阅读说明：本技术 复合型光伏背板及抗pid光伏组件 (Compound photovoltaic backplate and anti PID photovoltaic module ) 是由 林维红 桑燕 侯宏兵 郑炯洲 周光大 于 2020-06-09 设计创作，主要内容包括：本发明提供了一种复合型光伏背板及抗PID光伏组件。复合型光伏背板依次包括耐候层、透明支撑基材层、粘结层以及功能层；粘结层的材料包括羟基聚酯树脂、极性低聚物、第一固化剂和第一吸水填料；功能层的材料按重量百分比计包括80～99.9％的聚烯烃非极性树脂、0.001～10％的极性树脂和0.001～10％的第二吸水填料。本发明有效解决了背板材料自身存在的微量游离金属阳离子以及与背板外表面附着的来自空气中的微量游离金属阳离子导致的PID效应。(The invention provides a composite photovoltaic back plate and a PID (proportion integration differentiation) -resistant photovoltaic module. The composite photovoltaic back plate sequentially comprises a weather-resistant layer, a transparent support base material layer, a bonding layer and a functional layer; the material of the bonding layer comprises hydroxyl polyester resin, polar oligomer, a first curing agent and a first water-absorbing filler; the functional layer comprises 80-99.9 wt% of polyolefin nonpolar resin, 0.001-10 wt% of polar resin and 0.001-10 wt% of second water-absorbing filler. The invention effectively solves the PID effect caused by the trace free metal cations existing in the backboard material and the trace free metal cations from the air attached to the outer surface of the backboard.)

1. A composite photovoltaic backsheet, comprising:

a weathering layer (10);

a transparent support substrate layer (20) positioned on one side surface of the weather-resistant layer (10);

a bonding layer (30) positioned on one side surface of the transparent support substrate layer (20) far away from the weather-resistant layer (10), wherein the material of the bonding layer (30) comprises hydroxyl polyester resin, polar oligomer, a first curing agent and a first water-absorbing filler; and

and the functional layer (40) is positioned on one side surface, far away from the transparent support base material layer (20), of the bonding layer (30), and the material of the functional layer (40) comprises 80-99.9% of polyolefin nonpolar resin, 0.001-10% of polar resin and 0.001-10% of second water absorption filler in percentage by weight.

2. The composite photovoltaic backsheet according to claim 1, wherein the polar oligomer has a number average molecular weight of 200 to 10000g/mol and a glass transition temperature of-100 to 15 ℃; preferably, the polar oligomer is selected from one or more of polyvinyl alcohol, polycaprolactone diol, polycarbonate diol, polylactide diol, polyether diol, polyoxyethylene diol, polybutadiene diol, hydrogenated polybutadiene diol, polytetrahydrofuran diol, adipic acid-based polyester diol, sebacic acid-based polyester diol, bisphenol a-type epoxy resin, hydrogenated bisphenol a-type epoxy resin, bisphenol F-type epoxy resin, aliphatic glycidyl ether-type epoxy resin, and glycidyl ester-type epoxy resin;

preferably, the hydroxyl value of the hydroxyl polyester resin is 5-30 mgKOH/g, the acid value is 0.2-5 mgKOH/g, the number average molecular weight is 5000-50000 g/mol, and the glass transition temperature is-40-30 ℃.

3. The composite photovoltaic backsheet according to claim 1, wherein the total ratio of the polar oligomer and the hydroxyl polyester resin in the material of the adhesive layer (30) is 65 to 90% by weight, the ratio of the first water-absorbent filler in the material of the adhesive layer (30) is 0.001 to 10% by weight, and the ratio of the first curing agent in the material of the adhesive layer (30) is 3.5 to 25% by weight;

preferably, the sum of the weight of the polar oligomer and the weight of the hydroxy polyester resin is M, and the weight of the hydroxy polyester resin is recorded as N, wherein N/M is 60 to 99%;

preferably, the material of the bonding layer (30) further comprises 0.001-1% of a first auxiliary agent in percentage by weight.

4. A composite photovoltaic backsheet according to any one of claims 1 to 3, wherein the polyolefin non-polar resin comprises, in weight percent, 60 to 99% of polyethylene, 0.01 to 20% of polypropylene and 0.01 to 20% of an olefin copolymer, and the polar resin is one or more of polyvinyl alcohol, polyvinyl pyrrolidone, polyacrylic acid having a sodium neutralization degree of 20 to 80%;

preferably, the olefin copolymer comprises one or more of ethylene-propylene copolymer, ethylene-butene copolymer, ethylene-heptene copolymer, ethylene-octene copolymer;

preferably, the material of the functional layer (40) further comprises 0.001-0.5% of a second auxiliary agent in percentage by weight.

5. The composite photovoltaic back sheet according to any one of claims 1 to 3, wherein the material of the transparent support substrate layer (20) comprises, by weight percentage, 95 to 99% of one or more of polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate and polybutylene naphthalate with the number average molecular weight of 20000 to 60000, 0.001 to 1% of a third water-absorbing filler and 0.1 to 5% of a third auxiliary agent according to any mixture ratio;

preferably, the first water-absorbing filler, the second water-absorbing filler and the third water-absorbing filler are each independently selected from one or more of activated molecular sieve, activated zeolite, activated montmorillonite, potassium aluminum silicate, zirconium silicate, aluminum tripolyphosphate, aluminum phosphate, aluminum hydrogen phosphate, zirconium hydrogen phosphate, bismuth phosphate, titanium phosphate, tin phosphate, magnesium phosphate, disodium hydrogen phosphate, calcium oxide, zinc sulfate, calcium chloride, calcium oxalate, calcium sulfate, sodium sulfate, magnesium sulfate, potassium aluminum sulfate; the particle sizes of the first water-absorbing filler, the second water-absorbing filler and the third water-absorbing filler are preferably less than or equal to 5 micrometers respectively, and more preferably 0.1-2 micrometers respectively;

more preferably, the first water-absorbing filler, the second water-absorbing filler and the third filler are each independently selected from one or more of activated montmorillonite, potassium aluminum silicate, zirconium silicate, aluminum tripolyphosphate, aluminum phosphate, aluminum hydrogen phosphate, bismuth phosphate, titanium phosphate, tin phosphate, magnesium phosphate, disodium hydrogen phosphate, calcium oxalate, potassium aluminum sulfate.

6. Composite photovoltaic backsheet according to any one of claims 1 to 5, characterized in that the weatherable layer (10) is a cured layer of fluororesin;

preferably, the material of the weather-resistant layer (10) comprises, by weight, 60-90% of fluororesin, 0.001-20% of silicon dioxide, 1-20% of a second curing agent and 0.001-1% of a fourth auxiliary agent;

preferably, the first curing agent and the second curing agent are selected from one or more of hexamethylene diisocyanate trimer, hexamethylene diisocyanate prepolymer, isophorone diisocyanate trimer, isophorone diisocyanate prepolymer, hydrogenated xylylene isocyanate trimer, hydrogenated xylylene isocyanate prepolymer, methylated polymethylol melamine resin, butylated polymethylol melamine resin, mixed etherified polymethylol melamine resin, polyamide, polymethylene diamine, diethylene triamine, pentamethyl diethylene triamine, triethylene tetramine, (2, 3-dimethyl) dibutyl triamine.

7. A composite photovoltaic backsheet according to claim 6, wherein said fluororesin is selected from one or more of hydroxypolytrifluoroethylene ether-type fluorocarbon resin, hydroxypolytrifluoroethylene ester-type fluorocarbon resin, hydroxypolytetrafluoroethylene ether-type fluorocarbon resin, and hydroxypolytetrafluoroethylene ester-type fluorocarbon resin; preferably, the fluororesin has a number average molecular weight of 5000 to 30000 and a hydroxyl value of 40 to 65 mgKOH/g;

preferably, the silicon dioxide is modified nano silicon dioxide formed by surface treatment of one or more of methyl siloxane, fatty acid, stearic acid, rosin and titanate with the mass fraction of 0.01-5%.

8. The composite photovoltaic back sheet according to any one of claims 3 to 6, wherein the material of the functional layer (40) further comprises 0.001 to 0.5% by weight of a second auxiliary agent, the material of the transparent support substrate layer (20) comprises 95 to 99% of a polyethylene terephthalate resin with a number average molecular weight of 20000 to 60000, 0.001 to 1% of a third water-absorbing filler and 0.1 to 5% of a third auxiliary agent, and the material of the weather-resistant layer (10) comprises 60 to 90% of a fluororesin, 0.001 to 20% of silica, 1 to 20% of a second curing agent and 0.001 to 1% of a fourth auxiliary agent;

the first auxiliary agent, the second auxiliary agent, the third auxiliary agent and the fourth auxiliary agent are respectively and independently selected from one or more of an ultraviolet absorbent, a hindered amine light stabilizer, an antioxidant, a heat stabilizer, a catalyst and a hydrolysis stabilizer;

preferably, the hydrolysis stabilizer is selected from one or more of carbodiimide hydrolysis stabilizers, oxazoline hydrolysis stabilizers, monoglycidyl ester hydrolysis stabilizers of monocarboxylic acids, and epoxy hydrolysis stabilizers;

preferably, the catalyst is selected from one or more of pentamethyldiethylenetriamine, bis-dimethylaminoethyl ether, stannous octoate, dioctyltin dilaurate, monobutyltin oxide, monobutyltin triisooctoate, dibutyltin dilaurate, acetic acid, p-toluenesulfonic acid, phthalic acid, lauric acid and isooctanoic acid.

9. The composite photovoltaic backsheet according to any one of claims 1 to 3, wherein the weatherable layer (10) has a thickness of 5 to 30 μm, the transparent support substrate layer (20) has a thickness of 100 to 300 μm, the adhesive layer (30) has a thickness of 2 to 30 μm, and the functional layer (40) has a thickness of 25 to 200 μm.

10. An anti-PID photovoltaic module, comprising a cell sheet, an encapsulating adhesive film and a back sheet, characterized in that the back sheet is the composite photovoltaic back sheet of any one of claims 1 to 9, and a functional layer (40) in the composite photovoltaic back sheet is arranged in contact with the encapsulating adhesive film.

Technical Field

The invention relates to the field of photovoltaics, in particular to a composite photovoltaic back plate and a PID (proportion integration differentiation) -resistant photovoltaic module.

Background

In the existing energy system, the development of an industrial chain of a photovoltaic power generation system is vigorous by relying on inexhaustible resources, namely solar energy. However, in recent years, a phenomenon existing in photovoltaic modules has been troubling the industry, namely the PID (Potential Induced Degradation) effect of photovoltaic modules. The PID effect is called potential induced attenuation, and the direct damage is that a large amount of charges are accumulated on the surface of a battery piece, so that the passivation effect of the surface of the battery is deteriorated, the filling factor, the open-circuit voltage and the short-circuit current of the battery piece are reduced, and finally the power attenuation of the component is caused.

For the mechanism research of the PID phenomenon, the technical conclusion of the mechanism with higher acceptance belongs to the ion migration theory, namely the mechanism mainly originates from the migration of trace free metal cations (such as sodium ions, magnesium ions and the like) in the solar module. For example, as external water vapor continuously permeates into the photovoltaic module, an electrolyte microenvironment is formed inside the photovoltaic module, and metal cations such as Na + from photovoltaic glass, an encapsulation adhesive film, a photovoltaic back sheet and the external environment move in the microenvironment. The photovoltaic module forms an electric field under the action of photovoltaic, metal ions gradually move to the surface of the battery under the action of the electric field and are enriched in the antireflection layer, so that leakage current is increased, the metal ions are compounded with carriers in the battery piece, the carrier concentration in the battery piece is reduced, and finally the attenuation of module power is caused. It can be seen that minimizing the generation of electrolyte microenvironment or reducing the speed of metal cation enrichment to the surface of the cell plate would be the main method for eliminating or alleviating the PID phenomenon.

Both the component manufacturing end and the auxiliary material end are actively involved in the act of finding solutions. For example, the photovoltaic module manufactured by the module manufacturing end CN 207489890U in a manner of using a novel packaging material, namely a high-transmittance ETFE film, a PID-resistant EVA film, a fiber non-woven thin felt, an epoxy resin substrate, and a butyl hot-melt sealant shows better PID resistance than a conventional module. Photovoltaic glass end CN203553178U organizes sodium ion in the glass to separate out through reducing anti-membrane structure in glass two-sided design, has effectively reduced the PID phenomenon. The packaging adhesive film ends are reported more, and CN 109705442A reports a PID (potential induced degradation) resistant functional master batch containing illite/montmorillonite clay for a photovoltaic packaging film, which can be used for preparing an EVA packaging adhesive film material. CN108943936A discloses a three-layer co-extrusion packaging film to reduce the occurrence of PID phenomenon. The photovoltaic back plate end is also related to reports, and CN103252953B reports an integrated photovoltaic back plate material with a three-layer structure, wherein the integrated photovoltaic back plate material has high water vapor barrier property, high insulation property and high hydrolysis resistance, has excellent performance in the aspect of PID (proportion integration differentiation) resistance, and has attenuation lower than 1.5% in a 96PID test of a crystalline silicon single-sided battery. CN 108767042A reports a reflective gain type high-transmittance solar cell back film, the power gain of a double-sided crystal silicon module is improved and the PID phenomenon is obviously reduced through the design of reflected light, and the manufacturing process is complex. However, for photovoltaic backsheet materials, current research has mainly focused on solving the problem of moisture barrier properties, and there has been no report concerning the influence of a trace amount of free metal cations present in the backsheet material itself and a trace amount of free metal cations from the air adhering to the outer surface of the backsheet. Particularly for the double-sided power generation crystal silicon battery pack, the PID phenomenon of the battery back plate has greater connection with the back plate material.

Therefore, the transparent back plate with a relatively simple process is developed, can delay or even inhibit the PID performance of a photovoltaic module, particularly a double-sided power generation module, has excellent long-term stability in the aspects of light transmittance, heat resistance and the like, and is the most urgent problem to be solved in the crystalline silicon photovoltaic module packaging industry.

Disclosure of Invention

The invention mainly aims to provide a composite photovoltaic back plate and a PID (potential induced degradation) resistant photovoltaic assembly, and aims to solve the problem that the PID effect caused by trace free metal cations existing in a back plate material and trace free metal cations from the air and attached to the outer surface of the back plate in the prior art cannot be effectively solved.

In order to achieve the above object, according to one aspect of the present invention, there is provided a composite type photovoltaic backsheet including: a weatherable layer; the transparent support base material layer is positioned on one side surface of the weather-resistant layer; the bonding layer is positioned on the surface of one side, far away from the weather-resistant layer, of the transparent support base material layer, and the material of the bonding layer comprises hydroxyl polyester resin, polar oligomer, a first curing agent and a first water-absorbing filler; and the functional layer is positioned on the surface of one side, far away from the transparent support base material layer, of the bonding layer, and the functional layer is made of 80-99.9 wt% of polyolefin nonpolar resin, 0.001-10 wt% of polar resin and 0.001-10 wt% of second water absorption filler.

Further, the number average molecular weight of the polar oligomer is 200-10000 g/mol, and the glass transition temperature is-100-15 ℃; preferably, the polar oligomer is selected from one or more of polyvinyl alcohol, polycaprolactone diol, polycarbonate diol, polylactide diol, polyether diol, polyoxyethylene diol, polybutadiene diol, hydrogenated polybutadiene diol, polytetrahydrofuran diol, adipic acid-based polyester diol, sebacic acid-based polyester diol, bisphenol a-type epoxy resin, hydrogenated bisphenol a-type epoxy resin, bisphenol F-type epoxy resin, aliphatic glycidyl ether-type epoxy resin, and glycidyl ester-type epoxy resin; preferably, the hydroxyl polyester resin has a hydroxyl value of 5 to 30mgKOH/g, an acid value of 0.2 to 5mgKOH/g, a number average molecular weight of 5000 to 50000g/mol, and a glass transition temperature of-40 to 30 ℃.

Further, the total proportion of the polar oligomer and the hydroxyl polyester resin in the bonding layer material is 65-90%, the proportion of the first water-absorbing filler in the bonding layer material is 0.001-10%, and the proportion of the first curing agent in the bonding layer material is 3.5-25%; preferably, the sum of the weight of the polar oligomer and the weight of the hydroxy polyester resin is M, and the weight of the hydroxy polyester resin is recorded as N, wherein N/M is 60-99%; preferably, the material of the bonding layer further comprises 0.001-1% by weight of a first auxiliary agent.

Further, the polyolefin non-polar resin comprises 60-99% of polyethylene, 0.01-20% of polypropylene and 0.01-20% of olefin copolymer in percentage by weight, and the polar resin is one or more of polyvinyl alcohol, polyvinylpyrrolidone and polyacrylic acid with 20-80% of sodium neutralization degree; preferably, the olefin copolymer comprises one or more of ethylene-propylene copolymer, ethylene-butene copolymer, ethylene-heptene copolymer, ethylene-octene copolymer; preferably, the material of the functional layer further comprises 0.001-0.5% by weight of a second auxiliary agent.

Further, the material of the transparent support base material layer comprises, by weight, 95-99% of one or more of polyethylene terephthalate resin with the number average molecular weight of 20000-60000, polybutylene terephthalate, polyethylene naphthalate and polybutylene naphthalate, 0.001-1% of a third water-absorbing filler and 0.1-5% of a third auxiliary agent, which are formed according to any proportion; preferably, the first water absorbing filler, the second water absorbing filler and the third water absorbing filler are respectively and independently selected from one or more of activated molecular sieve, activated zeolite, activated montmorillonite, potassium aluminum silicate, zirconium silicate, aluminum tripolyphosphate, aluminum phosphate, aluminum hydrogen phosphate, zirconium hydrogen phosphate, bismuth phosphate, titanium phosphate, tin phosphate, magnesium phosphate, disodium hydrogen phosphate, calcium oxide, zinc sulfate, calcium chloride, calcium oxalate, calcium sulfate, sodium sulfate, magnesium sulfate and aluminum potassium sulfate; the particle sizes of the first water-absorbing filler, the second water-absorbing filler and the third water-absorbing filler are preferably less than or equal to 5 micrometers respectively, and more preferably 0.1-2 micrometers respectively; more preferably, the first water absorbing filler, the second water absorbing filler and the third filler are each independently selected from one or more of activated montmorillonite, potassium aluminum silicate, zirconium silicate, aluminum tripolyphosphate, aluminum phosphate, aluminum hydrogen phosphate, bismuth phosphate, titanium phosphate, tin phosphate, magnesium phosphate, disodium hydrogen phosphate, calcium oxalate, potassium aluminum sulfate.

Further, the weather-resistant layer is a fluororesin curing layer; preferably, the material of the weather-resistant layer comprises, by weight, 60-90% of fluororesin, 0.001-20% of silicon dioxide, 1-20% of a second curing agent and 0.001-1% of a fourth auxiliary agent; preferably, the first curing agent and the second curing agent are selected from one or more of hexamethylene diisocyanate trimer, hexamethylene diisocyanate prepolymer, isophorone diisocyanate trimer, isophorone diisocyanate prepolymer, hydrogenated xylylene isocyanate trimer, hydrogenated xylylene isocyanate prepolymer, methylated polymethylol melamine resin, butylated polymethylol melamine resin, mixed etherified polymethylol melamine resin, polyamide, polymethylene diamine, diethylene triamine, pentamethyl diethylene triamine, triethylene tetramine, dibutyl triamine.

Further, the fluororesin is selected from one or more of hydroxyl polytrifluoroethylene ether type fluorocarbon resin, hydroxyl polytrifluoroethylene ester type fluorocarbon resin, hydroxyl polytetrafluoroethylene ether type fluorocarbon resin and hydroxyl polytetrafluoroethylene ester type fluorocarbon resin; preferably, the fluororesin has a number average molecular weight of 5000 to 30000 and a hydroxyl value of 40 to 65 mgKOH/g; preferably, the silicon dioxide is modified nano silicon dioxide formed by surface treatment of one or more of methyl siloxane, fatty acid, stearic acid, rosin and titanate with the mass fraction of 0.01-5%.

Further, the functional layer comprises 0.001-0.5% of a second auxiliary agent by weight percentage, the transparent support base material layer comprises 95-99% of polyethylene terephthalate resin with the number average molecular weight of 20000-60000, 0.001-1% of a third water-absorbing filler and 0.1-5% of the third auxiliary agent by weight percentage, and the weather-resistant layer comprises 60-90% of fluororesin, 0.001-20% of silicon dioxide, 1-20% of a second curing agent and 0.001-1% of a fourth auxiliary agent by weight percentage; the first auxiliary agent, the second auxiliary agent, the third auxiliary agent and the fourth auxiliary agent are respectively and independently selected from one or more of an ultraviolet absorbent, a hindered amine light stabilizer, an antioxidant, a heat stabilizer, a catalyst and a hydrolysis stabilizer; preferably, the hydrolysis stabilizer is selected from one or more of carbodiimide hydrolysis stabilizers, oxazoline hydrolysis stabilizers, monoglycidyl ester hydrolysis stabilizers of monocarboxylic acids, and epoxy hydrolysis stabilizers; preferably, the catalyst is selected from one or more of pentamethyldiethylenetriamine, bis-dimethylaminoethyl ether, stannous octoate, dioctyltin dilaurate, monobutyltin oxide, monobutyltin triisooctoate, dibutyltin dilaurate, acetic acid, p-toluenesulfonic acid, phthalic acid, lauric acid and isooctanoic acid.

Furthermore, the thickness of the weather-resistant layer is 5-30 microns, the thickness of the transparent support substrate layer is 100-300 microns, the thickness of the bonding layer is 2-30 microns, and the thickness of the functional layer is 25-200 microns.

According to another aspect of the invention, the anti-PID photovoltaic module comprises a battery piece, an encapsulation adhesive film and a back plate, wherein the back plate is the composite photovoltaic back plate, and the functional layer in the composite photovoltaic back plate is arranged in contact with the encapsulation adhesive film.

The invention provides a composite photovoltaic back plate which comprises a weather-resistant layer, a transparent support base material layer, a bonding layer and a functional layer. In the actual packaging process, the functional layer is arranged in contact with a packaging adhesive film positioned on the periphery of the battery piece, and the weather-resistant layer is arranged far away from the battery piece. In the compound photovoltaic back plate, the functional layer close to the battery piece adopts the polyolefin non-polar material as a main body and is assisted by a certain amount of polar resin and second water-absorbing filler, so that a circulation and enrichment channel is provided for free metal cations through adsorption and chelation while insulation is ensured, favorable conditions are provided for the migration of the free metal cations in the component packaging material to the layer, and meanwhile, the functional layer has a good bonding effect with the bonding layer. The adhesive layer not only has an adhesive effect, but also provides a foundation for the fixing effect of metal cations under the combined action of the polar resin system and the first water-absorbing filler. The weather-resistant outer layer can effectively reduce the adhesion of water vapor and cations in the air; the transparent support base material layer is used as a support material of the back plate and also has the function of preventing trace free metal cations in the weather-resistant layer from continuously migrating to the bonding layer and the functional layer.

Therefore, the composite photovoltaic back plate provided by the invention not only can enable metal cations in the whole material of the back plate to achieve a good fixing effect, effectively slow down the speed of enriching free trace metal cations existing in the back plate material to the surface of a battery piece, but also increase the adsorption effect of the back plate material on the free metal cations in the component packaging material, simultaneously reduce the adhesion of the free trace metal cations in the air on the surface of the back plate material, and enhance the anti-PID effect through synergistic effect from multiple aspects. The photovoltaic back plate is applied to a crystalline silicon photovoltaic assembly, particularly a double-sided power generation crystalline silicon photovoltaic assembly, and has an obvious improvement effect on the PID resistance function of the assembly. Meanwhile, the photovoltaic back sheet has good light transmittance and excellent long-term stability in the aspects of heat resistance, water resistance, insulativity, aging resistance and the like.

Drawings

The accompanying drawings, which are incorporated in and constitute a part of this application, illustrate embodiments of the invention and, together with the description, serve to explain the invention and not to limit the invention. In the drawings:

fig. 1 shows a schematic structural diagram of a composite photovoltaic backsheet according to an embodiment of the present invention.

Wherein the figures include the following reference numerals:

10. a weatherable layer; 20. a transparent support substrate layer; 30. a bonding layer; 40. and a functional layer.

Detailed Description

It should be noted that the embodiments and features of the embodiments in the present application may be combined with each other without conflict. The present invention will be described in detail below with reference to the embodiments with reference to the attached drawings.

As described in the background section, the PID effect caused by the minute amount of free metal cations present in the backsheet material itself and the minute amount of free metal cations from the air adhering to the outer surface of the backsheet in the prior art cannot be effectively solved.

In order to solve the above problems, the present invention provides a composite photovoltaic back sheet, as shown in fig. 1, the composite photovoltaic back sheet includes a weather-resistant layer 10, a transparent support substrate layer 20, a bonding layer 30, and a functional layer 40; the transparent support substrate layer 20 is positioned on one side surface of the weather-resistant layer 10; the bonding layer 30 is positioned on the surface of one side of the transparent support substrate layer 20, which is far away from the weather-resistant layer 10, and the material of the bonding layer 30 comprises hydroxyl polyester resin, polar oligomer, a first curing agent and a first water-absorbing filler; the functional layer 40 is located on the surface of one side of the bonding layer 30, which is far away from the transparent support substrate layer 20, and the material of the functional layer 40 comprises 80-99.9% of polyolefin nonpolar resin, 0.001-10% of polar resin and 0.001-10% of second water-absorbing filler in percentage by weight.

In the compound photovoltaic back plate, the functional layer close to the battery piece adopts the polyolefin non-polar material as a main body and is assisted by a certain amount of polar resin and second water-absorbing filler, so that a circulation and enrichment channel is provided for free metal cations through adsorption and chelation while insulation is ensured, favorable conditions are provided for the migration of the free metal cations in the component packaging material to the layer, and meanwhile, the functional layer has a good bonding effect with the bonding layer. The adhesive layer not only has an adhesive effect, but also provides a foundation for the fixing effect of metal cations under the combined action of the polar resin system and the first water-absorbing filler. The weather-resistant outer layer can effectively reduce the adhesion of water vapor and cations in the air; the transparent support substrate layer serves as a support material for the back panel.

Therefore, the composite photovoltaic back plate provided by the invention not only can enable metal cations in the whole material of the back plate to achieve a good fixing effect, effectively slow down the speed of enriching free trace metal cations existing in the back plate material to the surface of a battery piece, but also increase the adsorption effect of the back plate material on the free metal cations in the component packaging material, simultaneously reduce the adhesion of the free trace metal cations in the air on the surface of the back plate material, and enhance the anti-PID effect through synergistic effect from multiple aspects. The photovoltaic back plate is applied to a crystalline silicon photovoltaic assembly, particularly a double-sided power generation crystalline silicon photovoltaic assembly, and has an obvious improvement effect on the PID resistance function of the assembly. Meanwhile, the photovoltaic back sheet has good light transmittance (light transmittance of more than 88% in a range of 400nm-1200 nm), and also has excellent long-term stability in the aspects of heat resistance, water resistance, insulation, aging resistance and the like.

In a preferred embodiment, the polar oligomer has a number average molecular weight of 200 to 10000g/mol and a glass transition temperature of-100 to 15 ℃; the polar oligomer is selected from one or more of polyvinyl alcohol, polycaprolactone diol, polycarbonate diol, polylactide diol, polycaprolactone diol, polyether diol (such as polytetramethylene ether diol, polyether diol, polypropylene ether diol, polytetramethylene ether diol), polyethylene oxide diol, polybutadiene diol, hydrogenated polybutadiene diol, polytetrahydrofuran diol, adipic acid polyester diol, sebacic acid polyester diol, bisphenol A epoxy resin, hydrogenated bisphenol A epoxy resin, bisphenol F epoxy resin, aliphatic glycidyl ether epoxy resin and glycidyl ester epoxy resin. With the polar oligomer of the above type, on the one hand, it is advantageous to further improve the adhesion of the adhesive layer, and at the same time, it is also advantageous to further fix a small amount of metal cations that have come out of the functional layer, so as to further improve the PID problem. Preferably, the hydroxyl polyester resin has a hydroxyl value of 5 to 30mgKOH/g, an acid value of 0.2 to 5mgKOH/g, a number average molecular weight of 5000 to 50000g/mol, and a glass transition temperature of-40 to 30 ℃. The hydroxy polyester resin, the polar oligomer and the first water absorption filler are matched to form the adhesive, so that the formed adhesive has better promotion effects on the aspects of cohesiveness, metal ion fixation, thermal stability, transparency, water resistance, insulativity and the like.

In order to further balance the properties of the bonding layer 30 in all aspects, in a preferred embodiment, the total proportion of the polar oligomer and the hydroxyl polyester resin in the material of the bonding layer 30 is 65-90%, the proportion of the first water-absorbing filler in the material of the bonding layer 30 is 0.001-10%, and the proportion of the first curing agent in the material of the bonding layer 30 is 3.5-25%; preferably, the sum of the weight of the polar oligomer and the weight of the hydroxy polyester resin is M, and the weight of the hydroxy polyester resin is N, wherein N/M is 60 to 99%. In addition, from the aspects of light stability, heat stability, hydrolysis resistance and the like, it is preferable that the material of the bonding layer 30 further includes 0.001 to 1% by weight of a first auxiliary agent.

The polar resin is selected from one or more of polyvinyl alcohol, polyvinylpyrrolidone and polyacrylic acid with the sodium neutralization degree of 20-80%, and can effectively improve the crosslinking density of the functional layer, so that the functional layer is favorable for improving the capability of fixing free metal cations, and the PID effect is further effectively reduced. In a preferred embodiment, the polyolefin non-polar resin comprises 60-99% of polyethylene, 0.01-20% of polypropylene and 0.01-20% of olefin copolymer by weight percentage, and the polar resin is one or more of polyvinyl alcohol, polyvinyl pyrrolidone and polyacrylic acid with 20-80% of sodium neutralization degree. Under the composition, the functional layer has better adsorption and chelation effects on free metal cations, and is favorable for further improving the PID resistance of the component.

Preferably, the olefin copolymer comprises one or more of an ethylene-propylene copolymer, an ethylene-butene copolymer, an ethylene-heptene copolymer, an ethylene-octene copolymer. The functional layer formed by using the olefin copolymers and matching with polar resin, polyolefin non-polar resin and second water-absorbing filler has better PID (proportion integration differentiation) resistance effect and better performances in the aspects of stability, transparency and the like. Preferably, the material of the functional layer 40 further comprises 0.001-0.5% by weight of a second auxiliary agent. The second auxiliary agent is more beneficial to improving various performances of the functional layer.

The transparent supporting substrate layer 20 is used for providing a supporting function, and in a preferred embodiment, the material of the transparent supporting substrate layer 20 comprises, by weight percentage, 95 to 99% of a substrate resin (one or more of polyethylene terephthalate resin, polybutylene terephthalate, polyethylene naphthalate, and polybutylene naphthalate) with a number average molecular weight of 20000 to 60000g/mol, and preferably the substrate resin is polyethylene terephthalate resin), 0.001 to 1% of a third water-absorbing filler, and 0.1 to 5% of a third auxiliary agent. Thus, in addition to the supporting function, the transparent support substrate layer 20 can also play a role in blocking trace free metal cations in the weather-resistant layer from continuously migrating to the bonding layer and the functional layer.

The water-absorbing fillers are used for improving the water vapor barrier property of the back plate, so that the PID problem caused by water vapor is reduced, and the insulativity of the back plate is improved. In a preferred embodiment, the first, second and third water absorbing fillers are each independently selected from one or more of activated molecular sieves, activated zeolites, activated montmorillonite, potassium aluminum silicate, zirconium silicate, aluminum tripolyphosphate, aluminum phosphate, aluminum hydrogen phosphate, zirconium hydrogen phosphate, bismuth phosphate, titanium phosphate, tin phosphate, magnesium phosphate, disodium hydrogen phosphate, calcium oxide, zinc sulfate, calcium chloride, calcium oxalate, calcium sulfate, sodium sulfate, magnesium sulfate, potassium aluminum sulfate. The particle diameters of the first water-absorbing filler, the second water-absorbing filler and the third water-absorbing filler are preferably less than or equal to 5 micrometers respectively, and more preferably 0.1-2 micrometers respectively. The water absorbing filler of the above type has a good water absorbing property, and in order to achieve both water absorbing property and transparency, it is more preferable that the first water absorbing filler, the second water absorbing filler and the third filler are each independently selected from one or more of activated montmorillonite, potassium aluminum silicate, zirconium silicate, aluminum tripolyphosphate, aluminum phosphate, aluminum hydrogen phosphate, bismuth phosphate, titanium phosphate, tin phosphate, magnesium phosphate, disodium hydrogen phosphate, calcium oxalate, potassium aluminum sulfate. The water-absorbing fillers have better water-absorbing performance, better dispersibility in resin base materials of all layers and capability of improving the water vapor barrier performance of the back plate under the condition of relatively less using amount.

The weather-resistant layer 10 is a fluororesin curing layer and is hydrophobic, so that the barrier of the back plate to external water vapor is improved, and the adhesion of free cations is reduced. In a preferred embodiment, the weather-resistant layer 10 is a fluororesin cured layer. The fluororesin solidified layer is hydrophobic, and has better barrier property for the adhesion of water vapor and cations in the air. Preferably, the material of the weather-resistant layer 10 comprises, by weight, 60-90% of fluororesin, 0.001-20% of silicon dioxide, 1-20% of a second curing agent and 0.001-1% of a fourth auxiliary agent. The weathering layer 10 formed by using the above materials has better hydrophobic property and property of preventing free cations from attaching, and simultaneously has better performance in the aspects of heat resistance, aging resistance and the like. It should be noted that the silica is used as a transparent filler, mainly to adjust the problems encountered in the process, and also to ensure the light transmittance and transparency.

Preferably, the curing agent is selected from one or more of hexamethylene diisocyanate trimer, hexamethylene diisocyanate prepolymer, isophorone diisocyanate trimer, isophorone diisocyanate prepolymer, hydrogenated xylylene isocyanate trimer, hydrogenated xylylene isocyanate prepolymer, methylated polymethylol melamine resin, butylated polymethylol melamine resin, mixed etherified polymethylol melamine resin, polyamide, polymethylene diamine, diethylene triamine, pentamethyl diethylene triamine, triethylene tetramine, 2, 3-dimethyl dibutyl triamine.

In a preferred embodiment, the fluororesin is selected from one or more of hydroxypolytrifluoroethylene ether type fluorocarbon resin, hydroxypolytrifluoroethylene ester type fluorocarbon resin, hydroxypolytetrafluoroethylene ether type fluorocarbon resin, and hydroxypolytetrafluoroethylene ester type fluorocarbon resin; preferably, the fluororesin has a number average molecular weight of 5000 to 30000 and a hydroxyl value of 40 to 65 mgKOH/g;

preferably, the silicon dioxide is modified nano silicon dioxide formed by surface treatment of one or more of methyl siloxane, fatty acid, stearic acid, rosin and titanate with the mass fraction of 0.01-5%. By adopting the modified silicon dioxide, the performance of the weather-resistant layer is better.

In a preferred embodiment, the material of the functional layer 40 further comprises 0.001-0.5% of a second auxiliary agent, the material of the transparent support substrate layer 20 comprises 95-99% of a polyethylene terephthalate resin with the number average molecular weight of 20000-60000, 0.001-1% of a third water-absorbing filler and 0.1-5% of a third auxiliary agent, and the material of the weather-resistant layer 10 comprises 60-90% of a fluororesin, 0.001-20% of silica, 1-20% of a second curing agent and 0.001-1% of a fourth auxiliary agent; the first auxiliary agent, the second auxiliary agent, the third auxiliary agent and the fourth auxiliary agent are respectively and independently selected from one or more of an ultraviolet absorbent, a hindered amine light stabilizer, an antioxidant, a heat stabilizer, a catalyst and a hydrolysis stabilizer; preferably, the ultraviolet absorbent is a mixture of one or more of the following components in any proportion: 2-hydroxy-4-methoxybenzophenone, 2-hydroxy-4-n-octyloxybenzophenone, 2, 4-dihydroxybenzophenone, 2, 4-trihydroxybenzophenone, 2- (2 '-hydroxy-3' -tert-butyl-5 '-methylphenyl) -5-chlorobenzotriazole, 2- (2' -hydroxy-3 ', 5' -di-tert-butyl-5 '-methylphenyl) -5-chlorobenzotriazole, 3- [3- (2-H-benzotriazol-2-yl) -4-hydroxy-5-tert-butylphenyl ] -propionic acid-polyethylene glycol ester, 2- (2' -hydroxy-5 '-tert-octyl) -benzotriazole, 2-hydroxy-5' -tert-octylbenzophenone, 2-hydroxy-3 '-tert-butylbenzotriazole, 5-chlorobenzotriazole, 2-hydroxy-5' -methyl, 2, 2' -methylene- (6- (2H-benzotriazole) -4-tert-octyl) phenol, 2- (2H-benzotriazol-2-yl) -6-dodecyl-4-methylphenol, 2- (2 ' -hydroxy-5 ' -tert-octylphenyl) benzotriazole, 2- (4, 6-bis (2, 4-dimethylphenyl) -1,3, 5-triazin-2-yl) -5-octyloxyphenol, 2- [4- [ 2-hydroxy-3-tridecyloxypropyl ] oxy ] -2-hydroxyphenyl ] -4, 6-bis (2, 4-dimethylphenyl) -1,3, 5-triazine, 2-methyl-phenyl-4-methyl-phenyl-5-methyl-phenyl-4, 6-triazine, 2- [4- [ 2-hydroxy-3-dodecyloxypropyl ] oxy ] -2-hydroxyphenyl ] -4, 6-bis (2, 4-dimethylphenyl) -1,3, 5-triazine.

Preferably, the hindered ammonia light stabilizer is a mixture of one or more of the following components in any proportion: bis (1,2,2,6, 6-pentamethyl-4-piperidinyl) -sebacate/mono (1,2,2,6, 6-pentamethyl-4-piperidinyl) sebacate combinations, bis (2,2,6, 6-tetramethyl-4-piperidinyl) sebacate, poly { [6- [ (1,1,3, 3-tetramethylbutyl) amino ] ] -1,3, 5-triazine-2, 4- [ (2,2,6,6, -tetramethyl-piperidinyl) imide, bis (1-octyloxy-2, 2,6, 6-tetramethyl-4-piperidinyl) sebacate, 2,2,6, 6-tetramethyl-4-piperidinyl stearate, polysuccinic acid (4-hydroxy-2, 2,6, 6-tetramethyl-1-piperidineethanol) ester, N- (2-ethoxyphenyl) -N ' - (4-ethylphenyl) ethanediamide, N- (4-ethylbenzoate) -N ', N ' - (methyl, phenyl) formamidine.

Preferably, the antioxidant is selected from the group consisting of pentaerythritol tetrakis (3, 5-di-tert-butyl-4-hydroxy) phenylpropionate, n-octadecyl beta- (3, 5-di-tert-butyl-4-hydroxyphenyl) propionate, 2 '-methylenebis- (4-methyl-6-tert-butylphenol), 1,3, 5-trimethyl-2, 4, 6-tris (3, 5-di-tert-butyl-4-hydroxybenzyl) benzene, 2, 6-di-tert-butyl-4-methylphenol, 4' -diisopropylphenyldiphenylamine, pentaerythritol beta-dodecylthiopropionate, triethylene glycol ether-bis (3-tert-butyl-4-hydroxy-5-methylphenyl) propionate, 1,3, 5-tris (4-tert-butyl-3-hydroxy-2, 6-dimethylbenzyl) -1,3, 5-triazine-2, 4,6- (1H,3H,5H) -trione, tris (2, 4-di-tert-butylphenyl) phosphite, bis (2, 4-di-tert-butylphenyl) pentaerythritol diphosphite, bis (2, 6-di-tert-butyl-4-methylphenyl) pentaerythritol diphosphite, 3, 9-dioctadecyloxy-2, 4,8, 10-tetraoxy-3, 9-diphosphospiro [5.5] undecane, 9, 10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide, 4' -p-isopropyldiphenyl C12-15-ol phosphite Forming;

preferably, the heat stabilizer is formed by uniformly mixing one or two of hydrotalcite with the particle size of 10 nm-0.2 um and N-phenylmaleimide-styrene-methyl methacrylate according to any proportion.

The hydrolysis stabilizer is one or more selected from carbodiimide hydrolysis stabilizer, oxazoline hydrolysis stabilizer, monocarboxylic acid glycidyl ester hydrolysis stabilizer and epoxy hydrolysis stabilizer; preferably, the catalyst is selected from one or more of pentamethyldiethylenetriamine, bis-dimethylaminoethyl ether, stannous octoate, dioctyltin dilaurate, monobutyltin oxide, monobutyltin triisooctoate, dibutyltin dilaurate, acetic acid, p-toluenesulfonic acid, phthalic acid, lauric acid and isooctanoic acid. The back plate has better comprehensive performances such as heat resistance, hydrolysis resistance, aging resistance and the like by selecting the auxiliary agents of the types.

The raw materials used in the invention can be obtained commercially.

In order to further balance the comprehensive performance of the photovoltaic back sheet, in a preferred embodiment, the thickness of the weather-resistant layer 10 is 5 to 30 μm, the thickness of the transparent support substrate layer 20 is 100 to 300 μm, the thickness of the adhesive layer 30 is 2 to 30 μm, and the thickness of the functional layer 40 is 25 to 200 μm.

The preparation method of the back plate is simple, and preferably comprises the following steps: the transparent support substrate layer is prepared by casting film forming and bidirectional stretching after melting processing at 250-300 ℃, the functional layer is prepared by casting film forming after melting processing at 60-150 ℃, the bonding layer is prepared by wet coating on one side of the transparent support layer and then thermocuring at 40-60 ℃, the weather-resistant layer is prepared by wet coating on the other side of the transparent support layer and then thermocuring at 100-200 ℃ after diluting with a solvent, the functional layer and the transparent support substrate layer are bonded together through the bonding layer, and particularly, the bonding can be performed in a rolling mode.

According to another aspect of the invention, a PID-resistant photovoltaic module is also provided, which includes a battery piece, an encapsulant film and a back plate, wherein the back plate is the composite photovoltaic back plate, and the functional layer 40 in the composite photovoltaic back plate is disposed in contact with the encapsulant film. By adopting the composite photovoltaic backboard, metal cations in the whole material of the backboard can achieve a good fixing effect, the speed of enriching free trace metal cations in the backboard material to the surface of a battery piece is effectively slowed down, the adsorption effect of the backboard material on the free metal cations in the component packaging material is also increased, the adhesion of the free trace metal cations in the air to the surface of the backboard material is also reduced, and the anti-PID effect is enhanced through the synergistic effect in multiple aspects. Therefore, the anti-PID function of the anti-PID photovoltaic module is obviously improved. Meanwhile, the photovoltaic back plate has good light transmittance and excellent long-term stability in the aspects of heat resistance, water resistance, insulativity, aging resistance and the like, so that the overall performance of the photovoltaic module is ensured.

The present application is described in further detail below with reference to specific examples, which should not be construed as limiting the scope of the invention as claimed.

It should be noted that, the performance indexes of the photovoltaic back sheet are measured by the following methods:

1. light transmittance

The test method refers to a spectrophotometer method with an integrating sphere in the standard GB/T29848 ethylene-vinyl acetate copolymer (EVA) adhesive film for packaging photovoltaic modules.

Testing an instrument: an ultraviolet-visible spectrophotometer.

And (3) testing conditions are as follows: 400nm-1200 nm.

2. Volume resistivity

The test method refers to the test method of volume resistivity and surface resistivity of materials in the standard GB/T1410.

Sample size: 100 mm.

And (3) testing conditions are as follows: test voltage 1500V

3. Tensile strength and elongation at break

The test method is referred to the standard GB/T13542.2 film for electrical insulation.

Sample size: 200mm 15 mm.

Stretching speed: 100mm/min.

4. Interlaminar peel strength

The test method refers to a standard GB/T2790 method for testing 180-degree peel strength of adhesive for flexible materials versus rigid materials.

Sample size: 200mm 15 mm.

Stretching speed: 100mm/min.

5. Back sheet/EVA Peel Strength

The test method refers to a standard GB/T2790 method for testing 180-degree peel strength of adhesive for flexible materials versus rigid materials.

Sample size: 300mm 10 mm.

Stretching speed: 100mm/min.

6. Constant resistance to wet heat aging

The test method refers to the standard GB/T2423.3 high and low temperature humid heat test method.

The test conditions are as follows: +85 ℃ and 85% relative humidity.

The samples were measured before and after the test.

7. Water vapor transmission rate

Test methods reference is made to the standard ASTM F1249 test method for measuring the water vapor permeability of plastic films and sheets with modulated infrared sensors.

The test conditions are as follows: +40 ℃ and relative humidity 100%; +65 ℃ and relative humidity 100%.

PID testing

The test method is referred to the standard IEC TS 2804-1.

The test conditions are as follows: +85 ℃ and relative humidity of 85%; -1500V constant dc voltage, 192 h.

In the embodiment of the invention, the solvent is one or more of ethanol, acetone, butanone, toluene, xylene, ethyl acetate, butyl acetate and propylene glycol methyl ether acetate.