JP2015095593A - Sealing material for solar cell and solar cell module - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a sealing material for solar cell in which both excellent adhesion and electrical characteristics are satisfied, and to provide a solar cell module having excellent PID tolerance in which adhesion failure, e.g., peeling, is less likely to occur.SOLUTION: A sealing material for solar cell contains a sealing resin, a silane coupling agent, and a crosslinking agent, in which the sealing resin has a water contact angle θ of the surface of 80-86°, in a state crosslinked with the crosslinking agent. A solar cell module 10 includes a plurality of solar cells 11, 11, ..., a pair of sealing materials for solar cell 12, 12, a transparent protective material 13, and a back sheet 14.

Description

  The present invention relates to a solar cell sealing material and a solar cell module.

  In a solar cell module, an ethylene-polar group-containing monomer copolymer (ethylene-vinyl acetate copolymer, etc.) excellent in transparency, workability, and crosslinkability, etc. for sealing and fixing solar cells. A sealing material for solar cells (hereinafter also simply referred to as a sealing material) formed of a sealing resin is widely used. In addition, a silane coupling agent is often blended in the sealing material for the purpose of enhancing the adhesiveness with a transparent protective material such as a glass plate disposed on the surface side of the solar cell module or a back sheet. (For example, patent document 1). In particular, when the transparent protective material is a glass plate, the glass plate in which the silane coupling agent is an inorganic substance and the sealing resin that is an organic substance are combined to play an important role in adhesion.

However, the silane coupling agent self-condenses in addition to the reaction with glass to form a silicon resin. Since the silicon resin has low electrical characteristics and causes a decrease in the electrical characteristics of the sealing material itself, as a result, the PID resistance of the solar cell module also decreases.
Since how much silicon resin is formed varies depending on the blending conditions of the silane coupling agent, it is difficult to stably achieve both the adhesion and the electrical characteristics of the sealing material.

JP 2000-174296 A

  The present invention provides a solar cell encapsulant that achieves both excellent adhesion and electrical characteristics, and a solar cell module that is resistant to adhesion failure such as peeling and has excellent PID resistance.

  The solar cell encapsulant of the present invention includes an encapsulating resin, a silane coupling agent, and a crosslinking agent, and the water contact angle of the surface in a state where the encapsulating resin is crosslinked with the crosslinking agent. θ is 80 to 86 °.

  The solar cell module of this invention is equipped with a photovoltaic cell and a pair of sealing material for solar cells of this invention which clamped this photovoltaic cell.

The sealing material for solar cells of the present invention has both excellent adhesion and electrical characteristics.
Moreover, the solar cell module of the present invention is less prone to adhesion failure such as peeling, and has excellent PID resistance.

It is sectional drawing which shows an example of the solar cell module of this invention.

<Encapsulant>
The sealing material of the present invention includes a sealing resin, a silane coupling agent, and a crosslinking agent. Moreover, the sealing material of this invention may also contain other additives other than sealing resin, a silane coupling agent, and a crosslinking agent.

[Resin for sealing]
As the sealing resin, a resin usually used for a sealing material can be used.
As the sealing resin, an ethylene-polar group-containing monomer copolymer is preferable from the viewpoint of excellent transparency, processability, and crosslinkability.
Examples of the polar group include an ester group (—C (O) O—R or R—C (O) O— (wherein R is an alkyl group)), a carboxy group, and the like.

  Specific examples of the monomer having a polar group include, for example, vinyl ester (vinyl acetate and the like), alkyl (meth) acrylate (methyl (meth) acrylate, ethyl (meth) acrylate, propyl (meth) acrylate), Butyl (meth) acrylate), unsaturated carboxylic acid (such as (meth) acrylic acid), anhydride of unsaturated dicarboxylic acid (such as maleic anhydride), ester of unsaturated dicarboxylic acid (monomethyl maleate, dimethyl maleate) Etc.).

  Examples of the ethylene-polar group-containing monomer copolymer include an ethylene-vinyl acetate copolymer (hereinafter also referred to as EVA) and an ethylene- (meth) acrylic acid alkyl ester copolymer from the viewpoint of flexibility and transparency. EVA is preferred, with EVA being particularly preferred.

  The ratio of the monomer unit having a polar group in the ethylene-polar group-containing monomer copolymer is that of all structural units (100% by mass) from the viewpoint of heat resistance, adhesiveness, flexibility, moldability, durability, and insulation. Among these, 10-40 mass% is preferable and 15-30 mass% is more preferable.

The mass average molecular weight of the ethylene-polar group-containing monomer copolymer is preferably 10,000 to 300,000, and more preferably 100,000 to 170,000. If the mass average molecular weight of the ethylene-polar group-containing monomer copolymer is not less than the lower limit, a sealing material having good mechanical properties can be easily obtained. If the mass average molecular weight of the ethylene-polar group-containing monomer copolymer is not more than the above upper limit value, it is easy to obtain a sealing material excellent in processability.
The mass average molecular weight is a value measured using gel permeation chromatography.

Further, as the sealing resin, polyethylene, polypropylene, acrylic resin, or the like may be used.
The sealing resin may be used alone or in combination of two or more.

[Silane coupling agent]
A silane coupling agent plays the role which improves the adhesiveness of a photovoltaic cell, a transparent protective material, a back sheet etc., and a sealing material. As a silane coupling agent, the silane coupling agent normally used for a sealing material can be used.
Specific examples of the silane coupling agent include, for example, vinyltriethoxysilane, vinyltrimethoxysilane, 3-methacryloxypropyltrimethoxysilane, 3-methacryloxypropyltriethoxysilane, 3-glycidoxypropyltrimethoxysilane, Examples include 3-mercaptopropyltrimethoxysilane and allyltrimethoxysilane.

As the silane coupling agent, a silane coupling agent having a trimethoxysilane group is preferable from the viewpoint of adhesive strength, and 3-methacryloxypropyltrimethoxysilane, 3-glycidoxypropyltrimethoxysilane, 3-mercaptopropyltrisilane. Methoxysilane and allyltrimethoxysilane are more preferable.
A silane coupling agent may be used individually by 1 type, and may use 2 or more types together.

[Crosslinking agent]
The crosslinking agent is a component that crosslinks the sealing resin.
Examples of the crosslinking agent include known organic peroxides (peroxyketals, dialkyl peroxides, peroxyesters, etc.), photosensitizers and the like.
A crosslinking agent may be used individually by 1 type, and may use 2 or more types together.

[Other additives]
Examples of other additives include ultraviolet absorbers, light stabilizers, antioxidants, crosslinking aids, pigments, dyes, fillers, and the like. The sealing material of the present invention preferably contains a crosslinking aid.

The crosslinking aid is a compound having one or more (preferably two or more) polymerizable unsaturated groups (vinyl group, allyl group, (meth) acryloxy group, etc.).
Examples of the crosslinking aid include triallyl isocyanurate, triallyl cyanurate, and trimethylolpropane trimethacrylate.
A crosslinking aid may be used individually by 1 type, and may use 2 or more types together.

Examples of the ultraviolet absorber include benzophenone-based ultraviolet absorbers, benzotriazole-based ultraviolet absorbers, and salicylic acid ester-based ultraviolet absorbers.
Examples of the light stabilizer include hindered amine light stabilizers.
Examples of the antioxidant include hindered phenol antioxidants and phosphite antioxidants.

[Ratio of each component]
The content of the silane coupling agent in the sealing material of the present invention is preferably 0.08 to 0.16 parts by mass, and 0.1 to 0.16 parts by mass with respect to 100 parts by mass of the sealing resin. More preferred. If content of a silane coupling agent is more than the said lower limit, the outstanding adhesiveness will be easy to be obtained. When the content of the silane coupling agent is not more than the above upper limit value, excellent electrical characteristics are easily obtained.

  0.1-2.0 mass parts is preferable with respect to 100 mass parts of sealing resin, and, as for content of the crosslinking agent in the sealing material of this invention, 0.2-1.0 mass part is more preferable. . If the content of the crosslinking agent is not less than the lower limit, sufficient crosslinking can be obtained and high heat resistance can be easily obtained. If content of a crosslinking agent is below the said upper limit, discoloration by the residue after heat processing will be suppressed.

  When the sealing material of the present invention contains a crosslinking aid, the amount of the crosslinking aid used is preferably more than 0 parts by mass and less than 5 parts by mass, more than 0 parts by mass and more than 2 parts by mass with respect to 100 parts by mass of the sealing resin. Part or less is more preferable.

[Water contact angle]
The present inventors paid attention to the point that the silicon resin has water repellency when considering obtaining a sealing material having both adhesiveness and electrical characteristics. And it tried to discriminate | determine the mixing | blending conditions of the silane coupling agent which obtains favorable adhesiveness, suppressing the fall of an electrical property on the basis of the water contact angle of the surface in the sealing material after bridge | crosslinking. As a result, if the water contact angle θ of the surface when the sealing resin is cross-linked with a cross-linking agent is within a specific range, it becomes a sealing material that achieves both good adhesion and electrical characteristics. I found it.

In the sealing material of the present invention, the surface water contact angle θ in a state where the sealing resin is crosslinked with a crosslinking agent is 80 to 86 °, and preferably 80 to 84 °. When the water contact angle θ is equal to or greater than the lower limit, a sealing material having excellent adhesiveness can be obtained. When the water contact angle θ is not more than the upper limit value, a sealing material having excellent electrical characteristics can be obtained.
The water contact angle θ is 25 ± 5 in accordance with JIS R 3257 “Wettability test method for substrate glass surface” for the sealing material after the crosslinking treatment by heating at 150 ° C. for 30 minutes. It is a value measured by a sessile drop method in an environment of 50 ° C. and 10% RH.

  The silicon resin produced by the condensation reaction of the silane coupling agent has a smaller volume resistivity value than ethylene-vinyl acetate and a larger water contact angle than ethylene-vinyl acetate. Therefore, the tendency of the value of water contact angle (theta) becoming large by the mixing | blending of a silane coupling is seen.

[thickness]
What is necessary is just to set the thickness of a sealing material suitably according to a solar cell module, and 0.05-1 mm is preferable. When the thickness of the sealing material is set to the lower limit value or more, it becomes easy to seal the solar battery cell. If the thickness of the sealing material is set to the upper limit value or less, the solar cell module can be thinned.

[Method of manufacturing sealing material]
The manufacturing method of the sealing material of the present invention is not particularly limited. For example, a resin composition is prepared by mixing a sealing resin, a silane coupling agent and a crosslinking agent, and other additives used as necessary. After obtaining, the method etc. of forming this resin composition into a sheet | seat are mentioned.
Examples of the sheet forming method include an extrusion molding method using a T die, a press molding method, and the like. Moreover, when making a resin composition into a solution, it can also be formed into a sheet by applying the resin composition to a release sheet and drying.

[Function and effect]
In the sealing material of this invention demonstrated above, favorable adhesiveness and an electrical property are compatible by the water contact angle (theta) of the surface of the sealing material after bridge | crosslinking being in a specific range. Therefore, by using the sealing material of the present invention, it is difficult to cause adhesion failure such as peeling, and a solar cell module having excellent PID resistance can be manufactured.

<Solar cell module>
Hereinafter, an example of the solar cell module of the present invention will be described with reference to FIG.
As shown in FIG. 1, the solar cell module 10 of this embodiment includes a plurality of solar cells 11, 11... And a pair of solar cell sealing materials 12, 12 (hereinafter referred to as a sealing material 12). ), A transparent protective material 13, and a back sheet 14.
The solar battery cell 11 is sandwiched and fixed between a pair of sealing materials 12 and 12. Further, the sealing materials 12 and 12 are disposed between the transparent protective material 13 and the back sheet 14.
The sealing material 12 is the sealing material of the present invention.

[Solar cells]
Examples of the solar battery cell 11 include a pn junction solar battery element having a structure in which a p-type semiconductor and an n-type semiconductor are joined.
Examples of the pn junction solar cell element include silicon (single crystal silicon, polycrystalline silicon, amorphous silicon, etc.), compound (GaAs, CIS, CdTe-CdS) and the like.
In the present embodiment example, the plurality of solar cells 11 are electrically connected in series via a tab string 15 having a conductive wire and a solder joint.

[Transparent protective material]
As the transparent protective material 13, a member usually used for protecting the surface side of the solar cell module can be used, and examples thereof include a glass plate and a resin plate.
As a glass plate, the template glass which formed the unevenness | corrugation in the surface from the point of light transmittance is preferable. As the material of the template glass, white plate glass (high transmission glass) with less iron content is preferable.

[Back sheet]
As the back sheet 14, what is normally used as a back sheet of a solar cell module can be used.
Examples of the material of the back sheet 14 include polyvinyl fluoride, polyester (polyethylene terephthalate, etc.), polyolefin (polyethylene, etc.), glass, metal (aluminum, etc.), and the like.
The backsheet 14 may be a single layer or a multilayer.

[Method for manufacturing solar cell module]
The manufacturing method of the solar cell module of this invention can employ | adopt a well-known manufacturing method except using the sealing material of this invention.
For example, the following method is mentioned as a manufacturing method of the solar cell module 10.
A plurality of solar cells 11, 11... Electrically connected using a tab string 15 are sandwiched between a pair of sealing materials 12, 12, and the sealing materials 12, 12 are further sandwiched between a transparent protective material 13 and a back sheet 14. And pinch. Then, it heats and the sealing materials 12 and 12, the sealing material 12, the transparent protective material 13, and the sealing material 12 and the back sheet | seat 14 are adhere | attached.

  When sealing with the sealing material 12, it heats more than the decomposition temperature of a crosslinking agent. When heated to a temperature equal to or higher than the decomposition temperature of the crosslinking agent, the sealing resin contained in the sealing material 12 is crosslinked by the crosslinking agent, and the durability of the sealing material 12 is improved.

[Function and effect]
Since the solar cell module of the present invention described above uses the sealing material of the present invention having good adhesiveness and electrical characteristics, adhesion failure such as peeling hardly occurs and has excellent PID resistance.
The solar cell module of the present invention is not limited to the solar cell module 10 described above.

EXAMPLES Hereinafter, although an Example demonstrates this invention in detail, this invention is not limited by the following description.
[Compound]
Abbreviations of the compounds used are shown below.
(Resin for sealing)
EVA-1: ethylene-vinyl acetate copolymer (product name “SEETEC VE700”, ratio of vinyl acetate unit: 28% by mass, manufactured by Hunan Petrochemical Co., Ltd.).

(Silane coupling agent)
a-1: 3-Methacryloxypropyltrimethoxysilane (product name “KBM-503”, manufactured by Shin-Etsu Silicone).

(Crosslinking agent)
b-1: t-Butylperoxy-2-ethylhexyl monocarbonate (product name “Kayahexa AD”, manufactured by Kayaku Akzo).

(Crosslinking aid)
c-1: triallyl isocyanurate (product name “TAIC (registered trademark)”, manufactured by Nippon Kasei Co., Ltd.).

(UV absorber)
d-1: 2-hydroxy-4-n-octyloxybenzophenone (product name “Chemisorb 81”, manufactured by BASF Japan Ltd.).

[Example 1]
100 parts by weight of EVA-1, 0.08 parts by weight of silane coupling agent (a-1), 0.5 parts by weight of crosslinking agent (b-1), and 0.5 to 0.5 of crosslinking aid (c-1) Part by mass and 0.2 part by mass of the ultraviolet absorber (d-1) were mixed to obtain a resin composition. The obtained resin composition was made into a sheet by extrusion molding using a single screw extruder to obtain a sealing material.

[Examples 2 to 4]
A sealing material was obtained in the same manner as in Example 1 except that the composition of each component was changed as shown in Table 1.

[Comparative Examples 1-2]
A sealing material was obtained in the same manner as in Example 1 except that the composition of each component was changed as shown in Table 1.

[Water contact angle]
The sealing material obtained in each example was heated in an oven at 150 ° C. for 30 minutes to obtain a crosslinked sealing material. Next, in accordance with JIS R 3257 “Method for testing wettability of substrate glass surface”, water contact of the surface of the cross-linked encapsulant by a sessile drop method in an environment of 25 ± 5 ° C. and 50 ± 10% RH. The angle θ was measured.

[Adhesiveness]
After a 3.2 mm thick white sheet glass (“White glass with grain” manufactured by Asahi Glass Co., Ltd.) is layered on the sealing material obtained in each example to form two layers, and after vacuum deaeration with a laminator at 128 ° C. for 4 minutes And pressure bonding at a pressure of 0.1 MPa for 2 minutes. Subsequently, it was crosslinked by heating at 150 ° C. for 30 minutes. After performing a dump heat test under conditions of 23 ° C. × 85% RH, a 180 ° peel test was performed at 23 ° C. using a 180 ° tensile test apparatus (“AG-5000A” manufactured by Shimadzu Corporation), and the peel strength was (N / cm) was measured. A peel strength of 19 N / cm or less was rejected.

[PID resistance]
Two sheets of sealing material obtained in each example sandwiched one polycrystalline silicon solar cell with a tab string fixed, and these were backed by a glass plate (3.2 mm thick), polyvinyl fluoride and polyester. A laminate was obtained by sandwiching with a sheet. The laminate was put into a resin bag, heated to 128 ° C. using a laminator for manufacturing a solar cell module, and compressed by pressing the inside of the bag for 4 minutes and then pressing for 2 minutes. Next, the compressed laminate was heated at 150 ° C. for 30 minutes using an oven to crosslink the sealing material. Then, the tab string which went out of the module was connected and the solar cell module for a test was obtained.
The power generation amount _{P 1} initial of the test for a solar cell module was measured using a solar simulator (Nisshinbo Mechatronics Co. PVS1114iD).
Next, a voltage of 1000 V was applied for 96 hours between the solar battery cell of the test solar battery module and the back sheet in a room temperature environment. It was then measured power generation amount P ₂ after the test of the solar cell module for testing.
Then, the power generation efficiency retention ratio was obtained from the formula [(power generation amount P ₂ after voltage application / initial power generation amount P ₁ ) × 100]. A power generation efficiency retention rate of 90% or more was considered acceptable.

  Table 1 shows the composition of each component of the sealing material in Examples and Comparative Examples, and the measurement results of the water contact angle θ, the peel strength, and the power generation efficiency retention rate after crosslinking.

As shown in Table 1, the sealing materials of Examples 1 to 4 in which the water contact angle θ of the surface in the state where the sealing resin is crosslinked are in the range of 80 to 86 ° have high peel strength and are bonded. In addition, the electrical characteristics were excellent, the power generation efficiency retention rate when the solar cell module was produced was high, and excellent PID resistance was obtained.
On the other hand, the sealing material of Comparative Example 1 having a surface water contact angle θ of less than 80 ° in the state where the sealing resin was crosslinked had a peel strength of 19 N / cm or less, and the adhesiveness was poor.
The sealing material of Comparative Example 2 having a surface water contact angle θ of more than 86 ° in the state where the sealing resin is cross-linked is inferior in electrical characteristics, and maintains power generation efficiency when a solar cell module is manufactured. The rate was low and the PID resistance was low.

DESCRIPTION OF SYMBOLS 10 Solar cell module 11 Solar cell 12 Solar cell sealing material 13 Transparent protective material 14 Back sheet 15 Tab string

Claims (2)

  A solar cell comprising a sealing resin, a silane coupling agent, and a crosslinking agent, wherein the surface water contact angle θ is 80 to 86 ° in a state where the sealing resin is crosslinked with the crosslinking agent. Sealing material.   A solar cell module comprising a solar cell and a pair of solar cell encapsulants according to claim 1 sandwiching the solar cell.

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