Radiative cooling multilayer film structure for architectural glass

Abstract

The application relates to the technical field of optical structure, in particular to a multilayer film structure for building glass radiation refrigeration. 6 / HfO2 / glass / HfO2 / (SiO2 / X / HfO2) 6 The ternary film layer structure is characterized in that (HfO2 / X / SiO2) 66 / HfO2 is a reflective ultraviolet ternary DBR, denoted as A structure, HfO2 / (SiO2 / X / HfO2) 6 The structure is a reflective near-infrared ternary DBR, denoted as B structure. The ultraviolet reflectance of the film system structure is 52.43%, the visible light transmittance is 76.22%, the near-infrared reflectance is 58.82%, and the surface emissivity is 83.38%, so that the performance is better, the radiation refrigeration effect can be achieved, and the film system structure can be applied to building glass.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of optical structure, and particularly relates to a multilayer film structure for building glass radiation refrigeration. BACKGROUND

[0002] In actual life, especially in hot summer, people have a strong demand for indoor space refrigeration, which can help high-temperature objects reduce temperature and reduce energy consumption. Refrigeration can be divided into active refrigeration and passive refrigeration. Active refrigeration refers to the refrigeration process that consumes a large amount of energy, while passive refrigeration does not consume energy.

[0003] As the most important cold source and heat source of the earth, outer space and the sun maintain the balance of energy of the earth. The energy on which human beings depend for survival on the earth is mainly obtained through the electromagnetic radiation of the sun. Therefore, a high-temperature object can always achieve its own cooling by the form of heat radiation. The temperature of the earth's surface is about 300K, and the temperature of outer space is only 3K. The temperature difference formed by the two provides an opportunity for the energy exchange between the objects on the ground and the universe, so that the objects can transmit their own heat energy to outer space in the form of heat radiation to achieve the purpose of refrigeration.

[0004] The wavelength segment with high atmospheric transmittance is called an atmospheric window (ATSW). There are three wave bands of 0.3-2.5 μm, 3.2-4.8 μm, and 8-13 μm in general, and the black body radiation at normal temperature is mainly concentrated in the 8-13 μm wave band. The object emits its own heat in the form of 8-13 μm electromagnetic waves to the absolute zero space of the universe without energy consumption, and the use of this wave band is the key to realizing the radiation refrigeration technology, so as to achieve the purpose of self-cooling, i.e. passive radiation refrigeration.

[0005] If the radiation refrigeration is to be realized in the daytime, a reflection module with high reflectivity in the visible near-infrared wave band is also needed, which can radiate heat outward while reducing the absorption of solar radiation by the device as much as possible, so as to realize the daytime radiation refrigeration. The key to realizing passive radiation refrigeration is to find and design ideal spectral selective materials.

[0006] In the coating of the building glass window, the ultraviolet (UV, 0.28-0.38 μm) wave band is high in reflectivity, the visible light (VIS, 0.38-0.78 μm) is high in transmittance, the near-infrared (NIR, 0.78-2.5 μm) wave band is high in reflectivity, and the thermal infrared (MIR, 8-13 μm) wave band is high in emission (absorption), which significantly reduces the atmospheric window thermal infrared emissivity, and achieves the effect of building glass radiation refrigeration. At the same time, it also has good color and luster, and does not affect the visual effect of people.

[0007] The principle of the radiation refrigeration energy-saving window is to reduce the indoor temperature and improve the energy utilization efficiency by enhancing the outward radiation heat capacity of the window and reducing the heat transfer between indoor and outdoor. In winter, the infrared heat loss is reduced by reflecting the infrared heat radiation emitted by objects with a temperature higher than absolute zero, and in summer, the refrigeration is achieved by absorbing the cold air outside and emitting the heat inside the building, so as to achieve the effect of indoor winter warm and summer cool and realize energy saving and emission reduction.

[0008] The existing patent 2024103653342 discloses a full-dielectric high-transmittance heat-insulating radiation refrigeration window, which is characterized by a structure of (HfO2 / SiO2) 6 / HfO2 / substrate / HfO2 / (SiO2 / HfO2) 6 The substrate can be glass or PET. The invention found in further research that the (HfO2 / SiO2) 6 / HfO2 / substrate / HfO2 / (SiO2 / HfO2) 6 The radiation refrigeration structure has a direct ultraviolet reflection ratio of 51.41%, a direct visible light transmittance of 70.66%, a direct near-infrared reflection ratio of 41.20%, and an average atmospheric window emissivity of 79.11%, and has high thermal infrared emissivity and visible light transmittance, but low ultraviolet and near-infrared reflectivity. SUMMARY

[0009] In order to further enhance the ultraviolet and near-infrared reflectivity of the solar spectrum and further improve the thermal infrared emissivity, the solar spectrum spectral characteristics and the atmospheric window spectral emissivity of the ternary periodic film layer are explored, and the present application constructs a (HfO2 / X / SiO2) 6 / HfO2 / substrate / HfO2 / (SiO2 / X / HfO2) 6 structure to realize radiation refrigeration.

[0010] The technical solution of the present application is a multilayer film structure for building glass radiation refrigeration, which has a structure of (HfO2 / X / SiO2) 6 / HfO2 / substrate / HfO2 / (SiO2 / X / HfO2) 6， ternary film layer structure, X represents one of TiO2, SiO and Al2O3, wherein (HfO2 / X / SiO2) 66 / HfO2 is an ultraviolet reflecting ternary DBR, denoted as A structure, and HfO2 / (SiO2 / X / HfO2) 6 structure is a near-infrared reflecting ternary DBR, denoted as B structure.

[0011] In the A structure, the HfO2 film thickness is selected to be 78nm-592nm, and in the B structure, the HfO2 film thickness is selected to be 134nm-1072nm.

[0012] The TiO2 film thickness in the A structure is selected as 27nm-864nm, and the TiO2 film thickness in the B structure is selected as 120nm-1920nm;

[0013] The SiO2 film thickness in the A structure is 50nm, and the SiO2 film thickness in the B structure is 170nm;

[0014] Further, a multilayer film structure for building glass radiation refrigeration is (HfO2 / TiO2 / SiO2) 6 / HfO2 / glass / HfO2 / (SiO2 / TiO2 / HfO2) 6 A ternary film layer structure,

[0015] The HfO2 film thickness in the A structure is selected as 148nm, and the HfO2 film thickness in the B structure is selected as 134nm;

[0016] The TiO2 film thickness in the A structure is selected as 54nm, and the TiO2 film thickness in the B structure is selected as 120nm;

[0017] The SiO2 film thickness in the A structure is 50nm, and the SiO2 film thickness in the B structure is 170nm.

[0018] Compared with the prior art, the film system structure has the following beneficial effects: the ultraviolet reflectance is 52.43%, the visible light transmittance is 76.22%, the near-infrared reflectance is 58.82%, and the surface emissivity is 83.38%, and the performance is better, and the radiation refrigeration effect can be achieved. BRIEF DESCRIPTION OF DRAWINGS

[0019] Figure 1 The (HfO2 / X / SiO2) proposed in the application is 6 / HfO2 / glass / HfO2 / (SiO2 / X / HfO2) 6 A film system structure schematic diagram;

[0020] Figure 2 The (HfO2 / Al2O3 / SiO2) proposed in the application is 6 / HfO2 / glass / HfO2 / (SiO2 / Al2O3 / HfO2) 6 Reflectivity, transmittance and emissivity of the film system structure;

[0021] Figure 3 The (HfO2 / TiO2 / SiO2) proposed in the application is 6 / HfO2 / glass / HfO2 / (SiO2 / TiO2 / HfO2) 6 Reflectivity, transmittance and emissivity of the film system structure;

[0022] Figure 4 Reflectance of the overall film stack for the A structure with Hf02film thickness of 74 nm and 148 nm; 6 Reflectance of the overall film stack for the A structure with Hf02film thickness of 296 nm, 592 nm; 6 Reflectance, transmittance, and emittance (absorptance) curves of the film stack;

[0023] Figure 5a Reflectance of the overall film stack for the A structure with Hf02film thickness of 74 nm and 148 nm;

[0024] Figure 5b Reflectance of the overall film stack for the A structure with Hf02film thickness of 296 nm, 592 nm;

[0025] Figure 6a Reflectance of the overall film stack for the A structure with Hf02film thickness of 74 nm and 148 nm;

[0026] Figure 6b Reflectance of the overall film stack for the A structure with Hf02film thickness of 296 nm, 592 nm;

[0027] Figure 7 Reflectance of the overall film stack for the A structure with Hf02film thickness of 74 nm and 148 nm;

[0028] Figure 8a Reflectance of the overall film stack for the A structure with Ti02film thickness of 27 nm and 54 nm;

[0029] Figure 8b Reflectance of the overall film stack for the A structure with Ti02film thickness of 108 nm and 216 nm;

[0030] Figure 8c Reflectance of the overall film stack for the A structure with Ti02film thickness of 432 nm and 864 nm;

[0031] Figure 9a Reflectance of the overall film stack for the A structure with Ti02film thickness of 27 nm and 54 nm;

[0032] Figure 9b Reflectance of the overall film stack for the A structure with Ti02film thickness of 108 nm and 216 nm;

[0033] Figure 9c Reflectance of the overall film stack for the A structure with Ti02film thickness of 432 nm and 864 nm;

[0034] Figure 10 Reflectance of the overall film stack for the A structure with Ti02film thickness of 27 nm and 54 nm;

[0035] Figure 11a The reflectance curves of the overall film system in structure B when the TiO2 film thickness is 120 nm and 240 nm;

[0036] Figure 11b The reflectance curves of the overall film system in structure B when the TiO2 film thickness is 480 nm and 960 nm;

[0037] Figure 12a The transmittance curves of the overall film system in structure B when the TiO2 film thickness is 120 nm and 240 nm.

[0038] Figure 12b The transmittance curves of the overall film system in structure B when the TiO2 film thickness is 480 nm and 960 nm.

[0039] Figure 13 Emissivity curves of the overall film system under different TiO2 film thicknesses in structure B;

[0040] Figure 14a The reflectance curves of the overall film system in structure B when the HfO2 film thickness is 268 nm and 536 nm.

[0041] Figure 14b The reflectance curves of the overall film system in structure B when the HfO2 film thickness is 1092 nm and 2144 nm.

[0042] Figure 15a The transmittance curves of the overall film system in structure B when the HfO2 film thickness is 268 nm and 536 nm.

[0043] Figure 15b The transmittance curves of the overall film system in structure B when the HfO2 film thickness is 1092 nm and 2144 nm.

[0044] Figure 16 Emissivity curves of the overall film system under different HfO2 film thicknesses in structure B;

[0045] Figure 17 (HfO2 / SiO2) 6 / HfO2 / glass / HfO2 / (SiO2 / HfO2) 6 Reflectance, transmittance, and emissivity curves of the membrane structure;

[0046] Figure 18 (148nm HfO2 / 54nm TiO2 / 50nm SiO2) 6 / 148nmHfO2 / glass / 134nmHfO2 / (170nmSiO2 / 120nmTiO2 / 134nmHfO2) 6 Reflectance, transmittance, and emissivity curves of the membrane structure. DETAILED DESCRIPTION

[0047] In order to make the objects, technical solutions and advantages of the embodiments of the present application clearer, the technical solutions in the embodiments of the present application will be described clearly and completely below. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments of the present application. Based on the embodiments in the present application, all other embodiments obtained by a person of ordinary skill in the art without creative work fall within the protection scope of the present application.

[0048] The present application adopts a ternary distributed Bragg reflector (DBR) to effectively reflect ultraviolet and near-infrared light in the solar spectrum and to control transmittance and thermal infrared emissivity to a certain extent. A radiation heat exchange model under hot weather conditions is constructed, and by analyzing the transmittance spectrum, reflectance spectrum, absorption spectrum, direct reflectance, transmittance and absorptance of various film system structures under different film thicknesses and cycle numbers, a better embodiment film layer structure is obtained.

[0049] Embodiment 1, constructing (HfO2 / X / SiO2) 6 / HfO2 / glass / HfO2 / (SiO2 / X / HfO2) 6 structure, X represents TiO2, wherein, (HfO2 / X / SiO2) 6 / HfO2 structure is a reflective ultraviolet ternary DBR, denoted as A structure, HfO2 / (SiO2 / X / HfO2) 6 structure is a reflective near-infrared ternary DBR, denoted as B structure.

[0050] Embodiment 2, constructing (HfO2 / X / SiO2) 6 / HfO2 / glass / HfO2 / (SiO2 / X / HfO2) 6 structure, X represents SiO.

[0051] Embodiment 3, constructing (HfO2 / X / SiO2) 6 / HfO2 / glass / HfO2 / (SiO2 / X / HfO2) 6 structure, X represents Al2O3.

[0052] The characterization method of color and spectral performance of the present application is as follows.

[0053] (1) Lab color mode

[0054] The present application adopts Lab color mode to represent the color of the structure. In Lab color mode, the color of a material is represented by a lightness component L and two color components a and b. The value range of L is 0-100, the a component represents the spectrum change from green to red, and the b component represents the spectrum change from blue to yellow, and the value range of a and b components is both -120-120. L represents black and white, also known as light and dark, + represents white bias, - represents dark bias, a represents red and green, + represents red bias, - represents green bias, b represents yellow and blue, + represents yellow bias, and - represents blue bias.

[0055] All colors can be perceived and measured by Lab color space, and these data can also be used to represent the color difference between a standard sample and a test sample, and are usually represented by ∆L, ∆a, ∆b. ∆L is positive, indicating that the test sample is lighter (white bias) than the standard sample, ∆L is negative, indicating that the test sample is darker (black bias) than the standard sample, ∆a is positive, indicating that the test sample is redder (red bias) than the standard sample, ∆a is negative, indicating that the test sample is greener (green bias) than the standard sample, ∆b is positive, indicating that the test sample is yellower (yellow bias) than the standard sample, ∆b is negative, indicating that the test sample is bluer (blue bias) than the standard sample, and ∆Eab color difference, which does not represent the direction of color difference shift, the greater the value, the greater the color difference. ∆E is a comprehensive evaluation index of color difference, and its relationship with ∆L, ∆a and ∆b is: ∆E=(∆L) 2 +(∆a) 2 +(∆b) 2 。

[0056] (2) Expression method of light and heat performance of solar spectrum layer

[0057] According to the national standard GB / T2680-94, the direct transmittance τe, the direct reflectance ρe and the direct absorption αe of the film system structure under the solar spectrum are calculated, and the change rule is analyzed.

[0058] The lower the τe, the better the sunshade effect of the film system structure; the higher the ρe, the better the heat insulation effect; the αe represents the heat absorption capacity of the film system structure, and a structure with smaller αe should be selected to reduce the influence of the film on the glass and the environment.

[0059]

[0060] In the formula, IAM1.5 is the relative spectral distribution of solar radiation, τ(λ) is the transmittance of the sample at each waveband of the sunlight, ρ(λ) is the reflectance of the sample at each waveband of the sunlight, and α(λ) is the emissivity of the sample at each waveband of the sunlight.

[0061] 1. Analysis and conclusion of the optimization process of different values of each embodiment in the present application

[0062] 1.1 Influence of component X on the spectral performance

[0063] The thickness of the component film is set to be... The influence of the X component on the overall properties of the (HfO2 / X / SiO2)6 / HfO2 / glass / HfO2 / (SiO2 / X / HfO2)6 structure was investigated.

[0064] Structure A: Reflective UV Tri-phase DBR: According to the formula When λ is 300nm, the corresponding film thicknesses of each layer of HfO2, Al2O3, TiO2, SiO and SiO2 are 37nm, 45nm, 27nm, 35nm and 50nm, respectively.

[0065] Structure B: Reflective near-infrared ternary DBR: According to the formula When λ is 1000nm, the corresponding film thicknesses of each layer of HfO2, Al2O3, TiO2, SiO and SiO2 are 134nm, 155nm, 120nm, 131nm and 170nm, respectively.

[0066] 1.2X represents the effect of Al2O3 on spectral performance.

[0067] Depend on Figure 2 It can be seen that the structure exhibits a peak ultraviolet reflectance of 90.73% at a wavelength of 240 nm, with reflectance in other wavelength bands not exceeding 45%. Visible light transmittance reaches its lowest point at 402 nm and 454 nm, at 14.59% and 13.82%, respectively, while visible light transmittance is greater than 80% in the continuous wavelength range of 521 nm to 780 nm. Near-infrared reflectance peaks at 792 nm and 1554 nm, at 85.95% and 82.03%, respectively, with values ​​below 30% in other wavelength bands. Emissivity continuously increases in the thermal infrared band, reaching a maximum of 32.58%. This structure exhibits good visible light transmittance, but its ultraviolet and near-infrared reflectance, as well as its thermal infrared emissivity, are very low.

[0068] 1.3X represents the effect of TiO2 on spectral performance.

[0069] (HfO2 / TiO2 / SiO2) 6 / HfO2 / glass / HfO2 / (SiO2 / TiO2 / HfO2) 6 The reflectivity, transmittance, and emissivity of the structure, such as Figure 3 As shown.

[0070] Depend on Figure 3It can be seen that the ultraviolet reflectance of this structure does not exceed 37.56% when the wavelength is less than 330nm. When the wavelength is greater than 330nm, the ultraviolet reflectance gradually increases, not less than 50%, and has a maximum value of 90.73%. At a wavelength of 425nm, the visible light transmittance reaches a low of 1.64%, and in the continuous band of 526nm-780nm, the visible light transmittance is greater than 80%. At wavelengths of 809nm and 1593nm, the near-infrared reflectance reaches peaks of 94.36% and 93.22%, respectively, and is less than 30% in the 857nm-1597nm band. The emissivity in the thermal infrared band continuously increases, reaching a maximum of 60.02%. This structure has good ultraviolet reflectance and visible light transmittance, but low near-infrared reflectance and thermal infrared emissivity.

[0071] 1.4X represents the effect of SiO on spectral properties.

[0072] Depend on Figure 4 It can be seen that the structure has the highest ultraviolet reflectance of 27.47%. Visible light transmittance increases continuously at 469 nm, exceeding 80% in the 556 nm-780 nm wavelength range. Near-infrared reflectance peaks at 83.75% and 85.89% at wavelengths of 783 nm and 1530 nm, respectively, and is less than 30% in the 838 nm-1384 nm band. Thermal infrared emissivity increases continuously in the 8000 nm-10600 nm wavelength range, decreases continuously in the 10600 nm-13000 nm range, reaching a maximum of 81.39%, and is greater than 50% in the 9032 nm-11000 nm wavelength range. This structure has very low ultraviolet and near-infrared reflectance, but high visible light transmittance and thermal infrared emissivity.

[0073] Table 1 compares the effects of X on structural reflectivity, transmittance, and emissivity.

[0074]

[0075] The results are shown in Table 1. When Al2O3 is selected, the maximum thermal infrared emissivity is less than 32.58%. Al2O3 is a high refractive index material, and its refractive index can be close to 1.62, or even reach 1.76 in some forms. High refractive index means that most of the light is reflected rather than absorbed or transmitted when passing through the film with Al2O3, so the emissivity of Al2O3 is lower than that of TiO2 and SiO. When SiO is selected, the ultraviolet reflectivity is only less than 27.47%. The refractive index of SiO is usually lower than that of some common metals or high refractive index media. Lower refractive index means that the refraction angle is smaller when light enters from air or other media, which can cause more light to be transmitted rather than reflected. Therefore, SiO is used as part of an anti-reflective coating, mostly to reduce surface reflection and increase transmission. SiO has lower emissivity than TiO2 and Al2O3. Compared with adding Al2O3 and SiO, TiO2 is more optimal, only the film thickness and other conditions need to be changed to increase the emissivity, and the reflectivity and transmittance remain unchanged, so (HfO2 / TiO2 / SiO2) is preferred. 6 / HfO2 / glass / HfO2 / (SiO2 / TiO2 / HfO2) 6 The reflectivity, transmittance and emissivity of the structure were studied.

[0076] 2. The effect of component film thickness on the performance of the radiation cooling model

[0077] In previous studies, the thickness of the SiO2 film had little effect on the structure emissivity. Increasing the thickness of the SiO2 film would reduce the overall film system structure transmittance. Without changing the thickness of the SiO2 film in structure A and the thickness of the SiO2 film in structure B, the effect of HfO2 and TiO2 film thickness on the performance was studied.

[0078] 2.1 The effect of HfO2 film thickness on spectral performance in ultraviolet three-element DBR

[0079] As shown in Figure 5, in the ultraviolet range, when the HfO2 film thickness is 74 nm and 148 nm, there is a peak at a wavelength of 380 nm, and the peak is 84.37% and 89.72% respectively, and the reflectivity in the remaining waveband is 35%-45%; when the HfO2 film thickness is 296 nm and 592 nm, there are two peaks in the waveband range, and the peak is greater than 90%, and the overall ultraviolet reflectivity fluctuates. In the near-infrared waveband range, the reflectivity peak does not change with the HfO2 film thickness, and the peak is taken at 808 nm and 1594 nm and is greater than 93%. Therefore, when the HfO2 film thickness is changed, the reflectivity is best when the HfO2 film thickness is 74 nm and 108 nm.

[0080] As shown in Figure 6, within the visible light range, the transmittance exhibits troughs of 4.36% and 19.56% at wavelengths of 425nm and 579nm when the HfO2 film thickness is 74nm. When the HfO2 film thickness is 148nm, the transmittance also exhibits a trough of 4.56% at wavelength 446nm. A continuous band with transmittance greater than 65% exists between 487nm and 704nm. When the HfO2 film thickness is 296nm, three transmittance troughs occur at wavelengths of 436nm, 493nm, and 734nm, with a continuous band with transmittance greater than 65% between 563nm and 704nm. However, when the HfO2 film thickness is 296nm, four transmittance troughs occur, and the continuous band with transmittance greater than 65% is relatively narrow. Therefore, when varying the HfO2 film thickness, a thickness of 148nm yields the best transmittance.

[0081] Depend on Figure 7 It can be seen that within the thermal infrared band, the emissivity increases continuously with the increase of HfO2 film thickness. When the film thickness is 592nm, the emissivity can reach 75%, but at the same time the overall structural transmittance will decrease. Therefore, considering both reflectivity and transmittance, 148nm is selected, at which point the emissivity can reach 61.2%.

[0082] The results show that changing the thickness of the HfO2 film in structure A has little effect on the near-infrared reflectivity. With the increase of HfO2 film thickness, both reflectivity and transmittance are good when the film thickness is 148 nm.

[0083] 2.2 Effect of TiO2 film thickness on performance in reflective ultraviolet ternary DBR

[0084] Without changing the SiO2 film thickness in structures B and A, the effect of TiO2 film thickness on its performance was studied by fixing the HfO2 film thickness at 148 nm.

[0085] As shown in Figure 8, within the ultraviolet (UV) band, comparing six different TiO2 film thicknesses, the reflectance exhibits two peaks at a thickness of 27 nm, one peak at 54 nm, three peaks at 108 nm and 216 nm, and more than five peaks at 432 nm and 864 nm. The reflectance in the remaining bands ranges from 25% to 50%. The reflectance is stable at 54 nm, but drastic changes occur at 432 nm and 864 nm. In the near-infrared (NIIR) band, peaks of 93.31% and 94.41% are observed at 808 nm and 1586 nm, respectively. Therefore, in the NIIR band, the NIIR reflectance does not change with TiO2 film thickness, making a 54 nm TiO2 film thickness the optimal choice for higher reflectance.

[0086] As shown in Figure 9, within the visible light range, when the TiO2 film thickness is 27 nm, a transmittance trough exists at wavelength 417 nm. A continuous band with transmittance greater than 60% exists in the wavelength range of 450 nm-650 nm. When the TiO2 film thickness is 54 nm, a transmittance trough of 1.79% exists at wavelength 443 nm. A continuous band with transmittance greater than 60% exists in the wavelength range of 460 nm-750 nm. When the TiO2 film thickness is 108 nm, three transmittance troughs exist, corresponding to wavelengths of 391 nm, 429 nm, and 563 nm, respectively, with a narrow continuous band transmittance. When the TiO2 film thickness is 216 nm, two transmittance troughs exist, corresponding to wavelengths of 445 nm and 548 nm, respectively, with a narrow continuous band transmittance. Multiple transmittance troughs exist at TiO2 film thicknesses of 432 nm and 864 nm, with transmittance fluctuating continuously. Therefore, the TiO2 film thickness of 54 nm results in the highest transmittance and the widest continuous wavelength range.

[0087] Depend on Figure 10 It can be seen that within the thermal infrared band, the emissivity increases continuously with the increase of TiO2 film thickness. When the film thickness is 864nm, the emissivity can reach 96.5%, which is the optimal value for both reflectivity and transmittance. When 54nm is selected, the emissivity can reach 82.3%, which is the strongest overall effect.

[0088] The results show that the reflectivity and transmittance of TiO2 film with structure A are optimal at 54 nm. Changing the TiO2 film thickness has a significant impact on thermal infrared emissivity. When the TiO2 film thickness is 54 nm, the thermal infrared emissivity is sufficiently high.

[0089] Table 2 shows the results after the first optimization (HfO2 / TiO2 / SiO2). 6 / HfO2 / glass / HfO2 / (SiO2 / TiO2 / HfO2) 6 Performance of membrane structures

[0090]

[0091] Table 2 shows that, compared with structure A before optimization, the optimized reflectivity, emissivity, and reflectance all show an increasing trend. Therefore, it is possible to try to coordinate structures A and B simultaneously to achieve optimal performance. Thus, the thickness of each thin film in structure B will be adjusted.

[0092] 2.3 Effect of TiO2 film thickness on performance in reflective near-infrared ternary DBR

[0093] Without changing the SiO2 and HfO2 film thicknesses in structures A and B, the influence of TiO2 film thickness on the performance of structure B is investigated.

[0094] From Figure 11, in the ultraviolet band range, compared with four different TiO2 film thicknesses, there are two reflection peaks when the TiO2 film thickness is 120 nm, two reflection peaks when the TiO2 film thickness is 240 nm, and three reflection peaks when the TiO2 film thickness is 480 nm and 960 nm, and the reflectivity in the remaining band is greater than 35%. In the near-infrared band range, when the TiO2 film thickness is 120 nm, there are two reflection peaks at wavelengths of 808 nm and 1586 nm, with reflectivities of 93.31% and 94.41%, respectively, and when the TiO2 film thickness is 240 nm, 480 nm, and 960 nm, there are multiple reflection peaks, and the band swings sharply. Therefore, in the near-infrared band range, to select a higher reflectivity, the TiO2 film thickness of 120 nm is optimal.

[0095] From Figure 12, in the visible light range, when the TiO2 film thickness is 120 nm, there is a transmission valley at a wavelength of 443 nm, with a transmission of 1.79%, and in the wavelength range of 460 nm-750 nm, there is a continuous band with a transmission of greater than 60%. When the TiO2 film thickness is 240 nm, there are four transmission valleys at wavelengths of 391 nm, 454 nm, 503 nm, and 729 nm, respectively, and the continuous band transmission is relatively narrow. When the TiO2 film thickness is 480 nm and 960 nm, there are multiple transmission valleys, and the transmission fluctuates constantly. Therefore, the TiO2 film thickness of 120 nm has the highest transmission and the widest continuous wavelength.

[0096] From Figure 13 It can be seen that in the thermal infrared band range, the emissivity increases with the increase of the TiO2 film thickness, and when the film thickness is 1920 nm, the emissivity can reach 97.98%. The transmission and reflectivity are the highest when the TiO2 film thickness is 120 nm. When the TiO2 film thickness is 120 nm, the emissivity is greater than 80% at wavelengths of 11000 nm-13000 nm. Therefore, 120 nm is selected.

[0097] The research results show that changing the TiO2 film thickness of the B structure, the reflectivity and transmission are the best at 120 nm. Changing the TiO2 film thickness has a greater impact on the thermal infrared emissivity. When the TiO2 film thickness is 120 nm, the thermal infrared emissivity is high enough.

[0098] Effect of HfO2 film thickness on performance in reflective near-infrared ternary DBR

[0099] Under the premise of fixing the SiO2 film thickness in the A structure and the B structure, and fixing the TiO2 film thickness at 120 nm, the effect of HfO2 film thickness on its performance is studied.

[0100] As shown in Figure 14, in the ultraviolet range, comparing the four different HfO2 film thicknesses, a single peak (91.23%) is present at a wavelength of 380 nm, and the overall images are basically consistent. In the near-infrared range, five peaks are present when the HfO2 film thickness is 134 nm, and the overall reflectivity is greater than 40%. Seven peaks are present when the HfO2 film thickness is 268 nm, but the transmittance is below 30% in several consecutive bands. Multiple peaks are present when the HfO2 film thickness is 536 nm and 1072 nm, and the transmittance is below 30% in several consecutive bands. Therefore, when changing the HfO2 film thickness, the 134 nm film thickness provides the best reflectivity.

[0101] As shown in Figure 15, within the visible light range, the transmittance exhibits troughs of 4.36% and 19.56% at HfO2 film thicknesses of 134 nm and wavelengths of 425 nm and 579 nm, respectively. A continuous band of transmittance exceeding 65% exists between 537 nm and 776 nm. Multiple transmittance troughs are observed at HfO2 film thicknesses of 268 nm, 536 nm, and 1072 nm, indicating a narrow continuous transmittance band. Therefore, when varying the HfO2 film thickness, a thickness of 134 nm yields the optimal transmittance.

[0102] Depend on Figure 16 It can be seen that within the thermal infrared band, the emissivity increases continuously with the increase of HfO2 film thickness. When the HfO2 film thickness is 2144nm, the emissivity can reach 99.23%, but the reflectivity and transmittance are low. When the HfO2 film thickness is 134nm, the emissivity is greater than 80% in the wavelength range of 11000nm-13000nm. Therefore, 134nm is chosen.

[0103] Optimized (HfO2 / TiO2 / SiO2) 6 / HfO2 / glass / HfO2 / (SiO2 / TiO2 / HfO2) 6 The structure was found to be optimal when the HfO2 film thickness was 134 nm and the TiO2 film thickness was 120 nm. Therefore, the results of the second optimization were no different from those of the first optimization.

[0104] The research results show that: (148nm HfO2 / 54nm TiO2 / 50nm SiO2) 6 / 148nmHfO2 / glass / 134nmHfO2 / (170nmSiO2 / 120nmTiO2 / 134nmHfO2) 6 The structure exhibits optimal reflectivity, transmittance, and emissivity.

[0105] According to TFCalc, the Lab value of this structure is shown in Table 3. The reflected color is dark blue, while the transmitted color is orange-yellow, which meets the requirements of this study.

[0106] Table 3 (HfO2 / TiO2 / SiO2) 6 (HfO2 / SiO2) / (HfO2 / TiO2 / SiO2) 6 Lab values and color of film system structure

[0107]

[0108] Comparison of binary and ternary structures

[0109] (1) Comparison of reflectivity, transmissivity and emissivity

[0110] By Figure 17 and Figure 18 Comparing binary and ternary structures shows that in the ultraviolet band, the reflectivity of the binary structure is less than 20%, while the reflectivity of the ternary structure continuously increases at wavelengths of 300nm-380nm, and when the wavelength is greater than 320nm, the reflectivity is greater than 40%. In the visible light band, there is a continuous band of transmissivity less than 20nm in the binary structure, and the overall transmissivity of the ternary structure is greater than 60%, and fluctuates above 60%. In the near-infrared band, the overall reflectivity of the binary structure is less than 40%, and the ternary structure still has a continuous band less than 40%, but there is a reflectivity greater than 60% at wavelengths of 1400nm-1837nm. In the thermal infrared band, the emissivity of the binary structure is greater than 80% at wavelengths of 9000nm-10000nm, and the emissivity of the ternary structure is greater than 80% at wavelengths of 11000nm-13000nm, and the wavelength band of the ternary structure is wider. Therefore, increasing the material TiO2 and changing the thickness of HfO2 and TiO2 in the DBR can effectively improve the ultraviolet and near-infrared reflectivity, visible light transmissivity and thermal infrared emissivity of the structure.

[0111] (2) Comparison of direct reflectance, transmittance and absorption

[0112] Table 4 Comparison of solar spectrum light and heat performance of composite film in different wavelength bands

[0113]

[0114] The direct transmittance, direct reflectance and direct absorption of the composite film in different wavelength bands of the solar spectrum when the solar incident angle is 0° are calculated by formulas (1), (2) and (3)

[0115] By comparison, (HfO2 / TiO2 / SiO2) 6 (HfO2 / SiO2) / (HfO2 / TiO2 / SiO2) 6 structure is better than (HfO2 / SiO2) 6 ​​​ / HfO2 / glass / HfO2 / (SiO2 / HfO2) 6 Compared with the structure, the direct reflectance in the ultraviolet band is higher, the direct transmittance is lower, and the direct absorption is higher. In the visible light band, the direct reflectance is lower, the direct transmittance is higher, and the direct absorption is higher. In the near-infrared band, the direct reflectance is higher, the direct transmittance is lower, and the direct absorption is lower. The direct reflectance in the ultraviolet band is increased by 1.02%, the direct transmittance in the visible light band is increased by 5.56%, and the direct reflectance in the near-infrared band is increased by 17.65%.

[0116] (3) Surface emissivity contrast

[0117] (HfO2 / TiO2 / SiO2) 6 / HfO2 / glass / HfO2 / (SiO2 / TiO2 / HfO2) 6 The surface emissivity of the film system structure is 73.11%, (148nm HfO2 / 54nm TiO2 / 50nm SiO2) 6 / 148nm HfO2 / glass / 134nm HfO2 / (170nm SiO2 / 120nm TiO2 / 134nm HfO2) 6 The surface emissivity of the structure in the atmospheric window of 8-13 microns is 83.38%. Compared with the final surface emissivity of the binary structure, it is increased by 10.27%.

[0118] In summary, the present application uses TFCalc simulation to design a new type of radiation cooling visible window structure, and constructs a full dielectric film system DBR, and the structure is (HfO2 / TiO2 / SiO2) 6 / HfO2 / glass / HfO2 / (SiO2 / TiO2 / HfO2) 6 , wherein (HfO2 / TiO2 / SiO2) 6 / HfO2 type is A structure, and HfO2 / (SiO2 / TiO2 / HfO2) 6 type is B structure.

[0119] In the A structure, the HfO2 film thickness is 148nm, the TiO2 film thickness is 54nm, and the SiO2 film thickness is 50nm,

[0120] In the B structure, the HfO2 film thickness is 134nm, the TiO2 film thickness is 120nm, and the SiO2 film thickness is 170nm.

[0121] To achieve high thermal emissivity, the structure needs to emit heat before reflection, thus acting as a cooling agent. The structure also reflects the solar spectrum in the ultraviolet and near-infrared regions. By changing the film thickness, emissivity can be increased without reducing reflectivity and transmittance. Through designing the film thickness and calculating the photothermal properties of the solar spectral layer, the optimal structure was selected. Simulations yielded the ultraviolet reflectivity, visible light transmittance, near-infrared reflectivity, and thermal infrared emissivity. The simulation results are as follows:

[0122] 1. The results obtained from the binary structure can still be improved by adding Al2O2 to the two materials. 3、 When choosing between TiO2 and SiO, the optimal structure among the three materials is selected for improvement. When Al2O3 is selected, its emissivity is too low, and when SiO is selected, its ultraviolet reflectivity is too low. Compared with adding these two materials, TiO2 is better. Only by changing the film thickness and other conditions, the emissivity can be improved, thus improving the current situation of low emissivity.

[0123] 2. As the HfO2 film thickness increases, in structure A, the emissivity in the infrared band continuously increases when the HfO2 film thickness is between 78nm and 592nm. The emissivity is optimal at a thickness of 148nm, while reflectivity and transmittance remain unaffected. In structure B, the HfO2 film thickness ranges from 134nm to 2144nm, with 134nm showing the best performance. Therefore, considering the reflectivity, transmittance, and emissivity across various solar wavelengths, the optimal HfO2 film thickness for structure A is 148nm, and for structure B, it is 134nm.

[0124] 3. When the TiO2 film thickness increases, in structure A, when the TiO2 film thickness is between 27nm and 864nm, the emissivity is best at a thickness of 432nm. Considering both reflectivity and transmittance, a TiO2 thickness of 54nm yields the best results. In structure B, when the TiO2 film thickness is between 120nm and 1920nm, 120nm yields the best results. Therefore, considering reflectivity, transmittance, and emissivity across various wavelengths of sunlight, the optimal TiO2 film thickness for structure A is 54nm, and for structure B, it is 120nm.

[0125] 4. Since the SiO2 film thickness has little effect on the emissivity of the structure, increasing the SiO2 film thickness will reduce the overall transmittance of the film system. Therefore, the thickness of the two SiO2 film layers remains unchanged. The SiO2 film thickness in structure A is 50nm, and the SiO2 film thickness in structure B is 170nm.

[0126] 5. The final optimized structure is (HfO2 / TiO2 / SiO2). 6 / HfO2 / glass / HfO2 / (SiO2 / TiO2 / HfO2) 6The ternary film layer structure has an ultraviolet reflectance of 52.43%, a visible light transmittance of 76.22%, a near-infrared reflectance of 58.82%, and a surface emissivity of 83.38%, and has good performance and can achieve the effect of radiation refrigeration.

[0127] Finally, it should be noted that: the above embodiments are only used to illustrate the technical solutions of the present application, but not to limit them; although the present application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that: it can still modify the technical solutions recorded in the foregoing embodiments, or make equivalent replacement for part or all of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the embodiments of the present application.

Claims

1. A multilayer film structure for architectural glass radiant cooling, characterized in that, The film system structure is (HfO2 / X / SiO2) 6 / HfO2 / glass / HfO2 / (SiO2 / X / HfO2) 6 The ternary film layer structure is X represents TiO2, wherein (HfO2 / X / SiO2) 6 / HfO2 is a reflective ultraviolet ternary DBR, denoted as A structure, HfO2 / (SiO2 / X / HfO2) 6 The structure is a reflective near-infrared ternary DBR, denoted as B structure; The HfO2film thickness in structure A is 74 nm, 148 nm, 286 nm or 592 nm, and the HfO2film thickness in structure B is 134 nm, 268 nm, 536 nm or 1072 nm; the TiO2film thickness in structure A is 27 nm, 54 nm, 108 nm, 216 nm, 432 nm or 864 nm, and the TiO2film thickness in structure B is 120 nm, 240 nm, 480 nm, 960 nm or 1920 nm.

2. The architectural glass radiant cooling multilayer film structure of claim 1, wherein, The SiO2film thickness in structure A is 50 nm, and the SiO2film thickness in structure B is 170 nm.

3. The architectural glass radiant-redding multilayer film structure of claim 1, wherein, The HfO2film thickness in structure A is 148 nm, and the HfO2film thickness in structure B is 134 nm. The TiO2film thickness in structure A is 54 nm, and the TiO2film thickness in structure B is 120 nm.

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