A silver nanowire-polyimide flexible transparent electrode film with a nanoporous structure, a preparation method thereof, and an electrode

Abstract

The application discloses a kind of silver nanowire-polyimide flexible transparent electrode film of nano-porous structure and its preparation method and electrode, method: silver nanowire suspension and polyimide solution are coated on substrate in turn, after solution diffusion is uniform, gradient heating solidification is carried out, and semi-embedded silver nanowire-polyimide flexible transparent electrode film is prepared after peeling off;It is soaked in organic solvent, after taking out, it is sealed in autoclave and carbon dioxide is introduced, it is placed in low-temperature constant-temperature reaction bath, and carbon dioxide is adsorbed to saturation;Release autoclave pressure, after taking out flexible transparent electrode film, it is heated and foamed, and obtain silver nanowire-polyimide flexible transparent electrode film with nano-porous structure;Film is prepared by the above preparation method;Flexible transparent electrode includes the above electrode film;The application can improve the comprehensive performance of silver nanowire-polyimide flexible transparent electrode.

Description

Technical Field

[0001] This invention relates to the field of flexible electrode fabrication technology, and in particular to a flexible transparent electrode film with a nanoporous structure of silver nanowires-polyimide, its fabrication method, and the electrode itself. Background Technology

[0002] Indium tin oxide (ITO) glass, a commonly used transparent electrode material, has long held a significant position in the optoelectronic device market, represented by light-emitting diodes (LEDs), solar cells, and touchscreen panels. However, rigid ITO glass can no longer meet the demands for lightweight and flexible optoelectronic devices. Flexible transparent electrodes using silver nanowire-polyimide composite films not only achieve high photoelectric performance but also possess excellent flexibility and high-temperature resistance. Based on development and application predictions in this field, silver nanowire-polyimide flexible transparent electrodes, with photoelectric performance comparable to ITO glass, will have broad application prospects in optoelectronic devices. Therefore, developing high-performance silver nanowire-polyimide flexible transparent electrodes is a bottleneck problem that urgently needs to be solved in the field of flexible optoelectronic devices.

[0003] Existing conductive films used in flexible electrodes, such as the silver nanowire-sodium gluconate composite transparent conductive film and its preparation method and application described in patent number CN202211189387.0, include the following steps: preparation of silver nanowire suspension and sodium gluconate solution; cleaning the substrate and performing hydrophilic treatment to obtain a pretreated substrate; firstly coating the pretreated substrate with silver nanowire suspension, and then heating and curing to form a silver nanowire film; then coating the silver nanowire film with sodium gluconate solution, and then heating and curing to form a silver nanowire-sodium gluconate composite transparent conductive film. This method uses a solution method to coat sodium gluconate material onto the surface of the silver nanowire film as a protective layer, directly forming a silver nanowire film with low surface roughness, high viscosity, mechanical stability, and thermal stability on a flexible polymer substrate without sacrificing its photoelectric properties, thus significantly improving the performance of the silver nanowire film in multiple aspects.

[0004] Existing conductive films used in flexible electrodes, such as the silver nanowire-biomaterial composite transparent conductive film disclosed in patent application CN202111243310.2, include a preparation method and application thereof. The preparation method includes the following steps: preparation of a silver nanowire solution (AgNWs solution) and a biomaterial solution; cleaning the substrate to obtain a pretreated substrate; firstly, coating the pretreated substrate with the AgNWs solution, then heating and curing to form an AgNWs film; next, coating the AgNWs film with the biomaterial solution, then heating and curing to form the AgNWs / biomaterial composite transparent conductive film. Using this method, environmentally friendly bio-modified materials can be used to achieve a smooth film surface, excellent mechanical stability, resistance to water and oxygen corrosion, resistance to acid corrosion, and high-temperature resistance while maintaining good photoelectric properties.

[0005] However, it is difficult for films prepared by existing technologies to guarantee that they possess both excellent light transmittance and mechanical flexibility while also having electrode conductivity. Summary of the Invention

[0006] The purpose of this invention is to provide a flexible transparent electrode film with a nanoporous structure of silver nanowires-polyimide, its preparation method and electrode, thereby solving the problem of how to improve the overall performance of the flexible transparent electrode film with silver nanowires-polyimide.

[0007] This invention is achieved by a method for preparing a flexible transparent electrode film of silver nanowires-polyimide with a nanoporous structure, the method comprising the following steps:

[0008] Step 1: Silver nanowire suspension and polyimide solution are sequentially coated on the substrate. After the solution is evenly diffused, gradient heating is performed for curing. After peeling, a semi-embedded silver nanowire-polyimide flexible transparent electrode film is obtained.

[0009] Step 2: Immerse the semi-embedded silver nanowire-polyimide flexible transparent electrode film in an organic solvent for 0.5-10 minutes, then remove it and seal it in an autoclave.

[0010] Step 3: Introduce carbon dioxide into the autoclave, and then place the autoclave in a low-temperature constant temperature reaction bath, so that the flexible transparent electrode film adsorbs carbon dioxide to saturation at saturation temperature and saturation pressure.

[0011] Step 4: Release the pressure in the autoclave, remove the flexible transparent electrode film, and heat it to foam, thus obtaining a silver nanowire-polyimide flexible transparent electrode film with a nanoporous structure.

[0012] The intermittent foaming process assisted by carbon dioxide and organic solvents provided by this invention can impart a nanoporous structure to silver nanowire-polyimide films. This process is environmentally friendly and highly controllable. During the process of introducing this process into the silver nanowire-polyimide flexible transparent electrode system to form a porous structure, carbon dioxide will squeeze the overlapping points of the silver nanowires, thereby improving the conductivity of the electrode. The formed nanoporous structure not only does not reduce the light transmittance of the material, but also releases the mechanical stress during bending and enhances the mechanical flexibility. Applying the film containing this nanoporous structure to the electrode can improve the overall performance of the silver nanowire-polyimide flexible transparent electrode.

[0013] A further technical solution of the present invention is: the silver nanowire suspension in step one is obtained by dispersing silver nanowires in a solvent, wherein the solvent is at least one of anhydrous ethanol, deionized water, isopropanol, and ethylene glycol, and the concentration of the silver nanowire suspension is 0.5 mg / mL to 5 mg / mL.

[0014] A further technical solution of the present invention is that the concentration of the silver nanowire suspension in step one is preferably 1 mg / mL to 3 mg / mL.

[0015] A further technical solution of the present invention is: the solvent of the polyimide solution in step one is at least one of DMAc, DMF, and DMSO, and the concentration of the polyimide solution is 10-30 wt%.

[0016] A further technical solution of the present invention is that the concentration of the DMAc solution of polyimide in step one is preferably 15-25 wt%.

[0017] A further technical solution of the present invention is that the substrate in step one is a rigid substrate or a flexible substrate.

[0018] A further technical solution of the present invention is that the substrate is a rigid substrate such as silicon wafer or glass, or a flexible substrate such as PET or PEN.

[0019] A further technical solution of the present invention is: the gradient heating curing in step one is: holding at 60℃, 90℃, 120℃, 150℃ and 180℃ for 30 minutes in sequence.

[0020] A further technical solution of the present invention is that the organic solvent in step two is at least one of DMAC, DMF and DMSO.

[0021] A further technical solution of the present invention is: in step two, the sample is immersed in an organic solvent for 1-3 minutes.

[0022] A further technical solution of the present invention is that the saturation temperature in step three is -40℃ to 20℃, and the saturation pressure is 5MPa to 35MPa.

[0023] A further technical solution of the present invention is that the saturation temperature in step three is preferably -20℃ to 0℃.

[0024] A further technical solution of the present invention is that the saturation pressure is preferably 15MPa to 25MPa.

[0025] A further technical solution of the present invention is that the low-temperature constant temperature reaction bath in step three is an aqueous solution of anhydrous ethanol or ethylene glycol.

[0026] A further technical solution of the present invention is: the foaming temperature in step four is 40℃~100℃, and the foaming time is 0.5min~3min.

[0027] A further technical solution of the present invention is: the foaming temperature in step four is preferably 60℃~80℃, and the foaming time is preferably 1min~2min.

[0028] The present invention also provides a flexible transparent electrode film with a nanoporous structure of silver nanowires-polyimide, which is prepared by the preparation method described above.

[0029] The present invention also provides a flexible transparent electrode, wherein the flexible transparent electrode comprises the electrode film described above.

[0030] The beneficial effects of this invention are:

[0031] This invention semi-embeds silver nanowires into polyimide and imparts a nanoporous structure to the polyimide with a wavelength less than one-tenth the wavelength of light through an intermittent foaming process assisted by carbon dioxide and organic solvents. The formation of this porous structure can improve the light transmittance, conductivity, and flexibility of the film material. Using the silver nanowire-polyimide flexible transparent electrode film containing this porous structure as a flexible transparent electrode not only does not reduce the light transmittance of the flexible transparent electrode, but also improves the conductivity and mechanical flexibility of the electrode. The resulting silver nanowire-polyimide flexible transparent electrode has excellent comprehensive performance.

[0032] The method provided by this invention is simple to operate, highly repeatable, and has practical application value. Attached Figure Description

[0033] Figure 1 This is a flowchart of the preparation method of the nanoporous silver nanowire-polyimide flexible transparent electrode film provided by the present invention;

[0034] Figure 2 This is a physical image of the silver nanowire-polyimide flexible transparent electrode film with a nanoporous structure prepared according to Example 1 of the present invention.

[0035] Figure 3This is a scanning electron microscope image of the silver nanowire-polyimide flexible transparent electrode film with a nanoporous structure prepared according to Example 1 of the present invention. Detailed Implementation

[0036] The following specific examples illustrate the implementation of the present invention. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and various details in this specification can also be modified or changed based on different viewpoints and applications without departing from the spirit of the present invention.

[0037] It should be noted that the structures, proportions, sizes, etc., illustrated in the accompanying drawings are merely for illustrative purposes to aid those skilled in the art and to facilitate understanding and reading. They are not intended to limit the scope of the invention and therefore have no substantial technical significance. Any modifications to the structure, changes in proportions, or adjustments to size, without affecting the effectiveness and purpose of the invention, should still fall within the scope of the technical content disclosed herein. Furthermore, the terms "upper," "lower," "left," "right," "middle," and "one" used in this specification are merely for clarity and not intended to limit the scope of the invention. Changes or adjustments to their relative relationships, without substantially altering the technical content, should also be considered within the scope of the invention.

[0038] Example 1:

[0039] An anhydrous ethanol suspension of silver nanowires with a concentration of 2 mg / mL and a DMAc solution of polyimide with a concentration of 20 wt% were spin-coated onto a glass substrate at a speed of 500 rpm / min. After the solution was uniformly diffused, gradient heating curing was performed. The gradient heating curing conditions were 60℃, 90℃, 120℃, 150℃ and 180℃, respectively, for 30 min.

[0040] A semi-embedded silver nanowire-polyimide flexible transparent electrode film was prepared after exfoliation. The obtained silver nanowire-polyimide flexible transparent electrode film was immersed in DMAc organic solvent for 1 minute, then removed and sealed in an autoclave. Carbon dioxide was introduced into the autoclave, and then the autoclave was placed in an anhydrous ethanol bath to allow the sample to adsorb carbon dioxide to saturation at a saturation temperature of -10℃ and a saturation pressure of 20MPa. The pressure in the autoclave was rapidly released, and the sample was quickly removed from the autoclave and immersed in a 70℃ water bath for 1.5 min to obtain a silver nanowire-polyimide flexible transparent electrode film with a nanoporous structure.

[0041] The flexible transparent electrode film prepared in this embodiment is shown in the scanning electron microscope image below. Figure 3 As shown, the film is a flexible transparent electrode film with a nanoporous structure of silver nanowires and polyimide. The sheet resistance, transmittance and mechanical flexibility of the film were tested. The results showed that the sheet resistance of the flexible transparent electrode film prepared by this method is 7.8 Ω / sq, the transmittance at 550 nm is 93.6%, and the sheet resistance increases by about 3% after 2000 bends.

[0042] Example 2:

[0043] A 2 mg / mL anhydrous ethanol suspension of silver nanowires and a 20 wt% DMAc solution of polyimide were sequentially spin-coated onto a glass substrate at 500 rpm / min. After uniform diffusion, gradient heating curing was performed at 60℃, 90℃, 120℃, 150℃, and 180℃ for 30 min each. After exfoliation, a semi-embedded silver nanowire-polyimide flexible transparent electrode film was obtained. The obtained silver nanowire-polyimide film was immersed in DMAc organic solvent for 1 minute, then removed and sealed in an autoclave. Carbon dioxide was introduced into the autoclave, and then the autoclave was placed in an anhydrous ethanol bath, allowing the sample to adsorb carbon dioxide to saturation at a saturation temperature of 20℃ and a saturation pressure of 35 MPa. The pressure in the autoclave was rapidly released, and the sample was quickly removed from the autoclave and immersed in a 70℃ water bath for 1.5 min to obtain a silver nanowire-polyimide flexible transparent electrode film with a nanoporous structure.

[0044] The flexible transparent electrode film prepared in this embodiment was tested for sheet resistance, transmittance and mechanical flexibility. The results showed that the sheet resistance of the flexible transparent electrode film prepared by this method was 11.6 Ω / sq, the transmittance at 550 nm was 89.7%, and the sheet resistance increased by about 7% after 2000 bends.

[0045] Example 3:

[0046] A 2 mg / mL anhydrous ethanol suspension of silver nanowires and a 20 wt% DMAc solution of polyimide were sequentially spin-coated onto a glass substrate at 500 rpm / min. After uniform diffusion, gradient heating curing was performed at 60℃, 90℃, 120℃, 150℃, and 180℃ for 30 min each. After exfoliation, a semi-embedded silver nanowire-polyimide flexible transparent electrode film was obtained. The obtained silver nanowire-polyimide film was immersed in DMAc organic solvent for 1 minute, then removed and sealed in an autoclave. Carbon dioxide was introduced into the autoclave, and then the autoclave was placed in an anhydrous ethanol bath, allowing the sample to adsorb carbon dioxide to saturation at a saturation temperature of -35℃ and a saturation pressure of 8 MPa. The pressure in the autoclave was rapidly released, and the sample was quickly removed from the autoclave and immersed in a 70℃ water bath for 1.5 min to obtain a silver nanowire-polyimide flexible transparent electrode film with a nanoporous structure.

[0047] The flexible transparent electrode film prepared in this embodiment was tested for sheet resistance, transmittance and mechanical flexibility. The results showed that the sheet resistance of the flexible transparent electrode film prepared by this method was 9.3 Ω / sq, the transmittance at 550 nm was 91.2%, and the sheet resistance increased by about 4% after 2000 bends.

[0048] Comparative Example 1:

[0049] An anhydrous ethanol suspension of silver nanowires with a concentration of 2 mg / mL and a DMAc solution of polyimide with a concentration of 20 wt% were spin-coated onto a glass substrate at a speed of 500 rpm / min. After the solution was evenly diffused, gradient heating curing was performed. The gradient heating curing conditions were 60℃, 90℃, 120℃, 150℃ and 180℃ for 30 min in sequence. After peeling, a semi-embedded silver nanowire-polyimide flexible transparent electrode film was obtained.

[0050] The flexible transparent electrode film prepared in this embodiment was tested for sheet resistance, transmittance and mechanical flexibility. The results showed that the sheet resistance of the flexible transparent electrode film prepared by this method was 19.3 Ω / sq, the transmittance at 550 nm was 94.2%, and the sheet resistance increased by about 18% after 2000 bends.

[0051] The comparison between the above embodiments and comparative examples shows that the overall performance of the electrode film prepared by the present invention is significantly better than that of the comparative examples. The carbon dioxide-assisted intermittent foaming method in the present invention is an environmentally friendly and highly controllable polymer pore-forming method. During the process of introducing this process into the silver nanowire-polyimide flexible transparent electrode system to form a porous structure, carbon dioxide squeezes the overlapping points of the silver nanowires, thereby improving the electrode conductivity. The intermittent foaming process assisted by carbon dioxide and organic solvents provided by the present invention can endow the silver nanowire-polyimide film with a nanoporous structure. The prepared porous structure not only does not reduce the light transmittance of the material but also releases the mechanical stress during bending, enhancing mechanical flexibility. Applying this film to the electrode improves the overall performance of the silver nanowire-polyimide flexible transparent electrode.

[0052] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for preparing a flexible transparent electrode film with a nanoporous structure of silver nanowires and polyimide, characterized in that, The preparation method includes the following steps: Step 1: Silver nanowire suspension and polyimide solution are sequentially coated on the substrate. After the solution is evenly diffused, gradient heating is performed for curing. After peeling, a semi-embedded silver nanowire-polyimide flexible transparent electrode film is obtained. Step 2: Immerse the semi-embedded silver nanowire-polyimide flexible transparent electrode film in an organic solvent, then remove it and seal it in an autoclave. Step 3: Introduce carbon dioxide into the autoclave, and then place the autoclave in a low-temperature constant temperature reaction bath, so that the flexible transparent electrode film adsorbs carbon dioxide to saturation at saturation temperature and saturation pressure. Step 4: Release the pressure in the autoclave, remove the flexible transparent electrode film, and heat it to foam, thus obtaining a silver nanowire-polyimide flexible transparent electrode film with a nanoporous structure.

2. The preparation method according to claim 1, characterized in that, In step one, the silver nanowire suspension is obtained by dispersing silver nanowires in a solvent, wherein the solvent is at least one of anhydrous ethanol, deionized water, isopropanol, and ethylene glycol, and the concentration of the silver nanowire suspension is 0.5 mg / mL to 5 mg / mL.

3. The preparation method according to claim 1 or 2, characterized in that, In step one, the solvent for the polyimide solution is at least one of DMAc, DMF, and DMSO, and the concentration of the polyimide solution is 10–30 wt%.

4. The preparation method according to claim 1 or 2, characterized in that, The gradient heating curing in step one is as follows: holding the temperature at 60℃, 90℃, 120℃, 150℃ and 180℃ for 30 minutes respectively.

5. The preparation method according to claim 1 or 2, characterized in that, The organic solvent in step two is at least one of DMAC, DMF, and DMSO.

6. The preparation method according to claim 1 or 2, characterized in that, The saturation temperature in step three is -40℃ to 20℃, and the saturation pressure is 5MPa to 35MPa.

7. The preparation method according to claim 1 or 2, characterized in that, In step three, the low-temperature constant-temperature reaction bath is an aqueous solution of anhydrous ethanol or ethylene glycol.

8. The preparation method according to claim 1 or 2, characterized in that, In step four, the foaming temperature is 40℃~100℃, and the foaming time is 0.5min~3min.

9. A flexible transparent electrode film of silver nanowires-polyimide with a nanoporous structure, characterized in that, The thin film is prepared by the preparation method described in any one of claims 1-8.

10. A flexible transparent electrode, characterized in that, The flexible transparent electrode comprises the electrode film as described in claim 9.

Images