Anti-ultraviolet ozone treatment silver nanowire composite transparent electrode and preparation method thereof

Abstract

The invention discloses an anti-ultraviolet ozone treatment silver nanowire composite transparent electrode and a preparation method thereof. The method comprises the following steps: firstly, coating a layer of silver nanowires on a transparent substrate, taking the silver nanowires as a cathode, taking a mixed aqueous solution of zinc nitrate and aluminum nitrate as an electrolyte, electrically depositing an aluminum-doped zinc oxide (AZO) protective layer on the silver nanowires, then coating a layer of stannic oxide nanocrystals (SnO2), and finally, carrying out electrodeposition on the transparent substrate. And carrying out heat treatment to obtain the silver nanowire composite transparent electrode subjected to anti-ultraviolet ozone treatment. The oxidation resistance and mechanical stability of the silver nanowire transparent conductive thin film can be remarkably improved, meanwhile, the excellent flexibility, conductivity and light transmission of the silver nanowire transparent conductive thin film are kept, the protection process of the silver nanowire is simplified, and the silver nanowire transparent conductive thin film has potential application in the field of flexible electronics.

Description

Technical Field

[0001] The invention relates to the field of transparent electrodes, and in particular to an anti-ultraviolet ozone treated silver nanowire composite transparent electrode and a preparation method thereof. Background Art

[0002] Silver nanowire transparent conductive film has excellent conductivity, high optical transmittance, good flexibility, ductility and low cost, so it has broad application prospects in flexible optoelectronic devices such as mobile phone touch screens, liquid crystal displays, flexible solar cells, etc. At present, silver nanowire transparent conductive film is considered to be an alternative material for traditional indium tin oxide (ITO) and fluorine-doped tin dioxide (FTO) transparent electrodes, which can solve the problems of ITO film brittleness, indium resource shortage and high cost. However, since the specific surface area of ​​nanostructured silver is much larger than that of macroscopic materials, the high surface activity brought about by it seriously reduces the stability of silver nanowires. In practical applications, it will face problems such as inability to withstand ultraviolet ozone treatment (poor antioxidant ability), local hot spot melting under high voltage causing device failure, poor mechanical stability, and easy detachment from the substrate. To solve this problem, the most common approach is to deposit a protective layer on the surface of the silver nanowire, such as forming a whole layer of inert metal, conductive oxide or organic matter on the surface of the film by sputtering, sol-gel method, etc., but this method will inevitably affect the light transmittance and conductivity of the transparent conductive film. The graphene protective layer reported so far still cannot avoid the problems of high price and complicated processing of graphene itself. Therefore, it is still necessary to find a simple and low-cost method to protect silver nanowires without affecting the performance of silver nanowires so that it can be applied in the field of flexible electronics. Summary of the invention

[0003] The technical problem to be solved by the present invention is to overcome the deficiencies of the prior art and provide a method for improving the antioxidant performance and mechanical stability of silver nanowire transparent electrodes while maintaining their excellent flexibility, conductivity, light transmittance and other advantages.

[0004] In order to solve the above technical problems, the present invention adopts the following technical solutions:

[0005] A silver nanowire composite transparent electrode resistant to ultraviolet ozone treatment, characterized in that the composite electrode comprises a transparent substrate, silver nanowires, an aluminum-doped zinc oxide (AZO) protective layer and a tin dioxide nanocrystal (SnO2) layer arranged in sequence from bottom to top.

[0006] In the above-mentioned anti-ultraviolet ozone treated silver nanowire composite transparent electrode, preferably, the transparent substrate layer is ultra-clear glass, transparent polyimide, etc.

[0007] A method for preparing a silver nanowire composite transparent electrode resistant to ultraviolet ozone treatment comprises the following steps:

[0008] (1) coating a silver nanowire ethanol solution on a transparent substrate, and preparing a silver nanowire transparent conductive film through a hot plate heat treatment;

[0009] (2) adding a soluble salt of zinc to water to obtain a zinc salt solution; adding a soluble salt of aluminum to water to obtain an aluminum salt solution; adding the aluminum salt solution to the zinc salt solution, controlling the atomic ratio of Al to Zn to be 0.75 to 1.25:100, stirring to obtain a mixed solution, and then heating to 80±3° C., using an inert electrode as an anode and a transparent substrate on which silver nanowires are deposited as a cathode, electrochemical deposition is performed, the voltage is controlled at -1.45 to -1.55 V, the deposition temperature is maintained at 80±3° C., the deposition time is controlled at 3 to 7 min, and a post-deposition heat treatment is performed to obtain a silver nanowire / AZO composite transparent conductive film;

[0010] (3) Preparing a SnO2 nanocrystal layer on the silver nanowire / AZO composite transparent conductive film to obtain an anti-ultraviolet ozone treated silver nanowire composite transparent electrode.

[0011] In the above-mentioned method for preparing a silver nanowire composite transparent electrode resistant to ultraviolet ozone treatment, preferably, in step (1), the silver nanowire ethanol solution is purchased from Zhejiang Xiwei Nano;

[0012] In the above-mentioned method for preparing a UV-resistant ozone-treated silver nanowire composite transparent electrode, preferably, in step (1), the coating method is spin coating;

[0013] In the above-mentioned method for preparing a UV-resistant ozone-treated silver nanowire composite transparent electrode, preferably, in step (1), the transparent substrate is a rigid glass or a flexible polymer;

[0014] The above-mentioned method for preparing a silver nanowire composite transparent electrode resistant to ultraviolet ozone treatment, preferably, in step (1), the temperature of the heat treatment is 115-125° C., and the time is 9-11 minutes;

[0015] In the above-mentioned method for preparing a silver nanowire composite transparent electrode resistant to ultraviolet ozone treatment, preferably, in step (1), the concentration of the silver nanowire solution is 4 to 6 mg / mL, and the solvent is ethanol;

[0016] In the above-mentioned method for preparing a silver nanowire composite transparent electrode resistant to ultraviolet ozone treatment, preferably, in step (1), the number of layers of the silver nanowire transparent conductive film spin-coated is 2 to 3 layers;

[0017] The above-mentioned method for preparing a UV-resistant ozone-treated silver nanowire composite transparent electrode, preferably, in step (2), the concentration of the zinc salt solution is 0.0025-0.0035 mol / L, the concentration of the aluminum salt solution is 0.0025-0.0035 mol / L, the soluble salt of zinc is zinc nitrate hexahydrate, and the soluble salt of aluminum is aluminum nitrate nonahydrate.

[0018] In the above-mentioned method for preparing the silver nanowire composite transparent electrode resistant to ultraviolet ozone treatment, preferably, in step (2), the stirring time is 30 to 35 minutes.

[0019] In the above-mentioned method for preparing a silver nanowire composite transparent electrode resistant to ultraviolet ozone treatment, preferably, in step (2), the inert electrode is a platinum titanium mesh or platinum, and the distance between the anode and the cathode is 2 to 3 cm.

[0020] In the above-mentioned method for preparing a UV-resistant ozone-treated silver nanowire composite transparent electrode, preferably, in step (2), the heat treatment temperature is 150-200° C., the heat treatment time is 15-20 min, and the heat treatment atmosphere is air.

[0021] In the above-mentioned method for preparing a silver nanowire composite transparent electrode resistant to ultraviolet ozone treatment, preferably, in step (2), the washing is rinsing with deionized water, and the rinsing time is 10 to 30 seconds.

[0022] The above-mentioned method for preparing a silver nanowire composite transparent electrode resistant to ultraviolet ozone treatment, preferably, in step (3), the method for preparing the SnO2 layer is: taking a soluble salt of tin and dissolving it in anhydrous isopropanol to obtain an isopropanol solution of tin salt, the concentration of tin salt in the ethanol solution of tin salt is controlled to be 0.05-0.15 mol / L, heating evaporation and condensation reflux at the boiling point ±5°C of the mixed solution, standing, aging, and filtering with a 0.22μm polytetrafluoroethylene filter membrane to obtain a SnO2 precursor sol. The prepared SnO2 precursor sol is spin-coated on the AZO layer, the spin-coating speed is 2500-3500rpm, the spin-coating time is 25-35s, and then heat-treated, the heat treatment temperature is 150-200°C, and the heat treatment time is 25-35min.

[0023] The method is used to prepare a silver nanowire composite transparent electrode resistant to ultraviolet and ozone treatment.

[0024] The silver nanowire composite transparent electrode treated with UV and ozone resistance not only has excellent flexibility, conductivity and light transmittance, but also has excellent antioxidant ability.

[0025] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0026] 1. UV-ozone treatment is one of the important methods to remove organic groups on the surface of transparent electrodes and enhance their surface wettability. It is widely used to clean transparent conductive glasses such as ITO and FTO, and is an important step in preparing solar cells. Ordinary silver nanowire transparent conductive films will be oxidized after only 5 minutes of UV-ozone treatment, and the film will turn black and be almost insulating. The silver nanowire composite transparent electrode resistant to UV-ozone treatment prepared by the present invention not only maintains good light transmittance and conductivity, but more importantly, greatly improves the antioxidant capacity of the silver nanowire transparent conductive film, and can still maintain excellent photoelectric properties after more than 15 minutes of UV-ozone treatment.

[0027] 2. Compared with ordinary silver nanowire transparent conductive films, the anti-ultraviolet ozone treated silver nanowire composite transparent electrode prepared by the present invention also has excellent mechanical stability. Silver nanowires are deposited on the substrate by spin coating-heat treatment, and their adhesion to the substrate is weak, and they will fall off with a slight scratch. The silver nanowire composite transparent electrode prepared by the present invention can not only enhance the adhesion of the transparent electrode to the substrate, but also improve the mechanical strength of the silver nanowire network structure. After being torn by the tape, the silver nanowire composite transparent electrode can still maintain the integrity of the structure.

[0028] 3. The present invention adopts the electrodeposition process to prepare the AZO layer, which provides a stable and controllable environment for the formation of the protective layer, is conducive to maintaining the flatness of the surface of the deposited layer and accurately adjusting the thickness of the deposited layer as required. The AZO layer is well combined with the silver nanowires and has high mechanical stability. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 This is a SEM image of an anti-ultraviolet ozone treated silver nanowire composite transparent electrode prepared in Example 1 of the present invention.

[0030] Figure 2 This is a SEM image of the silver nanowire transparent conductive film without a protective layer prepared in Comparative Example 1.

[0031] Figure 3 It is the transmission spectrum diagram of comparative example 1 and embodiment 1. DETAILED DESCRIPTION

[0032] The present invention is further described below in conjunction with the accompanying drawings and specific preferred embodiments, but the protection scope of the present invention is not limited thereby. The materials and instruments used in the following embodiments are all commercially available.

[0033] Example 1

[0034] A method for preparing a silver nanowire composite transparent electrode resistant to ultraviolet ozone treatment comprises the following steps:

[0035] (1) Cleaning the transparent slide

[0036] The glass slides (commercially available) were ultrasonically cleaned with glass cleaner, deionized water, acetone, isopropanol and anhydrous ethanol for 30 min each, and dried at 80° C. for 20 min. The glass slides were then cleaned with a UV-ozone cleaner for 25 min.

[0037] (2) Preparation of silver nanowire transparent conductive film

[0038] A glass sheet with a size of 15 mm × 15 mm was placed on a coating machine, and a silver nanowire ethanol suspension with a concentration of 5 mg / mL was spin-coated on the glass sheet. The specific spin-coating steps were as follows: 50 μL of the silver nanowire ethanol suspension was added to the glass sheet, and the glass sheet was rotated at a speed of 2000 rpm for 30 seconds; the spin-coating steps under the above conditions were repeated once, and the glass sheet after spin coating was placed on a constant temperature platform for heat treatment at 120°C for 10 minutes, thus completing the preparation of the transparent conductive electrode of the silver nanowires;

[0039] (3) Preparation of Al-doped ZnO protective layer

[0040] Take 0.2814g of aluminum nitrate 9hydrate [Al(NO3)3·9H2O] and dissolve it in 250mL of deionized water, stir at room temperature for 30min to obtain aluminum nitrate solution; take 0.4463g of zinc nitrate hexahydrate [Zn(NO3)2·6H2O] and dissolve it in 500mL of deionized water to obtain zinc nitrate solution. Take 5mL of aluminum nitrate solution and add it to zinc nitrate solution, control the Al / Zn atomic ratio to 1.00at.%, stir at room temperature for 30min, and obtain a mixed solution (i.e., electrodeposition solution). Add the electrodeposition solution to the Hall cell, heat it to 80℃, place the silver nanowire transparent conductive electrode at the cathode, place the platinum titanium mesh (inert electrode) at the anode, the distance between the positive and cathode is 2cm, the voltage is controlled at -1.5V, and electrochemical deposition is performed for 5min, during which the temperature is maintained at 80℃. After the deposition is completed, the deposited product is immersed in deionized water at room temperature under stirring for 20 seconds, and then heat-treated on a hot stage at 150°C for 15 minutes to obtain an Al-doped ZnO protective layer;

[0041] (4) Preparation of SnO2 layer

[0042] Take 0.2256g of stannous chloride dihydrate (SnCl2·2H2O) and dissolve it in 10ml of anhydrous isopropanol, stir and condense it at 85℃ for 3h to obtain a colloid, then let it stand at 40℃ for 3h, and age it at room temperature for more than 24h to obtain a SnO2 sol with anhydrous isopropanol as solvent, and filter it with a 0.22μm polytetrafluoroethylene filter membrane to finally obtain a SnO2 sol. Then, the SnO2 sol is spin-coated on the AZO layer with a sizing machine at 3000rmp and 30s, and then heat-treated at 150℃ for 30min to obtain a silver nanowire composite transparent electrode with UV-resistant ozone treatment.

[0043] The conductivity, light transmittance and stability of the silver nanowire composite transparent electrode prepared in this embodiment after UV ozone treatment were tested. Figure 3 As shown. In Example 1, Table 1 lists the photoelectric properties of transparent electrodes after different deposition times. It can be found that compared with the unprotected silver nanowire transparent conductive film, the transmittance of the transparent electrode with AZO / SnO2 protective layer has a certain decrease, and the transmittance at a wavelength of 550nm is 70.26%, and the square resistance is 8.1Ω / sq, showing excellent photoelectric performance. In addition, after 15 minutes of ultraviolet ozone treatment, the square resistance still remains at around 8Ω / sq, showing good antioxidant ability. After being torn by the tape, the silver nanowire composite transparent electrode can still maintain the integrity of the structure, reflecting good mechanical stability. The scanning electron microscopy (SEM) test results of the silver nanowire composite transparent electrode are shown in Figure 1 As shown by Figure 1 It can be seen that the surface of the silver nanowires is covered with a protective layer.

[0044] Comparative Example 1

[0045] The preparation method of the silver nanowire transparent conductive film without a protective layer comprises the following steps:

[0046] (1) Cleaning the transparent slide

[0047] The glass slides (commercially available) were ultrasonically cleaned with glass cleaner, deionized water, acetone, isopropanol and anhydrous ethanol for 30 min each, and dried at 80° C. for 20 min. The glass slides were then cleaned with a UV-ozone cleaner for 25 min.

[0048] (2) A glass sheet with a size of 15 mm × 15 mm was placed on a coating machine, and a silver nanowire ethanol suspension with a concentration of 5 mg / mL was spin-coated on the glass sheet. The specific spin-coating steps were as follows: 50 μL of the silver nanowire ethanol suspension was added to the glass sheet, and the glass sheet was rotated at a speed of 2000 rpm for 30 s; the spin-coating steps under the above conditions were repeated once, and the glass sheet after spin coating was placed on a constant temperature platform for heat treatment at 120°C for 10 min, thus completing the preparation of the transparent conductive electrode of the silver nanowires. The SEM test results are shown in FIG. Figure 2 As shown;

[0049] The preparation method of the silver nanowire transparent conductive film without a protective layer is the same as the first two steps of Example 1, with the only difference that no protective layer is deposited. The photoelectric performance and stability of the silver nanowire transparent conductive film without a protective layer prepared under this condition were tested. It can be seen from Table 1 that the transmittance at a wavelength of 550nm is 83.73%, and the square resistance is only 6.3Ω / sq, showing excellent photoelectric performance. However, after being torn by the tape, the unprotected silver nanowire transparent conductive film will be destroyed due to poor adhesion. After only 10 minutes of ultraviolet ozone treatment, the film will turn black and is almost insulating. It can be seen that the antioxidant ability and mechanical stability of the composite conductive film of Example 1 are better than those of Comparative Example 1.

[0050] Table 1 Photoelectric properties of silver nanowire transparent conductive films with and without protective layer

[0051]

[0052] The above is only a preferred embodiment of the present invention and does not limit the present invention in any form. Although the present invention has been disclosed as above in the preferred embodiment, it is not used to limit the present invention. Any technician familiar with the art can make many possible changes and modifications to the technical solution of the present invention by using the methods and technical contents disclosed above without departing from the spirit and technical solution of the present invention, or modify it into an equivalent embodiment of equivalent changes. Therefore, any simple modification, equivalent replacement, equivalent change and modification made to the above embodiments according to the technical essence of the present invention without departing from the content of the technical solution of the present invention, still fall within the scope of protection of the technical solution of the present invention.

Claims

1. A silver nanowire composite transparent electrode treated with UV and ozone resistance, characterized in that: The composite electrode comprises a transparent substrate, silver nanowires, an aluminum-doped zinc oxide (AZO) protective layer and a tin dioxide nanocrystal (SnO2) layer which are sequentially arranged from bottom to top.

2. The method for preparing a silver nanowire composite transparent electrode resistant to ultraviolet ozone treatment according to claim 1, characterized in that: The following steps are involved: S1, spin coating a silver nanowire solution on a transparent substrate, and preparing a silver nanowire transparent conductive film after heat treatment; S2. Preparing an AZO protective layer on the silver nanowire transparent conductive film, the preparation process comprising: adding a soluble salt of zinc to water to obtain a zinc salt solution, adding a soluble salt of aluminum to water to obtain an aluminum salt solution, adding the aluminum salt solution to the zinc salt solution, controlling the atomic ratio of Al to Zn to be 0.75-1.25:100, stirring to obtain a mixed solution, then heating to 80±3°C, using an inert electrode as an anode and a transparent substrate / silver nanowire as a cathode, and performing electrochemical deposition, wherein the distance between the anode and the cathode is 2-3 cm, the potential difference is -1.45--1.55 V, the deposition temperature is 80±3°C, the deposition time is 3-7 min, washing, and then heat treatment, wherein the heat treatment temperature is 150-200°C, and the heat treatment time is 15-20 min, to obtain an AZO protective layer on the silver nanowire transparent conductive film; S3. Preparing a SnO2 layer on the AZO protective layer.

3. The method for preparing a silver nanowire composite transparent electrode resistant to ultraviolet ozone treatment according to claim 2, characterized in that: In step S1, the concentration of the silver nanowire ethanol solution is controlled at 4-6 mg / ml, the spin coating speed is 2500-3500 rpm, the spin coating time is 25-35 s, the number of spin coating layers is 2-3 layers, the heat treatment temperature is 115-125° C., and the heat treatment time is 9-11 min.

4. The method for preparing a silver nanowire composite transparent electrode resistant to ultraviolet ozone treatment according to claim 2, characterized in that: In step S2, the concentration of the zinc salt solution is 0.0025-0.0035 mol / L, the concentration of the aluminum salt solution is 0.0025-0.0035 mol / L, the soluble zinc salt is zinc nitrate hexahydrate, and the soluble aluminum salt is aluminum nitrate nonahydrate.

5. The method for preparing a silver nanowire composite transparent electrode resistant to ultraviolet ozone treatment according to claim 2, characterized in that: In step S3, the preparation method of SnO2 is: taking a soluble salt of tin and dissolving it in anhydrous isopropanol to obtain an isopropanol solution of tin salt, the concentration of tin salt in the ethanol solution of tin salt is controlled to be 0.05-0.15 mol / L, heating evaporation and condensation reflux at the boiling point ±5°C of the mixed solution, standing, aging, and filtering with a 0.22 μm polytetrafluoroethylene filter membrane to finally obtain a SnO2 precursor sol; The prepared SnO2 precursor sol is spin-coated on the AZO layer at a speed of 2500-3500 rpm for 25-35 s, and then heat-treated at a temperature of 150-200° C. for 25-35 min.

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