A photoresist solution, its preparation method and application

Abstract

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

Description

TECHNICAL FIELD

[0001] The present application relates to the field of photoresist and light-emitting diode technology, and in particular to a photoresist solution, a preparation method thereof and application thereof in preparing high-resolution quantum dot light-emitting diodes. BACKGROUND

[0002] Colloidal quantum dots (QDs) have been widely studied due to their excellent optoelectronic properties, such as narrow emission spectrum, tunable emission wavelength, high luminescent efficiency and excellent stability. In the past decade, the performance of quantum dot light-emitting diodes (QLEDs) has made a breakthrough, showing a broad prospect for display applications. Facing the requirements of a large amount of information or near-eye display, the next generation of displays sets a higher standard for pixel resolution. At present, in order to meet the needs of the next generation of display technologies such as virtual reality, three-dimensional display and near-eye display, people are eager to realize the super-high-resolution QD pixel pattern with a pixel resolution of more than 10,000 pixels per inch (PPI). These display technologies achieve high information flow by redistributing graphical information from a two-dimensional screen to a three-dimensional space. Unfortunately, the performance of previous high-resolution QLEDs is low, with 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 in the non-light-emitting area between pixels due to the direct contact of the hole transport layer (HTL) and the electron transport layer (ETL).

[0003] At present, in order to solve the problem of large leakage current in the non-light-emitting area between pixels due to the direct contact of the HTL and the ETL, a common process is to use photolithography to fill a photoresist with electrical insulation between quantum dot pixels and pixels to physically isolate adjacent pixels. This structure can effectively block the direct contact of the HTL and the ETL between adjacent pixels, thereby inhibiting the large lateral leakage current generated thereby, which is crucial for improving device performance and achieving high-resolution display.

[0004] However, conventional photoresists have serious defects in the photolithography process. In the photolithography stage, SU-8, I-1000, AZ series and Shipley series chemical amplification photoresists release acid. Quantum dots, as the core light-emitting material in QLEDs, have a high activity due to the unsaturated state of their surface atoms. The presence of acid can easily react with quantum dots, causing changes in the chemical structure of the quantum dot surface and affecting their optical and electrical properties. For example, acid can destroy the ligands on the surface of quantum dots, increase the number of defects on the surface of quantum dots, increase non-radiative recombination centers and reduce the luminescent efficiency of quantum dots.

[0005] Secondly, in the subsequent development process, the commonly used developer is an alkaline aqueous solution (such as tetramethylammonium hydroxide, TMAH). Quantum dot materials, especially some semiconductor components (such as CdSe, ZnS, etc.) that are not stable to alkali, will suffer serious corrosion in an alkaline environment. This corrosion may cause changes in the size and morphology of the quantum dots, and even partial dissolution, thereby destroying the integrity of the quantum dot film. The direct consequence is to cause unevenness in the electrical properties (such as carrier injection and transport efficiency) of the quantum dot film between different pixels. This unevenness not only cannot completely eliminate the 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 the conventional photoresist not only reduce the yield and reliability of high-resolution QLED devices, but also hinder the improvement of external quantum efficiency (EQE) and brightness, thereby seriously restricting the performance improvement and large-scale commercial application of high-resolution QLED. SUMMARY

[0007] To solve the above problems, the present application provides a photoresist solution, a preparation method thereof and an application thereof in the preparation of high-resolution quantum dot light-emitting diodes. The photoresist solution fundamentally avoids the generation of acidic substances, and its development process can be carried out using an organic solvent instead of an alkaline aqueous solution, thereby completely eliminating the chemical corrosion of quantum dots by acid and alkali. The photoresist of the present application can perfectly achieve electrical isolation between the hole transport layer and the electron transport layer without damaging the quantum dot active layer, thereby effectively reducing the device leakage current and significantly improving the EQE, brightness and overall performance stability of high-resolution QLED.

[0008] Specifically, the following technical solutions are provided:

[0009] The first aspect of the present application provides a photoresist solution, comprising a fluorine-containing compound, a cation-loaded azobenzene compound and a photoinitiator; wherein,

[0010] The fluorine-containing compound is a fluorine-containing resin monomer and / or a fluorine-containing copolymer;

[0011] 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 a cation; the azobenzene compound comprises at least one of a hydroxyl group, a carboxyl group, a sulfonic acid group and a nitro group, and the cation is a metal ion and / or an alkyl imidazole ion.

[0012] Since the traditional photoresist has the defects of acid and alkali corrosion when used for isolating quantum dot pixels and isolating the isolation barrier of the hole transport layer and the electron transport layer in the preparation of high-resolution QLED devices, not only the problem of device leakage current cannot be effectively solved, but also the performance of high-resolution QLED devices such as EQE and brightness is reduced. Based on this, the photoresist solution can fundamentally avoid the chemical corrosion of quantum dots by acid and alkali, mainly including a fluorine-containing compound for film formation, a loaded azobenzene compound with light responsiveness and a photoinitiator for initiating crosslinking polymerization of the fluorine-containing compound. The coating formed by coating the above photoresist solution will be photoresponsive under ultraviolet light irradiation, and the molecular structure of the azobenzene compound modified by organic amine and / or organic ammonium salt will change, such as cis-trans isomerization, resulting in the release of the loaded cations. The released cations and the fluorine-containing dipole of the fluorine-containing compound have strong interaction (such as electrostatic interaction, etc.), and this interaction promotes the photoresist coating to form a special physical and chemical structure in the irradiation area. This structure can form an effective isolation barrier between the hole transport layer and the electron transport layer, preventing direct contact between the two, thereby avoiding the short circuit and leakage current problem caused by direct contact between the layers. At the same time, since the photoresist prepared by the present application does not involve components that release acid during the photoetching stage, and can use organic solvents instead of alkaline aqueous solution during the development process, the chemical corrosion of quantum dots by acid and alkali is completely eliminated, and the structure and performance integrity of the quantum dots are greatly protected, further ensuring the stability of the quantum dot pixels, significantly inhibiting the leakage current between the quantum dot pixels and the pixels, thereby effectively improving the electrical performance and display quality of high-resolution QLED.

[0013] Further, the photoresist solution comprises the following components by mass percentage: 20%-30% of the fluorine-containing compound, 6%-10% of the loaded azobenzene compound, 1%-2% of the photoinitiator, and the rest is solvent.

[0014] In the present application, in order to ensure the integrity and mechanical strength of the film formed after the photoresist is photocured, the content of the fluorine-containing compound in the photoresist solution cannot be too low, but too high content cannot be fully dissolved, and the mass fraction needs to be controlled in the range of 20%-30%, such as 20%, 21%, 22%, 23%, 24%, 25%, 26%, 27%, 28%, 29%, 30%, etc.; at the same time, the mass fraction of the azobenzene compound loaded with cations in the photoresist solution needs to be controlled, if the content is too low, the released cations are not enough, and the performance of the cured film cannot be effectively improved, if the content is too high, the released cations are too much, which will affect the photocuring effect of the fluorine-containing compound (metal ions have a certain absorption effect on ultraviolet light, and will quench free radicals), and the excessive cations which are not firmly combined with the polymer chain will migrate in the material and precipitate on the surface, affecting the mechanical properties and long-term stability of the film, resulting in that the effective barrier effect cannot be achieved, in order to effectively improve the mechanical properties of the film after the photoresist solution is photocured, the mass fraction of the azobenzene compound loaded with cations needs to be controlled in the range of 6%-10%, such as 6%, 7%, 8%, 9%, 10%, etc.

[0015] Further, the fluorine-containing resin monomer can be selected from one or more of 2,2,2-trifluoroethyl acrylate, trifluoroethyl methacrylate, hexafluorobutyl acrylate, and the fluorine-containing copolymer includes but is not limited to poly(vinylidene fluoride-co-hexafluoropropylene).

[0016] Further, the azobenzene compound can 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'-amino-azobenzene-4-sulfonic acid, 4-aminoazobenzene-4'-sodium sulfonate, 4'-nitro-4-dimethylaminoazobenzene.

[0017] Further, 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.

[0018] Further, the metal ion includes 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.

[0019] Furthermore, the method for preparing the cation-supported azobenzene compound includes the following steps:

[0020] 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.

[0021] 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.

[0022] 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.

[0023] 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.

[0024] 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.

[0025] Furthermore, in step S1, the temperature of the first stirring reaction is preferably 60-70 ℃, and the time is preferably 8-10 h.

[0026] Further, in step S2, the ratio of the molar mass of the modified azobenzene compound to the molar mass of the cation is preferably 1:(1-1.2), such as 1:1, 1:1.1, 1:1.2, etc.

[0027] Further, in step S2, the solvent of the salt solution is water, and the concentration is 0.08-0.15 mol / L.

[0028] The present application controls the molar mass of the modified azobenzene compound and the cation, so that the modified azobenzene compound can fully load the cation, thereby releasing a sufficient amount of cation to strongly interact with the fluorine-containing dipole of the fluorine-containing compound in the subsequent exposure process, forming a physical crosslinking network to further improve the mechanical properties of the film after light exposure and improve the isolation effect.

[0029] Further, in step S2, the temperature of the second stirring reaction is preferably 10-40 ℃, and the time is preferably 4-5 h.

[0030] Further, the photoinitiator can be selected from 1-hydroxycyclohexyl phenyl ketone and / or 2-hydroxy-2-methylpropiophenone.

[0031] Further, the solvent can be selected from one or more of propylene glycol methyl ether acetate, toluene, chlorobenzene, and n-hexane.

[0032] The second aspect of the present application provides a preparation method of the photoresist solution of the first aspect, which comprises weighing each component according to the formula of the photoresist solution and mixing uniformly to obtain the photoresist solution.

[0033] Further, in the mixing step, the stirring speed is preferably 300-400 rpm, and the stirring time is not less than 1 hour.

[0034] The third aspect of the present application provides an application of the photoresist solution of the first aspect in the preparation of a high-resolution quantum dot light-emitting diode.

[0035] Further, the preparation method of the high-resolution quantum dot light-emitting diode comprises the following steps:

[0036] A transparent electrode is provided.

[0037] A hole injection layer is formed on the transparent electrode.

[0038] A hole transport layer is formed on the hole injection layer.

[0039] A quantum dot pixel pattern is formed on the hole transport layer, and the quantum dot pixel pattern comprises a plurality of quantum dot pixels separated from each other.

[0040] Coating a photoresist on the hole transport layer with the quantum dot pixel pattern to form a photoresist coating layer, and after exposure and development, a photoresist pattern is formed on the non-quantum dot pixel pattern area of the hole transport layer, and the quantum dot pixel pattern and the photoresist pattern form a quantum dot light-emitting layer;

[0041] An electron transport layer is formed on the quantum dot light-emitting layer;

[0042] A metal electrode is formed on the electron transport layer to obtain the high-yield quantum dot light-emitting diode.

[0043] In the present application, the preparation of the above-mentioned hole injection layer, hole transport layer, quantum dot pixel pattern, electron transport layer and metal electrode are all conventional operations.

[0044] Further, the thickness of the photoresist coating layer is preferably 0.4-0.8 μm, so as to effectively play a role in isolation and blocking, and reduce the leakage current of the device.

[0045] Further, in the step of exposure, the wavelength of the ultraviolet light is preferably 320-380 nm, and the irradiation time is preferably 8-15 s.

[0046] Further, the developing reagent is selected from one or more of propylene glycol methyl ether acetate, toluene, chlorobenzene and n-hexane.

[0047] Further, the resolution of the high-yield quantum dot light-emitting diode is not less than 8400 PPI, and the leakage current of the high-yield quantum dot light-emitting diode is not higher than 0.2 mA / cm 2 .

[0048] The beneficial effects of the present application are:

[0049] The present application provides a photoresist solution, which fundamentally avoids the generation of acidic substances, and its development process can be carried out using an organic solvent instead of an alkaline aqueous solution, thereby completely eliminating the chemical corrosion of quantum dots by acid and base, and solving the problem of corrosion of quantum dots by acid released in the traditional photoresist lithography process and alkaline solvent in the development process.

[0050] The photoresist solution provided by the present application fills the isolation barrier formed between the quantum dot pixels and the pixels, has a double network structure of resin crosslinking network and physical crosslinking network formed by resin and cations, can effectively isolate adjacent pixels, block the direct contact between HTL and ETL between adjacent pixels, thereby significantly inhibiting the leakage current of high-resolution QLED devices and improving the external quantum efficiency and brightness of the device, and is conducive to further promoting the commercial application of high-resolution QLED. BRIEF DESCRIPTION OF DRAWINGS

[0051] Figure 1 A film formation mechanism diagram of the photoresist solution of the present application under ultraviolet light;

[0052] Figure 2 A photoresist pattern prepared by using the photoresist solution of the present application;

[0053] Figure 3 A scanning electron microscope diagram of the photoresist pattern prepared by using the photoresist solution of the present application;

[0054] Figure 4 A structural schematic diagram of a high-resolution quantum dot light-emitting diode provided by the present application, wherein 01 is a substrate, 02 is a transparent electrode, 03 is a hole injection layer, 04 is a hole transport layer, 051 is a quantum dot pixel pattern, 052 is a photoresist pattern, 06 is an electron transport layer, and 07 is a metal electrode;

[0055] Figure 5 An electroluminescence quantum dot pixel fluorescence diagram of a high-resolution quantum dot light-emitting diode prepared in Example 1;

[0056] Figure 6 An electroluminescence quantum dot pixel fluorescence diagram of a high-resolution quantum dot light-emitting diode prepared in Example 2;

[0057] Figure 7 An electroluminescence quantum dot pixel fluorescence diagram of a high-resolution quantum dot light-emitting diode prepared in Comparative Example 1;

[0058] Figure 8 An electroluminescence quantum dot pixel fluorescence diagram of a high-resolution quantum dot light-emitting diode prepared in Comparative Example 2;

[0059] Figure 9 An electroluminescence quantum dot pixel fluorescence diagram of a high-resolution quantum dot light-emitting diode prepared in Comparative Example 3;

[0060] Figure 10 A current density-voltage change diagram of a high-resolution quantum dot light-emitting diode prepared in Example 1 and Comparative Example 1;

[0061] Figure 11 A luminescence spectrum diagram (a), a current density-voltage-brightness curve (b), and an external quantum efficiency-luminescence brightness curve (c) of a high-resolution quantum dot light-emitting diode prepared in Example 2;

[0062] Figure 12 A luminescence spectrum diagram (a), a current density-voltage-brightness curve (b), and an external quantum efficiency-luminescence brightness curve (c) of a high-resolution quantum dot light-emitting diode prepared in Comparative Example 1;

[0063] Figure 13The luminescence 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. DETAILED DESCRIPTION

[0064] The present application will be further described below in conjunction with the drawings and specific examples so that those skilled in the art can better understand and implement the present application, but the examples are not intended to limit the present application.

[0065] 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 application belongs. The terminology used in the description of the application herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the application. As used herein, the term "and / or" includes any and all combinations of one or more of the associated listed items. The use of "including," "containing," or "comprising" in the description of the application herein is not intended to be limiting of the application. Rather, the use of "including," "containing," or "comprising" in the description of the application herein is intended to mean that the application encompasses the items listed thereafter, as well as those equivalents thereof, as if each were individually listed.

[0066] In the present application, all the equipment and raw materials can be purchased from the market or commonly used in the industry, unless specified. The methods in the following examples are conventional methods in the art, unless specified.

[0067] Example 1: This example relates to the preparation of a photoresist solution and a high-resolution quantum dot light-emitting diode, the specific operation is as follows:

[0068] Preparation of oil amine modified azobenzene-4,4'-dicarboxylic acid:

[0069] Dissolve 4 g of azobenzene-4,4'-dicarboxylic acid in 40 mL of N,N-dimethylformamide, stir until completely dissolved, to obtain an azobenzene-4,4'-dicarboxylic acid solution with a concentration of about 0.2 mol / L. Add 5 g of oil amine to the above solution, the molar ratio of oil amine to azobenzene-4,4'-dicarboxylic acid is about 1.6:1. The temperature of the reaction system is raised to 65 ℃, and the stirring reaction is carried out for 9 hours. After the reaction is completed, the product is separated and purified by silica gel column chromatography, using petroleum ether / ethyl acetate (volume ratio 3.5:1) as the eluent, collecting the eluent containing the target product, and removing the solvent by reduced pressure distillation to obtain 4.2 g of oil amine modified azobenzene-4,4'-dicarboxylic acid product.

[0070] Preparation of copper ion loaded oil amine modified azobenzene-4,4'-dicarboxylic acid:

[0071] Take 2.2 g of the above prepared oil amine modified azobenzene-4,4'-dicarboxylic acid, add it to 45 mL of 0.1 mol / L copper nitrate solution, the molar ratio of oil amine modified azobenzene-4,4'-dicarboxylic acid to copper ion is about 1:1.1. Adjust the pH of the solution to 5.5 with dilute hydrochloric acid, stir at room temperature for 4.5 hours. After the reaction is completed, the solid product is separated by centrifugation, washed with deionized water several times, and then dried in a vacuum drying oven at 55 ℃ to obtain the oil amine modified azobenzene-4,4'-dicarboxylic acid product loaded with copper ions.

[0072] Preparation of photoresist solution:

[0073] Take 1.3 g of the oil amine modified azobenzene-4,4'-dicarboxylic acid loaded with copper ions, 3.8 g of 2,2,2-trifluoroethyl acrylate, and 0.28 g of a photoinitiator (Irgacure 184), and add them to 11 mL of propylene glycol methyl ether acetate solvent. Stir uniformly at room temperature at a speed of 350 revolutions per minute to obtain a photoresist solution.

[0074] Preparation of high-efficiency quantum dot light-emitting diode:

[0075] First, the indium tin oxide (ITO) substrate is ultrasonically cleaned with acetone, ethanol and ultrapure water for 20 minutes, and then dried in an oven. Then, the filtered PEDOT:PSS 4083 solution (using a 0.22 μm water filter) is spin-coated onto the ITO substrate at 4000 rpm for 60 seconds. Then, the thin film is annealed at 140 degrees Celsius for 15 minutes to obtain a hole injection layer. Then, the hole transport material (chlorobenzene, 5 mg / mL) is spin-coated onto the PEDOT:PSS layer at 2000 rpm for 60 s, and then annealed at 120 degrees Celsius for 15 min. Then, the substrate is transferred to a nitrogen glove box, and the photosensitive quantum dots (Hefei Funan Technology Co., Ltd. CdSe / ZnS quantum dots) are diluted to a concentration of 20 mg / mL. The colloidal quantum dots are spin-coated onto the hole transport layer at 2000 rpm for 60 seconds, and then annealed at 60 degrees Celsius for 10 minutes, and the quantum dot pixel pattern is obtained by ultraviolet exposure.

[0076] Then the above photoresist solution is uniformly coated on the quantum dot pixel containing layer by spin coating at a speed of 3000 revolutions per minute to form a photoresist film with a thickness of about 0.6 μm. The photoresist film is selectively irradiated with ultraviolet light with a wavelength of 365 nm, and the exposure time is 12 seconds. After exposure, the silicon wafer is placed in a developing solution (n-hexane solvent) for 65 seconds, and then blown dry in a nitrogen atmosphere to form a photoresist pattern.

[0077] Finally, an electron transport layer and an aluminum electrode are prepared in sequence on the basis of the foregoing to obtain the high-resolution quantum dot light-emitting diode, and the resolution is 8400 PPI.

[0078] The high-resolution quantum dot light-emitting diode prepared in the embodiment is observed by a fluorescence microscope to observe the light-emitting performance of the quantum dots, and as shown in FIG. 6, no corrosion of the quantum dots is found, the fluorescence intensity and color purity of the quantum dots are maintained well, and the display image of the high-resolution quantum dot light-emitting diode is clear. Figure 5

[0079] Embodiment 2: The embodiment relates to a photoresist solution and preparation of a high-resolution quantum dot light-emitting diode, and the specific operation is as follows:

[0080] Preparation of oleylamine-modified azobenzene-4,4'-dicarboxylic acid

[0081] 3.5 g of azobenzene-4,4'-dicarboxylic acid is dissolved in 35 mL of N,N-dimethylformamide, and stirring is performed until complete dissolution to obtain an azobenzene-4,4'-dicarboxylic acid solution with a concentration of about 0.25 mol / L. 4.5 g of oleylamine is added to the above solution, and the molar ratio of oleylamine to azobenzene-4,4'-dicarboxylic acid is about 1.7:1. The temperature of the reaction system is increased to 68 ℃, and stirring is performed for 9.5 hours. After the reaction is completed, separation and purification are performed by silica gel column chromatography, petroleum ether / ethyl acetate (4:1 by volume) is used as an eluent, the eluent containing the target product is collected, and the solvent is removed by reduced pressure distillation to obtain 3.8 g of the oleylamine-modified azobenzene-4,4'-dicarboxylic acid product.

[0082] Preparation of zinc ion-loaded oleylamine-modified azobenzene-4,4'-dicarboxylic acid

[0083] 2 g of the oleylamine-modified azobenzene-4,4'-dicarboxylic acid prepared in the foregoing is weighed and added to 42 mL of a zinc sulfate solution with a concentration of 0.12 mol / L, and the molar ratio of the oleylamine-modified azobenzene-4,4'-dicarboxylic acid to zinc ions is about 1:1.15. The pH value of the solution is adjusted to 5.8 by using dilute hydrochloric acid, and stirring is performed at room temperature for 4.8 hours. After the reaction is completed, separation is performed by centrifugation, the solid product is washed with deionized water for multiple times, and then drying is performed in a vacuum drying box at 58 ℃ to obtain the oleylamine-modified azobenzene-4,4'-dicarboxylic acid product loaded with copper ions.

[0084] Preparation of a photoresist solution

[0085] ​Take 1.1 g of zinc ion loaded oleylamine modified azobenzene-4,4'-dicarboxylic acid, 3.3 g of 2,2,2-trifluoroethyl acrylate, 0.22 g of photoinitiator (Darocur 1173), and add them to 10 mL of propylene glycol methyl ether acetate solvent. Stir uniformly at room temperature at a speed of 380 revolutions per minute to obtain a photoresist solution.

[0086] Preparation of high-resolution quantum dot light-emitting diode:

[0087] The difference from Example 1 is only in the preparation of the photoresist pattern, specifically: the photoresist solution prepared in this example is uniformly coated on a glass substrate containing quantum dots by the method of spraying, and the substrate has been prepared with a hole transport layer and an electron transport layer, forming a photoresist film with a thickness of about 0.5 μm. The photoresist film is selectively irradiated with ultraviolet light with a wavelength of 350 nm, and the exposure time is 10 seconds. After exposure, the glass sheet is placed in a developing solution (tetramethylammonium hydroxide aqueous solution, mass fraction of 2.38%) for 70 seconds, then washed with deionized water, and dried under a nitrogen atmosphere to form a photoresist pattern. The resolution of the photoresist pattern can be observed by scanning electron microscopy, which can reach 0.3 μm.

[0088] The rest of the operations are consistent, and a high-resolution quantum dot light-emitting diode with a resolution of 8400 PPI is obtained.

[0089] The luminescent properties of the quantum dots in the high-resolution quantum dot light-emitting diode prepared in this example are observed by fluorescence microscopy, as shown in Figure 6 There is no evidence of any corrosion of the quantum dots, and the fluorescence intensity and color purity of the quantum dots remain good, and the display image of the high-resolution quantum dot light-emitting diode is clear.

[0090] Comparative Example 1: This comparative example relates to the preparation of a high-resolution quantum dot light-emitting diode, which is different from Example 1 only in that no photoresist treatment is performed, and the electron transport layer and aluminum electrode are directly prepared on the quantum dot pixel pattern; the rest of the operations are consistent, and a corresponding high-resolution quantum dot light-emitting diode with a resolution of 8400 PPI is prepared.

[0091] The luminescent properties of the quantum dots in the high-resolution quantum dot light-emitting diode prepared in this example are observed by fluorescence microscopy, as shown in Figure 7 The fluorescence intensity of the quantum dots is very low.

[0092] Comparative Example 2: This comparative example relates to the preparation of a high-resolution quantum dot light-emitting diode, which is different from Example 1 only in that a commercially available AZ524 photoresist is used for spin coating treatment, and an AZ400K developer is used for development treatment to prepare a corresponding photoresist pattern; the rest of the operations are consistent, and a corresponding high-resolution quantum dot light-emitting diode is prepared, with a resolution of 8400 PPI.

[0093] The luminescence performance of the quantum dots in the high-resolution quantum dot light-emitting diode prepared in this comparative example is observed by fluorescence microscopy, as shown in FIG. 2B, the quantum dots have obvious corrosion phenomenon and low fluorescence intensity. Figure 8

[0094] Comparative Example 3: This comparative example relates to the preparation of a high-resolution quantum dot light-emitting diode, which is different from Example 1 only in that a commercially available SU-8 photoresist is used for spin coating treatment, and a PGMEA developing solution is used for development treatment to prepare a corresponding photoresist pattern; the rest of the operations are consistent, and a corresponding high-resolution quantum dot light-emitting diode is prepared, with a resolution of 8400 PPI.

[0095] The luminescence performance of the quantum dots in the high-resolution quantum dot light-emitting diode prepared in this comparative example is observed by fluorescence microscopy, as shown in FIG. 3B, the quantum dots have obvious corrosion phenomenon and low fluorescence intensity, similar to Comparative Example 2. Figure 9

[0096] Performance test: The leakage current (2 V corresponding leakage current), maximum external quantum efficiency EQE and luminous brightness of the high-resolution quantum dot light-emitting diodes prepared in the above Examples 1, 2 and Comparative Examples 1, 2 are tested using an Ocean Optics system including a power meter (Keithley 2450), a spectrometer (QE Pro) and an integrating sphere (FOIS-1) in a nitrogen-filled glove box.

[0097] The test results are shown in Table 1 below:

[0098] Table 1

[0099]

[0100] As can be seen from Table 1, compared with the high-resolution quantum dot light-emitting diode prepared without using photoresist blocking (Comparative Example 1), the high-resolution quantum dot light-emitting diodes prepared using the photoresist solutions of Examples 1 and 2 have extremely low leakage current, and the EQE and brightness are significantly improved, showing excellent photoelectric performance and display quality.

[0101] In addition, as can be seen from Examples 1, 2 and Comparative Example 2, although the leakage current of the high-resolution quantum dot light-emitting diode prepared using AZ524 photoresist is lower than that of the high-resolution quantum dot light-emitting diode prepared without blocking (Comparative Example 1), the light-emitting pixels will be corroded in the photoetching stage, and the fluorescence intensity of the quantum dots will be reduced.​​Figure 8 ), resulting in inconsistent electrical performance between quantum dot pixels and pixels, and still a high leakage current (1 mA / cm 3 ), which restricts the improvement of the device light-emitting efficiency. The photoresist solution provided by the application is used to prepare the isolation barrier layer, which does not corrode the quantum dot pixels, and the leakage current of the device can be further greatly reduced. Compared with the comparative example 2, the leakage current is reduced by more than 80%, the corresponding maximum external quantum efficiency is increased by more than 147.6%, and the luminous intensity is also obviously improved, thereby significantly improving the overall performance of the high-efficiency quantum dot light-emitting diode.

[0102] The above-mentioned examples are only preferred examples for fully illustrating the application, and the protection scope of the application is not limited thereto. Any equivalent replacement or transformation made by the person skilled in the art on the basis of the application is within the protection scope of the application. The protection scope of the application is subject to 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; 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.

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+ 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, 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.

4. The photoresist solution according to claim 1, 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.

5. 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.

6. A method for preparing the photoresist solution according to any one of claims 1-5, characterized in that, Weigh each component according to the formula of the photoresist solution and mix them evenly to obtain the photoresist solution.

7. The use of the photoresist solution according to any one of claims 1-5 in the fabrication of high-resolution quantum dot light-emitting diodes.

8. The application according to claim 7, 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.

9. The application according to claim 8, 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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