Preparation method of quantum dot light-emitting device and display panel

Abstract

The invention provides a preparation method of a quantum dot light-emitting device and a display panel. The preparation method comprises the following steps: providing a substrate with a first electrode layer, and arranging a positive photoresist on the substrate; arranging a first mask plate above the substrate, and performing exposure treatment and development to obtain a positive photoresist curing layer with a first pit; a first quantum dot solution is arranged on the positive photoresist curing layer with the first pits, so that a solvent in the first quantum dot solution is dried, and a first quantum dot layer is obtained; a second mask plate is arranged above the substrate, the second mask plate is light-proof at the first pit, the positive photoresist curing layer is eluted after exposure treatment, the first quantum dot layer located on the surface, away from the substrate, of the positive photoresist curing layer is eluted along with elution of the positive photoresist curing layer, and the first quantum dot light-emitting device is obtained. And a first quantum dot layer is arranged at the position of the first pit. According to the preparation method, the damage of a photoetching process to the performance of the quantum dots is reduced.

Description

Technical Field

[0001] The present disclosure relates to the technical field of electro-induced quantum dot luminescence, and in particular, to a method for preparing a quantum dot light-emitting device and a display panel. Background Art

[0002] Quantum dot light-emitting diodes (QLEDs) are known as the next generation of new display technology due to their advantages such as high color purity, low power consumption and simple process. At present, there are two main QLED preparation processes: printed QLED and photolithography QLED. Compared with printed QLED, the resolution of photolithography QLED can reach more than 4000PPi, so its application field is wider, including mobile phones / micro displays (VR&AR), etc.

[0003] The most widely used method of photolithography QLED at present is the photo-crosslinking of quantum dot ligands. The preparation process is simple but there are very obvious problems such as insufficient performance and difficulty in mass production. Summary of the invention

[0004] The purpose of the present disclosure is to provide a method for preparing a quantum dot light-emitting device and a display panel to solve the problem of insufficient performance when preparing QLED by photo-crosslinking of existing quantum dot ligands.

[0005] In order to solve the above problems, according to the first aspect of the present disclosure, a method for preparing a quantum dot light-emitting device is provided, the method comprising: providing a substrate having a first electrode layer, and disposing a positive photoresist on the substrate; disposing a first mask plate above the substrate, performing exposure treatment and then developing to obtain a positive photoresist cured layer having a first pit, the position of the first pit corresponding to the through hole of the first mask plate; disposing a first quantum dot solution on the positive photoresist cured layer having the first pit, part of the first quantum dot solution being located in the first pit, and another part of the first quantum dot solution being located on the surface of the positive photoresist cured layer away from the substrate; drying the solvent in the first quantum dot solution to obtain a first quantum dot layer; disposing a second mask plate above the substrate, the second mask plate being opaque at the first pit, the positive photoresist cured layer being eluted after the exposure treatment, the first quantum dot layer located on the surface of the positive photoresist cured layer away from the substrate being eluted along with the elution of the positive photoresist cured layer, to obtain a first quantum dot light-emitting device, wherein the first quantum dot layer is located at the position of the first pit.

[0006] Optionally, the preparation method also includes: setting a positive photoresist on the first quantum dot light-emitting device; setting a third mask plate above the substrate, performing exposure treatment and then developing to obtain a positive photoresist cured layer having a second pit, the position of the second pit corresponding to the through hole of the third mask plate; setting a second quantum dot solution on the positive photoresist cured layer having the second pit, part of the second quantum dot solution is located in the second pit, and another part of the second quantum dot solution is located on the surface of the positive photoresist cured layer away from the substrate; allowing the solvent in the second quantum dot solution to dry to obtain a second quantum dot layer; setting a fourth mask plate above the substrate, the fourth mask plate is not light-transmissive at the second pit, the positive photoresist cured layer is eluted after the exposure treatment, and the second quantum dot layer located on the surface of the positive photoresist cured layer away from the substrate is eluted along with the elution of the positive photoresist cured layer, to obtain a second quantum dot light-emitting device, the first pit has the first quantum dot layer at the position, and the second pit has the second quantum dot layer at the position.

[0007] Optionally, the preparation method also includes: setting a positive photoresist on the second quantum dot light-emitting device; setting a fifth mask plate above the substrate, performing exposure treatment and then developing to obtain a positive photoresist cured layer having a third pit, the position of the third pit corresponding to the through hole of the fifth mask plate; setting a third quantum dot solution on the positive photoresist cured layer having the third pit, part of the third quantum dot solution is located in the third pit, and another part of the third quantum dot solution is located on the surface of the positive photoresist cured layer away from the substrate; allowing the solvent in the third quantum dot solution to dry to obtain a third quantum dot layer; setting a sixth mask plate above the substrate, the sixth mask plate is not light-transmissive at the third pit, the positive photoresist cured layer is eluted after the exposure treatment, and the third quantum dot layer located on the surface of the positive photoresist cured layer away from the substrate is eluted along with the elution of the positive photoresist cured layer, to obtain a third quantum dot light-emitting device, wherein the first quantum dot layer is located at the position of the first pit, the second quantum dot layer is located at the position of the second pit, and the third quantum dot layer is located at the position of the third pit.

[0008] Optionally, the drying method is heating drying, or the method when the first quantum dot solution is provided is a spin coating process and natural drying is performed during the spin coating process.

[0009] Optionally, the positive photoresist is selected from naphthoquinone diazide or polymethyl methacrylate.

[0010] Optionally, the developer used for development is an aqueous solution of TMAH or an aqueous solution of KOH.

[0011] Optionally, the preparation method further comprises: disposing one or more layers of a functional layer and a second electrode layer on each quantum dot light-emitting layer of the third quantum dot light-emitting device.

[0012] Optionally, the spacing distance between each quantum dot layer is 1-5 microns.

[0013] Optionally, the first quantum dot solution is lipophilic.

[0014] According to a second aspect of the present disclosure, a display panel is provided, the display panel comprising a quantum dot light-emitting device prepared by any one of the above-mentioned preparation methods.

[0015] By applying the above technical solution, there is no need to add a specific photocross-linking initiator to the quantum dot solution (usually the photocross-linking initiator is not conductive, which will greatly reduce the current of the device. At the same time, the electrical and optical properties of the QD will be damaged after cross-linking, which manifests as a significant decrease in device performance), thereby reducing the damage to the photoelectric properties of the quantum dots. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] The drawings constituting part of the present application are used to provide a further understanding of the present disclosure. The exemplary embodiments of the present disclosure and their descriptions are used to explain the present disclosure and do not constitute an improper limitation on the present disclosure. In the drawings:

[0017] Figure 1 The present invention is a schematic diagram of a process flow for preparing a quantum dot light-emitting device according to an embodiment of the present invention.

[0018] Figure 2 The present invention is a schematic diagram of a process flow for preparing a quantum dot light-emitting device according to another embodiment of the present invention.

[0019] Figure 3 A schematic diagram of the structure of a quantum dot light-emitting device obtained according to an embodiment of the present disclosure.

[0020] Figure 4 Microscope photos of red, green and blue quantum dot light-emitting devices obtained according to an embodiment of the present disclosure.

[0021] Figure 5 This is a microscope photograph of an RGB three-color quantum dot light-emitting device obtained according to an embodiment of the present disclosure.

[0022] Figure numerals: 11: substrate; 12: first electrode layer (and functional layer); 13: positive photoresist (not distinguished before and after curing); 14: red quantum dot layer; 15: green quantum dot layer; 16: blue quantum dot layer; 17: functional layer; 18: second electrode layer; 21-24 are all masks. DETAILED DESCRIPTION

[0023] It should be noted that the following detailed descriptions are illustrative and are intended to provide further explanation of the present application. Unless otherwise specified, all technical and scientific terms used herein have the same meanings as those commonly understood by those skilled in the art to which the present application belongs.

[0024] According to the first aspect of the present disclosure, a method for preparing a quantum dot light-emitting device is provided, and the method comprises: providing a substrate having a first electrode layer, and disposing a positive photoresist on the substrate; disposing a first mask plate above the substrate, performing an exposure treatment and then developing, to obtain a positive photoresist solidified layer having a first pit, the position of the first pit corresponding to the through hole of the first mask plate; disposing a first quantum dot solution on the positive photoresist solidified layer having the first pit, part of the first quantum dot solution being located in the first pit, and another part of the first quantum dot solution being located on the surface of the positive photoresist solidified layer away from the substrate; allowing the solvent in the first quantum dot solution to dry, to obtain a first quantum dot layer; disposing a second mask plate above the substrate, the second mask plate being opaque at the first pit, the positive photoresist solidified layer being eluted after the exposure treatment, the first quantum dot layer located on the surface of the positive photoresist solidified layer away from the substrate being eluted along with the elution of the positive photoresist solidified layer, to obtain a first quantum dot light-emitting device, with the first quantum dot layer at the position of the first pit. Figure 1 shown.

[0025] The first quantum dot layer located on the surface of the positive photoresist cured layer away from the substrate is easily washed away due to the disappearance of the positive photoresist cured layer (decomposition under light in the exposure process) and the lack of a (physical or chemical) adsorption / carrying substrate, so there is no need to first remove excess quantum dots and then peel off the excess photoresist cured layer. By applying the above technical solution, there is no need to add a specific photocrosslinking initiator to the quantum dot solution. Generally, the photocrosslinking initiator is non-conductive and will greatly reduce the current of the device. At the same time, the electrical and optical properties of the quantum dots will be damaged after crosslinking, which is manifested as a significant decrease in device performance.

[0026] The quantum dot layer is the light-emitting layer of the light-emitting device. The polarity of the quantum dots is opposite to that of the developer. Hydrophilic developers (or eluents) are used for lipophilic quantum dots. Hydrophilic developers have the advantage of being environmentally friendly in mass production. Compared with eluents such as organic solvents, hydrophilic developers have better mass production feasibility and low environmental protection costs.

[0027] In some embodiments, baking is performed after development to obtain a positive photoresist cured layer having first pits.

[0028] In some embodiments, the thickness of the positive photoresist cured layer having the first pit is 5-100 nm. In some embodiments, the thickness of the first light emitting layer is 15-30 nm.

[0029] In some embodiments, the exposure process of forming the positive photoresist cured layer having the first pit includes: i-line or g-line exposure, exposure time 3s-30s. In some embodiments, the development process is immersing the semi-finished device in a developer for 1-3min, or spray development for 1-3min.

[0030] The first quantum dot solution may be provided by spin coating, whole-surface coating or whole-surface printing.

[0031] In the present application, the mask or the pit is designed according to the required pixel size, shape and position. The number of the first pit and the second pit and the third pit described below is greater than or equal to 1, and can be arranged in an array to form each sub-pixel.

[0032] In some embodiments, the preparation method further includes: setting a positive photoresist on the first quantum dot light-emitting device; setting a third mask template above the substrate, performing exposure treatment and then developing to obtain a positive photoresist cured layer having a second pit, the position of the second pit corresponds to the through hole of the third mask template; setting a second quantum dot solution on the positive photoresist cured layer having the second pit, part of the second quantum dot solution is located in the second pit, and another part of the second quantum dot solution is located on the surface of the positive photoresist cured layer away from the substrate; allowing the solvent in the second quantum dot solution to dry to obtain a second quantum dot layer; setting a fourth mask template above the substrate, the fourth mask template is not light-transmissive at the second pit, the positive photoresist cured layer is eluted after the exposure treatment, and the second quantum dot layer located on the surface of the positive photoresist cured layer away from the substrate is eluted along with the elution of the positive photoresist cured layer, to obtain a second quantum dot light-emitting device, the first pit has a first quantum dot layer at the position, and the second pit has a second quantum dot layer at the position. Figure 2 The positive photoresist cured layer with the second pit covers the first quantum dot layer to protect the first quantum dot layer.

[0033] The positive photoresist can be provided by spin coating, full-surface coating or full-surface printing. The positive photoresist used to form the positive photoresist cured layer of the second pit can be the same as or different from the positive photoresist used to form the positive photoresist cured layer of the first pit.

[0034] In some embodiments, the exposure and development process for forming the positive photoresist cured layer having the second pits may be the same as or slightly different from the exposure and development process for forming the positive photoresist cured layer having the first pits.

[0035] In some embodiments, baking is performed after development to obtain a positive photoresist cured layer having second pits.

[0036] The second quantum dot solution may be provided by spin coating, whole-surface coating or whole-surface printing.

[0037] In some embodiments, the preparation method also includes: setting a positive photoresist on the second quantum dot light-emitting device; setting a fifth mask template above the substrate, performing exposure treatment and then developing to obtain a positive photoresist cured layer having a third pit, the position of the third pit corresponding to the through hole of the fifth mask template; setting a third quantum dot solution on the positive photoresist cured layer having the third pit, part of the third quantum dot solution is located in the third pit, and another part of the third quantum dot solution is located on the surface of the positive photoresist cured layer away from the substrate; allowing the solvent in the third quantum dot solution to dry to obtain a third quantum dot layer; setting a sixth mask template above the substrate, the sixth mask template is not light-transmissive at the third pit, the positive photoresist cured layer is eluted after the exposure treatment, and the third quantum dot layer located on the surface of the positive photoresist cured layer away from the substrate is eluted along with the elution of the positive photoresist cured layer, to obtain a third quantum dot light-emitting device, wherein the first quantum dot layer is located at the position of the first pit, the second quantum dot layer is located at the position of the second pit, and the third quantum dot layer is located at the position of the third pit.

[0038] The positive photoresist cured layer having the third pit covers the first quantum dot layer and the second quantum dot layer, thereby protecting the first quantum dot layer and the second quantum dot layer.

[0039] The positive photoresist can be provided by spin coating, full-surface coating or full-surface printing. The positive photoresist used to form the positive photoresist cured layer of the third pit can be the same as or different from the positive photoresist used to form the positive photoresist cured layer of the first pit.

[0040] In some embodiments, the exposure and development process for forming the positive photoresist cured layer having the third pits may be the same as or slightly different from the exposure and development process for forming the positive photoresist cured layer having the first pits.

[0041] In some embodiments, baking is performed after development to obtain a positive photoresist cured layer having third pits.

[0042] The third quantum dot solution may be provided by spin coating, whole-surface coating or whole-surface printing.

[0043] In some embodiments, the drying method is heat drying, or the method of setting the first quantum dot solution is a spin coating process and the solution is dried naturally during the spin coating process.

[0044] In some embodiments, the heating and drying process is 50-100° C. and the annealing time is 10-60 minutes.

[0045] The specific type of positive photoresist is not limited. In some embodiments, the positive photoresist is selected from naphthoquinone diazide or polymethyl methacrylate. It should be noted that naphthoquinone diazide or polymethyl methacrylate is the main component of the positive photoresist, not the only component.

[0046] In some embodiments, the developer used for development is an alkaline aqueous solution, which can be an aqueous solution of tetramethylammonium hydroxide (TMAH) or an aqueous solution of KOH. The developer does not need to use a traditional organic solvent (such as n-octane), and there are no safety and environmental issues. The mass fraction of the alkaline substance in the developer can be 0.01%-0.1% (KOH) or 1%-5% (TMAH).

[0047] In some embodiments, the preparation method further comprises: disposing one or more layers of a functional layer and a second electrode layer on each quantum dot light-emitting layer of the third quantum dot light-emitting device. The functional layer may be a hole injection layer, a hole transport layer, a hole blocking layer, an electron injection layer, an electron transport layer, an electron blocking layer, a smoothing layer, etc. Figure 3 The structure (cross section) of a quantum dot light emitting device according to an embodiment is shown.

[0048] In some embodiments, the spacing between the quantum dot layers is 1-5 microns to prevent light crosstalk between the quantum dot layers.

[0049] In some embodiments, the first quantum dot solution is lipophilic. The solvent of the first quantum dot solution can be n-octane or toluene. The ligand of the first quantum dot is a lipophilic ligand, such as oleic acid. In some embodiments, the first quantum dot solution, the second quantum dot solution, and the third quantum dot solution are all lipophilic.

[0050] In some embodiments, the second and third quantum dot solutions are lipophilic. Each (first, second, third) quantum dot solution includes quantum dots and one or more solvents, additives, etc., which facilitates the uniform arrangement of the quantum dot solutions. The solvent of the second and third quantum dot solutions can be n-octane or toluene.

[0051] According to a second aspect of the present disclosure, a display panel is provided, the display panel comprising a quantum dot light-emitting device prepared by any of the above methods, and the display panel has excellent lifespan and light-emitting efficiency.

[0052] Hereinafter, the embodiments are described in more detail with reference to specific examples. However, they are illustrative examples of the present disclosure, and the present disclosure is not limited thereto.

[0053] Examples 1 to 3

[0054]

Preparation of Monochrome Photolithography Light-Emitting Devices

[0055] (1) The anode ITO (indium tin oxide) with a thickness of 180 nm was cleaned by ultrasonic cleaning with ethanol, deionized water and acetone for 10 minutes respectively, and then the liquid attached to the ITO surface was blown dry with N2, and then treated with oxygen plasma for 10 minutes to remove impurities on the ITO surface, thereby obtaining a clean ITO transparent conductive glass.

[0056] (2) Preparation of hole injection layer and hole transport layer: In an air environment, PEDOT:PSS (poly(p-styrene sulfonic acid solution)) was spin-coated on a clean ITO transparent conductive glass at a speed of 4000 rpm for 50 seconds. After the spin coating, the glass was annealed at 150°C in air for 30 minutes. The glass was then transferred to a glove box in a nitrogen environment and annealed at 130°C for 20 minutes to finally form a PEDOT:PSS layer on the ITO surface, i.e., a hole injection layer. Then, a chlorobenzene solution (concentration of 8 mg / mL) of poly((9,9-dioctylfluorene-2,7-diyl)-co(4,4'-(N-(4-sec-butylphenyl)diphenylamine))(TFB)) was spin-coated on the PEDOT:PSS layer at a speed of 2000 rpm for 45 seconds. After the spin coating, the glass was annealed at 150°C in a glove box for 30 minutes to form a TFB hole transport layer.

[0057] (3) Preparation of positive photoresist layer: Spin-coat a positive photoresist (naphthoquinone diazide) on the hole transport layer at a rotation speed of 1000 rpm for 45 s.

[0058] (4) Exposure and development: Use a mask, ultraviolet exposure, and then use a developer (2.38% TMAH) to wash away the photoresist in the exposed area.

[0059] (5) Preparation of light-emitting layer: Spin-coat red quantum dot ink (quantum dots are CdSe / CdS, emission wavelength is 620nm-630nm, solvent is n-octane, concentration is 20mg / mL) on the photoresist film layer, the rotation speed is 2000 rpm, and the spin coating time is 45s. (6) Exposure and development 2: Use mask 2, ultraviolet exposure, and then use developer (2.38% TMAH) to wash away the photoresist in the exposed area. The quantum dots in the exposed area are washed away as the photoresist dissolves.

[0060] (7) Preparation of zinc oxide nanocrystalline film: spin coating a zinc oxide nanocrystalline solution on the light-emitting layer at a speed of 2500 rpm for 50 s. After spin coating, annealing was performed at 120°C in a glove box for 30 min to finally form a zinc oxide nanocrystalline film on the surface of the light-emitting layer.

[0061] (8) Electrode preparation: The device obtained in step (7) is placed in a vacuum deposition chamber and a cathode silver electrode is deposited to a thickness of 100 nm.

[0062] The obtained microscope photos of the red quantum dot light-emitting device, green quantum dot light-emitting device and blue quantum dot light-emitting device are shown in Figure 4 .

[0063] Example 4

[0064]

Preparation of three-color photolithography light-emitting devices

[0065] (1) Preparation of a positive photoresist layer: Spin-coat a positive photoresist (naphthoquinone diazide) on the prepared single-color photolithography QD film layer (reference example 1) at a rotation speed of 1000 rpm for 45 s.

[0066] (2) Exposure and development 1: Use mask 1, ultraviolet exposure, and then use developer (2.38% TMAH) to wash away the photoresist in the exposed area.

[0067] (3) Preparation of light-emitting layer: spin-coat green quantum dot ink (quantum dots are CdZnS / ZnS, emission wavelength is 520nm-530nm, solvent is n-octane, concentration is 20mg / mL) on the photoresist film layer at a rotation speed of 2000 rpm and a spin coating time of 45s.

[0068] (4) Exposure and development 2: Use mask 2, UV exposure, and then use developer (2.38% TMAH) to wash away the photoresist in the exposed area. The quantum dots in the exposed area are washed away as the photoresist dissolves.

[0069] (5) Preparation of positive photoresist layer: Continue to spin-coat the positive photoresist (naphthoquinone diazide) at a speed of 1000 rpm and a spin-coating time of 45 s.

[0070] (6) Exposure and development 3: Use mask 3, ultraviolet exposure, and then use developer (2.38% TMAH) to wash away the photoresist in the exposed area.

[0071] (7) Preparation of light-emitting layer: spin-coat blue quantum dot ink (quantum dots are CdZnS / ZnSeS, emission wavelength is 460 nm to 470 nm, solvent is n-octane, concentration is 20 mg / mL) on the hole transport layer at a rotation speed of 2000 rpm and a spin coating time of 45 s.

[0072] (8) Exposure and development 4: Use mask 4, UV exposure, and then use developer (2.38% TMAH) to wash away the photoresist in the exposed area. The quantum dots in the exposed area are washed away as the photoresist dissolves.

[0073] (9) Preparation of zinc oxide nanocrystalline film: Spin coating a zinc oxide nanocrystalline solution on the light-emitting layer at a speed of 2500 rpm for 50 s. After spin coating, annealing was performed at 120°C in a glove box for 30 min to finally form a zinc oxide nanocrystalline film on the surface of the light-emitting layer.

[0074] (10) Electrode preparation: The device obtained in step (9) is placed in a vacuum deposition chamber, and a cathode silver electrode is deposited with a thickness of 100 nm.

[0075] The microscope photo of the obtained red, green and blue quantum dot light-emitting device can be found in Figure 5 .

[0076] Comparative Examples 1 to 3:

[0077]

Preparation of Monochromatic Light-Emitting Devices

[0078] (1) The anode ITO (indium tin oxide) with a thickness of 180 nm was cleaned by ultrasonic cleaning with ethanol, deionized water and acetone for 10 minutes respectively, and then the liquid attached to the ITO surface was blown dry with N2, and then treated with oxygen plasma for 10 minutes to remove impurities on the ITO surface, thereby obtaining a clean ITO transparent conductive glass.

[0079] (2) Preparation of hole injection layer and hole transport layer: In an air environment, PEDOT:PSS (poly(p-styrene sulfonic acid solution)) was spin-coated on a clean ITO transparent conductive glass at a speed of 4000 rpm for 50 seconds. After the spin coating, the glass was annealed at 150°C in air for 30 minutes. The glass was then transferred to a glove box in a nitrogen environment and annealed at 130°C for 20 minutes to finally form a PEDOT:PSS layer on the ITO surface, i.e., a hole injection layer. Then, a chlorobenzene solution (concentration of 8 mg / mL) of poly((9,9-dioctylfluorene-2,7-diyl)-co(4,4'-(N-(4-sec-butylphenyl)diphenylamine))(TFB)) was spin-coated on the PEDOT:PSS layer at a speed of 2000 rpm for 45 seconds. After the spin coating, the glass was annealed at 150°C in a glove box for 30 minutes to form a TFB hole transport layer.

[0080] (3) Preparation of light-emitting layer: Spin-coat red quantum dot ink (quantum dots are CdSe / CdS, emission wavelength is 620 nm to 630 nm, solvent is n-octane, concentration is 20 mg / mL) on the hole transport layer at a rotation speed of 2000 rpm and a spin coating time of 45 s.

[0081] (4) Preparation of zinc oxide nanocrystalline film: Spin coating a zinc oxide nanocrystalline solution on the light-emitting layer at a speed of 2500 rpm for 50 s. After spin coating, annealing was performed at 120° C. for 30 min in a glove box to finally form a zinc oxide nanocrystalline film on the surface of the light-emitting layer.

[0082] (5) Electrode preparation: The device obtained in step (4) is placed in a vacuum deposition chamber, and a cathode silver electrode is deposited to a thickness of 100 nm.

[0083] Monochrome green and monochrome blue QLED devices can simply replace the above-mentioned red quantum dots with green or blue quantum dots.

[0084] Comparative Examples 4 to 6:

[0085]

Preparation of monochromatic ligand photocrosslinking lithography light-emitting devices

[0086] (1) The anode ITO (indium tin oxide) with a thickness of 180 nm was cleaned by ultrasonic cleaning with ethanol, deionized water and acetone for 10 minutes respectively, and then the liquid attached to the ITO surface was blown dry with N2, and then treated with oxygen plasma for 10 minutes to remove impurities on the ITO surface, thereby obtaining a clean ITO transparent conductive glass.

[0087] (2) Preparation of hole injection layer and hole transport layer: In an air environment, PEDOT:PSS (poly(p-styrene sulfonic acid solution)) was spin-coated on a clean ITO transparent conductive glass at a speed of 4000 rpm for 50 seconds. After the spin coating, the glass was annealed at 150°C in air for 30 minutes. The glass was then transferred to a glove box in a nitrogen environment and annealed at 130°C for 20 minutes to finally form a PEDOT:PSS layer on the ITO surface, i.e., a hole injection layer. Then, a chlorobenzene solution (concentration of 8 mg / mL) of poly((9,9-dioctylfluorene-2,7-diyl)-co(4,4'-(N-(4-sec-butylphenyl)diphenylamine))(TFB)) was spin-coated on the PEDOT:PSS layer at a speed of 2000 rpm for 45 seconds. After the spin coating, the glass was annealed at 150°C in a glove box for 30 minutes to form a TFB hole transport layer.

[0088] (3) Preparation of light-emitting layer: Spin-coat red quantum dot ink (quantum dots are CdSe / CdS, ligand is oleic acid, emission wavelength is 620nm-630nm, photoinitiator is (azide organic material), solvent is n-octane, concentration is 20mg / mL) on the hole transport layer at a rotation speed of 2000 rpm and a spin coating time of 45s.

[0089] (4) Exposure and development: Use a mask, ultraviolet exposure, and then use an organic solvent n-octane to wash away the quantum dot material in the non-exposed area.

[0090] (5) Preparation of zinc oxide nanocrystalline film: Spin coating a zinc oxide nanocrystalline solution on the light-emitting layer at a speed of 2500 rpm for 50 s. After spin coating, annealing was performed at 120° C. for 30 min in a glove box to finally form a zinc oxide nanocrystalline film on the surface of the light-emitting layer.

[0091] (6) Electrode preparation: The device obtained in step (5) is placed in a vacuum deposition chamber and a cathode silver electrode is deposited to a thickness of 100 nm.

[0092] Monochrome green and monochrome blue QLED devices can simply replace the above-mentioned red quantum dots with green or blue quantum dots.

[0093] Unless otherwise specified, the embodiments and comparative examples use the same materials or processes for ease of comparison.

[0094] The following tests were performed on each QLED device: the current density-voltage curve of the quantum dot light-emitting device was measured using Keithley 2400, and the brightness of the quantum dot light-emitting device was measured using an integrating sphere (FOIS-1) combined with an Ocean Optics spectrometer (QE-pro). The external quantum efficiency of the quantum dot light-emitting device was calculated based on the measured current density and brightness, and the results are recorded in Table 1. The external quantum efficiency represents the ratio between the number of photons emitted by the light-emitting device and the number of electrons injected into the device in the observation direction, and is an important parameter for characterizing the luminous efficiency of the light-emitting device. The higher the external quantum efficiency, the higher the luminous efficiency of the device.

[0095] Table 1

[0096]

[0097]

[0098] As can be seen from Table 1, the performance of QLED devices using photolithography is not as good as that of devices using non-photolithography (Comparative Examples 1-3), and the performance of devices using the embodiments is much higher than that of devices using traditional photolithography (Comparative Examples 4-6). Comparative Examples 4-6 use n-octane for elution. In order to cope with the elution solvent in mass production, it is necessary to design additional flameproof and explosion-proof equipment and organic solvent recovery devices, which makes mass production difficult and costly.

[0099] The above description is only a preferred embodiment of the present disclosure and is not intended to limit the present disclosure. For those skilled in the art, the present disclosure may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present disclosure shall be included in the protection scope of the present disclosure.

Claims

1. A method for preparing a quantum dot light-emitting device, characterized in that: The preparation method comprises: providing a substrate having a first electrode layer, and arranging a positive photoresist on the substrate; arranging a first mask plate above the substrate, performing exposure treatment and then developing to obtain a positive photoresist solidified layer having a first pit, wherein the position of the first pit corresponds to the through hole of the first mask plate; arranging a first quantum dot solution on the positive photoresist solidified layer having the first pit, wherein part of the first quantum dot solution is located in the first pit, and another part of the first quantum dot solution is located on the surface of the positive photoresist solidified layer away from the substrate; allowing the solvent in the first quantum dot solution to dry to obtain a first quantum dot layer; arranging a second mask plate above the substrate, wherein the second mask plate is opaque at the first pit, and the positive photoresist solidified layer is eluted after receiving the exposure treatment, and the first quantum dot layer located on the surface of the positive photoresist solidified layer away from the substrate is eluted along with the elution of the positive photoresist solidified layer, to obtain a first quantum dot light-emitting device, wherein the first quantum dot layer is located at the position of the first pit.

2. The preparation method according to claim 1, characterized in that: The preparation method also includes: arranging a positive photoresist on the first quantum dot light-emitting device; arranging a third mask plate above the substrate, performing exposure treatment and then developing to obtain a positive photoresist cured layer having a second pit, wherein the position of the second pit corresponds to the through hole of the third mask plate; arranging a second quantum dot solution on the positive photoresist cured layer having the second pit, wherein part of the second quantum dot solution is located in the second pit, and another part of the second quantum dot solution is located on the surface of the positive photoresist cured layer away from the substrate; allowing the solvent in the second quantum dot solution to dry to obtain a second quantum dot layer; arranging a fourth mask plate above the substrate, wherein the fourth mask plate is opaque at the second pit, the positive photoresist cured layer is eluted after exposure treatment, and the second quantum dot layer located on the surface of the positive photoresist cured layer away from the substrate is eluted along with the elution of the positive photoresist cured layer, thereby obtaining a second quantum dot light-emitting device, wherein the first pit has the first quantum dot layer at the position, and the second pit has the second quantum dot layer at the position.

3. The preparation method according to claim 2, characterized in that: The preparation method also includes: arranging a positive photoresist on the second quantum dot light-emitting device; arranging a fifth mask plate above the substrate, performing exposure treatment and then developing to obtain a positive photoresist cured layer having a third pit, wherein the position of the third pit corresponds to the through hole of the fifth mask plate; arranging a third quantum dot solution on the positive photoresist cured layer having the third pit, wherein part of the third quantum dot solution is located in the third pit and another part of the third quantum dot solution is located on the surface of the positive photoresist cured layer away from the substrate; and making the third quantum dot solution The solvent in the liquid is dried to obtain a third quantum dot layer; a sixth mask is set above the substrate, the sixth mask is opaque at the third pit, the positive photoresist cured layer is eluted after exposure treatment, and the third quantum dot layer located on the surface of the positive photoresist cured layer away from the substrate is eluted along with the elution of the positive photoresist cured layer, to obtain a third quantum dot light-emitting device, wherein the first pit has a first quantum dot layer, the second pit has a second quantum dot layer, and the third pit has a third quantum dot layer.

4. The preparation method according to claim 1, characterized in that: The drying method is heating drying, or the method of setting the first quantum dot solution is a spin coating process and natural drying is carried out during the spin coating process.

5. The preparation method according to claim 1, characterized in that: The positive photoresist is selected from naphthoquinone diazide or polymethyl methacrylate.

6. The preparation method according to claim 1, characterized in that: The developer used in the development is a TMAH aqueous solution or a KOH aqueous solution.

7. The preparation method according to claim 3, characterized in that: The preparation method further comprises: arranging one or more layers of a functional layer and a second electrode layer on each quantum dot light-emitting layer of the third quantum dot light-emitting device.

8. The preparation method according to claim 3, characterized in that: The spacing between the various quantum dot layers is 1-5 microns.

9. The preparation method according to claim 1, characterized in that: The first quantum dot solution is lipophilic.

10. A display panel, characterized in that: The display panel comprises a quantum dot light-emitting device prepared by any one of the preparation methods described in claims 1 to 9.

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