KR20130112515A - Electrode structural body based graphene oxide, optoelectrical devices and organic solar cell having the same - Google Patents

Abstract

PURPOSE: An electrode structural body using graphene oxide, an optoelectrical device and an organic solar cell having the same are provided to increase the efficiency of a battery by using the graphene oxide. CONSTITUTION: A conductive film (224) is formed on a substrate (222). The conductive film comprises graphene oxide. The conductive film is formed by the spin-coating of the graphene oxide. The conductive film is formed by the drop-casting of the graphene oxide. The conductivity and the transparency of the graphene oxide are turned by a reduction treatment.

Description

Electrode structure using graphene oxide, electro-optical device and organic solar cell having same {Electrode structural body based Graphene Oxide, optoelectrical devices and organic solar cell having the same}

The present invention relates to an electrode structure using graphene oxide capable of manufacturing at a low cost with high efficiency, an electro-optical device and an organic solar cell having the same.

With the recent depletion of existing energy resources such as oil and coal, interest in alternative energy to replace them is increasing. In particular, solar cells are attracting particular attention because they are rich in energy resources and have no problems with environmental pollution. Solar cells include solar cells that generate steam required to rotate turbines using solar heat, and solar cells that convert photons into electrical energy using the properties of semiconductors. In general, it refers to a solar cell (hereinafter referred to as a solar cell).

Figure 1 shows the structure of a general solar cell which is presented as a prior art in Korean Patent Laid-Open No. 2008-0054798. As shown in FIG. 1, a conventional solar cell has a junction structure of a p-type semiconductor 101 and an n-type semiconductor 102, such as a diode. When solar light is incident on the solar cell, the pn junction is formed. Exiton (electron-hole pair) is generated by the interaction between the material constituting the semiconductor and sunlight, and the electrons are directed to the n-type semiconductor (102) side by the electric field formed at the pn junction. Each of the p-type semiconductors 101 is pulled toward the n-type semiconductor 101 and the electrodes 103 and 104 bonded to the p-type semiconductor 102 to generate photovoltaic force between pn. do. At this time, when a load is connected to the electrodes 103 and 104 at both ends, a current flows to obtain power.

In the conventional solar cell having the above configuration, the electrodes 103 and 104 constituting the solar cell are manufactured using indium tin oxide (ITO), which is mostly a transparent electrode. However, the ITO used as the transparent electrode material of the solar cell is a relatively expensive material, which increases the material cost, and additional high temperature processes are required even when manufacturing the electrode using the ITO. There was a problem that the overall production cost is greatly increased. In addition, since the conventional solar cell has a rigid structure without flexibility, there is a limit that the use of the solar cell can be limited to a specific place.

Accordingly, the present invention has been made to solve the above problems, an object of the present invention is to replace the expensive ITO electrode conventionally used as a transparent electrode of the solar cell having excellent physical properties, productivity and applicability graphene oxide To provide an electrode structure that can manufacture a solar cell having high efficiency at low cost by using an electrode by using a pin (Graphene Oxide), to provide an electro-optical device and an organic solar cell having the electrode structure have.

The present invention for achieving the above object, in the electrode structure comprising a substrate and a conductive film formed on the substrate, characterized in that the conductive film is composed of graphene oxide (Graphene Oxide).

In this case, the conductive film formed on the substrate may be formed by spin coating a graphene oxide.

Alternatively, the conductive film may be formed by drop casting graphene oxide.

In addition, the graphene oxide may be tuned in electrical conductivity and transparency through a reduction treatment.

Alternatively, the graphene oxide may be tuned to electrical conductivity and transparency through plasma treatment.

Alternatively, the graphene oxide may be tuned to electrical conductivity and transparency through the addition of metal nanoparticles or metal oxides.

At this time, the added metal nanoparticles are gold (Au), silver (Ag), titanium (Ti), platinum (Pt), palladium (Pd), aluminum (Al), copper (Cu), chromium (Cr), Any one selected from nickel (Ni), iron (Fe), erbium (Eb) and europium (Eu) nanoparticles may be adopted.

In addition, the metal oxide to be added may be any one selected from titanium oxide (TiO ₂ ), zinc oxide (ZnO).

In addition, the graphene oxide may be tuned to the electrical conductivity and transparency through the addition of an organic material.

In addition, the material of the substrate may be a flexible material capable of bending or bending.

In this case, CVD graphene formed by chemical vapor deposition (CVD) of graphene may be applied as a material of the substrate.

Alternatively, the substrate may be made of a polydimethylsiloxane (PDMS) material.

On the other hand, the organic solar cell according to the present invention, the anti-reflection film for preventing the reflection of sunlight; An upper electrode on which the anti-reflection film is formed; A lower electrode disposed on a lower side spaced apart from the upper electrode; A base substrate on which the lower electrode is formed; And a P-N junction portion formed between the upper and lower electrodes, wherein the upper and lower electrodes include: a substrate; It includes a conductive film formed on the substrate, the conductive film is characterized in that consisting of graphene oxide (Graphene Oxide).

In addition, the electro-optical device according to the present invention may be manufactured with a transparent electrode manufactured using the graphene oxide described above.

The present invention having the above-described configuration uses graphene oxide, which has physical properties similar to graphene and has high productivity and industrial application, as an electrode of a solar cell. There is an advantage to manufacture a battery. In addition, there is an advantage that the electrode structure manufactured using graphene oxide having various optical and electrical properties can be applied to various types of optical electric devices such as LEDs as well as solar cells, It is possible to manufacture flexible organic solar cells using the inherent characteristics of graphene itself, which does not easily change its electrical characteristics even when it is bent, so that solar cells can be applied to various applications such as clothing and accessories. There is an advantage.

1 is a block diagram showing a structure of a conventional general solar cell.
Figure 2 is a cross-sectional view showing the configuration of an organic solar cell according to an embodiment of the present invention.
3 is a perspective view showing the configuration of the upper and lower electrodes shown in FIG.
Figure 4 is a process chart showing the production process of the graphene oxide employed as the electrode material for an organic solar cell of the present invention.
Figure 5 is a process chart showing a process of forming a graphene oxide conductive film on a substrate when the electrode for an organic solar cell of the present invention.
6 is a photograph of the surface of the graphene oxide conductive film formed through the process of FIG.
FIG. 7 is a graph showing the absorbance of graphene oxide and reduced graphene oxide with respect to a theoretical value. FIG.
FIG. 8 is a graph showing absorbance versus wavelength of light before and after graphene oxide is plasma treated.
9 is a graph showing a comparison of the transmittance of light before and after bending of the electrode structure made of graphene oxide.

The present invention is an organic solar cell having a high efficiency at a lower cost than conventional technology by configuring the electrode of an electro-optical device such as a solar cell using the excellent electrical / optical properties of graphene (Graphene), which is spotlighted as a next generation device, Provided are methods for manufacturing electro-optical elements such as LEDs.

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

2 is a cross-sectional view showing the configuration of an organic solar cell according to an embodiment of the present invention.

As shown in FIG. 2, the organic solar cell according to the present invention includes an antireflection film 210 disposed on a front side of a solar cell to which sunlight is incident and preventing reflection of sunlight, and the antireflection film 210. ), An upper electrode 220 disposed below the lower electrode, a lower electrode 240 disposed on the lower side spaced apart from the upper electrode 220, and a base substrate 250 disposed below the lower electrode 240. And a PN junction 230 interposed between the upper electrode 220 and the lower electrode 240. In this case, the upper electrode 220 and the lower electrode 240 constituting the organic solar cell are formed by coating a graphene oxide oxidized from graphite (graphene oxide) in a thin film form on a semiconductor substrate.

FIG. 3 is a detailed view illustrating a detailed structure of an upper electrode (or lower electrode) of the organic solar cell shown in FIG. 2.

Here, since the upper electrode 220 and the lower electrode 240 provided in the organic solar cell of the present invention have the same configuration, in FIG. 3, only the structure of the upper electrode 220 will be described for convenience of description. do.

As shown in FIG. 3, the upper electrode 220 provided in the organic solar cell of the present invention includes a substrate 222 made of a transparent material and a conductive film of transparent material formed in a thin film form on the substrate 222. 224).

The substrate 222 is formed of a flexible material such as a polymer that can be bent or bent. In addition, the conductive film 224 is a coating layer in which a graphene oxide produced by being oxidized from graphite is formed in a thin film form by spin coating on a substrate 222.

At this time, the graphene oxide used as the conductive film 224 of the upper electrode (or lower electrode) is a strong acid such as H ₂ SO ₄ and a plurality of metal catalysts to the π-π bond of the graphene having a laminated structure stacked layer layer Can be generated through the process of breaking the interlayer structure.

Figure 4 is a process chart showing the production process of the graphene oxide employed as a material of the electrode for an organic solar cell of the present invention.

Graphene oxide production according to the present invention is generally prepared through a method known as Modified hummer's method, the manufacturing process is shown in Figure 4, graphite (Graphite) H ₂ SO ₄ And by treating with various catalysts, the surface of each layer in the graphite is oxidized so that a part of carbon is bonded with oxygen to have a carbonyl group, and the interlayer distance of graphene having a structure in which layers are stacked is weakened and thus the bonding force is easily weakened. Peel off. Then, after the solution containing the exfoliated graphene sheet is dried to prepare graphene oxide powder, the graphene oxide dispersion may be prepared by dispersing the graphene oxide powder by dipping in DI (deionized water).

Here, the oxidation process for producing the graphene oxide as described above can be effectively performed by increasing the interlayer distance of the graphene and weakening the interlayer bond strength than the direct peeling of the graphene, after which a simple physical force such as high frequency (Sonication) The graphene oxide can be prepared by easily peeling off the graphene having a laminated structure. In this case, graphene oxide is produced by attaching various groups such as carbonyl group, carboxyl group and alcohol group to inside / outside of graphene having a hexagonal carbon crystal structure in the production process of graphene oxide as described above. Graphene oxide has different characteristics from those of general graphene due to various groups that stick to the inside and the outside.

Meanwhile, FIG. 5 shows a conductive film 224 on the substrate 222 of the upper electrode (or lower electrode) for the organic solar cell using the spin coating method of the graphene oxide dispersion prepared by the modified hummer's method of FIG. 4 described above. This is a flowchart showing the formation process.

First, as shown in FIG. 5A, the graphene oxide dispersion is dropped onto the substrate 222 of the upper electrode, and the substrate 222 is rotated at high speed so that the graphene oxide dispersion is thinly spread (b, c). . After that, when the graphene oxide dispersion is completely unfolded to a predetermined thickness, the rotation of the substrate 222 is stopped (d), and the moisture and volatile substances included in the graphene oxide dispersion are evaporated to conduct a predetermined thickness on the substrate 222. A film 224 thin film is formed (e). In this case, the thickness of the graphene oxide conductive film 224 layer formed on the substrate 222 may vary depending on the number of spin coating and the concentration of the graphene oxide dispersion.

6 shows the surface of the graphene oxide conductive film 224 formed through the spin coating process as described above. As shown in the surface photograph of FIG. 6, when the graphene oxide conductive film 224 is formed on the substrate 222 to manufacture the electrode 220, the electrode is subjected to a simple spin coating process as shown in FIG. 5. The graphene oxide conductive film thin film may be uniformly coated on the substrate. As such, the present invention can form the conductive film only by a simple spin coating process when forming the graphene oxide conductive film on the electrode substrate, it is possible to manufacture the electrode at a low cost without the complicated manufacturing process as conventional. In addition, the graphene oxide prepared through the above method has a transparent property such as graphene, and thus can be applied to various electro-optical devices using transparent electrodes such as organic solar cells.

Meanwhile, the present invention can form a graphene oxide conductive film on a substrate of an electrode through various methods in addition to the spin coating method as described above. As one method, a porous filter sheet is laminated on a transparent substrate. Thereafter, a graphene oxide thin film may be formed by injecting a graphene oxide dispersion through a plurality of holes formed in the filter sheet to disperse the graphene oxide on the electrode substrate.

In addition, as another method for forming a graphene oxide conductive film thin film on the substrate, by dropping the graphene oxide dispersion on the substrate (drop) to form a graphene oxide film to form a graphene oxide coating film of a certain thickness by drying ( Drop casting method may be applied.

Meanwhile, the graphene oxide produced through the manufacturing process of FIG. 4 described above may change physical properties through various post-treatment methods as follows. Here, two types of post-treatment methods for changing the physical properties of graphene oxide can be applied, one of which is ① to reduce the oxidized graphene again, the other is ② a different material to the graphene oxide There is a method of changing the physical properties of the graphene oxide or by adding a plasma process.

Among the methods for changing the physical properties of the graphene oxide, the graphene oxide reduction method shown in the above ① can be divided into a method of reducing by applying heat to the graphene oxide and reducing through chemical treatment. At this time, the graphene oxide reduction method by the heat treatment is preferably heat treatment under high temperature environmental conditions when heat is applied, the graphene oxide reduction method by chemical treatment is a graphene oxide using a hydrazine (hydrazine) as a reducing agent Reduction treatment.

7 is an experimental graph showing absorbance characteristics of light of graphene oxide reduced through heat treatment in the method of reducing graphene oxide described above. In this case, the dotted line in Figure 7 shows the theoretical absorbance characteristics of the graphene, the thin solid line represents the absorbance characteristics of the graphene oxide, the thick solid line represents the absorbance characteristics of the reduced graphene oxide.

As can be seen from the experimental graph results of FIG. 7, it can be seen that graphene oxide (rGO) reduced through heat treatment has absorbance characteristics similar to those of graphene. This indicates that the movement of electrons inside the reduced graphene oxide not only has a form very similar to graphene but also has a light transmission / absorption similar to graphene. As such, since graphene oxide can be implemented to have the same optical characteristics as graphene through an appropriate reduction treatment method, it is possible to appropriately tune the electrical conductivity and transparency by reducing the graphene oxide through an appropriate method. And, by applying the graphene oxide tuned electrical conductivity and transparency to the upper electrode 220 of the organic solar cell can implement a solar cell having a higher efficiency.

On the other hand, as another method that can change the physical properties of the graphene oxide, there is a method of adding other materials, such as metal nanoparticles, metal oxides, organic materials, etc. to the graphene oxide as described above ②.

At this time, the metal nanoparticles that can be added to the graphene oxide is gold (Au), silver (Ag), titanium (Ti), platinum (Pt), palladium (Pd), aluminum (Al), copper (Cu), chromium One of (Cr), nickel (Ni), iron (Fe), erbium (Eb), europium (Eu) nanoparticles may be added, or two or more nanoparticles may be mixed and added.

As the metal oxide that can be added to the graphene oxide, any one metal oxide selected from titanium oxide (TiO ₂ ) and zinc oxide (ZnO) may be added. In addition, it is possible to appropriately tune the electrical conductivity and transparency of the graphene oxide by adding an organic substance such as fetacin to the graphene oxide.

As such, by adding a variety of complexes using graphene oxide itself as a base material, the electrical conductivity of graphene oxide may be increased or light transmittance may be controlled in a specific energy portion through a band-gap.

On the other hand, the graphene oxide may be changed in physical properties through the plasma process in addition to the change of properties by the various additives as described above.

8 is an experimental graph showing the change in absorbance after graphene oxide oxygen treatment. Here, the dotted line shows the absorbance of graphene oxide before oxygen plasma treatment, and the solid line shows the absorbance of graphene oxide after oxygen plasma treatment.

As can be seen from the experimental results of FIG. 8, it can be seen that the graphene oxide treated through the oxygen plasma process has greatly increased the absorbance characteristics compared with before the oxygen plasma treatment. As such, the graphene oxide may be plasma-treated with various gases such as oxygen and nitrogen to change electrical and optical properties, and the light absorbing properties of the tunable graphene oxide may be used to change the electrical and optical properties. The ruler can be manufactured.

As described above, the lower electrode 240 of the organic solar cell may be configured by using graphene oxide in which electrical conductivity and light transmittance are tuned through a post-treatment process such as addition of metal nanoparticles or plasma treatment. . The opaque graphene oxide having the tuned electric conductivity and light transmittance is configured as the lower electrode 240 of the organic solar cell, thereby increasing the reflectivity of sunlight through the opaque lower electrode 240 and having a fast charge mobility. Since it is possible to implement an efficient solar cell with reduced light loss on the back side of the solar cell can be implemented.

Meanwhile, in the organic solar cell according to the present invention, the base substrate 250 forming the base of the solar cell may be manufactured using flexible CVD graphene or a polymer.

In this case, the CVD graphene is a graphene produced by chemical vapor deposition (CVD), and may be produced by the following known manufacturing method. That is, a single layer of nickel (Ni) is deposited on a Si / SiO ₂ substrate with a thickness of 300 nm or less using an E-beam evaporator, and then the substrate is heated to 1000 ° C. in a quartz tube. After flowing the reactant mixture (CH ₄ : H ₂ : Ar = 50: 65: 200, 1cm ³ / min) to the heated substrate, 25 ° C. while argon (Ar) was flowed at a rate of ˜10 ° C./S ⁻¹ . It is produced by cooling down quickly. Here, the rapid cooling of the substrate prevents the graphene from forming in multiple layers and makes it possible to effectively separate the graphene layer from the substrate in a subsequent graphene separation process. In addition, in order to obtain uniform monolayer graphene with high efficiency, it is important to set the conditions for growth control of the graphene. In particular, after graphene is grown, nickel (Ni) on the substrate for graphene growth is etched. It is most important to transfer the graphene film on the lower electrode fabricated for the suspension. In general, nickel (Ni) can be etched by a strong acid such as HNO _3, but often generates hydrogen bubbles and damages graphene. Therefore, graphene film can be used to increase the Q-factor when applied to a resonator. Pay particular attention to how you move it. Here, the following two methods should be considered in the process for transferring graphene to a new substrate. First, is to eliminate the nickel (Ni) layer on the magnetic pole is small pH range using iron chloride (FeCl ₃₎ as the etching solution for the removal of nickel (Ni) slowly effectively, Second, BOE as an etchant ( Buffered Oxide Echant (HF) or hydrogen fluoride (HF) solutions are used. Using this method, the silicon dioxide layer is removed and the patterned graphene and nickel (Ni) layers float together on the surface of the solution can effectively deposit graphene. In addition, another process point is to raise the surface of the graphene so that the film is not folded. When the graphene layer thus obtained is deposited on the base substrate 250, a base substrate 250 on which CVD graphene is deposited may be obtained. The base substrate 250 manufactured through the above method does not change the electrical characteristics even when bent or bent, so that it is possible to manufacture a flexible organic solar cell. In addition, by applying the CVD graphene obtained by the above method to the base substrate 250 located on the outermost surface of the organic solar cell there is an advantage that can secure additional mechanical strength. In addition, as the polymer material applicable to the base substrate 250 of the organic solar cell in addition to the CVD graphene, PDMS (polydimethylsiloxane), which is a flexible transparent material, may be applied.

On the other hand, Figure 9 is a graph showing the results of the experiment for the adaptability to the external bending of the graphene oxide prepared by the above-described process of Figure 4, a graph showing the transmission of light before and after the graphene oxide bend. Here, the thick line measures the light transmittance of light before bending the graphene oxide, and the thin line measures the light transmittance after bending the graphene oxide.

As can be seen from the experimental results of FIG. 9, it can be seen that the light transmittance characteristic after bending the graphene oxide is almost similar. As described above, even when the graphene oxide is bent or bent, a flexible solar cell having a flexible electrode may be manufactured using a property in which the light transmittance characteristics are hardly changed. Such a flexible solar cell can be applied to a variety of applications that require flexibility, such as clothing and accessories.

As described above, the present invention uses graphene oxide as an electrode of a solar cell, which has similar physical properties to graphene but has excellent productivity and industrial applicability. High efficiency solar cell can be manufactured. In addition, the electrode structure of the present invention manufactured using various optical / electrical properties of graphene oxide may be applied to electrodes of various types of optical electric elements such as LEDs as well as the solar cells of the aforementioned embodiments. It can be used to apply to a variety of fields that require flexibility, such as clothing, accessories by using the characteristics of the graphene oxide does not change the electrical properties even if bent or bent.

While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it is clearly understood that the same is by way of illustration and example only and is not to be construed as limited to the embodiments set forth herein. Will be possible.

210: antireflection film 220: upper electrode
222: substrate 224: conductive film
230: PN junction 240: lower electrode
250: base substrate

Claims (25)

An electrode structure comprising a substrate and a conductive film formed on the substrate,
The conductive film is an electrode structure, characterized in that consisting of graphene oxide (Graphene Oxide).
The electrode structure according to claim 1, wherein the conductive film is formed by spin coating graphene oxide.
The electrode structure according to claim 1, wherein the conductive film is formed by drop casting graphene oxide.
The electrode structure according to claim 1, wherein the graphene oxide is tuned in electrical conductivity and transparency through a reduction treatment.
The electrode structure according to claim 1, wherein the graphene oxide is tuned in electrical conductivity and transparency through plasma treatment.
The electrode structure according to claim 1, wherein the graphene oxide is tuned in electrical conductivity and transparency through addition of metal nanoparticles or metal oxides.
The metal nanoparticle to be added is gold (Au), silver (Ag), titanium (Ti), platinum (Pt), palladium (Pd), aluminum (Al), copper (Cu), chromium ( Electrode structure characterized in that any one selected from Cr), nickel (Ni), iron (Fe), erbium (Eb), europium (Eu) nanoparticles.
The electrode structure of claim 6, wherein the added metal oxide is any one selected from titanium oxide (TiO ₂ ) and zinc oxide (ZnO).
The electrode structure of claim 1, wherein the graphene oxide is tuned in electrical conductivity and transparency through addition of an organic material.
The electrode structure of claim 1, wherein the substrate is formed of a flexible material.
The electrode structure of claim 10, wherein the substrate comprises CVD graphene formed by chemical vapor deposition (CVD) of graphene.
The electrode structure of claim 10, wherein the substrate is made of polydimethylsiloxane (PDMS).
Anti-reflection film for preventing the reflection of sunlight;
An upper electrode on which the anti-reflection film is formed;
A lower electrode disposed on a lower side spaced apart from the upper electrode;
A base substrate on which the lower electrode is formed; And
Including the PN junction formed between the upper and lower electrodes,
The upper and lower electrodes include a substrate and a conductive film formed on the substrate,
The conductive film is an organic solar cell, characterized in that consisting of graphene oxide (Graphene Oxide).
The organic solar cell of claim 1, wherein the conductive film is formed by spin coating graphene oxide.
The organic solar cell of claim 1, wherein the conductive film is formed by drop casting graphene oxide.
The organic solar cell of claim 1, wherein the graphene oxide is tuned in electrical conductivity and transparency through a reduction treatment.
The organic solar cell of claim 1, wherein the graphene oxide is tuned in electrical conductivity and transparency through a plasma treatment.
The organic solar cell of claim 1, wherein the graphene oxide is tuned in electrical conductivity and transparency through addition of metal nanoparticles or metal oxides.
The metal nanoparticle to be added is gold (Au), silver (Ag), titanium (Ti), platinum (Pt), palladium (Pd), aluminum (Al), copper (Cu), chromium ( Organic solar cell, characterized in that any one selected from Cr), nickel (Ni), iron (Fe), erbium (Eb), europium (Eu) nanoparticles.
The organic solar cell of claim 6, wherein the metal oxide to be added is one selected from titanium oxide (TiO ₂ ) and zinc oxide (ZnO).
The organic solar cell of claim 1, wherein the graphene oxide is tuned in electrical conductivity and transparency through addition of an organic material.
The organic solar cell of claim 1, wherein the substrate is formed of a flexible material.
The organic solar cell of claim 10, wherein the substrate comprises CVD graphene formed by chemical vapor deposition (CVD) of graphene.
The organic solar cell of claim 10, wherein the substrate is made of polydimethylsiloxane (PDMS).
An electro-optical device manufactured with the electrode structure of claim 1.

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