Composite material and method for manufacturing the same, light emitting diode

Abstract

The application discloses a composite material and a preparation method and quantum dot light emitting diode thereof, wherein the composite material comprises three-dimensional graphene and zinc oxide nanoparticles or metal ion doped zinc oxide nanoparticles loaded on the three-dimensional graphene. In the composite material, the zinc oxide nanoparticles or the metal ion doped zinc oxide nanoparticles are loaded in the three-dimensional graphene, so that the three-dimensional graphene can improve the conductivity of the composite material on one hand and effectively avoid the agglomeration between the zinc oxide nanoparticles or between the metal ion doped zinc oxide nanoparticles on the other hand; and the three-dimensional graphene also has good rigidity and good ductility, and can improve the film forming uniformity of the composite material.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of light-emitting diodes, in particular to a composite material and a preparation method thereof, and a light-emitting diode. BACKGROUND

[0002] A quantum dot light-emitting diode (QLED) is a structure composed of a cathode, a hole transport layer, a quantum dot light-emitting layer, an electron transport layer and an anode. When an external voltage is applied, electrons and holes are injected from the respective electrodes, and the two are combined to emit light. QLED has been attracting more and more attention due to its excellent performance such as continuous tunable spectrum in the visible light region, wide absorption and narrow emission, high color purity and high luminous intensity.

[0003] ZnO is a common Ⅱ-Ⅵ semiconductor compound, and the band gap of the material can be as high as 3.34 eV, which has photoelectric performance coordination and is an ideal electron transport layer material. The electron transport layer material-ZnO-based nanocrystals have been widely studied as carrier transport materials for QLED devices.

[0004] In the application process of zinc oxide, inorganic nano zinc oxide particles need to be dispersed in an organic matrix, but agglomeration of inorganic nanoparticles is often caused by the following reasons: (1) particle aggregation caused by intermolecular forces, hydrogen bonds, electrostatic interactions, etc.; (2) due to quantum tunneling effect, charge transfer and mutual coupling of interface atoms between particles, the particles are prone to interact and solid-phase reaction through the interface to form agglomerates; (3) due to the large specific surface area of nano particles, they are prone to adsorb gases or media or react with them after contacting with air or various media, thereby losing their original surface properties and leading to adhesion and agglomeration; (4) the surface energy is extremely high, the contact interface is large, and it is in a non-thermodynamic stable state, which makes the grain growth speed faster, so it is difficult to keep the particle size unchanged. Agglomeration of inorganic nano zinc oxide particles will directly lead to low conductivity of zinc oxide, unbalanced carrier transport, and ultimately low device efficiency and easy quenching; zinc oxide is also susceptible to water and oxygen, which can accelerate the quenching process.

[0005] Therefore, the prior art still needs to be improved and developed. SUMMARY

[0006] In view of the above deficiencies of the prior art, the purpose of the present application is to provide a composite material and a preparation method thereof, and a light-emitting diode, which aims to solve the problem of easy agglomeration of existing nano zinc oxide particles, which leads to low conductivity and unbalanced carrier transport.

[0007] The technical scheme of the present application is as follows:

[0008] A composite material, comprising three-dimensional graphene and zinc oxide nanoparticles or metal ion doped zinc oxide nanoparticles loaded on the three-dimensional graphene.

[0009] A preparation method of a composite material, comprising the steps of:

[0010] dispersing a zinc source-containing powder into a solvent to obtain a first precursor solution;

[0011] adding the first precursor solution into an ion exchange resin to exchange metal ions in the first precursor solution with cations in the ion exchange resin to obtain a second precursor solution;

[0012] performing heat treatment on the second precursor solution under an inert atmosphere to obtain a composite material comprising three-dimensional graphene and zinc oxide nanoparticles or metal ion-doped zinc oxide nanoparticles supported on the three-dimensional graphene.

[0013] A light emitting diode comprising an electron transport layer, wherein the electron transport layer material is the composite material of the present application or the composite material prepared by the preparation method of the present application.

[0014] Beneficial effects: The composite material provided by the present application comprises three-dimensional graphene and zinc oxide nanoparticles or metal ion-doped zinc oxide nanoparticles supported on the three-dimensional graphene. Since the zinc oxide nanoparticles or metal ion-doped zinc oxide nanoparticles are supported in the three-dimensional graphene, the three-dimensional graphene can improve the conductivity of the composite material and effectively prevent the zinc oxide nanoparticles or metal ion-doped zinc oxide nanoparticles from agglomerating; the three-dimensional graphene also has good rigidity and good ductility, which can improve the film uniformity of the composite material. BRIEF DESCRIPTION OF DRAWINGS

[0015] Figure 1 A flowchart of a preferred embodiment of the preparation method of the composite material provided by the present application.

[0016] Figure 2 A structure schematic diagram of a preferred embodiment of the quantum dot light emitting diode with a normal structure provided by the present application.

[0017] Figure 3 A structure schematic diagram of a preferred embodiment of the quantum dot light emitting diode with an inverted structure provided by the present application.

[0018] Figure 4 A flowchart of a preferred embodiment of the preparation method of the quantum dot light emitting diode with a normal structure provided by the present application.

[0019] Figure 5 A flowchart of a preferred embodiment of the preparation method of the quantum dot light emitting diode with an inverted structure provided by the present application.

[0020] Figure 6TEM image of the composite material prepared in Example 1.

[0021] Figure 7 Comparison chart of external quantum efficiency test results of the quantum dot light emitting diode in Comparative Example 1 and Examples 1-3. DETAILED DESCRIPTION

[0022] The present application provides a composite material and a preparation method thereof, and a light emitting diode. To make the purpose, technical solutions and effects of the present application clearer and more explicit, the present application is further described in detail below. It should be understood that the specific examples described herein are only used to explain the present application and are not used to limit the present application.

[0023] Since defects occur on the surface of the zinc oxide nanoparticles, part of the Zn does not combine with O to form a dangling bond, so that the specific surface area of the zinc oxide nanoparticles is large, the surface energy is extremely high, and the zinc oxide nanoparticles are prone to agglomeration, thereby directly leading to a decrease in the conductivity of the zinc oxide nanoparticles and unbalanced carrier transport, and ultimately leading to low device efficiency and easy quenching.

[0024] Based on this, the present application provides a composite material, which comprises three-dimensional graphene and zinc oxide nanoparticles or metal ion doped zinc oxide nanoparticles loaded on the three-dimensional graphene.

[0025] In the present embodiment, since the zinc oxide nanoparticles or metal ion doped zinc oxide nanoparticles are loaded in the three-dimensional graphene, the three-dimensional graphene can improve the conductivity of the composite material on the one hand, and effectively avoid the agglomeration of the zinc oxide nanoparticles or metal ion doped zinc oxide nanoparticles on the other hand; the three-dimensional graphene also has good rigidity and good ductility, and can improve the film uniformity of the composite material.

[0026] In some embodiments, the mass ratio of the zinc oxide nanoparticles or metal ion doped zinc oxide nanoparticles to the three-dimensional graphene is 6-20:1. In the present embodiment, if the mass ratio of the zinc oxide nanoparticles or metal ion doped zinc oxide nanoparticles to the three-dimensional graphene is less than 6:1, the content of the three-dimensional graphene is too high, which can change the energy level of the composite material and directly lead to unbalanced carrier transport, thereby leading to quenching of the quantum dots; if the mass ratio of the zinc oxide nanoparticles or metal ion doped zinc oxide nanoparticles to the three-dimensional graphene is greater than 20:1, a large amount of graphene oxide particles or metal doped zinc oxide nanoparticles cannot be loaded into the three-dimensional graphene, which can easily accelerate the agglomeration of the zinc oxide nanoparticles or metal doped zinc oxide nanoparticles.

[0027] In some embodiments, the doped metal ions in the metal ion-doped zinc oxide nanoparticles account for 0.1-20% of the total molar amount of metal ions. In this embodiment, if the molar amount of doped metal ions is higher than 20%, second-phase oxide particles will be generated on the surface of the zinc oxide nanoparticles, which will easily reduce the conductivity of the composite material; if the molar amount of doped metal ions is less than 0.1%, the enhancement effect on the conductivity of the composite material is poor.

[0028] In some embodiments, the metal ion-doped zinc oxide nanoparticles can be either magnesium ion-doped zinc oxide nanoparticles or aluminum ion-doped zinc oxide nanoparticles, but are not limited thereto. This embodiment improves the flexibility of QLED design by preparing zinc oxide nanoparticles doped with different metal ions on three-dimensional graphene.

[0029] In some embodiments, a method for preparing a composite material is also provided, such as... Figure 1 As shown, it includes the following steps:

[0030] S10. Disperse the zinc source powder into a solvent to obtain the first precursor solution;

[0031] S20. The first precursor solution is added to the ion exchange resin to exchange the metal ions in the first precursor solution with the cations in the ion exchange resin to obtain the second precursor solution.

[0032] S30. The second precursor solution is heat-treated under an inert atmosphere to obtain the composite material.

[0033] In this embodiment, zinc-containing powder is first dispersed in an organic alcohol solvent, then an ion exchange resin is added. After stirring for a period of time, the metal ions in the first precursor solution exchange with the cations in the ion exchange resin to obtain an ion exchange resin that adsorbs metal ions. Finally, the ion exchange resin that adsorbs metal ions is heat-treated in an inert atmosphere furnace to obtain a composite material. The composite material includes three-dimensional graphene and zinc oxide nanoparticles or metal ion-doped zinc oxide nanoparticles loaded on the three-dimensional graphene.

[0034] The composite material preparation process provided in this embodiment is simple and easy to operate. In the obtained composite material, since zinc oxide nanoparticles or metal ion-doped zinc oxide nanoparticles are loaded in three-dimensional graphene, the three-dimensional graphene can improve the conductivity of the composite material on the one hand, and effectively prevent the aggregation of zinc oxide nanoparticles or metal ion-doped zinc oxide nanoparticles on the other hand. The three-dimensional graphene also has good rigidity and good ductility, which can improve the film uniformity of the composite material.

[0035] In some embodiments, when the prepared composite material consists of three-dimensional graphene and zinc oxide nanoparticles supported on the three-dimensional graphene, the zinc source powder is one or more of anhydrous zinc nitrate, zinc chloride, zinc acetate, zinc sulfate, and zinc acetylacetonate, but is not limited thereto. In this embodiment, the zinc source powder is dispersed in an organic alcohol solvent to obtain a first precursor solution containing only zinc ions. The first precursor solution undergoes ion exchange with an ion exchange resin during stirring to obtain an exchange resin solution that adsorbs zinc ions, i.e., a second precursor solution. After heat treatment of the second precursor solution under an inert atmosphere, the composite material is obtained.

[0036] In some embodiments, when the prepared composite material consists of three-dimensional graphene and metal ion-doped zinc oxide nanoparticles supported on the three-dimensional graphene, the zinc source powder is a mixed powder composed of at least one of anhydrous zinc nitrate, zinc chloride, zinc acetate, zinc sulfate, and zinc acetylacetonate, and one of magnesium or aluminum salts. In this embodiment, the zinc source powder is dispersed in an organic alcohol solvent to obtain a first precursor solution containing zinc and magnesium ions or zinc and aluminum ions. The first precursor solution undergoes ion exchange with an ion exchange resin during stirring to obtain an ion exchange resin solution that adsorbs zinc and magnesium ions or adsorbs zinc and aluminum ions, i.e., a second precursor solution. After heat treatment of the second precursor solution under an inert atmosphere, the composite material is obtained.

[0037] In some embodiments, the inert atmosphere is one of nitrogen, argon, or helium, but is not limited thereto.

[0038] In some embodiments, the heat treatment temperature for the second precursor solution is 650°C-950°C. For example, the second precursor solution can be added to a ceramic boat and heat-treated in a furnace to obtain a black powder, thus producing the composite material.

[0039] In some embodiments, the organic alcohol is one or more of methanol, ethanol, butanol, pentanol, and isopropanol, but is not limited thereto.

[0040] In some embodiments, the ion exchange resin is an insoluble polymer compound with functional groups (active groups that exchange ions), a network structure, and a network structure. The matrix of the ion exchange resin is mainly made from two types of raw materials: styrene and acrylic acid (esters). These react with the crosslinking agent divinylbenzene to form a polymer with a long molecular backbone and crosslinked cross-links forming a network framework. In this embodiment, the ion exchange resin contains -OH, -COOH, -NH2, and -NH4+. -, -SH, -CN, -SO3H, -SOOH, -NO2, -CONH2, -CONH - -COCl, -CO - A cation exchange resin containing at least one functional group selected from -CHO, -Cl, and -Br.

[0041] In some embodiments, a light-emitting diode is also provided, which includes an electron transport layer, the electron transport layer material being the composite material described in this invention.

[0042] In this embodiment, the light-emitting diode can be a QLED or an OLED. The present invention will be further explained below with reference to the light-emitting diode being a QLED.

[0043] In some specific embodiments, a quantum dot light-emitting diode with an upright structure is provided, such as... Figure 2 As shown, it includes a substrate 10, an anode 20, a hole functional layer 30, a quantum dot light-emitting layer 40, an electron transport layer 50, and a cathode 60, which are stacked sequentially from bottom to top. The electron transport layer material is the composite material described in this invention.

[0044] In this embodiment, since the composite material can reduce agglomeration, improve electron transport performance, and enhance film uniformity, it can enhance the luminous efficiency and display performance of the device.

[0045] In some embodiments, an inverted quantum dot light-emitting diode is also provided, such as... Figure 3 As shown, it includes a substrate 01, a cathode 02, an electron transport layer 03, a quantum dot light-emitting layer 04, a hole functional layer 05, and an anode 06 stacked sequentially from bottom to top. The electron transport layer material is the composite material described in this invention.

[0046] In this embodiment, the hole functional layer can be one or more of an electron blocking layer, a hole injection layer, and a hole transport layer, but is not limited thereto.

[0047] In some embodiments, the thickness of the electron transport layer is 70-90 nm.

[0048] In some embodiments, the anode material is selected from one or more of indium-doped tin oxide (ITO), fluorine-doped tin oxide (FTO), antimony-doped tin oxide (ATO), aluminum-doped zinc oxide (AZO), gallium-doped zinc oxide (GZO), indium-doped zinc oxide (IZO), magnesium-doped zinc oxide (MZO), and aluminum-doped magnesium oxide (AMO), but is not limited thereto.

[0049] In some embodiments, the material of the hole transport layer is selected from organic materials with good hole transport capabilities, such as, but not limited to, poly(9,9-dioctylfluorene-CO-N-(4-butylphenyl)diphenylamine) (TFB), polyvinylcarbazole (PVK), poly(N,N'-bis(4-butylphenyl)-N,N'-bis(phenyl)benzidine) (Poly-TPD), and poly(9,9-dioctylfluorene-co-bis-N,N-phenyl-1,4-phenylenediamine) (TFB). PFB), 4,4',4”-tris(carbazole-9-yl)triphenylamine (TCTA), 4,4'-di(9-carbazole)biphenyl (CBP), N,N'-diphenyl-N,N'-di(3-methylphenyl)-1,1'-biphenyl-4,4'-diamine (TPD), N,N'-diphenyl-N,N'-(1-naphthyl)-1,1'-biphenyl-4,4'-diamine (NPB), doped graphene, undoped graphene, and one or more of C60.

[0050] In some embodiments, the material of the quantum dot emitting layer is selected from one or more of red quantum dots, green quantum dots, and blue quantum dots, and may also be selected from yellow quantum dots. Specifically, the material of the quantum dot emitting layer is selected from one or more of CdS, CdSe, CdTe, ZnO, ZnS, ZnSe, ZnTe, GaAs, GaP, GaSb, HgS, HgSe, HgTe, InAs, InP, InSb, AlAs, AlP, CuInS, CuInSe, and various core-shell structure quantum dots or alloy structure quantum dots. The quantum dots of the present invention may be selected from cadmium-containing or cadmium-free quantum dots. The quantum dot emitting layer of this material has the characteristics of a broad and continuously distributed excitation spectrum and high emission spectrum stability.

[0051] In some specific embodiments, the thickness of the quantum dot light-emitting layer is 20-60 nm.

[0052] In some embodiments, the cathode material is selected from one or more of conductive carbon materials, conductive metal oxide materials, and metallic materials; wherein the conductive carbon materials include, but are not limited to, one or more of doped or undoped carbon nanotubes, doped or undoped graphene, doped or undoped graphene oxide, C60, graphite, carbon fibers, and porous carbon; the conductive metal oxide materials include, but are not limited to, one or more of ITO, FTO, ATO, and AZO; the metallic materials include, but are not limited to, Al, Ag, Cu, Mo, Au, or alloys thereof; wherein the metallic materials have morphologies including, but are not limited to, one or more of dense thin films, nanowires, nanospheres, nanorods, nanocones, and hollow nanospheres.

[0053] In some specific embodiments, the thickness of the cathode is 15-30 nm.

[0054] In some embodiments, a method for fabricating a quantum dot light-emitting diode with an upright structure is also provided, such as... Figure 4 As shown, the steps include:

[0055] S100, A substrate is provided, wherein an anode is disposed on the substrate;

[0056] S200, A hole transport layer is prepared on the anode;

[0057] S300. A quantum dot light-emitting layer is prepared on the hole transport layer;

[0058] S400. An electron transport layer is prepared on the quantum dot light-emitting layer. The electron transport layer material is a composite material, which includes three-dimensional graphene and zinc oxide nanoparticles or metal ion-doped zinc oxide nanoparticles loaded on the three-dimensional graphene.

[0059] S500: A cathode is fabricated on the electron transport layer to obtain the quantum dot light-emitting diode.

[0060] In this embodiment, the preparation method of each layer can be a chemical method or a physical method. The chemical method includes, but is not limited to, one or more of the following: chemical vapor deposition, continuous ion layer adsorption and reaction, anodic oxidation, electrolytic deposition, and coprecipitation. The physical method includes, but is not limited to, one or more of the following: solution method (such as spin coating, printing, blade coating, dip coating, immersion coating, spraying, roller coating, casting, slot coating, or strip coating), vapor deposition method (such as thermal vapor deposition, electron beam vapor deposition, magnetron sputtering, or multi-arc ion plating), and deposition method (such as physical vapor deposition, atomic layer deposition, and pulsed laser deposition).

[0061] In some specific embodiments, the step of preparing an electron transport layer on a quantum dot light-emitting layer specifically includes: placing a substrate with a prepared quantum dot light-emitting layer on a spin coater, spin-coating a composite material solution onto the substrate, and annealing it at 100°C to obtain an electron transport layer.

[0062] In some specific embodiments, the step of fabricating a cathode on the electron transport layer specifically includes: placing the substrate after the deposition of each functional layer in a vapor deposition chamber and thermally vapor-depositing a 15-30 nm layer of metallic silver or aluminum as a cathode using a mask, or using nano-Ag wires or Cu wires, etc. The above materials have low resistance, which allows charge carriers to be injected smoothly.

[0063] In some embodiments, a method for fabricating an inverted quantum dot light-emitting diode is also provided, such as... Figure 5 As shown, it includes the following steps:

[0064] S01. A substrate is provided, wherein a cathode is disposed on the substrate;

[0065] S02. An electron transport layer is prepared on the cathode. The electron transport layer material is a composite material, which includes three-dimensional graphene and zinc oxide nanoparticles or metal ion-doped zinc oxide nanoparticles loaded on the three-dimensional graphene.

[0066] S03. Prepare a quantum dot light-emitting layer on the electron transport layer;

[0067] S04. Prepare a hole transport layer on the quantum dot light-emitting layer;

[0068] S05. An anode is prepared on the hole transport layer to obtain the quantum dot light-emitting diode.

[0069] In some embodiments, the obtained quantum dot light-emitting diodes are encapsulated, which can be done using conventional machine encapsulation or manual encapsulation. Specifically, the encapsulation environment has oxygen and water content both below 0.1 ppm to ensure the stability of the QLED device.

[0070] The following specific embodiments further illustrate the composite material, its preparation method, and quantum dot light-emitting diode of the present invention:

[0071] Comparative Example 1

[0072] 1. The preparation steps of the zinc oxide nanoparticle solution are as follows:

[0073] 01. First, add an appropriate amount of zinc acetate to 50 ml of ethanol solution to prepare a 1 M zinc acetate ethanol solution. Stir and dissolve the solution at 70 °C to obtain precursor solution 1.

[0074] 02. Weigh potassium hydroxide according to the molar ratio of Zn to OH- of 1:1.1. Add sodium hydroxide to 50 ml of ethanol solution to prepare a 1.1 M potassium hydroxide solution. After stirring and dissolving, the precursor solution 2 is obtained.

[0075] 03. Inject precursor solution 1 into precursor solution 2 at an injection rate of 10 mL / min, wash the prepared solution, and obtain an ethanol solution of zinc oxide nanoparticles.

[0076] 2. The fabrication steps of a QLED device with an upright structure are as follows:

[0077] 01. A substrate is provided, wherein an ITO anode is disposed on the substrate;

[0078] 02. TFB solution is spin-coated onto the anode to prepare a hole transport layer;

[0079] 03. A CdSe solution was spin-coated onto the hole transport layer to prepare the quantum dot luminescent layer;

[0080] 04. An ethanol solution of the zinc oxide nanoparticles is spin-coated onto the quantum dot layer to obtain an electron transport layer;

[0081] 05. An Ag layer is deposited on the electron transport layer to serve as the cathode, thereby obtaining the upright QLED device.

[0082] Example 1

[0083] 1. The preparation steps of the composite material are as follows:

[0084] 01. First, add an appropriate amount of zinc acetate to 50 ml of ethanol solution to prepare a 1 M zinc acetate ethanol solution, and stir to dissolve at 70 °C. Add acrylic cation exchange resin and stir in the cation exchange resin for 24 hours to obtain precursor A;

[0085] 02. Add precursor A to a ceramic boat and place it in a tube furnace. Heat the furnace to 700°C for 1 hour in an inert nitrogen atmosphere at a heating rate of 5°C / min to obtain a black powder. After cooling and cleaning, disperse the powder in an ethanol solution to obtain a composite material solution.

[0086] 2. The fabrication steps for a QLED device with an upright structure are as follows:

[0087] 01. A substrate is provided, wherein an ITO anode is disposed on the substrate;

[0088] 02. A hole transport layer is prepared by spin-coating a TFB solution onto ITO.

[0089] 03. A CdSe solution was spin-coated onto the hole transport layer to prepare a quantum dot luminescent layer;

[0090] 04. Spin-coating the composite material solution onto the quantum dot layer to obtain an electron transport layer;

[0091] 05. An Ag layer is deposited on the electron transport layer as a cathode to obtain the upright QLED device.

[0092] Electron microscopy observation of the black powder obtained in Example 1 yielded the following results: Figure 6 As shown, from Figure 6 It can be seen that the zinc oxide nanoparticles are loaded on three-dimensional graphene.

[0093] Example 2

[0094] 1. The preparation steps of the composite material are as follows:

[0095] 01. First, add an appropriate amount of the zinc chloride and magnesium chloride mixture to 50 ml of ethanol solution to prepare a 1 M zinc chloride and magnesium chloride ethanol solution, and stir to dissolve at 70 °C. Add styrene-type cation exchange resin and stir in the cation exchange resin for 24 hours to obtain precursor B;

[0096] 02. Add precursor B to a ceramic boat and place it in a tube furnace. Heat the furnace to 650°C for 2 hours in an inert nitrogen atmosphere at a heating rate of 5°C / min to obtain a black powder. After cooling and cleaning, disperse the powder in an ethanol solution to obtain a composite material solution.

[0097] 2. The fabrication steps of a positive-position QLED device are as follows:

[0098] 03. A substrate is provided, wherein an ITO anode is disposed on the substrate;

[0099] 04. A layer of TFB solution is spin-coated onto ITO to obtain a hole transport layer;

[0100] 05. A CdSe solution was spin-coated onto the hole transport layer to prepare a quantum dot luminescent layer;

[0101] 06. Spin-coating the composite material solution onto the quantum dot layer to obtain an electron transport layer;

[0102] 07. An Ag layer is deposited on the electron transport layer to serve as the cathode, thereby obtaining the upright QLED device.

[0103] Example 3

[0104] 1. The preparation steps of the composite material are as follows:

[0105] 01. First, add an appropriate amount of the zinc chloride and aluminum chloride mixture to 50 ml of ethanol solution to prepare a 1 M zinc chloride and aluminum chloride ethanol solution, and stir to dissolve at 70 °C. Add an acrylic cation exchange resin and stir in the cation exchange resin for 24 hours to obtain precursor C;

[0106] 02. Add precursor C to a ceramic boat and place it in a tube furnace. Heat the furnace to 650°C for 2 hours in an inert nitrogen atmosphere at a heating rate of 5°C / min to obtain a black powder. After cooling and cleaning, disperse the powder in an ethanol solution to obtain a composite material solution.

[0107] 2. The fabrication steps of the inverted QLED device are as follows:

[0108] 01. A substrate is provided, wherein a cathode is disposed on the substrate;

[0109] 02. The composite material solution is spin-coated onto the cathode to obtain an electron transport layer;

[0110] 03. A CdSe solution was spin-coated onto the electron transport layer to prepare a quantum dot luminescent layer;

[0111] 04. A hole transport layer is prepared by spin-coating a TFB solution onto the quantum dot luminescent layer;

[0112] 05. An ITO layer is deposited on the hole transport layer as an anode to obtain the inverted QLED device.

[0113] The performance of the light-emitting diodes prepared in Examples 1-3 and Comparative Example 1 was tested, and the test results are as follows: Figure 7 As shown, from Figure 7 As can be seen, the external quantum efficiency of the quantum dot light-emitting diodes in Examples 1-3 is significantly higher than that in Comparative Example 1. Among them, the external quantum efficiency of the quantum dot light-emitting diode in Example 2 is the highest, indicating that the composite material prepared in Example 2 has a better electron transport rate as the electron transport layer material, which helps to improve the external quantum efficiency of the quantum dot light-emitting diode.

[0114] In summary, the present invention provides a composite material comprising three-dimensional graphene and zinc oxide nanoparticles or metal ion-doped zinc oxide nanoparticles loaded on the three-dimensional graphene. In this invention, since the zinc oxide nanoparticles or metal ion-doped zinc oxide nanoparticles are loaded in the three-dimensional graphene, the three-dimensional graphene can, on the one hand, improve the conductivity of the composite material, and on the other hand, effectively prevent agglomeration between zinc oxide nanoparticles or between metal ion-doped zinc oxide nanoparticles; the three-dimensional graphene also has good rigidity and good ductility, which can improve the film uniformity of the composite material.

[0115] It should be understood that the application of the present invention is not limited to the examples above. Those skilled in the art can make improvements or modifications based on the above description, and all such improvements and modifications should fall within the protection scope of the appended claims.

Claims

1. A light emitting diode, characterized by, The electron transport layer comprises a material prepared by the steps of: dispersing a zinc source-containing powder into a solvent to obtain a first precursor solution; adding the first precursor solution into an ion exchange resin to exchange metal ions in the first precursor solution with cations in the ion exchange resin to obtain a second precursor solution; performing heat treatment on the second precursor solution under an inert atmosphere to obtain the electron transport layer material; The electron transport layer material comprises three-dimensional graphene and zinc oxide nanoparticles or metal ion-doped zinc oxide nanoparticles supported on the three-dimensional graphene, and the mass ratio of the zinc oxide nanoparticles or metal ion-doped zinc oxide nanoparticles to the three-dimensional graphene is 6-20:

1.

2. The light emitting diode of claim 1, wherein, In the step of performing heat treatment on the second precursor solution, the temperature of the heat treatment is 650-950°C.

3. The light emitting diode of claim 1, wherein, The zinc source-containing powder is one or more of anhydrous zinc nitrate, zinc chloride, zinc acetate, zinc sulfate and zinc acetylacetonate; or the zinc source-containing powder is a mixed powder composed of at least one of anhydrous zinc nitrate, zinc chloride, zinc acetate, zinc sulfate and zinc acetylacetonate and one of a magnesium salt or an aluminum salt.

4. The light emitting diode of claim 1, wherein, The ion exchange resin contains -OH, -COOH, -NH2, and -NH. - , -SH, -CN, -SO3H, -SOOH, -NO2, -CONH2, -CONH - -COCl, -CO - A cation exchange resin containing at least one functional group selected from -CHO, -Cl, and -Br.

5. The light emitting diode of claim 1, wherein, In the metal ion-doped zinc oxide nanoparticles, the doping metal ions account for 0.1-20% of the total metal ion molar amount.

6. The light emitting diode of claim 1, wherein, The metal ion-doped zinc oxide nanoparticles are one of magnesium ion-doped zinc oxide nanoparticles or aluminum ion-doped zinc oxide nanoparticles.

7. The light emitting diode of claim 1, wherein, The light-emitting diode is an inverted structure quantum dot light-emitting diode, which comprises, from bottom to top, a substrate, a cathode, an electron transport layer, a quantum dot light-emitting layer, a hole functional layer and an anode.

8. The light emitting diode of claim 7, wherein, The hole functional layer comprises one or more of an electron blocking layer, a hole injection layer and a hole transport layer.

9. The light emitting diode of claim 7, wherein, The thickness of the electron transport layer is 70-90 nm.

10. The light emitting diode of claim 8, wherein, The anode material is selected from one or more of indium-doped tin oxide (ITO), fluorine-doped tin oxide (FTO), antimony-doped tin oxide (ATO), aluminum-doped zinc oxide (AZO), gallium-doped zinc oxide (GZO), indium-doped zinc oxide (IZO), magnesium-doped zinc oxide (MZO) and aluminum-doped magnesium oxide (AMO); The material of the hole transport layer is selected from one or more of poly(9,9-dioctylfluorene-CO-N-(4-butylphenyl)diphenylamine) (TFB), polyvinylcarbazole (PVK), poly(N,N'-bis(4-butylphenyl)-N,N'-bis(phenyl)benzidine) (Poly-TPD), poly(9,9-dioctylfluorene-co-bis-N,N-phenyl-1,4-phenylenediamine) (PFB), 4,4',4"-tris(carbazol-9-yl)triphenylamine (TCTA), 4,4'-bis(9-carbazolyl) biphenyl (CBP), N,N'-diphenyl-N,N'-di(3-methylphenyl)-1,1'-biphenyl-4,4'-diamine (TPD), N,N'-diphenyl-N,N'-(1-naphthyl)-1,1'-biphenyl-4,4'-diamine (NPB), doped graphene, undoped graphene, and C60; The material of the quantum dot light-emitting layer is selected from one or more of CdS, CdSe, CdTe, ZnO, ZnS, ZnSe, ZnTe, GaAs, GaP, GaSb, HgS, HgSe, HgTe, InAs, InP, InSb, AlAs, AlP, CuInS, CuInSe, and various core-shell structure quantum dots or alloy structure quantum dots, and the thickness of the quantum dot light-emitting layer is 20-60 nm; The material of the cathode is selected from one or more of conductive carbon materials, conductive metal oxide materials, and metal materials, wherein the conductive carbon materials include one or more of doped or undoped carbon nanotubes, doped or undoped graphene, doped or undoped graphene oxide, C60, graphite, carbon fibers, and porous carbon; the conductive metal oxide materials include one or more of ITO, FTO, ATO, and AZO; and the metal materials include Al, Ag, Cu, Mo, Au, or alloys thereof; Among the metal materials, the morphology includes one or more of dense thin films, nanowires, nanospheres, nanorods, nanotips, and nanohollow spheres; The thickness of the cathode is 15-30 nm.

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