阅读说明：本技术 复合材料及其制备方法和量子点发光二极管 (Composite material, preparation method thereof and quantum dot light-emitting diode ) 是由 聂志文 张旋宇 刘文勇 于 2020-06-15 设计创作，主要内容包括：本发明属于发光器件材料技术领域,具体涉及一种复合材料及其制备方法和量子点发光二极管。所述复合材料包括n型金属氧化物纳米颗粒和连接在所述n型金属氧化物纳米颗粒表面的式I所示的有机分子,所述有机分子上的羧基结合在所述n型金属氧化物纳米颗粒表面；式I中,R-(1)为-(CH-(2))-(n)-,n为大于或等于1的整数。该复合材料不仅有效缩短了金属氧化物纳米粒子间距,而且保证纳米颗粒之间不会团聚,同时双极性基团的有机分子结合在n型金属氧化物纳米颗粒表面,可以降低其表面缺陷,增强纳米粒子间的电子传导能力,从而提高了复合材料的电子迁移率,因此增强了复合材料的电子传输能力。(The invention belongs to the technical field of luminescent device materials, and particularly relates to a composite material, a preparation method thereof and a quantum dot light-emitting diode. The composite material comprises n-type metal oxide nanoparticles and n-type metal oxide nanoparticles connected to the n-type metal oxide nanoparticlesThe organic molecule is shown in the formula I on the surface, and carboxyl on the organic molecule is combined on the surface of the n-type metal oxide nano-particles; in the formula I, R 1 Is- (CH) 2 ) n N is an integer greater than or equal to 1. The composite material not only effectively shortens the distance between the metal oxide nano particles, but also ensures that the nano particles cannot be agglomerated, and meanwhile, the organic molecules of the bipolar group are combined on the surface of the n-type metal oxide nano particles, so that the surface defects of the n-type metal oxide nano particles can be reduced, and the electron conduction capability among the nano particles is enhanced, thereby improving the electron mobility of the composite material, and enhancing the electron transmission capability of the composite material.)

1. A composite material, which is characterized by comprising n-type metal oxide nanoparticles and organic molecules which are connected to the surfaces of the n-type metal oxide nanoparticles and are shown in the following formula I, wherein carboxyl groups on the organic molecules are bonded to the surfaces of the n-type metal oxide nanoparticles;

wherein R is₁Is- (CH)₂)_nN is an integer greater than or equal to 1.

2. The composite material of claim 1, wherein R of the organic molecule₁Wherein n is 2-20; and/or the presence of a gas in the gas,

the mass ratio of the organic molecules to the n-type metal oxide nanoparticles is (0.1-5): 30.

3. the composite material of claim 2, wherein R of the organic molecule₁Wherein n is 4-9; and/or the presence of a gas in the gas,

the mass ratio of the organic molecules to the n-type metal oxide nanoparticles is (1-4): 30.

4. the composite material of claim 1, wherein the n-type metal oxide nanoparticles are selected from one or more of zinc oxide, titanium oxide, tin oxide, zirconium oxide, and aluminum doped zinc oxide.

5. The composite material of any one of claims 1-4, wherein the composite material consists of n-type metal oxide nanoparticles and the organic molecule attached to the surface of the n-type metal oxide nanoparticles.

6. The preparation method of the composite material is characterized by comprising the following steps:

providing n-type metal oxide nanoparticles and a dicarboxylic acid monoester organic compound represented by formula II below;

dissolving the n-type metal oxide nanoparticles and the dicarboxylic acid monoester organic matter in a polar solvent, and heating to obtain a mixed solution;

carrying out solid-liquid separation on the mixed solution to obtain the composite material;

wherein R is₁Is- (CH)₂)_n-，R₂is-O (CH)₂)_mCH₃N is an integer of 1 or more, and m is an integer of 0 or more.

7. The method of claim 6, wherein R of the dicarboxylic acid monoester organic matter is₁Wherein n is 2-20; and/or the presence of a gas in the gas,

r of the dicarboxylic acid monoester organic matter₂Wherein m is 2-20.

8. The method for producing the composite material according to claim 6, wherein the mass ratio of the dicarboxylic acid monoester organic matter to the n-type metal oxide nanoparticles is (0.1 to 5): 30, of a nitrogen-containing gas; and/or the presence of a gas in the gas,

the temperature of the heating treatment is 60-120 ℃; and/or the presence of a gas in the gas,

and the solid-liquid separation comprises annealing and crystallization at the temperature of 80-120 ℃.

9. The method of any one of claims 6 to 8, wherein the n-type metal oxide nanoparticles are selected from one or more of zinc oxide, titanium oxide, tin oxide, zirconium oxide, and aluminum-doped zinc oxide.

10. A quantum dot light-emitting diode comprising an anode, a cathode and a quantum dot light-emitting layer between the anode and the cathode, wherein an electron transport layer is arranged between the cathode and the quantum dot light-emitting layer, and the electron transport layer is composed of the composite material according to any one of claims 1 to 5 or the composite material obtained by the method for preparing the composite material according to any one of claims 6 to 9.

Technical Field

The invention belongs to the technical field of luminescent device materials, and particularly relates to a composite material, a preparation method thereof and a quantum dot light-emitting diode.

Background

Quantum Dots (QDs), also known as semiconductor nanocrystals, are typically composed of group II-VI or III-V elements with particle sizes smaller than or close to the exciton Bohr radius. At present, the development of quantum dot synthesis technology makes a significant breakthrough, wherein the research of II-VI group quantum dots represented by CdSe tends to be perfected, such as: photoluminescence efficiency is close to 100%, the width of a generated peak is as narrow as 20-30 nm, and the device efficiency and the device service life of the red and green quantum dots are close to commercial application requirements. Because the high-quality quantum dots are all prepared by a full-solution synthesis method, the method is very suitable for preparing a film by adopting solution processing modes such as spin coating, printing and the like. Therefore, quantum dot light emitting diodes (QLEDs) using quantum dot materials as quantum dot light emitting layers are expected to be powerful competitors to the next generation of new display technologies.

However, the electroluminescent device of quantum dot still has the problems of low efficiency, short lifetime, etc., and the high-performance QLED device is usually prepared by a solution method, and an inorganic metal oxide such as zinc oxide is usually used as an Electron Transport Layer (ETL) of the QLED. In order to maintain excellent optical stability of the quantum dots, the surface ligands of the quantum dots are generally non-polar, and thus have poor contact with inorganic metal oxides, making electron injection difficult. In addition, the electron mobility of the conventional QLED device is generally much higher than the hole mobility, so that the charge accumulation phenomenon at the QD/ETL interface is very serious, and the efficiency and the lifetime of the QLED device are both adversely affected. Moreover, the film structure of the metal oxide nanoparticles after spin coating is often disordered and has a large amount of various defects, such as micropores. Meanwhile, stacking is easy to occur in certain specific directions, and uniformity is poor.

Therefore, the prior art is in need of improvement.

Disclosure of Invention

An object of the present invention is to overcome the above-mentioned deficiencies of the prior art, and to provide a composite material and a preparation method thereof, which aim to solve the technical problem that the electron transport performance of the metal oxide electron transport material is not ideal.

In order to achieve the purpose, the invention adopts the following technical scheme:

the invention provides a composite material, which comprises n-type metal oxide nano-particles and organic molecules connected to the surfaces of the n-type metal oxide nano-particles, wherein carboxyl on the organic molecules is combined on the surfaces of the n-type metal oxide nano-particles;

wherein R is₁Is- (CH)₂)_nN is an integer greater than or equal to 1.

The composite material provided by the invention comprises n-type metal oxide nanoparticles and an organic molecule shown in a formula I connected with the n-type metal oxide nanoparticles, wherein carboxyl groups in the organic molecule can be combined with metal ions on the surface of the n-type metal oxide nanoparticles, and the organic molecule is a dicarboxylic acid small molecule, so that the organic molecule can be connected with two n-type metal oxide nanoparticles through the carboxyl groups, and the n-type metal oxide nanoparticles are connected with each other to form a network structure. The mesh-shaped connecting structures not only effectively shorten the inter-particle distance, but also ensure that nano particles cannot be agglomerated, and meanwhile, organic molecules of bipolar groups are combined on the surfaces of the n-type metal oxide nano particles, so that the surface defects of the n-type metal oxide nano particles can be reduced, and the electron conduction capability among the nano particles is enhanced, so that the electron mobility of the composite material is improved, and the electron transmission capability of the composite material is enhanced.

The invention also provides a preparation method of the composite material, which comprises the following steps:

providing n-type metal oxide nanoparticles and a dicarboxylic acid monoester organic compound represented by formula II below;

dissolving the n-type metal oxide nanoparticles and the dicarboxylic acid monoester organic matter in a polar solvent, and heating to obtain a mixed solution;

carrying out solid-liquid separation on the mixed solution to obtain the composite material;

wherein R is₁Is- (CH)₂)_n-，R₂is-O (CH)₂)_mCH₃N is an integer of 1 or more, and m is an integer of 0 or more.

The preparation method of the composite material provided by the invention has the advantages that the n-type metal oxide nano-particles and the dicarboxylic acid monoester organic matter shown in the formula II are dissolved in the polar solvent for heating treatment, the dicarboxylic acid monoester organic matter shown in the formula II is hydrolyzed to form the organic molecule shown in the formula I, so in the composite material obtained by subsequent solid-liquid separation, the organic molecule can be combined with the two n-type metal oxide nano-particles through carboxyl, the n-type metal oxide nano-particles are mutually connected by the organic molecule, the composite material obtained by the preparation method not only effectively shortens the inter-particle distance, but also ensures that the nano-particles are not agglomerated, meanwhile, the organic molecule of a bipolar group is combined on the surface of the n-type metal oxide nano-particles, the surface defects can be reduced, the electronic conduction capability among the nano-particles is enhanced, and the electronic mobility of the composite material is improved, thus enhancing the electron transport capability of the composite.

The invention also aims to provide a quantum dot light emitting diode, aiming at solving the technical problem that the electron transmission performance of the quantum dot light emitting diode is not ideal. In order to achieve the purpose, the invention adopts the following technical scheme:

the invention provides a light-emitting diode which comprises an anode, a cathode and a quantum dot light-emitting layer positioned between the anode and the cathode, wherein an electron transmission layer is arranged between the cathode and the quantum dot light-emitting layer, and the electron transmission layer is composed of the composite material or the composite material prepared by the preparation method.

In the light-emitting diode and the light-emitting diode prepared by the preparation method of the light-emitting diode, the electron transmission layer is made of the special composite material or the special composite material prepared by the preparation method of the invention, the composite material has good electrical property of a crystal structure, can improve the electron mobility, and reduce the surface defects of n-type metal oxide nano particles, so that the device improves the effective utilization rate of electrons, reduces the defect recombination, enhances the electron injection, reduces the charge accumulation of the interface of the electron point light-emitting layer and the electron transmission layer, and improves the efficiency and the service life of the QLED device.

Drawings

FIG. 1 is a flow chart of a method of making a composite material according to an embodiment of the present invention;

fig. 2 is a schematic structural diagram of a quantum dot light-emitting diode according to an embodiment of the invention.

Detailed Description

In order to make the technical problems, technical solutions and advantageous effects to be solved by the present invention more clearly apparent, the present invention is further described in detail below with reference to the following embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.

In one aspect, embodiments of the present invention provide a composite material, which includes n-type metal oxide nanoparticles and an organic molecule, which is connected to the surface of the n-type metal oxide nanoparticles and is represented by formula I below, wherein carboxyl groups on the organic molecule are bound to the surface of the n-type metal oxide nanoparticles;

wherein R is₁Is- (CH)₂)_nN is an integer greater than or equal to 1.

The composite material provided by the embodiment of the invention comprises n-type metal oxide nanoparticles and an organic molecule shown in a formula I connected with the n-type metal oxide nanoparticles, wherein carboxyl groups in the organic molecule can be combined with metal ions on the surface of the n-type metal oxide nanoparticles, and the organic molecule is a dicarboxylic acid small molecule, so that the organic molecule can be connected with two n-type metal oxide nanoparticles through carboxyl groups, and the n-type metal oxide nanoparticles are connected with each other to form a network structure. The mesh-shaped connecting structures not only effectively shorten the inter-particle distance, but also ensure that nano particles cannot be agglomerated, and meanwhile, organic molecules of bipolar groups are combined on the surfaces of the n-type metal oxide nano particles, so that the surface defects of the n-type metal oxide nano particles can be reduced, and the electron conduction capability among the nano particles is enhanced, so that the electron mobility of the composite material is improved, and the electron transmission capability of the composite material is enhanced.

In one embodiment, R of the organic molecule₁Wherein n is 2-20; further, R of the organic molecule₁Wherein n is 4-9; unbranched linear R within the carbon number range₁The n-type metal oxide nanoparticles can be better connected. In one embodiment, the mass ratio of the organic molecules to the n-type metal oxide nanoparticles is (0.1-5): 30, of a nitrogen-containing gas; further, the mass ratio of the organic molecules to the n-type metal oxide nanoparticles is (1-4): 30, of a nitrogen-containing gas; the organic molecules shown in the formula I are doped in the mass ratio range, so that the electron transport performance of the composite material can be better improved.

In one embodiment, the n-type metal oxide nanoparticles are selected from one or more of zinc oxide, titanium oxide, tin oxide, zirconium oxide, and aluminum-doped zinc oxide, specifically zinc oxide such as ZnO, titanium oxide such as TiO₂Tin oxides such as SnO₂Zirconium oxides such as ZrO₂Aluminum doped zinc oxide such as AlZnO. Further, the n-type metal oxide nanoparticles are selected from ZnO nanoparticles, and ZnO has good electron transport propertyHowever, the film structure of the ZnO nanoparticles after spin-on film formation often shows a disordered loose structure and contains a large number of various defects such as micropores and the like. And the ZnO is poor in contact with the nonpolar ligand on the surface of the quantum dot, so that electron injection is difficult. Therefore, the organic molecules shown in the formula I are combined on the surfaces of the zinc oxide nano particles, so that the surface defects of the zinc oxide nano particles can be reduced, the electronic conduction capability among the nano particles is enhanced, and the electronic transmission performance of the zinc oxide is improved.

In one embodiment, the composite material is comprised of the n-type metal oxide nanoparticles and the organic molecule.

On the other hand, the embodiment of the invention also provides a preparation method of the composite material, as shown in fig. 1, the preparation method comprises the following steps:

s01: providing n-type metal oxide nanoparticles and a dicarboxylic acid monoester organic matter shown in a formula II;

s02: dissolving the n-type metal oxide nanoparticles and the dicarboxylic acid monoester organic matter in a polar solvent, and heating to obtain a mixed solution;

s03: carrying out solid-liquid separation on the mixed solution to obtain the composite material;

wherein R is₁Is- (CH)₂)_n-，R₂is-O (CH)₂)_mCH₃N is an integer of 1 or more, and m is an integer of 0 or more.

According to the preparation method of the composite material provided by the embodiment of the invention, n-type metal oxide nanoparticles and dicarboxylic acid monoester organic matter shown in formula II are dissolved in a polar solvent for heating treatment, and the dicarboxylic acid monoester organic matter shown in formula II is hydrolyzed to form organic molecules shown in formula I, so that in the composite material obtained by subsequent solid-liquid separation, the organic molecules can be combined with two n-type metal oxide nanoparticles through carboxyl groups, so that the n-type metal oxide nanoparticles are connected with one another by the organic molecules, the composite material obtained by the preparation method not only effectively shortens the inter-particle distance, but also ensures that the nanoparticles cannot be connected with one another, meanwhile, the organic molecules of bipolar groups are combined on the surfaces of the n-type metal oxide nanoparticles, the surface defects can be reduced, the electronic conduction capability among the nanoparticles is enhanced, and the electronic mobility of the composite material is improved, thus enhancing the electron transport capability of the composite.

In an embodiment, the composite material provided by the embodiment of the present invention is obtained by the above preparation method, and the composite material includes n-type metal oxide nanoparticles and an organic molecule connected to the n-type metal oxide nanoparticles and represented by formula II, where two carboxyl groups on the organic molecule may be respectively bound to metal ions on the surface of the n-type metal oxide nanoparticles, so that the organic molecule connects the n-type metal oxide nanoparticles to form a network structure, and the specific preparation steps are as described above.

In the step S01, the dicarboxylic acid monoester represented by the formula II R₁Wherein n is 2-20; r₂Wherein m is 2-20. Unbranched linear R within the carbon number range₁The n-type metal oxide nanoparticles can be better connected. Unbranched linear R within the carbon number range₂The organic molecules forming the ambipolar group of formula I can be better hydrolyzed. The n-type metal oxide nanoparticles are selected from one or more of zinc oxide, titanium oxide, tin oxide, zirconium oxide, and aluminum-doped zinc oxide.

In step S02, the n-type metal oxide nanoparticles and the organic dicarboxylic acid monoester are dissolved in a polar solvent under heating to obtain a mixed solution, and the organic dicarboxylic acid monoester is hydrolyzed to form the organic molecules with bipolar groups represented by formula I, wherein the conditions of the heating treatment include: the temperature is 60-120 ℃, the time is 30 min-4 h, and the dicarboxylic acid monoester organic matter can be hydrolyzed better under the conditions. For example, the mixed solution is a fatty acid solution of monomethyl suberate and zinc acetate, and the monomethyl suberate is converted to suberic acid after hydrolysis by heating and then combined with n-type metal oxide nanoparticles. Wherein the polar solvent comprises one or more of ethanol, methanol, water, N-dimethylformamide and N, N-dimethylacetamide.

In one embodiment, the mass ratio of the dicarboxylic acid monoester organic matter to the n-type metal oxide nanoparticles is (0.1-5): 30, of a nitrogen-containing gas; within the mass ratio range, the electron transport performance of the composite material can be better improved.

In step S03, the solid-liquid separation step includes an annealing crystallization treatment, for example, the solid-liquid separation step includes annealing crystallization at a temperature of 80 to 120 ℃, and the further annealing time is 20 to 40 min. In one embodiment, in order to obtain the composite film, the mixed solution is deposited on a substrate and annealed and crystallized, so as to obtain a composite film layer, which can be used as an electron transport film layer.

The composite material film layer obtained after annealing can improve the film forming crystallinity of the composite material, thereby improving the hole transmission. The existing n-type metal oxide nano-particles exist in the form of hydrated particles before film forming, the size of the hydrated particles is nearly doubled, and the spacing is larger without the action of mutual attraction after a film forming solvent is evaporated in the film forming process; in addition, the synthesized n-type metal oxide nanoparticles in the prior art and the solution-method film-forming technology generally cause the electron transport layer composed of the n-type metal oxide nanoparticles to have disordered structure, more micropore defects and low film crystallinity. In the embodiment of the invention, organic molecules shown in a formula I are doped to modify n-type metal oxide nanoparticles, so that the quality and crystallization performance of an ETL (ethylene-vinyl acetate) layer film are improved, on one hand, an unbranched linear chain dicarboxylic acid monoester organic matter can be completely hydrolyzed to form an organic molecule of a bipolar group shown in the formula I in the film forming and crystallization process, and the organic molecule can be used for mutually connecting adjacent metal oxide nanoparticles (such as ZnO nanoparticles) to form a structure of n-type metal oxide nanoparticles-organic molecule-n-type metal oxide nanoparticles shown in the formula I, so that the n-type metal oxide nanoparticles are connected to form a network structure; on the other hand, the bipolar group also effectively fills the surface defect of the n-type metal oxide nano-particles, reduces the loss of electron in the defect transition of the electron transmission film layer, reduces the accumulation of electrons in the layer, enhances the electron conduction capability among the nano-particles and improves the electron mobility of the zinc oxide layer. Therefore, the composite material obtained by the preparation method improves the conduction and recombination capability of electrons at the interface, improves the transmission efficiency of carriers between the interfaces, balances the hole and electron injection rates of the device, and improves the brightness and the service life of the device.

The embodiment of the invention also provides an application of the composite material or the composite material obtained by the preparation method of the composite material as an electron transmission material. The composite material crystal provided by the embodiment of the invention has more excellent plane electrical property and higher electron mobility, and the electrical property of an electron transmission layer is improved by doping bipolar group organic molecules in n-type metal oxide nano particles to form a plane layered crystal, so that the composite material can be used as an electron transmission material, and is particularly used for the electron transmission layer of a quantum dot light-emitting diode.

Finally, an embodiment of the present invention provides a light emitting diode, including an anode, a cathode, and a quantum dot light emitting layer located between the anode and the cathode, where an electron transport layer is disposed between the cathode and the quantum dot light emitting layer, and the electron transport layer is composed of the composite material according to the embodiment of the present invention or the composite material prepared by the preparation method according to the embodiment of the present invention.

According to the light-emitting diode provided by the embodiment of the invention, the electron transport layer is made of the special composite material in the embodiment of the invention or the special composite material prepared by the preparation method in the embodiment of the invention, the composite material has good electrical properties of a crystal structure, the electron mobility can be improved, and the surface defects of n-type metal oxide nanoparticles are reduced, so that the effective utilization rate of electrons is improved, the defect recombination is reduced, the electron injection is enhanced, the charge accumulation of the interface of the electron point light-emitting layer and the hole transport layer is reduced, and the efficiency and the service life of a QLED device are improved.

In one embodiment, an electron injection layer is further disposed between the electron transport layer and the cathode. In another embodiment, a hole function layer, such as a hole transport layer, or a stacked hole injection layer and hole transport layer, is disposed between the quantum dot light emitting layer and the anode, wherein the hole injection layer is adjacent to the anode.

The quantum dot light-emitting diode provided by the embodiment of the invention comprises an upright structure and an inverted structure.

In one embodiment, the front-mounted quantum dot light emitting diode comprises a laminated structure of an anode and a cathode which are oppositely arranged, a quantum dot light emitting layer arranged between the anode and the cathode, and an electron transport layer arranged between the cathode and the quantum dot light emitting layer, wherein the anode is arranged on a substrate. Furthermore, an electron injection layer can be arranged between the cathode and the electron transport layer, and an electron functional layer such as a hole blocking layer can be arranged between the cathode and the quantum dot light-emitting layer; and a hole functional layer such as a hole transport layer, a hole injection layer and an electron blocking layer can be arranged between the anode and the quantum dot light-emitting layer. In some embodiments of the front structure device, the quantum dot light emitting diode includes a substrate, an anode disposed on a surface of the substrate, a hole injection layer disposed on a surface of the anode, a hole transport layer disposed on a surface of the hole injection layer, a quantum dot light emitting layer disposed on a surface of the hole transport layer, an electron transport layer disposed on a surface of the quantum dot light emitting layer, and a cathode disposed on a surface of the electron transport layer.

In one embodiment, an inverted structure quantum dot light emitting diode includes a stacked structure of an anode and a cathode disposed opposite each other, a quantum dot light emitting layer disposed between the anode and the cathode, an electron transport layer disposed between the cathode and the quantum dot light emitting layer, and the cathode is disposed on a substrate. Furthermore, an electron injection layer can be arranged between the cathode and the electron transport layer, and an electron functional layer such as a hole blocking layer can be arranged between the cathode and the quantum dot light-emitting layer; and a hole functional layer such as a hole transport layer, a hole injection layer and an electron blocking layer can be arranged between the anode and the quantum dot light-emitting layer. In some embodiments of the device with an inverted structure, the quantum dot light emitting diode includes a substrate, a cathode disposed on a surface of the substrate, an electron transport layer disposed on a surface of the cathode, a quantum dot light emitting layer disposed on a surface of the electron transport layer, a hole transport layer disposed on a surface of the quantum dot light emitting layer, a hole injection layer disposed on a surface of the hole transport layer, and an anode disposed on a surface of the hole injection layer.

Correspondingly, the preparation method of the quantum dot light-emitting diode comprises the following steps:

e01: providing a substrate;

e02: the composite material or the composite material obtained by the preparation method provided by the embodiment of the invention is deposited on the substrate to obtain the electron transport layer.

According to the preparation method of the quantum dot light-emitting diode provided by the embodiment of the invention, the specific composite material provided by the embodiment of the invention is prepared into the electron transport layer of the device, and the composite material has good electron transport performance, so that the composite material can be used as the electron transport layer to improve the light-emitting efficiency and prolong the service life of the device.

Specifically, the preparation of the QLED device comprises the following steps:

(1) providing a substrate, and forming an anode on the substrate;

(2) forming a hole injection layer on the anode;

(3) a hole transport layer is formed on the hole injection layer.

(4) Depositing a quantum dot layer on the hole transport layer;

(5) depositing an electron transport layer on the quantum dot layer;

(6) a cathode is formed on the electron transport layer.

The substrate comprises a rigid, flexible substrate, specifically comprising glass, a silicon wafer, polycarbonate, polymethylmethacrylate, polyethylene terephthalate, polyethylene naphthalate, polyamide, polyethersulfone, or a combination thereof.

The anode comprises a metal or alloy thereof such as nickel, platinum, vanadium, chromium, copper, zinc, or gold; a conductive metal oxide such as zinc oxide, indium oxide, tin oxide, Indium Tin Oxide (ITO), Indium Zinc Oxide (IZO), or fluorine-doped tin oxide; or a combination of metals and oxides such as ZnO and Al or SnO₂And Sb, but is not limited thereto, and may be any two or a combination of two or more of the above.

The hole injection layer comprises a conductive compound including polythiophene, polyaniline, polypyrrole, poly (p-phenylene), polyfluorene, poly (3, 4-ethylenedioxythiophene) polysulfonylstyrene (PEDOT: PSS), MoO₃、WoO₃、NiO、HATCN、CuO、V₂O₅CuS, or a combination thereof.

The hole transport layer comprises poly (9, 9-dioctyl-fluorene-co-N- (4-butylphenyl) -diphenylamine) (TFB), polyarylamine, poly (N-vinylcarbazole), polyaniline, polypyrrole, N, N, N ', N' -tetrakis (4-methoxyphenyl) -benzidine (TPD), 4-bis [ N- (1-naphthyl) -N-phenyl-amino]Biphenyl (. alpha. -NPD), 4' -tris [ phenyl (m-tolyl) amino group]Triphenylamine (m-MTDATA), 4' -tris (N-carbazolyl) -triphenylamine (TCTA), 1-bis [ (di-4-tolylamino) phenylcyclohexane (TAPC), p-type metal oxide (e.g., NiO, WO)₃Or MoO₃) A carbonaceous material such as graphene oxide, or a combination thereof, but is not limited thereto.

The material of the quantum dot light emitting layer is CdS, CdSe, CdTe, ZnS, ZnSe, ZnTe, ZnO, HgS, HgSe, HgTe, CdSeS, CdSeTe, CdSTe, ZnSeS, ZnSeTe, HgSeS, HgSeTe, HgSTe, CdZnS, CdZnSe, CdZnTe, CdHgS, CdHgSe, CdHgTe, HgZnS, HgZnSe, HgZnTe, CdZnSeS, CdZnSeTe, CdHgSeS, CdHgSeTe, HgZnSeS, HgZnSeTe of II-VI groups; or group III-V GaN, GaP, GaAs, GaSb, AlN, AlP, AlAs, AlSb, InN, InP, InAs, InSb, GaNP, GaNAs, GaNSb, GaGaAs, GaPSb, AlNP, AlNAs, AlNSb, AlPAs, AlPSb, InNP, InNAs, InNSb, InPAs, InPSb, GaAlNP, GaAlNAs, GaAlNSb, GaAlPAs, GaAlPSb, GaInNP, GaInNAs, GaInNSb, GaInPAs, GaInPSb, InInInAlN, InLNAs, InAsInNSb, InAlGaAs, InLPSb; or group IV-VI SnS, SnSe, SnTe, PbS, PbSe, PbTe, SnSeS, SnSeTe, SnSTe, PbSeS, PbSeTe, PbSTe, SnPbS, SnPbSe, SnPbTe, SnPbSSe, SnPbSeTe, SnPbSTe; or a combination of any one or more of the above.

The electron transport layer is made of the composite material.

The cathode comprises a metal or alloy thereof such as magnesium, calcium, sodium, potassium, titanium, indium, yttrium, lithium, gadolinium, aluminum, silver, tin, lead, cesium, or barium; the multilayer structure material includes a structure of a first layer of an alkali metal halide, an alkaline earth metal halide, an alkali metal oxide, or a combination thereof, and a metal layer, wherein the metal layer includes an alkaline earth metal, a group 13 metal, or a combination thereof. For example LiF/Al, LiO₂Al, LiF/Ca, Liq/Al, and BaF₂and/Ca, but not limited thereto.

The thickness of the bottom electrode is 20-200 nm; the thickness of the hole injection layer is 20-200 nm; the thickness of the hole transport layer is 30-180 nm; the total thickness of the quantum dot mixed luminescent layer is 30-180 nm. The thickness of the electron transmission layer is 10-180 nm; the thickness of the top electrode is 40-190 nm.

The invention is described in further detail with reference to a part of the test results, which are described in detail below with reference to specific examples.

Example 1

The present embodiment provides a QLED device having a structure as shown in fig. 2, and the QLED device includes a substrate 1, an anode 2, a hole injection layer 3, a hole transport layer 4, a quantum dot light-emitting layer 5, an electron transport layer 6, and a cathode 7 in this order from bottom to top. The substrate 1 is made of a glass sheet, the anode 2 is made of an ITO (indium tin oxide) substrate, and the hole injection layer 3 is made of PEDOT: PSS, a hole transport layer 4 is made of TFB, a quantum dot light emitting layer 5 is made of CdZnSe/ZnSe quantum dots, an electron transport layer 6 is made of suberic acid doped ZnO, and a cathode 7 is made of Al.

The preparation method of the device comprises the following steps:

1. and depositing the TFB solution on a hole injection layer (PEDOT: PSS), spin-coating for 30s under the deposition condition of 3000r/min, and heating at 150 ℃ for 30min to complete crystallization to obtain the hole transport layer.

2. And depositing CdZnSe/ZnSe quantum dots on the hole transport layer, and spin-coating for 30s at a certain rotation number of 3000r/min to obtain the quantum dot light-emitting layer.

3. The ETL layer is deposited on the substrate,

to the ZnO solution dissolved in ethanol was added a certain amount of an n-octanoic acid solution of monomethyl suberate at room temperature. The mass ratio of the doped dicarboxylic acid monoester to the ZnO material is 1:30, and the dicarboxylic acid monoester is completely hydrolyzed to form suberic acid by heating at 80 ℃ for 2h, so as to obtain a solution 1. The solution 1 is spin-coated for 30s at 3000r/min and then heated for 30min at 80 ℃ to obtain the electron transport layer.

4. And then evaporating an Al electrode, and packaging by adopting electronic glue to obtain the QLED device.

Example 2

The present embodiment provides a QLED device having a structure as shown in fig. 2, and the QLED device includes a substrate 1, an anode 2, a hole injection layer 3, a hole transport layer 4, a quantum dot light-emitting layer 5, an electron transport layer 6, and a cathode 7 in this order from bottom to top. The substrate 1 is made of a glass sheet, the anode 2 is made of an ITO (indium tin oxide) substrate, and the hole injection layer 3 is made of PEDOT: PSS, a hole transport layer 4 is made of TFB, a quantum dot light emitting layer 5 is made of CdZnSe/ZnSe/ZnS quantum dots, an electron transport layer 6 is made of pimelic acid doped ZnO, and a cathode 7 is made of Al.

The preparation method of the device comprises the following steps:

1. and depositing the TFB solution on a hole injection layer (PEDOT: PSS), spin-coating for 30s under the deposition condition of 3000r/min, and heating at 150 ℃ for 30min to complete crystallization to obtain the hole transport layer.

2. And depositing CdZnSe/ZnSe/ZnS quantum dots on the hole transport layer, and spin-coating for 30s at a certain rotation number of 2000r/min to obtain the quantum dot light-emitting layer.

3. The ETL layer is deposited on the substrate,

at room temperature, a certain amount of n-octanoic acid solution of monomethyl pimelate was added to the ZnO solution dissolved in ethanol. The mass ratio of the doped dicarboxylic acid monoester to the ZnO material is 2:30, and the dicarboxylic acid monoester is completely hydrolyzed to form pimelic acid by heating at 80 ℃ for 2h, so as to obtain a solution 1. The solution 1 is spin-coated for 30s at 3000r/min and then heated for 30min at 80 ℃ to obtain the electron transport layer.

4. And then evaporating an Al electrode, and packaging by adopting electronic glue to obtain the QLED device.

Example 3

The present embodiment provides a QLED device having a structure as shown in fig. 2, and the QLED device includes a substrate 1, an anode 2, a hole injection layer 3, a hole transport layer 4, a quantum dot light-emitting layer 5, an electron transport layer 6, and a cathode 7 in this order from bottom to top. The substrate 1 is made of a glass sheet, the anode 2 is made of an ITO (indium tin oxide) substrate, and the hole injection layer 3 is made of PEDOT: PSS, a hole transport layer 4 is made of TFB, a quantum dot light emitting layer 5 is made of CdZnSe/ZnSe/CdZnS quantum dots, an electron transport layer 6 is made of ZnO doped with succinic acid, and a cathode 7 is made of Al.

The preparation method of the device comprises the following steps:

1. and depositing the TFB solution on a hole injection layer (PEDOT: PSS), spin-coating for 30s under the deposition condition of 3000r/min, and heating at 150 ℃ for 30min to complete crystallization to obtain the hole transport layer.

2. And depositing CdZnSe/ZnSe/CdZnS quantum dots on the hole transport layer, and spin-coating for 30s at a certain rotation speed of 4000r/min to obtain the quantum dot light-emitting layer.

3. The ETL layer is deposited on the substrate,

adding a certain amount of n-octanoic acid solution of monomethyl succinate into ZnO solution dissolved by ethanol at room temperature. The mass ratio of the doped dicarboxylic acid monoester to the ZnO material is 2:30, and the dicarboxylic acid monoester is completely hydrolyzed to form succinic acid by heating at 80 ℃ for 2h to obtain a solution 1. The solution 1 is spin-coated for 30s at 3000r/min and then heated for 60min at 80 ℃ to obtain the electron transport layer.

4. And then evaporating an Al electrode, and packaging by adopting electronic glue to obtain the QLED device.

Example 4

The present embodiment provides a QLED device having a structure as shown in fig. 2, and the QLED device includes a substrate 1, an anode 2, a hole injection layer 3, a hole transport layer 4, a quantum dot light-emitting layer 5, an electron transport layer 6, and a cathode 7 in this order from bottom to top. The substrate 1 is made of a glass sheet, the anode 2 is made of an ITO (indium tin oxide) substrate, and the hole injection layer 3 is made of PEDOT: PSS, a hole transport layer 4 is made of TFB, a quantum dot light emitting layer 5 is made of CdZnSeS/ZnS quantum dots, an electron transport layer 6 is made of azelaic acid doped ZnO, and a cathode 7 is made of Al.

The preparation method of the device comprises the following steps:

1. and depositing the TFB solution on a hole injection layer (PEDOT: PSS), spin-coating for 30s under the deposition condition of 3000r/min, and heating at 150 ℃ for 30min to complete crystallization to obtain the hole transport layer.

2. And depositing the CdZnSeS/ZnS quantum dots on the hole transport layer, and spin-coating for 30s at a certain rotation speed of 4000r/min to obtain the quantum dot light-emitting layer.

3. The ETL layer is deposited on the substrate,

at room temperature, a certain amount of an n-octanoic acid solution of monomethyl azelate was added to a ZnO solution dissolved in ethanol. The mass ratio of the doped dicarboxylic acid monoester to the ZnO material is 4:30, and the dicarboxylic acid monoester is completely hydrolyzed to form azelaic acid by heating at 80 ℃ for 2h, so as to obtain solution 1. The solution 1 is spin-coated for 30s at 3000r/min and then heated for 30min at 80 ℃ to obtain the electron transport layer.

4. And then evaporating an Al electrode, and packaging by adopting electronic glue to obtain the QLED device.

Example 5

The present embodiment provides a QLED device having a structure as shown in fig. 2, and the QLED device includes a substrate 1, an anode 2, a hole injection layer 3, a hole transport layer 4, a quantum dot light-emitting layer 5, an electron transport layer 6, and a cathode 7 in this order from bottom to top. The substrate 1 is made of a glass sheet, the anode 2 is made of an ITO (indium tin oxide) substrate, and the hole injection layer 3 is made of PEDOT: PSS, the material of the hole transport layer 4 is TFB, the material of the quantum dot light emitting layer 5 is CdZnSe/ZnSe quantum dots, and the material of the electron transport layer 6 is suberic acid doped TiO₂And the material of the cathode 7 is Al.

The preparation method of the device comprises the following steps:

1. and depositing the TFB solution on a hole injection layer (PEDOT: PSS), spin-coating for 30s under the deposition condition of 3000r/min, and heating at 150 ℃ for 30min to complete crystallization to obtain the hole transport layer.

2. And depositing CdZnSe/ZnSe quantum dots on the hole transport layer, and spin-coating for 30s at a certain rotation number of 3000r/min to obtain the quantum dot light-emitting layer.

3. The ETL layer is deposited on the substrate,

at room temperature, to TiO dissolved in ethanol₂To the solution was added a certain amount of a solution of monomethyl suberate in n-octanoic acid. The dicarboxylic acid monoester and TiO are doped₂The mass ratio of the materials is 1:30, and the dicarboxylic acid monoester is completely hydrolyzed to form suberic acid by heating at 80 ℃ for 2h, so as to obtain a solution 1. The solution 1 is spin-coated for 30s at 3000r/min and then heated for 30min at 80 ℃ to obtain the electron transport layer.

4. And then evaporating an Al electrode, and packaging by adopting electronic glue to obtain the QLED device.

Example 6

The present embodiment provides a QLED device having a structure as shown in fig. 2, and the QLED device includes a substrate 1, an anode 2, a hole injection layer 3, a hole transport layer 4, a quantum dot light-emitting layer 5, an electron transport layer 6, and a cathode 7 in this order from bottom to top. The substrate 1 is made of a glass sheet, the anode 2 is made of an ITO (indium tin oxide) substrate, and the hole injection layer 3 is made of PEDOT: PSS, the material of the hole transport layer 4 is TFB, the material of the quantum dot light emitting layer 5 is CdZnSe/ZnSe quantum dots, and the material of the electron transport layer 6 is SnO doped with suberic acid₂And the material of the cathode 7 is Al.

The preparation method of the device comprises the following steps:

1. and depositing the TFB solution on a hole injection layer (PEDOT: PSS), spin-coating for 30s under the deposition condition of 3000r/min, and heating at 150 ℃ for 30min to complete crystallization to obtain the hole transport layer.

2. And depositing CdZnSe/ZnSe quantum dots on the hole transport layer, and spin-coating for 30s at a certain rotation number of 3000r/min to obtain the quantum dot light-emitting layer.

3. The ETL layer is deposited on the substrate,

at room temperature, adding SnO dissolved by ethanol₂To the solution was added a certain amount of a solution of monomethyl suberate in n-octanoic acid. Doping dicarboxylic acid monoester with SnO₂The mass ratio of the materials is 1:30, and the materials are heated for 2h at 80 DEG CThe dicarboxylic acid monoester was now completely hydrolyzed to form suberic acid, giving solution 1. The solution 1 is spin-coated for 30s at 3000r/min and then heated for 30min at 80 ℃ to obtain the electron transport layer.

4. And then evaporating an Al electrode, and packaging by adopting electronic glue to obtain the QLED device.

Comparative example 1

This comparative example was prepared in the same manner as in example 1, except that the material of the electron transport layer was undoped ZnO material.

Comparative example 2

This comparative example was prepared in the same manner as example 2, except that the material of the electron transport layer was undoped ZnO material.

Comparative example 3

This comparative example was prepared in the same manner as in example 3, except that the material of the electron transport layer was undoped ZnO material.

Comparative example 4

This comparative example was prepared in the same manner as in example 4, except that the material of the electron transport layer was undoped ZnO material.

Comparative example 5

The comparative example was undoped TiO except that the material of the electron transport layer₂Except for the materials, the preparation method is the same as that of example 5.

Comparative example 6

The comparative example is undoped SnO except for the material of the electron transport layer₂Except for the materials, the preparation method is the same as that of the example 6.

Performance testing

The quantum dot light-emitting diodes prepared in the comparative examples 1 to 6 and the examples 1 to 6 were subjected to performance tests, and the test methods were as follows:

(1) external quantum dot efficiency:

the ratio of the number of electrons-holes injected into the quantum dots to the number of emitted photons, the unit is%, is an important parameter for measuring the quality of the electroluminescent device, and can be obtained by measuring with an EQE optical measuring instrument. The specific calculation formula is as follows:

in the formula eta_eFor light output coupling efficiency, η_rIs the ratio of the number of recombination carriers to the number of injection carriers, chi is the ratio of the number of excitons generating photons to the total number of excitons, K_RTo the rate of the radiation process, K_NRIs the non-radiative process rate.

And (3) testing conditions are as follows: the method is carried out at room temperature, and the air humidity is 30-60%.

(2) Life of QLED device:

the time required for the luminance of the device to decrease to a certain proportion of the maximum luminance under constant current or voltage driving, the time for the luminance to decrease to 95% of the maximum luminance is defined as T95, and the lifetime is the measured lifetime. To shorten the test period, the device lifetime test is usually performed at high luminance by accelerating device aging with reference to the OLED device test, and the lifetime at high luminance is obtained by fitting an extended exponential decay luminance fitting formula, for example: lifetime at 1000nit is measured as T95_1000nit. The specific calculation formula is as follows:

in the formula T95_LFor lifetime at low brightness, T95_HMeasured lifetime at high brightness, L_HFor acceleration of the device to maximum brightness, L_LThe brightness of the green QLED device is 1000nit, A is an acceleration factor, for the QLED, the value is usually 1.6-2, and the value A is 1.7 by measuring the service life of a plurality of groups of green QLED devices under rated brightness in the experiment.

And (3) carrying out life test on the corresponding device by adopting a life test system, wherein the test conditions are as follows: the method is carried out at room temperature, and the air humidity is 30-60%.

(3) Electron mobility: the average rate of the carrier under the action of unit electric field reflects the transport capacity of the carrier under the action of electric field, and the unit is cm²V · s. By preparing corresponding pure hole type devices and then usingCan be obtained by space charge limited amperometric (SCLC) measurement. The structure of the pure electronic device is as follows: anode/fixed electron transport layer/cathode. The specific calculation formula is as follows:

J＝(9/8)/ε_rε_oμ_eV²/d³

wherein J represents a current density in mA · cm-2; epsilon_rDenotes the relative dielectric constant,. epsilon_oRepresents a vacuum dielectric constant, μ_eElectron mobility in cm²V · s; v represents a driving voltage in units of V; d represents the film thickness in m.

And (3) testing conditions are as follows: the method is carried out at room temperature, and the air humidity is 30-60%.

The above test results are shown in table 1:

TABLE 1

As can be seen from table 1 above, the electron transport layer thin films according to the examples of the present invention have significantly higher electron mobility than the electron transport layer thin films according to the respective comparative examples. In addition, the external quantum efficiency and the service life of the quantum dot light-emitting diode provided by the embodiment of the invention are obviously higher than those of the quantum dot light-emitting diode in the corresponding comparative example, which shows that the quantum dot light-emitting diode provided by the embodiment of the invention has better luminous efficiency.

The above description is only for the purpose of illustrating the preferred embodiments of the present invention and is not to be construed as limiting the invention, and any modifications, equivalents and improvements made within the spirit and principle of the present invention are intended to be included within the scope of the present invention.