Photovoltaic module and method for manufacturing the same

Abstract

The present invention provides a photovoltaic module that can achieve a high light confinement effect and a method for manufacturing the same. [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 first electrode layer 3a provided on the uneven surface 25 and formed using a transparent first conductive material, and a transparent electrode 3 provided on the first electrode layer 3a and formed using a transparent second conductive material with a higher viscosity than the first conductive material.

Description

Technical Field

[0001] The present invention relates to a photovoltaic module and a method for manufacturing the same.

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 thermosettable resin composition provided on a 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] Since a conventional film substrate for a thin-film solar cell has a layer structure of a film substrate for a thin-film solar cell and a photocurable or thermosettable resin composition, it is difficult to control the shape and size of the concavo-convex portions having a polyhedral pyramid shape, and the apexes or bottom points of the concavo-convex portions are missing, and there is a possibility that a cavity is formed between the electrode layer formed thereon and the light confinement effect is reduced.

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

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 transparent electrode having a first electrode layer provided on the uneven surface and formed using a transparent first conductive material; and a second electrode layer provided on the first electrode layer and formed using a transparent second conductive material having a higher viscosity than the first conductive material.

[0008] Another aspect of the present invention provides a method for manufacturing a photovoltaic module, comprising: preparing a light-transmitting substrate; pressing a mold having an uneven shape onto the surface of the substrate to transfer the uneven shape of the mold to form an uneven surface consisting of multiple peaks and multiple valleys; forming a first electrode layer on the uneven surface using a transparent first conductive material; and forming a second electrode layer on the first electrode layer using a transparent second conductive material with a higher viscosity than the first conductive material to create a transparent electrode. [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 a transparent electrode of the photovoltaic module according to the first embodiment is provided, as seen from the direction of the arrow, when the substrate is cut along line AA in Figure 2. [Figure 4] Figures 4(a) and 4(b) show examples of uneven surfaces in a modified photovoltaic module. [Figure 5] Figures 5(a) and 5(b) show examples of uneven surfaces in a modified photovoltaic module. [Figure 6]Figures 6(a) to 6(e) show an example of a method for manufacturing a photovoltaic module according to the first embodiment. [Figure 7] Figure 7 is an example of a cross-sectional view of a photovoltaic module according to the second embodiment. [Modes for carrying out the invention]

[0011] (Summary of the embodiment) The photovoltaic module according to the 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 transparent electrode having a first electrode layer provided on the uneven surface and formed using a transparent first conductive material, and a second electrode layer provided on the first electrode layer and formed using a transparent second conductive material with a higher viscosity than the first conductive material.

[0012] Another embodiment of the method for manufacturing a photovoltaic module includes preparing a light-transmitting substrate, pressing a mold having an uneven shape onto the surface of the substrate to transfer the uneven shape of the mold to form an uneven surface consisting of multiple peaks and multiple valleys, forming a first electrode layer on the uneven surface using a transparent first conductive material, and forming a second electrode layer on the first electrode layer using a transparent second conductive material with a higher viscosity than the first conductive material to create a transparent electrode.

[0013] This photovoltaic module and its manufacturing method form a first electrode layer using a first conductive material with lower viscosity than a second conductive material, and then form a second electrode layer on top of it using a second conductive material. Compared to a configuration that does not employ this method, it is possible to form a transparent electrode with a high packing density of conductive material even if the conductive material has difficulty filling the valleys of uneven surfaces or if there are defects in the shape of the uneven surfaces, thereby achieving a high light confinement effect.

[0014] [First Embodiment] (Overview of Photovoltaic Module 1) FIG. 1 is an example of a cross-sectional view of a photovoltaic module according to the first embodiment. FIG. 2 is a perspective view showing an example of the concavo-convex portions 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 a cross-section obtained by cutting a substrate provided with a transparent electrode of the photovoltaic module according to the first embodiment along line A-A in FIG. 2.

[0015] In each of the figures according to the embodiments described below, the ratios and shapes between the figures may differ from the actual ratios and shapes. Also, "A~B" indicating a numerical range is used to mean A or more and B or less. Hereinafter, an overview of the photovoltaic module 1 of the present embodiment will be described.

[0016] As shown in FIGS. 1 to 3, the photovoltaic module 1 includes a substrate 2 that transmits light 9, a concavo-convex portion 25 on the surface 20 of the substrate 2, which is a concavo-convex shape composed of a plurality of mountain portions 23 and a plurality of valley portions 24, a first electrode layer 3a provided on the concavo-convex portion 25 and formed using a transparent first conductive material, and a transparent electrode 3 provided on the first electrode layer 3a and having a second electrode layer 3b formed using a transparent second conductive material having a higher viscosity than the first conductive material.

[0017] The photovoltaic module 1 is an organic solar cell, a silicon solar cell, a compound solar cell, an organic-inorganic hybrid solar cell, or the like. The photovoltaic module 1 of the present embodiment is, as an example, a perovskite solar cell. As shown in FIG. 2, the mountain portions 23 and the valley portions 24 are provided continuously alternately or randomly.

[0018] As an example, as shown in FIG. 1, the photovoltaic module 1 of the present embodiment includes the above-described substrate 2, a transparent electrode 3 provided on the substrate, a photoelectric conversion layer 4 provided on the transparent electrode 3 that converts the light energy of the incident light 9 from the back surface 21 of the substrate 2 into electrical energy, and an upper electrode 5 provided on the photoelectric conversion layer 4, and is schematically configured. The photovoltaic module 1 has at least the transparent electrode 3, the photoelectric conversion layer 4, and the upper electrode 5 sealed. Note that the photovoltaic module 1 may be configured to include a plurality of photovoltaic elements including at least the transparent electrode 3, the photoelectric conversion layer 4, and the upper electrode 5, as an example.

[0019] As an example, as shown in FIG. 3, the substrate 2 of the present embodiment has a vertex 230 of the mountain portion 23 with a curvature and a bottom point 240 of the valley portion 24 without a curvature. Having a curvature indicates that the radius of curvature is not zero.

[0020] (Configuration of Substrate 2) As an example, the substrate 2 is 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. The substrate 2 of the present embodiment is a film substrate using PET with excellent flexibility and high transparency. Note that the substrate 2 may be made more deformable at the upper part than at the lower part, for example.

[0021] As an example, the substrate 2 has a thickness of 200 to 700 μm. As an example, the substrate 2 of the present embodiment has a thickness of 300 μm. Further, the substrate 2 may have a configuration in which a plurality of layers are stacked.

[0022] (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 conductive 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.

[0023] The first conductive material is dissolved in the first solvent. The second conductive material is dissolved in the second solvent. The first and second conductive materials are the same conductive material. The first solvent has a higher viscosity than the second solvent.

[0024] The first conductive material of the first electrode layer 3a may be different from or the same as the second conductive material of the second electrode layer 3b. When the conductive materials of the first electrode layer 3a and the second electrode layer 3b are the same, at least the viscosity of the solvent used to dissolve the conductive material will be different. This solvent may be, but is not limited to, an organic solvent or IPA (isopropene alcohol). When the conductive material of the first conductive material is the same as that of the second conductive material, for example, the viscosity of the solvent may be 1 / 8 and more preferably 1 / 10 of that of the second conductive material, but is not limited to this.

[0025] The first electrode layer 3a is formed with a thickness of 0.2 μm or less, for example. The second electrode layer 3b is formed with a thickness of 3.0 μm or less, for example. Therefore, the transparent electrode 3 has a thickness of 0.05 to 1.0 μm, preferably 0.5 μm, for example.

[0026] 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.

[0027] (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.

[0028] (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.

[0029] (Regarding the uneven surface 25 of substrate 2) As shown in Figures 4(a) to 5(b) described later, the sum of the first distance L1 from the vertex 230 of the adjacent mountain 23 to the reference plane 22 and the second distance L2 from the bottom point 240 of the valley 24 to the reference plane 22 is within a predetermined distance range.

[0030] 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 between the vertex 230 and the base point 240 will be 2L1 or 2L2. For example, about 10 different variations in distance L may be intentionally created.

[0031] As shown in Figures 4(a) to 5(b) described later, the first interval P1 between the vertices 230 of adjacent peaks 23 and the second interval P2 between the base points 240 of adjacent valleys 24 are both within a predetermined interval range.

[0032] 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.

[0033] 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.

[0034] (Regarding variations) Figures 4(a) to 5(b) show examples of uneven surfaces in a modified photovoltaic module. In this photovoltaic module 1 shown in Figures 4(a) to 5(b), for example, the valleys 24 have no curvature and have a shape that makes it difficult to fill if the viscosity of the conductive material is high.

[0035] Figure 4(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 240 of the valley section 24 to the reference plane 22 is different, and the first interval P1 between the vertices 230 is the same, and the second interval P2 between the base points 240 is the same. The first distance L1 varies from vertex 230 to vertex 230. The second distance L2 also varies from base point 240 to base point 240. This variation indicates a state in which both identical and different distances are mixed. Note that the base point 240 does not have curvature.

[0036] Figure 4(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 240 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 is different, and at least a portion of the second interval P2 between the base points 240 is different. The first interval P1 varies for each adjacent vertex 230. The second interval P2 also varies for each adjacent base point 240. Note that the base point 240 does not have curvature.

[0037] Figure 5(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 240 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 240 are the same. The first distance L1 varies from vertex 230 to vertex 230. The second distance L2 also varies from bottom point 240 to bottom point 240. Note that the vertices 230 and bottom points 240 do not have curvature.

[0038] Figure 5(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 240 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 is different, and at least a portion of the second interval P2 between the base points 240 is different. The first interval P1 varies for each adjacent vertex 230. The second interval P2 also varies for each adjacent base point 240. Note that the vertices 230 and base points 240 do not have curvature.

[0039] (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 6.

[0040] As shown in Figure 6(a), a light-transmitting substrate 2 is prepared.

[0041] Next, as shown in Figure 6(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 and form an uneven surface 25 consisting of multiple peaks 23 and multiple valleys 24. After formation, as shown in Figure 6(c), the mold 6 is removed from the substrate 2.

[0042] Next, as shown in Figure 6(d), a first electrode layer 3a is formed on the uneven surface 25 using a transparent first conductive material.

[0043] Next, as shown in Figure 6(e), a transparent electrode 3 is created by forming a second electrode layer 3b on the first electrode layer 3a using a transparent second conductive material with a higher viscosity than the first conductive material. Subsequently, a photoelectric conversion layer 4 and an upper electrode 5 are formed to obtain a photovoltaic module 1.

[0044] (Effects of the first embodiment) The photovoltaic module 1 according to this embodiment can achieve a high light confinement effect. Specifically, the photovoltaic module 1 forms a first electrode layer 3a using a first conductive material with lower viscosity than the second conductive material, and then forms a second electrode layer 3b on top of it using the second conductive material. Compared to a configuration that does not employ this structure, even if the conductive material has difficulty filling the valleys 24 of the uneven portion 25, or if there are defects in the shape of the uneven portion 25, a transparent electrode 3 with a high filling rate of conductive material can be formed, and a high light confinement effect can be achieved. Because the photovoltaic module 1 has a high light confinement effect, it can improve the conversion efficiency of converting light energy into electrical energy.

[0045] The photovoltaic module 1 uses the same electrode material for the first electrode layer 3a and the second electrode layer 3b, creating a difference in the viscosity of the solvent that dissolves the conductive material. Compared to a configuration that does not employ this design, it is not necessary to use different conductive materials and solvents for the first electrode layer 3a and the second electrode layer 3b, thus reducing manufacturing costs.

[0046] Even if the photovoltaic module 1 has sharp-angled portions in the uneven portion 25 where voids are likely to occur, a first electrode layer 3a with a high filling rate can be formed using a first conductive material with low viscosity. Compared to a configuration that does not employ this method, the occurrence of areas where the transparent electrode 3 is not formed and the occurrence of voids between the substrate 2 and the transparent electrode 3 can be suppressed, and a decrease in conversion efficiency can be suppressed due to a high light confinement effect.

[0047] 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.

[0048] 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.

[0049] In the photovoltaic module 1, the sum of the first distance L1 from the peak 230 of the peak 23 to the reference plane 22 and the second distance L2 from the bottom point 240 of the valley 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.

[0050] 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.

[0051] [Second Embodiment] Figure 7 is an example of a cross-sectional view of a photovoltaic module according to the second embodiment. 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.

[0052] As shown in Figure 7, the photovoltaic module 1 of this embodiment has peaks 23 and valleys 24 formed at angles closer to acute angles compared to the uneven portion 25 of the first embodiment. In this photovoltaic module 1, for example, multiple defects 7 are present in the uneven portion 25. These defects 7 become cavities between the substrate 2 and the transparent electrode 3 if, for example, conductive material is not filled, causing a decrease in the light confinement effect.

[0053] However, the photovoltaic module 1 can fill the defects 7 with a first electrode layer 3a made of a first conductive material that has low viscosity and is easily filled into the defects 7, thereby suppressing the formation of cavities. This allows for an enhanced light confinement effect compared to cases where the defects are cavities.

[0054] As shown in Figure 7, the photovoltaic module 1 is designed so that even if a defect 7 occurs, the conductive material is filled in, and the first electrode layer 3a is easily formed in the defect 7. Therefore, compared to the case where the defect is a cavity, it is possible to select and use an uneven shape that has a high light confinement effect but is prone to generating defects 7. In other words, the photovoltaic module 1 offers greater freedom in the shape of the peaks 23 and valleys 24.

[0055] The photovoltaic module 1 may be configured by combining the above embodiments and modified examples.

[0056] 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]

[0057] 1...Photovoltaic module, 2...Substrate, 3...Transparent electrode, 3a...First electrode layer, 3b...Second electrode layer, 4...Photoelectric conversion layer, 5...Upper electrode, 6...Mold, 7...Defect, 9...Light, 20...Front surface, 21...Back surface, 22...Reference plane, 23...Peak, 24...Valley, 25...Rump, 60...Rump shape, 230...Vertex, 240...Base point

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 transparent electrode having a first electrode layer provided on the aforementioned uneven portion and formed using a transparent first conductive material, and a second electrode layer provided on the first electrode layer and formed using a transparent second conductive material having a higher viscosity than the first conductive material, A photovoltaic module equipped with this module.

2. The aforementioned uneven portion has a peak which is the highest point of the peak and a bottom which is the highest point of the valley, The aforementioned peak and valley are such that the sum of the first distance from the apex of the adjacent peak to the reference plane and the second distance from the bottom of the valley to the reference plane is within a predetermined distance range. The photovoltaic module according to claim 1.

3. The aforementioned uneven portion has a peak which is the highest point of the peak and a bottom which is the highest point of the valley, The aforementioned peaks and valleys are such that the first distance between the vertices of adjacent peaks and the second distance between the bottoms of adjacent valleys are both within a predetermined interval range. The photovoltaic module according to claim 1.

4. The first conductive material is dissolved in the first solvent, The second conductive material is dissolved in the second solvent, The first conductive material and the second conductive material are the same conductive material. The first solvent has a higher viscosity than the second solvent. A photovoltaic module according to any one of claims 1 to 3.

5. Prepare a light-transmitting substrate, A mold having an uneven shape is pressed against the surface of the substrate to transfer the uneven shape of the mold and form an uneven surface consisting of multiple peaks and multiple valleys. A first electrode layer is formed on the aforementioned uneven portion using a transparent first conductive material. A transparent electrode is created by forming a second electrode layer on the first electrode layer using a transparent second conductive material with a higher viscosity than the first conductive material. A method for manufacturing photovoltaic modules.

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