JPH06350115A - Film solar battery and its manufacture - Google Patents

Abstract

PURPOSE:To make a film solar battery, where an amorphous semiconductor layer is used, into a low-voltage and large-sized one, where the joule loss based on the current flowing in a transparent electrode layer is little, without putting it in series connection structure. CONSTITUTION:Output can be taken out of a metallic foil 5 by forming a solar battery structure consisting of a metallic electrode layer 2, an amorphous semiconductor layer 3, and a transparent electrode layer 4 from substrate side on the surface of an insulating substrate 1, and soldering (7) the metallic foil 5 stuck fast to the rear of the substrate 1 to the transparent electrode layer 4 through pores 6 being born scatteringly in the transparent substrate 1.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a thin film solar cell having a semiconductor thin film containing amorphous silicon as a main component as a photoelectric conversion layer and a method for manufacturing the same.

[0002]

2. Description of the Related Art A thin film of an amorphous semiconductor such as amorphous silicon formed by glow discharge decomposition of a raw material gas is vapor phase growth, so that it is easy to make a large area and photoelectric conversion of a low cost solar cell is performed. Expected as a membrane. As a well-known structure for efficiently extracting electric power from such a large-area thin film solar cell, as shown in FIG. 2, the thin film solar cell on one substrate is divided into a plurality of unit solar cells, There is a series connection of these. This is a transparent insulating substrate such as glass or transparent polymer film.
A transparent electrode 21, 22, 23 made of a thin film of a transparent conductive material such as tin oxide, ITO, or ZnO is formed in a strip shape on 11 and an amorphous semiconductor layer region which is a photovoltaic generation portion is formed thereon.
31, 32, 33-, and then metal electrodes 41, 42, 43-, which are made of a metal thin film such as Al or Ag, are formed. Then, the combination of the transparent electrode 21, the amorphous semiconductor layer 31, and the metal electrode 41, the combination of the transparent electrode 22, the amorphous semiconductor layer 32, and the metal electrode 42, and the like constitute each unit cell. And the extension parts 51, 52, 53 of the metal electrodes of one unit cell
Each unit cell is connected in series by forming a pattern of both electrodes and the amorphous semiconductor layer so that each of the unit cells contacts the edge of the transparent electrode of the adjacent unit cell.

The formation of such a series connection structure of solar cells is most generally performed by depositing each layer on the entire surface and then patterning by a laser scribing method each time.

[0004]

One of the reasons for adopting such a series connection structure in a large area solar cell is to obtain a high output voltage with a single solar cell. But,
In many cases, a system is often composed of a large number of solar cells, and it is not always necessary to output the output voltage with a single solar cell. However, when one unit cell of the solar cell is formed on the entire surface without forming a series connection structure, the generated carriers are long in the transparent electrode and the metal electrode on the back surface to the lead wire extraction portion provided at the end of the solar cell. Will travel over a distance. The metal electrode generally has a low resistance, and therefore the Joule loss due to the current flowing through the metal electrode can be ignored. However, the sheet resistance of the transparent conductive material thin film is usually 5 to
It is relatively large at 30Ω / □, and the Joule loss due to long-distance current flow through the transparent electrode layer cannot be ignored.

An object of the present invention is to solve the above problems and to obtain a large output current at a low output voltage. The object of the present invention is to form a serial connection structure on a large-sized substrate without causing joule loss. A thin-film solar cell and a method for manufacturing the same are provided.

[0006]

In order to achieve the above object, the thin film solar cell of the present invention comprises a metal electrode layer, an amorphous semiconductor layer and a transparent electrode layer laminated on one surface of an insulating substrate, The metal foil adheres to the other surface, and the transparent electrode layer and the metal foil penetrate the amorphous semiconductor layer, the metal electrode layer, and the insulating substrate while being dispersed at substantially equal intervals, and the metal electrode layer and the metal electrode layer. It is assumed that they are connected by a plurality of electrically insulated conductors. Then, it is effective that the anti-insulating substrate surface of the metal foil is covered with a weather resistant resin. In addition, such a method for manufacturing a thin-film solar cell is such that a metal electrode layer is deposited on one surface of an insulating substrate in which small holes are substantially evenly distributed and then the small holes are irradiated by laser light. The inner electrode and the metal electrode layer on the periphery are removed, then the amorphous semiconductor layer and the transparent electrode layer are sequentially laminated from one side of the insulating substrate, and the metal foil is further adhered to the other side to form the transparent electrode layer. The metal foil shall be connected by a low melting point alloy that fills the small holes.

[0007]

Since the transparent electrode layer thereabove is connected to the metal foil on the other surface of the substrate by the conductor penetrating the metal electrode layer and the amorphous semiconductor layer laminated on the one surface of the insulating substrate, the metal electrode Carriers generated by light incident from the layer and the metal foil to the semiconductor layer through the transparent electrode layer can be taken out without taking a long path to the transparent electrode layer having high sheet resistance. When each layer is formed on the insulating substrate in which the small holes are formed in advance, a thin film of each layer is also formed on the inner wall of the small holes. If the metal electrode layer that is formed first, including the area around the small hole, is removed by irradiation with laser light, the transparent electrode layer that passes through the small hole is formed by the amorphous semiconductor layer with a high resistivity that extends on the inner wall of the small hole. And the connection conductor of the metal foil are insulated.

[0008]

1 (a) and 1 (b) schematically show a thin-film solar cell according to an embodiment of the present invention, and FIG. 1 (c) shows an example of a small hole 6 as shown in FIG. 1 (a). It is sectional drawing which expanded one. Insulating substrate 1 made of polymer film has small holes 6 with a radius of 0.5 mm.
It is opened so that the closest distance between the two small holes is 20 mm. This small hole 6 is processed and formed by a CO ₂ laser or a punching device. Next, an aluminum thin film is sputter-deposited to a thickness of 300 mm on one surface of the polymer film 1 with small holes to form a metal electrode layer 2, and then this Al film is formed.
Laser light having a spot diameter of 0.9 mm or more is irradiated onto the small hole 6 from above the thin film to remove the Al film adhering to the inner wall of the small hole 6 and the surrounding Al film. Furthermore, this metal electrode layer 2
An amorphous semiconductor layer 3 is formed thereon by a plasma CVD method, and a transparent electrode layer 4 made of a ZnO film is formed by a sputtering method to have a thickness of 500 nm and a thickness of 0.1 to 1 μm, respectively. As shown in FIG. 1C, a part of the amorphous semiconductor layer and the transparent electrode material adheres to the inner wall of the small hole 6 of the polymer film 1. In the above process, the metal electrode layer 2 is formed of Ag thin film in addition to Ag
It may be formed of a thin film or may have a two-layer structure of a metal film and a transparent conductive film, but the material is not limited to these and any material having a sufficiently low sheet resistance can be used. . Further, the method of processing the metal electrode layer 2 includes
In addition to laser light, water jet etc. can be applied, or if there is a risk of damaging the polymer film,
This can be prevented by using a method of previously providing a spot-shaped mask on the polymer film before forming the metal electrode layer, and therefore the processing method is not limited.

Finally, as shown in FIG. 3, the polymer film 1 which has undergone the above steps is fed from the feeding roller 61 to the winding roller 64 via the auxiliary rollers 62 and 63 as indicated by the arrow, and the metal film A soldering iron that feeds the foil 5 from the feed roller 65 toward the take-up roller 54, makes it adhere to the lower surface of the polymer film 1 on the guide plate 71 with a built-in heater, and automatically moves in the horizontal and vertical directions. Using 72, the transparent electrode layer 4 and the metal foil 5 are soldered with the solder 7 as shown in FIG. 1 (c). The metal foil 5 has a thickness of about 50 μm, is a material that can be easily processed into a sheet shape, has a good brazing property, and is not particularly limited as long as it has a high resistance.

The method for electrically connecting the transparent electrode layer 4 and the metal foil 5 is not limited to soldering.
For example, laser welding, welding using ultrasonic waves, and use of a conductive paste dispenser are not limited as long as they can be electrically connected. With the solar cell structure shown in FIG. 1, the transparent electrode layer 4 and the metal foil 5 are electrically connected to each other through the solder 7 on the inner wall of the small hole 6 and in the vicinity thereof. On the other hand, in the metal electrode layer 2, since the vicinity of the small hole 6 is removed by laser irradiation and is electrically insulated from the inside of the small hole, the metal electrode layer 2 is not electrically connected to the transparent electrode layer 4 or the metal foil 5.

Further, as shown in FIG. 4, if weatherproof resin 8 is previously coated on the side of the metal foil 5 opposite to the side where the cells and the polymer film 1 are in close contact, the environment resistance can be maintained. It also becomes possible to serve as a protective material. Since the solar cell is usually used outdoors, it has a module structure to have environmental resistance. Considering the cost of the solar cell, about 1/3 is the cost of this modularization, and reducing the cost of this modularization is an important issue to reduce the cost of the solar cell. In the thin-film solar cell according to the present invention, by electrically connecting with the metal foil 5, not only a low-voltage, high-current solar cell can be produced without using an expensive vacuum device, but also the other side of the metal foil 5 is used. The surface is coated with the weather resistant resin 8 in advance, and the weather resistant film 1 having the oxide film 82 formed on the surface as shown in FIG. Is possible.

In order to obtain a predetermined voltage, generally, a required number of such thin-film solar cells may be connected in series. As shown in FIG. 5, the terminals 25 and the terminals 25 on the metal electrode layer 2 are connected to each other. Series connection is possible by a simple method such as brazing the metal foil 5 with solder 71. Further, depending on the application of the solar cell, it may be required to realize a voltage higher than the voltage of a single unit cell on a single substrate, though the voltage is lower than that of the conventional series connection type. In this case, the entire solar cell is divided into a plurality of unit cells determined by a predetermined voltage, and the unit cells are connected in the same manner as the conventional series connection type. Then, if the idea of the present invention is applied to each unit cell and the loss due to the current flowing through the transparent electrode is suppressed by using the small holes and the metal foil, any voltage can be efficiently extracted for any substrate size. be able to. In this case, the metal foil corresponding to each unit cell needs to be cut into strips in advance.

[0013]

According to the present invention, a solar cell layer structure for light incident from a side farther than the substrate is formed on an insulating substrate, and a transparent electrode layer on the upper surface of the solar cell layer structure is formed on the back surface of the substrate by a conductor penetrating the layer structure. By connecting to the electrode layer using a metal foil, most of the current drawn from the output terminals provided on the electrode layers on both sides of the substrate flows in the metal electrode layer, so there is little Joule loss in the transparent electrode layer, and the connection It was possible to obtain a thin-film solar cell with a non-series connection structure in which the dead space was reduced and the effective power generation area was increased. A metal layer formed by vapor deposition or the like can be used for the back electrode, but the cost is reduced by using the metal foil. Therefore, it is extremely effective in constructing a low voltage, large current thin film solar cell.

[Brief description of drawings]

FIG. 1 shows a thin film solar cell according to an embodiment of the present invention, (a)
Is a plan view, (b) is a sectional view, (c) is an enlarged sectional view near the small hole

FIG. 2 is a cross-sectional view of a conventional thin film solar cell.

3 is a side view of one of the thin-film solar cell manufacturing apparatuses of FIG.

FIG. 4 is a sectional view of a thin film solar cell according to another embodiment of the present invention.

5 shows two connection methods of the thin film solar cell of FIG.
(a) is a plan view, (b) is a sectional view

[Explanation of symbols]

 1 Insulating Substrate 2 Metal Electrode Layer 3 Amorphous Semiconductor Layer 4 Transparent Electrode Layer 5 Electrode Foil 6 Small Hole 7 Solder 8 Weatherproof Resin

Claims (3)

[Claims] 1. A metal electrode layer, an amorphous semiconductor layer, and a transparent electrode layer are laminated on one surface of an insulating substrate, and a metal foil is adhered on the other surface, and the transparent electrode layer and the metal foil are amorphous. Quality semiconductor layer,
A thin-film solar cell, comprising: a metal electrode layer and an insulating substrate, which are dispersed and penetrate through the metal electrode layer at substantially equal intervals, and are connected to each other by a plurality of conductors that are substantially insulated from the metal electrode layer. 2. The thin film solar cell according to claim 1, wherein the anti-insulating substrate surface of the metal foil is covered with a weather resistant resin. 3. A metal electrode layer is deposited on one surface of an insulating substrate in which small holes are distributed at substantially equal intervals, and then a metal electrode is applied to the inner wall and the periphery of the small holes by laser beam irradiation. The layer is removed, then the amorphous semiconductor layer and the transparent electrode layer are sequentially laminated from one side of the insulating substrate, and the metal foil is adhered to the other side, and the transparent electrode layer and the metal foil are filled with small holes. 2. The low melting point alloy for connecting is used for connection.
Alternatively, the method for manufacturing a thin film solar cell according to the item 2.