A method for preparing a flexible transparent conductive electrode based on copper-silver composite nanotube shell

Abstract

The application provides a flexible transparent conductive electrode preparation method based on copper-silver composite nanotube shells and belongs to the technical field of flexible transparent conductive electrode preparation; the technical problem to be solved is to provide a flexible transparent conductive electrode preparation method based on copper-silver composite nanotube shells; the technical scheme is that polyvinylpyrrolidone is dissolved in deionized water to form a mixture, the mixture is stirred in air to form a precursor solution, the precursor solution is placed in a syringe, and a semispherical droplet appears on the tip of the syringe; the semispherical droplet is polarized under high voltage, a nanofiber grid is formed in a square collector, anhydrous ethanol is placed in a culture dish, the nanofiber grid is placed above the culture dish after heating on a hot stage, the nanofiber grid is treated with anhydrous ethanol vapor, the nanofiber grid is subjected to thermal evaporation treatment, and metal silver is evaporated on the upper surface of the grid and metal copper is evaporated on the lower surface; the application is applied to the preparation of flexible transparent conductive electrodes.

Description

TECHNICAL FIELD

[0001] The application provides a flexible transparent conductive electrode preparation method based on a copper-silver composite nanotube shell, and belongs to the technical field of flexible transparent conductive electrode preparation. BACKGROUND

[0002] Flexible electronic technology is a technology for preparing electronic devices based on organic / inorganic materials on a flexible plastic or thin metal substrate. The electronic products prepared by the technology have the advantages of light weight and bendability, and have wide application prospects in the fields of information, energy, national defense, etc. For example, flexible electronic displays, flexible solar cells, flexible photodetectors, flexible sensors and other products have been put into use in recent years.

[0003] Flexible transparent conductive electrodes are important components of next-generation optoelectronic devices such as flexible solar cells and display screens. The flexible transparent electrodes prepared from indium tin oxide are widely used due to their good stability, high transmittance and conductivity, etc. However, they have problems such as complex preparation process, poor mechanical stability, high cost of raw materials and non-environmental preparation.

[0004] In order to find alternative materials, other flexible transparent electrodes such as graphene, conductive polymers, carbon nanotubes and metal nanowires are also used to prepare flexible devices. The graphene electrode has stable structure, but the preparation cost is high and the electrical performance is unstable. The conductive polymer electrode has low preparation cost, but its stability is poor. The carbon nanotube electrode has excellent flexibility, but the sheet resistance is large and the transmittance is low. The metal nanowire electrode has a network structure between fibers that enhances optical transmittance, and the multiple-path conductive channel makes it have low sheet resistance, so it is an ideal choice for flexible transparent electrodes.

[0005] However, the current manufacturing process of metal nanowire electrodes still has the following problems and defects:

[0006] Low quality factor of the electrode: reflected in low substrate transmittance, poor contact between nanowires of the electrode, resulting in low conductivity, and low transmittance and conductivity of the electrode leading to low quality factor;

[0007] Poor stability of the electrode: reflected in that the sheet resistance will increase significantly after bending, and there is a problem of poor air stability, the sheet resistance will increase significantly after being placed in air for a period of time;

[0008] High preparation cost of the electrode: reflected in the structure of completely coating nanowires with silver, increasing the consumption of silver, and the material used for the substrate is expensive, which is not conducive to the commercial production and application of transparent electrodes.

[0009] The defects and limitations above hinder the further application of the flexible transparent electrode, and therefore the preparation process thereof needs to be improved accordingly. SUMMARY

[0010] The present application aims to overcome the deficiencies in the prior art, and the technical problem to be solved is to provide a flexible transparent conductive electrode preparation method based on copper-silver composite nanotube shell.

[0011] To solve the above technical problems, the technical scheme adopted by the present application is as follows: a flexible transparent conductive electrode preparation method based on copper-silver composite nanotube shell, comprising the following preparation steps:

[0012] Step one: dissolve polyvinylpyrrolidone in deionized water to form a mixture, and after stirring in the air, the mixture forms a precursor solution, and the prepared precursor solution can be spun;

[0013] Step two: place the precursor solution into a syringe, and a hemispherical droplet appears on the tip of the syringe;

[0014] Step three: set the distance from the spinning needle to the square collector, the flow rate, and the applied voltage range;

[0015] Step four: the hemispherical droplet is polarized under high voltage, and the nanofiber grid is spun in the square collector;

[0016] Step five: place anhydrous ethanol into a culture dish, heat the nanofiber grid on the culture dish, and perform anhydrous ethanol vapor treatment on the nanofiber grid to fuse the nodes between the fibers;

[0017] Step six: perform thermal evaporation treatment on the nanofiber grid, and evaporate metal silver on the upper surface of the grid and metal copper on the lower surface;

[0018] Step seven: pretreat the white glass: ultrasonically clean the white glass with deionized water, acetone, and isopropyl alcohol at room temperature, and then perform UV irradiation to make the white glass hydrophilic;

[0019] Step eight: spin coat deionized water onto the surface of the pretreated white glass to form a water film;

[0020] Step nine: adhere the nanofiber grid on the square collector to the white glass through the action of the water film, and during the transfer process, the side of the nanofiber grid plated with metal silver is adhered to the white glass;

[0021] Step ten: dope benzoic acid in the polymethyl methacrylate solution to form a mixture, and heat and stir the mixture to form a benzoic acid modified polymethyl methacrylate solution;

[0022] Apply the prepared solution dropwise on the white glass with the metal grid attached, apply it evenly with a scraper, then anneal and wait for it to dry.

[0023] Step 11: Place the dried film in deionized water and let it stand, allowing the film to automatically fall off from the white glass, ultimately forming a flexible transparent conductive electrode based on a copper-silver composite nanotube shell.

[0024] The concentration of the mixture formed in step 1 is 0.18-0.22 g / ml;

[0025] Specifically, the mixture is stirred in air for 4-6 hours to form a precursor solution. The prepared precursor solution can be spun in an air humidity range of 25%-32%.

[0026] In the step 3, the distance from the spinneret to the square collector, the flow rate, and the applied voltage range are set to 10-12 cm, 0.06-0.10 mm / min, and 7.5-8.5 kV, respectively.

[0027] In the step 4, the spinning time in the square collector is 100-130 s, and the coverage is 18%-22%.

[0028] In the step 5, 20-25 ml of anhydrous ethanol is placed in a 35 ml culture dish, heated on a hot plate at 50° C., and the nanofiber grid is treated with anhydrous ethanol vapor for 2-3 minutes.

[0029] In the step six, when performing the thermal evaporation treatment, specifically, 50 nm of metallic silver is evaporated on the upper surface of the grid and 50 nm of metallic copper is evaporated on the lower surface, and the evaporation rate is 0.5-0.9 Å / s.

[0030] In the step seven, the white glass is ultrasonically cleaned for 15 minutes, and then UV-irradiated for 15 minutes.

[0031] In the step eight, 1-1.5 ml of deionized water is spread over the pretreated white glass surface, and spin coating is performed at a spin coating rate of 1500 rpm and a spin coating time of 30 s.

[0032] The step ten specifically comprises doping 7.5% solid benzoic acid into a 0.2 g / ml polymethyl methacrylate solution to form a mixture; and heating and stirring the mixture at a temperature of 80° C. and a stirring rate of 3000 rpm for 3 hours to form a benzoic acid-modified polymethyl methacrylate solution.

[0033] In the step eleven, the dried film is placed in deionized water and allowed to stand for 60 seconds.

[0034] The present invention has the following advantages over the prior art: the preparation method provided by the present invention can produce high-performance flexible transparent electrodes at low cost. On the one hand, the three innovations of using anhydrous ethanol vapor to fuse nanowire junctions, designing a copper-silver composite tube-shell structure, and using benzoic acid-modified polymethyl methacrylate as a substrate improve the photoelectric performance and stability of the electrode, and finally produce a flexible transparent electrode with a square resistance of 2.1Ω· The invention discloses a high-performance flexible transparent electrode with a transmittance of 93% and a quality factor of 0.23, which can withstand tens of thousands of bending cycles. On the other hand, the invention adopts a copper-silver composite structure and uses polymethyl methacrylate modified with benzoic acid as a substrate to reduce the preparation cost while ensuring the high performance of the electrode. The invention provides an effective solution for the commercial development of flexible transparent electrodes with high stability, high flexibility, high quality factor and low cost. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] The present invention will be further described below with reference to the accompanying drawings:

[0036] Figure 1 This is a flow chart of the steps of the method for preparing a flexible transparent conductive electrode according to the present invention;

[0037] Figure 2 This is a structural diagram of a flexible transparent conductive electrode based on a copper-silver composite nanotube shell prepared by the present invention;

[0038] Figure 3 This is a scanning electron micrograph of a single copper-silver composite nanotube shell of the present invention;

[0039] Figure 4 This is a scanning electron micrograph of the electrospun nanofiber mesh before and after being treated with anhydrous ethanol vapor;

[0040] Figure 5 This is a scanning electron micrograph of the flexible transparent conductive electrode of the present invention;

[0041] Figure 6 1 is a graph showing the photoelectric performance of the flexible transparent conductive electrode of the present invention;

[0042] Figure 7 is a diagram showing the mechanical stability of the flexible transparent conductive electrode of the present invention;

[0043] Figure 8 is a diagram showing the mechanical stability of the flexible transparent conductive electrode of the present invention;

[0044] Figure 9 is a graph showing the air stability of the flexible transparent conductive electrode of the present invention;

[0045] Figure 10 1 is a graph showing the adhesion test of the flexible transparent conductive electrode of the present invention;

[0046] Figure 11 This is a diagram showing the transformation effect of the polymethyl methacrylate substrate after bending, which is not modified with benzoic acid and modified with benzoic acid;

[0047] Figure 12 It is a test effect diagram of the water contact angle of the present invention. DETAILED DESCRIPTION

[0048] The present invention provides a method for preparing a flexible transparent conductive electrode based on a copper-silver composite nanotube shell. The prepared electrode has a structure similar to a "coaxial cable". The inner core is a PVP nanofiber prepared by an electrospinning process, and the outer shell is a copper-silver composite metal layer formed by depositing a metal silver film and a metal copper film on the upper and lower sides of a PVP nanofiber grid by a vacuum thermal evaporation process. Then, the copper-silver composite nanotube shell is embedded in a polymethyl methacrylate film substrate modified with benzoic acid by a substrate transfer method, and finally a transparent electrode with a copper-silver composite nanotube shell structure having high performance, high stability and low cost is prepared.

[0049] The copper-silver composite nanotube-shell structure prepared by the present invention combines the advantages of copper's good conductivity and silver's excellent stability, not only taking into account stability and conductivity, but also achieving the purpose of reducing costs. By embedding the copper-plated side of the copper-silver composite nanotube-shell structure in the substrate, the problem of easy oxidation of metallic copper can be effectively solved. The vast majority of the silver-plated side is also embedded in the substrate, with only a small portion exposed to the air, which can ensure the conductivity of the electrode and reduce the roughness of the electrode surface. When the electrode is bent, the PVP nanowires inside the shell structure provide support for the outer metal shell, which can improve the mechanical stability of the electrode and solve the problem of poor metal toughness.

[0050] The present invention utilizes anhydrous ethanol vapor to weld grid nodes and employs anhydrous ethanol to weld the electrospun nanofiber grid, primarily to fuse the nodes between the fibers and enhance connectivity between the nanofibers. After metal is evaporated onto the fiber grid, the conductivity at the fused nodes is improved, thereby enhancing the overall conductivity of the electrode. Furthermore, using benzoic acid-modified polymethyl methacrylate as a substrate can reduce substrate preparation costs and address the poor mechanical stability of the polymethyl methacrylate substrate while ensuring excellent optical transmittance.

[0051] The present invention provides a method for preparing a flexible transparent conductive electrode based on a copper-silver composite nanotube shell, and the specific preparation steps are as follows:

[0052] Step 1: Dissolve polyvinylpyrrolidone (PVP) in deionized water to form a mixture with a concentration of 0.18-0.22 g / ml. Stir the mixture in air for 4-6 hours to form a precursor solution. The solution can be spun at an air humidity range of 25%-32%.

[0053] Step 2: Place 5-10 ml of the precursor solution into a syringe (fixed on a spring pump) and a hemispherical droplet appears on the tip of the syringe.

[0054] Step 3: The distance from the spinneret to the square collector, the flow rate, and the applied voltage range were 10-12 cm, 0.06-0.10 mm / min, and 7.5-8.5 kV, respectively.

[0055] Step 4: The hemispherical droplets will be polarized under high voltage and turn into Taylor cones. When the electrostatic repulsion is greater than the surface tension, a charged jet will be generated at the bottom of the Taylor cone, usually passing in a nearly straight line, and finally forming a nanofiber grid in a square collector. The spinning time is about 100-130 s, and the coverage is about 18%-22%.

[0056] Step 5: Place 20-25 ml of anhydrous ethanol into a 35 ml culture dish, heat it on a hot plate at 50°C, place the nanofiber grid on top of the culture dish, and treat the grid with anhydrous ethanol vapor for 2-3 minutes to fuse the nodes between the fibers.

[0057] Step 6: The fiber mesh is subjected to thermal evaporation treatment. 50 nm of metallic silver is evaporated on the upper surface of the mesh and 50 nm of metallic copper is evaporated on the lower surface. The evaporation rate is 0.5-0.9 Å / s.

[0058] Step 7: Pre-treat the white glass. At room temperature, ultrasonically clean the white glass with deionized water, acetone, and isopropyl alcohol for 15 minutes, followed by UV irradiation for 15 minutes to make it hydrophilic.

[0059] Step 8: Spread 1-1.5 ml of deionized water on the pretreated white glass surface, and spin-coat at a speed of 1500 rpm and a spin-coating time of 30 s to form a water film.

[0060] Step 9: Use the water film to adhere the grid on the square collector to the white glass. During the transfer process, make sure the silver-plated side adheres to the glass.

[0061] Step 10: A 0.2 g / ml polymethyl methacrylate solution was doped with 7.5% benzoic acid to form a mixture. The mixture was heated and stirred at 80°C and 3000 rpm for 3 hours to form a benzoic acid-modified polymethyl methacrylate solution. The prepared solution was drop-coated onto a white glass plate attached to a metal grid and evenly applied with a spatula. The mixture was annealed at 50°C for 5 hours and allowed to dry.

[0062] Step 11: The dried film is placed in deionized water and allowed to stand for 60 seconds. The film will then automatically fall off the white glass, eventually forming a flexible, transparent conductive electrode based on a copper-silver composite nanotube shell.

[0063] The flexible transparent conductive electrode prepared by the above process steps has excellent performance and high quality factor. The polymethyl methacrylate substrate modified with benzoic acid has high transmittance. The junction is treated with anhydrous ethanol vapor to improve the conductivity of the electrode. The transmittance is 93%, the quality factor is as high as 0.23, and the flexible transparent electrode has no obvious change in square resistance after tens of thousands of bendings.

[0064] The flexible transparent conductive electrode prepared by the present invention has good stability, which is reflected in the copper-silver composite nanotube shell structure adopted, which combines the advantages of excellent copper conductivity and high silver stability, while taking into account the light transmittance and electrical conductivity of the electrode while improving stability. This structure can cleverly embed the copper-plated side in the substrate, leaving only a small part of the silver exposed. Its advantage is that the exposed silver is flush with the substrate surface without affecting the electrical conductivity, reducing the roughness of the electrode surface; the copper embedded in the substrate can avoid oxidation caused by contact with air, thereby improving the oxidation resistance of the electrode; the PVP nanofibers inside the copper-silver tube shell can provide the electrode with a good conductivity. The electrode provides a certain supporting force, thereby enhancing the mechanical stability of the shell-tube electrode; the polymethyl methacrylate film modified with benzoic acid improves the mechanical stability of the electrode while having high optical transmittance; the adhesion stability is good, and the square resistance remains basically unchanged after the tape is adhered hundreds of times; the flexible transparent electrode based on the copper-silver composite nanotube shell has strong hydrophobicity and high humidity stability; the preparation cost of the electrode prepared by the present invention is low, which is reflected in the use of a copper-silver composite structure, the use of copper to replace part of the expensive silver, reducing silver consumption and saving costs, and the use of polymethyl methacrylate modified with benzoic acid as a substrate, which has low raw material cost.

[0065] like Figure 1 The flexible transparent conductive electrode preparation process shown in the embodiment of the present invention includes:

[0066] Electrospun nanofibers are formed into a nanofiber grid on a square collector; metallic silver is evaporated on the upper surface of the nanofiber grid; the grid is turned over and copper is plated on the other surface; a water film is then formed on the surface of white glass by spin coating to impart a certain degree of adhesion; the copper-silver composite nanotube shell is transferred to the white glass under the action of the adhesion; a benzoic acid-modified polymethyl methacrylate solution is drop-coated on the transferred composite nanotube shell; the drop-coated solution is naturally air-dried to form a thin film; it is then soaked in deionized water to peel the benzoic acid-modified polymethyl methacrylate together with the nanotube shell from the white glass, finally obtaining a flexible transparent conductive electrode based on the copper-silver composite nanotube shell.

[0067] like Figure 2 The figure shows the structure of the flexible transparent conductive electrode based on the copper-silver composite nanotube shell prepared by the present invention. Specifically, the copper-silver composite nanotube shell is embedded in a polymethyl methacrylate substrate, and only part of the silver is exposed to the air to ensure the conductivity of the electrode.

[0068] like Figure 3 Shown is a scanning electron micrograph of a single copper-silver composite nanotube shell, with metallic copper and metallic silver on either side.

[0069] like Figure 4 Shown are scanning electron micrographs of the electrospun nanofiber mesh before and after treatment with anhydrous ethanol vapor. Figure 4 a is the morphology before anhydrous ethanol vapor treatment. It can be seen that the two nanofibers without steam treatment have poor connectivity, which will affect the conductivity of the electrode. Figure 4 b is the morphology after treatment with anhydrous ethanol vapor. It can be seen that the nodes of the two nanofibers are fused together, reducing the overall flatness and also improving the conductivity of the electrode.

[0070] like Figure 5 Shown is a scanning electron micrograph of a flexible transparent conductive electrode based on a copper-silver composite nanotube shell. It can be seen that the composite nanotube shell is completely embedded in the substrate. The substrate can not only provide a certain stress for the shell, but also reduce the roughness of the electrode surface.

[0071] like Figure 6 The figure shows the relationship between the photoelectric performance of the flexible transparent conductive electrode, which mainly explores the relationship between coverage and quality factor. It can be seen that when the coverage is about 20%, the square resistance is 2.1 Ω· , the transmittance is 93% and the quality factor is as high as 0.23.

[0072] like Figure 7 Shown is a diagram showing the mechanical stability relationship of flexible transparent conductive electrodes, which mainly explores the bending stability of commercial ITO, copper nanotube shell electrode, silver nanotube shell electrode, and copper-silver composite nanotube shell electrode at a bending radius of 5mm; during the bending process, the mesh structure of the nanotube shell enhances its flexibility; the PVP nanofibers inside the nanotube shell structure provide a certain stress for the outer metal, and the introduction of silver can also improve the mechanical stability of the electrode; after commercial ITO is bent hundreds of times, the square resistance change rate is as high as 375%, and the square resistance change rate of the copper nanotube shell electrode, copper-silver composite nanotube shell electrode, and silver nanotube shell electrode decreases successively during tens of thousands of bendings, but the change rate is within 0.03%, which proves that the mechanical stability is good. Therefore, the flexibility of the copper-silver composite nanotube shell electrode is better than that of commercial ITO and copper nanotube shell electrodes.

[0073] like Figure 8Shown is a diagram showing the mechanical stability relationship of flexible transparent conductive electrodes, which mainly explores the tensile stability of commercial ITO, copper nanotube shell electrodes, silver nanotube shell electrodes, and copper-silver composite nanotube shell electrodes; during the stretching process, the mesh structure can provide a good buffer and enhance its stretchability. The PVP nanofibers inside the nanotube shell structure provide a certain stress for the outer metal. Silver has good flexibility, and the introduction of silver can also improve the mechanical stability of the electrode; therefore, the tensile performance of the copper-silver composite nanotube shell electrode is better than that of commercial ITO and copper nanotube shell electrodes.

[0074] like Figure 9 The figure shows the air stability relationship of the flexible transparent conductive electrode, which mainly explores the comparison of the air stability of commercial ITO and copper-silver composite nanotube shell electrodes. Since part of the easily oxidized metallic copper is embedded in the substrate, it prevents direct contact with the air. Therefore, the copper-silver composite nanotube shell electrode has good air stability. It can be seen from the figure that the two have similar curves, proving that the air stability of the electrode prepared by the present invention can reach the level of commercial ITO.

[0075] like Figure 10 The figure shows the adhesion test relationship diagram of the flexible transparent conductive electrode, which mainly explores the adhesion stability of commercial ITO and copper-silver nanotube shell electrodes. During the adhesion test of the tape, since most of the metal nanotube shells are embedded in the substrate, the metal shells are prevented from falling off the substrate. It can be seen that the square resistance change rate does not change much compared with that of commercial ITO, proving that the adhesion stability of the electrode of the present invention can reach the level of commercial ITO.

[0076] like Figure 11 The figure shows the transformation of the polymethyl methacrylate substrate after bending without benzoic acid modification and with benzoic acid modification. Figure 11 a is a substrate that has not been modified with benzoic acid. After being bent thousands of times, the substrate broke in the middle. Figure 11 b is a substrate modified with benzoic acid. The introduction of benzoic acid enhances the flexibility of the substrate and can withstand tens of thousands of bends.

[0077] like Figure 12 The water contact angle test diagram is shown. Figure 12 a and b are the water contact angles of the film prepared in the present invention and the film prepared based on NOA63 in Journal of Materials Chemistry C (2017): 10.1039, respectively. It can be seen that the water contact angle of Figure a is larger than that of Figure b, which proves that the film prepared in the present invention has good hydrophobicity and high humidity stability.

[0078] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the above embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for preparing a flexible transparent conductive electrode based on a copper-silver composite nanotube shell, characterized by: The method comprises the following preparation steps: Step 1: dissolving polyvinyl pyrrolidone in deionized water to form a mixture, and stirring the mixture in air to form a precursor solution, wherein the prepared precursor solution can be spun; The concentration of the formed mixture is 0.18-0.22 g / ml; Specifically, the mixture is stirred in air for 4-6 hours to form a precursor solution, and the prepared precursor solution can be spun in an air humidity range of 25%-32%; Step 2: Place the precursor solution into the syringe, and a hemispherical droplet appears on the syringe tip; Step 3: Set the distance from the spinneret to the square collector, flow rate, and applied voltage range to 10-12 cm, 0.06-0.10 mm / min, and 7.5-8.5 kV, respectively. Step 4: The hemispherical droplets are polarized at high voltage and spun on a square collector to form a nanofiber mesh. The spinning time is 100-130 s and the coverage is 18%-22%. Step 5: Place anhydrous ethanol in a culture dish and heat it on a hot plate. Place the nanofiber grid on top of the culture dish and treat the nanofiber grid with anhydrous ethanol vapor to fuse the nodes between the fibers. Step 6: subjecting the nanofiber mesh to a thermal evaporation treatment, evaporating metallic silver on the upper surface of the mesh and metallic copper on the lower surface; Step 7: Pre-treat the white glass: ultrasonically clean the white glass with deionized water, acetone, and isopropyl alcohol at room temperature, and then irradiate it with UV light to make the white glass hydrophilic; Step 8: Spin-coat the pre-treated white glass surface with deionized water to form a water film; Step 9: The nanofiber mesh on the square collector is adhered to the white glass through the action of the water film. During the transfer process, the silver-plated side of the nanofiber mesh adheres to the white glass. Step 10: doping benzoic acid into the polymethyl methacrylate solution to form a mixture, and heating and stirring the mixture to form a benzoic acid-modified polymethyl methacrylate solution; Apply the prepared solution dropwise on the white glass with the metal grid attached, apply it evenly with a scraper, then anneal and wait for it to dry. Step 11: Place the dried film in deionized water and let it stand, allowing the film to automatically fall off from the white glass, ultimately forming a flexible transparent conductive electrode based on a copper-silver composite nanotube shell.

2. The method for preparing a flexible transparent conductive electrode based on a copper-silver composite nanotube shell according to claim 1, characterized in that: In the step 5, 20-25 ml of anhydrous ethanol is placed in a 35 ml culture dish, heated on a hot plate at 50° C., and the nanofiber grid is treated with anhydrous ethanol vapor for 2-3 minutes.

3. The method for preparing a flexible transparent conductive electrode based on a copper-silver composite nanotube shell according to claim 1, characterized in that: In the step six, when performing the thermal evaporation treatment, specifically, 50 nm of metallic silver is evaporated on the upper surface of the grid and 50 nm of metallic copper is evaporated on the lower surface, and the evaporation rate is 0.5-0.9 Å / s.

4. The method for preparing a flexible transparent conductive electrode based on a copper-silver composite nanotube shell according to claim 1, characterized in that: In the step seven, the white glass is ultrasonically cleaned for 15 minutes, and then UV-irradiated for 15 minutes.

5. The method for preparing a flexible transparent conductive electrode based on a copper-silver composite nanotube shell according to claim 1, characterized in that: In the step eight, 1-1.5 ml of deionized water is spread over the pretreated white glass surface, and spin coating is performed at a spin coating rate of 1500 rpm and a spin coating time of 30 s.

6. The method for preparing a flexible transparent conductive electrode based on a copper-silver composite nanotube shell according to claim 1, characterized in that: The step ten specifically comprises doping 7.5% solid benzoic acid into a 0.2 g / ml polymethyl methacrylate solution to form a mixture; and heating and stirring the mixture at a temperature of 80° C. and a stirring rate of 3000 rpm for 3 hours to form a benzoic acid-modified polymethyl methacrylate solution.

7. The method for preparing a flexible transparent conductive electrode based on a copper-silver composite nanotube shell according to claim 1, characterized in that: In the step eleven, the dried film is placed in deionized water and allowed to stand for 60 seconds.

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