Sealing material sheet with minimal voltage-induced degradation

Abstract

The sealing material sheet is 1×10 at 60℃. 14 Ω cm at 60℃ ~ 1×10 16 The material includes an ethylene / C4-C8 α-olefin copolymer having a resin volume resistivity (VR) of less than Ω·cm and 0.01% to 0.2% by weight of an ion scavenger. The encapsulant sheet has a transmittance of greater than 91%. The photovoltaic module (10) includes a front encapsulant sheet (12a) and a back encapsulant sheet (12b) made of the above-mentioned material. The photovoltaic module (10) has a power loss of less than 0.05% to 5% after potential-induced degradation (PID) testing.

Description

Background Art

[0001] An issue in maintaining long-term reliable and stable operation of crystalline silicon photovoltaic modules (PV modules) is the reduction of potential induced degradation (or "PID") phenomenon. In the presence of an electric field generated by the PV module, sodium ions (Na + ) move through the encapsulant sheet (made of a polymer material), deteriorate the encapsulant, and contribute to the PID phenomenon. PID can reduce the output power of a solar PV module by 20%, and in severe cases, PID can reduce the output power of a solar PV module by more than 50%.

[0002] The demand for bifacial PV modules (such as high-efficiency PERC bifacial PV modules) has increased dramatically in recent years. When conventional ethylene vinyl acetate EVA is used as the material for the encapsulant sheet, ion migration occurs through both the front glass cover sheet and the back glass cover sheet, resulting in unacceptably high PID. Conventional polyolefin elastomers have also not demonstrated the ability to withstand PID when used as the encapsulant sheet material in bifacial PV modules.

[0003] In the art, there is a recognized need for polymer materials that can withstand PID for encapsulant sheets in PV modules, particularly PID-resistant polymer materials in bifacial PV modules.

Summary of the Invention

[0004] This disclosure relates to an encapsulant sheet. In one embodiment, the encapsulant sheet has a resistivity greater than 1×10 14 Ω·cm at 60°C to 1×10 16The material comprises an ethylene / C4-C8α-olefin copolymer having a resin volume resistivity (VR) of less than Ω·cm, and 0.01% to 0.2% by weight of an ion scavenger. The encapsulating sheet has a transmittance of more than 91%.

[0005] This disclosure also relates to a photovoltaic module. In one embodiment, the photovoltaic module includes (A) a front cover sheet, (B) a front sealing sheet, (C) a photovoltaic cell, (D) a rear sealing sheet, and (E) a rear cover sheet. The front sealing sheet (B) has a temperature of 1 × 10 at 60°C. 14 Ω·cm above ~60℃: 1 × 10 16 The material consists of (ii) an ethylene / C4-C8α-olefin copolymer having a resin volume resistivity (VR) of less than Ω·cm, and (ii) 0.01% to 0.2% by weight of an ion scavenger. The back sealing sheet (D) is (i) 1 × 10 at 60°C 14 Ω·cm above ~60℃: 1 × 10 16 The material consists of (ii) an ethylene / C4-C8α-olefin copolymer having a resin volume resistivity (VR) of less than Ω·cm, and (ii) 0.01% to 0.2% by weight of an ion scavenger. The power loss of the photovoltaic module after potential-induced degradation (PID) testing is less than 0.05% to 5%. [Brief explanation of the drawing]

[0006] [Figure 1] This is an exploded perspective view of an exemplary photovoltaic module.

[0007] definition Any references to the periodic table refer to the edition published by CRC Press, Inc., 1990–1991. References to element groups in this table are based on a new notation for numbering groups.

[0008] For the purposes of United States patent practice, the content of any referenced patent, patent application, or publication is incorporated by reference in its entirety (or an equivalent U.S. version is incorporated by reference in that manner), subject to any definitions provided in the disclosure (to the extent not inconsistent with any definitions specifically provided in this disclosure) and common general knowledge in the art.

[0009] The numerical ranges disclosed herein include all values from the lower limit to the upper limit, including the lower and upper limits. In the case of ranges that include explicit values (e.g., 1, or 2, or 3 to 5, or 6, or 7), any sub-ranges between any two of the explicit values (e.g., sub-ranges such as 1 to 2, 2 to 6, 5 to 7, 3 to 7, 5 to 6, etc.) are included.

[0010] Unless otherwise indicated, implied by context, or not customary in the art, all parts and percentages are by weight and all test methods are the latest as of the filing date of this disclosure.

[0011] As used herein, "alpha-olefin" or "α-olefin" is a hydrocarbon molecule having ethylenic unsaturation at the primary (alpha) position. For example, as used herein, "(C3-C 20 ) alpha-olefin" is a hydrocarbon molecule consisting of a hydrocarbon molecule having (i) only one ethylenic unsaturation, which is located between the first and second carbon atoms, and (ii) at least 3 of the 3 to 20 carbon atoms. For example, as used herein, (C3-C 20 ) alpha-olefin refers to H2C=C(H)-R, where R is a straight-chain (C1-C 18 ) alkyl group. A (C1-C 18 ) alkyl group is a monovalent unsubstituted saturated hydrocarbon having 1 to 18 carbon atoms.

[0012] The terms “blend,” “polymer blend,” and similar terms mean a composition of two or more polymers. Such a blend may or may not be miscible. Such a blend may or may not be phase-separated. Such a blend may or may not contain one or more domain configurations, as determined by transmission electron spectroscopy, light scattering, X-ray scattering, and any other method used to measure and / or identify the domain configuration. A blend is not a laminate, but one or more layers of a laminate may contain a blend.

[0013] The term "auxiliary agent" refers to a compound that promotes crosslinking, i.e., a curing aid.

[0014] As used herein, “composition” includes mixtures of materials containing the composition, as well as reaction products and decomposition products formed from the materials of the composition.

[0015] The terms “comprising,” “including,” and “having,” and their derivatives, are not intended to exclude the presence of any additional components, processes, or procedures, whether or not they are specifically disclosed. To avoid any doubt, all compositions claimed through the use of the term “comprising” may include any additional additives, auxiliaries, or compounds, whether polymeric or otherwise, unless otherwise stated. In contrast, the term “consisting essentially of” excludes any other components, processes, or procedures from the scope of any subsequent description, except those not essential to operability. The term “consisting of” excludes any components, processes, or procedures not specifically enumerated. The term “or” refers to any individual member, or any combination thereof, unless otherwise specified.

[0016] The terms "curing" and "crosslinking" are used interchangeably herein and mean the formation of a crosslinked product (network polymer).

[0017] "Direct contact" refers to a layer configuration in which the first layer is directly adjacent to the second layer, and there are no intervening layers or structures between the first and second layers.

[0018] The term "elastomer" refers to a rubber-like polymer that can be stretched to at least twice its original length and, when the stretching force is released, contracts very rapidly back to almost its original length. Elastomers typically have an elastic modulus of about 10,000 psi (68.95 MPa) or less and an elongation of over 200% in an uncrosslinked state at room temperature using the ASTM D638-72 method.

[0019] As used herein, “ethylene polymer” is a polymer containing more than 50 weight percent polymerized ethylene monomers (based on the total amount of polymerizable monomers) and optionally containing at least one comonomer.

[0020] As used herein, “polymer” refers to a polymer compound prepared by polymerizing the same or different types of monomers. Thus, the general term polymer encompasses the term homopolymer (used to refer to a polymer prepared from a single type of monomer, with the understanding that trace amounts of impurities may be incorporated into the polymer structure) and the term interpolymer as defined herein. Trace amounts of impurities, such as catalyst residues, may be incorporated into and / or within the polymer.

[0021] Test method Density is measured according to ASTM D792, Method B. Results are reported in grams per cubic centimeter (g / cc).

[0022] Differential Scanning Calorimetry (DSC) Differential scanning calorimetry (DSC) can be used to measure the melting, crystallization, and glass transition behavior of polymers over a wide range of temperatures. For example, this analysis is performed using a TA Instruments Q2000DSC equipped with an RCS (refrigerated cooling system) and an autosampler. During the test, the nitrogen purge gas flow rate used is 50 mL / min. Each sample is melted and compressed into a thin film at approximately 175°C, and then the molten sample is air-cooled to room temperature (approximately 25°C). Test specimens of 3–10 mg, 6 mm in diameter are extracted from the cooled polymer, weighed, placed in a lightweight aluminum pan (approximately 50 mg), and pressed shut. The analysis is then performed to determine its thermal properties.

[0023] The thermal behavior of the sample is determined by raising and lowering the sample temperature to create a heat flow versus temperature profile. First, to remove its thermal history, the sample is rapidly heated to 180°C and held isothermally for 3 minutes. Next, the sample is cooled to -80°C at a cooling rate of 10°C / min and held isothermally at -80°C for 3 minutes. Then, the sample is heated to 180°C at a heating rate of 10°C / min (this is the "second heating" gradient). The cooling curve and the second heating curve are recorded. The cooling curve is analyzed by setting the baseline endpoint from the start of crystallization to -20°C. The thermal curve is analyzed by setting the baseline endpoint from -20°C to the end of melting. The values ​​to be determined are the extrapolated melting start point Tm and the extrapolated crystallization start point Tc. Heat of fusion (H f ) (Joules per gram), and the degree of crystallinity % of the polyethylene sample calculated using the following formula: Degree of crystallinity % = ((H f ) / 292J / g)×100.

[0024] From the second heating curve, the heat of fusion (H f The enthalpy of melting (also known as the peak melting temperature) and the peak melting temperature are reported.

[0025] The melting point Tm is first determined from the DSC heating curve by drawing a baseline between the start and end of the melting transition. Next, a tangent line is drawn to the lower temperature data of the melting peak. The point where this line intersects the baseline is the extrapolated melting start point (Tm). This is as described in Bernhard Wunderlich, The Basis of Thermal Analysis, in Thermal Characterization of Polymeric Materials 92, 277-278 (Edith A. Turi ed., 2d ed. 1997).

[0026] Melt Index As used herein, the terms “Melt Index” or “MI” refer to a measure of how easily a thermoplastic polymer flows when in a molten state. The Melt Index, or I2, is measured according to ASTM D 1238, under conditions of 190°C / 2.16 kg, and reported as grams of elution per 10 minutes (g / 10 min). I10 is measured according to ASTM D 1238, under conditions of 190°C / 10 kg, and reported as grams of elution per 10 minutes (g / 10 min).

[0027] PID testing Potential-induced degradation (PID) testing at the module level was performed according to the procedure described in IEC 62804-1. (1) The initial output of the module samples was recorded using a pulsed solar simulator (Burger PS8 / PSS8) according to the procedure described in IEC 60904. (2) PID stress treatment was performed in an environmental chamber under 85°C / 85%RH conditions. The module samples were connected to a power supply to generate a typical negative bias voltage of 1500V. A standard test takes 96 hours (h). (3) After stress treatment, all module samples were retested for output. The results were compared with the initial measurements to further calculate power loss. The IEC standard for power loss after 96 hours of PID testing is less than 5% for both the front and back of the PV module.

[0028] Transmittance The average transmittance of the sample sheets was determined using a LAMBDA 950 UV / Vis spectrophotometer (PerkinElmer) equipped with a 150 mm integrating sphere. At least three samples were tested, and the average transmittance from 380 nm to 1100 nm was collected.

[0029] The Vicat softening point was determined according to ASTM D1525.

[0030] Volume Resistivity (VR) Test Volume resistivity is tested according to ASTM D257 as follows. Measurements are performed using a Keithley 6517 B voltmeter and a Keithley 8009 test apparatus. The Keithley Model 8009 test chamber is located in a forced-air oven and can operate at high temperatures (the maximum oven temperature is 80°C). Leakage current is read directly from the instrument, and volume resistivity is calculated using the following equation. ρ = V × AI × t In the formula, ρ is the volume resistivity (ohms-cm), V is the applied voltage (volts), and A is the electrode contact area (cm²). 2 ) is the leakage current (amperes), and t is the average thickness of the sample. To obtain the average thickness of the sample, the thickness of each sample was measured before the test, and the average thickness was obtained by measuring five points on the sample. Volume resistivity tests were performed at room temperature (23°C) and 60°C at 1000 volts. Two compression-molded encapsulant sheets were tested and the average was obtained.

[0031] In the case of resin VR testing (or "resin VR"), the resin was compression-molded into a sample sheet (~500 nm), and the aforementioned VR test was performed on the sample sheet. In the case of sheet VR testing (or "sheet VR"), the extruded sample sheet was cured (crosslinked) by lamination. The lamination process was performed on a PENERGY L036 laminator at 150°C for 20 minutes, including 4 minutes of vacuum treatment and 16 minutes of pressing. The sample sheet was placed between two PTFE sheets during the lamination process. After lamination, the PTFE sheets were removed. Then, the aforementioned VR test was performed on the cured sample sheet. [Modes for carrying out the invention]

[0032] This disclosure provides a sealing sheet. In one embodiment, the sealing sheet is 1 × 10 at 60°C. 14 Ω·cm above ~60℃: 1 × 10 16 The material comprises a material formed from an ethylene / C4-C8α-olefin copolymer having a resin volume resistivity (VR) of less than Ω·cm. The encapsulating sheet contains 0.01% to 0.2% by weight of an ion scavenger. The encapsulating sheet has a transmittance of more than 91%.

[0033] 1. Ethylene / C4-C8α-olefin copolymer The sealing sheet contains an ethylene / C4-C8α-olefin copolymer. The ethylene / C4-C8α-olefin copolymer consists of (i) polymerization units of ethylene and (ii) polymerization units of C4-C8α-olefin comonomers. Non-limiting examples of preferred ethylene / C4-C8α-olefin copolymers include ethylene / butene copolymers, ethylene / hexene copolymers, and ethylene / octene copolymers. In one embodiment, the ethylene / C4-C8α-olefin copolymer lacks vinyl acetate or does not contain vinyl acetate.

[0034] Ethylene / C4-C8α-olefin copolymer is 1 × 10⁻¹⁶ at 60°C. 14 Ω·cm above ~60℃: 1 × 10 16 Resin volume resistivity (VR) less than Ω·cm, or 1 × 10 at 60°C. 14 Ω·cm above ~60℃: 1 × 10 15 It has a VR of Ω·cm.

[0035] In one embodiment, the ethylene / C4-C8α-olefin copolymer resin is an ethylene / octen copolymer having one, some, or all of the following properties. (i) 1 × 10 at 60°C 14 Ω·cm above ~60℃: 1 × 10 16 Resin VR less than Ω·cm, or 1 × 10 at 60℃ 14Ω·cm above ~60℃: 1 × 10 15 Ω·cm resin VR, and / or (ii) 1 × 10 at 23℃ 14 Ω·cm and above at ~23℃: 1 × 10 16 Sheet VR less than Ω·cm, and / or (iii) Densities of 0.860 g / cc to 0.890 g / cc, or 0.860 g / cc to 0.880 g / cc, or 0.865 g / cc to 0.875 g / cc, and / or (iv) Melt index (I2) of 10g / 10 min to 20g / 10 min, or 10g / 10 min to 15g / 10 min, or 11g / 10 min to 14g / 10 min, and / or (v) Melting temperature Tm of 50°C to 90°C, or 50°C to 80°C, or 55°C to 75°C, or 60°C to 70°C, and / or (vi) Vicat softening temperature of 30°C to 50°C, or 35°C to 39°C.

[0036] The sealing sheet contains an ion scavenger. The ion scavenger is a conductive substance (ion, radical, Na) that reduces insulation and PID resistance. + The ion scavenger captures ions, etc. The ion scavenger contributes to the PID resistance of the encapsulating sheet. The encapsulating sheet contains 0.01% to 0.2% by weight, or 0.02% to 0.2% by weight, or 0.02% to 0.1% by weight, or less than 0.03% to 0.1% by weight of the ion scavenger. The weight percentage is based on the total weight of the encapsulating sheet. Non-limiting examples of suitable ion scavengers include metal phosphates such as zirconium phosphate, bismuth phosphate, titanium phosphate, tin phosphate, tantalum phosphate, and combinations thereof.

[0037] In one embodiment, the ion scavenger is zirconium phosphate. In a further embodiment, the ion scavenger is Zr 1-X Hf X H a (PO4) b ·mH2O, in the formula 0 ≤ x ≤ 0.2, 2 <b≦2.1であり、 a is 3, ba=4, 0 ≤ m ≤ 2.

[0038] In one embodiment, the material for forming a encapsulant sheet includes a curing package. The curing package includes an organic peroxide, an optional curing agent, and an optional silane coupling agent. When a curing package is present, the material is a curable composition for forming a crosslinked encapsulant sheet.

[0039] If a coupling package is present, the material for forming the encapsulating sheet contains an organic peroxide in an amount of 0.1% to 3% by weight, or 0.1% to 2.5% by weight, or 0.1% to 2% by weight, or 0.5% to 1.5% by weight, or 1% to 1.5% by weight, based on the total weight of the material. The weight percentage is based on the total weight of the material for forming the encapsulating sheet. An organic peroxide is a molecule or aggregate of such molecules containing a carbon atom, a hydrogen atom, and two or more oxygen atoms, having at least one -OO- group, wherein if two or more -OO- groups are present, each -OO- group is indirectly bonded to another -OO- group via one or more carbon atoms. Non-limiting examples of organic peroxides include peroxycarbonates, diacyl peroxides, peroxyketals, dialkyl peroxides, peroxyesters, and combinations thereof.

[0040] In one embodiment, the organic peroxide is of formula R O -OOR O These are dialkylperoxides and monoperoxides, where each R is a dialkylperoxide in the formula. O (C1-C 20 )alkyl group or (C6-C 20 ) is an aryl group. Each (C1~C 20 The alkyl groups are independently unsubstituted or have one or two (C6~C) alkyl groups. 12 ) Substituted with an aryl group. Each (C6~C 20 The aryl group is either unsubstituted or has 1 to 4 (C1 to C) 10) is substituted with an alkyl group. Alternatively, organic peroxides have formula R O -OOROOR O It may also be a diperoxide of (C2-C 10 )Alkilen, (C3-C 10 ) A divalent hydrocarbon group such as cycloalkylene or phenylene, and each R O This is as defined above.

[0041] Non-limiting examples of suitable organic peroxides include tert-butylperoxy-2-ethylhexyl carbonate (TBEC), tert-amylperoxy-2-ethylhexyl carbonate (TAEC), 1,1-di(tert-butylperoxy)-3,3,5-trimethylcyclohexane, 1,1-di(tert-butylperoxy)cyclohexane, 3,6,9-triethyl-3,6,9-trimethyl-1,4,7-triperoxonane, tert-butylperoxy-2-ethylhexanoate dicumylperoxide, laurylperoxide, benzoylperoxide, tert-butylperbenzoate, di(tert-butyl)peroxide, and cumenehydroperoxide;2,5-Dimethyl-2,5-di(t-butyl-peroxy)hexyn-3, 2,5-Dimethyl-2,5-di(t-butyl-peroxy)hexane, tert-butylhydroperoxide, isopropyl parkervonate, α,α'-bis(tert-butylperoxy)diisopropylbenzene, t-butylperoxy-2-ethylhexyl-monocarbonate, 1,1-bis(t-butylperoxy)-3,5,5-trimethylcyclohexane, 2 ,5-dimethyl-2,5-dihydroxyperoxide, t-butylcumylperoxide, α,α'-bis(t-butylperoxy)-p-diisopropylbenzene, bis(1,1-dimethylethyl)peroxide, bis(1,1-dimethylpropyl)peroxide, 2,5-dimethyl-2,5-bis(1,1-dimethylethylperoxy)hexane, 2,5-dimethyl-2,5-bis(1,1-dimethylethylperoxy)hexine, 4,4-bis(1 Examples include 1-dimethylethyl peroxy)valeric acid, butyl esters, 1,1-bis(1,1-dimethylethyl peroxy)-3,3,5-trimethylcyclohexane, benzoyl peroxide, tert-butyl peroxybenzoate, di-tert-amyl peroxide ("DTAP"), bis(alpha-t-butyl-peroxyisopropyl)benzene ("BIPB"), isopropylcumyl t-butyl peroxide, t-butylcumyl peroxide, dibutyl peroxide, 2,5-bis(t-butyl peroxy)-2,5-dimethylhexane, 2,5-bis(t-butyl peroxy)-2,5-dimethylhexine-3,1,1-bis(t-butyl peroxy)-3,3,5-trimethylcyclohexane, isopropylcumyl peroxide, butyl 4,4-di(tert-butyl peroxy) valerate, di(isopropylcumyl) peroxide, and combinations thereof.

[0042] When an auxiliary agent is present in the curing package, the material for forming the encapsulant sheet contains an amount of the auxiliary agent in the range of 0.1% to 2.5% by weight, or 0.1% to 2% by weight, or 0.5% to 1.5% by weight, or 0.5% to 1.0% by weight, based on the total weight of the material used to form the encapsulant sheet. A non-limiting example of a suitable auxiliary agent is triallyl isocyanurate.

[0043] If a silane coupling agent is present in the cured package, the material for forming the sealing sheet includes 0.01% to 2% by weight of the silane coupling agent, or 0.05% to 1.5% by weight, or 0.1% to 1% by weight, 0.15% to 0.5% by weight, 0.2% to 0.4% by weight, or 0.25% to 0.3% by weight, based on the total weight of the material used to form the sealing sheet. Non-limiting examples of suitable silane coupling agents include γ-chloropropyltrimethoxysilane, vinyltrimethoxysilane, vinyltriethoxysilane, vinyl-tris-(β-methoxy)silane, allyltrimethoxysilane, γ-methacryloxypropyltrimethoxysilane, β-(3,4-ethoxycyclohexyl)ethyltrimethoxysilane, γ-glycidoxypropyltrimethoxysilane, γ-mercaptopropyltrimethoxysilane, γ-aminopropyltrimethoxysilane, N-β-(aminoethyl)-γ-aminopropyltrimethoxysilane, 3-(trimethoxysilyl)propyl methacrylate, and combinations thereof.

[0044] In one embodiment, the silane coupling agent is selected from vinyltrimethoxysilane, 3-(trimethoxysilyl)propyl methacrylate, or allyltrimethoxysilane.

[0045] The material for forming the sealing sheet may contain one or more optional additives. If any additives are present, they are present in an amount greater than zero, or 0.01% by weight, or 0.1% to 1% by weight, or 2% by weight, or 3% by weight, or 5% by weight, based on the total weight of the material. Non-limiting examples of suitable additives include antioxidants, anti-blocking agents, stabilizers, colorants, ultraviolet (UV) absorbers or stabilizers, flame retardants, compatibilizers, fillers, hindered amine stabilizers, tree retarders, methyl radical scavengers, scorch retarders, nucleating agents, processing aids, and combinations thereof.

[0046] In one embodiment, the material forming the sealing sheet is (i) 1 × 10 at 60°C 14 Ω·cm above ~60℃: 1 × 10 16 The invention relates to a curing package containing (ii) an ethylene / C4-C8α-olefin copolymer having a resin volume resistivity (VR) of less than Ω·cm, (ii) 0.01% to 0.2% by weight of an ion scavenger, and (iii) an organic peroxide, (iv) an auxiliary agent, (v) a silane coupling agent, and (vi) a UV stabilizer. The ion scavenger is compounded into the ethylene / C4-C8α-olefin copolymer pellets. The compounded ethylene / C4-C8α-olefin copolymer pellets are then mixed with a curing package containing the peroxide, auxiliary agent, and silane coupling agent (and optional additives). The pellets of the ethylene / C4-C8α-olefin copolymer (including the ion scavenger) are immersed in a curing package consisting of the organic peroxide, auxiliary agent, and silane coupling agent, and the immersed pellets are then further processed (e.g., compounding, extrusion, molding, etc.) to form a encapsulant sheet consisting of the crosslinked ethylene / C4-C8α-olefin copolymer, the ion scavenger, and optional additives.

[0047] The cross-linked encapsulant sheet is structurally and physically different from the material cured to produce the cross-linked encapsulant sheet. In one embodiment, the encapsulant sheet is a cross-linked sheet comprising 99.8% to 99.98% by weight of ethylene / C4-C8α-olefin copolymer and an ion scavenger which is 0.02% to 0.2% by weight of zirconium phosphate. The encapsulant sheet is cured at 23°C for 1 × 10⁻¹⁶ 14 Ω·cm and above at ~23℃: 1 × 10 16 VR less than Ω·cm (sheet VR), or 1 × 10 at 23℃ 14 Ω·cm and above at ~23℃: 7.0 × 10 15 It has a sheet VR of less than Ω·cm. Ethylene / C4-C8α-olefin copolymer is an ethylene / octen copolymer having one, some, or all of the following properties: (i) 1 × 10 at 60°C 14 Ω·cm above ~60℃: 1 × 10 16 Resin VR less than Ω·cm, or 1 × 10 at 60℃ 14 Ω·cm above ~60℃: 1 × 10 15 Ω·cm resin VR, and / or (ii) 1 × 10 at 23℃ 14 Ω·cm and above at ~23℃: 1 × 10 16 VR less than Ω·cm (sheet VR), or 1 × 10 at 23℃ 14 Ω·cm and above at ~23℃: 7.0 × 10 15 Sheet VR less than Ω·cm, and / or (iii) Densities of 0.860 g / cc to 0.890 g / cc, or 0.860 g / cc to 0.880 g / cc, or 0.865 g / cc to 0.875 g / cc, and / or (iv) Melt index (I2) of 10g / 10 min to 20g / 10 min, or 10g / 10 min to 15g / 10 min, or 11g / 10 min to 14g / 10 min, and / or (v) Melting temperature Tm of 50°C to 90°C, or 50°C to 80°C, or 55°C to 75°C, or 60°C to 70°C, and / or (vi) Vicat softening temperature of 30°C to 50°C, or 35°C to 39°C (hereinafter referred to as Sheet 1). The weight percentage is based on the total weight of the sealing material sheet.

[0048] 2. PV module The present invention provides a photovoltaic (PV) module. The terms “photovoltaic cell,” “PV cell,” and similar terms refer to a structure containing one or more photovoltaic effect materials of any of several inorganic or organic types. Non-limiting examples of photovoltaic effect materials include known photovoltaic effect materials such as crystalline silicon, polycrystalline silicon, amorphous silicon, copper indium gallium selenide (CIGS), copper indium selenide (CIS), cadmium telluride, gallium arsenide, dye-sensitized materials, and organic solar cell materials. As shown in Figure 1, a PV module is typically used in a laminated structure and typically has at least one photoreactive surface that converts incident light into an electric current, in outdoor applications. A PV cell may be inherently flexible or rigid and may include photovoltaic effect materials and any protective coating surface materials applied to their production, as well as appropriate wiring and electronic drive circuits.

[0049] "Photovoltaic module," "PV module," and similar terms refer to a structure containing PV cells. A PV module may also include a front cover sheet, front sealant sheet, rear sealant sheet, back sheet, or rear sealant sheet, with the PV cells sandwiched between the front sealant sheet and the rear sealant sheet.

[0050] A PV module includes (A) a front cover sheet, (B) a front sealing sheet, (C) a photovoltaic cell, (D) a rear sealing sheet, and (E) a rear cover sheet. Figure 1 shows an exemplary PV module. A rigid PV module 10 includes a photovoltaic cell 11 (PV cell 11) surrounded or sealed by a front sealing sheet 12a and a rear sealing sheet 12b. The front cover sheet 13 covers the front of the portion of the front sealing sheet 12a that is placed on the PV cell 11. The rear cover sheet 14 supports the rear of the portion of the rear sealing sheet 12b that is placed on the rear of the PV cell 11. The front cover sheet 13 and the rear cover sheet 14 are each made of glass, acrylic resin, or polycarbonate. In one embodiment, the front cover sheet 13 and the rear cover sheet 14 are each made of glass.

[0051] As shown in Figure 1, a portion of the front sealing sheet 12a is in direct contact with the PV cell 11, and another portion of the front sealing sheet is in direct contact with the rear sealing sheet 12b. A portion of the rear sealing sheet 12b is also in direct contact with the back of the PV cell 11. In this way, the front sealing sheet 12a and the rear sealing sheet 12b completely seal the PV cell 11. As shown in Figure 1, the front sealing sheet 12a is in direct contact with the front cover sheet 13, and the rear sealing sheet 12b is in direct contact with the rear cover sheet 14. The PV cell 11 is sandwiched between the front sealing sheet 12a and the rear sealing sheet 12b so that both the front sealing sheet 12a and the rear sealing sheet 12b are in direct contact with the PV cell 11. The front sealing sheet 12a and the rear sealing sheet 12b are also in direct contact with each other in locations where the PV cell 11 is not present.

[0052] The sealing sheet of this disclosure may be a front sealing sheet, a rear sealing sheet, or both a front sealing sheet and a rear sealing sheet. In one embodiment, the sealing sheet of this disclosure is a front sealing sheet. In another embodiment, the sealing sheet of this disclosure is both a front sealing sheet and a rear sealing sheet.

[0053] In one embodiment, the PV module includes a front sealing material sheet 12a, which is sheet 1, and a back sealing material sheet 12b, which is sheet 1.

[0054] In one embodiment, the encapsulant sheet of the present disclosure is attached to an electronic device by one or more lamination techniques. Through lamination, a cover sheet is in direct contact with a first surface of the encapsulant sheet, and the electronic device is in direct contact with a second surface of the encapsulant sheet. A front cover sheet is in direct contact with the first surface of the front encapsulant sheet, and a rear cover sheet is in direct contact with the second surface of the rear encapsulant sheet. The electronic device is fixed between the second surface of the front encapsulant sheet and the first surface of the rear encapsulant sheet and is in direct contact with them.

[0055] In one embodiment, the lamination temperature is sufficient to activate the organic peroxide and crosslink the curable material, namely, the ethylene / C4-C8α-olefin copolymer, ion scavenger, organic peroxide, silane coupling agent, and auxiliary agents (and optional additives). During crosslinking, the molecular chains of the ethylene / C4-C8α-olefin copolymer are bonded by carbon-carbon bonds. The silane coupling agent also interacts with the surface of the cover sheet to increase the adhesion between each encapsulant sheet and its respective cover sheet. After lamination, the material is the reaction product of the ethylene / C4-C8α-olefin copolymer, ion scavenger, organic peroxide, silane coupling agent, and auxiliary agents. The crosslinked encapsulant sheet is structurally and physically different from these crosslinkable materials.

[0056] In one embodiment, the photovoltaic module is (A) Front cover sheet and (B) Front sealing sheet, (i) 1 × 10 at 60°C 14 Ω·cm above ~60℃: 1 × 10 16 Ethylene / C4-C8α-olefin copolymer having a resin volume resistivity (VR) of less than Ω·cm, (ii) 0.01% to 0.2% by weight of an ion scavenger, A front sealing sheet consisting of, (C) Photovoltaic cell and, (D) A back sealing sheet, (i) 1 × 10 at 60°C 14 Ω·cm above ~60℃: 1 × 10 16 Resin volume resistivity (VR) less than Ω·cm, or 1 × 10 at 60°C. 14 Ω·cm above ~60℃: 1 × 10 15 Ethylene / C4-C8α-olefin copolymer having resin VR less than Ω·cm, (ii) 0.01% to 0.2% by weight of an ion scavenger, A back sealing sheet consisting of, (E) The rear cover sheet is included, and the power loss after the photovoltaic module's potential-induced degradation (PID) test is 0.05% to less than 5.0%, or 0.05% to less than 2%. In further embodiments, the front sealant sheet and the rear sealant sheet are each 1 × 10 at 23°C. 14 Ω·cm and above at ~23℃: 1 × 10 16 Sheet VR less than Ω·cm, or 1 × 10 at 23℃ 14 Ω·cm and above at ~23℃: 7.0 × 10 15 It has a sheet VR of less than Ω·cm.

[0057] In one embodiment, the photovoltaic module includes (A) a front cover sheet, (B) a front sealing sheet, (C) a photovoltaic cell, (D) a rear sealing sheet, and (E) a rear cover sheet. The front sealing sheet and the rear sealing sheet are each crosslinked sheets. It consists of 99.8% to 99.98% by weight of ethylene / C4-C8α-olefin copolymer, and ethylene / C4-C8α-olefin copolymer is (i) 1 × 10 at 60°C 14 Ω·cm above ~60℃: 1 × 10 16 Resin VR less than Ω·cm, or 1 × 10 at 60℃ 14 Ω·cm above ~60℃: 1 × 10 15 Resin VR less than Ω·cm, and / or (ii) Densities of 0.860 g / cc to 0.880 g / cc, and / or (iii) Melt index (I2) for 10g / 10 min to 15g / 10 min, and / or (iv) Melting temperature Tm between 50°C and 80°C, and / or (v) An ethylene / octen copolymer having a Vicat softening temperature of 30°C to 50°C, wherein the power loss after the photovoltaic module's potential-induced degradation (PID) test is less than 0.05% to 1%. In further embodiments, the front and back sealing sheets are each 1 × 10 at 23°C. 14 Ω·cm and above at ~23℃: 1 × 10 16 Sheet VR less than Ω·cm, or 1 × 10 at 23℃ 14 Ω·cm and above at ~23℃: 7.0 × 10 15 It has a sheet VR of less than Ω·cm.

[0058] Without limiting ourselves to any particular example, several embodiments of this disclosure will be described in detail in the following examples. [Examples]

[0059] The materials used in the examples (IE) and comparative samples (CS) of the present invention are shown in Table 1 below. [Table 1]

[0060] 1. Preparation of sealing material sheet Compounding of ion-scavenging powders (IXE-100 and IXEPLAS) and resin. The resin was supplied to a Brabender mixer at the set temperature (130°C) and a rotor speed of 10 rpm. Next, the ion-scavenging powder was weighed and gradually added to the Brabender mixer. Mixing was carried out for 5 minutes at the set temperature (130°C) and a rotor speed of 80 rpm. The finished compound was recovered and cut into small pieces. These pieces were supplied to the hopper of a Brabender single-screw extruder and extruded into a molten strand at a screw speed of 25 rpm and 110°C. The molten strand was supplied to a Brabender pelletizer to produce an ion-scavenging powder masterbatch pellet. Next, the ion-scavenging masterbatch sample was dry-blended with the polymer pellet using a mixer in the desired volume.

[0061] For each composition, polymer pellets (98.18% by weight) were mixed with a cured package (1.00% by weight peroxide, 0.50% by weight crosslinking agent, 0.25% by weight silane coupling agent, and 0.07% by weight UV stabilizer).

[0062] For each composition, the pellets were immersed at 40°C for 4 hours, and then fed into the Labtech casting line at an extruder temperature of 110°C to avoid peroxide decomposition. Films with a thickness of approximately 470 nm and a width of 250 mm were fabricated.

[0063] These films (simulating front / back sealing sheets) were used for the following module fabrication and performance testing.

[0064] Single-cell module stacking. The glass / glass bifacial modules used in this study were prepared using the following procedure.

[0065] A 4 x 6 square inch glass cover sheet was washed with water and then dried before use. The sealant sheet was cut into small pieces to match the size of the glass. The front glass cover sheet, front sealant sheet, photovoltaic cell, rear sealant film, and rear glass cover sheet were laminated together in the order described above. The lamination process was performed on a PENERGY L036 laminator at 150°C for 20 minutes, including 4 minutes of vacuum treatment and 16 minutes of pressing. The laminated samples were used for PID stress testing. Three identical single-cell PV module samples were prepared for PID testing, and the average value was obtained.

[0066] The characteristics of the front sealing sheet and the rear sealing sheet are shown in Table 2 below. [Table 2] CS = Comparative sample; IE = Example of invention

[0067] result (A) XUS 38679 (CS-2) Ethylene / Octene Copolymer has a temperature of 2.74 × 10⁻¹⁶ at 60°C. 14The power loss after PID testing for a PV module with a resin VR of Ω·cm and CS-2 was -3.57% / -9.25% (front / back). PV modules with CS-2 front / back encapsulant film exhibited a power loss exceeding 5% after voltage-induced degradation (PID) testing and are therefore unsuitable as encapsulant sheets for double-sided PV modules. An encapsulant sheet consisting of XUS 38679 ethylene / octen copolymer and 0.0625 wt% POEM (CS-2-1) showed a power loss of -3.38% / -5.79% (front / back) after PID testing. CS-2-1, with a power loss exceeding 5%, is unsuitable as an encapsulant sheet for double-sided PV modules. Encapsulation sheets consisting of XUS 38679 ethylene / octen copolymer and (i) 0.25 wt% POEM (IE-2-2), (ii) 0.5 wt% POEM (0.04 wt% IXE-100) (IE-2-3), (iii) 1 wt% POEM (IE-2-5), and (iv) 2.5 wt% POEM (IE-2-6) each showed a power loss of less than 2% after PID testing, which is acceptable and lower than the -2.86% power loss after PID testing for CS-1, ENGAGE PV 8669.

[0068] The power loss after PID testing for (C)ENGAGE 8411(CS-4) was -3.41% / -13.31% (front / back), and the power loss after PID testing for R04(CS-5) was -6.22% / -23.58% (front / back). Therefore, ENGAGE 8411 and R04 are not suitable for bifacial PV modules. Adding 0.5 wt% POEM to ENGAGE 8411(CS-4-1) or 1.0 wt% POEM to ENGAGE 8411(CS-4-2) did not improve power loss. Since there was no trend towards performance improvement, and increasing the dosage would affect economy and film transparency, the dosage was not further increased.

[0069] While not bound by any particular theory, VR is thought to represent the ion mobility and concentration within ethylene / C4-C8α-olefin copolymer resins. For example, R04 (CS-5) and ENGAGE 8411 (CS-4), the VR is 1 × 10⁻¹⁶ at 60°C. 14 In ethylene / C4-C8α-olefin copolymers with resin VR less than Ω·cm, ion mobility and concentration are high, and therefore, ion scavengers cannot effectively neutralize all ions. As a result, ion scavengers have a ion mobility of 1 × 10⁻⁶ at 60°C. 14 Power loss cannot be effectively prevented in ethylene / C4-C8α-olefin copolymers having a resin VR of less than Ω·cm.

[0070] This disclosure is not limited to the embodiments and examples contained herein, but is particularly intended to include some embodiments and modified forms of those embodiments, including combinations of elements of different embodiments, to the extent that they fall within the scope of the following claims. The present invention includes the following embodiments. [1] A sealing sheet, 1 x 10 at 60℃ 14 Ω·cm above ~60℃: 1 × 10 16 Ethylene / C resin with a resin volume resistivity (VR) of less than Ω·cm 4 -C 8 α-olefin copolymer and 0.01% to 0.2% by weight of an ion scavenger, Includes a material formed from, The aforementioned sheet has a transmittance of more than 91%. Sealing sheet. [2] The ethylene / C 4 -C 8 α-olefin copolymers exhibit 1 × 10⁻¹⁶ ions at 23°C. 14 Ω·cm and above at ~23℃: 1 × 10 16 The sealing sheet according to [1], having a sheet VR of less than Ω·cm. [3] The ethylene / C 4 -C 8 α-olefin copolymers are (i) 1 × 10 at 60°C 14 Ω·cm above ~60℃: 1 × 10 16 Resin VR less than Ω·cm, (ii) Densities of 0.860 g / cc to 0.890 g / cc, (iii) Melt index (I2) for 10g / 10 min to 20g / 10 min, (iv) Melting temperature Tm between 50°C and 90°C, (v) Vicat softening temperature of 30℃~50℃, The sealing sheet according to [2], which is an ethylene / octen copolymer having the following properties. [4] The ion scavenging agent is zirconium phosphate, the sealing sheet according to any one of the above [1] to [3]. [5] The sealing sheet according to any one of the above [1] to [4], wherein the material comprises a curing package comprising a peroxide, an optional curing agent, and an optional silane coupling agent. [6] The sealing sheet according to any one of the above [1] to [5], comprising an additive selected from the group consisting of UV stabilizers, antioxidants, and combinations thereof. [7] A photovoltaic module, (A) Front cover sheet and (B) Front sealing sheet, (i) 1 × 10 at 60°C 14 Ω·cm above ~60℃: 1 × 10 16 Ethylene / C resin with a resin volume resistivity (VR) of less than Ω·cm 4 -C 8 α-olefin copolymer and (ii) 0.01% to 0.2% by weight of an ion scavenger, A front sealing sheet consisting of, (C) Photovoltaic cell and, (D) A back sealing sheet, (i) 1 × 10 at 60°C 14 Ω·cm above ~60℃: 1 × 10 16 Ethylene / C resin with a resin volume resistivity (VR) of less than Ω·cm 4 -C 8 α-olefin copolymer and (ii) 0.01% to 0.2% by weight of an ion scavenger, A back sealing sheet consisting of, (E) Back cover sheet and Equipped with, The power loss of the aforementioned photovoltaic module after a potential-induced degradation (PID) test is between 0.05% and less than 5%. Photovoltaic module. [8] The photovoltaic module according to [7], wherein a portion of the front sealing sheet is in direct contact with the photovoltaic cell, and a portion of the front sealing sheet is in direct contact with a portion of the rear sealing sheet. [9] The photovoltaic module according to [8], wherein a portion of the back sealing sheet is in direct contact with a portion of the photovoltaic cell.

[10] The front sealing sheet and the rear sealing sheet are each 1 × 10 at 23°C 14 Ω·cm and above at ~23℃: 1 × 10 16 Ethylene / C with sheet VR less than Ω·cm 4 -C 8 A photovoltaic module according to any one of the above [7] to [9], comprising an α-olefin copolymer.

[11] The front sealing sheet and the back sealing sheet are each a crosslinked sheet, 99.80% to 99.98% by weight of ethylene / C 4 -C 8 It consists of an α-olefin copolymer, and the ethylene / C 4 -C 8 α-olefin copolymers are (i) 1 × 10 at 60°C 14 Ω·cm above ~60℃: 1 × 10 16 Resin VR less than Ω·cm, (ii) Densities of 0.860 g / cc to 0.890 g / cc, (iii) Melt index (I2) for 10g / 10 min to 20g / 10 min, (iv) Melting temperature Tm between 50°C and 90°C, (v) Vicat softening temperature of 30℃~50℃, It is an ethylene / octen copolymer having, The power loss of the aforementioned photovoltaic module after a potential-induced degradation (PID) test is between 0.05% and less than 1%. A photovoltaic module as described in any one of the above items [7] to

[10] .

Claims

1. A crosslinked sealing sheet, 99.8% to 99.98% by weight ethylene / C ４ -C ８ α-olefin copolymer, 1 x 10 at 60°C １４ Ω·cm above 1 × 10⁻¹⁰ at temperatures above 60°C １５ Having a resin volume resistivity (VR) of less than Ω·cm, (i) Melt index (I2) for 11g / 10 min to 14g / 10 min, (ii) Vicat softening temperature of 35°C to 39°C, Ethylene / C is an ethylene / octen copolymer having ４ -C ８ α-olefin copolymer and An ion scavenger consisting of 0.02% to 0.1% by weight of zirconium phosphate, Includes a material formed from, The aforementioned sheet has an average transmittance of over 91% when measured in the range of 380 nm to 1100 nm using a UV / Vis spectrophotometer equipped with a 150 mm integrating sphere. Cross-linked sealing sheet.

2. The ethylene / C ４ -C ８ α-olefin copolymer has a sheet VR of more than 1×10 １４ Ω·cm at 23°C to less than 1×10 １６ Ω·cm at 23°C. The crosslinked sealing material sheet according to claim 1.

3. The aforementioned ethylene / octen copolymer is (i) Densities of 0.860 g / cc to 0.890 g / cc, (ii) Melting temperature Tm of 50°C to 90°C, A crosslinking sealing sheet according to claim 2, having the characteristics described above.

4. The crosslinked encapsulant sheet according to any one of claims 1 to 3, wherein the material comprises a curing package containing a peroxide, an optional curing agent, and an optional silane coupling agent.

5. A crosslinked encapsulant sheet according to any one of claims 1 to 4, comprising an additive selected from the group consisting of UV stabilizers, antioxidants, and combinations thereof.

6. A photovoltaic module, (A) Front cover sheet and (B) A cross-linking front sealing sheet, (i) 99.8% to 99.98% by weight of ethylene / C ４ -C ８ α-olefin copolymer, 1 x 10 at 60°C １４ Ω·cm above 1 × 10⁻¹⁰ at temperatures above 60°C １５ Having a resin volume resistivity (VR) of less than Ω·cm, (a) Melt index (I2) for 11 g / 10 min to 14 g / 10 min, (b) Vicat softening temperature of 35°C to 39°C, Ethylene / C is an ethylene / octen copolymer having ４ -C ８ α-olefin copolymer and (ii) An ion scavenger which is zirconium phosphate in an amount of 0.01% to less than 0.1% by weight, A crosslinked front sealing material sheet consisting of, (C) Photovoltaic cell and (D) A crosslinked back sealing sheet, (i) 99.8% to 99.98% by weight of ethylene / C ４ -C ８ α-olefin copolymer, 1 x 10 at 60°C １４ Ω·cm above 1 × 10⁻¹⁰ at temperatures above 60°C １５ Having a resin volume resistivity (VR) of less than Ω·cm, (a) Melt index (I2) for 11 g / 10 min to 14 g / 10 min, (b) Vicat softening temperature of 35°C to 39°C, Ethylene / C is an ethylene / octen copolymer having ４ -C ８ α-olefin copolymer and (ii) An ion scavenger which is zirconium phosphate in an amount of 0.01% to less than 0.1% by weight, A crosslinked back sealing sheet consisting of, (E) Back cover sheet and Equipped with, The power loss of the aforementioned photovoltaic module after a potential-induced degradation (PID) test is between 0.05% and less than 5%. Photovoltaic module.

7. The photovoltaic module according to claim 6, wherein a portion of the crosslinked front sealing sheet is in direct contact with the photovoltaic cell, and a portion of the crosslinked front sealing sheet is in direct contact with a portion of the crosslinked back sealing sheet.

8. The photovoltaic module according to claim 7, wherein a portion of the crosslinked back sealing sheet is in direct contact with a portion of the photovoltaic cell.

9. The crosslinked front sealing sheet and the crosslinked back sealing sheet are each 1 × 10 at 23°C. １４ Ω·cm and above at ~23℃: 1 × 10 １６ Ethylene / C having a sheet VR of less than Ω·cm ４ -C ８ A photovoltaic module according to any one of claims 6 to 8, comprising an α-olefin copolymer.

10. The aforementioned crosslinked front sealing sheet and the aforementioned crosslinked back sealing sheet are each a crosslinked sheet. It consists of 99.80% to 99.98% by weight of an ethylene / octen copolymer, and the ethylene / octen copolymer is (i) Densities of 0.860 g / cc to 0.890 g / cc, (ii) Melting temperature Tm of 50°C to 90°C, It is an ethylene / octen copolymer having, The power loss of the aforementioned photovoltaic module after a potential-induced degradation (PID) test is between 0.24% and less than 1%. A photovoltaic module according to any one of claims 6 to 9.

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