A core-shell structure CsPbX3@ZnO quantum dot and its application in electroluminescent devices

Abstract

The present invention discloses a core-shell structured CsPbX3@ZnO quantum dot and its application in an electroluminescent device. A water dispersion system of amino-silane functionalized ZnO nanocrystals and an organic dispersion system of Cs4PbX6 quantum dots are respectively prepared, and then the two are mixed for a chemical reaction to obtain the core-shell structured CsPbX3@ZnO quantum dot with ZnO encapsulating CsPbX3. The core-shell structured quantum dot prepared by the present invention has good electrical conductivity. When used as a light-emitting layer in an electroluminescent device, a thicker thin film can be adopted, so that the carrier balance problem can be solved within a larger process window. At the same time, the energy level matching problem between the light-emitting layer and the ZnO electron transport layer can be solved by using the ultra-thin ZnO shell structure of the quantum dot, thus simplifying the structure of the electroluminescent device.

Description

Technical Field

[0001] The present invention relates to the field of semiconductor materials, and in particular to a core-shell structure quantum dot and a preparation method and application thereof. Background Art

[0002] All-inorganic lead halide perovskite (CsPbX 3 , X=Cl, Br, I) quantum dot luminescent materials and quantum dot electroluminescent devices (QLED) have developed rapidly since 2015. Compared with perovskite polycrystalline thin film materials, perovskite quantum dots have luminescence performance advantages due to the quantum confinement effect, which is manifested as a higher fluorescence quantum efficiency. However, the carrier mobility of quantum dot films is relatively low, and their electroluminescent devices can only use ultra-thin light-emitting layers. Therefore, carrier injection imbalance and non-radiative Auger recombination have become important factors that limit device efficiency. This problem is particularly prominent in blue and green QLEDs. The key to solving this problem is to prepare a high-mobility quantum dot light-emitting layer under the premise of ensuring the quantum efficiency of quantum dot fluorescence.

[0003] Compared with traditional quantum dot materials, all-inorganic perovskite quantum dots have the advantages of being suitable for mass production and high tolerance to surface defects. However, the deep energy level defects that may exist on the surface of the nanocrystals can still affect the optoelectronic properties and stability of the material through non-radiative recombination. As the light-emitting layer of QLED, the upper and lower surfaces of the quantum dot material are also the main sites for non-radiative recombination. Organic ligands have outstanding effects on improving the fluorescence quantum efficiency and photostability of perovskite quantum dots, but cannot significantly improve the conductivity of the quantum dot film. For example, aminopropyltrimethoxysilane (APTMS) can effectively inhibit the formation of surface cesium vacancies, thereby enhancing the stability of the nanocrystal structure, but it cannot improve the electrical properties of quantum dots. Therefore, the mobility of the perovskite QLED light-emitting layer is usually around 10 -6 cm 2 V -1 s -1 It requires an ultra-thin light-emitting layer of 20 to 40 nanometers to reach 10 mA cm -2 At higher current densities, problems such as carrier injection imbalance and non-radiative Auger recombination become prominent, resulting in a decrease in the external quantum efficiency (EQE) of QLEDs and a lifetime that does not meet application requirements.

[0004] The University of Toronto uses a bipolar shell surface replacement method to increase the mobility of the quantum dot light-emitting layer to 10 - 2 cm 2 V -1 s -1However, as the size of quantum dots and the thickness of the shell decrease, the wave function overlaps significantly between the adjacent quantum dot cores, and the quantum dot confinement effect is weakened, and the perovskite quantum dots lose their optical performance advantages over polycrystalline films (Y. Dong, Y.-K. Wang, F. Yuan, A. Johnston, Y. Liu, D. Ma, M.-J. Choi, B. Chen, M. Chekini, S.-W. Baek, L. K. Sagar, J. Fan, Y. Hou, M. Wu, S. Lee, B. Sun, S. Hoogland, R. Quintero-Bermudez, H. Ebe, P. Todorovic, F. Dinic, P. Li, H. T. Kung, M. Saidaminov, E. Kumacheva, E. Spiecker, L.-S. Liao, O. Voznyy, Z.-H. Lu and E. H. Sargent, "Bipolar-shell resurfacing for blue LEDs based on Strongly confined perovskite quantum dots." Nature Nanotechnology 15(8),668-+(2020).). The use of core-shell quantum dots with a certain shell thickness is expected to solve the contradiction between the above optical and electrical properties. By forming a high-quality heterojunction, the electronic structure of the heterojunction can be regulated while the surface of the quantum dots is passivated. This is also an effective way to improve the photoelectric properties and water-oxygen stability of the material and meet different application requirements. The common core-shell structure uses an insulator shell represented by silicon oxide, which cannot meet the requirements of high-brightness QLED for the electrical properties of the light-emitting layer.

[0005] Zinc oxide (ZnO) nanomaterials are high-performance electron transport materials that can form ohmic contacts with common electrodes such as Al, Ag, and ITO. ZnO prepared by the sol-gel method is suitable for making optoelectronic devices with simple structures, such as being used as an electron transport layer in QLEDs. Due to the interface defects, surface polarity, and type II heterojunction characteristics between zinc oxide films and perovskite quantum dots, the excitons in the quantum dots are unstable near their interface, which manifests as a decrease in the fluorescence intensity and fluorescence quantum efficiency of the film.

[0006] The optical band gap (Eg) of zinc oxide is about 3.4 eV, and the electron affinity (E EA) is about 4.2eV, which is larger than the affinity of lead halide perovskite and most organic semiconductors. Therefore, ZnO usually forms a type II heterojunction with these materials, which can be used in photodetectors. However, for perovskite light-emitting diodes, the type II heterojunction between the light-emitting layer and zinc oxide will cause carrier separation, resulting in a sharp drop in luminescence efficiency. High-performance electroluminescent devices require the insertion of an interface layer between the light-emitting layer and the zinc oxide electron transport layer to achieve the purpose of suppressing non-radiative recombination and improving carrier injection balance. However, the problems of non-radiative recombination caused by the interface between quantum dots and the decrease in fluorescence quantum efficiency caused by Förster energy transfer (FRET) have not been effectively solved. In summary, the development of QLEDs based on perovskite quantum dot light-emitting layers first requires the preparation of quantum dots of uniform size, the use of a core-shell structure or the use of a suitable composite matrix to improve the fluorescence quantum efficiency and photostability of the quantum dots, and further improve the carrier mobility of the light-emitting layer. Summary of the invention

[0007] Based on the above-mentioned shortcomings of the prior art, the present invention discloses a method for preparing a core-shell structure CsPbX 3 The method of @ZnO quantum dots aims to obtain high-mobility quantum dot materials with uniform size distribution and fully passivated surface. Applied to QLED, since its conductivity is significantly better than that of zinc oxide electron transport layer, the device can adopt a thicker light-emitting layer and a relatively simple device structure (that is, the ZnO electron transport layer can be used directly).

[0008] In order to achieve the purpose of the invention, the present invention adopts the following technical solution:

[0009] The present invention first discloses a core-shell structure CsPbX 3 The preparation method of ZnO quantum dots is characterized by: preparing the aqueous dispersion system of aminosilane-functionalized ZnO nanocrystals and Cs 4 PbX 6 The organic dispersion system of quantum dots is then mixed and chemically reacted to obtain CsPbX coated with ZnO. 3 Core-shell structure of CsPbX 3 @ZnO quantum dots. Dispersed system refers to a mixture of nanocrystals and their solvents, CsPbX 3 It represents an all-inorganic lead halide perovskite in which the halogen is X; there is no particular order in which the two dispersion systems are prepared, and the water dispersion system can be prepared first, or the organic dispersion system can be prepared first.

[0010] Furthermore, the preparation method of the aqueous dispersion system of aminosilane-functionalized ZnO nanocrystals is as follows: aminosilane is added to an ethanol dispersion of surface hydroxylated ZnO nanocrystals to react the ZnO nanocrystals with the aminosilane; the reaction solution is centrifuged, and the obtained precipitate is washed with a mixed solvent of ethyl acetate and ethanol and then centrifuged to remove unreacted aminosilane; and the obtained precipitate is then dispersed in pure water to obtain an aqueous dispersion system of aminosilane-functionalized ZnO nanocrystals, which is recorded as an aqueous dispersion system of AP-ZnO nanocrystals.

[0011] Furthermore, the Cs 4 PbX 6 The organic solvent in the organic dispersion system of quantum dots can be organic solvents such as benzene, alkane, cycloalkane, etc.

[0012] Furthermore, after the aqueous dispersion system and the organic dispersion system are mixed and reacted, the resulting solution is centrifuged to obtain the supernatant to obtain the core-shell structured CsPbX 3 @ZnO quantum dots.

[0013] Furthermore, the core-shell structure CsPbX 3 @The thickness of the ZnO shell in ZnO quantum dots or CsPbX 3 The heterojunction properties with ZnO are regulated by one of the following methods:

[0014] Method 1: When preparing a water dispersion system of aminosilane-functionalized ZnO nanocrystals, the molar ratio of aminosilane to surface hydroxylated ZnO nanocrystals is adjusted;

[0015] Method 2: Changing the concentration and / or volume ratio of the aqueous dispersion system to the organic dispersion system;

[0016] Method 3: When preparing the aqueous dispersion system of aminosilane-functionalized ZnO nanocrystals, aminosilane is used as the main ligand, and another type of silane ligand (such as trimethoxy(2-phenylethyl)silane (TMPES) or trichloro(phenylethyl)silane (PETS)) is used as an auxiliary to react with ZnO nanocrystals to regulate the surface chemical properties of the obtained aminosilane-functionalized ZnO nanocrystals, further affecting the core-shell structure CsPbX 3 @ZnO quantum dots heterojunction interface and surface properties, thereby regulating the thickness of the ZnO shell and the core-shell structure CsPbX 3 @The conductivity of ZnO quantum dots.

[0017] Furthermore, the preparation method of the ethanol dispersion of the surface hydroxylated ZnO nanocrystals is as follows: adding an ethanol solution of tetramethylammonium hydroxide (TMAH) dropwise to a dimethyl sulfoxide (DMSO) solution of zinc acetate dihydrate, and then stirring for reaction to obtain a ZnO nanocrystal dispersion; adding ethyl acetate to the ZnO nanocrystal dispersion, centrifuging, and adding ethanol to the obtained ZnO precipitate to obtain an ethanol dispersion of the surface hydroxylated ZnO nanocrystals.

[0018] Furthermore, when preparing a water dispersion system of aminosilane-functionalized ZnO nanocrystals, the molar ratio of surface hydroxylated ZnO nanocrystals to aminosilane is 4-14:1.

[0019] Furthermore, when the aqueous dispersion system is mixed with the organic dispersion system, the aminosilane-functionalized ZnO nanocrystals and Cs 4 PbX 6 The mass ratio of quantum dots is 0.1 to 15:1.

[0020] The core-shell structure CsPbX obtained by the present invention 3 @ZnO quantum dots can be used in quantum dot electroluminescent devices. Electroluminescent devices can be prepared by the full solution method. Due to their conductive properties, the thickness of the light-emitting layer can be controlled by preparing different numbers of light-emitting layers to achieve carrier balance.

[0021] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0022] 1. Core-shell structure CsPbX prepared by the present invention 3 @ZnO quantum dots have excellent conductive properties. When applied to QLED, a thicker quantum dot light-emitting layer can be used, thereby solving the carrier balance problem within a larger process window. As a QLED light-emitting layer, it has higher conductivity than the ZnO electron transport layer, which is conducive to obtaining higher device stability and longer life.

[0023] 2. Core-shell structure CsPbX prepared by the present invention 3 @ZnO quantum dots have the advantages of narrower size distribution and more stable surface passivation, and allow the use of thicker quantum dot light-emitting layers in QLED structures, which is beneficial to reducing the differences in device parameters such as electroluminescent color and operating voltage between different batches of products and improving product yield.

[0024] 3. Core-shell structure CsPbX prepared by the present invention 3@ZnO quantum dots, by linking aminosilane with the ZnO shell, on the one hand, achieve the surface passivation of quantum dots, improve the stability of the perovskite structure, on the other hand, increase the ionization potential of the quantum dot core, form a high-quality nano heterojunction, and ultimately improve the performance of the light-emitting layer. The present invention can also further adjust the thickness of the ZnO shell and the chemical composition and quantity of the surface ligands to a certain extent, and further regulate and optimize the performance of the device. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 2 is the XRD diagram of the ZnO nanocrystals and AP-ZnO nanocrystals prepared in Example 1.

[0026] Figure 2 FTIR images of ZnO nanocrystals and AP-ZnO nanocrystals prepared in Example 1.

[0027] Figure 3 is the Cs prepared in Example 2 4 PbB 6 TEM image of quantum dots.

[0028] Figure 4 is the CsPbBr prepared in Example 2 3 TEM image of quantum dots.

[0029] Figure 5 is the CsPbBr prepared in Example 2 3 @TEM image of ZnO quantum dots.

[0030] Figure 6 is the Cs prepared in Example 2 4 PbB 6 , CsPbBr 3 , CsPbBr 3 @UV-visible absorption spectrum of ZnO quantum dots.

[0031] Figure 7 The CsPbBr prepared in Example 2 3 , CsPbBr 3 @Fluorescence spectrum of ZnO quantum dots.

[0032] Figure 8 The CsPbBr prepared in Example 2 3 , CsPbBr 3 @XPS diagram of ZnO quantum dots, (a) full XPS spectrum, (bd) high-resolution XPS elemental spectra ((b) Zn 2p, (c) O 1s, (d) Si 2p).

[0033] Fig. 9 The CsPbBr prepared in Example 2 3 , CsPbBr 3 @FTIR image of ZnO quantum dots.

[0034] Fig.10 is CsPbCl in Example 3 3 With CsPbCl 3 @UV-visible absorption and fluorescence spectra of ZnO quantum dots.

[0035] Fig.11 is CsPbI in Example 4 3 With CsPbI 3 @UV-visible absorption and fluorescence spectra of ZnO quantum dots.

[0036] Fig.12 CsPbBr prepared by adding different volumes of AP-ZnO in Example 5 3 @Fluorescence spectrum of ZnO quantum dots.

[0037] Fig.13 CsPbBr prepared by adding different volumes of AP-ZnO in Example 5 3 @UV-visible absorption spectrum of ZnO quantum dots.

[0038] Fig.14 CsPbBr prepared by adding different volumes of AP-ZnO in Example 5 3 @The fluorescence quantum yield and UV-visible light absorption spectrum trend of ZnO quantum dots.

[0039] Fig.15 FTIR images of ZnO nanocrystals, AP-ZnO nanocrystals and APT-ZnO nanocrystals prepared in Example 1 and Example 6.

[0040] Fig.16 The CsPbBr prepared by APT-ZnO in Example 6 3 @Fluorescence spectrum of ZnO quantum dots.

[0041] Fig.17 FTIR images of ZnO nanocrystals, AP-ZnO nanocrystals and APP-ZnO nanocrystals prepared in Example 1 and Example 7.

[0042] Fig.18 The CsPbBr prepared by APP-ZnO in Example 7 3 @Fluorescence spectrum of ZnO quantum dots.

[0043] Fig.19In Example 8, CsPbBr 3 and CsPbBr 3 @Current density curve of single electron device made of ZnO quantum dots.

[0044] Fig. 20 In Example 8, CsPbBr 3 and CsPbBr 3 @Current density curve of single hole device made of ZnO quantum dots.

[0045] Fig.21 is CsPbBr in Example 9 3 , CsPbBr 3 @Current density curve of ZnO and ZnO.

[0046] Fig. 22 This is a current density curve diagram of different light-emitting layer numbers when TPBi in Example 10 is used as the electron transport layer.

[0047] Fig.23 This is a current density curve diagram of different light-emitting layer numbers when ZnO is used as the electron transport layer in Example 10.

[0048] Fig.24 This is a voltage-brightness relationship curve for different numbers of light-emitting layers when TPBi and ZnO are used as electron transport layers in Example 10. Specific implementation methods

[0049] In order to make the purpose, technical scheme and advantages of the present invention clearer, the present invention will be described clearly and completely in conjunction with the accompanying drawings and embodiments. Obviously, the described embodiments are part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0050] Unless otherwise specified, the test materials and reagents used in the following examples can be obtained from commercial sources.

[0051] The core-shell structure CsPbX prepared in the following example 3 @ZnO quantum dots can be characterized by the following methods:

[0052] Characterization of CsPbX by single electron devices, single hole devices, and ITO / EML / Ag devices 3 @ZnO quantum dots have excellent conductive properties.

[0053] Characterization of CsPbX by transmission electron microscopy (TEM) 3@The morphology and size distribution of ZnO quantum dots. CsPbX 3 @ZnO quantum dot shell thickness.

[0054] The thickness of the ZnO shell is determined by the ratio of the integrated intensity of the Zn 2p peak to the integrated intensity of the Pb 4f peak in X-ray photoelectron spectroscopy (XPS) (denoted as Zn / Pb). The larger the Zn / Pb ratio, the thicker the shell.

[0055] 1. Core-shell structure CsPbX 3 @Preparation of ZnO quantum dots

[0056] Example 1: Preparation of AP-ZnO Nanocrystals

[0057] 1. Synthesis of surface hydroxylated ZnO nanocrystals

[0058] 30 mL of dimethyl sulfoxide (DMSO) and 3 mmol of zinc acetate dihydrate were mixed and stirred at room temperature for 30 min. An ethanol solution (10 mL) containing 5.5 mmol of tetramethylammonium hydroxide (TMAH) was added dropwise to the solution within 5 min. The mixture was stirred at room temperature for 24 h until a clear colloid was obtained.

[0059] 2. Purification of zinc oxide nanocrystals

[0060] The nanocrystal mother liquor obtained in step 1 was mixed with ethyl acetate at a volume ratio of 1:2, and then centrifuged and washed. The resulting precipitate was dispersed in ethanol at a concentration of 0.3686 mol / L to obtain an ethanol dispersion of surface hydroxylated ZnO nanocrystals.

[0061] 3. Aqueous dispersion system of AP-ZnO nanocrystals

[0062] The ethanol dispersion of the surface hydroxylated ZnO nanocrystals obtained in step 2 containing 0.74 mmol ZnO was measured, 0.057 mmol APTMS was added, the reaction was stirred for 12 hours, the reaction solution was centrifuged, the obtained precipitate was washed with a mixed solvent of ethyl acetate and ethanol (the volume ratio of the two was 2:1) and then centrifuged to remove unreacted aminosilane; the obtained precipitate was dispersed in pure water to prepare a water dispersion system of aminosilane-functionalized ZnO nanocrystals with a concentration of 0.1229 mol / L, recorded as the water dispersion system of AP-ZnO nanocrystals (hereinafter referred to as AP-ZnO aqueous solution).

[0063] like Figure 1As shown, the X-ray diffraction patterns (XRD) of the surface hydroxylated ZnO nanocrystals and the aminosilane functionalized AP-ZnO nanocrystals prepared in this example have obvious characteristic peaks at 2θ=31.7°, 33.9°, 36.2°, 47.3°, 56.4°, 62.7° and 67.8°, corresponding to the (100), (002), (101), (102), (110), (103) and (112) crystal planes of hexagonal wurtzite zinc oxide, indicating that the AP-ZnO nanocrystals still maintain the hexagonal wurtzite structure of ZnO.

[0064] Figure 2 The Fourier transform infrared spectra (FTIR) of the surface hydroxylated ZnO nanocrystals and the aminosilane functionalized AP-ZnO nanocrystals prepared in this example are shown in Figure 3. -1 The hydroxyl groups on the surface of ZnO nanocrystals are significantly weakened, and AP-ZnO nanocrystals newly form 1101cm -1 This is because the silyl methoxy group of APTMS is first hydrolyzed in the reaction solution to form a silanol group (-SiOH), which further undergoes a condensation reaction with the hydroxyl group (-OH) on the ZnO surface to form a Zn-O-Si bridge bond connecting ZnO and aminosilane, proving that the ZnO surface is functionalized by amino groups. After APTMS treatment, the ZnO surface is located at 800-1200 cm -1 The absorption in the wavenumber range is significantly enhanced compared to the OH vibration absorption, and the absorption in the wavenumber range of 1300-1600 cm -1 The vibration bands in the wavenumber range are also significantly enhanced, indicating that a siloxane (Si-O-Si) passivation shell has been fully formed on the AP-ZnO surface.

[0065] Example 2: Core-shell structure CsPbBr 3 @Preparation of ZnO quantum dots

[0066] 1. Cs 4 PbB 6 Synthesis of quantum dots

[0067] Add 0.814 g of cesium carbonate, 2.5 mL of oleic acid and 40 mL of octadecene into a three-necked flask, pass nitrogen to remove water and oxygen, then evacuate the flask, raise the temperature to 120°C, pass nitrogen to positive pressure, keep warm for 5 minutes, then continue to raise the temperature to 150°C, stir at a constant temperature until dissolved, and obtain a cesium oleate precursor solution, which is stored at 100°C in nitrogen for later use.

[0068] In another three-necked flask, add 0.0367g of lead bromide and 5mL of octadecene, pass nitrogen to remove water and oxygen, then evacuate, heat to 120°C, pass nitrogen to positive pressure, stir at constant temperature for 1h, then add 0.5mL of oleic acid and 1mL of oleylamine, continue stirring until the lead bromide is completely dissolved; heat to 150°C again, stir for 10min, then drop the temperature to 90°C, inject the synthesized cesium oleate precursor solution, wait for 5s and cool to room temperature in an ice water bath to obtain Cs 4 PbB 6 Quantum dot masterbatch.

[0069] According to the volume ratio of 1:2, Cs 4 PbB 6 After the quantum dot mother solution was mixed with methyl acetate, it was centrifuged and washed. The resulting precipitate was dispersed in toluene at a concentration of 10 mg / mL to obtain the purified Cs 4 PbB 6 The toluene dispersion system of quantum dots (hereinafter referred to as Cs 4 PbB 6 solution).

[0070] 2. Core-shell structure CsPbBr 3 @Preparation of ZnO quantum dots

[0071] Take 2 mL of Cs prepared in step 1 4 PbB 6 The solution was added with 80 μL of the AP-ZnO aqueous solution prepared in Example 1, stirred at room temperature for 10 min, allowed to stand for 12 h, and then centrifuged at 8000 rpm for 5 min. The supernatant was taken to obtain a core-shell structure CsPbBr 3 @ZnO quantum dots.

[0072] For comparison, this example also prepared CsPbBr by conventional hydrolysis method. 3 Quantum dots, specifically: add 80 μL of water to 2 mL of Cs prepared in step 1 4 PbB 6 The solution was stirred at room temperature for 10 minutes, allowed to stand for 12 hours, and then centrifuged at 8000 rpm for 5 minutes. The supernatant was taken to obtain CsPbBr 3 Quantum dots.

[0073] Figure 3 , Figure 4 , Figure 5 are respectively Cs prepared in this example 4 PbB 6 , CsPbBr 3 , CsPbBr 3@TEM image of ZnO quantum dots, it can be seen that the method of the present invention can obtain a core-shell structure CsPbBr with uniform size 3 @ZnO quantum dots, the average size of quantum dots is 7nm. APTMS exists on the surface of AP-ZnO. 3 @ZnO quantum dots process, APTMS can react with CsPbBr through amino groups 3 Surface binding, due to the possible adsorption energy difference relative to oleylamine, the prepared CsPbBr 3 @ZnO quantum dots are more uniform in size.

[0074] Figure 6 The Cs prepared in this example 4 PbB 6 , CsPbBr 3 , CsPbBr 3 @Comparison of the UV-Vis absorption spectra of ZnO quantum dots shows that CsPbBr 3 @ZnO relative to CsPbBr 3 The absorption of quantum dots has blue shifted. Figure 7 The CsPbBr prepared in this example 3 , CsPbBr 3 @ZnO quantum dots PL peak comparison, we can see that CsPbBr 3 @The PL peak of ZnO quantum dots also blue-shifted, which may be due to the ZnO heterojunction causing the luminescence peak of quantum dots to blue-shift.

[0075] Figure 8 The CsPbBr prepared in this example 3 , CsPbBr 3 @XPS graph of ZnO quantum dots shows Zn 2p and Si 2p signals, and due to the presence of Zn-O bonds in zinc oxide, the binding energy of O is significantly increased. Figure 6 and Figure 7 The changing pattern of optical properties and the obvious weakening of the XPS characteristic peaks of elements such as Cs, Pb, and Br prove the formation of ZnO shell.

[0076] Fig. 9 The CsPbBr prepared in this example 3 , CsPbBr 3 @FTIR image of ZnO quantum dots, 1735cm -1 and 1641cm -1 They are the C=O stretching vibration of protonated oleic acid and the R-NH + Asymmetric vibration, CsPbBr 3 @ZnO at 1735cm-1 and 1641cm -1 The signal peak relative to CsPbBr 3 The oleylamine and oleic acid ligands were significantly weakened, so some of them were replaced. 3 @ZnO at 1261cm -1 and 800cm -1 Two new absorption peaks appeared at 720 cm-1, which are from the CO vibration of the monodentate oleic acid ligand. According to the significantly higher peak intensity of the latter, it can be judged that there is a contribution from Si-O vibration. -1 -(CH 2 ) n -The CH vibration of the long chain is greatly weakened, indicating that the non-monodentate binding of oleic acid ligands is greatly reduced, and the monodentate binding of oleic acid ligands becomes the main surface feature. 3 @ZnO at 1091cm -1 New absorption appeared, which is a typical Si-O-Si vibration feature, proving that the surface of the quantum dots was passivated by APTMS at the same time, and further formed a Si-O-Si network through hydrolysis and condensation reactions. 3 @ZnO surface has both oleylamine and APTMS passivation structures, because there may be a significant difference in adsorption energy between the two, so CsPbBr 3 @ZnO quantum dots have more uniform size.

[0077] Example 3: Core-shell structure CsPbCl 3 @Preparation of ZnO quantum dots

[0078] 1. Cs 4 PbCl 6 Synthesis of quantum dots

[0079] Add 0.814 g of cesium carbonate, 2.5 mL of oleic acid and 40 mL of octadecene into a three-necked flask, pass nitrogen to remove water and oxygen, then evacuate the flask, raise the temperature to 120°C, pass nitrogen to positive pressure, keep warm for 5 minutes, then continue to raise the temperature to 150°C, stir at a constant temperature until dissolved, and obtain a cesium oleate precursor solution, which is stored at 100°C in nitrogen for later use.

[0080] In another three-necked flask, add 0.0367g of lead chloride and 5mL of octadecene, pass nitrogen to remove water and oxygen, then evacuate, heat to 120°C, pass nitrogen to positive pressure, stir at constant temperature for 1h, then add 0.5mL of oleic acid and 1mL of oleylamine, continue stirring until the lead chloride is completely dissolved; heat to 150°C again, stir for 10min, then drop the temperature to 90°C, inject the synthesized cesium oleate precursor solution, wait for 5s and then cool to room temperature in an ice water bath to obtain Cs 4 PbCl 6Quantum dot masterbatch.

[0081] According to the volume ratio of 1:2, Cs 4 PbCl 6 After the quantum dot mother solution was mixed with methyl acetate, it was centrifuged and washed. The resulting precipitate was dispersed in toluene at a concentration of 10 mg / mL to obtain the purified Cs 4 PbCl 6 Toluene dispersion of quantum dots (hereinafter referred to as Cs 4 PbCl 6 solution).

[0082] 2. Core-shell structure CsPbCl 3 @Preparation of ZnO quantum dots

[0083] Take 2 mL of Cs prepared in step 1 4 PbCl 6 The solution was added with 80 μL of the AP-ZnO aqueous solution prepared in Example 1, stirred at room temperature for 10 min, allowed to stand for 12 h, and then centrifuged at 8000 rpm for 5 min. The supernatant was taken to obtain a core-shell structure CsPbCl 3 @ZnO quantum dots.

[0084] For comparison, this example also prepared CsPbCl by conventional hydrolysis method. 3 Quantum dots, specifically: add 80 μL of water to 2 mL of Cs prepared in step 1 4 PbB 6 The solution was stirred at room temperature for 10 minutes, allowed to stand for 12 hours, and then centrifuged at 8000 rpm for 5 minutes. The supernatant was taken to obtain CsPbCl 3 Quantum dots.

[0085] Fig.10 The CsPbCl prepared in this example 3 Quantum dots and core-shell structures CsPbCl 3 @The UV-visible absorption spectrum and fluorescence spectrum of ZnO quantum dots show that the CsPbCl prepared in this example 3 @ZnO quantum dots have a narrow emission width, excellent luminescence performance, and their optical properties are adjustable over the entire visible light range.

[0086] Example 4: Core-shell structure CsPbI 3 @Preparation of ZnO quantum dots

[0087] 1. Cs 4 PbI 6 Synthesis of quantum dots

[0088] Add 0.814 g of cesium carbonate, 2.5 mL of oleic acid and 40 mL of octadecene into a three-necked flask, pass nitrogen to remove water and oxygen, then evacuate the flask, raise the temperature to 120°C, pass nitrogen to positive pressure, keep warm for 5 minutes, then continue to raise the temperature to 150°C, stir at a constant temperature until dissolved, and obtain a cesium oleate precursor solution, which is stored at 100°C in nitrogen for later use.

[0089] In another three-necked flask, add 0.0367g of lead iodide and 5mL of octadecene, pass nitrogen to remove water and oxygen, then evacuate, heat to 120°C, pass nitrogen to positive pressure, stir at constant temperature for 1h, then add 0.5mL of oleic acid and 1mL of oleylamine, continue stirring until the lead iodide is completely dissolved; heat to 150°C again, stir for 10min, then drop the temperature to 90°C, inject the synthesized cesium oleate precursor solution, wait for 5s and cool to room temperature in an ice water bath to obtain Cs 4 PbI 6 Quantum dot masterbatch.

[0090] According to the volume ratio of 1:2, Cs 4 PbI 6 After the quantum dot mother solution was mixed with methyl acetate, it was centrifuged and washed. The resulting precipitate was dispersed in toluene at a concentration of 10 mg / mL to obtain the purified Cs 4 PbI 6 Toluene dispersion of quantum dots (hereinafter referred to as Cs 4 PbI 6 solution).

[0091] 2. Core-shell structure CsPbI 3 @Preparation of ZnO quantum dots

[0092] Take 2 mL of Cs prepared in step 1 4 PbI 6 The solution was added with 80 μL of the AP-ZnO aqueous solution prepared in Example 1, stirred at room temperature for 10 min, allowed to stand for 12 h, and then centrifuged at 8000 rpm for 5 min. The supernatant was taken to obtain a core-shell structure CsPbI 3 @ZnO quantum dots.

[0093] For comparison, this example also prepared CsPbI 3 Quantum dots, specifically: add 80 μL of water to 2 mL of Cs prepared in step 1 4 PbI 6 The solution was stirred at room temperature for 10 minutes, allowed to stand for 12 hours, and then centrifuged at 8000 rpm for 5 minutes. The supernatant was taken to obtain CsPbI 3 Quantum dots.

[0094] Fig.11The CsPbI prepared in this example 3 Quantum dots and core-shell structures CsPbI 3 The UV-visible absorption spectrum and fluorescence spectrum of @ZnO quantum dots show that the CsPbI prepared in this embodiment 3 @ZnO quantum dots have a narrow emission width, excellent luminescence performance, and their optical properties are adjustable over the entire visible light range.

[0095] 2. Core-shell structure CsPbX 3 @Control of ZnO layer thickness in ZnO quantum dots

[0096] To illustrate the CsPbX 3 @The method for regulating the thickness of the ZnO shell in ZnO quantum dots is given below through Examples 5-7. 3 @Specific steps of ZnO shell thickness in ZnO quantum dots.

[0097] Example 5: Changing the volume ratio of the aqueous dispersion system to the organic dispersion system to adjust the CsPbBr 3 @ZnO layer thickness in ZnO quantum dots

[0098] Based on Example 2, the volume of the AP-ZnO aqueous solution in step 2 was adjusted to 20, 40, 60, 80, 100, and 120 μL to obtain CsPbBr with different ZnO layer thicknesses. 3 @ZnO quantum dots.

[0099] Fig.12 , Fig.13 The CsPbBr prepared by adding different volumes of AP-ZnO in this example are 3 Comparison of PL peaks and UV-Vis absorption spectra of @ZnO quantum dots. With the increase of AP-ZnO, CsPbBr 3 @The PL of ZnO quantum dots first increases and then decreases, which may be due to the fluorescence quenching of perovskite quantum dots as the thickness of the ZnO shell increases. Therefore, the thickness of the ZnO shell can be regulated by controlling the concentration and volume ratio of the aqueous dispersion system to the organic dispersion system.

[0100] Fig.14 CsPbBr prepared by adding different volumes of AP-ZnO in this example 3 @The trend chart of the fluorescence quantum yield of ZnO quantum dots shows that the PLQY reaches a maximum value of 93% after adding 80μL of AP-ZnO aqueous solution, and the quantum dots are fully passivated. A thicker quantum dot light-emitting layer can be used in QLED products, which is conducive to reducing the differences in device parameters such as electroluminescent color and operating voltage between different batches and improving product yield.

[0101] The shell thickness of this embodiment is determined by the ratio of the integrated intensity of the Zn 2p peak to the integrated intensity of the Pb 4f peak in XPS (denoted as Zn / Pb). The larger the Zn / Pb ratio, the thicker the shell. 4 PbB 6 Different volumes of AP-ZnO were added to the quantum dots. By calculating the Zn / Pb of several groups of samples, it was shown that with the increase of AP-ZnO nanocrystals, Zn / Pb also increased from 0 to 0.06 and 0.13, proving that the thickness of the ZnO layer on the surface of the quantum dots increased.

[0102] Example 6: Using aminosilane as the main ligand and another type of silane ligand as an auxiliary to regulate CsPbBr 3 @ZnO layer thickness in ZnO quantum dots

[0103] On the basis of Example 1, the conditions of step 3 were modified as follows: an ethanol dispersion of surface hydroxylated ZnO nanocrystals obtained in step 2 containing 0.74 mmol ZnO was measured, 0.057 mmol APTMS was added, the reaction was stirred for 12 h, and then 0.03 mol trimethoxy(2-phenylethyl)silane (TMPES) was added, the reaction solution was centrifuged, and the resulting precipitate was washed with a mixed solvent of ethyl acetate and ethanol (the volume ratio of the two was 2:1) and then centrifuged to remove unreacted aminosilane; the resulting precipitate was dispersed in pure water to prepare an aqueous dispersion system of APT-ZnO nanocrystals with a concentration of 0.1229 mol / L.

[0104] Fig.15 The Fourier transform infrared spectra (FTIR) of the ZnO nanocrystals, AP-ZnO nanocrystals and APT-ZnO nanocrystals prepared in Example 1 and Example 6 are shown in Figure 1. The surface of the APT-ZnO nanocrystal has a wavelength of 3402 cm -1 The hydroxyl groups on the surface of ZnO nanocrystals and AP-ZnO nanocrystals basically disappeared, and at the same time, a new 1101cm -1 The Zn-O-Si bonds of AP-ZnO were clearly regulated, indicating that the surface chemistry of AP-ZnO was regulated and proving that the ZnO surface was functionalized by amino groups.

[0105] On the basis of Example 2, the AP-ZnO aqueous solution in step 2 was replaced with 20, 40, 60, 80, 100, and 120 μL of APT-ZnO aqueous solution to prepare CsPbBr 3 @ZnO quantum dots.

[0106] Fig.16 CsPbBr prepared by adding different volumes of APT-ZnO in this example 3@PL peak comparison of ZnO quantum dots shows that CsPbBr prepared based on APT-ZnO nanocrystals 3 The PL peak of @ZnO also blue-shifted, which is due to the blue-shift of the luminescence peak of the quantum dots caused by the ZnO heterojunction. At the same time, the PL weakened to a certain extent, reflecting the CsPbBr 3 @Changes in the ZnO shell of ZnO quantum dots.

[0107] Example 7, CsPbBr 3 @ZnO quantum dots ZnO layer thickness regulation

[0108] On the basis of Example 1, the conditions of step 3 were modified as follows: an ethanol dispersion of surface hydroxylated ZnO nanocrystals obtained in step 2 containing 0.74 mmol ZnO was measured, 0.057 mmol APTMS was added, the reaction was stirred for 12 h, 0.03 mol trichloro(phenethyl)silane (PETS) was added, the reaction solution was centrifuged, the obtained precipitate was washed with a mixed solvent of ethyl acetate and ethanol (the volume ratio of the two was 2:1) and then centrifuged to remove untreated silane; the obtained precipitate was dispersed in pure water to prepare an aqueous dispersion system of APP-ZnO nanocrystals with a concentration of 0.1229 mol / L.

[0109] Fig.17 The Fourier transform infrared spectra (FTIR) of the ZnO nanocrystals, AP-ZnO nanocrystals and APP-ZnO nanocrystals prepared in Example 1 and Example 7 are shown in Figure 1. The surface of the APP-ZnO nanocrystal has a wavelength of 3402 cm -1 The hydroxyl groups on the surface of ZnO nanocrystals and AP-ZnO nanocrystals also basically disappeared, and at the same time, a new 1101cm -1 The Zn-O-Si bonds of AP-ZnO were regulated, indicating that the surface chemistry of AP-ZnO was regulated and proving that the ZnO surface was functionalized.

[0110] On the basis of Example 2, the AP-ZnO aqueous solution in step 2 was replaced with 20, 40, 60, 80, 100, and 120 μL of APP-ZnO aqueous solution to prepare CsPbBr 3 @ZnO quantum dots.

[0111] Fig.18 CsPbBr prepared by adding different volumes of APP-ZnO in this example 3 @PL peak comparison of ZnO quantum dots shows that CsPbBr prepared based on APP-ZnO nanocrystals 3@ZnO quantum dots also have a blue shift in PL peak position, which is caused by the ZnO heterojunction causing the luminescence peak position of quantum dots to blue shift. At the same time, PL has weakened to a certain extent, reflecting the CsPbBr 3 @Changes in the ZnO shell of ZnO quantum dots.

[0112] Based on Example 6 and Example 7, the thickness of the ZnO shell layer on the surface of the quantum dots was further adjusted to a certain extent, thereby optimizing the performance of the device.

[0113] 3. Conductivity test and electroluminescent device preparation

[0114] Example 8, CsPbBr 3 @ZnO quantum dots conductivity test

[0115] This example tests the CsPbBr obtained in Example 2 by using single electron devices and single hole devices. 3 @ZnO conductivity, the device structure used in the single electron device is ITO / ZnO / EML / TPBi / Liq / Al, and the device structure used in the single hole device is ITO / PEDOT:PSS / EML / MoO 3 / Al, where EML is made of CsPbBr 3 @ZnO or control group CsPbBr 3 As the light-emitting layer in single-electron and single-hole devices.

[0116] The preparation method of the single electron device is as follows: the patterned etched indium tin oxide (ITO) glass is ultrasonically treated in a beaker with a volume ratio of 1:20 for 20 minutes, then immersed in plasma water for ultrasonic treatment for 20 minutes, and finally rinsed with deionized water to remove impurities remaining on the surface, dried with nitrogen, placed on a hot stage for annealing, and then treated with ultraviolet ozone (UV-Zone) for 10 minutes. The ethanol solution of ZnO with a concentration of 30 mg / mL was filtered through a 0.45 μm filter, spin-coated on the ITO glass substrate at a speed of 3000 rpm for 60 seconds, and annealed at 150°C for 20 minutes. CsPbBr was prepared by spin coating at 3000 rpm for 30 seconds. 3 @ZnO or CsPbBr 3 The TPBi electron transport layer and the Liq / Al cathode were placed in a high vacuum (<5×10 -6 Torr) by evaporation.

[0117] The preparation method of the single hole device is as follows: the patterned etched indium tin oxide (ITO) glass is ultrasonically treated for 20 minutes in a beaker containing ITO cleaning solution and deionized water in a volume ratio of 1:20, then soaked in plasma water for 20 minutes, and finally rinsed with deionized water to remove impurities remaining on the surface. After drying with nitrogen, it is placed on a hot stage for annealing, and then treated with ultraviolet ozone (UV-Zone) for 10 minutes. The PEDOT:PSS solution is filtered through a 0.45μm filter, spin-coated onto the ITO glass substrate at a speed of 4000rpm for 40s, and annealed at 120℃ for 15min. CsPbBr was prepared by spin coating at 3000rpm for 30s. 3 @ZnO or CsPbBr 3 The light-emitting layer. MoO 3 / Al cathode is placed in a high vacuum (<5×10 -6 Torr) by evaporation.

[0118] Fig.19 The current density curve of the single electron device shows that CsPbBr 3 @ZnO quantum dots relative to CsPbBr 3 The current density is increased by an order of magnitude. Fig. 20 The current density curve of the single hole device shows that CsPbBr 3 @ZnO quantum dots relative to CsPbBr 3 The current density of CsPbBr 3 @ZnO quantum dots have better conductivity than CsPbBr 3 Quantum dots have excellent conductive properties.

[0119] Example 9: Conductive performance test based on ITO / EML / Ag device

[0120] In this example, the CsPbBr obtained in Example 2 was synthesized by using an ITO / EML / Ag device. 3 The conductive properties of @ZnO were further tested. 3 , CsPbBr 3 @ZnO and AP-ZnO were prepared for comparison.

[0121] Device preparation: The patterned etched indium tin oxide (ITO) glass was ultrasonically treated in a beaker with a volume ratio of 1:20 for 20 minutes, then soaked in plasma water for 20 minutes, and finally rinsed with deionized water to remove the impurities remaining on the surface. After drying with nitrogen, it was placed on a hot stage for annealing, and then treated with ultraviolet ozone (UV-Zone) for 10 minutes. Then, CsPbBr was prepared by spin coating at 3000rpm for 30s. 3 or CsPbBr 3 @ZnO layer, annealed at 60℃ for 10min to form an EML layer; or AP-ZnO ethanol solution with a concentration of 30mg / mL was filtered through a 0.45μm filter, spin-coated onto an ITO glass substrate at a speed of 3000rpm for 60s, and annealed at 150℃ for 20min to form an EML layer. Metal Ag was formed in a high vacuum (<5×10 -6 Torr) by evaporation.

[0122] like Fig.21 As shown, based on CsPbBr 3 The current density of the ITO / EML / Ag device based on @ZnO is the highest, followed by the current density of the device based on AP-ZnO. 3 The current density of the device is the smallest, so CsPbBr 3 The conductivity of @ZnO is significantly better than that of ZnO electron transport layer and CsPbBr 3 As the QLED light-emitting layer has higher conductivity than the carrier transport layer, it is beneficial to obtain higher device stability and longer life.

[0123] Example 10: Preparation of a QLED

[0124] In this embodiment, an electroluminescent device is prepared by a full solution method. The device structure used is ITO / PEDOT:PSS / PTAA / EML / TPBi / Ag and ITO / PEDOT:PSS / PTAA / EML / ZnO / Ag, wherein EML is CsPbBr 3 @The light-emitting layer prepared by ZnO.

[0125] The preparation method of the electroluminescent device is as follows: the patterned etched indium tin oxide (ITO) glass is ultrasonically treated in a beaker with a volume ratio of 1:20 for 20 minutes, then immersed in plasma water for ultrasonic treatment for 20 minutes, and finally rinsed with deionized water to remove impurities remaining on the surface, dried with nitrogen, placed on a hot stage for annealing, and then treated with ultraviolet ozone (UV-Zone) for 10 minutes. The PEDOT:PSS solution is filtered through a 0.45μm filter, spin-coated on the ITO glass substrate at a speed of 4000rpm for 40s, and annealed at 120℃ for 15min. The PTAA chlorobenzene solution with a concentration of 5mg / mL is filtered through a 0.45μm filter, spin-coated at a speed of 3000rpm for 40s, and annealed at 120℃ for 15min. CsPbBr is prepared by spin coating at 3000rpm for 30s. 3 @ZnO light-emitting layer, prepare light-emitting layers with different numbers (1, 2, and 3 layers, respectively), and anneal at 60°C for 10 min. 4 mg / mL TPBi methyl acetate solution was filtered through a 0.45 μm filter, spin-coated at 2000 rpm for 30 s, and annealed at 50°C for 15 min; or ZnO was used as the electron transport layer, and 25 mg / mL ZnO methyl nonafluorobutyl ether solution was filtered through a 0.45 μm filter, spin-coated at 2000 rpm for 30 s, and annealed at 50°C for 15 min. Metal Ag was placed under high vacuum (<5×10 -6 Torr) by evaporation.

[0126] CsPbBr as the light-emitting layer 3 @ZnO quantum dots are realized by APTMS CsPbBr 3 Linked to the ZnO shell. On the one hand, the surface of the quantum dots is passivated, which improves the stability of the perovskite; on the other hand, the ionization potential of the quantum dot core is increased, forming a high-quality nano-heterojunction, inserting an interface layer between the light-emitting layer and ZnO, and ultimately improving the performance of the light-emitting layer. When ZnO is used as the electron transport layer, the device with two layers of EML has the highest brightness ( Fig.24 As shown), this is due to the CsPbBr 3 @ZnO has excellent electrical conductivity, and a thicker quantum dot light-emitting layer can be used. The ZnO in the quantum dots can solve the instability near the interface between the light-emitting layer and the ZnO as the transport layer, inhibit non-radiative recombination, and improve the carrier injection balance. Fig. 22 and Fig.23 As shown in the figure, based on the above two device structures, the current density of TPBi as the electron transport layer is larger than that of ZnO as the electron transport layer, but the brightness of the device is lower than that of CsPbBr 3@ZnO quantum dots have a ZnO shell, which is more compatible with the ZnO energy level, so that the interface between the light-emitting layer and the ZnO transport layer tends to be stable, making it easy to achieve carrier injection balance. 3 @ZnO quantum dots have excellent conductive properties. When applied to QLEDs, a thicker quantum dot light-emitting layer can be used, thereby solving the carrier balance problem within a larger process window.

Claims

1. A method for preparing core-shell structured CsPbX3@ZnO quantum dots, characterized in that: A water dispersion system of aminosilane-functionalized ZnO nanocrystals and an organic dispersion system of Cs4PbX6 quantum dots are prepared respectively, and then the two are mixed for chemical reaction, so as to obtain CsPbX3@ZnO quantum dots with a core-shell structure of CsPbX3 encapsulated by ZnO; when the water dispersion system and the organic dispersion system are mixed, the mass ratio of aminosilane-functionalized ZnO nanocrystals to Cs4PbX6 quantum dots is 0.1 to 15:1; The preparation method of the aqueous dispersion system of aminosilane-functionalized ZnO nanocrystals is as follows: adding an ethanol solution of tetramethylammonium hydroxide dropwise to a dimethyl sulfoxide solution of zinc acetate dihydrate, and then stirring for reaction to obtain a ZnO nanocrystal dispersion liquid; adding ethyl acetate to the ZnO nanocrystal dispersion liquid, centrifuging, and adding ethanol to the obtained ZnO precipitate to obtain an ethanol dispersion liquid of surface-hydroxylated ZnO nanocrystals; adding aminosilane to the ethanol dispersion liquid of surface-hydroxylated ZnO nanocrystals to react the ZnO nanocrystals with the aminosilane; centrifuging the reaction liquid, and washing the obtained precipitate with a mixed solvent of ethyl acetate and ethanol and then centrifuging to remove unreacted aminosilane; and then dispersing the obtained precipitate in pure water to obtain an aqueous dispersion system of aminosilane-functionalized ZnO nanocrystals, which is recorded as an aqueous dispersion system of AP-ZnO nanocrystals.

2. The method for preparing core-shell structure CsPbX3@ZnO quantum dots according to claim 1, characterized in that: The organic solvent in the organic dispersion system of the Cs4PbX6 quantum dots is a benzene, alkane or cycloalkane organic solvent.

3. The method for preparing core-shell structure CsPbX3@ZnO quantum dots according to claim 1, characterized in that: After the aqueous dispersion system and the organic dispersion system are mixed and reacted, the obtained solution is centrifuged to obtain the supernatant to obtain CsPbX3@ZnO quantum dots with a core-shell structure.

4. The method for preparing core-shell structure CsPbX3@ZnO quantum dots according to claim 1, characterized in that: The thickness of the ZnO shell layer in the core-shell structure CsPbX3@ZnO quantum dots or the heterojunction properties of CsPbX3 and ZnO are regulated by one of the following methods: Method 1: Changing the concentration and / or volume ratio of the aqueous dispersion system to the organic dispersion system; Method 2: When preparing the aqueous dispersion system of aminosilane-functionalized ZnO nanocrystals, aminosilane is used as the main ligand, and another type of silane ligand is used as an auxiliary to react with ZnO nanocrystals to regulate the surface chemical properties of the obtained aminosilane-functionalized ZnO nanocrystals, further affecting the heterojunction interface and surface properties of the core-shell structure CsPbX3@ZnO quantum dots, thereby regulating the thickness of the ZnO shell layer and the conductivity of the core-shell structure CsPbX3@ZnO quantum dots.

5. The method for preparing core-shell structure CsPbX3@ZnO quantum dots according to claim 1, characterized in that: When preparing a water dispersion system of aminosilane-functionalized ZnO nanocrystals, the molar ratio of surface hydroxylated ZnO nanocrystals to aminosilane is 4-14:

1.

6. A core-shell structured CsPbX3@ZnO quantum dot prepared by the preparation method according to any one of claims 1 to 5.

7. Use of the core-shell structure CsPbX3@ZnO quantum dots according to claim 6 in electroluminescent devices.

Images