Photovoltaic packaging adhesive film with water blocking function and photovoltaic module

Abstract

The invention provides a photovoltaic packaging adhesive film with a water blocking function and a photovoltaic module, the photovoltaic packaging adhesive film with the water blocking function is formed by a composition, the composition contains matrix resin, a cross-linking agent, an assistant cross-linking agent, a coupling agent, an anti-PID auxiliary agent and a water absorption auxiliary agent, the water absorption auxiliary agent is acrylic acid cross-linked resin and volatilizes water absorbed by the acrylic acid cross-linked resin at the temperature of 45 DEG C or above, so that the saturated water absorption rate of the photovoltaic packaging adhesive film with the water blocking function ranges from 0.1% to 0.3%. Therefore, the photovoltaic packaging adhesive film with the water-blocking function has a circulating water-blocking function of absorbing water and volatilizing water, and corrosion of a front electrode of an N-type TOPCon battery is avoided, so that power attenuation of a photovoltaic module applying the photovoltaic packaging adhesive film with the water-blocking function is reduced.

Description

Technical Field

[0001] The present invention relates to the technical field of encapsulating films and photovoltaic modules, and in particular to a photovoltaic encapsulating film with a water-blocking function and a photovoltaic module using the photovoltaic encapsulating film with a water-blocking function. Background Art

[0002] N-type TOPCon cells use silver-aluminum paste on the front side, creating a large potential difference between the two, making them prone to forming galvanic cells. Moisture intrusion creates a complex electrolyte environment, leading to electrochemical corrosion and thus affecting module power. Single-glass N-type TOPCon cells use a backsheet on the back side, allowing moisture to enter more easily through the backsheet, passing through the gaps between the cells to reach the cell surface, creating an electrolyte environment. The presence of the silver-aluminum paste creates galvanic cells, causing electrochemical corrosion and thus increasing power attenuation on the front side.

[0003] Existing technology can prevent the intrusion of water vapor by using an aluminum backplane to reduce the water vapor permeability of the backplane to near zero, but aluminum backplanes are expensive and have bonding problems, making them not an ideal choice. Silver paste can also be improved by not using aluminum-containing silver paste on the front, but the current metallization welding process has not yet achieved a breakthrough and does not meet the electrical connection requirements. It also only improves electrochemical corrosion but cannot eliminate it.

[0004] Traditional PV modules require polymer encapsulation materials to have as low a water vapor transmission rate and saturated water absorption rate as possible to ensure module lifespan. However, PV modules using both N-type TOPCon cells and polymer encapsulation materials have different requirements: the lower the water vapor transmission rate, the better, while the higher the saturated water absorption rate, the better, and the ability to release absorbed water. Summary of the Invention

[0005] The present invention provides a photovoltaic encapsulation film with a water-blocking function, which is suitable for N-type TOPCon cell single-glass modules. The photovoltaic encapsulation film with a water-blocking function has a cyclic function of absorbing moisture and volatilizing moisture, can block water for a long time, avoid corrosion of the front electrode of the N-type TOPCon cell, and thus reduce power attenuation.

[0006] An object of the present invention is to provide a photovoltaic encapsulation film with a water-blocking function, which is formed from a composition containing a base resin, a cross-linking agent, a co-cross-linking agent, a coupling agent, an anti-PID additive, and a functional additive. The functional additive is a water-absorbing additive, which is an acrylic cross-linked resin and volatilizes the water absorbed by the acrylic cross-linked resin under conditions above 45°C, so that the saturated water absorption rate of the composition is between 0.1% and 0.3%.

[0007] Furthermore, the acrylic cross-linked resin is polymerized from acrylic acid and a cross-linking unit, and the cross-linking unit is one or more of acrylic acid, alkyl saccharide, pentaerythritol, alkyl pentaerythritol or long-chain alkanol acrylate.

[0008] Furthermore, the matrix resin is one or more of ethylene homopolymer, propylene homopolymer, ethylene and α-olefin copolymer or ethylene and polar monomer copolymer.

[0009] Furthermore, the copolymer of ethylene and α-olefin is an ethylene-butene copolymer or an ethylene-octene copolymer.

[0010] Furthermore, the copolymer of ethylene and polar monomer is ethylene-vinyl acetate copolymer, ethylene-methyl acrylate copolymer or ethylene-butyl acrylate copolymer.

[0011] Furthermore, the ratio of the acrylic cross-linking resin content to the matrix resin content ranges from 0.1:100 to 1:100.

[0012] Furthermore, the anti-PID auxiliary agent is one or more of ethoxylated pentaerythritol triacrylate, propoxylated neopentyl glycol diacrylate, ethoxylated trimethylolpropane triacrylate, ethoxylated pentaerythritol tetraacrylate, propoxylated glycerol triacrylate, polyethylene glycol dimethacrylate, polyethylene glycol diacrylate or polypropylene glycol dimethacrylate.

[0013] Another object of the present invention is to provide a photovoltaic module comprising glass, an encapsulating film, a photovoltaic cell and a backplane, wherein the encapsulating film is a photovoltaic encapsulating film with a water-blocking function, and the photovoltaic cell is an N-type TOPCon cell.

[0014] Furthermore, a photovoltaic encapsulation film with a water-blocking function is arranged between the N-type TOPCon cell and the backsheet.

[0015] In summary, the present invention has the following beneficial effects:

[0016] 1. By adding acrylic cross-linked resin and utilizing the water absorption-heat volatilization cycle mechanism of acrylic cross-linked resin, the photovoltaic encapsulation film with water-blocking function is endowed with a water-blocking function, which prevents moisture from contacting the front of the N-type TOPCon cell, avoids corrosion of the front electrode of the N-type TOPCon cell, and thus reduces power attenuation.

[0017] 2. The N-type TOPCon cell single-glass module that uses a photovoltaic encapsulation film with a water-blocking function can prevent moisture from invading the back of the photovoltaic module into the interior of the photovoltaic module, and then invading the front of the N-type TOPCon cell through the cell gaps to cause electrochemical corrosion, thereby enhancing the protection of the back of the photovoltaic module. DETAILED DESCRIPTION

[0018] The detailed description of the present invention and its embodiments are set forth one by one in the following detailed description in a non-limiting manner; however, the described parts are merely embodiments of the present invention and have no direct impact on the scope of the present invention. Therefore, the following description should not be interpreted in a limiting manner.

[0019] Currently, the main components of photovoltaic encapsulation films are base resin, crosslinking agent, auxiliary crosslinking agent, coupling agent, anti-PID additive, and functional additive. The present invention provides a photovoltaic encapsulation film with water-blocking function. The functional additive in the photovoltaic encapsulation film is a water-absorbing additive. The water-absorbing additive is an acrylic crosslinking resin and evaporates the absorbed water under conditions above 45°C. After adding the water-absorbing additive, the saturated water absorption rate of the photovoltaic encapsulation film ranges from 0.1% to 0.3%. In some embodiments, the acrylic crosslinking resin is polymerized with acrylic acid and a crosslinking unit, and the crosslinking unit is one or more of acrylic acid, alkyl saccharide, pentaerythritol, alkyl pentaerythritol, or long-chain alkanol acrylate. Research has found that the acrylic crosslinking resin has weak acidity, gradually dissolves in water, and rapidly increases in viscosity. It forms a clear solution at low concentrations and a translucent gel with certain strength and elasticity at higher concentrations. The acrylic crosslinking resin can also evaporate water when heated above 45°C and can absorb water again. Therefore, upon contact with water, acrylic cross-linked resin rapidly swells, forming a cross-linked microgel that blocks further moisture from reaching the N-type TOPCon cells. During operation, the PV module can reach temperatures of 60°C to 80°C, which is sufficient to encourage the acrylic cross-linked resin to volatilize absorbed moisture and then reabsorb it. This repeated process effectively prevents moisture from reaching the N-type TOPCon cells, preventing electrochemical corrosion on the front of the cells and thus maintaining the PV module's output power. Furthermore, the layered molecular structure of acrylic cross-linked resin prolongs or even blocks the intrusion pathway for moisture. The acrylic cross-linked resin molecules contain acrylic functional groups, which form hydrogen bonds with water, rapidly capturing water molecules and further enhancing the microstructure of the PV encapsulation film, thereby preventing moisture from reaching the front of the N-type TOPCon cells and preventing electrochemical corrosion on the front of the cells.

[0020] In some embodiments, the matrix resin is specifically selected from one or more of an ethylene homopolymer, a propylene homopolymer, an ethylene-α-olefin copolymer, or an ethylene-polar monomer copolymer. The ethylene-α-olefin copolymer is preferably an ethylene-butene copolymer or an ethylene-octene copolymer; and the ethylene-polar monomer copolymer is preferably an ethylene-vinyl acetate copolymer, an ethylene-methyl acrylate copolymer, or an ethylene-butyl acrylate copolymer. The matrix resin exhibits good compatibility with the acrylic cross-linked resin, allowing the acrylic cross-linked resin to be evenly dispersed in the matrix resin. Furthermore, the acrylic cross-linked resin maintains a relatively stable position within the matrix resin and does not migrate erratically.

[0021] Of course, ensuring that the acrylic cross-linked resin is evenly dispersed in the matrix resin and prevents random migration also depends on the acrylic cross-linked resin content in the photovoltaic encapsulation film. The ratio of acrylic cross-linked resin content to matrix resin content ranges from 0.1:100 to 1:100. If the ratio is less than 0.1:100, the saturated water absorption rate is reduced, and moisture that penetrates the backsheet and enters the photovoltaic encapsulation film cannot be fully absorbed in a timely manner. If the ratio is greater than 0.1:100, due to the rapid swelling of acrylic cross-linked resin upon contact with water, adding too much acrylic cross-linked resin may cause deformation of the photovoltaic encapsulation film. In addition, the absorbed moisture cannot be quickly volatilized and released, which in turn reduces the water barrier effect of the photovoltaic encapsulation film. Therefore, in order to balance the water absorption rate and water volatilization rate of the acrylic cross-linked resin, while ensuring the water barrier effect of the photovoltaic encapsulation film using acrylic cross-linked resin, the ratio of the acrylic cross-linked resin content to the matrix resin content is more reasonable between 0.1:100 and 1:100.

[0022] In some embodiments, the anti-PID adjuvant is specifically selected from one or more of ethoxylated pentaerythritol triacrylate, propoxylated neopentyl glycol diacrylate, ethoxylated trimethylolpropane triacrylate, ethoxylated pentaerythritol tetraacrylate, propoxylated glycerol triacrylate, polyethylene glycol dimethacrylate, polyethylene glycol diacrylate, or polypropylene glycol dimethacrylate.

[0023] A conventional single-glass photovoltaic module comprises glass, an encapsulating film, a photovoltaic cell and a backsheet. The present invention further provides a photovoltaic module, wherein the encapsulating film is a photovoltaic encapsulating film with a water-blocking function, and the photovoltaic cell is an N-type TOPCon cell.

[0024] Preferably, a water-blocking photovoltaic encapsulation film is placed between the N-type TOPCon cells and the backsheet. In single-glass photovoltaic modules using N-type TOPCon cells, corrosion of the electrodes on the front of the N-type TOPCon cells occurs due to moisture intruding from the back of the module into the module, then through the gaps between the cells to the front of the N-type TOPCon cells, causing electrochemical corrosion. Placing a water-blocking photovoltaic encapsulation film between the N-type TOPCon cells and the backsheet can enhance protection of the back of the photovoltaic module.

[0025] The above-mentioned photovoltaic encapsulation film with water-blocking function contains a base resin, a cross-linking agent, a co-cross-linking agent, a coupling agent, an anti-PID agent and a water-absorbing agent. The water-absorbing agent is an acrylic cross-linking resin and evaporates the absorbed water under conditions above 45°C. The saturated water absorption rate of the photovoltaic encapsulation film with water-blocking function ranges from 0.1% to 0.3%.

[0026] Preferably, the acrylic cross-linked resin is polymerized with acrylic acid and a cross-linking unit, wherein the cross-linking unit is one or more of acrylic acid, alkyl glycosides, pentaerythritol, alkyl pentaerythritol, or long-chain alkanol acrylate. Thus, when a single-glass photovoltaic module using N-type TOPCon cells is operated, the water-blocking photovoltaic encapsulation film's moisture absorption and volatilization cycle prevents electrochemical corrosion on the front of the N-type TOPCon cells, achieving long-term stability and ensuring long-term power output stability.

[0027] Preferably, the matrix resin is selected from one or more of an ethylene homopolymer, a propylene homopolymer, an ethylene-α-olefin copolymer, or an ethylene-polar monomer copolymer. The ethylene-α-olefin copolymer is preferably an ethylene-butene copolymer or an ethylene-octene copolymer; the ethylene-polar monomer copolymer is preferably an ethylene-vinyl acetate copolymer, an ethylene-methyl acrylate copolymer, or an ethylene-butyl acrylate copolymer. All of these matrix resins are heat-meltable and can provide a bonding effect, bonding the encapsulation material on both sides of the N-type TOPCon cell to the N-type TOPCon cell.

[0028] Preferably, the ratio of the acrylic cross-linked resin content to the matrix resin content in the components constituting the water-blocking photovoltaic encapsulation film is between 0.1:100 and 1:100. This balances the water absorption rate of the water-absorbing agent with the water volatilization rate, thereby ensuring the water-blocking effect of the water-blocking photovoltaic encapsulation film and further guaranteeing the long-term stability of single-glass photovoltaic modules using N-type TOPCon cells.

[0029] Preferably, the anti-PID auxiliary agent is specifically selected from one or more of ethoxylated pentaerythritol triacrylate, propoxylated neopentyl glycol diacrylate, ethoxylated trimethylolpropane triacrylate, ethoxylated pentaerythritol tetraacrylate, propoxylated glycerol triacrylate, polyethylene glycol dimethacrylate, polyethylene glycol diacrylate or polypropylene glycol dimethacrylate.

[0030] Example

[0031] The present invention provides a photovoltaic encapsulation film with a water-blocking function, comprising a base resin, a cross-linking agent, a co-cross-linking agent, a coupling agent, an anti-PID additive, and a water-absorbing additive. After uniformly blending the components, the film is fed into an extruder, cast, cooled, and then wound to obtain the photovoltaic encapsulation film with a water-blocking function. The following examples and comparative examples further illustrate the photovoltaic encapsulation film with a water-blocking function.

[0032] Examples 1 to 15: The photovoltaic encapsulation film with water-blocking function provided is based on 100 parts by weight of the base resin, and the cross-linking agent is 0.5 parts of tert-butyl peroxy 2-ethylhexyl carbonate; the auxiliary cross-linking agent is 1 part of triallyl isocyanurate; the coupling agent is 0.5 parts of vinyltrioxysilane; and the anti-PID auxiliary agent is 0.5 parts of propoxylated neopentyl glycol diacrylate. The difference lies in the specific selection of the base resin, the specific selection and content of the water-absorbing auxiliary agent. Details are shown in Table 1.

[0033] Table 1 Components and contents of Example 1 to Example 15

[0034]

[0035]

[0036] Example 15: The photovoltaic encapsulation film with water barrier function provided is different from Example 5 in that the anti-PID auxiliary agent is ethoxylated pentaerythritol triacrylate.

[0037] Comparative Example 1: The photovoltaic encapsulation film with water-blocking function provided is different from Example 5 in that no water-absorbing auxiliary agent is added.

[0038] Comparative Example 2: The photovoltaic encapsulation film with water barrier function provided is different from Example 5 in that no anti-PID additive is added.

[0039] Performance testing

[0040] The performance of the photovoltaic encapsulation films with water barrier function provided in the above examples and comparative examples was tested with reference to the following method, and the test results are recorded in Table 2.

[0041] 1. Saturated water absorption rate: a) Take a 10cm*10cm photovoltaic encapsulation film with water barrier function and laminate it according to conventional technology; b) Weigh the laminated film as the initial weight, recorded as G1; c) Soak the weighed film in water (ensure that the water completely immerses the sample). After a period of time, filter the film from the water, wipe off the surface moisture, and then weigh it again until the weight remains unchanged, recorded as G2; d) Saturated water absorption rate = (G2-G1) / G1.

[0042] Table 2 Test results of saturated water absorption of photovoltaic encapsulation films with water barrier function

[0043] project Saturated water absorption project Saturated water absorption project Saturated water absorption Example 1 0.242％ Example 2 0.241％ Example 3 0.244％ Example 4 0.243％ Example 5 0.245％ Example 6 0.103％ Example 7 0.191％ Example 8 0.300％ Example 9 0.221％ Example 10 0.211％ Example 11 0.204％ Example 12 0.213％ Example 13 0.238％ Example 14 0.240％ Example 15 0.244％ Comparative Example 1 0.100％ Comparative Example 2 0.243％

[0044] As can be seen from the data in Table 2, the addition of a water-absorbing agent can greatly improve the saturated water absorption rate. When the water-absorbing agent is a cross-linked polyacrylic acid, an alkyl glycoside-acrylic acid cross-linked polymer, a pentaerythritol-acrylic acid cross-linked polymer, an alkyl pentaerythritol-acrylic acid cross-linked polymer or a long-chain alkanol acrylate-acrylic acid cross-linked polymer, replacing each other has little effect on the saturated water absorption rate. The specific selection of the matrix resin has a relatively large impact on the saturated water absorption rate, which may be related to the molecular polarity of the matrix resin. The polarity of the matrix resin molecules contributes to the improvement of the saturated water absorption rate, while the molecules of the matrix resin are non-polar and have excellent water-blocking function. Therefore, the combination of the non-polar matrix resin and the water-absorbing agent is different from the combination of the polar matrix resin and the water-absorbing agent, and the water-blocking and water-absorbing equilibrium point is more difficult to control. From the data of Example 15 and Comparative Example 2, it can be seen that the specific selection of the anti-PID auxiliary agent and whether it is added or not have little effect on the saturated water absorption rate.

[0045] The present invention also provides a photovoltaic module, which is further described through embodiments and comparative examples.

[0046] In the following embodiments and comparative examples, the front transparent glass encapsulation layer is ultra-white patterned glass, the back encapsulation layer is a KPF backplane; the first encapsulation film layer is an EVA film; and the battery cell is an N-type TOPCon battery.

[0047] Examples 16 to 30: The provided photovoltaic modules include a front transparent glass encapsulation layer, a first encapsulation film layer, a cell array, a second encapsulation film layer and a back encapsulation layer, wherein the second encapsulation film layer is the photovoltaic encapsulation film with water-blocking function provided in Examples 1 to 15.

[0048] Comparative Examples 3 to 4: The photovoltaic modules provided include a front transparent glass encapsulation layer, a first encapsulation film layer, a cell array, a second encapsulation film layer and a back encapsulation layer, wherein the second encapsulation film layer is the photovoltaic encapsulation film with water-blocking function provided in Comparative Examples 1 to 2 respectively.

[0049] Performance testing

[0050] The photovoltaic modules of the above embodiments and comparative examples were tested for performance using the following method, and the test results are recorded in Table 3.

[0051] 1. Potential Induced Degradation (PID) test: Place the PV module in an environmental chamber with a relative humidity of 85% and a temperature of 85°C for 1000 hours. Measure the power of the PV module before and after placement in the environmental chamber. Calculate the power change ratio and record its absolute value: power change ratio = (power after test - power before test) / power before test.

[0052] Table 3 Performance test results of photovoltaic modules

[0053] project Power change rate project Power change rate project Power change rate Example 16 -1.8％ Example 17 -1.7％ Example 18 -1.5％ Example 19 -1.6％ Example 20 -1.4％ Example 21 -3.1％ Example 22 -2.2％ Example 23 -1.2％ Example 24 -2.0％ Example 25 -2.1％ Example 26 -1.6％ Example 27 -1.8％ Example 28 -2.0％ Example 29 -2.2％ Example 30 -1.5％ Comparative Example 3 -5.9％ Comparative Example 4 -7.5％

[0054] A smaller absolute value of the power change rate indicates a smaller power variation, indicating better anti-PID performance. The data in Table 3 show that adding a water-absorbing agent helps improve PID resistance, and adding an anti-PID agent also helps improve PID resistance. The specific choice of the water-absorbing agent has little impact on anti-PID performance. Assuming a good balance between the water-absorbing properties of the water-absorbing agent and the water-blocking properties of the matrix resin, the polarity of the matrix resin has little impact on PID resistance. The amount of water-absorbing agent does affect the magnitude of the improvement in PID resistance.

[0055] In this specification, the present invention has been described with reference to specific embodiments thereof. However, it will be apparent that various modifications and variations may be made without departing from the spirit and scope of the present invention. Therefore, the description is to be regarded as illustrative rather than restrictive.

Claims

1. A photovoltaic encapsulation film with water-blocking function, formed from a composition comprising a base resin, a crosslinking agent, a co-crosslinking agent, a coupling agent, an anti-PID additive, and a functional additive, characterized in that: The functional auxiliary agent is a water-absorbing auxiliary agent, which is an acrylic cross-linked resin. The water absorbed by the acrylic cross-linked resin is volatilized at a temperature above 45° C., so that the saturated water absorption rate of the composition is between 0.1% and 0.3%.

2. The photovoltaic encapsulation film with water-blocking function according to claim 1, wherein: The acrylic cross-linked resin is formed by polymerization of acrylic acid and a cross-linking unit, wherein the cross-linking unit is one or more of acrylic acid, alkyl saccharide, pentaerythritol, alkyl pentaerythritol or long-chain alkanol acrylate.

3. The photovoltaic encapsulation film with water-blocking function according to claim 1 or 2, characterized in that: The base resin is one or more of ethylene homopolymer, propylene homopolymer, ethylene and α-olefin copolymer or ethylene and polar monomer copolymer.

4. The photovoltaic encapsulation film with water-blocking function according to claim 1 or 2, characterized in that: The base resin is one or more of ethylene homopolymer, propylene homopolymer, ethylene and α-olefin copolymer or ethylene and polar monomer copolymer, and the ethylene and α-olefin copolymer is ethylene-butene copolymer or ethylene-octene copolymer.

5. The photovoltaic encapsulation film with water-blocking function according to claim 1 or 2, characterized in that: The matrix resin is one or more of ethylene homopolymer, propylene homopolymer, ethylene and α-olefin copolymer or ethylene and polar monomer copolymer, and the ethylene and polar monomer copolymer is ethylene-vinyl acetate copolymer, ethylene-methyl acrylate copolymer or ethylene-butyl acrylate copolymer.

6. The photovoltaic encapsulation film with water-blocking function according to claim 1 or 2, characterized in that: The ratio of the acrylic cross-linked resin content to the matrix resin content ranges from 0.1:100 to 1:

100.

7. The photovoltaic encapsulation film with water-blocking function according to claim 1, wherein: The anti-PID auxiliary agent is one or more of ethoxylated pentaerythritol triacrylate, propoxylated neopentyl glycol diacrylate, ethoxylated trimethylolpropane triacrylate, ethoxylated pentaerythritol tetraacrylate, propoxylated glycerol triacrylate, polyethylene glycol dimethacrylate, polyethylene glycol diacrylate or polypropylene glycol dimethacrylate.

8. A photovoltaic module comprising glass, an encapsulating film, a photovoltaic cell and a backsheet, characterized in that: The encapsulation film is the photovoltaic encapsulation film with water-blocking function according to any one of claims 1 to 7, and the photovoltaic cell is an N-type TOPCon cell.

9. The photovoltaic module according to claim 8, wherein: The photovoltaic encapsulation film with water-blocking function is arranged between the N-type TOPCon cell and the back plate.

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