JP2000243986A - Solar cell and its manufacture - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a solar cell which prevents the generation of a crack or a pinhole due to a high-temperature firing operation and whose moisture resistance can be enhanced by a method wherein a room-temperature curing glass film is formed on the surface at least on the light incident side of a translucent surface protective film which is composed of a single layer or a plurality of layers. SOLUTION: A photoelectric conversion layer 3 is formed as a single-type which is composed of an n-layer, an I-layer and a P-layer which use amorphous silicon. A film as a transparent electrode layer 4 whose film thickness is 70 nm and which is composed of ITO is formed, by a sputtering method, on the photoelectric conversion layer 3. In addition, an Ag lattice- shaped collecting electrode 5 is formed on the transparent electrode layer 4. An output terminal 6 is attached to a rear electrode 2, and an output terminal 6 is attached to the collecting electrode 5. Then, the transparent electrode layer 4 is coated with a room-temperature curing glass coating agent (of a two-component type) by an air spray method. When the coating agent is held at room temperature for one hour, a translucent surface protective film 7 which is composed of polysiloxane and whose film thickness is at 3 μm is obtained. Thereby, it is possible to obtain this solar cell 10 which prevents the generation of a crack or a pinhole due to a high-temperature firing operation and whose moisture resistance is superior.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a solar cell and a method of manufacturing the same, and more particularly, to a solar cell having a light-transmitting surface protective film provided on a solar cell having a photoelectric conversion layer and a method of manufacturing the same.

[0002]

2. Description of the Related Art In recent years, from the viewpoint of addressing environmental issues,
Further development of clean energy sources is desired. Among them, solar cells are expected as an energy source because of their safety and ease of handling. Solar cells typified by amorphous silicon-based solar cells can be formed with a smaller amount of raw materials as compared to crystalline solar cells,
The advantage of integration is that the output voltage and current can be designed with a high degree of freedom. In addition, by selecting a base material, not only lightness and flexibility can be obtained, but also a wide degree of freedom in installation can be expected.

At present, a solar cell has a type in which a transparent insulating substrate such as glass is disposed on the light incident side, and a transparent electrode layer, a photoelectric conversion layer, and a back electrode layer are sequentially formed on this substrate. There is a type in which a film substrate or a metal substrate is disposed on the side opposite to the above, and a back electrode layer, a photoelectric conversion layer, and a transparent electrode layer are sequentially formed on this substrate. A solar cell using a film substrate or a metal substrate is lightweight and highly flexible, but unlike the former case using a translucent insulating substrate such as glass on the light incident side, the light incident side surface is It is necessary to cover the solar cell with a transparent surface protection material.

Conventionally, as this surface protective material, a method has been used in which a thin film layer using a fluorine-based resin film or an organic paint is provided on the outermost surface, and a thermoplastic transparent organic resin layer is formed inside the thin film layer. Was. However, the solar cell having the above-described configuration is easily affected by humidity, and the photoelectric conversion efficiency is reduced in a high-humidity environment. The cause is that a fluorine-based resin film or an organic paint does not have a sufficient barrier function against water vapor and the like.

[0005] Therefore, as a method for imparting a barrier function against water vapor or the like, that is, moisture resistance to the organic resin film which is the outermost surface layer of the surface protective material of the solar cell, sputtering, C
There is a method of forming a silicon oxide film by a VD method or the like. With this method, the moisture resistance of the organic resin film can be improved, but the deposited film on the film is colored, the light transmittance is reduced as compared to the organic resin film before the deposition, and the This causes the conversion efficiency to decrease. Further, when aluminum oxide is formed by a sputtering method, a CVD method, or the like, the light transmittance is better than that of silicon oxide, but sufficient moisture resistance cannot be obtained. In such a method of forming a metal oxide having relatively high transparency directly on the organic resin film, there is a problem that sufficient moisture resistance and translucency cannot be simultaneously obtained.

JP-A-9-199740 discloses a solar cell in which at least one surface of a transparent fluororesin film layer is coated with polysilazane and then provided with a transparent thin film layer of silicon oxide or the like obtained by firing. . In the method using polysilazane, it is necessary to perform firing at a high temperature of 80C to 200C. Since polysilazane generally has poor stability in air, it is used in a state containing about 80% of an organic solvent such as xylene. Therefore, the organic solvent rapidly volatilizes during firing after coating, and the volume decreases, so that cracks, pinholes, and the like are easily generated in the thin film layer during firing. Such cracks, pinholes, and the like cause moisture and the like to penetrate therefrom and cause a decrease in photoelectric conversion efficiency. Therefore, a thin film of silicon oxide or the like formed from polysilazane cannot obtain stable and sufficient moisture resistance. There is a problem.

Japanese Patent Application Laid-Open No. Hei 6-97482 discloses a method in which a transparent conductive film, an amorphous silicon layer, and a back electrode layer are sequentially laminated on a transparent insulating substrate, and then a silicon oxide film having a gas barrier property is formed under reduced pressure chemical vapor deposition. A solar cell formed by the method is disclosed. When the low pressure plasma enhanced chemical vapor deposition method is used, high cost is required for providing a vacuum apparatus. Further, since it takes a long time to form a film, it is not suitable for mass production, and it is difficult to reduce the production cost of a solar cell.

[0008]

As described above, in the prior art, fluorine-based resin films and organic paints do not have a sufficient barrier function against water vapor and the like.
Various attempts have been made to improve this. But,
In the method of increasing the moisture resistance by forming a relatively transparent metal oxide directly on the organic resin film, sufficient moisture resistance and light transmittance cannot be obtained. Further, in a film of silicon oxide or the like formed from polysilazane, cracks and pinholes are easily generated at the time of firing, so that stable and sufficient moisture resistance cannot be obtained. In addition, in a method in which a silicon oxide film is directly formed by a low-pressure plasma chemical vapor deposition method, mass production is difficult, and a large amount of capital investment is required.

The present invention has been made in view of the above problems, and has as its object to provide a solar cell having a surface protective film having excellent moisture resistance and light transmittance and high production efficiency.

[0010]

According to the present invention, there is provided a solar cell having a photoelectric conversion layer, comprising a light-transmitting surface protective film composed of a single layer or a plurality of layers, wherein the light-transmitting surface protective film is formed. Provided is a solar cell having a cold-setting glass coating on at least the surface on the light incident side.

According to another aspect of the present invention, there is provided a solar cell having a photoelectric conversion layer, wherein at least the light incident side surface of the solar cell is provided with a light-transmitting surface protective film made of a cold-curable glass film. A method for manufacturing a solar cell is provided, which comprises a step of forming a glass coating by dehydrating and condensing an organopolysiloxane at room temperature and curing the glass coating.

That is, in the solar cell of the present invention, a translucent surface protective film composed of a glass film formed by curing at room temperature is obtained, so that cracks and pinholes due to high-temperature sintering are prevented. A solar cell having excellent moisture resistance is provided. Further, by selecting a room-temperature-curable glass film having a high barrier function against water vapor and the like and high transparency, sufficient translucency for use as a protective film on the light incident side of the solar cell can be obtained. In addition, since the light-transmitting surface protective film is formed of a room-temperature-curable glass film, the light-transmitting property is maintained for a long time without yellowing due to ultraviolet rays or the like. Furthermore, equipment such as a vacuum apparatus and a high-temperature baking apparatus and each step performed using these equipment are not required, and the equipment cost and time required for forming the light-transmitting surface protective film are saved, whereby the light-transmitting surface protection The membrane production efficiency is improved.

[0013]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The solar cell of the present invention includes an amorphous silicon solar cell, a compound semiconductor solar cell, and an organic semiconductor solar cell. FIG. 1 shows an example of the configuration of the solar cell of the present invention. The solar cell 10 includes a substrate 1 and
It comprises a photoelectric conversion layer 3, a pair of electrode layers 2 and 4 sandwiching the photoelectric conversion layer 3, and a light-transmitting surface protection film 7 deposited on the transparent electrode layer 4 on the light incident side. Each of the back electrode layer 2 and the transparent electrode layer 4 has an output terminal 6. The substrate 1 includes a metal substrate made of stainless steel, aluminum, or the like, a resin substrate made of a vinyl chloride-based, polyester-based, polyimide-based, fluorine-based, or acrylic-based film, or a glass substrate.

The material of the back electrode layer 2 is Ag, A
1, Ti, Cr, Mo, W, Ni and the like can be used. The back electrode layer 2 can be formed by a sputtering method or an evaporation method. The photoelectric conversion layer 3 is a power generation region configured to convert irradiated light into electricity and extract the light from the pair of electrode layers 2 and 4, and is configured by an amorphous semiconductor layer or a microcrystalline semiconductor layer. It is possible to provide a flexible solar cell which can be formed at a relatively low cost and can have a large area. Specifically, these semiconductor layers include Si, SiC, SiN, SiGe, and SiO.

The material of the photoelectric conversion layer 3 includes amorphous silicon, microcrystalline silicon, and polycrystalline silicon.
For example, it can be formed by a plasma CVD apparatus. Among them, amorphous silicon or microcrystalline silicon is preferable because it has a small effect on the environment, can provide a relatively low cost, and can provide a flexible solar cell.

A grid-like current collecting electrode (grid) 5 may be provided on the transparent electrode layer 4 in order to efficiently collect current. Ag, Al, T
i, Cr, Mo, W, Ni, and Cu. As a method for forming the current collecting electrode 5, in addition to a sputtering method and a vapor deposition method using a mask, a method in which unnecessary portions are removed by etching after forming a film on the entire surface, or a conductive paste such as a silver paste is printed. There is a method to do. An output terminal 6 is attached to the back electrode layer 2 and the current collecting electrode 5 to extract an electromotive force from the electrode layers 2 and 4 such as a paste. Examples of the method of attaching the output terminal 6 include spot welding, soldering, and the like.

The translucent surface protective film 7 according to the present invention comprises:
It consists of a single layer or a plurality of layers provided on a solar cell.
Therefore, the light-transmitting surface protective film 7 is one of them.
Injury, a room temperature curing type formed by curing at room temperature
It may be made of a glass coating, or the entire film may be
It may be composed of a cold-setting glass coating.
Cold-curable glass coatings are, for example, organopolysiloxanes.
Addition of water to the sun and raw materials to which additives have been added if necessary
Can be formed mainly by polysiloxane or
It is composed of In addition, cold-curable glass coatings
As Al_TwoO _Three, TiO_Two, ZrO_TwoMetal oxides such as
May be included.

Examples of the additive include a crosslinking agent of an organosiloxane having a functional side chain (alkoxy group, acyloxy group, oxime group) and a curing agent of a halide of boron. Further, Zn, Al, Co, S
A curing agent comprising an organometallic compound such as n is also included. More specifically, GS-600-1, GS-600-2, GS-60 as raw materials that can be used for forming a glass film.
0-3, GS-600-4 and GS-300-1 (manufactured by Nikko Corporation).

The translucent surface protective film 7 is formed on the transparent electrode layer 4 so as to be located on the surface on the light incident side, but on both front and back sides of the solar cell, that is, on the side opposite to the transparent electrode layer 4 and the light incident side. May be formed on both surfaces on the back surface of the substrate 1. The light-transmitting surface protective film 7 preferably has a light transmittance of 90% or more with respect to light in a wavelength range of 400 to 1200 nm from the viewpoint that the power generation characteristics of the solar cell do not deteriorate.

In the method of manufacturing a solar cell according to the present invention, when manufacturing the light-transmitting surface protective film 7 made of the cold-curable glass coating shown in FIG. 1, the cold-curable glass coating dehydrates the organopolysiloxane at normal temperature. It includes a step of forming by condensing and curing. The translucent surface protection film 7 is preferably formed on the surface of the solar cell at least on the light incident side, that is, on the electrode layer 4 and additionally on the back surface of the substrate 1. The room temperature for obtaining the room temperature-curable glass film in the present invention is preferably room temperature of about 5 ° C. to 35 ° C.

First, a coating liquid containing the above-described raw materials is prepared. The coating liquid is preferably diluted with a solvent in order to adjust the above-mentioned raw material to a liquid having a viscosity suitable for coating and maintain the stability of the liquid. In particular,
An alcohol solution obtained by diluting the above-described raw materials with IPA or the like can be used. Since the hydrolysis is also performed by atmospheric moisture, the addition of water is not essential. Alternatively, an alcohol solution obtained by diluting the above-mentioned organopolysiloxane and an alcohol solution obtained by diluting the additive may be prepared, and both may be mixed at the time of application. An alcohol solution diluted with the substance may be added.

This coating liquid is coated on the transparent electrode layer 4, on the back surface of the substrate 1, or on the already coated surface protective film. Examples of the coating method include known methods such as a dip method, a roll coating method, a bar coater method, a printing method, an air spray method, and an airless spray method. The coating preferably has a thickness of about 0.1 to 10 μm after curing. Thickness 0.1
In the case of μm or less, sufficient cover cannot be provided for the fine irregularities on the surface of the solar cell, and moisture or the like in the air enters the solar cell, causing a reduction in power generation efficiency. Also, 10μ
If it is more than m, cracks and the like are apt to occur in the protective film itself, which allows moisture in the air to permeate and causes a reduction in power generation efficiency. For these reasons, the film thickness after curing is 0.1 to
About 10 μm is desirable, and when flexibility is required for the solar cell, about 2-3 μm is desirable.

In order to obtain a film having a thickness of about 0.1 to 10 μm and a high uniformity of the film thickness, an airless spray method is suitable. The operating condition of the airless spray device is that the distance between the airless spray gun and the work (solar cell) is 10
0-200mm, spray gun moving speed 250-120
0 mm / s and a liquid pressure of about ²⁰ to 50 kg / cm ² are suitable. In the airless spray method, a surface protective film having good adhesion can be formed.

The glass coating thus formed is
The light-transmitting surface protective film is coated on the surface electrode or the substrate, or is deposited on another layer to form at least one of the light-transmitting surface protective films composed of a plurality of layers. May be formed. By performing the curing at room temperature, a rapid decrease in the volume of the coating film is suppressed, and it becomes possible to prevent cracks and pinholes from occurring in the film.
The manufactured solar cells are connected in series or in parallel according to a desired voltage and current, and the end faces are sealed so as to prevent invasion of gas as a foreign substance from the end faces, thereby manufacturing a solar cell module.

An example of the structure and manufacturing method of the solar cell of the present invention will be described below. Example 1 In manufacturing the solar cell 10 shown in FIG. 1, a stainless steel plate is used as the solar cell substrate 1. This substrate 1
After about 500 nm of Ag was formed as the back electrode layer 2 by sputtering, ZnO was formed with a thickness of about 50 nm. After that, the photoelectric conversion layer 3 was formed by a plasma CVD apparatus.

The photoelectric conversion layer 3 is formed as a single type using amorphous silicon and composed of an n layer, an i layer, and a p layer, and has a thickness of 30 nm, 400 nm, and 20 n, respectively.
m. Note that not only such a single type but also a tandem type and a triple type photoelectric conversion layer can be formed. As the transparent electrode layer 4, a film thickness of 70 is formed on the photoelectric conversion layer 3 by a sputtering method.
A film made of ITO having a thickness of nm is formed. Note that SnO ₂ , ZnO, or the like can be used as the material of the transparent electrode layer 4, and a vapor deposition method may be used instead of the sputtering method.

Further, a grid-like collector electrode 5 made of Ag is provided on the transparent electrode layer 4 by a sputtering method using a mask. After that, the output terminal 6 is attached to the back electrode layer 2 and the current collecting electrode 5 by soldering in order to extract an electromotive force.
The manufactured solar cell elements are connected in series or in parallel according to the desired voltage and current. Next, a glass coating was formed by the following method using a two-part GS-600-1 (manufactured by Nikko Corporation) which is a room temperature curing type glass coating agent.

The first liquid and the second liquid were mixed, and the mixed coating liquid was immediately coated on the transparent electrode layer 4 by an airless spray method. The coating liquid immediately after mixing contained about 40% of IPA and had a viscosity of about 40 cps. The distance between the airless spray gun and the work (solar cell) was 150 mm, the moving speed of the spray gun was 1000 mm / s, and the liquid pressure was 40 kg / cm ² . The translucent surface protective film 7 made of the cured polysiloxane was obtained by holding at room temperature for about 1 hour. The thickness of the light-transmitting surface protective film cured at room temperature was 3 μm.

With respect to the solar cell 10 as a sample formed by the above method, the following (1) to (1) are shown.
An evaluation test was performed for the item (4). (1)-
For the item (3), ten samples were used. Regarding item (4), a film similar to that for surface protection was formed on glass, and an evaluation test was performed.

(1) High-Temperature Retention Test The sample was left for 1000 hours in an atmosphere maintained at 85 ° C. in the atmosphere. (2) High-Temperature and High-Humidity Holding Test The sample was allowed to stand for 1000 hours in an environment of 85 ° C. and 85% humidity. (3) Temperature cycle test A temperature cycle of 90 ° C for 15 minutes and -40 ° C for 15 minutes was repeated 200 times in the atmosphere. (4) Light irradiation test 100 mW / cm ^{2 on the} light-receiving surface using a solar simulator
Was allowed to stand for 1000 hours while irradiating the pseudo sunlight.

Table 1 shows the evaluation results of the items (1) to (3). Table 1 shows the change in power generation amount before and after the test when the power generation amount of the solar cell before the test was set to 1 (sample 10).
(Average value of individual pieces) and appearance observation results. For all samples, there was no significant decrease in power generation characteristics, and the sample had sufficient moisture resistance as a solar cell module (an assembly in which output terminals and the like were attached to a solar cell). There was no problem. In addition, since the raw material was applied by airless spraying when forming the room-temperature-curable glass coating, it is considered that a surface protective film having an appropriate thickness, high uniformity and good adhesion was obtained.

[0032]

[Table 1]

As a result of the evaluation of the item (4), no change was observed in the appearance and the spectral transmittance. Wavelength 400-12
Since the light transmittance in the range of 00 nm is 90% or more, there was no problem even when used on the light incident side of the solar cell. In the case where a surface protective film is formed of an organic material such as a light-transmitting resin and a light irradiation test is performed, light transmittance decreases due to yellowing of the resin. It can be said that this material has no problem in terms of light resistance. In addition, it is considered that the surface protective film 7 having an appropriate film thickness, high uniformity, and good adhesion was obtained by forming a room-temperature-curable glass film after application by airless spray.

Example 2 When a film or the like is used as a solar cell substrate, moisture penetrates also from the substrate side. Therefore, a surface protective film for preventing the penetration of moisture is provided on the light incident side and on the opposite side. Required.
Therefore, an example of a solar cell in which a surface protective film 8 is provided on the side opposite to the light incident side of the photoelectric conversion layer 3 in the same manner as in Example 1 is shown in FIG.
Shown in

In FIG. 2, a solar cell 20 comprises a resin substrate 11 made of polyester, a photoelectric conversion layer 3, a pair of electrode layers 2 and 4 sandwiching the photoelectric conversion layer 3, and a transparent electrode layer on the light incident side. 4, a light-transmitting surface protective film 7 formed on
The surface protection film 8 is formed on the back surface of the substrate 11.
The back electrode layer 2 and the transparent electrode layer 4 each have an output terminal 6
And a grid-like current collecting electrode 5 is provided on the transparent electrode layer 4 in order to efficiently collect current. Like the light-transmitting surface protective film 7, at least one of the surface protective films 8 includes a room-temperature-curable glass coating. This provides a solar cell 20 having a surface protective film that is excellent in moisture resistance and light transmission and has high production efficiency.

[0036]

According to the present invention, a light-transmitting surface protective film made of a cold-curable glass film can be obtained, so that cracks and pinholes due to high-temperature sintering are prevented, thereby providing excellent moisture resistance. A solar cell is provided. Further, by selecting a room-temperature-curable glass film having a high barrier function against water vapor and the like and high transparency, sufficient translucency for use as a protective film on the light incident side of the solar cell can be obtained. In addition, since the light-transmitting surface protective film is formed from a room-temperature-curable glass film, the light-transmitting property is maintained for a long period without yellowing due to ultraviolet rays or the like. Furthermore, equipment such as a vacuum apparatus and a high-temperature baking apparatus and each step performed using these equipment are not required, and the equipment cost and time required for forming the light-transmitting surface protective film are saved, whereby the light-transmitting surface protection The membrane production efficiency is improved.

[Brief description of the drawings]

FIG. 1 is a schematic cross-sectional view of a solar cell according to the present invention having a light-transmitting surface protective film on a light incident side.

FIG. 2 is a schematic cross-sectional view of a solar cell module according to the present invention in which a surface protective film is provided on the light incident side and on the opposite side.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 solar cell substrate 2 back electrode layer 3 photoelectric conversion layer 4 transparent electrode layer 5 current collecting electrode 6 output terminal 7 translucent surface protective film 8 surface protective film 10 solar cell 20 solar cell

Claims (8)

[Claims] 1. A solar cell having a photoelectric conversion layer,
A solar cell comprising a light-transmitting surface protective film composed of a single layer or a plurality of layers, wherein the light-transmitting surface protective film comprises a cold-curable glass coating on at least the surface on the light incident side. 2. The cold-curable glass coating is made of Al
_TwoO_Three, TiO_Two, ZrO _TwoAt least one of
The solar cell according to claim 1, comprising a metal oxide. 3. The cold-curable glass coating is 0.1-1.
The solar cell according to claim 1, having a thickness of 0 μm. 4. A light-transmitting surface protective film having a wavelength of 400 to 12
The solar cell according to any one of claims 1 to 3, which has a light transmittance of 90% or more for light in a range of 00 nm. 5. The solar cell according to claim 1, wherein the photoelectric conversion layer is an amorphous semiconductor layer or a microcrystalline semiconductor layer. 6. The solar cell according to claim 5, wherein the photoelectric conversion layer is an amorphous silicon layer or a microcrystalline silicon layer. 7. A method for manufacturing a solar cell, comprising forming a light-transmitting surface protective film made of a room-temperature-curable glass film on at least a light-incident side surface of a solar cell having a photoelectric conversion layer. A method for producing a solar cell, comprising a step of forming a polysiloxane by dehydration-condensation and curing at room temperature. 8. The method for manufacturing a solar cell according to claim 7, wherein the glass coating is formed by applying and curing an organopolysiloxane by airless spray.