Single-matrix lead-free double perovskite warm white light fluorescent powder, preparation method and application thereof

Abstract

The application provides a single-matrix lead-free double-perovskite warm white light fluorescent powder and a preparation method and application thereof, and relates to the fields of fluorescent materials and semiconductor lighting technology. + Partly replace Na + , Bi 3+ Partly replace Y 3+ Cs2Na 1‑x Ag x Y 1‑y Bi y Cl6 component, 0.3<=x<=0.5, 0.005<=y<=0.02, and is prepared by using a low-temperature solvothermal method. The core innovation is that the energy level distribution of the matrix is controlled by synergistic doping, high-efficiency excitation in the full visible light band of 400-800 nm is realized, the PLQY is as high as 96.59%, the emission spectrum continuously covers the full visible light and fills the "blue gap", the lead-free formula meets the environmental protection requirements, and the preparation process is mild and controllable. Based on the white light LED packaged by the fluorescent powder, the color coordinates are close to (0.41, 0.38), the color temperature is adjustable in the range of 2700-6500K, the color rendering index is greater than or equal to 90, the application is suitable for indoor lighting, display backlight and other scenes, and the industrialization application of the high-performance lead-free double-perovskite fluorescent powder in the white light LED is effectively promoted.

Description

Technical Field

[0001] This invention relates to the field of fluorescent materials and semiconductor lighting technology, specifically to a single-matrix lead-free double perovskite warm white phosphor, its preparation method, and its application. Background Technology

[0002] White LEDs, as a new generation of solid-state lighting sources, have advantages such as energy saving, long lifespan, and environmental friendliness; however, their performance improvement is limited by the core characteristics of phosphors. Currently, the mainstream implementation methods for white LEDs have significant drawbacks: Blu-ray chip + YAG:Ce 3+ Yellow phosphor combinations: lack red spectral components, have a low color rendering index (usually <80), and cannot meet the full spectrum requirements of indoor lighting; Near-ultraviolet chip + multi-matrix red / green / blue phosphor combination: There are large differences in energy utilization efficiency between different matrices, there is radiation reabsorption interference, low luminous efficiency, and color drift is easy to occur; Existing single-matrix phosphors: Sb-dependent 3+ / Ln 3+ (Ln=Sm, Ho, Eu) co-doping limits the excitation band to the ultraviolet region and has poor adaptability; the single component PLQY is low (usually <85%), and the emission spectrum has a "cyan gap" (missing 480-520nm band), which affects the light color quality; Lead-based perovskite phosphors: Although they have excellent luminescent properties, they contain lead, which is toxic and does not meet the environmental protection requirements of the green lighting industry; multi-component mixed systems are prone to anion exchange, resulting in insufficient stability.

[0003] Existing technologies have failed to simultaneously resolve the core contradictions of "lead-free and environmentally friendly, full-spectrum excitation, high PLQY, filling cyan gaps, and high stability".

[0004] Therefore, developing a lead-free, full-spectrum responsive, high-efficiency, and highly stable single-matrix warm white phosphor has become a key to promoting the upgrading of white LED technology. Summary of the Invention

[0005] To address the shortcomings of existing technologies, this invention provides a single-matrix lead-free double perovskite warm white phosphor, its preparation method, and its applications. It is suitable for white LED device packaging and can be widely used in indoor lighting, LCD backlighting, decorative lighting, and other scenarios. It solves the core contradictions of existing technologies that fail to simultaneously address "lead-free and environmentally friendly, full-spectrum excitation, high PLQY, filling cyan gaps, and high stability".

[0006] To achieve the above objectives, the present invention provides the following technical solution: A single-matrix lead-free double perovskite warm white phosphor, wherein the phosphor uses lead-free double perovskite Cs₂NaYCl₆ as the matrix and is activated by Ag. + with Bi 3+ Co-doping forms a substituted composite phosphor with the general chemical formula Cs₂Na. 1-x Ag x Y 1-y Bi y Cl6, where x is Ag + The doping molar ratio, with values ​​ranging from 0.3 ≤ x ≤ 0.5, where y is the molar ratio of Bi. 3+ The molar ratio of doping has a range of 0.005 ≤ y ≤ 0.02; The excitation spectrum of the phosphor covers the 220-380nm light band, the emission spectrum continuously covers the 400-800nm ​​band, the photoluminescence quantum yield (PLQY) is ≥90%, and the color rendering index (CRI) is ≥90.

[0007] Furthermore, in the general chemical formula, x=0.4 and y=0.01, meaning the specific component of the phosphor is Cs₂Na. 0.6 Ag 0.4 Y 0.99 Bi 0.01 Cl6 has a PLQY of 96.59%, color coordinates of (0.41, 0.38), color temperature of 3296K, and a color rendering index of 96.5.

[0008] Furthermore, the phosphor has a cubic perovskite crystal structure with a lattice constant a = 0.55-0.57 nm and a particle size of 10-50 nm. It exhibits good dispersion.

[0009] Furthermore, the preparation method of this single-matrix lead-free double perovskite warm white phosphor includes the following steps: Step 1: Raw material ratio Weigh out CsCl, NaCl, AgCl, YCl3·6H2O, and BiCl3 according to the stoichiometric ratio of the chemical formula, wherein the molar amount of CsCl is 1 mmol, the total molar amount of NaCl and AgCl is 0.4-0.6 mmol, and the total molar amount of YCl3·6H2O and BiCl3 is 0.5 mmol. Step 2: Mix and dissolve Add the above raw materials to the reaction vessel, add 0.6-1.0 mL of 12M concentrated hydrochloric acid, and stir until the raw materials are completely dissolved to form a homogeneous mixed solution; Step 3: Solvothermal reaction After sealing the reactor, place it in a drying oven and keep it at 170-190℃ for 10-14 hours to carry out a solvothermal reaction. Step 4: Post-processing After the reaction is complete, the reactor is naturally cooled to room temperature. The product is washed 2-3 times by centrifugation with isopropanol, and then dried in an oven at 55-65℃ for 4-6 hours. After grinding, a single-matrix lead-free double perovskite warm white phosphor can be obtained.

[0010] Furthermore, in step three, the temperature of the solvothermal reaction is 180°C, and the holding time is 12 hours. In step four, the centrifugal cleaning speed is 3000-8000 r / min, and the cleaning time is 5-10 min each time.

[0011] Furthermore, all raw materials are analytical grade reagents, with YCl3・6H2O having a purity ≥99.9% and AgCl and BiCl3 having a purity ≥99.5%, to avoid impurities affecting fluorescence performance.

[0012] Furthermore, the application method of this single-matrix lead-free double perovskite warm white phosphor is as follows: the phosphor is mixed with epoxy resin A and epoxy resin B to form a uniform suspension, which is then coated on the surface of a 340-365nm near-ultraviolet LED chip, dried at 55-65℃ for 2-4 hours, and then encapsulated to obtain a warm white LED device.

[0013] Furthermore, the white LED device has an adjustable color temperature range of 2700-6500K, an operating voltage of 2.8-3.2V, and an operating current of 20-100mA.

[0014] This invention provides a single-matrix lead-free double perovskite warm white phosphor, its preparation method, and its application. It possesses the following beneficial effects: 1. This invention provides a single-matrix lead-free double perovskite warm white phosphor, its preparation method, and its application, using Ag. + / Bi 3+ Dual-ion co-doped Cs₂NaYCl₆ matrix, Ag + Optimize the matrix crystal field environment, Bi 3+ As active luminescent centers, the two work together to regulate the matrix energy level distribution, achieving efficient excitation in the entire visible light band of 400-800nm. This breaks through the limitation of traditional doping, which can only respond to ultraviolet light. Furthermore, through precise control of the doping ratio, the emission spectrum can continuously cover the entire visible light region of 400-800nm, filling the "cyan gap" and solving the color drift problem caused by multi-matrix mixing.

[0015] 2. This invention provides a single-matrix lead-free double perovskite warm white phosphor, its preparation method, and its application. It adopts full-spectrum excitation and emission, fills the "cyan gap," achieves a PLQY of up to 96.59%, a color rendering index ≥90, and produces a natural and soft light color that is close to natural light, improving lighting comfort. It completely eliminates lead, complies with EU RoHS and other environmental standards, avoids lead pollution risks, and conforms to the development trend of the green lighting industry. The excitation spectrum covers 400-800nm ​​and can be adapted to various LED chips such as near-ultraviolet and blue light. The packaging process is simple and has strong compatibility. Attached Figure Description

[0016] Figure 1 This is a flowchart illustrating the preparation method of the single-matrix lead-free double perovskite warm white phosphor of the present invention. Figure 2 This is a schematic diagram of the molding process of the single-matrix lead-free double perovskite warm white phosphor of the present invention; Figure 3 The present invention relates to the double perovskite material Cs2Na. 0.6 Ag 0.4 Y 0.99 Bi 0.01 X-ray diffraction pattern of Cl6; Figure 4a \4b represents the double perovskite material Cs2Na of this invention. 0.6 Ag 0.4 Y 0.99 Bi 0.01 Spectrum of Cl6; Figure 5 A schematic diagram of the color coordinates of an LED device prepared with the phosphor of the present invention; Figure 6 This is a color coordinate site diagram of the LED device prepared with the phosphor of the present invention. Detailed Implementation

[0017] The present invention will now be described in further detail with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and not intended to limit it. Furthermore, it should be noted that, for ease of description, the accompanying drawings show only the parts relevant to the present invention, and not all of the structures.

[0018] In the description of this invention, unless otherwise explicitly specified and limited, the terms "connected," "linked," and "fixed" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0019] In this invention, unless otherwise explicitly specified and limited, "above" or "below" the second feature can include direct contact between the first and second features, or contact between the first and second features through another feature between them. Furthermore, "above," "over," and "on top" of the second feature includes the first feature directly above or diagonally above the second feature, or simply indicates that the first feature is at a higher horizontal level than the second feature. "Below," "below," and "under" the second feature includes the first feature directly below or diagonally below the second feature, or simply indicates that the first feature is at a lower horizontal level than the second feature.

[0020] In the description of this embodiment, the terms "upper," "lower," "right," etc., refer to the orientation or positional relationship shown in the accompanying drawings. They are used only for ease of description and simplification of operation, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on the present invention. In addition, the terms "first" and "second" are used only for distinction in description and have no special meaning.

[0021] The technical solution of the present invention will be further described below with reference to the accompanying drawings and specific embodiments.

[0022] like Figures 1-6 As shown, this embodiment of the invention provides a single-matrix lead-free double perovskite warm white phosphor, selecting Cs2NaYCl6 as the lead-free double perovskite matrix, which has a stable cubic crystal structure and a good photoluminescence basis, through Ag... + with Bi 3+ Co-doping forms substituted composite phosphors; Ag + radius and Na + Approaching (Ag) + Radius 115 pm, Na + (Radius 102 pm), can efficiently replace Na in the crystal lattice + Optimize the matrix electronic structure; Bi 3+ As a heavy atom, it enhances the probability of radiative transitions through spin-orbit coupling, becoming the core luminescent center. The two work together to achieve full-spectrum excitation and efficient luminescence.

[0023] The general chemical formula is: Cs₂Na 1-x Ag x Y 1-y Bi y Cl6, where x is Ag + The doping molar ratio, with values ​​ranging from 0.3 ≤ x ≤ 0.5, where y is the molar ratio of Bi. 3+The molar ratio of doping is taken in the range of 0.005 ≤ y ≤ 0.02; when x < 0.3, the matrix crystal structure is prone to distortion, and when x > 0.5, Ag... + It is prone to aggregation; when y < 0.005, the luminescence intensity is insufficient, and when y > 0.02, concentration quenching occurs, leading to a decrease in PLQY.

[0024] The excitation spectrum of the phosphor covers the 220-380nm light band, the emission spectrum continuously covers the 400-800nm ​​band, the photoluminescence quantum yield PLQY≥90%, and the color rendering index CRI≥90.

[0025] In the general chemical formula, x = 0.4 and y = 0.01, meaning the specific component of the phosphor is Cs₂Na. 0.6 Ag 0.4 Y 0.99 Bi 0.01 Cl6 has a PLQY of 96.59%, color coordinates of (0.41, 0.38), color temperature of 3296K, and a color rendering index of 96.5.

[0026] The preparation method of this single-matrix lead-free double perovskite warm white phosphor includes the following detailed steps: Step 1: Raw material ratio According to the general chemical formula Cs2Na 0.6 Ag 0.4 Y 0.99 Bi 0.01 For Cl6 measurement, weigh out 1 mmol CsCl, 0.24 mmol NaCl, 0.16 mmol AgCl, 0.495 mmol YCl3・6H2O, and 0.005 mmol BiCl3. All raw materials must be of analytical grade or higher to avoid the introduction of impurities.

[0027] Step 2: Mix and dissolve Add the above raw materials to a 20 mL polytetrafluoroethylene-lined reactor, add 0.8 mL of 12 M concentrated hydrochloric acid, and stir magnetically for 30 min to ensure that the raw materials are completely dissolved and form a transparent and uniform mixed solution. The role of concentrated hydrochloric acid is to inhibit the hydrolysis of the raw materials, maintain the acidic environment of the reaction system, and ensure the stability of the perovskite crystal structure.

[0028] Step 3: Solvothermal reaction The sealed reactor was placed in a programmed temperature drying oven and heated to 180°C at a rate of 5°C / min, and held at that temperature for 12 hours to carry out a solvothermal reaction. The mild reaction conditions can avoid excessive crystal growth and agglomeration, and ensure uniform particle morphology.

[0029] Step 4: Post-processing After the reaction was completed, the drying oven was closed and the reactor was allowed to cool naturally to room temperature. The reactor was then opened, and the product was transferred to a centrifuge tube. Isopropanol was added, and the product was centrifuged and washed three times at 9000 r / min for 8 min each time to remove unreacted raw materials and impurities. The washed product was then placed in a 60℃ oven and dried for 5 h. After grinding, a well-dispersed single-matrix lead-free double perovskite warm white phosphor was obtained.

[0030] The application scheme is as follows: White LED encapsulation: The prepared phosphor and epoxy resin A are mixed at a mass ratio of 1:5 and stirred to form a uniform suspension. Then, an equal mass of epoxy resin B (curing agent) is added and stirred for 15 minutes. The mixed colloid was uniformly coated onto the surface of a 340-365nm near-ultraviolet LED chip, with the thickness controlled at 0.1-0.2mm. The coated chip was placed in a 60℃ oven to dry for 3 hours to complete the curing and encapsulation, resulting in a warm white LED device.

[0031] Performance control: By adjusting the mixing ratio of phosphor and adhesive, the color temperature can be flexibly adjusted between 2700-6500K. The warm white light range is 2700-4000K with a color rendering index ≥92, which is suitable for indoor lighting; the cool white light range is 5000-6500K, which is suitable for display backlighting.

[0032] Implementation Case 1: Preparation of Phosphor Raw materials: CsCl (1 mmol, 0.168 g), NaCl (0.24 mmol, 0.014 g), AgCl (0.16 mmol, 0.023 g), YCl3·6H2O (0.495 mmol, 0.183 g), BiCl3 (0.005 mmol, 0.001 g), 0.8 mL of 12 M concentrated hydrochloric acid; Equipment: 20mL PTFE-lined reactor, magnetic stirrer, programmed temperature drying oven, high-speed centrifuge, electric constant temperature oven; Steps: Follow steps one through four of the above technical solution to finally obtain Cs2Na. 0.6 Ag 0.4 Y 0.99 Bi 0.01 Cl6 phosphor; Performance testing: The excitation spectrum covered 220-380 nm, the emission spectrum 400-800 nm, and the PLQY was 96.59% as measured by a fluorescence spectrometer. The color coordinates were (0.41, 0.38), the color temperature was 3296K, and the color rendering index was 96.5, as measured by a colorimeter.

[0033] Implementation Case 2: White LED Packaging Encapsulation materials: prepared phosphor, epoxy resin A, epoxy resin B, 365nm near-ultraviolet LED chip, power 1W; Packaging steps: Mix phosphor and A glue in a mass ratio of 1:5, add an equal mass of B glue, stir evenly, coat the chip surface, and dry at 60℃ for 3 hours; Device performance: operating voltage 3.0V, operating current 50mA, luminous efficiency 120lm / W, color temperature 3296K, color rendering index 96.5.

[0034] Implementation Case 3: Comparative Experiment The phosphor of the present invention is combined with existing Sb 3+ / Eu 3+ The results of co-doped Cs₂NaYCl₆ phosphors are shown in the table below: Performance indicators The fluorescent powder of this invention Existing phosphors Excitation band 220-380nm (ultraviolet) 300-380nm (ultraviolet) PLQY 96.59% 82.3% Color rendering index 96.5 81.5 Color temperature range 2700-6500K (adjustable) 4500-6000K (narrow range) Environmental protection Lead-free Lead-free (some contain heavy metal doping) The above comparison results show that the phosphor of the present invention is significantly superior to the phosphor of the prior art in terms of excitation band, luminous efficiency, color quality and stability.

[0035] The following points should be noted in this article: 1. The accompanying drawings of the embodiments disclosed herein only relate to the structures involved in the embodiments disclosed herein; other structures can be referred to in a general design.

[0036] 2. Where there is no conflict, the embodiments of this disclosure and the features in the embodiments can be combined with each other to obtain new embodiments.

[0037] Although embodiments of the present invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions, and variations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without inventive effort are within the scope of protection of the present invention.

Claims

1. A single-matrix lead-free double perovskite warm white phosphor, characterized in that, The phosphor uses lead-free double perovskite Cs2NaYCl6 as the matrix and is processed by Ag. + with Bi 3+ Co-doping forms a substituted composite phosphor with the general chemical formula Cs₂Na. 1- x Ag x Y 1-y Bi y Cl6, where x is Ag + The doping molar ratio, with values ​​ranging from 0.3 ≤ x ≤ 0.5, where y is the molar ratio of Bi. 3+ The molar ratio of doping has a range of 0.005 ≤ y ≤ 0.02; The excitation spectrum of the phosphor covers the 220-380nm light band, the emission spectrum continuously covers the 400-800nm ​​band, the photoluminescence quantum yield (PLQY) is ≥90%, and the color rendering index (CRI) is ≥90.

2. The single-matrix lead-free double perovskite warm white phosphor according to claim 1, characterized in that, In the general chemical formula, x = 0.4 and y = 0.01, meaning the specific component of the phosphor is Cs₂Na. 0.6 Ag 0.4 Y 0.99 Bi 0.01 Cl6 has a PLQY of 96.59%, color coordinates of (0.41, 0.38), color temperature of 3296K, and a color rendering index of 96.

5.

3. The single-matrix lead-free double perovskite warm white phosphor according to claim 1, characterized in that, The phosphor has a cubic perovskite crystal structure with a lattice constant a = 0.55-0.57 nm and a particle size of 10-50 nm. It exhibits good dispersion.

4. A method for preparing a single-matrix lead-free double perovskite warm white phosphor as described in any one of claims 1-3, characterized in that, Includes the following steps: Step 1: Raw material ratio Weigh out CsCl, NaCl, AgCl, YCl3·6H2O, and BiCl3 according to the stoichiometric ratio of the chemical formula, wherein the molar amount of CsCl is 1 mmol, the total molar amount of NaCl and AgCl is 0.4-0.6 mmol, and the total molar amount of YCl3·6H2O and BiCl3 is 0.5 mmol. Step 2: Mix and dissolve Add the above raw materials to the reaction vessel, add 0.6-1.0 mL of 12M concentrated hydrochloric acid, and stir until the raw materials are completely dissolved to form a homogeneous mixed solution; Step 3: Solvothermal reaction After sealing the reactor, place it in a drying oven and keep it at 170-190℃ for 10-14 hours to carry out a solvothermal reaction. Step 4: Post-processing After the reaction is complete, the reactor is allowed to cool naturally to room temperature. The product is washed 2-3 times with isopropanol by centrifugation, and then dried in an oven at 55-65℃ for 4-6 hours. Finally, it is ground in an agate mill for 20 minutes to obtain a single-matrix lead-free double perovskite warm white phosphor.

5. The preparation method of the single-matrix lead-free double perovskite warm white phosphor according to claim 4, characterized in that, The temperature of the solvothermal reaction in step three is 180℃, and the holding time is 12h. In step four, the centrifugal cleaning speed is 3000-8000 r / min, and the cleaning time is 5-10 min each time.

6. The method for preparing the single-matrix lead-free double perovskite warm white phosphor according to claim 4, characterized in that, All raw materials are analytical grade reagents, with YCl3・6H2O having a purity ≥99.9% and AgCl and BiCl3 having a purity ≥99.5%, to avoid impurities affecting fluorescence performance.

7. The application of a single-matrix lead-free double perovskite warm white phosphor as described in any one of claims 1-3, characterized in that, The phosphor is mixed with epoxy resin A and epoxy resin B to form a uniform suspension, which is then coated onto the surface of a 340-365nm near-ultraviolet LED chip. After drying at 55-65℃ for 2-4 hours, the chip is encapsulated to obtain a warm white LED device.

8. The application of the single-matrix lead-free double perovskite warm white phosphor according to claim 7, characterized in that, The white LED device has an adjustable color temperature range of 2700-6500K, an operating voltage of 2.8-3.2V, and an operating current of 20-100mA.

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