WO2021129706A1

WO2021129706A1 - Nanomaterial and preparation method therefor, quantum dot light-emitting diode and preparation method therefor

Info

Publication number: WO2021129706A1
Application number: PCT/CN2020/138838
Authority: WO
Inventors: 何斯纳; 吴龙佳; 吴劲衡
Original assignee: Tcl科技集团股份有限公司
Priority date: 2019-12-27
Filing date: 2020-12-24
Publication date: 2021-07-01
Also published as: CN113044875A

Abstract

A nanomaterial, comprising a ZnO nanomaterial and a doped element which is doped in a ZnO lattice, and is an Er element and an Yb element. By co-doping the Er element and the Yb element in the nanomaterial, the electron transport capability of the ZnO nanomaterial is improved. When the nanomaterial is used as an electron transport layer of a quantum dot light-emitting diode, the effective recombination of electrons and holes in a quantum dot light-emitting layer can be promoted, thereby reducing the influence of the accumulation of excitons on the performance of a device, and improving the light-emitting efficiency of a quantum dot light-emitting device.

Description

Nano material and preparation method thereof, quantum dot light-emitting diode and preparation method thereof

This application requires the Chinese Patent Application No. filed on December 27, 2019. The priority of 201911376470.7, the entire content of which is incorporated in this application by reference.

Technical field

This application relates to the field of display technology, in particular to a nano material and a preparation method thereof, and a quantum dot light-emitting diode and a preparation method thereof.

Background technique

ZnO is a direct band gap n-type semiconductor material with a wide band gap of 3.37 eV and a low work function of 3.7 eV. This energy band structure determines that ZnO can be a suitable electron transport layer material. Element-doped ZnO can change the electrical and optical properties of semiconductor materials, and can also further improve the various physical properties of nanomaterials. Doping with elements can adjust the forbidden band width, conductivity and enhance transmittance to a certain extent. The adjustable band gap provides good conditions for improving the performance of devices, such as quantum dot light emitting diodes, quantum dot laser diodes and so on. However, currently, the source of element-doped ZnO is single, and most of the element-doped ZnO is usually directly prepared in the film forming process, and the synthesis process is complicated.

technical problem

One of the objectives of the embodiments of the present application is to provide a nano material and a preparation method thereof, and a quantum dot light-emitting diode and a preparation method thereof, aiming to solve the problem of a single source of doped ZnO and a complicated preparation method.

Technical solutions

In order to solve the above technical problems, the technical solutions adopted in the embodiments of this application are:

In a first aspect, a nanomaterial is provided. The nanomaterial includes a ZnO nanomaterial and a doping element doped in a ZnO lattice, and the doping element is an Er element and a Yb element.

In the second aspect, a method for preparing nanomaterials is provided, which includes the following steps:

Dissolve zinc salt, erbium salt and ytterbium salt in an organic solvent to prepare a mixed solution of zinc salt, erbium salt and ytterbium salt;

A base is added to the mixed solution and heated to react to prepare a zinc oxide nanomaterial co-doped with Er element and Yb element, wherein the base is selected from organic bases or inorganic bases that can generate hydroxide ions in the reaction system .

In a third aspect, a quantum dot light-emitting diode is provided, comprising a cathode and an anode disposed oppositely, a quantum dot light-emitting layer disposed between the cathode and the anode, and a quantum dot light-emitting layer between the cathode and the quantum dot light-emitting layer. The electron transport layer is arranged in between, and the material of the electron transport layer includes ZnO nanomaterials and doping elements doped in the ZnO lattice, and the doping elements are Er elements and Yb elements.

In a fourth aspect, a method for manufacturing a quantum dot light-emitting diode is provided, which includes the following steps:

Provide substrate;

The zinc salt, erbium salt and ytterbium salt are dissolved in an organic solvent to prepare a mixed solution of zinc salt, erbium salt and ytterbium salt; an alkali is added to the mixed solution, and the reaction is heated to prepare a precursor solution, wherein the alkali Selected from organic bases or inorganic bases that can generate hydroxide ions in the reaction system;

After depositing the precursor solution on the surface of the substrate, annealing is performed to obtain an electron transport layer.

Beneficial effect

According to the nanomaterial of the present application, the injection balance of electrons and holes can be promoted, the luminous efficiency of the device can be improved, the influence of the accumulation of excitons on the performance of the device can be reduced, and the performance of the QLED can be finally improved.

Description of the drawings

FIG. 1 is a schematic diagram of the preparation process of nanomaterials provided by an embodiment of the present application;

Fig. 2 is a schematic diagram of the preparation of a quantum dot light-emitting diode provided by an embodiment of the present application.

Embodiments of the present invention

In order to make the purpose, technical solutions, and advantages of this application clearer and clearer, the following further describes the application in detail with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described here are only used to explain the application, and are not used to limit the application.

One aspect of the embodiments of the present application provides a nanomaterial, the nanomaterial includes a ZnO nanomaterial and a doping element doped in a ZnO lattice, and the doping element is an Er element and a Yb element.

The nano materials provided in the embodiments of the present application include ZnO nano materials and Er elements and Yb elements doped in a ZnO lattice. Among them, Er element doping can improve the photoelectric trapping ability of the material and the electron donating ability of nanomaterials; on this basis, Yb ³⁺ can sensitize Er ³⁺ , reduce the difficulty of Er energy level transition, and further improve Er ³⁺ The ability to donate electrons to ZnO. In addition, since the positions of the top and bottom of the valence band of ZnO nanomaterials are determined by the 2p orbitals of O atoms and the 3d orbitals of Zn atoms, respectively, Er ³⁺ and Yb ³⁺ have abundant 4f electrons. Therefore, after Er element and Yb element are doped into the ZnO lattice, they will induce the rearrangement of molecular orbitals, and move the bottom of the conduction band of ZnO toward the vacuum level, realizing the band gap of ZnO from 3.40 eV to 4.50. The eV is continuously adjustable, so that when the nanomaterial is used as the electron transport layer of the quantum dot light-emitting diode, the injection barrier of the electron vector dot light-emitting layer can be reduced, the injection balance of electrons and holes can be promoted, and the luminous efficiency of the device can be improved , Reduce the impact of exciton accumulation on device performance, and ultimately improve the performance of QLEDs.

In summary, the embodiment of the present application utilizes Er ³⁺ and Yb ^{3+ to} dope ZnO cooperatively to adjust the band gap, conductivity, and the like. In summary, through the co-doping of Er element and Yb element, the forbidden band width and conductivity of ZnO nanomaterials are adjusted, thereby improving the electron transport ability of ZnO nanomaterials. When the nano material is used as the electron transport layer of the quantum dot light-emitting diode, it can promote the effective recombination of electrons and holes in the quantum dot light-emitting layer, thereby reducing the influence of exciton accumulation on the device performance, and improving the luminescence of the quantum dot light-emitting device effectiveness.

In the examples of this application, the doping amount of the doping elements, namely the Er element and the Yb element, has a greater impact on the performance of the obtained doped nanomaterials, especially when the doped ZnO nanomaterials are used as quantum dots. The material of the electron transport layer of the light emitting diode will directly affect the performance of the electron transport layer. Specifically, the nano material is composed of a ZnO nano material and the doping element, and the molar ratio of the zinc element to the doping element is 1:0.1 to 0.2. When the doping ratio of the doping element, that is, the Er element and the Yb element is too high, exceeding the molar ratio of 1:0.2, the Er element and the Yb element enter the crystal lattice of ZnO, which may cause The expansion of the crystal lattice produces larger lattice distortion and strain energy, that is, the increase of the doping amount will cause the sudden change of the crystal lattice; at the same time, the excess of the Er element and the Yb element form a new phase, such as Er ₂ O _3. The formation of Yb ₂ O ₃ changes the properties of ZnO nanomaterials. When the doping ratio of the doping element, that is, the Er element and the Yb element, is too low, less than 1:0.1, the content of the Er element and the Yb element is too low, and the reaction process itself A certain loss will also occur, resulting in the inability to achieve effective doping, that is, the co-doping of Er element and Yb element cannot adjust the forbidden band width and conductivity of ZnO nanomaterials, thereby improving the electron transmission of ZnO nanomaterials ability.

In the embodiments of the present application, the Er element is more critical for adjusting the band gap of the ZnO nanomaterial. Specifically, the Er element doping can improve the photoelectric trapping ability of the material and improve the electron donating ability of the nanomaterial. Therefore, the doping amount of the Er element is greater than the doping amount of the Yb element. In some embodiments, in the nanomaterial, the molar ratio of the Er element to the Yb element is 2 to 3:1, and the molar ratio of the Er element to the Yb element is within this range, It can promote the sensitization of the Yb element to the Er element, and further strengthen the electron donating ability of the Er element.

The nanomaterials provided in the examples of this application can be prepared by the following methods.

Correspondingly, in conjunction with FIG. 1, the second aspect of the embodiments of the present application provides a method for preparing nanomaterials, including the following steps:

S01. Dissolve zinc salt, erbium salt and ytterbium salt in an organic solvent to prepare a mixed solution of zinc salt, erbium salt and ytterbium salt;

S02. Add an alkali to the mixed solution and heat to react to prepare a zinc oxide nanomaterial co-doped with Er element and Yb element, wherein the alkali is selected from organic bases that can generate hydroxide ions in the reaction system or Inorganic base.

The preparation method of the nano material provided in the examples of this application only needs to dissolve the zinc salt, the erbium salt and the ytterbium salt in an organic solvent, and then add a base to react. The method is simple to operate and easy to realize large-scale preparation. More importantly, the nanomaterial prepared by the method provided in the embodiments of the application can improve the electron transport ability, promote the effective recombination of electrons and holes in the quantum dot light-emitting layer, reduce the impact of exciton accumulation on device performance, and improve Quantum dot light-emitting layer performance.

Specifically, in the above step S01, zinc salt, erbium salt, and ytterbium salt for preparing the nanomaterial are provided, wherein the zinc salt is used as the zinc source of the ZnO nanomaterial in the nanomaterial, and the erbium The salt serves as the erbium source of the nanomaterial, and the ytterbium salt serves as the ytterbium source of the nanomaterial.

The zinc salt, erbium salt, and ytterbium salt are selected from the group that can be dissolved in an organic solvent, and in the organic solvent environment, the zinc ion in the zinc salt, the erbium ion in the erbium salt, and the ytterbium ion in the ytterbium salt can be The hydroxide ions provided by the alkali react and grow into a metal salt of nanocrystalline grains.

In the embodiment of the present application, the zinc salt is selected from at least one of zinc acetate, zinc nitrate, zinc chloride, zinc sulfate, and zinc acetate dihydrate, but is not limited thereto. In some embodiments, the zinc salt is selected from one of zinc acetate, zinc nitrate, zinc chloride, zinc sulfate, and zinc acetate dihydrate. In some embodiments, the zinc salt is selected from zinc acetate and zinc nitrate, zinc acetate and zinc chloride, zinc acetate and zinc sulfate, zinc acetate and zinc acetate dihydrate, zinc nitrate and zinc chloride. In some embodiments, the zinc salt is selected from zinc nitrate and zinc chloride and zinc sulfate, zinc acetate and zinc acetate and zinc nitrate dihydrate.

In the embodiment of the present application, the erbium salt is selected from at least one of erbium nitrate, erbium chloride, and erbium sulfate, but is not limited thereto. In some embodiments, the erbium salt is selected from one of erbium nitrate, erbium chloride, and erbium sulfate. In some embodiments, the erbium salt is selected from erbium nitrate and erbium chloride, erbium nitrate and erbium sulfate, or erbium chloride and erbium sulfate. In some embodiments, the erbium salt is selected from erbium nitrate, erbium chloride and erbium sulfate.

In the embodiment of the present application, the ytterbium salt is selected from at least one of ytterbium nitrate, ytterbium chloride, and ytterbium sulfate, but is not limited thereto. In some embodiments, the ytterbium salt is selected from one of ytterbium nitrate, ytterbium chloride, and ytterbium sulfate. In some embodiments, the ytterbium salt is selected from ytterbium nitrate and ytterbium chloride, ytterbium nitrate and ytterbium sulfate, or ytterbium chloride and ytterbium sulfate. In some embodiments, the ytterbium salt is selected from ytterbium nitrate, ytterbium chloride, and ytterbium sulfate.

In the examples of this application, zinc salt, erbium salt and ytterbium salt are dissolved in an organic solvent to prepare a mixed solution of zinc salt, erbium salt and ytterbium salt. In some embodiments, the zinc salt, erbium salt, and ytterbium salt are dissolved in an organic solvent to form a mixed solution of the three; in some embodiments, the zinc salt, erbium salt, and ytterbium salt are separately dissolved in an organic solvent. , The three solutions are mixed to form a mixed solution of the three; in some embodiments, after one of the zinc salt, erbium salt and ytterbium salt is dissolved, other metal salts are added to prepare zinc salt, erbium salt and A mixed solution of ytterbium salt; in some embodiments, after dissolving two of the zinc salt, erbium salt, and ytterbium salt, other metal salts are added to prepare a mixed solution of zinc salt, erbium salt, and ytterbium salt.

In some embodiments, the organic solvent is an organic alcohol solvent. The organic alcohol solvent not only has good solubility for the zinc salt, erbium salt and ytterbium salt listed above, but also is relatively mild as a reaction medium, which provides for the reaction of metal salt ions with alkali to grow into nanocrystalline particles. Good reaction environment. In some embodiments, the organic solvent is selected from at least one of isopropanol, ethanol, propanol, butanol, pentanol, and hexanol, but is not limited thereto.

Specifically, the zinc salt, erbium salt, and ytterbium salt are dissolved in an organic solvent, and the dissolution of the metal salt can be promoted by stirring at a constant temperature to prepare a mixed solution of the zinc salt, erbium salt and ytterbium salt. In some embodiments, the constant temperature stirring is performed at a temperature of 60°C to 80°C. This temperature can generally prevent the volatilization of the organic solvent that dissolves the metal salt, and can also promote the rapid dissolution of the zinc salt, erbium salt, and ytterbium salt.

In the embodiment of the present application, in the step of preparing a mixed solution of zinc salt, erbium salt and ytterbium salt, the zinc salt, erbium salt and ytterbium salt are mixed according to the molar ratio of zinc ion and doping element ion of 1:0.1 to 0.2 The salt is dissolved in an organic solvent to prepare a mixed solution of zinc salt, erbium salt and ytterbium salt, which is conducive to preparing composite materials with appropriate erbium and ytterbium doping content and significantly increased electron transport performance. When the ratio of the Er element and the Yb element is too high, exceeding the molar ratio of 1:0.2, during the reaction with alkali, the Er element and the Yb element enter the crystal lattice of ZnO, which will cause crystals. The expansion of the lattice produces larger lattice distortion and strain energy, that is, the increase of the doping amount will cause the sudden change of the lattice; at the same time, the excess of the Er element and the Yb element form a new phase, such as Er ₂ O ₃ , _{The formation of Yb 2} O ₃ , which in turn changes the properties of ZnO nanomaterials. When the doping element, that is, the doping ratio of the Er element and the Yb element is too low, less than 1:0.1, the content of the Er element and the Yb element is too low, and during the heating reaction process A certain loss will occur in itself, resulting in the inability to achieve effective doping, that is, the co-doping of Er element and Yb element cannot adjust the band gap and conductivity of ZnO nanomaterials, thereby improving the electrons of ZnO nanomaterials. Transmission capacity.

In some embodiments, in the step of the mixed solution of the erbium salt and the ytterbium salt, the zinc salt, the erbium salt and the ytterbium salt are dissolved according to the molar ratio of the Er element and the Yb element of 2 to 3:1 In an organic solvent, a mixed solution of zinc salt, erbium salt and ytterbium salt is prepared. The molar ratio of the Er element and the Yb element is within this range. In the prepared composite material, the molar ratio of the Yb element to the Er element is within a suitable range, so as to promote the Yb element to the The sensitization of the Er element further strengthens the electron donating ability of the Er element.

Specifically, in the above step S02, a base is added to the mixed solution, and the base is selected from organic bases or inorganic bases that can generate hydroxide ions in the reaction system. On the one hand, the hydroxide ion provided by the alkali acts as an oxygen source, and reacts with the zinc ion in the zinc salt, the erbium ion in the erbium salt, and the ytterbium ion in the ytterbium salt under alkaline conditions to prepare erbium , Ytterbium is co-doped into the nanomaterials inside the ZnO crystal core; on the other hand, the alkali provides suitable alkaline reaction conditions for the reaction of metal ions and hydroxide ions.

In some embodiments, an alkali is added to the mixed solution, and in the step of heating the reaction, the molar ratio of the sum of the zinc ions and the doping element ions to the hydroxide ions provided by the alkali is 1:1.8~ 2.5. Based on the above step S01, the molar ratio of zinc element and the doping element (erbium, ytterbium) is 1:0.1~0.2, when the sum of the zinc ion, the doping element ion and the hydroxide provided by the alkali When the molar ratio of ions is 1:1.8~2.5, not only can the reaction of metal ions and alkali be controlled, and the reaction of zinc atoms with alkali to form ZnO nuclei is the main factor, but also the doping content of doping elements (erbium, ytterbium) can be controlled Within a suitable range, a doped nanomaterial can be obtained in which the nanomaterial as a whole reflects the properties of the ZnO nanomaterial, but the forbidden band width and conductivity are improved. When the content of the alkali is too high, and the molar ratio of the sum of the zinc ions, doping element ions and the hydroxide ions provided by the alkali is not in the range of 1:1.8~2.5, the pH of the liquid will be too high. Reduce the reaction rate of metal ions and hydroxide ions provided by alkali in the reaction system; and because too many hydroxide ions provide a greater possibility for the reaction of doping elements (erbium, ytterbium), and reduce zinc The competitive advantage of the reaction between ions and hydroxide ions is not conducive to controlling the doping ratio of erbium and ytterbium. If the content of the alkali is too low, and the molar ratio of the sum of the zinc ions and the doping element ions to the hydroxide ions provided by the alkali is not in the range of 1:1.8~2.5, the hydrogen provided by the alkali The oxygen radical ions are limited, and the excessive metal ions cannot fully react, resulting in the doping ions (erbium, ytterbium) not being completely doped, affecting the doping ratio of the doping ions (erbium, ytterbium) in the final composite material, and ultimately affecting The effect of adjusting the forbidden band width and conductivity of nanomaterials.

In the embodiments of the present application, the base is selected from organic bases or inorganic bases that can provide hydroxide ions and can adjust the pH of the reaction system to 12-13. Specifically, the base is selected from at least one of ammonia, potassium hydroxide, sodium hydroxide, lithium hydroxide, ethanolamine, ethylene glycol, diethanolamine, triethanolamine, and ethylenediamine, but is not limited thereto. In some embodiments, the base is selected from one of ammonia, potassium hydroxide, sodium hydroxide, lithium hydroxide, ethanolamine, ethylene glycol, diethanolamine, triethanolamine, and ethylenediamine. In some embodiments, the base is selected from ammonia and ethylenediamine, diethanolamine and triethanolamine, potassium hydroxide and sodium hydroxide, ethylenediamine and ethanolamine, ethylenediamine and ethylene glycol. In some embodiments, the base is selected from ammonia water and ethylenediamine and ethylene glycol, diethanolamine and triethanolamine and ethanolamine, potassium hydroxide and sodium hydroxide and lithium hydroxide.

In the embodiment of the present application, in the step of adding an alkali to the mixed solution and heating the reaction, the temperature of the heating treatment is not higher than the boiling point temperature of the organic solvent. In some embodiments, the heating reaction is achieved by constant temperature stirring. In some embodiments, the step of adding alkali to the mixed solution and heating the reaction is carried out at a temperature of 60°C to 80°C, and the reaction time is 2h to 4h. Under this temperature condition, it is beneficial to dope erbium ions and ytterbium ions into the inside of the ZnO crystal core to obtain erbium and ytterbium co-doped zinc oxide nanomaterials.

After the completion of the reaction, the liquid phase system is cooled to room temperature. The room temperature mentioned in the embodiments of the present application refers to an indoor temperature of 10°C to 35°C. Then, sedimentation is performed to precipitate zinc oxide nanocrystals co-doped with erbium and ytterbium, and the sediments are collected, washed and dried to obtain nanomaterials. The settling treatment can be achieved by adding a precipitant. The precipitating agent is a weakly polar and non-polar solvent, such as ethyl acetate, heptane, octane, etc., but not limited thereto.

As another embodiment, the solution obtained after the reaction can be further prepared into a film to obtain an electron transport film. Specifically, the solution obtained after the reaction is deposited on a substrate, and an electron transport film is prepared by annealing. The specific process can refer to the preparation of the electron transport layer in the preparation method of the quantum dot light-emitting diode.

The third aspect of the embodiments of the present application provides a quantum dot light-emitting diode, which includes a cathode and an anode disposed oppositely, a quantum dot light-emitting layer disposed between the cathode and the anode, and a quantum dot light-emitting layer between the cathode and the quantum dot An electron transport layer is provided between the electron transport layer, and the material of the electron transport layer includes ZnO nanomaterials and doping elements doped in the ZnO lattice, and the doping elements are Er elements and Yb elements.

The quantum dot light-emitting diode provided by the embodiments of the present application uses the aforementioned Er element and Yb element co-doped ZnO nanomaterial as the electron transport layer material. Because Er element and Yb element co-doping can improve the electron donating ability of ZnO nanomaterials, and adjust the forbidden band width, conductivity, etc., therefore, the above-mentioned Er element and Yb element co-doped ZnO nanomaterials are used as The material of the electron transport layer can improve the electron transport ability, promote the effective recombination of electrons and holes in the quantum dot light-emitting layer, thereby reducing the influence of exciton accumulation on the performance of the device and improving the performance of the quantum dot light-emitting layer.

The material of the electron transport layer in the embodiments of the present application is the aforementioned nanomaterial, and the specific principle of using the material of the electron transport layer to improve the electron transport performance of the device is as described above. In order to save space, it will not be repeated here.

In some embodiments, the material of the electron transport layer is composed of a ZnO nanomaterial and the doping element, and the molar ratio of the zinc element to the doping element is 1:0.1~0.2. When the doping ratio of the doping element, that is, the Er element and the Yb element is too high, exceeding the molar ratio of 1:0.2, the Er element and the Yb element enter the crystal lattice of ZnO, which may cause The expansion of the crystal lattice produces larger lattice distortion and strain energy, that is, the increase of the doping amount will cause the sudden change of the crystal lattice; at the same time, the excess of the Er element and the Yb element form a new phase, such as Er ₂ O _3. The formation of Yb ₂ O ₃ changes the properties of ZnO nanomaterials. When the doping ratio of the doping element, that is, the Er element and the Yb element, is too low, less than 1:0.1, the content of the Er element and the Yb element is too low, and the reaction process itself A certain loss will also occur, resulting in the inability to achieve effective doping, that is, the co-doping of Er element and Yb element cannot adjust the forbidden band width and conductivity of ZnO nanomaterials, thereby improving the electron transmission of ZnO nanomaterials ability.

The Er element is more critical for adjusting the forbidden band width of the ZnO nanomaterial. Specifically, the Er element doping can improve the photoelectric trapping ability of the material and improve the electron donating ability of the nanomaterial. Therefore, the doping amount of the Er element is greater than the doping amount of the Yb element. In some embodiments, in the nanomaterial, the molar ratio of the Er element to the Yb element is 2 to 3:1, and the molar ratio of the Er element to the Yb element is within this range, It can promote the sensitization of the Yb element to the Er element, and further strengthen the electron donating ability of the Er element.

Specifically, the quantum dot light emitting diodes described in the embodiments of the present application are divided into positive structure quantum dot light emitting diodes and inverted structure quantum dot light emitting diodes. Among them, the positive structure is a substrate/anode/quantum dot light-emitting layer/electron transport layer/cathode, and optionally arranged between the anode and the quantum dot light-emitting layer such as a hole injection layer, a hole transport layer, and an electron blocking layer. The hole function layer such as the layer, the electron injection layer arbitrarily disposed between the electron transport layer and the cathode, and so on. The inverted structure is opposite to the positive structure.

Specifically, the choice of the anode is not strictly limited. For example, ITO can be selected, but it is not limited thereto. The thickness of the anode is 15-30 nm.

The material of the quantum dot light-emitting layer can be a conventional quantum dot type, for example, it can be Cd _X Zn _1-X S/InS or the like. The thickness of the quantum dot light-emitting layer is 20-60 nm.

The cathode can be selected from conventional cathode materials, for example, metal Al can be used. The thickness of the cathode is 15-30 nm.

The material of the hole transport layer is selected from, for example, TFB and PVK.

In some embodiments, the quantum dot light emitting diode may further include an encapsulation layer. The encapsulation layer can be provided on the surface of the top electrode (the electrode far from the substrate), or can be provided on the entire surface of the quantum dot light-emitting diode.

The quantum dot light-emitting diode provided in the embodiments of the present application can be prepared by the following method.

With reference to FIG. 2, the fourth aspect of the embodiments of the present application provides a method for manufacturing a quantum dot light-emitting diode, which includes the following steps:

E01. Provide substrate;

E02. Dissolve zinc salt, erbium salt, and ytterbium salt in an organic solvent to prepare a mixed solution of zinc salt, erbium salt and ytterbium salt; add alkali to the mixed solution, and heat the reaction to prepare a precursor solution, where The base is selected from organic bases or inorganic bases that can generate hydroxide ions in the reaction system;

E03. After depositing the precursor solution on the surface of the substrate, annealing is performed to obtain an electron transport layer.

In the method for preparing a quantum dot light-emitting diode provided in the embodiments of the present application, the precursor solution formed by the reaction of zinc salt, erbium salt and ytterbium salt with alkali is deposited on the surface of the substrate and then annealed to prepare the electron transport layer. The material of the obtained electron transport layer is a ZnO nanomaterial co-doped with Er element and Yb element. Therefore, the quantum dot light-emitting diode prepared in this application can improve the electron transport ability and promote the effective electron-hole in the quantum dot light-emitting layer. Ground recombination, thereby reducing the impact of exciton accumulation on device performance, and improving the performance of the quantum dot light-emitting layer. In addition, the method only needs to change the material of the electron transport layer on the basis of the conventional quantum dot light-emitting diode manufacturing method, the operation is simple, and the process is mature and reliable.

Specifically, in the above step E01, for the positive structure quantum dot light emitting diode, the bottom electrode provided on the substrate is the anode, that is, the substrate includes at least an anode substrate. In some embodiments of the present application, the substrate is an anode substrate provided with an anode on the substrate. In some embodiments of the present application, the substrate may also be a laminated substrate in which an anode is provided on the substrate and a hole injection layer is provided on the surface of the anode. It should be understood that the present application is not limited to the structure of the above-mentioned embodiments.

In the above step E01, for a quantum dot light emitting diode with an inversion structure, the bottom electrode provided on the substrate is a cathode, that is, the substrate at least contains a cathode substrate. In some embodiments of the present application, the substrate is a cathode substrate provided with a cathode on the substrate. In still other embodiments of the present application, the substrate may also be a laminated substrate in which a cathode is provided on the substrate and an electron injection layer is provided on the surface of the cathode. It should be understood that the present application is not limited to the structure of the above-mentioned embodiments.

For the positive structure quantum dot light emitting diode, the bottom electrode provided on the substrate is the anode, that is, the substrate contains at least the anode substrate. In some embodiments of the present application, the substrate is a laminated substrate in which an anode is provided on the substrate and a quantum dot light-emitting layer is provided on the surface of the anode. In still other embodiments of the present application, the substrate is a laminated substrate in which an anode is provided on the substrate, a hole transport layer is provided on the surface of the anode, and a quantum dot light emitting layer is provided on the surface of the hole injection layer. Of course, between the anode and the hole transport layer, other hole function layers, such as a hole injection layer, can also be provided. It should be understood that the present application is not limited to the structure of the above-mentioned embodiments.

In some embodiments of the method for manufacturing a quantum dot light-emitting diode provided in the embodiments of the present application, the anode substrate or the cathode substrate is pretreated before the functional layer is prepared on the surface of the anode substrate or the cathode substrate. In some embodiments, the pretreatment step includes: cleaning the anode substrate or the cathode substrate with a cleaning agent to initially remove the stains on the surface, and then sequentially apply deionized water, acetone, absolute ethanol, and Ultrasonic cleaning in ionized water for 10-30 minutes, which can be 20 minutes, to remove impurities on the surface; finally, it is blown dry with high-purity nitrogen to obtain the anode substrate or the cathode substrate surface.

In the above step E02, the zinc salt, the erbium salt and the ytterbium salt are dissolved in an organic solvent to prepare a mixed solution of the zinc salt, erbium salt and ytterbium salt; an alkali is added to the mixed solution, and the heating reaction steps are the same as the above, The details are as described above. In some embodiments, in the step of preparing a mixed solution of zinc salt, erbium salt, and ytterbium salt, the zinc salt, erbium salt, and ytterbium salt are mixed according to the molar ratio of zinc ion and doping element ion of 1:0.1 to 0.2. The salt is dissolved in an organic solvent to prepare a mixed solution of zinc salt, erbium salt and ytterbium salt. In some embodiments, in the step of preparing a mixed solution of zinc salt, erbium salt, and ytterbium salt, according to the molar ratio of the Er element and the Yb element of 2 to 3:1, the zinc salt, the erbium salt And ytterbium salt is dissolved in an organic solvent to prepare a mixed solution of zinc salt, erbium salt and ytterbium salt. In some embodiments, an alkali is added to the mixed solution, and in the step of heating the reaction, the molar ratio of the sum of the zinc ions and the doping element ions to the hydroxide ions provided by the alkali is 1:1.8~ 2.5. In some embodiments, the base is selected from at least one of ammonia, potassium hydroxide, sodium hydroxide, lithium hydroxide, ethanolamine, ethylene glycol, diethanolamine, triethanolamine, and ethylenediamine.

In the above step E03, depositing the precursor solution on the surface of the substrate can be achieved by conventional solution processing methods, including but not limited to spin coating, inkjet printing, and the like. In the embodiments of the present application, the film thickness can be controlled by adjusting the concentration of the solution, the printing or spin coating speed, and the deposition time.

After depositing the precursor solution on the surface of the substrate, an annealing treatment is performed to remove the solvent in the precursor solution, and at the same time improve the crystallization performance of the Er element and Yb element co-doped ZnO nanoparticles to obtain a compact and dense film. In some embodiments, the step of annealing treatment is performed at a temperature of 150°C to 250°C.

The preparation of each functional layer (including but not limited to the hole injection layer, electron transport layer, hole blocking layer, and electron blocking layer) except for the anode and cathode in the embodiments of this application can be prepared by conventional solution processing methods, including but not Limited to inkjet printing and spin coating. Similarly, the film thickness of each layer can be controlled by adjusting the concentration of the solution, the printing or spin coating speed, and the deposition time; and the thermal annealing treatment is performed after the solution is deposited.

In some embodiments, the method further includes encapsulating the obtained quantum dot light-emitting diode. The encapsulation process can adopt common machine encapsulation or manual encapsulation. In some embodiments, the oxygen content and water content in the environment of the packaging process are both lower than 0.1 ppm to ensure the stability of the device.

The description will be given below in conjunction with specific embodiments and comparative examples.

Example 1

A method for preparing an electron transport film includes the following steps:

Add appropriate amount of zinc sulfate, erbium sulfate and ytterbium sulfate to 50ml of ethanol, stir and dissolve at a temperature of 70°C to form a mixed solution with a total metal ion concentration of 1mol/L. In the mixed solution, zinc ions and doped The molar ratio of ions (erbium ion and ytterbium ion) is 1:0.1, and the molar ratio of erbium ion and ytterbium ion is 2:1;

According to the molar ratio of hydroxide ions to metal ions of 1.8:1, the ethanol solution of potassium hydroxide was added to the mixed solution, and the mixture was stirred for 4 hours at a temperature of 70°C to obtain a uniform transparent solution: Er -Yb/ZnO (Er-Yb/ZnO means Er and Yb co-doped ZnO nanomaterials) solution;

After depositing the Er-Yb/ZnO solution on the surface of the substrate, annealing is performed at a temperature of 200° C. to obtain an electron transport film.

Example 2

A method for preparing nanomaterials includes the following steps:

Appropriate amount of zinc nitrate, erbium nitrate and ytterbium nitrate were added to 50ml methanol, stirred and dissolved at 60°C to form a mixed solution with a total concentration of metal ions of 1mol/L. In the mixed solution, zinc ions and doped ions ( The molar ratio of erbium ion to ytterbium ion is 1:0.15, and the molar ratio of erbium ion to ytterbium ion is 2.5:1;

According to the molar ratio of hydroxide ions and metal ions of 2:1, the methanol solution of sodium hydroxide was added to the mixed solution, and the mixture was stirred for 3 hours at a temperature of 60°C to obtain a uniform transparent solution: Er -Yb/ZnO (Er-Yb/ZnO means Er and Yb co-doped ZnO nanomaterials) solution;

After depositing the Er-Yb/ZnO solution on the surface of the substrate, annealing is performed at a temperature of 150° C. to obtain an electron transport film.

Example 3

A method for preparing an electron transport film includes the following steps:

Add an appropriate amount of zinc chloride, erbium chloride and ytterbium chloride to 50ml of ethanol, stir and dissolve at a temperature of 80°C to form a mixed solution with a total metal ion concentration of 1mol/L. In the mixed solution, zinc The molar ratio of ions and doping ions (erbium ion and ytterbium ion) is 1:0.2, and the molar ratio of erbium ion and ytterbium ion is 3:1;

According to the molar ratio of hydroxide ions to metal ions of 2.5:1, a propanol solution of lithium hydroxide was added to the mixed solution, and the mixture was stirred for 4 hours at a temperature of 80°C to obtain a uniform transparent solution: Er-Yb/ZnO (Er-Yb/ZnO means Er and Yb co-doped ZnO nanomaterials) solution;

Example 4

A quantum dot light-emitting diode with a structure of glass sheet/ITO (20nm)/TFB (20nm)/quantum dot light-emitting layer (30nm)/electron transport layer (10nm)/Al (20nm). Among them, the Er-Yb/ZnO of Example 1 was used as the electron transport layer.

Example 5

A quantum dot light-emitting diode with a structure of glass sheet/ITO (20nm)/TFB (20nm)/quantum dot light-emitting layer (30nm)/electron transport layer (10nm)/Al (20nm). Among them, the Er-Yb/ZnO of Example 2 was used as the electron transport layer.

Example 6

A quantum dot light-emitting diode with a structure of glass sheet/ITO (20nm)/TFB (20nm)/quantum dot light-emitting layer (30nm)/electron transport layer (10nm)/Al (20nm). Among them, the Er-Yb/ZnO of Example 3 was used as the electron transport layer.

Example 7

A quantum dot light-emitting diode with a structure of glass sheet/ITO (20nm)/electron transport layer (10nm)/quantum dot light-emitting layer/TFB (20nm)/Al (20nm). Among them, the Er-Yb/ZnO of Example 1 was used as the electron transport layer.

Example 8

A quantum dot light-emitting diode with a structure of glass sheet/ITO (20nm)/electron transport layer (10nm)/quantum dot light-emitting layer/TFB (20nm)/Al (20nm). Among them, the Er-Yb/ZnO of Example 2 was used as the electron transport layer.

Example 9

A quantum dot light-emitting diode with a structure of glass sheet/ITO (20nm)/electron transport layer (10nm)/quantum dot light-emitting layer/TFB (20nm)/Al (20nm). Among them, the Er-Yb/ZnO of Example 3 was used as the electron transport layer.

Comparative example 1

Comparative Example 1 is basically the same as Example 4, with the main difference being that the material of the electron transport layer is a commercial ZnO material (purchased from sigma company).

The electron transport film prepared in Examples 1-3, the electron transport layer in Comparative Example 1, the quantum dot light-emitting diodes prepared in Examples 4-9 and Comparative Example 1 were tested for performance. The test indicators and test methods are as follows:

(1) Electron mobility: test the current density (J)-voltage (V) of the electron transport film, draw a curve relationship diagram, fit the space charge limited current (SCLC) area in the relationship diagram, and then use the famous Child ^, s law formula to calculate electron mobility:

J = (9/8)ε _r ε ₀ μ _e V ² /d ³

Among them, J represents the current density in mAcm ^-2 ; ε _r represents the relative permittivity, ε ₀ represents the vacuum permittivity; μ _e represents the electron mobility in cm ² V ^-1 s ^-1 ; V represents the driving voltage, The unit is V; d represents the thickness of the film in m.

(2) Resistivity: Use the same resistivity tester to measure the resistivity of the electronic transmission film.

(3) External quantum efficiency (EQE): measured by EQE optical test equipment.

Note: The electron mobility and resistivity tests are for single-layer thin film structure devices, namely: cathode/electron transport film/anode. The external quantum efficiency tests the external quantum efficiency of QLED devices, 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

项目组别 project Group	电子迁移率/(cm2/(V.s)) Electron mobility/(cm2/(V.s))	电阻率/(Ω.cm) Resistivity/(Ω.cm)	外量子效率（EQE）/(%) External quantum efficiency (EQE)/(%)
对比例 Comparison	2.14×102 2.14×102	5.67×10-4 5.67×10-4	3.76 3.76
实施例1 Example 1	3.25×102 3.25×102	1.26×10-4 1.26×10-4	To
实施例2 Example 2	3.08×102 3.08×102	1.57×10-4 1.57×10-4	To
实施例3 Example 3	2.73×102 2.73×102	2.08×10-4 2.08×10-4	To
实施例4 Example 4	To	To	7.65 7.65
实施例5 Example 5	To	To	6.43 6.43
实施例6 Example 6	To	To	5.86 5.86
实施例7 Example 7	To	To	7.12 7.12
实施例8 Example 8	To	To	5.88 5.88
实施例9 Example 9	To	To	5.29 5.29

It can be seen from Table 1 that the materials provided in Examples 1-3 of the present application are electron transport films of Er and Yb co-doped ZnO nanomaterials, and the resistivity is significantly lower than that of the electron transport films made of ZnO nanomaterials in Comparative Example 1. The electrical resistivity, and the electron mobility is significantly higher than the electron transport film made of ZnO nanomaterials in Comparative Example 1.

The external quantum efficiency of the quantum dot light-emitting diode (the material of the electron transport layer is Er and Yb co-doped ZnO nanomaterial) provided in Examples 4-9 of the present application is significantly higher than that of the electron transport layer of Comparative Example 1 where the material of the electron transport layer is ZnO nanomaterial The external quantum efficiency of the quantum dot light-emitting diode shows that the quantum dot light-emitting diode obtained in the embodiment has better luminous efficiency.

It is worth noting that the specific examples provided in this application all use blue quantum dots Cd _X Zn _1-X S/InS as the light-emitting layer material, which is based on the blue light-emitting system which uses more systems (in addition, the light-emitting system based on blue quantum dots The production of diodes is relatively difficult, so it has more reference value), which does not mean that this application is only used for blue light emitting systems.

The above are only optional embodiments of the application, and are not used to limit the application. For those skilled in the art, this application can have various modifications and changes. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of this application shall be included in the scope of the claims of this application.

Claims

A nano material, characterized in that the nano material comprises a ZnO nano material and a doping element doped in a ZnO lattice, and the doping element is an Er element and a Yb element.
The nanomaterial according to claim 1, wherein the nanomaterial is composed of a ZnO nanomaterial and the doping element, and the molar ratio of the zinc element to the doping element is 1:0.1~0.2.
The nanomaterial according to claim 1 or 2, wherein the molar ratio of the Er element and the Yb element is 2 to 3:1.
A method for preparing nanomaterials, which is characterized in that it comprises the following steps:

Dissolve zinc salt, erbium salt and ytterbium salt in an organic solvent to prepare a mixed solution of zinc salt, erbium salt and ytterbium salt;

A base is added to the mixed solution and heated to react to prepare a zinc oxide nanomaterial co-doped with Er element and Yb element, wherein the base is selected from organic bases or inorganic bases that can generate hydroxide ions in the reaction system .
The method for preparing nanomaterials according to claim 4, wherein in the step of preparing a mixed solution of zinc salt, erbium salt and ytterbium salt, the molar ratio of zinc ion to doping element ion is 1:0.1~0.2 Dissolve zinc salt, erbium salt and ytterbium salt in an organic solvent to prepare a mixed solution of zinc salt, erbium salt and ytterbium salt.
The method for preparing nanomaterials according to claim 5, wherein in the step of preparing a mixed solution of zinc salt, erbium salt and ytterbium salt, the molar ratio of Er element to Yb element is 2~3:1. , Dissolve zinc salt, erbium salt and ytterbium salt in an organic solvent to prepare a mixed solution of zinc salt, erbium salt and ytterbium salt.
The method for preparing nanomaterials according to any one of claims 4 to 6, wherein an alkali is added to the mixed solution, and in the step of heating the reaction, the sum of zinc ions and doping element ions is combined with the alkali The molar ratio of hydroxide ions provided is 1:1.8~2.5.
The method for preparing nanomaterials according to claim 7, wherein the alkali is selected from the group consisting of ammonia, potassium hydroxide, sodium hydroxide, lithium hydroxide, ethanolamine, ethylene glycol, diethanolamine, triethanolamine, and ethylene diethanolamine. At least one of amines.
The method for preparing nanomaterials according to any one of claims 4 to 6, 8, wherein the organic solvent is selected from organic alcohols.
The method for preparing nanomaterials according to claim 9, characterized in that, in the step of adding an alkali to the mixed solution and heating the reaction, the heating treatment is performed at a temperature of 60°C to 80°C, and The reaction time is 2h~4h.
The method for preparing nanomaterials according to any one of claims 4 to 6, 8, 10, wherein the zinc salt is selected from zinc acetate, zinc nitrate, zinc chloride, zinc sulfate, and zinc acetate dihydrate At least one of; and/or

The erbium salt is selected from at least one of erbium nitrate, erbium chloride, and erbium sulfate;

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

The organic solvent is selected from at least one of isopropanol, ethanol, propanol, butanol, and methanol.
A quantum dot light-emitting diode, which is characterized in that it comprises a cathode and an anode arranged oppositely, a quantum dot light-emitting layer arranged between the cathode and the anode, and a quantum dot light-emitting layer arranged between the cathode and the quantum dot light-emitting layer The electron transport layer is provided, and the material of the electron transport layer includes ZnO nanomaterials and doping elements doped in the ZnO lattice, and the doping elements are Er elements and Yb elements.
The quantum dot light-emitting diode of claim 12, wherein the material of the electron transport layer is composed of ZnO nanomaterial and the doping element, and the molar ratio of the zinc element to the doping element is 1: 0.1~0.2.
The quantum dot light-emitting diode according to claim 12 or 13, wherein in the material of the electron transport layer, the molar ratio of the Er element and the Yb element is 2 to 3:1.
A method for preparing a quantum dot light-emitting diode is characterized in that it comprises the following steps:

Provide substrate;

The zinc salt, erbium salt and ytterbium salt are dissolved in an organic solvent to prepare a mixed solution of zinc salt, erbium salt and ytterbium salt; an alkali is added to the mixed solution, and the reaction is heated to prepare a precursor solution, wherein the alkali Selected from organic bases or inorganic bases that can generate hydroxide ions in the reaction system;

After depositing the precursor solution on the surface of the substrate, annealing is performed to obtain an electron transport layer.
15. The method for manufacturing a quantum dot light-emitting diode according to claim 15, wherein the step of annealing treatment is performed at a temperature of 150°C to 250°C.
The method for preparing a quantum dot light-emitting diode according to claim 15 or 16, wherein in the step of preparing a mixed solution of zinc salt, erbium salt and ytterbium salt, the molar ratio of zinc ion to doping element ion is 1 : Dissolve zinc salt, erbium salt and ytterbium salt in an organic solvent in a ratio of 0.1 to 0.2 to prepare a mixed solution of zinc salt, erbium salt and ytterbium salt.
The method for preparing a quantum dot light-emitting diode according to claim 15 or 16, wherein in the step of preparing a mixed solution of zinc salt, erbium salt and ytterbium salt, the molar ratio of Er element and Yb element is 2~3 :1, dissolve zinc salt, erbium salt and ytterbium salt in an organic solvent to prepare a mixed solution of zinc salt, erbium salt and ytterbium salt.
The method for preparing a quantum dot light-emitting diode according to claim 15 or 16, wherein an alkali is added to the mixed solution, and in the step of heating the reaction, the sum of zinc ions and doped element ions is provided with the alkali The molar ratio of hydroxide ions is 1:1.8~2.5.
The method for preparing a quantum dot light-emitting diode according to claim 15 or 16, wherein the alkali is selected from the group consisting of ammonia, potassium hydroxide, sodium hydroxide, lithium hydroxide, ethanolamine, ethylene glycol, diethanolamine, and triethanolamine. At least one of ethanolamine and ethylenediamine.