JP3513032B2 - Integrated thin-film solar cell and method of manufacturing the same - 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 including a semiconductor photoelectric conversion layer, and more particularly to an integrated thin film solar cell in which a plurality of divided power generation regions are electrically connected in series.

[0002]

2. Description of the Related Art A thin-film solar cell may include, as its semiconductor photoelectric conversion layer, a thin film containing amorphous silicon as a main component, for example. Such a silicon thin film can be formed in a large area much easier and cheaper than a silicon single crystal wafer. Therefore, practical application of a thin-film solar cell that can be manufactured in a large area at low cost is desired.

By the way, in a thin film solar cell, in order to obtain a desired output voltage value and output current value, a large-area power generation region formed on one large substrate is divided into a plurality of power generation regions, The mainstream is the development of integrated thin-film solar cells in which divided power generation regions are electrically connected in series.

[0004]

In FIG. 2, an example of a prior art integrated thin film solar cell is shown in a schematic plan view (see Japanese Patent Laid-Open No. 3-196679). In addition,
Although only two power generation regions connected in series with each other are shown in FIG. 2, it goes without saying that more power generation regions can be connected in series on the left and right sides.

In this solar cell, lower electrodes 12a, 12 for the first and second power generation regions are formed on the insulating substrate 11.
b is formed. These lower electrodes 12a, 12b
Includes respective extensions 12ae, 12be. A semiconductor photoelectric conversion layer 13 is laminated on the lower electrodes 12a and 12b so as to cover them. On the photoelectric conversion layer 13, the upper electrode 1 for the first and second power generation regions is formed.
4a and 14b are formed. These upper electrodes 14
a and 14b include respective extensions 14ae and 14be. Then, the lower electrode 12a and the upper electrode 14a
The region in which is overlapped with each other forms the first power generation region, and the region in which the lower electrode 12b and the upper electrode 14b are overlapped forms the second power generation region.

Extension 1 of the upper electrode 14a in the first power generation region
4ae is partially overlapped with the semiconductor layer 13 on the extension 12be of the lower electrode 12b in the second power generation region. Then, by scanning the laser beam as represented by the dotted line 15, the extension 14ae of the upper electrode and the extension 12be of the lower electrode are scanned by the scanning line 1.
5 is welded. Thus, the first power generation region on the left side and the second power generation region on the right side are electrically connected in series on the substrate 11.

In a solar cell as shown in FIG. 2, lower electrodes 12a, 12b and upper electrodes 14a, 1
4b is usually formed using a metal mask. However, in the case of using a metal mask, the extension 1 of the upper and lower electrodes may be changed due to the lift or displacement of the mask from the substrate 11.
There is a case where the bonding of 4ae and 12be cannot be performed reliably, and the electrical resistance component increases at the bonding portion. Needless to say, such an increase in the resistance component deteriorates the output characteristics of the solar cell.

On the other hand, the upper and lower electrodes 12a, 12b, 14a,
When 14b is patterned with a laser beam, the area to be marked with the laser beam is very large, which impairs the mass productivity of solar cells. In addition, the lower electrode 12a,
An upper electrode 14 formed on the semiconductor layer 13 that covers 12b
It is difficult to selectively pattern only a and 14b with a laser, and the upper electrodes 14a and 14b must be formed by another method.

In FIG. 3, another example of an integrated type thin film solar cell according to the prior art is schematically shown in a partial sectional perspective view (see Japanese Patent Publication No. 62-14954). In this solar cell, the lower electrode layer 22 is formed on the insulating substrate 21.
Is formed, which is divided into a plurality of regions by a plurality of parallel separation grooves 22g. The semiconductor photoelectric conversion layer 23 is laminated so as to cover the lower electrode layer 22, and the semiconductor photoelectric conversion layer 23 is divided into a plurality of regions by a plurality of separating grooves 23g formed in parallel in proximity to the corresponding lower electrode separating groove 22g. There is. The upper electrode layer 24 is laminated so as to cover the semiconductor layer 23, and this is divided into a plurality of regions by a plurality of separation grooves 24g formed in parallel in proximity to the corresponding semiconductor layer separation groove 23g.

That is, a plurality of rectangular power generation regions are formed on the substrate 21 in parallel with each other. Then, the upper electrode 24 in any one power generation region is connected to the lower electrode 22 in the power generation region adjacent to the right side thereof via the semiconductor layer separation groove 23g. Thus, on the substrate 21, an integrated thin film solar cell in which a plurality of power generation regions are connected in series can be formed.

However, in the solar cell as shown in FIG. 3, a normal upper electrode layer separation groove 24g is formed by laser (for example, in the same manner as in the case of forming the lower electrode layer separation groove 22g and the semiconductor layer separation groove 23g). It is difficult to form using the second harmonic or the third harmonic of the YAG laser. That is, even if the laser scribe condition is selected, the upper electrode layer 24 itself cannot be cut (cannot be separated),
On the contrary, in many cases, the lower electrode layer 22 is also cut, and it is difficult to selectively draw the upper electrode layer 24 selectively, and it is difficult to obtain a normally integrated thin-film solar cell.

In order to avoid such a problem, the upper electrode layer 24 is patterned by using a metal mask as in the case of FIG. 2 or is separated by applying a resist pattern and then performing chemical etching. A method of forming the groove 24g has also been proposed. However, there are many cases where the integration is incomplete (the separation of the upper electrode layer 24 is incomplete) due to the deviation of the metal mask or the resist pattern, the etching failure, or the like. Further, in the chemical etching, a great amount of time and cost are required in the actual mass production of the solar cell for adjusting the etching liquid and treating the drainage liquid, which leads to a decrease in production yield and an increase in price. .

In view of the above problems in the prior art, the present invention aims to provide a normally integrated thin film solar cell efficiently with a high yield and at a low cost.

[0014]

An integrated thin-film solar cell according to the present invention includes a lower electrode layer, a semiconductor photoelectric conversion layer, and an upper electrode layer, which are formed on an insulating surface of a substrate in this order, and A solar cell in which a plurality of power generation regions are formed by forming separation grooves in a layer of a predetermined pattern, and the plurality of power generation regions are electrically connected in series, A conductive island is formed within the width of the separation groove for separating the lower electrode layer between the first power generation region, which is any one, and the second power generation region adjacent to the first power generation region. The upper electrode of the second power generation
It is characterized in that it is connected to the conductive island without being connected to the lower electrode of the region, and the conductive island is connected to the lower electrode of the second power generation region through a region other than the power generation region.

The conductive islands are preferably formed from the lower electrode layer by scoring the lower electrode layer with a laser beam. Further, it is preferable that the upper electrode separation groove is formed at the position of the separation groove between the lower electrode and the conductive island in the second power generation region.

[0016]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 illustrates an example of an integrated thin film solar cell as an embodiment of the present invention. FIG. 1 (A) schematically shows a partial sectional perspective view, and FIG. 1 (B) shows a schematic plan perspective view corresponding thereto. Although only two power generation regions connected in series with each other are partially shown in FIG. 1, it goes without saying that more power generation regions can be connected in series in the left and right directions in practice.

In this solar cell, an opaque substrate 1 made of a metal such as Al or stainless can be used. When the conductive metal substrate 1 is used, its surface is covered with an insulating film 1a such as polyimide. Such an insulating film 1a is formed by applying a solution of polyimide with a roll coater to obtain about 30 μm.
Can be formed to a thickness of. In the solar cell of the present invention, it goes without saying that the substrate 1 is not limited to metal and may be a transparent insulating substrate such as glass.

On the insulating film 1a, for example, Al or A
A lower electrode layer 2 made of g or the like is formed over a width 2L. This lower electrode layer 2 is separated by the separation groove 2g.
It is divided into first and second lower electrodes 2a and 2b corresponding to the first and second power generation regions. The lower electrode separation groove 2g is
Preferably, the ablation effect of a laser (for example, the second harmonic of a YAG laser) is used, for example, 7
It can be formed with a width of 00 μm.

A conductive island 5 is formed within the width of the lower electrode separation groove 2g. Such conductive islands 5 are formed by using a metal mask or the like to form a film of the same material as the lower electrode layer 2 or by using a mesh pattern to print a conductive paste (for example, conductive carbon or Ag paste). Can be formed. The dimensions of the conductive island 5 can be set to a width of 500 μm and a height of 100 μm, for example.
At this time, the central axis of the conductive island 5 is preferably arranged substantially along the center of the lower electrode separation groove 2g.

A more preferable method for forming the conductive island 5 is to form the lower electrode layer 2 by utilizing scoring with a laser beam. For example, the lower electrode layer 2 is scanned with a laser beam to form a groove 2h for separating the first lower electrode 2a and the conductive island 5, for example, 100 μm.
Formed with a width of. Next, a groove 2i for separating the second lower electrode 2b and the conductive island 5 is formed with a width of, for example, 100 μm by similar scoring with a laser beam. Thus, the conductive island 5 having a width of about 500 μm is formed at the center of the lower electrode separation groove 2g having a width of 700 μm.

Whichever method is used, the conductive island 5 is connected to the second lower electrode 2b through the connecting portion 5a provided outside the power generation region, as shown in FIG. 1 (B). ing. A method using a laser beam is also preferable for forming such a connecting portion 5a. That is,
When the separation groove 2i between the second lower electrode 2b and the conductive island 5 is formed by a laser beam, the length of the separation groove is 2iL.
The ablation by the laser may be stopped when the line A, which is indicated by the broken line, is reached. Stopping laser ablation can be easily accomplished by electrical switching of the laser device or by using a mechanical shutter for the beam.

On the lower electrode layer 2, the length 2 of the separation groove 2i is set.
The semiconductor photoelectric conversion layers 3 are stacked over a width 3L shorter than iL. The photoelectric conversion layer 3 can be formed to include, for example, an amorphous silicon layer, or can be formed to include a single layer of Si or a stacked layer of the single layer and Si. Such a semiconductor photoelectric conversion layer 3 can be formed by, for example, a plasma CVD method.

The semiconductor layer 3 is provided with a separation groove 3g for separating it into the first and second semiconductor layer regions 3a and 3b and connecting the upper electrode 4a to the conductive island 5. This separation groove 3g is also preferably formed by marking with a laser. At this time, the left side wall of the separation groove 3g is preferably located within the width of the separation groove 2h between the first lower electrode 2a and the conductive island 5. This is because by doing so, the upper electrode 4a can be bonded not only to the upper surface of the conductive island 5 but also to the left side surface thereof, and the electrical connection between them can be made more reliable.

The upper electrode layer 4 is formed on the semiconductor photoelectric conversion layer 3 over a width 4L slightly smaller than the width 3L of the semiconductor layer 3.
Are stacked. The width 4L of the upper electrode layer 4 determines the widths of the first and second power generation regions. That is,
In FIG. 1B, it can be seen that the connection region 5a between the conductive island 5 and the second lower electrode 2b is formed outside the power generation region.

When the substrate 1 is made of an opaque metal, the upper electrode layer 4 must be transparent in order to introduce light into the photoelectric conversion layer 3. Such a transparent electrode layer 4 is made of Zn
It can be formed using a transparent conductive oxide such as O, ITO, or SnO ₂ . For example, when ITO is used,
The upper electrode layer 4 can be formed by a sputtering method. The thickness of the ITO layer 4 can be preferably selected from about 600 to 700 μm, which can minimize reflection of incident light.

The upper electrode layer 4 is provided with a separation groove 4g for separating the first and second upper electrodes 4a and 4b corresponding to the first and second power generation regions. The upper electrode separation groove 4g is formed in the separation groove 2 between the conductive island 5 and the second lower electrode 2b.
It is preferably formed according to the position of i. This is because by doing so, the non-power generation region required for the separation between the first and second power generation regions can be reduced.

The upper electrode separation groove 4g may have a width smaller than that of the separation groove 2i between the conductive island 5 and the second lower electrode 2b and may be formed within the width of the separation groove 2i. preferable. This is because by doing so, it is possible to prevent a leak current between the second lower electrode 2b and the second upper electrode 4b through the side wall of the upper electrode separation groove 4g.

That is, when the upper electrode isolation groove 4g is formed by scoring using a laser beam, the amorphous silicon layer 3 is crystallized on the side wall surface of the groove 4g due to the thermal effect of the laser beam, and the electric resistance value is increased. It is possible that the resistance value may decrease or the evaporation material from the upper electrode layer 4 may adhere to the sidewall surface of the groove 4g to decrease the resistance value. Therefore,
If the upper electrode separation groove 4g is wide and the right side wall is the second
If it is connected to the upper surface of the lower electrode 2b, a leak current may occur between the second lower electrode 2b and the second upper electrode 4b via the right side wall thereof. However, as shown in FIG. 1A, if the right side wall of the upper electrode separation groove 4g is separated from the upper surface and the left side surface of the second lower electrode 2b, leakage through the side wall of such groove 4g. The current can be prevented.

In the integrated thin-film solar cell in which a plurality of power generation regions are connected in series in the left-right direction as described above, the output connected to the lower electrode of the power generation region at the left end is used to extract output power. A terminal and an output terminal connected to the upper electrode in the power generation region at the right end are provided. Corresponding to such an embodiment, when an integrated type thin film solar cell was actually produced on the metal substrate 1 and the output characteristics were measured, a value corresponding to the number of serial integrated stages was observed as the output voltage, It was confirmed that the power generation area was normally integrated.

An integrated type thin film solar cell using a white glass substrate 1 in place of the metal substrate was also actually manufactured.
In this case, the insulating layer 1a can be omitted and the lower electrode layer 2
A transparent electrode layer of ZnO, ITO or the like is formed, and a highly reflective metal layer of Al, Ag or the like is used as the upper electrode layer 4. Between the semiconductor photoelectric conversion layer 3 and the metal electrode layer 4, ZnO, in order to improve the reflection efficiency of the metal electrode layer,
A transparent conductive layer such as ITO may be inserted. Even when the output characteristics of the integrated type thin film solar cell manufactured on such a glass substrate 1 are measured, a value corresponding to the number of serial integration stages is observed as the output voltage, and a plurality of power generation regions are normally integrated. Was confirmed.

[0031]

As described above, according to the present invention, it is possible to provide a normally integrated thin film solar cell efficiently with a high yield and at a low cost.

[Brief description of drawings]

1A is a partial cross-sectional perspective view schematically showing an example of an integrated thin-film solar cell according to an embodiment of the present invention, and FIG. 1B is a schematic plan perspective view corresponding thereto.

FIG. 2 is a schematic plan view showing an example of an integrated thin-film solar cell according to the prior art.

FIG. 3 is a partial cross-sectional perspective view schematically showing another example of the integrated thin-film solar cell according to the prior art.

[Explanation of symbols]

1 substrate 1a insulating film 2 Lower electrode layer 2a, 2b First and second lower electrodes 2g Lower electrode separation groove 2h Separation groove between first lower electrode and conductive island 2i Separation groove between conductive island and second lower electrode 2L width of lower electrode layer 2iL Length of separation groove between conductive island and second lower electrode 3 Semiconductor photoelectric conversion layer 3a, 3b First and second semiconductor layer regions 3g Semiconductor layer region separation groove Width of 3L semiconductor layer region 4 Upper electrode layer 4a, 4b First and second upper electrodes 4g Upper electrode separation groove 4L width of upper electrode layer 5 Conductive island 5a Connection between conductive island and second lower electrode

Front page continuation (72) Inventor Shin Kidoguchi, 22-22 Nagaikecho, Abeno-ku, Osaka-shi, Osaka Prefecture, Sharp Corporation (72) Inventor Hiroshi Taniguchi, 22-22, Nagaike-cho, Abeno-ku, Osaka City, Osaka Prefecture (72) ) Inventor Katsuhiko Nomoto 22-22 Nagaike-cho, Abeno-ku, Osaka, Osaka Prefecture (56) References JP-A-60-81874 (JP, A) JP-A-63-37674 (JP, A) JP-A-SHO 61-183975 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) H01L 31/04-31/078

Claims (10)

(57) [Claims] 1. A lower electrode layer, a semiconductor photoelectric conversion layer, and an upper electrode layer formed on an insulating surface of a substrate are included in this order, and separation grooves are formed in a predetermined pattern in each layer. Multiple power generation areas are formed,
A solar cell in which the plurality of power generation regions are electrically connected in series, between a first power generation region that is any one of the plurality of power generation regions and a second power generation region that is adjacent to the first power generation region. A conductive island is provided within the width of the separation groove for separating the lower electrode layer, and the upper electrode of the first power generation region is lower than the second power generation region.
The integrated type thin film solar device is connected to the conductive island without being connected to an electrode, and the conductive island is connected to a lower electrode of the second power generation region through a region other than the power generation region. battery. 2. The solar cell according to claim 1, wherein the conductive island is made of the same material as the lower electrode layer. 3. The method for manufacturing a solar cell according to claim 2, wherein the separation groove of the lower electrode layer and the conductive island are formed by marking the lower electrode layer. A method for manufacturing a solar cell, comprising: 4. The manufacturing method according to claim 3, wherein the marking of the lower electrode layer is performed by a laser scribing method. 5. The separation groove for separating the upper electrode layer between the first and second power generation regions has a width of a separation groove between the lower electrode of the second power generation region and the conductive island. The solar cell according to claim 1 or 2, wherein the solar cell is formed inside. 6. The method for manufacturing the solar cell according to claim 5, wherein the separation groove for separating the upper electrode layer is formed by a laser scribing method. Manufacturing method. 7. The method for manufacturing a solar cell according to claim 2, wherein the isolation groove of the lower electrode layer and the conductive island are simultaneously formed by using a mask. Manufacturing method. 8. The method for manufacturing the solar cell according to claim 1, wherein the conductive island is formed by using a conductive paste. 9. The method for manufacturing the solar cell according to claim 1, wherein all the separation grooves for separating the lower electrode layer, the semiconductor photoelectric conversion layer, and the upper electrode layer are formed by a laser scribing method. And a solar cell manufacturing method. 10. The solar cell according to claim 1, wherein the semiconductor photoelectric conversion layer includes a layer containing amorphous silicon as a main component.