JP4650971B2 - Thin film solar cell backside sealing method - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a semiconductor thin film solar cell, and more particularly to a back surface sealing method for a thin film solar cell.
[0002]
[Prior art]
4 and 5 are schematic sectional partial views illustrating a conventional back surface sealing method in a thin film solar cell. In each drawing of the present application, the thickness, length, width, and the like are appropriately changed for clarity and simplification of the drawings, and do not represent actual dimensional relationships. Moreover, in each figure, the same referential mark represents the same part or the corresponding part.
[0003]
As shown in FIG. 4, in the manufacture of a conventional thin film solar cell, a photoelectric conversion unit layer 2 is generally formed on a transparent glass substrate 1 having a thickness of about 4 mm. The photoelectric conversion unit layer 2 generally has a very thin thickness of about several μm, and includes a front electrode layer of a transparent conductive oxide, a semiconductor photoelectric conversion layer, and a back metal electrode layer that are sequentially stacked on the substrate 1. It is out. Furthermore, in a thin film solar cell including a plurality of submodules on one substrate (see Japanese Patent Laid-Open No. 2000-49369), an electrical internal wiring 5 made of, for example, a copper foil having a thickness of about 0.2 mm is disposed. . A local insulating resin sheet 4 is inserted between the internal wiring 5 and the photoelectric conversion unit layer 2. As such an insulating sheet 4, for example, a PVF (polyvinyl fluoride) film having a thickness of about 0.04 mm can be used. Between each of the photoelectric conversion unit layer 2, the insulating resin sheet 4, and the internal wiring 5, the first and second local bonding resin sheets 3 a and 3 b are disposed. As these bonding resin sheets, for example, EVA (ethylene vinyl acetate copolymer) sheets having a thickness of about 0.6 mm and containing a curing agent can be used. Furthermore, the whole area bonding resin sheet 3c and the composite protective film 6a are overlapped as sealing protection means so as to cover the entire area of the internal wiring 5 and the photoelectric conversion unit layer 2. The same material as the locally bonded resin sheets 3a and 3b can be used for the entire bonded resin sheet 3c.
[0004]
The laminated body of FIG. 4 prepared in this way is placed on a hot plate of a vacuum laminator, and the laminator is evacuated. Then, after the bonding resin sheets 3a, 3b, 3c are melted, the composite protective film 6a is pressed by the diaphragm in the laminator. At that time, since the sealing resin film 6a has flexibility, as shown in FIG. 5, the sealing resin film 6a is slightly curved at a slight convex portion in the vicinity where the insulating resin sheet 4 and the internal wiring 5 are arranged. Can adapt to the convex part of the lever.
[0005]
In this state, the molten bonding resin layer 3 can be completely cured in a vacuum laminator. However, since the vacuum laminator is expensive and cannot process a large number of thin film solar cells at the same time, the thin film solar cell is taken out of the vacuum laminator when the bonding resin layer 3 is partially cured, so that the bonding resin layer 3 is completely formed. Curing is generally performed by simultaneously processing a plurality of thin film solar cells in a separate curing furnace.
[0006]
The reason why the vacuum laminator is used for forming the sealing protection means is to prevent air bubbles from being mixed into the boundary or inside of the sealing resin layer 3 that is cured after being melted.
[0007]
[Problems to be solved by the invention]
In the thin film solar cell by the conventional sealing method as shown in FIGS. 4 and 5, a composite film in which an aluminum foil is sandwiched between PVF films is generally used as the protective film 6a. Here, the reason why the aluminum foil is sandwiched is to effectively prevent the permeation of moisture. However, since the PVF film sandwiching the aluminum foil is thin, pinholes and scratches may occur in some cases, and a leakage current through the aluminum foil may occur on the back surface of the solar cell. Moreover, if such a leakage current flows in the presence of moisture, corrosion of the aluminum foil may proceed.
[0008]
In view of such problems in the conventional technology, an object of the present invention is to provide a more reliable back surface sealing method for a thin film solar cell.
[0009]
[Means for Solving the Problems]
In the back surface sealing method of a thin film solar cell according to one aspect of the present invention, an insulating sheet comprising a local bonding resin sheet and a non-woven fabric thereon on a back surface of a thin film photoelectric conversion unit layer formed on a glass substrate A laminated body in which a metal foil for internal electrical wiring thereon and a whole area bonding resin sheet covering the entire back surface of the thin film photoelectric conversion unit layer and a sealing glass plate are sequentially laminated, and this laminated body is a hot plate of a vacuum laminator It is characterized in that the sealing glass plate is pressed by a diaphragm in a laminator after the bonding resin sheet is melted, and finally the bonding resin is cured. As the nonwoven fabric, glass fibers or synthetic fibers can be preferably used.
[0010]
In the back surface sealing method of a thin film solar cell according to another aspect of the present invention, a local insulating resin sheet having both surfaces coated with a bonding resin on the back surface of a thin film photoelectric conversion unit layer formed on a glass substrate. A laminated body in which a metal foil for internal electrical wiring thereon and a whole area bonding resin sheet covering the entire back surface of the thin film photoelectric conversion unit layer and a sealing glass plate are sequentially laminated, and this laminated body is a hot plate of a vacuum laminator It is characterized in that it is placed on top and evacuated, and after the bonding resin is melted, the sealing glass plate is pressed by a diaphragm in a laminator to finally cure the bonding resin.
[0011]
DETAILED DESCRIPTION OF THE INVENTION
In view of the above-mentioned problem in the conventional method of sealing the back surface of a thin-film solar cell using a composite protective film 6a in which an aluminum foil is sandwiched with a PVF film, the present inventor has a thickness instead of the composite protective film 6a. A sealing method using a protective glass plate of about 3 to 4 mm was examined. This is because the glass plate is much stronger than the composite protective film 6a and has an excellent ability to block moisture permeation.
[0012]
Therefore, the present inventor first tried a back surface sealing method of a thin film solar cell as illustrated in FIG. 1 which is a schematic partial sectional view. The sealing method of FIG. 1 differs from the method of FIG. 4 only in that a sealing glass plate 6b having a thickness of 3 mm is used instead of the composite protective film 6a.
[0013]
That is, in the case of FIG. 1, on the thin film photoelectric conversion unit layer 2 having a thickness of several μm formed on the glass substrate 1 having a thickness of 4 mm, the first locally bonded EVA sheet 3a having a thickness of 0.6 mm, Insulating PVF sheet 4 having a thickness of 0.04 mm, second locally bonded EVA sheet 3 b having a thickness of 0.6 mm, copper foil 5 for internal wiring having a thickness of 0.2 mm, and EVA sheet having a total thickness of 0.6 mm. 3c and a protective glass plate 6b instead of the protective film 6a were sequentially laminated.
[0014]
However, it has been found that when the protective glass plate 6b is used instead of the protective film 6a for sealing the back surface of the thin film solar cell, another incidental problem occurs. This is a problem caused by the fact that the protective glass plate 6b has higher rigidity than the protective film 6a.
[0015]
That is, when the laminated body of FIG. 1 is sealed using a vacuum laminator as in the case of FIG. 4, the sealing glass plate 6b has higher rigidity than the composite protective film 6a. It is difficult to bend and be familiar with the slight convex portions where the insulating sheet 4 and the internal wiring 5 are disposed together with the locally bonded resin sheets 3a and 3b. As a result, as shown in FIG. 2, bubbles 7 are likely to remain in the cured bonding resin layer 3 in the vicinity of the insulating sheet 4 and the internal wiring 5 forming a slight convex portion. I understood.
[0016]
Therefore, the present inventor does not use the first and second locally bonded EVA sheets 3a and 3b each having a relatively large thickness in FIG. 1, but instead of the insulating PVF sheet, the insulating film has a thickness of 0.08 mm. Using PET (polyethylene terephthalate) sheet 4, an attempt was made to seal the back surface of the thin film solar cell. As a result, as shown in FIG. 3, a slight convex state associated with the arrangement of the insulating sheet 4 and the internal wiring 5 is reduced, and residual bubbles are present in the bonding resin layer 3 even in the vicinity of the convex portion. Not observed. However, in this case, the bonding resin 3 is not impregnated between each of the thin film photoelectric conversion unit layer 2, the insulating sheet 4, and the metal foil for internal wiring, and bonding between the respective layers is not achieved and is unstable. The problem of becoming.
[0017]
As described above, as a result of further examination by the inventor in view of incidental problems caused by using the sealing protective glass plate 6b instead of the conventional sealing composite protective film 6a, the following contrivances are obtained. It was found that these incidental problems can also be solved by applying.
[0018]
First, as a first device, the inventor uses an EVA sheet having a thickness of 0.4 mm as the first local bonding resin sheet 3 a in FIG. 1 and a glass fiber nonwoven fabric having a thickness of 0.2 mm as the insulating sheet 4. Was used. And the 2nd local joining resin sheet 3b was abbreviate | omitted.
[0019]
When a thin-film solar cell whose back surface was sealed using a vacuum laminator was produced from the laminated body thus devised, as shown in FIG. 3, the insulating sheet 4 and the internal wiring 5 were arranged. The slight convex state involved was reduced, and no residual bubbles were observed in the bonding resin layer 3 even in the vicinity of the convex portion. In addition, in this case, when the first locally bonded EVA sheet 3a is melted, the glass fiber nonwoven fabric 4 is impregnated, and the influence of the thickness of the locally EVA sheet 3a is reduced. Stable bonding not only between the layer 2 and the nonwoven fabric insulating sheet 4 but also between the nonwoven fabric insulating sheet 4 and the metal foil 5 could be realized.
[0020]
As a second contrivance, a PET insulating sheet coated on both sides with EVA as the insulating sheet 4 in FIG. 1 was used, and it had a thickness of 0.2 mm. And the 1st and 2nd local joining resin sheets 3a and 3b were abbreviate | omitted.
[0021]
Even in a thin film solar cell whose back surface is sealed by using a vacuum laminator from the laminate having such a second device, the arrangement of the insulating sheet 4 and the internal wiring 5 is arranged as shown in FIG. The slight convex state accompanying the reduction was reduced, and no residual bubbles were observed in the bonding resin layer 3 even in the vicinity of the convex portion. Moreover, in this case, since both surfaces of the PET insulating sheet 4 are coated with EVA, not only between the thin film photoelectric conversion unit layer 2 and the insulating sheet 4 but also between the insulating sheet 4 and the metal foil 5. Stable bonding was also realized.
[0022]
In addition, although the example which used the glass nonwoven fabric as the nonwoven fabric 4 was demonstrated in the above-mentioned 1st device, it cannot be overemphasized that the same effect can be acquired even if it uses the nonwoven fabric of another synthetic fiber.
[0023]
Moreover, although the example which used the EVA sheet | seat containing a hardening | curing agent as the joining resin sheet was demonstrated above, using other suitable joining resin sheets like a PVB (polyvinyl butyral) sheet | seat containing a hardening | curing agent is used, for example. it can.
[0024]
Furthermore, it goes without saying that the size of the above-described local bonding sheet may be a size that covers the entire back surface of the photoelectric conversion unit layer, if desired.
[0025]
【The invention's effect】
As described above, according to the present invention, it is possible to provide a back surface sealing method for a thin film solar cell that is more reliable than the conventional one.
[Brief description of the drawings]
FIG. 1 is a schematic cross-sectional partial view illustrating a method of sealing a back surface of a thin film solar cell using a protective glass plate.
2 is a schematic partial sectional view showing an example of a result of sealing the laminated body shown in FIG. 1 using a vacuum laminator.
3 is a schematic partial cross-sectional view showing a result of sealing a back surface of a thin film solar cell by omitting at least one of the locally bonded resin sheets 3a and 3b in FIG. 1. FIG.
FIG. 4 is a schematic partial sectional view illustrating a method for sealing the back surface of a conventional thin film solar cell.
FIG. 5 is a schematic partial sectional view showing a result of sealing the laminated body shown in FIG. 4 with a vacuum laminator.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Glass substrate, 2 Photoelectric conversion unit layer, 3 Bonding resin layer, 3a, 3b Local bonding resin sheet, 3c Whole area bonding resin sheet, 4 Local insulation sheet, 5 Metal foil for electrical wiring, 6a Composite protective film, 6b Protection Glass plate.

Claims (3)

On the back surface of the thin film photoelectric conversion unit layer formed on the glass substrate, a local bonding resin sheet, an insulating sheet made of non-woven fabric thereon, a metal foil for internal electrical wiring thereon, and the thin film photoelectric conversion unit layer Prepare a laminate in which the whole area bonded resin sheet and the sealing glass plate that cover the entire back surface of
The laminate is placed on a hot plate of a vacuum laminator and evacuated,
After melting the bonding resin sheet, press the sealing glass plate with a diaphragm in the laminator,
A method for sealing the back surface of a thin-film solar cell, wherein the bonding resin is finally cured. The method for sealing a back surface of a thin-film solar cell according to claim 1, wherein the nonwoven fabric is made of glass fiber or synthetic fiber. On the back surface of the thin film photoelectric conversion unit layer formed on the glass substrate, a local insulating resin sheet coated on both sides with a bonding resin, a metal foil for internal electric wiring thereon, and the thin film photoelectric conversion unit layer Prepare a laminate in which the whole area bonding resin sheet covering the entire back surface and the sealing glass plate are stacked in order,
The laminate is placed on a hot plate of a vacuum laminator and evacuated,
After melting the bonding resin, press the sealing glass plate with a diaphragm in the laminator,
A method for sealing the back surface of a thin-film solar cell, wherein the bonding resin is finally cured.

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