Preparation method and application of quantum dot fluorescent glass

Abstract

The present invention belongs to the field of fluorescent material technology, and specifically discloses a method for preparing quantum dot fluorescent glass and its application. The method for preparing quantum dot fluorescent glass mainly comprises the following steps: freeze-drying a dispersion of bismuth-based perovskite quantum dots with a core-shell structure to obtain a wet gel; then adding water to prepare a wet gel solution; dispersing the wet gel solution in the silane coupling agent, stirring and pre-hydrolyzing in the air to obtain a precursor of the quantum dot fluorescent glass. The present invention studies the conditions for spontaneous hydrolysis and condensation of APS to form glass, and in the absence of solvent, disperses bismuth-based perovskite quantum dots with a core-shell structure in spontaneously hydrolyzed and condensed APS to prepare clear, transparent, and smooth fluorescent glass, thereby realizing the spontaneous formation of quantum dot fluorescent glass in a room temperature atmospheric environment. The precursor of the quantum dot fluorescent glass is further coordinated with CdTe QDs to realize one-step dispensing of white light LEDs.

Description

Technical Field

[0001] The present invention belongs to the technical field of fluorescent materials, and particularly relates to a preparation method and application of quantum dot fluorescent glass. Background Art

[0002] Perovskite quantum dots (QDs) offer advantages such as high fluorescence efficiency, a broad excitation spectrum, and easily coordinated fluorescence peaks, making them ideal for use as emission layers in LEDs. However, due to surface effects, perovskite QDs exhibit high surface energy and are prone to aggregation, often requiring the use of insulating, long-chain organic ligands such as oleic acid and oleylamine, which limits their application in LEDs. Energy transfer between LED chips and perovskite QDs is the most feasible and effective method for fabricating perovskite QD-based LED devices.

[0003] Currently, in order to prepare white light LEDs, it is usually necessary to coordinate QDs and LED chips of two luminous colors, and dispense them through two types of silicone under vacuum or heating conditions. In this process, how to stabilize perovskite QDs in silicone and prevent the heat generated by the LED chip during long-term operation from causing thermal decomposition of QDs are problems that need to be solved. Summary of the Invention

[0004] The present invention aims to address at least one of the technical problems existing in the aforementioned prior art. To this end, the present invention proposes a method for preparing quantum dot fluorescent glass that can spontaneously form in an ambient air environment. Furthermore, the invention utilizes two luminescent colors of QDs to produce a white-light quantum dot fluorescent glass, enabling simple one-step dispensing of white-light LEDs.

[0005] To solve the above technical problems, the first aspect of the present invention provides a method for preparing quantum dot fluorescent glass, comprising the following steps:

[0006] (1) preparing a dispersion of bismuth-based perovskite quantum dots;

[0007] (2) adding a silane coupling agent to the dispersion of the bismuth-based perovskite quantum dots, and then adding water to disperse the dispersion to form an emulsion; heating to reflux the reaction, and then standing to separate the layers, and removing the lower layer solution to obtain a dispersion of bismuth-based perovskite quantum dots having a core-shell structure;

[0008] (3) freeze-drying the dispersion of the bismuth-based perovskite quantum dots having a core-shell structure to obtain a wet gel; and then adding water to prepare a wet gel solution;

[0009] (4) dispersing the wet gel solution in the silane coupling agent and pre-hydrolyzing it in air to obtain a quantum dot fluorescent glass precursor;

[0010] (5) The blue light glass precursor is drop-coated on a carrier and allowed to stand to obtain the quantum dot fluorescent glass.

[0011] Preferably, the silane coupling agent is selected from at least one of 3-aminopropyltriethoxysilane (APTES), 3-aminopropyltrimethoxysilane (APS), and tetraethoxysilane (TEOS).

[0012] Preferably, in step (2), the volume ratio of the silane coupling agent to the dispersion of the bismuth-based perovskite quantum dots is 1:10-100.

[0013] Preferably, in step (2), the reflux reaction is carried out at 100-110° C. and the reaction time is 3-24 h.

[0014] Preferably, in step (3), the concentration of the wet gel solution is 2-20 mg / μL; more preferably, the concentration of the wet gel solution is 10-20 mg / μL; further preferably, the concentration of the wet gel solution is 20 mg / μL.

[0015] Preferably, in step (4), the mass ratio of the wet gel solution to the silane coupling agent is 0.1-1:50, that is, the mass fraction of the wet gel is 0.2-2wt%; more preferably, the mass fraction of the wet gel is 1-2wt%; further preferably, the mass fraction of the wet gel is 1.02wt%.

[0016] Preferably, in step (4), the stirring pre-hydrolysis is carried out at a stirring speed of 100-300 rpm, a stirring time of 0-5 h, and room temperature; more preferably, the stirring time is 3-5 h; further preferably, the stirring time is 5 h.

[0017] Preferably, in step (5), the standing time is 1-6 hours.

[0018] Preferably, in step (5), the carrier is a cover glass.

[0019] Furthermore, the method for preparing the dispersion of bismuth-based perovskite quantum dots comprises the following steps:

[0020] 1) dispersing methylamine bromide and bismuth bromide in a mixed solvent consisting of N,N-dimethylformamide and ethyl acetate, and then adding octylamine to obtain a precursor solution;

[0021] 2) adding the precursor solution to a mixed solvent consisting of octane and oleic acid, stirring for reaction, centrifuging, and collecting the supernatant to obtain a dispersion of bismuth-based perovskite quantum dots.

[0022] Preferably, in step 1), the molar ratio of methylamine bromide, bismuth bromide and octylamine is 1:0.5-1.5:0.1-0.8.

[0023] Preferably, in step 1), the volume ratio of N,N-dimethylformamide to ethyl acetate is 1:0.5-2.

[0024] Preferably, in step 2), the volume ratio of octane to oleic acid is 1:0.1-0.2.

[0025] Preferably, in step 2), the stirring reaction is carried out at 25-85°C.

[0026] Preferably, in step 2), the centrifugation is carried out at a centrifuge speed of 7000-9000 rpm.

[0027] A second aspect of the present invention provides a quantum dot fluorescent glass prepared by the above preparation method.

[0028] A third aspect of the present invention provides a blue light LED, comprising the above-mentioned quantum dot fluorescent glass and an ultraviolet chip, wherein the quantum dot fluorescent glass is arranged on the surface of the ultraviolet chip.

[0029] Preferably, the preparation steps of the blue light LED are: drop-coating the precursor of the quantum dot fluorescent glass on the ultraviolet chip, letting it stand for 1-6 hours, and packaging to obtain the blue light LED.

[0030] A fourth aspect of the present invention provides a method for preparing a white light LED, comprising the following steps:

[0031] (1) dispersing CdTe quantum dots in the above quantum dot fluorescent glass precursor to obtain a white light glass precursor;

[0032] (2) 1-10 μL of the white light glass precursor is drop-coated on the UV chip, allowed to stand for 1-6 hours, and then packaged to obtain the white light LED.

[0033] Preferably, the concentration of the white glass precursor is 0.1-1 mg / mL; more preferably, the concentration of the white glass precursor is 0.5-1 mg / mL; further preferably, the concentration of the white glass precursor is 0.5 mg / mL.

[0034] Preferably, in step (2), the drop-coating amount of the white light glass precursor is 1-10 μL.

[0035] Preferably, in step (2), the standing time is 1-6 hours.

[0036] A fifth aspect of the present invention provides a white light LED, which is manufactured by the above-mentioned method for manufacturing a white light LED.

[0037] Compared with the prior art, the above technical solution of the present invention has at least the following technical effects or advantages:

[0038] By studying the conditions under which silane coupling agents (such as APS) spontaneously hydrolyze and condense to form glass, the present invention disperses core-shell bismuth-based perovskite quantum dots in the spontaneously hydrolyzed and condensed APS in the absence of solvents to produce clear, transparent, and smooth fluorescent glass. This quantum dot fluorescent glass spontaneously forms in an atmospheric environment at room temperature. Furthermore, the precursor for the quantum dot fluorescent glass is combined with CdTe QDs to achieve one-step dispensing of white light LEDs. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] Figure 1 This is a curve diagram showing the effect of pre-hydrolysis time on APS viscosity;

[0040] Figure 2 Fourier transform infrared spectra of glass precursors obtained at different pre-hydrolysis times;

[0041] Figure 3 Scanning electron micrographs of glasses prepared from glass precursors obtained with different pre-hydrolysis times;

[0042] Figure 4 Transparency curves of glasses prepared from glass precursors obtained with different pre-hydrolysis times;

[0043] Figure 5 Fluorescence intensity curves of blue light glasses prepared from glass precursors with different wet gel contents;

[0044] Figure 6 Photos of glasses prepared from glass precursors with different wet gel contents under sunlight and 365nm UV light;

[0045] Figure 7 The spectrum and color coordinate diagram of the blue LED prepared in Example 2;

[0046] Figure 8 The spectrum and color coordinate diagram of the white light LED prepared in Example 3;

[0047] Figure 9 This is a current density / brightness / voltage curve of the white light LED prepared in Example 3. DETAILED DESCRIPTION

[0048] The present invention is described in detail below with reference to the examples to facilitate understanding of the present invention by those skilled in the art. It is necessary to point out that the examples are only used to further illustrate the present invention and are not to be construed as limiting the scope of protection of the present invention. Non-essential improvements and adjustments made to the present invention by those skilled in the art based on the above-mentioned invention should still fall within the scope of protection of the present invention. At the same time, the raw materials mentioned below that are not described in detail are all commercially available products; the process steps or preparation methods that are not mentioned in detail are all process steps or preparation methods known to those skilled in the art.

[0049] Example 1

[0050] A method for preparing quantum dot blue light glass comprises the following steps:

[0051] (1) 0.0224 g of methylamine bromide and 0.0601 g of bismuth bromide were stirred and dispersed in a mixed solvent consisting of 1 mL of N,N-dimethylformamide and 1 mL of ethyl acetate, and 20 μL of octylamine was added to obtain a precursor solution;

[0052] (2) 5 mL of octane and 0.625 mL of oleic acid were mixed evenly and heated to 80° C., and then 0.5 mL of the precursor solution prepared in step (1) was quickly added and vigorously stirred for 1 min; then cooled to room temperature in a water bath, centrifuged at 8000 rpm, and the supernatant was collected to obtain a dispersion of bismuth-based perovskite quantum dots (denoted as MA3Bi2Br9);

[0053] (3) 75 μL of 3-aminopropyltrimethoxysilane (APS) was added to 5 mL of the dispersion of bismuth-based perovskite quantum dots, and then 5 mL of ultrapure water was added and stirred thoroughly to form an emulsion. The mixture was then heated to 105 °C and refluxed for 6 h. The mixture was naturally cooled to room temperature and allowed to stand for one day. The lower layer of solution was removed to obtain a dispersion of bismuth-based perovskite quantum dots (MA3Bi2Br9@SiO2) with a core-shell structure.

[0054] (4) The dispersion of bismuth-based perovskite quantum dots with a core-shell structure was placed at -20°C and transferred to a freeze dryer after one day. After three days, MA3Bi2Br9@SiO2 wet gel was obtained.

[0055] (5) 1 μL of water was added to every 20 mg of wet gel to assist its good dispersion in APS. The wet gel was dispersed in APS at 1.2 wt %, and pre-hydrolyzed by stirring in air to obtain a precursor of quantum dot blue light glass.

[0056] (6) 600 μL of blue light glass precursor was drop-coated on a coverslip (30 mm in diameter) and allowed to stand for 6 h to obtain quantum dot blue light glass.

[0057] Before preparing the quantum dot fluorescent glass of the present invention, the applicant conducted preliminary research on 3-aminopropyltrimethoxysilane (APS), that is, in step (5) of Example 1, the mass ratio of wet gel to APS was adjusted to 0:1, and the mass fraction of wet gel was 0wt%. The research results are as follows: Figure 1-4 shown.

[0058] Figure 1 The curve of the effect of pre-hydrolysis time on APS viscosity is shown in Figure 2. Figure 1 a is a graph showing the viscosity of the glass precursor obtained by changing the pre-hydrolysis time as a function of shear rate, and ... Figure 1 b) By Figure 1 It can be seen that when the pre-hydrolysis time is less than or equal to 2 hours, the viscosity of the glass precursor solution hardly changes and hardly changes with increasing shear rate, showing Newtonian fluid properties, indicating that the APS is mainly undergoing hydrolysis reaction at this time, that is, Si-OCH3 hydrolyzes to form Si-OH. However, when the pre-hydrolysis time reaches 3 hours, the viscosity increases significantly and shows an almost linear increase with time. At the same time, the viscosity of the glass precursor shows shear thinning at low shear rates, indicating that the APS begins to undergo condensation reaction, that is, Si-OH condenses to form Si-O-Si, and entangles with each other to gradually form a network structure.

[0059] Figure 2 Fourier transform infrared spectra of glass precursors obtained at different pre-hydrolysis times. Figure 2 The horizontal axis Wavenumber represents the wave number, and the vertical axis Transmitance represents the transmittance. Figure 2 It can be seen that when APS does not undergo hydrolysis and condensation, the -1 The peak of Si-OC appears at 925cm-1. When the pre-hydrolysis time is within 2h, the peak intensity gradually weakens. -1 The peak of Si-OH appeared at 1019cm and gradually increased, indicating the occurrence of hydrolysis reaction. As the pre-hydrolysis time continued to increase, the peak at 1019cm -1 The peak of Si-O-Si appears at the bottom and gradually becomes the strongest peak, indicating the occurrence of condensation reaction. Figure 1 The conclusions obtained support each other.

[0060] Figure 3 Scanning electron micrographs of the glass prepared from glass precursors obtained with different pre-hydrolysis times. Figure 3It can be seen that the surface of the glass formed by the precursor with a pre-hydrolysis time of less than 2 hours is relatively rough, with many small protrusions unevenly distributed. When the pre-hydrolysis time is greater than 3 hours, these protrusions gradually become smaller, but there are still many wrinkles on the surface. When the pre-hydrolysis time reaches 5 hours, the surface of the obtained glass is smooth and flat. This is because when the pre-hydrolysis time is short, the incompletely hydrolyzed precursor continuously generates methanol during the condensation stage, and the volatilization of methanol causes stress to form inside the glass, making the surface rough.

[0061] Figure 4 Transparency (T) curves of glasses prepared from glass precursors obtained with different pre-hydrolysis times. Figure 4 The horizontal axis Wavelength represents the wavelength. Figure 4 It can be seen that as the prehydrolysis time increases, the transparency of the obtained glass gradually increases. When the prehydrolysis time reaches 5 hours, the transmittance of the obtained glass reaches 90%.

[0062] Example 2

[0063] A preparation method of a blue light LED comprises the following steps:

[0064] 10 μL of the quantum dot blue light glass precursor prepared in Example 1 was dropped into a 365 nm ultraviolet chip, and the chip was allowed to stand for 1 hour before packaging to obtain a blue light LED.

[0065] Example 3

[0066] A preparation method of a white light LED comprises the following steps:

[0067] (1) Dispersing 0.4 mg of CdTe QDs in 800 μL of the quantum dot blue light glass precursor prepared in Example 1 to obtain a white light glass precursor;

[0068] (2) 10 μL of the white light glass precursor prepared in step (1) was dropped into a 365 nm UV chip, allowed to stand for 1 hour, and then packaged to obtain a white light LED.

[0069] Performance Testing

[0070] Referring to the method of Example 1 of the present invention, a series of fluorescent glasses were obtained by changing the mass fraction of the wet gel in step (5) (0.1wt%, 0.2wt%, 0.4wt%, 0.6wt%, 0.8wt%, 1wt%, 1.2wt%, 1.4wt%, 1.6wt%, 1.8wt%, 2wt%), and then the fluorescence intensity test was performed. The test results are as follows: Figure 5 As shown. Figure 5As the wet gel concentration increases from 0.1wt% to 1wt%, the brightness of the fluorescent glass precursor increases by approximately 4.2 times. As the wet gel concentration further increases to 2wt%, the brightness of the fluorescent glass is almost equivalent to that at 1wt%, indicating that the fluorescence intensity of the fluorescent glass reaches saturation when the wet gel concentration reaches 1wt%. The brightness-wet gel concentration data were fitted with a Chapman-Richards growth function, and the saturated wet gel concentration was determined to be 1.02wt% (saturation point).

[0071] Referring to the method of Example 1 of the present invention, by changing the mass fraction of the wet gel in step (5) to 0wt%, a control fluorescent glass was obtained, which was placed under daylight (room light) and 365nm ultraviolet light together with the quantum dot blue light glass obtained in Example 1, respectively, to obtain the following: Figure 6 The two pictures on the left are the control fluorescent glass, and the two pictures on the right are the quantum dot blue light glass prepared in Example 1. Figure 6 As can be seen, the quantum dot blue light glass prepared in Example 1 exhibits bright blue light emission under a 365nm UV lamp, indicating that it is feasible to form fluorescent glass by doping wet gel into APS. In daylight, both the glass containing and not containing wet gel are clear and transparent.

[0072] Figure 7 This is the spectral curve of the blue light LED prepared in Example 2 when driven by a voltage of 3V (the horizontal axis Wavelength represents wavelength, and the vertical axis Intensity represents intensity), and the color coordinates (0.196, 0.305). The inset is a physical picture of the blue light LED.

[0073] Figure 8 This is the spectral curve of the white light LED prepared in Example 3 when driven by a voltage of 3V, and the color coordinates are (0.318, 0.299). The color temperature is 6377K, which is positive white light. The color rendering index is 67.78, which has good color rendering properties. The illustration is a physical picture of the white light LED.

[0074] Figure 9 The current density / brightness / voltage (J / L / V) curve of the white light LED prepared in Example 3 is shown in FIG. Figure 9 It can be seen that it has a small turn-on voltage of about 2.9V, and with the increase of the driving voltage (Vlotage), the device brightness (Luminance) gradually increases, and its maximum brightness is as high as 95000cd / m 2 ; Figure 9As can be seen from Figure b, its maximum current efficiency (Current efficiency) and optical power efficiency (Power efficiency) are 0.26cd / A and 0.16lm / W respectively.

[0075] For those skilled in the art to which the present invention belongs, a number of simple deductions or substitutions can be made without departing from the concept of the present invention, without having to resort to creative work. Therefore, based on the disclosure of the present invention, simple improvements made by those skilled in the art to the present invention should be within the scope of protection of the present invention. The above embodiments are preferred embodiments of the present invention, and all processes similar to the present invention and equivalent changes made should fall within the scope of protection of the present invention.

Claims

1. A method for preparing quantum dot fluorescent glass, characterized in that: The following steps are involved: (1) Preparation of a dispersion of bismuth-based perovskite quantum dots; (2) adding a silane coupling agent to the dispersion of the bismuth-based perovskite quantum dots, and then adding water to disperse the dispersion to form an emulsion; heating to reflux the reaction, and then standing to separate the layers, taking out the lower layer solution, and obtaining a dispersion of the bismuth-based perovskite quantum dots having a core-shell structure; The silane coupling agent is selected from at least one of 3-aminopropyltriethoxysilane and 3-aminopropyltrimethoxysilane; (3) freeze-drying the dispersion of the core-shell bismuth-based perovskite quantum dots to obtain a wet gel; then adding water to prepare a wet gel solution with a concentration of 2-20 mg / μL; (4) dispersing the wet gel solution in the silane coupling agent, wherein the mass ratio of the wet gel solution to the silane coupling agent is (0.1-1):50, and pre-hydrolyzing the mixture in air at room temperature, wherein the stirring speed is 100-300 rpm and the stirring time is 0-5 h, to obtain a precursor of quantum dot fluorescent glass; (5) The precursor of the quantum dot fluorescent glass is drop-coated on a carrier and allowed to stand to obtain the quantum dot fluorescent glass.

2. The method for preparing quantum dot fluorescent glass according to claim 1, wherein: In step (2), the volume ratio of the silane coupling agent to the dispersion of the bismuth-based perovskite quantum dots is 1:10-100; the reflux reaction is carried out at 100-110° C. for 3-24 hours.

3. The method for preparing quantum dot fluorescent glass according to claim 1, wherein: In step (5), the standing time is 1-6 hours.

4. A quantum dot fluorescent glass, characterized in that: Prepared by the preparation method according to any one of claims 1 to 3.

5. A blue light LED, characterized in that: It comprises the quantum dot fluorescent glass according to claim 4 and an ultraviolet chip, wherein the quantum dot fluorescent glass is arranged on the surface of the ultraviolet chip.

6. A method for preparing a white light LED, characterized in that: The following steps are involved: (1) Dispersing CdTe quantum dots in the precursor of the quantum dot fluorescent glass according to claim 4 to obtain a white light glass precursor; (2) The white light glass precursor is drop-coated on the UV chip, allowed to stand, and packaged to obtain the white light LED.

7. A white light LED, characterized in that: The white light LED is prepared by the preparation method of claim 6.

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