Solar spectrum selective absorption metamaterial of non-uniform gradual change resonant cavity structure and preparation method

Abstract

The invention belongs to the field of solar photo-thermal utilization, and particularly relates to a solar spectrum selective absorption metamaterial with a non-uniform gradual change resonant cavity structure and a preparation method. The material structure comprises three layers of thin films which are concave and structured, 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 of the material and the thickness of the three layers of thin films are gradually reduced from top to bottom, absorption sites of solar wave bands are increased, electromagnetic response requirements of different wave bands are met in a customized mode, and selective absorption of spectrums is achieved. The material is suitable for a scene of efficiently converting solar radiation electromagnetic waves into heat energy through gradient structural design. The material has the remarkable characteristics of wide spectrum absorption range, namely efficient capturing capability on solar spectrum and low radiation performance in an infrared band. The material also has the advantages of thin thickness, high absorption, low cost, easiness in regulation and control, simple manufacturing process, high temperature resistance and the like, and is an efficient photo-thermal conversion material.

Description

Technical Field

[0001] The present invention belongs to the field of solar thermal utilization, and in particular relates to a solar spectrum selective absorption metamaterial with a non-uniform gradient resonance cavity structure and a preparation method thereof. Background Art

[0002] As a clean and renewable energy source, solar energy is receiving more and more attention and utilization around the world. The sustainable use of solar energy is of great significance to solving energy problems. Solar thermal materials have excellent performance in converting solar radiation into thermal energy and are widely used in thermal power generation, thermal catalysis, seawater desalination, sterilization, and thermal response sensors. With the continuous advancement of technology, the application prospects of solar energy will be broader, creating a more sustainable and environmentally friendly future for mankind.

[0003] Spectrally selective absorption materials play an important role in solar energy applications. They can selectively absorb energy from sunlight while reducing radiation losses in the infrared band. Although traditional photothermal materials perform well in absorbing sunlight, their high radiation characteristics in the infrared band limit the efficiency of energy utilization. As the material absorbs solar energy and heats up, according to the Stefan-Boltzmann law, the energy radiated to the environment increases, thereby reducing the overall photothermal conversion efficiency. Although attempts have been made to improve this situation through methods such as material doping and compounding, no fundamental breakthrough has been achieved. Currently, spectrally selective absorption materials on the market still have problems such as narrow absorption range, poor heat resistance, heavy structure, and high emissivity, which restrict their effectiveness in practical applications and cannot fully meet the dual needs of wide spectrum absorption and low infrared radiation in solar energy applications. Therefore, the development of new materials and technologies to overcome these challenges is the key to improving the efficiency of solar energy utilization. Summary of the invention

[0004] In view of the problems in the prior art, the present invention proposes a solar spectrum selective absorption metamaterial with a non-uniform gradient resonant cavity structure and a preparation method. By rationally structuring the planar film, the material is endowed with a non-uniform gradient resonant cavity, which not only greatly expands the absorption sites of the solar spectrum, but also can be customized to match the electromagnetic response requirements of different bands. This material is used in the scene of efficient conversion of solar radiation electromagnetic waves into thermal energy, and can achieve broadband absorption of the solar spectrum and low radiation characteristics of the infrared spectrum. It has the advantages of thin thickness, high absorption, low cost, easy control, simple manufacturing process, and high temperature resistance. It is an efficient photothermal conversion material.

[0005] The technical solution of the present invention is: A solar spectrum selective absorption metamaterial with a non-uniform gradient resonant cavity structure, wherein the material structure comprises a concave structured three-layer film, wherein the upper layer is a metal thin layer, the middle layer is a dielectric layer, and the bottom layer is a metal layer, and the total thickness ranges from 50nm to 2300nm. The material has an absorptivity of 95% in the solar spectrum region, an emissivity of less than 0.08, and an overall photothermal conversion efficiency of more than 90%.

[0006] Furthermore, the solar spectrum selective absorption metamaterial of the non-uniform gradient resonant cavity structure has a concave structure with a decreasing size from top to bottom, and the upper diameter of the concave structure is r 2 , the lower diameter is r 1 ,Right now r 2 > r 1 . r 2 The size range is 100 nm~2500 nm. r 1 The size range is 50 nm~2400 nm. The depth of the concave structure is h , h The size range is 50 nm~5000 nm.

[0007] Furthermore, the above-mentioned non-uniform gradient resonant cavity structure solar spectrum selective absorption metamaterial has three layers of thin films with non-uniform gradient decreasing thickness, and the thickness deposited on the concave top is h t Since the shadow effect is greater than the thickness of the deposit 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.

[0008] Furthermore, in the above-mentioned non-uniform gradient resonant cavity structure solar spectrum selective absorption metamaterial, the thickness of the upper metal thin layer is recorded as h 1 , the size range is 3 nm~20 nm, and the metal type is one metal or an alloy of multiple components such as Al, Ti, Au, Ag, Cu, Mo, W, etc.

[0009] Furthermore, in the above-mentioned solar spectrum selective absorption metamaterial with a non-uniform gradient resonant cavity structure, the thickness of the intermediate dielectric layer is recorded as h 2 , the size range is 20~200 nm, and the medium is oxide, nitride, carbide, sulfide, semiconductor or organic matter, specifically including SiO2, SiO, Al3O2, TiO2, Si3N4, ZnS or polyvinyl chloride, etc.

[0010] Furthermore, in the above-mentioned non-uniform gradient resonant cavity structured solar spectrum selective absorption metamaterial, the metal layer is 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, W, etc., and the thickness is recorded as h 3 , the size range is 30nm~2000nm.

[0011] Furthermore, in the above-mentioned solar spectrum selective absorption metamaterial with a non-uniform gradient resonant cavity structure, the concave structures can be periodically densely packed or randomly densely packed.

[0012] Furthermore, the above-mentioned solar spectrum selective absorption metamaterial with a non-uniform gradient resonant cavity structure can optimize and adjust the solar spectrum absorption performance and infrared radiation performance by adjusting structural parameters such as the type and size of the upper metal thin layer, the type and thickness of the intermediate dielectric layer, and the type and thickness of the bottom metal layer, so that the absorption range is optional, thereby achieving broadband perfect absorption for different bands.

[0013] A method for preparing a solar spectrum selective absorption metamaterial with a non-uniform gradient resonant cavity structure comprises the following steps: Step 1: preparing a concave structure substrate by nanoimprinting technology; Step 2: Using the shadow effect, a bottom metal layer, an intermediate dielectric layer and an upper metal thin layer are sequentially deposited on the substrate through a coating technique to achieve the preparation of a gradient structure.

[0014] The key point of the present invention is that by constructing a non-uniform gradient resonance cavity, the material is endowed with a non-uniform gradient resonance cavity, which not only greatly expands the absorption sites of the solar spectrum, but also can be customized to match the electromagnetic response requirements of different bands, thereby achieving selective absorption of the solar spectrum. In addition, due to the extremely thin film structure, the underlying metal thin layer makes the overall structure have an extremely low emissivity, which suppresses the thermal radiation energy loss caused by the temperature rise of the structure due to the absorption of solar energy, and greatly improves the photothermal conversion efficiency. The solar spectrum selective absorption metamaterial described in this patent has the advantages of relatively simple structure, wide absorption band, high absorption rate, thin thickness, low cost, easy regulation, high temperature resistance, and easy large-scale manufacturing.

[0015] Advantages and beneficial effects of the present invention: The present invention proposes a solar spectrum selective absorption metamaterial with a non-uniform gradient resonant cavity structure. By rationally structuring the planar film with gradients, the material is endowed with a non-uniform gradient resonant cavity, which not only greatly expands the absorption sites of the solar spectrum, but also can be customized to match the electromagnetic response requirements of different bands. This material is used in scenarios where solar radiation electromagnetic waves are efficiently converted into thermal energy. It can achieve broadband absorption of the solar spectrum and low radiation characteristics of the infrared spectrum. It has the advantages of thin thickness, high absorption, low cost, easy control, simple manufacturing process, and high temperature resistance. It is an efficient light-to-heat conversion material.

[0016] Patent CN202310165878.X discloses a high-temperature stable DMD structure solar spectrum selective absorption coating, which has a five-layer film structure, from the bottom to the surface, a diffusion barrier layer, an infrared reflection layer, a dielectric interference layer, a metal absorption layer and an 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 is used to form a resonant cavity to generate plasmon effects and multi-layer interference to enhance the absorption of the solar 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 invention can have an absorption rate of 95% in the 200 nm~2500 nm region of the solar spectrum, an emissivity as low as less than 0.08, an overall light-to-heat conversion efficiency of more than 90%, and a wider bandwidth of the material's efficient absorption band, which can be used for more efficient light-to-heat conversion.

[0017] The thinnest thickness of the present invention is only 60 nm. Compared with the publicly published CN201621076304.7 "Anti-oxidation Solar Spectrum Selective Absorption Composite Material Layer", the present invention has thinner material thickness and simpler material structure. In the process of large-scale production, it has the advantages of simple preparation process and low production cost, and has better application prospects. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 It is a schematic diagram of the structure of the metamaterial of the present invention; Figure 2 This is the absorption rate diagram of metamaterials with different dielectric layer thicknesses; Figure 3 This is a graph of metamaterial absorptivity for different upper metal thicknesses; Figure 4 Figure 2 is a graph showing the absorption rate of metamaterials with different concave structure diameters. DETAILED DESCRIPTION

[0019] The specific implementation modes of the present invention are further described in detail below in conjunction with the accompanying drawings and specific embodiments. The following embodiments are used to illustrate the present invention but cannot be used to limit the scope of the present invention. Example 1

[0020] A solar spectrum selective absorption metamaterial with a non-uniform gradient resonant cavity structure, the structure of which is as follows Figure 1 As shown in the figure, the material structure includes a concave structured three-layer film, the upper layer is a 10 nm thick Ti metal thin layer, the middle dielectric layer is a non-metallic SiO2 dielectric layer with a thickness of 70 nm; the bottom layer is a metal layer composed of metal Al with a thickness of 100 nm. The thickness of the metamaterial is a three-layer film with non-uniform gradient reduction. The thickness of the three-layer film deposited on the top of the concave h t 70 nm, which is greater than the thickness of the deposited h b The upper diameter of the concave structure of the metamaterial is 30 nm. r 2 900 nm, lower diameter r 1 The depth of the concave structure is 300nm. h 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; according to the template of the concave substrate and the shadow effect, a solar spectrum selective absorption metamaterial with a non-uniform gradient resonant cavity structure is prepared.

[0021] The performance analysis of the materials described in Example 1 is as follows: 1. Analysis of the influence of dielectric layer thickness on microwave absorption performance When the middle SiO2 dielectric layer h 2 When increasing from 70 nm to 130 nm, Figure 2 It can be seen that due to the interference principle of electromagnetic waves, the absorption peak of the metamaterial is red-shifted as a whole. Statistics show that the absorption intensity is also slightly reduced, from 0.91 to 0.84. This is because the red shift of the absorption peak is offset from the strongest point of the solar spectrum energy.

[0022] 2. Analysis of the influence of the thickness of the upper metal layer on the microwave absorption performance from Figure 3 As can be seen, as the thickness of the top layer Ti h 1When increasing from 3 nm, 6 nm to 12 nm, the absorption peak of the metamaterial first increases and then decreases. According to statistics, the absorption rate increases from 0.89 to 0.91 and then decreases to 0.85. When the top layer thickness is 6 nm, the absorber has the best solar energy absorption rate.

[0023] 3 Metamaterial absorption rate diagram with different concave structure diameters from Figure 4 It can be seen that as the aperture increases from 500 nm to 900 nm, the absorption of the solar radiation spectrum is enhanced to a certain extent. Statistically, the absorptivity increases from 87% to 91%, while the emissivity remains unchanged, maintaining at 0.09.

Claims

1. A solar spectrum selective absorption metamaterial with a non-uniform gradient resonant cavity structure, characterized in that: 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 total thickness ranges from 50 nm to 2300 nm. The material has an absorptivity of 95% in the solar spectrum region, an emissivity of less than 0.08, and an overall photothermal conversion efficiency of more than 90%.

2. The solar spectrum selective absorption metamaterial with a non-uniform gradient resonant cavity structure according to claim 1, characterized in that: The metamaterial structure has a concave structure with decreasing size from top to bottom, and the upper diameter of the concave structure is r 2 , the lower diameter is r 1 ,Right now r 2 > r 1 ; r 2 The size range is 100 nm~2500 nm. r 1 The size range is 50 nm~2400 nm; the depth of the concave structure is h , h The size range is 50 nm~5000 nm.

3. The solar spectrum selective absorption metamaterial with a non-uniform gradient resonant cavity structure according to claim 1, characterized in that: The metamaterial has three layers of thin films with non-uniform and gradually decreasing thickness, with the thickness deposited on the top of the concave h t Since the shadow effect is greater than the thickness of the deposit 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.

4. The solar spectrum selective absorption metamaterial with a non-uniform gradient resonant cavity structure according to claim 1, characterized in that: The thickness of the upper metal layer is recorded as h 1 , the size range is 3 nm~20 nm, and the metal type is an alloy composed of one or more metals among Al, Ti, Au, Ag, Cu, Mo, and W.

5. The solar spectrum selective absorption metamaterial with a non-uniform gradient resonant cavity structure according to claim 1, characterized in that: The thickness of the intermediate dielectric layer is recorded as h 2 , the size range is 20~200 nm, and the medium is oxide, nitride, carbide, sulfide, semiconductor or organic matter, specifically including SiO2, SiO, Al3O2, TiO2, Si3N4, ZnS or polyvinyl chloride.

6. The solar spectrum selective absorption metamaterial with a non-uniform gradient resonant cavity structure according to claim 1, characterized in that: The bottom metal layer is composed of metal, including but not limited to an alloy composed of one or more metals selected from Al, Ti, Au, Ag, Cu, Mo, and W, and the thickness is recorded as h 3 , the size range is 30nm~2000nm.

7. The broadband wave absorbing metamaterial based on the non-uniform gradient resonant cavity structure according to claim 1, characterized in that: The concave structures may be periodically densely packed or randomly densely packed.

8. A method for preparing a solar spectrum selective absorption metamaterial with a non-uniform gradient resonant cavity structure as claimed in claim 1, characterized in that: The following steps are involved: Step 1: preparing a concave structure substrate by nanoimprinting technology; Step 2: Using the shadow effect, a bottom metal layer, an intermediate dielectric layer and an upper metal thin layer are sequentially deposited on the substrate through a coating technology to achieve the preparation of a gradient structure and obtain the metamaterial.

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