JP2007172916A - Photoelectric conversion element - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a photoelectric conversion device capable of effectively using light irradiation from a plurality of different directions. <P>SOLUTION: The photoelectric conversion element includes a counter electrode faced in the different directions, and having an electrode surface comprising a plane surface or a curved surface having at least two surfaces electrically connected; a working electrode faced to each electrode surface of the counter electrode, having a porous oxide semiconductor layer carried with sensitizing dye, and functioning as a window electrode; and an electrolyte layer installed in at least one part between the counter electrode and the working electrode. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a photoelectric conversion element, and more particularly to a photoelectric conversion element that provides effective use of light by including a plurality of light receiving units arranged in different directions.

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 such as Gretzel 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 (not shown) made of, for example, carbon or platinum is provided on the surface in contact with the electrolyte layer 106, that is, on the transparent conductive layer 104 to further ensure electrochemical activity. The counter electrode 109 is configured by the second substrate 105, the transparent conductive layer 104, and the conductive layer (not shown).

The porous substrate layer 103 and a conductive layer (not shown) provided on the transparent conductive layer 104 are opposed to each other, and the first substrate 101 and the second substrate 105 are arranged so as to form a predetermined interval, and between the two substrates. A sealant 107 made of a thermoplastic resin is provided on the periphery of the substrate.
Then, the two substrates 101 and 105 are bonded to each other through the sealant 107, and the cells are stacked. Through the electrolyte injection port 110, oxidation / reduction of I ⁻ / I ₃ ⁻ or the like between the electrodes 108 and 109 is performed. An example is one in which an organic electrolyte containing a reducing electrode is filled and an electrolyte layer 106 for charge transfer is formed.

  However, with the above structure. Since the opening (light receiving portion) of the element faces only one direction, light incident from the back side or the like cannot be used substantially. There is no problem in the usage method in which light hits only from one direction such as the roof of a house, but it is disadvantageous in the effective use of incident light when both sides such as a signboard and an indoor partition can be used.

Although it is possible to use a plurality of elements in combination, there arises a disadvantage that the connection between the elements becomes complicated and the weight and volume increase. In addition, it is possible to combine the working electrode on both sides after forming the platinum counter electrode layer on both sides based on the structure of forming the platinum counter electrode layer on the glass substrate as conventionally used. In addition, for example, inconveniences such as an increase in the number of steps for forming a platinum layer on both surfaces by sputtering are caused.
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 devised in view of such a conventional situation, and an object thereof is to provide a photoelectric conversion element that can effectively use light irradiated from a plurality of different directions.

The photoelectric conversion element according to claim 1 of the present invention is provided with a counter electrode having two or more planes or curved surfaces that are arranged in different directions and are electrochemically connected, and each of the counter electrodes Provided at least partly between the working electrode that functions as a window electrode and has a porous oxide semiconductor layer that is provided facing the electrode surface and carries a sensitizing dye, and that functions as a window electrode And an electrolyte layer formed thereon.
The photoelectric conversion element according to claim 2 of the present invention is characterized in that, in claim 1, the counter electrode is provided with a communication hole for electrochemically connecting the electrode surfaces.
The photoelectric conversion element according to claim 3 of the present invention is characterized in that, in claim 1 or 2, the counter electrode is made of a material containing carbon as a main component.
The photoelectric conversion element according to claim 4 of the present invention is the photoelectric conversion element according to claim 1 or 2, wherein the counter electrode includes a conductive base material, and a conductive polymer layer or a platinum layer provided on the base material. It is comprised from these.

  Since the photoelectric conversion element of the present invention has a plurality of light receiving portions arranged in different directions, the light can be effectively used in an environment where light is irradiated from a plurality of different directions. it can.

  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 according to the present invention.
The photoelectric conversion element 20 is provided facing the respective electrode surfaces of the counter electrode 16 having two or more electrode surfaces that are arranged in different directions and are electrochemically connected to each other, and the counter electrode 16. The working electrode 14 and an electrolyte layer 15 made of an electrolyte enclosed between them are schematically configured.
In the example shown in FIG. 1, the counter electrode has two pole surfaces 16 a and 16 b that are both surfaces, but the present invention is not limited to this example.

  For example, the counter electrode may have three, four, or more polar surfaces. In this case, the cross-sectional shape of the counter electrode and the element can be a triangular shape (see FIG. 2A), a quadrangular shape, a pentagonal shape, a hexagonal shape (see FIG. 2B), or a higher polygonal shape. In addition, the pole surface is not limited to a flat surface, and may be a curved surface. In this case, for example, the cross-sectional shape of the counter electrode can be circular (see FIG. 2C). The curved surface may be a convex curved surface (see FIG. 3A) or a concave curved surface (see FIG. 3B). By using a concave curved surface, a light collecting effect can be imparted, and light applied to the element can be used more effectively. Furthermore, the shape (refer FIG.3 (c)) which combined the plane and the curved surface may be sufficient.

  The present invention relates to an element structure for effectively using incident light from a plurality of directions. That is, it has a working electrode on two or more sides of the element, and all working electrodes are not separated electrochemically but connected via an electrolyte layer.

  Specifically, as shown in FIG. 1, a structure in which the working electrode 14 is arranged on both surfaces of the counter electrode 16 can be exemplified. At this time, since the counter electrode 16 has a plurality of communication holes 19 provided so as to penetrate the two electrode surfaces 16a and 16b over the entire region, the inside can be filled with the electrolyte, and the action of both surfaces can be achieved. The poles 14 can be connected electrochemically. As a result, since the pair of counter electrodes 16 can be shared by the working electrodes 14 on both sides, it is possible to construct a single element having a simple and slim element structure and having light receiving portions in a plurality of directions. It becomes possible.

  Thus, since the photoelectric conversion element 20 of the present invention has a plurality of light receiving portions arranged in different directions, the light is effectively used in an environment where light is irradiated from different directions. can do. As a result, the photoelectric conversion element 20 has a large output.

In FIG. 1, reference numeral 10 is a transparent conductive substrate, 11 is a transparent substrate, 12 is a transparent conductive film, 13 is a porous oxide semiconductor layer, 14 is a working electrode, 15 is an electrolyte layer, 16 is a counter electrode, and 17 is a seal. The stop member, 18 is a laminate, and 20 is a dye-sensitized photoelectric conversion element.
In the photoelectric conversion element 20, a laminate 18 in which the counter electrode 16 is sandwiched between the working electrodes 14 with the electrolyte layer 15 interposed therebetween is bonded and integrated with a sealing member 17 to function as a photoelectric conversion element.

  The counter electrode 16 is made of a material whose main component is carbon. Here, the main component is the most frequent component excluding a portion that is merely a base material. By forming the counter electrode from a material mainly composed of carbon, charge transfer with the electrolyte proceeds promptly. Specifically, for example, a porous plate material or sheet material made of graphitized (crystallized) carbon or amorphous carbon can be used as a counter electrode.

  In addition, the base material is a mesh, non-woven fabric, perforated plate, etc. that is electrochemically inert to the electrolyte, and crystalline and amorphous carbon particles, carbon nanotubes (CNT), carbon nanohorns, and fullerenes. Fixed on both sides of the substrate by a technique such as coating, pressing, etc., formed on both sides of the substrate by a vacuum method such as sputtering or vapor deposition, or deposited on both sides of the substrate by plating Can also be used as the counter electrode 16.

In addition, as long as carbon is a main component, the base material or the electrode composition may contain other components such as a binder material.
In addition, when carbon is used as the counter electrode 16, it is preferable to remove unnecessary adsorbate by heating, baking treatment, or the like because the electrode reaction of the iodine redox couple proceeds smoothly.

  In addition, a conductive polymer derivative film or a platinum layer was formed on the above carbon material or a substrate made of a material that is electrically conductive and electrochemically inactive with respect to the electrolyte. A thing can also be used as the counter electrode 16. In such a counter electrode, charge transfer with the electrolyte proceeds promptly. In particular, a material in which a carbon mesh and a carbon sheet are used as a base material and a PEDOT [poly (ethylenedioxy) thiophene: “polyethylenedioxythiophene]] derivative film as a conductive polymer is formed on the base material is suitable as the counter electrode 16. It is.

The counter electrode 16 is provided with a communication hole 19. By this communication hole, the polar surfaces on both sides are electrochemically connected to function as a single cell.
Although it does not specifically limit as a magnitude | size of the communicating hole 19, It is preferable to set so that a surface area (effective area) may become large. However, if the communication hole 19 is too large, the effective area as the counter electrode is reduced and cell characteristics are deteriorated. On the other hand, if the communication hole 19 is too small, the electrolyte is not sufficiently charged, and the cell characteristics may be deteriorated. There is. Therefore, the size of the communication hole 19 is preferably 100 nm or more and 1 mm or less, but is not limited thereto.

The working electrode 14 includes a transparent conductive substrate 10 and a porous oxide semiconductor layer 13 formed on one surface of the transparent conductive film 12 constituting the transparent conductive substrate 10 and carrying a sensitizing dye. ing.
The transparent conductive substrate 10 is generally composed of a transparent base material 11 and a transparent conductive film 12 formed on one surface 11 a of the transparent base material 11.

  As the transparent base material 11, 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 photoelectric conversion elements can be used. Can be used. The transparent substrate 11 is appropriately selected from these in consideration of resistance to the electrolytic solution. Moreover, as a transparent base material 11, the board | substrate which is as excellent in light transmittance as possible is preferable on a use, and the board | substrate whose transmittance | permeability is 85% or more is more preferable.

  The transparent conductive film 12 is a thin film formed on one surface 11a in order to impart conductivity to the transparent substrate 11. In the present invention, the transparent conductive film 12 is preferably a thin film made of a conductive metal oxide in order to obtain a structure that does not significantly impair the transparency of the transparent conductive substrate.

As the conductive metal oxide forming the transparent conductive film 12, for example, tin-added indium oxide (ITO), fluorine-added tin oxide (FTO), tin oxide (SnO ₂ ), etc. are used. preferable. The transparent conductive film 12 is preferably a single layer film made of only ITO or FTO, or a laminated film in which a film made of FTO is stacked on a film made of ITO.
By making the transparent conductive film 12 a single layer film made of only ITO or a laminated film made by laminating a film made of FTO 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 13 is provided on the transparent conductive film 12, and a sensitizing dye is supported on the surface thereof. The semiconductor for forming the porous oxide semiconductor layer 13 is not particularly limited, and any semiconductor can be used as long as it is generally 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 13, for example, a dispersion obtained by dispersing commercially available oxide semiconductor fine particles in a desired dispersion medium, or a colloidal solution that can be prepared by a sol-gel method is used as necessary. In addition, after adding a desired additive, a method of forming using a known coating method such as a screen printing method, an ink jet printing method, a roll coating method, a doctor blade method, or a spray coating method may be used.

  As sensitizing dyes, ruthenium complexes containing a pyridin structure, terpyridine structure, etc. as ligands, metal-containing complexes such as polyphylline and phthalocyanine, and organic dyes such as eosin, 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 15 is formed by impregnating a porous oxide semiconductor layer 13 with an electrolytic solution, or after impregnating the porous oxide semiconductor layer 13 with an electrolytic solution, the electrolytic solution is applied to an appropriate gel. That is formed into an integral body with the porous oxide semiconductor layer 13 or that is formed based on an ionic liquid, and further, oxide semiconductor particles and A gel electrolyte containing conductive particles is used.

As said electrolyte solution, what melt | dissolved electrolyte components, such as an iodine, iodide ion, and tertiary butyl pyridine, in organic solvents and ionic liquids, 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, It is a liquid at room temperature, For example, the normal temperature molten salt which used the compound which has the quaternized nitrogen atom as a cation is mentioned.
Examples of the cation of the room temperature molten salt include quaternized imidazolium derivatives, quaternized pyridinium derivatives, and quaternized ammonium derivatives.
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. . Further, 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 the average particle size is preferably about 2 nm to 1000 nm.

  As the conductive fine particles, conductive particles such as a conductor and a semiconductor are used. 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 to be excellent in chemical stability against other coexisting components contained in the electrolyte. In particular, even when the electrolyte contains an oxidation / reduction pair such as iodine / iodide ion or bromine / bromide ion, an electrolyte that does not deteriorate due to 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.

  The sealing member 17 is not particularly limited as long as it has excellent adhesion to the transparent conductive substrate 10 that forms the working electrode 14. For example, an adhesive made of a thermoplastic resin having a carboxylic acid group in the molecular chain. Specifically, high Milan (made by Mitsui Dupont Chemical Co.), binel (made by DuPont), etc. are mentioned.

  Since the photoelectric conversion element 20 has a plurality of light receiving portions arranged in different directions, the light can be used effectively in an environment where light is irradiated from a plurality of different directions. . As a result, the photoelectric conversion element 20 has a large output.

  The photoelectric conversion element of the present invention has been described above, but the present invention is not limited to the above example, and can be appropriately changed as necessary.

A dye-sensitized photoelectric conversion element was produced as follows.
Example 1
As the counter electrode, a 1 mm thick graphite plate was used.
The titanium oxide nanoparticle-containing slurry was applied onto a glass substrate with a 2 cm × 2.5 cm FTO / ITO multilayer film, dried, and baked at 450 ° C. for 1 hour. This was immersed in the dye solution overnight to carry the dye, thereby forming a working electrode. An electrolyte solution injection hole was provided in advance at the end of the working electrode substrate. A ruthenium bipyridine complex (N3 dye) was used as the dye.

As the electrolytic solution, a solution obtained by dissolving a predetermined amount of lithium iodide, iodine, and 4-t-butylpyridine in 1-hexyl-3-methylimidazolium iodide (HMIm-I) was used.
In addition, in order to fully infiltrate electrolyte solution in a counter electrode, it was previously immersed in the electrolyte solution of the same composition for one night or more.

Two working electrodes were bonded together using a polypropylene spacer having a predetermined thickness and a thermoplastic resin sheet with a counter electrode sandwiched between them, and the electrolyte was filled from a liquid injection hole provided in advance, thereby closing the hole. At this time, in order to secure a current extraction terminal, the two working electrodes were bonded to each other while being shifted from each other by several mm.
Further, in order to secure a current extraction terminal from the counter electrode, sealing was performed in such a manner that a part of the counter electrode protruded from the short side direction of the working electrode. In order to prevent liquid leakage from the protruding portion of the counter electrode, a UV curable acrylic base resin layer was further formed around the sealing portion.
As described above, a test cell for a photoelectric conversion element having light receiving portions on both sides was produced.

(Example 2)
A photoelectric conversion element having light receiving portions on both sides was produced in the same manner as in Example 1 except that a 1 mm thick glassy carbon porous plate was used as the counter electrode.

(Example 3)
A photoelectric conversion element having light receiving portions on both sides was produced in the same manner as in Example 1 except that 200 μm thick porous carbon paper was used as the counter electrode.

Example 4
A porous carbon paper having a thickness of 200 μm was used as a substrate, and the substrate was immersed in a PEDOT / PSS (polystyrene sulfonic acid) dispersion, pulled up, and dried at 85 ° C. By repeating this operation, a photoelectric conversion element having a light receiving portion on both sides was produced in the same manner as in Example 1 except that a conductive polymer layer formed on both sides of the substrate was used as a counter electrode. .

(Example 5)
A nickel mesh was used as a base material, the base material was immersed in a PEDOT / PSS dispersion, pulled up, and dried at 85 ° C. By repeating this operation, a photoelectric conversion element having a light receiving portion on both sides was produced in the same manner as in Example 1 except that a conductive polymer layer formed on both sides of the substrate was used as a counter electrode. .

(Comparative example)
As a counter electrode, an FTO (fluorine-doped tin oxide) film was formed on a glass substrate, and a platinum film was further formed thereon by a sputtering method. A photoelectric conversion element having a conventional structure having a light receiving portion only on one side as shown in FIG. 2 was produced.

An evaluation test was performed on the photoelectric conversion elements of Examples and Comparative Examples obtained as described above. The evaluation test was performed by irradiating 100 mW / cm ² of light from both sides of the element using a xenon lamp, and the output current of each element was measured.
The results are shown below.

  As is clear from Table 1, the photoelectric conversion element of the example having the light receiving parts on both sides can obtain about twice the current of the comparative example having the light receiving part only on one side, and has a simple structure for incident light from both sides. It was found that it can be used effectively.

  The present invention is applicable to photoelectric conversion elements such as solar cells.

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 typically another example of the photoelectric conversion element which concerns on this invention. It is a schematic sectional drawing which shows typically another 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 Transparent conductive substrate, 11 Transparent base material, 12 Transparent electrically conductive film, 13 Porous oxide semiconductor layer, 14 Working electrode (window electrode), 15 Electrolyte layer, 16 Counter electrode, 17 Sealing member, 80 Laminated body, 19 Communication Hole, 20 photoelectric conversion element.

Claims (4)

A counter electrode having a polar surface composed of two or more planes or curved surfaces arranged in different directions and connected electrochemically;
A working electrode that is provided opposite to each electrode surface of the counter electrode, has a porous oxide semiconductor layer carrying a sensitizing dye, and functions as a window electrode;
A photoelectric conversion element comprising: an electrolyte layer provided at least in part between the counter electrode and the working electrode.   The photoelectric conversion element according to claim 1, wherein the counter electrode is provided with a communication hole for electrochemically connecting the electrode surfaces.   The photoelectric conversion element according to claim 1, wherein the counter electrode is made of a material mainly composed of carbon. The photoelectric conversion element according to claim 1, wherein the counter electrode includes a conductive base material and a conductive polymer layer or a platinum layer provided on the base material.

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