阅读说明：本技术 氧化锌薄膜及其制备方法、量子点发光二极管 (Zinc oxide film, preparation method thereof and quantum dot light-emitting diode ) 是由 郭煜林 吴龙佳 张天朔 李俊杰 于 2020-06-18 设计创作，主要内容包括：本发明涉及显示技术领域,提供了一种氧化锌薄膜的制备方法,包括以下步骤：配制氧化锌颗粒和卤离子有机盐的混合溶液；将所述混合溶液沉积在基板上,退火处理,制备氧化锌薄膜。本申请提供的氧化锌薄膜的制备方法,卤离子有机盐能够吸附在氧化锌的晶面,并显著调控薄膜晶型生长过程,从而优化氧化锌薄膜的成膜质量,提高氧化锌薄膜的电子传输性能。(The invention relates to the technical field of display, and provides a preparation method of a zinc oxide film, which comprises the following steps: preparing a mixed solution of zinc oxide particles and halide ion organic salt; and depositing the mixed solution on a substrate, and annealing to prepare the zinc oxide film. According to the preparation method of the zinc oxide film, the halide ion organic salt can be adsorbed on the crystal face of zinc oxide, and the crystal growth process of the film is obviously regulated, so that the film forming quality of the zinc oxide film is optimized, and the electron transmission performance of the zinc oxide film is improved.)

1. The preparation method of the zinc oxide film is characterized by comprising the following steps:

preparing a mixed solution of zinc oxide particles and halide ion organic salt;

and depositing the mixed solution on a substrate, and annealing to prepare the zinc oxide film.

2. The method according to claim 1, wherein the halide organic salt is at least one selected from the group consisting of ammonium iodide, dimethylammonium iodide, N-dimethylmethyleneammonium iodide, and tetraethylammonium iodide.

3. The method according to claim 1, wherein the mass of the organic salt of a halide ion in the mixed solution is 1 to 5% of the mass of the zinc oxide particles.

4. The method of producing a zinc oxide thin film according to any one of claims 1 to 3, wherein the annealing is carried out at a temperature of 80 ℃ to 120 ℃ for 0.5 to 2 hours.

5. The method for producing a zinc oxide thin film according to any one of claims 1 to 3, wherein the zinc oxide particles are zinc oxide nanoparticles; and/or

The preparation method of the mixed solution comprises the following steps:

providing a zinc salt solution, adding an alkali source into the zinc salt solution, reacting for 0.5-2 hours, adding the halide ion organic salt, and mixing for 1-4 hours.

6. A zinc oxide thin film produced by the production method according to any one of claims 1 to 5.

7. The quantum dot light-emitting diode is characterized by comprising an anode and a cathode which are oppositely arranged, a quantum dot light-emitting layer arranged between the anode and the cathode, and an electron transmission layer arranged between the cathode and the quantum dot light-emitting layer; wherein the electron transport layer is a zinc oxide film, and the zinc oxide film is prepared by the preparation method of any one of claims 1 to 5.

8. The qd-led of claim 7, wherein the qd-led further comprises: a hole function layer disposed between the anode and the quantum dot light emitting layer.

9. The quantum dot light-emitting diode of claim 8, wherein the hole functional layer comprises at least one of a hole injection layer, a hole transport layer, and an electron blocking layer.

10. The qd-led of any one of claims 7 to 9, wherein the qd-led further comprises: an electron injection layer disposed between the cathode and the electron transport layer.

Technical Field

The invention belongs to the technical field of display, and particularly relates to a zinc oxide film and a preparation method thereof, and a quantum dot light-emitting diode.

Background

In the conventional inorganic electroluminescent device, electrons and holes are injected from a cathode and an anode, respectively, and then are recombined in a light emitting layer to form excitons for light emission. Quantum Dots (QDs) have a variety of characteristics, including: (1) the emission spectrum can be adjusted by changing the particle size; (3) the excitation spectrum is wide, the emission spectrum is narrow, and the absorptivity is strong; (3) the light stability is good; (4) longer fluorescence lifetime, etc. The semiconductor quantum dot material has important commercial application value as a novel inorganic semiconductor fluorescent material. Conduction band electrons in wide bandgap semiconductors can be accelerated under high electric fields to obtain high enough energy to strike QDs to cause it to emit light. Due to its excellent Light Emitting characteristics, Quantum dots are rapidly developing in the application of Quantum Dot Light Emitting Diodes (QLEDs).

ZnO is an n-type semiconductor material with a direct band gap, has a wide forbidden band of 3.37eV and a low work function of 3.7eV, and has the advantages of good stability, high transparency, safety, no toxicity and the like, so that ZnO can be used as a proper electron transport layer material. ZnO has many potential advantages, its exciton confinement energy is as high as 60meV, far higher than other wide bandgap semiconductor materials (GaN is 25meV), and ZnO exciton confinement energy (60meV) is 2.3 times of its room temperature heat energy (26meV), so ZnO exciton can exist stably at room temperature.

ZnO exists as a thin film in the fabrication of QLED devices, while polycrystalline thin films are often accompanied by defective formation in spin-on or spray-on processes. Defects of the electron transport layer film can weaken the transport of carriers and reduce the recombination efficiency of electrons and holes in the light emitting layer.

Disclosure of Invention

The invention aims to provide a zinc oxide film, a preparation method thereof and a quantum dot light-emitting diode, and aims to solve the problems that surface defects are generated and the transmission of current carriers is weakened when ZnO is formed into a film.

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

in a first aspect, the present application provides a method for preparing a zinc oxide thin film, comprising the steps of:

preparing a mixed solution of zinc oxide particles and halide ion organic salt;

and depositing the mixed solution on a substrate, and annealing to prepare the zinc oxide film.

In a second aspect, the present application provides a zinc oxide thin film prepared by the above method.

In a third aspect, the present application provides a quantum dot light emitting diode, comprising an anode and a cathode oppositely arranged, a quantum dot light emitting layer arranged between the anode and the cathode, and an electron transport layer arranged between the cathode and the quantum dot light emitting layer; the electron transport layer is a zinc oxide film, and the zinc oxide film is prepared by the preparation method.

In the method for preparing the zinc oxide thin film provided by the first aspect of the present application, the halide ion organic salt is added before the zinc oxide is formed into a film by a solution processing method. The halide ion organic salt can be adsorbed on the crystal face of the zinc oxide, and the growth process of the crystal form of the film is obviously regulated and controlled, so that the film forming quality of the zinc oxide film is optimized, and the electron transmission performance of the zinc oxide film is improved. Specifically, the halogen ion organic salt adsorbed on the zinc oxide crystal face limits the growth speed of a ZnO polar face in the annealing process, and regulates the crystallinity of the ZnO crystallization process, so that the defects caused by film formation of the crystal are reduced, the crystal is smooth and complete in structure, the particle size of the crystal is regulated, and the like, and a more compact, uniform and flat film is finally prepared, and the electron transmission performance is favorably improved; meanwhile, the zinc oxide film prepared by the method repairs the defects of the film through the halide ion organic salt, reduces the defects of the film, and is beneficial to the transmission of electrons in the film because the electrons are not easy to be captured by the film, thereby improving the content of free electrons and further promoting the transmission of electrons. In addition, the organic salt of the halide ion can be sublimated slowly during the annealing treatment, and the film forming quality of the zinc oxide is not influenced.

According to the zinc oxide film provided by the second aspect of the application, the surface defects of zinc oxide are reduced, and the flatness and compactness of the film layer are improved; meanwhile, the content of free electrons is increased, so that the electron transmission performance of the zinc oxide is improved. When the zinc oxide film is used as the electron transport layer of the quantum dot light-emitting diode, the interface performance of the zinc oxide film is improved, the film forming quality of the zinc oxide film is improved, and the electron transport capability is enhanced, so that the electron-hole recombination efficiency can be improved, and the stability of a device can be enhanced.

In the quantum dot light-emitting diode provided by the third aspect of the present application, the electron transport layer is the above-mentioned zinc oxide film. Compared with a zinc oxide base film, the zinc oxide film optimized by adopting the halide ion organic salt has the advantages of increased electron transmission capability, improved electron-hole recombination efficiency, enhanced device stability and effectively improved photoelectric performance of the quantum dot light-emitting diode.

Drawings

In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the drawings needed to be used in the embodiments or the prior art descriptions will be briefly described below, and it is obvious that the drawings in the following description are only some embodiments of the present invention, and it is obvious for those skilled in the art to obtain other drawings based on these drawings without inventive exercise.

FIG. 1 is a flow chart of a process for preparing a zinc oxide thin film according to an embodiment of the present invention;

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

Detailed Description

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

In this application, the term "and/or" describes an association relationship of associated objects, meaning that there may be three relationships, e.g., a and/or B, which may mean: a is present alone, A and B are present simultaneously, and B is present alone. Wherein A and B can be singular or plural. The character "/" generally indicates that the former and latter associated objects are in an "or" relationship.

In the present application, "at least one" means one or more, "a plurality" means two or more. "at least one of the following" or similar expressions refer to any combination of these items, including any combination of the singular or plural items. For example, "at least one (a), b, or c", or "at least one (a), b, and c", may each represent: a, b, c, a-b (i.e., a and b), a-c, b-c, or a-b-c, wherein a, b, and c may be single or plural, respectively.

It should be understood that, in various embodiments of the present application, the sequence numbers of the above-mentioned processes do not mean the execution sequence, some or all of the steps may be executed in parallel or executed sequentially, and the execution sequence of each process should be determined by its function and inherent logic, and should not constitute any limitation to the implementation process of the embodiments of the present application.

The terminology used in the embodiments of the present application is for the purpose of describing particular embodiments only and is not intended to be limiting of the application. As used in the examples of this application and the appended claims, the singular forms "a", "an", and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise.

The terms "first" and "second" are used for descriptive purposes only and are used for distinguishing purposes such as substances, interfaces, messages, requests and terminals from one another and are not to be construed as indicating or implying relative importance or implicitly indicating the number of technical features indicated. For example, a first XX may also be referred to as a second XX, and similarly, a second XX may also be referred to as a first XX, without departing from the scope of embodiments of the present application. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature.

The weight of the related components mentioned in the description of the embodiments of the present application may not only refer to the specific content of each component, but also represent the proportional relationship of the weight among the components, and therefore, the content of the related components is scaled up or down within the scope disclosed in the description of the embodiments of the present application as long as it is scaled up or down according to the description of the embodiments of the present application. Specifically, the mass described in the specification of the embodiments of the present application may be a mass unit known in the chemical industry field such as μ g, mg, g, kg, etc.

As shown in fig. 1, a first aspect of the embodiments of the present application provides a method for preparing a zinc oxide thin film, including the following steps:

s01, preparing a mixed solution of zinc oxide particles and halide ion organic salt;

and S02, depositing the mixed solution on a substrate, and annealing to prepare the zinc oxide film.

According to the preparation method of the zinc oxide film provided by the embodiment of the application, the halide ion organic salt is added before the zinc oxide is formed into the film by a solution processing method. The halide ion organic salt can be adsorbed on the crystal face of the zinc oxide, and the growth process of the crystal form of the film is obviously regulated and controlled, so that the film forming quality of the zinc oxide film is optimized, and the electron transmission performance of the zinc oxide film is improved. Specifically, the halide ion organic salt adsorbed on the zinc oxide crystal face limits the growth speed of a ZnO polar face in the annealing process, and regulates the crystallinity of the ZnO crystallization process, so that the defects caused by film formation of the crystal are reduced, the crystal is smooth and complete in structure, the particle size (smaller crystal grain size) of the crystal is regulated, and the like, and a more compact, uniform and flat film is finally prepared, and the electron transmission performance is favorably improved; meanwhile, the zinc oxide film prepared by the method repairs the defects of the film through the halide ion organic salt, reduces the defects of the film, and is beneficial to the transmission of electrons in the film because the electrons are not easy to be captured by the film, thereby improving the content of free electrons and further promoting the transmission of electrons. In addition, the organic salt of the halide ion can be sublimated slowly during the annealing treatment, and the film forming quality of the zinc oxide is not influenced.

Specifically, in step S01, a mixed solution of zinc oxide particles and a halide organic salt is prepared, and the zinc oxide particle solution may be prepared first, and then the halide organic salt may be added; or preparing a halide ion organic salt solution and adding zinc oxide particles; and preparing a halide ion organic salt solution and a zinc oxide particle solution respectively, and mixing the two solutions to obtain a mixed solution of zinc oxide particles and a halide ion organic salt. In some embodiments, the zinc oxide particles in the mixed solution are zinc oxide nanoparticles.

In some embodiments, the mixed solution is prepared by:

providing a zinc salt solution, adding an alkali source into the zinc salt solution, reacting for 0.5-2 hours, adding halide ion organic salt, and mixing for 1-4 hours.

The zinc salt is selected from inorganic zinc salt and/or organic zinc salt capable of generating zinc ion by ionization, and specifically, at least one of zinc acetate, zinc nitrate, zinc chloride, zinc sulfate and zinc acetate dihydrate can be selected, but not limited thereto. The alkali source is selected from inorganic alkali and/or organic alkali which generates hydroxide ions in a mixed solution formed after the organic solution of the zinc salt is added into the alkali liquor, and includes but is not limited to at least one of sodium hydroxide, potassium hydroxide, lithium hydroxide and tetramethyl ammonium hydroxide.

In some embodiments, the zinc salt is first dissolved in an organic solvent and then mixed with a source of alkalinity. Among them, the organic solvent is preferably an organic alcohol, including but not limited to at least one of organic solvents such as isopropyl alcohol, ethanol, propanol, butanol, pentanol, hexanol, etc. In order to promote the dissolution of the zinc salt, a heating and stirring manner can be adopted. In some embodiments, dissolution is by stirring at 60 ℃ to 80 ℃.

Adding an alkali source into the zinc salt solution, and reacting for 0.5-2 hours to obtain the zinc oxide nano-particles. Further, adding halide ion organic salt into the reaction system, and mixing for 1-4 hours to ensure that the halide ion organic salt is fully adsorbed on the surface of the zinc oxide crystal. In some embodiments, the mixing process is accomplished by agitation.

In embodiments of the present application, the halide organic salt is an organic salt containing a halide, and in some embodiments, the halide organic salt is selected from at least one of ammonium iodide, dimethyl ammonium iodide, N-dimethyl methylene ammonium iodide, and tetraethyl ammonium iodide.

In some embodiments, the halide organic salt is selected from iodide organic salts such as ammonium iodide, dimethyl ammonium iodide, N-dimethyl methylene ammonium iodide, tetraethyl ammonium iodide, and the like. Due to the covalent radius of iodine and Zn²⁺The ionic radius of the iodine ion is close to that of the ZnO, so that iodine ion organic salt can be better combined on the surface of ZnO, the iodine ion organic salt is adsorbed on the crystal face of ZnO, and the growth speed of the polar face of ZnO can be limited in the annealing processTherefore, defects caused by the crystals during film formation can be reduced, and a more dense thin film can be prepared. In addition, when the iodide ion organic salt is selected as the halide ion organic salt, the alkalinity of ZnO is easy to induce the deprotonation reaction of organic amine ions, so that the iodide ion organic salt deposited on ZnO is easier to decompose and sublimate when a compact ZnO film is formed, and the residue of the iodide ion organic salt is reduced or even eliminated.

It should be noted that in the examples of the present application, the mixed solution was prepared by mixing with the organic salt of halide ion after the preparation of the zinc oxide nanomaterial, instead of adding the organic salt of halide ion during the preparation of the zinc oxide nanomaterial. If the organic salt of halide ion is added in the process of preparing the zinc oxide nano material, other reactions may occur in a mixed system of zinc salt, an alkali source and the organic salt of halide ion to generate organic impurities and consume the organic salt of halide ion.

In some embodiments, the mass of the halide ion organic salt in the mixed solution is 1% to 5% of the mass of the zinc oxide particles. When the content of the halide ion organic salt is lower than 1% of the mass of the zinc oxide particles, the zinc oxide is rapidly crystallized to form ZnO with poor crystallinity and large crystal grains, gaps are easily generated among the excessively large crystal grains, and the electron transmission capability is reduced; with the increase of the halide ion organic salt, the zinc oxide crystallization process is slow in the annealing film forming process, and ZnO nanoparticles with high crystallinity, smaller crystal grains and uniformity can be obtained. When the content of the halide organic salt is too high and is higher than 5% of the mass of the zinc oxide particles, the excess halide organic salt is not easy to be effectively removed in the annealing process, and the residual halide organic salt has poor effect of improving the electron transfer performance.

In the step S02, the mixed solution is deposited on the substrate by conventional solution processing methods, including but not limited to doctor blading, spin coating, ink-jet printing, etc.

The film layer after the mixed solution is deposited is annealed, the c-axis polar growth speed of ZnO is effectively controlled by using the halide ion organic salt in the mixed solution, the crystal defects are reduced, the crystal is smooth, the structure is complete, the crystallization quality is improved, and the surface of the film is uniform and flat. Finally, the preparation of the high-quality ZnO film is realized under mild conditions, and the stability of an electron transmission layer and application devices such as quantum dot light-emitting diodes can be improved.

In some embodiments, the annealing is at a temperature of 80 ℃ to 120 ℃ for a time of 0.5 to 2 hours. At the temperature, a small amount of halide organic salt (the mass of the halide organic salt is 1-5% of that of the zinc oxide particles) is slowly sublimated to finally obtain the zinc oxide film with good crystallinity, uniform crystal grains and compactness.

In the second aspect of the embodiments of the present application, a zinc oxide thin film is prepared by the above preparation method.

According to the zinc oxide film provided by the embodiment of the application, the surface defects of zinc oxide are reduced, and the flatness and compactness of the film layer are improved; meanwhile, the content of free electrons is increased, so that the electron transmission performance of the zinc oxide is improved. When the zinc oxide film is used as the electron transport layer of the quantum dot light-emitting diode, the interface performance of the zinc oxide film is improved, the film forming quality of the zinc oxide film is improved, and the electron transport capability is enhanced, so that the electron-hole recombination efficiency can be improved, and the stability of a device can be enhanced.

As shown in fig. 2, a quantum dot light emitting diode according to a third aspect of the embodiments of the present application includes an anode and a cathode that are oppositely disposed, a quantum dot light emitting layer disposed between the anode and the cathode, and an electron transport layer disposed between the cathode and the quantum dot light emitting layer; the electron transport layer is a zinc oxide film, and the zinc oxide film is prepared by the preparation method.

In the quantum dot light-emitting diode provided by the embodiment of the application, the electron transport layer is the zinc oxide film. Compared with a zinc oxide base film, the zinc oxide film optimized by adopting the halide ion organic salt has the advantages of increased electron transmission capability, improved electron-hole recombination efficiency, enhanced device stability and effectively improved photoelectric performance of the quantum dot light-emitting diode.

In the quantum dot light emitting diode provided by the embodiment of the application, the zinc oxide film is prepared as above, and is not described herein again for saving space.

In some embodiments, the quantum dot light emitting diode further comprises: and a hole function layer disposed between the quantum dot light emitting layer and the anode. Wherein the hole function layer comprises at least one of a hole injection layer, a hole transport layer and an electron blocking layer.

In some embodiments, the quantum dot light emitting diode further comprises a hole transport layer disposed between the anode and the quantum dot light emitting layer; in some embodiments, the quantum dot light emitting diode further comprises: a hole injection layer disposed between the anode and the quantum light-emitting layer; in some embodiments, the quantum dot light emitting diode further comprises a hole transport layer disposed between the anode and the quantum dot light emitting layer, and a hole injection layer disposed between the anode and the hole transport layer.

In some embodiments, the quantum dot light emitting diode further comprises: an electron injection layer disposed between the cathode and the electron transport layer.

In some embodiments, the quantum dot light emitting diode further comprises: the hole injection layer is arranged between the anode and the hole transport layer; and an electron injection layer disposed between the cathode and the electron transport layer.

In the embodiment of the application, the quantum dot light emitting diode may further include a substrate, and the anode or the cathode is disposed on the substrate. In some embodiments, the substrate may include a rigid substrate such as glass, metal foil, etc., commonly used rigid substrates, or a flexible substrate such as Polyimide (PI), Polycarbonate (PC), Polystyrene (PS), Polyethylene (PE), polyvinyl chloride (PV), polyvinyl pyrrolidone (PVP), polyethylene terephthalate (PET), etc., which primarily serves as a support.

The quantum dot light-emitting diode in the embodiment of the application is divided into a positive type structure quantum dot light-emitting diode and an inversion type structure quantum dot light-emitting diode.

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

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

In the embodiment of the present application, the anode may be made of a common anode material and thickness, and the embodiment of the present application is not limited. For example, the anode material may be Indium Tin Oxide (ITO), Indium Zinc Oxide (IZO) conductive glass, or indium tin oxide, indium zinc oxide electrode, or may be other metal materials such as gold, silver, aluminum, and the like.

In the embodiments of the present application, the cathode may be made of a common cathode material and thickness, and the embodiments of the present application are not limited. In some embodiments, the material of the cathode is selected from one or more of a conductive carbon material, a conductive metal oxide material, and a metallic material. Wherein the conductive carbon material includes, but is not limited to, one or more of doped or undoped carbon nanotubes, doped or undoped graphene oxide, C60, graphite, carbon fibers, and porous carbon; the conductive metal oxide material includes, but is not limited to, one or more of ITO, FTO, ATO, and AZO; the metal material includes, but is not limited to, Al, Ag, Cu, Mo, Au, or an alloy thereof. The metal material has a form including, but not limited to, one or more of a dense thin film, a nanowire, a nanosphere, a nanorod, a nanocone, and a hollow nanosphere. In which, materials such as nano-Ag wires or Cu wires are used, which have smaller resistance to enable carriers to be injected more smoothly. The thickness of the cathode is 15-30 nm.

The quantum dots of the quantum dot light-emitting layer can be made of conventional quantum dot materials according to conventional quantum dot types. For example, the quantum dots of the quantum dot light-emitting layer can be one of red quantum dots, green quantum dots, blue quantum dots and yellow quantum dots; the quantum dot material may or may not contain cadmium; the quantum dots can be oil-soluble quantum dots comprising binary phase, ternary phase and quaternary phase quantum dots. In some embodiments, the quantum dot material may be selected from at least one of semiconductor nanocrystals of CdS, CdSe, CdTe, ZnSe, ZnTe, GaAs, GaP, GaSb, HgS, HgSe, HgTe, InAs, InP, InSb, AlAs, AlP, CuInS, CuInSe, AgS, PbS, and PbSe, and core-shell structured quantum dots or alloy structured quantum dots formed of the above materials; in some embodiments, the quantum dot material may be selected from Zn_XCd_1-XS、Cu_XIn_1-XS、Zn_XCd_1-XSe、Zn_XSe_1-XS、Zn_XCd_1-XTe、PbSe_XS_1-XAnd at least one of a core-shell structure quantum dot or an alloy structure quantum dot formed by the material. In some embodiments, the quantum dot material may be selected from Zn_XCd_1-XS/ZnSe、Cu_XIn_1-XS/ZnS、Zn_XCd_1-XSe/ZnS、CuInSeS、Zn_XCd_1-XTe/ZnS、PbSe_XS_1-XThe nano-crystalline material comprises/ZnS semiconductor nano-crystalline and at least one of core-shell structure quantum dots or alloy structure quantum dots formed by the material. The above materialsThe quantum dot light emitting layer has the characteristics of wide and continuous excitation spectrum distribution, high emission spectrum stability and the like. The thickness of the quantum dot light-emitting layer is 20 nm-60 nm.

The material of the hole injection layer may be made of a hole injection material that is conventional in the art, and may be PEODT: PSS, CuPc, HATCN, WoO_x、MoO_x、CrO_x、NiO、CuO、VO_x、CuS、MoS₂、MoSe₂、WS₂、WSe₂But is not limited thereto. The thickness of the hole injection layer is 30nm-100 nm.

When the material of the hole transport layer can be a conventional hole transport material, including, but not limited to, high molecular weight polymers such as TFB, PVK, Poly-TPD, TCTA, PEDOT: PSS, F8, etc.; inorganic metal oxides such as copper oxide, nickel oxide, tungsten trioxide, molybdenum trioxide, and the like, or mixtures thereof in any combination, may also be other high performance hole transport materials. The thickness of the hole transport layer is 30nm-100 nm.

The materials of the electron transport layer are as above, and are not described in detail here. The thickness of the electron transport layer is 60nm-100 nm.

The quantum dot light-emitting diode provided by the third aspect of the embodiment of the application can be prepared by the following method.

In some embodiments, a method of making a quantum dot light emitting diode comprises the steps of:

s01, providing a substrate;

in this step, in one implementation case, the substrate is a composite substrate, including an anode substrate, and a quantum dot light emitting layer bonded at least to the anode substrate. In some embodiments, a hole function layer is further included between the anode and the quantum dot light emitting layer, wherein the hole function layer includes at least one of a hole transport layer and a hole injection layer. In one embodiment, the substrate is a cathode substrate.

In both cases of implementation, the anode substrate or the cathode substrate is pretreated in order to obtain a high-quality thin film when the functional layer is prepared on the anode substrate or the cathode substrate. The basic specific processing steps include: and sequentially carrying out ultrasonic cleaning on the anode substrate or the cathode substrate in deionized water, acetone, absolute ethyl alcohol and deionized water respectively to remove impurities existing on the surface, drying and then cleaning by using an ultraviolet cleaning machine.

S02, preparing an electronic transmission layer on a substrate;

in the step, according to the method, the mixed solution of the zinc oxide particles and the halide ion organic salt is deposited on the substrate, and the electron transport layer is prepared by annealing treatment.

Further, when the substrate includes an anode and a quantum dot light emitting layer, a cathode is prepared on the electron transport layer; when the substrate is a cathode substrate, the quantum dot light-emitting layer and the cathode are sequentially prepared on the electron transport layer.

Further, the preparation method also comprises the following steps: and packaging the obtained QLED device. The packaging process can be carried out by a common machine or manually. Preferably, the oxygen content and the water content are both lower than 0.1ppm in the packaging treatment environment, so as to ensure the stability of the QLED device.

The following description will be given with reference to specific examples.

Example 1

A preparation method of a zinc oxide film comprises the following steps:

weighing a proper amount of zinc chloride, and adding the zinc chloride into 50ml of methanol to form a zinc chloride solution with the total concentration of 0.5 mol/L; stirring to dissolve, adding 30ml of sodium hydroxide methanol lye (molar ratio, OH)^-：Zn²⁺1.5). Stirring for 1h, adding dimethyl ammonium iodide accounting for 3 percent of the weight of the zinc oxide nano particles, and stirring for 2h to obtain a clear and transparent solution. And then, precipitating with acetone to prepare ZnO nanoparticles (10-100 nm), and dispersing with a proper amount of ethanol.

And spin-coating the ZnO solution to form a film, annealing at 110 ℃ for 0.5h, and sublimating dimethyl ammonium iodide to obtain the ZnO film with good crystallinity and uniform and compact crystal grains.

Example 2

A preparation method of a zinc oxide film comprises the following steps:

proper amount of zinc nitrate hexahydrate is weighed and added into the container 50ml of methanol is added to form zinc nitrate hexahydrate solution with the total concentration of 0.5 mol/L; stirring to dissolve, adding 30ml of potassium hydroxide methanol lye (molar ratio, OH)^-：Zn²⁺1.5). Stirring for 1h, adding N, N-dimethyl methylene ammonium iodide (5 wt%) 5% of the weight of zinc oxide nano-particles, and stirring for 2h to obtain a clear and transparent solution. And then, precipitating with acetone to prepare ZnO nanoparticles (10-100 nm), and dispersing with a proper amount of ethanol.

And spin-coating the ZnO solution to form a film, annealing at 80 ℃ for 2 hours, and sublimating the N, N-dimethylmethylene ammonium iodide to obtain the ZnO film with good crystallinity, uniform and compact crystal grains.

Example 3

A preparation method of a zinc oxide film comprises the following steps:

weighing a proper amount of zinc acetate dihydrate, and adding the zinc acetate dihydrate into 50ml of methanol to form a zinc acetate dihydrate solution with the total concentration of 0.5 mol/L; stirring for dissolving, adding 30ml of ethanol alkali solution (molar ratio, OH) of tetrahydroxy ammonium hydroxide pentahydrate^-：Zn²⁺1.5). Stirring for 1h, adding tetraethyl ammonium iodide (1 wt%) with the weight of 1% relative to the weight of the zinc oxide nano particles, and stirring for 2h to obtain a clear and transparent solution. And then, precipitating with acetone to prepare ZnO nanoparticles (10-100 nm), and dispersing with a proper amount of ethanol.

And spin-coating the ZnO solution to form a film, annealing at 120 ℃ for 0.5h, and sublimating tetraethyl ammonium iodide to obtain the ZnO film with good crystallinity and uniform and compact crystal grains.

Example 4

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 TFB (thin film transistor), the electron transport layer is the zinc oxide film provided in the embodiment 1, and the cathode is made of Al.

Example 5

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 TFB (thin film transistor), the electron transport layer is the zinc oxide film provided in the embodiment 2, and the cathode is made of Al.

Example 6

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 TFB (thin film transistor), the electron transport layer is the zinc oxide film provided in the embodiment 2, and the cathode is made of Al.

Comparative example 1

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 TFB (thin film transistor), the electron transport layer is made of commercial ZnO (from sigma company), and the cathode is made of Al.

Comparative example 2

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 TFB (thin film transistor), the electron transport layer is made of a ZnO thin film modified without adding halide ion organic salt, and the cathode is made of Al.

The quantum dot light emitting diodes of examples 4 to 6 and the quantum dot light emitting diodes of comparative examples 1 to 2 were subjected to performance tests, and the test indexes and the test methods were as follows:

turn-on voltage and External Quantum Efficiency (EQE): the measurement is carried out by an EQE optical test instrument (external quantum efficiency test QLED device external quantum efficiency). The test results are shown in table 1 below:

TABLE 1

As can be seen from table 1, compared with comparative example 1 and comparative example 2, the quantum dot light emitting diode provided in the embodiment of the present application has a reduced turn-on voltage and an improved external quantum efficiency, and it can be seen that the performance of the zinc oxide film can be optimized by modifying zinc oxide in an annealing film forming process by using a halide ion organic salt, thereby improving the photoelectric performance of the quantum dot light emitting diode.

The present invention is not limited to the above preferred embodiments, and any modifications, equivalent substitutions and improvements made within the spirit and principle of the present invention should be included in the protection scope of the present invention.