Photovoltaic module

Abstract

This invention provides a photovoltaic module that can achieve a high light confinement effect. [Solution] The photovoltaic module 1 is generally configured to include a substrate 2 that transmits light 9, an uneven surface 20 of the substrate 2 having an uneven shape consisting of a plurality of peaks 23 and a plurality of valleys 24, a transparent electrode 3 provided on the uneven surface 25 and made of a transparent and conductive coating material, and a reservoir 27 provided on the bottom surface 240 side of the valleys 24, where the endpoint tangent of the endpoint 261 where the continuity of the tangents of the ridges 26 of the uneven surface 25 is interrupted is tilted toward the normal side of the surface 20 of the substrate 2, and the coating material accumulates such that the film thickness of the transparent electrode 3 on the bottom surface 240 is thicker than in other parts.

Description

Technical Field

[0001] The present invention relates to a photovoltaic module.

Background Art

[0002] As a conventional technique, a film substrate for a thin-film solar cell having a fine concavo-convex shape in which regular polyhedral pyramid shapes are spread without gaps is known (see, for example, Patent Document 1).

[0003] This fine concavo-convex shape is formed by pressing a mold against a photocurable or thermocurable resin composition provided on the film substrate for a thin-film solar cell.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] In the case of forming an electrode layer on a conventional film substrate for a thin-film solar cell, when forming a film by a coating method, the electrode material tends to accumulate in the concave portions of the concavo-convex shape, and when forming a film by a sputtering method, the electrode material tends to accumulate in the convex portions of the concavo-convex shape. As a result, an electrode layer corresponding to the concavo-convex shape of the film substrate for a thin-film solar cell is not formed, and there is a possibility that the expected light confinement effect cannot be obtained.

[0006] Therefore, an object of the present invention is to provide a photovoltaic module capable of obtaining a high light confinement effect.

Means for Solving the Problems

[0007] One aspect of the present invention provides a photovoltaic module comprising: a light-transmitting substrate; an uneven surface of the substrate having a plurality of peaks and a plurality of valleys; a coating film made of a transparent and conductive coating material provided on the uneven surface; and a reservoir provided on the bottom side of the valleys, where the coating material accumulates such that the endpoint tangents at the endpoints where the continuity of the tangents of the ridges of the uneven surface is interrupted are inclined toward the normal side of the substrate surface, and the film thickness of the coating film on the bottom surface is thicker than in other parts.

[0008] Another aspect of the present invention provides a photovoltaic module comprising: a light-transmitting substrate; an uneven surface of the substrate having a plurality of peaks and a plurality of valleys, wherein the curvature of the peaks is smaller than the curvature of the valley bottoms; and a generated film made of a transparent and conductive film-forming material, wherein the film thickness at the peaks of the peaks is greater than the film thickness at the valley bottoms. [Effects of the Invention]

[0009] According to the present invention, a high light confinement effect can be obtained. [Brief explanation of the drawing]

[0010] [Figure 1] Figure 1 is an example of a cross-sectional view of a photovoltaic module according to the first embodiment. [Figure 2] Figure 2 is a perspective view showing an example of the uneven surface of a photovoltaic module according to the first embodiment. [Figure 3] Figure 3 is an example of a cross-sectional view of a substrate on which the transparent electrodes of the photovoltaic module according to the first embodiment are provided, as seen from the direction of the arrow, when the substrate is cut along line AA in Figure 2. [Figure 4] Figure 4 is a diagram illustrating an example of the distance from the reference plane to the peak of the peak and the bottom of the valley of a photovoltaic module according to the first embodiment. [Figure 5] Figure 5 is a diagram illustrating an example of the inclination angle of the ridges of the photovoltaic module in the first embodiment. [Figure 6] Figures 6(a) and 6(b) show examples of uneven surfaces in a modified photovoltaic module. [Figure 7] Figures 7(a) and 7(b) show examples of uneven surfaces in a modified photovoltaic module. [Figure 8] Figures 8(a) to 8(d) show an example of a method for manufacturing a photovoltaic module according to the first embodiment. [Figure 9] Figure 9 is an example of a cross-sectional view of a substrate on which transparent electrodes of a photovoltaic module according to the second embodiment are provided. [Figure 10] Figure 10(a) is a diagram illustrating an example of the curvature of the peak portion of a photovoltaic module according to the second embodiment, and Figure 10(b) is a diagram illustrating an example of the curvature of the valley portion. [Figure 11] Figure 11 is a diagram illustrating an example of the distance from the reference plane to the peak of the peak and the bottom of the valley of a photovoltaic module according to the second embodiment. [Figure 12] Figure 12 shows an example of a method for manufacturing a photovoltaic module according to the second embodiment. [Modes for carrying out the invention]

[0011] (Summary of the embodiment) The photovoltaic module according to this embodiment is generally configured to include a light-transmitting substrate, an uneven surface of the substrate consisting of a plurality of peaks and a plurality of valleys, a coating film made of a transparent and conductive coating material provided on the uneven surface, and a reservoir provided on the bottom surface of the valleys, where the endpoint tangents at the endpoints where the continuity of the tangents of the ridges of the uneven surface is interrupted are inclined toward the normal side of the substrate surface, and the coating material accumulates such that the film thickness of the coating film on the bottom surface is thicker than in other parts.

[0012] Because the coating film tends to accumulate in the valleys of uneven surfaces and not in the peaks, the amount of coating material accumulated varies, preventing the initial uneven shape from being achieved. However, the photovoltaic module has a reservoir that allows the coating material to accumulate even if a large amount accumulates in the valleys. Therefore, compared to a configuration that does not employ this design, it is easier to obtain the desired uneven shape and achieve a high light confinement effect.

[0013] The photovoltaic module according to another embodiment includes a substrate that transmits light, an uneven shape on the surface of the substrate having a plurality of ridges and a plurality of valleys, the uneven portion having a curvature at the apex of the ridge smaller than the curvature at the bottom of the valley, and a formed film made of a transparent and conductive film-forming material and having a film thickness at the apex of the ridge thicker than that at the bottom of the valley. It is schematically configured with these components.

[0014] Since the formed film tends to accumulate on the ridges of the uneven portion and is difficult to accumulate in the valleys, there is a difference in the accumulation state of the film-forming material, and the original uneven shape cannot be obtained. However, in the photovoltaic module, since the curvature is smaller than that of the valleys so that the film-forming material can accumulate on the ridges, it is easier to obtain the expected uneven shape and a high light confinement effect can be obtained compared to the case where this configuration is not adopted.

[0015] [First Embodiment] (Outline of Photovoltaic Module 1) FIG. 1 is an example of a cross-sectional view of the photovoltaic module according to the first embodiment. FIG. 2 is a perspective view showing an example of the uneven portion of the photovoltaic module according to the first embodiment. FIG. 3 is an example of a cross-sectional view seen from the arrow direction of the cross-section of the substrate provided with the transparent electrode of the photovoltaic module according to the first embodiment cut along the line A-A of FIG. 2. FIG. 4 is a diagram for explaining an example of the distance from the reference plane of the photovoltaic module according to the first embodiment to the apex of the ridge and the bottom of the valley. FIG. 5 is a diagram for explaining an example of the inclination angle of the ridge line of the photovoltaic module according to the first embodiment.

[0016] In each of the figures according to the embodiments described below, the ratio and shape between the figures may be different from the actual ratio and shape. Also, "A~B" indicating a numerical range is used to mean A or more and B or less. Hereinafter, the outline of the photovoltaic module 1 will be described.

[0017] As shown in Figures 1 to 4, the photovoltaic module 1 is generally configured to include a light-transmitting substrate 2, an uneven surface 20 of the substrate 2 comprising a plurality of peaks 23 and a plurality of valleys 24, a transparent electrode 3 provided on the uneven surface 25 and being a coating film made of a transparent and conductive coating material, and a reservoir 27 provided on the bottom surface 240 side of the valleys 24, where the tangent at the endpoint 261 where the continuity of the tangents of the ridges 26 of the uneven surface 25 is interrupted is tilted toward the normal side of the surface 20 of the substrate 2, and the coating material accumulates such that the film thickness of the transparent electrode 3 on the bottom surface 240 is thicker than in other parts.

[0018] Furthermore, the solid lines in Figure 4 represent the ridges 26 of the uneven portions 25. These ridges 26 are curves that pass through the peaks 230 of the peaks 23 and the bottom points 241 of the valleys 24, and connect the outer shape of the cross-section obtained by cutting with a plane perpendicular to the surface 20 of the substrate 2.

[0019] The photovoltaic module 1 is an organic solar cell, a silicon solar cell, a compound solar cell, or an organic-inorganic hybrid solar cell. In this embodiment, the photovoltaic module 1 is, as an example, a perovskite solar cell.

[0020] As shown in Figure 2, the mountain sections 23 and valley sections 24 are arranged in a continuous alternating or random pattern.

[0021] As an example, the photovoltaic module 1 of this embodiment is generally configured to include the above-described substrate 2, a transparent electrode 3 provided on the substrate, a photoelectric conversion layer 4 provided on the transparent electrode 3 and converting the light energy of light 9 incident from the back surface 21 of the substrate 2 into electrical energy, and an upper electrode 5 provided on the photoelectric conversion layer 4. At least the transparent electrode 3, the photoelectric conversion layer 4, and the upper electrode 5 of the photovoltaic module 1 are sealed. As an example, the photovoltaic module 1 may also be configured to include multiple photovoltaic elements, each consisting of at least the transparent electrode 3, the photoelectric conversion layer 4, and the upper electrode 5.

[0022] As shown in Figures 4 and 5, the ridge line 26 is inclined in the direction of the normal to the substrate 2 at its endpoint 261, which is the starting point of the accumulation section 27. In Figure 5, the straight line obtained by extending the normal to the surface 20 is shown as the normal line 200 with a dashed line. Also, as shown in Figure 5, the ridge section 23 has an endpoint tangent 28 at the endpoint 261 on the vertex 230 side that is inclined towards the accumulation section 27 side to become an endpoint tangent 29a. This endpoint tangent 29a is inclined from the endpoint tangent 28 at a first angle θ1 in the direction of the normal line 200. This first angle θ1 is, for example, an angle in the range of 5° < θ1 < 30°.

[0023] The reservoir 27 is provided as a cylindrical space with the bottom surface 240 as its base. Preferably, the reservoir 27 is formed at a distance L from the bottom point 241 of the valley 24 to the apex 230, and less than halfway from the apex 230. In other words, the endpoint 261, which is the starting point of the reservoir 27, is located at a position of L / 2 or less from the apex 230.

[0024] The transparent electrode 3 has a section where the inclination angle of the ridge line 26 is maintained from near the vertex 230 of the uneven portion 25 of the substrate 2 to the endpoint 261. The section where the inclination angle is maintained is, for example, the electrode ridge line 33 corresponding to the maintenance region 34 shown by the diagonal lines, which is determined starting from endpoint 261 and the opposite endpoint 262, and endpoints 330 and 331, as shown in Figure 5. In other words, in the plane of Figure 5, the ridge line 263 between endpoint 261 and the opposite endpoint 262 is a straight line 263. Therefore, in the plane of Figure 5, the maintenance region 34 is parallel to the straight line 263 connecting endpoint 261 and the opposite endpoint 262, and is the region enclosed by the maintenance straight line 35 connecting endpoints 330 and 331. This maintenance region 34 is hollow, has a conical shape with the upper and lower parts cut out, and has a constant film thickness.

[0025] As an example, the peaks 23 and valleys 24 are separated by the reference plane 22 of the substrate 2, as shown in Figure 4. The ridge line 26 is, as an example, a curve formed by connecting the peak ridge line 26a of the peaks 23 and the valley ridge line 26b of the valleys 24. The reference plane 22 is, as an example, a plane that includes the center heights of the peaks 23 and valleys 24 and is parallel to the surface 20 of the substrate 2 before processing. In this embodiment, the center height is, as an example, the height at which the first distance L1 from the reference plane 22 to the apex 230 of the peaks 23 and the second distance L2 from the reference plane 22 to the bottom point 241 of the valleys 24 are equal. If there is variation in the heights of the peaks 23 and valleys 24, the center height can be determined using, for example, an arithmetic mean or a weighted mean.

[0026] (Configuration of circuit board 2) Substrate 2 is, for example, a substrate formed using a transparent resin material such as acrylic, PET (Polyethylene Terephthalate), polycarbonate, polyethersulfone, fluorine film, or triacetate, but is not limited thereto. In this embodiment, substrate 2 is a film substrate using PET, which has excellent flexibility and high transparency. Furthermore, the upper part of substrate 2 may be more easily deformed than the lower part.

[0027] The substrate 2 has a thickness of, for example, 200 to 700 μm. In this embodiment, the substrate 2 has a thickness of 300 μm as an example. The substrate 2 may also have a configuration in which multiple layers are stacked.

[0028] (Configuration of transparent electrode 3) The transparent electrode 3 is formed from a substantially transparent transparent conductive oxide (TCO) to allow light 9 incident from the substrate 2 side to be incident on the photoelectric conversion layer 4, as shown in Figure 1, for example. Such materials include metal oxides, transparent conductive polymers, transparent conductive inks, and transparent conductive glass (FTO: Fluorine-doped tin oxide). Metal oxides include, for example, indium tin oxide (ITO), indium zinc oxide (IZO), tin oxide (SnO2), and titanium oxide (TiO2), which extract the current generated in the photoelectric conversion layer 4. Transparent conductive polymers include, for example, PEDOT / PSS (poly-3,4-ethylenedioxythiophene / polysulfonic acid). Transparent conductive inks include, for example, those containing carbon nanotubes and silver nanofibers in a binder.

[0029] The transparent electrode 3 has a film thickness of approximately 0.05 to 200 μm, preferably 30 μm, excluding the accumulation portion 27.

[0030] The transparent electrode 3 in this embodiment is, for example, a transparent electrode made of indium tin oxide (ITO), but is not limited to this.

[0031] (Configuration of the photoelectric conversion layer 4) As described above, the photoelectric conversion layer 4 is configured to convert the light energy of the light 9 incident from the substrate 2 side into electrical energy.

[0032] (Configuration of upper electrode 5) The upper electrode 5 is formed from a conductive material such as gold, silver, aluminum, and copper. The upper electrode 5 is formed using gold as an example, but is not limited to this. For example, when light is taken in from the upper electrode 5 side, this upper electrode 5 may be configured as a transparent electrode.

[0033] (Regarding the uneven surface 25 of substrate 2) As shown in Figure 4(c), the distance L of the adjacent peak 23 and valley 24 is within a predetermined distance range, which is the sum of the first distance L1 from the vertex 230 of the adjacent peak 23 to the reference plane 22 and the second distance L2 from the bottom point 241 of the valley 24 to the reference plane 22.

[0034] This distance range is, for example, 0.2 to 5.0 μm, and more preferably 0.3 to 1.2 μm. In this embodiment, the peaks 23 and valleys 24 are 0.3 μm ≤ L1 + L2 ≤ 1.2 μm. The distance range is such that if there is no variation in the distances of the peaks 23 and valleys 24 from the reference plane 22, and the first distance L1 and the second distance L2 are equal, the distance L between the vertex 230 and the base point 241 will be 2L1 or 2L2. For example, about 10 different variations in distance L may be intentionally created.

[0035] Furthermore, as shown in Figure 4(c), the first interval P1 between the vertices 230 of adjacent peaks 23 and the second interval P2 between the base points 241 of adjacent valleys 24 are both within a predetermined interval range.

[0036] This spacing range is, for example, 0.2 to 6.0 μm, and more preferably 0.3 to 1.2 μm. In this embodiment, for example, the first spacing P1 and the second spacing P2 are equal. Note that variations in spacing, for example, around 10 different values, may be intentionally created.

[0037] Furthermore, it is preferable that the number obtained by dividing the height of adjacent peaks 23 and valleys 24 (L1+L2) by the width of the peaks 23 (second spacing P2) and the width of the valleys 24 (first spacing P1) is less than 1. In other words, it is preferable that the uneven portion 25 is formed such that at least one of the following conditions is met: [(L1+L2) / P1]<1 and [(L1+L2) / P2]<1.

[0038] (Regarding variations) Figures 6(a) to 7(b) show examples of uneven surfaces in a modified photovoltaic module.

[0039] Figure 6(a) shows a modified example in which, as an example, at least a portion of the first distance L1 from the vertex 230 of the peak section 23 to the reference plane 22 is different, at least a portion of the second distance L2 from the base point 241 of the valley section 24 to the reference plane 22 is different, and the first interval P1 between the vertices 230 and the second interval P2 between the base points 241 are the same. The first distance L1 varies from vertex 230 to vertex 230. The second distance L2 also varies from base point 241 to base point 241. This variation refers to a state in which both identical and different distances are mixed. Note that the vertex 230 does not have curvature.

[0040] Figure 6(b) shows a modified example in which the first distance L1 from the vertex 230 of the peak section 23 to the reference plane 22 is the same, the second distance L2 from the base point 241 of the valley section 24 to the reference plane 22 is the same, and at least a portion of the first interval P1 between the vertices 230 and at least a portion of the second interval P2 between the base points 241 are different. The first interval P1 varies for each adjacent vertex 230. The second interval P2 also varies for each adjacent base point 241. Note that the vertices 230 do not have curvature.

[0041] Figure 7(a) shows a modified example in which, as an example, at least a portion of the first distance L1 from the vertex 230 of the peak 23 to the reference plane 22 is different, at least a portion of the second distance L2 from the bottom point 241 of the valley 24 to the reference plane 22 is different, and the first interval P1 between the vertices 230 and the second interval P2 between the bottom points 241 are the same. The first distance L1 varies from vertex 230 to vertex 230. The second distance L2 also varies from bottom point 241 to bottom point 241. The vertices 230 and bottom plane 240 have curvature.

[0042] Figure 7(b) shows a modified example in which the first distance L1 from the vertex 230 of the peak section 23 to the reference plane 22 is the same, the second distance L2 from the base point 241 of the valley section 24 to the reference plane 22 is the same, and at least a portion of the first interval P1 between the vertices 230 and at least a portion of the second interval P2 between the base points 241 are different. The first interval P1 varies for each adjacent vertex 230. The second interval P2 also varies for each adjacent base point 241. The vertices 230 and base plane 240 have curvature.

[0043] (Manufacturing method for photovoltaic module 1) An example of a manufacturing method for the photovoltaic module 1 of this embodiment will be described below with reference to Figure 8.

[0044] As shown in Figure 8(a), a light-transmitting substrate 2 is prepared.

[0045] Next, as shown in Figure 8(b), the mold 6 having the uneven shape 60 is pressed onto the surface 20 of the substrate 2 to transfer the uneven shape 60 of the mold 6, thereby forming an uneven surface 25 on the surface 20 of the substrate 2 consisting of multiple peaks 23 and multiple valleys 24, with the edges 26 not having sharp angles. After formation, as shown in Figure 8(c), the mold 6 is removed from the substrate 2.

[0046] Next, as shown in Figure 8(d), a transparent electrode 3 is formed along the uneven shape of the formed uneven portion 25. In this embodiment, the transparent electrode 3 is a coated film. Therefore, the transparent electrode 3 is formed by coating the electrode material onto the substrate 2.

[0047] Next, the photoelectric conversion layer 4 and the upper electrode 5 are formed to obtain the photovoltaic module 1.

[0048] (Effects of the first embodiment) The photovoltaic module 1 according to this embodiment can achieve a high light confinement effect. Specifically, the transparent electrode 3 as a coated film tends to accumulate in the valleys 24 of the uneven portion 25 and does not accumulate easily in the peaks 23, resulting in differences in the accumulation of the coated material and preventing the initial uneven shape from being obtained. However, the photovoltaic module 1 of this embodiment has accumulation portions 27 so that even if a large amount of the conductive material of the transparent electrode 3 accumulates in the valleys 24, it is possible to obtain the desired uneven shape and achieve a high light confinement effect compared to a configuration that does not employ this setting.

[0049] The photovoltaic module 1 ensures the film thickness of the transparent electrode 3 by accumulating the coating material in the reservoir 27. Compared to cases where this configuration is not adopted, it suppresses the formation of cavities between the substrate 2 and the transparent electrode 3, and also suppresses the problem of the transparent electrode 3 not being formed on the uneven surface 25.

[0050] Since the photovoltaic module 1 forms an uneven surface on the substrate 2, positional misalignment with the mold 6 is less likely to occur compared to forming an uneven surface on a component on the substrate, and the uneven surface can be formed in micrometer units rather than nanometer units. Furthermore, because the photovoltaic module 1 has an uneven surface in micrometer units, a higher light confinement effect can be obtained compared to an uneven surface in nanometer units.

[0051] Since the photovoltaic module 1 forms an uneven surface on the substrate 2, it becomes easier to control the size and shape of the uneven surface compared to a configuration that does not employ this design.

[0052] Since the photovoltaic module 1 does not have any sharp angles on its edges 26, it is easier to remove the mold 6 and substrate 2 compared to the case where there are sharp angles, and damage during removal is less likely to occur. Also, because the photovoltaic module 1 does not have any sharp angles, cavities are less likely to form between the substrate 2 and the transparent electrode 3, and a higher light confinement effect can be obtained.

[0053] In the photovoltaic module 1, the sum of the first distance L1 from the peak 230 of the peak section 23 to the reference plane 22, and the second distance L2 from the bottom point 241 of the valley section 24 to the reference plane 22, is deliberately given a regular variation within the distance range. Therefore, compared to a configuration that does not employ this approach, a stable and high conversion efficiency can be obtained even if deviations occur. Furthermore, because the photovoltaic module 1 deliberately has multiple distances L set, it can be manufactured with higher overall precision and stability compared to a configuration that does not employ this approach.

[0054] In the manufacturing method of the photovoltaic module 1, the uneven shape can be formed by transferring the uneven shape of the mold 6, so compared to cases using etching methods, etc., size control is easier and manufacturing costs can be reduced.

[0055] [Second Embodiment] The second embodiment differs from the first embodiment in that the film thickness of the transparent electrode on the apex side is thicker than the film thickness on the base side.

[0056] Figure 9 is an example of a cross-sectional view of a substrate on which transparent electrodes of a photovoltaic module according to the second embodiment are provided. Figure 10(a) is a diagram illustrating an example of the curvature of a peak in the photovoltaic module according to the second embodiment, and Figure 10(b) is a diagram illustrating an example of the curvature of a valley. Figure 11 is a diagram illustrating an example of the distance from the reference plane to the peak of a peak and the bottom of a valley in the photovoltaic module according to the second embodiment. Figure 9 is an example of a cross-sectional view of the substrate 2 of this embodiment, cut along line AA in Figure 2, viewed from the direction of the arrow.

[0057] In the embodiments described below, parts having the same function and configuration as those in the first embodiment will be denoted by the same reference numerals as in the first embodiment, and their descriptions will be omitted. The outline of the photovoltaic module 1 of this embodiment will be described below.

[0058] (Overview of Photovoltaic Module 1) As shown in Figures 9 and 10, the photovoltaic module 1 is generally configured to include a light-transmitting substrate 2, an uneven surface 20 of the substrate 2 having a plurality of peaks 23 and a plurality of valleys 24, wherein the curvature of the peaks 230 of the peaks 23 is smaller than the curvature of the bottom points 241 of the valleys 24, and a transparent electrode 3 as a formed film made of a transparent and conductive film-forming material, wherein the film thickness at the peaks 230 of the peaks 23 is thicker than the film thickness at the bottom points 241 of the valleys 24.

[0059] The transparent electrode 3 is formed, for example, by sputtering or vapor deposition. The film deposition material is, for example, a metal oxide and a transparent conductive glass, but is not limited to these. As shown in Figure 11, the first film thickness T1 at the peak 230 of the peak portion 23 of the transparent electrode 3 is thicker than the second film thickness T2 at the bottom point 241 of the valley portion 24.

[0060] As shown in Figures 10(a) and 10(b), the vertex 230 of the peak 23 has a curvature smaller than the curvature of the base point 241 of the valley 24. The peak 23 has a radius of curvature R1, as shown in Figure 10(a). The valley 24 has a radius of curvature R3, as shown in Figure 10(b). Since the radius of curvature R1 is larger than the radius of curvature R3, the curvature of the peak 23 is smaller than the curvature of the valley 24.

[0061] The transparent electrode 3 on the vertex 230 side has a radius of curvature R2, as shown in Figure 10(a). The transparent electrode 3 on the base point 241 side has a radius of curvature R4, as shown in Figure 10(b). The curvature of the uneven portion 25 on the vertex 230 side is smaller than that on the base point 241 side.

[0062] The second angle θ2 is the angle between the endpoint tangent 28, which is an extension of the ridge line 26 of the slope 250 of the uneven portion 25, and the endpoint tangent 29b on the vertex 230 side at the opposite endpoint 262, as shown in Figure 11. This second angle θ2 is, as an example, an angle in the range of 5° < θ2 < 30°.

[0063] As shown in Figure 11, in the mountain section 23, the continuity of the ridge line 26 of the uneven section 25 is interrupted, and the intersection angle θ3 of the tangents at the opposing endpoints is obtuse. This interruption of the continuity of the ridge line 26 means, for example, that the tangent continuity of the ridge line 26 is interrupted. This tangent continuity means that the tangent at the opposing endpoint 262 on the vertex 230 side is the same as the tangent at the opposing endpoint 262 on the base 241 side. In other words, tangent continuity means that the differential value at the opposing endpoint 262 on the vertex 230 side is the same as the differential value at the opposing endpoint 262 on the base 241 side. Therefore, the interruption of tangent continuity means that at the opposing endpoint 262, the differential value on the vertex 230 side and the differential value on the base 241 side, i.e., the slope of the tangent, do not coincide.

[0064] In this embodiment, as shown in Figure 11, the angle between the two tangent lines 29b at opposing endpoints 262 on the vertex 230 side is defined as the intersection angle θ3. This intersection angle θ3 is an obtuse angle.

[0065] The opposite endpoint 262 where the tangent continuity is broken is preferably formed at a position at least one-third above the vertex 230 in the distance L from the base 241 of the valley 24 to the vertex 230. In other words, the opposite endpoint 262 is located at a position at least two-thirds of the way from the base 241.

[0066] (Manufacturing method for photovoltaic module 1) Below, an example of a manufacturing method for the photovoltaic module 1 of this embodiment will be described with reference to Figure 12.

[0067] As shown in Figure 12(a), a light-transmitting substrate 2 is prepared.

[0068] Next, as shown in Figure 12(b), the mold 6 having the uneven shape 60 is pressed onto the surface 20 of the substrate 2 to transfer the uneven shape 60 of the mold 6, thereby forming the uneven portion 25 of the surface 20 of the substrate 2, which consists of multiple peaks 23 and multiple valleys 24. After formation, as shown in Figure 12(c), the mold 6 is removed from the substrate 2.

[0069] Next, as shown in Figure 12(d), a transparent electrode 3 is formed along the uneven shape of the formed uneven portion 25. In this embodiment, the transparent electrode 3 is a generated film. Therefore, the transparent electrode 3 is formed by depositing the electrode material onto the substrate 2 using a sputtering method or a vapor deposition method.

[0070] Next, the photoelectric conversion layer 4 and the upper electrode 5 are formed to obtain the photovoltaic module 1.

[0071] (Effects of the second embodiment) The transparent electrode 3, as the formed film, tends to accumulate in the peaks 23 of the uneven surface 25 and not in the valleys 24, resulting in differences in the accumulation of the film-forming material and preventing the initial uneven shape from being obtained. However, in this embodiment, the photovoltaic module 1 has a smaller curvature than the valleys 24 so that the conductive material of the transparent electrode 3 can accumulate in the peaks 23. Therefore, compared to cases where this configuration is not adopted, it is easier to obtain the desired uneven shape and a high light confinement effect can be obtained.

[0072] According to the photovoltaic module 1 of at least one embodiment described above, a high light confinement effect can be obtained.

[0073] The photovoltaic module 1 may be configured by combining the above embodiments and modified examples.

[0074] Although several embodiments and modifications of the present invention have been described above, these embodiments and modifications are merely examples and do not limit the invention as defined in the claims. These novel embodiments and modifications can be implemented in various other forms, and various omissions, substitutions, and modifications can be made without departing from the spirit of the invention. Furthermore, not all combinations of features described in these embodiments and modifications are necessarily essential for solving the problem of the invention. Moreover, these embodiments and modifications are included in the scope and spirit of the invention, as well as in the invention described in the claims and its equivalents. [Explanation of Symbols]

[0075] 1…Photovoltaic module, 2…Substrate, 3…Transparent electrode, 4…Photoelectric conversion layer, 5…Upper electrode, 6…Mold, 9…Light, 20…Front surface, 21…Back surface, 22…Reference plane, 23…Peak, 24…Valley, 25…Rump, 26…Ridge, 26a…Peak ridge, 26b…Valley ridge, 27…Accumulation area, 28…Endpoint tangent, 29a…Endpoint tangent, 29b…Endpoint tangent, 33…Electrode ridge, 34…Maintaining region, 35…Maintaining straight line, 60…Rump shape, 200…Normal straight line, 230…Vertex, 240…Bottom surface, 241…Bottom point, 250…Slope, 261…Endpoint, 262…Opposite endpoint, 263…Straight line, 330…Endpoint, 331…Endpoint

Claims

1. A light-transmitting substrate, The surface of the substrate has an uneven shape, which consists of a plurality of peaks and a plurality of valleys, A coating film made of a transparent and conductive coating material is provided on the aforementioned uneven portion, A reservoir is provided on the bottom side of the valley portion, where the tangent at the endpoint where the continuity of the tangents of the ridges of the uneven portion is interrupted is inclined toward the normal side of the surface of the substrate, and the coating material accumulates such that the thickness of the coating film on the bottom surface becomes thicker than in other parts, A photovoltaic module equipped with this module.

2. A light-transmitting substrate, The surface of the substrate has an uneven shape having a plurality of peaks and a plurality of valleys, wherein the curvature of the peaks is smaller than the curvature of the valleys, The resulting film is made of a transparent and conductive film-forming material, and the film thickness at the peak of the peak is thicker than the film thickness at the bottom of the valley, A photovoltaic module equipped with this module.

3. The coating film has portions that maintain the inclination angle of the ridge line from the vicinity of the vertex of the uneven portion of the substrate to the endpoint. The photovoltaic module according to claim 1.

4. The vertex of the aforementioned peak has a curvature smaller than the curvature of the base of the aforementioned valley. The photovoltaic module according to claim 2.

5. In the aforementioned mountainous portion, the continuity of the ridges of the uneven portion is interrupted, and the intersection angle of the tangents at the opposing endpoints is obtuse. The photovoltaic module according to claim 4.

6. The peaks and valleys differ within a predetermined distance range, where the distance from the reference plane (based on the surface of the substrate) to the peak of the peak and the distance from the reference plane to the bottom of the valley differ within a predetermined distance range. A photovoltaic module according to any one of claims 1 to 5.

7. The aforementioned peaks and valleys differ within a predetermined interval range, such that the distance between the vertices of adjacent peaks and the distance between the bases of adjacent valleys are different. The photovoltaic module according to claim 6.

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