KR20140036089A - Surface plasmon resonance optical materials using conductive oxide nanoparticles, method for fabricating the same and optical devices comprising the same - Google Patents

Abstract

Provided are a surface plasmon resonance optical material using a conductive oxide nanoparticle, a method of manufacturing the same, and an optical device including the same. The optical material is a medium consisting of a dielectric or a semiconductor; And conductive oxide nanoparticles located on the surface or inside of the medium and interacting with light in the visible to ultraviolet region to cause surface plasmon resonance. According to this, it is possible to increase the photoreactivity of the existing optical element and to increase the selective absorption of the light energy of a specific wavelength band or to increase the emission.

Description

Surface plasmon resonance optical materials using conductive oxide nanoparticles, method for fabricating the same and optical devices comprising the same}

The present invention relates to an optical material and its application, and more particularly, to an optical material capable of improved light absorption and light emission by surface plasmon resonance using conductive oxide nanoparticles, a manufacturing method thereof, and an optical device including the same. will be.

Surface plasmons (SP) generated by the interaction between light and electron plasma waves at the interface of metals and dielectrics are attracting interest for applications to various optical materials and devices such as photocatalysts, solar cells, and light emitting diodes. .

Many of the free electrons inside the metal, which is a conductor, are not bound to metal atoms and thus can be easily reacted to specific external stimuli, and have the unique optical properties of surface plasmon properties caused by the behavior of these free electrons. Surface plasmon resonance (SPR) refers to a phenomenon in which free electrons on a metal surface vibrate collectively due to resonance of electromagnetic energy of a specific energy of light when light enters between a surface of a metal nanoparticle as a conductor and a dielectric. . In this case, the metal nanoparticles resonate with light in a specific region according to the type, shape, and size of the metal material, so that absorption and scattering of the light are very strong, thereby causing charge transfer and energy transfer.

A device using general photoreactivity, for example, a light receiving device, is limited in its properties only by basic physical properties such as bandgap energy of a photoreactive material. Therefore, there is a limit to increase the amount of light absorption by using a material having a high absorption coefficient or by increasing the thickness of the light absorption layer. Meanwhile, in the case of a light emitting device that is attracting attention as a next-generation light source, many researches and developments for improving light emission efficiency are in progress, but there is still a need for improvement in relation to quantum efficiency.

In this regard, one of the important applications of surface plasmons is the increased absorption of sunlight by light scattering and concentration. Certain materials, such as gold (Au) and silver (Ag), can cause localized surface plasmon resonance (LSPR) by controlling size and shape, resulting in improved light absorption and collection. Another important application of local surface plasmon resonance is to improve the quantum efficiency of light emitting materials and devices through surface plasmon mediated emission.

To this end, techniques for increasing light absorption and light emission per unit volume using local surface plasmon resonance of metal nanoparticles have been studied. However, since these nanoparticle materials are synthesized at a laboratory level mainly by solution synthesis methods such as colloidal growth methods, they are unlikely to be applied to actual mass production processes, and due to the characteristics of solution synthesis methods, surface contamination by solutions and surfactants used is a problem. And process limitations that make it difficult to control size and structure. In addition, there is a problem in that compatibility with various optical device processes to be injected such nanoparticles and application to a large area substrate is difficult.

Korea Patent Registration No. 10-0999739 Korea Patent Registration No. 10-1154577

SUMMARY OF THE INVENTION The present invention has been made to solve the above-described problems, and by introducing conductive oxide nanoparticles into a dielectric or semiconductor material, an optical material expressing surface plasmon resonance by interaction with incident or emitted light, and It is to provide an optical element used.

In addition, to solve the material contamination problem by removing the existing solution synthesis method in the production of nanoparticles, to provide a method having excellent suitability and reproducibility in the production of optical materials and devices.

In order to solve the above technical problem, an aspect of the present invention provides an optical material including conductive oxide nanoparticles.

The optical material is a medium consisting of a dielectric or a semiconductor; And conductive oxide nanoparticles located on the surface or inside of the medium and interacting with light in the visible to ultraviolet region to generate surface plasmon resonance.

The medium may be any one selected from glass, plastic, silicon, a II-VI compound semiconductor, a III-V compound semiconductor, and a I-III-VI compound semiconductor.

The conductive oxide nanoparticles are ruthenium oxide, indium oxide, indium tin oxide, indium zinc oxide, fluorine-doped tin oxide, aluminum-doped zinc oxide, gallium-doped zinc oxide, magnesium-doped zinc oxide, molybdenum- And may be any one nanoparticle selected from doped zinc oxide, aluminum-doped magnesium oxide, gallium-doped magnesium oxide, and indium-doped cadmium oxide.

The conductive oxide nanoparticles may have a diameter of 5 nm or more and less than 30 nm.

In one embodiment, the medium may be glass or zinc oxide, and the conductive oxide nanoparticles may be ruthenium oxide nanoparticles.

The optical material may increase at least one of absorption of visible light incident on the medium by the surface plasmon resonance and emission of ultraviolet light emitted through the medium.

In order to solve the above technical problem, another aspect of the present invention provides a method of manufacturing an optical material including the conductive oxide nanoparticles.

The manufacturing method comprises the steps of preparing a medium consisting of a dielectric or a semiconductor; And forming conductive oxide nanoparticles on the medium by atomic layer chemical vapor deposition, wherein the conductive oxide nanoparticles interact with light in the visible to ultraviolet region to cause surface plasmon resonance.

In addition, after the conductive oxide nanoparticles are formed, the method may further include covering the conductive oxide nanoparticles with a dielectric or semiconductor material constituting the medium.

In order to solve the above technical problem, another aspect of the present invention provides an optical device including the optical material described above.

The optical device may be a solar cell, a light emitting diode, or a display device.

According to the present invention, it is possible to increase the photoreactivity of the existing optical element and to increase the selective absorption of light energy in a specific wavelength band or to increase the emission. Therefore, the conductive oxide particles can be inserted into the solar cell to increase visible light absorption, and at the same time, to promote charge generation and conduction by using excellent conductive properties. In addition, by injecting into a light emitting electronic device, such as a display and a light emitting diode, it is possible to increase the light emission in the ultraviolet region and to improve the energy conversion efficiency. In addition, the optical material of the present invention may be applied to a photoreactive catalyst such as a photovoltaic hydrogen-producing catalyst to increase the production efficiency of the solar fuel source.

However, the effects of the present invention are not limited to the effects mentioned above, and other effects not mentioned can be clearly understood by those skilled in the art from the following description.

1 to 3 show schematic structures of optical elements according to an embodiment of the present invention.
4 is a TEM image of ruthenium oxide nanoparticles prepared in Experimental Example 1. FIG.
5 is a TEM image showing the change in the size of the nanoparticles with the atomic layer deposition cycle.
6a and 6b are UV-Vis absorption spectra measured according to Experimental Example 4.
7 is a graph showing the absorbance ratio measured according to Experimental Example 5.
8 is a graph showing the results of measuring light emission (PL) according to Experimental Example 6. FIG.
9 is a graph showing the PL attenuation effect measured according to Experimental Example 7.
10 is an energy band diagram showing a state in which conductive oxide nanoparticles cause an increase in light absorption and light emission by surface plasmon resonance.

Hereinafter, preferred embodiments of the present invention will be described in detail. It is to be understood, however, that the present invention is not limited to the embodiments described herein but may be embodied in other forms and includes all equivalents and alternatives falling within the spirit and scope of the present invention.

When a layer is referred to herein as being "on" another layer or substrate, it may be formed directly on another layer or substrate, or a third layer may be interposed therebetween. In the present specification, directional expressions of the upper side, upper side, upper side, and the like can be understood as meaning lower, lower, lower, and the like according to the standard. That is, the expression of the spatial direction should be understood in the relative direction and should not be construed as limiting in the absolute direction.

In the drawings, the thicknesses of layers and regions may be exaggerated or reduced for convenience or clarity of description. Like numbers refer to like elements throughout.

In the following description of the present invention, a detailed description of known functions and configurations incorporated herein will be omitted when it may make the subject matter of the present invention rather unclear.

According to an embodiment of the present invention, an optical material including conductive oxide nanoparticles having a surface plasmon resonance effect is provided.

The optical material is a medium consisting of a dielectric or a semiconductor; And conductive oxide nanoparticles located on the surface or inside of the medium and interacting with light in the visible to ultraviolet region to cause surface plasmon resonance.

The medium is a material in contact with the conductive oxide nanoparticles and has a refractive index different from that of the conductive oxide nanoparticle material. The medium may be made of a dielectric or a semiconductor having a positive refractive index and determining the photoreactivity and the intensity of light reacting at a particular wavelength band.

Specifically, the medium may be any one selected from glass, plastic, silicon, a II-VI compound semiconductor, a III-V compound semiconductor, and a I-III-VI compound semiconductor. The shape of the medium is not particularly limited, and may have various shapes such as a plate-like substrate and a one-dimensional structure such as a nanorod.

The conductive oxide nanoparticles may be, for example, ruthenium oxide, indium oxide, indium tin oxide, indium zinc oxide, or fluorine-doped tin oxide. -doped tin oxide, aluminum-doped zinc oxide, gallium-doped zinc oxide, magnesium-doped zinc oxide, molybdenum- It may be a nanoparticle selected from doped zinc oxide (molybdenum-doped zinc oxide), gallium-doped magnesium oxide and indium-doped cadmium oxide. However, it is not limited thereto.

That is, the conductive oxide nanoparticles include an oxide material having a high charge density, similar to a metal, and may be a surface plasmon phenomenon when contacted with the medium, and have a size smaller than the wavelength of the incident or emitted light. Has

When the size of the conductive oxide nanoparticles is smaller than the light wavelength under consideration, free electrons present in the nanoparticles cause resonance by incident light, thereby causing amplification of light intensity. Therefore, the conductive oxide nanoparticles may be designed in an appropriate size according to the energy of the desired wavelength band, but preferably may have a diameter of 5 nm or more and less than 30 nm. If the diameter is less than 5 nm, it is difficult to expect a sufficient improvement in light absorption or emission due to surface plasmon resonance in the visible or ultraviolet region. If the diameter is 30 nm or more, the nanoparticles overlap each other and no further surface isolation occurs. This is because plasmon resonance can disappear.

In a preferred embodiment, the optical material may include a medium consisting of glass or zinc oxide and ruthenium oxide nanoparticles formed in such a medium as conductive oxide nanoparticles.

As described above, the optical material according to the present embodiment may cause surface plasmon resonance using conductive oxide nanoparticles, thereby absorbing visible light incident on the medium and emitting ultraviolet light emitted through the medium. At least one may be increased.

According to another embodiment of the present invention, a method of manufacturing the above-described optical material is provided.

The method of manufacturing the optical material includes preparing a medium consisting of a dielectric or a semiconductor; And forming conductive oxide nanoparticles on the medium using atomic layer chemical vapor deposition (ALD).

Atomic layer chemical vapor deposition (hereinafter referred to as 'atomic layer deposition') is a thin film growth technique based on self-limiting surface reaction, and has an advantage that it can be applied to a process requiring large area and high step coverage. In particular, when conductive oxide nanoparticles are formed through atomic layer deposition, high quality nanoparticles can be formed, unlike interfacial impurities in the nanoparticle formation process by the conventional solution synthesis method, and nanoparticles are controlled by controlling the deposition cycle. The size of can be easily controlled.

In addition, after the conductive oxide nanoparticles are formed on the medium, the method further includes covering the conductive oxide nanoparticles with a dielectric or semiconductor material constituting the medium, thereby allowing the conductive oxide nanoparticles to be introduced into the medium. Optical material can be manufactured by This can be done by selecting appropriately from a variety of known solution processes and deposition processes depending on the specific materials used as the medium.

According to another embodiment of the present invention, there is provided an optical device comprising the above-described optical material. The optical element may be, for example, a solar cell, a light emitting diode, or a display element. However, it is not limited thereto.

As shown in FIG. 1, the basic structure of a solar cell or a light emitting diode includes a photoactive layer 130 interposed between a first electrode 110 and a second electrode 120 disposed to face each other. Here, the photoactive layer 130 is a term for convenience of description. In the case of a solar cell, a light absorption layer for converting solar energy into electrical energy, and in the case of a light emitting diode, a light emitting layer for converting electrical energy into light energy is referred to as a functional layer. It means to include. The photoactive layer 130 typically includes a p-type semiconductor (or p-type organic material) that plays a role of hole transport and an n-type semiconductor (or n-type organic material) that plays a role of electron transfer. In the case of an organic light emitting diode, a single organic material The light emitting layer may be formed.

At least one of the first electrode 110 and the second electrode 120 is made of a material having light transmittance for absorption of incident sunlight (solar cell) or emission of light generated in the light emitting layer (light emitting diode).

In this regard, in the optical device in which the optical material having the above-described surface plasmon resonance effect is introduced, the conductive oxide nanoparticles 200 may be formed on the surface of the photoactive layer 130, that is, the top surface or the bottom surface of the photoactive layer 130. It may have a structure introduced (a or b of FIG. 1), or may have a structure introduced into the photoactive layer 130 (c of FIG. 1).

In the solar cell, as shown in FIG. 1A, when the conductive oxide nanoparticles 200 are positioned on the upper surface of the light absorbing layer 130 (the surface located in the direction of incidence of sunlight), the conductive oxide having nano-sized conductive oxide The incident light is scattered to increase the optical path. Accordingly, light absorption may be increased by having an optical thickness longer than the thickness of the actual light absorbing layer 130. In addition, the conductivity at the junction interface between the second electrode 120 and the light absorption layer 130 may be increased due to the charge transfer characteristics due to the surface plasmon resonance effect. Such a structure would be advantageous when using an indirect transition semiconductor material having a relatively low extinction coefficient. On the other hand, in a semiconductor material having a large absorption coefficient and a direct transition characteristic, as shown in FIG. 1C, the surface plasmon resonance effect may be expressed inside the light absorption layer 130 to increase the effect by collecting incident light. In addition, as shown in FIG. 1B, the conductive oxide nanoparticles 200 are disposed on the lower surface of the light absorbing layer 130, that is, the interface between the first electrode 110 and the light absorbing layer 130 to lose the optical charge. You will get an effect that you can capture immediately.

Meanwhile, in the case of the light emitting diode, a resonance or coupling between the surface plasmon of the conductive oxide nanoparticle 200 and the excitons in the light emitting layer 130 may be induced through the structure as shown in FIG. The lifetime is reduced and in a short time many carriers (holes and electrons) can participate in luminescent bonds, thereby increasing the light emission efficiency. In addition, as shown in FIG. 2, a substrate (glass or transparent plastic) 100 may be positioned under the transparent first electrode 110, and the conductive oxide nanoparticles 200 may be formed of the first electrode 110. And an interface between the substrate 100 and the substrate 100.

In the application to the display device, as shown in FIG. Conductive oxide nanoparticles 200 may be introduced into 330. The diffusion layer 330 may be made of a transparent plastic resin such as polyolefin resin, polyacrylic resin, polycarbonate resin, or the like, and may serve as a medium for surface plasmon resonance of the conductive oxide nanoparticles 200.

Hereinafter, preferred examples for the understanding of the present invention will be described. It should be understood, however, that the following examples are intended to aid in the understanding of the present invention and are not intended to limit the scope of the present invention.

<Experimental Example 1>

A 30 nm thick ZnO seed layer was deposited using diethyl zinc (DEZ, Zn (CH ₂ CH ₃ ) ₂ ) and deionized water as zinc and oxidant precursors, respectively, on a 100 nm thick SiO ₂ substrate. It was. Argon was used as the carrier and purge gas. The process temperature was set at 150 ° C. and the operating pressure was maintained at 0.5 Torr.

After forming the zinc oxide seed layer, the substrate was subjected to zinc nitrate hexahydrate [Zn (NO ₃ ) ₂ .6H ₂ O, Sigma Aldrich, purity 99.0%] and hexamethylenetetramine (HMT) [C ₆ H ₁₂ N ₄ , Sigma Aldrich, 99.0% purity] was immersed in a Teflon beaker containing an equimolar amount solution (0.02M) of the zinc oxide nanorods were hydrothermally grown. Before placing the substrate into the growth solution, the Teflon beaker containing the precursor solution was kept in an oven at 90 ° C. for 1 hour to reduce the density of the free-floating zinc oxide nanoparticles.

The substrate was then placed in a heated solution and the temperature was maintained for 2 hours. After growth was complete, the sample was taken out of solution, washed with deionized water to remove surface residual salts and dried at room temperature in air.

After preparation of the zinc oxide nanorod, ruthenium oxide (RuO ₂ ) as a conductive oxide on the zinc oxide nanorod Nanoparticles were deposited. The atomic layer deposition (ALD) process involves bis (ethylcyclopentadienyl) ruthenium [Ru (EtCp) ₂ ] as a precursor and argon / oxygen mixed gas [flow; Ar / O = 15/15 sccm) at 350 ° C.

4 is a TEM image of ruthenium oxide nanoparticles prepared in Experimental Example 1. FIG. Referring to FIG. 4, it can be seen that ruthenium oxide nanoparticles can be uniformly formed along the shape of the zinc oxide nanorod using atomic layer deposition.

<Experimental Example 2>

The ruthenium oxide nanoparticles were deposited on the glass substrate by performing an atomic layer deposition method similar to Experimental Example 1, except that a glass substrate was used instead of the zinc oxide nanorod.

<Experimental Example 3>

In Experimental Examples 1 and 2, ruthenium oxide nanoparticles having various sizes were prepared by adjusting deposition conditions of an atomic layer deposition process.

FIG. 5 is a TEM image showing a change in size of nanoparticles according to an atomic layer deposition cycle (ALD cycle). Referring to FIG. 5, as the deposition period is changed to 10, 30, 50, and 70, the diameter of the nanoparticles may be increased to 5, 10, 20, 30 nm.

<Experimental Example 4>

In order to confirm the effect of increasing light absorption, the absorbance was measured by UV-Vis on the ruthenium oxide nanoparticles formed on the glass substrate and the zinc oxide nanorods according to Experimental Example 3.

6a and 6b are UV-Vis absorption spectra measured according to Experimental Example 4.

6A and 6B, it can be seen that light absorption in the visible region (1 to 3 eV) is increased by plasmon resonance of ruthenium oxide nanoparticles regardless of the type of substrate used. However, in the case of ruthenium oxide nanoparticles deposited on the zinc oxide nanorod, it can be seen that the light absorption in the ultraviolet region over the visible region (> 3 eV) is reduced than the light absorption of the zinc oxide nanorod itself (Fig. 6a). This is caused by the oscillation of the light absorption intensity of the zinc oxide conduction band due to the plasmon resonance phenomenon formed by the light absorption in the wide wavelength region of the ruthenium oxide nanoparticles. On the other hand, in the case of the glass substrate, light absorption due to its own conduction band does not occur even in the ultraviolet region, so this variation does not occur, and an increase in absorbance due to linear light absorption of ruthenium oxide itself is observed (FIG. 6B).

<Experimental Example 5>

Based on the absorbance intensity of the ruthenium oxide nanoparticles deposited at 70 cycles, the absorbance ratios of the ruthenium oxide nanoparticles deposited on the glass substrate and the zinc oxide nanorods were measured.

7 is a graph showing the absorbance ratio measured according to Experimental Example 5.

The size of ruthenium oxide particles increases in diameter to 5, 10, 20, and 30 nm as the ALD cycle changes to 10, 30, 50, and 70. At 30 nm, nanoparticles overlap each other. No more particle isolation occurs, so the surface plasmon resonance disappears. Therefore, as shown in FIG. 7, when the light energy of 1.6 eV, which is the visible light region, is selected and the ratio of the absorbance of particles of different sizes to the absorbance of 30 nm nanoparticles is plotted, similar absorption ratio regardless of substrate type It can be seen that it has. This means that absorption in the visible region is due to plasmon resonance of ruthenium oxide nanoparticles.

<Experimental Example 6>

Ruthenium oxide nanoparticles were deposited on zinc oxide nanorods and photoluminescence (PL) measurements were performed to measure the efficiency of light emission enhancement in the ultraviolet region (3.3 eV) emitted from pure zinc oxide nanorods.

8 is a graph showing the results of measuring light emission (PL) according to Experimental Example 6. FIG.

As shown in FIG. 8, it can be seen that ultraviolet light emission is increased until deposition of up to 50 deposition cycles (ALD cycle) to form particles having a diameter of 20 nm. However, since the particles deposited at 70 deposition cycles form a ruthenium oxide layer in the form of a thin film due to the continuous connection between the particles, the light emission enhancement effect due to the surface plasmon resonance phenomenon disappears, rather, the light emission intensity is weaker than that of pure zinc oxide.

<Experimental Example 7>

Time-resolved PL of the PL peak of 3.3 eV energy (corresponding to zinc oxide bandgap energy) to investigate the cause of surface plasmon resonance to increase the ultraviolet light emission of the zinc oxide nanorods. Measured using.

9 is a graph showing the PL attenuation effect measured according to Experimental Example 7.

As shown in FIG. 9, the decay time is shortest at 16 ps for the 10 nm ruthenium oxide nanoparticle having the highest PL intensity, which means that the electron-hole coupling rate for emitting light is the fastest. do. Therefore, it is interpreted that the coupling occurs within a short time with ultraviolet light emitted by the electromagnetic vibration due to surface plasmon resonance, resulting in an amplification of light intensity.

10 is an energy band diagram showing a state in which conductive oxide nanoparticles cause an increase in light absorption and light emission by surface plasmon resonance.

In particular, in this heterojunction structure, a charge transport phenomenon occurs in which the presence of hot electrons formed by the surface plasmons moves across the junction interface by surface plasmon resonance. As a result, the non-equilibrium local electron distribution according to the position affects the increase in light absorption and light emission. Therefore, by appropriately designing the interface electronic structure between the nanoparticles and the substrate (medium) -nanoparticles to enable the formation and charge transfer of such hot electrons, it is possible to improve the light efficiency at energy of a desired wavelength band.

While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it is to be understood that the invention is not limited to the disclosed exemplary embodiments, but, on the contrary, Change is possible.

100: substrate 110: first electrode
120: second electrode 130: photoactive layer (light absorption layer or light emitting layer)
200: conductive oxide nanoparticles 310: LED backlight
320: optical waveguide 330: diffusion layer
340: TFT array substrate

Claims (11)

A medium consisting of a dielectric or a semiconductor; And
Located on the surface or inside of the medium, the optical material including conductive oxide nanoparticles that interact with light in the visible to ultraviolet region to generate surface plasmon resonance. The method of claim 1,
The medium is any one selected from glass, plastic, silicon, a II-VI compound semiconductor, a III-V compound semiconductor, and a I-III-VI compound semiconductor. The method of claim 1,
The conductive oxide nanoparticles are ruthenium oxide, indium oxide, indium tin oxide, indium zinc oxide, fluorine-doped tin oxide, aluminum-doped zinc oxide, gallium-doped zinc oxide, magnesium-doped zinc oxide, molybdenum- An optical material that is any one nanoparticle selected from doped zinc oxide, aluminum-doped magnesium oxide, gallium-doped magnesium oxide, and indium-doped cadmium oxide. The method of claim 1,
The conductive oxide nanoparticles are optical materials having a diameter of 5 nm or more and less than 30 nm. The method of claim 1,
The medium is glass or zinc oxide, and the conductive oxide nanoparticles are ruthenium oxide nanoparticles. The method of claim 1,
Optical material which increases the absorption of visible light incident on the medium by the surface plasmon resonance or the emission of ultraviolet light emitted through the medium. The method of claim 1,
The optical material increases both the absorption of visible light incident on the medium by the surface plasmon resonance and the emission of ultraviolet light emitted through the medium. Preparing a medium consisting of a dielectric or a semiconductor; And
Forming conductive oxide nanoparticles on the medium using atomic layer chemical vapor deposition;
The conductive oxide nanoparticles interact with light in the visible or ultraviolet region to produce surface plasmon resonance. 9. The method of claim 8,
After forming the conductive oxide nanoparticles,
And covering the conductive oxide nanoparticles with a dielectric or semiconductor material constituting the medium. An optical element comprising the optical material of any one of claims 1 to 7. 11. The method of claim 10,
The optical device is a solar cell, a light emitting diode or a display device.

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