Photovoltaic encapsulation film and preparation method thereof

Abstract

A photovoltaic encapsulation film and its preparation method are disclosed. The film comprises the following components in parts by weight: 10-40 parts POE resin, 60-90 parts PVB resin, 5-20 parts POE grafted maleic anhydride, 1-10 parts CBT resin, and 0.3-0.7 parts high-efficiency lubricant. The preparation method includes the following steps: mixing POE resin, PVB resin, POE grafted maleic anhydride, and high-efficiency lubricant uniformly according to the specified ratio to obtain a mixture, drying at 60-80℃ for 4-6 hours to reduce the moisture content of the mixture to less than 100 PPM; feeding the dried mixture into an extruder for plasticization, adding CBT resin by feeding it into the homogenization section of the screw, and cooling and shaping it through a melt filter, melt pump, mold, and three-roll calender to obtain the POE / PVB encapsulation film substrate. This preparation process is simple and easy to implement; the photovoltaic encapsulation film obtained has excellent encapsulation and adhesion performance, no plasticizer precipitation, and excellent aging resistance.

Description

Technical Field

[0001] This invention relates to the field of photovoltaic encapsulation film technology, specifically to a photovoltaic encapsulation film and its preparation method. Background Technology

[0002] Perovskite solar cells are a novel type of solar cell that utilizes perovskite-type organometal halide semiconductors as light-absorbing materials. Perovskite materials, such as methylammonium lead halide and all-inorganic cesium halide, are inexpensive and easy to manufacture. Perovskite solar cells have the potential to achieve higher efficiency and extremely low production costs, making them the fastest-growing solar energy technology currently. However, a major challenge for perovskite solar cells is their short-term and long-term stability. Their instability is primarily related to environmental influences (moisture and oxygen). Due to the thermal stress and inherent stability of methylammonium-based perovskite, when heated under applied voltage, perovskite is susceptible to mechanical brittle fracture due to the influence of water, vapor, and ultraviolet radiation. Therefore, oxygen and water barrier properties are crucial for the widespread application of perovskite solar cells.

[0003] Photovoltaic encapsulation films are adhesive materials used to bond glass, cells, and backsheets in photovoltaic modules. Located on the top and bottom sides of the cells, their main functions include bonding, protection, and insulation. Therefore, photovoltaic encapsulation films need to possess characteristics such as good adhesion, high light transmittance, resistance to UV and humidity-induced yellowing, oxygen barrier properties, and water barrier properties. Currently, photovoltaic encapsulation films are mainly classified into EVA films, POE films, and PVB films.

[0004] EVA film is currently the mainstream encapsulation material, with good processing properties and ample supply, but its stability is poor. The vinyl acetate groups in EVA film make it susceptible to degradation and aging due to ultraviolet light and humid heat oxidation, manifesting as yellowing and delamination, affecting module efficiency and lifespan. The vinyl acetate groups in EVA material are hydrophilic; when moisture enters from the module edges, EVA easily hydrolyzes to produce acetic acid. Acetic acid reacts with glass to generate a large number of freely moving sodium ions. These sodium ions migrate from the glass surface to the cell surface through the encapsulation material, undergoing an electro-corrosion reaction with the silver grid lines on the cell surface, thus corroding the grid lines, leading to increased series resistance and degraded module performance.

[0005] POE film features low water vapor permeability, high volume resistivity, and good anti-PID performance, making it more suitable for N-type module encapsulation requirements. However, its processing properties are poor, and the supply of POE resin is limited. POE resin is a non-polar material with weaker adhesion than EVA. Currently, the additives used in film preparation are primarily polar, resulting in poor compatibility with POE resin. In application, POE film suffers from a series of processing problems, including additive precipitation and easy bubble formation, leading to low module lamination yield. Furthermore, the smooth surface of POE film makes it prone to displacement, impacting module production efficiency.

[0006] PVB (Polyvinyl Butyral) film is a film made primarily from PVB resin (polyvinyl butyral), modified with a large amount of plasticizer, and then melt-processed. It exhibits excellent mechanical strength, high safety, and strong adhesive properties. Patent CN107681015A discloses a method for preparing PVB photovoltaic film; however, the addition of a large amount of plasticizer leads to decreased stability, and plasticizer migration affects its adhesion and water resistance, making it difficult to apply to traditional modules. CN111834481A discloses a PVB / POE superposition method to improve product performance, but this method still fails to solve the stability problem of both; the migration of plasticizers and additives affects the product's lifespan. Currently, the commonly used method is a combination of POE film and butyl rubber, considered the most effective way to encapsulate perovskites. However, the coating of butyl rubber increases the processing steps and raises the defect rate. Summary of the Invention

[0007] The purpose of this invention is to provide a photovoltaic encapsulation film and its preparation method. The preparation process is simple and easy to implement. The photovoltaic encapsulation film prepared has excellent encapsulation and bonding performance, no plasticizer precipitation, and excellent aging resistance.

[0008] To achieve the above objectives, the present invention provides a photovoltaic encapsulation film comprising the following components in parts by weight: 10-40 parts of POE resin, 60-90 parts of PVB resin, 5-20 parts of POE grafted with maleic anhydride, 1-10 parts of CBT resin, and 0.3-0.7 parts of high-efficiency lubricant.

[0009] Preferably, the POE resin has a melt index of 10-30 g / 10 min and a Shore hardness of 40-75 degrees.

[0010] Preferably, the PVB resin is a film-grade PVB resin without plasticizer, and the PVB resin has a melt flow rate of 0.8-2.2 g / 10 min and a hydroxyl content of 17-20%.

[0011] Preferably, the grafting rate of the POE-grafted maleic anhydride is 1.0 to 1.3 MA, and the melt index is 0.6 to 2.0 g / 10 min.

[0012] Preferably, the CBT resin is CBT100.

[0013] Preferably, the high-efficiency lubricant is a hyperbranched lubricant.

[0014] Preferably, the hyperbranched lubricant is HyPer C182.

[0015] The present invention also provides a method for preparing the above-mentioned photovoltaic encapsulating film, comprising the following steps:

[0016] (1) Mix POE resin, PVB resin, POE grafted maleic anhydride and high-efficiency lubricant evenly according to the formula to obtain a mixture, and dry it at 60-80℃ for 4-6 hours to make the water content of the mixture less than 100PPM.

[0017] (2) The dried mixture is fed into an extruder for plasticization. CBT resin is added to the screw homogenization section and cooled and shaped by a melt filter, melt pump, mold, and three-roll calender to obtain POE / PVB film substrate, i.e. photovoltaic encapsulation film.

[0018] Preferably, in step (2), the process temperatures of each piece of equipment are 150-240℃ for the extruder, 160-235℃ for the filter, 180-240℃ for the melt pump, 160-240℃ for the die, and 20-70℃ for the three-roll calender.

[0019] Compared with existing technical solutions, the present invention has the following advantages:

[0020] This invention addresses the poor adhesion of POE by blending it with PVB resin, resulting in a photovoltaic encapsulating film with no plasticizer precipitation, excellent aging resistance, and stable adhesion. The addition of maleic anhydride grafted onto POE improves the compatibility of the two resins. The hyperbranched lubricant increases the melt index of the PVB resin during the initial plasticization stage, reducing the difficulty of plasticizing. Simultaneously, the addition of CBT100 at the screw homogenization end avoids incomplete plasticization caused by premature CBT100 addition. This stage effectively reduces the melt viscosity of the plasticized POE / PVB resin, making the PVB resin easier to process without plasticizers. The preparation method of this invention is simple and easy to implement, broadening the application prospects of POE / PVB films, advancing the process of material functionalization, and possessing enormous application potential. Detailed Implementation

[0021] The present invention will be further described in detail below with reference to specific embodiments.

[0022] All raw materials used in the following specific embodiments are commercially available. The POE-grafted maleic anhydride used in the following specific embodiments was purchased from Dow Chemical Company, USA.

[0023] Example 1

[0024] A photovoltaic encapsulating film comprises the following components in parts by weight:

[0025] 10 parts of POE resin, melt index of 10 g / 10 min, Shore hardness of 75 degrees;

[0026] 90 parts of PVB resin, melt flow rate of 0.8 g / 10 min, hydroxyl content of 17%;

[0027] Five portions of maleic anhydride were grafted onto POE, with a grafting rate of 1.0 MA and a melt index of 0.6 g / 10 min.

[0028] HyPer C182 0.7 copies;

[0029] 1 part of CBT100 resin.

[0030] The method for preparing the above-mentioned photovoltaic encapsulating film includes the following steps:

[0031] (1) Mix POE resin, PVB resin, POE grafted maleic anhydride and HyPer C182 evenly according to the formula to obtain a mixture, and dry it at 60℃ for 4h to make the water content of the mixture less than 100PPM.

[0032] (2) The dried mixture is fed into the extruder for plasticization. CBT100 resin is added to the screw homogenization section. The mixture is cooled and shaped by the melt filter, melt pump, mold, and three-roll calender to obtain POE / PVB film substrate. The process temperatures of each equipment are 150℃ for the extruder, 160℃ for the filter, 180℃ for the melt pump, 160℃ for the mold, and 20℃ for the three-roll calender.

[0033] Example 2

[0034] A photovoltaic encapsulating film comprises the following components in parts by weight:

[0035] 40 parts of POE resin, melt index of 30 g / 10 min, Shore hardness of 40 degrees;

[0036] 60 parts of PVB resin, melt flow rate of 2.2 g / 10 min, hydroxyl content of 20%;

[0037] 20 portions of maleic anhydride were grafted onto POE, with a grafting rate of 1.3 MA and a melt index of 2.0 g / 10 min.

[0038] HyPer C182 0.3 copies;

[0039] 10 parts of CBT100 resin.

[0040] The method for preparing the above-mentioned photovoltaic encapsulating film includes the following steps:

[0041] (1) Mix POE resin, PVB resin, POE grafted maleic anhydride and HyPer C182 evenly according to the ratio to obtain a mixture, and dry it at 80℃ for 6 hours to make the water content of the mixture less than 100PPM.

[0042] (2) The dried mixture is fed into the extruder for plasticization. CBT100 resin is added to the screw homogenization section. The mixture is cooled and shaped by the melt filter, melt pump, mold, and three-roll calender to obtain POE / PVB film substrate. The process temperatures of each equipment are 240℃ for the extruder, 235℃ for the filter, 240℃ for the melt pump, 240℃ for the mold, and 70℃ for the three-roll calender.

[0043] Example 3

[0044] A photovoltaic encapsulating film comprises the following components in parts by weight:

[0045] 20 parts of POE resin, melt index of 17 g / 10 min, Shore hardness of 55 degrees;

[0046] 80 parts of PVB resin, melt flow rate of 1.2 g / 10 min, hydroxyl content of 18%;

[0047] Ten portions of maleic anhydride were grafted onto POE, with a grafting rate of 1.3 MA and a melt index of 2.0 g / 10 min.

[0048] HyPer C182 0.6 copies;

[0049] 10 parts of CBT100 resin.

[0050] The method for preparing the above-mentioned photovoltaic encapsulating film includes the following steps:

[0051] (1) Mix POE resin, PVB resin, POE grafted maleic anhydride and HyPer C182 evenly according to the ratio to obtain a mixture, and dry it at 70℃ for 6 hours to make the water content of the mixture less than 100PPM.

[0052] (2) The dried mixture is fed into the extruder for plasticization. CBT100 resin is added to the side feed of the screw homogenization section. The POE / PVB film substrate is obtained by cooling and shaping through the melt filter, melt pump, mold, and three-roll calender. The process temperatures of each equipment are 200℃ for the extruder, 235℃ for the filter, 240℃ for the melt pump, 210℃ for the mold, and 50℃ for the three-roll calender.

[0053] Example 4

[0054] A photovoltaic encapsulating film comprises the following components in parts by weight:

[0055] 40 parts of POE resin, melt index of 30 g / 10 min, Shore hardness of 45 degrees;

[0056] 60 parts of PVB resin, melt flow rate of 2 g / 10 min, hydroxyl content of 17%;

[0057] Five portions of maleic anhydride were grafted onto POE, with a grafting rate of 1.3 MA and a melt index of 2.0 g / 10 min.

[0058] HyPer C182 0.7 copies;

[0059] 10 parts of CBT100 resin.

[0060] The method for preparing the above-mentioned photovoltaic encapsulating film includes the following steps:

[0061] (1) Mix POE resin, PVB resin, POE grafted maleic anhydride and HyPer C182 evenly according to the ratio to obtain a mixture, and dry it at 70℃ for 4 hours to make the water content of the mixture less than 100PPM.

[0062] (2) The dried mixture is fed into an extruder for plasticization. CBT100 resin is added to the feed side of the screw homogenization section. The mixture is then cooled and shaped through a melt filter, melt pump, die, and three-roll calender to obtain the POE / PVB film substrate. The process temperatures of each piece of equipment are as follows: extruder 210℃, filter 220℃, melt pump 240℃, die temperature 220℃, and three-roll calender 20℃.

[0063] Comparative Example 1

[0064] A photovoltaic encapsulating film comprises the following components in parts by weight:

[0065] 100 parts of PVB resin, melt flow rate of 2.2 g / 10 min, hydroxyl content of 20%;

[0066] HyPer C182 0.7 copies;

[0067] 10 parts of CBT100 resin.

[0068] The preparation method of the photovoltaic encapsulating film is as described in Example 2.

[0069] Comparative Example 2

[0070] A photovoltaic encapsulating film comprises the following components in parts by weight:

[0071] 40 parts of POE resin, melt index of 30 g / 10 min, Shore hardness of 40 degrees;

[0072] 60 parts of PVB resin, melt flow rate of 2.2 g / 10 min, hydroxyl content of 20%;

[0073] 20 portions of maleic anhydride were grafted onto POE, with a grafting rate of 1.3 MA and a melt index of 2.0 g / 10 min.

[0074] HyPer C182 0.3 copies.

[0075] The preparation method of the photovoltaic encapsulating film is as described in Example 2.

[0076] Comparative Example 3

[0077] A photovoltaic encapsulating film comprises the following components in parts by weight:

[0078] 40 parts of POE resin, melt index of 30 g / 10 min, Shore hardness of 40 degrees;

[0079] 60 parts of PVB resin, melt flow rate of 2.2 g / 10 min, hydroxyl content of 20%;

[0080] 20 portions of maleic anhydride were grafted onto POE, with a grafting rate of 1.3 MA and a melt index of 2.0 g / 10 min.

[0081] HyPer C182 0.3 copies;

[0082] 10 parts of CBT100 resin.

[0083] The method for preparing the above-mentioned photovoltaic encapsulating film includes the following steps:

[0084] (1) Mix POE resin, PVB resin, POE grafted maleic anhydride, HyPer C182 and CBT100 resin evenly according to the ratio to obtain a mixture, and dry it at 80℃ for 6 hours to make the water content of the mixture less than 100PPM.

[0085] (2) The dried mixture is fed into an extruder for plasticization, and then cooled and shaped through a melt filter, melt pump, mold, and three-roll calender to obtain the POE / PVB film substrate. The process temperatures of each piece of equipment are 240℃ for the extruder, 235℃ for the filter, 240℃ for the melt pump, 240℃ for the mold, and 70℃ for the three-roll calender.

[0086] Examples 1-4, Comparative Examples 1-3, and commercially available POE and PVB window films were tested for their encapsulation performance according to the photovoltaic encapsulation standard GB / T29848-2013. The results are shown in Table 1 below:

[0087] Table 1. Performance Test of Adhesive Film Encapsulation

[0088]

[0089] As can be seen from Table 1, the processing performance of Examples 1-4 and the comparative examples is compared with that of Example 2. In Comparative Example 1, no POE resin was added, and its plasticizing effect was poor, indicating that the addition of POE has a plasticizing effect on the resin system. In Comparative Example 2, no CBT resin was added, and the melt pump pressure was too high, so the resin could not be plasticized. This confirms that CBT resin can flow like water after exceeding 130°C, which greatly improves the plasticizing ability of the resin system. In Comparative Example 3, CBT resin was added in the raw material mixing stage. The extremely low viscosity CBT was plasticized first, resulting in insufficient plasticization of PVB in the first stage and many white spots on the product surface. CBT resin in the homogenization stage can solve the problem of insufficient plasticization and reduce the melt pump pressure. Furthermore, the 2000-hour accelerated UV aging test showed that the mixture of POE / PVB resins improved the anti-aging performance of the material. Compared with POE film and PVB window film, the material had a lower FF value decrease rate and excellent aging peel strength and yellowing resistance. This indicates that the addition of PVB improved the overall encapsulation and adhesion of the resin. The system does not contain small molecule additives or plasticizers, and no precipitation occurred after UV aging, ensuring the encapsulation durability of the material. The example yielded a high-performance photovoltaic encapsulation material.

Claims

1. A photovoltaic encapsulation film, characterized in that, The product comprises the following components in parts by weight: 10-40 parts POE resin, 60-90 parts PVB resin, 5-20 parts POE grafted with maleic anhydride, 1-10 parts CBT resin, and 0.3-0.7 parts high-efficiency lubricant; the POE resin has a melt flow rate of 10-30 g / 10 min and a Shore hardness of 40-75 degrees; the PVB resin has a melt flow rate of 0.8-2.2 g / 10 min and a hydroxyl content of 17-20%; the POE grafted with maleic anhydride has a grafting rate of 1.0-1.3 MA% and a melt flow rate of 0.6-2.0 g / 10 min; the CBT resin is CBT100; and the high-efficiency lubricant is a hyperbranched lubricant.

2. The photovoltaic encapsulation film according to claim 1, characterized in that, The PVB resin is a film-grade PVB resin without plasticizers.

3. The photovoltaic encapsulation film according to claim 1, characterized in that, The hyperbranched lubricant HyPerC182.

4. A method for preparing the photovoltaic encapsulating film as described in claim 1, characterized in that, Includes the following steps: (1) Mix POE resin, PVB resin, POE grafted maleic anhydride and high-efficiency lubricant evenly according to the formula to obtain a mixture, and dry it at 60-80℃ for 4-6 hours to make the water content of the mixture less than 100PPM. (2) The dried mixture is fed into the extruder for plasticization. CBT resin is added to the screw homogenization section and cooled and shaped by the melt filter, melt pump, mold and three-roll calender to obtain POE / PVB film substrate, i.e. photovoltaic encapsulation film.

5. The method for preparing a photovoltaic encapsulating film according to claim 4, characterized in that, In step (2), the process temperatures of each piece of equipment are 150-240℃ for the extruder, 160-235℃ for the filter, 180-240℃ for the melt pump, 160-240℃ for the die, and 20-70℃ for the three-roll calender.

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