JP7765980B2 - Solar cell module and its manufacturing method - Google Patents

Description

The present invention relates to a solar cell module that constitutes a daylight-transmitting solar cell and a method for manufacturing the same.

Light-transmitting solar cells are used in the windows of large buildings and other structures. When particularly superior design is required, light-transmitting solar cells are used in which the power-generating area of the thin-film solar cell is locally removed to allow light to pass through. However, in recent years, solar cells with roughly square cells arranged with gaps between them are often used in order to maximize output per window area.

However, solar cells using such roughly square cells have design challenges because the roughly square cells stand out, and there is a need for solutions such as using colors to make the cells less noticeable or hiding the metal electrodes of each cell and the wiring between the cells. One solution to this problem is to connect many elongated cells in one direction along their length to form cell strings, and then arrange the multiple cell strings with a set distance between them to create a see-through solar cell with a blind-like effect.

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 between a transparent resin sealant. As shown in Figure 4(A), during sealing, the sealant applies pressure to each cell string 101, 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.

One possible solution to this problem is to place narrow resin pieces 102 between multiple cell strings 101, as shown in Patent Document 1 (although the purpose of the invention disclosed in Patent Document 1 is different from that of the solution to the above problem). In this way, the resin pieces 102 resist the pressure applied to each cell string 101 by the sealing material, making each cell string 101 less likely to warp (see Figure 4(B)). However, placing such narrow resin pieces 102 one by one between multiple cell strings 101 requires a lot of labor. Furthermore, because alignment is difficult, it is difficult to mechanize the placement work, and it must be done manually. Furthermore, if the cell strings 101 were sealed by sandwiching them between glass plates while the resin pieces 102 were still resting on top of them, there was a risk that the cells that make up the cell strings 101 would be damaged due to the excessive load applied.

JP 2010-192909 A (FIG. 2)

The present invention aims 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 by the sealing material during sealing.

This invention relates to a solar cell module that uses elongated cells whose long sides are at least 10 times the length of their short sides in a planar view, and that electrically connects a plurality of the cells along the direction in which the long sides extend to form cell strings. 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 module also includes a first sealing material made of resin and a second sealing material made of resin with a melting point lower than that of the first sealing material. The first sealing material is arranged to sandwich the plurality of cell strings in the thickness direction, and the second sealing material is arranged in the gaps between the plurality of cell strings. When initially arranged in the gaps, the second sealing material is in a fluid state consisting of a collection of particles, and is then heated above the melting point to become molten and integrated.

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. Therefore, for example, the second sealing material can be placed in the gaps simply by scattering it over the multiple cell strings. Furthermore, 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 melt it and then integrated into a single unit.

Furthermore, the first sealing material and the second sealing material in the integrated state may have different refractive indices.

With 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 it is possible to check the history of two heating cycles even in the solar cell module state.

The present invention also uses elongated cells whose long sides are at least 10 times the length of their short sides in a plan view, and prepares cell strings in which a plurality of the cells are electrically connected along the direction in which the long sides extend. Also, the present invention prepares a first back-side sealing material and a first front-side sealing material that are made of resin and have a sheet-like shape, and a second sealing material that is made of resin and 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 placed on a transparent back plate, and the plurality of cell strings are arranged on the first back-side sealing material with gaps in the direction in which the short sides extend. a first heating step 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; a time period after the first heating step is completed, after the second sealing material has solidified, placing the front-side first sealing material on top of the cell strings, and then placing a front-side transparent plate on top of that; and a second heating step at a temperature higher than the melting points of the back-side first sealing material and the front-side first sealing material.

This method allows the second sealing material to be placed in the gaps between multiple cell strings while still in a fluid state where multiple particles are aggregated. For example, the second sealing material can be placed in the gaps simply by scattering it over the multiple cell strings. Furthermore, 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.

Furthermore, after the second sealing material is placed to cover the multiple cell strings, the second sealing material can be smoothed to remove it from the surfaces of the multiple cell strings and fill the gaps, and then the first heating can be performed.

With this method, the second sealing material can be easily removed from the unnecessary portions of the surface of the multiple cell strings by placing the second sealing material to cover the multiple cell strings and then smoothing it out.

The present invention therefore provides a simple solution to the distortion of each cell string caused by pressure applied to each cell string by the sealing material during sealing.

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. FIG. 2 is a diagram schematically illustrating a cross-sectional configuration of the solar cell module. 10A and 10B are diagrams showing 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. 1A and 1B are schematic diagrams related to the problem to be solved by the invention, in which (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.

The present invention will be described below with reference to the drawings, focusing on one embodiment. As shown in Figure 1, the solar cell module 1 of this embodiment constitutes a see-through solar cell with a blind-like effect, allowing light to pass through in the thickness direction (the front-to-back direction in Figure 1). As shown in Figures 1 and 2, this solar cell module 1 includes, as main components related to the present invention, multiple cell strings 2-2, an encapsulant 3, and a transparent plate 4, and is held together into a single unit by frame portions 5 located on the four edges, as shown in Figure 1 (note that the frame portions 5 are not shown in Figure 2). This solar cell module 1 is attached to a window frame in a building, for example, and used as a window.

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

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 this semiconductor substrate. The basic configuration of each cell for power generation and collection is similar to that of known solar cell structures, so a detailed explanation will be omitted here. Each cell has an elongated shape in plan view (plan view of each cell), with the length of its long side being at least 10 times the length of its short side.

Each cell string 2 is formed 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 Figure 1). Connections can be made using a variety of methods, 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.

The solar cell module 1 is composed of multiple cell strings 2-2 arranged in a planar direction. Specifically, the multiple cell strings 2-2 are arranged parallel to each other with gaps in the direction in which the short sides extend (widthwise, vertically in FIG. 1, horizontally in FIG. 2). The gaps contribute to natural lighting. The multiple cell strings 2-2 are electrically connected at one end of a reference cell string 2 to another adjacent cell string 2, for example, above in FIG. 1. The reference cell string 2 is also electrically connected at the other end of another adjacent cell string 2, for example, below in FIG. 1. In this way, several cell strings 2-2 are connected in series. In a single solar cell module 1, multiple such series-connected units are connected in parallel.

To secure each cell string 2 in the solar cell module 1, multiple cell strings 2 are arranged in parallel, with a second sealing material 32 placed in the gap between adjacent cell strings 2, 2. In other words, the second sealing material 32 is interposed between adjacent cell strings 2, 2.

The second sealing material 32 is made of resin, just like 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).

When the second sealing material 32 (32m) is initially placed in the gaps between adjacent cell strings 2, 2, it is in a powder or granular form, and is in a fluid state consisting of a collection of multiple particles. 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 based on 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 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 its integrated state. From the perspective of lighting, transparency is desirable. Similar to the first sealing materials 31F and 31B, materials that can be used to form the second sealing material 32 include, for example, EVA (ethylene vinyl acetate copolymer), POE (polyolefin), PVB (polyvinyl butyral), and ionomer. In this embodiment, POE is used.

As such, the solar cell module 1 of this embodiment uses two sealing materials: first sealing materials 31F, 31B and second sealing material. Both are transparent (at least translucent), but the refractive index of the first sealing materials 31F, 31B differs from that of the second sealing material in the integrated state. Therefore, even in the solar cell module 1 state, it is possible to confirm the history of two heating cycles (heating to melt the second sealing materials, and subsequent heating to melt the first sealing materials 31F, 31B).

The transparent plates 4 form 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 Figure 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.

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 multiple cell strings 2-2 are prepared, in which multiple cells are 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.

First, the rear-side first sealing material 31B is placed on the rear glass plate. Next, multiple cell strings 2-2 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, powdered or granular second sealing material 32 is placed in the gaps between the multiple cell strings 2-2. As shown in FIG. 3(A), the second sealing material 32 is scattered and placed to cover the multiple cell strings 2-2. 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 2-2 (some may remain), but 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 that it covers the multiple cell strings 2-2 and then smoothing it out, the unnecessary portions of the second sealing material 32 can be easily removed from the surfaces of the multiple cell strings 2-2.

Then, the 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 first heating, the second sealing material 32 solidifies (hardens), and then the front-side first sealing material 31F is placed on top of the multiple cell strings 2-2, and a front-side glass plate is placed on top of that. The 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 each cell string 2 less likely to warp. Incidentally, because 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, this resistance is effective even if the second sealing material 32 is melted.

The above method allows the second sealing material 32 to be placed in the gaps between the multiple cell strings 2-2 in a fluid state where multiple particles are aggregated (Figures 3A-3C). For example, the second sealing material 32 can be placed in the gaps simply by scattering it over the multiple cell strings 2-2. Furthermore, as mentioned above, the melting point of the second sealing material 32 is lower than that of the first sealing materials 31F, 31B, so the first heating cycle is less likely to affect the first sealing materials 31F, 31B. Specifically, because the first sealing materials 31F, 31B do not melt during the first heating cycle, pressure from the molten first sealing materials 31F, 31B is not applied to each cell string 2, as in the conventional method. Furthermore, during the second heating cycle, when the first sealing materials 31F, 31B melt, the integrated second sealing material 32 present between adjacent cell strings 2-2 reduces the risk of distortion of each cell string 2 due to the pressure from the molten first sealing materials 31F, 31B.

The present invention has been described above using one embodiment, but the present invention is not limited to this embodiment and various modifications are possible without departing from the spirit of the present invention.

In the above embodiment, EVA (ethylene vinyl acetate copolymer) was used for the first sealing materials 31F, 31B, and POE (polyolefin) was used for the second sealing material 32. However, this combination is not limited to this. For example, EVA or POE can be used for both the first sealing materials 31F, 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, 31B depending on the type of additive or the difference in additive content.

1 Solar cell module 2 Cell string 3 Sealing 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 plate, front glass plate 4B Back transparent plate, back glass plate 5 Frame part A Leveling tool, brush

Claims (4)

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. The solar cell module described in claim 1, wherein the first sealing material and the second sealing material in the integrated state have different refractive indices. 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; The method for manufacturing a solar cell module described in claim 3, wherein the second sealing material is placed to cover the plurality of cell strings, and then the second sealing material is smoothed to remove the second sealing material from the surfaces of the plurality of cell strings and fill the gaps, and then the first heating is performed.