KR102179698B1 - Preparation method of transparent electrode and transparent electrode prepared by the same - Google Patents

Abstract

In the present specification, a method for manufacturing a transparent electrode, comprising: forming a metal nanowire layer by coating a binder solution including a silver (Ag) nanowire and a solvent on a transparent substrate; Coating a metal ion solution on the metal nanowire layer; And thermally compressing the metal nanowire layer coated with the metal ion solution using a roll press; including, a method of manufacturing a transparent electrode, and a transparent electrode manufactured accordingly.

Description

Transparent electrode manufacturing method and transparent electrode manufactured accordingly {PREPARATION METHOD OF TRANSPARENT ELECTRODE AND TRANSPARENT ELECTRODE PREPARED BY THE SAME}

The present invention relates to a method of manufacturing a transparent electrode having improved contact resistance and excellent surface flatness, and a transparent electrode manufactured thereby.

A transparent electrode means that a conductive film is formed on a transparent substrate, and since it can transmit light, it is used in devices such as solar cells, display devices, and touch screen panels.

In particular, silver nanowire (AgNW) film is a transparent electrode material that can be applied to rollable and flexible devices called next-generation devices, and has a characteristic of maintaining low resistance even after repeated bending tests.

Due to these characteristics, it is recognized as a transparent electrode material that is highly likely to be used in the future, but when an electrode layer is formed by stacking each silver nanowire (AgNW) particle, the contact of silver nanowires (AgNW) due to the polymer layer on the silver nanowire surface There is a big problem with resistance.

Specifically, in general, the AgNW surface is coated with a polymer material. For example, AgNW A and AgNW B are stacked to conduct electricity. AgNW A -> a polymer layer on the A surface -> a polymer layer on the B surface -> AgNW B Therefore, there is a problem that the contact resistance becomes large.

In addition, for example, when a plurality of 20 nm-diameter silver nanowires (AgNW) are stacked, there is a disadvantage in that the thickness of the entire transparent electrode increases and the thickness uniformity of the surface is deteriorated.

Accordingly, there is a need to develop a method for manufacturing a transparent electrode capable of increasing thickness uniformity and lowering contact resistance between AgNWs.

Japanese Laid-Open Patent No. 2015-042717 Japanese Laid-Open Patent No. 2015-172984

In the present invention, compared to a conventional transparent electrode, it is intended to provide a method of manufacturing a transparent electrode capable of manufacturing a transparent electrode having low contact resistance and excellent surface flatness.

In still other exemplary embodiments of the present invention, forming a metal nanowire layer by coating a binder solution including a silver (Ag) nanowire and a solvent on a transparent substrate; Coating a metal ion solution on the metal nanowire layer; And thermally pressing the metal nanowire layer coated with the metal ion solution by using a roll press.

In exemplary embodiments of the present invention, a transparent electrode manufactured by the above-described method for manufacturing a transparent electrode is provided.

According to exemplary embodiments of the present invention, in the method for manufacturing a transparent electrode of the present invention, metal ions are coated on the surface of silver (Ag) nanowires having a three-dimensional network structure, and thermally compressed using a roll press, A transparent electrode having low contact resistance and excellent surface flatness can be manufactured.

1 is a schematic diagram of a method of manufacturing a transparent electrode according to an embodiment of the present invention.
2 shows a result of measuring surface roughness through AFM analysis according to an embodiment of the present invention.

In the present specification, when a certain part "includes" a certain constituent element, it means that other constituent elements may be further included rather than excluding other constituent elements unless otherwise specified.

In the present specification, the term "transparent electrode" refers to an electrode having light transmittance and electrical conductivity, and is a film having electrical conductivity capable of transmitting light including visible light.

In the specification, the "three-dimensional network" structure means a three-dimensional network structure in which a net and a net are entangled.

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

In exemplary embodiments of the present invention, forming a metal nanowire layer by coating a binder solution including a silver (Ag) nanowire and a solvent on a transparent substrate; Coating a metal ion solution on the metal nanowire layer; And thermally pressing the metal nanowire layer coated with the metal ion solution by using a roll press.

In general, in the case of forming an electrode with metal nanowires, it is important to maintain the shape of the metal nanowires well formed on the substrate, and it is also important to widen the contact surface between the metal nanowires and make the contact uniform, especially in the case of metal nanowires. Since it is sprayed in an irregular pattern by compressed air or a high voltage electric field, contact between the metal nanowires and the substrate and between the metal nanowires is not smooth, resulting in high resistance, and the thickness uniformity may deteriorate. Therefore, it is necessary to provide a transparent electrode having excellent surface flatness while increasing contact between metal nanowires and reducing resistance.

Therefore, in the case of the present invention, an electrode layer is formed using silver (Ag) nanowires, but it is coated with a metal ion solution and secondary thermal compression is performed to manufacture a transparent electrode having low contact resistance and excellent thickness uniformity. have. In the transparent electrode according to the embodiments of the present invention, an electrode layer including the metal nanowire layer is formed on a transparent substrate, or after the electrode layer is formed, a material capable of acting as another substrate is coated on the substrate, and then A new substrate on which an electrode layer is formed by removing the lower substrate may be used alone.

The transparent substrate may be a transparent substrate including at least one 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 is an organic material such as carbon nanotubes or graphene, or zinc oxide, tin oxide, indium oxide-tin oxide (ITO), and fluorine addition oxidation when necessary. An electrode layer of an inorganic material such as tin (FTO) may be further included.

As the solvent used in the embodiments of the present invention, distilled water and alcohols may be used, and for example, distilled water, methanol, ethanol, isopropanol, and the like may be used.

The step of forming the metal nanowire layer may be performed according to a general silver nanowire (AgNW) coating method, and then, when a drying process is performed, several silver nanowires as shown in FIG. 1 (#1 part) Wires (AgNW) may be stacked. Copper nanowires have low oxidation stability and gold nanowires are expensive, while silver nanowires have excellent price competitiveness compared to oxidation stability.

In an exemplary embodiment, the diameter of the silver (Ag) nanowire may be 10 to 100 nm, for example, 20 to 90 nm, 30 to 80 nm, or 40 to 70 nm. If the diameter is less than 10 nm, the physical strength may be weak, leading to a reliability problem, and if the diameter is more than 100 nm, the total light transmittance of the transparent electrode may decrease or haze may increase.

In an exemplary embodiment, the length of the silver (Ag) nanowire may be 10 to 50 μm, for example, 15 to 45 μm, 20 to 40 μm, or 25 to 35 μm. If the length is less than 10 μm, silver (Ag) nanowires are not well connected to each other, so it may be difficult to function as an electrode layer, and if the length is more than 50 μm, the total light transmittance may be increased, but the resistance uniformity may be lowered. ..

After that, when the metal ion solution is coated and additionally dried, metal ions are attached to the gap between the silver nanowire (AgNW) and the silver nanowire (AgNW) and are bonded, so that the silver nanowire (AgNW) and the silver nanowire (AgNW) Contact resistance is lower than when) are in direct physical contact with each other.

In an exemplary embodiment, the metal ion solution may include one or more metal ions selected from the group consisting of Ag ⁺ , Au ⁺ , Au ^{3 +} , Cu ^{2 +} , Fe ^{2 +} , and Fe ³⁺ , preferably For example, it may include Ag ⁺ .

In an exemplary embodiment, the metal ion may be 0.01 to 1% by weight based on the weight of the total metal ion solution, for example, 0.05% by weight or more, 0.07% by weight or more, 0.5% by weight or less, 0.3% by weight or less. I can.

Unlike the prior literature, the present invention does not use a compound containing a Thiol group when forming an electrode layer, and uses a metal ion solution containing metal ions, especially Ag ⁺ ions, to prevent electron flow between silver (Ag) nanowires. The electrical properties can be improved by covering the material with silver ions (Ag ⁺ ).

In an exemplary embodiment, the metal nanowire layer has a three-dimensional network structure, and the metal ions may be coated on the three-dimensional network structure, which is like a metal mesh network connected as a whole, in the case of a connected electrode The electrode reliability against repeated bending and oxidation is improved (refer to #2 in FIG. 1).

After the metal ion coating process, the contact resistance is lowered, but the surface flatness may be slightly lower, so in the present invention, an additionally roll press is used to pass the film between the thermocompression rolls to make the surface flatness excellent. Yes (see #3 in Figure 1). In addition, since the density of the electrode is further increased, a resistance reduction effect may be exhibited.

In an exemplary embodiment, in the step of thermocompression, the temperature may be 100° C. or higher, and the pressure may be 30 kg/cm ^{2 or} higher, for example, the temperature may be 100° C. or higher, 110° C. or higher, or 120° C. or higher, preferably May be more than 130℃, and the pressure is 30 kg/cm ² Or more, or 35 kg/cm ² It may be more than, preferably 40 kg / cm ² It can be more than that.

When the temperature is less than 100° C., there may be a limit to lowering the contact resistance, and when the temperature is 200° C. or more, there may be a problem that the silver nanowires melt. When the pressure is less than 30 kg/cm ^{2, the} effect of improving surface flatness may be insignificant, and the effect of reducing resistance may also be insignificant.

In exemplary embodiments of the present invention, a transparent electrode manufactured by the method for manufacturing a transparent electrode described above is provided.

In an exemplary embodiment, the contact resistance of the transparent electrode may be 100 kΩ or less, for example, 90 kΩ or less, 80 kΩ or less, 70 kΩ or less, or 60 kΩ or less, and preferably 50 kΩ or less. When the contact resistance exceeds 100 kΩ, when the device is manufactured, a problem of slowing the driving speed may occur.

In an exemplary embodiment, the surface flatness of the transparent electrode may be RMS 100 nm or less, such as RMS 80 nm or less, RMS 60 nm or less, RMS 40 nm or less, RMS 20 nm or less, RMS 10 nm or less, or RMS 5 nm or less, preferably RMS may be less than 1.67nm. When the surface flatness exceeds RMS 100 nm, a difference in height of the electrode surface occurs, and in the case of a device such as an OLED that is vertically stacked, electrons are concentrated in a high portion and a load may be applied, thereby reducing the lifespan. In an exemplary embodiment, the thickness of the transparent electrode may be 50 nm to 1 μm, which may vary depending on electrode resistance, but is not limited thereto.

Hereinafter, specific embodiments according to exemplary embodiments of the present invention will be described in more detail. However, the present invention is not limited to the following examples, and various types of examples may be implemented within the scope of the appended claims, and only the following examples are used to complete the disclosure of the present invention and It will be understood that it is intended to facilitate the implementation of the invention to those of skill.

Example

Preparation of transparent electrode

A metal nanowire layer was formed through coating and hot air drying using a solution containing AgNW (N&B SNW-006a, diameter 20 nm, length 15 μm) and a binder. After that, the difference between coating using an Ag ion (Inktec TEC-CO-011) aqueous solution (0.1% by weight of Ag ion based on the total weight of the aqueous solution) on the metal nanowire layer and not coating separately, metal After coating the ion solution, the change in the characteristics of the electrode according to the presence/absence of the roll press (50kg/cm ² , 130°C self-manufactured) process was confirmed.

Experimental example

Transparent electrode performance evaluation

1. Comparison before/after roll press

Looking at the surface roughness measurement result (Fig. 2) through AFM analysis, it can be seen that the surface roughness after the roll press is reduced, and the metal ion solution, Ag ion (Inktec TEC-CO-011) aqueous solution (based on the weight of the total aqueous solution) Surface roughness both before and after roll press than those coated with 0.1% by weight of Ag ions (indicated by addition of Ag ions on the drawing) than those without separate coating (indicated by no addition of Ag ions on the drawing) It can be seen that is low.

The lowered surface roughness is the same as the flattened, meaning that the gap between the silver nanowires and the silver nanowires has decreased, or that the contact resistance between the silver nanowires has decreased.

2. Measurement of contact resistance of transparent electrode

To check the contact resistance of the transparent electrode, after printing Ag pads with the same spacing (2mm) on the 4 types of films (coated/uncoated with metal ion solution + with/without roll press), the resistance between Ag pads was measured. It is shown in Table 1 below.

Surface roughness (Ra, nm) Contact resistance (kΩ) Additional coating with a metal ion solution containing Ag ions
(Metal nanowire layer + metal ion solution layer) Before Roll Press 7.319 68 After roll press 3.364 43 Not additionally coated with a metal ion solution containing Ag ions
(Metal nanowire layer only) Before Roll Press 9.470 84 After roll press 6.746 73

Referring to Table 1, the contact resistance of the film additionally coated with a metal ion solution containing Ag ions at the time of manufacture was lower than that of the film without Ag ion coating. This means that the electrode characteristics according to the Ag ion coating have been improved, and as a result of lowering the contact resistance after the roll press than before the roll press, it can be seen that the electrical characteristics of the electrode are also improved.

Claims (10)

Forming a metal nanowire layer by coating a binder solution containing silver (Ag) nanowires and a solvent on a transparent substrate;
Coating a metal ion solution on the metal nanowire layer; And
Including; the step of thermocompressing the metal nanowire layer coated with the metal ion solution using a roll press,
The metal ion solution will contain Ag ⁺ ions, transparent electrode manufacturing method. The method of claim 1,
The silver (Ag) nanowire has a diameter of 10 to 100 nm, characterized in that the transparent electrode manufacturing method. The method of claim 1,
The length of the silver (Ag) nanowires is characterized in that 10 to 50 μm, transparent electrode manufacturing method. delete The method of claim 1,
The metal nanowire layer has a three-dimensional network structure,
The method of manufacturing a transparent electrode, characterized in that the metal ions are coated on the three-dimensional network structure. The method of claim 1,
In the step of thermocompressing, the temperature is 100° C. or more, and the pressure is 30 kg/cm ² or more. A transparent electrode manufactured by the method for manufacturing a transparent electrode according to any one of claims 1 to 3, 5 and 6. The method of claim 7,
The transparent electrode, characterized in that the contact resistance of the transparent electrode is 100 kΩ or less. The method of claim 7,
The transparent electrode, characterized in that the surface flatness of the transparent electrode is less than RMS 100 nm. The method of claim 7,
The transparent electrode, characterized in that the thickness of the transparent electrode is 50nm to 1um.

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