Selective emitter with multilayer film structure and preparation method thereof

Abstract

The invention belongs to the technical field of nuclear science and optics, and relates to a selective emitter with a multilayer film structure and a preparation method of the selective emitter. The selective emitter of the multi-layer film structure comprises high-refractive-index refractory film layers and low-refractive-index refractory film layers which are sequentially and alternately arranged on a coated substrate, the number of the high-refractive-index refractory film layers and the number of the low-refractive-index refractory film layers are two to three, the thickness of the high-refractive-index refractory film layers is not larger than 500 nm, and the thickness of the low-refractive-index refractory film layers is not larger than 100 nm. The preparation method comprises the step of sequentially and alternately depositing the high-refractive-index refractory film layers and the low-refractive-index refractory film layers on the coating substrate by adopting a vacuum coating method. According to the selective emitter, the long-term working performance is basically unchanged in a 1473K environment, the selective emitter has an excellent spectrum selective emission function, the proportion of a wave band matched with an infrared photovoltaic device in a spectrum is larger than 59%, the preparation method is simple and controllable, and the selective emitter is suitable for being matched with various infrared photovoltaic devices.

Description

Technical Field

[0001] The present application relates to the fields of nuclear science and optical technology, and in particular to a selective emitter of a multi-layer film structure and a preparation method thereof. Background Art

[0002] The radioactive thermophotovoltaic (RTPV) system is a device that transfers the heat energy generated by the decay of radioactive isotopes to the emitter, causing it to generate high temperatures and emit infrared radiation. The infrared radiation then converts light energy into electrical energy through some semiconductor infrared photovoltaic conversion devices with specific bandgap widths, such as GaSb, InGaAs, InGaAsSb, InAsSbP, etc. Generally speaking, when designing an RTPV system, the infrared spectrum of the emitter should be considered to match the external quantum efficiency (EQE) of the back-end semiconductor infrared photovoltaic conversion device. For example, the cutoff wavelength of the GaSb cell is 1.78μm. When the wavelength of the incident infrared light exceeds 1.78μm, the GaSb cell cannot convert light energy into electrical energy because the photon energy is not enough to excite carriers. For blackbody radiation, the proportion of infrared radiation below the cutoff wavelength of the semiconductor infrared photovoltaic conversion device is very low, which will result in low output power of the photovoltaic device, low system thermoelectric conversion efficiency, and high heat dissipation requirements for semiconductor infrared photovoltaic conversion. The selective emitter can modulate the emission spectrum of the emitter to the range matched by the infrared photovoltaic device through its own structure, so that the proportion of infrared light in a specific spectral range in the entire radiation spectrum is greatly increased. On the one hand, it can improve the thermoelectric conversion efficiency of the RTPV system and reduce energy dissipation; on the other hand, it can reduce the heat dissipation pressure of the back-end photovoltaic device and lower the temperature of the photovoltaic device.

[0003] In the existing technology, the selective emitter is not stable enough for wavelengths greater than 1.7μm at high temperatures, the ability to suppress infrared light needs to be improved, and the efficiency of heat-to-light effective energy conversion also has much room for improvement. Summary of the invention

[0004] The present invention aims to solve at least one of the technical problems existing in the prior art or related art.

[0005] A first aspect of the present invention provides a selective emitter of a multi-layer film structure, comprising:

[0006] Coated substrates;

[0007] Multilayer film; wherein, the multilayer film includes high refractive index refractory film layers and low refractive index refractory film layers alternately arranged in sequence on the coated substrate, the high refractive index refractory film layers and the low refractive index refractory film layers are 2 to 3 layers in total, the thickness of the high refractive index refractory film layer is not more than 500nm, and the thickness of the low refractive index refractory film layer is not more than 100nm.

[0008] Furthermore, the material of the high refractive index refractory film layer is selected from one or more of Ta2O5, TiO2, HfO2, YSZ or Si3N4, and the material of the low refractive index refractory film layer is selected from one or more of MgO, Er2O3, TiN, Al2O3 or SiO2.

[0009] Furthermore, the thickness of the high refractive index refractory film layer is 140nm-160nm, and the thickness of the low refractive index refractory film layer is 20nm-40nm.

[0010] Furthermore, the coating substrate is a tungsten substrate, a molybdenum substrate or a tantalum substrate.

[0011] Furthermore, the selective emitter of the multilayer film structure is used to match a near-field infrared photovoltaic device, and the near-field infrared photovoltaic device includes but is not limited to a GaSb infrared photovoltaic device, an InGaAs infrared photovoltaic device, an InGaAsSb infrared photovoltaic device or an InAsSbP infrared photovoltaic device.

[0012] Furthermore, the operating temperature of the selective emitter of the multi-layer film structure is ≤1473K.

[0013] A second aspect of the present invention provides a method for preparing the selective emitter of the multilayer film structure, comprising:

[0014] Film system design: according to the external quantum efficiency of the near-field infrared photovoltaic device matched with the selective emitter of the multi-layer film structure, determine the cutoff wavelength and the center wavelength of the emission spectrum of the selective emitter of the multi-layer film structure at the target temperature, select the coating target material, and determine the film layer stacking method and the thickness of each film layer; wherein, the film layer stacking method is that the high refractive index refractory film layer and the low refractive index refractory film layer are alternately deposited on the coating substrate in sequence, and the high refractive index refractory film layer and the low refractive index refractory film layer are 2 to 3 layers in total, the thickness of the high refractive index refractory film layer is not more than 500nm, and the thickness of the low refractive index refractory film layer is not more than 100nm;

[0015] Pretreatment of the coated substrate;

[0016] Vacuum coating is performed on the coating substrate according to the film system design.

[0017] Furthermore, the preparation method further comprises: testing the performance of the selective emitter of the multilayer film structure;

[0018] The performance test of the selective emitter of the multi-layer film structure is specifically: using an ultraviolet-visible-near-infrared spectrophotometer to scan the coating surface of the selective emitter of the multi-layer film structure, testing the reflectivity of the selective emitter of the multi-layer film structure, and then calculating the emissivity of the selective emitter of the multi-layer film structure, and comparing it with the simulated emissivity of the selective emitter of the multi-layer film structure to determine whether the performance of the selective emitter of the multi-layer film structure meets the design requirements.

[0019] Furthermore, the effective interface method is used to calculate and determine the stacking mode of the film layers and the thickness of each film layer, and the transfer matrix method is used to simulate and obtain the emissivity spectrum of the selective emitter of the multilayer film structure at the target temperature.

[0020] Furthermore, the pretreatment of the coated substrate includes: performing rough polishing, fine polishing, acetone cleaning, ethanol cleaning and high-purity nitrogen blowing on the coated substrate in sequence before coating, so as to clean the surface of the coated substrate;

[0021] The vacuum coating method includes but is not limited to atomic layer deposition, chemical vapor deposition or vacuum electron beam coating.

[0022] Compared with the prior art, the present invention has at least the following beneficial effects:

[0023] The selective emitter of the multilayer film structure provided by the present invention has basically unchanged long-term working performance under 1473K environment, and has excellent spectral selective emission function, and the wavelength band matched by the infrared photovoltaic device in the spectrum accounts for more than 59%. The selective emitter of the multilayer film structure in the embodiment of the present invention is applied to the RTPV system. First, the film system emitter of the present invention can support the long-term stable operation of the RTPV system; second, under the same heat source temperature, due to the increase in the proportion of infrared light in the target band, the output power of the semiconductor infrared photovoltaic conversion device can be increased, and the demand for the heat source temperature in the required spectral range can be reduced; third, the film system emitter has a high heat-light conversion efficiency, which can improve the thermoelectric conversion efficiency of the RTPV system and reduce the energy dissipation of the heat source; finally, since most of the emitter emission spectrum is infrared light that can be converted by infrared photovoltaic devices, and the infrared light with lower energy than the cutoff wavelength of the photovoltaic device is significantly suppressed, that is, the heating effect on the infrared photovoltaic device is greatly weakened, which can reduce the heat dissipation requirements of the back-end photovoltaic device, so that the photovoltaic device can work in a suitable temperature range. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Various other advantages and benefits will become apparent to those of ordinary skill in the art by reading the detailed description of the preferred embodiments below. The accompanying drawings are only for the purpose of illustrating the preferred embodiments and are not to be considered as limiting the present application. Also, the same reference symbols are used throughout the accompanying drawings to represent the same components. In the accompanying drawings:

[0025] Figure 1 A schematic diagram of the film emitter preparation process provided in an embodiment of the present application.

[0026] Figure 2 This is a diagram of the external quantum efficiency of the GaSb device provided in the embodiment of the present application.

[0027] Figure 3 This is a schematic diagram of the film emitter structure provided in Example 1 of the present application.

[0028] Figure 4 This is the film emitter emissivity curve (simulation and measurement) provided in Example 1 of the present application.

[0029] Figure 5 The film system emitter spectrum, blackbody radiation spectrum, and tungsten spectrum at 1473K provided in Example 1 of the present application.

[0030] Figure 6 This is a comparison of the emitter emissivity of film system A before and after the 150h, 1473K high temperature test provided in Example 1 of the present application (10h×15 cycles).

[0031] Figure 7 The film-based emitter and tungsten plate provided in Example 1 of the present application are applied to a TPV system, and the output power diagram of the GaSb device when the radiation end temperature is 1473K. DETAILED DESCRIPTION

[0032] In order to better understand the above-mentioned technical scheme, the technical scheme of the embodiments of the present application is described in detail below through the accompanying drawings and specific embodiments. It should be understood that the embodiments of the present application and the specific features in the embodiments are detailed descriptions of the technical scheme of the embodiments of the present application, rather than limitations on the technical scheme of the present application. In the absence of conflict, the embodiments of the present application and the technical features in the embodiments may be combined with each other.

[0033] According to a first aspect of an embodiment of the present invention, there is provided a selective emitter of a multi-layer film structure, comprising:

[0034] Coated substrates;

[0035] Multilayer film; wherein, the multilayer film includes high refractive index refractory film layers and low refractive index refractory film layers alternately arranged in sequence on the coated substrate, the high refractive index refractory film layers and the low refractive index refractory film layers are 2 to 3 layers in total, the thickness of the high refractive index refractory film layer is not more than 500nm, preferably the thickness of the high refractive index refractory film layer is 140nm to 160nm, the thickness of the low refractive index refractory film layer is not more than 100nm, preferably the thickness of the low refractive index refractory film layer is 20nm to 40nm.

[0036] It can be understood that the multilayer film includes high refractive index refractory film layers and low refractive index refractory film layers alternately arranged in sequence on the coated substrate, and the high refractive index refractory film layers and the low refractive index refractory film layers are 2 to 3 layers in total, that is: the multilayer film is composed of high refractive index refractory film layers and low refractive index refractory film layers arranged in sequence on the coated substrate; or, the multilayer film is composed of high refractive index refractory film layers, low refractive index refractory film layers and high refractive index refractory film layers arranged in sequence on the coated substrate.

[0037] The selective emitter of the multilayer film structure provided in the embodiment of the present invention has substantially unchanged long-term working performance in a 1473K environment and has excellent spectral selective emission function, with the wavelength band matching the infrared photovoltaic device accounting for more than 59% of the spectrum.

[0038] In some embodiments, the material of the high refractive index refractory film layer is selected from one or more of Ta2O5, TiO2, HfO2, YSZ or Si3N4, and the material of the low refractive index refractory film layer is selected from one or more of MgO, Er2O3, TiN, Al2O3 or SiO2.

[0039] Specifically, the material selection principle of the high refractive index refractory film layer is as follows: (1) high temperature refractory material, the maximum operating temperature of the emitter must be lower than 70% of the melting point of the film material; (2) the refractive index is greater than 2; therefore, the material of the high refractive index refractory film layer is selected from one or more of Ta2O5, TiO2, HfO2, YSZ (yttrium stabilized zirconia) or Si3N4. The material selection principle of the low refractive index refractory film layer is as follows: (1) high temperature refractory material, the maximum operating temperature of the emitter must be lower than 70% of the melting point of the film material; (2) the refractive index is less than 2; therefore, the material of the low refractive index refractory film layer is selected from one or more of MgO, Er2O3, TiN, Al2O3 or SiO2.

[0040] In some embodiments, the film-coated substrate is a tungsten substrate, a molybdenum substrate or a tantalum substrate, and preferably the film-coated substrate is a tungsten substrate.

[0041] Specifically, the selection principles of the coating substrate are as follows: (1) high temperature refractory material, whose melting point is at least twice the maximum operating temperature of the emitter; (2) optical properties, the matching degree between the emissivity curve of the coating substrate and the external quantum efficiency curve of the infrared photovoltaic device, that is, the emissivity below the cut-off wavelength is high, and the emissivity above the cut-off wavelength is low. In summary, the coating substrate can be selected as a tungsten substrate, a molybdenum substrate or a tantalum substrate, preferably a tungsten substrate.

[0042] In some embodiments, the selective emitter of the multilayer film structure is used to match a near-field infrared photovoltaic device, including but not limited to a GaSb infrared photovoltaic device, an InGaAs infrared photovoltaic device, an InGaAsSb infrared photovoltaic device or an InAsSbP infrared photovoltaic device.

[0043] Specifically, the selective emitter of the multilayer film structure in the embodiment of the present invention is applied to the RTPV system. First, the film-based emitter of the present invention can support the long-term stable operation of the RTPV system. Secondly, under the same heat source temperature, due to the increase in the proportion of infrared light in the target band, the output power of the semiconductor infrared photovoltaic conversion device can be improved, and the demand for the heat source temperature in the required spectral range can be reduced. Thirdly, the film-based emitter has a high thermal-to-light conversion efficiency, which can improve the thermoelectric conversion efficiency of the RTPV system and reduce the energy dissipation of the heat source. Finally, since most of the emitter output spectrum is infrared light that can be converted by infrared photovoltaic devices, and the infrared light with lower energy than the cutoff wavelength of the photovoltaic device is significantly suppressed, that is, the heating effect on the infrared photovoltaic device is greatly weakened, which can reduce the heat dissipation requirements of the back-end photovoltaic device and make the photovoltaic device operate within a suitable temperature range.

[0044] In some embodiments, the operating temperature of the selective emitter of the multi-layer film structure is ≤1473K.

[0045] Specifically, the stability of the multilayer film selective emitter (radiator) at high temperature (referring to >1273K) in the prior art needs to be improved. On the other hand, the ability of this type of radiator to suppress infrared light with a wavelength greater than 1.7μm needs to be improved, and the efficiency of heat-light effective energy conversion also has a large room for improvement. The selective emitter of the multilayer film structure provided in the embodiment of the present application can work stably for a long time at a temperature ≤1473K. At the same temperature level, it increases the proportion of near-field infrared light required by photovoltaic conversion devices in the thermophotovoltaic system in the entire emission spectrum, has excellent spectral selective emission function, and the proportion of the wavelength band matched by infrared photovoltaic devices in the spectrum is greater than 59%.

[0046] A second aspect of the present invention provides a method for preparing the selective emitter of the multilayer film structure, comprising:

[0047] Film system design: according to the external quantum efficiency of the near-field infrared photovoltaic device matched with the selective emitter of the multi-layer film structure, determine the cutoff wavelength and the center wavelength of the emission spectrum of the selective emitter of the multi-layer film structure at the target temperature, select the coating target material, and determine the film layer stacking method and the thickness of each film layer; wherein, the film layer stacking method is to alternately deposit the high refractive index refractory film layer and the low refractive index refractory film layer on the coating substrate, and the high refractive index refractory film layer and the low refractive index refractory film layer are 2 to 3 layers in total, the thickness of the high refractive index refractory film layer is not more than 500nm, preferably the thickness of the high refractive index refractory film layer is 140nm to 160nm, the thickness of the low refractive index refractory film layer is not more than 100nm, preferably the thickness of the low refractive index refractory film layer is 20nm to 40nm;

[0048] Pretreatment of coated substrates;

[0049] Vacuum coating is performed on the coating substrate according to the film system design.

[0050] The method for preparing a selective emitter of a multi-layer film structure provided in an embodiment of the present invention is simple and controllable, the vacuum coating process is mature and has high precision, the prepared film-based emitter can work stably for a long time at high temperature, and has strong spectral modulation capability, high thermal-light conversion efficiency, good reliability, and is suitable for the preparation of selective emitters matched with a variety of infrared photovoltaic devices, and can be used not only in RTPV systems, but also can be expanded to TPV systems, CPV systems, etc.

[0051] In some embodiments, the preparation method also includes: testing the performance of the selective emitter of the multi-layer film structure, specifically: using an ultraviolet-visible-near-infrared spectrophotometer to scan the coating surface of the selective emitter of the multi-layer film structure, testing the reflectivity of the selective emitter of the multi-layer film structure, and then calculating the emissivity of the selective emitter of the multi-layer film structure, and comparing it with the simulated emissivity of the selective emitter of the multi-layer film structure to determine whether the performance of the selective emitter of the multi-layer film structure meets the design requirements.

[0052] In some embodiments, the effective interface method is used to calculate and determine the film layer stacking method and the thickness of each film layer, and the transfer matrix method is used to simulate and obtain the emissivity spectrum of the selective emitter of the multilayer film structure at the target temperature.

[0053] In this embodiment, the effective interface method is used to design the film system. This method calculates the optical properties of the film by equating the structural parameters of the multilayer dielectric film to the parameters of a single interface. The basic idea is that any optical thin film system can be represented by an equivalent interface, and its reflection, transmission and phase characteristics are determined by the combined admittance of the medium and the equivalent interface. The advantages of the effective interface method include: (1) The effective interface method greatly simplifies the calculation process by equating the multilayer film system to a single interface. (2) For most anti-reflection films, the error of the effective interface method is small enough. (3) During the design process, the effective interface method allows the designer to optimize the optical performance of the film by adjusting the admittance of the equivalent interface, thereby achieving specific design goals. (4) The difference between the theoretical value and the target value of the film system can be reduced by iterative calculation to seek the optimal solution, thereby improving the accuracy and efficiency of the film system design. (5) It can be used to design wide-band anti-reflection films from ultra-short ultraviolet to near-infrared, which is particularly important for applications that require specific optical properties in a specific band. (6) In general, the effective interface method provides a simplified, intuitive, and flexible approach in film design, which is particularly suitable for the design of multilayer and complex structured films while being able to meet both broadband and specific wavelength optical performance requirements.

[0054] In this embodiment, the film system designed according to the effective interface method uses the transmission matrix method to calculate the emissivity spectrum of the film system. This method is used to analyze and calculate the propagation characteristics of light waves in multilayer media. The core idea is to describe the propagation of light waves in each layer of the medium by constructing a matrix, and then multiply these matrices to obtain the transmission characteristics of the entire multilayer structure. This method can calculate the transmittance, absorption and reflectance of the light wave by inputting various parameters of the multilayer medium, and draw the spectrum accordingly. The advantage of the transmission matrix method is that it has clear logic, concise form, and is easy to use in computers, which makes it widely used in optical design and analysis.

[0055] In some embodiments, the pretreatment of the coated substrate includes: performing rough polishing, fine polishing, acetone cleaning, ethanol cleaning and high-purity nitrogen blowing on the coated substrate in sequence before coating to make the surface of the coated substrate clean; the vacuum coating method includes but is not limited to atomic layer deposition, chemical vapor deposition or vacuum electron beam coating.

[0056] Specifically, the coating substrate can be a tungsten substrate. The pretreatment of the tungsten substrate includes: (1) tungsten substrate surface polishing: the tungsten substrate is subjected to rough polishing and fine polishing. The surface roughness of the tungsten substrate must meet the requirements of optical coating to enhance the stability between the film layer and the substrate; (2) cleaning of the polished tungsten substrate: acetone and anhydrous ethanol are used to ultrasonically clean the polished tungsten substrate respectively. After the ultrasonic cleaning is completed, the tungsten substrate is dried and finally confirmed to be free of any impurities on the polished surface. The vacuum coating method is: vacuum coating the cleaned tungsten substrate according to the film system design data and materials. The coating method can be carried out by plasma enhanced atomic layer deposition (PEALD), plasma enhanced chemical vapor deposition (PECVD), vacuum electron beam coating, etc.

[0057] Example 1 A method for preparing a selective emitter with a multi-layer film structure

[0058] See also Figure 1 , a method for preparing a selective emitter of a multilayer film structure, comprising the following steps:

[0059] Step 1: According to the external quantum efficiency curve of infrared photovoltaic conversion device GaSb, such as Figure 2 As shown, the central wavelength of the emission spectrum of the film-based emitter at 1473K is set to 1.5μm.

[0060] Step 2: Select Al2O3 (low refractive index) and HfO2 (high refractive index) as the film materials. According to the above coating materials, the stacking method is HL (high refractive index-low refractive index). The thickness of each layer of the film is calculated by the effective interface method. The thickness of Al2O3 is 20nm~40nm, and the thickness of HfO2 is 140nm~160nm. Figure 3 shown.

[0061] Step 3: The emissivity spectrum of the film system emitter at 1473K is calculated by simulation using the transfer matrix method, and the emissivity spectrum of the film system emitter at 1473K is measured, such as Figure 4 The blackbody radiation spectrum B(λ,T) is calculated by Planck's radiation law. The film system emitter spectrum and tungsten spectrum are obtained by multiplying the measured emissivity by the blackbody radiation B(λ,T), as shown in Figure 5 shown.

[0062] Step 4: Rough polish the tungsten substrate, and then perform fine polishing. When the surface roughness of the tungsten substrate meets the requirements of optical coating, use acetone to ultrasonically clean the finely polished tungsten substrate for more than 10 minutes; then use anhydrous ethanol to ultrasonically clean it for more than 10 minutes; after the ultrasonic cleaning is completed, use high-purity nitrogen to blow dry the surface of the tungsten substrate to ensure that the polished surface of the tungsten substrate is free of stains, dust, etc.

[0063] Step 5: On the polished surface of the tungsten substrate cleaned in step 4, 140nm to 160nm of HfO2 is deposited by atomic layer deposition (ALD), and then 20nm to 40nm of Al2O3 is deposited. The aluminum source and hafnium source used in the experiment are trimethylaluminum (TMA) and tetrakis(dimethylamino)hafnium (TDMAH), the oxygen source used is pure water (15MΩ), and the carrier gas and purge gas used are (99.999%) high-purity nitrogen (N2); the substrate used in the experiment is a tungsten substrate prepared by non-powder metallurgy process. The rate of ALD preparation of Al2O3 monolayer film is The refractive index is 1.65; the rate of preparing HfO2 monolayer film is The refractive index is 2.03.

[0064] Step 6: After vacuum coating is completed, use a UV-visible-near infrared spectrophotometer to scan the coating surface of the film emitter, with a wavelength range of 400nm to 6000nm, test the reflectivity curve R(λ) of the film emitter in the above spectral range, and then calculate the emissivity curve ε(λ), and compare it with the simulation data in step 3, as shown in Figure 4 As shown. Figure 4 It can be seen that the change trend of the simulated value and the measured value of the emissivity is basically consistent. The Pearson correlation coefficient between the simulation curve and the measured value curve is 0.9992. In the range of 400nm to 1780nm, the Pearson correlation coefficient of the two curves is 0.9870. The test results show that the emitter meets the design requirements.

[0065] Step 7: In the film-based emitter prepared in this embodiment, in the emission spectrum at 1473K, the proportion of light waves below the cutoff wavelength of the GaSb device (i.e., the thermal-optical conversion efficiency) is 59.1%, and the thermal-optical conversion efficiency of the tungsten substrate is 56.7%. The film layer increases the thermal-optical conversion efficiency of the emitter by 2.4%; the light energy in the emitter spectrum that can be converted into electrical energy by the GaSb device is 2.13 times that of the tungsten substrate, and the spectral modulation capability is greatly improved. Figure 5 The film-based emitter of this embodiment is compared with the emissivity before and after the 150h (10h×15 cycles) 1473K high temperature test. The film-based emitter prepared in Example 1 has long-term high temperature stability. Figure 6 When the film-based emitter of Example 1 is applied to a TPV system, when the radiation end temperature is 1473K, the output power of the GaSb device is 4 times that of the tungsten substrate, which can significantly improve the output power of the TPV system. Figure 7 shown.

[0066] In the present invention, the terms "first", "second", and "third" are used for descriptive purposes only and should not be understood as indicating or implying relative importance; the term "plurality" refers to two or more, unless otherwise clearly defined. The terms "installed", "connected", "connected", "fixed", etc. should be understood in a broad sense. For example, "connected" can be a fixed connection, a detachable connection, or an integral connection; "connected" can be a direct connection or an indirect connection through an intermediate medium. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0067] In the description of the present invention, it is necessary to understand that the directions or positional relationships indicated by terms such as “upper”, “lower”, “left”, “right”, “front” and “back” are based on the directions or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or unit referred to must have a specific direction, be constructed and operated in a specific orientation, and therefore, cannot be understood as a limitation on the present invention.

[0068] In the description of this specification, the description of the terms "one embodiment", "some embodiments", "specific embodiments", etc. means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representation of the above terms does not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in any one or more embodiments or examples in a suitable manner.

[0069] The above are only preferred embodiments of the present invention and are not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A selective emitter of a multilayer film structure, characterized in that: include: Coated substrates; Multilayer film; wherein, the multilayer film includes high refractive index refractory film layers and low refractive index refractory film layers alternately arranged in sequence on the coated substrate, the high refractive index refractory film layers and the low refractive index refractory film layers are 2 to 3 layers in total, the thickness of the high refractive index refractory film layer is not more than 500nm, and the thickness of the low refractive index refractory film layer is not more than 100nm.

2. The selective emitter of the multi-layer film structure according to claim 1, characterized in that: The material of the high refractive index refractory film layer is selected from one or more of Ta2O5, TiO2, HfO2, YSZ or Si3N4, and the material of the low refractive index refractory film layer is selected from one or more of MgO, Er2O3, TiN, Al2O3 or SiO2.

3. The selective emitter of the multi-layer film structure according to claim 2, characterized in that: The thickness of the high refractive index refractory film layer is 140nm-160nm, and the thickness of the low refractive index refractory film layer is 20nm-40nm.

4. The selective emitter of the multi-layer film structure according to claim 1, characterized in that: The film-coated substrate is a tungsten substrate, a molybdenum substrate or a tantalum substrate.

5. The selective emitter of the multi-layer film structure according to claim 1, characterized in that: The selective emitter of the multilayer film structure is used to match with a near-field infrared photovoltaic device, and the near-field infrared photovoltaic device includes but is not limited to a GaSb infrared photovoltaic device, an InGaAs infrared photovoltaic device, an InGaAsSb infrared photovoltaic device or an InAsSbP infrared photovoltaic device.

6. The selective emitter of the multi-layer film structure according to any one of claims 1 to 5, characterized in that: The operating temperature of the selective emitter of the multi-layer film structure is ≤1473K.

7. A method for preparing a selective emitter of a multilayer film structure, characterized in that: The method for preparing a selective emitter of a multilayer film structure according to any one of claims 1 to 6 comprises: Film system design: according to the external quantum efficiency of the near-field infrared photovoltaic device matched with the selective emitter of the multi-layer film structure, determine the cutoff wavelength and the center wavelength of the emission spectrum of the selective emitter of the multi-layer film structure at the target temperature, select the coating target material, and determine the film layer stacking method and the thickness of each film layer; wherein, the film layer stacking method is that the high refractive index refractory film layer and the low refractive index refractory film layer are alternately deposited on the coating substrate in sequence, and the high refractive index refractory film layer and the low refractive index refractory film layer are 2 to 3 layers in total, the thickness of the high refractive index refractory film layer is not more than 500nm, and the thickness of the low refractive index refractory film layer is not more than 100nm; Pretreatment of the coated substrate; Vacuum coating is performed on the coating substrate according to the film system design.

8. The method for preparing a selective emitter of a multi-layer film structure according to claim 7, characterized in that: Also includes: Performance testing of the selective emitter of the multilayer film structure; The performance test of the selective emitter of the multi-layer film structure is specifically: using an ultraviolet-visible-near-infrared spectrophotometer to scan the coating surface of the selective emitter of the multi-layer film structure, testing the reflectivity of the selective emitter of the multi-layer film structure, and then calculating the emissivity of the selective emitter of the multi-layer film structure, and comparing it with the simulated emissivity of the selective emitter of the multi-layer film structure to determine whether the performance of the selective emitter of the multi-layer film structure meets the design requirements.

9. The method for preparing a selective emitter of a multi-layer film structure according to claim 8, characterized in that: The effective interface method is used to calculate and determine the stacking mode of the film layers and the thickness of each film layer, and the transfer matrix method is used to simulate and obtain the emissivity spectrum of the selective emitter of the multilayer film structure at the target temperature.

10. The method for preparing a selective emitter of a multi-layer film structure according to claim 7, characterized in that: The pretreatment of the coated substrate includes: performing rough polishing, fine polishing, acetone cleaning, ethanol cleaning and high-purity nitrogen blowing on the coated substrate in sequence before coating, so as to make the surface of the coated substrate clean; The vacuum coating method includes but is not limited to atomic layer deposition, chemical vapor deposition or vacuum electron beam coating.

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