KR101296809B1 - Conductivity enhanced carbon nanotube films by graphene oxide nanosheets - Google Patents

Abstract

The present invention relates to a carbon nanotube film having improved conductivity by graphene oxide, and a substrate; A carbon nanotube transparent conductive layer formed on the upper surface of the substrate; The functional group is formed on the surface and the edge, the graphene oxide layer is applied to the upper surface of the carbon nanotube transparent conductive layer to densify the network structure of the carbon nanotubes; Make film the technical point. Accordingly, the small size graphene oxide is applied to the upper portion of the carbon nanotube network film to densify the network structure of the carbon nanotube, thereby improving the conductivity, surface roughness, and wettability of the carbon nanotube transparent conductive film. There is this.

Description

Conductivity enhanced carbon nanotube films by graphene oxide nanosheets}

The present invention relates to a carbon nanotube film, by applying a small size graphene oxide on the upper layer of the carbon nanotube network film conductive properties by the graphene oxide to improve the characteristics such as conductivity, surface roughness, wettability of the transparent conductive film This improved carbon nanotube film.

In general, the transparent conductive film is used in a plasma display panel (PDP), a liquid crystal display (LCD) device, a light emitting diode device (LED), an organic electroluminescent device (OLED), a touch panel or a solar cell.

Since the transparent conductive film has high conductivity (for example, sheet resistance of ¹ × 10 ³ Ω / sq or less) and high transmittance in the visible region, various light-receiving elements other than solar cells, liquid crystal display devices, plasma display panels, smart windows, and the like In addition to being used as an electrode of a light emitting device, it is used as a transparent electromagnetic shielding body such as an antistatic film and an electromagnetic shielding film used in automobile window glass or building window glass, and a transparent heating element such as a heat ray reflecting film and a freezing showcase.

As the transparent conductive film, tin oxide (SnO ₂ ) film doped with antimony or fluorine, zinc oxide (ZnO) film doped with aluminum or potassium, indium oxide (In ₂ O ₃ ) doped with tin, etc. are widely used. have.

In particular, an indium oxide film doped with tin, that is, an In ₂ O ₃ -Sn-based film, is called an indium tin oxide (ITO) film and is widely used because a low-resistance film can be easily obtained. In the case of ITO, the physical properties are excellent and the experience of process input to date has many advantages. However, indium oxide (In ₂ O ₃ ) is produced as a by-product from zinc (Zn) mines, so supply and demand is unstable. In addition, the ITO membrane has a disadvantage in that it cannot be used in a flexible material such as a polymer substrate because it is inflexible, and there is a problem in that the production cost increases because it can be manufactured under a high temperature and high pressure environment.

In addition, the conductive polymer may be coated on the upper surface of the polymer substrate in order to obtain a flexible touch panel or display, but such a film has a problem in that electrical conductivity drops or is not transparent when exposed to the external environment, and its use is limited. This will be.

Recently, techniques for coating carbon nanotubes on top of various substrates have been widely studied in order to solve these problems. The carbon nanotubes have electrical conductivity comparable to that of metals with an electrical resistance of 10 ^-4 Ωcm, and the surface area is more than 1000 times higher than that of the bulk material and is thousands of times longer than the outer diameter, making it an ideal material for implementing conductivity. And, there is an advantage that can improve the binding force to the substrate through the surface functionalization. In particular, it is expected that the use of the flexible substrate can be infinite.

As a conventional technique using such carbon nanotubes, there is a "coating film containing carbon nanotubes" (Korean Patent Publication No. 10-2004-0030553). The prior art can use only carbon nanotubes having an outer diameter of 3.5 nm in consideration of the dispersibility and electrical conductivity of the carbon nanotubes, there is a problem that the use of the material is limited, dispersibility and adhesion of the carbon nanotubes in the coating film production There is a problem that the property is deteriorated and deteriorates with time.

As another prior art, Korean Patent Office Patent Publication No. 10-869163 introduces a patent application filed by the present applicant "a method for producing a transparent conductive film containing a carbon nanotube and a binder and a transparent conductive film produced thereby."

The prior art is a mixture of acid-treated carbon nanotubes having an outer diameter of less than 15nm and a binder, the carbon nanotube binder mixed coating liquid formed by adding the binder in an amount of 15 to 80 parts by weight based on 100 parts by weight of the carbon nanotubes and a binder substrate It is a composition that forms a transparent conductive film by coating on the upper surface.

The prior art has a fear that the conductivity of the carbon nanotube network is not large and the conductivity decreases due to an increase in the bonding resistance, and the carbon nanotube has a hydrophobic property, making it difficult to apply a hydrophilic material thereon. .

In addition, in the case of carbon nanotubes, there is a problem in that the use of the optoelectronic device is limited due to the rough surface of the pores.

Accordingly, the present invention has been made to solve the above problems of the prior art, by applying a small size graphene oxide to the upper portion of the carbon nanotube network film graphene oxide to improve the characteristics such as conductivity of the transparent conductive film It is an object of the present invention to provide a carbon nanotube film with improved conductivity, surface roughness, wettability, and the like.

The present invention for achieving the above object, a substrate; A carbon nanotube transparent conductive layer formed on the upper surface of the substrate; The functional group is formed on the surface and the edge, the graphene oxide layer is applied to the upper surface of the carbon nanotube transparent conductive layer to densify the network structure of the carbon nanotubes; Make film the technical point.

Here, the carbon nanotubes are preferably made of one selected from single-walled carbon nanotubes, double-walled carbon nanotubes, multi-walled carbon nanotubes, and mixtures thereof.

In addition, the graphene oxide may have a size of 10 nm to 5 μm, and the graphene oxide may be formed by peeling graphite oxide prepared through acid treatment of pure graphite. Wherein the acid treatment is performed by the Staudenmaier method (L. Staudenmaier, Ber. Dtsch. Chem. Ges., 31, 1481-1499, 1898), the Hummus method (W. Hummers et al., J. Am. Chem. Soc. , 80, 1339, 1958), Brody (BC Brodie, Ann. Chim. Phys., 59, 466-472, 1860) and modified methods for more effective oxidation and exfoliation of graphite are known and are referred to by the present invention. It also uses the above methods.

In addition, the substrate is made of one selected from the group consisting of glass, quartz, glass wafers, silicon wafers, plastics, and the coating is spray, dipping, spin coating, screen printing ( It is preferable to use one method selected from screen printing, inkjet printing, pad printing, knife coating, kiss coating and gravure coating.

On the other hand, the carbon nanotube film is preferably used for the electrode of the flexible solar cell.

Accordingly, by applying the graphene oxide having a small size to the upper layer of the carbon nanotube network film, there is an advantage in that the characteristics such as conductivity, surface roughness and wettability of the transparent conductive film are improved.

The carbon nanotube film having improved conductivity by graphene oxide formed by the above method is a touch panel, an organic solar cell, a dye-sensitized positive cell, a liquid crystal display (LCD) device, a light emitting diode device (LED), and an organic light emitting device (organic light emitting device). It can be used as a transparent electrode such as a light emitting diode).

According to the present invention according to the above configuration, by applying a small size graphene oxide on the upper layer of the carbon nanotube network film to densify the network structure of the carbon nanotube, the conductivity, surface roughness, wettability, etc. of the carbon nanotube transparent conductive film It is effective to improve the characteristics of the.

1 is a view showing a scanning electron microscope image of a carbon nanotube transparent conductive layer according to the present invention,
2 is a view showing an example of applying graphene oxide to the upper surface of the carbon nanotube transparent conductive layer according to the present invention,
3 is a view showing the physical properties of the graphene oxide prepared according to the present invention,
4 is a diagram showing a nuclear magnetic resonance spectrum according to the present invention,
5 is a view showing the sheet resistance value of the transmittance before and after the application of graphene oxide according to the present invention,
6 is a view showing a scanning electron microscope image of the surface morphology of the carbon nanotube transparent conductive film according to the graphene oxide coating,
7 is a view showing the water contact angle on the surface of the graphene oxide coated with the (S1) process in accordance with the present invention and the surface of the water contact angle when the graphene oxide is not applied,
8 is a view showing Raman spectroscopic spectrum of carbon nanotubes according to the graphene oxide coating,
9 is a schematic diagram showing the shape of the carbon nanotube network according to the size of the coated graphene oxide,
10 is a diagram illustrating an organic solar cell (a) and its characteristics (b) fabricated using a carbon nanotube transparent conductive film whose conductivity is controlled using graphene oxide as an electrode.

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

As shown, the carbon nanotube film having improved conductivity by graphene oxide according to the present invention is largely the substrate; A carbon nanotube transparent conductive layer; It consists of a graphene oxide layer.

First, the substrate was a plastic substrate, and a polyethylene terephthalate substrate was used among the plastic substrates.

The formation of the carbon nanotube transparent conductive layer on the upper surface of the substrate will be described.

First, 3 mg of single-walled carbon nanotubes were added to 100 ml of a surfactant solution (1% concentration), and the carbon nanotubes were dispersed for 1 hour using an ultrasonic sonicator, followed by 30 minutes at 1000 rpm using a centrifuge. Treatment to separate the supernatant to prepare a carbon nanotube solution.

Then, the prepared carbon nanotube solution is applied to a polyethylene terephthalate substrate heated to 70 ℃ by using a spray coater.

The carbon nanotube transparent conductive layer is formed on the substrate by the above process, and the surfactant remains on the transparent conductive layer. The surfactant is removed using distilled water to finally remove the carbon nanotube as shown in FIG. 1. A transparent conductive layer is formed.

As shown in FIG. 1, it can be seen that the carbon nanotube transparent conductive layer is satisfactorily formed on the substrate.

The graphene oxide layer is formed on the upper surface of the carbon nanotube transparent conductive layer.

2 is a diagram showing an example of applying graphene oxide to the upper surface of the carbon nanotube transparent conductive layer according to the present invention, graphene oxide having various functional groups such as carboxyl group, hydroxyl group on the upper surface of the carbon nanotube transparent conductive layer formed on the PET It is a schematic diagram which shows the shape in which a pin layer is formed.

Graphene oxide according to an embodiment of the present invention was prepared by peeling graphite oxide prepared by treating pure graphite with sulfuric acid and KMnO ₄ for one day and purifying with hydrogen peroxide and hydrochloric acid using an ultrasonic disperser.

The prepared graphene oxide was separated by size as shown in Figure 3 by centrifugation.

3, the graphene oxide of the supernatant (S1) after the treatment once for 30 minutes at 10000rpm was confirmed that the size is less than 1 micrometer, the precipitate was dispersed again and the supernatant (S2) after two centrifugation The graphene oxide increased in size. When centrifuged three times (S3), four times (S4) gradually increased the size of the graphene oxide. In other words, the graphene oxide was formed in the order of (S1) <(S2) <(S3) <(S4) in order of graphene oxide.

FIG. 3 (a) shows a supernatant photograph after centrifugation of graphene oxide formed by centrifuged solutions (S1), (S2), (S3) and (S4), and FIG. 3 (b) shows (S1). Scanning electron microscope (SEM) images for the particle size of the graphene oxide formed by the (S2), (S3) and (S4) process are shown, and FIG. 3 (c) shows (S1) and (S2). The particle size distribution of graphene oxide formed by the process of (S3) and (S4) is shown.

In FIG. 3, the graphene oxide of the supernatant (S1) after the treatment once for 30 minutes at 10000rpm was less than 1 micrometer in size, the process of (S1), (S2), (S3), (S4) It can be seen that the graphene oxide formed by a single layer.

The physical properties were measured using the graphene oxide formed by the process of the supernatant (S1), (S4) of Figure 3, the result of analyzing the graphene oxide prepared by nuclear magnetic resonance method as shown in Figure 4 It was confirmed that the graphene. The same result was obtained for the graphene oxide formed by the rest of the processes (S2) and (S3).

The graphene oxide prepared above was applied to the upper surface of the carbon nanotube transparent conductive layer using a spray coater to form a graphene oxide layer.

FIG. 5 is a diagram showing sheet resistance values of the graphene oxide formed by the processes of (S1), (S2), (S3) and (S4) before and after coating.

As shown in FIG. 5, in the case of coating the graphene oxide, the sheet resistance was decreased at the same permeability as compared to before the treatment. In particular, it can be seen that the sheet resistance of the graphene oxide (S1) having a size of 1 μm or less was greatly decreased.

6 is a scanning electron micrograph of the surface morphology of the carbon nanotube transparent conductive film according to the graphene oxide coating, Figure 6 (a) is a case of applying the graphene oxide (S1) process, Figure 6 ( b) is a case where the graphene oxide (S4) is applied, the smaller the size of the graphene oxide penetrates into the carbon nanotube network to make the network more dense.

7 is a view showing the water contact angle on the surface of the graphene oxide coated with the (S1) process according to the present invention and the water contact angle on the surface of the graphene oxide is not applied, As the water contact angle before the pin coating coated the graphene oxide at 113.6 degrees, it was confirmed that the water contact angle was reduced to 27.9 degrees to improve the wettability of water.

FIG. 8 is a diagram illustrating Raman spectroscopic spectra of carbon nanotubes according to graphene oxide coating, and the deformation of carbon nanotubes can be observed through the change of the G mode band in the Raman spectrum of carbon nanotubes.

As shown in FIG. 8, it was confirmed that the peak of the G-mode shifted to the right side as the graphene oxide was coated. This fact is based on the fact that as the graphene oxide was applied on the carbon nanotubes, the p-type doping was performed, which made the carbon nanotube network more dense and pulled electrons from the carbon nanotubes by the graphene oxide functional groups to increase the hole carriers. . In particular, it can be seen that the graphene oxide applied through the (S1) process has a higher peak shift in the G-mode than the graphene oxide applied through the (S4) process. The more the change appeared.

As described above, bar graphene oxide coated on the prepared carbon nanotube transparent conductive film using a spray coater, after coating compared with before coating the graphene oxide, as shown schematically in Figure 9, the size of the graphene oxide The smaller the density, the denser the carbon nanotube network and the larger the contact area between graphene oxide and carbon nanotube, resulting in greater doping effect, which is expected to be more effective in reducing the sheet resistance of the carbon nanotube transparent conductive film.

The organic solar cell was manufactured by using the carbon nanotube transparent conductive film whose conductivity was controlled using the graphene oxide, and the characteristics thereof were evaluated. FIG. 10 shows the carbon nanotube transparent conductive film whose conductivity was controlled using graphene oxide. Fig. 1 shows an organic solar cell (a) fabricated and used therein and its characteristics (b).

As shown in FIG. 10, a flexible flexible solar cell (a) was fabricated using the carbon nanotube transparent conductive film as an electrode. In the case of using the carbon nanotube transparent conductive film not coated with graphene oxide as shown in FIG. Although the efficiency is only 0.43%, when the carbon nanotube transparent conductive film having improved conductivity and wettability is coated as an electrode by coating graphene oxide of (S4) process, the photoelectric efficiency is 2.0 and the graphene oxide of (S1) process is coated. When the carbon nanotube transparent conductive film with improved conductivity and wettability was used as an electrode, the photoelectric efficiency was greatly increased to 2.7%.

As described above, when the graphene oxide layer is formed on the upper surface of the carbon nanotube transparent conductive layer according to the present invention, it can be seen that the conductivity of the carbon nanotube film is improved.

100: substrate 200: carbon nanotube transparent conductive layer
300: graphene oxide layer

Claims (7)

Claims [1]
A carbon nanotube transparent conductive layer formed on the upper surface of the substrate;
The functional group is formed on the surface and the edge, the graphene oxide layer is applied to the upper surface of the carbon nanotube transparent conductive layer to densify the network structure of the carbon nanotubes;
The carbon nanotubes are carbon nanotube films having improved conductivity by graphene oxide, characterized in that consisting of one selected from single-walled carbon nanotubes, double-walled carbon nanotubes, multi-walled carbon nanotubes and mixtures thereof. delete The carbon nanotube film having improved conductivity by graphene oxide according to claim 1, wherein the graphene oxide has a size of 10 nm to 5 μm. The carbon nanotube film having improved conductivity by graphene oxide according to claim 3, wherein the graphene oxide is formed by peeling graphite oxide prepared through acid treatment of pure graphite. According to claim 1, wherein the substrate is carbon nanotube film with improved conductivity by graphene oxide, characterized in that consisting of one kind selected from the group consisting of glass, quartz, glass wafer, silicon wafer, plastic. The method of claim 1, wherein the application is spraying, dipping, spin coating, screen printing, inkjet printing, pad printing, knife coating, kiss coating, gravure. Carbon nanotube film with improved conductivity by graphene oxide, characterized in that using one method selected from the coating. The carbon nanotube film according to claim 1, wherein the carbon nanotube film is used for an electrode of a flexible solar cell.

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