Radiative cooling film and methods of making and using the same

Abstract

The application belongs to the technical field of batteries, and provides a radiation cooling film and a preparation method and application thereof.The radiation cooling film comprises a base body and composite particles dispersed in the base body; the base body comprises a resin material; the composite particles comprise an ultraviolet absorber and a middle infrared emission material covering the ultraviolet absorber.The application reduces the refractive index of the resin material by matching the middle infrared emission material with the resin material, realizes the effect of reducing reflection, and through the covering of the middle infrared emission material on the ultraviolet absorber, the thin film can absorb ultraviolet light, and through the middle infrared emission characteristics of the middle infrared emission material and the resin material, the temperature of the assembly can be reduced, and the middle infrared emission material can also improve the stability of the coated ultraviolet absorber.The radiation cooling film can realize multiple effects of ultraviolet absorption, visible light transmittance increase and middle infrared radiation cooling.

Description

Technical Field

[0001] This invention belongs to the field of thin film manufacturing and battery technology, and relates to a radiation cooling thin film, its preparation method and application. Background Technology

[0002] In recent years, solar energy, as a green and environmentally friendly emerging energy source, has become increasingly important, and the application and development of solar cells have made significant progress. From small solar cell calculators in daily life to large-scale photovoltaic integrated buildings, solar cells have penetrated every corner of people's lives. Depending on the materials used, solar cells can be divided into various types, including crystalline silicon cells, copper indium gallium selenide (CIGS) cells, cadmium telluride (CdTe) cells, and perovskite cells.

[0003] Crystalline silicon solar cells have become the most widely used type of solar cell on the market due to their high absorption bandgap, high conversion efficiency, and relatively low cost. However, crystalline silicon solar cells also have some drawbacks in application. For example, when the energy absorbed by the cell exceeds its bandgap, the excess energy is released as heat, causing the cell temperature to rise. When operating at an ambient temperature of 35°C, the cell temperature can even exceed 60°C, which not only shortens the cell's lifespan but also reduces its power generation efficiency. Studies have shown that for every 1K increase in cell temperature, its relative efficiency decreases by approximately 0.45%.

[0004] To reduce the operating temperature of solar cells and improve their stability and power generation efficiency, researchers have begun exploring various methods. Among them, radiative cooling technology has attracted much attention due to its ability to reduce the temperature of solar cells over a long period without power consumption. For example, CN112086522B discloses a radiatively cooled solar cell module. By setting a metal reflective layer on the bottom surface and alternating stacking structures of visible-near-infrared high-transmittance / mid-infrared absorption film and visible-near-infrared high-transmittance / mid-infrared antireflection film on the top surface, it achieves 100% quantum efficiency in the range of 0.38–1.1 μm, while reflecting or transmitting in other wavelength bands. However, the complex process and the use of a metal reflective substrate without radiative cooling effect limit its application. CN115799372A discloses a method for preparing a passive solar cell cooling film, which forms a passive cooling structure by evaporating a SiO2 film on a P-type single-sided polished silicon substrate. This method is relatively simple and low-cost, but it has high reflectivity in the visible light band and weak cooling ability, limiting its use.

[0005] In conclusion, further research and development of passive radiative cooling technology for batteries is still needed. By exploring simpler, more convenient, and lower-cost solutions to achieve superior mid-infrared radiation, battery temperature can be reduced more effectively through radiative cooling, thus driving the further development of future solar cell technology. Summary of the Invention

[0006] In view of the problems existing in the prior art, the purpose of this invention is to provide a radiation cooling film, its preparation method, and its uses. The radiation cooling film includes a matrix and composite particles dispersed in the matrix; the matrix includes a resin material; the composite particles include an ultraviolet absorber and a mid-infrared emitting material coating the ultraviolet absorber. This invention reduces the refractive index of the resin material by combining the mid-infrared emitting material with the resin material, thereby reducing reflection. Furthermore, by coating the ultraviolet absorber with the mid-infrared emitting material, the film can absorb ultraviolet light, and the mid-infrared emission characteristics of the mid-infrared emitting material and the resin material can reduce the component temperature. Simultaneously, the mid-infrared emitting material can also improve the stability of the coated ultraviolet absorber. Therefore, the radiation cooling film can achieve multiple effects: ultraviolet absorption, visible light anti-reflection, and mid-infrared radiation cooling.

[0007] To achieve this objective, the present invention adopts the following technical solution:

[0008] In a first aspect, the present invention provides a radiation cooling film comprising a matrix and composite particles dispersed in the matrix; the matrix comprising a resin material; and the composite particles comprising an ultraviolet absorber and a mid-infrared emitting material mixed and coated with each other.

[0009] This invention utilizes an ultraviolet absorber to absorb ultraviolet light and convert it into heat. This heat is then used for radiative cooling through a mid-infrared emitting material. While achieving radiative cooling, the mid-infrared emitting material's coating of the ultraviolet absorber provides support, improving its stability and lifespan. Furthermore, mid-infrared emission reduces the refractive index of the resin material. The resin material, as the matrix, exhibits excellent light transmittance in the visible light region and good emissivity in the mid-infrared region. Therefore, it can synergistically enhance the radiative cooling effect with the mid-infrared emitting material, effectively reducing the battery temperature.

[0010] It should be noted that the mutual mixing and coating refers to the formation of a physical mixture and a coating state of ultraviolet absorber and mid-infrared emitting material, such as particles of mid-infrared emitting material coated with ultraviolet absorber (external load), and / or particles of ultraviolet absorber coated with mid-infrared emitting material (external load), and / or particles of ultraviolet absorber loaded inside the mid-infrared emitting material (such as hollow and pore).

[0011] The following are preferred technical solutions of the present invention, but are not intended to limit the technical solutions provided by the present invention. The technical objectives and beneficial effects of the present invention can be better achieved and realized through the following technical solutions.

[0012] As a preferred technical solution of the present invention, the resin material includes at least one of TPX (poly4-methylpentene), PMMA (polymethyl methacrylate), PVF (polyvinyl fluoride), PVC (polyvinyl chloride), PDMS (polydimethylsiloxane), PET (polyethylene terephthalate) or LDPE (low-density polyethylene).

[0013] Preferably, the ultraviolet absorber includes at least one of benzophenone compounds, salicylic acid compounds, triazine compounds, lignin compounds, benzotriazole compounds, zinc oxide materials, titanium oxide materials, and quantum dot materials.

[0014] As a preferred embodiment of the present invention, the mid-infrared emitting material includes hollow microspheres and / or porous materials.

[0015] Preferably, the hollow microspheres have a particle size of 20–200 nm, such as 20 nm, 30 nm, 50 nm, 70 nm, 80 nm, 90 nm, 100 nm, 120 nm, 140 nm, 160 nm, 180 nm, or 200 nm, and a wall thickness of 10–50 nm, such as 10 nm, 15 nm, 20 nm, 25 nm, 30 nm, 35 nm, 40 nm, 45 nm, or 50 nm, but are not limited to the listed values; other unlisted values ​​within the above range are also applicable.

[0016] In this invention, hollow microspheres are used to allow the ultraviolet absorber to penetrate the interior for loading. However, if the particle size of the hollow microspheres is too small, the ultraviolet absorbing material cannot effectively penetrate the interior; if the particle size is too large, it will affect sunlight transmission. If the wall thickness of the hollow microspheres is too small, it will reduce mechanical strength, easily causing a decrease in the mechanical strength of the radiative cooling film. Conversely, if the wall thickness of the hollow microspheres is too large, it will crowd out the hollow area inside, preventing the ultraviolet absorbing material from penetrating the interior or reducing the internal loading capacity. Furthermore, the hollow structure of the hollow microspheres can reduce the refractive index.

[0017] Preferably, the hollow microspheres comprise at least one of silicon dioxide, aluminum oxide, silicon carbide, silicon nitride, or titanium dioxide.

[0018] Preferably, the porous material has a particle size of 20–200 nm, such as 20 nm, 30 nm, 50 nm, 70 nm, 80 nm, 90 nm, 100 nm, 120 nm, 140 nm, 160 nm, 180 nm, or 200 nm, and a porosity of 30%–70%, such as 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, or 70%, and a pore size of 2–10 nm, such as 2 nm, 3 nm, 4 nm, 5 nm, 6 nm, 7 nm, 8 nm, 9 nm, or 10 nm, but is not limited to the listed values; other unlisted values ​​within the above range are also applicable.

[0019] In this invention, if the porosity of the selected porous material is too small, it will affect the loading of the ultraviolet absorber, resulting in a decrease in the ultraviolet absorption effect. If the porosity is too high, it will lead to a decrease in mechanical strength. If the pore size is too small, the ultraviolet absorber cannot effectively enter the pores. If the pore size is too large, it will lead to a decrease in mechanical strength. Compared with hollow microspheres, hollow microspheres help to achieve a lower refractive index, while porous materials have a larger specific surface area, which helps to achieve a higher coating or loading of ultraviolet absorber.

[0020] Preferably, the porous material includes at least one of molecular sieve materials, polymer materials, or MOF materials. MOF stands for Metal-Organic Framework, which is a novel type of crystalline porous material with a periodic network structure.

[0021] Preferably, the molecular sieve material includes MCM41 and / or SBA15.

[0022] As a preferred embodiment of the present invention, in the composite particles, the mass ratio of the ultraviolet absorber to the mid-infrared emitting material is 1:(1-20), for example 1:1, 1:1.3, 1:1.5, 1:1.8, 1:2, 1:2.3, 1:2.5, 1:2.8, 1:3, 1:3.3, 1:3.5, 1:3.8, 1:4, 1:4.3, 1:4.5, 1:4.8, 1 The range of values ​​is 5, 1:5.3, 1:5.5, 1:5.8, 1:6, 1:6.3, 1:6.5, 1:6.8, 1:7, 1:8, 1:9, 1:10, 1:11, 1:12, 1:13, 1:14, 1:15, 1:16, 1:17, 1:18, 1:19, or 1:20, etc., but is not limited to the listed values. Other unlisted values ​​within the above range also apply.

[0023] Preferably, in the radiation cooling film, the mass ratio of the composite particles to the matrix is ​​1:(50-400), for example 1:50, 1:60, 1:70, 1:80, 1:90, 1:100, 1:110, 1:120, 1:130, 1:140, 1:150, 1:160, 1:165, 1:170, 1:175, 1:180, 1:185, 1:19. 0, 1:195, 1:200, 1:205, 1:210, 1:215, 1:220, 1:225, 1:230, 1:235, 1:240, 1:260, 1:280, 1:300, 1:320, 1:340, 1:360, 1:380, or 1:400, etc., but not limited to the listed values; other unlisted values ​​within the above range also apply.

[0024] Preferably, the thickness of the radiation cooling film is 10 to 1000 μm, such as 10 μm, 30 μm, 50 μm, 80 μm, 100 μm, 200 μm, 300 μm, 400 μm, 500 μm, 600 μm, 700 μm, 800 μm, 900 μm or 1000 μm, but it is not limited to the values ​​listed above. Other unlisted values ​​within the above range are also applicable.

[0025] As a preferred embodiment of the present invention, a release film is provided on one side of the radiation cooling film.

[0026] Preferably, the release film comprises a PET film.

[0027] In this invention, the radiation cooling film can be pre-formed on the release film as needed. When it is needed, the side away from the release film is attached to the target surface in the form of an integral film material, and then the release film is peeled off.

[0028] In a second aspect, the present invention provides a method for preparing the radiation cooling film described in the first aspect, the method comprising: mixing hollow microspheres, an ultraviolet absorber and a solvent, separating the solid and liquid and drying them to obtain composite particles; mixing the composite particles with a resin material to obtain a slurry; coating the slurry and curing it to obtain a radiation cooling film.

[0029] As a preferred embodiment of the present invention, the solvent includes ethyl acetate.

[0030] Preferably, the ultraviolet absorber is first mixed with the solvent to obtain a mixed solution, and then the hollow microspheres are mixed with the mixed solution.

[0031] Preferably, the solid-liquid separation method includes centrifugation; the centrifugation speed is 7000-9000 rpm, such as 7000 rpm, 7300 rpm, 7500 rpm, 7800 rpm, 8000 rpm, 8300 rpm, 8500 rpm, 8800 rpm, or 9000 rpm, etc., and the time is 3-7 min, such as 3 min, 3.5 min, 4 min, 4.5 min, 5 min, 5.5 min, 6 min, 6.5 min, or 7 min, etc., but is not limited to the listed values, and other unlisted values ​​within the above range are also applicable.

[0032] Preferably, the solid-liquid separation is followed by cleaning, and the cleaning method includes rinsing with ethanol at least twice.

[0033] Preferably, the drying temperature is 70-90℃, such as 70℃, 73℃, 75℃, 78℃, 80℃, 83℃, 85℃, 88℃ or 90℃, and the time is 5-20min, such as 5min, 6min, 7min, 8min, 9min, 10min, 12min, 14min, 15min, 16min, 7min, 18min, 19min or 20min, but it is not limited to the listed values. Other unlisted values ​​within the above range are also applicable.

[0034] As a preferred technical solution of the present invention, after the slurry is coated, a microstructure template is covered on the wet coating layer, and after curing, the microstructure template is removed to obtain a radiation cooling film with surface microstructure.

[0035] Preferably, the microstructure template has an array of microprotrusions, the shape of which includes at least one of hemispherical, cylindrical, pyramidal, or prismatic shapes.

[0036] This invention provides a microstructure on the surface of the radiation-cooled film, thereby reducing reflection and mitigating the power loss caused by the addition of ultraviolet absorbers.

[0037] Preferably, the curing method includes at least one of heat curing, room temperature curing, or ultraviolet curing.

[0038] Preferably, the thermosetting temperature is 80-90°C, such as 80°C, 82°C, 84°C, 86°C, 88°C, or 90°C, and the time is 12-36 hours, such as 12 hours, 14 hours, 16 hours, 18 hours, 20 hours, 22 hours, 24 hours, 26 hours, 28 hours, 30 hours, 32 hours, 34 hours, or 36 hours.

[0039] Preferably, the coating is applied to a release film, such that one side of the resulting radiation-cooled film is coated with the release film.

[0040] Thirdly, the present invention provides a solar cell, wherein the solar cell is provided with the radiation cooling film described in the first aspect, or with the radiation cooling film obtained by the preparation method described in the second aspect.

[0041] In this invention, the radiation-cooling film is used in a single-layer film formation process on the battery, eliminating the need for complex multilayer film structures, yet still achieving excellent ultraviolet absorption, visible transmission, and mid-infrared radiation cooling effects. Therefore, the preparation method of the radiation-cooling film and its application in the battery are simpler, more convenient, and cost-effective.

[0042] As a preferred embodiment of the present invention, the radiation cooling film is disposed on the surface of the front panel of the light-receiving surface of the solar cell.

[0043] Preferably, the battery includes at least one of monocrystalline silicon battery, polycrystalline silicon battery, copper indium gallium selenide battery, cadmium telluride battery, gallium arsenide battery or perovskite battery.

[0044] Preferably, the battery includes a single-glass module, a double-glass module, or a flexible module.

[0045] Compared with existing technical solutions, the present invention has at least the following beneficial effects:

[0046] This invention provides a radiation-cooling thin film. This film reduces reflection by combining a mid-infrared emitting material with a resin material to lower the refractive index of the resin material. Furthermore, by coating an ultraviolet absorber with the mid-infrared emitting material, the film can absorb ultraviolet light while simultaneously reducing the module temperature through the mid-infrared emission characteristics of both the mid-infrared emitting material and the resin material. Additionally, the mid-infrared emitting material improves the stability of the coated ultraviolet absorber. Applying this radiation-cooling thin film in solar cells, a single-layer film structure can achieve multiple effects including excellent ultraviolet absorption, visible light anti-reflection, and mid-infrared radiation cooling. Detailed Implementation

[0047] The technical solution of the present invention will be further illustrated below through specific embodiments.

[0048] Those skilled in the art will understand that the embodiments described are merely illustrative of the invention and should not be construed as limiting the invention.

[0049] Example 1

[0050] This embodiment provides a radiation cooling film, which includes a matrix and composite particles dispersed in the matrix; the matrix includes a resin material; the composite particles include an ultraviolet absorber and a mid-infrared emitting material coating the ultraviolet absorber; the resin material is PDMS, the ultraviolet absorber is bis(ethylhexyloxyphenol)methoxytriazine, and the mid-infrared emitting material is hollow microspheres, which are hollow silica; the mass ratio of the ultraviolet absorber to the mid-infrared emitting material is 1:5; in the radiation cooling film, the mass ratio of the composite particles to the matrix is ​​1:200, and the thickness of the radiation cooling film is 200 μm;

[0051] The method for preparing the radiation-cooled thin film includes:

[0052] S1. Take 1g of bis(ethylhexyloxyphenol) methoxytriazine, add 20mL of ethyl acetate and stir until completely dissolved to obtain a mixed solution;

[0053] S2. Add 5g of hollow silica powder to the above mixed solution while stirring until the powder is evenly dispersed in the mixed solution. Then continue stirring for 8 hours to ensure thorough mixing.

[0054] S3. Centrifuge the solution obtained in step S2 at 8000 rpm for 5 min, remove the supernatant, add 20 mL of ethanol to wash twice, and then place the solid in a vacuum drying oven at 85 °C to dry under vacuum to obtain composite particles.

[0055] S4. Mix the obtained composite particles with PDMS, control the mass ratio to 1:200, stir evenly and degas to obtain a slurry. Use the slurry to coat the target surface, and then cover the wet coating layer with a microstructure template. The microstructure template has an array of microprotrusions arranged in a pyramid shape. Then, let it stand at 85°C for 24 hours for thermosetting. Remove the microstructure template to obtain the radiation cooling film.

[0056] Example 2

[0057] This embodiment provides a radiation cooling film in which the resin material is replaced by TPX instead of PDMS, the ultraviolet absorber is replaced by 2-(2'-hydroxy-5'-methylphenyl)benzotriazole instead of bis(ethylhexyloxyphenol)methoxybenzidine, and the hollow microspheres are replaced by hollow silica instead of hollow alumina. Furthermore, in the preparation method of the radiation cooling film, the shape of the micro-protrusions in the microstructure template is replaced by a prism shape instead of a pyramid shape. Apart from the above, the other conditions are exactly the same as in Example 1.

[0058] Example 3

[0059] This embodiment provides a radiation cooling film in which the mid-infrared emitting material is replaced by a porous material, and the porous material is a molecular sieve material MCM41. Except for the above, the other conditions are exactly the same as in Embodiment 1.

[0060] Example 4

[0061] This embodiment provides a radiation cooling film. In the preparation method of the radiation cooling film, the microstructure template is not used. After coating the slurry, it is directly cured. Except for the above, the other conditions are exactly the same as those in Embodiment 1.

[0062] Example 5

[0063] This embodiment provides a radiation cooling film in which the mass ratio of the ultraviolet absorber to the mid-infrared emitting material is adjusted from 1:5 to 1:0.5. Apart from the above, the other conditions are exactly the same as in Embodiment 1.

[0064] Example 6

[0065] This embodiment provides a radiation cooling film in which the mass ratio of the ultraviolet absorber to the mid-infrared emitting material is adjusted from 1:5 to 1:1. Except for the above, the other conditions are exactly the same as in Embodiment 1.

[0066] Example 7

[0067] This embodiment provides a radiation cooling film in which the mass ratio of the ultraviolet absorber to the mid-infrared emitting material is adjusted from 1:5 to 1:20. Except for the above, the other conditions are exactly the same as in Embodiment 1.

[0068] Example 8

[0069] This embodiment provides a radiation cooling film in which the mass ratio of the ultraviolet absorber to the mid-infrared emitting material is adjusted from 1:5 to 1:50. Except for the above, the other conditions are exactly the same as in Embodiment 1.

[0070] Example 9

[0071] This embodiment provides a radiation cooling film in which the mass ratio of the composite particles to the matrix is ​​adjusted from 1:200 to 1:20. Except for the above, the other conditions are exactly the same as in Embodiment 1.

[0072] Example 10

[0073] This embodiment provides a radiation cooling film in which the mass ratio of the composite particles to the matrix is ​​adjusted from 1:200 to 1:50. Except for the above, the other conditions are exactly the same as in Embodiment 1.

[0074] Example 11

[0075] This embodiment provides a radiation cooling film in which the mass ratio of the composite particles to the matrix is ​​adjusted from 1:200 to 1:400. Except for the above, the other conditions are exactly the same as in Embodiment 1.

[0076] Example 12

[0077] This embodiment provides a radiation cooling film in which the mass ratio of the composite particles to the matrix is ​​adjusted from 1:200 to 1:800. Except for the above, the other conditions are exactly the same as in Embodiment 1.

[0078] Example 13

[0079] This embodiment provides a radiation cooling film in which the thickness of the radiation cooling film is adjusted from 200 μm to 10 μm. Apart from the above, the other conditions are exactly the same as in Embodiment 1.

[0080] Example 14

[0081] This embodiment provides a radiation cooling film in which the thickness of the radiation cooling film is adjusted from 200 μm to 50 μm. Apart from the above, the other conditions are exactly the same as in Embodiment 1.

[0082] Example 15

[0083] This embodiment provides a radiation cooling film in which the thickness of the radiation cooling film is adjusted from 200 μm to 500 μm. Apart from the above, the other conditions are exactly the same as in Embodiment 1.

[0084] Example 16

[0085] This embodiment provides a radiation cooling film in which the thickness of the radiation cooling film is adjusted from 200 μm to 1000 μm. Apart from the above, the other conditions are exactly the same as in Embodiment 1.

[0086] Comparative Example 1

[0087] This comparative example provides a radiation cooling film that does not contain the ultraviolet absorber, and all other conditions are exactly the same as in Example 1.

[0088] Comparative Example 2

[0089] This comparative example provides a radiation cooling film that does not contain the mid-infrared emitting material. Except for the above, the other conditions are exactly the same as in Example 1.

[0090] Comparative Example 3

[0091] This comparative example provides a radiation cooling film that does not contain the ultraviolet absorber and mid-infrared emitting material. Except for the above, the other conditions are exactly the same as in Example 1.

[0092] Characterization and Testing

[0093] I. In Examples 1 to 16 and Comparative Examples 1 to 3, one side surface of a blank glass was used as the target surface, and a single-layer radiation cooling film was formed on the blank glass. The resulting film was subjected to absorptivity testing, transmittance testing, and UV15 aging testing using a UV-Vis device; the UV15 aging test involved irradiating the film with a 200W UV lamp for 750 hours, followed by testing the transmittance after irradiation.

[0094] II. In Examples 1 to 16 and Comparative Examples 1 to 3, the outer surface of the glass front plate of the light-receiving surface of the double-glass monocrystalline silicon cell was used as the target surface, and a single layer of radiation cooling film was formed on it to obtain each solar cell; a double-glass monocrystalline silicon cell without the radiation cooling film was taken as a control group; each cell was placed in an environment with an ambient temperature of 35°C and a wind speed of 1 m / s, and the solar cell was irradiated. After the cell stabilized, its temperature was tested.

[0095] The results are recorded in Table 1.

[0096] Table 1

[0097]

[0098]

[0099] As can be seen from Table 1:

[0100] (1) Samples with added ultraviolet absorbing materials and mid-infrared emitting materials exhibited excellent ultraviolet absorption and radiation cooling capabilities. At the same time, when the mid-infrared emitting material used has a hollow structure, it can effectively reduce the refractive index of the film and significantly increase the transmittance in the visible light region.

[0101] (2) When the ratio of ultraviolet absorbing material to mid-infrared emitting material is between 1:(1~20), ultraviolet absorption and transmittance / radiative heat dissipation can maintain a good balance. When the proportion of ultraviolet absorbing material is too high, the ultraviolet absorption rate will not increase significantly. Instead, the cost will increase due to the large amount of ultraviolet absorbing material used, and the transmittance will decrease slightly, resulting in a decrease in battery efficiency. For example, in Example 5, because the proportion of ultraviolet absorbent was increased, but the hollow microspheres were not adjusted, the amount entering the silica hollow microspheres will not increase significantly. Instead, it will cause material waste. At the same time, there will be ultraviolet absorbent residues that are not loaded / coated with the microspheres. Although this will slightly improve the performance of radiative heat dissipation, the transmittance will decrease. However, since it has been cleaned, the amount of residue will not be much, and the impact on the transmittance is relatively minor. In summary, when there is too much ultraviolet absorbing material, the absorption capacity of the radiative cooling film will not increase significantly, so the radiative heat dissipation capacity will not change much, but the material cost will increase significantly and the transmittance will decrease. When the proportion of ultraviolet absorbing material is too low, the ultraviolet absorption will decrease significantly.

[0102] (3) When the ratio of mid-infrared emitting material to resin material is between 1: (50-400), ultraviolet absorption, transmittance and radiative heat dissipation can maintain a good balance. When the ratio of mid-infrared emitting material is too high, it will affect the transmittance of the film to visible light. When the ratio of mid-infrared emitting material is too low, ultraviolet absorption will decrease significantly and radiative heat dissipation efficiency will decrease to a certain extent.

[0103] (4) When the thickness of the film is preferably between 50 and 500 μm, the ultraviolet absorption and radiation heat dissipation can maintain a good balance. When the film thickness is too low, the efficiency of ultraviolet absorption and radiation heat dissipation will decrease significantly. When the film thickness is too high, the visible light transmittance of the film will decrease to a certain extent.

[0104] In summary, the resin material and mid-infrared emitting material (such as hollow microspheres) used in this invention both possess high emissivity in the mid-infrared region, enabling daytime radiative cooling and improving the lifespan and power generation efficiency of solar cells. By coating the ultraviolet absorber with the mid-infrared emitting material, the heat emitted by the ultraviolet absorber is transferred and radiated, which is beneficial for extending the lifespan of the ultraviolet absorber. Simultaneously, the mid-infrared emitting material can bond with the ultraviolet absorber, anchoring it to the mid-infrared emitting material and inhibiting its migration. After coating, it facilitates the dispersion of the ultraviolet absorber in the resin material, expanding its application range. The resin material, mid-infrared emitting material (such as hollow microspheres), and the microstructure of the radiative cooling film surface used in this invention are all designed based on reducing the refractive index, which helps to further improve the visible light utilization rate of solar cells.

[0105] For solar cells using the radiation-cooled thin film provided by this invention, ultraviolet absorption, visible light anti-reflection, and mid-infrared radiation cooling functions can be integrated through a single layer. The process is simple, the effect is good, and it is easy to mass-produce. The radiation-cooled thin film manages the heat generated by the ultraviolet absorber, which helps improve the stability of the ultraviolet absorbing material. Simultaneously, it is equivalent to placing the ultraviolet absorber on the outer layer of the cell, which is more convenient for replacement and reduces the module scrap rate compared to existing technologies that place the ultraviolet absorber in the encapsulation film. Finally, by setting the radiation-cooled thin film, the degradation of cell life and power caused by ultraviolet light and heat is effectively avoided, while the anti-reflection in the visible light region further improves cell efficiency.

[0106] The preferred embodiments of the present invention have been described in detail above. However, the present invention is not limited to the specific details in the above embodiments. Within the scope of the technical concept of the present invention, various simple modifications can be made to the technical solution of the present invention, and these simple modifications all fall within the protection scope of the present invention.

[0107] It should also be noted that the various specific technical features described in the above specific embodiments can be combined in any suitable manner without contradiction. In order to avoid unnecessary repetition, the present invention will not describe the various possible combinations separately.

[0108] Furthermore, various different embodiments of the present invention can be combined in any way, as long as they do not violate the spirit of the present invention, they should also be regarded as the content disclosed by the present invention.

Claims

1. A radiation-cooled thin film, characterized in that, It includes a matrix and composite particles dispersed in the matrix; the matrix includes a resin material; the composite particles include a mixture of ultraviolet absorbers and mid-infrared emitting materials.

2. The radiation cooling film according to claim 1, characterized in that, The resin material includes at least one of TPX, PMMA, PVF, PVC, PDMS, PET, or LDPE; Preferably, the ultraviolet absorber includes at least one of benzophenone compounds, salicylic acid compounds, triazine compounds, lignin compounds, benzotriazole compounds, zinc oxide materials, titanium oxide materials, and quantum dot materials.

3. The radiation cooling film according to claim 1 or 2, characterized in that, The mid-infrared emitting material includes hollow microspheres and / or porous materials; Preferably, the hollow microspheres have a particle size of 20–200 nm and a wall thickness of 10–50 nm; Preferably, the hollow microspheres comprise at least one of silicon dioxide, aluminum oxide, silicon carbide, silicon nitride, or titanium dioxide; Preferably, the porous material has a particle size of 20–200 nm, a porosity of 30%–70%, and a pore size of 2–10 nm. Preferably, the porous material includes at least one of molecular sieve materials, polymer materials, or MOF materials; Preferably, the molecular sieve material includes MCM41 and / or SBA15.

4. The radiation cooling film according to any one of claims 1-3, characterized in that, In the composite particles, the mass ratio of the ultraviolet absorber to the mid-infrared emitting material is 1:(1-20); Preferably, in the radiation cooling film, the mass ratio of the composite particles to the matrix is ​​1:(50-400); Preferably, the thickness of the radiation cooling film is 10–1000 μm.

5. The radiation cooling film according to any one of claims 1-4, characterized in that, A release film is provided on one side of the radiation cooling film; Preferably, the release film comprises a PET film.

6. A method for preparing a radiation-cooled thin film according to any one of claims 1-5, characterized in that, The preparation method includes: mixing hollow microspheres, ultraviolet absorbers and solvents, separating the solid and liquid and drying them to obtain composite particles; mixing the composite particles with resin materials to obtain a slurry; coating the slurry and curing it to obtain a radiation cooling film.

7. The method for preparing a radiation-cooled thin film according to claim 6, characterized in that, The solvent includes ethyl acetate; Preferably, the ultraviolet absorber is first mixed with the solvent to obtain a mixed solution, and then the hollow microspheres are mixed with the mixed solution; Preferably, the solid-liquid separation method includes centrifugation; the centrifugation speed is 7000-9000 rpm and the time is 3-7 min; Preferably, the solid-liquid separation is followed by cleaning, and the cleaning method includes rinsing with ethanol at least twice; Preferably, the drying temperature is 70–90°C and the drying time is 5–20 min.

8. The method for preparing a radiation-cooled thin film according to claim 6 or 7, characterized in that, After the slurry is applied, a microstructure template is covered on the wet coating layer. After curing, the microstructure template is removed to obtain a radiation cooling film with surface microstructures. Preferably, the microstructure template has an array of microprotrusions, the shape of which includes at least one of hemispherical, cylindrical, pyramidal, or prismatic shapes.

9. The method for preparing a radiation-cooled thin film according to any one of claims 6-8, characterized in that, The curing method includes at least one of heat curing, room temperature curing, or ultraviolet curing; Preferably, the thermosetting temperature is 80–90°C and the time is 12–36 hours; Preferably, the coating is applied to a release film, such that one side of the resulting radiation-cooled film is coated with the release film.

10. A solar cell, characterized in that, The solar cell is provided with a radiation cooling film as described in any one of claims 1-5, or with a radiation cooling film obtained by the preparation method described in any one of claims 6-9.

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