Large-current quantum dot electroluminescent device and preparation method thereof

Abstract

The invention relates to the technical field of electroluminescent devices, in particular to a large-current quantum dot electroluminescent device and a preparation method thereof. The device comprises a substrate, a cathode, an electron transport layer, a quantum dot light-emitting layer, a current focusing layer, a hole transport layer, a hole generation layer and an anode which are tightly stacked in sequence, the current focusing layer is provided with a slit which is used for regulating and controlling the injection path of hole current to the quantum dot light-emitting layer and improving the bearable current density threshold value of the device. The material of the current focusing layer is one or more of lithium fluoride, magnesium fluoride and aluminum oxide; and the hole generation layer is used for efficiently enhancing hole injection. The invention further provides a preparation method for preparing each layered structure through spin coating and vacuum evaporation deposition. The electroluminescent device has the advantages that the hole generation layer and the current aggregation layer are utilized to construct the electroluminescent device capable of realizing large-current driving, the problem that carrier injection in the device under large-current driving is limited is solved, and the current tolerance and the luminous intensity of the device are effectively improved.

Description

Technical Field

[0001] The present invention relates to the technical field of electroluminescent devices, and particularly to a large-current quantum dot electroluminescent device and a preparation method thereof. Background Art

[0002] Electrical pump lasers are favored in many fields due to their high efficiency, high power, and compact structure. It directly excites the gain medium through electrical injection, avoiding the complexity of traditional optical pump systems, simplifying the process design, and reducing the overall complexity and maintenance cost of the system. However, traditional semiconductor electrical pump lasers rely on expensive ultra-high vacuum equipment (such as molecular beam epitaxy or chemical vapor deposition equipment), with high preparation costs, difficult heterogeneous integration, and still facing challenges in the efficiency and stability of the green light band, presenting the "green gap" problem. Therefore, developing a new type of semiconductor laser technology with low cost and a wide wavelength tuning range has become an important key factor in promoting the development of integrated optoelectronics and quantum technologies, and is of great significance for breaking through the existing technical bottlenecks and expanding application fields.

[0003] Colloidal quantum dots synthesized by wet chemical methods have quantum confinement effects. The large exciton binding energy and quasi-discrete energy level structure improve the thermal stability of material luminescence and inhibit the de-excitation of band-edge excitons caused by thermal perturbation, making them ideal gain materials for micro-nano semiconductor lasers. In addition, compared with traditional epitaxial growth technologies, colloidal quantum dots also have the advantages of low cost, high yield, easy heterogeneous integration, and a large wavelength tuning range, greatly simplifying the preparation process. One of the key problems in preparing electrical pump quantum dot lasers is how to achieve efficient large-current injection in the device, reach the quantum dot population inversion state, and thus achieve electrical pump quantum dot laser output. Summary of the Invention

[0004] To solve the above problems, the present invention provides a large-current quantum dot electroluminescent device and a preparation method thereof.

[0005] The purpose of the present invention is to provide a large-current quantum dot electroluminescent device, including a substrate, a cathode, an electron transport layer, a quantum dot light-emitting layer, a current focusing layer, a hole transport layer, a hole generation layer, and an anode, which are sequentially and tightly stacked; The current focusing layer has a slit for regulating the injection path of the hole current to the quantum dot light-emitting layer and increasing the current density threshold that the device can withstand; the material of the current focusing layer is one or more of lithium fluoride, magnesium fluoride, and aluminum oxide; The hole generation layer is used to efficiently enhance the injection of holes.

[0006] Preferably, the slit of the current focusing layer is 0.1 - 0.5 mm.

[0007] Preferably, the material of the current focusing layer is lithium fluoride; the slit of the current focusing layer is 0.1 mm.

[0008] Preferably, the hole generation layer includes a first hole generation layer and a second hole generation layer from bottom to top; the thin film material of the first hole generation layer close to the hole transport layer is one or more of poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonic acid), tungsten trioxide, and molybdenum trioxide; the thin film material of the second hole generation layer close to the anode is ZnO.

[0009] Preferably, the quantum dot light-emitting layer material includes at least one of Cd-based quantum dots, InP quantum dots, PbS quantum dots, and perovskite quantum dots; The material of the hole transport layer is one or more of poly(9,9-dioctylfluorene-co-N-(4-tert-butylphenyl)diphenylamine), poly(N-vinylcarbazole), poly[bis(4-phenyl)(4-butylphenyl)amine], 4,4',4''-tris(carbazol-9-yl)triphenylamine, and 4,4'-bis(carbazol-9-yl)biphenyl; The material of the electron transport layer is one or more of zinc oxide, titanium dioxide, and tin dioxide; The material of the cathode is one or more of transparent indium tin oxide, fluorine-doped tin oxide, and aluminum-doped zinc oxide; The material of the anode is one or more of Al, Pt, Ag, and Au.

[0010] Preferably, the quantum dot light-emitting layer material is CdSe quantum dots; the material of the electron transport layer is zinc oxide.

[0011] Preferably, it is prepared by the following method: S1. Perform oxygen plasma treatment on the substrate with a cathode for 3 to 10 minutes; S2. Prepare the electron transport layer by spin-coating a metal oxide solution on the substrate with a cathode and performing annealing treatment; S3. Spin-coat a quantum dot solution on the electron transport layer and perform annealing treatment to obtain the quantum dot light-emitting layer; S4. Deposit the current focusing layer on the quantum dot light-emitting layer by vacuum evaporation; use a copper wire with a diameter of 0.1 to 0.5 mm as a mask during evaporation to form a slit; after removing the copper wire mask, deposit the hole transport layer on the current focusing layer by vacuum evaporation; S5. Prepare the hole generation layer on the hole transport layer by spin-coating; S6. Deposit the anode on the hole generation layer by vacuum evaporation; encapsulate the prepared each film layer to obtain the quantum dot electroluminescent device.

[0012] Preferably, the metal oxide solution in step S2 is a ZnO solution, and the preparation method is as follows: Mix zinc acetate and 2-methoxyethanol to obtain solution 1; mix tetramethylammonium hydroxide and 2-methoxyethanol to obtain solution 2; vigorously stir and mix solution 1 and solution 2 evenly to obtain a zinc acetate solution; slowly add the TMAH solution to the zinc acetate solution and stir for 8 - 15 minutes, then add 2-ethanolamine to obtain a mixture; add toluene and n-hexane to the mixture, centrifuge and purify to obtain ZnO nanocrystals; disperse the ZnO nanocrystals in a mixture of 2-isopropanol and methanol, and filter to obtain a ZnO solution.

[0013] Preferably, the quantum dot solution in step S3 is a CdSe quantum dot solution, and the preparation method is as follows: Mix a cadmium source, oleic acid, and n-octadecene to prepare a cadmium-oleic acid solution; Mix a zinc source, oleic acid, and n-octadecene to prepare a zinc-oleic acid solution; Dissolve selenium in trioctylphosphine to prepare a trioctylphosphine-selenium solution; After vacuum degassing n-octadecene and the cadmium-oleic acid solution, heat it to 300 - 320 °C under nitrogen; then sequentially add the trioctylphosphine-selenium solution, trioctylphosphine, and the zinc-oleic acid solution, and continuously add a mixed solution containing the cadmium-oleic acid solution, the trioctylphosphine-selenium solution, and n-octadecene; after cooling to room temperature, add an ethanol solution, centrifuge to obtain a precipitate, and then disperse the precipitate in n-octane to obtain a CdSe quantum dot solution.

[0014] Preferably, step S5 specifically includes the following sub-steps: S501. Prepare a first hole generation layer on the hole transport layer by spin coating, and anneal it for 20 - 40 min under the condition of an annealing temperature of 110 - 130 °C; S502. Prepare a second hole generation layer on the first hole generation layer by spin coating, and anneal it for 20 - 40 min under the condition of an annealing temperature of 70 - 90 °C; The spin coating speed is 3500 - 5500 revolutions per minute; the thin film material of the first hole generation layer is PEDOT:PSS, and the thin film material of the second hole generation layer is ZnO.

[0015] Compared with the prior art, the present invention can achieve the following beneficial effects: Description of the Drawings Figure 1 It is an inverted structure schematic diagram of a large current quantum dot electroluminescent device provided by an embodiment of the present invention.

[0016] Figure 2It is a flowchart of a preparation method of a large-current quantum dot electroluminescent device according to an embodiment of the present invention.

[0017] Figure 3 It is a graph of the current density-voltage curve and the maximum tolerable current density of a large-current quantum dot electroluminescent device according to an embodiment of the present invention; A represents the current density-voltage curve; B represents the maximum tolerable current density of the device.

[0018] Reference numerals: 1. Substrate 2. Cathode 3. Electron transport layer 4. Quantum dot light-emitting layer 5. Current focusing layer 6. Hole transport layer 7. Hole generation layer 701. First hole generation layer; 702. Second hole generation layer 8. Anode Detailed implementation manners

[0019] In the following, embodiments of the present invention will be described with reference to the drawings. In the following description, the same modules are denoted by the same reference numerals. In the case of the same reference numerals, their names and functions are also the same. Therefore, their detailed descriptions will not be repeated.

[0020] In order to make the objectives, technical solutions and advantages of the present invention clearer, the present invention will be further described in detail below with reference to the drawings and specific embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention, rather than limiting the present invention.

[0021] The present invention provides a large-current quantum dot electroluminescent device, including a substrate, a cathode, an electron transport layer, a quantum dot light-emitting layer, a current focusing layer, a hole transport layer, a hole generation layer, and an anode that are sequentially and closely stacked; Specifically, the substrate material is one or more of transparent glass, quartz, and sapphire; Specifically, the cathode material is one or more of transparent indium tin oxide (ITO), fluorine-doped tin oxide (FTO), and aluminum-doped zinc oxide (AZO); Specifically, the electron transport layer material is one or more of zinc oxide (ZnO), titanium dioxide (TiO2), and tin dioxide (SnO2); Specifically, the quantum dot light-emitting layer material includes at least one of Cd-based quantum dots, InP quantum dots, PbS quantum dots, and perovskite quantum dots; Specifically, the material of the current focusing layer is one or more of lithium fluoride (LiF), magnesium fluoride (MgF2), and aluminum oxide (Al2O3); a current focusing layer is provided between the quantum dot light-emitting layer and the hole transport layer to regulate the injection path of the hole current into the quantum dot light-emitting layer, ultimately increasing the current density threshold that the device can withstand; the slit of the current focusing layer is 0.1 to 0.5 mm, preferably 0.1 to 0.3 mm; Specifically, the material of the hole transport layer is one or more of poly(9,9-dioctylfluorene-co-N-(4-tert-butylphenyl)diphenylamine) (TFB), poly(N-vinylcarbazole) (PVK), poly[bis(4-phenyl)(4-butylphenyl)amine] (poly-TPD), 4,4',4''-tris(carbazol-9-yl)triphenylamine (TCTA), and 4,4'-bis(carbazol-9-yl)biphenyl (CBP); Specifically, the structure of the hole generation layer includes two thin films, a first hole generation layer and a second hole generation layer; among them, the thin film material of the first hole generation layer close to the hole transport layer is one or more of poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonic acid) (PEDOT:PSS), tungsten trioxide (WO3), and molybdenum trioxide (MoO3), and the thin film material of the second hole generation layer close to the anode is ZnO; by adding a hole generation layer between the anode and the hole transport layer, the injection of holes is efficiently enhanced; Specifically, the anode material is one or more of Al, Pt, Ag, and Au.

[0022] The present invention also provides a method for preparing a large-current quantum dot electroluminescent device, which specifically includes the following steps: S1. The substrate with a cathode is subjected to oxygen plasma treatment for 3 to 10 minutes; in a specific embodiment, the treatment time is 5 minutes.

[0023] S2. An electron transport layer is prepared by spin-coating a metal oxide solution on the substrate with a cathode and then performing annealing treatment. Specifically, the spin-coating speed is 1500 to 2500 revolutions per minute; the annealing temperature is 110 to 130 °C, and the annealing time is 20 to 40 min; the metal oxide solution is a zinc oxide (ZnO) solution, a titanium dioxide (TiO2) solution, or a tin dioxide (SnO2) solution; Preferably, the metal oxide solution is a ZnO solution, and the preparation method is as follows: Zinc acetate and 2-methoxyethanol are mixed to obtain solution 1; tetramethylammonium hydroxide and 2-methoxyethanol are mixed to obtain solution 2; solution 1 and solution 2 are vigorously stirred and mixed evenly to obtain a zinc acetate solution; Slowly add the TMAH solution to the zinc acetate solution and stir for 8 - 15 minutes. Then add 2 - ethanolamine to obtain a mixture. Add toluene and n - hexane to the mixture, centrifuge and purify to obtain ZnO nanocrystals. Disperse the ZnO nanocrystals in a mixture of 2 - isopropanol and methanol, and filter to obtain a ZnO solution.

[0024] In a specific embodiment, the spin - coating speed is 2000 revolutions per minute; the annealing temperature is 120 °C, and the annealing time is 30 min. In a specific embodiment, the preparation method of the ZnO solution is as follows: Add 3 grams of zinc acetate and 200 milliliters of 2 - methoxyethanol to a flask equipped with a magnetic stir bar and mix well to obtain Solution 1; mix 4.5 grams of tetramethylammonium hydroxide (TMAH) and 20 milliliters of 2 - methoxyethanol to obtain Solution 2; vigorously stir Solution 1 and Solution 2 and mix them evenly until the reagents are completely dissolved. Slowly add the TMAH solution to the zinc acetate solution and stir for 10 minutes. Then add 4 milliliters of 2 - ethanolamine to obtain a mixture. Add 440 milliliters of toluene and 220 milliliters of n - hexane to the mixture, centrifuge and purify to obtain ZnO nanocrystals. Finally, disperse ZnO in a mixture of 44 milliliters of 2 - isopropanol and 11 milliliters of methanol, and filter through a 0.2 - micron needle filter.

[0025] S3. Spin - coat the quantum dot solution on the electron - transport layer and perform annealing treatment to obtain a quantum dot light - emitting layer. Specifically, the spin - coating speed is 1500 - 2500 revolutions per minute; the annealing temperature is 70 - 90 °C, and the annealing time is 20 - 40 min; in a specific embodiment, the spin - coating speed is 2000 revolutions per minute; the annealing temperature is 80 °C, and the annealing time is 30 min. Specifically, the preparation method of the quantum dot solution includes the following steps: Mix a cadmium source, oleic acid and n - octadecene to prepare a cadmium - oleic acid solution. Mix a zinc source, oleic acid and n - octadecene to prepare a zinc - oleic acid solution. Dissolve selenium in trioctylphosphine to prepare a trioctylphosphine - selenium solution. After vacuum - degassing n - octadecene and the cadmium - oleic acid solution, heat it to 300 - 320 °C under nitrogen; then sequentially add the trioctylphosphine - selenium solution, trioctylphosphine and the zinc - oleic acid solution, and continuously add a mixed solution containing the cadmium - oleic acid solution, the trioctylphosphine - selenium solution and n - octadecene; after cooling to room temperature, add an ethanol solution, centrifuge to obtain a precipitate, and then disperse the precipitate in n - octane to obtain a quantum dot solution. Preferably, the cadmium source is cadmium acetate dihydrate, and the zinc source is zinc acetate dihydrate; In a specific embodiment, the quantum dot solution is a CdSe quantum dot solution, and the preparation method is as follows: Mix 10 millimoles of cadmium acetate dihydrate (Cd(CH3COO)2·2H2O), 10 milliliters of oleic acid (OA), and 10 milliliters of 1-octadecene evenly, and prepare a 0.5 molar Cd-oleic acid solution in a three-necked flask. After degassing under vacuum at 120 °C for 1 hour, store it at 100 °C under nitrogen; Mix 20 millimoles of Zn(CH3COO)2·2H2O, 20 milliliters of OA, and 20 milliliters of ODE in a three-necked flask to prepare a 0.5 molar Zn-oleic acid solution. After degassing under vacuum at 130 °C for 1 hour, store it at 120 °C under nitrogen; Dissolve 40 millimoles of selenium in 20 milliliters of trioctylphosphine (TOP), and prepare a 2 molar TOP-Se solution in a glove box; Solution A: Prepared by mixing 0.5 milliliters of Cd-oleic acid (0.5 molar), 0.125 milliliters of TOP-Se (2 molar), and 0.375 milliliters of ODE; Solution B: Prepared by mixing 1.25 milliliters of Cd-oleic acid (0.5 molar), 1.25 milliliters of TOP-Se (2 molar), and 2.5 milliliters of ODE; Load 6 milliliters of ODE and 0.2 milliliters of Cd-oleic acid (0.5 molar) into a 100-milliliter three-necked flask, and degas under vacuum at 120 °C for 25 minutes; then heat the reaction flask to 310 °C under nitrogen and quickly inject 0.1 milliliters of TOP-Se (2 molar); 40 seconds after injecting TOP-Se, add dropwise 1 milliliter of TOP for 20 seconds; after 2 minutes, continuously add 1 milliliter of Solution A to the reaction flask at a rate of 5 milliliters per hour for 12 minutes; quickly inject 2 milliliters of the Zn-oleic acid (0.5 molar) solution at 310 °C into the reaction flask; then, continuously add Solution B at a rate of 4 milliliters per hour for 75 minutes; at the same time, inject the Zn-oleic acid (0.5 molar) solution 3 times at 18.75 minutes, 52.5 minutes, and 67.5 minutes, and the volume injected each time is 2 milliliters, 4 milliliters, and 2 milliliters respectively. After cooling to room temperature, add an equal volume of ethanol solution, centrifuge at 7000 revolutions per minute for 5 minutes in a centrifuge, and disperse the precipitate in n-octane to prepare a 12 milligram per milliliter CdSe quantum dot solution.

[0026] S4. Deposit a current focusing layer on the quantum dot light-emitting layer using a vacuum evaporation process; use a copper wire with a diameter of 0.1 - 0.5 millimeters as a mask during the evaporation process to form a slit; after removing the copper wire mask, deposit a hole transport layer on the current focusing layer through a vacuum evaporation process; Specifically, the degree of vacuum for vacuum evaporation is 4.5×10 -4 Pa; In a specific embodiment, the material of the current focusing layer is lithium fluoride; the material of the hole transport layer is CBP.

[0027] S5. Prepare a hole generation layer on the hole transport layer by a spin coating process; specifically, it includes the following sub-steps: S501. Prepare a first hole generation layer on the hole transport layer by a spin coating process, and anneal it for 20 - 40 min under the condition of an annealing temperature of 110 - 130 °C; S502. Prepare a second hole generation layer on the first hole generation layer by a spin coating process, and anneal it for 20 - 40 min under the condition of an annealing temperature of 70 - 90 °C; Specifically, the spin coating speed is 3500 - 5500 revolutions per minute; the thin film material of the first hole generation layer is PEDOT:PSS, and the thin film material of the second hole generation layer is ZnO; In a specific embodiment, the spin coating speed in step S501 is 4000 revolutions per minute, the annealing temperature is 120 °C, and the annealing time is 30 min; the annealing temperature in step S502 is 80 °C, and the annealing time is 30 min.

[0028] S6. Deposit an anode on the hole generation layer by a vacuum evaporation process; encapsulate the prepared each film layer to obtain a quantum dot electroluminescent device; Specifically, the deposition method is: put the device prepared in step S5 into a vacuum coating machine to evacuate, when the degree of vacuum reaches 4.5×10 -4 Pa, evaporate a 100 - nanometer - thick Al anode on the hole transport layer.

[0029] The core of the present invention lies in: by using the design of a hole generation layer (charge generation layer) and a current aggregation layer, constructing an electroluminescent device structure that can achieve high - current drive, solving the problem of limited carrier injection in the device under high - current drive, and effectively improving the current tolerance and luminous intensity of the device. This device structure is applicable to the preparation of high - power quantum dot light - emitting diodes and electrically pumped quantum dot lasers.

[0030] Example 1 Refer to Figure 1 , this embodiment provides a high - current quantum dot electroluminescent device, including a substrate 1, a cathode 2, an electron transport layer 3, a quantum dot light - emitting layer 4, a current focusing layer 5, a hole transport layer 6, a hole generation layer 7 (the first hole generation layer 701 and the second hole generation layer 702 from bottom to top) and an anode 8 that are tightly stacked in sequence; Among them, the material of the substrate 1 is glass, the material of the cathode 2 is transparent indium tin oxide (ITO), the material of the electron transport layer 3 is ZnO, the material of the quantum dot light-emitting layer 4 is CdSe quantum dots, the material of the current focusing layer 5 is LiF, the material of the hole transport layer 6 is CBP, the materials of the first hole generation layer 701 and the second hole generation layer 702 are PEDOT:PSS and ZnO respectively, and the material of the anode is Al; The slit of the current focusing layer 5 is 0.3 mm.

[0031] A method for preparing a quantum dot light-emitting device specifically includes the following steps: S1. Perform oxygen plasma treatment on the substrate 1 with the cathode 2, and the treatment time is 5 minutes; S2. Transfer the substrate 1 with the cathode 2 to a glove box filled with N2, spin-coat the ZnO solution at a speed of 2000 revolutions per minute, and perform annealing treatment. The annealing temperature is 120 °C and the annealing time is 30 minutes to prepare the electron transport layer 3; The preparation method of the above ZnO solution is as follows: Add 3.0 grams of zinc acetate and 200 milliliters of 2-methoxyethanol to a flask equipped with a magnetic stirrer; Mix 4.5 grams of tetramethylammonium hydroxide (TMAH) and 20 milliliters of 2-methoxyethanol; Vigorously stir the above two solutions until the reagents are completely dissolved; Slowly add the TMAH solution to the zinc acetate solution and stir for 10 minutes, then add 4 milliliters of 2-ethanolamine; Add 440 milliliters of toluene and 220 milliliters of n-hexane to the above mixture to centrifuge and purify the ZnO nanocrystals; Finally, disperse the ZnO nanocrystals in a mixture of 44 milliliters of 2-isopropanol and 11 milliliters of methanol, and filter through a 0.2-micron needle filter to obtain the ZnO solution.

[0032] S3. Spin-coat the CdSe quantum dot solution on the electron transport layer 3 at a speed of 2000 revolutions per minute, and place it on a heating table at 80 °C for annealing for 30 minutes to obtain the quantum dot light-emitting layer 4; The preparation method of the above CdSe quantum dot solution is as follows: Uniformly mix 10 millimoles of cadmium acetate dihydrate (Cd(CH3COO)2·2H2O), 10 milliliters of oleic acid (OA), and 10 milliliters of n-octadecene, and prepare a 0.5 molar Cd- oleic acid solution in a three-necked flask. After degassing under vacuum at 120 °C for 1 hour, store it at 100 °C under nitrogen; Mix 20 millimoles of Zn(CH3COO)2·2H2O, 20 milliliters of OA, and 20 milliliters of ODE in a three-necked flask to prepare a 0.5 molar Zn-oleic acid solution. After degassing under vacuum at 130 °C for 1 hour, store it at 120 °C under nitrogen; Dissolve 40 mmol of selenium in 20 mL of trioctylphosphine (TOP) to prepare a 2 M TOP-Se solution in a glove box; Solution A: Prepared by mixing 0.5 mL of Cd-oleate (0.5 M), 0.125 mL of TOP-Se (2 M), and 0.375 mL of ODE; Solution B: Prepared by mixing 1.25 mL of Cd-oleate (0.5 M), 1.25 mL of TOP-Se (2 M), and 2.5 mL of ODE; Load 6 mL of ODE and 0.2 mL of Cd-oleate (0.5 M) into a 100 mL three-necked flask, degas in vacuo at 120 °C for 25 minutes; then heat the reaction flask to 310 °C under nitrogen and quickly inject 0.1 mL of TOP-Se (2 M); 40 seconds after injecting TOP-Se, add dropwise 1 mL of TOP for 20 seconds; 2 minutes later, continuously add 1 mL of Solution A to the reaction flask at a rate of 5 mL per hour for 12 minutes; quickly inject 2 mL of Zn-oleate (0.5 M) solution at 310 °C into the reaction flask; then, continuously add Solution B at a rate of 4 mL per hour for 75 minutes; at the same time, inject 3 times of Zn-oleate (0.5 M) solution at 18.75 minutes, 52.5 minutes, and 67.5 minutes, with the volume of each injection being 2 mL, 4 mL, and 2 mL respectively. After cooling to room temperature, add an equal volume of ethanol solution, centrifuge at 7000 revolutions per minute in a centrifuge for 5 minutes, and disperse the precipitate in n-octane to prepare a 12 mg / mL CdSe quantum dot solution.

[0033] S4. Deposit a 50-nm-thick current focusing layer 5 on the quantum dot light-emitting layer 4 using a vacuum evaporation process; use a copper wire with a diameter of 0.3 mm as a mask during the evaporation process to form a slit; after removing the copper wire mask, deposit a 60-nm-thick hole transport layer 5 on the current focusing layer 4 by vacuum evaporation; the vacuum degree of vacuum evaporation is 4.5×10 -4 Pa; S5. Transfer the device to a glove box, spin-coat the PEDOT:PSS solution on the CBP hole transport layer 5 at a speed of 4000 revolutions per minute, and anneal on a hot stage at 120 °C for 30 minutes to form a PEDOT:PSS thin film, namely the first hole generation layer 701; spin-coat the ZnO solution on the PEDOT:PSS thin film at a speed of 4000 revolutions per minute and anneal at 80 °C for 30 minutes to obtain the second hole generation layer 702, completing the preparation of the hole generation layer 7.

[0034] S6. Place the device prepared in step S5 into a vacuum coating machine to evacuate. When the vacuum degree reaches 4.5×10 -4When the pressure is Pa, the anode 8 is deposited on the hole generation layer 7 by vacuum evaporation; the prepared film layers are encapsulated to obtain a quantum dot electroluminescent device. The preparation flow chart is shown in Figure 2 .

[0035] Example 2 This example provides a large-current quantum dot electroluminescent device. The device structure is basically the same as that of Example 1, except that the slit of the current focusing layer 5 is 0.1 mm.

[0036] The preparation method of the quantum dot electroluminescent device specifically includes the following steps: Steps S1 to S3 are the same as those in Example 1; S4. Deposit a 50-nm-thick current focusing layer 5 on the quantum dot light-emitting layer 4 by vacuum evaporation; use a 0.1-mm-diameter copper wire as a mask during the evaporation process to form a slit; after removing the copper wire mask, deposit a 60-nm-thick hole transport layer 5 on the current focusing layer 4 by vacuum evaporation; the vacuum degree of the vacuum evaporation is 4.5×10 -4 Pa; Steps S5 to S6 are the same as those in Example 1.

[0037] Example 3 This example provides a large-current quantum dot electroluminescent device. The device structure is basically the same as that of Example 1, except that the substrate 1 material is sapphire and the electron transport layer 3 material is TiO2; The preparation method of the quantum dot electroluminescent device specifically includes the following steps: Step S1 is the same as that in Example 1; S2. Transfer the substrate 1 with the cathode 2 to a glove box filled with N2, spin-coat the TiO2 solution at a speed of 2000 revolutions per minute, and perform annealing treatment. The annealing temperature is 120 °C and the annealing time is 30 minutes to prepare the electron transport layer 3; Steps S3 to S6 are the same as those in Example 1.

[0038] Example 4 This example provides a large-current quantum dot electroluminescent device. The device structure is basically the same as that of Example 1, except that the substrate 1 material is sapphire and the quantum dot light-emitting layer 4 material is InP quantum dots; The preparation method of the quantum dot electroluminescent device specifically includes the following steps: Steps S1 to S2 are the same as those in Example 1; S3. Spin-coat the InP quantum dot solution on the electron transport layer 3 at a speed of 2000 revolutions per minute, and place it on a heating table at 80 °C for annealing for 30 minutes to obtain the quantum dot light-emitting layer 4; Steps S4 to S6 are the same as those in Example 1.

[0039] Example 5 This example provides a high-current quantum dot electroluminescent device. The device structure is basically the same as that of Example 1, except that: the material of the current focusing layer 5 is MgF2, and the material of the hole transport layer 6 is TFB; The preparation method of the quantum dot electroluminescent device is the same as that of Example 1.

[0040] Example 6 This example provides a high-current quantum dot electroluminescent device. The device structure is basically the same as that of Example 1, except that: the thin film material of the first hole generation layer 701 is WO3, and the anode material is Au; The preparation method of the quantum dot electroluminescent device specifically includes the following steps: Steps S1 - S4 are the same as those of Example 1; S5. Transfer the device to a glove box. Spin-coat the WO3 solution on the CBP hole transport layer 5 at a speed of 4000 revolutions per minute, and anneal it on a hot stage at a temperature of 120°C for 30 minutes to form a WO3 thin film, that is, the first hole generation layer 701; Spin-coat the ZnO solution on the WO3 thin film at a speed of 4000 revolutions per minute, and anneal it at 80°C for 30 minutes to obtain the second hole generation layer 702, completing the preparation of the hole generation layer 7; Step S6 is the same as that of Example 1.

[0041] Comparative Example 1 This comparative example provides a quantum dot electroluminescent device. The device structure is different from that of Example 1. The difference is that: there is no current focusing layer between the quantum dot light-emitting layer and the hole transport layer; the structures of the other layers are the same as those of Example 1; The preparation method of the quantum dot electroluminescent device specifically includes the following steps: Steps S1 - S3 are the same as those of Example 1; S4. Perform vacuum thermal deposition on the quantum dot light-emitting layer. When the vacuum degree reaches 4.5×10-4 Pa, evaporate a 60-nanometer-thick CBP hole transport layer; Steps S5 - S6 are the same as those of Example 1.

[0042] Figure 3 Are the current-voltage curves of the quantum dot electroluminescent devices prepared in Example 1, Example 2, and Comparative Example 1. As Figure 3 shown, as the slit of the current focusing layer decreases, the current density flowing through the quantum dot electroluminescent device gradually increases at the same voltage. The result of Comparative Example 1 without a current focusing layer is inferior to that of Examples 1 - 2. This phenomenon is attributed to the introduction of the current focusing layer, which optimizes the current distribution and ensures the efficient utilization of the current.

[0043] In summary, in the electroluminescent device of the present invention, a hole generation layer is added between the anode and the hole transport layer to efficiently enhance the injection of holes. In addition, a current focusing layer is provided between the quantum dot light-emitting layer and the hole transport layer to regulate the injection path of the hole current into the light-emitting layer, and finally increase the current density threshold that the device can withstand. By designing the hole generation layer (charge generation layer) and the current aggregation layer, an electroluminescent device structure capable of realizing high-current driving is constructed, the problem of limited carrier injection in the device under high-current driving is solved, and the current tolerance and light-emitting intensity of the device are effectively improved. This device structure is applicable to the preparation of high-power quantum dot light-emitting diodes and electrically pumped quantum dot lasers.

[0044] It should be understood that various forms of the processes shown above can be used, steps can be reordered, added, or deleted. For example, the steps described in the disclosure of the present invention can be executed in parallel, sequentially, or in a different order, as long as the desired results of the technical solution disclosed in the present invention can be achieved, and no limitation is made herein.

[0045] The above specific embodiments do not constitute a limitation to the protection scope of the present invention. Those skilled in the art should understand that various modifications, combinations, sub-combinations, and substitutions can be made according to design requirements and other factors. Any modifications, equivalent substitutions, and improvements made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. A large-current quantum dot electroluminescent device, characterized in that: It includes a substrate, a cathode, an electron transport layer, a quantum dot light-emitting layer, a current focusing layer, a hole transport layer, a hole generation layer, and an anode that are closely stacked in sequence; The current focusing layer has slits for regulating the injection path of the hole current into the quantum dot light-emitting layer and increasing the current density threshold that the device can withstand; the material of the current focusing layer is one or more of lithium fluoride, magnesium fluoride, and aluminum oxide; The hole generation layer is used to efficiently enhance the injection of holes.

2. The large-current quantum dot electroluminescent device according to claim 1, characterized in that: The slits of the current focusing layer are 0.1 to 0.5 millimeters.

3. A large-current quantum dot electroluminescent device according to claim 2, characterized in that: The material of the current focusing layer is lithium fluoride; the slits of the current focusing layer are 0.1 millimeter.

4. A large-current quantum dot electroluminescent device according to claim 1, wherein: The hole generation layer includes a first hole generation layer and a second hole generation layer from bottom to top; the thin film material of the first hole generation layer close to the hole transport layer is one or more of poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonic acid), tungsten trioxide, and molybdenum trioxide; the thin film material of the second hole generation layer close to the anode is ZnO.

5. A large-current quantum dot electroluminescent device according to claim 1, characterized in that: The material of the quantum dot light-emitting layer includes at least one of Cd-based quantum dots, InP quantum dots, PbS quantum dots, and perovskite quantum dots; The material of the hole transport layer is one or more of poly(9,9-dioctylfluorene-co-N-(4-tert-butylphenyl)diphenylamine), poly(N-vinylcarbazole), poly[bis(4-phenyl)(4-butylphenyl)amine], 4,4',4''-tris(carbazol-9-yl)triphenylamine, and 4,4'-bis(carbazol-9-yl)biphenyl; The material of the electron transport layer is one or more of zinc oxide, titanium dioxide, and tin dioxide; The material of the cathode is one or more of transparent indium tin oxide, fluorine-doped tin oxide, and aluminum-doped zinc oxide; The material of the anode is one or more of Al, Pt, Ag, and Au.

6. The large-current quantum dot electroluminescent device according to claim 5, wherein: The material of the quantum dot light-emitting layer is CdSe quantum dots; the material of the electron transport layer is zinc oxide.

7. A large-current quantum dot electroluminescent device according to claim 1, characterized in that: It is prepared by the following method: S1. The substrate with the cathode is subjected to oxygen plasma treatment for 3 to 10 minutes; S2. The electron transport layer is prepared by spin-coating a metal oxide solution on the substrate with the cathode and then annealing; S3. The quantum dot solution is spin-coated on the electron transport layer and then annealed to obtain the quantum dot light-emitting layer; S4. The current focusing layer is deposited on the quantum dot light-emitting layer by vacuum evaporation; During the evaporation process, a copper wire with a diameter of 0.1 to 0.5 millimeters is used as a mask to form slits; After removing the copper wire mask, the hole transport layer is deposited on the current focusing layer by vacuum evaporation; S5. The hole generation layer is prepared by spin-coating on the hole transport layer; S6. The anode is deposited on the hole generation layer by vacuum evaporation; the prepared film layers are encapsulated to obtain the quantum dot electroluminescent device.

8. A large-current quantum dot electroluminescent device according to claim 7, wherein: The metal oxide solution in step S2 is a ZnO solution, and the preparation method is as follows: Zinc acetate and 2-methoxyethanol are mixed to obtain solution 1; tetramethylammonium hydroxide and 2-methoxyethanol are mixed to obtain solution 2; solution 1 and solution 2 are vigorously stirred and mixed evenly to obtain the zinc acetate solution; Slowly add the TMAH solution to the zinc acetate solution and stir for 8 to 15 minutes. Then add 2-ethanolamine to obtain a mixture. Add toluene and n-hexane to the mixture, centrifuge and purify to obtain ZnO nanocrystals. Disperse the ZnO nanocrystals in a mixture of 2-isopropanol and methanol, and filter to obtain a ZnO solution.

9. A large current quantum dot electroluminescent device according to claim 7, characterized in that: The quantum dot solution in step S3 is a CdSe quantum dot solution, and the preparation method is as follows: Mix a cadmium source, oleic acid, and n-octadecene to prepare a cadmium-oleic acid solution; Mix a zinc source, oleic acid, and n-octadecene to prepare a zinc-oleic acid solution; Dissolve selenium in trioctylphosphine to prepare a trioctylphosphine-selenium solution; After vacuum degassing n-octadecene and the cadmium-oleic acid solution, heat it to 300 - 320 °C under nitrogen. Then sequentially add the trioctylphosphine-selenium solution, trioctylphosphine, and the zinc-oleic acid solution, and continuously add a mixed solution containing the cadmium-oleic acid solution, the trioctylphosphine-selenium solution, and n-octadecene. After cooling to room temperature, add an ethanol solution, centrifuge to obtain a precipitate, and then disperse the precipitate in n-octane to obtain a CdSe quantum dot solution.

10. A large-current quantum dot electroluminescent device according to claim 7, characterized in that: Step S5 specifically includes the following sub-steps: S501. Prepare a first hole generation layer on the hole transport layer by spin coating, and anneal it for 20 - 40 min under the condition of an annealing temperature of 110 - 130 °C; S502. Prepare a second hole generation layer on the first hole generation layer by spin coating, and anneal it for 20 - 40 min under the condition of an annealing temperature of 70 - 90 °C; The spin coating speed is 3500 - 5500 revolutions per minute; The thin film material of the first hole generation layer is PEDOT:PSS, and the thin film material of the second hole generation layer is ZnO.

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