Color cooling film based on tam structure coupled resonant cavity and preparation method thereof

Abstract

The application discloses a color cooling film based on a TAMM structure coupled resonant cavity and a preparation method thereof. The film comprises, from bottom to top, a substrate Sub, a first dielectric layer D1, an absorbing layer A, a second dielectric layer D2, a phase change layer S, a metal layer M and a third dielectric layer D3. The first dielectric layer D1, the absorbing layer A, the second dielectric layer D2, the phase change layer S and the metal layer M jointly form a TAMM structure, and the TAMM structure is a metal-side TAMM structure. The third dielectric layer D3 and the metal layer M jointly form a resonant cavity, and the resonant cavity is a high-order resonant cavity. The film realizes narrow-band high reflection in a visible light band to present structural color and realizes high reflection in a near-infrared band to achieve passive cooling through the synergistic coupling of the TAMM structure and the resonant cavity. The application realizes a wide color gamut structural color and a cooling effect at the same time.

Description

Technical Field

[0001] This invention relates to the field of cooling film technology, and in particular to a colored cooling film based on a TAMM structure coupled resonant cavity and its preparation method. Background Technology

[0002] Driven by both soaring global energy demand and frequent extreme heat events, reducing the absorption of solar radiation heat by various surfaces (such as building facades, vehicle surfaces, and electronic device casings) has become a key direction for alleviating energy consumption and thermal management pressures. Traditional cooling methods heavily rely on active cooling technologies, such as air conditioning systems widely used in the automotive industry and air-cooled / liquid-cooled devices commonly used in electronic devices. These technologies require continuous consumption of electricity or other energy sources to achieve heat transfer, which not only increases operating costs but also exacerbates the energy supply and demand imbalance.

[0003] In solar radiation, the dominant wavelengths for heating objects are concentrated in the visible light (400-800nm) and near-infrared (800-2500nm) bands, accounting for over 90% of the total solar radiation energy. An ideal cooling film must simultaneously possess high reflectivity in both bands to minimize heat absorption; at the same time, to meet the aesthetic demands of architectural decoration, vehicle exterior design, and consumer electronics casings, the film must also possess rich and stable color performance. However, current cooling film products and related research findings generally struggle to simultaneously meet the dual requirements of "efficient cooling" and "color rendering," with the core challenge lying in balancing material design and performance. Currently, cooling films based on traditional pigment coloring can achieve a variety of colors through organic or inorganic pigments. However, pigment molecules or particles selectively absorb specific wavelengths of light in the visible light band (which is the core principle of their color presentation), resulting in a significant decrease in the reflectivity of the film to visible light. At the same time, some pigments also have a certain absorption in the near-infrared band, further aggravating heat accumulation.

[0004] Cooling films based on structural color (such as nanogratings and photonic crystal structures) achieve color by controlling the optical interference effect of the material's microstructure, avoiding heat loss caused by pigment absorption. Among them, photonic crystal films based on the photonic bandgap effect can achieve selective reflection (structural color) in the visible light band and near-infrared reflection through structural design. However, photonic crystals with a single periodic structure have inherent limitations: if the focus is on visible light color control, its bandgap is usually less than 100 nm, which cannot cover the entire near-infrared band; if the bandgap is widened to enhance near-infrared reflection, it will result in an excessively broad reflection peak in the visible light band, leading to a decrease in color purity.

[0005] In recent years, researchers in the field of color have proposed many excellent design and fabrication schemes, including (HL)n high and low refractive index repeating periodic structures, micro-nano porous structures, and organic coatings. For example, Chinese invention publication CN116540331A designs a thin-film structural color structure composed of stacked high and low refractive index materials, using all-dielectric materials for reflective structural color design. The number of film layers and the ratio of high to low refractive indices determine the reflectivity and reflection bandwidth. Chinese invention publication CN114369408A designs an organic coating composed of modified silicone resin, hydroxyl-containing resin, organic solvent, and curing agent, which can be applied to photovoltaic, architectural, and other applications. However, simultaneously achieving near-infrared reflection, high brightness, high purity, and a wide color gamut in layered cooling films still presents certain challenges.

[0006] Meanwhile, numerous challenges remain in the research and development of cooling films. Researchers are dedicated to achieving near-infrared reflective cooling without sacrificing aesthetics, requiring multi-band modulation across the visible light and solar spectrum. For example, Chinese invention publication CN112679223A designs a three-dimensional porous nanocomposite cooling film that radiates infrared heat into outer space, reducing surface temperature. This device requires no external power and achieves cooling in both the presence and absence of sunlight. Another Chinese invention publication CN118165355A proposes a passive cooling film with a surface ordered array and internal porosity, prepared using a combination of phase separation technology and template hot pressing to create a two-photon structure. This film effectively reflects most solar radiation and exhibits excellent infrared emission characteristics at atmospheric windows, achieving good passive cooling both day and night. However, the preparation of existing cooling films is extremely difficult, relying heavily on complex physicochemical methods or mechanical processing techniques, such as photolithography. Not only are the processes cumbersome and the equipment expensive, but it is also difficult to guarantee the dimensional accuracy, stability, and consistency of the structure, resulting in low yield and production efficiency, and posing numerous obstacles to large-scale standardized production. Meanwhile, the color effect of most films is unsatisfactory. Affected by factors such as abnormalities in uniformity correction components, inconsistent evaporation states of the film material, differences in substrate morphology, and processing contamination, uneven color distribution across the entire film or individual films is prone to occur, leading to poor optical performance. Regarding cooling effects, most films struggle to achieve precise spectral selectivity management, have insufficient reflectivity for near-infrared sunlight, and are limited in cooling efficiency due to material properties, environmental interference, and structural design defects, making it difficult to achieve ideal passive cooling effects.

[0007] The problems with traditional solutions can be summarized as follows: 1. Limitations in color purity: The traditional TAMM structure is an optical structure based on the TAMM resonance phenomenon. It generates unique spectral characteristics through the interaction between the metal layer and the DBR. The structure is affected by the wide reflection bandwidth of the DBR, resulting in a large full width at half maximum (FWHM) of the resonance peak. This makes it easy for stray light to be mixed in, leading to color deviation and lower color purity.

[0008] 2. Brightness has certain limitations: Traditional TAMM structures containing only a few DBRs have low DBR reflectivity and limited resonant peak reflectivity, resulting in a dull color visual effect.

[0009] 3. In traditional TAMM structures, the metal layer or DBR is directly exposed to air, making it susceptible to moisture and ultraviolet radiation, resulting in significant reflectivity degradation after long-term use. To improve the performance of traditional TAMM structures, the number of DBR cycles needs to be increased, but multilayer DBR fabrication requires high-precision coating equipment, which is costly and inefficient.

[0010] 4. Traditional colored materials (such as dye coatings) cannot achieve cooling due to strong near-infrared absorption; while traditional cooling materials (such as white coatings) lack color diversity.

[0011] In order to achieve both structural color and cooling effect, it is necessary to adopt new design and optimization methods to design a high-brightness, high-purity, wide-gamut structural color film with cooling function. Summary of the Invention

[0012] In view of this, the purpose of this invention is to propose a color cooling film based on a TAMM structure coupled resonant cavity, which achieves a cooling effect while realizing a wide color gamut structural color.

[0013] To achieve the above-mentioned technical objectives, the technical solution adopted by this invention is as follows: This invention provides a color cooling film based on a TAMM structure coupled resonant cavity, wherein the film comprises, from bottom to top: a substrate Sub, a first dielectric layer D1, an absorption layer A, a second dielectric layer D2, a phase change layer S, a metal layer M, and a third dielectric layer D3; The first dielectric layer D1, the absorption layer A, the second dielectric layer D2, the phase change layer S, and the metal layer M together constitute a TAMM structure, which is a metal-side TAMM structure; the third dielectric layer D3 and the metal layer M together constitute a resonant cavity, which is a high-order resonant cavity. The thin film achieves narrowband high reflectivity in the visible light band to present structural color through synergistic coupling with the resonant cavity via a TAMM structure, and achieves high reflectivity in the near-infrared band to achieve passive cooling. Furthermore, the thickness of the absorption layer A ranges from 5 nm to 400 nm; the material of the absorption layer A is selected from at least one of zinc selenide, tungsten trioxide, ferric oxide, ferric oxide, indium tin oxide, cobalt oxide, nickel oxide, copper sulfide, and bismuth sulfide.

[0014] Furthermore, the thickness of the phase change layer S ranges from 5 nm to 200 nm; the material of the phase change layer S is selected from at least one of silicon, germanium, GST, GSST, SS, GT, vanadium oxide and niobium dioxide.

[0015] Furthermore, the thickness of the metal layer M ranges from 20 nm to 60 nm; the material of the metal layer M is selected from at least one of gold, silver, aluminum, tungsten, and titanium.

[0016] Furthermore, the thickness of the first dielectric layer D1 and the second dielectric layer D2 are each independently between 5 nm and 400 nm, and the two thicknesses may be the same or different.

[0017] Furthermore, the thickness of the third dielectric layer D3 ranges from 20 nm to 1000 nm.

[0018] Furthermore, the materials of the first dielectric layer D1, the second dielectric layer D2, and the third dielectric layer D3 are selected from at least one of silicon oxide, titanium oxide, tantalum oxide, hafnium oxide, zirconium oxide, yttrium oxide, zinc oxide, chromium oxide, magnesium oxide, cerium oxide, zinc sulfide, magnesium fluoride, aluminum fluoride, cerium fluoride, lanthanum chloride, sodium hexachloroaluminate, neodymium fluoride, barium fluoride, calcium fluoride, lithium fluoride, lanthanum titanate, zinc sulfide, and silicon nitride.

[0019] Furthermore, the material of the substrate Sub is selected from glass, polished stainless steel, polished mirror aluminum, polyethylene terephthalate, cellulose triacetate, polymethyl methacrylate, polycarbonate / polymethyl methacrylate composite material, polyimide, polypropylene, polyvinyl chloride, polyvinyl butyral, ethylene vinyl acetate copolymer, polyurethane elastomer, polytetrafluoroethylene, fluoroethyl propylene, or polydifluoroethylene.

[0020] Furthermore, the resonant cavity is a high-order Fabry-Perot resonant cavity based on a metal-dielectric-air structure, and its resonance condition satisfies the following formula:

[0021] Where n is the refractive index of the third dielectric layer D3, d is the thickness of the third dielectric layer D3, λ is the center wavelength corresponding to the target color, and m is the resonance order.

[0022] The present invention provides a method for preparing the above-described thin film, comprising the following steps: Step 1: Based on the target color and cooling performance requirements, determine the thin film structure as Sub / D1 / A / D2 / S / M / D3, where: Sub represents the substrate, D1 represents the first dielectric layer, A represents the absorption layer, D2 represents the second dielectric layer, S represents the phase change layer, M represents the metal layer, and D3 represents the third dielectric layer; and calculate the material type and thickness parameters of each layer in the thin film structure. Step 2: Provide a clean and flat substrate (Sub) and place it in the vacuum chamber of the film deposition equipment; Step 3: Using physical vapor deposition or chemical vapor deposition, deposit the first dielectric layer D1, the absorption layer A, the second dielectric layer D2, the phase change layer S, the metal layer M and the third dielectric layer D3 sequentially on the substrate Sub; Step 4: During the deposition of the phase change layer S and the metal layer M, an inert protective gas is introduced to prevent material oxidation; Step 5: After all film layers are deposited, the colored cooling film is obtained.

[0023] By adopting the above technical solution, the present invention has the following beneficial effects compared with the prior art: 1. Improved color purity: This invention achieves high purity by adding a resonant cavity: the higher-order resonance of the resonant cavity is more sensitive to wavelength shift, and the number of reflections makes the phase condition easy to be destroyed. Combined with the optimization of the uniformity of the dielectric layer, the full width at half maximum (FWHM) of the resonance peak can be significantly compressed, while the intensity of the sidelobe peaks is suppressed to avoid interference from other colors. The final color purity is significantly improved, close to the standard pure color, which can meet the extremely high requirements of color accuracy in scenarios such as automotive exteriors and high-end electronic products, and solve the problem of "color distortion".

[0024] 2. Increased brightness: In this invention, the high-order resonance of the top resonant cavity forms strong feedback through multi-beam interference, which superimposes energy with the TAMM resonance on the metal side. The high-order resonance of the resonant cavity supplements the TAMM resonance with a large number of in-phase photons, increasing the number of photons participating in the coupling. At the same time, the TAMM resonance reflected light is coupled to the resonant cavity for a second time, further amplifying the light intensity. Finally, the reflectivity of the target color band is greatly improved, and the color visual effect is brighter in scenarios such as building curtain walls and high-end displays.

[0025] 3. The dielectric layer of the top resonant cavity in this invention forms a dense protective layer, blocking moisture and contaminants from contacting the DBR; simultaneously, the metal layer is covered by the dielectric layer, reducing oxidation loss. It can adapt to complex working conditions such as outdoor building applications and automotive applications, significantly extending product lifespan. This invention uses only a few DBRs, combined with high-order resonance in the resonant cavity (dielectric layer thickness is easily controlled, and accuracy requirements are within an achievable range), eliminating the need for complex equipment upgrades. Existing conventional equipment such as thermal evaporation coating, roll-to-roll coating, and atomic layer deposition (ALD) can meet production needs, significantly reducing equipment investment costs while improving manufacturing efficiency.

[0026] 4. The composite structure of this invention achieves high brightness and high purity colors while retaining near-infrared reflectivity: the high-order resonance design of the resonant cavity extends to the near-infrared band, and combined with the metal layer reflection of the TAMM structure, ensures that the total near-infrared reflectivity meets cooling requirements. In architectural settings, it can effectively reduce indoor temperature and reduce air conditioning energy consumption; in automotive settings, it can reduce in-vehicle temperature and improve driving comfort. Furthermore, the addition of the phase change layer allows the structure of this invention to achieve a color-changing effect while maintaining a wide color gamut, showing broad application potential in anti-counterfeiting and stealth applications. It integrates "color aesthetics," "dynamic control," and "passive cooling," solving the industry's pain point that "aesthetics and energy conservation cannot be simultaneously achieved." Attached Figure Description

[0027] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art 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.

[0028] Figure 1 This is a schematic diagram of a colored cooling thin film system based on a TAMM structure coupled resonant cavity according to the present invention.

[0029] Figure 2 This is a schematic diagram of the metal-side TAMM structure.

[0030] Figure 3 Example 1 shows the reflection spectra of a multilayer structure of a colored cooling thin film based on a TAMM structure coupled resonant cavity before and after phase transition under perpendicular incidence. Figure 4 This is a chromaticity coordinate diagram of a multilayer structure of a colored cooling thin film based on a TAMM structure coupled resonant cavity, before and after phase transition under perpendicular incidence, as shown in Example 1. Figure 5 Example 2 shows the reflection spectra of a multilayer structure of a colored cooling thin film based on a TAMM structure coupled resonant cavity before and after phase transition under perpendicular incidence. Figure 6 Example 2: Chromaticity coordinates of a multilayer structure of a colored cooling thin film based on a TAMM structure coupled resonant cavity before and after phase transition under perpendicular incidence. Figure 7 Example 3 shows the reflection spectra of a multilayer structure of a colored cooling thin film based on a TAMM structure coupled resonant cavity before and after phase transition under perpendicular incidence. Figure 8 This is a chromaticity coordinate diagram of a multilayer structure of a colored cooling thin film based on a TAMM structure coupled resonant cavity, before and after phase transition under perpendicular incidence, as shown in Example 3. Figure 9 Example 4 shows the reflection spectra of a multilayer structure of a colored cooling thin film based on a TAMM structure coupled resonant cavity before and after phase transition under perpendicular incidence. Figure 10 Example 4: Chromaticity coordinates of a multilayer structure of a colored cooling thin film based on a TAMM structure coupled resonant cavity before and after phase transition under perpendicular incidence. Figure 11 Example 5 shows the reflection spectra of a multilayer structure of a colored cooling thin film based on a TAMM structure coupled resonant cavity before and after phase transition under perpendicular incidence. Figure 12 Example 5: Chromaticity coordinates of a multilayer structure of a colored cooling thin film based on a TAMM structure coupled resonant cavity before and after phase transition under perpendicular incidence. Figure 13 Example 6 shows the reflection spectra of a multilayer colored cooling thin film structure based on a TAMM structure coupled resonant cavity before and after phase transition under perpendicular incidence. Figure 14 Example 6: Chromaticity coordinates of a multilayer structure of a colored cooling thin film based on a TAMM structure coupled resonant cavity before and after phase transition under perpendicular incidence. Detailed Implementation The present invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be particularly noted that the following embodiments are for illustrative purposes only and do not limit the scope of the invention. Similarly, the following embodiments are only some, not all, embodiments of the present invention, and all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0031] Please see Figure 1 and Figure 2 The present invention discloses a color cooling film based on a TAMM structure coupled resonant cavity, wherein the film comprises, from bottom to top: a substrate Sub, a first dielectric layer D1, an absorption layer A, a second dielectric layer D2, a phase change layer S, a metal layer M, and a third dielectric layer D3; The first dielectric layer D1, the absorption layer A, the second dielectric layer D2, the phase change layer S, and the metal layer M together constitute a TAMM structure, which is a metal-side TAMM structure; the third dielectric layer D3 and the metal layer M together constitute a resonant cavity, which is a high-order resonant cavity. The thin film achieves narrowband high reflectivity in the visible light band to present structural color through the synergistic coupling of the TAMM structure and the resonant cavity, and achieves high reflectivity in the near-infrared band to achieve passive cooling.

[0032] This invention introduces a third dielectric layer on top of the TAMM structure, with the top metal layer serving as a coupling layer. The metal layer and the third dielectric layer constitute a resonant cavity, forming a composite system of "TAMM structure + resonant cavity". Through the multi-beam interference effect of the top cavity, a triple optimization of "increased reflectivity in the target band, reduced reflectivity in the non-target band, and narrowed reflection bandwidth" is achieved. At the same time, a phase change layer is integrated to diversify display functions through the conversion between amorphous and crystalline states.

[0033] Metal-dielectric composite thin films achieve near-infrared reflection through the metal layer and control visible light transmission through the dielectric layer. However, the high conductivity of the metal layer leads to excessively high visible light reflectivity, requiring a complex anti-reflection layer design. Furthermore, the diffusion and migration of metal atoms can cause a decline in the long-term stability of the film. The recently developed TAMM plasmonic structure offers a new approach to solving this problem: the TAMM structure is formed by coupling a metal layer with a photonic crystal, generating a narrow-band resonance peak in the visible light band. By adjusting the thickness of the dielectric material in the photonic crystal, a wide color gamut can be achieved.

[0034] Traditional surface plasmon polaritons have wave vectors exceeding those of light in a vacuum and cannot be directly excited by light incident on the surface. TAMM resonance, as a special type of surface electromagnetic mode, can form plasmon polariton states (TPPs) at the boundary between a metal and a dielectric Bragg mirror. These TPPs can possess zero in-plane wave vectors, are independent of polarization, and can be excited by both TE and TM waves, thus allowing for direct optical excitation. TAMM resonant thin films combine the negative permittivity of the metal with the bandgap reflection of the DBR into a one-dimensional interface trap. Through simple multilayer film stacking, highly localized, easily tunable, and polarization-sensitive interface modes can be generated within the bandgap, providing a simple yet powerful planar platform for narrowband filtering, high-Q sensing, low-threshold microlasers, and high-intensity light-matter coupling devices.

[0035] A TAMM state is an interface mode existing in the photonic bandgap of a one-dimensional photonic crystal (DBR). Its range, linewidth, and dispersion sensitivity are directly determined by the DBR bandgap. λ constraint. When light is incident perpendicularly, its bandwidth... for:

[0036] in, , For the high and low refractive indices of the dielectric material, The center wavelength is [value missing]. A wider bandgap allows for a larger tunable range of the TAMM peak and a narrower linewidth, but also increases film stress and loss, requiring a trade-off during design. This invention uses phase change material (PCM) to replace the high-refractive-index material in traditional distributed Bragg reflectors (DBRs), combining it with a metal layer to construct a phase change TAMM resonant structure. This overcomes the limitations of traditional TAMM structures, which have "fixed optical parameters and single function." Furthermore, the addition of an absorption layer increases absorption in the target wavelength band, enhancing the purity of displayed colors. This demonstrates significant advantages in dynamic optical control, integrated photonic devices, and intelligent sensing.

[0037] Phase change materials (such as chalcogenides) undergo a significant abrupt change in refractive index during their crystalline / amorphous transition, allowing for precise alteration of the wavelength position of the TAMM resonance peak. This enables reversible, non-volatile switching of structural colors, overcoming the limitations of traditional TAMM structural colors' "static and singular" nature, and making them suitable for applications such as smart displays and optical coding. Absorbing media materials enhance the saturation and contrast of structural colors: Introducing moderately absorbing media materials can suppress stray reflections outside the TAMM resonance mode, reducing background light interference. Simultaneously, the full width at half maximum (FWHM) of the resonance peak can be tuned, resulting in higher color purity and stronger visual recognition of the structural colors. Furthermore, the absorption characteristics can be combined with phase change characteristics to achieve dual control of "color-absorption rate," expanding functional applications such as laser protection and stealth.

[0038] To understand the constraint energy in TPPs, relaxation time can be used. Let's define the ratio of stored energy E to leaked energy P:

[0039] Time-coupled mode theory can describe the Q factor of the TPP structure by considering the relaxation time:

[0040]

[0041] In the formula, The relaxation time is due to the transmission loss of the DBR mirror. The relaxation time is due to the transmission loss of the metal mirror. The relaxation time is due to the absorption loss of the metal mirror. It is the resonant frequency of the TPP. To achieve better energy storage (greater...) These three losses need to be minimized.

[0042] The critical coupling condition of DBR-side TPPs occurs during a longer relaxation time than that of metal-side TPPs. Therefore, DBR-side TPPs structures, due to their lower leakage power, can support resonance with a high Q factor. However, to ensure reflective performance and stability, DBR-side TAMM structures require a "thick metal layer + multi-layer DBR" design, resulting in increased overall film thickness and limited weight reduction. In weight-sensitive applications (such as aerospace equipment surfaces and ultra-thin flexible displays), the additional thickness and weight increase the burden on the carrier and may even affect the original function of the carrier (such as the bending curvature of the flexible screen). Furthermore, the combination of a thick metal layer and multi-layer DBRs leads to a significant increase in internal stress within the film. When flexible substrates (such as PET and PI) are bent, stress tends to concentrate at the interface between the DBR and the metal layer, causing film cracking and peeling, which cannot meet the long-term usage requirements of wearable devices, flexible sunshade films, and other applications.

[0043] The performance of metal-side TAMMs (such as resonant wavelength and Q factor) is mainly controlled by the thickness of the metal layer, rather than the number of DBR layers. This characteristic makes them more advantageous in narrowband functional designs: First, according to time-coupled mode theory, the relaxation time (τ) of metal-side TAMMs is more sensitive to the thickness of the metal layer—by fine-tuning the thickness of the metal layer, the transmission loss of the metal mirror can be precisely changed. ) and absorption loss ( This allows for the control of the linewidth and intensity of the resonance peak. Secondly, the absorption rate and resonance performance of the metal-side TAMM do not depend on the number of DBR layers; only 1-2 DBR layers are needed to meet the bandgap reflection requirements, reducing the interference of the DBR layers on performance. Therefore, this invention employs a metal-side TAMM structure.

[0044] For practical TPPs, a three-layer structure of "metal layer-dielectric layer-air" is commonly used. In this case, the reflection coefficient needs to consider the interference of reflected waves at the interface between the two layers, and the reflectance needs to be derived using the multi-beam interference formula:

[0045] Where R is the total reflectance. The Fresnel reflection coefficient at the metal-dielectric interface. Let d be the Fresnel reflection coefficient of the medium-air interface, and d be the thickness of the medium layer. This is the phase difference factor of the reflected wave within the dielectric layer. When TPPs resonance occurs, At this point, the multilayer satisfies the destructive reflection condition, and the reflectivity reaches a minimum. The magnitude of the reflection coefficient and the resonance characteristics are determined by the dielectric constant of the metal. Let the dielectric constant of the metal be... , , These are the real and imaginary parts of the dielectric constant, respectively. It is a loss term. The larger it is, the wider the resonance peak of TPPs and the higher the reflection minimum (the more energy is dissipated).

[0046] The reflection at the metal interface needs to be phase-matched with the bandgap reflection of the DBR. Therefore, the selected metal needs to satisfy the following conditions: the negative real part is less than -1 (strong specular reflection), the imaginary part is as small as possible (low absorption loss), and the film is dense and stable (process-friendly).

[0047] In this embodiment, the thickness of the absorption layer A ranges from 5 nm to 400 nm; the material of the absorption layer A is selected from at least one of zinc selenide (ZnSe), tungsten trioxide (WO3), ferric oxide (Fe2O3), iron tetroxide (Fe3O4), indium tin oxide (ITO), cobalt oxide (Co3O4), nickel oxide (NiO), copper sulfide (CuS), and bismuth sulfide (Bi2S3).

[0048] In this embodiment, the thickness of the phase change layer S ranges from 5 nm to 200 nm; the material of the phase change layer S is selected from at least one of silicon, germanium, GST, GSST, SS, GT, vanadium oxide, and niobium dioxide, wherein silicon (Si) and germanium (Ge) are elemental phase change materials, GST (Ge2Sb2Te5), GSST (Ge2Sb2Se4Te1), SS (Sb2S3), and GT (GeTe) are chalcogenide compound phase change materials, and vanadium oxide (VO2) and niobium dioxide (Nb2O5) are oxide phase change materials.

[0049] In this embodiment, the thickness of the metal layer M ranges from 20 nm to 60 nm; the material of the metal layer M is selected from at least one of gold (Au), silver (Ag), aluminum (Al), tungsten (W) and titanium (Ti), which have high reflectivity and low absorption coefficient.

[0050] In this embodiment, the thickness of the first dielectric layer D1 and the second dielectric layer D2 are each independently between 5 nm and 400 nm, and the thicknesses of the two layers may be the same or different.

[0051] In this embodiment, the thickness of the third dielectric layer D3 ranges from 20 nm to 1000 nm.

[0052] In this embodiment, the materials of the first dielectric layer D1, the second dielectric layer D2, and the third dielectric layer D3 are selected from at least one of silicon oxide (SiO2), titanium oxide (TiO2), tantalum oxide (Ta2O5), hafnium oxide (HfO2), zirconium oxide (ZrO2), yttrium oxide (Y2O3), zinc oxide (ZnO), chromium oxide (Cr2O3), magnesium oxide (MgO), cerium oxide (CeO2), zinc sulfide (ZnS), magnesium fluoride (MgF2), aluminum fluoride (AlF3), cerium fluoride (CeF3), lanthanum chloride (LaF3), sodium hexachloroaluminate (Na3AlF6), neodymium fluoride (NdF3), barium fluoride (BaF2), calcium fluoride (CaF2), lithium fluoride (LiF), lanthanum titanate (La2Ti2O7), zinc sulfide (ZnS), and silicon nitride (Si3N4).

[0053] In this embodiment, the material of the substrate Sub is selected from glass, polished stainless steel, polished mirror aluminum, polyethylene terephthalate (PET), cellulose triacetate (TAC), polymethyl methacrylate (PMMA), polycarbonate / polymethyl methacrylate composite (PC / PMMA), polyimide (PI), polypropylene (PP), polyvinyl chloride (PVC), polyvinyl butyral (PVB), ethylene vinyl acetate copolymer (EVA), polyurethane elastomer (TPU), polytetrafluoroethylene (PTFE), fluoroethyl propylene (FEP), or polyvinyl difluoroethylene (PVDF).

[0054] However, the color purity of colored thin films fabricated using the TAMM structure is easily affected by angle, resulting in poor stability. Furthermore, with a limited number of thin film layers, the absorption loss of the metal layer restricts the peak-to-valley reflectivity ratio across different optical bands, hindering the achievement of high-saturation color display. Since the optimization of the top-layer resonant cavity for non-target wavelengths is based on the principle of "destructive interference"—by adjusting the structural parameters of the resonant cavity, the reflected light from non-target wavelengths undergoes phase cancellation within the cavity, thereby reducing its reflectivity—and it also possesses "narrowband frequency selectivity," significantly compressing the reflection bandwidth, this invention utilizes the top-layer resonant cavity and the addition of an absorption layer to solve the problems of excessively wide bandwidth and low reflectivity inherent in the TAMM structure. The introduction of a phase change layer endows the structure with "dynamic adjustment" capabilities.

[0055] The structure used in this invention is: Sub / D1 / A / D2 / S / M / D3, as follows: Figure 1 As shown, Sub is the substrate, D1 / A / D2 / S are stacked layers of the first dielectric layer, absorption layer, second dielectric layer and phase change layer, forming a TAMM structure, M is the metal layer, and D3 is the third dielectric layer, which acts as the resonant cavity. The third dielectric layer shares the top metal layer with the TAMM structure to form the top resonant cavity.

[0056] In this embodiment, the resonant cavity is a high-order Fabry-Perot resonant cavity based on a metal (the original top metal layer of the TAMM structure)-dielectric-air structure, and its resonance condition satisfies the following formula:

[0057] Where n is the refractive index of the third dielectric layer D3, d is the thickness of the third dielectric layer D3, λ is the center wavelength corresponding to the target color, and m is the resonance order.

[0058] By precisely controlling the thickness of the dielectric layer, the higher-order resonant wavelength of the resonant cavity is matched with the TAMM resonant wavelength on the metal side, forming a dual-resonance synergistic effect. At this point, the higher-order resonance of the resonant cavity provides strong feedback to the TAMM resonance through multi-beam interference, significantly increasing the light intensity in the target wavelength band. The light reflected from the TAMM resonant region on the metal side is fed back into the top-layer resonant cavity, undergoing secondary coupling with the cavity, further amplifying the resonance peak intensity and significantly improving color brightness. In terms of bandwidth, the higher-order resonance of the resonant cavity and the TAMM resonance form a "narrowing" mechanism: the higher-order resonance corresponds to more reflections and is more sensitive to wavelength shifts—when the wavelength deviates from the target value, the phase condition is rapidly disrupted, the reflectivity drops sharply, and a steeper resonance peak edge is formed.

[0059] The top metal layer and the third dielectric layer form a resonant cavity. The split bandwidth can be easily controlled by changing the thickness of the third dielectric layer, resulting in a more "square" transmittance curve. Furthermore, optimal control of the resonant mode allows for maximizing transmission efficiency at resonance while suppressing unwanted resonances in non-resonant wavelength regions, significantly improving color purity. Compared to the 0th-order cavity resonance, higher-order resonances exhibit a narrower spectral effect, enhancing the cavity's Q-factor and reducing the bandwidth of reflection troughs to improve color purity. The higher-order resonances in the top cavity resonate with the lower TAMM structure, resulting in strong destructive interference at the resonance wavelength, thus improving color purity without sacrificing other wavelengths. Simultaneously, the phase transition layer and absorption layer in the TAMM structure further enhance absorption in the target wavelength range. The optical constants of the phase transition layer change significantly after transitioning between amorphous and crystalline states, causing a frequency shift in the visible light band, which in turn alters the color display, achieving the advantage of dynamic color control.

[0060] A method for preparing the above-described thin film according to the present invention includes the following steps: Step 1: Based on the target color and cooling performance requirements, determine the thin film structure as Sub / D1 / A / D2 / S / M / D3, where: Sub represents the substrate, D1 represents the first dielectric layer, A represents the absorption layer, D2 represents the second dielectric layer, S represents the phase change layer, M represents the metal layer, and D3 represents the third dielectric layer; and calculate the material type and thickness parameters of each layer in the thin film structure. Step 2: Provide a clean and flat substrate (Sub) and place it in the vacuum chamber of the film deposition equipment; Step 3: Using physical vapor deposition (PVD) or chemical vapor deposition (CVD), sequentially deposit a first dielectric layer D1, an absorption layer A, a second dielectric layer D2, a phase change layer S, a metal layer M, and a third dielectric layer D3 on the substrate Sub. The physical vapor deposition method includes combinations of different techniques such as ion beam sputtering deposition (IBS), magnetron sputtering deposition (MS), electron beam evaporation (EB), or electron beam evaporation ion-assisted deposition (EBD-IAD). The fabrication method for each layer can be arbitrarily selected based on actual conditions and requirements, without any particular restrictions.

[0061] Step 4: During the deposition of the phase change layer S and the metal layer M, an inert protective gas is introduced to prevent material oxidation. When depositing the metal and phase change material, in order to prevent the material from reacting with the gas and causing changes in optical constants, oxygen or other reactive gases cannot be introduced. Only protective gases such as argon are added to maintain the deposition process.

[0062] Step 5: After all film layers are deposited, the colored cooling film is obtained.

[0063] Example 1 This embodiment provides a multilayer structure of a cyan structural color thin film with cooling function. The structural color device consists of a substrate Sub, a third dielectric layer D3 (TiO2) in the resonant cavity, a metal layer M (Ag), and a first dielectric layer D1 (SiO2), an absorption layer A (ZnSe), a second dielectric layer D2 (SiO2), and a phase transition layer S (Sb2S3) for constructing a one-dimensional photonic crystal DBR. The specific thickness of each layer is given in Table 1. Figure 3 The image shows the reflection spectrum of Example 1 under perpendicular incidence. The solid line represents the reflection spectrum of Sb2S3 in the amorphous state, and the dashed line represents the reflection spectrum in the crystalline state. Figure 4 This is a chromaticity coordinate diagram of Example 1 at a vertical incident angle. From... Figure 3The reflectance spectrum shows that, compared to the traditional TAMM structure, the superposition of resonant cavities results in higher reflectance in the target wavelength band and a steeper change in the trough sidebands. This indicates that the structure can achieve higher brightness and higher saturation colors. Calculations show that in the amorphous state, the reflectance in the 800-2500nm range is 87.038%, the cyan brightness value L is 81.8396, the tristimulus values ​​for cyan coordinates are (45.5166, 68.2201, 84.7378), the converted RGB values ​​are (59, 229, 210), and the cyan chromaticity coordinates are (0.2293, 0.3437). In the crystalline state, the tristimulus values ​​for cyan-gray coordinates are (66.6352, 81.179, 80.4529), the converted RGB values ​​are (189, 245, 221), and the cyan chromaticity coordinates are (0.2919, 0.3556). This embodiment achieves a good cyan effect while also realizing high reflectivity in the near-infrared band, resulting in a cooling effect. Furthermore, the different colors displayed after the phase transition demonstrate its excellent dynamic control function.

[0064] Table 1

[0065] Example 2 This embodiment provides a multilayer structure of cyan structural color thin film with cooling function. The structural color device consists of a substrate Sub, a third dielectric layer D3 (TiO2) in the resonant cavity, a metal layer M (Au), a first dielectric layer D1 (SiO2) for constructing a one-dimensional photonic crystal DBR, an absorption layer A (WO3), a second dielectric layer D2 (SiO2), and a phase transition layer S (Si). The specific thickness of each layer is given in Table 2. Figure 5 The image shows the reflection spectrum of Example 2 under vertical incidence. The solid line represents the reflection spectrum of Si in the amorphous state, and the dashed line represents the reflection spectrum in the crystalline state. Figure 6 This is a chromaticity coordinate diagram of Example 2 at a vertical incident angle. From... Figure 5The reflectance spectrum shows that, compared to the traditional TAMM structure, the superposition of resonant cavities results in higher reflectance in the target wavelength band and a steeper change in the trough sidebands. This indicates that the structure can achieve higher brightness and higher saturation colors. Calculations show that in the amorphous state, the reflectance in the 800-2500nm range is 88.145%, the cyan brightness value L is 80.2846, the tristimulus values ​​for cyan are (41.1272, 64.4562, 47.2803), the converted RGB values ​​are (98, 222, 158), and the cyan chromaticity coordinates are (0.269, 0.4217). In the crystalline state, the tristimulus values ​​for blue are (26.742, 39.8846, 87.1541), the converted RGB values ​​are (0, 192, 238), and the blue chromaticity coordinates are (0.1739, 0.2594). This embodiment achieves a good cyan effect while also exhibiting high reflectivity in the near-infrared band, resulting in a cooling effect. Furthermore, the different colors displayed after the phase transition demonstrate its excellent dynamic control function.

[0066] Table 2

[0067] Example 3 This embodiment provides a multilayer structure of magenta structural color thin film with cooling function. The structural color device consists of a substrate Sub, a third dielectric layer D3 (TiO2) in the resonant cavity, a metal layer M (Ag), and a first dielectric layer D1 (SiO2), an absorption layer A (Fe2O3), a second dielectric layer D2 (SiO2), and a phase transition layer S (Sb2S3) for constructing a one-dimensional photonic crystal DBR. The specific thickness of each layer is given in Table 3. Figure 7 The image shows the reflection spectrum of Example 3 under vertical incidence. The solid line represents the reflection spectrum of Sb2S3 in the amorphous state, and the dashed line represents the reflection spectrum in the crystalline state. Figure 8 This is the chromaticity coordinate diagram of Example 3 at the vertical incident angle. From... Figure 7The reflectance spectrum shows that, compared to the traditional TAMM structure, the superposition of resonant cavities results in higher reflectance in the target wavelength band and a steeper change in the trough sidebands. This indicates that the structure can achieve higher brightness and higher saturation colors. Calculations show that the reflectance in the 800-2500nm range is 91.237%, the magenta brightness value L is 49.9026, the tristimulus values ​​for magenta are (44.9478, 24.9027, 89.0949), the converted RGB values ​​are (203, 75, 253), and the chromaticity coordinates for magenta are (0.2828, 0.1567). In the crystalline state, the tristimulus values ​​for blue are (44.5221, 44.0583, 94.0281), the converted RGB values ​​are (148, 176, 247), and the chromaticity coordinates for blue are (0.2438, 0.2413). This embodiment achieves a good magenta effect while also exhibiting high reflectivity in the near-infrared band, thus achieving a cooling effect. Furthermore, the different colors displayed after the phase transition demonstrate its excellent dynamic control function.

[0068] Table 3

[0069] Example 4 This embodiment provides a multilayer structure of a yellow structural color thin film with cooling function. The structural color device consists of a substrate Sub, a third dielectric layer D3 (Ta2O5) in the resonant cavity, a metal layer M (Au), and a first dielectric layer D1 (SiO2), an absorption layer A (Fe3O4), a second dielectric layer D2 (SiO2), and a phase transition layer S (Si) for constructing a one-dimensional photonic crystal DBR. The specific thickness of each layer is given in Table 3. Figure 9 The image shows the reflection spectrum of Example 4 under vertical incidence. The solid line represents the reflection spectrum of Si in the amorphous state, and the dashed line represents the reflection spectrum in the crystalline state. Figure 10 This is a chromaticity coordinate diagram of Example 5 at a vertical incident angle. From... Figure 9The reflectance spectrum shows that, compared to the traditional TAMM structure, the superposition of resonant cavities results in higher reflectance in the target wavelength band and a steeper change in the trough sidebands. This indicates that the structure can achieve higher brightness and higher saturation colors. Calculations show that the reflectance in the 800-2500nm range is 95.511%, the yellow brightness value L is 66.5377, the tristimulus values ​​for yellow coordinates are (47.6512, 44.2726, 3.928), the converted RGB values ​​are (237, 164, 0), and the chromaticity coordinates are (0.4971, 0.4619). In the crystalline state, the tristimulus values ​​for yellow coordinates are (48.6667, 45.4047, 3.1224), the converted RGB values ​​are (239, 166, 0), and the chromaticity coordinates are (0.5007, 0.4627). This embodiment achieves good yellow color while also achieving high reflectance in the near-infrared band, resulting in a cooling effect. At the same time, the phase change results in different color displays, demonstrating its excellent dynamic control function.

[0070] Table 4

[0071] Example 5 This embodiment provides a magenta structural color thin film multilayer structure with cooling function. The structural color device consists of a substrate Sub, a third dielectric layer D3 (Ta2O5) in the resonant cavity, a metal layer M (Ag), and a first dielectric layer D1 (MgF2), an absorption layer A (ZnSe), a second dielectric layer D2 (MgF2), and a phase transition layer S (GSST) for constructing a one-dimensional photonic crystal DBR. The specific thickness of each layer is given in Table 5. Figure 11 The image shows the reflection spectrum of Example 5 under vertical incidence. The solid line represents the reflection spectrum of GSST in the amorphous state, and the dashed line represents the reflection spectrum in the crystalline state. Figure 12 This is a chromaticity coordinate diagram of Example 5 at a vertical incident angle. From... Figure 11The reflectance spectrum shows that, compared to the traditional TAMM structure, the superposition of resonant cavities results in higher reflectance in the target wavelength band and a steeper change in the trough sidebands. This indicates that the structure can achieve higher brightness and higher saturation colors. Calculations show that the reflectance in the 800-2500nm range is 80.098%, the magenta brightness value L is 48.6631, the tristimulus values ​​for magenta are (33.2468, 23.6809, 70.3438), the converted RGB values ​​are (162, 108, 220), and the chromaticity coordinates for magenta are (0.2612, 0.1861). In the crystalline state, the tristimulus values ​​for violet are (56.5830, 50.4229, 82.942), the converted RGB values ​​are (210, 176, 232), and the chromaticity coordinates for violet are (0.2979, 0.2655). This embodiment achieves a good magenta effect while also exhibiting high reflectivity in the near-infrared band, thus achieving a cooling effect. Furthermore, the different colors displayed after the phase transition demonstrate its excellent dynamic control function.

[0072] Table 5

[0073] Example 6 This embodiment provides a multilayer structure of a yellow structural color thin film with cooling function. The structural color device consists of a substrate Sub, a third dielectric layer D3 (TiO2) in the resonant cavity, a metal layer M (Ag), and a first dielectric layer D1 (SiO2), an absorption layer A (ZnSe), a second dielectric layer D2 (SiO2), and a phase transition layer S (VO2) for constructing a one-dimensional photonic crystal DBR. The specific thickness of each layer is given in Table 3. Figure 13 This is the reflection spectrum of Example 6 under vertical incidence. Figure 14 This is a chromaticity coordinate diagram of Example 6 at a vertical incident angle. From... Figure 13The reflectance spectrum shows that, compared to the traditional TAMM structure, the superposition of resonant cavities results in higher reflectance in the target wavelength band and a steeper change in the trough sidebands. This indicates that the structure can achieve higher brightness and higher saturation colors. Calculations show that the reflectance in the 800-2500nm range is 85.676%, the yellow brightness value L is 93.1183, the tristimulus values ​​for yellow coordinates are (74.5881, 86.7102, 23.5189), the converted RGB values ​​are (251, 245, 95), and the chromaticity coordinates for yellow are (0.4036, 0.4692). In the crystalline state, the tristimulus values ​​for yellow coordinates are (74.7578, 87.4715, 15.8808), the converted RGB values ​​are (255, 246, 49), and the chromaticity coordinates for yellow are (0.4179, 0.4911). This embodiment achieves good yellow color while also achieving high reflectance in the near-infrared band, resulting in a cooling effect. At the same time, the phase change results in different color displays, demonstrating its excellent dynamic control function.

[0074] Table 6

[0075] The above description is only a part of the embodiments of the present invention and does not limit the scope of protection of the present invention. Any equivalent device or equivalent process transformation made based on the content of the present invention specification and drawings, or direct or indirect application in other related technical fields, are similarly included within the patent protection scope of the present invention.

Claims

1. A colored cooling thin film based on a TAMM structure coupled resonant cavity, characterized in that, The thin film comprises, from bottom to top: a substrate Sub, a first dielectric layer D1, an absorption layer A, a second dielectric layer D2, a phase change layer S, a metal layer M, and a third dielectric layer D3; The first dielectric layer D1, the absorption layer A, the second dielectric layer D2, the phase change layer S, and the metal layer M together constitute a TAMM structure, which is a metal-side TAMM structure; the third dielectric layer D3 and the metal layer M together constitute a resonant cavity, which is a high-order resonant cavity. The thin film achieves narrowband high reflectivity in the visible light band to present structural color through the synergistic coupling of the TAMM structure and the resonant cavity, and achieves high reflectivity in the near-infrared band to achieve passive cooling.

2. The colored cooling film based on a TAMM structure coupled resonant cavity as described in claim 1, characterized in that, The thickness of the absorber layer A ranges from 5 nm to 400 nm; the material of the absorber layer A is selected from at least one of zinc selenide, tungsten trioxide, ferric oxide, ferric oxide, indium tin oxide, cobalt oxide, nickel oxide, copper sulfide, and bismuth sulfide.

3. The colored cooling film based on a TAMM structure coupled resonant cavity as described in claim 1, characterized in that, The thickness of the phase change layer S ranges from 5 nm to 200 nm; the material of the phase change layer S is selected from at least one of silicon, germanium, GST, GSST, SS, GT, vanadium oxide and niobium dioxide.

4. The colored cooling film based on a TAMM structure coupled resonant cavity as described in claim 1, characterized in that, The thickness of the metal layer M ranges from 20 nm to 60 nm; the material of the metal layer M is selected from at least one of gold, silver, aluminum, tungsten and titanium.

5. A colored cooling film based on a TAMM structure coupled resonant cavity as described in claim 1, characterized in that, The thickness of the first dielectric layer D1 and the second dielectric layer D2 are each independently between 5 nm and 400 nm, and the two thicknesses may be the same or different.

6. A colored cooling film based on a TAMM structure coupled resonant cavity as described in claim 1, characterized in that, The thickness of the third dielectric layer D3 ranges from 20 nm to 1000 nm.

7. A colored cooling film based on a TAMM structure coupled resonant cavity as described in claim 1, characterized in that, The materials of the first dielectric layer D1, the second dielectric layer D2, and the third dielectric layer D3 are selected from at least one of silicon oxide, titanium oxide, tantalum oxide, hafnium oxide, zirconium oxide, yttrium oxide, zinc oxide, chromium oxide, magnesium oxide, cerium oxide, zinc sulfide, magnesium fluoride, aluminum fluoride, cerium fluoride, lanthanum chloride, sodium hexachloroaluminate, neodymium fluoride, barium fluoride, calcium fluoride, lithium fluoride, lanthanum titanate, zinc sulfide, and silicon nitride.

8. A colored cooling film based on a TAMM structure coupled resonant cavity as described in claim 1, characterized in that, The substrate Sub is made of a material selected from glass, polished stainless steel, polished mirror aluminum, polyethylene terephthalate, cellulose triacetate, polymethyl methacrylate, polycarbonate / polymethyl methacrylate composite material, polyimide, polypropylene, polyvinyl chloride, polyvinyl butyral, ethylene vinyl acetate copolymer, polyurethane elastomer, polytetrafluoroethylene, fluoroethyl propylene, or polydifluoroethylene.

9. A colored cooling film based on a TAMM structure coupled resonant cavity as described in claim 1, characterized in that, The resonant cavity is a high-order Fabry-Perot resonant cavity based on a metal-dielectric-air structure, and its resonance condition satisfies the following formula: Where n is the refractive index of the third dielectric layer D3, d is the thickness of the third dielectric layer D3, λ is the center wavelength corresponding to the target color, and m is the resonance order.

10. A method for preparing a thin film according to any one of claims 1 to 9, characterized in that, Includes the following steps: Step 1: Based on the target color and cooling performance requirements, determine the thin film structure as Sub / D1 / A / D2 / S / M / D3, where: Sub represents the substrate, D1 represents the first dielectric layer, A represents the absorption layer, D2 represents the second dielectric layer, S represents the phase change layer, M represents the metal layer, and D3 represents the third dielectric layer; and calculate the material type and thickness parameters of each layer in the thin film structure. Step 2: Provide a clean and flat substrate (Sub) and place it in the vacuum chamber of the film deposition equipment; Step 3: Using physical vapor deposition or chemical vapor deposition, deposit the first dielectric layer D1, the absorption layer A, the second dielectric layer D2, the phase change layer S, the metal layer M and the third dielectric layer D3 sequentially on the substrate Sub; Step 4: During the deposition of the phase change layer S and the metal layer M, an inert protective gas is introduced to prevent material oxidation; Step 5: After all film layers are deposited, the colored cooling film is obtained.

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