Solar cell modules and solar cell arrays

Abstract

To provide a solar cell module that can maintain good power generation efficiency even after humidity and heat resistance testing. [Solution] This disclosure provides a solar cell module in which a surface protective member, a surface sealing material layer, a solar cell element, a back sealing material layer, and a back protective member are stacked in this order, wherein the melting point Tm1 of the surface sealing material layer is 80°C or lower, and the melting point Tm2 of the back sealing material layer is 90°C or higher.

Description

[Technical Field]

[0001] This disclosure relates to solar cell modules and solar cell arrays. [Background technology]

[0002] In recent years, with growing awareness of environmental issues, solar cells have attracted attention as a clean energy source. Currently, solar cell modules in various forms are being developed. Generally, a solar cell module has a structure in which a surface protective member, a surface sealing material layer, a solar cell element, a back sealing material layer, and a back protective member are stacked in that order from the light-receiving side, and it has the function of generating electricity when sunlight is incident on the solar cell element.

[0003] Since solar cell modules are used outdoors for extended periods, each of the components that make up a solar cell module must be durable enough to withstand the harsh outdoor environment over long periods.

[0004] For encapsulating sheets used in solar cell modules, encapsulating sheets based on EVA (ethylene-vinyl acetate copolymer) or POE (polyolefin elastomer), which offer excellent transparency and adhesion, are widely used (see, for example, Patent Document 1). [Prior art documents] [Patent Documents]

[0005] [Patent Document 1] Japanese Patent Publication No. 2009-135200 [Overview of the project] [Problems that the invention aims to solve]

[0006] As the thickness of the solar cell element is reduced, cracks may occur in the solar cell element during heat - pressure bonding (e.g., vacuum heat lamination) when manufacturing a solar cell module, resulting in deterioration of the power generation performance. Also, after a damp heat test, which is a typical reliability test for solar cell modules and involves leaving them for 2000 hours in 85°C and 85% RH, it is required to maintain good power generation efficiency. However, during the damp heat test, the power generation efficiency may decrease after the test due to the shaking of the solar cell element.

[0007] This disclosure has been made in view of the above circumstances, and the main object is to provide a solar cell module capable of maintaining good power generation efficiency even after a damp heat test.

Means for Solving the Problems

[0008] One embodiment of this disclosure is a solar cell module in which a surface protection member, a surface encapsulant layer, a solar cell element, a back - side encapsulant layer, and a back - side protection member are laminated in this order, wherein the melting point Tm1 of the surface encapsulant layer is 80°C or less, and the melting point Tm2 of the back - side encapsulant layer is 90°C or more.

[0009] Another embodiment of this disclosure is a solar cell module in which a surface protection member, a surface encapsulant layer, a solar cell element, a back - side encapsulant layer, and a back - side protection member are laminated in this order, and in a region where the surface encapsulant layer and the back - side encapsulant layer are in direct contact, the reflectance of the interface between the surface encapsulant layer and the back - side encapsulant layer, measured from the surface encapsulant layer side, is 5.50% or more and 30% or less.

[0010] Another embodiment of this disclosure provides a solar cell array in which the above - described solar cell module is arranged.

Advantages of the Invention

[0011] According to this disclosure, it is possible to provide a solar cell module capable of maintaining good power generation efficiency even after a damp heat test.

Brief Description of the Drawings

[0012] [Figure 1] This is a schematic cross-sectional view showing an example of a solar cell module in this disclosure. [Figure 2] This is a schematic cross-sectional view illustrating a back-side sealing material sheet. [Figure 3] This is a schematic cross-sectional view showing an example of a solar cell module in this disclosure. [Figure 4] This is a schematic cross-sectional view showing an example of a solar cell module in this disclosure. [Figure 5] This is a schematic plan view showing an example of a solar cell array in this disclosure. [Modes for carrying out the invention]

[0013] Embodiments of this disclosure will be described below with reference to drawings and other figures. However, this disclosure can be implemented in many different ways and should not be interpreted as being limited to the embodiments described below. In addition, in order to make the explanation clearer, the drawings may schematically represent the width, thickness, shape, etc. of each part compared to the actual form, but these are merely examples and should not limit the interpretation of this disclosure. Furthermore, in this specification and each figure, elements similar to those described above with respect to previously shown figures will be denoted by the same reference numerals, and detailed explanations may be omitted as appropriate.

[0014] In this specification, when describing a configuration in which one component is placed on top of another component, unless otherwise specified, the terms "on top" or "below" include both cases: one where the other component is placed directly above or below the component in contact with it, and another where the other component is placed above or below the component via yet another component. Furthermore, when describing a configuration in this specification in which one component is placed on the surface of another component, unless otherwise specified, the terms "on the surface" or "on the surface" include both cases: one where the other component is placed directly above or below the component in contact with it, and another where the other component is placed above or below the component via yet another component.

[0015] A. Solar cell modules As solar cell elements become thinner, cracks may occur in the solar cell elements during the heat-pressing process when integrating them into a solar cell module (for example, during vacuum heat lamination), potentially degrading power generation performance. Furthermore, vibrations of the solar cell elements during humid and heat resistance testing may lead to a decrease in power generation efficiency after the test.

[0016] The inventors of this application conducted extensive research to obtain a solar cell module that can maintain good power generation efficiency even after a humidity and heat resistance test, and have found the following solar cell module, thereby solving the above problem. The solar cell module of this disclosure will be described in detail below, divided into a first embodiment and a second embodiment.

[0017] A1. First Embodiment Figure 1 is a schematic cross-sectional view showing an example of a solar cell module in this embodiment. As shown in Figure 1, the solar cell module 10 of this embodiment has a surface protective member 1, a surface sealing layer 2, a solar cell element 3, a back sealing layer 4, and a back protective member 5 stacked in this order. In this embodiment, the melting point Tm1 of the surface sealing layer 2 is 80°C or less, and the melting point Tm2 of the back sealing layer 4 is 90°C or higher.

[0018] According to this embodiment, the melting point Tm1 of the surface sealing layer 2 is 80°C or lower, and the melting point Tm2 of the back sealing layer 4 is 90°C or higher, so the melting points of the surface sealing layer and the back sealing layer are different. Therefore, during heat bonding, the surface sealing layer becomes more flexible than the back sealing layer, which suppresses cracking of the solar cell element and results in a solar cell module with high power generation performance. In particular, when using thin solar cell elements, the effects of this disclosure are especially pronounced because thin solar cell elements are prone to cracking. Furthermore, perovskite-based solar cell elements generally deteriorate due to heat, such as migration of additives, phase changes, and decomposition, so it is required to heat bond them at relatively low temperatures (for example, 120°C or lower). The lower the temperature during heat bonding, the more likely the solar cell element is to crack. Therefore, the effects of this disclosure are also significantly pronounced when using perovskite-based solar cell elements. Furthermore, since the melting point Tm2 of the back sealing layer 4 is 90°C or higher, the back sealing layer can prevent the solar cells from vibrating during a typical humidity and heat resistance test (85°C, 85%RH). Therefore, the decrease in power generation efficiency after the humidity and heat resistance test can be suppressed. Consequently, the solar cell module can maintain good power generation efficiency even after the humidity and heat resistance test.

[0019] Furthermore, in this disclosure, the transparency of the surface encapsulant layer can be expected to be improved by having a melting point of 80°C or lower. In resin sheets made of polyethylene resin or the like, a lower melting point tends to result in a lower density of the resin material and improved transparency. Also, the water vapor barrier properties of the back encapsulant layer can be expected to be improved by having a melting point of 90°C or higher. In resin sheets made of polyethylene resin or the like, a higher melting point tends to result in a higher density of the resin material and improved water vapor barrier properties. On the other hand, if the melting point of the back encapsulant layer is low, the mobility of water vapor increases, making the solar cell element more susceptible to degradation. Also, if the melting point of the back encapsulant layer is low, the mobility of additives also increases, causing them to mix with the material of the surface encapsulant layer and making the solar cell element more susceptible to degradation. For example, the encapsulant layer may contain additives such as ultraviolet absorbers, wavelength converters, and light stabilizers. In this case, either the surface encapsulant layer or the back encapsulant layer may contain a specific additive, or the amount of a specific additive in one encapsulant layer may be significantly higher than the amount in the other encapsulant layer. For example, the surface encapsulant layer may contain a wavelength conversion material, while the back encapsulant layer may not. Also, the surface encapsulant layer may not contain an ultraviolet absorber, while the back encapsulant layer does. In these cases, the additives are prone to migration during lamination and during humid and heat resistance testing. Therefore, for the reasons mentioned above, this results in a solar cell module that can maintain good power generation efficiency even after humid and heat resistance testing.

[0020] The following describes in detail each component of the solar cell module of this embodiment.

[0021] 1.Surface encapsulant layer (1) Melting point In this embodiment, the surface sealing layer has a melting point Tm1, measured by the method described below, of 80°C or less, preferably 70°C or less, more preferably 60°C or less, and particularly preferably 50°C or less. By having a melting point Tm1 of the surface sealing layer that is below the above value, cracking of the solar cell element can be suppressed during heat bonding (for example, during vacuum heat lamination) when integrating it as a solar cell module. In addition, the transparency of the surface sealing layer is improved, and an improvement in power generation efficiency can be expected. On the other hand, the melting point Tm1 may be, for example, 30°C or more, or 40°C or more.

[0022] Here, the melting point Tm1 of the surface encapsulant layer is the melting point of the surface encapsulant layer in the state of the solar cell module. The melting point Tm1 of the surface encapsulant layer is expressed as the maximum peak temperature of the absorption curve measured by differential scanning calorimetry (DSC) on a sample of the surface encapsulant layer. The maximum peak temperature refers to the temperature of the peak with the greatest height from the baseline when multiple peaks are shown in the endothermic curve obtained when heat flow (mW) is plotted on the vertical axis and temperature (°C) on the horizontal axis in a DSC measurement, or the temperature of that peak if there is only one peak.

[0023] The method for collecting the sample for measurement and the temperature profile for DSC measurement are as follows. (Sample for measurement) The material is collected by peeling off the surface protective material from the solar cell module and cutting it out from the surface sealing layer. (Temperature profile) Approximately 10 mg of the sample for measurement is placed in an aluminum pan, and the temperature is raised to 300°C at a rate of 10°C / min. After holding at 300°C for 1 minute, the temperature is lowered to 0°C at a rate of -10°C / min. After holding at 0°C for 15 minutes, the absorption curve obtained when the temperature is raised again at a rate of 10°C / min is defined as the melting point.

[0024] One method for controlling the melting point Tm1 of the surface sealing material layer to the above range is to select the type of base resin of the surface sealing material sheet that forms the surface sealing material layer.

[0025] (2) Hayes In this embodiment, it is possible to reduce the haze of the surface sealing material layer. For example, the haze of the surface sealing material layer is preferably 10 or less, and more preferably 5 or less. When the haze of the surface sealing material layer is within the above range, the amount of light reaching the solar cell element increases, and the power generation efficiency improves. In this disclosure, the melting point of the surface sealing material layer is below the above predetermined value. Generally, in resin sheets made of polyethylene resin or the like, a lower melting point results in a lower density of the resin material. When the density of the resin material decreases, transparency tends to improve. That is, in this disclosure, by having a melting point of the surface sealing material layer below the above value, the haze of the surface sealing material layer can be reduced. On the other hand, the haze of the surface sealing material layer is, for example, 2 or more.

[0026] The haze of the surface sealing layer was measured by peeling off the surface protective material from the solar cell module, cutting out the surface sealing layer, and measuring the value in accordance with JIS K7136.

[0027] (3) Surface sealing sheet The surface sealing layer in this embodiment is a layer formed by overlapping a surface sealing sheet with other components and heat-pressing them together (for example, by vacuum heat lamination). The surface sealing sheet only needs to contain a resin whose melting point is within the above range. For example, the surface sealing sheet preferably contains an olefin resin or EVA as the base resin. In this specification, "base resin" refers to the resin with the highest content ratio in the surface sealing sheet.

[0028] (a) Base resin (i) Olefin resins The surface sealing sheet preferably contains an olefin resin as the base resin. Examples of olefin resins include polyethylene resins and polypropylene resins. Among these, polyethylene resins are preferably used. Polyethylene resins include not only ordinary polyethylene obtained by polymerizing ethylene, but also copolymers of ethylene and α-olefins. As for α-olefins, α-olefins having 3 to 12 carbon atoms are preferred. Specifically, examples include propylene, 1-butene, 1-pentene, 1-hexene, 1-octene, 1-heptene, 4-methylpentene-1, 4-methylhexene-1, 4,4-dimethylpentene-1, etc. α-olefins may be used alone or in combination of two or more. Among these, unbranched α-olefins are preferred, and unbranched α-olefins having 3 to 8 carbon atoms are more preferred. Specifically, examples include 1-propene, 1-butene, 1-pentene, 1-hexene, 1-heptene, and 1-octene. By having 3 to 8 carbon atoms in the α-olefin, good flexibility and good strength can be provided. More preferably, the number of carbon atoms in the α-olefin is 4 to 6. As a result, the adhesion between the sealing sheet and other components can be improved. Specific examples of ethylene-α-olefin copolymers include ethylene-propylene copolymer, ethylene-1-butene copolymer, ethylene-1-hexene copolymer, ethylene-1-octene copolymer, and ethylene-4-methylpentene-1 copolymer.

[0029] Examples of the polyethylene resin include high-density polyethylene (HDPE), low-density polyethylene (LDPE), linear low-density polyethylene (LLDPE), metallocene linear low-density polyethylene (M-LLDPE), ultra-low density polyethylene (VLDPE), and the like. The polyethylene resin may be used alone or in combination of two or more. Among them, low-density polyethylene (LDPE), linear low-density polyethylene (LLDPE), metallocene linear low-density polyethylene (M-LLDPE), and ultra-low density polyethylene (VLDPE) can be preferably used because of their good flexibility, transparency, and processability. The metallocene linear low-density polyethylene (M-LLDPE) is synthesized using a metallocene catalyst which is a single-site catalyst. Such polyethylene has few side-chain branches and a uniform comonomer distribution. Therefore, it has a narrow molecular weight distribution and can be made low density, and can impart flexibility to the sealing material sheet. Further, as a result of imparting flexibility, the adhesion between the sealing material sheet and other members can be enhanced. Also, low-density polyethylene has a narrow crystalline distribution and uniform crystal sizes, so not only are there no large crystal sizes, but also the crystallinity itself is low due to its low density. Therefore, it has excellent transparency.

[0030] The lower limit value of the density of the polyethylene resin is not particularly limited, and for example, 0.870 g / cm 3 or more is preferable. Also, the upper limit value of the density of the polyethylene resin is not particularly limited, and for example, 0.930 g / cm 3 or less is preferable, 0.910 g / cm 3 or less is more preferable, and 0.890 g / cm 3 or less is even more preferable. Specifically, it is preferably 0.870 g / cm 3 or more and 0.930 g / cm 3 or less, more preferably 0.870 g / cm 3 or more and 0.910 g / cm 3 or less, and even more preferably 0.870 g / cm 3 or more and 0.890 g / cm 3The following is even more preferable: By having the density of the polyethylene resin within the above range, flexibility, transparency, and processability can be improved. Here, the density of the polyethylene resin can be measured, for example, by the pycnometer method in accordance with JIS K7112:1999.

[0031] The lower limit of the melt mass flow rate (MFR) of the olefin resin at a temperature of 190°C is preferably, for example, 2.0 g / 10 min or more, more preferably 3.0 g / 10 min or more, and even more preferably 10 g / 10 min or more. The upper limit of the melt mass flow rate (MFR) of the olefin resin at a temperature of 190°C is preferably, for example, 30 g / 10 min or less, more preferably 25 g / 10 min or less, and even more preferably 20 g / 10 min or less. Specifically, it is preferably 2.0 g / 10 min or more and 30 g / 10 min or less, more preferably 3.0 g / 10 min or more and 25 g / 10 min or less, and even more preferably 10 g / 10 min or more and 20 g / 10 min or less. By having the MFR of the olefin resin within the above range, good film-forming properties and flexibility can be achieved.

[0032] Here, the melt mass flow rate (MFR) of olefin resins can be measured in accordance with JIS K7210-1:2014. The measurement is performed using Method A, under the conditions of a temperature of 190°C and a load of 2.16 kg.

[0033] (ii) EVA The surface sealing sheet may contain ethylene-vinyl acetate copolymer (EVA resin) as the base resin. EVA resin is a copolymer containing at least ethylene monomer units and vinyl acetate monomer units. Ethylene monomer units refer to constituent units derived from ethylene monomer, and vinyl acetate monomer units refer to constituent units derived from vinyl acetate monomer. The ethylene content in the ethylene-vinyl acetate copolymer is not particularly limited, but is preferably 50% by mass or more and 95% by mass or less, and more preferably 60% by mass or more and 85% by mass or less. The vinyl acetate content in the ethylene-vinyl acetate copolymer is not particularly limited, but is preferably 5% by mass or more and 50% by mass or less, and more preferably 15% by mass or more and 40% by mass or less. In addition to ethylene monomer units and vinyl acetate monomer units, the ethylene-vinyl acetate copolymer may also contain a third monomer unit.

[0034] (b) Crosslinking agent The surface encapsulant sheet may contain a crosslinking agent, or it may not contain a crosslinking agent substantially. "Substantially free of a crosslinking agent" means that the crosslinking agent content in the surface encapsulant sheet is less than 0.0005% by mass. Preferably, the crosslinking agent content in the surface encapsulant sheet is 0.35% by mass or less, and may be 0.30% by mass or less. On the other hand, the crosslinking agent content in the surface encapsulant sheet may be, for example, greater than 0.0005% by mass. As the crosslinking agent, a crosslinking agent commonly used in encapsulant sheets for solar cell modules can be used, such as an organic peroxide. The crosslinking agent may be used alone, or two or more types may be mixed.

[0035] Examples of organic peroxides include peroxycarbonates, peroxyketals, and dialkylperoxides. Examples of peroxycarbonates include t-amyl-peroxy-2-ethylhexyl carbonate and t-butyl-peroxy-2-ethylhexyl carbonate. Examples of peroxyketals include n-butyl 4,4-di(t-butylperoxy)valerate, ethyl 3,3-di(t-butylperoxy)butyrate, and 2,2-di(t-butylperoxy)butane. Examples of dialkylperoxides include di-t-butylperoxide, t-butylcumylperoxide, dicumylperoxide, 2,5-dimethyl-2,5-di(t-butylperoxy)hexane, and 2,5-dimethyl-2,5-di(t-peroxy)hexyne-3.

[0036] If the crosslinking agent content in the surface sealing sheet is too high, outgassing due to the crosslinking agent will occur during the integration process or during humidity and heat resistance testing. This outgassing can cause bubbles, leading to a decrease in the power generation efficiency of the solar cell module and causing protective components to lift.

[0037] (c) Silane component When the surface encapsulant sheet uses an olefin-based resin as the base resin, it is preferable that it contains a silane component such as a silane coupling agent or a silane-modified polyolefin resin. By containing a silane component in the surface encapsulant sheet, the adhesion to the solar cell element, strength, durability, etc., can be improved.

[0038] As the silane coupling agent, silane coupling agents commonly used in encapsulating sheets for solar cell modules can be used. Examples include vinyl-based silane coupling agents, methacryloxy-based silane coupling agents, acryloxy-based silane coupling agents, epoxy-based silane coupling agents, and mercapto-based silane coupling agents. Examples of vinyl-based silane coupling agents include vinyltriethoxysilane and vinyltrimethoxysilane. Examples of methacryloxy-based silane coupling agents and acryloxy-based silane coupling agents include 3-acryloxypropyltrimethoxysilane, 3-acryloxypropyltriethoxysilane, 3-methacryloxypropyltrimethoxysilane, 3-methacryloxypropyltriethoxysilane, 3-acryloxypropylmethyldimethoxysilane, 3-acryloxypropylmethyldiethoxysilane, 3-methacryloxypropylmethyldimethoxysilane, and 3-methacryloxypropylmethyldiethoxysilane. Silane coupling agents may be used individually or in combination of two or more types.

[0039] The lower limit of the silane coupling agent content in the surface sealing sheet is preferably, for example, 0.10% by mass or more, and may be 0.20% by mass or more. The upper limit of the silane coupling agent content in the surface sealing sheet is preferably, for example, 2.0% by mass or less, and may be 1.5% by mass or less. Specifically, it is preferably 0.10% by mass or more and 2.0% by mass or less, and may be 0.20% by mass or more and 1.5% by mass or less. If the silane coupling agent content is too low, the effect of improving adhesion by the silane coupling agent may not be sufficiently obtained. On the other hand, if the silane coupling agent content is too high, the film formation performance may decrease or the silane coupling agent may bleed out.

[0040] Silane-modified polyolefin resins are copolymers of olefins and ethylenically unsaturated silane compounds. The copolymer may be, for example, a random copolymer, an alternating copolymer, a block copolymer, or a graft copolymer. Among these, a graft copolymer is preferred, specifically a graft copolymer in which polyolefin is the main chain and ethylenically unsaturated silane compounds are polymerized as side chains. Such graft copolymers offer a higher degree of freedom for the silanol groups that contribute to adhesion, thus further improving adhesion to solar cell elements.

[0041] Examples of polyolefins that constitute silane-modified polyolefin resins include polyethylene, polypropylene, and ethylene vinyl acetate copolymers. Among these, polyethylene is preferred as the polyolefin constituting the silane-modified polyolefin resin. In other words, the silane-modified polyolefin resin is preferably a silane-modified polyethylene resin. This is because silane-modified polyethylene resin has good compatibility with the first and second outer layers.

[0042] Examples of polyethylenes that make up silane-modified polyethylene resin include high-density polyethylene (HDPE), low-density polyethylene (LDPE), linear low-density polyethylene (LLDPE), metallocene-based linear low-density polyethylene (M-LLDPE), and very low-density polyethylene (VLDPE). Among these, low-density polyethylene (LDPE), linear low-density polyethylene (LLDPE), metallocene-based linear low-density polyethylene (M-LLDPE), and very low-density polyethylene (VLDPE) are preferred due to their good flexibility and processability. In particular, linear low-density polyethylene (LLDPE) and metallocene-based linear low-density polyethylene (M-LLDPE) are preferred due to their excellent flexibility, processability, and strength.

[0043] Examples of the ethylenically unsaturated silane compounds mentioned above include vinyltrimethoxysilane, vinyltriethoxysilane, vinyltripropoxysilane, vinyltriisopropoxysilane, vinyltributoxysilane, vinyltripentyloxysilane, vinyltriphenoxysilane, vinyltribenzyloxysilane, vinyltrimethylenedioxysilane, vinyltriethylenedioxysilane, vinylpropionyloxysilane, vinyltriacetoxysilane, and vinyltricarboxysilane. The ethylenically unsaturated silane compounds may be used individually or in combination of two or more.

[0044] Silane-modified polyolefin resin can be obtained, for example, by the manufacturing method described in Japanese Patent Publication No. 2003-46105.

[0045] Silane-modified polyolefin resins may be used individually or in combination of two or more types.

[0046] The content of silane-modified polyolefin resin in the surface sealing sheet is not particularly limited, but is preferably 1.0% to 14% by mass, more preferably 1.5% to 12% by mass, and even more preferably 2.0% to 10% by mass. If the content of silane-modified polyolefin resin is too low, the effect of improving adhesion by the silane-modified polyolefin resin may not be sufficiently obtained. On the other hand, if the content of silane-modified polyolefin resin is too high, the tensile elongation and heat weldability tend to be inferior.

[0047] (d) Other additives The surface sealing sheet may contain other additives besides the olefin resin, crosslinking agent, crosslinking aid, and silane coupling agent mentioned above. Examples of other additives include light stabilizers, ultraviolet absorbers, wavelength conversion materials, antioxidants, heat stabilizers, nucleating agents, dispersants, leveling agents, plasticizers, defoamers, flame retardants, and fillers.

[0048] (e) Formation method The surface sealing material sheet is formed using various molding methods commonly used with thermoplastic resins, such as injection molding, extrusion molding, hollow molding, compression molding, and rotational molding.

[0049] (4) Thickness The thickness of the surface sealing layer in this embodiment is not particularly limited, but is preferably 200 μm or more and 1000 μm or less, and may be 300 μm or more and 800 μm or less.

[0050] (5) Other physical properties The surface sealing layer in this embodiment has a shear rate of 2.43 × 10 sec at 190°C. -1 The melt viscosity is preferably 400 Pa·s to 10,000 Pa·s, and more preferably 500 Pa·s to 5,000 Pa·s. If the melt viscosity is within the above range, the molding properties during lamination as a encapsulant will be good, and the occurrence of microcracks and fractures in the solar cell element during heat bonding (for example, during vacuum heat lamination) can be further suppressed.

[0051] Here, the melt viscosity of the surface sealing layer can be measured according to the method in accordance with JIS K7199:1999. The measurement is performed at a temperature of 190°C and a shear rate of 2.43 × 10 sec. -1 The measurement is performed using a capillary with D=1mm and L / D=10. For the capillary rheometer, for example, a Capillograph 1-B manufactured by Toyo Seiki Seisakusho can be used. When measuring the melt viscosity of the surface encapsulant layer at 190°C, a sample of the surface encapsulant layer is taken from the solar cell module. The method for collecting the sample is as described above.

[0052] In this embodiment, the surface sealing layer preferably has a Vicat softening point of 30°C or higher and 90°C or lower, and more preferably 35°C or higher and 60°C or lower. If the Vicat softening point is within the above range, the molding properties during lamination as a sealing material will be good, and the occurrence of microcracks and cracks in the solar cell element during heat bonding can be further suppressed.

[0053] Here, the "Vicat softening point" of the surface encapsulant layer is the value measured based on ASTM D1525 by taking a sample of the surface encapsulant layer from a solar cell module. The method for taking the sample is as described above.

[0054] In this embodiment, the surface sealing layer preferably has a Shore A hardness of 50 to 100, and more preferably 55 to 85. If the Shore A hardness is within the above range, the flexibility of the sealing layer can be ensured, further suppressing microcracks and fractures of the solar cell element during humid and heat resistance testing.

[0055] Here, the "Shore A hardness" of the surface encapsulant layer is the value measured in accordance with JIS K6253 by taking a sample of the surface encapsulant layer from a solar cell module. The method for taking the sample is as described above.

[0056] 2. Backside sealing layer (1) Melting point In this embodiment, the melting point Tm2 of the back sealing material layer is 90°C or higher, preferably 95°C or higher, more preferably 100°C or higher, and particularly preferably 105°C or higher. By having a melting point Tm2 of the back sealing material layer equal to or greater than the above value, the back sealing material can prevent the solar cells from shaking during the humid heat resistance test at 85°C and 85%RH. Note that IEC61730-1:2023 ed.3 describes test conditions of 85°C and 85%RH as the humid heat resistance test for solar modules. Furthermore, by having a melting point Tm2 of the back sealing material layer equal to or greater than the above value, the water vapor barrier properties of the back sealing material layer are improved, and an improvement in power generation efficiency can be expected. On the other hand, the melting point Tm2 of the back sealing material layer may be, for example, 130°C or lower, 120°C or lower, or 110°C or lower.

[0057] The method for measuring the melting point Tm2 of the back-side sealing material layer is the same as the method for measuring the melting point Tm1 of the front-side sealing material layer described above. Furthermore, as will be described later, if the back-side sealing material layer has multiple layers, the melting point Tm2 of the back-side sealing material layer is measured using the above method while all layers are stacked integrally in a multilayer state, and the obtained measurement value is taken as the melting point Tm2 of the multilayer back-side sealing material layer. In this case, the sample for measurement is collected by peeling off the back-side protective member from the solar cell module and cutting it out from the back-side sealing material layer.

[0058] One method for controlling the melting point Tm2 of the back surface sealing layer to the above range is to select the type of base resin of the back surface sealing sheet that forms the back surface sealing layer.

[0059] (2) Hayes The haze of the back-side sealing material layer is not particularly limited, but for example it may be 10 or more, or 20 or more. On the other hand, the haze of the back-side sealing material layer may be 60 or less, or 40 or less.

[0060] The method for measuring the haze of the back-side sealing material layer is the same as the method for measuring the haze of the front-side sealing material layer described above. Note that, as will be described later, if the back-side sealing material layer has multiple layers, the haze of the back-side sealing material layer is the haze measured in a multi-layered state where all layers are integrally laminated.

[0061] (3) Sealing material sheet on the back In this embodiment, the back-side sealing layer is a layer formed by overlapping a back-side sealing sheet with other components and heat-pressing them together (for example, by vacuum heat lamination). The back-side sealing sheet is obtained by forming a back-side sealing composition into a sheet. The back-side sealing sheet preferably contains an olefin resin as the base resin. In this specification, "base resin" refers to the resin with the highest content ratio in the back-side sealing sheet.

[0062] The back-side sealing sheet preferably has, for example, multiple layers. Figure 2 is a schematic cross-sectional view illustrating a back-side sealing sheet in this disclosure. As shown in Figure 2, the back-side sealing sheet 4' may have a core layer 41 and skin layers 42 disposed on both sides of the core layer 41. In this specification, a skin layer refers to a layer disposed on both outermost surfaces of a multilayer sealing sheet, and a core layer refers to an intermediate layer other than the skin layer. A typical embodiment of the present invention is a three-layer structure in which the core layer has a single-layer structure, but the core layer itself may have a multilayer structure consisting of multiple layers.

[0063] (Core layer) As the resin for the encapsulant composition for the core layer, low-density polyethylene resin (LDPE), linear low-density polyethylene resin (LLDPE), or metallocene-based linear low-density polyethylene resin (M-LLDPE) can be preferably used. Among these, low-density polyethylene resin (LDPE) is particularly preferred as the composition for the core layer from the viewpoint of the long-term reliability of the solar cell module.

[0064] The sealing material composition for the core layer may use, for example, a high-melting-point polyethylene resin with a melting point of 100°C to 120°C as the base resin. Alternatively, the sealing material composition for the core layer may also contain a low-melting-point polyethylene resin with a lower melting point than the base resin.

[0065] High-melting-point polyethylene resin refers to a polyethylene resin with a melting point of 100°C or higher and 120°C or lower, and is the base resin for the core layer. The content of high-melting-point polyethylene resin in the encapsulant composition for the core layer is preferably 60% to 99% by mass, more preferably 65% ​​to 99% by mass, and even more preferably 70% to 99% by mass, relative to the total resin components in the encapsulant composition for the core layer. These may be used, for example, as additive resins, or as other resins for masterbatch formation of other additive components. In this specification, "total resin components" includes the other resins mentioned above. This encapsulant composition for the core layer is a thermoplastic encapsulant composition that does not require a crosslinking process during the molding of the encapsulant sheet.

[0066] The high-melting-point polyethylene resin used as the base resin for the core layer encapsulant composition is 0.910 g / cm³. 3 More than 0.930g / cm 3 It is preferable to use the following polyethylene resin, 0.910 g / cm³ 3 More than 0.920g / cm 3 It is more preferable to use the following polyethylene resins. By setting the density of the base resin of the core layer encapsulant composition within the above range, the heat resistance of the encapsulant sheet can be sufficiently improved.

[0067] The melt mass flow rate (MFR) of the high-melting-point polyethylene resin used as the base resin for the core layer encapsulant composition is preferably 2.0 g / 10 min to 7.5 g / 10 min at 190°C and a load of 2.16 kg, and more preferably 3.0 g / 10 min to 6.0 g / 10 min. By setting the MFR of the base resin for the core layer encapsulant composition within the above range, heat resistance and molding properties can be imparted to the encapsulant sheet. Furthermore, the processability during film formation can be sufficiently improved, contributing to increased productivity of the encapsulant sheet.

[0068] The content of the low-melting-point polyethylene resin is 5% by mass or more and 50% by mass or less, preferably 8% by mass or more and 30% by mass or less, and most preferably 10% by mass or more and 20% by mass or less, relative to the total resin components in the encapsulant composition for the core layer. These may be used, for example, as additive resins, or as other resins for masterbatching other additive components.

[0069] The melting point of the low-melting-point polyethylene resin in the core layer sealing material composition is, for example, 55°C to 95°C, preferably 60°C to 90°C. By setting the melting point of the low-melting-point polyethylene resin in the core layer sealing material composition to the above melting point range, heat resistance and molding properties can be imparted to the sealing material sheet.

[0070] (Skin layer) As a encapsulant composition for the skin layer, for example, a polyethylene-based resin with a relatively low melting point, such as one with a melting point of 100°C or less, more preferably one with a melting point of 40°C to 70°C, is used as the base resin.

[0071] The content of the base resin for the skin layer in the encapsulant composition for the skin layer is preferably 60% to 99% by mass, more preferably 70% to 99% by mass, and even more preferably 80% to 99% by mass, relative to the total resin components in the encapsulant composition for the skin layer. These may be used, for example, as additive resins, or as other resins for masterbatching other additive components. In this specification, "total resin components" includes the other resins mentioned above. This encapsulant composition for the skin layer is a thermoplastic encapsulant composition that does not require a crosslinking process during the molding of the encapsulant sheet.

[0072] As the base resin for the encapsulant composition for the skin layer, low-density polyethylene resin (LDPE), linear low-density polyethylene resin (LLDPE), or metallocene-based linear low-density polyethylene resin (M-LLDPE) can be preferably used.

[0073] The density of the polyethylene resin used as the base resin for the encapsulant composition for the skin layer is preferably 0.870 g / cm³. 3 More than 0.910g / cm 3 The following, and more preferably, 0.880 g / cm³ 3 More than 0.900g / cm 3 The following is true: By setting the density of the base resin of the encapsulant composition for the skin layer within the above range, sufficient adhesion to the encapsulant sheet can be provided when it is integrated into a solar cell module.

[0074] The melting point of the polyethylene resin used as the base resin for the encapsulant composition for the skin layer should be 100°C or lower, preferably 40°C to 70°C, and more preferably 55°C to 65°C. By setting the melting point of the base resin for the encapsulant composition for the skin layer within the above range, sufficient adhesion and molding properties can be imparted to the encapsulant sheet when it is integrated into a solar cell module.

[0075] The melt mass flow rate (MFR) of the polyethylene resin used as the base resin for the encapsulant composition for the skin layer is preferably 1.0 g / 10 min to 40 g / 10 min at 190°C and a load of 2.16 kg, and more preferably 2 g / 10 min to 40 g / 10 min. Having the MFR within this range allows for a encapsulant composition with excellent processability during film formation.

[0076] The sealing material composition may contain additives.

[0077] (c) Formation method The back-side sealing material sheet is formed using various molding methods commonly used with thermoplastic resins, such as injection molding, extrusion molding, hollow molding, compression molding, and rotational molding. When the back-side sealing material sheet is a multilayer film, one example of a method for forming it is co-extrusion using three types of melt-kneading extruders.

[0078] (3) Thickness The thickness of the back surface sealing layer in this embodiment is not particularly limited, but is preferably 200 μm or more and 1000 μm or less, and may be 300 μm or more and 800 μm or less.

[0079] (4) Other physical properties The back surface sealing layer in this embodiment has a shear rate of 2.43 × 10 sec at 190°C. -1 The melt viscosity is preferably 400 Pa·s to 10,000 Pa·s, and more preferably 500 Pa·s to 5,000 Pa·s. If the melt viscosity is within the above range, the molding properties during lamination as a encapsulant will be good, and the occurrence of microcracks and fractures in the solar cell element during heat bonding (for example, during vacuum heat lamination) can be further suppressed.

[0080] The method for measuring the melt viscosity of the back surface sealing material layer in this embodiment is the same as the method for measuring the melt viscosity of the front surface sealing material layer described above.

[0081] In this embodiment, the Vicat softening point of the back surface sealing material layer is preferably 30°C or higher and 90°C or lower, and more preferably 35°C or higher and 60°C or lower. If the Vicat softening point is within the above range, the molding properties during lamination as a sealing material will be good, and the occurrence of microcracks and cracks in the solar cell element during heat bonding can be further suppressed.

[0082] In this embodiment, the surface sealing layer preferably has a Shore A hardness of 50 to 100, and more preferably 55 to 85. If the Shore A hardness is within the above range, the flexibility of the sealing layer can be ensured, further suppressing microcracks and fractures of the solar cell element during humid and heat resistance testing.

[0083] The method for measuring the Vicat softening point and Shore A hardness of the back surface sealing material layer in this embodiment is the same as that for the front surface sealing material layer described above.

[0084] 3. Surface sealing layer and back sealing layer In this embodiment, the difference in melting points (Tm2-Tm1) between the melting point Tm2 of the back sealing material layer and the melting point Tm1 of the front sealing material layer is preferably 20°C or higher, more preferably 30°C or higher, and particularly preferably 40°C or higher. By having a melting point difference (Tm2-Tm1) of the above value or higher, the reflectance of the interface between the front sealing material layer and the back sealing material layer can be increased. On the other hand, the melting point difference may be, for example, 70°C or lower, or 60°C or lower.

[0085] In this embodiment, the reflectance of the interface between the surface sealant layer and the back sealant layer, measured from the surface sealant layer side in the region where the surface sealant layer and the back sealant layer are in direct contact, can be 5.50% or more, or 6.00% or more. A reflectance of the interface between the surface sealant layer and the back sealant layer equal to or greater than the above value increases the amount of light incident on the solar cell element, resulting in a solar cell module with superior power generation efficiency. On the other hand, the above interface reflectance may be, for example, 30% or less, or 20% or less.

[0086] The method for measuring the above-mentioned interfacial reflectance will be described in the second embodiment described later.

[0087] 4. Protective material on the back The back-side protective member is positioned on the back side of the solar cell element and is a member that protects the solar cell element.

[0088] In this embodiment, the water vapor permeability of the back surface protective member is 1.0 × 10 -4 g / (m 2 ·day) or more, 1.0g / (m 2 It is preferable that the water vapor permeability is less than or equal to (day). In this specification, a protective member having the above water vapor permeability is referred to as a barrier protective member. As described above, the back surface sealing material layer in this embodiment has a high melting point and high water vapor barrier properties. Therefore, the synergistic effect of the back surface sealing material layer and the barrier protective member can improve power generation efficiency.

[0089] (1) Water vapor transmission rate The barrier protective material has a water vapor transmission rate of 1.0 × 10⁻⁶. -4 g / (m 2 ·day) or more, 1.0g / (m 2 The water vapor transmission rate is preferably 1.0 × 10⁻⁶ days or less. -3 g / (m 2 • day) or more, 1.0 x 10 -1 The following applies: If the water vapor transmission rate is below the above value, the solar cell element can be protected from water vapor. Furthermore, the decrease in water vapor transmission rate after long-term use can be suppressed.

[0090] The water vapor transmission rate is measured as "water vapor transmission rate at 40°C and 90% RH" using the measurement method specified in ISO 15106-2. For example, a water vapor transmission rate measuring device such as the "AQUATRAN" manufactured by Mokon Corporation can be used. The measurement is performed so that the surface of the barrier protective material opposite to the solar cell element side in the solar cell module is the high-humidity side. At least three samples are measured, and the average of these measurements is taken as the water vapor transmission rate under those conditions.

[0091] (2) Layer composition The barrier protective member includes, for example, one or more barrier films, each comprising a base film and a barrier layer. The barrier protective member can be constructed by, for example, arranging one barrier film, but it may also include a laminate formed by stacking multiple barrier films. Figure 3 is a schematic cross-sectional view of a solar cell module in this embodiment when the barrier protective member 11 is used as the back surface protective member 5. The barrier protective member 11 shown in Figure 3 has a base film 11a and one barrier film F1 comprising a barrier layer 11b. As shown in Figure 3, it is preferable to arrange the base film 11a on the solar cell element 3 side. This is because if the base film 11a does not have hydrolysis resistance, the barrier layer 11b can suppress the deterioration of the base film 11a.

[0092] (a) Substrate film The base film is not particularly limited as long as it can support the barrier layer, but for example, it is a resin film. Examples of resins that make up the resin film include polyester resins such as polyethylene terephthalate, polyethylene naphthalate, and polybutylene terephthalate, polyimide resins, polycarbonate resins, polystyrene resins, polyamide resins such as various types of nylon, polyetherimide resins, polyetherketone resins, polyphenylene sulfide resins, polyacrylate resins, polyester ether resins, polyamideimide resins, polymethyl methacrylate resins, fluororesins, polyphenylene ether resins, and polyolefin resins.

[0093] The base film may contain additives. Examples of additives include lubricants, crosslinking agents, antioxidants, UV absorbers, light stabilizers, fillers, reinforcing agents, antistatic agents, pigments, and modifying resins.

[0094] Furthermore, the base film may be surface-treated. Surface treatment can improve adhesion with the barrier layer.

[0095] The base film may be unstretched, or it may be uniaxially or biaxially stretched.

[0096] Furthermore, the base film may or may not be transparent.

[0097] The thickness of the base film is not particularly limited as long as it can support the barrier layer, and can be, for example, 10 μm or more and 100 μm or less.

[0098] (b) Barrier layer The barrier layer is not particularly limited as long as it can provide water vapor barrier properties, and examples include metal films and inorganic compound films.

[0099] Examples of metals that make up the metal film include aluminum, nickel, stainless steel, iron, copper, titanium, and alloys containing these metals.

[0100] Inorganic compound films are primarily composed of inorganic compounds. Examples of inorganic compounds that make up an inorganic compound film include oxides, oxide nitrides, nitrides, oxide carbides, and oxide carbidine nitrides of metallic or nonmetallic elements such as silicon, aluminum, magnesium, calcium, potassium, tin, sodium, titanium, boron, yttrium, zirconium, cerium, and zinc. Specifically, examples include silicon oxide, aluminum oxide, magnesium oxide, titanium oxide, tin oxide, silicon-zinc alloy oxide, indium alloy oxide, silicon nitride, aluminum nitride, titanium nitride, silicon oxide nitride, and zinc silicon oxide. Inorganic compounds may be used individually or in mixtures of two or more.

[0101] In particular, the barrier layer is preferably an inorganic compound film. When the barrier layer is an inorganic compound film, the insulating properties can be increased, so even when electrodes and wiring are placed in contact with the barrier film, sufficient insulation can be ensured between the solar cell element and the electrodes and wiring.

[0102] The barrier layer may be a vapor-deposited film formed by a vapor deposition method, or a coated film formed by a coating method. Among these, a vapor-deposited film is preferred. A vapor-deposited film has high adhesion to the resin substrate and can exhibit high water vapor barrier properties. The barrier layer may be a single layer or a multilayer. Furthermore, if the barrier layer is a multilayer, films of the same composition may be combined, or films of different compositions may be combined.

[0103] The thickness of the barrier layer described above is not particularly limited as long as it can exhibit the desired gas barrier performance, and can be set appropriately depending on the type and composition of the barrier layer. For example, it can be in the range of 5 nm to 200 nm, and is preferably in the range of 10 nm to 100 nm. If the barrier layer is too thin, sufficient water vapor barrier performance may not be obtained. Also, if the barrier layer is too thick, cracks may easily occur. Note that if the barrier layer is a multilayer film, the thickness refers to the total thickness of the multilayer film constituting the barrier layer.

[0104] Methods for forming a barrier layer include, for example, vapor deposition and coating. Among these, vapor deposition is preferred for the reasons mentioned above. In the case of vapor deposition, the deposition may be performed only once or multiple times. That is, the vapor-deposited film may be a single layer formed by a single deposition or a multilayer formed by multiple depositions.

[0105] (c) Resin layer The barrier protective member preferably includes a resin layer on the side of the barrier layer opposite to the base film side. The manufacturing method of the barrier protective member may include a heating step. Such a heating step may cause curling due to shrinkage of the base material. If curling occurs, cracks may form in the barrier layer, potentially reducing its barrier properties.

[0106] In this disclosure, by arranging a resin layer to provide rigidity, curling of the barrier protective member can be suppressed, and a decrease in water vapor barrier properties can be suppressed. Furthermore, thermal shrinkage of the barrier protective member can be suppressed.

[0107] Furthermore, when using the barrier protective member in a solar cell module, it is preferable to position the resin layer so that it faces the atmosphere (i.e., the side opposite to the solar cell). By positioning the resin layer so that it faces the atmosphere, it can function as a protective layer for the barrier layer.

[0108] From the viewpoint of versatility, it is particularly preferable to use a polyester-based resin, such as polyethylene terephthalate resin, as the resin layer. Furthermore, it is preferable to use polyethylene terephthalate that has hydrolysis resistance.

[0109] Polyethylene terephthalate with such hydrolysis resistance is, for example, PET in which the elongation at break retention rate after treatment at 120°C and 85%RH for 48 hours in one direction and in another direction perpendicular to that direction is 20% or more compared to before treatment. The elongation at break shall be determined in accordance with JIS K7127. The aforementioned one direction may be the flow direction (MD) or the perpendicular direction (TD), or it may be a direction different from the flow direction (MD) or the perpendicular direction (TD).

[0110] The polyethylene terephthalate having the above-mentioned hydrolysis resistance preferably uses, for example, a hydrolysis-resistant polyethylene terephthalate obtained by subjecting a polyethylene terephthalate resin to a hydrolysis-resistant treatment as the base resin. Here, the hydrolysis-resistant treatment refers to treatments such as adding a hydrolysis-resistant agent such as carbodiimide, or adjusting the molecular weight to impart hydrolysis resistance.

[0111] The thickness of the resin layer is preferably 30 μm or more, and particularly preferably 50 μm or more. During the manufacturing process of the layered structure (heating process), curling caused by the shrinkage of the base material can be suppressed. This is for the purpose of [the above]. On the other hand, for example, it may be 250 μm or less, or 150 μm or less.

[0112] (d) Adhesive layer The barrier protective member may have an adhesive layer to increase the adhesive strength of each layer. The adhesive used to form such an adhesive layer is not particularly limited, and urethane-based adhesives, acrylic-based adhesives, and various conventionally known transparent adhesives can be appropriately selected.

[0113] The thickness of the adhesive layer is, for example, 3 μm or more, and may be 4 μm or more. A value greater than the above is preferable because it is easier to function as a stress relaxation layer. On the other hand, it may be, for example, 10 μm or less, and may be 7 μm or less.

[0114] (e) Others Furthermore, in this disclosure, it is preferable that the barrier protective member has a sealant layer on its outermost layer to improve adhesion to, for example, the back-side sealant layer or the front-side sealant layer. A polyethylene film is preferred as the sealant layer. The polyethylene film is not particularly limited as long as it is generally used to improve adhesion between the sealant and the protective sheet in a solar cell module.

[0115] (3) Others In this embodiment, the back protective member may be a general backsheet used in solar cell modules. For example, a metal sheet is one such example. Examples of metals that make up the metal sheet include tin, aluminum, and stainless steel. The water vapor transmission rate of the metal sheet is generally 1.0 × 10⁻⁶. -5 g / (m 2 The minimum is less than or equal to (day). On the other hand, the back surface member may be various resin films made of polyester, fluorine-containing resin, polyolefin, etc. The back surface protective member may have a higher water vapor barrier property than the above-mentioned barrier protective member. In this embodiment, since the back surface sealing material layer has water vapor barrier properties, even if the water vapor barrier property of the back surface protective member is low, the decrease in power generation efficiency can be suppressed.

[0116] 5. Surface protection material The surface protection member is positioned on the light-receiving side of the solar cell element and is a member that protects the solar cell element. The surface protection member may be a glass substrate. The water vapor transmission rate of the glass substrate is generally 1.0 × 10⁻⁶. -5 g / (m 2 It is less than or equal to (day).

[0117] 6. Solar cell element As solar cell elements, various types of solar cell elements can be used, such as silicon-based elements like monocrystalline silicon, polycrystalline silicon, and amorphous silicon; III-V and II-VI compound semiconductor elements like gallium-arsenide, copper-indium-selenium, and cadmium-tellurium; and perovskite elements. In a solar cell module, multiple solar cell elements are electrically connected in series via interconnectors equipped with conductors and solder joints.

[0118] For example, a solar cell element can be flat.

[0119] A solar cell module has multiple solar cell elements, for example, arranged vertically and horizontally. In this case, the multiple solar cell elements may be electrically connected by inner leads.

[0120] 7. Solar cell modules In this embodiment, it is more preferable that the solar cell module maintains a power generation efficiency of 95% or more after a 2000-hour humidity and heat resistance test at 85°C and 85%RH. The power generation efficiency maintenance rate is the value measured by the method described in the example.

[0121] The planar shape of the solar cell module may be various shapes, such as rectangular, square, or other polygonal shapes.

[0122] As shown in Figure 4(a), the solar cell module 10 in this embodiment may be a tandem solar cell module. In the tandem solar cell module 10 shown in Figure 4(a), a plurality of solar cell elements 3 are stacked in the thickness direction with sealing material layers in between. In the tandem solar cell module 10, of the plurality of sealing material layers, the sealing material layer located closest to the surface protective member 1 is the surface sealing material layer 2 described above, and the sealing material layer located closest to the back protective member 5 is the back sealing material layer 4 described above. The sealing material layer located between the surface sealing material layer 2 and the back sealing material layer 4 is referred to as the intermediate sealing material layer 6.

[0123] As the intermediate sealing layer, the same material as the surface sealing layer described above can be used. Specifically, the melting point Tm3 of the intermediate sealing layer is, for example, 80°C or less, preferably 70°C or less, more preferably 60°C or less, and particularly preferably 50°C or less. On the other hand, the melting point Tm3 may be, for example, 20°C or more, and may be 30°C or more.

[0124] As shown in Figure 4(b), the solar cell module 10 in this embodiment may have an impact-resistant layer 7. By having an impact-resistant layer, the impact when the module is subjected to an impact can be mitigated, and damage to the solar cell elements can be reduced. In this case, the surface sealing layer 2 may have a first surface sealing layer 2a and a second surface sealing layer 2b, and the impact-resistant layer 7 may be disposed between the first surface sealing layer 2a and the second surface sealing layer 2b. Alternatively, the back sealing layer 4 may have a first back sealing layer 4a and a second back sealing layer 4b, and the impact-resistant layer 7 may be disposed between the first back sealing layer 4a and the second back sealing layer 4b. The impact-resistant layer 7 may be disposed between the first surface sealing layer 2a and the second surface sealing layer 2b, and between the first back sealing layer 4a and the second back sealing layer 4b, or at least one of these.

[0125] Examples of impact-resistant layers include sheets with a structure in which a resin substrate is sandwiched between resin layers. Examples of resins that make up the resin substrate include polyethylene terephthalate, polyethylene naphthalate, and polyethylene. Examples of resins that make up the resin layers include polyethylene.

[0126] 8. Manufacturing method As a method for manufacturing a solar cell module in this disclosure, for example, one can first sequentially stack a surface protective member, a sealing sheet for the solar cell module, a solar cell element, another sealing sheet for the solar cell module, and a back surface protective member, and then heat-press them together using a vacuum heating lamination method or the like to integrate them. The heating temperature can be, for example, 110°C to 190°C, preferably 130°C or higher. The lamination time can be, for example, 5 minutes to 60 minutes.

[0127] A2. Second Embodiment Figure 1 is a schematic cross-sectional view showing an example of a solar cell module in this embodiment. As shown in Figure 1, the solar cell module 10 of this embodiment has a surface protective member 1, a surface sealing layer 2, a solar cell element 3, a back sealing layer 4, and a back protective member 5 stacked in this order. In this embodiment, the reflectance of the interface between the surface sealing layer and the back sealing layer, measured from the surface sealing layer side in the region where the surface sealing layer and the back sealing layer are in direct contact, is 5.50% or more and 30% or less.

[0128] The inventors of this invention have found that when the reflectance of the interface between the surface sealant layer and the back sealant layer, measured from the surface sealant layer side, is above a predetermined value, the power generation efficiency is excellent. On the other hand, if the back sealant layer is made white in order to increase the interface reflectance, the white sealant may wrap around to the light-receiving side of the solar cell element during the integration process in solar cell module manufacturing or during humidity and heat resistance tests, which can reduce the power generation efficiency.

[0129] According to this embodiment, by having a reflectivity of the interface between the surface sealing layer and the back sealing layer that is above a predetermined value, the amount of light incident on the solar cell element increases, resulting in a solar cell module with excellent power generation efficiency. Furthermore, because the above interface reflectivity is below a predetermined value, the back sealing layer does not contain a white coloring agent, which prevents the colored sealing material from wrapping around to the light-receiving side of the solar cell element during the integration process in solar cell module manufacturing and during humidity and heat resistance testing. For these reasons, the solar cell module can maintain good power generation efficiency even after humidity and heat resistance testing.

[0130] The following describes in detail each component of the solar cell module of this embodiment.

[0131] 1. Surface sealing layer and back sealing layer In this embodiment, the reflectance of the interface between the surface sealant layer and the back sealant layer, measured from the surface sealant layer side in the region where the surface sealant layer and the back sealant layer are in direct contact, is 5.50% or more, preferably 6.00% or more. On the other hand, the above interface reflectance is 30% or less, preferably 20% or less. By keeping the interface reflectance below the above value, the transparency of the back sealant layer can be improved. When a general white sealant layer is used as the back sealant layer, the above interface reflectance will be greater than 80%.

[0132] The interfacial reflectance of the surface sealant layer and the back sealant layer was determined by the following measurement method. First, a laminate of the surface sealant layer and the back sealant layer was cut from the region where the surface sealant layer and the back sealant layer are in direct contact with each other in the solar cell module. The "region where the surface sealant layer and the back sealant layer are in direct contact" refers to the region that does not overlap with the solar cell elements when the solar cell module is viewed from the thickness direction. A measurement sample was obtained by attaching black vinyl tape to the side of the back sealant layer opposite to the surface sealant layer. Using a spectrophotometer, light with a wavelength of 380 to 780 nm was incident at an incident angle of 5° from the surface sealant layer side of the measurement sample, and the reflectance (total reflectance) was measured, and the average reflectance was determined. As the black vinyl tape, a vinyl tape with an adhesive layer with a thickness of 100 μm to 200 μm, commonly used for insulation (for example, Nitto Denko Electrical Insulation Vinyl Tape No. 21) can be used. As the spectrophotometer, a JASCO V-670 can be used. The obtained average reflectance is divided by the thickness of the laminate of the measurement sample to convert it to a thickness of 1000 μm.

[0133] One method for setting the interfacial reflectance of the surface sealing layer and the back sealing layer within the above range is to increase the melting point difference (Tm2-Tm1) between the melting point Tm2 of the back sealing layer and the melting point Tm1 of the surface sealing layer. The preferred range for the melting point difference (Tm2-Tm1) is the same as that described in detail in the first embodiment above.

[0134] The back surface sealing layer in this embodiment typically does not contain a white coloring agent. Examples of white coloring agents include those conventionally used to make the sealing sheet white.

[0135] Other features of the surface sealing layer and the back sealing layer in this embodiment are the same as those described in detail in the first embodiment above.

[0136] 2. Others The surface protection member, back protection member, and solar cell element in this embodiment are the same as those described in detail in the first embodiment above. The method for manufacturing the solar cell module in this embodiment is the same as those described in detail in the first embodiment above.

[0137] B. Solar cell array This disclosure provides a solar cell array in which the aforementioned solar cell modules are arranged. Figure 5 is a plan view illustrating the solar cell array in this disclosure. As shown in Figure 5, the solar cell array 100 in this disclosure has one or more solar cell modules 10 arranged therein. The solar cell array is used by being installed on a frame, roof, etc.

[0138] The solar cell array in this disclosure has the solar cell modules described above, and is therefore capable of maintaining good power generation efficiency even after long-term use.

[0139] The number of solar cell modules in a single solar cell array may be 1 or more, and may be 10 or more. On the other hand, the number of solar cell modules may be, for example, 40 or less, and may be 30 or less.

[0140] This disclosure is not limited to the embodiments described above. The embodiments described above are illustrative, and any configuration that is substantially identical to the technical idea described in the claims of this disclosure and achieves similar effects is included within the technical scope of this disclosure. [Examples]

[0141] Examples and comparative examples are shown below to further illustrate this disclosure.

[0142] (Examples 1-4, Comparative Examples 1-4) <Fabrication of sealing material sheets> The resin components and additives listed below were used. • Polyethylene resin 1 (Resin 1): Density 0.880 g / cm³ 3α-olefin 13 mol%, α-olefin carbon number C4, C6, MFR 3.5 g / 10 min at 190°C • Polyethylene resin 2 (Resin 2): Density 0.886 g / cm³ 3 α-olefin 13 mol%, α-olefin carbon number C4, C6, MFR 30 g / 10 min at 190°C • Polyethylene resin 3 (resin 3): Density 0.919 g / cm³ 3 MFR 3.5g / 10min at 190℃ • Polyethylene resin 4 (resin 4): Density 0.898 g / cm³ 3 α-olefin 8 mol%, α-olefin carbon number C4, C6, MFR 3.5 g / 10 min at 190°C. • Ethylene-vinyl acetate copolymer (EVA)

[0143] Crosslinking agent 1: 2,5-dimethyl-2,5-di(t-butylperoxy)hexane • Crosslinking agent 2: t-butylperoxy-2-ethylhexyl carbonate • Silane coupling agent 1: Vinyltrimethoxysilane • Silane coupling agent 2: 3-methacryloxypropyltrimethoxysilane • UV absorber: 2-hydroxy-4-n-octyloxybenzophenone • HALS: Bis(2,2,6,6-tetramethyl-4-piperidyl) sebacate

[0144] The above resin components and additives were mixed in the proportions (mass%) shown in Table 1 below to obtain a encapsulant composition. The encapsulant composition was melted and extruded to form a film with the thickness shown in Table 1 to obtain a single-layer surface encapsulant sheet. The extrusion temperature is shown in Table 1.

[0145] A first encapsulant composition containing the first resin shown in Table 2 was melted and an extruded resin sheet for the skin layer was obtained. Similarly, a second encapsulant composition containing the second resin was melted and an extruded resin sheet for the skin layer was obtained. A third encapsulant composition containing the third resin was melted and an extruded resin sheet for the core layer was obtained. In Table 2, "First Resin:Second Resin:Third Resin" indicates the mass ratio of the first, second, and third resins used to form each resin sheet. These resin sheets were laminated to produce a 450 μm thick, three-layer back-side encapsulant sheet comprising a core layer and skin layers placed on both outermost surfaces (Examples 1-4). In addition, resin components and additives were mixed in the proportions (mass%) shown in Table 2 below to obtain encapsulant compositions. The above encapsulant compositions were melted and extruded to form films with the thickness shown in Table 2 to obtain single-layer back-side encapsulant sheets (Comparative Examples 1-4).

[0146] <Preparation of protective materials> In each example and comparative example, a barrier protective member having a PET film and a barrier layer (AlOx-based vapor-deposited film) was prepared as the back surface protective member. The water vapor transmission rate of the barrier protective member was 4.0 × 10⁻⁶. -3 g / (m 2 It was day ( ). A glass substrate was prepared as a surface protection material.

[0147] <Manufacturing of solar cell modules> The surface protection member, surface sealing sheet, solar cell element, back sealing sheet, and back protection member prepared above were sequentially stacked, and then heat-pressed and integrated by vacuum heating lamination at 150°C for 12 minutes (integration process). This resulted in a solar cell module in which the surface protection member, surface sealing layer, solar cell element, back sealing layer, and back protection member were stacked in this order. A TOPCon type silicon cell with a thickness of 130 μm was used as the solar cell element.

[0148] [Measurement of melting points Tm1 and Tm2] The melting points of the surface encapsulant layer and the back encapsulant layer in the integrated solar cell module were measured using the method described above. The results are shown in Tables 1 and 2. The melting point difference (Tm2-Tm1) is shown in Table 3.

[0149] [Measurement of Vicat softening point, Shore A hardness, and melt viscosity] The Vicat softening point, Shore A hardness, and melt viscosity of the surface encapsulant layer and the back surface encapsulant layer, respectively, were measured using the method described above. The results are shown in Tables 1 and 2.

[0150] [Measurement of interfacial reflectance] A laminate of the surface encapsulant layer and the back encapsulant layer was taken from the region where the surface encapsulant layer and the back encapsulant layer of the solar cell module are in direct contact, and the interfacial reflectance of the surface encapsulant layer and the back encapsulant layer was measured using the method described above. The results are shown in Table 3.

[0151] <Rating> • Initial short-circuit current Regarding the obtained solar cell modules (solar cell modules immediately after lamination), I SC The value (short-circuit current, in amperes) was measured using the following method. The short-circuit current Isc was measured using a solar simulator (XES-250S1, manufactured by Sanei Electric Works Co., Ltd.) under conditions of a cell back surface temperature of 25°C and an illuminance of 1000 W / m2. The results are shown in Table 3.

[0152] • Power generation efficiency maintenance rate The rate at which power generation efficiency was maintained after a 2000-hour humidity and heat resistance test at 85°C and 85%RH was measured using the following method. Specifically, the maximum output power Pmax was measured before and after the humidity and heat resistance test, and the ratio of Pmax after the humidity and heat resistance test to Pmax before the humidity and heat resistance test (%) was calculated. The maximum output power Pmax was measured using a solar simulator (XES-250S1, manufactured by Sanei Electric Works Co., Ltd.) with a cell back surface temperature of 25°C and an illuminance of 1000 W / m². 2 The maximum output power Pmax was measured under the specified conditions. The results are shown in Table 3.

[0153] [Table 1]

[0154] [Table 2]

[0155] [Table 3]

[0156] As shown in Table 1, solar cell modules in which the melting point Tm1 of the surface sealant layer is 80°C or lower and the melting point Tm2 of the back sealant layer is 90°C or higher were found to have high power generation efficiency and a power generation efficiency maintenance rate of 95% or higher after the humid heat resistance test (Examples 1-4). Furthermore, it was confirmed that high power generation efficiency and a power generation efficiency maintenance rate of 95% or higher after the humid heat resistance test were also found when the interfacial reflectance of the surface sealant layer and the back sealant layer were within a predetermined range (Examples 1-4).

[0157] On the other hand, in Comparative Examples 1-4, it was confirmed that the rate of maintaining power generation efficiency after the humidity and heat resistance test was low.

[0158] Thus, the present disclosure provides, for example, the following inventions. [1] A solar cell module in which a surface protective member, a surface sealing layer, a solar cell element, a back sealing layer, and a back protective member are stacked in this order, The melting point Tm1 of the above surface sealing layer is 80°C or lower. A solar cell module in which the melting point Tm2 of the back surface sealing material layer is 90°C or higher. [2] The solar cell module described in [1], wherein the difference between the above melting point Tm2 and the above melting point Tm1 (Tm2-Tm1) is 20°C or more. [3] The solar cell module according to [1] or [2], wherein the reflectance of the interface between the surface sealing layer and the back sealing layer, measured from the surface sealing layer side in the region where the surface sealing layer and the back sealing layer are in direct contact, is 5.50% or more and 30% or less. [4] The above-mentioned back-side protective material has a water vapor transmission rate of 1.0 × 10 -4 g / (m 2 ·day) or more, 1.0g / (m 2 A solar cell module listed in any of [1] to [3] below the specified day. [5] A solar cell module in which a surface protective member, a surface sealing layer, a solar cell element, a back sealing layer, and a back protective member are stacked in this order, A solar cell module in which the reflectance of the interface between the surface sealing layer and the back sealing layer, measured from the surface sealing layer side in the region where the surface sealing layer and the back sealing layer are in direct contact, is 5.50% or more and 30% or less. [6] The above-mentioned back-side protective material has a water vapor transmission rate of 1.0 × 10 -4 g / (m 2 ·day) or more, 1.0g / (m 2 The solar cell module described in [5] is less than or equal to day (day). [7] A solar cell array in which any of the solar cell modules described in [1] through [6] are arranged. [Explanation of Symbols]

[0159] 1 ... Surface protection material 2 … Surface sealing material layer 3… Click the solar panel button. 4. Backside sealing layer 5. Back surface protective material 10… Solar cell modules 100... Solar cell array

Claims

1. A solar cell module in which a surface protective member, a surface sealing layer, a solar cell element, a back sealing layer, and a back protective member are stacked in this order, The melting point Tm1 of the surface sealing material layer is 80°C or lower. The melting point Tm2 of the back surface sealing material layer is 90°C or higher. In the region where the surface sealing material layer and the back sealing material layer are in direct contact, the reflectance of the interface between the surface sealing material layer and the back sealing material layer, measured from the surface sealing material layer side, is 5.50% or more and 30% or less. The aforementioned back surface sealing layer does not contain a white coloring agent. The aforementioned back surface sealing layer has a plurality of layers, The back sealing material layer having the plurality of layers comprises a skin layer disposed on both outermost surfaces and a core layer which is an intermediate layer other than the skin layer, in a solar cell module.

2. The solar cell module according to claim 1, wherein the difference between the melting point Tm2 and the melting point Tm1 (Tm2 - Tm1) is 20°C or more.

3. The aforementioned back surface protective member has a water vapor transmission rate of 1.0 × 10 －４ g / (m) ２ ・day) or more, 1.0g / (m ２ The solar cell module according to claim 1, wherein the number of days is less than or equal to the number of days.

4. A solar cell module in which a surface protective member, a surface sealing layer, a solar cell element, a back sealing layer, and a back protective member are stacked in this order, In the region where the surface sealing material layer and the back sealing material layer are in direct contact, the reflectance of the interface between the surface sealing material layer and the back sealing material layer, measured from the surface sealing material layer side, is 5.50% or more and 30% or less. The aforementioned back-side sealing layer does not contain a white coloring agent in the solar cell module.

5. The aforementioned back surface protective member has a water vapor transmission rate of 1.0 × 10 －４ g / (m) ２ ・day) or more, 1.0g / (m ２ The solar cell module according to claim 4, wherein the number of days is less than or equal to the number of days.

6. A solar cell array in which solar cell modules according to any one of claims 1 to 5 are arranged.

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