KR20130046975A - Light emitting complex and light emitting apparatus having the same - Google Patents

Abstract

PURPOSE: A light emitting composite and a light emitting device including the same are provided to improve light emission efficiency, by transferring excited electrons of buffer particles to a nano particle. CONSTITUTION: An emitter emits electrons. A light emission composite receives electrons from the emitter. The light emitting complex includes a nano particle(310) and buffer particles(320). The nano particle includes a compound semiconductor. The buffer particle is combined with the nano particle. The buffer particle has higher bandgap energy than the nano particle.

Description

LIGHT EMITTING COMPLEX AND LIGHT EMITTING APPARATUS HAVING THE SAME}

Embodiments relate to a light emitting composite and a light emitting device including the same.

In general, a flat panel display may be largely classified into a light emitting display device and a light receiving display device. The light emitting display device includes a cathode ray tube (CRT), a plasma display panel (PDP), and a field emission display (FED). There is a liquid crystal display (LCD). The liquid crystal display has the advantages of light weight and low power consumption. However, since the LCD itself does not emit light to form an image, and the light is incident on the outside, the liquid crystal display device forms an image. There is no problem. In order to solve this problem, a backlight unit is provided on the back of the liquid crystal display.

Conventionally, a cold cathode fluorescent lamp (CCFL) as a light source and a light emitting diode (LED) as a point light source have been mainly used as a backlight unit. However, such a backlight unit generally has a disadvantage in that its construction is complicated and high in manufacturing cost, and the light source has a large power consumption due to reflection and transmission of light at the side. In particular, as the liquid crystal display becomes larger, it is difficult to secure uniformity of luminance.

Accordingly, recently, in order to solve the above problems, a field emission type backlight unit having a planar light emitting structure has been developed. The field emission type backlight unit consumes less power than a conventional backlight unit using a cold cathode fluorescent lamp, and has a relatively uniform luminance even in a wide range of light emitting regions. On the other hand, the field emission backlight unit as described above can also be used as illumination.

In the conventional field emission apparatus, the upper substrate and the lower substrate are arranged to face each other at a predetermined interval. An anode electrode is formed on the bottom surface of the upper substrate, and a phosphor layer is formed on the bottom surface of the anode electrode. The cathode is formed on the upper surface of the lower substrate. The cathode electrode may have a flat plate shape.

An insulating layer is formed on the cathode electrode, and gate electrodes are formed side by side at a predetermined interval in a stripe shape on the insulating layer. A gate hole and a cavity are formed in the gate electrode and the insulating layer, respectively, and a plurality of emitters made of electron-emitting materials such as carbon nanotubes (CNT) are provided on the cathode electrode exposed through the gate hole. have.

In the above structure, as voltage is applied between the cathode electrode and the gate electrode, electrons are emitted from the emitter provided on the cathode electrode, and the emitted electrons are accelerated by the voltage applied to the anode electrode to excite the phosphor layer. By emitting visible light.

Embodiments provide a light emitting device having improved performance and durability.

A light emitting device according to the embodiment includes an emitter emitting electrons; And a light emitting composite that receives electrons from the emitter, wherein the light emitting composite includes nanoparticles including a compound semiconductor; And buffer particles coupled to the nanoparticles and having a greater bandgap energy than the nanoparticles.

In one embodiment, a light emitting composite includes nanoparticles including a compound semiconductor; And buffer particles connected to the nanoparticles and having a greater bandgap energy than the nanoparticles.

The light emitting composite according to the embodiment includes the buffer particles having a greater bandgap energy than the nanoparticles. Accordingly, the electrons of the buffer particles are excited through the electrons from the emitter, and the electrons thus excited may be transferred to the nanoparticles.

Accordingly, the light emitting composite according to the embodiment may have an improved light emission efficiency.

In addition, the buffer particles may perform a scattering function. Accordingly, the light generated from the nanoparticles may be emitted uniformly as a whole. Thus, the light emitting device according to the embodiment may have improved luminance uniformity.

1 is a cross-sectional view illustrating a light emitting device according to an embodiment.
2 is a view showing a light emitting composite.
3 is a diagram illustrating a conduction band and a balance band of a light emitting composite.
4 is a diagram illustrating another example of a light emitting composite.
5 is a view showing another example of a light emitting composite.

In the description of the embodiments, it is described that each substrate, frame, sheet, layer or pattern is formed "on" or "under" each substrate, frame, sheet, In this case, "on" and "under " all include being formed either directly or indirectly through another element. In addition, the upper or lower reference of each component is described with reference to the drawings. The size of each component in the drawings may be exaggerated for the sake of explanation and does not mean the size actually applied.

1 is a cross-sectional view illustrating a light emitting device according to an embodiment. 2 is a view showing a light emitting composite. 3 is a diagram illustrating a conduction band and a balance band of a light emitting composite. 4 is a diagram illustrating another example of a light emitting composite. 5 is a view showing another example of a light emitting composite.

1 to 4, the light emitting device according to the embodiment may include a lower substrate 110, an upper substrate 210, a cathode electrode 120, an insulating layer 140, a gate electrode 150, and an emitter 130. ), A spacer 160, an anode electrode 220, a black matrix 230, and a plurality of light emitting composites 300.

The lower substrate 110 supports the cathode electrode 120, the insulating layer 140, the gate electrode 150, and the emitter 130. The lower substrate 110 faces the upper substrate 210. The lower substrate 110 is an insulator. A glass substrate or a plastic substrate may be used as the lower substrate 110.

The upper substrate 210 is disposed on the lower substrate 110. The upper substrate 210 faces the lower substrate 110. The upper substrate 210 supports the anode electrode 220, the black matrix 230, and the light emitting composites 300. The upper substrate 210 is transparent. The upper substrate 210 includes an insulator. A glass substrate or a plastic substrate may be used as the upper substrate 210.

The cathode electrode 120 is disposed on the lower substrate 110. The cathode electrode 120 may be disposed in a stripe shape on the upper surface of the lower substrate 110. A transparent conductor may be used as the cathode electrode 120. In more detail, indium tin oxide (ITO) or indium zinc oxide (IZO) may be used as the cathode electrode 120. The cathode electrode 120 may have a thickness of about 100 nm to about 250 nm.

The insulating layer 140 is disposed on the cathode electrode 120. The insulating layer 140 includes a plurality of gate holes 141. Examples of the material used as the insulating layer 140 may include silicon oxide, silicon nitride, or the like. The insulating layer 140 may have a thickness of several μm to several tens of μm.

The gate electrode 150 is disposed on the insulating layer 140. The gate electrode 150 may be formed of an opaque material. Examples of the material used as the gate electrode 150 include silver (Ag), copper (Cu), aluminum (Al), chromium (Cr), and the like.

The gate electrode 150 may have a shape extending in one direction. For example, the gate electrode 150 may be arranged in a stripe shape. In addition, the gate electrode 150 may extend in a direction crossing the cathode electrode 120. The gate electrode 150 may have a thickness of about 100 nm to about 300 nm.

In addition, a portion of the gate electrode 150 may overlap the gate holes 141. That is, a part of the gate electrode 150 may extend laterally to cover a part of inlets of the gate holes 141.

The emitter 130 is disposed on the cathode electrode 120. The emitter 130 is disposed in the gate holes 141. The emitter 130 may have a shape extending toward the anode electrode 220. That is, the emitter 130 extends upward.

Examples of the material used as the emitter 130 may include carbon nanotubes (CNTs). When the emitter 130 is made of carbon nanotubes, the emitter 130 may be driven at a low voltage.

The spacer 160 is disposed between the lower substrate 110 and the upper substrate 210. The spacer 160 keeps the gap between the lower substrate 110 and the upper substrate 210 constant. The spacer 160 may be disposed on the gate electrode 150. Curable polymer may be used as the spacer 160.

The anode electrode 220 is disposed below the upper substrate 210. The anode electrode 220 is coated on the lower surface of the upper substrate 210. The anode electrode 220 is transparent. The anode electrode 220 may be entirely coated on the bottom surface of the upper substrate 210. Examples of the material used as the anode electrode 220 may include indium tin oxide or indium zinc oxide.

The black matrix 230 is disposed below the upper substrate 210. The black matrix 230 may be disposed under the anode electrode 220. The black matrix 230 blocks light. By the black matrix 230, the upper substrate 210 may be divided in pixel units.

The light emitting composite 300 is disposed below the anode electrode 220. The light emitting composite 300 may be in direct contact with the anode electrode 220. The light emitting composite 300 is connected to the anode electrode 220. The light emitting composite 300 receives light from the emitter 130 to generate light.

In addition, the light emitting device according to the embodiment may include a sealing layer covering the light emitting composite 300. The sealing layer protects the light emitting composite 300 from external moisture and / or oxygen.

As shown in FIG. 2, the light emitting composite 300 includes nanoparticles 310 and buffer particles 320.

The nanoparticles 310 may include a semiconductor compound. The nanoparticles 310 may have a nanocrystal structure of a semiconductor compound. In more detail, the nanoparticles 310 may generate light by incident electrons. The nanoparticles 310 may be quantum dots.

The quantum dot may include a core nanocrystal and a shell nanocrystal surrounding the core nanocrystal.

The shell nanocrystals may be formed of two or more layers. The shell nanocrystals are formed on the surface of the core nanocrystals. The quantum dot can change the wavelength of light that is incident on the core nanocrystals to a longer wavelength through the shell nanocrystals forming the shell layer and increase the light efficiency.

The quantum dot may include at least one of a group II compound semiconductor, a group III compound semiconductor, a group V compound semiconductor, and a group VI compound semiconductor. In more detail, the core nanocrystals may include CdSe, InGaP, CdTe, CdS, ZnSe, ZnTe, ZnS, HgTe or HgS. The shell nanocrystals may include CuZnS, CdSe, CdTe, CdS, ZnSe, ZnTe, ZnS, HgTe or HgS.

The wavelength of the light emitted from the quantum dot can be adjusted according to the size of the quantum dot, for example.

Particularly, when the quantum dot has a size smaller than the Bohr radius of an exciton formed by electrons and holes excited by light, electricity or the like, a quantum confinement effect is generated to have a staggering energy level and an energy gap The size of the image is changed. Further, the charge is confined within the quantum dots, so that it has a high luminous efficiency.

Unlike general fluorescent dyes, the quantum dots vary in fluorescence wavelength depending on the particle size. That is, as the size of the particle becomes smaller, it emits light having a shorter wavelength, and the particle size can be adjusted to produce fluorescence in a visible light region of a desired wavelength. In addition, since the extinction coefficient is 100 to 1000 times higher than that of a general dye, and the quantum yield is also high, it produces very high fluorescence.

The quantum dot can be synthesized by a chemical wet process. Here, the chemical wet method is a method of growing particles by adding a precursor material to an organic solvent, and the quantum dots can be synthesized by a chemical wet method.

In addition, a ligand may be bound around the quantum dot. The ligand surrounds the quantum dot. In more detail, one end of the ligand may be bonded to the outer surface of the quantum dot, so as to surround the quantum dot.

In addition, the ligand serves to stabilize unstable quantum dots after synthesis. After synthesis, a dangling bond is formed on the outer periphery, and the quantum dots may become unstable due to the dangling bonds. However, one end of the ligand is in an unbound state, and one end of the unbound ligand may bind with a dangling bond to stabilize the quantum dot.

The ligand may include pyridine, mercapto alcohol, thiol, phosphine, or phosphine oxide. In addition, the ligand may include polyethyleneimine, 3-amino propyltrimethoxy silane, mercaptoacetic acid, 3-mercaptopropyl trimethoxy silane or 3-mercaptopropionic acid, and the like. have. In addition, various hydrophilic organic ligands may be used as the ligand.

The buffer particle 320 is coupled to the nanoparticle 310. The buffer particle 320 is coupled to the nanoparticle 310. In more detail, the buffer particles 320 may be coupled to the nanoparticles 310 through the connector 330.

The linker 330 may be an organic ligand. The connector 330 may be represented by Formula 1 below.

Formula 1

HS-R-COOH

Here, R may be an alkyl group having 1 to 30 carbon atoms.

For example, 3-mercaptopropionic acid, 3-mercaptoisobutyric acid, and the like may be mentioned as the linker 330.

One end of the connector 330 is coupled to the nanoparticles 310, and the other end of the connector 330 is connected to the buffer particles 320.

The buffer particle 320 may be transparent. Metal oxide may be used as the buffer particle 320. In more detail, the buffer particle 320 may include titanium oxide. The buffer particle 320 may have a diameter of about 10 nm to about 100 nm. The bandgap energy of the buffer particle 320 may be about 3.0 eV to about 3.5 eV.

The light emitting composite 300 may be formed by the following process.

First, core nanocrystals may be formed by a wet method. That is, precursor materials may react in a solvent, so that crystals may grow and the core nanocrystals may be formed.

For example, to form CdS core nanocrystals, tri-n-octylphosphine oxide (TOPO), tri-butylphosphine (TBP) and hexadecylamine (Hexadecylamine; HDA) Surfactants and solvents may be used.

In addition, cadmium precursor (CdO), cadmium sulfate or cadmium acetate may be used as the cadmium precursor material, and mercapto ethanol or sodium sulfide (Na ₂ S) may be used as the sulfur precursor material.

In addition, the shell nanocrystals may also be formed by a wet method. That is, the precursor material may be added to the solution including the core nanocrystals, reacted, and the crystals are grown to form the shell nanocrystals.

For example, to form a quantum dot having a CdS / ZnS structure, a zinc precursor material and the sulfur precursor material may be injected into a solution containing the CdS core nanocrystals. By reaction of the zinc precursor material and the sulfur precursor material, a shell nanocrystal may be formed, and a quantum dot of the CdS / ZnS structure may be formed. Examples of the zinc precursor material include zinc acetate (Zn (CH ₃ COO) ₂ ) and the like.

Thereafter, the buffer particles 320 may be added to the solution including the nanoparticles 310. The buffer particles 320 may be formed by sol-gel synthesis, gas phase condensation, chemical precipitation, or hydrothermal synthesis.

For example, in order to form the buffer particles 320, a metal organic compound or a metal salt is hydrolyzed to form a sol in which colloidal particles are dispersed. Then, through condensation polymerization, a gel in which the colloidal particles are bonded in a three-dimensional network structure is formed. Thereafter, the buffer particles 320 may be formed through a drying and milling process.

Thereafter, the connector 330 may be added to the solution including the nanoparticles 310 and the buffer particles 320, and the nanoparticles 310 and the buffer particles 320 may be coupled to each other. . That is, 3-mercaptopropionic acid or 3-mercaptoisobutyric acid is added to the solution containing the quantum dots and titanium oxide particles. Thereafter, at a temperature of about 70 ° C. to about 100 ° C., by the reaction process for about 1 hour to about 4 hours, the nanoparticles 310 and the buffer particles 320 are formed through the connector 330. Can be combined with each other.

The light emitting device according to the embodiment further includes a driver 400 for applying a driving signal to the cathode electrode 120, the gate electrode 150, and the anode electrode 220.

A negative voltage (−) is applied to the cathode electrode 120, and a ground voltage or a positive voltage (+) is applied to the gate electrode 150. In addition, a very high positive voltage (++) is applied to the anode electrode 220. For example, a pulse voltage of about −60 V may be applied to the cathode electrode 120 at a period of about 60 μs, and a ground voltage may be applied to the gate electrode 150. In addition, a positive voltage of + 10V to + 60V may be applied to the anode electrode 220.

Accordingly, electrons are emitted through the emitter 130, and the emitted electrons are incident on the anode electrode 220 through the light emitting composite 300.

As shown in FIG. 3, the buffer particles 320 have a greater energy bandgap energy than the nanoparticles 310. For example, the band gap energy of the buffer particle 320 may be 3.0 eV to 3.5 eV, and the band gap energy of the nanoparticle 310 may be about 1.3 eV to about 2.74 eV.

In addition, the conduction band of the buffer particle 320 may be substantially similar to the conduction band of the nanoparticle 310. The conduction band of the buffer particle 320 may be about 7.2 eV to about 8 eV. The conduction band of the nanoparticles 310 may be about 6.05 eV to about 7.13 eV. In this case, the difference between the conduction band of the buffer particle 320 and the conduction band of the nanoparticles 310 may be about 0.07 eV to about 1.95 eV.

In particular, when the buffer particles 320 are titanium oxide particles having a diameter of about 10 nm to about 100 nm, the nanoparticles have cadmium telluride (CdTe), cadmium seleide having a diameter of about 1 nm to about 20 nm. Nide (CdSe), cadmium sulfide (CdS), indium phosphide (InP), zinc selenide (ZeSe) or zinc telluride (ZnTe) particles.

Accordingly, the buffer particles 320 are excited by the electrons emitted from the emitter 130, the energy of the buffer particles 320 is transferred to the nanoparticles 310, and thus, the nanoparticles 310. ) Can emit light. That is, energy due to electrons from the emitter 130 may be transferred to the nanoparticles 310 through the buffer particles 320.

Accordingly, the buffer particles 320 may not correspond to the nanoparticles 310, but may correspond to energy transfer particles that transmit energy of electrons passing through the nanoparticles 310. Accordingly, even if the nanoparticles 310 are used less, the light emitting device according to the embodiment may have improved light emission efficiency.

In addition, the buffer particles 320 may receive electrons from the nanoparticles 310, may be excited, and then transfer energy to the nanoparticles 310 again. That is, the buffer particles 320 may be energy receiving particles.

As a result, the buffer particles 320 correspond to emission auxiliary particles that enhance the emission characteristics of the nanoparticles 310.

In addition, light generated from the nanoparticles 310 may be scattered by the buffer particles 320. Accordingly, light having an improved luminance uniformity may be emitted through the upper substrate 210. That is, the buffer particles 320 correspond to scattering particles.

Referring to FIG. 4, a plurality of nanoparticles 310 may be coupled to one buffer particle 320. Alternatively, although not shown in the drawing, a plurality of buffer particles 320 may be combined with one nanoparticle 310. By controlling the concentration of the buffer particles 320 and the nanoparticles 310, the ratio of the number of the buffer particles 320 and the nanoparticles 310 may be controlled.

Referring to FIG. 5, the nanoparticles 310 may be disposed in the buffer particles 320. That is, the buffer particles 320 may surround the nanoparticles 310.

As described above, the light emitting composite 300 includes the buffer particles 320 having a bandgap energy greater than that of the nanoparticles 310. Accordingly, the electrons of the buffer particle 320 may be excited through the electrons from the emitter 130, and the electrons thus excited may be transferred to the nanoparticles 310.

Accordingly, the light emitting device according to the embodiment may have improved luminous efficiency.

In addition, the buffer particles 320 may perform a scattering function. Accordingly, the light generated from the nanoparticles 310 may be emitted uniformly as a whole. Thus, the light emitting device according to the embodiment may have improved luminance uniformity.

In addition, the light emitting composite 300 is described as being used to emit light by electrons, but is not limited thereto.

That is, the light emitting composite 300 may generate light by receiving external energy, for example, light having a short wavelength band.

In addition, the features, structures, effects and the like described in the embodiments are included in at least one embodiment of the present invention, and are not necessarily limited to only one embodiment. Furthermore, the features, structures, effects, and the like illustrated in the embodiments may be combined or modified with respect to other embodiments by those skilled in the art to which the embodiments belong. Therefore, it should be understood that the present invention is not limited to these combinations and modifications.

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, It will be understood that various modifications and applications are possible. For example, each component specifically shown in the embodiments can be modified and implemented. It is to be understood that all changes and modifications that come within the meaning and range of equivalency of the claims are therefore intended to be embraced therein.

Claims (11)

Emitters that emit electrons; And
It includes a light emitting composite that receives the electrons from the emitter,
The light emitting complex is
Nanoparticles comprising a compound semiconductor; And
And a buffer particle coupled to the nanoparticle and having a greater bandgap energy than the nanoparticle. The method of claim 1, wherein the nanoparticles are quantum dots,
The buffer particle comprises a titanium oxide. The method of claim 2, wherein the band gap energy of the nanoparticles is 1.3eV to 2.74eV,
The light emitting device has a diameter of the buffer particles of 10nm to 100nm. The light emitting device of claim 3, wherein the conduction band of the nanoparticles is 6.05 eV to 7.13 eV. The light emitting device of claim 4, wherein the connector comprises a material represented by Chemical Formula 1 below.
Formula 1
HS-R-COOH
Here, R is an alkyl group having 1 to 30 carbon atoms. The light emitting device of claim 1, wherein the buffer particles are transparent. The light emitting device of claim 1, further comprising a connector connected to the nanoparticles and the buffer particles. Nanoparticles comprising a compound semiconductor; And
And a buffer particle connected to the nanoparticle, the buffer particle having a greater bandgap energy than the nanoparticle. The light emitting composite of claim 8, wherein a difference between the conduction band of the nanoparticles and the conduction band of the buffer particles is 0.07 eV to 1.95 eV. The method of claim 9, wherein the band gap energy of the nanoparticles is 1.3eV to 2.74eV,
The energy band gap of the buffer particles is 3.0eV to 3.5eV luminescent composite. The method of claim 8, wherein the buffer particles comprise titanium oxide,
The nanoparticles include cadmium telluride, cadmium selenide, cadmium sulfide, indium phosphide, zinc selenide or zinc telluride.

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