Photoresist solution as well as preparation method and application thereof

Abstract

The invention discloses a photoresist solution as well as a preparation method and application thereof. The photoresist solution comprises a fluorine-containing compound, a cation-loaded azobenzene compound and a photoinitiator, the fluorine-containing compound is a fluorine-containing resin monomer and / or a fluorine-containing copolymer, and the azobenzene compound loaded with the cations is obtained by modifying the azobenzene compound with organic amine and / or organic ammonium salt and then loading the cations. The azobenzene compound loaded with the cations in the photoresist solution has photoresponsiveness, and can release the cations to strongly interact with the fluorine-containing dipole in the fluorine-containing compound under the irradiation of ultraviolet light, so that special physical and chemical structures are formed in an irradiation area, and the photosensitivity of the photoresist solution is improved. The method is used for preparing an isolation barrier layer of a high-resolution quantum dot light-emitting diode, leakage current can be effectively inhibited, and the electrical performance and the display quality of a device are improved.

Description

Technical Field

[0001] This invention relates to the field of photoresist and light-emitting diode technology, specifically to a photoresist solution, its preparation method, and its application in the preparation of high-resolution quantum dot light-emitting diodes. Background Technology

[0002] Colloidal quantum dots (QDs) have been extensively studied due to their excellent optoelectronic properties, such as narrow emission spectra, tunable emission wavelengths, high luminous efficiency, and excellent stability. In the past decade, breakthroughs have been achieved in the performance of quantum dot light-emitting diodes (QLEDs), demonstrating broad prospects for display applications. Faced with the demands of massive information displays or near-eye displays, next-generation displays are setting higher standards for pixel resolution. Currently, to meet the needs of next-generation display technologies such as virtual reality, 3D displays, and near-eye displays, there is an urgent need to achieve ultra-high resolution QD pixel patterns with pixel resolutions exceeding 10,000 pixels per inch (PPI). These display technologies achieve high information flow by redistributing graphic information from a two-dimensional screen to three-dimensional space. Unfortunately, previous high-resolution QLEDs have had relatively low performance, with their external quantum efficiency (EQE) and brightness being about an order of magnitude lower than spin-coated QLEDs. This can be attributed to the poor quality of the transferred QD film and the large leakage current generated in the non-emitting regions between pixels due to the direct contact between the hole transport layer (HTL) and the electron transport layer (ETL).

[0003] Currently, to address the issue of significant leakage current in non-light-emitting areas between pixels caused by direct contact between the HTL and ETL, a common process involves using photolithography to fill the spaces between quantum dot pixels with electrically insulating photoresist, physically isolating adjacent pixels. This structure effectively blocks direct contact between the HTL and ETL between adjacent pixels, thereby suppressing the resulting large lateral leakage current. This is crucial for improving device performance and achieving high-resolution displays.

[0004] However, traditional photoresists suffer from serious defects during the photolithography process. During the photolithography stage, SU-8, I-1000, AZ series, and Shipley series chemically amplified photoresists release acid. Quantum dots, as the core light-emitting material in QLEDs, have surface atoms in an unsaturated state, exhibiting high reactivity. The presence of acid readily leads to chemical reactions with quantum dots, altering their surface chemical structure and consequently affecting their optical and electrical properties. For example, acid may damage ligands on the quantum dot surface, increasing surface defects, adding non-radiative recombination centers, and reducing the luminous efficiency of the quantum dots.

[0005] Secondly, in the subsequent development process, alkaline aqueous solutions (such as tetramethylammonium hydroxide, TMAH) are commonly used. Quantum dot materials, especially some semiconductor components that are unstable in alkali (such as CdSe, ZnS, etc.), will suffer severe corrosion in alkaline environments. This corrosion may cause changes in the size and morphology of quantum dots, or even partial dissolution, thereby destroying the integrity of the quantum dot film. The direct consequence is non-uniformity in the electrical properties of the quantum dot film (such as carrier injection and transport efficiency) between different pixels. This non-uniformity not only fails to completely eliminate leakage current, but may also introduce new current paths, becoming the root cause of device performance degradation and poor display uniformity.

[0006] The acid and alkaline corrosion problems caused by traditional photoresists not only reduce the yield and reliability of high-resolution QLED devices, but also hinder the improvement of their external quantum efficiency (EQE) and brightness, thus severely restricting the performance improvement and large-scale commercial application of high-resolution QLEDs. Summary of the Invention

[0007] To address the aforementioned problems, this invention provides a photoresist solution, its preparation method, and its application in the fabrication of high-resolution quantum dot light-emitting diodes (QLEDs). This photoresist solution fundamentally avoids the generation of acidic substances, and its development process can be performed using organic solvents instead of alkaline aqueous solutions, thereby completely eliminating the chemical corrosion of quantum dots by acids and alkalis. The photoresist of this invention can perfectly achieve electrical isolation between the hole transport layer and the electron transport layer without damaging the active layer of the quantum dots, thereby effectively reducing device leakage current and significantly improving the EQE, brightness, and overall performance stability of high-resolution QLEDs.

[0008] Specifically, the following technical solutions are provided: The first aspect of this invention provides a photoresist solution comprising a fluorinated compound, a cationic azobenzene compound, and a photoinitiator; wherein, The fluorinated compound is a fluorinated resin monomer and / or a fluorinated copolymer; The cation-loaded azobenzene compound is obtained by modifying an azobenzene compound with an organic amine and / or an organic ammonium salt, and then loading it with a cation; the azobenzene compound contains at least one of hydroxyl, carboxyl, sulfonic acid, and nitro groups, and the cation is a metal ion and / or an alkyl imidazole ion.

[0009] Traditional photoresists suffer from acid and alkaline corrosion when used as isolation layers between quantum dot pixels and hole transport layers in high-resolution QLED devices. This not only fails to effectively address leakage current issues but also degrades the EQE and brightness performance of high-resolution QLED devices. Therefore, this invention provides a photoresist solution that fundamentally avoids the chemical corrosion of quantum dots by acids and alkalis. The solution primarily comprises a fluorinated compound for film formation, a photoresponsive azobenzene compound loaded with cations, and a photoinitiator for initiating the cross-linking polymerization of the fluorinated compound. The coating formed by applying the above-mentioned photoresist solution undergoes a photoresist response under ultraviolet light irradiation. The molecular structure of the azobenzene compounds modified with organic amines and / or organic ammonium salts undergoes changes such as cis-trans isomerization, leading to the release of the loaded cations. These released cations interact strongly with the fluorinated dipoles of the fluorinated compounds (e.g., electrostatic interactions). This interaction promotes the formation of a special physical and chemical structure in the irradiated area of ​​the photoresist coating. This structure effectively isolates the hole transport layer and electron transport layer, preventing direct contact between them and thus avoiding short circuits and leakage current problems caused by direct interlayer contact. Furthermore, since the photoresist prepared in this invention does not involve acid-releasing components during the photolithography stage, and organic solvents can be used instead of alkaline aqueous solutions during development, the chemical erosion of quantum dots by acids and alkalis is completely eliminated. This prevents corrosion of the quantum dots, greatly protecting the structural and performance integrity of the quantum dots, further ensuring the stability of the quantum dot pixels, and significantly suppressing leakage current between quantum dot pixels, thereby effectively improving the electrical performance and display quality of high-resolution QLEDs.

[0010] Furthermore, the photoresist solution comprises the following components by mass percentage: 20%-30% of a fluorinated compound, 6%-10% of a cationic azobenzene compound, 1%-2% of a photoinitiator, and the remainder being a solvent.

[0011] In this invention, to ensure the integrity and mechanical strength of the film formed after photoresist curing, the content of the fluorinated compound in the photoresist solution cannot be too low, but too high a content will prevent complete dissolution. Therefore, its mass percentage needs to be controlled within the range of 20%-30%, for example, 20%, 21%, 22%, 23%, 24%, 25%, 26%, 27%, 28%, 29%, 30%, etc. Simultaneously, the mass percentage of the cationic azobenzene compound in the photoresist solution needs to be controlled. If the content is too low, insufficient cations will be released, failing to effectively improve the properties of the cured film. Yes, but if the content is too high, too many cations will be released, which will affect the photocuring effect of the fluorinated compound (metal ions have a certain absorption effect on ultraviolet light and will quench free radicals). In addition, excessive cations that are not firmly bound to the polymer chain will migrate inside the material and precipitate on the surface, affecting the mechanical properties and long-term stability of the film, resulting in an inability to play an effective barrier role. In order to effectively improve the mechanical properties of the film after photocuring of the photoresist solution, the mass ratio of the cation-loaded azobenzene compound should be controlled within the range of 6%-10%, such as 6%, 7%, 8%, 9%, 10%, etc.

[0012] Furthermore, the fluorinated resin monomer may be selected from one or more of 2,2,2-trifluoroethyl acrylate, trifluoroethyl methacrylate, and hexafluorobutyl acrylate, and the fluorinated copolymer may include, but is not limited to, poly(vinylidene fluoride-co-hexafluoropropylene).

[0013] Further, the azobenzene compound may be selected from one or more of azobenzene-4,4'-dicarboxylic acid, 2,2-dihydroxyazobenzene, azobenzene-3,3'-dicarboxylic acid, 4,4'-dihydroxymethylazobenzene, 4-(azobenzene)benzoic acid, 4'-hydroxyazobenzene-4-carboxylic acid, 4-hydroxyazobenzene-2'-carboxylic acid, (E)-azobenzene-4,4'-dicarboxylic acid, 4'-aminoazobenzene-4-sulfonic acid, sodium 4-aminoazobenzene-4'-sulfonate, and 4'-nitro-4-dimethylaminoazobenzene.

[0014] Furthermore, the organic amine includes, but is not limited to, oleylamine, and the organic ammonium salt includes, but is not limited to, tetrabutylammonium salt and / or hexadecyltrimethylammonium salt.

[0015] Furthermore, the metal ions include Li + Na + K + Mg 2+ Ca 2+ 、Sr 2+ Ba 2+ Al 3+ C 3+ Fe 3+ Co 3+ Mn2+ Ti 4+ Fe 2+ Co 2+ Ni 2+ Cu 2+ Zn 2+ Pb 2+ Sn 2+ Sb 3+ Cu + Ag + Au + Hg + Hg 2+ Cd 2+ Pd 2+ Pt 2+ 、Tl + 、Tl 3+ One or more of the following, wherein the alkyl imidazolium ion includes 1-ethyl-3-methylimidazolium ion and / or 1-butyl-3-methylimidazolium ion.

[0016] Furthermore, the method for preparing the cation-supported azobenzene compound includes the following steps: S1. Organic amines and / or organic ammonium salts are reacted with azobenzene compounds in the presence of an organic solvent to obtain the modified azobenzene compounds. S2. The modified azobenzene compound is added to a salt solution containing the cation, the pH is adjusted to 5-6, and a second stirring reaction is carried out to obtain the cation-loaded azobenzene compound.

[0017] Further, in step S1, the molar ratio of the organic amine and / or organic ammonium salt to the azobenzene compound is preferably (1.5-2):1, for example 1.5:1, 1.6:1, 1.7:1, 1.8:1, 1.9:1, 2:1, etc., including but not limited to the molar ratios listed above.

[0018] Further, in step S1, the organic solvent may be selected from one or more of N,N-dimethylformamide, dimethyl sulfoxide, toluene, chlorobenzene, and propylene glycol methyl ether.

[0019] Further, in step S1, the ratio of the molar amount of the azobenzene compound to the volume of the organic solvent is preferably (0.1-0.3) mol:1 L, for example, 0.2 mol:1 L, etc.

[0020] Furthermore, in step S1, the temperature of the first stirring reaction is preferably 60-70 ℃, and the time is preferably 8-10 h.

[0021] Further, in step S2, the ratio of the molar amount of the modified azobenzene compound to the molar amount of the cation is preferably 1:(1-1.2), for example 1:1, 1:1.1, 1:1.2, etc.

[0022] Further, in step S2, the solvent of the salt solution is water, with a concentration of 0.08-0.15 mol / L.

[0023] This invention regulates the molar amounts of modified azobenzene compounds and cations, enabling the modified azobenzene compounds to be fully loaded with cations. This allows sufficient cations to be released during subsequent exposure processes, where they interact strongly with the fluorinated dipoles of the fluorinated compounds to form a physical cross-linking network. This further enhances the mechanical properties of the film after light exposure and improves the isolation effect.

[0024] Furthermore, in step S2, the temperature of the second stirring reaction is preferably 10-40 °C, and the time is preferably 4-5 h.

[0025] Furthermore, the photoinitiator may be selected from 1-hydroxycyclohexylphenyl ketone and / or 2-hydroxy-2-methylpropanone.

[0026] Furthermore, the solvent may be selected from one or more of propylene glycol methyl ether acetate, toluene, chlorobenzene, and n-hexane.

[0027] The second aspect of the present invention provides a method for preparing the photoresist solution described in the first aspect, wherein the components are weighed according to the formula of the photoresist solution and mixed evenly to obtain the photoresist solution.

[0028] Furthermore, in the mixing step: the stirring speed is preferably 300-400 rpm, and the stirring time is not less than 1 hour.

[0029] The third aspect of this invention provides the application of the photoresist solution described in the first aspect in the fabrication of high-resolution quantum dot light-emitting diodes.

[0030] Furthermore, the method for fabricating the high-resolution quantum dot light-emitting diode includes the following steps: Provide a transparent electrode; A hole injection layer is formed on the transparent electrode; A hole transport layer is formed on the hole injection layer; A quantum dot pixel pattern is formed on the hole transport layer, the quantum dot pixel pattern comprising a plurality of quantum dot pixels separated from each other; Photoresist is coated on the hole transport layer on which the quantum dot pixel pattern is formed to form a photoresist coating. After exposure and development, a photoresist pattern is formed in the non-quantum dot pixel pattern area on the hole transport layer. The quantum dot pixel pattern and the photoresist pattern form a quantum dot light-emitting layer. An electron transport layer is formed on the quantum dot light-emitting layer; A metal electrode is formed on the electron transport layer to obtain the high-resolution quantum dot light-emitting diode.

[0031] In this invention, the preparation of the hole injection layer, hole transport layer, quantum dot pixel pattern, electron transport layer and metal electrode are all conventional operations.

[0032] Furthermore, the thickness of the photoresist coating is preferably 0.4-0.8 μm to effectively isolate and block the leakage current of the device.

[0033] Furthermore, in the exposure step: the wavelength of the ultraviolet light is preferably 320-380 nm, and the irradiation time is preferably 8-15 s.

[0034] Furthermore, the developing reagent is selected from one or more of propylene glycol methyl ether acetate, toluene, chlorobenzene, and n-hexane.

[0035] Furthermore, the high-resolution quantum dot light-emitting diode has a resolution of not less than 8400 PPI, and its leakage current is not higher than 0.2 mA / cm². 2 .

[0036] The beneficial effects of this invention are: This invention provides a photoresist solution that fundamentally avoids the generation of acidic substances, and its development process can be carried out using organic solvents instead of alkaline aqueous solutions, thereby completely eliminating the chemical erosion of quantum dots by acids and alkalis, and solving the problems of acid release during the photolithography process and the corrosion of quantum dots by alkaline solvents during the development process of traditional photoresists.

[0037] The photoresist solution provided by this invention fills the isolation barrier formed between quantum dot pixels, which has a dual network structure of resin cross-linking network and physical cross-linking network formed by resin and cations. It can effectively isolate adjacent pixels and block the direct contact between HTL and ETL between adjacent pixels, thereby significantly suppressing the leakage current of high-resolution QLED devices and improving the external quantum efficiency and brightness of the devices, which is conducive to further promoting the commercial application of high-resolution QLEDs. Attached Figure Description

[0038] Figure 1 This is a diagram illustrating the film formation mechanism of the photoresist solution of the present invention under ultraviolet light irradiation; Figure 2 The photoresist pattern prepared using the photoresist solution of the present invention; Figure 3 A scanning electron microscope image of a photoresist pattern prepared using the photoresist solution of the present invention; Figure 4 This is a schematic diagram of the structure of a high-resolution quantum dot light-emitting diode provided by the present invention, wherein 01 is the substrate, 02 is the transparent electrode, 03 is the hole injection layer, 04 is the hole transport layer, 051 is the quantum dot pixel pattern, 052 is the photoresist pattern, 06 is the electron transport layer, and 07 is the metal electrode. Figure 5 The image shows the electroluminescent quantum dot pixel fluorescence of the high-resolution quantum dot light-emitting diode prepared in Example 1. Figure 6 The image shows the electroluminescent quantum dot pixel fluorescence of the high-resolution quantum dot light-emitting diode prepared in Example 2. Figure 7 Electroluminescent quantum dot pixel fluorescence image of the high-resolution quantum dot light-emitting diode prepared for Comparative Example 1; Figure 8 Electroluminescent quantum dot pixel fluorescence image of the high-resolution quantum dot light-emitting diode prepared for Comparative Example 2; Figure 9 Electroluminescent quantum dot pixel fluorescence image of the high-resolution quantum dot light-emitting diode prepared for Comparative Example 3; Figure 10 The graph shows the current density versus voltage for the high-resolution quantum dot light-emitting diodes prepared in Example 1 and Comparative Example 1. Figure 11 The emission spectrum (a), current density-voltage-brightness curve (b), and external quantum efficiency-luminescence brightness curve (c) of the high-resolution quantum dot light-emitting diode prepared in Example 2 are shown. Figure 12 The emission spectrum (a), current density-voltage-brightness curve (b), and external quantum efficiency-luminescence brightness curve (c) of the high-resolution quantum dot light-emitting diode prepared for Comparative Example 1 are shown. Figure 13 The emission spectrum (a), current density-voltage-brightness curve (b), and external quantum efficiency-luminescence brightness curve (c) of the high-resolution quantum dot light-emitting diode prepared for Comparative Example 2 are shown. Detailed Implementation

[0039] The present invention will be further described below with reference to the accompanying drawings and specific embodiments, so that those skilled in the art can better understand and implement the present invention. However, the embodiments described are not intended to limit the present invention.

[0040] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. The terminology used herein in the specification of this invention is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. The term “and / or” as used herein includes any and all combinations of one or more of the associated listed items. The terms “comprising” or “including” as used herein may also be replaced with the closed form “is” or “consisting of”.

[0041] In this invention, unless otherwise specified, all equipment and raw materials are available from the market or commonly used in the industry. Unless otherwise specified, the methods in the following embodiments are conventional methods in the art.

[0042] Example 1: This example relates to the fabrication of a photoresist solution and a high-resolution quantum dot light-emitting diode. The specific operations are as follows: Preparation of oleylamine-modified azobenzene-4,4'-dicarboxylic acid: 4 g of azobenzene-4,4'-dicarboxylic acid was dissolved in 40 mL of N,N-dimethylformamide and stirred until completely dissolved to obtain an azobenzene-4,4'-dicarboxylic acid solution with a concentration of approximately 0.2 mol / L. 5 g of oleylamine was added to the above solution, with a molar ratio of oleylamine to azobenzene-4,4'-dicarboxylic acid of approximately 1.6:1. The reaction system was heated to 65 °C and stirred for 9 hours. After the reaction was completed, the product was purified by silica gel column chromatography using petroleum ether / ethyl acetate (volume ratio 3.5:1) as the eluent. The eluent containing the target product was collected, and the solvent was removed by vacuum distillation to obtain 4.2 g of oleylamine-modified azobenzene-4,4'-dicarboxylic acid product.

[0043] Preparation of copper ion-supported oleylamine-modified azobenzene-4,4'-dicarboxylic acid: 2.2 g of the oleylamine-modified azobenzene-4,4'-dicarboxylic acid prepared above was weighed and added to 45 mL of a 0.1 mol / L copper nitrate solution. The molar ratio of oleylamine-modified azobenzene-4,4'-dicarboxylic acid to copper ions was approximately 1:1.1. The pH of the solution was adjusted to 5.5 with dilute hydrochloric acid, and the reaction was stirred at room temperature for 4.5 hours. After the reaction was completed, the solid product was separated by centrifugation, washed repeatedly with deionized water, and then dried in a vacuum drying oven at 55 °C to obtain the copper-loaded oleylamine-modified azobenzene-4,4'-dicarboxylic acid product.

[0044] Preparation of photoresist solution: 1.3 g of copper-loaded oleylamine-modified azobenzene-4,4'-dicarboxylic acid, 3.8 g of 2,2,2-trifluoroethyl acrylate, and 0.28 g of photoinitiator (Irgacure 184) were added to 11 mL of propylene glycol methyl ether acetate solvent. The mixture was stirred at 350 rpm at room temperature to obtain a photoresist solution.

[0045] Fabrication of high-resolution quantum dot light-emitting diodes: First, the indium tin oxide (ITO) substrate was ultrasonically cleaned for 20 minutes using acetone, ethanol, and ultrapure water, and then dried in an oven. Next, a filtered PEDOT:PSS 4083 solution (using a 0.22 μm water filter) was spin-coated onto the ITO substrate at 4000 rpm for 60 seconds. The film was then annealed at 140°C for 15 minutes to obtain a hole injection layer. Subsequently, a hole transport material (chlorobenzene, 5 mg / mL) was spin-coated onto the PEDOT:PSS layer at 2000 rpm for 60 seconds, and then annealed at 120°C for 15 minutes. Finally, the substrate was transferred to a nitrogen glove box, and the photosensitizing quantum dots (CdSe / ZnS quantum dots from Hefei Funa Technology Co., Ltd.) were diluted to a concentration of 20 mg / mL. Colloidal quantum dots were spin-coated onto the hole transport layer at 2000 rpm for 60 seconds, then annealed at 60 degrees Celsius for 10 minutes, and then exposed to ultraviolet light to obtain a quantum dot pixel pattern.

[0046] The aforementioned photoresist solution was then uniformly coated onto the quantum dot pixels using a spin-coating method at a speed of 3000 rpm, forming a photoresist film with a thickness of approximately 0.6 μm. The photoresist film was selectively irradiated with ultraviolet light at a wavelength of 365 nm for 12 seconds. After exposure, the silicon wafer was immersed in a developer solution (n-hexane solvent) for 65 seconds and then dried under a nitrogen atmosphere to form a photoresist pattern.

[0047] Finally, based on this, an electron transport layer and an aluminum electrode were fabricated sequentially to obtain a high-resolution quantum dot light-emitting diode with a resolution of 8400 PPI.

[0048] The luminescent properties of the quantum dots in the high-resolution quantum dot light-emitting diode prepared in this embodiment were observed using a fluorescence microscope, such as... Figure 5 As shown, no signs of corrosion were found in the quantum dots, the fluorescence intensity and color purity of the quantum dots remained good, and the display images of the high-resolution quantum dot light-emitting diodes were clear.

[0049] Example 2: This example relates to the fabrication of a photoresist solution and a high-resolution quantum dot light-emitting diode. The specific operations are as follows: Preparation of oleylamine-modified azobenzene-4,4'-dicarboxylic acid: 3.5 g of azophenyl-4,4'-dicarboxylic acid was dissolved in 35 mL of N,N-dimethylformamide and stirred until completely dissolved to obtain an azophenyl-4,4'-dicarboxylic acid solution with a concentration of approximately 0.25 mol / L. 4.5 g of oleylamine was added to the above solution, with a molar ratio of oleylamine to azophenyl-4,4'-dicarboxylic acid of approximately 1.7:1. The reaction system was heated to 68 °C and stirred for 9.5 hours. After the reaction was completed, the product was purified by silica gel column chromatography using petroleum ether / ethyl acetate (volume ratio 4:1) as the eluent. The eluent containing the target product was collected, and the solvent was removed by vacuum distillation to obtain 3.8 g of oleylamine-modified azophenyl-4,4'-dicarboxylic acid product.

[0050] Preparation of zinc ion-supported oleylamine-modified azobenzene-4,4'-dicarboxylic acid: Weigh 2 g of the oleylamine-modified azobenzene-4,4'-dicarboxylic acid prepared above and add it to 42 mL of a 0.12 mol / L zinc sulfate solution. The molar ratio of oleylamine-modified azobenzene-4,4'-dicarboxylic acid to zinc ions is approximately 1:1.15. Adjust the pH of the solution to 5.8 with dilute hydrochloric acid and stir the reaction at room temperature for 4.8 hours. After the reaction is complete, separate the solid product by centrifugation, wash it several times with deionized water, and then dry it in a vacuum drying oven at 58 °C to obtain the copper-loaded oleylamine-modified azobenzene-4,4'-dicarboxylic acid product.

[0051] Preparation of photoresist solution: 1.1 g of zinc-ion-loaded oleylamine-modified azobenzene-4,4'-dicarboxylic acid, 3.3 g of 2,2,2-trifluoroethyl acrylate, and 0.22 g of photoinitiator (Darocur 1173) were added to 10 mL of propylene glycol methyl ether acetate solvent. The mixture was stirred at 380 rpm at room temperature to obtain a photoresist solution.

[0052] Fabrication of high-resolution quantum dot light-emitting diodes: The difference from Example 1 lies only in the preparation of the photoresist pattern. Specifically, the photoresist solution prepared in this example is uniformly coated onto a glass substrate containing quantum dots using a spraying method. This substrate already has a hole transport layer and an electron transport layer, forming a photoresist film with a thickness of approximately 0.5 μm. The photoresist film is selectively irradiated with ultraviolet light at a wavelength of 350 nm for 10 seconds. After exposure, the glass slide is immersed in a developer solution (tetramethylammonium hydroxide aqueous solution, mass fraction 2.38%) for 70 seconds, then rinsed with deionized water and dried under a nitrogen atmosphere to form a photoresist pattern. The resolution of the photoresist pattern observed by a scanning electron microscope reaches 0.3 μm.

[0053] All other operations were performed in the same manner, resulting in a high-resolution quantum dot light-emitting diode with a resolution of 8400 PPI.

[0054] The luminescent properties of the quantum dots in the high-resolution quantum dot light-emitting diode prepared in this embodiment were observed using a fluorescence microscope, such as... Figure 6 As shown, no signs of corrosion were found in the quantum dots, the fluorescence intensity and color purity of the quantum dots remained good, and the display images of the high-resolution quantum dot light-emitting diodes were clear.

[0055] Comparative Example 1: This comparative example relates to the fabrication of a high-resolution quantum dot light-emitting diode. The only difference from Example 1 is that no photoresist treatment was performed, and the electron transport layer and aluminum electrode were directly fabricated on the quantum dot pixel pattern. All other operations were the same, and a corresponding high-resolution quantum dot light-emitting diode with a resolution of 8400 PPI was obtained.

[0056] The luminescent properties of the quantum dots in the high-resolution quantum dot light-emitting diode prepared in this comparative example were observed using a fluorescence microscope, such as... Figure 7 As shown, the fluorescence intensity of quantum dots is extremely low.

[0057] Comparative Example 2: This comparative example relates to the fabrication of a high-resolution quantum dot light-emitting diode. The only difference from Example 1 is that commercially available AZ524 photoresist is used for spin coating, and AZ400K developer is used for development to obtain the corresponding photoresist pattern. All other operations are the same, and the corresponding high-resolution quantum dot light-emitting diode with a resolution of 8400 PPI is obtained.

[0058] The luminescent properties of the quantum dots in the high-resolution quantum dot light-emitting diode prepared in this comparative example were observed using a fluorescence microscope, such as... Figure 8 As shown, quantum dots exhibit significant corrosion and low fluorescence intensity.

[0059] Comparative Example 3: This comparative example relates to the fabrication of a high-resolution quantum dot light-emitting diode. The only difference from Example 1 is that commercially available SU-8 photoresist is used for spin coating, and PGMEA developer is used for development to obtain the corresponding photoresist pattern. All other operations are the same, and a corresponding high-resolution quantum dot light-emitting diode with a resolution of 8400 PPI is obtained.

[0060] The luminescent properties of the quantum dots in the high-resolution quantum dot light-emitting diode prepared in this comparative example were observed using a fluorescence microscope, such as... Figure 9 As shown, the quantum dots exhibited significant corrosion and low fluorescence intensity, similar to Comparative Example 2.

[0061] Performance testing: The leakage current (leakage current corresponding to 2 V), maximum external quantum efficiency (EQE), and luminous intensity of the high-resolution quantum dot light-emitting diodes prepared in Examples 1 and 2 and Comparative Examples 1 and 2 were tested in a nitrogen-filled glove box using a marine optical system including a power meter (Keithley 2450), a spectrometer (QE Pro), and an integrating sphere (FOIS-1).

[0062] The test results are shown in Table 1 below: Table 1

[0063] As shown in Table 1, compared with the high-resolution quantum dot light-emitting diode prepared without photoresist blocking in Comparative Example 1, the high-resolution quantum dot light-emitting diode prepared using photoresist solution blocking in Examples 1 and 2 has extremely low leakage current, and its EQE and brightness are significantly improved, demonstrating excellent optoelectronic performance and display quality.

[0064] Furthermore, as can be seen from Examples 1 and 2 and Comparative Example 2, although the leakage current of high-resolution quantum dot light-emitting diodes fabricated using AZ524 photoresist is lower than that of high-resolution quantum dot light-emitting diodes fabricated without obstruction (Comparative Example 1), the light-emitting pixels will be etched during the photolithography stage. Figure 8 This results in inconsistent electrical properties between quantum dot pixels, and still exhibits a high leakage current (1 mA / cm²). 3 This limitation restricts the improvement of device luminous efficiency. However, by using the photoresist solution provided in this invention to prepare the isolation barrier layer, the quantum dot pixels will not be corroded, and the leakage current of the device can be further reduced significantly. Compared with Comparative Example 2, the leakage current is reduced by more than 80%, and the corresponding maximum external quantum efficiency is increased by more than 147.6%, and the luminous brightness is also significantly improved, thereby significantly improving the overall performance of high-resolution quantum dot light-emitting diodes.

[0065] The above-described embodiments are merely preferred embodiments provided to fully illustrate the present invention, and the scope of protection of the present invention is not limited thereto. Equivalent substitutions or modifications made by those skilled in the art based on the present invention are all within the scope of protection of the present invention. The scope of protection of the present invention is defined by the claims.

Claims

1. A photoresist solution, characterized in that, It includes fluorinated compounds, cationic azobenzene compounds, and photoinitiators; among which, The fluorinated compound is a fluorinated resin monomer and / or a fluorinated copolymer; The cation-loaded azobenzene compound is obtained by modifying an azobenzene compound with an organic amine and / or an organic ammonium salt, and then loading it with a cation; the azobenzene compound contains at least one of hydroxyl, carboxyl, sulfonic acid, and nitro groups, and the cation is a metal ion and / or an alkyl imidazole ion.

2. The photoresist solution according to claim 1, characterized in that, It must contain at least one of the following characteristics: (1) The photoresist solution contains the following components by mass percentage: 20%-30% of fluorine-containing compound, 6%-10% of cationic azobenzene compound, 1%-2% of photoinitiator, and the remainder is solvent; (2) The fluorinated resin monomer is selected from one or more of 2,2,2-trifluoroethyl acrylate, trifluoroethyl methacrylate, and hexafluorobutyl acrylate, and the fluorinated copolymer includes poly(vinylidene fluoride-co-hexafluoropropylene). (3) The azobenzene compounds are selected from one or more of the following: azobenzene-4,4'-dicarboxylic acid, 2,2-dihydroxyazobenzene, azobenzene-3,3'-dicarboxylic acid, 4,4'-dihydroxymethylazobenzene, 4-(azobenzene)benzoic acid, 4'-hydroxyazobenzene-4-carboxylic acid, 4-hydroxyazobenzene-2'-carboxylic acid, (E)-azobenzene-4,4'-dicarboxylic acid, 4'-aminoazobenzene-4-sulfonic acid, sodium 4-aminoazobenzene-4'-sulfonate, and 4'-nitro-4-dimethylaminoazobenzene; (4) The organic amine includes oleylamine, and the organic ammonium salt includes tetrabutylammonium salt and / or hexadecyltrimethylammonium salt; (5) The metal ions include Li + Na + K + Mg 2+ Ca 2+ 、Sr 2+ Ba 2+ Al 3+ C 3+ Fe 3+ Co 3+ Mn 2+ Ti 4+ Fe 2+ Co 2+ Ni 2+ Cu 2+ Zn 2+ Pb 2+ Sn 2+ Sb 3+ Cu + Ag + Au + Hg + Hg 2+ Cd 2+ Pd 2+ Pt 2+ 、Tl + 、Tl 3+ One or more of the following, wherein the alkyl imidazolium ion includes 1-ethyl-3-methylimidazolium ion and / or 1-butyl-3-methylimidazolium ion.

3. The photoresist solution according to claim 1 or 2, characterized in that, The method for preparing the cation-loaded azobenzene compound includes the following steps: S1. Organic amines and / or organic ammonium salts are reacted with azobenzene compounds in the presence of an organic solvent to obtain the modified azobenzene compounds. S2. The modified azobenzene compound is added to a salt solution containing the cation, the pH is adjusted to 5-6, and a second stirring reaction is carried out to obtain the cation-loaded azobenzene compound.

4. The photoresist solution according to claim 3, characterized in that, Step S1 includes at least one of the following features: (1) The molar ratio of the organic amine and / or organic ammonium salt to the azobenzene compound is (1.5-2):1; (2) The organic solvent is selected from one or more of N,N-dimethylformamide, dimethyl sulfoxide, toluene, chlorobenzene, and propylene glycol methyl ether; (3) The molar ratio of the azobenzene compound to the volume of the organic solvent is (0.1-0.3) mol: 1 L; (4) The temperature of the first stirring reaction is 60-70 ℃ and the time is 8-10 h.

5. The photoresist solution according to claim 3, characterized in that, In step S2, the molar ratio of the modified azobenzene compound to the molar ratio of the cation is 1:(1-1.2). The second stirring reaction is carried out at a temperature of 10-40 °C for 4-5 h.

6. The photoresist solution according to claim 2, characterized in that, The photoinitiator is selected from 1-hydroxycyclohexylphenyl ketone and / or 2-hydroxy-2-methylpropanone; The solvent is selected from one or more of propylene glycol methyl ether acetate, toluene, chlorobenzene, and n-hexane.

7. A method for preparing the photoresist solution according to any one of claims 1-6, characterized in that, Weigh each component according to the formula of the photoresist solution and mix them evenly to obtain the photoresist solution.

8. The use of the photoresist solution according to any one of claims 1-6 in the fabrication of high-resolution quantum dot light-emitting diodes.

9. The application according to claim 8, characterized in that, The method for fabricating the high-resolution quantum dot light-emitting diode includes the following steps: Provide a transparent electrode; A hole injection layer is formed on the transparent electrode; A hole transport layer is formed on the hole injection layer; A quantum dot pixel pattern is formed on the hole transport layer, the quantum dot pixel pattern comprising a plurality of quantum dot pixels separated from each other; Photoresist is coated on the hole transport layer on which the quantum dot pixel pattern is formed to form a photoresist coating. After exposure and development, a photoresist pattern is formed in the non-quantum dot pixel pattern area on the hole transport layer. The quantum dot pixel pattern and the photoresist pattern form a quantum dot light-emitting layer. An electron transport layer is formed on the quantum dot light-emitting layer; A metal electrode is formed on the electron transport layer to obtain the high-resolution quantum dot light-emitting diode.

10. The application according to claim 9, characterized in that, The thickness of the photoresist coating is 0.4-0.8 μm; In the exposure step: the wavelength of the ultraviolet light is 320-380 nm, and the irradiation time is 8-15 s; The developing reagent is selected from one or more of propylene glycol methyl ether acetate, toluene, chlorobenzene, and n-hexane; The high-resolution quantum dot light-emitting diode has a resolution of no less than 8400 PPI and a leakage current of no more than 0.2 mA / cm². 2 .

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