Preparation method of passivated CsPbBr3 nano-cluster based on bifunctional ligand and application of passivated CsPbBr3 nano-cluster in luminescent device

Abstract

The invention discloses a preparation method of a passivated CsPbBr3 nano-cluster based on a bifunctional ligand and application of the passivated CsPbBr3 nano-cluster in a light-emitting device.The preparation method comprises the steps that a cesium carbonate n-octanoic acid solution is injected into a lead bromide and tetra-n-octyl ammonium bromide toluene mixed solution, stirring is conducted in the room temperature environment, and a precursor is obtained; injecting a didodecyl dimethyl ammonium fluoride toluene solution into the precursor to react, so as to obtain a bifunctional ligand modified CsPbBr3 nano-cluster original solution; and adding a centrifuging agent into the bifunctional ligand modified CsPbBr3 nano-cluster original solution, centrifuging, taking the precipitate, dispersing the precipitate in toluene, centrifuging, and taking the supernatant, thereby obtaining the green luminous CsPbBr3 nano-cluster product. The n-caprylic acid and the didodecyl dimethyl ammonium fluoride ligand synthesized later are introduced in the preparation process for modification, the photoluminescence quantum efficiency of the nano-cluster is effectively improved, and the obtained nano-cluster has high crystallinity and concentrated size.

Description

Technical Field

[0001] The present invention belongs to the technical field of nanocluster display technology, and specifically relates to a preparation method of CsPbBr nanoclusters passivated by bifunctional ligands and its application in light-emitting devices. 3 Background Art

[0002] In recent years, CsPbBr nanoclusters have shown great development potential due to their tunable emission wavelength, narrow emission bandwidth, high absorption coefficient, and high quantum yield. They have been widely studied and developed in the field of light-emitting devices, making them an ideal candidate for the next-generation LED technology. 3

[0003] Currently, the research on CsPbBr nanoclusters mainly focuses on optimizing their optical properties and improving stability. However, due to the highly dynamic adsorption-desorption state of the coating ligands, CsPbBr nanoclusters are easily affected by the environment. In addition, some defects will inevitably be introduced during the synthesis process, including halogen ion vacancies, Pb ion vacancies, and Pb interstitial ions. These defects act as non-radiative recombination centers, causing the recombination of photo-generated excitons and photo-generated carriers, thus greatly reducing the luminescence efficiency of CsPbBr nanoclusters. 3 3 3

[0004] To improve the stability and photoluminescence quantum efficiency of CsPbBr nanoclusters, researchers have carried out a large number of studies, such as methods of Cs / Pb site doping and surface engineering. Among these methods, capping ligand engineering is an effective method to regulate the surface ligands of CsPbBr nanoclusters, which can passivate surface defects, optimize the photoluminescence efficiency, and improve the stability of CsPbBr nanoclusters. For example, using (3-aminopropyl)triethoxysilane or 2-hexyldibenzyl decanoate to replace oleylamine oleic acid as the capping ligand. However, under a thermal environment, instability problems may occur when adjusting the length and structure of oleylamine oleic acid. 3 3 3

[0005] Recent studies have shown that the post-synthesis ligand modification strategy can be used to achieve the regulation of CsPbBr 3 ​​​​Stepwise regulation of crystallization kinetics provides new ideas for improving the photoluminescence efficiency and structural stability of materials. However, existing synthesis systems still generally rely on high-temperature injection processes, and this traditional method faces significant technical bottlenecks in large-scale production scenarios. Especially when implementing two-step ligand engineering, the preparation process of nanoclusters not only involves complex process parameter regulation but also has the industrialization problem of excessive time consumption. More notably, subsequent processing procedures may cause structural defects such as lattice distortion, leading to negative effects such as increased surface vacancy density and decreased carrier mobility in the material. Therefore, there is an urgent need to develop nanoclusters using a simple one-step controllable method at room temperature to obtain CsPbBr 3 nanoclusters with high luminescence efficiency and stability.

[0006] Generally speaking, in the research field of CsPbBr 3 nanoclusters, developing a synthesis strategy with both simple preparation processes and excellent optoelectronic properties while ensuring its long-term stable operation in complex environments has become the core topic for breaking through the industrial application bottleneck. With the continuous in-depth research, CsPbBr 3 nanoclusters have shown broad application prospects in optoelectronic engineering fields such as white light LED devices and flexible displays due to their unique photophysical properties. However, it should be noted that the significant sensitivity of CsPbBr 3 nanoclusters to the external environment easily causes enhanced non-radiative recombination and structural degradation phenomena, which seriously restricts the advancement of its commercialization process. Summary of the Invention

[0007] The purpose of this part is to outline some aspects of the embodiments of the present invention and briefly introduce some preferred embodiments.

[0008] In view of the above and / or problems existing in the prior art, the present invention is proposed.

[0009] Therefore, the purpose of the present invention is to overcome the deficiencies in the prior art and provide a preparation method of CsPbBr 3 nanoclusters based on bifunctional ligand passivation.

[0010] To solve the above technical problems, the present invention provides the following technical solutions: A preparation method of CsPbBr 3 nanoclusters based on bifunctional ligand passivation, including, Mix cesium carbonate and n-octanoic acid, stir at room temperature, and obtain a cesium carbonate n-octanoic acid solution when the solution is completely transparent; Mix lead bromide, tetra-n-octylammonium bromide with the solvent toluene, stir at room temperature, and obtain a lead bromide, tetra-n-octylammonium bromide toluene mixture when the solution is completely transparent; Dissolve dodecyl dimethyl ammonium bromide and sodium fluoride in solvents toluene and ultrapure water respectively. After complete dissolution, mix them under ultrasonic treatment and centrifuge to obtain a toluene solution of dodecyl dimethyl ammonium fluoride; Inject a cesium carbonate n - octanoic acid solution into a mixed solution of lead bromide and tetra - n - octylammonium bromide in toluene, and stir at room temperature to obtain a precursor; Inject the toluene solution of dodecyl dimethyl ammonium fluoride into the above - mentioned precursor for reaction to obtain a CsPbBr 3 nanocluster crude solution modified with a bifunctional ligand; Add a centrifuging agent to the CsPbBr 3 nanocluster crude solution modified with a bifunctional ligand for centrifugation. Take the precipitate, disperse the precipitate in toluene, centrifuge again and take the supernatant to obtain a CsPbBr 3 nanocluster product that emits green light.

[0011] As a preferred embodiment of the preparation method of the present invention, wherein: the molar ratio of cesium carbonate to n - octanoic acid is 1:63.

[0012] As a preferred embodiment of the preparation method of the present invention, wherein: the molar ratio of lead bromide, tetra - n - octylammonium bromide to toluene is 1:2:525.

[0013] As a preferred embodiment of the preparation method of the present invention, wherein: the molar ratio of dodecyl dimethyl ammonium bromide to sodium fluoride is 1:1.

[0014] As a preferred embodiment of the preparation method of the present invention, wherein: the volume ratio of toluene to ultrapure water is 1:1.

[0015] As a preferred embodiment of the preparation method of the present invention, wherein: the volume ratio of the cesium carbonate n - octanoic acid solution, the mixed solution of lead bromide, tetra - n - octylammonium bromide in toluene and the toluene solution of dodecyl dimethyl ammonium fluoride is 0.1:5:0.86.

[0016] As a preferred embodiment of the preparation method of the present invention, wherein: the centrifuging agent includes ethyl acetate, and the volume ratio of the centrifuging agent to the CsPbBr 3 nanocluster crude solution is 2:1.

[0017] Another object of the present invention is to overcome the deficiencies in the prior art and provide a CsPbBr 3 nanocluster, and the fluorescence emission peak of the CsPbBr 3 nanocluster is 510 - 520 nm.

[0018] Another object of the present invention is to overcome the deficiencies in the prior art and provide a CsPbBr 3Application of nanoclusters in the preparation of white light LED devices, including mixing CsPbBr 3 nanoclusters with CsPbBr 1.2 I 1.8 nanoclusters with toluene solution of polymethyl methacrylate respectively and fully mixing them to obtain a mixture; wherein, the mass ratio of the nanoclusters to the toluene solution of polymethyl methacrylate is 5:3; Using a 450 nm blue LED chip as the excitation light source, coating the above mixture on it in sequence, and annealing at 70 °C for 5 h to obtain a white light LED device based on bifunctional ligand passivated CsPbBr 3 nanoclusters.

[0019] Advantages of the present invention: (1) The present invention optimizes the ratio of lead bromide, tetraoctylammonium bromide and solvent toluene, making the photoluminescence efficiency of the nanoclusters higher, the crystallinity more obvious, and further improving the thermal stability, storage stability and polarity stability.

[0020] (2) By introducing n-octanoic acid and post-synthetic dimethyldidodecylammonium fluoride ligand modification in the preparation, the present invention effectively improves the photoluminescence quantum efficiency of the nanoclusters. The obtained nanoclusters have high crystallinity and relatively concentrated size; as a bifunctional ligand dimethyldidodecylammonium fluoride located on the particle surface can effectively passivate surface defects, significantly enhancing the stability of the nanoclusters and improving their optical properties, thus achieving efficient and stable luminescence; (3) The present invention optimizes the synthesis method and develops nanoclusters using a simple one-step controllable method, which can be used to fabricate high-efficiency white LEDs, providing reliable technical support for the commercial application of optoelectronic devices. Description of the drawings

[0021] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following will briefly introduce the drawings required for the description of the embodiments. Obviously, the following drawings are only some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained according to these drawings. Among them: Figure 1 Fluorescence emission spectrum of dimethyldidodecylammonium fluoride modified CsPbBr 3 nanoclusters prepared in Example 1 of the present invention; Figure 2 Ultraviolet absorption spectrum of dimethyldidodecylammonium fluoride modified CsPbBr 3 nanoclusters prepared in Example 1 of the present invention; Figure 3X-ray diffraction pattern of dodecyldimethylammonium fluoride modified CsPbBr prepared in Example 1 of the present invention 3 of the nanoclusters; Figure 4 X-ray diffraction pattern of dodecyldimethylammonium fluoride modified CsPbBr prepared in Example 1 of the present invention 3 Transmission electron microscope image of the nanoclusters; Figure 5 X-ray diffraction pattern of dodecyldimethylammonium fluoride modified CsPbBr prepared in Example 1 of the present invention 3 Storage stability graph of the nanoclusters; Figure 6 X-ray diffraction pattern of dodecyldimethylammonium fluoride modified CsPbBr prepared in Example 1 of the present invention 3 Thermal stability graph of the nanoclusters; Figure 7 X-ray diffraction pattern of dodecyldimethylammonium fluoride modified CsPbBr prepared in Example 1 of the present invention 3 Polarity stability graph of the nanoclusters; Figure 8 Device structure diagram of the white light emitting LED chip prepared in Example 2 of the present invention; Figure 9 Spectrum diagram of the white light LED prepared in Example 2 of the present invention; Figure 10 Chromaticity coordinate diagram of the white light LED prepared in Example 2 of the present invention.

[0022] Figure 11 Photoluminescence efficiency graph of CsPbBr nanoclusters modified with different molar amounts of dodecyldimethylammonium fluoride in Comparative Example 1 of the present invention 3 of the nanoclusters.

[0023] Figure 12 Storage stability graph of the sample prepared in Comparative Example 2 of the present invention; Figure 13 Thermal stability graph of the sample prepared in Comparative Example 2 of the present invention; Figure 14 Polarity stability graph of the sample prepared in Comparative Example 2 of the present invention.

[0024] Figure 15 X-ray diffraction pattern of the sample prepared in Comparative Example 3 of the present invention; Figure 16 Thermal stability graph of the sample prepared in Comparative Example 3 of the present invention; Figure 17 Polarity stability graph of the sample prepared in Comparative Example 3 of the present invention. Detailed implementation manners

[0025] To make the above objects, features, and advantages of the present invention more apparent and understandable, the following detailed description of the specific embodiments of the present invention will be provided in conjunction with the embodiments of the specification.

[0026] In the following description, many specific details are set forth to facilitate a full understanding of the present invention. However, the present invention may also be implemented in other ways different from those described herein. Those skilled in the art may make similar generalizations without departing from the spirit of the present invention. Therefore, the present invention is not limited by the specific embodiments disclosed below.

[0027] Secondly, the so-called "one embodiment" or "embodiment" herein refers to a specific feature, structure, or characteristic that may be included in at least one implementation manner of the present invention. The appearances of "in one embodiment" in different places in this specification do not all refer to the same embodiment, nor are they separate or alternative embodiments that exclude each other with other embodiments.

[0028] In the embodiments of the present invention, cesium carbonate, lead bromide, and tetraoctylammonium bromide were purchased from Sigma-Aldrich (Shanghai) Trading Co., Ltd. Cesium acetate, butyric acid, ethanol, didodecyldimethylammonium bromide, ethyl acetate, n-caprylic acid, oleic acid, sodium fluoride, and n-hexane were purchased from Shanghai Aladdin Biochemical Technology Co., Ltd. Zinc iodide, 1-octadecene, oleylamine, and polymethyl methacrylate were purchased from Shanghai Macklin Biochemical Co., Ltd. Toluene was purchased from Shanghai Lingfeng Chemical Reagent Co., Ltd.

[0029] In the embodiments of the present invention, the preparation method of the CsPbBr 1.2 I 1.8 nanocluster product is as follows: 1) Mix 10 mmol of cesium acetate with 5 mL of butyric acid, and stir at room temperature until the cesium acetate and butyric acid react completely to obtain a cesium acetate-butyric acid solution.

[0030] 2) Mix 0.3 mmol of lead bromide, 0.45 mmol of zinc iodide, 5 mmol of butyric acid, and 5 mmol of oleylamine with 15 ml of 1-octadecene. First, degas at room temperature for 30 min, and then heat to 160 °C under N 2 protection. Subsequently, quickly inject 0.3 mmol of the cesium acetate-butyric acid solution into the mixture within 5 s, and rapidly cool with an ice-water bath to obtain the CsPbBr 1.2 I 1.8 nanoprecursor solution.

[0031] 3) Add the obtained nanoprecursor solution of the nanoclusters to a centrifuge tube and simultaneously add ethyl acetate with twice the volume of the original solution. Centrifuge at a speed of 8000 r / min for 2 min. After centrifugation, pour off the supernatant and add a total of 6 ml of n-hexane to the precipitate. After washing again, finally, CsPbBr can be obtained.1.2 I 1.8 Nanocluster product.

[0032] Example 1 1) Mix 1 mmol of cesium carbonate and 10 mL of n - octanoic acid, stir at room temperature for 30 min, and obtain a cesium carbonate n - octanoic acid solution when the solution becomes completely transparent.

[0033] 2) Mix 0.09 mmol of lead bromide, 0.18 mmol of tetra - n - octylammonium bromide and 5 mL of toluene, stir at room temperature for 1 h, and obtain a lead bromide, tetra - n - octylammonium bromide toluene mixture when the solution becomes completely transparent.

[0034] 3) Dissolve 1 mmol of didodecyldimethylammonium bromide and 1 mmol of sodium fluoride in 10 ml of solvent toluene and 10 ml of ultrapure water respectively. After complete dissolution, mix them under ultrasonic treatment for 30 min, and centrifuge to obtain a didodecyldimethylammonium fluoride toluene solution.

[0035] 4) Inject 0.1 ml of the cesium carbonate n - octanoic acid solution into 5 ml of the lead bromide, tetra - n - octylammonium bromide toluene mixture, stir at room temperature for 3 min to obtain the final precursor. Inject 0.86 ml of the didodecyldimethylammonium fluoride toluene solution into the above - mentioned precursor and react for 2 min to obtain a CsPbBr 3 nanocluster stock solution.

[0036] 5) Add the obtained nanocluster stock solution to a centrifuge tube and simultaneously add ethyl acetate with twice the volume of the stock solution. Centrifuge at a speed of 8000 r / min for 5 min. After centrifugation, pour off the supernatant and add 2 ml of toluene in total to the precipitate. Shake the centrifuge tube until the precipitate is completely dissolved and then centrifuge at a speed of 8000 r / min for 5 min. The obtained supernatant is the pure green - emitting CsPbBr 3 nanocluster product.

[0037] As Figure 1 shown is the fluorescence emission spectrum of CsPbBr 3 nanoclusters modified with didodecyldimethylammonium fluoride, and its emission wavelength is around 513 nm.

[0038] As Figure 2 shown is the ultraviolet absorption spectrum of CsPbBr 3 nanoclusters modified with didodecyldimethylammonium fluoride, and its absorption peak coincides with the fluorescence emission spectrum.

[0039] As Figure 3 shown is the CsPbBr 3X-ray diffraction pattern of the nanoclusters, which shows a high crystallinity of the sample and indicates that the sample is a standard cubic-phase crystal.

[0040] As Figure 4 shown is the transmission electron microscope image of dodecyl dimethyl ammonium fluoride modified CsPbBr 3 nanoclusters, with an average size of about 9.8 nm and a relatively concentrated size. To test the stability of the product, we stored the product indoors and tested the change in luminescence intensity. As Figure 5 shown, after storing for 80 days, the luminescence intensity can still be maintained at about 82% of the initial intensity; we heated the product in an environment of 100 °C. As Figure 6 shown, after heating for 60 min, the luminescence intensity can still be maintained at about 76% of the initial intensity; we placed the product in ethanol. As Figure 7 shown, after 60 min, the luminescence intensity can still be maintained at about 88% of the initial intensity.

[0041] Example 2 1) Mix 1 mmol of cesium carbonate and 10 mL of n-octanoic acid, stir at room temperature for 30 min, and obtain a cesium carbonate n-octanoic acid solution when the solution becomes completely transparent.

[0042] 2) Mix 0.09 mmol of lead bromide, 0.18 mmol of tetra-n-octylammonium bromide and 5 mL of toluene, stir at room temperature for 1 h, and obtain a lead bromide, tetra-n-octylammonium bromide toluene mixture when the solution becomes completely transparent.

[0043] 3) Dissolve 1 mmol of dodecyl dimethyl ammonium bromide and 1 mmol of sodium fluoride in 10 ml of solvent toluene and 10 ml of ultrapure water respectively. After complete dissolution, mix them under ultrasonic treatment for 30 min, and centrifuge to obtain a dodecyl dimethyl ammonium fluoride toluene solution.

[0044] 4) Inject 0.1 ml of the cesium carbonate n-octanoic acid solution into 5 ml of the lead bromide, tetra-n-octylammonium bromide toluene mixture, stir at room temperature for 3 min to obtain the final precursor. Inject 0.86 ml of the dodecyl dimethyl ammonium fluoride toluene solution into the above precursor and react for 2 min to obtain a bifunctional ligand modified CsPbBr 3 nanocluster stock solution.

[0045] 5) Add the obtained nanocluster original solution to a centrifuge tube and add ethyl acetate twice the volume of the original solution, centrifuge at 8000 r / min for 5 min, pour out the supernatant after centrifugation and add 2 ml of toluene to the precipitate, shake the centrifuge tube until the precipitate is completely dissolved, and centrifuge at 8000 r / min for 5 min. The supernatant obtained is the pure green luminescent CsPbBr 3 Nanocluster products.

[0046] 6) Purify CsPbBr 3 Nanoclusters and CsPbBr 1.2 I 1.8 The nanoclusters were mixed with polymethyl methacrylate toluene solution in a ratio of 5:3. They were then coated on a 450 nm blue LED chip and annealed at 70 °C for 5 h to obtain a CsPbBr nanostructured ... 3 Nanocluster white light LED device, the structure of the device is as follows Figure 8 As shown, a blue LED is used as an excitation light source to excite the nanocluster coating to emit light, and white light is emitted through combination.

[0047] like Figure 9 The figure shows the spectrum of the prepared white light LED, from which the blue chip emission peak (455 nm) and the green nanocluster dispersion emission peak (527 nm) can be seen.

[0048] like Figure 10 Shown is the color coordinate diagram of the prepared white light LED, whose color coordinate values ​​are (0.33, 0.35).

[0049] Comparative Example 1 1) Mix 1 mmol of cesium carbonate and 10 mL of octanoic acid, stir at room temperature for 30 min, and obtain cesium carbonate octanoic acid solution when the solution becomes completely transparent.

[0050] 2) Mix 0.09 mmol lead bromide, 0.18 mmol tetra-n-octylammonium bromide and 5 mL toluene, stir at room temperature for 1 h, and when the solution is completely transparent, a mixed solution of lead bromide, tetra-n-octylammonium bromide and toluene is obtained.

[0051] 3) Dissolve 1 mmol of didodecyldimethylammonium bromide and 1 mmol of sodium fluoride in 10 ml of toluene and 10 ml of ultrapure water, respectively. After complete dissolution, mix under ultrasonic treatment for 30 min and centrifuge to obtain a didodecyldimethylammonium fluoride toluene solution.

[0052] 4) Inject 0.1 ml of cesium carbonate octanoate solution into 5 ml of a mixed solution of lead bromide and tetraoctylammonium bromide in toluene, and stir for 3 min at room temperature to obtain the final precursor. Inject 0.006, 0.010, 0.013, and 0.016 mmol of didodecyldimethylammonium fluoride toluene solution into the above precursor respectively and react for 2 min to obtain four kinds of CsPbBr nanocluster original solutions modified with different molar amounts of didodecyldimethylammonium fluoride ligands. 3 nanocluster original solution.

[0053] 5) Add the obtained nanocluster original solutions into centrifuge tubes respectively and add ethyl acetate with twice the volume of the original solution, centrifuge at 8000 r / min for 5 min. After centrifugation, pour off the supernatant and add 2 ml of toluene to the precipitate respectively. Shake the centrifuge tube until the precipitate is completely dissolved and then centrifuge at 8000 r / min for 5 min. The obtained supernatant is the pure green-emitting CsPbBr 3 nanocluster product.

[0054] Figure 11 CsPbBr nanoclusters modified with different molar amounts of didodecyldimethylammonium fluoride 3 photoluminescence efficiency diagram, and it is found that when the amount of didodecyldimethylammonium fluoride is 0.013 mmol (860 ul), the photoluminescence efficiency reaches the highest at 97.5%.

[0055] Comparative Example 2 1) Introduce 2 mmol of cesium carbonate into a three-necked flask containing 25 mL of 1-octadecene and 5 mL of oleic acid, and then conduct a vacuum treatment on the mixture for 0.5 h. Heat it to 120 °C under N2 protection until cesium carbonate reacts completely with oleic acid to obtain cesium carbonate oleate solution. 2 2) Mix 0.4 mmol of lead bromide, 2 ml of oleylamine and 2 ml of oleic acid with 20 ml of 1-octadecene, and heat to 160 °C under N2 protection. Then, quickly inject 2 mL of cesium carbonate oleate solution into the reaction mixture, cool it with an ice-water bath after reacting for 5 s to obtain an oleylamine oleate ligand-modified CsPbBr

[0056] nanocluster original solution. 2 2) Mix 0.4 mmol of lead bromide, 2 ml of oleylamine and 2 ml of oleic acid with 20 ml of 1-octadecene, and heat to 160 °C under N2 protection. Then, quickly inject 2 mL of cesium carbonate oleate solution into the reaction mixture, cool it with an ice-water bath after reacting for 5 s to obtain an oleylamine oleate ligand-modified CsPbBr 3 nanocluster original solution.

[0057] 3) Add the obtained original nanocluster solution into a centrifuge tube, and simultaneously add ethyl acetate with a volume twice that of the original solution. Centrifuge at a speed of 8000 r / min for 5 min. After centrifugation, pour off the supernatant and add 2 ml of toluene in total to the precipitate. Shake the centrifuge tube until the precipitate is completely dissolved, and then centrifuge at a speed of 8000 r / min for 5 min. The obtained supernatant is the pure green-emitting CsPbBr 3 nanocluster product.

[0058] As Figure 12 shown, after storing for 100 days, the luminescence intensity of this product only maintains at about 62% of the initial intensity; as Figure 13 shown, after heating at 100 °C for 60 min, the luminescence intensity of this product only maintains at about 10% of the initial intensity; as Figure 14 shown, after testing in ethanol for 60 min, the luminescence intensity of this product only maintains at about 47% of the initial intensity.

[0059] Comparative Example 3 1) Mix 1 mmol of cesium carbonate and 10 mL of n-octanoic acid, and stir at room temperature for 30 min. When the solution becomes completely transparent, a cesium carbonate n-octanoic acid solution is obtained.

[0060] 2) Mix 0.2 mmol of lead bromide, 0.4 mmol of tetra-n-octylammonium bromide and 5 mL of toluene, and stir at room temperature for 1 h. When the solution becomes completely transparent, a lead bromide, tetra-n-octylammonium bromide toluene mixture is obtained.

[0061] 3) Dissolve 1 mmol of didodecyldimethylammonium bromide and 1 mmol of sodium fluoride in 10 ml of solvent toluene and 10 ml of ultrapure water respectively. After complete dissolution, mix them under ultrasonic treatment for 30 min, and centrifuge to obtain a didodecyldimethylammonium fluoride toluene solution.

[0062] 4) Inject 0.1 ml of the cesium carbonate n-octanoic acid solution into 5 ml of the lead bromide, tetra-n-octylammonium bromide toluene mixture, and stir at room temperature for 3 min to obtain the final precursor. Inject 0.86 ml of the didodecyldimethylammonium fluoride toluene solution into the above precursor and react for 2 min to obtain a didodecyldimethylammonium fluoride-modified CsPbBr 3 nanocluster original solution.

[0063] 5) Add the obtained original nano - cluster solution into a centrifuge tube and simultaneously add ethyl acetate with a volume twice that of the original solution. Centrifuge at a speed of 8000 r / min for 5 min. After centrifugation, pour off the supernatant and add a total of 2 ml of toluene to the precipitate. Shake the centrifuge tube until the precipitate is completely dissolved and then centrifuge at a speed of 8000 r / min for 5 min. The obtained supernatant is the pure green - emitting CsPbBr 3 nano - cluster product.

[0064] As Figure 15 shown is the X - ray diffraction pattern of the CsPbBr 3 nano - cluster of this product. It is found that its peaks are less obvious, indicating a lower crystallinity.

[0065] As Figure 16 shown, the initial photoluminescence efficiency is at most 97%, slightly less than 97.5% in Comparative Example 1. And after heating in an environment of 100 °C for 60 min, the luminescence intensity of this product remains at about 70% of the initial intensity; As Figure 17 shown, after testing in ethanol for 60 min, the luminescence intensity of this product remains at about 84% of the initial intensity, but there is a red - shift of 2 - 3 nm.

[0066] It should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention rather than to limit them. Although the present invention has been described in detail with reference to the preferred embodiments, those of ordinary skill in the art should understand that the technical solutions of the present invention can be modified or equivalently replaced without departing from the spirit and scope of the technical solutions of the present invention, and they should all be covered within the scope of the present invention.

Claims

1. A method for preparing CsPbBr3 nanoclusters based on bifunctional ligand passivation, characterized in that: include, Mix cesium carbonate and n-octanoic acid, and stir at room temperature until the solution is completely transparent to obtain a cesium carbonate n-octanoic acid solution; Mixing lead bromide, tetra-n-octylammonium bromide and solvent toluene, stirring at room temperature, and obtaining a mixed solution of lead bromide, tetra-n-octylammonium bromide and toluene when the solution is completely transparent; Dissolving didodecyl dimethyl ammonium bromide and sodium fluoride in toluene and ultrapure water respectively, mixing under ultrasonic treatment after being completely dissolved, and centrifuging to obtain didodecyl dimethyl ammonium fluoride toluene solution; The cesium carbonate n-octanoate solution is injected into a mixed solution of lead bromide and tetra-n-octylammonium bromide in toluene, and stirred at room temperature to obtain a precursor; Injecting didodecyl dimethyl ammonium fluoride toluene solution into the above precursor to react and obtain a bifunctional ligand-modified CsPbBr3 nanocluster original solution; The centrifugal agent is added to the original solution of CsPbBr3 nanoclusters modified with the bifunctional ligand and centrifuged to obtain a precipitate. The precipitate is dispersed in toluene and the supernatant is obtained after centrifugation to obtain a green luminescent CsPbBr3 nanocluster product.

2. The preparation method according to claim 1, characterized in that: The molar ratio of the cesium carbonate to n-octanoic acid is 1:

63.

3. The preparation method according to claim 1 or 2, characterized in that: The molar ratio of the lead bromide, tetra-n-octylammonium bromide and toluene is 1:2:

525.

4. The preparation method according to claim 3, characterized in that: The molar ratio of the didodecyl dimethyl ammonium bromide to sodium fluoride is 1:

1.

5. The preparation method according to claim 1 or 4, characterized in that: The volume ratio of toluene to ultrapure water is 1:

1.

6. The preparation method according to claim 1, characterized in that: The volume ratio of the cesium carbonate n-octanoic acid solution, the lead bromide, the tetra-n-octylammonium bromide toluene mixed solution and the didodecyldimethylammonium fluoride toluene solution is 0.1:5:0.

86.

7. The preparation method according to claim 1 or 6, characterized in that: The centrifugal agent includes ethyl acetate, and the volume ratio of the centrifugal agent to the CsPbBr3 nanocluster original solution is 2:

1.

8. The CsPbBr3 nanocluster obtained by the preparation method according to any one of claims 1 to 7, characterized in that: The fluorescence emission peak of the CsPbBr3 nanocluster is 510-520 nm.

9. Use of the CsPbBr3 nanoclusters according to claim 8 in the preparation of white light LED devices.

10. The use according to claim 9, characterized in that: Including, CsPbBr3 nanoclusters and CsPbBr 1.2 I 1.8 The nanoclusters are fully mixed with the polymethyl methacrylate toluene solution to prepare a mixture; wherein the mass ratio of the nanoclusters to the polymethyl methacrylate toluene solution is 5:3; A 450 nm blue LED chip was used as the excitation light source, and the above mixtures were coated on it in sequence and annealed at 70°C for 5 h to obtain a white light LED device based on bifunctional ligand passivated CsPbBr3 nanoclusters.

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