Near-infrared luminescent material, near-infrared fluorescent powder conversion type light-emitting diode and preparation method

Abstract

The invention discloses a near-infrared light-emitting material, a near-infrared fluorescent powder conversion type light-emitting diode and a preparation method, and relates to the technical field of light-emitting materials. The chemical formula of the near-infrared luminescent material is Cs2Hf (1-a) ReaCl6, and a ranges from 0.005 to 0.08. The near-infrared luminescent material Cs2Hf1-aReaCl6 provided by the invention does not contain lead and organic components, has low toxicity, good humidity and thermal stability and good biocompatibility, and can effectively inhibit self-absorption of the organic components of the near-infrared luminescent material Cs2Hf1-aReaCl6. In addition, Cs2Hf1-aReaCl6 also has excellent luminescence stability and has strong multi-peak emission crossing a first near-infrared window and a second near-infrared window, and emission peaks are respectively located at the wavelength of 726nm and 1342nm; in addition, due to the multi-stage distribution emission of the Cs2Hf1-aReaCl6, the rare photoluminescence quantum yield as high as 91.88% is achieved.

Description

Technical Field

[0001] This invention relates to the field of luminescent materials technology, and in particular to a near-infrared luminescent material, a near-infrared phosphor-converted light-emitting diode, and a method for preparing it. Background Technology

[0002] The integration of near-infrared (NIR) light sources into intelligent devices for real-time identification and detection has become an advanced technology, extending into numerous fields such as non-destructive testing, optical communication, and biomedical imaging. Near-infrared phosphor-converted light-emitting diodes (NIR pc-LEDs) offer long lifespans and excellent spectral stability. Compared to incandescent, incoherent, and high-heat tungsten halogen lamps, NIR pc-LEDs boast compact size and broadband emission, facilitating miniaturization and integration. They also overcome the drawbacks of AlGaAs and other NIR LED arrays, such as high cost, small divergence angle, uneven emission, narrow emission spectrum (FWHM < 50 nm), high energy consumption, and relatively low output power. The development of NIR pc-LEDs, a promising next-generation solid-state light source technology, is largely constrained by the development of phosphors that control the radiant power and spectral bandwidth of the light source. Driven by materials, the application of near-infrared light sources in medical diagnostic equipment necessitates the customized development of near-infrared emitting phosphors with excellent stability and efficient emission characteristics, tailored to specific usage conditions. In particular, light in the near-infrared II region can avoid tissue fluorescence and has low signal transmission loss, making it very promising for information transmission and medical imaging.

[0003] Therefore, existing technologies still need to be improved and developed. Summary of the Invention

[0004] In view of the shortcomings of the prior art, the purpose of this invention is to provide a near-infrared luminescent material, a near-infrared phosphor-converted light-emitting diode and a preparation method thereof, with the aim of providing a phosphor with high luminous efficiency and good thermal stability suitable for near-infrared phosphor-converted light-emitting diodes.

[0005] The technical solution of the present invention is as follows: In a first aspect, the present invention provides a near-infrared luminescent material, wherein the chemical formula of the near-infrared luminescent material is Cs₂Hf. 1-a Re a Cl6, where a is 0.005~0.08.

[0006] A second aspect of the present invention provides a method for preparing the near-infrared luminescent material as described above, comprising the following steps: According to Cs2Hf 1-a Re aThe stoichiometric ratio of each element in Cl6 was determined by mixing CsCl, HfCl4, and K2ReCl6 with an acid solution to obtain a precursor mixture. The near-infrared luminescent material is obtained by subjecting the precursor mixture to a hydrothermal reaction.

[0007] Optionally, according to Cs2Hf 1-a Re a The specific steps for obtaining the precursor mixture by mixing CsCl, HfCl4, and K2ReCl6 with an acid solution, based on the stoichiometric ratio of each element in Cl6, include: According to Cs2Hf 1-a Re a The stoichiometric ratio of each element in Cl6 is used to mix CsCl with the acid solution to obtain the first mixture. HfCl4 and K2ReCl6 were mixed with an acid solution to obtain a second mixture; The first mixture is added dropwise to the second mixture to obtain a precursor mixture.

[0008] Optionally, the hydrothermal reaction temperature is 150~200℃, and the hydrothermal reaction time is 10~24h; and / or, The acid solution includes hydrochloric acid with a mass concentration of HCl of 20% to 36%.

[0009] Optionally, before obtaining the near-infrared luminescent material after the hydrothermal reaction, the process further includes the following steps: The product obtained after the hydrothermal reaction was washed and dried; The cleaning agent used in the cleaning includes at least one of isopropanol, methanol, and propanol. The cleaning is performed 2 to 5 times; The drying temperature is 60~80℃, and the drying time is 12~24h.

[0010] A third aspect of the present invention provides a near-infrared phosphor-converting light-emitting diode, comprising a light-emitting diode chip and a coating on the surface of the light-emitting diode chip, the coating comprising the near-infrared emitting material of the present invention as described above and / or the near-infrared emitting material prepared by the preparation method of the present invention as described above.

[0011] Optionally, the coating may also include silicone rubber.

[0012] A fourth aspect of the present invention provides a method for preparing a near-infrared phosphor-converting light-emitting diode as described above, comprising the following steps: Provide LED chips; The near-infrared luminescent material is coated onto the surface of the light-emitting diode chip to obtain the near-infrared phosphor conversion type light-emitting diode.

[0013] Optionally, the step of coating the near-infrared luminescent material onto the surface of the light-emitting diode chip specifically includes: Near-infrared luminescent material, siloxane, and curing agent are mixed and coated onto the surface of the light-emitting diode chip. After heating and curing, the near-infrared phosphor conversion type light-emitting diode is obtained.

[0014] Optionally, the mass ratio of the near-infrared luminescent material, siloxane, and curing agent is (5~15):10:(0.5~3); and / or, The siloxane includes at least one of ethylene-terminated polydimethylsiloxane and polydimethylsiloxane; and / or, The heating and curing temperature is 75~85℃, and the heating and curing time is 10min~2.2h.

[0015] Beneficial effects: The near-infrared luminescent material Cs2Hf provided in this invention 1-a Re a Cl6 is a completely inorganic metal halide perovskite, free of lead and organic components. It exhibits low toxicity, good humidity stability, good thermal stability, and good biocompatibility, and can effectively inhibit the self-absorption of its own organic components. Furthermore, Cs₂Hf 1-a Re a Cl6, as a photoluminescent material, exhibits excellent luminescence stability and strong multi-peak emission across the first and second near-infrared windows, with emission peaks located at wavelengths of 726 nm and 1342 nm, respectively; and Cs₂Hf 1-a Re a The multi-level emission distribution of Cl6 achieved a rare photoluminescence quantum yield of up to 91.88%. Furthermore, Cs₂Hf… 1-a Re a Cl6 integrated into a light-emitting chip can be used for the clinical diagnosis of dental caries. This novel and direct method utilizes the high transparency of enamel to 1300nm near-infrared light and the strong scattering and weak absorption of the underlying dentin to uniformly distribute diffuse near-infrared light under the transparent enamel of the crown, thereby promoting high-contrast near-infrared imaging of demineralized lesions in dental caries. Attached Figure Description

[0016] Figure 1 The image shows the X-ray diffraction results of Cs2HfCl6 prepared in Example 1.

[0017] Figure 2The X-ray diffraction results of the rhenium-doped chloride perovskite luminescent microcrystals prepared in Examples 2 to 7 are shown.

[0018] Figure 3 The Cs2Hf prepared in Example 2 0.995 Re 0.005 Energy spectrum and elemental distribution of Cl6.

[0019] Figure 4 The Cs2Hf prepared in Example 2 0.995 Re 0.005 Scanning electron microscope image of Cl6.

[0020] Figure 5 The Cs2Hf prepared in Example 2 0.995 Re 0.005 Photoluminescence spectrum of Cl6 excited by ultraviolet light at a wavelength of 288 nm.

[0021] Figure 6 The photoluminescence spectra of the rhenium-doped chloride perovskite luminescent microcrystals prepared in Examples 2 to 7 under ultraviolet excitation at a wavelength of 288 nm are shown.

[0022] Figure 7 The Cs2Hf prepared in Example 2 0.995 Re 0.005 Reference spectrum and emission spectrum of photoluminescence quantum yield of Cl6.

[0023] Figure 8 The Cs2Hf prepared in Example 2 0.995 Re 0.005 Photoluminescence spectra of Cl6 at different temperatures.

[0024] Figure 9 The image shows the electroluminescence spectrum of the near-infrared phosphor-converting light-emitting diode device prepared in Example 8 in the wavelength range of 1000~1600nm.

[0025] Figure 10 The image shows the electroluminescence spectrum of the near-infrared phosphor-converted light-emitting diode device prepared in Example 8 in the wavelength range of 480~780nm. Detailed Implementation

[0026] This invention provides a near-infrared luminescent material, a near-infrared phosphor-converted light-emitting diode, and a method for preparing it. To make the objectives, technical solutions, and effects of this invention clearer and more explicit, the invention is further described in detail below. It should be understood that the specific embodiments described herein are only for explaining the invention and are not intended to limit the invention.

[0027] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. The terminology used in this specification is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention.

[0028] If the embodiments of the present invention involve descriptions such as "first" or "second", such descriptions are for descriptive purposes only and should not be construed as indicating or implying their relative importance or implicitly specifying the number of technical features indicated.

[0029] This invention provides a near-infrared luminescent material (specifically, a rhenium-doped chloride perovskite photoluminescent crystal material, or a rhenium-doped chloride perovskite photoluminescent microcrystalline material), wherein the chemical formula of the near-infrared luminescent material is Cs₂Hf. 1-a Re a Cl6, a is 0.005~0.08 (for example, it can be 0.005, 0.006, 0.007, 0.008, 0.009, 0.01, 0.02, 0.03, 0.04, 0.05, 0.06, 0.07 or 0.08).

[0030] The near-infrared luminescent material Cs2Hf provided in this invention 1-a Re a Cs₆ (also known as Re-doped Cs₂HfCl₆) is a completely inorganic metal halide perovskite, free of lead and organic components. It exhibits low toxicity, good humidity stability, good thermal stability, and excellent biocompatibility, and can effectively inhibit the self-absorption of its own organic components. Furthermore, Cs₂Hf... 1- a Re a Cl6, as a photoluminescent material, exhibits excellent luminescent stability (retaining 92% of its initial emission intensity even at 420K), and strong multi-peak emission across the first and second near-infrared windows, with emission peaks located at wavelengths of 726nm and 1342nm, respectively; and Cs₂Hf 1-a Re a The multi-level emission distribution of Cl6 achieved a photoluminescence quantum yield as high as 91.88%. Furthermore, Cs₂Hf… 1-a Re a Cl6 integrated into a light-emitting chip can be used for the clinical diagnosis of dental caries. This novel and direct method utilizes the high transparency of enamel to 1300nm near-infrared light and the strong scattering and weak absorption of the underlying dentin to uniformly distribute diffuse near-infrared light under the transparent enamel of the crown, thereby promoting high-contrast near-infrared imaging of demineralized lesions in dental caries.

[0031] In this invention, unlike common Cr and rare-earth-doped near-infrared luminescent materials, rhenium (Re) doping achieves multi-peak near-infrared emission through spin-orbit coupling. Furthermore, Re ions (Re... 4+ 5d 3 Under an octahedral coordinated crystal field, the orbital triple degenerate state of an electron can be split into multiple excited states by spin-orbit coupling, and efficient multi-level near-infrared emission can be achieved through quantum trimming.

[0032] This invention also provides a method for preparing a near-infrared luminescent material, comprising the following steps: S11, according to Cs2Hf 1-a Re a The stoichiometric ratio of each element in Cl6 was determined by mixing CsCl, HfCl4, and K2ReCl6 with an acid solution to obtain a precursor mixture. S12. After subjecting the precursor mixture to a hydrothermal reaction, the near-infrared luminescent material is obtained.

[0033] The method provided by this invention is simple, requiring only a one-step hydrothermal reaction of the precursor mixture to prepare near-infrared luminescent materials.

[0034] In step S11, in some embodiments, according to Cs2Hf 1-a Re a The specific steps for obtaining the precursor mixture by mixing CsCl, HfCl4, and K2ReCl6 with an acid solution, based on the stoichiometric ratio of each element in Cl6, include: According to Cs2Hf 1-a Re a The stoichiometric ratio of each element in Cl6 is used to mix CsCl with the acid solution to obtain the first mixture. HfCl4 and K2ReCl6 were mixed with an acid solution to obtain a second mixture; The first mixture is added dropwise to the second mixture to obtain a precursor mixture.

[0035] In some embodiments, the acid solution comprises hydrochloric acid with a mass concentration of 20% to 36% HCl (e.g., 20%, 25%, 30%, 32%, 34%, or 36%, etc.).

[0036] In step S12, in some embodiments, the temperature of the hydrothermal reaction is 150~200℃, for example, it can be 150℃, 160℃, 170℃, 180℃, 190℃ or 200℃; the time of the hydrothermal reaction is 10~24h, for example, it can be 10h, 12h, 14h, 15h, 18h, 20h, 22h or 24h.

[0037] In some specific embodiments, the hydrothermal reaction temperature is 180°C, and the hydrothermal reaction time is 12~24h.

[0038] In some embodiments, the process of obtaining the near-infrared luminescent material after the hydrothermal reaction further includes the following steps: The product obtained after the hydrothermal reaction was washed and dried; The cleaning agent used in the cleaning includes at least one of isopropanol, methanol and propanol, but is not limited to these. The number of cleaning cycles is 2 to 5 (e.g., 2, 3, 4, or 5 times, etc.). The drying temperature is 60~80℃ (e.g., 60℃, 65℃, 70℃, 75℃ or 80℃, etc.), and the drying time is 12~24h (e.g., 12h, 13h, 15h, 18h, 20h, 22h or 24h, etc.).

[0039] This invention also provides a near-infrared phosphor conversion type light-emitting diode, which includes a light-emitting diode chip and a coating on the surface of the light-emitting diode chip. The coating includes the near-infrared emitting material described above and / or the near-infrared emitting material prepared by the preparation method described above.

[0040] In some embodiments, the coating also includes silicone rubber.

[0041] This invention also provides a method for preparing the near-infrared phosphor-converting light-emitting diode as described above, comprising the following steps: S21. Provides light-emitting diode chips; S22. The near-infrared luminescent material is coated on the surface of the light-emitting diode chip to obtain the near-infrared phosphor conversion type light-emitting diode.

[0042] In step S22, in some embodiments, the step of coating the near-infrared luminescent material onto the surface of the light-emitting diode chip specifically includes: Near-infrared luminescent material, siloxane, and curing agent are mixed and coated onto the surface of the light-emitting diode chip. After heating and curing, the near-infrared phosphor conversion type light-emitting diode is obtained.

[0043] In some embodiments, the mass ratio of the near-infrared luminescent material, siloxane, and curing agent is (5~15):10:(0.5~3), for example, it can be 5:10:0.5, 5:10:1, 5:10:3, 10:10:0.5, 10:10:1, 10:10:3, 12:10:0.5, 12:10:1, 12:10:3, 15:10:0.5, 15:10:1, or 15:10:3, etc.

[0044] In some embodiments, the siloxane includes at least one of ethylene-terminated long-chain dimethylsiloxane and polydimethylsiloxane, but is not limited thereto.

[0045] In some embodiments, the temperature for heat curing is 75~85℃ (e.g., 75℃, 78℃, 80℃, 82℃ or 85℃, etc.), and the time for heat curing is 10min~2.2h (e.g., 10min, 20min, 30min, 40min, 50min, 1h, 1.2h, 1.5h, 2h or 2.2h, etc.).

[0046] In some specific embodiments, the heating and curing temperature is 80°C, and the heating and curing time is 10~60 min, or more specifically 10~30 min.

[0047] The present invention will be further described below through specific embodiments.

[0048] Unless otherwise specified, the raw materials used in the following embodiments are all commercially available products.

[0049] Example 1 According to the stoichiometric ratio of each element in Cs₂HfCl₆, 1.0101 g of CsCl and 0.9609 g of HfCl₄ were weighed into different beakers, and 30 mL and 40 mL of 36% hydrochloric acid were added to them respectively to obtain CsCl solution and HfCl₄ solution respectively; then, the CsCl solution was slowly added dropwise to the HfCl₄ solution and stirred thoroughly with a magnetic stirrer for 30 minutes to obtain a precursor mixture; The precursor mixture was placed in the polytetrafluoroethylene liner of a hydrothermal reactor, and then the hydrothermal reactor was tightened and transferred to an oven at 180°C for 12 hours. After the reaction was complete, it was naturally cooled to room temperature, and the reaction product was obtained by filtration. The reaction product was washed three times with isopropanol and then dried in an oven at 60°C for 12 hours to obtain undoped chloride perovskite luminescent microcrystalline material, namely Cs2HfCl6.

[0050] Example 2 According to Cs2Hf 0.995 Re0.005 To determine the stoichiometric ratio of each element in Cl6, weigh 1.0101g of CsCl and place it in a beaker, then add 30mL of 36% hydrochloric acid to obtain the first mixture; place 0.9561g of HfCl4 in a beaker, then add 40mL of 36% hydrochloric acid, and then add 0.0071g of K2ReCl6 to obtain the second mixture. The first mixture was slowly added dropwise to the second mixture and stirred thoroughly with a magnetic stirrer for 30 minutes to obtain the precursor mixture; The precursor mixture was placed in a polytetrafluoroethylene liner within a hydrothermal reactor, which was then tightened and transferred to an oven at 180°C for 12 hours. After the reaction was complete, the mixture was allowed to cool naturally to room temperature. The reaction product was obtained by filtration, washed three times with isopropanol, and then dried in an oven at 60°C for 12 hours to obtain rhenium-doped chloride perovskite luminescent microcrystalline material, Cs₂Hf. 0.995 Re 0.005 Cl6.

[0051] Example 3 According to Cs2Hf 0.993 Re 0.007 To determine the stoichiometric ratio of each element in Cl6, weigh 1.0101g of CsCl and place it in a beaker, then add 30mL of 36% hydrochloric acid to obtain the first mixture; place 0.9542g of HfCl4 in a beaker, then add 40mL of 36% hydrochloric acid, and then add 0.0100g of K2ReCl6 to obtain the second mixture. The first mixture was slowly added dropwise to the second mixture and stirred thoroughly with a magnetic stirrer for 30 minutes to obtain the precursor mixture; The precursor mixture was placed in a polytetrafluoroethylene liner within a hydrothermal reactor, which was then tightened and transferred to an oven at 180°C for 12 hours. After the reaction was complete, the mixture was allowed to cool naturally to room temperature. The reaction product was obtained by filtration, washed three times with isopropanol, and then dried in an oven at 60°C for 12 hours to obtain rhenium-doped chloride perovskite luminescent microcrystalline material, Cs₂Hf. 0.993 Re 0.007 Cl6.

[0052] Example 4 According to Cs2Hf 0.99 Re 0.01To determine the stoichiometric ratio of each element in Cl6, weigh 1.0101g of CsCl and place it in a beaker, then add 30mL of 36% hydrochloric acid to obtain the first mixture; place 0.9513g of HfCl4 in a beaker, then add 40mL of 36% hydrochloric acid, and then add 0.0143g of K2ReCl6 to obtain the second mixture. The first mixture was slowly added dropwise to the second mixture and stirred thoroughly with a magnetic stirrer for 30 minutes to obtain the precursor mixture; The precursor mixture was placed in a polytetrafluoroethylene liner within a hydrothermal reactor, which was then tightened and transferred to an oven at 180°C for 12 hours. After the reaction was complete, the mixture was allowed to cool naturally to room temperature. The reaction product was obtained by filtration, washed three times with isopropanol, and then dried in an oven at 60°C for 12 hours to obtain rhenium-doped chloride perovskite luminescent microcrystalline material, Cs₂Hf. 0.99 Re 0.01 Cl6.

[0053] Example 5 According to Cs2Hf 0.97 Re 0.03 To determine the stoichiometric ratio of each element in Cl6, weigh 1.0101g of CsCl and place it in a beaker, then add 30mL of 36% hydrochloric acid to obtain the first mixture; place 0.9321g of HfCl4 in a beaker, then add 40mL of 36% hydrochloric acid, and then add 0.0429g of K2ReCl6 to obtain the second mixture. The first mixture was slowly added dropwise to the second mixture and stirred thoroughly with a magnetic stirrer for 30 minutes to obtain the precursor mixture; The precursor mixture was placed in a polytetrafluoroethylene liner within a hydrothermal reactor, which was then tightened and transferred to an oven at 180°C for 12 hours. After the reaction was complete, the mixture was allowed to cool naturally to room temperature. The reaction product was obtained by filtration, washed three times with isopropanol, and then dried in an oven at 60°C for 12 hours to obtain rhenium-doped chloride perovskite luminescent microcrystalline material, Cs₂Hf. 0.97 Re 0.03 Cl6.

[0054] Example 6 According to Cs2Hf 0.95 Re 0.05 To determine the stoichiometric ratio of each element in Cl6, weigh 1.0101g of CsCl and place it in a beaker, then add 30mL of 36% hydrochloric acid to obtain the first mixture; place 0.9129g of HfCl4 in a beaker, then add 40mL of 36% hydrochloric acid, and then add 0.0716g of K2ReCl6 to obtain the second mixture. The first mixture was slowly added dropwise to the second mixture and stirred thoroughly with a magnetic stirrer for 30 minutes to obtain the precursor mixture; The precursor mixture was placed in a polytetrafluoroethylene liner within a hydrothermal reactor, which was then tightened and transferred to an oven at 180°C for 12 hours. After the reaction was complete, the mixture was allowed to cool naturally to room temperature. The reaction product was obtained by filtration, washed three times with isopropanol, and then dried in an oven at 60°C for 12 hours to obtain rhenium-doped chloride perovskite luminescent microcrystalline material, Cs₂Hf. 0.95 Re 0.05 Cl6.

[0055] Example 7 According to Cs2Hf 0.92 Re 0.08 To determine the stoichiometric ratio of each element in Cl6, weigh 1.0101g of CsCl and place it in a beaker, then add 30mL of 36% hydrochloric acid to obtain the first mixture; place 0.8840g of HfCl4 in a beaker, then add 40mL of 36% hydrochloric acid, and then add 0.1145g of K2ReCl6 to obtain the second mixture. The first mixture was slowly added dropwise to the second mixture and stirred thoroughly with a magnetic stirrer for 30 minutes to obtain the precursor mixture; The precursor mixture was placed in a polytetrafluoroethylene liner within a hydrothermal reactor, which was then tightened and transferred to an oven at 180°C for 12 hours. After the reaction was complete, the mixture was allowed to cool naturally to room temperature. The reaction product was obtained by filtration, washed three times with isopropanol, and then dried in an oven at 60°C for 12 hours to obtain rhenium-doped chloride perovskite luminescent microcrystalline material, Cs₂Hf. 0.92 Re 0.08 Cl6.

[0056] Example 8 The Cs2Hf prepared in Example 2 0.995 Re 0.005 Cl6 was ground in an agate mortar for 30 minutes until fine, to obtain rhenium-doped chloride perovskite phosphor. Polydimethylsiloxane and curing agent (i.e., Dow Corning SYLGARD 184 silicone rubber) are mixed evenly with freshly ground rhenium-doped chloride perovskite phosphor to obtain a mixture; The mixture was placed on a light-emitting diode chip and cured at 80°C for 30 minutes to obtain a near-infrared phosphor conversion type light-emitting diode.

[0057] test: 1) The crystal phase of Cs₂HfCl₆ prepared in Example 1 was identified and analyzed. The powder X-ray diffraction results are as follows: Figure 1 As shown, the pure phase characteristics of the synthesized material were confirmed by comparing it with the standard card of Cs2HfCl6, indicating that the Cs2HfCl6 perovskite material was successfully synthesized.

[0058] 2) The crystal phases of the rhenium-doped chloride perovskite luminescent microcrystals prepared in Examples 2 to 7 were identified and analyzed. The powder X-ray diffraction results are as follows: Figure 2 As shown, the pure-phase characteristics of the synthesized material were confirmed by comparison with the standard card of Cs2HfCl6, demonstrating that Cs2Hf doped with different concentrations of rhenium ions can achieve high purity. 1-a Re a Cl6 perovskite materials do not undergo crystal phase changes.

[0059] 3) The Cs2Hf prepared in Example 2 0.995 Re 0.005 Elemental analysis of Cl6 yielded the following results: Figure 3 As shown, rhenium was successfully doped.

[0060] 4) The Cs2Hf prepared in Example 2 was examined using a scanning electron microscope. 0.995 Re 0.005 The crystal morphology of Cl6 was observed, and the results are as follows: Figure 4 As shown, the Cs2Hf prepared in Example 2... 0.995 Re 0.005 Cl6 has a complete polyhedral morphology, with only partial aggregation, showing flat crystal faces and regular crystal edges, exhibiting microcrystalline characteristics.

[0061] 5) The Cs2Hf prepared in Example 2 was tested using a fluorescence spectrometer at room temperature. 0.995 Re 0.005 Photoluminescence properties of Cl6, results Figure 5 As shown, Cs₂Hf under near-ultraviolet light excitation at a wavelength of 288 nm... 0.995 Re 0.005 Cl6 exhibits strong emission over an ultrawide span (700-1700 nm), with emission peaks at 726 nm, 1342 nm and 1600 nm in the near-infrared region.

[0062] 6) The concentration-dependent photoluminescence properties of the rhenium-doped chloride perovskite luminescent microcrystals prepared in Examples 2 to 7 were tested at room temperature using a fluorescence spectrometer. The results are as follows: Figure 6 As shown, Cs₂Hf under near-ultraviolet light excitation at a wavelength of 288 nm... 1-a Re aCl6 exhibits an emission intensity that gradually decreases with increasing rhenium doping concentration, proving that this series of near-infrared emissions originates from the dopant ions (i.e., rhenium ions).

[0063] 7) The Cs2Hf prepared in Example 2 was analyzed using a fluorescence spectrometer. 0.995 Re 0.005 The photoluminescence efficiency of Cl6 was tested, and the results are as follows: Figure 7 As shown (where reference refers to the integrating sphere standard whiteboard, the material of which is polytetrafluoroethylene), it can be seen that Cs2Hf 0.995 Re 0.005 Cl6 exhibits a photoluminescence quantum yield as high as 91.88%.

[0064] 8) The Cs2Hf prepared in Example 2 was analyzed using a fluorescence spectrometer. 0.995 Re 0.005 The temperature-dependent photoluminescence properties of Cl6 were tested, and the results are as follows: Figure 8 As shown, Cs₂Hf under near-ultraviolet light excitation at a wavelength of 288 nm... 0.995 Re 0.005 Cl6 exhibits relatively stable near-infrared emission, maintaining 92% of its initial emission intensity even at a high temperature of 420K.

[0065] 9) The electroluminescence performance of the near-infrared phosphor-converting light-emitting diode prepared in Example 8 was tested, and the results are as follows: Figure 9 and Figure 10 As shown, the near-infrared phosphor-converting light-emitting diode exhibits bright light emission after being forward biased, and the electroluminescence intensity increases significantly with the gradual increase of the driving current, showing a positive correlation with the input power.

[0066] In summary, this invention provides a near-infrared luminescent material, a near-infrared phosphor-converting light-emitting diode, and a method for preparing it. The near-infrared luminescent material Cs2Hf provided in this invention... 1-a Re a Cl6 is a completely inorganic metal halide perovskite, free of lead and organic components. It exhibits low toxicity, good humidity stability, good thermal stability, and good biocompatibility, and can effectively inhibit the self-absorption of its own organic components. Furthermore, Cs₂Hf 1-a Re a Cl6, as a photoluminescent material, exhibits excellent luminescence stability and strong multi-peak emission across the first and second near-infrared windows, with emission peaks located at wavelengths of 726 nm and 1342 nm, respectively; and Cs2Hf 1-a Re aThe multi-level emission distribution of Cl6 achieved a photoluminescence quantum yield as high as 91.88%. Furthermore, Cs₂Hf… 1-a Re a Cl6 integrated into a light-emitting chip can be used for the clinical diagnosis of dental caries. This novel and direct method utilizes the high transparency of enamel to 1300nm near-infrared light and the strong scattering and weak absorption of the underlying dentin to uniformly distribute diffuse near-infrared light under the transparent enamel of the crown, thereby promoting high-contrast near-infrared imaging of demineralized lesions in dental caries.

[0067] It should be understood that the application of the present invention is not limited to the examples above. Those skilled in the art can make improvements or modifications based on the above description, and all such improvements and modifications should fall within the protection scope of the appended claims.

Claims

1. A near-infrared light emitting material, characterized by comprising: The near-infrared luminescent material has a chemical formula of Cs2Hf 1-a Re a Cl6, wherein a is 0.005-0.

08.

2. A method for producing the near-infrared luminescent material according to claim 1, characterized by, The method comprises the following steps: The stoichiometric ratio of each element in Cs2Hf 1-a Re a Cl6, and K2ReCl6 are mixed with an acid solution to obtain a precursor mixture; The precursor mixture is subjected to a hydrothermal reaction to obtain the near-infrared luminescent material.

3. The production method according to claim 2, characterized by, According to Cs2Hf 1-a Re a The specific steps for obtaining the precursor mixture by mixing CsCl, HfCl4, and K2ReCl6 with an acid solution, based on the stoichiometric ratio of each element in Cl6, include: According to Cs2Hf 1-a Re a The stoichiometric ratio of each element in Cl6 is used to mix CsCl with the acid solution to obtain the first mixture. HfCl4 and K2ReCl6 are mixed with an acid solution to obtain a second mixed solution; The first mixed solution is added dropwise into the second mixed solution to obtain a precursor mixture.

4. The production method according to claim 2 or 3, characterized by, The temperature of the hydrothermal reaction is 150-200 DEG C, and the time of the hydrothermal reaction is 10-24 h; and / or, The acid solution comprises hydrochloric acid with a mass concentration of 20-36%.

5. The production method according to claim 2 or 3, characterized by, The method further comprises the following steps before the near-infrared luminescent material is obtained after the hydrothermal reaction: The product obtained after the hydrothermal reaction is cleaned and dried; The cleaning agent used in the cleaning process comprises at least one of isopropyl alcohol, methanol and propanol; The cleaning process is performed 2-5 times; The drying temperature is 60-80 DEG C, and the drying time is 12-24 h.

6. A near-infrared fluorescent powder converted light emitting diode, characterized by, The coating layer comprises the near-infrared luminescent material of claim 1 and / or the near-infrared luminescent material prepared by the preparation method of any one of claims 2-5.

7. The near infrared fluorescent powder converted light emitting diode according to claim 6, wherein, The coating layer further comprises silicone rubber.

8. A method for preparing the near-infrared fluorescent powder converted light emitting diode according to claim 6, characterized in that, The method comprises the following steps: A light-emitting diode chip is provided; The near-infrared luminescent material is coated on the surface of the light-emitting diode chip to obtain a near-infrared fluorescent powder conversion type light-emitting diode.

9. The production method according to claim 8, characterized by, The step of coating the near-infrared luminescent material on the surface of the light-emitting diode chip specifically comprises: The near-infrared luminescent material, silicone and curing agent are mixed, and then coated on the surface of the light-emitting diode chip; after heating and curing, the near-infrared fluorescent powder conversion type light-emitting diode is obtained.

10. The method of claim 9, wherein, The mass ratio of the near-infrared luminescent material, silicone and curing agent is (5-15):10:(0.5-3); and / or, The silicone comprises at least one of ethylene-terminated polydimethylsiloxane and polydimethylsiloxane; and / or, The heating and curing temperature is 75-85 DEG C, and the heating and curing time is 10 min-2.2 h.

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