JP5561722B2 - Manufacturing method of organic thin film solar cell and transfer sheet used therefor - Google Patents

Description

  The present invention is an invention that can be applied to improve the conversion efficiency of organic thin-film solar cells.

  Conventionally, organic thin-film solar cells are known to have a low photoelectric conversion efficiency due to a lack of a bonding area in a two-dimensional planar bonding. Therefore, as an invention for improving the conversion efficiency of an organic thin film solar cell, a layer structure in which a bulk heterojunction is formed by phase separation of a mixture of a donor and an acceptor as in Non-Patent Document 1 and Non-Patent Document 2, Attempts have been made to increase the photogenerated charge of organic thin-film solar cells by increasing the acceptor interface.

C.J.Brabec et al., Advanced Functional Materials, Vol. 11, p. 15. J.Xue, S.Uchida, B.P.Land, S.R.Forrest, Appl.Phys.Lett., 85, p.5757 (2004)

  However, even if a layer structure in which a bulk heterojunction is formed in the film by phase separation of a mixture of a donor and an acceptor as described above and a large number of photogenerated charges are generated, the photogenerated charges are not lost. Since the distance that can be moved is at most about 100 nm, when the thickness of the film of the mixture of the donor and the acceptor exceeds 100 nm, the photogenerated charge tends to disappear before reaching the electrode. Therefore, when the thickness is increased to 100 nm or more, the conversion efficiency is lowered, and there is a problem that the conversion efficiency cannot be improved by increasing the thickness of the donor-acceptor mixture film.

The present invention forms a layer in which a bulk heterojunction is formed by a donor and an acceptor on a substrate sheet having releasability, and a nanoscale width penetrating the layer in which the bulk heterojunction is formed by nanoimprint processing After forming a fine groove or a nanoscale sized island-shaped depression and forming an electrode in the fine groove or depression of the island-like structure, each layer is transferred to a substrate of a solar cell for release properties. And a donor layer, an acceptor layer, or a mixture layer of a donor and an acceptor is formed on the outermost surface after transfer .

  In addition, the organic thin film solar cell manufacturing method of the present invention forms a bulk heterojunction layer formed by donor and acceptor on a substrate sheet having releasability, and forms the bulk heterojunction by nanoimprinting. After forming a nanoscale-width fine groove or a nanoscale-sized island-like recess that penetrates the formed layer, and forming an electrode in the fine groove or island-like recess, the respective layers are formed on the solar cell. The substrate sheet having a releasing property is transferred to a substrate, and either a donor layer, an acceptor layer or a mixture layer of a donor and an acceptor is formed on the outermost surface after transfer. Therefore, even if the nanoimprint process is not elaborately controlled, the distance between the electrodes can be formed without being short-circuited at 100 nm or less, so that an organic thin-film solar cell with high conversion efficiency can be manufactured with high productivity.

BRIEF DESCRIPTION OF THE DRAWINGS It is a schematic cross section which shows one Example of the manufacturing method of the organic thin-film solar cell of this invention, (a) is a bulk heterojunction by a donor and an acceptor formed by nanoimprinting using an imprint type | mold. A step of forming a fine groove having a nanoscale width in the layer is shown, and (b) shows a step of forming an electrode in the fine groove. (A) is a schematic cross section which shows the organic thin-film solar cell formed by one Example of the manufacturing method of the organic thin-film solar cell of this invention, (b) is sunlight injecting it diagonally to a groove | channel It is a schematic cross section which shows a mode that it reflects with the formed electrode and is confine | sealed in a film | membrane, (c) is a schematic cross section which shows a mode that the electric charge which generate | occur | produced with sunlight moves through the electrode formed in the groove | channel. is there. BRIEF DESCRIPTION OF THE DRAWINGS It is a schematic cross section which shows one Example of the manufacturing method of the organic thin-film solar cell of this invention, (a) shows the layer by which the bulk heterojunction by the donor and the acceptor was formed on the base sheet which has mold release property. (B) shows a step of nanoimprinting the layer in which the bulk heterojunction is formed, and (c) shows a nanoscale width penetrating the layer in which the bulk heterojunction is formed. (D) shows the step of forming an electrode in the fine groove or the concave portion of the island-like structure, and (e) shows the step of forming each layer on the substrate of the solar cell. (F) shows the step of forming a donor layer, an acceptor layer or a donor-acceptor mixture layer, and the other electrode on the outermost surface after transfer. . BRIEF DESCRIPTION OF THE DRAWINGS It is a schematic cross section which shows one Example of the manufacturing method of the imprint type | mold base material used for the manufacturing method of the organic thin-film solar cell of this invention, (a) is ionizing radiation possible on the base material of an imprint type | mold base material. (B) shows a step of forming an island-shaped metal film on the ionizing radiation solubilized layer, and (c) shows ionizing radiation using the metal film as a mask. And (d) shows a step of solubilizing a part of the ionizing radiation solubilized layer by irradiating and removing a part of the solubilized ionizing radiation solubilized layer. The process which formed the recessed part is shown.

  The organic thin film solar cell 5 formed by the method of manufacturing an organic thin film solar cell of the present invention has a surface of the layer 7 on which a bulk heterojunction formed by a donor and an acceptor is formed by nanoimprinting using an imprint mold 30 A large number of island-like structures 9 and nanoscale-width fine grooves 1 surrounding them are formed (see FIG. 1A), and an electrode 21 is formed in the fine grooves 1 (FIG. 1). (See (b)). A counter electrode 20 is formed on the surface opposite to the electrode 21 (see FIG. 1). When the electrode 20 is a transparent electrode and the electrode 21 is an electrode such as a metal that reflects light, when light 51 such as sunlight enters the organic thin film solar cell 5 from an oblique direction, the light 51 enters the groove. Reflected by the formed electrode 21 and confined in the film (see FIGS. 2A and 2B). As a result, more photogenerated charges 2 can be generated in the vicinity of the electrode 21, so that a large amount of the photogenerated charges 2 can be moved through the electrode 21 without being lost, and a high electromotive force can be obtained. There is also an effect (see FIG. 2C).

  Examples of the donor material include cross-linked polythiophene, poly-3-hexylthiophene (P3HT), and phthalocyanine derivatives. Examples of the acceptor material include fullerene derivatives such as PCBM and PCPDTBT, and zinc oxide. Not. However, it is necessary that the donor and the acceptor be phase-separated to form a bulk heterojunction structure.

  Examples of the method for forming the layer 7 in which the bulk heterojunction is formed include various coating methods such as spin coating, various printing methods such as gravure printing, and the like, which are formed on the substrate 14 on which the electrode 20 is formed. . The thickness can be in the range of about 100 to 700 nm, and is preferably about 300 to 500 nm. In a conventional organic thin-film solar cell with a flat electrode, when the thickness is 100 nm or more, the photogenerated charge 2 disappears before reaching the electrode 21 and the conversion efficiency is greatly reduced. The photogenerated charges 2 can easily reach the electrode 21 even if the thickness is somewhat increased. Therefore, the thicker the thickness, the larger the interface where the photogenerated charges 2 are generated, and the conversion efficiency is improved. However, when the thickness exceeds 500 nm, the disappearance of the photogenerated charges 2 that move to the electrode 20 side increases.

  The method of forming the fine grooves 1 having a nanoscale width and a large number of island structures 9 surrounded by the fine grooves 1 is obtained by reversing the shapes of the desired fine grooves 1 and the large number of island structures 9. Is formed by the so-called room temperature nanoimprint method or thermal nanoimprint method in which the imprint mold 30 is set on the layer 7 on which the bulk heterojunction is formed and pressed at a constant pressure while applying room temperature or heat. To do. Alternatively, if the layer 7 on which the bulk heterojunction is formed can be made into an ultraviolet curable type, it is formed by a so-called UV nanoimprint method in which the layer 7 is cured by being irradiated with ultraviolet rays and pressed to a predetermined shape. May be.

The fine grooves 1 have a width of about 1 to 500 nm, and the average area per layer 7 in which bulk heterojunctions of a large number of island-like structures 9 surrounded by the fine grooves 1 are formed is 10 to 10,000 nm. It is preferably on the order of ^2, the average total area and fine total cross-sectional area and the same degree of grooves 1 of islands 9 among them, i.e. the width of the fine groove layer 1 100 to 300 nm, the island structure 9 Most preferably, the area is 100 to 6500 nm ² .

In order to make the width of the fine groove 1 less than 1 nm, it is necessary to make the width of the convex portion 38 of the imprint mold 30 less than 1 nm, which causes a problem that the strength and durability of the imprint mold 30 are insufficient. If the width of 1 is to be made larger than 500 nm, the ratio of the layer 7 in which the bulk heterojunction is formed is reduced, and the interface where the photogenerated charges are generated is reduced, so that the conversion efficiency is lowered. Further, it is necessary to the size of the convex portion of the island-like structure of the imprint mold base material 31 to be described below to the average area per one of the island structure 9 below 10 nm ² to less than 10 nm ² imprint type There arises a problem that the strength and resistance of the base material 31 are insufficient, and when it exceeds 10,000 nm ² , the rate at which photogenerated charges disappear before reaching the electrode 21 increases.

  As a method for producing an imprint base material 31 having a shape obtained by inverting the shapes of desired fine grooves 1 and a large number of island-like structures 9, first, an imprint base material 32 is prepared. An ionizing radiation solubilized layer 35 is formed on the base material 32 of the printing mold base material (see FIG. 4A), and a number of island-shaped metal films 3 are formed on the ionizing radiation solubilized layer 35. (See FIG. 4B), the ionizing radiation 33 is irradiated with the metal film 3 as a mask to solubilize a part of the ionizing radiation solubilized layer 35 (see FIG. 4C) and solubilized. A method of forming a concave portion 37 of a groove having a nanoscale width by peeling and removing a part of the ionizing radiation solubilized layer 35 (see FIG. 4D) can be mentioned. The imprint mold 30 having the convex portions 38 obtained by inverting the shape of the imprint mold base material 31 is obtained by a method such as nickel electroforming with respect to the obtained imprint mold base material 31.

  Alternatively, an ionizing radiation cured layer is formed instead of the ionizing radiation solubilized layer 35, and the ionizing radiation cured layer is cured by irradiating the ionizing radiation 33, and the uncured ionizing radiation cured layer other than the cured portion is cured. The method of forming the recessed part of an island-like structure of nanoscale size by peeling and removing is mentioned. In this case, a method such as nickel electroforming may be repeated twice, or the imprint mold base material 31 itself may be used as it is as the imprint mold 30.

  Alternatively, a method of forming a recess of a nanoscale width groove by forming a layer to be etched instead of the ionizing radiation solubilizing layer 35 and performing anisotropic etching described later using a metal film having an island-like structure as a mask Etc. If the base material 32 of the imprint base material itself has ionizing radiation solubilization, ionizing radiation curing or etching characteristics, the ionizing radiation solubilization layer 35 and the like are omitted, and The metal film 3 having an island structure may be directly formed on the base material 32 and processed.

  The island-shaped metal film 3 includes a layer made of tin, indium, bismuth, lead, and alloys thereof, and may be formed by a vacuum deposition method, a sputtering method, an ion plating method, or the like. The thickness is preferably about 3 to 80 nm, and when the light transmittance is measured, the thickness is preferably about 4% to 15%. The island-shaped metal film 3 is formed with the above metal material and an appropriate forming means with the value indicating the light transmittance, and the island-shaped metal film 3 is used as a mask to ionize radiation-solubilizing layer and ionizing radiation. If the hardened layer, the layer to be etched, etc. are patterned, the above-described fine groove recesses having a nanoscale width or nanoscale island-shaped recesses are formed. The island-shaped metal film 3 having the function of a mask may be left as it is after peeling or etching, or may be set to disappear by peeling or etching.

  Examples of the ionizing radiation solubilizing layer 35 include acrylic, pyrimidine, and novolak resists. Examples of the method for forming the ionizing radiation solubilizing layer 35 include general-purpose printing methods such as gravure printing, dipping, coater, and coating. The thickness is preferably about 0.02 to 2 μm. For the peeling of the ionizing radiation solubilized layer 35, an organic solvent such as toluene is used.

  Examples of the ionizing radiation-cured layer include resists such as calixarene. The formation method and thickness of the ionizing radiation cured layer may be the same method as the ionizing radiation solubilized layer 35. For removing the uncured ionizing radiation-cured layer, an organic solvent such as toluene can be used. Examples of ionizing radiation include visible light, ultraviolet light, infrared light, electron beam, X-ray, and gamma ray.

  Examples of the layer to be etched include acrylic, vinyl, polyester, polyamide, and urethane polymers. The formation method and thickness of the layer to be etched may be the same as that of the ionizing radiation solubilized layer 35. Etching may be performed by any method that allows the etched layer to be etched more easily than the metal film 3 having an island-like structure, and an anisotropic etching method is particularly preferable.

  Anisotropic etching is etching having a property that etching is suppressed with respect to the orientation in the film surface direction, and this makes it possible to dig a fine groove 1 that is thin and deep (high aspect ratio). is there. Specifically, a dry etching method using plasma of oxygen, argon, fluorine gas or the like can be used.

  The method of forming the electrode 21 in the fine groove 1 and the method of forming the electrode 20 include not only forming the metal material by a method such as vapor deposition, sputtering, and plating, but also ink containing the metal material and their nanowires. And the like by various coating methods such as spin coating and various printing methods such as gravure printing. It is best to form the electrode 21 so as to completely fill the fine groove 1, and a part of the electrode 21 may be covered up to many island-like structures 9.

  The electrode 20 and the electrode 21 are made of indium tin oxide, zinc oxide, or a transparent conductive film containing silver nanowires or carbon nanotubes on the side on which sunlight is incident. These electrodes may be formed of a material such as aluminum, gold, silver, or copper. Further, between the electrode 20 and the donor, poly 3,4-ethylenedioxythiophene (PEDOT / PSS) using polystyrene sulfonic acid as a dopant, and between the electrode 21 and the acceptor layer 8 such as titanium oxide A buffer layer may be provided, and the conversion efficiency is further improved by adding these layers.

  The fine groove 1 may completely penetrate the layer 7 in which the bulk heterojunction is formed, or may be up to the middle of the layer. However, if it is attempted to penetrate completely with the above-described configuration, the convex portion 38 of the imprint mold 30 is inserted not only into the layer 7 where the bulk heterojunction is formed but also to a part of the electrode 20 during the nanoimprint processing. There is a problem that the electrode 20 is damaged. Therefore, when forming the fine groove | channel 1 completely penetrating the layer 7 in which the bulk heterojunction was formed, the layer 7 in which the bulk heterojunction was formed was formed on the base sheet 12 having releasability. (See FIG. 3A), nanoimprinting the layer 7 in which the bulk heterojunction is formed (see FIG. 3B), and the nanoscale width penetrating the layer 7 in which the bulk heterojunction is formed Are formed (see FIG. 3C), electrodes 21 are formed in the fine grooves or the recesses of the island structure (see FIG. 3D), and the layers are formed on the substrate 14 of the solar cell. After releasing the substrate sheet 12 having releasability (see FIG. 3E), a donor layer, an acceptor layer, or a mixture layer of a donor and an acceptor (a bulk heterojunction is formed on the outermost surface after the transfer. 50 may or may not be formed) Moreover from the electrode 20 is formed (see FIG. 3 (f)) is preferably formed by the method.

  In this method, even if the convex portion 38 of the imprint mold 30 is inserted not only into the layer 7 in which the bulk heterojunction is formed but also to a part of the base sheet 12 having releasability, the electrode 20 is formed at that time. In addition, since the electrode 20 is formed after the transfer, the problem that the electrode 20 is damaged does not occur. The structure thus obtained is close to an ideal upright superlattice structure and can exhibit high conversion efficiency. Examples of the base sheet 12 having releasability include a polyester film coated with a fluoroacrylic resin having releasability and thermoformability, and a fluoroacrylic coextruded film.

  A polyethylene terephthalate film having a thickness of 25 μm is prepared as a base material for an imprint base material, and an ionizing radiation solubilized layer mainly composed of a 2,4-dichloropyrimidine derivative is gravured on the base material for the imprint base material. A number of island-like metal films having a thickness of 8 nm made of tin were formed on the ionizing radiation-solubilized layer by a vacuum evaporation method on the ionizing radiation solubilized layer. Next, an electron beam was irradiated using the metal film as a mask to solubilize a part of the ionizing radiation solubilized layer, and the solubilized portion was peeled and removed with an organic solvent containing toluene as a main component.

The imprint base material thus obtained was formed with concave portions having fine grooves with a width of about 100 nm, and the convex portions had a large number of island structures with an average area of about 400 nm ^2. the copper was vacuum-deposited on the entire surface against the timber, followed by nickel electroforming, the recess and the width 100nm approximately surrounding the said imprint basic material a number of islands average area of about 400 nm ² of the shape obtained by inverting the Thus, a sheet-like imprint mold having a convex portion with a height of about 150 nm was obtained.

  On the other hand, a polyethylene terephthalate film having a thickness of about 100 μm obtained by gravure printing on the surface with a fluoroacrylic resin having a thickness of about 1 μm is used as a substrate sheet having releasability, and poly-3-hexylthiophene (P3HT) is used as a donor layer on the printed surface. ) A mixture containing fullerene 60 as an acceptor layer was formed with a coater to a thickness of 200 nm. The formed layer had a bulk heterostructure. Next, the sheet-like imprint mold was placed on the layer where the bulk heterojunction was formed, and pressed at a pressure of 2 atm while being heated to 80 ° C., and the sheet-like imprint mold was laminated. After leaving to cool, the sheet-like imprint mold was peeled off, and a large number of fine grooves with a width of about 100 nm reaching the fluoroacrylic resin layer through the layer in which the bulk heterojunction was formed. .

  Next, a gold film is formed as an electrode in the formed many fine grooves by a vacuum deposition method, and a vinyl chloride adhesive layer is formed on the entire surface by gravure printing, placed on an acrylic plate, and heated. And the pressure was applied to transfer each layer into an acrylic plate.

  Next, the substrate sheet having releasability is peeled and removed, an aqueous dispersion of PEDOT / PSS is formed on the exposed outermost surface with a coater, and after drying, an indium tin oxide film is sputtered thereon as a transparent electrode With a thickness of 200 nm, an organic thin film solar cell was obtained. The cross section of this organic thin-film solar cell is an almost super-ideal nanostructure with an upright superlattice structure in which the donor layer and the acceptor layer completely penetrate both electrodes, and the conventional non-uniform bulk heterojunction junction structure Unlikely, the conversion efficiency was also greatly improved. In addition, this structure was almost maintained even in a large area.

  A polyethylene terephthalate film having a thickness of 25 μm is prepared as a base material for an imprint base material, and an ionizing radiation cured layer mainly composed of chloromethylated calixarene is formed on the base material of the imprint base material by a gravure printing method. A plurality of island-shaped metal films made of indium and having a thickness of 3 nm were formed on the ionizing radiation-cured layer using a vacuum deposition method. Next, an electron beam was irradiated using the metal film as a mask to cure a part of the ionizing radiation-cured layer, and an ineffective portion was peeled and removed with an organic solvent containing toluene as a main component.

The imprint base material thus obtained was formed with concave portions having fine grooves with a width of about 300 nm, and the convex portions had a large number of island structures with an average area of about 200 nm ^2. the copper was vacuum-deposited on the entire surface against the timber, followed by nickel electroforming, the recess and the width 300nm approximately surrounding the said imprint basic material a number of islands average area of about 200 nm ² of the shape obtained by inverting the Thus, a sheet-like imprint mold having a convex portion with a height of about 170 nm was obtained.

  On the other hand, a fluoroacrylic film having a thickness of 100 μm is used as a base sheet having releasability, and poly (hexylthiophene) (P3HT) is used as a donor on its surface, and C60 phenylbutyric acid methyl ester (PC60BM) is used as an acceptor. The coating solution contained at a weight ratio was formed with a coater to a thickness of 500 nm. The formed layer had a bulk heterostructure. Next, the sheet-like imprint mold was placed on the layer where the bulk heterojunction was formed, and pressed at a pressure of 5 atm while being heated to 50 ° C., thereby laminating the sheet-like imprint mold. When the sheet-like imprint mold was peeled off after being allowed to cool, a large number of fine grooves having a width of about 300 nm reaching the fluoroacrylic film through the acceptor layer were formed.

  Next, a transparent conductive ink containing silver nanowires as a transparent electrode is formed in a fine groove of the layer in which the bulk heterojunction is formed with a thickness of 500 nm by gravure printing, and a vinyl chloride adhesive layer is formed thereon. It was formed on the entire surface by printing, placed on an acrylic plate, and heat and pressure were applied to transfer each layer into an acrylic plate. Subsequently, the base sheet having releasability is peeled and removed, and the base sheet having releasability is peeled and removed on the exposed outermost surface, and poly-3hexylthiophene (P3HT) and C70 phenylbutyrate methyl are exposed on the exposed outermost surface. A mixture of ester (PC70BM) at a weight ratio of 1: 1 was formed by vacuum deposition with a thickness of 30 nm.

  Next, a film made of titanium oxide as a buffer layer was formed thereon with a thickness of 500 nm by a sputtering method, and an aluminum film was formed thereon as an electrode with a thickness of 800 nm by a vacuum evaporation method to obtain an organic thin film solar cell. . The cross section of this organic thin-film solar cell has an almost super-ideal nanostructure with an upright superlattice structure in which the bulk heterojunction layer completely penetrates both electrodes, and the conventional heterogeneous bulk heterojunction junction structure. Unlikely, the conversion efficiency was also greatly improved. In addition, this structure was almost maintained even in a large area.

  A 25 μm-thick polyethylene terephthalate film is prepared as a base material for an imprint base material, and an etching target layer mainly composed of a vinyl chloride vinyl acetate copolymer resin is formed on the base material for the imprint base material. A plurality of island-shaped metal films made of tin and having a thickness of 5 nm were formed on the layer to be etched using a vacuum deposition method. Next, reactive etching using argon plasma was performed using the metal film as a mask.

The imprint base material thus obtained was formed with concave portions of fine grooves having a width of about 300 nm, and the convex portions had a number of island structures with an average area of about 6500 nm ^2. Copper is vacuum-deposited on the entire surface of the material, then nickel electroforming is used to invert the shape of the imprint base material, and the average area is about 6500 nm ^{2 and} a large number of island-shaped recesses and the width surrounding it is about 300 nm. Thus, a sheet-like imprint mold having a convex portion having a height of about 80 nm was obtained.

  On the other hand, on the acrylic plate, an aluminum film is formed as an electrode on the surface with a thickness of 800 nm by a vacuum deposition method, and then a film made of titanium oxide is formed thereon with a thickness of 500 nm by a sputtering method as a buffer layer. A coating film of a mixture containing zinc-doped phthalocyanine as a donor layer and C70 phenylbutyric acid methyl ester (PC70BM) as an acceptor layer was formed with a coater to a thickness of 120 nm. The formed layer had a bulk heterostructure. Next, the sheet-like imprint mold was placed on the layer where the bulk heterojunction was formed, and pressed at a pressure of 3 atm while being heated to 60 ° C., thereby laminating the sheet-like imprint mold. When the sheet-like imprint mold was peeled off after standing cooling, many fine grooves having a depth of about 60 nm and a width of about 300 nm were formed in the layer in which the bulk heterojunction was formed.

  Next, a transparent conductive ink containing silver nanowires as electrodes was formed in the formed numerous fine grooves by a gravure printing method to obtain an organic thin film solar cell. Unlike the conventional flat electrode structure, this organic thin-film solar cell has a structure in which a transparent conductive ink electrode containing silver nanowires is embedded deep into the layer where the bulk heterojunction is formed, and the conversion efficiency is also high. It was much improved. In addition, this structure was almost maintained even in a large area.

DESCRIPTION OF SYMBOLS 1 Fine groove | channel 2 Photogenerated electric charge 3 Metal film 5 Organic thin film solar cell 7 Layer in which the bulk heterojunction was formed 9 Many island-like structures 12 Base sheet | seat which has releasability 14 Base material 20 of a solar cell 20, 21 Electrode 30 imprint mold 31 imprint mold base material 32 base material of imprint mold base material 33 ionizing radiation 35 ionizing radiation solubilized layer 37 concave portion of nanoscale width groove 38 imprint type convex portion 51 light

Claims (2)

  A layer having a bulk heterojunction formed by a donor and an acceptor is formed on a substrate sheet having releasability, and a nano-scale fine groove penetrating the layer having the bulk heterojunction formed by nanoimprint processing. Alternatively, a nanoscale sized island-shaped recess is formed, and an electrode is formed in the fine groove or the island-shaped recess, and then the respective layers are transferred to a solar cell substrate to provide a release sheet. A method for producing an organic thin-film solar cell, comprising peeling and forming either a donor layer, an acceptor layer, or a mixture layer of a donor and an acceptor on the outermost surface after transfer. A layer having a bulk heterojunction formed by a donor and an acceptor is formed on a substrate sheet having releasability, and a nano-scale fine groove penetrating the layer in which the bulk heterojunction is formed by nanoimprint processing Alternatively, a transfer sheet in which a recess having an island-like structure of nanoscale size is formed, and an electrode is formed in the minute groove or the recess having an island-like structure.

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