WO2022143566A1 - Light-emitting device and preparation method therefor - Google Patents

Abstract

Disclosed are a light-emitting device and a preparation method therefor. The preparation method for the light-emitting device comprises the following steps: obtaining a substrate deposited with a negative electrode; preparing an electron transport layer on the surface of the negative electrode away from the substrate, the electron transport layer comprising a metal oxide transport material; and after performing first ultraviolet irradiation treatment on the electron transport layer, sequentially preparing a quantum dot light-emitting layer and a positive electrode on the side surface of the electron transport layer away from the negative electrode, thereby obtaining the light-emitting device. According to the preparation method for the light-emitting device of the present application, after a metal oxide electron transport layer is prepared on a surface of a negative electrode, by means of ultraviolet irradiation treatment, fusion between a metal oxide electron transport material and the electrode is promoted, the barrier is reduced, and the electron injection efficiency is improved. In addition, internal bonding and a second crystal growth in the electron transport layer are promoted, so that the surface of the electron transport layer is smoother, the interface roughness is reduced, the interface gap is optimized, and the impact of charge accumulation on the service life of the device is avoided.

Description

Light-emitting device and preparation method thereof

This application claims the priority of the Chinese patent application with the application number 202011633001.1 and the invention title "Light-emitting device and its preparation method", which was filed in the China Patent Office on December 31, 2020, the entire contents of which are incorporated herein by reference. middle.

technical field

The present application relates to the technical field of display devices, and in particular, to a light-emitting device and a preparation method thereof.

Background technique

The statements herein merely provide background information related to the present application and do not necessarily constitute prior art. Quantum dots are nanocrystalline particles with a radius smaller than or close to the Bohr exciton radius, and their size and diameter are generally between one. Quantum dots have quantum confinement effect and can emit fluorescence when excited. Moreover, quantum dots have unique luminescence characteristics such as wide excitation peak, narrow emission peak, and tunable luminescence spectrum, which make quantum dot materials have broad application prospects in the field of optoelectronic luminescence. Quantum dot light-emitting diode (QLED) is a new type of display technology that has emerged rapidly in recent years. Quantum dot light-emitting diode is a device that uses colloidal quantum dots as the light-emitting layer. The quantum dot light-emitting layer is introduced between different conductive materials to obtain the required wavelength of light. Quantum dot light-emitting diodes have the advantages of high color gamut, self-luminescence, low startup voltage, and fast response speed.

At present, in order to balance the injection of carriers, OLED devices generally adopt a multi-layer device structure, and the quantum dot light-emitting layer mostly adopts quantum dot nanomaterials with a core-shell structure. In quantum dot light-emitting diodes, the organic surface ligands of quantum dot nanoparticles and the refined core-shell structure inside them make the annealing temperature not too high, so the interface roughness of the formed quantum dot layer is relatively high. In addition, the annealing temperature of the quantum dot layer also limits the annealing temperature of its adjacent electron transport layer ETL, making it difficult for the electron transport material to achieve a good crystallization temperature, resulting in discontinuous internal structure of the electron transport layer and reducing the electron transport mobility. Increased interface roughness. However, the high interface roughness between the QD light-emitting layer and the electron transport layer affects the continuity of carrier injection into the QD light-emitting layer, resulting in low injection efficiency and reduced carrier injection performance. In addition, the charge accumulation center is easily formed at the interface gap, which accelerates the aging of the material and seriously affects the life of the device.

technical problem

One of the purposes of the embodiments of the present application is to provide a light-emitting device and a preparation method thereof, aiming at solving the problems of poor interfacial fusion between the electron transport layer and the adjacent functional layer, affecting the electron injection efficiency, and easily forming charge accumulation .

technical solutions

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

In a first aspect, a method for preparing a light-emitting device is provided, comprising the following steps:

obtaining a substrate on which the cathode is deposited;

preparing an electron transport layer on the surface of the cathode facing away from the substrate, the electron transport layer comprising a metal oxide transport material;

After the electron transport layer is irradiated with ultraviolet light for the first time, a quantum dot light-emitting layer and an anode are sequentially prepared on the side surface of the electron transport layer away from the cathode to obtain a light-emitting device.

In a second aspect, a light-emitting device is provided, and the light-emitting device is manufactured by the above-mentioned method.

The beneficial effect of the method for preparing a light-emitting device provided by the embodiment of the present application is that: after preparing the metal oxide electron transport layer on the surface of the cathode, the electron transport layer is subjected to the first ultraviolet light irradiation treatment, and through the ultraviolet light irradiation treatment, electron The metal oxide in the transport layer has a strong absorption effect on ultraviolet and visible light, which leads to an increase in the internal temperature of the electron transport layer, and the bonding electrons are activated, which promotes the internal bonding and crystal regrowth in the electron transport layer. Reduce the structural defects of metal oxides, reduce the surface roughness of crystalline materials, so that the surface of the electron transport layer is smoother, the interface roughness is reduced, the bonding performance with the adjacent cathode is better, the interface gap is optimized, and the impact of charge accumulation on the device life is avoided. . At the same time, the UV light treatment promotes the fusion of the metal oxide electron transport material and the electrode, reduces the potential barrier, and improves the electron injection efficiency. In addition, the electron transport layer with a flatter surface is conducive to the subsequent preparation of the quantum dot light-emitting layer on its surface, which makes the interface between the quantum dot layer and the quantum dot layer have better bonding performance, improves the efficiency of electron transport and injection, and avoids the accumulation of charges at the interface. and safety performance.

The beneficial effects of the light-emitting device provided by the embodiments of the present application are that the first ultraviolet irradiation treatment is performed after the electron transport layer is prepared on the surface of the cathode, which promotes the fusion of the metal oxide electron transport material and the electrode, reduces the potential barrier, and improves the Electron injection efficiency. At the same time, the internal bonding and crystal regrowth in the electron transport layer are promoted, the internal physical structure defects and surface roughness of the electron transport layer are reduced, and the electron mobility in the electron transport layer is improved, thereby improving the efficiency and stability of optoelectronic devices. Extends the device life for a long time.

Description of drawings

In order to illustrate the technical solutions in the embodiments of the present application more clearly, the following briefly introduces the accompanying drawings that are used in the description of the embodiments or exemplary technologies. Obviously, the drawings in the following description are only for the present application. In some embodiments, for those of ordinary skill in the art, other drawings can also be obtained according to these drawings without any creative effort.

1 is a schematic flowchart of a method for preparing a light-emitting device provided in an embodiment of the present application;

2 is a schematic structural diagram of a quantum dot light-emitting diode provided by an embodiment of the present application;

3 is a graph of the efficiency of the quantum dot light-emitting diodes provided in Example 1 and Comparative Example 1 of the present application;

4 is a current density-voltage curve diagram of the quantum dot light-emitting diodes provided in Example 1 and Comparative Example 1 of the present application;

FIG. 5 is a graph showing the brightness of the quantum dot light-emitting diodes provided in Example 1 and Comparative Example 1 of the present application.

Embodiments of the present invention

In order to make the purpose, technical solutions and advantages of the present application more clearly understood, the present application will be described in further detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present application, but not to limit the present application.

In this application, the term "and/or", which describes the relationship between related objects, means that there can be three relationships, for example, A and/or B, which can mean that A exists alone, A and B exist at the same time, and B exists alone Happening. where A and B can be singular or plural.

In this application, "at least one" means one or more, and "plurality" means two or more. "At least one item(s) below" or similar expressions thereof refer to any combination of these items, including any combination of single item(s) or plural items(s). For example, "at least one (one) of a, b, or c", or, "at least one (one) of a, b, and c", can mean: a,b,c,a-b( That is, a and b), a-c, b-c, or a-b-c, where a, b, and c may be single or multiple, respectively.

It should be understood that, in various embodiments of the present application, the size of the sequence numbers of the above-mentioned processes does not imply the sequence of execution, some or all of the steps may be executed in parallel or sequentially, and the execution sequence of each process should be based on its functions and It is determined by the internal logic and should not constitute any limitation on the implementation process of the embodiments of the present application. The terms used in the embodiments of the present application are only for the purpose of describing specific embodiments, and are not intended to limit the present application. As used in the embodiments of this application and the appended claims, the singular forms "a" and "the" are intended to include the plural forms as well, unless the context clearly dictates otherwise.

In order to illustrate the technical solutions described in the present application, a detailed description is given below with reference to the specific drawings and embodiments.

As shown in FIG. 1 , a first aspect of an embodiment of the present application provides a method for preparing a light-emitting device, including the following steps:

S10. Obtain the substrate on which the cathode is deposited;

S20. Prepare an electron transport layer on the surface of the cathode away from the substrate, and the electron transport layer includes a metal oxide transport material;

S30. After the first ultraviolet light irradiation treatment is performed on the electron transport layer, a quantum dot light-emitting layer and an anode are sequentially prepared on the side surface of the electron transport layer away from the cathode to obtain a light-emitting device.

In the method for preparing a light-emitting device provided by the first aspect of the present application, after a metal oxide electron transport layer is prepared on the surface of the cathode, the electron transport layer is subjected to a first ultraviolet light irradiation treatment, and the metal oxide in the electron transport layer is oxidized by the ultraviolet light irradiation treatment. The material has a strong absorption effect on ultraviolet and visible light, which leads to an increase in the internal temperature of the electron transport layer, and the bonding electrons are activated, which promotes the internal bonding and crystal growth in the electron transport layer. Reduce the structural defects of metal oxides, reduce the surface roughness of crystalline materials, so that the surface of the electron transport layer is smoother, the interface roughness is reduced, the bonding performance with the adjacent cathode is better, the interface gap is optimized, and the impact of charge accumulation on the device life is avoided. . At the same time, the UV light treatment promotes the fusion of the metal oxide electron transport material and the electrode, reduces the potential barrier, and improves the electron injection efficiency. In addition, the electron transport layer with a flatter surface is conducive to the subsequent preparation of the quantum dot light-emitting layer on its surface, which makes the interface between the quantum dot layer and the quantum dot layer have better bonding performance, improves the efficiency of electron transport and injection, and avoids the accumulation of charges at the interface. and safety performance.

Specifically, in the above step S10, the substrate on which the cathode is deposited is obtained. In some embodiments, the cathode includes at least one metal material or at least two alloy materials among Mg, Ag, Al, and Ca. Under the condition of ultraviolet light irradiation, these cathode metal materials and metal oxide electron transport materials have a fusion effect. Well, the electron injection barrier can be reduced and the efficiency of electron injection into optoelectronic devices can be improved.

In some embodiments, the thickness of the cathode is 10-200 nm. In the embodiments of the present application, the thickness of the cathode is selected to be below 200 nm, and when the ultraviolet light wave is irradiated from the cathode side, the thickness is selected to be below 100 nm, so as to avoid the attenuation of the transition of the irradiation light by the cathode metal layer.

Specifically, in the above step S20, a metal oxide electron transport layer is prepared on the side surface of the cathode facing away from the substrate. In some embodiments, the metal oxide transport material is selected from at least one of ZnO, TiO ₂ , Fe ₂ O ₃ , SnO ₂ , Ta ₂ O ₃ ; these metal oxide materials have high electron mobility and are After excitation by ultraviolet light, it has good fusion with the cathode, which is beneficial to reduce the potential barrier and improve the efficiency of electron injection. In some embodiments, the metal oxide transport material may be one of ZnO, TiO ₂ , Fe ₂ O ₃ , SnO ₂ , and Ta ₂ O ₃ , or a mixture of two or more of them.

In some embodiments, the metal oxide transport material is selected from at least one of ZnO, TiO ₂ , Fe ₂ O ₃ , SnO ₂ , Ta ₂ O ₃ doped with metal elements, wherein the metal elements include aluminum, magnesium , at least one of lithium, lanthanum, yttrium, manganese, gallium, iron, chromium, and cobalt. The metal oxide transport materials of the embodiments of the present application are doped with metal elements such as aluminum, magnesium, lithium, lanthanum, yttrium, manganese, gallium, iron, chromium, cobalt, etc., which are beneficial to improve the electron transport and migration efficiency of the materials. In some embodiments, the metal oxide transport material is doped with one of aluminum, magnesium, lithium, lanthanum, yttrium, manganese, gallium, iron, chromium, and cobalt, or any two or more metal elements.

In some embodiments, the particle size of the metal transport material is less than or equal to 10 nm, and the transport material with small particle size is not only more favorable for forming an electron transport layer with dense, uniform thickness and smooth surface; and the metal oxide material with small particle size has more advantages. The large specific surface area has a better fusion effect with the metal electrode layer after being excited by ultraviolet light, which is more conducive to reducing the potential barrier and improving the electron injection efficiency.

Specifically, in the above step S30, the electron transport layer is subjected to a first ultraviolet light irradiation treatment. In some embodiments, the first step of irradiating with ultraviolet light includes: irradiating the electron transport layer for 10-60 minutes under the condition that the wavelength of ultraviolet light is 250-420 nm and the light wave density is 10-300 mJ/cm ² . The ultraviolet irradiation treatment conditions in the examples of the present application can not only promote the internal bonding and crystal regrowth of the metal oxide transport material in the electron transport layer, but also facilitate the interface fusion between the electron transport layer and the metal cathode layer. , make the bonding tighter, reduce the interface gap, optimize the interface roughness, and make the electron injection from the cathode to the electron transport layer more favorable.

In some embodiments, the step of the first ultraviolet light irradiation treatment includes: using ultraviolet light waves with a wavelength of 320 to 420 nm and an optical wave density of 10 to 150 mJ/cm ² to perform irradiation treatment from one side of the electron transport layer for 10 to 60 minutes. When the ultraviolet light wave in the embodiment of the present application is from one side of the electron transport layer, the metal oxide electron transport material can directly absorb the UV light to carry out crystal regrowth and internal bonding, and the attenuation of light is small, so a relatively long wavelength can be used for convenience. The treatment effect can be achieved, and the influence on the material is small.

In some embodiments, the step of the first ultraviolet irradiation treatment includes: using ultraviolet light waves with a wavelength of 250-320 nm and an optical wave density of 100-300 mJ/cm ² to perform irradiation treatment from the cathode side for 10-60 minutes. When the ultraviolet light wave in the embodiment of the present application is from one side of the cathode layer, since there are many free electrons in the metal cathode layer, the light loss is large, and the light passing through the cathode metal layer is greatly attenuated. At this time, it is necessary to use UV light with a shorter wavelength and a higher density processing to achieve better processing results.

In some embodiments, the conditions for the first ultraviolet light irradiation treatment further include: performing the treatment in an environment where the H ₂ O content is less than 1 ppm and the temperature is 80-120° C. In the examples of the present application, ultraviolet light irradiation treatment is performed in an environment where the H ₂ O content is less than 1 ppm and the temperature is 80-120° C., so as to avoid the influence on the material properties during the light treatment process caused by excessive water content in the environment. At the same time, the heating environment of 80-120 °C is conducive to promoting the formation of bonds between the electrons excited by O and the zinc ions, and is also conducive to the activation of the bonding electrons.

In some embodiments, the thickness of the electron transport layer is 10-200 nm, which meets the device performance requirements and structural requirements. In some specific embodiments, when the thickness of the electron transport layer is less than 80 nm, the duration of the ultraviolet light irradiation treatment is 15 minutes to 45 minutes. In the examples of the present application, when the thickness of the electron transport layer is less than 80 nm, the light wave energy of the low-thickness material layer is relatively easy to penetrate. At this time, the irradiation time required to achieve the treatment effect is short, and the duration of the ultraviolet light irradiation treatment is 15 minutes to 45 minutes. minutes are appropriate. In other specific embodiments, when the thickness of the electron transport layer is higher than 80 nm, the duration of the ultraviolet light irradiation treatment is 30 minutes to 90 minutes. In the embodiment of the present application, when the thickness of the electron transport layer is higher than 80 nm, the light wave energy of the thick material layer is difficult to penetrate, and at this time, the illumination time required to achieve the treatment effect is longer, and the duration of the ultraviolet light irradiation treatment is 30 minutes to 90 minutes. minutes are appropriate.

Specifically, in the above step S30, the step of preparing the quantum dot light-emitting layer on the side surface of the electron transport layer away from the cathode includes: after the quantum dot material is deposited on the side surface of the electron transport layer away from the cathode, performing a second ultraviolet light irradiation treatment, A quantum dot light-emitting layer is formed. In the embodiment of the present application, after the quantum dot material is deposited on the surface of the electron transport layer, a second ultraviolet light irradiation treatment is performed. Through the ultraviolet light irradiation treatment, the electrons of O in the metal oxide transport material in the electron transport layer are excited and the quantum dot light-emitting layer is excited. Active metal elements such as Zn form complexes, and the formation of complex bonds optimizes the ETL-QD interface, reduces interface defects, and facilitates the injection of electrons from the electron transport layer to the interior of the quantum dot light-emitting layer. And because the electrons of O are coordinated with the metal of the quantum dot material, the bonding defects inside the electron transport layer are increased, thereby improving the electron mobility in the electron transport layer. In addition, the formed complex has a strong absorption effect on UV, which leads to an increase in the temperature at the interface between the electron transport layer and the quantum dot light-emitting layer, and the bonding electrons are activated, which promotes the re-growth of crystals in the electron transport layer and reduces the electron transport layer. Internal physical structure defects and surface roughness make the QD-ETL interface more tightly bonded, reduce the electron accumulation center inside the electron transport layer and at the QD-ETL interface, improve the electron injection efficiency in the light-emitting layer, slow down the material aging, and improve the device. life.

In some embodiments, the quantum dot material has a core-shell structure, and the outer shell layer of the quantum dot material contains zinc. Since most of the current quantum dot synthesis uses II-VI group elements, Zn element and VI group elements have better matching in terms of lattice matching and band gap, which can cover the entire visible light band, and the outer shell of the quantum dot material The zinc-containing outer shell layer has suitable chemical activity, high flexibility and controllability, wide band gap, good exciton binding, high quantum efficiency, and good water-oxygen stability. In addition, the coordination effect of zinc element and O electrons is better and more stable. By UV irradiation, the electrons of O of the metal oxide transport material in the electron transport layer are excited, and it is easy to form a complex with the Zn element in the QD, that is, a ZnO complex. The formation of ZnO complex bonds facilitates electron injection and improves electron mobility in the electron transport layer. At the same time, the ZnO complex has a strong absorption effect on the wavelength of ultraviolet light, which is conducive to activating the bonding electrons, making the crystal in the ETL grow again, reducing the internal physical structure defects and surface roughness of the ETL, which is conducive to the injection of electrons and reduces the accumulation of electrons. , slow down the material aging, and help to improve the life of the device.

In some embodiments, the outer shell layer of the quantum dot material includes: at least one of ZnS, ZnSe, ZnTe, CdZnS, ZnCdSe, or an alloy material formed by at least two kinds of the outer shell materials, all of which contain zinc element, and the zinc element has high activity, It has a good coordination effect with the excited O electrons in the electron transport material.

In some embodiments, the thickness of the outer shell layer of the quantum dot material is 0.2-6.0 nm, which ensures the stability of the inner layer material of the quantum dot and the carrier injection effect, and at the same time ensures the zinc element and the metal oxide in the outer shell layer. Coordination effects of O element in transport materials.

In some embodiments, the thickness of the quantum dot light-emitting layer is 8-100 nm, which meets the requirements of device performance and structure.

In some embodiments, the second ultraviolet irradiation treatment step includes: irradiating the quantum dot material of the quantum dot light-emitting layer for 10 to 60 minutes under the condition that the wavelength of the ultraviolet light is 300-420 nm and the light wave density is 10-300 mJ/cm ² . . In some embodiments, the conditions of the second ultraviolet irradiation treatment include: performing in an environment where the H ₂ O content is less than 1 ppm. In the above-mentioned embodiments of the present application, the ultraviolet illumination conditions for the quantum dot light-emitting layer after the quantum dot material is deposited, on the one hand, is conducive to promoting the excitation of the electrons of O in the metal oxide transport material in the electron transport layer and the Zn in the quantum dot light-emitting layer. The formation of complexes with other active metal elements optimizes the ETL-QD interface through the formation of complex bonds, reduces interface defects, and facilitates the injection of electrons from the ETL to the interior of the QD. On the other hand, the characteristics of the core-shell structure quantum dot materials are fully considered. In order to avoid the damaging effect of ultraviolet light energy on the quantum dot materials, light with a longer wavelength and a lower light wave energy is used for processing.

In some specific embodiments, when the outer shell layer of the quantum dot material is ZnS, the wavelength of ultraviolet light irradiation treatment is 300-355 nm, and the optical wave density is 50-150 mJ/cm ² . In the examples of the present application, when the outer shell layer is ZnS, the bond energy of ZnS is about 3.5eV, and the bond energy of ZnO is about 3.3eV. Under the conditions of wavelength of 300-355nm and optical wave density of 50-150mJ/ ^cm2 , quantum dots can be induced. The transfer of the bonding charges of electron transport materials such as ZnS and ZnO in the material shell makes the zinc element in the shell layer and the O element in the electron transport material have a better coordination effect, forming a complex between the electron transport material and the quantum dot material.

In some specific embodiments, when the outer shell layer of the quantum dot material is ZnSe, the wavelength of ultraviolet light irradiation treatment is 320-375 nm, and the optical wave density is 30-120 mJ/cm ² . In the examples of this application, when the outer shell layer is ZnSe, the bond energy of ZnSe is about 2.9eV, and the bond energy of ZnO is about 3.3eV, and the wavelength of ultraviolet light irradiation treatment is 320～375nm, and the light wave density is 30～120mJ/ ^cm2 . It can cause the transfer of bonding charges of electron transport materials such as ZnSe and ZnO in the outer shell of the quantum dot material, so that the zinc element in the outer shell layer and the O element in the electron transport material have a better coordination effect, forming the electron transport material and the quantum dot material. complex.

In some specific embodiments, when the outer shell layer of the quantum dot material is ZnSeS, the wavelength of ultraviolet light irradiation treatment is 350-375 nm, and the optical wave density is 30-150 mJ/cm ² . In the examples of this application, when the outer shell layer is ZnSeS, the bond energy of ZnSeS is about 2.7eV, and the bond energy of ZnO is about 3.3eV, and the wavelength of ultraviolet light irradiation treatment is 350～375nm, and the optical wave density is 30～150mJ/ ^cm2 under the conditions It can cause the transfer of bonding charges of electron transport materials such as ZnSeS and ZnO in the shell of the quantum dot material, so that the zinc element in the shell layer and the O element in the electron transport material have a better coordination effect, forming the electron transport material and the quantum dot material. complex.

In some embodiments, after preparing the sub-dot light-emitting layer, the method further includes the steps of: preparing a hole transport layer on the surface of the quantum dot light-emitting layer facing away from the electron transport layer, and preparing an anode on the surface of the hole transport layer facing away from the quantum dot light-emitting layer.

In some specific embodiments, the preparation of the light-emitting device in the embodiments of the present application includes the steps:

S40. Provide a substrate on which the cathode is deposited;

S50. Prepare an electron transport layer on the side surface of the cathode away from the substrate, and the electron transport layer includes a metal oxide transport material;

S60. Perform the first ultraviolet light irradiation treatment on the electron transport layer;

S70. Prepare a quantum dot light-emitting layer on the side surface of the electron transport layer away from the cathode;

S80. Perform a second ultraviolet irradiation treatment on the quantum dot light-emitting layer;

S90. Prepare a hole transport layer on the surface of the quantum dot light-emitting layer;

S100. Evaporating an anode on the hole injection layer to obtain a light-emitting device.

Specifically, in step S40, in order to obtain a high-quality light-emitting device, the substrate needs to undergo a pretreatment process, including the steps of: cleaning the substrate with a cleaning agent to preliminarily remove the stains on the surface, and then sequentially cleaning the substrate with deionized water, acetone, and anhydrous Ultrasonic cleaning was performed in ethanol and deionized water for 20 minutes to remove impurities on the surface, and finally dried with high-purity nitrogen.

Specifically, in step S50, the step of preparing the electron transport layer includes: the electron transport layer is a metal oxide transport material, and on the cathode, a solution of the metal oxide transport material prepared with a certain concentration is passed through drop coating, spin coating, soaking, Coating, printing, evaporation and other processes are used to deposit films, and the thickness of the electron transport layer is controlled by adjusting the concentration of the solution, the deposition speed (for example, the rotation speed is between 3000 and 5000 rpm) and the deposition time, about 20 to 60 nm. Annealing at 150° C. to 200° C. to form a film, fully removing the solvent, and obtaining an electron transport layer.

Specifically, in step S60, the step of performing the first ultraviolet light irradiation treatment on the electron transport layer includes: in an environment where the H ₂ O content is less than 1 ppm and the temperature is 80-120° C., the wavelength of the ultraviolet light is 250-420 nm, The electron transport layer is irradiated vertically for 10 to 60 minutes by ultraviolet light with an optical wave density of 10 to 300 mJ/cm ² .

Specifically, in step S70, the step of preparing the quantum dot light-emitting layer includes: depositing a prepared solution of a certain concentration of light-emitting substance on the electron transport layer by processes such as drop coating, spin coating, soaking, coating, printing, evaporation, etc. The film is formed, and the thickness of the light-emitting layer is controlled by adjusting the concentration of the solution, the deposition speed and the deposition time, about 20-60 nm, and dried at an appropriate temperature.

Specifically, in step S80, the step of performing the second ultraviolet light treatment on the quantum dot light-emitting layer includes: in an environment where the H ₂ O content is less than 1 ppm and the temperature is 80-120° C., the wavelength of the ultraviolet light is 300-420 nm, The electron transport layer is irradiated vertically for 10 to 60 minutes by ultraviolet light with an optical wave density of 10 to 300 mJ/cm ² .

Specifically, in step S90, the step of preparing the hole transport layer includes: on the surface of the quantum dot light-emitting layer, applying the prepared solution of the hole transport material by drop coating, spin coating, soaking, coating, printing, evaporation It is deposited into a film by other processes; the film thickness is controlled by adjusting the concentration of the solution, the deposition speed and the deposition time, and then thermal annealing is performed at an appropriate temperature.

Specifically, in step S100, the substrate on which each functional layer has been deposited is placed in an evaporation chamber to deposit and prepare an anode.

In some embodiments, the obtained QLED device is packaged, and the package process can be packaged by a common machine or by manual packaging. In the packaging process environment, the oxygen content and water content are both lower than 0.1ppm to ensure the stability of the device.

A second aspect of the embodiments of the present application provides a light-emitting device, and the light-emitting device is manufactured by the above method.

In the light-emitting device provided in the second aspect of the present application, since the first ultraviolet irradiation treatment is performed after the electron transport layer is prepared on the surface of the cathode, the fusion of the metal oxide electron transport material and the electrode is promoted, the potential barrier is reduced, and the electron injection efficiency is improved . At the same time, the internal bonding and crystal regrowth in the electron transport layer are promoted, the internal physical structure defects and surface roughness of the electron transport layer are reduced, and the electron mobility in the electron transport layer is improved, thereby improving the efficiency and stability of optoelectronic devices. Extends the device life for a long time.

In some embodiments, the light emitting device includes a stacked structure of an anode and a cathode disposed oppositely, a light emitting layer disposed between the anode and the cathode, and the cathode disposed on the substrate. In addition, a hole functional layer such as a hole injection layer, a hole transport layer, and an electron blocking layer can also be arranged between the anode and the light-emitting layer; an electron transport layer, an electron injection layer, and a hole can also be arranged between the cathode and the light-emitting layer. Electronic functional layers such as barrier layers are shown in Figure 2. In some structural device embodiments, the light emitting device includes a substrate, a cathode disposed on the surface of the substrate, an electron transport layer disposed on the surface of the cathode, a light emitting layer disposed on the surface of the electron transport layer, holes disposed on the surface of the light emitting layer The transport layer is an anode disposed on the surface of the hole transport layer.

In some embodiments, the choice of the substrate is not limited, and a rigid substrate or a flexible substrate may be used. In some specific embodiments, the rigid substrate includes, but is not limited to, one or more of glass and metal foil. In some embodiments, the flexible substrate includes, but is not limited to, polyethylene terephthalate (PET), polyethylene terephthalate (PEN), polyetheretherketone (PEEK), polystyrene (PS), polyethersulfone (PES), polycarbonate (PC), polyarylate (PAT), polyarylate (PAR), polyimide (PI), polyvinyl chloride (PV), poly One or more of ethylene (PE), polyvinylpyrrolidone (PVP), and textile fibers.

In some embodiments, the choice of anode material is not limited and can be selected from doped metal oxides, including 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 (AMO) one or more. It can also be selected from doped or undoped transparent metal oxides sandwiched metal composite electrodes, including but not limited to AZO/Ag/AZO, AZO/Al/AZO, ITO/Ag/ITO, ITO/Al/ ITO, ZnO/Ag/ZnO, ZnO/Al/ZnO, TiO ₂ /Ag/TiO ₂ , TiO ₂ /Al/TiO ₂ , ZnS/Ag/ZnS, ZnS/Al/ZnS, TiO ₂ /Ag/TiO ₂ , One or more of TiO ₂ /Al/TiO ₂ .

In some embodiments, the hole injection layer includes, but is not limited to, one or more of organic hole injection materials, doped or undoped transition metal oxides, doped or undoped metal chalcogenides . In some specific embodiments, organic hole injection materials include, but are not limited to, poly(3,4-ethylenedioxythiophene)-polystyrenesulfonic acid (PEDOT:PSS), copper phthalocyanine (CuPc), 2,3, 5,6-Tetrafluoro-7,7',8,8'-tetracyanoquinone-dimethane (F4-TCNQ), 2,3,6,7,10,11-hexacyano-1,4,5 One or more of ,8,9,12-hexaazatriphenylene (HATCN). In some specific embodiments, transition metal oxides include, but are not limited to, one or more of MoO ₃ , VO ₂ , WO ₃ , CrO ₃ , and CuO. In some specific embodiments, the metal chalcogenide compounds include, but are not limited to, one or more of MoS ₂ , MoSe ₂ , WS ₂ , WSe ₂ , and CuS.

In some embodiments, the hole transport layer may be selected from organic materials with hole transport capability and/or inorganic materials with hole transport capability. In some specific embodiments, the organic material with hole transport capability includes, but is not limited to, poly(9,9-dioctylfluorene-CO-N-(4-butylphenyl)diphenylamine) (TFB), poly(9,9-dioctylfluorene-CO-N-(4-butylphenyl)diphenylamine) Vinylcarbazole (PVK), poly(N,N'bis(4-butylphenyl)-N,N'-bis(phenyl)benzidine) (poly-TPD), poly(9,9-dioctyl) Fluorene-co-bis-N,N-phenyl-1,4-phenylenediamine) (PFB), 4,4,4"-tris(carbazol-9-yl)triphenylamine (TCTA), 4, 4'-bis(9-carbazole)biphenyl (CBP), N,N'-diphenyl-N,N'-bis(3-methylphenyl)-1,1'-biphenyl-4, In 4'-diamine (TPD), N,N'-diphenyl-N,N'-(1-naphthyl)-1,1'-biphenyl-4,4'-diamine (NPB) One or more. In some specific embodiments, inorganic materials with hole transport capability include but are not limited to doped graphene, undoped graphene, C60, doped or undoped MoO ₃ , VO ₂ One or more of , WO ₃ , CrO ₃ , CuO, MoS ₂ , MoSe ₂ , WS ₂ , WSe ₂ , and CuS.

In some embodiments, the light-emitting layer includes a quantum dot material, the quantum dot material is a quantum dot material with a core-shell structure, and the outer shell layer of the quantum dot material contains zinc element. In some specific embodiments, the outer shell layer of the quantum dot material includes: at least one of ZnS, ZnSe, ZnTe, CdZnS, and ZnCdSe, or an alloy material formed by at least two of them. In some embodiments, the particle size of the quantum dot material is in the range of 2 to 10 nm. If the particle size is too small, the film-forming property of the quantum dot material becomes poor, and the energy resonance transfer effect between the quantum dot particles is significant, which is not conducive to the application of the material. , the particle size is too large, the quantum effect of the quantum dot material is weakened, resulting in a decrease in the optoelectronic properties of the material.

In some embodiments, the material of the electron transport layer adopts the above-mentioned metal oxide transport material.

In some embodiments, the cathode material may be one or more of various conductive carbon materials, conductive metal oxide materials, and metallic materials. In some embodiments, conductive carbon materials include, but are not limited to, doped or undoped carbon nanotubes, doped or undoped graphene, doped or undoped graphene oxide, C60, graphite, carbon fiber, multi- Empty carbon, or a mixture thereof. In some embodiments, the conductive metal oxide material includes, but is not limited to, ITO, FTO, ATO, AZO, or mixtures thereof. In some specific embodiments, the metal materials include, but are not limited to, Al, Ag, Cu, Mo, Au, or their alloys; among the metal materials, their forms include but are not limited to dense films, nanowires, nanospheres, nanometers Rods, nano cones, nano hollow spheres, or their mixtures; the cathode is Ag, Al.

In order to make the above implementation details and operations of the present application clearly understood by those skilled in the art, and to significantly reflect the improved performance of the light-emitting devices and their preparation methods in the embodiments of the present application, the above technical solutions are exemplified by multiple embodiments below.

Example 1

A light-emitting diode, comprising the following preparation steps:

(1) Provide a substrate on which Al cathode is deposited, and perform pre-cleaning treatment on the substrate.

(2) forming an electron transport layer on the Al cathode of step (1): in a glove box (water oxygen content is less than 0.1 ppm), spin-coat ZnO solution (concentration is 45 mg/mL, solvent is ethanol) on the ITO cathode , spin coating at 3000rpm for 30s and then anneal at 80℃ for 30min to form an electron transport layer.

(3) In an environment with H ₂ O content less than 1 ppm and a temperature of 100° C., the electron transport layer is irradiated vertically from the electron transport layer side, UV wavelength 400 nm, intensity 100 mJ/cm ² , and UV time 30 min.

(4) Form the light-emitting layer on the electron transport layer: take the CdSe/ZnS quantum dot solution (concentration is 30mg/mL, the solvent is n-octane), put the CdSe/ZnS quantum dot solution in a glove box (water oxygen content is less than 0.1ppm) ) was spin-coated on the electron transport layer at a speed of 3000 rpm to form a light-emitting layer.

(5) In an environment where the H ₂ O content is less than 1 ppm and the temperature is 100° C., the light-emitting layer is irradiated vertically for 10 minutes by UV light with a UV wavelength of 320 nm and an intensity of 150 mJ/cm ² .

(6) Forming a hole transport layer on the light-emitting layer: under an electric field, spin-coat TFB solution (concentration of 8 mg/mL, solvent is chlorobenzene) on the light-emitting layer, spin at 3000 rpm for 30 s, and then anneal at 80 °C for 30 min. A hole transport layer is formed; wherein the direction of action of the electric field is perpendicular to the anode and towards the hole transport layer, and the electric field strength is 10 ⁴ V/cm.

(7) Forming a hole injection layer on the hole transport layer: under an electric field, spin-coat the PEDOT:PSS solution on the hole transport layer, spin at 5000 rpm for 40 s, and then anneal at 150° C. for 15 minutes to form a hole injection layer; The action direction of the electric field is perpendicular to the anode and toward the hole injection layer, and the electric field strength is 10 ⁴ V/cm.

(8) An ITO anode is formed on the hole injection layer.

Example 2

A light-emitting diode, the difference between its preparation steps and Example 1 is: in step (3), vertical UV irradiation is performed from the cathode side, UV wavelength 300nm, intensity 200mJ/cm ² , and UV time 30min.

Example 3

A light-emitting diode, the preparation steps of which are different from those in Example 1 are: in step (2), a _TiO2 solution is used to spin-coat on the light-emitting layer.

Example 4

A light-emitting diode, the preparation steps of which are different from those in Example 1 are: ZnMgO is used in step (2).

Example 5

A light-emitting diode, the preparation steps of which are different from those in Example 1 are: CdZnSe/ZnSe is used in step (4). In step (5), the ultraviolet illumination conditions are as follows: UV light with a UV wavelength of 340 nm and an intensity of 100 mJ/cm ² is used to vertically irradiate the light-emitting layer for 10 minutes.

Example 6

A light-emitting diode, the preparation steps of which are different from those in Example 1 are: CdZnSe/ZnSeS is used in step (4). In step (5), the ultraviolet illumination conditions are as follows: UV light with a UV wavelength of 370 nm and an intensity of 120 mJ/cm ² is used to vertically irradiate the light-emitting layer for 10 minutes.

Comparative Example 1

A light-emitting diode whose preparation steps differ from those of Example 1 in that it is not UV-treated in steps (3) and (5).

Comparative Example 2

A light-emitting diode, the preparation steps of which are different from those in Example 1 are: no UV treatment in step (5).

Comparative Example 3

A light-emitting diode, the preparation steps of which are different from those in Example 1 are that step (3) UV treatment is not performed.

In order to verify the progress of the embodiments of the present application, the following performance tests were carried out on Examples 1 to 6 and Comparative Examples 1 to 3. The test indicators and test methods are as follows, and the test results are shown in Table 1 and accompanying drawings 3 to 5 below:

(1) Constructing a current density-voltage (J-V) curve

Under the environment of room temperature and air humidity of 30%-60%, use LabView to control the efficiency test system built by QE PRO spectrometer, Keithley 2400, and Keithley 6485 for testing, and measure parameters such as voltage and current to construct J-V curve.

(2) External quantum efficiency (EQE):

The ratio of the number of electron-hole pairs injected into the quantum dots converted to the number of photons emitted, the unit is %, is an important parameter to measure the quality of electroluminescent devices, and can be obtained by EQE optical testing instrument. The specific calculation formula is as follows:

In the formula, ηe is the optical output coupling efficiency, ηr is the ratio of the number of recombined carriers to the number of injected carriers, χ is the ratio of the number of excitons that generate photons to the total number of excitons, KR is the radiation process rate, KNR is the nonradiative process rate. Test conditions: At room temperature, the air humidity is 30-60%.

(3) Constructing a luminance-voltage (L-V) curve

Luminance (L) is the ratio (cd/m2) of the area of the luminous flux in the specified direction to the luminous flux perpendicular to the specified direction of the light-emitting surface. Using LabView to control the calibrated linear silicon light pipe system PDB-C613 to measure, and combine the spectral and visual functions to calculate the brightness of the device, and construct the L-V curve according to the change of brightness with voltage.

(4) Life test

In the following examples, the life test adopts the constant current method, under the constant current of 50mA/ ^cm2 , the silicon photosystem is used to test the brightness change of the device, and the time when the brightness of the device starts from the highest point and decays to 95% of the highest brightness is recorded LT95, Then extrapolate the 1000nit LT95S life of the device through the empirical formula:

1000nit LT95＝(L _Max /1000) ^1.7 ×LT95;

This method is convenient for comparing the lifetime of devices with different brightness levels, and has a wide range of applications in practical optoelectronic devices.

Table 1

From the test results of Table 1 of Examples 1 to 6 and Comparative Examples 1 to 3, and the efficiency curves of Figure 3 of Example 1 (S2) and Comparative Example 1 (S1) (the abscissa is the voltage, and the ordinate is the external quantum efficiency) , accompanying drawing 4 current density-voltage curve (abscissa is voltage, ordinate is current density), accompanying drawing 5 brightness curve (abscissa is time, ordinate is brightness), it can be known that the embodiment 1～6 of the present application is processed by UV Compared with the devices of Comparative Examples 1-3, the latter devices have better luminous efficiency and longer luminous lifetime.

The above are only optional embodiments of the present application, and are not intended to limit the present application. Various modifications and variations of this application are possible for those skilled in the art. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of this application shall be included within the scope of the claims of this application.

Claims (17)

1. A method for preparing a light-emitting device, comprising the following steps:

   obtaining a substrate on which the cathode is deposited;

   preparing an electron transport layer on the surface of the cathode facing away from the substrate, the electron transport layer comprising a metal oxide transport material;

   After the electron transport layer is irradiated with ultraviolet light for the first time, a quantum dot light-emitting layer and an anode are sequentially prepared on the side surface of the electron transport layer away from the cathode to obtain a light-emitting device.
2. The method for preparing a light-emitting device according to claim 1, wherein the step of the first ultraviolet irradiation treatment comprises: under the conditions that the wavelength of the ultraviolet light is 250-420 nm and the light wave density is 10-300 mJ/cm ² , irradiating the electron transport layer for 10-60 min.
3. The method for preparing a light-emitting device according to claim 2, wherein the step of the first ultraviolet irradiation treatment comprises: using an ultraviolet light wave with a wavelength of 320-420 nm and an optical wave density of 10-150 mJ/cm ² from the The side of the electron transport layer is subjected to irradiation treatment for 10 to 60 minutes.
4. The method for preparing a light-emitting device according to claim 2, wherein the step of the first ultraviolet irradiation treatment comprises: using an ultraviolet light wave with a wavelength of 250-320 nm and a light wave density of 100-300 mJ/cm ² from the The cathode side is irradiated for 10-60 min.
5. The method for preparing a light-emitting device according to claim 3 or 4, wherein the conditions for the first ultraviolet irradiation treatment further include: under an environment where the H ₂ O content is less than 1 ppm and the temperature is 80-120° C. conduct.
6. The method for preparing a light-emitting device according to claim 1, wherein the metal oxide transport material is selected from at least one of ZnO, TiO ₂ , Fe ₂ O ₃ , SnO ₂ , and Ta ₂ O ₃ .
7. The method for preparing a light-emitting device according to claim 1, wherein the metal oxide transport material is selected from the group consisting of: ZnO, TiO ₂ , Fe ₂ O ₃ , SnO ₂ , Ta ₂ O ₃ doped with metal elements At least one of the metal elements, wherein the metal element includes at least one of aluminum, magnesium, lithium, lanthanum, yttrium, manganese, gallium, iron, chromium, and cobalt.
8. The method for manufacturing a light-emitting device according to claim 1, wherein the particle size of the metal transport material is less than or equal to 10 nm.
9. The method for preparing a light-emitting device according to any one of claims 6 to 8, wherein the cathode comprises at least one metal material or at least two alloy materials among Mg, Ag, Al, and Ca;

   And/or, the thickness of the cathode is 10-200 nm.
10. The method for preparing a light-emitting device according to claim 9, wherein the step of preparing the quantum dot light-emitting layer on the side surface of the electron transport layer away from the cathode comprises: on the side surface of the electron transport layer away from the cathode After the quantum dot material is deposited on the side surface, a second ultraviolet light irradiation treatment is performed to form a quantum dot light-emitting layer.
11. The method for preparing a light-emitting device according to claim 9, wherein after preparing the quantum dot light-emitting layer, the method further comprises the step of: preparing a hole transport layer on the surface of the quantum dot light-emitting layer away from the electron transport layer and preparing the anode on the surface of the hole transport layer away from the quantum dot light-emitting layer.
12. The method for preparing a light-emitting device according to claim 10, wherein the quantum dot material has a core-shell structure, and the outer shell layer of the quantum dot material contains zinc.
13. The method for preparing a light-emitting device according to claim 10, wherein the outer shell layer of the quantum dot material comprises: an alloy material formed by at least one or at least two of ZnS, ZnSe, ZnTe, CdZnS, and ZnCdSe.
14. The method for preparing a light-emitting device according to claim 10, wherein the thickness of the outer shell layer of the quantum dot material is 0.2-6.0 nm.
15. The method for preparing a light-emitting device according to any one of claims 12 to 14, wherein the step of the second ultraviolet light irradiation treatment comprises: when the wavelength of the ultraviolet light is 300-420 nm, the light wave density is 10-300 mJ/ Under the condition of cm ² , the quantum dot light-emitting layer is irradiated for 10-60 min.
16. The method for preparing a light-emitting device according to any one of claims 12 to 14, wherein the conditions for the second ultraviolet irradiation treatment include: performing in an environment where the H ₂ O content is less than 1 ppm.
17. A light-emitting device, characterized in that, the light-emitting device is produced by the method according to any one of claims 1-16.

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