Solar cell module

Description: TECHNICAL FIELD [Detailed description of the invention]

【0001】

[Technical field to which the invention belongs]

The present invention relates to a solar cell module, and is particularly suitable for use in a double-sided solar cell module in which light can be incident from both front and back sides due to the translucency of the front surface member and the back surface member. It is a thing.

【0002】

[Conventional technology]

Since solar cell devices that directly convert light energy into electrical energy use inexhaustible sunlight as an energy source, they are expected to replace fossil energy such as oil and coal due to environmental problems, and are being put to practical use. There is. In order to use such a solar cell device as an actual energy source, a solar cell module whose output is increased by electrically connecting a plurality of solar cell elements in series or in parallel is usually used.

【0003】

As shown in FIG. 3, in the conventional solar cell module, as shown in FIG. 3, a plurality of solar cell elements 110 ... Between the front surface glass 100 and the back surface member 101 are EVA (ethylene vinyl acetate). ) And other translucent and insulating resin 102. Further, in the back surface member 101, a laminated film in which a metal foil such as an aluminum (Al) foil is sandwiched between plastic films is used in order to prevent the infiltration of moisture from the back surface.

【0004】

The solar cell element 110 is composed of single crystal silicon, polycrystalline silicon, or the like, and each solar cell element 110 is connected in series by a connecting member 111 ... Made of a thin metal plate such as a copper foil plate. In these solar cell elements 110, for example, as shown in FIG. 4, n-type impurities are diffused on a p-type single crystal silicon substrate 110a to form an n-type semiconductor layer 110b, and a semiconductor junction is formed. A back surface electrode 110d made of aluminum (Al) is provided on the back surface side of the substrate 110a. On the back surface side of the substrate 110a, Al of the back surface electrode 110d is diffused to form a p + type diffusion layer 110c. A comb-shaped electrode 110e made of silver (Ag) is provided on the surface side, and silicon dioxide (SiO) is further provided as an antireflection layer 110f.₂) A membrane is provided.

【0005】

As shown in FIG. 4, the conventional solar cell module has a structure in which a semiconductor junction is arranged on the surface glass 100 side on the light incident side. This is because many carriers are generated on the light incident side, and carrier separation is performed in this portion by using a strong electric field due to bonding.

【0006】

Further, in order to effectively utilize the light of the solar cell element, not only the electrode on the light incident side but also the electrode on the back surface side is configured as a transparent electrode, and the solar cell is configured so that light is incident from both the front and back surfaces of the solar cell element. Elements have been proposed. In such a structure, a translucent member is also used as the back surface member.

【0007】

[Problems to be Solved by the Invention]

By the way, since the solar cell module is generally used outdoors for a long period of time, it needs to have excellent weather resistance. When a laminated film in which a metal foil is sandwiched with a plastic film is used as the back surface member 101 described above, moisture intrusion from the outside is suppressed, and high power generation performance can be obtained over a long period of time.

【0008】

However, when a translucent resin film is used as the back surface member, moisture easily penetrates as compared with a laminated film in which a metal foil is sandwiched between plastic films, so it is necessary to take further measures against moisture intrusion. It has also been proposed to use a film having a low water transmittance as the translucent resin film, but there is still room for improvement.

【0009】

An object of the present invention is to provide a solar cell module having improved reliability by improving moisture resistance, which has been made to solve the above-mentioned conventional problems.

【0010】

[Means for solving problems]

First, in order to investigate the cause of the deterioration of power generation performance due to the intrusion of moisture described above, the present inventors sandwiched an aluminum (Al) foil on the back surface member 101 with PVF (polyvinyl fluoride) in the structure shown in FIG. We created two types of modules, a solar cell module using the laminated film and a solar cell module using only PVC film, and tested each of them for moisture resistance (JIS). C8917) was performed. The solar cell elements arranged in these solar cell modules have a semiconductor junction arranged on the surface glass side on the light incident side. In addition, the test examines the characteristics of the solar cell before and after 1000 hours in a constant temperature bath maintained at 85 ° C and humidity of 93%, and the output value of 95% or more is set as the acceptance criterion. Has been done. Here, the test was conducted with the time spent in the constant temperature bath set to 1000 hours. As a result, the obtained output change rate was 99.0% when the laminated film was used for the back surface member and 92.0% when the PVC film was used. Then, as a result of diligent studies on these two types of solar cell modules, the amount of sodium present in 1 g of the resin that seals the solar cell element is 0.3 μg / g when the laminated film is used, whereas it is PVF. When a film was used, it was 3 μg / g, which correlates with the output change rate, and it was found that the higher the amount of sodium in the resin, the lower the power generation performance.

【0011】

It is considered that such an increase in the amount of sodium is due to the presence of water that has entered the module. That is, when a laminated film is used for the back surface member, moisture invades from the outer peripheral portion of the solar cell module, but when a resin film is used for the back surface member, moisture invades even if it penetrates through this resin film. Therefore, the amount of water that penetrates into the solar cell module increases when the resin film is used for the back surface member.

【0012】

Then, when water enters the solar cell module, sodium ions precipitated from the surface glass move in the resin containing water and reach the surface of the solar cell element, forming a trap order in the solar cell element and carrier loss. It is presumed that the use of a resin film on the back surface deteriorated the power generation performance in order to cause the problem and reduce the power generation performance of the solar cell element. The cause of this is not clear at this time, but it seems that sodium (Na) does not bind directly to silicon (Si) but affects it via oxygen. Therefore, it is expected to act in combination with the impurity diffusion layer (dope layer) having a natural oxide film on the surface or the residual oxygen in the substrate. When the order is formed in the dope layer, it is considered that the built-in electric field is weakened by the decrease of carriers, and the influence on the interface portion may increase the recombination and deteriorate the characteristics.

【0013】

According to the present invention, an alkaline component such as sodium precipitated from the surface glass does not affect the semiconductor bonding of the solar cell element, and the reliability is improved.

【0014】

The solar cell module of the present invention is a solar cell module in which the solar cell element is sealed with a sealing resin between the front surface glass member and the back surface member, in consideration of the above. The solar cell element is arranged so that the semiconductor junction of the solar cell element is located on the opposite side of the surface glass member.

【0015】

The solar cell element is characterized in that it is configured so that light can be incident on the side opposite to the junction forming side.

【0016】

The back surface member can be made of a translucent member.

【0017】

According to the above configuration, since the alkaline component such as sodium ion is blocked by the thick bulk semiconductor, the influence on the joint portion, which is important for electric field formation, can be substantially eliminated. Therefore, it is possible to prevent a decrease in the power generation performance of the solar cell element.

【0018】

BEST MODE FOR CARRYING OUT THE INVENTION

Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a schematic cross-sectional view of the solar cell module according to the first embodiment of the present invention.

【0019】

In the solar cell module according to this embodiment, as shown in FIG. 1, a plurality of solar cell elements 3 ... Between the front surface glass 1 and the back surface member 2 are EVA (as shown in FIG. 1). It has a structure sealed with a translucent and insulating resin 4 such as ethylene / vinyl acetate). Further, a transparent plastic film made of PVF or the like is used for the back surface member 2 in order to allow light to enter from the back surface. Note that, in FIG. 1, only one solar cell element 3 portion is shown, and the other solar cell element 3 is connected in series and / or in parallel by a connection lead such as a copper foil. ..

【0020】

In the solar cell element 3 used in the solar cell module of the present invention, n-type impurities are diffused on a p-type single crystal silicon substrate 31 to form an n-type semiconductor layer 32, and a semiconductor junction is formed. A comb-shaped electrode 33 made of Ag is provided on the n-type semiconductor layer 32, and silicon dioxide (SiO) is further provided as the antireflection layer 34.₂) A membrane is provided.

【0021】

The solar cell element 3 is arranged in the solar cell module so that the semiconductor junction of the solar cell element 3 is located on the opposite side of the surface glass substrate 1. Therefore, it is necessary for the solar cell element 3 to allow light to be incident on the surface of the conventional solar cell element opposite to the junction forming side. Therefore, after forming the p + type diffusion layer 35 located on the glass substrate 1 side by aluminum (Al) diffusion, Al is removed to enable light incident, or the p + type amorphous semiconductor is formed by a film forming process. By forming a layer on the substrate 31, light can be incident. A comb-shaped electrode 36 made of Ag is provided on the p-type semiconductor layer 35, and silicon dioxide (SiO) is further provided as the antireflection layer 37.₂) A membrane is provided.

【0022】

The above-mentioned solar cell module is sandwiched between an EVA resin sheet so that the semiconductor junction of the solar cell element 3 is located on the opposite side of the front glass 1 between the front glass 1 and the back member 2, and heated under reduced pressure. , Integrated. Then, as shown in FIG. 1, a plurality of solar cell elements 3 ... are placed between the front surface glass 1 and the back surface member 2 with the EVA resin in a state where the semiconductor junction is arranged on the opposite side to the front surface glass 1. It will be sealed.

【0023】

As described above, when the semiconductor junction is moved away from the surface glass 1, the alkaline component such as sodium ion is blocked by the thick bulk semiconductor, so that the influence on the junction portion, which is important for electric field formation, can be substantially eliminated. Therefore, it is possible to prevent the power generation performance of the solar cell element 3 from deteriorating. As a result, it is possible to supply a highly reliable solar cell module that can withstand longer-term use outdoors.

【0024】

Next, the results of the moisture resistance test of the solar cell module of the present invention having the above-mentioned structure and the solar cell module having the conventional structure are shown. This test examines the characteristics of solar cells before and after 1000 hours in a constant temperature bath kept at 85 ° C and humidity of 93%, and the output value of 95% or more is set as a passing criterion. ing. The results are shown in Table 1.

【0025】

In the sample of the present invention, a transparent plastic film made of PVF (polyvinyl fluoride) was used as the back surface member 2 in order to allow light to enter from the back surface. Further, as the sample of the conventional example, a laminated film in which a metal (Al) foil was sandwiched with a plastic film made of PVF was used as a back surface member. The conventional example and the present invention have the same configuration except that the material of the back surface member is different and the semiconductor junction is located on the glass substrate side and the semiconductor junction is located on the opposite side of the glass substrate.

【0026】

[table 1]

<img file="JP2001237448A_D0001.tif" />【0027】

Each value in the table represents the rate of change from the initial characteristics. As is clear from Table 1, in the embodiment of the present invention in which the semiconductor junction is arranged on the opposite surface side of the surface glass 1, the characteristics are characteristic even though a plastic film having a large amount of water infiltration is used as the back surface member. It can be seen that the decrease is small.

【0028】

Next, a second embodiment of the present invention will be described with reference to FIG. As shown in FIG. 2, in this embodiment, substantially true amorphous silicon is sandwiched between a single crystal silicon substrate and an amorphous silicon layer, defects at the interface are reduced, and a heterojunction interface is formed. In a structure with improved characteristics (hereinafter referred to as a HIT structure), a solar cell element 5 that allows light to be incident from both the front and back surfaces is used.

【0029】

As shown in FIG. 2, the intrinsic amorphous silicon layer 52 is formed on the n-type single crystal silicon substrate 51, and the p-type amorphous silicon layer 53 is formed on the intrinsic amorphous silicon layer 52. Then, a transparent electrode 54 on the light receiving surface side made of ITO or the like is provided on the entire surface of the p-type amorphous silicon layer 53, and a comb-shaped collecting electrode 55 made of silver (Ag) or the like is formed on the transparent electrode 54 on the light receiving surface side. Has been done. Further, the opposite surface side of the substrate 51 has a so-called BSF (Back Surface Field) type structure in which an internal electric field is introduced on the back surface of the substrate. That is, a high-doped n-type amorphous silicon layer 57 is provided on the opposite surface side of the substrate 51 via the intrinsic amorphous silicon layer 56. A back surface side transparent electrode 58 made of ITO or the like is formed on the entire surface of the high-doped n-type amorphous silicon layer 57, and a comb-shaped collecting electrode 59 made of silver (Ag) or the like is formed on the back surface side transparent electrode 58. In this way, the back surface also has a BSF structure in which a true amorphous silicon layer is sandwiched between the crystalline silicon substrate and the high-doped amorphous silicon layer to reduce defects at the interface and improve the characteristics of the heterojunction interface. It has become.

【0030】

A plurality of the above-mentioned solar cell elements 5 are connected in series by a connecting member (not shown). Then, in this embodiment, the solar cell element 5 is arranged so that the semiconductor junction is located on the side opposite to the surface glass 1 side. That is, the comb-shaped collecting electrode 59 side, which is usually the side corresponding to the back surface side, is arranged on the glass substrate 1 side, and the p-type amorphous silicon layer 53 forming a semiconductor bond is arranged on the back surface film 2 side.

【0031】

In this way, the solar cell element 5 arranges the semiconductor junction between the front glass 1 and the transparent back film 2 such as PVF at a position opposite to that of the glass substrate 1, and EVA (ethylene vinyl acetate) resin 4 is placed. Sealed with use to form a solar cell module.

【0032】

As described above, when the semiconductor junction is moved away from the surface glass 1, the alkali is blocked by the thick bulk semiconductor, so that the influence on the junction portion, which is important for electric field formation, can be substantially eliminated. Therefore, it is possible to prevent a decrease in the power generation performance of the solar cell element 5. As a result, it is possible to supply a highly reliable solar cell module that can withstand longer-term use outdoors.

【0033】

Next, the results of the moisture resistance test of the solar cell module of the present invention having the above-mentioned structure and the solar cell module having the conventional structure are shown. This test examines the characteristics of solar cells before and after 1000 hours in a constant temperature bath kept at 85 ° C and humidity of 93%, and the output value of 95% or more is set as a passing criterion. ing. The results are shown in Table 2.

【0034】

Samples of the present invention, as the back member 2, Toru composed of PVF (polyvinyl fluoride) in order to enable incidence of light from the back surface using a light plastic film. Further, as the sample of the conventional example, a laminated film in which a metal (Al) foil was sandwiched with a plastic film made of PVF was used as a back surface member. The conventional example and the present invention have the same configuration except that the material of the back surface member is different and the semiconductor junction is located on the glass substrate side and the semiconductor junction is located on the opposite side of the glass substrate.

【0035】

[Table 2]

<img file="JP2001237448A_D0002.tif" />【0036】

Each value in the table represents the rate of change from the initial characteristics. As is clear from Table 2, in the embodiment of the present invention in which the semiconductor junction is arranged on the opposite surface side of the surface glass 1, the characteristics are characteristic even though a plastic film having a large amount of water infiltration is used as the back surface member. It can be seen that the decrease is small.

【0037】

In the above-described embodiment, the case where a heat diffusion type single crystal silicon solar cell element and a solar cell element having a HIT structure are used as the solar cell element has been described, but the present invention has described the case where other single crystal silicon and polycrystals are used. It can also be applied to a crystalline solar cell element using silicon and a solar cell module using an amorphous solar cell element.

【0038】

[Effect of the invention]

As described above, according to the present invention, the sodium ions precipitated from the surface glass are suppressed from reaching the solar cell element, the time until the element power generation performance of the solar cell is deteriorated is extended, and a longer period of time is taken outdoors. It is possible to provide a highly reliable solar cell module that can withstand various uses.

[Simple explanation of drawings]

[Figure 1]

It is a schematic cross-sectional view which shows the solar cell module which concerns on embodiment of this invention.

[Figure 2]

It is a schematic cross-sectional view which shows the solar cell module which concerns on other embodiment of this invention.

[Fig. 3]

It is a schematic cross-sectional view which shows the conventional solar cell module.

[Fig. 4]

It is a schematic cross-sectional view which shows the conventional solar cell module.

[Explanation of symbols]

1 Surface glass 2 Back side member 3 Solar cell element