CN114583069A - Core-shell metal oxide, preparation method thereof and light-emitting diode - Google Patents

Core-shell metal oxide, preparation method thereof and light-emitting diode Download PDF

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CN114583069A
CN114583069A CN202011295813.XA CN202011295813A CN114583069A CN 114583069 A CN114583069 A CN 114583069A CN 202011295813 A CN202011295813 A CN 202011295813A CN 114583069 A CN114583069 A CN 114583069A
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metal oxide
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cobalt
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oxide
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聂志文
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TCL Technology Group Co Ltd
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    • H10K50/00—Organic light-emitting devices
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    • H10K50/00—Organic light-emitting devices
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    • H10K50/11—OLEDs or polymer light-emitting diodes [PLED] characterised by the electroluminescent [EL] layers
    • H10K50/115—OLEDs or polymer light-emitting diodes [PLED] characterised by the electroluminescent [EL] layers comprising active inorganic nanostructures, e.g. luminescent quantum dots
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Abstract

The application relates to the technical field of display, and provides a core-shell metal oxide, a preparation method thereof and a light-emitting diode. The core-shell metal oxide includes: the shell layer is porous, and the shell layer material forming the shell layer comprises a magnetic metal oxide and an insulating metal oxide. The electron transport material provided by the application has electron injection transport capability, and is favorable for balancing the mobility of electrons and holes in a photoelectric device.

Description

Core-shell metal oxide, preparation method thereof and light-emitting diode
Technical Field
The invention belongs to the technical field of metal oxide materials, and particularly relates to a core-shell metal oxide and a preparation method thereof, and a light-emitting diode.
Background
Quantum Dots (QDs) are nano materials composed of a small number of atoms, the radius of the QDs is usually smaller than or close to the exciton Bohr radius, the QDs show obvious quantum confinement effect, and the QDs have unique optical properties, such as the fact that the size and components of a luminescent spectrum are continuously adjustable by materials, the half-peak width is narrow, the fluorescence efficiency is high, the service life is long, the monodispersity is excellent, the photo-thermal stability is strong, and the like. These unique properties have led to their widespread use in the fields of displays, lighting, biomarkers, and solar cells.
Through intensive research and rapid development for more than thirty years, various indexes of Quantum Dot Light Emitting diodes (QLEDs) are greatly improved and developed. The performance of the QLED device based on the red quantum dots and the performance of the QLED device based on the green quantum dots basically meet the application requirements. The electroluminescent device of the quantum dot still has the problems of low luminous efficiency, short service life and the like. Currently, high efficiency QLED devices typically use metal oxides, such as zinc oxide, as the material of the Electron Transport Layer (ETL). However, when the existing electron transport material is used as an electron transport layer of an optoelectronic device, the electron mobility of the existing electron transport material is much higher than that of a hole transport material, so that excessive electrons are accumulated in a light emitting layer, and not only is the light emitting material such as quantum dots charged, but also non-radiative transition is easily caused, and the performance of the device is greatly reduced.
Disclosure of Invention
The present application aims to provide a core-shell metal oxide, a method for preparing the same, and a light emitting diode using the core-shell metal oxide, and aims to solve the problem that when an existing electron transport material is used as an electron transport material of a photoelectric device, the electron mobility is high, and the migration of electrons and holes is unbalanced.
In order to achieve the purpose of the application, the technical scheme adopted by the application is as follows:
in a first aspect, the present application provides a core-shell metal oxide comprising: the shell layer is porous, and the shell layer material forming the shell layer comprises a magnetic metal oxide and an insulating metal oxide.
In a second aspect, the present application provides a method for preparing a core-shell metal oxide, the method comprising:
preparing a mixed system of water-soluble metal oxide, a magnetic metal source, an insulating metal source, an organic ligand and a solvent;
reacting the mixed system under the pressurization condition that the temperature is 150-300 ℃, and coating an infinite coordination polymer on the surface of the water-soluble metal oxide to obtain an infinite coordination polymer;
and calcining the infinite coordination polymer to obtain the core-shell metal oxide.
In a third aspect, the present application provides a light emitting diode, including an anode and a cathode oppositely disposed, a light emitting layer disposed between the anode and the cathode, and an electron transport layer disposed between the light emitting layer and the cathode, wherein the material of the electron transport layer is the core-shell metal oxide provided in the first aspect of the present application, or the core-shell metal oxide prepared by the method provided in the second aspect of the present application.
The core-shell metal oxide provided by the application forms at least one shell layer comprising magnetic metal oxide and insulating metal oxide on the surface of the metal oxide. The magnetic metal oxide can improve the dispersibility of the metal oxide, remarkably improve the solution film-forming property of the metal oxide and further endow the metal oxide with good electron transmission property. Meanwhile, the insulating metal oxide has an effect of blocking electron injection. Meanwhile, the magnetic metal oxide and the insulating metal oxide are used as shell layer materials, so that the metal oxide can be endowed with good electron transmission performance, the good stability of the shell layer is improved, and on the basis, the injection of electrons can be blocked to a certain degree. In addition, the shell layer is provided with a porous structure, electrons are injected along a path containing holes, and the difficulty of electron injection is increased in other areas except the hole structure due to the insulating metal oxide, so that good electron mobility can be obtained, and the problem of excessive electron injection in the charge transfer process of an electron transfer layer made of metal oxide is solved.
According to the preparation method of the core-shell metal oxide, a magnetic metal source and an organic ligand are aggregated and nucleated under the condition of high temperature and pressurization. Because the generated core has large specific surface area and poor stability, the core is aggregated, matured and grown, and thus the infinite coordination polymer with an amorphous state grows on the surface of the water-soluble metal oxide. Further, the infinite coordination polymer is calcined, organic ligands in the infinite coordination polymer are carbonized to form a porous structure, and finally a shell layer formed by the magnetic metal oxide and the insulating metal oxide is obtained on the surface of the water-soluble metal oxide. On one hand, compared with a single metal oxide, the mixed metal oxide generated on the surface of the water-soluble metal oxide can improve the stability of the water-soluble metal oxide, and the mixed metal oxide can effectively reduce dangling bonds and surface defect states on the surface of the water-soluble metal oxide layer and reduce the loss of photocurrent. Furthermore, the surface of the water-soluble metal oxide contains magnetic metal oxide, and the magnetic metal oxide endows the core-shell type metal oxide with magnetism, so that the core-shell type metal oxide keeps a space under the constraint of magnetism, and the agglomeration of metal oxide particles is effectively prevented, thereby improving the dispersion performance of the metal oxide, and further improving the film forming performance of the film based on the metal oxide. Particularly, when the core-shell metal oxide is formed into a film by a solution processing method, the displacement is avoided under the magnetic constraint under the action of an external magnetic field in the solvent volatilization process, the agglomeration phenomenon caused by mutual aggregation among particles is further reduced, the film forming performance of the core-shell metal oxide is remarkably improved, and the problems of a large number of stripes and the like in film forming are avoided. On the other hand, the insulating metal oxide has a function of blocking electron injection. Meanwhile, the magnetic metal oxide and the insulating metal oxide are used as shell layer materials, so that the metal oxide can be endowed with good electron transmission performance, the good stability of the shell layer is improved, and on the basis, the injection of electrons can be blocked to a certain degree. In addition, the shell layer is provided with a porous structure, electrons are injected along a path containing holes, and the difficulty of electron injection is increased in other areas except the hole structure due to the insulating metal oxide, so that good electron mobility can be obtained, and the problem of excessive electron injection in the charge transfer process of an electron transfer layer made of metal oxide is solved. In addition, through high-temperature pressurization, the magnetic metal source and the organic ligand react to form an infinite coordination polymer, and the infinite coordination polymer is combined on the surface of the water-soluble metal oxide, so that the crystallization performance of the metal oxide material is improved, the crystal lattice of the film layer is more ordered when the core-shell type metal oxide is formed into the film, the stability of the crystal is greatly improved, and the flatness and the uniformity of the film layer are improved.
The utility model provides a light-emitting diode adopts above-mentioned core-shell type metal oxide as electron transport layer, because above-mentioned core-shell type metal oxide's shell is the porous structure who comprises magnetic metal oxide and insulating metal oxide, consequently, electron transport layer can make some electron take place to inject to a certain extent, also can block excessive electron injection simultaneously to effectively balance the injection balance of electron and hole in the light-emitting diode, strengthen the effective complex of carrier in the luminescent layer, improve light-emitting diode's performance. In addition, the core-shell metal oxide has better crystallinity and film-forming property, so that the electron transmission layer has better smoothness and stability, and the electron transmission stability of the electron transmission layer is favorably improved, thereby improving the photoelectric property of the light-emitting diode.
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In order to more clearly illustrate the technical solutions in the embodiments of the present application, the drawings needed to be used in the embodiments or the prior art descriptions will be briefly described below, and it is obvious that the drawings in the following description are only some embodiments of the present application, and it is obvious for those skilled in the art to obtain other drawings based on these drawings without inventive exercise.
Fig. 1 is a schematic structural diagram of a core-shell metal oxide provided in an embodiment of the present application;
fig. 2 is a schematic structural diagram of a light emitting diode provided in an embodiment of the present application;
fig. 3 is a schematic structural diagram of a light emitting diode with a front-mounted structure according to an embodiment of the present disclosure;
fig. 4 is a schematic structural diagram of a light emitting diode with an inverted structure according to an embodiment of the present application.
Detailed Description
In order to make the technical problems, technical solutions and advantageous effects to be solved by the present application more clearly apparent, the present application is further described in detail below with reference to the embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the present application and are not intended to limit the present application.
In this application, the term "and/or" describes an association relationship of associated objects, meaning that there may be three relationships, e.g., a and/or B, which may mean: a is present alone, A and B are present simultaneously, and B is present alone. Wherein A and B can be singular or plural. The character "/" generally indicates that the former and latter associated objects are in an "or" relationship.
In the present application, "at least one" means one or more, "a plurality" means two or more. "at least one of the following" or similar expressions refer to any combination of these items, including any combination of the singular or plural items. For example, "at least one (a), b, or c", or "at least one (a), b, and c", may each represent: a, b, c, a-b (i.e., a and b), a-c, b-c, or a-b-c, wherein a, b, and c may be single or plural, respectively.
It should be understood that, in various embodiments of the present application, the sequence numbers of the above-mentioned processes do not mean the execution sequence, some or all of the steps may be executed in parallel or executed sequentially, and the execution sequence of each process should be determined by its function and inherent logic, and should not constitute any limitation to the implementation process of the embodiments of the present application.
The terminology used in the embodiments of the present application is for the purpose of describing particular embodiments only and is not intended to be limiting of the application. As used in the examples of this application and the appended claims, the singular forms "a", "an", and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise.
The terms "first" and "second" are used for descriptive purposes only and are used for distinguishing purposes such as substances, interfaces, messages, requests and terminals from one another and are not to be construed as indicating or implying relative importance or implicitly indicating the number of technical features indicated. For example, a first XX may also be referred to as a second XX, and similarly, a second XX may also be referred to as a first XX, without departing from the scope of embodiments of the present application. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature.
The weight of the related components mentioned in the specification of the embodiments of the present application may not only refer to the specific content of each component, but also refer to the proportional relationship of the weight of each component, and therefore, the proportional enlargement or reduction of the content of the related components according to the specification of the embodiments of the present application is within the scope disclosed in the specification of the embodiments of the present application. Specifically, the mass described in the specification of the embodiments of the present application may be a mass unit known in the chemical industry field such as μ g, mg, g, kg, etc.
In combination with fig. 1, a first aspect of embodiments of the present application provides a core-shell metal oxide, including: the shell layer B is porous, and the shell layer materials forming the shell layer B comprise magnetic metal oxide and insulating metal oxide.
According to the core-shell metal oxide provided by the embodiment of the application, the shell layer B comprising a magnetic metal oxide and an insulating metal oxide is formed on the surface of the metal oxide A. The magnetic metal oxide can improve the dispersibility of the metal oxide A, remarkably improve the solution film-forming property of the metal oxide A and further endow the metal oxide A with good electron transmission performance. Meanwhile, the insulating metal oxide has an effect of blocking electron injection. Meanwhile, the magnetic metal oxide and the insulating metal oxide are used as shell materials, so that the metal oxide A can be endowed with good electron transmission performance, the good stability of the shell is improved, and the injection of electrons can be blocked to a certain degree on the basis. In addition, the shell layer has a porous structure, electrons are injected along a path containing holes, and the difficulty of electron injection is increased in other areas except the hole structure due to the insulating metal oxide, so that good electron mobility can be obtained, and the problem of excessive electron injection in the charge transmission process of an electron transmission layer made of the metal oxide A is solved.
In the examples of the present application, the core-shell metal oxide is based on the metal oxide a, and the core-shell metal oxide exhibits the properties of the metal oxide a. In one possible embodiment, the metal oxide A is selected from ZnO, MgO, SnO2、ZrO2ZnMgO, ZnSnO, ZnZrO. In this case, a composition comprising a magnetic metal oxide andthe porous shell layer B of the insulating metal oxide coats the metal oxide A, and the magnetic metal oxide and the insulating metal oxide can improve the surface defects of the metal oxide A and improve the film forming property of the metal oxide A. More importantly, the shell layer B comprising the magnetic metal oxide and the insulating metal oxide has a porous structure, and the porous structure can adjust the electron injection of the core-shell metal oxide and prevent the excessive injection of electrons, so that the light-emitting diode using the core-shell metal oxide as an electron transport material can better balance the injection of electrons and holes, and the recombination efficiency of carriers in a light-emitting layer is improved. In some embodiments, the metal oxide a in the core-shell metal oxide is selected from ZnO, MgO, SnO2、ZrO2One of ZnMgO, ZnSnO and ZnZrO; in some embodiments, the metal oxide a in the core-shell metal oxide is selected from ZnO, MgO, SnO2、ZrO2A mixture of two or more of ZnMgO, ZnSnO and ZnZrO.
According to the embodiment of the application, the surface of the metal oxide A is coated with the porous shell layer B formed by the magnetic metal oxide and the insulating metal oxide, so that the purpose of electron injection can be achieved, and meanwhile, the excessive injection of electrons is prevented. In addition, the porous shell layer B can reduce the agglomeration among the metal oxides A, reduce dangling bonds and surface defect states on the surface of the metal oxides A, improve the crystallinity of metal oxide materials, improve the film forming property and film layer smoothness of the metal oxides A and finally improve the photoelectric property of the metal oxides A. In one possible embodiment, the surface of the metal oxide A is coated with a porous shell layer B formed by magnetic metal oxide and insulating metal oxide; in one possible embodiment, the surface of the metal oxide a is coated with two or more porous shell layers B formed of a magnetic metal oxide and an insulating metal oxide. It should be understood that when the surface of the metal oxide a is coated with the porous shell B formed of two or more layers of the magnetic metal oxide and the insulating metal oxide, each shell material is a mixed material formed of the magnetic metal oxide and the insulating metal oxide.
In the embodiment of the application, the shell material constituting the shell B includes a magnetic metal oxide and an insulating metal oxide. It should be understood that the embodiment of the present application includes shell materials of magnetic metal oxide and insulating metal oxide, and means that the material forming the shell is a mixture containing magnetic metal oxide and insulating metal oxide. In one possible embodiment, the shell material constituting the shell B is a mixture of a magnetic metal oxide and an insulating metal oxide.
When the surface of the metal oxide A is coated with a shell layer B containing the magnetic metal oxide, the magnetism of the shell layer B in the adjacent core-shell type metal oxide promotes the metal oxide A to keep a certain distance, so that the agglomeration of the metal oxide material is obviously prevented, and the dispersion uniformity of the metal oxide material is improved. The metal oxide material with improved uniformity has better film-forming property during film forming, thereby being beneficial to the metal oxide material to exert the property thereof.
In some embodiments, the magnetic metal oxide is selected from at least one of iron oxide, cobalt oxide, nickel oxide, manganese oxide, gadolinium oxide. In this case, the shell layer B formed by the magnetic metal oxide and the insulating metal oxide has magnetism, so that the metal oxide a particles maintain a proper distance therebetween by virtue of the shell layer B on the surface, thereby improving the performance of the metal oxide material. In addition, the shell layer B with the magnetic metal oxide is formed on the surface of the metal oxide A, so that the surface defects of the metal oxide A can be filled, the crystallinity of the metal oxide A is improved, and the performance of the metal oxide material is further improved.
In the embodiment of the application, the insulating metal oxide has the function of blocking electron injection. The insulating metal oxide is added into the shell layer B of the metal oxide A, the difficulty of injection and transmission of electrons can be increased through the doped insulating metal oxide, so that the electrons have proper transmission rate in the metal oxide A with the shell layer, the electrons and holes in the light-emitting diode using the metal transmission material have more balanced carrier mobility, and the composite luminescence of the carriers in the light-emitting layer is further improved. In some embodiments, the insulating metal oxide is selected from aluminum oxides having insulating properties.
In some embodiments, the molar ratio of the magnetic metal oxide to the insulating metal oxide in the shell material is 0.1-100: 1. in this case, the insulating metal oxide has an appropriate doping ratio in the shell layer B. Compared with the metal oxide of the core-shell structure without the insulating metal oxide in the shell layer B, the insulating metal oxide with the content in the shell layer B can have a blocking effect on the injection and transmission of electrons to a proper degree, so that electrons and holes in the light-emitting diode using the metal transmission material have more balanced carrier mobility, and the composite luminescence of carriers in the light-emitting layer is further improved.
In the embodiment of the present application, the shell layer B has a porous structure. In this case, electrons are injected along the path containing the holes, and the electron injection difficulty is increased in other regions except the hole structure due to the insulating metal oxide, so that good electron mobility can be obtained, and the problem of electron excess injection in the charge transport process of the electron transport layer made of the metal oxide a is solved. It is to be understood that when the surface of the metal oxide a is coated with the porous shell layer B formed of two or more layers of the magnetic metal oxide and the insulating metal oxide, each shell layer has a porous structure, thereby achieving the purpose of adjusting the electron injection efficiency.
In some embodiments, the shell layer B has a thickness of 10nm to 20 μm. The excessively thick shell layer B increases the particle size of the core-shell metal oxide, and causes a large interparticle distance between adjacent core-shell metal oxides, thereby affecting the electron transport performance of the electron transport layer after film formation.
The core-shell metal oxide provided by the first aspect of the embodiments of the present application can be prepared by the following method.
A second aspect of the embodiments of the present application provides a method for preparing a core-shell metal oxide, including:
s01, preparing a mixed system of a water-soluble metal oxide, a magnetic metal source, an insulating metal source, an organic ligand and a solvent;
s02, reacting the mixed system under a pressurizing condition at the temperature of 150-300 ℃, and coating an infinite coordination polymer on the surface of the water-soluble metal oxide to obtain an infinite coordination polymer;
s03, calcining the infinite coordination polymer to obtain the core-shell metal oxide.
According to the preparation method of the core-shell metal oxide provided by the embodiment of the application, under the condition of high temperature and pressurization, the magnetic metal source and the organic ligand are aggregated and nucleated. Because the generated core has large specific surface area and poor stability, the core is aggregated, matured and grown, and thus the infinite coordination polymer with an amorphous state grows on the surface of the water-soluble metal oxide. Further, the infinite coordination polymer is calcined, organic ligands in the infinite coordination polymer are carbonized to form a porous structure, and finally a shell layer formed by the magnetic metal oxide and the insulating metal oxide is obtained on the surface of the water-soluble metal oxide. On one hand, compared with a single metal oxide, the mixed metal oxide generated on the surface of the water-soluble metal oxide can improve the stability of the water-soluble metal oxide, and the mixed metal oxide can effectively reduce dangling bonds and surface defect states on the surface of the water-soluble metal oxide layer and reduce the loss of photocurrent. Furthermore, the surface of the water-soluble metal oxide contains magnetic metal oxide, and the magnetic metal oxide endows the core-shell type metal oxide with magnetism, so that the core-shell type metal oxide keeps a space under the constraint of magnetism, and the agglomeration of metal oxide particles is effectively prevented, thereby improving the dispersion performance of the metal oxide, and further improving the film forming performance of the film based on the metal oxide. Particularly, when the core-shell metal oxide is formed into a film by a solution processing method, the displacement is avoided under the magnetic constraint under the action of an external magnetic field in the solvent volatilization process, the agglomeration phenomenon caused by mutual aggregation among particles is further reduced, the film forming performance of the core-shell metal oxide is remarkably improved, and the problems of a large number of stripes and the like in film forming are avoided. On the other hand, the insulating metal oxide has a function of blocking electron injection. Meanwhile, the magnetic metal oxide and the insulating metal oxide are used as shell layer materials, so that the metal oxide can be endowed with good electron transmission performance, the good stability of the shell layer is improved, and on the basis, the injection of electrons can be blocked to a certain degree. In addition, the shell layer is provided with a porous structure, electrons are injected along a path containing holes, and the difficulty of electron injection is increased in other areas except the hole structure due to the insulating metal oxide, so that good electron mobility can be obtained, and the problem of excessive electron injection in the charge transfer process of an electron transfer layer made of metal oxide is solved. In addition, through high-temperature pressurization, a magnetic metal source and an organic ligand react to form an infinite coordination polymer, and the infinite coordination polymer is combined on the surface of the water-soluble metal oxide, so that the crystallization performance of the metal oxide material is improved, the crystal lattice of the film layer is more ordered when the core-shell type metal oxide is formed into the film, the stability of the crystal is greatly improved, and the flatness and the uniformity of the film layer are improved.
In the above step S01, the water-soluble metal oxide as the main material for preparing the core-shell metal oxide, the magnetic metal source, the insulating metal source and the organic ligand as the reaction raw materials of the infinite coordination polymer are reacted on the surface of the water-soluble metal oxide to form the outer shell of the infinite coordination polymer. It should be noted that when the water-soluble metal oxide is used in the examples of the present application, the magnetic metal source, the insulating metal source and the organic ligand can be used to prepare the shell of the infinite coordination polymer under the high-temperature heating condition. When the metal oxide is an oil-soluble metal oxide, the magnetic metal source, the insulating metal source and the organic ligand are difficult to react even on the surface of the obtained metal oxide to form an infinite coordination polymer-coated shell under the same conditions.
In some embodiments, the water-soluble metal oxide is selected from metal oxides having electron transport properties, and in one possible embodiment, the water-soluble metal oxide is selected from ZnO, MgO, SnO2、ZrO2ZnMgO, ZnSnO, ZnZrO. In some embodiments, the water-soluble metal oxide is selected from ZnO, MgO, SnO2、ZrO2One of ZnMgO, ZnSnO and ZnZrO; in some embodiments, the water-soluble metal oxide is selected from ZnO, MgO, and,SnO2、ZrO2A mixture of two or more of ZnMgO, ZnSnO and ZnZrO.
In one possible embodiment, the magnetic metal source is selected from a salt of a magnetic metal, an oxide of a magnetic metal. In some embodiments, the magnetic metal source is selected from at least one of an iron source, a cobalt source, a nickel source, a manganese source, a gadolinium source. Illustratively, the iron source is selected from at least one of ferric chloride, ferric iodide, ferric bromide, ferric fluoride, ferric acetate, ferric acetylacetonate, ferric sulfate, ferric nitrate, ferrous oxide, ferroferric oxide, ferrous hydroxide, ferric oleate, ferric myristate, ferric stearate, and ferric palmitate; the cobalt source is selected from at least one of cobalt ammonium sulfate, lithium cobalt oxide, cobalt carbonate, cobalt chromate, cobalt aluminate, cobalt ammonium phosphate, cobalt chloride, cobalt iodide, cobalt bromide, cobalt fluoride, cobalt acetate, cobalt acetylacetonate, cobalt sulfate, cobalt nitrate, cobalt oxide, cobalt hydroxide, cobalt oleate, cobalt myristate, cobalt stearate and cobalt palmitate; the nickel source is at least one of nickel chloride, nickel nitrate, nickel sulfate, nickel hydroxide, nickel sesquioxide and nickel monoxide; the manganese source is selected from at least one of manganese carbonate, manganese chloride, manganese iodide, manganese bromide, manganese fluoride, manganese acetate, manganese acetylacetonate, manganese sulfate, manganese nitrate, manganese oxide, manganese hydroxide, manganese oleate, manganese myristate, manganese stearate and manganese palmitate; the gadolinium source is at least one selected from gadolinium carbonate, gadolinium chloride, gadolinium iodide, gadolinium bromide, gadolinium fluoride, gadolinium acetate, gadolinium acetylacetonate, gadolinium sulfate, gadolinium nitrate, gadolinium oxide, gadolinium hydroxide, gadolinium oleate, gadolinium myristate, gadolinium stearate and gadolinium palmitate.
In one possible embodiment, the source of the insulating metal is selected from a source of aluminum. Illustratively, the aluminum source is selected from at least one of aluminum phosphate, aluminum acetate, aluminum acetylacetonate, aluminum iodide, aluminum bromide, aluminum chloride, aluminum fluoride, aluminum carbonate, aluminum cyanide, aluminum nitrate, aluminum oxide, aluminum peroxide, and aluminum sulfate.
In the embodiments of the present application, the organic ligand at least contains a reactive group capable of coordinating with the magnetic metal source and the insulating metal source, and the functional reactive group coordinated with the magnetic metal source and the insulating metal source in the organic ligand is, for example, selected from a carboxyl group, a hydroxyl group, a thiol group, an amino group, and the like. In some embodiments, the organic ligand is selected from a ligand containing a carboxyl group, and the carboxylic ligand has relatively strong coordination capacity, so that the carboxylic ligand can coordinate with the magnetic metal source and the insulating metal source without too harsh conditions, thereby forming an infinite coordination polymer.
In one possible embodiment, the organic ligand is selected from organic compounds containing a benzene ring and an active group capable of coordinating with the magnetic metal ion. In this case, the benzene ring of the organic ligand is carbonized during the calcination in the following step, thereby forming pores of a suitable size in the shell layer to provide a channel for the injection and transport of electrons. In some embodiments, the organic ligand is selected from carboxylic acids containing a benzene ring. Illustratively, the organic ligand is selected from one or more of benzoic acid, p-toluic acid, o-toluic acid, m-toluic acid, terephthalic acid, isophthalic acid, phthalic acid.
In the examples of the present application, the solvent is used to disperse the water-soluble metal oxide, the magnetic metal source, the insulating metal source, and the organic ligand. Illustratively, the solvent is selected from the group consisting of N, N-dimethylformamide, N-dimethylacetamide, dimethylsulfoxide, ethanolamine, formamide, hydrazine hydrate, acetonitrile, water, but is not limited thereto.
The process of preparing the mixed system of the water-soluble metal oxide, the magnetic metal source, the insulating metal source, the organic ligand and the solvent is not strictly limited, and other raw materials and solvents can be added into one raw material to prepare the mixed system of the water-soluble metal oxide, the magnetic metal source, the insulating metal source, the organic ligand and the solvent; or adding raw materials, a mixed system of water-soluble metal oxide, a magnetic metal source, an insulating metal source, an organic ligand and a solvent into the solvent; or a mixed system of the water-soluble metal oxide, the magnetic metal source, the insulating metal source, the organic ligand and the solvent. It is to be understood that the order of addition of the respective raw materials is not strictly limited when the other raw materials are added to one or more raw materials or the raw materials are added to a solvent. Illustratively, a mixed system is prepared by adding a magnetic metal source, an insulating metal source, an organic ligand and a solvent to a water-soluble metal oxide.
In some embodiments, the ratio of the total molar amount of the magnetic metal source and the insulating metal source to the molar amount of the water-soluble metal oxide in the mixed system is 0.1 to 100: 1. In this case, the metal source participates in the reaction with the water-soluble metal oxide in a proper molar ratio, and finally an infinite coordination polymer with a proper thickness is prepared on the surface of the water-soluble metal oxide, so that the crystallinity and the solution film-forming property of the water-soluble metal oxide are improved. If the content of the magnetic metal source is too high, the thickness of the coordination polymer is easily too thick, so that the shell layer of the finally calcined core-shell metal oxide is too thick, and the distance between adjacent core-shell metal oxides is large, thereby affecting the electron transport performance of the film-formed electron transport layer.
In some embodiments, the molar ratio of the magnetic metal source to the insulating metal source in the mixed system is 0.1 to 1: 1. In this case, the insulating metal oxide has a suitable doping ratio in the shell layer obtained by the following steps. Compared with the metal oxide with the core-shell structure without the insulating metal oxide in the shell layer, the insulating metal oxide with the content in the shell layer has a blocking effect on the injection and transmission of electrons to a proper degree, so that electrons and holes in the light-emitting diode using the metal transmission material have more balanced carrier mobility, and the composite luminescence of the carriers in the light-emitting layer is further improved.
In some embodiments, the ratio of the total molar amount of the magnetic metal source and the insulating metal source to the molar amount of the organic ligand in the mixed system is 2 to 7: 1. In this case, the organic ligand and the metal source are reacted in a suitable ratio to form an infinite coordination polymer.
In the step S02, the mixed system is reacted under a pressure condition at a temperature of 150 ℃ to 300 ℃, under a high-temperature pressure condition, the magnetic metal source and the insulating metal source aggregate and nucleate with active groups such as carboxyl groups in the organic ligand under a driving force of coordination chemistry, the formed nuclei further aggregate and mature and grow due to large specific surface area and poor stability, and finally, an infinite coordination polymer with an amorphous state is formed on the surface of the water-soluble metal oxide.
One or more layers of magnetic infinite coordination polymers are carried out on the surface of the water-soluble metal oxide in a high-temperature and high-pressure mode through high-temperature pressurization, namely, a shell layer is generated on the surface of the water-soluble metal oxide. By growing the magnetic infinite coordination polymer on the surface of the water-soluble metal oxide, the lattice order of the water-soluble metal oxide can be improved, and the crystallization stability of the obtained core-shell metal oxide can be improved. Particularly, when the water-soluble metal oxide is prepared by a low-temperature solution method, the crystal lattice of the water-soluble metal oxide can be more ordered by pressurizing at 150-300 ℃, and the stability of the crystal is greatly improved. In addition, the magnetic infinite coordination polymer can reduce the surface defects of the water-soluble metal oxide, remarkably improve the dispersion performance of the water-soluble metal oxide in the solution and further improve the film-forming performance of the solution.
In the embodiment of the application, the pressurizing condition of 150-300 ℃ can be determined by the pressure condition of the heating reaction kettle at the corresponding temperature. Illustratively, the temperature is 150 ℃ to 300 ℃ and the corresponding pressure conditions are 3MPa to 25 MPa.
In some embodiments, the mixed system is reacted under pressurized conditions at a temperature of 150 ℃ to 300 ℃ for a reaction time of 5min to 24 h. In this case, the metal source and the organic ligand form an infinite coordination polymer of suitable thickness on the surface of the water-soluble metal oxide.
In step S03, the infinite coordination polymer is calcined to carbonize the organic ligand in the infinite coordination polymer, and the metal source is correspondingly sintered to form a metal oxide, thereby finally obtaining a shell layer containing a magnetic metal oxide and an insulating metal oxide.
In some embodiments, the temperature of the calcination treatment is 500 to 800 ℃. If the calcination temperature is too low, organic components in the infinite coordination polymer can not be completely decomposed easily, so that the formation of a pore channel is not facilitated; if the calcination temperature is too high, the skeleton of the infinite coordination polymer is easily damaged, and the formation of the pore channel is also not facilitated.
According to the core-shell metal oxide prepared by the embodiment of the application, because the surface of the water-soluble metal oxide has magnetism, when the water-soluble metal oxide is acted by an external magnetic field to form a film, the magnetic core-shell metal oxide can be firmly fixed on a substrate, so that the core-shell metal oxide can be prevented from moving due to the volatilization of a solvent in the annealing process, the agglomeration phenomenon caused by the mutual aggregation among particles is reduced, and the film forming quality is remarkably improved. Even at high concentrations of greater than 30mg/ml, the problem of large streaks caused by the deposition of high concentrations of core-shell metal oxides is effectively suppressed.
A third aspect of the embodiments of the present application provides a method for manufacturing an electron transport film, including:
E01. preparing the core-shell metal oxide provided by the first aspect or the core-shell metal oxide prepared by the method provided by the second aspect into a solution;
E02. under the action of an external magnetic field, the solution is processed into a film on the surface of the substrate by a solution processing method, and the electron transmission film is prepared.
According to the preparation method of the electronic transmission film, when the solution of the core-shell type metal oxide is formed into the film by a solution processing method, the core-shell type metal oxide is magnetically restrained without displacement under the action of an external magnetic field in the solvent volatilization process, so that the agglomeration phenomenon caused by mutual aggregation among particles can be effectively reduced, the film forming performance of the core-shell type metal oxide is remarkably improved, and the problems of a large number of stripes and the like in film forming are avoided.
In the step E01, the composition of the core-shell metal oxide, the preparation method thereof, and the like, as mentioned above, are not described herein again for saving space.
The core-shell metal oxide is dissolved in an organic solvent to prepare a core-shell metal oxide solution, which is not strictly limited.
In the step E02, the solution is processed into a film on the surface of the substrate by the solution processing method and is performed in an environment where an applied magnetic field is present, and in this case, the core-shell metal oxides are aligned in order under the constraint of the applied magnetic field and do not undergo displacement with the volatilization of the solvent under the constraint of the applied magnetic field during the heating annealing.
The external magnetic field can be an object capable of generating a magnetic field or an electromagnetic field environment. Illustratively, when the solution is applied to the surface of the substrate by the solution processing method, a large magnet is added to the bottom of the substrate. Under the action of the magnetic field of the large magnet, the magnetic core-shell metal oxide can be firmly fixed on the substrate, so that the problem that the solvent volatilizes to drive the core-shell metal oxide to move in annealing can be prevented, the agglomeration phenomenon caused by mutual aggregation among particles is reduced, and the film forming quality is obviously improved. Particularly, the problem of a large amount of stripes caused by the deposition of high-concentration core-shell metal oxide can be effectively inhibited.
In the embodiments of the present application, the solution processing method includes various methods of forming a core-shell type metal oxide on a substrate by solution deposition, such as spin coating, doctor blading, and inkjet printing.
With reference to fig. 2, a fourth aspect of the embodiments of the present application provides a light emitting diode, including an anode 1 and a cathode 5 oppositely disposed, a light emitting layer 3 disposed between the anode 1 and the cathode 5, and an electron transport layer 4 disposed between the light emitting layer 3 and the cathode 2, where the material of the electron transport layer 4 is the core-shell metal oxide described above, or the core-shell metal oxide prepared by the above method.
The light emitting diode provided by the embodiment of the application adopts the electron transport material core-shell type metal oxide as the electron transport layer 4, and the shell layer of the core-shell type metal oxide is a porous structure consisting of a magnetic metal oxide and an insulating metal oxide, so that part of electrons can be injected into the electron transport layer 4 to a certain extent, and excessive electron injection can be blocked, so that the injection balance of electrons and holes in the light emitting diode is effectively balanced, the effective recombination of carriers in a light emitting layer is enhanced, and the performance of the light emitting diode is improved. In addition, the core-shell metal oxide has better crystallinity and film-forming property, so that the electron transport layer has better flatness and stability, and the electron transport stability of the electron transport layer 4 is favorably improved, thereby improving the photoelectric property of the light-emitting diode.
In some embodiments, the quantum dot light emitting diode further comprises a hole functional layer 2 disposed between the anode 1 and the light emitting layer 3; in some embodiments, the light emitting diode further comprises an electron injection layer disposed between the cathode 5 and the electron transport layer 4; in some embodiments, the light emitting diode further comprises a hole function layer disposed between the anode 1 and the quantum dot light emitting layer 3, and an electron injection layer disposed between the cathode 5 and the electron transport layer 4. The hole function layer comprises at least one of a hole injection layer, a hole transport layer and a hole blocking layer.
In the embodiment of the present application, the light emitting diode may further include a substrate, and the anode 1 or the cathode 5 is disposed on the substrate 6. The light emitting diode provided by the embodiment of the application is divided into a light emitting diode with a positive structure and a light emitting diode with an inverted structure.
In one embodiment, the light emitting diode in a front-up structure includes an anode 1 and a cathode 5 disposed opposite each other, a light emitting layer 3 disposed between the anode 1 and the cathode 5, and an electron transport layer 4 disposed between the cathode 5 and the light emitting layer 3, with the anode 1 disposed on a substrate. Further, an electron injection layer may be provided between the cathode 5 and the electron transport layer 4; a hole-functional layer such as a hole-transport layer 2, a hole-injection layer, and an electron-blocking layer may be provided between the anode 1 and the light-emitting layer 3. As shown in fig. 3, in some embodiments of the light emitting diode with an upright structure, the light emitting diode includes a substrate 6, an anode 1 disposed on a surface of the substrate 6, a hole transport layer 2 disposed on a surface of the anode 1, a light emitting layer 3 disposed on a surface of the hole transport layer 2, an electron transport layer 4 disposed on a surface of the light emitting layer 3, and a cathode 5 disposed on a surface of the electron transport layer 4.
In one embodiment, the inverted structure light emitting diode includes a stacked structure of an anode 1 and a cathode 5 disposed opposite each other, a light emitting layer 3 disposed between the anode 1 and the cathode 5, and an electron transport layer 4 disposed between the cathode 5 and the light emitting layer 3, with the cathode 5 disposed on a substrate. Further, an electron injection layer may be provided between the cathode 5 and the electron transport layer 4; a hole-functional layer such as a hole-transport layer 2, a hole-injection layer, and an electron-blocking layer may be provided between the anode 1 and the light-emitting layer 3. As shown in fig. 4, in some embodiments of the light emitting diode with the inverted structure, the light emitting diode includes a substrate 6, a cathode 5 disposed on a surface of the substrate 6, an electron transport layer 4 disposed on a surface of the cathode 5, a light emitting layer 3 disposed on a surface of the electron transport layer 4, a hole transport layer 2 disposed on a surface of the light emitting layer 3, and an anode 1 disposed on a surface of the hole transport layer 2.
The light emitting diode provided by the embodiment of the application can be divided into an organic light emitting diode and a quantum dot light emitting diode according to the type of a light emitting material.
In the above embodiments, the substrate 6 may include a rigid substrate such as glass, a silicon wafer, a metal foil, or the like, or a flexible substrate such as a combination formed of one or more of Polyimide (PI), Polycarbonate (PC), Polystyrene (PS), Polyethylene (PE), polyvinyl chloride (PV), polyvinyl pyrrolidone (PVP), polymethyl methacrylate, polyethylene terephthalate (PET), polyethylene naphthalate, polyamide, polyether sulfone, or the like.
The anode 1 may be made of common anode materials and thicknesses, and the embodiment of the present application is not limited thereto. In some embodiments, the anode material is selected from elemental metals or alloys. Illustratively, the anode material may be a conductive metal oxide. In some embodiments, the anode material is selected from conductive metal oxides. Illustratively, the anode material may be zinc oxide, indium oxide, tin oxide, Indium Tin Oxide (ITO), Indium Zinc Oxide (IZO), fluorine-doped tin oxide, or the like. In some embodiments, the anode material is selected from a combination of elemental metals or alloys and conductive metal oxides. Illustratively, the anode material may be a combination of ZnO and Al, SnO2And Sb, but is not limited thereto.
The material of the hole injection layer may be selected from materials having good hole injection properties, including but not limited to: poly (3, 4-ethylenedioxythiophene) -polystyrenesulfonic acid (PEDOT: PSS), copper phthalocyanine (CuPc), 2,3,5, 6-tetrafluoro-7, 7',8,8' -tetracyanoquinodimethane (F4-TCNQ), 2,3,6,7,10, 11-hexacyano-1, 4,5,8,9, 12-Hexaazatriphenylene (HATCN), doped or undoped transition metal oxides, doped or undoped metal chalcogenide compoundsOne or more of (a); wherein the transition metal oxide includes, but is not limited to, MoO3、VO2、WO3One or more of CuO and CuO; metal chalcogenide compounds including but not limited to MoS2、MoSe2、WS2、WSe2And CuS. In some embodiments, the hole injection layer has a thickness of 10-150 nm.
The hole transport layer 2 may be made of a hole transport material conventional in the art, 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 ″ -tris (carbazol-9-yl) triphenylamine (TCTA), 4' -bis (9-Carbazole) Biphenyl (CBP), N ' -diphenyl-N, N ' -bis (3-methylphenyl) -1,1 ' -biphenyl-4, 4' -diamine (TPD), N ' -diphenyl-N, n ' - (1-naphthyl) -1,1 ' -biphenyl-4, 4' -diamine (NPB), doped graphene, undoped graphene, C60. In some embodiments, the hole transport layer has a thickness of 10-150 nm.
When the light emitting diode is an organic light emitting diode, the material of the light emitting layer 3 is an organic light emitting material. When the light emitting diode is a quantum dot light emitting diode, the material of the light emitting layer is quantum dots. The quantum dots of the quantum dot light-emitting layer are direct band gap compound semiconductors with light-emitting capability, and conventional quantum dot materials can be selected according to conventional quantum dot types. For example, the quantum dots of the quantum dot light emitting layer can be one or more of II-VI compound, III-V compound, II-V compound, III-VI compound, IV-VI compound, I-III-VI compound, II-IV-VI compound or IV elementary substance, and the quantum dots can be single-component quantum dots, core-shell structure quantum dots, or at least one of alloy structure quantum dots, organic-inorganic hybrid perovskite quantum dots and all-inorganic quantum dot materials. Exemplary, group II-VI quantum dots include, but are not limited to: CdS, CdSe, CdTe, ZnS, ZnSe, ZnTe, ZnO, HgS, HgSe, HgTe, CdSeS, CdSeTe, CdSeSE, ZnSeS, ZnSeTe, HgSeS, HgSeTe, HgSTe, CdZnS, CdZnSe, CdZnTe, CdHgS, CdHgSe, CdHgTe, HgZnS, HgZnSe, HgZnTe, CdZnSeS, CdZnSeTe, CdHgSeS, CdHgSeTe, HgSTe, HgZnSeS, HgZnSeTe; group III-V quantum dots include, but are not limited to: GaN, GaP, GaAs, GaSb, AlN, AlP, AlAs, AlSb, InN, InP, InAs, InSb, GaNP, GaNAs, GaNSb, GaGaAs, GaSb, AlNP, AlNAs, AlNSb, AlPAs, AlPSb, InNP, InNAs, InNSb, InPAs, InPSb, GaAlNP, GaAlNAs, GaAlNSb, GaAlPAs, GaAlPSb, GaInNP, GaInNAs, GaInNSb, GaInPAs, GaInPSb, InInInInInInNP, InAlNAs, InAlNSb, InPAs, InAlPSb; group IV-VI quantum dots include, but are not limited to: SnS, SnSe, SnTe, PbS, PbSe, PbTe, SnSeS, SnSeTe, SnSTe, PbSeS, PbSeTe, PbSTe, SnPbS, SnPbSe, SnPbTe, SnPbSSe, SnPbSeTe, SnPbSTe.
The material of the electron transport layer 4 is the above core-shell type metal oxide, and includes: the shell layer is of a porous structure, and the shell layer material forming the shell layer comprises a magnetic metal oxide and an insulating metal oxide. In some embodiments, the magnetic metal oxide is selected from at least one of iron oxide, cobalt oxide, nickel oxide, manganese oxide, gadolinium oxide. In some embodiments, the insulating metal oxide is selected from aluminum oxide. In some embodiments, the molar ratio of the magnetic metal oxide to the insulating metal oxide in the shell material is 0.1-100: 1. in some embodiments, the shell layer has a thickness of 10nm to 20 μm. In some embodiments, the metal oxide is selected from at least one of ZnO, MgO, SnO2, ZrO2, ZnMgO, ZnSnO, ZnZrO.
In the embodiment of the present application, the cathode 5 may be made of a common cathode material and thickness, and the embodiment of the present application is not limited. In some embodiments, the material of the cathode 5 is selected from one or more of a metallic material, a conductive metal compound. Exemplary metallic materials include, but are not limited to, magnesium, calcium, sodium, potassium, titanium, indium, yttrium, lithium, gadolinium, aluminum, silver, tin, lead, cesium, barium, or alloys thereof. Exemplary, conductive metal compounds include, but are not limited to: alkali metal halides, alkaline earth metal halides, alkali metal oxides. In aIn a possible embodiment, the cathode is a multilayer cathode. In some embodiments, the multi-layer cathode has at least one of an alkali metal halide, an alkaline earth metal halide, an alkali metal oxide as a first layer and a metal layer as a second layer, wherein the metal in the metal layer includes, but is not limited to, an alkaline earth metal, a group 13 metal, or a combination thereof. Illustratively, the multi-layer cathode is a composite layer of LiF thin film and Al thin film, LiO2Composite layer of thin film and Al thin film, composite layer of LiF thin film and Ca thin film, composite layer of Liq thin film and Al thin film, and BaF2A composite layer of the film and the Ca film, but is not limited thereto.
The following description will be given with reference to specific examples.
Example 1
A method for preparing a core-shell metal oxide, comprising:
(1) ZnO with the grain diameter of 5nm is selected to prepare ZnO ethanol solution.
(2) Adding gadolinium nitrate, aluminum acetate, p-toluic acid and N, N-dimethylformamide (wherein the molar ratio of the metal source to ZnO is 5: 1; the molar ratio of p-toluic acid to the metal source is 3: 1; and the molar ratio of gadolinium nitrate to aluminum acetate is 1:1) into the ethanol solution of ZnO in the step (1) to obtain a mixed solution; and (3) placing the mixed solution in a high-pressure reaction kettle at 200 ℃ for reaction for 10min to obtain the composite material of which the ZnO surface is coated with the mixed metal-based infinite coordination polymer. After the reaction is finished, the product is dissolved and precipitated by water and ethanol, and then is dried.
(3) Calcining the product obtained in the step (2) at 660 ℃ for 12h, and coating a shell layer formed by a mixed material containing gadolinium oxide and aluminum oxide on the surface of ZnO to obtain ZnO/GdxAl1-xCore-shell metal oxides of O.
Example 2
A method for preparing a core-shell metal oxide, comprising:
(1) ZnO with the grain diameter of 5nm is selected to prepare ZnO ethanol solution.
(2) Adding ferric nitrate, aluminum acetate, p-toluic acid and N, N-dimethylformamide (wherein the molar ratio of the metal source to ZnO is 6: 1; the molar ratio of p-toluic acid to the metal source is 3: 1; and the molar ratio of ferric nitrate to aluminum acetate is 1:1) into the ethanol solution of ZnO in the step (1) to obtain a mixed solution; and placing the mixed solution in a high-pressure reaction kettle at 220 ℃ for reaction for 12min to obtain the composite material of which the ZnO surface is coated with the mixed metal-based infinite coordination polymer. After the reaction is finished, the product is dissolved and precipitated by water and ethanol, and then is dried.
(3) Calcining the product obtained in the step (2) at 500 ℃ for 16h, and coating a shell layer formed by a mixed material containing iron oxide and aluminum oxide on the surface of ZnO to obtain ZnO/FexAl1-xCore-shell metal oxides of O.
Example 3
A method for preparing a core-shell metal oxide, comprising:
(1) ZnO with the grain diameter of 5nm is selected to prepare ZnO ethanol solution.
(2) Adding ferric nitrate, aluminum chloride, phthalic acid and N, N-dimethylformamide (wherein the molar ratio of the metal source to ZnO is 5.5: 1; the molar ratio of phthalic acid to the metal source is 3: 1; and the molar ratio of ferric nitrate to aluminum chloride is 2:3) into the ethanol solution of ZnO in the step (1) to obtain a mixed solution; and (3) placing the mixed solution in a high-pressure reaction kettle at 250 ℃ for reaction for 20min to obtain the composite material of which the ZnO surface is coated with the mixed metal-based infinite coordination polymer. After the reaction is finished, the product is dissolved and precipitated by water and ethanol and then dried.
(3) Calcining the product obtained in the step (2) at 500 ℃ for 20h, and coating a shell layer formed by a mixed material containing iron oxide and aluminum oxide on the surface of ZnO to obtain ZnO/FexAl1-xCore-shell metal oxides of O.
Example 4
A method for preparing a core-shell metal oxide, comprising:
(1) ZnO with the grain diameter of 5nm is selected to prepare ZnO ethanol solution.
(2) Adding cobalt chloride, aluminum chloride, diphenylacetic acid and N, N-dimethylformamide (wherein the molar ratio of the metal source to ZnO is 6: 1; the molar ratio of the diphenylacetic acid to the metal source is 3.2: 1, and the molar ratio of the cobalt chloride to the aluminum chloride is 3:2) into the ethanol solution of the ZnO obtained in the step (1) to obtain a mixed solution; and (3) placing the mixed solution in a high-pressure reaction kettle at 250 ℃ for reaction for 40min to obtain the composite material of which the ZnO surface is coated with the mixed metal-based infinite coordination polymer. After the reaction is finished, the product is dissolved and precipitated by water and ethanol, and then is dried.
(3) Calcining the product obtained in the step (2) at 550 ℃ for 24h, and coating a shell layer formed by a mixed material containing cobalt oxide and aluminum oxide on the surface of ZnO to obtain ZnO/CoxAl1-xCore-shell metal oxides of O.
Example 5
A method for preparing a core-shell metal oxide, comprising:
(1) ZnO with the grain diameter of 5nm is selected to prepare ZnO ethanol solution.
(2) Adding manganese acetylacetonate, aluminum acetylacetonate, diphenylacetic acid and N, N-dimethylformamide (wherein the molar ratio of the metal source to ZnO is 7: 1; the molar ratio of the diphenylacetic acid to the metal source is 3.5: 1; and the molar ratio of the manganese acetylacetonate to the aluminum acetylacetonate is 2:3) into the ethanol solution of the ZnO obtained in the step (1) to obtain a mixed solution; and (3) placing the mixed solution in a high-pressure reaction kettle at 260 ℃ for reaction for 20min to obtain the composite material of which the ZnO surface is coated with the mixed metal-based infinite coordination polymer. After the reaction is finished, the product is dissolved and precipitated by water and ethanol, and then is dried.
(3) Calcining the product obtained in the step (2) at 500 ℃ for 24h, and coating a shell layer formed by a mixed material containing manganese oxide and aluminum oxide on the surface of ZnO to obtain ZnO/MnxAl1-xCore-shell metal oxides of O.
Example 6
A quantum dot light-emitting diode comprises a substrate, an anode combined on the substrate, a hole injection layer combined on the surface of the anode, which is deviated from the surface of the substrate, a hole transport layer combined on the surface of the hole injection layer, which is deviated from the anode, an electron transport layer combined on the surface of the hole transport layer, which is deviated from the surface of a quantum dot light-emitting layer, and a cathode combined on the surface of the electron transport layer, which is deviated from the surface of the quantum dot light-emitting layer. Wherein the substrate is a glass substrate; the anode is ITO with the thickness of 120 nm; PSS, the thickness of the hole injection layer is 70 nm; the hole transport layer is TFB and is 90nm thick; the thickness of the quantum dot light-emitting layer is 60 nm; the top electrode was Al and the thickness was 60 nm. The material of the electron transport layer was the core-shell metal oxide prepared in example 1 and had a thickness of 40 nm.
Comparative example 1
The difference from example 6 is that: the material of the electron transport layer was ZnO in step (1) of example 1.
Example 7
A quantum dot light emitting diode, which is different from embodiment 6 in that: the hole injection layer was 80nm thick, the hole transport layer was 80nm thick, the top electrode was 60nm thick, and the electron transport layer was the core-shell metal oxide prepared in example 2.
Comparative example 2
The difference from example 7 is that: the material of the electron transport layer was ZnO in step (1) of example 2.
Example 8
A quantum dot light emitting diode, which is different from embodiment 6 in that: the thickness of the hole injection layer is 80 nm; the thickness of the hole transport layer is 80 nm; the thickness of the top electrode was 50nm, and the material of the electron transport layer was the core-shell type metal oxide prepared in example 3.
Comparative example 3
The difference from example 8 is that: the material of the electron transport layer was ZnO in step (1) of example 3.
Example 9
A quantum dot light emitting diode, which is different from embodiment 6 in that: the anode was 110nm thick, the hole injection layer was 80nm thick, the hole transport layer was 80nm thick, the top electrode was 50nm thick, and the electron transport layer was the core-shell metal oxide prepared in example 4.
Comparative example 4
The difference from example 9 is that: the material of the electron transport layer was ZnO in step (1) of example 4.
Example 10
A quantum dot light emitting diode, which is different from embodiment 6 in that: the thickness of the anode is 110nm, the thickness of the hole injection layer is 80nm, the thickness of the hole transport layer is 80nm, the thickness of the quantum dot light emitting layer is 50nm, the thickness of the top electrode is 50nm, and the material of the electron transport layer is the core-shell type metal oxide prepared in example 5.
Comparative example 5
The difference from example 10 is that: the material of the electron transport layer was ZnO in step (1) of example 5.
The quantum dot light-emitting diodes prepared in examples 6 to 10 were subjected to a performance test, the test method was as follows:
external quantum dot efficiency (EQE): 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:
Figure BDA0002785269110000231
where η e is the light output coupling efficiency, η γ is the ratio of the number of recombination carriers to the number of injection carriers, χ is the ratio of the number of excitons generating photons to the total number of excitons, KRTo the rate of the radiation process, KNRIs the non-radiative process rate.
The test results are shown in table 1 below:
TABLE 1
Figure BDA0002785269110000232
As can be seen from table 1, the quantum dot light emitting diodes prepared in examples 6-10 have higher EQE due to: in the quantum dot light-emitting diode, after the material of the electron transmission layer is coated by the mixture of the magnetic metal oxide and the insulating metal oxide, the injection of holes and electrons of the quantum dot light-emitting diode is more balanced, the recombination efficiency of carriers in the quantum dot light-emitting layer is improved, and the device performance is improved.
The present invention is not intended to be limited to the particular embodiments shown and described, but is to be accorded the widest scope consistent with the principles and novel features herein disclosed.

Claims (10)

1. A core-shell metal oxide, comprising: the shell layer has a porous structure, and the shell layer material forming the shell layer comprises a magnetic metal oxide and an insulating metal oxide.
2. The core-shell metal oxide according to claim 1, wherein the magnetic metal oxide is at least one selected from the group consisting of iron oxide, cobalt oxide, nickel oxide, manganese oxide, and gadolinium oxide.
3. The core-shell metal oxide according to claim 1, wherein the insulating metal oxide is selected from the group consisting of aluminum oxides.
4. The core-shell metal oxide according to any one of claims 1 to 3, wherein a molar ratio of the magnetic metal oxide to the insulating metal oxide in the shell material is 0.1 to 100: 1; and/or
The thickness of the shell layer is 10 nm-20 mu m; and/or
The metal oxide is selected from ZnO, MgO and SnO2、ZrO2At least one of ZnMgO, ZnSnO and ZnZrO.
5. A method for preparing a core-shell metal oxide, comprising:
preparing a mixed system of water-soluble metal oxide, a magnetic metal source, an insulating metal source, an organic ligand and a solvent;
reacting the mixed system under the pressurization condition that the temperature is 150-300 ℃, and coating an infinite coordination polymer on the surface of the water-soluble metal oxide to obtain an infinite coordination polymer;
and calcining the infinite coordination polymer to obtain the core-shell metal oxide.
6. The method according to claim 5, wherein the magnetic metal source is selected from the group consisting of a salt of a magnetic metal, an oxide of a magnetic metal,
preferably, the magnetic metal source is selected from at least one of an iron source, a cobalt source, a nickel source, a manganese source and a gadolinium source,
more preferably, the iron source is selected from at least one of ferric chloride, ferric iodide, ferric bromide, ferric fluoride, ferric acetate, ferric acetylacetonate, ferric sulfate, ferric nitrate, ferrous oxide, ferroferric oxide, ferrous hydroxide, ferric oleate, ferric myristate, ferric stearate, and ferric palmitate;
the cobalt source is selected from at least one of cobalt ammonium sulfate, lithium cobalt oxide, cobalt carbonate, cobalt chromate, cobalt aluminate, cobalt ammonium phosphate, cobalt chloride, cobalt iodide, cobalt bromide, cobalt fluoride, cobalt acetate, cobalt acetylacetonate, cobalt sulfate, cobalt nitrate, cobalt oxide, cobalt hydroxide, cobalt oleate, cobalt myristate, cobalt stearate and cobalt palmitate;
the nickel source is selected from at least one of nickel chloride, nickel nitrate, nickel sulfate, nickel hydroxide, nickel sesquioxide and nickel monoxide;
the manganese source is selected from at least one of manganese carbonate, manganese chloride, manganese iodide, manganese bromide, manganese fluoride, manganese acetate, manganese acetylacetonate, manganese sulfate, manganese nitrate, manganese oxide, manganese hydroxide, manganese oleate, manganese myristate, manganese stearate and manganese palmitate;
the gadolinium source is at least one selected from gadolinium carbonate, gadolinium chloride, gadolinium iodide, gadolinium bromide, gadolinium fluoride, gadolinium acetate, gadolinium acetylacetonate, gadolinium sulfate, gadolinium nitrate, gadolinium oxide, gadolinium hydroxide, gadolinium oleate, gadolinium myristate, gadolinium stearate and gadolinium palmitate.
7. The method of claim 5, wherein the source of the insulating metal is selected from the group consisting of aluminum sources,
preferably, the aluminum source is selected from at least one of aluminum phosphate, aluminum acetate, aluminum acetylacetonate, aluminum iodide, aluminum bromide, aluminum chloride, aluminum fluoride, aluminum carbonate, aluminum cyanide, aluminum nitrate, aluminum oxide, aluminum peroxide, and aluminum sulfate.
8. The method for producing a core-shell metal oxide according to any one of claims 5 to 7, wherein the temperature of the calcination treatment is 500 to 800 ℃.
9. The method for producing a core-shell metal oxide according to any one of claims 5 to 7, wherein in the mixed system, the ratio of the total molar amount of the magnetic metal source and the insulating metal source to the molar amount of the water-soluble metal oxide is 1:0.1 to 100; and/or
In the mixed system, the ratio of the total molar weight of the magnetic metal source and the insulating metal source to the molar weight of the organic ligand is 1: 2-7; and/or
In the mixed system, the molar ratio of the magnetic metal source to the insulating metal source is 0.1-1: 1; and/or
The organic ligand is selected from organic matters containing benzene rings and active groups capable of coordinating with the magnetic metal ions.
10. A light-emitting diode comprising an anode and a cathode disposed opposite to each other, a light-emitting layer disposed between the anode and the cathode, and an electron transport layer disposed between the light-emitting layer and the cathode, wherein the electron transport layer is made of the core-shell metal oxide according to any one of claims 1 to 4 or the core-shell metal oxide prepared by the method according to any one of claims 5 to 9.
CN202011295813.XA 2020-11-18 2020-11-18 Core-shell metal oxide, preparation method thereof and light-emitting diode Pending CN114583069A (en)

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