A core-shell structure of csPbBr3 perovskite quantum dots and a synthesis method and application thereof

Abstract

The application belongs to the technical field of synthesis of semiconductor perovskite quantum dots, and particularly relates to a core-shell structure CsPbBr3 perovskite quantum dot and a synthesis method and application thereof. The synthesis method of the core-shell structure CsPbBr3 perovskite quantum dot of the application is to dissolve a ligand-assisted metal salt in a non-polar solvent, to precipitate the CsPbBr3 perovskite quantum dot of an end olefin through supersaturation crystallization, and then to generate an organic cross-linking molecular layer as a shell of the CsPbBr3 perovskite quantum dot through a click reaction of a cross-linking molecule tetra(3-mercaptopropionic acid) pentaerythritol ester with an olefin on the surface of the CsPbBr3 perovskite quantum dot. Since the quantum dot has a core-shell structure of an inorganic perovskite crystal core and an organic ligand shell, the CsPbBr3 perovskite quantum dot can be endowed with excellent fluorescence quantum yield and structural stability, which is very consistent with the preparation and application requirements of perovskite quantum dot materials for a new generation of high-efficiency lighting and display.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of synthesis of semiconductor perovskite quantum dots, and particularly relates to a core-shell structure CsPbBr3 perovskite quantum dot and a synthesis method and application thereof. BACKGROUND

[0002] Perovskite quantum dots refer to a new type of semiconductor luminescent material with nanoscale size and perovskite crystal structure. Perovskite quantum dots have great potential in the fields of lighting and display due to high color purity, high fluorescence quantum yield, high defect tolerance, high light absorption coefficient, and low-temperature solution synthesis. Among many perovskite materials, CsPbBr3 materials have attracted widespread attention due to their all-inorganic crystal nucleus and high tolerance factor.

[0003] At present, existing CsPbBr3 perovskite quantum dots usually have a structure in which organic ligands are adsorbed on the surface of the CsPbBr3 perovskite crystal nucleus. Notably, the above structure has the following problems: first, the surface ligands have high freedom and are extremely easy to desorb and adsorb on the surface of the CsPbBr3 perovskite quantum dots, which can introduce surface defects and cause a decrease in fluorescence quantum yield; second, the organic ligand layer cannot form a dense package around the CsPbBr3 perovskite crystal nucleus, and external water and oxygen can easily diffuse to the defects on the surface of the crystal nucleus and react, ultimately leading to decomposition of the CsPbBr3 perovskite quantum dots.

[0004] Based on the above deficiencies, how to develop a synthesis method of efficient and stable CsPbBr3 perovskite quantum dots, which can not only inhibit the desorption process of surface ligands, but also form a dense and stable organic shell, so as to simultaneously improve the fluorescence quantum efficiency and stability, has become a technical problem to be solved. SUMMARY

[0005] The main purpose of the present application is to provide a synthesis method of CsPbBr3 perovskite quantum dots with a core-shell structure, which can simultaneously improve the efficiency and stability of the quantum dots by optimizing the perovskite synthesis path and designing the cross-linked ligand organic shell, and is suitable for the synthesis and application of perovskite semiconductor luminescent materials for lighting and display.

[0006] Another purpose of the present application is to provide a CsPbBr3 perovskite quantum dot with a core-shell structure, which has a dense and stable organic shell and high fluorescence quantum efficiency and stability, and meets the use requirements of perovskite quantum dots for high-efficiency lighting and display devices.

[0007] Another purpose of the present application is to provide a CsPbBr3 perovskite quantum dot with a core-shell structure.

[0008] To achieve the above object, the synthesis method of the core-shell structure CsPbBr3 perovskite quantum dots of the application adopts the technical scheme of:

[0009] A synthesis method of core-shell structure CsPbBr3 perovskite quantum dots, comprising the following steps:

[0010] (1) Dissolve cesium carbonate and 10-undecenoic acid in toluene to obtain a cesium precursor solution;

[0011] Dissolve lead bromide and tetra-n-octylammonium bromide in toluene to obtain a lead bromide precursor solution;

[0012] (2) Inject the cesium precursor solution into the lead bromide precursor solution to precipitate CsPbBr3 perovskite quantum dots with an end olefin ligand on the surface;

[0013] (3) Add tetra(3-mercaptopropionic acid) pentaerythritol ester and a photosensitizer to the system after the quantum dots are precipitated in step (2), and then induce the thiol-olefin click reaction between the CsPbBr3 perovskite quantum dots with an end olefin ligand on the surface and the tetra(3-mercaptopropionic acid) pentaerythritol ester under ultraviolet light, to obtain the core-shell structure CsPbBr3 perovskite quantum dots.

[0014] The synthesis method of the core-shell structure CsPbBr3 perovskite quantum dots of the application dissolves the ligand-assisted metal salt in toluene, precipitates the CsPbBr3 perovskite quantum dots with an end olefin through supersaturation crystallization, and then generates an organic cross-linking molecular layer as the shell of the CsPbBr3 perovskite quantum dots through the click reaction between the cross-linking molecule tetra(3-mercaptopropionic acid) pentaerythritol ester and the olefin on the surface of the CsPbBr3 perovskite quantum dots. Since the quantum dots have the core-shell structure of inorganic perovskite crystal nucleus and organic ligand shell, the CsPbBr3 perovskite quantum dots can be endowed with excellent fluorescence quantum yield and structural stability.

[0015] The application provides a synthesis method of CsPbBr3 perovskite quantum dots, which has the following advantages: (i) the introduction of the organic shell can inhibit the desorption and adsorption process of the inner layer ligand of the CsPbBr3 perovskite quantum dots, and avoid the reduction of the fluorescence quantum yield caused by the surface defects introduced by the dynamic process of the ligand; (ii) the organic shell can act as a peripheral physical barrier of the CsPbBr3 perovskite quantum dot crystal nucleus, effectively isolating the corrosion of water and oxygen on the perovskite crystal nucleus, so that the material has high stability. The CsPbBr3 perovskite quantum dots have a novel surface organic shell structure, high fluorescence quantum yield and good stability, and are expected to replace the current synthesis path of the quantum dot material, and have important application prospects in the synthesis field of perovskite semiconductor luminescent materials for lighting and display.

[0016] Based on the consideration of ensuring the dissolution of raw materials and the quantum dot precipitation effect, the application uses nonpolar toluene as the only solvent for the reaction and does not involve any other polar solvents, and does not need to use polar solvents such as dimethyl sulfoxide or dimethyl formamide as auxiliary solvents for the reaction, which is more conducive to the precipitation of quantum dots and the improvement of the fluorescence yield of quantum dots.

[0017] Preferably, in step (1), the use amount ratio of cesium carbonate, 10-undecenoic acid and toluene is 0.5 mmol: 1 mL: (5-20) mL.

[0018] Further, in step (1), the use amount ratio of lead bromide, tetra-n-octylammonium bromide and toluene is 1 mmol: 2 mmol: (5-20) mL.

[0019] Preferably, in step (2), when the injection is performed, the volume ratio of the cesium precursor solution to the lead bromide precursor solution is 1: (1-2); and the injection rate of the injection is 2-3 mL / s.

[0020] In step (3), the application generates the organic shell of the CsPbBr3 perovskite quantum dots through a thiol-olefin click reaction. Preferably, the use amount of the tetra(3-mercaptopropionic acid) pentaerythritol ester is 80wt.%-120wt.% of the mass of the CsPbBr3 perovskite quantum dots with terminal olefin ligands.

[0021] Preferably, in step (3), the photosensitizer is 2,2-dimethoxy-phenyl phenyl ethanone; and the addition amount of the photosensitizer is 0.1wt.%-0.5wt.% of the mass of the CsPbBr3 perovskite quantum dots with terminal olefin ligands.

[0022] Further preferably, in step (3), the wavelength of the ultraviolet light is 365 nm.

[0023] Preferably, in step (3), the time of the thiol-alkene click reaction is 10-15 min.

[0024] The application also provides a synthesis method of the core-shell structured CsPbBr3 perovskite quantum dot.

[0025] The application also provides an application of the core-shell structured CsPbBr3 perovskite quantum dot, in particular, an application in a perovskite semiconductor light-emitting material.

[0026] The core-shell structured CsPbBr3 perovskite quantum dot of the application can not only inhibit the desorption and adsorption process of the surface ligand of the perovskite quantum dot by introducing a dense and stable organic shell, but also serve as a physical barrier against water and oxygen corrosion of the crystal core. The use of nonpolar toluene as a solvent can avoid damage to the perovskite quantum dot by nonpolar molecules. Therefore, the material purification process does not need to be performed immediately after synthesis. The obtained CsPbBr3 perovskite quantum dot has high fluorescence quantum efficiency and stability, and meets the use requirements of a new generation of high-efficiency lighting and display devices for perovskite quantum dots. BRIEF DESCRIPTION OF DRAWINGS

[0027] Figure 1 FIG. 1 is a flowchart of a synthesis method of the core-shell structured CsPbBr3 perovskite quantum dot of the application;

[0028] Figure 2 FIG. 4 is a fluorescence spectrum and fluorescence quantum efficiency of the CsPbBr3 perovskite quantum dot prepared by the synthesis method of Example 1 and Comparative Example 1 of the application;

[0029] Figure 3 FIG. 5 shows the influence of the amount of pentaerythritol tetra(3-mercaptopropionate) on the fluorescence intensity of the CsPbBr3 perovskite quantum dot in Test Example 1 of the application;

[0030] Figure 4 FIG. 6 is a transmission electron microscope (TEM) image of the CsPbBr3 perovskite quantum dot prepared by the synthesis method of Example 1 and Comparative Example 1 of the application under high-energy electron beam irradiation;

[0031] Figure 5 FIG. 7 is a nuclear magnetic resonance hydrogen spectrum (H 1 -NMR) of the CsPbBr3 perovskite quantum dot prepared by the synthesis method of Example 1 and Comparative Example 1 of the application. DETAILED DESCRIPTION

[0032] In order to more clearly illustrate the technical solutions of the present application, the present application will be further described below in conjunction with specific examples and drawings. However, those skilled in the art should understand that the following examples and drawings are only used to understand and illustrate the present application, and should not be regarded as limiting the scope of the present application. Based on the examples in the present application, all other examples obtained by those skilled in the art without creative labor are within the scope of protection of the present application. The raw materials and operation techniques involved in the following examples are conventional raw materials and techniques in the prior art unless otherwise specified.

[0033] Example 1

[0034] The core-shell structured CsPbBr3 perovskite quantum dots provided in this example have an inorganic CsPbBr3 perovskite crystal core and an organic molecule cross-linked shell. The cross-linked shell is induced by a thiol-alkene click reaction.

[0035] The flow chart of the synthesis method of the core-shell structured CsPbBr3 perovskite quantum dots of this example is shown in Figure 1 The synthesis process mainly includes two parts of non-polar solvent supersaturation crystallization of CsPbBr3 perovskite quantum dot crystal core and surface reaction shell of cross-linked molecules.

[0036] The specific synthesis method includes the following steps:

[0037] (1) Dissolve 0.5 mmol of cesium carbonate and 1 ml of 10-undecenoic acid in 9 mL of toluene to form a cesium precursor solution;

[0038] Separately dissolve 1.0 mmol of lead bromide and 2.0 mmol of tetra-n-octylammonium bromide in 20 mL of toluene to form a lead halide precursor solution;

[0039] (2) Inject 10 mL of the cesium precursor solution into the 20 mL of the lead bromide precursor solution within 5 s to precipitate CsPbBr3 perovskite quantum dots with an end-alkene ligand on the surface;

[0040] (3) Continue to add 700 mg of pentaerythritol tetra(3-mercaptopropionate) (100 wt% of the mass of the quantum dots) and 1 mg of photosensitizer 2,2-dimethoxy-phenyl phenyl ethanone to the system after the quantum dots are precipitated in step (2), and under ultraviolet light (365 nm) excitation, induce the thiol-alkene click reaction between the end-alkene CsPbBr3 perovskite quantum dots and the pentaerythritol tetra(3-mercaptopropionate), and the reaction time is 10 min, to obtain the core-shell structured CsPbBr3 perovskite quantum dots.

[0041] Comparative Example 1

[0042] The method for synthesizing perovskite quantum dots provided in this comparative example is basically the same as that in Example 1, except that only steps (1) and (2) are performed, i.e., CsPbBr3 shell-less perovskite quantum dots are produced.

[0043] Experimental Example 1: Optical Quality Test

[0044] The CsPbBr3 perovskite quantum dots with core-shell structure prepared in Example 1 and the CsPbBr3 shell-less perovskite quantum dots prepared in Comparative Example 1 were subjected to spectral analysis using a fluorescence spectrometer. 365 nm was used as the excitation light for the perovskite quantum dots, and the fluorescence intensity was recorded using an ocean optical integrating sphere.

[0045] Depend on Figure 2 It is known that the core-shell structured CsPbBr3 perovskite quantum dots prepared by this invention have relatively high fluorescence intensity compared with the shell-less CsPbBr3 perovskite quantum dots, and the fluorescence quantum dot efficiency has increased from 81% to 96%.

[0046] Further comparison was made of the fluorescence intensity of CsPbBr3 perovskite quantum dots obtained by changing the amount of pentaerythritol tetrakis(3-mercaptopropionic acid) ester in step (3) to 0%, 300%, 500%, 700%, 900%, and 1100 mg, respectively, which accounted for 0%, 43%, 71%, 100%, 129%, and 157% of the quantum dot mass. The results are as follows. Figure 3 As shown.

[0047] Depend on Figure 3 It is evident that the core-shell CsPbBr3 perovskite quantum dots prepared in Example 1 of this invention can achieve maximum fluorescence intensity with an appropriate amount of pentaerythritol tetrakis(3-mercaptopropionic acid) ester (700 mg). This indicates that the amount of pentaerythritol tetrakis(3-mercaptopropionic acid) ester is crucial for the click reaction of thiols and olefins, as well as the performance of the quantum dots.

[0048] Experimental Example 2: Stability and Morphology Testing

[0049] The morphology and stability of the core-shell CsPbBr3 perovskite quantum dots prepared in Example 1 and the shell-less CsPbBr3 perovskite quantum dots prepared in Comparative Example 1 were analyzed by transmission electron microscopy. The electron beam acceleration voltage was 200 kV.

[0050] Depend on Figure 4 The transmission electron microscopy results show that the core-shell CsPbBr3 perovskite quantum dots obtained by the synthesis method of the present invention have a large cubic structure of about 10 nm. Compared with the shell-less CsPbBr3 perovskite quantum dots, no obvious decomposition was observed under continuous electron beam bombardment, indicating that its stability has been improved and can meet the higher stability requirements of the next generation of high-efficiency lighting and display devices.

[0051] Crosslinking shell test

[0052] The surface molecular crosslinking of the core-shell structure CsPbBr3 perovskite quantum dots prepared in Example 1 and the CsPbBr3 unshell perovskite quantum dots obtained in Comparative Example 1 was analyzed by means of nuclear magnetic resonance hydrogen spectrum.

[0053] From the nuclear magnetic resonance hydrogen spectrum results of Figure 5 It can be known from the nuclear magnetic resonance hydrogen spectrum results that the signal of the surface olefin characteristic peak signal (5.8ppm and 4.9ppm) is reduced, and the signal of the mercapto characteristic peak signal is enhanced (2.54ppm and 2.95ppm), and the change of the above characteristic signals indicates that the thiol-alkene click reaction occurs on the surface of the CsPbBr3 perovskite quantum dots, and the organic shell is effectively formed.

[0054] As can be known above, the synthesis method of the core-shell structure CsPbBr3 perovskite quantum dots provided in the application greatly improves the fluorescence quantum efficiency and stability of the CsPbBr3 perovskite quantum dots through the optimization of the perovskite synthesis path, the design of the surface ligand and the introduction of the organic shell, and meets the preparation and application requirements of the perovskite quantum dot material for the new generation of high-efficiency lighting and display.

Claims

1. A method for synthesizing core-shell structured CsPbBr3 perovskite quantum dots, characterized in that, Includes the following steps: (1) Dissolve cesium carbonate and 10-undecenoic acid in toluene to obtain a cesium precursor solution; Lead bromide and tetra-n-octylammonium bromide were dissolved in toluene to obtain a lead bromide precursor solution; (2) The cesium precursor solution was injected into the lead bromide precursor solution to precipitate CsPbBr3 perovskite quantum dots with terminal olefin ligands on the surface; (3) Add pentaerythritol tetrakis(3-mercaptopropionic acid) and photosensitizer to the system after quantum dots are precipitated in step (2), and then induce the CsPbBr3 perovskite quantum dots with terminal olefin ligands on the surface to undergo a thiol-olefin click reaction with pentaerythritol tetrakis(3-mercaptopropionic acid) under ultraviolet light to obtain core-shell structured CsPbBr3 perovskite quantum dots.

2. The method for synthesizing core-shell structured CsPbBr3 perovskite quantum dots according to claim 1, characterized in that, In step (1), the ratio of cesium carbonate, 10-undecenoic acid and toluene is 0.5 mmol: 1 mL: (5-20) mL.

3. The method for synthesizing core-shell structured CsPbBr3 perovskite quantum dots according to claim 1, characterized in that, In step (1), the ratio of lead bromide, tetra-n-octylammonium bromide and toluene is 1 mmol: 2 mmol: (5-20) mL.

4. The method for synthesizing core-shell structured CsPbBr3 perovskite quantum dots according to any one of claims 1 to 3, characterized in that, In step (2), the volume ratio of the cesium precursor solution to the lead bromide precursor solution during injection is 1:(1-2); the injection rate is 2-3 mL / s.

5. The method for synthesizing core-shell structured CsPbBr3 perovskite quantum dots according to any one of claims 1 to 3, characterized in that, In step (3), the amount of the tetra(3-mercaptopropionic acid) pentaerythritol ester used is 80 wt.% to 120 wt.% of the mass of the CsPbBr3 perovskite quantum dots of the terminal olefin ligand.

6. The method for synthesizing core-shell structured CsPbBr3 perovskite quantum dots according to any one of claims 1 to 3, characterized in that, In step (3), the photosensitizer is 2,2-dimethoxy-phenylacetophenone; the amount of photosensitizer added is 0.1 wt.% to 0.5 wt.% of the mass of the CsPbBr3 perovskite quantum dots with terminal olefin ligands.

7. The method for synthesizing core-shell structured CsPbBr3 perovskite quantum dots according to any one of claims 1 to 3, characterized in that, In step (3), the wavelength of the ultraviolet light is 365nm.

8. The method for synthesizing core-shell structured CsPbBr3 perovskite quantum dots according to any one of claims 1 to 3, characterized in that, In step (3), the time for the click reaction of thiol olefins is 10-15 min.

9. Core-shell CsPbBr3 perovskite quantum dots prepared by the synthesis method of core-shell CsPbBr3 perovskite quantum dots according to any one of claims 1 to 8.

10. The application of the core-shell structured CsPbBr3 perovskite quantum dots as described in claim 9 in perovskite semiconductor luminescent materials.

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