Narrow-spectrum narrow-angle directional heat radiator and preparation method thereof

Abstract

The invention discloses a narrow-spectrum narrow-angle directional heat radiator which comprises a distributed Bragg reflector component and a resonant cavity component, the distributed Bragg reflector component and the resonant cavity component are arranged in an overlapped mode, the distributed Bragg reflector component is of a multi-layer structure, and the distributed Bragg reflector component can directionally transmit a spectrum. The resonant cavity component is of a multi-layer structure and can emit narrow-spectrum heat radiation. The invention further discloses a preparation method of the narrow-spectrum narrow-angle directional heat radiator. According to the narrow-spectrum narrow-angle directional heat radiator, independent regulation and control over the angle and the wave spectrum are achieved.

Description

Technical Field

[0001] The invention relates to the technical field of thermal radiation, and in particular to a narrow-spectrum and narrow-angle directional thermal radiator and a preparation method thereof. Background Art

[0002] The thermal radiation of macroscopic objects has the characteristics of incoherence, wide spectrum, and emissivity that does not change with angle, which limits the efficient use of thermal radiation in infrared detection, gas sensing, etc. In recent years, for various micro-nano structures such as gratings, photonic crystals, metamaterials, and metasurfaces, thermal radiation is used as the interference effect of electromagnetic waves to achieve active regulation of the spectrum, direction, and polarization of thermal radiation, and has been applied in many fields, such as infrared light sources, radiation detection, and thermal photovoltaic (TPV) waste heat utilization. For example, in TPV cells, effective spectral modulation methods are crucial. On the one hand, the introduction of narrow-spectrum and narrow-angle directional radiators can enhance the matching between the emitted photons and the photovoltaic band gap, significantly improving the hotspot conversion efficiency; different photovoltaic devices have different viewing angles, so improving the ability of the radiator to independently control the direction and spectrum can relax the requirements for device design; on the other hand, the use of thermal radiators with directional characteristics can place photovoltaic devices outside the vacuum shell, thereby providing other effective cooling methods for photovoltaic systems. In addition, the production of coherent incandescent lamps requires limiting the wide spectrum and spatial diffusion characteristics of blackbody radiation to a narrow spectral and angular range. Narrow-spectrum and narrow-angle directional thermal emitters can be regarded as coherent thermal light sources, which are of great significance in the field of lighting design such as coherent incandescent lamps.

[0003] However, although the selective thermal emitters designed by the current methods have good narrow-spectrum or directional characteristics, their emission angle range is either omnidirectional and cannot be adjusted, or the original emission angle cannot be maintained when the wavelength is changed, showing significant angular dispersion. In addition, the emission angle and emission wavelength of these thermal emitters show a strong correlation with the refractive index of the material itself, making it difficult to achieve independent control of the angle and spectrum. At the same time, there are few existing designs of thermal radiators with narrow-band and directional emission characteristics, with complex structures, difficult processing and production, and a lack of practical equipment. Therefore, considering the demand for narrow-spectrum, narrow-angle, directional thermal emitters with independent control capabilities in the fields of TPV systems, thermal radiation coherent light source design, infrared detection, etc., it is very necessary to explore simple and effective preparation methods.

[0004] Therefore, technicians in this field are committed to providing a narrow-spectrum and narrow-angle directional thermal radiator and a preparation method thereof, based on microcavity resonance theory and the Brewster effect, to achieve independent control of the angle and spectrum, and make the thermal radiator easy to process. Summary of the invention

[0005] In view of the defects in the prior art, the technical problem to be solved by the present invention is how to provide a narrow-spectrum and narrow-angle directional thermal radiator with independently adjustable angle and spectrum and a preparation method thereof.

[0006] To achieve the above-mentioned purpose, the present invention provides a narrow-spectrum and narrow-angle directional thermal radiator, comprising a distributed Bragg reflector component and a resonance cavity component, wherein the distributed Bragg reflector component and the resonance cavity component are arranged in a superimposed manner, the distributed Bragg reflector component is a multi-layer structure, the distributed Bragg reflector component can directionally transmit a spectrum, and the resonance cavity component is a multi-layer structure, and the resonance cavity component can emit narrow-spectrum thermal radiation.

[0007] Furthermore, the distributed Bragg reflector component is formed by alternately stacking a first medium and a second medium, the first medium and the second medium are made of dielectric materials, and the refractive index of the first medium is greater than the refractive index of the second medium.

[0008] Preferably, the first medium and the second medium are alternately stacked into four layers, and the first medium and the second medium are non-periodically stacked along the direction from the distributed Bragg reflector component to the resonance cavity component.

[0009] Furthermore, the resonance cavity component is formed by superposition of metal and a third medium, and the third medium is made of dielectric material.

[0010] Preferably, the resonance cavity component is a three-layer structure of metal-third medium-metal.

[0011] Furthermore, the thickness of the metal layer of the resonance cavity component on a side close to the distributed Bragg reflector component is less than the metal skin depth, and the thickness of the metal layer of the resonance cavity component on a side away from the distributed Bragg reflector component is greater than the metal skin depth.

[0012] Preferably, the layers between the distributed Bragg reflector components, the layers between the resonance cavity components, and the distributed Bragg reflector components and the resonance cavity components are connected by vacuum coating.

[0013] The present invention also provides a method for preparing a narrow-spectrum and narrow-angle directional thermal radiator, comprising:

[0014] Using silicon wafer as substrate, electron beam evaporation equipment is used to process the metal layer;

[0015] Processing a third dielectric layer on the metal layer using a plasma enhanced chemical vapor deposition process;

[0016] Processing a metal layer on the third dielectric layer using an electron beam evaporation device;

[0017] The first dielectric layer and the second dielectric layer are processed in an alternating manner using a plasma enhanced chemical vapor deposition process.

[0018] Preferably, the method further comprises connecting the metal layer and the third dielectric layer by discrete vacuum coating.

[0019] Preferably, the method further comprises connecting the second dielectric layer and the metal layer, the first dielectric layer and the second dielectric layer by a single vacuum coating method.

[0020] The present invention has at least the following beneficial technical effects:

[0021] The narrow-spectrum and narrow-angle directional thermal radiator based on microcavity resonance theory and Brewster effect of the present invention has the advantages of excellent performance and easy implementation; the thermal radiator can realize narrow-spectrum and narrow-angle directional thermal emission, with an angle broadening of less than 20°, a spectrum broadening of less than 25nm, a maximum emissivity of up to 0.97, and excellent selectivity; by adjusting the size parameters and materials of the structure, the spectrum and angle corresponding to the high emission area can be independently controlled and freely designed, which has significant control advantages; the thermal radiation device is only composed of a film structure, and the materials used are all common metals and dielectric materials, and there are fewer restrictions on the selection of materials.

[0022] The preparation method of the narrow-spectrum and narrow-angle directional thermal radiator of the present invention realizes the processing of multi-layer films, which can reduce the generation of impurities, ensure the good film forming property of the device and the stable optical properties of the material; the processing method includes five vacuum operations, in which the introduction of oxides into the metal layer and the dielectric layer can greatly increase the close bonding force between the layers.

[0023] The concept, specific structure and technical effects of the present invention will be further described below in conjunction with the accompanying drawings to fully understand the purpose, characteristics and effects of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 is a schematic structural diagram of a narrow-spectrum and narrow-angle directional heat radiator according to an embodiment of the present invention;

[0025] Figure 2 is a polarized emission spectrum of the thermal radiator according to an embodiment of the present invention calculated theoretically under environmental matching conditions;

[0026] Figure 3 is a flow chart of a method for preparing a thermal radiator according to an embodiment of the present invention;

[0027] Figure 4 is a schematic diagram of a measurement method of a thermal radiator according to an embodiment of the present invention;

[0028] Figure 5 is a polarized emission spectrum experimentally measured under environmental matching conditions of the thermal radiator according to an embodiment of the present invention;

[0029] Figure 6 It is a schematic diagram of the emission spectrum decoupling and adjustable capability of the thermal radiator according to an embodiment of the present invention. DETAILED DESCRIPTION

[0030] The following describes the preferred embodiments of the present invention to make its technical content clearer and easier to understand. The present invention can be embodied in many different forms of embodiments, and the protection scope of the present invention is not limited to the embodiments mentioned in the text.

[0031] In the drawings, components with the same structure are indicated by the same numerical reference numerals, and components with similar structures or functions are indicated by similar numerical reference numerals. The size and thickness of each component shown in the drawings are arbitrarily shown, and the present invention does not limit the size and thickness of each component. In order to make the illustration clearer, the thickness of the components is appropriately exaggerated in some places in the drawings.

[0032] The present invention provides a narrow-spectrum and narrow-angle directional thermal radiator, which can independently control the spectrum and angle corresponding to the high-emission area by adjusting the size parameters and materials of the structure, and has a good narrow-spectrum and narrow-angle directional thermal radiation effect.

[0033] like Figure 1 The figure shows a schematic diagram of the structure of the narrow-spectrum and narrow-angle directional heat radiator of the present embodiment. The heat radiator is formed by superposition of a distributed Bragg reflector component 1 and a resonant cavity component 2. Normally, the distributed Bragg reflector component 1 is located above the resonant cavity component 2, and the signal enters the resonant cavity component 2 from the distributed Bragg reflector component 1. The distributed Bragg reflector component 1 is based on the Brewster effect and has a spectral directional transmission characteristic, and the corresponding equivalent Brewster angle (i.e., the selection angle) can be adjusted according to the dielectric material used. The resonant cavity component 2 is based on the microcavity resonance effect and has a narrow-spectrum thermal emission characteristic, and its resonant wavelength can be adjusted according to the dielectric material used and its thickness.

[0034] The distributed Bragg reflector component 1 is formed by alternately stacking the first medium and the second medium to form a multilayer structure. In the direction from the distributed Bragg reflector component 1 to the resonant cavity component 2, the first medium layer and the second medium layer are non-periodic structures, that is, the thickness of the first medium layer and the second medium layer is non-periodic distribution.

[0035] Specifically, the distributed Bragg reflector component 1 of this embodiment is a four-layer structure, and the first dielectric layer and the second dielectric layer each have two layers, which are the first dielectric layer 11, the second dielectric layer 12, the first dielectric layer 13, and the second dielectric layer 14. The thickness of the first dielectric layer 11, the second dielectric layer 12, the first dielectric layer 13, and the second dielectric layer 14 is non-periodically distributed and can be selected according to actual needs.

[0036] The resonance cavity component 2 is formed by alternately stacking metal and a third medium to form a multi-layer structure. Specifically, the resonance cavity component 2 of this embodiment is a three-layer structure, with two metal layers and one third medium layer, which are metal layer 21, third medium layer 22, and metal layer 23 in sequence, forming a metal-third medium-metal structure.

[0037] In this embodiment, the first medium, the second medium and the third medium are all made of dielectric materials and are optically transparent materials, specifically semiconductor materials such as silicon and germanium, or oxide materials such as silicon dioxide and aluminum oxide; wherein the refractive index of the first medium must be greater than the refractive index of the second medium. The metal can be common materials such as gold, chromium, and tungsten, the thickness of the metal layer 21 must be less than the metal skin depth, and the thickness of the metal layer 23 must be greater than the metal skin depth.

[0038] The distributed Bragg reflector component 1 and the resonant cavity component 2 are decoupled from each other and jointly undertake the task of regulating the spectrum and angle. The layers of the distributed Bragg reflector component 1, the layers of the resonant cavity component 2, and the resonant cavity component 2 and the distributed Bragg reflector component 1 are all connected by vacuum coating.

[0039] In a specific embodiment of the narrow-spectrum and narrow-angle directional heat radiator, the first dielectric layer is made of silicon, the second dielectric layer is made of silicon dioxide, the third dielectric layer is made of silicon, and the metal is gold. Under the condition of environmental matching, the following is obtained through theoretical calculation: Figure 2 The p-polarized emission spectrum shown in the figure shows that there is an obvious selective high emission region (emissivity E>0.5) in the p-polarization state. The angular broadening of the high emission region is less than 20°, the spectral broadening is less than 0.025μm, and the maximum emissivity can reach 0.97 when p-polarized light is incident.

[0040] The present invention also provides a method for preparing a narrow-spectrum and narrow-angle directional thermal radiator, such as Figure 3 As shown, the process of the preparation method is as follows.

[0041] Using silicon wafer as substrate, electron beam evaporation equipment is used to process the film system of metal layer 23, the thickness of which needs to be greater than the skin depth of the metal, and it needs to contain 10nm of chromium metal as an adhesion layer; before processing the third dielectric layer 22, a 5nm oxide protective layer is processed on the metal layer 23 by atomic layer deposition, and then the third dielectric layer 22 is processed by plasma enhanced chemical vapor deposition process at a temperature of about 300°C, which will not damage the metal layer 23; finally, electron beam evaporation equipment is used to process the metal layer 21, and the thickness of which needs to be less than the skin depth of the metal. Electron beam evaporation, atomic layer deposition and plasma enhanced chemical vapor deposition are all carried out under vacuum.

[0042] For the dielectric alternating distributed Bragg reflector component, a plasma enhanced chemical vapor deposition process is used under vacuum conditions to process the required second dielectric layer 14, first dielectric layer 13, second dielectric layer 12, and first dielectric layer 11 in an alternating manner at a processing temperature of about 300°C.

[0043] The preparation method of this embodiment only requires 5 vacuum processes ( Figure 3 The process indicated by the right-pointing arrow in the figure is conducive to the close bonding of each layer, ensuring the good film-forming properties of the final film structure.

[0044] like Figure 4 As shown, the thermal radiator of this embodiment needs to use a prism with a certain refractive index to match the environment during the actual measurement process. The signal is emitted from one end and does not refract when passing through the semi-cylindrical prism, and enters the surface of the thermal radiator sample according to the original optical path. Similarly, the reflected light does not refract when leaving the prism, and the signal is absorbed by the receiving end. The background sample used in the measurement is an aluminum mirror.

[0045] according to Figure 4 The measurement scheme shown in the figure is used to measure the angle-resolved spectrum of the thermal radiator sample, and the results are as follows: Figure 5 The p-polarized emission spectrum of the thermal radiator shown is experimentally measured under environmental matching conditions; the experimental results are basically consistent with the theoretical calculations, proving the rationality and feasibility of the preparation method and the prepared thermal radiator.

[0046] like Figure 6 The figure shows the decoupling adjustable capability of the emission spectrum of the thermal radiator in the near-infrared region with p-polarized light incident on the structure with different parameters such as material and size. In the figure, n0 refers to the refractive index of the ambient condition, n1 refers to the refractive index of the first dielectric material, n2 refers to the refractive index of the second dielectric material, and d die Refers to the thickness of the third medium; As can be seen from the figure, the narrow spectrum and narrow angle directional spectrum has independent decoupling adjustability. Furthermore, by changing the material, thickness, number of layers, environmental matching conditions, etc., the position of the high emission area can be freely adjusted. The narrow spectrum and narrow angle directional selection area of ​​the structure can be extended to the visible light region or the infrared region, and the regulation method is universal.

[0047] The preferred specific embodiments of the present invention are described in detail above. It should be understood that a person skilled in the art can make many modifications and changes based on the concept of the present invention without creative work. Therefore, any technical solution that can be obtained by a person skilled in the art through logical analysis, reasoning or limited experiments based on the concept of the present invention on the basis of the prior art should be within the scope of protection determined by the claims.

Claims

1. A narrow spectrum and narrow angle directional heat radiator, characterized in that: It comprises a distributed Bragg reflector component and a resonance cavity component. The distributed Bragg reflector component and the resonance cavity component are arranged in a superimposed manner. The distributed Bragg reflector component is a multi-layer structure and can transmit a spectrum in a direction. The resonance cavity component is a multi-layer structure and can emit narrow-spectrum thermal radiation.

2. The narrow-spectrum and narrow-angle directional heat radiator according to claim 1, characterized in that: The distributed Bragg reflector component is formed by alternately stacking a first medium and a second medium. The first medium and the second medium are made of dielectric materials. The refractive index of the first medium is greater than the refractive index of the second medium.

3. The narrow-spectrum and narrow-angle directional heat radiator according to claim 2, characterized in that: The first medium and the second medium are alternately stacked into four layers, and the first medium and the second medium are non-periodically stacked along the direction from the distributed Bragg reflector component to the resonance cavity component.

4. The narrow-spectrum and narrow-angle directional heat radiator according to claim 1, characterized in that: The resonance cavity component is formed by stacking metal and a third medium, and the third medium is made of dielectric material.

5. The narrow-spectrum and narrow-angle directional heat radiator according to claim 4, characterized in that: The resonance cavity component is a three-layer structure of metal-third medium-metal.

6. The narrow-spectrum and narrow-angle directional heat radiator according to claim 5, characterized in that: The thickness of the metal layer of the resonance cavity component on a side close to the distributed Bragg reflector component is less than the metal skin depth, and the thickness of the metal layer of the resonance cavity component on a side away from the distributed Bragg reflector component is greater than the metal skin depth.

7. The narrow-spectrum and narrow-angle directional heat radiator according to claim 1, characterized in that: The layers between the distributed Bragg reflector components, the layers between the resonance cavity components, and the distributed Bragg reflector components and the resonance cavity components are connected by vacuum coating.

8. The method for preparing a narrow-spectrum and narrow-angle directional thermal radiator according to any one of claims 1 to 7, characterized in that: include: Using silicon wafer as substrate, electron beam evaporation equipment is used to process the metal layer; Processing a third dielectric layer on the metal layer using a plasma enhanced chemical vapor deposition process; Processing a metal layer on the third dielectric layer using an electron beam evaporation device; The first dielectric layer and the second dielectric layer are processed in an alternating manner using a plasma enhanced chemical vapor deposition process.

9. The method for preparing a narrow-spectrum and narrow-angle directional thermal radiator according to claim 8, characterized in that: The method also includes connecting the metal layer and the third dielectric layer by discrete vacuum coating.

10. The method for preparing a narrow-spectrum and narrow-angle directional thermal radiator according to claim 8, characterized in that: The method also includes connecting the second dielectric layer and the metal layer, the first dielectric layer and the second dielectric layer by a single vacuum coating method.

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