JPH08306943A - Thin film solar cell and its manufacture - Google Patents

Abstract

PURPOSE: To prevent short-circuit between a connection electrode layer, which is connected with a rear electrode layer, and a transparent electrode layer by creeping of a transparent layer into a through hole in a structure wherein the transparent electrode layer and the rear electrode layer holding a photoelectric conversion layer between them on a flexible substrate are respectively connected with the connection electrode layer on the rear of the substrate through holes opened in the substrate. CONSTITUTION: A connection electrode layer 2 is covered with an insulating layer 7 in the vicinities of the apertures, which are located in the rear of a substrate, of through holes 11 for connecting a rear electrode layer 3 with the layer 2 and short-circuit between the layer 2 on the rear and a transparent electrode layer, which creeps in the holes 11, is made to prevent from being caused along with an amorphous semiconductor layer which creeps in the holes 11.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention connects a plurality of unit solar cells each having a thin film semiconductor layer formed on one surface of an insulating substrate as a photoelectric conversion layer by using a back electrode layer on the other surface of the substrate. The present invention relates to a thin film solar cell and a method for manufacturing the same.

[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. In such a thin film solar cell, a transparent electrode such as a SnO ₂ film or a ZnO film is provided on the side where sunlight is incident. However, since such a transparent electrode has a large sheet resistance, a power loss due to a current flowing through the transparent electrode becomes large. Therefore, conventionally, the solar cell is divided into a plurality of solar cells (unit cells), and the divided unit cells are electrically connected to adjacent unit cells in series connection structure. On the other hand, in the thin film solar cell described in JP-A-6-342924, a hole is made in the insulating substrate on the light incident side, and the transparent electrode layer is used as the connection electrode layer on the back surface of the substrate by utilizing this hole. By connecting, the distance of the path of the current flowing through the transparent electrode layer having a high sheet resistance can be shortened. As a result, a thin-film unit solar cell that can be configured as a low-voltage, large-current type without dividing into unit solar cells with limited dimensions, has a small Joule loss, and has a reduced dead space part to increase the effective power generation area. I was able to get it.
Therefore, it is extremely effective in constructing a low voltage, large current thin film solar cell. Further, an exposed region of the back electrode layer under the photoelectric conversion layer is formed in a part of the unit solar cell, and the separated connection electrode layer connected to the conductor penetrating the substrate and the separated electrode layer is connected to the connection electrode of the adjacent unit solar cell. By connecting the layers, a series connection structure can be easily formed without using a precise patterning technique. Such a structure is
F (Series-Connection through Apertures on Film)
It is called a structure, and FIG. 3 shows Japanese Patent Application No. 6-326795.
2 shows a thin-film solar cell having the SCAF structure described in the specification. In the figure, (a) is a top view, (b) is a bottom view, and (c) is
It is an AA line expanded sectional view of (a). This solar cell is manufactured as follows. The first through hole 11 is opened in the flexible substrate 1 using a plastic film, the back electrode layer 3 made of metal is formed on the front surface, and the connection electrode layer 2 made of metal is formed on the back surface, and then the second through hole 12 is opened. . Therefore, the back electrode layer 3 and the extension of the connection electrode layer 2 of the connection electrode layer 2 are formed on the inner wall of the first through hole 11, but these electrode layers are formed inside the second through hole 12. It has not been. Next, an amorphous silicon (a-Si) layer 4 having a pin structure is formed on the back electrode layer 3. At this time, at the same time, a-
The Si layer 4 is formed. After forming the a-Si layer 4, the transparent electrode layer 5 is formed. Here, the transparent electrode layer also adheres to the inner walls of the through holes 11 and 12, but the transparent electrode layer 5 and the connection electrode layer 2 are short-circuited by the i layer of the a-Si layer 4 formed on the back surface of the substrate. There is no such thing. Then, the additional connection electrode layer 6 is formed on the connection electrode layer 2 and the a-Si layer 4 on the back surface of the substrate.
To form. The additional connection electrode layer 6 is made of the same metal material as the connection electrode layer 2, but is not formed in the vicinity of the first through hole 11. To selectively form the additional connection electrode 6 in this way, a mask may be used or a printed electrode method may be used. The patterning line 8 separates the transparent electrode layer 5, the a-Si layer 4, and the back electrode layer 3 on the substrate surface into a plurality of photoelectric conversion regions. Further, the patterning line 9 on the back surface of the substrate separates the connection electrode layers 2 and 6 from one photoelectric conversion region on the front surface and the other in the connection region between the adjacent photoelectric conversion regions. This structure has the advantage that the photoelectric conversion effective area ratio is high because there is no risk of short-circuiting with the connection electrode layer on the back surface even if the transparent electrode layer 5 is formed up to the vicinity of the first through hole 11.

[0003]

In order to manufacture the SCAF structure solar cell shown in FIG. 2, in order to wrap the a-Si layer 4 around the outer peripheral portions of the first and second through holes 11 and 12 on the back surface of the substrate 1. Has a problem in that it is difficult to manufacture due to restrictions on the deposition conditions of a-Si, the thickness of the substrate 1, the sizes and shapes of the through holes 11 and 12. Also, from the weather resistance test results,
It has been clarified that the key point of the weather resistance of such a SCAF structure solar cell is the outer peripheral portions of the through holes 11 and 12. This is because the layer structure is complicated in the through-hole portion, and the layer thickness is likely to be non-uniform, and water vapor from the through-hole penetrates through the thin portion of the layer or the interface between layers to cause corrosion of the electrode layer. This is because In particular, the a-Si layer has a low adhesion to the metal electrode layer, and there is a problem that water vapor easily enters from the interface.

An object of the present invention is to solve the above problems and provide a thin film solar cell which is easy to manufacture and has good weather resistance, and a method for manufacturing the same.

[0005]

In order to achieve the above object, the present invention provides a back electrode layer, an amorphous semiconductor layer having a junction, and a back electrode layer on one surface of an insulating flexible substrate from the substrate side, respectively. A plurality of photoelectric conversion regions composed of transparent electrode layers are arranged, and on the other surface of the substrate, a connection electrode layer is formed so as to face parts of adjacent two photoelectric conversion regions that are close to each other. The back electrode layer and the connection electrode layer are connected via the back electrode layer, the substrate and the extension of the back electrode layer and the connection electrode layer attached to the inner wall of the first through hole penetrating the connection electrode layer, and are adjacent to each other. The transparent electrode layer and the connection electrode in which the transparent electrode layer and the connection electrode layer in the photoelectric conversion region are adhered to the inner wall of the second through hole penetrating the transparent electrode layer, the amorphous semiconductor layer, the back electrode layer and the connection electrode layer. By being connected through the extension of the layers , In a thin-film solar cell in which photoelectric conversion regions are connected in series, from the surface of the connection electrode layer around the first through hole to the surface of the back electrode layer on the inner wall of the first through hole or the surface of the extension of the connection electrode layer. It is assumed that it is covered with an insulating layer. It is also effective that the surface of the connection electrode layer around the second through hole is covered with an insulating layer from the surface of the transparent electrode layer on the inner wall of the second through hole or the surface of the extension of the connection electrode layer. Insulators are Si, Ti, W, Ni,
It is preferably made of one oxide or nitride of Mo, Ag, Al, Cu and Ta. The connection electrode layer extending on the inner wall of the second through hole and provided for connection with the transparent electrode layer,
The additional connection electrode layer is laminated on the connection electrode layer formed on the other surface of the substrate, and the extension is attached to the inner wall of the second through hole via the amorphous semiconductor layer. Is effectively not formed in the peripheral portion of the first through hole. The manufacturing method of the present invention for such a thin film solar cell comprises a step of forming a plurality of first through holes in an insulating flexible substrate, a back electrode layer on one surface of the substrate, and a connection electrode layer on the other surface. Forming and connecting the respective extension portions on the inner wall of the first through hole, and the back electrode layer or the connection electrode layer on the inner wall of the first through hole from the surface of the connection electrode layer around the first through hole. A step of covering with an insulating layer over the extended portion of, a step of forming a plurality of second through holes penetrating the back electrode layer, the substrate and the connection electrode layer after these steps, and covering the back electrode layer,
A step of forming an amorphous semiconductor layer that extends to at least the surface of the insulating layer deposited via the electrode layer on the inner wall of the first through hole, and covering the amorphous semiconductor layer, And a step of forming a transparent electrode layer in which the extension on the inner wall is connected to the connection electrode layer.

[0006]

When the transparent electrode layer is formed on the entire surface to expand the photoelectric conversion effective area, the transparent electrode layer extends into the first through hole formed in the flexible substrate and short-circuits with the connection electrode layer on the back surface of the substrate. In order to prevent this, the insulating layer formed before forming the amorphous semiconductor layer is used without utilizing the wraparound of the amorphous semiconductor layer. As a result, the wraparound condition from the first through hole of the amorphous semiconductor layer to the back surface becomes irrelevant. Further, the formation of such an insulating layer prevents water vapor from penetrating, and since the insulating layer has a high adhesive force with the metal electrode and the amorphous semiconductor layer, invasion of water vapor from the interface is also eliminated. Furthermore, by providing an insulating layer near the opening of the second through hole on the back surface of the substrate,
Water vapor permeation in this portion is also prevented, and the weather resistance is improved.

[0007]

Embodiments of the present invention will be described below with reference to the drawings in which the same parts as those in FIG. FIG.
2 (a) to (e) and FIGS. 2 (a) to (e) show a method of manufacturing a thin film solar cell according to an embodiment of the present invention in accordance with a flow of manufacturing steps. FIG. 1A is a cross section of a flexible plastic substrate 1 which is an insulator serving as a substrate. As the substrate 1, aramid and polyimide having a thickness of 50 μm were used in this embodiment, but in addition, polyether sulfone (PES), polyethylene naphthalate (PEN),
It is also possible to use an insulating plastic film such as polyethylene terephthalate (PET). The flexible substrate 1 is of an arbitrary thickness that can be wound up on a roll and has excellent handleability at the time of film formation by a stepping roll method or a roll-to-roll method, and at the same time has sufficient mechanical strength. Can be used. This board 1
First through hole 11 used for series connection is opened in [Fig. 1
(b)]. Next, a back electrode layer 3 and a connection electrode layer 2 are deposited on the upper surface and the back surface of the substrate 1, respectively (FIGS. 1C and 1D).
]. Since the back electrode layer 3 and the connection electrode layer 2 wrap around the first through hole, the front surface and the back surface are electrically connected. Next, an insulating layer 7 was formed of a weather resistant Si oxide film on the connection electrode layer 4 around the first through hole 11 on the back surface of the film substrate 1 by mask film formation [FIG. 1 (e)]. . This insulating layer 7 is made of a nitride of Si or Ti, W, Ni, M.
Oxides of Ag, Ag, Al, Cu and Ta and nitrides may be used. The insulating layer 7 is formed by a sputtering method or a CVD method using a stepping roll method or a roll-to-roll method to continuously achieve high productivity. The region where the insulating layer 7 is formed as a mask has only to be sufficiently wider than the wraparound region to the back surface side through the first through hole 11 of the transparent electrode layer described later. For example, the diameter of the first through hole is 1 mm. In this case, the first through hole 1 of the transparent electrode layer
The wraparound area to the back side through 1 has a diameter of at most 2
Since the area is about mm or less, the mask opening width is sufficiently wider than this, for example, 4 mm or more. Next, the second through hole 12 is opened [Fig. 2 (a)]. This second through hole is
Used for collecting current, the transparent electrode layer is connected to the connection electrode layer 2 on the back surface and the additional connection electrode layer described later, and the power loss is reduced by the transparent electrode layer having a high sheet resistance. At this time, the back electrode layer 3 and the connection electrode layer 2 are not connected to the second through hole 12
The cross section is cut cleanly and there are no electrodes in the second through hole as shown. After the processing of the second through hole 12, the a-Si photoelectric conversion layer 4 and the transparent electrode layer 5 are formed on the back electrode layer 3.
Are deposited [FIG. 2 (b), (c)]. Next, the additional connection electrode layer 6 is mask-formed on the back surface of the connection electrode layer 2 so as to prevent deposition around the first through hole 11 [FIG. 2 (d)].
]. The additional connection electrode layer 6 has a role of connecting the transparent electrode layer 5 in the second through hole 12 portion and the connection electrode layer 2 on the back surface, and at the same time, has a role of reducing the sheet resistance of the back surface connection electrode layer 2. . Then, the back electrode layer 3, the a-Si layer 4, the transparent electrode layer 5 are formed on the patterning line 8 on the upper surface by the laser.
Are separated into a plurality of photoelectric conversion units, and each series-connected cell is separated by the patterning line 9 on the back surface.

FIGS. 4 and 5 are plan views showing the pattern of the insulating layer 7 in the thin film solar cell of the embodiment of the present invention, in which (a) is a top view and (b) is a bottom view. .
For ease of understanding, only the insulating layer 7 is shown by hatching. FIG. 4 shows a case where the film is formed by the stepping roll method. In the stepping roll method, the position accuracy of the mask film formation is high, and the deposition region of the insulating layer 7 is formed in the first through hole 1.
It is possible to keep it small only in the peripheral part of 1. Figure 5
When the film is formed by the roll-to-roll method, the insulating layer 5 is formed in a band shape in the portion where the first through hole 11 exists. The roll-to-roll method has a very low position accuracy of mask film formation, but has extremely high productivity, and this method can be applied by using a mask film formation pattern as shown in FIG.

In the above embodiments, the formation of the insulating layer 7 improves the weather resistance of the first through hole 11 portion, but does not improve the weather resistance of the second through hole 12 portion. Therefore, the second through hole 1
In order to improve the weather resistance of the two portions, as shown in FIG. 6, at the end of the manufacturing process, the insulating layer 7 made of Si oxide or the like is masked from the peripheral portion of the second through hole 12 to the inner wall.

[0010]

According to the present invention, a short circuit due to the transparent electrode wrapping around in the first through hole for connecting the back electrode layer on the flexible substrate and the connection electrode layer on the back surface of the substrate is eliminated. As a result of preventing the holes by covering the vicinity of the opening to the back surface of the substrate with an insulating layer, control of the wraparound of the amorphous semiconductor layer becomes unnecessary. In addition, the formation of the insulating film on the through-hole portion, which is unfavorable to the weather resistance, improves the weather resistance and enables the production of highly reliable thin film solar cells as well as the prevention of short circuits by the insulating layer. A stepping roll method or a roll-to-roll method can be applied to the deposition of such an insulating layer, and the productivity can be improved.

[Brief description of drawings]

FIG. 1 is a sectional view showing the first half of a manufacturing process in a method for manufacturing a thin-film solar cell according to an embodiment of the present invention in the order of (a) to (e).

FIG. 2 is a cross-sectional view showing the latter half of the manufacturing process in the method of manufacturing a thin-film solar cell of one embodiment of the present invention in the order of (a) to (e).

FIG. 3 shows a conventional SCAF thin film solar cell,
(a) is a top view, (b) is a bottom view, and (c) is A- in (a).
A line cross section

FIG. 4 shows a part of a thin film solar cell according to an embodiment of the present invention, (a) is a top view and (b) is a bottom view.

FIG. 5 shows a part of a thin film solar cell according to another embodiment of the present invention, (a) is a top view and (b) is a bottom view.

FIG. 6 is a sectional view showing a part of a thin film solar cell according to still another embodiment of the present invention.

[Explanation of symbols]

 1 flexible substrate 11 1st penetration hole 12 2nd penetration hole 2 connection electrode layer 3 back electrode layer 4 a-Si layer 5 transparent electrode layer 6 additional connection electrode layer 7 insulating layers 8 and 9 patterning line

Claims (5)

[Claims] 1. A plurality of photoelectric conversion regions composed of a back electrode layer, an amorphous semiconductor layer having a junction, and a transparent electrode layer are arranged on one surface of an insulating flexible substrate from the substrate side, respectively.
On the other surface of the substrate, the connection electrode layer is formed so as to face the mutually adjacent portions of the two adjacent photoelectric conversion regions, the back electrode layer and the connection electrode layer of one photoelectric conversion region, the back electrode layer, Connected via an extension of the back electrode layer and the connection electrode layer attached to the inner wall of the first through hole penetrating the substrate and the connection electrode layer, the transparent electrode layer and the connection electrode layer of the adjacent photoelectric conversion region, By being connected through the transparent electrode layer, the amorphous semiconductor layer, the back electrode layer, the substrate and the extension of the connection electrode layer and the transparent electrode layer adhered to the inner wall of the second through hole penetrating the connection electrode layer. , In a thin-film solar cell in which photoelectric conversion regions are connected in series, from the surface of the connection electrode layer around the first through hole to the surface of the back electrode layer on the inner wall of the first through hole or the surface of the extension of the connection electrode layer. That it was covered with an insulating layer over Thin film solar cells to be. 2. The insulating layer covering from the surface of the connection electrode layer around the second through hole to the surface of the transparent electrode layer on the inner wall of the second through hole or the surface of the extension of the connection electrode layer. The thin film solar cell described. 3. The thin film solar cell according to claim 1, wherein the insulating material is one of oxides or nitrides of silicon, titanium, tungsten, nickel, molybdenum, silver, aluminum, copper and tantalum. 4. A connection electrode layer, which extends on the inner wall of the second through hole and contributes to connection with the transparent electrode layer, is laminated on the connection electrode layer formed on the other surface of the substrate, and the extension portion is formed. The additional connection electrode layer deposited on the inner wall of the second through hole via the amorphous semiconductor layer, and the additional connection electrode layer is not formed in the peripheral portion of the first through hole. A thin film solar cell according to the item Crab. 5. A step of forming a plurality of first through holes in an insulative flexible substrate, a back electrode layer on one surface of the substrate, and a connection electrode layer on the other surface of the substrate. One step of connecting on the inner wall of the through hole, and covering with an insulating layer from the surface of the connection electrode layer around the first through hole to the back electrode layer on the inner wall of the first through hole or the extension of the connection electrode layer. Steps, after these steps, a step of forming a plurality of second through holes penetrating the back electrode layer, the substrate and the connection electrode layer, and covering the back electrode layer, at least the electrode layer on the inner wall of the first through hole A step of forming an amorphous semiconductor layer extended to the surface of the insulating layer deposited through the, and the extension on the inner wall of the second through hole covering the amorphous semiconductor layer is connected to the connection electrode layer. And a step of forming a transparent electrode layer according to claim 1. Method of manufacturing a thin film solar cell according to any one of.