JP2019216144A - Solar cell module - Google Patents

Abstract

To provide a power generation deterioration rate null solar cell module that enables a null guarantee of a power generation deterioration rate for 20 years in operation without depending on an installation environment.SOLUTION: It was found that passage of sodium ions to a silicon device is completely inhibited by applying a composite filling material 7, made of an ethylene-norbornene random copolymer film, sandwiched between EVA encapsulation materials to a gap between cover glass 3 and a power generation element 2. The present invention can completely prevent three deterioration modes of degradation over time, delamination power generation degradation, and PID degradation without correlation with an amount of water vapor intruding into a solar cell module. The invented solar cell module has a module structure having an acetic acid volatilization function by providing a passage capable of making acetic acid generated by deterioration of the EVA encapsulation materials in the module volatilize to a module edge part, which perfectly eliminates possibility of solder separation between an inter-connector and a cell.SELECTED DRAWING: Figure 4

Description

  The present invention relates to a solar cell module in which the power generation deterioration rate of a solar cell module in an actual field is extremely small and a state of almost zero can be guaranteed for 20 years.

  There are three directions for research and development of photovoltaic modules. One is to improve the power generation efficiency of solar cells. Higher power generation efficiency in polycrystalline and single crystal systems is achieved by double-sided power generation using PERC technology and N-type, and commercialization using a heterojunction structure. In addition, power generation efficiency has been improved by increasing the number of Ag finger electrodes and the number of interconnectors. Furthermore, since the power generation efficiency can be improved by halving the silicon cell, it is becoming a mainstay in the future.

  The second is a study on technology for improving the reliability of the solar cell module. Many products have a guaranteed power generation period of 20 to 25 years. Further, a product in which the back sheet of the solar cell module is replaced with glass, which is a so-called glass / glass type, which is guaranteed for 30 years, has appeared.

The third is to reduce the manufacturing cost of the solar cell module. Product prices have been falling according to the empirical curve, and the cost of procurement and manufacturing of the applicable BOM has been reduced.
The reduction in BOM procurement costs is due to the large number of orders and the narrowing down of varieties to be used. On the other hand, the reduction of manufacturing cost is mainly achieved by reducing the unit price per W by improving the power generation efficiency of the power generating element and improving the production amount by shortening the press working time in the laminator process.

The technology for improving the long-term reliability of a solar cell module is often in conflict with the cost reduction of the solar cell, and the current direction has not been determined. In recent years, efforts have been made to reduce the unit cost per watt by improving the power generation performance by actively taking in ultraviolet rays. So-called highly transparent EVA (ethylene-vinyl acetate copolymer) does not add an ultraviolet absorber, which is essential as a light-resistant stabilizer, and therefore improves +1 to 2 W. However, the deterioration of the sealing material is extremely rapid, and the increase in the amount of acetic acid generated by the deterioration of the EVA sealing material is promoted, and the power generation deterioration speed is increasing. Further, cost reduction is also being carried out by shortening the press time in the laminator process. It is known that when production is terminated with insufficient crosslinking reaction of EVA, residual organic peroxide accelerates the deterioration of the EVA encapsulant during operation in a real field.
As described above, development is proceeding with priority given to cost reduction without achieving both reduction of the power generation deterioration rate and cost reduction of the solar cell module.

There are many documents and patents related to the technology for reducing the power generation deterioration rate of the solar cell module. Japanese Patent Application Laid-Open No. 2014-22473 is an invention using a light-transmitting substrate having high moisture barrier properties. Japanese Patent Application Laid-Open No. 2013-41911 is an invention relating to a solar cell module to which a cyclic olefin-based copolymer sheet having a property of high water vapor barrier properties is applied. Japanese Patent Application Laid-Open No. 2013-21451 is an invention relating to a solar cell module to which a silane-modified ethylene-based resin having excellent moisture resistance and excellent long-term weather resistance is applied. WO2011 / 108600A1 is an invention relating to a solar cell module using a water vapor barrier property, flexibility, a resin composition comprising a cyclic olefin polymer, and the like. JP-A-7-74378, JP-A-10-25357, and JP-T-2002-520820 propose a sheet member for a solar cell comprising a resin film on which an oxide is deposited instead of aluminum. .

At the AIST photovoltaic power generation research report meeting 2015, Atsushi Masuda, module reliability research team leader of the photovoltaic power generation research center, said that the power generation degradation was due to the acetic acid generated by the hydrolysis of the EVA encapsulant between the Ag finger electrode and silicon cell interface With corrosion. As described above, from the patents and documents relating to power generation deterioration, in order to reduce the power generation deterioration rate, the resin members constituting the solar cell module are pursuing improvements in waterproofness and moisture resistance. The pursuit of sealing technology has been pursued. While the elucidation of the mechanism of power generation deterioration is uncertain, the existing power generation deterioration reduction technology is a technology to reduce the amount of water vapor entering the solar cell module, and its purpose is to reduce the generation of acetic acid by hydrolysis of the EVA sealant . In order to reduce the power generation degradation rate to zero on an extension of the existing technology, it is necessary to reduce the amount of water vapor penetration to zero. This can only be achieved by packaging in a vacuum around the silicon cell. Although this is technically possible, it is not realistic because it goes against the cost reduction of the product. In other words, there has been no technology that can achieve zero power generation deterioration rate. Therefore, the power generation deterioration rate of the solar cell module made of the existing technology greatly differs depending on the environment of the installation place, and therefore, the power generation deterioration of the product cannot be technically guaranteed.

  It is practically impossible to eliminate water vapor that enters the solar cell module, and it is also impossible to eliminate acetic acid due to deterioration of the EVA sealing material. That is, in the related art, there is no solar cell module that realizes the zero power generation deterioration rate. Therefore, an object of the present invention is to completely eliminate ionization of sodium in a cover glass and transfer and attachment of sodium ions to a crystalline silicon element, which are deep causes of power generation deterioration phenomenon due to water vapor intrusion, and An object of the present invention is to provide a solar cell module having a power generation deterioration rate of zero in which a volatile passage is formed in a module so that acetic acid, which is one power generation deterioration factor, does not accumulate in the module.

  The power generation deterioration phenomena of a solar cell include so-called delamination power generation deterioration and PID (Potentioal induced degradation) accompanied by aging, deterioration of a filler, and yellow discoloration, which deteriorate at a constant rate every year. Furthermore, power generation deterioration occurs due to elution and peeling of the solder joints due to acetic acid generated due to deterioration of the EVA sealing material. That is, there are four types of deterioration modes. In order to achieve the zero power generation deterioration rate, respective measures are necessary.

First, the aging phenomenon will be described. A solar cell module installed in a real field inhales moisture in the air; water vapor. The invading water vapor wets the inner surface of the cover glass, and sodium present in the glass elutes from the surface, adheres and deposits on the cell surface in an ionized state, and forms sodium hydroxide to form silver on the cell. This is a phenomenon in which the finger current is ionized and the cross-sectional area of the electrode is reduced, thereby lowering the electron collection performance.
Delamination power generation deterioration occurs from around the interconnector.Sodium ions are attracted to the current flowing through the interconnector, and the surrounding area becomes alkaline due to the sodium ions. The progress causes peeling along the interconnector. The yellow discoloration of the encapsulant is evidence that sodium ionized and migrated in the filler and changed to alkaline, although the amount of decrease in light transmittance by itself was slight, and the coloring was Due to the molecular structure transition of the stabilizer of the additive.

  PID degradation is a phenomenon in which a large amount of sodium ions adhere to the surface of a silicon cell crystal, and the attached portion is electrically short-circuited, so that the silicon cell stops generating power. The deep layer that causes any decrease in power generation is due to the attachment of sodium ions eluted from the cover glass to the silicon cell surface. When the existing technology is evaluated from the above reasons, the waterproof performance and thickness of the back sheet, and the denseness of the packaging molding processing, the amount of water vapor intrusion is reduced, leading to a decrease in the amount of sodium movement, It is considered that technology development for improving waterproofness has been performed.

  Most of the water vapor infiltration into the solar cell module comes from the back sheet, and a countermeasure against power generation deterioration has been taken by replacing the resin material with glass and greatly reducing the amount of water vapor entering the module. The only way to achieve zero power generation degradation with existing technology is to seal the silicon cell with a vacuum glass container.However, this is contrary to module manufacturing costs. Above is impossible.

  After diligent studies, they found that applying an ethylene norbornene random copolymer film sandwiched with an EVA encapsulant between the cover glass and the silicon cell completely prevented sodium ions from passing through the silicon device. . INDUSTRIAL APPLICABILITY The present invention can completely eliminate three deterioration modes of aging deterioration, delamination power generation deterioration, and PID power generation deterioration, regardless of the amount of water vapor entering the solar cell module.

Specifically, as a filler between the cover glass and the silicon cell, (A) the glass transition temperature is from 70 ° C to 82 ° C, preferably from 75 ° C to 80 ° C, and the film thickness is from 20 µm to 50 µm, preferably Is a composite sealing material (B / A / B) obtained by sandwiching an ethylene / norbornene random copolymer film having a thickness of 30 μm to 48 μm with an EVA sealing material having a thickness of 200 μm to 500 μm, preferably 300 μm to 450 μm. Invented.
FIG. 1 shows the relationship between each environmental degradation factor and the amount of sodium ionized in the cover glass ionized and deposited on the silicon cell surface. The melting point of the EVA encapsulant is about 60 ° C. ± 10 ° C., its glass transition temperature is about −20 ° C., and the solar cell module during power generation is about 40 ° C. to 70 ° C. In other words, the EVA encapsulant has holes at the molecular level sufficient to allow sodium ions to pass through. On the other hand, since the glass transition temperature of the ethylene-norbornene random copolymer film is designed to be 70 ° C. to 82 ° C., the molecules are in a solidified state (glass state), and the free volume is almost zero. Therefore, sodium ions do not pass through. Therefore, since no sodium is deposited on the silicon cell, power generation deterioration in all three deterioration modes of aging, delamination power generation deterioration, and PID deterioration does not occur.

In the case of a power plant that has been operating for more than 10 years in the actual field, a deterioration mode of solder joint peeling due to acetic acid may occur. When the amount of acetic acid generated due to the deterioration of the EVA sealing material exceeds 1000 μg / g, there is a possibility that the solder of the interconnector on the back surface of the silicon cell is peeled off. In particular, it is known that acetic acid generated due to deterioration of the EVA filler between the back sheet of the solar cell module and the back surface of the silicon cell is liable to cause peeling of the solder joint between the back surface interconnector and the silicon cell.
It has been found that this solder peeling occurs due to acetic acid remaining in the solar cell module, particularly in the uneven portions of the interconnector.
We have invented a module structure that eliminates the possibility of solder peeling by completely evaporating the acetic acid generated by the deterioration of the EVA filler from the backsheet and from the edge around the glass to create a structure. In the means, by cutting the cut size of the film size of the EVA encapsulant and the ethylene / norbornene random copolymer to be smaller than the glass periphery by 5 mm to 8 mm, a passage for volatilizing acetic acid generated in the module can be formed. The part may use a butyl tape or a silicon sealer. However, at the time of lay-up, it is essential to lay each EVA sheet and the ethylene-norbornene random copolymer film in a state of covering the entire silicon cell matrix.

  Further, in order to volatilize acetic acid, the back sheet employing the solar cell module has a water vapor transmission rate of 1.1 to 3.0 g / (square meter / 24 h), preferably 1.3 to 2.5 g / (square meter / 24 h). It has the property. If it is lower than 1.1 g / (square meter / 24 h), the acetic acid accumulated in the solar cell module is difficult to volatilize, which is not preferable. If it exceeds 3.0 g / (square meter / 24 h), the hydrolysis rate of EVA is high. In the balance between the volatilization and generation of acetic acid, the amount of acetic acid accumulated is undesirably increased.

  According to the invention described above, it is possible to provide a solar cell module having a zero power generation deterioration rate for at least 20 years without depending on an installation environment, particularly, humidity and temperature.

Transfer amount of sodium ion Delamination Clearance between interconnector and EVA sheet Invented zero power generation deterioration rate solar cell module structure PID test sequence

Hereinafter, a module for a solar cell with a zero power generation deterioration rate as one example of an embodiment of the present invention will be described. However, the scope of the present invention is not limited to the embodiments described below.

The following qualities are obtained for the composite encapsulant consisting of a three-layer structure of a composite encapsulant; EVA encapsulant / ethylene / cyclic olein copolymer film / EVA encapsulant as a filler for the super straight solar cell module. It is a solar cell module having a super straight structure on which the filled composite encapsulant and back sheet are mounted.
EVA sealing material: melting point measured by DSC; Tm is 55 ° C to 75 ° C.
Ethylene-norbornene random copolymer: glass transition temperature Tg measured by DSC; 70 ° C. to 82 ° C., and film thickness of 20 μm to 50 μm.
-Solar cell back sheet: The water vapor permeability is 1.1 g / (square meter / 24 h) to 3.0 g / (square meter / 24 h).

First, the technology for preventing delamination power generation deterioration will be described. FIG. 2 shows delamination occurring on a crystalline silicon cell. The occurrence is related to the fluidity of the EVA sealing material exerted by the laminator molding processing conditions. The gap between the EVA encapsulant due to the step between the interconnector and the silicon cell surface (Fig. 3) must be completely filled with EVA resin material. Therefore, the melting point of EVA must be 55 ° C to 75 ° C. It is. Depending on its quality, the solar cell module of the present invention is a composite encapsulant of the present invention whose quality is designed so that the gap is filled under any conditions considered to be ordinary by those skilled in the art.

  By having a vinyl acetate structure in the molecular structure of EVA, strong adhesion to a silicon cell or glass can be exhibited through a silane coupling reaction. In order to prevent the occurrence of delamination from a mechanical point of view, an EVA sealing material capable of obtaining strong adhesion was used as a component of the composite sealing material. The melting point of EVA is 55C to 75C, preferably 58C to 70C. A quality of less than 55 ° C. means that the content of vinyl acetate is high, so that the quality tends to deteriorate at the laminator molding temperature and the acetic acid is easily removed, which is not preferable. If the temperature exceeds 75 ° C., the temperature around the glass at the time of laminator processing is low, and if it does not melt, the “gap” around the interconnector will not be filled, which is not preferable.

  The mechanism of delamination generation from a chemical point of view is that the molecular structure of EVA and the polysilanol structure at the bonding interface are weak against moisture (water vapor), that is, the structure is easily hydrolyzed. Further, it is known that alkali hydrolysis easily proceeds at room temperature under an alkaline environment. In order to prevent delamination power generation deterioration for a long period of 10 or 20 years, it has been discovered that sodium does not adhere to or accumulate on a silicon cell so that sodium transferred from glass does not become alkaline. .

  It is essential that the Tg of the ethylene / norbornene random copolymer film sandwiched by the EVA sealing material is 70 ° C. to 82 ° C. If the temperature exceeds 82 ° C., the “gap” around the interconnector may not be filled in the laminating process, which is not preferable. If the temperature is lower than 70 ° C., if the temperature of the module becomes high under the actual field, the free volume increases, and a hole through which sodium ions pass may be formed, which is not preferable. Further, "film tear" due to shrinkage of the film may occur, which is not preferable.

Furthermore, the presence of the ethylene-norbornene random copolymer film as a composite filler improves the electrical insulation properties and reduces the "leakage current" flowing inside the solar cell module to almost zero, so that sodium ions eluted from the cover glass The electric force attracted toward the silicon cell is greatly reduced.
In the ethylene-norbornene copolymer film of the present invention, since the free volume of the molecule is almost zero under the use environment, sodium ions do not pass through. Therefore, since no sodium ions reach the silicon cell surface, aging, PID deterioration, and delamination power generation deterioration do not occur at all because the alkaline atmosphere does not occur.

Therefore, the solar cell module mounted with the composite EVA encapsulant capable of preventing the delamination power generation deterioration can completely prevent the power generation deterioration except in the power generation deterioration mode due to the peeling of the solder joint due to acetic acid.
It has been found that the delamination phenomenon has a surprisingly large effect on the thickness of the ethylene / norbornene random copolymer film.
The ethylene-norbornene random copolymer film shrinks when the use environment temperature rises above its glass transition temperature. Generally, it is sold as a shrink film.
As a result of intensive studies, it has been found that, in addition to the glass transition temperature, a large shrinkage occurs at an environment temperature higher than 20 ° C. In the step of laminating the solar cell module using the composite sealing material, the solar cell module is compressed and thermally cured at 140 ° C. or higher. At this processing temperature, it was discovered that the film should be as thin as possible in order to prevent the film from shrinking and peeling immediately after molding.

As a result of intensive studies, it was found that when the film thickness exceeds 50 μm, turtle-like wrinkles and tears occur. With a thin film of 50 μm or less, it was found that the film interface was chemically bonded to the EVA molecule by co-crosslinking, and thus did not shrink, that is, delamination did not occur.
The present inventors have found that the film thickness of the ethylene-norbornene random copolymer film is an extremely important physical property value for reducing the power generation deterioration rate to zero, and have led to the present invention. In addition, if the film thickness is less than 20 μm, there is a risk of breakage in the film winding step, which is not preferable.

<Resin composition and molding method>
As the ethylene-norbornene random copolymer constituting the composite sealing material of the present invention, TOPAS (registered trademark) (manufactured by Topas Advanced Polymers, Germany) and APEL (registered trademark) (manufactured by Mitsui Chemicals, Inc.) can be used. It is preferable that an ultraviolet absorber, an antioxidant, and a weather stabilizer are added. Here, the compounding used a kneader. The molding temperature of this master batch processing is 180 ° C. or more and 300 ° C. or less, preferably 230 ° C. or more and 290 ° C. or less.

  It is preferable to add a benzophenone-based, benzotriazole-based, triazine-based, or salicylate-based ultraviolet absorber. Further, addition of a hindered amine light stabilizer is preferred.

The method for forming the solar cell encapsulant in the present invention can be formed by a known method, for example, an extrusion casting method using a T-die at the tip of an extruder head or a calendering method. Here, a film was prepared by an extrusion casting method using a T-die.
The temperature of the T-die is from 80 ° C to 250 ° C, preferably from 120 ° C to 180 ° C. The surface of the formed film is preferably subjected to processing such as embossing and unevenness for the purpose of preventing blocking.
The thickness of the film is from 20 μm to 50 μm, preferably from 30 to 48 μm. If the thickness is less than 20 μm, film formation processing becomes difficult, which is not preferable. If it exceeds 50 μm, delamination may occur, which is not preferable.

<Solar cell module>
The production of the crystalline solar cell module is as follows. 1. lay-up process; 2. laminating step; It consists of three framing steps. In the lay-up step, an EVA encapsulant, a cell matrix in which silicon cell strings are soldered in series on a cover glass, and an EVA encapsulant are laid thereon, and a back sheet is covered.
The laminating step is performed by setting the temperature of the hot plate, the vacuum time and the pressing time. The vacuum time was 5 minutes, the pressurization time was 10 minutes, and the temperature of the hot plate was set at 160 ° C.
FIG. 4 shows a solar cell having an existing superstrate structure. FIG. 5 is a schematic sectional view showing an example of the solar cell module of the present invention.
The solar cell module of the present invention includes, in order from the transparent glass on the light-receiving surface, the composite filler of the present invention, a solar cell element, a commercially available EVA sealing material, and a commercially available back sheet. The composite encapsulant of the invention is cut 3 mm to 8 mm small from the periphery of the glass, confirms that the entire silicon cell strings are covered, and can provide a acetic acid volatilization path by a lay-up method.

<Solar solar cell silicon cell>
For example, silicon (single crystal, polycrystal, amorphous), P-type, N-type, heterojunction cell, PERC cell, or the like can be used.

The present invention will be described more specifically with reference to the following examples, but the present invention is not limited to the following examples. Various measurements and evaluations of the solar cell module of the present invention equipped with the composite sealing material of the present invention were performed as follows.
(1) Measurement of Tg (° C.) of Glass Transition Temperature The glass transition temperature of the cyclic olefin resin and the EVA resin was measured by a DSC method at a heating rate of 20 ° C./min and a second run.
(2) Water vapor transmission rate (ASTMF1249)
The test was performed using a water vapor permeation tester (PERMATRAN W3 / 33, manufactured by MOCON) at a temperature of 40 ° C. and a humidity of 90% RH.
As a sample, a back sheet product was used as it was.
(3) Quantification of the amount of acetic acid in the EVA sealing material inside the solar cell module: EVA adhering to the silicon cells was manually collected from the center of the solar cell module and quantified by ion chromatography.
(4) Delamination (white turbidity) test (
Using TOS7210S manufactured by KIKUSUI, -1000 Vdc was applied for 1000 hours in a thermostat at 80 ° C. and 85% RH.
FIG. 5 shows an electric wiring sequence. The evaluation was performed by the following sensory test method.
The “state without delamination” of the present invention is four or more points.
5 points (highest point): no change in appearance compared to the original 4 points: slight color change (yellowing) around the interconnector.
3 points: White turbid peeling was less than 5 mm in at least one portion of the interconnector portion of the silicon cell.
2 points: cloudiness peeling of at least one portion of the interconnector portion of the silicon cell is 5 mm or more and less than 20 mm.
1 point: cloudiness peeling of at least one part of the interconnector portion of the silicon cell is 20 mm or more.
(5) PID test and leakage current test
Using TOS7210S manufactured by KIKUSUI, -1000 Vdc was applied for 1000 hours in a thermostat at 80 ° C. and 85% RH. FIG. 5 shows the PID test sequence. Cover the entire surface of the photovoltaic module with a 20μm thick aluminum foil (made by UACJ Co., Ltd.) on the light-receiving surface, and attach the wiring on the positive application side using the pre-processed mounting holes in the aluminum frame. The test was started after confirming the continuity with the tester.
(6) Simulator test
The power generation performance of the test specimen before and after the PID test was measured with a cell tester manufactured by NPC. The test was performed under the conditions of a test temperature of 25 ° C. ± 1 ° C. and an irradiation intensity of 1000 W / square meter.

Example 1
<Preparation of ethylene-norbornene random copolymer film>
The raw material of the film is 8007: 100 parts by weight of TOPAS (registered trademark), 0.3 parts by weight of 2-hydroxy-4-n-octoxybenzophenone as an ultraviolet absorber, and bis (2,2,6) as a light stabilizer. , 6-Tetramethyl-4-piperidyl) sebacate 0.1 part by weight. And it knead | mixed at 230 degreeC using the twin-screw extruder, and obtained the cyclic olefin resin composition. Next, the pellets were used to obtain films of various thicknesses at a resin temperature of 120 ° C. at a T-die portion having a width of 1000 mm. In Examples 1, 2, 3, and 4, 35, 40, 45, and 48 μm were prepared, respectively.
In the solar cell module, the obtained film was laminated with the commercially available EVA having a melting point of 58 ° C. in a sandwiched state (“filler” of the invention) in Example 1, and vacuum was applied to the film using an OAC2236 laminator manufactured by Boost Solar, China. Under the conditions of a time of 5 minutes, a press time of 10 minutes and a molding temperature of 160 ° C., a polycrystalline 5-busbar silicon cell: manufactured by CECEP, China: a solar cell module laid up in a configuration of 60 series was molded. The glass for solar cells used had a thickness of 3.2 mm, a width of 920 mm, and a length of 1650 mm. After molding, Teraoka Seisakusho's butyl tape is applied as an edge seal, an aluminum frame purchased by CECEP is attached, and the terminal box of PVU-B80 made by Onamba Japan is fixed with Shin-Etsu Silicone, a one-component RTVKE45T, solar cell module Was prepared. The cut size of the EVA sealing material and the ethylene / norbornene random copolymer film was 5 mm smaller than the outer periphery of the glass, and specifically, the width was 915 mm and the length was 1645 mm. The backsheet used was FFC-JW30 manufactured by Jolywood sunwatt, China. The water vapor permeability was 1.3 g / (square meter / 24 h).

Example 2 was the same as Example 1 except that an EVA encapsulant having a melting point of 67 ° C., an ethylene-norbornene random copolymer film thickness of 40 μm, and a water vapor permeability of 1.8 g of the back sheet (square meter, 24 h) were used. The same procedure was followed.

In Example 3, an EVA sealing material having a melting point of 71 ° C., an ethylene-norbornene random copolymer film thickness of 45 μm, and a water vapor permeability of the back sheet; The procedure was performed in the same manner as in Example 1 except that the cut size of the copolymer film was reduced by 7 mm.

In Example 4, an EVA sealing material having a melting point of 67 ° C., an ethylene / norbornene random copolymer film thickness of 48 μm, and a water vapor permeability of a back sheet;
The process was performed in the same manner as in Example 1 except that the cut size of the 1.8 g / (square meter, 24 h) EVA and ethylene / norbornene random copolymer film was reduced by 3 mm.

In Comparative Example 1, the thickness of the ethylene / norbornene random copolymer film was changed to 95 μm, and the glass transition temperature was 85 ° C. The cut size was prepared +10 mm larger than the glass periphery. EVA used a melting point of 71 ° C. The back sheet was prepared in the same manner as in Example 1 except that the water vapor y-permeability: 1.0 g / (square meter, 24 h) was used.

Comparative Example 2 was compared with KIS Corporation 60 straight polycrystalline module; PS255P-20 / U.
Comparative Example 3 was compared with Loop; NEXTOUGH: LP-275P-60W; glass / glass type.

Renewable energy is spreading and developing around the world. Among them, photovoltaic power generation has been the main role because it can be installed in various places from small to large scales systematically. On the other hand, since the power generation life has been developed with a target of 20 years, the problem of the waste photovoltaic module is increasing.
In order for solar power generation to become the main power source to replace thermal power generation and nuclear power generation, it is essential to have a life of 40 years or more while adding maintenance. The zero power generation deterioration rate solar cell module of the present invention has been developed and completed with this goal.
EVA is used as a filler to protect power generation elements in more than 90% of solar cell modules produced worldwide. It is characterized by good transparency, high adhesiveness and high heat resistance. However, over 20 years, appearance changes such as yellow discoloration and white turbidity, significant aging deterioration, and PID deterioration occur at the same time, ending the product life. Modern solar cell modules have a similar lifetime.
Chemical companies around the world have developed and introduced alternative materials for EVA in order to prevent these power generation deterioration phenomena, but because of their high cost and lack of track record, they have been widely used because they cannot be guaranteed for more than 20 years. Absent.
The solar cell module of the present invention is the world's first product that can technically guarantee power generation. Conventional fillers have been developed from the viewpoints of increasing the electric resistance value and improving the moisture resistance. In a humid installation environment, the absolute amount of water vapor intrusion increases, and the power generation deterioration rate increases. That is, the range of power generation deterioration guarantee at a place corresponding to any installation environment cannot be set to 20% or less.
The composite filler of the present invention is an ethylene-norbornene copolymer film that inherits the excellent properties of an EVA sealing material and can block the movement of sodium ions, which is the main cause of power generation deterioration (free volume is almost zero). It is a hybrid and can completely prevent power generation deterioration without depending on the installation environment. Therefore, it is a solar cell module that contributes to the formation of large-scale solar power plants, power plants for self-consumption, and used market businesses.

1: Interconnector 2: Silicon cell EVA sealing material 3: Cover glass 4: EVA sealing material 5: Gap 6: Back sheet 7: Composite sealing material (EVA sealing material / ethylene / norbornene random copolymer film / EVA) Sealing material)
8: Aluminum foil with a thickness of 20 μm 9: Conductive wire that combines plus and minus poles from horizontal tab wire 10: PID Insulation Tester TOS7210S

<Solar cell module>
The production of the crystalline solar cell module is as follows. 1. lay-up process; 2. laminating step; It consists of three framing steps. In the lay-up step, an EVA encapsulant, a cell matrix in which silicon cell strings are soldered in series on a cover glass, and an EVA encapsulant are laid thereon, and a back sheet is covered.
The laminating step is performed by setting the temperature of the hot plate, the vacuum time and the pressing time. The vacuum time was 5 minutes, the pressurization time was 10 minutes, and the temperature of the hot plate was set at 160 ° C.
The left side of FIG. 4 shows a solar cell having an existing superstrate structure. The right side of FIG. 4 is a schematic sectional view showing an example of the solar cell module of the present invention.
The solar cell module of the present invention includes, in order from the transparent glass on the light-receiving surface, the composite filler of the present invention, a solar cell element, a commercially available EVA sealing material, and a commercially available back sheet. The composite encapsulant of the invention is cut 3 mm to 8 mm small from the periphery of the glass, confirms that the entire silicon cell strings are covered, and can provide a acetic acid volatilization path by a lay-up method.

The present invention will be described more specifically with reference to the following examples, but the present invention is not limited to the following examples. Various measurements and evaluations of the solar cell module of the present invention equipped with the composite sealing material of the present invention were performed as follows.
(1) Measurement of Tg (° C.) of Glass Transition Temperature The glass transition temperature of the cyclic olefin resin and the EVA resin was measured by a DSC method at a heating rate of 20 ° C./min and a second run.
(2) Water vapor transmission rate (ASTMF1249)
The test was carried out using a water vapor permeation tester (PERMATRAN W3 / 33, manufactured by MOCON) at a temperature of 40 ° C. and a humidity of 90% RH.
As a sample, a back sheet product was used as it was.
(3) Quantification of the amount of acetic acid in the EVA sealing material inside the solar cell module: EVA attached to the silicon cell was manually collected from the center of the solar cell module and quantified by ion chromatography.
(4) delamination (cloudiness) test
With KIKUSUI Co. TOS7210S, in a constant temperature bath, 8 5 ° C., under the conditions of RH 85%, was applied to -1000Vdc 1000 hours.
FIG. 5 shows an electric wiring sequence. The evaluation was performed by the following sensory test method.
The “state without delamination” of the present invention is four or more points.
5 points (highest point): no change in appearance compared to the original 4 points: slight color change (yellowing) around the interconnector.
3 points: White turbid peeling was less than 5 mm in at least one portion of the interconnector portion of the silicon cell.
2 points: cloudiness peeling of at least one portion of the interconnector portion of the silicon cell is 5 mm or more and less than 20 mm.
1 point: cloudiness peeling of at least one part of the interconnector portion of the silicon cell is 20 mm or more.
(5) PID test and leakage current test
With KIKUSUI Co. TOS7210S, in a constant temperature bath, 8 5 ° C., under the conditions of RH 85%, was applied to -1000Vdc 1000 hours. FIG. 5 shows a PID test sequence. The entire surface of the solar cell module is covered with a 20 μm thick aluminum foil (made by UACJ) on the light-receiving surface, and the wiring for the positive application side is attached using the pre-processed mounting holes in the aluminum frame. The test was started after confirming the continuity of the test with a tester.
(6) Simulator test
The power generation performance of the specimen before and after the PID test was measured with a cell tester manufactured by NPC. The test was performed under the conditions of a test temperature of 25 ° C. ± 1 ° C. and an irradiation intensity of 1000 W / square meter.

Claims (3)

  In the superstrate structure of the solar cell module, (A) an ethylene / norbornene random copolymer film having a film thickness of 30 μm to 50 μm is sandwiched between (B) an ethylene vinyl acetate copolymer sheet having a thickness of 200 μm to 500 μm. A solar cell module comprising a back sheet having a water vapor permeability of 1.1 g / day or more and 3.0 g / day by applying a filler (A / B / A) between the cover glass and the crystalline silicon element. And 1000 hours accelerated deterioration test in a constant temperature bath of 85 ° C. and 85% RH with -1000 V applied; solar cell module with zero power generation deterioration rate of 0 to 2% in PID test 2. The solar cell module according to claim 1, wherein the size of the ethylene vinyl acetate copolymer sheet is 3 mm to 8 mm smaller than the outer edge of the cover glass.   The glass transition temperature is 70 ° C. to 82 ° C., and the size of the ethylene / norbornene random copolymer film is cut from the outer periphery of the cover glass by 3 mm to 8 mm smaller than the outer periphery of the cover glass, and the filler ( 2. The solar cell module according to claim 1, wherein the solar cell module is a layer of B).

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