CN113130631B - A kind of heterojunction nanomaterial and its preparation method, thin film, quantum dot light-emitting diode - Google Patents

Abstract

The invention discloses a heterojunction nano material and a preparation method thereof, a thin film, and a quantum dot light-emitting diode, wherein the preparation method of the heterojunction nano material comprises the steps of: providing a ZnMgO nano particle; The particles are added into the sulfur source aqueous solution and heated to form a ZnS layer on the surface of the ZnMgO nano particles to prepare the heterojunction nano material. In the heterojunction nanomaterial of the present invention, the ZnS layer can passivate the surface defects of ZnMgO nanoparticles, improve the quality of the contact surface with the quantum dot light-emitting layer when the heterojunction nanomaterial is used as the electron transport layer, and at the same time the After the surface Zn atoms of ZnMgO nanoparticles are closely combined with the surface S atoms, a new electron transfer pathway is created, which can accelerate electron transfer, thereby synergistically improving the luminous efficiency and stability of quantum dot light-emitting diodes.

Description

A kind of heterojunction nanomaterial and its preparation method, thin film, quantum dot light-emitting diode

technical field

The invention relates to the field of quantum dot light-emitting diodes, in particular to a heterojunction nanomaterial, a preparation method thereof, a thin film, and a quantum dot light-emitting diode.

Background technique

Quantum dots have been rapidly developed in the application of quantum dot light-emitting diodes (QLEDs) due to their excellent light-emitting properties. Quantum dots have many characteristics, including: (1) the emission spectrum can be adjusted by changing the particle size; (2) the excitation spectrum is relatively broad, the emission spectrum is narrow, and the absorption is strong; (3) the photostability is very good; (4) Longer fluorescence lifetime, etc. In traditional inorganic electroluminescent devices, electrons and holes are injected from the cathode and anode respectively, and then recombine in the light-emitting layer to form excitons to emit light. Conduction band electrons in wide bandgap semiconductors can be accelerated under high electric field to obtain high enough energy to hit QDs to make them emit light; semiconductor quantum dot materials, as a new type of inorganic semiconductor fluorescent materials, have important commercial application value.

ZnO is an n-type semiconductor material with a direct band gap, which has a wide band gap of 3.37eV and a low work function of 3.7eV, and has the advantages of good stability, high transparency, safety and non-toxicity, etc., making ZnO a suitable electronic material. transport layer material. ZnO has many potential advantages. Its exciton binding energy is as high as 60meV, which is much higher than that of other wide-bandgap semiconductor materials (GaN is 25meV), and it is 2.3 times of room temperature thermal energy (26meV). Therefore, ZnO excitons can be released at room temperature. Stable existence. Secondly, ZnO has a hexagonal wurtzite structure, which exhibits strong spontaneous polarization; in ZnO-based heterostructures, the strain of the material will cause the polarization effect of the ZnO-based heterostructures, and the polarization electric field generated by the polarization is in the The ZnO heterojunction surface induces a high concentration of interface polarization charges, which can regulate the energy band of the material, and then affect the related structure and device performance.

Compared with nano-ZnO, nano-ZnMgO increases the atomic fraction of Mg in the alloy, and the conduction band of the alloy will be closer to the vacuum energy level with the increase of the Mg atomic fraction, and the injection barrier between the energy band of the quantum dot is lower, which can The injection of electrons is more efficient, so the research on ZnMgO has gradually increased in recent years. Mg doping increases the position of the bottom energy level of the conduction band of ZnO, reduces the electron injection barrier between the quantum dots and reduces the fluorescence quenching of the quantum dot layer by ZnO, and the device shows higher current density and brightness. . However, when ZnMgO nanoparticles are used as electron transport layer materials, ZnMgO surface defects such as hydroxyl groups and oxygen vacancies inevitably lead to device performance degradation.

Therefore, prior art still needs to be improved.

Contents of the invention

The purpose of the present invention is to provide a heterojunction nanomaterial and its preparation method, thin film, and quantum dot light-emitting diode. There are defects such as hydroxyl groups and oxygen vacancies on the surface of the particles, which lead to the degradation of the performance of quantum dot light-emitting diodes.

Technical scheme of the present invention is as follows:

A heterojunction nano material, which includes ZnMgO nano particles and a ZnS layer grown on the surface of the ZnMgO nano particles.

A method for preparing a heterojunction nanomaterial, comprising the steps of:

A ZnMgO nanoparticle is provided;

adding the ZnMgO nanometer particles into the sulfur source aqueous solution and heating to form a ZnS layer on the surface of the ZnMgO nanometer particles to prepare the heterojunction nanomaterial.

The preparation method of the heterojunction nanomaterial, wherein, the mass ratio of the ZnMgO nanoparticles to the sulfur element in the sulfur source aqueous solution is 2-4:1.

The preparation method of the heterojunction nanomaterial, wherein, the ZnMgO nanoparticle is added to the sulfur source aqueous solution and heated to generate a ZnS layer on the surface of the ZnMgO nanoparticle to obtain the heterojunction nanomaterial The steps include:

Adding the ZnMgO nano particles into the sulfur source aqueous solution and heating to 80-120° C., and reacting for 1-3 hours, a ZnS layer is formed on the surface of the ZnMgO nano particles to prepare the heterojunction nano material.

The preparation method of the heterojunction nanomaterial, wherein, the sulfur source aqueous solution is one or more of thiourea aqueous solution, thioacetamide aqueous solution and L-cysteine aqueous solution.

The preparation method of the heterojunction nanomaterial, wherein, the preparation of the ZnMgO nanoparticles comprises the steps of:

Disperse zinc salt and magnesium salt in an organic solvent to form a mixed solution;

Alkaline solution is added to the mixed solution to react to prepare ZnMgO nanoparticles.

The preparation method of the heterojunction nanomaterial, wherein the mass ratio of the zinc salt to the magnesium salt is 1:10-20.

The preparation method of the heterojunction nanomaterial, wherein, the molar ratio of ^OH- in the alkaline solution to Zn ²⁺ in the mixed solution is 1.5-3:1.

A thin film, wherein the material of the thin film is the heterojunction nanomaterial described in the present invention.

A quantum dot light-emitting diode, including an electron transport layer, wherein the electron transport layer is the thin film described in the present invention.

Beneficial effects: the present invention generates a ZnS layer on the surface of the ZnMgO nanoparticles by vulcanizing the ZnMgO nanoparticles to obtain a heterojunction nanomaterial. The ZnS layer can passivate the surface defects of the ZnMgO nanoparticles and improve the When the heterojunction nanomaterial is used as an electron transport layer and the quality of the contact surface of the quantum dot light-emitting layer, at the same time, after the surface Zn atoms of the ZnMgO nanoparticles are closely combined with the surface S atoms, a new electron transfer path is created, which can accelerate electrons. transfer, thereby synergistically improving the luminous efficiency and stability of quantum dot light-emitting diodes. In addition, the preparation method of the heterojunction nanomaterial provided by the present invention is simple to operate, and is suitable for large-scale and large-scale preparation.

Description of drawings

Fig. 1 is a flowchart of a method for preparing a heterojunction nanomaterial in an embodiment of the present invention.

Fig. 2 is a flow chart of a thin film preparation method in an embodiment of the present invention.

FIG. 3 is a schematic structural view of a quantum dot light-emitting diode with a front-mounted structure in an embodiment of the present invention.

FIG. 4 is a schematic structural diagram of a quantum dot light-emitting diode with an inverted structure in an embodiment of the present invention.

Detailed ways

The present invention provides a heterojunction nanomaterial and its preparation method, thin film, and quantum dot light-emitting diode. In order to make the purpose, technical solution and effect of the present invention clearer and clearer, the present invention will be further described in detail below. It should be understood that the specific embodiments described here are only used to explain the present invention, not to limit the present invention.

Please refer to Fig. 1, Fig. 1 is a flowchart of a preferred embodiment of a method for preparing a heterojunction nanomaterial provided by the present invention, as shown in the figure, it includes steps:

S10, providing a ZnMgO nanoparticle;

S20. Adding the ZnMgO nanoparticles into the sulfur source aqueous solution and heating to form a ZnS layer on the surface of the ZnMgO nanoparticles to prepare the heterojunction nanomaterial.

In this embodiment, the heterojunction nanomaterial is prepared by sulfurizing the ZnMgO nanoparticles to form a ZnS layer on the surface of the ZnMgO nanoparticles. ZnS is an n-type semiconductor with a wide direct band gap. It has a relatively high electron mobility (100-150cm ² V ^-1 s ^-1 ), starting from the interface energy level matching theory, the heterojunction nanomaterial has a suitable surface work function, which can well promote the interface electron Transport, which is beneficial to electron extraction and transfer; the ZnS layer can passivate the surface defects of ZnMgO nanoparticles, improve the quality of the contact surface with the quantum dot light-emitting layer when the heterojunction nanomaterial is used as the electron transport layer, and at the same time the After the surface Zn atoms of ZnMgO nanoparticles are closely combined with the surface S atoms, a new electron transfer pathway is created, which can accelerate electron transfer, thereby synergistically improving the luminous efficiency and stability of quantum dot light-emitting diodes. In addition, the preparation method of the heterojunction nanomaterial provided by the present invention is simple to operate, and is suitable for large-scale and large-scale preparation.

In some embodiments, the preparation of the ZnMgO nanoparticles includes the steps of: dispersing zinc salt and magnesium salt in an organic solvent to form a mixed solution; adding lye to the mixed solution to react to prepare ZnMgO nanoparticles.

Specifically, the zinc salt and the magnesium salt are dispersed in an organic solvent at a mass ratio of 1:10-20 to form a mixed solution, and lye is added to the mixed solution to undergo polycondensation reaction to generate ZnMgO nanoparticles . In this embodiment, the doping of magnesium ions not only improves the position of the bottom energy level of the conduction band of ZnO, reduces the electron injection barrier between the electron transport layer and the quantum dot light-emitting layer, but also reduces the impact of ZnO on the quantum dot light-emitting layer. Fluorescence quenching makes quantum dot light-emitting diodes exhibit higher current density and brightness.

In some embodiments, the total concentration of zinc ions and magnesium ions in the mixed solution is 0.1-1M.

In some embodiments, lye is added dropwise to the mixed solution and stirred for 1-4 hours to obtain a clear and transparent solution. After the clear and transparent solution is cooled, it is precipitated with acetone, and after centrifugation, it is dissolved with an organic alcohol solvent to prepare Obtain the ZnMgO nanoparticles. In this embodiment, the molar ratio of OH ⁻ of the lye to Zn ²⁺ in the mixed solution is 1.5-3:1, and the pH of the lye is 12-14.

In some embodiments, the zinc salt is one or more of zinc chloride, zinc nitrate, zinc acetate and zinc acetate dihydrate, but not limited thereto.

In some embodiments, the magnesium salt is one or more of magnesium chloride, magnesium nitrate, magnesium acetate and magnesium acetate dihydrate, but is not limited thereto.

In some embodiments, the organic solvent is one or more of DMF, DMSO and isopropanol, but is not limited thereto.

In some embodiments, the lye is one or more of sodium hydroxide solution, potassium hydroxide solution and tetramethylammonium hydroxide solution, but is not limited thereto.

In some embodiments, the ZnMgO nanoparticles are added to the sulfur source aqueous solution and heated to 80-120°C, and after reacting for 1-3h, a ZnS layer is formed on the surface of the ZnMgO nanoparticles to obtain a heterojunction nanomaterial . In this example, the ZnMgO nanoparticles and the sulfur source aqueous solution undergo a hydrothermal reaction under heating conditions, and a ZnS layer is formed on the surface of the ZnMgO nanoparticles to obtain the heterojunction nanomaterial. ZnS is a kind of An n-type semiconductor with a direct band gap, which has a relatively high electron mobility (100-150cm ² V ^-1 s ^-1 ), starting from the theory of interface energy level matching, the ZnMgO-ZnS heterostructure nanoparticles have a suitable The surface work function can well promote interface electron transport, which is beneficial to electron extraction and transfer; the ZnS layer can passivate the surface defects of ZnMgO nanoparticles, and improve the contact with quantum when the heterojunction nanomaterial is used as the electron transport layer. At the same time, after the surface Zn atoms of the ZnMgO nanoparticles are closely combined with the surface S atoms, a new electron transfer pathway can be created, which can accelerate electron transfer, thereby synergistically improving the luminous efficiency and efficiency of quantum dot light-emitting diodes. stability.

In some embodiments, the mass ratio of the ZnMgO nanoparticles to the sulfur element in the sulfur source aqueous solution is 2-4:1. The mass ratio of ZnMgO in the ZnMgO-ZnS heterostructure nanoparticles to the sulfur element in the sulfur source has a great influence on the material composition, thereby affecting the device performance. In this embodiment, when the sulfur source is used too much, the ZnMgO-ZnS heterogeneous The composition of the structural nanoparticles is mostly ZnS; when the amount of the sulfur source is too low, the generated ZnS cannot be effectively combined on the surface of the ZnMgO nanoparticles.

In some embodiments, the sulfur source aqueous solution is one or more of thiourea aqueous solution, thioacetamide aqueous solution and L-cysteine aqueous solution, but is not limited thereto.

In some embodiments, a heterojunction nanomaterial is also provided, which includes ZnMgO nanoparticles and a ZnS layer grown on the surface of the ZnMgO nanoparticles.

In some embodiments, also provide a kind of preparation method of thin film, as shown in Figure 2, it comprises steps:

S100, dispersing the zinc salt and the magnesium salt in an organic solvent to form a mixed solution;

S200, adding lye to the mixed solution to react to prepare ZnMgO nanoparticles;

S300, adding the ZnMgO nanoparticles into the sulfur source aqueous solution and heating to form a ZnS layer on the surface of the ZnMgO nanoparticles to prepare a heterojunction nanomaterial;

S400. Dispersing the nano-heterojunction material in an organic solvent to prepare a film to obtain the film.

In this embodiment, a ZnS layer is formed on the surface of the ZnMgO nanoparticles by vulcanizing the ZnMgO nanoparticles to obtain a heterojunction nanomaterial. ZnS is an n-type semiconductor with a wide direct band gap, which has a relatively high Electron mobility (100-150cm ² V ^-1 s ^-1 ), starting from the interface energy level matching theory, the heterojunction nanomaterial has a suitable surface work function, which can well promote the interface electron transport, which is beneficial to the Extraction and transfer; the ZnS layer can passivate the surface defects of ZnMgO nanoparticles, improve the contact surface quality of the thin film (electron transport layer) and the quantum dot light-emitting layer, and the surface Zn atoms of the ZnMgO nanoparticles are closely connected to the surface S atoms After the combination, a new electron transfer pathway is created, which can accelerate electron transfer, thereby synergistically improving the luminous efficiency and stability of quantum dot light-emitting diodes. In addition, the preparation method of the thin film provided by the invention is simple to operate and is suitable for large-scale and large-scale preparation.

In some embodiments, a thin film is also provided, wherein the material of the thin film is a heterojunction material, and the heterojunction nanomaterial includes ZnMgO nanoparticles and a ZnS layer grown on the surface of the ZnMgO nanoparticles.

The method for preparing the film will be described in detail below through examples.

Example 1

The following is a detailed introduction using zinc chloride, magnesium chloride, sodium hydroxide, and thiourea as examples:

1. Add zinc chloride and magnesium chloride to DMF at a mass ratio of 1:20 to form a solution with a total concentration of 0.5M, and add 0.6M NaOH ethanol solution dropwise at room temperature (molar ratio OH ^- : Zn ²⁺ =(1.5 ～3.0): 1, pH=12～14), continue to stir for 1.5h to obtain a clear and transparent solution, precipitate with acetone, collect after centrifugation, and obtain ZnMgO nanoparticles;

2. Put the ZnMgO nanoparticles prepared above in a high-pressure reactor, add thiourea aqueous solution (mass ratio ZnMgO:S=2:1), and react at 100°C for 2 hours to prepare ZnMgO-ZnS heterostructure nanoparticles , dissolved with a small amount of ethanol to obtain a ZnMgO-ZnS heterostructure nanoparticle solution, which is spin-coated on the treated ITO with a homogenizer and annealed to obtain a thin film.

Example 2

The following takes zinc nitrate hexahydrate, magnesium chloride, thioacetamide, and potassium hydroxide as examples for a detailed introduction:

1. Add zinc nitrate and magnesium chloride to DMF at a mass ratio of 1:20 to form a solution with a total concentration of 0.5M, and add 0.6M KOH ethanol solution dropwise at room temperature (molar ratio OH ^- : Zn ²⁺ = (1.5～3.0) : 1, pH=12～14), continue stirring for 1.5h to obtain a clear and transparent solution. Precipitate with acetone, collect after centrifugation, and make ZnMgO nanoparticles;

2. Put the above-prepared ZnMgO nanoparticles in a high-pressure reactor, add thioacetamide aqueous solution (mass ratio ZnMgO:S=2:1), and react at 100°C for 2 hours to obtain a ZnMgO-ZnS heterostructure Nanoparticles are dissolved with a small amount of ethanol to obtain a ZnMgO-ZnS heterostructure nanoparticle solution, and the ZnMgO-ZnS heterostructure nanoparticle solution is spin-coated on the treated ITO with a homogenizer and annealed to obtain a thin film .

Example 3

The following is a detailed introduction using zinc acetate dihydrate, magnesium acetate dihydrate, L-cysteine, and tetramethylammonium hydroxide as examples:

1. Add zinc acetate and magnesium chloride (mass ratio Mg:Zn=1:20) into DMF to form a solution with a total concentration of 0.5M, and add dropwise 0.6M tetramethylammonium hydroxide ethanol solution at room temperature (molar ratio ^OH- : Zn ²⁺ =(1.5-3.0): 1, pH=12-14), continue stirring for 1.5h to obtain a clear and transparent solution. Precipitate with acetone, collect after centrifugation, and make ZnMgO nanoparticles;

2. Put the ZnMgO nanoparticles prepared above in a high-pressure reactor, add thiourea aqueous solution (mass ratio ZnMgO:S=2:1), and react at 100°C for 2 hours to prepare ZnMgO-ZnS heterostructure nanoparticles , dissolved with a small amount of ethanol to obtain a ZnMgO-ZnS heterostructure nanoparticle solution, which is spin-coated on the treated ITO with a homogenizer and annealed to obtain a thin film.

In some embodiments, there is also provided a quantum dot light-emitting diode, including an electron transport layer, wherein the electron transport layer is the thin film described in the present invention.

In some embodiments, the quantum dot light-emitting diode includes a stacked anode, a quantum dot light-emitting layer, an electron transport layer and a cathode, wherein the electron transport layer is the thin film described in the present invention.

In some specific embodiments, the quantum dot light-emitting diode includes a stacked anode, a hole transport layer, a quantum dot light-emitting layer, an electron transport layer and a cathode, wherein the electron transport layer is the thin film described in the present invention .

It should be noted that the present invention is not limited to the quantum dot light-emitting diode with the above structure, and may further include an interface functional layer or an interface modification layer, including but not limited to an electron blocking layer, a hole blocking layer, an electrode modification layer, and an isolation protection layer. one or more of . The quantum dot light emitting diode of the present invention can be partially encapsulated, fully encapsulated or not encapsulated.

The quantum dot light-emitting diode with an electron transport layer and its preparation method are described in detail below:

According to the different light emitting types of the quantum dot light emitting diodes, the quantum dot light emitting diodes can be divided into quantum dot light emitting diodes with a front-mounted structure and quantum dot light-emitting diodes with a flip-chip structure.

As one of the implementations, when the quantum dot light-emitting diode is a front-mounted structure, as shown in Figure 3, the QLED device includes an anode 2 stacked from bottom to top (the anode 2 is stacked on the substrate Bottom 1), hole transport layer 3, quantum dot luminescent layer 4, electron transport layer 5 and cathode 6, wherein the electron transport layer 5 is the thin film described in the present invention.

As another embodiment, when the quantum dot light-emitting diode is a flip-chip structure, as shown in Figure 4, the QLED device includes a cathode 6 stacked from bottom to top (the cathode 6 is stacked on the substrate 1), an electron transport layer 5, a quantum dot light-emitting layer 4, a hole transport layer 3 and an anode 2, wherein the electron transport layer 5 is the thin film described in the present invention.

In some embodiments, the material of the anode is selected from doped metal oxide; wherein, the doped metal oxide includes but not limited to indium doped tin oxide (ITO), fluorine doped tin oxide (FTO), Antimony doped tin oxide (ATO), aluminum doped zinc oxide (AZO), gallium doped zinc oxide (GZO), indium doped zinc oxide (IZO), magnesium doped zinc oxide (MZO), aluminum doped magnesium oxide One or more of (AMO).

In some embodiments, the material of the hole transport layer is selected from organic materials with good hole transport capability, such as but not limited to poly(9,9-dioctylfluorene-CO-N-(4- Butylphenyl) diphenylamine) (TFB), polyvinylcarbazole (PVK), poly(N,N'bis(4-butylphenyl)-N,N'-bis(phenyl)benzidine)( Poly-TPD), poly(9,9-dioctylfluorene-co-bis-N,N-phenyl-1,4-phenylenediamine) (PFB), 4,4',4"-tri(carba Azol-9-yl)triphenylamine (TCTA), 4,4'-bis(9-carbazole)biphenyl (CBP), N,N'-diphenyl-N,N'-bis(3-methyl Phenyl)-1,1'-biphenyl-4,4'-diamine (TPD), N,N'-diphenyl-N,N'-(1-naphthyl)-1,1'-bi One or more of benzene-4,4'-diamine (NPB), doped graphene, non-doped graphene, C60, F8, copper oxide, nickel oxide, tungsten trioxide and molybdenum trioxide.

In some embodiments, the material of the quantum dot light-emitting layer is selected from one or more of red quantum dots, green quantum dots, and blue quantum dots, and can also be selected from yellow quantum dots. Specifically, the material of the quantum dot light-emitting layer is selected from CdS, CdSe, CdTe, ZnO, ZnS, ZnSe, ZnTe, GaAs, GaP, GaSb, HgS, HgSe, HgTe, InAs, InP, InSb, AlAs, AlP, CuInS , CuInSe, and one or more of various core-shell structure quantum dots or alloy structure quantum dots. The quantum dots in the present invention can be selected from cadmium-containing or cadmium-free quantum dots. The quantum dot light-emitting layer of the material has the characteristics of wide excitation spectrum and continuous distribution, and high stability of emission spectrum.

In some embodiments, the material of the cathode is selected from one or more of conductive carbon materials, conductive metal oxide materials and metal materials; wherein the conductive carbon materials include but are not limited to doped or non-doped carbon nanotubes , doped or undoped graphene, doped or undoped graphene oxide, C60, graphite, carbon fiber and porous carbon; conductive metal oxide materials include but not limited to ITO, FTO, ATO and one or more of AZO; metal materials include but not limited to Al, Ag, Cu, Mo, Au, or their alloys; wherein in the metal materials, its morphology includes but not limited to dense films, nanowires, One or more of nanospheres, nanorods, nanocones and nanohollow spheres.

The present invention also provides a method for preparing a quantum dot light-emitting diode with a positive structure, comprising the following steps:

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

Prepare a quantum dot luminescent layer on the hole transport layer;

preparing an electron transport layer on the quantum dot luminescent layer, wherein the electron transport layer is the thin film of the present invention;

A cathode is prepared on the electron transport layer to obtain the quantum dot light emitting diode.

As one of the implementations, taking ITO conductive glass as the substrate as an example, in order to obtain a high-quality film, the ITO conductive glass needs to undergo a pretreatment process. The basic specific processing steps include: etching the ITO conductive glass into a narrow strip, Then ultrasonically clean them in deionized water, acetone, absolute ethanol and deionized water respectively to remove impurities on the surface. After drying, clean them with an ultraviolet cleaner to obtain the ITO anode.

As one of the implementation methods, the solution of the prepared hole transport material is spin-coated on ITO to form a film; the film thickness is controlled by adjusting the concentration of the solution, the spin-coating speed and the spin-coating time, and then thermal annealing treatment at an appropriate temperature , to make a hole transport layer; the solution of the prepared hole transport material is spin-coated on ITO to form a film; the prepared quantum dot solution of a certain concentration is spin-coated on the hole transport layer to form a film, by The concentration of the solution, the spin-coating speed and the spin-coating time are used to control the thickness of the quantum dot light-emitting layer, which is about 20-60nm, and dried at an appropriate temperature.

As one of the implementations, the step of preparing an electron transport layer on the quantum dot light-emitting layer specifically includes: spin-coating a heterojunction nanomaterial solution prepared with a certain concentration on the quantum dot light-emitting layer to form a film, by adjusting the heterojunction The thickness of the electron transport layer is controlled by the concentration of the nanomaterial solution, the spin coating speed and the spin coating time, which is about 20-60nm, and then annealed to form a film.

In some specific embodiments, the spin coating speed is 3000-5000 rpm.

As one of the implementation methods, the step of preparing the cathode on the electron transport layer specifically includes: placing the substrate on which each functional layer has been deposited in an evaporation chamber and thermally evaporating a layer of 15-30nm metallic silver or aluminum through a mask plate. etc. as the cathode, or use nano-Ag wires or Cu wires, etc., the above-mentioned materials have a small resistance so that carriers can be injected smoothly.

The present invention also provides a method for preparing a quantum dot light-emitting diode with an inverted structure, comprising the following steps:

A substrate containing a cathode is provided, and an electron transport layer is prepared on the cathode, wherein the electron transport layer is the thin film according to the present invention;

preparing a quantum dot luminescent layer on the electron transport layer;

Prepare a hole transport layer on the quantum dot light-emitting layer;

An anode is prepared on the hole transport layer to obtain a quantum dot light emitting diode.

As one of the implementations, the step of preparing an electron transport layer on the cathode specifically includes: spin-coating a heterojunction nanomaterial solution with a certain concentration on the quantum dot light-emitting layer to form a film, and adjusting the heterojunction nanomaterial The concentration of the solution, the spin-coating speed and the spin-coating time are used to control the thickness of the electron transport layer, which is about 20-60nm, and then annealed to form a film.

The present invention also includes the step of: encapsulating the obtained quantum dot light-emitting diodes. The encapsulation process can be carried out by commonly used machine encapsulation or manual encapsulation. Preferably, in the encapsulation environment, both the oxygen content and the water content are lower than 0.1 ppm, so as to ensure the stability of the quantum dot light-emitting diode.

The preparation method of the above-mentioned layers can be a chemical method or a physical method, wherein the chemical method includes but is not limited to one or Various; physical methods include but not limited to physical coating method or solution method, where solution methods include but not limited to spin coating method, printing method, scrape coating method, dipping and pulling method, soaking method, spraying method, roll coating method, casting method, slit coating method, strip coating method; physical coating methods include but not limited to thermal evaporation coating method, electron beam evaporation coating method, magnetron sputtering method, multi-arc ion coating method, physical vapor deposition method, One or more of atomic layer deposition and pulsed laser deposition.

In summary, the present invention generates a ZnS layer on the surface of the ZnMgO nanoparticles by vulcanizing the ZnMgO nanoparticles to obtain a heterojunction nanomaterial. The ZnS layer can passivate the surface defects of the ZnMgO nanoparticles and improve The quality of the interface between the thin film (electron transport layer) and the quantum dot light-emitting layer, while the surface Zn atoms of the ZnMgO nanoparticles are closely combined with the surface S atoms to create a new electron transfer pathway, which can accelerate electron transfer, thereby synergistically improving Luminous efficiency and stability of quantum dot light-emitting diodes. In addition, the preparation method of the thin film provided by the invention is simple to operate and is suitable for large-scale and large-scale preparation.

It should be understood that the application of the present invention is not limited to the above examples, and those skilled in the art can make improvements or transformations according to the above descriptions, and all these improvements and transformations should belong to the protection scope of the appended claims of the present invention.

Claims (8)

1. A preparation method of a heterojunction nano material is characterized by comprising the following steps:

dispersing zinc salt and magnesium salt in an organic solvent to form a mixed solution;

adding alkali liquor into the mixed solution, and reacting to obtain ZnMgO nano-particles;

adding the ZnMgO nano-particles into a sulfur source aqueous solution, heating, and generating a ZnS layer on the surfaces of the ZnMgO nano-particles to prepare the heterojunction nano-material;

the total concentration of zinc ions and magnesium ions in the mixed solution is 0.1-1M.

2. The method for preparing the heterojunction nano-material of claim 1, wherein the mass ratio of the ZnMgO nano-particles to the sulfur element in the sulfur source aqueous solution is 2-4:1.

3. The method for preparing heterojunction nano-material according to claim 1, wherein the step of adding the ZnMgO nanoparticles into a sulfur source aqueous solution and heating to form a ZnS layer on the surface of the ZnMgO nanoparticles to obtain the heterojunction nano-material comprises:

and adding the ZnMgO nano-particles into a sulfur source water solution, heating to 80-120 ℃, reacting for 1-3h, and generating a ZnS layer on the surfaces of the ZnMgO nano-particles to obtain the heterojunction nano-material.

4. The method for preparing the heterojunction nano-material according to claim 1, wherein the sulfur source aqueous solution is one or more of a thiourea aqueous solution, a thioacetamide aqueous solution and an L-cysteine aqueous solution.

5. The preparation method of the heterojunction nano-material according to claim 1, wherein the mass ratio of the zinc salt to the magnesium salt is 1:10-20.

6. The method for preparing a heterojunction nano-material as claimed in claim 1, wherein OH of the alkali solution is ^- With Zn in the mixed solution ²⁺ In a molar ratio of 1.5 to 3:1.

7. a thin film, wherein the material of the thin film is the heterojunction nano-material prepared by the preparation method of claim 1.

8. A quantum dot light emitting diode comprising an electron transport layer, wherein the electron transport layer is the film of claim 7.

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