A solar spectrum-selective absorbing metamaterial with a non-uniformly graded cavity structure and a preparation method thereof

Abstract

The application belongs to the field of solar light and heat utilization, and particularly relates to a solar spectrum selective absorption metamaterial with a non-uniform gradually changing resonant cavity structure and a preparation method. The material structure comprises a three-layer film with a concave structure, wherein the upper layer is a metal thin layer, the middle layer is a dielectric layer, and the bottom layer is a metal layer. The size of the concave structure cavity and the thickness of the three-layer film gradually decrease from the top to the bottom, thereby increasing the absorption sites of the solar wave band, customizing the matching of electromagnetic response requirements of different wave bands, and realizing the selective absorption of the spectrum. The material is suitable for the scene of efficiently converting solar radiation electromagnetic waves into heat energy through the gradually changing structural design. The material has the characteristics of a wide spectrum absorption range, i.e. high efficient capturing ability of the solar spectrum, and low radiation performance in the infrared wave band. The material also has the advantages of thin thickness, high absorption, low cost, easy control, simple manufacturing process, high temperature resistance and the like, and is a high efficient light and heat conversion material.

Description

TECHNICAL FIELD

[0001] The application belongs to the field of solar photothermal utilization, and particularly relates to a solar spectrum-selective absorption metamaterial with a non-uniformly gradually changing resonant cavity structure and a preparation method. BACKGROUND

[0002] Solar energy, as a clean and renewable energy source, is receiving increasing attention and utilization worldwide. Sustainable utilization of solar energy is of great significance in addressing energy issues. Solar photothermal materials exhibit excellent performance in converting solar radiation into heat energy and are widely used in fields such as thermal power generation, thermal catalysis, seawater desalination, sterilization, and thermal response sensors. With continuous technological advancements, the application prospects of solar energy will be even broader, creating a more sustainable and environmentally friendly future for humanity.

[0003] Spectrum-selective absorption materials play an important role in solar applications, as they can selectively absorb energy from sunlight while reducing infrared radiation loss. Traditional photothermal materials perform well in absorbing sunlight, but their high infrared radiation characteristics limit energy utilization efficiency. As the material absorbs solar energy and warms up, according to the Stefan-Boltzmann law, the energy radiated to the environment increases, thereby reducing the overall photothermal conversion efficiency. Despite attempts to improve this situation through material doping and compounding, no fundamental breakthrough has been made. Currently available spectrum-selective absorption materials still have problems such as narrow absorption range, poor heat resistance, thick structure, and high emissivity, which restrict their performance in practical applications and cannot fully meet the dual requirements of wide spectrum absorption and low infrared radiation in solar applications. Therefore, developing new materials and technologies to overcome these challenges is crucial to improving solar energy utilization efficiency. SUMMARY

[0004] To address the problems in the prior art, the present application proposes a solar spectrum-selective absorption metamaterial with a non-uniformly gradually changing resonant cavity structure and a preparation method. By structuring the planar thin film reasonably, the material is endowed with a non-uniformly gradually changing resonant cavity, which not only greatly expands the absorption sites of the solar spectrum but also can be customized to match different waveband electromagnetic response requirements. This material, when applied to scenarios where solar radiation electromagnetic waves are efficiently converted into heat energy, can achieve wide-frequency absorption of the solar spectrum and low-radiation characteristics of the infrared spectrum, and has advantages such as thin thickness, high absorption, low cost, easy control, simple manufacturing process, and high temperature resistance, making it a highly efficient photothermal conversion material.

[0005] The technical solution of the present application is as follows:

[0006] A solar spectrum selective absorption metamaterial with non-uniformly graded resonant cavity structure, the material structure comprises a three-layer thin film with concave structure, the upper layer is a metal thin layer, the middle layer is a dielectric layer, and the bottom layer is a metal layer, the total thickness ranges from 50 nm to 2300 nm, the material has an absorption rate of 95% in the solar spectrum region, an emissivity of 0.08 or less, and an overall light-heat conversion efficiency of 90% or more.

[0007] Further, the above-mentioned solar spectrum selective absorption metamaterial with non-uniformly graded resonant cavity structure has a concave structure with decreasing size from top to bottom, the upper diameter of the concave structure is r 2 , and the lower diameter is r 1 , that is r 2 r 1 r 2 The size range of r 1 is 100 nm to 2500 nm. h h The depth of the concave structure is in the size range of 50 nm to 5000 nm.

[0008] Further, the above-mentioned solar spectrum selective absorption metamaterial with non-uniformly graded resonant cavity structure has a three-layer thin film with non-uniformly graded thickness, the thickness deposited at the top of the concave structure is h t Due to the shadow effect, the thickness deposited at the bottom of the concave structure is h t , that is h t h b h t and h b The size range of

[0009] Further, the above-mentioned solar spectrum selective absorption metamaterial with non-uniformly graded resonant cavity structure, the thickness of the upper metal thin layer is h 1 , the size range is 3 nm to 20 nm, and the metal type is one of Al, Ti, Au, Ag, Cu, Mo, W, or an alloy composed of multiple metals.

[0010] ​​​​​Further, the solar spectrum selective absorption metamaterial with the non-uniformly graded resonant cavity structure has the intermediate medium layer with a thickness of h 2 The size ranges from 20nm to 200nm, and the medium is oxide, nitride, carbide, sulfide, semiconductor or organic matter, and specifically includes SiO2, SiO, Al3O2, TiO2, Si3N4, ZnS or polyvinyl chloride.

[0011] Further, the solar spectrum selective absorption metamaterial with the non-uniformly graded resonant cavity structure has the metal layer composed of metal, including but not limited to one metal or an alloy composed of multiple metals selected from Al, Ti, Au, Ag, Cu, Mo and W, with a thickness of h 3 The size ranges from 30nm to 2000nm.

[0012] Further, the solar spectrum selective absorption metamaterial with the non-uniformly graded resonant cavity structure has the concave structure which can be periodic close packing or random close packing.

[0013] Further, the solar spectrum selective absorption metamaterial with the non-uniformly graded resonant cavity structure has the structure parameters such as the type and size of the upper metal thin layer, the type and thickness of the intermediate medium layer and the type and thickness of the bottom metal layer, which can be adjusted to optimize and adjust the solar spectrum absorption performance and infrared radiation performance, so that the absorption range is optional, and then the wideband perfect absorption for different wave bands is realized.

[0014] A preparation method of a solar spectrum selective absorption metamaterial with a non-uniformly graded resonant cavity structure, comprising the following steps:

[0015] Step 1, preparing a concave structure substrate by nanoimprint technology;

[0016] Step 2, depositing a bottom metal layer, an intermediate medium layer and an upper metal thin layer on the substrate by plating technology through shadow effect to realize the preparation of the graded structure.

[0017] The key point of the present application is to give the material a non-uniformly graded resonant cavity by constructing a non-uniformly graded resonant cavity, which not only greatly expands the absorption sites of the solar spectrum, but also can customize the electromagnetic response requirements of different wave bands, so as to realize the selective absorption of the solar spectrum. In addition, due to the extremely thin film structure, the bottom metal layer makes the overall structure have extremely low emissivity, which suppresses the heat radiation energy loss caused by the temperature rise of the structure due to the absorption of solar energy, greatly improving the photo-thermal conversion efficiency. The solar spectrum selective absorption metamaterial described in the present patent has the advantages of simple structure, wide absorption band, high absorption rate, thin thickness, low cost, easy control, high temperature resistance, and easy large-scale manufacturing.

[0018] Advantages and benefits of the present application:

[0019] The present application proposes a solar spectrum selective absorption metamaterial with a non-uniformly graded resonant cavity structure. By reasonably grading the structure of the planar film, the material is given a non-uniformly graded resonant cavity, which not only greatly expands the absorption sites of the solar spectrum, but also can customize the electromagnetic response requirements of different wave bands. The material is applied to the scene of efficiently converting solar electromagnetic waves into heat energy, which can realize the wide frequency absorption of the solar spectrum and the low radiation characteristics of the infrared spectrum, and has the advantages of thin thickness, high absorption, low cost, easy control, simple manufacturing process, high temperature resistance, etc. It is a kind of high-efficiency photo-thermal conversion material.

[0020] Patent CN202310165878.X discloses a high-temperature stable DMD structure solar spectrum selective absorption coating with a five-layer film structure, from the bottom to the surface in turn diffusion barrier layer, infrared reflection layer, dielectric interference layer, metal absorption layer and anti-reflection layer. Taking AlN / TiB2 / AlN / Mo / AlN / substrate as an example, the diffusion barrier layer, the dielectric interference layer and the anti-reflection layer are all AlN, the infrared reflection layer is Mo, and the metal absorption layer is TiB2. The DMD structure forms a resonant cavity to produce plasmonic effect and multi-layer interference to enhance the absorption of solar wave band. The selective absorption coating has a solar spectrum band absorption ratio greater than 90% and an emission ratio less than 0.10. The present application can have an absorption rate of 95% in the solar spectrum 200 nm~2500 nm region, an emissivity as low as 0.08 or less, and an overall photo-thermal conversion efficiency of 90% or more. The material has a wider absorption band, and can more effectively perform photo-thermal conversion.

[0021] The thinnest thickness of the present application is only 60 nm, compared with the published CN201621076304.7 "Antioxidant solar spectrum selective absorption composite material layer", the present application has a thinner material thickness and a simpler material structure. In the process of large-scale production, it has the advantages of simple preparation process and low manufacturing cost, and has better application prospect. BRIEF DESCRIPTION OF DRAWINGS

[0022] Figure 1 This is a schematic diagram of the metamaterial structure of the present invention;

[0023] Figure 2 Absorption rate diagrams of metamaterials with different dielectric layer thicknesses;

[0024] Figure 3 Absorption rate diagrams of metamaterials with different upper metal thicknesses;

[0025] Figure 4 The diagram shows the absorption rate of metamaterials with different concave structure diameters. Detailed Implementation

[0026] The following detailed description of specific embodiments of the present invention, in conjunction with the accompanying drawings and specific examples, is intended to illustrate the present invention but should not be construed as limiting its scope. Example 1

[0027] A solar spectrally selective absorption metamaterial with a non-uniformly graded resonant cavity structure, the structure of which is as follows: Figure 1 As shown, the material structure comprises a recessed three-layer film. The upper layer is a 10 nm thick Ti metal layer; the middle dielectric layer is a 70 nm thick non-metallic SiO2 dielectric layer; and the bottom layer is a 100 nm thick metallic Al layer. The thickness of this metamaterial is a non-uniformly decreasing three-layer film. The thickness of the three-layer film deposited on the top of the recess is shown in the figure. h t The thickness is 70 nm, which is greater than the thickness deposited at the bottom of the depression. h b The upper diameter is 30 nm. r 2 900 nm, lower diameter r 1 The depth of the concave structure is 300nm. h The wavelength is 700 nm. The concave structure is a periodic hexagonal close-packed structure. The preparation method is as follows: a concave structure substrate is prepared by nanoimprinting technology, and a bottom Al layer, an intermediate SiO2 dielectric layer, and an upper Ti layer are sequentially deposited on the substrate by coating technology; based on the template of the concave substrate and the shadowing effect, a solar spectrally selective absorption metamaterial with a non-uniformly graded resonant cavity structure is prepared.

[0028] Performance analysis of the material described in Example 1:

[0029] 1. Analysis of the Influence of Dielectric Layer Thickness on Wave Absorption Performance

[0030] When the intermediate SiO2 dielectric layer h 2From 70 nm to 130 nm, the absorption peak of the metamaterials red-shifts as a whole, and the absorption intensity also slightly decreases from 0.91 to 0.84, which is caused by the red-shift of the absorption peak deviating from the point of the strongest solar spectrum energy. Figure 2

[0031] 2. The influence of the thickness of the upper metal layer on the wave-absorbing performance

[0032] From 70 nm to 130 nm, the absorption peak of the metamaterials red-shifts as a whole, and the absorption intensity also slightly decreases from 0.91 to 0.84, which is caused by the red-shift of the absorption peak deviating from the point of the strongest solar spectrum energy. Figure 3 h 1 From 3 nm, 6 nm to 12 nm, the absorption peak of the metamaterials first increases and then decreases, and the absorption rate increases from 0.89 to 0.91 and then decreases to 0.85, and the metamaterials have the best solar energy absorption rate when the thickness of the top layer is 6 nm.

[0033] 3. The absorption rate graph of metamaterials with different concave structure diameters

[0034] From 70 nm to 130 nm, the absorption peak of the metamaterials red-shifts as a whole, and the absorption intensity also slightly decreases from 0.91 to 0.84, which is caused by the red-shift of the absorption peak deviating from the point of the strongest solar spectrum energy. Figure 4 From 500 nm to 900 nm, the absorption of the solar radiation spectrum increases to a certain extent, and the absorption rate increases from 87% to 91%, while the emissivity remains unchanged at 0.09.​​

Claims

1. A solar spectrally selective absorption metamaterial with a non-uniformly graded resonant cavity structure, characterized in that, The metamaterial comprises a concave structured three-layer thin film: an upper metal layer, a middle dielectric layer, and a bottom metal layer, with a total thickness ranging from 50 nm to 2300 nm. The metamaterial has an absorptivity of 95% in the solar spectrum region, an emissivity of less than 0.08, and an overall photothermal conversion efficiency of over 90%. This metamaterial features a recessed structure that decreases in size from top to bottom, with an upper diameter of [missing information]. r 2 The lower diameter is r 1 ,Right now r 2 > r 1 ; r 2 The size range is 100 nm to 2500 nm. r 1 The size range is 50 nm to 2400 nm; the depth of the recessed structure is h , h The size range is 50 nm to 5000 nm; This metamaterial consists of three thin films with a non-uniformly decreasing thickness, deposited at the concave top with a thickness of [missing information]. h t Because the shadow effect is greater than the thickness deposited at the bottom of the depression. h t ,Right now h t > h b , h t and h b The size range is 20~900 nm.

2. The solar spectral selective absorption metamaterial with a non-uniformly graded resonant cavity structure according to claim 1, characterized in that, The thickness of the metal thin layer is denoted as h 1 The size ranges from 3 nm to 20 nm, and the metal is an alloy composed of one or more metals selected from Al, Ti, Au, Ag, Cu, Mo, and W.

3. The solar spectral selective absorption metamaterial with a non-uniformly graded resonant cavity structure according to claim 1, characterized in that, The thickness of the dielectric layer is denoted as h 2 The size range is 20~200 nm, and the medium is an oxide, nitride, carbide, sulfide, semiconductor or organic material, specifically including SiO2, SiO, Al3O2, TiO2, Si3N4, ZnS or polyvinyl chloride.

4. The solar spectral selective absorption metamaterial with a non-uniformly graded resonant cavity structure according to claim 1, characterized in that, The metal layer is composed of metals, including but not limited to alloys of one or more metals selected from Al, Ti, Au, Ag, Cu, Mo, and W, with a thickness denoted as . h 3 The size range is 30nm~2000nm.

5. The solar spectral selective absorption metamaterial with a non-uniformly gradient resonant cavity structure according to claim 1, wherein the concave structure is either periodically densely packed or randomly densely packed.

6. A method for preparing a solar spectral selective absorption metamaterial with a non-uniformly graded resonant cavity structure as described in claim 1, characterized in that, Includes the following steps: Step 1: Prepare a recessed structure substrate using nanoimprint lithography; Step 2: Using the shadow effect, a metal layer, a dielectric layer, and a thin metal layer are sequentially deposited on the substrate through a coating technique to achieve the preparation of a gradient structure and obtain the metamaterial.

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