Light-emitting diode and preparation method thereof

Abstract

The present invention discloses a quantum dot light-emitting diode and a method for manufacturing the same. The method comprises the following steps: depositing a hole transport material solution, wherein the hole transport material is PVK, on ​​a prefabricated device; applying a first electric field in the upper and lower directions of the prefabricated device, and performing a first heat treatment on the hole transport material solution to form a hole transport layer on the prefabricated device. The present invention uses PVK as the hole transport layer material and anneals the hole transport layer under the combined action of an electric field and high temperature, effectively improving the photoelectric performance of the quantum dot light-emitting diode.

Description

Technical Field

[0001] The present invention relates to the field of light emitting diodes, and in particular to a light emitting diode and a preparation method thereof. Background Art

[0002] In traditional quantum dot light-emitting diodes (QLEDs), the device structure primarily consists of a conductive glass substrate, a hole transport layer, a quantum dot composite light-emitting layer, an electron transport layer, and a metal cathode. Studies have found that during QLED device operation, the internal electron migration rate is high and the hole migration rate is low, which can easily lead to electron accumulation within the device, causing the device operating voltage to rise and, in turn, affecting the device's optoelectronic performance. Therefore, finding a suitable device fabrication solution, balancing the internal electron and hole transport, and eliminating charge accumulation within the device are effective methods for improving the optoelectronic performance of QLED devices.

[0003] Currently, polyvinylcarbazole (PVK) is a polymer hole transport material. During the molecular motion, some of the carbazole groups inside it will spontaneously form a stable face-to-face structure. The hole transport efficiency of this structure is much greater than that of the ordinary π-bond conjugated system. Therefore, PVK, as a hole transport layer material, has a large hole transport rate and can alleviate the electron-hole imbalance phenomenon inside the QLED device. Nevertheless, since PVK is a polymer, its molecular chains are very entangled and entangled, which leads to a large steric hindrance for the carbazole groups to form a face-to-face structure. Only a small number of carbazole groups can form a face-to-face structure. Therefore, the improvement of the hole transport rate of the PVK hole transport layer is greatly limited, and the charge accumulation phenomenon still exists inside its QLED device.

[0004] Therefore, the existing technology still needs to be improved and developed. Summary of the Invention

[0005] In view of the above-mentioned deficiencies in the prior art, the object of the present invention is to provide a light-emitting diode and a method for preparing the same, aiming to solve the problem that the prior art uses PVK as a hole transport layer material, whose hole transport rate is limited, resulting in poor photoelectric performance of the light-emitting diode.

[0006] The technical solutions of the present invention are as follows:

[0007] A method for preparing a light emitting diode, comprising the steps of:

[0008] Depositing a hole transport material solution on the prefabricated device, wherein the hole transport material is PVK;

[0009] A first electric field is applied in the upper and lower directions of the prefabricated device, and the hole material solution is subjected to a first heating treatment to form a hole transport layer on the prefabricated device.

[0010] A light emitting diode is manufactured using the light emitting diode manufacturing method of the present invention.

[0011] Beneficial effects: The present invention uses PVK as the hole transport layer material. By annealing the hole transport layer under the combined action of an electric field and high temperature, more carbazole groups in the PVK molecules in the hole transport layer form a regular and orderly face-to-face configuration, thereby improving the hole transport efficiency of the hole transport layer, reducing the operating voltage of the device, and optimizing the photoelectric performance of the device. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] Figure 1 This is a first flow chart of a method for preparing a light emitting diode provided by the present invention.

[0013] Figure 2 This is a second flow chart of a method for preparing a light emitting diode provided by the present invention.

[0014] Figure 3 This is a schematic structural diagram of an annealing device provided by the present invention.

[0015] Figure 4 The present invention provides a flowchart of a preferred embodiment of a method for preparing an upright structure quantum dot light-emitting diode.

[0016] Figure 5 The present invention provides a flowchart of a preferred embodiment of a method for preparing an inverted structure quantum dot light-emitting diode.

[0017] Figure 6 This is a schematic structural diagram of an upright structure quantum dot light-emitting diode provided by the present invention.

[0018] Figure 7 This is a schematic structural diagram of an inverted structure quantum dot light-emitting diode provided by the present invention. DETAILED DESCRIPTION

[0019] The present invention provides a light emitting diode and a method for manufacturing the same. To make the objectives, technical solutions, and effects of the present invention more clear and explicit, the present invention is further described in detail below. It should be understood that the specific embodiments described herein are merely for the purpose of explaining the present invention and are not intended to limit the present invention.

[0020] The present invention provides a method for preparing a light emitting diode, such as Figure 1 As shown, it includes the steps of:

[0021] S01, depositing a hole transport material solution on a prefabricated device, wherein the hole transport material is PVK;

[0022] S02 , applying a first electric field in the upper and lower directions of the prefabricated device, performing a first heating treatment on the hole material solution, and forming a hole transport layer on the prefabricated device.

[0023] This embodiment uses PVK as the hole transport material. The purpose of the first heat treatment is to increase the kinetic energy of the PVK molecules, giving the polymer chains and carbazole groups greater mobility. At the same time, it promotes the evaporation of solvent molecules and ensures the subsequent complete removal of solvent molecules in the hole transport layer. The purpose of applying a first electric field in the upper and lower directions of the prefabricated device is to guide the carbazole groups in the PVK molecules to rotate and form an orderly face-to-face structure. Because the carbazole group is an electron-rich functional group, under the action of the electric field, the electron-rich carbazole group can regularly adjust its spatial orientation according to the direction of the electric field, forming a large and stable face-to-face configuration, which greatly improves the hole transport rate of the hole transport layer. The QLED device prepared by the embodiment method has a relatively balanced electron and hole injection, which can effectively reduce the internal charge accumulation of the device, reduce the device operating voltage, and improve the device photoelectric performance.

[0024] In other embodiments, another method for preparing a light emitting diode is provided, such as Figure 2 As shown, it includes the steps of:

[0025] S10, depositing a hole transport material solution on the prefabricated device, wherein the hole transport material is PVK;

[0026] S20, placing the prefabricated device with the hole transport material solution deposited on the surface and an organic solvent horizontally spaced apart in a culture dish, and sealing the opening of the culture dish, wherein the organic solvent is a solvent that can dissolve the hole transport material;

[0027] S30 , applying a first electric field in the upper and lower directions of the prefabricated device to subject the hole transport layer material solution to a first heat treatment, thereby forming a hole transport layer on the prefabricated device.

[0028] In this embodiment, PVK is used as the hole transport layer material. By annealing the hole transport layer under the combined action of an electric field, solvent vapor, and high temperature, the photoelectric performance of the light-emitting diode can be effectively improved. The mechanism of action is as follows:

[0029] During the annealing process, the organic solvent forms solvent vapor under the first heating treatment condition. In order to prevent the solvent vapor from escaping into the external environment, the opening of the culture dish needs to be sealed so that the solvent vapor can be emitted to the surface of the spaced prefabricated device, thereby keeping the hole transport layer on the surface of the prefabricated device moist, making the PVK molecules in the hole transport layer in a semi-dispersed state, and making the polymer chains and carbazole groups in the PVK molecules have stronger mobility; the role of the first heating treatment is to increase the kinetic energy of the PVK molecules, so that the polymer chains and carbazole groups have stronger mobility, at the same time, promote the evaporation of solvent molecules, and ensure that the solvent molecules in the hole transport layer are subsequently completely removed; the role of applying the first electric field in the upper and lower directions of the prefabricated device is to guide the carbazole groups in the PVK molecules to rotate and form an ordered face-to-face structure. Since the carbazole group is an electron-rich functional group, under the action of the electric field, the electron-rich carbazole group can regularly adjust its spatial direction according to the direction of the electric field, forming a large and stable face-to-face configuration, greatly improving the hole transport rate of the hole transport layer, and the solvent vapor and high temperature both provide assistance for the rotation of the carbazole group.

[0030] The light-emitting diode prepared by the method of the embodiment has a relatively balanced electron and hole injection, which can effectively reduce the charge accumulation inside the device, reduce the device operating voltage, and improve the photoelectric performance of the device. At the same time, under the action of solvent vapor, the PVK molecules produce a dissolution-precipitation equilibrium, and the polymer molecules are rearranged, making the hole transport layer thickness more uniform, the surface flatness better, and the contact between the functional layers closer, which is also beneficial to improving the photoelectric performance of the device.

[0031] In some embodiments, as Figure 3 As shown, an annealing device is also provided, which includes a support plate 10, a two-grid culture dish 20 placed on the support plate 10, a heater 30 for heating the two-grid culture dish 20, and an upper electrode 41 and a lower electrode 42 arranged at the upper and lower ends of the two-grid culture dish 10 for providing an electric field in the vertical direction; the upper electrode 41 and the lower electrode 42 are connected to a power supply 43 via a wire, and a controller 44 for controlling the magnitude of the electric field is also provided between the power supply 43 and the upper electrode 41. As an example, if the heater is an oven, the steps of forming a hole transport layer on the prefabricated device based on the annealing device include:

[0032] A prefabricated device with a hole transport material solution deposited on its surface and an organic solvent are horizontally spaced apart in the two grids of the two-grid culture dish, the top of the two-grid culture dish is sealed, a partition is provided at the bottom between the two grids of the two-grid culture dish, and a gap is provided between the top of the partition and the top of the two-grid culture dish, so that the organic solvent can enter the hole transport layer through the gap after being heated into solvent vapor, thereby keeping the hole transport layer in a moist state; the two-grid culture dish with the prefabricated device and the organic solvent is transferred to a heater, the upper electrode and the lower electrode are connected to a power supply, a first electric field is provided in the upper and lower directions of the prefabricated device, the hole transport layer material solution is first heated by the heater, and a hole transport layer is formed on the prefabricated device.

[0033] In this embodiment, the volume of the organic solvent placed in the two-divided culture dish grid is 10-30 ml. If the solvent is too little, the amount of steam generated during the solvent vapor annealing process is insufficient and the annealing effect is poor; if the solvent volume is too large, the solvent is wasted.

[0034] In some embodiments, depositing a hole transport material solution on the prefabricated device, wherein the hole transport material is PVK, comprises: providing a PVK solution comprising an organic solvent and PVK dispersed in the organic solvent; and spin-coating the PVK solution on a substrate.

[0035] In this embodiment, PVE is dispersed in an organic solvent to prepare a PVK solution. A certain volume of the PVK solution is measured with a pipette and added dropwise to the surface of the prefabricated device. The spin coater is started and spin-coated at a certain speed for a certain time, and then the spin coater is turned off.

[0036] During the spin coating process, the volume of PVK solution measured by the pipette is in the range of 80 to 300 μl. If the solution volume is too small, it cannot be ensured that PVK completely covers the substrate. If the solution volume is too large, a large amount of PVK solution is wasted, and the production cost increases. During the spin coating process, the spin coating speed is 1000 rpm-5000 rpm. If the spin coating speed is too low, the hole transport layer obtained after annealing will be too thick. If the spin coating speed is too high, the hole transport layer obtained after annealing will be too thin. Both too thin and too thick hole transport layers will lead to electron-hole imbalance inside the device, thereby causing poor device performance. During the spin coating process, the spin coating time ranges from 30 to 90 s. If the time is too short, the hole transport layer contains a large amount of solvent that has not volatilized. In the subsequent drying process, the hole transport layer has a poor film-forming effect. If the spin coating time is too long, the production efficiency decreases.

[0037] In this embodiment, the concentration range of the PVK solution is 10-50 mg / ml. If the concentration is too low, the hole transport layer in the optoelectronic device is too thin. If the concentration is too high, the hole transport layer is too thick. If the hole transport layer is too thin or too thick, it will lead to electron-hole imbalance inside the device, thereby causing poor device performance.

[0038] In some embodiments, the organic solvent is one or more of dichlorobenzene, chlorobenzene, toluene, xylene, tetrahydrofuran, and chloroform, but is not limited thereto.

[0039] In some embodiments, during the step of performing a first heat treatment on the bisection culture dish, the temperature of the first heat treatment is 60-150° C. In this embodiment, if the temperature of the first heat treatment is too low, the vaporization rate of the organic solvent in the bisection culture dish is slow, the solvent vapor content in the bisection culture dish is low, and the annealing time is long, which is not conducive to practical application. If the temperature of the first heat treatment is too high, the organic solvent in the bisection culture dish boils violently, and droplets are easily splashed onto the surface of the hole transport layer, thereby destroying the film-forming effect of the hole transport layer.

[0040] In this embodiment, the first heat treatment duration is 10-60 minutes, i.e., the annealing time of the hole transport layer is 10-60 minutes. If the annealing time is too short, the carbazole groups in the PVK molecules will not be fully rotated, resulting in a small number of face-to-face carbazole groups, which will not improve the hole transport capacity of the hole transport layer. If the annealing time is too long, the device preparation cycle will be too long, which is not conducive to actual production applications.

[0041] In some embodiments, the two-grid culture dish is subjected to a first heat treatment, and in the step of applying a first electric field in a direction perpendicular to the substrate, the intensity of the first electric field is 10-50 V / mm. If the intensity of the first electric field is too small, the driving force for the carbazole group to form a face-to-face configuration is insufficient, the carbazole group is difficult to form a target configuration, and the hole transmission rate of the PVK film is not significantly improved; if the intensity of the first electric field is too large, discharge is likely to occur in the electric field, breaking down the PVK film and the ITO film, causing damage to the device.

[0042] In some embodiments, after forming the hole transport layer on the prefabricated device, the method further includes the steps of: removing the prefabricated device from the two-divided culture dish; applying a second electric field in a direction perpendicular to the prefabricated device and performing a second heating treatment on the prefabricated device.

[0043] Specifically, after annealing is completed, the substrate is taken out of the two-grid culture dish and placed on an insulating support plate, subjected to a second heating treatment and a second electric field is applied to remove the residual organic solvent in the hole transport layer to prevent the residual organic solvent from affecting the film formation effect.

[0044] In this embodiment, the second heat treatment temperature is 100-150°C. If the temperature is too low, the organic solvent molecules are difficult to completely remove. If the temperature is too high, the film structure of the functional layer of the optoelectronic device is easily damaged, affecting the optoelectronic performance of the device. The second heat treatment duration is 10-60 minutes. If the duration is too short, the organic solvent molecules are difficult to completely remove. If the duration is too long, the film structure of the functional layer of the device is easily damaged, affecting the optoelectronic performance of the device.

[0045] In the present embodiment, after annealing is completed, the hole transport layer still contains more organic solvent molecules, the PVK molecules are in a semi-dispersed state, the PVK molecules and the carbazole groups therein have strong mobility, and when heated again, the face-to-face configuration between the carbazole groups is easily destroyed. Therefore, in the process of completely removing the organic solvent in the hole transport layer, the purpose of applying the second electric field is to prevent the carbazole groups in the PVK molecules from turning again when the solvent is removed, destroying the face-to-face structure of the carbazole groups and reducing the hole transport rate of the hole transport layer. In the present embodiment, the second electric field strength range is 10-50V / mm. The electric field strength is too small, and the protection ability of the face-to-face configuration of the carbazole groups is insufficient. The face-to-face configuration of the carbazole groups may be destroyed. The electric field strength is too large, and discharge is likely to occur in the electric field, breaking through the PVK film and the ITO film, causing device damage.

[0046] In some embodiments, the light emitting diode may be a QLED or an OLED.

[0047] In some embodiments, when the prepared quantum dot light-emitting diode is a vertical structure, the prefabricated device includes a substrate and an anode stacked in sequence from bottom to top, such as Figure 4 As shown, the preparation of the upright structure quantum dot light-emitting diode includes the following steps:

[0048] S01, preparing an anode on a substrate to obtain a prefabricated device;

[0049] S02, preparing a hole transport layer on the anode, wherein the hole transport layer material is PVK;

[0050] S03, transferring the prefabricated device and the organic solvent into two compartments of a two-compartment culture dish, respectively, and sealing the two-compartment culture dish;

[0051] S04, applying a first electric field in the up-down direction of the prefabricated device to perform a first heating treatment on the two-divided culture dish to complete the annealing process of the hole transport layer;

[0052] S05, preparing a quantum dot light-emitting layer on the hole transport layer;

[0053] S06, preparing an electronic functional layer on the quantum dot light-emitting layer;

[0054] S07. Prepare a cathode on the electronic functional layer to obtain the quantum dot light emitting diode.

[0055] In this embodiment, the electronic functional layer includes one or more of a hole blocking layer, an electron injection layer, and an electron transport layer, but is not limited thereto.

[0056] In this embodiment, the preparation method of each layer can be a chemical method or a physical method, wherein the chemical method includes but is not limited to one or more of chemical vapor deposition, continuous ion layer adsorption and reaction method, anodization method, electrolytic deposition method, and co-precipitation method; the physical method includes but is not limited to one or more of solution method (such as spin coating, printing method, doctor blade method, dip pulling method, immersion method, spraying method, roll coating method, casting method, slit coating method or strip coating method, etc.), evaporation method (such as thermal evaporation method, electron beam evaporation method, magnetron sputtering method or multi-arc ion plating method, etc.), deposition method (such as physical vapor deposition method, atomic layer deposition method, pulsed laser deposition method, etc.).

[0057] The following is a further explanation of the preparation process of quantum dot light-emitting diodes using the spin coating method as an example:

[0058] In some embodiments, the step of preparing a quantum dot light-emitting layer on the hole transport layer includes:

[0059] The quantum dot material is dissolved in an organic solvent to prepare a quantum dot solution of a certain concentration, and the solution is spin-coated on top of the hole transport layer; and the wafer after spin coating is heated to remove the residual solvent in the quantum dot light-emitting layer.

[0060] In this embodiment, the quantum dot material can be at least one of Group II-VI single-component quantum dots, core-shell quantum dots, or alloy quantum dot materials; Group III-V single-component quantum dots, core-shell quantum dots, or alloy quantum dot materials; organic-inorganic hybrid perovskite quantum dot materials; or all-inorganic perovskite quantum dot materials. For example, the quantum dot material can be one or more of CdS, CdSe, CdTe, ZnO, ZnS, ZnSe, ZnTe, GaAs, GaP, GaSb, HgS, HgSe, HgTe, InAs, InP, InSb, AlAs, AlP, CuInS, CuInSe, and various core-shell quantum dots or alloy quantum dots.

[0061] In this embodiment, the particle size range of the quantum dot material is 8 to 15 nm. If the particle size is too small, the film-forming property of the quantum dot material will deteriorate, and the energy resonance transfer effect between the quantum dot particles will be significant, which is not conducive to the application of the material. If the particle size is too large, the quantum effect of the quantum dot material will be weakened, resulting in a decrease in the photoelectric performance of the material.

[0062] In this embodiment, the concentration range of the quantum dot solution is 10 to 50 mg / ml. If the concentration of the quantum dot material is too low, the quantum dot layer in the optoelectronic device will be too thin, and the brightness of the optoelectronic device will be weak. If the concentration of the quantum dot material is too high, the quantum dot layer will be too thick, and the internal resistance of the device will increase, which is not conducive to improving the performance of the optoelectronic device.

[0063] In this embodiment, the spin coating speed of the quantum dot light-emitting layer is 1000rpm~5000rpm. If the spin coating speed is too low, the quantum dot layer is too thick, the internal resistance of the device increases, which is not conducive to improving the performance of the optoelectronic device. If the spin coating speed is too high, the quantum dot layer in the optoelectronic device is too thin, and the brightness of the device is relatively low.

[0064] In this embodiment, the spin coating time range of the quantum dot light-emitting layer is 30-90s. If the time is too short, the quantum dot layer contains a large amount of solvent that has not volatilized. In the subsequent drying process, the quantum dot layer is easily damaged, and the film-forming effect is poor. If the spin coating time is too long, the production efficiency is reduced.

[0065] In this embodiment, the purpose of heating the spin-coated wafer is to completely remove the solvent molecules in the quantum dot light-emitting layer, preventing residual solvent from affecting the film formation effect of the quantum dot layer. The heating temperature range is 80°C-150°C. If the temperature is too low, the solvent molecules are difficult to completely remove. If the temperature is too high, the film structure of the quantum dot layer is easily damaged, affecting the optoelectronic performance of the device. The heating time range is 10-60 minutes. If the time is too short, the solvent molecules are difficult to completely remove. If the time is too long, the device preparation cycle is prolonged, which is not conducive to production.

[0066] In some embodiments, the step of preparing an electron transport layer on the quantum dot light-emitting layer includes: dissolving an N-type nano-metal oxide in an organic solvent to obtain an N-type nano-metal oxide dispersion; spin-coating the N-type nano-metal oxide dispersion on the quantum dot light-emitting layer, and placing the spin-coated wafer on a heating plate and subjecting it to constant temperature treatment to form an electron transport layer on the quantum dot light-emitting layer.

[0067] In this embodiment, the N-type nano-metal oxide may be at least one of zinc oxide, titanium dioxide, magnesium oxide, aluminum oxide, and their metal alloy oxides, but is not limited thereto.

[0068] In this embodiment, the concentration range of the N-type nano-metal oxide dispersion is 10 to 30 mg / ml. If the concentration is too low, the electron transport layer in the optoelectronic device will be too thin. If the concentration is too high, the electron transport layer will be too thick. If the electron transport layer is too thin or too thick, it will lead to electron-hole imbalance inside the device, thereby causing poor device performance.

[0069] In this embodiment, the spin coating speed of the electron transport layer is 1000rpm-5000rpm. If the spin coating speed is too low, the electron transport layer is too thick; if the spin coating speed is too high, the electron transport layer is too thin. If the electron transport layer in the optoelectronic device is too thin or too thick, it will lead to electron-hole imbalance inside the device, and thus cause poor device performance.

[0070] In this embodiment, the spin coating time of the electron transport layer is 30-90s. If the time is too short, the electron transport layer contains a large amount of solvent that has not volatilized. In the subsequent drying process, the electron transport layer is easily damaged, and the film forming effect is poor. If the spin coating time is too long, the production efficiency is reduced.

[0071] In this example, the spin-coated wafer is placed on a hot plate for constant temperature treatment to completely remove the solvent molecules in the electron transport layer, preventing residual solvent from affecting the film formation of the electron transport layer. The heating temperature range is 80°C-150°C. Too low a temperature makes it difficult to completely remove the solvent molecules, while too high a temperature increases energy consumption. The heating time range is 10-60 minutes. Too short a time makes it difficult to completely remove the solvent molecules, while too long a time prolongs the device preparation cycle, hindering production.

[0072] In some embodiments, a cathode is formed on the electron transport layer by vacuum thermal evaporation. In this process, a metal material is heated by a constant current electron beam in a vacuum environment, vaporizing it into atoms. The atomic vapor then moves freely within the vacuum chamber and collides with the cooler substrate surface, condensing to form a thin film, thus forming the cathode.

[0073] In this embodiment, the metal material may be aluminum, magnesium, calcium, silver, or other materials and alloys thereof.

[0074] In this embodiment, the current range of the electron beam bombardment is 100 to 250 A. If the current is too small, it is difficult to evaporate the metal material and the evaporation is difficult to carry out. If the current is too high, there is a large amount of pure metal atomic vapor in the vacuum chamber, the evaporation process proceeds quickly, the flatness of the metal electrode film decreases, affecting the contact between the electrode and the electron transport layer, which is not conducive to the transmission of carriers in the device.

[0075] In this embodiment, the thickness of the cathode ranges from 20 to 200 nm. If the metal cathode is too thin, the electrode is easily damaged, affecting the use of the device. If the metal cathode is too thick, the raw material consumption increases, the evaporation time is prolonged, and the production cost increases.

[0076] In some embodiments, when the prepared quantum dot light-emitting diode is an inverted structure, the prefabricated device includes a substrate, a cathode, an electronic functional layer, and a quantum dot light-emitting layer stacked in sequence from bottom to top, such as Figure 5As shown, the preparation of the inverted structure quantum dot light-emitting diode includes the following steps:

[0077] S100, preparing a cathode on a substrate;

[0078] S200, preparing an electronic functional layer on the cathode;

[0079] S300, preparing a quantum dot light-emitting layer on the electronic functional layer to obtain a prefabricated device;

[0080] S400, preparing a hole transport layer on the quantum dot light-emitting layer, wherein the hole transport layer material is PVK;

[0081] S500, transferring the prefabricated device and the organic solvent into two compartments of a two-compartment culture dish, respectively, and sealing the two-compartment culture dish;

[0082] S600, applying a first electric field in the up-down direction of the prefabricated device to perform a first heating treatment on the two-divided culture dish to complete the annealing process of the hole transport layer;

[0083] S700, preparing an anode on the hole transport layer to obtain the quantum dot light emitting diode.

[0084] In this embodiment, the electronic functional layer includes one or more of a hole blocking layer, an electron injection layer, and an electron transport layer, but is not limited thereto.

[0085] In this embodiment, the preparation method of each layer can be a chemical method or a physical method, wherein the chemical method includes but is not limited to one or more of chemical vapor deposition, continuous ion layer adsorption and reaction method, anodization method, electrolytic deposition method, and co-precipitation method; the physical method includes but is not limited to one or more of solution method (such as spin coating, printing method, doctor blade method, dip pulling method, immersion method, spraying method, roll coating method, casting method, slit coating method or strip coating method, etc.), evaporation method (such as thermal evaporation method, electron beam evaporation method, magnetron sputtering method or multi-arc ion plating method, etc.), deposition method (such as physical vapor deposition method, atomic layer deposition method, pulsed laser deposition method, etc.).

[0086] In some embodiments, a quantum dot light-emitting diode is further provided, which is prepared using the method for preparing a quantum dot light-emitting diode of the present invention.

[0087] In some specific embodiments, such as Figure 6As shown, a quantum dot light-emitting diode with an upright structure is provided, which includes a substrate 10, an anode 20, a hole transport layer 30, a quantum dot light-emitting layer 40, an electron transport layer 50 and a cathode 60 stacked in sequence from bottom to top, wherein the hole transport layer 30 is made of PVK, and the hole transport layer is annealed under the combined action of an electric field, solvent vapor and high temperature.

[0088] In some specific embodiments, such as Figure 7 As shown, an inverted quantum dot light-emitting diode is also provided, which includes a substrate 01, a cathode 02, an electron transport layer 03, a quantum dot light-emitting layer 04, a hole transport layer 05 and an anode 06 stacked in sequence from bottom to top, wherein the hole transport layer 05 is made of PVK, and the hole transport layer is annealed under the combined action of an electric field, solvent vapor and high temperature.

[0089] In some embodiments, the anode material is selected from one or more of indium-doped tin oxide (ITO), fluorine-doped tin oxide (FTO), antimony-doped tin oxide (ATO), aluminum-doped zinc oxide (AZO), gallium-doped zinc oxide (GZO), indium-doped zinc oxide (IZO), magnesium-doped zinc oxide (MZO) and aluminum-doped magnesium oxide (AMO), but is not limited thereto.

[0090] In some embodiments, the hole transport layer material is selected from one or more of poly(9,9-dioctylfluorene-co-N-(4-butylphenyl)diphenylamine) (TFB), polyvinylcarbazole (PVK), poly(N,N'-bis(4-butylphenyl)-N,N'-bis(phenyl)benzidine) (Poly-TPD), poly(9,9-dioctylfluorene-co-bis-N,N-phenyl-1,4-phenylenediamine) (PFB), 4,4',4"-tris(carbazol-9-yl)triphenylamine (TCTA), 4,4'-bis(9-carbazol)biphenyl (CBP), N,N'-diphenyl-N,N'-bis(3-methylphenyl)-1,1'-biphenyl-4,4'-diamine (TPD), and N,N'-diphenyl-N,N'-(1-naphthyl)-1,1'-biphenyl-4,4'-diamine (NPB), but is not limited thereto.

[0091] In some embodiments, the electron transport layer material is selected from one or more of ZnO, TiO, NiO, W2O3, Mo2O3, SnO, ZrO2 and Ta2O3, but is not limited thereto.

[0092] In some embodiments, the cathode may be Au, Ag, Al, Cu, Mo, or alloys thereof, but is not limited thereto.

[0093] In some embodiments, the thickness of the anode is 5-120 nm.

[0094] In some embodiments, the hole transport layer has a thickness of 30-120 nm.

[0095] In some embodiments, the thickness of the quantum dot light-emitting layer is 10-200 nm.

[0096] In some embodiments, the thickness of the electron transport layer is 5-100 nm;

[0097] In some embodiments, the cathode has a thickness of 5-120 nm.

[0098] The following is a further explanation of a quantum dot light-emitting diode and a preparation method thereof according to the present invention through specific embodiments:

[0099] Example 1

[0100] 1. First, provide an ITO glass substrate and a 10mg / ml PVK dichlorobenzene solution. Take 0.1ml of PVK dichlorobenzene solution, add it dropwise onto the ITO substrate, and spin-coat it at 3000rpm for 30s to prepare a hole transport layer on the ITO substrate; after the spin coating is completed, transfer the wafer to a two-grid culture dish, and add 15ml of dichlorobenzene to the culture dish (one grid for the wafer and one for the solvent), seal the culture dish, and transfer it to an oven. When the oven is heated to 125°C, apply an electric field in the vertical direction of the wafer (the distance between the cathode and the anode is 15mm, and the voltage is 500V), and let it stand for 20 minutes to anneal the device; after the annealing is completed, transfer the wafer out of the culture dish and place it on an insulating support plate, and continue to treat it under the combined action of high temperature and electric field for 30 minutes to remove the remaining solvent and complete the preparation of the device hole transport layer;

[0101] 2. Fix the conductive glass after spin coating the hole transport layer in the above step 1 on a spin coater, take 0.1 ml of a 30 mg / ml CdSe / CdS quantum dot n-octane solution, add it dropwise onto the hole transport layer, and spin coat at 3000 rpm for 40 seconds to prepare the quantum dot layer; after spin coating, transfer the wafer to a 110°C hot plate and heat treat for 30 minutes to remove the residual solvent, completing the preparation of the device quantum dot layer;

[0102] 3. Then, the wafer was re-fixed on the spin coater, 0.1 ml of nano zinc oxide ethanol solution was added dropwise onto the quantum dot layer, and spin-coated at 2000 rpm for 45 seconds to prepare the electron transport layer. After spin coating, the wafer was transferred to a 100° hot plate and heat-treated for 30 minutes to remove the remaining solvent, completing the preparation of the electron transport layer.

[0103] 4. The wafer is transferred to an evaporation machine, and an electron beam with a current of 35A bombards the silver element, causing the silver element to evaporate into atomic vapor, forming a 100nm thick silver electrode above the hole transport layer, and encapsulating it to obtain the final optoelectronic device.

[0104] Example 2

[0105] 1. First, provide an ITO glass substrate and a 10mg / ml PVK toluene solution. Take 0.1ml of PVK toluene solution, add it dropwise onto the ITO substrate, and spin-coat it at 3000rpm for 30s to prepare a hole transport layer on the ITO substrate; after the spin coating is completed, transfer the wafer to a two-grid culture dish, and add 15ml of toluene to the culture dish (one grid for the wafer and one for the solvent), seal the culture dish, and transfer it to an oven. When the oven is heated to 110°C, apply an electric field in the vertical direction of the wafer (the distance between the cathode and the anode is 15mm, and the voltage is 500V), and let it stand for 20 minutes to anneal the device; after the annealing is completed, transfer the wafer out of the culture dish and place it on an insulating support plate, and continue to treat it under the combined action of high temperature and electric field for 30 minutes to remove the remaining solvent and complete the preparation of the device's hole transport layer;

[0106] 2. Fix the conductive glass after spin coating the hole transport layer in the above step 1 on a spin coater, take 0.1 ml of a 30 mg / ml CdSe / CdS quantum dot n-octane solution, add it dropwise onto the hole transport layer, and spin coat at 3000 rpm for 40 seconds to prepare the quantum dot layer; after spin coating, transfer the wafer to a 110°C hot plate and heat treat for 30 minutes to remove the residual solvent, completing the preparation of the device quantum dot layer;

[0107] 3. Then, the wafer was re-fixed on the spin coater, 0.1 ml of nano zinc oxide ethanol solution was added dropwise onto the quantum dot layer, and spin-coated at 2000 rpm for 45 seconds to prepare the electron transport layer. After spin coating, the wafer was transferred to a 100° hot plate and heat-treated for 30 minutes to remove the remaining solvent, completing the preparation of the electron transport layer.

[0108] 4. The wafer is transferred to an evaporation machine, and an electron beam with a current of 35A bombards the silver element, causing the silver element to evaporate into atomic vapor, forming a 100nm thick silver electrode above the hole transport layer, and encapsulating it to obtain the final optoelectronic device.

[0109] Example 3

[0110] 1. First, provide an ITO glass substrate and a 10mg / ml PVK dichlorobenzene solution. Take 0.1ml of PVK dichlorobenzene solution, add it dropwise onto the ITO substrate, and spin-coat it at 3000rpm for 30s to prepare a hole transport layer on the ITO substrate; after the spin coating is completed, transfer the wafer to a two-grid culture dish, and add 15ml of dichlorobenzene to the culture dish (one grid for the wafer and one for the solvent), seal the culture dish, and transfer it to an oven. When the oven is heated to 125°C, apply an electric field in the vertical direction of the wafer (the distance between the cathode and the anode is 15mm, and the voltage is 500V), and let it stand for 20 minutes to anneal the device; after the annealing is completed, transfer the wafer out of the culture dish and place it on an insulating support plate, and continue to treat it under the combined action of high temperature and electric field for 30 minutes to remove the remaining solvent and complete the preparation of the device hole transport layer;

[0111] 2. Fix the conductive glass after spin coating the hole transport layer in the above step 1 on a spin coater, take 0.1 ml of a 30 mg / ml CsPbBr3 quantum dot n-octane solution, add it dropwise onto the hole transport layer, and spin coat at 3000 rpm for 40 seconds to prepare the quantum dot layer; after spin coating, transfer the wafer to a 110°C hot plate and heat treat for 30 minutes to remove the residual solvent, completing the preparation of the device quantum dot layer;

[0112] 3. Then, the wafer was re-fixed on the spin coater, 0.1 ml of nano zinc oxide ethanol solution was added dropwise onto the quantum dot layer, and spin-coated at 2000 rpm for 45 seconds to prepare the electron transport layer. After spin coating, the wafer was transferred to a 100° hot plate and heat-treated for 30 minutes to remove the remaining solvent, completing the preparation of the electron transport layer.

[0113] 4. The wafer is transferred to an evaporation machine, and an electron beam with a current of 35A bombards the silver element, causing the silver element to evaporate into atomic vapor, forming a 100nm thick silver electrode above the hole transport layer, and encapsulating it to obtain the final optoelectronic device.

[0114] Example 4

[0115] 1. First, provide an ITO glass substrate and a 10mg / ml PVK dichlorobenzene solution. Take 0.1ml of PVK dichlorobenzene solution, add it dropwise onto the ITO substrate, and spin-coat it at 3000rpm for 30s to prepare a hole transport layer on the ITO substrate; after the spin coating is completed, transfer the wafer to a two-grid culture dish, and add 15ml of dichlorobenzene to the culture dish (one grid for the wafer and one for the solvent), seal the culture dish, and transfer it to an oven. When the oven is heated to 125°C, apply an electric field in the vertical direction of the wafer (the distance between the cathode and the anode is 15mm, and the voltage is 500V), and let it stand for 20 minutes to anneal the device; after the annealing is completed, transfer the wafer out of the culture dish and place it on an insulating support plate, and continue to treat it under the combined action of high temperature and electric field for 30 minutes to remove the remaining solvent and complete the preparation of the device hole transport layer;

[0116] 2. Fix the conductive glass after spin coating the hole transport layer in the above step 1 on a spin coater, take 0.1 ml of a 30 mg / ml CdSe / CdS quantum dot n-octane solution, add it dropwise onto the hole transport layer, and spin coat at 3000 rpm for 40 seconds to prepare the quantum dot layer; after spin coating, transfer the wafer to a 110°C hot plate and heat treat for 30 minutes to remove the residual solvent, completing the preparation of the device quantum dot layer;

[0117] 3. Then, the wafer was re-fixed on the spin coater, 0.1 ml of nano magnesium zinc oxide ethanol solution was added dropwise onto the quantum dot layer, and spin-coated at 2000 rpm for 45 seconds to prepare the electron transport layer; after spin coating, the wafer was transferred to a 100° hot plate and heat-treated for 30 minutes to remove the residual solvent, completing the preparation of the electron transport layer;

[0118] 4. The wafer is transferred to an evaporation machine, and an electron beam with a current of 35A bombards the silver element, causing the silver element to evaporate into atomic vapor, forming a 100nm thick silver electrode above the hole transport layer, and encapsulating it to obtain the final optoelectronic device.

[0119] Example 5

[0120] 1. First, provide an ITO glass substrate and a 10mg / ml PVK dichlorobenzene solution. Take 0.1ml of PVK dichlorobenzene solution, add it dropwise onto the ITO substrate, and spin-coat it at 3000rpm for 30s to prepare a hole transport layer on the ITO substrate; after the spin coating is completed, transfer the wafer to a two-grid culture dish, and add 15ml of dichlorobenzene to the culture dish (one grid for the wafer and one for the solvent), seal the culture dish, and transfer it to an oven. When the oven is heated to 125°C, apply an electric field in the vertical direction of the wafer (the distance between the cathode and the anode is 15mm, and the voltage is 500V), and let it stand for 20 minutes to anneal the device; after the annealing is completed, transfer the wafer out of the culture dish and place it on an insulating support plate, and continue to treat it under the combined action of high temperature and electric field for 30 minutes to remove the remaining solvent and complete the preparation of the device hole transport layer;

[0121] 2. Fix the conductive glass after spin coating the hole transport layer in the above step 1 on a spin coater, take 0.1 ml of a 30 mg / ml CdSe / CdS quantum dot n-octane solution, add it dropwise onto the hole transport layer, and spin coat at 3000 rpm for 40 seconds to prepare the quantum dot layer; after spin coating, transfer the wafer to a 110°C hot plate and heat treat for 30 minutes to remove the residual solvent, completing the preparation of the device quantum dot layer;

[0122] 3. Then, the wafer was re-fixed on the spin coater, 0.1 ml of zinc oxide ethanol solution was added dropwise onto the quantum dot layer, and spin-coated at 2000 rpm for 45 seconds to prepare the electron transport layer. After spin coating, the wafer was transferred to a 100° hot plate and heat-treated for 30 minutes to remove the remaining solvent, completing the preparation of the electron transport layer.

[0123] 4. The wafer is transferred to a vapor deposition machine, and an electron beam with a current of 35A bombards the aluminum element, causing the aluminum element to evaporate into atomic vapor, forming a 100nm thick aluminum electrode above the hole transport layer, and encapsulating it to obtain the final optoelectronic device.

[0124] In summary, the present invention uses PVK as the hole transport layer material. By annealing the hole transport layer under the combined effects of an electric field, solvent vapor, and high temperature, more carbazole groups in the PVK molecules in the hole transport layer are formed into a regular, orderly face-to-face configuration, thereby improving the hole transport efficiency of the hole transport layer, reducing the operating voltage of the device, and optimizing the device's optoelectronic performance. Simultaneously, under the action of solvent vapor, the PVK polymer molecules in the hole transport layer rearrange themselves, making the hole transport layer thickness more uniform and smooth, and improving the contact between the functional layers, which also helps improve the device's optoelectronic performance.

[0125] It should be understood that the application of the present invention is not limited to the above examples. For those skilled in the art, improvements or changes can be made based on the above description. All these improvements and changes should fall within the scope of protection of the claims attached to the present invention.

Claims

1. A method for preparing a light emitting diode, characterized in that: Including steps: Depositing a hole transport material solution on the prefabricated device, wherein the hole transport material is PVK; placing a prefabricated device with a hole transport material solution deposited on its surface and an organic solvent horizontally spaced apart in a sealed space, wherein the organic solvent is a solvent that can dissolve the hole transport material; applying a first electric field in the upper and lower directions of the prefabricated device to perform a first heating treatment on the hole transport material solution to form a hole transport layer on the prefabricated device; taking the prefabricated device out of the sealed space; applying a second electric field in the up-down direction of the prefabricated device and performing a second heating treatment on the hole transport layer on the prefabricated device; The intensity of the first electric field is 10-50 V / mm.

2. The method for preparing a light emitting diode according to claim 1, wherein: The steps of placing a prefabricated device with a hole transport material solution deposited on its surface and an organic solvent horizontally spaced apart in a sealed space include: The prefabricated device with the hole transport material solution deposited on the surface and the organic solvent were placed horizontally in a culture dish with spacing, and the opening of the culture dish was sealed.

3. The method for preparing a light emitting diode according to claim 2, wherein: An annealing device is used to form a hole transport layer on the prefabricated device. The annealing device includes a heater, a support frame, a bisection culture dish placed on the support frame, and an upper electrode and a lower electrode provided at the upper and lower ends of the bisection culture dish for providing an electric field in a vertical direction. The steps of forming the hole transport layer on the prefabricated device using the annealing device include: placing a prefabricated device with a hole transport material solution deposited on its surface and an organic solvent horizontally spaced apart in two grids of the two-grid culture dish, and sealing the opening of the two-grid culture dish; The upper electrode and the lower electrode are connected to a power source to provide a first electric field in the upper and lower directions of the prefabricated device, and the two-grid culture dish is subjected to a first heating treatment by the heater to form a hole transport layer on the prefabricated device.

4. The method for preparing a light emitting diode according to any one of claims 1 to 3, characterized in that: The temperature of the first heating treatment is 60-150° C.; and / or the volume of the organic solvent is 10-30 ml.

5. The method for preparing a light emitting diode according to any one of claims 2-3, characterized in that: The organic solvent includes one or more of dichlorobenzene, chlorobenzene, toluene, xylene, tetrahydrofuran and chloroform.

6. The method for preparing a light emitting diode according to claim 1, wherein: The temperature of the second heat treatment is 100-150° C.; and / or the intensity of the second electric field is 10-50 V / mm.

7. The method for preparing a light emitting diode according to claim 1, wherein: The prefabricated device includes a substrate and an anode stacked in sequence from bottom to top, and the preparation of the prefabricated device includes the following steps: preparing an anode on a substrate; preparing a hole transport layer on the anode; Alternatively, the prefabricated device includes a substrate, a cathode, an electronic functional layer, and a light-emitting layer stacked in sequence from bottom to top, and the preparation of the prefabricated device includes the following steps: preparing a cathode on a substrate; preparing an electronic functional layer on the cathode; preparing a light-emitting layer on the electronic functional layer; A hole transport layer is formed on the light-emitting layer.

8. The method for preparing a light emitting diode according to claim 1, wherein: After the second heat treatment of the hole transport layer is completed, the method further comprises the following steps: preparing an anode on the hole transport layer to obtain the light-emitting diode; Alternatively, a light-emitting layer is prepared on the hole transport layer; preparing an electronic functional layer on the light-emitting layer; A cathode is prepared on the electronic functional layer to obtain the light emitting diode.

9. A light emitting diode, characterized in that: The light emitting diode is prepared by the method for preparing the light emitting diode according to any one of claims 1 to 8.

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