Lead-free halogen double perovskite near-infrared fluorescent powder and preparation method thereof

Abstract

The invention discloses lead-free halogen double perovskite near-infrared fluorescent powder and a preparation method thereof, and the chemical general formula of the fluorescent powder is Cs2M1-x-yCl6: xPt < 4 + >, yEr < 3 + >, wherein M is any one of Zr, Sn and Hf, and 0 lt; x is less than or equal to 0.02, 0lt; y < = 0.35. The preparation method comprises the following steps: adding an erbium acetate solution into a platinum tetrachloride solution, and sealing and stirring; adding the obtained solution into an MCl4 solution, and sealing and stirring at 50-70 DEG C; adding a cesium chloride solution, sealing and stirring at 40-60 DEG C, and after the solution is cooled to room temperature, carrying out centrifugal separation and centrifugal washing; and drying at 40-60 DEG C, and cooling. The emission peak of the obtained fluorescent powder Pt < 4 + > well covers the excitation peak of Er < 3 + >, energy is effectively transmitted to a light-emitting center Er < 3 + >, and the light-emitting efficiency of Er < 3 + > is remarkably improved; strong absorption is realized in ultraviolet, near ultraviolet and blue light areas.

Description

Technical Field

[0001] The invention relates to luminescent materials and a preparation method thereof, in particular to a lead-free halogen double perovskite near-infrared phosphor and a preparation method thereof. Background Art

[0002] Near-infrared (NIR) light sources have shown great application prospects in the fields of biological analysis, food testing and night vision equipment due to their advantages such as low thermal effect, non-destructiveness, suitable energy and penetration. However, traditional near-infrared light sources such as halogen lamps and tungsten filament lamps have disadvantages such as large size, low efficiency and poor matching with infrared detectors, which are difficult to adapt to the needs of modern technological development, which provides motivation for exploring new high-efficiency near-infrared emission devices.

[0003] A large number of studies have shown that perovskite has broad application prospects in optoelectronic materials due to its unique structure. However, the previously reported perovskite materials lack stability and contain Pb elements, which are very polluting to the environment. In order to solve this problem, researchers used +4 valence elements (Zr, Sn, Hf) to replace +2 valence Pb elements, leaving 50% vacancies in the perovskite structure, and synthesized vacancy-ordered lead-free halogen double perovskite (Cs2MCl6). Among them, the octahedral coordinated [MCl6] 3- It is considered to be doped with Ln 3+ However, due to the forbidden transitions in the 4f electronic configuration of rare earth ions, double perovskite near-infrared phosphors doped with rare earth ions exhibit low quantum efficiency.

[0004] In recent years, researchers have proposed that utilizing the energy transfer from self-trapping excitation (STE) in double perovskite luminescent materials to rare earth ions is an effective way to enhance the near-infrared emission of rare earth ions, and have developed a series of Ln 3+ Doped lead-free halogen double perovskite near-infrared phosphors, such as Cs2ZrCl6:Te 4+ / Ln 3+ (Ln 3+ =Er 3+ ,Nd 3+ ,Yb 3+ ),Cs2AglnCl6:Sb 3+ / Yb 3+ et al. (Angew. Chem. Int. Ed. 134 (2022) e202201993, Adv. Funct. Mater. 33 (2023) 2212135). However, due to the low sensitization efficiency of the STE emission of the matrix to the rare earth ions, the luminescence efficiency of these near-infrared phosphors is very low. Summary of the invention

[0005] Purpose of the invention: In order to overcome the deficiencies in the prior art, the purpose of the present invention is to provide a lead-free halogen double perovskite near-infrared phosphor with high luminous efficiency. Another purpose of the present invention is to provide a convenient and controllable method for preparing a lead-free halogen double perovskite near-infrared phosphor.

[0006] Technical solution: The lead-free halogen double perovskite near-infrared phosphor described in the present invention has the general chemical formula: Cs2M 1-x-y Cl6:xPt 4+ ,yEr 3+ ; Wherein, M is any one of Zr, Sn, Hf, 0 <x≤0.02,0<y≤0.35。

[0007] The method for preparing a lead-free halogen double perovskite near-infrared phosphor according to the present invention comprises the following steps:

[0008] Step 1, adding the erbium acetate solution into the platinum tetrachloride solution, sealing and stirring;

[0009] Step 2, add the solution obtained in step 1 into the MCl4 solution, seal and stir at 50-70°C;

[0010] Step 3, adding the cesium chloride solution to the solution obtained in step 2, sealing and stirring at 40-60° C., and centrifuging and washing the solution after cooling it to room temperature;

[0011] Step 4: Dry the product obtained in step 3 at 40-60° C. and cool it to obtain a lead-free halogen double perovskite near-infrared phosphor.

[0012] Furthermore, in step 1, the erbium acetate solution is an aqueous solution of erbium acetate hexahydrate with a concentration of 0.2 to 5.0 mol / L.

[0013] Furthermore, in step 1, the platinum tetrachloride solution is prepared by dissolving platinum tetrachloride powder in a mixed solution of concentrated hydrochloric acid and ethanol, with a concentration of 0.1 to 1.0 mol / L.

[0014] Furthermore, in step 2, the solvent of the MCl4 solution is concentrated hydrochloric acid, the temperature is 50-70°C, the concentration is 0.5-6.0 mol / L, and the sealed stirring time is 10-15 min. The concentration of the cesium chloride solution is 0.5-8.0 mol / L, and the solvent is concentrated hydrochloric acid.

[0015] Furthermore, in step 3, the cesium chloride solution is added by a peristaltic pump at a rate of 1 to 5 mL / min. The sealed stirring time is 20 to 40 min. The speed of the centrifugal washing is 6000 to 9000 r / min, and the washing solvent is one or more of concentrated hydrochloric acid, ethanol, and isopropanol.

[0016] Furthermore, in step 4, the drying time is 4 to 6 hours.

[0017] Preparation principle: Choose the chemically stable, lead-free vacancy-ordered double perovskite Cs2MCl6 as the matrix, Pt 4+ As sensitizer, Er 3+ The luminescent center forms a single-phase Cs2M 1-x-y Pt x Er y Cl6 solid solution. Phosphor Cs2M 1-x-y Cl6:xPt 4+ ,yEr 3+ Medium Pt 4+ The emission peak of Er 3+ The excitation peak can effectively transfer energy to the luminescent center Er 3+ , significantly improving Er 3+ luminous efficiency.

[0018] Beneficial effects: Compared with the prior art, the present invention has the following significant features:

[0019] 1. The obtained phosphor is Pt 4+ As sensitizer, Pt 4+ The emission peak of Er 3+ The excitation peak can effectively transfer energy to the luminescent center Er 3+ , significantly improving Er 3+ The luminous efficiency;

[0020] 2. With Cs2MCl6 type lead-free halogen double perovskite as the matrix, it has strong absorption in the ultraviolet, near-ultraviolet and blue light regions, has a good match with commercial chips, and can be used in the preparation of near-infrared LEDs;

[0021] 3. The emission peak of the obtained phosphor is 1540nm, which is located in the second near-infrared region. It has high luminous efficiency and has great application prospects in the fields of biological analysis, food testing and night vision equipment.

[0022] 4. During the preparation process, the temperature was strictly controlled and solvents such as hydrochloric acid, ethanol and deionized water were used to dissolve the raw materials, which improved the stability of the sample solution. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 It is Cs2Zr prepared in Example 1 of the present invention. 0.738 Pt 0.002 Er 0.260 Emission spectrum of Cl6 phosphor at 460nm excitation wavelength;

[0024] Figure 2 It is Cs2Sn prepared in Example 2 of the present invention0.823 Pt 0.007 Er 0.170 Excitation spectrum of Cl6 phosphor at 1540nm excitation wavelength;

[0025] Figure 3 It is Cs2Hf prepared in Example 3 of the present invention 0.637 Pt 0.013 Er 0.350 Quantum efficiency diagram of Cl6 phosphor;

[0026] Figure 4 It is Cs2Zr prepared in Example 4 of the present invention. 0.990 Pt 0.02 Er 0.08 XRD patterns of Cl6 phosphor before and after 3 months of storage;

[0027] Figure 5 It is Cs2Hf prepared in Example 5 of the present invention 0.964 Pt 0.016 Er 0.02 Cl6 phosphor cycle stability test chart. DETAILED DESCRIPTION

[0028] In the following embodiments, the purity of CsCl powder is 99.99%, the purity of ZrCl4 powder is 99.99%, the purity of SnCl4·5H2O is 99.9%, the purity of HfCl4 powder is 99.99%, the purity of PtCl4 powder is 99.99%, the purity of (CH3CO2)3Er·6H2O powder is 99.9%, and the solvent is 37% by mass concentrated hydrochloric acid.

[0029] Table 1 Ingredients of Example

[0030]

[0031] Example 1

[0032] A lead-free halogen double perovskite near-infrared phosphor (Cs2Zr 0.738 Pt 0.002 Er 0.260 C16) preparation method, comprising the following steps:

[0033] (1) Erbium acetate hexahydrate was dissolved in deionized water to prepare a solution with a concentration of 0.8 mol / L; platinum tetrachloride powder was dissolved in a mixed solution of concentrated hydrochloric acid and ethanol (volume ratio 4:6) to prepare a solution with a concentration of 0.5 mol / L; ZrCl4 was dissolved in concentrated hydrochloric acid to prepare a solution with a concentration of 0.5 mol / L; CsCl powder was dissolved in concentrated hydrochloric acid to prepare a solution with a concentration of 8 mol / L.

[0034] (2) Measure the solution according to Table 1.

[0035] (3) Add the (CH3CO2)3Er solution into the PtCl4 solution and stir continuously with a magnetic stirrer. Stir in a sealed container for 5 min. Maintain the temperature of the mixture at 45°C.

[0036] (4) After stirring evenly, the above mixed solution was added to the ZrCl4 solution, sealed and stirred for 12 minutes, and the temperature of the mixed solution was maintained at 50°C.

[0037] (5) Add CsCl solution to the mixed solution using a peristaltic pump at a rate of 2 mL / min.

[0038] (6) After adding the CsCl solution, continue to stir with a sealed magnetic stirrer and maintain the temperature at 40°C. After stirring for 35 min, turn off the magnetic stirrer and wait for the solution to cool to room temperature before centrifuging.

[0039] (7) The obtained solution was centrifuged and washed 6 times at a centrifugal speed of 6000 r / min. The solvents used for the centrifugal washing were in the following order: a mixed solution of concentrated hydrochloric acid and ethanol (volume ratio of 4:6), concentrated hydrochloric acid, isopropanol, isopropanol, concentrated hydrochloric acid and isopropanol.

[0040] (8) The product obtained by centrifugation is placed in a drying oven at 45°C for 6 h, and then cooled to room temperature to obtain the lead-free halogen double perovskite near-infrared phosphor Cs2Zr 0.738 Pt 0.002 Er 0.260 Cl6.

[0041] The test results are as follows:

[0042] The powder samples were subjected to fluorescence spectroscopy (FLS1000, Edinburgh) test, and the emission spectrum was measured with 460nm as the excitation wavelength. The test results are shown in Figure 1 .Depend on Figure 1 It can be seen that the emission peak of the phosphor obtained in Example 1 is near 1540 nm, located in the second near-infrared region, and can be applied to fields such as biological analysis and food testing.

[0043] Example 2

[0044] A lead-free halogen double perovskite near-infrared phosphor (Cs2Sn 0.823 Pt 0.007 Er 0.170 C16) preparation method, comprising the following steps:

[0045] (1) Erbium acetate hexahydrate was dissolved in deionized water to prepare a solution with a concentration of 0.2 mol / L; platinum tetrachloride powder was dissolved in a mixed solution of concentrated hydrochloric acid and ethanol (volume ratio 4:6) to prepare a solution with a concentration of 1 mol / L; SnCl4·5H2O was dissolved in concentrated hydrochloric acid to prepare a solution with a concentration of 1.7 mol / L; CsCl powder was dissolved in concentrated hydrochloric acid to prepare a solution with a concentration of 4 mol / L.

[0046] (2) Measure the solution according to Table 1.

[0047] (3) Add the (CH3CO2)3Er solution into the PtCl4 solution and stir continuously with a magnetic stirrer. Stir in a sealed container for 10 min. Maintain the temperature of the mixture at 40°C.

[0048] (4) After stirring evenly, the above mixed solution was added to the SnCl4 solution, sealed and stirred for 11 minutes, and the temperature of the mixed solution was maintained at 60°C.

[0049] (5) Using a peristaltic pump, add CsCl solution into the mixed solution at a rate of 5 mL / min.

[0050] (6) After adding the CsCl solution, continue to stir with a sealed magnetic stirrer and maintain the temperature at 60°C. After stirring for 20 min, turn off the magnetic stirrer and wait for the solution to cool to room temperature before centrifuging.

[0051] (7) The obtained solution was centrifuged and washed 6 times at a centrifugal speed of 7000 r / min. The solvents used for the centrifugal washing were in the following order: a mixed solution of concentrated hydrochloric acid and ethanol (volume ratio of 4:6), concentrated hydrochloric acid, isopropanol, isopropanol, concentrated hydrochloric acid and isopropanol.

[0052] (8) The product obtained by centrifugation is placed in a drying oven at 40°C and dried for 5 h. After cooling to room temperature, the lead-free halogen double perovskite near-infrared phosphor Cs2Sn is obtained. 0.823 Pt 0.007 Er 0.170 Cl6.

[0053] The test results are as follows:

[0054] The obtained powder samples were subjected to fluorescence spectroscopy (FLS1000, Edinburgh) test, and the excitation spectrum was measured with 1540nm as the excitation wavelength. The test results are shown in Figure 2 .Depend on Figure 2 It can be seen that: Cs2Sn 0.823 Pt 0.007 Er 0.170 Cl6 phosphor exhibits broad peak excitation in the range of 250-500nm, and has a high degree of matching with ultraviolet, near-ultraviolet and blue light chips.

[0055] Example 3

[0056] A lead-free halogen double perovskite near-infrared phosphor (Cs2Hf 0.637 Pt 0.013 Er 0.350 C16) preparation method, comprising the following steps:

[0057] (1) Erbium acetate hexahydrate was dissolved in deionized water to prepare a solution with a concentration of 5 mol / L; platinum tetrachloride powder was dissolved in a mixed solution of concentrated hydrochloric acid and ethanol (volume ratio 4:6) to prepare a solution with a concentration of 0.1 mol / L; HfCl4 was dissolved in concentrated hydrochloric acid to prepare a solution with a concentration of 4 mol / L; CsCl powder was dissolved in concentrated hydrochloric acid to prepare a solution with a concentration of 0.5 mol / L.

[0058] (2) Measure the solution according to Table 1.

[0059] (3) Add the (CH3CO2)3Er solution into the PtCl4 solution and stir continuously with a magnetic stirrer. Stir in a sealed container for 6 min. Maintain the temperature of the mixture at 55°C.

[0060] (4) After stirring evenly, the above mixed solution was added to the HfCl4 solution, sealed and stirred for 10 min, and the temperature of the mixed solution was maintained at 70°C.

[0061] (5) Using a peristaltic pump, add CsCl solution into the mixed solution at a rate of 4 mL / min.

[0062] (6) After adding the CsCl solution, continue to stir with a sealed magnetic stirrer and maintain the temperature at 50°C. After stirring for 27 minutes, turn off the magnetic stirrer and wait for the solution to cool to room temperature before centrifuging.

[0063] (7) The obtained solution was centrifuged and washed 6 times at a centrifugal speed of 8000 r / min. The solvents used for the centrifugal washing were in the following order: a mixed solution of concentrated hydrochloric acid and ethanol (volume ratio of 4:6), concentrated hydrochloric acid, isopropanol, isopropanol, concentrated hydrochloric acid and isopropanol.

[0064] (8) The product obtained by centrifugation was placed in a drying oven at 47°C and dried for 5.5 h. After cooling to room temperature, the lead-free halogen double perovskite near-infrared phosphor Cs2Hf 0.637 Pt 0.013 Er 0.350 Cl6.

[0065] The test results are as follows:

[0066] The obtained powder samples were subjected to quantum efficiency test (FLS1000, Edinburgh), and the test results are shown in Figure 3 .Depend on Figure 3 It can be seen that under the excitation of 300nm, Cs2Zr 0.990 Pt 0.02 Er 0.08 The quantum efficiency of Cl6 phosphor reaches 40%.

[0067] Example 4

[0068] A lead-free halogen double perovskite near-infrared phosphor (Cs2Zr 0.990 Pt 0.02 Er 0.08 C16) preparation method, comprising the following steps:

[0069] (1) Erbium acetate hexahydrate was dissolved in deionized water to prepare a solution with a concentration of 3.2 mol / L; platinum tetrachloride powder was dissolved in a mixed solution of concentrated hydrochloric acid and ethanol (volume ratio 4:6) to prepare a solution with a concentration of 0.36 mol / L; ZrCl4 was dissolved in concentrated hydrochloric acid to prepare a solution with a concentration of 6 mol / L; CsCl powder was dissolved in concentrated hydrochloric acid to prepare a solution with a concentration of 1 mol / L.

[0070] (2) Measure the solution according to Table 1.

[0071] (3) Add the (CH3CO2)3Er solution into the PtCl4 solution and stir continuously with a magnetic stirrer. Stir in a sealed container for 7 min. Maintain the temperature of the mixture at 60°C.

[0072] (4) After stirring evenly, the above mixed solution was added to the ZrCl4 solution, sealed and stirred for 15 minutes, and the temperature of the mixed solution was maintained at 65°C.

[0073] (5) Using a peristaltic pump, add CsCl solution into the mixed solution at a rate of 3 mL / min.

[0074] (6) After adding the CsCl solution, continue to stir with a sealed magnetic stirrer and maintain the temperature at 46°C. After stirring for 32 minutes, turn off the magnetic stirrer and wait for the solution to cool to room temperature before centrifuging.

[0075] (7) The obtained solution was centrifuged and washed 6 times at a centrifugal speed of 9000 r / min. The solvents used for the centrifugal washing were in the following order: a mixed solution of concentrated hydrochloric acid and ethanol (volume ratio of 4:6), concentrated hydrochloric acid, isopropanol, isopropanol, concentrated hydrochloric acid and isopropanol.

[0076] (8) The product obtained by centrifugation was placed in a drying oven at 52°C for 4 h and then cooled to room temperature to obtain the lead-free halogen double perovskite near-infrared phosphor Cs2Zr 0.990 Pt 0.02 Er 0.08 Cl6.

[0077] The test results are as follows:

[0078] The obtained powder samples were subjected to XRD (SmartLabSE) test. The samples were placed for 3 months before being tested again for XRD test. The test results are shown in Figure 4 .Depend on Figure 4 It can be seen that: Cs2Zr 0.990 Pt 0.02 Er 0.08 The Cl6 sample remained in the pure phase of Cs2ZrCl6 before and after 3 months, indicating that the sample has good stability.

[0079] Example 5

[0080] A lead-free halogen double perovskite near-infrared phosphor (Cs2Hf 0.964 Pt 0.016 Er 0.02 C16) preparation method, comprising the following steps:

[0081] (1) Erbium acetate hexahydrate was dissolved in deionized water to prepare a solution with a concentration of 1.8 mol / L; platinum tetrachloride powder was dissolved in a mixed solution of concentrated hydrochloric acid and ethanol (volume ratio 4:6) to prepare a solution with a concentration of 0.65 mol / L; HfCl4 was dissolved in concentrated hydrochloric acid to prepare a solution with a concentration of 2.5 mol / L; CsCl powder was dissolved in concentrated hydrochloric acid to prepare a solution with a concentration of 5.5 mol / L.

[0082] (2) Measure the solution according to Table 1.

[0083] (3) Add the (CH3CO2)3Er solution into the PtCl4 solution and stir continuously with a magnetic stirrer. Stir in a sealed container for 9 minutes. Maintain the temperature of the mixture at 48°C.

[0084] (4) After stirring evenly, the above mixed solution was added to the HfCl4 solution, sealed and stirred for 14 minutes, and the temperature of the mixed solution was maintained at 55°C.

[0085] (5) Using a peristaltic pump, add CsCl solution into the mixed solution at a rate of 1 mL / min.

[0086] (6) After adding the CsCl solution, continue to stir with a sealed magnetic stirrer and maintain the temperature at 54°C. After stirring for 40 min, turn off the magnetic stirrer and wait for the solution to cool to room temperature before centrifuging.

[0087] (7) The obtained solution was centrifuged and washed 6 times at a centrifugal speed of 6000 r / min. The solvents used for the centrifugal washing were in the following order: a mixed solution of concentrated hydrochloric acid and ethanol (volume ratio of 4:6), concentrated hydrochloric acid, isopropanol, isopropanol, concentrated hydrochloric acid and isopropanol.

[0088] (8) The product obtained by centrifugation was placed in a drying oven at 60°C and dried for 4.5 h. After cooling to room temperature, the lead-free halogen double perovskite near-infrared phosphor Cs2Hf 0.964 Pt 0.016 Er 0.02 Cl6.

[0089] The test results are as follows:

[0090] The obtained powder samples were subjected to cyclic stability test (FLS1000, Edinburgh), and the test results are shown in Figure 5 .Depend on Figure 5 It can be seen that the luminous intensity of the phosphor decreases during the heating process, and when the temperature drops back to 303K, the luminous intensity of Cs2Hf 0.964 Pt 0.016 Er 0.02 The luminescence intensity of Cl6 phosphor maintains the initial intensity and has good cycle stability.

[0091] Among the above embodiments, the best embodiment is 3.

[0092] Comparative Example 1

[0093] The remaining steps of this comparative example are the same as those of Example 2, except that no PtCl4 powder is added and step (3) is omitted. The obtained powder sample is subjected to quantum efficiency test (FLS1000, Edinburgh) under 300nm excitation. The results show that: 3+ The quantum efficiency of phosphors is very low, less than 5%.

[0094] Comparative Example 2

[0095] The remaining steps of this comparative example are the same as those of Example 1, except that the drying temperature in step (8) is replaced with 35° C. It is found that the obtained sample is not dry enough, which is not conducive to the storage of the sample.

[0096] Comparative Example 3

[0097] The remaining steps of this comparative example are the same as those of Example 3, except that the centrifugal washing in step (7) is done with concentrated hydrochloric acid. The obtained powder sample is subjected to XRD (SmartLabSE) testing, and the results show that the sample contains a small amount of CsCl impurity phase.

[0098] Comparative Example 4

[0099] The remaining steps of this comparative example are the same as those of Example 4, except that the centrifugal washing in step (7) is only washed with isopropanol. The obtained powder sample is subjected to XRD (SmartLabSE) test, and the results show that the sample contains a small amount of CsCl impurity phase.

[0100] Comparative Example 5

[0101] The remaining steps of this comparative example are the same as those of Example 5, except that the concentrated hydrochloric acid in step (7) is replaced by dilute hydrochloric acid diluted 2 to 3 times, i.e., 15% dilute hydrochloric acid. The results show that the obtained powder sample is significantly reduced and the yield is relatively low.

Claims

1. A lead-free halogen double perovskite near-infrared phosphor, characterized in that: Its chemical formula is: Cs2M 1-x-y Cl6:xPt 4 + ,yEr 3+ ; Wherein, M is any one of Zr, Sn, Hf, 0 <x≤0.02,0<y≤0.35。 2. The method for preparing a lead-free halogen double perovskite near-infrared phosphor according to claim 1, characterized in that: The following steps are involved: Step 1, adding the erbium acetate solution into the platinum tetrachloride solution, sealing and stirring; Step 2, add the solution obtained in step 1 into the MCl4 solution, seal and stir at 50-70°C; Step 3, adding the cesium chloride solution to the solution obtained in step 2, sealing and stirring at 40-60° C., and centrifuging and washing the solution after the solution is cooled to room temperature; Step 4: Dry the product obtained in step 3 at 40-60° C. and cool it to obtain a lead-free halogen double perovskite near-infrared phosphor.

3. The method for preparing a lead-free halogen double perovskite near-infrared phosphor according to claim 2, characterized in that: In the step 1, the erbium acetate solution is an aqueous solution of erbium acetate hexahydrate with a concentration of 0.2 to 5.0 mol / L.

4. The method for preparing a lead-free halogen double perovskite near-infrared phosphor according to claim 2, characterized in that: In the step 1, the platinum tetrachloride solution is prepared by dissolving platinum tetrachloride powder in a mixed solution of concentrated hydrochloric acid and ethanol, with a concentration of 0.1 to 1.0 mol / L.

5. The method for preparing a lead-free halogen double perovskite near-infrared phosphor according to claim 2, characterized in that: In the step 2, the solvent of the MCl4 solution is concentrated hydrochloric acid, the temperature is 50-70°C, the concentration is 0.5-6.0 mol / L, and the sealed stirring time is 10-15 min.

6. The method for preparing a lead-free halogen double perovskite near-infrared phosphor according to claim 2, characterized in that: In the step 3, the concentration of the cesium chloride solution is 0.5-8.0 mol / L, and the solvent is concentrated hydrochloric acid.

7. The method for preparing a lead-free halogen double perovskite near-infrared phosphor according to claim 2, characterized in that: In the step 3, the cesium chloride solution is added by a peristaltic pump at a rate of 1 to 5 mL / min.

8. The method for preparing a lead-free halogen double perovskite near-infrared phosphor according to claim 2, characterized in that: In the step 3, the sealing and stirring time is 20 to 40 minutes.

9. The method for preparing a lead-free halogen double perovskite near-infrared phosphor according to claim 2, characterized in that: In the step three, the rotation speed of the centrifugal washing is 6000-9000 r / min, and the washing solvent is one or more of concentrated hydrochloric acid, ethanol, and isopropanol.

10. The method for preparing a lead-free halogen double perovskite near-infrared phosphor according to claim 2, characterized in that: In the step 4, the drying time is 4 to 6 hours.

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