Solar Cell Module

Abstract

To provide a solar cell module that has improved durability against a high-temperature and high-humidity environment.SOLUTION: A solar cell module has a solar battery cell, a sealant, and a translucent substrate. The sealant is located on the solar battery cell. The translucent substrate is located on the sealant. The sealant has a main agent, an acid acceptor as a first additive, and an isocyanurate component as a second additive. A loss coefficient of an inner layer part of the sealant separated from the translucent substrate is less than 0.13.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a solar cell module.

Background Art

[0002] A solar cell module is configured by sealing solar cells with a sealing material (see, for example, the descriptions in Patent Document 1 and Patent Document 2).

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0004] There is room for improvement in the durability of a solar cell module against high-temperature and high-humidity environments.

Means for Solving the Problems

[0005] A solar cell module according to an embodiment of the present disclosure includes a solar cell, a sealing material located on the solar cell, and a light-transmissive substrate located on the sealing material. The sealing material includes a main agent, an acid acceptor as a first additive, and an isocyanurate component as a second additive, and a loss coefficient of an inner layer portion of the sealing material away from the light-transmissive substrate is less than 0.13. Based on the attenuation curves obtained by the CPMG method using a TD-NMR device, the T of component 1, which is the component with the highest abundance ratio, was determined for the encapsulating material. 2 The relaxation time is less than 2.08 msec. .

[0006] Also, a solar cell module according to an embodiment of the present disclosure includes a solar cell, a sealing material located on the solar cell, and a light-transmitting substrate located on the sealing material, the sealing material including a base material, a metal hydroxide as a first additive, and an isocyanurate component as a second additive, and a loss coefficient of an inner layer portion of the sealing material away from the light-transmitting substrate is less than 0.13. Based on the attenuation curves obtained by the CPMG method using a TD-NMR device, the T of component 1, which is the component with the highest abundance ratio, was determined for the encapsulating material. 2 The relaxation time is less than 2.08 msec. do.

[0007] Also, a solar cell module according to an embodiment of the present disclosure includes a solar cell, a sealing material located on the solar cell, and a light-transmitting substrate located on the sealing material, the sealing material including a base material, a metal oxide as a first additive, and an isocyanurate component as a second additive, and a loss coefficient of an inner layer portion of the sealing material away from the light-transmitting substrate is less than 0.13. Based on the attenuation curves obtained by the CPMG method using a TD-NMR device, the T of component 1, which is the component with the highest abundance ratio, was determined for the encapsulating material. 2 The relaxation time is less than 2.08 msec. do.

[0008] Also, a solar cell module according to an embodiment of the present disclosure includes a solar cell, a sealing material located on the solar cell, and a light-transmitting substrate located on the sealing material, the sealing material including a base material, a carbonate as a first additive, and an isocyanurate component as a second additive, and a loss coefficient of an inner layer portion of the sealing material away from the light-transmitting substrate is less than 0.13. Based on the attenuation curves obtained by the CPMG method using a TD-NMR device, the T of component 1, which is the component with the highest abundance ratio, was determined for the encapsulating material. 2 The relaxation time is less than 2.08 msec. do. Effect of the Invention

[0009] The solar cell module according to one embodiment is not easily deteriorated even when installed in a high-temperature and high-humidity environment. [Brief description of the drawings]

[0010] [Figure 1] FIG. 1 is a drawing showing a schematic diagram of an example of a solar cell module according to one embodiment of the present disclosure, in which FIG. 1(a) is a plan view of the solar cell module seen from the light-receiving surface side, and FIG. 1(b) is a cross-sectional view taken along line AA in FIG. 1(a). [Diagram 2] FIG. 2 is an exploded perspective view of a solar cell module according to one embodiment of the present disclosure, in which FIG. 2(a) is a perspective view showing a solar cell group formed by connecting a plurality of solar cells with an interconnector and connection wiring, and FIG. 2(b) is an exploded perspective view illustrating the stacked state of a module stack consisting of a translucent substrate, a first sealing material, a solar cell group, a second sealing material, and a rear surface protective material. [Diagram 3] FIG. 3 is a diagram showing the lamination process of a method for manufacturing a solar cell module according to one embodiment of the present disclosure, in which FIG. 3(a) is a schematic diagram showing how a module stack is placed in a laminator, and FIG. 3(b) is a schematic diagram showing how the module stack is pressed in the laminator. [Figure 4] FIG. 4 is a diagram showing the relationship between time and temperature in the crosslinking step in the method for producing a solar cell module according to the present disclosure. [Diagram 5] FIG. 5 is a diagram showing, using structural formulas, how the sealing material is peeled off from the light-transmitting substrate in the solar cell module. [Figure 6] FIG. 6 is a model diagram showing FT-IR imaging of an isocyanurate component measured using an FT-IR device in an embodiment of a solar cell module according to the present disclosure. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0011] In general, a sealing material containing an ethylene-vinyl acetate copolymer as a main agent is used in a solar cell module. Ethylene-vinyl acetate copolymer has a drawback in that acetic acid generated by hydrolysis corrodes and damages solar cells and the like. Specifically, acetic acid generated by hydrolysis may corrode the contact glass layer between the electrode of the solar cell and the semiconductor silicon. Therefore, a solar cell module using an ethylene-vinyl acetate copolymer may cause insulation failure when used in a high-temperature environment, and the power generation performance of the solar cell module may be reduced. Therefore, a technology is known in which an acid acceptor (Mg(OH)2) is added to the sealing material to neutralize acetic acid, thereby reducing the corrosion damage of the contact glass layer between the electrode of the solar cell and the semiconductor silicon (see Patent Document 1). In addition, a technology is known in which a crosslinking assistant such as triallyl isocyanurate is added to the sealing material to increase the volume resistivity of the sealing material, suppress the occurrence of insulation failure, and reduce the decrease in the power generation performance of the solar cell module (see Patent Document 2).

[0012] However, when a solar cell module is installed in a high-temperature and high-humidity environment where moist heat stress is relatively strong, it is known that the encapsulant containing an acid acceptor generates hydroxide ions (OH-) as the acid acceptor ionizes in the presence of moisture. When there is an excess of these hydroxide ions (OH-), the bonds of the polymers that make up the encapsulant are broken (basic hydrolysis reaction). This reduces the adhesive strength of the encapsulant. Therefore, if the breakage of these polymer bonds occurs near the adhesive interface between the light-transmitting substrate of the solar cell module and the encapsulant, the adhesive strength is reduced, and there is a risk that the encapsulant will peel off from the light-transmitting substrate.

[0013] In the future, when solar cell modules are installed in hot and humid environments such as tropical and subtropical regions such as Southeast Asia and India, solar cell modules that are less susceptible to peeling will be required.

[0014] Therefore, the inventor of the present disclosure has created a technology related to a solar cell module whose adhesive strength is unlikely to decrease in a high-temperature and high-humidity environment. An example of an embodiment of a solar cell module according to one aspect of the present disclosure will be described in detail below with reference to the drawings. Note that the drawings are schematic, and therefore the dimensional ratios and positional relationships of each component in the drawings are not necessarily accurate.

[0015] <<Solar cell module configuration>> A solar cell module X according to an embodiment of the present disclosure will be described with reference to Fig. 1 and Fig. 2. In the following, in the normal direction to the main surface of the solar cell module X, the side that mainly receives light will be referred to as the light-receiving surface side, and the side behind the light-receiving surface side will be referred to as the back surface side.

[0016] A solar cell module X according to one embodiment of the present disclosure is configured by sequentially stacking a light-transmitting substrate 1, a first sealing material 2a, solar cells 3 electrically connected to each other by interconnectors 5 and connection wiring 6, a second sealing material 2b, and a back surface protection material 4.

[0017] The solar cell module X includes, for example, a terminal box 7 for extracting the power generated by the solar cell 3 to the outside on the outside of the rear surface protective material 4. The solar cell module X may also include, for example, a frame 8 for protecting the outer periphery of the solar cell module X.

[0018] In a solar cell module X according to one embodiment of the present disclosure, a plurality of solar cells 3 are electrically connected to each other via interconnectors 5 and connection wiring 6 to form a solar cell group 11. As an alternative embodiment, the solar cell group 11 may be replaced by a single large-area solar cell.

[0019] Next, each of the components constituting the solar cell module X of this embodiment will be described.

[0020] <Transparent substrate> The light-transmitting substrate 1 can protect the light-receiving surface side of the solar cell 3 from water, for example. The light-transmitting substrate 1 may have light-transmitting properties for light of a specific range of wavelengths. The specific range of wavelengths may be, for example, the wavelength of light that the solar cell 3 can convert photoelectrically. The material of such a light-transmitting substrate 1 may be, for example, a hard substrate having light-transmitting properties. The hard substrate having light-transmitting properties may be, for example, glass or a transparent synthetic resin. As the glass, for example, blue plate glass (soda-lime glass), white plate glass obtained by removing iron from blue plate glass, or hard glass may be used. In addition, as the transparent synthetic resin, a transparent polycarbonate resin or a transparent acrylic resin may be used. The light-transmitting substrate 1 has a light-receiving surface where light is mainly incident, and a back surface to which the first sealing material 2a is bonded. The shape of the light-transmitting substrate 1 is not limited to a flat plate shape, and may be a shape having a curved surface according to the application. The thickness of such a light-transmitting substrate 1 may be, for example, about 3 mm in the case of glass, and may be, for example, about 5 mm in the case of synthetic resin.

[0021] <Sealing material> The sealing material 2 includes a first sealing material 2a and a second sealing material 2b. Hereinafter, the first sealing material 2a and the second sealing material 2b are collectively referred to as the sealing material 2. The first sealing material 2a is located between the light-transmitting substrate 1 and the solar cell group 11, and the second sealing material 2b is located between the solar cell group 11 and the back surface protection material 4. The first sealing material 2a protects the light-receiving surface side of the solar cell group 11, and the second sealing material 2b protects the back surface side of the solar cell group 11. The first sealing material 2a is in contact with the second sealing material 2b, and bonds the light-transmitting substrate 1 and the solar cell group 11. The second sealing material 2b bonds the solar cell group 11 and the back surface protection material 4.

[0022] The first sealing material 2a and the second sealing material 2b are stacked with the solar cell group 11 and other members, and are heated and pressed under reduced pressure by a laminating device, so that they are fused and integrated with the solar cell group 11 and other members. The first sealing material 2a has translucency for light of a specific wavelength. Therefore, light irradiated to the light receiving surface side of the solar cell module X can be transmitted through the translucent substrate 1 and the first sealing material 2a and enter the solar cell group 11. The second sealing material 2b may have translucency for light of a specific wavelength, or may not have translucency for light of a specific wavelength. When the second sealing material 2b does not have translucency for light of a specific wavelength, for example, the second sealing material 2b may have a pigment. In other words, the second sealing material 2b may be colored. For such first sealing material 2a and second sealing material 2b, for example, a flexible sheet-like member can be adopted. In addition, the first sealing material 2a and the second sealing material 2b may have different thicknesses. The first sealing material 2a and the second sealing material 2b may have a thickness of, for example, about 0.4 to 1 mm.

[0023] In the following, the interface formed by the adhesion between the light-transmitting substrate 1 and the first seal 2a will be referred to as the adhesive interface 10, the portion of the first sealant 2a near the adhesive interface 10 will be referred to as the adhesive portion 2a1 or the surface layer portion 2a1, and the portion farther from the light-transmitting substrate 1 than the adhesive portion 2a1 will be referred to as the inner layer portion 2a2.

[0024] <Sealant composition> The encapsulant 2 includes a base material, a first additive, a second additive, and a third additive. Each component of the encapsulant 2 will be described in detail below.

[0025] (Base material: ethylene-vinyl acetate copolymer) The main component of the encapsulant 2 may be, for example, an ethylene-vinyl acetate copolymer. Here, the term "mainly made of ethylene-vinyl acetate copolymer" means that the encapsulant 2 contains 50 parts by weight or more and 100 parts by weight or less of ethylene-vinyl acetate copolymer in 100 parts by weight of all components. The encapsulant 2 has an increased flexibility by using ethylene-vinyl acetate copolymer as the main component. This protects the solar cell 3 from load and impact applied to the solar cell module X. The melting point of such an ethylene-vinyl acetate copolymer may be around 60°C. The content of the ethylene-vinyl acetate copolymer in the encapsulant 2 may be, for example, 70 parts by weight or more and 99.5 parts by weight or less, or may be, for example, 90 parts by weight or more and 99 parts by weight or less.

[0026] (First additive: acid acceptor) The first additive is an acid acceptor. The acid acceptor may contain at least one of metal hydroxides, metal oxides, and carbonates. The metal hydroxide may be, for example, magnesium hydroxide, calcium hydroxide, barium hydroxide, aluminum hydroxide, iron hydroxide, etc. The metal oxide may be, for example, magnesium oxide, calcium oxide, aluminum oxide, zinc oxide, etc., and the carbonate may be, for example, magnesium carbonate, calcium carbonate, barium carbonate, etc. For example, by using magnesium hydroxide as the metal hydroxide, magnesium oxide as the metal oxide, and calcium carbonate as the carbonate, it is possible to make it difficult for rust to occur on the conductors and electrodes inside the solar cell module. Since the sealing material 2 has the first additive, the first additive can neutralize acetic acid generated by hydrolysis or the like from the ethylene-vinyl acetate copolymer in the solar cell module X. As a result, the solar cell module X can be reduced in occurrence of corrosion damage caused by acid. When the content of the main agent is 100 parts by weight, the content of the acid acceptor may be, for example, 0.05 to 2 parts by weight.

[0027] (Second additive: isocyanurate component) The second additive is a crosslinking aid. The crosslinking aid may have, for example, a radical polymerizable group as a functional group. For example, a trifunctional isocyanurate-based crosslinking aid may be used as the crosslinking aid. Such a crosslinking aid is referred to as an isocyanurate component in the present disclosure. The isocyanurate component may be, for example, triallyl isocyanurate, tris[(meth)acryloyloxyethyl]isocyanurate, or the like. The crosslinking temperature of the second additive may be, for example, higher than the melting point of the ethylene-vinyl acetate copolymer, which is the main agent. More specifically, the crosslinking temperature of the second additive may be, for example, around 170°C.

[0028] It is known that the isocyanurate component has a low degree of freedom of deformation after crosslinking due to the nitrogen contained in the composition. Therefore, while the isocyanurate component can reduce the water permeability of the sealing material 2, there is a risk of reducing the flexibility of the sealing material 2 as the amount of the isocyanurate component added to the sealing material 2 increases. Therefore, when the content of the main agent is taken as 100 parts by weight, the content of the isocyanurate component may be, for example, 0.2 to 3 parts by weight. This allows the sealing material 2 to protect the solar cell 3 from load and impact while maintaining the flexibility of the sealing material 2.

[0029] (Third additive (meth)acrylate component) The third additive is a (meth)acrylate component. In the present disclosure, the term "(meth)acrylate component" refers to at least one of acrylate and methacrylate.

[0030] The (meth)acrylate component may be, for example, a polyfunctional acrylate crosslinking aid. In other words, the polyfunctional acrylate crosslinking aid is a polyfunctional acrylate compound that is a monomer having a plurality of acryloyl groups in the molecule. More specifically, the polyfunctional acrylate crosslinking aid may be, for example, trimethylolpropane tri(meth)acrylate, pentaerythritol tri(meth)acrylate, dimethylolpropane tetra(meth)acrylate, pentaerythritol tetra(meth)acrylate, pentaerythritol ethoxy tetra(meth)acrylate, dipentaerythritol penta(meth)acrylate, dipentaerythritol hexa(meth)acrylate, etc.

[0031] The crosslinking temperature of the third additive may be higher than the melting point of the ethylene-vinyl acetate copolymer, which is the main component, and lower than the crosslinking temperature of the isocyanurate component, which is the second additive. More specifically, the crosslinking temperature of the third additive may be, for example, around 125°C.

[0032] The (meth)acrylate component is a material that is difficult to dissolve in ethylene-vinyl acetate copolymer. Therefore, when the content of the main agent is 100 parts by weight, the content of the (meth)acrylate component may be, for example, 0.2 to 1.0 parts by weight. This makes it easier for the (meth)acrylate component, which is the third additive, to dissolve in the sealing material 2.

[0033] The compounding ratio of the second additive to the third additive can be, for example, in the range of 10:90 to 90:10.

[0034] (Other additives) The composition of the present disclosure is not limited to the above-mentioned main agent, first additive, second additive, and third additive. That is, various physical properties, such as mechanical strength, adhesiveness, optical properties such as transparency, heat resistance, light resistance, crosslinking speed, etc., may be improved or adjusted within a range that does not impair the effects of the present disclosure. Therefore, the composition of the present disclosure may contain various additives such as adhesion improvers (silane coupling agents, etc.), plasticizers, ultraviolet absorbers, light stabilizers, anti-aging agents, acryloxy group-containing compounds, methacryloxy group-containing compounds, and / or epoxy group-containing compounds, as necessary.

[0035] <Solar cell group> The solar cell group 11 has a function of converting incident sunlight into electricity. The solar cell group 11 in this embodiment is formed by electrically connecting a plurality of solar cells 3 with an interconnector 5 and a connection wiring 6. As the solar cell 3, a crystalline solar cell or a thin-film solar cell can be adopted. In the example of FIG. 1 and FIG. 2, a crystalline solar cell 3 is adopted as the solar cell 3. In the case of the crystalline solar cell 3, for example, a solar cell having a substrate of monocrystalline or polycrystalline semiconductor silicon with a thickness of about 0.1 to 0.4 mm can be used. A pn ​​junction is formed inside such a solar cell 3. Then, electrodes are provided on the light-receiving surface and the back surface of the solar cell 3, respectively, and further, an anti-reflection film may be provided on the light-receiving surface of the solar cell 3. The size of the solar cell 3 is about 150 to 220 mm square if it is a crystalline solar cell 3. Such solar cells 3 are electrically connected in series or in parallel by the interconnector 5 and the connection wiring 6 to constitute the solar cell group 11.

[0036] <Backside protection material> The back surface protective material 4 is positioned opposite the light-transmitting substrate 1. A solar cell group 11 sealed with a sealing material 2 is positioned in the region between the light-transmitting substrate 1 and the back surface protective material 4. Therefore, the back surface protective material 4 can protect the back surface side of the solar cell group 11. In addition, the back surface protective material 4 can reduce the intrusion of moisture from the back surface side into the solar cell 3, the first sealing material 2a, and the second sealing material 2b. The back surface protective material 4 may or may not be transparent to light of a specific wavelength range, for example.

[0037] For example, a plate-like member or a flexible sheet-like member is adopted as the back surface protective material 4. For example, the same material as the light-transmitting substrate 1 may be used as the back surface protective material 4, and specifically, a polyethylene terephthalate (PET) sheet, a polyethylene naphthalate (PEN) sheet, a polyvinyl fluoride (PVF) sheet, a laminate of these sheets, a weather-resistant fluorine-based resin sheet sandwiched with aluminum foil, or a polyethylene terephthalate (PET) sheet on which alumina or silica is vapor-deposited may be used.

[0038] <Interconnectors and connection wiring> The interconnector 5 and the connection wiring 6 have the function of electrically connecting the solar cells 3 to each other. There are no particular limitations on the shape, material, etc. of such interconnector 5 and connection wiring 6, but for example, a strip of copper foil with a thickness of about 0.1 mm and a width of about 1 mm to 6 mm may be entirely solder-coated, cut to a predetermined length, and soldered onto the electrodes of the solar cells 3, etc.

[0039] <Terminal box> The terminal box 7 can, for example, extract to the outside the output obtained by the solar cell 3. As the terminal box 7, for example, one having a box body made of modified polyphenylene ether (modified PPE) resin or polyphenylene oxide (PPO) resin, a terminal plate disposed within the box body, and an output cable that leads out electric power to the outside of the box body is adopted.

[0040] <frame> Frame 8 may be made of aluminum alloy or plastic and have a fitting portion that is shaped to sandwich the light-receiving surface side of light-transmitting substrate 1 and the back surface side of back surface protection material 4 .

[0041] <<Solar cell module manufacturing method>> Next, a method for manufacturing the solar cell module X of the present disclosure will be described with reference to Figures 2 to 4. The method for manufacturing the solar cell module X includes a preparation step, a lamination step, and a cross-linking step, in that order.

[0042] <Preparation process> First, as shown in Fig. 2, a solar cell group 11 is formed by integrating solar cells 3 with interconnectors 5 and connection wiring 6. Then, a first encapsulant 2a, the solar cell group 11, a second encapsulant 2b, and a back surface protection material 4 are stacked in this order on a light-transmitting substrate 1 to form a module laminate 9.

[0043] <Lamination process> As shown in FIG. 3(a), the module stack 9 is placed on the heating plate 22 in the lower housing 21a of the laminator 20 with the light-transmitting substrate 1 facing down, and the upper housing 21b is lowered toward the lower housing 21a to close the housing 21.

[0044] Next, as shown in FIG. 3(b), the module stack 9 is heated and pressurized to a temperature equal to or higher than the melting point temperature of the first sealing material 2a and the second sealing material 2b. More specifically, the module stack 9 is heated for about 10 to 15 minutes in a reduced pressure atmosphere of about 50 to 400 Pa at a temperature equal to or higher than the melting point of the main agent of the first sealing material 2a and the second sealing material 2b and lower than the exothermic peak temperature exhibited by the polymerization reaction of the second additive and the third additive (for example, about 95°C to 105°C), while the entire module stack 9 is pressed as uniformly as possible by the diaphragm 23 at about 10 to 100 KPa, thereby softening the first sealing material 2a and the second sealing material 2b and bonding them to other members to integrate the members constituting the module stack 9. The exothermic peak temperature exhibited by the polymerization reaction of the crosslinking auxiliary can be obtained, for example, by differential scanning calorimetry (DSC).

[0045] <Crosslinking process> After the above lamination process, the pressure inside the housing 21 of the laminator 20 is returned to atmospheric pressure. The laminated module stack 9 is transferred to a crosslinking furnace and heated until the degree of crosslinking of the sealing material 2 reaches at least 80%. The crosslinking furnace heats the module stack 9 to crosslink the sealing material 2, and a conventionally known heating device such as a hot air heating furnace or an infrared heating furnace can be used. The laminator 20 may be substituted for the crosslinking furnace by continuing to increase the temperature inside the laminator 20.

[0046] The rate of the crosslinking reaction of the crosslinking coagent is temperature dependent, and the higher the temperature, the faster the reaction proceeds. Also, the temperature range in which the crosslinking reaction proceeds varies depending on the type of crosslinking coagent. Therefore, by controlling the temperature and time in the crosslinking process, the concentration distribution of the second additive after crosslinking can be adjusted more efficiently.

[0047] This method is described below.

[0048] The crosslinking reaction of the second additive, the isocyanurate component, starts at a temperature of about 150°C to 155°C, and the crosslinking reaction is most intense at a temperature of about 165°C to 175°C.

[0049] The crosslinking initiation temperature of the (meth)acrylate component which is the third additive is about 105°C to 110°C, and the temperature at which the crosslinking reaction rate is strongest is about 120°C to 130°C.

[0050] Hereinafter, among the temperatures to which the module laminate 9 is heated in the crosslinking step, a temperature in the range of 150°C to 155°C will also be referred to as the initiation temperature of the crosslinking reaction of the isocyanurate component, and a temperature in the range of 105°C to 110°C will also be referred to as the crosslinking initiation temperature of the (meth)acrylate component.

[0051] The temperature at which the second additive starts crosslinking is the temperature at which heat begins to be generated by the polymerization reaction of the second additive in a graph showing the relationship between temperature and heat obtained by differential scanning calorimetry (DSC). The temperature at which the crosslinking reaction of the second additive occurs most strongly is the temperature at which the heat generated by the polymerization reaction of the second additive is the largest in a graph showing the relationship between temperature and heat obtained by differential scanning calorimetry (DSC). In other words, the temperature at which the crosslinking reaction of the second additive occurs most strongly is the peak temperature at which the heat generated by the heat generated by the polymerization reaction of the second additive reaches a peak.

[0052] The temperature at which the third additive starts crosslinking is the temperature at which heat begins to be generated by the polymerization reaction of the third additive in a graph showing the relationship between temperature and heat obtained by differential scanning calorimetry (DSC). The temperature at which the crosslinking reaction of the third additive occurs most strongly is the temperature at which the heat generated by the polymerization reaction of the third additive is the largest in a graph showing the relationship between temperature and heat obtained by differential scanning calorimetry (DSC). In other words, the temperature at which the crosslinking reaction of the third additive occurs most strongly is the peak temperature at which the heat generated by the polymerization reaction of the third additive reaches a peak.

[0053] The crosslinking process consists of a first half, a middle half and a second half, which will be described below.

[0054] The first half is a process of heating to a crosslinking initiation temperature of the (meth)acrylate component, which is the third additive. Since the first sealing material 2a and the second sealing material 2b are heated to a temperature higher than the melting point of the ethylene-vinyl acetate copolymer, which is the main agent, the polymers such as the second additive and the third additive are in a state where they can move in the sealing material 2. The temperature rise rate in the first half is higher than the temperature rise rates in the middle and latter half, which will be described later. For example, the temperature rise rate in the first half may be set to 0.6 to 1.0°C / sec. Since the temperature in the first half of the crosslinking process is lower than the temperature at which the polymerization reaction of the isocyanurate component, which is the second additive, and the (meth)acrylate component, which is the third additive, begins, the time required for the crosslinking process can be shortened by increasing the temperature rise rate in the first half without affecting the crosslinking of the second additive and the third additive.

[0055] The intermediate portion is a step of increasing the temperature from the crosslinking initiation temperature of the (meth)acrylate component, which is the third additive, to the crosslinking initiation temperature of the isocyanurate component, which is the second additive. In the intermediate portion, the (meth)acrylate component, which is the third additive, starts a crosslinking reaction, and a crosslinked network structure formed by the crosslinking of the (meth)acrylate component, which is the third additive, is formed accordingly. This makes it difficult for the second additive (isocyanurate) to move. The temperature increase rate of such an intermediate portion is preferably smaller than the temperature increase rate of the first half portion and larger than the temperature increase rate of the second half portion described below. In other words, the temperature increase rate in the temperature range between the crosslinking initiation temperature of the second additive and the crosslinking initiation temperature of the third additive in the crosslinking step may be smaller than the temperature increase rate of the first half portion. By increasing the temperature increase rate of the intermediate portion larger than the second half rate, a crosslinked network structure of the (meth)acrylate component, which is the third additive, is formed at an earlier stage than the isocyanurate component, which is the second additive, starts to move due to crosslinking shrinkage, and the movement of the second additive can be reduced. Specifically, for example, the temperature rise rate in the intermediate portion may be about 0.2 to 0.4° C. / sec, and the time may be about 110 to 220 seconds.

[0056] The latter part is a process of heating in the range of 155°C or more, which is the crosslinking initiation temperature of the isocyanurate component, the second additive. Through the latter part, the crosslinking of the second additive and the third additive progresses further, and the degree of crosslinking of the encapsulant 2 can be increased to 80% or more. In the latter part, the isocyanurate component, the second additive, starts crosslinking and starts linking multiple molecules by chemical covalent bonds. The crosslinking reaction at this time causes a phenomenon called crosslinking shrinkage, in which the distance between the molecules constituting the isocyanurate component, the second additive, tends to decrease. When this phenomenon occurs, the molecules constituting the isocyanurate component, the second additive, tend to be drawn and gathered from the interface between the first encapsulant 2a and the light-transmitting substrate 1 toward the inside of the first encapsulant 2a, so that the concentration becomes low in the surface layer 2a1 of the first encapsulant 2a and the concentration becomes high in the inner layer 2a2. A similar phenomenon also occurs between the second encapsulant 2b and the back surface protective material 4. That is, the molecules constituting the isocyanurate component have a low concentration in the surface layer portion of the second sealing material 2b that contacts the interface between the two materials, and a high concentration in the inner layer portion away from the interface.

[0057] However, as described above, the (meth)acrylate component, which is the third additive, starts crosslinking first to form a crosslinked network structure, so that the molecules of the isocyanurate component, which is the second additive, are less likely to move. This makes it possible to reduce the decrease in concentration of the isocyanurate component, which is the second additive, in the surface layer portion 2a1 of the first sealing material 2a that contacts the adhesive interface 10 between the first sealing material 2a and the light-transmitting substrate 1. Similarly, it is possible to reduce the decrease in concentration of the isocyanurate component, which is the second additive, in the surface layer portion of the second sealing material 2b that contacts the adhesive interface 10 between the second sealing material 2b and the back surface protective material 4.

[0058] The heating rate in the latter part may be lower than that in the former part and the middle part. By lowering the heating rate, the temperature of the module stack 9 can be gradually brought closer to the temperature of the heating plate 22 over time, so that the sealing material 2 is less likely to locally foam due to an excessively high temperature of the heating plate 22. Specifically, for example, the heating rate in the latter part may be 0.05 to 0.1°C / sec. In addition, in order to sufficiently polymerize the isocyanurate component as the second additive and the (meth)acrylate component as the third additive to increase the degree of crosslinking of the sealing material 2, the heating time in the latter part may be longer than that in the middle part. Specifically, for example, it may be 200 seconds or more.

[0059] In addition, if there is a difference in the temperature rise rate among the first half, the middle half, and the second half, the temperature rise rates in the first half, the middle half, and the second half may be compared by taking the average temperature rise rate in the first half, the middle half, and the second half, respectively.

[0060] <Action and Effects> According to this embodiment, it is possible to provide a solar cell module X that reduces the decrease in adhesive strength of the sealing material 2 caused by moist heat and has improved reliability. The operation and effects of this will be described below.

[0061] When the solar cell module has a sealing material 2 mainly composed of an ethylene-vinyl acetate copolymer, there is a risk that acetic acid generated by hydrolysis of the sealing material 2 may corrode the solar cell group 11. Therefore, in order to neutralize the acetic acid generated from the sealing material 2 or to reduce the increase in the generation of acetic acid itself, a first additive that functions as an acid acceptor is added.

[0062] However, when the first additive is added, there is a risk that hydroxide ions generated from the first additive due to excessive moist heat may easily deteriorate the adhesive strength between the light-transmitting substrate 1 and the first sealing material 2a, and may also deteriorate the adhesive strength between the second sealing material 2b and the back surface protection material 4.

[0063] Thus, in addition to measures to reduce the possibility of corrosion occurring due to the generation of acetic acid from the sealing material 2, measures to reduce deterioration caused by the acid acceptor of the sealing material 2 itself are required.

[0064] The mechanism by which the adhesive strength of the sealing material 2 is deteriorated due to the acid acceptor and the countermeasures therefor will be described in detail below.

[0065] First, regarding the humidity stress, the vicinity of the adhesive interface 10 between the adherend, the light-transmitting substrate 1, and the adhesive, the sealant 2, i.e., the surface layer of the sealant 2, is a portion that is more susceptible to moisture penetration than other portions. When moisture penetrates, the metal hydroxide (magnesium hydroxide, etc.) that is the first additive obtains moisture, ionizes, and generates hydroxide ions (OH-), and the surface layer of the sealant 2 near the adhesive interface 10 between the light-transmitting substrate 1 and the first sealant 2a becomes basic. Then, at the position of the BB line shown in FIG. 5, the hydroxide ions generated from the metal hydroxide cut the ester bond in the first sealant 2a by a basic hydrolysis reaction. When the ester bond is cut, the adhesive portion (surface layer) 2a1 between the first sealant 2a and the light-transmitting substrate 1 deteriorates, and moisture becomes more likely to penetrate from the adhesive interface 10. As a result, the deterioration of the adhesive portion (surface layer) 2a1 progresses further, and the adhesive strength decreases.

[0066] Next, the mechanism of deterioration of the encapsulant 2 caused by temperature difference stress will be described. Since the adhesive interface 10 between the light-transmitting substrate 1 and the first encapsulant 2a is a joint between materials with different thermal expansion coefficients, thermal stress is repeatedly generated at the adhesive interface 10 due to temperature changes in the natural environment. As a result, the adhesive portion 2a1 of the first encapsulant 2a undergoes repeated shear deformation. From a more microscopic perspective, the first encapsulant 2a has a three-dimensional mesh-like molecular structure in which chain polymers are polymerized and bonded together by crosslinking. The adhesive portion (surface layer) 2a1 of the first encapsulant 2a is repeatedly subjected to mechanical stress associated with shear deformation, which causes fatigue deterioration (bond scission) of the adhesive molecules (silane coupling agent, etc.), and the adhesive strength of the first encapsulant 2a to the light-transmitting substrate 1 decreases.

[0067] Next, a method for preventing deterioration of the adhesive strength between the light-transmitting substrate 1 and the sealing material 2 in the solar cell module X will be described.

[0068] The first sealing material 2a of the solar cell module X has an isocyanurate component as a second additive. The crosslinked structure formed by the isocyanurate component after crosslinking has a molecular structure with low degree of freedom of deformation (rigid) and high crosslinking density because the isocyanurate component has nitrogen atoms in its molecular chain, and has the advantage of being able to reduce moisture penetration. Reducing moisture penetration reduces the scission of ester bonds due to hydrolysis in the first sealing material 2a, which leads to reduced deterioration of adhesive strength.

[0069] However, since the crosslinked structure formed by the isocyanurate component is rigid and highly brittle, if the amount of the isocyanurate component added to the sealing material is excessively increased, the rigidity of the entire sealing material increases, and the deformation resistance of the first sealing material 2a increases. In other words, the viscoelastic effect decreases, and the consumption of shear stress (shear momentum) in the entire sealing material 2 when stress is applied to the sealing material 2 decreases. Then, when the solar cell module X is exposed to a temperature change (temperature difference stress), the thermal stress generated at the adhesive interface 10 between the translucent substrate 1 and the first sealing material 2a increases, and the transfer rate of the thermal stress to the adhesive interface 10 increases. As a result, the adhesive portion 2a1 is easily deteriorated and peeled off. In this way, if the amount of the isocyanurate component added as the second additive is simply increased, the storage modulus becomes too high in exchange for reducing the deterioration of the adhesive strength caused by the hydrolysis of the first sealing material 2a, and the viscous properties become insufficient, which may impair durability against temperature changes.

[0070] Furthermore, since the isocyanurate component as the second additive has a property of shrinking during crosslinking, the isocyanurate component has a property of easily moving in the softened base material from the adhesive portion (surface layer portion) 2a1 of the first sealing material 2a toward the inner layer side 2a2. Therefore, the effect of adding the isocyanurate component to the first sealing material 2a may be difficult to obtain.

[0071] Therefore, in order to utilize the advantages of the isocyanurate component while reducing its disadvantages, it is important to intentionally distribute the isocyanurate component in the first sealing material 2a in a region that is useful for reducing deterioration in adhesive strength. Therefore, in the solar cell module X, many crosslinked structures of the isocyanurate component are disposed in the adhesive portion (surface layer portion) 2a1 of the first sealing material 2a near the adhesive interface 10 between the light-transmitting substrate 1 and the first sealing material 2a, thereby reducing deterioration in adhesive strength between the light-transmitting substrate 1 and the first sealing material 2a.

[0072] Specifically, by utilizing the property of the (meth)acrylate component as the third additive to crosslink at a lower temperature than the isocyanurate component as the second additive, it is possible to induce the crosslinked structure of the isocyanurate component as the second additive to be formed more in the adhesive portion (surface layer portion) 2a1 in contact with the adhesive interface 10. Since the (meth)acrylate component as the third additive has the property of crosslinking at a lower temperature than the isocyanurate component as the second additive, when the solar cell module X is heated in the crosslinking step, the (meth)acrylate component polymerizes at an earlier timing than the isocyanurate component to form a crosslinked network structure.

[0073] On the other hand, the isocyanurate component has a property of causing crosslinking shrinkage during crosslinking. Therefore, if there is no factor that inhibits the isocyanurate component from moving in the first sealing material 2a, the isocyanurate component moves from the adhesive portion (surface layer portion) 2a1 side of the first sealing material 2a to the inner layer portion 2a2 side during crosslinking. However, as described above, the (meth)acrylate component crosslinks before the isocyanurate component to form a crosslinked network structure. Therefore, if the crosslinked network structure formed by the (meth)acrylate component is formed sufficiently densely in advance in the first sealing material 2a, the possibility that the crosslinked network structure of the (meth)acrylate component will move due to the crosslinking shrinkage of the isocyanurate component can be reduced.

[0074] As a result, the isocyanurate component remains in a large amount in the adhesive portion (surface portion) 2a1 in contact with the adhesive interface 10, and crosslinks upon subsequent heating, forming a high-density crosslinked structure in the adhesive portion (surface portion) 2a1 in contact with the adhesive interface 10 between the light-transmitting substrate 1 and the first sealing material 2a.

[0075] As a result, without adding an excessive amount of the isocyanurate component, which is rigid and highly brittle, to the first sealing material 2a, a crosslinked network structure of a large amount of the isocyanurate component can be formed in the adhesive portion (surface portion) 2a1 that contacts the adhesive interface 10 between the light-transmitting substrate 1 and the first sealing material 2a, thereby obtaining the effect of reducing the penetration of moisture into the first sealing material 2a.

[0076] However, if the amount of the (meth)acrylate component is insufficient, a sufficient amount of the isocyanurate component cannot form a crosslinked structure near the interface with the glass, but conversely, if the amount of the (meth)acrylate component is excessive, the (meth)acrylate component becomes saturated and cannot dissolve in the base material, making it difficult to mold the first sealing material 2a into a sheet. For this reason, it is important to add the (meth)acrylate component in an amount that is not saturated and that allows the isocyanurate component to be placed at a desired position during the heating process during crosslinking. Note that, although the above description has been given taking the example between the light-transmitting substrate 1 and the first sealing material 2a, the same can be said for the relationship between the second sealing material 2b and the back surface protection material 4.

[0077] In addition, the above description has focused on the hydroxide ions that are generated when a metal hydroxide is used as the first additive, but the effects of the present invention can also be preferably obtained when a metal oxide or carbonate is used as the first additive, since the penetration of water into the sealing material 2 can be suppressed. EXAMPLES

[0078] The present disclosure will be described with reference to examples, but the present disclosure is not limited to the following examples.

[0079] Example 1 The solar cell module X of Example 1 was manufactured using the following members (1) to (6) by the above-mentioned method. (1) Light-transmitting substrate 1: White tempered glass (2) Encapsulating material 2 (2.1) Main component of sealing material: Ethylene-vinyl acetate copolymer 100 parts by weight (2.2) First additive for sealing material: Magnesium hydroxide 0.1 parts by weight (2.3) Second additive for sealing material Triallyl isocyanurate 2 parts by weight (2.4) Third additive for sealing material: Trimethylolpropane tri(meth)acrylate 0.32 parts by weight (3) Solar cell: Crystalline silicon solar cell (4) Back surface protection material: Polyethylene terephthalate resin film (5) Interconnector Solder-coated copper foil (6) Connection wiring: solder-coated copper foil

[0080] (Examples 2, 3, 4, 5, 6, 7 and Comparative Example 1) Solar cell modules X of Examples 2, 3, 4, 5, 6, 7, and Comparative Example 1 were manufactured in the same manner as in Example 1, except that the amounts of the second additive and the third additive in the encapsulant 2 were blended as shown in Table 1. The solar cell modules X manufactured in each Example and Comparative Example 1 were evaluated as follows, and the results are shown in Tables 2 and 3.

[0081] [Table 1]

[0082] <Accelerated test method> For each of the Examples and Comparative Example 1, in order to reproduce a solar cell module X in a state equivalent to a state in which it is used in a hot and humid natural environment and deteriorates over time, an accelerated test was performed in which high temperature and high humidity stress was applied to the solar cell module X. Specifically, the accelerated test was performed by changing the stress conditions to a more severe level (temperature 95°C, relative humidity 95%) with reference to the humidity resistance test (temperature 85°C, relative humidity 85%) of JIS-C-8917 (environmental test method and durability test method for crystalline solar cell module). The time for which the solar cell module X was put into the accelerated test was set to four types: 0 hours, 50 hours, 100 hours, and 200 hours, in consideration of the state of a solar cell module actually installed in a natural environment.

[0083] <Method for evaluating the rate of adhesive strength retention> Next, a method for evaluating the adhesive strength of the sealing material 2 to the light-transmitting substrate 1 after the accelerated test will be described. First, a method for preparing a sample will be described. Using a cutter knife or the like, an incision is made from the back surface protective material 4 side of the solar cell module X to a depth that reaches the light-transmitting substrate 1. With the sealing material 2 adhered to the light-transmitting substrate 1, a strip-shaped piece of the sealing material 2 with a sample width of 10 mm is cut out. Next, a part of the sealing material 2 at one end side of the piece is peeled off from the light-transmitting substrate 1 and processed to become a gripping portion of a jig of a tensile tester, thereby preparing a sample.

[0084] Next, the method of measuring the adhesive strength will be described. Under the conditions of room temperature (15 to 25°C), a tensile tester (Tensilon universal testing machine) was used to obtain a chart of load change under the conditions of a sample width of 10 mm, a peel angle of 90 degrees (T-shaped peel), and a peel speed of 10 mm / min, and the maximum value (maximum adhesive strength) in the chart was read. Then, in order to express the adhesive strength maintenance rate for each Example and Comparative Example 1, the initial maximum adhesive strengths of Comparative Example 1 and each Example, and the maximum adhesive strengths of Comparative Example 1 and each Example after 50 hours, 100 hours, and 200 hours of accelerated testing were divided by the initial maximum adhesive strength of Comparative Example 1 to normalize the adhesive strength maintenance rate. Note that, in the above, the initial value of the maximum adhesive strength means the maximum adhesive strength before the accelerated test, that is, the time of introduction into the accelerated test is 0 hours.

[0085] <Method of evaluating the physical properties of encapsulating materials> Evaluation method 1. Evaluation method for the concentration distribution of isocyanurate components For the first sealing material 2a of the solar cell modules X produced in each Example and Comparative Example 1, the ratio of the concentration of the isocyanurate component within a range of up to 50 μm away from the adhesive interface 10 with the light-transmitting substrate 1 to the concentration of the isocyanurate component within a range of 200 to 300 μm away from the adhesive interface 10 was calculated by the following method. In the following, the portion of the first sealing material 2a within a range of up to 50 μm away from the adhesive interface 10 between the light-transmitting substrate 1 and the first sealing material 2a is also referred to as a surface layer portion 2a1, and the portion of the first sealing material 2a within a range of 200 to 300 μm away from the adhesive interface 10 is also referred to as an inner layer portion 2a2.

[0086] The method for preparing the sample will be described.

[0087] First, the solar cell module X is disassembled from the back surface protective material side 4 to expose the sealing material 2. For example, if the back surface protective material 4 is a resin sheet, it may be cut open, and if the back surface protective material 4 is glass, it may be removed by crushing, etc. The adhesive portion 2a1 between the light-transmitting substrate 1 and the first sealing material 2a is peeled off from the light-transmitting substrate 1 to be sampled. As an example of a sampling method, a method of processing the sealing material 2 into a thin slice using a blade as a sample can be given. In addition, a cross-sectional sample preparation device such as a microtome, an FIB device (focused ion beam device), or a CP device (cross-section polisher device) may be used. Note that the method of preparing the sample is not limited to the method of preparing from the disassembled solar cell module X, and for example, the light-transmitting substrate 1, the sealing material 2, the solar cell 3, and the back surface protective material 4 obtained as members may be subjected to the above-mentioned lamination process and cross-linking process, and then may be prepared by the same method as the above-mentioned cross-sectional processing method. At this time, the solar cell 3 may be omitted. In addition, a film material having a mold release property may be used instead of the back surface protective material 4.

[0088] Next, a method for evaluating the concentration distribution of the isocyanurate component will be described.

[0089] An index relating to the concentration of the isocyanurate component, which is the second additive, can be obtained by measuring with an FT-IR device (Fourier transform infrared spectrophotometer) by the ATR method (attenuated total reflection measurement method). Specifically, imaging measurement is performed with the FT-IR device on a cross section perpendicular to the main surface (the surface in contact with the light-transmitting substrate 1) of the first encapsulant 2a. At this time, if the measurement range is too narrow, the measured values ​​are likely to vary, so it is preferable to measure a cross section having a width of 400 μm or more in a direction parallel to the main surface of the first encapsulant 2a.

[0090] The measurement conditions are as follows.

[0091] Light source: Special ceramics Detector: 2D detector Purge: Nitrogen gas Detection pixel size: 8μm / pixel Resolution: 4cm -1 Measurement wavelength range: 3900cm -1 ~750cm -1 Number of times: 16 As a result of measurement using an FT-IR device, it is possible to obtain an imaging image showing a signal intensity proportional to the density of the isocyanurate component, as shown in Figure 6. In Figure 6, the strength of the signal intensity is represented by the density of black dots. In addition, the light-transmitting substrate shown in Figure 1 is removed during FT-IR measurement.

[0092] In addition, in the measurement by the FT-IR device, a prism is pressed against the sample, but the state of contact between the prism and the sample affects the measured peak intensity, and so the measured value (absolute value) contains errors, so the evaluation was carried out by appropriately standardizing the measured value. In other words, the wavelength of 1690 cm, which is thought to be derived from the isocyanurate component, the second additive, -1 The peak at 1370 cm can be attributed to the CH bending vibration of the ethylene-vinyl acetate copolymer, which is the main component. -1 The evaluation was performed by normalizing the peak in the vicinity to the reference peak.

[0093] Specifically, for the surface layer 2a1, the isocyanurate component-derived (1690 cm -1 The first peak area value of the CH group of ethylene-vinyl acetate copolymer (1370 cm -1 A second peak area value derived from a region near the first peak (near the first peak area) is derived. Then, the first peak area value is divided by the second peak area value to calculate a first peak area ratio (first value) evaluating the peak area of ​​the isocyanurate component on the surface layer side. The first peak area ratio is proportional to the abundance ratio of the isocyanurate component in the sealing material surface layer portion 2a1.

[0094] In the same manner, the inner layer portion 2a2 was subjected to isocyanurate-derived (1690 cm -1 The area value of the third peak (around 1370 cm) and the CH group of EVA -1 A fourth peak area value derived from a region adjacent to the inner layer 2a2 of the sealing material is derived. The third peak area value is divided by the fourth peak area value to calculate a second peak area ratio (second value) evaluating the peak area of ​​the isocyanurate component on the inner layer side. The second peak area ratio is proportional to the proportion of the isocyanurate component in the sealing material inner layer portion 2a2.

[0095] The first peak area ratio was divided by the second peak area ratio to calculate the intensity ratio between the surface layer portion 2a1 and the inner layer portion 2a2, which indicates the concentration distribution (concentration ratio) of the isocyanurate component in the surface layer portion 2a1 and the inner layer portion 2a2.

[0096] The peak area was calculated by integrating the area surrounded by the baseline and the peak for the IR spectrum obtained by measurement using an FT-IR device.

[0097] More specifically, isocyanurate-derived (1690cm -1 The first and third peak areas are at a wavenumber of 1713 cm for the waveform of the isocyanurate component. -1 The left end is 1671cm -1The line connecting the right ends of the peaks was used as the baseline, and the area surrounded by the baseline and the peaks derived from the isocyanurate component was integrated to obtain the peak.

[0098] Next, the CH group of ethylene-vinyl acetate copolymer (1370cm -1 The area values ​​of the second and fourth peaks originating from the CH group of ethylene-vinyl acetate copolymer are at a wave number of 1394 cm -1 is the left end, 1333cm -1 The line connecting the right end of the line was taken as the baseline, and the area enclosed by the baseline and the peak derived from the CH group of the ethylene-vinyl acetate copolymer was integrated to obtain the value. The results of the measurement using the above "Evaluation method 1. Evaluation method for the concentration distribution of the isocyanurate component" are shown in the First Value / Second Value columns of Table 2.

[0099] [Table 2]

[0100] Evaluation method 2: Mechanical property measurement For the first encapsulant 2a of the solar cell module X produced in each Example and Comparative Example, the storage modulus was measured by the following method in order to evaluate the difference in the mechanical properties of the encapsulant, which correlates with the difference in the susceptibility to deterioration of the peel strength.

[0101] First, a method for preparing the sample will be described.

[0102] Solar cell module X is cut into pieces of about 10 mm x 10 mm using cutting tools such as a blade or grinder. Next, the cross section is processed using a Cryo-CP (Cross section Polisher) to create a sample.

[0103] Note that the method for preparing the sample is not limited to the method of preparing it from the disassembled solar cell module X. For example, after the translucent substrate 1, the encapsulant 2, the solar cell 3, and the back surface protective material 4, each obtained as a member, have undergone the above-mentioned lamination process and crosslinking process, they may be processed into a size of about 10 mm × 10 mm and prepared by the same method as the above cross-sectional processing.

[0104] Next, the measurement method will be described.

[0105] The storage elastic modulus can be obtained by measuring the cross-section of the above-mentioned sample by the nanoindentation method using, for example, a nanoindenter device as described below.

[0106] The measurement conditions are as follows.

[0107] Indenter used: Berkovich (triangular pyramid type) Measurement method: Dynamic measurement Measurement temperature: At room temperature (20 - 25°C) Indentation depth setting: Approximately 900 - 1000 nm Frequency: 100 Hz Sample size: 10 mm × 10 mm The measured value of the storage elastic modulus is obtained by shifting the position and performing the same measurement 5 times or more for a 200 - μm portion closer to the solar cell 3 from the adhesion interface 10 included in the inner layer portion 2a2, and taking the average value. On the side closer to the solar cell 3, for a 200 - μm portion, the position is shifted and the same measurement is performed 5 times or more, and the average value is taken.

[0108] The results measured by the above "Evaluation Method 2. Measurement of Mechanical Properties" are described in the column of the storage elastic modulus in Table 2. done.

[0109] Evaluation Method 3. Measurement of Loss Coefficient For the first encapsulant 2a of the solar cell module X produced in each example and each comparative example, the loss coefficient was measured by the following method in order to evaluate the difference in the mechanical properties of the encapsulant, which correlates with the difference in the ease of deterioration of the peel strength.

[0110] First, the method for preparing the samples is the same as that for 1. Mechanical property measurement.

[0111] Solar cell module X is cut into pieces of about 10 mm x 10 mm using cutting tools such as a blade or grinder. Next, the cross section is processed using a Cryo-CP (Cross section Polisher) to create a sample.

[0112] The method for preparing the sample is not limited to the method of preparing it from a disassembled solar cell module X. For example, the light-transmitting substrate 1, the sealing material 2, the solar cell 3, and the back surface protective material 4, each of which is obtained as a component, may be processed into a size of about 10 mm × 10 mm after undergoing the lamination process and cross-linking process described above, and then the sample may be prepared in the same manner as the cross-sectional processing described above.

[0113] Next, the measurement method is the same as Evaluation Method 2. Mechanical property measurement.

[0114] The loss factor can be obtained by measuring the cross section of the above-mentioned sample by a nanoindentation method using, for example, a nanoindenter device as described below.

[0115] The measurement conditions are as follows.

[0116] Indenter used: Berkovich (triangular pyramid type) Measurement method: Dynamic measurement Measurement temperature: room temperature (20~25℃) Indentation depth setting: approx. 900~1000nm Frequency: 100Hz Sample size: 10mm x 10mm The loss factor was measured by taking the same measurement five or more times at different positions over a 200 μm area from adhesive interface 10 included in inner layer portion 2a2 closer to solar cell 3 and averaging the measurements.

[0117] The results of the measurement in "Evaluation method 3. Loss factor measurement" above are shown in the loss factor column of Table 2.

[0118] Evaluation method 4. Relaxation time measurement For the first sealing material 2a of the solar cell modules X produced in Example 2 and Comparative Example 1, relaxation times were measured by the following method in order to evaluate differences in the crosslinking structure in the first sealing material 2a, which correlate with differences in the susceptibility to deterioration of the peel strength.

[0119] First, a method for preparing the sample will be described.

[0120] Using a cutting tool such as a blade or a grinder, a piece of the first encapsulant 2a was cut out from the solar cell module X. Then, the piece of the first encapsulant 2a was filled into a tube with a diameter of about 10 mm for a measuring device to prepare a sample.

[0121] Next, the measurement method will be described.

[0122] The relaxation time can be calculated by analyzing the decay curve of the above sample measured by the CPMG method using a TD-NMR (pulse nuclear magnetic resonance) device as shown below. 2 The relaxation time is obtained. The measurement conditions are as follows.

[0123] Measurement method: CPMG method (T 2 ) Measurement nuclear frequency: 19.95 MHz ( 1 H nucleus) Pulse width: Comparative example 1 2.34 μsec (90° pulse) Example 2 2.18 μsec (90° pulse) Pulse repetition time: 4sec Temperature: 150℃ Measurements were performed after the sample was allowed to stabilize by placing it in the instrument's probe for 20 minutes.

[0124] The T obtained by analyzing the decay curves obtained from the measurements 2 The amount of cross-linked structures in the first sealing material 2a can be evaluated based on the relaxation time. 2A shorter relaxation time indicates a lower molecular mobility in the sample, which in turn indicates a higher cross-linking structure, i.e., a higher cross-linking density.

[0125] From the measured decay curve, T 2 To extract the relaxation times, a waveform separation analysis method was applied, which assumes three components with different relaxation times, and the relaxation times for each of the three components and the abundance ratios of the three components were obtained.

[0126] The results of the measurements made in the above "Evaluation method 4. Relaxation time measurement" are shown in Table 3.

[0127] [Table 3]

[0128] <Adhesive strength evaluation results> Comparative Example 1, Example 1, Example 2, and Example 3 in Table 2 are results in which the amount of the second additive is fixed at 2 parts by weight and the amount of the third additive is changed. Also, Examples 2, 4, 5, 6, and 7 are results in which the amount of the third additive is fixed at 0.64 parts by weight and the amount of the second additive is changed.

[0129] As shown in Table 2, Comparative Example 1 is a solar cell module in which the strength ratio of surface layer portion 2a1 to inner layer portion 2a2 is less than 0.95, which indicates the concentration of the second additive (isocyanurate component) in surface layer portion 2a1 and inner layer portion 2a2 in sealing material 2. The initial value of the maximum adhesive strength of each example is significantly higher than the initial value of the adhesive strength of Comparative Example 1.

[0130] In Comparative Example 1, the adhesive strength retention rate after 50 hours, 100 hours, and 200 hours is lower than the adhesive strength retention rate of each of the Examples.

[0131] Next, each example is a solar cell module having a strength ratio of 0.95 or more between surface layer portion 2a1 and inner layer portion 2a2, which indicates the concentration of the isocyanurate component in surface layer portion 2a1 and inner layer portion 2a2 in sealing material 2. In each of these examples, the adhesion strength retention rate was 0.637 or more after 50 hours, 0.252 or more after 100 hours, and 0.053 or more after 200 hours, and it was found that the adhesion strength could be maintained at a higher level than in Comparative Example 1.

[0132] This indicates that the deterioration of adhesive strength can be significantly reduced by setting the concentration distribution ratio of the isocyanurate component to 0.95 or more.

[0133] It was also found that when deterioration in adhesive strength can be reduced, the strength ratio (first value / second value) of the surface layer portion 2a1 to the inner layer portion 2a2 of the isocyanurate component as the second additive falls within the range of at least 0.95 to 1.1.

[0134] Comparing Example 7 with Examples 1 to 6, the strength ratio of the surface layer 2a1 to the inner layer 2a2 in Example 7 is 0.95 or more, but the maintenance rate of the adhesive strength after 50 hours, 100 hours, and 200 hours is less than half that of Examples 1 to 6. This is because the storage modulus exceeds the appropriate range (does not fall within 0.036 GPa or less). In other words, it is considered that the proportion of viscous components constituting the viscoelastic properties of the sealing material 2 is reduced, making it easier for large shear stress to occur at the adhesive interface.

[0135] As shown in Table 2, when the loss factor was measured for the inner layer portion of Comparative Example 1 and each Example, it was found that the inner layer portions of Examples 1 to 6, which have a high retention rate of adhesive strength, have the characteristic of having a loss factor of less than 0.13.

[0136] Furthermore, when comparing Example 7 shown in Table 2 with Examples 1 to 6, it is clear that by setting the amount of the second additive, the isocyanurate component, to 2.5 parts by weight or less, the maintenance rate of the adhesive strength can be further increased compared to when the amount of the second additive is set to a range greater than 2.5 parts by weight, as in Example 7.

[0137] Furthermore, as shown in Table 3, for Comparative Example 1 and Example 2, the T 2 Comparison of the relaxation times revealed the following:

[0138] Although the details of the molecular structure attribution of components 1, 2, and 3 are unknown, a comparison between Example 2 and Comparative Example 1 shows that the T 2 Among the relaxation times, T of component 1, which is the component with the highest abundance ratio, 2 It was found that the relaxation time was shorter in Example 2.

[0139] Considering that the measurement environment (temperature conditions) was an environment in which the ethylene-vinyl acetate copolymer, the main component, melted before crosslinking, this is believed to be due to the difference in the amount of the (meth)acrylate component added as the third additive. That is, in Example 2, the amount of the (meth)acrylate component added was greater than in Comparative Example 1, so that T 2 It is believed that the relaxation time is shortened. 2 A short relaxation time indicates low molecular mobility. Low molecular mobility indicates many crosslinked structures, i.e., high crosslink density. From this, it is considered that Example 2 has more crosslinked structures of the (meth)acrylate component as the third additive, i.e., has a higher crosslink density, than Comparative Example 1.

[0140] Similarly, in Examples 1, 3, 4, 5, and 6, the amount of the (meth)acrylate component added as the second additive is greater than in Comparative Example 1, and therefore it is considered that the crosslinked structure of the (meth)acrylate component is greater than in Comparative Example 1. For this reason, the T of component 1 in Examples 1, 3, 4, 5, and 6 is 2 The relaxation time was the same as in Example 2, and the T 2 This is estimated to be less than the relaxation time of 2.08 [msec].

[0141] In other words, for Example 1 and Examples 2 to 6, the T of Component 1, which is the component with the highest abundance ratio among the three components based on the attenuation curves obtained by the CPMG method using a TD-NMR device, is 2 The relaxation time is estimated to be at least less than 2.08 msec. [Explanation of symbols]

[0142] X: Solar cell module 1: Translucent substrate 2: Encapsulating material 2a: First encapsulant 2a1: Adhesive part (surface part) 2a2: Inner layer 2b: Second sealing material 3: Solar cell 4: Back protection material 5: Interconnector 6: Connection wiring 7: Terminal box 8: Frame 9: Module stack 10: Adhesive interface 11: Solar cell group 20: Laminating device 21: Housing 21a: Lower housing 21b: Upper housing 22: Heating plate 23: Diaphragm

Claims

1. A solar cell; An encapsulant positioned over the solar cell; a light-transmitting substrate located on the sealing material; The sealing material has a base material, an acid acceptor as a first additive, and an isocyanurate component as a second additive, a loss factor of an inner layer portion of the encapsulant away from the light-transmitting substrate is less than 0.13; A solar cell module, characterized in that, of the three components of the encapsulant based on decay curves obtained by a CPMG method using a TD-NMR apparatus, the T 2 relaxation time of component 1, which is the component with the highest abundance ratio, is less than 2.08 msec.

2. A solar cell; An encapsulant positioned over the solar cell; a light-transmitting substrate located on the sealing material; The sealing material has a base material, a metal hydroxide as a first additive, and an isocyanurate component as a second additive, a loss factor of an inner layer portion of the encapsulant away from the light-transmitting substrate is less than 0.13; A solar cell module, characterized in that, of the three components of the encapsulant based on decay curves obtained by a CPMG method using a TD-NMR apparatus, the T 2 relaxation time of component 1, which is the component with the highest abundance ratio, is less than 2.08 msec.

3. A solar cell; An encapsulant positioned over the solar cell; a light-transmitting substrate located on the sealing material; The sealing material has a base material, a metal oxide as a first additive, and an isocyanurate component as a second additive, a loss factor of an inner layer portion of the encapsulant away from the light-transmitting substrate is less than 0.13; A solar cell module, characterized in that, of the three components of the encapsulant based on decay curves obtained by a CPMG method using a TD-NMR apparatus, the T 2 relaxation time of component 1, which is the component with the highest abundance ratio, is less than 2.08 msec.

4. A solar cell; An encapsulant positioned over the solar cell; a light-transmitting substrate located on the sealing material; The sealing material has a base material, a carbonate as a first additive, and an isocyanurate component as a second additive, a loss factor of an inner layer portion of the encapsulant away from the light-transmitting substrate is less than 0.13; A solar cell module, characterized in that, of the three components of the encapsulant based on decay curves obtained by a CPMG method using a TD-NMR apparatus, the T 2 relaxation time of component 1, which is the component with the highest abundance ratio, is less than 2.08 msec.

5. A solar cell module described in any one of claims 1 to 4, characterized in that the sealing material has a cross-linked mesh structure that can inhibit the movement of the isocyanurate component.

6. 6. The solar cell module according to claim 1, wherein the sealing material has a storage modulus of 0.036 GPa or less.

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