Aluminum-doped zinc oxide film with homogeneous multilayer structure as well as preparation method and application of aluminum-doped zinc oxide film

Abstract

The invention discloses an aluminum-doped zinc oxide film with a homogeneous multilayer structure and a preparation method and application thereof, belongs to the field of environmental function material preparation, and provides a preparation method of the aluminum-doped zinc oxide film with the homogeneous multilayer structure. The influence of lattice mismatch and grain boundary scattering is reduced, and the uniformity of the conductivity is further improved by gradually changing the concentration. According to the finally prepared AZO film, due to the fact that the concentration is gradually reduced from a high-doping-concentration layer to a low-doping-concentration layer from the bottom layer to the top layer, the conductivity is more uniform, the carrier concentration reaches 4.9 * 10 < 20 > cm <-3 >, the mobility reaches 23 cm < 2 > / V.s, the light transmittance is larger than 80%, and compared with a single-layer aluminum-doped zinc oxide film with the same concentration, the carrier concentration is higher, the mobility is higher, and the conductivity and the transmittance are better.

Description

Technical Field

[0001] The present invention belongs to the field of transparent conductive materials, and particularly relates to an aluminum-doped zinc oxide thin film with a homogeneous multi-layer structure, a preparation method thereof, and an application thereof. Background Art

[0002] Transparent conductive materials play a crucial role in electronic devices. They not only need to provide an efficient current transmission channel but also must enable the electronic device to maintain excellent light transmittance. Among numerous transparent conductive materials, transparent conductive oxide (TCO) thin films are widely used in solar cells, flat panel displays, touch screens, and other optoelectronic devices due to their good electrical conductivity, transparency, and chemical stability. Currently, the mainstream TCO materials mainly include indium tin oxide (ITO) and fluorine-doped tin oxide (FTO), etc. However, these materials have problems such as expensive raw materials and environmental pollution, which limit their wide application.

[0003] The aluminum-doped zinc oxide (AZO) target, through the method of aluminum doping, significantly improves the electrical conductivity of zinc oxide, while maintaining its good transparency and reducing costs, and is widely used in fields such as optoelectronic devices, flat panel displays, and solar cells.

[0004] However, traditional AZO thin films are basically single-layer structures. When increasing the carrier concentration, high-concentration aluminum doping is often used. Although the number of carriers increases, it is also accompanied by large lattice mismatch and grain boundary scattering; lower doping concentrations can improve the lattice mismatch and grain boundary scattering problems, but there are not enough carriers, so it is easy to cause a decrease in electrical conductivity and a decrease in film stability. To solve this problem, existing multi-layer AZO thin films are designed with different concentrations in layers. Although these problems are improved to a certain extent, the abrupt concentration between different layers will still lead to uneven conductivity and affect the overall performance of the film. Therefore, it is of great significance to develop a preparation method for AZO thin films that can achieve continuous gradual change in aluminum doping concentration. Summary of the Invention

[0005] The purpose of the present invention is to provide an aluminum-doped zinc oxide thin film with a homogeneous multi-layer structure, a preparation method thereof, and an application thereof, so as to solve the problems existing in the above-mentioned prior art. Through innovative design of a mixed target with multi-region gradually changing concentration and the use of a magnetron sputtering process, continuous gradual change in aluminum doping concentration in the AZO thin film is achieved, effectively improving the electrical conductivity, stability, and uniformity of the thin film.

[0006] One of the technical solutions provided by the present invention:

[0007] A method for preparing an aluminum-doped zinc oxide thin film with a homogeneous multi-layer structure, using an AZO target as the cathode, depositing a thin film on a substrate by magnetron sputtering, in-situ annealing the obtained thin film, and cooling to room temperature to prepare the aluminum-doped zinc oxide thin film with the homogeneous multi-layer structure; the aluminum doping concentration in the AZO target decreases gradually from the center to the edge of the target, with the highest concentration in the central region, and the AZO target is an AZO target with a gradually changing concentration in multiple regions.

[0008] The present invention prepares a mixed target with a gradually changing concentration in multiple regions and uses magnetron sputtering technology to deposit a thin film with a gradually changing concentration. This method overcomes the defects of traditional AZO thin films with a single concentration or a sudden change in concentration in terms of conductivity and stability. By utilizing the gradually changing characteristics of the aluminum doping concentration in different regions of the target, a continuously transitional structure is formed during the growth of the thin film, effectively reducing interface scattering. At the same time, a reasonable distribution of carrier concentration is ensured, improving the conductive uniformity and overall performance of the thin film.

[0009] The substrate is selected from transparent conductive glass or a flexible polymer substrate. During the magnetron sputtering process, the temperature of the substrate is controlled at 50 - 200°C.

[0010] Preferably, the method for preparing the AZO target includes the following steps: According to a preset concentration gradient, weigh sub-micron ZnO and sub-micron Al2O3, mix and grind them in different proportions to obtain powder mixtures with different mixing ratios, use a mixing device to layer by layer load and cold press the powder mixtures into a formed body, calcine the obtained green body, polish the surface to expose the layered interface, and prepare the AZO target; or, according to a preset concentration gradient, weigh pre-doped AZO powders with different Al ion doping ratios, use a mixing device to layer by layer load and cold press the pre-doped AZO powders into a formed body, calcine the obtained green body, polish the surface to expose the layered interface, and prepare the AZO target.

[0011] More preferably, when loading the powder mixture, the mass ratio of sub-micron ZnO to sub-micron Al2O2 in the obtained green body is (97∶3)-(98∶2) in the central region, and gradually transitions to (99∶1)-(99.5∶0.5) towards the edge according to a gradient decrease.

[0012] More preferably, when loading the pre-doped AZO powder, the Al ion doping ratio in the obtained green body is 3 - 5 mol% in the central region, and gradually decreases to 0.5 - 1.5 mol% towards the edge according to a gradient decrease.

[0013] The purity of the ZnO and Al2O3 oxide powders is greater than 99.5%, the purity of the pre-doped AZO powder is greater than 99.5%, and the average particle size of all powders is 0.1 - 1 μm.

[0014] More preferably, the conditions for cold pressing are as follows: the pressure is 30 - 50 Mpa, and the time is 30 - 60 s.

[0015] More preferably, the conditions for calcination are as follows: the heating rate is 8 - 12 °C / min, the sintering temperature is 1150 - 1350 °C, and the heat preservation time is 3 - 5 h.

[0016] The key of the present invention lies in preparing a target with a special structure. During the preparation of the target, according to the gradually changing requirement of the aluminum doping concentration, ZnO and Al2O3 powders or pre-doped aluminum AZO powders with different ratios are loaded layer by layer and cold pressed. After high-temperature sintering, a multi-region gradually changing concentration AZO target is made, and a hybrid target with a high central concentration and a gradually decreasing concentration outward is prepared. In the magnetron sputtering stage, by finely adjusting parameters such as the target rotation speed, sputtering time, sputtering power, and gas flow rate, atoms or ions on the target surface are sputtered and deposited on the substrate according to a predetermined concentration gradient, forming a continuous transition thin film structure from a high carrier concentration region to a low lattice mismatch and interface scattering region. Thus, while ensuring an adequate supply of carriers, the influence of interface defects on the film performance is minimized, and the optimization of the film performance is achieved.

[0017] Preferably, the in-situ annealing temperature is 100 - 150 °C, and the time is 10 - 30 min. In-situ annealing can improve the crystallization quality and structural stability of the thin film.

[0018] The second technical solution provided by the present invention:

[0019] An aluminum-doped zinc oxide thin film with a homogeneous multi-layer structure prepared by the above preparation method.

[0020] The third technical solution provided by the present invention:

[0021] An application of the above aluminum-doped zinc oxide thin film with a homogeneous multi-layer structure in the preparation of optoelectronic devices.

[0022] Preferably, the optoelectronic device includes a transparent conductive film, a solar cell, or a flat panel display.

[0023] Compared with the prior art, the present invention has the following advantages and technical effects:

[0024] The present invention provides a preparation method for an aluminum-doped zinc oxide thin film with a homogeneous multi-layer structure. The aluminum-doped zinc oxide thin film prepared by this method has excellent electrical conductivity, reduces the influence of lattice mismatch and grain boundary scattering, and improves the uniformity of conductivity through gradually changing concentration. The finally prepared AZO thin film has a more uniform conductivity from the bottom layer to the top layer because the doping concentration gradually decreases. The carrier concentration reaches 4.9×10 20 cm -3 , and the mobility reaches 23 cm2 / V·s, with a light transmittance greater than 80%. Compared with single-layer aluminum-doped zinc oxide films of the same concentration, it has a higher carrier concentration, a higher mobility, better electrical conductivity and transmittance. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required in the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.

[0026] Figure 1 It is a sample diagram of the AZO target prepared by the present invention.

[0027] Figure 2 It is a schematic diagram of the preparation process of the AZO target of the present invention, where a and b are schematic diagrams of the pressing of high-concentration and small-diameter blocks in the center, and c and d are schematic diagrams of filling powders with lower doping concentrations around. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0028] Now, various exemplary embodiments of the present invention will be described in detail. This detailed description should not be considered as a limitation of the present invention, but rather as a more detailed description of certain aspects, characteristics and implementation schemes of the present invention.

[0029] It should be understood that the terms used in the present invention are only for describing specific embodiments and are not used to limit the present invention. Additionally, for the numerical ranges in the present invention, it should be understood that each intermediate value between the upper and lower limits of the range is also specifically disclosed. Each intermediate value within any stated value or stated range, as well as each smaller range between any other stated value or intermediate value within the stated range, is also included in the present invention. The upper and lower limits of these smaller ranges can be independently included or excluded from the range.

[0030] Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by those of ordinary skill in the art to which the present invention pertains. Although the present invention only describes preferred methods and materials, any methods and materials similar or equivalent to those described herein can also be used in the implementation or testing of the present invention. All documents mentioned in this specification are incorporated by reference to disclose and describe the methods and / or materials related to the documents. In case of conflict with any incorporated document, the content of this specification shall prevail.

[0031] Without departing from the scope or spirit of the present invention, various modifications and variations can be made to the specific embodiments of the description of the present invention, which will be apparent to those skilled in the art. Other embodiments obtained from the description of the present invention will be apparent to those skilled in the art. The description of the present invention and the examples are merely exemplary.

[0032] Regarding the use of "comprising", "including", "having", "containing", etc. in this article, they are all open-ended terms, meaning including but not limited to.

[0033] The embodiment of the present invention provides a method for preparing an aluminum-doped zinc oxide thin film with a homogeneous multi-layer structure. Using an AZO target as the cathode, a thin film is deposited on a substrate by magnetron sputtering, and the obtained thin film is annealed in-situ and cooled to room temperature to prepare the aluminum-doped zinc oxide thin film with the homogeneous multi-layer structure; the aluminum doping concentration in the AZO target decreases gradually from the center to the edge of the target, and the concentration in the central region is the highest. The AZO target is an AZO target with a gradually changing concentration in multiple regions.

[0034] In some embodiments of the present invention, the substrate is a transparent conductive glass or a flexible polymer substrate. During the magnetron sputtering process, the temperature of the substrate is controlled to be 50 - 200 °C. In some preferred embodiments, when the substrate is a transparent conductive glass, the substrate temperature is controlled to be 50 °C, and when the substrate is a flexible polymer, such as polyimide (PI), the substrate temperature is controlled to be 50 °C.

[0035] Magnetron sputtering is a commonly used method in Physical Vapor Deposition (PVD). The working principle of magnetron sputtering is based on the interaction of charged particles in electric and magnetic fields. Specifically: Under high vacuum conditions, an appropriate amount of argon gas is filled. A direct current voltage of several hundred kilovolts is applied between the cathode (cylindrical target or planar target) and the anode (coating chamber wall), generating a magnetron-type abnormal glow discharge in the coating chamber. Under the action of the electric field E, during the process of electrons flying towards the substrate, they collide with argon atoms, ionizing them to produce Ar positive ions and new electrons. This process is called ionization. The newly generated electrons continue to fly towards the substrate, while the Ar ions are accelerated towards the cathode target under the action of the electric field and bombard the target surface with high energy. This bombardment causes neutral atoms or molecules on the target surface to gain sufficient kinetic energy to break away from the target surface. These sputtered atoms or molecules are then deposited on the substrate surface to form a thin film. Secondary electrons are also generated when bombarding the target. These secondary electrons are affected by the electric and magnetic fields and drift in the direction indicated by E (electric field) × B (magnetic field), simply referred to as E × B drift. In a toroidal magnetic field, electrons move in a circular motion on the target surface in an approximate cycloid form. Their movement paths are not only very long but also confined to the plasma region near the target surface. In these regions, the secondary electrons ionize a large number of Ar ions to bombard the target, thus achieving a high deposition rate.

[0036] In the embodiments of the present invention, the specific operation of magnetron sputtering is as follows: Install the prepared target on the target holder of the magnetron sputtering equipment, fix the substrate on the sample stage, and adjust the distance between the substrate and the target to 5 - 10 cm. Evacuate to 10 -5 -10 -4After reaching Pa, an appropriate amount of working gas (such as argon) is introduced into the vacuum chamber, the gas flow rate is adjusted to 20 - 50 sccm, and the sputtering power is 100 - 300 W. The magnetron sputtering equipment is turned on, and the atoms or ions on the surface of the target are sputtered out by the action of the magnetic field and electric field and deposited on the substrate to form an AZO thin film. During the sputtering process, the rotation speed of the target is 5 - 15 rpm. When the target rotates to the central region, the sputtering power is increased, and when it rotates to the outer ring, the sputtering power is appropriately decreased. The rotation speed is regulated according to the required evaporation concentration layer. At high concentrations, the rotation speed in the central region is slow, and vice versa. The sputtering time is determined according to the required film thickness and deposition rate. The film deposition rate is controlled at 0.2 - 1 nm / s to ensure that the aluminum doping concentration in the film is deposited according to the preset gradual change law during the growth process, realizing a continuous transition from high concentration to low concentration, and forming a gradually changing concentration thin film structure with stable performance. After the film deposition is completed, the sputtering is stopped and the vacuum environment is maintained, and the film is naturally cooled to room temperature to obtain the required multi-region gradually changing concentration AZO thin film. During the film deposition process, the sputtering power and gas flow rate can be adjusted according to actual needs to further optimize the film growth rate and doping concentration distribution to meet the requirements of different optoelectronic devices for film performance.

[0037] In some embodiments of the present invention, the preparation method of the AZO target includes the following steps: According to the preset concentration gradient, submicron ZnO and submicron Al2O3 are weighed and mixed and ground in different proportions to obtain powder mixtures with different mixing ratios. The powder mixtures are loaded layer by layer and cold-pressed into shape using a mixing device. The obtained green body is calcined, and the surface is polished to expose the layered interface to prepare the AZO target; or, according to the preset concentration gradient, pre-doped aluminum AZO powders with different Al ion doping ratios are weighed, and the pre-doped aluminum AZO powders are loaded layer by layer and cold-pressed into shape using a mixing device. The obtained green body is calcined, and the surface is polished to expose the layered interface to prepare the AZO target. Figure 1 This is a sample diagram of the AZO target prepared by the present invention.

[0038] Figure 2 This is a schematic diagram of the preparation process of the AZO target of the present invention, as shown in a and b in Figure 2 First, a high-concentration small-diameter block in the center is pressed; as shown in c and d in Figure 2 The pressed high-concentration small-diameter block is placed in a larger-diameter mold, and powders with a lower doping concentration are filled around it and pressed continuously. And so on. After all concentration samples are pressed, the final green body is sintered densely, and the surface is polished to expose the layered interface.

[0039] In some embodiments of the present invention, when loading the powder mixture, the mass ratio of sub-micron ZnO to sub-micron Al2O2 in the obtained green body is (97:3)-(98:2) in the central region, and gradually transitions to (99:1)-(99.5:0.5) towards the edge in a gradient decrease. Exemplarily, in some preferred embodiments, the mass ratios of sub-micron ZnO to sub-micron Al2O3 are 97:3, 98:2, 98.5:1.5, 99:1, and 99.5:0.5 respectively.

[0040] In some embodiments of the present invention, when loading the pre-doped aluminum AZO powder, the aluminum ion doping ratio in the obtained green body is 3-5 mol% in the central region, and gradually decreases to 0.5-1.5 mol% towards the edge in a gradient decrease. Exemplarily, in some preferred embodiments, the aluminum doping concentrations in the pre-doped aluminum AZO powder are 5 mol%, 4 mol%, 3 mol%, 2 mol%, and 1 mol% respectively.

[0041] In the embodiments of the present invention, the purity of the ZnO and Al2O3 powders is greater than 99.5%, the purity of the pre-doped AZO powder is greater than 99.5%, and the average particle size of all powders is 0.1-1 μm.

[0042] In the embodiments of the present invention, the operation of mixing and grinding is as follows: mixing is carried out by high-energy ball milling method, zirconia grinding balls are used, the ball-to-material ratio is (8-15):1, wet grinding method is adopted, the additive is anhydrous ethanol, the agent-to-powder ratio is (1.5-2):1, and the solid content of the slurry is 80%. The revolution speed of the ball mill is 300-600 rpm, the ball milling time is 4-6 h, and the drying method adopted for the powder after ball milling is vacuum drying.

[0043] In some embodiments of the present invention, the parameters of the cold pressing are: the pressure is 30-50 Mpa and the time is 30-60 s.

[0044] In some embodiments of the present invention, the parameters of the calcination are: the heating rate is 8-12 °C / min, the sintering temperature is 1150-1350 °C, and the holding time is 3-5 h.

[0045] In some embodiments of the present invention, the in-situ annealing temperature is 100-150 °C and the time is 10-30 min.

[0046] The embodiments of the present invention also provide a doped aluminum zinc oxide thin film with a homogeneous multi-layer structure prepared by the above preparation method.

[0047] In the embodiments of the present invention, the prepared aluminum-doped zinc oxide thin film is measured for its electrical properties and light transmittance to determine that the method for preparing the multi-region gradually varying concentration AZO thin film provided by the present invention can effectively overcome the defects of traditional preparation methods, and prepare an AZO thin film with excellent performance and good uniformity, providing strong support for the development of optoelectronic devices, and the optoelectronic devices include transparent conductive films, solar cells, and flat panel displays.

[0048] In the present invention, the method for testing the carrier concentration of the thin film is the capacitance-voltage method (C-V method);

[0049] The method for testing the mobility of the thin film is the four-probe method;

[0050] The method for testing the light transmittance of the thin film is the spectrophotometer method.

[0051] The room temperature in the present invention refers to 25 ± 2 °C.

[0052] Example 1 A method for preparing an aluminum-doped zinc oxide thin film with a homogeneous multi-layer structure, comprising the following steps:

[0053] S1. According to the mass ratio of ZnO powder to Al2O3 powder in the central region being 97:3, and gradually tapering to 99.5:0.5 towards the edge, 5 portions of ZnO powder and Al2O3 powder are weighed respectively. After mixing according to the ratios of 97:3, 98:2, 98.5:1.5, 99:1, and 99.5:0.5, the ZnO powder and Al2O3 powder are pre-mixed by high-energy ball milling to obtain five powder mixtures with different ratios. The five powder mixtures with different ratios are Figure 2 layer-by-layer filled and cold-pressed as shown, with a pressure of 40 MPa and a time of 45 s. Subsequently, the green body is placed in a vacuum sintering furnace and heated to 1250 °C at a heating rate of 10 °C / min, and held for 4 h to prepare an AZO target with multi-region gradually varying concentration.

[0054] S2. The AZO target is installed in a magnetron sputtering device. The substrate is selected as transparent conductive glass, and the temperature of the substrate is 50 °C, fixed at a distance of 8 cm from the target. After pumping to 10 -4 Pa, argon is introduced, and the flow rate is adjusted to 30 sccm. The sputtering power is set to 200 W. The magnetron sputtering device is turned on, and the rotation speed of the target is controlled to be 10 rpm, and the film deposition rate is 0.2 nm / s. During the sputtering process, according to the preset concentration gradient and time program, the film is gradually deposited with an aluminum doping concentration varying from 4 mol% to 0.8 mol% from the center to the edge. The total thickness of the film is 200 nm. After deposition, it is annealed in situ at 150 °C for 30 min in a vacuum environment and slowly cooled to room temperature to prepare an aluminum-doped zinc oxide thin film with a homogeneous multi-layer structure. After detection, the carrier concentration of the aluminum-doped zinc oxide thin film reaches 4.2×1020 cm -3 and the mobility reaches 19 cm 2 / V·s, and the light transmittance is greater than 80%.

[0055] Example 2 A method for preparing an aluminum-doped zinc oxide thin film with a homogeneous multi-layer structure, comprising the following steps:

[0056] S1. Weigh 5 portions of sub-micron pre-doped aluminum AZO powders with different aluminum doping concentrations (5 mol%, 4 mol%, 3 mol%, 2 mol% and 1 mol%). The doping ratio of metal ions in the central region is 5 mol%, and it gradually decreases to 1 mol% towards the edge. Arrange the five different proportions of AZO powders in accordance with Figure 2 as shown for layer-by-layer filling and cold pressing. Apply a pressure of 40 MPa for 45 s. Then place the green body into a vacuum sintering furnace, heat it to 1250 °C at a heating rate of 10 °C / min, and hold for 4 h to prepare a multi-region gradually changing concentration AZO target.

[0057] S2. Install the AZO target in a magnetron sputtering device. Select a polyimide (PI) flexible polymer substrate as the substrate. The temperature of the substrate is 50 °C, the distance from the target is 6 cm, the argon flow rate is 40 sccm, the sputtering power is 250 W, the target rotation speed is 12 rpm, and the film deposition rate is 0.3 nm / s. During the sputtering process, according to the preset concentration gradient and time program, achieve a gradual change in the aluminum doping concentration of the film from 5 mol% to 1 mol% from the center to the edge. The film thickness is 250 nm. After deposition, anneal in vacuum at 160 °C for 40 min and cool to room temperature to prepare an aluminum-doped zinc oxide thin film with a homogeneous multi-layer structure. After testing, the carrier concentration of this aluminum-doped zinc oxide thin film reaches 4.9×10 20 cm -3 and the mobility reaches 23 cm 2 / V·s, and the light transmittance is greater than 80%, which can meet the requirements of flexible optoelectronic devices.

[0058] Comparative Example 1

[0059] A method for preparing an aluminum-doped zinc oxide thin film with a homogeneous multi-layer structure, comprising the following steps:

[0060] S1. Weigh 2 portions of ZnO powder and Al2O3 powder respectively according to the ratio requirements that the mass ratio of ZnO powder to Al2O3 powder in the central region is 97:3 and the edge mass ratio is 99.5:0.5. Mix them according to the ratios of 97:3 and 99.5:0.5 respectively (mix the ZnO powder and Al2O3 powder by high-energy ball milling) to obtain powder mixtures. Arrange the two powder mixtures in accordance with Figure 2Perform layer-by-layer filling and cold pressing and forming as shown, apply a pressure of 40 MPa for 45 s. Subsequently, place the green body into a vacuum sintering furnace, heat it to 1250 °C at a heating rate of 10 °C / min, and hold for 4 h to prepare an AZO target.

[0061] S2. Install the AZO target in a magnetron sputtering device, select transparent conductive glass as the substrate, keep the temperature of the substrate at 50 °C, and fix it at a distance of 8 cm from the target. After evacuating to 10 -4 Pa, introduce argon gas, adjust the flow rate to 30 sccm, and set the sputtering power to 200 W. Start sputtering, control the target rotation speed at 10 rpm, and the film deposition rate at 0.2 nm / s. After deposition, anneal in situ at 150 °C for 30 min in a vacuum environment, and slowly cool to room temperature to prepare an aluminum-doped zinc oxide film. The central aluminum doping concentration of this aluminum-doped zinc oxide film is about 5 mol%, and the edge aluminum doping concentration is about 1 mol%. The carrier concentration of this aluminum-doped zinc oxide film reaches 3.2×10 20 cm -3 , and the mobility reaches 9 cm 2 / V·s, and the transmittance is greater than 80%.

[0062] Comparative Example 2

[0063] A preparation method of a single-layer structure aluminum-doped zinc oxide film includes the following steps:

[0064] S1. Weigh ZnO powder and Al2O3 powder according to a mass ratio of 98:2, use high-energy ball milling to mix the ZnO powder and Al2O3 powder to obtain a powder mixture, cold press and form the powder mixture, apply a pressure of 40 MPa for 45 s. Subsequently, place the green body into a vacuum sintering furnace, heat it to 1250 °C at a heating rate of 10 °C / min, and hold for 4 h to prepare a single-concentration aluminum-doped AZO target;

[0065] S2. Install the single-concentration aluminum-doped AZO target in a magnetron sputtering device, select transparent conductive glass as the substrate, keep the temperature of the substrate at 50 °C, and fix it at a distance of 6 cm from the target. After evacuating to 10 -4 Pa, introduce argon gas, adjust the flow rate to 40 sccm, and set the sputtering power to 250 W. Start sputtering, control the target rotation speed at 10 rpm, and the film deposition rate at 0.2 nm / s. After deposition, anneal in situ at 150 °C for 30 min in a vacuum environment, and slowly cool to room temperature to prepare a single-layer aluminum-doped zinc oxide film with the same concentration. After testing, the aluminum doping concentration of this aluminum-doped zinc oxide film is 3 mol%, and the carrier concentration of this aluminum-doped zinc oxide film reaches 2.6×10 20 cm -3 , and the mobility reaches 6 cm 2 / V·s, and the light transmittance is greater than 80%.

[0066] The above is only a preferred specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed by the present invention should be covered within the protection scope of the present invention. Therefore, the protection scope of the present invention should be subject to the protection scope of the claims.

Claims

1. A method for preparing a homogeneous multilayer aluminum-doped zinc oxide thin film, characterized in that: Using an AZO target as a cathode, a thin film is deposited on a substrate by magnetron sputtering, the obtained overall thin film is in-situ annealed, and cooled to room temperature to prepare the aluminum-doped zinc oxide thin film with the homogeneous multilayer structure; the aluminum doping concentration in the AZO target decreases gradually from the center to the edge of the target, and the concentration in the central area is the highest. The AZO target is an AZO target with multi-region gradient concentration.

2. The method for preparing a homogeneous multilayer aluminum-doped zinc oxide thin film according to claim 1, characterized in that: The preparation method of the AZO target comprises the following steps: according to a preset concentration gradient, weighing submicron ZnO and submicron Al2O3, mixing and grinding in different proportions to obtain powder mixtures with different mixing proportions, using a mixing device to perform layer-by-layer filling and cold pressing of the powder mixture, calcining the obtained embryo, grinding and polishing the surface to expose the layered interface, and preparing the AZO target; or, according to a preset concentration gradient, weighing AZO powders pre-doped with aluminum with different Al ion doping ratios, using a mixing device to perform layer-by-layer filling and cold pressing of the pre-doped with aluminum AZO powder, calcining the obtained embryo, grinding and polishing the surface to expose the layered interface, and preparing the AZO target.

3. The method for preparing the aluminum-doped zinc oxide thin film with a homogeneous multilayer structure according to claim 2, characterized in that: When the powder mixture is filled, the mass ratio of submicron ZnO to submicron Al2O2 in the obtained embryo is (97:3)-(98:2) in the central area, and gradually decreases toward the edge to (99:1)-(99.5:0.5).

4. The method for preparing a homogeneous multilayer aluminum-doped zinc oxide thin film according to claim 2, characterized in that: When the AZO powder pre-doped with aluminum is filled, the aluminum ion doping ratio in the obtained embryo is 3-5 mol % in the central area, and gradually decreases to 0.5-1.5 mol % toward the edge according to a gradient decrease.

5. The method for preparing the aluminum-doped zinc oxide thin film with a homogeneous multilayer structure according to claim 2, characterized in that: The cold pressing forming conditions are: pressure of 30-50 MPa and time of 30-60 s.

6. The method for preparing the aluminum-doped zinc oxide thin film with a homogeneous multilayer structure according to claim 2, characterized in that: The calcination conditions are: heating rate of 8-12°C / min, sintering temperature of 1150-1350°C, and holding time of 3-5h.

7. The method for preparing a homogeneous multilayer aluminum-doped zinc oxide thin film according to claim 1, characterized in that: The in-situ annealing is performed at a temperature of 100-150° C. and for a time of 10-30 minutes.

8. A homogeneous multilayer aluminum-doped zinc oxide thin film prepared by the preparation method according to any one of claims 1 to 7.

9. Use of the aluminum-doped zinc oxide thin film with a homogeneous multilayer structure as claimed in claim 8 in the preparation of optoelectronic devices.

10. The use according to claim 9, characterized in that: The optoelectronic device includes a transparent conductive film, a solar cell or a flat panel display.

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