InP-based patterned QLED device with high efficiency and high resolution and preparation method thereof

Abstract

The invention belongs to the technical field of quantum dot patterned devices and display, and particularly relates to an InP-based patterned QLED device with high efficiency and high resolution and a preparation method thereof. The preparation method comprises the following steps: S1, spin-coating a hole injection layer material on a clean substrate to obtain a hole injection layer; s2, spin-coating a hole transport layer material to obtain a hole transport layer; s3, spin-coating photoresist, carrying out ultraviolet photoetching by using a mask plate, and carrying out developing, washing and baking to obtain a photoresist pixel pit array; s4, dropwise adding the InP quantum dot solution on the substrate with the photoresist pixel pit array, covering the substrate with the micro-column template with asymmetric wettability, enabling the InP quantum dot solution to form a liquid bridge between the substrate and the micro-column template, and uniformly applying a certain balance pressure; s5, the solvent is completely volatilized within 2-6 h, and a light-emitting layer containing a quantum dot array is formed; s6, spin-coating an electron transport layer material to obtain an electron transport layer; and S7, depositing a metal electrode, and packaging.

Description

Technical Field

[0001] This invention belongs to the field of quantum dot patterned devices and display technology, specifically relating to an InP-based patterned QLED device with both high efficiency and high resolution and its fabrication method. Background Technology

[0002] Quantum dot light-emitting diodes (QLEDs) are considered strong contenders for next-generation display and lighting technologies due to their low power consumption and high color purity. For green light-emitting materials, indium phosphide (InP)-based quantum dots, free of heavy metals, have become a key research focus for commercial applications due to their environmentally friendly properties. In recent years, with advancements in synthesis processes, green InP-based QLEDs have achieved significant breakthroughs in external quantum efficiency (EQE), approaching the level of cadmium-based quantum dots.

[0003] However, transforming high-performance InP-based QLEDs from laboratory-grade uniform thin films into high-resolution pixel arrays for practical applications still faces significant technical challenges. Current methods for fabricating patterned devices often suffer from a substantial decrease in device efficiency and a shortened lifespan as pixel size shrinks, failing to meet the demands of high-resolution displays. Spin coating is simple to operate but cannot achieve patterning; inkjet printing is prone to the coffee ring effect during solvent evaporation, leading to uneven quantum dot distribution, poor device luminescence consistency, and severely impacting device efficiency and stability; photolithography involves chemical processing, and the removal of photoresist may cause physical or chemical damage to the quantum dot emitting layer, compromising the optical properties of the quantum dots.

[0004] Existing quantum dot assembly strategies are prone to surface roughness and pinhole formation. Increased surface irregularities and defects make it easier for non-radiative centers and leakage pathways to form, leading to a significant performance degradation as pixel size decreases. Optimizing quantum dot morphology can improve the uniformity and density of quantum dot assembly, making it more suitable for high-resolution displays and providing core material support for near-eye displays and ultra-high-definition home displays.

[0005] Therefore, developing a method for preparing InP-based QLEDs that can achieve both high-resolution patterning and high efficiency is of great significance for promoting the commercialization of cadmium-free QLEDs. Summary of the Invention

[0006] To address the technical problems existing in the prior art, one objective of this invention is to provide a method for fabricating InP-based patterned QLED devices that combines high efficiency and high resolution.

[0007] Another object of the present invention is to provide an InP-based patterned QLED device that combines high efficiency and high resolution.

[0008] To achieve the first objective mentioned above, the present invention adopts the following technical solution: This invention discloses a method for fabricating an InP-based patterned QLED device that combines high efficiency and high resolution, comprising the following steps: S1. Spin-coat a hole injection layer material onto a clean substrate to obtain a hole injection layer; S2. Spin-coat the hole transport layer material onto the hole injection layer to obtain the hole transport layer; S3. Photoresist is spin-coated onto the hole transport layer, ultraviolet lithography is performed using a mask, and the photoresist pixel pit array is obtained after development, rinsing and baking. S4. An InP quantum dot solution is dropped onto a substrate with a photoresist pixel pit array, covering it with a micropillar template having asymmetric wettability. The photoresist pixel pit substrate and the micropillar template are precisely aligned using an alignment system, so that the InP quantum dot solution forms a liquid bridge between the substrate and the micropillar template, and a certain balance pressure is uniformly applied. Here, precise alignment means that each pixel pit in the photoresist pixel pit substrate is aligned with each micropillar in the micropillar template. S5. The solvent evaporates completely within 3-8 hours, and the InP quantum dots are uniformly deposited in the photoresist pixel pit array through directional dewetting, forming a light-emitting layer containing the quantum dot array. S6. Spin-coat an electron transport layer material onto the light-emitting layer to obtain an electron transport layer; S7. Deposit metal electrodes on the electron transport layer and encapsulate them.

[0009] This invention provides a method for fabricating green InP-based patterned QLEDs that balances ultra-high resolution, high efficiency retention, and compatibility with large-scale manufacturing processes. It aims to solve two problems inherent in previous heavy metal-free quantum dot liquid-phase assembly patterning methods: the sensitivity of heavy metal-free quantum dots to water and oxygen, the difficulty of non-destructive patterning, and the coffee ring effect caused by uneven evaporation leading to thickness inconsistencies, cracks, and pinholes. Specifically, this invention first fabricates photoresist pixel pits and then precisely fills them with luminescent material (i.e., quantum dot material). This avoids damage to the quantum dot material in the early stages of the process, maximizing the protection of the luminescent layer's performance. Simultaneously, the quantum dot assembly employs a confined space with controllable evaporation rate adjustment, while directional Laplace pressure promotes directional dewetting, enabling the quantum dots to stably and orderly assemble along the gas-liquid-solid contact lines, thereby overcoming the coffee ring effect.

[0010] Under applied equilibrium pressure, the quantum dot liquid film is divided into independent liquid bridges at the top of each micropillar on the micropillar template and filled into the photoresist pixel pits. During the dewetting process, through parameter optimization (ensuring complete solvent evaporation within 3-8 hours), the three-phase contact lines on the substrate side maintain uniform sliding speed, and the quantum dots are stably precipitated and deposited.

[0011] Furthermore, the micropillar template is a periodic array of square micropillars. The side length of a single square micropillar is 1.5-20 μm, the height of a single square micropillar is 15-20 μm, and the spacing between adjacent square micropillars is 1.5-2 μm. Each micropillar has asymmetric wettability at its top and sidewalls, with a water contact angle <20° at the top and >90° at the sidewalls. Due to the hydrophilic nature of the top of the square micropillars, the quantum dot solution spreads rapidly on the top, while the sidewalls are superhydrophobic. This asymmetric wettability creates an interfacial tension gradient along the top surface of the solution within the gaps in the square micropillar array, providing a driving force for directional dewetting.

[0012] Furthermore, the equilibrium pressure is 5-19 MPa. This range ensures that quantum dot deposition layers of uniform and controllable thickness are obtained for micropillar arrays of different sizes (1.5-20 μm scale), while maximizing the protection of the template and sensitive organic functional layers. At low pressure, the liquid film is higher, the exposed cross-sectional area is larger, and solvent evaporation is accelerated; the opposite is true at high pressure. Precise control of pressure and solution concentration can precisely regulate the height of the quantum dot microstructure. Pressures exceeding 19 MPa can easily cause the micropillars to bend, break, and damage the surface morphology of other QLED layers.

[0013] Furthermore, the concentration of the InP quantum dot solution is 20-100 mg / mL, and the drop volume is 6-12 μL. For preparing high-resolution QLEDs with quantum dot arrays of different sizes, the required concentration and evaporation rate of the InP quantum dot solution vary, necessitating extensive experimental trials.

[0014] Furthermore, the solvent of the InP quantum dot solution is one of n-hexane, n-octane, toluene, and chlorobenzene, preferably n-octane.

[0015] Furthermore, the depth of a single pixel pit in the photoresist pixel pit array is 10-40 μm, preferably 25 μm. It should be noted that, considering the need for precise alignment between the photoresist pixel pit substrate and the micropillar template, those skilled in the art will understand that the size and spacing of the pixel pits in the photoresist pixel pit substrate are consistent with the size and spacing of the square micropillar array in the micropillar template, so that a high-precision alignment system can be used to precisely align the photoresist patterned substrate with the micropillar template during subsequent assembly.

[0016] Furthermore, in step S3, the spin coating speed is 2500-5000 rpm, the spin coating time is 20-40 seconds, the selected photoresist is a negative photoresist, the photolithography time is 5 seconds, the baking temperature is 90-120°C, and the baking time is 40-60 seconds.

[0017] Furthermore, the substrate is selected from ITO glass; The hole injection layer material is a polymer PEDOT:PSS; The hole transport layer material is PF8Cz; The electron transport layer material is ZnMgO.

[0018] Furthermore, in step S1, the spin coating speed is 3000-5000 rpm, and the spin coating time is 20-40 seconds; In step S2, the spin coating speed is 2000-3000 rpm, and the spin coating time is 15-30 seconds; In step S6, the spin coating speed is 2000-2500 rpm, and the spin coating time is 15-30 seconds; In step S7, the metal electrode is deposited by thermal evaporation, with a deposition thickness of 80-100 nm.

[0019] To achieve the second objective mentioned above, the present invention adopts the following technical solution: This invention discloses an InP-based patterned QLED device that combines high efficiency and high resolution as described above.

[0020] The beneficial effects of this invention are as follows: This invention provides a method for fabricating InP-based patterned QLED devices with both high efficiency and high resolution. In this method, a photoresist pixel pit array that can be precisely aligned with a micropillar template is first prepared, and then an InP quantum dot solution is precisely filled in. This avoids damage to the quantum dots during the initial patterning process, solving the problems of heavy metal-free quantum dots being sensitive to water and oxygen and the difficulty of non-destructive patterning. Furthermore, the micropillar template used in this invention is asymmetrically wettable, with each micropillar having a hydrophilic top and hydrophobic sidewalls. The water contact angle at the top of each micropillar is <20°, and the water contact angle at the sidewalls is >90°. This allows for precise control of the evaporation rate and directional dewetting within a confined space within a sandwich-like system formed by the substrate, quantum dot solution, and micropillar template. This enables the acquisition of quantum dot arrays with high uniformity and low defect density across a wide scale range from 1.5 μm to 20 μm, achieving a maximum resolution of 8460 PPI. The average peak EQE of the devices remains above 20%, laying the foundation for the large-scale commercial application of heavy metal-free quantum dots in the display field.

[0021] This invention solves the coffee ring effect caused by uneven solvent evaporation by precisely controlling the concentration and amount of quantum dot solution added, thereby achieving uniform quantum dot deposition and excellent device luminescence consistency. Attached Figure Description

[0022] The specific embodiments of the present invention will be described in further detail below with reference to the accompanying drawings.

[0023] Figure 1This is a schematic diagram of the process flow for preparing a green InP-based patterned QLED that combines high efficiency and high resolution, as described in an embodiment of the present invention.

[0024] Figure 2 These are scanning microscope images of micropillar templates of various sizes in Embodiments 1-6 of the present invention.

[0025] Figure 3 This is a schematic diagram of the modification process of the micropillar template with asymmetric wettability in Embodiment 1 of the present invention.

[0026] Figure 4 This is a schematic diagram of the assembly process of the InP-based quantum dot array in an embodiment of the present invention.

[0027] Figure 5 This is a schematic diagram of the structure of a high-resolution InP-based QLED device in an embodiment of the present invention.

[0028] Figure 6 These are electroluminescence microscope images of InP-based QLED devices at different resolutions in embodiments of the present invention.

[0029] Figure 7 These are the electroluminescence brightness curves of InP-based QLED devices with different resolutions in embodiments of the present invention.

[0030] Figure 8 This is an EQE-current density curve of InP-based QLED devices with different resolutions in embodiments of the present invention.

[0031] Figure 9 These are electroluminescence microscope images and electroluminescence brightness curves of the InP-based patterned QLED device in Comparative Example 1 of the present invention.

[0032] Figure 10 This is the EQE-current density curve of the InP-based patterned QLED device in Comparative Example 1 of this invention.

[0033] Figure 11 This is a confocal microscope image of the InP-based patterned QLED device in Comparative Example 2 of the present invention.

[0034] Figure 12 These are fluorescence micrographs of InP-based quantum dot assembly arrays with different concentrations in embodiments of the present invention.

[0035] Figure 13 This is a schematic diagram and a physical image of a butterfly-patterned QLED device according to one embodiment of the present invention.

[0036] Figure 14 This is a magnified pixel display image of a high-resolution display device according to an embodiment of the present invention, shown under a microscope. Detailed Implementation

[0037] To more clearly illustrate the present invention, the following description, in conjunction with preferred embodiments and accompanying drawings, further clarifies the invention. Those skilled in the art should understand that the specific description below is illustrative rather than restrictive and should not be construed as limiting the scope of protection of the present invention.

[0038] In this invention, the preparation methods are all conventional unless otherwise specified, and the raw materials used can be obtained from publicly available commercial sources or prepared according to existing technology unless otherwise specified.

[0039] Example 1 This embodiment provides a green InP-based patterned QLED that combines high efficiency and high resolution, obtained according to the following fabrication method, the process flow diagram of which is shown below. Figure 1 : Step 1: Prepare a block array of micropillar templates with a side length of 10 μm and a spacing of 2 μm. A 10 μm square array mask pattern with a 2 μm spacing was transferred onto a photoresist-coated silicon wafer using ultraviolet lithography, achieving a precision of approximately 1 μm. Then, deep reactive ion etching with a fluorine-based reagent was performed to fabricate a periodic micropillar structure with a height of 15 μm. After stripping the photoresist with a photoresist and cleaning with ethanol and acetone, the square array micropillar template was obtained. (See scanning microscope image). Figure 2 b.

[0040] Step 2: Perform asymmetric wetting modification on the microcolumn template. The surface of the micropillars was treated with ozone / plasma (O3-Plasma) to make them hydrophilic. SU-8 photoresist was spin-coated onto a flat substrate, and the photoresist-coated side of the substrate was then placed over the top of each micropillar in the block array micropillar template, ensuring photoresist adhesion to the micropillar tips for protection during subsequent chemical processing. The protected micropillar template was placed in a desiccator, and 20 μL of perfluorodecyltriethoxysilane (FAS) solution was added. Vacuum treatment was maintained at room temperature for 1 hour, followed by placing the desiccator in a 90°C oven for 2 hours. After removal and cooling, the SU-8 photoresist on the top of the pillars was dissolved in acetone. This process resulted in a hydrophilic top and hydrophobic sidewalls for each micropillar in the block array micropillar template, as shown in the figure. Figure 3 As shown, the water contact angle at the top of each micropillar is <20°, and the water contact angle on the sidewall of each micropillar is >90°.

[0041] Step 3: Fabrication of Green InP-based High-Resolution QLEDs The ITO-coated glass substrate was ultrasonically cleaned sequentially with detergent, deionized water, acetone, and isopropanol for 15 min each, followed by plasma hydrophilic treatment for 15 min. PEDOT:PSS was spin-coated onto the ITO substrate at 4000 rpm for 40 s, and annealed at 150°C for 30 min to obtain the hole injection layer. Then, the substrate was transferred to a nitrogen-filled glove box for subsequent functional layer spin-coating. PF8Cz (8 mg / mL, chlorobenzene solution) was spin-coated at 3000 rpm for 30 s, and then baked at 120°C for 30 min to obtain the hole transport layer.

[0042] Next, a photoresist pixel pit array was fabricated on the substrate using photolithography. A negative photoresist diluted with m-xylene at a 1:1 volume ratio was spin-coated at 3000 rpm for 30 seconds, baked at 90°C for 1 min, and then exposed to a custom-designed square array mask with 10 μm sides and 2 μm spacing for 5 seconds. This was followed by development, rinsing, and drying to form a square pixel pit array with a depth of 25 μm. Then, 9 μL of a 50 mg / mL InP quantum dot solution (solvent: n-octane) was dropped onto the substrate with the square pixel pit array, and a micropillar template with asymmetric wettability prepared above was immediately placed on top, forming a sandwich structure (each pixel pit was aligned with each micropillar on the micropillar template using an alignment system). A self-made pressure device was used to provide a uniform pressure of 13 MPa to the substrate-solution-template sandwich system. The device was placed in a 25 °C incubator, and the solution was evaporated at a nitrogen flow rate of 45 mL / min for 6 h to allow the solvent to evaporate uniformly and slowly. As the solvent evaporates, under the induction of the asymmetric wettability template, the continuous liquid film of InP quantum dots confined between the top of the micropillar and the substrate undergoes directional dewetting and is uniformly segmented into independent liquid bridges pinned to the top of the pillar. The three-phase contact lines on the side of the micropillar top are pinned due to the sudden change in wettability and geometry, while the three-phase contact lines on the substrate side slip as the solvent evaporates. Therefore, as the solvent further evaporates, quantum dots are uniformly deposited on the photoresist substrate side along the gas-liquid-solid three-phase contact lines, as shown below. Figure 4 As shown, a high-quality quantum dot array was obtained on a glass substrate after the pressure device was removed.

[0043] Subsequently, a ZnMgO nanoparticle solution (20 mg / mL, ethanol solution) was spin-coated onto the substrate at 2000 rpm for 30 s, and then baked at 60°C for 30 min to obtain an electron transport layer. The substrate was then transferred to a vacuum coating machine and coated at 2.5 × 10⁻⁶ ppm. -4 Under a vacuum of Pa, a 100 nm thick aluminum electrode was thermally evaporated and deposited. After deposition, the device was returned to a nitrogen glove box and encapsulated with UV-cured epoxy resin and a cover glass to obtain a green InP-based high-resolution QLED, with the structure shown below. Figure 5 As shown.

[0044] Electroluminescence microscopy images of the high-resolution QLEDs containing a quantum dot array with a side length of 10 μm and a spacing of 2 μm are shown below. Figure 6 As shown in b, the brightness curve is as follows Figure 7 As shown in Figure b, the pixels emit light uniformly, and the highest external quantum efficiency of the QLED device reaches 23.1% ( Figure 8 (b), with a resolution of 2110 PPI.

[0045] Example 2 This embodiment provides a green InP-based patterned QLED that combines high efficiency and high resolution, obtained according to the following fabrication method, the process flow diagram of which is shown below. Figure 1 : Step 1: Prepare a block array of micropillar templates with a side length of 5 μm and a spacing of 2 μm. A 5 μm square array mask pattern with a 2 μm spacing was transferred onto a photoresist-coated silicon wafer using ultraviolet lithography, achieving a precision of approximately 1 μm. Then, deep reactive ion etching with a fluorine-based reagent was performed to fabricate a periodic micropillar structure with a height of 15 μm. After stripping the photoresist with a photoresist and cleaning with ethanol and acetone, the square array micropillar template was obtained. (See scanning microscope image). Figure 2 c.

[0046] Step 2: Perform asymmetric wetting modification on the microcolumn template. The micropillar surfaces were treated with ozone / plasma (O3-Plasma) to make them hydrophilic. SU-8 photoresist was spin-coated onto a flat substrate, and the photoresist-coated side of the substrate was then placed over the tip of each micropillar in the block array micropillar template, ensuring photoresist adhesion to the micropillar tips for protection during subsequent chemical processing. The protected micropillar template was placed in a desiccator, and 20 μL of FAS solution was added. Vacuum treatment was maintained at room temperature for 1 hour, followed by placing the desiccator in a 90°C oven for 2 hours. The template was then removed, cooled, and the SU-8 photoresist on the pillar tips was dissolved in acetone. This process resulted in a hydrophilic tip and hydrophobic sidewalls for each micropillar in the block array micropillar template, with a water contact angle of <20° at the tip and >90° on the sidewalls of each micropillar.

[0047] Step 3: Fabrication of Green InP-based High-Resolution QLEDs The ITO-coated glass substrate was ultrasonically cleaned sequentially with detergent, deionized water, acetone, and isopropanol for 15 min each, followed by plasma hydrophilic treatment for 15 min. PEDOT:PSS was spin-coated onto the ITO substrate at 4000 rpm for 40 s, and annealed at 150°C for 30 min to obtain the hole injection layer. Then, the substrate was transferred to a nitrogen-filled glove box for subsequent functional layer spin-coating. PF8Cz (8 mg / mL, chlorobenzene solution) was spin-coated at 3000 rpm for 30 s, and then baked at 120°C for 30 min to obtain the hole transport layer.

[0048] Next, a photoresist pixel pit array was fabricated on the substrate using photolithography. A negative photoresist diluted with m-xylene at a 1:1 volume ratio was spin-coated at 3000 rpm for 30 seconds, baked at 90°C for 1 min, and then exposed to a custom-designed square array mask with 5 μm sides and 2 μm spacing for 5 seconds. This was followed by development, rinsing, and drying to form a square pixel pit array with a depth of 25 μm. Then, 6 μL of a 40 mg / mL InP quantum dot solution (solvent: n-octane) was dropped onto the substrate with the square pixel pit array, and the aforementioned asymmetric wettability micropillar template was then placed on top, forming a sandwich structure (each pixel pit was aligned with each micropillar on the micropillar template using an alignment system). A self-made pressure device was used to provide a uniform 10 MPa pressure to the substrate-solution-template sandwich system. The device was placed in a 30 °C incubator, and the solution was evaporated at a nitrogen flow rate of 55 mL / min for 4.5 h to ensure uniform and slow solvent evaporation. Under the induction of an asymmetric wettability template, InP quantum dot solution undergoes directional dewetting and uniform deposition at the three-phase contact line, as shown in the figure. Figure 4 As shown, a high-quality quantum dot array was obtained on a glass substrate after the pressure device was removed.

[0049] Subsequently, a ZnMgO nanoparticle solution (20 mg / mL, ethanol solution) was spin-coated onto the substrate at 2000 rpm for 30 s, followed by baking at 60°C for 30 min to obtain an electron transport layer. The substrate was then transferred to a vacuum coating machine and coated at 2.5 × 10⁻⁶ rpm. - 4 Under a vacuum of Pa, a 100 nm thick aluminum electrode was thermally evaporated and deposited. After deposition, the device was returned to a nitrogen glove box and encapsulated with UV-cured epoxy resin and a cover glass to obtain a green InP-based high-resolution QLED, with the structure shown below. Figure 5 As shown.

[0050] Electroluminescence microscopy images of the prepared high-resolution QLEDs with a side length of 5 μm and a spacing of 2 μm are shown below. Figure 6As shown in Figure c, the brightness curve is as follows: Figure 7 As shown in Figure c, the pixels emit light uniformly, and the highest external quantum efficiency of the QLED device reaches 22.3% ( Figure 8 (c), with a resolution of 3620 PPI.

[0051] Example 3 This embodiment provides a green InP-based patterned QLED that combines high efficiency and high resolution, obtained according to the following fabrication method, the process flow diagram of which is shown below. Figure 1 : Step 1: Prepare a block array of micropillar templates with a side length of 1.5 μm and a spacing of 1.5 μm. A 1.5 μm square array mask pattern with a side length and a spacing of 1.5 μm was transferred onto a photoresist-coated silicon wafer using ultraviolet lithography, achieving a precision of approximately 1 μm. Then, deep reactive ion etching with a fluorine-based reagent was performed to fabricate a periodic micropillar structure with a height of 15 μm. After stripping the photoresist with a photoresist and cleaning with ethanol and acetone, the square array micropillar template was obtained. (See scanning microscope image). Figure 2 f.

[0052] Step 2: Perform asymmetric wetting modification on the microcolumn template. The micropillar surfaces were treated with ozone / plasma (O3-Plasma) to make them hydrophilic. SU-8 photoresist was spin-coated onto a flat substrate, and the photoresist-coated side of the substrate was then placed over the tip of each micropillar in the block array micropillar template, ensuring photoresist adhesion to the micropillar tips for protection during subsequent chemical processing. The protected micropillar template was placed in a desiccator, and 20 μL of FAS solution was added. Vacuum treatment was maintained at room temperature for 1 hour, followed by placing the desiccator in a 90°C oven for 2 hours. The template was then removed, cooled, and the SU-8 photoresist on the pillar tips was dissolved in acetone. This process resulted in a hydrophilic tip and hydrophobic sidewalls for each micropillar in the block array micropillar template, with a water contact angle of <20° at the tip and >90° on the sidewalls of each micropillar.

[0053] Step 3: Fabrication of Green InP-based High-Resolution QLEDs The ITO-coated glass substrates were ultrasonically cleaned sequentially with detergent, deionized water, acetone, and isopropanol for 15 min each, followed by plasma hydrophilic treatment for 15 min. PEDOT:PSS was spin-coated onto the ITO substrate at 4000 rpm for 40 s, and annealed at 150°C for 30 min to obtain the hole injection layer. These substrates were then transferred to a nitrogen-filled glove box for the subsequent spin-coating of functional layers. PF8Cz (8 mg / mL, chlorobenzene solution) was spin-coated at 3000 rpm for 30 s, and then baked at 120°C for 30 min to obtain the hole transport layer.

[0054] Next, photoresist pixel pit arrays were fabricated on these substrates using photolithography. Negative photoresist diluted with m-xylene at a 1:1 volume ratio was spin-coated at 3000 rpm for 30 seconds, baked at 90°C for 1 min, and then exposed on a photolithography machine for 5 seconds using a custom-designed 1.5 μm square array mask with a 1.5 μm spacing. This was followed by development, rinsing, and drying to form a 25 μm deep square pixel pit array. Then, 6 μL of a 20 mg / mL InP quantum dot solution (in n-octane) was dropped onto the substrate with the square pixel pit array, and the aforementioned asymmetric wettable micropillar template was immediately placed on top, forming a sandwich structure (each pixel pit was aligned with each micropillar on the micropillar template using an alignment system). A self-made pressure device was used to provide a uniform 5 MPa pressure to the substrate-solution-template sandwich system. The device was placed in a 45 °C incubator, and the solution was evaporated at a nitrogen flow rate of 90 mL / min for 3 h to ensure complete solvent evaporation. Under the induction of an asymmetric wettability template, the quantum dot solution undergoes directional dewetting and uniform deposition at the three-phase contact line, as shown below. Figure 4 As shown, a high-quality quantum dot array was obtained on a glass substrate after the pressure device was removed.

[0055] Subsequently, a ZnMgO nanoparticle solution (20 mg / mL, ethanol solution) was spin-coated onto the substrate at 2000 rpm for 30 s, followed by baking at 60°C for 30 min to obtain an electron transport layer. The substrate was then transferred to a vacuum coating machine and coated at 2.5 × 10⁻⁶ rpm. - 4 Under a vacuum of Pa, a 100 nm thick aluminum electrode was thermally evaporated and deposited. After deposition, the device was returned to a nitrogen glove box and encapsulated with UV-cured epoxy resin and a cover glass to obtain a green InP-based high-resolution QLED, with the structure shown below. Figure 5 As shown.

[0056] Electroluminescence microscopy images and brightness curves of the prepared high-resolution QLEDs with a side length of 1.5 μm and a spacing of 1.5 μm are shown below. Figure 6 As shown in f, the brightness curve is as follows Figure 7 As shown in Figure f, the pixels emit light uniformly, and the highest external quantum efficiency of the QLED device reaches 23.5% ( Figure 8 (Medium f). Resolution is 8460 PPI.

[0057] Example 4 This embodiment provides a green InP-based patterned QLED that combines high efficiency and high resolution, obtained according to the following fabrication method, the process flow diagram of which is shown below. Figure 1 : Step 1: Prepare a block array of micropillar templates with a side length of 20 μm and a spacing of 2 μm. A 20 μm square array mask pattern with a 2 μm spacing was transferred onto a photoresist-coated silicon wafer using ultraviolet lithography, achieving a precision of approximately 1 μm. Then, deep reactive ion etching with a fluorine-based reagent was performed to fabricate a periodic micropillar structure with a height of 15 μm. After stripping the photoresist with a photoresist and cleaning with ethanol and acetone, the square array micropillar template was obtained. (See scanning microscope image). Figure 2 a.

[0058] Step 2: Perform asymmetric wetting modification on the microcolumn template. The micropillar surfaces were treated with ozone / plasma (O3-Plasma) to make them hydrophilic. SU-8 photoresist was spin-coated onto a flat substrate, and the photoresist-coated side of the substrate was then placed over the tip of each micropillar in the block array micropillar template, ensuring photoresist adhesion to the micropillar tips for protection during subsequent chemical processing. The protected micropillar template was placed in a desiccator, and 20 μL of FAS solution was added. Vacuum treatment was maintained at room temperature for 1 hour, followed by placing the desiccator in a 90°C oven for 2 hours. The template was then removed, cooled, and the SU-8 photoresist on the pillar tips was dissolved in acetone. This process resulted in a hydrophilic tip and hydrophobic sidewalls for each micropillar in the block array micropillar template, with a water contact angle of <20° at the tip and >90° on the sidewalls of each micropillar.

[0059] Step 3: Fabrication of Green InP-based High-Resolution QLEDs The ITO-coated glass substrate was ultrasonically cleaned sequentially with detergent, deionized water, acetone, and isopropanol for 15 min each, followed by plasma hydrophilic treatment for 15 min. PEDOT:PSS was spin-coated onto the ITO substrate at 4000 rpm for 40 s, and annealed at 150°C for 30 min to obtain the hole injection layer. Then, the substrate was transferred to a nitrogen-filled glove box for subsequent functional layer spin-coating. PF8Cz (8 mg / mL, chlorobenzene solution) was spin-coated at 3000 rpm for 30 s, and then baked at 120°C for 30 min to obtain the hole transport layer.

[0060] Next, a photoresist pixel pit array was fabricated on the substrate using photolithography. A negative photoresist diluted with m-xylene at a 1:1 volume ratio was spin-coated at 3000 rpm for 30 seconds, baked at 90°C for 1 min, and then exposed to a custom-designed square array mask with 20 μm sides and 2 μm spacing for 5 seconds. This was followed by development, rinsing, and drying to form a square pixel pit array with a depth of 25 μm. Then, 9 μL of an 80 mg / mL InP quantum dot solution (solvent: n-octane) was dropped onto the substrate with the square pixel pit array, and the aforementioned asymmetric wettability micropillar template was then placed on top, forming a sandwich structure (each pixel pit was aligned with each micropillar on the micropillar template using an alignment system). A self-made pressure device was used to provide a uniform 19 MPa pressure to the substrate-solution-template sandwich system. The device was placed in a 20 °C incubator, and the solution was evaporated at a nitrogen flow rate of 40 mL / min for 8 h to allow the solvent to evaporate uniformly and slowly. Under the induction of an asymmetric wettability template, InP quantum dot solution undergoes directional dewetting and uniform deposition at the three-phase contact line, as shown in the figure. Figure 4 As shown, a high-quality quantum dot array was obtained on a glass substrate after the pressure device was removed.

[0061] Subsequently, a ZnMgO nanoparticle solution (20 mg / mL, ethanol solution) was spin-coated onto the substrate at 2000 rpm for 30 s, followed by baking at 60°C for 30 min to obtain an electron transport layer. The substrate was then transferred to a vacuum coating machine and coated at 2.5 × 10⁻⁶ rpm. - 4 Under a vacuum of Pa, a 100 nm thick aluminum electrode was thermally evaporated and deposited. After deposition, the device was returned to a nitrogen glove box and encapsulated with UV-cured epoxy resin and a cover glass to obtain a green InP-based high-resolution QLED, with the structure shown below. Figure 5 As shown.

[0062] Electroluminescence microscopy images of the prepared high-resolution QLEDs with a side length of 20 μm and a spacing of 2 μm are shown below. Figure 6 As shown in Figure a, the brightness curve is as follows: Figure 7 As shown in Figure a, the pixels emit light uniformly, and the highest external quantum efficiency of the QLED device reaches 22.2% ( Figure 8 (a), with a resolution of 1150 PPI.

[0063] Example 5 This embodiment provides a green InP-based patterned QLED that combines high efficiency and high resolution, obtained according to the following fabrication method, the process flow diagram of which is shown below. Figure 1 : Step 1: Prepare a block array of micropillar templates with a side length of 3 μm and a spacing of 2 μm. A 3 μm square array mask pattern with a 2 μm spacing was transferred onto a photoresist-coated silicon wafer using ultraviolet lithography, achieving a precision of approximately 1 μm. Then, deep reactive ion etching with a fluorine-based reagent was performed to fabricate a periodic micropillar structure with a height of 15 μm. After stripping the photoresist with a photoresist and cleaning with ethanol and acetone, the square array micropillar template was obtained. (See scanning microscope image for details.) Figure 2 d.

[0064] Step 2: Perform asymmetric wetting modification on the microcolumn template. The micropillar surfaces were treated with ozone / plasma (O3-Plasma) to make them hydrophilic. SU-8 photoresist was spin-coated onto a flat substrate, and the photoresist-coated side of the substrate was then placed over the tip of each micropillar in the block array micropillar template, ensuring photoresist adhesion to the micropillar tips for protection during subsequent chemical processing. The protected micropillar template was placed in a desiccator, and 20 μL of FAS solution was added. Vacuum treatment was maintained at room temperature for 1 hour, followed by placing the desiccator in a 90°C oven for 2 hours. The template was then removed, cooled, and the SU-8 photoresist on the pillar tips was dissolved in acetone. This process resulted in a hydrophilic tip and hydrophobic sidewalls for each micropillar in the block array micropillar template, with a water contact angle of <20° at the tip and >90° on the sidewalls of each micropillar.

[0065] Step 3: Fabrication of Green InP-based High-Resolution QLEDs The ITO-coated glass substrate was ultrasonically cleaned sequentially with detergent, deionized water, acetone, and isopropanol for 15 min each, followed by plasma hydrophilic treatment for 15 min. PEDOT:PSS was spin-coated onto the ITO substrate at 4000 rpm for 40 s, and annealed at 150°C for 30 min to obtain the hole injection layer. Then, the substrate was transferred to a nitrogen-filled glove box for subsequent functional layer spin-coating. PF8Cz (8 mg / mL, chlorobenzene solution) was spin-coated at 3000 rpm for 30 s, and then baked at 120°C for 30 min to obtain the hole transport layer.

[0066] Next, a photoresist pixel pit array was fabricated on the substrate using photolithography. A negative photoresist diluted with m-xylene at a 1:1 volume ratio was spin-coated at 3000 rpm for 30 seconds, baked at 90°C for 1 min, and then exposed to a custom-designed square array mask with 3 μm sides and 2 μm spacing for 5 seconds. Development, rinsing, and drying were then performed to form a square pixel pit array with a depth of approximately 25 μm. Then, 6 μL of a 35 mg / mL InP quantum dot solution (solvent: n-octane) was dropped onto the substrate with the square pixel pit array, followed by the preparation of an asymmetric wettability micropillar template, forming a sandwich structure (each pixel pit was aligned with each micropillar on the micropillar template using an alignment system). A self-made pressure device was used to provide a uniform 8 MPa pressure to the substrate-solution-template sandwich system. The device was placed in a 30 °C incubator, and the solution was evaporated at a nitrogen flow rate of 60 mL / min for 3 h to allow the solvent to evaporate uniformly and slowly. Under the induction of an asymmetric wettability template, InP quantum dot solution undergoes directional dewetting and uniform deposition at the three-phase contact line, as shown in the figure. Figure 4 As shown, a high-quality quantum dot array was obtained on a glass substrate after the pressure device was removed.

[0067] Subsequently, a ZnMgO nanoparticle solution (20 mg / mL, ethanol solution) was spin-coated onto the substrate at 2000 rpm for 30 s, followed by baking at 60°C for 30 min to obtain an electron transport layer. The substrate was then transferred to a vacuum coating machine and coated at 2.5 × 10⁻⁶ rpm. - 4 Under a vacuum of Pa, a 100 nm thick aluminum electrode was thermally evaporated and deposited. After deposition, the device was returned to a nitrogen glove box and encapsulated with UV-cured epoxy resin and a cover glass to obtain a green InP-based high-resolution QLED, with the structure shown below. Figure 5 As shown.

[0068] Electroluminescence microscopy images of the prepared high-resolution QLEDs with a side length of 3 μm and a spacing of 2 μm are shown below. Figure 6 As shown in d, the brightness curve is as follows Figure 7 As shown in d, the pixel emission is uniform, and the highest external quantum efficiency of the QLED device reaches 23.6% ( Figure 8 (d). Resolution is 5080 PPI.

[0069] Example 6 This embodiment provides a green InP-based patterned QLED that combines high efficiency and high resolution, obtained according to the following fabrication method, the process flow diagram of which is shown below. Figure 1 : Step 1: Prepare a block array of micropillar templates with a side length of 2 μm and a spacing of 2 μm. A 2 μm square array mask pattern with 2 μm side length and 2 μm spacing was transferred onto a photoresist-coated silicon wafer using ultraviolet lithography, achieving a precision of approximately 1 μm. Then, deep reactive ion etching with a fluorine-based reagent was performed to fabricate a periodic micropillar structure with a height of 15 μm. After stripping the photoresist with a photoresist and cleaning with ethanol and acetone, the square array micropillar template was obtained. (See scanning microscope image). Figure 2 e.

[0070] Step 2: Perform asymmetric wetting modification on the microcolumn template. The micropillar surfaces were treated with ozone / plasma (O3-Plasma) to make them hydrophilic. SU-8 photoresist was spin-coated onto a flat substrate, and the photoresist-coated side of the substrate was then placed over the tip of each micropillar in the block array micropillar template, ensuring photoresist adhesion to the micropillar tips for protection during subsequent chemical processing. The protected micropillar template was placed in a desiccator, and 20 μL of FAS solution was added. Vacuum treatment was maintained at room temperature for 1 hour, followed by placing the desiccator in a 90°C oven for 2 hours. The template was then removed, cooled, and the SU-8 photoresist on the pillar tips was dissolved in acetone. This process resulted in a hydrophilic tip and hydrophobic sidewalls for each micropillar in the block array micropillar template, with a water contact angle of <20° at the tip and >90° on the sidewalls of each micropillar.

[0071] Step 3: Fabrication of Green InP-based High-Resolution QLEDs The ITO-coated glass substrate was ultrasonically cleaned sequentially with detergent, deionized water, acetone, and isopropanol for 15 min each, followed by plasma hydrophilic treatment for 15 min. PEDOT:PSS was spin-coated onto the ITO substrate at 4000 rpm for 40 s, and annealed at 150°C for 30 min to obtain the hole injection layer. Then, the substrate was transferred to a nitrogen-filled glove box for subsequent functional layer spin-coating. PF8Cz (8 mg / mL, chlorobenzene solution) was spin-coated at 3000 rpm for 30 s, and then baked at 120°C for 30 min to obtain the hole transport layer.

[0072] Next, a photoresist pixel pit array was fabricated on the substrate using photolithography. A negative photoresist diluted with m-xylene at a 1:1 volume ratio was spin-coated at 3000 rpm for 30 seconds, baked at 90°C for 1 min, and then exposed to a custom-designed square array mask with 2 μm sides and 2 μm spacing for 5 seconds. Development, rinsing, and drying were then performed to form a square pixel pit array with a depth of 25 μm. Then, 6 μL of a 30 mg / mL InP quantum dot solution (solvent: n-octane) was dropped onto the substrate with the square pixel pit array, followed by the covering of the aforementioned asymmetric wettability micropillar template, forming a sandwich structure (each pixel pit was aligned with each micropillar on the micropillar template using an alignment system). A self-made pressure device was used to provide a uniform 7 MPa pressure to the substrate-solution-template sandwich system. The device was placed in a 35 °C incubator, and the solution was evaporated at a nitrogen flow rate of 75 mL / min for 3 h to ensure uniform and slow solvent evaporation. Under the induction of an asymmetric wettability template, InP quantum dot solution undergoes directional dewetting and uniform deposition at the three-phase contact line, as shown in the figure. Figure 4 As shown, a high-quality quantum dot array was obtained on a glass substrate after the pressure device was removed.

[0073] Subsequently, a ZnMgO nanoparticle solution (20 mg / mL, ethanol solution) was spin-coated onto the substrate at 2000 rpm for 30 s, followed by baking at 60°C for 30 min to obtain an electron transport layer. The substrate was then transferred to a vacuum coating machine and coated at 2.5 × 10⁻⁶ rpm. - 4 Under a vacuum of Pa, a 100 nm thick aluminum electrode was thermally evaporated and deposited. After deposition, the device was returned to a nitrogen glove box and encapsulated with UV-cured epoxy resin and a cover glass to obtain a green InP-based high-resolution QLED, with the structure shown below. Figure 5 As shown.

[0074] Electroluminescence microscopy images of the prepared high-resolution QLEDs with a side length of 2 μm and a spacing of 2 μm are shown below. Figure 6 As shown in Figure e, the brightness curve is as follows: Figure 7 As shown in Figure e, the pixels emit light uniformly, and the highest external quantum efficiency of the QLED device reaches 22.1% ( Figure 8 (e). Resolution is 6350 PPI.

[0075] Comparative Example 1 This comparative example provides a green InP-based patterned QLED, which directly utilizes spin coating to fabricate a quantum dot array, obtained according to the following preparation method: The ITO-coated glass substrate was ultrasonically cleaned sequentially with detergent, deionized water, acetone, and isopropanol for 15 minutes each, followed by a plasma hydrophilic treatment for 15 minutes. PEDOT:PSS was spin-coated onto the ITO substrate at 4000 rpm for 40 seconds, and annealed at 150°C for 30 minutes to obtain the hole injection layer. Then, the substrate was transferred to a nitrogen-filled glove box for the subsequent spin-coating of functional layers. PF8Cz (8 mg / mL, chlorobenzene solution) was spin-coated at 3000 rpm for 30 seconds, and then baked at 120°C for 30 minutes to obtain the hole transport layer.

[0076] Next, a photoresist pixel pit array was fabricated on these substrates using photolithography. A negative photoresist diluted with m-xylene at a 1:1 volume ratio was spin-coated at 3000 rpm for 30 seconds and baked at 90°C for 1 min. The photoresist was exposed for 5 seconds using a custom-designed square array mask with 10 μm sides and 2 μm spacing, followed by development, rinsing, and drying to form a square pixel pit array with a height of 25 μm. Subsequently, 30 μL of InP quantum dot solution (30 mg / mL, n-octane solvent) was spin-coated at 2000 rpm and baked at 80 °C for 5 min.

[0077] Subsequently, a ZnMgO nanoparticle solution (20 mg / mL, ethanol solution) was spin-coated onto the substrate at 2000 rpm for 30 s, and then baked at 60°C for 30 min to obtain an electron transport layer. The substrate was then transferred to a vacuum coating machine and coated at 2.5 × 10⁻⁶ ppm. -4 Under a vacuum of Pa, a 100 nm thick aluminum electrode was thermally evaporated and deposited. After deposition, the device was returned to a nitrogen glove box and encapsulated with UV-cured epoxy resin and a cover glass to obtain a green InP-based patterned QLED.

[0078] Electroluminescence microscopy images of patterned QLEDs containing quantum dot arrays with a side length of 10 μm and a spacing of 2 μm, prepared by spin coating. Figure 9 a) and brightness curve ( Figure 9 b) such as Figure 9 As shown, the pixel emission uniformity is poor, and the coffee ring effect is obvious. Figure 10 The EQE-current density curve shows that the highest external quantum efficiency of spin-coated QLED devices is only 10.1%.

[0079] contrast Figure 6 and Figure 9 It can be seen that the quantum dot array QLED prepared by the asymmetric wettability-mediated assembly strategy adopted in this invention effectively suppresses the obvious coffee ring effect in spin coating and displays uniform electroluminescence when integrated into a high-resolution display panel.

[0080] Comparative Example 2 This comparative example provides a green InP-based patterned QLED, which is obtained according to the following preparation method: The preparation method is the same as in Example 1, except that in step three, a self-made pressure device is used to provide a uniform pressure of 8 MPa to the sandwich sandwich system formed by the substrate-solution-template. After the sandwich structure is formed, the device is moved into a constant temperature chamber at 45 °C, and the solution is evaporated at a nitrogen flow rate of 100 mL / min for 0.5 h to allow the solvent to evaporate rapidly.

[0081] Photoluminescence microscope images as follows Figure 11 As shown, due to the increase in temperature, the nitrogen flow rate increases, causing the solvent to evaporate rapidly. This results in uneven distribution of materials in each pixel, leading to poor uniformity of light emission in the resulting square array pixels and a significant coffee ring effect.

[0082] For the fabrication of high-resolution QLEDs with quantum dot arrays of different sizes, precise control of the concentration and evaporation rate of the InP quantum dot solution is required to ensure uniform layer-by-layer stacking of quantum dots. Too low or too high a concentration of the quantum dot solution will lead to a decrease in array quality.

[0083] Comparative Example 3: Quantum dot solution concentration too low The preparation process was the same as in Example 1, except that the concentration of the quantum dot solution was changed to 40 mg / ml. Due to insufficient available material (i.e., quantum dot solute), the quantum dots were insufficient to cover the entire top of the column, resulting in an irregularly shaped assembled array. See the image for an example of this defect. Figure 12 The confocal microscope image.

[0084] Comparative Example 4: Quantum dot solution concentration is too high The preparation process was the same as in Example 1, except that the concentration of the quantum dot solution was changed to 60 mg / ml. Excess material resulted in difficulty in controlling the height and overflow of excess material into the gaps. See the undesirable images. Figure 12 The confocal microscope image.

[0085] Example 7 Referring to the fabrication process of Example 4, the pattern of the photoresist layer pixel pit array and the pattern of the micropillar array are designed as a butterfly pattern. Other fabrication processes are the same as in Example 4, enabling patterned high-resolution display. Figure 13 The exhibition showcases a high-resolution structural diagram and physical image of a butterfly-patterned device. Magnifying the luminescent area reveals a uniformly emitting array of square blocks, as shown. Figure 14 As shown.

[0086] Obviously, the above embodiments of the present invention are merely examples for clearly illustrating the present invention, and are not intended to limit the implementation of the present invention. For those skilled in the art, other variations or modifications can be made based on the above description. It is impossible to exhaustively list all the implementation methods here. All obvious variations or modifications derived from the technical solutions of the present invention are still within the protection scope of the present invention.

Claims

1. A method for fabricating an InP-based patterned QLED device that combines high efficiency and high resolution, characterized in that, Includes the following steps: S1. Spin-coat a hole injection layer material onto a clean substrate to obtain a hole injection layer; S2. Spin-coat the hole transport layer material onto the hole injection layer to obtain the hole transport layer; S3. Photoresist is spin-coated onto the hole transport layer, ultraviolet lithography is performed using a mask, and the photoresist pixel pit array is obtained after development, rinsing and baking. S4. Drop InP quantum dot solution onto a substrate with a photoresist pixel pit array, cover it with a micropillar template with asymmetric wettability, and precisely align the photoresist pixel pit substrate with the micropillar template so that the InP quantum dot solution forms a liquid bridge between the substrate and the micropillar template, and apply a certain balance pressure evenly. S5. The solvent evaporates completely within 3-8 hours, and the InP quantum dots are uniformly deposited in the photoresist pixel pit array through directional dewetting, forming a light-emitting layer containing the quantum dot array. S6. Spin-coat an electron transport layer material onto the light-emitting layer to obtain an electron transport layer; S7. Deposit metal electrodes on the electron transport layer and encapsulate them.

2. The preparation method according to claim 1, characterized in that, In the micropillar template, the side length of a single square micropillar is 1.5-20 μm, the height of a single square micropillar is 15-20 μm, the spacing between adjacent square micropillars is 1.5-2 μm, the top and sidewalls of each micropillar have asymmetrical wettability, the water contact angle at the top of each micropillar is <20°, and the water contact angle at the sidewalls of each micropillar is >90°.

3. The preparation method according to claim 1, characterized in that, The balancing pressure is 5-19 MPa.

4. The preparation method according to claim 1, characterized in that, The concentration of the InP quantum dot solution is 20-100 mg / mL, and the drop volume is 6-12 μL.

5. The preparation method according to claim 4, characterized in that, The solvent for the InP quantum dot solution is one of n-hexane, n-octane, toluene, and chlorobenzene, preferably n-octane.

6. The preparation method according to claim 1, characterized in that, The depth of a single pixel pit in the photoresist pixel pit array is 10-40 μm, preferably 25 μm.

7. The preparation method according to claim 1, characterized in that, In step S3, the spin coating speed is 2500-5000 rpm, the spin coating time is 20-40 seconds, the selected photoresist is a negative photoresist, the photolithography time is 5 seconds, the baking temperature is 90-120°C, and the baking time is 40-60 seconds.

8. The preparation method according to claim 1, characterized in that, The substrate is selected from ITO glass; The hole injection layer material is a polymer PEDOT:PSS; The hole transport layer material is PF8Cz; The electron transport layer material is ZnMgO.

9. The preparation method according to claim 1, characterized in that, In step S1, the spin coating speed is 3000-5000 rpm, and the spin coating time is 20-40 seconds; In step S2, the spin coating speed is 2000-3000 rpm, and the spin coating time is 15-30 seconds; In step S6, the spin coating speed is 2000-2500 rpm, and the spin coating time is 15-30 seconds; In step S7, the metal electrode is deposited by thermal evaporation, with a deposition thickness of 80-100 nm.

10. An InP-based patterned QLED device that combines high efficiency and high resolution, characterized in that, It is prepared by the preparation method according to any one of claims 1-9.

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