Micro-led full-color display device manufacturing method based on microfluidic and quantum dot lithography

Abstract

The application discloses a Micro-LED full-color display device structure and a preparation method based on micro-fluid technology and quantum dot ligand engineering photolithography technology, and is characterized in that: quantum dot solution is passed into a micro-channel on a substrate and deposited, and then, through photolithography technology, arraying of a color conversion layer based on quantum dot ligand engineering is realized, and then, the color conversion layer is corresponded with a Micro-LED chip array, a Micro-LED driving layer and a corresponding color filter array above the Micro-LED driving layer one by one, so that the preparation of a Micro-LED full-color light-emitting device is realized. The application breaks through the problems of low material utilization and high cost caused by a traditional quantum dot photolithography technology preparation method of a color conversion layer, and the problems of a complex preparation process in a color conversion layer patterning design scheme based on micro-fluid technology. The application has the advantages of simple preparation process, high material utilization, improved color conversion efficiency and retained high-resolution characteristics of traditional photolithography technology.

Description

Technical Field

[0001] This invention relates to the field of micro-semiconductor displays, and in particular to a Micro-LED full-color display device and its fabrication method based on microfluidic technology and quantum dot ligand engineering lithography. Background Technology

[0002] Compared to LCD and OLED, Micro-LED boasts significant advantages such as high brightness, wide color gamut, high contrast, fast response speed, high maximum resolution, and long lifespan, and is considered the next-generation display technology in the consumer electronics field. Due to its superior performance and potential application value, it has sparked a wave of research in the industry since its inception.

[0003] In the full-color technology of Micro-LED, the technical route of combining ultraviolet / blue light Micro-LED with quantum dot color conversion array is a more feasible full-color solution. It avoids the problems of high circuit design difficulty and different material aging rates in the traditional three-color RGB method. Moreover, the preparation process is mature and the cost is relatively low. At present, the mainstream preparation methods of quantum dot color conversion layer are inkjet printing, traditional photolithography, and patterned microfluidic technology. However, there are still some parts that need to be improved: (1) Inkjet printing has high equipment requirements and is easily affected by the coffee ring effect, which reduces resolution and uniformity, making it difficult to achieve high-precision resolution quantum dot arrays; (2) Although traditional photolithography can achieve high-precision resolution quantum dot patterns, the doped photoresist is easy to damage the quantum dots, and the high-temperature development process further reduces the quantum yield. In addition, the raw material utilization rate of the spin coating process is extremely low, and the cost is high. In addition, the pattern luminescence efficiency has certain requirements for the thickness of the color conversion layer, and traditional photolithography is difficult to accurately control the pattern thickness. (3) At present, there are methods to prepare the color conversion layer through microfluidic chip technology, which can effectively control the quantum dot deposition thickness and prevent light crosstalk. Quantum dots are typically patterned by bonding a surface-modified substrate to a microchannel cover plate, but these methods still suffer from cumbersome preparation processes and high operational difficulty. Summary of the Invention

[0004] This invention addresses the problems existing in the prior art by providing a Micro-LED full-color display device and its fabrication method based on microfluidic technology and quantum dot ligand engineering lithography. This method features a simple fabrication process, high raw material utilization, and controllable thickness, improving color conversion efficiency while retaining the high resolution characteristics of traditional lithography techniques.

[0005] To achieve the above objectives, the technical solution of the present invention is as follows:

[0006] A method for fabricating a Micro-LED full-color display device based on microfluidic technology and quantum dot ligand engineering lithography includes the following steps:

[0007] 1) Construct several microchannels by combining a microchannel cover plate with the surface of a transparent substrate;

[0008] 2) Quantum dot solution is introduced into several microchannels respectively, and after drying, the microchannel cover plate is peeled off to obtain a continuous quantum dot structure with the same pattern as the microchannel on a transparent substrate; the quantum dot solution contains ligands that can undergo photocrosslinking or ligands that can be crosslinked by a photoacid-producing agent;

[0009] 3) Selective exposure of the continuous quantum dot structure using a photomask allows direct or internal cross-linking between the quantum dot ligands in the exposed area;

[0010] 4) The continuous quantum dot structure is arrayed through the development process to obtain a quantum dot array forming a quantum dot color conversion layer;

[0011] 5) Integrating the quantum dot color conversion layer onto the Micro-LED chip array;

[0012] 6) By combining a color filter layer on the quantum dot color conversion layer, a full-color Micro-LED light-emitting device can be fabricated.

[0013] Optionally, the quantum dot solution includes quantum dots, ligands, crosslinking ligands, and a solvent. The ligands are coated on the surface of the quantum dots and are generally long-chain alkyl groups such as oleic acid or oleylamine. The mass percentage of the quantum dots in the quantum dot solution is 5-15 wt%, and the crosslinking ligands are determined according to the concentration of the quantum dots and generally do not exceed 10 wt%.

[0014] Optionally, the crosslinking ligand includes one or more of the following: long alkyl chain unsaturated organic ligands, multifunctional small molecule ligands containing thiols or nitroenes, nitro or carbene crosslinking agents, diazid molecular compounds, and photoacid-producing agents; the solvent includes one or more of the following: distilled water, ethanol, toluene, acetone, chloroform, hexadecylamine (HDA), tributylphosphine (TBP), trioctylphosphine oxide (TOPO), and trioctyl phosphate (TOP).

[0015] Optionally, the ligands coated on the quantum dot surface can undergo rapid polymerization directly under light conditions or through ligand exchange to form a stable network structure that is insoluble in nonpolar organic solvents. The crosslinking ligands can be long alkyl-chain unsaturated organic ligands such as oleic acid (OA), oleylamine, octadecene (ODE), trimercaptopropionic acid (MPA), dodecanethiol (DDT), etc.; or multifunctional small molecule ligands containing thiols, nitroenes, etc., such as ammonium dithiocarbamate (ADC), butyl dithiocarbamate (DTC), 5-mercapto-1-methyltetrazole (MTT), 1,3,4-thiadiazole-2,5-dithiol (TDD), etc.; or nitro, carbene, diazid molecular compounds, and those capable of generating H+ under light. + One or more of the photoacid-producing agents that cause the suspension groups to detach.

[0016] Optionally, the photomask can be any type of quartz photomask, film, etc.

[0017] Optionally, the transparent substrate is glass, quartz, or an organic polymer, including polyethylene terephthalate (PET), polyvinyl alcohol (PVA), polydimethylsiloxane (PDMS), polymethyl methacrylate (PMMA), polyimide (PI), or polyethylene naphthalate (PEN); step 1) further includes surface physicochemical modification of the transparent substrate.

[0018] Optionally, in step 4), the developer includes any one or more of polar or nonpolar solvents such as toluene, acetone, chloroform, isopropanol, N,N-dimethylformamide, and N-methylformamide.

[0019] Optionally, the microchannel is a plurality of parallel strip-shaped groove structures; in step 2), green quantum dot solution and red quantum dot solution are introduced into different microchannels respectively, and dried at 35-45°C for 20-200 min.

[0020] Optionally, the selective exposure causes the strip-shaped continuous quantum dot structure to form alternating exposed and unexposed areas. The development process uses a non-polar solvent as the developer to remove the exposed areas or a polar solution as the developer to remove the unexposed areas, resulting in a quantum dot array. During the development process, a non-polar solvent can be used to obtain an array pattern opposite to the mask pattern, or a polar solvent can be used to obtain an array pattern identical to the mask pattern.

[0021] Optionally, the light source for the exposure includes ultraviolet light, deep ultraviolet light, extreme deep ultraviolet light, electron beams, or X-rays.

[0022] Optionally, the depth of the microchannel is 10–100 micrometers, and the exposure time is 30–200 s. The minimum size of the quantum dot unit in the quantum dot matrix can be accurate to 10 μm, and the spacing can be accurate to 10 μm.

[0023] Optionally, the Micro-LED chip array is further combined with a driving substrate, and the color filter layer includes a color filter array. The Micro-LED chip array, the quantum dot array, and the color filter array correspond one-to-one to form RGB pixel units.

[0024] Optionally, the Micro-LED chip array is an ultraviolet or blue light Micro-LED chip array, comprising a plurality of Micro-LED chip units corresponding to the color conversion layer.

[0025] Optionally, the material of the microchannel cover can be glass, quartz, and organic polymers such as epoxy resin, polycarbonate (PC), polystyrene (PS), polydimethylsiloxane (PDMS), polymethyl methacrylate (PMMA), cyclic olefin copolymer (COC), etc.

[0026] Optionally, the quantum dot can be any of the group II-IV semiconductor quantum dots such as CdSe, CdS, CdTe, ZnS, ZnSe, ZnO, ZnCdS, ZnSeS, and CdZnS, group VI-IV semiconductor quantum dots such as PbSe and PbS, group III-V semiconductor quantum dots such as InP, and perovskite quantum dots such as CsPbX3, or a core-shell structure composed of several materials.

[0027] A Micro-LED full-color display device prepared by the above-mentioned preparation method includes, in sequence, a Micro-LED chip array, a quantum dot color conversion layer and a color filter layer, and also includes an encapsulation cover plate disposed on the color filter layer.

[0028] Optionally, the Micro-LED chip further includes a Micro-LED driving substrate located below it, including a driving circuit, a P-type substrate, an N-type electrode, a buffer insulating layer, multiple quantum wells, and metal electrodes, which are respectively connected to the electrodes of a plurality of Micro-LED chip units in the Micro-LED chip array.

[0029] Optionally, the color filter layer is an RGB filter array corresponding to the quantum dot color conversion layer.

[0030] The beneficial effects of this invention are as follows:

[0031] (1) The quantum dot color conversion layer array is prepared by combining microfluidics and quantum dot lithography. The thickness and pattern accuracy of the color conversion layer can be precisely controlled. It retains the high resolution of traditional lithography and greatly simplifies the process and operation compared with other color conversion layer patterning design schemes based on microfluidics technology.

[0032] (2) The photolithography process directly utilizes ligand engineering photolithography technology without the participation of photoresist, reducing the damage of photoresist to quantum dots and effectively improving quantum yield. Furthermore, photolithography on quantum dots patterned in microfluidic channels can achieve the simultaneous fabrication of quantum dots of multiple colors, enabling rapid color conversion of Micro-LEDs, saving materials, and greatly reducing costs. Attached Figure Description

[0033] Figure 1 A process flow diagram of the manufacturing method for this embodiment;

[0034] Figure 2 This is a top view of the microchannel cover plate in step 3 of the embodiment;

[0035] Figure 3 This is a cross-sectional schematic diagram of step 4 of the embodiment after the quantum dot solution is introduced into the microchannel;

[0036] Figure 4 This is a top view of the quantum dot pattern obtained after peeling off the microchannel cover plate in step 5 of the embodiment.

[0037] Figure 5 This is a top view schematic diagram of the photomask coverage in step 6 of the embodiment;

[0038] Figure 6 This is a top view diagram obtained from step 6 of the embodiment;

[0039] Figure 7 A top view of the red and green transition layers obtained in step 7 of the embodiment;

[0040] Figure 8 This is a schematic diagram of the structure obtained in step 8 of the embodiment;

[0041] Figure 9 This is a top view of the blue Micro-LED chip and driving substrate in step 8 of the embodiment.

[0042] Figure 10 This is a schematic diagram of the structure obtained in step 9 of the embodiment;

[0043] Figure 11 This is a schematic diagram of the structure of the Micro-LED full-color display device prepared as an example. Detailed Implementation

[0044] The present invention will be further explained below with reference to the accompanying drawings and specific embodiments. The accompanying drawings are merely illustrative to facilitate understanding of the invention, and their specific proportions can be adjusted according to design requirements. The vertical relationships of relative elements and the definitions of front / back in the graphics described herein should be understood by those skilled in the art to refer to the relative positions of the components; therefore, they can all be flipped to present the same component, and all of this should fall within the scope disclosed in this specification.

[0045] refer to Figure 1 and combined Figures 2 to 11 The fabrication method of the Micro-LED full-color display device structure based on microfluidic technology and quantum dot lithography in this embodiment is as follows:

[0046] 1. Cleaning the substrate. The substrate is preferably a light-transmitting rigid material such as a glass substrate. In this embodiment, a glass substrate is used. It is cleaned in acetone and ethanol in sequence, then sonicated for 5 minutes, and rinsed with deionized water for 5 minutes.

[0047] 2. Surface physicochemical modification of the substrate. In this embodiment, a layer of octadecyltrichlorosilane (OTS) was modified on the substrate surface using chemical vapor deposition. The substrate was exposed to an OTS atmosphere at a temperature of 80°C for 2 hours. Surface modification can improve the adhesion between the substrate and the quantum dot solution.

[0048] 3. Substrate bonding to microchannels. For example... Figure 2 As shown, in this embodiment, PDMS is used to fabricate the microchannel cover plate 1. The resulting microchannel structure includes several first microchannels 11 and several second microchannels 12, each channel having a solution inlet and a solution outlet. In this embodiment, the first microchannels 11 and second microchannels 12 are strip-shaped groove structures, arranged in parallel and spaced apart, with a depth of approximately 4 micrometers. After the surface of the resulting microchannel cover plate 1 is treated with oxygen plasma, it is bonded to the aforementioned substrate 2. The first microchannels 11 and second microchannels 12 then enclose the surface of the substrate 21 to form a microchannel structure with inlets and outlets at both ends.

[0049] 4. Pass the quantum dot solution through. For example... Figure 3 As shown, a red CdSe / CdZnS quantum dot solution R was injected into the constructed first microchannel 11 using a syringe pump, and a green CdSe / CdZnS quantum dot solution G was injected into the constructed second microchannel 12. The quantum dots were coated with oleic acid ligands, and 2-(4-methoxystyryl)-4,6-bis(trichloromethyl)-1,3,5-triazine (MBT) was used as the crosslinking ligand. Toluene was used as the solvent. In this embodiment, the concentration of the quantum dot solution was 15 mg / mL, and the concentration of the MBT solution was 10 mg / mL. The required amount of MBT was added to the quantum dot solution and stirred to make the mixed solution contain 3 wt% MBT.

[0050] The quantum dot solution is filled into the corresponding microchannels and dried at 40°C for 30 minutes. After the solvent evaporates, the quantum dots are deposited on the substrate surface within the microchannels.

[0051] 5. Peel off the microchannel cover plate 1 to obtain a continuous quantum dot structure R / G on the substrate 21, consistent with the pattern of the microchannel, as shown below. Figure 4 As shown.

[0052] 6. A photomask 3 with the designed pattern is overlaid on the obtained continuous quantum dot structure R / G, such as... Figure 5 As shown, in this embodiment, a film is used as a mask. After being exposed to 365nm ultraviolet light for approximately 45 seconds, the continuous quantum dot structure R / G alternately forms unexposed and exposed areas along its extension direction. The quantum dots in the exposed areas undergo cross-linking, as shown... Figure 6 As shown.

[0053] 7. The quantum dots in the cross-linked regions become insoluble in nonpolar organic solvents. Toluene is used as a developer to pattern the obtained quantum dots, causing the uncross-linked regions to dissolve and be removed in the toluene, resulting in a quantum dot R / G array on substrate 21, which serves as the quantum dot color conversion layer 2. Figure 7 As shown, a column of quantum dots R, a column of quantum dots G, and a blank column are arranged alternately. The blank column is used to directly emit blue light, and the units at the corresponding positions of the quantum dot units and the blank column are used as light-emitting units.

[0054] 8. For example Figure 8 As shown, the obtained quantum dot color conversion layer 2 is aligned and bonded to the corresponding blue Micro-LED chip array 4. Each Micro-LED chip unit 4a corresponds to a light-emitting unit (including a quantum dot R array, a quantum dot G array, and a blank array for directly emitting blue light), thus obtaining red, green, and blue pixel units. The Micro-LED chip array 4 is bonded to its driving substrate 5 before or after, as shown... Figure 9 As shown, the substrate 41 of the Micro-LED chip array 4 can be made of materials such as sapphire, SiC, or Si; in this embodiment, it is a sapphire substrate. A SiO2 buffer layer is used between the P-type electrode 42 and the N-type electrode 43. A flip-chip bonding process is preferred. In the driving array of the driving substrate 5, each chip unit 4a, serving as a pixel on the Micro-LED chip, corresponds to a driving unit, so that the electrodes of the chip unit 4a are assembled one-to-one with the driving units, achieving light emission with the assistance of the driving circuit 51.

[0055] 9. Bonded to color filter layer 6. (e.g.) Figure 10As shown, a color filter layer 6 containing an RGB color filter array is bonded to the surface of the fabricated Micro-LED device. The color filter layer 6 has an RGB color filter array, including an R filter 61, a G filter 62 and a B filter 63. This array is assembled one-to-one with the red, green and blue pixel units of the fabricated quantum dot color conversion layer.

[0056] 10. Bonded to the package cover 7. (e.g.) Figure 11 As shown, adding an encapsulation cover plate 7 to the fabricated Micro-LED device can isolate the effects of water, oxygen, etc. on the quantum dot color conversion layer and improve its service life.

[0057] refer to Figure 11 The resulting Micro-LED full-color display device includes a quantum dot color conversion layer 2, a blue Micro-LED chip array 4, a Micro-LED driving substrate 5, a color filter layer 6, and an encapsulation cover plate 7. The quantum dot color conversion layer 2 includes a red, green, and blue pixel unit matrix formed by a red quantum dot R array, a green quantum dot G array, and a blank array. The chip units 4a of the blue Micro-LED chip array 4 located at the bottom of the color conversion layer correspond one-to-one with it. RGB full-color display is achieved through the color filter array located above the color conversion layer 2.

[0058] In this invention:

[0059] Quantum dot patterns are deposited using constructed microchannels. Photolithography is then performed on an array of pre-deposited quantum dot solutions using the photosensitivity of the quantum dot patterns themselves. This eliminates the need for large-area spin coating of quantum dot solutions, allowing multi-color quantum dot patterns to be formed in a single process. This improves raw material utilization and significantly reduces costs.

[0060] This avoids the step of using photoresist and its photolithography process to define the quantum dot pattern, avoids damage to the quantum dots by the photoresist, improves quantum yield, and further improves color conversion efficiency.

[0061] Ligand engineering lithography utilizes the photosensitivity of resin and certain special organic ligand molecules to directly cure the quantum dots under specified conditions such as UV, electron beam, and X-rays. This eliminates the further damage to quantum dots caused by high temperatures and photoresist in traditional lithography, enabling rapid fabrication of Micro-LED color conversion layers. Moreover, the process is simple and low-cost.

[0062] The above embodiments are only used to further illustrate the structure and fabrication method of a Micro-LED full-color display device based on microfluidic technology and quantum dot lithography technology of the present invention. However, the present invention is not limited to the embodiments. Any simple modifications, equivalent changes and alterations made to the above embodiments based on the technical essence of the present invention shall fall within the protection scope of the technical solution of the present invention.

Claims

1. A method for fabricating a Micro-LED full-color display device based on microfluidic technology and quantum dot ligand engineering lithography, characterized in that, Includes the following steps: 1) Construct several microchannels by combining a microchannel cover plate with the surface of a transparent substrate; 2) A quantum dot solution is introduced into several microchannels, dried, and then the microchannel cover is peeled off to obtain a continuous quantum dot structure with the same pattern as the microchannels on a transparent substrate; the quantum dot solution contains ligands that can undergo photocrosslinking or ligands that are crosslinked by a photoacid-producing agent; the quantum dot solution includes quantum dots, ligands, crosslinked ligands, and a solvent, with the ligands coating the surface of the quantum dots; the mass percentage of the quantum dots in the quantum dot solution is 5-15 wt%, and the mass percentage of the crosslinked ligands is no more than 10 wt%; The ligand is a long-chain alkyl group, including oleic acid or oleylamine; the crosslinking ligand includes one or more of the following: long-chain unsaturated organic ligands, multifunctional small molecule ligands containing thiols or nitroenes, nitro or carbene crosslinking agents, diazid molecular compounds, and photoacid-producing agents; the solvent includes one or more of the following: distilled water, ethanol, toluene, acetone, chloroform, hexadecylamine, tributylphosphine, trioctylphosphine oxide, and trioctyl phosphate. 3) Selective exposure of the continuous quantum dot structure using a photomask allows direct or internal cross-linking between the quantum dot ligands in the exposed area; 4) The continuous quantum dot structure is arrayed through the development process to obtain a quantum dot array forming a quantum dot color conversion layer; 5) Integrating the quantum dot color conversion layer onto the Micro-LED chip array; 6) By combining a color filter layer on the quantum dot color conversion layer, a full-color Micro-LED light-emitting device can be fabricated.

2. The preparation method according to claim 1, characterized in that: The transparent substrate is glass, quartz, or an organic polymer, including polyethylene terephthalate, polyvinyl alcohol, polydimethylsiloxane, polymethacrylate, polyimide, or polyethylene naphthalate; step 1) further includes surface physicochemical modification of the transparent substrate.

3. The preparation method according to claim 1, characterized in that: In step 4), the developing solution includes toluene, acetone, chloroform, isopropanol, N,N -Dimethylformamide, N One or more of methylformamides.

4. The preparation method according to claim 1, characterized in that: The microchannels are a number of parallel strip-shaped groove structures; in step 2), green quantum dot solution and red quantum dot solution are introduced into different microchannels respectively, and dried at 35~45℃ for 20~200 min.

5. The preparation method according to claim 4, characterized in that: The selective exposure causes the strip-shaped continuous quantum dot structure to form alternating exposed and unexposed areas. The development process uses a non-polar solvent as the developer to remove the exposed areas or a polar solution as the developer to remove the unexposed areas, thus obtaining a quantum dot array.

6. The preparation method according to claim 1, characterized in that: The light source for the exposure includes ultraviolet light, deep ultraviolet light, extreme deep ultraviolet light, electron beams, or X-rays.

7. The preparation method according to claim 1, characterized in that: The Micro-LED chip array is also combined with a driving substrate, and the color filter layer includes a color filter array. The Micro-LED chip array, the quantum dot array, and the color filter array correspond one-to-one to form RGB pixel units.

8. A Micro-LED full-color display device prepared by the preparation method according to any one of claims 1 to 7, characterized in that, The components, in sequence, include a Micro-LED chip array, a quantum dot color conversion layer, and a color filter layer, as well as a packaging cover plate disposed on the color filter layer.

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