JP2013207162A - Organic photoelectric conversion element - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an organic photoelectric conversion element which is capable of effectively utilizing incident light and thus has excellent energy conversion efficiency.SOLUTION: The organic photoelectric conversion element, in which a transparent substrate, a transparent electrode layer, a photoelectric conversion layer, and a metal electrode layer are laminated in this order, includes a structure layer provided in contact with one surface of the organic photoelectric conversion element and having an uneven structure. The uneven structure has a plurality of recesses including slopes, and flat portions positioned around the recesses.

Description

  The present invention relates to an organic photoelectric conversion element used as a solar cell, for example.

Solar cells that use sunlight as an energy source to replace fossil fuels are attracting attention. The mainstream of solar cells currently in practical use is to use polycrystalline or amorphous silicon. However, such solar cells have a high manufacturing cost and have been an obstacle to their spread. On the other hand, organic photovoltaic elements such as dye-sensitized solar cells and organic thin-film solar cells are attracting attention as solar cells that can be manufactured at a relatively low cost and can have a large area. A dye-sensitized solar cell as an example of an organic photoelectric conversion element has a structure in which a metal electrode substrate and a transparent electrode substrate face each other with a dye-sensitized semiconductor porous layer and an electrolyte layer sandwiched therebetween, The peripheral part of the electrode substrate and the transparent electrode substrate has a structure sealed with a sealing material so that the electrolyte layer does not leak (Patent Document 1).
However, organic photoelectric conversion elements such as dye-sensitized solar cells have a problem that light absorption is small and incident light cannot be used effectively because the photoelectric conversion layer is very thin. Therefore, a structure is known in which a re-reflection layer is provided on a light incident surface of a solar cell in order to effectively use incident light (Patent Document 2). The re-reflection layer has the function of re-reflecting the light reflected by the metal electrode layer of the dye-sensitized solar cell, and is expected to improve the photoelectric efficiency of the dye-sensitized solar cell. There is a need to.

Japanese Patent No. 2664194 JP 2007-317565 A

  An object of this invention is to provide the organic photoelectric conversion element which can use the incident light effectively and was excellent in energy conversion efficiency.

As a result of studying the above-described problems in order to solve the above-described problems, the present inventors have found that the above-described problems can be solved by providing a structure layer having a characteristic structure on the light incident surface in the organic photoelectric conversion element. Completed the invention.
That is, according to the present invention, the following is provided.

[1] Organic photoelectric conversion comprising a structure layer having a concavo-convex structure provided in contact with one surface of an organic photoelectric conversion element in which a transparent substrate, a transparent electrode layer, a photoelectric conversion layer, and a metal electrode layer are laminated in this order An element,
The concavo-convex structure is an organic photoelectric conversion element having a plurality of concave portions including a slope and a flat portion located around the concave portion.
[2] When the structural layer having the concavo-convex structure is observed from a vertical direction, the ratio of the area occupied by the flat portion to the total of the area of the flat portion and the area occupied by the concave portion is 10 to 75%. The organic photoelectric conversion device according to [1].
[3] The organic photoelectric conversion element according to [1] or [2], wherein the uneven structure of the structure layer having the uneven structure is a pyramid shape or a truncated pyramid shape.

  The organic photoelectric conversion element of the present invention is a solar cell that is excellent in energy conversion efficiency and advantageous in cost.

FIG. 1 is a perspective view schematically showing an organic photoelectric conversion element according to the first embodiment of the present invention. FIG. 2 is a diagram for explaining the organic photoelectric conversion element according to the first embodiment of the present invention. The organic photoelectric conversion element shown in FIG. 1 passes through the line 1a-1b and is perpendicular to the sunlight incident surface. FIG. 3 is a cross-sectional view schematically showing a cross section cut by a plane. FIG. 3 is a partial plan view schematically showing an enlarged view of a part of the sunlight incident surface of the organic photoelectric conversion element according to the first embodiment of the present invention viewed from the thickness direction of the organic photoelectric conversion element. It is. 4 is a partial cross-sectional view schematically showing a cross section of the concavo-convex structure layer according to the first embodiment of the present invention cut along a plane that passes through the line 3a of FIG. 3 and is perpendicular to the sunlight incident surface. . FIG. 5 is a perspective view schematically showing an organic photoelectric conversion element according to the second embodiment of the present invention. FIG. 6 is a diagram for explaining the organic photoelectric conversion element according to the second embodiment of the present invention. The organic photoelectric conversion element shown in FIG. 5 passes through the line 5a-5b and is perpendicular to the sunlight incident surface. FIG. 3 is a cross-sectional view schematically showing a cross section cut by a plane. FIG. 7 is a diagram schematically illustrating a state of manufacturing the metal mold used in Example 1. FIG. 8 is a diagram schematically showing a state of a cross section obtained by cutting the concavo-convex structure layer in Example 1 along a plane perpendicular to the cutting direction.

Hereinafter, the present invention will be described in detail with reference to embodiments and examples, but the present invention is not limited to the embodiments and examples described below, and the gist of the present invention and its equivalent scope. Any change can be made without departing from the scope of the invention. In particular, with respect to the concavo-convex structure, a mode in which the position, orientation, shape, number, and combination of the flat surface portion and the slope portion are changed can be considered as long as the effects of the present invention are not impaired.

<First embodiment>
1 and 2 are diagrams for explaining the organic photoelectric conversion element 10 according to the first embodiment of the present invention. FIG. 1 is a perspective view schematically showing the organic photoelectric conversion element, and FIG. It is sectional drawing which shows typically the cross section which cut | disconnected the organic photoelectric conversion element shown in FIG. 1 by the surface perpendicular | vertical with respect to a sunlight incident surface through line 1a-1b.

As shown in FIG. 1, the organic photoelectric conversion element 10 according to the first embodiment of the present invention is a device having a rectangular flat plate structure, and includes a transparent electrode layer 121, a photoelectric conversion layer 122, a metal electrode layer 123, and And a structural layer 110 having a concavo-convex structure and an adhesive layer 130.

[Solar cells]
The material of the transparent electrode layer 141 is preferably made of, for example, ITO, IZO, ITiO, SnO2, FTO, ZnO, GZO, AZO, etc. Among them, the material made of ITO is preferable. The metal electrode layer 143 can be formed of, for example, a metal such as MgAg co-deposited body, Pt, or Al. The thickness of each electrode layer varies depending on the type of electrode material, but is preferably 500 nm or less from the viewpoint of improving light transmittance and reducing the electrical resistance. Examples of the method for forming the electrode layer include a vacuum deposition method, a sputtering method, an ion plating method, and a plating method.

  The photoelectric conversion layer 142 may have a publicly known configuration. For example, the configuration of the photoelectric conversion layer used in a dye-sensitized solar cell, an organic thin film solar cell, or the like can be used as it is.

The photoelectric conversion layer 142 used for the organic thin film solar cell (pin junction type organic solar cell) is a nanostructure layer in which an n-type organic semiconductor layer, a p-type organic semiconductor and an n-type organic semiconductor are co-deposited on the metal electrode layer 143. (I layer) and the p-type organic-semiconductor layer are vapor-deposited in order, and are laminated | stacked.
Examples of p-type semiconductors include pyrazoline derivatives, arylamine derivatives, stilbene derivatives, triphenyldiamine derivatives, oligothiophene and derivatives thereof, polyvinylcarbazole and derivatives thereof, polysilane and derivatives thereof, and aromatic amines in side chains or main chains. And polysiloxane derivatives, polyaniline and derivatives thereof, polythiophene and derivatives thereof, polypyrrole and derivatives thereof, polyphenylene vinylene and derivatives thereof, and polythienylene vinylene and derivatives thereof. Examples of n-type semiconductors include oxadiazole derivatives, anthraquinodimethane and its derivatives, benzoquinone and its derivatives, naphthoquinone and its derivatives, anthraquinone and its derivatives, tetracyanoanthraquinodimethane and its derivatives, fluorenone derivatives, diphenyl Dicyanoethylene and derivatives thereof, diphenoquinone derivatives, metal complexes of 8-hydroxyquinoline and derivatives thereof, polyquinoline and derivatives thereof, polyquinoxaline and derivatives thereof, polyfluorene and derivatives thereof, fullerenes such as C60, and phenanthrenes such as bathocuproin Examples thereof include derivatives, metal oxides such as titanium dioxide, and carbon nanotubes. The nanostructure layer (i layer) can be formed by, for example, co-depositing the p-type organic semiconductor and the n-type organic semiconductor with co-deposited copper phthalocyanine and fullerene, and using the buffer layer such as bathocuproine. Can be formed.

The photoelectric conversion layer 142 used in the dye-sensitized solar cell is formed by a dye adsorption layer formed on the transparent electrode layer 141 and an electrolyte layer formed on the dye adsorption layer. As the dye adsorbing layer, for example, a dye made of a ruthenium complex or titanium oxide or zinc oxide adsorbed with various organic dyes is used. The electrolyte solution forming the electrolyte layer is not particularly limited as long as it is a substance capable of transporting electrons, holes, ions, etc. For example, p-type semiconductor solid holes such as CuI, CuSCN, NiO, Cu2O, KI, etc. A solution in which a redox electrolyte such as a transport material, iodine / iodide, bromine / bromide, etc. is dissolved in an organic solvent can be used.

[Structural layer with uneven structure]
The structure layer 110 having a concavo-convex structure is a layer provided on the side of the solar battery cell 120 on which sunlight is incident in the organic photoelectric conversion element 10. The sunlight incident surface 10U is the surface opposite to the solar battery cell 120 in the structure layer 110 having an uneven structure, and this sunlight incident surface 10U is the outermost surface of sunlight incident on the photoelectric conversion element 10. The surface exposed to

When viewed macroscopically, the sunlight incident surface 10U is a surface parallel to the light incident surface 150 of the solar battery cell layer 120 and parallel to the main surface of the photoelectric conversion element 10. However, since the sunlight incident surface 10U has a concavo-convex structure to be described later when viewed microscopically, the surface on the concave portion or the convex portion can form an angle that is not parallel to the light incident surface 130. Therefore, in the following description, being parallel or perpendicular to the sunlight incident surface is parallel or perpendicular to the incident light surface macroscopically ignored unless otherwise noted. It means that. Further, the organic photoelectric conversion element 10 will be described in a state where the sunlight incident light 10U is placed so as to be parallel and upward with respect to the horizontal direction unless otherwise specified.
Further, the fact that the component is “parallel” or “vertical” may include an error within a range that does not impair the effects of the present invention, for example, ± 5 °.

  The structure layer 110 having an uneven structure includes an uneven structure layer 111 and a base film layer 112. The uneven structure layer 111 is a layer located on the upper surface of the organic photoelectric conversion element 10. The concavo-convex structure layer 111 has a plurality of concave portions including slopes and a flat portion located around the concave portions. Here, since the concave portion 113 is a portion that is relatively depressed as compared with the flat portion 114, the concave portion 113 hits the concave portion according to the present invention, and the flat portion 114 protrudes relative to the concave portion 113, so that the present invention is applied. It hits the convex part. And the sunlight entrance surface 10U is prescribed | regulated by the said uneven structure.

  In the present specification, since the drawings are schematic, only a small number of recesses 113 are shown on the sunlight incident surface 10U. However, in an actual organic photoelectric conversion element, one A much larger number of recesses can be provided on the sunlight incident surface of the single organic photoelectric conversion element.

Hereinafter, the uneven structure of the sunlight incident surface 10U will be described in detail with reference to the drawings.
FIG. 3 is a partial plan view schematically showing an enlarged view of a part of the sunlight incident surface 10U of the organic photoelectric conversion element 10 as seen from the thickness direction of the organic photoelectric conversion element 10. FIG. 4 is a partial cross-sectional view schematically showing a cross section of the concavo-convex structure layer 111 taken along a plane that passes through the line 3a of FIG. 3 and is perpendicular to the sunlight incident surface 10U. In the following description, unless otherwise specified, “thickness direction” represents the thickness direction of the organic photoelectric conversion element.

  As shown in FIG. 3, the concavo-convex structure layer 111 includes a plurality of concave portions 113 including slopes 11 </ b> A to 11 </ b> D and a flat portion 114 positioned around the concave portion 113 on the sunlight incident surface 10 </ b> U. Here, the “slope” is a surface that forms an angle that is not parallel to the sunlight incident surface 10U. On the other hand, the surface on the flat portion 114 is a flat surface parallel to the sunlight incident surface 10U.

  Each of the plurality of recesses 113 is a depression having a regular quadrangular pyramid shape. Accordingly, the slopes 11A to 11D of the recess 113 have the same shape, and the bases 11E to 11H of the regular quadrangular pyramid form a square. In FIG. 3, the line 3 a is a line that passes over all the vertices 11 </ b> P of the row of recesses 113 and is parallel to the bases 11 </ b> E and 11 </ b> G of the recess 113.

  Each recess 113 can have a base 11F to 11H having a length of usually 1 μm to 200 μm, preferably 2 μm to 100 μm. The depth of each recess 113 can usually be 1 μm to 50 μm, and preferably 2 μm to 40 μm.

  The recess 113 is continuously disposed along two orthogonal in-plane directions X and Y at a constant interval. In the in-plane directions X and Y, the portion corresponding to the gap between the adjacent recesses 113 constitutes a flat portion 114. Therefore, the structure layer 110 having the concavo-convex structure has the concave portions 113 and the flat portions 114 alternately in the in-plane directions X and Y parallel to the sunlight incident surface 10U. Here, of the two in-plane directions X and Y, one in-plane direction X is parallel to the bases 11E and 11G. In the in-plane direction X, the plurality of recesses 113 are aligned at a constant interval 11J. Of the two in-plane directions X and Y, the other in-plane direction Y is parallel to the bases 11F and 11H. In the in-plane direction Y, the plurality of recesses 113 are aligned at a constant interval 11K. Here, the flat part 114 which is a part corresponding to the gap can have a width dimension of usually 0.1 μm to 50 μm.

  As shown in FIG. 4, the angles 11L and 11M formed by the inclined surfaces 11A to 11D constituting each of the concave portions 113 and the flat portion 114 (and hence the sunlight incident surface 10U) are preferably 10 ° or more, and preferably 20 ° or more. More preferably, it is preferably 170 ° or less, and more preferably 160 ° or less. Moreover, when the shape of the recessed part 113 is a quadrangular pyramid like this embodiment, it is preferable that the vertex angle 11N shall be 30 degrees-120 degrees. In the present embodiment, as shown in FIG. 4, the angles 11L and 11M formed by the inclined surfaces 11A to 11D with the flat portion 114 are set to 60 °. As a result, the apex angle of the regular quadrangular pyramid that forms the recess 113, that is, the angle formed by the opposing inclined surfaces at the apex 11P (the angle 11N shown in FIG. 4 for the angles formed by the inclined surfaces 11B and 11D) is also 60 °. .

Furthermore, in the sunlight incident surface 10U of the organic photoelectric conversion element 10 of the present embodiment, the distance in the thickness direction of the organic photoelectric conversion element 10 of the present embodiment between the bottom of the adjacent concave 113 and the tip of the convex is It may be uneven within a predetermined range, or may be aligned.
Here, the bottom of the recess 113 indicates the most depressed portion in each of the recesses 113 and indicates a portion where the distance to the light emitting surface 144 in the thickness direction of the organic photoelectric conversion element 10 is the shortest. In the present embodiment, the apex 11P of each recess 113 hits the bottom of the recess 113.
Further, the tip of the convex portion refers to a portion that protrudes most in each convex portion, and refers to a portion that has the longest distance to the light emitting surface 144 in the thickness direction of the organic photoelectric conversion element 10. In the present embodiment, since the flat portion 114 is a flat surface parallel to the light incident surface 144, the flat portion 114 itself hits the tip of the convex portion.

  When the concavo-convex structure layer 111 is observed from a direction perpendicular to the sunlight incident surface 10U, the ratio of the area occupied by the flat portion 114 to the total area occupied by the flat portion 114 and the area occupied by the concave portion 113 (hereinafter, “ The flat portion ratio ") can be adjusted as appropriate. Specifically, by setting the flat portion ratio to 10% to 75%, good photoelectric conversion efficiency can be realized, and the mechanical strength of the sunlight incident surface 10U can be increased.

(Description of the material of the structure layer having an uneven structure)
The structure layer 110 having the concavo-convex structure may be composed of a plurality of layers, but may be composed of a single layer. In this embodiment, as shown in FIG. 1, the structure layer 110 having an uneven structure includes the structure layer 110 having an uneven structure in which the uneven structure layer 111 and the base film layer 112 are combined. To do.

  The uneven structure layer 111 and the base film layer 112 can usually be formed of a resin composition containing a transparent resin. That the transparent resin is “transparent” means that it has a light transmittance suitable for use in an optical member. In the present embodiment, each layer constituting the concavo-convex structure layer 111 may have a light transmittance suitable for use in an optical member, and the entire structural layer 110 having the concavo-convex structure has a total light beam of 80% or more. What is necessary is just to have the transmittance | permeability.

  The transparent resin contained in the resin composition is not particularly limited, and various resins that can form a transparent layer can be used. Examples thereof include a thermoplastic resin, a thermosetting resin, an ultraviolet curable resin, and an electron beam curable resin. Among these, thermoplastic resins are preferable because they can be easily deformed by heat, and ultraviolet curable resins have high curability and high efficiency, so that the uneven structure layer 111 can be efficiently formed.

  Examples of the thermoplastic resin include polyester, polyacrylate, and cycloolefin polymer resins. Examples of the ultraviolet curable resin include epoxy resins, acrylic resins, urethane resins, ene / thiol resins, and isocyanate resins. As these resins, those having a plurality of polymerizable functional groups can be preferably used. In addition, the said resin may be used individually by 1 type, and may be used combining two or more types by arbitrary ratios.

  Among them, the material of the concavo-convex structure layer 111 constituting the structural layer 110 having the concavo-convex structure is cured from the viewpoint that it is easy to form the concavo-convex structure of the sunlight incident surface 10U and easily obtain the scratch resistance of the concavo-convex structure. A material with high hardness at the time is preferred. Specifically, when a resin layer having a film thickness of 7 μm is formed on a substrate without a concavo-convex structure, a material having a pencil hardness of HB or higher is preferable, and a material of H or higher is more preferable. The material which becomes 2H or more is more preferable. On the other hand, the material of the base film layer 112 facilitates the handling when forming the concavo-convex structure layer 111 and the structure layer 110 having the concavo-convex structure after forming the film base 110 having the concavo-convex structure. Therefore, the thing with a certain amount of flexibility is preferable. By combining such materials, it is possible to obtain the structure layer 110 having a concavo-convex structure that is easy to handle and excellent in durability, and as a result, the high-performance organic photoelectric conversion element 10 can be easily manufactured. .

  Such a combination of materials can be obtained by appropriately selecting the transparent resin exemplified above as the resin constituting each material. Specifically, an ultraviolet curable resin such as acrylate is used as the transparent resin constituting the material of the concavo-convex structure layer 111, while the transparent resin constituting the material of the base film layer 112 is made of an alicyclic olefin polymer. It is preferable to use a film (such as a ZEONOR film described later) or a polyester film.

  As in this embodiment, when the structure layer 110 having an uneven structure includes the uneven structure layer 111 and the base film layer 112, the refractive index of the uneven structure layer 111 and the base film layer 112 is as close as possible. Also good. In this case, the refractive index difference between the uneven structure layer 111 and the base film layer 112 is preferably within 0.1, and more preferably within 0.05.

  Furthermore, the resin composition can contain arbitrary components as needed. Examples of the optional component include additives such as phenol-based and amine-based degradation inhibitors; surfactant-based, siloxane-based antistatic agents; triazole-based, 2-hydroxybenzophenone-based light-resistant agents; Can be mentioned.

  The thickness T of the uneven structure layer 111 is not particularly limited, but is preferably 1 μm to 70 μm. In this embodiment, the thickness T of the concavo-convex structure layer 111 is the distance between the surface on the base film layer 112 side where the concavo-convex structure is not formed and the flat portion 114 of the concavo-convex structure. Moreover, it is preferable that the thickness of the base film layer 112 is 20 micrometers-300 micrometers.

(Adhesive layer)
The light emitting element 10 of the present embodiment includes an adhesive layer 130 between the structural layer 110 having an uneven structure and the solar battery cell 120. The adhesive layer 130 is a layer that is interposed between the base film layer 112 of the structural layer 110 having a concavo-convex structure and the transparent metal layer 121 of the solar battery cell 120 and adheres these two layers.
The adhesive that is the material of the adhesive layer 130 is a narrowly defined adhesive (a so-called hot-melt adhesive having a shear storage elastic modulus at 23 ° C. of 1 to 500 MPa and not showing tackiness at room temperature).
In addition, a pressure-sensitive adhesive having a shear storage modulus at 23 ° C. of less than 1 MPa is also included.
Specifically, a material having a refractive index close to that of the support substrate 131 or the base film layer 112 and transparent can be used as appropriate. More specifically, an acrylic adhesive or a pressure-sensitive adhesive can be used. The thickness of the adhesive layer is preferably 5 μm to 100 μm.

[Other layers]
(Light diffusive layer)
Using a light diffusive material as a material for a layer that is a constituent element of the structural layer 110 having a concavo-convex structure such as the concavo-convex structure layer 111 and the base film layer 112, or as an adhesive layer for adhering the layers. Also good. Accordingly, light transmitted through the structure layer 110 having a concavo-convex structure can be diffused and the optical path of the light can be changed. By increasing the optical path length, the light can be easily taken into the photoelectric conversion layer.

  Examples of the light diffusing material include a material containing particles, and an alloy resin that diffuses light by mixing two or more kinds of resins. Among these, from the viewpoint that the light diffusibility can be easily adjusted, a material including particles is preferable, and a resin composition including particles is particularly preferable.

  The particles may be transparent or opaque. Examples of the material of the particles include metals and metal compounds, and resins. Examples of the metal compound include metal oxides and nitrides. Specific examples of metals and metal compounds include metals having high reflectivity such as silver and aluminum; metal compounds such as silicon oxide, aluminum oxide, zirconium oxide, silicon nitride, tin-added indium oxide, and titanium oxide. be able to. On the other hand, examples of the resin include methacrylic resin, polyurethane resin, and silicone resin. In addition, the particle | grain material may be used individually by 1 type, and may be used combining two or more types by arbitrary ratios.

The shape of the particles can be, for example, a spherical shape, a cylindrical shape, a cubic shape, a rectangular parallelepiped shape, a pyramid shape, a conical shape, a star shape, or the like.
The particle diameter of the particles is preferably 0.1 μm or more, preferably 10 μm or less, more preferably 5 μm or less. Here, the particle diameter is a 50% particle diameter in an integrated distribution obtained by integrating the volume-based particle amount with the particle diameter as the horizontal axis. The larger the particle size, the larger the content ratio of particles necessary for obtaining the desired effect, and the smaller the particle size, the smaller the content. When the particle shape is other than spherical, the diameter of the sphere having the same volume is used as the particle size.

  In the case where the particles are transparent particles and the particles are contained in the transparent resin, the difference between the refractive index of the particles and the refractive index of the transparent resin is preferably 0.05 to 0.5. More preferably, it is 07-0.5. Here, either the particle or the refractive index of the transparent resin may be larger. If the refractive index of the particles and the transparent resin is too close, the diffusion effect may not be obtained and the desired effect may not be obtained. Conversely, if the difference is too large, the diffusion increases and the external light reaching the photoelectric conversion layer decreases. However, the desired effect may not be obtained.

  The content ratio of the particles is a volume ratio in the total amount of the layer containing the particles, preferably 1% or more, more preferably 5% or more, 80% or less, and more preferably 50% or less. By setting the content ratio of the particles to the lower limit or higher, desired effects such as a diffusion effect can be obtained. Moreover, by setting it as this upper limit or less, aggregation of particle | grains can be prevented and particle | grains can be disperse | distributed stably.

(UV absorbing layer)
Since the organic photoelectric element of this embodiment uses an organic material, there is a possibility that the organic material is easily deteriorated by ultraviolet rays of sunlight. For this reason, it is considered effective to provide an ultraviolet absorbing layer containing an ultraviolet absorber. As the ultraviolet absorber, an organic material or an inorganic material may be used. Examples of ultraviolet absorbers include benzophenone-based, benzotriazole-based, triazine-based, and phenyl salicylate-based ultraviolet absorbers as organic materials. Among these, preferred specific examples include 2,4-dihydroxy-benzophenone, 2-hydroxy-4-methoxybenzophenone, 4-dodecyloxy-2-hydroxybenzophenone, 2-hydroxy-4-methoxy-5-sulfobenzophenone, 2- (2'-hydroxy-5-methylphenyl) benzotriazole, 2- (2'-hydroxy-3 ', 5'-ditertiarybutylphenyl) benzotriazole, 2,4-bis "2-hydroxy-4-butoxyphenyl ] -6- (2,4-dibutoxyphenyl) -1,3-5-triazine, phenyl salicylate, p-octylphenyl salicylate, p-tertiarybutylphenyl salicylate, etc. Inorganic Examples of the ultraviolet absorber made of the material include titanium dioxide, zinc oxide, and oxide oxide. Among them, it is preferable to use an inorganic material.

As the ultraviolet absorber, a wavelength conversion material capable of converting the wavelength of the absorbed ultraviolet light into light having a longer wavelength than the absorbed ultraviolet light may be used. The light whose wavelength is converted by the absorbed ultraviolet light includes, for example, visible light, near infrared light, infrared light, etc., but a wavelength conversion material that can convert the wavelength to visible light is preferable from the viewpoint of increasing photoelectric conversion efficiency. . An example of the wavelength conversion material is a phosphor. The phosphor is usually a material that can absorb excitation light and emit fluorescence having a wavelength longer than that of the excitation light. Therefore, when a phosphor is used as the ultraviolet absorber, a phosphor that can absorb ultraviolet rays as excitation light and can emit fluorescence having a wavelength that can be used for charge generation in the active layer may be used. Among phosphors, rare earth complexes can be cited as examples of organic phosphors. Rare earth complexes are phosphors having excellent fluorescence characteristics. Specific examples include [Tb (bpy) 2] Cl3 complex, [Eu (phen) 2] Cl3 complex, and [Tb (terpy) 2] Cl3 complex. It is done. “Bpy” represents 2,2-bipyridine, “phen” represents 1,10-phenanthroline, and “terpy” represents 2,2 ′: 6 ′, 2 ″ -terpyridine. Inorganic phosphor Examples of MgF2: Eu2 + (absorption wavelength: 300 nm to 400 nm, fluorescence wavelength: 400 nm to 550 nm), 1.29 (Ba, Ca) O.6Al2O3: Eu2 + (absorption wavelength: 200 nm to 400 nm, fluorescence wavelength: 400 nm to 600 nm), Examples include BaAl2O4: Eu2 + (absorption wavelength: 200 nm to 400 nm, fluorescence wavelength: 400 nm to 600 nm), Y3Al5O12: Ce3 + (absorption wavelength: 250 nm to 450 nm, fluorescence wavelength: 500 nm to 700 nm), etc. Among phosphors, inorganic phosphors are used. preferable.

One type of ultraviolet absorber may be used, or two or more types may be used. The ultraviolet absorbing layer may contain a binder in order to hold the ultraviolet absorber. As the binder, it is preferable to use a material that can hold the ultraviolet absorber in the ultraviolet absorbing layer without significantly impairing the effects of the present invention, and a resin is usually used. Examples of resins that can be used as the binder include polyester resins, epoxy resins, acrylic resins, and fluorine resins. In addition, a binder may be used individually by 1 type and may be used combining two or more types by arbitrary ratios. The thickness of the ultraviolet absorbing layer is usually 1 μm or more, preferably 10 μm or more, more preferably 100 μm or more, and usually 10,000 μm or less, preferably 5000 μm or less, more preferably 3000 μm or less. The position where the ultraviolet absorbing layer is provided is not particularly limited, but the solar light incident surface side of the transparent electrode layer, the solar battery cell side of the concavo-convex structure layer, and the like are conceivable.

〔Production method〕
Although the manufacturing method of the organic photoelectric conversion element 10 is not specifically limited, For example, it can manufacture by sticking each layer which comprises the structure layer 110 which has an uneven structure on the surface at the side of the transparent electrode of the photovoltaic cell 120. FIG.

The manufacture of the structure layer having the concavo-convex structure having the concavo-convex structure layer 111 and the base film layer 112 is performed, for example, by preparing a mold such as a mold having a desired shape, This can be done by transferring to a layer. As a more specific method,
(Method 1) An unprocessed concavo-convex structure having a layer of the resin composition A constituting the base film layer 112 and a layer of the resin composition B constituting the concavo-convex structure layer 111 (the concavo-convex structure is not yet formed) A method of forming a concavo-convex structure on the surface of the resin composition B side of the structural layer having a raw concavo-convex structure;
(Method 2) On the base film layer 112, the resin composition B in a liquid state is applied, a mold is applied to the layer of the applied resin composition B, and the resin composition B is cured in that state, thereby forming irregularities. A method for forming the structural layer 111 can be given.

In Method 1, the structure layer having an unprocessed uneven structure can be obtained by, for example, extrusion molding in which the resin composition A and the resin composition B are coextruded. A concavo-convex structure can be formed by pressing a mold having a desired surface shape onto the surface of the film base having a raw concavo-convex structure on the resin composition B side.
More specifically, a film base material having a raw concavo-convex structure formed by a transfer roll and a nip roll having a desired surface shape is formed by continuously forming a structural layer having a long raw concavo-convex structure by extrusion molding. So that continuous production can be efficiently performed. The pinching pressure between the transfer roll and the nip roll is preferably several MPa to several tens of MPa. The temperature at the time of transfer is preferably Tg or more (Tg + 100 ° C.) or less, where Tg is the glass transition temperature of the resin composition B. The contact time between the transfer layer and the structure layer having an unprocessed uneven structure can be adjusted by the film feed speed, that is, the roll rotation speed, and is preferably 5 seconds or more and 600 seconds or less.

  In Method 2, as the resin composition B constituting the concavo-convex structure layer 111, it is preferable to use a composition that can be cured by energy rays such as ultraviolet rays. The resin composition B is applied on the base film layer 112, and in a state where the mold is applied, the resin composition B is located on the back side of the application surface (the side opposite to the surface on which the resin composition B is applied). By irradiating energy rays such as ultraviolet rays from a light source, curing the resin composition B, and then peeling the mold, the coating layer of the resin composition B is used as the concavo-convex structure layer 111, and the structure layer 110 having the concavo-convex structure is formed. Can be obtained.

When the structure layer having the concavo-convex structure is composed only of the concavo-convex structure layer 111 (Method 3), it has a layer of the resin composition B constituting the concavo-convex structure layer 111 (the concavo-convex structure has not yet been formed). A method of forming a concavo-convex structure on a surface of the film base having a raw concavo-convex structure on the resin composition B side of the film base having such a concavo-convex structure (Method 4) for any peeling A liquid resin composition B is applied on the film layer, a mold is applied to the applied resin composition B layer, and the resin composition B is cured in that state to form the concavo-convex structure layer 111, It can form by the method of peeling the film for peeling from an uneven | corrugated structure layer.

[Main advantages of organic photoelectric conversion elements]
Since the organic photoelectric conversion element 10 of this embodiment is configured as described above, the amount of light taken into the photoelectric conversion layer can be increased, and the photoelectric effect can be improved.

<Second Embodiment>
In the organic photoelectric conversion element of the present invention, the shape of the concave portion and the convex portion constituting the sunlight incident surface is not limited to the pyramid shape exemplified in the first embodiment, and may be a truncated pyramid shape. Here, the truncated pyramid shape refers to a shape in which a flat portion is provided at the top of the pyramid and the surface is flattened. Hereinafter, the example is demonstrated using drawing.

5 and 6 are diagrams for explaining the organic photoelectric conversion element according to the second embodiment of the present invention. FIG. 5 is a perspective view schematically showing the organic photoelectric conversion element. FIG. 5 is a cross-sectional view schematically showing a cross section of the concavo-convex structure layer of the organic photoelectric conversion element shown in FIG. 5 cut along a plane that passes through the line 5a-5b and is perpendicular to the sunlight incident surface.
As shown in FIG. 5, the organic photoelectric conversion element 20 according to the second embodiment includes a structure layer 210 having a concavo-convex structure, and a shape of a recess 213 formed on a sunlight incident surface 20U that is the surface of the concavo-convex structure layer 211. Otherwise, the configuration is the same as that of the first embodiment.

  As shown in FIG. 6, the recess 213 formed on the surface of the concavo-convex structure layer 211 has a shape (pyramidal frustum shape) obtained by flat chamfering the top of a regular quadrangular pyramid, and has a constant shape on the sunlight incident surface 20U. It is provided at intervals. A gap is provided between adjacent recesses 213, and this gap constitutes a flat portion 214. Furthermore, since the concave portion 213 has a truncated pyramid shape, the concave portion 213 has a bottom surface portion 21P on the bottom as a flat surface parallel to the sunlight incident surface 20U.

  Even in the case of having the sunlight incident surface 20U having the concave portion 213 having the truncated pyramid shape and the flat portion 214 that is a gap therebetween, as in the first embodiment, the photoelectric conversion layer is formed. The amount of light taken in can be increased, and the photoelectric effect can be improved. Further, if dust and debris accumulate in the recess 213, the amount of light taken in may decrease, but if the bottom of the recess 213 is a flat bottom surface portion 21P, dust and debris etc. It is preferable because it is difficult to accumulate. Furthermore, according to this embodiment, the same advantage as 1st embodiment can also be acquired.

As in the present embodiment, when the recess 213 has a truncated pyramid shape, the height of the bottom surface portion 21P and the top portion 21Q when the top portion of the truncated pyramid is not flat but a sharp pyramid shape. The difference 21R may normally be 20% or less of the height 21S of the pyramid when the top of the truncated pyramid is not flat and has a sharp pyramid shape.
Moreover, when the shape of the recessed part 213 is a truncated pyramid shape, let the angle of slope 215A and 215B except the bottom face part 21P be an angle of a slope. By setting the angle of the inclined surface of the recess 213 to such an angle, the light capturing efficiency can be increased. However, the slopes are not necessarily all at the same angle, and slopes having different angles may coexist within the above range.

Hereinafter, the present invention will be described in more detail based on examples. In addition, this invention is not limited to the following Example.

[Example 1]
(1) Manufacture of structure having concavo-convex structure Roll-shaped film substrate (trade name “ZEONOR FILM”, manufactured by Nippon Zeon Co., Ltd., alicyclic structure-containing polymer resin film, thickness 100 μm, refractive index 1. A UV curable resin (refractive index of 1.54) mainly composed of urethane acrylate was applied to 53) to form a coating film, and a metal mold was pressed onto the coating film. In this state, ultraviolet rays were irradiated at 1.5 mJ / cm 2 to cure the coating film, thereby forming an uneven structure layer having an uneven structure. The metal mold for forming the concavo-convex structure uses a cutting tool having an apex angle of 60 degrees and a tip width of 6 μm, and the repeating unit shown in FIG. It was obtained by cutting and then cutting along a direction perpendicular to the direction. Cutting was performed at a constant cutting pitch P. Moreover, the depth of the groove | channel formed by cutting was changed into five steps of H1-H5, and it cut repeatedly using the five groove | channels formed in this way as a repeating unit. In this embodiment, the cutting pitch P is set to 20 μm, and the groove depths H1 to H5 included in the repeating unit are 10.6 μm for H1, 10.3 μm for H2, 10.0 μm for H3, and 9.7 μm for H4. , And H5 were set to 9.4 μm. The widths W1 to W5 of the five grooves thus formed were 18.24 μm for W1, 17.89 μm for W2, 17.55 μm for W3, 17.20 μm for W4, and 16.85 μm for W5. .

  FIG. 7 is a diagram schematically showing a cross section of the concavo-convex structure layer obtained in Example 1 cut along a plane perpendicular to the cutting direction. As shown in FIG. 8, the surface of the obtained concavo-convex structure layer 3 is formed with a concavo-convex structure having a large number of quadrangular pyramid-shaped concave portions corresponding to the grooves formed in the metal mold. A plurality of flat surfaces having different height positions and pitches were provided.

(2) Preparation of metal oxide semiconductor photoelectrode A transparent electrode made of ITO having a thickness of 200 nm was formed on a ZEONOR film by sputtering. In that case, sputtering was performed by using an ITO target and using a sputtering apparatus (SBH-5215RD made by ULVAC).

The obtained transparent electrode substrate was cut and pretreated for 5 minutes using a UV washer. Thereafter, a ZnO dispersion paste was applied by screen printing and dried at 100 ° C. for 1 hour to form a film having a thickness of 2.5 μm. (Electrode area: 2 cm2)

An organic dye D149 (manufactured by Mitsubishi Paper Industries) was added to a solvent of acetonitrile: t-butanol = 1: 1 (volume ratio) to prepare a 5.0 × 10 −4 M dye solution. In order to prevent aggregation, chenodeoxycholic acid (1.0 × 10 −3 M) was added as a co-adsorbent to the dye solution.
And after drying the obtained board | substrate at 120 degreeC for 10 minute (s), it was put into the pigment | dye solution and immersed at room temperature for 1 hour, and the metal oxide semiconductor photoelectrode was obtained.

(3) Manufacture of dye-sensitized solar cell A transparent electrode made of ITO having a thickness of 200 nm was formed on a ZEONOR film by a sputtering method, and a counter electrode was prepared by supporting platinum. Next, an electrolyte solution using an imidazolium-based ionic liquid as a solvent is injected between the metal oxide semiconductor photoelectrode and the counter electrode, and the overlapped portion is sealed with a resin to form a dye-sensitized solar cell (thickness). : 250 μm).

(4) Production of organic photoelectric conversion element 1)
The obtained dye-sensitized solar cell is bonded with a structure having a concavo-convex structure layer via an adhesive layer (acrylic resin, refractive index 1.49, manufactured by Nitto Denko Corporation, CS9621), and the dye-sensitized solar cell. -The organic photoelectric conversion element 1 which has a layer structure with-adhesion layer-film base material-uneven structure layer was obtained.

[Example 2]
The cutting tool was changed to one having an apex angle of 30.0 ° and a tip width of 4 μm, and the widths W1 to W5 of the grooves formed in the metal mold were W1 of 8.61 μm, W2 of 8.45 μm, and W3 of 8.29 μm, W4 is 8.13 μm, and W5 is 7.97 μm. The heights H1 to H5 of these grooves are H1 of 8.6 μm, H2 of 8.3 μm, and H3 of 8.0 μm, respectively. A metal mold was manufactured in the same manner as in Example 1 except that H4 was 7.7 μm, H5 was 7.4 μm, and the cutting pitch P was 40 μm, and a concavo-convex structure was formed. In the same manner as in Example 1, an organic photoelectric conversion element 2 was produced.

Example 3
The cutting tool was changed to one with an apex angle of 90.0 ° and a tip width of 4 μm, and the widths W1 to W5 of the grooves formed in the metal mold were W1 of 37.20 μm, W2 of 36.60 μm, and W3 of 36.00 μm, W4 is 35.40 μm, and W5 is 34.80 μm. The heights H1 to H5 of these grooves are H1 of 16.6 μm, H2 of 16.3 μm, and H3 of 16.0 μm, respectively. A metal mold was manufactured in the same manner as in Example 1 except that H4 was 15.7 μm, H5 was 15.4 μm, and the cutting pitch P was 40 μm, and a concavo-convex structure was formed. In the same manner as in Example 1, an organic photoelectric conversion element 3 was produced.

[Comparative Example 2]
The cutting tool was changed to one having an apex angle of 60.0 ° and a tip width of 0 μm, and the widths W1 to W5 of the grooves formed in the metal mold were W1 of 12.24 μm, W2 of 11.89 μm, and W3 of A metal mold was produced in the same manner as in Example 1 except that 11.55 μm, W4 was 11.20 μm, and W5 was 10.85 μm, and a concavo-convex structure was formed, as in Example 1. Thus, an organic photoelectric conversion element 5 was produced.

[Comparative Example 3]
The cutting tool was changed to one having an apex angle of 30.0 ° and a tip width of 0 μm, and the widths W1 to W5 of the grooves formed in the metal mold were W1 of 4.61 μm, W2 of 4.45 μm, and W3 of A metal mold was produced in the same manner as in Example 2 except that the thickness was 4.29 μm, W4 was 4.13 μm, and W5 was 3.97 μm, and a concavo-convex structure was formed, as in Example 1. Thus, an organic photoelectric conversion element 6 was produced.

[Comparative Example 4]
The cutting tool was changed to one having an apex angle of 90.0 ° and a tip width of 0 μm, and the widths W1 to W5 of the grooves formed in the metal mold were W1 of 33.20 μm, W2 of 32.60 μm, and W3 of A metal mold was produced in the same manner as in Example 3 except that 32.00 μm, W4 was 31.40 μm, and W5 was 30.80 μm, and a concavo-convex structure was formed, and the same as in Example 1. Thus, an organic photoelectric conversion element 7 was produced.

(Evaluation of photoelectric conversion characteristics)
About the organic photoelectric conversion element obtained by the Example and the comparative example, the photoelectric conversion efficiency ((eta)) was measured using the solar simulator whose light source intensity | strength is 1 SUN (100 mW / cm <2>). A dye-sensitized solar cell having no concavo-convex structure was handled as Comparative Example 1 and used as a reference. The results are shown in Table 1. The rate of increase in the table is calculated as photoelectric conversion efficiency measured in each example / photoelectric conversion efficiency measured in Comparative Example 1 × 100. Notation.

DESCRIPTION OF SYMBOLS 10 Organic photoelectric conversion element 10U Sunlight incident surface 110 Structure layer which has uneven structure 111 Uneven structure layer 112 Base film layer 113 Recessed part 114 Flat surface part 115 Slope part 120 Solar cell 130 Adhesive layer 121 Transparent electrode layer 122 Photoelectric conversion element 123 Metal electrode layer 144 Light emitting surface 160 Phase difference film 20 Organic photoelectric conversion element 20U Sun light incident surface 210 Structure layer having uneven structure 211 Uneven structure layer 213 Recess 214 Flat surface 215 Slope

Claims (3)

An organic photoelectric conversion element comprising a structural layer having a concavo-convex structure provided in contact with one surface of an organic photoelectric conversion element in which a transparent substrate, a transparent electrode layer, a photoelectric conversion layer, and a metal electrode layer are laminated in this order. And
The concavo-convex structure is an organic photoelectric conversion element having a plurality of concave portions including a slope and a flat portion located around the concave portion. When the structure layer having the concavo-convex structure is observed from a vertical direction, the ratio of the area occupied by the flat portion to the sum of the area of the flat portion and the area occupied by the concave portion is 10 to 75%. The organic photoelectric conversion element according to claim 1. The organic photoelectric conversion element according to claim 1, wherein the uneven structure of the structure layer having the uneven structure is a pyramid shape or a truncated pyramid shape.

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