitizing dye to an oxide semiconductor film composed of a plurality of oxide semiconductor layers,
Before the oxide semiconductor layer is disposed on the transparent electrode, the porous film into which the solution of metal oxide fine particles has permeated is sintered.
A dye-sensitized solar cell, wherein the oxide semiconductor film is formed by sintering a stacked oxide semiconductor layer before being disposed on the transparent electrode.   2. The dye-sensitized solar cell according to claim 1, wherein the photocatalytic film has a larger particle size of the metal oxide fine particles as the porous film is closer to the counter electrode.   The dye-sensitized solar cell according to claim 1 or 2, wherein the photocatalyst film contains a conductive material. Dye-sensitized solar cell comprising a transparent electrode made of thermoplastic resin, a counter electrode having a substrate, an electrolyte disposed between both electrodes, and a photocatalyst film disposed between both electrodes and on the transparent electrode side A manufacturing method of
A process of forming an oxide semiconductor layer by infiltrating a solution of metal oxide fine particles into the porous film and sintering the porous film;
Stacking the oxide semiconductor layer and sintering the stacked oxide semiconductor layer to form an oxide semiconductor film; and
A step of disposing the oxide semiconductor film on the transparent electrode and adsorbing a photosensitizing dye to the oxide semiconductor film to form a photocatalytic film;
A step of disposing an electrolyte and a counter electrode on the transparent electrode on which the photocatalytic film is formed;
A method for producing a dye-sensitized solar cell, comprising:

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