Preparation method of surface passivation red light perovskite quantum dots

Abstract

The invention relates to a preparation method of surface-passivated red-light perovskite quantum dots, which comprises the following steps: preparing an amine sulfate solution from primary amine, sulfuric acid and an organic solvent; preparing a monovalent cation precursor from at least one of cesium carbonate, methylamine and formamidine, oleic acid and 1-octadecene; preparing a lead source precursor from lead halide, zinc halide, oleylamine, oleic acid and 1-octadecene; and thermally injecting the monovalent cation precursor into the lead source precursor, cooling, and injecting an amine sulfate solution to prepare a surface passivation red light perovskite quantum dot solution. The purpose of preparing the halogen perovskite quantum dots with excellent optical performance and good stability is achieved.

Description

Technical Field

[0001] The invention relates to the technical field of perovskite quantum dots, and in particular to a method for preparing surface passivated red light perovskite quantum dots. Background Art

[0002] Halogen perovskite quantum dots have many excellent properties, such as direct band gap, high fluorescence quantum efficiency, high luminescence color purity, adjustable luminescence color, large light absorption coefficient, large carrier mobility, high defect tolerance, convenient synthesis and low preparation cost. Therefore, halogen perovskite quantum dots have great potential in practical applications such as optoelectronic devices, such as LEDs that cover the entire field and display a variety of red patterns.

[0003] The synthesis methods of halogen perovskite quantum dots include hot injection, ligand-assisted coprecipitation and ball milling. Usually, organic ligands, such as oleic acid, oleylamine, etc., are added when synthesizing halogen perovskite quantum dots. On the one hand, they are used to passivate the surface defects of quantum dots, and on the other hand, they are used to avoid quantum dot agglomeration. However, the organic ligands used in these syntheses have poor conductivity on the one hand, and on the other hand, they are not stable when combined with the surface of halogen perovskite quantum dots, which makes the stability of halogen perovskite quantum dots poor, which is not conducive to the preparation of efficient and stable optoelectronic devices. Therefore, the synthesis of halogen perovskite quantum dots usually requires further modification, such as cleaning, ligand replacement, surface passivation, etc., so as to obtain halogen perovskite quantum dots with higher fluorescence quantum yield, better conductivity and better stability.

[0004] Halogen perovskites are usually cleaned, ligand replaced, surface passivated and other measures are taken after nucleation to improve their fluorescence quantum yield, conductivity and stability. For example, it is reported that after synthesizing halogen perovskite quantum dots, the cleaned perovskite quantum dots are ligand replaced to obtain halogen perovskite quantum dots with improved fluorescence quantum yield, but the quantum dots obtained by this synthesis method have poor stability. Therefore, it is still quite difficult to perform efficient surface passivation to obtain halogen perovskite quantum dots with excellent optical properties and good stability, and the existing technology needs to be improved. Summary of the invention

[0005] The problem to be solved by the present invention is to provide a method for preparing surface passivated red light perovskite quantum dots in view of the above-mentioned deficiencies in the prior art, which achieves the purpose of preparing halogen perovskite quantum dots with excellent optical properties and good stability.

[0006] The above-mentioned object of the present invention is achieved through the following technical solutions: A method for preparing surface passivated red light perovskite quantum dots, comprising: A process for preparing amine sulfate solutions from primary amines, sulfuric acid and organic solvents; A process for preparing a monovalent cation precursor from cesium carbonate, at least one of methylamine and formamidine, oleic acid and 1-octadecene; A process for preparing a lead source precursor from lead halide, zinc halide, oleylamine, oleic acid and 1-octadecene; The process of hot injecting the monovalent cation precursor into the lead source precursor, cooling and injecting an amine sulfate solution to prepare a surface passivated red light perovskite quantum dot solution.

[0007] Furthermore, in the process of preparing the amine sulfate solution, the primary amine is selected from one or a combination of methylamine, octylamine, α-phenylethylamine, β-phenylethylamine, and 2-thiophenylamine.

[0008] Furthermore, in the process of preparing the amine sulfate solution, the organic solvent is selected from one or a mixed solvent of ethyl acetate, methyl acetate, isopropanol, toluene, xylene, chlorobenzene, and chloroform. Preferably, the organic solvent is selected from a mixed solvent of isopropanol and toluene in a volume ratio of 1:5.

[0009] Furthermore, in the process of preparing the amine sulfate solution, the primary amine is preliminarily dissolved in half of the organic solvent to obtain a primary amine solution, and sulfuric acid is dissolved in the other half of the organic solvent to obtain a sulfuric acid solution, and then the sulfuric acid solution is dripped into the primary amine solution for reaction to obtain an amine sulfate solution.

[0010] Furthermore, in the process of preparing the amine sulfate solution, the concentration of the primary amine solution is controlled to be 2-64 mM.

[0011] Furthermore, in the process of preparing the amine sulfate solution, the concentration of sulfuric acid is 1-32 mM.

[0012] Furthermore, in the process of preparing the monovalent cation precursor, cesium carbonate, at least one of methylamine and formamidine, oleic acid and 1-octadecene are continuously stirred at a speed of more than 600 r / min, heated to 70-90°C and vacuum dried for 40-60 min, and then the temperature is raised to 120°C while nitrogen is passed through and maintained for more than 10 min to obtain a monovalent cation precursor.

[0013] Furthermore, in the process of preparing the lead source precursor, the lead halide is selected from lead iodide or lead bromide, and the zinc halide is selected from zinc iodide or zinc bromide.

[0014] Furthermore, in the process of preparing the lead source precursor, the molar ratio of lead halide to zinc halide is controlled to be 1:1~10.

[0015] Furthermore, in the process of preparing the lead source precursor, the volume ratio of oleylamine to oleic acid is 0.9-1.2:1.0 Furthermore, in the process of preparing the lead source precursor, lead halide, zinc halide, oleylamine, oleic acid and 1-octadecene are continuously stirred at a rotation speed of more than 600 r / min, and nitrogen is pumped and charged for multiple cycles at room temperature. Then, the temperature is raised to 160~180℃ while nitrogen is maintained for more than 10 minutes to obtain the lead source precursor.

[0016] Furthermore, in the process of preparing the surface passivated red light perovskite quantum dot solution, the molar ratio of amine sulfate, cesium carbonate and lead halide is controlled to be 1.00 mol: 1.50~7.50 mmol: 0.02~1.00 mol.

[0017] Furthermore, in the process of preparing a surface passivated red light perovskite quantum dot solution, the monovalent cation precursor is hot injected into the lead source precursor under stirring at 150~180°C, and then cooled in an ice water bath to 80~140°C after 5s, and the amine sulfate solution is injected into the red light perovskite quantum dots during nucleation growth, and then cooled to 40°C again to obtain a surface passivated red light perovskite quantum dot solution with a light emission wavelength of 610~660nm.

[0018] In summary, the beneficial technical effects of the present invention are as follows: the present invention provides a method for preparing red light perovskite quantum dots, which provides different passivation effects by regulating different amines, and directly introduces amine sulfates as replacement ligands into the quantum dot nucleation growth stage, thereby changing the kinetic process of crystal growth, thereby obtaining red light perovskite quantum dots with good stability, good luminescence performance, and suitable for electroluminescent diodes. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 Photoluminescence spectrum of the sample of Example 3 of the present invention; Figure 2 XRD test pattern of the sample of Example 3 of the present invention; Figure 3 This is a PLQY storage stability test diagram of the sample of Example 3 of the present invention; Figure 4 This is the TEM detection image of the sample in Example 3 of the present invention. DETAILED DESCRIPTION

[0020] In order to make the technical means, creative features, objectives and functions achieved by the present invention clearer and easier to understand, the present invention is further explained below in conjunction with the accompanying drawings and specific implementation methods.

[0021] Embodiment 1: A method for preparing surface passivated red light perovskite quantum dots disclosed in the present invention, comprising: A process for preparing amine sulfate solutions from primary amines, sulfuric acid and organic solvents; A process for preparing a monovalent cation precursor from cesium carbonate, at least one of methylamine and formamidine, oleic acid and 1-octadecene; A process for preparing a lead source precursor from lead halide, zinc halide, oleylamine, oleic acid and 1-octadecene; The invention relates to a process of hot injecting a monovalent cation precursor into a lead source precursor, cooling the precursor and then injecting an amine sulfate solution to prepare a surface passivated red light perovskite quantum dot solution.

[0022] Embodiment 2: A preparation method of surface passivated red light perovskite quantum dots disclosed in the present invention, which is different from Embodiment 1 in that it comprises the following steps: S1: 3.7 μL of octylamine was dissolved in 2.5 mL of a mixed solvent of isopropanol and toluene in a volume ratio of 1:5 to obtain a primary amine solution; 0.6 μL of concentrated sulfuric acid was dissolved in 2.5 mL of a mixed solvent of isopropanol and toluene in a volume ratio of 1:5 to obtain a sulfuric acid solution; Then, 2.5 mL of sulfuric acid solution was added dropwise to 2.5 mL of primary amine solution to react and obtain an amine sulfate solution; S2: 100 mg of cesium carbonate was added to a 25 mL three-necked flask, and 3.5 mL of 1-octadecene and 0.4 mL of oleic acid were added in sequence. The mixture was stirred continuously at a speed of 850 r / min, heated to 80 ° C and dried under vacuum for 30 min, and then heated to 120 ° C with nitrogen flow for more than 10 min. 100 mg of cesium carbonate was placed in a 25 mL three-necked flask and kept warm for later use to obtain a monovalent cation precursor. S3: 88 mg of lead iodide, 244 mg of zinc iodide, 5.0 mL of 1-octadecene, 1.8 mL of oleic acid and 1.8 mL of oleylamine were added to a 25 mL three-necked flask, stirred continuously at a speed of 850 r / min, and nitrogen was pumped and charged for multiple cycles at room temperature, and then the temperature was raised to 170°C while nitrogen was passed through, and maintained for more than 10 min to obtain a lead source precursor; S4 hot-injects a monovalent cation precursor into a lead source precursor under stirring at 170°C, cools in an ice-water bath to 120°C after 5 seconds, injects an amine sulfate solution into the nucleation-growing red light perovskite quantum dots, and continues to cool to 40°C to obtain a surface-passivated red light perovskite quantum dot solution.

[0023] Embodiment 3: A preparation method of surface passivated red light perovskite quantum dots disclosed in the present invention, which is different from Embodiment 1 in that it comprises the following steps: S1: Dissolve 25 μL of β-phenylethylamine in 5.0 mL of a mixed solvent of isopropanol and toluene in a volume ratio of 1:5 to obtain a primary amine solution; 5.5 μL of concentrated sulfuric acid was dissolved in 5.0 mL of a mixed solvent of isopropanol and toluene in a volume ratio of 1:5 to obtain a sulfuric acid solution; Then, 2.5 mL of sulfuric acid solution was added dropwise to 2.5 mL of primary amine solution to react and obtain an amine sulfate solution; S2: 100 mg of cesium carbonate was added to a 25 mL three-necked flask, and 3.5 mL of 1-octadecene and 0.4 mL of oleic acid were added in sequence. The mixture was stirred continuously at a speed of 850 r / min, heated to 80 ° C and dried under vacuum for 30 min, and then heated to 120 ° C with nitrogen flow for more than 10 min. 100 mg of cesium carbonate was placed in a 25 mL three-necked flask and kept warm for later use to obtain a monovalent cation precursor. S3: 88 mg of lead iodide, 244 mg of zinc iodide, 5.0 mL of 1-octadecene, 1.8 mL of oleic acid and 1.8 mL of oleylamine were added to a 25 mL three-necked flask, stirred continuously at a speed of 850 r / min, and nitrogen was pumped and charged for multiple cycles at room temperature, and then the temperature was raised to 170°C while nitrogen was passed through, and maintained for more than 10 min to obtain a lead source precursor; S4 hot-injects a monovalent cation precursor into a lead source precursor under stirring at 170°C, cools in an ice water bath to 140°C after 5s, injects an amine sulfate solution into the nucleation-growing red light perovskite quantum dots, and continues to cool to 40°C to obtain a surface-passivated red light perovskite quantum dot solution.

[0024] Embodiment 4: A preparation method of surface passivated red light perovskite quantum dots disclosed in the present invention is different from Embodiment 1 in that it comprises the following steps: S1: 32 μL of 2-thiophenylamine was dissolved in 5.0 mL of a mixed solvent of chlorobenzene and toluene in a volume ratio of 1:5 to obtain a primary amine solution; 11 μL of concentrated sulfuric acid was dissolved in 5.0 mL of a mixed solvent of chlorobenzene and toluene in a volume ratio of 1:5 to obtain a sulfuric acid solution; Then, 2.5 mL of sulfuric acid solution was added dropwise to 2.5 mL of primary amine solution to react and obtain an amine sulfate solution; S2: 100 mg of cesium carbonate was added to a 25 mL three-necked flask, and 3.5 mL of 1-octadecene and 0.4 mL of oleic acid were added in sequence. The mixture was stirred continuously at a speed of 850 r / min, heated to 80 ° C and dried under vacuum for 30 min, and then heated to 120 ° C with nitrogen flow for more than 10 min. 100 mg of cesium carbonate was placed in a 25 mL three-necked flask and kept warm for later use to obtain a monovalent cation precursor. S3: 88 mg of lead iodide, 366 mg of zinc iodide, 5.0 mL of 1-octadecene, 1.8 mL of oleic acid and 2.0 mL of oleylamine were added to a 25 mL three-necked flask, stirred continuously at a speed of 850 r / min, and nitrogen was pumped and charged for multiple cycles at room temperature, and then the temperature was raised to 170°C while nitrogen was passed through, and maintained for more than 10 min to obtain a lead source precursor; S4 hot-injects a monovalent cation precursor into a lead source precursor under stirring at 170°C, cools in an ice water bath to 140°C after 5s, injects an amine sulfate solution into the nucleation-growing red light perovskite quantum dots, and continues to cool to 40°C to obtain a surface-passivated red light perovskite quantum dot solution.

[0025] Experimental Example 1: The sample of Example 3 was irradiated with an excitation light source of 450 nm, and the spectrum generated by the sample of Example 3 after irradiation was collected to obtain Figure 1 Photoluminescence spectrum shown.

[0026] Experimental Example 2: Irradiated with an excitation light source of 450 nm, and collected spectra of the blank solvent cuvette and the sample of Example 3, and obtained the following Figure 2 The photoluminescence spectrum shown in the figure is obtained by converting the light intensity of the blank and experimental samples into the number of photons, and then dividing the number of photoluminescence photons after the sample is photoluminescent by the number of photoluminescence photons when the blank solvent is irradiated, and finally obtaining the corresponding photoluminescence quantum yield (PLQY). The PLQY of the sample in Example 3 is increased from 79.2% to 90.2% relative to the sample without surface passivation, indicating that the surface passivation treatment can effectively improve the PLQY of the perovskite and reduce the defects of the perovskite itself.

[0027] Test Example 3: The untreated sample and the sample of Example 3 were placed in the atmosphere, and the PLQY of the samples was tested at regular intervals to compare the stability before and after the ligand passivation treatment. For the sample of Example 3, the PLQY test was performed on the 1st, 5th, and 10th days. Figure 3 It can be seen that the PLQY of the sample in Example 3 hardly changed, while the PLQY of the blank sample dropped rapidly after placement, from 72.6% on the first day to 41.3% on the tenth day.

[0028] Experimental Example 4: The sample of Example 3 was dripped onto the ultra-thin carbon film and naturally air-dried. The sample was characterized by TEM and the following results were obtained: Figure 4 From the TEM image shown, it can be seen that the particle size of the sample is below 10 nm.

[0029] Finally, it should be noted that the above embodiments are only used to illustrate the technical solution of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solution of the present invention can be modified or replaced by equivalents without departing from the purpose and scope of the technical solution of the present invention, which should be included in the scope of the claims of the present invention.

Claims

1. A method for preparing surface passivated red light perovskite quantum dots, characterized in that: include, A process for preparing amine sulfate solutions from primary amines, sulfuric acid and organic solvents; A process for preparing a monovalent cation precursor from cesium carbonate, at least one of methylamine and formamidine, oleic acid and 1-octadecene; A process for preparing a lead source precursor from lead halide, zinc halide, oleylamine, oleic acid and 1-octadecene; The process of hot injecting the monovalent cation precursor into the lead source precursor, cooling and injecting an amine sulfate solution to prepare a surface passivated red light perovskite quantum dot solution.

2. The method for preparing surface passivated red light perovskite quantum dots according to claim 1, characterized in that: In the process of preparing the amine sulfate solution, the primary amine is selected from one or a combination of methylamine, octylamine, α-phenylethylamine, β-phenylethylamine, and 2-thiophenylamine.

3. The method for preparing surface passivated red light perovskite quantum dots according to claim 1, characterized in that: In the process of preparing the amine sulfate solution, the organic solvent is selected from one or a mixed solvent of ethyl acetate, methyl acetate, isopropanol, toluene, xylene, chlorobenzene and chloroform.

4. The method for preparing surface passivated red light perovskite quantum dots according to claim 1, characterized in that: In the process of preparing the amine sulfate solution, the primary amine is dissolved in half of the organic solvent in advance to obtain a 2-64 mM primary amine solution, and sulfuric acid is dissolved in the other half of the organic solvent to obtain a 1-32 mM sulfuric acid solution, and the sulfuric acid solution is then added dropwise to the primary amine solution to react to obtain the amine sulfate solution.

5. The method for preparing surface passivated red light perovskite quantum dots according to claim 1, characterized in that: In the process of preparing a monovalent cation precursor, cesium carbonate, at least one of methylamine and formamidine, oleic acid and 1-octadecene are continuously stirred at a speed of more than 600 r / min, heated to 70-90° C. and vacuum dried for 40-60 min, then heated to 120° C. while maintaining nitrogen flow and maintained for more than 10 min to obtain a monovalent cation precursor.

6. The method for preparing surface passivated red light perovskite quantum dots according to claim 1, characterized in that: In the process of preparing the lead source precursor, the lead halide is selected from lead iodide or lead bromide, and the zinc halide is selected from zinc iodide or zinc bromide.

7. The method for preparing surface passivated red light perovskite quantum dots according to claim 1, characterized in that: In the process of preparing the lead source precursor, the molar ratio of lead halide to zinc halide is controlled to be 1:1-10.

8. The method for preparing surface passivated red light perovskite quantum dots according to claim 1, characterized in that: In the process of preparing the lead source precursor, lead halide, zinc halide, oleylamine, oleic acid and 1-octadecene are continuously stirred at a rotation speed of more than 600 r / min, and nitrogen is pumped and charged for multiple cycles at room temperature. Then, the temperature is raised to 160-180°C while nitrogen is maintained for more than 10 minutes to obtain the lead source precursor.

9. The method for preparing surface passivated red light perovskite quantum dots according to claim 1, characterized in that: In the process of preparing the surface passivated red light perovskite quantum dot solution, the molar ratio of amine sulfate, cesium carbonate and lead halide is controlled to be 1.00 mol: 1.50~7.50 mmol: 0.02~1.00 mol.

10. The method for preparing surface passivated red light perovskite quantum dots according to claim 1, characterized in that: In the process of preparing the surface passivated red light perovskite quantum dot solution, the monovalent cation precursor is hot injected into the lead source precursor under stirring at 150~180°C, and then cooled in an ice water bath to 80~140°C after 5s, and the amine sulfate solution is injected into the red light perovskite quantum dots during nucleation growth, and then cooled to 40°C again to obtain a surface passivated red light perovskite quantum dot solution with a luminescent wavelength of 610~660nm.

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