JP2007335197A - Photoelectric conversion element - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a photoelectric conversion element having excellent sealability, capable of reducing the weight of the element. <P>SOLUTION: The photoelectric conversion element 10 is equipped with a counter electrode 12 comprising a conductive first substrate 11, an insulative transparent second substrate 13, and a porous oxide semiconductor layer 15 disposed on a face of the second substrate via a transparent conductive film 14 and supporting a pigment in at least one part. The porous oxide semiconductor layer 15 is composed of an acting electrode 16 disposed opposing a face of the first substrate, and an electrolyte layer 17 disposed on at least one part between the counter electrode 12 and the acting electrode 16. The first substrate 11 and the second substrate 13 are overlapped with each other, and have substantially a same surface shape. A sealing material 18 is disposed to cover side face parts of the first substrate 11 and the second substrate 13. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a photoelectric conversion element. More specifically, the present invention relates to a photoelectric conversion element having excellent durability due to a new sealing structure.

  Against the backdrop of environmental problems and resource problems, solar cells as clean energy are attracting attention. Some solar cells use single crystal, polycrystalline or amorphous silicon. However, conventional silicon-based solar cells still have problems such as high production costs and insufficient supply of raw materials, and have not been widely spread.

  In addition, compound solar cells such as Cu-In-Se (also referred to as CIS) have been developed and have excellent characteristics such as extremely high photoelectric conversion efficiency. There is a problem, and it is still an obstacle to widespread use.

  On the other hand, the dye-sensitized solar cell has been proposed by a group of Gretzel et al. In Switzerland, and has attracted attention as a photoelectric conversion element that can obtain high photoelectric conversion efficiency at low cost (see Non-Patent Document 1). reference).

FIG. 4 is a cross-sectional view showing an example of a conventional dye-sensitized solar cell.
This dye-sensitized solar cell 100 includes a first substrate 101 on which a porous semiconductor layer 103 carrying a sensitizing dye is formed on one surface, a second substrate 105 on which a transparent conductive layer 104 is formed, The main component is an electrolyte layer made of, for example, a gel electrolyte enclosed between them.

As the first substrate 101, a light transmissive plate material is used, and a transparent conductive layer 102 is disposed on the surface of the first substrate 101 in contact with the dye-sensitized semiconductor layer 103 in order to provide conductivity. A working electrode 108 is formed by one substrate 101, the transparent conductive layer 102, and the porous semiconductor layer 103.
As the second substrate 105, a conductive layer 104 made of, for example, carbon or platinum is provided on the surface on the side in contact with the electrolyte layer 106, and a counter electrode 109 is configured by the second substrate and the conductive layer 104. is doing.

The first substrate 101 and the second substrate 105 are arranged at a predetermined interval so that the porous semiconductor layer 103 and the conductive layer 104 face each other, and a sealing material made of a thermosetting resin is provided at the periphery between the two substrates. 107 is provided.
The two substrates 101 and 105 are bonded to each other through the sealant 107 and the cells are stacked, and oxidation / reduction of iodine / iodide ions or the like between the electrodes 108 and 109 through the electrolyte inlet 110 is performed. An example is one in which an organic electrolyte solution containing an electrode is filled and an electrolyte layer 106 for charge transfer is formed.

  However, since the gel electrolyte used in such a photoelectric conversion element is actually a paste-like object in which the nano inorganic filler is dispersed in an electrolyte containing iodine, if left as it is, Gradually, solid-liquid separation is performed and only the electrolyte solution flows out. This iodine electrolyte solution has a strong attack against many polymers and metals, and the resins and metals that can be tolerated are limited. In the case of polymers, only the polyolefin resin is suitable.

In addition to this situation, there is a demand for reducing the weight of the cell, and there is a demand for a simple method for sealing the cell. Therefore, the transparent electrode plate and the back electrode plate on the window side are directly sealed with silicon sealant, photosensitive epoxy, acrylic resin, or the like, but there is a problem in durability because of insufficient resistance to iodine electrolyte.
O 'Regan B, Gratzel M. A low cost, high-efficiency solar cell based on dye-sensitized colloidal TiO2 films, Nature 1991; 353: 737-739

  The present invention has been proposed in view of such a conventional situation, and an object thereof is to provide a photoelectric conversion element capable of reducing the weight of the element while having excellent sealing properties. To do.

The photoelectric conversion element according to claim 1 of the present invention includes a counter electrode made of a conductive first base material, an insulating transparent second base material, and a transparent conductive film on one surface of the second base material. A working electrode in which the porous oxide semiconductor layer is disposed to face one surface of the first substrate, and the counter electrode. And an electrolyte layer disposed in at least a part between the first electrode and the working electrode, wherein the first base material overlaps with the second base material and has substantially the same surface shape, A sealing material is provided so as to cover the side surface of the base material and the second base material.
The photoelectric conversion element according to a second aspect of the present invention is the photoelectric conversion element according to the first aspect, wherein the sealing material is arranged so as to enter an outer peripheral portion between the first base material and the second base material. It is characterized by that.
The photoelectric conversion element according to claim 3 of the present invention is the photoelectric conversion element according to claim 1 or 2, wherein a protective member is disposed so as to cover the sealing material. The photoelectric conversion element according to any one of claims 1 to 3, wherein the sealing material is made of a polyolefin-based resin.

  In the present invention, since the sealing is performed by arranging the sealing material so as to cover the side portion of the counter electrode having the substantially same surface shape as the working electrode, while having excellent sealing properties, A photoelectric conversion element capable of reducing the weight of the element can be provided.

  Hereinafter, an embodiment of a photoelectric conversion element according to the present invention will be described with reference to the drawings.

FIG. 1 is a schematic cross-sectional view showing an embodiment of a photoelectric conversion element 10A (10) according to the present invention.
The photoelectric conversion element 10 of the present invention includes a counter electrode 12 made of a conductive first base material 11, an insulating transparent second base material 13, and a transparent conductive film 14 on one surface of the second base material 13. And a porous oxide semiconductor layer 15 supporting at least a part of the pigment, and the porous oxide semiconductor layer 15 is disposed to face one surface of the first substrate 11. And an electrolyte layer 17 disposed at least at a part between the counter electrode 11 and the working electrode 16.

In the photoelectric conversion element 10 of the present invention, the first base material 11 overlaps the second base material 13 and has substantially the same surface shape, and the side surfaces of the first base material 11 and the second base material 13 are the same. The sealing material 18 is arranged so as to cover the portion.
In the conventional photoelectric conversion element, the sealing material is disposed between the working electrode and the counter electrode. However, in the present invention, the sealing material is provided so as to cover at least the side portions of the stacked working electrode 16 and counter electrode 12. Since the sealing is performed by arranging 18, it is possible to reduce the thickness and weight of the element while having excellent sealing performance and preventing electrolyte leakage.

  Further, as shown in FIG. 2, the sealing material 18 is arranged so as to enter the outer peripheral portion between the working electrode 16 (second base material 13) and the counter electrode 12 (first base material 11). It is preferable. By arranging the sealing material 18 so as to enter between the substrates, the sealing material 18 can be firmly sealed. Thereby, sealing property improves and it can prevent the liquid leakage of electrolyte reliably.

  Further, as shown in FIG. 3, a protective member 19 is preferably arranged so as to cover the sealing material 18. By providing the protective member 19, the sealing performance can be further improved, and electrolyte leakage can be prevented more reliably.

  As the second base material 13, a substrate made of a light-transmitting material is used, and any glass, polyethylene terephthalate, polycarbonate, polyethersulfone, or the like that is usually used as a transparent base material for the photoelectric conversion element 10 can be used. Even things can be used. The second base material 13 is appropriately selected from these in consideration of resistance to the electrolytic solution. Moreover, as the 2nd base material 13, the board | substrate which is excellent in the light transmittance as much as possible is preferable on a use, and the board | substrate whose transmittance | permeability is 90% or more is more preferable.

The transparent conductive film 14 is a thin film formed on one surface of the second base material 13 in order to impart conductivity. In order to obtain a structure that does not significantly impair the transparency of the transparent conductive substrate, the transparent conductive film 14 is preferably a thin film made of a conductive metal oxide.
Examples of the conductive metal oxide that forms the transparent conductive film 14 include tin-added indium oxide (ITO), fluorine-added tin oxide (FTO), and tin oxide (SnO ₂ ). Among these, ITO and FTO are preferable from the viewpoint of easy film formation and low manufacturing costs. The transparent conductive film 14 is preferably a single layer film made of only ITO or a laminated film in which a film made of FTO is laminated on a film made of ITO.

  By making the transparent conductive film 14 a single-layer film made of only ITO or a laminated film in which a film made of FTO is laminated on a film made of ITO, the amount of light absorption in the visible region is small, and the conductivity A transparent conductive substrate having a high thickness can be formed.

The porous oxide semiconductor layer 15 is provided on the transparent conductive film 14, and a sensitizing dye is supported on the surface thereof. The semiconductor for forming the porous oxide semiconductor layer 15 is not particularly limited, and any semiconductor can be used as long as it is usually used for forming a porous oxide semiconductor for a photoelectric conversion element. As such a semiconductor, for example, titanium oxide (TiO ₂ ), tin oxide (SnO ₂ ), tungsten oxide (WO ₃ ), zinc oxide (ZnO), niobium oxide (Nb ₂ O ₅ ), or the like can be used. .

  As a method for forming the porous oxide semiconductor layer 15, for example, a dispersion in which commercially available oxide semiconductor fine particles are dispersed in a desired dispersion medium or a colloidal solution that can be prepared by a sol-gel method is used as necessary. After adding desired additives, the polymer microbeads are applied by heat treatment or chemical treatment after coating by a known coating method such as screen printing method, ink jet printing method, roll coating method, doctor blade method, spray coating method, etc. It is possible to apply a method of removing the void to form a porous structure.

  As sensitizing dyes, ruthenium complexes containing a pyridin structure, a terpyridine structure, etc. as ligands, metal-containing complexes such as polyphylline and phthalocyanine, and organic dyes such as eonin, rhodamine and merocyanine can be applied. Therefore, those exhibiting behavior suitable for the intended use and the semiconductor used can be selected without particular limitation.

  The electrolyte layer 17 is formed by impregnating the porous oxide semiconductor layer 15 with the electrolytic solution, or after impregnating the porous oxide semiconductor layer 15 with the electrolytic solution, the electrolytic solution is applied to an appropriate gel. Gelled (pseudo-solidified) using an agent and formed integrally with the porous oxide semiconductor layer 15, or a gel-like material containing ionic liquid, oxide semiconductor particles and conductive particles An electrolyte is used.

As said electrolyte solution, what melt | dissolved electrolyte components, such as an iodine, iodide ion, and tertiary butyl pyridine, in organic solvents, such as ethylene carbonate and methoxyacetonitrile, is used.
Examples of the gelling agent used for gelling the electrolytic solution include polyvinylidene fluoride, a polyethylene oxide derivative, and an amino acid derivative.

Although it does not specifically limit as said ionic liquid, Room temperature meltable salt which is a liquid at room temperature and made the compound which has the quaternized nitrogen atom into a cation or an anion is mentioned.
Examples of the cation of the room temperature melting salt include quaternized imidazolium derivatives, quaternized pyridinium derivatives, quaternized ammonium derivatives and the like.
Examples of the anion of the room temperature molten salt include BF ₄ ⁻ , PF ₆ ⁻ , F (HF) _n ⁻ , bistrifluoromethylsulfonylimide [N (CF ₃ SO ₂ ) ₂ ⁻ ], iodide ions, and the like.
Specific examples of the ionic liquid include salts composed of a quaternized imidazolium cation and iodide ion or bistrifluoromethylsulfonylimide ion.

The oxide semiconductor particles are not particularly limited in terms of the type and particle size of the substance, but those that are excellent in mixing with an electrolytic solution mainly composed of an ionic liquid and that gel the electrolytic solution are used. . In addition, the oxide semiconductor particles are required to have excellent chemical stability against other coexisting components contained in the electrolyte without reducing the semiconductivity of the electrolyte. In particular, even when the electrolyte contains a redox pair such as iodine / iodide ions or bromine / bromide ions, the oxide semiconductor particles are preferably those that do not deteriorate due to an oxidation reaction.
Examples of such oxide semiconductor particles include TiO ₂ , SnO ₂ , WO ₃ , ZnO, Nb ₂ O ₅ , In ₂ O ₃ , ZrO ₂ , Ta ₂ O ₅ , La ₂ O ₃ , SrTiO ₃ , Y ₂ O. ₃ , Ho ₂ O ₃ , Bi ₂ O ₃ , CeO ₂ , Al ₂ O ₃ are preferably selected from one or a mixture of two or more, and titanium dioxide fine particles (nanoparticles) are particularly preferable. The average particle diameter of the titanium dioxide is preferably about 2 nm to 1000 nm.

As the conductive fine particles, conductive particles such as a conductor and a semiconductor are used. The range of the specific resistance of the conductive particles is preferably 1.0 × 10 ⁻² Ω · cm or less, and more preferably 1.0 × 10 ⁻³ Ω · cm or less. Further, the type and particle size of the conductive particles are not particularly limited, and those that are excellent in miscibility with an electrolytic solution mainly composed of an ionic liquid and that gel the electrolytic solution are used. Furthermore, it is necessary that the oxide film 19 (insulating film 19) or the like is not formed in the electrolyte to lower the conductivity, and that the chemical stability against other coexisting components contained in the electrolyte is excellent. In particular, even when the electrolyte contains an oxidation-reduction pair such as iodine / iodide ions or bromine / bromide ions, an electrolyte that does not deteriorate due to an oxidation reaction is preferable.
Examples of such conductive fine particles include those composed mainly of carbon, and specific examples include particles such as carbon nanotubes, carbon fibers, and carbon black. All methods for producing these substances are known, and commercially available products can also be used.

As the 1st base material 11, it consists of a base material which has electroconductivity, a metal plate, a synthetic resin board, etc. are used from the thing similar to the 2nd base material 13, and since it does not need to have a light transmittance especially.
When the first substrate is made of glass, a synthetic resin plate, or the like, a thin film (conductive film) made of metal, carbon, or the like may be formed on one surface in order to impart conductivity. As the conductive film, for example, a layer of carbon, platinum, or the like, which has been heat-treated after vapor deposition, sputtering, and chloroplatinic acid coating is preferably used, but is not particularly limited as long as it functions as an electrode. .

The sealing material 18 is preferably made of a polyolefin resin. By using a sealing material made of a polyolefin-based resin, it is possible to prevent deterioration of the sealing material due to the electrolytic solution, thereby preventing leakage of the electrolytic solution and improving durability. Moreover, deterioration of the pigment can be suppressed.
As such polyolefin resin, for example, Himiran (registered trademark, manufactured by Mitsui DuPont Polychemical Co., Ltd.) and the like are preferably used.

  Moreover, as shown in FIG. 3, when arrange | positioning the protection member 19 so that the sealing material 18 may be coat | covered, as such a protection member 19, a heat shrinkable tube etc. are used, for example.

Next, a method for manufacturing the photoelectric conversion element 10C of this embodiment will be described.
First, the transparent conductive film 14 is formed so as to cover the entire area of one surface of the transparent second base material 13 to produce a transparent conductive substrate.
The method for forming the transparent conductive film 14 is not particularly limited, and examples thereof include thin film formation methods such as sputtering, CVD (chemical vapor deposition), spray pyrolysis (SPD), and vapor deposition. Can be mentioned.

  Among them, the transparent conductive film 14 is preferably formed by a spray pyrolysis method. By forming the transparent conductive film 14 by spray pyrolysis, the haze rate can be easily controlled. In addition, the spray pyrolysis method is preferable because it does not require a decompression system and can simplify the manufacturing process and reduce costs.

Next, the porous oxide semiconductor layer 15 is formed so as to cover the transparent conductive film 14. The formation of the porous oxide semiconductor layer 15 mainly includes a coating process and a drying / firing process.
The coating process is a process in which, for example, a paste of TiO ₂ colloid obtained by mixing TiO ₂ powder and a surfactant at a predetermined ratio is applied to the surface of the transparent conductive film 14 that has been made hydrophilic. At that time, it is applied to the surface of the transparent conductive film 14 which has been made hydrophilic. At this time, as a coating method, a pressing unit (for example, a glass rod) is used to press the colloid onto the transparent conductive film 14 so that the applied colloid maintains a uniform thickness. A method of moving the sky above the transparent conductive film 14 is exemplified.

  The drying / firing process is, for example, a method in which the coated colloid is allowed to stand at room temperature for about 30 minutes in an air atmosphere and dried, and then fired at a temperature of 350 ° C. for about 30 minutes using an electric furnace. Can be mentioned.

Next, a dye is supported on the porous oxide semiconductor layer 15 formed by the coating process and the drying / firing process.
As the dye solution for supporting the dye, for example, a solution prepared by adding an extremely small amount of N719 powder to a solvent of acetonitrile and t-butanol in a volume ratio of 1: 1 is prepared in advance.
The porous oxide semiconductor layer 15 that has been separately heated in an electric furnace at about 120 to 150 ° C. is immersed in a dye solvent placed in a petri dish-like container, and is immersed for a whole day and night (approximately 20 hours) in a dark place. To do. Thereafter, the porous oxide semiconductor layer 15 taken out from the dye solution is washed using a mixed solution of acetonitrile and t-butanol.
Through the above-described steps, a working electrode 16 (also referred to as a window electrode) obtained by providing a porous oxide semiconductor layer 15 made of a dye-supported TiO ₂ thin film on a transparent first substrate 13 is obtained.

  On the other hand, a counter electrode 12 formed by forming a conductive film made of, for example, platinum by a vapor deposition method or the like is provided on one surface of another base material (not necessarily transparent). The counter electrode 12 is provided with at least two holes penetrating in the thickness direction. This hole is an inlet for injecting an electrolyte solution to be described later.

The working electrode 16 is disposed so that the porous oxide semiconductor layer 15 made of a dye-supported TiO ₂ thin film faces upward, and the counter electrode is disposed so that the porous oxide semiconductor layer 15 and the first substrate 11 face each other. 12 is provided so as to overlap the working electrode 16. After that, the sealing material 18 is disposed so as to cover the side surface portion where the working electrode 16 and the counter electrode 12 overlap.

  Specifically, for example, first, a sealing material 18 made of a polyolefin-based resin molded into a ring shape is fitted around the laminated body in which the working electrode 16 and the counter electrode 12 are stacked, and further, heat shrinkage is applied thereon. A protective member 19 made of a tube is fitted.

  Next, heating is performed using an industrial high-temperature dryer (Blajet), and the heat-shrinkable tube (protective member 19) is contracted. As a result, the heat-shrinkable tube contracts while having a strong contraction stress, and the sealing material 18 is more firmly pressed against the side surface of the laminate, and the sealing material 18 is also in a state where it can flow by receiving heat, Effectively seal the cell. Thereafter, the cell can be sealed more reliably by applying pressure using a thermocompression bonding device.

  After the sealing material 18 is solidified, the electrolyte solution is injected from the inlet provided in the counter electrode 12 into the gap of the laminate 20, that is, the space surrounded by the working electrode 16, the counter electrode 12, and the sealing material 18. Thereby, the dye-sensitized photoelectric conversion element 10 is formed.

The photoelectric conversion element thus obtained is sealed by providing a sealing material so as to cover the side surface portion of the counter electrode that overlaps the working electrode and has substantially the same surface shape. It has a sealing property and can prevent deterioration of the sealing material due to the electrolytic solution and leakage of the electrolyte, thereby improving durability. Further, the element can be thinned.
Furthermore, since the protective member is disposed so as to cover the sealing material, the sealing member can be more firmly sealed, and the leakage of the electrolyte can be more reliably prevented.

(Example)
An ITO transparent conductive film having a thickness of 700 nm was formed on a glass substrate (20 mm × 20 mm) by spray pyrolysis.
A titanium oxide fine particle porous layer (area 5 × 9 mm ² ) was formed to a thickness of about 6 μm on the transparent conductive layer of the transparent conductive substrate. Then, a porous oxide semiconductor layer is formed by supporting the N3 dye (Ru (2,2′-bipyridine-4,4′-dicarboxylic acid) ₂ (NCS) ₂ ) on the titanium oxide fine particle porous film, A working electrode was obtained.

The counter electrode was produced by forming a film of platinum on a titanium substrate (thickness 0.5 mm) by a sputtering method.
A dye-sensitized photoelectric conversion element is manufactured by laminating an electrolyte between the obtained working electrode and the counter electrode, and sealing by placing a sealing material on the side surface of the counter electrode and the electrolyte layer. did. As the electrolyte, a volatile electrolytic solution using methoxyacetonitrile as a solvent was used.

Here, HiMilan (registered trademark, manufactured by Mitsui DuPont Polychemical Co., Ltd.) was used as the sealing material, and a heat shrinkable tube (Sumitomo Electric Co., Ltd.) was used as the protective member.
First, a sheet having a thickness of 0.5 mm was prepared by hot pressing a high millan. The sheet was cut into a width of 15 mm and a length of 80 mm, and 5 mm at both ends were overlapped and thermocompression bonded to prepare a ring having a circumference of 75 mm. A heat-shrinkable tube having a circumference of 85 mm was prepared and cut to a width of 20 mm.

  Next, while stretching a high-Milan sheet in a ring shape, it is fitted around a 20 mm square cell, and further, a shrink tube is fitted on it, so that a high-Milan sheet and then a shrink tube are placed outside the circumference of the 20 mm square. I made it.

The cell thus formed was first heated and shrunk using an industrial high-temperature dryer (Blajet) used for shrinking the heat-shrinkable tube. Thereafter, pressurization was further performed using a thermocompression bonding device, and the cell was more reliably sealed.
The total thickness of the photoelectric conversion element thus obtained was 2.8 mm.
Even if this photoelectric conversion element was allowed to stand for one month, it was confirmed that the sealing material was not deteriorated by the electrolytic solution and the electrolytic solution did not leak.

  The present invention can be applied to a photoelectric conversion element represented by a dye-sensitized solar cell.

It is a schematic sectional drawing which shows an example of the photoelectric conversion element which concerns on this invention. It is a schematic sectional drawing which shows an example of the photoelectric conversion element which concerns on this invention. It is a schematic sectional drawing which shows an example of the photoelectric conversion element which concerns on this invention. It is a schematic sectional drawing which shows an example of the conventional photoelectric conversion element.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Photoelectric conversion element, 11 1st base material, 12 Counter electrode, 13 2nd base material, 14 Transparent electrically conductive film, 15 Porous oxide semiconductor layer, 16 Working electrode, 17 Electrolyte layer, 18 Sealing material, 19 Protection member.

Claims (4)

A counter electrode made of a conductive first substrate;
An insulating transparent second base material, and a porous oxide semiconductor layer disposed on one surface of the second base material via a transparent conductive film and supporting a pigment at least in part. A working electrode in which a physical semiconductor layer is disposed to face one surface of the first base;
An electrolyte layer disposed at least in part between the counter electrode and the working electrode,
The first base material overlaps with the second base material and has substantially the same surface shape, and a sealing material is disposed so as to cover the side surfaces of the first base material and the second base material. A photoelectric conversion element characterized by the above.   2. The photoelectric conversion element according to claim 1, wherein the sealing material is disposed so as to enter an outer peripheral portion between the first base material and the second base material.   The photoelectric conversion element according to claim 1, wherein a protective member is disposed so as to cover the sealing material. The photoelectric conversion element according to claim 1, wherein the sealing material is made of a polyolefin-based resin.

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