CN114388712A

CN114388712A - Electron transport material, method for producing the same, and photoelectric device

Info

Publication number: CN114388712A
Application number: CN202011107189.6A
Authority: CN
Inventors: 何斯纳; 吴龙佳; 吴劲衡
Original assignee: TCL Technology Group Co Ltd
Current assignee: TCL Technology Group Co Ltd
Priority date: 2020-10-16
Filing date: 2020-10-16
Publication date: 2022-04-22
Also published as: WO2022078510A1

Abstract

The application belongs to the technical field of photoelectric devices, and particularly relates to an electron transport material which is provided with a core-shell structure and comprises a ZnO core and a precious metal shell layer coated outside the ZnO core. The electron transmission material has a core-shell structure, wherein the surface defects of ZnO are reduced by modifying a noble metal shell layer, and the capture of carriers by the surface defects of ZnO is inhibited, so that the electron transmission performance of a ZnO core is improved. And the formation of the noble metal shell layer is equivalent to the construction of a channel for rapidly and effectively transferring excited electrons from the electron transport material to the quantum dot luminescent material. Meanwhile, the noble metal shell layer has the characteristic of surface plasmon resonance, when the electron transport material is applied to photoelectric devices, the electron transport material can induce the enhancement of a local electromagnetic field through the surface plasmon resonance effect, so that the output coupling and the composite light emitting rate of light are increased, the light emitting efficiency of the device is effectively improved, and the photoelectric performance of the photoelectric devices such as the QLED is improved.

Description

Electron transport material, method for producing the same, and photoelectric device

Technical Field

The application belongs to the technical field of photoelectric devices, and particularly relates to an electron transport material, a preparation method thereof and a photoelectric device.

Background

The semiconductor quantum dots have quantum size effect, and people can realize the required luminescence with specific wavelength by regulating and controlling the size of the quantum dots. In the conventional inorganic electroluminescent device, electrons and holes are injected from a cathode and an anode, respectively, and then recombined in a light emitting layer to form excitons for light emission.

In recent years, inorganic semiconductors have been studied as an electron transport layer in a relatively hot manner. Nano ZnO, TiO₂、ZrO₂The material is a wide-bandgap semiconductor material, and has the advantages of quantum confinement effect, size effect, excellent fluorescence characteristic and the like, so that the material has great development potential in the research of the fields of photocatalysis, sensors, transparent electrodes, fluorescent probes, diodes, solar cells, lasers and the like. The nano ZnO is a direct band gap n-type semiconductor material, has a wide forbidden band of 3.37eV and a low work function of 3.7eV, and the structural characteristics of the energy band determine that the nano ZnO can become a proper electron transport layer material. Meanwhile, the nano ZnO has better and more excellent performances in photoelectric devices of solution processes due to good conductivity, high visible light transmittance, excellent water and oxygen stability and mature preparation processes.

The conductivity and electron transmission of the nano ZnO semiconductor material are one of the key factors influencing the electrochemical performance of photoelectric devices. At present, the conductivity and electron transmission of semiconductor materials such as ZnO and the like are still to be further improved.

Disclosure of Invention

The application aims to provide an electron transport material, a preparation method thereof and a photoelectric device, and aims to solve the problems of poor conductivity and poor electron transport of the existing nano ZnO semiconductor material to a certain extent.

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 an electron transport material having a core-shell structure, including a ZnO core and a noble metal shell layer covering a surface of the ZnO core.

According to the electron transport material, the precious metal shell layer coated on the outer surface of the ZnO core fills oxygen vacancy on the surface of ZnO, reduces oxygen defects on the surface of ZnO, reduces radiation combination of electron hole pairs, improves electron transport performance, and enhances luminous efficiency of devices. And the noble metal shell layer has the surface plasma resonance characteristic, and when the noble metal shell layer is applied to photoelectric devices such as QLEDs and the like, the noble metal shell layer can induce the enhancement of a local electromagnetic field, so that the output coupling and the composite luminous rate of light are increased, the luminous efficiency of the devices is effectively improved, and the photoelectric performance of the photoelectric devices such as the QLEDs and the like is improved.

In a second aspect, the present application provides a method for preparing an electron transport material, comprising the steps of:

obtaining a zinc oxide nano material;

obtaining a silane coupling agent, dissolving the silane coupling agent and the zinc oxide nano material in a first organic solvent, carrying out coupling reaction, and separating to obtain a modified zinc oxide nano material;

and dissolving the modified zinc oxide nano material in a second organic solvent, adding a noble metal precursor and a reducing agent for coating reaction, and separating to obtain the electron transport material.

According to the preparation method, the process is simple, flexible and controllable, the prepared material with the core-shell structure is good in stability, the surface defects of ZnO are reduced by the precious metal shell layer, the capture of current carriers by the surface defects of ZnO is inhibited, and the electron transmission performance of the material is improved. Meanwhile, the noble metal shell layer has the characteristic of surface plasma resonance, can induce local electromagnetic field enhancement, increase light output coupling and composite light emitting rate, and effectively improve the light emitting efficiency of the device, thereby improving the photoelectric performance of photoelectric devices such as QLEDs and the like.

In a third aspect, the present application provides an optoelectronic device comprising an electron transport layer disposed between the light emitting layer and the cathode; wherein, the electron transmission layer contains the electron transmission material or the electron transmission material prepared by the method.

According to the photoelectric device, the electron transmission layer comprises the electron transmission material or the electron transmission film with excellent conductivity and electron transmission performance, so that the electron transmission efficiency of the photoelectric device is improved; and the hole can be prevented from being transmitted from the light-emitting layer to the anode, so that the ineffective recombination of electrons and holes in the electronic function layer is avoided, the electron and hole recombination efficiency in the light-emitting layer is improved, and the light-emitting efficiency of the device is improved.

Drawings

FIG. 1 is a schematic flow chart of a method for preparing an electron transport material provided in an embodiment of the present application;

fig. 2 is a light-emitting device of a positive type configuration according to an embodiment of the present invention.

Fig. 3 is an inverted light emitting device according to an embodiment of the present invention.

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.

A first aspect of an embodiment of the present application provides an electron transport material, which has a core-shell structure and includes a ZnO core and a precious metal shell layer covering the ZnO core.

The electron transport material provided by the first aspect of the application has a core-shell structure, and on the one hand, the modification of the precious metal shell layer reduces the surface defects of ZnO, and inhibits the capture of the surface defects of ZnO to current carriers, thereby improving the electron transport performance of a ZnO core. On the other hand, the formation of the noble metal shell layer is equivalent to the construction of a channel for rapidly and effectively transferring excited electrons from the electron transport material to the quantum dot luminescent material, and the electron transport performance of the material is enhanced. On the other hand, the precious metal shell layer has the surface plasmon resonance characteristic, when the electron transport material is applied to a photoelectric device, the surface plasmon resonance effect of the precious metal can induce the enhancement of a local electromagnetic field, so that the output coupling and the composite luminescence rate of light are increased, the luminescence efficiency of the device is effectively improved, and the photoelectric performance of the photoelectric device such as a QLED is improved.

In some embodiments, the ZnO core is doped with a second metal, where the inner core of the material is ZnAO_xA is a second metal, and the ionic valence of the second metal is + 3- + 4. The ions of the second metal doped in the embodiment of the application have high valence state and can occupy Zn in ZnO nuclear crystal lattice²⁺The position of (a). Two of the valence electrons of the second metal are combined with oxygen to form saturated bonds, and the rest electrons are separated from the impurity atoms to form redundant valence electrons. The energy level of the electron is positioned in the energy gap and is slightly lower than the bottom of the conduction band, enough energy can be obtained at normal temperature and is transferred to the conduction band to form free electrons, the conduction is realized by the directional movement under the action of an external electric field, and the conductivity of the intrinsic ZnO is improved.

In some embodiments, the second metal is selected from: the ionic valence of the second metal is +3 to +4, the second metal has high valence, and metal oxides corresponding to the metal elements have certain conductivity, so that the conductivity of the material is improved.

In some embodiments, the ZnO core is doped with Sn⁴⁺At this time, the inner core of the material is ZnSnO_x. The tin oxide is an excellent electron transfer material, has higher electron mobility, and further improves the electron transfer performance of the ZnO body; and the atomic radius of Sn is closer to that of Zn, so that effective doping is easy to carry out. When Sn is doped in the ZnO inner core, the doped Sn atoms are Sn⁴⁺In a solid solution form, Sn⁴⁺Occupying Zn in crystal lattice²⁺Two of four valence electrons of Sn are combined with oxygen to form saturated bonds, two electrons are separated from impurity atoms to form 2 redundant valence electrons, the energy level of the electrons is slightly lower than the bottom of a conduction band in an energy gap, enough energy can be obtained at normal temperature and is transferred to the conduction band to form free electrons, the free electrons move directionally under the action of an external electric field to conduct electricity, and the conductivity of intrinsic ZnO is improved.

In some embodiments, the molar ratio of zinc element to the second metal element in the ZnO core is 1: (0.05-0.2). If the doping amount of the second metal is too high, the second metal can be gathered on the surface of the ZnO crystal grain to form a new phase, so that the effective specific surface area of the nano ZnO is reduced; in addition, excessive second metal can also enter the interior of the crystal lattice of ZnO to cause the expansion of the crystal lattice, generate larger crystal lattice distortion and strain energy, cause the mutation of the crystal lattice, form new crystal lattice and second metal oxide and destroy the electrochemical performance of the ZnO body. If the doping amount of the second metal is too low, the conductivity of the ZnO nano material cannot be effectively improved.

In some embodiments, the noble metal shell layer comprises: ag and/or Au, and the shell layer formed by the noble metals is equivalent to the construction of a channel for quickly and effectively transferring excited electrons from the electron transport material to the quantum dot luminescent material, so that the electron transport performance of the material is enhanced. Meanwhile, the precious metal shell layers have surface plasmon resonance characteristics, and when the electron transport material is applied to a photoelectric device, a local electromagnetic field can be induced to be enhanced through the surface plasmon resonance effect of the precious metal, so that the light output coupling and the composite luminescence rate are increased, and the luminescence efficiency of the photoelectric device is effectively improved.

In some embodiments, the thickness of the noble metal shell layer is 1 nm to 2 nm, if the noble metal shell layer in the material is too thin, the shell layer formed by a small amount of noble metal is too thin and uneven, the surface plasma resonance effect cannot be effectively triggered, and the electron transmission performance and the conductivity of the material cannot be effectively improved; if the thickness of the noble metal shell layer in the material is too large, the noble metal shell layer can generate a quenching phenomenon, and the component proportion of the nano ZnO in the material is reduced, so that the electron transmission performance of the material is also reduced. In some embodiments, the particle size of the ZnO core is 4 nm to 8 nm, the zinc oxide with the particle size has better conductivity and electron transmission efficiency, and if the particle size is too small, the zinc oxide is easy to agglomerate and settle, which is not beneficial to the preparation and application of subsequent films, and the electrochemical performance of the zinc oxide is reduced; if the particle size is too large, the electrochemical performance of zinc oxide is lowered.

In some embodiments, in the electron transport material, the noble metal shell layer has a thickness of 1 nm to 2 nm and the ZnO core has a particle size of 4 nm to 8 nm.

In other embodiments, in the electron transport material, the particle size of the ZnO core is 4 nm to 8 nm, the ZnO core is a ZnO material doped with a second metal, and the ionic valence of the second metal is +3 to + 4.

In other embodiments, in the electron transport material, the noble metal shell layer has a thickness of 1 nm to 2 nm, the ZnO core has a particle size of 4 nm to 8 nm, the ZnO core is a ZnO material doped with a second metal, and the ionic valence of the metal is +3 to + 4.

In some embodiments, in the electron transport material, the noble metal shell layer is bonded on the outer surface of the ZnO core through a silane coupling agent, and the bonding is stable, so that the electrochemical stability of the material is ensured.

In some embodiments, the electron transport material is comprised of a ZnO core and a noble metal shell layer encasing the ZnO core. Wherein, the grain diameter of the ZnO nucleus is 4-8 nanometers, at least one second metal with valence of +3 to +4 in tin, titanium, iron, zirconium and yttrium is doped in the ZnO nucleus, the molar ratio of the zinc element to the second metal element is 1: (0.05-0.2). And the noble metal shell layer is combined on the surface of the ZnO core through a silane coupling agent, the noble metal shell layer is Ag and/or Au, and the thickness of the noble metal shell layer is 1-2 nanometers.

The electron transport material provided in the examples of the present application can be prepared by the following methods.

As shown in fig. 1, a second aspect of the embodiments of the present application provides a method for preparing an electron transport material, including the following steps:

s10, obtaining a zinc oxide nano material;

s20, obtaining a silane coupling agent, dissolving the silane coupling agent and the zinc oxide nano material in a first organic solvent, carrying out coupling reaction, and separating to obtain a modified zinc oxide nano material;

s30, dissolving the modified zinc oxide nano material in a second organic solvent, adding a noble metal precursor and a reducing agent for coating reaction, and separating to obtain the electron transport material.

According to the preparation method of the electron transport material provided by the second aspect of the application, the silane coupling agent is adopted to perform surface modification on the zinc oxide nano material, organic functional groups in the silane coupling agent have binding property with oxygen vacancies and ligands on the surface of nano ZnO, and the surface of ZnO can be modified to form the ZnO nano material modified with the silane coupling agent; and then reducing the noble metal precursor into a noble metal simple substance by adopting a reducing agent, wherein a silicon alkoxy group in the ZnO surface modified silane coupling agent has binding property to the free noble metal simple substance in the reaction system, and capturing and coating the noble metal simple substance on the surface of the ZnO nano material to form a noble metal coating shell layer to obtain the material of the ZnO nano material/the noble metal shell layer with the core-shell structure. The preparation method of the electronic transmission material in the embodiment of the application is simple in process, flexible and controllable, and the prepared material with the core-shell structure is good in stability. In the material, the precious metal shell layer reduces the surface defects of ZnO and inhibits the capture of carriers by the surface defects of ZnO, thereby improving the electron transmission performance of the material. Meanwhile, the noble metal shell layer has the characteristic of surface plasma resonance, can induce local electromagnetic field enhancement, increase light output coupling and composite light emitting rate, and effectively improve the light emitting efficiency of the device, thereby improving the photoelectric performance of photoelectric devices such as QLEDs and the like.

In some embodiments, in step S10, the step of obtaining the zinc oxide nanomaterial includes: dissolving a first zinc salt and a first alkaline substance in a third organic solvent, reacting for 2-4 hours at 60-80 ℃, and reacting the zinc salt with an alkali liquor to generate zinc hydroxide (Zn (OH)₂) Then Zn (OH)₂And carrying out polycondensation reaction, dehydrating to generate ZnO nuclear crystal particles, and separating to obtain the zinc oxide nano material.

In some embodiments, the reaction system after the first zinc salt and the first basic substance are dissolved in the third organic solvent has a pH of 12 to 13, the total substance concentration of the solution is 0.5mol/L to 1mol/L, and the molar ratio of the first zinc salt to the second basic substance is 1: (1.8-2.5); the raw material components with the proportion and concentration fully ensure the formation of a zinc oxide material, so that the pH value in a reaction system is maintained at 12-13, and the preparation of the ZnO nuclear crystal material with uniform particles is facilitated. When the molar ratio of the alkaline substance to the zinc salt in the reaction system is less than 1.8: 1, when the total mass concentration of the solution is too low, the pH value in a reaction system is too low, and the generated zinc hydroxide is insufficient, so that the zinc salt is not favorably converted into a zinc oxide nano material; when the molar ratio of the alkaline substance to the zinc salt in the reaction system is more than 2.5: 1, when the total mass concentration of the solution is too high, the pH value in the reaction system is too high, so that the polycondensation speed of the zinc hydroxide in the reaction system is too low, and the preparation of the zinc oxide nano material is also not facilitated.

In some embodiments, the first zinc salt is selected from: at least one of zinc acetate, zinc nitrate, zinc chloride, zinc sulfate, zinc acetate dihydrate; the organic or inorganic zinc salt has better solubility, can be converted into zinc hydroxide in an alkaline solution, and can obtain the zinc oxide nano material through polycondensation reaction.

In some embodiments, the first alkaline material is selected from: at least one of ammonia water, potassium hydroxide, sodium hydroxide, lithium hydroxide, ethanolamine, ethylene glycol, diethanolamine, triethanolamine and ethylenediamine; these basic substances can react with zinc salts to form zinc hydroxide, then Zn (OH)₂Polycondensation reaction is carried out, and ZnO nuclear crystal particles are generated after dehydration.

In some embodiments, the third organic solvent is selected from: at least one of isopropanol, ethanol, propanol, butanol, and methanol; the organic solvents have good solubility to zinc salt and alkaline substances, and provide a solvent system for the reaction between the zinc salt, the alkaline substances and other components.

In some embodiments, the step of separating comprises: and precipitating the zinc oxide nano material by adopting a precipitator. In some embodiments, after the reaction is completed, a weak polar and nonpolar solvent such as ethyl acetate, heptane, octane, and the like is used as a precipitant to precipitate the zinc oxide nanomaterial in the reaction system.

In other embodiments, in step S10, the step of obtaining the zinc oxide nano-material includes: dissolving a second zinc salt, a second metal salt and a second alkaline substance in a fourth organic solvent, reacting for 2-4 hours at the temperature of 60-80 ℃, simultaneously adding the second metal salt into a reaction system to ensure that the second metal is doped into zinc oxide particles in an ionic form while generating the zinc oxide nanocrystalline particles, and separating to obtain a zinc oxide nanomaterial ZnAO doped with the second metal_xWherein A is a second metal, of the second metalThe valence state of the ions is + 3- +4, and the zinc oxide nano particles are doped with second metal with high valence state, so that Zn in ZnO nuclear crystal lattice can be occupied²⁺And redundant valence electrons are formed and are easy to transition into free electrons, and the valence electrons conduct through directional movement under the action of an external electric field, so that the conductivity of intrinsic ZnO is improved, and the photoelectric performance of the device is improved.

In some embodiments, the reaction system after the second zinc salt, the second metal salt and the second basic substance are dissolved in the organic solvent for the third year has a pH value of 12 to 13, the total substance concentration of the solution is 0.5mol/L to 1mol/L, and the ratio of the total mol amount of the second zinc salt and the second metal salt to the mol amount of the third basic substance is 1: (1.8-2.5). When the ratio of the molar amount of base to the total molar amount of zinc ions and transition metal ions is less than 1.8: 1, when the total mass concentration of the solution is too low, the metal salt is excessive, and the second metal is added, so that the doping cannot be completely carried out; when the ratio of the molar amount of base to the total molar amount of zinc ions and transition metal ions is greater than 2.5: 1, when the total mass concentration of the solution is too high, the pH value is too high, so that the polycondensation speed in the system is reduced, and the preparation of the zinc oxide nano material doped with the second metal is also not facilitated.

In some embodiments, the molar ratio of the second zinc salt to the second metal salt is 1: (0.05-0.2), when the addition amount of the second metal salt is too high and the doping amount reaches a certain value, the solid solubility of the second metal in ZnO reaches saturation, and when the doping amount continues to increase, the second metal can be gathered on the surface of ZnO crystal grains to form a new phase, so that the effective specific surface area of the nano ZnO is reduced. In addition, excessive second metal can enter the interior of the crystal lattice of ZnO to cause the expansion of the crystal lattice, generate larger crystal lattice distortion and strain energy, cause the mutation of the crystal lattice, form new crystal lattice and second metal oxide and destroy the intrinsic electrochemical performance of the zinc oxide nano-particles. When the addition amount of the second metal salt is too low, the second metal salt is lost in the reaction process, effective doping cannot be realized, and the conductivity and the electron transmission performance of the zinc oxide nano material cannot be improved.

In some embodiments, the second zinc salt is selected from: at least one of zinc acetate, zinc nitrate, zinc chloride, zinc sulfate, zinc acetate dihydrate; the organic or inorganic zinc salt has better solubility, can be converted into zinc hydroxide in an alkaline solution, and can obtain the zinc oxide nano material through polycondensation reaction.

In some embodiments, the second basic substance is selected from: at least one of ammonia water, potassium hydroxide, sodium hydroxide, lithium hydroxide, ethanolamine, ethylene glycol, diethanolamine, triethanolamine and ethylenediamine; the alkaline substances can react with zinc salt and second metal salt to generate hydroxide, and then the hydroxide is subjected to polycondensation reaction to dehydrate to generate the zinc oxide nuclear crystal particles ZnAO doped with the second metal_xWherein A is a second metal.

In some embodiments, the fourth organic solvent is selected from: at least one of isopropanol, ethanol, propanol, butanol, and methanol; the organic solvents have good solubility to zinc salt, second metal salt and alkaline substances, and provide a solvent system for the reaction among the components of zinc salt, alkaline substances and the like.

In some embodiments, the second metal salt is selected from: the ionic valence of the second metal in the second metal salt is +3 to +4, the second metal has high valence, and metal oxides corresponding to the metal elements have certain conductivity, so that the conductivity of the material is improved. In some embodiments, the titanium salt is selected from: at least one of titanium acetate, titanium tetrachloride, titanium nitrate, titanium sulfate and tetrabutyl titanate. In some embodiments, the tin salt is selected from: at least one of tin nitrate, tin chloride, tin sulfate, tin methane sulfonate, tin ethane sulfonate and tin propane sulfonate. In some embodiments, the iron salt is selected from: at least one of ferric nitrate, ferric sulfate, ferric chloride and ferric acetate. In some embodiments, the zirconium salt is selected from: at least one of zirconium nitrate, zirconium sulfate and zirconium chloride. In some embodiments, the yttrium salt is selected from: at least one of yttrium nitrate, yttrium sulfate and yttrium chloride.

In some embodiments, the step of obtaining the zinc oxide nanomaterial comprises: according to the molar ratio of the second zinc salt to the tin salt of 1: (0.05 to 0.2) second zincRatio of the total molar amount of the salt and the tin salt to the molar amount of the second basic substance 1: (1.8-2.5), dissolving a second zinc salt, a tin salt and a second alkaline substance in a fourth organic solvent, reacting for 2-4 hours at the temperature of 60-80 ℃ with the total substance concentration of the reaction system solution being 0.5-1 mol/L, and separating to obtain ZnSnO_x. In the embodiment of the application, Sn is doped in ZnO nucleus⁴⁺At this time, the inner core of the material is ZnSnO_x. The tin oxide is an excellent electron transfer material, has higher electron mobility, and further improves the electron transfer performance of the ZnO body; and the atomic radius of Sn is closer to that of Zn, so that effective doping is easy to carry out. Doped Sn⁴⁺Occupying Zn in crystal lattice²⁺Two of four valence electrons of Sn are combined with oxygen to form saturated bonds, two electrons are separated from impurity atoms to form 2 redundant valence electrons, the energy level of the electrons is slightly lower than the bottom of a conduction band in an energy gap, enough energy can be obtained at normal temperature and is transferred to the conduction band to form free electrons, the free electrons move directionally under the action of an external electric field to conduct electricity, and the conductivity of intrinsic ZnO is improved.

In some embodiments, the step of separating comprises: and precipitating the zinc oxide nano material doped with the second metal by adopting a precipitator. In some embodiments, after the reaction is completed, a weak polar and nonpolar solvent such as ethyl acetate, heptane, octane, and the like is used as a precipitant to precipitate the zinc oxide nanomaterial doped with the second metal in the reaction system.

In the embodiments of the present application, the surface of the zinc oxide nanomaterial prepared by the sol-gel method is bound with abundant ligands such as hydroxyl groups, which is beneficial to the subsequent modification of the surface of the zinc oxide nanomaterial by the silane coupling agent, and the organic functional group in the silane coupling agent is bound with the oxygen vacancy on the surface of the zinc oxide nanomaterial and is simultaneously bound with the ligands such as the surface hydroxyl groups, so as to form a more stable zinc oxide nanomaterial modified by the silane coupling agent.

Specifically, in the step S20, after the silane coupling agent is obtained, the silane coupling agent and the zinc oxide nanomaterial are dissolved in a first organic solvent, and a coupling reaction is performed at a room temperature of 20 to 40 ℃ for 6 to 8 hours, so that the silane coupling agent is combined with vacancies and ligands on the surface of the zinc oxide through organic functional groups and is grafted on the surface of the zinc oxide nanomaterial, which is beneficial to coating a subsequent precious metal shell layer, and the modified zinc oxide nanomaterial is obtained.

In some embodiments, the molar ratio of the silane coupling agent to the zinc oxide nanomaterial is (1-2): 1, the molar ratio ensures that the silane coupling agent fully modifies the surface of the zinc oxide, and provides conditions for the formation of a subsequent noble metal coating layer. When the molar ratio of the ZnO nano material to the silane coupling agent is less than 1:1, the concentration of the silane coupling agent is smaller and smaller along with the progress of the raw material reaction, the counter strain is slow, and the ZnO nano material cannot be completely adsorbed on the surface of the nano particles; when the molar ratio of the ZnO nano material to the silane coupling agent is more than 1:2, the reaction is too fast to be stable, and the ZnO nano material cannot be uniformly adsorbed on the surface of the nano particles.

In some embodiments, the silane coupling agent is selected from: at least one of amino silane coupling agent, mercapto silane coupling agent and vinyl silane coupling agent, wherein amino, mercapto, vinyl and other organic functional groups contained in the silane coupling agent have binding performance with the vacancy and the ligand on the surface of the zinc oxide nano material, so that the surface of the zinc oxide can be effectively modified, and the subsequent coating of noble metal is facilitated. In some embodiments, the silane coupling agent is selected from: the zinc oxide coating comprises at least one of 3-aminopropyltriethoxysilane, aminopropyltrimethoxysilane, N-aminoethyl-gamma-aminopropyltriethoxysilane, phenylaminomethyltriethoxysilane, 3-mercaptopropyl-trimethoxysilane, vinyltriethoxysilane and 3- [ 3-carboxyl allylamido ] propyltriethoxysilane, wherein the silane coupling agents contain organic functional groups reactive with zinc oxide and siloxane groups compatible with free noble metal simple substances in a reaction system, so that the zinc oxide coating is stably combined with the subsequent noble metals, and the subsequent noble metals are favorably combined to the surface of the zinc oxide through the coupling agents to form a stable and compact noble metal coating layer on the surface of the zinc oxide.

In some embodiments, the first organic solvent is selected from: at least one of isopropanol, ethanol, propanol, butanol, and methanol; the organic solvents have better solubility to the silane coupling agent and the zinc oxide nano material, and provide a solvent system for the coupling reaction between the silane coupling agent and the zinc oxide nano material.

In some specific embodiments, the molar ratio of the silane coupling agent to the zinc oxide nano material is (1-2): dissolving a zinc oxide nano material in a first organic solvent, adding a silane coupling agent, stirring and reacting for 6-8 hours at room temperature, and then taking weak-polarity and non-polar solvents such as ethyl acetate, heptane, octane and the like as a precipitator to separate out the modified zinc oxide nano material in a reaction system.

Specifically, in the step S30, the modified zinc oxide nanomaterial is dissolved in a second organic solvent, a noble metal precursor and a reducing agent are added, the noble metal precursor is reduced to a free noble metal simple substance by the reducing agent at a temperature of 40 to 50 ℃, an amino group on the coupling agent modified on the surface of the zinc oxide has compatibility with the free noble metal simple substance, the free noble metal simple substance in the reaction system can be captured, the noble metal simple substance is more stably coated on the surface of the zinc oxide, and the reaction is carried out for 1 to 2 hours, so that the electronic transmission material of the zinc oxide nanomaterial/noble metal coating layer with the core-shell structure is formed.

In some embodiments, the modified zinc oxide nanomaterial, the noble metal precursor and the reducing agent are in a molar ratio of (1-2): 1: (3-5), when the precious metal precursor is less, the shell layer formed after the reduction of a small amount of precious metal salt is too thin and uneven, and the surface plasma resonance effect cannot be effectively triggered. Along with the thickening of the noble metal shell layer, the efficiency of the device is also continuously improved. However, the noble metal shell is too thick, and the noble metal shell not only can generate a quenching phenomenon, but also reduces the content of zinc oxide in the material, so that the efficiency of the device can also be sharply reduced. In addition, when the reducing agent is less, the noble metal salt cannot be well reduced into a free noble metal simple substance; when the reducing agent is more, the reduction reaction rate is faster, resulting in poor uniformity of the shell thickness.

In some embodiments, the noble metal precursor is at least one noble metal salt which is very soluble in a polar solvent and is selected from silver nitrate, gold chloride and gold bromide, so that the noble metal salt is reduced into a noble metal simple substance, and the noble metal simple substance is combined and coated on the surface of the zinc oxide through a coupling agent to form a noble metal shell layer.

In some embodiments, the reducing agent is selected from: at least one of sodium citrate, sodium borohydride and hydroxylamine hydrochloride. In the embodiments of the present application, the noble metal precursor can be stably reduced into a noble metal simple substance under the action of the reducing agent, which is beneficial to the formation of the subsequent noble metal coating shell layer.

In some embodiments, the second organic solvent is selected from: the organic solvents have good solubility for noble metal precursors, reducing agents and zinc oxide nano materials, and provide a solvent system for reducing noble metal salts to form noble metal coating layers.

In some specific embodiments, the modified zinc oxide nano-material, the noble metal precursor and the reducing agent are mixed according to a molar ratio of (1-2): 1: (3-5), dissolving the modified zinc oxide nano material in a second organic solvent, then sequentially dropwise adding at least one of a silver nitrate solution, gold chloride and gold bromide and a reducing agent, stirring and reacting for 1-2 hours at 40-50 ℃, and then adopting weak-polarity and non-polar solvents such as ethyl acetate, heptane, octane and the like as precipitating agents to precipitate the zinc oxide nano material/precious metal coating layer material with the core-shell structure in the reaction system.

In some embodiments, the electron transport material is prepared by the steps of:

s11, obtaining a zinc oxide nano material and/or a zinc oxide nano material doped with a transition metal second metal; wherein the ionic valence of the doped second metal is + 3- + 4;

s21, obtaining a silane coupling agent, dissolving the silane coupling agent and the zinc oxide nano material in a first organic solvent, carrying out coupling reaction for 6-8 hours at the temperature of 20-40 ℃, and separating to obtain a modified zinc oxide nano material;

s31, dissolving the modified zinc oxide nano material in a second organic solvent, adding a noble metal precursor and a reducing agent, carrying out coating reaction for 1-2 hours at the temperature of 40-50 ℃, and separating to obtain the electron transport material.

A third aspect of the embodiments of the present application provides an electron transport film, including: electron transport material with nano ZnO as core and noble metal as shell, and/or,

the electron transport film includes: the electron transport material takes ZnO doped with the second metal as a core and takes the noble metal as a shell, and the ionic valence state of the second metal is + 3- + 4.

According to the electron transmission film provided by the third aspect of the application, as the electron transmission film comprises the electron transmission material taking the ZnO nano material as the core and the precious metal as the shell, the modification of the precious metal shell reduces the surface defects of ZnO, inhibits the capture of the ZnO surface defects to carriers, and improves the electron transmission performance of the ZnO core. And the noble metal shell layer has the characteristic of surface plasmon resonance, and can induce the enhancement of a local electromagnetic field through the surface plasmon resonance effect, so that the light output coupling and the composite light emitting rate are increased, and the light emitting efficiency of the device is effectively improved. In addition, the inner core ZnO nano material can be doped with a second metal with an ionic valence state of + 3- +4, and the second metal with a high valence state can occupy Zn in a ZnO core crystal lattice²⁺And redundant valence electrons are formed and are easy to jump into free electrons, and the valence electrons conduct electricity by directionally moving under the action of an external electric field, so that the conductivity of the intrinsic ZnO is improved.

In some embodiments, the noble metal shell layer has a thickness of 1 nm to 2 nm.

In some embodiments, the noble metal shell layer comprises: ag and/or Au.

In some embodiments, the ZnO core or the ZnO core doped with the second metal has a particle size of 4 nm to 8 nm.

In some embodiments, the second metal is selected from: at least one of titanium, tin, iron, zirconium and yttrium.

In some embodiments, the molar ratio of zinc element to second metal element in the ZnO core doped with the second metal is 1: (0.05-0.2).

The beneficial effects of the above embodiments of the present application are discussed in the foregoing, and are not described herein again.

A fourth aspect of embodiments of the present application provides a photovoltaic device comprising an electron transport layer disposed between the light emitting layer and the cathode; the electron transport layer contains the electron transport material, the electron transport material prepared by the method, or the electron transport film.

According to the photoelectric device provided by the fourth aspect of the present application, since the electron transport layer includes the electron transport material or the electron transport film having excellent conductivity and electron transport performance, the photoelectric device provided by the embodiment of the present application has high electron transport efficiency; in addition, the zirconium oxide coating layer in the material can block holes from being transmitted to the anode from the light-emitting layer, so that the invalid recombination of electrons and holes in the electronic function layer is avoided, the recombination efficiency of the electrons and the holes in the light-emitting layer is improved, and the light-emitting efficiency of the device is improved.

In some embodiments, the light emitting device of the embodiments of the present application is divided into a positive type structure and a negative type structure.

In one embodiment, a light emitting device of a positive type structure includes a stacked structure of an anode and a cathode which are oppositely disposed, a light emitting layer disposed between the anode and the cathode, and the anode is disposed on a substrate. Further, a hole functional layer such as a hole injection layer, a hole transport layer, an electron blocking layer and the like can be arranged between the anode and the light-emitting layer; an electron-transporting layer, an electron-injecting layer, a hole-blocking layer, and other electron-functional layers may also be provided between the cathode and the light-emitting layer, as shown in fig. 2. In some embodiments of a positive-working device, the light-emitting device comprises a substrate, an anode disposed on a surface of the substrate, a hole transport layer disposed on a surface of the anode, a light-emitting layer disposed on a surface of the hole transport layer, an electron transport layer disposed on a surface of the light-emitting layer, and a cathode disposed on a surface of the electron transport layer.

In one embodiment, an inversion structure light emitting device includes a stacked structure of an anode and a cathode disposed opposite to each other, a light emitting layer disposed between the anode and the cathode, and the cathode disposed on a substrate. Further, a hole functional layer such as a hole injection layer, a hole transport layer, an electron blocking layer and the like can be arranged between the anode and the light-emitting layer; an electron functional layer such as an electron transport layer, an electron injection layer, and a hole blocking layer may be further provided between the cathode and the light emitting layer, as shown in fig. 3. In some embodiments of the device having an inverted structure, the light emitting device includes a substrate, a cathode disposed on a surface of the substrate, an electron transport layer disposed on a surface of the cathode, a light emitting layer disposed on a surface of the electron transport layer, a hole transport layer disposed on a surface of the light emitting layer, and an anode disposed on a surface of the hole transport layer.

In some embodiments, the substrate layer comprises a rigid, flexible substrate, or the like.

In some embodiments, the anode comprises: ITO, FTO, ZTO, or the like.

In some embodiments, the hole injection layer comprises PEODT: PSS (poly (3, 4-ethylenedioxythiophene): poly (styrenesulfonic acid)), WoO₃、MoO₃、NiO、V₂O₅HATCN (2,3,6,7,10, 11-hexacyano-1, 4,5,8,9, 12-hexaazatriphenylene), CuS, and the like.

In some embodiments, the hole transport layer can be either a small organic molecule or a high molecular conductive polymer, including: TFB (Poly [ (9, 9-di-N-octylfluorenyl-2, 7-diyl) -alt- (4,4' - (N- (4-N-butyl) phenyl) -diphenylamine)]) PVK (polyvinylcarbazole), TCTA (4,4 '-tris (carbazol-9-yl) triphenylamine), TAPC (4,4' -cyclohexylbis [ N, N-bis (4-methylphenyl) aniline)]) Poly-TBP, Poly-TPD, NPB (N, N ' -diphenyl-N, N ' - (1-naphthyl) -1,1' -biphenyl-4, 4' -diamine), CBP (4,4' -bis (9-carbazole) biphenyl), peot: PSS, MoO₃、WoO₃、NiO、CuO、V₂O₅CuS, and the like or a mixture of any combination thereof, and can also be other high-performance hole transport materials.

In some embodiments, the light emitting layer includes quantum dot materials therein, including, but not limited to: at least one of the semiconductor compounds of II-IV group, II-VI group, II-V group, III-VI group, IV-VI group, I-III-VI group, II-IV-VI group and II-IV-V group of the periodic table of the elements, or at least two of the semiconductor compounds. In some embodiments, the quantum dot functional layer material is selected from: at least one semiconductor nanocrystal compound of CdSe, CdS, CdTe, ZnO, ZnSe, ZnS, ZnTe, HgS, HgSe, HgTe and CdZnSe, or at least two semiconductor nanocrystal compounds with mixed type, gradient mixed type, core-shell structure type or combined type structures. In other embodiments, the quantum dot functional layer material is selected from the group consisting of: at least one semiconductor nanocrystal compound of InAs, InP, InN, GaN, InSb, InAsP, InGaAs, GaAs, GaP, GaSb, AlP, AlN, AlAs, AlSb, CdSeTe and ZnCdSe, or a semiconductor nanocrystal compound with a mixed type, a gradient mixed type, a core-shell structure type or a combined type of at least two components. In other embodiments, the quantum dot functional layer material is selected from: at least one of a perovskite nanoparticle material (in particular a luminescent perovskite nanoparticle material), a metal nanoparticle material, a metal oxide nanoparticle material. The quantum dot materials have the characteristics of quantum dots and have good photoelectric properties.

In some embodiments, the particle size range of the quantum dot material is 2-10 nm, the particle size is too small, the film forming property of the quantum dot material is poor, the energy resonance transfer effect among quantum dot particles is significant, the application of the material is not facilitated, the particle size is too large, the quantum effect of the quantum dot material is weakened, and the photoelectric property of the material is reduced.

In some embodiments, the material of the electron transport layer comprises the electron transport material described above.

In some embodiments, the cathode comprises: al, Ag, Au, Cu, Mo, or an alloy thereof.

In some embodiments, the fabrication of a light emitting device of embodiments of the present application includes the steps of:

s30, obtaining a substrate deposited with an anode;

s40, growing a hole transport layer on the surface of the anode;

s50, depositing a quantum dot light-emitting layer on the hole transport layer;

and S60, finally, depositing an electron transmission layer on the quantum dot light-emitting layer, and evaporating a cathode on the electron transmission layer to obtain the light-emitting device.

Specifically, in step S30, in order to obtain a high-quality zinc oxide nanomaterial film, the ITO substrate needs to undergo a pretreatment process. The basic specific processing steps include: and cleaning the ITO conductive glass with a cleaning agent to primarily remove stains on the surface, then sequentially and respectively ultrasonically cleaning the ITO conductive glass in deionized water, acetone, absolute ethyl alcohol and deionized water for 20min to remove impurities on the surface, and finally drying the ITO conductive glass with high-purity nitrogen to obtain the ITO anode.

Specifically, in step S40, the step of growing the hole transport layer includes: placing the ITO substrate on a spin coating instrument, and spin coating a prepared solution of the hole transport material to form a film; the film thickness is controlled by adjusting the concentration of the solution, the spin-coating speed and the spin-coating time, and then a thermal annealing process is performed at an appropriate temperature.

Specifically, in step S50, the step of depositing the quantum dot light-emitting layer on the hole transport layer includes: and (3) placing the substrate on which the hole transport layer is coated on a spin coater, spin-coating the prepared luminescent substance solution with a certain concentration to form a film, controlling the thickness of the luminescent layer to be about 20-60 nm by adjusting the concentration of the solution, the spin-coating speed and the spin-coating time, and drying at a proper temperature.

Specifically, in step S60, the step of depositing the electron transport layer on the quantum dot light emitting layer includes: the electron transport layer is an electron transport material of the present application: the substrate which is coated with the quantum dot light emitting layer in a spinning mode is placed on a spinning machine, the electronic transmission material solution with a certain concentration is prepared to be subjected to spin coating film forming through processes of dropping coating, spin coating, soaking, coating, printing, evaporation and the like, the thickness of the electronic transmission layer is controlled by adjusting the concentration of the solution, the spin coating speed (preferably, the rotating speed is 3000-5000 rpm) and the spin coating time to be about 20-60 nm, and then the substrate is annealed to form a film at the temperature of 150-200 ℃, and the solvent is fully removed.

Specifically, in step S60, the step of preparing the cathode includes: and (3) placing the substrate on which the functional layers are deposited in an evaporation bin, and thermally evaporating a layer of 60-100nm metal silver or aluminum as a cathode through a mask plate.

In a further embodiment, the obtained QLED device is subjected to a packaging process, and the packaging process may be performed by a common machine or by a manual method. Preferably, the oxygen content and the water content are both lower than 0.1ppm in the packaging treatment environment to ensure the stability of the device.

In order to make the details and operation of the above-described embodiments of the present invention clearly understandable to those skilled in the art and to make the advanced performances of the electron transport material and the method of manufacturing the same, the electron transport film and the light emitting device of the embodiments of the present invention remarkably manifest, the above-described technical solutions are exemplified by a plurality of embodiments below.

Example 1

An electron transport film comprising the following preparation steps:

adding a proper amount of zinc chloride into 50mL of ethanol to form a solution with the concentration of 0.5M, and stirring and dissolving at 70 ℃. Adding alkali solution (molar ratio, OH) of potassium hydroxide dissolved in 10mL of ethanol^-：Zn²⁺1.8: pH 12, 1). Stirring was continued at 70 ℃ for 4h to give a homogeneous solution. And then, after the solution is cooled, using ethyl acetate to separate out, centrifuging, using a small amount of ethanol to dissolve, repeating the separating out and dissolving steps for 3 times, and drying to obtain the ZnO nanoparticles.

② weighing a proper amount of ZnO in a flask, adding 50M L absolute ethyl alcohol to form a solution with the concentration of 0.5M. 3-Aminopropyltriethoxysilane (APTES) (molar ratio, ZnO: APTES ═ 1: 1) was added to the flask, and the mixture was stirred under an inert atmosphere at room temperature under reflux for 7 hours. And then, separating out the precipitate by using ethyl acetate, centrifuging, dissolving the precipitate in ethanol, and storing for later use to prepare the APTES-ZnO nano-particles.

③ 20mL of ethanol solution (with the concentration of 0.5M) dissolved with APTES-ZnO nanoparticles is taken in a flask, and then 10mL of silver nitrate solution and 5mL of sodium citrate solution (molar ratio, ZnO: Ag) are respectively dripped in sequence at the speed of 10mL/h⁺＝1:0.5，Ag⁺: sodium citrate ═ 1:3), stirred at 40 ℃ for 1 h. And after the reaction is finished, performing centrifugal separation and drying to obtain the ZnO/Ag core-shell nano material.

Fourthly, after the solution is cooled, a spin coater is used for spin coating on the processed substrate and annealing is carried out at 200 ℃, and the electronic transmission film is obtained.

Example 2

An electron transport film comprising the following preparation steps:

first, an appropriate amount of zinc nitrate was added to 50mL of methanol to form a solution having a total concentration of 0.8M. Then dissolved at 60 ℃ with stirring, and then added with an alkaline solution of sodium hydroxide dissolved in 10mL of ethanol (molar ratio, OH)^-：Zn²⁺1.8: pH 12, 1). Stirring was continued at 60 ℃ for 4h to give a homogeneous solution. Subsequently, the solution was separated out with heptane after cooling, centrifuged and dissolved with a small amount of methanol (repeat operation, wash 3 times) to obtain ZnO nanoparticles.

② weighing a proper amount of ZnO in a flask, adding 50M L absolute ethyl alcohol to form a solution with the concentration of 0.8M. Aminopropyltrimethoxysilane (APS) (molar ratio, ZnO: APS ═ 1: 1.5) was added to the flask, and the mixture was stirred at room temperature under an inert atmosphere and refluxed for 8 hours. And then, separating out the precipitate by using heptane, and dissolving the precipitate in ethanol after centrifugation for storage to prepare the APS-ZnO nanoparticles.

③ 20mL of ethanol solution (with the concentration of 0.8M) dissolved with APS-ZnO nanoparticles is put into a flask, and then 10mL of silver nitrate solution and 5mL of sodium borohydride solution (molar ratio, ZnO: Ag) are respectively dripped in turn at the speed of 10mL/h⁺＝1:1，Ag⁺: sodium borohydride ═ 1:4), stirred at 40 ℃ for 1 h. And after the reaction is finished, performing centrifugal separation and drying to obtain the ZnO/Ag core-shell nano material.

Example 3

The preparation method of the electron transmission film is the same as that of the embodiment 1, and the difference is that gold nitrate is dripped in the step III to prepare the ZnO/Au nuclear shell nano material, so that the electron transmission film of the ZnO/Au nuclear shell nano material is prepared.

Example 4

An electron transport film comprising the following preparation steps:

firstly, appropriate amounts of zinc sulfate and tin sulfate are added to 50mL of propanol to form a solution with a total concentration of 1M (molar ratio, Zn)²⁺：Sn⁴⁺1: 0.2). Then dissolved at 80 ℃ with stirring, and then a solution of lithium hydroxide dissolved in 10mL of propanol (molar ratio, OH) is added^-：Zn²⁺+Sn⁴⁺2.5: pH 13, 1). Stirring was continued at 80 ℃ for 2h to give a homogeneous, clear solution. Then, after the solution was cooled, it was precipitated with octane, centrifuged, and dissolved in a small amount of propanol (repeated operation, washing 3 times) to obtain ZnSnO_xAnd (3) nanoparticles.

② weighing appropriate amount of ZnSnO_xIn a flask, 50M L absolute ethanol was added to form a 1M solution. To the flask was added N-aminoethyl-gamma-aminopropyltriethoxysilane (KH-591) (molar ratio, ZnSnO)_x: KH-591 ═ 1: 2) stirring and refluxing for 8h at room temperature under an inert atmosphere. Then, octane is used for separation, and after centrifugation, the precipitate is dissolved in ethanol for storage to prepare KH-591-ZnSnO_xAnd (3) nanoparticles.

③ dissolving KH-591-ZnSnO in 20mL_xEthanol solution of nanoparticles (concentration of 1M) was put in a flask, and then 10mL of silver nitrate solution and 5mL of hydroxylamine hydrochloride solution (molar ratio, ZnSnO) were respectively added dropwise at a rate of 10mL/h in this order_x：Ag⁺＝1:0.8，Ag⁺: hydroxylamine hydrochloride 1:5), stirred at 40 ℃ for 1 h. After the reaction is finished, centrifugal separation and drying are carried out to prepare ZnSnO_xAg core-shell nano material.

Example 5

An electron transport film was prepared in the same manner as in example 4 except that "in the step (r)," appropriate amounts of zinc sulfate and titanium sulfate were added to 50mL of propanol to form a solution (molar ratio, Zn) having a total concentration of 1M²⁺：Ti⁴⁺1:0.2) ", and ZnTiO was obtained_xAnd (3) nanoparticles. Thus preparing ZnTiO through the steps from two to four_xAn electron transmission film of Ag core-shell nano material.

Example 6

An electron transport film was prepared in the same manner as in example 4, except that in the step (i)' appropriate amounts of zinc sulfate and iron sulfate were addedAdded to 50mL of propanol to form a solution with a total concentration of 1M (molar ratio, Zn)²⁺：Fe³⁺1:0.2) ", ZnFeO was obtained_xAnd (3) nanoparticles. Thus preparing ZnFeO through the steps from two to four_xAn electron transmission film of Ag core-shell nano material.

Example 7

An electron transport film was prepared in the same manner as in example 4 except that "in the step (r)," appropriate amounts of zinc sulfate and zirconium sulfate were added to 50mL of propanol to form a solution (molar ratio, Zn) having a total concentration of 1M²⁺：Zr⁴⁺1:0.2) ", and ZnZrO was obtained_xAnd (3) nanoparticles. Step three, gold nitrate is dripped to prepare ZnZrO_xAu core-shell nano material. Thereby obtaining ZnZrO_x/Au nuclear shell nanometer material electron transmission film.

Example 8

An electron transport film was prepared in the same manner as in example 4 except that "in the step (r)," appropriate amounts of zinc sulfate and yttrium sulfate were added to 50mL of propanol to form a solution (molar ratio, Zn) having a total concentration of 1M²⁺：Y³⁺1:0.2) ", to obtain ZnYO_xAnd (3) nanoparticles. Step three, gold nitrate is dripped to prepare ZnYO_xAu core-shell nano material. Thereby obtaining ZnYO_x/Au nuclear shell nanometer material electron transmission film.

Example 9

A 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, an electron transport layer arranged between the cathode and the quantum dot light-emitting layer, and a hole transport layer arranged between the anode and the quantum dot light-emitting layer, wherein the anode is arranged on a substrate. The substrate is made of a glass sheet, the anode is made of an ITO (indium tin oxide) substrate, the hole transport layer is made of a TFB (tunneling glass) material, the quantum dot light emitting layer is made of CdSe, the electron transport layer is made of a ZnO/Ag core-shell nano material, and the cathode is made of Al.

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

providing an ITO substrate, and preparing a hole transport layer on the ITO substrate;

depositing quantum dot luminous layer on the hole transmission layer;

thirdly, depositing the ZnO/Ag nuclear shell nanometer material obtained by the method of the embodiment 1 on the quantum dot light-emitting layer to prepare an electronic transmission layer;

and fourthly, a cathode is arranged on the electron transport layer.

Example 10

The quantum dot light-emitting diode is mainly different from the quantum dot light-emitting diode in the embodiment 9 in that the ZnO/Ag core-shell nano material obtained in the embodiment 2 is adopted as an electron transport layer.

Example 11

A quantum dot light-emitting diode is mainly different from the quantum dot light-emitting diode in the embodiment 9 in that the ZnO/Au core-shell nano material obtained in the embodiment 3 is adopted as an electron transport layer.

Example 12

A quantum dot light emitting diode is different from the quantum dot light emitting diode in the embodiment 9 mainly in that the ZnSnO obtained in the method of the embodiment 4 is adopted as an electron transport layer_xAg core-shell nano material.

Example 13

A quantum dot light emitting diode is different from the quantum dot light emitting diode in the embodiment 9 mainly in that an electron transport layer adopts ZnTiO obtained by the method in the embodiment 5_xAg core-shell nano material.

Example 14

A quantum dot light emitting diode is different from the LED of the embodiment 9 mainly in that the electron transport layer adopts ZnFeO obtained by the method of the embodiment 6_xAg core-shell nano material.

Example 15

A quantum dot light emitting diode is different from the quantum dot light emitting diode in example 9 mainly in that the ZnZrO obtained in the method of example 7 is adopted as an electron transport layer_xAu core-shell nano material.

Example 16

A quantum dot light emitting diode is different from the quantum dot light emitting diode in the embodiment 9 mainly in that an electron transport layer adopts ZnYO obtained by the method in the embodiment 8_xAu core-shell nano material.

Example 17

A 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, an electron transport layer arranged between the cathode and the quantum dot light-emitting layer, and a hole transport layer arranged between the anode and the quantum dot light-emitting layer, wherein the cathode is arranged on a substrate. The substrate is made of a glass sheet, the cathode is made of an ITO (indium tin oxide) substrate, the hole transport layer is made of TFB (thin film transistor), the quantum dot light emitting layer is made of CdSe, the electron transport layer is made of ZnO/Ag core-shell nano materials, and the anode is made of Al.

firstly, providing a cathode substrate, depositing the ZnO/Ag core-shell nano material obtained in the method of the embodiment 1 on the cathode substrate, and preparing an electron transport layer;

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

and thirdly, preparing an anode on the hole transport layer.

Example 18

A quantum dot light emitting diode is different from the quantum dot light emitting diode in the embodiment 7 mainly in that the ZnO/Ag core-shell nano material obtained in the embodiment 2 is adopted as an electron transport layer.

Example 19

A quantum dot light emitting diode is different from the quantum dot light emitting diode in example 7 mainly in that the ZnSnO obtained in the method of example 4 is adopted as an electron transport layer_xAg core-shell nano material.

Comparative example 1

A quantum dot light emitting diode, which is different from example 9 in that the material of the electron transport layer is a commercial ZnO material (available from sigma).

Comparative example 2

An electron transport film was prepared in the same manner as in example 4 except that "in the step (r)," appropriate amounts of zinc sulfate and tin sulfate were added to 50mL of propanol to form a solution (molar ratio, Zn) having a total concentration of 1M²⁺：Sn⁴⁺1:0.5) ", to obtain ZnSnO_xAnd (3) nanoparticles. Thereby passing through the steps ofObtaining ZnSnO_xAn electron transmission film of Ag core-shell nano material.

A quantum dot light emitting diode, which is different from example 9 in that the material of an electron transport layer is Zn prepared in comparative example 2²⁺：Sn⁴⁺1:0.5 ZnSnO_xAg core-shell nano material.

Comparative example 3

An electron transport film was prepared in the same manner as in example 4 except that "in the step (r)," appropriate amounts of zinc sulfate and tin sulfate were added to 50mL of propanol to form a solution (molar ratio, Zn) having a total concentration of 1M²⁺：Sn⁴⁺1:0.02) ", to obtain ZnSnO_xAnd (3) nanoparticles. Thereby preparing ZnSnO through the steps from two to four_xAn electron transmission film of Ag core-shell nano material.

A quantum dot light emitting diode, which is different from example 9 in that the material of an electron transport layer is Zn prepared in comparative example 3²⁺：Sn⁴⁺1:0.02 ZnSnO_xAg core-shell nano material.

Further, the performance of the electron transport films prepared in examples 1 to 8, the electron transport film made of the ZnO material in comparative example 1, and the quantum dot light emitting diodes prepared in examples 9 to 19 and comparative examples 1 to 3 were tested, and the test indexes and the test methods were as follows:

(1) electron mobility: testing the current density (J) -voltage (V) of the quantum dot light-emitting diode, drawing a curve relation diagram, fitting a Space Charge Limited Current (SCLC) region in the relation diagram, and then calculating the electron mobility according to a well-known Child's law formula: j ═ 9/8 epsilon_rε₀μ_eV²/d³；

Wherein J represents current density in mAcm^-2；ε_rDenotes the relative dielectric constant,. epsilon₀Represents the vacuum dielectric constant; mu.s_eDenotes the electron mobility in cm²V^-1s^-1(ii) a V represents the drive voltage, in units of V; d represents the film thickness in m.

(2) Resistivity: the resistivity of the electron transport film is measured by the same resistivity measuring instrument.

(3) External Quantum Efficiency (EQE): measured using an EQE optical test instrument.

Note: the electron mobility and resistivity were tested as single layer thin film structure devices, namely: cathode/electron transport film/anode. QLED device for external quantum efficiency test, namely: anode/hole transport film/quantum dot/electron transport film/cathode, or cathode/electron transport film/quantum dot/hole transport film/anode.

The test results are shown in table 1 below:

TABLE 1

As can be seen from the test results in Table 1, the samples provided in examples 1-8 of the present application are ZnO/Ag, ZnO/Au, ZnSnO_x/Ag、ZnTiO_x/Ag、ZnFeO_x/Ag、ZnZrO_x/Au、ZnYO_xThe resistivity of the electron transmission film made of the Au nuclear shell nanometer material is obviously lower than that of the electron transmission film made of the ZnO nanometer material in the comparative example 1, and the electron mobility of the electron transmission film made of the ZnO nanometer material in the comparative example 1 is obviously higher than that of the electron transmission film made of the ZnO nanometer material in the comparative example 1. In addition, the electron transport thin films of the core-shell nanomaterial in which the ZnO cores are doped with the second metal such as tin, titanium, iron, zirconium, and yttrium in examples 3 to 8 have higher electron mobility and lower resistivity than the undoped electron transport thin films in examples 1 to 3, which shows that the electron transport efficiency of the material is effectively improved after the ZnO cores are doped with the metal such as tin, titanium, iron, zirconium, and yttrium.

Quantum dot light-emitting diodes (electron transport layer materials ZnO/Ag, ZnO/Au, ZnSnO) provided in embodiments 9 to 19 of the present invention_x/Ag、ZnTiO_x/Ag、ZnFeO_x/Ag、ZnZrO_x/Au、ZnYO_xAu nuclear shell nano material) is obviously higher than that of the quantum dot light-emitting diode made of the ZnO nano material in the comparative example 1, and the quantum dot light-emitting diode obtained in the embodiment has better luminous efficiency. Also, examples 12 to 16 Quantum dot light emitting diodes have an electron transport layerCompared with undoped quantum dot light-emitting diodes in examples 9-11, the medium ZnO core is doped with second metals such as tin, titanium, iron, zirconium, yttrium, and the like, and has higher external quantum efficiency, which indicates that after the ZnO core is doped with metals such as tin, titanium, iron, zirconium, yttrium, and the like, the electron transfer efficiency is improved, and thus the light-emitting efficiency of the device is further improved.

In addition, as can be seen from the comparison between example 4 and comparative examples 2 and 3, when the second metal is doped too much or too little in the ZnO core, the electron transfer efficiency of the thin film is also reduced, and the resistivity is increased. It can be seen from the comparison of example 12 with comparative examples 2 and 3 that when the second metal is doped too much or too little in the ZnO core, the external quantum efficiency of the quantum dot light emitting diode is also reduced.

It is noted that the embodiments provided herein all use blue quantum dots Cd_XZn_1-XS/ZnS is used as a material of a luminescent layer, is based on that a blue light luminescent system uses more systems (the blue light quantum dot luminescent diode has more reference value because high efficiency is difficult to achieve), and does not represent that the invention is only used for the blue light luminescent system. The above description is only exemplary of the present application and should not be taken as limiting the present application, as any modification, equivalent replacement, or improvement made within the spirit and principle of the present application should be included in the protection scope of the present application.

Claims

1. The electron transport material is characterized by having a core-shell structure and comprising a ZnO core and a precious metal shell layer coating the ZnO core.

2. The electron transport material of claim 1, wherein the noble metal shell layer has a thickness of 1 nm to 2 nm; and/or

The grain diameter of the ZnO core is 4-8 nanometers; and/or

The ZnO core is doped with a second metal, and the valence state of the second metal is + 3- + 4.

3. The electron transport material of claim 2, wherein the second metal is selected from the group consisting of: at least one of tin, titanium, iron, zirconium, yttrium; and/or

In the second metal-doped ZnO core, the molar ratio of the zinc element to the second metal element is 1: (0.05-0.2).

4. The electron transport material according to any one of claims 1 to 3, wherein in the electron transport material, the noble metal shell layer is bonded to the surface of the ZnO core by a silane coupling agent; and/or

The noble metal shell layer includes: ag and/or Au.

5. The electron transport material according to claim 4, wherein the electron transport material is composed of the ZnO core and the noble metal shell layer covering the ZnO core; wherein the noble metal shell layer is Ag and/or Au.

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

obtaining a zinc oxide nano material;

7. The method for preparing an electron transport material according to claim 6, wherein the step of obtaining the zinc oxide nanomaterial comprises: dissolving a first zinc salt and a first alkaline substance in a third organic solvent, reacting for 2-4 hours at the temperature of 60-80 ℃, and separating to obtain a zinc oxide nano material; or

The method for obtaining the zinc oxide nano material comprises the following steps: dissolving a second zinc salt, a second metal salt and a second alkaline substance in a fourth organic solvent, reacting for 2-4 hours at the temperature of 60-80 ℃, and separating to obtain a zinc oxide nano material doped with a transition metal second metal; the ionic valence of the second metal is + 3- + 4; and/or

The conditions of the coupling reaction include: reacting for 6-8 hours at the temperature of 20-40 ℃; and/or

The conditions of the coating reaction include: reacting for 1-2 hours at 40-50 ℃.

8. The method for preparing an electron transport material according to claim 7, wherein the first zinc salt and the second basic substance are dissolved in the third organic solvent, the reaction system has a pH of 12 to 13, and the molar ratio of the first zinc salt to the second basic substance is 1: (1.8-2.5); and/or

Dissolving the second zinc salt, the second metal salt and the second basic substance in the fourth organic solvent, wherein the pH value is 12-13, and the ratio of the total molar amount of the second zinc salt and the second metal salt to the molar amount of the second basic substance is 1: (1.8-2.5); and/or

The molar ratio of the second zinc salt to the second metal salt is 1: (0.05-0.2); and/or

The silane coupling agent and the zinc oxide nano material have a molar ratio of (1-2): 1; and/or

The modified zinc oxide nano material, the noble metal precursor and the reducing agent have a molar ratio of (1-2): 1: (3-5).

9. The method for producing an electron transport material according to claim 8, wherein the silane coupling agent is selected from the group consisting of: at least one of an aminosilane coupling agent, a mercaptosilane coupling agent, and a vinylsilane coupling agent; and/or

The noble metal precursor is selected from: at least one of silver nitrate, gold chloride and gold bromide; and/or

The reducing agent is selected from: at least one of sodium citrate, sodium borohydride and hydroxylamine hydrochloride; and/or

The second metal salt is selected from: at least one of titanium salt, tin salt, iron salt, zirconium salt and yttrium salt; and/or

The first zinc salt and the second zinc salt are respectively and independently selected from the group consisting of: at least one of zinc acetate, zinc nitrate, zinc chloride, zinc sulfate, zinc acetate dihydrate; and/or

The first and second basic substances are each independently selected from: at least one of ammonia water, potassium hydroxide, sodium hydroxide, lithium hydroxide, ethanolamine, ethylene glycol, diethanolamine, triethanolamine and ethylenediamine; and/or

The first, second, third, and fourth organic solvents are each independently selected from: at least one of isopropanol, ethanol, propanol, butanol, and methanol.

10. The method for producing an electron transport material according to claim 9, wherein the silane coupling agent is selected from the group consisting of: at least one of 3-aminopropyltriethoxysilane, aminopropyltrimethoxysilane, N-aminoethyl-gamma-aminopropyltriethoxysilane, phenylaminomethyltriethoxysilane, 3-mercaptopropyl-trimethoxysilane, vinyltriethoxysilane, and 3- [ 3-carboxyallylamido ] propyltriethoxysilane; and/or

The titanium salt is selected from: at least one of titanium acetate, titanium tetrachloride, titanium nitrate, titanium sulfate and tetrabutyl titanate; and/or

The tin salt is selected from: at least one of tin nitrate, tin chloride, tin sulfate, tin methane sulfonate, tin ethane sulfonate and tin propane sulfonate; and/or

The iron salt is selected from: at least one of ferric nitrate, ferric sulfate, ferric chloride and ferric acetate; and/or

The zirconium salt is selected from: at least one of zirconium nitrate, zirconium sulfate and zirconium chloride; and/or

The yttrium salt is selected from: at least one of yttrium nitrate, yttrium sulfate and yttrium chloride.

11. An optoelectronic device comprising an electron transport layer comprising an electron transport material according to any of claims 1 to 5 or comprising an electron transport material prepared by a process according to any of claims 6 to 10.