JP2011244020A - Organic thin-film solar cell - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an organic thin-film solar cell excellent in electric charge extraction efficiency using a mesh electrode as a light receiving side electrode without using a transparent conductive film composed of metal oxide such as ITO.SOLUTION: The organic thin-film solar cell comprises: a substrate; the mesh electrode disposed so as to be buried in grooves formed in the substrate; a conductive polymer layer, formed at least in an aperture area of the mesh electrode, capable of transporting holes; a photoelectric conversion layer formed on the conductive polymer layer; and a counter electrode formed on the photoelectric conversion layer.

Description

  The present invention relates to an organic thin film solar cell having a mesh electrode.

  An organic thin film solar cell is a solar cell in which an organic thin film having an electron donating function and an electron accepting function is disposed between two different electrodes, and a manufacturing process compared to an inorganic solar cell typified by silicon or the like. Is easy, and has the advantage that the area can be increased at low cost.

  In the solar cell, the electrode on the light receiving side is a transparent electrode. Conventionally, metal oxides such as ITO have been used for this transparent electrode, and ITO is mainly used because of its high conductivity and transparency and high work function. However, since ITO is expensive, an electrode that can replace the ITO electrode is required.

  In recent years, it has been proposed to use a mesh electrode instead of a transparent electrode in a dye-sensitized solar cell (see, for example, Patent Document 1). By using a mesh electrode, it becomes possible to reduce the manufacturing cost of the electrode, or to use a metal having higher conductivity than the metal oxide used for the transparent electrode. Furthermore, since the mesh electrode has a larger specific surface area than the conventional transparent electrode, there is an advantage that the contact area between the mesh electrode and the semiconductor material or the electrolyte material is increased, and the movement of electric charges becomes smooth.

JP 2006-523369 A

  Therefore, it is assumed that a mesh electrode is used instead of the transparent electrode in the organic thin film solar cell. In a solar cell having a mesh electrode, the mesh electrode side serves as a light receiving surface, and the mesh electrode itself does not transmit light, so that light is transmitted from the opening of the mesh electrode. When the organic thin film solar cell has a mesh electrode, the charge generated in the organic thin film having the electron donating and electron accepting functions by the incident light from the opening of the mesh electrode is in contact with the mesh electrode in the organic thin film. It moves to the interface and is taken out to the mesh electrode.

However, in the organic thin film solar cell, the movement distance of the charge in the film thickness direction of the organic thin film is several hundred nm, whereas the movement distance of the charge in the film surface direction of the organic thin film is the line interval of the mesh electrode ( Depending on the width of the opening, it is several tens of μm or more. Therefore, the movement of charges in the film surface direction of the organic thin film has a larger resistance value defined as the product of conductivity and distance per unit distance than the movement of charges in the film thickness direction of the organic thin film, As a result, energy loss increases.
If the energy loss is large, the charge cannot be taken out efficiently. Therefore, since the movement of the charges in the direction of the film surface of the organic thin film has a large energy loss, the charges generated in the organic thin film due to the incident light from the opening of the mesh electrode cannot be efficiently taken out to the mesh electrode. As described above, in the organic thin film solar cell, there is a problem that it is difficult to take out charges to the outside only by using a mesh electrode instead of the transparent electrode.

  The present invention has been made in view of the above problems, and uses a mesh electrode as an electrode on the light receiving side, and does not use a transparent conductive film made of a metal oxide such as ITO, and has a good charge extraction efficiency. The main purpose is to provide solar cells.

  In order to achieve the above object, the present invention provides a mesh electrode, a conductive polymer layer formed at least in the opening of the mesh electrode, and capable of transporting holes, the mesh electrode, and the conductive polymer layer. An organic thin-film solar cell comprising a photoelectric conversion layer formed on the substrate and a counter electrode formed on the photoelectric conversion layer is provided.

  According to the present invention, the conductive polymer layer is formed at least in the opening of the mesh electrode, and the conductive polymer layer contributes to the movement of charges in the film surface direction. Charge generated in the photoelectric conversion layer by incident light can be efficiently taken out to the mesh electrode through the conductive polymer layer.

  In the said invention, it is preferable that the said mesh electrode contains Ag. This is because a mesh electrode can be formed using a metal paste containing Ag, and the mesh electrode can be formed by a simple method.

  In the present invention, the conductive polymer layer preferably contains polyethylene dioxythiophene / polystyrene sulfonic acid (PEDOT / PSS). This is because PEDOT / PSS is excellent in conductivity, and charges are easily transferred in the film surface direction of the conductive polymer layer.

  In the present invention, the conductive polymer layer is formed at least in the opening of the mesh electrode, so that the movement of charges from the photoelectric conversion layer to the mesh electrode can be made smooth and the charge extraction efficiency can be improved. There is an effect.

It is a schematic sectional drawing which shows an example of the organic thin film solar cell of this invention. It is a schematic sectional drawing which shows the other example of the organic thin film solar cell of this invention. It is a schematic sectional drawing which shows the other example of the organic thin film solar cell of this invention. It is a schematic sectional drawing which shows the other example of the organic thin film solar cell of this invention. It is a schematic sectional drawing which shows the other example of the organic thin film solar cell of this invention. It is a schematic sectional drawing which shows the other example of the organic thin film solar cell of this invention. It is a schematic sectional drawing which shows the other example of the organic thin film solar cell of this invention.

Hereinafter, the organic thin film solar cell of the present invention will be described in detail.
The organic thin film solar cell of the present invention includes a mesh electrode, a conductive polymer layer formed at least in the opening of the mesh electrode, and capable of transporting holes, on the mesh electrode and the conductive polymer layer. It has the formed photoelectric converting layer and the counter electrode formed on the said photoelectric converting layer, It is characterized by the above-mentioned.

The organic thin-film solar cell of this invention is demonstrated referring drawings.
FIG. 1 is a schematic sectional view showing an example of the organic thin film solar cell of the present invention. In the example shown in FIG. 1, an organic thin film solar cell 10 includes a substrate 1, a mesh electrode 2 formed on the substrate 1, a conductive polymer layer 3 formed so as to cover the mesh electrode 2, The photoelectric conversion layer 4 formed on the conductive polymer layer 3 and the counter electrode 5 formed on the photoelectric conversion layer 4 are included.

  In the organic thin film solar cell 10, first, the charge generated in the photoelectric conversion layer 4 by the incident light 11 from the opening of the mesh electrode 2 moves in the film thickness direction of the photoelectric conversion layer 4 to form a conductive polymer. Extracted into layer 3. Next, the electric charge taken out by the conductive polymer layer 3 moves in the film surface direction in the conductive polymer layer 3. Subsequently, charges are taken out to the mesh electrode 2 at the contact interface between the conductive polymer layer 3 and the mesh electrode 2.

  According to the present invention, since the conductive polymer layer is formed at least in the opening of the mesh electrode and the photoelectric conversion layer is in contact with the conductive polymer layer, the charge from the photoelectric conversion layer to the mesh electrode is reduced. It is possible to smooth the movement and improve the charge extraction efficiency. Specifically, since the conductive polymer layer is capable of transporting holes, it is possible to facilitate the movement of holes from the photoelectric conversion layer to the mesh electrode and improve the hole extraction efficiency. .

According to the present invention, it is possible to achieve good charge extraction efficiency by using a mesh electrode and a conductive polymer layer without using a transparent electrode made of a metal oxide such as ITO, thereby reducing costs. Is possible.
Hereinafter, each structure of such an organic thin film solar cell is demonstrated.

1. Mesh electrode The mesh electrode used in the present invention is a mesh-like electrode, and is an electrode (hole extraction electrode) for extracting holes generated in the photoelectric conversion layer.

  The material for forming the mesh electrode is not particularly limited as long as it has conductivity. For example, metal, conductive polymer fiber, metal-coated synthetic polymer fiber (for example, nylon), metal-coated, etc. Mention may be made of natural fibers (for example flax, cotton, wool, silk, etc.). Among these, metals, metal-coated synthetic polymer fibers, and metal-coated natural fibers are preferable. This is because by using these, an electrode having high conductivity can be obtained.

  Examples of the metal used for the mesh electrode include Al, Au, Ag, Co, Ni, Pt, Cu, Fe, stainless steel, and aluminum alloy. In general, in a dye-sensitized solar cell, in order to prevent corrosion of an electrode by an electrolyte material containing iodine or the like, Pt or the like having high corrosion resistance is used for the electrode. On the other hand, in an organic thin film solar cell, since the material which corrodes an electrode is not normally used, the electrode does not need to have corrosion resistance. Therefore, in the present invention, the above-described metal can be used for the mesh electrode, and an inexpensive metal can also be used.

A preferable metal is appropriately selected according to the work function of the material for forming the counter electrode, the method for forming the mesh electrode, and the like.
For example, when considering the work function of the material for forming the counter electrode, the mesh electrode is a hole extraction electrode, and thus the metal preferably has a high work function. Specifically, Al is preferably used.
Further, when the mesh electrode is formed by a wet coating method using a coating solution, the metal is preferably capable of being made into a paste. Specifically, Al, Au, Ag, Ni, Cu, stainless steel, aluminum alloy and the like are preferably used, and Ag is particularly preferable.

  The shape of the mesh electrode is not particularly limited as long as it is a mesh shape, and is appropriately selected depending on desired conductivity, permeability, strength, and the like. For example, a polygonal shape or a circular lattice shape may be used.

  Since the mesh electrode itself basically does not transmit light, light enters the photoelectric conversion layer from the opening of the mesh electrode. Therefore, the mesh electrode opening is preferably relatively large. Specifically, the ratio of the openings of the mesh electrode is preferably about 50% to 95%, more preferably 70% to 95%. This is because if the ratio of the openings is less than the above range, light cannot be sufficiently transmitted. Conversely, if the ratio of the openings exceeds the above range, the area of the mesh electrode is reduced, and the charge transfer efficiency at the mesh electrode is reduced, or the contact area between the mesh electrode and the conductive polymer layer is reduced. This is because the charge extraction efficiency may be reduced.

The size of the openings of the mesh electrode is suitably selected according to the area of the entire mesh electrode preferably from 1μm ² ~2500μm ² mm, more preferably in the range of 1μm ² ~100μm ² is there. This is because if the size of the opening is less than the above range, light cannot be sufficiently transmitted. Conversely, if the size of the opening exceeds the above range, the area of the mesh electrode becomes small, the charge transfer efficiency at the mesh electrode decreases, or the contact area between the mesh electrode and the conductive polymer layer decreases. This is because the charge extraction efficiency may be reduced due to a decrease in the size.

  The line width of the mesh electrode is appropriately selected depending on the area of the entire mesh electrode and the like, but is preferably about 5 μm to 5000 μm, and more preferably in the range of 50 μm to 1000 μm. This is because if the line width of the mesh electrode is less than the above range, it may be difficult to form the mesh electrode. On the other hand, if the line width of the mesh electrode exceeds the above range, the area of the opening becomes small and light may not be sufficiently transmitted.

  Moreover, it is preferable that the thickness of a mesh electrode is about 0.02 micrometer-10 micrometers, More preferably, it exists in the range of 0.05 micrometer-1 micrometer. This is because if the thickness is less than the above range, the sheet resistance of the mesh electrode becomes too large, and the generated charge may not be sufficiently transmitted to the external circuit. Conversely, when the thickness is greater than the above range, there is a possibility that a short circuit may occur between the electrodes.

As described above, the mesh electrode itself basically does not transmit light, but the entire mesh electrode (including the opening) transmits light. The total light transmittance of the mesh electrode as a whole is preferably 50% or more, and more preferably 70% or more. On the other hand, the upper limit of the total light transmittance is about 95%. This is because when the total light transmittance is within the above range, light can be sufficiently transmitted from the mesh electrode side.
In addition, the said total light transmittance is the value measured in the visible light area | region using the Suga Test Co., Ltd. total light transmittance apparatus (COLOUR S & M COMPUTER MODEL SM-C: model number).

The mesh electrode may be formed on the substrate. In this case, for example, the mesh electrode 2 may be formed on the surface of the substrate 1 as shown in FIG. 1, or the mesh electrode 2 may be embedded in the substrate 1 as shown in FIG. When the mesh electrode is embedded in the substrate, a short circuit between the electrodes can be suppressed.
In addition, when the mesh electrode is embedded in the substrate, the entire mesh electrode 2 may be embedded in the substrate 1 as illustrated in FIG. 2, and although not shown, a part of the mesh electrode is included in the substrate. It may be embedded. When the entire mesh electrode is embedded in the substrate, a short circuit between the electrodes can be effectively suppressed.

  The method for forming the mesh electrode is not particularly limited, and examples thereof include a method of forming a conductive film on the entire surface and then patterning into a mesh shape, a method of directly forming a mesh-like conductor, and the like. These methods are appropriately selected according to the formation order of the respective constituent members, the arrangement of the mesh electrodes, and the like.

  For example, when the mesh electrode 2 is formed on the substrate 1 in the manufacturing process of the organic thin film solar cell 10 as shown in FIGS. 1 and 3, a method of patterning in a mesh after forming a conductive film on the entire surface of the substrate. And a method of directly forming a mesh-like conductor on the substrate can be employed. For example, in the manufacturing process of the organic thin film solar cell 10 as shown in FIGS. 4 and 5, when the mesh electrode 2 is formed on the conductive polymer layer 3, and the organic thin film as shown in FIGS. When the mesh electrode 2 is formed on the photoelectric conversion layer 4 in the manufacturing process of the solar cell 10, a method of directly forming a mesh-like conductor on each layer can be employed.

In the case of a method of patterning in a mesh after forming a conductive film on the entire surface, examples of the method for forming a conductive film include PVD methods such as vacuum deposition, sputtering, and ion plating, and CVD methods. Examples thereof include a dry coating method and a wet coating method in which a coating liquid is applied.
As the coating liquid used in the wet coating method, a metal paste containing a metal colloid such as Ag can be used. Examples of the coating method include a die coating method, a spin coating method, a dip coating method, a roll coating method, a bead coating method, a spray coating method, a bar coating method, and a gravure coating method.
Further, the method for patterning the conductive film is not particularly limited as long as it can be accurately formed into a desired pattern, and examples thereof include a photolithography method.

  On the other hand, in the case of a method of directly forming a mesh-like conductor, for example, a mask vapor deposition method, a screen printing method, an offset printing method, a gravure printing method, and the like can be given. Alternatively, a mesh-like conductor can be prepared in advance, and the mesh-like conductor can be stacked on a substrate or the like.

For example, when the mesh electrode is embedded in the substrate as shown in FIG. 2, a method of first forming a groove in the substrate and then embedding the mesh electrode in the groove can be employed.
Examples of the method for forming the groove on the substrate include a chemical method such as etching, excavation by collision of fine sand such as sand blasting, and the like. When forming the groove, a photosensitive resist layer may be formed on the substrate before etching or sandblasting, and a resist pattern corresponding to the mesh electrode may be formed by photolithography. In addition, it is preferable to perform cleaning after the etching or sandblast treatment.
Moreover, as a method of embedding the mesh electrode in the groove, a method of applying a metal paste to the groove can be mentioned. Examples of the method for applying the metal paste include a barcode method and a screen printing method. After applying the metal paste, a baking process may be performed to fix the metal paste in the groove. At this time, since the metal paste shrinks, the metal paste may be applied and baked a plurality of times in order to fill the groove with the metal paste.
Next, it is preferable that the metal paste embedded in the groove removes a portion protruding from the substrate surface by lightly polishing the substrate surface. This is because a short circuit between the electrodes can be suppressed.

2. Conductive polymer layer The conductive polymer layer used in the present invention is formed at least in the opening of the mesh electrode, and is provided so as to be in direct contact with the mesh electrode and the photoelectric conversion layer.
The conductive polymer layer is a layer that can transport holes and is provided so that holes can be easily taken out from the photoelectric conversion layer to the mesh electrode. Since the conductive polymer layer is formed, the efficiency of extracting holes from the photoelectric conversion layer to the mesh electrode is increased, so that the photoelectric conversion efficiency can be improved.

  The arrangement of the conductive polymer layer is not particularly limited as long as the conductive polymer layer is formed at least in the opening of the mesh electrode. For example, as shown in FIGS. 1, 2, and 4 to 6. The conductive polymer layer 3 may be formed on the opening of the mesh electrode 2 and on the mesh electrode 2, and the conductive polymer layer 3 is formed only on the opening of the mesh electrode 2 as shown in FIGS. May be formed.

  In addition, when the conductive polymer layer is formed on the mesh electrode opening and the mesh electrode, the conductive polymer layer may be formed as shown in FIG. 1, FIG. 2, and FIG. The mesh electrode 2, the conductive polymer layer 3, and the photoelectric conversion layer 4 may be laminated so that the conversion layer 4 does not directly contact the mesh electrode 2, and photoelectric conversion is performed as illustrated in FIGS. 4 and 6. The conductive polymer layer 3, the mesh electrode 2, and the photoelectric conversion layer 4 may be laminated so that the layer 4 is in direct contact with the mesh electrode 2.

In the present invention, since light enters the photoelectric conversion layer from the opening of the mesh electrode, the conductive polymer layer formed in the opening of the mesh electrode needs to have transparency. Specifically, the total light transmittance of the conductive polymer layer is preferably 70% or more, more preferably 80% or more, and further preferably 90% or more. This is because when the total light transmittance is within the above range, light can be sufficiently transmitted from the mesh electrode side.
In addition, about the measuring method of the said total light transmittance, it is as having described in the term of the said mesh electrode.

  The conductive polymer material used for the conductive polymer layer is not particularly limited as long as it satisfies the above characteristics and stabilizes the extraction of holes from the photoelectric conversion layer to the mesh electrode. It is preferable to have a relatively high conductivity. This is because the higher the conductivity, the easier the charge moves in the film surface direction of the conductive polymer layer. Specifically, examples of the conductive polymer material include doped polyaniline, polyphenylene vinylene, polythiophene, polypyrrole, polyparaphenylene, polyacetylene, and triphenyldiamine (TPD). Of these, polyethylenedioxythiophene (PEDOT) and triphenyldiamine (TPD) are preferably used. As PEDOT, polyethylene dioxythiophene / polystyrene sulfonic acid (PEDOT / PSS) is particularly preferable.

  The film thickness of the conductive polymer layer is preferably in the range of 10 nm to 500 nm. This is because if the film thickness is thinner than the above range, the charge may not easily move in the film surface direction of the conductive polymer layer. Further, if the film thickness is thicker than the above range, the volume resistance may increase.

  As a method for forming the conductive polymer layer, a wet coating method is usually used. Specifically, the conductive polymer layer can be formed by applying a conductive polymer layer coating liquid containing a conductive polymer material or the like.

  At this time, a solvent may be added to the conductive polymer layer coating solution for the purpose of improving the film formability. In this case, a conductive polymer layer coating solution is prepared by dispersing the conductive polymer material in a solvent. As the solvent, a water-soluble solvent is preferably used. In general, a water-insoluble solvent is often used for the coating liquid for the photoelectric conversion layer for forming the photoelectric conversion layer, and the photoelectric conversion layer is stably laminated on the conductive polymer layer or photoelectric conversion is performed. This is because, in order to stably laminate the conductive polymer layer on the layer, it is preferable to prepare a coating solution for the conductive polymer layer using a water-soluble solvent. Thereby, when the coating liquid for photoelectric conversion layers is apply | coated on a conductive polymer layer, it can prevent that a conductive polymer material elutes from a conductive polymer layer. Moreover, when the coating liquid for conductive polymer layers is apply | coated on a photoelectric converting layer, it can prevent that a material elutes from a photoelectric converting layer.

  Examples of the water-soluble solvent include water, methanol, ethanol, 1-propanol, 2-propanol, 1-butanol, 2-butanol, t-butanol, ethylene glycol, propylene glycol, acetone, methyl ethyl ketone, acetonitrile, tetrahydrofuran, dioxane and the like. Is mentioned. These water-soluble solvents may be used alone or in combination of two or more.

  The coating method for the conductive polymer layer coating solution is not particularly limited as long as it can be uniformly formed to a predetermined film thickness. For example, a die coating method, a spin coating method, a dip coating method, and the like. Examples thereof include a coating method, a roll coating method, a bead coating method, a spray coating method, a bar coating method, a gravure coating method, an ink jet method, a screen printing method, and an offset printing method.

3. Photoelectric Conversion Layer The photoelectric conversion layer used in the present invention is formed between the mesh electrode and the counter electrode. The “photoelectric conversion layer” refers to a member that contributes to charge separation of the organic thin film solar cell and has a function of transporting generated electrons and holes toward electrodes in opposite directions.

  The photoelectric conversion layer in the present invention may be a single layer having both an electron-accepting function and an electron-donating function (first aspect), or an electron-accepting layer having an electron-accepting function and an electron donating function. It is also possible to laminate an electron donating layer having a functional function (second embodiment). Hereinafter, each aspect will be described.

(1) 1st aspect The 1st aspect of the photoelectric converting layer in this invention is a single layer which has both an electron-accepting function and an electron-donating function, and contains an electron-donating material and an electron-accepting material It is. In this photoelectric conversion layer, since charge separation occurs using a pn junction formed in the photoelectric conversion layer, it functions as a photoelectric conversion layer alone.

The electron donating material is not particularly limited as long as it has a function as an electron donor, but it is preferable that the material can be formed by a wet coating method. A polymer material is preferred.
The conductive polymer is a so-called π-conjugated polymer, which is composed of a π-conjugated system in which double bonds or triple bonds containing carbon-carbon or hetero atoms are alternately linked to single bonds, and exhibits semiconducting properties. It is. In the conductive polymer material, π conjugation is developed in the polymer main chain, so that charge transport in the main chain direction is basically advantageous. In addition, since the electron transfer mechanism of the conductive polymer is mainly hopping conduction between molecules by π stacking, it is advantageous not only for the main chain direction of the polymer but also for the charge transport in the film thickness direction of the photoelectric conversion layer. is there. Furthermore, since the conductive polymer material can be easily formed by a wet coating method using a coating solution in which the conductive polymer material is dissolved or dispersed in a solvent, a large-area organic thin film solar cell Can be manufactured at low cost without requiring expensive equipment.

  Examples of the electron-donating conductive polymer material include polyphenylene, polyphenylene vinylene, polysilane, polythiophene, polycarbazole, polyvinyl carbazole, porphyrin, polyacetylene, polypyrrole, polyaniline, polyfluorene, polyvinyl pyrene, polyvinyl anthracene, and derivatives thereof. And copolymers thereof, or phthalocyanine-containing polymers, carbazole-containing polymers, organometallic polymers, and the like.

Among the above, thiophene-fluorene copolymer, polyalkylthiophene, phenylene ethynylene-phenylene vinylene copolymer, phenylene ethynylene-thiophene copolymer, phenylene ethynylene-fluorene copolymer, fluorene-phenylene vinylene copolymer A thiophene-phenylene vinylene copolymer is preferably used. This is because the energy level difference is appropriate for many electron-accepting materials.
For example, a phenylene ethynylene-phenylene vinylene copolymer (Poly [1,4-phenyleneethynylene-1,4- (2,5-dioctadodecyloxyphenylene) -1,4-phenyleneethene-1,2-diyl-1,4- ( 2,5-dioctadodecyloxyphenylene) ethene-1,2-diyl]) is described in detail in Macromolecules, 35, 3825 (2002) and Micromol. Chem. Phys., 202, 2712 (2001).

  Further, the electron-accepting material is not particularly limited as long as it has a function as an electron acceptor, but it is preferable that the material can be formed by a wet coating method. A conductive polymer material is preferable. This is because the conductive polymer material has the advantages as described above.

Examples of the electron-accepting conductive polymer material include polyphenylene vinylene, polyfluorene, and derivatives thereof, and copolymers thereof, or carbon nanotubes, fullerene derivatives, CN group or CF ₃ group-containing polymers, and the like. -CF ₃ substituted polymer, and the like. Specific examples of the polyphenylene vinylene derivative include CN-PPV (Poly [2-Methoxy-5- (2′-ethylhexyloxy) -1,4- (1-cyanovinylene) phenylene]), MEH-CN-PPV (Poly [2 -Methoxy-5- (2′-ethylhexyloxy) -1,4- (1-cyanovinylene) phenylene]) and the like.

  Further, an electron accepting material doped with an electron donating compound, an electron donating material doped with an electron accepting compound, or the like can also be used. Among these, a conductive polymer material doped with an electron donating compound or an electron accepting compound is preferably used. Conductive polymer materials are basically advantageous in charge transport in the direction of the main chain because of the development of π conjugation in the polymer main chain, and are doped with electron-donating compounds and electron-accepting compounds. This is because electric charges are generated in the π-conjugated main chain, and the electrical conductivity can be greatly increased.

Examples of the electron-accepting conductive polymer material doped with the electron-donating compound include the above-described electron-accepting conductive polymer material. As the electron-donating compound to be doped, for example, a Lewis base such as an alkali metal such as Li, K, Ca, or Cs or an alkaline earth metal can be used. The Lewis base acts as an electron donor.
Examples of the electron-donating conductive polymer material doped with the electron-accepting compound include the above-described electron-donating conductive polymer material. As the electron-accepting compound to be doped, for example, a Lewis acid such as FeCl ₃ (III), AlCl ₃ , AlBr ₃ , AsF ₆ or a halogen compound can be used. In addition, Lewis acid acts as an electron acceptor.

  As the film thickness of the photoelectric conversion layer, the film thickness generally employed in bulk heterojunction organic thin film solar cells can be employed. Specifically, it can be set within a range of 0.2 nm to 3000 nm, and preferably within a range of 1 nm to 600 nm. This is because when the film thickness is thicker than the above range, the volume resistance in the photoelectric conversion layer may increase. On the other hand, if the film thickness is thinner than the above range, light may not be sufficiently absorbed.

  The mixing ratio of the electron-donating material and the electron-accepting material is appropriately adjusted to an optimal mixing ratio depending on the type of material used.

  The method for forming the photoelectric conversion layer is not particularly limited as long as it can be uniformly formed in a predetermined film thickness, but a wet coating method is preferably used. This is because if the wet coating method is used, the photoelectric conversion layer can be formed in the air, and the cost can be reduced and the area can be easily increased.

  The method for applying the photoelectric conversion layer coating solution is not particularly limited as long as it can uniformly apply the photoelectric conversion layer coating solution. For example, a die coating method, a spin coating method, a dip coating method, and the like. Examples thereof include a coating method, a roll coating method, a bead coating method, a spray coating method, a bar coating method, a gravure coating method, an ink jet method, a screen printing method, and an offset printing method. Of these, spin coating or die coating can be preferably used. This is because these methods make it easy to accurately form the photoelectric conversion layer so as to have a predetermined film thickness.

After application of the coating liquid for photoelectric conversion layer, a drying treatment for drying the formed coating film may be performed. It is because productivity can be improved by removing the solvent etc. which are contained in the coating liquid for photoelectric conversion layers at an early stage.
As a method for the drying treatment, for example, a general method such as heat drying, air drying, or vacuum drying can be used.

(2) Second Aspect In the second aspect of the photoelectric conversion layer in the present invention, an electron accepting layer having an electron accepting function and an electron donating layer having an electron donating function are laminated. Hereinafter, the electron-accepting layer and the electron-donating layer will be described.

(Electron-accepting layer)
The electron accepting layer used in the present invention has an electron accepting function and contains an electron accepting material.

  The electron-accepting material is not particularly limited as long as it has a function as an electron acceptor, but is preferably a material that can be formed into a film by a wet coating method. A polymer material is preferred. This is because the conductive polymer material has the advantages as described above. Specific examples include the same electron-accepting conductive polymer materials used for the photoelectric conversion layer of the first aspect.

  As the film thickness of the electron-accepting layer, a film thickness generally employed in a bilayer type organic thin film solar cell can be employed. Specifically, it can be set within a range of 0.1 nm to 1500 nm, and preferably within a range of 1 nm to 300 nm. This is because if the film thickness is larger than the above range, the volume resistance in the electron-accepting layer may be increased. On the other hand, if the film thickness is thinner than the above range, light may not be sufficiently absorbed.

  The method for forming the electron-accepting layer can be the same as the method for forming the photoelectric conversion layer of the first aspect.

(Electron donating layer)
The electron donating layer used in the present invention has an electron donating function and contains an electron donating material.

  The electron donating material is not particularly limited as long as it has a function as an electron donor, but it is preferable that the material can be formed by a wet coating method. A polymer material is preferred. This is because the conductive polymer material has the advantages as described above. Specific examples include the same electron donating conductive polymer materials used for the photoelectric conversion layer of the first aspect.

  As a film thickness of the electron donating layer, a film thickness generally employed in a bilayer type organic thin film solar cell can be employed. Specifically, it can be set within a range of 0.1 nm to 1500 nm, and preferably within a range of 1 nm to 300 nm. This is because if the film thickness is larger than the above range, the volume resistance in the electron donating layer may be increased. On the other hand, if the film thickness is thinner than the above range, light may not be sufficiently absorbed.

  The method for forming the electron donating layer can be the same as the method for forming the photoelectric conversion layer of the first aspect.

4). Counter electrode The counter electrode used in the present invention is an electrode facing the mesh electrode, and is an electrode (electron extraction electrode) for extracting electrons generated in the photoelectric conversion layer. In the present invention, since the light is transmitted from the opening of the mesh electrode, the counter electrode may not be transparent.

  The material for forming the counter electrode is not particularly limited as long as it has conductivity. However, since the counter electrode is an electron extraction electrode, it preferably has a low work function. Specific examples of the material having a low work function include Li, In, Al, Ca, Mg, Sm, Tb, Yb, Zr, and LiF.

The counter electrode may be a single layer or may be stacked using materials having different work functions.
The film thickness of the counter electrode is in the range of 0.1 nm to 500 nm, especially 1 nm to 300 nm when the thickness of the counter electrode is a single layer. It is preferable to be within the range. If the film thickness is smaller than the above range, the sheet resistance of the counter electrode may be too large, and the generated charge may not be sufficiently transmitted to the external circuit. This is because the transmittance is lowered and the photoelectric conversion efficiency may be lowered.

  Moreover, the said counter electrode may be formed in the whole surface on the photoelectric converting layer, and may be formed in pattern shape.

As a method for forming the counter electrode, a general electrode forming method can be used, for example, a PVD method such as a vacuum deposition method, a sputtering method, or an ion plating method, or a dry coating method such as a CVD method. it can. Moreover, the wet coating method apply | coated using the metal paste etc. containing metal colloids, such as Ag, can also be used.
Further, the method for patterning the counter electrode is not particularly limited as long as it can be accurately formed into a desired pattern, and examples thereof include a photolithography method.

5). Substrate In the present invention, the mesh electrode 2 and the conductive polymer layer 3 may be formed on the substrate 1 as illustrated in FIGS. 1 to 4, and face each other as illustrated in FIGS. 5 to 7. The electrode 5 may be formed on the substrate 1.

  The substrate used in the present invention may be transparent or opaque, but when the mesh electrode and the conductive polymer layer are formed on the substrate, the substrate side is the light receiving surface. Therefore, a transparent substrate is preferable. The transparent substrate is not particularly limited, and for example, a non-flexible transparent rigid material such as quartz glass, Pyrex (registered trademark), synthetic quartz plate, or a transparent resin film, an optical resin plate, etc. The transparent flexible material which has flexibility can be mentioned.

  In the present invention, among the above, the substrate is preferably a flexible material such as a transparent resin film. Transparent resin films are excellent in processability, and are useful in the realization of organic thin-film solar cells that reduce manufacturing costs, reduce weight, and are difficult to break, and expand the applicability to various applications such as application to curved surfaces. is there.

6). Electron Extraction Layer In the present invention, an electron extraction layer may be formed between the photoelectric conversion layer and the counter electrode. The electron extraction layer is a layer provided so that electrons can be easily extracted from the photoelectric conversion layer to the counter electrode (electron extraction electrode). Thereby, since the electron extraction efficiency from the photoelectric conversion layer to the electron extraction electrode is increased, the photoelectric conversion efficiency can be improved.

  The material used for such an electron extraction layer is not particularly limited as long as it is a material that stabilizes the extraction of electrons from the photoelectric conversion layer to the electron extraction electrode. Specifically, doped polyaniline, polyphenylene vinylene, polythiophene, polypyrrole, polyparaphenylene, polyacetylene, conductive organic compounds such as triphenyldiamine (TPD), or electron donation such as tetrathiofulvalene, tetramethylphenylenediamine, etc. An organic material that forms a charge transfer complex composed of an organic compound and an electron-accepting compound such as tetracyanoquinodimethane and tetracyanoethylene. Moreover, the metal dope layer with an alkali metal or alkaline-earth metal is mentioned. Suitable materials include bathocuproin (BCP) or bathophenantrone (Bphen) and metal doped layers such as Li, Cs, Ba, Sr.

7). Other constituent members The organic thin-film solar cell of the present invention may have constituent members to be described later as needed in addition to the constituent members described above. For example, the organic thin film solar cell of the present invention includes a protective sheet, a filler layer, a barrier layer, a protective hard coat layer, a strength support layer, an antifouling layer, a high light reflection layer, a light containment layer, an ultraviolet / infrared shielding layer, a sealing You may have functional layers, such as a material layer. In addition, an adhesive layer may be formed between the functional layers depending on the layer configuration.
These functional layers can be the same as those described in JP 2007-73717 A.

  The present invention is not limited to the above embodiment. The above-described embodiment is an exemplification, and the present invention has any configuration that has substantially the same configuration as the technical idea described in the claims of the present invention and that exhibits the same effects. Are included in the technical scope.

Hereinafter, the present invention will be specifically described with reference to examples.
[Example 1]
A mesh-like Ag thin film (mesh electrode) was formed on the surface of a PEN film substrate having a thickness of 125 μm by a vacuum deposition method using a patterning mask. The mesh electrode had a line width of 500 μm, a line interval of 2500 μm, and a thickness of 0.1 μm.

  Next, a highly conductive conductive polymer paste (poly- (3,4-ethylenedioxythiophene) dispersion, manufactured by Nagase Sangyo Co., Ltd., Denatron series) was applied onto the substrate by a spin coating method. Thereafter, the film was dried at 100 ° C. for 30 minutes to form a conductive polymer layer (film thickness 100 nm).

Next, polythiophene (P3HT; poly-3-hexylthiophene-2,5-diyl (resiregular)) and fullerene derivative (PCBM; 1- (3-methoxycarbonyl) propyl-1-phenyl (6,6) -C ₆₀ ) Was dissolved in chlorobenzene so that the polythiophene concentration was 1.0 wt% and the fullerene concentration was 0.4 wt% to prepare a coating solution for a photoelectric conversion layer. Next, this photoelectric conversion layer coating solution was applied on the conductive polymer layer by a spin coating method at a rotation speed of 700 rpm. Then, it was dried at 110 ° C. for 10 minutes to form a photoelectric conversion layer.

Next, a Ca thin film (film thickness: 30 nm) and an Al thin film (film thickness: 80 nm) were sequentially formed on the photoelectric conversion layer by a vapor deposition method to form a metal electrode.
Finally, it was sealed from above the metal electrode with a sealing glass material and an adhesive sealing material to obtain an organic thin film solar cell.

Regarding the solar cell characteristics, A. M1.5, simulated sunlight (100mW / cm ² ) was used as an irradiation light source, and current-voltage characteristics were evaluated by applying voltage with a source measure unit (HP, HP4100). Obtained.

[Example 2]
An Ag thin film was formed on the surface of a 125 μm thick PEN film substrate by vacuum deposition. Next, the Ag thin film was patterned by etching using a photolithography method to form a mesh electrode. The mesh electrode had a line width of 10 μm, a line interval of 100 μm, and a thickness of 0.1 μm.
Then, it carried out similarly to Example 1, and produced the organic thin film solar cell.

Regarding the solar cell characteristics, A. M1.5, simulated sunlight (100mW / cm ² ) was used as an irradiation light source, and current-voltage characteristics were evaluated by applying voltage with a source measure unit (HP, HP4100). Obtained.

DESCRIPTION OF SYMBOLS 1 ... Substrate 2 ... Mesh electrode 3 ... Conductive polymer layer 4 ... Photoelectric conversion layer 5 ... Counter electrode 10 ... Organic thin film solar cell

Claims (3)

  A substrate, a mesh electrode arranged to be embedded in a groove formed in the substrate, a conductive polymer layer formed at least in an opening of the mesh electrode and capable of transporting holes, and the conductive high layer An organic thin film solar cell comprising a photoelectric conversion layer formed on a molecular layer and a counter electrode formed on the photoelectric conversion layer.   The organic thin-film solar cell according to claim 1, wherein the mesh electrode contains Ag.   The organic thin-film solar cell according to claim 1 or 2, wherein the conductive polymer layer contains polyethylene dioxythiophene / polystyrene sulfonic acid (PEDOT / PSS).

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