Use of an inorganic fluorescent material emitting visible and near infrared light under blue and green light excitation

Abstract

The application belongs to the field of inorganic fluorescent materials, and particularly relates to application of an inorganic fluorescent material to emitting visible light and near-infrared light under blue and green light excitation. x S2:D y wherein A is one or two or more of Li, Na, K, Rb and Cs, B is one or two or more of La, Lu, Y, Sc, In, Al and Ga, D is a doping ion selected from one or two or more of Yb, Nd, Eu, Er, Ce, Bi, Tb, Ni, Fe, Mn, Pr and Cr, x and y are mole fractions, and x+y=1; the inorganic fluorescent material realizes down-conversion luminescence in the 460-780 nm visible light region and / or the 780-2000 nm near-infrared region under blue and green light excitation. The inorganic fluorescent material of the application is based on charge transfer band absorption, so that it has a wide and adjustable excitation bandwidth, covering the ultraviolet, violet, green and blue light regions, and can realize blue and green light excitation.

Description

Technical Field

[0001] This invention belongs to the field of inorganic fluorescent materials, specifically relating to the application of an inorganic fluorescent material that emits visible and near-infrared light under blue and green light excitation. Background Technology

[0002] A light-emitting diode (LED) is a semiconductor device that utilizes the pn structure of p-type and n-type semiconductors to emit light through the recombination of electrons and holes. Since the advent of the earliest red LED, LED development has involved decades of effort, encompassing multiple fields such as semiconductor materials, epitaxial growth technology, and doping processes. It wasn't until the early 1990s that groundbreaking research by Japanese scientists Isamu Akasaki, Hiroshi Amano, and Nakamura Shuji made the realization of blue LEDs possible. This breakthrough not only laid the foundation for the commercialization of blue LEDs but also enabled the output of white light excited by blue light. As the "fourth generation of lighting sources," LEDs have gained widespread adoption in daily life due to their smaller size, higher efficiency, longer lifespan, and lower energy consumption compared to traditional light sources. In particular, phosphor-converted LEDs (pc-LEDs), with their low cost and good color rendering, have become the mainstream of commercial white LEDs. However, currently, phosphors used to achieve blue light excitation and emission of visible or near-infrared light are all based on ion absorption, such as Ce2. 3+ Cr 3+ Eu 2+ Bi 3+ Plasma. Chinese invention patent CN112159660B discloses a plasma with the composition mA2S·nBS·kC. 2-x S3:D x Multi-component sulfide upconversion luminescent materials emit ultraviolet, blue, blue-green, green, red, and near-infrared light at excitation wavelengths of 1450-1600 nm or 780-860 nm. This is achieved through absorption via the ff transitions of rare-earth ions, but the blue-violet excitation characteristics are not described. The absorption efficiency of ion absorption mainly depends on the doping concentration of ions in the matrix material, the absorption cross-section, and the degree of matching between the ion transition energy levels and the frequency of the excitation light. Moreover, these ions exist in a doped form, typically with a low doping concentration, resulting in low light absorption efficiency.

[0003] In contrast, charge transfer band (CTS) absorption is another efficient form of light absorption, typically referring to the absorption caused by the transfer of electrons from ligands (such as oxygen or halide ions) to a central metal cation. CTS absorption allows for transitions and has high absorption efficiency; however, the CTS absorption peak is usually located at a high energy level, for example, approximately 7 eV (177 nm) in fluorides and approximately 4 eV (310 nm) in oxides, making it difficult to achieve blue-green light excitation. Recently, Shiteng Wang et al. (A general strategy via charge transfer sensitization to achieve efficient NIR luminescence in lanthanide-doped NaGdS2 nanocrystals, J. Mater. Chem. C, 2021, 9, 5148.) successfully redshifted the CTS absorption peak in NaGdS2 matrix materials, achieving a peak at 3.53 eV (351 nm). This discovery allows the CTS absorption peak to be matched with ultraviolet LEDs (395-410 nm). However, in the blue light region, especially the emission region of blue LEDs (440-470nm), the absorption peak intensity of this CTS drops significantly, making it difficult to achieve blue light excitation. In practical applications, commercial blue LEDs have higher luminous efficiency and are more economical than ultraviolet LEDs. (Sidney E. Creutz et al., A Selective Cation Exchange Strategy for the Synthesis of Colloidal Yb) 3+ (Doped Chalcogenide Nanocrystals with Strong Broadband Visible Absorption and Long-Lived Near-Infrared Emission, J. Am. Chem. Soc. 2017, 139, 11814) Through ion exchange, the excited state position in PbInS2:Yb is red-shifted to 2.68 eV (462 nm), satisfying the blue light excitation requirement, but Pb 2+ The toxicity of ions greatly limits their applications. Therefore, developing non-toxic, environmentally friendly fluorescent materials that are excited by blue and green light and emit in the visible and near-infrared regions has significant advantages and importance in lighting, displays, and near-infrared applications (such as solar cells, near-infrared spectroscopy analysis, and imaging). Summary of the Invention

[0004] In view of the above situation, the purpose of this invention is to provide an application of an inorganic fluorescent material that emits visible and near-infrared light under blue and green light excitation. The inorganic fluorescent material is excited by 400-550nm blue and green light with charge migration band absorption matching, the excitation peak range is adjustable in the range of 250-600nm, and it has emission in the visible light region and / or near-infrared region.

[0005] To achieve the above objectives, the technical solution of the present invention is as follows:

[0006] An application of an inorganic fluorescent material that emits visible and near-infrared light under blue and green light excitation, wherein the inorganic fluorescent material is a ternary sulfide with the chemical formula AB. x S2:D y Where A is one or more of Li, Na, K, Rb, and Cs; B is one or more of La, Lu, Y, Sc, In, Al, and Ga; D is a dopant ion selected from one or more of Yb, Nd, Eu, Er, Ce, Bi, Tb, Ni, Fe, Mn, Pr, and Cr; and x and y are mole fractions, where x + y = 1.

[0007] The inorganic fluorescent material achieves downconversion luminescence in the 460-780nm visible light region and / or the 780-2000nm near-infrared region under blue and green light excitation.

[0008] In the above technical solution, the excitation peak of the inorganic fluorescent material is further defined as 250-600 nm.

[0009] In the above technical solution, further, 0.7≤x≤0.999 and 0.001≤y≤0.3.

[0010] The beneficial effects of this invention are as follows:

[0011] 1. This invention is based on charge migration band absorption. By controlling and designing factors such as the ligand-cation type and spacing, coordination number, crystal field, crystal structure, ionic electronegativity, and ionic radius of inorganic fluorescent materials, it enables them to possess a wide and tunable excitation bandwidth, covering the ultraviolet, violet, blue, and green light regions, and achieving blue and green light excitation. Moreover, its excitation peak value is tunable over a wide range in the 400-550nm blue and green light regions, enabling simultaneous high-efficiency visible light and near-infrared emission.

[0012] 2. The broad absorption band of the inorganic fluorescent material of this invention belongs to S. 2- -D 3+ / 2+ and / or S 2- -B 3+It features charge migration band absorption and an excitation peak range that is tunable from 250 to 600 nm, fully covering and matching the emission wavelengths of commercial ultraviolet, violet, blue, and green LED chips.

[0013] 3. This invention achieves efficient visible light and / or near-infrared emission under blue and green light excitation, realizing a novel, convenient, and efficient LED light source.

[0014] 4. The inorganic fluorescent material of the present invention has the advantages of good chemical stability, good thermal stability, high luminous efficiency, non-toxicity, and environmental friendliness. At the same time, it is prepared by high-temperature solid-state method, which is mature, simple and easy to implement, with readily available raw materials, green and environmentally friendly, and has good commercial application prospects. Attached Figure Description

[0015] Figure 1 NaLa prepared in Example 1 of this invention 0.98 S2:Yb 3+ 0.02 NaGd in Comparative Example 2 0.98 S2:Yb 3+ 0.02 XRD pattern;

[0016] Figure 2 The NaLa prepared in Example 1 of this invention 0.98 S2:Yb 3+ 0.02 SEM image;

[0017] Figure 3 NaLa prepared in Example 1 0.98 S2:Yb 3+ 0.02 NaGd in Comparative Example 2 0.98 S2:Yb 3+ 0.02 The excitation spectrum;

[0018] Figure 4 NaLa prepared in Example 1 0.98 S2:Yb 3+ 0.02 NaGd in Comparative Example 2 0.98 S2:Yb 3+ 0.02 Emission spectrum under 450 nm excitation;

[0019] Figure 5 NaLa prepared in Example 4 0.995 S2:Bi 0.005 Comparison with the emission spectrum of Comparative Example 1;

[0020] Figure 6 NaY prepared in Example 220.99 S2:Mn 0.01 The excitation and emission spectra;

[0021] Figure 7 NaLa prepared in Example 1 0.98 S2:Yb 3+ 0.02 A schematic diagram of light emission after application in a phosphor-converting near-infrared LED device;

[0022] Figure 8 NaLa prepared using Example 1 0.98 S2:Yb 3+ 0.02 The prepared near-infrared LED light source was applied to the results of X-ray imaging.

[0023] Figure 9 NaLa valued in Example 4 0.995 S2:Bi 0.005 A schematic diagram of light emission after application to a phosphor-converted white LED device. Detailed Implementation

[0024] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0025] All raw materials and other reagents used below are commercially available.

[0026] Comparative Example 1

[0027] Commercial Y3Al5O 12 :Ce 3+ LED phosphor.

[0028] Comparative Example 2

[0029] NaGd 0.98 S2:Yb 3+ 0.02 The phosphor was prepared by a solid-phase reaction method.

[0030] The ternary sulfide ABS2:D of the present invention is prepared by solid-phase reaction method. The raw materials are weighed according to the stoichiometric ratio of the target sample. The raw materials can be oxides, carbonates, nitrates, acetates, sulfates, or oxalates containing elements A, B, and D. The raw materials are thoroughly ground, mixed evenly, and placed in a high-temperature furnace for calcination in a sulfidation atmosphere (CS2 or H2S) at a temperature of 800-1400℃ for 1-30 hours. A small amount of co-solvent may also be added during calcination.

[0031] Example 1

[0032] Blue light-excited near-infrared phosphor NaLa 0.98 S2:Yb 3+ 0.02 .

[0033] Preparation of NaLa by solid-state method 0.98 S2:Yb 3+ 0.02 The specific steps for obtaining the fluorescent powder are as follows: Accurately weigh the oxide raw materials according to the molar ratio of Na:La:Yb = 1.3:0.98:0.02, and grind them in an agate mortar until uniform, obtaining a mixed raw material. Then, calcine the above mixed raw material at a high temperature of 900℃ under a sulfidation atmosphere for 2 hours to obtain NaLa. 0.98 S2:Yb 3+ 0.02 .

[0034] Figure 1 The target powder NaLa was prepared using the above steps. 0.98 S2:Yb 3+ 0.02 Compared with the comparative example NaGd 0.98 S2:Yb 3+ 0.02 The X-ray diffraction (XRD) pattern shows that NaLa 0.98 S2:Yb 3+ 0.02 The XRD diffraction peaks of the sample agree well with the standard card (PDF#89-4012) for the cubic phase structure of NaLaS2, indicating a cubic phase structure. NaGd 0.98 S2:Yb 3+ 0.02 As a comparative example 2, it conforms well to standard cards PDF#73-2444, PDF#89-5281 and PDF#81-2055, and belongs to the trigonal phase structure.

[0035] Figure 2 Target powder NaLa 0.98 S2:Yb 3+ 0.02 SEM images of the map.

[0036] Figure 3 NaLa, as in Example 1 0.98 S2:Yb 3+ 0.02 Compared with NaGd in Comparative Example 2 0.98 S2:Yb 3+ 0.02A comparison of the excitation spectra shows that the center of the excitation peak in Comparative Example 2 is located at 395 nm, while that in Example 1, NaLaS2:2%Yb 3+ The excitation peak center is located at 450nm, which can be well matched with the emission of blue LEDs (440-470nm). Meanwhile, Figure 4 For NaLa 0.98 S2:Yb 3+ 0.02 Compared with NaGd in Comparative Example 2 0.98 S2:Yb 3+ 0.02 The emission spectrum of NaLa excited by a 450nm blue LED shows that, at 450nm excitation, NaLa... 0.98 S2:Yb 3+ 0.02 It emits strong near-infrared emission at 1000 nm with a relative luminous efficiency of 103%, while NaGd... 0.02 S2:Yb 3+ 0.02 It is difficult to be excited by blue light and exhibits very weak luminescence, with a relative luminous efficiency of 6%.

[0037] Examples 2-36

[0038] Different types of A and B, and different values ​​of x and y, were prepared by solid-state method. x S2:D y The calcination conditions for the materials and samples were as follows: calcination at 850°C for 2 hours in a sulfur atmosphere, followed by heating to 900°C and holding for another 2 hours, and then natural cooling to room temperature to obtain the target powders, as described in Examples 2-36.

[0039] Table 1

[0040]

[0041]

[0042]

[0043] Application Example 1

[0044] The target powder NaLa obtained in Example 1 0.98 S2:Yb 3+ 0.02 A schematic diagram of light emission applied to phosphor-converting near-infrared LED devices. Figure 7 Commercial blue LEDs (emission center: 450nm) are used as the excitation source, emitting strong near-infrared light. This near-infrared LED light source is used in non-destructive testing. Figure 8(a1-b1) White plastic bottles photographed with a regular digital camera under indoor lighting conditions; (a2-c2) and (a3-c3) Near-infrared images of the fabricated phosphor-converting near-infrared LED device before and after irradiation, photographed with a near-infrared camera under indoor lighting conditions. It can be seen that under near-infrared light irradiation, non-destructive testing can be performed on opaque containers, allowing observation of the liquid volume within the container.

[0045] Application Example 2

[0046] The target powder NaLa obtained in Example 4 0.995 S2:Bi 0.005 A schematic diagram of light emission applied to phosphor-converting white LED devices. Figure 9 Using commercial blue LEDs (emission center: 450nm) as the excitation source, a high-efficiency white LED with a wide spectral range was fabricated by emitting in the visible light region with a emission range of 500-800 nm and combining it with blue light.

[0047] The above embodiments are merely preferred embodiments of the present invention and are not intended to limit the implementation. The scope of protection of the present invention should be determined by the scope defined in the claims. Other variations or modifications can be made based on the above description. Obvious variations or modifications derived therefrom are still within the scope of protection of the present invention.

Claims

1. An application of an inorganic fluorescent material that emits near-infrared light under blue and green light excitation, characterized in that, The inorganic fluorescent material is a ternary sulfide with the chemical formula NaLa. x S2:Yb y x and y are mole fractions, x + y = 1, 0.7 ≤ x ≤ 0.999, 0.001 ≤ y ≤ 0.3; The inorganic fluorescent material achieves downconversion luminescence in the 780-2000nm near-infrared region under blue and green light excitation.

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