Quantum dot light emitting diode and preparation method thereof

Abstract

The application discloses a quantum dot light emitting diode and a preparation method thereof. The quantum dot light emitting diode comprises an anode, a quantum dot light emitting layer arranged on the anode, and a cathode arranged on the quantum dot light emitting layer. The spacing of quantum dots in the quantum dot light emitting layer in a first direction is greater than the spacing of the quantum dots in a second direction. Alternatively, the spacing of the quantum dots in the first direction is greater than 0.1 nm and less than or equal to 20 nm, and the spacing of the quantum dots in the second direction is greater than 0.1 nm and less than or equal to 20 nm. The first direction is perpendicular to the second direction. The application can avoid the red shift phenomenon caused by the dense packing of quantum dots, thereby improving the color performance of the quantum dot light emitting diode.

Description

TECHNICAL FIELD

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

[0002] Quantum dots are nanocrystal particles with a radius less than or close to the Bohr exciton radius. Quantum dots have quantum confinement effect and can emit fluorescence after excitation. Moreover, quantum dots have unique light emitting properties, such as excitation peak width, emission peak narrowness, and light emission spectrum adjustability, which make them have broad application prospects in the field of photoelectric light emission.

[0003] A quantum dot light emitting diode is a device in which colloidal quantum dots are used as a light emitting layer, and the light emitting layer is introduced between different conductive materials to obtain light of a required wavelength. Quantum dot light emitting diodes have the advantages of high color gamut, self-light emission, low starting voltage, and fast response speed. However, there is a problem of red shift of the light emitting wavelength in the application of quantum dot light emitting diodes, which further affects the color gamut of display devices based on quantum dot light emitting diodes.

[0004] Therefore, the prior art still needs to be improved and developed. SUMMARY

[0005] In view of the deficiencies of the prior art, the purpose of the present application is to provide a quantum dot light emitting diode and a preparation method thereof, aiming to solve the problem of red shift of the light emitting wavelength of the quantum dot light emitting layer in the quantum dot light emitting diode.

[0006] A quantum dot light emitting diode includes an anode, a cathode, and a quantum dot light emitting layer disposed between the anode and the cathode, wherein the spacing of quantum dots in the quantum dot light emitting layer in a first direction is greater than the spacing of the quantum dots in a second direction.

[0007] Alternatively, the spacing of the quantum dots in the first direction is greater than 0.1 nm and less than or equal to 20 nm, and the spacing of the quantum dots in the second direction is greater than 0.1 nm and less than or equal to 20 nm.

[0008] Wherein, the first direction and the second direction are perpendicular to each other.

[0009] The quantum dot light emitting diode, wherein when the spacing of the quantum dots in the quantum dot light emitting layer in the first direction is greater than the spacing of the quantum dots in the second direction, the spacing of the quantum dots in the first direction is 5 nm to 20 nm, and the spacing of the quantum dots in the second direction is 0.1 nm to 1 nm.

[0010] The quantum dot light emitting diode, wherein the spacing of the quantum dots in the first direction and the spacing of the quantum dots in the second direction are both greater than 0.1 nm and less than or equal to 20 nm.

[0011] The quantum dot light emitting diode, wherein the quantum dot light emitting diode further comprises a blocking layer disposed between the anode and the quantum dot light emitting layer for reducing leakage current.

[0012] The quantum dot light emitting diode, wherein the band gap of the blocking layer material is greater than or equal to 3 eV.

[0013] The quantum dot light emitting diode, wherein the blocking layer material is selected from one or more of polymethyl methacrylate, polyvinylpyrrolidone.

[0014] A method of manufacturing a quantum dot light emitting diode, comprising:

[0015] providing an anode;

[0016] forming a quantum dot light emitting layer on the anode;

[0017] forming a cathode on the quantum dot light emitting layer;

[0018] or, providing a cathode;

[0019] forming a quantum dot light emitting layer on the cathode;

[0020] forming an anode on the quantum dot light emitting layer;

[0021] wherein the spacing of the quantum dots in a first direction in the quantum dot light emitting layer is greater than the spacing of the quantum dots in a second direction, or the spacing of the quantum dots in the first direction and the spacing of the quantum dots in the second direction are both greater than 0.1 nm and less than or equal to 20 nm, wherein the first direction and the second direction are perpendicular to each other.

[0022] The method of manufacturing a quantum dot light emitting diode, wherein the method of forming the quantum dot light emitting layer comprises:

[0023] depositing quantum dots on a substrate, stretching the substrate to form a quantum dot light emitting layer;

[0024] transferring the quantum dot light emitting layer to the anode or the cathode.

[0025] The method of manufacturing a quantum dot light emitting diode, wherein the stretching the substrate comprises:

[0026] stretching the substrate in a first direction;

[0027] Alternatively, the substrate is stretched in both the first direction and the second direction.

[0028] The preparation method of the quantum dot light emitting diode, wherein the temperature for stretching the substrate is a preset stretching temperature.

[0029] The preset stretching temperature is greater than or equal to the glass transition temperature of the substrate.

[0030] Beneficial effects: In the present application, the spacing in the first direction is greater than the spacing in the second direction, thereby reducing the accumulation of quantum dots in the first direction, or the spacing in the first direction and the spacing in the second direction are both greater than 0.1 nm, thereby reducing the accumulation of quantum dots in the first direction and the second direction, thereby avoiding the red shift phenomenon caused by the dense accumulation of quantum dots, and improving the color performance of the quantum dot light emitting diode. BRIEF DESCRIPTION OF DRAWINGS

[0031] Figure 1 A schematic diagram of the arrangement of quantum dots in a densely packed quantum dot light emitting layer prepared by a spin coating method.

[0032] Figure 2 A schematic diagram of the formation of a quantum dot grating by arranging quantum dots in rows in an embodiment of the present application.

[0033] Figure 3 A schematic diagram of the formation of a quantum dot spaced dot array by spacing quantum dots in an embodiment of the present application.

[0034] Figure 4 A schematic diagram of the structure of a quantum dot light emitting diode in an embodiment of the present application.

[0035] Figure 5 A schematic diagram of the structure of another quantum dot light emitting diode in an embodiment of the present application.

[0036] Figure 6 A flowchart of the preparation of a quantum dot light emitting diode in an embodiment of the present application.

[0037] Figure 7 A schematic diagram of the process of forming a quantum dot grating by stretching a substrate in an embodiment of the present application.

[0038] Figure 8 A schematic diagram of the process of stamp adsorption in an embodiment of the present application.

[0039] Figure 9 A schematic diagram of the process of stamp imprinting in an embodiment of the present application.

[0040] Figure 10 A schematic diagram of the device structure after transferring the quantum dot light emitting layer to the barrier layer in an embodiment of the present application. DETAILED DESCRIPTION

[0041] The present application provides a quantum dot light emitting diode and a preparation method thereof. In order to make the purpose, technical scheme and effect of the present application more clear and explicit, the present application is further described in detail below. It should be understood that the specific embodiments described herein are only used to explain the present application and not to limit the present application.

[0042] In the preparation of the current quantum dot light emitting diode, the quantum dot light emitting layer is generally prepared by spin coating. After the quantum dot particles are dispersed in a solution, they are directly spin coated onto the surface of the device. After drying, the quantum dots form a film in a close-packed manner, i.e., a close-packed quantum dot light emitting layer as shown in Figure 1 , wherein the spacing between the quantum dots in the quantum dot light emitting layer is less than or equal to 0.1 nm.

[0043] It has been found through research that when the spacing between the quantum dots in the close-packed quantum dot light emitting layer is close, strong energy resonance transfer occurs during light emission, causing red shift of the emission wavelength, which affects the color gamut of the display device based on the quantum dot light emitting diode. Moreover, when the quantum dot light emitting diode is working, the quantum dots will be charged. When the density of the quantum dots is too high, it is easy to cause high charge density and large electric field strength in the quantum dot light emitting layer, resulting in obvious Auger recombination, reducing the efficiency of the quantum dot light emitting diode, accelerating material aging, and reducing the service life of the quantum dot light emitting diode.

[0044] In order to avoid the red shift of the emission wavelength and the obvious Auger recombination of the quantum dots in the quantum dot light emitting diode, please refer to Figures 2 to 4 , the present application provides a quantum dot light emitting diode, which comprises an anode 1, a cathode 7, and a quantum dot light emitting layer 5 disposed between the anode 1 and the cathode 7, wherein the spacing of the quantum dots in the quantum dot light emitting layer 5 in a first direction is greater than the spacing in a second direction.

[0045] Alternatively, the spacing of the quantum dots in the first direction is greater than 0.1 nm and less than or equal to 20 nm, and the spacing of the quantum dots in the second direction is greater than 0.1 nm and less than or equal to 20 nm.

[0046] Wherein, the first direction and the second direction are perpendicular to each other.

[0047] The spacing described in the present application refers to the distance between two adjacent quantum dots (the gap distance between two adjacent quantum dots), i.e., the shortest distance between the edge of one quantum dot and the edge of an adjacent quantum dot. For example, the quantum dots are spherical quantum dots, and the spacing is the shortest distance between the spherical surfaces of two adjacent quantum dots.

[0048] Compared with the quantum dots in the prior art quantum dot dense packing, the quantum dots in the quantum dot light-emitting layer 5 are arranged in a first direction and a second direction, and the spacing of the quantum dots in the first direction is greater than the spacing of the quantum dots in the second direction, so that the spacing of the quantum dots in the first direction is increased relative to the second direction, the packing of the quantum dots in the first direction is reduced, and the light-emitting red shift phenomenon caused by the dense packing of the quantum dots is avoided, and the color performance of the quantum dot light-emitting diode is improved. When the quantum dot light-emitting diode is working, the problem of high charge density of the quantum dot light-emitting layer 5 caused by the high density of the quantum dots is also avoided, the purpose of reducing Auger recombination is achieved, the efficiency of the quantum dot light-emitting diode is improved, the material aging is slowed down, and the effect of improving the service life of the quantum dot light-emitting diode is achieved.

[0049] The spacing of the quantum dots in the first direction and the spacing of the quantum dots in the second direction are both greater than 0.1 nm, so that the quantum dots have a large spacing in the first direction and the second direction, the light-emitting red shift phenomenon caused by the dense packing of the quantum dots is avoided, and the color performance of the quantum dot light-emitting diode is improved. When the quantum dot light-emitting diode is working, the problem of high charge density of the quantum dot light-emitting layer 5 caused by the high density of the quantum dots is also avoided, the purpose of reducing Auger recombination is achieved, the efficiency of the quantum dot light-emitting diode is improved, the material aging is slowed down, and the effect of improving the service life of the quantum dot light-emitting diode is achieved.

[0050] For example, the first direction is the horizontal direction (left-right direction), and the second direction is the vertical direction (front-back direction). The gap width between the quantum dots in the quantum dot light-emitting layer 5 and the adjacent quantum dots on the left or right side (the spacing of the quantum dots in the left-right direction) is greater than the gap width between the quantum dots and the adjacent quantum dots on the front or back side (the spacing of the quantum dots in the front-back direction). The gap width between the quantum dots in the quantum dot light-emitting layer 5 and the adjacent quantum dots on the left or right side is greater than 0.1 nm, which is greater than the spacing of the quantum dots in the prior art dense packing, i.e., less than or equal to 0.1 nm. The gap of the quantum dots in the left-right direction is increased, and the arrangement density of the quantum dots (the number of quantum dots per unit area) is reduced, so that the light-emitting red shift phenomenon caused by the dense packing of the quantum dots is effectively avoided.

[0051] Please refer to Figure 2When the spacing of the quantum dots in the quantum dot light-emitting layer 5 in the first direction is greater than that in the second direction, the quantum dots in the quantum dot light-emitting layer 5 of the present application can realize linear arrangement of the quantum dots, forming a quantum dot grating. Specifically, the smaller spacing of the quantum dots in the front-back direction makes the quantum dots arranged in multiple lines end to end, while the larger spacing of the quantum dots in the left-right direction forms a gap between the two adjacent lines, thereby forming a grating. The linearly arranged quantum dots are the non-transparent part of the grating, and the gap between the two adjacent lines is the transparent gap of the grating. The linear arrangement can be irregular curved arrangement or regular straight line arrangement. The straight line arrangement of the quantum dots can also be referred to as row arrangement of the quantum dots, i.e., the quantum dots are arranged in multiple rows.

[0052] In an embodiment of the present application, when the spacing of the quantum dots in the first direction is greater and the spacing of the quantum dots in the second direction is smaller, the quantum dots are arranged in a line in the second direction and spaced apart in the first direction, thereby forming the quantum dot grating. Optionally, the spacing of the quantum dots in the first direction is 5-20 nm, and the spacing of the quantum dots in the second direction is 0.1 nm. Specifically, the spacing of the quantum dots in the first direction can be 6 nm, 10 nm or 15 nm, and the spacing of the quantum dots in the second direction can be 0.1-1 nm.

[0053] For example, the quantum dots arranged in rows form a quantum dot grating, the spacing between the quantum dots in the same row is small, specifically, the spacing between the adjacent quantum dots in the same row is 0.1-1 nm, such as 0.5 nm, while the spacing between the quantum dots in the adjacent two rows (the spacing between the two rows) is large, specifically, the spacing between the adjacent two rows is 15-20 nm, such as 18 nm.

[0054] Moreover, the arrangement of the quantum dots to form a grating can also improve the light-emitting efficiency and the viewing angle of the device. Specifically, the quantum dots arranged to form a quantum dot grating in the light-emitting diode have a light splitting effect, which can make the emitted light uniformly distributed at a larger angle, thereby improving the viewing angle. The quantum dot grating can produce a coupling effect, which can improve the light extraction rate and improve the light-emitting efficiency.

[0055] For example, the quantum dots arranged in rows form a quantum dot grating, the spacing between the quantum dots in the same row is small, specifically, the spacing between the adjacent quantum dots in the same row is 0.1-1 nm, such as 0.5 nm, while the spacing between the quantum dots in the adjacent two rows (the spacing between the two rows) is large, specifically, the spacing between the adjacent two rows is 15-20 nm, such as 18 nm. Figure 3 The quantum dots in the quantum dot light-emitting layer 5 of the present application are arranged at intervals to form a quantum dot interval lattice, which means that the quantum dots are spaced apart from each other to form independent quantum dots, i.e., the quantum dots do not contact the surrounding adjacent quantum dots but are distributed apart from each other. That is, compared with the existing densely packed quantum dots, the quantum dots of the present application are spaced apart by a certain distance, so that the spacing between the quantum dots is increased, thereby avoiding the red shift phenomenon of the light-emitting wavelength caused by the dense packing of the quantum dots and improving the color performance of the quantum dot light-emitting diode.

[0056] For the quantum dot interval lattice, the adjacent quantum dots are spaced apart by a certain distance. Specifically, the quantum dots can be uniformly distributed, i.e., the distance between the quantum dots and the surrounding adjacent quantum dots can be the same. In an embodiment of the present application, the distance in the first direction is the same as the distance in the second direction. Optionally, the distance in the first direction and the distance in the second direction are both 1-20 nm, for example, the distance in the first direction and the distance in the second direction are both 5 nm, 10 nm or 15 nm. In the present application, the distances between the quantum dots are the same and arranged at a large distance, thereby forming a uniform quantum dot interval lattice. It can be seen that, compared with the existing densely packed quantum dots, the present application can reduce the red shift phenomenon of light emission caused by energy resonance transfer between quantum dots, and improve the color performance of the quantum dot light emitting diode. Moreover, the present application increases the quantum dot gap, which can also effectively reduce the charge density of the quantum dot light emitting layer 5, reduce Auger recombination and material aging, and improve the efficiency and life of the quantum dot light emitting diode.

[0057] In the present application, the distance of the quantum dots in the first direction in the quantum dot light emitting layer is greater than or equal to the distance in the second direction. The distance of the quantum dots in the first direction is greater than 0.1 nm and less than or equal to 20 nm, which can avoid the red shift phenomenon of light emission caused by dense packing of quantum dots, and improve the color performance of the quantum dot light emitting diode.

[0058] In an embodiment of the present application, the quantum dots include but are not limited to nanocrystals of II-VI semiconductor, such as CdS quantum dots, CdSe quantum dots, CdTe quantum dots; the quantum dots can also be perovskite quantum dots, etc. Optionally, the diameter (size) of the quantum dots is 3-20 nm.

[0059] Please refer to Figure 5 In an embodiment of the present application, the quantum dot light emitting diode further comprises a barrier layer 4 (electron barrier layer) arranged between the anode 1 and the quantum dot light emitting layer 5. In the present application, the large distance between the quantum dots can cause the increase of the leakage current of the quantum dot light emitting diode, which affects the device performance of the quantum dot light emitting diode. In the present application, a barrier layer 4 is arranged between the anode 1 and the quantum dot light emitting layer 5 (between HTL / QD), so as to reduce the leakage current of the quantum dot light emitting diode.

[0060] In order to realize the blocking effect of the barrier layer 4 on electrons, the barrier layer material needs to satisfy certain band gap and conduction band top energy level (LOMO energy level). In an embodiment of the present application, the band gap of the barrier layer material is not less than (greater than or equal to) 3 eV, for example, the band gap of the barrier layer material is 3-10 eV, and the LOMO (greater than or equal to) is not less than -2 eV, for example, the LOMO is -2--1 eV.

[0061] In one embodiment of the present application, the barrier layer material has certain adsorption to the quantum dots, which facilitates the transfer of the quantum dots in the preparation process. Optionally, the barrier layer material is one or more of polymethyl methacrylate (PMMA) and polyvinylpyrrolidone (PVP).

[0062] In the present application, the distance between the quantum dots is increased, and the barrier layer 4 is too thin to effectively block the electrons, so that the electrons directly tunnel to the hole side, reducing the efficiency of the quantum dot light emitting diode. If the barrier layer 4 is too thick, the conductivity of the device is poor, and the hole injection is reduced, resulting in poor device performance. In one embodiment of the present application, the thickness of the barrier layer 4 is 0.1-5 nm.

[0063] In one embodiment of the present application, in order to improve the device performance of the quantum dot light emitting diode, the quantum dot light emitting diode of the present application further comprises a hole functional layer between the anode 1 layer and the barrier layer 4, and an electron functional layer between the quantum dot light emitting layer 5 and the cathode 7 layer. Specifically, the hole function includes a hole injection layer 2 and a hole transport layer 3, wherein the hole injection layer 2 is located on the anode 1 layer, and the hole transport layer 3 is located on the hole injection layer 2; the electron functional layer includes an electron transport functional layer.

[0064] Compared with the existing dense packing quantum dot light emitting layer 5, in the quantum dot light emitting layer 5 of the present application, the quantum dots form the quantum dot light emitting layer 5 with a larger distance, which can reduce the red shift phenomenon caused by energy resonance transfer between quantum dots and achieve the effect of reducing Auger recombination and reducing material aging.

[0065] Please refer to Figure 6 The present application provides a preparation method of a quantum dot light emitting diode, which comprises: preparation of a front functional layer, transfer of a quantum dot light emitting layer 5, and preparation of a rear functional layer; wherein the preparation of the quantum dot light emitting layer 5 comprises: depositing quantum dots on a substrate 8 to prepare a quantum dot substrate 8; and stretching the quantum dot substrate 8 to obtain a quantum dot light emitting layer 5 formed on the substrate 8. In one embodiment of the present application, the preparation method of the quantum dot light emitting diode comprises:

[0066] S101, providing an anode 1;

[0067] S201, forming a quantum dot light emitting layer 5 on the anode 1;

[0068] S301, forming a cathode 7 on the quantum dot light emitting layer 5;

[0069] Alternatively, S102, providing a cathode 7;

[0070] S202, forming a quantum dot light emitting layer 5 on the cathode 7;

[0071] S302, forming an anode 1 on the quantum dot light emitting layer 5;

[0072] The interval of the quantum dots in the first direction is greater than the interval of the quantum dots in the second direction, or the interval of the quantum dots in the first direction is greater than 0.1 nm and less than or equal to 20 nm, and the interval of the quantum dots in the second direction is greater than 0.1 nm and less than or equal to 20 nm.

[0073] Compared with the prior art for preparing quantum dots in a dense packing, the interval of the quantum dots in the first direction is greater than the interval of the quantum dots in the second direction, or the interval of the quantum dots in the first direction and the interval of the quantum dots in the second direction are both greater than 0.1 nm and less than or equal to 20 nm, so that the interval of the quantum dots in the first direction is increased, the packing (arrangement) of the quantum dots is reduced, the phenomenon of red shift caused by the dense packing of the quantum dots is avoided, and the color performance of the quantum dot light emitting diode is improved. When the quantum dot light emitting diode prepared based on the preparation method works, the problem of high charge density of the quantum dot light emitting layer 5 caused by the excessively high density of the quantum dots is also avoided, the Auger recombination is reduced, the efficiency of the quantum dot light emitting diode is improved, the material aging is slowed down, and the service life of the quantum dot light emitting diode is improved.

[0074] Please refer to Figures 7 to 10 In an embodiment of the present application, the method for forming the quantum dot light emitting layer 5 comprises:

[0075] S211, depositing quantum dots on a substrate 8, stretching the substrate 8 to form a quantum dot light emitting layer 5;

[0076] S221, transferring the quantum dot light emitting layer 5 to the anode 1 or the cathode 7.

[0077] In the embodiment of the present application, the interval of the quantum dots in the quantum dot light emitting layer 5 is first increased by stretching the substrate, and then the quantum dot light emitting layer 5 is transferred to the anode 1 or the cathode 7, so as to prepare a quantum dot light emitting diode. It can be seen that, by combining the method of stretching the substrate and transferring, the interval of the quantum dots in the stretching direction can be increased, and the other functional layers will not be damaged and the performance of the other functional layers will not be affected.

[0078] In an embodiment of the present application, the S211 comprises:

[0079] S2111, stretching the substrate in the first direction;

[0080] Alternatively, S2112, stretching the substrate in the first direction and the second direction.

[0081] The S2111 stretches the substrate 8 in the first direction, so that the interval of the quantum dots in the first direction is enlarged, and the interval in the second direction remains unchanged. That is, the S2111 unidirectionally stretches the substrate, forms linear arrangement of quantum dots, and obtains quantum dot grating. Alternatively, in the S2111, the quantum dots are first deposited on the substrate 8, the substrate 8 is heated, and then stretched in the lateral direction, so that the lateral interval of the quantum dots on the substrate 8 is enlarged, and the quantum dot light-emitting layer 5 in which the quantum dots are arranged in rows is formed. Then, the quantum dot light-emitting layer 5 is transferred to the device prepared in the previous process (such as the anode 1 or the cathode 7), so as to prepare the quantum dot light-emitting diode.

[0082] Alternatively, in the preparation method of the quantum dot light-emitting diode, the quantum dots are first deposited on the substrate 8, the substrate 8 is heated, and then stretched in the lateral direction, so that the interval of the quantum dots on the substrate 8 is enlarged, and the quantum dot light-emitting layer 5 in which the quantum dots are linearly arranged is formed. Then, the quantum dot light-emitting layer 5 is transferred to the device prepared in the previous process (such as the anode 1 or the cathode 7), so as to prepare the quantum dot light-emitting diode. Generally, if the quantum dots on the substrate 8 are regularly arranged, the quantum dot light-emitting layer 5 in which the quantum dots are arranged in rows (linearly arranged) can be obtained after the lateral stretching; if the quantum dots on the substrate 8 are regularly arranged, the quantum dot light-emitting layer 5 in which the quantum dots are arranged in curves can be obtained after the lateral stretching.

[0083] The S2112 stretches the substrate 8 in the first direction and the second direction, so that the interval of the quantum dots in the first direction and the second direction is enlarged. That is, the S2111 bidirectionally stretches the substrate, when the stretching distance in the first direction and the second direction is the same, the quantum dot lattice in which the quantum dots are uniformly distributed is formed; when the stretching distance in the first direction is greater than that in the second direction, the quantum dot light-emitting layer 5 in which the interval of the quantum dots in the first direction is greater than that in the second direction can be obtained, for example, the stretching distance in the second direction is greater, so that the interval of the quantum dots in the first direction is greater than 5 nm, and the stretching distance in the second direction is smaller, so that the interval of the quantum dots in the second direction is 0.1-1 nm.

[0084] Alternatively, in the S2112, the quantum dots are first deposited on the substrate 8, the substrate 8 is heated, and then stretched in the lateral and longitudinal directions, so that the interval of the quantum dots on the substrate 8 is enlarged, and the quantum dot light-emitting layer 5 in which the quantum dots are arranged at intervals is formed. Then, the quantum dot light-emitting layer 5 is transferred to the device prepared in the previous process (such as the anode 1 or the cathode 7), so as to prepare the quantum dot light-emitting diode.

[0085] In an embodiment of the present application, the anode 1 can be indium tin oxide (ITO).

[0086] In the S200, the substrate 8 requires a material with good ductility and stability, for example, the substrate 8 is a polyvinyl alcohol substrate 8 or a polypropylene substrate 8.

[0087] In an embodiment of the present application, when stretching the substrate 8, in order to facilitate stretching and improve the stretching effect, the substrate 8 can be heated to above the glass transition temperature of the substrate 8. That is, the temperature for stretching the substrate 8 is a preset stretching temperature; the preset stretching temperature is greater than or equal to the glass transition temperature of the substrate 8. The glass transition temperature of the substrate material is less than 120℃, because a too high heating temperature can affect the luminescence performance of the quantum dots, and when the heating temperature is not higher than 120℃, the luminescence performance of the quantum dots is not affected.

[0088] Referring to Figure 7 In an embodiment of the present application, the stretching of the substrate 8 includes: stretching the substrate 8 in a single direction, or stretching the substrate 8 in two perpendicular directions. When the substrate 8 is stretched in a single direction (uniaxial stretching), the spacing of the quantum dots on the substrate 8 in that direction increases, while the spacing of the quantum dots in the direction perpendicular to that direction does not change, thereby forming quantum dots arranged in a row, i.e., forming a grating (forming a quantum dot luminescent layer after uniaxial stretching). When the substrate 8 is stretched in two perpendicular directions (biaxial stretching), the spacing of the quantum dots on the substrate 8 in the two perpendicular directions increases, thereby forming quantum dots spaced apart from each other, i.e., forming a quantum dot spacing lattice (forming a quantum dot luminescent layer after biaxial stretching).

[0089] In an embodiment of the present application, by controlling the stretching of the substrate 8, the spacing of the quantum dots is controlled to be between 0.1-20nm. For example, by determining the corresponding relationship between the stretching ratio of the substrate 8 and the spacing of the quantum dots, the purpose of controlling the spacing of the quantum dots by controlling the stretching ratio of the substrate 8 is achieved.

[0090] In the embodiment of the present application, the quantum dot luminescent layer 5 is transferred to the anode 1 by transfer. Referring to Figures 8 to 10 In an embodiment of the present application, the S300 includes:

[0091] S301, the stamp 9 adsorbs the quantum dots;

[0092] S302, the quantum dots adsorbed on the stamp 9 are imprinted on the anode 1.

[0093] Optionally, the stamp 9 is a PDMS (polydimethylsiloxane) stamp 9.

[0094] In one embodiment of the present application, the thickness of the quantum dot light emitting layer 5 is 3-20 nm.

[0095] In one embodiment of the present application, the cathode 7 is an aluminum cathode 7.

[0096] In one embodiment of the present application, after the S100, before the S200, further comprising:

[0097] S500, forming a barrier layer 4 on the anode 1.

[0098] The barrier layer 4 is used to reduce the leakage current. The band gap of the material of the barrier layer 4 is not less than 3eV, the LOMO is not less than -2eV, and has a certain adsorption effect on the quantum dots. Optionally, the barrier layer material is one or more of polymethyl methacrylate (PMMA) and polyvinylpyrrolidone (PVP).

[0099] In order to improve the light emitting efficiency of the quantum dot light emitting diode, in one embodiment of the present application, after the S100, before the S500, further comprising:

[0100] S600, forming a hole functional layer on the anode 1.

[0101] The S600 specifically comprises:

[0102] S601, forming a hole injection layer 2 on the anode 1 layer;

[0103] S602, forming a hole transport layer 3 on the hole injection layer 2.

[0104] Optionally, the hole injection layer 2 is a poly(3,4-ethylenedioxythiophene):polystyrene sulfonate hole injection layer 2 (PEDOT:PSS hole injection layer); the hole transport layer 3 is a poly(9,9-dioctylfluorene-CO-N-(4-butylphenyl)diphenylamine) hole transport layer 3 (TFB hole transport layer).

[0105] In order to improve the light emitting efficiency of the quantum dot light emitting diode, in one embodiment of the present application, after the S300, before the S400, further comprising:

[0106] S700, forming an electron transport layer 6 on the quantum dot light emitting layer 5.

[0107] Optionally, the electron transport layer 6 is a ZnO electron transport layer 6, and the thickness of the ZnO electron transport layer 6 is 60-150 nm.

[0108] The preparation method of the quantum dot light emitting diode provided in the embodiment of the application comprises the following steps: firstly, spin coating quantum dots on a substrate 8; then, heating the substrate 8 and performing lateral and longitudinal stretching to increase the spacing of the quantum dots on the substrate 8; and finally, transferring the quantum dot film layer to the device prepared in the previous process (for example, an anode 1) by transfer to form a quantum dot light emitting layer 5.

[0109] The technical solutions of the application will be described below through specific embodiments.

[0110] Embodiment: 1

[0111] The embodiment provides a quantum dot light emitting diode, and a preparation method thereof specifically comprises the following steps:

[0112] (1) providing an ITO anode 1, and performing pretreatment on the anode 1: sequentially performing ultrasonic cleaning with an alkaline cleaning solution (for example, a sodium hydroxide solution with a PH value greater than 10) for 15 min, deionized water for 15 min twice, isopropyl alcohol for 15 min, and then drying at 80 ℃ for 2 h and ozone ultraviolet treatment for 15 min;

[0113] (2) forming a hole injection layer 2 on the anode 1: spin coating a PEDOT:PSS solution on the anode 1, performing 5000 rpm spin coating for 40 s, and then performing 150 ℃ annealing treatment for 15 min to form the hole injection layer 2;

[0114] (3) forming a hole transport layer 3 on the hole injection layer 2: spin coating a TFB solution (concentration: 8 mg / mL, solvent: chlorobenzene) on the hole injection layer 2, performing 3000 rpm spin coating for 30 s, and then performing 80 ℃ annealing treatment for 30 min to form the hole transport layer 3;

[0115] (4) forming a blocking layer 4 on the hole transport layer 3: taking a PMMA solution (concentration: 0.5 mg / mL, solvent: acetone), spin coating the PMMA solution on the hole transport layer 3 in a glove box (water and oxygen content: less than 0.1 ppm) at a speed of 4000 rpm to form the blocking layer 4;

[0116] (5) preparing a gap quantum dot light emitting layer 5: taking a CdSe / ZnS quantum dot solution (concentration: 10 mg / mL, solvent: n-octane), spin coating the CdSe / ZnS quantum dot solution on a PVA substrate 8 in a glove box (water and oxygen content: less than 0.1 ppm) at a speed of 3000 rpm, placing the substrate 8 on a stretching machine, heating to a temperature above the PVA glass transition temperature (80 ℃) to perform lateral stretching, and the stretching multiple (stretching rate) is 0.5; then heating to 100 ℃, transferring the quantum dot film after stretching to the hole transport layer 3 by a PDMS stamp 9 to form the quantum dot light emitting layer 5;

[0117] (6) Forming an electron transport layer 6 on the quantum dot light emitting layer 5: in a glove box (water and oxygen content less than 0.1 ppm), a ZnO solution (concentration 45 mg / mL, solvent ethanol) is spin-coated on the quantum dot light emitting layer 5, spin-coated at 3000 rpm for 30 s, and then annealed at 80°C for 30 min to form the electron transport layer 6.

[0118] (7) Forming a cathode 7 on the electron transport layer 6: Al is evaporated on the electron transport layer 6 by evaporation to form an Al electrode.

[0119] The embodiment can prepare a quantum dot light emitting diode in which quantum dots are arranged in lines to form a grating.

[0120] Embodiment: 2

[0121] The embodiment provides a quantum dot light emitting diode, and a preparation method thereof specifically includes the following steps.

[0122] (1) Providing an ITO anode 1, and pre-treating the anode 1: ultrasonic cleaning with an alkaline cleaning solution (such as a sodium hydroxide solution with PH>10) for 15 min, ultrasonic cleaning with deionized water for 15 min twice, ultrasonic cleaning with isopropyl alcohol for 15 min, and then drying at 80°C for 2 h and ozone ultraviolet treatment for 15 min;

[0123] (2) Forming a hole injection layer 2 on the anode 1: spin-coating a PEDOT:PSS solution on the anode 1, spin-coating at 5000 rpm for 40 s, and then annealing at 150°C for 15 min to form the hole injection layer 2;

[0124] (3) Forming a hole transport layer 3 on the hole injection layer 2: spin-coating a TFB solution (concentration 8 mg / mL, solvent chlorobenzene) on the hole injection layer 2, spin-coating at 3000 rpm for 30 s, and then annealing at 80°C for 30 min to form the hole transport layer 3;

[0125] (4) Forming a blocking layer 4 on the hole transport layer 3: taking a PMMA solution (concentration 0.5 mg / mL, solvent acetone), spin-coating the PMMA solution on the hole transport layer 3 in a glove box (water and oxygen content less than 0.1 ppm) at a speed of 4000 rpm to form the blocking layer 4.

[0126] (5) Preparation of the interstitial quantum dot light-emitting layer 5: Take CdSe / ZnS quantum dot solution (concentration of 10 mg / mL, solvent of n-octane), spin-coat the CdSe / ZnS quantum dot solution on the PVA substrate 8 in a glove box (water and oxygen content less than 0.1 ppm) at a rotation speed of 3000 rpm, place the substrate 8 on a stretcher, heat to above the PVA glass transition temperature (80°C) to perform transverse and longitudinal stretching respectively, the stretching multiple is 0.5. Heat to 100°C again, transfer the stretched quantum dot film to the hole transport layer 3 by the PDMS stamp 9 to form the quantum dot light-emitting layer 5.

[0127] (6) Forming the electron transport layer 6 on the quantum dot light-emitting layer 5: In the glove box (water and oxygen content less than 0.1 ppm), spin-coat the ZnO solution (concentration of 45 mg / mL, solvent of ethanol) on the quantum dot light-emitting layer 5, after spin-coating at 3000 rpm for 30 s, perform annealing treatment at 80°C for 30 min to form the electron transport layer 6.

[0128] (7) Forming the cathode 7 on the electron transport layer 6: Use the evaporation method to evaporate Al on the electron transport layer 6 to form an Al electrode with a thickness of 60-150 nm.

[0129] The quantum dot light-emitting diode with quantum dot interstitial lattices can be prepared by the embodiment.

[0130] It should be understood that the application of the present application is not limited to the above examples, and those of ordinary skill in the art can make improvements or changes according to the above description, and all these improvements and changes shall belong to the protection scope of the appended claims of the present application.

Claims

1. A quantum dot light emitting diode comprising an anode, a cathode, a quantum dot light emitting layer disposed between the anode and the cathode, characterized in that, The spacing of the quantum dots in the quantum dot light emitting layer in a first direction is greater than the spacing of the quantum dots in a second direction, the spacing of the quantum dots in the first direction is 5-20 nm, and the spacing of the quantum dots in the second direction is 0.1-1 nm. The first direction is perpendicular to the second direction.

2. The quantum dot light emitting diode of claim 1, wherein, The quantum dot light emitting diode further comprises a barrier layer disposed between the anode and the quantum dot light emitting layer for reducing leakage current.

3. The quantum dot light emitting diode of claim 2, wherein the quantum dot layer is disposed on the first electrode layer. The band gap of the barrier layer material is greater than or equal to 3 eV.

4. The quantum dot light emitting diode of claim 3, wherein the first electrode is a transparent electrode. The barrier layer material is selected from one or more of polymethyl methacrylate, polyvinylpyrrolidone.

5. A method for fabricating a quantum dot light-emitting diode, characterized in that, Comprising: providing an anode; depositing quantum dots on a substrate, stretching the substrate to form a quantum dot light emitting layer; transferring the quantum dot light emitting layer to the anode; forming a cathode on the quantum dot light emitting layer; Alternatively, providing a cathode; depositing quantum dots on a substrate, stretching the substrate to form a quantum dot light emitting layer; transferring the quantum dot light emitting layer to the cathode; forming an anode on the quantum dot light emitting layer; The spacing of the quantum dots in the quantum dot light emitting layer in a first direction is greater than the spacing of the quantum dots in a second direction, the spacing of the quantum dots in the first direction is 5-20 nm, and the spacing of the quantum dots in the second direction is 0.1-1 nm; wherein the first direction is perpendicular to the second direction. The temperature at which the substrate is stretched is a preset stretching temperature; The preset stretching temperature is greater than or equal to the glass transition temperature of the substrate.

6. The method for fabricating a quantum dot light-emitting diode according to claim 5, characterized in that, The stretching of the substrate comprises: stretching the substrate in a first direction; or stretching the substrate in both a first direction and a second direction.

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