Encapsulant sheet for solar cell module and solar cell module

Abstract

To provide a sealing-material sheet for solar battery module, which allows an isolation distance to be ensured between solar battery elements when used for a tandem-type solar battery module, and which is superior in the followability to irregularities coming from a solar battery element, a wiring line, etc.SOLUTION: A sealing-material sheet 1 for solar battery module comprises a first external layer 2, an internal layer 3, a second external layer 4 in this order. The internal layer 3 has a storage elastic modulus of 1.0×107 Pa or more and 5.0×108 Pa or less at 120°C. The first external layer 2 and the second external layer 4 have a melt viscosity of 5.0×102 Pa s or more and 5.0×105 Pa s or less at a shear rate of 2.43×10 sec-1 at 120°C, and an average transmittance of 70% or more under the condition of a wavelength of 400 nm or more and 1200 nm or less.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present disclosure relates to a tandem solar cell module in which a plurality of solar cell elements having different maximum absorption wavelengths are stacked via an insulating layer, a solar cell module sealing material sheet used in the insulating layer, and a solar cell module using the same. [Background technology]

[0002] In recent years, global warming caused by carbon dioxide has become a worldwide problem. In response to this problem, solar cells that utilize solar energy have attracted attention as an environmentally friendly, clean energy source, and active research and development is being carried out. In particular, there is a demand for even higher efficiency solar cells.

[0003] As one of the high efficiency technologies, research and development of tandem solar cells in which different types of solar cell elements are stacked has been actively conducted in recent years (see, for example, Patent Documents 1 to 3). In tandem solar cells, the absorption wavelength range of sunlight can be broadened as a whole, improving the utilization efficiency of sunlight and achieving high efficiency. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 3-272186 [Patent Document 2] JP 2009-289946 A [Patent Document 3] JP 2001-230437 A Summary of the Invention [Problem to be solved by the invention]

[0005] As a method for manufacturing a tandem solar cell module, for example, a general sealing method in which each solar cell element is sealed with a sealing material can be used. However, when laminating each solar cell element with the sealing material, the thickness of the sealing material becomes thin due to heating and pressure during lamination, and it is therefore difficult to ensure an insulation distance between each solar cell element.

[0006] For example, by increasing the melting point of the resin contained in the sealing material, the fluidity of the resin can be suppressed, and thus the thickness of the sealing material can be secured even after lamination, and it is possible to secure the insulation distance between each solar cell element. However, if the melting point of the resin contained in the sealing material is increased, there is a risk that the ability to conform to the unevenness caused by the solar cell elements, wiring, etc. will decrease. In that case, the unevenness and gaps caused by the solar cell elements, wiring, etc. will not be filled sufficiently, and cracks or residual air bubbles may occur in the solar cell elements.

[0007] The present disclosure has been made in consideration of the above-mentioned circumstances, and has as its main object to provide an encapsulant sheet for solar cell modules which, when used in a tandem solar cell module, is capable of ensuring an insulation distance between each solar cell element and has excellent conformability to irregularities caused by the solar cell elements, wiring, etc. [Means for solving the problem]

[0008] One embodiment of the present disclosure is a solar cell module encapsulant sheet having a first outer layer, an inner layer, and a second outer layer in this order, wherein the inner layer has a storage modulus of 1.0×10 at 120° C. 7 Pa or more 5.0×10 8 Pa or less, and the shear rate of the first outer layer and the second outer layer at 120°C is 2.43 x 10 sec -1 The melt viscosity at is 5.0×10 2 Pa·s or more 5.0×10 5 The present invention provides an encapsulant sheet for a solar cell module, which has a transmittance of 70% or more in a wavelength range of 400 nm or more and 1,200 nm or less.

[0009] Another embodiment of the present disclosure provides a solar cell module in which a plurality of solar cell elements having different maximum absorption wavelengths are stacked via an insulating layer, the insulating layer being the above-mentioned solar cell module encapsulant sheet. Effect of the Invention

[0010] The present disclosure has the effect of providing an encapsulant sheet for solar cell modules that, when used in a tandem solar cell module, is capable of ensuring an insulation distance between each solar cell element and has excellent conformability to unevenness due to the solar cell elements, unevenness, etc. [Brief description of the drawings]

[0011] [Figure 1] FIG. 1 is a schematic cross-sectional view illustrating an example of a solar cell module encapsulant sheet according to the present disclosure. [Diagram 2] 1 is a schematic cross-sectional view illustrating a solar cell module according to the present disclosure. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0012] The following describes the embodiments of the present disclosure with reference to the drawings. However, the present disclosure can be implemented in many different forms, and should not be interpreted as being limited to the description of the embodiments exemplified below. In addition, the drawings may be schematic in terms of the width, thickness, shape, etc. of each part compared to the actual form in order to make the explanation clearer, but these are merely examples and do not limit the interpretation of the present disclosure. In this specification and each figure, elements similar to those described above with respect to the previous figures may be given the same reference numerals, and detailed explanations may be omitted as appropriate.

[0013] In this specification, when describing a mode in which another component is disposed on a certain component, the term "above" or "below" is intended to include both a case in which another component is disposed directly above or below a certain component so as to be in contact with the component, and a case in which another component is disposed above or below a certain component with another component interposed therebetween, unless otherwise specified. Also, in this specification, when describing a mode in which another component is disposed on the surface of a certain component, the term "on the surface" is intended to include both a case in which another component is disposed directly above or below a certain component so as to be in contact with the component, and a case in which another component is disposed above or below a certain component with another component interposed therebetween, unless otherwise specified.

[0014] In this specification, the term "sheet" also includes a member called a "film." The term "film" also includes a member called a "sheet."

[0015] The solar cell module encapsulant sheet and the solar cell module according to the present disclosure will be described in detail below.

[0016] A. Solar cell module encapsulant sheet The present disclosure provides a solar cell module encapsulant sheet having a first outer layer, an inner layer, and a second outer layer in this order, the inner layer having a storage modulus of 1.0×10 at 120° C. 7 Pa or more 5.0×10 8 Pa or less, and the shear rate of the first outer layer and the second outer layer at 120°C is 2.43 x 10 sec -1 The melt viscosity at is 5.0×10 2 Pa·s or more 5.0×10 5 The optical transmittance is 70% or more at wavelengths of 400 nm or more and 1,200 nm or less.

[0017] Fig. 1 is a schematic cross-sectional view showing an example of a solar cell module encapsulant sheet according to the present disclosure. As shown in Fig. 1, the solar cell module encapsulant sheet 1 has, in this order, a first outer layer 2, an inner layer 3, and a second outer layer 4. The inner layer 3 has a storage modulus at 120°C within a predetermined range, the first outer layer 2 and the second outer layer 4 have melt viscosities at 120°C within predetermined ranges, and the solar cell module encapsulant sheet 1 has a predetermined transmittance in a predetermined wavelength region.

[0018] In the present disclosure, since the storage modulus at 120°C of the inner layer is within a predetermined range, when the solar cell module sealant sheet of the present disclosure is used in a tandem solar cell module, deformation of the inner layer due to heating and pressure during lamination can be suppressed when laminating multiple solar cell elements via the solar cell module sealant sheet, and the thickness of the inner layer can be ensured after lamination. Therefore, in the tandem solar cell module, an insulation distance can be ensured between the upper solar cell element and the lower solar cell element.

[0019] Furthermore, in the present disclosure, since the melt viscosity at 120°C of the first outer layer and the second outer layer is within a predetermined range, when the solar cell module encapsulant sheet of the present disclosure is used in a tandem solar cell module, when a plurality of solar cell elements are laminated via the solar cell module encapsulant sheet, the flowability of the resin contained in the first outer layer and the second outer layer during lamination can be improved, and conformability to irregularities due to the solar cell elements, wiring, etc. can be improved. Thus, the resin contained in the first outer layer and the second outer layer can fill in irregularities and gaps due to the solar cell elements, wiring, etc., and cracks in the solar cell elements and residual air bubbles can be suppressed.

[0020] Here, when laminating a plurality of solar cell elements via an encapsulant sheet in manufacturing a tandem solar cell module, the heating temperature during lamination is generally set to 120°C to 150°C. In addition, during vacuum lamination, the encapsulant sheet generally begins to exhibit adhesion at about 70°C to 90°C, and then the area where it adheres increases stepwise, and while flowing at about 120°C, it follows the unevenness of the solar cell elements, wiring, etc., thereby performing vacuum lamination. Therefore, in the present disclosure, attention is paid to the deformation of the inner layer during lamination, and the storage modulus at 120°C of the inner layer is set to a predetermined range. In addition, attention is paid to the fluidity of the resin contained in the first outer layer and the second outer layer during lamination, and the melt viscosity at 120°C of the first outer layer and the second outer layer is set to a predetermined range.

[0021] As described above, in the present disclosure, a three-layer structure consisting of a first outer layer, an inner layer, and a second outer layer is used, and each layer has predetermined characteristics, so that when used in a tandem solar cell module, it is possible to ensure both the insulation distance between each solar cell element and the ability to conform to unevenness caused by the solar cell elements, wiring, etc.

[0022] In general, in a tandem solar cell module, solar cell elements with a relatively large band gap are arranged on the light-receiving surface side, and solar cell elements with a relatively small band gap are arranged on the back surface side. In such a tandem solar cell module, the solar cell elements on the light-receiving surface side absorb light in the short wavelength range, and the solar cell elements on the back surface side absorb light in the long wavelength range, thereby expanding the absorption wavelength range of sunlight.

[0023] Therefore, in the present disclosure, attention is focused on the transmittance in the long wavelength range, and the average transmittance in the wavelength range of 400 nm or more and 1200 nm or less is set to a predetermined range. By setting the average transmittance in the above wavelength range of the encapsulant sheet for solar cell modules in the present disclosure to be within the predetermined range, light in the long wavelength range can be sufficiently transmitted, and when the encapsulant sheet for solar cell modules in the present disclosure is used in a tandem solar cell module, the solar cell element arranged on the back side of the encapsulant sheet for solar cell modules can efficiently absorb light in the long wavelength range, thereby achieving high efficiency.

[0024] In addition, in the present disclosure, since the storage modulus at 120° C. of the inner layer is within a predetermined range, the heat resistance and rigidity of the inner layer can be increased, and therefore, a solar cell module encapsulant sheet having excellent heat resistance and easy handling can be obtained.

[0025] Hereinafter, each component of the encapsulant sheet for a solar cell module in the present disclosure will be described.

[0026] 1. Inner layer The inner layer in the present disclosure is a layer disposed between the first outer layer and the second outer layer, and has a storage modulus at 120° C. within a predetermined range.

[0027] The storage modulus of the inner layer at 120°C is 1.0×10 7 Pa or more, 3.0×10 7 Pa or more, and 7 Pa or more. If the storage modulus is too small, when the solar cell module encapsulant sheet of the present disclosure is used in a tandem solar cell module, the inner layer may be easily deformed by heating and pressure during lamination when laminating multiple solar cell elements via the solar cell module encapsulant sheet, and the thickness of the inner layer may not be maintained. As a result, the thickness of the inner layer after lamination may be thin overall or partially, and an insulating distance may not be ensured between the upper solar cell element and the lower solar cell element. On the other hand, the storage modulus of the inner layer at 120°C may be, for example, 5.0 x 108 Pa or less, 2.0×10 8 Pa or less, and 9.0×10 7 If the storage modulus is too large, the rigidity of the inner layer becomes too high, and thus, when a plurality of solar cell elements are laminated via the solar cell module encapsulant sheet in the manufacturing process of the solar cell module, the conformability to irregularities due to the solar cell elements, wiring, etc. decreases, and air bubbles and the like may be easily generated after lamination.

[0028] Here, the storage modulus can be measured by a method conforming to JIS K7244-4:1999 using a dynamic viscoelasticity measuring device. The measurement is performed by a tensile method, in which the inner layer is separated from the solar cell module encapsulant sheet as described below, a sample of a desired size is cut out from the inner layer, both ends of the sample are attached to the chucks of the dynamic viscoelasticity measuring device so that the tensile direction is the longitudinal direction of the sample, and a tensile load is applied. As the dynamic viscoelasticity measuring device, for example, Rheogel-E4000 manufactured by UBM Co., Ltd. can be used. Specific measurement conditions are shown below.

[0029] (Storage modulus measurement conditions) Measurement sample: 5mm x 20mm rectangle Measurement mode: Tensile method (sine wave strain, tension mode, strain amount: automatic strain) Heating rate: 3℃ / min Frequency: 10Hz Tensile load (static load): 100g

[0030] As a method for separating the inner layer from the encapsulant sheet for a solar cell module, for example, a method can be used in which the interfaces between the first outer layer, the inner layer, and the second outer layer are confirmed using an optical microscope, and the encapsulant sheet for a solar cell module is sliced ​​at the interfaces between each layer.

[0031] The storage modulus of the inner layer at 120°C can be adjusted, for example, by the type and composition of the resin in the resin composition contained in the inner layer. In addition, for example, when the inner layer contains a polyolefin resin, the storage modulus can be adjusted by the type of polyolefin resin, the addition of materials other than the polyolefin resin, the composition of the resin composition, etc. For example, the storage modulus can be adjusted by the melting point, molecular weight, density, etc. of the polyolefin resin. Specifically, when the melting point of the polyolefin resin is increased, the storage modulus tends to increase, and when the melting point of the polyolefin resin is decreased, the storage modulus tends to decrease. When the molecular weight of the polyolefin resin is increased, the melting point tends to increase and the storage modulus tends to increase, and when the molecular weight of the polyolefin resin is decreased, the melting point tends to decrease and the storage modulus tends to decrease. When the density of the polyolefin resin is increased, the melting point tends to increase and the storage modulus tends to increase, and when the density of the polyolefin resin is decreased, the melting point tends to decrease and the storage modulus tends to decrease. Also, for example, the storage modulus can be adjusted by including resins having different storage moduli or melting points at 120°C as polyolefin resins. Specifically, the storage modulus can be increased by adding a resin having a higher storage modulus or a higher melting point than the base resin. More specifically, the storage modulus can be increased by using a polyethylene resin as the base resin and adding a polypropylene resin. Also, for example, the storage modulus can be increased by adding a filler.

[0032] In addition, the melting point of the inner layer is preferably higher than that of the first outer layer and the second outer layer. By having the melting point of the inner layer higher than that of the first outer layer and the second outer layer, the fluidity of the resin contained in the inner layer can be suppressed, and when the solar cell module sealant sheet of the present disclosure is used in a tandem solar cell module, when a plurality of solar cell elements are laminated through the solar cell module sealant sheet, the resin contained in the inner layer can be prevented from flowing due to heating and pressure during lamination, and the thickness of the inner layer after lamination can be prevented from becoming thin. In addition, by having the melting points of the first outer layer and the second outer layer lower than that of the inner layer, the fluidity of the resin contained in the first outer layer and the second outer layer can be increased, and the ability to follow unevenness caused by solar cell elements, wiring, etc. can be improved.

[0033] Specifically, the melting point of the inner layer is 120°C or higher, may be 130°C or higher, or may be 140°C or higher. If the melting point of the inner layer is too low, the fluidity of the resin contained in the inner layer increases, and when the solar cell module encapsulant sheet of the present disclosure is used in a tandem solar cell module, when a plurality of solar cell elements are laminated through the solar cell module encapsulant sheet, the resin contained in the inner layer may flow due to heating and pressure during lamination. As a result, the thickness of the inner layer after lamination may be thin overall or partially, and it may be difficult to ensure an insulating distance between the upper solar cell element and the lower solar cell element. On the other hand, the melting point of the inner layer may be, for example, 190°C or lower, may be 180°C or lower, or may be 170°C or lower. If the melting point of the inner layer is too high, the resin contained in the inner layer may be difficult to melt during lamination, making it difficult to perform appropriate lamination.

[0034] Here, the melting point of the inner layer can be obtained by, for example, measurement by differential scanning calorimetry (DSC). When there are multiple valley peaks in the DSC curve, the melting point indicated by the peak with the largest peak area among them can be the melting point of the inner layer. In addition, as another method for identifying the melting point of the inner layer, for example, when the measured linear expansion coefficient measured in accordance with JIS K7179 is expressed as a function of the resin temperature, a method of approximately determining the melting point by measuring the linear expansion peak temperature, which is the temperature at the maximum value when the linear expansion coefficient changes from increasing to decreasing, may be adopted. When measuring the melting point of the inner layer, for example, the inner layer can be separated from the solar cell module encapsulant sheet and the measurement can be performed. As a method for separating the inner layer from the solar cell module encapsulant sheet, as described above, for example, a method of confirming the interfaces of the first outer layer, the inner layer, and the second outer layer using an optical microscope and slicing the solar cell module encapsulant sheet at the interfaces of each layer can be used.

[0035] The inner layer contains a resin. The resin contained in the inner layer is not particularly limited as long as it is a resin that can provide an inner layer that satisfies the above-mentioned storage modulus, and examples thereof include polyolefin resin, polyethylene terephthalate, acrylic resin, etc. Among them, it is preferable that the inner layer contains a polyolefin resin.

[0036] The polyolefin resin is not particularly limited as long as it is a polyolefin resin that can obtain an inner layer that satisfies the above-mentioned storage modulus, and examples thereof include polyethylene resin, polypropylene resin, propylene-ethylene copolymer resin, ethylene-α-olefin copolymer resin, etc. Among them, the inner layer preferably contains a polyethylene resin and a polypropylene resin. By containing the polyethylene resin and the polypropylene resin, it is possible to obtain an inner layer that satisfies the above-mentioned storage modulus and has excellent heat resistance and dimensional stability.

[0037] Examples of polyethylene resins include high density polyethylene (HDPE), low density polyethylene (LDPE), linear low density polyethylene (LLDPE), metallocene linear low density polyethylene (M-LLDPE), very low density polyethylene (VLDPE), etc. The polyethylene resins may be used alone or in combination of two or more kinds.

[0038] Among them, low density polyethylene (LDPE), linear low density polyethylene (LLDPE), metallocene linear low density polyethylene (M-LLDPE), and very low density polyethylene (VLDPE) are preferred because of their good flexibility and processability. In particular, linear low density polyethylene (LLDPE) and metallocene linear low density polyethylene (M-LLDPE) are preferred because of their excellent flexibility, processability, and strength. Furthermore, metallocene linear low density polyethylene (M-LLDPE) is preferred. 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 distribution of comonomers. For this reason, the molecular weight distribution is narrow, and it is possible to reduce the density as described below, and flexibility can be imparted to the inner layer.

[0039] The density of the polyethylene resin is not particularly limited, and is, for example, 0.870 g / cm 3 More than 0.93g / cm 3 It is preferable that the density is 0.875 g / cm or less. 3 More than 0.92g / cm 3 More preferably, it is 0.880 g / cm or less. 3 More than 0.91g / cm 3 When the density of the polyethylene resin is within the above range, the inner layer can have excellent flexibility and processability.

[0040] Here, the density of the polyethylene resin can be measured, for example, by a pycnometer method in accordance with JIS K7112.

[0041] The melting point of the polyethylene resin is not particularly limited, and is preferably 45°C or higher and 105°C or lower, more preferably 50°C or higher and 100°C or lower, and even more preferably 55°C or higher and 95°C or lower. If the melting point of the polyethylene resin is too high, when the solar cell module encapsulant sheet of the present disclosure is used in a tandem solar cell module, the heating temperature needs to be increased when laminating a plurality of solar cell elements through the solar cell module encapsulant sheet, which may increase the manufacturing cost. On the other hand, if the melting point of the polyethylene resin is too low, the inner layer may melt in the usage environment of the solar cell module.

[0042] In this specification, the melting point of the resin can be measured by differential scanning calorimetry (DSC) in accordance with JIS K7121 (Method for measuring transition temperature of plastics). In this case, when two or more melting point peaks exist, the higher temperature can be regarded as the melting point.

[0043] The melt mass flow rate (MFR) of the polyethylene resin at 190° C. is, for example, preferably 1.0 g / 10 min or more and 10.0 g / 10 min or less, more preferably 1.0 g / 10 min or more and 7.0 g / 10 min or less, and even more preferably 1.0 g / 10 min or more and 5.0 g / 10 min or less. By having the MFR of the polyethylene resin within the above range, it is possible to obtain an inner layer having excellent flexibility and processability.

[0044] Here, the melt mass flow rate (MFR) of the polyethylene resin can be measured in accordance with JIS K7210-1 under the measurement conditions of a temperature of 190° C. and a load of 2.16 kg.

[0045] The content of the polyethylene resin is, for example, preferably 10 parts by mass or more and 60 parts by mass or less, more preferably 10 parts by mass or more and 50 parts by mass or less, and even more preferably 20 parts by mass or more and 40 parts by mass or less, relative to 100 parts by mass of all resin components contained in the inner layer.

[0046] Here, the ratio of each resin component contained in each layer of the encapsulant sheet for solar cell module in the present disclosure can be analyzed, for example, from peak ratios detected by differential scanning calorimetry (DSC), infrared spectroscopy (IR), nuclear magnetic resonance (NMR), or the like.

[0047] The polypropylene resin may be, for example, homopolypropylene, which is a propylene homopolymer, random polypropylene, which is a random copolymer of propylene and α-olefin, or block polypropylene, which is a block copolymer. The polypropylene resin may be used alone or in combination of two or more kinds. Among them, the polypropylene resin is preferably homopolypropylene. Since homopolypropylene has high rigidity, it can increase the storage elasticity of the inner layer.

[0048] The melting point of the polypropylene resin is not particularly limited, and is preferably 130°C or higher and 180°C or lower, more preferably 140°C or higher and 180°C or lower, and even more preferably 150°C or higher and 180°C or lower. If the melting point of the polypropylene resin is too high, when the solar cell module encapsulant sheet of the present disclosure is used in a tandem solar cell module, the heating temperature needs to be increased when laminating a plurality of solar cell elements through the solar cell module encapsulant sheet, which may increase the manufacturing cost. On the other hand, if the melting point of the polypropylene resin is too low, the storage modulus of the inner layer may be insufficient.

[0049] The melt mass flow rate (MFR) of the polypropylene resin at 230° C. is, for example, preferably 3 g / 10 min or more and 20 g / 10 min or less, more preferably 5 g / 10 min or more and 15 g / 10 min or less, and even more preferably 7 g / 10 min or more and 11 g / 10 min or less. By having the MFR of the polypropylene resin within the above range, it is possible to obtain an inner layer having excellent flexibility.

[0050] The melt mass flow rate (MFR) of the polypropylene resin can be measured in accordance with JIS K7210-1 under the following measurement conditions: temperature 230° C., load 2.16 kg.

[0051] The content of the polypropylene resin is, for example, preferably 30 parts by mass or more and 90 parts by mass or less, more preferably 40 parts by mass or more and 80 parts by mass or less, and even more preferably 50 parts by mass or more and 70 parts by mass or less, based on 100 parts by mass of the total resin components contained in the inner layer. If the content of the polypropylene resin is too high, the flexibility of the solar cell module encapsulant sheet as a whole may decrease. If the content of the polypropylene resin is too low, the desired storage modulus may not be obtained.

[0052] In addition, the inner layer preferably contains a compatibilizer to improve the compatibility between the polyethylene resin and the polypropylene resin. By containing the compatibilizer, the transparency of the inner layer can be improved.

[0053] As the compatibilizer, a general compatibilizer for polyethylene resins and polypropylene resins can be used, and examples thereof include polypropylene-based elastomers and polyethylene-based elastomers.

[0054] Among them, it is preferable to use a polypropylene-based elastomer and a polyethylene-based elastomer in combination as the compatibilizer. By containing a polypropylene-based elastomer and a polyethylene-based elastomer in the inner layer, the compatibility of the polyethylene resin and the polypropylene resin can be improved and the transparency of the inner layer can be increased.

[0055] An example of the polypropylene-based elastomer is a copolymer of propylene and an α-olefin other than propylene (hereinafter, sometimes referred to as a propylene-α-olefin copolymer). The α-olefin other than propylene constituting the propylene-α-olefin copolymer may be one type or two or more types.

[0056] The polypropylene-based elastomer may be, for example, a commercially available product, such as "TAFMER PN-0040 (product name)" or "TAFMER PN-2060 (product name)" manufactured by Mitsui Chemicals, Inc.

[0057] The content of the polypropylene-based elastomer in the inner layer is, for example, 3% by mass or more, may be 5% by mass or more, or may be 8% by mass or more. If the content of the polypropylene-based elastomer is too small, the effect of improving the compatibility of the polyethylene resin and the polypropylene resin may not be sufficiently obtained. On the other hand, the content of the polypropylene-based elastomer in the inner layer is, for example, 25% by mass or less, may be 20% by mass or less, or may be 15% by mass or less. If the content of the polypropylene-based elastomer is too high, the heat resistance of the inner layer may be reduced.

[0058] An example of the polyethylene elastomer is a copolymer of ethylene and an α-olefin other than ethylene (hereinafter, sometimes referred to as an ethylene-α-olefin copolymer). The α-olefin other than ethylene constituting the ethylene-α-olefin copolymer may be one type or two or more types.

[0059] The polyethylene elastomer may be, for example, a commercially available product, such as "TAFMER DF-110 (product name)" or "TAFMER DF-640 (product name)" manufactured by Mitsui Chemicals.

[0060] The content of the polyethylene-based elastomer in the inner layer is, for example, 5% by mass or more, may be 10% by mass or more, or may be 15% by mass or more. If the content of the polyethylene-based elastomer is too small, the effect of improving the compatibility of the polyethylene resin and the polypropylene resin may not be sufficiently obtained. On the other hand, the content of the polyethylene-based elastomer in the inner layer is, for example, 40% by mass or less, may be 35% by mass or less, or may be 30% by mass or less. If the content of the polyethylene-based elastomer is too high, the heat resistance of the inner layer may be reduced.

[0061] The inner layer may also contain a silane component such as a silane coupling agent or a silane-modified polyolefin resin, etc. By containing a silane component in the inner layer, strength, durability, etc. can be improved.

[0062] As the silane coupling agent, a silane coupling agent used in a general solar cell module sealing material sheet can be used. The silane coupling agent may be used alone or in combination of two or more kinds.

[0063] The silane-modified polyolefin resin will be described later in the sections on the first outer layer and the second outer layer, and therefore the description here will be omitted. The silane-modified polyolefin resin may be used alone or in combination of two or more kinds.

[0064] The content of the silane component in the inner layer is not particularly limited, and is, for example, preferably from 5% by mass to 40% by mass, more preferably from 8% by mass to 30% by mass, and even more preferably from 10% by mass to 25% by mass.

[0065] The inner layer may contain additives as necessary. Examples of additives include light stabilizers, ultraviolet absorbers, heat stabilizers, antioxidants, and fillers. A masterbatch may be used as a weathering agent such as a light stabilizer or an ultraviolet absorber. The content of the additives in the inner layer varies depending on the particle shape, density, and the like, and may be, for example, 0.001% by mass or more and 5% by mass or less. The inner layer may contain additives to improve mechanical strength stably over a long period of time and to suppress yellowing, cracking, and the like.

[0066] The thickness of the inner layer is preferably equal to or greater than the insulation distance required between an upper solar cell element and a lower solar cell element in a solar cell module in which a plurality of solar cell elements having different maximum absorption wavelengths are stacked via an insulating layer. This is because, in a solar cell module in which a plurality of solar cell elements having different maximum absorption wavelengths are stacked via an insulating layer, when the solar cell module encapsulant sheet of the present disclosure is used for the insulating layer, an insulation distance can be ensured between the upper solar cell element and the lower solar cell element.

[0067] Here, in a solar cell module in which a plurality of solar cell elements having different maximum absorption wavelengths are stacked with an insulating layer interposed therebetween, the insulation distance required between the upper solar cell element and the lower solar cell element refers to the insulation distance required between any two solar cell elements stacked with an insulating layer interposed therebetween. For example, in a solar cell module, when two solar cell elements are stacked with an insulating layer interposed therebetween, that is, when a first solar cell element, an insulating layer, and a second solar cell element are arranged in order, it is preferable that the thickness of the inner layer is equal to or greater than the insulation distance required between the first solar cell element and the second solar cell element. Also, for example, in a solar cell module, when three solar cell elements are stacked with an insulating layer interposed therebetween, that is, when a first solar cell element, an insulating layer, a second solar cell element, an insulating layer, and a third solar cell element are arranged in order, it is preferable that the thickness of the inner layer is equal to or greater than the insulation distance required between the first solar cell element and the second solar cell element, or equal to or greater than the insulation distance required between the second solar cell element and the third solar cell element.

[0068] Specifically, the thickness of the inner layer is 200 μm or more, may be 300 μm or more, or may be 400 μm or more. When the thickness of the inner layer is in the above range, in a solar cell module in which a plurality of solar cell elements having different maximum absorption wavelengths are laminated via an insulating layer, a sufficient insulation distance can be secured between the upper solar cell element and the lower solar cell element when the solar cell module encapsulant sheet of the present disclosure is used for the insulating layer. In addition, when the thickness of the inner layer is in the above range, good dimensional stability can be obtained. On the other hand, the thickness of the inner layer is, for example, 800 μm or less, may be 700 μm or less, or may be 600 μm or less. If the thickness of the inner layer is too thick, the transparency may be reduced.

[0069] The thickness ratio of the first outer layer, the inner layer, and the second outer layer is not particularly limited as long as the thickness of the inner layer is within the above range, but for example, when the first outer layer: the inner layer: the second outer layer is, it is preferably 1:1:1 to 1:10:1, more preferably 1:1:1 to 1:9:1, and even more preferably 1:1:1 to 1:8:1. When the thickness ratio is within the above range, the thickness of the inner layer can be relatively thick, and insulation can be easily ensured. Furthermore, if the thicknesses of the first outer layer and the second outer layer are relatively too thin, there is a risk that the embedding ability for unevenness caused by solar cell elements, wiring, etc. will decrease.

[0070] Here, the thickness of each layer can be the average value of thicknesses at any 10 points obtained by measuring a cross section in the thickness direction of the solar cell module encapsulant sheet observed with a transmission electron microscope (TEM), a scanning electron microscope (SEM), or a scanning transmission electron microscope (STEM). Unless otherwise specified, the same method can be used to measure the thickness of other members.

[0071] As a molding method of the inner layer, for example, only the inner layer may be molded as a single layer, or the first outer layer, the inner layer, and the second outer layer may be molded integrally as a multilayer. As a molding method of a single layer, a molding method of a normal thermoplastic resin can be used, and examples of the molding methods include various molding methods such as extrusion molding such as inflation method and T-die method, injection molding, blow molding, compression molding, and rotational molding. In addition, as an example of a molding method of a multilayer, a method of molding by co-extrusion using two or more types of melt kneading extruders can be mentioned.

[0072] 2. First and second outer layers In the present disclosure, a first outer layer is disposed on one surface of the inner layer, and a second outer layer is disposed on the other surface of the inner layer. The first outer layer and the second outer layer have melt viscosities at 120° C. within a predetermined range.

[0073] Shear rate of the first and second outer layers at 120°C: 2.43 x 10 sec -1 The melt viscosity at is 5.0×10 5 Pa s or less, 1.0×10 5 Pa s or less, and 5.0×10 4 If the melt viscosity is too high, the flowability of the resin contained in the first outer layer and the second outer layer may be reduced, and the ability to conform to irregularities due to the solar cell elements, wiring, etc. may be reduced. On the other hand, the melt viscosity of the first outer layer and the second outer layer at 120° C. may be, for example, 5.0×10 2 Pa s or more, 1.0×10 3 Pa s or more, and 3.0×10 3 If the melt viscosity is too low, blocking resistance decreases, and the solar cell module encapsulant sheet may become difficult to handle.

[0074] The melt viscosity can be measured by a method conforming to JIS K7199. The measurement is performed at a temperature of 120° C. and a shear rate of 2.43×10 sec -1The measurement is performed using a capillary with a melt viscosity of 1 mm, D=1 mm, and L / D=10. For example, a Capillograph 1-B manufactured by Toyo Seiki Seisakusho can be used as the capillary rheometer. When measuring the melt viscosity of the first outer layer and the second outer layer at 120° C., the first outer layer and the second outer layer are separated from the solar cell module encapsulant sheet. As a method for separating the first outer layer and the second outer layer from the solar cell module encapsulant sheet, for example, a method can be used in which the interfaces of the first outer layer, the inner layer, and the second outer layer are confirmed using an optical microscope, and the solar cell module encapsulant sheet is sliced ​​at the interfaces of the layers.

[0075] The melt viscosity of the first outer layer and the second outer layer at 120°C can be adjusted, for example, by the type and composition of the resin in the resin composition contained in the first outer layer and the second outer layer. In addition, for example, when the first outer layer and the second outer layer contain a polyolefin resin, the melt viscosity can be adjusted by the type of polyolefin resin, the addition of materials other than the polyolefin resin, the composition of the resin composition, and the like. For example, the melt viscosity can be adjusted by the molecular structure, molecular weight, density, and the like of the polyolefin resin. As the molecular structure of the polyolefin resin, for example, the type and number of polymerizations of the polyolefin resin, the length of the linear portion, the number and length of the branched portions, and the type, number, and length of the side chain portion can be adjusted. Specifically, when the length of the linear portion of the polyolefin resin is increased, the melt viscosity tends to be decreased, and when the length of the linear portion of the polyolefin resin is decreased, the melt viscosity tends to be increased. When the number of branched portions of the polyolefin resin is increased, the melt viscosity tends to be decreased, and when the number of branched portions of the polyolefin resin is decreased, the melt viscosity tends to be increased. When a polar group is introduced into the side chain portion of the polyolefin resin, the melt viscosity tends to increase. When the molecular weight of the polyolefin resin is increased, the melt viscosity tends to increase, and when the molecular weight of the polyolefin resin is decreased, the melt viscosity tends to decrease. When the density of the polyolefin resin is increased, the melt viscosity tends to increase, and when the density of the polyolefin resin is decreased, the melt viscosity tends to decrease. In addition, for example, the melt viscosity can be adjusted by including resins having different melt viscosities or melting points at 120°C as the polyolefin resin. Specifically, the melt viscosity can be reduced by adding a resin having a lower melt viscosity or melting point at 120°C than the base resin.

[0076] As described above, the melting points of the first outer layer and the second outer layer are preferably lower than the melting point of the inner layer.

[0077] Specifically, the melting points of the first and second outer layers are 105°C or lower, may be 100°C or lower, or may be 95°C or lower. If the melting points are too high, the fluidity of the resin contained in the first and second outer layers may decrease, and the ability to conform to irregularities due to solar cell elements, wiring, etc. may decrease. On the other hand, the melting points of the first and second outer layers are, for example, 45°C or higher, may be 50°C or higher, or may be 55°C or higher. If the melting points are too low, the first and second outer layers may melt in the environment in which the solar cell module is used.

[0078] Here, the method for measuring the melting points of the first and second outer layers can be the same as the method for measuring the melting point of the inner layer described above. When measuring the melting points of the first and second outer layers, for example, the first and second outer layers can be separated from the solar cell module sealant sheet and the measurement can be performed. As a method for separating the first and second outer layers from the solar cell module sealant sheet, as described above, for example, a method can be used in which the interfaces of the first, inner and second outer layers are confirmed using an optical microscope, and the solar cell module sealant sheet is sliced ​​at the interfaces of each layer.

[0079] The first and second outer layers contain a resin. The resin contained in the first and second outer layers is not particularly limited as long as it is a resin that can obtain the first and second outer layers that satisfy the above-mentioned melt viscosity, and resins used in general sealing materials for solar cell modules can be used. For example, polyolefin resins such as polyethylene resin, ethylene vinyl acetate copolymer (EVA), and polyolefin elastomer (POE); ionomer resin; polyvinyl butyral (PVB) resin, etc. can be mentioned.

[0080] Among these, polyolefin resins are preferred, and polyethylene resins are more preferred, because polyethylene resins have excellent embedding properties for unevenness caused by solar cell elements, wiring, and the like.

[0081] Examples of polyethylene resins include high density polyethylene (HDPE), low density polyethylene (LDPE), linear low density polyethylene (LLDPE), metallocene linear low density polyethylene (M-LLDPE), very low density polyethylene (VLDPE), etc. The polyethylene resins may be used alone or in combination of two or more kinds.

[0082] Among them, low density polyethylene (LDPE), linear low density polyethylene (LLDPE), metallocene linear low density polyethylene (M-LLDPE), and very low density polyethylene (VLDPE) are preferred because of their good flexibility and processability. In particular, linear low density polyethylene (LLDPE) and metallocene linear low density polyethylene (M-LLDPE) are preferred because of their excellent flexibility, processability, and strength. Furthermore, metallocene linear low density polyethylene (M-LLDPE) is preferred. Such polyethylene has few side chain branches and a uniform distribution of comonomers. Therefore, the molecular weight distribution is narrow. This makes it possible to reduce the density as described below, and can impart flexibility to the first outer layer and the second outer layer. As a result of imparting flexibility to the first outer layer and the second outer layer, it is possible to increase the adhesion between the first outer layer and the second outer layer and the solar cell element. Furthermore, when the solar cell module encapsulant sheet of the present disclosure is used in a tandem solar cell module, when a plurality of solar cell elements are laminated via the solar cell module encapsulant sheet, the resin contained in the first outer layer and the second outer layer is prevented from flowing out excessively, and the thickness of the solar cell module encapsulant sheet after lamination can be maintained, making it possible to suppress warping of the transparent front substrate and rear substrate.

[0083] The density of the polyethylene resin is not particularly limited, and is, for example, 0.870 g / cm 3 More than 0.93g / cm 3 It is preferable that the density is 0.875 g / cm or less. 3 More than 0.92g / cm 3 More preferably, it is 0.880 g / cm or less. 3 More than 0.91g / cm3 It is more preferable that the density of the polyethylene resin is not more than 1.0 m / s. When the density of the polyethylene resin is within the above range, the first outer layer and the second outer layer can have excellent flexibility and processability, and excellent adhesion to the solar cell element.

[0084] The method for measuring the density of the polyethylene resin is as described above.

[0085] The melting point of the polyethylene resin is not particularly limited, and is preferably, for example, 45° C. or higher and 105° C. or lower, more preferably 50° C. or higher and 100° C. or lower, and even more preferably 55° C. or higher and 95° C. or lower. If the melting point of the polyethylene resin is too high, the heating temperature during lamination needs to be high, which may increase the manufacturing cost. On the other hand, if the melting point of the polyethylene resin is too low, the first outer layer and the second outer layer may melt in the environment in which the solar cell module is used.

[0086] The content of the polyethylene resin is, for example, 50 parts by mass or more, optionally 60 parts by mass or more, or optionally 70 parts by mass or more, relative to 100 parts by mass of all resin components contained in the first outer layer or the second outer layer. Also, the content of the polyethylene resin is, for example, 100 parts by mass or less, optionally 99 parts by mass or less, optionally 95 parts by mass or less, or optionally 90 parts by mass or less, relative to 100 parts by mass of all resin components contained in the first outer layer or the second outer layer.

[0087] In addition, the first outer layer and the second outer layer preferably contain a silane component such as a silane coupling agent or a silane-modified polyolefin resin, etc. By containing a silane component in the first outer layer and the second outer layer, it is possible to improve adhesion to the solar cell element, strength, durability, etc.

[0088] As the silane coupling agent, a silane coupling agent used in a general solar cell module sealing material sheet can be used. The silane coupling agent may be used alone or in combination of two or more kinds.

[0089] The silane-modified polyolefin resin is a copolymer of an olefin and an ethylenically unsaturated silane compound. The copolymer may be, for example, any of a random copolymer, an alternating copolymer, a block copolymer, and a graft copolymer. Among them, the copolymer is preferably a graft copolymer, and is preferably a graft copolymer in which a polyolefin is used as a main chain and an ethylenically unsaturated silane compound is polymerized as a side chain. Such a graft copolymer has a high degree of freedom of the silanol group that contributes to adhesion, and therefore can further improve adhesion to solar cell elements.

[0090] Examples of polyolefins constituting the silane-modified polyolefin resin include polyethylene, polypropylene, and ethylene-vinyl acetate copolymer. Among them, the polyolefin constituting the silane-modified polyolefin resin is preferably polyethylene. That is, the silane-modified polyolefin resin is preferably a silane-modified polyethylene resin. This is because the silane-modified polyethylene resin has good compatibility with the first outer layer and the second outer layer.

[0091] Examples of polyethylene constituting the 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 them, 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 because of their good flexibility and processability. In particular, linear low-density polyethylene (LLDPE) and metallocene-based linear low-density polyethylene (M-LLDPE) are preferred because of their excellent flexibility, processability, and strength.

[0092] Examples of the ethylenically unsaturated silane compound include vinyltrimethoxysilane, vinyltriethoxysilane, vinyltripoxysilane, vinyltriisopropoxysilane, vinyltributoxysilane, vinyltripentyloxysilane, vinyltriphenoxysilane, vinyltribenzyloxysilane, vinyltrimethylenedioxysilane, vinyltriethylenedioxysilane, vinylpropionyloxysilane, vinyltriacetoxysilane, and vinyltricarboxysilane. The ethylenically unsaturated silane compound may be used alone or in combination of two or more.

[0093] The silane-modified polyolefin resin can be obtained, for example, by the production method described in JP-A-2003-46105.

[0094] The silane-modified polyolefin resin may be used alone or in combination of two or more kinds.

[0095] The content of the silane-modified polyolefin resin in the first outer layer and the second outer layer is not particularly limited, and is preferably 1.0% by mass or more and 14% by mass or less, more preferably 1.5% by mass or more and 12% by mass or less, and even more preferably 2.0% by mass or more and 10% by mass or less. If the content of the silane-modified polyolefin resin is too small, the effect of improving adhesion due to the silane-modified polyolefin resin may not be sufficiently obtained. Also, if the content of the silane-modified polyolefin resin is too high, the tensile elongation and heat welding property tend to be inferior.

[0096] The first outer layer and the second outer layer may contain additives as necessary. Examples of additives include light stabilizers, ultraviolet absorbers, heat stabilizers, antioxidants, antiblocking agents, and fillers. A masterbatch may also be used as a weathering agent such as a light stabilizer or an ultraviolet absorber. The content of the additives in the first outer layer and the second outer layer varies depending on the particle shape, density, and the like, but may be, for example, 0.001% by mass or more and 5% by mass or less. The first outer layer and the second outer layer may contain additives to improve mechanical strength stably over a long period of time and to suppress yellowing, cracking, and the like.

[0097] The thickness of the first outer layer and the second outer layer is, for example, preferably 10 μm or more and 170 μm or less, more preferably 20 μm or more and 160 μm or less, and even more preferably 30 μm or more and 150 μm or less, from the viewpoint of embedding properties in unevenness caused by solar cell elements, wiring, etc. If the thickness of the first outer layer and the second outer layer is too thin, embedding properties in unevenness caused by solar cell elements, wiring, etc. may decrease. In addition, if the thickness of the first outer layer and the second outer layer is too thick, when the solar cell module sealant sheet of the present disclosure is used in a tandem solar cell module, when a plurality of solar cell elements are laminated through the solar cell module sealant sheet, the resin contained in the first outer layer and the second outer layer may easily protrude.

[0098] As a method for forming the first outer layer and the second outer layer, for example, only the first outer layer or the second outer layer may be formed as a single layer, or the first outer layer, the inner layer, and the second outer layer may be integrally formed as a multi-layer. The forming method can be the same as the forming method for the inner layer described above.

[0099] 3. Solar cell module encapsulant sheet The solar cell module encapsulant sheet of the present disclosure has transparency. The transparency of the solar cell module encapsulant sheet allows the transmission of light in the absorption wavelength range of the solar cell element arranged on the back side of the solar cell module encapsulant sheet when the solar cell module encapsulant sheet of the present disclosure is used in a tandem solar cell module. This allows the absorption wavelength range of sunlight to be expanded, and the overall power generation efficiency to be improved.

[0100] The average transmittance of the solar cell module encapsulant sheet of the present disclosure in the wavelength range of 400 nm or more and 1200 nm or less is, for example, preferably 70% or more, and more preferably 80% or more. If the average transmittance is within the above range, light in the long wavelength range can be sufficiently transmitted, and when the solar cell module encapsulant sheet of the present disclosure is used in a tandem solar cell module, the solar cell element arranged on the back side of the solar cell module encapsulant sheet can efficiently absorb light.

[0101] Here, the average transmittance in the wavelength range of 400 nm or more and 1200 nm or less can be measured using a spectrophotometer. The average transmittance is the average value of the transmittance in the wavelength range.

[0102] The total light transmittance of the encapsulant sheet for solar cell modules in the present disclosure is, for example, preferably 70% or more, and more preferably 80% or more. If the total light transmittance is within the above range, sunlight can be sufficiently transmitted, and when the encapsulant sheet for solar cell modules in the present disclosure is used in a tandem solar cell module, the solar cell element arranged on the back side of the encapsulant sheet for solar cell modules can efficiently absorb light.

[0103] Here, the total light transmittance can be measured in accordance with JIS K7361 1. For measuring the total light transmittance, for example, a haze meter HM150 manufactured by Murakami Color Research Laboratory Co., Ltd. can be used.

[0104] The haze of the solar cell module encapsulant sheet of the present disclosure is, for example, preferably 50% or less, more preferably 40% or less. When the haze is within the above range, sunlight can be sufficiently transmitted, and when the solar cell module encapsulant sheet of the present disclosure is used in a tandem solar cell module, the solar cell element disposed on the back side of the solar cell module encapsulant sheet can efficiently absorb light.

[0105] Here, the haze can be measured in accordance with JIS K 7136. For measuring the haze, for example, a haze meter HM150 manufactured by Murakami Color Research Laboratory Co., Ltd. can be used.

[0106] The manufacturing method of the encapsulant sheet for solar cell modules in the present disclosure is not particularly limited, and for example, a multilayer film of a first outer layer, an inner layer, and a second outer layer may be formed by a co-extrusion method, and the first outer layer, the inner layer, and the second outer layer may each be laminated via an adhesive layer.

[0107] Among them, it is preferable to form a multilayer film of a first outer layer, an inner layer, and a second outer layer by a co-extrusion method. In the case of a co-extrusion film having a first outer layer, an inner layer, and a second outer layer, since it is not necessary to laminate the first outer layer, the inner layer, and the second outer layer via an adhesive layer, the thickness of the entire solar cell module encapsulant sheet can be made thin. In addition, the production efficiency can be improved.

[0108] B. Solar cell module The solar cell module according to the present disclosure is a solar cell module in which a plurality of solar cell elements having different maximum absorption wavelengths are stacked via an insulating layer, and the insulating layer is the above-mentioned solar cell module encapsulant sheet.

[0109] Fig. 2 is a schematic cross-sectional view showing an example of a solar cell module according to the present disclosure. As shown in Fig. 2, in a solar cell module 20, two solar cell elements 22A and 22B having different maximum absorption wavelengths are laminated via an insulating layer 23, and the insulating layer 22 is the above-mentioned solar cell module sealant sheet. The solar cell module 20 also has a transparent front substrate 21, a solar cell element 22A, an insulating layer 23, a solar cell element 22B, a back surface sealant sheet 24, and a back substrate 25, in this order. In this solar cell module 20, the surface on the transparent front substrate 21 side is a light receiving surface for sunlight L.

[0110] In the present disclosure, by having the above-mentioned encapsulant sheet for a solar cell module, it is possible to ensure an insulation distance between a plurality of solar cell elements and to improve the ability to fill irregularities and gaps caused by the solar cell elements, wiring, etc.

[0111] The configuration of the solar cell module according to the present disclosure will be described below.

[0112] 1. Encapsulant sheet for solar cell modules The solar cell module encapsulant sheet in the present disclosure is similar to the content described above in the section "A. Solar cell module encapsulant sheet," and therefore will not be described here.

[0113] 2. Solar cell element In the solar cell module of the present disclosure, a plurality of solar cell elements having different maximum absorption wavelengths are stacked via an insulating layer. The plurality of solar cell elements may be solar cell elements having different maximum absorption wavelengths. For example, a tandem solar cell module in which a thin-film amorphous silicon solar cell element and a crystalline silicon solar cell element (monocrystalline silicon solar cell element, polycrystalline silicon solar cell element, microcrystalline silicon solar cell element) are stacked, a tandem solar cell module in which a thin-film crystalline silicon solar cell element (thin-film monocrystalline silicon solar cell element, thin-film polycrystalline silicon solar cell element, thin-film microcrystalline silicon solar cell element) and an amorphous silicon solar cell element are stacked, a tandem solar cell module in which a thin-film amorphous silicon solar cell element and an amorphous silicon solar cell element are stacked, a tandem solar cell module in which a perovskite solar cell element and a crystalline silicon solar cell element are stacked, a tandem solar cell module in which a perovskite solar cell element and a CIGS solar cell element are stacked, a tandem solar cell module in which a cuprous oxide solar cell element and a crystalline silicon solar cell element are stacked, etc. can be mentioned.

[0114] The number of stacked solar cell elements may be more than one, for example, it may be two or three.

[0115] The configuration of each of the solar cell elements may be the same as that of a solar cell element in a known tandem solar cell module.

[0116] 3.Transparent front board The transparent front substrate in the present disclosure is a member for protecting the solar cell element. The transparent front substrate is disposed on the light receiving surface side of the solar cell element and functions as a surface protection member. The transparency of the transparent front substrate is not particularly limited as long as it does not inhibit the power generation of the solar cell element. The transparent front substrate can be the same as the transparent front substrate used in a general solar cell module, and therefore a description thereof will be omitted here.

[0117] 4. Backside sealing sheet The back surface sealant sheet in the present disclosure is a member for sealing the solar cell element. The back surface sealant sheet is disposed between the solar cell element disposed on the back side of the sealant sheet for solar cell module and the back substrate. The back surface sealant sheet can be the same as a sealant sheet used in a general solar cell module, and therefore a description thereof will be omitted here. Since the back surface sealant sheet does not need to transmit light that contributes to power generation in the solar cell element, for example, an inexpensive sealant sheet with high haze can be applied.

[0118] 5. Rear board The rear substrate in the present disclosure is a member that protects the solar cell element. The rear substrate is disposed on the rear side of the solar cell element and functions as a rear surface protection member. The rear substrate can be the same as a rear substrate used in a general solar cell module, and therefore a description thereof will be omitted here.

[0119] 6. Manufacturing method of solar cell module The manufacturing method of the solar cell module in the present disclosure is not particularly limited as long as it is a method capable of manufacturing a solar cell module in which a plurality of solar cell elements are stacked via the above-mentioned solar cell module sealant sheet. For example, when manufacturing a tandem type solar cell module in which two solar cell elements are stacked via the above-mentioned solar cell module sealant sheet, a method of manufacturing a first solar cell element on a transparent substrate, and then thermocompressing and integrating a laminate having a transparent front substrate, a first solar cell element, a solar cell module sealant sheet, a second solar cell element, a back sealant sheet, and a back substrate can be exemplified. For example, a thermocompression method can be exemplified by a vacuum thermal lamination method.

[0120] The present disclosure is not limited to the above-described embodiments. The above-described embodiments are merely examples, and anything that has substantially the same configuration as the technical idea described in the claims of the present disclosure and exhibits similar effects is included in the technical scope of the present disclosure. EXAMPLES

[0121] The present disclosure will be further described below with reference to examples and comparative examples.

[0122] [Examples 1 to 3 and Comparative Examples 1 to 4] Resin compositions for forming the first outer layer, the inner layer and the second outer layer were prepared using the resin components and additives shown in Table 1. The resin components and additives are shown below.

[0123] Low density polyethylene (LDPE): density 0.919g / cm 3 Melting point 106℃ MFR 3.5g / 10min (190℃) Metallocene-based linear low-density polyethylene (M-LLDPE) (1): Density 0.880 g / cm 3 Melting point 60℃ MFR 3.5g / 10min (190℃) Metallocene-based linear low-density polyethylene (M-LLDPE) (2): Density 0.903 g / cm 3 Melting point: 98℃ MFR: 1.2g / 10min (190℃) Homopolypropylene (Homo PP): Density 0.905, Melting point 165℃, MFR 9g / 10min (230℃) Random polypropylene (random PP): density 0.900g / cm 3 Melting point 135℃ MFR 9g / 10min (230℃) Polypropylene elastomer (PP elastomer): Mitsui Chemicals "Toughmer PN2060" Density 0.868g / cm 3 Melting point 160℃ MFR 6g / 10min (230℃) Polyethylene elastomer (PE elastomer): Mitsui Chemicals "Toughmer DF110" Density 0.905g / cm 3 Melting point: 94℃ MFR: 1.2g / 10min (230℃) Silane-modified polyolefin resin: density 0.902g / cm 3 Melting point: 90℃ MFR: 1.0g / 10min (190℃) Weatherproofing masterbatch (MB): density 0.902g / cm 3100 parts by mass of powder obtained by pulverizing the Ziegler linear low-density polyethylene was mixed with 3.8 parts by mass of a benzophenol-based ultraviolet absorber, 5 parts by mass of a hindered amine-based light stabilizer, and 0.5 parts by mass of a phosphorus-based heat stabilizer, and the mixture was melted, processed, and pelletized to obtain a master batch.

[0124] Using an extruder equipped with a T-die and a film molding machine having a 300 mm wide T-die (each layer is an extruder with a diameter of 30 mm), each resin composition was melted at 230°C, and the thickness ratio of each layer was adjusted so that the thickness of the encapsulant sheet was first outer layer: inner layer: second outer layer = 1:6:1, and the encapsulant sheet had a predetermined total film thickness. The three layers were co-extruded to obtain an encapsulant sheet in which the first outer layer, inner layer, and second outer layer were laminated in that order.

[0125] [evaluation] (Storage modulus of inner layer) First, the interfaces of the first outer layer, the inner layer, and the second outer layer of the encapsulant sheet were confirmed using an optical microscope, and the encapsulant sheet was sliced ​​at the interfaces of the layers to separate only the inner layer.

[0126] The storage modulus was measured using a dynamic viscoelasticity measuring device according to the method of JIS K7244-4:1999. The measurement was performed by cutting out a sample of 5 mm x 20 mm from the inner layer, attaching both ends of the sample to the chucks of the dynamic viscoelasticity measuring device so that the tensile direction was the longitudinal direction of the sample, and applying a tensile load to the sample. The dynamic viscoelasticity measuring device used was Rheogel-E4000 manufactured by UBM. The measurement conditions are shown below.

[0127] <Storage modulus measurement conditions> Measurement sample: 5mm x 20mm rectangle Measurement mode: Tensile method (sine wave strain, tension mode, strain amount: automatic strain) Heating rate: 3℃ / min Frequency: 10Hz Tensile load (static load): 100g

[0128] (Melt Viscosity of the First Outer Layer and the Second Outer Layer) First, the interfaces of the first outer layer, the inner layer, and the second outer layer of the encapsulant sheet were confirmed using an optical microscope, and the encapsulant sheet was sliced ​​at the interfaces of each layer to separate the first outer layer and the second outer layer from each other.

[0129] The melt viscosity of each layer at 120°C was measured in accordance with JIS K7199 using Capillograph 1-B manufactured by Toyo Seiki Seisakusho, at a temperature of 120°C and a shear rate of 2.43 x 10 sec. -1 The measurements were performed using a capillary with D=1 mm and L / D=10.

[0130] (Average transmittance at wavelengths between 400nm and 1200nm) An ethylene-tetrafluoroethylene copolymer (ETFE) film having a thickness of 100 μm, an encapsulant sheet, and an ethylene-tetrafluoroethylene copolymer (ETFE) film having a thickness of 100 μm were laminated in this order, and vacuum lamination was performed using a vacuum laminator (PVL0505S manufactured by Nisshinbo Co., Ltd.) for manufacturing solar cell modules under conditions of a temperature of 150° C., a vacuum drawing time of 3 minutes, a press holding time of 7 minutes, and a pressure of 100 KPa, to perform an initial lamination process. After that, the product was cooled, and the ETFE film was peeled off. The transmittance of the encapsulant sheet alone in the wavelength region of 400 nm to 1200 nm was measured using a spectrophotometer (V-650 manufactured by JASCO Corporation), and the average value was calculated.

[0131] (Total light transmittance) The total light transmittance of the encapsulant sheet was measured in accordance with JIS K7361-1 using a haze meter HM150 manufactured by Murakami Color Research Laboratory.

[0132] (Hayes) The haze of the encapsulating material sheet was measured using a haze meter HM150 manufactured by Murakami Color Research Laboratory Co., Ltd. in accordance with JIS K7136.

[0133] (Thickness of sealing material sheet after lamination) A pseudo solar cell module was produced using the sealing material sheet, and the thickness of the sealing material sheet after lamination was measured.

[0134] First, two encapsulant sheets were cut to a size of 75 mm x 50 mm. In addition, an aluminum plate (Nippon Takuto Co., Ltd. Al050P, thickness 200 μm, size 156 mm x 156 mm) was cut to a size of 30 mm x 50 mm using a router as a pseudo solar cell element. In addition, a white semi-tempered glass plate with a size of 75 mm x 50 mm and a thickness of 3.3 mm, an ethylene-tetrafluoroethylene copolymer (ETFE) film (release film) with a thickness of 100 μm, and a wiring with a thickness of 260 μm and a length of 50 mm (Marusho Co., Ltd. CU-0-160-2-B) were prepared. Next, the white semi-tempered glass, the ETFE film, the sealant sheet, the wiring, the aluminum plate as a pseudo solar cell element, the wiring, the sealant sheet, the ETFE film, and the white semi-tempered glass were laminated, and a vacuum lamination process was performed using a vacuum laminator (Nisshinbo PVL0505S) for manufacturing solar cell modules under conditions of a temperature of 150°C, a vacuuming time of 3 minutes, a press holding time of 7 minutes, and a pressure of 100 kPa to produce a test specimen of a pseudo solar cell module. Then, the white semi-tempered glass was peeled off from the test specimen, and the area where the wiring was arranged was cut with a razor blade to produce a cross section. Next, the ETFE film was peeled off from the test specimen, and the cross section was observed with an optical microscope. Then, the thickness of the sealant sheet on the wiring was measured.

[0135] (Embeddability) The optical microscope photographs of the above test specimens were visually observed, and the embedding ability of the test specimens into the irregularities was evaluated according to the following evaluation criteria. A: The encapsulant sheet completely conformed to the unevenness of the aluminum plate and wiring. No void formation was observed. B: 2mm 2 Three or fewer bubbles of the following were observed: C: A part of the sealing material sheet did not completely conform to the unevenness of the aluminum plate and wiring, and some lamination defects (voids) were formed near the aluminum plate and wiring.

[0136] [Table 1]

[0137] As can be seen from Table 1, in Examples 1 to 3, since the inner layer and the first and second outer layers have the specified properties, the thickness of the sealing material sheet on the wiring is sufficiently secured and the embeddability is good. [Explanation of symbols]

[0138] 1 ... Solar cell module encapsulant sheet 2 … 1st outer layer 3. Inner layer 4…Second outer layer 20 … Solar cell module 21 … Transparent front board 22A, 22B ... Solar cell element 23 ... Insulating layer 24 … Backside sealing sheet 25 ... Rear board

Claims

1. A sealing material sheet for a solar cell module having a first outer layer, an inner layer, and a second outer layer in this order, The storage modulus of the inner layer at 120° C. is 1.0×10 ７ Pa or more 5.0×10 ８ Pa or less, The shear rate of the first outer layer and the second outer layer at 120° C. is 2.43×10 sec －１ The melt viscosity at ２ Pa・s or more 5.0×10 ５ Pa s or less, An encapsulant sheet for a solar cell module, having an average transmittance of 70% or more in the wavelength range of 400 nm or more and 1200 nm or less.

2. 2. The solar cell module encapsulant sheet according to claim 1, in which a plurality of solar cell elements having different maximum absorption wavelengths are stacked via an insulating layer, the inner layer having a thickness of 200 μm or more and 800 μm or less.

3. The solar cell module sealing material sheet according to claim 1 or 2, wherein a thickness ratio of the first outer layer to the inner layer to the second outer layer is first outer layer: inner layer: second outer layer = 1:1:1 to 1:10:

1.

4. The sealing material sheet for a solar cell module according to claim 1 , wherein the inner layer contains a polyolefin resin.

5. The sealing material sheet for a solar cell module according to claim 1 , wherein the inner layer contains a polyethylene resin and a polypropylene resin.

6. The sealing material sheet for a solar cell module according to claim 5 , wherein the polypropylene resin is a homopolypropylene.

7. The sealing material sheet for a solar cell module according to claim 5 or 6, wherein the inner layer contains a compatibilizer.

8. The sealing material sheet for a solar cell module according to claim 1 , wherein the first outer layer and the second outer layer contain a polyolefin resin.

9. The solar cell module sealing material sheet according to claim 8 , wherein the first outer layer and the second outer layer contain a silane coupling agent or a silane-modified polyolefin resin.

10. A solar cell module in which a plurality of solar cell elements having different maximum absorption wavelengths are stacked with an insulating layer interposed therebetween, A solar cell module, wherein the insulating layer is the solar cell module encapsulant sheet according to any one of claims 1 to 9.

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