A color-adjustable, non-injection multilayer quantum dot AC-QLED and its preparation method

Abstract

The present invention provides a color-adjustable, non-injection-type multi-layer quantum dot AC‑QLED and a preparation method thereof. The color-adjustable, non-injection-type multi-layer quantum dot AC‑QLED comprises: a transparent substrate and an insulating layer, a hole generation layer, a multi-layer quantum dot film body, an electron generation layer, an insulating layer and an electrode sequentially located on the surface of one side of the transparent substrate; wherein the multi-layer quantum dot film body is formed by stacking quantum dot film layers with different colors; the non-injection-type multi-layer quantum dot AC‑QLED achieves color adjustment by controlling the voltage and frequency of an alternating current electric field. Based on the traditional AC‑QLED structure, the present invention adds an electron generation layer and a hole generation layer in the middle of the insulating layer of the AC‑QLED. Driven by the alternating current electric field, carriers are generated from the electron generation layer and the hole generation layer and injected into the quantum dot film layer to recombine and emit light. Compared with traditional AC‑QLEDs, the carrier concentration in the AC‑QLED device provided by the present invention is greatly improved, so the luminous efficiency of the device is significantly improved.

Description

Technical Field

[0001] The present invention relates to the field of display lighting technology, and in particular to a color-adjustable, non-injection multi-layer quantum dot AC-QLED and a preparation method thereof. Background Art

[0002] To meet the demand for higher color saturation in display products and accommodate advanced industrial production methods like inkjet printing and transfer printing, quantum dot (QD) materials and QLED (quantum dot light-emitting diode) technology have been extensively researched in academia and the display industry in recent years. Compared to other types of electroluminescent devices, QLEDs offer advantages such as tunable emission wavelength, narrow half-height width, high quantum efficiency, and high color purity.

[0003] Traditional QLEDs generate electroluminescence under a DC driving voltage, meaning that external electrodes continuously inject electrons and holes into the QD layer, generating radiation. However, high DC current densities can easily lead to charge accumulation within the QLED, damaging the functional layers and ultimately shortening the device's lifespan and luminous efficiency. Furthermore, DC-type QLEDs require an additional converter and rectifier to convert AC power to DC, which increases power loss, reduces device integration, and increases product processing costs. Altering current QLEDs (AC-QLEDs) offer the potential to address these issues. This is because the driving signal for AC-QLEDs is an alternating signal. Under the alternating electric field, electrons and holes within the device continuously recombine, emit light, and then separate, preventing the long-term accumulation of charge in a single area. This is expected to improve device lifespan and luminous efficiency. Furthermore, AC-QLEDs can be driven directly by AC power, eliminating the need for an integrated AC converter and rectifier, reducing product costs.

[0004] A non-injection light-emitting device is a quantum dot light-emitting device that does not inject external carriers into the device. It relies on the periodic oscillation of the inherent carriers in the material to achieve periodic light output. Non-injection AC-QLEDs usually use an insulating layer between the electrode and the functional material layer to block the injection of external electrons and holes. Under the protection of the insulating layer, the non-injection AC-QLED can be used stably in the air, which not only saves the time and cost required to package the device, but also simplifies the structure of the device again. However, since there is no external carrier injection, the periodic light output is achieved only by relying on the periodic oscillation of the inherent carriers in the material, which makes the carrier concentration inside the AC-QLED low and the device luminous efficiency low. Summary of the Invention

[0005] To address the above-mentioned problems in the prior art, the present invention provides a color-adjustable, non-injection, multi-layer quantum dot AC-QLED and a method for preparing the same. The specific invention contents are as follows:

[0006] In a first aspect, the present invention provides a color-adjustable, non-injection, multi-layer quantum dot AC-QLED, comprising:

[0007] A transparent substrate and an insulating layer, a hole generating layer, a multi-layer quantum dot thin film, an electron generating layer, an insulating layer and an electrode sequentially located on a surface of one side of the transparent substrate;

[0008] Wherein, the multi-layer quantum dot film body is formed by stacking quantum dot film layers with different colors;

[0009] The non-injection multi-layer quantum dot AC-QLED achieves color adjustment by controlling the voltage and frequency of the alternating current electric field.

[0010] In a second aspect, the present invention provides a method for preparing the color-adjustable, non-injection, multi-layer quantum dot AC-QLED described in the first aspect, the preparation method comprising the following steps:

[0011] S1. Spin coating an insulating material and a hole generating layer on a cleaned transparent substrate in sequence;

[0012] S2. Dropping a quantum dot solution onto the surface of solvent B and allowing the solution to stand until solvent A in the solution evaporates, thereby obtaining a quantum dot film layer on the surface of solvent B; the quantum dot solution is obtained by dissolving quantum dot material in solvent A;

[0013] S3, transferring the quantum dot film layer from the surface of solvent B to the transparent substrate subjected to step S1 to obtain a quantum dot film;

[0014] S4, repeatedly performing steps S2 and S3 to obtain a multilayer quantum dot film;

[0015] S5. Further preparing an electron generation layer, an insulating layer, and electrodes on the multilayer quantum dot film to obtain a color-adjustable non-injection multilayer quantum dot AC-QLED;

[0016] The surface tension of the solvent A is smaller than the surface tension of the solvent B, and the quantum dot material is insoluble in the solvent B.

[0017] Optionally, in step S2, the quantum dot material is a pure quantum dot material or a mixed material of a pure quantum dot material and an organic material, the solvent A is a mixed solvent of octane and chlorobenzene, and the mass ratio of octane to chlorobenzene is 1:1;

[0018] The solvent B is water.

[0019] Optionally, in step S3, the transferring includes: transferring the quantum dot film on the surface of the solvent B to the hole generating layer of the transparent substrate by means of intermolecular forces between the transparent substrate and the quantum dot film layer.

[0020] Optionally, in step S3, after the quantum dot film layer is transferred from the surface of solvent B to the transparent substrate on which step S1 has been performed, the method further comprises: performing an annealing treatment at 100°C for 5 minutes.

[0021] Optionally, in step S4, repeatedly performing steps S2 and S3 includes:

[0022] Select the same quantum dot solution and repeat steps S2 and S3 to thicken the quantum dot film layer; or select different quantum dot solutions and repeat steps S2 and S3 to add different types of quantum dot film layers.

[0023] Optionally, step S5 includes: spin-coating an electron generation layer and an insulating layer in sequence on the multi-layer quantum dot film, and evaporating an electrode to obtain a color-adjustable multi-layer quantum dot AC-QLED.

[0024] Optionally, the transparent substrate is a hard substrate or a flexible substrate;

[0025] The hard substrate is glass, silicon dioxide or quartz;

[0026] The flexible substrate is polyethylene terephthalate, polyethylene naphthalate or polyimide.

[0027] Optionally, the pure quantum dot material is cadmium-based quantum dots or other quantum dot materials insoluble in solvent B;

[0028] The organic material is TPBI, PFN, MEH-PPV, TmPyPb or PMMA.

[0029] Optionally, in step S1, the cleaning process includes:

[0030] S11, ultrasonically cleaning the transparent substrate using an ultrasonic cleaning apparatus containing a washing solution, deionized water, and anhydrous ethanol to remove organic matter and dust on the transparent substrate;

[0031] S12, performing nitrogen drying on the transparent substrate after ultrasonic cleaning to remove residual organic solvent and dust on the transparent substrate.

[0032] Compared with the prior art, the present invention has the following advantages:

[0033] (1) The color-adjustable, non-injection, multi-layer quantum dot AC-QLED provided by the present invention builds upon the conventional AC-QLED structure by adding an electron generation layer and a hole generation layer between the insulating layers of the AC-QLED. Driven by an alternating electric field, carriers are generated from the electron generation layer and the hole generation layer and injected into the quantum dot film layer, where they recombine to emit light. Compared to conventional AC-QLEDs, the carrier concentration within the AC-QLED device provided by the present invention is significantly increased, significantly improving the device's luminous efficiency.

[0034] (2) The color-adjustable non-injection multilayer quantum dot AC-QLED provided by the present invention is prepared by adding a multilayer quantum dot film with different colors to the non-injection AC-QLED. The color of the device can be adjusted by controlling the voltage and frequency of the AC electric field (e.g. Figure 3 、 4 As shown in the figure, it effectively simplifies the structure of the color QLED panel, which is of great significance for improving the resolution of current QLED devices and simplifying the device structure.

[0035] (3) In the preparation method provided by the present invention, the preparation of a multilayer quantum dot film is achieved by means of the Marangoni effect. The present invention uses a low surface tension solvent to dissolve the quantum dot material to obtain a quantum dot solution, and then drips it onto the surface of a solvent with high surface tension. Since the two solvents have obvious differences in solubility, volatility and surface tension, after the low surface tension solvent evaporates, the quantum dot material forms a film on the surface of the high surface tension solvent. The quantum dot film is transferred by imprinting (dipping) with a substrate to prepare a dry quantum dot film. In addition, the quantum dot material selected when preparing each layer of quantum dot film is not unique. The film thickness (changing the number of repetitions in step S4) and the type of quantum dots (changing the quantum dot material selected when preparing the quantum dot film each time) can be flexibly adjusted according to actual needs to achieve effective control of the thickness and type of the quantum dot film. The obtained multilayer quantum dot film has few interface defect states, excellent morphology, good thermal stability, is suitable for mechanical processing, and is particularly suitable for the production of large-scale QLED devices, which greatly reduces the preparation cost of color AC-QLED and facilitates large-scale production. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without any creative work.

[0037] Figure 1 A schematic structural diagram of a color-adjustable, non-injection multi-layer quantum dot AC-QLED provided by an embodiment of the present invention is shown;

[0038] Figure 2 A flow chart showing a method for preparing a color-adjustable, non-injection multi-layer quantum dot AC-QLED provided by an embodiment of the present invention is shown;

[0039] Figure 3 The relative spectrum of the color-adjustable, non-injection multi-layer quantum dot AC-QLED provided by an embodiment of the present invention as the AC voltage changes is shown;

[0040] Figure 4 The relative spectrum of the color-adjustable, non-injection multi-layer quantum dot AC-QLED provided by an embodiment of the present invention as the AC electric field frequency changes is shown;

[0041] Figure 5 The relative spectra of the color-adjustable non-injection multi-layer quantum dot AC-QLED provided by an embodiment of the present invention and the traditional non-injection red light AC-QLED as the AC voltage changes are shown. DETAILED DESCRIPTION

[0042] The following examples are provided for a better understanding of the present invention and are not intended to limit the best mode of implementation. They do not limit the content and scope of protection of the present invention. Any product identical or similar to the present invention obtained by anyone under the guidance of the present invention or by combining the features of the present invention with other prior arts shall fall within the scope of protection of the present invention.

[0043] If no specific experimental steps or conditions are specified in the examples, the experiments can be carried out according to the conventional experimental steps or conditions described in the prior art. The reagents and other instruments used, if the manufacturers are not specified, are all commercially available conventional reagents.

[0044] In view of the fact that an insulating layer is added between the electrode and the functional material layer of the traditional non-injection AC-QLED, an insulating layer is directly added on both sides of the DC device or quantum dot layer to block the injection of external electrons and holes. This makes the carrier concentration inside the AC-QLED low and the luminous efficiency of the device low. For this reason, the inventor proposed the idea of adding a double generation layer (hole generation layer and electron generation layer) structure in the middle of the insulating layer of the traditional non-injection AC-QLED structure, which greatly improves the luminous efficiency of the non-injection AC-QLED device. In addition, the quantum dot film body of the non-injection AC-QLED provided by the present invention contains quantum dot film layers of different colors, and the color emitted by the device can be adjusted by adjusting the voltage and frequency. The non-injection AC-QLED provided by the present invention has the characteristics of adjustable color, excellent performance and simple structure, which helps to achieve ultra-high resolution display and is of great significance to improving the resolution of current QLED devices and simplifying the device structure. Based on the above technical concept, the specific implementation content of the present invention is as follows:

[0045] In a first aspect, the present invention provides a color-adjustable, non-injection multi-layer quantum dot AC-QLED. Figure 1 FIG. 4 shows a schematic structural diagram of a color-adjustable, non-injection multi-layer quantum dot AC-QLED according to an embodiment of the present invention. Figure 1 As shown, the color-adjustable non-injection multilayer quantum dot AC-QLED includes: a transparent substrate 1 and an insulating layer 2, a hole generating layer 3, a multilayer quantum dot film 4, an electron generating layer 5, an insulating layer 2 and an electrode 6 sequentially located on one side surface of the transparent substrate 1;

[0046] Wherein, the multi-layer quantum dot film body is formed by stacking quantum dot film layers with different colors;

[0047] The non-injection multi-layer quantum dot AC-QLED achieves color adjustment by controlling the voltage and frequency of the alternating current electric field.

[0048] In practice, the color-adjustable, non-injection, multi-layer quantum dot AC-QLED provided by the present invention builds upon the traditional non-injection AC-QLED structure (specifically comprising an insulating layer, a multi-layer quantum dot film, an insulating layer, and electrodes) by further adding an electron generation layer and a hole generation layer to both sides of the multi-layer quantum dot film. Due to the characteristics of AC-QLEDs, under the drive of an alternating current electric field, carriers are generated from the electron generation layer and the hole generation layer and injected into the quantum dot film layer to produce composite light. Compared to traditional AC-QLEDs, the non-injection AC-QLED device provided by the present invention has a significantly increased carrier concentration, significantly improving the device's luminous efficiency. In addition, the multi-layer quantum dot film in the color-adjustable non-injection multi-layer quantum dot AC-QLED provided by the present invention is formed by stacking quantum dot film layers with different colors. By adjusting the voltage and frequency of the alternating current electric field, the recombination area where carriers recombine in the multi-layer quantum dot film can be adjusted, thereby regulating the color emitted by the device, greatly simplifying the device structure of the full-color QLED panel and reducing the wiring within the panel, which is helpful to achieve ultra-high-resolution display and is of great significance to improving the resolution of current QLED devices and simplifying the device structure.

[0049] In a second aspect, the present invention provides a method for preparing a color-adjustable non-injection multi-layer quantum dot AC-QLED. Figure 2 The flowchart of the preparation method of the color-adjustable non-injection multi-layer quantum dot AC-QLED provided by the embodiment of the present invention is shown as follows Figure 2 As shown, the preparation method comprises the following steps:

[0050] S1. Spin-coating an insulating material and a hole generating layer sequentially on the cleaned transparent substrate.

[0051] In some embodiments, the transparent substrate is a hard substrate or a flexible substrate; the hard substrate may be glass, silicon dioxide, or quartz; the flexible substrate may be polyethylene terephthalate, polyethylene naphthalate, or polyimide, and the cleaning process for the substrate comprises the following steps:

[0052] S11, ultrasonically cleaning the transparent substrate using an ultrasonic cleaning apparatus containing a washing solution, deionized water, and anhydrous ethanol to remove organic matter and dust on the transparent substrate;

[0053] S12, performing nitrogen drying on the transparent substrate after ultrasonic cleaning to remove residual organic solvent and dust on the transparent substrate.

[0054] In specific implementation, cleaning the transparent substrate through the above steps can effectively remove organic matter, impurities, etc. on the surface of the substrate, and spin-coating the insulating material and the hole generating layer on the transparent substrate can effectively form a hydrophobic layer, which is conducive to imprinting the quantum dot film onto the substrate to form a uniform quantum dot film.

[0055] S2. Dropping a quantum dot solution onto the surface of solvent B and allowing the solution to stand until solvent A in the solution evaporates, thereby forming a quantum dot film on the surface of solvent B. The quantum dot solution is obtained by dissolving a quantum dot material in solvent A. The surface tension of solvent A is less than that of solvent B, and the quantum dot material is insoluble in solvent B.

[0056] In specific implementations, solvents A and B have different solubilities, with the quantum dot material soluble in solvent A but not in solvent B. Solvents A and B have different surface tensions, with solvent A having a lower surface tension than solvent B. Furthermore, solvents A and B have different volatility, with solvent A being more volatile and solvent B being less volatile. This list of all possible implementations is not exhaustive. Therefore, any obvious changes or modifications arising from the technical solutions of the present invention should fall within the scope of protection of the present invention.

[0057] In some embodiments, the quantum dot material is a pure quantum dot material or a mixture of a pure quantum dot material and an organic material, solvent A can be a mixed solvent of octane and chlorobenzene, wherein the mass ratio of octane to chlorobenzene is 1:1, and solvent B can be water.

[0058] In some embodiments, the pure quantum dot material may be cadmium-based quantum dots or other quantum dot materials insoluble in solvent B, and the organic material may be TPBI, PFN, MEH-PPV, TmPyPb, or PMMA.

[0059] S3. Transferring the quantum dot film layer from the surface of solvent B to the transparent substrate on which step S1 has been performed to obtain a quantum dot thin film.

[0060] In specific implementation, the embodiment of the present invention utilizes the Marangoni effect when preparing quantum dot films. That is, when a solution with low surface tension is dropped into a medium with high surface tension, a local surface tension gradient will appear between the materials, causing the surface of the solution to flow toward the higher surface tension. By utilizing two solvents with significantly different solubility, volatility, and surface tension, after the upper layer of low surface tension solvent evaporates, the quantum dot material can form a film on the lower layer of high surface tension solvent, and will not be affected by the lower layer of solvent and will remain in the film-forming state.

[0061] In some embodiments, the specific operation of transferring includes: transferring the quantum dot film on the surface of solvent B to the hole generating layer of the transparent substrate by imprinting the quantum dot film on the surface of solvent B using the intermolecular force between the transparent substrate and the quantum dot film layer.

[0062] In practice, the preparation method provided by the present invention utilizes a substrate to dip the quantum dot film. The bonding force between the substrate and the film is greater than the intermolecular forces between the film and the underlying high-surface-tension solvent. Therefore, a simple dipping operation using a transparent substrate can effectively transfer the quantum dot film to the substrate.

[0063] In some embodiments, after the quantum dot film layer is transferred from the surface of solvent B to the transparent substrate after performing step S1, further annealing treatment is required. The specific operation includes: annealing the transparent substrate after the film layer is transferred at 100°C for 5 minutes to obtain a pure and dry quantum dot film.

[0064] S4. Repeat steps S2 and S3 multiple times to obtain a multilayer quantum dot thin film.

[0065] During specific implementation, the embodiment of the present invention repeats steps S2 and S3 to achieve free adjustment of the thickness of the quantum dot film according to actual use requirements. Moreover, each time steps S2 and S3 are repeated, the type of each layer of quantum dot film prepared is not unique, and quantum dot materials of different colors can be transferred as needed. Repeating steps S2 and S3 multiple times specifically includes: selecting the same quantum dot solution to repeat steps S2 and S3 to thicken the quantum dot film layer; or selecting different quantum dot solutions to repeat steps S2 and S3 to add different types of quantum dot film layers. The quantum dot device (multi-layer quantum dot film body) prepared by this method can realize color control with a single device, which greatly simplifies the preparation process of the color QLED panel and the device structure of the full-color QLED panel, and reduces the wiring within the panel, which helps to achieve ultra-high-resolution display, and is of great significance to improving the resolution of current QLED devices and simplifying the device structure.

[0066] When the embodiment of the present invention adopts the imprint transfer method to prepare the film, the film thickness (just change the number of repetitions in step S4), the type of quantum dots (just change the quantum dot material selected each time the quantum dot film is repeatedly prepared) and other factors can be flexibly adjusted according to actual needs to achieve effective regulation of the thickness and type of the quantum dot film. It effectively avoids the problem of mutual dissolution of solvents between quantum dot film layers during the preparation of existing multi-layer quantum dot films, which causes the quantum dot film of the upper layer to be washed away, damages the upper quantum dot film, and leads to poor device performance. The multi-layer quantum dot film obtained by this preparation method has few interface defect states, excellent morphology, and good thermal stability, is suitable for mechanical processing, and is particularly suitable for the production of large-size QLED devices, which greatly reduces the preparation cost of color AC-QLED and is conducive to large-scale production and large-scale production.

[0067] S5. Further prepare an electron generation layer, an insulating layer and an electrode on the multi-layer quantum dot film to obtain a color-adjustable non-injection multi-layer quantum dot AC-QLED.

[0068] In some embodiments, the specific operation of further preparing an electron generation layer, an insulating layer, and an electrode on the multilayer quantum dot film may be: spin coating the electron generation layer and the insulating layer on the multilayer quantum dot film in sequence, and evaporating the electrode.

[0069] In specific implementation, after transferring the quantum dot film multiple times, an electron generation layer, an insulating layer and an electrode are further prepared on the quantum dot film body, which can effectively protect the quantum dot film and prevent the quantum dot film from directly contacting the water and oxygen in the air; in addition, after the AC-QLED is prepared, an alternating electric field is applied to the electrode to make the electron-hole generation layer in the device generate an induced current, thereby allowing the carriers to enter the quantum dot film layer and recombine to emit light.

[0070] In order to enable those skilled in the art to understand the present application more clearly, the color-adjustable non-injection multi-layer quantum dot AC-QLED and its preparation method described in the present application are now described in detail through the following examples.

[0071] Example 1

[0072] The preparation method of non-injection multilayer quantum dot AC-QLED is as follows:

[0073] Step 1: Soak the transparent substrate 1 in a washing solution, deionized water, and anhydrous ethanol, respectively, and clean it with an ultrasonic cleaner. Finally, blow it dry with nitrogen to remove organic matter and dust on the surface of the substrate. Then, spin-coat an insulating layer and a hole generation layer on the transparent substrate. The transparent substrate 1 can be a hard substrate or a flexible substrate. The hard substrate can be glass, silicon dioxide, or quartz, and the flexible substrate can be polyethylene terephthalate, polyethylene naphthalate, or polyimide.

[0074] Step 2: Dropping the quantum dot solution onto the water surface, the quantum dot solution spontaneously diffuses into a liquid film on the water surface. Then, the dried single-layer quantum dot film is dipped into the transparent substrate 1 after executing step 1, and the quantum dot film is transferred from the water surface to the transparent substrate 1 by intermolecular forces to complete the preparation of the quantum dot film.

[0075] Step 3: Repeat step 2 and transfer the quantum dot film to the transparent substrate 1 after step 2 to obtain a multilayer quantum dot film body 4. Finally, prepare an electron generation layer, an insulating layer and an electrode on the multilayer quantum dot film to prepare a non-injection multilayer quantum dot AC-QLED.

[0076] Example 2

[0077] The preparation method of the color-tunable non-injection multilayer quantum dot AC-QLED is as follows:

[0078] Step 1: The transparent substrate 1 is immersed in a washing solution, deionized water, and anhydrous ethanol, respectively, and cleaned using an ultrasonic cleaner. Finally, it is blown dry with nitrogen gas to remove organic matter and dust on the surface of the substrate. Then, an insulating layer and a hole generation layer are spin-coated on the transparent substrate.

[0079] Step 2: Dissolve the red and blue CdSe / ZnS core-shell quantum dot dispersions at 17.5 mg / ml in a 1:1 mixed solvent of n-octane and chlorobenzene, and mix 4 mg / ml of the organic material PMMA therein, and stir at room temperature for 12 hours; use a pipette to take 20 μl of the blue quantum dot solution, and drop the quantum dot solution into a culture dish with a diameter of 10 cm and a water-covered bottom. The quantum dot solution spontaneously diffuses into a liquid film on the water surface, and is allowed to stand until the solvent evaporates. Then, a vacuum suction cup is used to suck the bottom of the transparent substrate 1, and a dry single-layer quantum dot film is dipped on the front. The quantum dot film is transferred from the water surface to the transparent substrate 1 after step 1 by using intermolecular forces, and then placed on a heating table at 100 degrees Celsius for annealing for 5 minutes; this completes the preparation of the blue quantum dot film.

[0080] Step 3: Replace the quantum dot solution with a red quantum dot solution and repeat step 2. Transfer the red quantum dot film to the transparent substrate 1 after step 2 to obtain a multilayer quantum dot film of different colors. Finally, prepare an electron generation layer and electrodes on the multilayer quantum dot film to prepare a color-tunable, non-injection multilayer quantum dot AC-QLED.

[0081] Figure 3 The relative spectrum of the color-adjustable non-injection multi-layer quantum dot AC-QLED provided by an embodiment of the present invention as the AC voltage changes is shown. Figure 4 The relative spectrum of the color-adjustable non-injection multi-layer quantum dot AC-QLED provided by an embodiment of the present invention as the AC electric field frequency changes; Figure 3 、 Figure 4 As shown, the color-tunable, non-injection, multi-layer quantum dot AC-QLED provided by the present invention gradually increases the proportion of green light as the AC voltage increases. Similarly, the proportion of green light in the device changes as the frequency of the AC field increases. Therefore, the color of the device can be adjusted by varying the voltage and frequency of the AC field.

[0082] Comparative Example

[0083] The preparation method of traditional non-injection red AC-QLED is as follows:

[0084] Step 1: Soak the transparent substrate 1 in washing solution, deionized water, and anhydrous ethanol respectively, clean it with an ultrasonic cleaner, and finally blow it dry with nitrogen to remove organic matter and dust on the surface of the substrate; then spin-coat an insulating layer on the transparent substrate; the transparent substrate 1 can be a hard substrate or a flexible substrate, the hard substrate is glass, silicon dioxide, or quartz, and the flexible substrate is polyethylene terephthalate, polyethylene naphthalate, or polyimide.

[0085] Step 2: Dissolve the red light CdSe / ZnS core-shell quantum dot dispersion in n-octane at 17.5 mg / ml and stir at room temperature for 12 hours; use a pipette to take 70 μl of the red light quantum dot solution, use a spin coater to spin-coat a quantum dot film on the transparent substrate 1 after performing step 1, and then place it on a heating table at 100 degrees Celsius for annealing for 5 minutes; this completes the preparation of the red light quantum dot film.

[0086] Step 3: Prepare an insulating layer and electrodes on the quantum dot film to prepare a traditional non-injection red light AC-QLED.

[0087] Figure 5 The relative spectrum of the color-adjustable non-injection multi-layer quantum dot AC-QLED and the traditional non-injection red light AC-QLED as the AC voltage changes is shown. Figure 5 As shown, the device performance of the color-adjustable non-injection type multi-layer quantum dot AC-QLED provided by the embodiment of the present invention is much higher than that of the traditional non-injection type red light AC-QLED, and can withstand higher voltage.

[0088] The above is a detailed introduction to a color-adjustable, non-injected multi-layer quantum dot AC-QLED and its preparation method provided by the present invention. Specific examples are used herein to illustrate the principles and implementation methods of the present invention. The description of the above embodiments is only used to help understand the method of the present invention and its core idea. At the same time, for those skilled in the art, according to the ideas of the present invention, there will be changes in the specific implementation methods and application scopes. In summary, the content of this specification should not be understood as limiting the present invention.

Claims

1. A color-adjustable, non-injection multi-layer quantum dot AC-QLED, characterized in that: The color-adjustable non-injection multi-layer quantum dot AC-QLED includes: A transparent substrate and an insulating layer, a hole generating layer, a multi-layer quantum dot thin film, an electron generating layer, an insulating layer and an electrode sequentially located on a surface of one side of the transparent substrate; The multi-layer quantum dot film is formed by stacking quantum dot film layers with different colors; the non-injection multi-layer quantum dot AC-QLED achieves color adjustment by controlling the voltage and frequency of the alternating current electric field; The multilayer quantum dot thin film is prepared by the following method: S2. Dropping a quantum dot solution onto the surface of solvent B and allowing the solution to stand until solvent A in the solution evaporates, thereby obtaining a quantum dot film layer on the surface of solvent B; the quantum dot solution is obtained by dissolving quantum dot material in solvent A; S3, transferring the quantum dot film layer from the surface of solvent B to the transparent substrate subjected to step S1 to obtain a quantum dot film, and annealing the film at 100° C. for 5 minutes; S4, repeatedly performing steps S2 and S3 to obtain a multilayer quantum dot film; Repeating steps S2 and S3 multiple times specifically includes: selecting the same quantum dot solution and repeating steps S2 and S3 to thicken the quantum dot film layer; or selecting different quantum dot solutions and repeating steps S2 and S3 to add different types of quantum dot film layers; The transferring comprises: transferring the quantum dot film on the surface of the solvent B to the hole generating layer of the transparent substrate by means of the intermolecular force between the transparent substrate and the quantum dot film layer; The solvent A is a mixed solvent of octane and chlorobenzene, and the mass ratio of the octane to the chlorobenzene is 1:1; the solvent B is water.

2. A method for preparing the color-adjustable, non-injection multi-layer quantum dot AC-QLED according to claim 1, characterized in that: The preparation method comprises the following steps: S1. Spin coating an insulating material and a hole generating layer on a cleaned transparent substrate in sequence; S2. Dropping a quantum dot solution onto the surface of solvent B and allowing the solution to stand until solvent A in the solution evaporates, thereby obtaining a quantum dot film layer on the surface of solvent B; the quantum dot solution is obtained by dissolving quantum dot material in solvent A; S3, transferring the quantum dot film layer from the surface of solvent B to the transparent substrate subjected to step S1 to obtain a quantum dot film, and annealing the film at 100° C. for 5 minutes; S4, repeatedly performing steps S2 and S3 to obtain a multilayer quantum dot film; Repeating steps S2 and S3 multiple times includes: selecting the same quantum dot solution to repeat steps S2 and S3 to thicken the quantum dot film layer; or selecting different quantum dot solutions to repeat steps S2 and S3 to add different types of quantum dot film layers; S5. Further preparing an electron generation layer, an insulating layer, and electrodes on the multilayer quantum dot film to obtain a color-adjustable non-injection multilayer quantum dot AC-QLED; Wherein, the surface tension of the solvent A is less than the surface tension of the solvent B, and the quantum dot material is insoluble in the solvent B; The transferring comprises: transferring the quantum dot film on the surface of the solvent B to the hole generating layer of the transparent substrate by means of the intermolecular force between the transparent substrate and the quantum dot film layer; The solvent A is a mixed solvent of octane and chlorobenzene, and the mass ratio of the octane to the chlorobenzene is 1:1; the solvent B is water.

3. The preparation method according to claim 2, characterized in that In step S2, the quantum dot material is a pure quantum dot material or a mixed material of a pure quantum dot material and an organic material.

4. The preparation method according to claim 2, characterized in that Step S5 includes: spin-coating an electron generation layer and an insulating layer on the multi-layer quantum dot film in sequence, and evaporating an electrode to obtain a color-adjustable multi-layer quantum dot AC-QLED.

5. The preparation method according to any one of claims 2 to 4, characterized in that: The transparent substrate is a hard substrate or a flexible substrate; The hard substrate is glass, silicon dioxide or quartz; The flexible substrate is polyethylene terephthalate, polyethylene naphthalate or polyimide.

6. The preparation method according to any one of claims 3-4, characterized in that The pure quantum dot material is a cadmium-based quantum dot or other quantum dot material insoluble in solvent B; The organic material is TPBI, PFN, MEH-PPV, TmPyPb or PMMA.

7. The preparation method according to any one of claims 2 to 4, characterized in that: In step S1, the cleaning process includes: S11, ultrasonically cleaning the transparent substrate using an ultrasonic cleaning apparatus containing a washing solution, deionized water, and anhydrous ethanol to remove organic matter and dust on the transparent substrate; S12, performing nitrogen drying on the transparent substrate after ultrasonic cleaning to remove residual organic solvent and dust on the transparent substrate.

Images