Green fluorescent material excited by purple light as well as preparation method and application of green fluorescent material

Abstract

The invention relates to a green fluorescent material excited by purple light as well as a preparation method and application of the green fluorescent material. The green fluorescent material is a Ce < 3 + > doped garnet structure material, the chemical formula of the green fluorescent material is CaLu2ZrSc1-xAl3O12: xCe < 3 + >, x is larger than or equal to 0.02 and smaller than or equal to 0.06, the excitation spectrum range of the green fluorescent material is 300-480 nm, and the emission spectrum range of the green fluorescent material is 450-700 nm. Compared with the prior art, the purple light excited Ce < 3 + > doped oxide-based green light emitting fluorescent material is brand new and unreported, can be matched with an existing purple light chip, and can effectively avoid blue light harm; the material has the outstanding advantages of stable physical and chemical properties, simple preparation, low cost and the like, and is suitable for visible light communication in space-air-ground-sea environments.

Description

Technical Field

[0001] This invention relates to the field of fluorescent materials technology, and in particular to a green fluorescent material excited by violet light, its preparation method and application. Background Technology

[0002] White LEDs, as a green and energy-saving lighting source, have been widely used in residential lighting, display backlighting, and functional lighting. The mainstream implementation method for white LEDs is to excite YAG:Ce using a blue LED chip. 3+ Yellow phosphors, when mixed, produce white light. However, this technology has significant drawbacks: First, the strong blue light emitted by the blue light chip may cause retinal damage and circadian rhythm disruption, known as "blue light hazard," which is of particular concern in healthy lighting scenarios; second, YAG:Ce... 3+ Phosphors have a long fluorescence lifetime (approximately 60-100 ns), resulting in a limited frequency response bandwidth (approximately 12.5 MHz), making it difficult to support high-speed signal modulation and thus restricting their application in optical communication.

[0003] Meanwhile, visible light communication (VLC), as an emerging wireless communication technology, utilizes the visible light band to transmit data, offering advantages such as abundant spectrum resources, no electromagnetic radiation, high security, and integration with lighting systems. VLC is particularly suitable for integrated air-space-ground-sea communication scenarios, such as aerial drone relay, land-based indoor positioning, underwater sensor networks, and space station communication, where optical signals need to maintain stable transmission in complex environments such as the atmosphere and water. However, existing YAG:Ce... 3+ Phosphors have a low frequency response bandwidth, which cannot meet the requirements of VLC for high speed and low latency.

[0004] Therefore, developing a phosphor that is excited by violet light (avoiding the harm of blue light), has a short lifespan, high bandwidth, and combines stability with high-efficiency light emission characteristics has become an urgent need to achieve safe and healthy lighting and high-speed VLC. Summary of the Invention

[0005] The purpose of this invention is to overcome the defects of the prior art by providing a green fluorescent material excited by violet light, its preparation method and application, so as to meet the urgent need for high-speed, low-latency and blue light-free light sources in visible light communication in air, space, sea and air environments.

[0006] The objective of this invention can be achieved through the following technical solutions: This invention first provides a green fluorescent material excited by violet light, wherein the green fluorescent material is Ce. 3+ Doped garnet-structured materials with the chemical formula CaLu₂ZrSc 1-x Al3O 12 :x Ce 3+ , where 0.02≤ x ≤0.06; The excitation spectrum of the green fluorescent material is in the range of 300-480 nm. The emission spectrum of the green fluorescent material is in the range of 450-700 nm.

[0007] Furthermore, the green fluorescent material emits green light with a center wavelength of 494-512 nm under 419 nm violet light excitation, thus it can be efficiently matched with commercial violet light chips.

[0008] Furthermore, the fluorescence lifetime of the green fluorescent material is less than 50 ns, which is significantly better than that of traditional commercial YAG:Ce. 3+ Phosphor (lifetime 60~100 ns). Based on Ce 3+ The 4f-5d transition characteristics enable high-speed signal modulation, meeting the high bandwidth requirements of visible light communication.

[0009] Furthermore, the frequency response bandwidth of the green fluorescent material is not less than 15 MHz.

[0010] Furthermore, the green fluorescent material is an oxide-based powder material, which has the advantages of stable physical and chemical properties and strong resistance to environmental interference, and can adapt to the light transmission needs of various complex scenarios such as air, land, underwater, and space.

[0011] This invention also provides a method for preparing a green fluorescent material excited by violet light, the method comprising the following steps: S1: Weigh the calcium source compound, lutetium source compound, zirconium source compound, scandium source compound, aluminum source compound, cerium source compound, and flux according to the stoichiometric ratio, and grind and mix them evenly; S2: The mixed powder obtained in S1 is pre-sintered in air atmosphere and naturally cooled to obtain the precursor; S3: After grinding the precursor obtained in S2 evenly, it is sintered again under a reducing atmosphere and then cooled to room temperature to finally obtain the green fluorescent material excited by purple light.

[0012] Furthermore, in step S1, the calcium source compound is CaCO3.

[0013] Further, in step S1, the lutetium source compound is Lu2O3.

[0014] Further, in step S1, the zirconium source compound is ZrO2.

[0015] Further, in step S1, the scandium source compound is Sc2O3.

[0016] Further, in step S1, the aluminum source compound is Al2O3.

[0017] Further, in step S1, the cerium source compound is CeO2.

[0018] Furthermore, in step S1, the flux is CaF2. The addition of flux CaF2 can lower the sintering temperature, promote crystal growth, and improve the luminescence performance of the phosphor.

[0019] Furthermore, in step S1, the amount of flux added is 2-5% of the total mass of the raw materials.

[0020] Furthermore, in step S2, the pre-sintering temperature is 500-700℃; Furthermore, in step S2, the pre-sintering time is 4-6 hours. Pre-calcination in an air atmosphere can remove impurity gases (such as CO2) from the raw materials and initially form a precursor of the target crystal structure, laying the foundation for subsequent reduction sintering.

[0021] Furthermore, in step S3, the temperature of the secondary sintering is 1300-1600℃.

[0022] Furthermore, in step S3, the secondary sintering time is 6-10 hours.

[0023] Furthermore, in step S3, the reducing atmosphere is a mixture of H2 and N2.

[0024] Further, in step S3, the volume fraction of H2 is 3-10%, preferably 5%. Reduction under a hydrogen-nitrogen mixed reducing atmosphere of 5% H2-95% N2 can reduce Ce. 4+ Efficient reduction to Ce 3+ This ensures the activity of the phosphor's luminescent centers while avoiding excessive reduction that could damage the matrix structure.

[0025] This invention also provides an application of a violet-excited green fluorescent material in a visible light communication system, the visible light communication system comprising: At the transmitting end, LED light-emitting devices encapsulated with green fluorescent materials excited by violet light are used as the signal emission source to modulate electrical signals into optical signals; The receiver is configured to receive the optical signal emitted by the transmitter and convert it into an electrical signal.

[0026] Furthermore, the chip of the LED light-emitting device is a violet chip, and green fluorescent material is coated on the chip surface.

[0027] Furthermore, the emission wavelength of the violet light chip is 380~420 nm.

[0028] Furthermore, the green fluorescent material is mixed with a transparent encapsulation material (such as silicone) to form a fluorescent adhesive, which is then applied to the chip surface using a dispensing process. After curing, it can produce stable green light.

[0029] Furthermore, the LED light-emitting device can transmit light signals in land, air, and underwater environments.

[0030] Furthermore, the -3dB bandwidth of the visible light communication system is no less than 15 MHz, or even no less than 19.71 MHz, making it suitable for various environments including air, land, sea, and air, such as aerial drone communication, land-based indoor positioning, underwater sensor networks, and space station auxiliary communication scenarios.

[0031] Based on the stringent requirements of high speed, low latency, and light source safety for visible light communication in integrated air-space-ground-sea applications, this invention innovatively designs and successfully prepares a novel violet-excited green fluorescent material, CaLu2ZrSc. 1- x Al3O 12 : x Ce 3+ (CLZS:Ce) 3+ The core of this material design strategy lies in abandoning quantum dot materials, which have short lifespans but poor stability, and instead using Ce. 3+ The doped oxide matrix system combines nanosecond-level short fluorescence lifetime with excellent physicochemical stability. Its excitation spectrum covers 300-480 nm, which can be efficiently matched with commercial violet light chips (380-420 nm), effectively avoiding blue light hazards at the light source end; its emission spectrum is located in the green light region of 450-700 nm, and the center wavelength can be detected by Ce. 3+ The doping concentration (x=0.02-0.06) can be finely controlled between 494-512nm.

[0032] In terms of lattice structure design, this invention selects a garnet structure with tunable structure and excellent stability as the matrix. Among them, Sc 3+ The introduction of Ce 3+ It provides ideal doping sites. Because the ionic radii of the two are similar, lattice distortion can be effectively reduced, optimizing the local crystal field environment of the luminescent center, thereby achieving high-efficiency and ideal wavelength green light emission. 4+ The incorporation of [a substance] further plays a key role in broadening the excitation band.

[0033] Compared with the prior art, the present invention has the following technical advantages: (1) This invention successfully prepared a series of novel, previously unreported violet-excited Ce 3+The doped oxide-based green fluorescent material, with a garnet structure, can be matched with existing violet light chips, effectively avoiding blue light hazards. Furthermore, its excitation spectrum covers 300–480 nm, its emission wavelength includes 450 nm–700 nm, it has a short fluorescence lifetime (36 ns), and a high frequency response bandwidth (19.71 MHz), far superior to commercial YAG:Ce. 3+ (Lifetime 61 ns, frequency response bandwidth 12.5MHz), visible light communication suitable for air, land, sea and air environments.

[0034] (2) The phosphor of the present invention is an oxide-based green light emitting phosphor, which has the advantages of stable physicochemical properties and strong resistance to temperature and humidity changes. At the same time, the phosphor can be prepared by conventional solid-phase reaction method, which is simple in preparation process, low in cost and conducive to industrial production, and can provide a good candidate material for mass application in the fields of air, space, sea and air communication.

[0035] (3) The phosphor of the present invention has far superior properties compared to commercial YAG:Ce 3+ The short fluorescence lifetime and high frequency response bandwidth of phosphors enable LED devices and visible light communication systems to meet the requirements of high-speed, low-latency optical transmission and achieve stable communication in complex environments such as air and underwater.

[0036] (4) This invention encapsulates green light-emitting phosphor in an LED device and uses the LED device as the transmitting light source of the communication system to modulate electrical signals into optical signals, and constructs a complete visible light communication system in conjunction with the receiving end. The system has a -3dB bandwidth of not less than 19.71 MHz, and is suitable for various environments including air, land, sea and air, including aerial UAV communication, land indoor positioning, underwater sensor networks and space station auxiliary communication scenarios, providing a new solution for the development of integrated air, land, sea and air communication technology. Attached Figure Description

[0037] Figure 1 The images show the photoexcitation and photoemission spectra of the green phosphors excited by violet light prepared in Examples 1-5 of this invention.

[0038] Figure 2 The XRD patterns of the green phosphors excited by violet light prepared in Examples 1-5 of this invention are shown.

[0039] Figure 3 The CaLu2ZrScAl3O prepared in Example 2 of this invention 12 :Ce 3+ Phosphors and Commercial YAG:Ce 3+ Comparison of fluorescence lifetimes of phosphors.

[0040] Figure 4This is the frequency response test result in an application example of the present invention.

[0041] Figure 5 This is an eye diagram in an application example of the present invention.

[0042] Figure 6 This is a schematic diagram of the optical communication of the LED device prepared in the application example of the present invention in an air environment.

[0043] Figure 7 This is a schematic diagram of an LED device prepared in an application example of the present invention being tested in underwater optical communication. Detailed Implementation

[0044] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments. These embodiments are based on the technical solution of the present invention and provide detailed implementation methods and specific operating procedures. However, the scope of protection of the present invention is not limited to the following embodiments.

[0045] Unless otherwise specified, the reagents, methods, instruments, and equipment used in this invention are conventional in the art. Unless otherwise specified, the reagents and materials used in the following examples are all commercially available.

[0046] Example 1: This embodiment provides a method for preparing a green phosphor excited by violet light, the steps of which are as follows: (1) Weigh 1g of raw material powders of CaCO3, ZrO2, Sc2O3, Lu2O3, Al2O3, and CeO2 according to the stoichiometric ratio (e.g., the mass ratio of each raw material is CaCO3, ZrO2, Sc2O3, Lu2O3, Al2O3, CeO2 = 0.1184 : 0.1457 : 0.0799 : 0.4708 : 0.1809 : 0.0040), and select 0.03g of CaF2 as flux, and weigh it together with the above raw material powders.

[0047] (2) Place the above raw material mixture in an agate mortar and grind for 30 to 60 minutes. After the materials are mixed evenly, load the mixture into an alumina crucible and pre-sinter at 600°C for about 5 hours in an air atmosphere, and then cool naturally to obtain the precursor.

[0048] (3) After grinding the precursor evenly, it was calcined at 1550 °C for 8 h in a reducing atmosphere of hydrogen and nitrogen mixture (5% H2-95% N2), and then cooled to room temperature to obtain the target product with the general formula CaLu2ZrSc. 1-x Al3O 12 : x Ce 3+ ,in x = 0.02.

[0049] The spectral properties of the phosphor in this system were tested using a Hitachi F-7000 fluorescence spectrometer. For example... Figure 1 As shown in the figure. The results indicate that the phosphor in this system has a broad excitation band, covering the ultraviolet and violet regions, with a peak value near 419 nm. The high spectral peak value allows for good matching with commercial violet light chips. Under excitation by a 419 nm violet light source, the phosphor emits bright green light, with an emission spectral peak value at 494 nm.

[0050] The crystal structure of the phosphor in this system was determined using X-ray diffraction (Ultima IV-185). Cu-Kα was used as the target material, and the scanning angle 2θ ranged from 10° to 80°. The resulting XRD patterns are shown below. Figure 2 As shown, from Figure 2 It can be seen that the fluorescent material is consistent with the standard card (PDF#00-044-0227).

[0051] Example 2: This embodiment provides a method for preparing a green phosphor excited by violet light. Compared to Example 1, the difference lies in the raw material mass ratio: CaCO3, ZrO2, Sc2O3, Lu2O3, Al2O3, CeO2 = 0.1182 : 0.1456 : 0.0790 : 0.4702 : 0.1807 : 0.0061. The target product has the general formula CaLu2ZrSc 1-x Al3O 12 : x Ce 3+ ,in x = 0.03.

[0052] like Figure 1 As shown, the phosphor in this system has a broad excitation band, covering the ultraviolet and violet regions, with a peak value near 419 nm. Its high spectral peak value allows for good matching with commercial violet light chips. Under excitation by a 419 nm violet light source, the phosphor emits bright green light, with an emission spectral peak value at 500 nm.

[0053] like Figure 2 The XRD pattern shows that the fluorescent material is consistent with the standard card (PDF#00-044-0227).

[0054] Example 3: This embodiment provides a method for preparing a green phosphor excited by violet light. Compared to Example 1, the difference lies in the raw material mass ratio: CaCO3, ZrO2, Sc2O3, Lu2O3, Al2O3, CeO2 = 0.1181 : 0.1454 : 0.0781 : 0.4696 : 0.1805 : 0.0081. The target product has the general formula CaLu2ZrSc 1-x Al3O 12 : x Ce 3+ ,in x = 0.04.

[0055] like Figure 1 As shown, the phosphor in this system has a broad excitation band, covering the ultraviolet and violet regions, with a peak value near 419 nm. Its high spectral peak value allows for good matching with commercial violet light chips. Under excitation by a 419 nm violet light source, the phosphor emits bright green light, with an emission spectral peak at 510 nm.

[0056] like Figure 2 The XRD pattern shows that the fluorescent material is consistent with the standard card (PDF#00-044-0227).

[0057] Example 4: This embodiment provides a method for preparing a green phosphor excited by violet light. Compared to Example 1, the difference lies in the raw material mass ratio: CaCO3, ZrO2, Sc2O3, Lu2O3, Al2O3, CeO2 = 0.1179 : 0.1452 : 0.0772 : 0.4690 : 0.1802 : 0.0101. The target product has the general formula CaLu2ZrSc 1-x Al3O 12 : x Ce 3+ ,in x = 0.05.

[0058] like Figure 1 As shown, the phosphor in this system has a broad excitation band, covering the ultraviolet and violet regions, with a peak value near 419 nm. Its high spectral peak value allows for good matching with commercial violet light chips. Under excitation by a 419 nm violet light source, the phosphor emits bright green light, with an emission spectral peak value at 511 nm.

[0059] like Figure 2 The XRD pattern shows that the fluorescent material is consistent with the standard card (PDF#00-044-0227).

[0060] Example 5: This embodiment provides a method for preparing a green phosphor excited by violet light. Compared to Example 1, the difference lies in the raw material mass ratio: CaCO3, ZrO2, Sc2O3, Lu2O3, Al2O3, CeO2 = 0.1178 : 0.1450 : 0.0763 : 0.4685 : 0.1800 : 0.0121. The target product has the general formula CaLu2ZrSc 1-x Al3O 12 : x Ce 3+ ,in x = 0.06.

[0061] like Figure 1 As shown, the phosphor in this system has a broad excitation band, covering the ultraviolet and violet regions, with a peak value near 419 nm. Its high spectral peak value allows for good matching with commercial violet light chips. Under excitation by a 419 nm violet light source, the phosphor emits bright green light, with an emission spectral peak value at 512 nm.

[0062] like Figure 2 The XRD pattern shows that the fluorescent material is consistent with the standard card (PDF#00-044-0227).

[0063] Based on the successful preparation of the violet-excited green phosphor described above, this invention uses the green fluorescent material prepared in Example 2 as an example to test the fluorescence lifetime of the prepared violet-excited green phosphor using an Edinburgh fluorescence spectrophotometer FS5. The tested fluorescence lifetime diagram is shown below. Figure 3 As shown, and compared with commercial phosphor YAG:Ce 3+ In comparison, its fluorescence lifetime (36 ns) is far superior to that of commercial phosphor YAG:Ce. 3+ The fluorescence lifetime is 61 ns.

[0064] To further explore the application of the green phosphor prepared by this invention in visible light communication in air, space, sea and air environments, this invention further encapsulates the green phosphor into an LED light-emitting device and uses the LED device as the transmitting light source of the communication system.

[0065] Application example: The CaLu2ZrScAl3O prepared in Example 2 12 : x Ce 3+ Taking green phosphor as an example, the specific method for preparing the LED device of the present invention is as follows: (1) Provide a purple LED chip with an emission wavelength of 420 nm (wavelength range 380-420 nm) as an excitation source.

[0066] (2) CaLu2ZrScAl3O 12 : x Ce 3+ Green phosphors are mixed with transparent encapsulation materials (such as silicone) to form fluorescent adhesives.

[0067] (3) Apply fluorescent adhesive to the purple LED chip through a dispensing process and cure it at 120°C for 2 hours to form an LED device.

[0068] Next, the output signal of the Lite Vector Network Analyzer (Lite VNA) is connected to the fabricated LED device. The emitted light is collected by a photodetector. The light signal emitted by the LED is then detected by the photodetector (KSD Technology, DT-20-1).

[0069] Figure 4 The electro-optical (EOE) frequency response diagram of the VLC system shows that the sample's -3dB bandwidth is no less than 19.71 MHz, as determined by testing.

[0070] Figure 5 The image shows an open-eye pattern captured using an oscilloscope (MSO7204X). As shown, the measured eye width is 8.474 μs. In the lower frequency range (0.1-100 MHz), it exhibits good response characteristics, with rise and fall times of 5.029 μs and 4.791 μs, respectively, indicating a good balance in time response characteristics.

[0071] Figure 6 This is a schematic diagram of the optical communication of the LED device prepared above in an air environment. Figure 7 The above-mentioned LED device is shown in a schematic diagram of underwater optical communication testing, demonstrating that the visible light communication system prepared by this invention can adapt to the optical transmission needs of various complex scenarios such as air, land, sea and air environments (including communication scenarios in the air, on land, underwater and in space).

[0072] The above description of the embodiments is provided to enable those skilled in the art to understand and use the invention. It will be apparent to those skilled in the art that various modifications can be made to these embodiments, and the general principles described herein can be applied to other embodiments without inventive effort. Therefore, the present invention is not limited to the above embodiments, and any improvements and modifications made by those skilled in the art based on the disclosure of the present invention without departing from the scope of the invention should be within the protection scope of the present invention.

Claims

1. A green fluorescent material excited by violet light, characterized in that, The green fluorescent material is Ce. 3+ Doped garnet-structured materials with the chemical formula CaLu₂ZrSc 1-x Al3O 12 : x Ce 3+ , where 0.02≤ x ≤0.06; The excitation spectrum of the green fluorescent material is in the range of 300-480 nm. The emission spectrum of the green fluorescent material is in the range of 450-700 nm.

2. The green fluorescent material excited by violet light according to claim 1, characterized in that, The green fluorescent material emits green light with a central wavelength of 494-512 nm when excited by 419 nm violet light.

3. The green fluorescent material excited by violet light according to claim 1, characterized in that, The fluorescence lifetime of the green fluorescent material is less than 50 ns.

4. A method for preparing a green fluorescent material excited by violet light according to any one of claims 1-3, characterized in that, The preparation method includes the following steps: S1: Weigh the calcium source compound, lutetium source compound, zirconium source compound, scandium source compound, aluminum source compound, cerium source compound, and flux according to the stoichiometric ratio, and grind and mix them evenly; S2: The mixed powder obtained in S1 is pre-sintered in air atmosphere and naturally cooled to obtain the precursor; S3: After grinding the precursor obtained in S2 evenly, it is sintered again under a reducing atmosphere and then cooled to room temperature to finally obtain the green fluorescent material excited by purple light.

5. The method for preparing a violet-excited green fluorescent material according to claim 4, characterized in that, In step S1, the calcium source compound is CaCO3, the lutetium source compound is Lu2O3, the zirconium source compound is ZrO2, the scandium source compound is Sc2O3, the aluminum source compound is Al2O3, and the cerium source compound is CeO2. The flux is CaF2, and its addition amount is 2-5% of the total mass of the raw materials.

6. The method for preparing a violet-excited green fluorescent material according to claim 4, characterized in that, In step S2, the pre-sintering temperature is 500-700℃; The pre-sintering time is 4-6 hours.

7. The method for preparing a violet-excited green fluorescent material according to claim 4, characterized in that, In step S3, the temperature of the secondary sintering is 1300-1600℃; The secondary sintering time is 6-10 hours; The reducing atmosphere is a mixture of H2 and N2, wherein the volume fraction of H2 is 3-10%.

8. The application of a violet-excited green fluorescent material according to any one of claims 1-3 in a visible light communication system, characterized in that, The visible light communication system includes: At the transmitting end, LED light-emitting devices encapsulated with green fluorescent materials excited by violet light are used as signal emission light sources to modulate electrical signals into optical signals; The receiver is configured to receive the optical signal emitted by the transmitter and convert it into an electrical signal.

9. The application of the violet-excited green fluorescent material according to claim 8 in a visible light communication system, characterized in that, The LED light-emitting device has a violet light chip with green fluorescent material coated on its surface. The LED light-emitting device can transmit light signals in land, air, and underwater environments.

10. The application of the violet-excited green fluorescent material according to claim 8 in a visible light communication system, characterized in that, The -3dB bandwidth of the visible light communication system is no less than 15 MHz.

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