Photothermal selective absorber based on Bi2Se3 / SiO2 alternate multilayer film

Abstract

The invention discloses a photo-thermal selective absorber based on a Bi2Se3 / SiO2 alternate multilayer film, and belongs to the field of solar energy application. The bottommost layer is a metal substrate, and the thickness of the substrate is larger than the skin depth of incident light in metal, so that the incident light cannot be transmitted out after entering the coating; the SiO2 films and the Bi2Se3 films with different thicknesses are sequentially and alternately arranged on the metal substrate to form an impedance matching regulation and control layer, and the refractive index and the extinction coefficient of the Bi2Se3 / SiO2 alternate multilayer film are regulated and controlled through the thicknesses; the Bi2Se3 film on the topmost layer is a black body heat radiation control function layer, and the heat radiation frequency domain is located in the metal reflection area of the film by adjusting the thickness of the film. Electrodes are additionally arranged at the two ends of the Bi2Se3 film on the top layer to apply voltage, and the electrical transport characteristics of each film are regulated and controlled through the voltage, so that the refractive index and the extinction coefficient of the Bi2Se3 film are changed, the equivalent impedance of different incident angles is regulated, and the Bi2Se3 / SiO2 alternating multilayer film is ensured to always keep an overall equivalent impedance matching state at each incident angle.

Description

Technical Field

[0001] The present invention belongs to the field of solar energy technology and application, and specifically relates to a method based on Bi 2 Se 3 / SiO 2 Photothermal selective absorbers based on alternating multilayer films. Background Art

[0002] Solar thermal conversion is the most direct and effective way for people to utilize solar energy. It has broad application prospects in the fields of solar hot water utilization, solar desalination and solar thermal power generation. Photothermal selective absorption coating is the most critical part of solar thermal conversion devices. Its optical properties determine the heat capture performance of the photothermal system. The ideal selective absorption coating should have an absorptivity of 100% in the strong solar radiation spectrum region, realizing the complete conversion of solar energy into heat. At the same time, the emissivity in the blackbody thermal radiation spectrum region is 0, which can prevent the energy from being radiated out secondary. That is, the photothermal selective absorption coating is required to meet the impedance matching in the strong solar radiation spectrum region and the impedance is completely mismatched in the blackbody thermal radiation spectrum region. At present, the most widely studied photothermal selective absorption coatings mainly include metal ceramics and surface superstructures. It is difficult to further improve the photothermal conversion efficiency of metal ceramic photothermal selective absorption coatings by simply changing the concentration and size of metal particles. Moreover, the mutual diffusion and aggregation between particles at high temperatures will lead to changes in optical parameters, thereby weakening its spectral absorption performance. Surface superstructure photothermal selective absorption coatings use surface plasmon resonance to have a wide-band advantage in equivalent impedance matching design. However, due to the unevenness of the surface structure, it will cause scattering of high-frequency light waves, and its photothermal conversion efficiency is difficult to further improve. The micro-nano-sized superstructure processing also poses great challenges to the preparation process. In addition, the photothermal conversion efficiency of both types of photothermal selective absorption coatings depends on the incident angle of light, and it is impossible to achieve spectral matching absorption in a wide angle range.

[0003] Bi 2 Se 3 It is a typical third-generation topological insulator material. Its bulk phase has a large band gap, and the surface state has a large adjustable space for the electrical transport properties of two-dimensional topological insulator materials. By regulating the gate voltage, Bi 2 Se 3 The surface conductivity of the bulk can be significantly improved, and the high adjustability of its surface state electrical transport provides more room for impedance adjustment. At the same time, the concentration of Dirac-type conduction carriers on the surface will also affect the conductivity loss. Changing the thickness of the topological insulator film can effectively regulate the impedance matching performance, which is conducive to achieving excellent spectral selective absorption, thereby obtaining higher solar thermal conversion efficiency. Summary of the invention

[0004] Aiming at the problem that existing photothermal conversion materials are difficult to further improve the photothermal conversion efficiency, a novel Bi 2 Se 3 / SiO 2 Alternating multilayer photothermal selective absorber using Bi 2 Se 3 Taking advantage of the material's unique and adjustable surface electrical transport, the impedance matching design in the optical frequency band is optimized, enabling the multilayer film to achieve efficient photothermal conversion while maintaining matching absorption of the sun's strong radiation spectrum over a wide range of incident angles.

[0005] A Bi-based 2 Se 3 / SiO 2 The photothermal selective absorber of the alternating multilayer film has a metal substrate at the bottom. The specific metal material is not limited. The thickness of the substrate should be greater than the skin depth of the incident light in the metal, which will ensure that the incident light cannot be transmitted out after entering the coating. 2 Thin Film and Bi 2 Se 3 The films are arranged alternately to form an impedance matching control layer, and the topological surface state is used to control Bi 2 Se 3 / SiO 2 Refractive index and extinction coefficient of alternating multilayer films, Bi 2 Se 3 The topological surface state of the film is mainly controlled by changing its refractive index and extinction coefficient through thickness control. The finite difference time domain method is used to simulate and optimize Bi 2 Se 3 / SiO 2 The thickness of the alternating multilayer film makes it match the impedance in the frequency domain of strong solar radiation, so that the multilayer film can efficiently absorb the strong solar radiation spectrum; the top layer of Bi 2 Se 3 The film is a blackbody thermal radiation control functional layer. By adjusting the film thickness, the thermal radiation frequency domain is in the metal reflection area of ​​the film, thereby reducing the infrared emissivity of the coating blackbody thermal radiation and realizing efficient solar thermal conversion of the coating. 2 Se 3 By adding electrodes to both ends of the film and applying voltage, the electrical transport properties of each layer of the film can be regulated by voltage, which will effectively change the Bi 2 Se 3 The refractive index and extinction coefficient of the film can flexibly adjust the equivalent impedance at different incident angles to ensure Bi 2 Se 3 / SiO 2The alternating multilayer film always maintains an overall equivalent impedance matching state at all incident angles, ultimately achieving wide-angle absorption of sunlight. 2 Se 3 / SiO 2 The photothermal selective absorption structure of the alternating multilayer film structure can be prepared by the magnetron sputtering method, which has a simple preparation process and a mature process flow. In a vacuum environment, an inert gas is used as a sputtering gas to deposit the bottom metal film on the substrate by magnetron sputtering, and then alternately deposit SiO 2 Thin Film and Bi 2 Se 3 Thin film, by changing the sputtering power, pressure, annealing temperature and other parameters to control the film quality and thin film crystal growth orientation. BRIEF DESCRIPTION OF THE DRAWINGS

[0006] Figure 1 Based on Bi 2 Se 3 / SiO 2 Schematic diagram of the three-dimensional structure of the photothermal selective absorber with alternating multilayer films

[0007] Figure 2 Based on Bi 2 Se 3 / SiO 2 Schematic diagram of the side structure of the photothermal selective absorber with alternating multilayer films

[0008] Figure 3 Based on Bi 2 Se 3 / SiO 2 Spectral absorption effect of photothermal selective absorber with alternating multilayer films

[0009] Figure 4 Based on Bi 2 Se 3 / SiO 2 Spectral absorption effect of photothermal selective absorber with alternating multilayer films at wide angle of incidence DETAILED DESCRIPTION

[0010] Bi-based 2 Se 3 / SiO 2 The photothermal selective absorption coating with alternating multilayer film structure. With silicon wafer as substrate and argon as sputtering gas in vacuum environment, Au, Bi 2 Se 3 and SiO 2 The sputtering target material is sputtered, and the sputtering time is controlled according to the required thickness of each layer and the deposition rate of different materials. First, a layer of gold film is sputtered on the silicon substrate, and then SiO 2Layer and Bi 2 Se 3 layer, and finally get Bi 2 Se 3 / SiO 2 The photothermal selective absorption coating with alternating multilayer film structure can regulate the electrical transport characteristics of each layer by applying voltage, flexibly adjust the equivalent impedance at different incident angles, and ensure Bi 2 Se 3 / SiO 2 The alternating multilayer film always maintains an equivalent impedance matching state at an incident angle of 0-60°, thereby achieving wide-angle absorption of sunlight. The overall structural diagram is shown in Figure 1 As shown. Based on Bi 2 Se 3 / SiO 2 Photothermal selective absorption coatings with alternating multilayer film structures, such as Figure 2 As shown, the first layer is an Au metal layer (thickness is 80-100nm), and the second layer is SiO 2 layer (thickness is 40-60nm), the third layer is Bi 2 Se 3 layer (thickness is 80-100nm), the fourth layer is SiO 2 layer (thickness is 100-120nm), the fifth layer is Bi 2 Se 3 layer (thickness is 40-60nm), the sixth layer is SiO 2 layer (thickness is 60-80nm). Bi based on this structural design 2 Se 3 / SiO 2 The photothermal selective absorber with alternating multilayer films has an average absorption rate of up to 94% in the solar high radiation spectrum region of 0.3-2.5μm and an infrared emissivity as low as 8% in 2.5-25μm. It has high-efficiency photothermal conversion performance and spectral absorption effect. Figure 3 As shown. And the absorber has the ability to absorb sunlight omnidirectionally and is insensitive to the incident angle, such as Figure 4 It is shown that there is good absorption effect in the wide angle range of 0°-60°.

Claims

1. A photothermal selective absorber based on Bi2Se3 / SiO2 alternating multilayer films, characterized in that: The bottom layer is a metal substrate, the thickness of which should be greater than the skin depth of the incident light in the metal, which will ensure that the incident light cannot be transmitted out after entering the coating; SiO2 films and Bi2Se3 films of different thicknesses are arranged alternately on a metal substrate to form an impedance matching control layer. The refractive index and extinction coefficient of the Bi2Se3 / SiO2 alternating multilayer film are controlled by thickness. The top Bi2Se3 film is a blackbody thermal radiation control functional layer, and the thermal radiation frequency domain is adjusted to be in the metal reflection area of ​​the film by adjusting the film thickness.

2. A photothermal selective absorber based on Bi2Se3 / SiO2 alternating multilayer films according to claim 1, characterized in that: By adding electrodes at both ends of the top Bi2Se3 film and applying voltage, the electrical transport properties of each layer of the film can be regulated by voltage, which will change the refractive index and extinction coefficient of the Bi2Se3 film, thereby adjusting the equivalent impedance at different incident angles and ensuring that the Bi2Se3 / SiO2 alternating multilayer film always maintains an overall equivalent impedance matching state at all incident angles.

3. The photothermal selective absorber based on Bi2Se3 / SiO2 alternating multilayer films according to claim 1, characterized in that: In a vacuum environment, an inert gas is used as a sputtering gas to deposit a bottom metal film on a substrate by magnetron sputtering, and then SiO2 film and Bi2Se3 film are alternately deposited in sequence. The film quality and the film crystal growth orientation are controlled by changing one or more of the sputtering power, pressure, and annealing temperature.

4. A photothermal selective absorber based on Bi2Se3 / SiO2 alternating multilayer films according to claim 1, characterized in that: The first layer is an Au metal layer with a thickness of 80-100nm; the second layer is a SiO2 layer with a thickness of 40-60nm; the third layer is a Bi2Se3 layer with a thickness of 80-100nm; the fourth layer is a SiO2 layer with a thickness of 100-120nm; the fifth layer is a Bi2Se3 layer with a thickness of 40-60nm; and the sixth layer is a SiO2 layer with a thickness of 60-80nm.

Images