Quantum dot light-emitting diode and preparation method thereof

Abstract

The present invention discloses a quantum dot light-emitting diode and a preparation method thereof. The preparation method comprises depositing an alcohol solution of a metal oxide on a quantum dot light-emitting layer; preparing a double-end organic solution on the alcohol solution of the metal oxide; the end groups of the double-end organic solution are functional groups capable of reacting with hydroxyl groups; depositing a hydroxyl polymer solution on the double-end organic solution, and performing an annealing treatment to sequentially form a metal oxide layer, a connecting layer, and a polymer layer on the quantum dot light-emitting layer. The hydroxyl polymer is connected to an alcohol solvent via the double-end organic solution, thereby achieving a completely seamless connection between the polymer layer of the quantum dot light-emitting diode and the metal oxide layer serving as an electron transport layer. This reduces the interface barrier between the polymer layer and the electron transport layer, reduces charge accumulation, and slows down material degradation caused by charge accumulation at the interface, thereby improving the device's luminous efficiency and lifespan.

Description

Technical Field

[0001] The present invention relates to the technical field of light-emitting diodes, and in particular to a quantum dot light-emitting diode and a preparation method thereof. Background Art

[0002] Quantum dot electroluminescence (QDEL) is a new solid-state lighting technology with advantages such as low cost, light weight, fast response speed, and high color saturation. It holds broad development prospects and has become a key research direction for the next generation of LED display devices. Quantum dot light-emitting diodes (QLEDs) offer broad application prospects in the display and lighting fields due to their improved monochromaticity, color saturation, and low production costs. After rapid development in recent years, key performance indicators such as brightness, external quantum efficiency (EQE), and lifetime of QD LED devices have been significantly improved.

[0003] Balancing the carrier injection of electrons and holes is an effective way to obtain high-efficiency quantum dot light-emitting diode devices. In existing QLED devices, a transition layer is usually set between the electrode and the electron transport layer to slow down the electron transfer efficiency. However, the transition layer and the electron transport layer cannot be seamlessly connected together, resulting in a large interface potential barrier, which reduces the luminescence performance and lifespan of the quantum dot light-emitting diode device.

[0004] Therefore, the existing technology still needs to be improved and developed. Summary of the Invention

[0005] In view of the above-mentioned deficiencies in the prior art, the object of the present invention is to provide a quantum dot light-emitting diode and a preparation method thereof, aiming to balance the transmission rates of electrons and holes and improve the luminous efficiency of quantum dot light-emitting diode devices.

[0006] The technical solutions of the present invention are as follows:

[0007] A method for preparing a quantum dot light-emitting diode, comprising the steps of:

[0008] preparing a quantum dot light-emitting layer on an anode substrate;

[0009] depositing a metal oxide solution on the quantum dot light-emitting layer, wherein the metal oxide solution comprises an alcohol solvent and a metal oxide dispersed in the alcohol solvent;

[0010] A double-terminal organic solution is prepared on the metal oxide solution, wherein the double-terminal organic solution has a structural formula of X1-R-X2, wherein R is a hydrocarbon group, and X1 and X2 are functional groups that react with hydroxyl groups;

[0011] Depositing a hydroxyl polymer solution on the double-terminal organic solution and performing solvent evaporation treatment to sequentially form a metal oxide layer, a connecting layer, and a polymer layer on the quantum dot light-emitting layer;

[0012] A cathode is prepared on the polymer layer to obtain the quantum dot light emitting diode.

[0013] In the method for preparing a quantum dot light-emitting diode, the double-end organic solution and the metal oxide solution are insoluble in each other; and the double-end organic solution and the polymer solution are insoluble in each other.

[0014] In the method for preparing a quantum dot light-emitting diode, the time interval between the deposition of the double-end organic solution and the polymer solution is within 3 minutes, and the time interval between the solvent evaporation treatment and the deposition of the polymer solution is 3 minutes.

[0015] In the method for preparing a quantum dot light-emitting diode, the metal oxide solution, the double-end organic solution and the polymer solution are deposited by inkjet printing.

[0016] In the method for preparing a quantum dot light-emitting diode, the hydrocarbon group is a straight-chain hydrocarbon group having more than 3 carbon atoms.

[0017] In the method for preparing a quantum dot light-emitting diode, the functional group is selected from one of an isocyanate group, an acyl halide group, a carboxyl group, and an anhydride group.

[0018] In the method for preparing a quantum dot light-emitting diode, the hydroxy polymer is selected from one or more of polyenol compounds, polyacrylic resin hydroxy derivatives, and hydroxy-substituted polystyrene compounds.

[0019] In the method for preparing the quantum dot light-emitting diode, the relative molecular mass of the hydroxyl polymer is 50,000 to 120,000.

[0020] The method for preparing a quantum dot light-emitting diode, wherein the metal oxide includes one or more of ZnO, TiO2, SnO2, Ta2O3, ZrO2, NiO, TiLiO, ZnAlO, ZnMgO, ZnSnO, ZnLiO, and InSnO.

[0021] In the method for preparing a quantum dot light-emitting diode, the solvent evaporation treatment is annealing, the annealing temperature is 80 to 120° C., and the annealing time is 0.5 to 1.5 hours.

[0022] In the quantum dot light-emitting diode, the thickness of the polymer layer is 9 to 17 nm.

[0023] A quantum dot light-emitting diode, comprising, in order: an anode, a quantum dot light-emitting layer, an electron transport layer, a polymer layer, and a cathode;

[0024] The electron transport layer is a metal oxide, the polymer layer includes a long-chain branched polymer, and the long branches of the long-chain branched polymer are inserted into the electron transport layer, so that the metal oxide is embedded between the long branches.

[0025] The quantum dot light-emitting diode, wherein the long chain branches of the long-chain branched polymer are obtained by grafting with a double-terminal organic matter, and during the grafting process, at least one end of at least part of the double-terminal organic matter is connected to the main body of the long-chain branched polymer, and at least the other end of at least part of the double-terminal organic matter is connected to the electron transport layer.

[0026] The quantum dot light-emitting diode, wherein the long branched chain is a straight chain with more than 4 carbon atoms.

[0027] In the quantum dot light-emitting diode, the thickness of the connecting layer is 1 to 5 nm; the thickness of the polymer layer is 8 to 12 nm.

[0028] Beneficial effects: The present invention adopts an alcohol solvent as the solvent of the metal oxide solution. After the metal oxide solution is deposited, a double-end organic solution is deposited, and then a hydroxyl polymer solution is deposited on the double-end organic solution. The two end groups of the double-end organic matter are functional groups that can react with hydroxyl groups, so that the double-end organic matter reacts with the alcohol solvent molecules and the hydroxyl polymer respectively, so that the double-end organic matter connected to the alcohol solvent molecules is grafted onto the polymer to form a branch on the polymer, so that the polymer layer of the finally prepared QLED device is completely seamlessly connected to the metal oxide, reducing the interface barrier between the polymer layer and the electron transport layer, reducing charge accumulation, and slowing down the material degradation caused by the accumulation of charge at the interface, which is beneficial to improving the luminous efficiency and life of the device. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 The present invention provides a schematic flow chart of a preferred embodiment of a method for preparing a quantum dot light-emitting diode.

[0030] Figure 2 This is a schematic structural diagram of a quantum dot light-emitting diode provided by the present invention. DETAILED DESCRIPTION

[0031] The present invention provides a quantum dot light-emitting diode device and a method for preparing the same. To clarify the objectives, technical solutions, and effects of the present invention, the present invention is described in further detail below. It should be understood that the specific embodiments described herein are intended only to illustrate the present invention and are not intended to limit the present invention.

[0032] See Figure 1 , Figure 1 The present invention provides a flow chart of a preferred embodiment of a method for preparing a quantum dot light-emitting diode, which includes the following steps:

[0033] S10, forming a quantum dot light-emitting layer on the anode substrate;

[0034] S20, depositing a metal oxide solution on the quantum dot light-emitting layer, wherein the metal oxide solution includes an alcohol solvent and a metal oxide dispersed in the alcohol solvent;

[0035] S30, preparing a double-terminal organic solution on the metal oxide solution, wherein the double-terminal organic solution has a structural formula of X1-R-X2, wherein R is a hydrocarbon group, and X1 and X2 are functional groups that react with hydroxyl groups;

[0036] S40, depositing a hydroxyl polymer solution on the double-terminal organic solution and performing solvent evaporation treatment to form a metal oxide layer and a polymer layer on the quantum dot light-emitting layer;

[0037] S50, preparing a cathode on the polymer layer to obtain the quantum dot light-emitting diode.

[0038] Electrons in the electron transport layer have high mobility and a low injection barrier, while holes typically have low mobility and a high injection barrier. This creates an imbalance between the electron and hole transport rates, leading to unstable carrier recombination in the light-emitting layer. Excessive electron injection also causes spontaneous emission from the device's functional layers, impacting the luminescence purity and recombination efficiency of quantum dot light-emitting diodes. Placing an insulating transition layer, such as polymethyl methacrylate, between the electrode and the electron transport layer can slow electron transport efficiency. However, a large interface barrier often exists between the insulating transition layer and the electron transport layer, leading to charge accumulation and impacting the performance and lifespan of quantum dot devices.

[0039] In the present embodiment, alcoholic solvent is adopted as the solvent of metal oxide solution. After depositing the metal oxide solution, drying process is not carried out, but then depositing biterminal organic solution on the metal oxide solution, and then depositing hydroxy polymer solution on the biterminal organic solution. The two end groups of the biterminal organic matter are respectively functional groups that can react with hydroxyl group. The functional groups of the two end groups can be the same or different, as long as both can react with hydroxyl group. One of the end groups of the biterminal organic matter reacts with the hydroxyl group of the alcoholic solvent, and the other end group reacts with the hydroxyl group of the hydroxy polymer, thereby making the biterminal organic matter that has been connected with the alcoholic solvent molecule be grafted on the polymer, becoming the side chain on the polymer. The reaction formula of biterminal organic matter, hydroxy polymer and alcoholic solvent is:

[0040]

[0041] After solvent evaporation, a metal oxide layer and a polymer layer are sequentially formed on the quantum dot light-emitting layer, forming an electronic functional layer with a grafted mosaic structure. The polymer layer can slow the electron transmission rate and block excess electron transmission, thereby balancing the transmission and injection of electrons and holes. The double-terminal organic compound connected to the alcohol solvent molecules acts as a polymer branch extending from the polymer layer through the connecting layer to the metal oxide layer. The metal oxide crystals are embedded in the branch chain, thus achieving a completely seamless connection between the polymer layer and the metal oxide layer. This reduces the interface barrier between the polymer layer and the metal oxide layer, reduces charge accumulation, slows down the material degradation caused by charge accumulation at the interface, and improves the luminous efficiency and lifespan of the quantum dot light-emitting diode.

[0042] In one embodiment, the di-terminal organic solution and the metal oxide solution are mutually immiscible. When the solutions are deposited, there is a certain degree of interfacial intermiscibility between adjacent solution layers. The metal oxide solution forms the electron transport layer of the quantum dot light-emitting diode. To prevent the di-terminal organic in the di-terminal organic solution from entering the metal oxide solution and causing a decrease in the electron transport capacity of the electron transport layer, the di-terminal organic solution and the metal oxide solution are mutually immiscible. This allows the di-terminal organic and metal oxide alcohol solutions to react at the interface.

[0043] In one embodiment, the deposition time interval between the dual-terminal organic solution and the polymer solution is within 3 minutes, and the deposition time interval between the solvent evaporation treatment and the deposition of the polymer solution is within 3 minutes. After the dual-terminal organic solution, one end group of the dual-terminal organic rapidly reacts with the solvent of the metal oxide solution. During the reaction, due to the elongation orientation of the hydrocarbon chain segments, the other end group of the dual-terminal organic elongates in a direction away from the metal oxide solution. The polymer solution is deposited within 3 minutes, which facilitates the reaction between the polymer in the polymer solution and the other end group of the dual-terminal organic. The simultaneous rapid deposition and solvent evaporation treatment can reduce the degree of diffusion between adjacent solution layers and avoid mixing between adjacent layers.

[0044] In one embodiment, the metal oxide solution, the double-terminated organic solution, and the polymer solution are deposited by inkjet printing. Inkjet printing can prevent movement between adjacent deposited solution layers, reduce the diffusion rate of solutes from a solution layer to an adjacent layer, and prevent mixing between adjacent layers.

[0045] Furthermore, since the electron transport materials of QLED devices are typically nanomaterials, they are prone to agglomeration during long-term use, resulting in poor luminous uniformity and a stronger sense of graininess. The metal oxide layer of this embodiment serves as the electron transport layer of the QLED device. Its crystals are embedded in the middle of the polymer side chains and are evenly dispersed by the side chains, reducing the lateral transmission of electrons within the transport layer, which is beneficial for protecting the electron transport characteristics in the transport layer. At the same time, it effectively avoids the agglomeration of metal oxide crystals, reduces the sense of graininess, and improves the uniformity of the device's luminous emission.

[0046] In one embodiment, the hydrocarbon group is a straight-chain hydrocarbon group having more than 3 carbon atoms. When the number of carbon atoms in the straight-chain hydrocarbon group is greater than 3, a branched-chain oriented structure parallel to the direction of electron transport is obtained. The polymer branches have a tensile orientation, and a larger number of carbon atoms can increase the length of the polymer branches in the orientation direction, increase the delocalization of the charge, and reduce the potential barrier in charge transfer. On the other hand, the heat generated by the light emission of the QLED device can cause the branches to expand, elongate, and straighten, further improving the degree of branch orientation and facilitating charge transfer. The effective transfer of charge improves the luminous efficiency and generates more heat, thereby forming a dynamic equilibrium.

[0047] In one embodiment, the functional groups include, but are not limited to, one of an isocyanate group (-NCO), an acyl halide group (-COX, where X is a halogen element), a carboxyl group (-COOH), and an anhydride group. Preferably, the dual-end organic compound is one or more of an isocyanate compound and an anhydride compound, such as biphenyltetracarboxylic dianhydride and p-phenylene diisocyanate. Functional groups such as isocyanates and anhydrides can directly react with water and have strong water absorption. Unreacted dual-end organic compounds can prevent excess moisture from entering the device, reducing the risk of water damage to other functional layers.

[0048] In one embodiment, the alcohol solvent includes, but is not limited to, one or more of ethanol, methanol, n-butanol, n-propanol, and n-pentanol. These alcohol solvents are all straight-chain alcohols, which have good dispersibility for metal oxides, can evenly disperse the metal oxides, and reduce agglomeration during metal oxide deposition.

[0049] In one embodiment, the hydroxy polymer includes, but is not limited to, one or more of polyenol compounds, polyacrylic acid resin hydroxy derivatives, and hydroxy-substituted polystyrene compounds.

[0050] In one embodiment, the relative molecular weight of the polymer is 50,000 to 120,000. Too high a relative molecular weight will result in poor film-forming properties and a large thickness of the polymer layer, which greatly hinders the transmission of electrons.

[0051] In one embodiment, the electron transport layer material includes one or more of ZnO, TiO2, SnO2, Ta2O3, ZrO2, NiO, TiLiO, ZnAlO, ZnMgO, ZnSnO, ZnLiO, and InSnO.

[0052] In one embodiment, the solvent evaporation treatment is annealing, the annealing temperature is 80-120°C, and the annealing time is 0.5-1.5 hours. Suitable heat treatment temperature and time also facilitate the reaction of the double-terminal organic compound with the solvent and polymer of the metal oxide solution, further improving the connection between the electron transport layer and the polymer layer of the QLED device and enhancing the electron transport properties.

[0053] In one embodiment, the anode may be selected from one or more of indium-doped tin oxide (ITO), fluorine-doped tin oxide (FTO), antimony-doped tin oxide (ATO), and aluminum-doped zinc oxide (AZO).

[0054] In one embodiment, the quantum dot material includes, but is not limited to, one or more of a II-VI compound, a III-V compound, a II-V compound, a III-VI compound, a IV-VI compound, a I-III-VI compound, a II-IV-VI compound, or a group IV element. The semiconductor material used in the quantum dot light-emitting layer includes, but is 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, and nanocrystals of III-V semiconductors, such as GaP, GaAs, InP, InAs, and other binary, ternary, and quaternary III-V compounds.

[0055] In one embodiment, the cathode includes but is not limited to one or more of a metal material, a carbon material, and a metal oxide. Wherein, the metal material includes one or more of Al, Ag, Cu, Mo, Au, Ba, Ca, and Mg; the carbon material includes one or more of graphite, carbon nanotubes, graphene, and carbon fiber; the metal oxide can be a doped or undoped metal oxide, including one or more of ITO, FTO, ATO, AZO, GZO, IZO, MZO, and AMO, and also includes a composite electrode in which a metal is sandwiched between doped or undoped transparent metal oxides, wherein the composite electrode includes one or more of AZO / Ag / AZO, AZO / Al / AZO, ITO / Ag / ITO, ITO / Al / ITO, ZnO / Ag / ZnO, ZnO / Al / ZnO, TiO2 / Ag / TiO2, TiO2 / Al / TiO2, ZnS / Ag / ZnS, ZnS / Al / ZnS, TiO2 / Ag / TiO2, and TiO2 / Al / TiO2.

[0056] In one embodiment, before preparing the quantum dot light-emitting layer on the anode substrate, the preparation method further comprises the steps of: preparing a hole injection layer on the anode substrate, and then preparing a hole transport layer on the hole injection layer.

[0057] In one embodiment, the hole transport layer material is selected from organic materials having hole transport capability, including 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), 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-carbazole)biphenyl (CBP), N,N'-diphenyl-N,N'-bis(3-methylphenyl)-1,1'-biphenyl-4,4'-diamine (TPD), N,N'-diphenyl-N,N'-(1-naphthyl)-1,1'-biphenyl-4,4'-diamine (NPB) or more. The hole transport layer material can also be selected from inorganic materials with hole transport capability, including but not limited to doped or undoped NiO, WO3, MoO3, CuO, doped graphene, undoped graphene, C 60 One or more of .

[0058] In one embodiment, the hole injection layer includes, but is not limited to, one or more of poly(3,4-ethylenedioxythiophene)-polystyrene sulfonic acid (PEDOT:PSS), undoped transition metal oxides, doped transition metal oxides, metal sulfides, and doped metal sulfides.

[0059] The present invention also provides a quantum dot light-emitting diode, which comprises in sequence: an anode, a quantum dot light-emitting layer, an electron transport layer, a polymer layer and a cathode;

[0060] The electron transport layer is a metal oxide, the polymer layer includes a long-chain branched polymer, and the long branches of the long-chain branched polymer are inserted into the electron transport layer, so that the metal oxide is embedded between the long branches.

[0061] In this embodiment, the polymer layer can slow down the electron transport rate and block excess electron transport, thereby balancing the transport and injection of electrons and holes. Furthermore, because the long branches of the long-chain branched polymer are inserted into the electron transport layer, the metal oxide is embedded between the long branches, thereby achieving a completely seamless connection between the polymer layer and the electron transport layer (i.e., the metal oxide layer). This reduces the interface barrier between the polymer layer and the electron transport layer, reduces charge accumulation, slows down the material degradation caused by charge accumulation at the interface, and improves the luminous efficiency and lifespan of the quantum dot light-emitting diode.

[0062] Furthermore, the metal oxide layer serves as the electron transport layer of the QLED device, and its crystals are embedded in the middle of the polymer side chains and are evenly dispersed by the side chains, which reduces the lateral transmission of electrons in the transport layer and is beneficial to protecting the transmission characteristics of electrons in the transport layer. At the same time, it effectively avoids the agglomeration of metal oxide crystals, reduces the granularity of the luminescence, and improves the luminescence uniformity of the device.

[0063] In one embodiment, the long chain branches of the long chain branched polymer are obtained by grafting with a double-terminal organic matter. During the grafting process, at least one end of at least part of the double-terminal organic matter is connected to the main body of the long chain branched polymer, and at least the other end of at least part of the double-terminal organic matter is connected to the electron transport layer.

[0064] Specifically, during the preparation of quantum dot light-emitting diodes, some double-end organics may not be grafted with hydroxyl polymers and solvents in the metal oxide solution, and these residual double-end organics are located between the long branches of the long-chain branched polymer. Functional groups such as isocyanates and anhydrides can directly react with water and have strong water absorption, such as biphenyltetracarboxylic dianhydride, paraphenylene diisocyanate, etc., so these residual double-end organics can prevent excess water from entering the device and reduce the risk of other functional layers being damaged by water. Furthermore, the long branches of the long-chain branched polymer extend to the metal oxide layer, and the chain ends of the long branches are between the metal oxides, and the metal oxide crystals are embedded in the middle of the branches, so that the polymer layer and the metal oxide layer are completely seamlessly connected, reducing the interface barrier between the polymer layer and the metal oxide layer, reducing charge accumulation, slowing down the material degradation caused by the accumulation of charge at the interface, and improving the luminous efficiency and life of the quantum dot light-emitting diode. In this embodiment, the quantum dot light-emitting diode has various forms, specifically, such as Figure 2 As shown, Figure 2 This is a schematic structural diagram of a quantum dot light-emitting diode provided in this embodiment, which includes an anode 10, a hole injection layer 20, a hole transport layer 30, a quantum dot light-emitting layer 40, an electron transport layer 50, a polymer layer 60 and a cathode 70 arranged in sequence from bottom to top.

[0065] In one embodiment, the long chain branch is a straight chain with more than 4 carbon atoms.

[0066] In one embodiment, the thickness of the connecting layer is 1 to 5 nm; the thickness of the polymer layer is 8 to 12 nm.

[0067] The present invention will be further described below by means of specific examples.

[0068] Example 1

[0069] Step S11: depositing PEDOT:PSS as a hole injection layer on a transparent anode substrate; depositing TFB as a hole transport layer on the hole injection layer; and depositing a quantum dot light-emitting layer on the hole transport layer;

[0070] Step S12: depositing a ZnO ethanol solution on the quantum dot light-emitting layer;

[0071] Step S13: depositing a n-hexane solution of pyromellitic dianhydride on the ethanol solution of ZnO;

[0072] Step S14: depositing a polyvinyl alcohol solution on the n-hexane solution of pyromellitic dianhydride;

[0073] Step S15: heat-treating the ZnO ethanol solution, the pyromellitic dianhydride n-hexane solution and the polyvinyl alcohol solution at 80° C. for 30 min, to sequentially form a metal oxide layer, a connecting layer and a polymer layer on the quantum dot light-emitting layer.

[0074] Step S16: depositing a metal cathode on the polymer layer by evaporation;

[0075] Step S17: After packaging, a quantum dot light emitting diode is obtained.

[0076] Example 2

[0077] Step S21: depositing PEDOT:PSS as a hole injection layer on a transparent anode substrate; depositing TFB as a hole transport layer on the hole injection layer; and depositing a quantum dot light-emitting layer on the hole transport layer;

[0078] Step S22: depositing a ZnO ethanol solution on the quantum dot light-emitting layer;

[0079] Step S23: depositing a diethyl ether solution of adipoyl chloride on the ethanol solution of ZnO;

[0080] Step S24: depositing the poly(hydroxyethyl methacrylate) solution on the ether solution of adipoyl chloride;

[0081] Step S25: irradiate the ZnO ethanol solution, the adipic acid chloride ether solution and the poly(hydroxyethyl methacrylate) solution with ultraviolet light for 2 minutes, and then heat treat them at 80°C for 30 minutes to form a metal oxide layer, a connecting layer and a polymer layer on the quantum dot light-emitting layer.

[0082] Step S26: depositing a metal cathode on the polymer layer by evaporation;

[0083] Step S27: After packaging, a quantum dot light-emitting diode is obtained.

[0084] Example 3

[0085] Step S31: depositing PEDOT:PSS as a hole injection layer on a transparent anode substrate; depositing TFB as a hole transport layer on the hole injection layer; and depositing a quantum dot light-emitting layer on the hole transport layer;

[0086] Step S32: depositing a ZnO ethanol solution on the quantum dot light-emitting layer;

[0087] Step S33: depositing a toluene solution of hexamethylene diisocyanate on the ethanol solution of ZnO;

[0088] Step S34: depositing a polyvinyl alcohol solution on the toluene solution of hexamethylene diisocyanate;

[0089] Step S35: irradiating the ZnO ethanol solution, hexamethylene diisocyanate toluene solution, and polyvinyl alcohol solution with ultraviolet light for 2 minutes, and then heat-treating them at 80° C. for 30 minutes to sequentially form a metal oxide layer, a connecting layer, and a polymer layer on the quantum dot light-emitting layer;

[0090] Step S36: depositing a metal cathode on the polymer layer by evaporation;

[0091] Step S37: After packaging, a QLED device is obtained.

[0092] In summary, the present invention uses an alcohol solvent as a solvent for the metal oxide solution. After the metal oxide solution is deposited, a double-end organic solution is deposited, and then a hydroxyl polymer solution is deposited on the double-end organic solution. The two end groups of the double-end organic are functional groups that can react with hydroxyl groups, so that the double-end organic reacts with the alcohol solvent molecules and the hydroxyl polymer respectively, thereby connecting the double-end organic to the alcohol solvent molecules and grafting them onto the polymer to form a branch on the polymer, so that the polymer layer of the QLED device finally prepared is completely seamlessly connected to the metal oxide, reducing the interface barrier between the polymer layer and the electron transport layer, reducing charge accumulation, and slowing down the material degradation caused by the accumulation of charge at the interface, which is beneficial to improving the luminous efficiency and life of the device. At the same time, the electron transport material crystals are embedded in the side chains of the polymer. The side chains evenly disperse the metal oxide crystals, reduce the lateral transmission of electrons in the transport layer, effectively avoid the agglomeration of the metal oxide crystals, and are beneficial to protecting the electron transport characteristics, reducing the luminous granularity, and improving the luminous uniformity of the device.

[0093] It should be understood that the application of the present invention is not limited to the above examples. For those skilled in the art, improvements or changes can be made based on the above description. All these improvements and changes should fall within the scope of protection of the claims attached to the present invention.

Claims

1. A method for preparing a quantum dot light-emitting diode, characterized in that: Including steps: preparing a quantum dot light-emitting layer on an anode substrate; depositing a metal oxide solution on the quantum dot light-emitting layer, wherein the metal oxide solution comprises an alcohol solvent and a metal oxide dispersed in the alcohol solvent; A double-terminal organic solution is prepared on the metal oxide solution, wherein the double-terminal organic solution has a structural formula of X1-R-X2, wherein R is a hydrocarbon group, and X1 and X2 are functional groups that can react with hydroxyl groups; A hydroxyl polymer solution is deposited on the double-terminal organic solution, and a solvent evaporation process is performed to form a metal oxide layer and a polymer layer on the quantum dot light-emitting layer; wherein one end group of the double-terminal organic reacts with a hydroxyl group of an alcohol solvent, and the other end group reacts with a hydroxyl group of the hydroxyl polymer, so that the double-terminal organic connected to the alcohol solvent molecule is grafted onto the polymer to form a branch chain on the polymer; the branch chain of the polymer extends from the polymer layer through the connecting layer to the metal oxide layer, and the metal oxide crystals are embedded in the middle of the branch chain; preparing a cathode on the polymer layer to obtain the quantum dot light-emitting diode; The time interval between the deposition of the double-terminal organic solution and the polymer solution is within 3 minutes, and the time interval between the solvent evaporation treatment and the deposition of the polymer solution is within 3 minutes.

2. The method for preparing a quantum dot light-emitting diode according to claim 1, wherein: The double-terminal organic solution and the metal oxide solution are insoluble in each other.

3. The method for preparing a quantum dot light-emitting diode according to claim 1, wherein: The metal oxide solution, the double-terminal organic solution and the polymer solution are all deposited by inkjet printing.

4. The method for preparing a quantum dot light-emitting diode according to claim 1, wherein: The hydrocarbon group is a straight-chain hydrocarbon group having more than 3 carbon atoms.

5. The method for preparing a quantum dot light-emitting diode according to claim 1, wherein: The functional group is selected from one of an isocyanate group, an acyl halide group, a carboxyl group, and an acid anhydride group.

6. The method for preparing a quantum dot light-emitting diode according to claim 1, wherein: The alcohol solvent is selected from one or more of ethanol, methanol, n-butanol, n-propanol and n-pentanol.

7. The method for preparing a quantum dot light-emitting diode according to claim 1, wherein: The relative molecular mass of the hydroxy polymer is 50,000 to 120,000.

8. The method for preparing a quantum dot light-emitting diode according to claim 1, wherein: The metal oxide includes one or more of ZnO, TiO2, SnO2, Ta2O3, ZrO2, NiO, TiLiO, ZnAlO, ZnMgO, ZnSnO, ZnLiO, and InSnO.

9. The method for preparing a quantum dot light-emitting diode according to claim 1, wherein: The solvent evaporation treatment is annealing, the annealing temperature is 80-120° C., and the annealing time is 0.5-1.5 h.

10. The method for preparing a quantum dot light-emitting diode according to claim 1, wherein: The thickness of the polymer layer is 9-17 nm.

11. A quantum dot light-emitting diode prepared by the preparation method according to claim 1, characterized in that: Including in order: Anode, quantum dot light-emitting layer, electron transport layer, polymer layer and cathode; The electron transport layer is a metal oxide, the polymer layer includes a long-chain branched polymer, and the long branches of the long-chain branched polymer are inserted into the electron transport layer, so that the metal oxide is embedded between the long branches.

12. The quantum dot light-emitting diode according to claim 11, characterized in that: The long chain branch is a straight chain with more than 4 carbon atoms.

13. The quantum dot light-emitting diode according to claim 11, characterized in that: The length of the long chain branch is 1-5 nm; the thickness of the polymer layer is 9-17 nm.

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