JPH11121780A - Solar cell and manufacture thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To protect a glass board against cracking, by a method wherein a transparent electrode layer is formed through a patterning method where a laser is not used, and a photoelectric conversion layer and a back electrode layer are formed on the transparent electrode layer through a patterning method where a laser is used. SOLUTION: A transparent conductive film is formed on a glass substrate, and a prescribed pattern is provided to the transparent conductive film through a patterning method where no laser is used. Then, a groove is provided to form the transparent conductive film up to the surface of the glass substrate so as to form a transparent electrode layer. Then, an amorphous silicon layer is formed on the transparent electrode layer and filled into the groove. A groove is provided to the upside of the transparent electrode layer by a patterning method where a laser is used to form a photoelectric conversion layer. Then, a metal layer is formed on the photoelectric conversion layer, and a prescribed pattern is provided to the metal layer through a patterning method where a laser is used for the formation of a back electrode layer.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a solar cell and a method of manufacturing the same, and more particularly, to a method of manufacturing without causing cracks in a glass substrate, improving the production yield and reducing the cost. Also, the present invention relates to a solar cell having high reliability and mechanical strength because there is no crack in a glass substrate, and a method for manufacturing the same.

[0002]

2. Description of the Related Art In general, as a solar cell, a transparent electrode layer having a light transmitting property, a photoelectric conversion layer made of amorphous silicon, and a back electrode made of a conductive metal are formed on a glass substrate which is a light transmitting insulating substrate. Some have a structure in which layers are stacked. Since this solar cell cannot obtain a required electromotive force by itself, usually, as shown in FIG.
On a glass substrate 1, a transparent electrode layer 2a and a back electrode layer 4a
Has a structure in which a plurality of photovoltaic cells 5a each composed of a photoelectric conversion layer 3a sandwiched between are arranged, for example, a back electrode layer 4b of a photovoltaic cell 5b and a transparent electrode layer 2a of an adjacent photovoltaic cell 5a. And connect the respective solar cells 5a, 5
are connected in series by communication portions 6ab, 6bc, 6cd,.

As shown in FIG. 1A, a solar cell is manufactured by forming a transparent conductive film 7 on a glass substrate 1,
As shown in FIG. 1B, grooves 8 reaching the surface of the glass substrate 1 in a predetermined pattern are formed (scribed) to form transparent electrode layers 2a, 2b,... Corresponding to each solar cell. I do. Further, as shown in FIG. 2A, an amorphous silicon layer 9 is deposited thereon, and then, as shown in FIG. 2B, the transparent electrode layers 2a, 2b,.
The grooves 10 corresponding to the communication portions 6ab, 6bc, 6cd... (The communication portions 6ab, 6b in FIG.
c, 6cd...), and the photoelectric conversion layers 3a,
3b,... Are formed. Next, as shown in FIG. 2C, a conductive film 11 (for example, a metal film) constituting the back electrode layer is formed on the photoelectric conversion layers 3a, 3b,. After filling the conductive coating material to form the connecting portions 6ab, 6bc, 6cd,..., Grooves 12 reaching the photoelectric conversion layers 3a, 3b,. As shown in FIG.
4b,... Can be performed. In the manufacture of this solar cell, the grooves 8, 10 and 1
The work of engraving 2, so-called scribing, is mainly performed using a laser. Since this is a dry process, it can be easily connected to a vacuum process such as CVD or sputtering, which is a manufacturing process of a solar cell, and the equipment cost is low, and a fine pattern with a width of 50 μm or less can be quickly cut. And so on.

However, in the conventional solar cell, the glass substrate is broken in the heat treatment in the manufacturing process, for example, in the film forming process of the photoelectric conversion layer, the film forming process of the back electrode layer, and the production yield is lowered. And increased costs. Also, since solar cells are exposed outdoors during actual use, the glass substrate may be exposed to mechanical shock due to the impact of pebbles or falling objects, temperature rise due to solar radiation, temperature difference between day and night, temperature difference between seasons, etc. In some cases, cracks in the glass substrate occurred due to the thermal stress generated in the glass substrate. Further, even when tempered glass was used for the glass substrate for the purpose of improving the strength, the glass was similarly cracked, and the expected strength could not be obtained.

[0005]

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to prevent a glass substrate from cracking in a manufacturing process involving heat treatment, improve production yield and reduce cost, and reduce the cost of actual use. In some cases, it is an object of the present invention to provide a solar cell having high reliability and high mechanical strength by preventing a glass substrate from cracking.

A second object of the present invention is to provide a method for manufacturing the solar cell at a high yield and at low cost.

[0007]

Means for Solving the Problems Accordingly, the present inventors have:
The cause of the crack in the glass substrate of the solar cell was investigated. As a result, all of the starting points of the generated cracks were the portions where the transparent electrode layer was cut by laser scribing, that is, FIG.
3B, the bottom of the groove 8 of the glass substrate 1 (1 in FIG. 3).
3). In general, if the scribing of the groove 8 by the laser is incomplete, FIG.
As shown in (b), adjacent transparent electrode layers 2a and 2b,
.., 2c or 2c and 2c... Are connected, and independent electrodes cannot be formed.
Then, in order to completely separate the adjacent transparent electrode layers, scribing by a laser having a strong and powerful output is performed, and as shown in FIG.
Since the transparent electrode layer is locally strongly heated by the laser irradiation in the portion in contact with the bottom 13 of the substrate, it is presumed that the glass substrate surface in contact with the cut portion is also locally thermally damaged. In particular, when the glass substrate 1 is a tempered glass, since the strengthening stress on the glass surface necessary for expressing the strength is reduced by local heating of the glass surface by laser scribing, the original strength of the tempered glass is reduced. It is considered that the effect is no longer exhibited, and the effect of the decrease in the glass strength appears remarkably. Therefore, the present inventors have solved the above-mentioned problem by performing engraving of a transparent electrode layer by a patterning method without using a laser in the manufacture of a solar cell unless thermal and mechanical damage is given to a glass substrate. What is possible is that the engraving of the photoelectric conversion layer and the back electrode layer does not damage the glass substrate even when performed by the laser patterning method, and further, the engraving of the transparent electrode layer is performed by a patterning method without using a laser. And a dry process, so that it can be easily connected to a vacuum process such as CVD or sputtering, which is a manufacturing process of a solar cell, the device cost is low, and a fine pattern with a width of 50 μm or less is easily carved. By combining the above, it is possible to prevent the glass substrate from cracking during the solar cell manufacturing process involving heat treatment, Ri and found that it is possible to reduce the cost by improving, leading to envision the present invention.

That is, in order to solve the above problems, the present invention provides a glass substrate, and a transparent electrode layer formed on the glass substrate by a patterning method without using a laser.
It is intended to provide a solar cell having a photoelectric conversion layer formed on the transparent electrode layer by a patterning method using a laser and a back electrode layer.

Further, according to the present invention, as a method of manufacturing the solar cell, a transparent conductive film is formed on a glass substrate, and the transparent conductive film is processed by a patterning method without using a laser to have a predetermined pattern. An object of the present invention is to provide a method for manufacturing a solar cell, comprising a step of forming a photoelectric conversion layer and a back electrode layer on a transparent electrode layer by using a patterning method using a laser after forming the transparent electrode layer.

Hereinafter, the solar cell of the present invention and the method of manufacturing the same will be described in detail.

The solar cell of the present invention has a glass substrate and a transparent electrode layer, a photoelectric conversion layer and a back electrode layer on the glass substrate.

The glass substrate forming the glass substrate of the solar cell of the present invention is not particularly limited. Examples thereof include a glass having a normal soda-lime glass composition, a glass having a white plate glass composition having a reduced iron content, and a soda glass. Various base materials such as glass having a reduced heat-resistant glass composition and borosilicate glass can be used. In particular, since the solar cell of the present invention is required to reduce the absorption of visible light and have a high visible light transmittance, the iron content is 0.1% as iron oxide content.
A glass substrate having a content of not more than 05% by weight, preferably 0 to 0.01% by weight, is preferable because transmittance in a long wavelength region of 1 to 2 μm can be improved. Alternatively, borosilicate glass may be used as the base having an iron content of 0 wt%. Specifically, the visible light transmittance is higher than that of soda lime glass, and particularly, the visible light transmittance is 8%.
It is preferable to use a glass base material having a visible light transmittance of 5% or more and a visible light transmittance of 88% to 92%. In the solar cell of the present invention, the glass substrate may be made of tempered glass. In this case, a transparent conductive layer may be formed on glass that has been reinforced in advance, or a transparent conductive layer may be formed on a glass substrate, and then a reinforced glass substrate with a transparent conductive layer may be used. Is also good.

[0013] In the solar cell of the present invention, the thickness of the glass substrate is usually in the range of 0.5 to 10 mm, and when the tempered glass or the tempered glass with a transparent conductive layer is used as the substrate, it is at least 3 mm. Is desirable.

In the solar cell of the present invention, the transparent electrode layer formed on the glass substrate is formed by forming a transparent conductive film on the glass substrate and then patterning the transparent conductive film without using a laser. This is performed by processing to form a predetermined pattern.

The formation of the transparent conductive film on the glass substrate can be performed by, for example, a CVD method, a plasma CVD method, a sputtering method, an electron beam evaporation method, a resistance heating evaporation method, an ion plating method, or a coating solution for forming a transparent conductive film. Any method that can form a transparent conductive thin film on the surface of a glass substrate, such as a spray method for spray coating and a dipping method for dipping in a coating liquid for forming a transparent conductive film, may be performed according to any method, and is not particularly limited. .

In the present invention, as a patterning method without using a laser for forming a transparent conductive film into a predetermined pattern, a photo-etching method, a lift-off method and the like can be mentioned.

In the solar cell of the present invention, examples of the transparent electrode layer include a transparent conductive oxide layer containing tin oxide as a main component. The transparent conductive oxide layer containing tin oxide as a main component contains fluorine in an amount of about 0.1 to 5% by weight, preferably about 0.3 to 2% by weight, based on the tin oxide. The provided fluorine-doped tin oxide conductive film or antimony doped with antimony is contained in an amount of about 0.1 to 30% by weight, preferably about 0.3 to 5% by weight, based on tin oxide. A tin oxide conductive film is desirable. Further, the transparent conductive oxide layer containing tin oxide as a main component, in addition to fluorine and antimony, indium,
It may contain zinc, cadmium, arsenic, phosphorus, chlorine and the like.

The thickness of the transparent electrode layer is usually 2,000
程度 15000 Å, and preferably 6,000 to 12,000 Å in terms of conductivity and surface shape.

Further, the glass substrate of the solar cell of the present invention comprises:
In addition to the transparent electrode layer, if necessary, an undercoating layer made of silicon oxide or the like or a surface protection layer (plasma resistant layer, heat resistant layer) containing zinc oxide as a main component may be provided.

In the solar cell of the present invention, the photoelectric conversion layer is formed by forming a semiconductor layer made of amorphous silicon, and forming a predetermined pattern on the semiconductor layer by a patterning method using a laser. it can. This photoelectric conversion layer is made of, for example, boron-doped amorphous S
iC, non-doped amorphous Si, boron-doped amorphous Si
Are sequentially laminated, and a pin junction semiconductor layer or the like is exemplified. The formation of the semiconductor layer made of amorphous silicon can be performed by a plasma CVD method or the like.

In the solar cell of the present invention, the back electrode layer is constituted by a metal layer, a metal oxide layer, or a composite layer comprising a metal layer and a metal oxide layer. As the metal constituting the metal layer, for example, Ti, Al, Ag, Ni or the like is used, and as the metal oxide, for example, ZnO, TiO
₂ , SnO ₂ or the like is used. The lamination of the metal layer or the metal oxide layer can be performed according to a method such as a sputtering method, a CVD method, and a vacuum evaporation method. In the present invention, the formation of the back electrode layer, after forming a film made of the metal or metal oxide on the photoelectric conversion layer,
It can be performed by forming a predetermined pattern by a patterning method using a laser.

In the present invention, as a laser used for engraving the photoelectric conversion layer and the back electrode layer, for example, YAG
Laser and the like.

The manufacture of the solar cell of the present invention is similar to that of FIG.
2 (a) and 2 (b) and FIGS. 2 (a) to 2 (d), which can be performed in accordance with the steps of forming a transparent electrode layer, forming a photoelectric conversion layer, and forming a back electrode layer. In the present invention, in this step, the formation of the grooves 8 in the formation of the transparent electrode layer shown in FIG. 1B is performed by a patterning method without using a laser to form the photoelectric conversion layer shown in FIG. Of the groove 10 in FIG.
In this method, the grooves 12 in the formation of the back electrode layer are formed by a patterning method using a laser. By performing the engraving of the groove 8 by a patterning method without using a laser, a heat treatment in a manufacturing process, for example,
In the heat treatment in the film forming step of the photoelectric conversion layer, the film forming step of the back electrode layer, the sealing step on the back side with a resin or the like,
The glass substrate can be prevented from breaking. Further, it is possible to prevent cracks due to stress generated in the glass due to heat shock due to mechanical shock during actual use of the solar cell, heating due to solar radiation, temperature difference between day and night, temperature difference in seasonal change, and the like. The same effect can be obtained when a tempered glass is used instead of a normal glass substrate.

[0024]

EXAMPLES The present invention will be described below more specifically based on examples of the present invention and comparative examples.

(Example 1) Chamfered plate thickness 4 mm, 30
On a glass substrate of cm square, a thickness of 1
A tin oxide transparent conductive film having a thickness of μm was formed. Next, a predetermined pattern of the solar cell is resist-printed on the surface of the formed tin oxide transparent conductive film, dried, and then etched to reach the surface of the glass substrate by etching using zinc powder and a 1N hydrochloric acid solution. And a plurality of transparent electrode layers made of tin oxide and defined by the grooves were formed on the glass substrate. Next, a boron-doped amorphous SiC layer, a non-doped amorphous Si layer, and a boron-doped amorphous Si layer are sequentially stacked on the transparent electrode layer by a plasma CVD method (substrate temperature: 200 ° C.) to have a thickness of 5000 A. After the amorphous silicon layer is formed and the grooves defining the transparent electrode layer are also filled with the amorphous silicon, the amorphous silicon layer reaches the upper surface of the transparent electrode layer by YAG laser scribe (wavelength: 0.53 μm). A plurality of grooves were carved to form a plurality of pin photoelectric conversion layers defined by each groove.

Next, on the formed pin photoelectric conversion layer, a thickness of 2,000 .ANG.
After the Ag layer was formed and the groove defining the pin photoelectric conversion layer was also filled with Ag, a plurality of grooves reaching the upper surface of the pin photoelectric conversion layer were formed by YAG laser scribe (wavelength: 0.53 μm). Engraving was performed to form a plurality of Ag back surface electrodes defined by each groove.

Through the above steps, a glass substrate is
Thirty solar cells composed of a transparent electrode layer, a pin photoelectric conversion layer, and an Ag back electrode layer are arranged. In each solar cell, the transparent electrode layer and the back electrode layer of the adjacent cell are the same as those shown in FIG. As shown in (1), a solar cell module having a structure connected by a connecting portion was produced. In this example, fifteen solar cell modules were produced by the same steps. In the manufacturing process of this solar cell module, no crack was generated in the glass substrate in the process of raising the temperature to 200 ° C. or the process of lowering the temperature to room temperature in the pin photoelectric conversion layer forming process. Further, as a result of performing an outdoor exposure test for 15 months on the manufactured 15 solar cell modules, no crack was generated.

(Example 2) Chamfered plate thickness 4 mm, 30
On a glass substrate of cm square, a thickness of 1
A μm tin oxide transparent conductive film was produced. This glass substrate with a tin oxide transparent conductive film was heated to 620 ° C. and then air-cooled to obtain a tempered glass with a tin oxide transparent conductive film. Next, in the same manner as in Example 1, the formation of the transparent electrode layer by the photoresist method, the formation of the pin photoelectric conversion layer, and the formation of the Ag back electrode layer were performed.
Thirty solar cells including a pin photoelectric conversion layer and an Ag back electrode layer are arranged. In each solar cell, the transparent electrode layer and the back electrode layer of the adjacent cell are arranged as shown in FIG. Then, 15 solar cell modules having a structure connected by the connecting portion were manufactured.

In the manufacturing process of this solar cell module, no crack was generated in the glass substrate in the process of raising the temperature to 200 ° C. or the process of lowering the temperature to room temperature in the pin photoelectric conversion layer forming process. In addition, as for 15 solar cell modules having the substrate made of the tempered glass, a ball drop test was performed from a height of 2 m using a 227 g iron ball.
All five sheets did not crack and exhibited the original strength of tempered glass. Furthermore, as a result of performing an outdoor exposure test for 15 months on the manufactured 15 solar cell modules, no crack was generated.

(Comparative Example 1) Chamfered plate thickness 4 mm, 30
1μm thick on a cm square glass substrate by atmospheric pressure CVD
m, after forming the tin oxide transparent conductive film, the wavelength: 1.06 μm
15 solar cell modules were produced in the same manner as in Example 1, except that the tin oxide transparent conductive layer was patterned by a scribe method using a YAG laser of m. In the manufacturing process of this solar cell module, in the process of increasing the temperature to 200 ° C. or the process of decreasing the temperature to room temperature in the pin photoelectric conversion layer forming process, cracks occurred in two of the 15 solar cell modules in the glass substrate. When the cracked solar cell module was examined, it was found that the place where the tin oxide transparent electrode layer was laser scribed was the starting point of the crack.

Further, an outdoor exposure test was performed for 13 solar cell modules for 2 months. As a result, cracks occurred in two of the thirteen glass substrates.
When the cracked solar cell module was examined, the place where the tin oxide transparent conductive layer was laser-scribed was the starting point of the crack. From this result, it can be seen that the strength of the glass is lower than that of Example 1.

Comparative Example 2 Chamfered plate thickness 4 mm, 30
1μm thick on a cm square glass substrate by atmospheric pressure CVD
m of tin oxide transparent conductive film was produced. This glass substrate with a tin oxide transparent conductive film was heated to 620 ° C. and then air-cooled to obtain a tempered glass. Next, 15 solar cell modules were manufactured in the same manner as in Example 1 except that the tin oxide transparent conductive layer was patterned by a scribe method using a YAG laser having a wavelength of 1.06 μm.

In the manufacturing process of this solar cell module, in the process of increasing the temperature to 200 ° C. or the process of lowering the temperature to room temperature in the pin photoelectric conversion layer forming process, two glass substrates out of 15 of the solar cell modules crack. Was. When the cracked solar cell module was examined, it was found that the place where the tin oxide transparent electrode layer was laser scribed was the starting point of the crack. In addition, as a result of performing a falling ball test on 13 solar cell modules having the substrate made of the tempered glass from a height of 2 m using an iron ball of 227 g, no crack was generated in any of the 13 solar cell modules.

An outdoor exposure test was conducted for 13 solar cell modules for 2 months. As a result, cracks occurred in one of the 13 solar cell modules.
When the cracked solar cell module was examined, the place where the tin oxide transparent conductive layer was laser-scribed was the starting point of the crack. As compared with Example 2, it was clear that the original strength of the tempered glass was reduced.

In the above Examples 1 and 2 and Comparative Examples 1 and 2, the number of broken glass substrates in the manufacturing process, the falling ball test, and the outdoor exposure test was shown in Table 1 among 15 solar cells each manufactured. Are shown together.

[0036]

The solar cell module manufactured in the example is
A high production yield can be realized without causing thermal cracking during outdoor exposure and thermal cracking during battery fabrication. On the other hand, it has been found that, in the conventional method of patterning all with a laser, thermal damage to the substrate by the laser is liable to occur, so that cracks are likely to occur. Further, the effect of strengthening is easily lost in the patterning step by laser, and the original strength of the strengthened glass could not be secured.

[0038]

According to the solar cell of the present invention, there is no breakage of the glass substrate in the manufacturing process involving heat treatment, so that the production yield can be improved and the cost can be reduced. Since it has no cracks, it has high reliability and mechanical strength. Further, according to the method for manufacturing a solar cell of the present invention, the solar cell can be manufactured at a high yield and at low cost.

[Brief description of the drawings]

FIGS. 1A and 1B are schematic cross-sectional views illustrating a process for forming a transparent electrode layer in the manufacture of a solar cell.

FIGS. 2A to 2D are schematic cross-sectional views illustrating a process of forming a photoelectric conversion layer and a back electrode layer in the manufacture of a solar cell.

FIGS. 3A and 3B are diagrams illustrating a problem in a step of forming a transparent electrode layer in a conventional solar cell manufacturing process.

DESCRIPTION OF SYMBOLS 1 Glass substrate 2a, 2b Transparent electrode layer 3a, 3b Photoelectric conversion layer 4a, 4b Back electrode layer 5a, 5b Solar cell 6ab, 6bc, 6cd Contact part 7 Transparent conductive film 8 Groove 9 Amorphous silicon Layer 10 Groove 11 Conductive coating 12 Groove 13 Bottom of groove 8

Claims (4)

[Claims] 1. A glass substrate, a transparent electrode layer formed on the glass substrate by a patterning method without using a laser, a photoelectric conversion layer formed on the transparent electrode layer by a patterning method using a laser, and a back surface. A solar cell having an electrode layer. 2. The solar cell according to claim 1, wherein the patterning method without using a laser is a photo-etching process or a lift-off process. 3. The solar cell according to claim 1, wherein said glass substrate is made of tempered glass. 4. A transparent conductive film is formed on a glass substrate, and the transparent conductive film is processed by a patterning method without using a laser to form a transparent electrode layer having a predetermined pattern. A method for manufacturing a solar cell, comprising a step of forming a photoelectric conversion layer and a back electrode layer on a substrate by using a patterning method using a laser.