A lead-free halogen double perovskite near-infrared fluorescent powder and a preparation method thereof

Abstract

The application discloses a kind of lead-free halogen double perovskite near-infrared fluorescent powder and preparation method thereof, and fluorescent powder chemical general 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.Preparation method includes the following steps: adding erbium acetate solution to platinum tetrachloride solution, sealed stirring;The obtained solution is added to MC14 solution, 50-70 ℃ sealed stirring;Add cesium chloride solution, 40-60 ℃ sealed stirring, after solution cooling to room temperature, centrifugal separation, centrifugal washing is carried out;40-60 ℃ drying is carried out, cooling.The emission peak of fluorescent powder Pt 4+ of the application covers the excitation peak of Er 3+ very well, effectively transfers energy to luminescent center Er 3+ , significantly improves the luminescent efficiency of Er 3+ ;There is strong absorption in ultraviolet and near ultraviolet and blue light region.

Description

TECHNICAL FIELD

[0001] The application belongs to luminescent materials and its preparation method, and in particular to a lead-free halogen double perovskite near-infrared fluorescent powder and a preparation method thereof. BACKGROUND

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

[0003] A large number of studies have shown that perovskites have broad application prospects in optoelectronic materials due to their unique structure. However, the previously reported perovskite materials lack stability and contain Pb elements, which pollute the environment greatly. In order to solve this problem, researchers use +4 valence elements (Zr, Sn, Hf) to replace +2 valence Pb elements, leaving 50% vacancies in the perovskite structure, and synthesize vacancy-ordered lead-free halogen double perovskite (Cs2MCl6). Among them, the octahedral coordination of [MCl6] 3- is considered to be an ideal matrix for doping Ln 3+ to produce near-infrared luminescence. However, due to the forbidden optical transition in the 4f electron configuration of rare earth ions, the double perovskite near-infrared fluorescent powder doped with rare earth ions shows low quantum efficiency.

[0004] In recent years, researchers have proposed that the energy transfer from self-trapped excitation (STE) in double perovskite luminescent materials to rare earth ions is an effective way to improve the near-infrared emission of rare earth ions, and have developed a series of Ln 3+ doped lead-free halogen double perovskite near-infrared fluorescent powders, such as Cs2ZrCl6:Te 4+ / Ln 3+ (Ln 3+ =Er 3+ ,Nd 3+ ,Yb 3+ ), Cs2AglnCl6:Sb 3+ / Yb 3+ , etc. (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 luminescent efficiency of these near-infrared fluorescent powders is very low. SUMMARY

[0005] The application aims at providing a lead-free halogen double perovskite near-infrared fluorescent powder with high luminous efficiency and a preparation method of the lead-free halogen double perovskite near-infrared fluorescent powder.

[0006] The lead-free halogen double perovskite near-infrared fluorescent powder has a chemical general formula of Cs2M 1-x-y Cl6:xPt 4+ ,yEr 3+ ; wherein M is any one of Zr, Sn and Hf, 0 < x ≤ 0.02 and 0 < y ≤ 0.35.

[0007] The preparation method of the lead-free halogen double perovskite near-infrared fluorescent powder comprises the following steps.

[0008] In step one, the erbium acetate solution is added into the platinum tetrachloride solution, and then sealed and stirred.

[0009] In step two, the solution obtained in step one is added into the MCl4 solution, and then sealed and stirred at 50-70 DEG C.

[0010] In step three, the cesium chloride solution is added into the solution obtained in step two, and then sealed and stirred at 40-60 DEG C; after the solution is cooled to room temperature, centrifugal separation and centrifugal washing are performed.

[0011] In step four, the product obtained in step three is dried at 40-60 DEG C, and then cooled to obtain the lead-free halogen double perovskite near-infrared fluorescent powder.

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

[0013] Further, in step one, the platinum tetrachloride solution is prepared by dissolving platinum tetrachloride powder in a mixed solution of concentrated hydrochloric acid and ethanol, and has a concentration of 0.1-1.0 mol / L.

[0014] Further, in step two, the solvent of the MCl4 solution is concentrated hydrochloric acid, the temperature is 50-70 DEG 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] Further, in step three, the cesium chloride solution is added by using a peristaltic pump, and the adding speed is 1-5 mL / min; the sealed stirring time is 20-40 min; the centrifugal washing speed is 6000-9000 r / min; and the washing solvent is one or more of concentrated hydrochloric acid, ethanol and isopropanol.

[0016] Further, in step four, the drying time is 4-6h.

[0017] Principle of preparation: select Cs2MCl6 with good chemical stability and no lead as a matrix, Pt 4+ as a sensitizing agent, Er 3+ as a luminescent center, to form a single-phase Cs2M 1-x-y Pt x Er y Cl6 solid solution. The fluorescent powder Cs2M 1-x-y Cl6:xPt 4+ ,yEr 3+ The emission peak of Pt 4+ very well covers the excitation peak of Er 3+ , which can effectively transfer energy to the luminescent center Er 3+ , and significantly improve the luminescent efficiency of Er 3+ .

[0018] Advantages: compared with the prior art, the present application has the following significant features:

[0019] 1. The obtained fluorescent powder selects Pt 4+ as a sensitizing agent, and the emission peak of Pt 4+ very well covers the excitation peak of Er 3+ , which can effectively transfer energy to the luminescent center Er 3+ , and significantly improve the luminescent efficiency of Er 3+ ;

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

[0021] 3. The emission peak 1540nm of the obtained fluorescent powder is located in the near-infrared region II, and the luminescent efficiency is high, which has great application prospect in the fields of biological analysis, food detection and night vision equipment;

[0022] 4. The stability of the sample solution is improved by strictly controlling the temperature and using hydrochloric acid, ethanol and deionized water and other solvents to dissolve the raw materials during preparation. BRIEF DESCRIPTION OF DRAWINGS

[0023] Figure 1 is the emission spectrum diagram of the Cs2Zr 0.738 Pt 0.002 Er 0.260 Cl6 fluorescent powder prepared in example 1 of the present application under 460nm excitation wavelength;

[0024] Figure 2 is the Cs2Sn0.823 Pt 0.007 Er 0.170 The excitation spectrum of the Cl6 fluorescent powder at an excitation wavelength of 1540 nm;

[0025] Figure 3 Cs2HfCl6 prepared in Example 3 of the present application 0.637 Pt 0.013 Er 0.350 The quantum efficiency diagram of the Cl6 fluorescent powder;

[0026] Figure 4 Cs2ZrCl6 prepared in Example 4 of the present application 0.990 Pt 0.02 Er 0.08 The XRD diagrams of the Cl6 fluorescent powder before and after being placed for 3 months;

[0027] Figure 5 Cs2HfCl6 prepared in Example 5 of the present application 0.964 Pt 0.016 Er 0.02 The cycling stability test diagram of the Cl6 fluorescent powder. DETAILED DESCRIPTION

[0028] In each of the following examples, the purity of the CsCl powder is 99.99%, the purity of the ZrCl4 powder is 99.99%, the purity of the SnCl4·5H2O is 99.9%, the purity of the HfCl4 powder is 99.99%, the purity of the PtCl4 powder is 99.99%, the purity of the (CH3CO2)3Er·6H2O powder is 99.9%, and the solvent is selected to be concentrated hydrochloric acid with a mass percentage of 37%.

[0029] Table 1: Example ingredient table

[0030]

[0031] Example 1

[0032] A preparation method of a lead-free halogen double perovskite near-infrared fluorescent powder (Cs2ZrPtCl6), comprising the following steps: 0.738 Pt 0.002 Er 0.260 Cl6), comprising the following steps:

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

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

[0035] (3) Add the (CH3CO2)3Er solution to the PtCl4 solution and continuously stir with a magnetic stirrer, seal and stir for 5 min, and maintain the temperature of the mixture at 45°C.

[0036] (4) After stirring evenly, add the above mixture to the ZrCl4 solution, seal and stir for 12 min, and maintain the temperature of the mixture at 50°C.

[0037] (5) Add the CsCl solution to the above mixture solution with a peristaltic pump, and the speed of adding the CsCl solution is 2 mL / min.

[0038] (6) After adding the CsCl solution, continue to seal and stir with a magnetic stirrer, maintain the temperature at 40°C, and turn off the magnetic stirrer after stirring for 35 min. After the solution cools to room temperature, centrifugal separation is performed.

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

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

[0041] The test results are as follows:

[0042] The obtained powder sample is tested by fluorescence spectrum (FLS1000, Edinburgh), the emission spectrum is measured with 460 nm as the excitation wavelength, and the test results are shown in Figure 1 . It can be seen from Figure 1 that the emission peak of the fluorescent powder obtained in Example 1 is near 1540 nm, which is in the near-infrared two area, and can be applied in the fields of biological analysis and food detection.

[0043] Example 2

[0044] A preparation method of a lead-free halogen double perovskite near-infrared fluorescent powder (Cs2Sn 0.823 Pt 0.007 Er 0.170 Cl6) includes the following steps:

[0045] (1) Dissolve erbium acetate hexahydrate in deionized water to prepare a solution with a concentration of 0.2 mol / L; dissolve platinum tetrachloride powder 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; dissolve SnCl4·5H2O in concentrated hydrochloric acid to prepare a solution with a concentration of 1.7 mol / L; dissolve CsCl powder in concentrated hydrochloric acid to prepare a solution with a concentration of 4 mol / L.

[0046] (2) Take the solutions according to Table 1.

[0047] (3) Add the (CH3CO2)3Er solution to the PtCl4 solution and continuously stir with a magnetic stirrer, seal and stir for 10 min, and maintain the temperature of the mixed solution at 40°C.

[0048] (4) After stirring evenly, add the above mixed solution to the SnCl4 solution, seal and stir for 11 min, and maintain the temperature of the mixed solution at 60°C.

[0049] (5) Add the CsCl solution to the above mixed solution using a peristaltic pump, and the speed of adding the CsCl solution is 5 mL / min.

[0050] (6) After adding the CsCl solution, continue to seal and stir with a magnetic stirrer, maintain the temperature at 60°C, and stir for 20 min, then turn off the magnetic stirrer. After the solution cools to room temperature, centrifugal separation is performed.

[0051] (7) Centrifugal wash the obtained solution 6 times at a centrifugal rate of 7000 r / min, and use the following solvents for centrifugal washing in the following order: a mixed solution of concentrated hydrochloric acid and ethanol (volume ratio 4:6), concentrated hydrochloric acid, isopropanol, isopropanol, concentrated hydrochloric acid, and isopropanol.

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

[0053] The test results are as follows:

[0054] The obtained powder sample is tested by fluorescence spectrum (FLS1000, Edinburgh), the excitation spectrum is measured at an excitation wavelength of 1540 nm, and the test results are shown in Figure 2 . It can be seen from Figure 2 that the Cs2Sn 0.823 Pt 0.007 Er 0.170 Cl6 fluorescent powder has a wide peak excitation in the range of 250-500 nm, and has high matching degree with ultraviolet, near-ultraviolet and blue light chips.

[0055] Example 3

[0056] A preparation method of a lead-free halogen double perovskite near-infrared fluorescent powder (Cs2Hf 0.637 Pt 0.013 Er 0.350 Cl6) comprises the following steps:

[0057] (1) Dissolve erbium acetate hexahydrate in deionized water to prepare a solution with a concentration of 5 mol / L; dissolve platinum tetrachloride powder 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; dissolve HfCl4 in concentrated hydrochloric acid to prepare a solution with a concentration of 4 mol / L; and dissolve CsCl powder in concentrated hydrochloric acid to prepare a solution with a concentration of 0.5 mol / L.

[0058] (2) Take the solutions according to Table 1.

[0059] (3) Add the (CH3CO2)3Er solution to the PtCl4 solution, and continuously stir with a magnetic stirrer, seal and stir for 6 min, and maintain the temperature of the mixed solution at 55°C.

[0060] (4) After uniform stirring, add the above mixed solution to the HfCl4 solution, seal and stir for 10 min, and maintain the temperature of the mixed solution at 70°C.

[0061] (5) Add the CsCl solution to the above mixed solution with a peristaltic pump, and the speed of adding the CsCl solution is 4 mL / min.

[0062] (6) After adding the CsCl solution, continue to seal and stir with a magnetic stirrer, maintain the temperature at 50°C, and stop the magnetic stirrer after stirring for 27 min. After the solution cools to room temperature, perform centrifugal separation.

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

[0064] (8) Place the product obtained by centrifugation in a drying box at 47°C for 5.5 h, and after cooling to room temperature, a lead-free halogen double perovskite near-infrared fluorescent powder Cs2Hf 0.637 Pt 0.013 Er 0.350 Cl6 is obtained.

[0065] The test results are as follows:

[0066] The obtained powder sample was subjected to quantum efficiency (FLS1000, Edinburgh) test, and the test result is shown in Table 1 Figure 3 . It can be seen that under the excitation of 300 nm, the Cs2Zr Figure 3 fluorescent powder has a quantum efficiency of 40%. 0.990 Pt 0.02 Er 0.08 Cl6fluorescent powder reaches 40%.

[0067] Example 4

[0068] A preparation method of a lead-free halogen double perovskite near-infrared fluorescent powder (Cs2Zr 0.990 Pt 0.02 Er 0.08 Cl6) includes the following steps:

[0069] (1) Dissolve erbium acetate hexahydrate in deionized water to prepare a solution with a concentration of 3.2 mol / L; dissolve PtCl4 powder 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; dissolve ZrCl4 in concentrated hydrochloric acid to prepare a solution with a concentration of 6 mol / L; and dissolve CsCl powder in concentrated hydrochloric acid to prepare a solution with a concentration of 1 mol / L.

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

[0071] (3) Add the (CH3CO2)3Er solution to the PtCl4 solution, and continuously stir with a magnetic stirrer. Seal and stir for 7 min, and maintain the temperature of the mixed solution at 60°C.

[0072] (4) After uniform stirring, add the above mixed solution to the ZrCl4 solution, seal and stir for 15 min, and maintain the temperature of the mixed solution at 65°C.

[0073] (5) Add the CsCl solution to the above mixed solution using a peristaltic pump, and the speed of adding the CsCl solution is 3 mL / min.

[0074] (6) After adding the CsCl solution, continue to seal and stir with a magnetic stirrer, and maintain the temperature at 46°C. Stir for 32 min, then turn off the magnetic stirrer. After the solution cools to room temperature, perform centrifugal separation.

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

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

[0077] The test results are as follows:

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

[0079] Example 5

[0080] A preparation method of a lead-free halogen double perovskite near-infrared fluorescent powder (Cs2Hf 0.964 Pt 0.016 Er 0.02 Cl6) comprises the following steps:

[0081] (1) Dissolve erbium acetate hexahydrate in deionized water to prepare a solution with a concentration of 1.8 mol / L; dissolve platinum tetrachloride powder 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; dissolve HfCl4 in concentrated hydrochloric acid to prepare a solution with a concentration of 2.5 mol / L; dissolve CsCl powder in concentrated hydrochloric acid to prepare a solution with a concentration of 5.5 mol / L.

[0082] (2) The solutions are measured according to Table 1.

[0083] (3) The (CH3CO2)3Er solution is added to the PtCl4 solution, and a magnetic stirrer is used for continuous stirring. The mixture is sealed and stirred for 9 min, and the temperature of the mixture is maintained at 48°C.

[0084] (4) After uniform stirring, the above mixture is added to the HfCl4 solution, and the mixture is sealed and stirred for 14 min, and the temperature of the mixture is maintained at 55°C.

[0085] (5) The CsCl solution is added to the above mixture solution using a peristaltic pump, and the speed of adding the CsCl solution is 1 mL / min.

[0086] (6) After adding CsCl solution, continue to stir with a magnetic stirrer in a sealed manner, keep the temperature at 54℃, stir for 40 minutes, then turn off the magnetic stirrer and wait for the solution to cool to room temperature before centrifugation.

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

[0088] (8) The product obtained by centrifugation is placed in a drying oven at 60°C for 4.5 hours and dried. After cooling to room temperature, the lead-free halide double perovskite near-infrared phosphor Cs2Hf is obtained. 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 testing (FLS1000, Edinburgh), and the test results are shown below. Figure 5 .Depend on Figure 5 It can be seen that the luminescence intensity of the phosphor decreases during the heating process, and when the temperature drops back to 303K, the luminescence intensity of Cs2Hf... 0.964 Pt 0.016 Er 0.02 The luminescence intensity of Cl6 phosphor remains at its initial intensity, exhibiting good cycling stability.

[0091] Of the above embodiments, the preferred embodiment is 3.

[0092] Comparative Example 1

[0093] The remaining steps of this comparative example are the same as those in Example 2, except that PtCl4 powder is not added and step (3) is omitted. The quantum efficiency (FLS1000, Edinburgh) of the obtained powder sample was tested under 300nm excitation. The results showed that the obtained sample was only doped with Er 3+ The quantum efficiency of the phosphor is very low, less than 5%.

[0094] Comparative Example 2

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

[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 of step (7) is only washed with concentrated hydrochloric acid. The obtained powder sample is tested by XRD (SmartLab SE), and it is found 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 of step (7) is only washed with isopropanol. The obtained powder sample is tested by XRD (SmartLab SE), and it is found 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 centrifugal washing of step (7) is replaced with 2-3 times diluted dilute hydrochloric acid, i.e. 15% dilute hydrochloric acid. It is found that the obtained powder sample is significantly reduced, and the yield is relatively low.

Claims

1. A lead-free halide double perovskite near-infrared phosphor, characterized in that: Its general chemical formula is: Cs2M 1-x-y Cl6: x Pt 4+ , y Er 3+ Where M is any one of Zr, Sn, and Hf, 0 < x ≤0.02, 0< y ≤0.

35.

2. The method for preparing a lead-free halide double perovskite near-infrared phosphor according to claim 1, characterized in that, Includes the following steps: Step 1: Add the erbium acetate solution to the platinum tetrachloride solution, seal and stir; the erbium acetate solution is an aqueous solution of erbium acetate hexahydrate; the platinum tetrachloride solution is a mixed solution of platinum tetrachloride powder dissolved in concentrated hydrochloric acid and ethanol; Step 2: Add the solution obtained in Step 1 to the MCl4 solution and stir in a sealed container at 50-70°C; the solvent for the MCl4 solution is concentrated hydrochloric acid. Step 3: Add the cesium chloride solution to the solution obtained in Step 2, seal and stir at 40~60℃, and after the solution cools to room temperature, perform centrifugation and washing. The solvent for cesium chloride solution is concentrated hydrochloric acid; Step four: Dry the product obtained in step three at 40~60℃ and cool it to obtain lead-free halide double perovskite near-infrared phosphor.

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

4. The method for preparing a lead-free halide double perovskite near-infrared phosphor according to claim 2, characterized in that: In step one, the concentration of the platinum tetrachloride solution is 0.1~1.0 mol / L.

5. The method for preparing a lead-free halide double perovskite near-infrared phosphor according to claim 2, characterized in that: In step two, the concentration of the MCl4 solution is 0.5~6.0 mol / L, and the stirring time is 10~15 min.

6. The method for preparing a lead-free halide double perovskite near-infrared phosphor according to claim 2, characterized in that: In step three, the concentration of the cesium chloride solution is 0.5~8.0 mol / L.

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

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

9. The method for preparing a lead-free halide double perovskite near-infrared phosphor according to claim 2, characterized in that: In step three, the centrifugal washing speed 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 halide double perovskite near-infrared phosphor according to claim 2, characterized in that: In step four, the drying time is 4-6 hours.

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