CN112310253B - Quantum dot light-emitting diode and preparation method thereof - Google Patents
Quantum dot light-emitting diode and preparation method thereof Download PDFInfo
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- CN112310253B CN112310253B CN201910708550.1A CN201910708550A CN112310253B CN 112310253 B CN112310253 B CN 112310253B CN 201910708550 A CN201910708550 A CN 201910708550A CN 112310253 B CN112310253 B CN 112310253B
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- H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
- H01L33/00—Semiconductor devices having potential barriers specially adapted for light emission; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof
- H01L33/02—Semiconductor devices having potential barriers specially adapted for light emission; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof characterised by the semiconductor bodies
- H01L33/04—Semiconductor devices having potential barriers specially adapted for light emission; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof characterised by the semiconductor bodies with a quantum effect structure or superlattice, e.g. tunnel junction
- H01L33/06—Semiconductor devices having potential barriers specially adapted for light emission; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof characterised by the semiconductor bodies with a quantum effect structure or superlattice, e.g. tunnel junction within the light emitting region, e.g. quantum confinement structure or tunnel barrier
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- H01L33/02—Semiconductor devices having potential barriers specially adapted for light emission; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof characterised by the semiconductor bodies
- H01L33/14—Semiconductor devices having potential barriers specially adapted for light emission; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof characterised by the semiconductor bodies with a carrier transport control structure, e.g. highly-doped semiconductor layer or current-blocking structure
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- H01L33/00—Semiconductor devices having potential barriers specially adapted for light emission; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof
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Abstract
The invention belongs to the technical field of display, and particularly relates to a quantum dot light-emitting diode and a preparation method thereof. The quantum dot light-emitting diode comprises an anode, a composite layer and a quantum dot light-emitting layer positioned between the anode and the composite layer; the surface of the composite layer, which is close to the quantum dot light-emitting layer, is made of aluminum oxide, and the aluminum content of the composite layer is gradually increased from the surface, which is close to the quantum dot light-emitting layer, along the surface direction which is far away from the quantum dot light-emitting layer. The device is not only favorable for injecting the electron vector quantum dot light emitting layer, but also can well block the diffusion between the aluminum material in the composite layer and the electron transmission layer, thereby preventing more deep energy level defects such as oxygen vacancies from being formed, and finally improving the efficiency and the service life of the device.
Description
Technical Field
The invention belongs to the technical field of display, and particularly relates to a quantum dot light-emitting diode and a preparation method thereof.
Background
Quantum dots are nanocrystalline particles with a radius less than or near the bohr exciton radius, typically ranging in size from 2 to 20nm in diameter. The quantum dots have quantum confinement effect, can emit fluorescence after being excited, and have unique luminescence characteristics, such as wide excitation peak, narrow emission peak, adjustable luminescence spectrum and the like, so that the quantum dots have wide application prospect in the field of photoelectric luminescence. Quantum Dot Light Emitting Diodes (QLEDs) are devices that use colloidal Quantum dots as the Light Emitting layer, and the Light Emitting layer is introduced between different conductive materials to obtain Light of a desired wavelength, and such devices have the advantages of high color gamut, self-luminescence, low starting voltage, and fast response speed.
In order to improve the efficiency of the device and enable carriers to be compounded in the quantum dot light emitting layer, an electron transport layer is commonly adopted to block holes and adjust the electron injection rate at present, and the commonly used electron transport layer is prepared by spin coating of a nano ZnO solution. The electron affinity of ZnO is 4.1eV, while the electron affinity of CdSe-based quantum dots with higher efficiency is about 3.6eV, i.e. the potential barrier between the electron transport layer and the quantum dot light-emitting layer is larger (0.5eV), so Schottky contact is easily formed, energy loss exists in the injection process of electrons to influence the efficiency of the device, and the electron affinity of ZnO is larger than that of the quantum dot light-emitting layer to be not beneficial to the injection of electrons; meanwhile, a ZnO electron transport layer prepared by spin-coating a nano ZnO solution has deep-level defects such as oxygen vacancies, and is easy to capture electron recombination to reduce the efficiency of the device.
The cathode material commonly used in the present quantum dot light emitting diode device is an evaporated Al layer. When Al is used as an active metal and is in contact with a ZnO electron transmission layer or a quantum dot light emitting layer, mutual diffusion can be generated, so that a large number of deep energy level defects such as oxygen vacancies and the like are generated on the electron transmission layer and a cathode layer, and electrons are easily compounded at the deep energy level to reduce the efficiency of a device. In addition, the Al electrode is easy to react with water and oxygen in the air and even the packaging layer material, thereby damaging the structure of the device and influencing the performance and the service life of the device.
Therefore, the prior art is in need of improvement.
Disclosure of Invention
The invention aims to provide a quantum dot light-emitting diode and a preparation method thereof, and aims to solve the technical problem that the efficiency of a device is influenced because an aluminum cathode of the conventional quantum dot light-emitting diode is easy to diffuse.
In order to achieve the purpose, the invention adopts the following technical scheme:
the invention provides a quantum dot light-emitting diode on one hand, which comprises an anode, a composite layer and a quantum dot light-emitting layer positioned between the anode and the composite layer; the surface of the composite layer, which is close to the quantum dot light-emitting layer, is made of aluminum oxide, and the aluminum content of the composite layer is gradually increased from the surface, which is close to the quantum dot light-emitting layer, along the surface direction which is far away from the quantum dot light-emitting layer.
In the quantum dot light-emitting diode provided by the invention, a specific composite layer consisting of aluminum and aluminum oxide is arranged on one surface of the quantum dot light-emitting layer, which is far away from the anode, the aluminum oxide has an electron transmission function, the aluminum is a cathode material, the composite layer can be used as electron transmission and a cathode, the electron affinity of the composite layer is between 3.5eV and less than that of the commonly used quantum dot material at present, and the barrier with the quantum dot light-emitting layer is smaller, so that the interface resistance can be reduced, the injection of electrons into the quantum dot light-emitting layer is facilitated, and the device efficiency is improved; the surface that this composite bed is close to quantum dot luminous layer is transmission electron that aluminium oxide can be fine, and the surface that the composite bed is close to quantum dot luminous layer is along deviating from the surperficial direction aluminium content of quantum dot luminous layer and increase gradually, and the composite bed that aluminium oxide and aluminium that journey ladder distribution become like this can block the diffusion between the aluminium material in the composite bed and the electron transport layer well to prevent to form more deep energy level defects such as oxygen vacancy, finally improve the efficiency and the life-span of device.
The invention also provides a preparation method of the quantum dot light-emitting diode, which comprises the following steps:
providing a substrate, wherein the surface of the substrate is provided with an anode;
preparing a quantum dot light emitting layer on the substrate;
preparing a composite layer on the quantum dot light-emitting layer;
the surface of the composite layer, which is close to the quantum dot light-emitting layer, is made of aluminum oxide, and the aluminum content of the composite layer is gradually increased from the surface, which is close to the quantum dot light-emitting layer, along the surface direction which is far away from the quantum dot light-emitting layer.
According to the preparation method of the quantum dot light-emitting diode, the special composite layer consisting of aluminum and aluminum oxide is prepared on the surface, away from the anode, of the quantum dot light-emitting layer, the composite layer can be used as an electron transmission layer and a cathode, the electron affinity is smaller than that of a commonly used quantum dot material at present, the potential barrier with the quantum dot light-emitting layer is smaller, the interface resistance can be reduced, and therefore the injection of electrons into the quantum dot light-emitting layer is facilitated, and the device efficiency is improved; meanwhile, the composite layer composed of the alumina and the aluminum in the step distribution can well block the diffusion between the aluminum material in the composite layer and the electron transmission layer, thereby preventing the formation of more oxygen vacancies and other deep level defects, and finally improving the efficiency and the service life of the device.
Drawings
FIG. 1 is a schematic flow chart of a method for manufacturing a quantum dot light-emitting diode according to the present invention;
FIG. 2 is a schematic diagram of the fabrication steps of the composite layer of the quantum dot light emitting diode of the present invention;
fig. 3 is a schematic structural diagram of a quantum dot light-emitting diode according to embodiment 1 of the present invention;
fig. 4 is a schematic structural diagram of a quantum dot light emitting diode in embodiment 2 of the present invention.
Detailed Description
In order to make the technical problems, technical solutions and advantageous effects to be solved by the present invention more clearly apparent, the present invention is further described in detail below with reference to the following embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.
In one aspect, an embodiment of the present invention provides a quantum dot light emitting diode, including an anode, a composite layer, and a quantum dot light emitting layer located between the anode and the composite layer; the surface of the composite layer, which is close to the quantum dot light-emitting layer, is made of aluminum oxide, and the aluminum content of the composite layer is gradually increased from the surface, which is close to the quantum dot light-emitting layer, along the surface direction which is far away from the quantum dot light-emitting layer.
In the quantum dot light-emitting diode provided by the embodiment of the invention, a specific composite layer consisting of aluminum and aluminum oxide is arranged on one surface of the quantum dot light-emitting layer, which is far away from the anode, the aluminum oxide has an electron transmission function, the aluminum is a cathode material, the composite layer can be used as electron transmission and a cathode, the electron affinity of the composite layer is about 3.5eV and is smaller than that of the commonly used quantum dot material at present, the potential barrier with the quantum dot light-emitting layer is smaller, the interface resistance can be reduced, and therefore, the injection of electrons into the quantum dot light-emitting layer is facilitated, and the device efficiency is improved; the surface that this composite bed is close to quantum dot luminous layer is transmission electron that aluminium oxide can be fine, and the surface that the composite bed is close to quantum dot luminous layer is along deviating from the surperficial direction aluminium content of quantum dot luminous layer and increase gradually, and the composite bed that aluminium oxide and aluminium that journey ladder distribution become like this can block the diffusion between the aluminium material in the composite bed and the electron transport layer well to prevent to form more deep energy level defects such as oxygen vacancy, finally improve the efficiency and the life-span of device.
In one embodiment, the surface of the composite layer facing away from the quantum dot light emitting layer is pure aluminum. Namely, the aluminum content of the composite layer gradually increases from the surface close to the quantum dot light-emitting layer along the surface direction deviating from the quantum dot light-emitting layer until the surface of the composite layer deviating from the quantum dot light-emitting layer is pure aluminum (the aluminum content is 100%).
In the quantum dot light-emitting diode provided in an embodiment of the present invention, an electron transport layer is disposed between the composite layer and the quantum dot light-emitting layer; the composite layer not only has an electron transport function, but also can be used as a cathode, so that the quantum dot light-emitting diode in the embodiment of the invention does not need to be provided with other electron transport layers, and certainly, preferably, an electron transport layer can be additionally arranged between the composite layer and the quantum dot light-emitting layer, and the composite layer can well block the diffusion of the aluminum material to the electron transport layer. Specifically, the material of the electron transport layer is selected from ZnO and TiO2、Fe2O3、SnO2、Ta2O3At least one of AlZnO, ZnSnO and InSnO, more preferably, the material of the electron transport layer is selected from zinc oxide. In the quantum dot light-emitting diode provided by the embodiment of the invention, the composite layer has a wider band gap than zinc oxide, so that the injection of electrons into the quantum dot light-emitting layer is slowed down, the injection of carriers in the quantum dot light-emitting layer is balanced, and the quantum efficiency is further improved. The electron transport layer composed of aluminum oxide and zinc oxide in the composite layer is combined, so that the defects of oxygen vacancy and the like of the zinc oxide electron transport layer can be well improved, meanwhile, the diffusion between the zinc oxide and the aluminum material can be well blocked, the formation of more deep energy level defects of oxygen vacancy and the like is prevented, and the efficiency and the service life of the device are improved.
In the quantum dot light-emitting diode of the embodiment of the invention, if the electron transport layer is not arranged, the thickness of the pure alumina on the surface of the composite layer close to the quantum dot light-emitting layer is 25-35 nm; if an electron transport layer is arranged between the composite layer and the quantum dot light-emitting layer, the thickness of the pure alumina close to the surface of the electron transport layer in the composite layer is 5-10 nm. And the thickness of the portion containing aluminum in the composite layer (i.e. the portion close to the surface of the quantum dot light-emitting layer and with the aluminum content gradually increasing along the direction away from the surface of the quantum dot light-emitting layer) can be 50-70 nm. Thus, the total thickness of the composite layer may range from 55-105 nm: when no other electron transport layer is arranged in the device, the total thickness of the composite layer is 75-105nm, and when the electron transport layer is additionally arranged in the device, the total thickness of the composite layer is 55-80 nm.
In the quantum dot light emitting diode provided in an embodiment of the present invention, a passivation layer is disposed on a surface of the composite layer away from the quantum dot light emitting layer. The passivation layer can prevent the aluminum electrode from reacting with water oxygen in the air or the material of the encapsulation layer. Preferably, the material of the passivation layer in this embodiment is selected from alumina. The uniform and compact composite layer can well prevent the diffusion of the aluminum electrode and other layers in the device and maintain the stability of each device layer, and the compact aluminum oxide layer is arranged on the outer surface of the composite layer to serve as a passivation layer, so that the device can be well protected, the influence of the external environment on the device function layer is reduced, the service life of the device material is further prolonged, and the efficiency of the device material is further improved.
In the quantum dot light-emitting diode provided in an embodiment of the present invention, a hole function layer is disposed between the quantum dot light-emitting layer and the anode; for example, it may be a hole transport layer, or may include a hole injection layer and a hole transport layer which are stacked.
In addition, the aluminum in the composite layer is used as a cathode material, the aluminum content of the surface of the composite layer close to the quantum dot light-emitting layer is gradually increased along the surface direction deviating from the quantum dot light-emitting layer, and finally pure aluminum on the surface is formed.
On the other hand, the embodiment of the invention also provides a preparation method of the quantum dot light emitting diode, as shown in fig. 1, the preparation method comprises the following steps:
s01: providing a substrate, wherein the surface of the substrate is provided with an anode;
s02: preparing a quantum dot light emitting layer on the substrate;
s03: preparing a composite layer on the quantum dot light-emitting layer;
the surface of the composite layer, which is close to the quantum dot light-emitting layer, is made of aluminum oxide, and the aluminum content of the composite layer is gradually increased from the surface, which is close to the quantum dot light-emitting layer, along the surface direction which is far away from the quantum dot light-emitting layer.
According to the preparation method of the quantum dot light-emitting diode provided by the embodiment of the invention, the special composite layer consisting of aluminum and aluminum oxide is prepared on the surface of the quantum dot light-emitting layer, which is far away from the anode, the composite layer can be used as electron transmission and cathode, the electron affinity is smaller than that of the commonly used quantum dot material at present, the barrier with the quantum dot light-emitting layer is smaller, the interface resistance can be reduced, and therefore, the injection of electrons into the quantum dot light-emitting layer is facilitated, and the device efficiency is improved; meanwhile, the composite layer composed of the alumina and the aluminum in the step distribution can well block the diffusion between the aluminum material in the composite layer and the electron transmission layer, thereby preventing the formation of more oxygen vacancies and other deep level defects, and finally improving the efficiency and the service life of the device.
In the preparation method of the embodiment of the invention, a new evaporation process can be used for the composite layer. On the basis of the existing vacuum evaporation equipment, a pipeline interface is additionally arranged, as shown in figure 2, a micro-flow controller (MFC) is adopted to control the inflow of micro oxygen, and a high-vacuum micro-oxygen environment is created when aluminum metal is evaporated. By controlling the evaporation rate, oxygen flow and pressure of the evaporation chamber of the aluminum, composite layers with different proportions and spatial distribution can be generated in a controllable manner.
If other electron transmission layers are not prepared in the device, the step of preparing the composite layer on the quantum dot light-emitting layer comprises the following steps: depositing aluminum on the surface of the quantum dot light-emitting layer under the oxygen atmosphere condition to form an aluminum oxide layer; and then, continuously depositing aluminum under the condition of reducing the oxygen flow in a stepped manner until pure aluminum is formed on the quantum dot light-emitting layer, wherein the aluminum oxide layer, the pure aluminum and the material between the aluminum oxide layer and the pure aluminum form the composite layer. Under the condition that the device is not provided with an electron transmission layer, the composite layer needs to have a good electron transmission effect, so that the thickness of aluminum oxide on the surface, close to the quantum dot light-emitting layer, of the composite layer is relatively thick (for example, the thickness of the aluminum oxide is 25-35nm), and the preparation of the aluminum oxide layer specifically comprises the following steps: and depositing aluminum on the surface of the quantum dot light-emitting layer, and then continuously depositing the aluminum under the condition that the oxygen flow is increased in a stepped manner to form an aluminum oxide layer on the surface of the quantum dot light-emitting layer. In order to reduce the influence of oxygen on the quantum dot light-emitting layer in the deposition process, a layer of aluminum layer with the thickness of about 5nm can be deposited firstly, then oxygen is injected to oxidize the aluminum layer to obtain an aluminum oxide layer, subsequently, along with the step reduction of the oxygen flow, a composite layer is formed step by step, the content ratio of aluminum oxide to aluminum is gradually regulated and controlled, and the surface of the composite layer, which is close to the quantum dot light-emitting layer, is along the surface direction deviating from the quantum dot light-emitting layer: the composite layer can be used as a cathode to finish the preparation of a device without additionally evaporating other cathodes.
In the process: in the step of preparing the composite layer on the quantum dot light-emitting layer, the speed of depositing aluminum is 0.2-0.3 nm/s; depositing aluminum under the condition that the oxygen flow is increased to 65-70sccm in a stepwise manner at the speed of 4-6sccm/s, and forming an aluminum oxide layer on the surface of the quantum dot light-emitting layer; and then continuously depositing aluminum under the condition of the speed step reduction of the oxygen flow of 4-6sccm/s until pure aluminum is formed on the surface of the quantum dot light-emitting layer.
If the device is provided with an electron transport layer, namely after the step of preparing the quantum dot light-emitting layer on the substrate, the device also comprises the step of preparing the electron transport layer on the quantum dot light-emitting layer, and the preparation step of the composite layer comprises the following steps: depositing aluminum on the surface of the electron transport layer under the condition of oxygen atmosphere to form an aluminum oxide layer; and then continuing to deposit aluminum under the condition that the oxygen flow is reduced in a stepped manner until pure aluminum is formed on the electron transport layer, wherein the aluminum oxide layer, the pure aluminum and the material between the aluminum oxide layer and the pure aluminum form the composite layer. Under the condition that the device is provided with an electron transport layer, the thickness of the aluminum oxide on the surface, close to the quantum dot light emitting layer, in the composite layer is relatively thin (for example, the thickness of the aluminum oxide is 5-10nm), and the preparation of the aluminum oxide layer specifically comprises the following steps: if zinc oxide is used as the electron transport layer, the oxygen injection concentration can be increased at the initial stage of forming the composite layer, and an aluminum oxide layer with the thickness of about 5nm is formed. The high oxygen concentration is used for repairing oxygen vacancy defects of the zinc oxide electron transport layer, the aluminum oxide layer can prevent mutual diffusion between aluminum and zinc oxide, the content ratio of zinc oxide to aluminum is gradually regulated and controlled along with gradual formation of a composite layer, and the surface of the composite layer close to the electron transport layer is along the surface direction departing from the electron transport layer: from up the higher and higher aluminum content down, finally form surperficial pure aluminium, the composite bed is as the negative pole, accomplishes the preparation of device, does not need other negative poles of extra coating by vaporization.
In the process, in the preparation step of the composite layer, the speed of depositing the aluminum is 0.2-0.3 nm/s; depositing aluminum under the condition that the oxygen flow is 65-70sccm, and depositing aluminum on the surface of the electron transport layer to form an aluminum oxide layer; then, the oxygen flow is reduced in a speed step of 4-6sccm/s, and aluminum deposition is continued until pure aluminum is formed on the surface of the electron transport layer.
In one embodiment, after the step of preparing the composite layer, a step of preparing a passivation layer on the surface of the composite layer is further included, and the preparation method of the passivation layer includes: and depositing aluminum on the surface of the composite layer under the condition of oxygen atmosphere to obtain an aluminum oxide passivation layer. For example, after a composite layer is formed by evaporating aluminum metal by an evaporation process, aluminum oxide can be formed on the composite layer for passivation layer packaging, and the device is manufactured in one cavity. Specifically, after the step of preparing the composite layer, the method further comprises the following steps: and continuously depositing aluminum under the condition of oxygen atmosphere to obtain an aluminum oxide passivation layer. The oxygen flow rate may be 90-110 sccm.
In one embodiment, a method for manufacturing a QLED device is provided: the method comprises the following steps:
a transparent anode layer (e.g., ITO) is deposited on a transparent rigid (e.g., glass) or flexible (e.g., polyimide) substrate. When the nano Si film is deposited on the surface of an anode (such as ITO), pointed bulges are easy to grow, influence on subsequent film forming is caused, a subsequent functional layer can be punctured, the structure of a device is damaged, and nano Si can be adoptedO2And treating the polishing solution to obtain a smoother anode surface. Then the surface of the anode is cleaned and dried by alkaline cleaning liquid, deionized water and isopropanol, and then UVO treatment is carried out, so that the contact angle of the surface of the anode is reduced, the work function of the anode is improved, and hole injection is facilitated.
A hole injection layer is formed on the anode layer, and a hole transport layer is formed on the hole injection layer. And forming a quantum dot light-emitting layer on the hole transport layer. An electron transport layer is formed on the quantum dot light emitting layer, ZnO can be selected as the electron transport layer, and the electron transport layer can also be made of the composite layer, and is mainly matched according to the energy levels of different quantum dot light emitting layers.
The invention is described in further detail with reference to a part of the test results, which are described in detail below with reference to specific examples.
Example 1
A quantum dot light emitting diode has a structure shown in FIG. 3, and sequentially comprises a substrate, a transparent electrode (anode), a hole injection layer, a hole transport layer, a quantum dot light emitting layer, an electron transport layer (ZnO material), a composite layer, and Al from bottom to top2O3A passivation layer; wherein the composite layer comprises 5nm Al laminated from bottom to top2O3Layer and 60nm Al2O3A layer of/Al.
The preparation method of the quantum dot light-emitting diode comprises the following steps:
providing a substrate, forming a transparent electrode, namely an anode, on the substrate, wherein the transparent electrode is made of Indium Tin Oxide (ITO);
the transparent electrode (i.e., anode) is pretreated. Ultrasonic cleaning with alkaline cleaning solution (preferably pH <2) for 15min, ultrasonic cleaning with deionized water for 15min twice, ultrasonic cleaning with isopropanol for 15min, oven drying at 80 deg.C for 2h, and ozone ultraviolet treating for 15 min.
And forming a hole injection layer on the pretreated transparent electrode, wherein the hole injection layer is made of PEDOT: PSS, spin-coating at 5000rpm for 40s, and annealing at 150 ℃ for 15 min.
A hole transport layer is formed on the hole injection layer, the hole transport layer is made of TFB (8 mg/mL is preferred, solvent chlorobenzene), spin-coating is carried out in a glove box (the water oxygen content is less than 0.1ppm) at 3000rpm, and then annealing treatment is carried out for 30min at 150 ℃.
And forming a quantum dot light-emitting layer on the hole transport layer, wherein the quantum dot material is CdSe/ZnS (preferably 30mg/mL, solvent n-octane), and spin-coating at 3000rpm in a glove box (the water oxygen content is less than 0.1 ppm).
And forming an electron transmission layer on the quantum dot light-emitting layer. The material of the quantum dot transmission layer is ZnO (preferably 45mg/mL, solvent ethanol), and the material is subjected to returning treatment for 30min at 80 ℃ after being spin-coated in a glove box (the water oxygen content is less than 0.1ppm) at 3000 rpm.
And (3) evaporating a composite layer on the electron transport layer by adopting the evaporation way. Evaporating Al particles, O, using tungsten basket2The flow rate is 65sccm, the vacuum valve is normally opened, and the pressure in the cavity is stabilized at 3x10-4Pa, controlling the evaporation rate of Al to be 0.25nm/s, and finally depositing a layer of Al with the thickness of about 5nm on the electron transport layer2O3Namely the barrier layer. While maintaining the above condition, O is decreased at a decreasing rate of 5sccm/s2Flow rate of Al2O3Converting into Al layer, and evaporating a 60nm layer of Al2O3A layer of/Al.
Maintaining the above conditions, adjusting O2Flow to 100sccm in Al2O3A layer of 30nm Al is deposited on the surface of the Al layer2O3And a passivation layer.
Example 2
A quantum dot light emitting diode has a structure shown in FIG. 4, and sequentially comprises a substrate, a transparent electrode (anode), a hole injection layer, a hole transport layer, a quantum dot light emitting layer, a composite layer, and Al from bottom to top2O3A passivation layer; wherein the composite layer comprises 30nm Al laminated from bottom to top2O3Layer and 60nmAl2O3A layer of/Al.
The preparation method of the quantum dot light-emitting diode comprises the following steps:
providing a substrate, forming a transparent electrode, namely an anode, on the substrate, wherein the transparent electrode is made of Indium Tin Oxide (ITO);
the transparent electrode (i.e., anode) is pretreated. Ultrasonic cleaning with alkaline cleaning solution (preferably pH <2) for 15min, ultrasonic cleaning with deionized water for 15min twice, ultrasonic cleaning with isopropanol for 15min, oven drying at 80 deg.C for 2h, and ozone ultraviolet treating for 15 min.
And forming a hole injection layer on the pretreated transparent electrode, wherein the hole injection layer is made of PEDOT: PSS, spin-coating at 5000rpm for 40s, and annealing at 150 ℃ for 15 min.
A hole transport layer is formed on the hole injection layer, the hole transport layer is made of TFB (8 mg/mL is preferred, solvent chlorobenzene), spin-coating is carried out in a glove box (the water oxygen content is less than 0.1ppm) at 3000rpm, and then annealing treatment is carried out for 30min at 150 ℃.
And forming a quantum dot light-emitting layer on the hole transport layer, wherein the quantum dot material is CdSe/ZnS (preferably 30mg/mL, solvent n-octane), and spin-coating at 3000rpm in a glove box (the water oxygen content is less than 0.1 ppm).
And forming a composite layer on the quantum dot light-emitting layer by adopting the evaporation method. Adopting a tungsten basket to evaporate Al particles, normally opening a vacuum valve, and allowing the pressure in a cavity to be stabilized at 3x10-4Pa, controlling the deposition rate of Al to be 0.25nm/s, and controlling the lower O2The flux is chosen to reduce its effect on the quantum dot light emitting layer, preferably 50 sccm. After the start of the deposition, O was increased at an increasing rate of 5sccm/s2Flow to 70sccm, make oxygen excess, Al2O3The generation is complete, thereby depositing a layer of Al of about 30nm on the quantum dot luminescent layer2O3Namely the barrier layer. While maintaining the above condition, O is decreased at a decreasing rate of 5sccm/s2Flow rate of Al2O3Transformation to Al layer in Al2O3A 60nm layer of Al is evaporated on the layer2O3A layer of/Al.
Maintaining the above conditions, adjusting O2Flow to 100sccm in Al2O3A layer of 30nm Al is deposited on the surface of the Al layer2O3And a passivation layer.
The above description is only for the purpose of illustrating the preferred embodiments of the present invention and is not to be construed as limiting the invention, and any modifications, equivalents and improvements made within the spirit and principle of the present invention are intended to be included within the scope of the present invention.
Claims (10)
1. A quantum dot light-emitting diode is characterized by comprising an anode, a composite layer and a quantum dot light-emitting layer positioned between the anode and the composite layer; the surface of the composite layer, which is close to the quantum dot light-emitting layer, is made of aluminum oxide, and the aluminum content of the composite layer is gradually increased from the surface, which is close to the quantum dot light-emitting layer, along the surface direction which is far away from the quantum dot light-emitting layer.
2. The quantum dot light-emitting diode of claim 1, wherein a surface of the composite layer facing away from the quantum dot light-emitting layer is pure aluminum.
3. The quantum dot light-emitting diode of claim 1, wherein an electron transport layer is disposed between the composite layer and the quantum dot light-emitting layer; and/or the presence of a gas in the gas,
a hole function layer is arranged between the quantum dot light-emitting layer and the anode; and/or the presence of a gas in the gas,
and a passivation layer is arranged on the surface of the composite layer departing from the quantum dot light-emitting layer.
4. The qd-led of claim 3, wherein the electron transport layer is made of a material selected from ZnO, TiO and mixtures thereof2、Fe2O3、SnO2、Ta2O3At least one of AlZnO, ZnSnO and InSnO; and/or the presence of a gas in the gas,
the material of the passivation layer is selected from alumina.
5. A preparation method of a quantum dot light-emitting diode is characterized by comprising the following steps:
providing a substrate, wherein the surface of the substrate is provided with an anode;
preparing a quantum dot light emitting layer on the substrate;
preparing a composite layer on the quantum dot light-emitting layer;
the surface of the composite layer, which is close to the quantum dot light-emitting layer, is made of aluminum oxide, and the aluminum content of the composite layer is gradually increased from the surface, which is close to the quantum dot light-emitting layer, along the surface direction which is far away from the quantum dot light-emitting layer.
6. The method of claim 5, wherein the step of preparing a composite layer on the quantum dot light emitting layer comprises: depositing aluminum on the surface of the quantum dot light-emitting layer under the oxygen atmosphere condition to form an aluminum oxide layer; and then, continuously depositing aluminum under the condition of reducing the oxygen flow in a stepped manner until pure aluminum is formed on the quantum dot light-emitting layer, wherein the aluminum oxide layer, the pure aluminum and the material between the aluminum oxide layer and the pure aluminum form the composite layer.
7. The method of claim 6, wherein in the step of preparing a composite layer on the quantum dot light emitting layer, the rate of depositing aluminum is 0.2 to 0.3 nm/s; and/or the presence of a gas in the gas,
depositing aluminum on the surface of the quantum dot light-emitting layer to form an aluminum oxide layer under the condition that the oxygen flow is increased to 65-70sccm in a stepwise manner at the speed of 4-6 sccm/s; and/or the presence of a gas in the gas,
and depositing aluminum under the condition of the speed step reduction of the oxygen flow of 4-6sccm/s until pure aluminum is formed on the quantum dot light-emitting layer.
8. The method of claim 5, wherein the step of preparing the quantum dot light emitting layer on the substrate is followed by preparing an electron transport layer on the quantum dot light emitting layer, and the step of preparing the composite layer comprises: depositing aluminum on the surface of the electron transport layer under the condition of oxygen atmosphere to form an aluminum oxide layer; and then, continuously depositing aluminum under the condition that the oxygen flow is reduced in a stepped manner until pure aluminum is formed on the surface of the electron transport layer, wherein the aluminum oxide layer, the pure aluminum and the material between the aluminum oxide layer and the pure aluminum form the composite layer.
9. The production method according to claim 8, wherein in the production step of the composite layer, the rate of depositing aluminum is 0.2 to 0.3 nm/s; and/or the presence of a gas in the gas,
depositing aluminum on the surface of the electron transport layer under the condition that the oxygen flow is 65-70sccm to form an aluminum oxide layer; and/or the presence of a gas in the gas,
and depositing aluminum under the condition of speed step reduction of oxygen flow of 4-6sccm/s until pure aluminum is formed on the electron transport layer.
10. The method according to any one of claims 5 to 9, further comprising a step of preparing a passivation layer on a surface of the composite layer after the step of preparing the composite layer, the method for preparing the passivation layer comprising: and depositing aluminum on the surface of the composite layer under the condition of oxygen atmosphere to obtain an aluminum oxide passivation layer.
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