Solar battery and method for manufacturing same

Abstract

Provided is a solar cell 10 having a laminate body 11 formed of protective layers 13 sandwiching a photovoltaic power generation layer 12. A ceramic coating 15 containing a polysilazane component is fixed to both end surfaces 11a of the laminate 11.

Description

Solar cell and its manufacturing method

[0001] The present invention relates to a solar cell having a laminate in which a photovoltaic layer is sandwiched between protective layers, and a method for manufacturing the same.

[0002] In order to improve the gas barrier properties against oxygen and water vapor in this type of conventional solar cell, a technique has been proposed in which the photovoltaic layer is covered with a polysilazane coating having high gas barrier properties in addition to or instead of protective layers (e.g., synthetic resin barrier films) disposed on the front and back sides. In the technique disclosed in Patent Document 1, the entire photovoltaic layer is protected by being disposed within a sealing layer made of polysilazane.

[0003] Patent No. 6876480

[0004] However, in a method such as that described in Patent Document 1, in which polysilazane is arranged so as to surround the photovoltaic layer from all directions, a large amount of expensive polysilazane is required to form one solar cell, which may result in high costs.

[0005] The present invention has been proposed in consideration of the above circumstances, and its object is to provide a solar cell that can ensure gas barrier properties while reducing the amount of polysilazane used, and a method for manufacturing the same.

[0006] In order to achieve the above object, the solar cell of the present invention is a solar cell having a laminate in which a photovoltaic layer is sandwiched between protective layers, and is characterized in that a ceramic coating containing a polysilazane component is fixed to the end faces of the entire periphery of the laminate.

[0007] The method for manufacturing a solar cell of the present invention is characterized in that a hydrophilic region and a water-repellent region adjacent to the hydrophilic region are formed on a working surface, the laminate is placed on the working surface so that its outer edge is contained within the hydrophilic region in a planar view, and a liquid ceramic coating agent is dripped onto the end surface to form the ceramic coating.

[0008] Another method for manufacturing a solar cell of the present invention is characterized in that a water-repellent region and an ultra-water-repellent region adjacent to the water-repellent region are formed on a work surface, a liquid ceramic coating agent is dripped onto the water-repellent region to form liquid protrusions, and the laminate is positioned so that its end face is in contact with the liquid protrusions, thereby forming the ceramic coating.

[0009] Since the solar cell of the present invention has the above-described configuration, it is possible to ensure gas barrier properties while reducing the amount of polysilazane used.

[0010] Since the method for producing a solar cell of the present invention employs the above-described procedure, it is possible to produce a solar cell that ensures gas barrier properties while reducing the amount of polysilazane used.

[0011] Fig. 2 is a schematic vertical cross-sectional view of a solar cell according to one embodiment of the present invention. Fig. 3 is a schematic vertical cross-sectional view showing a method for manufacturing the solar cell of Fig. 1. Fig. 4 is a schematic vertical cross-sectional view showing another method for manufacturing the solar cell of Fig. 1. Fig. 5 is a schematic vertical cross-sectional view showing an example of a flexible solar cell.

[0012] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the accompanying drawings. First, the basic configuration of a solar cell 10 according to the embodiment will be described.

[0013] The solar cell 10 has a laminate 11 formed by sandwiching a photovoltaic layer 12 between protective layers 13. A ceramic coating 15 containing a polysilazane component is fixed and formed on the end face 11a of the entire periphery of the laminate 11.

[0014] The polysilazane component includes silica glass that is formed by the transformation (conversion) of polysilazane through a chemical reaction with water.

[0015] Next, details of the solar cell 10 according to this embodiment will be described. The solar cell 10 exemplified below is a perovskite solar cell, and is assumed to have a thickness of approximately 0.1 mm to 1.0 mm. This solar cell 10 is used as a flexible solar cell 30, as will be described later with reference to FIG. 4. The present invention is applicable not only to perovskite solar cells, but also to amorphous silicon solar cells, dye-sensitized solar cells, and organic thin-film solar cells.

[0016] A perovskite solar cell is a solar cell 10 that has a perovskite layer made of an organic material with a unique crystal structure called a perovskite structure as a power generation layer (not shown). The perovskite layer itself is extremely thin, about 1 μm thick.

[0017] As shown in the longitudinal cross section of Figure 1, the laminate 11 of the solar cell 10 has protective layers 13 arranged so as to be in close contact with the upper and lower surfaces of the photovoltaic layer 12, and the protective layers 13 are fixed between each other with an adhesive.

[0018] Although plan views of the solar cell 10 and the laminate 11 are omitted, the planar shape and dimensions of the upper and lower protective layers 13 are the same, with no misalignment in plan. The planar shape of the laminate 11 is a substantially rectangular shape that matches the planar shape of the protective layer 13. The photovoltaic layer 12 has planar dimensions smaller than those of the protective layer 13, and is disposed in the center of the protective layer 13 in plan view. At least one surface of this photovoltaic layer 12 serves as a light-receiving surface for receiving light.

[0019] An adhesive layer 14 is filled between the protective layers 13 on the sides of the photovoltaic layer 12 up to the periphery of the protective layer 13. This adhesive layer 14 is a layer formed by hardening an adhesive used to bond the protective layers 13 to each other, and is disposed without gaps in the space on the sides of the photovoltaic layer 12 disposed between the protective layers 13.

[0020] The protective layer 13 may be formed by coating a synthetic resin film as a base material with an inorganic material by vapor deposition or the like. Specifically, a polypropylene film or the like may be coated with silica, alumina, aluminum, silicon nitride, or the like.

[0021] Assuming that the laminate 11 has a thickness of, for example, about 0.1 mm to 1.0 mm, it is desirable to use a thin synthetic resin film for the protective layer 13. Since it is required to reduce the thickness and also increase the light conversion efficiency, the protective layer 13 must also be able to sufficiently block oxygen and water vapor. In order to improve the gas barrier properties against oxygen and water vapor, it is desirable to use a synthetic resin film coated with an inorganic material that has high gas barrier properties as the protective layer 13. Methods for coating a synthetic resin film with an inorganic material include vapor deposition (PVD), sputtering, and chemical vapor deposition (CVD).

[0022] Furthermore, in consideration of the gas barrier properties against oxygen and water vapor, specific types of synthetic resin material that is the base material of the protective layer 13 include low-density polyethylene (LDPE), high-density polyethylene (HDPE), solid polypropylene (CPP), oriented polypropylene (OPP), polyethylene terephthalate (PET), and cycloolefin polymer (COP), etc., as suitable materials.

[0023] The gas barrier property can be measured by oxygen permeability (unit: ml / m2 day MPa) and water vapor permeability (unit: g / m2 day), and it can be determined that the smaller these values ​​are, the higher the gas barrier property is. The water vapor permeability of the protective layer 13 is 5×10 －３ The oxygen permeability of the protective layer 13 is preferably 1×10 －4 It is desirable to set it to ml / m2·day·MPa or less.

[0024] PET has an oxygen permeability of approximately 600 ml / m²-day-MPa and a water vapor permeability of approximately 27 g / m²-day, which are smaller than those of other materials, making it an organic material with high gas barrier properties. PET is also inexpensive, making it a particularly suitable material among the synthetic resin materials mentioned above.

[0025] LDPE, HDPE, CPP, and OPP have water vapor permeabilities comparable to those of PET, but oxygen permeabilities of 5000 ml / m2·day·MPa or higher. Other synthetic resin materials, such as unstretched nylon, stretched nylon, stretched polystyrene, and polycarbonate, may also be used.

[0026] The protective layer 13 may be any such synthetic resin film coated with an inorganic material to enhance its gas barrier properties. For example, a single-layer PET film with alumina vapor deposition has an oxygen permeability of approximately 0.1 ml / m2·day·MPa and a water vapor permeability of approximately 0.05 g / m2·day. By stacking multiple sheets of alumina vapor-deposited single-layer PET, the water vapor permeability of the protective layer 13 can be increased to 5×10 －３ It is particularly important to reduce the water vapor permeability of the photovoltaic layer 12 because the photovoltaic layer 12 ionizes in the presence of water vapor.

[0027] The protective layer 13 is preferably made of an inorganic material such as a glass plate or a laminate of a glass plate and a synthetic resin film. In other words, three types of materials are conceivable for the protective layer 13: a synthetic resin film, a glass plate, and a laminate of these. Also, different types of protective layers 13 may be disposed above and below.

[0028] Glass has a water vapor permeability and oxygen permeability of almost zero and has high gas barrier properties, making it suitable for use as protective layer 13. However, thin glass is more fragile than synthetic resin films, so it is desirable to use a synthetic resin film or a laminate of synthetic resin film and glass as the base material for protective layer 13 of a flexible solar cell.

[0029] In order to properly and efficiently receive light, it is desirable to use a highly transparent material for at least the protective layer 13 disposed on the light-receiving side of the solar cell 10. Of course, highly transparent materials may be used for both protective layers 13.

[0030] It is desirable to use an adhesive that has excellent transparency, adhesion, thermal expansion absorption, and shock absorption properties, such as a transparent acrylic, silicone, polyolefin, polyurethane, or ethylene vinyl acetate adhesive, as the adhesive for forming the adhesive layer 14. The water vapor permeability of polyurethane adhesives is approximately 37 g / m2·day.

[0031] 1, the solar cell 10 further includes a ceramic coating 15, primarily made of an inorganic material, formed on the end surface 11a of the laminate 11. The ceramic coating 15 contains silica glass formed by the reaction of the polysilazane liquid with moisture in the air.

[0032] The ceramic coating 15 may be made of only silica glass obtained by converting polysilazane liquid, or may contain materials other than the polysilazane component, such as indium oxide, silica, alumina, etc. Silica glass obtained by converting polysilazane liquid has extremely high gas barrier properties, with water vapor permeability and oxygen permeability being almost zero.

[0033] In this way, since the end face 11a of the laminate 11 is covered with the ceramic coating 15 containing a polysilazane component, the photovoltaic layer 12 in the laminate 11 is also suitably protected from the end face 11a side.

[0034] In this way, the gas barrier properties are improved by covering the top and bottom of the photovoltaic layer 12 with the protective layer 13 containing an inorganic material, while the gas barrier properties are improved by covering the side surface of the photovoltaic layer 12 (the end surface 11a of the laminate 11) with the ceramic coating 15 containing a polysilazane component.

[0035] In particular, since a layered surface (cross section of multiple layers) including an organic adhesive layer 14 appears on the end surface 11a of the laminate 11, it is effective to use a ceramic coating 15 with strong gas barrier properties as the coating for the end surface 11a.

[0036] Although an organic adhesive layer 14 is disposed on the side of the photovoltaic layer 12 so as to be adjacent to the photovoltaic layer 12, as described above, the organic adhesive layer 14 does not have good gas barrier properties by itself, and therefore it is naturally insufficient to enhance the gas barrier properties for the photovoltaic layer 12 by using only the adhesive layer 14. In other words, it is extremely difficult to ensure high gas barrier properties for the photovoltaic layer 12 by constructing the solar cell 10 using only the laminate 11 without covering the end face 11 a with the ceramic coating 15.

[0037] Furthermore, instead of an organic adhesive, a ceramic coating agent containing a polysilazane liquid may be used as the adhesive between the protective layers 13. That is, the adhesive layer 14 between the protective layers 13 and the ceramic coating 15 covering the end surface 11a of the laminate 11 may be integrally formed from a cured material containing a polysilazane component. Furthermore, the adhesive layer 14 and the ceramic coating 15 may be formed from different inorganic materials.

[0038] In this type of solar cell 10, the adhesive layer 14 and the ceramic coating 15 of the laminate 11 are both made of inorganic materials, so that the gas barrier properties on the side surfaces of the photovoltaic layer 12 can be strengthened.

[0039] Next, a method for manufacturing the solar cell 10 will be described with reference to Figures 2 and 3. As described above, the solar cell 10 according to this embodiment is in the form of a thin film, and the surface area of ​​the end face 11a is extremely small, so it is difficult to use a vapor deposition method to form the ceramic coating 15 on the end face 11a. Of course, it is also difficult to apply a material directly to the end face 11a.

[0040] Therefore, the following procedure for forming a coating on the end surface 11a is preferably used. The method for manufacturing this solar cell 10 is a method having the following procedure for forming a coating. Note that a description of the procedure for forming the laminate 11 will be omitted. The following description will be given along steps A1 to A4 shown in FIG. 2.

[0041] First, the planar work surface 20 is subjected to surface modification to form a hydrophilic region 21 and a water-repellent region 22 adjacent to the hydrophilic region 21. Specifically, a strip-shaped hydrophilic region 21 is formed along the outer edge of a rectangle that roughly matches the planar shape of the laminate 11, and water-repellent regions 22 are formed on both the inside and outside of the strip-shaped hydrophilic region 21.

[0042] In other words, the water-repellent region 22 is formed in the center of the work surface 20 to match the planar dimensions of the laminate 11, and the hydrophilic region 21 in a square ring shape is formed around the water-repellent region 22, which is then formed around the hydrophilic region 21. The width of the hydrophilic region 21 may be determined appropriately to match the height of the end face 11a of the laminate 11 (see step A1 in FIG. 2 for the above).

[0043] Next, the laminate 11 is placed in the water-repellent region 22 surrounded by the hydrophilic region 21 so that the outer periphery of the laminate 11 fits within the hydrophilic region 21 in a plan view (see step A2 in FIG. 2).

[0044] Then, a liquid ceramic coating agent 26 containing a polysilazane liquid is dropped onto the end face 11a. The dropped ceramic coating agent 26 covers the entire end face 11a (layered surface) by adsorption, and excess liquid is diffused over the surface into the hydrophilic region 21 on the working surface 20 (see step A3 in FIG. 2).

[0045] At this time, no droplets form on the hydrophilic region 21, which remains wet, and the ceramic coating agent 26 remains covering the end surface 11a of the laminate 11. Furthermore, if there is excess liquid that cannot be absorbed by the hydrophilic region 21, the excess liquid moves to the water-repellent region 22, but the liquid is repelled by the water-repellent region 22, forming droplets.

[0046] When the ceramic coating agent 26 has completely covered the end face 11a, or when droplets begin to form in the water-repellent region 22, the dripping of the ceramic coating agent 26 is stopped, and the ceramic coating agent 26 on the end face 11a is heated in this state. By heating the ceramic coating agent 26 on the end face 11a, the ceramic coating agent 26 hardens. Specifically, while the ceramic coating agent 26 is being heated, the polysilazane liquid contained in the ceramic coating agent 26 reacts with moisture in the air and is converted into silica glass, resulting in a ceramic coating 15 containing silica glass (see step A4 in FIG. 2).

[0047] In this way, the ceramic coating 15 can be formed on the end surface 11a of the laminate 11 by simple work on the work surface 20. Because this method effectively utilizes the functions of the hydrophilic region 21 and the water-repellent region 22, the ceramic coating agent 26 is not wasted, and expensive materials can be saved.

[0048] 3 also makes it possible to easily form ceramic coating 15 and reduce the amount of material used for ceramic coating agent 26. The following describes steps B1 to B4 shown in FIG.

[0049] First, a water-repellent region 23 and an ultra-water-repellent region 24 (or highly water-repellent region; hereinafter the same) adjacent to the water-repellent region 23 are formed on the work surface 20. Specifically, the ultra-water-repellent region 24 is formed in the center of the work surface 20 to match the planar dimensions of the laminate 11, and then a square-ring-shaped water-repellent region 23 is formed around the ultra-water-repellent region 24, and another ultra-water-repellent region 24 is formed around the ring-shaped water-repellent region 23. The width of the water-repellent region 23 can be determined appropriately to match the height of the end face of the laminate 11 (see step B1 in FIG. 3 for the above).

[0050] Next, a liquid ceramic coating agent 26 containing a polysilazane liquid is dropped onto the water-repellent region 23 to form liquid protrusions 28. Since the liquid agent is dropped onto the water-repellent region 23, droplets are formed due to the water-repellent effect, and these droplets form continuous protrusions along the water-repellent region 23.

[0051] At this time, since the area adjacent to the water-repellent area 23 is the ultra-water-repellent area 24, the ceramic coating agent 26 does not easily move to the adjacent area, and a liquid protrusion 28 is formed around the water-repellent area 23 (see step B2 in Figure 3 for the above).

[0052] Then, the laminate 11 is placed in the ultra-water-repellent region 24 surrounded by the water-repellent region 23 so that the end face 11a contacts the liquid protrusion 28, and the ceramic coating agent 26 that constitutes the liquid protrusion 28 is adsorbed onto the end face 11a so as to cover it (see step B3 in Figure 3).

[0053] After confirming that the ceramic coating agent 26 has covered substantially the entire end face 11 a, the ceramic coating agent 26 covering the end face 11 a is heated. Heating the ceramic coating agent 26 causes the ceramic coating agent 26 to harden. Specifically, while the ceramic coating agent 26 is being heated, the polysilazane liquid contained in the ceramic coating agent 26 reacts with moisture in the air and is converted into silica glass, thereby obtaining a ceramic coating 15 containing silica glass (see step B4 in FIG. 3).

[0054] 2 and 3, the ceramic coating agent 26 is heated and cured, but the polysilazane liquid can be converted to silica glass if it contains moisture, so a method without heating may be used. Also, a curing agent may be added to the ceramic coating agent 26 to cause it to harden.

[0055] Furthermore, as a method for manufacturing solar cell 10 in which adhesive layer 14 between protective layers 13 and ceramic coating 15 covering end face 11 a of laminate 11 are integrally formed from a cured product containing a polysilazane component, the following method, for example, can be adopted instead of directly using the method shown in FIG. 2 or FIG. 3 .

[0056] That is, this type of solar cell 10 can be manufactured by sequentially placing a protective layer 13 (protective film), a photovoltaic layer 12 (photovoltaic film), and a protective layer 13 (protective film) on a porous water-repellent sheet, dropping a ceramic coating agent 26 containing a polysilazane liquid onto the end surfaces of the layers, and, before the coating agent hardens, drawing a vacuum from below the porous water-repellent sheet while applying pressure from above.

[0057] In other words, in this method, the ceramic coating agent 26 containing the polysilazane liquid is used instead of an adhesive to form the adhesive layer 14. In this case, it is desirable to apply pressure as described above to prevent the polysilazane liquid from flowing between the photovoltaic layer 12 and the protective layer 13 and having adverse effects on the photovoltaic layer 12, such as a decrease in the photoelectric effect. When an organic adhesive is used, the amount of organic solvent (concentration of the adhesive component) can be adjusted so that the organic solvent evaporates before the ceramic coating agent 26 is applied to the end face 11a of the laminate 11.

[0058] According to the method of using the ceramic coating agent 26 as the adhesive layer 14 in this manner, the adhesive layer 14 between the protective layers 13 and the ceramic coating 15 covering the end surface 11 a of the laminate 11 are integrally formed from a cured product containing a polysilazane component, thereby further improving the gas barrier properties.

[0059] 2 or 3 may be used to form the ceramic coating 15 from the ceramic coating agent 26 on the laminate 11 on which the adhesive layer 14 is formed using the ceramic coating agent 26. In particular, when the adhesive layer 14 and the ceramic coating 15 are made of different inorganic materials, these manufacturing methods may be used.

[0060] Next, a flexible solar cell 30 formed by assembling a plurality of solar cells 10 shown in Fig. 1 to form, for example, a grid-like structure in a plan view will be described with reference to the partial vertical cross-sectional view of Fig. 4. Note that a plan view is not shown.

[0061] The flexible solar cell 30 in Figure 4 is made up of multiple solar cells 10 arranged in a grid pattern and sandwiched between protective films 31. The solar cells 10 are separated into individual battery blocks 32, and connecting portions 34 are formed between adjacent battery blocks 32 by thermally welding the upper and lower protective films 31 together.

[0062] One laminate 11 is placed in a block space 33 surrounded by upper and lower protective films 31 in one battery block 32, and ceramic coatings 15 are fixed to the four peripheral end faces 11a of the laminate 11. In other words, one solar cell 10 is placed without any gaps within the block space 33.

[0063] The flexible solar cell 30 has connecting portions 34 formed lengthwise and widthwise to separate each battery block 32. The connecting portions 34 extend while linearly intersecting each other in the lengthwise and widthwise directions, and the solar cell can be bent along the connecting portions 34.

[0064] The connecting portions 34 may be arranged only in either the vertical or horizontal direction. In this case, the block space 33 extends long in the vertical or horizontal direction, and a plurality of solar cells 10 are arranged side by side in the block space 33.

[0065] The flexible solar cell 30 can be used by being wrapped around a cylindrical object, for example, and furthermore, because it is a thin film, it can be attached to a curved or uneven surface without losing its curvature. For example, the flexible solar cell 30 can be attached to the outer surface of a bronze statue or other object to be installed outdoors, or to an indoor ornament.

[0066] The configurations and shapes of the solar cell 10 and flexible solar cell 30 according to the embodiments described above are merely examples, and it goes without saying that they can be appropriately changed to configurations and shapes other than those shown in the figures.

[0067] REFERENCE SIGNS LIST 10 Solar cell 11 Laminate 11a End surface 12 Photovoltaic layer 13 Protective layer 14 Adhesive layer 15 Ceramic coating 20 Working surface 21 Hydrophilic area 22, 23 Water-repellent area 24 Ultra-water-repellent area 26 Ceramic coating agent 28 Liquid protrusion 30 Flexible solar cell 31 Protective film 32 Battery block 33 Block space 34 Connecting portion

Claims

1. A solar cell having a laminate in which a photovoltaic layer is sandwiched between protective layers, characterized in that a ceramic coating containing a polysilazane component is adhered to the entire peripheral end face of the laminate.

2. A solar cell according to claim 1, wherein a cured adhesive is disposed on the side of the photovoltaic layer between the protective layers, and the end face is a layered surface of multiple layers including a central layer of the adhesive.

3. A solar cell according to claim 1, wherein the protective layer is formed by coating a synthetic resin film with an inorganic material.

4. A solar cell according to claim 1, wherein the protective layer is made of a glass plate or a laminate of a glass plate and a synthetic resin film.

5. A method for manufacturing a solar cell according to claim 1, comprising forming a hydrophilic region and a water-repellent region adjacent to the hydrophilic region on a working surface, placing the laminate on the working surface so that its outer edge is contained within the hydrophilic region in a plan view, and dropping a liquid ceramic coating agent containing a polysilazane liquid onto the end surface to form the ceramic coating.

6. A method for manufacturing a solar cell according to claim 5, wherein the laminate is rectangular in plan view, the hydrophilic region is a strip-shaped region along the outer edge of the rectangle that roughly matches the planar shape of the laminate, while the water-repellent region is a region adjacent to each of the inside and outside of the hydrophilic region, and the laminate is placed on the water-repellent region located inside the hydrophilic region.

7. A method for manufacturing a solar cell according to claim 1, comprising forming a water-repellent region and an ultra-water-repellent region adjacent to the water-repellent region on a working surface, dripping a liquid ceramic coating agent containing a polysilazane liquid onto the water-repellent region to form liquid protrusions, and positioning the laminate so that its end faces contact the liquid protrusions to form the ceramic coating.

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