A room temperature self-crosslinking silicone-modified polyurethane sealant and its preparation and application methods

Abstract

This invention relates to a room-temperature self-crosslinking silicone-modified polyurethane sealant and its preparation and application methods. First, a silicone-modified polyurethane polymer is prepared. By controlling the ratio of silicone monomers to polyurethane raw materials, a room-temperature self-crosslinking polymer sealant with excellent sealing properties, adhesion, and mechanical strength is prepared. Then, the synthesized polymer sealant is coated onto a cover glass using a spin-coating device. The glass is then placed on the surface of a solar photovoltaic device, and the solar photovoltaic cell is encapsulated through rapid crosslinking and curing of the silicone-modified polyurethane resin at room temperature. This silicone-modified polyurethane encapsulant is transparent, resistant to moisture and heat, and has high toughness, meeting the requirements of high-quality and rapid production of solar photovoltaic devices, improving their service life, and is very suitable for the encapsulation process of commercial photovoltaic devices.

Description

Technical Field

[0001] This invention relates to the research of sealants for solar photovoltaic encapsulation materials, specifically a room-temperature self-crosslinking silicone-modified polyurethane sealant and its preparation and application methods, particularly a room-temperature self-crosslinking silicone-modified polyurethane sealant for use in solar photovoltaic cells. Background Technology

[0002] In recent years, with the increasing prominence of energy crises and environmental problems, developing clean energy sources such as solar energy to accelerate the replacement of traditional fossil fuels has become a focal point of current social development. Solar photovoltaic cells, as a typical representative of solar energy utilization, can directly convert sunlight into electricity, demonstrating enormous commercial potential. During use, solar photovoltaic cells typically require encapsulation to ensure excellent operational stability. Currently, the encapsulation material used in solar cells is mainly ethylene-vinyl acetate copolymer (EVA). EVA is inexpensive and has good adhesion to glass and backsheets; however, EVA is prone to hydrolysis under light, oxygen, and humid conditions, producing acetic acid, which can easily corrode the cell surface and solder ribbons. Simultaneously, EVA is prone to yellowing under light and heat, affecting light transmittance and causing overall module efficiency loss. Therefore, researchers have developed a new encapsulation material: polyolefin elastomer (POE). POE material possesses excellent properties such as high resistivity, high water vapor barrier properties, low-temperature resistance, and resistance to yellowing; however, POE has drawbacks such as higher cost, greater processing difficulty, and the tendency for material to accumulate on the membrane lip. Furthermore, both commonly used encapsulation materials require vacuum thermocompression during use, which increases the manufacturing cost of photovoltaic devices to some extent. (Adv.Funct.Mater.2021,31,2100151,Energy Environ.Sci.2022,15,13,ACS Materials Au 2022,2,215.)

[0003] To address the current problems with photovoltaic encapsulation materials, there is an urgent need to develop new polymer encapsulation materials to meet the industry's development needs. For polymer encapsulation materials used in solar photovoltaic devices, they must not only possess excellent water vapor and oxygen barrier properties but also ensure good adhesion and mechanical properties. Silicone polymers have advantages such as high light transmittance, UV resistance, low internal stress, and resistance to yellowing, making them an ideal choice for photovoltaic device encapsulation materials. However, silicone polymers suffer from poor adhesion and low mechanical strength, which to some extent limits their application. Polyurethane encapsulation materials have good adhesion, excellent electrical insulation, good hydrophobicity, and low corrosivity to electronic devices. However, polyurethane encapsulation materials have poor high-temperature resistance and yellowing resistance, and require vacuum hot-pressing processes during use. Therefore, combining the performance advantages of silicone and polyurethane to prepare silicone-modified polyurethane sealants can achieve complementary advantages in encapsulation materials, greatly expanding the application range of polymer encapsulation materials. However, there are currently few reports on the use of silicone-modified polyurethane resin as an encapsulation material for solar photovoltaic devices. Summary of the Invention

[0004] Technical problems to be solved

[0005] To avoid the shortcomings of existing technologies, this invention proposes a room-temperature self-crosslinking silicone-modified polyurethane sealant and its preparation and application methods.

[0006] Technical solution

[0007] A room-temperature self-crosslinking silicone-modified polyurethane sealant, characterized in that its components are: diisocyanate, polypropylene glycol, and 3-(methacryloyloxy)propyltrimethoxysilane.

[0008] The weight ratio of the components is: 5-10g diisocyanate, 50-60g polypropylene glycol, and 5-10g 3-(methacryloyloxy)propyltrimethoxysilane.

[0009] The diisocyanates include, but are not limited to, 4,4'-diphenylmethane diisocyanate (MDI).

[0010] The polypropylene glycol includes, but is not limited to, PPG-200 type polypropylene glycol.

[0011] A method for preparing the room-temperature self-crosslinking silicone-modified polyurethane sealant, characterized by the following steps:

[0012] Step 1: Dissolve 5-10g of diisocyanate in 30-40mL of tetrahydrofuran at room temperature;

[0013] Step 2: Add 50-60g of polypropylene glycol to the reaction system to carry out the polymerization reaction;

[0014] Step 3: Then add 5-10 g of 3-(methacryloyloxy)propyltrimethoxysilane to the system and stir to react the polymerization reaction;

[0015] Step 4: Add ethanol to the reaction system to terminate the reaction. After removing the residual tetrahydrofuran by vacuuming, a colorless viscous liquid organosilicon-modified polyurethane resin sealant is obtained.

[0016] The reaction conditions for step 2 are: stirring and polymerization reaction at 55-75°C for 1-1.5 hours.

[0017] The reaction conditions for step 3 are: heating to 80-100℃ and stirring for 1-2 hours for polymerization.

[0018] A method for using the aforementioned room-temperature self-crosslinking silicone-modified polyurethane sealant is characterized in that: for encapsulating solar photovoltaic cells, SPU and the catalyst dibutyltin dilaurate are mixed and stirred at room temperature. The uncured polymer is then dropped onto a cover glass using a pipette. A silicone-modified polyurethane film of uniform thickness is prepared using a spin coater at a speed of 1000–3000 rpm for 30–60 s. The cover glass coated with the silicone-modified polyurethane coating is then pressed onto the solar photovoltaic cell and allowed to stand for the encapsulation material to fully cure, thus obtaining the encapsulated solar photovoltaic cell.

[0019] The ratio of SPU to catalyst dibutyltin dilaurate is 3-5g SPU and 20-30mg catalyst dibutyltin dilaurate.

[0020] The solar photovoltaic cells include, but are not limited to, monocrystalline silicon solar cells, cadmium telluride thin-film cells, organic solar cells, dye-sensitized nanocells, or perovskite solar cells.

[0021] Beneficial effects

[0022] This invention proposes a room-temperature self-crosslinking silicone-modified polyurethane sealant and its preparation and application method. First, a silicone-modified polyurethane polymer is prepared. By controlling the ratio of silicone monomers to polyurethane raw materials, a room-temperature self-crosslinking polymer sealant with excellent sealing, adhesion, and mechanical strength is prepared. Then, the synthesized polymer sealant is coated onto a cover glass using a spin-coating device. The glass is then placed on the surface of a solar photovoltaic device, and the solar photovoltaic cell is encapsulated through rapid crosslinking and curing of the silicone-modified polyurethane resin at room temperature. This silicone-modified polyurethane encapsulant is transparent, resistant to moisture and heat, and has high toughness, meeting the requirements of high-quality and rapid production of solar photovoltaic devices, improving their service life, and is very suitable for the encapsulation process of commercial photovoltaic devices.

[0023] Compared with the prior art, the present invention has the following beneficial effects:

[0024] (1) Compared with existing polyvinyl butyral encapsulation materials, which suffer from high cost, complex processing technology, and excessively long vacuum lamination time, this silicone-modified polyurethane sealant possesses excellent transparency, resistance to yellowing, and resistance to ultraviolet radiation. The polyurethane crosslinking network in the polymer exhibits good sealing and mechanical properties, while maintaining excellent crosslinking solvent resistance and hydrophobicity, which can significantly improve the damp heat stability and operational stability of perovskite solar cells. Furthermore, this encapsulation material has a simple synthesis process, low cost, widely available raw materials, and convenient application.

[0025] (2) Compared with the damage to the perovskite layer caused by degassing vapor during UV curing and the vacuum high pressure environment during vacuum hot pressing, this silicone-modified polyurethane sealant can achieve cross-linking and curing at room temperature without the need for vacuum hot pressing equipment. The encapsulation process is simple, efficient and low cost.

[0026] A rapid encapsulation process for perovskite solar cell devices was achieved using silicone-modified polyurethane encapsulant. Application studies revealed that the efficiency loss of the encapsulated perovskite cells was ≤0.5%. Furthermore, the encapsulated devices maintained 93%–97% of their initial efficiency after 1000 hours of operation under maximum power point tracking at 50–60°C, while conventional encapsulation processes resulted in efficiency losses of 3%–5%, and the encapsulated devices only retained 80%–90% of their initial efficiency after 1000 hours of operation under maximum power point tracking at 50–60°C. This process demonstrates excellent commercial potential and will contribute to the further industrialization of perovskite photovoltaic devices. Attached Figure Description

[0027] Figure 1 This is a picture of a packaged perovskite solar cell.

[0028] Figure 2 This is a graph showing the changes in photoelectric conversion efficiency of perovskite solar cells before encapsulation and after using this silicone-modified polyurethane sealant.

[0029] Figure 3 This refers to the operational stability testing of perovskite solar cells before encapsulation and after using this silicone-modified polyurethane sealant. Detailed Implementation

[0030] The present invention will now be further described in conjunction with the embodiments and accompanying drawings:

[0031] The main steps of this invention, which describes a room-temperature self-crosslinking silicone-modified polyurethane sealant, are as follows:

[0032] Step 1, Preparation of polymer materials: The room temperature self-crosslinking silicone-modified polyurethane sealant is mainly prepared by the polymerization reaction of diisocyanate, polypropylene glycol and 3-(methacryloyloxy)propyltrimethoxysilane (5-10g), wherein the diisocyanate is preferably 4,4'-diphenylmethane diisocyanate (MDI, 5-10g) and the polypropylene glycol is preferably PPG-200 type polypropylene glycol (50-60g).

[0033] 4,4'-Diphenylmethane diisocyanate (MDI, 5–10 g) was dissolved in 50 mL of tetrahydrofuran at room temperature. Polypropylene glycol (PPG-200, 50–60 g) was added to the reaction system, and the mixture was stirred and polymerized at 55 °C for 1 h. Subsequently, 3-(methacryloyloxy)propyltrimethoxysilane (5–10 g) was added to the system, and the mixture was heated to 80 °C and stirred and polymerized for 1 h. Then, 0.5 mL of ethanol was added to the reaction system to terminate the reaction. After removing residual tetrahydrofuran under vacuum, a colorless, viscous liquid silicone-modified polyurethane resin (SPU) was obtained.

[0034] Step 2, Rapid Encapsulation Process: Mix 3-5g SPU and 20-30mg dibutyltin dilaurate catalyst in a glass bottle. Stir at room temperature for 5-10 minutes. Then, use a pipette to drop 0.3-0.6mL of the uncured polymer onto the cover glass. Prepare a uniform silicone-modified polyurethane film using a spin coater at 1000-3000 rpm for 30 seconds. Press the cover glass coated with the silicone-modified polyurethane onto the solar photovoltaic cell and let it stand for 15-30 minutes. Allow the encapsulation material to fully cure to obtain the encapsulated solar photovoltaic cell.

[0035] Example 1:

[0036] 4,4'-diphenylmethane diisocyanate (MDI, 5 g) was dissolved in 50 mL of tetrahydrofuran at room temperature. Polypropylene glycol (PPG-200, 60 g) was added to the reaction system, and the mixture was stirred and polymerized at 55 °C for 1 h. Subsequently, 3-(methacryloyloxy)propyltrimethoxysilane (10 g) was added to the system, and the mixture was heated to 80 °C and stirred and polymerized for 1 h. Then, 0.5 mL of ethanol was added to the reaction system to terminate the reaction. After removing residual tetrahydrofuran under vacuum, a colorless, viscous liquid silicone-modified polyurethane material [SPU] was obtained.

[0037] 3g of SPU and 25mg of dibutyltin dilaurate catalyst were mixed in a glass bottle and stirred at room temperature for 10 min. Then, 0.6 mL of the uncured polymer was dropped onto the cover glass using a pipette. A uniform silicone-modified polyurethane film was prepared using a spin coater at 2000 rpm for 30 s. The cover glass with the silicone-modified polyurethane coating was then pressed onto the perovskite solar cell and allowed to stand for 15 min. After the encapsulation material had completely cured, the encapsulated perovskite solar cell was obtained.

[0038] Test results: The device efficiency was 22.12% before packaging and 22.00% after packaging, with an efficiency decrease of 0.5%. The packaged device maintained 94.1% of its initial efficiency after 1000 hours of operation at maximum power point tracking at 50-60℃.

[0039] Example 2:

[0040] 4,4'-diphenylmethane diisocyanate (MDI, 8 g) was dissolved in 50 mL of tetrahydrofuran at room temperature. Polypropylene glycol (PPG-200, 55 g) was added to the reaction system, and the mixture was stirred and polymerized at 55 °C for 1 h. Subsequently, 3-(methacryloyloxy)propyltrimethoxysilane (5 g) was added to the system, and the mixture was heated to 80 °C and stirred and polymerized for 1 h. Then, 0.5 mL of ethanol was added to the reaction system to terminate the reaction. After removing residual tetrahydrofuran under vacuum, a colorless, viscous liquid silicone-modified polyurethane material [SPU] was obtained.

[0041] 4g of SPU and 20mg of dibutyltin dilaurate catalyst were mixed in a glass bottle and stirred at room temperature for 8 minutes. Then, 0.4mL of the uncured polymer was dropped onto the cover glass using a pipette. A uniform silicone-modified polyurethane film was prepared using a spin coater at 3000 rpm for 30 seconds. The cover glass with the silicone-modified polyurethane coating was then pressed onto the perovskite solar cell and allowed to stand for 15 minutes. After the encapsulation material had completely cured, the encapsulated perovskite solar cell was obtained.

[0042] Test results: The device efficiency was 22.34% before packaging and 22.27% after packaging, with an efficiency decrease of 0.3%. The packaged device maintained 94.9% of its initial efficiency after 1000 hours of operation at maximum power point tracking at 50-60℃.

[0043] Example 3:

[0044] 4,4'-Diphenylmethane diisocyanate (MDI, 10 g) was dissolved in 50 mL of tetrahydrofuran at room temperature. Polypropylene glycol (PPG-200, 50 g) was added to the reaction system, and the mixture was stirred and polymerized at 55 °C for 1 h. Subsequently, 3-(methacryloyloxy)propyltrimethoxysilane (8 g) was added to the system, and the mixture was heated to 80 °C and stirred and polymerized for 1 h. Then, 0.5 mL of ethanol was added to the reaction system to terminate the reaction. After removing residual tetrahydrofuran under vacuum, a colorless, viscous liquid silicone-modified polyurethane material [SPU] was obtained.

[0045] 5g of SPU and 30mg of dibutyltin dilaurate catalyst were mixed in a glass bottle and stirred at room temperature for 5 minutes. Then, 0.5mL of the uncured polymer was dropped onto the cover glass using a pipette. A uniform silicone-modified polyurethane film was prepared using a spin coater at 1000 rpm for 30 seconds. The cover glass with the silicone-modified polyurethane coating was then pressed onto the perovskite solar cell and allowed to stand for 20 minutes. After the encapsulation material had completely cured, the encapsulated perovskite solar cell was obtained.

[0046] Test results: The device efficiency was 22.01% before packaging and 21.92% after packaging, with an efficiency decrease of 0.4%. The packaged device maintained 95.1% of its initial efficiency after 1000 hours of operation at maximum power point tracking at 50-60℃.

[0047] Example Control Group:

[0048] In a nitrogen-filled glove box, conductive tape is tightly adhered to the electrodes of the perovskite solar cell. Then, a clean, contaminant-free cover glass is directly pressed onto the surface of the perovskite solar cell and left to stand for 5 minutes. Once the contact between the cover glass and the perovskite device surface has stabilized, a perovskite solar cell without encapsulant protection is obtained.

[0049] Figure 1 The metal electrode of the encapsulated perovskite solar cell shows that the successful encapsulation of perovskite solar cells can be achieved based on the silicone-modified polyurethane sealant.

[0050] Figure 2 The encapsulation of perovskite devices using silicone-modified polyurethane sealant showed no significant performance degradation before and after encapsulation, indicating that silicone-modified polyurethane sealant can achieve efficient and non-destructive encapsulation of perovskite devices.

[0051] Figure 3Operational stability tests were conducted on unencapsulated and silicone-modified polyurethane (PMPC)-encapsulated perovskite solar cells. The efficiency of the unencapsulated perovskite device decreased to 60% of the initial efficiency after 500 hours, while the perovskite solar cell encapsulated with PMPC maintained 94% of the initial efficiency after 1000 hours of operation. This indicates that encapsulation with PMPC can achieve excellent operational stability of perovskite devices.

[0052] Although the present invention has been described in detail through the preferred embodiments above, it should be understood that the above description should not be considered as a limitation of the present invention. Various modifications and substitutions to the present invention will be apparent to those skilled in the art after reading the above description. Therefore, the scope of protection of the present invention should be defined by the appended claims.

Claims

1. A method for using a room-temperature self-crosslinking silicone-modified polyurethane sealant, characterized in that, include: 5 g of 4,4'-diphenylmethane diisocyanate was dissolved in 50 mL of tetrahydrofuran at room temperature. 60 g of polypropylene glycol was added to the reaction system, and the mixture was stirred and polymerized at 55 °C for 1 h. Then, 10 g of 3-(methacryloyloxy)propyltrimethoxysilane was added to the system, and the mixture was heated to 80 °C and stirred and polymerized for 1 h. Finally, 0.5 mL of ethanol was added to the reaction system to terminate the reaction. After removing the residual tetrahydrofuran by vacuum, a colorless viscous liquid silicone-modified polyurethane material SPU was obtained. 3 g of SPU and 25 mg of dibutyltin dilaurate catalyst were mixed in a glass bottle and stirred at room temperature for 10 min. Then, 0.6 mL of the uncured polymer was dropped onto the cover glass using a pipette. A uniform silicone-modified polyurethane film was prepared using a spin coater at 2000 rpm for 30 s. The cover glass coated with silicone-modified polyurethane was then pressed onto the perovskite solar cell and left to stand for 15 min to allow the encapsulation material to fully cure, thus obtaining the encapsulated perovskite solar cell.

2. A method for using a room-temperature self-crosslinking silicone-modified polyurethane sealant, characterized in that, include: 8 g of 4,4'-diphenylmethane diisocyanate was dissolved in 50 mL of tetrahydrofuran at room temperature. 55 g of polypropylene glycol was added to the reaction system, and the mixture was stirred and polymerized at 55 °C for 1 h. Then, 5 g of 3-(methacryloyloxy)propyltrimethoxysilane was added to the system, and the mixture was heated to 80 °C and stirred and polymerized for 1 h. Finally, 0.5 mL of ethanol was added to the reaction system to terminate the reaction. After removing the residual tetrahydrofuran by vacuum, a colorless viscous liquid silicone-modified polyurethane material SPU was obtained. 4 g of SPU and 20 mg of dibutyltin dilaurate catalyst were mixed in a glass bottle and stirred at room temperature for 8 min. Then, 0.4 mL of the uncured polymer was dropped onto the cover glass using a pipette. A uniform silicone-modified polyurethane film was prepared using a spin coater at 3000 rpm for 30 s. The cover glass coated with silicone-modified polyurethane was then pressed onto the perovskite solar cell and left to stand for 15 min to allow the encapsulation material to fully cure, thus obtaining the encapsulated perovskite solar cell.

3. A method for using a room-temperature self-crosslinking silicone-modified polyurethane sealant, characterized in that, include: 10 g of 4,4'-diphenylmethane diisocyanate was dissolved in 50 mL of tetrahydrofuran at room temperature. 50 g of polypropylene glycol was added to the reaction system, and the mixture was stirred and polymerized at 55 °C for 1 h. Then, 8 g of 3-(methacryloyloxy)propyltrimethoxysilane was added to the system, and the mixture was heated to 80 °C and stirred and polymerized for 1 h. Finally, 0.5 mL of ethanol was added to the reaction system to terminate the reaction. After removing the residual tetrahydrofuran by vacuum, a colorless viscous liquid silicone-modified polyurethane material SPU was obtained. 5 g of SPU and 30 mg of dibutyltin dilaurate catalyst were mixed in a glass bottle and stirred at room temperature for 5 min. Then, 0.5 mL of the uncured polymer was dropped onto the cover glass using a pipette. A uniform silicone-modified polyurethane film was prepared using a spin coater at 1000 rpm for 30 s. The cover glass with the silicone-modified polyurethane coating was then pressed onto the perovskite solar cell and allowed to stand for 20 min to allow the encapsulation material to fully cure, thus obtaining the encapsulated perovskite solar cell.

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