A high-resolution full-color display device and a method for manufacturing the same

Abstract

The application belongs to the technical field of light emitting display devices, and discloses a high-resolution full-color display device and a preparation method thereof.The method comprises the following steps: (1) sequentially depositing and preparing a hole injection layer and a hole transport layer on a substrate with an anode; (2) depositing a light emitting material on the hole transport layer to prepare a light emitting layer; (3) preparing a pixel definition layer on the light emitting layer; (4) sequentially depositing and preparing an electron transport layer and an electron injection layer on the pixel definition layer; and (5) preparing a metal electrode as a cathode on the electron injection layer to obtain a full-color display device.The application changes the preparation sequence, first deposits the light emitting layer and then prepares the pixel definition layer, thereby improving the thin film quality and light emitting efficiency of the light emitting layer, reducing the leakage current and enhancing the performance of the device.Meanwhile, the light emitting display device pixel obtained by combining the high-resolution electrofluid jet printing process can reach the micron-submicron level, full-color display can be realized, the cost is low and the device is compatible with flexible equipment.

Description

Technical Field

[0001] This invention belongs to the technical field of light-emitting display devices, and more specifically, relates to a high-resolution full-color display device and its preparation method. Background Technology

[0002] Display devices such as PeLED, QLED, and OLED have attracted widespread attention in recent years due to their advantages such as high emission efficiency, high color purity, high contrast, fast response speed, and ultra-thin, flexible, and bendable properties, and are expected to become the most promising display technologies of the future. However, facing the demands of ultra-high definition and near-eye displays, high-resolution patterning of display devices remains one of the key challenges.

[0003] Currently, high-resolution patterning is mainly achieved through processes such as vapor deposition and printing. However, vapor deposition suffers from low yield rates when used for mass production of RGB three-color display devices. Furthermore, the process has low utilization of expensive luminescent materials, requires extremely high precision from the screen forming and coating machines, and is very costly, making it unsuitable for large-area substrates. Traditional inkjet printing offers advantages such as non-contact operation, maskless operation, high material efficiency, and large-area production, but its resolution is relatively low. Electrochemical inkjet printing uses an electric field to pull ink from the nozzle, offering unique advantages such as high resolution (50nm) and compatibility with a wide range of inks (1-10000cP), making it one of the most promising technologies for full-color display applications. Direct contact between the electron transport layer, luminescent layer, and hole transport layer of a display device can generate significant leakage current, affecting the device's luminescent performance. The traditional solution is to create a pixel definition layer between the electron / hole transport layers and then fill the pixel pits with luminescent material. However, these pixel pits affect the printing and drying processes, leading to uneven morphology of the luminescent layer film and low luminous efficiency. Summary of the Invention

[0004] To address the shortcomings and improvement needs of existing technologies, this invention provides a high-resolution full-color display device and its fabrication method. By improving the fabrication sequence, the light-emitting layer is deposited first, followed by the pixel definition layer. This reduces leakage current and improves external quantum efficiency through the pixel definition layer, while solving the problems of low printing efficiency and poor film quality in traditional inkjet printing where the pixel definition layer is deposited first and then the light-emitting layer is deposited in the pixel definition layer pits.

[0005] To achieve the above objectives, in a first aspect, the present invention provides a method for fabricating a high-resolution full-color display device, comprising the following steps:

[0006] (1) A hole injection layer and a hole transport layer are sequentially deposited on a substrate with an anode;

[0007] (2) A light-emitting layer is prepared by depositing a light-emitting material on the hole transport layer;

[0008] (3) A pixel definition layer is prepared on the light-emitting layer;

[0009] (4) An electron transport layer and an electron injection layer are sequentially deposited on the pixel definition layer;

[0010] (5) A metal electrode is prepared on the electron injection layer as a cathode to obtain a full-color display device.

[0011] Further, in step (2), the light-emitting layer is prepared by electrohydraulic inkjet printing.

[0012] Furthermore, in step (2), the diameter and thickness of a single pixel of the light-emitting layer are adjusted by adjusting the characteristics of the electrohydraulic printing solution, the applied voltage amplitude or frequency during the printing process. After printing, vacuum drying and heating annealing are used to ensure the uniformity of the film formation.

[0013] Furthermore, the size of a single pixel in the light-emitting layer is 500nm to 60μm, and its specific shape is adjustable, and can be circular, elliptical, rhomboid, rectangular or waist-shaped.

[0014] Furthermore, step (3) includes:

[0015] An insulating material is deposited on the light-emitting layer, and then patterned and slotted to obtain a pixel definition layer. Each slot corresponds one-to-one with each pixel of the light-emitting layer, and the size of a single slot in the pixel definition layer is smaller than that of a single pixel in the light-emitting layer, so that the light-emitting layer can directly contact the electron transport layer and the hole transport layer, while the electron transport layer and the hole transport layer do not directly contact each other.

[0016] Furthermore, the method for depositing the insulating material is vapor deposition, spraying, or spin coating.

[0017] Furthermore, in step (1), the substrate is one of ITO glass, a substrate with a TFT backplane, or a flexible substrate with patterned electrodes.

[0018] Further, in step (1), the material of the hole injection layer is one or a mixture of several materials selected from CuPc, TiOPc, m-MTDATA, and 2-TNATA; the material of the hole transport layer is one or a mixture of several materials selected from the polymer PEDOT:PSS, molybdenum oxide, nickel oxide, propylene oxide-based system, crosslinked TPD (N-N'-diphenyl-N-N'-di(3-methylphenyl)-1,1'-diphenyl-4,4'-diamine, QUPD (N-N'-di(4-(6-(3-oxabutanol-3-yl)methoxy)-ethoxy)phenyl-N-N'-di(4-methoxyphenyl)diphenyl-4,4'-diamine, styrene-based system, PFCB (perfluorocyclobutane), ZnMgO, and cuprous thiocyanate.

[0019] In step (2), the material of the light-emitting layer is one or a mixture of several materials selected from cadmium-based quantum dots, indium phosphide quantum dots, zinc selenide quantum dots and lead sulfide quantum dots, perovskite, aluminum complexes, anthracene compounds, rare earth complexes, indium complexes, and various fluorescent pigments; the solution of the light-emitting layer is one or a mixture of several materials selected from dimethyl sulfoxide, dimethylformamide, γ-butyrolactone, N,N-dimethylacetamide, acetonitrile, tetramethylsilane, polycarbonate, N-methylpyrrolidone, dimethylacetamide, N,N-dimethylpropenylurea, methylammonium acetate, methylammonium formate, and butylammonium acetate.

[0020] In step (4), the electron transport layer is made of one or a mixture of several materials selected from ZnO nanoparticles, ZnO nanoparticles doped with metal cations, TiO2 nanoparticles, 1,3,5-tris(1-phenyl-1H-benzimidazol-2-yl)benzene, and TCTA; the electron injection layer is made of one or a mixture of several materials selected from LiF, MgP, MgF2, Al2O3, and MoOx.

[0021] In step (5), the material of the metal electrode is an alloy of one or more of the following materials: aluminum, silver, copper, gold, lithium, and magnesium.

[0022] Further, in step (1), the hole injection layer has a thickness of 1–50 nm and the hole transport layer has a thickness of 20–100 nm; in step (2), the light-emitting layer has a thickness of 10–100 nm; in step (3), the pixel definition layer has a thickness of 20–2000 nm; in step (4), the electron transport layer has a thickness of 20–100 nm and the electron injection layer has a thickness of 1–50 nm; and in step (5), the cathode has a thickness of 100–300 nm.

[0023] Secondly, the present invention provides a high-resolution full-color display device, which is prepared by the preparation method of the high-resolution full-color display device described in the first aspect.

[0024] In summary, the above-described technical solutions conceived in this invention can achieve the following beneficial effects:

[0025] (1) Unlike the prior art, the present invention changes the order of preparation of the light-emitting layer and the pixel definition layer. The light-emitting layer is deposited first and then the pixel definition layer is prepared, which improves the thin film quality and light-emitting efficiency of the light-emitting layer, while reducing leakage current and enhancing the performance of the device.

[0026] (2) This invention employs electrohydraulic inkjet printing, which enables precise positioning and high-resolution deposition of droplets. It has high material utilization efficiency, can deposit various materials to achieve full-color display, and saves costs.

[0027] (3) The present invention can be fabricated on a variety of substrates, including flexible substrates and curved substrates, and therefore can be used for flexible wearable devices with good accuracy and flexibility. Attached Figure Description

[0028] Figure 1 This is a schematic flowchart of the fabrication method of the high-resolution full-color display device provided by the present invention;

[0029] Figure 2 This is a schematic diagram of the structure of the high-resolution full-color display device provided by the present invention;

[0030] Figure 3 This is an exploded view of the high-resolution full-color display device provided by the present invention;

[0031] Figure 4 This is a cross-sectional view of a high-resolution full-color display device fabricated according to the process of the present invention; wherein, ① to ⑨ are the processes of placing a substrate, fabricating a hole injection layer, fabricating a hole transport layer, fabricating a light-emitting layer, depositing an insulating material, patterning and grooving, fabricating an electron transport layer, fabricating an electron injection layer, and fabricating a metal electrode, respectively.

[0032] In all the accompanying drawings, the same reference numerals are used to denote the same elements or structures, wherein: 1-ITO glass substrate, 2-hole injection layer, 3-hole transport layer, 4-light emission layer, 5-pixel definition layer, 6-electron transport layer, 7-electron injection layer, 8-cathode. Detailed Implementation

[0033] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention. Furthermore, the technical features involved in the various embodiments of this invention described below can be combined with each other as long as they do not conflict with each other.

[0034] In this invention, the terms "first," "second," etc. (if present) in the invention and the accompanying drawings are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence.

[0035] See Figure 1 , combined Figures 2 to 4 This invention provides a method for fabricating a high-resolution full-color display device, the method comprising the following steps:

[0036] (1) A hole injection layer and a hole transport layer are sequentially deposited on a substrate with an anode.

[0037] Specifically, the substrate is one of ITO glass, a substrate with a TFT backplane, or a flexible substrate with patterned electrodes. Taking ITO glass as an example, the ITO glass substrate is first cleaned, and then a hole injection layer and a hole transport layer are spin-coated onto the cleaned substrate. The hole injection layer is preferably made of one or a mixture of several materials selected from CuPc, TiOPc, m-MTDATA, and 2-TNATA, with a thickness preferably of 1–50 nm. The hole transport layer is preferably made of one or a mixture of several materials selected from the polymer PEDOT:PSS, molybdenum oxide, nickel oxide, propylene oxide-based systems, crosslinked TPD (N-N'-diphenyl-N-N'-di(3-methylphenyl)-1,1'-diphenyl-4,4'-diamine), QUPD (N-N'-di(4-(6-(3-oxabutane-3-yl)methoxy)-ethoxy)phenyl-N-N'-di(4-methoxyphenyl)diphenyl-4,4'-diamine), styrene-based systems, PFCB (perfluorocyclobutane), ZnMgO, and cuprous thiocyanate, with a thickness preferably of 20–100 nm.

[0038] (2) A light-emitting layer is prepared by depositing a light-emitting material on the hole transport layer.

[0039] Specifically, the method used for depositing the luminescent material is electrohydrodynamic inkjet printing, which can be extended to thermal printing, piezoelectric printing, inkjet printing, screen printing, spraying, etc. The preferred printheads are metal printheads, gold-plated glass printheads, glass filament printheads, and dispensing printheads. The printing environment is preferably a nitrogen atmosphere, followed by vacuum drying and thermal annealing to ensure film uniformity and density. During the inkjet printing process, the substrate can move freely in the XY plane, and the nozzle can move up and down in the Z-axis direction to adjust the distance from the substrate. The preferred diameter of the luminescent layer lattice is 500nm-60μm. The diameter and thickness of individual pixels in the luminescent layer are adjusted by adjusting the voltage amplitude and frequency applied during the electrohydrodynamic inkjet printing process to achieve the optimal luminescent display effect. RGB pixels can be simultaneously deposited on the substrate using different printheads via electrohydrodynamic inkjet printing, and their specific shapes are adjustable, including circular, elliptical, rhomboid, rectangular, or oblong shapes.

[0040] The material of the luminescent layer is preferably one or a mixture of several materials selected from cadmium-based quantum dots, indium phosphide quantum dots, zinc selenide quantum dots and lead sulfide quantum dots, perovskite, aluminum complexes, anthracene compounds, rare earth complexes, indium complexes, and various fluorescent dyes. The solution for the luminescent layer is preferably one or a mixture of several materials selected from ethanol, isopropanol, butanol, ethyl acetate, chloroform, chlorobenzene, butyl acetate, dichlorobenzene, anisole, trifluorotoluene, diethyl ether, m-xylene, toluene, mesitylene, and N-cyclohexylpyrrolidone.

[0041] (3) A pixel definition layer is prepared on the light-emitting layer.

[0042] Specifically, an insulating material is first deposited on the light-emitting layer, followed by patterned slots. The pixel definition layer is an insulating material that prevents direct contact between the electron transport layer and the hole transport layer, thereby reducing leakage current. The insulating material is preferably deposited by vapor deposition, spraying, or spin coating. The thickness of the insulating material is preferably 20–2000 nm. Preferably, the pixel definition layer of the display device is patterned using photolithography, laser etching, electrochemical etching, transfer, etc., with each slot slightly smaller than a single pixel in the light-emitting layer, allowing the light-emitting layer to directly contact the electron transport layer and the hole transport layer without damaging the light-emitting layer during the slotting process. The thickness of the pixel definition layer is preferably 20–2000 nm.

[0043] (4) An electron transport layer and an electron injection layer are deposited sequentially on the pixel definition layer.

[0044] Specifically, the electron transport layer and the electron injection layer are preferably prepared by at least one of spin coating, vacuum evaporation, and vacuum sputtering. The electron transport layer is preferably made of one or a mixture of several materials selected from ZnO nanoparticles, ZnO nanoparticles doped with metal cations, TiO2 nanoparticles, 1,3,5-tris(1-phenyl-1H-benzimidazol-2-yl)benzene, and TCTA, with a thickness preferably of 20–100 nm. The electron injection layer is preferably made of one or a mixture of several materials selected from LiF, MgP, MgF2, Al2O3, and MoOx, with a thickness preferably of 1–50 nm.

[0045] (5) A metal electrode is prepared on the electron injection layer as a cathode to obtain a full-color display device.

[0046] Specifically, the metal electrode fabrication process of the display device is at least one of magnetron sputtering and vacuum evaporation. The preferred material for the metal electrode is an alloy of one or more of aluminum, silver, copper, gold, lithium, and magnesium. The preferred electrode thickness is 100–300 nm.

[0047] The present invention will be further described in detail below with reference to three specific embodiments.

[0048] Unless otherwise specified in the embodiments of this invention, the conditions shall be performed according to conventional conditions or conditions recommended by the manufacturer. All raw materials and reagents used, unless otherwise specified, are commercially available conventional products.

[0049] Example 1:

[0050] (1) The ITO glass substrate was ultrasonically cleaned for 8 minutes in sequence with glass cleaning agent, acetone, isopropanol, anhydrous ethanol and deionized water. The cleaned substrate was dried in nitrogen. After the cleaned substrate was coated with a CuPc layer with a thickness of 20 nm, a layer of PEDOT was spin-coated in a spin coater (3000 rpm / s, 30 s). Then it was annealed at 150 °C for 15 minutes.

[0051] (2) Perovskite lattices were prepared by electrohydraulic ink deposition of CsPbI3, CsPbBr3, and CsPbCl3 onto a spin-coated substrate. The ink solution was dimethyl sulfoxide, and the lattice diameter was 10 μm. After deposition, the substrate was annealed at 80 °C for 10 min.

[0052] (3) After annealing, spin coat the substrate with a layer of Z5214 photoresist in multiple steps in a spin coater (200 rpm, 3 s, acceleration 500 rpm / s; 500 rpm, 2 s, acceleration 500 rpm / s; 3000 rpm, 30 s, acceleration 1000 rpm / s; 4000 rpm, 5 s, acceleration 800 rpm / s), and heat it on a hot plate at 95°C for 60 s; expose the treated substrate in a photolithography machine for 6.5 seconds, and then place the exposed substrate in a plasma etching machine to wait for the photoresist in the exposed part of the substrate to be removed.

[0053] (4) A layer of 1,3,5-tris(1-phenyl-1H-benzimidazole-2-yl)benzene with a thickness of 100 nm was deposited on the substrate after development using a magnetron sputtering device.

[0054] (5) First, deposit a 1 nm thick LiF layer on the substrate using a magnetron sputtering device, and then deposit a 100 nm thick Al layer.

[0055] Example 2:

[0056] The difference from Example 1 is that the spin-coating solution in step (1) is replaced with ZnMgO (20 mg / ml, soluble in ethanol), and the spin-coating parameters are 2000 rpm and 30 s.

[0057] In step (2), the solute of the ink used for printing is changed to three types of quantum dots: CsPbI3, CsPbBr3, and CsPbCl3.

[0058] In step (4), the material for vapor deposition is changed to TCTA with a thickness of 40 nm.

[0059] In step (5), the sputtering materials are changed to MoOx (thickness 8nm) and Al (thickness 100nm).

[0060] Example 3:

[0061] The difference from Example 1 is that the spin-coating solution in step (1) is replaced with PEDOT:PSS.

[0062] In step (2), the ink used for printing is replaced with super yellow luminescent PPV copolymer, and the solvent is chlorobenzene.

[0063] Those skilled in the art will readily understand that the above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for fabricating a high-resolution full-color display device, characterized in that, The method includes the following steps: (1) A hole injection layer and a hole transport layer are sequentially deposited on a substrate with an anode; (2) A light-emitting layer is prepared by depositing a light-emitting material on the hole transport layer; (3) A pixel definition layer is prepared on the light-emitting layer; (4) An electron transport layer and an electron injection layer are sequentially deposited on the pixel definition layer; (5) A metal electrode is prepared on the electron injection layer as a cathode to obtain a full-color display device.

2. The method for fabricating a high-resolution full-color display device according to claim 1, characterized in that, In step (2), the light-emitting layer is prepared by electrohydraulic inkjet printing.

3. The method for fabricating a high-resolution full-color display device according to claim 2, characterized in that, In step (2), the diameter and thickness of a single pixel of the light-emitting layer are adjusted by adjusting the characteristics of the electrohydraulic printing solution, the applied voltage amplitude or frequency during the printing process. After printing, vacuum drying and heating annealing are used to ensure the uniformity of the film formation.

4. The method for fabricating a high-resolution full-color display device according to claim 3, characterized in that, The size of a single pixel in the light-emitting layer is 500 nm to 60 μm, and its specific shape is adjustable, including circular, elliptical, rhomboid, rectangular, or waist-shaped.

5. The method for fabricating a high-resolution full-color display device according to any one of claims 1 to 4, characterized in that, Step (3) includes: An insulating material is deposited on the light-emitting layer, and then patterned and slotted to obtain a pixel definition layer. Each slot corresponds one-to-one with each pixel of the light-emitting layer, and the size of a single slot in the pixel definition layer is smaller than that of a single pixel in the light-emitting layer, so that the light-emitting layer can directly contact the electron transport layer and the hole transport layer, while the electron transport layer and the hole transport layer do not directly contact each other.

6. The method for fabricating a high-resolution full-color display device according to claim 5, characterized in that, The method for depositing the insulating material is vapor deposition, spraying, or spin coating.

7. The method for fabricating a high-resolution full-color display device according to claim 1, characterized in that, In step (1), the substrate is one of ITO glass, a substrate with a TFT backplate, or a flexible substrate with patterned electrodes.

8. The method for fabricating a high-resolution full-color display device according to claim 1, characterized in that, In step (1), the hole injection layer is made of one or a mixture of several materials selected from CuPc, TiOPc, m-MTDATA, and 2-TNATA; the hole transport layer is made of one or a mixture of several materials selected from the polymer PEDOT:PSS, molybdenum oxide, nickel oxide, propylene oxide-based system, crosslinked TPD (N-N'-diphenyl-N-N'-di(3-methylphenyl)-1,1'-diphenyl-4,4'-diamine, QUPD (N-N'-di(4-(6-(3-oxabutan-3-yl)methoxy)-ethoxy)phenyl-N-N'-di(4-methoxyphenyl)diphenyl-4,4'-diamine, styrene-based system, PFCB (perfluorocyclobutane), ZnMgO, and cuprous thiocyanate. In step (2), the material of the light-emitting layer is one or a mixture of several materials selected from cadmium-based quantum dots, indium phosphide quantum dots, zinc selenide quantum dots and lead sulfide quantum dots, perovskite, aluminum complexes, anthracene compounds, rare earth complexes, indium complexes, and various fluorescent pigments; the solvent of the light-emitting layer is one or a mixture of several materials selected from dimethyl sulfoxide, dimethylformamide, γ-butyrolactone, N,N-dimethylacetamide, acetonitrile, tetramethylsilane, polycarbonate, N-methylpyrrolidone, N,N-dimethylpropenylurea, methylammonium acetate, methylammonium formate, and butylammonium acetate. In step (4), the electron transport layer is made of one or a mixture of several materials selected from ZnO nanoparticles, ZnO nanoparticles doped with metal cations, TiO2 nanoparticles, 1,3,5-tris(1-phenyl-1H-benzimidazol-2-yl)benzene, and TCTA; the electron injection layer is made of one or a mixture of several materials selected from LiF, MgP, MgF2, Al2O3, and MoOx. In step (5), the material of the metal electrode is an alloy of one or more of the following materials: aluminum, silver, copper, gold, lithium, and magnesium.

9. The method for fabricating a high-resolution full-color display device according to claim 1, characterized in that, The hole injection layer in step (1) has a thickness of 1~50 nm and the hole transport layer has a thickness of 20~100 nm; the light emission layer in step (2) has a thickness of 10~100 nm; the pixel definition layer in step (3) has a thickness of 20~2000 nm; the electron transport layer in step (4) has a thickness of 20~100 nm and the electron injection layer has a thickness of 1~50 nm; the cathode in step (5) has a thickness of 100~300 nm.

10. A high-resolution full-color display device, characterized in that, The high-resolution full-color display device is manufactured using the manufacturing method of the high-resolution full-color display device according to any one of claims 1-9.

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