Quantum dot light-emitting film high-resolution patterning method based on laser deposition technology

Abstract

The invention belongs to the technical field of photoelectric material preparation, and particularly discloses a quantum dot light-emitting film high-resolution patterning method based on a laser deposition technology, which comprises the following steps: forming a thermoplastic polyurethane particle colloidal solution; forming a thermoplastic polyurethane film; evaporating the metal film; performing laser deposition on a quantum dot light-emitting material; and releasing the tension. According to the quantum dot light-emitting film high-resolution patterning method based on the laser deposition technology, the quantum dot light-emitting material induces the quantum dot solution to flow on the pre-stretching elastic substrate and deposits the quantum dot solution into any two-dimensional pattern, the pre-stretching stress of the elastic substrate is released, pattern deformation assisted by mechanical deformation of the substrate is achieved, and the patterning quality of the quantum dot light-emitting film is improved. Therefore, a high-resolution pattern and a pixel array are obtained.

Description

Technical Field

[0001] The present invention relates to the technical field of optoelectronic materials, and in particular to a high-resolution patterning method for quantum dot light-emitting thin films based on laser deposition technology. Background Art

[0002] Quantum dot light-emitting materials have the advantages of high luminescence quantum yield, high color purity, and adjustable bandgap, and show advantages such as wide color gamut, high chromatic purity, and low power consumption in the display field. However, with the increasing demand for ultra-small pixels and ultra-high pixel density in ultra-high resolution display technology, the high-precision patterning preparation technology of liquid-based optoelectronic materials such as colloidal semiconductor quantum dot light-emitting materials faces great challenges. At present, the patterning technologies of quantum dot light-emitting materials mainly include inkjet printing, imprint transfer, and lithography and other technologies.

[0003] However, the coffee ring effect and nozzle blockage problems existing in the inkjet printing technology limit the uniformity of pixel dots; the disadvantage of the imprint transfer technology is the use of a template, which has risks of template wear, deformation, and contact contamination, and the controllability and repeatability of pixel shapes are limited; the direct lithography of existing quantum dot light-emitting materials requires customized crosslinkable ligands, making this technology lack universality, and usually requires complex organic chemical synthesis reactions, which undoubtedly increases the preparation cost and the risk that the optoelectronic properties of the quantum dots themselves are affected. Summary of the Invention

[0004] The purpose of the present invention is to provide a high-resolution patterning method for quantum dot light-emitting thin films based on laser deposition technology. By inducing the flow of quantum dot solution on a pre-stretched elastic substrate and depositing it into any two-dimensional pattern, and by releasing the pre-stretched stress of the elastic substrate, the pattern deformation assisted by the mechanical deformation of the substrate is realized, so as to obtain high-resolution patterns and pixel arrays.

[0005] To achieve the above purpose, the present invention provides a high-resolution patterning method for quantum dot light-emitting thin films based on laser deposition technology, including the following steps:

[0006] S1. Preparation of thermoplastic polyurethane particle colloidal solution: Disperse thermoplastic polyurethane particles in N,N-dimethylformamide solution and stir on a magnetic stirrer to obtain a colloidal solution for standby;

[0007] S2. Formation of thermoplastic polyurethane thin film: Place a clean glass substrate on a spin coater, use a pipette to drop the thermoplastic polyurethane particle colloidal solution on the glass substrate and spin coat it, and place the spin-coated glass substrate on a constant temperature hot stage. After 25 minutes, a thermoplastic polyurethane thin film can be obtained;

[0008] S3. Metal thin film evaporation treatment: Peel the thermoplastic polyurethane film from the glass substrate, stick it on the mask plate of the vacuum evaporation instrument with 3M tape in the stretched state of the thermoplastic polyurethane, and then use the vacuum evaporation instrument to evaporate a metal film on the surface of the thermoplastic polyurethane film for standby. Keep the thermoplastic polyurethane in the pre-stretched state during the evaporation process to obtain a thermoplastic polyurethane substrate.

[0009] S4. Laser deposition of quantum dot luminescent materials: Take the quantum dot solution and drop it on the thermoplastic polyurethane substrate prepared in advance in step S3, make the solution fall at the center of the thermoplastic polyurethane substrate, cover the thermoplastic polyurethane substrate with a cover glass, use a computer program to control the laser to directly act on the quantum dot luminescent materials to induce the preparation of patterns, and put the processed thermoplastic polyurethane substrate into n-octane and oscillate for 1 - 2 min to obtain patterns composed of quantum dot luminescent materials on the thermoplastic polyurethane substrate.

[0010] S5. Release the tension: Move the processed thermoplastic polyurethane substrate to a dry place to air dry. After the thermoplastic polyurethane substrate releases the tension, it shrinks, and patterns composed of quantum dot luminescent materials can be obtained.

[0011] Preferably, in step S1, the ratio of thermoplastic polyurethane particles to N,N-dimethylformamide solution is 200 mg / ml.

[0012] Preferably, in step S2, the glass substrate is a clean substrate, and the size of the glass substrate is 19.8 * 17.8 * 0.7 mm; the rotation speed of the spin coater is set at 1000 rpm, the time is 40 s, and the acceleration is 1000 rpm / s.

[0013] Preferably, in step S3, when the vacuum degree in the vacuum thermal evaporation system chamber reaches below 5 * 10 -4 Pa, start the evaporation.

[0014] Preferably, in step S4, the laser wavelength is 800 nm, the pulse frequency is 80 MHz, the laser power used is 1.38 - 12.6 mW, and the single-point exposure time is 50 - 1000 μs.

[0015] Preferably, in step S5, the tension is pre-stretched by 20 - 80%.

[0016] The advantages and beneficial effects of the present invention adopting the above-mentioned high-resolution patterning method of quantum dot luminescent thin film based on laser deposition technology are as follows:

[0017] 1. The method of the present invention can rapidly obtain programmable and uniform high-resolution patterns on the thermoplastic polyurethane elastic substrate by using the method of laser-induced deposition, and has great potential in the application field of displays.

[0018] 2. The high-resolution quantum dot pattern of the present invention using laser-induced deposition does not require a mask, and by utilizing the characteristics of femtosecond laser cold processing, the time for electron-phonon coupling to occur for heat transfer to reach thermal equilibrium between electrons and ions is on the picosecond scale. Therefore, during the action of the femtosecond laser, the electrons and ions are a typical non-thermal equilibrium system of hot electrons and cold ions in a two-temperature model. The thermoplastic polyurethane substrate and the quantum dot luminescent material are not heated, avoiding thermal damage to the substrate and the quantum dots.

[0019] 3. The pre-stretched thermoplastic polyurethane elastic substrate used in the present invention has many remarkable advantages. The high elasticity of the thermoplastic polyurethane material is one of its most important characteristics, and its elongation rate can reach more than 100%. Through its high elasticity, the resolution of the quantum dot luminescent thin film pattern can be improved.

[0020] The technical solution of the present invention will be further described in detail below through the drawings and embodiments. Description of the Drawings

[0021] Figure 1 It is a schematic flow chart of the method for depositing a high-resolution pattern on an elastic substrate using a laser in the present invention;

[0022] Figure 2 It is a fluorescence photograph, a scanning electron microscope photograph, and an atomic force microscope photograph of changing different laser parameters on an elastic substrate using laser deposition technology in the present invention; where a is the matrix fluorescence microscope photograph formed by processing, b is the scanning electron microscope photograph, and c is the atomic force microscope photograph of the deposited quantum dot thin film;

[0023] Figure 3 It is a fluorescence microscope photograph of quantum dot matrices with different spacings prepared on an elastic substrate using laser deposition technology in the present invention before and after releasing the pre-stretching under different pre-stretching degrees, where a is the fluorescence microscope photograph, and b and c are the spacing changes after releasing the tensile force;

[0024] Figure 4 It is a fluorescence spectrum curve, a fluorescence lifetime curve, and a two-dimensional code pattern of the high-resolution quantum dot pattern prepared using laser deposition technology in the present invention after releasing the tensile force, where a is the fluorescence spectrum curve, b is the fluorescence lifetime curve of the quantum dot pattern prepared under 60% pre-stretching before and after releasing the tensile force, and c is the fluorescence microscope photograph of the two-dimensional code pattern prepared under 60% pre-stretching at 20%, 40%, 60%, and 80% stretching degrees. Detailed Embodiments

[0025] The technical solution of the present invention will be further described below through the drawings and embodiments.

[0026] Unless otherwise defined, the technical terms or scientific terms used in the present invention shall have the ordinary meanings understood by those of ordinary skill in the art to which the present invention pertains.

[0027] Unless otherwise defined, the reagents, equipment and other materials used in the present invention are all obtained from regular commercial sources.

[0028] Example 1

[0029] A high-resolution patterning method for quantum dot light-emitting thin films based on laser deposition technology, which uses a laser to induce deposition on an elastic substrate to form an arbitrarily two-dimensional patterned quantum dot light-emitting thin film, and obtains a pattern with high resolution through pre-stretching of the elastic substrate, including the following steps:

[0030] S1. Formation of thermoplastic polyurethane (TPU) particle colloidal solution: Weigh 4 g of TPU particles with an average particle size of 800 nm and mix them with 20 mL of N,N-dimethylformamide solution in a centrifuge tube and centrifuge for 5 min. The ratio of thermoplastic polyurethane particles to N,N-dimethylformamide solution is 200 mg / ml. Then transfer the mixed solution to a transparent glass bottle, place a polytetrafluoroethylene stir bar with a size of 6*10 mm, and place it on a magnetic stirrer with a set temperature of 25°C and a rotation speed of 1000 rpm and stir for 8 h to form a colloidal solution with a concentration of 200 mg / ml.

[0031] S2. Formation of thermoplastic polyurethane thin film: The size of the glass substrate is 19.8*17.8*0.7 mm. Perform standardized cleaning treatment on the glass substrate. Place the glass substrate in acetone, absolute ethanol, and deionized water in sequence and ultrasonically clean for 60 minutes, then wipe it with a medical degreasing cotton ball containing absolute ethanol, then wash it with deionized water, blow dry the water droplets on the surface of the glass substrate with nitrogen, and then place the cleaned glass substrate in an oven at a constant temperature of 95°C and bake for 5 minutes; then, place the treated glass substrate on a spin coater, use a pipette to drop 450 μL of thermoplastic polyurethane particle colloidal solution on the glass, set the rotation speed of the spin coater to 1000 rpm, the time to 40 s, and the acceleration to 1000 rpm / s and start spin coating; finally, place the spin-coated glass on a hot plate at a constant temperature of 50°C for annealing, and a thermoplastic polyurethane thin film can be obtained after 25 minutes.

[0032] S3. Metal thin film evaporation treatment: Peel the TPU thin film from the glass substrate, and use Scotch 3M810 invisible tape with a width of 12.7 mm to stick it on the mask plate of the vacuum evaporation instrument in different degrees of stretching states (stretch the TPU thin film and paste it on the glass substrate, maintain the tensile stress of the TPU thin film, and then paste the glass substrate on the mask plate). Move the mask plate into the vacuum thermal evaporation system and evaporate a layer of metal thin film on the substrate. When the vacuum degree in the cavity of the vacuum thermal evaporation system reaches 5*10 -4When the pressure is below Pa, evaporation coating starts. During the evaporation coating process, the glass substrate rotates to ensure the uniformity of the thin film. The thin film deposited is a silver thin film. A quartz crystal oscillator in the system is used to monitor the film thickness and deposition rate of the deposited material. The deposition rate of the thin film is A silver film with a thickness of 10 nm is obtained. The thermoplastic polyurethane thin film coated with the metal thin film is peeled off from the glass substrate of the mask plate of the vacuum evaporation coater and re-pasted onto a new glass substrate to obtain a thermoplastic polyurethane substrate.

[0033] S4. Laser deposition of quantum dot luminescent materials. The quantum dots used are CdSe / ZnS quantum dots, emission peak: 625 nm, PLQY > 90%, FWHM < 25 nm, concentration: 50 mg / ml, solvent: n-octane. First, take 0.006 - 0.01 mL of the quantum dot solution and drop it on the processed thermoplastic polyurethane substrate. The natural convection and Marangoni convection induced by the interaction of the laser and the solution are used to deposit the quantum dot luminescent material on the surface of the thermoplastic polyurethane substrate to form a programmable pattern. First, according to the designed structure and the layer-by-layer scanning method, the solution is scanned layer by layer. The femtosecond laser wavelength used in this process is 800 nm, the pulse repetition frequency is 80 MHz, the pulse width is 120 fs, the experiment uses a 60 - 100 times objective lens for focusing, and its numerical aperture is 1.4; the laser power used is 1.38 - 12.6 mW, the dot-line-plane scanning spacing is 100 - 200 nm, and the single-point exposure time is 50 - 1000 μs. The movement trajectory of the laser focus is designed by presetting with 3Dmax software and then exported from the software as a txt format file and imported into the control computer of the femtosecond laser direct writing system. During the processing, it is necessary to ensure that the TPU substrate is perpendicular to the laser traveling direction. In this way, a quantum dot thin film with a preset pattern can be obtained. Use n-octane to clean the quantum dots that have not been processed by the laser and the remaining processing debris, and finally release the tension. With the shrinkage deformation assistance of the TPU substrate, the resolution is improved.

[0034] S5. Release the tension, move the processed thermoplastic polyurethane substrate to a dry place to air dry. Then, tear off the tapes on both sides of the thermoplastic polyurethane substrate from the glass substrate. After the thermoplastic polyurethane thin film releases the tension, it shrinks, and the tension is 20 - 80% of the pre-stretching, and a pattern composed of quantum dot luminescent materials can be obtained.

[0035] From Figure 1 It can be seen that it is a schematic flow chart of depositing a high-resolution pattern on an elastic substrate using a laser.

[0036] From Figure 2It can be seen that by using a laser to deposit a high-resolution pattern on an elastic substrate, it can be seen from the fluorescence microscope images and scanning electron microscope images that when the power is 3.82 mW and the exposure time is 1000 μs, the morphology of the deposited quantum pattern is good. At the same time, it can be seen from the atomic force microscope that the roughness increases slightly before and after stretching. Among them Figure 2 a in it is a 2×2 matrix fluorescence microscope image formed after processing under the conditions of laser powers of 1.38 mW, 3.82 mW, 8 mW, 12.6 mW and exposure times of 50 μs, 100 μs, 200 μs, 500 μs, 1000 μs respectively. The side length of each small square is 20 μm and the interval is 30 μm. Figure 2 b in it is a scanning electron microscope image under the conditions of laser powers of 1.38 mW, 3.82 mW, 8 mW, 12.6 mW and exposure times of 50 μs, 100 μs, 200 μs, 500 μs, 1000 μs respectively. Figure 2 c in it is an atomic force microscope image of a quantum dot thin film deposited under the conditions of a laser power of 3.82 mW and an exposure time of 1000 μs. The left figure is the condition without pre-stretching, and the right figure is the condition after pre-stretching by 60% and then releasing the tensile force.

[0037] It can be seen from Figure 3 that by using a laser to deposit a high-resolution pattern on an elastic substrate, the resolution is improved to different degrees under different pre-stretching conditions. Among them Figure 3 a in it are fluorescence microscope images before and after stretching of an elastic substrate pre-stretched by 20%, 40%, 60%, 80% from left to right respectively, and 2×2 square arrays with initial spacings of 30 μm, 25 μm, 20 μm, 15 μm, 10 μm, 5 μm from top to bottom respectively. Figure 3 b in it and Figure 3 c in it are the spacing changes after releasing the tensile force under the conditions of pre-stretching by 20%, 40%, 60%, 80% with initial spacings of 30 μm, 25 μm, 20 μm, 15 μm, 10 μm, 5 μm.

[0038] It can be seen from Figure 4 that due to the stretching of the elastic substrate, the concentration of quantum dots per unit area increases for the two-dimensional code patterns under different stretching degrees, thus increasing the fluorescence lifetime and fluorescence intensity. The two-dimensional code patterns of quantum dots under different stretching degrees all show clear and uniform luminescence.

[0039] A high-resolution patterning method for quantum dot light-emitting thin films based on laser deposition technology, which precisely direct-writes quantum dot light-emitting materials on an elastic substrate by using laser-induced deposition. By dispersing an appropriate amount of thermoplastic polyurethane particles in N,N-dimethylformamide solvent to form a stable colloidal solution, spin-coating on a spin coater and annealing at 50 °C for 25 minutes, a TPU elastic substrate is formed. The laser acts on the quantum dot light-emitting material solution on the pre-stretched elastic substrate, inducing the aggregation of quantum dots and finally forming a programmatically controllable pattern on the elastic substrate. After releasing the pre-stretching tension of the substrate, the shrinkage deformation of the elastic substrate can induce the reduction of the quantum dot light-emitting thin film pattern thereon, obtaining a reduction in the size of the quantum dot light-emitting thin film pattern and an improvement in resolution. By using the interaction between the laser and the quantum dots, the locally increased temperature induced by the laser will reduce the density, and the buoyancy force with low density induces natural convection; at the same time, the increase in temperature will also induce a change in the local surface tension, generating Marangoni convection. The quantum dots moving towards the substrate caused by natural convection and Marangoni convection interact with the substrate through van der Waals forces and are finally deposited on the pre-stretched elastic substrate. After releasing the tension, with the shrinkage deformation of the elastic substrate, the line width and line pitch of the quantum dot light-emitting material pattern are reduced, thereby obtaining an improvement in resolution.

[0040] Therefore, the present invention adopts the above-mentioned high-resolution patterning method for quantum dot light-emitting thin films based on laser deposition technology. By inducing the flow of the quantum dot solution on the pre-stretched elastic substrate and depositing it into any two-dimensional pattern, and by releasing the pre-stretching stress of the elastic substrate, mechanical deformation of the substrate is used to assist pattern deformation, thereby obtaining a high-resolution pattern and pixel array.

[0041] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit them. Although the present invention has been described in detail with reference to the preferred embodiments, those of ordinary skill in the art should understand that they can still modify or equivalently replace the technical solutions of the present invention, and these modifications or equivalent replacements cannot make the modified technical solutions deviate from the spirit and scope of the technical solutions of the present invention.

Claims

1. A high-resolution patterning method for quantum dot luminescent thin films based on laser deposition technology, characterized in that: The steps include: S1. Preparation of a colloidal solution of thermoplastic polyurethane particles: dispersing thermoplastic polyurethane particles in an N,N-dimethylformamide solution and stirring the solution on a magnetic stirrer to obtain a colloidal solution for later use; S2, thermoplastic polyurethane film formation, a clean glass substrate is placed on a coating machine, a thermoplastic polyurethane particle colloidal solution is dropped on the glass substrate with a pipette gun and spin-coated, and the glass substrate after spin coating is placed on a constant temperature hot stage, and a thermoplastic polyurethane film can be obtained after 25 minutes; S3, metal film evaporation treatment, peeling the thermoplastic polyurethane film from the glass substrate, sticking it to the mask of the vacuum evaporation device with 3M tape in the stretched state of the thermoplastic polyurethane, and then using the vacuum evaporation device to evaporate a metal film on the surface of the thermoplastic polyurethane film for standby use, keeping the thermoplastic polyurethane in a pre-stretched state during the evaporation process, and obtaining a thermoplastic polyurethane substrate; S4, laser deposition of quantum dot luminescent material, taking a quantum dot solution and dropping it on the thermoplastic polyurethane substrate prepared in step S3, so that the solution falls on the center of the thermoplastic polyurethane substrate, covering the thermoplastic polyurethane substrate with a cover glass, using a computer program to control the laser to directly interact with the quantum dot luminescent material to induce the preparation of a pattern, putting the processed thermoplastic polyurethane substrate into n-octane for oscillation for 1-2 minutes, and obtaining a pattern composed of quantum dot luminescent material on the thermoplastic polyurethane substrate; S5, releasing the tension, moving the processed thermoplastic polyurethane substrate to a dry place for air drying, and the thermoplastic polyurethane substrate shrinks after releasing the tension, thereby obtaining a pattern composed of quantum dot luminescent materials.

2. The method for high-resolution patterning of quantum dot light-emitting thin films based on laser deposition technology according to claim 1, characterized in that: In step S1, the ratio of thermoplastic polyurethane particles to N,N-dimethylformamide solution is 200 mg / ml.

3. The method for high-resolution patterning of quantum dot light-emitting thin films based on laser deposition technology according to claim 1, characterized in that: In step S2, the glass substrate is a clean substrate, and the size of the glass substrate is 19.8*17.8*0.7 mm; the speed of the coating machine is set to 1000 rpm, the time is 40 s, and the acceleration is 1000 rpm / s.

4. The method for high-resolution patterning of quantum dot light-emitting thin films based on laser deposition technology according to claim 1, characterized in that: In step S3, when the vacuum degree in the vacuum thermal evaporation system chamber reaches 5*10 -4 Pa and start evaporation.

5. The method for high-resolution patterning of quantum dot light-emitting thin films based on laser deposition technology according to claim 1, characterized in that: In step S4, the laser wavelength is 800 nm, the pulse frequency is 80 MHz, the laser power used is 1.38-12.6 mW, and the single point exposure time is 50-1000 μs.

6. The method for high-resolution patterning of quantum dot light-emitting thin films based on laser deposition technology according to claim 1, characterized in that: In step S5, the tension is pre-stretched by 20-80%.

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