KR101777016B1 - Metal grid-Silver nanowire mixed transparent electrodes and the preparation method of metal grid using polymeric nanofiber mask - Google Patents

Abstract

The present invention relates to a composite transparent electrode including a metal grid and a silver nanowire, and a manufacturing method thereof. The metal grid according to the present invention is manufactured without a photolithography process and is characterized by using a polymer nanofiber grid printed in a grid shape as a mask for metal etching. First, a metal thin film layer is deposited on a glass substrate or a plastic substrate using a physical deposition process such as sputtering, and polymer nanofibers are patterned in a grid pattern using an electrohydrodynamic dynamic (EHD) jet printing process. Then, The metal thin film layer is removed through the etching solution containing the metal salt, and the polymer nanofiber mask is melted to produce the metal grid. The upper layer is further coated with nanowires if necessary to provide excellent electrical conduction characteristics while maintaining high transmittance. The present invention provides a novel method of fabricating a transparent electrode that can be manufactured inexpensively and quickly using a EHD jet printing process without the use of a photomask and having a desired diameter and spacing between the grids.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention [0001] The present invention relates to a metal grid-silver nanowire composite transparent electrode and a method of manufacturing a metal grid using the polymer nanofiber mask,

The present invention is characterized in that a metal grid and a silver nanowire network are laminated to each other so that a contact point between a metal grid composed of a metal grid, a contact point between the silver nanowires, and a contact point between the metal grid and the silver nanowire coexist, The present invention relates to a metal grid-metal nano wire composite transparent electrode in which a metal grid and a silver nanowire are combined with each other while simultaneously using silver nanowires and high light transmittance and excellent electrical conduction characteristics, and a method of manufacturing the same. In particular, the present invention provides a new metal grid fabrication method using a grid made of a polymer fiber that can easily fabricate a metal grid at high speed without a photomask, as an etching mask, and is used for photolithography, The present invention relates to a transparent electrode in which a metal grid and a silver nanowire fabricated without a process are composited with each other, and a manufacturing method thereof.

Beyond smart electronic devices, transparent electrode technology is emerging as a key area in the fields of displays, lighting, solar cells, batteries, and touch panels. According to a report released by IDTechEx, the market for transparent electrodes of $ 190 million in 2014 is expected to increase by more than 250% to $ 5.1 billion by 2020.

Indium tin oxide (ITO) is the most widely used transparent electrode, but it has very high transparency and conductivity, but it is not flexible. Indium, which is a raw material, is likely to be depleted in the next 10-15 years. Is being actively researched. Nevertheless, Nitto Denko of Japan occupies 85% of the global ITO market and has to cut down the price of ITO to prevent the penetration of technologies that use transparent electrode materials to secure competitiveness.

Typical alternative materials to replace ITO include Graphene, Carbon nanotube, Silver nanowire, and Metal grid. Silver nanowires and metal grids are the closest candidates to mass production. They have the best merits as flexible transparent electrode materials because of their excellent flexibility and low resistance. Metal grids are cost competitive and are applied in the current industry It has advantages. In the case of nanowires, products that are applied as transparent electrodes are being launched, and the market is expected to grow gradually. Carbon nanotubes have succeeded in commercialization but have difficulty in securing mass production. They are withdrawn from the next generation of transparent electrode materials, and graphene, which is called as dream material, has difficulty in large-area synthesis, difficulty in mass production, Additional research and development is necessary.

In particular, silver nanowires can be synthesized at a temperature of 120 ° C or higher by adding a metal salt, a dispersant, and a stabilizer to a polyol solvent. With the above synthesis method, it is possible to grow from several μm to several hundred μm in diameter with a diameter of several tens of nanometers, and it has a high purity and a high electrical conductivity because it grows into a single crystal form by a growth mechanism. Silver nanowires are widely used as next-generation transparent electrode materials because they can achieve high electrical conductivity with a small amount depending on the shape of the material. However, in order to obtain excellent electric conductivity characteristics of 20 W / sq or less in a wide area using nanowires, A large amount of silver nanowires must be applied. In this case, it is important to increase the price competitiveness by reducing the amount of silver nanowires used because the price is comparable to that of ITO.

The patterning method used in semiconductor devices and liquid crystal display devices is made by a photolithography method using a photoresist. This method has many advantages such as coating, exposure, development, cleaning, curing, etching, stripping, etc., although it has the merit of finely and precisely obtaining the desired pattern. In addition to using expensive vacuum equipment, it is used for patterning Photomask is also required to have high price and high technology. In the case of a solar cell electrode requiring no high-precision patterning, a screen printing method, a blanket roll method, and a gravure printing method have been proposed. However, when a silver electrode is transferred to a silicon wafer, a noncontact type inkjet printing method has been developed due to a problem of substrate breakage caused by direct contact.

In the inkjet printing method, the surface of the substrate is coated with a hydrophobic or hydrophilic state depending on the type of the ink, and the ink ejected from the nozzle is cured according to the pattern of the pattern drawn on the computer to obtain the electrode. However, this method is disadvantageous in that it is necessary to contain an additive to improve the stability of the ink, and since a high viscosity solution is used, the tip of the nozzle is clogged when a large number of nozzles are used for mass production.

Recently, an electrohydrodynamic (EHD) patterning technique has been developed which can reliably pattern the ejection solution at a desired position with the help of electric energy unlike the conventional inkjet method. The above-mentioned technique is an improved technique devised from electrospinning, and overcomes the disadvantage that patterning was impossible due to random irradiation, and the nanofiber having a diameter of 10 nm to 100 mm from the polymer spinning solution was directly patterned at a desired position It is a technology that can be. In the above EHD technique, Korean Patent Laid-Open Publication No. 2014-0060442 proposes a method of manufacturing a transparent electrode using conductive nano ink including metal nano-particles, polymer, and organic solvent by EHD patterning method, I showed the possibility.

Currently, silver nanowires are attracting the most attention because they are flexible transparent electrodes. However, in order to further reduce the cost, it is important to minimize the amount of silver nanowires used and to solve the problem of decreasing the electrical conductivity Techniques should be secured.

In order to produce a transparent electrode by the EHD process, a conductive polymer or a metal ink solution is directly printed on a substrate to be subjected to post-heat treatment and used as an electrode. Polyaniline, Polypyrrole, Polythiophene, and PEDOT-PSS, which are well known as conductive polymers, have low electrical conductivity and thermal stability compared to metals. When exposed to air, their electrical properties gradually deteriorate Has characteristics. In the case of an electrode made of a solution containing a metal ink paste, the dispersing agent is used in addition to the disadvantages of the process and the price due to the use of the metal nanoparticles, resulting in a conductivity lower than that of the metal. Particularly, in order to improve the viscosity control and dispersion characteristics, a dispersing agent added is removed and a sintering process of metal particles is accompanied by a heat treatment process of less than 200 ° C. However, due to the restriction of the polymer substrate which can withstand high temperature heat treatment, , And it is difficult to obtain excellent electric conduction characteristics.

In order to fabricate a metal grid at a high speed and at a low cost, a new method of using a polymer nanofiber as a hard mask for etching after manufacturing polymer nanofibers in a grid form using the EHD method is provided. By using this, a metal grid having a maximum transmittance as high as possible, and further silver nanowires are bonded and coated on a metal grid, whereby a metal grid and a silver nanowire, which have high transmittance and excellent electrical conduction characteristics, Metal nano wire composite transparent electrode and a method of manufacturing the same.

A metal grid-silver nanowire composite transparent electrode manufactured according to an embodiment of the present invention is provided. The method for fabricating the metal grid-metal nano wire composite transparent electrode may include the following steps.

Depositing a metal thin film layer on a glass or plastic substrate; A pattern mask forming step using a polymer nanofiber to coat the polymer nanofibers in a grid shape on the metal thin film layer; Etching the metal thin film layer coated with the polymer nanofibers to remove the metal thin film layer not coated with the pattern mask using the polymer nanofibers; Removing the polymer nanofiber grid to form a protected metal grid below the polymer nanofiber grid; And coating silver nanowires on the metal grid to produce a metal grid-silver nanowire composite transparent electrode.

The metal thin film layer used in the manufacturing step may be selected from Al, Cu, Ni, and Ag by a thermal evaporation method, an E-beam evaporation method, or a sputtering method in a metal forming the grid One metal thin film layer may be coated on a plastic or glass substrate to a thickness selected between 50 nm and 500 nm. Considering the price and electrical conductivity of the metal grid material, it is desirable to coat the copper or aluminum metal thin film layer.

Among the polymer materials, polymers that are not damaged by the etching solution can be used as an etching mask. Therefore, polymer nanofibers can be applied as an etching mask material for metal grid fabrication.

The polymer which can be used as an etching polymer nanofiber mask for the production of a metal grid in the above-mentioned manufacturing step includes polyacrylonitrile, polyvinyl alcohol, polyethylene, polypropylene, polystyrene Polystyrene, Polystyrene, Polyvinylacetate, Polyvinylidene fluoride, and Polymethyl methacrylate may be selected and used.

The etching solution used for removing the metal thin film layer in the manufacturing step may be prepared by using a solution containing a metal salt in a range of 0.0001 mol to 1 mol and may be used in consideration of the standard reduction level between the metal element and the etching solution element, Can be selected. The standard reduction level of the etchant metal salt should be lower than that of the metal sacrificial layer, and the molar concentration is determined according to the difference of the standard reduction levels.

The solvent for removing the polymer nanofiber mask in the above-mentioned manufacturing step does not limit the kind of the specific solvent if it is a solvent capable of dissolving the polymer. However, in the case of a solvent containing an acid or a strongly basic type, it may damage the metal grid electrode and the substrate. Therefore, it is preferable to use the diluted solution at a low temperature.

The width of the individual metal lines constituting the metal grid and the interval between the individual metal lines can be adjusted by the line width and the interval of the polymer nanofiber mask. In order to obtain a high transmittance, the line width of the polymer nanofibers is preferably in the range of 200 nm to 100 mm, and the interval between the nanofibers may be selected in the range of 10 mm to 1,000 mm. When the polymer nanofibers are used as an etching mask, the shape of the pattern of the metal grid formed by the dry etching and the wet etching may be different. A clearer pattern may be formed in the case of dry etching, and in the case of wet etching, a metal line width smaller than the width of the polymer nanofibers can be obtained by an under-etching effect.

The polymer nanofibers can be formed on a glass substrate or a plastic substrate coated with a metal thin film layer at a high speed by the EHD (Electrohydrodynamic Deposition) method, and thus the manufacturing cost of the metal grid can be drastically reduced.

FIG. 1 is a flowchart schematically showing a method of manufacturing a copper grid-silver nanowire composite transparent electrode according to an embodiment of the present invention.
2 is a schematic view, an enlarged view, and a cross-sectional view of a copper grid-silver nanowire composite transparent electrode according to an embodiment of the present invention.
FIG. 3 is a cross-sectional photograph of a copper thin film deposited by a sputtering method, according to an embodiment of the present invention. FIG.
FIG. 4 is a photomicrograph of a surface of an atomic force microscope of a copper thin film deposited by a sputtering method according to an embodiment of the present invention. FIG.
FIG. 5 is a graph showing thickness variation and sheet resistance characteristics of a copper thin film sacrificial layer formed on a glass substrate according to a deposition time in an embodiment of the present invention. FIG.
6 is a micrograph showing the diameter of the patterned fiber according to the solution injection rate of EHD jet printing in one embodiment of the present invention.
7 is an optical microscope photograph of an electrode formed on a copper thin film layer of a PAN nanofiber grid mask obtained by EHD jet printing in one embodiment of the present invention.
8 is an optical microscope photograph of an electrode after etching a copper thin film layer formed with a PAN nanofiber grid mask by EHD jet printing in an embodiment of the present invention with an etching solution.
9 is an optical microscope photograph of an electrode in which a metal sacrificial layer is etched with an etchant and then a PAN nanofiber mask is removed in an embodiment of the present invention.
10 is an electron micrograph of a silver nanowire produced by a polyol synthesis method according to an embodiment of the present invention.
11 is a high-resolution transmission scanning microscope photograph of silver nanowires produced by a polyol synthesis method in an embodiment of the present invention.
12 is an optical microscope photograph of a copper grid-silver nanowire composite transparent electrode in an embodiment of the present invention.
13 is a photograph showing a glass substrate on which a polyvinyl acetate polymer mask and a copper grid are formed, according to an embodiment of the present invention.
14 is a graph and a table showing sheet resistance and transmittance of a copper grid, silver nanowire, and copper grid-silver nanowire transparent electrode, according to an embodiment of the present invention.
15 is a view showing a copper grid electrode fabricated by using a polyvinyl acetate polymer nanofiber as a grid mask in an embodiment of the present invention.

Hereinafter, a method for manufacturing a metal grid-silver nanowire composite transparent electrode will be described in detail with reference to the accompanying drawings.

FIG. 1 is a schematic view showing a method of manufacturing a metal grid-silver nanowire composite transparent electrode according to an experimental example of the present invention in order. The manufacturing method of FIG. 1 is merely to illustrate the present invention, and the present invention is not limited thereto.

As shown in FIG. 1, a method for fabricating a metal grid-metal nano wire composite transparent electrode includes the steps of: i) depositing a metal thin film layer on a glass or plastic substrate (S110); ii) depositing a polymer nanofiber mask on a metal thin film layer Iii) etching the metal thin film layer coated with the polymer nanofiber mask to remove the metal thin film layer region where the polymer nanofiber mask is not coated (S130), iv) step of coating the polymer nanofiber mask (S140) forming a protected metal grid under the polymer nanofiber mask, v) preparing a metal grid-silver nanowire composite transparent electrode by coating silver nanowires on the entire surface of the substrate on which the metal grid is formed S150).

In step S120, polymer nanofibers for use as a hard mask for grid etching on the metal thin film layer may be printed in a grid shape at a high speed to form a polymer nanofiber mask. In addition, a step (not shown) may be included between step S120 and step S130 to increase the binding force between the polymer nanofiber mask and the metal thin film layer. At this time, in the above-described non-illustrated step, the polymer nanofibers printed in the grid shape are thermally compressed at a temperature near the glass transition temperature (T _g ) of the polymer, so that the adhesion between the polymer nanofiber mask and the metal thin film layer Or the polymer nanofiber mask may be strongly adhered to the metal thin film layer through a process of melting the polymer due to solvent evaporation in a beaker containing the solvent.

Fig. 2 shows a schematic view, an enlarged view, and a cross-sectional view of a metal grid-silver nanowire composite transparent electrode. In FIG. 2, reference numeral 100 denotes a metal grid, reference numeral 200 denotes silver nanowires, and reference numeral 300 denotes a substrate. As can be seen from the schematic diagram, the metal line constituting the metal grid has a diameter ranging from 200 nm to 100 μm, and the silver nanowire shown in the enlarged view has a diameter of 20 nm to 100 nm and a length of 10 μm to 100 μm I have. In the cross section, it is shown that the metal grid and the silver nanowire form a contact point with each other. It can be seen that the electrical conduction characteristics are greatly improved as the contacts between the metal grid-silver nanowire and the silver nanowire-nanowire are connected to each other. In the case of metal grids, it is possible to control the light transmittance and sheet resistance characteristics by adjusting the spacing between the grids. In particular, the silver nanowire network is coated on the substrate on which the metal grid is formed, thereby allowing electrical conduction to the empty space between the grids. Thus, even though the silver nanowire is used at the minimum, a light transmittance of 85% It is advantageous to obtain a low sheet resistance characteristic of less than W / sq. Especially, due to the influence of the metal grid positioned at the lower part, it is possible to obtain a sufficiently high electric conductivity characteristic even though a smaller amount of silver nanowires are used, thereby achieving cost reduction effect.

In Fig. 2, the conductive metal material constituting the metal grid 100 may be selected from among Al, Ni, Cu, and Ag. In particular, the metal grid may include a glue layer such as Ti, TiO ₂ , or Cr to improve adhesion between the lower substrate 300 and the metal grid. In this case, the glue layer is first coated thinly on the lower substrate 300, and a metal thin film sacrificial layer selected from Al, Ni, Cu, and Ag, which is a conductive metal material, may be coated on the glue layer.

The metal thin film sacrificial layer can be used by coating with a thickness selected between 50 nm and 500 nm on a plastic or glass substrate by stuttering, thermal evaporation or electron beam evaporation. The wiring interval between the metal grids (100) can be selected in the range of 10 μm to 1,000 μm. The wider the wiring interval, the more advantageous the transparency is, and the more narrow the wiring distance, the better the conductivity.

[ Example  1] Copper Metal layer  deposition

A sputtering method with a 3-inch copper target was used to deposit the copper metal thin film sacrificial layer. A 2 cm x 2 cm glass substrate was placed on a substrate support placed in a sputter chamber and the vacuum chamber was sealed. Since the sputter is a device for depositing a thin film using a plasma, the vacuum chamber must be made ultra-high vacuum. First, a roughing valve connecting a rotary pump, which is a primary pump, and a vacuum chamber is opened to evacuate the chamber at an atmospheric pressure to a degree of vacuum of a secondary pump of 1.0 × 1.0 ^-2 Torr, And the vacuum degree of the chamber was set to 1.0 × 1.0 ^-5 Torr by using a turbo pump as a secondary pump. When sufficient vacuum is achieved, argon (Ar) gas is introduced at a rate of 20 sccm (standard cubic centimeter per minute) and the vacuum is maintained at 1.0 × 1.0 ^-2 Torr by controlling the gate valve, (RF) power is applied, a plasma is generated and copper atoms can be sputtered to deposit a copper thin film on the substrate. After stabilizing the plasma for about 15 minutes, the substrate stopper was removed and the glass substrate was rotated to deposit copper thin films for 1 minute, 3 minutes, 5 minutes, 10 minutes, and 20 minutes. FIG. 3 shows a cross section of the copper metal sacrificial layer deposited for 20 minutes, and the thickness of the copper sacrificial layer is 200 nm, which is a uniform thickness. In addition, AFM (Atomic Force Microscopy, N3800 Seiko) analysis was performed to confirm the surface roughness of the Cu thin film having a thickness of 200 nm. As a result of checking the average surface roughness (RMS) roughness with AFM, it was found that the surface had a relatively smooth surface at 2.20 nm as shown in FIG.

Figure 5 is a graph of thickness and conductivity versus deposition time of a copper metal sacrificial layer made on a glass substrate in accordance with an embodiment of the present invention. The sheet resistance was analyzed using a 4-point meter (Keithley 236). It was found that the deposition rate with time was constantly about 10 nm / min (10 nm / min), and the copper thin film having a thickness of 50 nm deposited for 5 minutes had a sheet resistance of 10 Ω / sq, It was confirmed that the copper thin film having a thickness or more had sufficient electric conductivity. In the present invention, a 200 nm copper thin film sacrificial layer deposited for 20 minutes was used for the copper grid fabrication.

[ Example  2] Copper Thin film layer  Manufacture of polymer nanofiber grid mask on top

In order to form a copper grid on the copper thin film, the method of using a polymer nanofiber grid mask using a polymer nanofiber as an etching mask is applied instead of a photolithography method using a patterned photomask. First, a copper grid was formed. Next, the polymer nanofiber mask was directly coated on the copper substrate in the form of a grid using an EHD apparatus (ENJET, cNP-Expert-C). In Example 2, a polyacrylonitrile (PAN) polymer was prepared to form a polymer mask, but the polymer was not restricted. 5 mg of CTAB (Cetylammonium bromide) was mixed with 300 mg of PAN (polyacrylonitrile) in 3.0 g of DMF (N, N-dimethylformamide) for control of surface tension and smooth nanofiber patterning during EHD jet printing. And the mixture was stirred at a rotation speed of 500 rpm to prepare a polymer nanofiber solution.

The solution was placed in a syringe (ILS, 500 μl micro-syringes) and connected to a syringe pump. The spinning solution was pushed at a discharge rate of 0.6 μl / min. μm of outer diameter) and the collector substrate was set to 1.4 kV. As the collector plate on which the PAN nanofibers are patterned, a glass substrate on which a Cu thin film with a thickness of 200 nm fabricated in Example 1 was deposited was used, and the distance between the nozzle and the collector was set to 500 μm.

FIG. 6 is a photograph of the change in diameter of the solution prepared by the EHD jet printing method with an ejection speed observed with an optical microscope. At a discharge rate of 0.6 μl / min, the polymer nanofibers had a diameter of 15 μm and the polymer nanofibers had a diameter of 35 μm at a discharge rate of 2 μl / min. In addition to the above methods, the diameter of the polymer nanofibers can be controlled by changing the conditions such as the viscosity of the polymer spinning solution, the distance between the nozzle and the substrate, the diameter of the nozzle, and the moving speed of the substrate. Since the width of the individual metal lines constituting the metal grid and the interval between the individual metal lines are adjusted by the line width and the interval of the polymer nanofiber mask, it is very important to select the line width of the nanofibers and the interval between the nanofibers. In order to obtain a high transmittance, the line width of the polymer nanofibers is preferably in the range of 200 nm to 100 μm, and the interval between the nanofibers can be selected in the range of 10 μm to 1,000 μm.

Fig. 7 is an optical microscope photograph of PAN nanofibers obtained after EHD jet printing patterned as a grid. One-dimensional nanofibers were synthesized. The diameters were between 10 μm and 20 μm, and the spacing between nanofibers was between 350 and 450 μm.

In the EHD jet printing equipment used in this embodiment, the discharge speed can be freely adjusted by software, and the interval between nanofibers can be selected within a range of several tens of nanometers to several tens of centimeters. In this embodiment, the patterning is performed in the form of a grid, but the patterning can be performed in the form of a straight line, a curved line, a diagonal line, and the solution is discharged only when an electric field is formed.

[ Example  3] Manufacture of copper grid transparent electrode

The patterned substrate was immersed in DMF (N, N-dimethylformamide) vapor to improve the adhesion property between the PAN polymer nanofiber patterned in a grid pattern on the metal sacrifice layer obtained in Example 2 and the glass substrate coated with the copper thin film. Minute exposure. In the case where a space is formed between the PAN polymer used as the patterning mask for metal etching and the glass substrate coated with the copper thin film, since the etching solution can not penetrate and a copper grid having a uniform line width can not be manufactured, the copper thin film layer and the PAN polymer Adhesion between masks is very important. At this time, in order to prevent the PAN polymer from washing out in the DMF solution, a small amount of DMF solvent is added to the beaker, the substrate is put in direct contact with DMF, the temperature is adjusted to 60 ° C and the lid of the beaker is closed. To bond well to the copper substrate. Polymer PAN nanofibers coated on a copper foil in a grid shape can serve as a hard mask and can etch copper thin film portions that are not protected with a nanofiber mask by dry etching or wet etching. have. In the second embodiment, chemical etching is carried out. If the process is capable of producing a stable copper grid, then there are no specific constraints on dry etch and wet etch. In the wet etching used in the present invention, 0.486 g of FeCl ₃ was added to 1 L of deionized water and sufficiently dissolved at room temperature for 10 minutes in order to etch the copper thin film layer. At this time, for the fine etching, a low concentration solution containing 0.243 g of FeCl _{3 in} 1 L of deionized water was prepared. The etching solution was placed in a separating funnel and the polymer nanofiber mask was evenly sprayed onto the grid-like copper foil layer. Etching was performed until the substrate became transparent with a high concentration etching solution, and then etching was performed with a low concentration etching solution for 1 minute. After the copper thin film sacrificial layer except for the protected part patterned with the PAN nanofibers was etched, deionized water flowing several times was rinsed several times.

8 is an optical microscope photograph of the electrode after etching the copper thin film layer formed with the PAN nanofiber grid mask. It is an optical microscope photograph which is observed. As can be seen from FIG. 8, the copper thin film layer except for the patterned polymer nanofibers is completely removed by the etching solution, and only the portion of the PAN nanofiber mask remains as a grid. Thereafter, to remove the polyacrylonitrile polymer nanofiber, which had been protecting the copper thin film sacrificial layer, the DMF solvent was washed several times, and the remaining solution was dried to prepare a copper grid transparent electrode.

9 is an optical microscope photograph after removing the polymer nanofiber protecting the metal sacrificial layer. The polymer protective layer is removed by the solvent, and a metal grid electrode having a copper color can be identified.

[ Example  4] Nanowire  Produce

200 ml of ethylene glycol, 6.68 g of polyvinylpyrrolidone (PVP) polymer, 0.1 g of KBr additive, which is a high boiling point solution capable of withstanding temperatures of 170 ° C or higher, is introduced into a three neck flask, Was stirred with a magnetic bar and heated to 170 DEG C to stabilize for 30 minutes. At this time, the PVP helps to grow the silver nanowire into the wire shape by preventing the growth to the specific surface of the silver nanowire, and the additive KBr helps to keep the silver ion concentration in the solution constant.

Next, an initial precursor was prepared by adding 0.5 g of finely polished AgCl powder which had undergone a ball-milling process to a stable solution. The remaining AgCl powder, which does not participate in the reaction, may remain on the bottom, and the silver nanowire growth affinity varies depending on the degree of fine grinding and the abrasive crystal plane. After 1 hour, the AgNO ₃ major reactants Titrate 2.2 g. At this time, AgNO ₃ is first dissolved in 5 ml of ethylene glycol, and injected at a rate of 5 ml / hour using a syringe in a solution state. It is then heated to 170 ° C for 2 hours.

FIGS. 10 and 11 show a scanning electron microscope and a transmission electron microscope photograph of silver nanowires synthesized according to an embodiment of the present invention. As can be seen from FIG. 10, it can be seen that uniformly shaped silver nanowires (30 to 60 nm in diameter, 10 to 50 μm in length) were very well synthesized. From the high-resolution transmission electron microscope photograph, we could confirm the microstructure of silver nanowire and crystal growth direction. The nanowire was grown in the [011] direction, the lattice spacing of the (111) plane was 0.2325 nm, and single crystal and one-directional growth was confirmed based on the FFT (Fast Fourier Transformation) transformation image.

The purified silver nanowires were diluted with purified water or ethanol at a ratio of 1: 4 to separate pure silver nanowires from ethylene glycol and PVP, followed by centrifugation and washing. Since the separation was not smooth at one time, the above procedure was repeated 6 to 8 times. First, centrifuge at 2000 rpm in purified water for 30 minutes, discard the underlying silver particles, use a floating solution, centrifuge at 2000 rpm for 30 minutes in purified water, The process of repeating the process of using the silver nanowires that are floating down and discarding the floating silver particles is repeated three times. After washing with purified water, the above procedure was repeated 4 times in ethanol.

[ Example  5] Copper grid - silver Nanowire  Composite transparent electrode manufacturing

In Example 5, an experiment was conducted to produce a transparent electrode in which a copper grid transparent electrode prepared in Example 3 and a silver nanowire synthesized in Example 4 were combined to form a composite of copper grid and silver nanowire. 0.5 ml of the silver nanowire dispersed in the ethanol synthesized in Example 4 and 50 ml of ethanol are sufficiently mixed. Using an ultrasonic disperser (Sonicator), silver nanowires can be effectively dispersed within a few seconds to several minutes. The silver nanowire solution is decompressed together with the nylon filter paper to distribute the silver nanowires to the nylon filter paper. The nylon filter paper was superimposed on the copper grid transparent electrode prepared in Example 3 so as to be in contact with the exposed portion of the silver nanowire, and the silver nanowire was transferred onto the copper grid transparent electrode by applying pressure to form a copper grid- .

FIG. 12 shows an optical microscope picture of a copper grid-silver nanowire composite transparent electrode. It shows that the silver nanowires are evenly distributed while maintaining the shape of the copper grid. Silver nanowires are located on top of the metal grid and on the substrate and serve to reinforce the movement of electrons in spaces where no metal grid exists. The greater the amount of nanowire loading, the lower the light transmittance and the higher the electrical conductivity. Thus, it is desirable to transfer a minimal amount of silver nanowires onto a copper grid substrate while maintaining high light transmittance.

[ Example  6] Polyvinyl acetates  Copper grid using polymer nanofiber mask - Silver Nanowire  Composite transparent electrode manufacturing

In Examples 2 and 3, polyvinylpyrrolidone was used as a polymer nanofiber mask material for producing a copper grid. However, in Example 6, the polymer mask material was changed to polyvinyl acetate (PVAc) or polyvinylacetate To form a finer copper pattern. PVAc polymer was dissolved in DMF and THF to prepare spinning solution. The nozzle was a ceramic nozzle with a diameter of 100 mm. The EHD process speed was controlled in the range of 0.05 ~ 1 ml / min.

13 (a) and 13 (b) show photographs of PVAc polymer nanofibers printed in a grid pattern on a copper thin film layer coated on a glass substrate. As shown in FIG. 13 (a), it can be seen that the PVAc polymer nanofibers having a line width of about 5 mm are patterned in a very uniform grid pattern on the upper layer of the copper thin film layer. The PVAc grid was directly printed using the EHD jet printing process as in Example 2 and after PVAc grid formation was exposed to N, N-dimethylformamide (DMF) steam for 3 minutes as in Example 3, PVAc nanofibers And the copper thin film layer. After that, using a low-concentration etching solution containing 0.243 g of FeCl _{3 in} 1 L of deionized water, the copper thin film coated on the portions other than the portions formed by the mask with PVAc was removed by etching, and finally the PVAc polymer was dissolved in the DMF solution To form the copper grid shown in Figs. 13 (c) and 13 (d). As shown in FIG. 13 (c), it was confirmed that the copper grid had a line width of about 4 mm, which is smaller than the fiber diameter of PVAc, and was formed very uniformly. As shown in FIG. 13 (d) Permeability.

FIG. 14 is a graph and table showing optical transparency and sheet resistance of a copper grid, silver nanowire, and copper grid-silver nanowire transparent electrode. As shown in FIG. 13, a copper grid fabricated on a glass substrate made of polymer nanofibers as a pattern mask exhibited excellent electrical conduction characteristics of a sheet resistance of 35 W / sq even at a high light transmittance of 94.7%. The transparent electrode composed of nanowires showed a surface resistance of 102 W / sq at a light transmittance of 93.6%, and the electrical conductivity of the copper grid was superior to silver nanowires at a light transmittance of 93% or more . It is important to ensure the electric conductivity of the sheet resistance of 20 W / sq in order to be able to be used as a transparent electrode. In the present invention, in order to further enhance the electrical conductivity of the copper grid, a transparent electrode in which a copper grid and a silver nanowire are combined is prepared. The results obtained after coating the silver nanowire electrode on the copper grid showed that the sheet resistance was lowered to 21 W / sq while maintaining the relatively high light transmittance of 87.4%, which was lower than the sheet resistance of 35 W / sq of the copper grid by 14 W / sq, respectively.

FIG. 15 is a photograph showing further adjustment of the grid line width of the PVAc polymer nanofibers by further optimizing the discharge speed of the PVAc and the moving speed of the substrate. 15 (a) and (c) show that PVAc polymer nanofiber grids having line widths of 4 mm and 1.5 mm are well formed. Fig. 15 (c) shows that a PVAc polymer grid having a line width of 4 mm was etched under the same process conditions as in Example 3, and a photograph of the obtained copper grid succeeded in manufacturing a transparent electrode having a Cu grid of about 3 mm. It is possible to make finer copper grids through optimization.

The foregoing description is merely illustrative of the technical idea of the present invention, and various changes and modifications may be made by those skilled in the art without departing from the essential characteristics of the present invention. Therefore, the embodiments described in the present invention are not intended to limit the technical spirit of the present invention but to illustrate the present invention. The scope of protection of the present invention should be construed according to the following claims, and all technical ideas within the scope of equivalents thereof should be construed as being included in the scope of the present invention.

Claims (15)

A method of manufacturing a metal grid-metal nano wire composite transparent electrode,
a) depositing a metal thin film layer on a glass or plastic substrate;
b) forming a polymer nanofiber mask on the metal thin film layer by printing the polymer nanofibers for use as a hard mask for grid etching at high speed in a grid shape;
c) The polymer nanofibers printed in the grid shape are thermally pressed at a temperature based on the glass transition temperature (Tg) of the polymer to increase the binding force between the polymer nanofiber mask and the metal thin film layer, Increasing a binding force between the polymer nanofiber mask and the metal thin film layer through a melting process of the polymer due to solvent evaporation in the beaker;
d) etching the coated metal thin film layer by printing the polymer nanofiber mask in a grid shape to remove the metal thin film layer except the coated portion of the polymer nanofiber mask;
e) removing the polymer nanofiber mask from the metal thin film layer to form a metal grid; And
f) coating silver nanowires on the metal grid to produce a metal grid-silver nanowire composite transparent electrode;
Wherein the metal grid-silver nanowire composite transparent electrode is formed of a metal. The method according to claim 1,
The step a)
Characterized in that one metal sacrificial layer selected from Al, Cu, Ni and Ag is coated as a metal thin film layer with a thickness selected from 50 to 500 nm by using a thermal evaporation method, an electron beam evaporation method, or a sputtering method A method of manufacturing a metal grid-silver nanowire composite transparent electrode. The method according to claim 1,
The step b)
A method of manufacturing a metal grid-silver nanowire composite transparent electrode, characterized in that the polymer nanofiber mask is prepared in a grid form by using an electrohydrodynamic deposition (EHD) jet printing (jet printing) method from a spinning solution in which a polymer is dissolved in a solvent Gt; The method according to claim 1,
The polymer used as the polymer nanofiber mask in the step b) is a polymer that can be used as a nanofiber mask for etching polymer for manufacturing a metal grid. Examples of the polymer include polyacrylonitrile, polyvinyl alcohol, polyethylene ), A polypropylene, a polystyrene, a polyvinylacetate, a polyvinylidene fluoride, and a polymethyl methacrylate. Method for manufacturing a grid - silver nanowire composite transparent electrode. The method according to claim 1,
In the polymer nanofiber mask of the step b), the line width of the polymer nanofibers is in the range of 200 nm to 100 μm, and the interval between the nanofibers is in the range of 10 μm to 500 μm. Method for manufacturing a grid - silver nanowire composite transparent electrode. delete The method according to claim 1,
The step d)
Only the remaining metal thin film layer excluding the metal thin film layer coated with the polymer nanofiber mask is selectively removed by dry etching or chemical etching without affecting the coated portion of the polymer nanofiber mask Wherein the transparent electrode is formed of a metal. The method according to claim 1,
The step e)
The metal grid is finally formed by dissolving and removing the polymer nanofiber mask coated on the grid-shaped metal thin film layer with a solvent in the metal thin film layer remaining after the etching, thereby forming a metal grid. ≪ / RTI > The method according to claim 1,
The step (f)
Characterized in that the nanowire dispersion solution is printed on the substrate on which the metal grid obtained from the polymer nanofiber mask is formed or coated by a spray method so that the contact between the silver nanowires and the contact between the metal grid and the nanowires coexist Method for manufacturing a grid - silver nanowire composite transparent electrode. Polymer nanofibers are printed on a metal thin film layer coated on a glass or plastic substrate in a grid shape by an electrohydrodynamic (EHD) method to be used as a hard mask for metal etching, and polymer nanofibers printed in a grid shape The adhesion between the polymer nanofiber mask and the metal thin film layer is increased by thermocompression at a temperature based on the glass transition temperature (Tg), or the melting process of the polymer due to solvent evaporation in a beaker containing the solvent The metal nanofiber mask is removed by etching after the metal thin film layer is etched by increasing the binding force between the polymer nanofiber mask and the metal thin film layer through the metal grid layer,
And a transparent electrode. 11. The method of claim 10,
Wherein the diameter of the metal line constituting the metal grid is in the range of 200 nm to 100 μm and the wiring interval is in the range of 10 μm to 1,000 μm. 11. The method of claim 10,
Wherein the metal constituting the metal grid comprises one selected from the group consisting of Al, Cu, Ni and Ag. 11. The method of claim 10,
Further comprising a silver nanowire coupled to the metal grid transparent electrode,
Wherein a contact between the metal wire and the silver nanowire forming the metal grid and a contact between the silver nanowire and the teeth coexist to form a metal grid-silver nanowire composite transparent electrode. 14. The method of claim 13,
Wherein at least one buffer layer selected from the group consisting of graphene, ZnO, Al-doped ZnO, Ga-doped ZnO, ITO, and SnO ₂ is coated on the upper layer of the metal grid-silver nanowire composite transparent electrode. An apparatus comprising a transparent electrode according to any one of claims 10 to 14.

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