CN111384273B - Quantum dot light-emitting diode and preparation method thereof - Google Patents

Abstract

The invention discloses a quantum dot light-emitting diode and a preparation method thereof, wherein the quantum dot light-emitting diode comprises a cathode, an anode and a quantum dot light-emitting layer arranged between the cathode and the anode, an electron transport layer is also arranged between the cathode and the quantum dot light-emitting layer, the electron transport layer is made of nano metal oxide which is crosslinked together through a chelating agent, and the chelating agent contains at least three carboxyl functional groups. The invention adopts the nano metal oxide crosslinked by the chelating agent as the electron transport layer material, and can improve the electron mobility of the quantum dot light-emitting diode, thereby balancing the electron hole injection rate of the quantum dot light-emitting diode and further improving the luminous efficiency of the quantum dot light-emitting diode.

Description

Quantum dot light-emitting diode and preparation method thereof

Technical Field

The invention relates to the field of quantum dots, in particular to a quantum dot light-emitting diode and a preparation method thereof.

Background

The quantum dot light emitting diode is an important new display technology in the future, and the commercialization of the quantum dot display technology still has many technical problems, such as unstable device efficiency, poor lifetime, etc., and the main factor influencing the devices is caused by unbalanced charge injection of the devices.

When quantum dots of different structural systems are used for preparing quantum dot light emitting diodes (QLEDs) under the same device structure, the device efficiency and the lifetime are different, because the quantum dots of different structural systems have different requirements for electron hole injection balance, and therefore, the charge injection balance of the device needs to be adjusted and optimized.

When quantum dots of the same structural system are used for preparing quantum dot light emitting diodes (QLEDs) by using different device structures, the device efficiency and the service life are different due to different device structures, and the reason is that the electron hole injection balance caused by different device structures is inconsistent, so the charge injection balance also needs to be adjusted and optimized for different device structures.

Aiming at the problem of unbalanced charge injection of quantum dots of different structural systems under the same device structure and different device structures of quantum dots of the same structural system, the corresponding technology is still to be improved and developed.

Disclosure of Invention

In view of the above-mentioned deficiencies of the prior art, the present invention aims to provide a quantum dot light emitting diode and a method for manufacturing the same, which aims to solve the problem of low light emitting efficiency caused by unbalanced charge injection of the conventional quantum dot light emitting diode.

The technical scheme of the invention is as follows:

a quantum dot light-emitting diode comprises a cathode, an anode and a quantum dot light-emitting layer arranged between the cathode and the anode, wherein an electron transport layer is further arranged between the cathode and the quantum dot light-emitting layer, the electron transport layer is made of nano metal oxide which is crosslinked together through a chelating agent, and the chelating agent contains at least three carboxyl functional groups.

A preparation method of a quantum dot light-emitting diode comprises the following steps:

providing an anode substrate, preparing a quantum dot light-emitting layer on the anode substrate, preparing an electron transport layer on the quantum dot light-emitting layer, and preparing a cathode on the electron transport layer to prepare the quantum dot light-emitting diode;

or, providing a cathode substrate, preparing an electron transport layer on the cathode substrate, preparing a quantum dot light-emitting layer on the electron transport layer, and preparing an anode on the quantum dot light-emitting layer to obtain the quantum dot light-emitting diode;

wherein the electron transport layer material is a nano metal oxide crosslinked together by a chelating agent, the chelating agent containing at least three carboxyl functional groups.

Has the advantages that: the quantum dot light-emitting diode provided by the invention comprises a cathode, an anode and a quantum dot light-emitting layer arranged between the cathode and the anode, wherein an electron transport layer is also arranged between the cathode and the quantum dot light-emitting layer, the electron transport layer is made of nano metal oxide which is crosslinked together through a chelating agent, and the chelating agent contains at least three carboxyl functional groups. The charge transport performance of the electron transport layer can be improved by using the nano metal oxide crosslinked by the chelating agent as an electron transport layer material, so that the electron hole injection rate of the quantum dot light-emitting diode is balanced, and the light-emitting efficiency of the quantum dot light-emitting diode is improved.

Drawings

Fig. 1 is a schematic structural diagram of a quantum dot light emitting diode according to a preferred embodiment of the invention.

Fig. 2 is a schematic structural diagram of another quantum dot light-emitting diode according to a preferred embodiment of the invention.

Fig. 3 is a flowchart of a preferred embodiment of a method for manufacturing the quantum dot light emitting diode shown in fig. 1 according to the present invention.

Detailed Description

The invention provides a quantum dot light-emitting diode and a preparation method thereof, and the invention is further described in detail below in order to make the purpose, technical scheme and effect of the invention clearer and clearer. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.

The quantum dot light emitting diode has various forms, and the quantum dot light emitting diode is divided into a positive type structure and an inverse type structure, and in some embodiments, the quantum dot light emitting diode with the positive type structure includes a substrate, a bottom electrode, a quantum dot light emitting layer, an electron transport layer, and a top electrode, which are stacked from bottom to top. In the case of a quantum dot light emitting diode with a positive structure, the bottom electrode disposed on the substrate is an anode, and in one embodiment of the present invention, the substrate may include a substrate, a bottom electrode stacked on a surface of the substrate, and a hole injection layer stacked on a surface of the bottom electrode; in still another embodiment of the present invention, the substrate may include a substrate, a bottom electrode stacked on a surface of the substrate, a hole injection layer stacked on a surface of the bottom electrode, and a hole transport layer stacked on a surface of the hole injection layer; in still another embodiment of the present invention, the substrate may include a substrate, a bottom electrode stacked on a surface of the substrate, a hole injection layer stacked on a surface of the bottom electrode, a hole transport layer stacked on a surface of the hole injection layer, and an electron blocking layer stacked on a surface of the hole transport layer.

In some embodiments, the quantum dot light emitting diode with the inversion structure may include a substrate, a bottom electrode, a quantum dot light emitting layer, and a top electrode, which are stacked from bottom to top. For quantum dot light emitting diodes with an inversion structure, the bottom electrode disposed on the substrate is a cathode, and in one embodiment of the present invention, the substrate may include a substrate, a bottom electrode stacked on the surface of the substrate, and an electron injection layer stacked on the surface of the substrate; in still another embodiment of the present invention, the substrate may include a substrate, a bottom electrode stacked on a surface of the substrate, an electron injection layer stacked on a surface of the bottom electrode, and an electron transport layer stacked on a surface of the electron injection layer; in still another embodiment of the present invention, the substrate may include a substrate, a bottom electrode stacked on a surface of the substrate, an electron injection layer stacked on a surface of the substrate, an electron transport layer stacked on a surface of the electron injection layer, and a hole blocking layer stacked on a surface of the electron transport layer.

The embodiments of the present invention will be described mainly by taking a quantum dot light emitting diode of a positive type structure as shown in fig. 1 as an example. Specifically, as shown in fig. 1, the quantum dot light emitting diode with the positive structure includes asubstrate 10, ananode 20, a quantum dotlight emitting layer 30, anelectron transport layer 40, and acathode 50, which are stacked from bottom to top, wherein the electron transport layer is made of nano metal oxides cross-linked together by a chelating agent, and the chelating agent contains at least three carboxyl functional groups.

In the present embodiment, for the positive quantum dot light emitting diode, a hole functional layer such as a hole transport layer, a hole injection layer, and an electron blocking layer may be further disposed between the anode and the quantum dot light emitting layer; besides the electron transport layer, an electron injection layer, a hole blocking layer and other electronic functional layers can be arranged between the cathode and the quantum dot light-emitting layer.

The invention adopts the nano metal oxide crosslinked by the chelating agent as the material of the electron transport layer, and can improve the electron mobility of the electron transport layer, thereby balancing the electron hole injection rate of the quantum dot light-emitting diode and further improving the luminous efficiency of the quantum dot light-emitting diode. The mechanism for achieving the above effects is specifically as follows:

the chelating agent contains at least three carboxyl functional groups, and the carboxyl functional groups are easy to remove H under certain conditions⁺Formation of carboxylate ions (-COO)^-) The adjacent nanometer metal oxides can be effectively crosslinked and firmly combined together through the carboxylate ions on the chelating agent, so that the electron transport layer formed by using the nanometer metal oxides crosslinked by the chelating agent as an electron transport layer material can effectively improve the charge transport performance of the electron transport layer, the electron hole injection rate of the quantum dot light-emitting diode is balanced, and the light-emitting efficiency of the quantum dot light-emitting diode is improved. Further, the chelating agent containing at least three carboxyl functional groups has certain hydrophilic property, so that the nano metal oxide crosslinked together by the chelating agent is used as the electron transport layer material, and the film forming property of the electron transport layer is favorably improved. In a preferred embodiment, the chelating agent contains 3 to 5 carboxyl functional groups.

In a preferred embodiment, the chelating agent is selected from one or more of DOTA (1,4,7, 10-tetraazacyclododecane-1, 4,7, 10-tetracarboxylic acid), NOTA (1,4, 7-triaza-cyclononane-N, N', N "-triacetic acid), TETA (1,4,8, 11-tetraazacyclotetradecane-1, 4,8, 11-tetraacetic acid) and NODAGA (1,4, 7-triazacyclononane-1-glutaric acid-4, 7-diacetic acid), but is not limited thereto. In this embodiment, the chemical structural formula of DOTA is:

the NOTA has a chemical structural formula as follows:

the chemical structural formula of the TETA is as follows:

the chemical structural formula of the NODAGA is as follows:

. The center of the chelating agent is a neutral closed-loop structure formed by at least three nitrogen atoms, each nitrogen atom is connected with a carboxyl functional group, the neutral closed-loop structure has no charge effect and cannot form the obstruction of an electronic channel, and lone-pair electrons of N atoms on the neutral closed-loop structure are conjugated with carboxyl, so that the chelating agent has better electronic transmission performance. Therefore, the nano metal oxide crosslinked by the chelating agent is used as an electron transport layer material, and the formed electron transport layer can effectively improve the charge transport performance of the electron transport layer, so that the electron hole injection rate of the quantum dot light-emitting diode is balanced, and the light-emitting efficiency of the quantum dot light-emitting diode is improved.

More preferably, the chelating agent is selected from one or both of DOTA and TETA. The DOTA and the TETA both have four carboxyl functional groups, and can be simultaneously coordinated and combined with a plurality of nano metal oxides, so that the crosslinking degree among the nano metal oxides can be improved, and the electron mobility of an electron transport layer formed by the crosslinked nano metal oxides can be further improved.

Preferably, the nano metal oxide is selected from ZnO, NiO and W₂O₃、Mo₂O₃、TiO₂、SnO、ZrO₂And Ta₂O₃But is not limited thereto.

In a preferred embodiment, the invention further provides an inverted quantum dot light emitting diode, as shown in fig. 2, which includes asubstrate 101, acathode 102, anelectron transport layer 103, a quantum dotlight emitting layer 104, ahole transport layer 105, and ananode 106, which are sequentially stacked from bottom to top, wherein the electron transport layer is made of nano metal oxides crosslinked together by a chelating agent, and the chelating agent contains at least three carboxyl functional groups.

It should be noted that the invention is not limited to the quantum dot light emitting diode with the above structure, and may further include an interface functional layer or an interface modification layer, including but not limited to one or more of an electron blocking layer, a hole blocking layer, an electrode modification layer, and an isolation protection layer. The quantum dot light emitting diode can be partially packaged, fully packaged or not packaged.

Preferably, the material of the anode is selected from doped metal oxides; wherein the doped metal oxide includes, but is not limited to, 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).

Preferably, the material of the hole transport layer is selected from organic materials having good hole transport ability, 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), Poly (9, 9-dioctylfluorene-CO-bis-N, N-phenyl-1, 4-Phenylenediamine) (PFB), 4', 4 "-tris (carbazol-9-yl) triphenylamine (TCTA), 4' -bis (9-Carbazole) Biphenyl (CBP), N '-diphenyl-N, N' -bis (3-methylphenyl) -1, one or more of 1 '-biphenyl-4, 4' -diamine (TPD), N '-diphenyl-N, N' - (1-naphthyl) -1,1 '-biphenyl-4, 4' -diamine (NPB), doped graphene, undoped graphene, and C60.

Preferably, the material of the quantum dot light-emitting layer is selected from one or more of red quantum dots, green quantum dots and blue quantum dots, and can also be selected from yellow quantum dots. Specifically, 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. The quantum dots of the present invention can be selected from cadmium-containing or cadmium-free quantum dots. The quantum dot light emitting layer of the material has the characteristics of wide and continuous excitation spectrum distribution, high emission spectrum stability and the like.

Preferably, 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; wherein the conductive carbon material includes, but is not limited to, one or more of doped or undoped carbon nanotubes, doped or undoped graphene oxide, C60, graphite, carbon fibers, and porous carbon; the conductive metal oxide material includes, but is not limited to, one or more of ITO, FTO, ATO, and AZO; metallic materials include, but are not limited to, Al, Ag, Cu, Mo, Au, or alloys thereof; wherein, the metal material has a form including but not limited to one or more of a compact film, a nanowire, a nanosphere, a nanorod, a nanocone and a hollow nanosphere.

Further, the present invention provides a method for preparing a quantum dot light emitting diode with a positive structure as shown in fig. 1, wherein as shown in fig. 3, the method comprises the steps of:

s10, providing an anode substrate;

s20, preparing a quantum dot light-emitting layer on the anode substrate;

s30, preparing an electron transport layer on the quantum dot light-emitting layer;

s40, preparing a cathode on the electron transport layer to obtain the quantum dot light-emitting diode, wherein the electron transport layer is made of nano metal oxide which is crosslinked together through a chelating agent, and the chelating agent contains at least three carboxyl functional groups.

The preparation method of each layer can be a chemical method or a physical method, wherein the chemical method comprises one or more of but not limited to a chemical vapor deposition method, a continuous ion layer adsorption and reaction method, an anodic oxidation method, an electrolytic deposition method and a coprecipitation method; physical methods include, but are not limited to, physical coating methods or solution methods, wherein solution methods include, but are not limited to, spin coating, printing, knife coating, dip-coating, dipping, spraying, roll coating, casting, slot coating, bar coating; 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 coating, physical vapor deposition, atomic layer deposition, pulsed laser deposition.

In a preferred embodiment, the step of preparing an electron transport layer on the quantum dot light emitting layer comprises: providing a nano metal oxide solution and a chelating agent solution; and depositing the nano metal oxide solution on the quantum dot light-emitting layer to form a film layer, and soaking the film layer in the chelating agent solution to prepare the electron transmission layer. In this embodiment, after the film layer is formed, the film layer is soaked in the chelating agent solution for a predetermined time to crosslink the chelating agent with the nano metal oxide in the film layer, so as to obtain the electron transport layer.

In another more preferred embodiment, the step of preparing an electron transport layer on the quantum dot light emitting layer comprises: depositing a nano metal oxide solution on the quantum dot light-emitting layer to form a sub-film layer, soaking the sub-film layer in a chelating agent solution, continuing to deposit another sub-film layer on the sub-film layer, soaking the other sub-film layer in the chelating agent solution, repeating the steps for a plurality of times until the last sub-film layer is deposited on the penultimate sub-film layer according to the preset thickness, and obtaining the electron transmission layer.

In this embodiment, each sub-film layer formed by depositing a nano metal oxide is prepared on the quantum dot light-emitting layer, and the sub-film layer is soaked in the chelating agent solution for a predetermined time to crosslink the chelating agent with the nano metal oxide in the film layer; and stopping preparing the film layer until the thickness of the prepared plurality of sub-film layers after superposition reaches the thickness requirement of the electron transmission layer. That is, the nanometal oxide in each of the sub-film layers forming the electron transport layer is over-crosslinked with the chelating agent. The chelating agent has a certain coordination effect, and the sub-film layer formed by the nano metal oxide can effectively crosslink the nano metal oxide after being soaked in the chelating agent and is very firmly combined, so that the electron transmission performance of the nano metal oxide film layer crosslinked by the chelating agent can be effectively improved.

Preferably, the concentration of the nano metal oxide solution is 15-60mg/ml, and if the concentration of the nano metal oxide is too high (greater than 60 mg/ml), a single-layer film layer prepared from the nano metal oxide solution is too thick and uneven, so that the nano metal oxide and the chelating agent in the later-stage film layer are insufficiently crosslinked, and the electron transmission efficiency of the electron transmission layer is reduced; if the concentration of the nano metal oxide is too low (less than 15 mg/ml), the probability of the cross-linking reaction between the nano metal oxide and the chelating agent in the film layer is reduced, and the electron transmission efficiency of the electron transmission layer is also reduced.

Preferably, the preparation method of the chelating agent solution comprises the following steps: dispersing the chelating agent in a polar solvent to prepare a chelating agent solution. The chelating agent contains at least three carboxyl functional groups, so that the chelating agent can be dispersed in a polar solvent; preferably, the polar solvent is selected from one or more of methanol, ethanol and cyclohexane, but is not limited thereto. More preferably, the concentration of the chelating agent solution is 0.1wt% to 10 wt%. If the concentration of the chelating agent solution is greater than 10wt%, when the nano metal oxide film layer is soaked in the chelating agent solution, an excessive amount of chelating agent may remain in a free state in the film layer, thereby reducing the electron transport ability of the film layer; if the concentration of the chelating agent solution is less than 0.1wt%, when the nano metal oxide film layer is soaked in the chelating agent solution, the chelating agent is less, and the nano metal oxide cannot be fully crosslinked, so that the electron transport capability of the film layer is reduced.

Preferably, in this embodiment, the thickness of each sub-film layer formed of nano metal oxide is 10 to 30 nm. If the thickness of the film layer is too thick (more than 30 nm), the crosslinking between the nano metal oxide and the chelating agent in the film layer is insufficient, and the electron transmission efficiency of the film layer is reduced; if the thickness of the film layer is too thin (less than 10 nm), the thickness requirement of the electron transport layer can be met only by preparing a plurality of film layers, and the preparation efficiency of the electron transport layer is reduced. More preferably, the thickness of the electron transport layer is 30 to 200 nm.

The invention also provides a preparation method of the QLED with the hole transport layer in the inversion structure, which comprises the following steps:

providing a cathode substrate;

preparing an electron transport layer on the cathode substrate, wherein the electron transport layer is made of nano metal oxides crosslinked together by a chelating agent, and the chelating agent contains at least three carboxyl functional groups;

preparing a quantum dot light-emitting layer on the electron transport layer;

preparing a hole transport layer on the quantum dot light emitting layer;

and preparing an anode on the hole transport layer to obtain the quantum dot light-emitting diode.

The preparation method of each layer can be a chemical method or a physical method, wherein the chemical method comprises one or more of but not limited to a chemical vapor deposition method, a continuous ion layer adsorption and reaction method, an anodic oxidation method, an electrolytic deposition method and a coprecipitation method; physical methods include, but are not limited to, physical coating methods or solution methods, wherein solution methods include, but are not limited to, spin coating, printing, knife coating, dip-coating, dipping, spraying, roll coating, casting, slot coating, bar coating; 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 coating, physical vapor deposition, atomic layer deposition, pulsed laser deposition.

Preferably, the step of preparing an electron transport layer on the cathode substrate includes: providing a nano metal oxide solution and a chelating agent solution; and depositing a nano metal oxide solution on the cathode substrate to form a film layer, and soaking the film layer in a chelating agent solution to prepare the electron transport layer.

More preferably, the step of preparing an electron transport layer on the cathode substrate includes: depositing a nano metal oxide solution on the cathode substrate to form a sub-film layer, soaking the sub-film layer in a chelating agent solution, continuing to deposit another sub-film layer on the sub-film layer, soaking the other sub-film layer in the chelating agent solution, repeating the steps for a plurality of times until the last sub-film layer is deposited on the penultimate sub-film layer according to a preset thickness, and obtaining the electron transport layer.

In this embodiment, each sub-film layer formed by depositing a nano metal oxide is prepared on a cathode substrate, and the sub-film layer is soaked in the chelating agent solution for a predetermined time to crosslink the chelating agent with the nano metal oxide in the film layer; and stopping preparing the film layer until the thickness of the prepared plurality of sub-film layers after superposition reaches the thickness requirement of the electron transmission layer. That is, the nanometal oxide in each of the sub-film layers forming the electron transport layer is over-crosslinked with the chelating agent. The chelating agent has a certain coordination effect, and the sub-film layer formed by the nano metal oxide can effectively crosslink the nano metal oxide after being soaked in the chelating agent and is very firmly combined, so that the electron transmission performance of the nano metal oxide film layer crosslinked by the chelating agent can be effectively improved.

In summary, the quantum dot light emitting diode provided by the invention includes a cathode, an anode, and a quantum dot light emitting layer disposed between the cathode and the anode, wherein an electron transport layer is further disposed between the cathode and the quantum dot light emitting layer, the electron transport layer is made of nano metal oxide crosslinked together by a chelating agent, and the chelating agent contains at least three carboxyl functional groups. The charge transport performance of the electron transport layer can be improved by using the nano metal oxide crosslinked by the chelating agent as an electron transport layer material, so that the electron hole injection rate of the quantum dot light-emitting diode is balanced, and the light-emitting efficiency of the quantum dot light-emitting diode is improved.

It is to be understood that the invention is not limited to the examples described above, but that modifications and variations may be effected thereto by those of ordinary skill in the art in light of the foregoing description, and that all such modifications and variations are intended to be within the scope of the invention as defined by the appended claims.

Claims (10)

1. A quantum dot light-emitting diode comprises a cathode, an anode and a quantum dot light-emitting layer arranged between the cathode and the anode, wherein an electron transport layer is arranged between the cathode and the quantum dot light-emitting layer, the electron transport layer is made of nano metal oxides which are crosslinked together through a chelating agent, the chelating agent contains at least three carboxyl functional groups, and carboxylate ions are formed through the carboxyl functional groups on the chelating agent so as to crosslink the adjacent nano metal oxides.

2. The quantum dot light-emitting diode of claim 1, wherein the chelating agent contains 3 to 5 carboxyl functional groups.

3. The quantum dot light-emitting diode of claim 1, wherein the chelating agent is selected from one or more of 1,4,7, 10-tetraazacyclododecane-1, 4,7, 10-tetracarboxylic acid, 1,4, 7-triaza-cyclononane-N, N', N "-triacetic acid, 1,4,8, 11-tetraazacyclotetradecane-1, 4,8, 11-tetraacetic acid, and 1,4, 7-triazacyclononane-1-glutaric acid-4, 7-diacetic acid.

4. The quantum dot light-emitting diode of claim 1, wherein the nano metal oxide is selected from ZnO, NiO, W₂O₃、Mo₂O₃、TiO₂、SnO、ZrO₂And Ta₂O₃One or more of (a).

5. A preparation method of a quantum dot light-emitting diode is characterized by comprising the following steps:

providing an anode substrate, preparing a quantum dot light-emitting layer on the anode substrate, preparing an electron transport layer on the quantum dot light-emitting layer, and preparing a cathode on the electron transport layer to prepare the quantum dot light-emitting diode;

or, providing a cathode substrate, preparing an electron transport layer on the cathode substrate, preparing a quantum dot light-emitting layer on the electron transport layer, and preparing an anode on the quantum dot light-emitting layer to obtain the quantum dot light-emitting diode;

wherein the electron transport layer material is nano metal oxide crosslinked together by a chelating agent, the chelating agent contains at least three carboxyl functional groups, and carboxylate ions are formed by the carboxyl functional groups on the chelating agent so as to crosslink adjacent nano metal oxide.

6. The method of claim 5, wherein the step of preparing an electron transport layer on the quantum dot light emitting layer comprises:

depositing a nano metal oxide solution on the quantum dot light-emitting layer to form a film layer, and soaking the film layer in a chelating agent solution to prepare the electron transport layer;

alternatively, the step of preparing an electron transport layer on the cathode substrate comprises:

and depositing a nano metal oxide solution on the cathode substrate to form a film layer, and soaking the film layer in a chelating agent solution to prepare the electron transport layer.

7. The method of claim 5, wherein the step of preparing an electron transport layer on the quantum dot light emitting layer comprises:

depositing a nano metal oxide solution on the quantum dot light-emitting layer to form a sub-film layer, soaking the sub-film layer in a chelating agent solution, continuing to deposit another sub-film layer on the sub-film layer, soaking the other sub-film layer in the chelating agent solution, repeating the steps for a plurality of times until the last sub-film layer is deposited on the penultimate sub-film layer according to a preset thickness, and preparing the electron transmission layer;

alternatively, the step of preparing an electron transport layer on the cathode substrate comprises:

depositing a nano metal oxide solution on the cathode substrate to form a sub-film layer, soaking the sub-film layer in a chelating agent solution, continuing to deposit another sub-film layer on the sub-film layer, soaking the other sub-film layer in the chelating agent solution, repeating the steps for a plurality of times until the last sub-film layer is deposited on the penultimate sub-film layer according to a preset thickness, and obtaining the electron transport layer.

8. The method for preparing a quantum dot light-emitting diode according to any one of claims 6 to 7, wherein the method for preparing the chelating agent solution comprises the steps of:

dispersing the chelating agent in a polar solvent to prepare a chelating agent solution, wherein the concentration of the chelating agent solution is 0.1-10 wt%; and/or the presence of a gas in the gas,

the chelating agent is selected from one or more of 1,4,7, 10-tetraazacyclododecane-1, 4,7, 10-tetracarboxylic acid, 1,4, 7-triaza-cyclononane-N, N', N "-triacetic acid, 1,4,8, 11-tetraazacyclotetradecane-1, 4,8, 11-tetraacetic acid and 1,4, 7-triazacyclononane-1-glutaric acid-4, 7-diacetic acid.

9. The method for preparing a quantum dot light-emitting diode according to claim 8, wherein the polar solvent is one or more selected from methanol, ethanol and cyclohexane.

10. The method of claim 7, wherein the thickness of each sub-film layer is 10-30 nm.

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