Method for preparing metal grid transparent electrode by phase separation method

Abstract

The invention discloses a phase separation method for preparing a metal grid transparent electrode, and the method comprises the following steps: S1, dissolving PVP (Polyvinyl Pyrrolidone) and PVB (Polyvinyl Butyral) in absolute ethyl alcohol respectively to form a PVP ethanol solution and a PVB ethanol solution; s2, mixing the PVP ethanol solution with the PVB ethanol solution to obtain a transparent mixed solution; s3, spin-coating the transparent mixed solution on the surface of a transparent substrate, and drying to form a PVP and PVB two-phase composite film; s4, immersing the composite film into deionized water, dissolving and removing the PVP film, and forming a through groove network in the PVB film; s5, depositing a metal layer in the groove network through vacuum evaporation to form a metal grid; s6, absolute ethyl alcohol is adopted for dissolving and removing the residual PVB film, and a metal grid transparent electrode is obtained; according to the method, ethyl alcohol is used as a solvent, use of a high-corrosion solvent is avoided, pollution to the environment and potential damage to a substrate and a metal layer are reduced, the micron-sized interpenetrating structure is formed by accurately controlling the mixing proportion of PVP and PVB, and preparation of a high-resolution metal grid is facilitated.

Description

Technical Field

[0001] The invention relates to the technical field of metal grid transparent electrodes, in particular to preparing metal grid transparent electrodes by a phase separation method. Background Art

[0002] As an alternative to traditional indium tin oxide electrodes, metal grid transparent electrodes have shown significant application potential in flexible electronics, touch screens, solar cells, and other fields due to their high conductivity, high transmittance, and flexible processability. Currently, the preparation of metal grids is highly dependent on patterned template technology. Its structural parameters, such as line width, spacing, and density, directly affect the optoelectronic properties of the electrode, including haze, square resistance, and transmittance. Existing template preparation technologies mainly include photolithography and nanoimprinting, but these methods generally have problems such as complex processes, high equipment costs, and difficulty in large-scale preparation. To reduce production costs, researchers have developed template preparation methods based on natural cracks. For example, a microcrack network is formed by drying and shrinking a gel film, followed by metal filling and template removal to obtain a metal grid. However, the core drawback of the crack method is that the crack morphology, such as density, distribution, and width, is strongly affected by the mechanical properties of the material and environmental conditions, such as humidity and temperature, making it difficult to achieve precise control. This results in poor uniformity of the metal grid and low line width consistency, which in turn affects the stability of the electrode's optoelectronic performance.

[0003] Template preparation techniques based on polymer phase separation have attracted considerable attention. By regulating the phase separation behavior of mixed polymer solutions with different solubility parameters during film formation, controllable micro-nanostructures can be formed. However, existing phase separation methods still face the following technical bottlenecks: most studies use polymer combinations in a single solvent system, such as those that are all soluble in water or organic solvents. This results in the use of highly corrosive solvents or complex processing steps for the subsequent selective removal of a single phase, which may damage the substrate or metal layer. The size of the phase structure formed by traditional phase separation is difficult to meet the requirements of high-resolution metal grids, and the phase interface is relatively rough, affecting the conductive continuity after metal deposition. Summary of the Invention

[0004] The purpose of the present invention is to provide a phase separation method for preparing a metal grid transparent electrode to solve the problems raised in the above background technology.

[0005] To achieve the above object, the present invention provides the following technical solution: a metal grid transparent electrode is prepared by a phase separation method, the method comprising the following steps:

[0006] S1: Dissolve PVP and PVB in anhydrous ethanol to form a PVP ethanol solution and a PVB ethanol solution with a concentration of 5-15 mg / mL;

[0007] S2: mixing the PVP ethanol solution and the PVB ethanol solution in a mass ratio of 1:0.1 to 1:1 to obtain a transparent mixed solution;

[0008] S3: Spin-coating the transparent mixed solution onto the surface of the transparent substrate at a spin-coating speed of 2000-5000 rpm to form a PVP and PVB two-phase composite film with a thickness of 0.5-10 μm after drying;

[0009] S4: immersing the composite film in deionized water to dissolve and remove the PVP film, thereby forming a through-groove network in the PVB film;

[0010] S5: depositing a metal layer within the groove network by vacuum evaporation to form a metal grid;

[0011] S6: using anhydrous ethanol to dissolve and remove the remaining PVB film to obtain a metal grid transparent electrode.

[0012] Preferably, the concentrations of the PVP and PVB ethanol solutions are both 10 mg / mL, and the mixing ratio of the PVP ethanol solution to the PVB ethanol solution is 1:1. The dissolution temperature of the two polymers in ethanol is 25-40° C., and the dissolution time is 1-3 h.

[0013] Preferably, after the spin coating, the composite film is subjected to a gradient drying process, drying at 40-60° C. for 2-5 minutes to remove the surface solvent; and annealing at 80-100° C. for 10-30 minutes to promote phase separation of PVP and PVB.

[0014] Preferably, the dissolution method adopts pulsed ultrasound-assisted dissolution, with an ultrasound frequency of 40-100 kHz, a pulse interval of 0.1-1 s, and a processing time of 5-20 min.

[0015] Preferably, the metal layer is a copper and silver composite layer with a thickness of 50-300 nm, and the groove network is subjected to plasma treatment before evaporation with a power of 50-200 W and a treatment time of 1-5 min to enhance the bonding strength between the metal and the substrate.

[0016] Preferably, the transparent substrate is one of flexible polyimide and polyethylene terephthalate, and the substrate is subjected to ultraviolet ozone treatment before spin coating, and the treatment time is 5-20 minutes.

[0017] Preferably, 0.1-1 wt% of silicon dioxide nanoparticles with a particle size of 10-100 nm are added to the mixed solution to regulate the phase separation interface to form a three-dimensional interpenetrating network structure.

[0018] Preferably, after removing the PVP film, the metal grid is subjected to in-situ passivation treatment, the passivating agent is a thiol compound, the treatment method is vapor deposition, and the thickness of the passivation layer is 2-20 nm.

[0019] Preferably, the mixed solution is adjusted to adjust the mixing ratio of PVP and PVB through a microfluidic chip to achieve directional control of the groove network density in different areas of the substrate.

[0020] Compared with the prior art, the present invention has the following beneficial effects:

[0021] 1. The present invention avoids the use of highly corrosive solvents by using ethanol as a solvent, reduces environmental pollution and potential damage to the substrate and metal layer, and achieves the formation of a micron-scale interpenetrating structure by precisely controlling the mixing ratio of PVP and PVB, which helps to prepare high-resolution metal grids.

[0022] 2. The present invention regulates the phase separation interface by introducing silica nanoparticles to form a uniform three-dimensional interpenetrating network structure, thereby improving the uniformity of the grooves. By selecting the water-soluble polymer PVP and the water-insoluble polymer PVB, the step of selectively removing a certain phase is simplified. Only water is needed to remove the PVP phase, reducing the processing difficulty.

[0023] 3. The present invention optimizes the line width and connectivity of the metal grid, which is beneficial to improving the conductivity of the electrode. The copper / silver composite layer is used as the metal layer and the silver layer as the antioxidant layer to effectively inhibit metal oxidation and improve the stability of the electrode. The thiol self-assembled monolayer formed by the in-situ passivation treatment further enhances the environmental stability of the metal grid and extends the service life of the electrode. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 This is a schematic diagram of the structure of the metal grid transparent electrode prepared by the phase separation method of the present invention. DETAILED DESCRIPTION

[0025] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0026] See also Figure 1 The present invention provides a technical solution: a metal grid transparent electrode is prepared by a phase separation method, polyvinyl pyrrolidone is PVP, and polyvinyl butyral is PVB. The method comprises the following steps:

[0027] S1: Dissolve PVP and PVB in anhydrous ethanol respectively to form a PVP ethanol solution and a PVB ethanol solution with a concentration of 5-15 mg / mL; the concentration of the ethanol solution of PVP and PVB is 10 mg / mL, and the mixing ratio of the PVP ethanol solution to the PVB ethanol solution is 1:1. Control the dissolution temperature at 25-40°C and stir magnetically for 1-3 hours until completely dissolved to ensure that no particles remain.

[0028] Among them, PVP and PVB have similar properties and are both soluble in ethanol, but PVP is a water-soluble polymer and PVB is insoluble in water.

[0029] The dissolution temperature is controlled at 25-40°C. Temperature control prevents ethanol from volatilizing too quickly and ensures that the polymer is fully dissolved. PVP and PVB form a uniform solution in ethanol, providing a basis for subsequent phase separation.

[0030] S2: PVP ethanol solution and PVB ethanol solution are mixed in a mass ratio of 1:0.1 to 1:1 to obtain a transparent mixed solution; 0.1-1wt% of silica nanoparticles with a particle size of 10-100nm are added to the mixed solution to regulate the phase separation interface to form a three-dimensional interpenetrating network structure.

[0031] Silica nanoparticles act as nucleating agents to regulate the phase separation interface between PVP and PVB, forming a three-dimensional interpenetrating network structure and improving the uniformity of the grooves. The hydroxyl groups on the surface of the nanoparticles interact with the polymer chains to inhibit macroscopic phase separation and promote the formation of microstructures.

[0032] The mixed solution is adjusted to the mixing ratio of PVP and PVB through a microfluidic chip, with a channel width of 100-500 μm, to achieve directional control of the groove network density in different areas of the substrate. High-density grids are used for conductive areas, and low-density grids are used for light-transmitting areas.

[0033] At the chip exit, program control is used to achieve alternating distribution of PVP:PVB=7:3 and PVP:PVB=1:1 in the local area. PVP:PVB=7:3 is the phase separation area, and PVP:PVB=1:1 is the homogeneous area, avoiding the ratio error of manual mixing and improving patterning accuracy.

[0034] S3: Spin-coating the transparent mixed solution onto the surface of the transparent substrate at a spin-coating speed of 2000-5000 rpm. High-speed spin coating ensures uniform film thickness. After drying, a PVP and PVB two-phase composite film with a thickness of 0.5-10 μm is formed.

[0035] After spin coating, the composite film is subjected to gradient drying treatment. The wet film is placed on a 40-60°C hot plate to dry for 2-5 minutes to quickly remove residual ethanol on the surface and form a preliminary solid film; it is transferred to an 80-100°C vacuum oven for annealing for 10-30 minutes to promote phase separation of PVP and PVB.

[0036] Gradient drying prevents the solvent from volatilizing too quickly and causing the film to crack; the annealing process reduces the resistance to the movement of the polymer chain, promotes the separation of the two phases, and forms a micron-level interpenetrating structure.

[0037] The transparent substrate is one of flexible polyimide and polyethylene terephthalate, and the substrate is subjected to ultraviolet ozone treatment before spin coating. The ultraviolet ozone treatment adopts a wavelength of 185nm, a power of 50W, and a treatment time of 5-20min. The ultraviolet ozone treatment forms hydroxyl active groups on the surface of the substrate to enhance the adhesion of the polymer film.

[0038] After drying, the phase separation results were obtained according to different mixing ratios as follows:

[0039]

[0040] From the table above, it can be seen that when the mixing ratio is between 6:4 and 7:3, the solubility parameters of PVP and PVB are significantly different, resulting in thermodynamic incompatibility and promoting phase separation; when the ratio is too high, such as 8:2, one phase dominates and inhibits phase separation.

[0041] S4: The composite film is immersed in deionized water, and the dissolution method adopts pulsed ultrasonic assisted dissolution with an ultrasonic frequency of 40-100 kHz, a pulse interval of 0.1-1s, and a processing time of 5-20min. During the ultrasonic process, the PVP phase is dissolved by water, forming a penetrating groove network in the PVB film with a groove line width of 0.3-5μm.

[0042] The groove network was observed by scanning electron microscopy to confirm its connectivity and line width uniformity. If PVP was not completely removed locally, the ultrasonic time could be extended or the water temperature could be increased to 40°C.

[0043] The pulse mode avoids damage to the PVB membrane structure caused by continuous ultrasound; the cavitation effect accelerates the dissolution of PVP and ensures smooth groove edges.

[0044] S5: A metal layer is deposited in the groove network by vacuum evaporation to form a metal grid; the metal layer is a copper and silver composite layer, with the copper layer serving as the conductive body and the silver layer serving as the anti-oxidation layer. The thickness of the metal layer is 50-300nm, and the deposition rate is controlled to 0.5nm / s for copper and 0.2nm / s for silver to avoid metal splashing that causes line width expansion. The copper / silver composite layer combines high conductivity and anti-oxidation properties; the silver layer covers the copper surface to inhibit the increase in resistivity caused by oxidation.

[0045] Before evaporation, the groove network is plasma treated. The PVB film with grooves is placed in a plasma chamber and argon gas is introduced with a power of 50-200W for 1-5 minutes to form a nano-scale rough structure on the groove surface, thereby improving the bonding strength between the metal layer and the substrate, removing residual contaminants in the groove, and ensuring continuous metal deposition.

[0046] S6: The sample is immersed in anhydrous ethanol and the PVB film is dissolved with ultrasound assistance to obtain a metal grid transparent electrode.

[0047] After removing the PVP film, the metal grid is passivated in situ. The passivating agent is a thiol compound, and the treatment method is vapor deposition. The metal grid is placed in a closed chamber and 1-octanethiol vapor is introduced to form a 2-20 nm thick thiol self-assembled monolayer.

[0048] Thiol molecules bond to the copper / silver surface through -SH groups to form a dense passivation layer; inhibit metal oxidation and sulfidation, and improve the environmental stability of the electrode.

[0049] The present invention avoids the use of highly corrosive solvents by using ethanol as a solvent, reduces environmental pollution and potential damage to the substrate and the metal layer, and realizes the formation of a micron-scale interpenetrating structure by precisely controlling the mixing ratio of PVP and PVB, which is conducive to the preparation of a high-resolution metal grid. The phase separation interface is regulated by introducing silicon dioxide nanoparticles to form a uniform three-dimensional interpenetrating network structure, thereby improving the uniformity of the grooves. By selecting water-soluble polymer PVP and water-insoluble polymer PVB, the step of selectively removing a certain phase is simplified, and the PVP phase can be removed using only water, reducing the processing difficulty. The line width and connectivity of the metal grid are optimized, which is conducive to improving the conductivity of the electrode. The copper / silver composite layer is used as the metal layer and the silver layer is used as the anti-oxidation layer to effectively inhibit metal oxidation and improve the stability of the electrode. The thiol self-assembled monolayer formed by the in-situ passivation treatment further improves the environmental stability of the metal grid and extends the service life of the electrode.

[0050] While embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions, and variations may be made to these embodiments without departing from the principles and spirit of the invention, and that the scope of the invention is defined by the appended claims and their equivalents.

Claims

1. Preparation of metal grid transparent electrode by phase separation method, characterized by: The method comprises the following steps: S1: Dissolve PVP and PVB in anhydrous ethanol to form a PVP ethanol solution and a PVB ethanol solution with a concentration of 5-15 mg / mL; S2: mixing the PVP ethanol solution and the PVB ethanol solution in a mass ratio of 1:0.1 to 1:1 to obtain a transparent mixed solution; S3: Spin-coating the transparent mixed solution onto the surface of the transparent substrate at a spin-coating speed of 2000-5000 rpm to form a PVP and PVB two-phase composite film with a thickness of 0.5-10 μm after drying; S4: immersing the composite film in deionized water to dissolve and remove the PVP film, thereby forming a through-groove network in the PVB film; S5: depositing a metal layer within the groove network by vacuum evaporation to form a metal grid; S6: using anhydrous ethanol to dissolve and remove the remaining PVB film to obtain a metal grid transparent electrode.

2. The method for preparing a metal grid transparent electrode by the phase separation method according to claim 1, wherein: The concentrations of the PVP and PVB ethanol solutions are both 10 mg / mL, and the mixing ratio of the PVP ethanol solution to the PVB ethanol solution is 1:

1. The dissolution temperature of the two polymers in ethanol is 25-40° C., and the dissolution time is 1-3 hours.

3. The method for preparing a metal grid transparent electrode by the phase separation method according to claim 1, wherein: After the spin coating, the composite film is subjected to a gradient drying process, wherein the composite film is dried at 40-60° C. for 2-5 minutes to remove the surface solvent; and the composite film is annealed at 80-100° C. for 10-30 minutes to promote the phase separation of PVP and PVB.

4. The method for preparing a metal grid transparent electrode by the phase separation method according to claim 1, wherein: The dissolution method adopts pulsed ultrasound-assisted dissolution, the ultrasound frequency is 40-100 kHz, the pulse interval is 0.1-1 s, and the processing time is 5-20 min.

5. The method for preparing a metal grid transparent electrode by the phase separation method according to claim 1, wherein: The metal layer is a copper and silver composite layer with a thickness of 50-300nm. Before evaporation, the groove network is subjected to plasma treatment with a power of 50-200W and a treatment time of 1-5min to enhance the bonding strength between the metal and the substrate.

6. The method for preparing a metal grid transparent electrode by the phase separation method according to claim 1, wherein: The transparent substrate is one of flexible polyimide and polyethylene terephthalate, and the substrate is subjected to ultraviolet ozone treatment before spin coating, and the treatment time is 5-20 minutes.

7. The method for preparing a metal grid transparent electrode by the phase separation method according to claim 1, wherein: 0.1-1 wt% of silicon dioxide nanoparticles with a particle size of 10-100 nm are added to the mixed solution to regulate the phase separation interface to form a three-dimensional interpenetrating network structure.

8. The method for preparing a metal grid transparent electrode by the phase separation method according to claim 1, wherein: After removing the PVP film, the metal grid is subjected to in-situ passivation treatment, the passivation agent is a thiol compound, the treatment method is vapor deposition, and the passivation layer thickness is 2-20nm.

9. The method for preparing a metal grid transparent electrode by the phase separation method according to claim 1, wherein: The mixed solution is used to adjust the mixing ratio of PVP and PVB through a microfluidic chip, thereby achieving directional control of the groove network density in different areas of the substrate.

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