Quantum dot light emitting diode, preparation method thereof, and display device

Abstract

In the present application, by placing the first semi-finished product in an environment containing organic acid vapor under an inert atmosphere for a first preset time, the speed of modification of the ligands on the surface of the metal oxide of the electron transport layer by the organic acid molecules is controlled by controlling the temperature, pressure, reaction time, type and concentration of the organic acid in the environment, thereby controllably reducing the concentration of defects on the electron transport layer, which is conducive to controllably improving the carrier mobility. At the same time, the speed and concentration of the diffusion of the organic acid molecules to the interface between the electron transport layer and the quantum dot light-emitting layer can be further controlled, and the reaction speed of the in-situ reaction of the organic acid molecules at the interface between the electron transport layer and the quantum dot light-emitting layer is controlled, thereby controllably modifying the interface between the electron transport layer and the quantum dot light-emitting layer, thereby forming a stable structure at the interface that can effectively inhibit exciton quenching, and further improving the stability of the quantum dot light-emitting diode.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of quantum dot light-emitting diodes, in particular to a quantum dot light-emitting diode, a preparation method thereof and a display device. BACKGROUND

[0002] QLED (Quantum Dots Light-Emitting Diode) is a new display device. The characteristic of QLED is that its light-emitting material uses inorganic quantum dots with more stable performance. The unique quantum size effect, macroscopic quantum tunneling effect and surface effect of quantum dots make them exhibit excellent physical properties, especially their optical properties.

[0003] It is found in existing research that the positive aging and the negative aging of a device are a parallel process. When the promotion ability of the positive aging is greater than the attenuation ability of the negative aging, the device shows a performance promotion state, which is called positive aging effect. The positive aging effect can be used to improve the performance of the device, but it has certain uncontrollability, and some by-products may be formed in the positive aging process of the device, which will accelerate the negative aging of the device, shorten the time of the device to form the positive aging effect, and is not conducive to the improvement of the performance of the device. SUMMARY

[0004] The present application provides a preparation method of a quantum dot light-emitting diode, a quantum dot light-emitting diode and a display device to solve the technical problem of unsatisfactory performance of an existing QLED device.

[0005] The present application provides a preparation method of a quantum dot light-emitting diode, which comprises the following steps:

[0006] A first semi-product is provided, which comprises an anode substrate, a quantum dot light-emitting layer and a first electron transport layer, and the quantum dot light-emitting layer is arranged between the anode substrate and the first electron transport layer;

[0007] The first semi-product is placed in an environment containing organic acid vapor under an inert atmosphere for a first preset time to obtain a second semi-product;

[0008] A cathode layer is formed on the first electron transport layer to obtain a quantum dot light-emitting diode.

[0009] In some embodiments of the present application, the step of forming a cathode layer on the first electron transport layer comprises:

[0010] A second electron transport layer is formed on the first electron transport layer, wherein the material forming the second electron transport layer is the same as the material forming the first electron transport layer;

[0011] forming a cathode layer on the second electron transport layer.

[0012] In some embodiments of the present application, the first electron transport layer has a thickness greater than that of the second electron transport layer.

[0013] In some embodiments of the present application, the first electron transport layer has a thickness of 20-60 nm, the second electron transport layer has a thickness of 10-15 nm, and the sum of the thicknesses of the first and second electron transport layers is 30-70 nm.

[0014] In some embodiments of the present application, the step of forming a cathode layer on the first electron transport layer is preceded by a deacidification and water removal treatment of the second semi-finished product.

[0015] In some embodiments of the present application, the deacidification and water removal treatment of the second semi-finished product comprises heating the second semi-finished product in an inert environment to remove organic acid molecules and water molecules remaining on the second semi-finished product.

[0016] In some embodiments of the present application, the organic acid vapor environment comprises a saturated organic acid vapor environment.

[0017] In some embodiments of the present application, the concentration of organic acid vapor in the organic acid vapor environment is 0.01-0.05 kg / m 3 3 .

[0018] In some embodiments of the present application, the temperature of the organic acid vapor environment is 20-25°C.

[0019] In some embodiments of the present application, the step of forming a cathode layer on the first electron transport layer is followed by encapsulation of the functional layer with an epoxy resin.

[0020] Another aspect of the present application provides a quantum dot light emitting diode prepared by the above preparation method.

[0021] Still another aspect of the present application provides a display device comprising the above quantum dot light emitting diode.

[0022] ​In the present application, the first semi-finished product is placed in an environment containing organic acid vapor under an inert atmosphere for a first preset time. By controlling the standing time, the reaction progress of the organic acid molecules modifying the surface ligands of the metal oxide on the electron transport layer is controlled, thereby controllably reducing the concentration of defects on the electron transport layer, which is conducive to controllably improving the carrier mobility and improving the performance of the quantum dot light emitting diode. At the same time, by controlling the standing time, the concentration of the organic acid molecules diffusing to the interface between the electron transport layer and the quantum dot light emitting layer can be further controlled, and by controlling the reaction progress of the in-situ reaction of the organic acid molecules at the interface between the electron transport layer and the quantum dot light emitting layer, the interface between the electron transport layer and the quantum dot light emitting layer can be controllably modified, thereby forming a stable structure at the interface that can effectively suppress exciton quenching, further improving the performance of the quantum dot light emitting diode. BRIEF DESCRIPTION OF DRAWINGS

[0023] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the drawings needed in the embodiment description will be briefly introduced. Obviously, the drawings in the following description are only some embodiments of the present application, and other drawings can be obtained by those skilled in the art without creative labor.

[0024] Figure 1 is a flowchart of an embodiment of a quantum dot light emitting diode preparation method provided in the embodiments of the present application;

[0025] Figure 2 is Figure 1 is a flowchart of an embodiment of step S3 in

[0026] Figure 3 is an atomic force microscope photo of a quantum dot light emitting diode in the embodiments of the present application;

[0027] Figure 4 is an electron microscope photo of a quantum dot light emitting diode in the embodiments of the present application. DETAILED DESCRIPTION

[0028] The technical solutions in the embodiments of the present application will be described in detail below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only some embodiments of the present application, not all embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor are within the scope of protection of the present application.

[0029] In the description of the present application, it needs to be understood that the terms "center", "length", "width", "thickness", "upper", "lower", "front", "back", "left", "right", "vertical", "horizontal", "inner", "outer" and the like indicate the orientation or positional relationship shown in the drawings, which are only for the convenience of describing the present application and simplifying the description, and do not indicate or imply that the device or element referred to must have a particular orientation, be constructed and operated in a particular orientation, and therefore cannot be understood as a limitation on the present application. In addition, the terms "first", "second" are only for descriptive purposes, and cannot be understood as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Therefore, the features defined as "first", "second" can explicitly or implicitly include one or more of the features. In the description of the present application, the meaning of "a plurality of" is two or more, unless otherwise explicitly specified.

[0030] In this application, the word "exemplary" is used to mean "serving as an example, instance, or illustration." Any implementation described as "exemplary" is not necessarily to be construed as preferred or advantageous over other implementations. The following description is presented to enable any person skilled in the art to make and use the application. In the following description, for purposes of explanation, specific details are set forth. It is apparent to those skilled in the art that the present application can be practiced without using these specific details. In other instances, well-known structures and processes are not described in detail in order to avoid obscuring the description of the present application. Thus, the present application is not intended to be limited to the embodiments shown, but is to be accorded the widest scope consistent with the principles and features presented herein.

[0031] Please refer to Figure 1 In one aspect, the embodiments of the present application provide a preparation method of a quantum dot light emitting diode, comprising the following steps:

[0032] S1 provides a first semi-finished product, the first semi-finished product comprising an anode substrate, a quantum dot light emitting layer, and a first electron transport layer, the quantum dot light emitting layer being disposed between the anode substrate and the first electron transport layer;

[0033] S2, under an inert atmosphere, places the first semi-finished product in an environment containing organic acid vapor and stands for a first preset time to obtain a second semi-finished product;

[0034] S3 forms a cathode layer on the first electron transport layer to obtain a quantum dot light emitting diode.

[0035] In the present application, by placing the first semi-finished product in an environment containing organic acid vapor under an inert atmosphere for a first preset time, the reaction progress of the organic acid molecules modifying the surface ligands of the metal oxide on the electron transport layer is controlled by controlling the standing time, thereby controllably reducing the concentration of defects on the electron transport layer, which is conducive to controllably improving the carrier mobility and improving the performance of the quantum dot light emitting diode. At the same time, by controlling the standing time, the concentration of organic acid molecules diffusing to the interface between the electron transport layer and the quantum dot light emitting layer can be further controlled, and by controlling the reaction progress of the in-situ reaction of the organic acid molecules at the interface between the electron transport layer and the quantum dot light emitting layer, the interface between the electron transport layer and the quantum dot light emitting layer can be controllably modified, thereby forming a stable structure at the interface that can effectively suppress exciton quenching, further improving the performance of the quantum dot light emitting diode.

[0036] In the present application, a first semi-finished product is provided in step S1, which includes an anode substrate, a quantum dot light emitting layer, and a first electron transport layer, wherein the quantum dot light emitting layer is disposed between the anode substrate and the first electron transport layer.

[0037] Specifically, an anode substrate is provided in step S1.

[0038] Further, the anode substrate can include a substrate and an anode layer disposed on the substrate. Specifically, the substrate can be a rigid substrate or a flexible substrate, which is not limited herein. The rigid substrate includes but is not limited to one or more of glass, metal foil. The flexible substrate includes but is not limited to one or more of polyethylene terephthalate, terephthalate, polyether ether ketone, polystyrene, polycarbonate, polyaryl acid ester, polyarylate, polyimide, polyvinyl chloride, polyethylene, textile fibers. The anode layer can be an anode layer formed of a conventional anode material of a quantum dot light emitting diode. The material of the anode layer includes but is not limited to indium tin oxide, indium zinc oxide. For example, the anode layer can be an ITO substrate. Further, the thickness of the anode layer is between 30 nm and 100 nm.

[0039] The quantum dot light emitting layer and the first electron transport layer are sequentially stacked on the side of the anode substrate close to the anode layer to obtain a first semi-finished product.

[0040] It should be noted that in the present application, the first semi-finished product and the second semi-finished product refer to an intermediate product form formed during the preparation of the quantum dot light emitting diode.

[0041] In some embodiments of the present application, the quantum dot light-emitting layer and the first electron transport layer are sequentially stacked on the side of the anode substrate close to the anode layer, and the specific steps for obtaining the first semi-finished product include forming a hole injection layer, a hole transport layer, a quantum dot light-emitting layer and a first electron transport layer sequentially stacked on the side of the anode substrate close to the anode layer.

[0042] Further, the material for preparing the hole injection layer includes but is not limited to one or more of PEDOT:PSS, CuPc, F4-TCNQ, HATCN, transition metal oxide and transition metal chalcogenide. The transition metal oxide includes one or more of NiOx, MoOx, WOx, CrOx and CuO. The transition metal chalcogenide includes one or more of MoSx, MoSex, WSx, WSex and CuS.

[0043] Further, the hole injection layer is prepared on the surface of the anode layer by chemical deposition.

[0044] Further, the thickness of the hole injection layer is 10-100 nm.

[0045] Further, the material for preparing the hole transport layer includes organic material and inorganic material with hole transport capability.

[0046] Further, the organic material includes but is not limited to one or more of poly(9,9-dioctylfluorene-co-bis-N,N-phenyl-1,4-phenylenediamine), 4,4'-bis(9-carbazolyl)biphenyl, poly(9,9-dioctylfluorene-CO-N-(4-butylphenyl)naphthalen-1-amine), polyvinylcarbazole, poly(N,N'bis(4-butylphenyl)-N,N'-bis(phenyl)benzidine), N,N'-diphenyl-N,N'-di(3-methylphenyl)-1,1'-biphenyl-4,4'-diamine, 15N,N'-diphenyl-N,N'-(1-naphthyl)-1,1'-biphenyl-4,4'-diamine, graphene and C60.

[0047] Further, the inorganic material includes but is not limited to at least one or more of nickel oxide, tungsten oxide, chromium oxide, copper oxide and copper sulfide.

[0048] Further, the thickness of the hole transport layer is 30-80 nm.

[0049] Further, the material for preparing the quantum dot light-emitting layer includes direct bandgap compound semiconductor with light-emitting capability, and / or doped or non-doped inorganic perovskite semiconductor, and / or organic-inorganic hybrid perovskite semiconductor.

[0050] Further, the thickness of the quantum dot light-emitting layer is 10-40 nm.

[0051] Furthermore, the material used to prepare the first electron transport layer includes oxide semiconductor nanoparticles with electron transport capabilities. Oxide semiconductor nanoparticles include, but are not limited to, one or more of titanium dioxide, zinc oxide, zirconium dioxide, thallium trioxide, and tin oxide.

[0052] Furthermore, the thickness of the first electron transport layer is 20nm-60nm.

[0053] Step S2, which involves placing the first semi-finished product in an environment containing organic acid vapor under an inert atmosphere for a period of time, specifically includes:

[0054] The first semi-finished product is placed in an organic acid vapor environment under a nitrogen atmosphere. This organic acid vapor environment can be either saturated or unsaturated, and is not limited thereto.

[0055] Preferably, the organic acid vapor environment is a saturated organic acid vapor environment. Further, the organic acid vapor environment is a saturated vapor environment of a saturated weak organic acid, such as at least one of acetic acid vapor, propionic acid vapor, and isobutyric acid vapor.

[0056] Understandably, saturated organic acids have lower saturated vapor pressures, which facilitates controlling the rate at which organic acid molecules modify the surface ligands of metal oxides on the electron transport layer. This allows for a controllable reduction in the concentration of defects on the electron transport layer, thus contributing to a controllable increase in carrier mobility. Furthermore, the lower saturated vapor pressure of saturated organic acids further allows for controllability of the diffusion rate and concentration of organic acid molecules at the interface between the electron transport layer and the quantum dot emitting layer. By controlling the reaction rate of the in-situ reaction at this interface, controllable modification of the interface can be achieved, resulting in a stable structure at the interface that effectively suppresses exciton quenching and further improving the stability of the quantum dot light-emitting diode.

[0057] Furthermore, the density of organic acid vapor in the environment is 0.01 kg / m³. 3 Up to 0.05kg / m 3 The inventors discovered through experiments that the concentration of organic acid vapor is between 0.01 kg / m³. 3 Up to 0.05kg / m 3 This allows for better control over the rate at which organic acid molecules modify the surface ligands of metal oxides on the electron transport layer, which is beneficial for optimizing the performance of quantum dot light-emitting diodes and giving them excellent stability.

[0058] It should be noted that in the present application, the environment refers to a set of factors that can affect the chemical reaction of organic acid molecules with metal oxides on the electron transport layer or affect the diffusion of organic acid molecules to the interface between the electron transport layer and the quantum dot light-emitting layer for modification. It includes factors such as environmental temperature, environmental pressure, organic acid type, organic acid density, and reaction time. The inventors have found through numerous experiments that placing the first semi-finished product in a saturated steam environment of saturated organic acid for 10H to 30H at an environmental temperature of 20°C to 25°C is beneficial to significantly improving the performance of quantum dot light-emitting diodes.

[0059] It is well known to those skilled in the art that a completed device will undergo a few days of placement, and if there is a significant improvement in performance, we call it positive aging. If there is a significant decrease in performance, we call it negative aging. In fact, the change in performance of the device after molding is the result of positive and negative aging. When the effect of positive aging on the device is greater than the effect of negative aging on the device, the performance of the device will improve; otherwise, the performance of the device will decrease.

[0060] It should be emphasized that compared with the prior art of using acrylic resin packaging or adding active reagents to the packaging glue to improve the performance of quantum dot light-emitting diodes, the present application has better controllability by using organic acid vapor to acid treat the first semi-finished product in the preparation process to improve the performance of quantum dot light-emitting diodes. The quantum dot light-emitting diodes prepared by the present application have excellent stability. The prior art of using acrylic resin packaging or adding active reagents to the packaging glue to improve the performance of quantum dot light-emitting diodes is to allow the device to undergo positive aging effect to improve the performance of the device after the device is molded. However, using positive aging effect to improve the performance of the device, the device may form some by-products during the positive aging process. For example, using acrylic resin packaging to improve the performance of quantum dot light-emitting diodes, organic acid molecules in the acrylic resin diffuse into the QLED device. The organic acid molecules diffused into the QLED device react in situ at the interface of the electron transport layer to generate by-products water and carboxylate, thereby accelerating the negative aging of the device and not conducive to improving the performance of the device.

[0061] Meanwhile, the inventors have found through research that the prior art has certain uncontrollability in improving the performance of the device by using the positive aging effect, and since the improvement of the performance of the device is a comprehensive result of the positive aging effect and the negative aging, the device performance cannot be optimized. Meanwhile, the chemical reaction between the acrylic acid molecules or active reagents and other materials in the device is also uncontrollable, resulting in a large change in the performance of the device during storage. In the present application, the first semi-finished product is treated by using organic acid vapor before the device is packaged, and the reaction speed and progress of the chemical reaction between the organic acid molecules and the metal oxide on the electron transport layer can be controlled by factors such as ambient temperature, ambient pressure, type of organic acid, density of organic acid, and reaction time, so that the performance of the device can be improved controllably.

[0062] Please refer to Figure 2 The step S3 of forming a cathode layer on the first electron transport layer specifically includes:

[0063] S3.1. Deacidification and dehydration treatment is performed on the second semi-finished product.

[0064] Specifically, the second semi-finished product is taken out of the environment and placed in a glove box in a nitrogen environment, and then heated at 80-100℃ for 15-30min to remove the organic acid molecules and water molecules remaining on the second semi-finished product. The inventors have found through experiments that heating at a temperature lower than 80℃ or for a time lower than 15min will result in incomplete deacidification and dehydration of the second semi-finished product. Heating at a temperature higher than 100℃ or for a time longer than 30min will damage the quantum dot light-emitting layer of the device. Of course, in other embodiments of the present application, the organic acid molecules and water molecules remaining on the second semi-finished product can also be removed by inert gas flushing, freeze-drying or adsorption, which is not limited herein.

[0065] It can be understood that in the embodiments of the present application, by removing the organic acid molecules and water molecules in the second semi-finished product before packaging, damage to the device caused by the residual organic acid molecules and water molecules in the second semi-finished product can be avoided, which is conducive to further improving the performance of the device.

[0066] S3.2. A second electron transport layer is formed on the first electron transport layer.

[0067] The second electron transport layer is formed on the first electron transport layer by a spin coating process. It can be understood that the first electron transport layer will inevitably be damaged after the first semi-finished product is placed in an environment containing organic acid vapor for a period of time, thereby forming defects on the surface of the first electron transport layer, which is not conducive to improving the performance of the device. By forming a second electron transport layer on the first electron transport layer. Illustratively, forming a second electron transport layer on the first electron transport layer by a spin coating process can make the side of the second electron transport layer away from the first electron transport layer have better flatness, which is conducive to subsequent processing procedures. Of course, in other embodiments of the present application, the second electron transport layer can also be formed on the first electron transport layer by other processes, as long as the flatness requirement of the second electron transport layer in the device is met.

[0068] Further, the material forming the second electron transport layer is the same as the material forming the first electron transport layer, which can make the formed first electron transport layer and second electron transport layer integrate, which is conducive to reducing the defects between the first electron transport layer and the second electron transport layer, improving the electron transport efficiency, and further improving the performance of the device.

[0069] Further, the thickness of the first electron transport layer is greater than the thickness of the second electron transport layer. It can be understood that since the first semi-finished product is treated with organic acid vapor after the first electron transport layer is formed, it is conducive to improving the carrier mobility. Designing the thickness of the first electron transport layer to be greater than the thickness of the second electron transport layer is conducive to improving the performance of the device.

[0070] Further, the thickness of the second electron transport layer is between 10 nm and 15 nm.

[0071] Further, the sum of the thickness of the first electron transport layer and the thickness of the second electron transport layer is between 30 nm and 70 nm. It can be understood that if the thickness of the first electron transport layer and the second electron transport layer is too thick, the resistance will increase, which is not conducive to balancing the performance of the QLED device. If the thickness of the first electron transport layer and the second electron transport layer is too thin, the electron transport performance is poor, and even the electron transport performance is lost due to the inability to form a complete thin film.

[0072] S3.3 Forming a cathode layer on the second electron transport layer.

[0073] Further, the material for preparing the cathode layer includes, but is not limited to, one or more of metal material, carbon material, metal oxide. The metal material includes one or more of Al, Ag, Cu, Mo, Au, Ba, Ca, Mg. The carbon material includes one or more of graphite, carbon nanotube, graphene, carbon fiber. The metal oxide can be doped or non-doped metal oxide, including one or more of ITO, FTO, ATO, AZO, GZO, IZO, MZO, AMO. The metal oxide can also be a composite electrode with metal sandwiched between doped or non-doped transparent metal oxides, wherein the composite electrode includes one or more of AZO / Ag / AZO, AZO / Al / AZO, ITO / Ag / ITO, ITO / Al / ITO, ZnO / Ag / ZnO, ZnO / Al / ZnO, TiO2 / Ag / TiO2, TiO2 / Al / TiO2, ZnS / Ag / ZnS, ZnS / Al / ZnS, TiO2 / Ag / TiO2, TiO2 / Al / TiO2, wherein the thickness of the metal part should not exceed 20 nm, and the transmittance of visible light should not be lower than 90%.

[0074] Specifically, Ag is evaporated on the second electron transport layer to form a cathode layer with a thickness of 60-120 nm.

[0075] It should be noted that the specific forming process of the anode layer, the hole injection layer, the hole transport layer, the quantum dot light-emitting layer, the first electron transport layer, the second electron layer, and the cathode layer can adopt the technology disclosed in the prior art, which is not limited here.

[0076] In some embodiments of the present application, step S3 further includes encapsulating the light-emitting functional layer with epoxy resin after the step of forming a cathode layer on the first electron transport layer. It can be understood that the epoxy resin has excellent water resistance, insulation and moisture resistance, and encapsulation with epoxy resin is conducive to improving the stability of the device.

[0077] Embodiment 1

[0078] Step S1: spin-coat PEDOT:PSS on the ITO substrate at a spin speed of 5000 RPM for 30 seconds, and then heat at 150°C for 15 minutes to form a hole injection layer;

[0079] Step S2: spin-coat TFB (8 mg / mL) on the hole injection layer at a spin speed of 3000 RPM for 30 seconds, and then heat at 80°C for 10 minutes to form a hole transport layer;

[0080] Step S3: spin-coat quantum dots (20 mg / mL) on the hole transport layer at a spin speed of 2000 RPM for 30 seconds, and then heat at 80°C for 10 minutes to form a quantum dot light-emitting layer;

[0081] Step S4: spin-coat ZnO (25 mg / mL) on the quantum dot light-emitting layer at a spin speed of 4000 RPM for 30 seconds, and then heat at 80°C for 30 minutes to form a first electron transport layer, the thickness of the first electron transport layer being 30 nm, to obtain a first semi-product.

[0082] Step S5: place the first semi-product in an isobutyric acid vapor environment for 20 hours under a nitrogen atmosphere, the density of the isobutyric acid being 0.03 kg / m3, to obtain a second semi-product;

[0083] Step S6: re-place the second semi-product in a nitrogen atmosphere and heat treat the second semi-product at 80°C for 30 minutes;

[0084] Step S7: spin-coat ZnO (25 mg / mL) on the first electron transport layer at a spin speed of 4000 RPM for 30 seconds, and then heat at 80°C for 30 minutes to form a second electron transport layer, the sum of the thicknesses of the first electron transport layer and the second electron transport layer being 55 nm;

[0085] Step S8: evaporate Ag on the second electron transport layer by thermal evaporation, the vacuum degree being no higher than 3x10 -4 Pa, the speed being 1 angstrom / second, the time being 200 seconds, to form a cathode layer, the thickness of the cathode layer being 20 nm;

[0086] Step S9: encapsulate the device using an epoxy resin encapsulating glue and perform UV curing to obtain a test sample.

[0087] Steps S1 to S3 in Example 2 are the same as in Example 1;

[0088] Step S4: spin-coat ZnO (30 mg / mL) on the quantum dot light-emitting layer at a spin speed of 4000 RPM for 30 seconds, and then heat at 80°C for 30 minutes to form an electron transport layer, the thickness being 55 nm;

[0089] Step S5: place the product obtained in Step S4 in an isobutyric acid vapor environment for 20 hours, the density of the isobutyric acid being 0.03 kg / m 3 ;

[0090] Step S6: re-place the product obtained in Step S5 in a nitrogen atmosphere and heat treat it at 80°C for 30 minutes;

[0091] Subsequent processes of forming a cathode layer and encapsulation on the electron transport layer are the same as in Example 1, to obtain a test sample.

[0092] Comparative Example 1

[0093] Steps S1 to S3 are the same as in Example 1;

[0094] Step S4: spin-coating ZnO (30 mg / mL) on the quantum dot light-emitting layer at a spin speed of 4000 RPM for 30 seconds, followed by heating at 80°C for 30 minutes to form an electron transport layer with a thickness of 55 nm;

[0095] The subsequent process of forming a cathode layer on the electron transport layer is the same as in Example 1, and the only difference in the encapsulation process step from Example 1 is that the encapsulation glue is replaced with an acrylic resin to obtain the test sample.

[0096] Comparative Example 2

[0097] Steps S1 to S3 are the same as in Example 1;

[0098] Step S4: spin-coating ZnO (30 mg / mL) on the quantum dot light-emitting layer at a spin speed of 4000 RPM for 30 seconds, followed by heating at 80°C for 30 minutes to form an electron transport layer with a thickness of 55 nm;

[0099] The subsequent process of forming a cathode layer on the electron transport layer and encapsulation is the same as in Example 1 to obtain the test sample.

[0100] To further illustrate that the quantum dot light-emitting diode prepared by the scheme of the present application has better stability, the inventors tested the stability of the quantum dot light-emitting diodes obtained in Example 1, Example 2 to Comparative Example 3, and the test results are shown in Figure 3 , Figure 4 and Table 1.

[0101] Please refer to Figure 3 , Figure 3 The morphology photos of the test samples prepared in each example and comparative example are shown in Table 1, respectively, when placed for 1 day, 7 days, and 20 days. Figure 3It can be seen that the morphology of the samples of Example 1 and Comparative Example 2 has no obvious change after being stored for 20 days, while the samples of Example 1 and Comparative Example 1 have obvious black spots in the light-emitting area after being stored for 20 days. It can be seen from the morphology of the samples of Example 1 and Example 2 at 20 days that, compared with the process of forming an electron transport layer on the quantum dot light-emitting layer once and then treating the electron transport layer with active acid, the process of forming a first electron transport layer on the quantum dot light-emitting layer first, treating the first electron transport layer with active acid, and then forming a second electron transport layer on the first electron transport layer can significantly improve the stability of the device. It can be seen from the morphology of the samples of Comparative Example 1 and Comparative Example 2 at 20 days that the device encapsulated by epoxy resin has better stability than the device encapsulated by acrylic resin. It can be seen from the morphology of the samples of Example 1 and Comparative Example 2 at 20 days that the sample in Example 1 has a smaller decrease in the light-emitting area, which can indicate that forming a first electron transport layer on the quantum dot light-emitting layer, treating the first electron transport layer with active acid, and then forming a second electron transport layer on the first electron transport layer are beneficial to providing the stability of the device.

[0102] Please refer to Figure 4 , the atomic force microscope photos of the test samples prepared in the examples and comparative examples after being stored for 20 days. It can be seen from Figure 4 that the root mean square roughness (Rq) of the samples of Example 2 and Comparative Example 1 is large, which may be due to the fact that the sample of Example 2 is treated with organic acid vapor during the preparation process, resulting in a large root mean square roughness. The sample of Comparative Example 1 is encapsulated with acrylic resin, and the acrylic molecules diffuse into the quantum dot light-emitting diode layer of the sample after being stored for a period of time, resulting in a large root mean square roughness. The sample of Example 1 has the smallest root mean square roughness after being stored for 20 days, and has better stability.

[0103] Table 1

[0104]

[0105]

[0106] Please refer to Table 1 and Figure 4 , Table 1 shows the test data of the brightness, T95, T95-1K and current efficiency of the samples in the examples and comparative examples under the driving of 2mA constant current. Among them, L represents the brightness of the device; T95 represents the time used for the brightness of the device to decay from 100% to 95%; T95-1K represents the time used for the brightness of the device to decay from 100% to 95% when the device is at 1000nit brightness; C.E represents the current efficiency of the device; Rq represents the root mean square roughness.

[0107] As shown in Table 1, the T95 of the sample in Example 2 is higher than that of the sample in Comparative Example 1. The T95-1k values ​​of the samples in Example 2 and Comparative Example 1 are approximately the same, further illustrating that the organic acid vapor treatment of the first electron transport layer in this application is beneficial to improving device performance. After 20 days of storage, the brightness and current efficiency of the sample in Example 2 are both lower than those of the sample in Comparative Example 1. Combined with... Figure 3 It can be seen that the main reason is that the morphology of the sample in Example 2 showed obvious black spots, which affected the brightness and current efficiency of the device. One possible reason is that the organic acid treatment damaged the surface morphology of the electron transport layer, thus affecting the performance of the device. Compared with Comparative Example 2, the brightness, current efficiency, T95, and T95-1k of the samples in Examples 1 and 2 were significantly improved, which shows that the preparation method in this application has the effect of suppressing exciton quenching, which can significantly improve the performance of the device, making the device have higher efficiency, longer operating life, and better stability.

[0108] The present application provides a detailed description of a quantum dot light-emitting diode, its preparation method, and a display device. Specific examples have been used to illustrate the principles and implementation methods of the present invention. The descriptions of the above embodiments are only for the purpose of helping to understand the method and core ideas of the present invention. At the same time, those skilled in the art will recognize that there will be changes in the specific implementation methods and application scope based on the ideas of the present invention. Therefore, the content of this specification should not be construed as a limitation of the present invention.

Claims

1. A method for fabricating a quantum dot light-emitting diode, characterized in that, The preparation method comprises the following steps: providing a first semi-product comprising an anode substrate, a quantum dot light-emitting layer, and a first electron transport layer, the quantum dot light-emitting layer being arranged between the anode substrate and the first electron transport layer; placing the first semi-product in an environment containing organic acid vapor under an inert atmosphere for a first preset time to obtain a second semi-product; heat baking the second semi-product at 80-100℃ for 15-30min to remove organic acid molecules and water molecules remaining on the second semi-product; forming a cathode layer on the first electron transport layer to obtain a quantum dot light-emitting diode.

2. The production method according to claim 1, wherein The step of forming a cathode layer on the first electron transport layer comprises: forming a second electron transport layer on the first electron transport layer, wherein the material forming the second electron transport layer is the same as the material forming the first electron transport layer; forming a cathode layer on the second electron transport layer.

3. The production method according to claim 2, wherein The thickness of the first electron transport layer is greater than the thickness of the second electron transport layer.

4. The production method according to claim 3, wherein The thickness of the first electron transport layer is 20-60nm, the thickness of the second electron transport layer is 10-15nm, and the sum of the thickness of the first electron transport layer and the thickness of the second electron transport layer is 30-70nm.

5. The production method according to claim 1, wherein The organic acid vapor comprises at least one of acetic acid vapor, propionic acid vapor, and isobutyric acid vapor.

6. The production method according to claim 1, wherein The environment of the organic acid vapor comprises a saturated organic acid vapor environment.

7. The production method according to claim 6, wherein Placing the first semi-product in an environment containing organic acid vapor for a first preset time comprises: placing the first semi-product in the saturated organic acid vapor environment at an ambient temperature of 20-25℃ for 10-30h.

8. The production method according to claim 1, wherein The concentration of organic acid vapor in the environment of the organic acid vapor is between 0.01 kg / m 3 and 0.05 kg / m 3 .

9. The production method according to claim 1, wherein The temperature of the environment of the organic acid vapor is 20-25℃.

10. The production method according to any one of claims 1 to 9, characterized by, The step of forming a cathode layer on the first electron transport layer further comprises encapsulating the light-emitting functional layer with epoxy resin.

11. A quantum dot light emitting diode, comprising: The quantum dot light-emitting diode is formed by the preparation method of any one of claims 1-10.

12. A display device, characterized by The display device comprises the quantum dot light-emitting diode of claim 11.

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