Solar battery

Abstract

To provide a flexible solar battery that uses glass plates to achieve high power generation efficiency.SOLUTION: A flexible solar battery 1 includes a plurality of solar battery bodies 10, each having a solar power generation layer 12 and a light-receiving side plate layer 11a laminated on the light-receiving side of the solar power generation layer, and the solar battery bodies are arranged with gaps 15 spaced apart, and both sides in the thickness direction are sealed with protective layers 13, and the light-receiving side plate layer is a glass plate with a thickness of 0.1 mm or less.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a flexible solar cell. [Background technology]

[0002] In order to provide this type of conventional solar cell with flexibility and designability, Patent Document 1 below discloses the use of a resin film having a predetermined storage modulus as a first encapsulating layer laminated on a solar cell element. Patent Document 2 below also discloses a laminate having a resin sheet and a glass layer that can be used as an encapsulant for a solar cell module, and describes the use of a resin sheet made of a resin composition containing ethylene ionomer as a main component to improve transparency. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2016-189466 [Patent Document 2] Japanese Patent Application Laid-Open No. 2016-188158 Summary of the Invention [Problem to be solved by the invention]

[0004] In recent years, there has been a demand for flexible solar cells that can be installed on curved surfaces, as disclosed in Patent Document 1. However, in this case, the solar cell element is sealed with a resin film, and the challenge is how to reduce the oxygen permeability and water vapor permeability of the resin film. In other words, to improve the power generation efficiency of solar cells, it is ideal to completely block the permeation of oxygen and water vapor, but it is extremely difficult to obtain a resin film with a transmittance comparable to that of a glass plate. Patent Document 2 discloses the use of a glass layer as a sealing material for solar cell modules, but this is not flexible, and when a glass plate is used as a sealing material, there is a problem in that even a very thin glass plate will crack when bent.

[0005] The present invention has been proposed in consideration of the above circumstances, and its object is to provide a solar cell that uses glass plates to achieve high power generation efficiency while also being flexible. [Means for solving the problem]

[0006] In order to achieve the above-mentioned object, the solar cell of the present invention is a flexible solar cell having a plurality of solar cell bodies, each having a solar power generation layer and a light-receiving side plate layer laminated on the light-receiving side of the solar power generation layer, wherein the solar cell bodies are arranged with a gap therebetween and both sides of the thickness direction are sealed with a protective layer, and the light-receiving side plate layer is a glass plate having a thickness of 0.1 mm or less.

[0007] In the above-mentioned configuration, the interlayer gap and the gap between the photovoltaic layer and the light-receiving-side plate layer may be sealed with a transparent, elastic elastomer. Furthermore, in the above-mentioned configuration, the installation-side plate layer laminated on the installation surface side of the photovoltaic layer may be a glass plate having a thickness of 0.1 mm or less. Furthermore, in the above-mentioned configuration, the installation-side plate layer laminated on the installation surface side of the photovoltaic layer may be an acrylic plate. [Effects of the Invention]

[0008] Since the solar cell of the present invention has the above-described structure, it can be made flexible while using a glass plate to achieve high power generation efficiency. [Brief explanation of the drawings]

[0009] [Figure 1] 1 is a vertical cross-sectional view schematically showing a solar cell according to one embodiment of the present invention. [Figure 2] 1(a) is a plan view showing a schematic example of the solar cell, and FIG. 1(b) is a cross-sectional view taken along the line X1-X1 showing a schematic state of the solar cell bent. [Figure 3] 1(a) to 1(c) are diagrams showing a schematic layer structure for explaining an example of a solar cell body that constitutes the solar cell. [Figure 4] (a) to (c) are diagrams for explaining the bending evaluation test conducted by the inventor, (a) is a plan view of the test sheet, (b) is a cross-sectional view taken along line X2-X2 of (a), (c) is a diagram for explaining the conditions of the bending test, and (d) is a table for explaining the results of the evaluation test. [Figure 5] (a) to (c) are diagrams for explaining a bending evaluation test conducted by the inventor, where (a) is a plan view of a test sheet, (b) is a cross-sectional view taken along line X3-X3 of (a), (c) is a diagram for explaining the conditions of the bending test, and (d) is a table for explaining the test results of the evaluation test. DETAILED DESCRIPTION OF THE INVENTION

[0010] Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. The solar cell 1 (module) according to this embodiment is flexible and includes multiple solar cell bodies 10 (cells), each of which has a photovoltaic layer 12 and a light-receiving-side plate layer 11a laminated on the light-receiving side of the photovoltaic layer 12. The solar cell bodies 10 are arranged with gaps 15 between them, and both sides in the thickness direction are sealed with protective layers 13. The light-receiving-side plate layer 11a is made of a glass plate with a thickness of 0.1 mm or less. This will be explained in detail below.

[0011] A solar cell 1 is a device that converts light energy into electricity. As shown in Figures 1 and 2(a), the solar cell 1 has a stacked structure including multiple solar cell bodies 10, each having a photovoltaic layer 12. The photovoltaic layer 12 used here may be flexible and may be silicon-based, compound-based, organic, or other materials. Specifically, the solar cell 10 may be an amorphous silicon solar cell, a dye-sensitized solar cell, an organic thin-film solar cell, or a perovskite solar cell. A perovskite-type photovoltaic layer 12 is preferable because it allows the solar cell body 10 to be thin and lightweight. The perovskite-type refers to a solar cell 12 that uses a perovskite layer made of an organic material with a unique crystalline structure called a perovskite structure. The photovoltaic layer 12 can be extremely thin, measuring 10 μm or less. At least one surface of the photovoltaic layer 12 serves as a light-receiving surface for receiving light. In the accompanying drawings, the upper side is referred to as the light-receiving side, and the lower side is referred to as the installation side.

[0012] 2(a), the solar cell 1 is formed by arranging a plurality of solar cell bodies 10 in a grid pattern in a plan view, and each surface on both sides in the thickness direction is covered with a protective layer 13 and fixed in a sealed state. The solar cell bodies 10 are separated one by one, and adjacent solar cell bodies 10 are arranged with gaps 15 between them.

[0013] The light-receiving-side plate layer 11a, the photovoltaic power generation layer 12, and the installation-side plate layer 11b that make up the solar cell body 10 are each substantially rectangular, with the photovoltaic power generation layer 12 being slightly smaller than the light-receiving-side plate layer 11a and the installation-side plate layer 11b. The photovoltaic power generation layer 12 is placed on the installation-side plate layer 11b, and the light-receiving-side plate layer 11a is layered on top of that, with interlayer gaps 14 formed around the photovoltaic power generation layer 12 being sealed with elastomer 20 (see the enlarged view of FIG. 1). As described above, gaps 15 are provided between the solar cell bodies 10, and both sides of the solar cell body 10 are covered with protective layers 13, so elastomer 20 is provided in the gaps 15 between the protective layers 13 (see the enlarged view of FIG. 1). Furthermore, the protective layer 13 and the light-receiving side plate layer 11a, the light-receiving side plate layer 11a and the solar power generation layer 12, the solar power generation layer 12 and the installation side plate layer 11b, and the installation side plate layer 11b and the protective layer 13 are each fixed with an adhesive (not shown).

[0014] The light-receiving-side plate layer 11a is made of a flexible glass plate with a thickness of 0.1 mm or less, and the thickness of the glass plate constituting the light-receiving-side plate layer 11a is preferably 20 μm to 100 μm. The properties of the glass plate are not particularly limited, but for example, a glass plate formed into a film by overflow molding may be used. Preferably, the glass plate has high light transmittance, heat resistance sufficient for outdoor use in sunlight, and dimensional stability (low thermal expansion and shrinkage).

[0015] The elastomer 20 used to seal the interlayer gap 14 and gap 15 between the photovoltaic layer 12 and the light-receiving side plate layer 11a is preferably an acrylic, silicone, polyolefin, polyurethane, or ethylene vinyl acetate elastomer, which has excellent adhesive properties, thermal expansion absorption, and shock absorption. In this embodiment, the elastomer 20 functions as both a sealant and an adhesive, and is preferably elastic enough not to impair the flexibility of the solar cell 1. Furthermore, the elastomer 20 used to seal the interlayer gap 14 between the photovoltaic layer 12 and the light-receiving side plate layer 11a, as well as the adhesives used to bond the protective layer 13 and the light-receiving side plate layer 11a and the light-receiving side plate layer 11a and the photovoltaic layer 12, must be transparent enough to allow light to pass through. The water vapor permeability of polyurethane-based adhesives is approximately 37 g / m²·day. The adhesive used to bond the photovoltaic power generation layer 12 to the installation-side plate layer 11b and between the installation-side plate layer 11b and the protective layer 13 does not need to be transparent, but it goes without saying that the same adhesive as that used on the light-receiving side may be used. Furthermore, the adhesives used to bond the elastomer 20 to each layer may be different or the same.

[0016] The dimensions D1 and D2 of the gaps 15 may be equally spaced in both directions as shown in FIG. 2(a), allowing for easy bending in either direction (see FIG. 2(b)). Furthermore, the gaps 15 between adjacent solar cell bodies 10 do not contain solar cell bodies 10, but contain only elastomer 20, allowing for extreme flexibility as shown in FIG. 5(c). Therefore, the gaps 15 may be positioned at desired bending locations to accommodate the three-dimensional shape of the installation surface on which the solar cells 1 are installed. The dimension D1 of the gaps 15 is the distance between one end of the solar cell body 10 and the opposing end of the adjacent solar cell body 10, i.e., between one end of the light-receiving side plate layer 11a and the opposing end of the adjacent light-receiving side plate layer 11a. The dimension D1 of the gaps 15 can be set depending on the size of the solar cell body 10, the size of the solar cell 1, and the radius of curvature of the installation surface on which the solar cells 1 are installed.

[0017] The protective layer 13 is disposed on the outermost layer of the solar cell 1, covering the entire solar cell body 10. It protects the solar cell body 10 and prevents cracking and shattering of the light-receiving-side plate layer 11a, which is made of a glass plate. As shown in the partial plan view of FIG. 2(a), the planar shape and dimensions of the upper and lower protective layers 13 are identical, with no planar misalignment. The protective layer 13 disposed on the light-receiving side is made of a material that is transparent enough to transmit light and efficiently convert it into electricity, and that absorbs the thermal expansion difference with the photovoltaic layer 12 to maintain interlayer adhesion and is impact-resistant. The protective layer 13 is typically made of a transparent, flexible synthetic resin film. Specific examples of suitable synthetic resin materials include low-density polyethylene (LDPE), high-density polyethylene (HDPE), unstretched polypropylene (CPP), oriented polypropylene (OPP), polyethylene terephthalate (PET), cycloolefin polymer (COP), and elastic fluorine films and urethane films. The thickness of the protective layer 13 is not particularly limited, but is preferably 20 μm to 500 μm, for example. The outer periphery of the protective layer 13 may be welded with an adhesive or by heat sealing to prevent peeling due to deterioration.

[0018] According to the above configuration, a thin glass plate of 0.1 mm or less, which is almost impermeable to oxygen and water vapor, is laminated on the light-receiving side of the photovoltaic layer 12, resulting in a solar cell 1 with high photovoltaic efficiency. Perovskite-type photovoltaic layers 12 in particular have a problem in that their photovoltaic efficiency is significantly reduced by oxygen and humidity. However, using a perovskite-type material for the photovoltaic layer 12 according to this embodiment is advantageous because it maintains gas barrier properties for a long period of time and allows for thin and flexible structures. While the overall thickness of the solar cell 10 is not particularly limited, the configuration of this embodiment allows for a thickness of 0.01 mm to 1 mm. Furthermore, since a gap 15 is provided between the solar cell bodies 10, the solar cell 1 can be flexible even when equipped with a glass plate. Furthermore, the solar cell body 10 is sealed with a protective layer 13, which prevents scratches and cracks on the glass plate and protects the light-receiving side plate layer 11a. For example, a glass plate with a thickness of 30 μm to 50 μm, which is less than 100 μm, can be bent, but it tends to be weak and prone to cracks when subjected to impact.However, since the glass plate that is the light-receiving side plate layer 11a is covered with protective layer 13, a solar cell body 10 that can withstand impact can be constructed.

[0019] Furthermore, if the interlayer gap 14 and gap portion 15 that occur between the solar power generation layer 12 and the light-receiving side plate layer 11a are sealed with a transparent and elastic elastomer 20, the solar cell 1 can be made flexible while not affecting the photovoltaic efficiency.

[0020] Next, with reference to FIG. 3, an example of a solar cell body 10 constituting the solar cell 1 will be described. First, FIG. 3(a) shows an example in which both the light-receiving-side plate layer 11a and the installation-side plate layer 11b are glass plates. In this case, the light-receiving-side plate layer 11a and the installation-side plate layer 11b are made of the same plate thickness of 0.1 mm or less. Because glass plates have nearly zero water vapor permeability and oxygen permeability and high gas barrier properties, the protective layers 13 arranged on the light-receiving side and the installation side do not need to consider gas barrier properties such as water vapor permeability and oxygen permeability. This has the advantage of providing a wider range of materials to choose from for the protective layer 13. To ensure efficient light reception, it is desirable to use a highly transparent material for the protective layer 13 arranged on the light-receiving side. Of course, both protective layers 13 may be made of highly transparent materials.

[0021] Figure 3(b) shows an example in which the light-receiving-side plate layer 11a is a glass plate with a thickness of 0.1 mm or less, there is no installation-side plate layer 11b, and a protective layer 13 with high gas barrier properties is arranged on the installation side of the photovoltaic layer 12. In this case, like the example of Figure 3(a), there is no need to consider the water vapor permeability, oxygen permeability, or gas barrier properties of the protective layer 13 arranged on the light-receiving side, and since there is no installation-side plate layer 11b, it is possible to further reduce the thickness of the solar cell 1. In this case, it is preferable that the installation-side protective layer 13 has low water vapor permeability and oxygen permeability and high gas barrier properties.

[0022] Figure 3(c) is an example that can be considered a modification of Figure 3(a) or Figure 3(b). This example has the same light-receiving-side plate layer 11a and protective layers 13 on both the top and bottom surfaces (both in the thickness direction), but differs from the above examples in that it includes a flexible resin plate material as the installation-side plate layer 11b. Examples of resin plate materials include polycarbonate (PC), acrylic resin (PMMA), polyethylene terephthalate (PET), copolymer polyester (PETG), polyvinyl chloride (PVC), cyclic olefin polymer (COC, COP), and polyethylene (PE). The thickness of the installation-side plate layer 11b may be selected depending on the installation location and is not particularly limited, but a thin thickness allows for thinner solar cells 1.

[0023] Next, with reference to FIGS. 4 and 5, a bending evaluation test of a glass plate conducted by the inventors will be described. In this evaluation test, sheet bodies 100 and 100A simulating solar cells were prepared. Both sheet bodies 100 and 100A had the same laminated structure, and glass plates and films of the same thickness were used. The evaluation was conducted to determine the difference and effect on the bendability of the glass plate depending on whether or not there was a gap 150. The bendability was evaluated by bending the sheet body 100 or 100A at approximately its center, maintaining the bent state with a pair of clamping plates 300, 300, and checking for cracks in the glass plate after release. The bending gap L (see FIGS. 4(c) and 5(c)) of the sheet body 100 or 100A was varied to 50 mm, 40 mm, 30 mm, 20 mm, 10 mm, and 5 mm. The evaluation was conducted while maintaining a constant speed when bending the approximately center portion of the sheet body 100 or 100A.

[0024] Each of the sheets 100 and 100A was approximately rectangular, with sides measuring approximately 20 cm. A 150 μm thick polyethylene terephthalate protective film 130, equivalent to the protective layer 13, was disposed on the outermost surface of each of the sheets 100 and 100A in the thickness direction. A 38 μm polyethylene terephthalate film 120 was disposed on both thickness directions of a 50 μm thick glass plate layer 110 to form a glass layer 101 equivalent to the solar cell 10. The protective film 130 and the film 120 were bonded together with an adhesive 200. An EVA (ethylene vinyl acetate) adhesive that becomes transparent when heated was used as the adhesive 200. G-Leaf (registered trademark) thin glass manufactured by Nippon Electric Glass Co., Ltd. was used as the glass plate layer 110.

[0025] The sheet body 100 has one glass layer 101 formed slightly smaller than the approximately rectangular protective film 130, while the sheet body 100A has two glass layers 101 within a pair of approximately rectangular protective films 130, with a gap D3 of 10 mm between the glass layers 101 (see Figure 5(b)).

[0026] When a bending evaluation test was performed on the sheet body 100, as shown in the table in FIG. 4(d), no cracks were observed in the glass layer 101 when the bending gap L was between 50 mm and 20 mm. However, when the bending gap L was set to 10 mm, cracks were observed. Therefore, when the bending gap L was checked in 1 mm increments from 20 mm, it was found that cracks occurred when the bending gap L was 13 mm. The radius of curvature of the sheet body 100 at this time was R6.5 mm. On the other hand, when a bending evaluation test was performed on the sheet body 100A, as shown in the table in FIG. 5(d), no cracks were observed in the glass layer 101 when the bending gap L was between 50 mm and 5 mm. This evaluation test revealed that when the gap portion 150 was set to 10 mm, no cracks occurred even when the sheet was bent up to a bending gap L of 5 mm (radius of curvature R2.5 mm).

[0027] From the above, it was found that if a 50 μm glass plate is protected with a protective film as described above, it can maintain flexibility without cracking even if the bending gap L is 20 mm (curvature radius R 10 mm). In addition, if gap 150 is provided between the glass plates, it was found that no cracks will occur even if the bending gap L is 5 mm, so it was demonstrated that if this structure is applied to a solar cell module, it can be made to have sufficient flexibility.

[0028] The configurations and structures of the solar cell 1 and solar cell body 10 according to the above-described embodiments are not limited to those described above. The protective layer 13 may be configured by laminating multiple layers, and the light-receiving side plate layer 11a may be configured by a film layer in addition to a glass plate. The configurations of the modules that make up the solar cell 1 and the photovoltaic layer 12 that make up the solar cell body 10 are also not limited to the shapes and numbers shown in FIG. 2(a). [Explanation of symbols]

[0029] 1. Solar cells 10 Solar cell body 11a Light-receiving side plate layer 11b Installation side plate layer 12 Photovoltaic layer 13 Protective layer 14 Interlayer gap 15 Gap 20 Elastomer

Claims

1. A flexible solar cell including a plurality of solar cell assemblies, each of which has a photovoltaic layer and a light-receiving side plate layer laminated on the light-receiving side of the photovoltaic layer, the solar cell bodies are arranged with a gap therebetween, and both sides of the solar cell bodies in the thickness direction are sealed with protective layers; The solar cell is characterized in that the light-receiving side plate layer is a glass plate having a thickness of 0.1 mm or less.

2. In claim 1, A solar cell, characterized in that an interlayer gap occurring between the photovoltaic power generation layer and the light-receiving side plate layer and the gap portion are sealed with a transparent, elastic elastomer.

3. In claim 1 or claim 2, A solar cell, wherein the installation-side plate layer laminated on the installation surface side of the photovoltaic power generation layer is a glass plate having a plate thickness of 0.1 mm or less.

4. In claim 1 or claim 2, A solar cell, wherein an installation-side plate layer laminated on the installation surface side of the photovoltaic power generation layer is a flexible resin plate material.

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