COLORED RADIATIVE COOLER BASED ON TAMM STRUCTURE

Abstract

The present invention provides a colored radiative cooler based on a Tamm structure, including a substrate on which metal film and dielectric layers A to G are sequentially provided from bottom to top, where the Tamm structure is formed from the metal film and the dielectric layers A to D; a distributed Bragg reflector is formed from the dielectric layers A to D; and a selective emitter is formed from the dielectric layers E to G. Compared to the conventional radiative cooler, the colored radiative cooler not only has better cooling performance, but it has a wide applications in many aspects such as aesthetics and decoration.

Claims

1. A colored radiative cooler based on a Tamm structure, comprising: a substrate; wherein a metal film, a distributed Bragg reflector (DBR) and a selective emitter are sequentially provided on the substrate from bottom to top; wherein the Tamm structure is formed from the metal film and the distributed Bragg reflector; and a function of a thickness d, a Bragg wavelength .sub.B and a refractive index n of the distributed Bragg reflector (DBR) is d=.sub.B/4 n.

2. The colored radiative cooler of claim 1, wherein the metal film and dielectric layers A to G are sequentially provided on the substrate from bottom to top; the Tamm structure is formed by the metal film and the dielectric layers A to D; the distributed Bragg reflector is formed by the dielectric layers A to D; and the selective emitter is formed by dielectric layers E to G.

3. The colored radiative cooler of claim 2, wherein a thickness of the substrate is 300-3000 m.

4. The colored radiative cooler of claim 2, wherein the substrate is made of SiO.sub.2 glass.

5. The colored radiative cooler of claim 2, wherein a thickness of the metal film ranges from 10 to 80 nm, and an optimal thickness of the metal film is determined by a minimum color difference.

6. The colored radiative cooler of claim 2, wherein a thickness of the dielectric layer A ranges from 20 to 50 nm; a thickness of the dielectric layer B ranges from 50 to 100 nm; a thickness of the dielectric layer C ranges from 20 to 50 nm and a thickness of the dielectric layer D ranges from 50 to 100 nm, and optimal thicknesses of the dielectric layers A to D are determined by the calculated minimum color difference.

7. The colored radiative cooler of claim 2, wherein the metal film is made of Ag, and the dielectric layers A to D are made of SiC, MgF.sub.2, SiC and MgF.sub.2, respectively; wherein SiC and MgF.sub.2 have a small extinction coefficient in a solar band to avoid a parasitic heat generation; and an auxiliary heat radiation characteristic is shown in an transparent atmospheric window, which ensures a cooling effect of the colored radiative cooler.

8. The colored radiative cooler of claim 2, wherein a thickness of the dielectric layer E of the selective emitter is 52 nm; a thickness of the dielectric layer F of the selective emitter is 900 nm; a thickness of the dielectric layer G of the selective emitter is 85 nm, and optimal thicknesses of the dielectric layers E, F and G are determined through genetic algorithm.

9. The colored radiative cooler of claim 2, wherein the dielectric layers E to G of the selective emitter are made of SiO.sub.2, SiN and SiO.sub.2, respectively; wherein the selective emitter has a high transmittance in the visible region to ensure the color purity and a high emission/absorption in the atmospheric transparent window to enable the cooling effect.

10. A method for fabricating a yellow radiative cooler based on a Tamm structure, comprising: S1) selecting a SiO.sub.2 glass substrate cleaned by an ion beam, and depositing, using electron beam evaporation, an Ag film with a thickness of 24 nm on the SiO.sub.2 glass substrate; S2) performing pre-sputtering for the Ag film for 15 minutes; depositing a SiC dielectric layer A with a thickness of 30 nm on the Ag film under room temperature using RF magnetron reactive sputtering; and performing high-temperature annealing; S3) depositing a MgF.sub.2 dielectric layer B with a thickness of 56 nm on the dielectric layer A using the electron beam evaporation, wherein a vacuum degree is 210.sup.4 Pa during the electron beam evaporation; S4) performing per-sputtering for the dielectric layer B for 15 minutes; depositing a SiC dielectric layer C with a thickness of 30 nm on the dielectric layer B using the RF magnetron reactive sputtering under the room temperature; and performing high-temperature annealing; S5) depositing a MgF.sub.2 dielectric layer D with a thickness of 56 nm on the dielectric layer C using the electron beam evaporation, wherein a vacuum degree is 210.sup.4 Pa during the electron beam evaporation; S6) performing pre-sputtering with Ar; depositing a SiO.sub.2 dielectric layer E with a thickness of 52 nm on the dielectric layer D using the RF magnetron reactive sputtering, wherein Ar is a sputtering gas, and O.sub.2 is a reaction gas; S7) performing pre-sputtering for 10 minutes with Ar to remove impurities such as oxides on a target surface; depositing a SiN dielectric layer F with a thickness of 900 nm on the dielectric layer E using the RF magnetron reactive sputtering, wherein the sputtering gas and the reaction gas are high-purity Ar and high-purity N.sub.2, respectively; and S8) performing pre-sputtering with Ar; depositing a SiO.sub.2 dielectric layer G with a thickness of 85 nm on the dielectric film layer F using the RF magnetron reactive sputtering, wherein Ar is the sputtering gas, and O.sub.2 is the reaction gas.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0032] FIG. 1 is a schematic diagram of a colored radiative cooler of the present invention;

[0033] FIG. 2 is a reflectance spectrum of the colored radiative cooler of the present invention as a function of thickness (d) of the distributed Bragg reflector, where d=.sub.B/4n, and .sub.B represents the Bragg wavelength and n represents the refractive index; and

[0034] FIG. 3 is a spectrogram of the colored radiative cooler of the present invention, in which the reflectance of the colored radiative cooler is a function of thickness (d.sub.Ag) of a metal film.

REFERENCE NUMERALS

[0035] 1, substrate; 2, metal film; 3, dielectric layer A; 4, dielectric layer B; 5, dielectric layer C; 6, dielectric layer D; 7, dielectric layer E; 8, dielectric layer F; 9, dielectric layer G.

DETAILED DESCRIPTION OF EMBODIMENTS

[0036] The technical solutions of the present invention will be further described in the following embodiments of the present invention, which are only a part of the embodiments of the present invention.

EXAMPLE 1

[0037] In this embodiment, illustrated is a method for fabricating a yellow radiative cooler based on a Tamm structure, comprising the following steps.

[0038] S1) A SiO.sub.2 glass substrate cleaned by an ion beam is selected, on which an Ag film with a thickness of 24 nm is deposited using an electron beam evaporation.

[0039] S2) Pre-sputtering is performed for 15 minutes; a SiC dielectric layer A with a thickness of 30 nm is deposited on the Ag film using RF magnetron reactive sputtering under the room temperature; and high-temperature annealing is performed.

[0040] S3) A MgF.sub.2 dielectric layer B with a thickness of 56 nm is deposited on the dielectric layer A using the electron beam evaporation, where a vacuum degree is 210.sup.4 Pa during the electron beam evaporation.

[0041] S4) Pre-sputtering is performed for 15 minutes; a SiC dielectric layer C with a thickness of 30 nm is deposited on the dielectric layer B using the RF magnetron reactive sputtering under the room temperature; and high-temperature annealing is performed;

[0042] S5) A MgF.sub.2 dielectric layer D with a thickness of 56 nm is deposited on the dielectric layer C using the electron beam evaporation, where a vacuum degree of the evaporation background is 210.sup.4 Pa;

[0043] S6) Pre-sputtering with Ar is performed; a SiO.sub.2 dielectric layer E with a thickness of 52 nm is deposited on the dielectric layer D using the RF magnetron reactive sputtering, where Ar is a sputtering gas, and O.sub.2 is a reaction gas.

[0044] S7) Pre-sputtering is performed for 10 minutes with Ar to remove impurities such as oxides on a target surface; a SiN dielectric layer F with a thickness of 900 nm is deposited on the dielectric layer E using the RF magnetron reactive sputtering, where the sputtering gas and the reaction gas are high-purity Ar and high-purity N.sub.2, respectively.

[0045] S8) Pre-sputtering with Ar is performed; a SiO.sub.2 dielectric layer G with a thickness of 85 nm is deposited on the dielectric film layer F using the RF magnetron reactive sputtering, where Ar is a sputtering gas, and O.sub.2 is a reaction gas.

EXAMPLE 2

[0046] In this embodiment, a method for fabricating a magenta radiative cooler based on a Tamm structure, comprising the following steps.

[0047] S1) A SiO.sub.2 glass substrate cleaned by an ion beam is selected, on which an Ag film with a thickness of 22 nm is deposited using an electron beam evaporation.

[0048] S2) Pre-sputtering is performed for 15 minutes; a SiC dielectric layer A with a thickness of 38 nm is deposited on the Ag film using RF magnetron reactive sputtering under the room temperature; and high-temperature annealing is performed.

[0049] S3) A MgF.sub.2 dielectric layer B with a thickness of 72 nm is deposited on the dielectric layer A using the electron beam evaporation, where the vacuum degree is 210.sup.4 Pa during the electron beam evaporation.

[0050] S4) Pre-sputtering is performed for 15 minutes; a SiC dielectric layer C with a thickness of 38 nm is deposited on the dielectric layer B using the RF magnetron reactive sputtering under the room temperature, and high-temperature annealing is performed.

[0051] S5) A MgF.sub.2 dielectric layer D with a thickness of 72 nm is deposited on the dielectric layer C using the electron beam evaporation, where the vacuum degree is 210.sup.4 Pa during the electron beam evaporation.

[0052] S6) Pre-sputtering with Ar is performed; a SiO.sub.2 dielectric layer E with a thickness of 52 nm is deposited on the dielectric layer D using the RF magnetron reactive sputtering, where Ar is a sputtering gas, and O.sub.2 is a reaction gas.

[0053] S7) Pre-sputtering is performed for 10 minutes with Ar to remove impurities such as oxides on a target surface; a SiN dielectric layer F with a thickness of 900 nm is deposited on the dielectric layer E using the RF magnetron reactive sputtering, where the sputtering gas and the reaction gas are high-purity Ar and high-purity N.sub.2, respectively.

[0054] S8) Pre-sputtering with Ar is performed; a SiO.sub.2 dielectric layer G with a thickness of 85 nm is deposited on the dielectric film layer F using the RF magnetron reactive sputtering, where Ar is a sputtering gas, and O.sub.2 is a reaction gas.

EXAMPLE 3

[0055] In this embodiment, illustrated is a method for fabricating a cyan radiative cooler based on a Tamm structure, comprising the following steps.

[0056] S1) A SiO.sub.2 glass substrate cleaned by an ion beam is selected, on which an Ag film with a thickness of 23 nm is deposited using an electron beam evaporation;

[0057] S2) Pre-sputtering is performed for 15 minutes; a SiC dielectric layer A with a thickness of 47 nm is deposited on the Ag film using RF magnetron reactive sputtering under the room temperature; and high-temperature annealing is performed.

[0058] S3) A MgF.sub.2 dielectric layer B with a thickness of 88 nm is deposited on the dielectric layer A using the electron beam evaporation, where the vacuum degree is 210.sup.4 Pa during the electron beam evaporation.

[0059] S4) Pre-sputtering is performed for 15 minutes; a SiC dielectric layer C with a thickness of 47 nm is deposited on the dielectric layer B using the RF magnetron reactive sputtering under the room temperature, and high-temperature annealing is performed.

[0060] S5) A MgF.sub.2 dielectric layer D with a thickness of 88 nm is deposited on the dielectric layer C using the electron beam evaporation, where the vacuum degree is 210.sup.4 Pa during the electron beam evaporation.

[0061] S6) Pre-sputtering with Ar is performed; a SiO.sub.2 dielectric layer E with a thickness of 52 nm is deposited on the dielectric layer D using the RF magnetron reactive sputtering, where Ar is a sputtering gas, and O.sub.2 is a reaction gas.

[0062] S7) Pre-sputtering is performed for 10 minutes with Ar to remove impurities such as oxides on a target surface, and a SiN dielectric layer F with a thickness of 900 nm is deposited on the dielectric layer E using the RF magnetron reactive sputtering, where the sputtering gas and the reaction gas are high-purity Ar and high-purity N.sub.2, respectively.

[0063] S8) Pre-sputtering with Ar is performed; a SiO.sub.2 dielectric layer G with a thickness of 85 nm is deposited on the dielectric film layer F using the RF magnetron reactive sputtering, where Ar is a sputtering gas, and O.sub.2 is a reaction gas.

[0064] The thickness is monitored by a quartz crystal monitor during the deposition process. The reflectance of the colored radiative cooler in the visible region and the near-infrared region is characterized by a spectrophotometer which has an unpolarized light source and a calibrated high specular reflectance standard. In the infrared region, a Fourier transform infrared spectrometer, which has an unpolarized light source and uses a reflectance of a gold film as a reflectance standard, is used to characterize the reflectance of the colored radiative cooler. A resistance temperature sensor is provided on the back of the colored radiative cooler and is connected to the data logger to measure the temperature of the colored radiative cooler. The incident solar irradiance on the surface of the colored radiative cooler is measured by a pyranometer and recorded by the data logger, where the pyranometer and the colored radiative cooler are placed on the same platform. The ambient temperature is measured by a resistance temperature sensor, the probe should be placed at the free airflow area near the sample, except for the air pockets around the sample, to carry out the measurement.

[0065] As shown in FIG. 1, the colored radiative cooler of the present invention comprises a selective emitter and a Tamm structure. The selective emitter is formed by dielectric layers E, F and G, and structural parameters thereof are obtained through genetic algorithm. The Tamm structure is formed by dielectric layers A, B, C and D and the metal film, and the structural parameters thereof are obtained by calculating the minimum color difference.

[0066] FIGS. 2 and 3 are reflectance spectrograms of the colored radiative cooler of the present invention as fucntions of a thickness d of a distributed Bragg reflector (DBR) and a thickness (d.sub.Ag) of a metal film. As the DBR thickness increases, the peak wavelength shifts to the right, so that different color hues can be obtained by adjusting the DBR thickness. As the metal film thickness increases, the peak wavelength slightly moves, and the reflectance corresponding to the peak wavelength is reduced, which lightens the color, and thus colors with different purities can be obtained by adjusting the metal film thickness.

[0067] Therefore, a thickness of Ag is firstly determined, and the DBR thickness corresponding to the minimum color difference is determined by calculating the color difference between the standard yellow and the colors obtained by changing the DBR thickness, and then a thickness of Ag corresponding to the minimum color difference is determined by calculating the color difference between the standard yellow and the colors by changing the Ag thickness. In summary, the yellow radiative cooler after the optimization comprises a SiO.sub.2 glass substrate with a thickness of 500 m, on which an Ag film layer with a thickness of 24 nm, a SiC dielectric layer A with a thickness of 30 nm, a MgF.sub.2 dielectric layer B with a thickness of 56 nm, a SiC dielectric layer C with a thickness of 30 nm, a MgF.sub.2 dielectric layer D with a thickness of 56 nm, a SiO.sub.2 dielectric layer E with a thickness of 52 nm, a SiN dielectric layer F with a thickness of 900 nm and a SiO.sub.2 dielectric layer G with 85 nm are sequentially deposited from bottom to top. Similarly, a magenta and cyan radiative coolers can be obtained.

[0068] It should be noted that the above description is only a preferred embodiment of the present invention and is not intended to limit the scope of the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, modifications of the described technical solutions or equivalent replacement of the technical features can be made by the skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and scope of the present invention shall fall within the scope of the present invention.