A method for manufacturing a transparent electrode film, a transparent electrode film, and applications thereof

Abstract

This invention discloses a method for preparing a transparent electrode film, the transparent electrode film itself, and its applications, relating to the field of conductive thin films. The method involves stacking a substrate, a transparent crystalline thin layer, and several spaced metal thin layers. A voltage is applied to the metal thin layers, causing the transparent crystalline metal thin layers to break down and form fine, filamentary conductive channels. Annealing is then performed to allow metal atoms in the metal thin layers to diffuse into these filamentary conductive channels, forming conductive fibers. The remaining metal thin layers are then removed to form the transparent electrode film. The substrate can be an epitaxial wafer for an ultraviolet LED, detector, or solar cell; the transparent crystalline thin layers can be AlN, GaN, or Al... x Ga （1‑x） The metal layers are made of materials such as N, Al2O3, or TiO2, with thin metal layers of Au, Ag, Ti, Cu, or Al. They possess both high conductivity and high transparency, have a simple structure, and are easy to mass-produce. As a key component of ultraviolet optoelectronic devices, they can improve the photoelectric conversion efficiency of the devices and can be applied in many fields such as flexible electronics and transparent smart devices.

Description

Technical Field

[0001] This invention relates to the field of conductive thin films, specifically to a method for preparing a transparent electrode film, the transparent electrode film itself, and its applications. Background Technology

[0002] Transparent conductive electrodes, as unique materials that combine excellent conductivity with superior optical transparency, not only provide a solid foundation for the leap forward in modern electronic devices but also serve as a core driving force for continuous innovation and development in the field of optoelectronic devices. Their applications are widely integrated into cutting-edge technology products such as solar cells, organic light-emitting diodes (OLEDs), liquid crystal displays (LCDs), touch screens, transparent heating devices, and smart windows, playing an indispensable role. With the booming development of emerging fields such as flexible display technology and wearable devices, the future application prospects of transparent conductive electrodes are becoming increasingly broad, indicating that they will play a crucial role in many more high-tech fields.

[0003] However, the research on transparent conductive electrodes still faces a series of challenges and difficulties. For example... Figure 3 and Figure 4 As shown, traditional GaN and ITO surface electrode extension layers, while possessing low resistivity, exhibit strong absorption and insufficient transmittance in short-wavelength regions such as the ultraviolet and deep ultraviolet, severely limiting the improvement of photoelectric conversion efficiency. In contrast, AlxG1-xN materials show a significant increase in transmittance in the ultraviolet band with increasing Al content, but this is accompanied by a sharp increase in resistivity, which adversely affects the uniform distribution of current. Therefore, exploring effective modification strategies to reduce the resistivity of materials like AlGaN, which possess both high ultraviolet transmittance and high resistivity, is of great significance for accelerating the research and development of ultraviolet optoelectronic devices and broadening their application range.

[0004] Currently, research on transparent conductive electrodes is entering a new era of diversification and rapid development. Among them, metal nanofibers, especially silver nanowires (AgNWs) and copper nanowires (CuNWs), have shown great application potential in the field of flexible transparent conductive electrodes due to their excellent conductivity and transparency. Researchers are continuously driving leaps in the performance of metal nanofiber transparent conductive electrodes by optimizing the size, aspect ratio, and arrangement structure of nanowires and innovating fabrication processes. Furthermore, through advanced technologies such as chemical doping, composite material construction, and surface modification, researchers are dedicated to comprehensively improving the conductivity, transparency, and mechanical strength of transparent conductive electrodes, and are actively exploring low-cost, large-area production processes to achieve large-scale applications. In addition, researchers are also working to improve the conductivity, transparency, and mechanical properties of transparent conductive electrodes through doping, compositing, and surface modification methods, and are exploring low-cost, large-area fabrication processes to achieve large-scale production.

[0005] Despite these challenges, research on transparent conductive electrodes remains fraught with difficulties, particularly in the ultraviolet and deep ultraviolet short-wavelength regions. The high cost and complex processes involved in fabricating new materials hinder large-scale commercialization; the stability and durability of some materials require further improvement to meet long-term usage requirements; and significant challenges exist in flexible design, environmental friendliness, and sustainability. Therefore, continued in-depth research and exploration, aiming for breakthroughs in AlGaN material modification and the reduction of resistivity by incorporating the properties of metal nanofibers, are crucial for driving the rapid development of ultraviolet optoelectronic devices. Summary of the Invention

[0006] The purpose of this invention is to provide a method for preparing a transparent electrode film, the transparent electrode film and its application. The purpose is to overcome the above-mentioned problems existing in the prior art, and it has both high conductivity and high transparency. It has a simple structure, low cost and is easy to prepare and produce on a large scale. As a key part of optoelectronic devices, it can improve the photoelectric conversion efficiency of the device and can be applied to many fields such as flexible electronics and transparent smart devices.

[0007] To achieve the above objectives, the present invention provides the following technical solution:

[0008] A method for preparing a transparent electrode film includes the following steps:

[0009] Step (1): Prepare a transparent crystalline thin layer on the surface of the substrate;

[0010] Step (2): Prepare several metal thin layers arranged at intervals on the surface of the transparent crystal thin layer;

[0011] Step (3): Apply voltage to two adjacent metal thin layers to break down the transparent crystal thin layer between the two adjacent metal thin layers, forming several fine wire-shaped conductive channels;

[0012] Step (4): Annealing is performed to allow metal atoms in the thin metal layer to diffuse into the fine wire-like conductive channels and form conductive fibers;

[0013] Step (5): Remove the remaining metal layer to form a transparent electrode film.

[0014] Furthermore, the substrate is an ultraviolet LED epitaxial wafer, a detector epitaxial wafer, or a solar cell epitaxial wafer.

[0015] Furthermore, the transparent crystal thin layer is one of AlN, GaN, AlxGa(1-x)N, and Al2O3, and its doping type is undoped, n-type doped, or p-type doped; the metal thin layer is one of Au, Ag, Ti, Cu, Cr, Ru, Ta, Pt, Pd, and Al.

[0016] Furthermore, the thickness of the transparent crystal thin layer ranges from [10nm, 100nm].

[0017] Furthermore, the thickness of the transparent crystal thin layer is 500 nm.

[0018] Furthermore, the thickness of the metal thin layer ranges from (0 to 40 nm), the width ranges from (0 nm to 300 nm), and the spacing between two adjacent metal thin layers ranges from (0 nm to 500 nm).

[0019] Furthermore, the thickness of the metal thin layer is 30nm, the width is 200nm, and the spacing between two adjacent metal thin layers ranges from 300nm.

[0020] Furthermore, in step (2), a number of patterned windows are first set at intervals on a transparent crystal thin layer by one of nanoimprinting, mask lithography, laser direct writing, or electron beam lithography; then, the metal thin layer is prepared in each patterned window by one of electron beam evaporation or magnetron sputtering.

[0021] Furthermore, in step (5), the residual metal layer is removed by one of mechanical polishing, chemical polishing, or etching.

[0022] The present invention also discloses a transparent conductive film obtained by any of the preparation methods described above, comprising a transparent crystalline thin layer, wherein the interior of the transparent crystalline thin layer has a plurality of fine linear conductive channels formed by electrical breakdown, and metal atoms diffuse and fill the interior of the fine linear conductive channels to form conductive fibers.

[0023] The present invention also discloses the application of a transparent conductive film with the structure described above, which is prepared on an ultraviolet LED epitaxial wafer and used as the positive electrode of the ultraviolet LED.

[0024] Compared with the prior art, the beneficial effects of the present invention are:

[0025] This invention involves preparing a transparent crystalline thin layer on a substrate surface, and then preparing periodically arranged metal thin layers on top of this transparent crystalline thin layer. By applying a voltage between adjacent metal thin layers, the transparent crystalline metal thin layers between them break down, forming fine, filamentary conductive channels. Annealing then allows metal atoms in the metal thin layers to diffuse into these filamentary conductive channels, forming conductive fibers. Finally, the metal thin layers above the transparent crystalline thin layer are removed, resulting in a transparent electrode film. This invention's transparent electrode film possesses both high conductivity and high transparency, with a simple structure, low cost, and ease of large-scale fabrication and production. In particular, it exhibits high transmittance in the ultraviolet and deep ultraviolet short-wavelength regions, making it ideal for use as the conductive positive electrode in ultraviolet LEDs, significantly improving the transmittance of ultraviolet LEDs in these regions. As a key component of optoelectronic devices, it can improve the photoelectric conversion efficiency of the devices and can also be applied in flexible electronics, transparent smart devices, and many other fields. Attached Figure Description

[0026] Figure 1 This is a schematic diagram of the layer structure of the substrate and multilayer transparent conductive film before annealing in this invention.

[0027] Figure 2 This is a schematic diagram of the layer structure of the substrate and multilayer transparent conductive film after annealing in this invention.

[0028] Figure 3 This is a schematic diagram of the structure of the substrate and the transparent conductive film in this invention.

[0029] Figure 4 The transmittance of different materials.

[0030] Figure 5 The resistivity of different compound materials. Detailed Implementation

[0031] Specific embodiments of the present invention will now be described with reference to the accompanying drawings. Many details are described below to provide a comprehensive understanding of the invention; however, those skilled in the art will be able to implement the invention without these details.

[0032] like Figures 1 to 3 As shown, a method for preparing a transparent electrode film includes the following steps:

[0033] Step (1): Prepare a transparent crystalline thin layer 1 on the surface of substrate a.

[0034] Specifically, a transparent crystalline thin layer 1 is prepared by one of the following methods: metal-organic chemical vapor deposition, atomic layer deposition, physical vapor deposition, magnetron sputtering, or electron beam evaporation.

[0035] The substrate a can be an ultraviolet LED epitaxial wafer, a detector epitaxial wafer, or a solar cell epitaxial wafer. The thickness of the transparent crystal thin layer 1 ranges from [10 nm to 100 nm]; preferably, the thickness is 50 nm. The transparent crystal thin layer 1 is made of AlN, GaN, or Al x Ga （1-x） One of N and Al2O3, whose doping type is undoped, n-type doped, or p-type doped; Al x Ga （1-x） N includes, but is not limited to, Al. 0.2 Ga 0.8 N.

[0036] Step (2): Prepare several metal thin layers 2 arranged at intervals on the surface of the transparent crystal thin layer 1; thus, as shown in the figure. Figure 1 As shown.

[0037] Specifically, firstly, several windows are set at intervals on a transparent crystal thin layer 1 using one of the following methods: nanoimprinting, photomask lithography, laser direct writing, or electron beam lithography; then, a metal thin layer 2 is prepared in each window using one of the following methods: electron beam evaporation or magnetron sputtering.

[0038] The thickness of the metal thin layer 2 ranges from (0 to 40 nm), the width ranges from (0 nm to 300 nm), and the spacing between two adjacent metal thin layers 2 ranges from (0 nm to 500 nm). Preferably, the thickness of the metal thin layer 2 is 30 nm, the width is 200 nm, and the spacing between two adjacent metal thin layers 2 ranges from 300 nm.

[0039] The metal thin layer 2 can be one of Au, Ag, Ti, Cu, Cr, Ru, Ta, Pt, Pd, and Al.

[0040] Step (3): Apply voltage to two adjacent metal thin layers 2, causing the transparent crystal thin layer 1 between the two adjacent metal thin layers 2 to break down and form several fine wire-shaped conductive channels.

[0041] Specifically, the voltage range is (0, 100V).

[0042] Step (4) involves annealing to allow metal atoms in the thin metal layer 2 to diffuse into the fine linear conductive channels, forming conductive fibers 3. Thus, as... Figure 2 As shown.

[0043] Specifically, the annealing temperature is 250–800℃, and the annealing time is 30 min–3 h.

[0044] Step (5): Remove the remaining metal thin layer 2, thereby forming a transparent electrode film on substrate a. Thus, as... Figure 3 As shown.

[0045] Specifically, the residual metal thin layer 2 is removed by one of mechanical polishing, chemical polishing, or etching.

[0046] By controlling parameters such as the thickness of the transparent crystal thin layer, the thickness, size, periodic arrangement of the metal structure, and the annealing temperature and time in steps (1) to (5) above, the conductivity characteristics of the transparent conductive electrode can be controlled.

[0047] In addition, this invention also discloses a transparent conductive film obtained using the above-described preparation method, comprising a transparent crystalline thin layer 1, the interior of which has a plurality of fine linear conductive channels formed by electrical breakdown, and metal atoms diffuse and fill the interior of the fine linear conductive channels to form conductive fibers 3. The above-described transparent conductive film includes, but is not limited to, applications on ultraviolet LEDs, wherein the transparent conductive film is prepared on the surface of an ultraviolet LED epitaxial wafer and serves as the positive electrode of the ultraviolet LED.

[0048] Example 1

[0049] Step (a1): Obtain a clean UV LED epitaxial wafer by chemical cleaning (using acetone, ethanol, deionized water, and ultrasonic cleaning).

[0050] Step (1b): Using physical vapor deposition (PVD), an undoped AlN transparent crystal thin layer with a thickness of 50 nm is prepared on the surface of the LED epitaxial wafer.

[0051] Step (1c): A printing layer is formed on a transparent AlN crystal thin film using nanoimprint lithography. This printing layer creates several spaced patterned windows. Then, an Au thin film, 30 nm thick, is deposited in each patterned window using electron beam evaporation deposition, thus forming several spaced Au thin films, i.e., an Au thin film array. The patterned windows include, but are not limited to, squares with a cross-section of 200 nm × 200 nm and grooves with a depth of 30 nm. The spacing between adjacent patterned windows is 300 nm. Several patterned windows are arranged spaced apart to form a patterned array. In other words, the Au thin film is a prism with a thickness of 30 nm, a cross-section of 200 nm × 200 nm, a spacing of 300 nm between adjacent Au thin films, and a period of 500 nm for the Au thin film array.

[0052] Step (1d): Apply a voltage of 50V between two adjacent Au thin layers to break down the AlN transparent crystal thin layer between them, forming several fine linear conductive channels.

[0053] Step (1e): Place the UV LED epitaxial wafer in an annealing furnace for annealing. The annealing temperature is 500℃ and the annealing time is 1 hour, allowing Au atoms in the Au thin layer to diffuse into the filamentous conductive channels to form conductive fibers.

[0054] Step (1f): Place the UV LED epitaxial wafer in aqua regia to completely remove the remaining Au thin layer and printed layer on the AlN transparent crystal thin layer, thereby forming a transparent conductive film as an electrode on the surface of the UV LED epitaxial wafer.

[0055] Example 2

[0056] Step (2a): Obtain a clean solar cell epitaxial wafer by chemical cleaning (using acetone, ethanol, deionized water, and ultrasonic cleaning).

[0057] Step (2b), 10 -4 In a high-vacuum environment, high-purity argon gas was ionized into high-energy argon ions using a radio frequency power supply. These argon ions then bombarded the surface of a high-purity Al₂O₃ target, causing target atoms to be sputtered and deposited onto the surface of the solar cell epitaxial wafer. During the experiment, the sputtering power was precisely controlled within the range of 70W–300W, the argon gas flow rate within the range of 50cm³ / min–200cm³ / min, and the working pressure within the range of 0.5Pa–3.5Pa to obtain a high-quality, high-performance transparent Al₂O₃ crystalline thin layer. Ultimately, a 50nm thick transparent Al₂O₃ crystalline thin layer was formed on the solar cell epitaxial wafer.

[0058] Step (2c): A plurality of spaced-apart patterned arrays are formed on a thin Al2O3 transparent crystal coated with photoresist using electron beam lithography. After development, a plurality of patterned windows are formed. Then, an Ag thin layer is prepared in each patterned window using electron beam evaporation, thereby forming a plurality of spaced-apart Ag thin layers with a thickness of 30 nm, thus forming an Ag thin layer array. The patterned windows include, but are not limited to, grooves with a cross-section of 300 nm in diameter and a depth of 30 nm. A plurality of such grooves are arranged at intervals, with a spacing of 250 nm between adjacent patterned windows, forming a patterned array. In other words, the Ag thin layer is a cylinder with a thickness of 30 nm, a diameter of 300 nm, a spacing of 250 nm between adjacent Ag thin layers, and a period of 550 nm for the Ag thin layer array.

[0059] Step (2d): Apply a voltage of 30V between two adjacent Ag thin layers to break down the transparent Al2O3 crystal thin layer between them, forming several fine linear conductive channels.

[0060] Step (2e): The solar cell epitaxial wafer is placed in an annealing furnace for annealing. The annealing temperature is 400℃ and the annealing time is 2 hours, allowing Ag atoms in the Ag thin layer to diffuse into the filamentous conductive channels to form conductive fibers.

[0061] Step (2f): The remaining Ag layer on the AlN transparent crystal thin layer is completely removed by mechanical polishing, thereby forming a transparent conductive film as an electrode on the surface of the solar cell epitaxial wafer.

[0062] The above are merely specific embodiments of the present invention, but the design concept of the present invention is not limited thereto. Any non-substantial modifications made to the present invention using this concept shall be considered as infringing upon the protection scope of the present invention.

Claims

1. A method for preparing a transparent electrode film, characterized in that, Includes the following steps: Step (1): Prepare a transparent crystal thin layer on the surface of the substrate; the transparent crystal thin layer is one of AlN, GaN, AlxGa(1-x)N, and Al2O3, and its doping type is undoped, n-type doped or p-type doped; Step (2): Prepare a plurality of metal thin layers arranged at intervals on the surface of the transparent crystal thin layer; the metal thin layer is one of Au, Ag, Ti, Cu, Cr, Ru, Ta, Pt, Pd, and Al; Step (3): Apply voltage to two adjacent metal thin layers to break down the transparent crystal thin layer between the two adjacent metal thin layers, forming several fine wire-shaped conductive channels; Step (4): Annealing is performed to allow metal atoms in the thin metal layer to diffuse into the fine wire-like conductive channels and form conductive fibers; Step (5): Remove the remaining metal layer to form a transparent electrode film.

2. The method for preparing a transparent electrode film according to claim 1, characterized in that: The substrate is an ultraviolet LED epitaxial wafer, a detector epitaxial wafer, or a solar cell epitaxial wafer.

3. The method for preparing a transparent electrode film according to claim 1, characterized in that: The thickness of the transparent crystal thin layer ranges from [10nm, 100nm].

4. The method for preparing a transparent electrode film according to claim 3, characterized in that: The thickness of the transparent crystalline thin layer is 50 nm.

5. The method for preparing a transparent electrode film according to claim 1, characterized in that: The thickness of the metal thin layer ranges from (0, 40 nm), the width ranges from (0 nm, 300 nm), and the spacing between two adjacent metal thin layers ranges from (0 nm, 500 nm).

6. The method for preparing a transparent electrode film according to claim 5, characterized in that: The metal thin layer has a thickness of 30 nm, a width of 200 nm, and a spacing of 300 nm between two adjacent metal thin layers.

7. The method for preparing a transparent electrode film according to claim 3, characterized in that: In step (2), a number of spaced patterned windows are first formed on a transparent crystal thin layer by one of nanoimprinting, mask lithography, laser direct writing, or electron beam lithography; then, the metal thin layer is prepared in each patterned window by one of electron beam evaporation or magnetron sputtering.

8. The method for preparing a transparent electrode film according to claim 1, characterized in that: In step (5), the residual metal layer is removed by one of mechanical polishing, chemical polishing, or etching.

9. A transparent conductive film obtained using the preparation method according to any one of claims 1-8, characterized in that: It includes a transparent crystalline thin layer, the interior of which has several fine linear conductive channels formed by electrical breakdown, and metal atoms diffuse and fill the interior of the fine linear conductive channels to form conductive fibers.

10. The application of a transparent conductive film with the structure described in claim 9, characterized in that: This transparent conductive film is fabricated on the epitaxial wafer of a UV LED and used as the positive electrode of the UV LED.

Images