KR101385684B1 - Preparation method of transparent electrod - Google Patents

Abstract

Formed is a complex transparent electrode layer having a stack structure or a single layer of an Ag nanowire and a conductive polymer by using an electrohydrodynamic (EHD) print process. Accordingly, a uniform surface electrode with various patterns can be manufactured by a simple print process. A transparent electrode with good transmittance and conductivity can be manufactured. The transparent electrode can be applied to a display device, a lighting device, a touch screen, an image sensor, and a solar cell, etc.

Description

Manufacturing method of transparent electrode {Preparation method of transparent electrod}

The present invention relates to a method of manufacturing a transparent electrode having high transmittance and conductivity.

The transparent electrode means that a conductive film is formed on a transparent substrate, and is used in devices such as solar cells, display devices, and touch screen panels because light can be transmitted therethrough.

Recently, the price of oxidized inorganic material, which is a material mainly used for manufacturing transparent electrodes, has increased, and there is a need for developing a material to replace.

A transparent electrode using tin-doped indium oxide (ITO), which is commonly used, is sputtered onto a glass substrate cleaned with a solvent or an ion, and the ionized atoms are accelerated by an electric field to collide with the thin film material. At this time, a conductive film was formed by using a deposition method using atoms of the thin film material that protruded.

However, due to the rising price of indium, carbon nanotubes (CNTs), graphenes, and metal electrodes have been proposed to replace them. In the case of the metal transparent electrode having the highest conductivity, the silver is usually formed by using a thermal evaporation method to form a semi-transparent electrode having a thickness of about 10 nm, or fine silver particles are saturated on the substrate by a drop on demand method. A method of forming a transparent electrode by forming a pattern using a method of directly dropping the ink droplets to form a pattern) is commonly used.

However, when the thermal evaporation method is used, the conductivity is high, but the transmittance is not high, so the efficiency as an electrode is disadvantageous. In particular, the efficiency of the electrode may be extremely reflected by reflecting back the emitted light. In addition, the deposition method requires a high vacuum environment and has a disadvantage of a complicated process requiring a precise mask. In addition, there is difficulty in the large area, which impairs fairness.

In the case of the inkjet method, the drop of the ink is not only high in the pattern height but also has a disadvantage in that the difference in the result of the condition is large and difficult to use in the continuous process. In particular, the behavior of the ink is irregular according to the surface energy may cause defects due to disconnection, etc., it is difficult to form a surface electrode, there is a limit to the electrode formation.

Republic of Korea Patent Publication No. 10-2010-0027842

Compared to the conventional process, the present invention is to provide a transparent electrode and a method of manufacturing the same, which is simple in manufacturing process, easy to control, economical in terms of cost, and good in both permeability and conductivity.

In embodiments of the present invention, the method comprises printing the ink solution containing the metal nanowires, the conductive polymer and the solvent by an electrohydrodynamic printing method on a transparent substrate, wherein the metal nanowires for 100 total volumes of the ink solution It provides a transparent electrode manufacturing method, characterized in that 33 to 67% by volume and the conductive polymer is contained in 33 to 67% by volume.

Embodiments of the present invention also comprises the steps of printing a first ink solution comprising a metal nanowires and a solvent on the transparent substrate by an electrohydrodynamic printing method to form a metal nanowire layer; Printing a second ink solution including a conductive polymer and a solvent on the metal nanowire layer by electrohydrodynamic printing to form a conductive polymer layer, wherein the first ink solution includes a total of 100 first ink solutions. It provides a transparent electrode manufacturing method, characterized in that the metal nanowires are contained 50 to 67% by volume with respect to the volume, and the second solution contains 33 to 50% by volume of the conductive polymer relative to a total of 100 volumes of the second ink solution.

According to embodiments of the present invention, even without an oxidizing transparent electrode such as indium tin oxide (ITO), indium zinc oxide (IZO), etc., for example, having a high transmittance of 70% or more, for example, several kΩ / sq to 10 kΩ / sq levels Therefore, it is possible to provide a transparent electrode having low surface resistance and high electrical conductivity. Such an electrode can replace an existing oxidized transparent electrode such as ITO, and while the oxidized transparent electrode is difficult to be enlarged and applied to a flexible substrate, various types of transparent electrodes such as display elements, lighting elements, and touch screens are required. It is easy to apply to electronic devices.

In addition, according to embodiments of the present invention by using an electro-hydraulic printing method to form a composite transparent electrode layer including a mixed layer of a metal nanowire and a conductive polymer or a conductive polymer layer on the metal nanowire layer, a conventional electrode formation method Unlike phosphorus oxide sputtering or metal thin film deposition, it does not use a high vacuum environment, so the process is simple and can form a uniform electrode surface. In addition, it is easy to control the formation of the composite transparent electrode layer based on the network structure of the metal nanowires.

1 is a schematic view showing a transparent electrode including a composite transparent electrode layer prepared according to one embodiment of the present invention.
2 is a schematic diagram showing a transparent electrode including a composite transparent electrode layer prepared according to another embodiment of the present invention.
3 is an optical micrograph showing a single silver nanowire electrode layer (left; Comparative Example 1) and a single PEDOT: PSS electrode layer (right; Comparative Example 2) according to the comparative examples of the present invention.
4 shows a composite electrode layer of silver nanowires and PEDOT: PSS (left; Example 1) and a composite electrode layer having a PEDOT: PSS layer formed on the silver nanowire layer (right; Example 2) in the embodiments of the present invention. Scanning electron microscope (SEM) (upper left) and optical micrograph.
5 is a composite of a single silver nanowire electrode layer (Comparative Example 1), a single PEDOT: PSS electrode layer (Comparative Example 2), a single layer of silver nanowires and PEDOT: PSS in Comparative Examples and Examples of the present invention. The transmittance (%) according to the transparent electrode structure of the composite electrode layer (Example 2) in which the PEDOT: PSS layer is formed on the electrode layer (Example 1) and the silver nanowire layer is shown.
6 is a composite of a single silver nanowire electrode layer (Comparative Example 1), a single PEDOT: PSS electrode layer (Comparative Example 2), a single layer of silver nanowires and PEDOT: PSS in Comparative Examples and Examples of the present invention. Surface resistance characteristics of the electrode layer (Example 1) and the composite electrode layer (Example 2) having the PEDOT: PSS layer formed on the silver nanowire layer are shown in a graph.
FIG. 7 is a graph illustrating transmittance according to a mixing ratio of silver nanowires and PEDOT: PSS in the composite electrode layer of silver nanowires and PEDOT: PSS of the present invention.
8 is a scanning electron microscope (top), an optical photomicrograph (bottom), and surface resistance of an electrode layer according to a mixing ratio of silver nanowires and PEDOT: PSS in the composite electrode layer of silver nanowires and PEDOT: PSS of the present invention. It is shown.

As used herein, the term “transparent electrode” refers to an electrode that is light transmissive and electrically conductive, and has a film having electrical conductivity capable of transmitting light including visible light.

As used herein, the term “three-dimensional network” refers to a three-dimensional network structure in which a net and a net are entangled.

In the present specification, the "composite" of the composite transparent electrode layer means that the inorganic material and the organic material are composited.

Hereinafter, embodiments of the present invention will be described in detail.

When forming electrodes with metal nanowires, it is important to keep the metal nanowires well formed on the substrate to maintain their shape, and also to make the contact surface between the metal nanowires and to make the contact uniform, especially in the case of metal nanowires. Alternatively, since a high voltage electric field is sprayed in an irregular pattern, the contact between the metal nanowires and the substrate and the metal nanowires is not smooth, and thus high resistance is obtained. In addition, when forming an electrode using only metal nanowires, in order to improve conductivity, a relatively large amount of metal nanowires must be sprayed. In this case, permeability may decrease due to the high integration of metal nanowires. Therefore, it is necessary to increase the contact between the metal nanowires and to provide high transmittance while reducing the resistance.

Accordingly, in the embodiments of the present invention, a composite transparent electrode layer including a metal nano wire and a conductive transparent polymer layer comprising a conductive polymer or a metal nanowire layer and a conductive polymer layer formed on the metal nanowire layer It provides a manufacturing method for providing a transparent electrode comprising an electrode layer.

When manufacturing a transparent electrode using a metal nanowire and a conductive polymer, for example, using a general spray coating method such as spin coating or aerosol spray deposition method, it is difficult to form a uniform pattern to form a uniform network. It cannot be formed, and the material consumption is severe. In addition, since the nozzle size is small, there is a limitation in the amount of metal nanowires that can be used.

On the other hand, although the use of a bubble jet method or a piezoelectric method, which is an inkjet nozzle method for electronic materials, can be considered, the bubble jet method includes a process of spraying by applying heat, thus making it difficult to select ink materials. Inkjet using is also difficult to apply to the actual process due to the limitation of the unit output energy of the nozzle, the viscosity of the ink, the morphology of the droplet (morphology).

Embodiments of the present invention, as a type of jetting method, applies an electrohydrodynamic printing technique, which is a technique of controlling a fluid discharged from a nozzle using an electric field. This electrohydraulic printing technique is particularly advantageous for forming a composite transparent electrode layer according to embodiments of the present invention. For reference, in the electrohydrodynamic printing technique, applying a constant voltage between the spray nozzle and the substrate generates an electric field and simultaneously concentrates the charge on the surface of the fluid near the nozzle. In this case, when the pressure of the nozzle is injected by the electric field and the electric charge generated on the surface of the fluid is greater than the surface tension of the fluid, the droplets are much smaller than the size of the nozzle as the spherical surface is transformed into a so-called Taylor Cone shape. do.

In the embodiments of the present invention, the metal nanowire-containing ink is printed by the electrohydrodynamic printing method, and then the conductive polymer-containing ink is printed on the printing layer, or the metal nanowire and the conductive polymer are contained by the electrohydrodynamic printing method. Print the ink.

According to the electro-hydraulic printing method, the composite electrode layer according to the embodiments of the present invention can be uniformly formed or stacked, the formation of fine patterns is simple, easy to control, and it is also easy to continuously form the pattern. Therefore, compared with other printing processes, a high density and uniform composite transparent electrode layer can be manufactured by a simple process. In addition, the degree of electrode formation or lamination can be visually confirmed. In addition, it is possible to realize a high resolution while the surface patterning that can be printed to have a predetermined pattern on the surface. In addition, it is possible to coat only the desired portion, so that excessive consumption of the material can be prevented. In addition, since it is not influenced by the nozzle size, it is possible to use the metal nanowires in a relatively large amount, which is advantageous in forming the three-dimensional network structure intended by the embodiments of the present invention and thereby improving conductivity. Moreover, an aging process that enhances contact between metal nanowires and prevents resistance from occurring. In certain parts and devices, their properties remain essentially stable under certain periods of time, in some cases under moderate stress. This process can be simplified since it is not necessary to perform additional processes such as metal nanowires based on heat treatment.

Specifically, in other embodiments of the present invention, an ink solution including a mixture of a metal nanowire and a conductive polymer and a solvent may be printed by an electrohydrodynamic printing method.

In an exemplary embodiment, the method includes printing an ink solution including silver nanowires, PEDOT: PSS, and a solvent on an transparent substrate by electrohydrodynamic printing (EHD).

Here, the metal nanowires are included in an amount of 33 to 67% by volume and conductive polymers in an amount of 33 to 67% by volume with respect to the total volume of the ink solution. Preferably, 40 to 67% by volume of the metal nanowires and 33 to 60% by volume of the conductive polymer are included with respect to the total volume of the ink solution, and more preferably 50 to 50% by volume of the total amount of the ink solution. 67% by volume and conductive polymer in 33-50% by volume.

When printing the ink containing the metal nanowires and the conductive polymer by the electro-hydraulic printing method as described above, it is possible to produce a composite transparent electrode layer which is a single layer containing the metal nanowires and the conductive polymer.

Specifically, FIG. 1 is a schematic diagram illustrating a transparent electrode including a composite transparent electrode layer according to one embodiment of the present invention.

The composite transparent electrode layer 11 according to the embodiments of the present invention is a thin film layer having a three-dimensional network structure in which metal nanowires are integrated on the transparent substrate 10, and a composite transparent electrode layer in which all of the thin film layers are filled with a conductive polymer. . That is, it is a composite transparent electrode layer in which the network ratio of the thin film layer is adjusted by adjusting the ink ratio and the whole is filled with the conductive polymer regardless of the size of the gap.

Here, the volume ratio of the metal nanowires and the conductive polymer is 1: 0.5 to 1: 2, preferably 1: 0.5 to 1: 1.5, and more preferably 1: 0.5 to 1: 1. When the volume ratio is out of the range of 1: 0.5 to 1: 2, it is out of the limit range of the conductive network formation, and when the ratio is within the range of 1: 0.5 to 1: 1, the composite transparent electrode layer of the present invention can be used without limitation. It is possible.

When the electrode layer is formed only with the metal nanowires, the network network structure is densely formed to increase the conductivity, but it is difficult to expect the transmittance. When forming the electrode layer using only the conductive polymer, the transmittance can be expected to be improved. It is difficult to expect enough conductivity.

However, when the composite transparent electrode layer including the metal nanowires and the conductive polymer is formed in this way, when the three-dimensional network structure of the metal nanowires is formed and the conductive polymer is properly infiltrated into the empty space between the net and the net of the network structure, The conductivity can be improved without affecting the transmittance.

In addition, in the embodiments of the present invention, after printing the first ink solution containing the metal nanowires and the solvent on the transparent substrate by an electrohydrodynamic printing method, the second ink solution containing the conductive polymer and the solvent is electrically Printing may be performed by electrohydrodynamic printing (EHD printing).

In an exemplary embodiment, (a) printing a first ink solution including silver nanowires and a solvent on an transparent substrate by electrohydrodynamic printing (EHD); And (b) printing a second ink solution containing PEDOT: PSS and a solvent on the nanowire printed layer by an electrohydrodynamic printing method.

Here, the first ink solution contains 33 to 67% by volume of metal nanowires, preferably 40 to 67% by volume, more preferably 50 to 67% by volume, based on a total of 100 volumes of the first ink solution. The conductive polymer contains 33 to 66% by volume, preferably 33 to 60% by volume, and more preferably 33 to 50% by volume, based on 100 total volumes of the second ink solution.

In the process including the steps (a) and (b), since the conductive polymer is printed after the three-dimensional network formation of the metal nanowires, the conductive polymers do not interfere with the network formation of the metal nanowires. At the interface between the metal nanowire layer and the conductive polymer layer, the conductive polymer not only fills the empty space between the net and the net of the three-dimensional network of the metal nanowire, but also forms a layer on top of the three-dimensional network. Accordingly, the surface roughness due to the network structure of the metal nanowires is alleviated and flattened, making it more suitable as an element of a touch screen. In addition, where the printing of the ink containing the metal nanowires and the printing of the ink containing the conductive polymer are carried out with the same electrohydrodynamic printing apparatus, the process can be performed continuously. In addition, since the continuous process can be performed in the same environment, it is possible to solve the surface damage problem that has previously occurred between process movements.

2 is a schematic view showing a transparent electrode including a composite transparent electrode layer according to another embodiment of the present invention.

In the embodiments of the present invention, the metal nanowire thin film layer 12 having a three-dimensional network structure is integrated on the transparent substrate 10 and the conductive polymer layer formed on the metal nanowire thin film layer 12 ( It provides a transparent electrode including a composite transparent electrode layer comprising a 13).

Here, the volume ratio of the metal nanowires and the conductive polymer solvent is 1: 0.1 to 1: 5, preferably 1: 0.3 to 1: 3.5, more preferably 1: 0.5 to 1: 2.

As such, when the metal nanowires form a metal nanowire layer having a three-dimensional network structure and then form a conductive polymer layer, the surface roughness can be reduced compared to the case where the metal nanowires form a surface. Lowering the resistance can increase the conductivity even further. In addition, since the conductive polymer has a high transmittance, even if the composite electrode layer of the lower metal nanowire layer and the upper conductive polymer layer is formed, high transmittance can be realized.

The metal nanowires used in the embodiments of the present invention are, for example, having a diameter of 80 to 120 nm and a length of 5 to 13 μm, preferably having a diameter of 90 to 100 nm and a length of 8 to 10 μm. .

As the metal nanowires used in the embodiments of the present invention, gold nanowires, silver nanowires, and the like may be used, and in particular, it is preferable to use silver nanowires. Copper nanowires have low oxidation stability and gold nanowires are expensive, while silver (Ag) constituting silver nanowires has a superior price competitiveness compared to oxidation stability. It is also particularly suitable for use in electrohydraulic printing methods.

Non-limiting examples of the conductive polymer used in the embodiments of the present invention may use a known conductive polymer, such as polyaniline, polypyrrole, polythiophene, in particular PEDOT (Poly (3,4-ethylene dioxythiophene) and PSS (Poly ( styrenesulfonate)) (preferably referred to as PEDOT: PSS) is preferable because the polymer particles are well dispersed during printing ink formation and can be uniformly coated during coating, especially for electro-hydraulic printing. In this case, PEDOT itself is not dissolved in a solvent, making it difficult to manufacture as an ink, but by mixing PSS together, PSS acts as an oxidizing agent to facilitate dispersion in a solvent, and PEDOT: PSS has good electrical conductivity and permeability. It can be excellent to compensate for the decrease in transmittance according to the network formation of the metal nanowires.

In the composite transparent electrode layer according to the embodiments of the present invention, the size of the net and the empty space formed by the net of the three-dimensional network of the metal nanowires may be, for example, 1 to 3 μm on average.

In the transparent electrode according to the embodiments of the present invention, after the composite transparent electrode layer is formed on the transparent substrate or the composite transparent electrode layer is formed, the lower substrate is coated after coating a material that can act as another substrate on the substrate. Therefore, it may be used alone as a new substrate on which a composite transparent electrode layer is formed.

For example, the transparent substrate may be a transparent substrate including one or more selected from the group consisting of glass, quartz, acrylic, polyester, polyimide, and polyethersulfone. It can be used without limitation as long as it can transmit light and has good mechanical strength and thermal stability.

The transparent electrode according to the embodiments of the present invention may be an organic material such as carbon nanotube, graphene or zinc oxide, tin oxide, indium oxide-tin oxide (ITO), or fluorinated oxide, if necessary. It may further include an electrode layer of an inorganic material such as tin (FTO).

Alcohols may be used as the solvent used in the embodiments of the present invention, for example, methanol, ethanol, isopropanol and the like may be used.

In the electrohydrodynamic printing according to the embodiments of the present invention, the line width and the degree of integration can be precisely controlled by adjusting the DC voltage intensity of the electrohydrodynamic printing, the injection amount per minute of the ink, the printing speed, and the distance between the nozzle and the substrate. .

In the electro-hydraulic printing process according to the embodiments of the present invention, for example, each ink is injected into the electro-hydraulic printing equipment at 100-200 nL per minute, and the transparent substrate (or the above-described state) is applied while applying a voltage of 3.0-3.4 kV. The continuous process may include printing in a cone-jet mode at a speed of 8,000 to 1,200 μm / s at a height of 2500 to 3500 μm from the metal nanowire layer. In this case, the volume of ink injected per minute means a volume at a standard state, that is, at a temperature of 0 ° C., a humidity of 0%, and a pressure of 1.01325 bar. In this case, by controlling the number of prints, transparency and conductivity can be controlled, and fine patterns can be controlled continuously and in real time.

As a non-limiting example, when the composite transparent electrode layer according to the embodiments of the present invention is a mixed layer of the metal nanowire and the conductive polymer described above, the number of printing may be, for example, 1 to 8 times, and the thickness thereof is, for example, 0.1 to 1 It may be a μm, preferably 0.1 to 0.5 μm.

In addition, when the composite transparent electrode layer according to the embodiments of the present invention is a laminated structure of the metal nanowire layer and the conductive polymer layer described above, the number of printing is 1 to 8 times, for example, in the metal nanowire layer forming step, In the forming step may be 1 to 5 times. The thickness of the metal nanowire layer may be, for example, 0.1 μm to 0.5 μm, preferably 0.1 μm to 0.3 μm, and the conductive polymer layer may be, for example, 0.01 μm to 0.06 μm. It may be 0.03 ~ 0.05 μm.

Hereinafter, the present invention will be described through the following examples and experimental examples. Examples and Experimental Examples are intended to describe the present invention in more detail, but the scope of the present invention is not limited to the scope of the following examples. In addition, the comparative examples described below are merely described as being in contrast with the examples, and are not described as prior art. In addition, any person with ordinary skill in the art may make various modifications and imitations within the scope of the appended claims without departing from the scope of the technical idea of the present invention.

Comparative Example 1 Silver Nanowire Single Transparent Electrode Layer

UV-O3 was irradiated after the cleaning process of a glass substrate. Next, a polyol reaction was performed by stirring polyvinylpyrrolidone (PVP) based on ethylene glycol (EG) and adding silver chloride (AgCl) and silver nitrate (AgNO3). The prepared silver nanowires were dispersed at 1.8 wt% based on the total weight of ethanol and then mixed with isopropanol in a volume ratio of 1: 9 to prepare an electrohydrodynamic printing process ink. And it was electrohydrodynamically printed on the cleaned glass substrate to prepare a transparent electrode.

The printing process conditions of silver nanowires were printed under cone condition at a speed of 10,000 μm / s at a printing distance of 3000 μm from a 1.85 kV voltage applied to a glass substrate, and then fired at 200 ° C. for 15 minutes. (anode) was formed to manufacture Comparative Example 1.

Comparative Example 2 PEDOT: PSS Single Transparent Electrode Layer

Comparative Example 2 was prepared in the same manner as in Comparative Example 1 except that a single layer including only PEDOT: PSS (AI4083; Clevious) was not formed on the glass substrate and did not include silver nanowires.

3 is an optical micrograph showing a single silver nanowire electrode layer (left; Comparative Example 1) and a single PEDOT: PSS electrode layer (right; Comparative Example 2) according to the comparative examples of the present invention.

Example 1 Composite Electrode Layer Mixed with Silver Nanowires and PEDOT: PSS

After irradiating UV-O3 after the cleaning process of the glass substrate, ethylene glycol (EG) -based polyvinylpyrrolidone (PVP) was stirred and silver chloride (AgCl) and silver nitrate (silver nitrate) AgNO ₃ ) was dispersed in a volume fraction of 1: 9 in silver isopropanol (IPA) solvent. PEDOT: PSS (AI4083; Clevious) was added to the silver nanowires in a volume ratio of 1: 0.5 to prepare an ink for an electrohydrodynamic printing process, and then electrohydrodynamically printed on the cleaned glass substrate.

That is, 250L per minute of ink prepared using the electro-hydraulic printing equipment (HIG-NP200 of Enjet Co., Ltd.) is injected, and 10,000μm / s is applied at a printing distance of 3000μm from a substrate with a 2.8kV voltage applied thereto. A single transparent electrode layer was formed by printing (face printing) under cone jet spray conditions at a speed, which was baked at 100 ° C. for 30 minutes to prepare a transparent electrode.

Example 2 Composite Electrode Layer with PEDOT: PSS Layer Formed on Silver Nanowire Layer

After irradiating UV-O3 after the cleaning process of the glass substrate, ethylene glycol (EG) -based polyvinylpyrrolidone (PVP) was stirred and silver chloride (AgCl) and silver nitrate (silver nitrate) Silver nanowires synthesized by a polyol reaction adding AgNO 3) were mixed with an isopropanol solvent in a volume ratio of 1: 9 to prepare an electrohydrodynamic printing process ink. Then, 150L of the ink prepared above was injected onto the glass substrate subjected to the cleaning process by using an electro-hydraulic printing equipment (HIG-NP200, manufactured by Enjet Co., Ltd.), and a printing of 3000um was carried out from the substrate and a state in which a 1.85kV voltage was applied. The electrode layer was formed by printing (face patterning) under cone spray conditions at a rate of 10,000 um / s at a distance.

The PEDOT: PSS (AI4083; Clevious) ink was then placed on top of the silver nanowire print layer under a control jet spraying condition at 3000 μm printing height under a 3.2 kV voltage, 150 L per minute ink injection and 10,000 μm / s. After printing (side patterning), the baking process was performed at 100 ° C. for 30 minutes to prepare Example 2. At this time, the volume ratio of silver nanowires and PEDOT: PSS included in Example 2 was 1: 1.

4 shows a composite electrode layer of silver nanowires and PEDOT: PSS (left; Example 1) and a composite electrode layer having a PEDOT: PSS layer formed on the silver nanowire layer (right; Example 2) in the embodiments of the present invention. Scanning electron microscope (SEM) and optical micrographs showing.

[Transmittance and Surface Resistance Measurement 1]

In order to evaluate the transmittance efficiency of the four transparent electrodes of Examples 1 and 2 and Comparative Examples 1 and 2, the transmittance (%) was measured under a wavelength condition of 350 nm to 750 nm using an UV-visible spectroscopy. In order to evaluate the sheet resistance characteristics (Ω / sq), 4-probe Keithley was used to determine the current characteristics according to the voltage application of 10 mV.

5 is a composite of a single silver nanowire electrode layer (Comparative Example 1), a single PEDOT: PSS electrode layer (Comparative Example 2), a single layer of silver nanowires and PEDOT: PSS in Comparative Examples and Examples of the present invention. The transmittance (%) according to the transparent electrode structure of the composite electrode layer (Example 2) in which the PEDOT: PSS layer is formed on the electrode layer (Example 1) and the silver nanowire layer is shown.

6 is a composite of a single silver nanowire electrode layer (Comparative Example 1), a single PEDOT: PSS electrode layer (Comparative Example 2), a single layer of silver nanowires and PEDOT: PSS in Comparative Examples and Examples of the present invention. In order to compare the sheet resistance characteristics (Ω / sq) according to the transparent electrode structure of the electrode layer (Example 1) and the composite electrode layer (Example 2) in which the PEDOT: PSS layer was formed on the silver nanowire layer, the graph is shown. Sheet resistance in y-axis is expressed in arbitrary units.

The actual sheet resistance measurement values of Examples 1 and 2 and Comparative Examples 1 and 2 are shown in Table 1 below. At this time, the volume ratio of SNWs and PEDOT: PSS of Example 1 is 100: 50 (= 1: 0.5), and the volume ratio of SNWs and PEDOT: PSS of Example 2 is 100: 100 (= 1: 1).

SNWs
(Comparative Example 1) PEDOT: PSS
(Comparative Example 2) SNWs (100) + PEDOT: PSS (50)
(Example 1) SNWs 100 / PEDOT: PSS 100 (Example 2) Sheet resistance 17 Ω / sq 0.23 MΩ / sq 4.6 KΩ / sq 9.2 Ω / sq

As can be seen from FIG. 5, in Comparative Example 2, since the conductive polymer alone is present, the transmittance is high, but as can be seen from Table 1, the sheet resistance is considerably high and the conductivity is low.

In the case of Comparative Example 1, the sheet resistance was lower than that of Comparative Example 2 or Example 1 (see Table 1), but the transmittance was particularly reduced in the wavelength range of 400 to 500 nm. In Comparative Example 1, it is thought that a decrease in the transmittance appeared because the entire network was formed very densely due to the formation of a single silver nanowire layer.

In the case of Example 1, the transmittance was good as 80% or more and the surface resistance was also excellent compared to Comparative Example 2.

In Example 2, the transmittance (%) was slightly reduced by laminating the PEDOT: PSS layer on top of the silver nanowire layer, but the average was 75 to 85%. The sheet resistance was significantly lower than that of Comparative Example 2, and the sheet resistance was about half that of Comparative Example 1, which is a silver nanowire layer alone. In addition, the sheet resistance value was significantly lower than that of Example 1.

[Transmittance and Sheet Resistance Measurement 2]

In order to compare the permeability and the sheet resistance according to the mixing ratio of silver nanowires and PEDOT: PSS, the experiment was carried out as follows.

After irradiating UV-O3 after the glass substrate cleaning process, ethylene glycol (EG) -based polyvinylpyrrolidone (PVP) was stirred, and silver chloride (AgCl) and silver nitrate ( The silver nanowires synthesized by the polyol reaction of adding silver nitrate (AgNO3) were dispersed in a volume fraction of 1: 9 in isopropanol (IPA) solvent. PEDOT: PSS (AI4083; Clevious) was added to the silver nanowires in volume ratios of 1: 0, 1: 0.5, 1: 1, 1: 1.5, 1: 2, and 0: 1, respectively, for electro-hydraulic printing process. After the ink was prepared, it was electrohydrodynamically printed on the cleaned glass substrate.

That is, six inks prepared using electro-hydraulic printing equipment are injected at 250 L / min each, and the jet is applied at a speed of 10,000 μm / s at a printing distance of 3000 μm from a substrate with a 2.8 kV voltage applied thereto. Printing (face printing) under spray conditions to form a single transparent electrode layer, which was baked for 30 minutes at 100 ℃ to prepare a transparent electrode.

In order to evaluate the transmittance efficiency of the transparent electrode having six different mixing ratios, the transmittance (%) was measured under a wavelength condition of 350 nm to 750 nm by using an ultraviolet-visible spectroscopy. In order to evaluate (Ω / sq), 4-probe Keithley was used to determine the current characteristics according to the voltage application of 10 mV.

7 shows a single silver nanowire electrode layer (SNWs (1) + PEDOT: PSS (0)), a composite electrode layer (SNWs (1) + PEDOT: PSS) in which a single layer of silver nanowires and PEDOT: PSS is mixed at 1: 0.5. (0.5)), a composite electrode layer (SNWs (1) + PEDOT: PSS (1)), a single layer of silver nanowires and PEDOT: PSS mixed 1: 1, and silver nanowires and PEDOT: PSS 1: 1.5. Composite electrode layer (SNWs (1) + PEDOT: PSS (1.5)), which is a mixed monolayer, and composite electrode layer (SNWs (1) + PEDOT: PSS, which is a single layer where silver nanowires and PEDOT: PSS are mixed 1: 2 2)) and the transmittance (%) according to the transparent electrode structure of a single PEDOT: PSS electrode layer (SNWs (0) + PEDOT: PSS (1)).

8 shows a single silver nanowire electrode layer (SNWs (1) + PEDOT: PSS (0)), a composite electrode layer (SNWs (1) + PEDOT: PSS) in which a single layer of silver nanowires and PEDOT: PSS is mixed at 1: 0.5. (0.5)), a composite electrode layer (SNWs (1) + PEDOT: PSS (1)), a single layer of silver nanowires and PEDOT: PSS mixed 1: 1, and silver nanowires and PEDOT: PSS 1: 1.5. Composite electrode layer (SNWs (1) + PEDOT: PSS (1.5)), which is a mixed monolayer, and composite electrode layer (SNWs (1) + PEDOT: PSS, which is a single layer where silver nanowires and PEDOT: PSS are mixed 1: 2 2)) and sheet resistance values (Ω / sq) according to the transparent electrode structure of the single PEDOT: PSS electrode layer (SNWs (0) + PEDOT: PSS (1)), scanning electron micrographs (top), and optical micrographs (bottom) ).

As can be seen from FIG. 7, the six electrode layers showed similar transmittances in the wavelength region of 550 nm or more, but the single PEDOT: PSS electrode layer had the highest transmittance and the single silver nanowire electrode layer had the lowest transmittance in the wavelength region below. Among the mixed electrode layers, the composite electrode layer (SNWs (1) + PEDOT: PSS (0.5)), which is a single layer in which silver nanowires and PEDOT: PSS were mixed at 1: 0.5, exhibited excellent transmittance in the wavelength region of 400 nm to 450 nm. In addition, the mixed electrode layer having the mixed ratio showed a slightly lower transmittance in the wavelength range of 400 nm to 450 nm, but showed good transmittance and increased transmittance in the wavelength range of 450 nm to 500 nm.

As shown in FIG. 8, the single PEDOT: PSS electrode layer exhibiting the highest transmittance showed the highest sheet resistance, indicating poor conductivity. Among the mixed electrode layers, the composite electrode layer (SNWs (1) + PEDOT: PSS (0.5)), which is a single layer of silver nanowires and PEDOT: PSS mixed at 1: 0.5, exhibited the lowest sheet resistance, and the ratio of PEDOT: PSS was As it increased, sheet resistance increased.

Therefore, as a temporary embodiment of the present invention, the mixed electrode layer in which silver nanowires and PEDOT: PSS are mixed at a ratio of 1: 0.5 to 2 shows good transmittance and conductivity, and when mixed at a ratio of 1: 0.5, The best properties were shown.

As described above, the transparent electrode according to the embodiments of the present invention has a high transmittance, for example, higher than 70% of the deposited metal thin film having a low transmittance, but has a high current due to a low sheet resistance of, for example, several kΩ / sq to 10 kΩ / sq. -Can exhibit voltage characteristics. In addition, it is possible to manufacture uniform surface electrodes of various patterns with a simple printing process, so that they can be applied to display devices, lighting devices, touch screens, image sensors, and solar cells that require transparent electrodes. In light of this, it is suitable for touch screen.

Claims (8)

Printing an ink solution including a metal nanowire, a conductive polymer, and a solvent by an electrohydrodynamic printing method on a transparent substrate,
The method of manufacturing a transparent electrode, characterized in that the metal nanowires 50 to 67% by volume and the conductive polymer 33 to 50% by volume relative to the total volume of the ink solution. The method according to claim 1,
The metal nanowire is a silver nanowire, the conductive polymer is a transparent electrode manufacturing method characterized in that the mixture of poly (3,4-ethylene dioxythiophene) (PEDOT) and poly (styrenesulfonate) (PSS). Printing the first ink solution including the metal nanowires and the solvent on the transparent substrate by electrohydrodynamic printing to form a metal nanowire layer; And
And printing a second ink solution including a conductive polymer and a solvent on the metal nanowire layer by electrohydrodynamic printing to form a conductive polymer layer.
The first ink solution contains 50 to 67% by volume of metal nanowires based on the total volume of the first ink solution.
The second solution comprises a transparent polymer 33 to 50% by volume based on the total volume of the second ink solution. The method of claim 3, wherein
The metal nanowire is a silver nanowire, the conductive polymer is a transparent electrode manufacturing method characterized in that the mixture of poly (3,4-ethylene dioxythiophene) (PEDOT) and poly (styrenesulfonate) (PSS). 5. The method according to any one of claims 1 to 4,
The electrohydraulic printing method injects the ink solution into the electrohydrodynamic printing equipment at 100-200 L / min, and 2500-3500 μm from the transparent substrate or metal nanowire layer to be printed under the application of 3.0-3.4 kV voltage. Transparent electrode manufacturing method characterized in that printing in the cone-jet mode at a speed of 8,000 ~ 1,200μm / s at the height of. 3. The method according to claim 1 or 2,
The number of electro-hydraulic printing is 1 to 8 times, the thickness of the printed layer is 100 to 500nm characterized in that the transparent electrode manufacturing method. The method according to claim 3 or 4,
When forming the metal nanowire layer, the number of electrohydrodynamic printing is 1-8, the thickness of the printed layer is 100-300 nm,
When the conductive polymer layer is formed, the number of electro-hydraulic printing is 1 to 5 times, the thickness of the printed layer is 30 to 50nm characterized in that the transparent electrode manufacturing method. The method according to claim 3 or 4,
Forming a metal nanowire layer and forming a conductive polymer layer are carried out continuously by the same electro-hydraulic printing apparatus.

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