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

Abstract

The application discloses a quantum dot light emitting diode, a preparation method thereof and a display device. The quantum dot light emitting diode comprises a bottom electrode, a top electrode, a functional layer and a quantum dot light emitting layer which are arranged in a stack between the bottom electrode and the top electrode. The quantum dot light emitting layer comprises quantum dots and polymer fillers. The polymer fillers are filled in the gaps between the quantum dots and the defect positions on the surface of the functional layer. The polymer fillers filled in the gaps between the quantum dots can reduce the particle agglomeration of the quantum dots, reduce the surface roughness of the quantum dot light emitting layer, and make the quantum dot light emitting layer more uniform and dense. The polymer fillers are also filled in the defect positions on the surface of the functional layer, which increases the adhesion between the quantum dots and the functional layer, reduces the leakage current, improves the transmission capacity of the carriers, and further improves the device performance of the quantum dot light emitting diode.

Description

TECHNICAL FIELD

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

[0002] Quantum dots are composed of a limited number of atoms, and the three-dimensional size is in the order of nanometers. Due to quantum size effect, the half peak width of quantum dot light emission is very narrow, so it has excellent color purity. Quantum dot light emitting diodes (QLED) made of quantum dot materials can achieve a better color gamut than organic light-emitting diodes (OLED) display devices.

[0003] The quantum dot light emitting layer generally uses a printing method to add quantum dot ink to the pixel pits of the substrate, but the existing preparation method is prone to the problem of uneven film thickness of the quantum dot light emitting layer after the quantum dot ink is dried. SUMMARY

[0004] The present application provides a quantum dot light emitting diode, a preparation method thereof and a display device, aiming to solve the problem of uneven film thickness of the quantum dot light emitting layer.

[0005] The first aspect of the present application provides a quantum dot light emitting diode, comprising a bottom electrode, a top electrode, a functional layer and a quantum dot light emitting layer which are stacked between the bottom electrode and the top electrode, the quantum dot light emitting layer comprising quantum dots and a polymer filler, the polymer filler filling the gaps between the quantum dots and the defect positions on the surface of the functional layer.

[0006] In some embodiments, the light transmittance of the polymer filler is greater than 90%;

[0007] Preferably, the molecular weight of the polymer filler is 3000-10000.

[0008] In some embodiments, the functional layer is a hole transport layer or a hole injection layer, and the polymer contains at least one of aniline, thiophene or carbazole groups.

[0009] In some embodiments, the functional layer is an electron transport layer or an electron injection layer, and the polymer contains at least one of pyrimidine, triazine or pyridine groups.

[0010] The second aspect of the present application provides a preparation method of a quantum dot light emitting diode, comprising the following steps:

[0011] A substrate is provided, and a bottom electrode and a functional layer are prepared on the substrate in sequence;

[0012] The quantum dot ink is printed to the surface of the functional layer, wherein the quantum dot ink contains polymer fillers;

[0013] The substrate is placed in an evaporation device, the evaporation device is adjusted to decrease from a first gas pressure P1 to a second gas pressure P2, and a first solvent evaporation is performed;

[0014] The evaporation device is adjusted to decrease from the second gas pressure P2 to a third gas pressure P3, a second solvent evaporation is performed, and a quantum dot light-emitting layer is obtained;

[0015] A top electrode is prepared on the quantum dot light-emitting layer.

[0016] In some embodiments, P2 is 100-500 Pa, and P3 is 0.1-10 Pa.

[0017] Preferably, P1 is a standard atmospheric pressure.

[0018] In some embodiments, the time for the first solvent evaporation is 1-20 min, and the time for the second solvent evaporation is 10-60 min.

[0019] Preferably, the evaporation temperature of the evaporation device is set to 25-80℃.

[0020] In some embodiments, in the quantum dot ink, the concentration of the polymer fillers is 0.1-10 g / ml; preferably, the concentration of the polymer fillers is 1-5 g / ml.

[0021] The concentration of the quantum dots is 10-100 mg / ml; preferably, the concentration of the quantum dots is 30-50 mg / ml.

[0022] In some embodiments, the quantum dot ink satisfies the following formula:

[0023] wherein Z is 1-20, Oh is the Ozenog number, ρ is the density of the quantum dot ink, d is the diameter of the nozzle of the printing device, μ is the viscosity of the quantum dot ink, and γ is the surface tension of the quantum dot ink.

[0024] Preferably, the density of the quantum dot ink is 1-200 mg / cm 3 , the viscosity of the quantum dot ink is 1-20 mPa·S, and the surface tension of the quantum dot ink is 1-50 mN / m.

[0025] The third aspect of the present application provides a display device comprising the quantum dot light-emitting diode of any of the above embodiments or the quantum dot light-emitting diode prepared by the preparation method of any of the above embodiments.

[0026] The quantum dot light-emitting diode according to the embodiment of the present application, the quantum dot light-emitting layer comprises quantum dots and polymer fillers, the polymer fillers fill the gaps between the quantum dots, can reduce the particle agglomeration of the quantum dots, reduce the surface roughness of the quantum dot light-emitting layer, and make the quantum dot light-emitting layer more uniform and dense. The polymer fillers also fill the defect positions on the surface of the functional layer, increase the adhesion between the quantum dots and the functional layer, reduce the leakage current, improve the transport capacity of the carriers, and further improve the device performance of the quantum dot light-emitting diode. BRIEF DESCRIPTION OF DRAWINGS

[0027] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings needed to be used in the embodiments of the present application will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application, and other drawings can be obtained by those skilled in the art without creative labor on the basis of these drawings.

[0028] Figure 1 The schematic diagram of the change of the conventional quantum dot light-emitting layer in the preparation process;

[0029] Figure 2 The schematic diagram of the structure of the quantum dot light-emitting layer provided by the embodiment of the present application;

[0030] Figure 3 The schematic diagram of the film layer structure of the quantum dot light-emitting diode provided by the embodiment of the present application;

[0031] Figure 4 The schematic diagram of the change of the quantum dot light-emitting layer provided by the embodiment of the present application in the preparation process;

[0032] Figure 5 The flowchart of the preparation method of the quantum dot light-emitting layer provided by the embodiment of the present application.

[0033] The reference signs are as follows:

[0034] Substrate 10; bottom electrode 20; functional layer 30; quantum dot light-emitting layer 40; hole injection layer 31; hole transport layer 32; electron injection layer 33; electron transport layer 34; top electrode 50; quantum dot 60; polymer filler 70. DETAILED DESCRIPTION

[0035] The embodiments of the present application will be further described in detail below in combination with the drawings and the embodiments. The detailed description of the following embodiments and the drawings are used to exemplarily illustrate the principles of the present application, but cannot be used to limit the scope of the present application, that is, the present application is not limited to the described embodiments.

[0036] In the description of the application, it should be noted that, unless otherwise specified, the meaning of "a plurality of" is more than two; The orientation or positional relationship indicated by the terms "upper", "lower", "left", "right", "inner", "outer" and the like is only for the purpose of facilitating the description of the application and simplifying the description, and does not indicate or imply that the device or element referred to must have a particular orientation, be constructed and operated in a particular orientation, therefore it cannot be understood as a limitation to the application. In addition, the terms "first", "second", "third" and the like are only for descriptive purposes and cannot be understood as indicating or implying relative importance. "Vertical" is not strictly vertical, but within the allowable range of error. "Parallel" is not strictly parallel, but within the allowable range of error.

[0037] In the present application, the term "embodiment" means that the specific features, structures or characteristics described in conjunction with the embodiment can be included in at least one embodiment of the present application. The appearance of this phrase at various places in the specification does not necessarily refer to the same embodiment, nor is it an independent or alternative embodiment to other embodiments. It is explicitly and implicitly understood by those skilled in the art that the described embodiments of the present application can be combined with other embodiments.

[0038] The orientation words appearing in the following description are the directions shown in the drawings, and are not a specific structure of the present application. In the description of the present application, it should be noted that, unless otherwise specified and limited, the terms "mounting", "connecting", "connecting" should be understood broadly, for example, it can be fixedly connected, or it can be detachably connected, or integrally connected; It can be directly connected, or indirectly connected through an intermediate medium. For those skilled in the art, the specific meaning of the above terms in the present application can be understood according to the specific circumstances.

[0039] Quantum dots, also known as semiconductor nanocrystals, are a new type of semiconductor nanomaterial. Due to quantum size effect and electric confinement effect, they have unique photoluminescence and electroluminescence properties. Compared with traditional organic fluorescent dyes, quantum dots have high quantum yield, high photochemical stability, and are not easy to photolyze, as well as wide excitation, narrow emission, high color purity, and the emission color can be adjusted by controlling the size of quantum dots. At present, quantum dot light emitting diodes generally use quantum dot ink printing method to prepare quantum dot light emitting layer. When quantum dot ink is printed on the substrate, as the solvent evaporates, the quantum dots are easy to agglomerate, resulting in poor film thickness uniformity of the quantum dot light emitting layer. Figure 1Figure 1 shows a schematic diagram of a conventional quantum dot light-emitting layer in a preparation process; in a conventional inkjet printing technology, when the quantum dot light-emitting layer is completed in an inkjet printing chamber, a mechanical hand delivers it to a drying chamber for film drying, and then the film is baked and enters the next step of preparing a film layer. In the film drying process, after the ink is printed in the pixel pits, the three-phase contact line is fixed, and when the ink volatilizes, the evaporation rate of the ink at the edge of the three-phase contact line is greater than that at the middle of the liquid surface, causing the ink to flow from the inside to the outside to supplement, and at the same time, driven by different evaporation rates and concentrations, the liquid at the middle of the liquid surface also supplements to the three-phase contact line, thereby depositing the solute at the edge and forming a coffee ring phenomenon. In general, due to the evaporation rate of the solvent in the surrounding area of the printed substrate being greater than that in the middle area, the film after drying is not uniform, which causes the film to have many defects and a high roughness. When a voltage is applied, the interface defects are filled with current, causing a leakage current.

[0040] To solve the above problems, the embodiments of the present application provide a quantum dot light-emitting diode and a preparation method thereof, and a display device, which will be described below in conjunction with the accompanying drawings.

[0041] Please refer to Figure 2 and Figure 3 , Figure 2 Figure 1 shows a schematic diagram of a quantum dot light-emitting layer provided by the embodiments of the present application; Figure 3 Figure 2 shows a schematic diagram of a film layer structure of a quantum dot light-emitting diode provided by the embodiments of the present application. The quantum dot light-emitting diode comprises a bottom electrode 20, a top electrode 50, a functional layer 30 and a quantum dot light-emitting layer 40, which are sequentially stacked between the bottom electrode 20 and the top electrode 50. The quantum dot light-emitting layer 40 comprises quantum dots 60 and a polymer filler 70, and the polymer filler 70 fills the gaps between the quantum dots 60 and the defect positions on the surface of the functional layer 30.

[0042] The quantum dot light-emitting diode of the present embodiment further comprises a substrate 10, wherein the substrate 10, the bottom electrode 20, the functional layer 30, the quantum dot light-emitting layer 40 and the top electrode 50 are sequentially stacked. The quantum dot light-emitting diode of the present embodiment can be a normal quantum dot light-emitting diode, wherein the bottom electrode 20 is an anode and the top electrode 50 is a cathode. It should be noted that in other embodiments, the quantum dot light-emitting diode can also be an inverted quantum dot light-emitting diode, wherein the bottom electrode 20 is a cathode and the top electrode 50 is an anode.

[0043] The functional layer 30 can be a hole injection layer 31, a hole transport layer 32, or an electron injection layer 33, an electron transport layer 34. In an embodiment, as shown in Figure 3As shown, the quantum dot light emitting diode comprises a substrate 10, a bottom electrode 20 (anode), a hole injection layer 31, a hole transport layer 32, a quantum dot light emitting layer 40, an electron transport layer 34, an electron injection layer 33 and a top electrode 50 (cathode), wherein the substrate 10, the anode, the hole injection layer 31, the hole transport layer 32 and the quantum dot light emitting layer 40 are sequentially stacked, and the electron transport layer 34 is arranged between the quantum dot light emitting layer 40 and the cathode. When the electrons and holes enter the quantum dot light emitting layer 40 through the electron transport layer 34 and the hole transport layer 32 respectively, the quantum dots 60 will be excited by the exciton energy to emit light. In addition, due to the quantum confinement effect of the quantum dots 60, the wavelength of the light emitted by the electron-hole recombination will change with the size of the quantum dots 60, and quantum dots 60 of different sizes will emit light of different colors. The material of the quantum dots 60 is blue quantum dots, green quantum dots or red quantum dots, and the blue quantum dots can be ZnCdS, ZnCdS / ZnS, ZnSe / ZnS, etc.; the green quantum dots and yellow quantum dots 60 can be ZnCdSeS, ZnCdSeS / ZnS, etc., wherein the size of the green quantum dots is smaller than that of the yellow quantum dots 60; and the red quantum dots can be CdSe / CdS, CdSe / ZnSe, ZnCdSeS / ZnS, etc.

[0044] The substrate 10 can be rigid glass or flexible PI film (Polyimide Film). The material of the anode can be high work function metal and metal oxide, such as indium tin oxide, indium zinc oxide or elemental gold. The material of the hole injection layer 31 is PEDOT:PSS (a mixed aqueous solution of poly 3,4-ethylenedioxythiophene and polystyrene sulfonate), WO3, MoO3 or V2O5. The material of the hole transport layer 32 is Poly-TPD (polytriphenylamine), TFB (1,2,4,5-tetrakis(trifluoromethyl)benzene), PVK (polyvinyl carbazole), NPB (N,N'-diphenyl-N,N'-(1-naphthyl)-1,1'-biphenyl-4,4'-diamine), TAPC (4,4'-cyclohexylbis[N,N-bis(4-methylphenyl)amine]), TCTA (4,4',4"-tris(carbazol-9-yl)triphenylamine), mCP (2,6-dimethoxyphenol), CBP (4,4'-bis(9-carbazol) biphenyl), mCBP (3,3-di(carbazolyl) biphenyl), CDBP (4,4'-bis(9-carbazolyl)-2,2'-dimethyl biphenyl), NiO, Cu2O or CuSCN. The material of the electron transport layer 34 is ZnO, SnO2, ZnMgO, ZnAlO, ZnGaO or TiO2. The material of the cathode can be low work function metal or its alloy, such as Al, Ag or Mg-Ag alloy.

[0045] In the embodiment, the polymer filler 70 is a long chain structure, and can also have partial branches. Since the quantum dots 60 are circular or ellipsoidal structures, and have many gaps between each other, the polymer contains branches and groups that can fill the gaps between the quantum dots 60, prevent the quantum dots 60 from agglomerating, and make the quantum dot light-emitting layer 40 more uniform and dense. In the process of printing the quantum dot 60 ink, the polymer filler 70 can be fully mixed with the quantum dots 60, the polymer filler 70 uniformly fills the gaps between the quantum dots 60, can slow down the capillary flow of the quantum dots 60 to the edge of the substrate 10, avoid the aggregation of the quantum dot 60 particles at the boundary, balance the Marangoni flow and the capillary flow, improve the coffee ring effect, and further improve the thickness uniformity of the quantum dot light-emitting layer 40. In addition, the functional layer 30 located below the quantum dot light-emitting layer 40 is generally formed by a spin coating or printing process, and the surface can contain holes or defects. The addition of the polymer filler 70 can fill the defects and holes on the surface of the lower film layer. Therefore, repairing the interface defects can improve the leakage current and improve the device efficiency.

[0046] In some embodiments, the light transmittance of the polymer filler 70 is greater than 90%. The light transmittance of the polymer filler 70 is relatively large, and does not affect the light-emitting efficiency of the quantum dot light-emitting layer 40. Optionally, the polymer filler 70 can be prepared by polymerization of monomers with relatively high light transmittance, for example, the monomers can be selected from any one or several of methyl methacrylate, styrene, bisphenol A, aniline, thiophene, carbazole, aniline, thiophene, and carbazole.

[0047] Preferably, the molecular weight of the polymer filler 70 is 3000-10000. The molecular weight of the polymer filler 70 is in the above range, which can sufficiently fill the gaps between the quantum dots 60, prevent the agglomeration of the quantum dots 60, and sufficiently fill the defects and holes of the functional layer 30 located below the quantum dot light-emitting layer 40, further ensure the thickness uniformity of the quantum dot light-emitting layer 40, and improve the leakage current.

[0048] In some embodiments, the functional layer 30 is a hole transport layer 32 or a hole injection layer 31, and the polymer contains at least one of aniline, thiophene, or carbazole groups. Aniline, carbazole, and thiophene have relatively weak electronegativity and relatively strong electron-donating ability, and also have relatively high hole mobility, so that the hole transport capacity of the hole transport layer 32 or the hole injection layer 31 can be increased.

[0049] Optionally, only the hole transport layer 32 or the hole injection layer 31 can be arranged between the substrate 10 and the quantum dot light-emitting layer 40, or the hole injection layer 31 and the hole transport layer 32 can be stacked.

[0050] In some embodiments, the functional layer 30 is an electron transport layer 34 or an electron injection layer 33, and the polymer contains at least one of a pyrimidine, a triazine or a pyridine group. The pyrimidine, triazine or pyridine group has strong electronegativity, strong electron-withdrawing ability and high electron mobility, and thus can increase the electron transport capability.

[0051] Please refer to Figure 4 and Figure 5 , Figure 4 a schematic diagram of a change in the preparation process of the quantum dot light-emitting layer provided in the embodiments of the present application; Figure 5 a flowchart of a preparation method of the quantum dot light-emitting layer provided in the embodiments of the present application. The second aspect of the present application provides a preparation method of a quantum dot light-emitting diode, comprising the following steps:

[0052] S100, providing a substrate 10, and sequentially preparing a bottom electrode 20 and a functional layer 30 on the substrate 10. The bottom electrode 20 and the functional layer 30 can be prepared by spin coating or printing process. If it is a normal quantum dot light-emitting diode, the bottom electrode 20 is an anode, and the functional layer 30 is a hole injection layer 31 and / or a hole transport layer 32. If it is an inverted quantum dot light-emitting diode, the bottom electrode 20 is a cathode, and the functional layer 30 is an electron injection layer 33 and / or an electron transport layer 34.

[0053] S200, printing quantum dot 60 ink to the surface of the functional layer 30, wherein the quantum dot 60 ink contains a polymer filler 70;

[0054] The quantum dot light-emitting layer 40 can be prepared by inkjet printing. The ink containing the light-emitting semiconductor quantum dot 60 material is injected into the pixel range defined by the pre-patterned and isolated material in the form of ink droplets. After the solvent is completely volatilized, the light-emitting layer composed of the quantum dot 60 material is formed. Since the quantum dot 60 ink of the present embodiment contains the polymer filler 70, the branched chains and groups contained in the polymer can fill the gaps between the quantum dots 60, prevent the agglomeration of the quantum dots 60, and make the quantum dot light-emitting layer 40 more uniform and dense. In addition, the addition of the polymer filler 70 can fill the defects and pores on the surface of the lower film layer. Therefore, repairing the interface defects can improve the leakage current and improve the device efficiency.

[0055] Optionally, the light transmittance of the polymer filler 70 is greater than 90%. The molecular weight of the polymer filler 70 is 3000-10000. If the functional layer 30 is a hole transport layer 32 or a hole injection layer 31, the polymer contains at least one of an aniline, a thiophene or a carbazole group. If the functional layer 30 is an electron transport layer 34 or an electron injection layer 33, the polymer contains at least one of a pyrimidine, a triazine or a pyridine group.

[0056] Further, the solvent of the quantum dot 60 ink can be selected from polar organic solvents such as alcohols and ethers, for example at least one of ethanol, propanol, isopropanol, butanol, isobutanol, methyl ether, and diethyl ether. The alcohol and ether solvents have the advantages of low boiling point, easy evaporation, and easy preparation.

[0057] S300, placing the substrate 10 in the evaporation device, adjusting the evaporation device to reduce from the first gas pressure P1 to the second gas pressure P2, and performing first solvent evaporation;

[0058] In step S300 of the embodiment, the quantum dot light-emitting layer 40 is prepared by gradient drying. In the first step of gradient drying, the evaporation device is adjusted to reduce from the first gas pressure P1 to the second gas pressure P2. Since the pressure is inversely proportional to the evaporation rate of the solvent, the pressure in the first step of gradient drying is relatively high, and thus the first solvent evaporation rate is relatively slow. During the boundary shaping process of the quantum dots 60, the polymer filler 70 and the quantum dots 60 can be fully mixed, the quantum dot 60 filler can fully fill the gaps between the quantum dots 60, prevent the agglomeration of the quantum dots 60, slow down the capillary flow of the quantum dots 60 to the edge, avoid the aggregation of particles at the boundary, balance the Marangoni flow and capillary flow, avoid the coffee ring effect, and thus form a relatively flat surface.

[0059] S400, adjusting the evaporation device to reduce from the second gas pressure P2 to the third gas pressure P3, performing second solvent evaporation, and obtaining the quantum dot light-emitting layer 40;

[0060] Since the pressure in the second step of gradient drying is relatively low, the second solvent evaporation rate is relatively fast, and a flat quantum dot light-emitting layer 40 can be quickly obtained.

[0061] S500, preparing the top electrode 50 on the quantum dot light-emitting layer 40.

[0062] The top electrode 50 can be prepared by spin coating or printing process. If it is a normal quantum dot light-emitting diode, the top electrode 50 is a cathode. If it is an inverted quantum dot light-emitting diode, the top electrode 50 is an anode.

[0063] In the embodiments of the application, the quantum dot 60 ink is printed to the surface of the functional layer 30, the substrate 10 is placed in the evaporation device, and the gradient drying is performed by first adjusting the evaporation device to decrease from the first air pressure P1 to the second air pressure P2 to perform the first solvent evaporation. Since the quantum dot 60 ink contains the polymer filler 70, the polymer filler 70 can be fully mixed with the quantum dots 60 in the boundary definition process of the quantum dot 60 colloid, the polymer filler 70 is uniformly filled in the gap between the quantum dots 60, the capillary flow of the quantum dots 60 to the edge of the substrate 10 is slowed down, the aggregation of the quantum dot 60 particles at the boundary is avoided, the balance between the Marangoni flow and the capillary flow is achieved, the coffee ring effect is improved, and thus the uniform quantum dot 60 colloid surface is obtained. Then the evaporation device is adjusted to decrease from the second air pressure P2 to the third air pressure P3, the solvent is quickly evaporated, and the smooth quantum dot light-emitting layer 40 is obtained.

[0064] Optionally, the evaporation device can be a vacuum drying device, and the air pressure in the evaporation device can be controlled by vacuum pumping.

[0065] In some embodiments, P2 is 100-500 Pa, and optionally, P2 is 100 Pa, 200 Pa, 300 Pa, 400 Pa or 500 Pa. The air pressure in the first step of the gradient drying is controlled in a suitable range to ensure that the solvent evaporation rate is slow, and the polymer filler 70 can be fully filled between the quantum dots 60 and the functional layer 30 of the lower film layer.

[0066] Specifically, P3 is 0.1-10 Pa, and optionally, P3 is 0.1 Pa, 1 Pa, 3 Pa, 6 Pa or 10 Pa. The air pressure in the second step of the gradient drying decreases from 100-500 Pa to 0.1-10 Pa, and the air pressure is controlled in a suitable range to ensure that the solvent evaporation rate is fast, and the solvent can be completely evaporated within a certain time to obtain the quantum dot light-emitting layer 40.

[0067] Preferably, P1 is the standard atmospheric pressure, and the air pressure in the first step of the gradient drying decreases from the standard atmospheric pressure to 100-500 Pa. The evaporation device is opened, the substrate 10 is placed in the evaporation device, and the vacuum pumping is directly performed until the air pressure decreases to the extent that the substrate 10 does not need to be placed in the evaporation device which has been pre-evacuated.

[0068] In some embodiments, the time of the first solvent evaporation is 1-20 min. The time of the first solvent evaporation is set reasonably, and the solvent evaporation rate is slow, so that the polymer filler 70 can be fully mixed with the quantum dots 60.

[0069] The time of the second solvent evaporation is 10-60 min. The time of the second solvent evaporation is set reasonably, and the solvent evaporation rate is fast, so that the solvent can be completely evaporated to form the film structure of the quantum dot light-emitting layer 40.

[0070] Preferably, the evaporation temperature of the evaporation device is set to 25-80°C, such as 30°C, 50°C or 70°C, so that the quantum dots 60 and the polymer filler 70 can be mixed sufficiently and the structure of the quantum dots 60 and the polymer filler 70 can be avoided from being damaged.

[0071] In some embodiments, the concentration of the polymer filler 70 in the quantum dot 60 ink is 0.1-10 g / ml; the concentration of the polymer filler 70 is in a suitable range, which can ensure that there is sufficient polymer filler 70 to fill between the quantum dots 60 and at the defect position of the functional layer 30, and can avoid that the concentration of the polymer filler 70 is too large and the quantum dots 60 are insufficient, which affects the light-emitting efficiency. Alternatively, the concentration of the polymer filler 70 is 0.5 g / ml, 1 g / ml, 3 g / ml, 5 g / ml, 7 g / ml or 9 g / ml.

[0072] Preferably, the concentration of the polymer filler 70 is 1-5 g / ml; which can further ensure that there is sufficient quantum dot 60 to improve the light-emitting efficiency.

[0073] The concentration of the quantum dots 60 is 10-100 mg / ml; the concentration of the quantum dots 60 is in a suitable range, which can ensure the light-emitting efficiency and can prevent the concentration of the quantum dots 60 from being too high and the quantum dots 60 from being agglomerated. Alternatively, the concentration of the quantum dots 60 is 10 mg / ml, 20 mg / ml, 30 mg / ml, 40 mg / ml, 50 mg / ml, 60 mg / ml, 70 mg / ml, 80 mg / ml, 90 mg / ml or 100 mg / ml. Preferably, the concentration of the quantum dots 60 is 30-50 mg / ml.

[0074] In some embodiments, the quantum dot 60 ink satisfies the following formula:

[0075] Wherein, Z is 1-20, Oh is the Ohneseog number, p is the density of the quantum dot 60 ink, d is the diameter of the nozzle of the printing device, m is the viscosity of the quantum dot 60 ink, and g is the surface tension of the quantum dot 60 ink.

[0076] The Reynolds number Re represents the relative size of the inertial force and the viscous force of the ink in fluid motion, and Re satisfies the following formula:

[0077] The Weber number We represents the relative size of the inertial force and the surface tension of the ink droplet, and We satisfies the following formula:

[0078] The Onsager number Oh is expressed by the Reynolds number and the Weber number, and comprehensively represents the relationship among the viscous force, the inertial force and the surface tension. The Oh satisfies the following formula:

[0079] The derivation process of the Z value is as follows:

[0080]

[0081] The Z value of the embodiment is in a proper range, which can ensure that the quantum dot 60 ink can be normally printed and ensure the printing effect.

[0082] Preferably, the density of the quantum dot 60 ink is 1-200 mg / cm 3 , such as 10 mg / cm 3 , 50 mg / cm 3 , 100 mg / cm 3 , 150 mg / cm 3 or 200 mg / cm 3 , the viscosity of the quantum dot 60 ink is 1-20 mPa·S, such as 5 mPa·S, 10 mPa·S, 15 mPa·S or 20 mPa·S, and the surface tension is 1-50 mN / m, such as 5 mN / m, 10 mN / m, 20 mN / m, 30 mN / m, 40 mN / m or 50 mN / m. The density, viscosity and surface tension of the quantum dot 60 ink are in a proper range, which further improves the printing effect and can obtain a uniform and dense quantum dot light-emitting layer 40.

[0083] The third aspect of the present application provides a display device comprising the quantum dot light-emitting diode of any of the above embodiments or the quantum dot light-emitting diode prepared by the preparation method of any of the above embodiments. Since the display device adopts all the technical solutions of the above embodiments, it at least has all the beneficial effects brought by the technical solutions of the above embodiments, which will not be repeated here.

[0084] The display device can be any device with display function, for example, can be a mobile device such as a mobile phone, a tablet computer, a notebook computer, a palm computer, a vehicle-mounted electronic device, a wearable device, an ultra-mobile personal computer (UMPC), a netbook or a personal digital assistant (PDA), etc., and can also be a non-mobile device such as a personal computer (PC), a television (TV), a teller machine or a self-service machine, etc.

[0085] The above merely illustrates the specific embodiments of the present application, but the protection scope of the present application is not limited thereto, and any skilled person in the art can easily think of various equivalent modifications or replacements within the technical range disclosed by the present application, and these modifications or replacements shall be covered within the protection scope of the present application. Therefore, the protection scope of the present application shall be subject to the protection scope of the claims.

Claims

1. A quantum dot light-emitting diode, characterized in that, The system includes a bottom electrode, a top electrode, a functional layer stacked between the bottom electrode and the top electrode, and a quantum dot light-emitting layer. The quantum dot light-emitting layer comprises quantum dots and a polymer filler. The polymer filler has a long-chain structure with partial branches. The branches and groups contained in the polymer filler fill the gaps between the quantum dots and the defect locations on the surface of the functional layer. The molecular weight of the polymer filler is 3000~10000. The preparation method of the quantum dot light-emitting layer includes: printing quantum dot ink onto the surface of the functional layer, wherein the quantum dot ink contains the polymer filler; placing the substrate in an evaporation device; adjusting the evaporation device from a first pressure P1 to a second pressure P2 to perform a first solvent evaporation; adjusting the evaporation device from the second pressure P2 to a third pressure P3 to perform a second solvent evaporation to obtain the quantum dot light-emitting layer.

2. The quantum dot light-emitting diode according to claim 1, characterized in that, The light transmittance of the polymer filler is greater than 90%.

3. The quantum dot light-emitting diode according to claim 1, characterized in that, The functional layer is a hole transport layer or a hole injection layer, and the polymer contains at least one of aniline, thiophene, or carbazole groups.

4. The quantum dot light-emitting diode according to claim 1, characterized in that, The functional layer is an electron transport layer or an electron injection layer, and the polymer contains at least one of pyrimidine, triazine, or pyridine groups.

5. A method for fabricating a quantum dot light-emitting diode according to any one of claims 1-4, characterized in that, Includes the following steps: A substrate is provided, on which a bottom electrode and a functional layer are sequentially fabricated; A quantum dot luminescent layer was prepared; A top electrode is fabricated on the quantum dot light-emitting layer.

6. The preparation method according to claim 5, characterized in that, The P2 is 100~500 Pa, and the P3 is 0.1~10 Pa.

7. The preparation method according to claim 5, characterized in that, P1 is the standard atmospheric pressure.

8. The preparation method according to claim 5, characterized in that, The first solvent evaporation time is 1~20 min, and the second solvent evaporation time is 10~60 min.

9. The preparation method according to claim 5, characterized in that, The evaporation temperature of the evaporation equipment is set to 25~80℃.

10. The preparation method according to claim 5, characterized in that, In the quantum dot ink, the concentration of the polymer filler is 0.1~10 mg / ml.

11. The preparation method according to claim 10, characterized in that, The concentration of the polymer filler is 1~5 mg / ml.

12. The preparation method according to claim 5, characterized in that, The concentration of the quantum dots is 10~100 mg / ml.

13. The preparation method according to claim 12, characterized in that, The concentration of the quantum dots is 30~50 mg / ml.

14. The preparation method according to any one of claims 5 to 13, characterized in that, The quantum dot ink satisfies the following formula: Where Z is 1~20, Oh is the Ohzog number, ρ is the density of quantum dot ink, d is the diameter of the nozzle of the printing device, μ is the viscosity of quantum dot ink, and γ is the surface tension of quantum dot ink.

15. The preparation method according to claim 14, characterized in that, The density of the quantum dot ink is 1~200 mg / cm³. 3 The viscosity of the quantum dot ink is 1~20 mPa·S and the surface tension is 1~50 mN / m.

16. A display device, characterized in that, It includes quantum dot light-emitting diodes as described in any one of claims 1 to 4, or quantum dot light-emitting diodes prepared by the preparation method as described in any one of claims 5 to 15.

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