A near-infrared luminescent material, a preparation method and use thereof

Abstract

The application discloses a near-infrared luminescent material, a preparation method and application thereof. 3‑y M 2‑x‑z (PO4)2F3:xCr 3+ , yR 3+ , zN, wherein M is a trivalent metal element, Cr 3+ is a luminescent center ion, R is a trivalent rare earth element, N is a divalent doping element and / or a trivalent doping element, x is selected from 0.0001 at.%-30 at.%, y is selected from 0 at.%-50 at.%, and z is selected from 0 at.%-50 at.%. The luminescent material is packaged with a blue light or red light chip to obtain an LED device, and the LED device can be used as a near-infrared light source in the fields of analysis and detection, iris recognition, automobile sensing, security and the like.

Description

Technical Field

[0001] This invention belongs to the field of luminescent materials, specifically relating to a near-infrared luminescent material, its preparation method, and its applications. Background Technology

[0002] Near-infrared light refers to electromagnetic waves emitted in the 700nm to 2500nm range. Since Herschel's discovery of near-infrared radiation in 1800, it has attracted widespread attention. In recent years, researchers have conducted in-depth studies on this type of radiation and developed various applications that promote modern technological advancements, such as medical diagnostics, bioimaging, plant lighting, food and pharmaceuticals, and night vision security. Traditional near-infrared light sources include halogen tungsten lamps and laser diodes. However, specific commercial applications have placed demands on the size and manufacturing cost of near-infrared light sources, prompting the development of more portable, efficient, and cost-effective near-infrared light sources. Since the invention of blue light-emitting diodes (LEDs), phosphor-converted LEDs (pc-LEDs), obtained by integrating inorganic phosphor materials with blue LED chips, have revolutionized the lighting and display industries. In 2016, Osram announced the industry's first commercially available broadband near-infrared LED based on this technology, coating a high-efficiency blue LED chip with near-infrared broadband phosphor, and achieving broadband near-infrared emission by exciting the near-infrared phosphor with blue light.

[0003] Near-infrared light emitted at different wavelengths has different applications; for example, 730nm red light can be absorbed by plant pigment protein P. FR Near-infrared light is absorbed and used for plant lighting; 810nm near-infrared light is often used in biometric technology in mobile devices; 830nm near-infrared light is often used in automatic card swiping applications on highways due to its good night vision effect; 840nm near-infrared light is used in color zoom infrared cameras; 850-870nm infrared light has good applications in video shooting and surveillance cameras; 940nm is used in remote controls due to its strong anti-light interference ability; 970nm near-infrared light is often used in food analysis because it can measure the content of moisture, protein, etc., while longer wavelength infrared light is more used in fields such as solar cells.

[0004] Despite the proliferation of near-infrared phosphors developed to date, most suffer from issues such as low luminous efficiency and poor stability. Thermal quenching is particularly severe for near-infrared phosphors. The heat generated during LED chip operation (≥150℃) leads to a decrease in phosphor emission intensity, typically attributed to nonradiative relaxation of excited electrons in activating ions under high-temperature thermal activation. This thermal quenching significantly impacts the luminous efficiency of NIR-LEDs. Therefore, developing a near-infrared phosphor with excellent thermal stability is of paramount importance. Summary of the Invention

[0005] This invention provides a near-infrared luminescent material, wherein the chemical formula of the near-infrared luminescent material is Na. 3-y M 2-x-z (PO4)2F3:xCr 3+ yR 3+ ,zN,

[0006] Where M is a trivalent metallic element, Cr 3+ R is the luminescent central ion, N is a trivalent rare earth element, and X is a divalent and / or trivalent dopant element. The ion is selected from 0.0001 at.% to 30 at.%, Y from 0 at.% to 50 at.%, and Z from 0 at.% to 50 at.%.

[0007] According to an embodiment of the present invention, M is selected from one, two or more of Al, V, Cr, Fe, Ga, and Sc.

[0008] According to an embodiment of the present invention, R is selected from one, two or more of Eu, Pr, Sm, and Er.

[0009] According to embodiments of the present invention, N is selected, for example, from one, two or more of Mg, Zn, Fe, and In.

[0010] According to embodiments of the invention, x is 0.0001 at.% to 10 at.%, for example, 1 at.%, 2 at.%, 3 at.%, or 5 at.%.

[0011] According to an embodiment of the invention, y is 0 at.% to 5 at.%, for example, 0 at.%, 1 at.%, 2 at.%, 3 at.%, or 5 at.%.

[0012] According to an embodiment of the invention, z is 0 at.% to 5 at.%, for example, 0 at.%, 1 at.%, 2 at.%, 3 at.%, or 5 at.%.

[0013] According to an exemplary embodiment of the present invention, the near-infrared luminescent material is Na. 3-y Al 2-x-z (PO4)2F3:xCr 3+ yR 3 + , zN, where y and z are 0, and x is 1 at.%, 3 at.%, or 5 at.%.

[0014] According to an exemplary embodiment of the present invention, the near-infrared luminescent material is Na. 3-y Al 2-x-z (PO4)2F3:xCr 3+ yR 3+ , zN, where z is 0, and x and y are both 3at.%.

[0015] According to an exemplary embodiment of the present invention, the near-infrared luminescent material is Na. 3-y AlGa 1-x-z (PO4)2F3:xCr 3+ yR 3+ , zN, where y and z are 0, and x is 3at.%.

[0016] According to an embodiment of the present invention, the near-infrared luminescent material, when excited by blue or red light, can emit near-infrared light with a wavelength range of 650-1200 nm.

[0017] Preferably, the blue light or red light is selected from blue light or red light in the range of 350-750nm.

[0018] Preferably, the peak value of the near-infrared light is between 750-850 nm, for example, around 810 nm.

[0019] This invention also provides a method for preparing the above-mentioned near-infrared luminescent material, wherein the preparation method is a solid-state synthesis method, specifically including the following steps:

[0020] According to the stoichiometric ratio of each element in the chemical formula of the near-infrared luminescent material, the raw materials are weighed, mixed, and then subjected to heat treatment and sintering to obtain the near-infrared luminescent material.

[0021] According to an embodiment of the present invention, the raw material includes a Na-containing compound, a M-containing compound, a P-containing compound, an F-containing compound, a Cr-containing compound, and at least one of the following substances: an R-containing compound and an N-containing compound.

[0022] According to an exemplary embodiment of the present invention, the raw materials include compounds containing Na, compounds containing M, compounds containing P, compounds containing F, and compounds containing Cr.

[0023] According to an embodiment of the present invention, the Na-containing compound is selected from one or both of Na2CO3 and NaF.

[0024] According to an embodiment of the present invention, the compound containing M is selected from one, two or more of the oxides of M, fluorides of M, and phosphates of M.

[0025] According to an embodiment of the present invention, the P-containing compound is selected from one or more of NH4H2PO4, (NH4)2HPO4, and AlPO4.

[0026] According to an embodiment of the present invention, the Cr-containing compound is one or both of Cr2O3 and CrF3.

[0027] According to an embodiment of the present invention, the R-containing compound is selected from oxides of R.

[0028] According to an embodiment of the present invention, the N-containing compound is selected from one, two or more of N oxides, N carbonates, and N fluorides.

[0029] According to an embodiment of the present invention, the raw materials may be pre-dried before or after mixing.

[0030] Preferably, the pre-drying treatment refers to treating the raw material at a temperature above 150°C (e.g., 190°C, 250°C) for a period of time (e.g., 3-5 hours) and then allowing it to cool naturally to room temperature.

[0031] According to an embodiment of the present invention, the mixing method is selected from one or both of dry grinding and wet grinding. Preferably, the mixing method is wet grinding with an appropriate amount of anhydrous ethanol for 10-200 min, for example at least 30 min or 60 min.

[0032] According to an embodiment of the present invention, the heat treatment includes heating, holding, and cooling.

[0033] According to an embodiment of the present invention, the heating refers to raising the temperature from room temperature to the holding temperature at a heating rate of 1-5°C / min.

[0034] According to an embodiment of the present invention, the conditions for heat preservation are: the heat preservation temperature is less than 600℃, for example, 400℃; and the heat preservation time is 1-5h, for example, 4h.

[0035] According to an embodiment of the present invention, the cooling refers to reducing the temperature to room temperature at a rate of 1-5°C / min.

[0036] According to an embodiment of the present invention, the sintering treatment time is greater than 6 hours, for example, 10-48 hours.

[0037] According to an embodiment of the present invention, the sintering temperature is 600-720°C, more preferably 680-700°C, for example 690°C.

[0038] According to an embodiment of the present invention, the sintering process includes heating before the sintering process and cooling after the sintering process, wherein the heating and cooling have the meanings described above.

[0039] According to an exemplary embodiment of the present invention, the sintering process includes: heating from room temperature to the sintering temperature at a heating rate of 1-5°C / min for 10-48 hours, and then cooling down to room temperature at a cooling rate of 1-5°C / min.

[0040] According to an embodiment of the present invention, after sintering, the material is optionally ground, and the ground material is collected to obtain the near-infrared luminescent material.

[0041] According to an embodiment of the present invention, after heat treatment and / or sintering, grinding may optionally be performed. The grinding may be performed under conditions known in the art, as long as a uniform powder can be obtained, for example, dry grinding in a mortar for more than 30 minutes.

[0042] According to an exemplary embodiment of the present invention, the preparation method includes, for example, the following steps:

[0043] (1) According to the stoichiometric ratio of each element in the chemical formula of the near-infrared luminescent material, weigh out the Na-containing compound, the M-containing compound, the P-containing compound, the F-containing compound, the Cr-containing compound, and the optional R-containing compound and N-containing compound, and mix them to obtain a mixed powder.

[0044] Pre-drying may also be performed before or after mixing;

[0045] (2) After heat treatment and sintering of the mixed powder in step (1), the near-infrared luminescent material is obtained.

[0046] The present invention also provides the use of the above-mentioned near-infrared luminescent material, which can be used as a near-infrared luminescent material in a variety of fields using near-infrared light sources, such as detection, marking, identification, optoelectronic devices, etc.

[0047] According to an embodiment of the present invention, the near-infrared luminescent material of the present invention is used in LEDs.

[0048] The present invention also provides an LED device, comprising at least one of the near-infrared luminescent materials.

[0049] According to an embodiment of the present invention, the LED device further includes an LED chip, which can be a blue LED chip or a red LED chip, preferably a 420nm blue LED chip.

[0050] According to an embodiment of the present invention, in the LED device, the near-infrared luminescent material is disposed on the surface of the LED chip.

[0051] According to an exemplary scheme of the present invention, the LED device is excited by a 350-750nm blue LED chip or a red LED chip to obtain near-infrared light with an emission wavelength of 650-1200nm, which can be used as a near-infrared light source.

[0052] The present invention also provides the application of the above-mentioned LED device as a near-infrared light source in the fields of analysis and detection, iris recognition, automotive sensing and security.

[0053] Beneficial effects:

[0054] This invention provides a near-infrared luminescent material, using Cr 3+ As the luminescent center, it can effectively emit near-infrared light of 650-1200nm when excited by light of 350-750nm.

[0055] The present invention uses a solid-state method to synthesize the near-infrared luminescent material, which has the advantages of low raw material cost, simple process, and easy operation, and can easily realize the large-scale preparation of luminescent materials.

[0056] The near-infrared luminescent material provided by this invention can be effectively excited by existing commercial blue or red LED chips and packaged into LED devices, thus realizing the commercialization of near-infrared LED devices. Attached Figure Description

[0057] Figure 1 The images show a comparison of the XRD patterns of different phosphors prepared in Examples 1-5 of this invention with the XRD patterns calculated using COD#1521541.

[0058] Figure 2 The excitation spectrum of the phosphor prepared in Example 2 of this invention was obtained at a monitoring wavelength of 810 nm.

[0059] Figure 3 Comparison of emission spectra of phosphor samples prepared in Examples 1-3 of this invention under 426nm blue light excitation.

[0060] Figure 4 The phosphor sample prepared in Example 1 of this invention exhibits a temperature-varying spectrum from 25 to 200°C under 426 nm blue light excitation.

[0061] Figure 5 The excitation spectrum of the phosphor prepared in Example 4 of this invention was obtained at a monitoring wavelength of 830 nm and the emission spectrum was obtained at a monitoring wavelength of 426 nm.

[0062] Figure 6 This is a comparison of the emission spectra of the phosphors prepared in Examples 2 and 5 of this invention under 426nm blue light excitation. Detailed Implementation

[0063] The preparation method of the present invention will be further described in detail below with reference to specific embodiments. It should be understood that the following embodiments are merely illustrative and explanatory of the present invention and should not be construed as limiting the scope of protection of the present invention. All technologies implemented based on the above content of the present invention are covered within the scope of protection intended by the present invention.

[0064] Unless otherwise specified, the experimental methods used in the following examples are conventional methods; unless otherwise specified, the reagents and materials used in the following examples are commercially available.

[0065] The monitoring wavelength in this invention refers to selecting the peak position of the emission peak or the vicinity of that band as the monitoring wavelength in order to obtain an excitation spectrum with a high signal-to-noise ratio; the testing instrument is an FLS980 fluorescence spectrometer.

[0066] Examples 1-5: Na 3-y M 2-x-z (PO4)2F3:xCr 3+ Preparation of luminescent materials

[0067] Examples 1-5 were synthesized using a high-temperature solid-state method, differing only in the types and amounts of raw materials used. For details on the types and amounts of raw materials used, please refer to Table 1, where the amount of raw materials is in grams.

[0068] The specific steps of the high-temperature solid-state synthesis are as follows: Weigh the reactants according to the stoichiometric ratio, place them in an agate mortar and grind them thoroughly for 3-5 minutes. Add an appropriate amount of alcohol to place the powdered raw materials in the mortar and grind for 30-60 minutes. Then, place the mixture in an oven at 60-80℃ for 5-10 minutes to dry it. After cooling to room temperature, remove it and grind it appropriately to mix the powder adhering to the mortar again. After mixing, collect the powder in a corundum crucible. Cover the crucible containing the powder and place it in an oven at 190℃ for 3-5 hours. After allowing it to cool naturally to room temperature, transfer the mixture to an agate mortar and dry grind it for 10-30 minutes. Collect the mixed powder in a corundum crucible, cover it, and then place it in a muffle furnace. The sample was pre-calcined, with the temperature set to increase from room temperature to 400℃ at a rate of 1-5℃ / min, held at 400℃ for 4 hours, and then cooled to room temperature at a rate of 1-5℃ / min. The pre-calcined powder was then removed and placed in an agate mortar, ground for 15-30 minutes, and then collected in a corundum crucible. The crucible was then covered and transferred to a muffle furnace for sintering. The temperature was increased from room temperature to 690℃ at a rate of 1-5℃ / min, held at 690℃ for 6 hours, and then cooled to room temperature at a rate of 1-5℃ / min. Finally, the sintered phosphor sample was removed, placed in a mortar, and ground for 20-30 minutes. This collected phosphor is the near-infrared luminescent material. X-ray diffraction was used to analyze the phase composition of the sample, and an FLS980 (Edinburgh Instruments) fluorescence spectrometer was used to measure the spectral characteristics of the sample.

[0069] Table 1 Preparation parameters for Examples 1-5

[0070]

[0071] The samples synthesized using the high-temperature solid-state method in this invention, as shown by XRD analysis, are all pure phases in Examples 1-5: (e.g.) Figure 1 The XRD patterns of samples 'ae' in Examples 1-5 are shown in the image below, and all of them match the COD cards (see [link]). Figure 1 Na3Al2(PO4)2F3).

[0072] Figure 2 The excitation spectrum of the phosphor prepared in Example 2 of this invention was obtained at a monitoring wavelength of 810 nm. The results show that the prepared luminescent material has a broadband excitation peak between 350-750 nm, with the optimal excitation positions located at 426 nm and 640 nm.

[0073] Figure 3 This is a comparison of the emission spectra of the phosphor samples prepared in Examples 1-3 of this invention under 426nm blue light excitation. Figure 3 Lines a, b, and c in the middle represent Cr in the chemical formula of the phosphor sample, respectively.3+ The room-temperature emission spectra of the samples with doping levels x of 1 at.%, 3 at.%, and 5 at.% were obtained. The results show that compared with the samples with doping levels of 1 at.% and 5 at.%, Cr 3+ When the doping amount is 3 at.%, the emission intensity of the sample is higher.

[0074] Figure 4 The phosphor sample prepared in Example 1 of this invention exhibits a temperature-varying spectrum within the range of 25-200℃ under 426nm blue light excitation. Figure 4 Lines a, b, and c in the figure represent the emission spectra of the phosphor sample from Example 1 at room temperature, 150°C, and 200°C, respectively. The results show that the luminescent material prepared in this invention exhibits negative thermal quenching properties in the temperature range from room temperature to 150°C. At 150°C, its emission intensity is 100.33% of the room temperature emission intensity; at 200°C, its emission intensity maintains 81.49% of the room temperature emission intensity.

[0075] Figure 5 The images show the excitation spectrum of the phosphor prepared in Example 4 of this invention at a monitoring wavelength of 830 nm and the emission spectrum at a monitoring wavelength of 426 nm. High concentrations of Ga are visible. 3+ The introduction of this technology can achieve a redshift in the emission wavelength of the phosphor, while the excitation spectrum remains almost unchanged.

[0076] Figure 6 This is a comparison of the emission spectra of the phosphors prepared in Examples 2 and 5 of this invention under 426 nm blue light excitation. Lines a and b represent the emission spectra of Examples 2 and 5, respectively, showing that the simultaneous introduction of Ga... 3+ and Eu 3+ The luminescence intensity decreased slightly.

[0077] Example 6: Fabrication of LED Devices

[0078] The luminescent material synthesized in Example 2 was tested, and its luminescence quantum yield PL QY was recorded in Table 2.

[0079] The luminescent material synthesized in Example 2 was mixed with silicone and coated onto a blue LED chip, wherein the mass ratio of the luminescent material to the silicone was 1:1. Subsequently, curing and encapsulation were performed to obtain a near-infrared emitting LED device, which can be used as a near-infrared light source in various analytical and testing equipment. The near-infrared output power of the LED device is shown in Table 2.

[0080] Table 2 Performance Test Results

[0081] Luminescent materials PL QY(%) Near-infrared output power (mW) Example 2 64％ 28.13

[0082] Test case

[0083] The phosphor from Example 2 was used to test its emission spectra at room temperature and 150°C, respectively. The integrated areas S1 and S2 were calculated, and the ratio of the integrated areas S2 / S1 of the emission spectra at 150°C and room temperature was calculated. The results were compared with those of the previously reported ScBO3:Cr 3+ The results were compared with phosphors of similar emission bands and recorded in Table 3. As shown in Table 3, the luminescent material of this invention has a significant advantage in thermal stability compared to phosphors of the same band.

[0084] Table 3 Performance Comparison

[0085]

[0086] The above embodiments illustrate the implementation of the present invention. However, the scope of protection of the present invention is not limited to the above embodiments. Any modifications, equivalent substitutions, improvements, etc., made by those skilled in the art within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for preparing a near-infrared luminescent material, characterized in that, The preparation method is a solid-state synthesis method, which specifically includes the following steps: According to the stoichiometric ratio of each element in the chemical formula of the near-infrared luminescent material, the raw materials are weighed, mixed, and then subjected to heat treatment and sintering to obtain the near-infrared luminescent material. The heat treatment includes heating, holding, and cooling; the heating refers to raising the temperature from room temperature to the holding temperature at a heating rate of 1-5℃ / min; the holding conditions are: the holding temperature is less than 600℃; the holding time is 1-5h; the cooling refers to lowering the temperature to room temperature at a cooling rate of 1-5℃ / min. The sintering process includes: heating from room temperature to the sintering temperature at a heating rate of 1-5℃ / min for 10-48 hours, and then cooling down to room temperature at a cooling rate of 1-5℃ / min; the sintering temperature is 600-720℃. The chemical formula of the near-infrared luminescent material is Na3M 2-x (PO4)2F3:xCr 3+ , Among them, Cr 3+ The luminescent central ion, x is selected from 0.0001 at.% to 10 at.%; M is selected from Al or from Al and Ga.

2. The preparation method according to claim 1, characterized in that, When the near-infrared luminescent material is excited by blue or red light, it emits near-infrared light with a wavelength range of 650-1200nm. The blue or red light is selected from blue or red light in the range of 350-750nm; The peak value of the near-infrared light is between 750-850 nm.

3. The preparation method according to claim 1, characterized in that, The raw materials include compounds containing Na, compounds containing M, compounds containing P, compounds containing F, and compounds containing Cr.

4. The preparation method according to claim 3, characterized in that, The Na-containing compound is selected from one or two of Na2CO3 and NaF; The compound containing M is selected from one or more of the oxides of M, the fluorides of M, and the phosphates of M. The P-containing compound is selected from one or more of NH4H2PO4, (NH4)2HPO4, and AlPO4; The Cr-containing compound is one or both of Cr2O3 and CrF3.

5. The preparation method according to claim 1, characterized in that, The mixing method is selected from one or both of dry grinding and wet grinding; After sintering, the material is optionally ground, and the ground material is collected to obtain the near-infrared luminescent material.

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