Quantum dot light emitting device, preparation method thereof and display device

Abstract

The application discloses a quantum dot light-emitting device, a preparation method thereof and a display device. The quantum dot light-emitting device comprises an anode, a functional layer arranged on the anode, and a cathode arranged on a side of the functional layer away from the anode. The functional layer comprises an electron transport auxiliary layer and a quantum dot light-emitting layer arranged in a stack. The electron transport auxiliary layer is close to the anode, and the quantum dot light-emitting layer is close to the cathode. The material of the electron transport auxiliary layer comprises a metal chloride and a metal oxide. The metal oxide can promote the acceleration of electron enrichment in the hole transport layer. The insulating property of the metal chloride can temporarily and rapidly enrich the electron in the electron transport auxiliary layer. When a preset potential is formed, the electron can be transferred to the hole transport layer, so that the quantum dot light-emitting device can realize the transmission balance of electrons and holes under the condition of low brightness and low current, and effectively improve the efficiency roll-off problem of the existing quantum dot light-emitting device under the condition of low brightness and low current.

Description

Technical Field

[0001] This application relates to the field of optoelectronic technology, specifically to a quantum dot light-emitting device, its fabrication method, and a display device. Background Technology

[0002] Quantum dot light-emitting diodes (QLEDs) are quantum dot light-emitting devices with advantages such as tunable emission spectrum, narrow emission spectrum, and high luminous efficiency. QLED display panels are currently a research hotspot in the field of display technology. Compared with traditional liquid crystal display (LCD) and organic light-emitting diode (OLED) display panels, QLED display panels have significant competitive advantages in color purity and color saturation.

[0003] Currently, QLED technology is still in its immature stage, and efficiency roll-off is the main reason limiting its application. Display panels often need to operate at low brightness, but QLEDs suffer from low current efficiency and low external quantum efficiency (EQE) at low brightness, which negatively impacts their energy consumption and luminous efficiency. The main reason for this is that normal operation of QLEDs requires an electron-hole transport balance. After being powered on, QLEDs need to accumulate a certain amount of electrons to achieve this balance. Since electron injection is typically stronger than hole injection in QLEDs, achieving this balance requires excessive electron injection, which enriches the hole transport layer to create a certain electron suppression effect. Because the amount of electron injection is less at low brightness, electrons cannot accumulate excessively in the hole transport layer, leading to an imbalance in electron-hole injection and a decrease in QLED luminous efficiency, resulting in the efficiency roll-off problem at low brightness.

[0004] Therefore, improving the current efficiency and EQE of QLED at low brightness is a technical problem that urgently needs to be solved in the field of QLED display technology. Summary of the Invention

[0005] To address the problems existing in the prior art, this application provides a quantum dot light-emitting device, its fabrication method, and a display device, in order to improve the efficiency roll-off problem of existing quantum dot light-emitting devices under low brightness and low current conditions.

[0006] The technical solution of this application is as follows:

[0007] In a first aspect, this application provides a quantum dot light-emitting device, the quantum dot light-emitting device comprising:

[0008] anode;

[0009] A functional layer is disposed on the anode; and

[0010] The cathode is disposed on the side of the functional layer away from the anode;

[0011] The functional layer includes an electron transport auxiliary layer and a quantum dot light-emitting layer stacked together, with the electron transport auxiliary layer close to the anode and the quantum dot light-emitting layer close to the cathode;

[0012] The materials of the electron transport auxiliary layer include metal chlorides and metal oxides.

[0013] In some embodiments of this application, the electron injection energy level of the quantum dots in the quantum dot light-emitting layer is -4.0 eV to -3.5 eV, and the conduction band top energy level of the metal oxide is -4.3 eV to -2.8 eV.

[0014] In some embodiments of this application, the difference between the conduction band top energy level of the metal oxide and the electron injection energy level of the quantum dot in the quantum dot light-emitting layer is no greater than 0.3 eV; and / or, the band gap of the metal oxide is greater than 0.5 eV.

[0015] In some embodiments of this application, the metal element of the metal oxide and the metal element of the metal chloride are independently selected from magnesium, titanium, calcium, strontium, or aluminum.

[0016] In some embodiments of this application, the metal element of the metal oxide is the same as the metal element of the metal chloride.

[0017] In some embodiments of this application, the functional layer further includes a hole transport layer and an electron transport layer, wherein the hole transport layer is disposed between the anode and the electron transport auxiliary layer, and the electron transport layer is disposed between the quantum dot light-emitting layer and the cathode.

[0018] In some embodiments of this application, the electron transport layer is made of zinc oxide nanomaterials doped with 2% to 15% molar percentage of magnesium, wherein the zinc oxide nanomaterials comprise zinc oxide nanoparticles; in the electron transport auxiliary layer, the metal oxide is magnesium oxide and the metal chloride is magnesium chloride.

[0019] In some embodiments of this application, the material of the quantum dot luminescent layer includes oil-soluble quantum dots and ligands attached to the surface of the oil-soluble quantum dots. The ligands include one or more of acid ligands, thiol ligands, amine ligands, (oxy)phosphine ligands, phospholipids, lecithin, and polyvinylpyridine.

[0020] In some embodiments of this application, the metal oxide has a molar percentage of 50% to 80% in the material of the electron transport auxiliary layer, and the metal chloride has a molar percentage of 20% to 50% in the material of the electron transport auxiliary layer.

[0021] Secondly, this application provides a method for fabricating a quantum dot light-emitting device, the method comprising the following steps:

[0022] A substrate is provided, the substrate including a first electrode, the first electrode being predefined as an anode or a cathode; and

[0023] An electron transport assist layer, a quantum dot light-emitting layer, and a second electrode are formed on one side of the first electrode. The second electrode is configured to have the opposite polarity to the first electrode, and the electron transport assist layer is close to the anode, while the quantum dot light-emitting layer is close to the cathode.

[0024] Wherein, when the first electrode is an anode and the second electrode is a cathode, the step of forming an electron transport auxiliary layer, a quantum dot light-emitting layer, and a second electrode on one side of the first electrode includes the following steps:

[0025] The electron transport auxiliary layer is deposited in situ on one side of the first electrode;

[0026] The quantum dot light-emitting layer is formed on the side of the electron transport auxiliary layer away from the first electrode; and

[0027] The second electrode is formed on the side of the quantum dot light-emitting layer away from the electron transport auxiliary layer;

[0028] When the first electrode is a cathode and the second electrode is an anode, the step of forming an electron transport auxiliary layer, a quantum dot light-emitting layer, and a second electrode on one side of the first electrode includes the following steps:

[0029] The quantum dot light-emitting layer is formed on one side of the first electrode;

[0030] The electron transport auxiliary layer is deposited in situ on the side of the quantum dot light-emitting layer away from the first electrode; and

[0031] The second electrode is formed on the side of the electron transport auxiliary layer away from the quantum dot light-emitting layer.

[0032] In some embodiments of this application, the in-situ deposition method of the electron transport assist layer includes the following steps:

[0033] A solution containing a metal chloride is applied to one side of the first electrode or the side of the quantum dot light-emitting layer away from the first electrode, and leveled to wet one side of the first electrode or the side of the quantum dot light-emitting layer away from the first electrode with the solution containing the metal chloride, thereby obtaining a wetted first electrode or the quantum dot light-emitting layer; and

[0034] An alkaline solution is applied to the impregnated first electrode or quantum dot light-emitting layer to convert some of the metal ions in the metal chloride into metal hydroxide precipitates. The metal hydroxide precipitates are then dehydrogenated to generate metal oxides, thus obtaining the electron transport auxiliary layer.

[0035] In some embodiments of this application, the solution containing the metal chloride includes the metal chloride and a first solvent, and the solution containing the alkali includes the alkali and a second solvent, wherein both the first solvent and the second solvent are polar organic solvents.

[0036] In some embodiments of this application, the first solvent and the second solvent are the same.

[0037] Thirdly, this application provides a display device, which includes a quantum dot light-emitting device as described in any of the first aspects, or a quantum dot light-emitting device prepared by any of the preparation methods described in any of the second aspects.

[0038] Beneficial Effects: This application provides a quantum dot light-emitting device, its fabrication method, and a display device. The quantum dot light-emitting device adds an electron transport auxiliary layer between the hole transport layer and the quantum dot light-emitting layer. The semiconductor-grade metal oxide in the electron transport auxiliary layer promotes the accelerated accumulation of electrons in the hole transport layer, allowing the hole transport layer to quickly reach electron saturation. Furthermore, the metal chloride in the electron transport auxiliary layer, due to its insulating properties, allows electrons to temporarily and rapidly accumulate in the electron transport auxiliary layer, preventing leakage current in the quantum dot light-emitting device. Moreover, once a certain weak potential is formed, electrons can be instantly transferred to the hole transport layer, thereby achieving electron enrichment in the hole transport layer. This enables the quantum dot light-emitting device to achieve electron-hole transport balance even under low brightness and low current conditions, thereby improving the current efficiency and luminous efficiency of the quantum dot light-emitting device under low brightness and low current conditions. Attached Figure Description

[0039] The technical solution and other beneficial effects of this application will become apparent from the following detailed description of specific embodiments in conjunction with the accompanying drawings.

[0040] Figure 1 This is a schematic diagram of a quantum dot light-emitting device with a positive structure provided in the embodiments of this application.

[0041] Figure 2 This is a schematic diagram of a quantum dot light-emitting device with an inversion structure provided in the embodiments of this application.

[0042] Figure 3 This is a schematic diagram of a method for fabricating a quantum dot light-emitting device with a positive structure, as provided in the embodiments of this application.

[0043] Figure 4 This is a schematic diagram of a method for fabricating a quantum dot light-emitting device with an inversion structure, as provided in an embodiment of this application. Detailed Implementation

[0044] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of this application, and not all of them. All other embodiments obtained by those skilled in the art based on the embodiments of this application without creative effort are within the scope of protection of this application.

[0045] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those familiar to those skilled in the art. Furthermore, any methods and materials similar to or equivalent to those described herein may be applied to this invention. The preferred embodiments and materials described herein are for illustrative purposes only and do not limit the scope of this application.

[0046] It should be noted that the order of description of the following embodiments is not intended to limit the preferred order of embodiments. Furthermore, in the description of this application, the term "comprising" means "including but not limited to". Various embodiments of this application may exist in the form of a range; it should be understood that the description in the form of a range is merely for convenience and brevity and should not be construed as a rigid limitation on the scope of the invention; therefore, it should be considered that the range description has specifically disclosed all possible sub-ranges and single numerical values ​​within that range. For example, it should be considered that the range description from 1 to 6 has specifically disclosed sub-ranges, such as from 1 to 3, from 1 to 4, from 1 to 5, from 2 to 4, from 2 to 6, from 3 to 6, etc., and single digits within the range, such as 1, 2, 3, 4, 5, and 6, regardless of the range. Additionally, whenever a numerical range is indicated herein, it means including any referenced number (fraction or integer) within the indicated range.

[0047] This application provides a quantum dot light-emitting device, which includes an anode, a functional layer, and a cathode arranged sequentially. The functional layer includes an electron transport auxiliary layer and a quantum dot light-emitting layer stacked together, with the electron transport auxiliary layer closer to the anode and the quantum dot light-emitting layer closer to the cathode. The electron transport auxiliary layer is made of metal oxides and metal chlorides.

[0048] As used in this application, "metal oxide" refers to a compound formed by a metal and oxygen, including metal oxide semiconductor materials. Metal oxide semiconductor materials are prone to being insulators but possess semiconductor properties, and are broadly classified into n-type and p-type. In the embodiments of this application, the metal oxide may be, for example, magnesium oxide (MgO), calcium oxide (CaO), titanium oxide (TiO2), strontium oxide (SrO), aluminum oxide (Al2O3), etc.

[0049] In some embodiments of this application, the electron injection energy level of the quantum dots in the quantum dot light-emitting layer is -4.0 eV to -3.5 eV, and the conduction band top energy level of the metal oxide is -4.3 eV to -2.8 eV.

[0050] In some embodiments of this application, the difference between the conduction band top energy level of the metal oxide and the electron injection energy level of the quantum dot in the quantum dot light-emitting layer is no greater than 0.3 eV, so that the conduction band top energy level of the metal oxide in the electron transport auxiliary layer is close to the electron injection energy level of the quantum dot in the quantum dot light-emitting layer. When the quantum dot light-emitting device is powered on, electrons will quickly pass through the quantum dot light-emitting layer and reach the electron transport auxiliary layer; and / or, the band gap of the metal oxide is greater than 0.5 eV, so that the metal oxide has the ability to transport electrons.

[0051] In some embodiments of this application, the metal element of the metal oxide and the metal element of the metal chloride are independently selected from magnesium, titanium, calcium, strontium or aluminum.

[0052] In some embodiments of this application, the metal element of the metal oxide is the same as that of the metal chloride, which helps to simplify the preparation process.

[0053] In some embodiments of this application, the functional layer further includes a hole transport layer and an electron transport layer, wherein the hole transport layer is disposed between the anode and the electron transport auxiliary layer, and the electron transport layer is disposed between the quantum dot light-emitting layer and the cathode.

[0054] In some embodiments of this application, the electron transport layer is made of zinc oxide nanomaterials doped with 2% to 15% molar percentage of magnesium, the zinc oxide nanomaterials comprising zinc oxide nanoparticles; in the electron transport auxiliary layer, the metal oxide is magnesium oxide, and the metal chloride is magnesium chloride. Doping the zinc oxide nanomaterials with a specific molar percentage of magnesium, such as 5% molar percentage, can raise the conduction band top of the electron transport layer, bringing it closer to the conduction band top energy level of magnesium oxide, which is beneficial for electron injection and further improves the current efficiency and luminous efficiency of the quantum dot light-emitting device at low brightness and low current. If the magnesium doping amount is too low, such as below 2% molar percentage, the performance improvement of the quantum dot light-emitting device is limited; if the magnesium doping amount is too high, such as above 15% molar percentage, the electron mobility of the electron transport layer will decrease significantly, which will negatively affect the performance of the quantum dot light-emitting device.

[0055] In some embodiments of this application, the material of the quantum dot luminescent layer includes oil-soluble quantum dots and ligands attached to the surface of the oil-soluble quantum dots; the ligands are readily soluble in solvents with low polarity, and the ligands include one or more of acid ligands, thiol ligands, amine ligands, (oxy)phosphine ligands, phospholipids, lecithin, and polyvinylpyridine. Acid ligands include, but are not limited to, one or more of decaic acid, undecenoic acid, tetradecanoic acid, oleic acid, and stearic acid; thiol ligands include, but are not limited to, one or more of octaalkylthiol, dodecylthiol, and octadecylthiol; amine ligands include, but are not limited to, one or more of oleylamine, octadecylamine, and octadecylamine; and (oxy)phosphine ligands include, but are not limited to, trioctylphosphine and / or trioctylphosphine oxide.

[0056] When quantum dot ink is used to prepare a quantum dot light-emitting layer, the concentration of oil-soluble quantum dots in the quantum dot ink is 1 mg / mL to 200 mg / mL, preferably 20 mg / mL to 50 mg / mL. Within the concentration range of 20 mg / mL to 50 mg / mL, the quantum dot ink has ideal processing performance and good dispersibility.

[0057] In some embodiments of this application, the molar percentage of metal oxide in the electron transport auxiliary layer is 50% to 80% to ensure the conduction band top energy level of the metal oxide and the necessary electron attraction ability, so that electrons can quickly pass through the quantum dot light-emitting layer to reach the electron transport auxiliary layer after the quantum dot light-emitting device is powered on. The molar percentage of metal chloride in the electron transport auxiliary layer is 20% to 50%, that is, the molar ratio of metal oxide to metal chloride is (1 to 4):1, to ensure that the electron transport auxiliary layer has a certain insulating property, so that electrons can quickly accumulate in the electron transport auxiliary layer without generating leakage current after the quantum dot light-emitting device is powered on, and after forming a certain weak potential, electrons can be instantly transferred to the hole transport layer, so that the hole transport layer reaches an electron-rich state. If the molar ratio of metal oxide to metal chloride is higher than 4:1 or lower than 1:1, the improvement on the current efficiency and external quantum efficiency of the quantum dot light-emitting device at low brightness is limited.

[0058] It should be noted that quantum dot light-emitting devices can be either positive or negative structures.

[0059] As an example, such as Figure 1 As shown, the quantum dot light-emitting device 1 has a positive structure. In the direction from bottom to top, the quantum dot light-emitting device 1 includes a substrate 11, an anode 12, a functional layer 13 and a cathode 14 arranged sequentially. The functional layer 13 includes a hole transport layer 131, an electron transport auxiliary layer 132, a quantum dot light-emitting layer 133 and an electron transport layer 134 arranged sequentially.

[0060] As an example, such as Figure 2 As shown, the quantum dot light-emitting device 1 has an inverted structure. In the direction from bottom to top, the quantum dot light-emitting device 1 includes a substrate 11, a cathode 14, a functional layer 13 and an anode 12 arranged sequentially. The functional layer 13 includes an electron transport layer 134, a quantum dot light-emitting layer 133, an electron transport auxiliary layer 132 and a hole transport layer 131 arranged sequentially.

[0061] It is understandable that a hole injection layer and an electron blocking layer can be set between the anode and the hole transport layer, and a hole blocking layer and an electron injection layer can be set between the cathode and the electron transport layer.

[0062] In the embodiments of this application, the materials of the other layer structures in the quantum dot light-emitting device, excluding the electron transport auxiliary layer, can be materials commonly found in the art, such as:

[0063] The substrate can be a rigid substrate or a flexible substrate; the example substrate is made of glass.

[0064] The anode material can be a transparent metal oxide; for example, the anode material is indium tin oxide (In2O3:Sn,ITO).

[0065] The cathode material can be a pure metal, an alloy, or a transparent metal oxide; for example, the cathode material is aluminum.

[0066] The hole transport layer material can be one or more of the following: TFB (poly(9,9-dioctylfluorene-CO-N-(4-butylphenyl)diphenylamine)), P3HT (3-hexyl-substituted polythiophene), PVK (poly(9-ethylenecarbazole)), Poly-TPD (poly[bis(4-phenyl)(4-butylphenyl)amine]), TCTA (4,4',4'-tris(carbazole-9-yl)triphenylamine), CBP (4,4'-bis(9-carbazole)biphenyl), PEDOT (3,4-ethylenedioxythiophene monomer), and PSS (polystyrene sulfonate).

[0067] The quantum dots in the quantum dot emitting layer can be one or more of binary oil-soluble quantum dots, ternary oil-soluble quantum dots, and quaternary oil-soluble quantum dots. Binary oil-soluble quantum dots include, but are not limited to, one or more of CdS, CdSe, CdTe, InP, AgS, PbS, PbSe, and HgS. Ternary oil-soluble quantum dots include, but are not limited to, Zn. x Cd 1-x S, Cu x In 1-x S, Zn x Cd 1-x Se、Zn x Se 1-x S, Zn x Cd 1-x Te and PbSe x S 1-x One or more of the following, quaternary phase oil-soluble quantum dots include, but are not limited to, Zn. x Cd 1-x S / ZnSe, Cu x In 1-x S / ZnS, Zn x Cd 1-x Se / ZnS, CuInSeS, Zn x Cd 1-x Te / ZnS and PbSe x S 1-x / ZnS.

[0068] The materials of the electron transport layer include, but are not limited to, one or more of ZnO, TiO2, CsF, LiF, CsCO3, and AlQ3.

[0069] Compared to existing quantum dot light-emitting devices, the quantum dot light-emitting device of this application adds an electron transport auxiliary layer between the hole transport layer and the quantum dot light-emitting layer. The semiconductor-grade metal oxide in the electron transport auxiliary layer promotes the accelerated accumulation of electrons in the hole transport layer, allowing the hole transport layer to quickly reach electron saturation. The metal chloride in the electron transport auxiliary layer, due to its insulating properties, allows electrons to temporarily and rapidly accumulate in the electron transport auxiliary layer. These accumulated electrons form excess negative charges, enhancing the electronegativity of the electron transport auxiliary layer. The electron transport layer generates a repulsive force on electrons, thereby enhancing the electron transport layer's ability to block electrons and reducing leakage current. In addition, when the electron transport layer forms a certain weak potential, electrons can be instantly transferred to the hole transport layer, thus making the hole transport layer electron-rich. The enriched electrons form excess negative charges to enhance the electronegativity of the hole transport layer, thereby attracting positively charged holes in the hole injection layer and promoting the transport of holes from the hole injection layer to the hole transport layer. This enables quantum dot light-emitting devices to achieve electron-hole transport balance even under low brightness and low current conditions.

[0070] This application also provides a method for fabricating a quantum dot light-emitting device, used to fabricate any of the quantum dot light-emitting devices described above, the fabrication method comprising the following steps:

[0071] B1. A substrate is provided, the substrate including a first electrode, the first electrode being predefined as an anode or a cathode;

[0072] B2. An electron transport auxiliary layer, a quantum dot light-emitting layer, and a second electrode are formed on one side of the first electrode. The second electrode is configured to have the opposite polarity to the first electrode, with the electron transport auxiliary layer closer to the anode and the quantum dot light-emitting layer closer to the cathode.

[0073] It should be noted that the substrate can be a single-layer structure or a multi-layer structure. For example, the substrate includes a substrate and a first electrode formed on the substrate.

[0074] It should be noted that for step B2, when the first electrode is the anode and the second electrode is the cathode, the process of forming the electron transport auxiliary layer, the quantum dot light-emitting layer, and the second electrode on one side of the first electrode includes the following steps:

[0075] B2.1 An electron transport auxiliary layer is deposited in situ on one side of the first electrode;

[0076] B2.2 A quantum dot light-emitting layer is formed on the side of the electron transport auxiliary layer away from the first electrode in step B2.1;

[0077] B2.3. A second electrode is formed on the side of the quantum dot light-emitting layer away from the electron transport auxiliary layer in step B2.2.

[0078] It should be noted that "in-situ deposition of an electron transport auxiliary layer on one side of the first electrode" includes both direct in-situ deposition of an electron transport auxiliary layer on one side of the first electrode and indirect in-situ deposition of an electron transport auxiliary layer on one side of the first electrode. That is, other functional layers, such as hole injection layers and hole transport layers, can be prepared between the first electrode and the electron transport auxiliary layer. When the hole injection layer and hole transport layer are also arranged sequentially between the first electrode and the electron transport auxiliary layer, the hole injection layer and hole transport layer need to be prepared sequentially on one side of the first electrode first, and then the electron transport auxiliary layer is deposited in-situ on the side of the hole transport layer away from the first electrode.

[0079] Similarly, other functional layers can be fabricated between the electron transport auxiliary layer and the quantum dot light-emitting layer on the side away from the first electrode, or between the quantum dot light-emitting layer and the second electrode on the side away from the electron transport auxiliary layer.

[0080] When the first electrode is a cathode and the second electrode is an anode, the step of forming an electron transport auxiliary layer, a quantum dot light-emitting layer, and a second electrode on one side of the first electrode includes the following steps:

[0081] B2.1', A quantum dot light-emitting layer is formed on one side of the first electrode;

[0082] B2.2' An electron transport auxiliary layer is deposited in situ on the side of the quantum dot light-emitting layer away from the first electrode;

[0083] B2.3' A second electrode is formed on the side of the electron transport auxiliary layer away from the quantum dot light-emitting layer.

[0084] It should be noted that "preparing a quantum dot light-emitting layer on one side of the first electrode" includes both directly preparing a quantum dot light-emitting layer on one side of the first electrode and indirectly preparing a quantum dot light-emitting layer on one side of the first electrode. That is, other functional layers, such as an electron injection layer and an electron transport layer, can be prepared between the first electrode and the quantum dot light-emitting layer. When there are also electron injection layers and electron transport layers arranged sequentially between the first electrode and the quantum dot light-emitting layer, it is necessary to first prepare an electron injection layer and an electron transport layer sequentially on one side of the first electrode, and then prepare a quantum dot light-emitting layer on the side of the electron transport layer away from the first electrode.

[0085] Similarly, other functional layers can be fabricated between the quantum dot light-emitting layer and the electron transport auxiliary layer on the side of the quantum dot light-emitting layer away from the first electrode, or between the electron transport auxiliary layer and the second electrode on the side of the electron transport auxiliary layer away from the quantum dot light-emitting layer.

[0086] Apart from the electron transport auxiliary layer, the fabrication methods for other layer structures in quantum dot light-emitting devices can employ techniques commonly used in this field, such as:

[0087] Methods for fabricating the first electrode, the second electrode, and the functional layers between the first and second electrodes include, but are not limited to, deposition methods and solution methods. Deposition methods include, but are not limited to, physical vapor deposition (PVD), including, but are not limited to, vacuum evaporation and sputtering. Solution methods include, but are not limited to, spin coating, coating, printing, blade coating, dip-coating, immersion coating, spraying, roller coating, and casting. The process parameters for fabricating the anode and cathode are not specifically limited and can be selected according to actual needs.

[0088] In some embodiments of this application, step B2.1 includes the following steps:

[0089] B2.1.1 Apply a solution containing metal chloride to one side of the first electrode and level it so that one side of the first electrode is fully wetted by the solution containing metal chloride to obtain a first electrode that has been wetted.

[0090] B2.1.2. An alkaline solution is applied to the first electrode after it has been impregnated to convert some of the metal ions in the metal chloride into metal hydroxide precipitate. Then, the metal hydroxide precipitate is dehydrogenated to generate metal oxide, thereby obtaining the electron transport auxiliary layer.

[0091] Similarly, in some embodiments of this application, step B2.2' includes the following steps:

[0092] B2.2'.1 Apply a solution containing metal chloride to the side of the quantum dot light-emitting layer away from the first electrode and level it so that the side of the quantum dot light-emitting layer away from the first electrode is fully wetted with the solution containing metal chloride to obtain a wetted quantum dot light-emitting layer;

[0093] B2.2'.2. An alkaline solution is applied to the impregnated quantum dot light-emitting layer to convert some of the metal ions in the metal chloride into metal hydroxide precipitates. Then, the metal hydroxide precipitates are dehydrogenated to generate metal oxides, thereby obtaining the electron transport auxiliary layer.

[0094] Specifically, in steps B2.1.1 and B2.2'.1, the solution containing the metal chloride is formed by dissolving the metal chloride in a first solvent other than water. The first solvent is a polar organic solvent, such as one or more of methanol, ethanol, formamide, dimethyl sulfoxide (DMSO), acetonitrile, and N,N-dimethylformamide (DMF). Water is not chosen as the first solvent because its high polarity results in a high ionization rate after dissolving the metal chloride. Adding an alkaline solution might cause the metal chloride to be lost entirely as ions, preventing the final formation of a metal oxide-metal chloride complex. Furthermore, the solution containing the metal chloride can be applied to the membrane layer dropwise.

[0095] In steps B2.1.2 and B2.2'.2, the alkali-containing solution is formed by dissolving a solid alkali in a second solvent other than water. The second solvent is a polar organic solvent, preferably the same as the first solvent. For example, the second solvent can also be one or more of methanol, ethanol, formamide, DMSO, acetonitrile, and DMF. The annealing process parameters are not specifically limited and can be selected according to actual needs, only requiring that all metal hydroxides be converted into metal oxides.

[0096] In some embodiments of this application, in steps B2.1.2 and B2.2'.2, the amount of alkali-containing solution added is sufficient to convert 50% to 80% molar percentage of the metal ions in the metal chloride into metal hydroxide precipitates.

[0097] If the amount of alkali-containing solution added is sufficient to convert less than 50% molar percentage of metal ions in the metal chloride into metal hydroxide precipitate, then the final metal oxide will have a molar percentage of less than 50% in the electron transport auxiliary layer material, and the metal chloride will have a molar percentage of more than 50% in the electron transport auxiliary layer material. If the amount of alkali-containing solution added is sufficient to convert more than 80% molar percentage of metal ions in the metal chloride into metal hydroxide precipitate, then the final metal oxide will have a molar percentage of more than 80% in the electron transport auxiliary layer material, and the metal chloride will have a molar percentage of less than 20% in the electron transport auxiliary layer material. In both cases, the improvement in current efficiency and external quantum efficiency of quantum dot light-emitting devices at low brightness is limited.

[0098] In some embodiments of this application, in steps B2.1.2 and B2.2'.2, the method for precipitating and dehydrogenating the metal hydroxide to generate metal oxide may be, for example, annealing or dehydration by introducing a dehydrating agent.

[0099] It is understood that the fabrication method of quantum dot light-emitting devices may also include a packaging process, which can be machine packaging or manual packaging. Preferably, the concentrations of oxygen and water in the environment where the packaging process is carried out are both below 0.1 ppm.

[0100] The following section uses a positive-structure quantum dot light-emitting device as an example to explain the fabrication method in detail. Figure 3 As shown, the preparation method includes the following steps:

[0101] B10. Provide a substrate, deposit an anode on the substrate by vapor deposition, and then pretreat the substrate including the anode. The pretreat includes the following steps: first, clean the substrate including the anode with a cleaning agent to initially remove surface stains; then, ultrasonically clean it for 20 minutes each in deionized water, acetone, anhydrous ethanol and deionized water to remove impurities present on the surface; finally, dry it with high-purity nitrogen.

[0102] B20. A hole transport layer material is vapor-deposited on the side of the anode away from the substrate in step B10, and then the hole transport layer is formed by thermal annealing.

[0103] B30. In step B20, a solution containing metal chloride is dropped onto the side of the hole transport layer away from the anode and leveled so that the side of the hole transport layer away from the anode is fully wetted with the solution containing metal chloride. Then, a solution containing alkali is dropped onto the hole transport layer to convert some of the metal ions in the metal chloride into metal hydroxide precipitates. Finally, the layer is annealed to obtain an electron transport auxiliary layer.

[0104] B40. A quantum dot light-emitting layer is formed on the side of the electron transport auxiliary layer away from the hole transport layer in step B30 using an inkjet printing process.

[0105] B50. An electron transport layer material is vapor-deposited on the side of the quantum dot light-emitting layer away from the hole transport layer in step B40, and then the electron transport layer is formed by thermal annealing.

[0106] B60. Using a mask plate, thermally evaporate cathode material on the side of the electron transport layer away from the quantum dot light-emitting layer in step B50 to obtain the cathode.

[0107] The following section uses an inverted quantum dot light-emitting device as an example to explain the fabrication method in detail. Figure 4 As shown, the preparation method includes the following steps:

[0108] B100. A substrate is provided, and a cathode is formed by vapor deposition on the substrate. The substrate including the cathode is then pretreated. The pretreatment includes the following steps: first, the substrate including the cathode is cleaned with a cleaning agent to initially remove surface stains; then, it is ultrasonically cleaned in deionized water, acetone, anhydrous ethanol and deionized water for 20 minutes each to remove impurities present on the surface; finally, it is dried with high-purity nitrogen.

[0109] B200: An electron transport layer material is vapor-deposited on the side of the cathode away from the substrate in step B100, and then thermally annealed to form the electron transport layer.

[0110] B300: A quantum dot light-emitting layer is formed on the side of the electron transport layer away from the cathode in step B200 using an inkjet printing process;

[0111] B400: In step B300, a solution containing metal chloride is dropped onto the side of the quantum dot light-emitting layer away from the electron transport layer and leveled so that the side of the quantum dot light-emitting layer away from the electron transport layer is fully wetted with the solution containing metal chloride. Then, a solution containing alkali is dropped on to convert some of the metal ions in the metal chloride into metal hydroxide precipitates. After annealing, an electron transport auxiliary layer is obtained.

[0112] B500, A hole transport layer material is vapor-deposited on the side of the electron transport auxiliary layer away from the quantum dot light-emitting layer in step B400, and then the hole transport layer is formed by thermal annealing.

[0113] B600, in step B500, the anode material is vapor-deposited on the side of the hole transport layer away from the quantum dot light-emitting layer to obtain the anode.

[0114] This application also provides a display device, which includes any of the quantum dot light-emitting devices described above, or quantum dot light-emitting devices prepared using any of the above-described methods. The display device can be an electronic product with display functions, such as a smartphone, tablet computer, laptop computer, digital camera, digital camcorder, smart wearable device, smart weighing scale, in-vehicle display, television, or e-book reader. The smart wearable device can be, for example, a smart bracelet, smartwatch, or virtual reality (VR) headset.

[0115] The quantum dot light-emitting device and its fabrication method of this application will be described in detail below with reference to specific embodiments, comparative examples and experimental examples.

[0116] Example 1

[0117] This embodiment provides a quantum dot light-emitting device and its fabrication method. The quantum dot light-emitting device has a positive structure. From bottom to top, the quantum dot light-emitting device includes a substrate, an anode, a hole injection layer, a hole transport layer, an electron transport auxiliary layer, a quantum dot light-emitting layer, an electron transport layer, and a cathode arranged sequentially.

[0118] The materials and thicknesses of each layer in the quantum dot light-emitting device are as follows: the substrate is glass with a thickness of 2 mm; the anode is ITO with a thickness of 120 nm; the hole injection layer is made of PEDOT and PSS in a 1:1 molar ratio with a thickness of 80 nm; the hole transport layer is TFB with a thickness of 70 nm; and the electron transport auxiliary layer is made of MgCl2 (magnesium chloride) and MgO (magnesium oxide) in a 1:4 molar ratio with a thickness of 4 nm. The quantum dot emitting layer is made of CdSeS / ZnS green quantum dots. The surface of the CdSeS / ZnS green quantum dots is connected to octylthiol ligands, and there are 0.2 mmol of ligands in every 1 mg of quantum dots. The quantum dot emitting layer is made of quantum dot ink with a quantum dot concentration of 30 mg / mL and a thickness of 70 nm. The electron transport layer is made of zinc oxide nanomaterials (the particle size of zinc oxide nanoparticles is 2 nm to 5 nm) and has a thickness of 50 nm. The cathode is made of Ag (silver) and has a thickness of 60 nm.

[0119] The fabrication method of quantum dot light-emitting devices includes the following steps:

[0120] S1.1. Provide a substrate, deposit an anode on the substrate by vapor deposition, and then pretreat the substrate including the anode. The pretreat includes the following steps: first, clean the substrate including the anode with a cleaning agent to initially remove surface stains; then, ultrasonically clean it for 20 minutes each in deionized water, acetone, anhydrous ethanol and deionized water to remove impurities present on the surface; finally, dry it with high-purity nitrogen.

[0121] S1.2. A hole injection layer material is vapor-deposited on the side of the anode away from the substrate in step S1.1, and then heat-annealed at 200°C to form a hole injection layer.

[0122] S1.3. A hole transport layer material is vapor-deposited on the side of the hole injection layer away from the anode in step S1.2, and then heat-annealed at 200°C to form a hole transport layer.

[0123] S1.4. In step S1.3, 30 μL of a 5 mmol / mL MgCl2-methanol solution (MgCl2 as solute and anhydrous methanol as solvent) is added dropwise to the side of the hole transport layer away from the hole injection layer, and leveled to fully wet the surface of the hole transport layer with the MgCl2-methanol solution. Then, 30 μL of an 8 mmol / mL tetramethylammonium hydroxide-methanol solution (tetramethylammonium hydroxide as solute and anhydrous methanol as solvent) is added dropwise to convert 80% of the magnesium ions in MgCl2 into magnesium hydroxide precipitate. After standing for a period of time, the mixture is annealed at 150°C for 30 minutes to obtain the electron transport auxiliary layer.

[0124] S1.5. Inkjet print quantum dot ink onto the side of the electron transport auxiliary layer away from the hole transport layer in step S1.4 to form a quantum dot light-emitting layer;

[0125] S1.6. Electron transport layer material is vapor-deposited on the side of the quantum dot light-emitting layer away from the hole transport layer in step S1.5, and then thermally annealed at 200°C to form the electron transport layer.

[0126] S1.7. A cathode is formed by evaporating the electron transport layer in step S1.6 using a mask, and then encapsulation is performed to obtain a quantum dot light-emitting device.

[0127] Example 2

[0128] This embodiment provides a quantum dot light-emitting device and its preparation method. The only difference between the quantum dot light-emitting device in this embodiment and the quantum dot light-emitting device in Embodiment 1 is that the electron transport auxiliary layer is made of MgCl2 and MgO, and the molar ratio of MgCl2 to MgO is 7:13.

[0129] Correspondingly, compared with the quantum dot light-emitting device preparation method in Example 1, the only difference in the preparation method of the quantum dot light-emitting device in this example is that the amount of tetramethylammonium hydroxide-methanol solution with a concentration of 8 mmol / mL added in step S1.4 is different, so as to convert 65% of the magnesium ions in MgCl2 into magnesium hydroxide precipitate.

[0130] Example 3

[0131] This application provides a quantum dot light-emitting device and its preparation method. The only difference between the quantum dot light-emitting device in this embodiment and the quantum dot light-emitting device in Example 1 is that the electron transport auxiliary layer is made of MgCl2 and MgO, and the molar ratio of MgCl2 to MgO is 1:1.

[0132] Correspondingly, compared with the quantum dot light-emitting device preparation method in Example 1, the only difference in the preparation method of the quantum dot light-emitting device in this example is that the amount of tetramethylammonium hydroxide-methanol solution with a concentration of 8 mmol / mL added in step S1.4 is different, so as to convert 50% of the magnesium ions in MgCl2 into magnesium hydroxide precipitate.

[0133] Example 4

[0134] This embodiment provides a quantum dot light-emitting device and its preparation method. The only difference between the quantum dot light-emitting device in this embodiment and the quantum dot light-emitting device in Embodiment 1 is that the material of the electron transport layer is different. In this embodiment, the material of the electron transport layer is magnesium-doped zinc oxide nanomaterial.

[0135] Based on molar percentage, the electron transport layer in this embodiment consists of 95% zinc oxide nanomaterials as described in Example 1 and 5% magnesium. The fabrication method of the quantum dot light-emitting device in this embodiment is the same as in Example 1.

[0136] Example 5

[0137] This embodiment provides a quantum dot light-emitting device and its fabrication method. The only difference between the quantum dot light-emitting device in this embodiment and the quantum dot light-emitting device in Embodiment 4 is that the molar fraction of magnesium doping in the electron transport layer material is different.

[0138] Based on molar percentage, the electron transport layer in this embodiment consists of 98% zinc oxide nanomaterials as described in Example 1 and 2% magnesium. The fabrication method of the quantum dot light-emitting device in this embodiment is the same as in Example 1.

[0139] Example 6

[0140] This embodiment provides a quantum dot light-emitting device and its fabrication method. The only difference between the quantum dot light-emitting device in this embodiment and the quantum dot light-emitting device in Embodiment 4 is that the molar fraction of magnesium doping in the electron transport layer material is different.

[0141] Based on molar percentage, the electron transport layer in this embodiment consists of 85% zinc oxide nanomaterials as described in Example 1 and 15% magnesium. The fabrication method of the quantum dot light-emitting device in this embodiment is the same as in Example 1.

[0142] Example 7

[0143] This embodiment provides a quantum dot light-emitting device and its preparation method. The only difference between the quantum dot light-emitting device in this embodiment and the quantum dot light-emitting device in Embodiment 1 is that the material of the electron transport auxiliary layer is different. In this embodiment, the material of the electron transport auxiliary layer is AgCl3 (aluminum chloride) and Al2O3 (aluminum oxide), wherein the molar ratio of AgCl3 to Al2O3 is 1:4.

[0144] Correspondingly, compared with the quantum dot light-emitting device fabrication method of Example 1, the only difference in the fabrication method of the quantum dot light-emitting device in this embodiment is step S1.4. In the fabrication method of this embodiment, step S1.4 is as follows: 30 μL of AgCl3-methanol solution with a concentration of 5 mmol / mL (AgCl3 is the solute and anhydrous methanol is the solvent) is added dropwise to the side of the hole transport layer away from the hole injection layer in step S1.3, and leveled so that the surface of the hole transport layer is fully wetted with AgCl3-methanol solution. Then, 30 μL of tetramethylammonium hydroxide-methanol solution with a concentration of 12 mmol / mL (tetramethylammonium hydroxide is the solute and anhydrous methanol is the solvent) is added dropwise to convert 80% of the aluminum ions in MgCl2 into aluminum hydroxide precipitate. After standing for a period of time, it is annealed at 150°C for 30 minutes to obtain the electron transport auxiliary layer.

[0145] Example 8

[0146] This embodiment provides a quantum dot light-emitting device and its preparation method. The only difference between the quantum dot light-emitting device in this embodiment and the quantum dot light-emitting device in Example 7 is that the electron transport auxiliary layer is made of AgCl3 and Al2O3, and the molar ratio of AgCl3 to Al2O3 is 7:13.

[0147] Correspondingly, compared with the quantum dot light-emitting device preparation method in Example 7, the only difference in the preparation method of the quantum dot light-emitting device in this example is that the amount of tetramethylammonium hydroxide-methanol solution with a concentration of 12 mmol / mL added in step S1.4 is different, so as to convert 65% of the aluminum ions in AlCl3 into aluminum hydroxide precipitate.

[0148] Example 9

[0149] This embodiment provides a quantum dot light-emitting device and its preparation method. The only difference between the quantum dot light-emitting device in this embodiment and the quantum dot light-emitting device in Example 7 is that the electron transport auxiliary layer is made of AgCl3 and Al2O3, and the molar ratio of AgCl3 to Al2O3 is 1:1.

[0150] Correspondingly, compared with the quantum dot light-emitting device preparation method in Example 7, the only difference in the preparation method of the quantum dot light-emitting device in this example is that the amount of tetramethylammonium hydroxide-methanol solution with a concentration of 12 mmol / mL added in step S1.4 is different, so as to convert 50% of the aluminum ions in AlCl3 into aluminum hydroxide precipitate.

[0151] Comparative Example 1

[0152] This comparative example provides a quantum dot light-emitting device and its fabrication method. The only difference between the quantum dot light-emitting device in this example and the quantum dot light-emitting device in Example 1 is that there is no electron transport auxiliary layer.

[0153] Correspondingly, compared with the quantum dot light-emitting device fabrication method of Example 1, the only difference in the fabrication method of the quantum dot light-emitting device in this comparative example is that the step S1.4 of fabricating the electron transport auxiliary layer is omitted.

[0154] Comparative Example 2

[0155] This comparative example provides a quantum dot light-emitting device and its preparation method. The only difference between the quantum dot light-emitting device in this example and the quantum dot light-emitting device in Example 1 is that the electron transport auxiliary layer is made of MgCl2 and MgO, and the molar ratio of MgCl2 to MgO is 1:9.

[0156] Correspondingly, compared with the quantum dot light-emitting device preparation method of Example 1, the only difference in the preparation method of the quantum dot light-emitting device in this comparative example is that the amount of tetramethylammonium hydroxide-methanol solution with a concentration of 8 mmol / mL added in step S1.4 is different, so as to convert 90% of the magnesium ions in MgCl2 into magnesium hydroxide precipitate.

[0157] Comparative Example 3

[0158] This comparative example provides a quantum dot light-emitting device and its preparation method. The only difference between the quantum dot light-emitting device in this comparative example and the quantum dot light-emitting device in Example 1 is that the electron transport auxiliary layer is made of MgCl2 and MgO, and the molar ratio of MgCl2 to MgO is 4:1.

[0159] Correspondingly, compared with the quantum dot light-emitting device preparation method of Example 1, the only difference in the preparation method of the quantum dot light-emitting device in this comparative example is that the amount of tetramethylammonium hydroxide-methanol solution with a concentration of 8 mmol / mL added in step S1.4 is different, so as to convert 20% of the magnesium ions in MgCl2 into magnesium hydroxide precipitate.

[0160] Comparative Example 4

[0161] This comparative example provides a quantum dot light-emitting device and its fabrication method. The only difference between this comparative example and the quantum dot light-emitting device of Example 4 is that the molar fraction of magnesium doping in the electron transport layer material is different.

[0162] Based on molar percentage, the electron transport layer in this comparative example consists of 99% zinc oxide nanomaterials as described in Example 1 and 1% magnesium. The quantum dot light-emitting device in this comparative example was fabricated according to Example 1.

[0163] Comparative Example 5

[0164] This comparative example provides a quantum dot light-emitting device and its fabrication method. The only difference between this comparative example and the quantum dot light-emitting device of Example 4 is that the molar fraction of magnesium doping in the electron transport layer material is different.

[0165] Based on molar percentage, the electron transport layer in this comparative example consists of 84% zinc oxide nanomaterials as described in Example 1 and 16% magnesium. The quantum dot light-emitting device in this comparative example was fabricated according to Example 1.

[0166] Comparative Example 6

[0167] This comparative example provides a quantum dot light-emitting device and its fabrication method. The only difference between this comparative example and the quantum dot light-emitting device of Example 4 is that the molar fraction of magnesium doping in the electron transport layer material is different.

[0168] Based on molar percentage, the electron transport layer in this comparative example consists of 80% zinc oxide nanomaterials as described in Example 1 and 20% magnesium. The quantum dot light-emitting device in this comparative example was fabricated according to Example 1.

[0169] Comparative Example 7

[0170] This comparative example provides a quantum dot light-emitting device and its preparation method. The only difference between this quantum dot light-emitting device and the quantum dot light-emitting device in Example 7 is that the electron transport auxiliary layer is made of AgCl3 and Al2O3, and the molar ratio of AgCl3 to Al2O3 is 1:9.

[0171] Correspondingly, compared with the quantum dot light-emitting device preparation method of Example 7, the only difference in the preparation method of the quantum dot light-emitting device in this comparative example is that the amount of tetramethylammonium hydroxide-methanol solution with a concentration of 12 mmol / mL added in step S1.4 is different, so as to convert 90% of the aluminum ions in AlCl3 into aluminum hydroxide precipitate.

[0172] Comparative Example 8

[0173] This comparative example provides a quantum dot light-emitting device and its preparation method. The only difference between the quantum dot light-emitting device in this example and the quantum dot light-emitting device in Example 7 is that the electron transport auxiliary layer is made of AgCl3 and Al2O3, and the molar ratio of AgCl3 to Al2O3 is 4:1.

[0174] Correspondingly, compared with the quantum dot light-emitting device preparation method of Example 7, the only difference in the preparation method of the quantum dot light-emitting device in this comparative example is that the amount of tetramethylammonium hydroxide-methanol solution with a concentration of 12 mmol / mL added in step S1.4 is different, so as to convert 20% of the aluminum ions in AlCl3 into aluminum hydroxide precipitate.

[0175] Test case

[0176] The quantum dot light-emitting devices of Examples 1 to 9 and Comparative Examples 1 to 8 were tested using an external quantum efficiency optical testing instrument. The performance test items were: maximum external quantum efficiency (EQEmax,%), external quantum efficiency at 100 nits (EQE-100,%), external quantum efficiency at 1000 nits (EQE-1k,%), electron mobility (%), resistivity (%), and turn-on voltage (V). The performance test results are detailed in Table 1 below:

[0177] Table 1 shows the performance test results of each quantum dot light-emitting device in the experimental examples.

[0178]

[0179] As shown in Table 1, the electron mobility, resistivity, and turn-on voltage of the quantum dot light-emitting devices in Examples 1 to 9 are close to those in Comparative Example 1, indicating that the added electron transport auxiliary layer did not negatively affect the electron mobility performance and operating voltage of the quantum dot light-emitting devices. Furthermore, the EQE-1k of the quantum dot light-emitting devices in Examples 1 to 9 are all close to their respective EQEmax, and the EQE-100 and EQE-1k of the quantum dot light-emitting devices in Examples 1 to 9 are significantly higher than those in Comparative Example 1. This indicates that the added electron transport auxiliary layer is beneficial for improving the current efficiency of the quantum dot light-emitting devices at low brightness, thereby increasing the electron-hole recombination rate in the quantum dot light-emitting layer and thus improving the luminous efficiency of the quantum dot light-emitting devices.

[0180] As demonstrated in Examples 1 to 3, Comparative Examples 2 and 3, and Examples 7 to 9, Comparative Examples 7 and 8, when the molar percentage of metal oxide in the electron transport auxiliary layer is 50% to 80%, it is beneficial to improve the current efficiency and luminous efficiency of quantum dot light-emitting devices under low brightness conditions. When the molar percentage of metal oxide in the electron transport auxiliary layer is less than 50%, for example, 20%, the electron mobility of the electron transport auxiliary layer decreases significantly. When the molar percentage of metal oxide in the electron transport auxiliary layer is greater than 80%, for example, 90%, the effect on improving the current efficiency and external quantum efficiency of quantum dot light-emitting devices under low brightness and low current conditions is limited.

[0181] As can be seen from Examples 1 and 4 to 6, for the electron transport auxiliary layer material in the quantum dot light-emitting device being a composition of MgCl2 and MgO in a specific ratio, optimizing the electron transport layer material from zinc oxide nanomaterials (including zinc oxide nanoparticles with a particle size of 2nm to 5nm) to zinc oxide nanomaterials doped with 2% to 15% molar percentage of magnesium can raise the conduction band top of the electron transport layer, thereby bringing it closer to the conduction band top energy level of magnesium oxide, which is beneficial for electron injection, and further improves the current efficiency and luminous efficiency of the quantum dot light-emitting device under low brightness and low current.

[0182] As can be seen from Examples 4 to 6 and Comparative Examples 4 to 6, for the electron transport layer material in a quantum dot light-emitting device that is magnesium-doped zinc oxide nanomaterial (including zinc oxide nanoparticles with a particle size of 2 nm to 5 nm), the preferred molar percentage of magnesium doping is 2% to 15%. If the magnesium doping amount is too low, for example, 1% molar percentage, the performance improvement of the quantum dot light-emitting device will be limited; if the magnesium doping amount is too high, for example, 16% and 20%, the electron mobility of the electron transport layer will decrease significantly, which will have a negative impact on the light-emitting performance of the quantum dot light-emitting device.

[0183] The foregoing has provided a detailed description of a quantum dot light-emitting device, its fabrication method, and a display device according to embodiments of this application. Specific examples have been used to illustrate the principles and implementation methods of this application. The descriptions of the embodiments above are merely for the purpose of helping to understand the technical solutions and core ideas of this application. Those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features; and these modifications or substitutions do not cause the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of this application.

Claims

1. A quantum dot light-emitting device, characterized in that, The quantum dot light-emitting device includes: anode; A functional layer is disposed on the anode; and The cathode is disposed on the side of the functional layer away from the anode; The functional layer includes an electron transport auxiliary layer and a quantum dot light-emitting layer stacked together, with the electron transport auxiliary layer close to the anode and the quantum dot light-emitting layer close to the cathode; The electron transport auxiliary layer is made of metal chlorides with insulating properties and metal oxides with semiconductor properties. The electron injection energy level of the quantum dots in the quantum dot light-emitting layer is -4.0 eV to -3.5 eV, and the conduction band top energy level of the metal oxide is -4.3 eV to -2.8 eV.

2. The quantum dot light-emitting device according to claim 1, characterized in that, The difference between the conduction band top energy level of the metal oxide and the electron injection energy level of the quantum dot in the quantum dot emitting layer is no greater than 0.3 eV; and / or, the band gap of the metal oxide is greater than 0.5 eV.

3. The quantum dot light-emitting device according to claim 1, characterized in that, The metal element of the metal oxide and the metal element of the metal chloride are independently selected from magnesium, titanium, calcium, strontium or aluminum.

4. The quantum dot light-emitting device according to claim 3, characterized in that, The metal element of the metal oxide is the same as the metal element of the metal chloride.

5. The quantum dot light-emitting device according to claim 1, characterized in that, The functional layer further includes a hole transport layer and an electron transport layer. The hole transport layer is disposed between the anode and the electron transport auxiliary layer, and the electron transport layer is disposed between the quantum dot light-emitting layer and the cathode.

6. The quantum dot light-emitting device according to claim 5, characterized in that, The electron transport layer is made of zinc oxide nanomaterials doped with 2% to 15% molar percentage of magnesium, and the zinc oxide nanomaterials include zinc oxide nanoparticles; in the electron transport auxiliary layer, the metal oxide is magnesium oxide and the metal chloride is magnesium chloride.

7. The quantum dot light-emitting device according to claim 1, characterized in that, The material of the quantum dot luminescent layer includes oil-soluble quantum dots and ligands attached to the surface of the oil-soluble quantum dots. The ligands include one or more of acid ligands, thiol ligands, amine ligands, (oxy)phosphine ligands, phospholipids, and polyvinylpyridine.

8. The quantum dot light-emitting device according to any one of claims 1 to 7, characterized in that, In the electron transport auxiliary layer, the molar percentage of the metal oxide is 50% to 80%, and the molar percentage of the metal chloride is 20% to 50%.

9. A method for fabricating a quantum dot light-emitting device, characterized in that, The preparation method includes the following steps: A substrate is provided, the substrate including a first electrode, the first electrode being predefined as an anode or a cathode; and An electron transport assist layer, a quantum dot light-emitting layer, and a second electrode are formed on one side of the first electrode. The second electrode is configured to have the opposite polarity to the first electrode, and the electron transport assist layer is close to the anode, while the quantum dot light-emitting layer is close to the cathode. Wherein, when the first electrode is an anode and the second electrode is a cathode, the step of forming an electron transport auxiliary layer, a quantum dot light-emitting layer, and a second electrode on one side of the first electrode includes the following steps: The electron transport auxiliary layer is deposited in situ on one side of the first electrode; The quantum dot light-emitting layer is formed on the side of the electron transport auxiliary layer away from the first electrode; and The second electrode is formed on the side of the quantum dot light-emitting layer away from the electron transport auxiliary layer; When the first electrode is a cathode and the second electrode is an anode, the step of forming an electron transport auxiliary layer, a quantum dot light-emitting layer, and a second electrode on one side of the first electrode includes the following steps: The quantum dot light-emitting layer is formed on one side of the first electrode; The electron transport auxiliary layer is deposited in situ on the side of the quantum dot light-emitting layer away from the first electrode; and The second electrode is formed on the side of the electron transport auxiliary layer away from the quantum dot light-emitting layer; The electron transport auxiliary layer is made of metal chlorides with insulating properties and metal oxides with semiconductor properties. The electron injection energy level of the quantum dots in the quantum dot light-emitting layer is -4.0 eV to -3.5 eV, and the conduction band top energy level of the metal oxide is -4.3 eV to -2.8 eV.

10. The preparation method according to claim 9, characterized in that, The in-situ deposition method of the electron transport auxiliary layer includes the following steps: A solution containing metal chloride is applied to one side of the first electrode or the side of the quantum dot light-emitting layer away from the first electrode and leveled so that the side of the first electrode or the side of the quantum dot light-emitting layer away from the first electrode is wetted with the solution containing metal chloride, thereby obtaining the first electrode or the quantum dot light-emitting layer that has been wetted. as well as An alkaline solution is applied to the first electrode or quantum dot light-emitting layer that has been impregnated to convert some of the metal ions in the metal chloride into metal hydroxide precipitates. Then, the metal hydroxide precipitates are dehydrogenated to generate metal oxides, thereby obtaining the electron transport auxiliary layer.

11. The preparation method according to claim 10, characterized in that, The solution containing the metal chloride includes the metal chloride and a first solvent, and the solution containing the alkali includes the alkali and a second solvent, wherein both the first solvent and the second solvent are polar organic solvents.

12. The preparation method according to claim 11, characterized in that, The first solvent and the second solvent are the same.

13. A display device, characterized in that, This includes quantum dot light-emitting devices as described in any one of claims 1 to 8, or quantum dot light-emitting devices prepared by the preparation method described in any one of claims 9 to 12.

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