KR100416493B1 - White light emission device and the method thereof - Google Patents

Abstract

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a white light emitting device using a polymer or an inorganic material capable of dispersing and immobilizing quantum dots well prepared by a wet chemical method and a method of manufacturing the same. The white light emitting device includes an active layer including a substrate layer supporting a quantum dot and a conductive polymer, an anode electrode layer formed on the substrate layer, and semiconductor quantum dots formed on the anode to emit red, green, and blue colors, and the active layer. And a matrix layer formed on upper and lower surfaces of the cathode electrode and the active layer formed thereon to promote charge transport to the active layer.

Description

White light emitting device and method for manufacturing same

TECHNICAL FIELD The present invention relates to a semiconductor light source, and more particularly, to a white light emitting device and a method of manufacturing the same.

The white light emitting device is used as a substitute for an illuminator and as a light source having an application such as a back light of a liquid crystal display (LCD) device.

The conventional white light emitting device is implemented by a method of combining light sources emitting different colors or using a polymer material having luminescence. A method of combining light sources emitting different colors combines a blue light source with a yellow light source, resulting in white light. It is known to combine white YAG phosphors that absorb yellow from GaN blue LEDs (light emitting diodes) and blue from the GaN blue LEDs themselves to realize white light. This method requires expensive MOCVD or MBE equipment in order to manufacture GaN blue LED, which is a blue light source, and has a disadvantage of requiring a large facility cost in the early stage. In addition, when light emitting monomolecules or polymer materials are used, the maximum light emission efficiency is about 25% due to spin statistical dynamics for light emission that complies with the electron transition selection rule. In addition, in the case of single molecules containing heavy metals in which the electron transition selection rule is not well observed, the emission efficiency is about 75% due to the electrophosphorescence phenomenon using triplets. Therefore, when the light emitting monomolecule or the polymer material is used, the light emission efficiency is within 25% to 75% at maximum. However, a white light emitting device using semiconductor quantum dots as a light source has a luminous efficiency of 100%. In addition, semiconductor quantum dots have excellent photochemical and thermal stability compared to the above-mentioned organic monomolecules or polymers.

Therefore, the development of a white light emitting device and a cheap and easy manufacturing technology capable of producing the same through a quantum dot having a high luminous efficiency is required.

SUMMARY OF THE INVENTION An object of the present invention is to provide a white light emitting device using semiconductor quantum dots which is low in production cost, easy, has high luminous efficiency and is excellent in photochemical and thermal stability.

1 is a view showing a white light emitting device according to a first embodiment of the present invention.

4 is a view showing equipment for manufacturing a white light emitting device of the present invention.

* Explanation of symbols for main parts of the drawings

10 white light emitting device 20 substrate layer

30: active layer 32: hole transport layer

36: electron transport layer 50, 52: electrode 100: glove box 200: reaction vessel

In order to achieve the above object, a white light emitting device according to an embodiment of the present invention includes a substrate layer supporting a quantum dot and a conductive polymer, an anode electrode layer formed on the substrate layer, and formed on the anode electrode to be red, green, and blue. And an active layer including semiconductor quantum dots emitting light, a cathode electrode formed on the active layer, and a matrix layer formed on upper and lower surfaces of the active layer to promote charge transport to the active layer.

According to another aspect of the present invention, there is provided a method of manufacturing a white light emitting device, the method including forming an anode electrode on a substrate layer, forming a polymer charge transport layer on the anode electrode, and red, green, and blue colors on the charge transport layer. Forming an active layer including quantum dots emitting light and forming a cathode on the active layer.

The advantage of the white light emitting device of the present invention is that by using the quantum localization phenomenon, the quantum dots emitting red, the quantum dots emitting green, and the quantum dots emitting blue, which emit red with high color purity, respectively, by controlling the size of quantum dots without changing the material When the three quantum dots of each primary color are mixed, white color can be produced, and these quantum dots have almost 100% of their luminous efficiency.

Advantages of the method of manufacturing a white light emitting device of the present invention can realize a desired color, that is, red, green, and blue, only through size adjustment of quantum dots formed from a selected semiconductor material without using different materials to realize each color. As a result, the light emitting device can be made easily and inexpensively.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings. For each figure, like reference numerals denote like elements.

1 is a cross-sectional view of a white light emitting device 10 of the first embodiment according to the present invention. Referring to this, the white light emitting device 10 includes a substrate layer 20, an anode electrode 50 formed on the substrate layer 20 and acting like a transparent electrode, and a single film or a multilayer film structure. The active layer 30, which is a light expression layer, and a polymer material such as PPV (p-paraphenylene vinylene) having high conductivity and high band gap with respect to electrons or holes (charges) are formed on and under the active layer 30. The matrix 32 and 36 and the cathode electrode 52 are sequentially formed. In particular, the active layer 30 is an RGB quantum dot layer composed of RGB quantum dots. to be. The active layer 30 may be formed of a single layer quantum mucosa containing RGB quantum dots simultaneously, or alternatively, a multilayer film in which red, green, and blue quantum mucosa layers are stacked separately. Here, the quantum dots are core / shell structures, and the quantum dots of the core / shell structures have cadmium selenide quantum as a core and are surrounded by zinc sulfide (ZnS) around the core. It is preferable that the active layer 30 has a thickness of several hundreds to thousands of micrometers.

In addition, the matrices 32 and 36 specifically include a hole transport layer 32 made of a polymer material such as PPV, PMA, SPS, and TPD having a large band gap, and an electron composed of an inorganic semiconductor or a polymer having a large electron transfer coefficient. Although divided into the transport layer 36, substantially the same function as the charge transport layer to facilitate the transport of electrons, holes and the like to the active layer 30.

In addition, the electrodes 50 and 52 smoothly supply electrons or holes from the power source to activate the white light emitting device 10 so that white light can be generated.

In other words, the white light emitting device 10 of FIG. 1 preferably has a substrate layer 20-an anode electrode 50-a hole transport layer 32-an active layer 30-an electron transport layer 36-a cathode electrode 52 Has a structure composed of However, there is no need for the electron transport layer 36 to function as a charge transport layer. The white light emitting device 10 according to the embodiment of the present invention described above is dispersed with RGB quantum dots to form an active layer having a single layer structure. Or an active layer having a multilayer film structure in which each of the red quantum dot layer, the green quantum dot layer, and the blue quantum dot layer is laminated. In this case, quantum dots of different sizes emit a unique emission wavelength at each size due to quantum localization. That is, white light is expressed by mixing light of red, green, and blue emission wavelengths.

In other words, the white light emitting device 10 transmits the three primary colors of light emitted from the RGB quantum dots through the anode electrode 50, which is a transparent electrode, and the three primary colors of the light are mixed to realize white light. Close to 100%. As a result, the emission spectrum line width from the semiconductor quantum dots is very narrow, resulting in high color purity. This means that it has high luminous efficiency and good color purity as compared with the conventional white light emitting device.

The method of manufacturing the white light emitting device (hereinafter referred to as "LED") of the present invention will now be described.

4 is a view schematically showing a cross section of a glove box and a reaction vessel 200 used to manufacture the LED 10 of the present invention. The glove box 100 and the reaction vessel 200 are sensitive to the initial reaction oxygen and water and are prepared in the glove box to maintain the reactivity of the precursors through isolation therefrom.

First, trioctylphosphine selenium (TOPSe) is stored in the glove box 100, and the internal atmosphere gas is nitrogen (N ₂ ) or argon (Ar) gas. Trioctylphosphine selenium is mixed with trioctyl phosphine ([(CH ₃ (CH ₂ ) ₇ )] ₃ P) and selenium (Se) in vials to make compound TOPSe. 10 ml of trioctylphosphine When 0.7896 g of selenium reacts, about 1 mole (M) of trioctylphosphine selenium solution is produced. Trioctylphosphine selenium is used by taking the required amount using a pipette.

First step

The first step represents a series of processes for forming cadmium selenide quantum dots. Trioctylphosphine oxide ([(CH ₃ (CH ₂ ) ₇ )] ₃ P = O) in the solid state was added to the reaction vessel 200 and heated for 20 minutes at a pressure of 1 tor and a temperature of 200 ° C. Eliminate any extra oxygen that may be present in the compound. In this way, trioctylphosphine oxide is dried. Thereafter, the dried trioctylphosphine oxide is heated to 310 ° C. under an atmosphere of nitrogen (N ₂ ) gas or argon (Ar) gas at 1 atmosphere (atm).

Meanwhile, in the glove box 100, 1 ml of trioctylphosphine selenium and dimethyl cadmium (Me₂Cd) 82 μl are mixed. When this mixture at room temperature is rapidly injected into the reaction vessel heated to 310 캜, the temperature of the reaction vessel drops rapidly to 180 캜. At this time, the rapid temperature difference makes the inside of the reaction vessel supersaturated, so that it promotes the nucleation reaction similar to the precipitation process, thereby uniform cadmium selenide (CdSe) Nuclei are produced. Thereafter, when the temperature of the reaction vessel 200 is gradually raised, cadmium selenide grows. During growth, the temperature of the reaction vessel 200 is maintained at 230 ° C. or 260 ° C., and the cadmium selenium quantum dots are grown to a desired size through growth time and temperature control of the reaction vessel. The grown cadmium selenium quantum dots will be cadmium selenium quantum dots, 55-65 55 red, 40-50Å green, and 25-35Å blue.

2nd step

The second step represents a series of processes for forming the quantum dots of the core / shell structure. First, the temperature of the reaction vessel 200 containing the cadmium selenide quantum dots formed in the first step is maintained at 230 ℃ to 260 ℃. Hexamethyldisilasyene ((TMS) ₂ S) and diethylzinc (Et ₂ Zn) are injected into the reaction vessel 200 to react with cadmium selenide quantum dots for a certain time. Specifically, 0.16 ml of hexamethyldisilasyene and 62 μl of diethyl zinc are injected and reacted for 24 hours. As a result of the reaction, a structure in which cadmium selenide quantum dots is used as a core and zinc sulfide (ZnS) is surrounded around the core is formed. This structure is called a core / shell structure. The core / shell structure forms quantum dots that emit red, green, and blue, respectively, depending on the size of the bare-dots forming the core mentioned above. The core-shell structure is intended to reduce stabilization and surface defect states of quantum dots. For example, the core shell structure may have a quantum dot size of 55 to 65 microseconds red, a size of 40 to 50 microns green, and a size of 25 to 35 microns blue.

3rd step

The third step represents a series of processes for forming an active layer that expresses white light. The quantum dots of the core / shell structure formed through the first and second steps are mixed well and then dissolved in hexane. Thereafter, the quantum dots are dispersed in a polymer to be immobilized and a solvent which simultaneously dissolves the quantum dots to form a quantum dot film by a spin coating method. This quantum dot film becomes an active layer and is formed of a single layer film or a multilayer film. The polymer containing quantum dots to fix the quantum dots is a material having a larger band gap than the semiconductor quantum dots, and as one example, a PPV polymer or the like is used. PPV polymers have excellent conductivity with respect to carriers, that is, electrons and holes, and have a large bandgap.

The quantum dot film is formed by a spin coating method to form a single layer film or a multilayer film structure and has a thickness of about 0.1 μm to 1.0 μm. The RGB quantum dot single layer film is formed by mixing RGB quantum dots together, and the multilayer film structure is formed by stacking quantum dot layers emitting red, green, and blue colors in a stacked structure. RGB quantum dot film is vacuum thin film deposition (vaccumn thin film deposition) method or dispersed in a polymer to form a thickness of about several hundred to thousands Å by spin coating method. That is, the layer which consists of RGB quantum mucosa is an active layer, and this layer expresses white light.

4th step

The fourth step represents a series of processes to form the LED. A charge transport layer is formed above and below the RGB quantum dot monolayer or multilayer film, which is an active layer that is a white light expression layer formed in the third step. The charge transport layer forms a polymer such as TPD by spin coating.

Thereafter, electrodes are formed on the upper and lower ends of the charge transport layer in contact with the upper and lower sides. The upper electrode and the lower electrode are composed of any one material of ITO, ZnO, Al, Ca, Sc, Eu, Ni, Pt, Au, Mg or more. The electrode is formed to form an ohmic contact electrically at the time of electrode formation, and finally, an LED is formed.

Accordingly, a method of manufacturing a white light emitting device of the present invention is to manufacture a quantum dots by a wet chemical method and to adjust the size of the quantum dots, to implement a white light emitting device that emits white with high luminous efficiency.

In the manufacturing method of the present invention, a light emitting device can be easily and inexpensively made using a glove box, etc., compared to a method for manufacturing light emitting devices using a general semiconductor manufacturing process, which requires a large cost for installing and maintaining semiconductor devices. In addition, only the size of a quantum dot of one material may be adjusted without adding various other materials to achieve a desired color, ie, red, green, and blue.

Although the present invention has been described with reference to one embodiment shown in the drawings, this is merely exemplary, and it will be understood by those skilled in the art that various modifications and equivalent other embodiments are possible. In the method of manufacturing a white light emitting device of the present invention, when forming a composite with a solid laser, a chemical catalyst, and a conductive polymer material, a plastic diode, a plastic transistor, a collapsible display, a lighting device, etc. It may be used across several fields. Therefore, the true technical protection scope of the present invention will be defined by the technical spirit of the appended claims.

According to the white light emitting device of the present invention described above, quantum dots emitting red, quantum dots emitting green, and quantum dots emitting blue have high color purity and emit white by mixing three primary colors of light therefrom. The luminous efficiency of these quantum dots is almost 100%. In addition, the manufacturing method of the white light emitting device of the present invention can realize a desired color, that is, red, green, and blue by only adjusting the size of the quantum dots without adding other materials, thereby making it easy and inexpensive to manufacture the light emitting device.

Claims (29)

A substrate layer supporting the quantum dots and the conductive polymer; An anode electrode layer formed on the substrate layer; An active layer formed on the anode and including semiconductor quantum dots emitting red, green, and blue light; A cathode electrode formed on the active layer; And And a matrix layer formed on upper and lower surfaces of the active layer to facilitate charge transport to the active layer. The method of claim 1, wherein the substrate layer A white light emitting device characterized in that the material having a large band gap composed of glass, ITO or ZnO, is a transparent material in the visible region. The method of claim 2, wherein the polymer matrix layer A white light emitting device, characterized in that composed of PPV (P-Paraphenylene Vinylene). The method of claim 1, wherein the active layer And a quantum dot film structure in which quantum dots of a core / shell structure in which cadmium selenide quantum dots are used as a core and zinc sulfide is wrapped around the core are fixed. The method of claim 1, wherein the electrodes ITO, ZnO, Al, Ca, Sc, Eu, Ni, Pt, Au, Mg or a white light emitting device characterized in that any one or more of the materials are coated on Ag. delete Forming an anode electrode over the substrate layer; Forming a polymer charge transport layer on the anode electrode; Forming an active layer including quantum dots emitting red, green, and blue on the charge transport layer; And And forming a cathode on the active layer. The method of claim 7, wherein the forming of the active layer comprises forming a quantum dot film in which quantum dots of a core / shell structure in which cadmium selenide quantum dots are used as cores and zinc sulfide are wrapped around the core are fixed. Method of manufacturing a white light emitting device. delete The method of claim 8, wherein forming the quantum mucosa (I) drying the trioctylphosphine oxide; (Ii) heating the dried trioctylphosphine oxide under nitrogen gas and argon gas atmosphere; (Iii) mixing trioctylphosphine selenium and dimethyl cadmium; (Iv) growing the cadmium selenide quantum dot in a reaction vessel by using the mixture of step (iii) in the reaction solvent using the resultant of step (ii) as a high temperature solvent; (V) reacting the cadmium selenide quantum dots with hexamethyldisilasyene and diethylzinc to form a first quantum dot of the core / shell structure; And And (vi) mixing the first quantum dots of the core / shell structure well and dissolving them in hexane to disperse the first quantum dots to form the first quantum dot film. . The method of claim 10, wherein the trioctylphosphine selenium is A method of manufacturing a white light emitting device, characterized in that it is made by reacting trioctylphosphine and selenium. The method of claim 11, wherein the trioctylphosphine selenium is 10 ml of the trioctylphosphine and 0.7896 g of the selenium react to form 1 mole (M). The method of claim 10, wherein step (i) And drying the trioctylphosphine oxide at a pressure of 1 torr and a temperature of 200 ° C. for 20 minutes. The method of claim 10, wherein step (ii) And heating to 310 ° C. under an atmosphere of nitrogen gas and argon (Ar) at 1 atmosphere. The method of claim 10, wherein step (iii) And mixing 1 ml of the trioctylphosphine selenium and 82 µl of dimethyl cadmium (Me ₂ Cd). The method of claim 10, wherein step (iv) During the growth, the temperature of the reaction vessel 200 is maintained at 230 ° C. to 260 ° C., and a method of manufacturing a white light emitting device characterized in that the growth of cadmium selenide quantum dots to a desired size by controlling the temperature of the reaction vessel. . The method of claim 16, wherein the grown cadmium selenium quantum dot is A method of manufacturing a white light emitting device, characterized in that the size is 55 ~ 65 Å red, the size 40 ~ 50 녹색 green, the size 25 ~ 35 Å blue. The method of claim 10, wherein step (v) Method of manufacturing a white light emitting device, characterized in that the step of reacting for 24 hours by injecting 0.16 ml of hexamethyldisilasyene and 62 μl of diethyl zinc. The method of claim 10, wherein the quantum dot of the core / shell structure grown in the step (v) is A method of manufacturing a white light emitting device, characterized in that the size is 55 ~ 65 Å red, the size 40 ~ 50 녹색 green, the size 25 ~ 35 Å blue. delete delete delete The method of claim 2, wherein the polymer matrix layer White light emitting device, characterized in that consisting of SPS (sulfonated polystyrene). The method of claim 2, wherein the polymer matrix layer White light emitting device, characterized in that consisting of PMA (polymethacrylic acid). The method of claim 2, wherein the polymer matrix layer A white light emitting device comprising TPD (N, N'-diphenyl-N, N'-bis (3-methylphenyl)-(1,1'-biphenyl) -4,4'-diamine). The method of claim 4, wherein the quantum mucosal structure A white light emitting device, characterized in that a single layer structure formed by mixing together red, green, and blue quantum dots. The method of claim 4, wherein the quantum mucosal structure A white light emitting device comprising a multi-layered film structure formed by stacking a red quantum dot film, a green quantum dot film, and a blue quantum dot film. The method of claim 8, The forming of the quantum dot film is a method of manufacturing a white light emitting device, characterized in that to form a single layer by mixing together the quantum dots emitting red, green, blue. The method of claim 8, Formation of the quantum dot film is a multilayer film by laminating a red quantum film, a green quantum film and a blue quantum film Forming a white light emitting device characterized in that it is formed.