WO2021136044A1 - Quantum dot light-emitting diode and manufacturing method therefor - Google Patents

Abstract

A quantum dot light-emitting diode and a manufacturing method therefor. The manufacturing method for the quantum dot light-emitting diode comprises the steps: providing an anode (2); forming a quantum dot light-emitting layer (4) on the anode (2); forming an electron transport layer (5) on the quantum dot light-emitting layer (4), the electron transport layer (5) comprising a ZnO layer and a ZnMgO layer which are provided in a stacked manner, and the ZnO layer being provided at a side close to the quantum dot light-emitting layer (4); and forming a cathode (6) on the electron transport layer (5), so as to obtain a quantum dot light-emitting diode. Without the introduction of other heterogeneous material layers, the use of interface barriers can control the injection of electrons, so as to balance the injection of electrons and holes. The ZnMgO can adjust the width of forbidden band of the electron transport layer (5), adjust the injection barriers for electrons, reduce the injection efficiency of electrons, and can balance the injection of electrons and holes, so as to achieve the purpose of promoting the effective radiative recombination of electrons and holes in the quantum dot light-emitting layer (4), thereby improving the efficiency of the device.

Description

Quantum dot light-emitting diode and preparation method thereof

This disclosure claims the priority of a Chinese patent application filed with the Chinese Patent Office on December 30, 2019, the application number is "201911398448.2", and the application name is "A quantum dot light-emitting diode and its preparation method", all of which The content is incorporated into this disclosure by reference.

Technical field

The present disclosure relates to the field of quantum dot light-emitting devices, in particular to a quantum dot light-emitting diode and a preparation method thereof.

Background technique

Quantum dots are semiconductor clusters with a size of 1-10 nm. Due to the quantum size effect, they have photoelectronic properties with adjustable band gaps and can be used in light-emitting diodes, solar cells, bioluminescent labels and other fields. People adjust the size of quantum dots to achieve the required specific wavelength of light emission. According to the elements of quantum dots, quantum dots can be divided into group II-VI quantum dots (such as CdSe, CdS, CdTe, ZnSe, ZnS, etc.), group III-V Quantum dots (such as GaAs, InAs, InP, etc.), carbon quantum dots and silicon quantum dots. At present, CdSe QDs are more researched, and their emission wavelength tuning range can be from blue light to red light. 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. The conduction band electrons in wide-bandgap semiconductors can be accelerated under high electric fields to obtain high enough energy to hit QDs to make them emit light. As a new type of inorganic semiconductor fluorescent material, semiconductor quantum dot material has important commercial application value.

ZnO is a direct bandgap n-type semiconductor material, with 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, making ZnO a suitable electronic Transmission layer material. ZnO has many potential advantages. Its exciton binding energy is as high as 60meV, which is much higher than other wide-gap semiconductor materials (GaN is 25meV), and it is 2.3 times the room temperature thermal energy (26meV), so the excitons of ZnO can be at room temperature. Stable existence. Secondly, ZnO has a hexagonal wurtzite structure, showing strong spontaneous polarization; in the ZnO-based heterostructure, the strain of the material will lead to extremely strong piezoelectric polarization, leading to a polarization effect in the ZnO-based heterostructure . The polarization electric field generated by the polarization induces a high concentration of interface polarization charges on the ZnO heterojunction surface, thereby regulating the energy band of the material, and then affecting the performance of related structural devices.

However, at present, QLED devices widely adopt a mixed structure of organic and inorganic carrier transport layers, which are composed of an anode, an organic hole transport layer, a light-emitting layer, an inorganic electron transport layer, and a cathode. This device structure often uses p-type organic semiconductors, such as PVK, Poly-TPD, TFB, etc., as the hole transport layer material, and n-type inorganic semiconductor ZnO as the electron transport layer material. The hole mobility of these organic semiconductor materials is less than that of ZnO. Therefore, the electron injection and transport efficiency in QLED devices is much greater than the hole injection and transport efficiency, resulting in an imbalance of electron and hole injection and limiting the improvement of device efficiency. .

In the past research work, whether it is optimizing the transport layer material or inserting various buffer layers, it involves the introduction of new functional layers in the device, thereby forming more interfaces between different materials inside the device, which will affect the charge transfer. Too many factors have greatly increased the complexity of the research, which is not conducive to a deep understanding of the physical mechanism of the impact of implant imbalance on the device.

Therefore, the existing technology needs to be improved and developed.

Summary of the invention

In view of the above-mentioned shortcomings of the prior art, the purpose of the present disclosure is to provide a quantum dot light-emitting diode and a manufacturing method thereof, aiming to solve the problem that the existing method of improving the electron transmission efficiency requires the introduction of new materials.

The technical solutions of the present disclosure are as follows:

A method for preparing a quantum dot light-emitting diode, which comprises the steps:

Provide anode;

Forming a quantum dot light-emitting layer on the anode;

Forming an electron transport layer on the quantum dot light-emitting layer, the electron transport layer including a stacked ZnO layer and a ZnMgO layer, and the ZnO layer is arranged close to the quantum dot light-emitting layer;

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

A quantum dot light emitting diode, comprising: an anode, a cathode, 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, wherein the electron The transmission layer includes a laminated ZnO layer and a ZnMgO layer, and the ZnO layer is arranged close to the quantum dot light-emitting layer side.

Beneficial effects: The present disclosure introduces an interface inside the electron transport layer by setting the ZnO layer/ZnMgO layer double layer as the electron transport layer, and uses the newly added interface to effectively block the excess electrons from reaching the QD interface, thereby reducing the exciton quenching caused by the charging of the QD. And efficiency roll-off. The method does not need to introduce new materials, nor does it involve contact with other functional layers. It just adds an interface to the existing ZnO electron transport layer to control the injection of electrons and achieve a balance between it and hole injection. In addition, ZnMgO (Mg-doped ZnO) can adjust the forbidden band width of the electron transport layer, adjust the electron injection barrier, reduce the electron injection efficiency, and balance the electron-hole injection to promote electron-hole in the quantum dot The purpose of effective radiation recombination in the light-emitting layer, thereby improving the efficiency of the device. ZnMgO has a wide band gap, so it can also play a role in blocking holes in the device, enabling the device to achieve better performance. In addition, in the present disclosure, the preparation of the electron transport layer is simple, which is suitable for large-area and large-scale preparation.

Description of the drawings

FIG. 1 is a schematic structural diagram of a quantum dot light-emitting diode provided in an embodiment of the disclosure.

FIG. 2 is a schematic flow chart of a method for manufacturing a quantum dot light-emitting diode provided in an embodiment of the disclosure.

Detailed ways

The present disclosure provides a quantum dot light-emitting diode and a preparation method thereof. In order to make the objectives, technical solutions, and effects of the present disclosure clearer and clearer, the present disclosure will be described in further detail below. It should be understood that the specific embodiments described herein are only used to explain the present disclosure, but not used to limit the present disclosure.

The embodiment of the present disclosure provides a method for manufacturing a quantum dot light-emitting diode, which includes the following steps:

Provide anode;

Forming a quantum dot light-emitting layer on the anode;

Forming an electron transport layer on the quantum dot light-emitting layer, the electron transport layer including a stacked ZnO layer and a ZnMgO layer, and the ZnO layer is arranged close to the quantum dot light-emitting layer;

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

In this embodiment, the electron transport layer is composed of a stacked ZnO layer and a ZnMgO (a small amount of Mg doped ZnO) layer. By setting a ZnO layer/ZnMgO layer as the electron transport layer, the inside of the electron transport layer Introduce an interface, use the new interface to effectively block the excess electrons from reaching the QD interface, and reduce the exciton quenching and efficiency roll-off caused by the charging of the QD. In other words, in this embodiment, the existing single-layer ZnO electron transport layer is configured as a ZnO layer/ZnMgO layer double layer as the electron transport layer to increase the electron transport barrier and delay the electron injection. It should be noted that in this embodiment, ZnMgO is a small amount of Mg-doped ZnO, the main material in the ZnMgO layer is still ZnO, and Mg and Zn are approximately the same quality, so this method does not introduce new materials (such as no need to introduce heterogeneous Material), it does not involve contact with other functional layers, but an interface is added to the existing ZnO electron transport layer to control the injection of electrons and achieve a balance with hole injection. In addition, ZnMgO can adjust the forbidden band width of the electron transport layer, adjust the electron injection barrier, reduce the electron injection efficiency, and balance the electron-hole injection to promote effective electron-hole radiation in the quantum dot light-emitting layer The purpose of recombination, thereby improving the efficiency of the device. ZnMgO has a wide band gap, so it can also play a role in blocking holes in the device, enabling the device to achieve better performance. In addition, in this embodiment, the preparation of the electron transport layer is simple, which is suitable for large-area and large-scale preparation.

In this embodiment, the quantum dot light-emitting diode has many forms, and the quantum dot light-emitting diode is divided into a positive structure and an inverted structure. This embodiment will mainly use a quantum dot light-emitting diode with a positive structure as shown in FIG. 1 As an example, the above preparation method is introduced in detail. In one embodiment, as shown in FIG. 1, the quantum dot light emitting diode includes a substrate 1, an anode 2, a hole transport layer 3, a quantum dot light emitting layer 4, an electron transport layer 5 and Cathode 6; wherein, the electron transport layer 5 includes a stacked ZnO layer and a ZnMgO layer, and the ZnO layer is located close to the quantum dot light-emitting layer 4 side. The manufacturing method of the quantum dot light-emitting diode, as shown in FIG. 2, includes the steps:

S10. Provide a substrate containing an anode;

S20, forming a hole transport layer on the anode;

S30, forming a quantum dot light-emitting layer on the hole transport layer;

S40, forming an electron transport layer on the quantum dot light-emitting layer, the electron transport layer including a stacked ZnO layer and a ZnMgO layer, and the ZnO layer is disposed close to a side of the quantum dot light-emitting layer;

S50, forming a cathode on the electron transport layer to obtain a quantum dot light emitting diode.

In an embodiment, step S40 specifically includes:

S41. Provide a ZnO nanoparticle solution, cover the ZnO nanoparticle solution on the quantum dot light-emitting layer, and obtain a ZnO layer after annealing;

S42. Provide a ZnMgO nanoparticle solution, cover the ZnMgO nanoparticle solution on the ZnO layer, and obtain a ZnMgO layer after annealing.

In one embodiment, the method for preparing ZnO nanoparticles includes the steps of mixing zinc salt and alkali, and reacting to obtain ZnO nanoparticles.

In a specific embodiment, the method for preparing ZnO nanoparticles specifically includes the steps of: adding zinc salt to an organic solvent to form a zinc salt solution; adding lye to the zinc salt solution and stirring for 1-4 hours, A clear and transparent solution is obtained, and ZnO nanoparticles are obtained after purification (such as precipitation with acetone and centrifugation). Further, the concentration of the zinc salt solution is 0.1-1M. Further, according to the ^{molar ratio of OH-} to Zn ²⁺ of (1.5-3.0):1, the zinc salt solution is mixed with the lye. Further, the pH of the lye is 12-14.

In one embodiment, the zinc salt is a soluble inorganic zinc salt or a soluble organic zinc salt. As an example, the zinc salt includes zinc acetate, zinc nitrate, zinc chloride, zinc sulfate, and zinc acetate dihydrate, etc., which are not limited to one or more of these.

In this embodiment, the lye is prepared by dispersing an alkali in a solvent, and the concentration of the lye is 0.1-1M. In one embodiment, the base includes potassium hydroxide, sodium hydroxide, and tetramethylammonium hydroxide, etc., which are not limited to one or more of these. In one embodiment, the solvent includes DMF, DMSO, etc., which are not limited to one or more of them.

In one embodiment, the method for preparing ZnMgO nanoparticles includes the steps of mixing zinc salt, magnesium salt and alkali, and reacting to obtain ZnMgO nanoparticles.

In a specific embodiment, the method for preparing ZnMgO nanoparticles specifically includes the steps of: adding zinc salt and magnesium salt to an organic solvent to form a salt solution; adding lye to the salt solution and stirring for 1-4 hours , To obtain a clear and transparent solution, after purification (such as precipitation with acetone, centrifugation) to obtain ZnMgO nanoparticles. Further, the total concentration of the salt solution is 0.1-1M. Further, the pH of the lye is 12-14.

In one embodiment, the mass ratio of the zinc salt to the magnesium salt is (10-20):1.

In one embodiment, the molar ratio of the Zn element in the zinc salt to the OH ^- in the alkali is 1: (1.5-3.0).

In one embodiment, the zinc salt is a soluble inorganic zinc salt or a soluble organic zinc salt. As an example, the zinc salt includes zinc acetate, zinc nitrate, zinc chloride, zinc sulfate, and zinc acetate dihydrate, etc., which are not limited to one or more of these.

In one embodiment, the magnesium salt is a soluble inorganic magnesium salt or a soluble organic magnesium salt. As an example, the magnesium salt includes magnesium acetate, magnesium nitrate, magnesium chloride, magnesium sulfate, and magnesium acetate dihydrate, etc., which are not limited to one or more of these.

In this embodiment, the lye is prepared by dispersing an alkali in a solvent, and the concentration of the alkali in the lye is 0.1-1M. In one embodiment, the base includes potassium hydroxide, sodium hydroxide, and tetramethylammonium hydroxide, etc., which are not limited to one or more of these. In one embodiment, the solvent includes DMF, DMSO, etc., which are not limited to one or more of them.

In an embodiment, the method of covering the ZnO nanoparticle solution may be spin coating, spraying, printing, etc., but is not limited thereto. Wherein, the spin coating speed may be 3000-5000 rpm/min, and the spin coating time may be 0.5-1.5 min. The thickness of the ZnO layer is controlled by adjusting the concentration of the ZnO nanoparticle solution, the spin coating speed and the spin coating time, and then annealed to form a film. The annealing temperature may be 60-120°C.

In an embodiment, the method of covering the ZnMgO nanoparticle solution may be spin coating, spray coating, printing, etc., but is not limited thereto. Wherein, the spin coating speed may be 3000-5000 rpm/min, and the spin coating time may be 0.5-1.5 min. The thickness of the ZnMgO layer is controlled by adjusting the concentration of the ZnMgO nanoparticle solution, the spin coating speed and the spin coating time, and then annealed to form a film. The annealing temperature may be 60-120°C.

In this embodiment, in order to obtain a high-quality hole transport layer, the anode needs to undergo a pretreatment process. The pretreatment process specifically includes: cleaning the anode with a cleaning agent to initially remove the stains on the anode surface, followed by ultrasonic cleaning in deionized water, acetone, absolute ethanol, and deionized water for 20 minutes to remove the stains on the surface. Impurities are finally blown dry with high-purity nitrogen to obtain the anode.

In one embodiment, the step of forming a hole transport layer on the anode includes: placing the substrate on a homogenizer and spin-coating the prepared solution of the hole transport material to form a film; by adjusting the concentration of the solution, The film thickness is controlled by spin coating speed and spin coating time, and then thermally annealed at an appropriate temperature to obtain the hole transport layer.

In one embodiment, the step of preparing a quantum dot light-emitting layer on the hole transport layer includes: placing the substrate on which the hole transport layer has been prepared on a homogenizer, and preparing a solution of a certain concentration of light-emitting substance The film is formed by spin coating, the thickness of the quantum dot light-emitting layer is controlled by adjusting the concentration of the solution, the spin-coating speed, and the spin-coating time, and finally the quantum dot light-emitting layer is dried at an appropriate temperature to obtain the quantum dot light-emitting layer.

In one embodiment, the obtained quantum dot light emitting diode is packaged. Wherein, the packaging process can adopt common machine packaging or manual packaging. In one embodiment, 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.

In this embodiment, the preparation method of each layer can be a chemical method or a physical method, and the chemical method includes but not limited to chemical vapor deposition method, continuous ion layer adsorption and reaction method, anodic oxidation method, electrolytic deposition method, co-precipitation method. One or more; physical methods include, but are not limited to, solution methods (such as spin coating, printing, blade coating, dipping, dipping, dipping, spraying, roller coating, casting, slit coating Method or strip coating method, etc.), evaporation method (such as thermal evaporation method, electron beam evaporation method, magnetron sputtering method or multi-arc ion coating method, etc.), deposition method (such as physical vapor deposition method, element One or more of layer deposition method, pulsed laser deposition method, etc.).

The embodiments of the present disclosure provide a quantum dot light emitting diode, which includes an anode, a cathode, 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, Wherein, the electron transport layer material includes a laminated ZnO layer and a ZnMgO layer, and the ZnO layer is arranged on a side close to the quantum dot light-emitting layer.

In one embodiment, the electron transport layer is a ZnO layer and a ZnMgO layer that are stacked.

In one embodiment, as shown in FIG. 1, the quantum dot light emitting diode includes a substrate 1, an anode 2, a hole transport layer 3, a quantum dot light emitting layer 4, an electron transport layer 5 and Cathode 6; wherein, the material of the electron transport layer 5 is a laminated ZnO layer and a ZnMgO layer, and the ZnO layer is located close to the quantum dot light-emitting layer 4 side.

The electron transport layer is composed of two layers of laminated ZnO layer and ZnMgO layer. By setting the ZnO layer/ZnMgO layer as the electron transport layer, an interface is introduced inside the electron transport layer, and the new interface is used to effectively block excess Electrons reach the QD interface, reducing the exciton quenching and efficiency roll-off caused by the charging of the QD. In this method, without introducing other heterogeneous material layers, the interface barrier can be used to control the injection of electrons to achieve a balance with the injection of holes. This method does not need to introduce new materials, nor does it involve contact with other functional layers. It just adds an interface to the existing ZnO electron transport layer to control the transport of electrons. In addition, ZnMgO (Mg-doped ZnO) can adjust the forbidden band width of the electron transport layer, adjust the electron injection barrier, reduce the electron injection efficiency, and balance the electron-hole injection to promote electron-hole in the quantum dot The purpose of effective radiation recombination in the light-emitting layer, thereby improving the efficiency of the device. ZnMgO has a wide band gap, so it can also play a role in blocking holes in the device, enabling the device to achieve better performance.

In one embodiment, the thickness of the ZnO layer is 20-50 nm.

In one embodiment, the thickness of the ZnMgO layer is 20-50 nm.

In one embodiment, the thickness of the electron transport layer is 20 nm-60 nm. If the thickness of the electron transport layer is too thin, the carrier transport performance cannot be guaranteed, resulting in electrons failing to reach the quantum dot light-emitting layer, which causes hole-electron recombination in the transport layer, thereby causing quenching; If the thickness of the layer is too thick, the light transmittance of the film layer will decrease, and the carrier passability of the device will decrease, resulting in a decrease in the overall conductivity of the device.

In this embodiment, the substrate may be a substrate made of rigid material, such as glass, or it may be a substrate made of flexible material, such as one of PET or PI.

In this embodiment, the anode may be selected from one of indium-doped tin oxide (ITO), fluorine-doped tin oxide (FTO), antimony-doped tin oxide (ATO), and aluminum-doped zinc oxide (AZO). Kind or more.

In this embodiment, the material of the hole transport layer can be selected from materials with good hole transport properties, for example, can include but not limited to TFB, PVK, Poly-TPD, TCTA, PEDOT: PSS, CBP, NiO, MoO One or more of _{3 grades.}

In this embodiment, the material of the quantum dot light-emitting layer may be oil-soluble quantum dots, and the oil-soluble quantum dots include one or more of binary phase, ternary phase, quaternary phase quantum dots, etc.; wherein Binary phase quantum dots include one or more of CdS, CdSe, CdTe, InP, AgS, PbS, PbSe, HgS, etc., and ternary phase quantum dots include ZnCdS, CuInS, ZnCdSe, ZnSeS, ZnCdTe, PbSeS, etc. One or more, quaternary phase quantum dots include one or more of ZnCdS/ZnSe, CuInS/ZnS, ZnCdSe/ZnS, CuInSeS, ZnCdTe/ZnS, PbSeS/ZnS, etc. The material of the quantum dot light-emitting layer may be any one of the common red, green, and blue quantum dots or other yellow light. The quantum dots may contain cadmium or not contain cadmium. The quantum dot light-emitting layer of the material has the characteristics of wide excitation spectrum and continuous distribution, and high emission spectrum stability. In this embodiment, the thickness of the quantum dot light-emitting layer is about 20 nm to 60 nm.

In this embodiment, the cathode can be selected from one of aluminum (Al) electrodes, silver (Ag) electrodes, gold (Au) electrodes, etc., and can also be selected from nano aluminum wires, nano silver wires, and nano gold wires. One of them. The above-mentioned materials have relatively low resistance, which enables smooth injection of carriers. In this embodiment, the thickness of the cathode is about 15 nm-30 nm.

It should be noted that the quantum dot light emitting diode of the present disclosure may also include one or more layers of the following functional layers: a hole injection layer arranged between the hole transport layer and the anode, and a hole injection layer arranged between the electron transport layer and the cathode. Electron injection layer.

This embodiment will be described in detail below through specific embodiments.

Example 1

This embodiment uses zinc chloride, magnesium chloride, and sodium hydroxide (NaOH) as examples for detailed introduction.

Zinc chloride was added to DMF to form a solution with a total concentration of 0.5M, 0.6M NaOH ethanol solution was added dropwise at room temperature, and stirring was continued for 1.5 hours to obtain a clear and transparent solution. Precipitated with acetone, collected after centrifugation, and prepared ZnO nanoparticles. Dissolve the ZnO nanoparticles with ethanol for use.

Zinc chloride and magnesium chloride (mass ratio Mg:Zn=1:20) were added to DMF to form a solution with a total concentration of 0.5M, 0.6M NaOH ethanol solution was added dropwise at room temperature, and stirring was continued for 1.5 hours to obtain a clear and transparent solution. Precipitated with acetone, collected after centrifugation, and prepared ZnMgO nanoparticles. Dissolve the ZnMgO nanoparticles with ethanol for use.

Example 2

This embodiment takes zinc nitrate hexahydrate, magnesium chloride, and potassium hydroxide (KOH) as examples for detailed introduction.

Zinc nitrate was added to DMF to form a solution with a total concentration of 0.5M, 0.6M KOH ethanol solution was added dropwise at room temperature, and stirring was continued for 1.5 hours to obtain a clear and transparent solution. Precipitated with acetone, collected after centrifugation, and prepared ZnO nanoparticles. Dissolve the ZnO nanoparticles with ethanol for use.

Add zinc nitrate and magnesium chloride (mass ratio Mg:Zn=1:20) to DMF to form a solution with a total concentration of 0.5M, add 0.6M KOH ethanol solution dropwise at room temperature, and continue to stir for 1.5 hours to obtain a clear and transparent solution. Precipitated with acetone, collected after centrifugation, and prepared ZnMgO nanoparticles. Dissolve the ZnMgO nanoparticles with ethanol for use.

Example 3

This embodiment uses zinc acetate dihydrate, magnesium acetate dihydrate, and tetramethylammonium hydroxide as examples for detailed introduction.

Zinc acetate was added to DMF to form a solution with a total concentration of 0.5M, 0.6M tetramethylammonium hydroxide ethanol solution was added dropwise at room temperature, and stirring was continued for 1.5h to obtain a clear and transparent solution. Precipitated with acetone, collected after centrifugation, and prepared ZnO nanoparticles. Dissolve the ZnO nanoparticles with ethanol for use.

Zinc acetate and magnesium acetate (mass ratio Mg:Zn=1:20) were added to DMF to form a solution with a total concentration of 0.5M, 0.6M KOH ethanol solution was added dropwise at room temperature, and stirring was continued for 1.5 hours to obtain a clear and transparent solution. Precipitated with acetone, collected after centrifugation, and prepared ZnMgO nanoparticles. Dissolve the ZnMgO nanoparticles with ethanol for use.

Example 4

A quantum dot light-emitting diode includes a laminated structure of an anode and a cathode disposed oppositely, a quantum dot light-emitting layer disposed between the anode and the cathode, and a quantum dot light-emitting layer disposed between the cathode and the quantum dot light-emitting layer The electron transport layer is provided on the hole transport layer between the anode and the quantum dot light-emitting layer, and the anode is provided on the substrate. Among them, the material of the substrate is a glass sheet, the material of the anode is an ITO substrate, the hole transport layer is a material TFB, the electron transport layer is a ZnO layer/ZnMgO layer, and the material of the cathode is Al.

The manufacturing method of the quantum dot light-emitting diode includes the following steps:

Provide an ITO substrate, and prepare a hole transport layer on the ITO substrate;

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

Depositing the ZnO nanoparticle solution obtained in the method described in Example 1 on the quantum dot light-emitting layer, and annealing to prepare a ZnO layer;

Depositing the ZnMgO nanoparticle solution obtained in the method described in Example 1 on the ZnO layer, and annealing to prepare a ZnMgO layer;

A cathode is prepared on the ZnMgO layer.

Example 5

A quantum dot light-emitting diode, comprising a laminated structure of an anode and a cathode arranged oppositely, a quantum dot light-emitting layer arranged between the anode and the cathode, and a quantum dot light-emitting layer arranged between the cathode and the quantum dot light-emitting layer The electron transport layer is provided on the hole transport layer between the anode and the quantum dot light-emitting layer, and the anode is provided on the substrate. Among them, the material of the substrate is a glass sheet, the material of the anode is an ITO substrate, the material of the hole transport layer is TFB, the electron transport layer is a ZnO layer/ZnMgO layer, and the material of the cathode is Al.

The manufacturing method of the quantum dot light-emitting diode includes the following steps:

Provide an ITO substrate, and prepare a hole transport layer on the ITO substrate;

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

Depositing the ZnO nanoparticle solution obtained in the method described in Example 2 on the quantum dot light-emitting layer, and annealing to prepare a ZnO layer;

Depositing the ZnMgO nanoparticle solution obtained in the method described in Example 2 on the ZnO layer, and annealing to prepare a ZnMgO layer;

A cathode is prepared on the ZnMgO layer.

Example 6

A quantum dot light-emitting diode, comprising a laminated structure of an anode and a cathode arranged oppositely, a quantum dot light-emitting layer arranged between the anode and the cathode, and a quantum dot light-emitting layer arranged between the cathode and the quantum dot light-emitting layer The electron transport layer is provided on the hole transport layer between the anode and the quantum dot light-emitting layer, and the anode is provided on the substrate. Among them, the material of the substrate is a glass sheet, the material of the anode is an ITO substrate, the material of the hole transport layer is TFB, the electron transport layer is a ZnO layer/ZnMgO layer, and the material of the cathode is Al.

The manufacturing method of the quantum dot light-emitting diode includes the following steps:

Provide an ITO substrate, and prepare a hole transport layer on the ITO substrate;

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

Depositing the ZnO nanoparticle solution obtained in the method described in Example 3 on the quantum dot light-emitting layer, and annealing to prepare a ZnO layer;

Depositing the ZnMgO nanoparticle solution obtained in the method described in Example 3 on the ZnO layer, and annealing to prepare a ZnMgO layer;

A cathode is prepared on the ZnMgO layer.

Example 7

A quantum dot light-emitting diode, comprising a laminated structure of an anode and a cathode arranged oppositely, a quantum dot light-emitting layer arranged between the anode and the cathode, and a quantum dot light-emitting layer arranged between the cathode and the quantum dot light-emitting layer The electron transport layer is provided on the hole transport layer between the anode and the quantum dot light-emitting layer, and the cathode is provided on the substrate. Among them, the material of the substrate is a glass sheet, the material of the cathode is an ITO substrate, the material of the hole transport layer is TFB, the electron transport layer is a ZnO layer/ZnMgO layer, and the material of the anode is Al.

The manufacturing method of the quantum dot light-emitting diode includes the following steps:

Providing a cathode substrate, depositing the ZnMgO nanoparticle solution obtained in the method described in Example 1 on the cathode substrate, and annealing to prepare a ZnMgO layer;

Depositing the ZnO nanoparticle solution obtained in the method described in Example 1 on the ZnMgO layer, and annealing to prepare a ZnO layer;

A quantum dot light-emitting layer is prepared on the ZnO layer, and a hole transport layer is prepared on the quantum dot light-emitting layer;

An anode is prepared on the hole transport layer.

Example 8

A quantum dot light-emitting diode, comprising a laminated structure of an anode and a cathode arranged oppositely, a quantum dot light-emitting layer arranged between the anode and the cathode, and a quantum dot light-emitting layer arranged between the cathode and the quantum dot light-emitting layer The electron transport layer is provided on the hole transport layer between the anode and the quantum dot light-emitting layer, and the cathode is provided on the substrate. Among them, the material of the substrate is a glass sheet, the material of the cathode is an ITO substrate, the material of the hole transport layer is TFB, the electron transport layer is a ZnO layer/ZnMgO layer, and the material of the anode is Al.

The manufacturing method of the quantum dot light-emitting diode includes the following steps:

Providing a cathode substrate, depositing the ZnMgO nanoparticle solution obtained in the method described in Example 2 on the cathode substrate, and annealing to prepare a ZnMgO layer;

Depositing the ZnO nanoparticle solution obtained in the method described in Example 2 on the ZnMgO layer, and annealing to prepare a ZnO layer;

A quantum dot light-emitting layer is prepared on the ZnO layer, and a hole transport layer is prepared on the quantum dot light-emitting layer;

An anode is prepared on the hole transport layer.

Example 9

A quantum dot light-emitting diode, comprising a laminated structure of an anode and a cathode arranged oppositely, a quantum dot light-emitting layer arranged between the anode and the cathode, and a quantum dot light-emitting layer arranged between the cathode and the quantum dot light-emitting layer The electron transport layer is provided on the hole transport layer between the anode and the quantum dot light-emitting layer, and the cathode is provided on the substrate. Among them, the material of the substrate is a glass sheet, the material of the cathode is an ITO substrate, the material of the hole transport layer is TFB, the electron transport layer is a ZnO layer/ZnMgO layer, and the material of the anode is Al.

The manufacturing method of the quantum dot light-emitting diode includes the following steps:

Providing a cathode substrate, depositing the ZnMgO nanoparticle solution obtained in the method described in Example 3 on the cathode substrate, and annealing to prepare a ZnMgO layer;

Depositing the ZnO nanoparticle solution obtained in the method described in Example 3 on the ZnMgO layer, and annealing to prepare a ZnO layer;

A quantum dot light-emitting layer is prepared on the ZnO layer, and a hole transport layer is prepared on the quantum dot light-emitting layer;

An anode is prepared on the hole transport layer.

Comparative example 1

A quantum dot light-emitting diode, comprising a laminated structure of an anode and a cathode arranged oppositely, a quantum dot light-emitting layer arranged between the anode and the cathode, and a quantum dot light-emitting layer arranged between the cathode and the quantum dot light-emitting layer The electron transport layer is provided on the hole transport layer between the anode and the quantum dot light-emitting layer, and the anode is provided on the substrate. Among them, the material of the substrate is a glass sheet, the material of the anode is an ITO substrate, the material of the hole transport layer is TFB, the material of the electron transport layer is a commercial ZnO material (purchased from sigma), and the material of the cathode is Al.

Comparative example 2

A quantum dot light-emitting diode, comprising a laminated structure of an anode and a cathode arranged oppositely, a quantum dot light-emitting layer arranged between the anode and the cathode, and a quantum dot light-emitting layer arranged between the cathode and the quantum dot light-emitting layer The electron transport layer is provided on the hole transport layer between the anode and the quantum dot light-emitting layer, and the anode is provided on the substrate. The material of the substrate is a glass sheet, the material of the anode is an ITO substrate, the material of the hole transport layer is TFB, the material of the electron transport layer is the ZnMgO material synthesized in the embodiment, and the material of the cathode is Al.

The electron transport films prepared in Examples 1-3, the electron transport films in Comparative Examples 1-2, the quantum dot light-emitting diodes prepared in Examples 4-9 and Comparative Examples 1-2 were tested for performance, and the test indicators and The test method is as follows:

(1) Electron mobility: test the current density (J)-voltage (V) of the quantum dot light-emitting diode, draw a curve relationship diagram, fit the space charge limited current (SCLC) area in the relationship diagram, and then according to Child,s The law formula calculates the 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, and the unit is m.

(2) Starting potential: Measured with EQE optical testing instrument.

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

Note: The electron mobility test is a single-layer film structure device, namely: cathode/electron transport film/anode. The initial potential and external quantum efficiency test are for the QLED device, 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

It can be seen from Table 1 above that the ZnO/ZnMgO double-layer electron transport film formed by the materials provided in Examples 1-3 of the present disclosure has an electron mobility significantly lower than that of the single-layer electron transport film in Comparative Example 1-2.

The external quantum efficiency of the quantum dot light-emitting diode (the material of the electron transport layer is ZnO/ZnMgO double-layer electron transport film) provided by Examples 4-9 of the present disclosure is significantly higher than that of the quantum dots of the single-layer electron transport layer in Comparative Example 1-2 The external quantum efficiency of the light-emitting diode indicates that the quantum dot light-emitting diode obtained in the embodiment has better luminous efficiency.

It is worth noting that the specific embodiments provided in the present disclosure all use blue quantum dots Cd _X Zn _1-X S/ZnS as the light-emitting layer material, which is based on the blue light-emitting system which uses more systems (due to the blue quantum dot light-emitting diode It is more difficult to achieve high efficiency, so it has more reference value), which does not mean that the present disclosure is only used for blue light emitting systems.

In summary, the present disclosure provides a quantum dot light-emitting diode and a manufacturing method thereof. The present disclosure adopts the ZnO layer/ZnMgO layer double layer as the electron transport layer, introduces an interface inside the electron transport layer, and uses the new interface to effectively block excess electrons from reaching the QD interface, delay the electron injection rate, and reduce the excitation caused by the charging of the QD. Sub-quenching and efficiency roll-off. In this method, without introducing other heterogeneous material layers, the interface barrier can be used to control the injection of electrons to achieve a balance with the injection of holes. The method does not need to introduce new materials, nor does it involve contact with other functional layers, but only adds an interface to the existing ZnO electron transport layer to control the transport of electrons. In addition, ZnMgO (Mg-doped ZnO) can adjust the forbidden band width of the electron transport layer, adjust the electron injection barrier, reduce the electron injection efficiency, and balance the electron-hole injection to promote electron-hole in the quantum dot The purpose of effective radiation recombination in the light-emitting layer, thereby improving the efficiency of the device. ZnMgO has a wide band gap, so it can also play a role in blocking holes in the device, enabling the device to achieve better performance. In addition, in the present disclosure, the preparation of the electron transport layer is simple, which is suitable for large-area and large-scale preparation.

It should be understood that the application of the present disclosure is not limited to the above examples, and those of ordinary skill in the art can make improvements or changes based on the above description, and all these improvements and changes should fall within the protection scope of the appended claims of the present disclosure.

Claims (20)

1. A method for preparing a quantum dot light-emitting diode, which comprises the steps:

   Provide anode;

   Forming a quantum dot light-emitting layer on the anode;

   Forming an electron transport layer on the quantum dot light-emitting layer, the electron transport layer including a stacked ZnO layer and a ZnMgO layer, and the ZnO layer is arranged close to the quantum dot light-emitting layer;

   A cathode is formed on the electron transport layer to obtain a quantum dot light-emitting diode.
2. The method for manufacturing a quantum dot light-emitting diode according to claim 1, wherein an electron transport layer is formed on the quantum dot light-emitting layer, the electron transport layer includes a ZnO layer and a ZnMgO layer that are stacked, and the ZnO layer The step of disposing one side close to the quantum dot light-emitting layer includes:

   Provide a ZnO nanoparticle solution, cover the ZnO nanoparticle solution on the quantum dot light-emitting layer, and obtain a ZnO layer after annealing;

   Provide a ZnMgO nanoparticle solution, cover the ZnMgO nanoparticle solution on the ZnO layer, and obtain a ZnMgO layer after annealing.
3. The method for preparing a quantum dot light-emitting diode according to claim 2, wherein the method for preparing ZnO nanoparticles includes the step of mixing zinc salt and alkali, and reacting to obtain ZnO nanoparticles.
4. The method for preparing a quantum dot light emitting diode according to claim 2, wherein the method for preparing ZnMgO nanoparticles includes the step of mixing zinc salt, magnesium salt and alkali, and reacting to obtain ZnMgO nanoparticles.
5. The method for preparing a quantum dot light emitting diode according to claim 4, wherein the mass ratio of the zinc salt to the magnesium salt is (10-20):1.
6. The method for preparing a quantum dot light-emitting diode according to claim 4, wherein ^{the molar ratio of the Zn element in the zinc salt to the OH-} in the alkali is 1: (1.5-3.0).
7. 4. The method for preparing a quantum dot light emitting diode according to claim 4, wherein the reaction time is 1-4 hours.
8. The method for manufacturing a quantum dot light-emitting diode according to claim 2, wherein the annealing temperature is 60-120°C.
9. The method for manufacturing a quantum dot light emitting diode according to claim 1, wherein the electron transport layer is composed of two layers of a ZnO layer and a ZnMgO layer which are stacked.
10. The method for manufacturing a quantum dot light-emitting diode according to claim 1, wherein the step of forming a quantum dot light-emitting layer on the anode comprises:

    Forming a hole transport layer on the anode;

    The quantum dot light-emitting layer is formed on the hole transport layer.
11. A method for preparing a quantum dot light-emitting diode, which comprises the steps:

    Provide cathode;

    Forming an electron transport layer on the cathode, the electron transport layer including a ZnO layer and a ZnMgO layer arranged in a stack, and the ZnMgO layer is arranged close to the side of the cathode;

    Forming a quantum dot light-emitting layer on the electron transport layer;

    An anode is formed on the quantum dot light-emitting layer to obtain a quantum dot light-emitting diode.
12. The method for manufacturing a quantum dot light emitting diode according to claim 11, wherein an electron transport layer is formed on the cathode, the electron transport layer includes a ZnO layer and a ZnMgO layer that are stacked, and the ZnMgO layer is close to the The steps of setting the cathode side include:

    Provide a ZnMgO nanoparticle solution, cover the ZnMgO nanoparticle solution on the cathode, and obtain a ZnMgO layer after annealing;

    A ZnO nano particle solution is provided, the ZnO nano particle solution is covered on the ZnMgO layer, and the ZnO layer is obtained by annealing.
13. The method for preparing a quantum dot light-emitting diode according to claim 12, wherein the method for preparing ZnMgO nanoparticles includes the step of mixing zinc salt, magnesium salt and alkali, and reacting to obtain ZnMgO nanoparticles.
14. 11. The method for manufacturing a quantum dot light-emitting diode according to claim 11, wherein the electron transport layer is composed of two layers of a ZnO layer and a ZnMgO layer that are stacked.
15. The method for manufacturing a quantum dot light-emitting diode according to claim 11, wherein the step of forming an anode on the quantum dot light-emitting layer comprises:

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

    The anode is formed on the hole transport layer.
16. A quantum dot light emitting diode, comprising: an anode, a cathode, 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, wherein the electron The transmission layer includes a laminated ZnO layer and a ZnMgO layer, and the ZnO layer is arranged close to the quantum dot light-emitting layer side.
17. The quantum dot light emitting diode of claim 16, wherein the thickness of the ZnO layer is 20-50 nm.
18. The quantum dot light emitting diode of claim 16, wherein the thickness of the ZnMgO layer is 20-50 nm.
19. 16. The quantum dot light-emitting diode according to claim 16, wherein the electron transport layer is composed of two layers of a ZnO layer and a ZnMgO layer which are stacked.
20. The quantum dot light emitting diode according to claim 16, wherein the quantum dot light emitting diode further comprises a hole transport layer disposed between the anode and the quantum dot light emitting layer.

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