KR20210069849A - Method for manufacturing high conductive transparent electrode - Google Patents

Abstract

According to the present invention, a highly conductive transparent electrode manufacturing method comprises: a first step of producing a silver nanowire ink; a second step of coating the silver nanowire ink on a substrate; and a third step of exposing silver nanowires included in the silver nanowire ink to a surface by a set amount and connecting them to each other.

Description

Method for manufacturing high conductive transparent electrode

The present invention relates to a method for manufacturing a highly conductive transparent electrode.

Electrodes are widely used in various fields. The role of the electrode is to transfer electric charge to each electric element, thereby performing an energy transfer role for driving each electric element.

A transparent electrode, which is one type of such an electrode, usually has a high transparency of 80% or more and a sheet resistance of 500 Ω/sqm or less, and is widely used in touch screens, solar cells, optoelectronic devices, and the like.

Currently, ITO (Indium Tin Oxide), a material for manufacturing a transparent electrode, is continuously increasing in price due to limited reserves.

In order to replace such ITO, efforts are being made to manufacture transparent electrodes with various materials such as carbon nanotubes, silver nanowires, graphene, and conductive polymers. Among them, silver nanowire has excellent electrical conductivity and transmittance and is evaluated as an optimal material to replace ITO.

Korean Patent Registration (10-1328859) discloses a method of coating such a silver nanowire coating solution on a substrate. The silver nanowire coating solution is composed of an adhesive and silver nanowires dispersed therein.

This method has an advantage in that the transparent electrode can be manufactured simply and conveniently. However, since most of the silver nanowires are coated on the substrate in a state where they are buried in the non-conductive adhesive, there is a problem in that it is difficult to exhibit 100% of the excellent electrical conductivity inherent to the silver nanowires.

Korean Patent (10-1328859)

It is an object of the present invention to provide a method for manufacturing a highly conductive transparent electrode capable of solving the above problems.

A method of manufacturing a highly conductive transparent electrode for achieving the above object,

A first step of producing a silver nanowire ink;

a second step of coating the silver nanowire ink on a substrate; and

and a third step of exposing the silver nanowires included in the silver nanowire ink to the surface by a set amount and connecting them to each other.

Using the present invention, it is possible to expose a set amount of silver nano-wires to the surface of the transparent electrode and connect them to each other.

For this reason, in a state in which the silver nanowires are connected to each other, the collecting electrode installed on the surface of the transparent electrode can directly contact the silver nanowire to move electricity, thereby exhibiting 100% of the inherent electrical conductivity of the silver nanowire.

1 is a flowchart illustrating a method of manufacturing a highly conductive transparent electrode according to an embodiment of the present invention.
2 is a view showing a state in which the silver nanowire ink is coated on the substrate.
3 is a view showing a flame throwing device for implementing the third step shown in FIG.
4 is a view comparing the surface exposure degree of silver nanowires before and after emitting a flame to the silver nanowire ink, or before and after spraying a high temperature gas to the silver nanowire ink.
5 is an SEM photograph of a silver nanowire positioned on the surface of the silver nanowire ink before emitting a flame to the silver nanowire ink, or before spraying a high temperature gas on the silver nanowire ink, FIG. A) is an SEM image magnified by 3 times.
6 is an SEM photograph of the silver nanowire exposed outside the surface of the silver nanowire ink after emitting a flame to the silver nanowire ink or after spraying a high temperature gas to the silver nanowire ink. A) is an SEM image magnified by 3 times.
7 is a view showing the coating state and thickness measurement results of the silver nanowire ink before emitting a flame to the silver nanowire ink or before spraying a high temperature gas on the silver nanowire ink.
8 is a view showing the coating state and thickness measurement results of the silver nanowire ink after emitting a flame to the silver nanowire ink or after spraying a high temperature gas on the silver nanowire ink.
9 is a table showing the measurement results of the sheet resistance of the highly conductive transparent electrode according to the movement speed of the flame and the amount of gas.
10 is a view showing a high-temperature gas injection device for implementing the third step shown in FIG.
11 is a view showing a silicon solar cell to which a highly conductive transparent electrode is applied, manufactured by the method for manufacturing a highly conductive transparent electrode according to an embodiment of the present invention. FIG. 11 (a) is a photograph of the silicon solar cell, and FIG. (b) shows the structure of a silicon solar cell.

Hereinafter, a method for manufacturing a highly conductive transparent electrode according to an embodiment of the present invention will be described in detail.

As shown in Fig. 1, the method for manufacturing a highly conductive transparent electrode according to an embodiment of the present invention,

A first step (S11) of producing a silver nanowire ink;

a second step of coating the silver nanowire ink on the substrate (S12);

It consists of a third step (S13) of exposing the silver nanowires contained in the silver nanowire ink to the surface by a set amount and connecting them to each other.

Hereinafter, the first step (S11) will be described.

[Example 1]

① Silver nanowire synthesis step

Add 1.6L of ethylene glycol and 0.4L of glycerol and heat to 150 degrees while stirring. A halogen compound (common name) is used as the catalyst, and -Cl, -Br, and -I bonding materials can be used. In particular, NaCl, AgCl, KBr, etc. are excellent. In this example, NaCl is used as a catalyst.

Stir until 20 g of polyvinylpinolidone and 0.05 g of NaCl are both dissolved. Then, a reducing solution is prepared. Raise the reducing solution to 160 degrees.

Put 10 g of silver nitrate in 90 ml of ethylene glycol and heat to 60 degrees to dissolve silver nitrate. Add 90 ml of ethylene glycol in which 10 g of silver nitrate is dissolved into the reducing solution at a rate of 1.5 ml/min.

② Silver nano wire detection step

Silver nanowires with an average diameter of 100 nm and an average length of 50 μm are detected. Silver nanowires are observed only through an electron microscope, but are shown in the drawings of the present invention for convenience of explanation. as below.

③ Silver nano wire recovery step

Cool the reducing solution for more than 4 hours to bring it to room temperature. Slowly mix 3L of acetone with the reducing solution to aggregate silver nanowires and polyvinylpinolidone and precipitate them. Discard the float. Again, 1L of acetone is poured to precipitate, and the suspension is discarded. Again, 1L of acetone is poured to precipitate, and the suspension is discarded. 5g of silver nanowires are recovered.

5 g of the recovered silver nanowires are put in 1L of ethanol, and the silver nanowires are dispersed to prepare a silver nanowire ink.

As shown in FIG. 2 , the silver nanowire ink 10 is composed of an adhesive 11 and silver nanowires 12 dispersed therein. Hereinafter, the same

[Example 2]

① Silver nanowire synthesis step

- Preparation of reducing agent

Ethylene glycol, diethylene glycol, glycerol, and propylene glycol have a reducing power of silver nitrate at 140 degrees or higher, and using these properties, silver nitrate is reduced and a capping agent is used to make silver nanowires.

A polyol (common name) is used as a solvent, and a mixture of one or more of ethylene glycol, diethylene glycol, glycerol, propylene glycol, and dipropylene glycol is used as a 2L solvent and prepared as a reducing agent.

The solvent is heated to 130 DEG C, and 67 g of polyvinylpyrrolidone, a capping agent, is added to dissolve. Alternatively, 67 g of polyvinylpinolidone copolymer, a capping agent, may be added.

As a silver nanowire seed material, 3.5g of a soluble halogen element-containing material such as AgCl, KBr, and NaCl is added. After that, when it changes to AgCl, AgBr, etc., it becomes a seed.

- Prepare the silver sauce

Dissolve 17 g of AgNO3 in 100 ml of ethylene glycol, diethylene glycol, glycerol, or propylene glycol.

- Silver nanowire synthesis reaction

Raise the temperature of the reducing agent to 145 degrees or more and slowly inject the silver source for 1 hour to 1 hour and 30 minutes. All reactions are completed after about 20 minutes after injection.

② Silver nano wire detection step

Silver nanowires with an average diameter of 20 to 100 nm and an average length of 20 to 100 μm are detected.

③ Silver nano wire recovery step

Add 1.2 L of acetone to the reaction solution. Discard the supernatant solution in which ethylene glycol and glycerol and silver nanoparticles are dispersed. Add 1L of distilled water, ethanol, or IPA (isopropyl alcohol) to disperse the agglomerated silver nanowires and silver nanoparticles. After adding 4L of acetone, the supernatant solution in which ethylene glycol and glycerol and silver nanoparticles are dispersed is discarded. This process is repeated 3 times. Store the silver nanowires in 1L of distilled water, ethanol, or IPA. The silver nanowire that comes out like this is about 1g. Short silver nanowires and 16.7 g of spherical silver particles are included in the upper layer solution and discarded.

1 g of the recovered silver nano-wire is put in 200 mL of ethanol, and the silver nano-wire is dispersed to prepare a silver nano-wire ink.

Hereinafter, the second step (S12) will be described.

See FIG. 2 .

The silver nanowire ink 10 prepared by Example 1 or Example 2 is coated on the substrate 9 . For this purpose, it is sprayed onto the substrate 9 with an airspray through a 0.5mm diameter spray gun. The spray angle is 90 degrees and sprays in a zigzag with an interval of 5mm. The coating amount of the silver nanowire ink 10 proceeds while measuring the transmittance of the substrate 9 . Visible light transmittance is made between 85-95%. Then, as shown in FIG. 2 , the silver nanowire ink 10 is coated on the substrate 9 . The substrate 9 is made _{of SiO 2 .} For reference, the thickness of the silver nanowire ink 10 is much thinner than that of the substrate 9 , but for convenience of explanation, the thickness of the substrate 9 is similar to that of the substrate 9 in FIG. 2 .

Hereinafter, the third step (S13) will be described.

There are two representative methods for executing the third step (S13).

[Method 1]

By emitting a flame on the surface of the silver nanowire ink 10 coated on the substrate 9, the adhesive 11 contained in the silver nanowire ink 10 is burned, and the silver nanowire 12 dispersed in the adhesive 11 is removed. Make it exposed to the surface by a set amount, melt it, and connect it to each other

First, with reference to FIG. 3, a flame-throwing apparatus 100 for emitting a flame on the surface of the silver nano-wire ink 10, which can perform method 1, will be described.

The flame thrower 100 is a head unit 101, a flow rate unit 102, a gas storage unit 103, an X axis driving unit 104, a Y axis driving unit 105, a Z axis driving unit 106, a control unit ( 107) is composed.

The head portion 101 emits a flame. The head 101 is provided with a nozzle capable of adjusting the flame emission angle. The nozzle contains a gas spark plug, which ignites the gas to create a flame.

The flow unit 102 supplies gas to the head unit 101 through the tube (T). The flow unit 109 controls the amount of gas supplied. In this embodiment, the gas is a combustible gas such as butane gas.

The gas storage unit 103 stores gas. The gas storage unit 103 supplies gas to the flow unit 102 through the tube (T).

The X axis driving unit 104 moves the head unit 101 along the X axis. The X-axis driving unit 104 is located on both sides of the stage S, respectively. The X-axis driving unit 104 is composed of a linear motor or a ball screw motor set. A ball screw motor set is a known driving part composed of a ball screw, a motor, and a coupling. A Z-axis support (ZS) is installed on the upper end of the X-axis shaft 104 . One Y-axis support (YS) is installed at the top between the two Z-axis supports (ZS) in the Y-axis direction.

The Y axis driving unit 105 moves the head unit 101 along the Y axis. The Y-axis driving unit 105 is installed in the Y-axis direction on the front side of the Y-axis support (YS). The Y-axis driving unit 105 is composed of a linear motor or a ball screw motor set.

The Z-axis driving unit 106 moves the head unit 101 in the Z-axis. The Z axis driving unit 106 is installed at the lower end of the Y axis driving unit 105 . A head part 101 is installed at the lower end of the Z-axis driving part 106 .

The control unit 107 communicates with the head unit 101, the flow rate unit 102, the gas storage unit 103, the X axis driving unit 104, the Y axis driving unit 105, and the Z axis driving unit 106 by wire and wireless, while the head The unit 101 precisely controls the position at which the flame is radiated on the surface of the silver nanowire ink 10, the amount of flame, the flame temperature, the time to radiate the flame, and the speed of movement of the flame. Reference numeral W denotes a wired/wireless communication line, and S denotes a stage on which the substrate 9 is mounted.

When a flame is radiated on the surface of the silver nanowire ink 10 coated on the substrate 9 with the above-described flame throwing device 100 , the adhesive 11 contained in the silver nanowire ink 10 burns. Then, as shown in FIG. 4 , the silver nanowires 12 dispersed in the adhesive 11 are exposed to the surface and melted and connected to each other, thereby forming the highly conductive transparent electrode 1 .

Meanwhile, as shown in FIG. 5 , the silver nanowires 12 that were simply in contact (the blue circle part) are melted and connected to each other, as shown in FIG. 6 . (red circle part) In this way, the silver nanowires 12 ) are connected to each other, so that the electrical conductivity of the highly conductive transparent electrode 1 is further improved.

On the other hand, the more the silver nanowire 12 is exposed, the greater the amount of direct contact with the collecting electrode (see FIG. 10 ), the better the electrical conductivity of the highly conductive transparent electrode 1 is. However, if a large amount of the silver nanowire 12 is unconditionally exposed, the silver nanowire 12 may come off the substrate 9, so it is necessary to properly burn the adhesive 11 to expose the silver nanowire 12 by the amount set to the surface. do.

To this end, in this embodiment, as shown in FIG. 4 , the coating thickness of the silver nanowire ink 10 is reduced by half (H1->H2), so that the silver nanowire 12 is half exposed to the surface.

As a result, as shown in FIG. 7 , the coating thickness was measured at three points before emitting a flame on the surface of the silver nanowire ink 10 , and was measured as 193 nm, 240 nm, and 227 nm, respectively, but shown in FIG. As described above, after radiating the screen on the surface of the silver nanowire ink 10, the coating thickness was measured at three points, and as a result, 110 nm, 101 nm, and 104 nm were respectively measured.

On the other hand, the amount of silver nanowires 12 exposed to the surface can be controlled by the amount of flame emitted to the silver nanowire ink 10 , flame temperature, flame radiation time, flame radiation location, and flame movement speed. As a result, by controlling the amount of silver nanowires 12 exposed to the surface in this way, the electrical conductivity of the highly conductive transparent electrode 1 can be controlled.

For example, as shown in FIG. 9 , when the Y-axis movement speed of the flame is 93.7 mm/s and the gas amount is 450 ml/min, the sheet resistance of the highly conductive transparent electrode 1 is adjusted to 1.44 Ω/sqm.

As another example, when the Y-axis movement speed of the flame is 93.7 mm/s and the gas amount is 350 ml/min, the sheet resistance of the highly conductive transparent electrode 1 is adjusted to 2.72 Ω/sqm.

As another example, when the Y-axis movement speed of the flame is 250 mm/s and the gas amount is 450 ml/min, the sheet resistance of the highly conductive transparent electrode 1 is adjusted to 6.52 Ω/sqm.

[Method 2]

A high-temperature gas is sprayed on the surface of the silver nanowire ink 10 coated on the substrate 9 to melt the adhesive 11 contained in the silver nanowire ink 10, and the silver nanowire 12 dispersed in the adhesive 11 are exposed to the surface by a set amount and melted to connect them together.

First, with reference to FIG. 10 , a high-temperature gas spraying device 100 ′ for spraying high-temperature gas on the surface of the silver nanowire ink 10 , capable of performing method 2, will be described. In the high-temperature gas injection device 100', the same reference numerals are assigned to the same components as those of the flame throwing device 100 shown in FIG. 3 .

The high-temperature gas injection device 100' includes a head unit 101', a flow rate unit 102, a gas storage unit 103', an X axis driving unit 104, a Y axis driving unit 105, and a Z axis driving unit 106. , a control unit 107 ′, and a heater unit 108 .

The head part 101' injects high-temperature gas. The head unit 101' is provided with a nozzle capable of adjusting the hot gas injection angle.

The flow unit 102 supplies gas to the head unit 101 through the tube (T). The flow unit 109 adjusts the amount of gas supplied. In this embodiment, the gas may be an inert gas or air.

The gas storage unit 103' stores gas. The gas storage unit 103 ′ supplies gas to the flow unit 102 through the tube T.

The X axis driving unit 104 moves the head unit 101 along the X axis. The X-axis driving unit 104 is located on both sides of the stage S, respectively. The X-axis driving unit 104 is composed of a linear motor or a ball screw motor set. A ball screw motor set is a known driving part composed of a ball screw, a motor, and a coupling. A Z-axis support (ZS) is installed on the upper end of the X-axis shaft 104 . One Y-axis support (YS) is installed at the top between the two Z-axis supports (ZS) in the Y-axis direction.

The Y axis driving unit 105 moves the head unit 101 along the Y axis. The Y-axis driving unit 105 is installed in the Y-axis direction on the front side of the Y-axis support (YS). The Y-axis driving unit 105 is composed of a linear motor or a ball screw motor set.

The Z-axis driving unit 106 moves the head unit 101 in the Z-axis. The Z axis driving unit 106 is installed at the lower end of the Y axis driving unit 105 . A head part 101 is installed at the lower end of the Z-axis driving part 106 .

The control unit 107' includes a head unit 101', a flow rate unit 102, a gas storage unit 103', an X axis driving unit 104, a Y axis driving unit 105, a Z axis driving unit 106, and a heater unit. During wired/wireless communication with the 108, the head unit 101' precisely determines the position, the amount of injection, the gas temperature, the time to radiate the high-temperature gas, and the movement speed of the high-temperature gas on the surface of the silver nanowire ink 10. to control Reference numeral W denotes a wired/wireless communication line, and S denotes a stage on which the substrate 9 is mounted.

The heater unit 108 heats the gas to a high temperature.

When high-temperature gas is sprayed on the surface of the silver nanowire ink 10 coated on the substrate 9 with the above-described high-temperature gas spraying device 100', the adhesive 11 contained in the silver nanowire ink 10 is melted. Then, as shown in FIG. 4 , the silver nanowires 12 dispersed in the adhesive 11 are exposed to the surface and melted and connected to each other, thereby forming the highly conductive transparent electrode 1 .

Meanwhile, as shown in FIG. 5 , the silver nanowires 12 that were simply in contact (the blue circle part) are melted and connected to each other, as shown in FIG. 6 . (red circle part) In this way, the silver nanowires 12 ) are connected to each other, so that the electrical conductivity of the highly conductive transparent electrode 1 is further improved.

On the other hand, the more the silver nanowire 12 is exposed, the greater the amount of direct contact with the collecting electrode (see FIG. 10 ), the better the electrical conductivity of the highly conductive transparent electrode 1 is. However, if a large amount of the silver nanowire 12 is unconditionally exposed, the silver nanowire 12 may come off the substrate 9, so it is necessary to properly melt the adhesive 11 to expose the silver nanowire 12 by the amount set on the surface. do.

To this end, in this embodiment, as shown in FIG. 4 , the coating thickness of the silver nanowire ink 10 is reduced by half (H1->H2), so that the silver nanowire 12 is half exposed to the surface.

As a result, as shown in FIG. 7 , the coating thickness was measured at three points before spraying the high-temperature gas on the surface of the silver nanowire ink 10 , and was measured as 193 nm, 240 nm, and 227 nm, respectively, but in FIG. As shown, after high-temperature gas is sprayed on the surface of the silver nanowire ink 10, the coating thickness is measured at three points, and as a result, 110 nm, 101 nm, and 104 nm are respectively measured.

On the other hand, the amount of silver nanowire 12 exposed to the surface is controlled by the amount of high-temperature gas radiated to the silver nanowire ink 10, the high-temperature gas temperature, the time to radiate the high-temperature gas, the position where the high-temperature gas is emitted, and the movement speed of the high-temperature gas can be As a result, the electrical conductivity of the highly conductive transparent electrode 1 can be controlled by controlling the amount of silver nanowires 12 exposed to the surface in this way.

Through the first step (S11) to the third step (S13), the highly conductive transparent electrode 1 is manufactured. As shown in FIG. 11 , the highly conductive transparent electrode 1 can be used as a configuration of a silicon solar cell, and is in direct contact with the collecting electrode, thereby exhibiting 100% of the intrinsic electrical conductivity of the silver nanowire.

In addition, the highly conductive transparent electrode 1 may be used in fields requiring high electrical conductivity, such as touch screens and optoelectronic devices.

1: Highly conductive transparent electrode 9: Substrate
10: silver nanowire ink 11: adhesive
12: silver nano wire 100: flame thrower
100': high-temperature gas injection device 101, 101': head part
102: flow unit 103,103': gas storage unit
104: East X soccer 105: East Y axis
106: Z axis east 107,107': control unit
108: heater part T: tube

Claims (5)

A first step of producing a silver nanowire ink;
a second step of coating the silver nanowire ink on a substrate; and
and a third step of exposing the silver nanowires contained in the silver nanowire ink to the surface by a set amount and connecting them to each other. According to claim 1,
In the first step,
The silver nanowire ink,
A method for manufacturing a highly conductive transparent electrode, characterized in that it is prepared by dispersing the silver nanowires recovered through the silver nanowire synthesis step, the silver nanowire detection step, and the silver nanowire recovery step in ethanol. According to claim 1,
In the second step,
The amount of the silver nanowire ink to be coated on the substrate,
Controlled while measuring the transmittance of the substrate, a method for manufacturing a highly conductive transparent electrode, characterized in that the visible light transmittance is made between 85 and 95%. According to claim 1, wherein the third step,
By emitting a flame on the surface of the silver nanowire ink coated on the substrate, the adhesive contained in the silver nanowire ink is burned, and the silver nanowire dispersed in the adhesive is exposed to the surface by a set amount and melted to connect with each other A method for manufacturing a highly conductive transparent electrode. According to claim 1, wherein the third step,
By spraying a high-temperature gas on the surface of the silver nano-wire ink coated on the substrate, the adhesive contained in the silver nano-wire ink is melted, and the silver nano-wire dispersed in the adhesive is exposed to the surface by a set amount and melted to connect with each other A method for manufacturing a highly conductive transparent electrode.

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