JPH0888388A - Solar battery module - Google Patents

Abstract

PURPOSE: To provide a lightweight solar battery module which can be installed readily in various places without using a frame and is excellent in long-term reliability. CONSTITUTION: In a solar battery module 100 wherein a thin film solar battery 103 buried by filler 104 is arranged between a light transmitting surface film 101 and a rear film 102, the light transmitting surface film 101 at an end part of the solar battery module 100 and the rear film 102 are bonded by hot-melt adhesive.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a solar cell module, and more particularly to a frameless solar cell module excellent in long-term reliability.

[0002]

2. Description of the Related Art In recent years, people's awareness of ecology has increased and expectations for solar cells, which are clean energy, have been increasing. In Japan as well, much research is being conducted with the aim of popularizing solar cell photovoltaic power generation systems.

Among the solar cells, the monocrystalline silicon and polycrystalline silicon solar cell modules use a thick glass plate as a surface material because the solar cell element itself is weak against impact.
A filler such as EVA (ethylene-vinyl acetate copolymer) is filled between the solar cell element and the glass plate to protect the solar cell element.

Also, in the case of an amorphous silicon solar cell module formed on a glass substrate, it is protected by a thick glass plate and EVA as in the crystalline silicon solar cell module.

A rigid frame is attached to the solar cell module having the glass substrate on its surface in order to protect the periphery of the glass substrate, reinforce the mechanical strength, and connect the modules or install them on a stand. As the frame, metal, plastic, wood, etc. are often used,
Since a solar cell module using a glass substrate has a weight per square meter of 10 kg or more, hollow extruded aluminum products are often used from the viewpoint of strength and weight.

However, when a solar cell module using an aluminum frame is installed on the roof or the ground,
Due to its weight, it is not easy to handle, and a heavy mount is required to install a heavy solar cell module, and the solar cell module is fixed to the mount using bolts and other fixtures. There is a need to. As described above, in the above solar cell module, much cost is required for material cost, installation cost, and gantry cost.

On the other hand, an amorphous silicon solar cell using a polymer resin substrate or a metal substrate such as a stainless steel foil is flexible and has excellent impact resistance, and therefore is used as a protective material for the surface of the amorphous silicon solar cell. It is not necessary to use glass and can be protected with a transparent surface film such as a fluororesin film.

Such a bendable solar cell module is
In order to take advantage of the bendability of solar cells, it is often installed without using a frame of aluminum or the like. For example, an example in which a solar cell module is installed on a roof with an adhesive without using an aluminum frame (JP-A-4-235933) and an example in which a magnet is installed (JP-A-4-23593).
No. 8), an example of installation using a double-sided tape (Japanese Patent Laid-Open No. Hei 4)
No. 236152), various methods have been proposed for installing a solar cell module.

FIG. 11 shows an example of a conventional frameless solar cell module. In the figure, 1100 is a solar cell module, 1101 is a translucent surface film, 1102.
Is a back film, 1103 is a solar cell element, and 1104 is a filler.

However, as a result of a long-term reliability test conducted by the present inventor, the structure of the conventional solar cell module shown in FIG. 11 is inferior in long-term reliability to a solar cell module using an aluminum frame. I found out. As a result of studying the cause, in the case of the solar cell module of FIG. 11, since the end portion is not covered with the frame, the module end portion is exposed, and the end portion is directly exposed to rain or wind for a long time, It has been found that when a general stress is applied to the end portion of the solar cell module, peeling occurs from the end portion at the interface between the translucent front surface film 1101 or the back surface film 1102 and the filler 1104, which reduces the reliability of the module.

[0011]

SUMMARY OF THE INVENTION The present invention solves the above problems and provides a lightweight solar cell module which can be easily installed in various places without using a frame and has excellent long-term reliability. With the goal.

[0012]

The present invention has been completed based on the above-mentioned pursuit of the cause of the decrease in reliability of the solar cell module.

The solar cell module of the present invention is a solar cell module in which a thin film solar cell embedded with a filler is disposed between a translucent front surface film and a back surface film. It is characterized in that the translucent front surface film and the back surface film are adhered to each other with a hot melt adhesive.

The hot melt adhesive is preferably a thermoplastic rubber hot melt adhesive, and the thickness of the adhesive is preferably 10 μm to 200 μm.

The translucency expressing film is an ethylene-tetrafluoroethylene copolymer resin film or a tetrafluoroethylene-hexafluoropropylene copolymer resin film.

[0016]

In the solar cell module of the present invention, the translucent front surface film and the back surface film are firmly adhered to each other by the hot melt adhesive at the ends thereof, so that the solar cell module is installed outdoors without using a frame. Even if
The film is not peeled off between the translucent front surface film and the filler and between the back surface film and the filler, and the reliability of the solar cell module can be maintained for a long period of time.

[0017]

Embodiments Embodiments of the present invention will be described in detail below with reference to FIG.

FIG. 1 is a schematic sectional view showing an example of the solar cell of the present invention. In the solar cell module 100, a solar cell 103 is embedded in a filler 104, further covered with a translucent front surface film 101 and a rear surface film 102, and ends (X portion, Y portion) are bonded with a hot melt adhesive 105. Has been done.

The individual components of the solar cell module will be described in detail below.

<Adhesion> In the present invention, the translucent front surface film and the back surface film are adhered to each other by applying a predetermined amount of a hot melt adhesive to the adhering portion of the film, heating and melting this, and then cooling and solidifying. .

Examples of the hot melt adhesive used in the present invention include thermoplastic rubber hot melt adhesives, polyamide hot melt adhesives, polyester hot melt adhesives, EVA (ethylene-vinyl acetate copolymer) adhesives. Examples of the hot melt adhesive include thermoplastic rubber hot melt adhesives, from the viewpoint of high adhesiveness to the front surface film and the back surface film and improving long-term reliability of solar cell characteristics. Further, among the thermoplastic rubbers, those using a copolymer rubber of polystyrene and polybutadiene (or polyisoprene) are preferable.

<Translucent Surface Film> The translucent surface film used in the present invention is not particularly limited, but a fluororesin film is preferable in consideration of weather resistance, mechanical strength and transparency. Specifically, for example, ethylene-tetrafluoroethylene, polyvinyl fluoride or the like can be used.

If necessary, the adhesive surface of the translucent surface film used in the present invention is subjected to corona discharge treatment or treatment in a nitrogen stream with a mixed solution of metallic sodium and liquid ammonia or a naphthalene solution. A surface activation treatment such as a method may be carried out, whereby the adhesiveness can be further enhanced.

<Backside Film> The backside film used in the present invention is not particularly limited, and can be selected in consideration of adhesiveness with a hot melt adhesive, weather resistance, mechanical strength, and moisture permeation resistance. Specifically, for example, a nylon film, a laminated multilayer film of fluororesin / metal foil / fluororesin, a resin-coated steel plate, a resin-laminated steel plate or the like can be used. As with the surface film, it is preferable to carry out a surface activation treatment.

<Filler> Examples of the filler used in the present invention include ethylene-vinyl acetate copolymer (EV).
Examples thereof include, but are not limited to, A), polyvinyl butyrol, and silicone resin.

<Solar Cell> The type of the solar cell element of the present invention is not particularly limited, but is preferably a flexible solar cell, more preferably amorphous silicon formed on a stainless substrate. It is a semiconductor.

By using a flexible solar cell, the solar cell module itself becomes flexible, so that the solar cell module can be installed in any shape, and the frameless solar cell of the present invention can be installed. The application of the module can be further expanded.

Furthermore, by using an amorphous silicon semiconductor formed on a stainless steel substrate, a solar cell module having high mechanical strength and flexibility can be obtained.

An example of a solar cell element used in the solar cell module of the present invention is shown in FIG. In FIG. 2, 201
Is a conductive substrate, 202 is a back electrode layer, 203 is a semiconductor layer as a photoelectric conversion member, 204 is a transparent conductive layer, and 205 is a collector electrode. The back electrode layer 202 can also serve as the conductive substrate 201.

As the conductive substrate 201, in addition to stainless steel, for example, aluminum, copper, titanium, carbon sheet, galvanized steel sheet, or polyimide, polyester, polyethylene naphthalide having a conductive layer formed thereon,
A resin film such as epoxy or ceramics is used.

As the thin film semiconductor layer 203, an amorphous silicon semiconductor, a polycrystalline silicon semiconductor, a crystalline silicon semiconductor, or copper indium selenide (CuInSe ₂ / Cd) is used.
Compound semiconductors such as S) can be used.

As the method for forming the semiconductor layer, in the case of an amorphous silicon semiconductor, a plasma CVD method using, for example, silane gas is preferably used. In the case of a polycrystalline silicon semiconductor, it can be formed by, for example, forming a sheet of molten silicon or heat treating an amorphous silicon semiconductor. CuInSe ₂ / CdS is formed, for example, by
Methods such as electron beam evaporation, sputtering, and electrodeposition (precipitation by electrolysis of an electrolytic solution) are used.

The semiconductor layer is composed of a pin junction, p
N-junction or Schottky junction is used. The semiconductor layer has a structure sandwiched at least by the back electrode layer 202 and the transparent conductive layer 204.

For the back electrode layer 202, a metal layer, a metal oxide, or a composite layer of a metal layer and a metal oxide layer is used. As the material of the metal layer, for example, Ti, A
l, Ag, Ni, etc. are used, and as the metal oxide layer,
For example, ZnO, TiO ₂ , SnO ₂ or the like is used. Examples of the method for forming the metal layer and the metal oxide layer include resistance heating vapor deposition, electron beam vapor deposition, sputtering method, and CVD method.

Further, as the material of the grid-shaped collector electrode 205 for efficiently collecting the current generated by the photovoltaic power on the transparent conductive layer, for example, Ti,
A conductive paste such as Cr, Mo, W, Al, Ag, Ni, Cu, Sn, and a silver paste is used. As a method of forming the grid electrode, for example, a vapor deposition method such as sputtering using a mask pattern, resistance heating, and CVD,
Alternatively, a method of depositing a metal layer on the entire surface and then patterning by etching, a method of directly forming a grid electrode pattern by photo CVD, a method of forming a negative pattern mask of the grid electrode and then forming by plating, and printing a conductive paste And the like are used.

The conductive paste is usually prepared by adding a conductive fine powder (eg gold, silver, copper, nickel, carbon etc.) to a binder polymer (eg polyester, epoxy, acryl, alkyd, polyvinyl acetate, rubber, urethane, phenol etc.). What is dispersed in resin) is used.

In the case of a large area solar cell, a bus bar may be provided for further collecting and transporting the current collected by the grid electrode. As the material of this bus bar,
For example, tin, solder-coated copper, nickel, or the like is used, and the bus bar and the grid electrode are connected by a conductive adhesive, solder, welding, or the like.

[0038]

The present invention will be described in detail below with reference to examples.
The present invention is not limited to these examples.

(Example 1) This example is an example of a solar cell module in which amorphous silicon solar cell elements produced on a stainless steel substrate were connected in series and then resin-sealed with EVA. Is a fluororesin film, and the back film is a fluororesin film / aluminum foil / fluororesin film laminate material.
A solar cell module obtained by bonding the above film with a hot melt adhesive will be described.

First, the amorphous silicon solar cell element shown in FIG. 3 was manufactured as follows.

On the cleaned 0.1 mm roll-shaped long stainless steel substrate 301, Al containing 1% of Si was formed into a film by the sputtering method, and the back surface reflection layer 302 having a film thickness of 500 nm was formed.
Was formed.

Next, the semiconductor layer 303 is formed on the back surface reflection layer.
As a plasma CVD method, PH ₃ , SiH ₄ , H ₂
30 nm of n-type semiconductor using gas, followed by SiH ₄ ,
The i-type semiconductor is 400 nm, B ₂ H ₆ , and S using H ₂ gas.
A p-type semiconductor was sequentially formed to a thickness of 10 nm using iH ₄ and H ₂ gases.

After that, ITO 304 having a film thickness of 80 nm was formed by resistance heating vapor deposition to produce an amorphous silicon solar cell 300.

Next, the long solar cell element 300
Punching into a shape shown in FIG. 4 with a size of m × 15 cm using a press machine, a plurality of solar cell elements were manufactured.

On the cut surface of the solar cell element cut by the press machine, the solar cell element is crushed and the ITO electrode and the stainless steel substrate are short-circuited. In order to repair this short circuit, as shown in FIGS. 4 and 5, a part of the periphery of the ITO electrode of each solar cell element is removed to remove the separating portion 4.
01 was formed. Here, the removal of the periphery of the ITO electrode is
An etching material (FeCl ₃ solution) that dissolves ITO but does not dissolve amorphous silicon semiconductor is screen printed around the ITO slightly inside the cut surface of each solar cell element to dissolve the ITO, and then washed with water. I
The element isolation portion 401 of the TO electrode was formed.

Next, a collecting grid electrode 40 is formed on the ITO.
2 was formed by screen-printing a silver paste (5007 manufactured by DuPont) using a polyester resin as a binder.

Subsequently, a bus bar 403 for further collecting the current of the grid electrode 402 is used, and the diameter thereof is 0.4 m.
After the tin-plated copper wire 403 of m is arranged so as to be orthogonal to the grid electrode 402, an adhesive silver ink (C-220 manufactured by Emerson and Cumming) 4 at the intersection with the grid electrode.
04 was dropped and dried at 150 ° C. for 60 minutes to connect the grid electrode 402 and the tin-plated copper wire 403. At this time, the insulating member 4 is provided under the tin-plated copper wire 403 so that the tin-plated copper wire and the end surface of the stainless steel substrate do not come into electrical contact with each other.
A polyimide tape was attached as 05.

Next, the ITO layer and the semiconductor layer 403 in a part of the non-power generation region of the amorphous silicon solar cell element are removed by a grinder to expose the stainless steel substrate, and then a copper foil 406 is spot welded to the part. Welded.

Next, as shown in FIG. 6, the above-mentioned solar cell element is subjected to, for example, a tin-plated copper wire 613 of the solar cell element 610.
And the copper foil 624 of the solar cell element 620 were connected by soldering, and the tin-plated copper wire and the copper foil of the adjacent solar cell element were soldered in the same manner to manufacture 13 solar cells 600 connected in series. In addition, in FIG. 6, only three solar cell elements are shown, and the others are omitted.

Wiring for the plus and minus terminals was made on the back side of the stainless steel substrate as shown in FIG. FIG. 7 is a rear surface wiring diagram of solar cell elements connected in series. In the wiring on the plus side, an insulating polyester tape 703 was attached to the center of the thirteenth solar cell element 730, a copper foil 702 was attached thereon, and then a copper foil 702 and a tin-plated copper wire were soldered. . In the wiring on the minus side, after wiring the copper foil 706 to the first solar cell element 610 as shown in FIG. 7, it is soldered to the copper foil 705 spot-welded to the solar cell element 610. As shown in FIG. 8, back film 802 / filler (1) 804 / the above-mentioned 13 solar cells 600 connected in series / filler (2) 804 / surface film 801 were sequentially stacked. Here, a 50 μm thick ethylene-tetraethylene copolymer fluororesin film (Neoflon manufactured by Daikin Industries, Ltd.) was used as the front surface film, and a back film was made of the same material as the front surface film and had a thickness of 50 μm. With aluminum foil (30
A laminated material sandwiching (.mu.m) was used. The side surface of the front surface film and the back surface film that contacted with the filler was previously subjected to corona discharge treatment. As the fillers (1) and (2), EVA having a thickness of 450 μm (High Sheet Industry Co., Ltd.)
Manufactured by Solar EVA) was used.

EV at 150 ° C. using a vacuum laminator
As shown in FIG. 8A, the solar cell 8 was melted.
03 was sandwiched with a fluororesin film and resin-sealed to produce a solar cell module 800.

Next, as shown in FIG. 8 (b), a thermoplastic rubber hot melt adhesive (block copolymer rubber of polystyrene and polybutadiene (Kraton manufactured by Shell)) is applied to the edges of the front and back films. ) Was applied, and the end portions of the translucent front surface film and the back surface film were pressure-bonded at 130 ° C. to bond the front surface film and the back surface film to each other, whereby the solar cell module having the structure of FIG. The adhesive thickness after adhesion was 100 μm.

(Comparative Example 1) In the same manner as in Example 1, a solar cell module having a conventional structure shown in FIG. 11 was prepared in which the translucent front surface film and the back surface film had the same size as the filler (EVA).

The solar cell module of Example 1 and Comparative Example 1 and a solar cell module using a conventional aluminum frame were placed on a structure along the coast of Okinawa Prefecture where relatively good wind was applied to the structure double-sided tape (Sumitomo 3M It was attached to a metal roof using VHB manufactured by Co., Ltd. and exposed outdoors to examine the time change of the module output.

The results are shown in FIG. In FIG. 9, the vertical axis represents the output retention ratio standardized by the output of the module using the aluminum frame.

As is clear from FIG. 9, the output of the solar cell module of Comparative Example 1 began to decrease in about one and a half years,
After 3 years, the output of the module of the present embodiment did not change at all, while the output of the module of the present embodiment did not change at all, indicating that the module had the same level of reliability as the aluminum frame module.

Observation of the adhesiveness at the edges revealed that the module of Comparative Example 1 showed that the film at the edges had a thickness of 5 m after 2 years.
It was found that the peeling was about m and the peeling was about 30 mm after 3 years. On the other hand, in the module of this example, no peeling of the film was observed.

In this embodiment, the sealing by melting the filler and the end bonding by the hot melt adhesive are performed in different steps, but the melting point temperature of the filler and the adhesive is higher than the melting point of the filler. Both may be performed in the same step, for example, at the same time as the sealing with the filler at the temperature, the end portions of the front film and the back film are bonded together.

(Example 2) In this example, the effect of the thickness of the hot melt adhesive on the time variation of the output retention rate was examined.

A block copolymer rubber of polystyrene and polybutadiene (Kraton manufactured by Shell Co.) and EVA (solar EVA manufactured by High Sheet Industry Co., Ltd.) were used as the hot melt adhesive, except that the thickness was changed to various values. Manufactured a solar cell module in the same manner as in Example 1, and
In the same manner as above, the sample was exposed outdoors, and the relationship between the output retention rate and the adhesive thickness after 3 years was examined. The results are shown in Fig. 10.

As shown in FIG. 10, it can be seen that the output retention rate changes depending on the thickness of the hot melt adhesive. In particular, a solar cell module using a thermoplastic rubber-based adhesive shows higher reliability than EVA and has a reliability of 10 to 200 μm.
Particularly excellent output retention was shown in the range of m. The output decreased when the thickness was less than 10 μm because the adhesive effect was not fully exhibited, and when the thickness exceeded 200 μm, stress was apt to be applied at the module end, and the output decreased due to the influence of wind and rain. it is conceivable that.

Example 3 As a hot melt adhesive,
Polyester hot melt adhesive (Asahi Kasei Co., Ltd.)
A solar cell module was prepared in the same manner as in Example 1 except that Harded manufactured by Hadec Co., Ltd.) and a polyamide hot melt adhesive (Meltron manufactured by Diabond Industry Co., Ltd.) were used.
When an experiment similar to that of Example 2 was performed, the relationship between the output retention rate and the film thickness was almost the same as that when the thermoplastic rubber hot melt adhesive was used. Detachment was observed.

[0063]

According to the solar cell module of the present invention, the ends of the translucent front surface film and the rear surface film are bonded together by using a hot melt adhesive, so that the solar cell module can be installed outdoors without using a frame. Even in this case, it is possible to provide an inexpensive solar cell module having excellent long-term reliability.

[Brief description of drawings]

FIG. 1 is a schematic sectional view showing an example of a solar cell module of the present invention.

FIG. 2 is a schematic cross-sectional view showing an example of the solar cell element of the present invention.

FIG. 3 is a schematic cross-sectional view showing the solar cell element of Example 1.

4 is a schematic top view showing the solar cell element of Example 1. FIG.

5 is a schematic cross-sectional view showing the solar cell element of Example 1. FIG.

FIG. 6 is a schematic top view in which the solar cell elements of Example 1 are connected in series.

FIG. 7 is a schematic rear view in which the solar cell elements of Example 1 are connected in series.

FIG. 8 is a schematic cross-sectional view showing the solar cell module of Example 1.

FIG. 9 is a graph showing the change over time in the output retention rate of the solar cell module.

FIG. 10 is a graph showing the relationship between the output retention rate of the solar cell module and the adhesive film thickness.

FIG. 11 is a schematic cross-sectional view of a conventional solar cell module.

[Explanation of symbols]

 100, 800, 1100 solar cell module, 101, 801, 1101 translucent surface film, 102, 802, 1102 back surface film, 103, 803, 1103 solar cell element, 104, 804, 1104 filler, 105, 805 hot melt Adhesive, 200, 300 Solar cell element, 201, 301 Conductive substrate, 202, 302 Back electrode layer, 203, 303 Semiconductor layer, 204, 304 Transparent conductive layer, 205 Current collecting electrode, 402 Grid electrode, 403, 613 Bus bar Electrodes, 404 silver ink, 405, 603 insulating tape, 406, 624, 702, 706 copper foil, 600 13 solar cells connected in series, 610, 620, 630, 730 solar cell, 703 polyester tape.

Claims (6)

[Claims] 1. A solar cell module in which a thin film solar cell embedded with a filler is disposed between a translucent front surface film and a back surface film, the translucent surface at an end portion of the solar cell module. A solar cell module, characterized in that the film and the back film are adhered to each other with a hot melt adhesive. 2. The solar cell module according to claim 1, wherein the hot melt adhesive is a thermoplastic rubber hot melt adhesive. 3. The thickness of the hot melt adhesive is 10
3. The solar cell module according to claim 1 or 2, wherein the solar cell module has a thickness of μm to 200 μm. 4. The translucent expression film is an ethylene-tetrafluoroethylene copolymer resin film or a tetrafluoroethylene-hexafluoropropylene copolymer resin film, according to any one of claims 1 to 3.
The solar cell module according to item. 5. The thin-film solar cell is an amorphous silicon solar cell having a metal electrode layer, an amorphous silicon semiconductor layer, a transparent conductive layer, and a grid electrode on a conductive substrate. 4. The solar cell module according to any one of 4 above. 6. The solar cell module according to claim 5, wherein the thin film solar cells are connected in series and / or in parallel.