KR20170106093A - Transparent electrode and fabrication method thereof - Google Patents

Abstract

Provided is a transparent electrode which has a graphene sandwich structure having flexibility. The transparent electrode comprises: a first graphene layer; a transparent conductive layer arranged on the first graphene layer; and a second graphene layer arranged on the transparent conductive layer. The first and second graphene layers include at least one of monolayer graphene and a multi-layer graphene. The transparent conductive layer includes a conductive nanowire network including a plurality of conductive nanowires. At least one point of one conductive nanowire can be electrically connected to other conductive nanowires.

Description

TECHNICAL FIELD [0001] The present invention relates to a transparent electrode,

The present invention relates to a transparent electrode and a method of manufacturing the same.

ITO is used as a transparent electrode of electronic devices and display devices. The ITO-containing transparent electrode (hereinafter referred to as " ITO transparent electrode ") has high electrical conductivity and excellent light transmittance.

Since the ITO transparent electrode is generally formed through a deposition process such as sputtering, the manufacturing process cost of the ITO transparent electrode is larger than the manufacturing process cost of a general metal electrode. Therefore, the ITO transparent electrode may cause a rise in manufacturing cost of the electronic device and the display device.

The ITO transparent electrode has a dense thin film structure. When the electronic device and the display are repeatedly deformed, for example, bent or bent, a crack may occur in the ITO transparent electrode. Therefore, the ITO transparent electrode is not suitable as a flexible transparent electrode.

It is an object of the present invention to provide a transparent electrode having a flexible graphene sandwich structure.

Another object of the present invention is to provide a method of manufacturing the transparent electrode.

A transparent electrode according to one aspect of the present invention includes a first graphene layer; A transparent conductive layer disposed on the first graphene layer; And a second graphene layer disposed on the transparent conductive layer. The first and second graphene layers may comprise at least one of a single layer graphene and a multi-layer graphene. The transparent conductive layer includes a conductive nanowire network including a plurality of conductive nanowires, wherein at least one point of one conductive nanowire may be electrically connected to another conductive nanowire.

According to another aspect of the present invention, there is provided a method of fabricating a transparent electrode, comprising: forming a first graphene layer on a metal catalyst; Forming a transparent conductive layer on the first graphene layer; Disposing a second graphene layer on the transparent conductive layer; And improving adhesion of the first graphene layer, the transparent conductive layer, and the second graphene layer.

Since the transparent electrode as described above has a graphene sandwich structure, the transparent electrode may have flexibility. In addition, the transparent electrode is manufactured separately and then transferred to a substrate of an electronic device or a substrate of a display device. Therefore, the transparent electrode can be freely manufactured without being affected by the substrate of the electronic element or the substrate of the display apparatus.

1 is a perspective view illustrating a transparent electrode according to an embodiment of the present invention.
FIG. 2 is a cross-sectional view illustrating an organic light emitting display device to which the transparent electrode shown in FIG. 1 is applied.
FIG. 3 is a flow chart for explaining a method of manufacturing the transparent electrode shown in FIGS. 1 and 2. FIG.
4 to 9 are process perspective views illustrating a method of manufacturing the transparent electrode shown in FIG.
10 is an optical photograph of a state in which silver nanowires are distributed on graphenes grown on a metal catalyst.
FIG. 11 is a graph for explaining Raman spectrum of a conductor in which silver nanowires are distributed on the graphene of FIG. 10; FIG.

The present invention is capable of various modifications and various forms, and specific embodiments are illustrated in the drawings and described in detail in the text. It should be understood, however, that the invention is not intended to be limited to the particular forms disclosed, but includes all modifications, equivalents, and alternatives falling within the spirit and scope of the invention.

Like reference numerals are used for like elements in describing each drawing. In the accompanying drawings, the dimensions of the structures are shown enlarged from the actual for the sake of clarity of the present invention. The terms first, second, etc. may be used to describe various components, but the components should not be limited by the terms. The terms are used only for the purpose of distinguishing one component from another. For example, without departing from the scope of the present invention, the first component may be referred to as a second component, and similarly, the second component may also be referred to as a first component. The singular expressions include plural expressions unless the context clearly dictates otherwise.

In the present application, the terms "comprises" or "having" and the like are used to specify that there is a feature, a number, a step, an operation, an element, a component or a combination thereof described in the specification, But do not preclude the presence or addition of one or more other features, integers, steps, operations, components, parts, or combinations thereof. Also, where a section such as a layer, a film, an area, a plate, or the like is referred to as being "on" another section, it includes not only the case where it is "directly on" another part but also the case where there is another part in between. On the contrary, where a section such as a layer, a film, an area, a plate, etc. is referred to as being "under" another section, this includes not only the case where the section is "directly underneath"

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings.

1 is a perspective view illustrating a transparent electrode according to an embodiment of the present invention.

Referring to FIG. 1, the transparent electrode TE may be a graphene-conductive nanowire-graphene stacked transparent electrode. More specifically, the transparent electrode TE includes a first graphene layer GL1, a transparent conductive layer TCL disposed on the first graphene layer GL1, and a transparent conductive layer TCL on the transparent conductive layer TCL. And a second graphene layer (GL2) disposed thereon.

The transparent conductive layer (TCL) may include a conductive nanowire network having a plurality of conductive nanowires. Here, the conductive nanowires may include silver nanowires (AgNW, Ag nano-wires). At least one point of each conductive nanowire may be in contact with another conductive nanowire. Thus, each conductive nanowire can be electrically connected to another conductive nanowire to form a conductive nanowire network.

The diameter of the conductive nanowires may be 10 nm to 100 nm, and the length of the conductive nanowires may be 2 to 100 μm.

The first and second graphene layers GL1 and GL2 may be disposed above and below the transparent conductive layer TCL to prevent moisture or oxygen from penetrating into the transparent conductive layer TCL. That is, the first and second graphene layers GL1 and GL2 are protective layers of the transparent conductive layer TCL to prevent the conductive nanowires of the transparent conductive layer TCL from being oxidized have.

The first graphene layer GL1 and the second graphene layer GL2 may include at least one of a single-layer graphene and a multi-layer graphene.

As described above, the transparent electrode TE is formed between the first graphene layer GL1, the second graphene layer GL2, and the first graphene layer GL1 and the second graphene layer GL2 And may have a graphene sandwich structure including a disposed transparent conductive layer (TCL). Here, the first graphene layer GL1 and the second graphene layer GL2 may have flexibility. Also, since the transparent conductive layer (TCL) includes a conductive nanowire network, for example, a silver nanowire network, the transparent conductive layer (TCL) may also have flexibility. Therefore, the transparent electrode TE may have flexibility.

The transparent electrode TE prevents the conductive nanowires from being oxidized by the first graphene layer GL1 and the second graphene layer GL2, Degradation of the performance of the apparatus can be prevented.

Hereinafter, an organic light emitting display device to which the transparent electrode TE is applied will be described with reference to FIG.

FIG. 2 is a cross-sectional view illustrating an organic light emitting display device to which the transparent electrode shown in FIG. 1 is applied.

1 and 2, an OLED display includes a first substrate BS, an organic light emitting diode OLED disposed on the first substrate BS, and a second organic light emitting diode OLED disposed on the organic light emitting diode OLED. And a second substrate (ES).

The first substrate BS may include an insulating substrate (not shown) including a plurality of pixel regions, and at least one thin film transistor (not shown) disposed in each pixel region on the insulating substrate.

The insulating substrate may include a transparent insulating material to transmit light. Further, the insulating substrate may be a flexible substrate. The flexible substrate may include a film substrate including a polymer organic substance and a plastic substrate. For example, the flexible substrate may be formed of a material selected from the group consisting of polyethersulfone (PES), polyacrylate, polyetherimide (PEI), polyethylene naphthalate (PEN), polyethylene terephthalate (PET) polyethylene terephthalate, polyphenylene sulfide (PPS), polyarylate (PAR), polyimide (PI), polycarbonate (PC), triacetate cellulose (TAC) And cellulose acetate propionate (CAP). In addition, the flexible substrate may include fiberglass reinforced plastic (FRP).

The material to be applied to the insulating substrate preferably has resistance (or heat resistance) to a high processing temperature in the manufacturing process of the display device.

The thin film transistor includes a semiconductor layer, a gate electrode, a source electrode, and a drain electrode, and the drain electrode may be connected to the organic light emitting diode OLED.

The semiconductor layer may include a source region connected to the source electrode, a drain region connected to the drain electrode, and a channel region between the source region and the drain region. A portion of the channel region may overlap the gate electrode.

A gate insulating film is disposed between the semiconductor layer and the gate electrode, and the gate insulating film can insulate the semiconductor layer and the gate electrode.

The organic light emitting device OLED includes a first electrode 100 disposed on the first substrate BS, an organic layer 200 disposed on the first electrode 100, And a second electrode 300 disposed on the second electrode 300.

One of the first electrode 100 and the second electrode 300 may be an anode and the other may be a cathode electrode. For example, the first electrode 100 may be an anode electrode, and the second electrode 300 may be a cathode electrode.

At least one of the first electrode 100 and the second electrode 300 may be a transmissive electrode. For example, when the organic light emitting diode OLED is a back emission organic light emitting diode, the first electrode 100 may be a transmissive electrode, and the second electrode 300 may be a reflective electrode. When the organic light emitting diode OLED is a front emission type organic light emitting diode, the first electrode 100 may be a reflective electrode and the second electrode 300 may be a transmissive electrode. When the organic light emitting diode OLED is a double-sided light emitting organic light emitting diode, both the first electrode 100 and the second electrode 300 may be a transmissive electrode. In this embodiment, the organic light emitting device OLED is a back light emitting organic light emitting device, the first electrode 100 is an anode electrode, and the second electrode 300 is a cathode electrode.

The first electrode 100 may be disposed on the first substrate BS and may be connected to the drain electrode. In addition, the first electrode 100 may be the transparent electrode TE shown in FIG. That is, the first electrode 100 includes a first graphene layer GL1, a transparent conductive layer TCL disposed on the first graphene layer GL1 and including a conductive nanowire network, And a second graphene layer (GL2) disposed on the second semiconductor layer (TCL). One of the first graphene layer GL1 and the second graphene layer GL2 may be connected to the drain electrode.

The organic layer 200 may be disposed on the exposed surface of the first electrode 100. The organic layer 200 may have a multi-layered structure including at least an emission layer (EML). For example, the organic layer 200 may include a hole injection layer (HIL) for injecting holes, a hole injection layer (HIL) for injecting holes, an electron transport layer A hole transport layer (HTL) for increasing the hole transport layer (HTL), a light emitting layer for emitting light by recombination of injected electrons and holes, a hole blocking layer for suppressing movement of holes not coupled in the light emitting layer, HBL), an electron transport layer (ETL) for smoothly transporting electrons to the light emitting layer, and an electron injection layer (EIL) for injecting electrons.

The color of light generated in the light emitting layer may be one of red, green, blue, and white, but the present invention is not limited thereto. For example, the color of light generated in the light emitting layer of the organic layer 200 may be one of magenta, cyan, and yellow.

The second electrode 300 may include a material capable of reflecting light. For example, the second electrode 300 may be formed of a metal such as molybdenum (Mo), tungsten (W), silver (Ag), magnesium (Mg), aluminum (Al), platinum (Pt), palladium ), At least one of nickel (Ni), neodymium (Nd), iridium (Ir), chromium (Cr), lithium (Li), calcium (Ca) and alloys thereof.

The second substrate ES isolates the organic light emitting device from the external environment and may be attached to the first substrate BS through a sealing material such as a sealant. The second substrate ES may include the same material as the insulating substrate. For example, the second substrate ES may be a flexible substrate. On the other hand, when the organic light emitting device is sealed with a transparent insulating film or the like, the second substrate ES may be omitted.

As described above, the transparent electrode TE may have flexibility both in the first graphene layer GL1, the transparent conductive layer TCL, and the second graphene layer GL2. Therefore, the transparent electrode TE may have flexibility.

Even if the organic light emitting display device is bent or bent repeatedly, the transparent electrode TE has flexibility, so that cracks can be prevented from being generated in the transparent electrode TE.

Hereinafter, a method of manufacturing the transparent electrode TE will be described with reference to FIGS.

FIG. 3 is a flow chart for explaining the method of manufacturing the transparent electrode shown in FIGS. 1 and 2, FIGS. 4 to 9 are process perspective views for explaining the method of manufacturing the transparent electrode shown in FIG. 3, FIG. 11 is a graph for explaining Raman spectrum of a conductor in which silver nanowires are distributed on the graphene of FIG. 10; FIG. 11 is a graph illustrating the distribution of silver nanowires on the graphenes grown on a metal catalyst .

3 to 11, a method of fabricating a transparent electrode includes forming a first graphene layer on a metal catalyst (S1), forming a transparent conductive layer on the first graphene layer (S2) Forming a transparent electrode including a first graphene layer, a transparent conductive layer, and a second graphene layer by disposing a second graphene layer on the transparent conductive layer; Improving the adhesion of the second graphene layer (S4), and removing the metal catalyst (S5).

In the step (S1) of forming the first graphene layer on the metal catalyst, the first graphene layer (GL1) may be formed on the metal catalyst (MC) capable of growing graphene.

As shown in FIG. 4, the metal catalyst MC may include a base substrate MC1 and a metal catalyst layer MC2 formed on the base substrate MC1. The base substrate MC1 may be a substrate including silicon (Si). The metal catalyst layer MC2 may include one of copper (Cu) and nickel (Ni).

The metal catalyst MC may be introduced into a process chamber capable of performing chemical vapor deposition (CVD), and the first graphene layer GL1 may be grown on the metal catalyst layer MC2. Here, the process chamber is a quartz tube, and the temperature inside the process chamber may be about 800 ° C to 1200 ° C. The process gas supplied to the process chamber may be a mixed gas of hydrogen (H2) and methane (CH4). Further, the metal catalyst (MC) may be put into the process chamber while being placed on a quartz plate.

When the metal catalyst MC is injected into the process chamber, a first graphene layer GL1 is formed on the metal catalyst layer MC2 as shown in FIG. The first graphene layer GL1 may include at least one of a single-layer graphene and a muti-layer graphene.

When the metal catalyst layer (MC2) comprises nickel, and some of the carbon atoms supplied by the methane (CH ₄₎ may be growing graphene on the metal catalyst (MC2). While the remainder of the carbon atoms can penetrate into the lattice of the nickel. The carbon atoms penetrating into the lattice of the nickel may be precipitated outside the lattice of the nickel, for example, the metal catalyst layer (MC2) and the graphene in the chemical vapor deposition process. The precipitated carbon atoms may form separate graphenes. Accordingly, the first graphene layer GL1 formed on the metal catalyst layer MC2 including nickel may include a multi-layer graphene.

Further, when the metal catalyst layer (MC2) comprises copper, the carbon atoms supplied by the methane (CH ₄₎ are able to form a yes pin on the metal catalyst (MC2). However, the carbon atoms can not penetrate into the lattice of copper. Therefore, in the chemical vapor deposition process, carbon atoms may not be precipitated between the metal catalyst layer MC2 and the graphene. Therefore, the first graphene layer GL1 formed on the metal catalyst layer MC2 including copper may be a single-layer graphene.

In step S2 of forming a transparent conductive layer on the first graphene layer, a transparent conductive layer TCL may be formed on the first graphene layer GL1 as shown in FIG.

The transparent conductive layer TCL may be formed by applying a plurality of conductive nanowires on the first graphene layer GL1. The conductive nanowires may be applied by a drop casting coating, an air spray coating, a dip coating, a spin coating, and stamping using the conductive nanowire dispersion solution. One of stamping coatings may be used. The conductive nanowire dispersion solution is a solution in which the conductive nanowires are dispersed in a solution of one of ethanol, methanol and isopropanol.

As shown in FIGS. 6 and 10, the transparent conductive layer (TCL) may have a shape in which the conductive nanowires are dispersed. Here, the conductive nanowire may include silver nanowires (AgNW, Ag nano-wires). Also, at least one point of each conductive nanowire may be in contact with another conductive nanowire.

The conductor including the first graphene layer GL1 and the transparent conductive layer TCL may have a Raman spectrum as shown in FIG. In particular, since in the Raman spectrum of the conductor, a peak is confirmed to about 1600 ㎝ ^-1 2400㎝ and ^-1, respectively, the conductor can be seen that it comprises a single layer of graphene.

In the step (S3) of forming a transparent electrode including a first graphene layer, a transparent conductive layer and a second graphene layer by disposing a second graphene layer on the transparent conductive layer, as shown in Fig. 7, A second graphene layer GL2 may be disposed on the conductive layer TCL.

The second graphene layer GL2 may include the same material as the first graphene layer GL1. For example, the second graphene layer GL2 may include at least one of a single-layer graphene and a muti-layer graphene.

When the second graphene layer GL2 is disposed on the transparent conductive layer TCL, a transparent layer including the first graphene layer GL1, the transparent conductive layer TCL, and the second graphene layer GL2, An electrode TE can be manufactured. That is, the transparent electrode TE is formed of the first graphene layer GL1, the second graphene layer GL2, and a transparent layer disposed between the first graphene layer GL1 and the second graphene layer GL2 And may have a graphene sandwich structure including a conductive layer (TCL).

The first graphene layer GL1 and the second graphene layer GL2 are disposed above and below the transparent conductive layer TCL so that the first graphene layer GL1 and the second graphene layer GL2, Can protect the transparent conductive layer (TCL). Therefore, the conductive nanowires of the transparent conductive layer (TCL) can be prevented from being oxidized by moisture and oxygen.

In addition, since the first graphene layer GL1, the transparent conductive layer TCL, and the second graphene layer GL2 are flexible, the transparent electrode TE can also be flexible.

In the step S4 of improving the adhesion between the first graphene layer, the transparent conductive layer and the second graphene layer, the transparent electrode TE is heated to form the first graphene layer, The bonding strength between the transparent conductive layer GL1, the transparent conductive layer TCL, and the second graphene layer GL2 can be improved.

The heating of the transparent electrode TE may be carried out at a temperature of about 100 DEG C to 150 DEG C in a hot plate or an oven.

The thermal conductivity of the first graphene layer GL1 and the second graphene layer GL2 is lower than the thermal conductivity of the conductive nanowires. Therefore, when the transparent electrode TE is heated, the heat can be concentrated on the conductive nanowires rather than the heat is released to the atmosphere. When the heat is concentrated by the conductive nanowires, a part of each conductive nanowire can be melted. During the melting and cooling of the conductive nanowires, the conductive nanowires are bonded to the contacting nanowires. When the conductive nanowires contacting each other are bonded, a conductive nanowire network can be formed.

In addition, the bonding strength between the conductive nanowire network and the graphene layers 110 and 130 may be improved during the heating and cooling of the transparent electrode TE.

In the step S5 of removing the metal catalyst, the metal catalyst MC under the transparent electrode TE may be removed as shown in FIG. The metal catalyst MC is removed by etching the metal catalyst layer MC2 using an etchant to separate the transparent electrode TE and the metal catalyst MC and to remove the metal catalyst MC will be.

The etchant may comprise ferric chloride (FeCl ₃ ) or ammonium persulfate ((NH ₄ ) ₂ S ₂ O ₈ ).

The etchant containing ferric chloride can remove copper through a chemical reaction according to the following formulas (1) and (2).

As shown in Formula 1, ferric chloride may react with copper to form ferrous chloride (FeCl ₂ ) and cuprous chloride (CuCl). In addition, ferric chloride can react with cuprous chloride to form ferrous chloride and cupric chloride (CuCl ₂ ). That is, two ferric chloride reacts with one copper to ultimately produce two ferrous chloride and one copper chloride. Thus, the etchant containing ferric chloride can remove copper.

Further, the ammonium persulfate is a strong oxidizing agent and can oxidize nickel. Therefore, the etchant containing ammonium persulfate can remove nickel.

After the metal catalyst MC is removed, the transparent electrode TE may be transferred onto the first substrate BS shown in FIG. The transfer of the transparent electrode TE may be transferred to the first substrate BS through a wet transfer method or a dry transfer method.

The wet transfer method may be a method of transferring the transparent electrode TE suspended in the DI water to the first substrate BS.

The dry transfer method may be carried out as follows.

First, the transparent electrode TE is attached to a PDMS (polydimethylsiloxane) substrate. Then, the transparent electrode TE is arranged to face the first substrate BS. When the PDMS substrate is heated to a temperature of about 80 캜 and pressure is applied to the PDMS substrate with the transparent electrode TE facing the first substrate BS, And transferred to the substrate (BS). In addition, the PDMS substrate may be separated from the transparent electrode TE.

The transparent electrode TE is formed and transferred onto the first substrate BS so that the transparent electrode TE can be formed on the first substrate BS regardless of the type and the shape of the first substrate BS, May be transferred onto the first substrate (BS).

The foregoing description is intended to illustrate and describe the present invention. It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory only and are not restrictive of the invention, It is to be understood that the invention is not limited to the disclosed embodiments, but, on the contrary, is intended to cover various modifications and equivalent arrangements included within the spirit and scope of the invention. Accordingly, the foregoing description of the invention is not intended to limit the invention to the precise embodiments disclosed. In addition, the appended claims should be construed to include other embodiments.

TE: transparent electrode GL1: first graphene layer
TCL: transparent conductive layer GL2: second graphene layer
100: first electrode 200: organic film
300: second electrode BS: first substrate
ES: Second substrate OLED: Organic light emitting element
MC: Metal catalyst MC1: Base substrate
MC2: metal catalyst layer

Claims (1)

A first graphene layer;
A transparent conductive layer disposed on the first graphene layer; And
And a second graphene layer disposed on the transparent conductive layer,
Wherein the first graphene layer and the second graphene layer comprise at least one of a single layer graphene and a multilayer graphene,
Wherein the transparent conductive layer comprises a conductive nanowire network comprising a plurality of conductive nanowires, wherein at least one point of one conductive nanowire is electrically connected to another conductive nanowire.

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