Solar battery cell, solar battery, and antireflection film

Abstract

A solar battery cell 30 comprises: a fine uneven structure layer 11; a first electrode layer 32; a photoelectric conversion layer 34; and a second electrode layer 36. The fine uneven structure layer 11 includes: a fine uneven structure 12 having a plurality of protrusions 13 disposed at a pitch P which is no more than the wavelength of visible light; and wavelength conversion nanoparticles 15 dispersed and contained in the fine uneven structure 12.

Description

Solar cell, solar cell, and anti-reflection film

[0001] The present invention relates to a solar cell, a solar cell, and an anti-reflection film. This application claims the benefit of priority from Japanese Patent Application No. 2024-091945 filed on June 6, 2024, the contents of which are incorporated herein by reference.

[0002] In recent years, solar power generation has become increasingly important as a measure against global warming from the perspective of decarbonization. Conventional solar power generation mainly uses silicon solar cells. Methods for improving the power generation efficiency of solar cells include reducing the reflection of incident light on the solar cell and converting near-infrared light from sunlight into visible light for use in power generation.

[0003] For example, Patent Document 1 discloses providing an anti-reflection film on the outermost surface of a solar cell module to reduce reflection of received light in order to improve the power generation efficiency of the solar cell. Also, Patent Document 2 discloses providing a solar cell with a light up-conversion film that converts long-wavelength near-infrared light into short-wavelength visible light in order to effectively utilize light in a wide wavelength range contained in sunlight.

[0004] International Publication No. 2011 / 155614 Japanese Patent Application Laid-Open No. 2018-194684

[0005] Conventional silicon-based solar cells generally have a structure in which an electrode is provided linearly on the outermost surface (see, for example, the light-receiving surface electrode 13 shown in FIG. 8 of Patent Document 2). Compound solar cells, organic thin-film (organic semiconductor) solar cells, perovskite solar cells, and the like are attracting attention as next-generation solar cells. These next-generation solar cells, unlike the structure of conventional silicon-based solar cells, generally have an electrode layer provided on the entire surface of the solar cell. That is, the electrode layer and another layer (e.g., an electron transport layer or a hole transport layer) are in surface contact with each other, resulting in a large interfacial area between the two layers. Therefore, incident light can be reflected across the entire wide interface between the electrode layer and the other layer, which can lead to significant reflection of incident light within the solar cell.

[0006] In this regard, the technology of Patent Document 1 provides an anti-reflection film on the outermost surface of the solar cell module, and has the problem of being unable to suppress reflection inside the solar cell.

[0007] Furthermore, when a new wavelength conversion layer is provided using a light up-conversion film as in Patent Document 2, a new interface with a large refractive index difference may be generated, which causes a problem of increased reflection of incident light.

[0008] Therefore, the present invention has been made in consideration of the above problems, and an object of the present invention is to provide a solar cell, a solar cell, and an anti-reflection film that can suppress reflection of incident light at layer interfaces inside the cell in various solar cells and effectively utilize unused light from the incident light, thereby improving power generation efficiency.

[0009] In order to solve the above problem, according to one aspect of the present invention, there is provided a solar cell comprising a microrelief structure layer, a first electrode layer, a photoelectric conversion layer, and a second electrode layer, wherein the microrelief structure layer has a microrelief structure having a plurality of convex portions arranged at a pitch equal to or less than the wavelength of visible light, and wavelength conversion nanoparticles dispersed within the microrelief structure.

[0010] The solar cell may further include an electron transport layer and a hole transport layer, and at least some of the first electrode layer, the electron transport layer, the photoelectric conversion layer, the hole transport layer, and the second electrode layer may be stacked in accordance with the fine uneven structure of the fine uneven structure layer, and the fine uneven structure may also be formed on some of the layers.

[0011] The thickness of the part of the layer may be smaller than the height of the convex portions of the fine concave-convex structure.

[0012] The solar cell may further include a base material layer, an electron transport layer, and a hole transport layer, and the solar cell may be a laminate in which the base material layer, the microrelief structure layer, the first electrode layer, the electron transport layer, the photoelectric conversion layer, the hole transport layer, and the second electrode layer are stacked in this order from the light-receiving surface side of the solar cell.

[0013] The first electrode layer and the electron transport layer may be stacked in accordance with the fine uneven structure of the fine uneven structure layer, and the first electrode layer and the electron transport layer may also have a fine uneven structure formed thereon.

[0014] The thickness of the first electrode layer and the thickness of the electron transport layer may be smaller than the height of the convex portions of the fine concave-convex structure.

[0015] The wavelength-converting nanoparticles may be made of a hybrid material including organic and inorganic materials.

[0016] The wavelength-converting nanoparticles may include up-conversion nanoparticles that convert at least a portion of near-infrared light into visible light.

[0017] The wavelength-converting nanoparticles may include down-conversion nanoparticles that convert at least a portion of ultraviolet light into visible light.

[0018] The wavelength-converting nanoparticles may have an average particle size smaller than the height and pitch of the convex portions of the fine uneven structure.

[0019] The solar cell may be a solar cell provided in a perovskite solar cell.

[0020] In order to solve the above-mentioned problems, according to another aspect of the present invention, there is provided a solar cell comprising: the solar cell; and an encapsulation layer that encapsulates the solar cell.

[0021] The solar cell may be a perovskite solar cell.

[0022] In order to solve the above-mentioned problems, according to another aspect of the present invention, there is provided an antireflection film comprising: a base layer; and a microrelief structure layer laminated on the base layer, wherein the microrelief structure layer has a microrelief structure having a plurality of convex portions arranged at a pitch equal to or less than the wavelength of visible light; and wavelength-converting nanoparticles contained and dispersed within the microrelief structure.

[0023] The anti-reflection film may be provided on the solar cell.

[0024] The solar cell may be a solar cell provided in a perovskite solar cell.

[0025] The wavelength-converting nanoparticles may be made of a hybrid material including organic and inorganic materials.

[0026] The wavelength-converting nanoparticles may include up-conversion nanoparticles that convert at least a portion of near-infrared light into visible light.

[0027] The wavelength-converting nanoparticles may include down-conversion nanoparticles that convert at least a portion of ultraviolet light into visible light.

[0028] The wavelength-converting nanoparticles may have an average particle size smaller than the height and pitch of the convex portions of the fine uneven structure.

[0029] According to the present invention, in various solar cells, the reflection of incident light at the layer interfaces inside the cell can be suppressed, and unused light of the incident light can be effectively utilized, thereby improving the power generation efficiency.

[0030] FIG. 1 is a cross-sectional view showing an anti-reflection film according to a first embodiment of the present invention. FIG. 2 is a plan view showing the arrangement of a plurality of convex portions of a microrelief structure according to the same embodiment. FIG. 3 is a plan view showing the arrangement of a plurality of convex portions of a microrelief structure according to a modified example of the same embodiment. FIG. 4 is a perspective view showing an example of convex portions of a microrelief structure according to the same embodiment. FIG. 5 is a perspective view showing an example of convex portions of a microrelief structure according to the same embodiment. FIG. 6 is a perspective view showing an example of convex portions of a microrelief structure according to the same embodiment. FIG. 7 is a cross-sectional view showing a perovskite solar cell according to the same embodiment. FIG. 8 is a partially enlarged cross-sectional view showing a solar cell having a planar structure according to the same embodiment. FIG. 9 is a partially enlarged cross-sectional view showing a solar cell according to Reference Example 1 of the same embodiment. FIG. 10 is a partially enlarged cross-sectional view showing a solar cell according to Reference Example 2 of the same embodiment. FIG. 11 is a partially enlarged cross-sectional view showing a solar cell according to a modified example of the same embodiment. FIG. 12 is a partially enlarged cross-sectional view showing a solar cell having an inverted planar structure according to a second embodiment of the present invention. FIG. 13 is a perspective view schematically showing a master according to the first and second embodiments. Fig. 14 is an explanatory diagram showing a schematic configuration of an exposure apparatus according to the embodiment, and Fig. 15 is a schematic diagram showing a configuration of a transfer apparatus that produces a transferred object using a master according to the embodiment.

[0031] Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. Specific dimensions, materials, numerical values, etc. shown in the embodiments are merely examples for facilitating understanding of the invention and do not limit the present invention unless otherwise specified. In this specification and drawings, elements having substantially the same functions and configurations are designated by the same reference numerals to avoid redundant explanation, and elements not directly related to the present invention are not shown.

[0032] [1. Structure of Antireflection Film] First, the structure of an antireflection film 1 according to a first embodiment of the present invention will be described with reference to Fig. 1. Fig. 1 is a cross-sectional view showing the antireflection film 1 according to this embodiment. The antireflection film 1 is a film that is provided inside a solar cell 30 (see Fig. 8) of a perovskite solar cell 20 according to this embodiment and is used as an antireflection coating.

[0033] As shown in Figure 1, the antireflection film 1 according to this embodiment includes a substrate layer 10 and a microrelief structure layer 11 laminated on the substrate layer 10. The microrelief structure layer 11 includes a microrelief structure 12 on its surface. The microrelief structure 12 has a plurality of minute convex portions 13 and concave portions 14 arranged at a pitch P that is equal to or less than the wavelength of visible light (e.g., 380 to 830 nm). A large number of wavelength-converting nanoparticles 15 are dispersed within the microrelief structure 12.

[0034] The substrate layer 10 is a layer that constitutes the substrate of the anti-reflection film 1. The substrate layer 10 is made of, for example, a flexible film-like substrate. Therefore, the entire anti-reflection film 1 is also flexible. The substrate layer 10 may be, for example, a flat film as shown in FIG. 1 , or a curved or corrugated film. The planar shape (XY plane) and size of the substrate layer 10 preferably correspond to the installation range of the anti-reflection film 1 in the solar cell 30 of the perovskite solar cell 20 (see FIG. 8 ). The thickness (Z direction) of the substrate layer 10 is not particularly limited, but may be appropriately adjusted depending on, for example, the required strength and thickness of the solar cell 30.

[0035] The substrate layer 10 is formed, for example, from a transparent material, preferably from a transparent organic material. The substrate layer 10 is preferably formed from a resin material with excellent light transmittance. The substrate layer 10 is preferably formed from a resin material with excellent visible light transmittance in particular. "Transparent" means high transmittance of light having wavelengths in the visible light range (e.g., 380 to 830 nm). For example, "transparent" may mean a visible light transmittance of 70% or more, preferably 90% or more. Visible light transmittance can be measured using a spectrophotometer. From the measurement results, transmittance from wavelengths of 380 nm to 900 nm is calculated in accordance with JIS R 3106:1998, and the visible light transmittance can be calculated as the average of the transmittances in this wavelength range.

[0036] Examples of the resin material of the base layer 10 include organic resins such as polyethylene terephthalate (PET), polycarbonate, polymethyl methacrylate, triacetyl cellulose (TAC), cyclic olefin polymer (COP), and cyclic olefin copolymer (COC).

[0037] The base layer 10 may also be formed of an inorganic material that has excellent transmittance to visible light. For example, the base layer 10 may be formed of a transparent glass material such as quartz glass, soda lime glass, or lead glass.

[0038] The microrelief structure layer 11 is a layer laminated on the base material layer 10. On the surface of the microrelief structure layer 11, a microrelief structure 12 having microreliefs (protrusions 13 and recesses 14) is formed.

[0039] The fine uneven structure 12 may be, for example, a structure having nano-order fine unevenness formed on the surface of the base layer 10 (a so-called moth-eye structure). The pitch P (average period) of the unevenness of the fine uneven structure 12 is equal to or less than the wavelength of visible light (e.g., 380 to 830 nm). The fine uneven structure 12 has a function of suppressing light reflection on the surface of the antireflection film 1 (reflection suppression function). By providing such a fine uneven structure 12, the antireflection film 1 functions as an antireflection film.

[0040] The microrelief structure 12 is provided on at least one surface of the base layer 10. In the example of Fig. 1, the microrelief structure 12 is provided on only one surface (i.e., the front surface 10A) of the base layer 10. However, this is not limited to such an example, and for example, the microrelief structure 12 may be provided on both surfaces of the base layer 10 (i.e., the front surface 10A and the back surface 10B).

[0041] The fine uneven structure 12 has a plurality of convex portions 13 and a plurality of concave portions 14. The convex portions 13 are protruding structures that protrude vertically from the surface of the base material layer 10. The concave portions 14 are recessed portions between adjacent convex portions 13. The size and arrangement pitch P of the convex portions 13 are approximately several tens to several hundreds of nanometers (nanometer order), and are very fine.

[0042] In order for the microrelief structure 12 to exhibit its function of suppressing reflection of visible light and the like, the recesses and projections (protrusions 13 and recesses 14) of the microrelief structure 12 are arranged on the surface of the base material layer 10 at a pitch P that is equal to or less than the wavelength of visible light. In other words, the pitch P of the multiple protrusions 13 that make up the microrelief structure 12 is equal to or less than the wavelength of visible light. For example, when the wavelength range of visible light (i.e., the visible light range) is, for example, 380 to 830 nm, the pitch P is 380 nm or less.

[0043] By providing the microrelief structure 12 consisting of a plurality of convex portions 13 arranged at the above-described fine pitch P on the surface of the microrelief structure layer 11, a moth-eye structure with excellent anti-reflection performance for visible light can be formed on the surface of the antireflection film 1. This creates an effective refractive index gradient at the interface between the microrelief structure layer 11 and another layer laminated on the microrelief structure layer 11. Therefore, when light (visible light, etc.) enters the surface of the antireflection film 1 and passes through the microrelief structure 12, it is gently refracted, and surface reflection of light (visible light, etc.) is suppressed.

[0044] 1 , the microrelief structure 12 may be formed only on one surface (surface 10A) of the base layer 10, and the other surface (back surface 10B) may not be formed with the microrelief structure 12. This makes it possible to suppress reflection of incident light on the surface 10A of the base layer 10, and to suppress reflection of incident light on one surface of the antireflection film 1.

[0045] Furthermore, although not shown, if a fine uneven structure 12 is formed on both surfaces (front surface 10A and back surface 10B) of the base layer 10, it is possible to suppress reflection of incident light and outgoing light on the front surface 10A and back surface 10B of the base layer 10. Although not shown, the fine uneven structure 12 may be provided on one surface of the base layer 10, and a multilayer anti-reflection film may be provided on the other surface.

[0046] 1 , a large number of wavelength-converting nanoparticles 15 are dispersed within the microrelief structure 12 of the microrelief structure layer 11 (particularly within the convex portions 13). The wavelength-converting nanoparticles 15 are intended to impart the wavelength conversion function (up-conversion function or down-conversion function) of incident light to the anti-reflection film 1 according to this embodiment. Details of the wavelength-converting nanoparticles 15 will be described later.

[0047] 2. Configuration of the Microrelief Structure Next, the configuration of the microrelief structure 12 according to this embodiment will be described in more detail with reference to Fig. 2 to Fig. 6. Fig. 2 is a plan view showing the arrangement of a plurality of convex portions 13 of the microrelief structure 12 according to this embodiment. Fig. 3 is a plan view showing the arrangement of a plurality of convex portions 13 of the microrelief structure 12 according to a modified example of this embodiment. Figs. 4 to 6 are perspective views showing examples of the convex portions 13 of the microrelief structure 12 according to this embodiment.

[0048] The plurality of convex portions 13 of the microrelief structure 12 may be arranged regularly or irregularly on the surface (XY plane) of the base layer 10. Fig. 2 shows an example in which the plurality of convex portions 13 having an elliptical planar shape are arranged regularly. Fig. 3 shows an example in which the plurality of convex portions 13 having a circular planar shape are arranged regularly.

[0049] 2 and 3, in the microrelief structure 12 according to this embodiment, a plurality of convex portions 13 are regularly arranged in a hexagonal lattice pattern on the surface (on the XY plane) of the base layer 10. The convex portions 13 are arranged at predetermined intervals (dot pitch P) along a plurality of tracks T extending in the X direction. Ｄ The tracks T are imaginary lines that represent the arrangement direction of the convex portions 13. The tracks T are parallel to each other and are arranged at a predetermined interval (track pitch P) in the Y direction. Ｔ ) are arranged.

[0050] Here, the dot pitch P Ｄ is the pitch of the convex portions 13 along the track direction (X direction), which is the length direction of the track T. In other words, the dot pitch P Ｄis the distance between the vertices of two adjacent convex portions 13 in the track direction (X direction), and is equal to the pitch P (P Ｄ On the other hand, the track pitch P Ｔ is the pitch of the convex portions 13 along the track perpendicular direction (Y direction), which is a direction perpendicular to the track direction (X direction), and is equal to the interval between two tracks T, T adjacent to each other in the track perpendicular direction (Y direction). As shown in FIG. 2, when the convex portions 13 are arranged in a hexagonal lattice pattern, the track pitch P Ｔ is a value smaller than the pitch P (P Ｔ <P). Although not shown, when the convex portions 13 are arranged in a square lattice pattern, the dot pitch P Ｄ and track pitch P Ｔ is equal to the pitch P (P Ｄ =P Ｔ =P).

[0051] 2 and 3, the plurality of convex portions 13 are regularly arranged in a hexagonal lattice pattern along the plurality of tracks T. Therefore, between any two arbitrarily extracted convex portions 13, 13, the dot pitch P Ｄ is a nearly constant value, and the track pitch P Ｔ Also, when two rows of convex portions 13 arranged along two tracks T, T adjacent to each other in the Y direction are compared, the arrangement of the convex portions 13 in one row in the X direction is different from the arrangement of the convex portions 13 in the other row by the dot pitch P Ｄ Half of (P Ｄ In this way, the convex portion 13 is shifted in the X direction by P Ｄ By arranging the protrusions 13 with a shift of 1 / 2 in the X direction, the plurality of protrusions 13 are regularly arranged in a hexagonal lattice pattern throughout the fine uneven structure 12. This allows the protrusions 13 to be closest packed on the surface of the base layer 10, thereby increasing the packing rate of the protrusions 13. Therefore, the anti-reflection performance of the fine uneven structure 12 per unit area on the surface of the base layer 10 can be improved.

[0052] The filling rate is the percentage of the area occupied by the multiple convex portions 13 on the surface (XY plane) of the base layer 10. When the surface (flat surface) of the base layer 10 is completely filled with the multiple convex portions 13 and there are no flat surfaces between the convex portions 13, the filling rate is 100%. On the other hand, as shown in FIG. 2, when the multiple convex portions 13 are arranged on the surface (flat surface) of the base layer 10 with a certain amount of gap between them and there is a flat surface in the recess 14 between the multiple convex portions 13, the filling rate is less than 100%. Even when the multiple convex portions 13 are arranged with gaps between them as shown in FIG. 2, it is preferable to make the gaps as small as possible and increase the filling rate to, for example, 80% or more, preferably 90% or more. This can improve the anti-reflection performance of the fine concave-convex structure 12.

[0053] Furthermore, as shown in Figures 2 and 3, the microrelief structure 12 preferably has a hexagonal lattice arrangement on the surface of the substrate layer 10, in which multiple protrusions 13 are arranged at the vertices and centers of hexagons. This allows the multiple protrusions 13 to be arranged so as to be closely packed on the surface of the substrate layer 10 (on the XY plane), thereby improving the anti-reflection performance of the moth-eye structure. However, the multiple protrusions 13 of the microrelief structure 12 are not limited to the above-mentioned hexagonal lattice example, and may be regularly arranged in other modes, such as a square lattice, a rectangular lattice, or a triangular lattice. Alternatively, the multiple protrusions 13 may be irregularly arranged on the surface of the substrate layer 10. For example, the multiple protrusions 13 may be irregularly arranged at positions randomly shifted from the reference position within a predetermined range of variation, while using the above-mentioned various lattice-shaped arrangements as a reference.

[0054] [2.1. Preferred ranges of pitch P and height H of convex portions] The pitch P of the convex portions 13 of the fine concave-convex structure 12 may be a design value determined when the fine concave-convex structure 12 is designed, or may be an average pitch calculated from the measured values ​​of the pitch between a plurality of pairs of convex portions 13, 13. Specifically, the pitch P is the pitch of a plurality of pairs of adjacent convex portions 13, 13 (dot pitch P Ｄ or track pitch P ＴFor example, a plurality of pairs of two adjacent convex portions 13, 13 in the track direction (X direction) are picked up, and the dot pitch P Ｄ Then, the calculated or measured dot pitches P Ｄ The arithmetic mean value of the pitch P may be calculated.

[0055] The size of the pitch P is preferably equal to or less than the wavelength of visible light and less than the minimum value of the wavelength range of the visible light. For example, when the wavelength range of visible light (i.e., the visible light range) is, for example, 380 to 830 nm, the pitch P may be 380 nm or less, preferably 100 nm to 350 nm, more preferably 120 nm to 280 nm, and even more preferably 130 to 270 nm. This allows the fine uneven structure 12 to function favorably as a moth-eye structure that suppresses reflection of incident sunlight (visible light, near-infrared light, etc.) over a wide wavelength range.

[0056] However, if the pitch P is less than 100 nm, it is difficult to form the fine uneven structure 12 by nanoimprinting or the like, which is not preferable. Therefore, although the lower limit of the pitch P is not particularly limited, from the viewpoint of stably forming the fine uneven structure 12, the lower limit of the pitch P is preferably 100 nm or more. Furthermore, if the pitch P exceeds the lower limit of the wavelength of visible light incident on the perovskite solar cell 20 (e.g., 350 nm), diffraction of the incident visible light may occur, increasing the intensity of the diffracted light, and there is a risk of degrading the anti-reflection performance of the moth-eye structure. For this reason, it is not preferable for the pitch P to exceed the lower limit of the wavelength of visible light incident on the perovskite solar cell 20 (e.g., 350 nm). Therefore, from the viewpoint of improving the anti-reflection performance of visible light, it is preferable that the upper limit of the pitch P be equal to or less than the lower limit of the wavelength of the incident visible light (e.g., 350 nm). Note that the dot pitch P Ｄ and track pitch P Ｔ The sizes of the pitches P may be the same or different as long as they are within the preferred range of the pitch P described above.

[0057] The height H of the convex portions 13 is the distance in the Z direction from the bottom to the top of one convex portion 13 (height difference) (see FIGS. 4 to 6). The height H of the convex portions 13 is not particularly limited as long as it is on the nanometer order of less than 1 μm, but may be, for example, preferably 100 nm to 300 nm, more preferably 130 nm to 300 nm, and even more preferably 150 nm to 230 nm. If the height H of the convex portions 13 is too low below the lower limit, the anti-reflection performance of the micro-relief structure 12 is reduced, which is undesirable. On the other hand, if the height H of the convex portions 13 is too high above the upper limit, the mold releasability when molding the micro-relief structure 12 is reduced, which is undesirable.

[0058] The height H of the convex portions 13 may be a design value, or may be an average height calculated from the measured heights of the plurality of convex portions 13. The heights of a predetermined plurality of convex portions 13 in the fine concave-convex structure 12 may be measured, and the arithmetic mean value of the measured heights may be determined, and this arithmetic mean value may be used as the height H.

[0059] [2.2. Shape of the Convex Portions] As shown in Figures 4 to 6, the three-dimensional shape of the convex portions 13 of the microrelief structure 12 may be any shape, such as a cone shape (circular cone shape, elliptical cone shape, or pyramid shape), a truncated cone shape (circular cone shape, elliptical cone shape, or pyramid shape), a bell shape, a dome shape, or a protrusion or needle shape, as long as it protrudes in a direction perpendicular to the surface of the base layer 10 (Z direction). The planar shape of the convex portions 13 is preferably, for example, a circle (see Figure 3) or an ellipse (see Figure 2), but may also be any shape such as a polygon. The planar shape of the convex portions 13 is a planar shape that shows the outer shape of the convex portions 13 when the convex portions 13 are projected onto the surface of the base layer 10 (XY plane).

[0060] From the viewpoint of ease of molding, the three-dimensional shape of the protrusions 13 is preferably a three-dimensional shape whose planar shape is substantially elliptical (see FIG. 2). Specifically, the three-dimensional shape of the protrusions 13 is preferably a substantially elliptical cone shape (see FIG. 4), a truncated elliptical cone shape with a flat top (see FIG. 5), or a bell or dome shape whose planar shape is elliptical (see FIG. 6).

[0061] As such, the three-dimensional shape of the convex portions 13 is preferably a shape such as an elliptical cone obtained by stretching or shrinking a cone shape in the track direction (X direction). Thus, if the convex portions 13 have a three-dimensional shape having an elliptical planar shape (see FIG. 2 ), it becomes easier to efficiently manufacture a microrelief structure 12 having a large number of such convex portions 13. For example, according to a manufacturing method of the master 100 using the laser exposure method described below (see FIG. 14 ), the planar shape of the recesses 123 (see FIG. 13 ) of the microrelief structure 120 formed on the outer peripheral surface of the roll-shaped master 100 tends to be elliptical, and it is difficult to make them perfectly circular. The recesses 123 of the microrelief structure 120 of this master 100 have an inverted shape of the convex portions 13 of the microrelief structure 12 of the anti-reflection film 1. Therefore, if the shape of the convex portions 13 of the fine uneven structure 12 formed by the roll-shaped master 100 is allowed to be a three-dimensional shape having an elliptical planar shape, it becomes possible to easily and highly precisely manufacture the fine uneven structure 12 having the elliptical convex portions 13 by utilizing the master manufacturing method using the laser exposure method.

[0062] In this specification, "substantially elliptical" is not limited to a geometrically strict elliptical shape, but is a concept that includes shapes that can be roughly regarded as an ellipse, such as an oval shape, an egg shape, etc. Similarly, "substantially an elliptical cone shape" or "elliptical truncated cone shape" is not limited to a geometrically strict elliptical cone shape or an elliptical truncated cone shape, but is a concept that includes shapes that can be roughly regarded as an elliptical cone or an elliptical truncated cone (for example, a shape distorted by stretching or shrinking a cone shape or a truncated cone shape in the track direction (X direction)).

[0063] [2.3. Material of the Microrelief Structure] Although details will be described later, the microrelief structure 12 is formed, for example, by roll-to-roll imprinting using a roll-shaped master 100 (hereinafter sometimes referred to as the "roll master 100") shown in FIG. 13 (described later). The recessed and projected shape formed on the outer peripheral surface of the roll master 100 has an inverted shape of the microrelief structure 12. The recessed and projected shape on the outer peripheral surface of the roll master 100 is transferred to an uncured resin layer laminated on the surface of the substrate layer 10, and the uncured resin layer is then cured to form the microrelief structure 12. In this way, by using the roll master 100 to transfer the microrelief structure 12 to the surface of the substrate layer 10 of the antireflection film 1, an antireflection film 1 having antireflection properties can be easily manufactured. In order to manufacture the antireflection film 1 using such an imprinting technique, the fine relief structure 12 may be formed, for example, in a resin layer laminated on the surface of the base layer 10, or may be formed in a resin layer that constitutes the base layer 10. The resin layer in which the fine relief structure 12 is formed is made of, for example, a cured product of a curable resin.

[0064] The cured product of the curable resin preferably has transparency. The curable resin contains a polymerizable compound and a curing initiator. The polymerizable compound is a resin that is cured by the curing initiator. Examples of the polymerizable compound include epoxy polymerizable compounds and acrylic polymerizable compounds. The epoxy polymerizable compound is a monomer, oligomer, or prepolymer having one or more epoxy groups in the molecule. Examples of the epoxy polymerizable compound include various bisphenol-type epoxy resins (bisphenol A type, F type, etc.), novolac-type epoxy resins, various modified epoxy resins such as rubber and urethane, naphthalene-type epoxy resins, biphenyl-type epoxy resins, phenol novolac-type epoxy resins, stilbene-type epoxy resins, triphenolmethane-type epoxy resins, dicyclopentadiene-type epoxy resins, triphenylmethane-type epoxy resins, and prepolymers thereof.

[0065] The acrylic polymerizable compound is a monomer, oligomer, or prepolymer having one or more acrylic groups in the molecule. Here, the monomer is further classified into a monofunctional monomer having one acrylic group in the molecule, a bifunctional monomer having two acrylic groups in the molecule, and a polyfunctional monomer having three or more acrylic groups in the molecule.

[0066] Examples of "monofunctional monomers" include carboxylic acids (acrylic acid), hydroxyls (2-hydroxyethyl acrylate, 2-hydroxypropyl acrylate, 4-hydroxybutyl acrylate), alkyl or alicyclic monomers (isobutyl acrylate, t-butyl acrylate, isooctyl acrylate, lauryl acrylate, stearyl acrylate, isobornyl acrylate, cyclohexyl acrylate), and other functional monomers (2-methoxyethyl acrylate, methoxyethylene glycol acrylate, 2-ethoxyethyl acrylate, tetrahydrofurfuryl acrylate, benzyl acrylate, ethyl carbitol acrylate, phenoxyethyl acrylate, N,N-dimethylaminoethyl acrylate). , N,N-dimethylaminopropylacrylamide, N,N-dimethylacrylamide, acryloylmorpholine, N-isopropylacrylamide, N,N-diethylacrylamide, N-vinylpyrrolidone, 2-(perfluorooctyl)ethyl acrylate, 3-perfluorohexyl-2-hydroxypropyl acrylate, 3-perfluorooctyl-2-hydroxypropyl acrylate, 2-(perfluorodecyl)ethyl acrylate, 2-(perfluoro-3-methylbutyl)ethyl acrylate), 2,4,6-tribromophenol acrylate, 2,4,6-tribromophenol methacrylate, 2-(2,4,6-tribromophenoxy)ethyl acrylate), 2-ethylhexyl acrylate, and the like.

[0067] Examples of the "bifunctional monomer" include tri(propylene glycol) diacrylate, trimethylolpropane diallyl ether, and urethane acrylate.

[0068] Examples of the "polyfunctional monomer" include trimethylolpropane triacrylate, dipentaerythritol penta- and hexaacrylate, and ditrimethylolpropane tetraacrylate.

[0069] Examples of the acrylic polymerizable compound other than those listed above include acrylic morpholine, glycerol acrylate, polyether acrylate, N-vinylformamide, N-vinylcaprolactone, ethoxydiethylene glycol acrylate, methoxytriethylene glycol acrylate, polyethylene glycol acrylate, EO-modified trimethylolpropane triacrylate, EO-modified bisphenol A diacrylate, aliphatic urethane oligomer, polyester oligomer, etc. From the viewpoint of the transparency of the antireflection film 1, the polymerizable compound is preferably an acrylic polymerizable compound.

[0070] A curing initiator is a material that hardens a curable resin. Examples of curing initiators include a heat-curing initiator and a photo-curing initiator. The curing initiator may be one that hardens by heat, some kind of energy ray other than light (e.g., electron beam), or the like. When the curing initiator is a heat-curing initiator, the curable resin is a thermosetting resin. When the curing initiator is a photo-curing initiator, the curable resin is a photo-curable resin.

[0071] Here, from the viewpoint of the transparency of the antireflection film 1, the curing initiator is preferably an ultraviolet curing initiator. Therefore, the curable resin is preferably an ultraviolet curing acrylic resin. The ultraviolet curing initiator is a type of photocuring initiator. Examples of the ultraviolet curing initiator include 2,2-dimethoxy-1,2-diphenylethan-1-one, 1-hydroxy-cyclohexyl phenyl ketone, and 2-hydroxy-2-methyl-1-phenylpropan-1-one.

[0072] The resin forming the fine uneven structure 12 may be a resin that has been given functionality such as hydrophilicity, water repellency, and anti-fogging properties.

[0073] The resin forming the microrelief structure 12 may contain additives according to the intended use of the anti-reflection film 1. Examples of such additives include inorganic fillers, organic fillers, leveling agents, surface conditioners, and antifoaming agents. Examples of the inorganic fillers include SiO ２ , TiO ２ , ZrO ２ , SnO ２ , Al ２ O ３ and other metal oxide fine particles.

[0074] As described above, the resin forming the microrelief structure 12 is preferably, for example, a photocurable resin composition. The photocurable resin composition is a resin that hardens when irradiated with light of a predetermined wavelength. Specifically, the photocurable resin composition may be an ultraviolet-curable resin such as an acrylic resin acrylate or an epoxy acrylate. Furthermore, the photocurable resin composition may contain an initiator, a filler, a functional additive, a solvent, an inorganic material, a pigment, a static inhibitor, or a sensitizing dye, as necessary.

[0075] The microrelief structure 12 may be formed directly on a resin layer (microrelief structure layer 11) laminated on the surface of the base layer 10 by imprinting using the roll master 100 as described above. However, without being limited to such an example, for example, a resin film (e.g., a thermoplastic resin film) on which the microrelief structure 12 is formed may be adhered to the surface of the base layer 10 as the microrelief structure layer 11.

[0076] 7 and 8, the overall configuration of the perovskite solar cell 20 according to this embodiment will be described. Fig. 7 is a cross-sectional view showing the perovskite solar cell 20 according to this embodiment. Fig. 8 is a partially enlarged cross-sectional view showing a solar cell 30 according to this embodiment.

[0077] The perovskite solar cell 20 is a solar cell manufactured using a compound having a perovskite crystal structure. Perovskite has the general formula R-M-X, like the crystal structure of perovskite. ３(where R is an organic molecule, M is a metal atom, and X is a halogen atom or a chalcogen atom.) Compounds having this crystal structure are collectively referred to as "perovskite compounds." Compared to conventional silicon-based solar cells, perovskite solar cells 20 have advantages such as being lighter, thinner, and less expensive, being able to generate electricity even with weak light, and being flexible, allowing them to be used in a variety of shapes and applications. For this reason, perovskite solar cells 20 can be used in a variety of items and applications, such as building windows and walls, electric vehicles, drones, wearable items such as clothing, bags, hats, glasses, and watches, wearable devices, portable terminals such as smartphones and tablet PCs, agricultural greenhouses, and indoor items. To popularize perovskite solar cells 20 with these characteristics, improving their power generation efficiency is desirable.

[0078] Therefore, in this embodiment, the objective is to improve the power generation efficiency of the perovskite solar cell 20 from two perspectives: suppressing reflection of incident light inside the solar cell 30 (first perspective), and effectively utilizing unused light from the incident light (second perspective).

[0079] That is, in the perovskite solar cell 20 according to this embodiment, as shown in Figures 7 and 8, the microrelief structure layer 11 of the antireflection film 1 (see Figure 1) described above is disposed inside the stack of solar cells 30. In this case, the microrelief structure layer 11 is disposed at the interface between multiple layers with different refractive indices inside the stack of solar cells 30 (for example, the interface between the base layer 10 and the transparent electrode layer 32 shown in Figure 8). As shown in Figure 1, the microrelief structure layer 11 has a microrelief structure 12, which contains a large number of wavelength-converting nanoparticles 15 dispersed therein. Such a microrelief structure 12 reduces the reflection of incident light at the layer interfaces inside the solar cells 30 (first aspect), and the wavelength-converting nanoparticles 15 in the microrelief structure 12 convert near-infrared light, which is unused light from the incident sunlight, into visible light (second aspect). This allows incident light with reduced reflection to be efficiently introduced into the photoelectric conversion layer (perovskite layer 34) and effectively used for power generation, and also allows unused light (e.g., near-infrared light) to be effectively used for power generation. Therefore, the synergistic effect of the above two aspects can significantly improve the power generation efficiency of the perovskite solar cell 20. Below, the configuration of the perovskite solar cell 20 for achieving this synergistic effect will be described in detail.

[0080] As shown in FIG. 7 , the perovskite solar cell 20 according to this embodiment includes a transparent protective sheet 21, a sealing layer 26, a back sheet 27, and a stack (solar cell stack) of at least one solar cell 30. The transparent protective sheet 21 includes, for example, a weather-resistant layer 22, a UV absorption layer 23, a barrier layer 24, and a substrate layer 25. The weather-resistant layer 22, the UV absorption layer 23, the barrier layer 24, the substrate layer 25, the sealing layer 26, and the back sheet 27 are stacked in this order. One or more solar cells 30 are sealed within the sealing layer 26. The perovskite solar cell 20 is composed of a stack in which the transparent protective sheet 21, the sealing layer 26, the back sheet 27, and the solar cell 30 are stacked. The perovskite solar cell 20 as a whole constitutes a flexible, plate-shaped solar cell panel.

[0081] The backsheet 27 is a sheet formed of a base resin layer made of, for example, a fluorine-based resin, and is a layer that serves as the base material for the entire perovskite solar cell 20. The backsheet 27 has the function of supporting the transparent protective sheet 21, the sealing layer 26, and the solar cell 30, and the function of maintaining waterproofness for the non-light-receiving side (back side) of the perovskite solar cell 20. The backsheet 27 corresponds to a back protective sheet that protects the back side of the perovskite solar cell 20. For excellent water vapor barrier properties, it is preferable that the backsheet 27 further include a waterproof layer made of Al or the like.

[0082] The encapsulation layer 26 is laminated on the backsheet 27 and functions to encapsulate one or more solar cell units 30. In the example of FIG. 7 , multiple solar cell units 30 are arranged at predetermined intervals in the surface direction (X direction) within the encapsulation layer 26. The encapsulation layer 26 surrounds and encapsulates the entire solar cell units 30. The thickness (Z direction) of the encapsulation layer 26 is sufficiently greater than the thickness of the solar cell units 30. The encapsulation layer 26 prevents moisture, such as humidity, from entering the solar cell units 30 and suppresses deterioration of the perovskite solar cell 20. As shown in FIG. 7 , the encapsulation layer 26 may be composed of a front-side encapsulation layer 26A and a back-side encapsulation layer 26B. The front-side encapsulation layer 26A encapsulates the front half of the solar cell unit 30, and the back-side encapsulation layer 26B encapsulates the back half of the solar cell unit 30. The solar cell unit 30 is sandwiched between the front-side encapsulation layer 26A and the back-side encapsulation layer 26B.

[0083] The material of the sealant forming the sealing layer 26 is preferably a resin, such as EVA resin (ethylene-vinyl acetate copolymer resin). Other sealant materials may include, for example, thermoplastic resins, thermosetting resins, or photocurable resins. The refractive index of these resins is not particularly limited, but is typically approximately 1.42 to 1.60. Examples of the thermoplastic resin include butyl rubber, polyester, polyurethane, polyethylene, polypropylene, polyvinyl chloride, polystyrene, polyvinyl alcohol, polyvinyl acetate, ABS resin, polybutadiene, polyamide, polycarbonate, polyimide, polyisobutylene, and cycloolefin resins. Examples of the thermosetting resin include epoxy resins, acrylic resins, silicone resins, phenolic resins, melamine resins, and urea resins. Examples of the photocurable resin include epoxy resins, acrylic resins, allyl phthalate resins, vinyl resins, and ene-thiol resins. Among these, acrylic resins are preferred from the viewpoints of transparency and barrier properties.

[0084] The transparent protective sheet 21 is laminated on the sealing layer 26. The transparent protective sheet 21 corresponds to a light-receiving surface protective sheet that protects the light-receiving surface side (front side) of the perovskite solar cell 20. The transparent protective sheet 21 is preferably made of a transparent material that transmits incident light. The transparent protective sheet 21 may be composed of a laminate sheet in which, for example, a weather-resistant layer 22, a UV absorbing layer 23, a barrier layer 24, and a base layer 25 are laminated in this order.

[0085] The base material layer 25 is laminated on the sealing layer 26 and is formed of a thermoplastic resin such as polyethylene naphthalate (PEN) or polyethylene terephthalate (PET). The base material layer 25 is preferably a resin that is transparent and weather-resistant. By providing various conventionally known adhesive layers or the like on both sides of the base material layer 25, the barrier layer 24 and the sealing layer 26 can be easily bonded via the base material layer 25.

[0086] The barrier layer 24 is laminated on the substrate layer 25. The barrier layer 24 is a layer having barrier properties such as water vapor barrier properties. The barrier layer 24 functions, for example, as a water vapor barrier layer that protects the perovskite solar cell 20 from water vapor and the like. The barrier layer 24 may be composed of, for example, a barrier film in which an inorganic film is formed on the surface of a barrier film resin substrate. The inorganic film of the barrier layer 24 is formed, for example, by a vapor deposition film of an inorganic material such as a metal oxide, or by a coating of a metal or other inorganic material. By providing the barrier layer 24, a high degree of weather resistance can be exhibited in the perovskite solar cell 20, which is expected to be used for long periods in harsh humid and hot environments.

[0087] The UV absorbing layer 23 is laminated on the barrier layer 24. The UV absorbing layer 23 may be, for example, a layer made of a UV absorbing resin film formed from a resin having UV absorbing properties, or may be a layer in which a UV absorber is mixed into an adhesive layer. The UV absorbing layer 23 is formed, for example, by dispersing various conventionally known organic or inorganic UV absorbers, either alone or in a mixture of multiple types, in a binder resin. The UV absorbing layer 23 functions to absorb ultraviolet light (UV) from sunlight incident on the perovskite solar cell 20. This UV absorbing layer 23 can prevent the components of the solar cell 30 from being deteriorated by ultraviolet light. For example, it can prevent the wavelength conversion nanoparticles 15 (e.g., fine particles of an upconversion phosphor) contained in the microrelief structure 12 of the solar cell 30 from being deteriorated by ultraviolet light.

[0088] The weather-resistant layer 22 is laminated on the UV absorbing layer 23 and is disposed on the outermost surface of the perovskite solar cell 20. The weather-resistant layer 22 may be, for example, a weather-resistant fluororesin layer formed from a fluorine-based resin, and has excellent weather resistance, chemical resistance, heat resistance, water repellency, and the like. The weather-resistant layer 22 has the function of protecting the layers 23 to 26 constituting the perovskite solar cell 20 and the solar cell 30. By providing the weather-resistant layer 22, the weather resistance of the perovskite solar cell 20 can be improved, and dirt on the outermost surface on the light-receiving surface side can be easily removed.

[0089] The perovskite solar cell 20 may not include some or all of the above-mentioned weather-resistant layer 22, UV absorption layer 23, barrier layer 24, substrate layer 25, and back sheet 27. Furthermore, the perovskite solar cell 20 may further include, in addition to the above-mentioned layers, a mesoporous oxide layer, for example.

[0090] 8 to 10, a description will be given of a stack (solar cell stack) of solar cells 30 provided in a perovskite solar cell 20 according to this embodiment. Fig. 9 is a partially enlarged cross-sectional view showing a solar cell 30A according to Reference Example 1 of this embodiment (an example in which a microrelief structure layer 11 is not provided). Fig. 10 is a partially enlarged cross-sectional view showing a solar cell 30B according to Reference Example 2 of this embodiment (an example in which a microrelief structure layer 11 does not contain wavelength-converting nanoparticles 15).

[0091] 8 , a solar cell 30 according to this embodiment is a laminate in which a base material layer 10, a microrelief structure layer 11, a transparent electrode layer 32 (first electrode layer), an electron transport layer 33, a perovskite layer 34 (photoelectric conversion layer), a hole transport layer 35, and a metal electrode layer 36 (second electrode layer) are laminated in this order.

[0092] On the other hand, as shown in Fig. 9 , solar cell 30A according to Reference Example 1 is a laminate in which a base material layer 10, a transparent electrode layer 32, an electron transport layer 33, a perovskite layer 34, a hole transport layer 35, and a metal electrode layer 36 are laminated in this order. However, solar cell 30A according to Reference Example 1 differs from solar cell 30 according to the present embodiment ( Fig. 8 ) in that it does not include a microrelief structure layer 11. Furthermore, as shown in Fig. 10 , solar cell 30B according to Reference Example 2 is a laminate in which a base material layer 10, a microrelief structure layer 11, a transparent electrode layer 32, an electron transport layer 33, a perovskite layer 34, a hole transport layer 35, and a metal electrode layer 36 are laminated in this order. However, solar cell 30B according to Reference Example 2 differs from solar cell 30 according to the present embodiment ( Fig. 8 ) in that the microrelief structure layer 11 does not contain wavelength-converting nanoparticles 15.

[0093] Here, all of the solar cells 30, 30A, and 30B shown in Figures 8 to 10 are solar cells with a planar structure. In a solar cell with a planar structure, an electron transport layer 33 is disposed closer to the light-receiving surface than a perovskite layer 34, which is a photoelectric conversion layer (upper side in Figures 8 to 10), and a hole transport layer 35 is disposed on the opposite side of the light-receiving surface than the perovskite layer 34 (lower side in Figures 8 to 10). Therefore, in the solar cells 30 and 30B with a planar structure shown in Figures 8 and 10, a base layer 10, a microrelief structure layer 11, a transparent electrode layer 32, an electron transport layer 33, a perovskite layer 34, a hole transport layer 35, and a metal electrode layer 36 are stacked in this order from the light-receiving surface side of the solar cell 30 and 30B (i.e., from the top of the figures).

[0094] As described above, in the solar cell 30 ( FIG. 8 ) according to this embodiment and the solar cell 30B ( FIG. 10 ) according to Reference Example 2, a microrelief structure layer 11 is interposed between the base layer 10 and the transparent electrode layer 32. On the other hand, in the solar cell 30A ( FIG. 9 ) according to Reference Example 1, a microrelief structure layer 11 is not provided between the base layer 10 and the transparent electrode layer 32. Furthermore, in the solar cell 30 ( FIG. 8 ) according to this embodiment, wavelength-converting nanoparticles 15 are dispersed within the microrelief structure layer 11. On the other hand, in the solar cell 30B ( FIG. 10 ) according to Reference Example 2, wavelength-converting nanoparticles 15 are not contained within the microrelief structure layer 11. Thus, the solar cell 30 ( FIG. 8 ) according to this embodiment differs from Reference Examples 1 and 2 ( FIGS. 9 and 10 ) in that it includes a microrelief structure layer 11 that includes wavelength-converting nanoparticles 15. The differences in action and effect resulting from these differences will be described later.

[0095] Hereinafter, each layer constituting the stack of solar cell 30 according to this embodiment will be described with reference to FIG.

[0096] (1) Substrate Layer 10 and Microrelief Structure Layer 11 (Anti-Reflection Film 1) As shown in FIG. 8 , the substrate layer 10 is the outermost layer of the solar cell 30, arranged on the light-receiving surface side (the uppermost side in FIG. 8 ), and is in contact with the sealing layer 26. The substrate layer 10 is formed of a resin such as PET, and functions as a base material supporting the entire solar cell 30. The microrelief structure layer 11 is laminated on the substrate layer 10. A microrelief structure 12 is formed on the surface of the microrelief structure layer 11. The substrate layer 10 and the microrelief structure layer 11 correspond to the anti-reflection film 1 described above (see FIG. 1 ). Therefore, detailed description of the substrate layer 10 and the microrelief structure layer 11 will be omitted.

[0097] The thickness of the substrate layer 10 is not particularly limited, but is preferably 0.1 to 1000 μm, and more preferably 0.5 to 100 μm, for example. This has the effect of facilitating handling during manufacturing and preventing excess light loss. The thickness of the microrelief structure layer 11 is also not particularly limited, but is preferably 10 to 400 nm, and more preferably 50 to 300 nm, for example. This has the effect of allowing wavelength-converting nanoparticles 15 to be appropriately dispersed in the microrelief structure layer 11, while exhibiting excellent anti-reflection properties.

[0098] The refractive index of the base material layer 10 is not particularly limited, but is preferably 1.5 to 1.7, and more specifically, may be approximately 1.58. It is preferable that the difference between the refractive index of the sealing layer 26 (e.g., n = 1.6) and the refractive index of the base material layer 10 (e.g., n = 1.58) is as small as possible. This makes it possible to suppress reflection of incident light at the interface between the base material layer 10 and the sealing layer 26.

[0099] The refractive index of the microrelief structure layer 11 is not particularly limited, but is preferably, for example, about 1.5 to 1.7, and specifically may be about 1.58. The difference between the refractive index of the base layer 10 and the refractive index of the microrelief structure layer 11 is preferably as small as possible, for example, preferably 0.1 or less. This makes it possible to suppress reflection of incident light at the interface between the base layer 10 and the microrelief structure layer 11. The refractive index of each layer can be measured using, for example, a spectroscopic ellipsometer, an automatic thin film measuring device, or the like.

[0100] Furthermore, one surface of the microrelief structure layer 11 (the upper surface in FIG. 8 ) is flat and does not have the microrelief structure 12 formed thereon. Therefore, the upper surface of the microrelief structure layer 11 is in contact with the lower surface of the base material layer 10 at a flat surface. That is, the interface between the base material layer 10 and the microrelief structure layer 11 is flat.

[0101] On the other hand, a microrelief structure 12 is formed on the other surface (the lower surface in FIG. 8 ) of the microrelief structure layer 11, forming a rough surface. Therefore, the lower surface of the microrelief structure layer 11 contacts the upper surface of the transparent electrode layer 32 via a rough surface. In other words, the interface between the microrelief structure layer 11 and the transparent electrode layer 32 is a rough surface following the microrelief structure 12.

[0102] Furthermore, numerous wavelength-converting nanoparticles 15 are dispersed within the microrelief structure 12 of the microrelief structure layer 11. The wavelength-converting nanoparticles 15 are nano-sized particles (e.g., with an average particle size of less than 1 μm) that have the function of converting the wavelength of incident light. The wavelength-converting nanoparticles 15 have the function of converting, for example, at least a portion of near-infrared light having a predetermined wavelength or longer (e.g., near-infrared light having a wavelength of 830 to 1800 nm) into visible light having a predetermined wavelength or shorter (e.g., visible light having a wavelength of 380 to 830 nm). This conversion function is referred to as an "upconversion function." When the wavelength-converting nanoparticles 15 have the upconversion function, the material of the wavelength-converting nanoparticles 15 may be, for example, an upconversion phosphor.

[0103] Wavelength-converting nanoparticles 15 may have the function of converting ultraviolet light of a predetermined wavelength or less (e.g., ultraviolet light with a wavelength of 280 to 380 nm) into visible light of a predetermined wavelength or more (e.g., visible light with a wavelength of 380 to 830 nm). This conversion function is referred to as a "down-conversion function." In this case, the material of wavelength-converting nanoparticles 15 may be, for example, a down-conversion phosphor. Details of the material of wavelength-converting nanoparticles 15 will be described later.

[0104] (2) Transparent Electrode Layer 32 The transparent electrode layer 32 (first electrode layer) is laminated on the microrelief structure layer 11. The transparent electrode layer 32 (first electrode layer) is an opposing electrode to the metal electrode layer 36 (second electrode layer). The transparent electrode layer 32, together with the metal electrode layer 36, constitutes a pair of electrodes of the solar cell 30. In a solar cell 30 with a planar structure, the transparent electrode layer 32 on the light-receiving surface side is the negative electrode (negative electrode), and the metal electrode layer 36 on the opposite side from the light-receiving surface is the positive electrode (positive electrode). The transparent electrode layer 32 has the function of collecting electrons from the electron transport layer 33 and transmitting them to an external circuit. The transparent electrode layer 32 is disposed closer to the light-receiving surface (upper side in FIG. 8 ) than the perovskite layer 34, which is a photoelectric conversion layer. Therefore, sunlight incident on the solar cell 30 from the light-receiving surface side passes through the transparent electrode layer 32 and the electron transport layer 33 and toward the perovskite layer 34.

[0105] For this reason, the transparent electrode layer 32 is preferably formed of a transparent material (e.g., a conductive transparent material, a conductive transparent polymer, etc.) that is conductive and has excellent transmittance for sunlight, particularly for visible light. The visible light transmittance of the transparent electrode layer 32 is preferably, for example, 70% or more. On the other hand, the upper limit of the visible light transmittance of the transparent electrode layer 32 is not particularly limited, but may be, for example, 95% or less.

[0106] Examples of materials that can be used for the transparent electrode layer 32 include transparent materials such as ITO (indium tin oxide), FTO (fluorine-doped tin oxide), AZO (aluminum zinc oxide), GZO (gallium zinc oxide), and IZO (indium zinc oxide), as well as metal mesh and silver nanoparticles. These materials may be used alone or in combination of two or more.

[0107] Of the two electrode layers (first electrode layer and second electrode layer) included in the solar cell 30, the first electrode layer is provided closer to the light-receiving surface than the perovskite layer 34 (upper side in FIGS. 8 to 10 ). The first electrode layer is preferably formed of the various transparent materials described above, like the transparent electrode layer 32. However, the first electrode layer is not limited to this example. For example, like the metal electrode layer 36 (second electrode layer) described below, the first electrode layer may be formed of various metals, a laminate containing a metal, a metal mesh, AgNW (Ag nanowires), PEDOT (conductive polymer), or the like.

[0108] The thickness of the transparent electrode layer 32 is not particularly limited as long as it is a thickness that allows the transparent electrode to maintain a visible light transmittance of, for example, 70% or more, but in order to obtain good conductivity, it is preferably 1 nm or more, more preferably 5 nm or more, and specifically may be about 20 nm. On the other hand, in order to prevent a decrease in the light transmittance of the transparent electrode layer 32 and a decrease in the amount of light incident on the perovskite layer 34, the thickness of the transparent electrode layer 32 is preferably 60 nm or less, and more preferably 40 nm or less.

[0109] The refractive index of the transparent electrode layer 32 is not particularly limited, but is preferably, for example, 1.8 to 2.2. Specifically, when the transparent electrode layer 32 is formed of ITO, the refractive index of the transparent electrode layer 32 may be, for example, approximately 1.9. Note that the fine unevenness structure 12 is provided at the interface between the transparent electrode layer 32 and the fine unevenness structure layer 11, so that reflection of incident light at the interface can be suppressed. Therefore, even if there is a difference between the refractive index of the fine unevenness structure layer 11 and the refractive index of the transparent electrode layer 32, there is almost no problem with reflection of incident light.

[0110] As shown in FIG. 8 , when the transparent electrode layer 32 according to this embodiment is laminated on the microrelief structure layer 11, it is laminated so as to follow the microrelief structure 12 of the microrelief structure layer 11. Therefore, a microrelief structure corresponding to the microrelief structure 12 is formed on both the upper and lower surfaces of the transparent electrode layer 32. The upper surface of the transparent electrode layer 32 is in contact with the lower surface of the microrelief structure layer 11 (i.e., the surface of the microrelief structure 12) via an uneven surface. Meanwhile, the lower surface of the transparent electrode layer 32 is in contact with the upper surface of the electron transport layer 33 via an uneven surface. In this way, the interface between the microrelief structure layer 11 and the transparent electrode layer 32 is the uneven surface of the microrelief structure 12, and the interface between the transparent electrode layer 32 and the electron transport layer 33 is also an uneven surface following the microrelief structure 12.

[0111] (3) Electron Transport Layer 33 The electron transport layer 33 is laminated on the transparent electrode layer 32 and disposed between the transparent electrode layer 32 and the perovskite layer 34. The electron transport layer 33 has the function of collecting electrons generated in the perovskite layer 34 and transporting them to the transparent electrode layer 32, and the function of preventing the flow of holes.

[0112] The material of the electron transport layer 33 is, for example, titanium oxide (TiO ２ ), tin oxide (SnO ２ ) or other n-type semiconductors can be used. However, the material of the electron transport layer 33 is not limited to these examples and may be, for example, an n-type conductive polymer, an n-type small molecule organic semiconductor, an n-type metal oxide, an n-type metal sulfide, an alkali metal halide, an alkali metal, a surfactant, or the like. Specifically, for example, the material may be a cyano group-containing polyphenylene vinylene, a boron-containing polymer, bathocuproine, bathophenanthrene, hydroxyquinolinatoaluminum, an oxadiazole compound, a benzimidazole compound, or the like. Furthermore, for example, the material may be a naphthalene tetracarboxylic acid compound, a perylene derivative, a phosphine oxide compound, a phosphine sulfide compound, a fluoro group-containing phthalocyanine, titanium oxide, zinc oxide, indium oxide, tin oxide, gallium oxide, tin sulfide, indium sulfide, zinc sulfide, or the like.

[0113] The electron transport layer 33 may consist of, for example, only a thin-film electron transport layer, but preferably includes a porous electron transport layer. In particular, when the perovskite layer 34 is a composite film formed by combining an organic semiconductor or inorganic semiconductor portion with an organic-inorganic perovskite compound portion, a more complex composite film (a more intricately intricate structure) is obtained, resulting in higher photoelectric conversion efficiency. Therefore, it is preferable that a composite film of the perovskite layer 34 be formed on the porous electron transport layer 33.

[0114] The thickness of the electron transport layer 33 is preferably, for example, 1 nm or more, which allows for sufficient hole blocking. The thickness of the electron transport layer 33 is preferably, for example, 2000 nm or less, which prevents resistance during electron transport and increases photoelectric conversion efficiency. The thickness of the electron transport layer 33 is more preferably 3 nm or more and 1000 nm or less, and even more preferably 5 nm or more and 500 nm or less. The thickness of the electron transport layer 33 may be, for example, approximately 20 nm.

[0115] The refractive index of the electron transport layer 33 is not particularly limited, but is preferably, for example, 2.4 to 2.8. Specifically, when the electron transport layer 33 is formed of titanium oxide, the refractive index of the electron transport layer 33 may be, for example, approximately 2.6. Furthermore, by forming the transparent electrode layer 32 to conform to the microrelief structure 12, if a microrelief structure is also present at the interface between the transparent electrode layer 32 and the electron transport layer 33, reflection at the interface can be suppressed. Therefore, even if there is a difference between the refractive index of the transparent electrode layer 32 and the refractive index of the electron transport layer 33, there is almost no problem with reflection of incident light. On the other hand, when the transparent electrode layer 32 does not conform to the microrelief structure 12 and the interface between the transparent electrode layer 32 and the electron transport layer 33 is a flat surface, it is preferable that the difference between the refractive index of the transparent electrode layer 32 and the refractive index of the electron transport layer 33 be as small as possible. This can suppress reflection of incident light at the interface between the transparent electrode layer 32 and the electron transport layer 33.

[0116] As shown in FIG. 8 , when the electron transport layer 33 according to this embodiment is laminated on the microrelief structure layer 11 together with the transparent electrode layer 32, it is laminated so as to follow the microrelief structure 12 of the microrelief structure layer 11. Therefore, a microrelief structure corresponding to the microrelief structure 12 is formed on both the upper and lower surfaces of the electron transport layer 33. The upper surface of the electron transport layer 33 is in contact with the lower surface of the transparent electrode layer 32 via a rough surface. Meanwhile, the lower surface of the electron transport layer 33 is in contact with the upper surface of the perovskite layer 34 via a rough surface. In this way, the interface between the transparent electrode layer 32 and the electron transport layer 33 is an uneven surface following the microrelief structure 12, and the interface between the electron transport layer 33 and the perovskite layer 34 is also an uneven surface following the microrelief structure 12.

[0117] (4) Perovskite Layer 34 The perovskite layer 34 is stacked on the electron transport layer 33. The perovskite layer 34 functions as a photoelectric conversion layer (power generation layer) that converts light into electricity, absorbing sunlight to generate electrons and holes. The perovskite layer 34 is made of perovskite crystals formed from organic and inorganic materials. The perovskite crystals in the perovskite layer 34 absorb light, and the light energy generates negatively charged electrons and positively charged holes within the perovskite crystals. The electrons generated in the perovskite layer 34 are extracted to the transparent electrode layer 32 via the electron transport layer 33. Similarly, the holes generated in the perovskite layer 34 are extracted to the metal electrode layer 36 via the hole transport layer 35.

[0118] The perovskite layer 34 may be formed of a perovskite compound having perovskite crystals. The perovskite compound is not particularly limited, and any known perovskite compound may be used. When the perovskite layer 34 is formed using a perovskite compound, a porous film such as titanium oxide may be provided as an underlayer of a hybrid compound of an organic material and an inorganic material.

[0119] The perovskite layer 34 may also be formed of a laminated structure of semiconductor compounds. The layer configuration of this laminated structure may be, for example, a thin film laminated type in which a layer containing a p-type semiconductor compound and a layer containing an n-type semiconductor compound are laminated, or a bulk heterojunction type in which a layer (mixed layer) of a p-type semiconductor compound and an n-type semiconductor compound is mixed.

[0120] The p-type organic semiconductor compound may be, for example, a p-type small molecule organic semiconductor compound, a p-type organic semiconductor oligomer, a p-type organic semiconductor polymer, or the like. Specifically, the p-type small molecule organic semiconductor compound may be, for example, a porphyrin compound such as tetrabenzoporphyrin, tetrabenzocopperporphyrin, or tetrabenzozincporphyrin; a phthalocyanine compound such as phthalocyanine, copper phthalocyanine, or zinc phthalocyanine; a naphthalocyanine compound; or a polyacene such as tetracene or pentacene. The p-type organic semiconductor oligomer may be, for example, an oligothiophene such as sexithiophene, or a derivative containing these compounds as a skeleton. The p-type organic semiconductor polymer may be, for example, a polythiophene including poly(3-alkylthiophene), polyfluorene, polyphenylenevinylene, polytriallylamine, polyacetylene, polyaniline, polypyrrole, or a polymer containing a thiophene ring or a thiophene-fused ring.

[0121] The n-type semiconductor compound is not particularly limited, and examples thereof include fullerene; fullerene derivatives; quinolinol derivative metal complexes typified by 8-hydroxyquinoline aluminum; fused-ring tetracarboxylic acid diimides such as naphthalene tetracarboxylic acid diimide and perylene tetracarboxylic acid diimide; perylene diimide derivatives, terpyridine metal complexes, tropolone metal complexes, flavonol metal complexes, perinone derivatives, benzimidazole derivatives, benzoxazole derivatives, thiazole derivatives, benzthiazole derivatives, benzothiadiazole derivatives, oxadiazole derivatives, thiadiazole derivatives, triazole derivatives, aldazine derivatives, bisstyryl derivatives, pyrazine derivatives, phenanthroline derivatives, quinoxaline derivatives, benzoquinoline derivatives, bipyridine derivatives, borane derivatives; perfluorides of fused polycyclic aromatic hydrocarbons such as anthracene, pyrene, naphthacene, and pentacene; single-walled carbon nanotubes, and n-type polymers (n-type polymer semiconductor materials).

[0122] The thickness (layer thickness) of the perovskite layer 34 is not particularly limited, but may be, for example, 50 nm or more, preferably 100 nm or more, and 1000 nm or less, preferably 500 nm or less, and specifically may be approximately 400 nm. If the thickness of the perovskite layer 34 is 50 nm or more, the uniformity of the thickness of the perovskite layer 34 is maintained, making it less likely to cause a short circuit. Furthermore, if the thickness of the perovskite layer 34 is 1000 nm or less, the internal resistance of the perovskite layer 34 is reduced, the distance between the transparent electrode layer 32 and the metal electrode layer 36 is not too great, and charge diffusion is improved.

[0123] The refractive index of the perovskite layer 34 is not particularly limited, but is preferably 2.2 to 2.6, and specifically may be approximately 2.4. By forming the transparent electrode layer 32 and the electron transport layer 33 to conform to the fine unevenness structure 12, if a fine unevenness structure is also present at the interface between the electron transport layer 33 and the perovskite layer 34, reflection at the interface can be suppressed. Therefore, even if there is a difference between the refractive index of the electron transport layer 33 and the refractive index of the perovskite layer 34, there is almost no problem with reflection of incident light. On the other hand, if the transparent electrode layer 32 and the electron transport layer 33 do not conform to the fine unevenness structure 12 and the interface between the electron transport layer 33 and the perovskite layer 34 is a flat surface, it is preferable that the difference between the refractive index of the electron transport layer 33 and the refractive index of the perovskite layer 34 be as small as possible. This can suppress reflection of incident light at the interface between the electron transport layer 33 and the perovskite layer 34.

[0124] (5) Hole Transport Layer 35 The hole transport layer 35 is laminated on the perovskite layer 34 and disposed between the perovskite layer 34 and the metal electrode layer 36. The hole transport layer 35 has the function of collecting holes (positive holes) generated in the perovskite layer 34 and transporting them to the metal electrode layer 36, and the function of impeding the flow of electrons.

[0125] Examples of materials that can be used for the hole transport layer 35 include p-type conductive polymers, p-type small-molecular-weight organic semiconductors, p-type metal oxides, p-type metal sulfides, surfactants, etc. More specifically, examples of materials that can be used for the hole transport layer 35 include polystyrene sulfonate adducts of polyethylenedioxythiophene, carboxyl group-containing polythiophenes, phthalocyanines, and porphyrins. Other examples include molybdenum oxide, vanadium oxide, tungsten oxide, nickel oxide, copper oxide, tin oxide, molybdenum sulfide, tungsten sulfide, copper sulfide, and tin sulfide; fluoro-group-containing phosphonic acids; carbonyl-group-containing phosphonic acids; copper compounds such as CuSCN and CuI; and carbon-containing materials such as carbon nanotubes and graphene. In the perovskite solar cell 20, organic materials (organic hole transport materials) used for the hole transport layer 35 are expected to provide higher performance than inorganic materials.

[0126] The thickness of the hole transport layer 35 is preferably, for example, 1 nm or more, which allows for sufficient electron blocking. The thickness of the hole transport layer 35 is preferably, for example, 2000 nm or less, which prevents resistance during hole transport and increases photoelectric conversion efficiency. The thickness of the hole transport layer 35 is more preferably 3 nm or more and 1000 nm or less, and even more preferably 5 nm or more and 500 nm or less. The thickness of the hole transport layer 35 may be, for example, approximately 40 nm.

[0127] (6) Metal Electrode Layer 36 The metal electrode layer 36 (second electrode layer) is laminated on the hole transport layer 35. The metal electrode layer 36 has the function of collecting holes from the hole transport layer 35 and transmitting them to an external circuit. The metal electrode layer 36 is disposed on the side opposite to the light-receiving surface (the lower side in FIG. 8 ) of the perovskite layer 34, which is a photoelectric conversion layer. For this reason, the metal electrode layer 36 does not need to transmit incident sunlight, and therefore does not necessarily have to be a transparent electrode having transparency.

[0128] For this reason, the metal electrode layer 36 may be formed of a conductive material, such as various metal materials. Examples of the material for the metal electrode layer 36 include at least one or more metals selected from copper (Au), silver (Ag), molybdenum (Mo), and aluminum (Al), or alloys thereof. However, the material for the metal electrode layer 36 is not limited to the above examples and may include, for example, gold, platinum, nickel, titanium, magnesium, calcium, barium, sodium, chromium, and cobalt, or alloys thereof. Among these, the material for the metal electrode layer 36 is preferably silver or a silver alloy, which has high electrical conductivity and high visible light transmittance in a thin film. Silver alloys may include, for example, silver-gold alloys, silver-copper alloys, silver-palladium alloys, silver-copper-palladium alloys, and silver-platinum alloys, in order to improve the stability of the thin film and to be less susceptible to sulfidation or chlorination. In this way, the metal electrode layer 36 can be made of the various metals mentioned above, a laminate containing the metal, a metal mesh, AgNW (silver nanowire), or the like.

[0129] As described above, the transparent electrode layer 32 (first electrode layer) and the metal electrode layer 36 (second electrode layer) constitute a pair of electrodes of the solar cell 30. If one of the transparent electrode layer 32 and the metal electrode layer 36 is a transparent electrode, the other electrode does not necessarily have to be a transparent electrode and may be a non-transparent electrode. When the metal electrode layer 36 is a non-transparent electrode, for example, the non-transparent electrode can be formed by thickening the metal layer described above. When both the transparent electrode layer 32 (first electrode layer) and the metal electrode layer 36 (second electrode layer) are transparent electrodes, it is preferable that both the transparent electrode layer 32 and the metal electrode layer 36 have a laminate structure of a metal layer and a transparent conductive layer. When the second electrode layer is a transparent electrode layer, it is preferable that the material of the second electrode layer is a transparent material that has electrical conductivity and excellent transmittance for sunlight, particularly for visible light, similar to the transparent material of the transparent electrode layer 32 (first electrode layer) described above. For example, ITO, FTO, GZO, IZO, etc. may be used.

[0130] The thickness of the metal electrode layer 36 is not particularly limited and may be appropriately selected in consideration of the optical and electrical characteristics. In order to reduce the sheet resistance, the thickness of the metal electrode layer 36 is preferably 10 nm or more, more preferably 20 nm or more, and even more preferably 50 nm or more. From the viewpoint of productivity, the thickness of the metal electrode layer 36 is preferably 20 μm or less.

[0131] The first electrode layer and the second electrode layer (e.g., the transparent electrode layer 32 and the metal electrode layer 36) may be layers of film-like electrodes (thin film layers) as shown in FIG. 8 , or layers of mesh-like electrodes (mesh layers). For example, Ag nanowires can be used as the mesh-like electrode. Ag nanowire ink is a material in which nanometer-sized, wire-like silver fillers (Ag nanowires) are dispersed in a transparent resin. Because the Ag nanowires cannot be seen with the naked eye, a transparent electrode film can be formed. Therefore, Ag nanowires can be used as an electrode material as an alternative to ITO. In Ag nanowire ink, the Ag nanowires function as electrical contacts. Because the Ag nanowires are dispersed and entangled in the resin, when a flexible resin material is used, the Ag nanowire contacts are maintained even when the electrode film is bent. Therefore, Ag nanowire ink is suitable for use as an electrode for flexible devices such as the perovskite solar cell 20.

[0132] Furthermore, one or both of the first electrode layer and the second electrode layer (e.g., the transparent electrode layer 32, the metal electrode layer 36) may be configured by combining a plurality of linear electrodes arranged at a predetermined interval with a filler material filling the gaps between the linear electrodes. In this case, the linear electrodes may be arranged parallel to each other at intervals on the XY plane, and the filler material may be filled to fill the gaps between the linear electrodes. Here, the linear electrodes may be arranged in a stripe pattern extending in a single direction (e.g., the Y direction) on the XY plane, or in a mesh pattern extending in two intersecting directions (e.g., the X direction and the Y direction) on the XY plane. In either the stripe pattern or the mesh pattern, the filler material fills the gaps between the linear electrodes. In this way, an electrode layer consisting of linear electrodes and a filler material can be formed and used as the first electrode layer and the second electrode layer (e.g., the transparent electrode layer 32, the metal electrode layer 36) described above.

[0133] The above describes each layer of the solar cell 30 with a planar structure according to this embodiment. The solar cell 30 according to this embodiment has a laminated structure in which a perovskite layer 34, which is a photoelectric conversion layer, is sandwiched between an electron transport layer 33 and a hole transport layer 35. Sunlight incident on the light-receiving surface side (the upper substrate layer 10 side) of the solar cell 30 passes through the substrate layer 10, the microrelief structure layer 11, the transparent electrode layer 32, and the electron transport layer 33, and is introduced into the perovskite layer 34. Then, primarily visible light of the sunlight is absorbed by the perovskite crystals of the perovskite layer 34, and electrons and holes are generated by the energy of the absorbed light. In this way, photoelectric conversion of visible light occurs within the perovskite layer 34. As a result, electrons generated in the perovskite layer 34 are extracted to an external circuit via the electron transport layer 33 and the transparent electrode layer 32. Meanwhile, holes generated in the perovskite layer 34 are extracted to an external circuit via the hole transport layer 35 and the metal electrode layer 36. This generates a current and a voltage in the solar cell 30 with a planar structure, enabling light energy to be converted into electrical energy.

[0134] 4.2. Suppression of Reflection Inside the Solar Cell Next, the principle of suppressing reflection of incident light at the layer interfaces inside the solar cell 30 according to this embodiment will be described with reference to FIGS. 8 and 9. FIG.

[0135] As shown in Figure 9, the solar cell 30A according to Reference Example 1 does not have a microrelief structure layer 11 provided inside the solar cell 30A. Therefore, the base layer 10 and the transparent electrode layer 32 are in contact with each other at flat surfaces, and the interface between the two layers is also flat. Therefore, a portion of the incident light 51 is likely to be reflected at an interface between layers with a large refractive index difference, such as the interface between the base layer 10 and the transparent electrode layer 32, resulting in the generation of reflected light 53. Furthermore, the interface between the transparent electrode layer 32 and the electron transport layer 33 is also flat, and a portion of the incident light 51 is likely to be reflected at this interface, resulting in the generation of reflected light 54. As a result, the amount of incident light 52 reaching the perovskite layer 34 is smaller than the amount of the original incident light 51 by the amount of reflected light 53 and 54, thereby reducing the power generation efficiency of the perovskite layer 34.

[0136] Furthermore, in the electrodes of conventional silicon-based solar cells, the electrode layer is composed of a patterned linear electrode, and the electrode area is small. Therefore, if the linear electrode is a transparent electrode, the impact of reflection of incident light at the interface between the electrode and other layers is small. Furthermore, if the linear electrode is not transparent, incident light does not pass through the opaque linear electrode portion. Therefore, interfacial reflection between the electrode and other layers does not occur, and the area where an anti-reflection layer is meaningful is relatively small, thereby reducing the impact of reflection of incident light. In contrast, in the perovskite solar cell 20, the transparent electrode layer 32 is applied to the entire surface of the solar cell 30, and the transparent electrode layer 32 is in surface contact with other layers (e.g., the substrate layer 10, the electron transport layer 33, etc.), resulting in a large interface area between the two layers. Therefore, in the perovskite solar cell 20, incident light 51 is likely to be reflected across the entire wide interface between the transparent electrode layer 32 and other layers. This also creates the problem of the reflection of incident light 51 at the layer interfaces within the solar cell 30 becoming more pronounced.

[0137] Therefore, in the solar cell 30 of the perovskite solar cell 20 according to this embodiment, as shown in Figure 8, a fine uneven structure 12 is provided between the base material layer 10 and the transparent electrode layer 32, and the fine uneven structure 12 is interposed between the base material layer 10 and the transparent electrode layer 32. This fine uneven structure 12 is a moth-eye structure that has excellent anti-reflection properties.

[0138] As described above, the interface between the base layer 10 and the transparent electrode layer 32 is a large-area interface in which there is a large difference in refractive index and which is in surface contact. Therefore, as shown in Fig. 9, incident light 51 is likely to be reflected at the interface, resulting in reflected light 53. In contrast, in this embodiment, as shown in Fig. 8, by providing a fine uneven structure 12 at the interface between the base layer 10 and the transparent electrode layer 32, reflection of incident light 51 at the interface can be suitably suppressed.

[0139] Furthermore, according to this embodiment, the transparent electrode layer 32 and the electron transport layer 33 are laminated on the microrelief structure 12 by sputtering or vapor deposition. Therefore, the transparent electrode layer 32 and the electron transport layer 33 are laminated in a wavy manner following the microrelief structure 12. As a result, a microrelief structure corresponding to the microrelief structure 12 is formed on both surfaces (upper and lower surfaces) of the transparent electrode layer 32 and the electron transport layer 33. Therefore, reflection of incident light 51 can be suppressed and the generation of reflected light 53 and 54 can be reduced not only at the interface between the base layer 10 and the transparent electrode layer 32, but also at the interface between the transparent electrode layer 32 and the electron transport layer 33 and the interface between the electron transport layer 33 and the perovskite layer 34.

[0140] Even when the first electrode layer (e.g., transparent electrode layer 32) is constructed as described above from a thin film of a mesh-like electrode (hereinafter referred to as a "mesh-like electrode film") in which Ag nanowires or the like are dispersed in a transparent resin, it is possible to laminate the mesh-like electrode film made of the nanowires so that it conforms to the fine unevenness of the fine unevenness of the fine unevenness of the fine unevenness of the fine unevenness, and therefore a fine unevenness is also formed in the mesh-like electrode film. In this case, the nanowires are dispersed and entangled in the resin. Therefore, even if the mesh-like electrode film made of nanowires is curved and deformed so that it conforms to the fine unevenness of the fine unevenness of the fine unevenness, the contact points of the nanowires are maintained in the mesh-like electrode film. Therefore, the conductivity of the electrode can be ensured.

[0141] Therefore, according to this embodiment, it is possible to suitably suppress reflection of incident light 51 at a plurality of interfaces inside the solar cell 30. As a result, it is possible to increase the amount of incident light 52 that reaches the perovskite layer 34, thereby improving power generation efficiency.

[0142] Furthermore, according to this embodiment, it is preferable that the thickness (T2) of the transparent electrode layer 32 and the thickness (T3) of the electron transport layer 33 are smaller than the height (H) of the convex portions 13 of the microrelief structure 12 (T2<H, T3<H). For example, the height (H) of the microrelief structure layer 11 is 200 nm, while the thickness (T2) of the transparent electrode layer 32 and the thickness (T3) of the electron transport layer 33 may be 20 nm. In this way, T2 and T3 are preferably 50% or less of H, more preferably 25% or less, and even more preferably 10% or less.

[0143] This makes it easier for the thin transparent electrode layer 32 and electron transport layer 33 to conform to the uneven surface of the fine uneven structure 12 when they are laminated on the fine uneven structure layer 11. Therefore, a fine uneven structure corresponding to the fine uneven structure 12 can be appropriately formed on the surfaces of the transparent electrode layer 32 and the electron transport layer 33. This fine uneven structure therefore makes it possible to more suitably suppress reflection of the incident light 51 at the interface between the transparent electrode layer 32 and the electron transport layer 33 and at the interface between the electron transport layer 33 and the perovskite layer 34. This therefore further increases the amount of incident light 52 that reaches the perovskite layer 34, thereby further improving power generation efficiency.

[0144] Furthermore, the microrelief structure layer 11 is an insulating layer made of resin and is not electrically conductive. Therefore, in order to maintain the power generation function of the solar cell 30, the microrelief structure layer 11 cannot be disposed between the transparent electrode layer 32 and the electron transport layer 33, or between the electron transport layer 33 and the perovskite layer 34. Therefore, in order to additionally install the microrelief structure layer 11 inside the stack of the solar cell 30, the microrelief structure layer 11 must be disposed between the base layer 10 and the transparent electrode layer 32, as shown in FIG. 8 . Even with such a microrelief structure layer 11 disposed, it is a great advantage that the following action of the microrelief structure 12 allows microrelief structures to be formed on the surfaces of the other transparent electrode layer 32, the electron transport layer 33, and the perovskite layer 34, thereby suppressing reflection at each interface.

[0145] 8 and 10 , the principle of converting unused light such as near-infrared light into visible light and effectively using it for power generation in the microrelief structure layer 11 of the solar cell 30 according to this embodiment will be described.

[0146] 10 , in solar cell 30B according to Reference Example 2, a microrelief structure layer 11 is provided inside solar cell 30B, but wavelength conversion nanoparticles 15 are not contained inside microrelief structure layer 11. Therefore, in solar cell 30B according to Reference Example 2, of the incident light 52 that is incident on solar cell 30 and reaches perovskite layer 34, visible light can be used to generate power, but near-infrared light 55 cannot be used to generate power. The reason for this is that there is no layer containing wavelength conversion nanoparticles 15 that can convert near-infrared light 55 to visible light inside solar cell 30B.

[0147] As described above, silicon-based solar cells can generate electricity by utilizing not only visible light but also a portion of near-infrared light (shorter wavelengths) from incident sunlight. In contrast, perovskite solar cells can use visible light to generate electricity, but cannot use near-infrared light to generate electricity, resulting in the problem that near-infrared light remains completely unused. For this reason, there has been a strong demand for a method that enables perovskite solar cells to effectively utilize unused light outside the visible light wavelength range (e.g., near-infrared light, ultraviolet light) for power generation. In this regard, no suitable method has been proposed to convert the wavelength of unused light, such as near-infrared light, in perovskite solar cells.

[0148] Therefore, in the solar cell 30 of the perovskite solar cell 20 according to this embodiment, as shown in FIG. 8 , wavelength conversion nanoparticles 15 are dispersed and contained within the microrelief structure 12 of the microrelief structure layer 11. As a result, when near-infrared light 55 of the incident light 51 passes through the microrelief structure layer 11, the wavelength conversion nanoparticles 15 can convert the near-infrared light 55 into visible light 56. As a result, the visible light 56 ​​converted from the near-infrared light 55 in the microrelief structure layer 11 can be made to enter the perovskite layer 34 and used for photoelectric conversion. Therefore, not only the visible light of the incident light 51 but also the near-infrared light 55, which was previously unused light, can be effectively used for power generation in the perovskite layer 34, further improving the power generation efficiency of the perovskite solar cell 20.

[0149] Here, the wavelength conversion nanoparticles 15 are nano-sized particles formed of a material having a light wavelength conversion function (up-conversion function or down-conversion function). The wavelength conversion nanoparticles 15 according to this embodiment have, for example, an up-conversion function for converting near-infrared light 55 to visible light 56, and are formed of up-conversion phosphor particles having this function. This allows the near-infrared light 55 of unused light contained in the incident light 51 to be converted into visible light 56, which can be effectively used for power generation. However, without being limited to this example, the wavelength conversion nanoparticles 15 may also have, for example, a down-conversion function for converting ultraviolet light to visible light, and may be formed of down-conversion phosphor particles having this function. This also allows the ultraviolet light of unused light contained in the incident light 51 to be converted into visible light, which can be effectively used for power generation.

[0150] As described above, according to this embodiment, the microrelief structure layer 11 inside the solar cell 30 contains wavelength conversion nanoparticles 15, so that unused near-infrared light 55 can be suitably converted into visible light 56 ​​and made to enter the perovskite layer 34, thereby making it possible to effectively use the light for power generation. Therefore, the amount of visible light used for power generation can be increased, and the power generation efficiency of the solar cell 30 can be further improved.

[0151] Furthermore, according to this embodiment, the wavelength conversion nanoparticles 15 are contained in the microrelief structure layer 11, which exhibits the above-described antireflection function. This allows the microrelief structure layer 11 to function not only as an antireflection layer but also as a wavelength conversion layer that converts unused light into visible light. Therefore, the antireflection layer and the wavelength conversion layer can be realized in a single microrelief structure layer 11, eliminating the need for two separate layers for the antireflection layer and the wavelength conversion layer. This reduces the number of layers in the solar cell 30 stack, thereby reducing the manufacturing process to a single stacking step during the manufacture of the solar cell 30, which is advantageous in terms of the manufacturing efficiency of the solar cell 30. Furthermore, in terms of the functionality of the solar cell 30, the single microrelief structure layer 11 suppresses surface reflection at the layer interfaces within the solar cell 30, while converting unused light (near-infrared light 55) of the incident light 51 into visible light 56 ​​for effective use in power generation, thereby improving power generation efficiency.

[0152] Furthermore, if a wavelength conversion layer (e.g., an up-conversion sheet) without anti-reflection function is newly installed on a solar cell, the number of layer interfaces increases by the amount of the additional layer, which causes an increase in internal reflection of the solar cell. In contrast, according to this embodiment, the functions of both the anti-reflection layer and the wavelength conversion layer can be realized by a single microrelief structure layer 11. Therefore, the increase in the number of layer interfaces can be kept to a necessary minimum, thereby suppressing an increase in internal reflection of the solar cell 30.

[0153] Furthermore, when wavelength-converting nanoparticles 15 are formed from an upconversion phosphor, irradiation of the wavelength-converting nanoparticles 15 with ultraviolet light may cause the upconversion phosphor to deteriorate. In this regard, in the perovskite solar cell 20 according to this embodiment (see FIG. 7 ), a UV absorption layer 23 is provided on the light-receiving surface side of the solar cell 30. This UV absorption layer 23 can prevent the wavelength-converting nanoparticles 15 (e.g., fine particles of an upconversion phosphor) contained in the microrelief structure 12 of the solar cell 30 from being deteriorated by ultraviolet light.

[0154] Furthermore, it is preferable that the average particle size of the wavelength-converting nanoparticles 15 is sufficiently smaller than the height H and pitch P of the convex portions 13 of the fine uneven structure 12. This allows the wavelength-converting nanoparticles 15 to suitably penetrate into the interior of the convex portions 13 of the fine uneven structure 12 and be dispersed and arranged therein. Furthermore, the wavelength-converting nanoparticles 15 are arranged and dispersed evenly throughout the fine uneven structure layer 11.

[0155] From this perspective, the average particle size of the wavelength-converting nanoparticles 15 may be, for example, 400 nm or less, preferably 200 nm or less, more preferably 100 nm or less, and even more preferably 50 nm or less, and may be, for example, approximately 10 nm. This allows the wavelength-converting nanoparticles 15 to be suitably dispersed and evenly arranged within the fine uneven structure 12. Furthermore, if the average particle size of the wavelength-converting nanoparticles 15 is too large, there is a risk of the incident light 51 being scattered by the wavelength-converting nanoparticles 15. However, as long as the average particle size of the wavelength-converting nanoparticles 15 is within the above-mentioned average particle size range, this scattering can be suppressed. Furthermore, the lower limit of the average particle size of the wavelength-converting nanoparticles 15 is not particularly limited, but may be, for example, 1 nm or more, and from a manufacturing standpoint, 5 nm or more is preferred.

[0156] [4.4. Modified Example of Solar Cell (Planar Structure)] Next, the configuration of a solar cell 30 having a planar structure according to a modified example of this embodiment will be described with reference to Fig. 11. Fig. 11 is a partially enlarged cross-sectional view showing a solar cell 30 according to a modified example of this embodiment.

[0157] As shown in Figure 11, the solar cell 30 according to the modified example of this embodiment differs from the solar cell 30 according to the above-mentioned embodiment (see Figure 8) in that the transparent electrode layer 32 and the electron transport layer 33 are not stacked in accordance with the fine uneven structure 12, but the other stacked structures are substantially the same.

[0158] 11 , the transparent electrode layer 32 is laminated on the fine concave-convex structure 12 of the fine concave-convex structure layer 11. Therefore, the upper surface of the transparent electrode layer 32 is an uneven surface, but the lower surface of the transparent electrode layer 32 is a flat surface. In other words, the transparent electrode layer 32 serves as a planarizing layer that covers the fine concave-convex structure 12.

[0159] In the solar cell 30 according to this modified example, a microrelief structure layer 11 is interposed between the base material layer 10 and the transparent electrode layer 32, and the interface between the base material layer 10 and the transparent electrode layer 32 is an uneven surface of the microrelief structure 12. This microrelief structure 12 can suitably suppress reflection of incident light 51 at the interface between the base material layer 10 and the transparent electrode layer 32, thereby reducing reflected light 53. This increases the amount of incident light 52 that reaches the perovskite layer 34, thereby improving power generation efficiency. However, from the viewpoint of suppressing reflection at the interface between the transparent electrode layer 32 and the electron transport layer 33, and the interface between the electron transport layer 33 and the perovskite layer 34, the solar cell 30 according to the above-described embodiment (see FIG. 8) is preferable to the solar cell 30 according to the modified example (see FIG. 11).

[0160] Furthermore, in the solar cell 30 according to the modified example (see FIG. 11 ), similarly to the solar cell 30 according to the embodiment described above (see FIG. 8 ), the microrelief structure 12 of the microrelief structure layer 11 contains a large number of wavelength conversion nanoparticles 15 dispersed therein. As a result, when incident light 51 passes through the microrelief structure layer 11, near-infrared light 55 of the incident light 51 is converted by the wavelength conversion nanoparticles 15 into visible light 56, which is then incident on the perovskite layer 34. Therefore, the near-infrared light 55, which is unused light, can be effectively used to generate electricity in the perovskite layer 34.

[0161] 5. Second Embodiment (Inverted Planar Structure) Next, the configuration of a solar cell 30 with an inverted planar structure according to a second embodiment of the present invention will be described with reference to Fig. 12. Fig. 12 is a partially enlarged cross-sectional view showing a solar cell 30 with an inverted planar structure according to the second embodiment.

[0162] The solar cell 30 according to the second embodiment (see FIG. 12) is different from the solar cell 30 according to the first embodiment (see FIG. 8) in the stacking order of the layers of the solar cell 30, but the other configurations are substantially the same. The following description will focus on the differences, and a detailed description of the other configurations will be omitted.

[0163] As shown in Fig. 12 , a solar cell 30 according to the second embodiment is a solar cell with an inverted planar structure. In the solar cell 30 with an inverted planar structure, a hole transport layer 35 is disposed on the light-receiving surface side (upper side in Fig. 12 ) of a perovskite layer 34, which is a photoelectric conversion layer, and an electron transport layer 33 is disposed on the opposite side of the light-receiving surface (lower side in Fig. 12 ) of the perovskite layer 34. Therefore, in the solar cell 30 with an inverted planar structure shown in Fig. 12 , a base layer 10, a microrelief structure layer 11, a transparent electrode layer 32 (first electrode layer), a hole transport layer 35, a perovskite layer 34 (photoelectric conversion layer), an electron transport layer 33, and a metal electrode layer 36 (second electrode layer) are stacked in this order from the light-receiving surface side of the solar cell 30 (i.e., from the top of the figure).

[0164] The microrelief structure layer 11 is disposed between the substrate layer 10 and the transparent electrode layer 32. The hole transport layer 35 is laminated on the transparent electrode layer 32 and disposed between the transparent electrode layer 32 and the perovskite layer 34. The hole transport layer 35 has the function of collecting holes (positive holes) generated in the perovskite layer 34 and transporting them to the transparent electrode layer 32, and the function of impeding the flow of electrons. The transparent electrode layer 32 has the function of collecting holes (positive holes) from the hole transport layer 35 and sending them to an external circuit.

[0165] On the other hand, the electron transport layer 33 is laminated on the perovskite layer 34 and disposed between the perovskite layer 34 and the metal electrode layer 36. The electron transport layer 33 has the function of collecting electrons generated in the perovskite layer 34 and transporting them to the metal electrode layer 36, and the function of preventing the flow of holes. The metal electrode layer 36 has the function of collecting electrons from the electron transport layer 33 and flowing them to an external circuit.

[0166] In the solar cell 30 with an inverted planar structure according to the second embodiment, the transparent electrode layer 32 on the light-receiving surface side serves as a positive electrode (+ electrode), and the metal electrode layer 36 on the opposite side from the light-receiving surface serves as a negative electrode (- electrode). The solar cell 30 with an inverted planar structure also has a laminated structure in which a perovskite layer 34, which is a photoelectric conversion layer, is sandwiched between an electron transport layer 33 and a hole transport layer 35. Sunlight incident light 51 entering the light-receiving surface side (the upper substrate layer 10 side) of the solar cell 30 passes through the substrate layer 10, the microrelief structure layer 11, the transparent electrode layer 32, and the hole transport layer 35, and is introduced into the perovskite layer 34. Then, primarily visible light of the incident light 52 is absorbed by the perovskite crystals of the perovskite layer 34, and the energy of the absorbed light generates electrons and holes. The holes generated in the perovskite layer 34 are extracted to an external circuit via the hole transport layer 35 and the transparent electrode layer 32. Meanwhile, the electrons generated in the perovskite layer 34 are extracted to an external circuit via the electron transport layer 33 and the metal electrode layer 36. This generates a current and a voltage in the solar cell 30 with an inverted planar structure, enabling light energy to be converted into electrical energy.

[0167] Furthermore, in the solar cell 30 according to the second embodiment, similarly to the first embodiment, the fine uneven structure 12 is provided between the base material layer 10 and the transparent electrode layer 32, and the fine uneven structure 12 is interposed between the base material layer 10 and the transparent electrode layer 32. By providing the fine uneven structure 12 at the interface between the base material layer 10 and the transparent electrode layer 32, it is possible to suitably suppress reflection of incident light 51 at the interface, and reduce the generation of reflected light 53.

[0168] Furthermore, according to the second embodiment, the transparent electrode layer 32 and the hole transport layer 35 are laminated in a wavy pattern following the microrelief structure 12. As a result, a microrelief structure corresponding to the microrelief structure 12 is formed on both surfaces (upper and lower surfaces) of the transparent electrode layer 32 and the hole transport layer 35. Therefore, reflection of incident light 51 can be suppressed and the generation of reflected light 54 can be reduced not only at the interface between the substrate layer 10 and the transparent electrode layer 32, but also at the interface between the transparent electrode layer 32 and the hole transport layer 35 and the interface between the hole transport layer 35 and the perovskite layer 34.

[0169] Therefore, the second embodiment also effectively suppresses reflection of incident light 51 at multiple interfaces inside the solar cell 30. This increases the amount of incident light 52 that reaches the perovskite layer 34, thereby improving power generation efficiency.

[0170] Furthermore, according to the second embodiment, the thickness (T2) of the transparent electrode layer 32 and the thickness (T5) of the hole transport layer 35 are preferably smaller than the height (H) of the convex portions 13 of the microrelief structure 12 (T2<H, T5<H). For example, the height (H) of the microrelief structure layer 11 may be 200 nm, while the thickness (T2) of the transparent electrode layer 32 and the thickness (T5) of the hole transport layer 35 may be 20 nm. Thus, T2 and T5 are preferably 50% or less of H, more preferably 25% or less, and more preferably 10% or less.

[0171] This makes it easier for the thin transparent electrode layer 32 and hole transport layer 35 to conform to the uneven surface of the microrelief structure 12 when they are laminated on the microrelief structure layer 11. Therefore, a microrelief structure corresponding to the microrelief structure 12 can be appropriately formed on the surfaces of the transparent electrode layer 32 and the hole transport layer 35. This microrelief structure therefore makes it possible to more effectively suppress reflection of the incident light 51 at the interface between the transparent electrode layer 32 and the hole transport layer 35 and at the interface between the hole transport layer 35 and the perovskite layer 34. This therefore further increases the amount of incident light 52 that reaches the perovskite layer 34, thereby further improving power generation efficiency.

[0172] In the first and second embodiments described above, an example has been described in which, among the layers constituting the laminate of the solar cell 30, the transparent electrode layer 32 and the electron transport layer 33, or the transparent electrode layer 32 and the hole transport layer 35, are stacked so as to follow the fine unevenness 12 of the fine unevenness structure layer 11. However, the present invention is not limited to such an example. For example, the solar cell 30 may further include another layer between the fine unevenness structure layer 11 and the transparent electrode layer 32. In this case, the other layer may be stacked so as to follow the fine unevenness 12 of the fine unevenness structure layer 11. In this way, the layer stacked so as to follow the fine unevenness 12 may be any part of the multiple layers constituting the laminate of the solar cell 30, which is arranged on the light-receiving surface side of the perovskite layer 34.

[0173] 6. Wavelength-Converting Nanoparticles Next, the wavelength-converting nanoparticles 15 used in the solar cell 30 according to the first and second embodiments will be described.

[0174] As described above, the wavelength conversion nanoparticles 15 have a conversion function of converting sunlight with wavelengths that cannot be used for power generation by the perovskite solar cell 20 (unused light) into light with wavelengths that can be used for power generation (i.e., visible light).

[0175] This conversion function may be an upconversion function that converts near-infrared light (near-infrared light with a wavelength of 830 nm or more) into visible light (visible light with a wavelength of 830 nm or less). In this case, the wavelength conversion nanoparticles 15 are composed of upconversion nanoparticles (e.g., upconversion phosphor particles) that convert near-infrared light into visible light.

[0176] The conversion function may also be a down-conversion function that converts ultraviolet light (ultraviolet light with a wavelength of 380 nm or less) into visible light (visible light with a wavelength of 380 nm or more). In this case, the wavelength-converting nanoparticles 15 are composed of down-conversion nanoparticles (e.g., down-conversion phosphor particles) that convert ultraviolet light into visible light.

[0177] By dispersing and arranging such wavelength-converting nanoparticles 15 inside the microrelief structure 12 of the microrelief structure layer 11, it is possible to simultaneously achieve an antireflection function and a wavelength-converting function with a single microrelief structure layer 11. This has the advantage of suppressing the reflection and scattering of incident light inside the wavelength-converting layer, which can occur when the antireflection layer and the wavelength-converting layer are realized as separate layers.

[0178] The material for the wavelength-converting nanoparticles 15 can be, for example, a known inorganic material, organic material, or hybrid material containing an organic material and an inorganic material, which has the function of converting the wavelength of light. However, when an organic material is used, the durability of the wavelength-converting nanoparticles 15 is an issue. Furthermore, when an inorganic material is used, it is difficult to convert the wavelength with a weak light intensity. Therefore, from the viewpoint of improving the durability and wavelength conversion efficiency of the wavelength-converting nanoparticles 15, it is preferable to use a hybrid material containing an organic material and an inorganic material as the material for the wavelength-converting nanoparticles 15.

[0179] Nanoparticles made of a known hybrid material can be used as wavelength-converting nanoparticles 15 made of a hybrid material containing an organic material and an inorganic material. In particular, core / shell Ln complex nanoparticles described in JP 2018-168056 A can be used as wavelength-converting nanoparticles 15.

[0180] The core / shell type Ln complex nanoparticles have: 1) a core / shell structure; 2) the core is made of nanoparticles containing Ln; 3) the shell is made of an Ln metal layer; and 4) the shell is coordinated with a ligand having a moiety represented by the following formula: -O-(A)m-(B)n-NH- (wherein A and B are the same or different and are -CR １ R ２ -or-CR ３ =CR ４ -, m is 0 to 2, n is 0 to 2, R １ , R ２ , R ３ and R ４ each independently represents a hydrogen atom or a substituent having a C, N or O atom.

[0181] The core may be a Ln oxide nanoparticle, a Ln halide nanoparticle, or a Ln oxyhalide nanoparticle. ２ O ３ particles, TmCl ３ particles, TmF ３ particle, Er ２ O ３ particles, ErCl ３ particles, ErF ３ Particles, Ho ２ O ３ particles, HoCl ３ particles or HoF ３ The core Ln oxide nanoparticle may be a Tm ２ O ３ Particles or Er ２ O ３ It may be a particle.

[0182] The Ln metal of the shell layer is Ln ２ O ３ , Ln(NO ３ ) ３ , Ln(CH ３ COO) ３ , Ln(CF ３ SO ３ ) ３ , Ln ２ (SO ４ ) ３ , Ln ２ (CO ３ ) ３ , LnCl ３ , LnBr ３ or LnI ３ The Ln metal of the shell layer may be Yb(NO ３ ) ３ , Yb(CH ３ COO) ３ , Yb(CF ３ SO ３ ) ３ , Yb ２ (SO ４ ) ３ , Yb ２ (CO ３ ) ３ , YbCl ３ , YbBr ３ , YbI ３ or Er２ O ３ The Ln metal of the shell layer may be YbCl ３ or Er ２ O ３ It may be.

[0183] The ligand may be an organic dye. The ligand may be a quinone (quinoid) dye, a squarium dye, a cyanine dye, a phthalocyanine dye, a porphyrin dye, an azo compound, a coumarin dye, an indoline dye, eosin, fluorescein, rhodamine, merocyanine, coumarin, or indoline. The ligand may be a ligand selected from an indigo dye, a quinone dye, or a squarium dye.

[0184] The particle diameter (eg, average particle diameter) of the core / shell type Ln complex nanoparticles may be, for example, 10 nm to 1000 nm, preferably 10 nm to 30 nm, and more preferably 15 nm to 25 nm.

[0185] The core / shell Ln complex nanoparticles exhibit upconversion emission even under low excitation light such as sunlight irradiation, and therefore, by using the core / shell Ln complex nanoparticles as wavelength-converting nanoparticles 15, the durability and wavelength conversion efficiency of the wavelength-converting nanoparticles 15 can be improved.

[0186] 7. Configuration of Master Next, a master 100 used to mold the fine concave-convex structure 12 of the antireflection film 1 according to this embodiment will be described with reference to Fig. 13. Fig. 13 is a perspective view schematically showing the master 100 according to this embodiment.

[0187] The master 100 is a mold for transferring a fine relief structure 120 to the surface of a transfer object (for example, the anti-reflection film 1 according to this embodiment) by roll-to-roll imprinting. From the viewpoint of efficiently producing the transfer object, the master 100 is preferably a roll-shaped master having a cylindrical or columnar shape, but may also be a flat plate-shaped master. If the master 100 is a roll-shaped master, the fine relief structure 120 of the master 100 can be seamlessly transferred to the substrate of the transfer object by the roll-to-roll method. This allows the transfer object to which the fine relief structure 120 of the master 100 has been transferred to be manufactured with high production efficiency.

[0188] As shown in FIG. 13, the master 100 includes a roll-shaped substrate 110 and a fine concave-convex structure 120 formed on the outer peripheral surface of the substrate 110 .

[0189] The substrate 110 is, for example, a roll-shaped member that serves as the substrate of a roll master. The shape of the substrate 110 may be a hollow cylindrical shape as shown in FIG. 13, or may be a solid cylindrical shape without a cavity inside. The material of the substrate 110 is not particularly limited, and may be quartz glass (SiO ) such as fused silica glass or synthetic silica glass. ２ ), or a metal such as stainless steel can be used. The size of the substrate 110 is not particularly limited, but for example, the length of the substrate 110 in the direction of the central axis 110a (hereinafter sometimes referred to as the axial direction) may be 100 mm or more, and the outer diameter of the substrate 110 may be 50 mm or more and 300 mm or less. Furthermore, the radial thickness of the cylindrical substrate 110 may be 2 mm or more and 50 mm or less.

[0190] The fine concave-convex structure 120 is a fine concave-convex pattern formed on the outer peripheral surface of the master 100. The fine concave-convex structure 120 includes a plurality of fine recesses 123 arranged at a predetermined pitch P and a plurality of fine protrusions 124 provided between two adjacent recesses 123, 123. The fine concave-convex structure 120 of the master 100 has an inverted shape of the fine concave-convex structure of the transferred object (e.g., the fine concave-convex structure 12 of the antireflection film 1). For example, the shape of the recesses 123 of the fine concave-convex structure 120 of the master 100 is the inverted shape of the protrusions 13 of the fine concave-convex structure 12 of the antireflection film 1 (see FIGS. 1 to 6). Similarly, the shape of the protrusions 124 of the fine concave-convex structure 120 of the master 100 is the inverted shape of the recesses 14 of the fine concave-convex structure 12 of the antireflection film 1 (see FIGS. 1 to 6). The pitch (circumferential dot pitch) of the recesses 123 of the fine uneven structure 120 of the master 100 is substantially the same as the pitch P of the protrusions 13 of the fine uneven structure 12 of the anti-reflection film 1. The depth of the recesses 123 of the fine uneven structure 120 of the master 100 is substantially the same as the height H of the protrusions 13 of the fine uneven structure 12 of the anti-reflection film 1.

[0191] The master 100 having such a configuration is provided in a roll-to-roll imprint transfer device, for example, a transfer device 300 shown in Fig. 15. The master 100 can be used to produce a transferred product (for example, the antireflection film 1 according to this embodiment) in which a fine relief structure 120 formed on the outer peripheral surface of the master 100 has been transferred. For example, the fine relief structure 120 on the outer peripheral surface of the master 100 can be continuously transferred to a resin layer on the surface of the antireflection film 1, thereby molding the fine relief structure 12 on the surface of the antireflection film 1 with high precision and efficiency.

[0192] [8. Master Manufacturing Method] [8.1. Overview of Master Manufacturing Method] Next, a method (steps S10 to S50) for manufacturing the master 100 using the master manufacturing apparatus according to this embodiment will be described. The master 100 manufacturing apparatus according to this embodiment includes, for example, a film forming apparatus, an exposure control apparatus, an exposure apparatus, a developing apparatus, an etching apparatus, an exposure control apparatus, and various other control apparatuses.

[0193] (S10: Resist Film Forming Step) According to the method for manufacturing the master 100 according to this embodiment, first, a resist layer is formed on the outer peripheral surface of the substrate 110 of the master 100 by a film forming device.

[0194] More specifically, it is preferable to use a substrate made of, for example, quartz glass as the substrate 110 of the master 100. The substrate 110 is a roll-shaped substrate having a cylindrical or columnar shape. A resist layer is formed on the outer peripheral surface of this substrate 110 using a resist material.

[0195] The resist layer is formed from an inorganic or organic material capable of forming a latent image by laser light. As the inorganic material, a metal compound containing a transition metal can be used, and preferably, a metal oxide containing one or more transition metals such as tungsten (W) or molybdenum (Mo) can be used. Such inorganic materials can be formed into a resist layer by, for example, a sputtering method. On the other hand, as the organic material, novolac resists or chemically amplified resists can be used. Such organic materials can be formed into a resist layer by, for example, a spin coating method.

[0196] (S20: Exposure Control Signal Generating Step) Next, an exposure control signal corresponding to the concave-convex pattern (exposure pattern) of the fine concave-convex structure 120 of the master 100 is generated by the exposure control device.

[0197] (S30: Exposure step) Furthermore, the exposure device irradiates the resist layer with laser light based on the exposure control signal generated in S20 above. This exposes the resist layer with a predetermined exposure pattern, and forms a latent image corresponding to the fine concave-convex structure 120.

[0198] More specifically, the exposure device irradiates the resist layer with laser light, and the portions of the resist layer irradiated with the laser light are modified. This exposes the resist layer, forming multiple latent images in the resist layer. During this exposure, the laser light as exposure light may be irradiated onto the resist layer continuously or intermittently.

[0199] (S40: Development Step) Next, the resist layer on which the latent image has been formed is developed by a developing device, thereby forming a resist pattern corresponding to the fine concave-convex structure 120 on the resist layer.

[0200] More specifically, the developing device drops a developer onto the resist layer on which the latent image was formed in S30, thereby developing the resist layer. As a result, a resist pattern having a three-dimensional uneven structure is formed on the resist layer. The resist pattern is composed of a plurality of recesses each having a three-dimensional shape. The three-dimensional shapes of the plurality of recesses in the resist pattern each correspond to the three-dimensional shapes of each recess 123 in the fine uneven structure 120.

[0201] When the resist layer is a positive resist, the exposed portion exposed to the laser light dissolves faster in a developer compared to the non-exposed portion, and is therefore removed by the development process. As a result, a resist pattern is formed in the resist layer, with the latent image portion of the resist layer removed. On the other hand, when the resist layer is a negative resist, the exposed portion exposed to the laser light dissolves slower in a developer compared to the non-exposed portion, and is therefore removed by the development process. As a result, a resist pattern is formed in the resist layer, with the latent image portion remaining.

[0202] (S50: Etching step) Then, using an etching device, the resist layer on which the resist pattern is formed is used as a mask to etch the outer peripheral surface of the substrate 110 of the master 100. As a result, a concavo-convex pattern corresponding to the fine concavo-convex structure 120 is formed on the outer peripheral surface of the substrate 110.

[0203] More specifically, the outer peripheral surface of the substrate 110 is etched using as a mask the resist layer on which the resist pattern corresponding to the fine concave-convex structure 120 has been formed in S40. As a result, a fine concave-convex structure 120 (convex-convex pattern) consisting of a plurality of recesses 123 is formed on the outer peripheral surface of the substrate 110. The concave-convex shape of the fine concave-convex structure 120 of the master 100 corresponds to the concave-convex shape of the resist pattern, and corresponds to the inverted shape of the three-dimensional shape of the fine concave-convex structure 12 of the antireflection film 1, which is the transferred product.

[0204] The substrate 110 can be etched by either dry etching or wet etching. For example, when the substrate 110 is made of silica glass (SiO ２ ), a fluorocarbon gas (e.g., CHF ３ The substrate 110 can be etched by dry etching using a solvent such as fluorine, or by wet etching using hydrofluoric acid or the like.

[0205] [8.2. Exposure Apparatus and Exposure Method] Next, the exposure apparatus 200 and exposure method used in the master manufacturing method according to this embodiment will be described in more detail with reference to Fig. 14. Fig. 14 is an explanatory diagram showing the schematic configuration of the exposure apparatus 200 according to this embodiment.

[0206] 14, the exposure device 200 includes a laser light source 201, a first mirror 203, a photodiode 205, a deflection optical system, a control mechanism 230, a second mirror 213, a movable optical table 220, a spindle motor 225, and a turntable 227. The substrate 110 is placed on the turntable 227 and is rotatable about a central axis 110a.

[0207] The laser light source 201 is a light source that emits laser light 200A, and is, for example, a solid-state laser or a semiconductor laser. The wavelength of the laser light 200A emitted by the laser light source 201 is not particularly limited, but may be, for example, a wavelength in the blue light band of 400 nm to 500 nm. The spot diameter of the laser light 200A (the diameter of the spot irradiated on the resist layer) only needs to be smaller than the diameter of the opening surface of the recess 123 of the microrelief structure 120, and may be, for example, about 200 nm. The laser light 200A emitted from the laser light source 201 is controlled by a control mechanism 230.

[0208] A laser beam 200A emitted from a laser light source 201 travels straight as a parallel beam, is reflected by a first mirror 203, and is guided to a deflection optical system.

[0209] The first mirror 203 is configured as a polarizing beam splitter and has the function of reflecting one polarized component and transmitting the other polarized component. The polarized component that has transmitted through the first mirror 203 is received by a photodiode 205 and photoelectrically converted. The photoelectrically converted light reception signal is input to the laser light source 201, and the laser light source 201 performs phase modulation of the laser light 200A based on the input light reception signal.

[0210] The deflection optical system includes a condenser lens 207 , an electro-optic deflector (EOD) 209 , and a collimator lens 211 .

[0211] In the deflection optical system, the laser beam 200A is focused onto an electro-optical deflector 209 by a condenser lens 207. The electro-optical deflector 209 is an element capable of controlling the irradiation position of the laser beam 200A. The exposure apparatus 200 is also capable of changing the irradiation position of the laser beam 200A guided onto the movable optical table 220 by the electro-optical deflector 209 (a so-called wobble mechanism). After the irradiation position of the laser beam 200A is adjusted by the electro-optical deflector 209, the laser beam 200A is collimated again by a collimator lens 211. The laser beam 200A emitted from the deflection optical system is reflected by a second mirror 213 and guided horizontally and parallel onto the movable optical table 220.

[0212] The movable optical table 220 includes a beam expander 221 and an objective lens 223. The laser light 200A guided to the movable optical table 220 is shaped into a desired beam shape by the beam expander 221, and then irradiated onto the resist layer formed on the substrate 110 of the master 100 via the objective lens 223.

[0213] Furthermore, the movable optical table 220 moves by one feed pitch (track pitch) in the direction of arrow 224 (feed pitch direction) along the axial direction of the substrate 110 for each rotation of the substrate 110. The substrate 110 is placed on a turntable 227. A spindle motor 225 rotates the turntable 227, thereby rotating the substrate 110 around the central axis 110a of the cylindrical master 100. By moving the movable optical table 220 in the R direction while rotating the substrate 110 in this manner, the laser beam 200A is irradiated along a spiral trajectory onto the resist layer on the outer peripheral surface of the substrate 110. As a result, a latent image is formed on the resist layer along the spiral irradiation trajectory of the laser beam 200A.

[0214] The control mechanism 230 includes a formatter 231 and a driver 233, and controls the irradiation of the laser light 200A.

[0215] The driver 233 controls the emission of the laser light source 201 based on the exposure signal generated by the formatter 231. Specifically, the driver 233 may control the laser light source 201 so that the output intensity of the laser light 200A increases as the waveform amplitude of the exposure signal increases. The driver 233 may also control the irradiation position of the laser light 200A by controlling the emission timing of the laser light 200A based on the waveform shape of the exposure signal. As the output intensity of the laser light 200A increases, the size and depth of the latent image formed in the resist layer can be increased, and therefore the size and depth of the opening of the recess 123 ultimately formed in the substrate 110 can be increased.

[0216] Through exposure control by such control mechanism 230, the resist layer on the outer peripheral surface of the substrate 110 of the master 100 is exposed, and a latent image of any pattern is formed on the resist layer. The resist layer is then developed, and the outer peripheral surface of the substrate 110 is etched using the developed resist layer as a mask. This makes it possible to form a fine concavo-convex structure 120 having a concavo-convex pattern corresponding to the drawing pattern of the input image on the outer peripheral surface of the substrate 110 of the master 100. Therefore, by preparing a concavo-convex pattern in which the inverted shape of the fine concavo-convex structure 12 of the antireflection film 1, which is the transfer product, is drawn, it is possible to suitably form a fine concavo-convex structure 120 having the inverted shape of the fine concavo-convex structure 12 of the antireflection film 1 on the outer peripheral surface of the master 100.

[0217] 9. Manufacturing Method of Antireflection Film Next, a method for efficiently manufacturing a transferred product such as the antireflection film 1 according to this embodiment using a transfer device 300 including the master 100 will be described with reference to Fig. 15. Fig. 15 is a schematic diagram showing the configuration of the transfer device 300 that manufactures a transferred product using the master 100 according to this embodiment.

[0218] 15 , the transfer device 300 is a roll-to-roll imprint transfer device. The transfer device 300 transfers the fine relief structure 120 of the master 100 to a resin layer of a transfer target using the roll-to-roll method. This makes it possible to continuously produce a transfer target (e.g., an anti-reflection film 1) to which the fine relief structure 120 formed on the outer peripheral surface of the master 100 has been transferred.

[0219] As shown in FIG. 15, the transfer device 300 includes the master 100 , a substrate supply roll 301 , a take-up roll 302 , guide rolls 303 and 304 , a nip roll 305 , a peeling roll 306 , a coating device 307 , and a light source 309 .

[0220] The substrate supply roll 301 is, for example, a roll on which a film-like substrate 311 is wound. The take-up roll 302 is a roll for winding up a film-like substrate 331 having a resin layer 312 to which the microrelief structure 120 has been transferred. The guide rolls 303 and 304 are rolls for transporting the film-like substrate 311 before and after transfer. The nip roll 305 is a roll for pressing the film-like substrate 311 on which the resin layer 312 has been laminated against the master 100. The peeling roll 306 is a roll for peeling the film-like substrate 311, on which the microrelief structure 120 has been transferred to the resin layer 312, from the master 100.

[0221] The film-like substrate 311 may be the same substrate as the substrate layer 10 (see FIG. 1, etc.) of the anti-reflection film 1 described above, or may be a substrate different from the substrate layer 10. In the latter case, the anti-reflection film 1 may be manufactured by attaching the substrate 311 having the resin layer 312 to which the microrelief structure 120 has been transferred by the transfer device 300 of FIG. 15 to the surface of the substrate layer 10 (see FIG. 1, etc.) of the anti-reflection film 1. In this embodiment, for example, an example will be described in which the film-like substrate 311 is the same substrate as the substrate layer 10 (see FIG. 1, etc.) of the anti-reflection film 1 described above.

[0222] The coating device 307 includes a coating means such as a coater, and coats the photocurable resin composition on the film-like substrate 311 to form a resin layer 312. The coating device 307 may be, for example, a gravure coater, a wire bar coater, or a die coater. The light source 309 is a light source that emits light of a wavelength capable of curing the photocurable resin composition, and may be, for example, an ultraviolet lamp.

[0223] The photocurable resin composition is a resin that cures when irradiated with light of a predetermined wavelength. Specifically, the photocurable resin composition may be, for example, an ultraviolet-curable resin such as an acrylic resin acrylate or an epoxy acrylate. The photocurable resin composition may also contain an initiator, a filler, a functional additive, a solvent, an inorganic material, a pigment, a charge inhibitor, a sensitizing dye, or the like, as needed.

[0224] Furthermore, the photocurable resin composition (e.g., an ultraviolet-curable resin composition) that is the material for the resin layer 312 according to this embodiment contains a large number of wavelength-converting nanoparticles 15 dispersed therein. For example, before the photocurable resin composition is applied to the film-like substrate 311 by the application device 307, the photocurable resin composition and the wavelength-converting nanoparticles 15 are mixed together in advance to disperse the wavelength-converting nanoparticles 15 in the photocurable resin composition. A known mixing method can be used for this mixing. The application device 307 then applies the photocurable resin composition containing the wavelength-converting nanoparticles 15 to the film-like substrate 311, forming a resin layer 312 in which the wavelength-converting nanoparticles 15 are dispersed. A microrelief structure 12 is then nanoimprinted into the resin layer 312. This makes it possible to easily manufacture an antireflection film 1 in which a microrelief structure layer 11 containing wavelength-converting nanoparticles 15 is laminated on a substrate layer 10 (substrate 311) as shown in FIG. 1 .

[0225] The material of the resin layer 312 may be a thermosetting resin composition. In this case, the transfer device 300 is provided with a heater instead of the light source 309, and the resin layer 312 is heated by the heater to harden the resin layer 312 and transfer the fine uneven structure 120. The thermosetting resin composition may be, for example, a phenolic resin, an epoxy resin, a melamine resin, or a urea resin.

[0226] 9.2. Method for Producing Antireflection Film Using Transfer Device Next, a method for producing a transferred product (antireflection film 1) using the above-described transfer device 300 will be described.

[0227] First, film-like substrate 311 is continuously delivered from substrate supply roll 301 and transported by guide roll 303. Next, a photocurable resin composition is applied to the surface of delivered substrate 311 by coating device 307, and uncured resin layer 312 is laminated on the surface of substrate 311. The applied photocurable resin composition contains the above-mentioned wavelength-converting nanoparticles 15. As a result, the applied uncured resin layer 312 also contains wavelength-converting nanoparticles 15.

[0228] Furthermore, the uncured resin layer 312 laminated on the surface of the substrate 311 is pressed against the outer peripheral surface of the master 100 by the nip rolls 305. As a result, the fine uneven structure 120 formed on the outer peripheral surface of the master 100 is transferred to the uncured resin layer 312. Thereafter, light such as ultraviolet light is irradiated from the light source 309 onto the resin layer 312 onto which the fine uneven structure 120 has been transferred. As a result, the uncured resin layer 312 is cured, and the shape of the uneven pattern transferred to the cured resin layer 312 is stabilized.

[0229] Next, substrate 311 on which cured resin layer 312 is laminated is peeled off from the outer peripheral surface of master 100 by peeling roll 306. As a result, microrelief structure 12 having an inverted shape of microrelief structure 120 of master 100 is formed in resin layer 312. Resin layer 312 on which microrelief structure 12 is formed corresponds to microrelief structure layer 11 of antireflection film 1 (see FIG. 1 ). Microrelief structure 12 is made up of a plurality of convex portions 13 and concave portions 14, and wavelength conversion nanoparticles 15 described above are dispersed and arranged inside microrelief structure 12.

[0230] Thereafter, the substrate 311 having the fine concave-convex structure 12 peeled off from the master 100 is transported via a guide roll 304 and taken up by a take-up roll 302 .

[0231] As described above, the roll-to-roll transfer device 300 can be used to continuously produce a transferred product (for example, the anti-reflection film 1 according to this embodiment) onto which the fine concave-convex structure 120 formed on the master 100 has been transferred. This makes it possible to efficiently and inexpensively mass-produce transferred products onto which the fine concave-convex structure 120 has been transferred with high precision.

[0232] 11. Method for Manufacturing Solar Cell Next, a method for manufacturing the perovskite solar cell 20 according to this embodiment will be described with reference to FIGS. 7, 8, 15, etc.

[0233] The method for manufacturing the perovskite solar cell 20 according to this embodiment includes a step of manufacturing the anti-reflection film 1 (S100), a step of manufacturing the solar cell 30 (S200), and a step of manufacturing the perovskite solar cell 20 (S300).

[0234] [11.1. Antireflection Film Manufacturing Process (S100)] The antireflection film 1 manufacturing process (S100) is a process for manufacturing the antireflection film 1 shown in FIG. 1 by, for example, roll-to-roll nanoimprinting.

[0235] In the manufacturing process (S100) of the antireflection film 1, as described above, the microrelief structure 120 of the master 100 may be transferred by a roll-to-roll method using, for example, the transfer device 300 shown in FIG. 15 to the resin layer 312 (microrelief structure layer 11) on the substrate 311 (substrate layer 10) of the antireflection film 1. In this way, the microrelief structure 120 formed on the outer peripheral surface of the master 100 can be transferred to the uncured resin layer 312 of the antireflection film 1, thereby manufacturing an antireflection film 1 having a microrelief structure layer 11 on which the microrelief structure 12 is formed. By such roll-to-roll nanoimprinting, the antireflection film 1 can be manufactured continuously and efficiently.

[0236] [11.2. Solar Cell Manufacturing Process (S200)] The solar cell manufacturing process (S200) for the solar cell 30 is, for example, a process for manufacturing a stack of solar cell 30 shown in FIG. 8 .

[0237] The manufacturing process (S200) of the solar cell 30 includes steps (S202 to S210) of sequentially stacking the layers 32, 33, 34, 35, and 36 of the solar cell 30 shown in Figure 8 on the anti-reflection film 1 manufactured by the manufacturing process (S100) of the anti-reflection film 1 described above.

[0238] Specifically, first, the antireflection film 1 manufactured in the manufacturing process (S100) for the antireflection film 1 is prepared. Next, a transparent electrode layer 32 is laminated on the microrelief structure layer 11 of the antireflection film 1 (S202), and further, an electron transport layer 33 is laminated on the transparent electrode layer 32 (S204). In this lamination process (S202, 204), the transparent electrode layer 32 and the electron transport layer 33 are laminated following the microrelief structure 12 of the microrelief structure layer 11, so that a microrelief structure is also formed on the surfaces of the transparent electrode layer 32 and the electron transport layer 33 (see FIG. 8 ).

[0239] Next, the perovskite layer 34 is laminated on the electron transport layer 33 (S206). After that, the hole transport layer 35 is laminated on the perovskite layer 34 (S208), and further, the metal electrode layer 36 is laminated on the hole transport layer 35 (S210). In this manner, the stack of the solar cell 30 according to this embodiment is manufactured.

[0240] As a film formation method in the lamination steps (S202, S210) of the transparent electrode layer 32 and the metal electrode layer 36, a known coating method can be used depending on the materials used. For example, a vacuum method such as vapor deposition or sputtering, or a wet method of applying an ink containing nanoparticles or a precursor can be used. Among these, sputtering is preferred from the viewpoint of productivity.

[0241] As a film formation method in the lamination steps (S204, S218) of the electron transport layer 33 and the hole transport layer 35, a known coating method can be used depending on the material to be used. For example, when a sublimable material is used, a vacuum method such as vapor deposition or sputtering can be used. When a solvent-soluble material is used, a wet method such as spin coating or inkjet printing can be used.

[0242] Furthermore, as the film formation method in the lamination step (S206) of the perovskite layer 34, a known coating method can be used depending on the material used. For example, a vacuum method such as vapor deposition or sputtering, or a wet method using an ink containing a p-type semiconductor compound and / or an n-type semiconductor compound and a solvent can be used. Examples of wet film formation methods include die coating, reverse roll coating, gravure coating, kiss coating, spray coating, air knife coating, bar coating, pipe doctor coating, impregnation / coating, and curtain coating. When the perovskite layer 34 is formed using a perovskite compound, for example, methods described in International Publication No. 2014 / 045021, Japanese Patent Application Laid-Open No. 2014-49596, Japanese Patent Application Laid-Open No. 2016-82003, etc. may be used.

[0243] Furthermore, in the manufacturing process (S200) for the solar cell 30 according to this embodiment, at least one layer selected from the perovskite layer 34, the electron transport layer 33, and the hole transport layer 35, among the multiple layers 32 to 36 constituting the solar cell 30, may be coated by a roll-to-roll method. In this case, for example, a roll-to-roll coating method described in JP 2018-137365 A or the like can be used.

[0244] A manufacturing apparatus (not shown) coats one or more of the layers of the solar cell 30 using a roll-to-roll process. This manufacturing apparatus may include, for example, a supply roll around which the substrate is wound, a coating device that forms a coating film on the transported substrate, a preheating device that preheats the coating film, a main heating device that main heats the coating film, and a take-up roll that winds up the substrate on which the coating film has been formed. Such a roll-to-roll manufacturing apparatus can continuously and simultaneously perform the substrate transport process, the coating film application process, the coating film preheating process and main heating process, and the substrate winding process. Therefore, of the layers of the solar cell 30, at least one layer selected from the perovskite layer 34, the electron transport layer 33, and the hole transport layer 35 can be efficiently formed. This improves the manufacturing efficiency and productivity of the solar cell 30 and reduces manufacturing costs.

[0245] According to the manufacturing process (S200) for the solar cell 30 as described above, the base material layer 10 and the microrelief structure layer 11 of the solar cell 30 can be manufactured efficiently and with high precision using the antireflection film 1 manufactured in advance in the manufacturing process (S100) for the antireflection film 1. Furthermore, the microrelief structure 12 is a highly accurate nano-sized moth-eye structure, and the microrelief structure 12 can be suitably disposed inside the solar cell 30. Therefore, the microrelief structure 12 can appropriately suppress internal reflection in the solar cell 30. Furthermore, the microrelief structure layer 11, which combines the above-described antireflection function and wavelength conversion function, can be suitably embedded in a required location inside the solar cell 30.

[0246] [11.3. Perovskite solar cell manufacturing process (S300)] The perovskite solar cell 20 manufacturing process (S300) is, for example, a process for manufacturing the perovskite solar cell 20 shown in Fig. 7. In this perovskite solar cell 20 manufacturing process (S300), the perovskite solar cell 20 is manufactured using the solar cell 30 manufactured in the solar cell 30 manufacturing process (S200) described above.

[0247] The manufacturing process (S300) of the perovskite solar cell 20 includes, for example, a step (S302) of manufacturing the transparent protective sheet 21 shown in FIG. 7, a step (S304) of stacking the back sheet 27, the sealing layer 26, the solar cell 30, and the transparent protective sheet 21, and a step (S306) of thermocompression molding the stack.

[0248] Specifically, in the step (S302) of producing the transparent protective sheet 21, as shown in FIG. 7 , the barrier layer 24 is laminated on the base layer 25, then the UV absorbing layer 23 is laminated on the barrier layer 24, and further the weather-resistant layer 22 is laminated on the UV absorbing layer 23. These layers 22 to 25 may be bonded to each other by adhesive layers (not shown). That is, the base layer 25 and the barrier layer 24 may be bonded together by a first adhesive layer, the barrier layer 24 and the UV absorbing layer 23 may be bonded together by a second adhesive layer, and the UV absorbing layer 23 and the weather-resistant layer 22 may be bonded together by a third adhesive layer. In this way, the transparent protective sheet 21 is produced as a laminate in which the base layer 25, the barrier layer 24, the UV absorbing layer 23, and the weather-resistant layer 22 are laminated in this order. The UV absorbing layer 23 does not have to be formed as a single independent layer (thin film). For example, an ultraviolet absorber may be contained in the adhesive layer that bonds the barrier layer 24 and the weather-resistant layer 22, so that the adhesive layer functions as the UV absorbing layer 23.

[0249] Next, the transparent protective sheet 21 produced in S302, the sheet of front-side sealing layer 26A (first sealing material sheet), the plurality of solar cells 30 produced in S200, the sheet of back-side sealing layer 26B (second sealing material sheet), and the back sheet 27 are laminated in this order (S304). The laminate is then integrated by vacuum suction or the like, and then the laminate is thermocompression molded into an integrally molded body by a molding method such as lamination (S306). In this manner, the transparent protective sheet 21, the sheet of front-side sealing layer 26A, the solar cells 30, the sheet of back-side sealing layer 26B, and the back sheet 27 are thermocompression molded into an integrally molded body, thereby producing the perovskite solar cell 20.

[0250] According to the manufacturing process (S300) for the perovskite solar cell 20 described above, the solar cell 30, which combines the above-described anti-reflection function and wavelength conversion function, can be suitably protected by the backsheet 27, sealing layer 26, barrier layer 24, UV absorption layer 23, weather-resistant layer 22, etc. Therefore, it is possible to suitably manufacture a perovskite solar cell 20 that has excellent water resistance, UV resistance, weather resistance, chemical resistance, heat resistance, water repellency, etc., and the durability and lifespan of the perovskite solar cell 20 can be improved.

[0251] In the perovskite solar cell 20 according to this embodiment, a microrelief structure layer 11 is provided inside the solar cell 30 as an anti-reflection film. However, without being limited to this example, the perovskite solar cell 20 may also include another anti-reflection film in addition to the microrelief structure layer 11. For example, another anti-reflection film may be provided on the outermost surface (outside the weather-resistant layer 22) on the light-receiving side of the perovskite solar cell 20 shown in FIG. 7 , or another anti-reflection film may be provided between the layers 22 to 26. Furthermore, the other anti-reflection film is not limited to a moth-eye structure layer, and may be a multi-layer anti-reflection film, for example.

[0252] [12. Summary] The anti-reflection film (1), perovskite solar cell (20), solar cell (30), and methods for manufacturing these according to this embodiment have been described in detail above.

[0253] According to this embodiment, there is provided a solar cell (30) which is a laminate in which a fine uneven structure layer (11), a first electrode layer (32), a photoelectric conversion layer (34), and a second electrode layer (36) are stacked, and the fine uneven structure layer (11) has a fine uneven structure (12) having a plurality of convex portions (13) arranged at a pitch (P) equal to or less than the wavelength of visible light, and wavelength conversion nanoparticles (15) dispersed and contained inside the fine uneven structure (12).

[0254] With this configuration, the microrelief structure (12) of the microrelief structure layer (11) can suppress reflection of incident light at interfaces between multiple layers of the solar cell (30). At the same time, the wavelength conversion nanoparticles (15) contained in the microrelief structure (12) can convert unused light from the incident light into visible light that can be used for power generation. Therefore, by suppressing reflection of incident light at the layer interfaces within the solar cell (30) in the solar cell and effectively utilizing unused light from the incident light, the power generation efficiency of the solar cell can be improved.

[0255] In particular, when the solar cell is a perovskite solar cell (20), the transparent electrode layer (32), the electron transport layer (33), and the hole transport layer (35) are applied to the entire surface of the solar cell (30), resulting in a large interface between these layers, which tends to reduce power generation efficiency due to reflection of incident light at the large interface. However, according to the solar cell (30) of this embodiment, the fine unevenness (12) of the fine unevenness structure layer (11) adjacent to the large interface can effectively suppress reflection at the large interface, thereby improving power generation efficiency. Furthermore, both the antireflection function and the wavelength conversion function can be achieved with a single fine unevenness structure layer (11). This improves the manufacturing efficiency of the solar cell (30) and reduces the problem of reflection and scattering of incident light by nanoparticles in the wavelength conversion layer, compared to when each function is achieved with two layers, a wavelength conversion layer and an antireflection layer.

[0256] The solar cell (30) may further include an electron transport layer (33) and a hole transport layer (35), and at least some of the first electrode layer (32), the electron transport layer (33), the photoelectric conversion layer (34), the hole transport layer (35), and the second electrode layer (36) may be stacked in accordance with the fine unevenness (12) of the fine unevenness structure layer (11), and the fine unevenness structure may also be formed on the partial layer. With this configuration, reflection of incident light can be suppressed not only at the interface of the fine unevenness structure layer (11) but also at the interface between the partial layers.

[0257] The thickness of the part of the layer may be smaller than the height (H) of the convex portions (13) of the fine concave-convex structure (12). With this configuration, the part of the layer can be made to suitably follow the fine concave-convex structure (12), and a fine concave-convex structure layer corresponding to the fine concave-convex structure (12) can be suitably formed on the part of the layer as well.

[0258] The solar cell (30) may further include a substrate layer (10), an electron transport layer (33), and a hole transport layer (35), and may be a laminate in which the substrate layer (10), the microrelief structure layer (11), the first electrode layer (32), the electron transport layer (33), the photoelectric conversion layer (34), the hole transport layer (35), and the second electrode layer (36) are stacked in this order from the light-receiving surface side of the solar cell (30). This configuration makes it possible to provide a solar cell (30) with a planar structure. This configuration makes it possible to suppress internal reflection at the interface between the microrelief structure layer (11) and the first electrode layer (32) in the solar cell (30) with a planar structure, and to effectively utilize unused light for power generation.

[0259] The first electrode layer (32) and the electron transport layer (33) are laminated in accordance with the fine uneven structure (12) of the fine uneven structure layer (11), and a fine uneven structure may also be formed on the first electrode layer (32) and the electron transport layer (33). With this configuration, reflection of incident light can be suppressed not only at the interface between the fine uneven structure layer (11) and the first electrode layer (32), but also at the interface between the first electrode layer (32) and the electron transport layer (33) and the interface between the electron transport layer (33) and the photoelectric conversion layer (34).

[0260] The thickness (T2) of the first electrode layer (32) and the thickness (T3) of the electron transport layer (33) may be smaller than the height (H) of the convex portions (13) of the fine unevenness structure (12). With this configuration, the first electrode layer (32) and the electron transport layer (33) can be made to suitably follow the fine unevenness structure (12), and a fine unevenness structure layer corresponding to the fine unevenness structure (12) can be suitably formed on the first electrode layer (32) and the electron transport layer (33).

[0261] The wavelength-converting nanoparticles (15) may be made of a hybrid material containing an organic material and an inorganic material, which can improve the durability and wavelength conversion efficiency of the wavelength-converting nanoparticles (15).

[0262] The wavelength conversion nanoparticles (15) may include upconversion nanoparticles that convert at least a portion of near-infrared light into visible light. By using wavelength conversion nanoparticles (15) of this configuration, unused near-infrared light can be converted into visible light, which can be effectively used for power generation.

[0263] The wavelength conversion nanoparticles (15) may include down-conversion nanoparticles that convert at least a portion of ultraviolet light into visible light. By using wavelength conversion nanoparticles (15) of this configuration, unused ultraviolet light can be converted into visible light, which can be effectively used for power generation.

[0264] The average particle size of the wavelength-converting nanoparticles (15) may be smaller than the height (H) and pitch (P) of the convex portions (13) of the fine uneven structure (12). With this configuration, a large number of smaller wavelength-converting nanoparticles (15) can be suitably dispersed and arranged within the fine convex portions (13) of the fine uneven structure (12), thereby further improving the wavelength conversion efficiency of the fine uneven structure (12).

[0265] The solar cell (30) may be a solar cell provided in a perovskite solar cell (20). With this configuration, reflection of incident light at the internal layer interfaces of the solar cell (30) in the perovskite solar cell (20) can be suppressed, and unused light of the incident light can be effectively utilized, thereby improving the power generation efficiency of the perovskite solar cell (20).

[0266] Furthermore, according to this embodiment, there is provided a solar cell comprising: a solar cell (30); and an encapsulation layer (26) that encapsulates the solar cell (30).

[0267] With this configuration, reflection of incident light at the layer interfaces inside the solar cell (30) in the solar cell is suppressed, and unused light from the incident light is effectively utilized, thereby improving the power generation efficiency of the solar cell.

[0268] The solar cell may be a perovskite solar cell (20). With this configuration, reflection of incident light at the internal layer interfaces of the solar cell (30) in the perovskite solar cell (20) can be suppressed, and unused light of the incident light can be effectively utilized, thereby improving the power generation efficiency of the perovskite solar cell (20).

[0269] Furthermore, according to the present embodiment, there is provided an antireflection film (1), comprising: a base layer (10); and a fine concave-convex structure layer (11) laminated on the base layer (10), wherein the fine concave-convex structure layer (11) has a fine concave-convex structure (12) having a plurality of convex portions (13) arranged at a pitch (P) equal to or less than the wavelength of visible light; and wavelength-converting nanoparticles (15) dispersed and contained within the fine concave-convex structure (12).

[0270] By applying the anti-reflection film (1) having such a configuration to various optical devices, it is possible to suppress the reflection of incident light in the optical device and effectively utilize unused light from the incident light, thereby improving the functionality of the optical device.

[0271] The antireflection film (1) may also be an antireflection film provided on the solar cell (30) described above. The solar cell (30) may also be a solar cell provided on a perovskite solar cell (20). By applying the antireflection film (1) having such a configuration to the solar cell (30) of the perovskite solar cell (20), reflection of incident light at the internal layer interfaces of the solar cell (30) can be suppressed, and unused light of the incident light can be effectively utilized, thereby improving the power generation efficiency of the perovskite solar cell (20).

[0272] While the present invention has been described above with reference to the accompanying drawings, it goes without saying that the present invention is not limited to such embodiments. It is clear that those skilled in the art can conceive of various modifications and alterations within the scope of the claims, and it is understood that such modifications and alterations also fall within the technical scope of the present invention.

[0273] For example, in the above embodiment, an example has been described in which the present invention is applied to a perovskite solar cell as a solar cell, but the present invention is not limited to such an example. In addition to perovskite solar cells, the present invention may also be applied to next-generation solar cells such as compound solar cells and organic thin-film (organic semiconductor) solar cells, or to silicon-based solar cells.

[0274] For example, the solar cell 30 according to the above embodiment includes the electron transport layer 33 and the hole transport layer 35, which can improve the transport efficiency of electrons and holes. However, the present invention is not limited to this example, and for example, the solar cell 30 does not need to include the electron transport layer 33 and the hole transport layer 35. Even in this case, the transport efficiency of electrons and holes decreases, but it is possible for the first electrode layer (e.g., the transparent electrode layer 32) and the second electrode layer (e.g., the metal electrode layer 36) to transport the electrons and holes generated in the photoelectric conversion layer and extract them to the outside.

[0275] In the above embodiment, an example in which the microrelief structure layer 11 is provided inside the solar cell 30 as shown in Fig. 8 has been described, but the present invention is not limited to such an example. For example, the microrelief structure layer 11 may be provided on the outermost layer of the solar cell 30. This makes it possible to suppress reflection of incident light on the outermost layer of the solar cell 30 and convert the wavelength of the incident light.

[0276] Although the above embodiment describes an example in which the antireflection film 1 is applied to a solar cell 30, the present invention is not limited to such an example. For example, the antireflection film 1 may be applied to applications other than solar cells. For example, the antireflection film 1 may be applied to light concentrators known as LSCs (Luminescent Light Concentrators) or photocatalytic devices. For example, when the antireflection film 1 is provided on the light receiving section of the concentrator, the microrelief structure 12 can suppress reflection of incident light at the light receiving section of the concentrator, and the wavelength conversion nanoparticles 15 can convert the incident light to light with a wavelength suitable for the concentrator, thereby increasing the amount of collected light. Furthermore, when the antireflection film 1 is provided on a photocatalytic device, the microrelief structure 12 can suppress reflection of incident light at the light receiving section of the photocatalytic device, and the wavelength conversion nanoparticles 15 can convert the incident light to light with a wavelength suitable for the photochemical reaction of the photocatalyst, thereby promoting the photochemical reaction and improving the photocatalytic function.

[0277] REFERENCE SIGNS LIST 1 anti-reflection film 10 substrate layer 11 fine concave-convex structure layer 12 fine concave-convex structure 13 convex portion 14 concave portion 15 wavelength conversion nanoparticles 20 perovskite solar cell 26 sealing layer 30 solar cell 32 transparent electrode layer (first electrode layer) 33 electron transport layer 34 perovskite layer (photoelectric conversion layer) 35 hole transport layer 36 metal electrode layer (second electrode layer) 100 master 110 substrate 120 fine concave-convex structure 123 concave portion 124 convex portion 300 transfer device 311 substrate 312 resin layer

Claims

1. A solar cell comprising a microrelief structure layer, a first electrode layer, a photoelectric conversion layer, and a second electrode layer, wherein the microrelief structure layer has a microrelief structure having a plurality of convex portions arranged at a pitch equal to or less than the wavelength of visible light, and wavelength conversion nanoparticles dispersed within the microrelief structure.

2. The solar cell according to claim 1, further comprising an electron transport layer and a hole transport layer, wherein at least some of the first electrode layer, the electron transport layer, the photoelectric conversion layer, the hole transport layer and the second electrode layer are stacked in accordance with the fine uneven structure of the fine uneven structure layer, and a fine uneven structure is also formed on some of the layers.

3. The solar cell according to claim 2, wherein the thickness of the part of the layer is smaller than the height of the convex portions of the fine concave-convex structure.

4. The solar cell according to claim 1, further comprising a base material layer, an electron transport layer, and a hole transport layer, and the solar cell is a laminate in which the base material layer, the fine uneven structure layer, the first electrode layer, the electron transport layer, the photoelectric conversion layer, the hole transport layer, and the second electrode layer are laminated in this order from the light-receiving surface side of the solar cell.

5. A solar cell as described in claim 4, wherein the first electrode layer and the electron transport layer are stacked in accordance with the fine unevenness of the fine unevenness structure layer, and a fine unevenness structure is also formed on the first electrode layer and the electron transport layer.

6. The solar cell according to claim 5, wherein the thickness of the first electrode layer and the thickness of the electron transport layer are smaller than the height of the convex portions of the fine concave-convex structure.

7. The solar cell of claim 1, wherein the wavelength-converting nanoparticles are made of a hybrid material containing an organic material and an inorganic material.

8. The solar cell of claim 1, wherein the wavelength-converting nanoparticles include up-conversion nanoparticles that convert at least a portion of near-infrared light into visible light.

9. The solar cell of claim 1, wherein the wavelength-converting nanoparticles include down-conversion nanoparticles that convert at least a portion of ultraviolet light into visible light.

10. The solar cell according to claim 1, wherein the average particle size of the wavelength-converting nanoparticles is smaller than the height and pitch of the convex portions of the fine uneven structure.

11. The solar cell according to claim 1, wherein the solar cell is a solar cell provided in a perovskite solar cell.

12. A solar cell comprising: a solar cell according to any one of claims 1 to 11; and an encapsulation layer that encapsulates the solar cell.

13. The solar cell according to claim 12, wherein the solar cell is a perovskite solar cell.

14. An antireflection film comprising: a base layer; and a fine concave-convex structure layer laminated on the base layer, wherein the fine concave-convex structure layer has a fine concave-convex structure having a plurality of convex portions arranged at a pitch equal to or less than the wavelength of visible light; and wavelength-converting nanoparticles contained and dispersed within the fine concave-convex structure.

15. The anti-reflection film according to claim 14, which is an anti-reflection film provided on the solar cell according to any one of claims 1 to 11.

16. The anti-reflection film according to claim 15, wherein the solar cell is a solar cell provided in a perovskite solar cell.

17. The anti-reflective film of claim 14, wherein the wavelength-converting nanoparticles are made of a hybrid material containing an organic material and an inorganic material.

18. The antireflective film of claim 14, wherein the wavelength-converting nanoparticles include upconversion nanoparticles that convert at least a portion of near-infrared light into visible light.

19. The antireflective film of claim 14, wherein the wavelength-converting nanoparticles include down-conversion nanoparticles that convert at least a portion of ultraviolet light into visible light.

20. The anti-reflection film according to claim 14, wherein the average particle size of the wavelength-converting nanoparticles is smaller than the height and pitch of the convex portions of the fine uneven structure.

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