JPH0918032A - Solar battery and its manufacturing method - Google Patents

Abstract

PURPOSE: To check the deterioration in the electric characteristics due to the water content in an power generation element by effectively checking the bubbling due to the release between the power generation element and a front film thereby sealing a peripheral sealing part in a perfect state. CONSTITUTION: In this solar battery, the back of a power generation element 1 is coated with a back film 3 while the front of the power generation element 1 is coated with a front film 2 made of transparent plastics. The back film 3 and the front film 2 are formed into peripheral sealing parts 5 protruding from the periphery of the power generation element 1. The peripheral sealing parts 5 are bonded onto each other through the intermediary of a bonding layer 4. In such a constitution, the adhesive force of the back film 3 adhering to the back of the power generation element 1 is made less powerful than that adhering the front film 2 to the front of the power generation element 1.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a solar cell in which both sides of a power generating element are covered with films and a method for manufacturing the same.

[0002]

2. Description of the Related Art A solar cell is covered with a structure that seals a power generating element in a watertight manner. This is because if the water enters the power generation element, the power generation characteristics of the power generation element deteriorate. FIG. 8 shows a cross-sectional view of a conventional solar cell. The solar cell in this figure is a power generation element 1
The front surface and the back surface are covered with the front film 2 and the back film 3 to be sealed. The front film 2 and the back film 3 are airtightly bonded to each other by an outer peripheral sealing portion 5 extending to the outside of the power generation element 1.

In the solar cell having this structure, the power generating element 1 is disposed between the front film 2 and the back film 3, the front film 2 is bonded to the front surface of the power generating element 1, and the back film 3 is bonded to the back surface of the power generating element 1. Then, the outer peripheral sealing portion 5 is heat-welded to be manufactured. The front film 2 and the back film 3 are provided by laminating an adhesive layer 4 of a thermoplastic plastic film on the inner surface so that the front film 2 and the back film 3 can be closely attached to the power generation element 1 and the outer peripheral sealing portion 5 can be heat-welded. For example, polyethylene film or EVA may be used on the inner surface of the front and back films.
The film is laminated as an adhesive layer.

[0004]

The solar cell shown in this figure is adhered to both sides of the power generating element 1 by an adhesive layer 4 provided on the inner surfaces of the front film 2 and the back film 3 in a close contact state. In this solar cell, the front film may locally peel off from the surface of the power generating element depending on the use environment.
When the front film is peeled off from the power generation element, bubbles 8 are formed on the back surface of the front film. The bubbles 8 hinder the efficient entry of the light rays passing through the front film into the power generating element. This is because light is reflected on the surface of the bubbles and does not enter the power generating element. If you look at the solar cell with air bubbles from the front, you can see that the air bubbles look whiter than the other parts and that light is reflected.

Bubbles are likely to be generated when the solar cell is heated and cooled. Bubbles are formed when heated and cooled because the front film and the back film, which are in close contact with the power generation element, are deformed in the direction indicated by arrow A in FIG.

The first object of the present invention was developed for the purpose of solving this problem, and an important object of the present invention is that the power generation element and the front film are separated from each other to form bubbles. It is an object of the present invention to provide a solar cell and a manufacturing method thereof that can effectively prevent

Further, in the solar cell having the sectional structure shown in FIG. 8, it is difficult to seal the outer peripheral sealing portion in an ideal state.
If the outer peripheral sealing portion is not sufficiently sealed and moisture enters from this portion, an adverse effect of deteriorating the electrical characteristics of the power generating element occurs. This adverse effect can be reduced by increasing the width of the outer peripheral sealing portion and increasing the bonding area of the outer peripheral sealing portion. However, when the outer peripheral sealing portion is widened, there is a drawback that the outer shape of the solar cell becomes large and the effective heat generation area with respect to the entire area becomes small.

A second object of the present invention is to prevent this adverse effect, that is, to seal the outer peripheral sealing portion in a more complete state and prevent deterioration of electrical characteristics due to moisture in the power generating element. A method for manufacturing a solar cell is provided.

[0009]

The solar cell of the present invention and the method for manufacturing the same are as follows in order to achieve the above-mentioned object. In the solar cell according to claim 1 of the present invention, the back surface of the power generation element 1 is covered with the back film 3, and the front surface of the power generation element 1 is covered with the front film 2 made of a transparent plastic. . The back film 3 and the front film 2 project from the outer circumference of the power generation element 1 to form an outer circumference sealing portion 5. The outer peripheral sealing portion 5 is adhered to each other via the adhesive layer 4. Furthermore, in the solar cell of the present invention, the adhesive force for attaching the back film 3 to the back surface of the power generating element 1 is made weaker than the adhesive force for attaching the front film 2 to the front surface of the power generating element 1.

Further, in the solar cell according to claim 2 of the present invention, the front film 2 is adhered to the front surface of the power generation element 1, and the back film 3 is not bonded to the back surface of the power generation element 1. The outer peripheral sealing portion 5 is adhered to each other via the adhesive layer 4 of the front film 2.

Furthermore, in the method for manufacturing a solar cell according to claim 3 of the present invention, the back surface of the power generation element 1 is covered with the back film 3, and the front surface of the power generation element 1 is made of a transparent plastic. The front film 2 is covered, the back film 3 and the front film 2 are projected from the outer periphery of the power generating element 1 to form the outer peripheral sealing portion 5, and the outer peripheral sealing portion 5 is adhered to each other via the adhesive layer 4 to be manufactured. . Further, in this method for manufacturing a solar cell, after the outer peripheral sealing portion 5 projecting to the outer periphery of the power generation element 1 is bonded with the adhesive layer 4, the outer peripheral sealing portion 5 bonded by secondary heat sealing is thermocompression bonded. Then, the front film 2 and the back film 3 are heat-welded at the outer peripheral sealing portion 5.

[0012]

In the solar cells according to claims 1 and 2 of the present invention, the front film 2 is strongly adhered to the power generating element 1, but the back film 3 is weakly bonded to the power generating element 1. Alternatively, do not bond. The power generating element 1 strongly adheres the front film 2 to the front surface, but does not strongly adhere the back surface to the back film 3. Therefore, even if the solar cell is heated and cooled and a force acts on the front film 2 and the back film 3 in the direction indicated by the arrow A in FIG.
Hold the state of close contact with. This is because the back film 3 does not strongly pull the power generating element 1 to the back. The solar cell in which the front film 2 is not peeled from the power generation element 1 is held in a state where the front film 2 is in close contact with the power generation element 1,
There are no bubbles 8 on the inner surface. Therefore, the bubbles 8 do not reflect the light transmitted through the front film 2 to reduce the power generation efficiency of the power generation element 1.

Further, in the method for manufacturing a solar cell according to claim 3 of the present invention, the front film 2 and the back film 3 are used.
Are bonded to each other with the adhesive layer 4 of the outer peripheral sealing portion 5 of the power generation element 1, and then the outer peripheral sealing portion 5 bonded by the second heat sealing is heated and pressure-bonded. As shown in the cross-sectional view of FIG. 1, the peripheral sealing portion 5 bonded in this manner is in a state where the adhesive layer 4 and the film are mixed, and the front film 2 and the back film 3 are ideal. Can be welded in the state. As for the outer peripheral sealing portion 5 adhered by the conventional method, the film is adhered via the adhesive layer 4 as shown in the sectional view of FIG. Since the solar cell manufactured by the method of the present invention is welded in a state where films are mixed as shown in FIG. 1, the outer peripheral sealing portion 5 can be sealed in an ideal state. Therefore, it is possible to effectively prevent the moisture from entering the inside through the outer peripheral sealing portion 5, and effectively prevent the deterioration of the power generation element 1 due to the moisture.

[0014]

Embodiments of the present invention will be described below with reference to the drawings. However, the examples described below exemplify a solar cell and its manufacturing method for embodying the technical idea of the present invention, and the present invention does not specify the solar cell and its manufacturing method as follows. .

Further, in this specification, in order to facilitate understanding of the claims, the numbers corresponding to the members shown in the embodiments will be referred to as "claims", "action", and "action". In the column of "Means for solving the problem". However, the members shown in the claims are
It is by no means specific to the members of the embodiment.

In the solar cell shown in the perspective view of FIG. 3, the sectional view of FIG. 4 and the sectional view of FIG. 5, the back surface of the power generating element 1 is covered with the back film 3, and the front surface of the power generating element 1 is transparent. It is covered with a plastic front film 2 having properties.

In the power generating element 1, an amorphous silicon layer (a-Si layer) is laminated on a metal layer which is a back electrode, and a conductive and transparent I layer is formed on the front surface of the a-Si layer.
TO is laminated as a front electrode, and a plastic film layer such as a polyimide resin is further adhered to the back surface of the metal layer. The power generation element 1 in this figure has a polyimide resin 6 laminated on the back surface thereof, but the polyimide resin is not always necessary.

The back film 3 and the front film 2 covering the power generating element 1 cover the power generating element 1 to prevent the power generating element 1 from being deteriorated by moisture. The front film 2 and the back film 3 are larger than the outer shape of the power generation element 1 and project from the outer circumference of the power generation element 1. The outer peripheral sealing portion 5 protruding from the power generation element 1 is adhered to each other via an adhesive layer 4 provided on the front film 2. The front film 2 and the back film 3 are adhered to each other by the outer peripheral sealing portion 5 to seal the power generation element 1 in an airtight structure.

The front film 2 and the back film 3 are transparent plastic films having a low moisture permeation, such as 3
A fluorinated ethylene film or polyester film can be used. The back film 3 is not required to have translucency. Therefore, any plastic film having a low moisture permeability can be used as the back film. A film obtained by laminating aluminum foil can be used as the back film. The back film laminated with aluminum foil has a feature that it can effectively prevent the permeation of moisture. However, in the case of a film in which aluminum foil is laminated, the aluminum foil cannot be heated and welded to the front film, so the surface without the aluminum foil is welded to the front film. Alternatively, in order to weld the surface having the aluminum foil to the front film, a thermoplastic plastic is laminated and provided on the surface of the aluminum foil corresponding to the outer peripheral sealing portion.

The front film 2 has an adhesive layer 4 on its inner surface. Since the back film 3 is not adhered to the power generation element 1, no adhesive layer is provided on the inner surface. This is because the front film 2 is firmly attached to the power generating element 1 and the back film 3 is not attached to the power generating element 1. However, the back film may be provided with an adhesive layer that is attached to the power generation element with a weaker adhesive force than the front film. For the adhesive layer 4 of the front film 2, a thermoplastic plastic film or a hot melt adhesive can be used. The thermoplastic plastic films are laminated and adhered to the inner surface of the front film 2, and the hot melt adhesive is applied to the front film 2 and adhered thereto. The thermoplastic plastic film that can be used for the adhesive layer 4 is a polyethylene film, an EVA film, a polypropylene film, or the like.

The solar cell shown in the sectional view of FIG. 4 is manufactured as follows. The front film 2 is laminated on the front surface of the power generation element 1 to be in close contact therewith. A back film 3 is provided on the back surface of the power generation element 1. The outer peripheral sealing portion 5 of the front film 2 and the rear film 3 is heated while being pressed, the adhesive layer 4 of the front film 2 is heated and melted, and the front film 2 and the rear film 3 are welded at the outer peripheral sealing portion 5. . Front film 2 and back film 3
Is heated by a press having a built-in heater, or is pressed by an ultrasonic horn to be heated and welded. By welding the outer periphery sealing portion 5, the solar cell covers the power generation element 1 with the front film 2 and the back film 3. When the outer peripheral sealing portion 5 is welded, the front film 2 is heated in close contact with the front surface of the power generating element 1 and bonded to the power generating element 1.

The solar cell manufactured as described above has a front film 2 as shown in the sectional views of FIGS.
The outer peripheral sealing portion 5 is welded via the adhesive layer 4 of 1. and the front film 2 is adhered to the power generation element 1 in a close contact state. Since the back film 3 has no adhesive layer, it is not bonded to the back surface of the power generation element 1. However, when the back film is provided with an adhesive layer having a weaker adhesive force than the front film, the back film is also bonded to the back surface of the power generation element.

As shown in FIG. 2, the front surface film 2 and the rear surface film 3 of the solar cell outer peripheral sealing portion 5 thus manufactured are bonded via the adhesive layer 4. In order to more securely seal the outer peripheral sealing portion 5 and prevent moisture from entering the inside, the solar cells shown in FIGS. 6 and 7 have a part of the outer peripheral sealing portion 5 already welded. It is heat-pressed and secondarily heat-sealed. The secondary heat seal melts the front film 2 and the back film 3 by heating the front film 2 and the back film 3 in a pressed state with a width narrower than the welding width of the outer peripheral sealing portion 5 which is already welded. To weld. The secondary heat seal is applied not only to the adhesive layer 4 but also to the front film 2
Then, the back film 3 is welded to heat-seal the outer peripheral sealing portion 5 more reliably. Therefore, the secondary heat seal is performed at a higher temperature than when the outer peripheral sealing portion 5 is first heated and pressed to be welded, or by being pressed more strongly to the outer peripheral sealing portion 5.
Is welded.

The secondary heat sealing is performed in the same manner as the outer peripheral sealing portion 5 is first welded, for example, by pressing a press having a built-in heater at a higher temperature to press it, or to increase the output. Weld by pressing with an ultrasonic horn with a small pressing area. As shown in the enlarged cross-sectional view of FIG. 1, the secondary heat-sealed outer peripheral sealing portion 5 is in a state in which the film and the adhesive layer 4 are mixed and is more reliably welded.

In the solar cell shown in the figure, the portion to be subjected to the secondary heat sealing is located on the outer peripheral portion of the outer peripheral sealing portion 5. The solar cell of this structure has a feature that the outside of the portion welded by the adhesive layer 4 can be more reliably sealed by the secondary heat seal portion 7. That is, the outer peripheral sealing portion 5 is doubly sealed by the welded adhesive layer 4 and the secondary heat sealing portion 7.

The secondary heat seal portion can be arranged inside the welded adhesive layer. However, if the secondary heat seal portion is located inside the welded adhesive layer, the probability of a defective seal at the secondary heat seal portion increases. This is because the secondary heat seal is welded at a higher temperature than when the adhesive layer is welded, or in a state in which the outer peripheral sealing portion is strongly pressed and thinly crushed. Since the film is thin in the peripheral heat-sealed portion subjected to the secondary heat sealing, the local portion of the film is easily damaged as compared with the case where the adhesive layer is welded. Therefore, if the secondary heat seal part is inside and the film is damaged at this part, the power generation element cannot be sealed in an ideal state. By disposing the secondary heat seal portion outside the welded adhesive layer, even if the secondary heat seal damages the film, it can be sealed because it is welded by the adhesive layer.

[0027]

In the solar cells according to the first and second aspects of the present invention, the front film is adhered to the front surface of the power generating element, but the back film is not bonded to the power generating element, or more than the front film. It adheres with a weak adhesive force. Therefore, even if the solar cell is heated or cooled and the front film and the back film are deformed in the direction away from the power generation element, the front film is not peeled from the power generation element.
This is because the back film is not strongly adhered to the power generating element. The power generation element is deformed together with the front film and is not separated between the front film and the power generation element. Therefore, it is possible to effectively prevent the formation of bubbles between the front film and the power generation element. A bubble-free solar cell
Bubbles do not reflect incident light rays. The light transmitted through the front film efficiently irradiates the power generation element, and the power generation element generates power with high efficiency.

Further, in the method for manufacturing a solar cell according to claim 3 of the present invention, the outer peripheral sealing portion welded by the adhesive layer is further heat-sealed to ensure more reliable welding. The secondary heat-sealed outer peripheral sealing portion is in a state in which the film and the adhesive layer are mixed, so that the outer peripheral sealing portion is more reliably heat-sealed. Therefore, there is a feature that it is possible to more reliably prevent moisture from entering from the outer peripheral sealing portion and effectively prevent deterioration of the power generation element due to moisture.

[Brief description of the drawings]

FIG. 1 is an enlarged sectional view of an outer peripheral sealing portion showing a method for manufacturing a solar cell according to an embodiment of the present invention.

FIG. 2 is an enlarged cross-sectional view of an outer peripheral sealing portion showing a conventional solar cell manufacturing method.

FIG. 3 is a perspective view of a solar cell according to an embodiment of the present invention.

4 is a cross-sectional view of the solar cell shown in FIG. 3 taken along the line BB.

FIG. 5 is a sectional view of a solar cell according to an embodiment of the present invention.

FIG. 6 is a sectional view of a solar cell according to another embodiment of the present invention.

FIG. 7 is a perspective view of a solar cell according to another embodiment of the present invention.

FIG. 8 is a sectional view of a conventional solar cell.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Power generating element 2 ... Front film 3 ... Back film 4 ... Adhesive layer 5 ... Peripheral sealing part 6 ... Polyimide resin 7 ... Secondary heat seal part 8 ... Air bubbles

 ─────────────────────────────────────────────────── ─── Continuation of front page (72) Inventor Nobuo Hanawa 2-5-5 Keihan Hondori, Moriguchi-shi, Osaka Sanyo Electric Co., Ltd.

Claims (3)

[Claims] 1. The back surface of the power generation element (1) is covered with a back film (3), and the front surface of the power generation element (1) is covered with a front film (2) made of a translucent plastic. The film (3) and the front film (2) project from the outer periphery of the power generation element (1) to form an outer peripheral sealing part (5), and the outer peripheral sealing part (5) is mutually attached via an adhesive layer (4). In a bonded solar cell, the adhesive force with which the back film (3) is attached to the back surface of the power generation element (1) is greater than the adhesive force with which the front film (2) is attached to the front surface of the power generation element (1). A solar cell characterized by its weakness. 2. The front film (2) is bonded to the surface of the power generating element (1), the back film (3) is not bonded to the power generating element (1), and is bonded to the inner surface of the front film (2). A solar cell comprising an outer peripheral sealing part (5) bonded via a layer (4). 3. The back surface of the power generation element (1) is covered with a back film (3), and the front surface of the power generation element (1) is covered with a front film (2) made of a light-transmissive plastic. 3) and the front film (2) are projected from the outer periphery of the power generation element (1) to form the outer peripheral sealing part (5), and the outer peripheral sealing part (5) is bonded to each other via the adhesive layer (4). In the battery manufacturing method, the outer peripheral sealing portion (5) protruding to the outer periphery of the power generation element (1) is provided with an adhesive layer.
After bonding with (4), secondary heat sealing is further performed, and the bonded outer peripheral sealing part (5) is heat-pressed to form a front film.
A method for manufacturing a solar cell, which comprises heat-welding the (2) and the back film (3) at the outer peripheral sealing part (5).