Flexible miniature ultrathin LED based on quantum dots and preparation method and application thereof

Abstract

The invention relates to the technical field of semiconductor light-emitting devices, and discloses a flexible miniature ultrathin LED based on quantum dots and a preparation method and application thereof, and the flexible miniature ultrathin LED comprises a flexible substrate, an anode layer, a quantum dot light-emitting layer, a cathode layer and a packaging layer which are sequentially arranged from bottom to top. The obtained micro LED has good flexibility, the quantum dots are used as a light-emitting material of the LED, the flexible substrate is combined, and the characteristics of high brightness, low power consumption and flexibility are achieved.

Description

Technical Field

[0001] The present invention relates to the technical field of semiconductor light-emitting devices, and in particular to a quantum dot-based flexible micro-ultra-thin LED and a preparation method and application thereof. Background Art

[0002] With the continuous development of display technology, the market demand for high resolution, high contrast, high color saturation and flexible display is growing. The development of ultra-thin, lightweight, flexible, high color purity light-emitting diodes (LEDs) is of great significance to the next generation of lighting and display technology. At present, organic light-emitting diodes and quantum dot light-emitting diodes (QLEDs) have achieved flexible commercial applications. As the core of the next generation of display and lighting technology, micro-LEDs have the advantages of high resolution, low power consumption and long life. However, the luminescent materials of traditional micro-LEDs are mostly inorganic semiconductor materials, and their preparation process is complicated and costly. In addition, the rigidity of micro-LEDs is too strong to be further promoted. Summary of the invention

[0003] In order to solve the above technical problems, the present invention provides a flexible micro-ultra-thin LED based on quantum dots and a preparation method and application thereof. The micro-LED obtained by the present invention has good flexibility. The LED uses quantum dots as light-emitting materials and combines with a flexible substrate to achieve high brightness, low power consumption and bendability.

[0004] The present invention provides a flexible micro ultra-thin LED based on quantum dots, wherein the flexible micro ultra-thin LED comprises a flexible substrate, an anode layer, a quantum dot light-emitting layer, a cathode layer, and a packaging layer which are sequentially arranged from bottom to top.

[0005] Furthermore, the flexible substrate includes a flexible substrate material, and the flexible substrate material includes one or more of polyimide (PI) and polyethylene terephthalate (PET).

[0006] Furthermore, the anode layer includes an anode material, and the anode material includes one or more of indium tin oxide (ITO) and poly(3,4-ethylenedioxythiophene)-polystyrene sulfonic acid (PEDOT:PSS).

[0007] Furthermore, the quantum dot light-emitting layer includes one or more of cadmium-based quantum dots, sulfur-based quantum dots, perovskite quantum dots, carbon-based quantum dots, metal phosphide quantum dots, metal oxide quantum dots, metal nitride quantum dots, silicon-based quantum dots, organic quantum dots, etc.

[0008] Furthermore, the general formula of the cadmium-based quantum dots is CdW, wherein W is selected from S2- 、Se 2- 、Te 2- One or more of .

[0009] Furthermore, the general formula of the sulfur-based quantum dots is M1 x S y , where M1 is selected as Zn 2+ 、Cd 2+ 、Ag + One or more of, x and y are determined by the method of balancing the chemical formula of sulfur-based quantum dots.

[0010] Furthermore, the general formula of the perovskite quantum dot is ABR3, wherein A is selected from one or more of formamidinium ion, methylamine ion, and cesium ion; B is selected from Pb 2+ Sn 2+ 、Eu 2+ , Cu 2+ 、Ni 2+ One or more of; R is selected from one or more of halogen ions.

[0011] Furthermore, the carbon-based quantum dots include carbon-based quantum dots composed of one or more elements selected from C, O, N and H.

[0012] Furthermore, the general formula of the metal phosphide quantum dot is M2 x1 P y1 , wherein M2 is selected from In 3+ , Ga 3+ 、Zn 2+ , Cu 2+ One or more of, x1 and y1 are determined by the method of balancing the chemical formula of metal phosphide quantum dots.

[0013] Furthermore, the general formula of the metal oxide quantum dot is M3 x2 O y2 , wherein M3 is selected from Cu 2+ 、Zn 2+ , Fe 3+ , Ba 2+ 、Ti + , Li + , Mn 3+ , Mn 4+ One or more of, x2 and y2 are determined by the chemical formula balancing method of metal oxide quantum dots.

[0014] Furthermore, the general formula of the metal nitride quantum dot is M4 x3 N y3 , wherein M4 is selected from Ti 3+ 、Al 3+ , Ga3+ , Fe 3+ , Fe 4+ One or more of, x3 and y3 are determined by the method of chemical formula balancing of metal nitride quantum dots.

[0015] Furthermore, the silicon-based quantum dots include one or more of intrinsic silicon-based quantum dots and doped silicon-based quantum dots.

[0016] Furthermore, the organic quantum dots include one or more of conjugated polymer quantum dots, dendrimer quantum dots, and organic small molecular weight quantum dots.

[0017] Furthermore, the size of the quantum dots is 3nm~30nm.

[0018] Furthermore, the main absorption band of the quantum dots is lower than 1000 nm, and the emission wavelength is between 300 and 1000 nm.

[0019] Furthermore, the cathode layer includes one or more of metal and conductive material.

[0020] Furthermore, the metal includes one or more of aluminum, silver, and calcium.

[0021] Furthermore, the conductive material includes one or more of lithium fluoride, graphene and carbon nanotubes.

[0022] Furthermore, the encapsulation layer includes an encapsulation material, and the encapsulation material includes one or more of epoxy resin, silica gel, organic silicon material, and polyurethane.

[0023] Furthermore, Poly-TPD (poly[bis(4-phenyl)(4-butylphenyl)amine]) is also arranged between the anode layer and the quantum dot light-emitting layer.

[0024] Furthermore, TPBi (triphenylbismuth) is disposed between the cathode layer and the quantum dot light-emitting layer.

[0025] The present invention also provides a method for preparing the flexible micro ultra-thin LED, the method comprising: S1: mixing quantum dots and dispersant to form a quantum dot solution; S2: coating a solution containing an anode material on the pretreated flexible substrate, and performing an annealing treatment once to obtain an anode layer; S3: coating the Poly-TPD chlorobenzene solution on the anode layer and performing secondary annealing treatment; S4: coating the quantum dot solution obtained in S1 on the product after the secondary annealing treatment in S3, and performing the annealing treatment three times to obtain a quantum dot light-emitting layer; S5: Depositing TPBi on the quantum dot light-emitting layer; S6: after depositing TPBi, depositing a cathode material to obtain a cathode layer; S7: Disposing a packaging layer on the cathode layer.

[0026] Furthermore, the dispersant includes one or more of toluene, n-hexane, octadecene, octane, dodecane, N,N-dimethylformamide (DMF), dimethyl sulfoxide (DMSO), water, and ethanol.

[0027] Furthermore, the ratio of the quantum dots to the dispersant is 1:30 by mass.

[0028] Furthermore, the step of coating the solution containing the anode material on the pretreated flexible substrate specifically includes: when there are multiple types of anode materials, coating the anode materials in sequence in multiple steps.

[0029] Furthermore, the anode material includes indium tin oxide and poly(3,4-ethylenedioxythiophene)-polystyrene sulfonic acid, the indium tin oxide is coated on the flexible substrate and annealed at 120°C-130°C for 10min-20min; then the poly(3,4-ethylenedioxythiophene)-polystyrene sulfonic acid is coated on the indium tin oxide and annealed at 100°C-120°C for 8min-12min.

[0030] In the present invention, the annealing temperature and time can be adjusted by those skilled in the art according to the selected anode material.

[0031] Furthermore, the method for pretreating the flexible substrate is as follows: the flexible substrate is washed with ultrasound, acetone, ethanol, and isopropanol in sequence, then treated with ultraviolet light and ozone simultaneously for 25 minutes to 35 minutes, dried, plasma treated, and cooled to room temperature.

[0032] Furthermore, the drying temperature is 75° C.-85° C., and the drying time is 2.5 h-3.5 h.

[0033] Furthermore, the plasma treatment time is 25 min-35 min.

[0034] Furthermore, the method for preparing the Poly-TPD chlorobenzene solution includes dispersing Poly-TPD in chlorobenzene.

[0035] Furthermore, the mass concentration of the Poly-TPD chlorobenzene solution is 7 mg / mL-9 mg / mL.

[0036] Furthermore, the secondary annealing treatment is performed at a temperature of 110° C.-130° C. and for a time of 15 min-25 min.

[0037] Furthermore, the temperature of the three annealing treatments is 25°C-30°C, and the time is 10min-20min.

[0038] Furthermore, the depositing of cathode materials is specifically as follows: when there are multiple cathode materials to be selected, the cathode materials are deposited sequentially in multiple steps.

[0039] Furthermore, the cathode material includes lithium fluoride and aluminum, and the lithium fluoride is deposited first and then the aluminum is deposited.

[0040] Furthermore, those skilled in the art may select a deposition method according to actual conditions. As an example, evaporation is used.

[0041] Furthermore, the coating method can be selected by those skilled in the art according to the actual situation. As an example, by using a spin coating method, the thickness and uniformity of the coating can be controlled by controlling the rotation speed and the rotation time. Alternatively, inkjet printing, slit coating, blade coating, dip coating, etc. can be used.

[0042] The present invention also provides applications of the flexible micro ultra-thin LED in wearable devices, foldable screen mobile phones, micro displays, lighting and biomedical fields.

[0043] The embodiments of the present invention have the following technical effects: 1. The flexible micro-ultra-thin LED in the present invention uses quantum dots as light-emitting materials, combines the advantages of a flexible substrate, achieves high brightness, low power consumption and bendability, and is suitable for miniaturized and integrated applications in the fields of display, lighting and biomedicine.

[0044] 2. The flexible micro ultra-thin LED of the present invention not only has good flexibility, but can also be prepared into a flexible micro ultra-thin LED with a thickness of 200 microns through the thickness of the coating layer, and still has luminous performance.

[0045] 3. The flexible micro-ultra-thin LED provided by the present invention combines the high brightness, low power consumption and adjustable band gap of quantum dots with the flexibility of the flexible substrate, realizing the miniaturization, integration and bendability of the device. By precisely controlling the synthesis and dispersion process of quantum dots and optimizing the preparation process, high brightness, low power consumption and stable luminous performance are achieved. The flexible micro-ultra-thin LED of the present invention also has good mechanical strength and durability, and is suitable for miniaturization and integration applications in various display, lighting and biomedical fields. BRIEF DESCRIPTION OF THE DRAWINGS

[0046] In order to more clearly illustrate the specific implementation methods of the present invention or the technical solutions in the prior art, the drawings required for use in the specific implementation methods or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are some implementation methods of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0047] Figure 1 UV test graph (dashed line) and PL test graph (solid line) of CdSe quantum dots provided in Example 1 of the present invention; Figure 2 UV test graph (dashed line) and PL test graph (solid line) of ZnS quantum dots provided in Example 2 of the present invention; Figure 3 It is the UV test graph (dashed line) and PL test graph (solid line) of CsPbBr3 perovskite quantum dots provided in Example 3 of the present invention; Figure 4 It is the UV test graph (dashed line) and PL test graph (solid line) of CsPbI3 perovskite quantum dots provided in Example 4 of the present invention; Figure 5 is a TEM image of CsPbBr3 perovskite quantum dots provided in Example 3 of the present invention; Figure 6 It is a structural diagram of the flexible micro ultra-thin LED prepared by the present invention; Figure 7 is an energy level structure diagram of different layers of the flexible micro ultra-thin LED prepared in Example 3 of the present invention; Figure 8 is the brightness-current characteristic curve of the flexible micro ultra-thin LED prepared in Example 3 of the present invention; Fig. 9 This is the current-voltage characteristic curve of the flexible micro ultra-thin LED prepared in Example 3 of the present invention. DETAILED DESCRIPTION

[0048] In order to make the purpose, technical solution and advantages of the present invention clearer, the technical solution of the present invention will be described clearly and completely below. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work belong to the scope of protection of the present invention.

[0049] In a first aspect, some embodiments of the present invention provide a quantum dot-based flexible micro-ultra-thin LED, wherein the flexible micro-ultra-thin LED includes a flexible substrate, an anode layer, a quantum dot light-emitting layer, a cathode layer, and a packaging layer arranged in sequence from bottom to top.

[0050] The anode layer and cathode layer prepared by the present invention are used to inject current and stimulate the quantum dots to emit light.

[0051] In some embodiments, the flexible substrate includes a flexible substrate material, and the flexible substrate material includes one or more of polyimide (PI) and polyethylene terephthalate (PET).

[0052] In some embodiments, the anode layer includes an anode material, and the anode material includes one or more of indium tin oxide (ITO) and poly(3,4-ethylenedioxythiophene)-polystyrene sulfonic acid (PEDOT:PSS).

[0053] In some embodiments, the quantum dot light-emitting layer includes one or more of cadmium-based quantum dots, sulfur-based quantum dots, perovskite quantum dots, carbon-based quantum dots, metal phosphide quantum dots, metal oxide quantum dots, metal nitride quantum dots, silicon-based quantum dots, organic quantum dots, etc.

[0054] In some embodiments, the general formula of the cadmium-based quantum dots is CdW, wherein W is selected from S 2- 、Se 2- 、Te 2- One or more of .

[0055] In some embodiments, the general formula of the sulfur-based quantum dots is M1 x S y , where M1 is selected as Zn 2+ 、Cd 2+ 、Ag + One or more of, x and y are determined by the method of balancing the chemical formula of sulfur-based quantum dots.

[0056] In some embodiments, the general formula of the perovskite quantum dot is ABR3, wherein A is selected from one or more of formamidinium ion, methylamine ion, and cesium ion; B is selected from Pb 2+ Sn 2+ 、Eu 2+ , Cu 2+ 、Ni 2+ One or more of; R is selected from one or more of halogen ions.

[0057] In some embodiments, the carbon-based quantum dots include carbon-based quantum dots composed of one or more elements selected from C, O, N and H.

[0058] In some embodiments, the general formula of the metal phosphide quantum dot is M2 x1 P y1 , wherein M2 is selected from In 3+ , Ga 3+、Zn 2+ , Cu 2+ One or more of, x1 and y1 are determined by the method of balancing the chemical formula of metal phosphide quantum dots.

[0059] In some embodiments, the general formula of the metal oxide quantum dot is M3 x2 O y2 , wherein M3 is selected from Cu 2+ 、Zn 2+ , Fe 3+ , Ba 2+ 、Ti + , Li + , Mn 3+ , Mn 4+ One or more of, x2 and y2 are determined by the chemical formula balancing method of metal oxide quantum dots.

[0060] In some embodiments, the general formula of the metal nitride quantum dot is M4 x3 N y3 , wherein M4 is selected from Ti 3+ 、Al 3+ , Ga 3+ , Fe 3+ , Fe 4+ One or more of, x3 and y3 are determined by the method of chemical formula balancing of metal nitride quantum dots.

[0061] In some embodiments, the silicon-based quantum dots include one or more of intrinsic silicon-based quantum dots and doped silicon-based quantum dots.

[0062] In some embodiments, the organic quantum dots include one or more of conjugated polymer quantum dots, dendrimer quantum dots, and organic small molecular weight quantum dots.

[0063] In some embodiments, the size of the quantum dots is 3nm~30nm.

[0064] In the present invention, the preparation of quantum dots can be obtained by selecting a preparation method according to actual conditions by a person skilled in the art. The preparation methods include hot injection method, sol-gel method, and ligand-assisted reprecipitation method. Specifically, the main absorption band of the quantum dots of the present invention is below 1000nm, the emission wavelength is within the range of 300-1000nm, the fluorescence yield of the quantum dots is greater than 70%, and the half-peak width is less than 50nm.

[0065] The quantum dot light-emitting layer prepared by the present invention refers to a light-emitting layer containing quantum dots formed on a flexible substrate, which achieves high brightness, low power consumption and stable light-emitting performance by precisely controlling the synthesis and dispersion process of the quantum dots.

[0066] In some embodiments, the cathode layer includes one or more of metal and conductive material.

[0067] In some embodiments, the metal includes one or more of aluminum, silver, and calcium.

[0068] In some embodiments, the conductive material includes one or more of lithium fluoride, graphene and carbon nanotubes.

[0069] In some embodiments, the encapsulation layer includes an encapsulation material, and the encapsulation material includes one or more of epoxy resin, silica gel, organic silicon material, and polyurethane.

[0070] The encapsulation layer prepared in the present invention refers to an encapsulation layer arranged outside the LED structure to protect the internal light-emitting material and electrodes and improve the stability and life of the device.

[0071] In some embodiments, Poly-TPD is further disposed between the anode layer and the quantum dot light-emitting layer.

[0072] In some embodiments, TPBi is further disposed between the cathode layer and the quantum dot light-emitting layer.

[0073] In a second aspect, some embodiments of the present invention further provide a method for preparing the flexible micro ultra-thin LED, the method comprising: S1: mixing quantum dots and dispersant to form a quantum dot solution; S2: coating a solution containing an anode material on the pretreated flexible substrate, and performing an annealing treatment once to obtain an anode layer; S3: coating the Poly-TPD chlorobenzene solution on the anode layer and performing secondary annealing treatment; S4: coating the quantum dot solution obtained in S1 on the product after the secondary annealing treatment in S3, and performing the annealing treatment three times to obtain a quantum dot light-emitting layer; S5: Depositing TPBi on the quantum dot light-emitting layer; S6: after depositing TPBi, depositing a cathode material to obtain a cathode layer; S7: Disposing a packaging layer on the cathode layer.

[0074] In the method of the present invention, those skilled in the art can adjust the thickness of each layer according to actual needs.

[0075] In some embodiments, the dispersant includes one or more of toluene, n-hexane, octadecene, octane, dodecane, N,N-dimethylformamide (DMF), dimethyl sulfoxide (DMSO), water, and ethanol.

[0076] In some embodiments, the ratio of the quantum dots to the dispersant is 1:30 by mass.

[0077] In some embodiments, coating the solution containing the anode material on the pretreated flexible substrate specifically includes: when multiple anode materials are selected, coating the anode materials sequentially in multiple steps.

[0078] In some embodiments, the anode material includes indium tin oxide and poly(3,4-ethylenedioxythiophene)-polystyrene sulfonic acid, the indium tin oxide is coated on a flexible substrate and annealed at 120°C-130°C for 10min-20min; then the poly(3,4-ethylenedioxythiophene)-polystyrene sulfonic acid is coated on the indium tin oxide and annealed at 100°C-120°C for 8min-12min.

[0079] In some embodiments, the method for pretreating the flexible substrate is as follows: the flexible substrate is washed with ultrasound, acetone, ethanol, and isopropanol in sequence, then treated with ultraviolet light and ozone simultaneously for 25 minutes to 35 minutes, dried, plasma treated, and cooled to room temperature.

[0080] In some embodiments, the drying temperature is 75° C.-85° C., and the drying time is 2.5 h-3.5 h.

[0081] In some embodiments, the plasma treatment lasts for 25 min to 35 min.

[0082] In some embodiments, the method for preparing the Poly-TPD chlorobenzene solution comprises dispersing Poly-TPD in chlorobenzene.

[0083] In some embodiments, the mass concentration of the Poly-TPD chlorobenzene solution is 7 mg / mL-9 mg / mL.

[0084] In some embodiments, the secondary annealing treatment is performed at a temperature of 110° C.-130° C. and for a time of 15 min-25 min.

[0085] In some embodiments, the temperature of the three annealing treatments is 25° C.-30° C., and the time is 10 min-20 min.

[0086] In some embodiments, the depositing of the cathode material is specifically: when there are multiple cathode materials selected, the cathode materials are deposited sequentially in multiple steps.

[0087] In some embodiments, the cathode material includes lithium fluoride and aluminum, and the lithium fluoride is deposited first and then the aluminum is deposited.

[0088] On the third aspect, some embodiments of the present invention also provide applications of the flexible micro ultra-thin LED in wearable devices, foldable screen mobile phones, micro displays, lighting and biomedical fields.

[0089] The following is a comparison with specific embodiments and comparative examples: Embodiment 1:

[0090] (1): Mix 2.5 mmol of selenium powder, 1.0 mL of trioctylphosphine sulfide (TOP) and 10.0 mL of 1-octadecene (ODE), evacuate the reaction bottle for 80 min, then increase the temperature and heat to 250 °C under nitrogen protection for 2 h to obtain a selenium precursor for use.

[0091] (2): 3 mmol of CdO, 5.5 mL of oleic acid (OA) and 50 mL of ODE were mixed, vacuumed and heated to 180°C. After the solid was completely dissolved, it was cooled to room temperature, 3.5 mL of OA and 3.5 mL of oleylamine (OAm) were added, and the temperature was then raised to 240°C. After reaching the temperature, the selenium precursor (3 mL) in step (1) heated to 250°C was immediately injected. After reacting for 30 seconds, the heating jacket was removed, and the mixture was cooled to room temperature using an ice water bath. The mixture was centrifuged and purified with methyl acetate at a speed of 6500 rpm for 10 minutes to obtain CdSe quantum dots, which were then stored in n-hexane for standby use to obtain a quantum dot solution. The mass ratio of quantum dots to n-hexane was 1:30. In the present invention, CdSe quantum dots can also be obtained commercially.

[0092] (3): The PET flexible substrate material was cleaned in an ultrasonic cleaner with acetone, ethanol and isopropanol in sequence, and then treated with ultraviolet (UV) ozone for 30 minutes to enhance its hydrophilicity to obtain a flexible substrate layer.

[0093] (4): After the flexible substrate layer was dried at 80 °C for 3 h, it was treated with oxygen plasma for 30 min. After the PET flexible substrate layer was cooled to room temperature, an ITO solution (commercially available) with a mass concentration of 20% was spin-coated on the flexible substrate layer at 1000 rpm for 50 s, and annealed in air at 125 °C for 15 min.

[0094] (5): The PEDOT:PSS solution was filtered through a 0.45 μm filter and then spin coated on ITO at 3000 r / min for 60 s, followed by de-baking at 110 °C for 10 min to remove moisture from the solvent.

[0095] (6): The product obtained in (5) was transferred to a glove box and spin-coated with 8 mg / mL Poly-TPD chlorobenzene solution to prepare a hole transport layer. The layer was then spin-coated at 4000 r / min for 40 s and annealed at 120 °C on a heating stage for 20 min to remove excess chlorobenzene.

[0096] (7): Spin coat the CdSe quantum dot solution on Poly-TPD at a spin coating speed of 1500 r / min for 40 s to control the film thickness of the perovskite light-emitting layer, and then anneal at room temperature for 15 min.

[0097] (8): The product after treatment in (7) is transferred to a vacuum evaporation system, and 40 nm thick TPBi is evaporated as an electron transport layer, 1 nm thick lithium fluoride (LiF) intermediate layer and 100 nm thick Al electrode are sequentially evaporated; (9): The product treated in (8) is taken out from the evaporation system and encapsulated on the surface of the Al electrode with an encapsulation material epoxy resin in a glove box.

[0098] Embodiment 2:

[0099] (1): Mix 2.5 mmol sulfur powder, 1.0 mL TOP and 10.0 mL ODE, evacuate the reaction bottle for 80 min, then increase the temperature and heat to 200 °C under nitrogen protection for 2 h to obtain a sulfur precursor for use.

[0100] (2): 3 mmol of zinc acetate (Zn(CH3COO)2) and 5.5 mL of OA and 50 mL of ODE were mixed, vacuumed and heated to 150°C. After the solid was completely dissolved, it was cooled to room temperature, and 3.5 mL of OA and 3.5 mL of OAm were added. Then the temperature was raised to 180°C. After reaching the temperature, the selenium precursor (3 mL) in step (1) heated to 200°C was immediately injected. After reacting for 30 s, the heating jacket was removed, and the mixture was cooled to room temperature using an ice water bath. It was centrifuged and purified with methyl acetate at a speed of 6500 rpm for 10 min to obtain ZnS quantum dots, which were then stored in n-hexane for standby use to obtain a quantum dot solution. The mass ratio of quantum dots to n-hexane was 1:30. In the present invention, ZnS quantum dots can also be obtained commercially.

[0101] (3)~(9): Same as Example 1.

[0102] Embodiment 3:

[0103] (1): After mixing 2.5 mmol of cesium carbonate (Cs2CO3), 2 mL of oleic acid (OA) and 30 mL of 1-octadecene (ODE), the reaction bottle was evacuated for 80 min, and then the temperature was increased and heated to 150 °C under nitrogen protection and maintained for 2 h to obtain a clear cesium oleate solution.

[0104] (2): 35 mL of ODE and 2 mmol of lead bromide (PbBr2) were mixed, vacuum heated to 150°C, and then 3 mL of OA and 3 mL of oleylamine (OAm) were added under nitrogen protection. The temperature was then raised to 180°C. After reaching the temperature, the cesium oleate heated to 150°C in step (1) was immediately injected, and then quickly cooled to room temperature with an ice water bath. Centrifugal purification was performed with methyl acetate at a speed of 8000 rpm for 5 min to obtain CsPbBr3 perovskite quantum dots, which were then stored in n-hexane for later use to obtain a quantum dot solution. The mass ratio of quantum dots to n-hexane was 1:30.

[0105] (3)~(9): Same as Example 1.

[0106] Embodiment 4:

[0107] The difference between Example 4 and Example 3 is that the prepared quantum dots are CsPbI3, so lead iodide is used instead of lead bromide when preparing perovskite quantum dots, and the rest are the same as Example 3.

[0108] Comparative Example 1: The difference between this comparative example and Example 3 is that the added amount of quantum dots CsPbBr3 is 0 g, and the rest is the same as Example 3.

[0109] The embodiments and comparative examples were tested: Transmission Electron Microscope (TEM): This experiment uses JEOL's JEM-2800 TEM to observe microstructures at the micrometer and nanometer scales. Before scanning, the quantum point solution to be measured needs to be dispersed on a micro-grid copper mesh covered with an ultra-thin carbon film and observed after it is fully dried.

[0110] Steady-state Photoluminescence Spectra (PL): When the sample is excited by light, electrons jump from the valence band to the conduction band and leave holes in the valence band. The electrons in the conduction band and the holes in the valence band relax to the bottom of the conduction band or the top of the valence band, and then emit photons through radiation recombination to return to the ground state, thus forming a spectrum of light with different wavelengths and intensities. The steady-state photoluminescence spectrometer used in this experiment is Edinburgh's FS5, with an excitation wavelength of 450 nm.

[0111] UV-Vis Absorption Spectrum: Prepare the quantum film on the substrate, ensure the uniformity and integrity of the film, put it into the sample cell of the UV-visible spectrophotometer, set the wavelength range to 200~800nm, and measure the absorbance or transmittance at different wavelengths. According to the formula T=10 -A (Where T is transmittance and A is absorbance) Calculate the transmittance at each wavelength. The UV spectrophotometer used in this experiment is Cary 100 from Varian.

[0112] Current Density-Voltage-Luminance Curve (JVL) The LED optoelectronic characteristics test system is mainly composed of Keithley 2400 power supply and PMA-12 spectrometer. After placing the LED device in the test system, it can apply voltage to make the LED work normally and emit light. Then, the current density (J), brightness (L), and luminous peak (EL) of the light-emitting device are collected through photodetectors, etc., and a series of basic parameters of LED devices can be obtained. Current density usually refers to the intensity of current flowing through a unit area. Voltage is the key factor in driving the flow of current. When voltage is applied to the device, current begins to flow, thereby generating brightness. As the voltage increases, the current density gradually increases, and the brightness of the device also increases. The relationship between current density and voltage reveals the brightness performance of the device under different working conditions, reflecting important properties such as the device's turn-on characteristics, brightness saturation characteristics, linear range, and performance stability.

[0113] Results and Analysis: like Figure 1 This is a PL test image of the CdSe quantum dots prepared in Example 1, with an emission position at 549 nm and a FWHM of 35 nm.

[0114] like Figure 2 This is a PL test image of the ZnS quantum dots prepared in Example 2, with an emission position at 509 nm and a FWHM of 27 nm.

[0115] like Figure 3This is a PL test image of the CsPbBr3 quantum dots prepared in Example 3, with an emission position at 510 nm and a FWHM of 25 nm.

[0116] like Figure 4 This is a PL test image of the CsPbI3 quantum dots prepared in Example 4, with an emission position at 687 nm and a FWHM of 35 nm.

[0117] like Figure 5 This is a TEM image of the CsPbBr3 quantum dots prepared in Example 3, where the morphology of the CsPbBr3 quantum dots with uniform and monodisperse cubic shapes can be observed; like Figure 6 This is a schematic diagram of the structure of a flexible micro ultra-thin LED obtained in Example 3 of the present invention.

[0118] like Figure 7 The energy level structure diagram of different layers of the flexible micro ultra-thin LED obtained in Example 3 of the present invention is shown in FIG. Figure 5 The energy level matching relationship between each layer of material in Example 3 of the present invention is found. Through the energy level difference of each layer of material and the action of the electric field, electrons and holes can move in a directed manner in the device and recombine in the quantum dot light-emitting layer, thereby realizing the electroluminescence process.

[0119] like Figure 8 and Fig. 9 The brightness-current curve and current-voltage curve of the LED prepared using the CsPbBr3 quantum dots prepared in Example 3 as the luminescent material. From these two curves, it can be seen that as the voltage increases, the current increases; as the current increases, the luminous intensity of the CsPbBr3 quantum dot LED increases.

[0120] In summary, the micro-LED obtained by the present invention has good flexibility. The LED uses quantum dots as light-emitting materials and combines them with a flexible substrate to achieve the characteristics of high brightness, low power consumption and bendability.

[0121] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or replace some or all of the technical features therein by equivalents. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the technical solutions of the embodiments of the present invention.

Claims

1. A flexible micro ultra-thin LED based on quantum dots, characterized in that: The flexible micro ultra-thin LED includes a flexible substrate, an anode layer, a quantum dot light-emitting layer, a cathode layer, and a packaging layer which are arranged in sequence from bottom to top.

2. The flexible micro ultra-thin LED according to claim 1, characterized in that: The flexible substrate comprises a flexible substrate material, and the flexible substrate material comprises one or more of polyimide and polyethylene terephthalate; The packaging layer includes packaging materials, and the packaging materials include one or more of epoxy resin, silica gel, organic silicon material, and polyurethane.

3. The flexible micro ultra-thin LED according to claim 1, characterized in that: The anode layer includes an anode material, and the anode material includes one or more of indium tin oxide and poly(3,4-ethylenedioxythiophene)-polystyrene sulfonic acid; The cathode layer includes one or more of metal and conductive material; The metal includes one or more of aluminum, silver, and calcium; The conductive material includes one or more of lithium fluoride, graphene and carbon nanotubes.

4. The flexible micro ultra-thin LED according to claim 1, characterized in that: The quantum dot light-emitting layer includes one or more of cadmium-based quantum dots, sulfur-based quantum dots, perovskite quantum dots, carbon-based quantum dots, metal phosphide quantum dots, metal oxide quantum dots, metal nitride quantum dots, silicon-based quantum dots, and organic quantum dots; The general formula of the cadmium-based quantum dots is CdW, wherein W is selected from S 2- 、Se 2- 、Te 2- One or more of; The general formula of the sulfur-based quantum dots is M1 x S y , where M1 is selected as Zn 2+ 、Cd 2+ 、Ag + One or more of, x and y are determined by the method of balancing the chemical formula of sulfur-based quantum dots; The general formula of the perovskite quantum dot is ABR3, wherein A is selected from one or more of formamidinium ion, methylamine ion, and cesium ion; B is selected from Pb 2+ Sn 2+ 、Eu 2+ , Cu 2+ 、Ni 2+ One or more of; R is selected from one or more of halogen ions; The carbon-based quantum dots include carbon-based quantum dots composed of one or more elements selected from C, O, N and H; The general formula of the metal phosphide quantum dot is M2 x1 P y1 , wherein M2 is selected from In 3+ , Ga 3+ 、Zn 2+ , Cu 2+ One or more of, x1 and y1 are determined by a method of balancing the chemical formula of metal phosphide quantum dots; The general formula of the metal oxide quantum dot is M3 x2 O y2 , wherein M3 is selected from Cu 2+ 、Zn 2+ , Fe 3+ , Ba 2+ 、Ti + , Li + , Mn 3 + , Mn 4+ One or more of, x2 and y2 are determined by a method of balancing the chemical formula of metal oxide quantum dots; The general formula of the metal nitride quantum dot is M4 x3 N y3 , wherein M4 is selected from Ti 3+ 、Al 3+ , Ga 3+ , Fe 3+ , Fe 4+ One or more of, x3 and y3 are determined by a method of balancing the chemical formula of metal nitride quantum dots; The silicon-based quantum dots include one or more of intrinsic silicon-based quantum dots and doped silicon-based quantum dots; The organic quantum dots include one or more of conjugated polymer quantum dots, dendrimer quantum dots, and organic small molecular weight quantum dots; The size of the quantum dots is 3nm~30nm.

5. The flexible micro ultra-thin LED according to claim 1, characterized in that: Poly-TPD is also arranged between the anode layer and the quantum dot light-emitting layer; TPBi is also arranged between the cathode layer and the quantum dot light-emitting layer.

6. The method for preparing the flexible micro ultra-thin LED according to any one of claims 1 to 5, characterized in that: The preparation method comprises: S1: mixing quantum dots and dispersant to form a quantum dot solution; S2: coating a solution containing an anode material on the pretreated flexible substrate, and performing an annealing treatment once to obtain an anode layer; S3: coating the Poly-TPD chlorobenzene solution on the anode layer and performing secondary annealing treatment; S4: coating the quantum dot solution obtained in S1 on the product after the secondary annealing treatment in S3, and performing the annealing treatment three times to obtain a quantum dot light-emitting layer; S5: Depositing TPBi on the quantum dot light-emitting layer; S6: after depositing TPBi, depositing a cathode material to obtain a cathode layer; S7: Disposing a packaging layer on the cathode layer.

7. The preparation method according to claim 6, characterized in that: The dispersant includes one or more of toluene, n-hexane, octadecene, octane, dodecane, N,N-dimethylformamide, dimethyl sulfoxide, water, and ethanol.

8. The preparation method according to claim 6, characterized in that: The ratio of the quantum dots to the dispersant is 1:30 by mass; The mass concentration of the Poly-TPD chlorobenzene solution is 7 mg / mL-9 mg / mL.

9. The preparation method according to claim 6, characterized in that: The secondary annealing treatment is performed at a temperature of 110°C-130°C and a time of 15min-25min; The temperature of the three annealing treatments is 25°C-30°C, and the time is 10min-20min.

10. Application of the flexible micro ultra-thin LED described in any one of claims 1 to 5 or the flexible micro ultra-thin LED obtained by the preparation method described in any one of claims 6 to 9 in wearable devices, foldable screen mobile phones, micro displays, lighting and biomedical fields.

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