Battery encapsulation adhesive film, its application and n-type topcon photovoltaic module

Abstract

The present application relates to the field of encapsulation materials for solar photovoltaic cell modules, and provides a cell encapsulation adhesive film, application thereof and an n-type Topcon photovoltaic module. The cell encapsulation adhesive film of the present application is used in a photovoltaic module, in particular an n-type Topcon photovoltaic module, which is conducive to good water blocking effect and PID resistance, and is conducive to improving the long-term stability of the module. The cell encapsulation adhesive film is prepared from raw materials comprising the following components by mass: ethylene / alpha-olefin copolymer 90-95 parts, functional resin 5-10 parts, and main crosslinking agent 0.2-2 parts. The functional resin is metallocene homopolymerized polypropylene containing carbon-carbon double bonds at the end of the molecular chain, and the mass ratio of the main crosslinking agent to the functional resin is 1:(5-10).

Description

TECHNICAL FIELD

[0001] The present application relates to the field of encapsulation materials for solar photovoltaic cell modules, in particular to the field of n-type Topcon cell encapsulation adhesive film technology, and further relates to a cell encapsulation adhesive film, its application and an n-type Topcon photovoltaic module. BACKGROUND

[0002] The use of solar energy requires photovoltaic modules, which are mainly composed of five layers of photovoltaic glass, photovoltaic adhesive film, crystalline silicon cell, photovoltaic adhesive film, photovoltaic glass or back plate; the role of the photovoltaic adhesive film is to provide structural support and positioning of the cell, to act as physical isolation of the cell and other elements, and to maintain electrical insulation between the cell and other elements. The photovoltaic adhesive film mainly uses polyolefin materials, and the current mainstream material is ethylene-vinyl acetate copolymer (EVA), but due to the presence of vinyl acetate groups, it will release acetic acid to corrode the cell during outdoor use, and it has low volume resistivity, high water vapor transmission, and poor PID resistance. Ethylene / alpha-olefin copolymer (POE, or described as ethylene-alpha-olefin copolymer) has excellent water resistance and better PID resistance, and is gradually replacing EVA as the main photovoltaic adhesive film application material. Because the latest n-type TOPCon cell front coating is silver aluminum paste, water vapor intrusion will corrode the grid silver paste in a high temperature and high humidity environment, resulting in blackening of the module and power decay, and POE is more suitable for n-type Topcon cells due to its excellent water resistance.

[0003] However, POE itself has poor compatibility with polar additives in the formula, and the additives are prone to migrate during long-term storage or heating; at the same time, some polar by-products formed due to the presence of additives during lamination will also migrate to the surface of the cell, causing corrosion of the cell and affecting the power generation efficiency of the module.

[0004] The existing technology mainly adds some porous materials or cage compounds as anti-precipitation agents, or adds some adsorbents for adsorption.

[0005] CN111662655A discloses a POE photovoltaic adhesive film and a preparation method thereof, which comprises POE resin, antioxidant, crosslinking agent, coupling agent and anti-precipitation agent; the content of the anti-precipitation agent is 0.1-4%; the anti-precipitation agent is mainly some porous materials or cage compounds, which can prevent liquid additives from migrating during storage or transportation, but the addition of porous materials or cage compounds will affect the light transmission and other properties of the adhesive film.

[0006] CN118222197 A discloses a composite adhesive film for Topcon solar cells, characterized in that it comprises two acid-absorbing adhesive layers and a water-blocking layer sandwiched between the two acid-absorbing adhesive layers, the acid-absorbing adhesive layer comprises a silane derivative and a modified hydrotalcite, the silane derivative comprises one or both of a modified silane and an oligomer of silane; the water-blocking layer comprises an ethylene-modified resin and a compounded acrylate. However, the introduction of new additives still causes the problem of additive migration. SUMMARY

[0007] The application provides a battery packaging adhesive film, its application and an n-type Topcon photovoltaic module. The battery packaging adhesive film is used in a photovoltaic module, especially an n-type Topcon photovoltaic module, which is beneficial to taking into account good water-blocking effect and PID resistance, and improving the long-term stability of the module.

[0008] To achieve the purpose, the application provides the following technical solutions.

[0009] The application provides a battery packaging adhesive film, which is prepared from raw materials comprising the following components by mass:

[0010] Ethylene / alpha-olefin copolymer 90-95 parts,

[0011] Functional resin 5-10 parts,

[0012] Main crosslinking agent 0.2-2 parts;

[0013] The functional resin is metallocene homopolypropylene containing a carbon-carbon double bond at the end of a molecular chain, and the mass ratio of the main crosslinking agent to the functional resin is 1:(5-10), preferably 1:(6-8).

[0014] The application also provides the application of the battery packaging adhesive film described above in a photovoltaic module, preferably the photovoltaic module is an n-type Topcon photovoltaic module.

[0015] The application also provides an n-type Topcon photovoltaic module, which comprises upper photovoltaic glass, a first packaging adhesive film, an n-type Topcon cell, a second packaging adhesive film and lower photovoltaic glass arranged in sequence; the first packaging adhesive film and / or the second packaging adhesive film is the battery packaging adhesive film described above.

[0016] The technical solutions provided by the application have the following beneficial effects.

[0017] The application uses metallocene homopolymer polypropylene with carbon-carbon double bond at the end of molecular chain as functional resin in the battery packaging adhesive film system with ethylene / alpha-olefin copolymer as base resin, and ethylene / alpha-olefin copolymer, functional resin and main crosslinking agent are combined and matched according to the use amount range of the application, so that the crosslinking degree of the adhesive film can be improved, the additive migration problem in the adhesive film can be improved, and the obtained packaging adhesive film applied in n-type Topcon photovoltaic module can have good PID resistance and water resistance, and other comprehensive performances, thereby providing guarantee for long-term stability of Topcon module. DETAILED DESCRIPTION

[0018] In order to facilitate the understanding of the present application, the present application will be further described below in combination with examples. It should be understood that the following examples are only for better understanding of the present application, and do not mean that the present application is limited to the following examples only.

[0019] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. The term "and / or" as can be used herein includes any and all combinations of one or more of the associated listed items.

[0020] The application provides a battery packaging adhesive film, which is prepared from raw materials including the following components by mass fraction:

[0021] ethylene / alpha-olefin copolymer 90-100 parts,

[0022] functional resin 5-10 parts,

[0023] main crosslinking agent 0.2-2 parts;

[0024] The functional resin is metallocene homopolymer polypropylene with carbon-carbon double bond at the end of molecular chain, and the mass ratio of the main crosslinking agent to the functional resin is 1:(5-10).

[0025] In the present application, in the battery packaging adhesive film system with ethylene / alpha-olefin copolymer as the base resin, metallocene homopolymer polypropylene with carbon-carbon double bond at the end of the molecular weight is used as the functional resin, and the ethylene / alpha-olefin copolymer, the functional resin and the main crosslinking agent are combined and matched according to the above-mentioned dosage range, which can improve the crosslinking degree of the adhesive film, improve the additive migration problem in the adhesive film, and the obtained packaging adhesive film applied in the n-type Topcon photovoltaic module can have good PID resistance and water resistance, which provides guarantee for the long-term stability of the Topcon module. In addition, the present inventors found that compared with other types of polypropylene, the functional resin using metallocene homopolymer polypropylene is not easy to form crystal points during the preparation of the packaging adhesive film, and the obtained adhesive film applied in the n-type Topcon photovoltaic module is not easy to cause the damage of the battery piece structure, which is beneficial to obtain the n-type Topcon photovoltaic module with excellent performance.

[0026] In some examples, the amount of ethylene / alpha-olefin copolymer is, for example, 90, 93, 95, 97, 100 parts by mass, etc.; the amount of functional resin is, for example, 5, 7, 9, 10 parts by mass, etc.; the amount of main crosslinking agent is, for example, 0.2, 0.5, 0.7, 1.0, 1.5, 1.7, 2 parts by mass, etc.; and the mass ratio of the main crosslinking agent to the functional resin is, for example, 1:5, 1:6, 1:7, 1:8, 1:9, 1:10, etc.

[0027] In a preferred embodiment, the mass ratio of the main crosslinking agent to the functional resin is 1:(6-8), and the amount of the two is controlled in the preferred range, which is beneficial to further improve the performance of the obtained battery packaging adhesive film.

[0028] Preferably, the functional resin is an organic powder made of metallocene homopolymer polypropylene. Preferably, the melt index of the metallocene homopolymer polypropylene is 10-30 g / 10 min, for example, 10 g / 10 min, 15 g / 10 min, 20 g / 10 min, 25 g / 10 min, 30 g / 10 min, etc., preferably 15-25 g / 10 min; and the melting temperature is 140-160℃, for example, 140℃, 145℃, 150℃, 155℃, 160℃, etc., preferably 145-155℃. The metallocene homopolymer polypropylene is a homopolymer polypropylene produced by using a metallocene catalyst, and the metallocene homopolymer polypropylene used in the present application can use commercially available corresponding products, for example, but not limited to MR2001, Metocene HM562S, etc. Preferably, the metallocene homopolymer polypropylene is a powder with a particle size range of 10-100 μm, for example, 10 μm, 30 μm, 50 μm, 70 μm, 90 μm, 100 μm, etc., preferably the particle size range is 30-70 μm.

[0029] Due to the intrinsic property of metallocene catalyst, β-H elimination and β-CH3 chain transfer reaction easily occur during catalytic propylene polymerization, molecular chain termination growth, thus forming double bond at the end of molecular chain, which is formed as follows:

[0030] (1) β-H elimination chain transfer reaction schematic:

[0031]

[0032] (2) β-CH3 elimination chain transfer reaction schematic:

[0033]

[0034] In some embodiments, the ethylene / α-olefin copolymer is one or more of ethylene and butene copolymer, ethylene and hexene copolymer, ethylene and octene copolymer. Preferably, the ethylene / α-olefin copolymer has a density of 0.85-0.88 g / cm 3 , for example 0.85, 0.86, 0.87, 0.88 g / cm 3 , etc.; melt index of 1-30 g / 10 min, for example 1 g / 10 min, 5 g / 10 min, 10 g / 10 min, 15 g / 10 min, 20 g / 10 min, 25 g / 10 min, 30 g / 10 min, etc.

[0035] Further, the main crosslinking agent is, for example, selected from but not limited to a combination of one or more of tert-butyl peroxy-2-ethylhexyl carbonate, tert-amyl peroxy-2-ethylhexyl carbonate, dicumyl peroxide, 1,1-bis(tert-butyl peroxy)-3,3,5-trimethylcyclohexane, 1,1-bis(tert-amyl peroxy)-3,3,5-trimethylcyclohexane, tert-butyl peroxy isopropyl carbonate; preferably tert-butyl peroxy-2-ethylhexyl carbonate.

[0036] Preferably, the raw material further comprises 0.2-1 parts by mass of a co-crosslinking agent. The co-crosslinking agent is, for example, selected from but not limited to a combination of one or more of triallyl isocyanurate, triallyl cyanurate, trimethylolpropane triacrylate, trimethylolpropane trimethacrylate; preferably triallyl isocyanurate.

[0037] Preferably, the raw material further comprises 0.1-1 parts by mass of a silane coupling agent, and the amount is specifically for example 0.1, 0.3, 0.5, 0.7, 1 parts by mass, etc. The silane coupling agent is for example selected from but not limited to a combination of one or more of γ-aminopropyltriethoxysilane, γ-(2,3-epoxypropoxy)propoxytrimethoxysilane, γ-methacryloxypropoxytrimethoxysilane, γ-mercaptopropyltrimethoxysilane, γ-glycidoxypropyltrimethoxysilane, vinyltrimethoxysilane, vinyltriethoxysilane; preferably vinyltrimethoxysilane.

[0038] Preferably, the raw material further comprises 0.1-1 parts by mass of a light stabilizer, and the amount is specifically for example 0.1, 0.3, 0.5, 0.7, 1 parts by mass, etc. The light stabilizer is preferably a hindered amine light stabilizer, for example selected from but not limited to a combination of one or more of bis(2,2,6,6-tetramethyl-4-piperidyl)sebacate, mono(2,2,6,6-tetramethyl-4-piperidyl)sebacate, bis(1,2,2,6,6-pentamethyl-4-piperidyl)sebacate, poly(4-hydroxy-2,2,6,6-tetramethyl-1-piperidinethanol) succinate;

[0039] Preferably, the raw material further comprises 0.1-1 parts by mass of an antioxidant, and the amount is specifically for example 0.1, 0.3, 0.5, 0.7, 1 parts by mass, etc. The antioxidant can be of a type commonly used in the art, and there is no particular limitation thereto; for example the antioxidant is a composite antioxidant, for example with octadecyl β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate as the primary antioxidant and tris(2,4-di-tert-butylphenyl) phosphite as the secondary antioxidant, and the mass ratio of the primary antioxidant to the secondary antioxidant is for example but not limited to 3:(1-3).

[0040] Further, the battery packaging adhesive film provided by the present application is preferably a packaging adhesive film for n-type Topcon batteries. The battery packaging adhesive film provided by the present application is particularly suitable as a packaging adhesive film for n-type Topcon batteries, and has good application performance.

[0041] The battery packaging adhesive film of the present application can be prepared by using the existing preparation process in the art. As a preferred embodiment, the preparation steps of the battery packaging adhesive film specifically include:

[0042] S1, uniformly mixing the ethylene / α-olefin copolymer and the functional resin, and then extruding and granulating to obtain a polyolefin master batch;

[0043] S2, uniformly mixing the polyolefin master batch and other components, and then performing flow extrusion molding after aging, for example, passing through plasticization, extrusion, stretching, traction and winding in a flow coater to obtain a packaging adhesive film.

[0044] Preferably, in step S1, the extrusion granulation is performed in a twin-screw extruder.

[0045] Preferably, in step S2, the maturation is performed at 40-60℃, for example for 3-5h, and the maturation is performed, for example, in an oven.

[0046] Preferably, in step S2, the cast extrusion molding is performed at 70-120℃, for example in a casting machine.

[0047] The application also provides a use of the battery packaging adhesive film described above in a photovoltaic module, preferably the photovoltaic module is an n-type Topcon photovoltaic module. The battery packaging adhesive film of the application can effectively reduce the residual of additives in the adhesive film after lamination, effectively reduce the generation of by-products, thereby avoiding the corrosion of the battery sheet, and ultimately obtaining better PID resistance and water resistance.

[0048] The application also provides an n-type Topcon photovoltaic module, comprising an upper photovoltaic glass, a first packaging adhesive film, an n-type Topcon battery sheet, a second packaging adhesive film and a lower photovoltaic glass which are sequentially stacked; the first packaging adhesive film and / or the second packaging adhesive film is the battery packaging adhesive film described above. The above technical solution provided by the application has the following beneficial effects:

[0049] ①Based on the formula system of ethylene / α-olefin copolymer as the base resin, the metallocene homopolymer polypropylene with carbon-carbon double bond at the end of the molecular chain and the main crosslinking agent are used according to the above ratio range, and the main crosslinking agent and the functional resin meet the above ratio range, which can improve the additive precipitation problem and is easy to process, and the obtained packaging adhesive film is especially suitable for application in the n-type Topcon photovoltaic module, which can balance the good water resistance and PID resistance;

[0050] ②In the application, the metallocene homopolymer polypropylene with carbon-carbon double bond at the end of the molecular chain is used as the functional resin, which contains double bonds at the end of the molecular chain, can participate in crosslinking, improve the crosslinking degree of the adhesive film, improve the additive migration, and improve the overall water resistance of the adhesive film, and avoid the corrosion of the battery sheet caused by water vapor intrusion;

[0051] ③When the crosslinking agent in the adhesive film is excessive, the specific functional resin (metallocene polypropylene with carbon-carbon double bond at the end of the molecular chain) added in the application contains a large amount of side methyl groups, which can participate in the reaction to consume free radicals, and can avoid the occurrence of side reactions to produce some polar substances to corrode the battery sheet.

[0052] IV. The application controls the functional resin and the main crosslinking agent in the formula system within the above-mentioned ratio range, and is used in combination in the encapsulation adhesive film system based on the ethylene / alpha-olefin copolymer as the matrix resin, so that the obtained encapsulation adhesive film has excellent PID resistance, can greatly reduce the influence of the additive residue on the battery piece, and ensures the long-term stability of the module.

[0053] In the following examples, the specific experimental steps or conditions not specified can be operated according to the corresponding conventional experimental steps or conditions in the technical field. The reagents or instruments not specified by the manufacturer are conventional products that can be obtained by purchase.

[0054] Some raw materials in the following examples and comparative examples are described as follows:

[0055] Ethylene-octene copolymer: DOW ENGAGE PV 8669, density 0.865 g / cm 3 , melt index 14 g / 10 min;

[0056] Functional resin: metallocene homopolymer polypropylene containing carbon-carbon double bonds at the end of the molecular chain, trade name MR 2001, melt index 25 g / 10 min, melting temperature 151℃, particle size 40 μm;

[0057] Example 1

[0058] The present embodiment provides an n-type Topcon battery encapsulation adhesive film, and the preparation steps include:

[0059] Step S1: 95 parts by mass of ethylene-octene copolymer (DOW ENGAGE PV 8669) and 5 parts by mass of functional resin are uniformly mixed, and then extruded and granulated by a double-screw extruder to obtain polyolefin master batch A1;

[0060] Step S2: 100 parts by mass of polyolefin master batch A1, 1 part by mass of 2-ethylhexyl tert-butyl peroxide, 0.5 parts by mass of triallyl isocyanurate, 0.2 parts by mass of vinyl trimethoxysilane, 0.15 parts by mass of bis(2,2,6,6-tetramethyl-4-piperidyl) sebacate, and 0.1 parts by mass of composite antioxidant (β-(3,5-di-tert-butyl-4-hydroxyphenyl) octadecyl propionate: tris(2,4-di-tert-butylphenyl) phosphite = 3:2, mass ratio) are uniformly mixed, and then placed in a 45℃ oven for curing and absorption for 4 h to obtain formula B1;

[0061] Step S3: The formula B1 that is completely absorbed and surface-dried is put into a casting machine, the die head temperature is 90℃, and the die temperature is 100℃, and then the n-type Topcon battery encapsulation adhesive film C1 with a thickness of 0.6 mm is prepared by plasticizing, extruding, stretching, pulling and winding.

[0062] Example 2

[0063] Example 2 was implemented with the difference that 93 parts by mass of ethylene-octene copolymer (DOW ENGAGE PV 8669) and 7 parts by mass of functional resin were selected in step S1 of the example; the remaining steps were the same as in Example 1, and an n-type Topcon battery encapsulating adhesive film C2 was prepared.

[0064] Example 3

[0065] Example 3 was implemented with the difference that 90 parts by mass of ethylene-octene copolymer (DOW ENGAGE PV 8669) and 10 parts by mass of functional resin were selected in step S1 of the example; the remaining steps were the same as in Example 1, and an n-type Topcon battery encapsulating adhesive film C3 was prepared.

[0066] Example 4

[0067] Example 4 was implemented with the difference that 93 parts by mass of ethylene-octene copolymer (DOW ENGAGE PV 8669) and 7 parts by mass of functional resin were selected in step S1 of the example; 1,1-bis(tert-butyl peroxy)-3,3,5-trimethylcyclohexane was selected as the main crosslinking agent in step S2; the remaining steps were the same as in Example 1, and an n-type Topcon battery encapsulating adhesive film C4 was prepared.

[0068] Example 5

[0069] Example 5 was implemented with the difference that 93 parts by mass of ethylene-octene copolymer (DOW ENGAGE PV 8669) and 7 parts by mass of functional resin were selected in step S1 of the example; 0.8 parts by mass of tert-butyl peroxy-2-ethylhexyl carbonate was selected as the main crosslinking agent in step S2; the remaining steps were the same as in Example 1, and an n-type Topcon battery encapsulating adhesive film C5 was prepared.

[0070] Example 6

[0071] Example 6 was implemented with the difference that 93 parts by mass of ethylene-octene copolymer (DOW ENGAGE PV 8669) and 7 parts by mass of functional resin were selected in step S1 of the example; 0.9 parts by mass of tert-butyl peroxy-2-ethylhexyl carbonate was selected as the main crosslinking agent in step S2; the remaining steps were the same as in Example 1, and an n-type Topcon battery encapsulating adhesive film C6 was prepared.

[0072] Example 7

[0073] The procedure of Example 1 was followed, except that in this example, 93 parts by mass of ethylene-octene copolymer (DOW ENGAGE PV 8669) and 7 parts by mass of functional resin were selected in step S1; 1.1 parts by mass of tert-butyl peroxy-2-ethylhexyl carbonate was used as the main crosslinking agent in step S2, and the remaining steps were the same as in Example 1, to produce an n-type Topcon battery encapsulant film C7.

[0074] Comparative Example 1 (without adding functional resin)

[0075] The procedure of Example 1 was followed, except that in this comparative example, 100 parts by mass of ethylene-octene copolymer (DOW ENGAGE PV 8669) and 0 parts by mass of functional resin were selected in step S1; 1 part by mass of tert-butyl peroxy-2-ethylhexyl carbonate was used as the main crosslinking agent in step S2, and the remaining steps were the same as in Example 1, to produce an n-type Topcon battery encapsulant film D1.

[0076] Comparative Example 2

[0077] The procedure of Example 1 was followed, except that in this comparative example, 80 parts by mass of ethylene-octene copolymer (DOW ENGAGE PV 8669) and 20 parts by mass of functional resin were selected in step S1; 1 part by mass of tert-butyl peroxy-2-ethylhexyl carbonate was used as the main crosslinking agent in step S2, and the remaining steps were the same as in Example 1, to produce an n-type Topcon battery encapsulant film D2.

[0078] Comparative Example 3 (changing the ratio of main crosslinking agent and functional resin)

[0079] The procedure of Example 1 was followed, except that in this comparative example, 95 parts by mass of ethylene-octene copolymer (DOW ENGAGE PV 8669) and 5 parts by mass of functional resin were selected in step S1; 2 parts by mass of tert-butyl peroxy-2-ethylhexyl carbonate was used as the main crosslinking agent in step S2, and the remaining steps were the same as in Example 1, to produce an n-type Topcon battery encapsulant film D3.

[0080] Comparative Example 4

[0081] The procedure of Example 1 was followed, except that in this example, the functional resin used in step S1 was ordinary polypropylene Z30s (Zhenhai Refinery and Chemical, melt index 28 g / 10 min, melting point 167°C, particle size 40 μm); the remaining steps were the same as in Example 1, to produce an n-type Topcon battery encapsulant film D4.

[0082] The encapsulant films obtained in the above examples and comparative examples were applied to the encapsulation of n-type Topcon photovoltaic modules, which were evaluated by the following test methods, and the evaluation results are shown in Table 1.

[0083] 1. Crosslinking degree test

[0084] The test method refers to the China Photovoltaic Industry Association Standard T / CPIA 0006—2017 “Copolyolefin adhesive film for encapsulating photovoltaic modules”.

[0085] Sample preparation: After two pieces of adhesive film were laminated and cured at 150°C for 18 min in a laminator, 0.5 g ± 0.01 g was weighed and cut into small particles with a size of less than 3 mm x 3 mm. Three test samples were prepared for each group.

[0086] After extraction with xylene at 140°C for 5 h, the sample was placed in a vacuum oven at 140°C and dried to constant weight.

[0087] 2. Glass / encapsulation adhesive film peel strength

[0088] The test method refers to the National Standard GB / T2790 “Adhesives - Test methods for 180° peel strength - Flexible to rigid materials”.

[0089] Sample preparation: 2.1 mm thick ultra-white textured tempered glass, encapsulation adhesive film prepared according to each example or comparative example, and n-type Topcon cell were assembled into a pre-pressing piece in the order of tempered glass, encapsulation adhesive film, crystalline silicon cell, encapsulation adhesive film, and tempered glass. The pre-pressing piece was placed in a vacuum laminator and cured at 150°C for 18 min to prepare a peel strength test sample.

[0090] The test was performed on a tensile testing machine at a tensile speed of 100 mm / min and a tensile stroke of 200 mm. The peel strength value was recorded.

[0091] 3. Water vapor transmission rate test

[0092] The test method refers to the Standard ASTM F1249 “Standard Test Methods for Water Vapor Transmission Rate of Materials Using a Modulated Infrared Sensor”.

[0093] Sample preparation: The release film / adhesive film / release film were placed in a vacuum laminator and laminated and cured at 150°C for 18 min. The laminated adhesive film was then tested.

[0094] The water vapor transmission rate (WVTR) was tested on a water vapor transmission rate instrument under the conditions of 38°C and 100% relative humidity.

[0095] 4. Yellowing index ΔYI

[0096] The test method refers to the Standard ASTM E313-3010 “Standard Practice for Calculation of Yellowness Index Using the CIE 1976 Color Coordinate System”.

[0097] Sample preparation: Take a certain area of encapsulation adhesive film, laminate at 150℃ for 18min, cut 30mm x 50mm three rectangular samples from the laminated adhesive film, and measure the yellowing index ΔYI on the color difference meter.

[0098] Measure the yellowness index once before and after high temperature and high humidity aging (DH1000h, test conditions: 85℃, relative humidity 85%, 1000h), and record the difference before and after high temperature and high humidity aging, i.e. the yellowing index ΔYI.

[0099] 5. Appearance evaluation of encapsulated double glass assembly

[0100] Use the encapsulation adhesive film to perform double glass assembly encapsulation test, assemble the tempered glass, encapsulation adhesive film, n-type Topcon cell sheet, encapsulation adhesive film, and tempered glass in the order of steel glass, encapsulation adhesive film, n-type Topcon cell sheet, encapsulation adhesive film, and steel glass to form a pre-pressing piece, and place it in a vacuum laminating machine for curing at 150℃ for 18min, and observe whether there are bubbles and other appearance defects in the double glass assembly.

[0101] √: normal appearance; ▲: presence of bubbles and other defects;

[0102] 6. High temperature and high humidity aging test

[0103] The high temperature and high humidity aging test is performed according to the test method of national standard GB / T 2423.3 "Basic Environmental Test Procedures for Electrical and Electronic Products Test Ca: Constant Temperature and Humidity Test Method".

[0104] Test conditions: 85℃, relative humidity 85%, 1000h.

[0105] The peel strength test method refers to the national standard GB / T 2790 "Adhesives 180° Peel Strength Test Method Flexible Materials to Rigid Materials". The experimental results are shown in Table 1 corresponding to the results of "DH1000h".

[0106] 7. Assembly power test

[0107] Use the encapsulation adhesive film in the above examples and comparative examples to prepare photovoltaic assemblies, which are composed of tempered glass, encapsulation adhesive film, n-type Topcon cell sheet, encapsulation adhesive film, and tempered glass; laminate at 150℃ for 18min, and test the PID power change of the prepared assembly before and after aging (85℃, 85%RH, -1500V, 192h).

[0108] The performance comparison of the encapsulation adhesive films prepared in the examples and comparative examples is shown in Table 1.

[0109] Table 1 Performance comparison of encapsulation adhesive films prepared in examples and comparative examples

[0110]

[0111]

[0112] From the performance data of the above examples and comparative examples, it can be seen that the n-type Topcon cell encapsulating adhesive film provided by the present application has a high crosslinking degree (the crosslinking degree is above 81%), which can effectively ensure that the module is not affected by high temperature of outdoor environment during use, effectively block the invasion of water vapor, and has a low water vapor transmission rate; at the same time, it can also take into account good initial peel strength (>220 N / cm) and peel strength after aging (>140 N / cm), low yellowness index (ΔYI <3); when applied in n-type Topcon cell modules, it not only has good initial appearance and moisture aging resistance, but also has good PID resistance, effectively reduces the power attenuation of the module, and ensures the long-term stability of the module, with a 192h power attenuation of <2.0%.

[0113] In preferred examples 2, 4, 6-7, the preferred mass ratio of the main crosslinking agent to the functional resin is 1:(6-8), which can achieve more excellent results, with a higher crosslinking degree (above 84%) and a lower water vapor transmission rate; and it can also take into account more excellent initial peel strength (>235 N / cm) and peel strength after aging (>155 N / cm), and has more excellent PID resistance when applied in n-type Topcon cell modules.

[0114] In the comparative examples, it is difficult to achieve a good balance among high crosslinking degree, excellent water blocking performance, moisture aging resistance, and PID resistance.

[0115] It is easily understood that the above examples are only examples for clear illustration, and do not mean that the present application is limited to this. Based on the above description, other different forms of changes or variations can also be made by those skilled in the art. It is not necessary and impossible to exhaust all the embodiments. The obvious changes or variations derived therefrom are still within the protection scope of the present application.

Claims

1. A battery encapsulation film, characterized in that, It is prepared using raw materials comprising the following components in parts by weight: 90-95 parts of ethylene / α-olefin copolymer, 5-10 parts of functional resin, 0.2-2 parts of main crosslinking agent; The functional resin is a metallocene homopolymer polypropylene with carbon-carbon double bonds at the ends of its molecular chains, and the mass ratio of the main crosslinking agent to the functional resin is 1:(5-10).

2. The battery encapsulation film according to claim 1, characterized in that, The mass ratio of the main crosslinking agent to the functional resin is 1:(6-8).

3. The battery encapsulation film according to claim 1, characterized in that, The metallocene homopolymer polypropylene has a melt index of 10-30 g / 10 min and a melting temperature of 140-160 °C.

4. The battery encapsulation film according to claim 3, characterized in that, The metallocene homopolymer polypropylene is a powder with a particle size range of 10-100 μm.

5. The battery encapsulation film according to any one of claims 1-4, characterized in that, The ethylene / α-olefin copolymer is one or more of the following: ethylene-butene copolymer, ethylene-hexene copolymer, and ethylene-octene copolymer; And / or, the density of the ethylene / α-olefin copolymer is 0.85-0.88 g / cm³. 3 The melt flow index is 1-30 g / 10 min.

6. The battery encapsulation film according to any one of claims 1-4, characterized in that, The main crosslinking agent is selected from one or more combinations of 2-ethylhexyl tert-butyl peroxide, 2-ethylhexyl tert-amyl peroxide, dicumyl peroxide, 1,1-bis(tert-butylperoxy)-3,3,5-trimethylcyclohexane, 1,1-bis(tert-amylperoxy)-3,3,5-trimethylcyclohexane, and tert-butylperoxyisopropyl carbonate.

7. The battery encapsulation film according to claim 6, characterized in that, The main crosslinking agent is tert-butyl peroxide-2-ethylhexyl carbonate.

8. The battery encapsulation film according to any one of claims 1-4, characterized in that, The raw materials also include 0.2-1 parts by weight of a crosslinking agent; And / or, the raw material further includes 0.1-1 parts by weight of a silane coupling agent.

9. The battery encapsulation film according to claim 8, characterized in that, The crosslinking agent is selected from one or more combinations of triallyl isocyanurate, triallyl cyanurate, trimethylolpropane triacrylate, and trimethylolpropane trimethacrylate; And / or, the silane coupling agent is selected from one or more combinations of γ-aminopropyltriethoxysilane, γ-(2,3-epoxypropoxy)propoxytrimethoxysilane, γ-methacryloxypropoxytrimethoxysilane, γ-mercaptopropyltrimethoxysilane, γ-glycidyl etheroxypropyltrimethoxysilane, vinyltrimethoxysilane, and vinyltriethoxysilane.

10. The battery encapsulation film according to any one of claims 1-4, characterized in that, The raw materials also include 0.1-1 parts by weight of light stabilizer; And / or, the raw material further includes 0.1-1 parts by weight of an antioxidant.

11. The battery encapsulation film according to claim 10, characterized in that, The light stabilizer is a hindered amine light stabilizer.

12. The battery encapsulation film according to claim 11, characterized in that, The light stabilizer is selected from one or more combinations of bis(2,2,6,6-tetramethyl-4-piperidinyl) sebacate, mono(2,2,6,6-tetramethyl-4-piperidinyl) sebacate, bis(1,2,2,6,6-pentamethyl-4-piperidinyl) sebacate, and poly(4-hydroxy-2,2,6,6-tetramethyl-1-piperidinol) ester.

13. The battery encapsulation film according to any one of claims 1-4, characterized in that, The battery encapsulation film is an encapsulation film for n-type Topcon batteries.

14. The battery encapsulation film according to any one of claims 1-4, characterized in that, The preparation steps of the battery encapsulation film include: S1, the ethylene / α-olefin copolymer and the functional resin are mixed evenly, and then extruded and granulated to obtain polyolefin masterbatch; S2, the polyolefin masterbatch and other components are mixed evenly, and after curing, they are cast extrusion molding.

15. The battery encapsulation film according to claim 14, characterized in that, In step S1, the extrusion granulation is carried out in a twin-screw extruder.

16. The battery encapsulation film according to claim 14, characterized in that, In step S2, the ripening process is carried out at 40-60°C.

17. The battery encapsulation film according to claim 16, characterized in that, In step S2, the maturation time is 3-5 hours.

18. The battery encapsulation film according to claim 14, characterized in that, In step S2, the casting extrusion molding is carried out at 70-120°C.

19. The application of the battery encapsulating film according to any one of claims 1-18 in photovoltaic modules.

20. The application according to claim 19, characterized in that, The photovoltaic module is an n-type Topcon photovoltaic module.

21. An n-type Topcon photovoltaic module, comprising an upper photovoltaic glass layer, a first encapsulating film, an n-type Topcon solar cell, a second encapsulating film, and a lower photovoltaic glass layer stacked sequentially; characterized in that, The first encapsulating film and / or the second encapsulating film are battery encapsulating films according to any one of claims 1-18.

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