CN104034072B - Coating for selective absorption of sunlight spectrum and preparation method thereof and application - Google Patents

Abstract

The present invention proposes a kind of coating for selective absorption of sunlight spectrum and preparation method thereof and application, and this coating for selective absorption of sunlight spectrum comprises successively: basalis, infrared reflecting layer, absorbed layer and anti-reflection layer; Described absorbed layer is made up of three layers of gradual change solar spectrum absorbed layer, is followed successively by outer absorbed layer, middle absorbed layer and interior absorbed layer, and the material of described interior absorbed layer is TiN _x1o _y1, the material of described middle absorbed layer is TiN _x2o _y2, the material of described outer absorbed layer is TiN _x3o _y3.The optical parametric gradient of described absorbed layer, achieves the efficient absorption of coating to solar spectrum, higher heat endurance and low radiative thermal emissivity.

Description

Solar Spectrum Selective Absorbing Coating and Its Preparation Method and Application

technical field

The invention relates to a solar light-to-heat conversion material used at medium and low temperatures and a preparation method thereof, in particular to a solar spectrum selective absorption coating and a preparation method thereof which can be used in vacuum tube and flat solar water heaters.

Background technique

Solar thermal utilization is one of the most direct and effective ways to develop new energy and renewable energy. Among them, solar collectors used at medium and low temperatures (80-400°C) have the advantages of easy promotion and high penetration rate, and have become an energy-saving important means of platooning. The heat absorber is the core component of the solar heat collector. The early heat absorbers used black paint, electroplated black chrome or black nickel as the absorbing material, although these materials have a high absorption rate in the sunlight band, which can effectively convert solar energy into At the same time, due to the increase of the temperature of the heat absorber, the surface of the material radiates electromagnetic waves through thermal radiation, so the actual light-to-heat conversion efficiency is generally not high.

The solar spectrum selective absorption coating has been widely concerned in the past 20 to 30 years. It can have a high absorption rate in the spectral range of 300nm-2500nm (98% of the energy of sunlight is concentrated in this band). The difference from black body materials is In the infrared band other than 2500nm, it has low absorption rate (that is, low thermal radiation rate), which greatly reduces radiation heat dissipation and improves light-to-heat conversion efficiency. According to the scope of application, the solar spectrum selective absorption coating can be divided into two categories: 1) the solar spectrum selective absorption coating used in the vacuum tube solar collector. The requirements for thermal stability are relatively low; 2) The selective absorption coating used in flat-plate solar collectors, this kind of material directly faces the atmosphere, and the structure and composition should not change after long-term use, and should have high thermal stability. stability.

At present, the solar collectors used at medium and low temperatures mostly adopt the vacuum tube type, and the absorbing materials are mostly ceramic materials doped with stainless steel or Al in AlN or alumina. The light-to-heat conversion efficiency of this type of material can be as high as 90%, but it is easily oxidized in the atmosphere, which limits the application of this type of material in flat-plate solar collectors. Doping metals such as Ag, Au, W, Mo or Pt in oxides or nitrides by physical vapor deposition has been found to have strong thermal stability in the atmosphere, and these materials have also been applied to special high temperatures In photothermal conversion devices, however, the relatively high preparation cost limits the application of such materials in the field of medium and low temperature solar heat collection. In order to better promote flat-plate collectors, it is indispensable to develop a light-to-heat conversion material with high light-to-heat conversion efficiency, strong thermal stability and low cost.

Contents of the invention

The object of the present invention is to provide a solar spectrum selective absorption coating used at medium and low temperatures and a preparation method thereof, so that it can realize high-efficiency absorption of the solar spectrum, has high thermal stability in the use temperature range, and can also A low thermal radiation rate is achieved.

The purpose of the present invention and the solution to its technical problems are achieved by adopting the following technical solutions. According to a solar spectrum selective absorption coating proposed by the present invention, the absorption coating is prepared by the following steps:

Step 1, using Al, Cu or glass as the base layer material, placing the base layer material in a vacuum cleaning chamber, passing a certain amount of argon gas, and performing radio frequency argon ion cleaning;

Step 2, using magnetron sputtering aluminum target, copper target or silver target to prepare an infrared reflective layer on the above-mentioned base layer;

Step 3, under the condition of feeding argon and nitrogen, the above-mentioned infrared reflective layer is placed under the titanium target, and the internal absorption layer is prepared on the above-mentioned infrared reflective layer by magnetron sputtering; finally, a certain amount of Oxygen, continue to use metal titanium as the target material to prepare the middle absorption layer on the above-mentioned internal absorption layer by reactive magnetron sputtering method; then increase the flow rate of oxygen, continue to use metal titanium as the target material to absorb in the above-mentioned internal absorption layer Prepare the outer absorbent layer on the layer;

Step 4, placing the product obtained in step 3 in front of the silicon target, introducing argon and oxygen, and preparing a silicon oxide layer on the above-mentioned outer absorbing layer by reactive magnetron sputtering as an antireflection layer;

Wherein, the material of the internal absorption layer is TiN _x1 O _y1 , 1.10>x1>0.90, 0.70>y1>0.50, the material of the middle absorption layer is TiN _x2 O _y2 , 0.80>x2>0.70, 1.15>y2> 1.05, the material of the outer absorption layer is TiN _x3 O _y3 , 0.55>x3>0.45, 1.30>y3>1.10; the thickness of the outer absorption layer is 10nm-50nm, the thickness of the middle absorption layer is 10nm-50nm, the inner The thickness of the absorbing layer is 20nm-50nm;

The solar spectrum selective absorption coating obtained by the above steps has an absorption rate of 94.6%-94.7% in the solar light band of 300nm-2500nm, and a thermal radiation rate of 3% at 100 degrees Celsius.

On the other hand, the present invention provides a kind of preparation method of solar spectrum selective absorption coating, it comprises the following steps:

Step 1, using Al, Cu or glass as the base layer material, placing the base layer material in a vacuum cleaning chamber, passing a certain amount of argon gas, and performing radio frequency argon ion cleaning;

Step 2, using magnetron sputtering aluminum target, copper target or silver target to prepare an infrared reflective layer on the above-mentioned base layer;

Step 3, under the condition of feeding argon and nitrogen, the above-mentioned infrared reflective layer is placed under the titanium target, and the internal absorption layer is prepared on the above-mentioned infrared reflective layer by magnetron sputtering; then a certain amount of Oxygen, continue to use metal titanium as the target material to prepare the middle absorption layer on the above-mentioned internal absorption layer by reactive magnetron sputtering method; then increase the flow rate of oxygen, continue to use metal titanium as the target material to absorb in the above-mentioned internal absorption layer Prepare the outer absorbent layer on the layer;

In step 4, the product obtained in step 3 is placed in front of the silicon target, argon and oxygen are introduced into it, and a silicon oxide layer is prepared on the above-mentioned outer absorbing layer by reactive magnetron sputtering as an antireflection layer.

Preferably, the aforementioned preparation method of the solar spectrum selective absorption coating, wherein the thickness of the base layer is 0.2-10mm; the thickness of the infrared reflection layer is 90-500nm; the internal absorption layer, middle The total thickness of the absorption layer and the outer absorption layer is 40-150nm, and the thickness of the anti-reflection layer is 80-100nm.

Preferably, the aforementioned method for preparing a solar spectrum selective absorption coating, wherein the material of the internal absorption layer is TiN _x1 O _y1 , wherein part of the oxygen contained in the material of this layer comes from the residual water vapor and Oxygen, and the other part is caused by oxidation in the air. In the wavelength range of 400nm-600nm, the refractive index is between 1.9-2.5, and the extinction coefficient is between 0.6-1.2; in the wavelength range of 900nm-1100nm, the refractive index is 2.2-2.8, and the extinction coefficient is 2.1-2.5; In the wavelength range of 2000nm-2300nm, the refractive index is 3.8-4.1, and the extinction coefficient is 2.8-3.0.

Preferably, the aforementioned method for preparing a solar spectrum selective absorbing coating, wherein the material of the middle absorbing layer is TiN _x2 O _y2 , within the wavelength range of 400nm-600nm, the refractive index is between 2.0-2.4, and the extinction coefficient Between 0.5-0.9; in the wavelength range of 900nm-1100nm, the refractive index is in the range of 2.7-3.1, and the extinction coefficient is in the range of 1.3-1.5; in the wavelength range of 2000nm-2300nm, the refractive index is in the range of 3.6-3.8, and the extinction coefficient is in the 1.0-1.2.

Preferably, the aforementioned method for preparing a solar spectrum selective absorbing coating, wherein the material of the outer absorbing layer is TiN _x3 O _y3 , within the wavelength range of 400nm-600nm, the refractive index is between 2.2-2.5, and the extinction coefficient between 0.3-0.5; such materials have a refractive index of 2.6-2.9 and an extinction coefficient of 0.4-0.6 in the wavelength range of 900nm-1100nm; and a refractive index of 2.8-3.0 in the wavelength range of 2000nm-2300nm The coefficients are in the range of 0.2-0.3.

The present invention also proposes a solar heat collector, which is characterized in that the above-mentioned solar spectrum selective absorption coating is included in the solar heat collector.

By virtue of the above technical solutions, the present invention has at least the following advantages:

The solar spectrum selective absorption coating disclosed by the invention can realize efficient absorption of the solar spectrum and high thermal stability of the coating through the gradual change of the optical parameters of the absorption layer. The titanium oxynitride absorbing material has high transmittance to light waves in the infrared band (beyond 2.5 microns). When the light in the infrared band penetrates the absorbing layer, it will be reflected by the infrared reflective layer, thereby achieving a lower thermal radiation rate. The outermost layer selects silicon oxide that can match the optical parameters of the material of the absorbing layer as the anti-reflection layer, so that the absorbing layer can absorb the solar spectrum to a greater extent. This type of coating has the following main advantages: a. It can have an absorption rate of more than 94% in the solar light band (300nm-2500nm), and the thermal radiation rate at 100 degrees Celsius can be lower than 4%, and the overall photothermal conversion efficiency is as high as 90% % or more; b. By preparing a gradient absorbing layer, the mechanical properties of the coating can be improved, and it is not easy to release the film at high temperature, which can increase the service life of the coating at high temperature; c. The coating can not only be used for vacuum tube solar heat collection The device can also directly face the atmosphere and is applied to a flat-plate solar collector.

In addition, the present invention also has the following characteristics:

a. The infrared reflective layer prepared by DC sputtering is selected from metals such as Al, Cu or Ag with high extinction coefficients in the entire light wave band. These metal layers with high extinction coefficients have a strong reflection effect on the spectrum of the entire band. It is especially beneficial to reflect the infrared spectrum (beyond 2500nm) that passes through the absorbing layer; b, above the infrared reflecting layer is a three-layer gradient solar spectrum absorbing layer. Considering that the gradual change of the reaction gas will cause the continuous change of the optical parameters of the absorbing layer, a continuous The method of changing the reaction gas oxygen to prepare a gradient gradient absorption layer of titanium oxynitride; c. The main optical feature of the internal absorption layer is that the extinction coefficient is greater than 0.6 in the entire solar spectrum band (0.3 μm-2.5 μm), and there is a significant increase with the wavelength This material has a relatively strong absorption effect on the entire solar spectrum; d, the extinction coefficient of the middle absorbing layer has a minimum value between 380nm-420nm, as low as 0.5, and between 900nm-1000nm There will be a maximum extinction coefficient between 1.5, so this material has a high absorption rate in the 900nm-1000nm band; e, the outer absorption layer has a trough in the extinction coefficient between 380nm-420nm, and There is a peak of the extinction coefficient between 700nm-800nm, and then the extinction coefficient decreases with the increase of the wavelength. This material has a relatively high absorption rate for the solar spectrum in the 700nm-800nm band; f, using reactive magnetron sputtering Methods A silicon oxide layer was prepared as an anti-reflection layer. During the preparation process, the refractive index of the silicon oxide layer in the 300nm-2500nm micron band should be controlled between 1.45-1.52.

The above description is only an overview of the technical solutions of the present invention. In order to understand the technical means of the present invention more clearly and implement them according to the contents of the description, the preferred embodiments of the present invention and accompanying drawings are described in detail below.

Description of drawings

Fig. 1 is a schematic structural view of the solar spectrum selective absorption coating proposed by the present invention.

Fig. 2 is the reflectance spectrogram of example 1 and example 2.

Fig. 3 is a schematic diagram of the absorptivity and thermal emissivity of the samples of Example 2 after annealing in the atmosphere.

detailed description

In order to further elaborate the technical means and effects that the present invention adopts to achieve the intended purpose of the invention, the specific implementation of the solar spectrum selective absorption coating and its preparation method according to the present invention will be described below in conjunction with the accompanying drawings and preferred embodiments. , structure, feature and effect thereof, detailed description is as follows.

Please refer to FIG. 1 , which is a schematic structural view of the solar spectrum selective absorption coating proposed by the present invention. The solar spectrum selective absorption coating includes a base layer 4 , an infrared reflection layer 3 , an absorption layer 2 , and an antireflection layer 1 in sequence. The base layer 4 can be a glass plate with a thickness in the range of 0.5-10 mm; it can also be a metal material with a thickness in the range of 0.2-2 mm, such as copper or aluminum, and the infrared reflection layer 3 can be omitted when the metal base layer is used. In order to increase the surface activity of the base layer 4, it is necessary to carry out radio frequency ion cleaning after mechanical cleaning, so as to remove the contamination layer and the oxide layer on the surface of the base layer. The infrared reflective layer 3 is disposed on the base layer, and the function of the infrared reflective layer 3 is to reflect the entire incident spectrum, especially the infrared spectrum, especially the infrared light with a wavelength of 2.5 microns or more. The material of the infrared reflection layer is aluminum, copper or silver. The thickness of the infrared reflection layer is 90-500nm. The absorbing layer 2 is composed of three gradient solar spectrum absorbing layers, which are an outer absorbing layer 21 , a middle absorbing layer 22 and an inner absorbing layer 23 , and the inner absorbing layer 23 is prepared on the infrared reflective layer 3 . The outer absorption layer 21 is made of TiN _x3 O _y3 with a thickness of 10nm-50nm. The material of this layer has a trough of extinction coefficient between 380nm-420nm and a peak of extinction coefficient between 700nm-800nm, and then the extinction The coefficient decreases with the increase of the wavelength, and the material of this layer has a relatively high absorption rate for the solar spectrum in the 700nm-800nm band. The middle absorbing layer 22 is made of TiN _x2 O _y2 with a thickness of 10nm-50nm. The extinction coefficient of this layer material has a minimum value between 380nm-420nm, as low as 0.5, and a The maximum value of the extinction coefficient can reach 1.5, so this material has a high absorption rate in the 900nm-1000nm band. The material of the internal absorption layer 23 is TiN _x1 O _y1 with a thickness of 20nm-50nm. The main optical feature of this layer material is that the extinction coefficient is greater than 0.6 in the entire solar spectrum band (300nm-2500nm), and it increases significantly with the increase of wavelength. The trend of this material has a relatively strong absorption effect on the entire solar spectrum. On the outer receiving layer 21 is the anti-reflection layer 1, which is made of silicon oxide, and its refractive index for light in the 300nm-2500nm band is between 1.45-1.52.

Preparation

The present invention also proposes a method for preparing the above-mentioned solar spectrum selective absorption coating, the method comprising the following steps:

For the preparation of the base layer, a polished metal plate or glass plate is selected, and after mechanical cleaning, radio frequency argon ion cleaning is performed to remove the surface contamination layer and oxide layer, and to improve the surface activity of the base layer.

Infrared reflective layer preparation, a layer of metal infrared reflective layer is prepared on the surface of the above-mentioned base layer by DC magnetron sputtering method, and the selected target material can be aluminum, copper or silver.

The preparation of the absorbing layer is to prepare the internal absorbing layer on the above-mentioned infrared reflective layer by reactive magnetron sputtering method, using metal titanium as the target material, and feeding 50sccm argon and 8sccm nitrogen to make TiN _x1 with a thickness of 20nm-50nm The internal absorption layer of O _y1 material; Pass into the oxygen of 2-2.5sccm then, continue to use metal titanium as the target material to prepare the medium absorption layer on the above-mentioned internal absorption layer by reactive magnetron sputtering method, the thickness control of this medium absorption layer At 10-50nm, the material of the medium absorbing layer is TiN _x2 O _y2 ; then increase the flow rate of oxygen to 2.5-3.5sccm, and continue to use metal titanium as the target material to prepare external absorption on the above medium absorbing layer by reactive magnetron sputtering layer, the thickness of the outer absorption layer is controlled at 10-50nm, and the material of the outer absorption layer is TiN _x3 O _y3 .

The anti-reflection layer is prepared by using the reactive magnetron sputtering method to prepare a silicon oxide layer on the above-mentioned outer absorption layer as an anti-reflection layer. This method is a mature technology, and the refractive index of the silicon oxide layer is controlled in the 300nm-2500nm band during the preparation process. Between 1.45-1.52.

The above-mentioned absorbing layer is a graded absorbing layer, and its refractive index and extinction coefficient in different wavelength bands are shown in Table 1.

Table 1

Example 1

Carry out following operation steps according to above-mentioned preparation method:

1) Carry out radio frequency ion cleaning to the glass base layer, remove the surface contamination layer and oxide layer, and increase the surface activity of the base;

2) Transfer the base layer to the front of the aluminum target. After the background vacuum is better than 6×10 ^-6 Torr, inject 50 sccm argon gas, control the pressure to 5 mTorr, turn on the sputtering power supply, keep the power at 1200W, and set the transfer rate to 0.4 m/min, make the base layer pass through the aluminum target 12 times to prepare the infrared reflective aluminum layer;

3) Transfer the base layer coated with a metal aluminum layer to the front of the titanium target, inject 50 sccm argon gas, 8 sccm nitrogen gas, control the air pressure 5mTorr, turn on the sputtering power supply, keep the power at 1000W, and the transfer rate is 0.4m/min, so that the base layer Pass through the titanium target 3 times to prepare an internal absorption layer made of TiN _0.94 O _0.60 ;

4) Under the condition that other parameters remain unchanged, 2 sccm of oxygen is introduced to make the base layer run 3 times under the titanium target at a rate of 0.4 m/min, so as to prepare a medium absorbing layer whose material is TiN _0.72 O _1.11 ;

5) Then increase the oxygen flow rate to 2.5 sccm, increase the transmission speed to 0.6m/min, keep other parameters unchanged, and run the base layer under the titanium target 5 times to prepare the outer absorbing layer made of TiN _0.51 O _1.12 ;

6) After completing the above steps, transfer the base layer to the front of the silicon target, inject 50sccm argon gas, 26sccm oxygen gas, control the air pressure to 5mTorr, turn on the sputtering power supply, keep the power at 2000W, set the transmission speed to 1m/min, and let the base layer pass through Silicon target 9 times;

7) After the above preparation steps are completed, the sample is cooled for 20 minutes, the tablet is released, and the machine is stopped.

Adopt the reflectance spectrum (300nm-2500nm) of the coating sample of example 1 to be measured by the spectrophotometer with integrating sphere, as shown in Figure 2, the absorptivity of this coating is 94.6% in this waveband; Adopt thermal radiometer to measure coating The thermal radiation rate at 100 degrees Celsius is 3.7%.

The annealing treatment of the coating sample prepared in Example 1 in a vacuum atmosphere is performed to verify the high temperature stability and durability of the coating in vacuum. Put the coated sample in a vacuum state (less than 1×10 ^-5 Torr), heat the sample to 380 degrees Celsius and anneal for 14 hours. The absorptivity (94.6%) and heat radiation rate (3.7%) of the layer change slightly, but not obviously, it proves that the coating prepared in Example 1 can be applied to the evacuated tube solar collector.

Example 2

Carry out following operation steps according to above-mentioned preparation method:

1) Carry out radio frequency ion cleaning on the Al base layer to remove the surface contamination layer and oxide layer, and increase the surface activity of the base. The thermal emissivity of the Al plate after sputtering cleaning is lower than 1.7%. At this time, the Al base layer has an infrared reflective layer at the same time role;

2) Transfer the base layer to the front of the magnetron sputtering titanium target. After the background vacuum is better than 6×10 ^-6 Torr, introduce 50 sccm argon gas, 8 sccm nitrogen gas, control the air pressure at 5 mTorr, turn on the sputtering power supply, and keep the power at 1000W. The transmission rate is 0.4m/min, so that the base layer passes through the titanium target 3 times to prepare an internal absorption layer made of TiN _0.94 O _0.60 ;

3) Under the condition that other parameters remain unchanged, 2 sccm of oxygen is introduced to make the base layer run 3 times under the titanium target at a speed of 0.4 m/min, so as to prepare a medium absorbing layer whose material is TiN _0.72 O _1.11 ;

4) Then increase the oxygen flow rate to 2.5sccm, increase the transmission speed to 0.6m/min, and keep other parameters unchanged, so that the base layer runs 5 times under the titanium target to prepare the outer absorption layer made of TiN _0.51 O _1.12 ;

5) Transfer the base layer to the front of the silicon target, inject 50 sccm argon gas, 26 sccm oxygen gas, control the air pressure to 5mTorr, turn on the sputtering power supply, keep the power at 2000W, set the transmission speed to 1m/min, and make the base layer pass through the silicon target 9 times;

6) After the above preparation steps are completed, the sample is cooled for 20 minutes, the tablet is released, and the machine is stopped.

Adopt the reflectance spectrum (300nm-2500nm) of the spectrophotometer measurement example 2 coating sample of band integrating sphere, as shown in Figure 2, the absorptivity of coating in this band is 94.7%; Adopt thermal radiometer to measure coating at 100 The thermal radiation rate in Celsius is 5.0%.

The coating sample prepared in Example 2 was annealed in the atmosphere to verify the high-temperature stability and durability of the coating in the atmosphere. The coated sample was placed in a muffle furnace and annealed successively at 100°C, 250°C, 300°C and 350°C for 36h, 10h, 5h and 5h, as shown in Figure 3, the coating was annealed at 100°C for 36 hours The absorption rate is 94.6%, and the thermal radiation rate is 5.0%; the absorption rate and thermal radiation rate of the coating have not changed significantly after annealing at 250 °C for 10 hours; the absorption rate of the coating is 93.3% after annealing at 300 °C for 5 hours , the thermal emissivity is 4%; the absorptivity of the coating is 91.1% and the thermal emissivity is 2.4% after annealing at 350°C for 5 hours. After annealing, the absorptivity and thermal emissivity of the coating only change slightly, and the photothermal conversion efficiency of the coating does not significantly decrease, which proves that the coating prepared in Example 2 can be used in flat-plate solar water heaters.

The above description is only a preferred embodiment of the present invention, and does not limit the present invention in any form. Although the present invention has been disclosed as above with preferred embodiments, it is not intended to limit the present invention. Anyone familiar with this field Those skilled in the art, without departing from the scope of the technical solution of the present invention, can use the technical content disclosed above to make some changes or modify them into equivalent embodiments with equivalent changes, but any content that does not depart from the technical solution of the present invention, according to the present invention Any simple modifications, equivalent changes and modifications made to the above embodiments by the technical essence still belong to the scope of the technical solutions of the present invention.

Claims (8)

1. a coating for selective absorption of sunlight spectrum, is characterized in that, described absorber coatings is prepared by following steps:

Step 1, adopts Al, Cu or glass as base layer material, base layer material is placed in vacuum cleaned room, passes into a certain amount of argon gas, carry out the cleaning of radio frequency argon ion;

Step 2, adopts Magnetron Sputtered Al target, copper target or silver-colored target to prepare infrared reflecting layer on above-mentioned basalis;

Step 3, under the condition passing into argon gas and nitrogen, under above-mentioned infrared external reflection is placed on titanium target, adopt magnetron sputtering method prepare on above-mentioned infrared reflecting layer in absorbed layer; Finally pass into a certain amount of oxygen, continuing take Titanium as absorbed layer during target is prepared on above-mentioned interior absorbed layer by reactive magnetron sputtering method; Then increase oxygen flow, continue to be that target prepares outer absorbed layer by reactive magnetron sputtering method on above-mentioned middle absorbed layer with Titanium;

Step 4, before product step 3 obtained is placed in silicon target, passes into argon gas and oxygen, prepares silicon oxide layer as anti-reflection layer with reactive magnetron sputtering method on above-mentioned outer absorbed layer;

Wherein, the material of described interior absorbed layer is TiN _x1o _y1, 1.10 > x1 > 0.90,0.70 > y1 > 0.50, the material of described middle absorbed layer is TiN _x2o _y2, 0.80 > x2 > 0.70,1.15 > y2 > 1.05, the material of described outer absorbed layer is TiN _x3o _y3, 0.55 > x3 > 0.45,1.30 > y3 > 1.10; The thickness of described outer absorbed layer is 10nm-50nm, and the thickness of middle absorbed layer is 10nm-50nm, and the thickness of interior absorbed layer is 20nm-50nm.

2. a preparation method for coating for selective absorption of sunlight spectrum, is characterized in that comprising the following steps:

Step 1, adopts Al, Cu or glass as base layer material, base layer material is placed in vacuum cleaned room, passes into a certain amount of argon gas, carry out the cleaning of radio frequency argon ion;

Step 2, adopts Magnetron Sputtered Al target, copper target or silver-colored target to prepare infrared reflecting layer on above-mentioned basalis;

Step 3, under the condition passing into argon gas and nitrogen, under above-mentioned infrared external reflection is placed on titanium target, adopt magnetron sputtering method prepare on above-mentioned infrared reflecting layer in absorbed layer; Finally pass into a certain amount of oxygen, continuing take Titanium as absorbed layer during target is prepared on above-mentioned interior absorbed layer by reactive magnetron sputtering method; Then increase oxygen flow, continue to be that target prepares outer absorbed layer by reactive magnetron sputtering method on above-mentioned middle absorbed layer with Titanium;

Step 4, before product step 3 obtained is placed in silicon target, passes into argon gas and oxygen, adopts reactive magnetron sputtering method to prepare silicon oxide layer as anti-reflection layer on above-mentioned outer absorbed layer.

3. the coating for selective absorption of sunlight spectrum prepared of method according to claim 2, it is characterized in that, the thickness of described basalis is 0.2-10mm; The thickness of described infrared reflecting layer is 90-500nm; The gross thickness of described interior absorbed layer, middle absorbed layer and outer absorbed layer is 40-150nm, and the thickness of described anti-reflection layer is 80-100nm.

4. the coating for selective absorption of sunlight spectrum prepared of method according to claim 2, it is characterized in that, the material of described interior absorbed layer is TiN _x1o _y1, be within the scope of 400nm-600nm at wavelength, refractive index is between 1.9-2.5, and extinction coefficient is between 0.6-1.2; Be that within the scope of 900nm-1100nm, refractive index is in 2.2-2.8 at wavelength, extinction coefficient is in 2.1-2.5; Be that within the scope of 2000nm-2300nm, refractive index is in 3.8-4.1 at wavelength, extinction coefficient is in 2.8-3.0.

5. the coating for selective absorption of sunlight spectrum prepared of method according to claim 2, it is characterized in that, the material of described middle absorbed layer is TiN _x2o _y2, be within the scope of 400nm-600nm at wavelength, refractive index is between 2.0-2.4, and extinction coefficient is between 0.5-0.9; Be within the scope of 900nm-1100nm at wavelength, refractive index is in 2.7-3.1, and extinction coefficient is in 1.3-1.5; Be that within the scope of 2000nm-2300nm, refractive index is in 3.6-3.8 at wavelength, extinction coefficient is in 1.0-1.2.

6. the coating for selective absorption of sunlight spectrum prepared of method according to claim 2, it is characterized in that, the material of described outer absorbed layer is TiN _x3o _y3, be within the scope of 400nm-600nm at wavelength, refractive index is between 2.2-2.5, and extinction coefficient is between 0.3-0.5; This type of material is that within the scope of 900nm-1100nm, refractive index is in 2.6-2.9 at wavelength, and extinction coefficient is 0.4-0.6; Be that within the scope of 2000nm-2300nm, refractive index is in 2.8-3.0 at wavelength, extinction coefficient is in 0.2-0.3.

7. a solar thermal collector, is characterized in that, comprises coating for selective absorption of sunlight spectrum according to claim 1.

8. the application of coating for selective absorption of sunlight spectrum according to claim 1 in solar thermal collector.