JP2785886B2 - Photovoltaic element and its electrode forming method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a photovoltaic device and a method for forming electrodes thereof.

[0002]

2. Description of the Related Art Conventionally, in a photovoltaic element, its electrode is formed by directly depositing a low-resistance metal on an electrode forming surface by a vacuum evaporation method or a sputtering method, or by forming a conductive resin by a screen printing method. It is formed by attaching and firing on the surface.

[0005] FIG. 5 shows an example of electrode formation using a vacuum evaporation method. In the figure, a metal mask 113 having an opening is provided on an electrode forming surface 112 of a photovoltaic element 111. Then, the low resistance metal 114 is heated and evaporated by the irradiation of the electron beam 116 from the electron gun 115, and is evaporated on the electrode forming surface 112 in a high vacuum. Then, an electrode made of a metal thin film is formed on the electrode forming surface 112 by the vacuum deposition.

FIG. 6 shows an example of forming electrodes by screen printing. In this method, the conductive resin 122 is
The printing squeegee 121 is used to attach the electrode to the electrode forming surface 125 of the photovoltaic element 124 through the opening of the screen mask 123, and then sinter to form an electrode.

[0005] In addition, as a method of forming an electrode, there is a method described in, for example, JP-A-3-6867 (hereinafter referred to as a "wire wiring method"). In this wire wiring method, as shown in FIG. 7, a linear metal body 131 is used, and a conductive adhesive 132 obtained by dispersing silver spherical fine particles or the like in a resin material such as epoxy is attached to the metal body 131. After that, it is stretched on the electrode forming surface 134 of the photovoltaic element 133. Next, FIG.
The linear metal body 131 is pressed toward the electrode forming surface 134 as shown by an arrow P as shown in FIG.
Thereafter, a procedure of curing and fixing the conductive adhesive 132 by heat treatment or the like is adopted. In this case, a linear metal body 131 having a diameter t of about 50 μm is used. The conductive adhesive 1 on the electrode forming surface 134
32 is a light shielding portion A.

[0006]

However, in the above conventional photovoltaic device, in order to form a low-resistance electrode by a vacuum deposition method or a sputtering method, a low-resistance metal is deposited on the electrode formation surface by vapor deposition or sputtering. Need to be formed. This makes it difficult to form a thick film,
In addition, there is a problem that a large amount of energy is required for forming an electrode, resulting in an increase in cost.

When the electrodes are formed by a screen printing method, an epoxy resin or polyester resin as an insulator, or a conductive resin in which fine particles such as silver or copper as a conductor are dispersed in a polyimide resin are used for the electrodes. Therefore, the electric resistance of the electrode increases. Therefore, in order to reduce power loss, it is necessary to increase the width of the electrodes or increase the number of electrodes. For this reason, the occupied area of the electrode on the electrode formation surface increases, and accordingly, the effective area, which is the light incident area of the photovoltaic element, decreases, and the generated photocurrent decreases.

On the other hand, in the case of the wire wiring method, there is no problem as described above, but there is a problem in the bonding step. That is, for example, in order to ensure conductivity between the electrode forming surface of the photovoltaic element and the linear metal body, it is necessary to closely adhere to the electrode forming surface. The pressing performed at that time is transmitted to the linear metal body as tension. Here, the efficiency of the photovoltaic element generally improves as the line width of the electrode material decreases. With current screen printing technology, printing of about 50 μm is possible.
If a linear metal body made of copper is used and its line width is 50 μm, the tensile strength of the linear metal body is only 0.236 N (about 24 g). Therefore, if the pressing force is increased, the linear metal body is cut, which causes a problem that the manufacturing process itself is stopped. Further, in order to reduce the power generation unit price of the photovoltaic element, it is necessary to increase the area of the electrode formation surface. In this case, for example, when a photovoltaic element having an electrode forming surface of 30 cm square is to be manufactured by a wire wiring method, a linear metal body may be adjusted to a predetermined position by disturbance such as vibration generated from equipment or the like. There is also a problem that it becomes difficult.

[0009] Therefore, an object of the present invention is to form an electrode with low cost and low resistance loss, and it is possible to press and adhere a metal body to an electrode forming surface without causing disconnection of the metal body. Another object of the present invention is to provide a photovoltaic element and a method for forming an electrode thereof.

[0010]

According to the present invention, according to the present invention, a composite comprising a linear metal body made of at least one kind of metal and a transparent resin is provided on an electrode forming surface of a photovoltaic element. A photovoltaic element characterized by being fixedly adhered via an adhesive is obtained.

Further, according to the present invention, a step of attaching a conductive adhesive to at least a part of at least a metal exposed portion of a composite made of a transparent metal and a linear metal body made of at least one kind of metal. Bonding the composite at a predetermined position on the electrode forming surface of the photovoltaic element, and solidifying the conductive adhesive to bond and fix the metal body at the predetermined position. Thus, a method for forming an electrode of a photovoltaic element is obtained. The transparent resin may be removed from the composite after bonding and fixing the metal body.

As the linear metal body, metal materials such as copper, silver, gold, aluminum, nickel and iron can be used. Alternatively, an alloy wire of these with tin, lead, indium, manganese, zinc or the like can be used.

The resin may be polyethylene, polyimide, polyester, nylon, vinyl,
Acrylic or the like can be used.

[0014]

Since a composite containing a low-resistance metal is directly bonded and fixed to the electrode forming surface via a conductive adhesive, an electrode having low cost and low resistance loss can be formed. In addition, by using a composite made of a transparent resin having a high tensile strength and a linear metal body for the electrode of the photovoltaic element as described above, without impairing the light incident area, the linear shape can be obtained. The tensile strength of the metal body is increased, and disconnection during pressing in the bonding step can be prevented.

[0015]

The present invention will be described below in detail with reference to examples. FIG. 1 shows a first embodiment of the present invention. In FIG. 1A, a copper wire 2 is fixed to a polyethylene film 1 by an adhesive applied thereto. A conductive adhesive 3 is attached to a lower portion of the copper wire 2.

FIG. 1B shows a state in which the copper wire 2 is fixed to the polyethylene film 1 as described above.
As described above, the pressure is applied to the electrode forming surface 5 of the amorphous silicon solar cell (amorphous filicom web) 4. Then, the conductive adhesive 3 is heated and cured by performing a heat treatment in the state of being pressed as described above, and the copper wire 2 is fixed to the electrode forming surface 5.

Incidentally, the polyethylene film 1 fixed to the copper wire 2 by the adhesive may be removed after the bonding of the conductive adhesive 3 is completed.

Next, a second embodiment of the present invention will be described with reference to FIG. In FIG. 2A, the width is 50 μm and the height is 30 μm.
The copper wire 22 is fixed to an EVA (ethylene vinyl acetate) sheet 21 in a pre-heated state. E
The VA sheet 21 is a filling layer material that fills a space between the electrode forming surface 25 of the amorphous silicon solar cell (amorphous silicon web) 24 and the skin of the solar cell module.
As a method of pre-heating the copper wire 22 as described above, a method of heating the copper wire 22 itself in advance by a heater or the like, and a method of applying an electric current to the copper wire 22 and fixing the copper wire 22 by own heat are used. Further, a conductive adhesive 24 is attached to the copper wire 22 fixed to the EVA sheet 21.

Then, the copper wire 22 fixed to the EVA sheet 21 is attached to the electrode forming surface 25 of the amorphous silicon solar cell 24 together with the EVA sheet 21 by the conductive adhesive 24.
Adhesion and fixation while pressing through. As shown in FIG. 2B, by performing a heat treatment thereafter, the EVA sheet 21 is melted, and the copper wire 22 is fixed to the electrode forming surface 25 of the amorphous silicon solar cell 24.

Here, during the heat treatment, the electrode forming surface 25 of the amorphous silicon solar cell 24 may be heated in advance. With this configuration, EV
By lowering the A sheet 21 gently on the electrode forming surface 25 from above, the conductive adhesive 2 adhered to the copper wire 22
4 can be heated first. For this reason, it is possible to reduce the protrusion of the conductive adhesive, which is generated at the time of pressing, to portions other than the lower portion of the copper wire 22.

Next, a third embodiment of the present invention will be described with reference to FIG. In FIG. 3A, the EVA resin molded body 31 is
At the center thereof, there is a concave recess 35 formed to a width of 100 μm and a depth of 30 μm.

The copper wire 32 is made of an EVA resin molded body 31.
Is formed in the depression 35 of the first embodiment. That is, the copper wire 32
A copper wire thinner than 100 μm is placed in advance in the EVA depression, and then copper plating is performed to grow along the EVA depression 35. In addition, the conductive adhesive 33 is injected into the depression 35 by a dispenser or the like and is embedded therein.

Then, a composite comprising the copper wire 32, which is a metal body constituted as described above, and the EVA resin molded body 31, which is a transparent resin, is combined with a pre-heated amorphous silicon solar cell (amorphous silicon solar cell). Web) 3
4 is pressed against the electrode forming surface 36, and then slowly cooled and fixed. At this time, the water level of the injected conductive adhesive 33 is set to the depression 3 of the EVA resin molded body 31 as shown in FIG.
If it is slightly lower than the wall of No. 5, there is an effect that the conductive adhesive 33 can be prevented from protruding during the pressing.

In the configuration of the third embodiment, the contact area between the EVA resin molded body 31 and the electrode forming surface is smaller than that of the second embodiment shown in FIG. For this reason, it is possible to prevent the generation of bubbles which are likely to be generated when the EVA resin molded body 31 is bonded. Furthermore, mass productivity can be improved by arranging a plurality of composites of the above-mentioned ENA resin molded body 31 and copper wires 32 on an EVA sheet as in Example 2 of FIG.

[0025]

As described above, according to the present invention, a composite including a low-resistance metal is directly bonded and fixed to the electrode forming surface of the photovoltaic element via a conductive adhesive. An electrode with low resistance loss can be formed at low cost.

Further, by forming the electrode formed body as a composite made of a metal and a transparent resin, the strength against pressure during the electrode bonding step is further increased. Therefore, the metal body can be pressed against the electrode formation surface without occurrence of disconnection or the like, and the degree of adhesion between the metal body and the electrode formation surface is improved. Further, for this reason, conditions such as unevenness with respect to the electrode formation surface are moderated, and there is an effect that the formation process can be facilitated.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram of a photovoltaic device according to a first embodiment of the present invention.

FIG. 2 is an explanatory diagram of a photovoltaic device according to a second embodiment of the present invention.

FIG. 3 is an explanatory diagram of a photovoltaic device according to a third embodiment of the present invention.

FIG. 4 shows a third embodiment.

FIG. 5 is an explanatory diagram of a conventional example in which an electrode is manufactured by a vacuum evaporation method.

FIG. 6 is an explanatory diagram of a conventional example in which an electrode is manufactured by a screen printing method.

FIG. 7 is an explanatory diagram of a conventional example in which an electrode is manufactured by a wire wiring method.

FIG. 8 is a sectional view of a conventional example in which an electrode is manufactured by a wire wiring method.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Polyethylene film 2 Copper wire 3 Conductive adhesive 4 Amorphous silicon solar cell 5 Electrode formation surface 21 EVA sheet 22 Copper wire 23 Conductive adhesive 24 Amorphos silicon solar cell 25 Electrode formation surface 31 Ethylene vinyl acetate 32 Copper wire 33 Conductive adhesive 34 Amorphous silicon solar cell 35 Depression 36 Electrode forming surface 111 Photovoltaic element 112 Electrode forming surface 113 Metal mask 114 Low resistance metal 115 Electron gun 116 Electron beam 121 Printing squeegee 122 Conductive resin 123 Screen mask 124 Photovoltaic power generation Element 125 Electrode forming surface 131 Metal body 132 Conductive adhesive 133 Photovoltaic element 134 Electrode forming surface

Claims (3)

(57) [Claims] 1. A composite comprising a linear metal body made of at least one kind of metal and a transparent resin is bonded and fixed to a surface of an electrode of a photovoltaic element via a conductive adhesive. Photovoltaic element. 2. a step of attaching a conductive adhesive to at least a part of at least a metal exposed portion of a composite made of a linear metal body made of at least one or more types of metals and a transparent resin; Bonding the metal body to a predetermined position on the electrode forming surface of the photovoltaic element, and solidifying the conductive adhesive to bond and fix the metal body to the predetermined position. Method for forming electrodes of a photovoltaic element. 3. The method according to claim 2, wherein the transparent resin is removed from the composite after the metal body is bonded and fixed.