Low-threshold turn-on QLED device based on novel hole injection layer and preparation method

Abstract

The invention provides a low-threshold turn-on QLED device based on a novel hole injection layer and a preparation method, and belongs to the technical field of quantum light-emitting display illumination. The QLED device comprises a transparent substrate, a hole injection layer, a hole transport layer, a quantum dot light-emitting layer, an electron transport layer and a metal electrode which are sequentially overlapped, wherein the novel hole injection layer comprises a metal oxide nano material and a hole injection material, and the doping concentration of the metal oxide nano particles in the hole injection material is 1%-70%; wherein the HOMO energy level of the metal oxide nano material is lower than the HOMO energy level of the hole injection material. According to the QLED device provided by the invention, the hole injection layer is optimized by modifying the traditional hole injection material based on doping of the metal oxide nano material, the threshold voltage of the QLED device is reduced, the overall energy consumption is reduced, and the luminescence performance is improved.

Description

Technical Field

[0001] The present invention relates to the field of quantum luminescence display lighting technology, and in particular to a low-threshold lighting QLED device based on a novel hole injection layer and a preparation method thereof. Background Art

[0002] In the field of display and lighting, developments in recent years have focused on low energy consumption and performance improvement technologies. Threshold voltage is a key parameter. Lowering the threshold voltage not only means lower energy consumption, but also helps to extend the life of light-emitting devices. QLED (Quantum dot light-emitting diode) is regarded as a strong candidate for the next generation of display technology due to its advantages such as high brightness, high contrast, wide color gamut and long life. However, as energy consumption issues become increasingly prominent, the energy efficiency and performance requirements of QLED devices are getting higher and higher, among which the threshold voltage is the focus of attention. The threshold voltage refers to the minimum voltage required for the LED to start emitting visible light. Lowering the threshold voltage of QLED devices can help reduce overall energy consumption and improve the startup capability under low voltage, so that less energy is used to produce visible light.

[0003] Low-threshold QLED devices are of great significance in portable and flexible display devices, which can significantly improve the performance and reliability of the devices. First, by optimizing the threshold voltage of different color sub-pixels in OLED, low-threshold QLED technology can not only improve color performance, but also reduce energy consumption, thereby extending the use time of the device. Secondly, when the voltage fluctuation range is large, traditional QLED devices may have problems of instability and poor durability, but low-threshold QLED devices can work stably in such an environment, improving the reliability and durability of the device. Finally, the requirement of low threshold voltage has prompted researchers to study new semiconductor materials and quantum dot materials, which can still show excellent luminescence performance at low voltage, bringing new breakthroughs to display technology. Therefore, low-threshold QLED technology not only improves the user experience, but also promotes the development of the entire display technology field.

[0004] Low-threshold QLED devices are also of great significance in fully transparent display devices. Current display technology is moving towards a highly integrated direction, in which the driving method is gradually transitioning to CMOS technology. The driving voltage of CMOS is below 5V, while the threshold voltage of current transparent display devices is between 2V and 10V, which means that existing CMOS driving technology may not be able to achieve the best performance of the device. Summary of the invention

[0005] In view of the above problems existing in the prior art, the present invention provides a low-threshold start-up QLED device based on a new hole injection layer and a preparation method, which optimizes the hole injection layer based on the modification of traditional hole injection materials by doping with metal oxide nanomaterials and reduces the threshold voltage of the QLED device.

[0006] To solve the above problems, the specific content of the present invention is as follows:

[0007] In a first aspect, the present invention provides a low-threshold start-up QLED device based on a novel hole injection layer, the QLED device comprising:

[0008] A transparent substrate, a hole injection layer, a hole transport layer, a quantum dot light-emitting layer, an electron transport layer and a metal electrode are sequentially overlapped; wherein,

[0009] The novel hole injection layer comprises a metal oxide nano material and a hole injection material, wherein the doping concentration of the metal oxide nano particles in the hole injection material is 1%-70%;

[0010] Wherein, the HOMO energy level of the metal oxide nanomaterial is lower than the HOMO energy level of the hole injection material.

[0011] Furthermore, the metal oxide nanoparticles include NiO nanoparticles.

[0012] Furthermore, the hole transport layer is made of any one of PVK, Poly-TPD, TFB and PF8CZ.

[0013] Furthermore, the constituent material of the quantum dot light-emitting layer includes any one of CdSe / ZnS quantum dots, CdSe / ZnSe quantum dots, InP / ZnS quantum dots and ZnSe / ZnS quantum dots.

[0014] Furthermore, the constituent material of the electron transport layer includes ZnO or ZnMgO.

[0015] Furthermore, the transparent substrate is a hard substrate or a flexible substrate; wherein the constituent material of the hard substrate includes any one of glass, silicon dioxide and quartz, and the constituent material of the flexible substrate includes polyethylene terephthalate, polyethylene naphthalate or polyimide.

[0016] Furthermore, the metal electrode is a non-transparent metal electrode or a transparent metal electrode; wherein the non-transparent metal electrode includes Al or Ag; and the transparent metal electrode includes a metal oxide / ultra-thin metal / metal oxide structure or an ultra-thin metal electrode.

[0017] Furthermore, the metal oxide / ultra-thin metal / metal oxide structure includes any one of MoO3 / Ag / MoO3, WO3 / Ag / WO3, AZO / Ag / AZO and ZnO / Ag / ZnO.

[0018] In a second aspect, the present invention provides a method for preparing a low-threshold start-up QLED device based on a novel hole injection layer, the preparation method is applied to the low-threshold start-up QLED device based on the novel hole injection layer provided in the first aspect, the method comprising:

[0019] S1, immersing the transparent substrate in a washing solution, deionized water and anhydrous ethanol respectively for ultrasonic cleaning to remove organic matter and dust on the transparent substrate;

[0020] S2, performing nitrogen drying treatment on the transparent substrate after ultrasonic cleaning to remove residual organic solvent and dust on the transparent substrate;

[0021] S3, on the cleaned transparent substrate, sequentially spin-coating a novel hole injection layer, a hole transport layer, a quantum dot light-emitting layer and an electron transport layer; the novel hole injection layer is spin-coated with a mixed solution of metal oxide nanoparticles and hole injection material;

[0022] S4. After spin coating each functional layer, the transparent substrate is transferred into the evaporation chamber, and metal electrodes are evaporated under vacuum to obtain a low-threshold QLED device.

[0023] Furthermore, in step S3, the step of preparing the mixed solution includes:

[0024] S3-1, dissolving the hole injection material and the metal oxide nanoparticles in a solvent at the same concentration to obtain solution A and solution B;

[0025] S3-2, doping the solution B into the solution A at a concentration ratio of 1%-70% to obtain the mixed solution.

[0026] Compared with the prior art, the present invention has the following technical effects:

[0027] The low-threshold QLED device based on the novel hole injection layer provided by the present invention comprises a transparent substrate, a hole injection layer, a hole transport layer, a quantum dot light-emitting layer, an electron transport layer and a metal electrode which are arranged in sequence and overlapped; wherein the novel hole injection layer comprises a metal oxide nanomaterial and a hole injection material, and the doping concentration of the metal oxide nanoparticles in the hole injection material is 1%-70%; wherein the HOMO energy level of the metal oxide nanomaterial is lower than the HOMO energy level of the hole injection material. Therefore, the present invention dopes metal oxide nanoparticles into the hole injection material in the novel hole injection layer, and since the HOMO energy level of the metal oxide material is lower than the HOMO energy level of the hole injection material, the hole injection is limited. Therefore:

[0028] When there is no external voltage or the external voltage is small, the diffusion current and carrier recombination in the quantum dot light-emitting layer are prohibited by the built-in electric field;

[0029] When the applied voltage is greater than zero but less than the flat band voltage of the quantum dot light-emitting layer, the thermal electron emission of holes is gradually allowed, but is limited by the lower carrier concentration in the hole transport layer;

[0030] When the applied voltage is greater than the flat-band voltage of the quantum dot light-emitting layer, hole injection will increase significantly due to the reduction of the injection barrier between the new hole injection layer and the hole transport layer, which will help balance the concentration of electrons and holes injected into the quantum dot light-emitting layer. The electrons and holes injected into the quantum dot light-emitting layer have a higher probability of recombination, allowing the device to achieve effective electron-hole recombination and light emission at a lower voltage, thereby reducing the threshold voltage.

[0031] Thus, the QLED device provided by the present invention further reduces the threshold voltage of the QLED device by modifying the hole injection material by doping metal oxide nanoparticles. The doping of metal oxide nanoparticles can improve the energy level matching between the hole injection layer and the adjacent layer, thereby improving the injection efficiency of carriers, making the recombination of carriers in the light-emitting layer more complete, helping to reduce non-radiative recombination losses, and thus reducing the threshold voltage.

[0032] In addition, the QLED device provided by the present invention can also be applied to fully transparent display technology. The driving voltage of CMOS technology is usually below 5V. By optimizing the hole injection layer through doping modification to reduce the threshold voltage of the device, the transparent display device can be better compatible with the existing CMOS driving technology, avoiding the replacement of the entire driving system, thereby reducing costs and complexity. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] In order to more clearly illustrate the technical solution of the present application, the drawings required for use in the description of the present application will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative labor.

[0034] Figure 1 A schematic diagram of the structure of a low-threshold QLED device based on a novel hole injection layer provided in an embodiment of the present invention is shown;

[0035] Figure 2 A flowchart showing the steps of a method for preparing a low-threshold start-up QLED device based on a novel hole injection layer provided in an embodiment of the present invention;

[0036] Figure 3 A state trend diagram showing how the threshold voltage of a low-threshold start-up QLED device based on a novel hole injection layer provided by an embodiment of the present invention changes with the change of the doping concentration (1%-70%) of the metal oxide nanomaterial.

[0037] Description of reference numerals:

[0038] 1. Transparent substrate; 2. New hole injection layer; 3. Hole transport layer; 4. Quantum dot light-emitting layer; 5. Electron transport layer; 6. Metal electrode. DETAILED DESCRIPTION

[0039] In order to make the above-mentioned purpose, feature and a little bit of the present invention more obvious and easy to understand, the present invention is further described in detail below in conjunction with the accompanying drawings and specific embodiments. The following is a detailed description of the embodiment of the present invention. The present embodiment is implemented on the premise of the technical solution of the present invention, and a detailed implementation method and a specific operation process are given, but the protection scope of the present invention is not limited to the following embodiments. If the specific experimental steps or conditions are not indicated in the embodiment, the operation or conditions of the conventional experimental steps described in the prior art in this field can be carried out. The reagents used and other instruments that do not indicate the manufacturer are all conventional reagent products that can be obtained commercially.

[0040] In view of the challenges faced by current display technology in terms of energy consumption, brightness and lifespan, a new low-threshold start-up high-efficiency QLED device based on hole injection layer optimization will bring new breakthroughs in the display field. The present invention aims to achieve low energy consumption, high brightness, fast response and extremely sensitive to voltage changes, and proposes a design scheme for a low-threshold start-up QLED device based on a new hole injection layer 2:

[0041] The QLED device provided by the present invention improves the device energy level matching by doping metal oxide nanoparticles into the hole injection material for modification, and adjusts the charge injection and recombination mechanism by controlling the HOMO energy level difference, in order to change the limitation of the single approach of adjusting hole injection by the traditional technical route of generally adopting the multi-layer structure of anode-hole injection layer-hole transport layer-light-emitting layer.

[0042] What needs to be explained is that the traditional technical route lacks means to adjust the injection balance, especially in traditional QLED devices, which only adjust the simple energy level matching between the hole injection layer and the hole transport layer. Under different operating voltages, the injection barrier cannot be dynamically adjusted, resulting in some holes being recombined or dissipated before entering the light-emitting layer, resulting in unnecessary energy loss. At the same time, a higher operating voltage is required to drive carrier injection, which together leads to weak improvement in hole injection efficiency and difficulty in achieving effective recombination and luminescence at lower voltages. Even if the device can emit light under low voltage conditions, its own performance cannot be effectively optimized.

[0043] In view of this, in this design, a new technical route is proposed to optimize the hole injection and electron-hole recombination process by using energy level difference. Hole injection is regulated under different voltage conditions, and efficient recombination is ensured at low voltage. In the specific implementation and application process, when a lower voltage is applied, electrons and holes can be quickly generated from their respective injection layers and injected into the quantum dot film layer, achieving efficient energy conversion and luminescence.

[0044] Based on the above technical concept, the specific implementation contents of the present invention are as follows:

[0045] In the first aspect, the present invention provides a novel low-threshold start-up high-efficiency QLED device based on hole injection layer optimization. Figure 1 FIG. 1 shows a schematic structural diagram of a low threshold start-up QLED device based on a novel hole injection layer 2 provided in an embodiment of the present invention. Figure 1 As shown, a low-threshold start-up QLED device based on a novel hole injection layer comprises: a transparent substrate 1 and a novel hole injection layer 2, a hole transport layer 3, a quantum dot light-emitting layer 4, an electron transport layer 5 and a metal electrode 6 sequentially located on the upper surface of the transparent substrate 1; wherein the novel hole injection layer 2 is composed of metal oxide nanoparticles and hole injection materials, the HOMO energy level of the metal oxide nanomaterial is lower than the HOMO energy level of the hole injection material, and the quantum dot light-emitting layer 4 comprises quantum dot materials.

[0046] Specifically, when metal oxide nanoparticles are doped in the hole injection material, the HOMO (Highest Occupied Molecular Orbital) energy level of the hole injection material is reduced, and the hole injection is dynamically regulated. When there is no applied voltage or the applied voltage is small, the diffusion current and carrier recombination in the quantum dot light-emitting layer 4 are prohibited by the built-in electric field, avoiding energy loss caused by premature carrier recombination. When the applied voltage is greater than zero but less than the flat band voltage of the quantum dot light-emitting layer 4, the thermal electron emission of holes is gradually allowed, but is limited by the lower carrier concentration in the hole transport layer 3. When the applied voltage is greater than the flat band voltage of the quantum dot light-emitting layer 4, due to the reduction of the injection barrier between the new hole injection layer 2 and the hole transport layer 3, the hole injection will increase significantly, which helps to balance the concentration of electrons and holes injected in the quantum dot light-emitting layer 4. The electrons and holes injected in the quantum dot light-emitting layer 4 have a higher probability of recombination, so that the QLED device can achieve effective electron-hole recombination and light emission at a lower voltage, thereby reducing the threshold voltage.

[0047] In this embodiment, the QLED device modifies the hole injection layer, specifically by modifying the hole injection material by doping metal oxide nanoparticles, to regulate the carrier transmission performance under different voltage conditions, thereby effectively reducing the threshold voltage. This modification not only optimizes the conductive mechanism inside the material, but also improves the charge injection efficiency, thereby achieving the ability to stimulate the QLED light-emitting device to light up at a lower voltage. Therefore, when the hole injection material modified material is used in a light-emitting device, its low threshold voltage characteristics enable the device to achieve efficient light emission at lower energy consumption.

[0048] The low-threshold QLED device based on the novel hole injection layer 2 has a simple structure, which enables it to be flexibly adapted to various application scenarios. Whether it is a traditional rigid display panel or an emerging flexible display technology, this new low-threshold high-efficiency QLED device can be used as a display element.

[0049] As an illustration of this embodiment, the electrode selection is also very wide. Both ordinary non-transparent metal electrodes 6 and new transparent electrode devices can use this optimized hole injection layer to reduce the threshold voltage. Its compact size and thin design provide an ideal choice for wearable devices, mobile devices, and ultra-light and ultra-thin displays. Compared with traditional display technology, the new low-threshold start-up high-efficiency QLED device based on hole injection layer optimization has significant advantages in energy consumption. With its low threshold voltage characteristics, the low-threshold start-up high-efficiency QLED device has lower energy consumption at the same brightness, thereby extending the use time of the device.

[0050] In some embodiments, the novel hole injection layer 2 can be used in combination with other light-emitting layers, such as the quantum dot light-emitting layer 4, which can further reduce the energy consumption of the entire device while ensuring the light-emitting efficiency. Therefore, by modifying the hole injection layer to reduce the threshold voltage, not only the performance of the light-emitting device is improved, but also a new idea is provided for the development of efficient and energy-saving light-emitting devices.

[0051] In a preferred embodiment, the metal oxide nanoparticles include NiO nanoparticles or other metal oxide nanoparticles that can reduce the HOMO energy level of the hole injection material. In this embodiment, the metal oxide nanoparticles can reduce the valence band of the hole injection material, so the new hole injection layer 2 can further reduce the threshold voltage of the QLED device.

[0052] Specifically, metal oxide nanoparticles such as NiO are used, whose HOMO energy level is not only lower than the HOMO energy level of the hole injection material, and the hole injection is regulated under different voltage conditions; they also have good charge injection ability and electrode matching, so they are suitable for loading in DC injection devices to promote efficient carrier injection. In this way, this solution is suitable for DC injection devices, and the valence band of the hole injection material is reduced by doping with metal oxide nanoparticles to enhance its hole injection ability. When specifically applied to the field of quantum dot light-emitting devices, it has good compatibility with the specific device structure configured with the interface characteristics, material system and light-emitting mechanism of the quantum dot light-emitting layer 4, so it is very suitable for QLEDs that have higher requirements for balanced recombination of electrons and holes.

[0053] As a further illustration of this embodiment, the doped metal oxide is used as nano-metal particles, and the size of the nano-particles is generally in the range of 1-100 nanometers. The particle size is smaller but the specific surface area and surface energy are larger. The surface effect improves its interaction with the hole injection material. Therefore, the structure of NiO nano-particles doped with hole injection materials has good applicability and doping agglomeration effect.

[0054] Furthermore, by optimizing the doping concentration and distribution of nanoparticles, the injection barrier is further reduced, the hole injection efficiency is improved, and the threshold voltage of the device is reduced, thereby enhancing the stability and life of the device. As a specific explanation of the present embodiment, the HOMO energy level of the metal oxide nano material is relatively low, which can reduce the threshold voltage of hole injection. If the concentration of the metal oxide nano material is too high, it will cause insufficient hole transmission efficiency and affect the electron-hole recombination efficiency. If the concentration of the metal oxide nano material is too low, it will cause insufficient hole injection efficiency and affect the electron-hole recombination efficiency.

[0055] Therefore, the doping concentration of the metal oxide nanoparticles in the hole injection material is 1%-70%, which can take into account lower threshold voltage, higher hole transport efficiency and higher hole injection efficiency at the same time, thereby achieving optimal device performance.

[0056] For example, the doping concentration of the metal oxide nanoparticles in the hole injection material may be 1%;

[0057] The doping concentration of the metal oxide nanoparticles in the hole injection material can be 30%;

[0058] The doping concentration of the metal oxide nanoparticles in the hole injection material can be 50%;

[0059] The doping concentration of the metal oxide nanoparticles in the hole injection material may be 70%.

[0060] In some embodiments, the hole transport layer 3 is made of any one of PVK, POLY-TPD, TFB and PF8CZ.

[0061] In some embodiments, the constituent material of the quantum dot light-emitting layer 4 is a pure color quantum dot material, and the quantum dot material is CdSe / ZnS quantum dots, CdSe / ZnSe quantum dots, InP / ZnS quantum dots or ZnSe / ZnS quantum dots.

[0062] In some embodiments, the electron transport layer 5 is made of ZnO or ZnMgO or other electron transport materials that match the energy level of quantum dots.

[0063] In some embodiments, the metal electrode 6 is a non-transparent metal electrode 6 or a transparent metal electrode 6, wherein the non-transparent metal electrode 6 includes Al, Ag or other metal electrodes 6 that match the work function of the device. The transparent metal electrode 6 is a metal oxide / ultra-thin metal / metal oxide structure, such as MoO3 / Ag / MoO3, WO3 / Ag / WO3, AZO / Ag / AZO, ZnO / Ag / ZnO; or other ultra-thin metal electrodes 6 that match the work function of the device.

[0064] In summary, in addition, the QLED device provided by the present invention can also be applied to fully transparent display technology. The driving voltage of CMOS technology is usually below 5V. By optimizing the hole injection layer through doping modification to reduce the threshold voltage of the device, the transparent display device can be better compatible with the existing CMOS driving technology, avoiding the replacement of the entire driving system, thereby reducing costs and complexity.

[0065] In a second aspect, the present invention provides a method for preparing a low-threshold QLED device based on a novel hole injection layer 2. Figure 2The flowchart of the steps of a method for preparing a low threshold QLED device based on a novel hole injection layer provided by an embodiment of the present invention is shown. Figure 2 As shown, the preparation method comprises the following steps:

[0066] S1. Ultrasonic cleaning is performed on the transparent substrate 1 using a cleaning solution, deionized water and anhydrous ethanol respectively to remove organic matter and dust on the transparent substrate 1.

[0067] In some embodiments, the transparent substrate 1 is a hard substrate or a flexible substrate; the hard substrate may be glass, silicon dioxide or quartz; the flexible substrate may be polyethylene terephthalate, polyethylene naphthalate or polyimide. In specific implementation, the transparent substrate 1 is cleaned by the above steps to effectively remove organic matter, impurities, etc. on the surface of the substrate.

[0068] S2, performing nitrogen drying treatment on the transparent substrate 1 after ultrasonic cleaning to remove residual organic solvent and dust on the transparent substrate 1.

[0069] S3, on the cleaned transparent substrate 1, a novel hole injection layer 2, a hole transport layer 3, a quantum dot light-emitting layer 4 and an electron transport layer 5 are sequentially prepared by spin coating, wherein the novel hole injection layer 2 is prepared by spin coating a mixed solution of metal oxide nanoparticles and hole injection materials;

[0070] In this embodiment, the doping concentration of the metal oxide nanoparticles in the mixed solution in the hole injection material is 1%-70%. For example:

[0071] The doping concentration of the metal oxide nanoparticles in the hole injection material can be 1%;

[0072] The doping concentration of the metal oxide nanoparticles in the hole injection material can be 30%;

[0073] The doping concentration of the metal oxide nanoparticles in the hole injection material can be 50%;

[0074] The doping concentration of the metal oxide nanoparticles in the hole injection material may be 70%.

[0075] The doping concentration of the metal oxide nanoparticles in the hole injection material is 1%-70%, so as to take into account lower threshold voltage, higher hole transport efficiency and higher hole injection efficiency at the same time, thereby achieving the best device performance.

[0076] Furthermore, step S3 further includes:

[0077] The novel hole injection layer 2 is obtained by mixing metal oxide nanomaterials and hole injection materials, and the preparation steps of the mixed solution are as follows:

[0078] S3-1, dissolving the hole injection material and the metal oxide nanoparticles in a solvent at the same concentration to obtain solution A and solution B;

[0079] S3-2, doping the solution B into the solution A at a concentration ratio of 1%-70% to obtain the mixed solution.

[0080] S4, transfer the transparent substrate 1 after spin coating each functional layer into the evaporation chamber, evaporate the metal electrode 6 under vacuum, and obtain a low threshold light-on QLED device. Among them, each functional layer is a new hole injection layer 2, a hole transport layer 3, a quantum dot light-emitting layer 4 and an electron transport layer 5.

[0081] Therefore, when metal oxide nanoparticles are doped in the hole injection material, the HOMO (Highest Occupied Molecular Orbital) energy level of the hole injection material is reduced, and the hole injection is dynamically regulated. When there is no external voltage or the external voltage is small, the diffusion current and carrier recombination in the quantum dot light-emitting layer 4 are prohibited by the built-in electric field, avoiding energy loss caused by premature carrier recombination. When the applied voltage is greater than zero but less than the flat band voltage of the quantum dot light-emitting layer 4, the thermal electron emission of holes is gradually allowed, but is limited by the lower carrier concentration in the hole transport layer 3. When the applied voltage is greater than the flat band voltage of the quantum dot light-emitting layer 4, due to the reduction of the injection barrier between the new hole injection layer 2 and the hole transport layer 3, the hole injection will increase significantly, which helps to balance the concentration of electrons and holes injected in the quantum dot light-emitting layer 4. The electrons and holes injected in the quantum dot light-emitting layer 4 have a higher probability of recombination, so that the QLED device can achieve effective electron-hole recombination and light emission at a lower voltage, thereby reducing the threshold voltage. In this way, by controlling the HOMO energy level difference to regulate charge injection and recombination, the invention purpose of the QLED device with many advantages such as low energy consumption, high brightness, fast response and extremely sensitive to voltage changes is achieved.

[0082] In order to enable those skilled in the art to understand the present application more clearly, a low-threshold high-efficiency QLED device based on hole injection layer optimization and a preparation method thereof described in the present application are now described in detail through the following examples.

[0083] Example 1

[0084] A method for preparing a low-threshold QLED device based on a novel hole injection layer comprises the following steps:

[0085] Step 1: ultrasonically clean the transparent base 1 using an ultrasonic cleaner containing a washing solution, deionized water and anhydrous ethanol;

[0086] Step 2: After the ultrasonic cleaning, the glass substrate is dried with nitrogen to remove organic matter and dust on the glass substrate;

[0087] Step 3: dissolving the NiO nanoparticle dispersion in anhydrous ethanol, and mixing it with the PEDOT:PSS solution in a ratio of 30%, 50%, and 70%, and stirring at room temperature to obtain an optimized hole injection material; placing the transparent substrate 1 into a coating machine, then sucking the bottom of the transparent substrate 1 with a vacuum suction cup, spin coating the new hole injection layer 2 on the transparent substrate 1, and annealing it on a heating table at 150° C. for 20 minutes; thereby completing the preparation of the hole injection layer;

[0088] Step 4: Spin-coat the TFB solution on the novel hole injection layer 2 formed in step 4, and place the glass substrate on a heating platform for annealing after spin coating to form a hole transport layer 3;

[0089] Step 5: Spin-coating CdSe / ZnS quantum dots on the hole transport layer 3 formed in step 4, and placing the glass substrate on a heating platform for annealing after spin coating to form a quantum dot light-emitting layer 4;

[0090] Step 6, spin coating ZnMgO on the quantum dot light-emitting layer 4 formed in step 5, and placing the glass substrate on a heating platform for annealing after spin coating to form an electron transport layer 5;

[0091] Step 7: Place the substrate into a vacuum coating system, increase the current under vacuum and finally increase the current to heat the metal electrode 6 to a gaseous state, open the baffle after the evaporation rate stabilizes, and evaporate to obtain the metal electrode 6 of the QLED device, thereby obtaining a low-threshold start-up and high-efficiency QLED device.

[0092] Comparative Example 1

[0093] Step 1: ultrasonically clean the transparent base 1 using an ultrasonic cleaner containing a washing solution, deionized water and anhydrous ethanol;

[0094] Step 2: After the ultrasonic cleaning, the glass substrate is dried with nitrogen to remove organic matter and dust on the glass substrate;

[0095] Step 3: Place the transparent substrate 1 into a coating machine, then use a vacuum suction cup to suck the bottom of the transparent substrate 1 1, spin-coat the hole injection layer material PEDOT:PSS on the transparent substrate 1, and place it on a heating table at 150°C for annealing for 20 minutes; thereby completing the preparation of the hole injection layer;

[0096] Step 4: Spin-coat the TFB solution on the novel hole injection layer 2 formed in step 4, and place the glass substrate on a heating platform for annealing after spin coating to form a hole transport layer 3;

[0097] Step 5: Spin-coating CdSe / ZnS quantum dots on the hole transport layer 3 formed in step 4, and placing the glass substrate on a heating platform for annealing after spin coating to form a quantum dot light-emitting layer 4;

[0098] Step 6, spin coating ZnMgO on the quantum dot light-emitting layer 4 formed in step 5, and placing the glass substrate on a heating platform for annealing after spin coating to form an electron transport layer 5;

[0099] Step 7: Place the substrate into a vacuum coating system, increase the current under vacuum and finally increase the current to heat the metal electrode 6 to a gaseous state, open the baffle after the evaporation rate stabilizes, and evaporate to obtain the metal electrode 6 of the QLED device, thereby obtaining a low-threshold start-up and high-efficiency QLED device.

[0100] like Figure 3 As shown, the low-threshold start-up high-efficiency QLED device provided by the embodiment of the present invention is tested for threshold voltage as the doping concentration changes. The QLED device based on hole injection layer optimization obtained in Example 1 and the QLED device with a common hole injection layer obtained in Comparative Example 1 are tested, wherein the horizontal axis represents the doping concentration of metal oxide nanoparticles, and the vertical axis represents the threshold voltage of the device. Figure 3 The figure shows that the threshold voltage of the QLED device provided by the embodiment of the present invention changes with the concentration of the doped metal oxide nanoparticles; it can be seen that with the doping of the metal oxide nanoparticles, the threshold voltage of the QLED device is significantly reduced. Therefore, by optimizing the doping of the hole injection layer, high efficiency and low voltage lighting can be achieved.

[0101] For the method embodiments, for the sake of simplicity, they are all described as a series of action combinations, but those skilled in the art should know that the present invention is not limited by the order of the actions described, because according to the present invention, some steps can be performed in other orders or simultaneously. Secondly, those skilled in the art should also know that the embodiments described in the specification are all preferred embodiments, and the actions and components involved are not necessarily required by the present invention.

[0102] It should also be noted that, in this article, the orientation or position relationship indicated by the terms "upper", "lower", "left", "right", "inside", "outside", etc. is based on the orientation or position relationship shown in the drawings, which is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation of the present invention. In addition, relational terms such as "first" and "second" are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply that there is any such actual relationship or order between these entities or operations, nor can they be understood as indicating or implying relative importance. Moreover, the term "include" or any other variant thereof is intended to cover non-exclusive inclusion, so that a process, method, article or terminal device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or terminal device.

[0103] The above is a detailed introduction to an electroluminescent device based on a novel hole generating structure and a preparation method provided by the present application. The principle and implementation method of the present application are described in detail using specific examples. The description of the above embodiments is only used to help understand the present application, and the content of this specification should not be understood as limiting the present application. At the same time, for a person skilled in the art, according to the present application, there will be different forms of changes in the specific implementation methods and application scopes. It is not necessary and impossible to list all the implementation methods here, and the obvious changes or modifications derived therefrom are still within the protection scope of the present application.

Claims

1. A low threshold start-up QLED device based on a novel hole injection layer, characterized in that: The QLED device comprises: A transparent substrate, a hole injection layer, a hole transport layer, a quantum dot light-emitting layer, an electron transport layer and a metal electrode are sequentially overlapped; wherein, The novel hole injection layer comprises a metal oxide nano material and a hole injection material, wherein the doping concentration of the metal oxide nano particles in the hole injection material is 1%-70%; Wherein, the HOMO energy level of the metal oxide nanomaterial is lower than the HOMO energy level of the hole injection material.

2. The low threshold start-up QLED device based on a novel hole injection layer according to claim 1, characterized in that: The metal oxide nanoparticles include NiO nanoparticles.

3. The low threshold start-up QLED device based on a novel hole injection layer according to claim 1, characterized in that: The hole transport layer may be made of any one of PVK, Poly-TPD, TFB and PF8CZ.

4. The low threshold start-up QLED device based on a novel hole injection layer according to claim 1, characterized in that: The constituent material of the quantum dot light-emitting layer includes any one of CdSe / ZnS quantum dots, CdSe / ZnSe quantum dots, InP / ZnS quantum dots and ZnSe / ZnS quantum dots.

5. The low threshold start-up QLED device based on a novel hole injection layer according to claim 1, characterized in that: The electron transport layer is made of ZnO or ZnMgO.

6. The low threshold start-up QLED device based on a novel hole injection layer according to claim 1, characterized in that: The transparent substrate is a hard substrate or a flexible substrate; wherein the constituent material of the hard substrate includes any one of glass, silicon dioxide and quartz, and the constituent material of the flexible substrate includes polyethylene terephthalate, polyethylene naphthalate or polyimide.

7. The low threshold start-up QLED device based on a novel hole injection layer according to claim 1, characterized in that: The metal electrode is a non-transparent metal electrode or a transparent metal electrode; wherein the non-transparent metal electrode includes Al or Ag; and the transparent metal electrode includes a metal oxide / ultra-thin metal / metal oxide structure or an ultra-thin metal electrode.

8. The low threshold start-up QLED device based on a novel hole injection layer according to claim 7, characterized in that: The metal oxide / ultra-thin metal / metal oxide structure includes any one of MoO3 / Ag / MoO3, WO3 / Ag / WO3, AZO / Ag / AZO and ZnO / Ag / ZnO.

9. A method for preparing a low-threshold QLED device based on a novel hole injection layer, characterized in that: The preparation method is applied to prepare the low-threshold start-up QLED device based on the novel hole injection layer as described in any one of claims 1 to 8, and the method comprises: S1, immersing the transparent substrate in a washing solution, deionized water and anhydrous ethanol respectively for ultrasonic cleaning to remove organic matter and dust on the transparent substrate; S2, performing nitrogen drying on the transparent substrate after ultrasonic cleaning to remove residual organic solvent and dust on the transparent substrate; S3, on the cleaned transparent substrate, sequentially spin-coating a novel hole injection layer, a hole transport layer, a quantum dot light-emitting layer and an electron transport layer; the novel hole injection layer is spin-coated with a mixed solution of metal oxide nanoparticles and hole injection material; S4. After spin coating each functional layer, the transparent substrate is transferred into the evaporation chamber, and metal electrodes are evaporated under vacuum to obtain a low-threshold QLED device.

10. The method for preparing a low-threshold QLED device based on a novel hole injection layer according to claim 9, characterized in that: In step S3, the steps of preparing the mixed solution include: S3-1, dissolving the hole injection material and the metal oxide nanoparticles in a solvent at the same concentration to obtain solution A and solution B; S3-2, doping the solution B into the solution A at a concentration ratio of 1%-70% to obtain the mixed solution.

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