Synthesis method of quantum dot photoresist and application thereof in mini led / micro led

Abstract

The application discloses a synthesis method of quantum dot photoresist, which adopts long-chain ligands of oleic acid and oleylamine, takes a polar solvent as a reaction solvent, adds lead halide and a cesium source as precursor substances, generates high-quality perovskite quantum dots in one step, then removes surface ligands of the perovskite quantum dots through reagents to form surface defects, makes the perovskite quantum dots have electronegativity, and then adds halide ligands capped with ammonium to combine with defects on the surface of the quantum dots to prepare the photoresist. The application not only improves the stability of the quantum dot photoresist, but also enhances the force between the quantum dots and the photosensitive ligands, thereby realizing controllable preparation of a high-precision quantum dot display array device, facilitating mass production, solving the complex process of multi-color conversion of a small display screen, and having a simpler process, higher stability, higher color purity and larger display color gamut compared with other existing products, and being helpful to promote Mini LED / Micro LED colorization application.

Description

Technical Field

[0001] This invention belongs to the field of diode technology, specifically relating to a method for synthesizing quantum dot photoresist and its application in MiniLED / Micro LED. Background Technology

[0002] Mini LED / Micro LED display technology uses individual micrometer-scale LED chips as the smallest pixel unit, combining them with a driving module to form a high-density display array. However, the industrialization of Micro LED still faces many challenges. For example, due to limitations in color conversion and integration technology, it is difficult to integrate the three primary colors (red, green, and blue) at the micrometer scale, making it impossible to guarantee ultra-high resolution while achieving full-color display. Therefore, a simple process for integrating the three primary colors (RGB) is crucial for the color display of Mini LED / Micro LED.

[0003] Perovskite quantum dots have attracted widespread attention in the field of display materials due to their narrow full width at half maximum (FWHM), tunable luminescence, and high quantum yield, and are highly anticipated for their role in color conversion. However, the weak interaction between quantum dots and surface ligands often leads to instability in air. Furthermore, in photolithography, the common method involves mixing quantum dots into photoresist and then spin-coating to prepare the quantum dot film. This method is prone to problems such as low lithography precision, uneven quantum dot distribution, and inability of photopolymers to encapsulate the quantum dots, resulting in poor color conversion and low quantum efficiency, thus hindering their application in Mini LED / Micro LED full-color displays.

[0004] In existing technologies, such as CN109976089A, organic ligands are adsorbed onto the surface of quantum dots. The larger dipole moment of the organic ligands transfers the exciton energy of the ligands to the quantum dot material, thereby enhancing the fluorescence intensity of the quantum dots and effectively preventing quantum dot aggregation. However, the quantum dots proposed in this invention only connect to the surface ligands through chemical adsorption, thus failing to form a strong interaction between the quantum dots and the ligands. This is detrimental to improving the accuracy of subsequent exposures and the stability of the photolithographic pattern, thereby hindering the realization of micron-level high-precision patterning applications.

[0005] For example, CN106479503A utilizes ligands with electronegative hydrophilic ends to modify the surface of quantum dots, and then forms a quantum dot solid film using electrophoresis. However, the electronegative ligands proposed in this invention can only achieve disordered binding of ligands to the quantum dot surface, and cannot achieve precise targeting of ligands on the quantum dot surface. This will compromise the uniformity and accuracy of subsequent large-area photolithography. Therefore, how to precisely target ligands on the quantum dot surface becomes particularly crucial for the precision and uniformity of photolithography.

[0006] Therefore, accurately targeting ligands onto the surface of perovskite quantum dots to generate a strong force without affecting their stability and luminescence properties will play a key role in improving the patterning accuracy of perovskite quantum dot photoresists, and ultimately expand their application capabilities in Mini LED / Micro LED full-color displays. Summary of the Invention

[0007] To address the problems existing in the prior art, this invention provides a method for synthesizing quantum dot photoresist and its application. By selecting a suitable stripping solvent, a uniform electronegativity is formed on the surface of the quantum dot material, allowing ammonium halide-terminated photosensitive polyfunctional polymer ligands to be accurately targeted on the quantum dot surface. This significantly improves the precision of the photoresist, enabling micron-level patterned manufacturing of quantum dots, and its application in wide color gamut, high color accuracy Mini LED / Micro LED full-color displays.

[0008] One of the technical solutions adopted in this invention is a method for synthesizing quantum dot photoresist, which uses oleic acid and oleylamine long-chain ligands, a polar solvent as the reaction solvent, and adds lead halide and cesium source as precursor materials to generate high-quality perovskite quantum dots in one step. Then, the surface ligands of the perovskite quantum dots are removed by reagents to form surface defects, so that the perovskite quantum dots have electronegativity. Finally, ammonium halide-terminated ligands are added to bind with the defects on the surface of the quantum dots. The specific steps include:

[0009] Step 1: Weigh out the cesium source and lead halide and add them to the reaction solvent, then add oleic acid and oleylamine dropwise;

[0010] Step 2: Heat the above solution in air to form a stable perovskite solution;

[0011] Step 3: Cool the solution prepared in Step 2, and wash it by centrifugation with ethyl acetate and toluene. The resulting precipitate is dispersed in toluene to obtain a dispersion.

[0012] Step 4: Weigh a certain amount of ammonium halide-terminated photosensitive polyfunctional polymer ligand and dissolve it in the dispersion solution of Step 3. After stirring and mixing, centrifuge to disperse the precipitate into a polar or non-polar solvent to form a uniform quantum dot photoresist.

[0013] Preferably, the reaction solvent is one of octadecene, n-octane, dimethylformamide, acetonitrile, n-hexane, or toluene.

[0014] Preferably, the cesium source is one of cesium trifluoroacetate, cesium carbonate, cesium bromide, or cesium chloride.

[0015] Preferably, the lead halide is one of lead chloride, lead bromide, or lead iodide.

[0016] Preferably, step 3 specifically involves: taking out the cooled solution with a dropper, washing it with a mixture of ethyl acetate and toluene, wherein the volume ratio of the ethyl acetate / toluene mixture to the solution is 1:1-4:1, mixing and stirring for 4-8 hours, centrifuging at 8000 r / min for about 10 minutes, taking the precipitate, and repeating the above steps 1-4 times to disperse the precipitate in a hexane or n-octane solution.

[0017] Preferably, in step 4, the ligand is ammonium halide (NH3X (X=Cl,Br,I)) as the end-capping agent and the photosensitive polyfunctional polymer, with the following specific structural formula:

[0018]

[0019] The polyfunctional polymer is poly(2-cinnamoyloxymethacrylate), and the mass ratio of ligand to perovskite quantum dots is 1:1. The mixture is stirred for 48 hours, centrifuged at 10000 r / min for 10 min, and then dispersed in a polar or non-polar solvent to form a uniform quantum dot photoresist.

[0020] The second technical solution adopted in this invention is: the application of a quantum dot photoresist, wherein the quantum dot photoresist is coated on a substrate to form a coating, specifically: the quantum dot photoresist is attached to a Mini LED / Micro LED panel to form a thin film by scraping, spin coating or inkjet printing, and an array of light-emitting quantum dots is formed on the panel under 365nm ultraviolet light using photomasks of different sizes.

[0021] The beneficial effects of this invention are:

[0022] This invention utilizes a controlled exfoliation process with a ethyl acetate / toluene mixture to create uniform defects on the quantum dot surface, resulting in strong electronegativity while avoiding any impact on the optical properties of the quantum dots. This ensures high color conversion efficiency and a wide color gamut. Subsequently, ammonium halide-terminated photosensitive polyfunctional polymer ligands passivate the quantum dot surface through hydrogen bonding or halogen element filling, achieving precise targeting of the photosensitive ligands on the quantum dot surface. Adhesive is then applied to the surface of a Mini LED / Micro LED substrate using methods such as blade coating, spin coating, or inkjet printing. Leveraging the photosensitive polymerization properties of the cinnamoyl groups at the ligand ends, direct writing is achieved under 365nm ultraviolet light using masks of different sizes. After development with toluene, an array of 1-100μm luminescent quantum dots is ultimately formed on the panel pixels. By precisely targeting a single quantum dot on its surface, more precise exposure can be achieved, enabling the fabrication of pixels with dimensions of 1-100μm, thereby realizing full-color displays of Mini LED / Micro LED. Attached Figure Description

[0023] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, as well as the beneficial effects of the present invention, the accompanying drawings used in the description of the embodiments or the prior art will be introduced below. Obviously, the accompanying drawings described below are only some embodiments of the present invention. For those skilled in the art, other structures can be obtained based on the structures shown in these drawings without creative effort.

[0024] Figure 1 This is a schematic diagram of the morphology of quantum dot photoresist;

[0025] Figure 2 A schematic diagram of the overall fabrication of quantum dots;

[0026] Figure 3 This is a schematic diagram of the direct-write photolithography technique using photomasks.

[0027] Figure 4 This is a schematic diagram of a high-precision quantum dot after photolithography.

[0028] Figure 5 A schematic diagram of a single pixel on a quantum dot Mini LED / Micro LED panel;

[0029] Figure 6 This is a schematic diagram of the photoluminescence spectrum of a quantum dot Mini LED / Micro LED panel.

[0030] Explanation of reference numerals: 1-Long-chain ligands such as oleic acid and oleylamine; 2-Perovskite quantum dots; 3-Ammonium halide-terminated photosensitive polyfunctional polymer ligands; 4-UV lithography beam; 5-Photolithography mask; 6-Quantum dot photoresist; 7-Mini LED / Micro LED panel; 8-Patterned quantum dot film; 9-Single blue light chip pixel in Mini LED / Micro LED panel. Detailed Implementation

[0031] Specific embodiments of the present invention are as follows:

[0032] A method for synthesizing quantum dot photoresist and its application in Mini LED / Micro LED is disclosed. The quantum dot photoresist uses oleic acid and oleylamine long-chain ligands, with octadecene and other solvents as the reaction solvent, and adds lead halide (PbX2) and cesium source as precursors to generate high-quality perovskite quantum dots in one step. Then, surface defects are removed from the perovskite surface using a mixture of ethyl acetate and toluene, giving the perovskite electronegativity. At this point, ammonium halide-terminated ligands can precisely bind to the defects on the quantum dot surface through hydrogen bonds or halogen elements, achieving precise targeting. Then, using 365nm ultraviolet light and masks of different sizes, luminescent quantum dots of 1-100μm size are directly written onto the blue pixels of a Mini LED / Micro LED panel to form an array of luminescent quantum dots. Combined with blue light, full-color display can be achieved. The high absorbance, wide color gamut, and high color accuracy of perovskite quantum dots can significantly improve the color display of Mini LED / Micro LED panels, enhancing the user experience and product quality.

[0033] A method for synthesizing quantum dot photoresist and its application in Mini LED / Micro LED includes the following steps:

[0034] Step 1: Weigh a certain amount of cesium source and a certain amount of lead halide using a pan balance and add them to the reaction solution. Use a pipette to add a certain proportion of oleic acid and oleylamine to the above solution.

[0035] Step 2: Then place the above solution in a flask and heat it in air to form a stable perovskite solution at a temperature of 60°C to 120°C.

[0036] Step 3: After cooling the solution prepared in Step 2, wash it with an ethyl acetate / toluene mixture, centrifuge for about ten minutes, and repeat the washing twice. The precipitate is dispersed in n-hexane.

[0037] Step 4: Weigh a certain amount of ammonium halide-terminated photosensitive polyfunctional polymer ligand and dissolve it in the perovskite quantum dot solution from Step 3. After mixing and stirring, centrifuge to disperse the precipitate into a polar solvent to form a uniform quantum dot photoresist.

[0038] Step 5: The quantum dot photoresist from Step 4 is applied to the Mini LED / Micro LED panel using a scraping technique. Then, using masks of different sizes, it is directly written onto the panel pixels under 365nm ultraviolet light to form an array of 1-100μm luminescent quantum dots per pixel.

[0039] During preparation, the solution from step 3 is taken out with a dropper and washed with ethyl acetate / toluene, with a volume ratio of ethyl acetate / toluene to solution of 1:1 to 4:1. Centrifuge at 8000 rpm for approximately 10 minutes and collect the precipitate. Repeat the above steps twice to disperse the precipitate in hexane or toluene solution.

[0040] In step 4, the mass ratio of the ammonium halide-encapsulated photosensitive multifunctional ligand to the perovskite quantum dots is 1:1-4:1. After mixing and stirring for 48 hours, the mixture is centrifuged at 10,000 r / min for 10 min to disperse the precipitate in a polar solvent.

[0041] By etching with masks of different sizes under 365nm ultraviolet light and then developing with toluene, an array of luminescent quantum dots with individual pixel sizes of 1 to 100μm is finally formed on the panel pixels.

[0042] The reaction solvent can be any one of the polar solvents such as octadecene, n-octane, dimethylformamide, acetonitrile, n-hexane, and toluene.

[0043] The ammonium halide-terminated photosensitive polyfunctional polymer ligand described herein should have the following structural formula: ammonium halide (NH3X (X=Cll,Br,I)) as the terminator and the photosensitive polyfunctional polymer (cinnamoyl) as poly(2-cinnamoyloxymethacrylate), specifically:

[0044]

[0045] The cesium source for the reaction includes any one of cesium trifluoroacetate, cesium carbonate, cesium bromide, and cesium chloride;

[0046] The lead halide includes any one of lead chloride, lead bromide, and lead iodide.

[0047] The present invention is further illustrated below with reference to specific embodiments, wherein octadecene is used as a reaction solvent and green quantum dots are used as examples:

[0048] Example 1 uses 1 ml of oleic acid and 1 ml of oleylamine as ligands, 10 ml of octadecene as the reaction solvent, and adds 0.2 g of lead bromide and 0.13 g of cesium carbonate. The mixture is heated to 120 degrees Celsius, cooled, and centrifuged. Afterward, it is washed with a mixture of ethyl acetate and toluene (1:1 ratio) for approximately ten minutes, and the washing process is repeated twice. A schematic diagram of the quantum dot exfoliation process is shown below. Figure 2 As shown, the resulting precipitate is dispersed in n-hexane.

[0049] Example 2 uses the same quantum dot synthesis process as Example 1, except that it uses a 2:1 mixed solution of ethyl acetate and toluene.

[0050] Example 3 uses the same quantum dot synthesis process as Example 1, except that it uses a 3:1 mixed solution of ethyl acetate and toluene.

[0051] Example 4 uses the same quantum dot synthesis process as Example 1, except that it uses a 4:1 mixed solution of ethyl acetate and toluene.

[0052] Example 5 uses the same quantum dot synthesis process as Example 1, except that only ethyl acetate is used as the stripping agent.

[0053] Example 6 uses the same quantum dot synthesis process as Example 1, except that only toluene is used as the stripping agent.

[0054] Example 7 uses the same quantum dot synthesis process as Example 1, except that only dimethyl sulfoxide is used as the stripping agent.

[0055] Example 8 uses the same quantum dot synthesis process as Example 1, except that only cyclohexane is used as the stripping agent.

[0056] The peeling rate, luminescence stability, and luminescence intensity of the precipitates generated in Examples 1-8 were measured. The results are shown in Table 1 below. The peeling rate was calculated by thermogravimetric analysis (TGA), while the luminescence stability, luminescence peak position, and luminescence intensity were measured using conventional techniques.

[0057] Table 1

[0058]

[0059]

[0060] The highly polar dimethyl sulfoxide essentially strips all the ligands from the quantum dot surface, creating large non-uniform defects, which ultimately leads to a decrease in luminescence intensity. The luminescence intensity is compared with the fluorescence intensity before stripping.

[0061] A quantum dot photoresist was prepared by mixing a solution dispersed in n-hexane (as described in Example 3) with an ammonium halide-terminated photosensitive polyfunctional polymer ligand (poly(2-cinnamoyloxymethacrylate)) at a 1:1 ratio. A high-resolution structural diagram of the quantum dot photoresist is shown below. Figure 1 As shown, the exterior is uniformly coated with photoresist and then subjected to a scraping photolithography process, with the exposure process as follows: Figure 3 As shown.

[0062] Exposed quantum dot photoresist pixels, such as Figure 4 As shown, uniform size results in better photolithography, and a photolithography precision of 4μm can be fully achieved.

[0063] And perform single-pixel exposure on the Mini LED / Micro LED panel, such as Figure 5 As shown.

[0064] The photoluminescence properties of quantum dot photoresists were tested, such as... Figure 6 As shown. By Figure 6 Test results show that the quantum dot photoresist obtained by the technical solution of this application has good light-emitting performance, excellent color purity and full width at half maximum (FWHM), which can ensure the full-color application of Mini LED / Micro LED.

[0065] In summary, this invention pre-synthesizes high-quality quantum dots using long-chain ligands, then cleans the quantum dots with a ethyl acetate / toluene mixture to remove ligand-induced surface defects, resulting in uniform high electronegativity. Next, ammonium halide-terminated photosensitive polyfunctional polymer ligands are used to passivate the quantum dots through hydrogen bonds of the ammonium halide or halogen elements. Finally, 365nm ultraviolet light, combined with masks of different sizes, is used to directly write 1-100μm luminescent quantum dots onto the blue pixels of a Mini LED / Micro LED panel, forming an array of luminescent quantum dots. Combined with blue light, this enables full-color display. Due to the high absorbance, wide color gamut, and high color accuracy of perovskite quantum dots, the color display of Mini LED / Micro LED panels can be significantly improved, facilitating the integration of RGB primary colors and greatly enhancing the user viewing experience.

[0066] The above are merely preferred embodiments of the present invention and do not limit the scope of the patent. Any equivalent structural or procedural transformations made based on the description and drawings of the present invention, or direct or indirect applications in other related technical fields, are similarly included within the scope of patent protection of the present invention.

Claims

1. A method for synthesizing quantum dot photoresist, characterized in that, Oleic acid and oleylamine long-chain ligands were weighed, and lead halide and cesium source were added as precursors to generate high-quality perovskite quantum dots in a reaction solvent in one step. Then, the ligands on the surface of the perovskite quantum dots were removed by a mixture of ethyl acetate and toluene to form surface defects, making the surface of the perovskite quantum dots electronegative. Finally, ammonium halide-terminated ligands were added to combine with the defects on the surface of the quantum dots to prepare a quantum dot photoresist. The specific steps include: Step 1: Weigh out the cesium source and lead halide and add them to the reaction solvent, then add oleic acid and oleylamine. The reaction solvent is one of octadecene, n-octane, dimethylformamide, acetonitrile, n-hexane, or toluene. The cesium source is one of cesium trifluoroacetate, cesium carbonate, cesium bromide, or cesium chloride. The lead halide is one of lead chloride, lead bromide, or lead iodide. Step 2: Heat the solution obtained in Step 1 in air to form a stable perovskite solution; Step 3: Cool the solution prepared in Step 2, remove the solution with a dropper, and centrifuge and wash it with a mixed solvent of ethyl acetate and toluene. The volume ratio of the mixed solvent to the solution is 1:1-4:

1. After mixing and stirring, centrifuge for 10 min, take the precipitate, and repeat the washing step 1-2 times. The obtained precipitate is dispersed in n-hexane or n-octane. Step 4: Weigh a certain amount of ammonium halide-terminated photosensitive polyfunctional polymer ligand and dissolve it in the dispersion solution from Step 3. After stirring and mixing, centrifuge to disperse the precipitate in a polar or non-polar solvent to form a uniform quantum dot photoresist. The specific structural formula of the ligand is as follows: The mass ratio of ligand to perovskite quantum dot dispersion is 1:

1. After mixing and stirring, the mixture is centrifuged and then dispersed in a polar or non-polar solvent to form a uniform quantum dot photoresist.

2. An application of a quantum dot photoresist, wherein the quantum dot photoresist prepared according to the synthesis method described in claim 1 is applied to a Mini LED / Micro LED panel, characterized in that, The quantum dot photoresist is applied to the Mini LED / Micro LED panel by scraping, spin coating, or inkjet printing, and an array of luminescent quantum dots is formed on the panel under 365nm ultraviolet light using photomasks of different sizes.

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