A color sub-environment radiation cooling film and a preparation method thereof

Abstract

The present application relates to the technical field of radiation cooling, and discloses a color sub-environment radiation cooling film and a preparation method thereof.The radiation cooling film comprises a multilayer film structure, which comprises alternately stacked metal layers and non-metal layers, the metal layers are selected from one of Al, Au, Ag and Ti, and the non-metal layers are selected from one of Al2O3, SiO2, ZnS, TiO2, WO3 and Si3N4; and a polymer emitter is arranged on the surface of the multilayer film structure.In the present application, the single-peak subtractive color system is expanded to an additive color system through the optimized design of the multilayer film structure based on Fabry-Perot resonance, and the color gamut area is increased by 180%; meanwhile, the color is accurately controlled by taking RGB color values and solar reflectivity as objective functions; the polymer emitter is solidified on the surface of the multilayer film structure, and high infrared emissivity is provided, and the resonance structure is protected and encapsulated.The columnar grating structure on the surface reduces the impedance mismatch with air, further improves the infrared emissivity, and makes up for the loss of cooling power.

Description

Technical Field

[0001] This invention relates to the field of radiation cooling technology in heat transfer, and more particularly to a colored sub-environment radiation cooling film and its preparation method. Background Technology

[0002] With population growth and the intensification of extreme weather events, energy consumption for maintaining building interior temperatures has increased dramatically. Traditional active cooling technologies consume large amounts of energy and contribute to environmental problems such as harmful gas emissions and the urban heat island effect. Radiative cooling technology, as an energy-free and environmentally friendly passive cooling technology, has attracted significant attention in recent years. It uses infrared radiation to transfer heat from the surface of an object through atmospheric windows to the low-temperature space, thereby lowering the object's temperature.

[0003] To achieve efficient solar reflection, most daytime radiative cooling devices have a silver or white appearance. However, such designs can generate light pollution and even pose health and safety hazards to pedestrians. From an aesthetic point of view, the white appearance is too monotonous and fails to meet practical application requirements. Therefore, colored radiative cooling materials have high research and application value. Based on the mechanism of color generation, colored radiative cooling materials can be divided into pigment-based and structural-based colors. Pigment-based colors typically have additional absorption peaks, resulting in excessive solar heat absorption, and the degradation of organic pigments also affects the lifespan of colored radiative cooling materials. Structural colors are physical colors generated by the interference and diffraction of light through micro- and nano-structures. Through structural design, precise control of the solar spectrum can be achieved, reducing unnecessary heat absorption. This physical coloring method also has the advantages of being fade-resistant and environmentally friendly.

[0004] Multilayered photonic crystals can generate narrowband absorption in the visible light band through Fabry-Perot resonance, and then reflect the remaining sunlight using a metallic mirror, thus allowing the material to exhibit complementary colors. However, currently common single-cavity resonant structures can only display a limited range of colors; achieving a wide color gamut depends on more complex structures and corresponding optimization design methods. Furthermore, the emissivity of the atmospheric window needs to be further improved to balance the energy absorbed for color rendering and further enhance radiative cooling efficiency. Therefore, developing radiative cooling materials with rich colors, low solar absorptivity, and high infrared emissivity is crucial. Summary of the Invention

[0005] The purpose of this section is to outline some aspects of embodiments of the present invention and to briefly describe some preferred embodiments. Simplifications or omissions may be made in this section, as well as in the abstract and title of this application, to avoid obscuring the purpose of these documents; however, such simplifications or omissions should not be construed as limiting the scope of the invention.

[0006] In view of the problems existing in the above-mentioned radiation cooling films, the present invention is proposed.

[0007] Therefore, the purpose of this invention is to provide a colored sub-environmental radiation cooling film, which aims to overcome the shortcomings of existing structural color radiation cooling materials, such as small color gamut, poor color controllability, and low cooling performance.

[0008] To solve the above-mentioned technical problems, the present invention provides the following technical solution: a colored sub-environmental radiation cooling film, the radiation cooling film comprising a multilayer film structure and a polymer emitter, wherein the multilayer film structure comprises alternating layers of metal and non-metal, the metal layers being selected from Al, Au, Ag, and Ti; the non-metal layers being selected from Al2O3, SiO2, ZnS, TiO2, WO3, and Si3N4; and the polymer emitter being disposed on the surface of the multilayer film structure.

[0009] As a preferred embodiment of the colored sub-environmental radiation cooling film of the present invention, wherein: the substrate of the multilayer film structure is a metal layer with a thickness of 100-200 nm; the thickness of the remaining metal layers is 20-50 nm; and the thickness of the non-metal layers is 30-150 nm.

[0010] As a preferred embodiment of the colored sub-environmental radiation cooling film of the present invention, the polymer emitter uses a polymer including polyvinyl alcohol or polydimethylsiloxane, whose surface microstructure is a periodically arranged cylindrical grating, and whose feature size is 5-10 μm.

[0011] Another objective of this invention is to provide a method for preparing a colored sub-environmental radiation cooling film, which aims to produce a colored sub-environmental radiation cooling film that can overcome the defects of existing structural color radiation cooling materials, such as small color gamut, poor color controllability, and low cooling performance.

[0012] To solve the above-mentioned technical problems, the present invention provides the following technical solution: a method for preparing a colored sub-environmental radiation cooling film, comprising the following steps:

[0013] S1: A multilayer film structure was deposited using electron beam evaporation technology;

[0014] S2: A polymer emitter is fabricated on the surface of a multilayer film structure using polymer molding and thermosetting.

[0015] As a preferred embodiment of the method for preparing the colored sub-environmental radiation cooling thin film of the present invention, the step of depositing a multilayer film structure using electron beam evaporation technology includes the following steps:

[0016] S11: Based on the optical parameters of the selected material, the reflectivity, absorptivity and transmittance of the multilayer film structure are calculated using the equivalent interface method.

[0017] S12: Calculate the reflectance of the multilayer film structure 100 for incident light of various wavelengths, and calculate the color stimulus function XYZ by combining the standard observer spectral tristimulus values ​​and the spectral power distribution of the D65 standard light source.

[0018] S13: Convert to the standard RGB color space through gamma transformation and value range mapping;

[0019] S14: Determine the objective function based on the RGB color value range of the design target and the limitation of the average solar absorption rate, and set the weight parameters according to the importance of the two and the optimization results;

[0020] S15: Establish a genetic algorithm model, using the thickness of each metal layer and non-metal layer as variables, and optimize the color resonance structure according to the objective function.

[0021] As a preferred embodiment of the method for preparing the colored sub-environmental radiation cooling film of the present invention, wherein: the reflectivity of the multilayer film structure to incident light of each wavelength is calculated, and the color stimulus function XYZ is calculated by combining the standard observer spectral tristimulus values ​​and the spectral power distribution of the D65 standard light source;

[0022] The formula for calculating the color stimulus function XYZ is as follows:

[0023]

[0024] Where X, Y, and Z are the tristimulus values ​​for color, and R(λ) is the spectral reflectance. Here, k is the color matching function, and the expression is as follows:

[0025]

[0026] The color is converted to the standard RGB color space through gamma transformation and value range mapping; the formulas for gamma transformation and value range mapping are as follows:

[0027]

[0028]

[0029] The expression for the gamma() function is as follows:

[0030]

[0031] As a preferred embodiment of the method for preparing the colored sub-environmental radiation cooling film of the present invention, the objective function is determined according to the RGB color value range of the design target and the limitation of the average solar absorption rate, and the weight parameters are set according to the importance of the two and the optimization results.

[0032] The expression for the objective function Q is as follows:

[0033]

[0034] in, R represents the average solar emissivity; R, G, and B represent the color values ​​of the current structure; R0, G0, and B0 represent the desired color values; a and b are the weighting coefficients for each item, set according to the requirements for solar reflectivity and color during the design process.

[0035] As a preferred embodiment of the method for preparing the colored sub-environmental radiation cooling thin film of the present invention, the step of establishing a genetic algorithm model, using the thickness of each metal layer and non-metal layer as variables, and optimizing the multilayer film structure 100 according to the objective function, includes the following steps:

[0036] Generate 100 initial individuals with random thicknesses for each layer, and calculate the objective function for each initial individual;

[0037] Based on the evaluation results, individuals are selected for crossover and mutation operations to generate offspring;

[0038] The entire population is evaluated again, and individuals with poor performance are removed from the population based on the objective function to maintain a stable population size.

[0039] After each round, check if the convergence condition is met. If not, repeat the operation. If it is met, terminate and obtain the optimal solution.

[0040] As a preferred embodiment of the method for preparing the colored sub-environmental radiation cooling film of the present invention, the step of preparing the polymer emitter on the surface of the multilayer film structure by polymer molding and thermosetting includes the following steps:

[0041] S21: Silicon templates are prepared using photolithography and etching techniques;

[0042] S22: Mix and stir the two polymer precursor solutions, and then perform vacuum degassing.

[0043] S23: Spray the release agent evenly onto the silicon template, and after drying, spin-coat the solution onto the silicon template;

[0044] S24: The silicon template is inverted and placed on the prepared multilayer film structure for bonding, and dried under vacuum at 70°C for 2 hours; with the assistance of ultrasonic resonance in ethanol, the cured radiation-cooled film is peeled off from the surface of the silicon template.

[0045] In a preferred embodiment of the method for preparing the colored sub-environmental radiation cooling film of the present invention, the silicon template is fixed on a spin coater and spin-coated at a speed of 600 r / min for 60 s during the spin coating process.

[0046] The beneficial effects of this invention are:

[0047] In this invention, through optimized design of the multi-cavity Fabry-Perot resonant multilayer film structure, the subtractive color system of a single peak is expanded to an additive color system, increasing the color gamut area by 180%. Simultaneously, using RGB color values ​​and solar reflectance as objective functions, precise color control is achieved while minimizing solar absorption. A polymer emitter is solidified on the surface of the multilayer film structure, providing high infrared emissivity while also encapsulating and protecting the resonant structure. The columnar grating structure on its surface reduces impedance mismatch with air, further improving infrared emissivity and, to some extent, compensating for the cooling power loss caused by absorptive color rendering. Attached Figure Description

[0048] To more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings used in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort. Wherein:

[0049] Figure 1 This is a structural diagram illustrating the construction of the colored sub-environmental radiation cooling film of the present invention.

[0050] Figure 2 This is a schematic diagram of the structural optimization design algorithm of the present invention.

[0051] Figure 3 This is a schematic diagram of the fabrication process of the metasurface infrared emitter of the present invention.

[0052] Figure 4 This is the solar spectrum of the red, green, and blue color radiation cooling films of this invention.

[0053] Figure 5 The infrared spectrum of the colored radiation cooling film of the present invention is shown.

[0054] Figure 6 The results of outdoor temperature measurement experiments on the red, green and blue three-color radiation cooling films of this invention are shown. Detailed Implementation

[0055] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, the specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings.

[0056] Many specific details are set forth in the following description in order to provide a full understanding of the invention. However, the invention may also be practiced in other ways different from those described herein, and those skilled in the art can make similar extensions without departing from the spirit of the invention. Therefore, the invention is not limited to the specific embodiments disclosed below.

[0057] Secondly, the term "one embodiment" or "embodiment" as used herein refers to a specific feature, structure, or characteristic that may be included in at least one implementation of the present invention. The phrase "in one embodiment" appearing in different places in this specification does not necessarily refer to the same embodiment, nor is it a single or selective embodiment that is mutually exclusive with other embodiments.

[0058] Secondly, the present invention is described in detail with reference to the schematic diagrams. When detailing the embodiments of the present invention, for ease of explanation, the cross-sectional views illustrating the device structure may be partially enlarged, not according to the usual scale. Furthermore, the schematic diagrams are merely examples and should not limit the scope of protection of the present invention. In addition, actual fabrication should include three-dimensional spatial dimensions of length, width, and depth.

[0059] Example 1

[0060] Reference Figure 1 and 3 This first embodiment of the invention provides a colored sub-environmental radiation-cooling film, comprising a multilayer film structure 100 and a polymer emitter 200. The multilayer film structure 100 is a multi-cavity Fabry-Perot resonant multilayer film structure, used for selectively reflecting sunlight and expanding the single-peak subtractive color system to an additive color system, increasing the color gamut area by 180%. It can achieve precise color control while minimizing sunlight absorption, using RGB color values ​​and sunlight reflectance as objective functions. The polymer emitter 200 provides high infrared emissivity and encapsulates and protects the Fabry-Perot resonant multilayer film structure.

[0061] Specifically, the multilayer film structure 100 includes alternating layers of metal layers 101 and non-metal layers 102. The metal layers 101 are selected from one or more of Al, Au, Ag, and Ti; the non-metal layers 102 are selected from one or more of Al2O3, SiO2, ZnS, TiO2, WO3, and Si3N4. The substrate of the multilayer film structure 100 is the metal layer 101, which has a thickness of 100–200 nm. The thickness of the other metal layers 101 is 20–50 nm, and the thickness of the non-metal layers 102 is 30–150 nm.

[0062] Furthermore, the metal layer 101 of the substrate of the multilayer film structure 100 forms a metal mirror, which has extremely high reflectivity in the solar light band and plays the role of reflecting sunlight as a whole; the remaining metal layers 101 are absorption layers, which realize the absorption of visible light of specific wavelengths; so that the film absorbs as little sunlight as possible and presents a specific color.

[0063] The thickness of the non-metallic layer 102 determines the wavelength of the interference, i.e. the position of the absorption peak; the numerical optimization of the thickness of each film layer is based on a genetic algorithm model to achieve the best effect of the Fabry-Perot resonant multilayer film structure.

[0064] A polymer emitter 200 is cured on the surface of a multilayer film structure 100. The polymer used in the emitter 200 includes polyvinyl alcohol or polydimethylsiloxane, and its surface microstructure consists of periodically arranged cylindrical gratings with a characteristic dimension of 5-10 μm. This surface microstructure reduces the reflection of infrared light at the air / PDMS interface, thereby improving the infrared emissivity of the radiation-cooled film and giving it better heat dissipation capabilities.

[0065] Example 2

[0066] Reference Figures 1-6 This is a second embodiment of the present invention, providing a method for preparing a colored sub-environmental radiation cooling film. The method for manufacturing the colored sub-environmental radiation cooling film of Example 1 as described above comprises the following steps:

[0067] S1: A multilayer film structure 100 was deposited using electron beam evaporation technology. Specifically, the multilayer film structure was deposited on a smooth 125 μm polyimide film. Before deposition, the polyimide film was ultrasonically cleaned sequentially with acetone, ethanol, and deionized water, and then dried with nitrogen. The chamber was evacuated before deposition, and the metal and non-metal layers were deposited sequentially.

[0068] S11: Based on the optical parameters of the selected material, such as the complex refractive index data, the equivalent interface method is used to sequentially convert two adjacent interfaces into one interface. The effect on the incident light is the same before and after the conversion. Based on the reflection coefficient and transmission coefficient of the final equivalent interface in two mutually perpendicular polarization directions, the reflectivity and transmittance of the interface are calculated, and then the absorptivity is calculated, that is, the reflectivity, absorptivity and transmittance of the multilayer film structure 100.

[0069] Specifically, the equivalent reflection coefficient R of the first m-layer interface m and equivalent transmission coefficient T m The recursive calculation formula is as follows:

[0070]

[0071] Wherein, the reflection coefficient r of interface m for light polarized in the s direction m,s The reflection coefficient r of p-polarized light m,p The calculation formula is as follows:

[0072]

[0073] The transmission coefficient t of interface m for s-direction polarized light m,s The transmission coefficient t of p-direction polarized light m,p The calculation formula is as follows:

[0074]

[0075] Where, N m-1 Let θ be the complex refractive index of the (m-1)th layer. m Let β be the angle of the incident light at the m-th layer. m Let m be the phase thickness of the m-th layer, expressed as follows:

[0076]

[0077] Where λ is the wavelength of the incident light, h m Let be the thickness of the m-th layer of film.

[0078] The reflectivity R is based on the equivalent reflectance R of the first m+1 layers for s-direction polarized light. m+1,s and the equivalent reflection coefficient R for p-direction polarized light m+1,p Calculation; Transmittance T is based on the equivalent transmission coefficient R of the first m+1 layers for s-direction polarized light. m+1,s and the equivalent transmission coefficient R for p-direction polarized light m+1,p calculate:

[0079]

[0080] According to Kirchhoff's laws, the absorption rate α can be calculated using the following formula:

[0081] α(λ,θ)=1-R(λ,θ)-T(λ,θ)

[0082] S12: Following the steps in S11, calculate the reflectance of the multilayer film structure 100 for incident light of various wavelengths. Combine the standard observer spectral tristimulus values ​​and the spectral power distribution of the D65 standard light source to calculate the color stimulus function XYZ. Then, convert it to the standard RGB color space through gamma transformation and value range mapping.

[0083] Specifically, the calculation formula for the color stimulus function XYZ is as follows:

[0084]

[0085] Where X, Y, and Z are the tristimulus values ​​for color, and R(λ) is the spectral reflectance. Here, k is the color matching function, and the expression is as follows:

[0086]

[0087] The gamma transform and the value range mapping formula are as follows:

[0088]

[0089]

[0090] The expression for the gamma() function is as follows:

[0091]

[0092] S13: Determine the objective function based on the RGB color value range of the design target and the limitation of average solar absorption rate, and set weight parameters according to the importance of both and the optimization results.

[0093] Furthermore, for structures with target color values ​​of R0, G0, and B0, the objective function is set as follows:

[0094]

[0095] in, R represents the average solar emissivity; R, G, and B represent the color values ​​of the current structure; R0, G0, and B0 represent the target color values; a and b are the weighting coefficients for each item, set according to the requirements for solar reflectivity and color during the design process.

[0096] S14: Establish a genetic algorithm model, using the thickness of each metal and non-metal layer as variables, and optimize the multilayer film structure according to the objective function.

[0097] Furthermore, the parameters for the genetic algorithm are set as follows:

[0098] The population size was set to 100, with each individual having one chromosome. The number of genes on each chromosome was twice the number of layers, corresponding sequentially to the material number and layer thickness of each layer. The thickness of the bottom metal mirror was fixed, the thickness of the metal absorption layer ranged from 10-100 nm, and the thickness of the dielectric cavity ranged from 10-300 nm, using integer constraints. The selection method was a combination of uniform and random selection, with a crossover probability of 0.8, a constraint-dependent mutation probability, and a mobility rate of 0.2.

[0099] Furthermore, the optimization process of the genetic algorithm is as follows:

[0100] First, 100 initial individuals of random thickness at each layer are generated, and the objective function for each individual is calculated according to methods S11-S13. Based on the evaluation results, individuals are selected for crossover and mutation operations to generate offspring, and all individuals are evaluated again. Individuals with poor performance are removed from the population according to the objective function to maintain population stability. After each round, the convergence condition is checked. If it is not met, the operation is repeated; if it is met, the process terminates and the optimal solution is obtained.

[0101] S2: A polymer emitter is fabricated on the surface of a multilayer film structure using polymer molding and thermosetting. Specifically, the polymer is cross-linked and thermoset to bond the multilayer film deposited on the substrate. The outer surface of the polymer, used to enhance radiative heat dissipation, features microstructures formed through transfer using a silicon template. The specific steps include:

[0102] S21: Prepare silicon templates using photolithography and etching techniques; that is, prepare silicon templates using standard ultraviolet photolithography and wet etching techniques, with the etching pattern of the template matching the dimensions of the designed grating structure.

[0103] S22: Mix and stir the two polymer precursor liquids and perform vacuum degassing treatment; specifically, mix the two polymer precursor liquids at a volume ratio of 10:1 and stir evenly, then place them in a vacuum drying oven at room temperature for 30 minutes to remove the air bubbles generated during stirring.

[0104] S23: Evenly spray the release agent onto the silicone template, and after drying, spin-coat the solution onto the silicone template; more specifically, shake the fluorinated release agent well, spray it evenly onto the surface of the silicone template from a distance of 20cm, wait 5 minutes, and then pour the polymer solution onto the template. Fix the silicone template on the spin coater and spin coat at a speed of 600r / min for 60s.

[0105] S24: The silicon template coated with polymer solution is inverted and placed on the prepared multilayer film structure 100 for bonding. The sample is placed in a vacuum drying oven and dried under vacuum conditions at 70°C for 2 hours. After the sample is cured, the silicon template is slowly peeled off from the four corners. With the assistance of ultrasonic resonance with ethanol, the cured radiation cooling film is peeled off from the surface of the silicon template to prevent the microstructure grating from breaking during the demolding process.

[0106] Test Instance

[0107] See attached document Figures 4-6 An outdoor temperature measurement experiment was conducted using red, green, and blue radiation-cooled thin film samples. The experimental environmental conditions were as follows:

[0108] Based on the solar spectra of the three samples, two reflection valleys were observed in the visible light band, which were formed by Fabry-Perot resonance in the multilayer film. The average solar absorptivity of the red, green, and blue samples were 0.12, 0.12, and 0.13, respectively.

[0109] The three colors of radiation-cooled thin film samples maintained an emissivity close to 1 in the wavelength range greater than 8 μm, especially in the 8-13 μm range, where the average emissivity reached 0.98.

[0110] During the day, the highest solar irradiance is 984 W / m². 2 Under normal conditions, the average temperature drop of the three samples relative to the ambient temperature was 3.3℃, ​​3.8℃, and 4.5℃, respectively; at night, the average temperature drop of the three samples relative to the ambient temperature was 5.2℃, 5.3℃, and 5.6℃, respectively.

[0111] In summary, the test results show that all three colors of samples have good radiative cooling effects.

[0112] It should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention, and all such modifications or substitutions should be covered within the scope of the claims of the present invention.

Claims

1. A method for preparing a colored sub-environmental radiation cooling thin film, characterized in that: The colored sub-environmental radiation cooling film includes: A multilayer film structure (100) includes alternating layers of metal layers (101) and non-metal layers (102), wherein the metal layers (101) are selected from Al, Au, Ag, and Ti; and the non-metal layers (102) are selected from Al2O3, SiO2, ZnS, TiO2, WO3, and Si3N4. A polymer emitter (200) is cured on the surface of the multilayer film structure (100); The preparation method of the colored sub-environmental radiation cooling film includes the following steps: A multilayer film structure (100) was deposited using electron beam evaporation technology. A polymer emitter (200) on a multilayer membrane structure (100) is prepared by polymer molding and thermosetting. The structural design of the multilayer membrane structure (100) includes the following steps: Based on the optical parameters of the selected material, the reflectivity, absorptivity and transmittance of the multilayer film structure (100) were calculated using the equivalent interface method. The reflectance of the multilayer film structure (100) to incident light of various wavelengths was calculated. Combined with the standard observer spectral tristimulus values ​​and the spectral power distribution of the D65 standard light source, the color stimulus function XYZ was calculated. Converted to the standard RGB color space through gamma transformation and value range mapping; The objective function is determined based on the RGB color value range of the design target and the limitation of the average solar absorption rate, and the weight parameters are set according to the importance of the two and the optimization results. A genetic algorithm model was established, with the thickness of each metal layer and non-metal layer as variables, to optimize the multilayer film structure (100) according to the objective function; The reflectivity of the multilayer film structure (100) to incident light of various wavelengths was calculated, and the color stimulation function XYZ was calculated by combining the standard observer spectral tristimulus values ​​and the spectral power distribution of the D65 standard light source. The formula for calculating the color stimulus function XYZ is as follows: ； Where X, Y, and Z are the tristimulus values ​​for color, and R(λ) is the spectral reflectance. Here, k is the color matching function, and the expression is as follows: ； The color is converted to the standard RGB color space through gamma transformation and value range mapping; the formulas for gamma transformation and value range mapping are as follows: ； ； The expression for the gamma() function is as follows: ； The objective function is determined based on the RGB color value range of the design target and the limitation of the average solar absorption rate, and weight parameters are set according to the importance of the two and the optimization results. The objective function Q The expression is as follows: ； in, Represents average solar emissivity; R , G , B Indicates the color value of the current structure; R 0、 G 0、 B 0 represents the desired color value; a , b The weighting coefficients for each item are set according to the requirements for solar reflectivity and color during the design process.

2. The method for preparing a colored sub-environmental radiation cooling film according to claim 1, characterized in that: The establishment of the genetic algorithm model, using the thickness of each metal and non-metal layer as variables, optimizes the multilayer film structure (100) according to the objective function, including the following steps: Generate 100 initial individuals with random thicknesses for each layer, and calculate the objective function for each initial individual; Based on the evaluation results, individuals are selected for crossover and mutation operations to generate offspring; The entire population is evaluated again, and individuals with poor performance are removed from the population based on the objective function to maintain a stable population size. After each round, check if the convergence condition is met. If not, repeat the operation. If it is met, terminate and obtain the optimal solution.

3. The method for preparing a colored sub-environmental radiation cooling film according to claim 2, characterized in that: The method of setting the polymer emitter (200) on the surface of the multilayer film structure (100) by polymer molding and thermosetting includes the following steps: Silicon templates were prepared using photolithography and etching techniques. The two polymer precursor solutions were mixed and stirred, and then subjected to vacuum degassing. Spray the release agent evenly onto the silicon template, and after drying, spin-coat the solution onto the silicon template. The silicon template was inverted and placed on the prepared multilayer film structure (100) for bonding, and dried under vacuum at 70 °C for 2 h; with the assistance of ultrasonic resonance in ethanol, the cured radiation-cooled film was peeled off from the surface of the silicon template.

4. The method for preparing a colored sub-environmental radiation cooling film according to claim 3, characterized in that: During the spin coating of the silicon template, the silicon template is fixed on the spin coater and spin coated at a speed of 600 r / min for 60 s.

5. A colored sub-environmental radiation cooling film, prepared by the method described in any one of claims 1 to 4, characterized in that: include, A multilayer film structure (100) includes alternating layers of metal layers (101) and non-metal layers (102), wherein the metal layers (101) are selected from Al, Au, Ag, and Ti; and the non-metal layers (102) are selected from Al2O3, SiO2, ZnS, TiO2, WO3, and Si3N4. A polymer emitter (200) is cured on the surface of the multilayer film structure (100).

6. The colored sub-environmental radiation cooling film according to claim 5, characterized in that: The substrate of the multilayer film structure (100) is a metal layer (101) with a thickness of 100~200nm; the thickness of the remaining metal layers (101) is 20~50nm. The thickness of the non-metallic layer (102) is 30~150nm.

7. The colored sub-environmental radiation cooling film according to claim 6, characterized in that: The polymer emitter (200) uses polymers including polyvinyl alcohol or polydimethylsiloxane, and its surface microstructure consists of periodically arranged cylindrical gratings. Its characteristic size is 5-10 μm.

Images