Solar cell module and its manufacturing method

Abstract

To provide a simple countermeasure against deformation of each cell string due to application of a pressure to each cell string from a sealing material in sealing.SOLUTION: Cell strings 2 are constituted by electrical connection of a plurality of slender cells in a direction at which long sides extend, the plurality of cell strings 2 to 2 are arranged in parallel with a gap in a direction at which the short sides extend, and have first sealing materials 31F and 31b made of a resin, and a second sealing material 32 which has a melting point lower than those of the first sealing materials 31F an 31B and is made of a resin, the first sealing materials 31F and 31B are arranged so as to sandwich the plurality of cell strings 2 to 2 in a thickness direction, the second sealing material 32 is arranged in the gap in the plurality of cell strings 2 to 2, at the beginning when the second sealing material 32 is arranged in the gap, the plurality of particles have aggregated flowability, and are integrated through a molten state by heating to be equal to or higher than the melting point.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to a solar cell module that constitutes a see-through solar cell, and a method for manufacturing the same. [Background technology]

[0002] Light-transmitting solar cells are used in windows of large buildings, etc. When particularly excellent design is required, light-transmitting solar cells are used in which the power generation area of ​​the thin-film solar cell is locally removed to allow light to pass through. However, in recent years, from the perspective of output per unit area of ​​the window, solar cells of a type in which roughly square cells are arranged with gaps between them are often used.

[0003] However, solar cells using such roughly square cells have design problems because the roughly square cells stand out, and there is a need for ingenuity to make the cells less noticeable by color, to hide the metal electrodes of each cell, and the wiring between the cells, etc. One solution to this problem is to connect many elongated cells in one direction along their length to form a cell string, and to arrange the multiple aligned cell strings with a fixed gap between them to create a see-through solar cell with a blind-like appearance.

[0004] Incidentally, the cell strings of a blind-style see-through solar cell are extremely long and narrow (each cell string has a very large length-to-width ratio), and multiple cell strings must be arranged in parallel at regular intervals. These must then be sealed by sandwiching them with a transparent resin sealant. However, as shown in Figure 4(A), pressure is applied to each cell string 101 from the sealant during sealing, making it prone to distortion. This makes it extremely difficult to maintain the straightness of each cell string 101 after sealing and the parallelism between adjacent cell strings 101, 101, both of which are elements directly related to the design.

[0005] One possible solution to this problem is to place narrow resin pieces 102 between the multiple cell strings 101, as described in Patent Document 1 (although the purpose of the invention disclosed in Patent Document 1 is different from the solution to the above problem). This allows the resin pieces 102 to resist the pressure applied to each cell string 101 by the sealing material, making each cell string 101 less likely to warp (see FIG. 4(B)). However, placing such narrow resin pieces 102 one by one between the multiple cell strings 101 requires a lot of man-hours. Furthermore, because alignment is difficult, it is difficult to mechanize the placement process, and it must be done manually. Furthermore, if the cell strings 101 were sealed by sandwiching them between glass plates with the resin pieces 102 resting on them, there is a risk that the cells constituting the cell strings 101 could be damaged due to the excessive load. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] JP 2010-192909 A (Fig. 2) Summary of the Invention [Problem to be solved by the invention]

[0007] Therefore, an object of the present invention is to provide a solar cell module and a manufacturing method thereof that can easily address the distortion of each cell string caused by pressure applied to each cell string from the sealing material during sealing. [Means for solving the problem]

[0008] The present invention provides a solar cell module in which a plurality of elongated cells, whose long sides are at least 10 times the length of their short sides in a planar view, are used, and a cell string is formed by electrically connecting the plurality of cells along the direction in which the long sides extend, and the plurality of cell strings are arranged parallel to each other with gaps between them in the direction in which the short sides extend, the solar cell module comprising: a first sealing material made of resin; and a second sealing material made of resin having a melting point lower than that of the first sealing material, the first sealing material being arranged so as to sandwich the plurality of cell strings in the thickness direction, and the second sealing material being arranged in the gaps between the plurality of cell strings, and when arranged in the gaps, the plurality of particles are in a fluid state with agglomerations, and when heated above the melting point, they are melted and then integrated into one body.

[0009] With this configuration, when the second sealing material is initially placed in the gaps between the multiple cell strings, it is in a fluid state where multiple particles are aggregated, so that it can be placed in the gaps by simply scattering the second sealing material over the multiple cell strings. Moreover, because the melting point of the second sealing material is lower than that of the first sealing material, the second sealing material is less likely to affect the first sealing material when it is heated to a molten state and then integrated.

[0010] The first sealing material and the second sealing material in the integrated state may have different refractive indices.

[0011] According to this configuration, the refractive index of the second sealing material is different from that of the first sealing material when it is integrated with the first sealing material, so that the history of the two heating processes can be confirmed even in the state of a solar cell module.

[0012] The present invention also provides a method for manufacturing a battery using elongated cells whose long sides are 10 times or more longer than their short sides in a plan view, and for electrically connecting a plurality of the cells along the direction in which the long sides extend to form a cell string; a first back-side sealing material and a first front-side sealing material that are made of resin and have a sheet shape; and a second sealing material that is made of resin, has a lower melting point than the first back-side sealing material and the first front-side sealing material, and is in a fluid state in which a plurality of particles are aggregated; the first back-side sealing material is overlaid on a back-side transparent plate; and the plurality of the cell strings are arranged on the first back-side sealing material with gaps in the direction in which the short sides extend. the second sealing material is placed in the gaps between the plurality of cell strings in parallel with each other, and a first heating is performed at a temperature higher than the melting point of the second sealing material and lower than the melting points of the first back-side sealing material and the first front-side sealing material; after a time has elapsed since the end of the first heating and the second sealing material has solidified, the first front-side sealing material is placed on top of the plurality of cell strings, and a front-side transparent plate is further placed on top of the first front-side sealing material; and a second heating is performed at a temperature higher than the melting points of the first back-side sealing material and the first front-side sealing material.

[0013] This method allows the second sealing material to be placed in the gaps between the cell strings while retaining fluidity due to the aggregation of particles. For example, the second sealing material can be placed in the gaps simply by scattering it over the cell strings. Moreover, because the melting point of the second sealing material is lower than that of the first sealing material, it is less likely to affect the first sealing material during the first heating cycle.

[0014] Furthermore, after the second sealing material is placed so as to cover the plurality of cell strings, the second sealing material can be leveled to remove the second sealing material from the surfaces of the plurality of cell strings and fill the gaps, and then the first heating can be performed.

[0015] According to this method, the second sealing material is placed so as to cover the plurality of cell strings and then smoothed out, whereby the second sealing material can be easily removed from the surfaces of the plurality of cell strings, which are unnecessary portions. [Effects of the Invention]

[0016] Therefore, the present invention can easily prevent distortion of each cell string caused by pressure applied from the sealing material to each cell string when sealing is performed. [Brief explanation of the drawings]

[0017] [Figure 1] 1 is a front view showing an example of the appearance of a solar cell module according to an embodiment of the present invention, with the light-receiving surface side facing forward. [Figure 2] FIG. 2 is a diagram schematically illustrating a cross-sectional configuration of the solar cell module. [Figure 3] 10A and 10B are diagrams showing a schematic diagram of the manufacturing procedure of the solar cell module, in which (A) shows the state in which the second sealing material is being spread on the cell string, (B) shows the state in which the second sealing material is being leveled, and (C) shows the state after the second sealing material has been leveled. [Figure 4] Schematic diagrams related to the problem to be solved by the invention, where (A) shows a state in which distortion has occurred in each cell string, and (B) shows a state in which distortion is less likely to occur in each cell string due to the opposing resin pieces. DETAILED DESCRIPTION OF THE INVENTION

[0018] The present invention will be described below with reference to the drawings, taking one embodiment as an example. As shown in FIG. 1, a solar cell module 1 of this embodiment constitutes a see-through solar cell with a blind-like structure, in which light is transmitted in the thickness direction (the front-to-back direction in FIG. 1). As shown in FIGS. 1 and 2, this solar cell module 1 includes, as main components related to the present invention, a plurality of cell strings 2-2, a sealing material 3, and a transparent plate 4, and as shown in FIG. 1, the solar cell module 1 is held together as a single unit by frame portions 5 located on four edges (note that the frame portions 5 are not shown in FIG. 2). This solar cell module 1 is attached to a window frame of a building, for example, and used as a window.

[0019] As shown in FIG. 2, the solar cell module 1 is configured (layered) from the light-receiving surface side to the back surface side, with a transparent plate 4 as a front glass plate 4F made of high-transmittance (float) untempered glass, and two front-side first encapsulants 31F (two in this embodiment) of the first encapsulant, each of which is made of a transparent resin and has approximately the same size as the front glass plate 4F. From the back surface side opposite the light-receiving surface side, a transparent plate 4 as a back glass plate 4B made of high-transmittance (float) untempered glass, and three back-side first encapsulants 31B (three in this embodiment) of the first encapsulant, each of which is made of a transparent resin and has approximately the same size as the back glass plate 4B. A plurality of cell strings 2-2 (see FIG. 1) are disposed between the front-side first encapsulant 31F (upper side) and the back-side first encapsulant 31B (lower side). The front-side first encapsulant 31F and the back-side first encapsulant 31B are sheet-shaped. 2, gaps are shown between the first front-side sealing material 31F and the cell strings 2-2, but these are formed by spacers (not shown) arranged at the left and right ends in FIG. 1. The first sealing material, consisting of the first front-side sealing material 31F and the first back-side sealing material 31B, is arranged to sandwich the cell strings 2-2 in the thickness direction. Materials that can be used to form the first sealing materials 31F and 31B include, for example, EVA (ethylene vinyl acetate copolymer), POE (polyolefin), PVB (polyvinyl butyral), and ionomer. In this embodiment, EVA is used.

[0020] Each cell string 2 is composed of multiple electrically connected cells (individual cells not shown). Each cell is plate-shaped and has a semiconductor substrate and multiple collector electrodes formed on the semiconductor substrate. The basic configuration of each cell regarding power generation and collection is similar to that of a known solar cell, so a detailed description will be omitted here. Each cell has an elongated shape in plan view (plan view of each cell), with the length of the long side being 10 times or more the length of the short side.

[0021] Each cell string 2 is constructed by electrically connecting multiple cells of the above shape along the direction in which the long sides of each cell extend (longitudinal direction, left-right direction in FIG. 1). Connection can be performed by various means, for example, a "shingling connection" can be used in which the longitudinal ends of each cell are sequentially arranged so that they overlap in the thickness direction.

[0022] The solar cell module 1 is configured by arranging a plurality of cell strings 2-2 in a planar direction. Specifically, the plurality of cell strings 2-2 are arranged parallel to each other with gaps in the direction in which the short sides extend (the width direction, the vertical direction in FIG. 1, and the horizontal direction in FIG. 2). The gaps contribute to natural lighting. The plurality of cell strings 2-2 are electrically connected at one end of a reference cell string 2 and at the other adjacent cell strings 2, for example, at the top in FIG. 1. Furthermore, the reference cell string 2 is electrically connected at the other end of another adjacent cell string 2, for example, at the bottom in FIG. 1. In this way, several cell strings 2-2 are connected in series. In one solar cell module 1, a plurality of the series-connected units are connected in parallel.

[0023] Each cell string 2 in the solar cell module 1 is fixed by arranging the plurality of cell strings 2 in parallel, and disposing a second sealing material 32 in the gap between adjacent cell strings 2, 2. In other words, the second sealing material 32 is interposed between the adjacent cell strings 2, 2.

[0024] The second sealing material 32 is made of resin, similar to the first sealing materials 31F and 31B, but is made of a material with a lower melting point than the first sealing materials 31F and 31B. The melting point can be determined using the nominal melting point values ​​published by the manufacturers of the first sealing materials 31F and 31B and the second sealing material 32. If the manufacturer does not publish the melting point, it can be obtained from the peak value actually measured using a differential scanning calorimeter (DSC).

[0025] The second sealing material 32 (32m) is initially in a powder or granular form when placed in the gaps between adjacent cell strings 2, 2, and is in a fluid state where multiple particles are aggregated. Note that this fluidity is sufficient to allow the second sealing material 32 to penetrate and fill the gaps. Therefore, the size (particle size) and particle size distribution of the individual particles of the second sealing material 32 can be determined according to the desired fluidity and ease of handling. After being placed in the gaps, the second sealing material 32 (32m) is heated above its melting point to become molten and integrated. The "integrated state" refers to a state in which the individual particles have lost their shape or, at least, have become connected to each other and have lost their original fluidity. The hardness of the second sealing material 32 after integration may be either hardened or softened. In this embodiment, the second sealing material 32 is softened during the second heating step described below, but is hardened in other states, such as after the product is completed. The second sealing material 32 is transparent or translucent in the integrated state. From the viewpoint of lighting, it is desirable that the second sealing material 32 be transparent. As with the first sealing materials 31F and 31B, for example, EVA (ethylene vinyl acetate copolymer), POE (polyolefin), PVB (polyvinyl butyral), or ionomer can be used as the material for the second sealing material 32. In this embodiment, POE is used.

[0026] As described above, in the solar cell module 1 of this embodiment, two sealing materials, the first sealing materials 31F, 31B and the second sealing material, are used, and although both are transparent (at least translucent), the refractive indexes of the first sealing materials 31F, 31B and the second sealing material in the integrated state are different. Therefore, even in the state of solar cell module 1, it is possible to confirm the history of the two heating processes (heating to melt the second sealing materials, and the subsequent heating to melt the first sealing materials 31F, 31B).

[0027] The transparent plates 4 constitute the outer layers of the solar cell module 1. In this embodiment, hard glass plates (front glass plate 4F and back glass plate 4B) are used as the transparent plates 4, which are transparent and allow light to pass through in the thickness direction for natural lighting. As shown in Fig. 2, various components for power generation, including multiple cell strings 2-2, and a sealing material 3, are sandwiched between two pairs of transparent plates 4, 4 that overlap in the thickness direction.

[0028] Next, a method for manufacturing the solar cell module 1 according to this embodiment will be described. First, as described above, elongated cells are used, and a plurality of cell strings 2-2 are prepared, each of which is electrically connected along the direction in which the long sides of the cells extend. In addition, a first back-side sealing material 31B, a first front-side sealing material 31F, and a second sealing material 32 are prepared.

[0029] First, a rear-side first sealing material 31B is placed on the rear-side glass plate. Next, multiple cell strings 2 are arranged parallel to each other with gaps between them in the direction of their short sides on the rear-side first sealing material 31B. Then, a powder or granular second sealing material 32 is placed in the gaps between the multiple cell strings 2. The second sealing material 32 is scattered and placed to cover the multiple cell strings 2 as shown in FIG. 3(A). Then, as shown in FIG. 3(B), a leveling tool, brush A, is used to smooth the second sealing material 32. As shown in FIG. 3(C), the second sealing material 32 is removed from the surfaces of the multiple cell strings 2 (though some may remain), and the gaps are filled. The "filled state" does not necessarily mean that the multiple particles constituting the second sealing material 32 are densely packed; gaps may exist between the particles. In this way, by arranging the second sealing material 32 so as to cover the plurality of cell strings 2-2 and then smoothing it out, the second sealing material 32 can be easily removed from the surfaces of the plurality of cell strings 2-2, which are unnecessary portions.

[0030] Then, a first heating is performed. This first heating is performed at a temperature higher than the melting point of the second sealing material 32 but lower than the melting points of the back-side first sealing material 31B and the front-side first sealing material 31F. This first heating causes the particles of the second sealing material 32 to melt and then become integrated. After a certain time has passed since the end of the first heating, the second sealing material 32 solidifies (hardens). Then, the front-side first sealing material 31F is placed on the cell strings 2, and a front-side glass plate is placed on top of that. A second heating is performed at a temperature higher than the melting points of the back-side first sealing material 31B and the front-side first sealing material 31F. The integrated second sealing material 32 resists the pressure applied to each cell string 2 by the molten first sealing materials 31F and 31B, making it less likely that each cell string 2 will be distorted. Incidentally, since the second heating is performed at a temperature higher than the melting point of the second sealing material 32, the second sealing material 32 also melts again. However, compared to when there is a space between adjacent cell strings 2, 2, the above-mentioned countermeasure is effective even if the second sealing material 32 is melted.

[0031] According to the above method, the second sealing material 32 can be placed in the gaps between the cell strings 2 while being in a fluid state where multiple particles are aggregated (FIGS. 3A to 3C). For example, the second sealing material 32 can be placed in the gaps by simply scattering it over the cell strings 2. Furthermore, as described above, the melting point of the second sealing material 32 is lower than that of the first sealing materials 31F and 31B. Therefore, the first sealing materials 31F and 31B are less likely to be affected during the first heating. Specifically, the first sealing materials 31F and 31B do not melt during the first heating. Therefore, unlike conventional methods, the pressure of the molten first sealing materials 31F and 31B is not applied to each cell string 2. Furthermore, during the second heating, when the first sealing materials 31F and 31B melt, the integrated second sealing material 32 present between the adjacent cell strings 2 prevents distortion of each cell string 2 due to the pressure of the molten first sealing materials 31F and 31B.

[0032] Although one embodiment of the present invention has been described above, the present invention is not limited to the above embodiment, and various modifications are possible without departing from the spirit of the present invention.

[0033] In the above embodiment, EVA (ethylene vinyl acetate copolymer) is used for the first sealing materials 31F and 31B, and POE (polyolefin) is used for the second sealing material 32. However, the present invention is not limited to this combination. For example, EVA or POE may be used for both the first sealing materials 31F and 31B and the second sealing material 32. In this case, the melting point of the second sealing material 32 is adjusted to be lower than the melting point of the first sealing materials 31F and 31B depending on the type of additive or the difference in the amount of the additive. [Explanation of symbols]

[0034] 1. Solar cell module 2 Cell String 3. Encapsulating material 31F Front side first sealing material 31B Back side first sealing material 32 Second sealing material 32m Second sealing material (before melting) 4 Transparent plate 4F Front transparent panel, front glass panel 4B Back transparent plate, back glass plate 5 Frame A Leveling tool, brush

Claims

1. Using cells having an elongated shape in which the length of the long side is 10 times or more the length of the short side in a plan view, A cell string is formed by electrically connecting a plurality of the cells along the direction in which the long sides extend, The plurality of cell strings are arranged in parallel with gaps in the direction in which the short sides extend, a first sealing material made of resin and a second sealing material made of resin having a melting point lower than that of the first sealing material; the first sealing material is disposed so as to sandwich the plurality of cell strings in a thickness direction, the second sealing material is disposed integrally in the gaps between the plurality of cell strings.

2. The solar cell module according to claim 1 , wherein the first sealing material and the second sealing material in the integrated state have different refractive indices.

3. a cell string is prepared by using elongated cells whose long sides are at least 10 times longer than their short sides in a plan view, and electrically connecting a plurality of the cells along the direction in which the long sides extend; preparing a first back-side sealing material and a first front-side sealing material, each of which is made of resin and has a sheet shape; and a second sealing material, which is made of resin, has a melting point lower than that of the first back-side sealing material and the first front-side sealing material, and is in a fluid state in which a plurality of particles are aggregated; the rear-side first sealing material is placed on the rear-side transparent plate; a state in which the plurality of cell strings are arranged in parallel with gaps in the direction in which the short sides extend on the back-side first sealing material, the second sealing material is disposed in the gaps in the plurality of cell strings; performing a first heating at a temperature higher than the melting point of the second sealing material and lower than the melting points of the back-side first sealing material and the front-side first sealing material; After a time has elapsed since the end of the first heating, after the second sealing material has solidified, the front-side first sealing material is placed on the plurality of cell strings, and a front-side transparent plate is further placed on the front-side first sealing material, a second heating step at a temperature higher than the melting points of the first back-side sealing material and the first front-side sealing material;

4. 4. The method for manufacturing a solar cell module according to claim 3, wherein the second sealing material is disposed so as to cover the plurality of cell strings, and then the second sealing material is smoothed to remove the second sealing material from surfaces of the plurality of cell strings and fill the gaps, and then the first heating is performed.

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