Silver nanowire and polymer composite transparent conductive film and preparation method thereof

Abstract

The invention discloses a silver nanowire and polymer composite transparent conductive film and a preparation method thereof, and belongs to the field of conductive films. According to the preparation method disclosed by the invention, hydroxylation treatment is performed on the surface of AgNWs through ultraviolet irradiation induction to generate a large number of-OH groups, and the-OH groups and sulfonic acid groups (-SO3H) in PEDOT: PSS form chemical bonding, so that the contact resistance between the AgNWs and the PEDOT: PSS is remarkably reduced, and a continuous and efficient conductive network is constructed. Meanwhile, the tight coating structure of hydroxylated AgNWs and PEDOT: PSS effectively inhibits oxidation and ion migration of the silver nanowires in a humid and hot environment, and the stability of the transparent conductive film is remarkably improved.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of conductive thin films, and particularly relates to a composite transparent conductive thin film of silver nanowires and polymer and a preparation method thereof. BACKGROUND

[0002] Silver nanowires (AgNWs) thin films exhibit broad application prospects in the field of flexible transparent electrodes due to their high conductivity, excellent light transmittance and flexible characteristics. However, single AgNWs thin films still have significant defects: the van der Waals force between nanowires plays a dominant role, resulting in high contact resistance, especially under dynamic bending conditions, contact point separation is prone to occur, and conductivity is rapidly attenuated; silver material is prone to sulfur / oxidation reaction in a humid and hot or oxidizing environment, a non-conductive Ag2S or Ag2O layer is formed on the surface, resulting in a decrease in long-term stability; in addition, the mechanical strength of the thin film is limited by the weak interaction force between the nanowires, and it is difficult to resist the structural damage caused by repeated stress deformation.

[0003] In order to overcome the above limitations, research has shifted to the strategy of compounding AgNWs with polymer poly(3,4-ethylenedioxythiophene)-polystyrene sulfonic acid (PEDOT:PSS). The introduction of PEDOT:PSS can theoretically fill the pores of the AgNWs network to reduce the contact resistance, and its intrinsic flexibility and environmental stability are also expected to synergistically improve the comprehensive performance of the thin film. However, existing compounding techniques face key bottlenecks: the interface bonding efficiency between AgNWs and PEDOT:PSS is insufficient.

[0004] Traditional processes rely on physical mixing or simple surface wetting treatment, and cannot effectively build a stable chemical coupling interface. For example: through oxidation treatment (such as immersion in hydrogen peroxide solution), the chemical reagent (such as hydrogen peroxide) in this method is easy to remain and affect the conductivity and stability, the reaction conditions (time, concentration, temperature) need to be strictly controlled to prevent over-oxidation from causing structural damage or silver nanowire dissolution; the treatment process may cause local corrosion, loss and uneven modification of the material, especially in the dense nanowire network, the permeability difference is obvious, and the process is time-consuming, which is difficult to meet the demand of efficient continuous production, and needs to be optimized in cooperation with other methods to balance performance and process feasibility. Existing interface enhancement methods (such as high-temperature annealing or chemical coupling agent modification) have significant side effects: high-temperature treatment will deteriorate the thermal stability of the flexible substrate, and the introduction of silane coupling agent and other additives may increase the electron transport barrier at the interface, and even induce charge scattering; the non-uniform coating of PEDOT:PSS on the surface of AgNWs may form a local PSS insulating layer, hindering the effective transmission of carriers between the two-phase interface. SUMMARY

[0005] The present application aims to provide a composite transparent conductive thin film of silver nanowires and polymer and a preparation method thereof, which can improve the conductivity and stability of the composite transparent conductive thin film.

[0006] The specific technical solutions are as follows.

[0007] A preparation method of a composite transparent conductive film of silver nanowires and a polymer, comprising the following steps:

[0008] (1) dispersing silver nanowires in deionized water to form a dispersion liquid with a concentration of 0.1-1wt%, and performing ultraviolet irradiation treatment on the dispersion liquid in an oxygen-containing environment;

[0009] (2) centrifuging and washing the dispersion liquid obtained in step (1) and then dispersing it in deionized water to obtain a modified silver nanowire dispersion liquid;

[0010] (3) mixing an aqueous solution of poly(3,4-ethylenedioxythiophene):polystyrene sulfonic acid with the modified silver nanowire dispersion liquid obtained in step (2), and adding an additive to the mixed solution;

[0011] (4) configuring the mixed solution obtained in step (3) into a composite coating liquid, wherein the mass percentage of silver nanowires in the coating liquid is 0.15%-0.2%, and the mass percentage of poly(3,4-ethylenedioxythiophene):polystyrene sulfonic acid is 0.05%-0.2%;

[0012] (5) coating the composite coating liquid onto a flexible substrate, and drying the substrate in a vacuum drying box to prepare a composite transparent conductive film.

[0013] A composite transparent conductive film prepared by the foregoing method, comprising the following mass percentages of components:

[0014] Silver nanowires: 0.15%-0.2%, poly(3,4-ethylenedioxythiophene):polystyrene sulfonic acid: 0.05%-0.2%, aqueous adhesive: 0.2%-0.5%, and surfactant: 0.05%-0.1%.

[0015] A composite transparent conductive film prepared by the foregoing method, wherein the sheet resistance of the conductive film is not higher than 43Ω / □.

[0016] The present application has the following beneficial effects: the surface of AgNWs is treated by hydroxylation under the induction of ultraviolet light, generating a large number of —OH groups. These —OH groups form chemical bonds with the sulfonic acid groups (—SO3H) in PEDOT:PSS, significantly reducing the contact resistance between AgNWs and PEDOT:PSS, thereby constructing a continuous and efficient conductive network. At the same time, the tight coating structure of the hydroxylated AgNWs and PEDOT:PSS effectively inhibits the oxidation and ion migration of silver nanowires in a humid and hot environment, significantly improving the stability of the transparent conductive film. BRIEF DESCRIPTION OF DRAWINGS

[0017] Figure 1 The combination mechanism diagram of AgNWs and PEDOT:PSS after UV irradiation treatment. DETAILED DESCRIPTION

[0018] The specific embodiments of the present application are described in detail below. It should be understood that the specific embodiments described herein are merely intended to illustrate and explain the present application, and are not intended to limit the present application.

[0019] The interface combination efficiency between AgNWs and PEDOT:PSS is insufficient, which is the main bottleneck restricting the performance improvement of the composite material. The inventors found that the fundamental reason is the chemical inertness of the surface of AgNWs, which leads to the combination of the two mainly relying on weak physical adsorption, rather than strong chemical bonding. The surface of silver nanowires lacks active functional groups, and the electronic structure is stable, and the surface energy is low, so that its combination with other materials is mainly through physical action such as van der Waals force or hydrogen bond, and lacks firm chemical combination. This weak binding force makes the interface between AgNWs and PEDOT:PSS unstable, and easy to be affected by external stress, bending or changes in temperature and humidity, leading to interface separation or phase separation, and then affecting the conductivity and stability of the composite film. Therefore, the inventors improve the surface modification technology-ultraviolet irradiation treatment of silver nanowire surface modification, enhance the chemical bonding force between the two, overcome the limitation of relying on weak physical adsorption, and thus improve the conductivity and long-term stability of the transparent conductive film.

[0020] The purpose of the present application is to solve the problem of insufficient interface combination efficiency between AgNWs and PEDOT:PSS when PEDOT:PSS is combined with silver nanowires. By improving the surface modification technology, the chemical bonding force between the two is enhanced, the limitation of relying on weak physical adsorption is overcome, and thus the conductivity and long-term stability of the transparent conductive film are improved.

[0021] The preparation method of the silver nanowire and polymer composite transparent conductive film of the present application comprises the following steps:

[0022] (1) Disperse silver nanowires in deionized water to form a dispersion liquid with a concentration of 0.1-1wt%, and perform ultraviolet irradiation treatment on the dispersion liquid in an oxygen-containing environment;

[0023] (2) After centrifugal cleaning of the dispersion liquid obtained in step (1), the modified silver nanowire dispersion liquid is obtained by re-dispersing in deionized water;

[0024] (3) Mix the aqueous solution of poly(3,4-ethylenedioxythiophene):polystyrene sulfonic acid with the modified silver nanowire dispersion liquid obtained in step (2), and add an additive to the mixed solution;

[0025] (4) preparing a composite coating solution from the mixed solution obtained in step (3), wherein the weight percentage of silver nanowires in the coating solution is 0.15%-0.2%, and the weight percentage of poly(3,4-ethylenedioxythiophene):polystyrene sulfonic acid is 0.05%-0.2%;

[0026] (5) The composite coating liquid is coated on a flexible substrate, and the substrate is placed in a vacuum drying oven for drying. After the solvent is completely evaporated, a composite transparent conductive film is prepared.

[0027] Furthermore, the conditions for the ultraviolet light irradiation treatment in step (1) are: the wavelength of the ultraviolet light is 200-400 nm, and the irradiation time is 30-60 min.

[0028] Furthermore, when the silver nanowire dispersion is treated with ultraviolet light in step (1), the temperature of the dispersion is controlled to be no higher than 40°C.

[0029] The dispersion can be stirred to ensure uniform dispersion of the silver nanowires; a water bath or cooling device can be used to control the temperature of the dispersion to no higher than 40°C.

[0030] Preferably, the light source of the ultraviolet light is a low-pressure mercury lamp with a main wavelength of 254 nm.

[0031] Furthermore, the oxygen-containing environment is aerated with air or oxygen.

[0032] Preferably, the oxygen-containing environment is formed by introducing oxygen into the dispersion liquid at an oxygen flow rate of 0.5-2 L / min.

[0033] Furthermore, the additives in step (3) include an aqueous adhesive and a surfactant.

[0034] Furthermore, the mass percentage of the water-based adhesive is 0.2%-0.5%, and the mass percentage of the surfactant is 0.05%-0.1%.

[0035] Furthermore, the aqueous binder is preferably hydroxypropyl methylcellulose, and the surfactant is preferably a fluorine-containing nonionic surfactant.

[0036] Furthermore, the coating method is spin coating, spray coating, rod coating or slit coating.

[0037] Furthermore, the substrate is polyethylene terephthalate, polycarbonate, polytetrafluoroethylene or polymethyl methacrylate.

[0038] The mass percentage of each component in the composite transparent conductive film obtained by the above preparation method is:

[0039] Silver nanowires: 0.15%-0.2%, poly(3,4-ethylenedioxythiophene): poly(styrenesulfonic acid) mass percentage: 0.05%-0.2%, aqueous binder: 0.2%-0.5%, surfactant: 0.05%-0.1%.

[0040] The composite transparent conductive film obtained by the above preparation method has a sheet resistance of not more than 43 Ω / □.

[0041] The PEDOT:PSS aqueous solution in the examples and comparative examples is commercially available, and the type is ICP1020 produced by Belgium Agfa Company.

[0042] Example 1:

[0043] (1) Disperse AgNWs with a diameter of 30 nm and a length of 20 μm in deionized water, mechanically stir for 30 min at a stirring rate of 500 rpm, and obtain a uniform dispersion liquid, and the concentration of AgNWs is 1.0 wt%.

[0044] (2) Take 50 g of the AgNWs dispersion liquid in step (1) and place it in a beaker, and magnetically stir at a stirring rate of 400 rpm. Use a low-pressure mercury lamp with a wavelength of 254 nm, continuously introduce oxygen during ultraviolet irradiation, the oxygen flow is 2 L / min, and irradiate for 30 minutes, and the water bath temperature is controlled at 35°C.

[0045] (3) After irradiation, the dispersion liquid is centrifuged for 3 times, 15 min each time, at a speed of 3000 rpm, and is redispersed in deionized water to obtain a hydroxylated AgNWs dispersion liquid.

[0046] (4) Mix the PEDOT:PSS aqueous solution with the hydroxylated AgNWs dispersion liquid, and stir uniformly at 600 r / min.

[0047] (5) Add various additives to the mixed solution, and the mass percentage of each component in the total solution is: PEDOT:PSS 0.1%, silver nanowires 0.2%, fluorine-containing nonionic surfactant 0.05%, hydroxypropyl methyl cellulose 0.2%, and the rest is water, and stir uniformly at 800 rpm to obtain a composite coating liquid.

[0048] (6) Spin-coat the composite coating liquid on a polyethylene terephthalate (PET) substrate at a speed of 500 rpm for 10 seconds, and bake at a high temperature of 120°C for 5 minutes to complete the preparation of the transparent conductive film.

[0049] Example 2:

[0050] (1) AgNWs with diameter of 30 nm and length of 20 μm were dispersed in deionized water, and mechanical magnetic stirring was performed for 30 min at a stirring rate of 500 rpm to obtain a uniform dispersion liquid, and the concentration of AgNWs was 0.5 wt%.

[0051] (2) 50 g of the AgNWs dispersion liquid in step (1) was placed in a beaker and subjected to magnetic stirring at a stirring rate of 400 rpm. A low-pressure mercury lamp with a wavelength of 365 nm was used, and oxygen was continuously introduced during ultraviolet light irradiation, and the oxygen flow rate was 0.5 L / min, and the irradiation time was 30 min, and the water bath temperature was controlled at 40 °C.

[0052] (3) After the irradiation was completed, the dispersion liquid was subjected to three times of centrifugal washing, each time for 15 min at a speed of 3000 rpm, and was then redispersed in deionized water to obtain a hydroxylated AgNWs dispersion liquid.

[0053] (4) The PEDOT:PSS aqueous solution was mixed with the hydroxylated AgNWs dispersion liquid, and stirring was performed at 600 r / min until the mixture was uniform;

[0054] (5) Various additives were added to the mixture, and the mass percentage of each component in the total solution was as follows: PEDOT:PSS 0.05%, silver nanowires 0.15%, fluorine-containing non-ionic surfactant 0.1%, hydroxypropyl methyl cellulose 0.5%, and the rest was water, and stirring was performed at 800 rpm until the mixture was uniform, to obtain a composite coating liquid;

[0055] (6) The composite coating liquid was spin-coated on a polyethylene terephthalate (PET) substrate at a speed of 500 rpm for 10 s, and high-temperature baking was performed at 120 °C for 5 min, to complete the preparation of the transparent conductive film.

[0056] Example 3:

[0057] (1) AgNWs with diameter of 30 nm and length of 20 μm were dispersed in deionized water, and mechanical magnetic stirring was performed for 30 min at a stirring rate of 500 rpm to obtain a uniform dispersion liquid, and the concentration of AgNWs was 1.0 wt%.

[0058] (2) 50 g of the AgNWs dispersion liquid in step (1) was placed in a beaker and subjected to magnetic stirring at a stirring rate of 400 rpm. A low-pressure mercury lamp with a wavelength of 254 nm was used, and oxygen was continuously introduced during ultraviolet light irradiation, and the oxygen flow rate was 1.5 L / min, and the irradiation time was 50 min, and the water bath temperature was controlled at 35 °C.

[0059] (3) After the irradiation was completed, the dispersion liquid was subjected to three times of centrifugal washing, each time for 15 min at a speed of 3000 rpm, and was then redispersed in deionized water to obtain a hydroxylated AgNWs dispersion liquid.

[0060] (4) The PEDOT:PSS aqueous solution is mixed with the hydroxylated AgNWs dispersion liquid, and stirred uniformly at 600 r / min;

[0061] (5) Various additives are added to the mixed solution, and the mass percentage of each component in the total solution is: PEDOT:PSS 0.2%, silver nanowires 0.2%, fluorine-containing non-ionic surfactant 0.1%, hydroxypropyl methyl cellulose 0.4%, and the rest is water, and the mixture is stirred uniformly at 800 rpm to obtain a composite coating liquid;

[0062] (6) The composite coating liquid is spin-coated on a polyethylene terephthalate (PET) substrate at a rotation speed of 500 rpm for 10 seconds, and baked at a high temperature of 120°C for 5 minutes to complete the preparation of the transparent conductive film.

[0063] Example 4:

[0064] The difference between this example and Example 1 is that oxygen is not introduced during ultraviolet irradiation, but air is introduced, and other conditions remain unchanged.

[0065] Comparative Example 1: The difference between this comparative example 1 and Example 1 is that no ultraviolet irradiation is performed, and other conditions remain unchanged.

[0066] Comparative Example 2: The difference between this comparative example 2 and Example 1 is that the AgNWs dispersion liquid without ultraviolet irradiation is mixed with the PEDOT:PSS aqueous solution, and then ultraviolet irradiation is performed, and the ultraviolet irradiation conditions remain unchanged, and other conditions remain unchanged.

[0067] Comparative Example 3: The difference between this comparative example 3 and Example 1 is that the AgNWs dispersion liquid is not ultraviolet irradiated, the composite coating liquid is spin-coated on a polyethylene terephthalate substrate, and then ultraviolet irradiation is performed, and the ultraviolet irradiation conditions remain unchanged, and other conditions remain unchanged.

[0068] For the transparent conductive film products of Examples 1-4 and Comparative Examples 1-3 described above, the sheet resistance is tested using a four-probe tester, and the light transmittance and haze are tested using a photoelectric haze meter, and the relevant test results are shown in Table 1.

[0069] Table 1

[0070]

[0071]

[0072] From Table 1, it can be seen that Comparative Example 1 is different from Example 1 in that it is not subjected to ultraviolet irradiation, and other conditions are the same, and the sheet resistance of the conductive film obtained in Comparative Example 1 is 55 Ω / D, which is obviously higher than the sheet resistance 34 Ω / D of the conductive film obtained in Example 1; Comparative Example 2 is different from Example 1 in that it mixes the AgNWs dispersion liquid not subjected to ultraviolet irradiation with the PEDOT:PSS aqueous solution and then is subjected to ultraviolet irradiation, and the ultraviolet irradiation conditions are the same, and other conditions are the same, and the sheet resistance of the conductive film obtained in Comparative Example 2 is 50 Ω / D, which is obviously higher than the sheet resistance 34 Ω / D of the conductive film obtained in Example 1; Comparative Example 3 is different from Example 1 in that it does not subject the AgNWs dispersion liquid to ultraviolet irradiation, and the composite coating liquid is spin-coated on a polyethylene terephthalate substrate and then is subjected to ultraviolet irradiation, and the ultraviolet irradiation conditions are the same, and other conditions are the same, and the sheet resistance of the conductive film obtained in Comparative Example 3 is 49 Ω / D, which is obviously higher than the sheet resistance 34 Ω / D of the conductive film obtained in Example 1;

[0073] It can be seen that, under the same conditions, the sheet resistance of the conductive film obtained in Comparative Examples 1-3 is obviously higher than the sheet resistance 34 Ω / D of the conductive film obtained in Example 1, and it can be seen that the conductive film obtained by the preparation method of the present application has better conductivity.

[0074] Although Comparative Examples 1-3 and Examples 2-4 are different in process parameters in the preparation of the conductive film, from the performance of the conductive film prepared, the sheet resistance of the conductive film obtained by the preparation method of the present application is not higher than 43 Ω / D, and the conductivity is better.

[0075] At this point, those skilled in the art should recognize that, although the exemplary embodiments of the present application have been shown and described in detail herein, many other variations or modifications can be determined or deduced directly from the disclosure of the present application in accordance with the principles of the present application without departing from the spirit and scope of the present application. Therefore, the scope of the present application should be understood and recognized as covering all these other variations or modifications.

Claims

1. A method for preparing a composite transparent conductive film of silver nanowires and polymers, characterized in that: The method comprises the following steps: (1) dispersing silver nanowires in deionized water to form a dispersion having a concentration of 0.1-1 wt%, and irradiating the dispersion with ultraviolet light in an oxygen-containing environment; (2) The dispersion obtained in step (1) is centrifuged and washed, and then redispersed in deionized water to obtain a modified silver nanowire dispersion; (3) mixing the poly(3,4-ethylenedioxythiophene):polystyrenesulfonic acid aqueous solution with the modified silver nanowire dispersion obtained in step (2), and adding additives to the mixture; (4) The mixed solution obtained in step (3) is prepared into a composite coating solution, wherein the mass percentage of silver nanowires in the coating solution is 0.15%-0.2%, and the mass percentage of poly(3,4-ethylenedioxythiophene):polystyrene sulfonic acid is 0.05%-0.2%; (5) The composite coating liquid is coated on a flexible substrate, and the substrate is placed in a vacuum drying oven for drying to prepare a composite transparent conductive film.

2. The method for preparing a composite transparent conductive film according to claim 1, characterized in that: The conditions for the ultraviolet light irradiation treatment in step (1) are: the wavelength of the ultraviolet light is 200-400 nm, and the irradiation time is 30-60 min.

3. The method for preparing a composite transparent conductive film according to claim 1, characterized in that: When the silver nanowire dispersion is treated with ultraviolet light in step (1), the temperature of the dispersion is controlled to be no higher than 40°C.

4. The method for preparing a composite transparent conductive film according to claim 1, wherein: The light source of the ultraviolet light is a low-pressure mercury lamp with a main wavelength of 254 nm.

5. The method for preparing a composite transparent conductive film according to claim 1, characterized in that: The oxygen-containing environment is a process of introducing oxygen or air into the dispersion, with the flow rate of oxygen or air being 0.5-2 L / min.

6. The method for preparing a composite transparent conductive film according to claim 1, wherein: The additives in step (3) include a water-based binder and a surfactant.

7. The method for preparing a composite transparent conductive film according to claim 6, wherein: The mass percentage of the water-based adhesive is 0.2%-0.5%, and the mass percentage of the surfactant is 0.05%-0.1%.

8. The method for preparing a composite transparent conductive film according to claim 7, wherein: The aqueous binder is preferably hydroxypropyl methylcellulose, and the surfactant is preferably a fluorine-containing nonionic surfactant.

9. A composite transparent conductive film obtained by the preparation method according to any one of claims 1 to 8, characterized in that: The composite transparent conductive film comprises the following components in percentage by mass: Silver nanowires: 0.15%-0.2%, the mass percentage of poly(3,4-ethylenedioxythiophene):polystyrene sulfonic acid is 0.05%-0.2%, the water-based adhesive is 0.2%-0.5%, and the surfactant is 0.05%-0.1%.

10. A composite transparent conductive film obtained by the preparation method according to any one of claims 1 to 9, characterized in that: The sheet resistance of the conductive film is no higher than 43Ω / □.

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