JPH0750427A - Thin film solar cell - Google Patents

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 formed on a flexible insulating substrate as a photoelectric conversion layer.

[0002]

2. Description of the Related Art An amorphous semiconductor film such as amorphous silicon formed by glow discharge decomposition of a raw material gas is a vapor phase growth, so that it is easy to increase the area and is expected as a photoelectric conversion film for a low-cost solar cell. ing. As a well-known method for extracting electric power from such a large area thin film solar cell, the thin film solar cell is divided into a plurality of unit cells on one substrate, and these are connected in series,
There is a series-connected solar cell as shown in FIG. This is a method of forming metal electrodes 21, 22, 23-made of a metal thin film in a strip shape on an insulating substrate 10 such as a glass plate polymer film or a metal plate having an insulating film coated on the surface thereof, and then forming the strip-shaped metal electrodes on the insulating substrate 10. Amorphous semiconductor layer regions 31, 32, which are photovoltaic generators,
33-, and then transparent electrodes 41, 42, 43-made of a transparent conductive film such as ITO or ZnO. Metal electrode
21, a combination of the amorphous semiconductor layer 31 and the transparent electrode 41, a combination of the metal electrode 22, the amorphous semiconductor layer 32 and the transparent electrode 42, etc. form each unit cell. Then, the transparent electrode of one unit cell, for example, 41 is formed such that a pattern of both electrodes and the amorphous semiconductor layer is formed so as to have a structure in which a metal electrode of an adjacent unit cell, for example, an edge of 22 is electrically contacted. Each unit cell is connected in series. The formation of such a series-connected solar cell is most generally performed by depositing each layer on the entire surface and then patterning by a laser scribing method each time.

One of the main 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. However, in reality,
In many cases, a system is composed of a large number of solar cells, and it is not always necessary for a single solar cell to output a high output voltage. Furthermore, since the output current of a series-connected solar cell is proportional to the unit cell area, it is disadvantageous to use the series-connected solar cell in applications where a high output current is required even if the voltage is low. . Another more basic reason for the series connection structure is to reduce Joule loss in the transparent electrode. That is, when a solar cell is formed with one unit cell on the entire surface without forming a series connection structure, the generated carriers have a long distance in the metal electrode and the transparent electrode to a lead wire extraction portion provided at the end of the solar cell. Will be moved over. The metal electrodes 21, 22, and 23 generally have low resistance, so that Joule disappearance due to the current flowing through the metal electrodes can be ignored. However, the transparent electrode
The sheet resistance of the transparent conductive film made of the materials 41, 42, and 43-is 5 to 5.
The resistance is relatively large at 30Ω / □, and the Joule loss due to the current flowing through the transparent electrode layer cannot be ignored. Therefore, in the prior art, a large area solar cell is divided into a plurality of strip-shaped unit cells, and the width of the unit cell is set to 5
It is generally about 20 mm.

[0004]

However, such a thin film solar cell has the following two problems. one,
When a large-area solar cell is divided into a plurality of unit cells, a linear dead space (51, 52, 53 in Fig. 2) that does not contribute to power generation occurs between the unit cells. Due to this dead space, the effective power generation area is reduced and the solar cell output is reduced. Another problem is that a solar cell corresponding to low voltage and large current cannot be formed. That is, since the unit cell has an appropriate width mainly determined by the sheet resistance of the transparent electrode, the optimum number of unit cells increases as the substrate area increases, and the solar cell is compatible with high voltage. If the number of cells is ignored and a low-voltage solar cell is formed, the maximum output will be remarkably lost.

The applicant of the present invention proposes a new solar cell structure which solves this problem, does not require a series connection structure even on a large-sized substrate, and has extremely small power loss due to current collection, and a manufacturing method thereof. Filed under No. 347394. Its structure is
As shown in FIGS. 3 (a) and 3 (b), a large number of small holes 6 are formed in the substrate 1 at regular intervals, and the first metal electrode 2, the amorphous semiconductor layer 3, and the transparent electrode 4 are formed on one surface thereof. In this order,
The second metal electrode 5 is formed on the other surface. In this case, after forming the first metal electrode 2, the small holes 6 of the substrate are irradiated with a laser beam having a diameter slightly larger than the small holes 6 to remove the first metal electrode 2 around the small holes, and then the amorphous semiconductor The layer 3, the transparent electrode 4, and the second metal electrode 5 are formed. When such a method is adopted, the connection conductor 45 is formed by the metal layer of the second metal electrode filled in the small hole 6, and the transparent electrode 4 and the second metal electrode 5 are brought into an electrically good conductive state, It is possible to form a low-voltage high-current solar cell having one metal electrode and a second metal electrode as output ends.

However, in this method, since the number of series connections is 1, regardless of the substrate area, a lower voltage than the conventional series connection type and a voltage higher than the voltage of one unit cell on one substrate. 2 has to be combined with the structure of FIG. 3, the manufacturing process becomes complicated and costly in terms of accuracy of laser processing. .

The object of the present invention is to solve the above problems,
An object of the present invention is to provide a thin film solar cell capable of obtaining an arbitrary voltage on a large area substrate.

[0008]

In order to achieve the above object, a thin film solar cell of the present invention comprises a first electrode layer, a semiconductor layer and a transparent electrode layer laminated on a first surface of an insulating substrate. An extension of only the electrode layer is formed and divided into a plurality of regions each of which includes a laminate and a first electrode layer extension, and the second electrode layer divided into the plurality of regions is deposited on the other surface to form a laminate. The transparent electrode layer in each of the divided regions of the semiconductor layer, the first electrode layer and the insulating substrate, and a region that is separated from each other of the second electrode layer by a conductor substantially insulated from the first electrode layer and A second electrode layer region connected to the transparent electrode layer, where each divided region of the first electrode layer extension is connected to a mutually separated region of the second electrode layer by a conductor penetrating the insulating substrate. A plurality of transparent electrode layers connected to each other and to each other And those connected to the second electrode layer region connected to the extended portion of the first electrode layer just below the pass. The connection between the second electrode layer regions is preferably made by contacting a conductor on another insulating substrate. The conductor penetrating the insulating substrate is an extension of the second electrode layer into the through hole of the insulating substrate, and the conductor connecting the transparent electrode layer and the second electrode layer has an insulating property of the transparent electrode layer. It is effective that it is an extension into the through hole of the substrate or that the conductor connecting the first electrode layer and the second electrode layer is an extension into the through hole of the insulating substrate of the first electrode layer. is there.

[0009]

Since the transparent electrode layer on the laminate and the exposed first electrode layer are connected to the separated areas of the second electrode layer on the back surface of the substrate by the conductor penetrating the insulating substrate, one unit is formed. The second electrode layer regions respectively connected to the transparent electrode layer and the first electrode layer of the cell are present on the back surface side of the substrate. Therefore, the output voltage of the thin-film solar cell can be set to a desired level by appropriately connecting the second electrode layer regions as terminals to each other by a method such as contact with a conductor on another insulating substrate. .

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT An embodiment of the present invention will be described below with reference to the drawing in which the same parts as those in FIG. Figure 1
The thin-film solar cell of one embodiment of the present invention shown in Fig. 3 has unit cells arranged in 3 series and 4 parallel, (a) is a plan view, (b) is
It is a bottom view which excludes the bonded polymer film shown in (c). The laminated structure on the insulating substrate 1 using the polymer film of this thin-film solar cell is similar to that of FIG. 3 (b) in the part A, and the first metal electrode is removed around the small hole 6,
Although the amorphous semiconductor layer and the transparent electrode 4 are formed thereon, in the portion B, only the first metal electrode 2 is not removed around the small hole 6. Then, as shown in FIG. 3A, a plurality of unit cell portions are divided by a dividing line 61 passing through the portions A and B. On the other hand, the second metal electrode 5 formed on the back surface of the substrate 1 has a dividing line 62 as shown in FIG.
The back side of the A section and the back side of the B section are divided by, and the back side of the A section is divided by the dividing line 63 facing the dividing line 61 on the front side.
On the back side of part B, a dividing line that is offset from the extension of the dividing line 63
It is divided by 64. The polymer film 11 to be bonded on the back surface has metal layer patterns 81 and 82 as shown in FIG. 7 (c), which are adhered to each other as shown by a dotted line in FIG. In addition, the four unit cells in the part A are connected in parallel by contacting the second metal electrode 5 connected to the transparent electrode 4 by the connecting conductor passing through the small hole 6 to the metal layer 81. The second metal electrode 5 connected to the first metal electrode 2 of each unit cell by the connection conductor passing through the small hole 6 is connected in series by contacting the L-shaped metal layer 82.

Such a thin film solar cell is manufactured as follows. (1) A large number of small holes 6 having a radius of 0.5 mm are formed on a polymer film 1 having a thickness of 200 μm by CO ₂ laser or punching. (2) Next, an Al thin film having a thickness of 300 nm is formed on one surface of the polymer film with small holes 1 by sputtering to form the first metal electrode 2, and a spot diameter of 0.9 mm is used at the portion A. Laser light is irradiated to remove the Al thin film around the small hole portion 6.

(3) An amorphous semiconductor layer 3 is formed by plasma CVD on the first metal electrode 2 in the section A, and a transparent electrode 4 made of a ZnO film by sputtering is 500 nm and 1 nm, respectively.
It is formed to a thickness of μm. At this time, the amorphous semiconductor layer 3 and the transparent electrode 4 partially adhere to the inner wall of the small hole 6 and the vicinity of the small hole portion on the opposite surface of the substrate 1 as shown in FIG.

(4) An Al thin film having a thickness of 300 nm is formed on the opposite surface of the polymer film substrate 1 by the sputtering method to form the second metal electrode 5. Similarly, the second metal electrode 5 has a part of the inner wall of the small hole 6 and the opposite surface side of the polymer film 1,
That is, it is attached in the vicinity of the small hole 6 on the transparent electrode 4 side, comes into contact with the transparent electrode 4 and becomes conductive. On the other hand, the second metal electrode 5 is brought into conduction by contacting the first metal electrode 2 in the inner wall of the small hole 6 and in the vicinity of the small hole in the portion B as shown in FIG.

(5) As shown in FIG. 1 (a), the first metal electrode 2 / amorphous semiconductor layer 3 /
The laminated structure of the transparent electrode 4 is divided by dividing lines 61, and the second metal electrode 5 is divided by dividing lines 62, 63, 64 on the back surface. This division is performed by laser light irradiation. In this way, the laminated structure of the first metal electrode 2, the amorphous semiconductor layer 3, and the transparent electrode 4 is divided into a plurality of unit cells, and the first metal electrode 2 and the transparent electrode 4 of each unit cell are formed of the polymer film 1. Of the second metal electrode 5 on the back surface, the state is completed in which the second metal electrode 5 is connected to the B section and the A section which are electrically separated by the dividing line 62.

(6) Separately, a polymer film 1 different from the substrate 1
A metal layer pattern 81, 82 shown in FIG. 1 (c) is formed on 1 by a sputtering method using a mask. This is shown in Figure 1 (b).
By stacking and laminating on the surface of the second metal electrode 5 shown in (3), 3 series and 4 parallel unit cell connections are realized. In order to obtain different output voltages, for example, when 2 series, 6 parallel or 4 series, 3 parallel are desired, this can be easily realized by changing the patterns 81 and 82 of the third metal electrode.

[0016]

According to the present invention, both terminals of a unit cell formed on an insulative substrate are led out to separate regions of a second electrode layer formed on the back surface side by conductors penetrating the insulative substrate. By appropriately connecting these regions, it has become extremely easy to efficiently extract an arbitrary output voltage for an arbitrary substrate size.

[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 bottom view without the bonded polymer film, and (c) is a plan view of the bonded polymer film.

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

FIG. 3 shows another conventional thin film solar cell, where (a) is a plan view and (b) is a sectional view.

FIG. 4 is a cross-sectional view in the vicinity of a through hole in a portion A of the thin film solar cell of FIG.

5 is a cross-sectional view in the vicinity of the through hole in the B portion of the thin film solar cell of FIG.

[Explanation of symbols]

 1 Insulating Substrate 11 Polymer Film 2 First Metal Electrode 3 Amorphous Semiconductor Layer 4 Transparent Electrode 5 Second Metal Electrode 6 Small Hole 61, 62, 63, 64 Dividing Line 81, 82 Metal Layer Pattern

Claims (5)

[Claims] 1. A laminated portion of a first electrode layer, a semiconductor layer and a transparent electrode layer and an extended portion of only the first electrode layer are formed on one surface of an insulating substrate to form a laminated portion and a first electrode layer extended portion, respectively. The second electrode layer is divided into a plurality of regions, which is divided into a plurality of regions on the other surface, and the transparent electrode layer in each divided region of the laminated portion forms a semiconductor layer, a first electrode layer and an insulating substrate. Penetrate,
Each of the divided regions of the first electrode layer extension is connected to a mutually separated region of the second electrode layer by a conductor that is substantially insulated from the first electrode layer, and each of the divided regions of the first electrode layer extension extends through the insulative substrate. A plurality of second electrode layer regions connected to the mutually separated regions of the two electrode layers and connected to the transparent electrode layer are connected to each other, and the first electrode immediately below the other mutually connected transparent electrode layer region. A thin-film solar cell, wherein the thin-film solar cell is connected to a second electrode layer region connected to an extension of the electrode layer. 2. The thin-film solar cell according to claim 1, wherein the second electrode layer regions are connected to each other by contacting a conductor on another insulating substrate. 3. The thin film solar cell according to claim 1, wherein the conductor penetrating the insulating substrate is an extension of the second electrode layer into the through hole of the insulating substrate. 4. The thin film solar cell according to claim 1, wherein the conductor connecting the transparent electrode layer and the second electrode layer is an extension of the transparent electrode layer into the through hole of the insulating substrate. 5. The thin-film solar cell according to claim 1, wherein the conductor connecting the first electrode layer and the second electrode layer is an extension of the first electrode layer into the through hole of the insulating substrate.