Polymer-coated perovskite quantum dot and green preparation method thereof

Abstract

The invention provides a polymer-coated perovskite quantum dot and a green preparation method thereof, and the method comprises the following steps: dissolving a lead salt, a cesium salt and oleic acid in a solvent to obtain a precursor solution; mixing the precursor solution and 3-aminopropyltrimethoxysilane in a green solvent containing PVP (Polyvinyl Pyrrolidone), and stirring to obtain a perovskite quantum dot coated with a polymer; the green solvent in the green solvent containing PVP comprises ethyl acetate and ethanol. According to the preparation method, the stability and the quantum yield of the quantum dot are improved by coating the CsPbBr3 quantum dot with the PVP polymer, so that the quantum dot is superior to the prior art in the aspects of monodispersity, stability and fluorescence efficiency. Due to high quantum yield and stability, the quantum dot disclosed by the invention is particularly suitable for the fields of white light LEDs and Micro-LEDs, and shows potential application value in a low-cost, wide-color-gamut and high-definition display technology.

Description

Technical Field

[0001] The present invention belongs to the field of nanotechnology, and particularly relates to a polymer-coated perovskite quantum dot and a green preparation method thereof. Background Art

[0002] In the field of modern display technology, perovskite quantum dots are widely regarded as one of the key materials for the next-generation display technology due to their unique optical properties and wide color gamut coverage ability. The size controllability and tunable bandgap of perovskite quantum dots enable them to exhibit great application potential in fields such as light-emitting diodes (LEDs), solar cells, and photodetectors. Especially in Micro-LED and quantum dot display technology (QLED), perovskite quantum dots can achieve high-efficiency light conversion and high color saturation, thus providing a more delicate and vivid visual experience.

[0003] Traditional perovskite preparation methods often rely on toxic organic solvents and complex high-temperature thermal injection operations. Commonly used toxic solvents are toluene and chlorobenzene. These solvents not only cause environmental pollution but also pose a threat to the health of operators. The extensive use of toxic antisolvents seriously affects the sustainable development of perovskite quantum dots. Therefore, there is an urgent need to develop more green and efficient solvents to replace toxic solvents and achieve sustainable development.

[0004] In the research of green synthesis of perovskite quantum dots, common preparation techniques are achieved by replacing toluene with green solvents such as water, n-hexane, isopropanol, and ethyl acetate through room-temperature ligand-assisted reprecipitation method. This synthesis method and the used solvents are environmentally friendly and simple. However, the perovskite structure has poor structural stability in polar solvents and will destroy the surface ligands of perovskite, resulting in generally low photoluminescence properties such as quantum yield of the prepared quantum dots and poor optical and thermal stability. Summary of the Invention

[0005] In view of this, the purpose of the present invention is to provide a polymer-coated perovskite quantum dot and a green preparation method thereof. The quantum dot solution prepared by this method has good optical properties, high quantum yield, and monodispersity; the preparation method is green and environmentally friendly, can achieve large-scale industrial production, realize high-resolution and high-precision patterning, and is widely used in fields such as Mini / Micro-LED and LCD backlight modules.

[0006] The present invention provides a green preparation method of a polymer-coated perovskite quantum dot, comprising the following steps:

[0007] Dissolve a lead salt, a cesium salt, and oleic acid in a solvent to obtain a precursor solution;

[0008] Mix the precursor solution and 3-aminopropyltrimethoxysilane in a green solvent containing PVP, and stir to obtain polymer-coated perovskite quantum dots.

[0009] In the green solvent containing PVP, the green solvent includes ethyl acetate and ethanol.

[0010] The present invention relates to a method for preparing CsPbBr3 perovskite quantum dots at room temperature using a green solvent coated with the polymer polyvinylpyrrolidone (PVP). This method is synthesized in one step in a green mixed solvent of ethyl acetate and ethanol through a ligand (3-aminopropyltrimethoxysilane and oleic acid as ligands) assisted reprecipitation technique, avoiding the use of toxic organic solvents, achieving efficient preparation at room temperature, and the prepared perovskite quantum dot solution has a high fluorescence quantum yield of 97%.

[0011] In the present invention, a lead salt, a cesium salt, and oleic acid are dissolved in a solvent to obtain a precursor solution. The lead salt is PbBr2; the cesium salt is CsBr; the solvent is dimethylformamide (DMF).

[0012] In the present invention, the molar amount of the lead salt, the molar amount of the cesium salt, the volume of oleic acid, and the volume ratio of the solvent are 0.4 mmol: 0.4 mmol: 200 μL: (9.8 - 10.2) mL.

[0013] After obtaining the precursor solution, the present invention mixes the precursor solution and 3-aminopropyltrimethoxysilane in a green solvent containing PVP, and stirs to obtain perovskite quantum dots.

[0014] In the present invention, 3-aminopropyltrimethoxysilane (APTMS) and oleic acid are used as ligands to guide the oriented growth of crystals during the formation of quantum dots; APTMS also forms a silica layer through two steps of hydrolysis and polycondensation to increase the stability of quantum dots. APTMS reacts with water through hydrolysis to generate silanol (Si-OH), and then the silanols undergo dehydration condensation to form Si-O-Si bonds, that is, the silica layer, and the silica layer is formed inside the PVP layer. The metal element of the quantum dots is Pb, and the halogen is Br.

[0015] In the present invention, the volume ratio of the precursor solution, 3-aminopropyltrimethoxysilane, and the green solvent containing PVP is 1 mL: (5 - 20) μL: (95 - 105) mL.

[0016] In the present invention, the green solvent in the green solvent containing PVP includes ethyl acetate and ethanol; the volume ratio of ethyl acetate and ethanol is 4.5 - 5.5:1. Compared with the traditional antisolvent toluene, ethyl acetate and ethanol have lower environmental impact and toxicity, and are more suitable for large-scale industrial production.

[0017] In the present invention, the concentration of PVP in the green solvent containing PVP is 30 - 40 mmol / L. PVP plays an auxiliary role in the synthesis of quantum dots. It can not only bind to the surface vacancies of perovskite as a ligand, but also coat the surface of the quantum dots with a PVP shell layer.

[0018] In the present invention, the stirring rate is 580 - 620 rpm, and the stirring time is 55 - 65 min. The present invention promotes the mixing of reactants through high-speed stirring, realizes the nucleation and growth of perovskite quantum dots, and inhibits aggregation.

[0019] The preparation of the perovskite quantum dot solution in the present invention is carried out at room temperature without high-temperature thermal injection, which simplifies the operation process and reduces energy consumption.

[0020] The perovskite quantum dots prepared by the above method provided by the present invention are coated with a PVP shell layer on the surface. The PVP coating significantly improves the photothermal stability and quantum yield of the quantum dots; the polymer PVP coating layer helps to achieve the monodispersion of the quantum dots, avoids the aggregation of the quantum dots in the solution, and improves the uniform deposition and pattern clarity during the patterning process; the PVP coating layer makes the quantum dots superior to the prior art in terms of monodispersity, stability, and fluorescence efficiency.

[0021] After stirring in the present invention, a perovskite quantum dot solution is obtained. Preferably, after stirring again, vacuum drying is carried out to obtain a precipitate, that is, a phosphor, as a polymer-coated perovskite quantum dot. In the present invention, the centrifugation rate of the re-stirring is 9900 - 11000 rpm, and the re-stirring time is 9.5 - 10.5 min.

[0022] The method provided by the present invention reduces the preparation cost of perovskite quantum dots, which is beneficial to large-scale production and commercial application.

[0023] The present invention provides a polymer-coated perovskite quantum dot, which is prepared by the green preparation method described in the above technical solution; the emission wavelength of the polymer-coated perovskite quantum dot is 513 nm.

[0024] The quantum dots prepared by the present invention are particularly suitable for the fields of white light LEDs and Micro-LEDs due to their high quantum yield and stability, and exhibit potential application value in low-cost, wide-color gamut high-definition display technologies.

[0025] The present invention provides a green preparation method of polymer-coated perovskite quantum dots, comprising the following steps: dissolving a lead salt, a cesium salt and oleic acid in a solvent to obtain a precursor solution; mixing the precursor solution and 3-aminopropyltrimethoxysilane in a green solvent containing PVP, and stirring to obtain polymer-coated perovskite quantum dots; the green solvent in the green solvent containing PVP comprises ethyl acetate and ethanol. The present invention uses polyvinylpyrrolidone (PVP) polymer to coat CsPbBr3 quantum dots, which improves the stability and quantum yield of the quantum dots, and makes them superior to the prior art in terms of monodispersity, stability and fluorescence efficiency. Due to their high quantum yield and stability, the quantum dots of the present invention are particularly suitable for the fields of white light LEDs and Micro-LEDs, and show potential application value in low-cost, wide-color gamut high-definition display technologies. Description of the Drawings

[0026] Figure 1 It is a synthesis flow chart of CsPbBr3 perovskite quantum dot solution in Example 1 of the present invention;

[0027] Figure 2 It is a daylight and fluorescence photo excited by a 365 nm ultraviolet lamp of CsPbBr3 perovskite quantum dot solution in Example 1 of the present invention;

[0028] Figure 3 It is the fluorescence spectrum and absorption spectrum of CsPbBr3 perovskite quantum dot solution in Example 1 of the present invention;

[0029] Figure 4 It is a transmission electron microscope image and a high-resolution transmission electron microscope image of CsPbBr3 perovskite quantum dot solution in Example 1 of the present invention;

[0030] Figure 5 It is a front and back photo of CsPbBr3 perovskite quantum dot solution placed in air at room temperature for one month in Example 1 of the present invention;

[0031] Figure 6 It is a comparison diagram of the photostability of CsPbBr3 perovskite quantum dot solution in Example 1 of the present invention. Detailed Embodiments

[0032] In order to further illustrate the present invention, the following examples are used to describe in detail a polymer-coated perovskite quantum dot and its green preparation method provided by the present invention, but they should not be construed as limiting the protection scope of the present invention.

[0033] Example 1

[0034] Based on Figure 1 the shown process to prepare perovskite quantum dots:

[0035] (a) At room temperature (25 °C), 0.4 mmol of PbBr2, 0.4 mmol of CsBr, 200 μL of oleic acid were dissolved in 10 mL of DMF solvent and sonicated until the solution became clear to obtain a precursor solution;

[0036] (b) 0.3 g of PVP powder was added to a mixed solvent of 70 ml of ethyl acetate and 30 ml of ethanol and stirred until clear;

[0037] (c) 1 mL of the precursor solution was mixed with 15 μL of APTMS and added to 100 mL of a mixed solvent of ethyl acetate and ethanol containing PVP, and stirred at high speed at 600 rpm for 60 min to obtain a perovskite quantum dot solution.

[0038] The fluorescence images of the perovskite quantum dot solution prepared in Example 1 under sunlight and excitation with a 365 nm ultraviolet lamp are shown as Figure 2 shown. It can be seen from Figure 2 that the prepared perovskite quantum dot solution is bright green, emits bright fluorescence under excitation light, and the emission wavelength is 513 nm, as shown in Figure 3 shown.

[0039] In Example 1, the polymer PVP was added to the green mixed solvent to coat a layer of PVP micelles around the quantum dots to achieve a monodisperse effect. Its coating shell is shown in the microscope image of Figure 4 , and the particle size is uniform. At the same time, the surface of the perovskite was modified to improve the stability. The brightness of the solution did not change after being placed at room temperature for one month, as shown in Figure 5 shown; the photo-stability is shown in Figure 6 shown. Compared with Comparative Example 1, the stability of Example 1 was significantly enhanced: the quantum dots were centrifuged and mixed with 20% PMMA and spin-coated on a glass slide, and irradiated with 365 nm light to compare their optical stability, that is, the change in the emission intensity of the quantum dots under long-term light irradiation. It can be seen from the test data of Figure 6 that under continuous illumination for 12 h, the light intensity of the PVP-coated quantum dots reached 93%, while the light intensity of the uncoated quantum dots decayed to 63%, proving that the addition of PVP has a role in improving its stability.

[0040] The present invention uses the integrating sphere method (absolute measurement method): an integrating sphere is used to collect all emitted photons and directly measure the total luminous efficiency without using a standard sample. The high fluorescence quantum yield of the perovskite quantum dot solution prepared in Example 1 is 96.55%.

[0041] Comparative Example 1

[0042] (a) At room temperature (25 °C), 0.4 mmol of PbBr2, 0.4 mmol of CsBr, 200 μL of oleic acid were dissolved in 10 mL of DMF solvent and sonicated until the solution became clear to obtain a precursor solution;

[0043] (b) 1 mL of the precursor solution was mixed with 15 μL of APTMS and added to a mixed solvent of 70 mL of ethyl acetate and 30 mL of ethanol, and vigorously stirred at 600 rpm for 60 min to obtain a perovskite quantum dot solution.

[0044] Comparative Example 2

[0045] At room temperature, 0.4 mmol of PbBr2 and 0.4 mmol of CsBr were dissolved in 10 mL of DMF solvent and sonicated until the solution became clear to obtain a precursor. 1 mL of the DMF precursor solution was mixed with 15 μL of APDEMS and added to a mixed solution of 10 mL of toluene and 200 μL of oleic acid, and vigorously stirred for 60 min to obtain CsPbBr3 quantum dots.

[0046] In Comparative Example 2, the antisolvent used was the traditional toxic toluene solvent, which would cause environmental pollution and was not suitable for large-scale production. Moreover, the full width at half maximum of the quantum dots was relatively wide, reaching 24 nm, the crystallization quality was worse than that of the example, and the PLQY was only 78%, with poor optical performance.

[0047] Comparative Example 3

[0048] At room temperature, 1 mL of the precursor was mixed with 10 mL of n-hexane in a beaker under vigorous stirring. Then, 0.5 mL of isopropanol was quickly added to the beaker, and after a few seconds, CsPbBr3 quantum dots could be obtained.

[0049] In Comparative Example 3, the antisolvent used was the low-toxic green solvent isopropanol, but its polar conditions affected the synthesis morphology and optical properties of the quantum dots. The full width at half maximum was 24 nm and the PLQY was 80%.

[0050] Comparative Example 4

[0051] Methyl acetate was used to replace ethyl acetate, and the rest of the operations were the same as in Example 1, but luminescent perovskite quantum dots could not be prepared.

[0052] As can be seen from the above embodiments, the present invention provides a green preparation method of polymer-coated perovskite quantum dots, comprising the following steps: dissolving a lead salt, a cesium salt and oleic acid in a solvent to obtain a precursor solution; mixing the precursor solution and 3-aminopropyltrimethoxysilane in a green solvent containing PVP, and stirring to obtain polymer-coated perovskite quantum dots; the green solvent in the green solvent containing PVP comprises ethyl acetate and ethanol. The present invention uses polyvinylpyrrolidone (PVP) polymer to coat CsPbBr3 quantum dots, which improves the stability and quantum yield of the quantum dots, making them superior to the prior art in terms of monodispersity, stability and fluorescence efficiency. The quantum dots of the present invention are particularly suitable for the fields of white light LEDs and Micro-LEDs due to their high quantum yield and stability, and exhibit potential application value in low-cost, wide-color gamut high-definition display technologies.

[0053] The above are only the preferred embodiments of the present invention. It should be noted that for those of ordinary skill in the art, without departing from the principle of the present invention, several improvements and modifications can be made, and these improvements and modifications should also be regarded as the protection scope of the present invention.

Claims

1. A green preparation method of polymer-coated perovskite quantum dots, comprising the following steps: dissolving lead salt, cesium salt and oleic acid in a solvent to obtain a precursor solution; The precursor solution and 3-aminopropyltrimethoxysilane are mixed in a green solvent containing PVP and stirred to obtain polymer-coated perovskite quantum dots; The green solvent in the PVP-containing green solvent includes ethyl acetate and ethanol.

2. The green preparation method according to claim 1, characterized in that: The volume ratio of ethyl acetate to ethanol is 4.5-5.5:

1.

3. The green preparation method according to claim 1, characterized in that: The concentration of PVP in the green solvent containing PVP is 30-40 mmol / L.

4. The green preparation method according to claim 1, characterized in that: Lead salt is PbBr2; The cesium salt is CsBr.

5. The green preparation method according to claim 1, characterized in that: The solvent in the precursor solution is dimethylformamide.

6. The green preparation method according to claim 1, characterized in that: The centrifugal stirring speed is 9900-11000 rpm, and the stirring time is 9.5-10.5 min.

7. The green preparation method according to claim 1, characterized in that: The volume ratio of the amount of lead salt, the amount of cesium salt, the volume of oleic acid and the solvent is 0.4 mmol:0.4 mmol:200 μL:(9.8-10.2) mL.

8. The green preparation method according to claim 1, characterized in that: The volume ratio of the precursor solution, 3-aminopropyltrimethoxysilane and the green solvent containing PVP is 1 mL: (5-20) μL: (95-105) mL.

9. The green preparation method according to claim 1, characterized in that: The surface of perovskite quantum dots is coated with a PVP shell.

10. A polymer-coated perovskite quantum dot prepared by the green preparation method according to any one of claims 1 to 9; The emission wavelength of the polymer-coated perovskite quantum dots is 513 nm.

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