Electronic transport materials, their preparation methods, and quantum dot light-emitting diodes

Abstract

This application relates to the field of display technologies, and provides an electron transport material, which includes zinc oxide nanoparticles and aluminum oxide; wherein, the aluminum oxide is bound to the surface of the zinc oxide nanoparticles. The electron transport material provided by the present invention passivates the surface defects of the zinc oxide nanoparticles by binding aluminum oxide to the surface, thereby improving the electron transport ability and stability of the electron transport material.

Description

Technical Field

[0001] The present invention belongs to the technical field of displays, and particularly relates to an electron transport material and a preparation method thereof, and a quantum dot light emitting diode. Background Art

[0002] Due to the advantages of high optical color purity, high luminescence quantum efficiency, tunable luminescence color, high quantum yield, etc. of semiconductor quantum dots (QDs), and the fact that they can be prepared using printing processes, quantum dot light emitting diodes (QLEDs) with quantum dots as the light emitting center have become a highly potential next-generation display and solid-state lighting light source, attracting widespread attention, and their device performance indicators have also developed rapidly.

[0003] In QLED devices, the imbalance of carrier injection and transport will affect the service life of QLED devices. Zinc oxide nanomaterials are widely used as the electron transport layer of electroluminescent devices because of their advantages such as high transmittance, high electron mobility, low cost, environmental compatibility, and simple preparation process. However, even so, the electron transport performance of zinc oxide nanomaterials still has deficiencies, which in turn affect the light emitting efficiency and service life of the devices, especially the problem of low blue light device life. Summary of the Invention

[0004] The purpose of this application is to provide an electron transport material and a preparation method thereof, and a quantum dot light emitting diode, aiming to solve the problem of insufficient electron transport performance of zinc oxide nanomaterials as electron transport materials.

[0005] To achieve the above application purpose, the technical solutions adopted in this application are as follows:

[0006] In the first aspect, this application provides an electron transport material, including zinc oxide nanoparticles and aluminum oxide; wherein, the aluminum oxide is combined on the surface of the zinc oxide nanoparticles.

[0007] In the second aspect, this application provides a preparation method of an electron transport material, including the following steps:

[0008] Provide a zinc oxide nanoparticle solution and an aluminum oxide precursor solution;

[0009] Under heating conditions, add the aluminum oxide precursor solution to the zinc oxide nanoparticle solution for reaction to obtain the electron transport material in which aluminum oxide is combined on the surface of the zinc oxide nanoparticles.

[0010] In a third aspect, the present application provides a quantum dot light-emitting diode, which includes an anode and a cathode disposed opposite to each other, a quantum dot light-emitting layer disposed between the anode and the cathode, and an electron transport layer disposed between the quantum dot light-emitting layer and the cathode; wherein, the material of the electron transport layer includes zinc oxide nanoparticles and aluminum oxide; wherein, the aluminum oxide is bonded to the surface of the zinc oxide nanoparticles.

[0011] The electron transport material provided by the present application uses zinc oxide nanoparticles as the main body, and aluminum oxide is bonded to the surface of the zinc oxide nanoparticles. By bonding aluminum oxide on the surface, the surface defects of the zinc oxide nanoparticles are passivated, thereby improving the electron transport ability and stability of the electron transport material.

[0012] The preparation method of the electron transport material provided by the present application is to add an aluminum oxide precursor solution to a zinc oxide nanoparticle solution. The aluminum oxide precursor gradually reacts to form aluminum oxide under heating conditions and slowly bonds to the surface of the zinc oxide nanoparticles, passivating the surface of the zinc oxide nanoparticles, and finally obtaining an electron transport material with improved electron transport ability and stability.

[0013] In the quantum dot light-emitting diode provided by the present application, the material of the electron transport layer is the above-mentioned electron transport material. Compared with zinc oxide nanoparticles, the zinc oxide nanoparticles of the material passivated by aluminum oxide have higher stability, and the luminous efficiency and service life of the quantum dot light-emitting diode are improved. Description of the Drawings

[0014] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the following will briefly introduce the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings in the following description are only some embodiments of the present application. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative efforts.

[0015] Figure 1 is a process flow chart of the preparation of the electron transport material provided by the embodiment of the present application;

[0016] Figure 2 is a schematic structural diagram of the quantum dot light-emitting diode provided by the embodiment of the present application;

[0017] Figure 3 is a schematic structural diagram of the positive-type quantum dot light-emitting diode provided by the embodiment of the present application;

[0018] Figure 4 is a schematic structural diagram of the inverted quantum dot light-emitting diode provided by the embodiment of the present application. Detailed Embodiments

[0019] In order to make the technical problems to be solved, technical solutions and beneficial effects of this application more clear and understandable, the following further details this application in conjunction with embodiments. It should be understood that the specific embodiments described herein are only used to explain this application and are not used to limit this application.

[0020] In this application, the term "and / or" describes the association relationship of associated objects, indicating that there can be three relationships. For example, A and / or B can represent: A exists alone, A and B exist simultaneously, or B exists alone. Where A and B can be singular or plural. The character " / " generally represents an "or" relationship between the associated objects before and after.

[0021] In this application, "at least one" means one or more, and "a plurality" means two or more. "At least one of the following" or its similar expressions refer to any combination of these items, including any combination of single item(s) or plural item(s). For example, "at least one of a, b, or c", or, "at least one of a, b, and c" can both represent: a, b, c, a - b (i.e., a and b), a - c, b - c, or a - b - c, where a, b, and c can be single or plural respectively.

[0022] It should be understood that in various embodiments of this application, the magnitudes of the sequence numbers of the above processes do not mean the order of execution. Some or all of the steps can be executed in parallel or sequentially. The execution order of each process should be determined by its function and internal logic, and should not constitute any limitation to the implementation process of the embodiments of this application.

[0023] The terms used in the embodiments of this application are only for the purpose of describing specific embodiments, and are not intended to limit this application. The singular forms "a", "the", and "said" used in the embodiments of this application and the appended claims are also intended to include the plural forms, unless the context clearly indicates otherwise.

[0024] The terms "first" and "second" are only used for descriptive purposes to distinguish objects such as substances, interfaces, messages, requests, and terminals from each other, and should not be understood as indicating or implying relative importance or implicitly specifying the quantity of the indicated technical features. For example, without departing from the scope of the embodiments of this application, the first XX can also be referred to as the second XX, and similarly, the second XX can also be referred to as the first XX. Thus, the features defined with "first" and "second" can explicitly or implicitly include one or more of such features.

[0025] In the description of the embodiments of the present application, the weight of the relevant components mentioned not only can refer to the specific content of each component, but also can represent the proportional relationship of the weights between the components. Therefore, as long as the content of the relevant components in the description of the embodiments of the present application is scaled up or down proportionally, it is within the scope disclosed in the description of the embodiments of the present application. Specifically, the mass described in the description of the embodiments of the present application can be mass units well-known in the chemical industry such as μg, mg, g, kg, etc.

[0026] In quantum dot light-emitting diodes, especially in blue light devices, the injection and transport of electrons are weaker than those of holes, which results in the easy generation of more exciton-hole three-particle systems during the operation of the device. Since the quenching effect of holes on excitons is usually stronger than that of electrons, blue light devices with insufficient electron injection face serious exciton quenching. In addition, there are -OH (hydroxyl groups) and residual organic ligands on the surface of zinc oxide nanoparticles. Excess holes may react with -OH on the surface of zinc oxide to generate highly oxidizing OH radicals. The active OH radicals can oxidize many organic substances, leading to the shedding of ligands on the surface of quantum dots, an increase in surface defects of zinc oxide particles, and an increase in the carrier transport barrier, thus severely reducing the lifespan of QLED devices. In view of this,

[0027] The first aspect of the embodiments of the present application provides an electron transport material, including zinc oxide nanoparticles and aluminum oxide; wherein, the aluminum oxide is bonded to the surface of the zinc oxide nanoparticles.

[0028] The electron transport material provided by the embodiments of the present application uses zinc oxide nanoparticles as the main body, and aluminum oxide is bonded to the surface of the zinc oxide nanoparticles. By bonding aluminum oxide on the surface, the surface defects of the zinc oxide nanoparticles are passivated, thereby improving the electron transport ability and stability of the electron transport material.

[0029] Specifically, the aluminum oxide is bonded to the surface of the zinc oxide nanoparticles to fill the surface defects of the zinc oxide nanoparticles. The zinc oxide nanoparticles passivated by aluminum oxide have fewer surface defects and no hydroxyl groups hanging on the surface, thereby avoiding the oxidation reaction of the hanging hydroxyl groups by excess holes to generate highly oxidizing hydroxyl radicals, and further reducing the risk of ligand shedding on the surface of quantum dots. At the same time, the electron transport performance of zinc oxide is effectively exerted. When this electron transport material is used as the electron transport layer material of a quantum dot light-emitting diode, especially as the electron transport layer material of a quantum dot light-emitting diode, the luminous efficiency and service life of the device can be effectively improved.

[0030] In some embodiments, the molar ratio of zinc oxide nanoparticles to aluminum oxide is (5 to 10):1. In this case, a thin aluminum oxide coating layer is bonded to the surface of the zinc oxide nanoparticles, which can effectively reduce the surface defects of the zinc oxide nanoparticles and does not affect the electron transport function of the main functional material, zinc oxide nanoparticles, thereby essentially improving the electron transport ability of the zinc oxide nanoparticles.

[0031] The electron transport material provided in the first aspect of the embodiments of the present application can be obtained by the following method.

[0032] Combined with Figure 1 , the second aspect of the embodiments of the present application provides a method for preparing an electron transport material, including the following steps:

[0033] S01. Provide a zinc oxide nanoparticle solution and an aluminum oxide precursor solution;

[0034] S02. Under heating conditions, add the aluminum oxide precursor solution to the zinc oxide nanoparticle solution for reaction to obtain an electron transport material in which aluminum oxide is bonded to the surface of the zinc oxide nanoparticles.

[0035] In the method for preparing the electron transport material provided in the embodiments of the present application, the aluminum oxide precursor solution is added to the zinc oxide nanoparticle solution. The aluminum oxide precursor gradually reacts to form aluminum oxide under heating conditions and slowly binds to the surface of the zinc oxide nanoparticles, passivating the surface of the zinc oxide nanoparticles, and finally obtaining an electron transport material with improved electron transport ability and stability.

[0036] Specifically, in the above step S01, the main raw material of the electron transport material is provided, and the main raw material is zinc oxide nanoparticles. The zinc oxide nanoparticles are dissolved in a solvent to prepare a zinc oxide nanoparticle solution. In some embodiments, the zinc oxide nanoparticles can be prepared by heating a zinc oxide nanoparticle precursor at room temperature (5°C to 40°C). In some embodiments, the method for preparing zinc oxide nanoparticles is: dissolving a zinc oxide nanoparticle precursor in a solvent to obtain a precursor solution, adding an alkali for reaction to obtain zinc oxide nanoparticles. In some embodiments, ethylene glycol monomethyl ether and ethanolamine are added to the precursor solution to slowly generate zinc oxide nanoparticles, obtaining zinc oxide nanoparticles with uniform particle size.

[0037] Aluminum oxide precursor is used as the raw material of aluminum oxide, and aluminum oxide is formed by reaction during the heating process of the following steps; in the embodiments of the present application, aluminum oxide is gradually formed by reaction to control the content of aluminum oxide, so that aluminum oxide is combined on the surface of zinc oxide nanoparticles. It should be noted that the embodiments of the present application use an aluminum oxide precursor capable of generating aluminum oxide as the reaction raw material, rather than using aluminum oxide as the raw material, to prevent the content of aluminum oxide in the reaction system from being too high, and aluminum oxide and zinc oxide nanoparticles form a blend, and the coating of zinc oxide nanoparticles cannot be achieved.

[0038] In the above step S02, under heating conditions, an aluminum oxide precursor solution is added to the zinc oxide nanoparticle solution for reaction. Here, it should be understood that the zinc oxide nanoparticle solution is heated, and the aluminum oxide precursor solution is added for reaction under heating conditions. The aluminum oxide precursor in the aluminum oxide precursor solution gradually forms aluminum oxide and coats on the surface of the zinc oxide nanoparticles. In some embodiments, the temperature of the heating conditions is 80°C to 300°C. In this case, the aluminum oxide precursor in the aluminum oxide precursor solution gradually undergoes a hydrolysis reaction to form aluminum oxide, so that the concentration of aluminum oxide in the reaction system is within a suitable range and combines on the surface of the zinc oxide nanoparticles. If the heating temperature is relatively high, such as 300°C to 350°C, the hydrolysis reaction time of the aluminum oxide precursor is too short, and the grown aluminum oxide is unevenly wrapped on the surface of the zinc oxide nanoparticles, and the morphology of the zinc oxide nanoparticles wrapped by aluminum oxide is irregular, which affects the electron transport performance of ZnO; at the same time, since it is not easy to control the concentration of aluminum oxide in the reaction system, the obtained Al 2 O 3 coating layer has a relatively thick thickness, which also affects the electron transport performance of ZnO. When the heating temperature is higher than 500°C, the hydrolysis reaction of the aluminum oxide precursor is violent, and the grown aluminum oxide cannot nucleophilically coat the zinc oxide nanoparticles, and finally a mixture of the two is obtained, which cannot play an electron transport role. Of course, it should be understood that when the reaction system contains a zinc oxide nanoparticle precursor, the zinc oxide nanoparticle precursor can also react to form zinc oxide nanoparticles under this heating condition.

[0039] In some embodiments, in the step of adding the aluminum oxide precursor solution to the zinc oxide nanoparticle solution for reaction, based on the molar content of the zinc oxide nanoparticles in the zinc oxide nanoparticle solution being 1 mol, the addition rate of the aluminum oxide precursor in the aluminum oxide precursor solution is 0.1 to 1 mol / h. In this case, the generation rate of aluminum oxide can be controlled by the addition rate, so that the slowly generated aluminum oxide can be evenly and effectively combined on the surface of the zinc oxide nanoparticles to passivate the surface defects of the zinc oxide nanoparticles.

[0040] In some embodiments, in the step of adding an aluminum oxide precursor solution to a zinc oxide nanoparticle solution for reaction, the total amount of the zinc oxide nanoparticle solution and the added aluminum oxide precursor solution satisfies: the molar ratio of zinc oxide nanoparticles to the aluminum oxide precursor is 1:0.1 to 1:1. In this case, the content of the aluminum oxide precursor is relatively excessive, which is conducive to the reaction proceeding in the direction of forming aluminum oxide. At the same time, in the reaction system, when the molar ratio of the participating zinc oxide nanoparticles to the aluminum oxide precursor is 1:0.1 to 1, the amount of aluminum oxide formed can be regulated. In the finally obtained electron transport material, the molar ratio of zinc oxide nanoparticles to aluminum oxide bound to the surface of the zinc oxide nanoparticles is in the range of 1:0.05 to 0.5, so that a thin aluminum oxide coating layer is bound to the surface of the zinc oxide nanoparticles.

[0041] In some embodiments, in the step of adding an aluminum oxide precursor solution to a zinc oxide nanoparticle solution for reaction, the reaction time is 1 to 12 hours.

[0042] On the basis of the above embodiments, it further includes: ultrasonically dispersing the prepared aluminum oxide-passivated zinc oxide nanoparticles and storing them in an organic alcohol to form an electron transport material solution. In some embodiments, in the electron transport material solution, the concentration of the electron transport material is 10 to 100 mg / ml.

[0043] Combined Figure 2 , a third aspect of the embodiments of the present application provides a quantum dot light-emitting diode, including an anode and a cathode arranged opposite to each other, a quantum dot light-emitting layer arranged between the anode and the cathode, and an electron transport layer arranged between the quantum dot light-emitting layer and the cathode; wherein, the material of the electron transport layer includes zinc oxide nanoparticles and aluminum oxide; wherein, the aluminum oxide is bound to the surface of the zinc oxide nanoparticles.

[0044] For the quantum dot light-emitting diode provided by the embodiments of the present application, the material of the electron transport layer is the above-mentioned electron transport material. Compared with zinc oxide nanoparticles, the zinc oxide nanoparticles of the material passivated with aluminum oxide have higher stability, and the luminous efficiency and service life of the quantum dot light-emitting diode are improved.

[0045] Specifically, the zinc oxide nanoparticles passivated with aluminum oxide have more stable performance, fewer surface defects, and no hydroxyl groups hanging on the surface. When it is applied to a quantum dot light-emitting diode, especially a blue quantum dot light-emitting diode device, it can avoid the oxidation reaction of the hanging hydroxyl groups by excessive holes to generate highly oxidizing OH radicals, thereby reducing the shedding of ligands on the surface of the quantum dots, and at the same time effectively exerting the electron transport performance of zinc oxide, and improving the efficiency and life of the device.

[0046] In some embodiments, the molar ratio of zinc oxide nanoparticles to aluminum oxide is (5 - 10):1. In this case, a thin aluminum oxide coating layer is bonded to the surface of the zinc oxide nanoparticles, which can effectively reduce the surface defects of the zinc oxide nanoparticles and will not affect the electron transport function of the main functional material, zinc oxide nanoparticles. Essentially, the electron transport ability of the zinc oxide nanoparticles is improved, thereby improving the luminous efficiency and service life of quantum dot light-emitting diodes, especially blue quantum dot light-emitting diode devices.

[0047] In some embodiments, the quantum dot light-emitting diode further includes a hole functional layer disposed between the anode and the quantum dot light-emitting layer; in some embodiments, the quantum dot light-emitting diode further includes an electron injection layer disposed between the cathode and the electron transport layer; in some embodiments, the quantum dot light-emitting diode further includes a hole functional layer disposed between the anode and the quantum dot light-emitting layer, and an electron injection layer disposed between the cathode and the electron transport layer. Among them, the hole functional layer includes at least one of a hole injection layer, a hole transport layer, and a hole blocking layer.

[0048] In the embodiments of the present application, the quantum dot light-emitting diode may further include a substrate, and the anode or the cathode is disposed on the substrate.

[0049] The quantum dot light-emitting diode provided by the embodiments of the present application is divided into a normal structure quantum dot light-emitting diode and an inverted structure quantum dot light-emitting diode.

[0050] In one embodiment, the normal structure quantum dot light-emitting diode includes an anode and a cathode disposed opposite to each other, a quantum dot light-emitting layer disposed between the anode and the cathode, and an electron transport layer disposed between the cathode and the quantum dot light-emitting layer, and the anode is disposed on the substrate. Further, an electron injection layer may be disposed between the cathode and the electron transport layer; hole functional layers such as a hole transport layer, a hole injection layer, and an electron blocking layer may be disposed between the anode and the quantum dot light-emitting layer. As Figure 3 shown, in some embodiments of the normal structure quantum dot light-emitting diode, the quantum dot light-emitting diode includes a substrate, an anode disposed on the surface of the substrate, a hole injection layer disposed on the surface of the anode, a hole transport layer disposed on the surface of the hole injection layer, a quantum dot light-emitting layer disposed on the surface of the hole transport layer, an electron transport layer disposed on the surface of the quantum dot light-emitting layer, and a cathode disposed on the surface of the electron transport layer.

[0051] In one embodiment, an inverted-structure quantum dot light-emitting diode includes a stacked structure including an anode and a cathode disposed opposite to each other, a quantum dot light-emitting layer disposed between the anode and the cathode, and an electron transport layer disposed between the cathode and the quantum dot light-emitting layer, and the cathode is disposed on a substrate. Further, an electron injection layer may be disposed between the cathode and the electron transport layer; hole functional layers such as a hole transport layer, a hole injection layer, and an electron blocking layer may be disposed between the anode and the quantum dot light-emitting layer. As Figure 4 shown, in some embodiments of the inverted-structure quantum dot light-emitting diode, the quantum dot light-emitting diode includes a substrate, a cathode disposed on the surface of the substrate, an electron transport layer disposed on the surface of the cathode, a quantum dot light-emitting layer disposed on the surface of the electron transport layer, a hole transport layer disposed on the surface of the quantum dot light-emitting layer, a hole injection layer disposed on the surface of the hole transport layer, and an anode disposed on the surface of the hole injection layer.

[0052] In the above embodiments, the substrate may include a rigid substrate such as common rigid substrates like glass and metal foils, or a flexible substrate such as polyimide (PI), polycarbonate (PC), polystyrene (PS), polyethylene (PE), polyvinyl chloride (PV), polyvinylpyrrolidone (PVP), polyethylene terephthalate (PET), and other similar materials, which mainly serves as a support.

[0053] The anode may adopt common anode materials and thicknesses, which are not limited in the embodiments of the present application. For example, the anode material may be indium tin oxide (ITO), indium zinc oxide (IZO) conductive glass or indium tin oxide, indium zinc oxide electrodes, or other metal materials such as gold, silver, aluminum, etc.

[0054] In the embodiments of the present application, the cathode may adopt common cathode materials and thicknesses, which are not limited in the embodiments of the present application. In some embodiments, the material of the cathode is selected from one or more of a conductive carbon material, a conductive metal oxide material, and a metal material. Among them, the conductive carbon material includes, but is not limited to, one or more of doped or undoped carbon nanotubes, doped or undoped graphene, doped or undoped graphene oxide, C60, graphite, carbon fiber, and porous carbon; the conductive metal oxide material includes, but is not limited to, one or more of ITO, FTO, ATO, and AZO; the metal material includes, but is not limited to, Al, Ag, Cu, Mo, Au, Ba, Ca, Mg, or their alloys. Among the metal materials, their forms include, but are not limited to, one or more of a dense thin film, nanowire, nanosphere, nanorod, nanocone, and nano-hollow sphere. Among them, using materials such as nano Ag wires or Cu wires has a smaller resistance, enabling carriers to be injected more smoothly. In some embodiments, the thickness of the cathode is 60 nm to 120 nm.

[0055] The quantum dots in the quantum dot light-emitting layer are direct bandgap compound semiconductors with the ability to emit light. Conventional quantum dot materials can be selected according to conventional quantum dot types. For example, the quantum dots in the quantum dot light-emitting layer can be one of red quantum dots, green quantum dots, blue quantum dots, and yellow quantum dots; the quantum dot materials can contain cadmium or not; the quantum dots can be oil-soluble quantum dots including binary phase, ternary phase, and quaternary phase quantum dots. The materials of the quantum dot light-emitting layer provided by the embodiments of the present application include, but are not limited to, one or more of II-VI group compounds, III-V group compounds, II-V group compounds, III-VI compounds, IV-VI group compounds, I-III-VI group compounds, II-IV-VI group compounds, or group IV elements. In some embodiments, the semiconductor materials used in the quantum dot light-emitting layer include, but are not limited to, nanocrystals of II-VI semiconductors, such as CdS, CdSe, CdTe, ZnS, ZnSe, ZnTe, HgS, HgSe, HgTe, PbS, PbSe, PbTe, and other binary, ternary, and quaternary II-VI compounds; nanocrystals of III-V group semiconductors, such as GaP, GaAs, InP, InAs, and other binary, ternary, and quaternary III-V compounds; and also not limited to II-V group compounds, III-VI compounds, IV-VI group compounds, I-III-VI group compounds, II-IV-VI group compounds, group IV elements, etc. In some embodiments, the materials of the quantum dot light-emitting layer can also be doped or undoped inorganic perovskite semiconductors and / or organic-inorganic hybrid perovskite semiconductors. Specifically, the general structural formula of the inorganic perovskite semiconductor is AMX 3 , where A is Cs + ions, M is a divalent metal cation, including but not limited to Pb 2+ , Sn 2+ , Cu 2+ , Ni 2+ , Cd 2+ , Cr 2+ , Mn 2+ , Co 2+ , Fe 2+ , Ge 2+ , Yb 2+ , Eu 2+ , and X is a halogen anion, including but not limited to Cl - , Br - , I - ; the general structural formula of the organic-inorganic hybrid perovskite semiconductor is BMX 3 , where B is an organic amine cation, including but not limited to CH 3 (CH 2 ) n -2NH 3+ (n≥2) or CH3 (CH 2 ) n NH 3 2+ (n≥2). When n = 2, the inorganic metal halide octahedra MX 6 4- are connected by sharing vertices. The metal cation M is located at the center of the halogen octahedron, and the organic amine cation B fills the voids between the octahedra, forming an infinitely extended three-dimensional structure; when n > 2, the inorganic metal halide octahedra MX 6 4- extend in two-dimensional directions to form a layered structure. A bilayer of organic amine cations (protonated monoamine) or a monolayer of organic amine cations (protonated diamine) is inserted between the layers, and the organic layer and the inorganic layer overlap with each other to form a stable two-dimensional layered structure; M is a divalent metal cation, including but not limited to Pb 2+ , Sn 2+ , Cu 2+ , Ni 2+ , Cd 2+ , Cr 2+ , Mn 2+ , Co 2+ , Fe 2+ , Ge 2+ , Yb 2+ , Eu 2+ ; X is a halogen anion, including but not limited to Cl - , Br - , I - .

[0056] The material of the hole injection layer can be a conventional hole injection material in the art, including but not limited to PEODT:PSS, CuPc, HATCN, WO 3 , MoO 3 , CrO x , NiO, CuO, V 2 O 5 , CuS, MoS 2 , MoSe 2 , WS 2 , WSe 2 among others, but not limited to this. The thickness of the hole injection layer is 10 nm - 100 nm.

[0057] The material of the hole transport layer can be a conventional hole transport material in the art, including but not limited to: poly(9,9-dioctylfluorene-co-N-(4-butylphenyl)diphenylamine), polyvinylcarbazole, poly(N,N'-bis(4-butylphenyl)-N,N'-bis(phenyl)benzidine), poly(9,9-dioctylfluorene-co-bis-N,N-phenyl-1,4-phenylenediamine), 4,4',4''-tris(carbazol-9-yl)triphenylamine, 4,4'-bis(9-carbazolyl)biphenyl, N,N'-diphenyl-N,N'-bis(3-methylphenyl)-1,1'-biphenyl-4,4'-diamine, 15N,N'-diphenyl-N,N'-(1-naphthyl)-1,1'-biphenyl-4,4'-diamine, graphene, at least one of C60. As another embodiment, the hole transport layer is selected from inorganic materials having hole transport ability, including but not limited to NiO x , MoO x , WO x , CrO x , CuO, MoS x , MoSe x , WS x , WSe x , at least one of CuS. The thickness of the hole injection layer is 1 nm - 100 nm.

[0058] The material of the electron transport layer is as described above. For the sake of brevity, it will not be repeated here. In some embodiments, the thickness of the electron transport layer is 10 nm to 60 nm.

[0059] In some embodiments, before use, the bottom electrode substrate is first cleaned. In some embodiments, it is sequentially placed in acetone, cleaning solution, deionized water, and isopropanol for ultrasonic cleaning. Each step of ultrasonic cleaning needs to last for 10 - 20 minutes, such as 15 minutes. After ultrasonic cleaning is completed, the bottom electrode substrate is placed in a clean oven for drying and standby. After the ITO substrate is dried, the ITO surface is treated with ultraviolet ozone for 5 minutes to further remove the organic substances attached to the ITO surface and improve the work function of the ITO.

[0060] In the embodiments of the present application, the quantum dot light-emitting layer, the electron transport layer, the hole transport layer, and the hole injection layer can be fabricated by conventional chemical or physical methods. Among them, the chemical methods include, but are not limited to, one or more of chemical vapor deposition, sequential ionic layer adsorption and reaction, anodic oxidation, electrodeposition, and coprecipitation; the physical methods include, but are not limited to, physical coating or solution methods, where the solution methods include, but are not limited to, spin coating, printing, blade coating, dip coating, immersion, spraying, roll coating, casting, slot die coating, and bar coating; the physical coating methods include, but are not limited to, one or more of thermal evaporation coating, electron beam evaporation coating, magnetron sputtering, multi-arc ion plating, physical vapor deposition, atomic layer deposition, and pulsed laser deposition. In a preferred embodiment, the electron transport layer is prepared by a solution method.

[0061] Furthermore, the preparation method further includes: encapsulating the obtained quantum dot light-emitting diode. The encapsulation can be carried out by using common machine encapsulation or manual encapsulation. Preferably, in the environment of the encapsulation process, the oxygen content and the water content are both lower than 0.1 ppm to ensure the stability of the quantum dot light-emitting diode.

[0062] The following will be described in conjunction with specific embodiments.

[0063] Example 1

[0064] A method for preparing an electron transport material includes the following steps:

[0065] Mix and stir anhydrous aluminum chloride and excessive anhydrous glacial acetic acid, heat and react fully at 100 °C to obtain a semi-transparent white colloid, and obtain aluminum acetate colloid by high-speed centrifugation; take 300 mg of newly prepared aluminum acetate colloid and dissolve it in 10 ml of ethylene glycol monomethyl ether and 0.28 ml of ethanolamine, and stir fully for 1 hour to obtain an Al 2 O 3 precursor solution with a concentration of 30 mg / ml.

[0066] Dissolve 1 g of zinc acetate in 0.24 ml of ethanolamine and 10 ml of ethylene glycol monomethyl ether, stir the solution at 60 °C for 12 hours to prepare a zinc oxide nanoparticle solution; then heat the zinc oxide nanoparticle solution to 150 °C, and slowly add the Al 2 O 3 precursor solution during stirring and continuously stir for 2 hours, and then centrifuge, wash, and dry the obtained precipitate to prepare Al 2 O 3 -coated ZnO nanoparticles.

[0067] The prepared Al 2 O 3The coated ZnO nanoparticles are dispersed into an ethanol solution by ultrasonic method, with a concentration of 10 - 100 mg / ml.

[0068] Example 2

[0069] A preparation method of an electron transport material, comprising the following steps:

[0070] Mix and stir anhydrous aluminum chloride and excessive anhydrous glacial acetic acid, heat at 100 °C for sufficient reaction to obtain a translucent white colloid, and obtain aluminum acetate colloid by high-speed centrifugation; take 300 mg of newly prepared aluminum acetate colloid and dissolve it in 10 ml of ethylene glycol monomethyl ether and 0.28 ml of ethanolamine, stir well for 1 hour to obtain an Al 2 O 3 precursor solution with a concentration of 30 mg / ml.

[0071] Dissolve 1 g of zinc acetate in 0.24 ml of ethanolamine and 10 ml of ethylene glycol monomethyl ether, stir the solution at 60 °C for 12 hours to prepare a zinc oxide nanoparticle solution; then heat the zinc oxide nanoparticle solution to 80 °C, and slowly add the Al 2 O 3 precursor solution during stirring, and continuously stir for 8 hours, then centrifuge, wash, and dry the obtained precipitate to prepare Al 2 O 3 coated ZnO nanoparticles.

[0072] Disperse the prepared Al 2 O 3 coated ZnO nanoparticles into an ethanol solution by ultrasonic method, with a concentration of 10 - 100 mg / ml.

[0073] Example 3

[0074] A preparation method of an electron transport material, comprising the following steps:

[0075] Mix and stir anhydrous aluminum chloride and excessive anhydrous glacial acetic acid, heat at 100 °C for sufficient reaction to obtain a translucent white colloid, and obtain aluminum acetate colloid by high-speed centrifugation; take 300 mg of newly prepared aluminum acetate colloid and dissolve it in 10 ml of ethylene glycol monomethyl ether and 0.28 ml of ethanolamine, stir well for 1 hour to obtain an Al 2 O 3 precursor solution with a concentration of 30 mg / ml.

[0076] Dissolve 1 g of zinc acetate in 0.24 ml of ethanolamine and 10 ml of ethylene glycol monomethyl ether, stir the solution at 60 °C for 12 hours to prepare a zinc oxide nanoparticle solution; then heat the zinc oxide nanoparticle solution to 250 °C, and slowly add the Al 2 O3 The precursor solution was continuously stirred for 30 minutes, and then the obtained precipitate was centrifuged, washed, and dried to prepare Al 2 O 3 -coated ZnO nanoparticles.

[0077] The prepared Al 2 O 3 -coated ZnO nanoparticles were dispersed into an ethanol solution by ultrasonic method, and the concentration was 10 - 100 mg / ml.

[0078] Example 4

[0079] A preparation method of an electron transport material, comprising the following steps:

[0080] Anhydrous aluminum chloride and excessive anhydrous glacial acetic acid were mixed and stirred. After heating and fully reacting at 100 °C, a translucent white colloid was obtained, and aluminum acetate colloid was obtained by high-speed centrifugation; 300 mg of the newly prepared aluminum acetate colloid was dissolved in 10 ml of ethylene glycol monomethyl ether and 0.28 ml of ethanolamine, and stirred for 1 hour to obtain an Al 2 O 3 precursor solution with a concentration of 30 mg / ml.

[0081] 1 g of zinc acetate was dissolved in 0.24 ml of ethanolamine and 10 ml of ethylene glycol monomethyl ether. The solution was stirred at 60 °C for 12 hours to prepare a zinc oxide nanoparticle solution; then the zinc oxide nanoparticle solution was heated to 300 °C, and the Al 2 O 3 precursor solution was slowly added during stirring, and continuously stirred for 10 minutes. Then the obtained precipitate was centrifuged, washed, and dried to prepare Al 2 O 3 -coated ZnO nanoparticles.

[0082] The prepared Al 2 O 3 -coated ZnO nanoparticles were dispersed into an ethanol solution by ultrasonic method, and the concentration was 10 - 100 mg / ml.

[0083] Comparative Example 1

[0084] A preparation method of an electron transport material, comprising the following steps:

[0085] Anhydrous aluminum chloride and excessive anhydrous glacial acetic acid were mixed and stirred. After heating and fully reacting at 100 °C, a translucent white colloid was obtained, and aluminum acetate colloid was obtained by high-speed centrifugation; 300 mg of the newly prepared aluminum acetate colloid was dissolved in 10 ml of ethylene glycol monomethyl ether and 0.28 ml of ethanolamine, and stirred for 1 hour to obtain an Al 2 O3 Precursor solution with a concentration of 30 mg / ml.

[0086] Dissolve 1 g of zinc acetate in 0.24 ml of ethanolamine and 10 ml of ethylene glycol monomethyl ether. Stir the solution at 60 °C for 12 hours to prepare a zinc oxide nanoparticle solution; then heat the zinc oxide nanoparticle solution to 350 °C and slowly add the Al 2 O 3 precursor solution while continuously stirring for 10 minutes. Then centrifuge, wash, and dry the obtained precipitate to prepare Al 2 O 3 -coated ZnO nanoparticles.

[0087] Disperse the prepared Al 2 O 3 -coated ZnO nanoparticles into an ethanol solution by ultrasonic method with a concentration of 10 - 100 mg / ml.

[0088] Comparative Example 2

[0089] A preparation method of an electron transport material, comprising the following steps:

[0090] Mix and stir anhydrous aluminum chloride and excessive anhydrous glacial acetic acid, heat at 100 °C for full reaction to obtain a translucent white colloid, and obtain aluminum acetate colloid by high-speed centrifugation; take 300 mg of the newly prepared aluminum acetate colloid and dissolve it in 10 ml of ethylene glycol monomethyl ether and 0.28 ml of ethanolamine, and stir well for 1 hour to obtain an Al 2 O 3 precursor solution with a concentration of 30 mg / ml.

[0091] Dissolve 1 g of zinc acetate in 0.24 ml of ethanolamine and 10 ml of ethylene glycol monomethyl ether. Stir the solution at 60 °C for 12 hours to prepare a zinc oxide nanoparticle solution; then heat the zinc oxide nanoparticle solution to 500 °C and slowly add the Al 2 O 3 precursor solution while continuously stirring for 10 minutes. Then centrifuge, wash, and dry the obtained precipitate to prepare a mixture of Al 2 O 3 and ZnO nanoparticles.

[0092] Disperse the prepared mixture of Al 2 O 3 and ZnO nanoparticles into an ethanol solution by ultrasonic method with a concentration of 10 - 100 mg / ml.

[0093] Example 5

[0094] A method for preparing a quantum light-emitting diode, comprising the following steps:

[0095] Place the patterned ITO substrate in acetone, cleaning solution, deionized water, and isopropanol in sequence for ultrasonic cleaning. Each step of ultrasonic cleaning needs to last about 15 minutes. After the ultrasonic cleaning is completed, place the ITO substrate in a clean oven to dry for later use. After the ITO substrate is dried, treat the ITO surface with ultraviolet ozone for 5 minutes to further remove the organic substances attached to the ITO surface and improve the work function of the ITO.

[0096] Spin-coat a layer of PEDOT:PSS on the surface of the treated ITO substrate, with a thickness of 30 nm; place the substrate on a heating stage at 150 °C and heat for 30 minutes to remove moisture. This step is completed in air.

[0097] Place the substrate coated with the hole injection layer after drying in a nitrogen atmosphere, spin-coat a layer of hole transport layer material PVK, with a thickness of 30 nm for this layer, and place the substrate on a heating stage at 150 °C and heat for 30 minutes to remove the solvent.

[0098] After the film processed in the previous step is cooled, spin-coat the blue quantum dot light-emitting material on the surface of the hole transport layer, with a thickness of 20 nm. After the deposition of this step is completed, place the film on a heating stage at 80 °C and heat for 10 minutes to remove the residual solvent.

[0099] Spin-coat the electron transport material (Al 2 O 3 coated ZnO nanoparticles) provided in Example 1 to prepare the electron transport layer, with a thickness of 30 nm. After the deposition is completed, place the film on a heating stage at 80 °C and heat for 10 minutes to remove the residual solvent.

[0100] Place the film deposited with each functional layer in an evaporation chamber and thermally evaporate a layer of aluminum as the cathode through a mask plate, with a thickness of 100 nm, and the device preparation is completed.

[0101] Example 6

[0102] A method for preparing a quantum light-emitting diode, comprising the following steps:

[0103] Place the patterned ITO substrate in acetone, cleaning solution, deionized water, and isopropanol in sequence for ultrasonic cleaning. Each step of ultrasonic cleaning needs to last about 15 minutes. After the ultrasonic cleaning is completed, place the ITO substrate in a clean oven to dry for later use. After the ITO substrate is dried, treat the ITO surface with ultraviolet ozone for 5 minutes to further remove the organic substances attached to the ITO surface and improve the work function of the ITO.

[0104] Spin-coat a layer of PEDOT:PSS on the surface of the treated ITO substrate with a thickness of 30 nm; place the substrate on a heating stage at 150 °C and heat for 30 minutes to remove moisture. This step is completed in air.

[0105] Place the dried substrate coated with the hole injection layer in a nitrogen atmosphere, spin-coat a layer of hole transport layer material PVK with a thickness of 30 nm, and place the substrate on a heating stage at 150 °C and heat for 30 minutes to remove the solvent.

[0106] After the film processed in the previous step is cooled, spin-coat the blue quantum dot luminescent material on the surface of the hole transport layer with a thickness of 20 nm. After the deposition of this step is completed, place the film on a heating stage at 80 °C and heat for 10 minutes to remove the residual solvent.

[0107] Spin-coat the electron transport material (Al 2 O 3 coated ZnO nanoparticles) provided in Example 2 to prepare the electron transport layer with a thickness of 30 nm. After the deposition is completed, place the film on a heating stage at 80 °C and heat for 10 minutes to remove the residual solvent.

[0108] Place the film deposited with each functional layer in an evaporation chamber and thermally evaporate a layer of aluminum as the cathode through a mask plate with a thickness of 100 nm, and the device preparation is completed.

[0109] Example 7

[0110] A method for preparing a quantum light-emitting diode includes the following steps:

[0111] Place the patterned ITO substrate in acetone, cleaning solution, deionized water, and isopropanol in sequence for ultrasonic cleaning. Each ultrasonic step needs to last for about 15 minutes. After the ultrasonic cleaning is completed, place the ITO substrate in a clean oven to dry for later use. After the ITO substrate is dried, treat the ITO surface with ultraviolet ozone for 5 minutes to further remove the organic matter attached to the ITO surface and improve the work function of the ITO.

[0112] Spin-coat a layer of PEDOT:PSS on the surface of the treated ITO substrate with a thickness of 30 nm; place the substrate on a heating stage at 150 °C and heat for 30 minutes to remove moisture. This step is completed in air.

[0113] Place the dried substrate coated with the hole injection layer in a nitrogen atmosphere, spin-coat a layer of hole transport layer material PVK with a thickness of 30 nm, and place the substrate on a heating stage at 150 °C and heat for 30 minutes to remove the solvent.

[0114] After the wafer processed in the previous step is cooled, a blue quantum dot light-emitting material is spin-coated on the surface of the hole transport layer, with a thickness of 20 nm. After the deposition of this step is completed, the wafer is placed on a heating stage at 80 °C and heated for 10 minutes to remove the residual solvent.

[0115] Spin-coat the electron transport material (Al 2 O 3 -coated ZnO nanoparticles) provided in Example 3 to prepare an electron transport layer with a thickness of 30 nm. After the deposition is completed, the wafer is placed on a heating stage at 80 °C and heated for 10 minutes to remove the residual solvent.

[0116] Place the wafer with all functional layers deposited in an evaporation chamber and thermally evaporate a layer of aluminum as the cathode through a mask plate, with a thickness of 100 nm, and the device fabrication is completed.

[0117] Example 8

[0118] A method for fabricating a quantum dot light-emitting diode includes the following steps:

[0119] Place the patterned ITO substrate in acetone, cleaning solution, deionized water, and isopropanol in sequence for ultrasonic cleaning, and each ultrasonic step needs to last for about 15 minutes. After the ultrasonic cleaning is completed, place the ITO substrate in a clean oven to dry for later use. After the ITO substrate is dried, treat the ITO surface with ultraviolet ozone for 5 minutes to further remove the organic substances attached to the ITO surface and improve the work function of the ITO.

[0120] Spin-coat a layer of PEDOT:PSS on the surface of the treated ITO substrate, with a thickness of 30 nm; place the substrate on a heating stage at 150 °C and heat for 30 minutes to remove the moisture, and this step is completed in the air.

[0121] Place the substrate with the hole injection layer coated and dried in a nitrogen atmosphere, spin-coat a hole transport layer material PVK, with a thickness of 30 nm for this layer, and place the substrate on a heating stage at 150 °C and heat for 30 minutes to remove the solvent.

[0122] After the wafer processed in the previous step is cooled, a blue quantum dot light-emitting material is spin-coated on the surface of the hole transport layer, with a thickness of 20 nm. After the deposition of this step is completed, the wafer is placed on a heating stage at 80 °C and heated for 10 minutes to remove the residual solvent.

[0123] Spin-coat the electron transport material (Al 2 O 3 -coated ZnO nanoparticles) provided in Example 4 to prepare an electron transport layer with a thickness of 30 nm. After the deposition is completed, the wafer is placed on a heating stage at 80 °C and heated for 10 minutes to remove the residual solvent.

[0124] The wafer with all functional layers deposited is placed in an evaporation chamber, and a layer of aluminum with a thickness of 100 nm is thermally evaporated through a mask plate as the cathode, and the device fabrication is completed.

[0125] Comparative Example 3

[0126] A method for fabricating a quantum dot light-emitting diode, which is different from Example 2 in that: the material of the electron transport layer is pure ZnO nanoparticles.

[0127] Comparative Example 4

[0128] The patterned ITO substrate is sequentially placed in acetone, cleaning solution, deionized water, and isopropanol for ultrasonic cleaning, and each step of ultrasonic cleaning needs to last for about 15 minutes. After ultrasonic cleaning, the ITO substrate is placed in a clean oven to dry for later use. After the ITO substrate is dried, the ITO surface is treated with ultraviolet ozone for 5 minutes to further remove the organic substances attached to the ITO surface and improve the work function of the ITO.

[0129] A layer of PEDOT:PSS with a thickness of 30 nm is spin-coated on the surface of the treated ITO substrate; the substrate is placed on a heating table at 150 °C and heated for 30 minutes to remove moisture, and this step is completed in air.

[0130] The substrate coated with the hole injection layer after drying is placed in a nitrogen atmosphere, and a layer of hole transport layer material PVK with a thickness of 30 nm is spin-coated, and the substrate is placed on a heating table at 150 °C and heated for 30 minutes to remove the solvent.

[0131] After the wafer from the previous step is cooled, a blue quantum dot light-emitting material is spin-coated on the surface of the hole transport layer with a thickness of 20 nm. After the deposition of this step is completed, the wafer is placed on a heating table at 80 °C and heated for 10 minutes to remove the residual solvent.

[0132] Spin-coat the electron transport material (Al 2 O 3 passivated ZnO nanoparticles) provided by Comparative Example 1 to prepare the electron transport layer with a thickness of 30 nm. After the deposition is completed, the wafer is placed on a heating table at 80 °C and heated for 10 minutes to remove the residual solvent.

[0133] The wafer with all functional layers deposited is placed in an evaporation chamber, and a layer of aluminum with a thickness of 100 nm is thermally evaporated through a mask plate as the cathode, and the device fabrication is completed.

[0134] Comparative Example 5

[0135] The patterned ITO substrate was sequentially placed in acetone, cleaning solution, deionized water, and isopropyl alcohol for ultrasonic cleaning. Ultrasonic cleaning in each of the above steps needed to last for about 15 minutes. After ultrasonic cleaning was completed, the ITO substrate was placed in a clean oven for drying and standby. After the ITO substrate was dried, the ITO surface was treated with ultraviolet ozone for 5 minutes to further remove the organic matter attached to the ITO surface and improve the work function of the ITO.

[0136] A layer of PEDOT:PSS with a thickness of 30 nm was spin-coated on the surface of the treated ITO substrate; the substrate was placed on a heating stage at 150 °C and heated for 30 minutes to remove moisture, and this step was completed in air.

[0137] The dried substrate coated with the hole injection layer was placed in a nitrogen atmosphere, and a layer of hole transport layer material PVK with a thickness of 30 nm was spin-coated, and the substrate was placed on a heating stage at 150 °C and heated for 30 minutes to remove the solvent.

[0138] After the film processed in the previous step was cooled, a blue quantum dot luminescent material was spin-coated on the surface of the hole transport layer with a thickness of 20 nm. After the deposition of this step was completed, the film was placed on a heating stage at 80 °C and heated for 10 minutes to remove the residual solvent.

[0139] Spin-coat the electron transport material (a mixture of Al 2 O 3 and ZnO nanoparticles) provided in Comparative Example 2 to prepare an electron transport layer with a thickness of 30 nm. After the deposition was completed, the film was placed on a heating stage at 80 °C and heated for 10 minutes to remove the residual solvent.

[0140] The film deposited with each functional layer was placed in an evaporation chamber, and a layer of aluminum was thermally evaporated as the cathode through a mask plate with a thickness of 100 nm, and the device preparation was completed.

[0141] Test the external quantum efficiency (EQE, measured by an EQE optical test instrument) and service life of the QLEDs prepared in Examples 5-8 and Comparative Examples 3-5. The results show that:

[0142] Compared with Comparative Example 3 using ZnO nanoparticles as the electron transport layer, the luminous efficiency of the QLED prepared in Example 5 was increased from 5.6% (Comparative Example 3) to 8.2%, and the life T95@1000nits was increased from 2 hours (Comparative Example 3) to 37 hours.

[0143] The luminous efficiency of the QLED prepared in Example 6 was increased from 5.6% (Comparative Example 3) to 8.2%, and the life T95@1000nits was increased from 2 hours (Comparative Example 1) to 37 hours; and the effect was basically the same as that of Example 5.

[0144] The luminous efficiency of the QLED prepared in Example 7 was increased from 5.6% (Comparative Example 3) to 6.4%, and the lifetime T95@1000nits was increased from 2 hours (Comparative Example 3) to 13 hours.

[0145] The luminous efficiency of the QLED prepared in Example 8 was increased from 5.6% (Comparative Example 3) to 6.1%, and the lifetime T95@1000nits was increased from 2 hours (Comparative Example 1) to 4 hours.

[0146] The luminous efficiency of the QLED prepared in Comparative Example 4 was decreased from 5.6% (Comparative Example 3) to 5.5%, and the lifetime T95@1000nits was decreased from 2 hours (Comparative Example 3) to 1.9 hours.

[0147] The QLED device prepared in Comparative Example 5 could not be lit because: under high temperature conditions, the hydrolysis reaction of the aluminum oxide precursor was intense, and the generated aluminum oxide could not nucleophilically coat the surface of the zinc oxide nanoparticles, and finally a mixture of the two was obtained, which could not be used as an electron transport layer.

[0148] Example 9

[0149] A method for preparing a quantum light-emitting diode includes the following steps:

[0150] The patterned ITO substrate was sequentially placed in acetone, cleaning solution, deionized water, and isopropanol for ultrasonic cleaning, and each ultrasonic step needed to last about 15 minutes. After the ultrasonic cleaning was completed, the ITO substrate was placed in a clean oven for drying. After the ITO substrate was dried, the surface of the ITO was treated with ultraviolet ozone for 5 minutes to further remove the organic substances attached to the ITO surface.

[0151] The electron transport material (Al 2 O 3 passivated ZnO nanoparticles) provided in Example 1 was printed on the surface of the treated ITO substrate to prepare an electron transport layer with a thickness of 25 nm. After the deposition was completed, the wafer was placed on a heating stage at 80 °C for 10 minutes to remove the residual solvent

[0152] After the wafer was cooled, the blue quantum dot light-emitting material was spin-coated on the surface of the electron transport layer with a thickness of 20 nm. After the deposition of this step was completed, the wafer was placed on a heating stage at 80 °C for 10 minutes to remove the residual solvent.

[0153] A hole transport layer material NPB was evaporated, and the thickness of this layer was 10 nm.

[0154] A hole injection layer material MoO 3 was evaporated, and the thickness of this layer was 30 nm.

[0155] The wafer on which each functional layer has been deposited is placed in an evaporation chamber, and a layer of silver with a thickness of 80 nm is thermally evaporated as the anode through a mask plate, and the device fabrication is completed.

[0156] Comparative Example 6

[0157] A method for preparing a quantum dot light-emitting diode, which is different from Example 9 in that the material of the electron transport layer is pure ZnO nanoparticles.

[0158] The external quantum efficiency (EQE, measured by an EQE optical test instrument) and service life of the QLEDs prepared in Example 9 and Comparative Example 6 were tested. The results show that: compared with Comparative Example 6 using ZnO nanoparticles as the electron transport layer, the luminous efficiency of the QLED prepared in Example 9 increased from 6.6% (Comparative Example 6) to 10.2%, and the service life T95@1000nits increased from 3 hours (Comparative Example 6) to 52 hours.

[0159] The above are only the preferred embodiments of the present application and are not intended to limit the present application. Any modifications, equivalent replacements, and improvements made within the spirit and principle of the present application shall be included within the protection scope of the present application.

Claims

1. A preparation method of an electron transport material, characterized in that, it comprises the following steps: providing a zinc oxide nanoparticle solution and an aluminum oxide precursor solution; wherein, the aluminum oxide precursor solution contains an aluminum acetate colloid; the molar ratio of the zinc oxide nanoparticles to the aluminum oxide precursor is 1:0.1 - 1; under heating conditions, adding the aluminum oxide precursor solution to the zinc oxide nanoparticle solution for reaction to obtain the electron transport material with aluminum oxide bound to the surface of the zinc oxide nanoparticles.

2. The preparation method of the electron transport material according to claim 1, characterized in that, the temperature of the heating conditions is 80°C - 300°C.

3. The preparation method of the electron transport material according to claim 2, characterized in that, in the step of adding the aluminum oxide precursor solution to the zinc oxide nanoparticle solution for reaction, based on 1 mol of the molar content of the zinc oxide nanoparticles in the zinc oxide nanoparticle solution, the addition rate of the aluminum oxide precursor in the aluminum oxide precursor solution is 0.1 - 1 mol / h.

4. The preparation method of the electron transport material according to any one of claims 1 to 3, characterized in that, in the step of adding the aluminum oxide precursor solution to the zinc oxide nanoparticle solution for reaction, the reaction time is 1 - 12 hours.

5. The preparation method of the electron transport material according to claim 1, characterized in that, the zinc oxide nanoparticles are prepared through the following steps: preparing zinc oxide nanoparticles from a zinc oxide nanoparticle precursor at 5°C - 40°C or under heating conditions; or, dissolving the zinc oxide nanoparticle precursor in a solvent to obtain a precursor solution, adding an alkali for reaction to obtain zinc oxide nanoparticles; or, adding ethylene glycol monomethyl ether and ethanolamine to the zinc oxide nanoparticle precursor solution to obtain zinc oxide nanoparticles.

6. An electron transport material, characterized in that, it comprises zinc oxide nanoparticles and aluminum oxide; wherein, the aluminum oxide coats the zinc oxide nanoparticles, and the molar ratio of the zinc oxide nanoparticles to the aluminum oxide is (5 - 10):

1.

7. A quantum dot light-emitting diode, characterized in that, it comprises an anode and a cathode arranged opposite to each other, a quantum dot light-emitting layer arranged between the anode and the cathode, and an electron transport layer arranged between the quantum dot light-emitting layer and the cathode; wherein, the material of the electron transport layer comprises zinc oxide nanoparticles and aluminum oxide; wherein, the aluminum oxide coats the zinc oxide nanoparticles; the molar ratio of the zinc oxide nanoparticles to the aluminum oxide is (5 - 10):

1.

8. The quantum dot light-emitting diode according to claim 7, characterized in that, it further comprises a hole functional layer arranged between the anode and the quantum dot light-emitting layer.

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