KR20140058892A - Transparent composite electrode using nanowire having core-shell structure and method for preparing the same - Google Patents

Abstract

The present invention relates to a transparent composite electrode using a nanowire having a core-shell structure and a manufacturing method thereof. The transparent composite electrode according to the present invention has a multilayer structure in which a transparent conductive oxide layer and a metal layer formed on a substrate are alternately stacked. The metal layer is made of the nanowire having the core-shell structure in which a metal shell is formed on a metal nanowire core and the surface of the metal nanowire core. The transparent composite electrode forming the metal layer using the nanowire having the core-shell structure and the transparent conductive oxide layer together according to the present invention have high permeability and excellent adhesion and surface properties by reducing the roughness and haze of the surface of the electrode.

Description

TECHNICAL FIELD [0001] The present invention relates to a transparent composite electrode to which a nanowire having a core-shell structure is applied, and a method of manufacturing the transparent composite electrode.

The present invention relates to a transparent composite electrode to which a nanowire having a core-shell structure is applied, and a manufacturing method thereof. More particularly, the present invention relates to a transparent composite electrode having nanowires having a core-shell structure applied to a transparent conductive oxide (TCO) composite electrode to reduce roughness and haze of the electrode surface, thereby achieving high transmittance, .

Recently, there is an increasing demand for transparent electronic devices. Especially, a transparent touch panel including a transparent display and a transparent display pioneer new application fields, and electronic information devices which are transparent and capable of inputting and outputting information are being actively developed.

However, transparent conductive oxide (TCO), for example, ITO (indium tin oxide) thin film is a typical transparent conductive film that is currently being developed. However, the ITO thin film generally has a resistance of 10 Ω / □ or more, which is problematic in that the ITO thin film is used to supply power to the display pixel or the thin-film electronic device with sufficient voltage. As an alternative to this, a transparent composite electrode composed of a transparent conductive oxide layer / a metal layer / a transparent conductive oxide layer has been proposed. However, there are still process limitations and it is difficult to satisfy conductivity and transparency at the same time.

On the other hand, in order to simultaneously improve the conductivity and transmittance required for the transparent conductive film material, the conductive metal is reduced in size in the form of nanowires, for example, in the form of nanowires, and has excellent conductivity and high transmittance . However, such a method is still limited by the process.

For example, when silver nanowires are cut at a high temperature under the processing conditions of a transparent conductive film with a silver (Ag) nanowire, the conductivity is rapidly lowered, and there are restrictions in process conditions. In addition, There is a problem that it is very difficult to perform lamination printing of the next material for realizing devices such as TFTs because the surface is rough during the production of transparent electrodes.

When copper (Cu) nanowire is applied to realize a transparent electrode material, copper easily oxidizes upon contact with oxygen to form copper oxide. If the contact with oxygen is not completely physically / chemically blocked, the conductivity It is difficult to secure the conductivity of the transparent electrode.

Of course, there is a way to block the oxygen by clotting a generally known organic shell in the method of preventing oxidation of copper. However, since this organic material acts as a resistor, it can not be applied as an electrode.

Therefore, development of an electrode material having an excellent conductivity and a high transmittance, which is still inexpensive in price, is desperately required.

Accordingly, the present inventors have found that by using a phase transition phenomenon in which a reactant is distributed to an organic phase and a water phase, a metal nano wire, which is relatively inexpensive and susceptible to oxidation, for example, copper nano wire is used as a core, A nanowire having a core-shell structure in which a metal having conductivity is made of silver, for example, a shell is manufactured, and then a nanowire having a multilayer structure made of a metal layer / transparent conductive oxide layer or transparent conductive oxide layer / metal layer / transparent conductive oxide layer It is possible to produce a transparent composite electrode having high transparency, excellent adhesive force and surface property by reducing surface roughness and turbidity when used as a metal layer of a composite electrode, and completed the present invention.

A problem to be solved by the present invention is to apply a nanowire having a core-shell structure in which metal nanowires vulnerable to oxidation are used as a core and a metal having a high conductivity is used as a core while preventing oxidation of the core metal, Thereby providing a transparent composite electrode with reduced roughness and haze.

Another problem to be solved by the present invention is to apply a nanowire having a core-shell structure in which metal nanowires vulnerable to oxidation are used as a core and a metal having a high conductivity is used as a shell while preventing oxidation of the core metal Provided is a method for producing a transparent composite electrode having surface roughness and reduced haze.

In order to solve the above problems,

A transparent composite electrode having a multilayer structure in which a transparent conductive oxide layer and a metal layer are alternately stacked on a substrate,

Wherein the metal layer is formed of a nanowire having a metal-nanowire core and a core-shell structure in which a metal shell is formed on a surface of the core.

The transparent composite electrode according to the present invention has a structure in which n oxide layers and n or n-1 metal layers are alternately laminated, wherein n is preferably 1 to 4.

In the transparent composite electrode according to the present invention, the transparent conductive oxide layer is preferably selected from the group consisting of ITO, IZO, ZTO, AZO, and GIOO.

In the metal nanowire having the core-shell structure constituting the metal layer, at least one metal nano wire selected from the group consisting of copper, Al, Zn and Ni is preferably used as the metal nanowire of the core. Is preferably at least one selected from the group consisting of Ag, Au, Ag-Au alloy, Ni, Zn, In, and Pt.

In the transparent composite electrode according to the present invention, it is preferable that the transparent conductive oxide layer has a thickness of 50 to 200 nm and the metal layer has a thickness of 100 to 300 nm.

In order to solve the other problems,

Forming a transparent conductive oxide layer on the substrate; And

And forming a metal layer from the metal nanowire having a core-shell structure in which a metal nanowire core is formed on the transparent conductive oxide layer and a metal shell is formed on the surface of the metal nanowire core. .

The transparent composite electrode may further include a transparent conductive oxide layer formed on the metal layer. The method may further include forming a metal layer and a transparent conductive oxide layer on the conductive oxide layer, And repeating the step of forming the first insulating film.

In addition, it is preferable that both the transparent conductive oxide layer and the metal layer are formed by a wet process.

In addition, the nanowire having the core-shell structure for forming the metal layer is preferably prepared by mixing the metal nanowire dispersion liquid dispersed in the polar solvent and the metal precursor solution dissolved in the non-polar solvent.

Here, the metal nanowire dispersed in the polar solvent is preferably one or more selected from the group consisting of copper, Al, Zn, and Ni.

The metal precursor dissolved in the non-polar solvent preferably has a structure represented by the following formula 1:

Formula 1

Wherein M is selected from the group consisting of Ag, Au, Ag-Au alloys Ni, Zn, In, and Pt, and n is an integer of 0 to 23, wherein X is hydrogen, an alkyl group having 1 to 6 carbon atoms or a halogen.

In addition, it is preferable that the metal precursor solution further contains an amine.

The transparent composite electrode in which the metal layer using the nanowire having the core-shell structure according to the present invention is combined with the transparent conductive oxide layer reduces the roughness and haze of the electrode surface, thereby achieving high transmittance, excellent adhesion and surface property.

In addition, the transparent composite electrode having a layered structure according to the present invention has excellent thermal stability.

1 is a schematic view of a transparent composite electrode to which a nanowire having a core-shell structure according to an embodiment of the present invention is applied.
2 is a schematic view of a transparent composite electrode to which a nanowire having a core-shell structure according to another embodiment of the present invention is applied.
FIG. 3 is an image of a surface of a transparent composite electrode to which a nanowire having a core-shell structure according to an embodiment of the present invention is applied, using a ball microscope.

Hereinafter, the present invention will be described in more detail with reference to the drawings.

FIG. 1 is a schematic view of a transparent composite electrode to which a nanowire having a core-shell structure according to an embodiment of the present invention is applied, and FIG. 2 is a cross-sectional view illustrating a nanowire having a core-shell structure according to another embodiment of the present invention. FIG. 2 is a schematic view of a transparent composite electrode applied.

Referring to FIGS. 1 and 2, the transparent composite electrode according to the present invention includes a transparent conductive oxide layer 110, a metal layer 120 of a nanowire having a core-shell structure / a transparent conductive oxide layer 130, or may have the structure of a metal layer 120 of a nanowire having a transparent conductive oxide layer 110 / core-shell structure as shown in FIG. 2, but is not limited thereto, In general, n oxide layers and n or n-1 metal layers are alternately laminated, wherein n is preferably 1 to 4.

In the transparent composite electrode according to the present invention, the transparent conductive oxide layers 110 and 130 have a transparent characteristic and can be generally used in this field. More specifically, the transparent conductive oxide layers 110 and 130 may be formed of a transparent conductive oxide, such as ITO, IZO, ZTO, AZO, More than one type may be selected, but is not limited to this.

The transparent conductive oxide layers 110 and 130 may be formed through a general method in the art, and the thickness of the transparent conductive oxide layers 110 and 130 may be formed to have a thickness generally used in this field. Preferably by a wet process such as gravure, gravure offset, reverse offset, ink jet, spin coating, bar coating, slit die coating, silk screen, roll coating and the like And it is preferable that the thickness is independently selected within the range of 50 to 200 nm.

The metal layer 120 may also be formed by a method such as spin coating, bar coating, slit die coating, silk screen, or roll coating using metal nanowires having a core-shell structure. The thickness of the metal layer 120 And can be formed to have a thickness generally suitable for the purpose in this field. And preferably in the range of 100 to 300 nm.

Both the transparent conductive oxide layers 110 and 130 and the metal layer 120 may be subjected to UV or plasma treatment after heat treatment, followed by drying or firing.

Although not shown, the substrate on which the transparent conductive oxide layer 110 is formed may be a substrate commonly used in this field. Specifically, a plastic substrate such as PET (polyethylene terephthalate) or PI (polyimide) And the like can be used.

The metal nanowire having the core-shell structure forming the metal layer 120 is prepared by mixing the metal nanowire dispersion liquid dispersed in the polar solvent and the metal precursor solution dissolved in the non-polar solvent.

In the dispersion of metal nanowires dispersed in the polar solvent, the metal nanowires can be used which can be generally used in this field, and a metal which is vulnerable to oxidation may be more effective. Specifically, it may be selected from copper nanowires, Al, Zn, and Ni, and most preferably copper nanowires.

The metal nanowires having a diameter in the range of 5 to 200 and a length in the range of 5 to 200? May have excellent electrical properties and high transmittance in the electrode implementation.

As the polar solvent in which the metal nanowires are dispersed, a polar solvent common in the field may be used, and preferably at least one selected from the group consisting of water, methanol, ethanol, isopropanol, DMSO, methylene chloride, and THF .

In this case, it is preferable that the metal nanowires are dispersed in the range of 1 to 30 wt% based on the total weight of the metal nanowire dispersion. Depending on the concentration of the dispersion, the degree of shelling can be controlled and proper concentration is very important for proper shelling.

When the metal nanowires are dispersed in the polar solvent, a dispersant such as an aliphatic amine, carboxylic acid, thiol, PVP (polyvinylpyrrolidone), or PAA (polyacrylic acid) is added to the total weight of the metal nanowire dispersion in an amount of 0.001 By weight to 10% by weight. The even dispersion of the nanowires plays an important role in applying a uniform shell over the surface of the nanowire.

In the metal precursor solution dissolved in the nonpolar solvent, the metal precursor may be prepared from a fatty acid, and the process for synthesizing the metal precursor prepared from the fatty acid according to the present invention is as follows:

Scheme 1

Wherein M is selected from the group consisting of Ag, Au, Ni, Zn, In, and Pt, and n is an integer of 0 to 23.

Referring to Scheme 1, the synthesis of the metal precursor is a synthesis of a metal precursor by reacting a metal with a fatty acid in the presence of an organic solvent and a base.

Specifically, in the present invention, the metal precursor is formed by dissolving a fatty acid in an organic solvent and adding a base to produce a fatty acid solution; Dropping a metal solution into the fatty acid solution and reacting; And forming a metal precursor precipitate from the mixed solution.

In the step of dissolving the fatty acid in an organic solvent to prepare a fatty acid solution, examples of the fatty acid include hexanoic acid, heptanoic acid, octanoic acid, nonanoic acid, decanoic acid, undecanoic acid, dodecanoic acid, At least one member selected from the group consisting of eicosanoic acid, docosanoic acid, 2-ethylhexanoic acid, 2-methylhexanoic acid, 2-methylheptanoic acid, 2-ethylheptanoic acid, 2-ethylhexanoic acid, oleic acid, linoleic acid, linolenic acid, Fatty acids.

Examples of the solvent include H ₂ O, CH ₂ CN, CH ₃ OH, CH ₃ CH ₂ OH, THF, DMSO, DMF, 1-methoxy-2-propanol, 2,2- Methyl-2-pentanone, and dibutyl ether.

With the base is _{KOH, NaOH, NH 3, NH} 2 CH 3, NH 4 OH, NH (CH 3) 2, N (CH 3) 3, NH 2 Et, NH (Et) 2, NEt 3 , and Ca (OH ) ≪ ₂ >).

In the step of dropping and reacting the metal solution in the fatty acid solution, the metal is first dissolved in an organic solvent to prepare a metal solution.

Subsequently, the metal solution is added dropwise to the fatty acid solution and allowed to react. In this case, it is preferable that stirring accompanies vigorous stirring at the same time.

As the metal, a metal generally used in this field can be used, and it is preferable to have a high conductivity while being able to prevent the oxidation of the metal nanowire, and specifically, a group of Ag, Au, Ni, Zn, In and Pt Among these metals, noble metals such as Ag and Au are preferably selected, and Ag is most preferable. The metal salt may be a nitride, an oxide, a sulfide, or a halide, and is preferably used in the form of a nitride.

The metal salt solution is preferably added dropwise to the fatty acid solution at a rate of 500 ml to 1000 ml per hour, and the fatty acid solution and the metal salt solution are mixed in a weight ratio of 1: 1 to 5: 1. The reaction is preferably carried out at room temperature.

In the step of forming the metal precursor precipitate from the mixed solution, the mixed solution, to which the metal salt solution has been added, is further stirred for 1 minute to 30 minutes to form a precipitate.

In the step of separating the precipitate, the method of separating the precipitate may be removed by a general method in the field, and a method such as filtration or recrystallization may be used.

Then, the separated precipitate is washed with a solvent several times and dried to obtain a final metal precursor having the following structure.

Formula 1

Wherein M is selected from the group consisting of Ag, Au, Ni, Zn, In, and Pt, and n is an integer of 0 to 23.

As the solvent in which the metal precursor is dissolved, a nonpolar solvent is preferable, and it is preferable that at least one solvent is selected from the group consisting of xylene, toluene, benzene and hexane.

In this case, the metal precursor is preferably dispersed in the range of 1 to 10% by weight based on the total weight of the metal precursor solution. If the concentration of the metal precursor solution is too low, the shell may be inadequate to be coated. In addition, when the concentration is too high, metal particles other than shells can be formed, making it impossible to form a core-shell structure.

In addition, the metal precursor solution may optionally contain an amine and may be included in an amount of 0.1 to 10 wt% based on the total weight of the metal precursor solution. The amine serves to promote dissociation of the metal precursor. Therefore, it is possible to control the shell reaction rate and the shell thickness by controlling the amount of amine.

The amine ionizes a metal precursor, such as a silver precursor, in a non-polar solvent as shown in the following reaction formula (2).

Scheme 2

Here, x is hydrogen, alkyl having 1 to 6 carbon atoms or halogen, and n is an integer of 0 to 23.

The amine may be an alkylamine having a straight chain or branched structure, and the size or structure of the alkylamine is not particularly limited, and it may be a primary to tertiary amine, a polyamine such as a monoamine, a diamine, do. For example, there can be mentioned amine compounds such as butylamine, hexylamine, octylamine, nonylamine, decylamine, dodecylamine, hexadodecylamine, octadecylamine, cocoamine, tallowamine, hydrogenated tallowamine, oleylamine, Amines and stearylamines, secondary amines such as dicocoamine, dihydrogenated tallowamine and distearylamine, and secondary amines such as dodecyldimethylamine, didodecylmonomethylamine, tetradecyldimethylamine, Tertiary amines such as octadecyldimethylamine, cocodimethylamine, dodecyltetradecyldimethylamine, triethylamine and trioctylamine, and diamines such as naphthalene diamine, stearyl propylenediamine, octamethylenediamine and nonanediamine, . Of these amines, hexylamine, heptylamine, octylamine, decylamine, dodecylamine, 2-ethylhexylamine, 1,3-dimethyl-n-butylamine, 1-aminoundecane and 1- Do.

When the metal nanowire solution and the metal precursor solution are mixed, the copper nanowire dispersion may be dropped into the metal precursor solution or may be mixed simply by stirring.

The metal nanowire dispersion and the metal precursor dispersion are preferably mixed at a weight ratio of 10: 1 to 1: 1. The ratio of the metal precursor dispersion to the metal nanowire dispersion is very important in order to coat even shells, and it is preferable to mix them in a ratio of 10: 1 to 1: 1 in order to coat an appropriate shell.

The nanowires of the core-shell structure are synthesized by the distribution and reduction of the metal precursor according to the phase transition phenomenon in which the reaction material is distributed to the organic phase and the water phase according to the mixing of the metal nanowire dispersion and the metal precursor solution. In addition, as the reaction material is distributed and reduced, the rate of shelling reaction is controlled to obtain a uniform shell.

Here, the thickness of the shell in the nanowire of the core-shell structure is adjustable within the range of 5 to 50 nm. The thickness of the shell can be controlled according to the dispersion and dissolution state, solvent, concentration and mixing ratio of the metal nanowires and the metal precursor mentioned above.

A manufacturing process of a nanowire having a core-shell structure and a nanowire having a core-shell structure is described as follows.

As the dispersion liquid in which the copper nanowires are dispersed in the polar solvent is mixed with the silver precursor solution in which the silver precursor is dissolved in the non-polar solvent and the amine is added, the organic phase is decomposed into the phase transition in which the reactant is distributed to the precursor solution and the aqueous copper- As the phenomenon occurs, a core-shell structure is formed. When metal copper is in contact with Ag + ions, a reaction occurs in which metal copper reduces Ag + ions by a standard reduction potential difference. However, such an oxidation-reduction reaction is very fast and leads to the formation of Ag particles rather than a shell on the copper surface, making it impossible to form a core-shell structure. However, since the Ag + ions generated from the Ag precursor as in the present invention are distributed / reduced by the water phase due to the phase transition phenomenon, the Ag + ions in the copper nanowires existing in the water due to the difference in density have a nonpolar surface, -Reduction reaction occurs to produce Ag nanoparticles, and the thus obtained Ag nanoparticles have a non-polar surface, which is selectively adsorbed on the surface of copper nanowires to obtain a nanowire having a copper-silver core-shell structure

Scheme 3

Since the nanowire having the core-shell structure according to the present invention is composed of an anti-oxidized core metal and a metal shell having a high conductivity, it is possible to manufacture a nanowire electrode having excellent electrical properties and high transmittance.

Hereinafter, the present invention will be described in more detail with reference to the following examples, but the present invention is not limited by the following examples.

Example 1

Synthesis of nanowires with Cu-Ag core-shell structure

In a 250 ml flask, 50 mg of copper nanowire having an average diameter of 80 nm and an average length of 80 nm was dispersed in 100 ml of water as a polar solvent. Then, another 250 ml flask was charged with 30 g of Ag oleate dissolved in 50 ml of xylene, the non-polar solvent, and 1 mg of triethylamine was added. 50 ml of the copper nanowire dispersion was mixed with 10 ml of the Ag orolate solution, followed by shaking lightly. As the color of the copper nanowires changed from light red to gray over time, 20 mg of nanowires having a copper-silver core-shell structure were obtained.

Synthesis of transparent composite electrode

An ITO solution in which 20 g of ITO was dissolved in 100 ml of a 2-methyl ether solvent was coated on a glass substrate by spin coating. Then, heat was applied at 200 DEG C, followed by drying and firing, to form a 50 nm thick ITO layer. Next, a nanowire solution having a copper-silver core-shell structure obtained by dissolving 2 g of the nanowire having the copper-silver core-shell structure obtained above in 100 ml of isopropanol solvent was coated on the fired ITO layer by spin coating Respectively. Subsequently, heat was applied at 150 ° C., followed by drying and firing, to form a 200 nm-thick nanowire layer having a copper-silver core-shell structure. Then, an ITO solution in which 2 g of ITO was dissolved in 100 ml of a 2-methyl ether solvent was coated on the fired nanowire layer by spin coating. Subsequently, heat was applied at 200 ° C, followed by drying and firing to form a 300 nm thick ITO layer, thereby forming a transparent composite electrode.

Example 2

A transparent composite electrode was formed in the same manner as in Example 1, except that the ITO layer was not formed on the nanowire layer having the copper-silver core-shell structure.

Test Example 1

The surface of the transparent composite electrode obtained in Examples 1 and 2 was photographed using a ball-sight microscope and the image thereof is shown in FIG.

As shown in FIG. 3, the surface of the transparent composite electrode according to the present invention is not rough and very smooth.

Test Example 2

The sheet resistance and transmittance of the transparent composite electrode obtained in Examples 1 and 2 were measured by the following method, and the results are shown in Table 1 below.

Sheet resistance: BEGA (g) Measured using 4 point probe of RS8-1G model.

Transmittance: Average value measured by transmission through a wavelength of 400 to 800 nm using UV-spectroscopy of JASCO V-600 model was recorded.

division Sheet resistance value Permeability Example 1 30Ω / □ 85% Example 2 50 Ω / □ 90%

As can be seen from the above examples and test examples, it can be confirmed that the metal nanowires having the core-shell structure prepared according to the method of the present invention are superior in terms of conductivity and permeability. This indicates that the metal nanowires having a core-shell structure manufactured by the method according to the present invention can be applied as a transparent electrode material.

Comparative Example 1

Cambrios Corporation Transparent electrode realized with Ag nanowire

Ag nanowire of Cambrios Co. was spin-coated at 3000 rpm for 30 seconds, heated at 200 degrees, dried and fired to form a transparent electrode. The sheet resistance and the permeability for comparison are shown in Table 2 below. These measurements were made in the same manner as in Test Example 2.

division Sheet resistance Permeability Comparative Example 1 70Ω / □ 70%

110, 130: transparent conductive oxide layer
120: metal nanowire metal layer having a core-shell structure

Claims (13)

A transparent composite electrode having a multilayer structure in which a transparent conductive oxide layer and a metal layer are alternately stacked on a substrate,
Wherein the metal layer is formed of a nanowire having a metal-nanowire core and a core-shell structure having a metal shell formed on the surface of the metal nanowire core.
The method according to claim 1,
Wherein the transparent composite electrode has a structure in which n oxide layers and n or n-1 metal layers are alternately laminated, wherein n is 2 to 4.
The method according to claim 1,
Wherein the transparent conductive oxide layer is one or more selected from the group consisting of ITO, IZO, ZTO, AZO and GIO.
The method according to claim 1,
Wherein the metal in the metal nanowire of the core is at least one selected from the group consisting of Cu, Al, Zn, and Ni.
The method according to claim 1,
Wherein the metal of the shell is at least one selected from the group consisting of Ag, Au, Ag-Au alloy, Ni, Zn, In, and Pt.
The method according to claim 1,
Wherein the transparent conductive oxide layer has a thickness of 50 to 200 nm and the metal layer has a thickness of 100 to 300 nm.
Forming a metal layer with a metal nanowire having a core-shell structure composed of a metal nanowire core on the substrate and a metal shell on the surface of the metal nanowire core; And
Forming a metal transparent conductive oxide layer on the metal layer;
Wherein the transparent composite electrode is formed of a transparent conductive material.
8. The method of claim 7,
And forming a transparent conductive oxide layer before the step of forming the metal layer.
9. The method of claim 8,
Wherein the transparent conductive oxide layer and the metal layer are both formed by a wet process.
9. The method of claim 8,
Wherein the nanowire having a core-shell structure for forming the metal layer is manufactured by mixing a metal nanowire dispersion liquid dispersed in a polar solvent and a metal precursor solution dissolved in a non-polar solvent.
11. The method of claim 10,
Wherein at least one metal is selected from the group consisting of Cu, Al, Zn and Ni in the metal nanowires dispersed in the polar solvent.
11. The method of claim 10,
Wherein the metal precursor dissolved in the non-polar solvent has a structure represented by the following formula 1:
Formula 1

Wherein M is at least one element selected from the group consisting of Ag, Au, Ag-Au alloys Ni, Zn, In, and Pt , And n is an integer of 0 to 23.
11. The method of claim 10,
Wherein the metal precursor solution further contains an amine.

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