A lead-free halogen double perovskite full-spectrum fluorescent powder and a preparation method thereof

Abstract

The application discloses a lead-free halogen double-perovskite full-spectrum fluorescent powder and a preparation method thereof. 1‑x Cl6:xPt 4+ Wherein, M is one of Zr, Sn and Hf, 0

Description

TECHNICAL FIELD

[0001] The present application relates to fluorescent powder and its preparation method, specifically to a lead-free halogen double perovskite full-spectrum fluorescent powder and a preparation method thereof. BACKGROUND

[0002] With the gradual deterioration of global climate environment, people pay more and more attention to environmental protection and low carbon, thus some new devices with low energy consumption, high efficiency and environmental friendliness are vigorously promoted. White light LED occupies a dominant position in the field of solid-state lighting because of its high energy efficiency, environmental protection and easy adjustment. The traditional commercial white light LED is obtained by coating three primary color fluorescent powders (red, green and blue) on an ultraviolet or blue light chip. However, this scheme has problems such as low color rendering index, poor color stability and low luminous efficiency, which cannot meet the needs of modern technology. Therefore, the development of single-matrix full-spectrum fluorescent powder excited by ultraviolet or near-ultraviolet light has become a research hotspot. However, the single-matrix white light emitting fluorescent powder developed at present always lacks cold / warm white light tuning to match the changes of sunlight.

[0003] A large number of studies have shown that perovskite has broad application prospects in optoelectronic materials due to its unique structure. However, most of 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 in recent years, leaving 50% vacancies in the perovskite structure, and synthesizing vacancy-ordered lead-free halogen double perovskite (Cs2MCl6). Compared with the traditional composite perovskite, this kind of lead-free halogen double perovskite has the advantages of large absorption coefficient, long carrier diffusion distance, adjustable band gap and photoluminescence covering the entire visible light region.

[0004] Cs2MCl6 type double perovskite shows a wide self-trapped exciton (STE) emission in the blue region, and after doping a luminescent center, the spectrum can be regulated to obtain tunable single-matrix white light emitting fluorescent powder. However, the white light LED based on Cs2MCl6 type double perovskite obtained at present is mostly not tunable and lacks red light emission, resulting in insufficient color rendering. SUMMARY

[0005] The present application aims at overcoming the deficiencies in the prior art, and provides a lead-free halogen double perovskite full-spectrum fluorescent powder which is convenient to control, has good luminescent performance and good dispersity, and a preparation method of the lead-free halogen double perovskite full-spectrum fluorescent powder.

[0006] Technical scheme: The lead-free halogen double perovskite full-spectrum fluorescent powder provided by the present application has the chemical composition of Cs2M 1-x Cl6:xPt 4+wherein M is one of Zr, Sn, Hf, and 0 < x ≤ 0.01.

[0007] Further, the fluorescent powder presents full spectrum emission in the range of 350-800 nm, and the emission peaks are respectively located at 430 nm and 660 nm.

[0008] The preparation method of the lead-free halogen double perovskite full spectrum fluorescent powder comprises the following steps:

[0009] Step one, the raw materials are weighed according to the stoichiometric ratio, and the CsCl powder is dissolved in concentrated hydrochloric acid; MCl4 is dissolved in concentrated hydrochloric acid under the condition of 50-70℃, and magnetic stirring; PtCl4 powder is dissolved in the mixed solution of concentrated hydrochloric acid and ethanol under the condition of 40-60℃;

[0010] Step two, the PtCl4 solution is added to the MCl4 solution while hot, and the stirring is continuously carried out;

[0011] Step three, after the PtCl4 solution and the MCl4 solution are uniformly mixed, the CsCl solution is added to the mixed solution at a speed of 2-10 mL / min by using a peristaltic pump;

[0012] Step four, the magnetic stirring is continuously carried out, and the temperature is kept at 40-60℃; after the stirring is carried out for 20-40 min, the centrifugal separation is carried out after the cooling to room temperature;

[0013] Step five, the obtained solution is centrifugally washed;

[0014] Step six, the obtained product in step five is dried, and the lead-free halogen double perovskite full spectrum fluorescent powder can be obtained after the cooling to room temperature.

[0015] Further, in step one, the mass percentage of concentrated hydrochloric acid is 36-38wt%. The volume ratio of concentrated hydrochloric acid to ethanol in the mixed solution of concentrated hydrochloric acid and ethanol is 6-7:3-4, and is preferably 6:4. The rotating speed of the magnetic stirring is 100-500 r / min.

[0016] Further, in step two, the rotating speed of the stirring is 100-500 r / min, and the stirring is carried out for 10-15 min.

[0017] Further, in step four, the rotating speed of the magnetic stirring is 100-500 r / min.

[0018] Further, in step five, the centrifugal washing is carried out for 5-7 times, the centrifugal speed is 6000-9000 r / min, and the solvents used for the centrifugal washing include one or more of the mixed solution of equal volume of concentrated hydrochloric acid and ethanol, concentrated hydrochloric acid, and isopropyl alcohol.

[0019] Further, in step six, the drying temperature is 40-60 DEG C, and the drying time is 6-10h.

[0020] Principle of preparation: selecting Cs2MCl6 with good chemical stability and no lead as a matrix, Pt 4+ ions as the luminescent center, forming a single-phase Cs2M 1-x Pt x Cl6 solid solution. The phosphor Cs2M 1-x Cl6:xPt 4+ has a large Stokes shift, and the triplet state STE emission of the [PtCl6] 2- octahedron with excitation state Jahn-Teller distortion is significantly improved, thereby improving the luminescent performance. The stability of the sample solution is improved by strictly controlling the temperature during synthesis and using a mixed solution of hydrochloric acid and ethanol to dissolve the raw materials. Pt 4+ Benefiting from the relatively narrow direct allowed band gap and the localized band edge, the triplet state STE emission of the [PtCl6] 2- octahedron with excitation state Jahn-Teller distortion is realized, and broadband red light emission is realized at 670nm in the halogen double perovskite.

[0021] Beneficial effects: compared with the prior art, the present application has the following remarkable features:

[0022] 1. The prepared phosphor emits full-spectrum light in the range of 350-800nm, and the emission peaks are located at 430nm and 660nm, respectively, and the color rendering index of the prepared white light LED is high.

[0023] 2. The phosphor has a strong absorption in the ultraviolet and near-ultraviolet and blue light regions with Cs2MCl6 type lead-free halogen double perovskite as the matrix, and has good matching with commercial chips, and can be applied to the preparation of white light LED;

[0024] 3. The phosphor can be tuned to emit cold or warm light by changing the doping concentration, cold white light to warm white light emission is realized, and a quantitative relationship between the CIE coordinates and the doping concentration is established, thereby providing theoretical guidance for the preparation of white light LED devices;

[0025] 4. The obtained phosphor has good dispersibility, which is beneficial to the preparation of LED devices. BRIEF DESCRIPTION OF DRAWINGS

[0026] Figure 1 is the Cs2Sn 0.995 Cl6:0.005Pt phosphor obtained in Example 1 of the present application. 4+ is the excitation spectrum of the phosphor;

[0027] Figure 2 is the Cs2Hf0.992 Cl6: 0.008 Pt 4+ The emission spectrum of the phosphor;

[0028] Figure 3 is a scanning electron microscope image of the phosphor obtained in Example 4 of the present application, wherein a and b are Cs2Hf 0.996 Pt 0.004 The scanning electron microscope images of different regions of the Cl6 sample;

[0029] Figure 4 is the emission spectrum of the phosphor obtained in the present application at different doping concentrations;

[0030] Figure 5 is the CIE coordinate diagram of the phosphor obtained in the present application at different doping concentrations. DETAILED DESCRIPTION

[0031] In each of the following examples, the Cs raw material is selected as high-purity (99.99%) CsCl powder; the Zr raw material is selected as high-purity (99.99%) ZrCl4 powder; the Sn raw material is selected as high-purity liquid anhydrous SnCl4 (99.99%); the Hf raw material is selected as high-purity (99.99%) HfCl4 powder; and the Pt raw material is selected as high-purity (99.99%) PtCl4 powder.

[0032] Table 1: ingredient table

[0033] Examples 1 2 3 4 Raw materials (g) Cs2Sn 0.995 Pt 0.005 Cl6]]> Cs2Hf 0.992 Pt 0.008 Cl6]]> Cs2Zr 0.994 Pt 0.006 Cl6]]> Cs2Hf 0.996 Pt 0.004 Cl6]]> CsCl 0.6734 0.6734 0.6734 0.6734 [ZrCl4] 0 0 0.4632 0 SnCl4 0.5184 0 0 0 [HfCl4] 0 0.6354 0 0.6348 PtCl4 0.0033 0.0053 0.0041 0.0061

[0034] Example 1

[0035] A preparation method of a lead-free halogen double perovskite full-spectrum phosphor (Cs2Sn 0.995 Pt 0.005 Cl6) includes the following steps:

[0036] (1) The raw materials are weighed according to the composition in Table 1.

[0037] (2) At room temperature, the CsCl powder weighed according to the stoichiometric ratio is dissolved in 10 mL of concentrated hydrochloric acid; at 50°C, the SnCl4 raw material weighed according to the stoichiometric ratio is dissolved in 10 mL of concentrated hydrochloric acid, and a magnetic stirrer is used for stirring at a speed of 200 r / min; at 45°C, the PtCl4 powder weighed according to the stoichiometric ratio is dissolved in 5 mL of a mixed solution of concentrated hydrochloric acid and ethanol (volume ratio 6:4).

[0038] (3) The PtCl4 solution is added to the SnCl4 solution while hot, and a magnetic stirrer is used for continuous stirring at a speed of 300 r / min for 10 min.

[0039] (4) After the PtCl4 solution is mixed with the SnCl4 solution, the CsCl solution is added to the mixed solution by using a peristaltic pump, and the CsCl solution is added at a speed of 2 mL / min.

[0040] (5) The magnetic stirrer is continuously used for stirring at a speed of 100 r / min, and the temperature is kept at 45°C. After stirring for 20 min, the magnetic stirrer is turned off. After the solution is cooled to room temperature, centrifugal separation is performed.

[0041] (6) The obtained solution is centrifugally washed for 6 times at a centrifugal speed of 8000 r / min, and the solvents used for centrifugal washing are used in the following order: a mixed solution of concentrated hydrochloric acid and ethanol (volume ratio 1:1), concentrated hydrochloric acid, isopropanol, isopropanol, concentrated hydrochloric acid and isopropanol.

[0042] (7) The product obtained by centrifugation is placed in a drying box at 40°C for drying for 9 h. After cooling to room temperature, the lead-free halogen double perovskite full-spectrum fluorescent powder Cs2Sn 0.995 Cl6:0.005Pt 4+ .

[0043] The fluorescent powder powder sample obtained in the example is subjected to fluorescence spectrum (Hitachi F-4600, Japan) test. The excitation spectrum is measured at a monitoring wavelength of 660 nm, and the test result is shown in Figure 1 . It can be seen from Figure 1 that the prepared fluorescent powder has strong absorption in the near ultraviolet, ultraviolet and blue light regions.

[0044] Example 2

[0045] A preparation method of a lead-free halogen double perovskite full-spectrum fluorescent powder (Cs2Hf 0.992 Pt 0.008 Cl6) includes the following steps:

[0046] (1) The raw materials are weighed according to the composition in Table 1.

[0047] (2) At room temperature, the CsCl powder weighed according to the stoichiometric ratio is dissolved in 10 mL of concentrated hydrochloric acid. At 60°C, the HfCl4 raw material weighed according to the stoichiometric ratio is dissolved in 10 mL of concentrated hydrochloric acid, and the magnetic stirrer is used for stirring at a speed of 100 r / min. At 40°C, the PtCl4 powder weighed according to the stoichiometric ratio is dissolved in 5 mL of a mixed solution of concentrated hydrochloric acid and ethanol (volume ratio 6:4).

[0048] (3) The PtCl4 solution is added to the HfCl4 solution while hot, and the magnetic stirrer is continuously used for stirring at a speed of 100 r / min for 12 min.

[0049] (4) After the PtCl4 solution and HfCl4 solution are mixed evenly, the CsCl solution is added to the above mixed solution using a peristaltic pump at a rate of 10 mL / min.

[0050] (5) Continue stirring with a magnetic stirrer at a speed of 500 r / min and keep the temperature at 40℃. After stirring for 40 min, turn off the magnetic stirrer and wait for the solution to cool to room temperature before centrifugation.

[0051] (6) 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 1:1), concentrated hydrochloric acid, isopropanol, isopropanol, concentrated hydrochloric acid and isopropanol.

[0052] (7) The product obtained by centrifugation is placed in a drying oven at 45°C and dried for 10 hours. After cooling to room temperature, the lead-free halide double perovskite full-spectrum phosphor Cs2Hf is obtained. 0.992 Cl6: 0.008Pt 4+ .

[0053] The phosphor sample obtained in this embodiment was subjected to fluorescence spectroscopy (Hitachi F-4600, Japan). The emission spectrum was measured with an excitation wavelength of 254 nm. The test results are shown below. Figure 2 .Depend on Figure 2 It can be seen that the prepared phosphor exhibits full-spectrum emission in the 350–800 nm region, with emission peaks located at 430 nm and 660 nm, respectively. This is due to the Pt... 4+ After its introduction, self-captured exciton (STE) emission occurred.

[0054] Example 3

[0055] A lead-free halide double perovskite full-spectrum phosphor (Cs2Zr) 0.994 Pt 0.006 The preparation method of Cl6 includes the following steps:

[0056] (1) Weigh the raw materials according to the composition in Table 1.

[0057] (2) At room temperature, CsCl powder weighed according to the stoichiometric ratio was dissolved in 10 mL of concentrated hydrochloric acid; at 70 °C, ZrCl4 raw material weighed according to the stoichiometric ratio was dissolved in 10 mL of concentrated hydrochloric acid and stirred with a magnetic stirrer at a speed of 300 r / min; at 60 °C, PtCl4 powder weighed according to the stoichiometric ratio was dissolved in a mixed solution of 5 mL of concentrated hydrochloric acid and ethanol (volume ratio 6:4).

[0058] (3) While hot, add the PtCl4 solution to the ZrCl4 solution, and continuously stir with a magnetic stirrer at a speed of 500 r / min for 13 min.

[0059] (4) After the PtCl4 solution and the ZrCl4 solution are mixed evenly, 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.

[0060] (5) Continue to stir with a magnetic stirrer at a speed of 400 r / min, and keep the temperature at 60°C. After stirring for 25 min, turn off the magnetic stirrer, and then centrifuge after the solution cools to room temperature.

[0061] (6) Centrifuge the obtained solution 6 times at a speed of 7000 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 1:1), concentrated hydrochloric acid, isopropanol, isopropanol, concentrated hydrochloric acid, and isopropanol.

[0062] (7) Place the product obtained by centrifugation in a drying oven at 50°C for 8 h, and then cool to room temperature to obtain a lead-free halogen double perovskite full-spectrum fluorescent powder Cs2Zr 0.994 Cl6:0.006Pt 4+ .

[0063] The fluorescent powder powder sample obtained in this example is subjected to fluorescence spectrum (Hitachi F-4600, Japan) test, scanning electron microscope (Regulus 8100) test, and CIE coordinate determination, and the comprehensive performance is best.

[0064] Example 4

[0065] A preparation method of a lead-free halogen double perovskite full-spectrum fluorescent powder (Cs2Hf 0.996 Pt 0.004 Cl6) includes the following steps:

[0066] (1) Weigh the raw materials according to the composition in Table 1.

[0067] (2) At room temperature, dissolve the CsCl powder weighed according to the stoichiometric ratio in 10 mL of concentrated hydrochloric acid; at 65°C, dissolve the HfCl4 raw material weighed according to the stoichiometric ratio in 10 mL of concentrated hydrochloric acid, and stir using a magnetic stirrer at a speed of 500 r / min; at 45°C, dissolve the PtCl4 powder weighed according to the stoichiometric ratio in 5 mL of a mixed solution of concentrated hydrochloric acid and ethanol (volume ratio 6:4).

[0068] (3) While the PtCl4 solution is still hot, add it to the HfCl4 solution and stir continuously with a magnetic stirrer at a speed of 200 r / min for 15 min.

[0069] (4) After the PtCl4 solution and HfCl4 solution are mixed evenly, the CsCl solution is added to the above mixed solution using a peristaltic pump at a rate of 8 mL / min.

[0070] (5) Continue stirring with a magnetic stirrer at a speed of 200 r / min and keep the temperature at 50℃. After stirring for 30 min, turn off the magnetic stirrer and wait for the solution to cool to room temperature before centrifugation.

[0071] (6) The obtained solution was centrifuged and washed 6 times at a centrifugation rate of 9000 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 1:1), concentrated hydrochloric acid, isopropanol, isopropanol, concentrated hydrochloric acid and isopropanol.

[0072] (7) Place the product obtained by centrifugation in a drying oven at 60°C for 6 hours, and cool it to room temperature to obtain the lead-free halide double perovskite full-spectrum phosphor Cs2Hf. 0.996 Cl6: 0.004Pt 4+ .

[0073] The phosphor powder sample obtained in this embodiment was tested using a scanning electron microscope (Regulus 8100). The test results are shown in [Figure number missing]. Figure 3 .Depend on Figure 3 It can be seen that the prepared phosphor is uniformly distributed with a particle size of about 1 μm, which is beneficial for the fabrication of LED devices.

[0074] Example 5

[0075] The remaining steps in this embodiment are the same as in Example 3, except that the raw material ratios are different, with x being 0.01, 0.008, 0.007, 0.006, 0.005, 0.004, and 0.003 respectively. The molecular formulas of the resulting phosphors are Cs2M. 0.99 Cl6:0.01Pt 4+ Cs2M 0.992 Cl6: 0.008Pt 4+ Cs2M 0.993 Cl6:0.007Pt 4+ Cs2M 0.994 Cl6: 0.006Pt 4+ Cs2M 0.995 Cl6: 0.005Pt 4+、 Cs2M 0.996 Cl6: 0.004Pt4+、 Cs2M 0.997 Cl6: 0.003Pt 4+ .

[0076] like Figure 4 As shown, by changing Pt 4+ With varying doping concentrations, the relative intensities of the red and blue emission peaks changed in a regular manner, achieving the goal of controlling the temperature of white light.

[0077] like Figure 5 As shown, with Pt 4+ As the concentration increases, the x and y values ​​of the CIE coordinates both show an increasing trend, and the emission position also shifts towards red light, thus achieving the purpose of tuning the warm and cool white light.

[0078] Comparative Example 1

[0079] The remaining steps of this comparative example are the same as those in Example 3, except that Pt is replaced with Sn. Fluorescence spectroscopy (Hitachi F-4600, Japan) was performed, and the results showed that there was a lack of red light emission, insufficient color development, and full-spectrum emission could not be achieved.

[0080] Comparative Example 2

[0081] The remaining steps of this comparative example are the same as those in Example 3, except that x = 0.12, i.e., the chemical composition is Cs2M. 0.88 Cl6:0.12Pt 4+ Fluorescence spectroscopy (Hitachi F-4600, Japan) was performed, and the results showed that the red light emission was too strong, the color rendering was insufficient, and the full spectrum emission could not be achieved.

[0082] Comparative Example 3

[0083] The remaining steps of this comparative example are the same as those in Example 3, except that step (2) is replaced by: dissolving the stoichiometric CsCl powder in 10 mL of concentrated hydrochloric acid at room temperature; dissolving the stoichiometric ZrCl4 raw material in 10 mL of concentrated hydrochloric acid at room temperature, stirring with a magnetic stirrer at 300 r / min; and dissolving the stoichiometric PtCl4 powder in a mixed solution of concentrated hydrochloric acid and ethanol (volume ratio 6:4) in 5 mL of concentrated hydrochloric acid and ethanol at room temperature. XRD analysis revealed that the prepared phosphor contained impurities.

[0084] Comparative Example 4

[0085] The remaining steps of this comparative example are the same as those in Example 3, except that the rate at which the CsCl solution is added in step (4) is replaced with 0.5 mL / min. XRD analysis revealed that the prepared phosphor contained impurities.

[0086] Comparative Example 5

[0087] The remaining steps of this comparative example are the same as those in Example 3, except that the rate at which the CsCl solution is added in step (4) is replaced with 12 mL / min. XRD analysis revealed that the prepared phosphor contained impurities.

Claims

1. A lead-free halide double perovskite full-spectrum phosphor, characterized in that: Its chemical composition is: Cs2M 1-x Cl6: x Pt 4+ Where M is one of Zr and Hf, 0 < x ≤0.

01.

2. The lead-free halide double perovskite full-spectrum phosphor according to claim 1, characterized in that: The phosphor exhibits full-spectrum emission in the 350~800nm ​​region, with emission peaks at 430nm and 660nm, respectively.

3. The method for preparing a lead-free halide double perovskite full-spectrum phosphor according to claim 1, characterized in that, Includes the following steps: Step 1: Weigh the raw materials according to the stoichiometric ratio and dissolve the CsCl powder in concentrated hydrochloric acid; At 50~70℃, MCl4 was dissolved in concentrated hydrochloric acid and stirred magnetically; at 40~60℃, PtCl4 powder was dissolved in a mixed solution of concentrated hydrochloric acid and ethanol. Step 2: While the PtCl4 solution is still hot, add it to the MCl4 solution and stir continuously. Step 3: After the PtCl4 solution and MCl4 solution are mixed evenly, add the CsCl solution to the mixed solution at a rate of 2~10 mL / min. Step 4: Continue magnetic stirring, maintain the temperature at 40~60℃, stir for 20~40 minutes, cool to room temperature and then centrifuge. Step 5: Centrifuge and wash the resulting solution; Step six: Dry the product obtained in step five and cool it to room temperature to obtain lead-free halide double perovskite full-spectrum phosphor.

4. The method for preparing a lead-free halide double perovskite full-spectrum phosphor according to claim 3, characterized in that: In step one, the mass percentage of concentrated hydrochloric acid is 36-38 wt%.

5. The method for preparing a lead-free halide double perovskite full-spectrum phosphor according to claim 3, characterized in that: In step one, the volume ratio of concentrated hydrochloric acid to ethanol in the mixed solution of concentrated hydrochloric acid and ethanol is 6~7:3~4.

6. The method for preparing a lead-free halide double perovskite full-spectrum phosphor according to claim 3, characterized in that: In step one, the magnetic stirring speed is 100~500 r / min.

7. The method for preparing a lead-free halide double perovskite full-spectrum phosphor according to claim 3, characterized in that: In step two, the stirring speed is 100~500 r / min, and the stirring time is 10~15 min.

8. The method for preparing a lead-free halide double perovskite full-spectrum phosphor according to claim 3, characterized in that: In step four, the magnetic stirring speed is 100~500 r / min.

9. The method for preparing a lead-free halide double perovskite full-spectrum phosphor according to claim 3, characterized in that: In step five, the number of centrifugal washing cycles is 5 to 7, the centrifugation rate is 6000 to 9000 r / min, and the solvent used for centrifugal washing includes one or more of the following: a mixed solution of equal volume of concentrated hydrochloric acid and ethanol, concentrated hydrochloric acid, and isopropanol.

10. The method for preparing a lead-free halide double perovskite full-spectrum phosphor according to claim 3, characterized in that: In step six, the drying temperature is 40~60℃ and the drying time is 6~10h.

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