KR20170097825A - Quantum dot structure capped metal or semiconductor oxide nanoparticle and manufacturing method at the same - Google Patents

Abstract

The present invention proposes a semiconductor nanoparticle surrounded by a nanometal or semiconductor oxide particle, that is, a quantum dot structure and a manufacturing method thereof. In the quantum dot structure according to the present invention, oxide surrounded by quantum dots shows excellent reliability by blocking an external environment and has high optical affinity due to high electron affinity so that it can be used for the manufacture of devices requiring high reliability such as a photo conversion device and an electroluminescent device. The manufacturing method includes a step of forming the structure of a shell, and a step of forming the outermost shell of metal oxide or semiconductor oxide.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a quantum dot structure capped with a nano metal or a semiconductor oxide,

The present invention relates to a quantum dot structure, and more particularly, to a quantum dot structure composed of a shell capable of confining its energy to a core whose wavelength is controlled by the composition ratio of four components, and oxide nanoparticles are bonded to the outermost shell, The present invention relates to a quantum dot structure capable of securing mass productivity due to a core which is excellent in heat and heat, and can be easily controlled in wavelength due to the content ratio of the four components.

Quantum dots can regulate the size of semiconductor nanoparticles so that light of various wavelengths can be excited to reproduce high purity colors with a narrow emission line width. A single material can excite various wavelengths of the visible light region. As a result, quantum dot technology is the most ideal technology to reproduce natural colors, and is a technology that has a lot of interest in the display field in order to realize a natural color on a screen.

These semiconductor nanoparticles, that is, quantum dots, can be classified into two types: photoluminescence (PL) that excites light when light is irradiated in the UV wavelength region, and electroluminescence (EL) that excites light when an electric field is applied It can be applied in various fields such as medical, lighting, and display.

The structure of the quantum dot includes a core for determining excitation wavelength due to particles having a size of several nanometers, a shell for covering energy of a core having a narrow band gap with a material having a wide band gap ). In addition, the shell serves to confine the energy of the core, thereby forming an energy structure in which the particles of the core can emit light, thereby increasing the luminous efficiency. And a ligand for facilitating energy transfer to the outside and for facilitating the dispersion and the dispersion.

Among the studies based on the QD structure, the design of the energy bandgap of the core-shell structure is based on the assumption that the organic ligands, which are vulnerable to heat or the external environment, Many researches are proceeding in the height direction. Among them, the oxidation stability of the organic ligand is very poor and capturing electrons generated by the excitation light deteriorates the light conversion efficiency.

As a prior art to solve this problem, according to Korean Patent Laid-Open Publication No. 10-2005-0074779 (Highly luminous I type laminated structure core / double shell quantum dot made of II-VI compound semiconductor and its production method), II-VI compound core; A II-VI compound first shell formed on the surface of the II-VI compound core and having a band gap larger than the band gap of the II-VI compound core; And a II-VI compound second shell formed on the surface of the II-VI compound first shell and having a band gap larger than the band gap of the II-VI compound first shell, the I-type laminated structure core / Shell quantum dots and wet chemical methods.

However, the core of the quantum dots determines the excitation wavelength. Since the process for fabricating the core has a high reaction speed, it is difficult to control the process, and the process equipment and process time required for core and shell synthesis are consumed. There is a falling problem.

Korean Patent Laid-Open No. 10-2005-0074779 (published on July 19, 2005)

DISCLOSURE Technical Problem Accordingly, the present invention has been made in order to solve the above problems, and it is an object of the present invention to provide a method of manufacturing a quantum dot having a four-component core / shell / oxide outermost shell structure, The outer shell of the outer shell is made of quantum dots of an oxide structure and quantum dots having stability against moisture and heat are fabricated to secure reliability.

In order to solve the above problems, the present invention provides a quantum dot comprising a four-component core / shell / oxide outermost shell, and a photocatalyst, a photoconversion device and an electroluminescent device using the same.

(A) reacting a precursor solution selected from group 11 to 17 at a temperature of from 280 to 320 ° C to form a structure of a four-component core and a shell formed on the surface of the core; And (b) mixing the quantum dot nanoparticles of the four-component core / shell with the solution in which the metal or semiconductor oxide is dissolved in step (a), and reacting the mixed solution with the hydroxide solution at a temperature of 50 ° C to 80 ° C, And forming an outermost shell of an oxide or a semiconductor oxide on the surface of the quartz-based core / shell / oxide outermost shell structure.

Preferably, in the step (a), (a-1) synthesizing a cation precursor by mixing two or more elements selected from group 11 to group 14 elements with an unsaturated fatty acid and adding an ethylenic hydrocarbon organic solvent thereto; (a-2) synthesizing an anion precursor by selectively mixing at least two elements selected from Group 14 to Group 17 in a solvent selected from the group consisting of alkylphosphine series, alkylphosphine series and trialkylphosphine series; (a-3) at least one element selected from the two or more elements selected in the step (a-2) is selected and mixed in any one solvent selected from the group consisting of an alkylphosphine series, an alkyloxphosphine series and a trialkylphosphine series, Thereby synthesizing an anion precursor of the shell component; And (a-4) mixing the cation precursor synthesized in the step (a-1) and the anion precursor synthesized in the step (a-2) in a predetermined volume ratio, Of an anionic precursor of the anion precursor.

Preferably, in the step (b), (b-1) dispersing the quantum dots of the four-component core / shell formed in the step (a) in a hydrophobic solvent; (b-2) dissolving a metal or semiconductor oxide precursor in a polar solvent to form a precursor solution; (b-3) mixing the quantum dot solution formed in the step (b-1) and the precursor solution formed in the step (b-2) at a predetermined volume ratio; And (b-4) mixing the solution mixed in step (b-3) with the hydroxide solution in a predetermined volume ratio and reacting to cap the metal or semiconductor oxide into the outermost shell; .

Preferably, the metal oxide or semiconductor oxide, zinc oxide (ZnOx), vanadium oxide (V ₂ Ox), nickel oxide (NiO), tin oxide (SnO _2), indium oxide (In ₂ O _3), molybdenum oxide ( MoO ₃ ), tungsten oxide (WO ₃ ), titanium oxide (TiO ₂ ), alumina (Al ₂ O ₃ ), silica (SiO ₂ ), and the like.

The present invention forms the quantum dot structure of a four component core / shell / oxide outermost shell.

As a result, the synthesis of the four-component core is not dominant over the reaction temperature and time as compared with the synthesis of the two-component core since the wavelength is determined by the composition ratio of the four elements. Do.

In addition, the oxide outermost shell can prevent deterioration of quantum dots due to moisture and heat, thereby improving reliability and ensuring quantum dot characteristics not dominant in the ligand.

In addition, the oxide-capped quantum dot has excellent heat resistance and chemical resistance, and is easily mixed with polar solvents by providing a hydrophilic surface, and has excellent dispersion stability in solvent.

The oxide surrounding the quantum dots has a high refractive index and a high transmittance and thus can extract light with high electron affinity and can be applied to a high efficiency electroluminescent device using quantum dots capped with a metal and a semiconductor oxide.

The accompanying drawings, which are included to provide a further understanding of the invention and are incorporated in and constitute a part of this specification, illustrate embodiments of the invention and, together with the description, serve to explain the principles of the invention.
1 illustrates quantum dots of a four-component core / shell / oxide outermost shell structure according to a preferred embodiment of the present invention,
FIG. 2 is a schematic view showing a manufacturing process of a quantum dot having the four-component core / shell / oxide outermost shell structure of FIG. 1, FIG. 2B is a schematic view of a fabrication sequence showing a process of forming an outermost shell of an oxide on a quantum dot prepared in the first step of FIG. 2A in a second step, FIG.
FIG. 3 is a transmission electron microscope image of a four-component core / shell / oxide outermost shell structure according to a preferred embodiment of the present invention. FIG. 3A is a transmission electron microscope FIG. 3B is a FE-TEM image of the quantum dots surrounded by the outermost shell of zinc oxide according to Example 2,
FIG. 4 is a graph showing the results of a comparison between a metal oxide-capped quantum dot 210 and a general organic ligand quantum dot 220 according to Example 3 of the present invention. A PL intensity of the quantum dot 210, and a percentage value of the PL intensity of a general organic ligand quantum dot 220.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Reference will now be made in detail to the preferred embodiments of the present invention, examples of which are illustrated in the accompanying drawings, wherein like reference numerals refer to like elements throughout.

FIG. 1 is a view showing quantum dots of a four-component core / shell / oxide outermost shell structure according to a preferred embodiment of the present invention, and FIG. 2 is a cross-sectional view of a quantum dot having a structure of a four- 2A is a schematic diagram for the synthesis of a quantum dot structure of a four-component core / shell using Group 11 to Group 17 precursors as Step 1, and FIG. 2B is a schematic diagram for the synthesis of a quantum dot structure of a four- FIG. 2 is a schematic view showing a process of forming an outermost shell of an oxide on a quantum dot. FIG.

1 and 2, a method of manufacturing a quantum dot structure according to a preferred embodiment of the present invention will be described.

As shown in FIG. 2A, first, Step 1 is a step of preparing a solution of at least two precursors selected from Elements 11 through 14 as a solution of two or more precursors selected from Elements 14 through 17 in a first solution (Solution 1) Solution (Solution 2) is added to synthesize the four-component core 110 (see FIG. 1).

Next, a third solution (Solution 3) is added as a precursor solution in which a component of any one element among two or more elements selected from the elements of Groups 14 to 17 of the second solution (Solution 2) is dissolved to form a shell 120 ). At this time, the reaction temperature of step 1 may be in the range of 280 ° C. to 320 ° C., reacted in an inert gas atmosphere, and the optical characteristics may be controlled according to the content ratio of elements used in the core.

The metal precursor of the shell component of Solution 1 is preferably added in an excess amount relative to the content for participating in the core synthesis, and it is preferable to react with the added Solution 3 component to form a two-component shell.

The solvent of Solution 1 is a mixture containing an ethylenic hydrocarbon organic solvent and an unsaturated fatty acid. At this time, the ethylenic organic solvent may be C _n H _{2n, and} may be selected from the group consisting of pentene, hexene, heptene, octadecene, nonene, decene, undecene, At least one of dodecene, tridecene, tetradecene, and pentadecene may be used in combination. The unsaturated fatty acid may be an acetylenic fatty acid having excellent reactivity and may be selected from the group consisting of myristoleic acid, palmitoleic acid, oleic acid, linoleic acid, At least one fatty acid among eicosapentaenoic acid, docosapentaenoic acid, and the like can be mixed and used.

The solvent of Solution 2 and Solution 3 may be an alkylphosphine series including trialkylphosphine methylphosphine, ethylphosphine, and triphenylphosphine, diamylphosphine oxide, Tripropylphosphine, tributylphosphien, tripentylphosphine, and the like, which include diethylphosphine oxide, tripropylphosphine oxide, and the like, .

Thus, the first solution (Solution 1), the second solution (Solution 2), and the third solution (Solution 3) are mixed to obtain reaction-terminated nanoparticles in the fourth solution (Solution 4). For this, the hydrophobic solvent and the hydrophilic solvent were mixed, and centrifugation was carried out 2 to 4 times at 6000 rpm for 15 minutes to obtain purified nanoparticles (220). In this case, the hydrophobic solvent may include hexane, toluene, chloroform and the like. The hydrophilic solvent may include ethanol, methanol, acetone, isopropyl alcohol, ), And the like. Here, the purified nanoparticles 220 are quantum dot structures composed of a four-component core / shell.

Hereinafter, step 2 will be described with reference to FIG. 2B.

In step 2, a fifth solution (Solution 5) is prepared by dissolving the quantum dot nanoparticles 220 obtained in step 1 in hexane, toluene, chloroform or the like, which is a hydrophobic solvent, and the fifth solution A sixth solution (Solution 6) is prepared as a precursor solution of a metal or a semiconductor oxide and a seventh solution (Solution 7) in which the fifth solution (Solution 5) and the sixth solution (Solution 6) are mixed at a volume ratio of 7: 1.

Then, the seventh solution (Solution 7) and the eighth solution (Solution 8) as a hydroxide solution were mixed at a volume ratio of 8:11 and reacted at a temperature of 50 ° C to 80 ° C for about one hour to form a nano- Solution (Solution 9).

In order to purify the nanoparticles surrounding the metal oxide in the ninth solution (Solution 9), centrifugation was performed as in the purification process of Step 1 of FIG. At this time, reaction-terminated nanoparticles are obtained in the ninth solution (Solution 9). To this end, the hydrophobic solvent and the hydrophilic solvent were mixed, followed by centrifugation at 6000 rpm for 15 minutes for 2 to 4 times to obtain purified nanoparticles (210). In this case, the hydrophobic solvent may include hexane, toluene, chloroform and the like. The hydrophilic solvent may include ethanol, methanol, acetone, isopropyl alcohol, ), And the like. Here, the purified nanoparticles 210 are quantum dots having an organic ligand bound thereto, and are a quantum dot structure composed of a four-component core 110 / shell 120 / outermost shell 130.

The polar solvent used in the sixth solution (Solution 6) and the eighth solution (Solution 8) in Step 2 is the same as the hydrophilic solvent in Step 1, and thus the hydrophilic solvent may be ethanol, methanol, acetone, , Isopropyl alcohol, and the like.

In addition, an oxide of a ninth solution (Solution9) is zinc oxide (ZnOx), vanadium oxide (V ₂ Ox), nickel oxide (NiO), tin oxide (SnO _2), indium oxide (In ₂ O _3), molybdenum oxide ( MoO ₃ , tungsten oxide (WO ₃ ), titanium oxide (TiO ₂ ), alumina (Al ₂ O ₃ ), and silica (SiO ₂ ).

In addition, the eighth solution (Soluion 8) may include a hydroxide combined with an alkaline element, and examples thereof may include potassium hydroxide (KOH) and lithium hydroxide (LiOH).

In addition, the reaction temperature of step 2 can be a temperature of less than 80 캜, which does not cause thermal damage to the quantum dots, and is susceptible to temperature and humidity due to the characteristics of organic matters of the quantum dots to which the organic ligands obtained in step 1 are bonded. It was difficult to secure reliability.

In addition, it is preferable to form the inert atmosphere in both step 1 and step 2. Therefore, the inert gas may be a nitrogen gas, an argon gas, a Neon gas, a helium gas, or the like.

As described above, conventionally, an inorganic material is capped at a high temperature to cause a loss of quantum efficiency. However, the present invention can produce a metal oxide or a semiconductor oxide having a high refractive index without losing quantum efficiency by producing a metal oxide or a semiconductor oxide at a low temperature. It is possible to obtain high optical characteristics due to high light extraction and to manufacture quantum dots which are not affected by the external environment.

Thus, the quantum dots of the structure of the four-component core / shell / oxide outermost shell obtained in the step 2 are shielded from the external environment due to the outermost shell 130 of the metal oxide or semiconductor oxide nanoparticles, It can be applied to devices requiring a high temperature environment.

≪ Example 1 >

First, 1 mmol of cadmium (Cadmium) and 4 mmol of zinc (Zinc) were sufficiently dissolved in oleic acid at a temperature of 100 ° C to 150 ° C. After removing acetic acid as a reaction by-product, octadecyne was added in an amount of 3 parts by volume of oleic acid To prepare a cation precursor.

Next, 0.1 mmol of selenium and 4 mmol of sulfur are mixed with trioctylphosphine, and the mixture is heated to a sufficiently soluble temperature to prepare an anion precursor.

Subsequently, 10 mmol of sulfur was mixed with trioctylphosphine and heated to a temperature at which it was sufficiently soluble to prepare an anion precursor of the shell component.

The cation precursor and the anion precursor synthesized according to the above method were mixed at a ratio of 10: 1 by volume, reacted in an inert gas atmosphere at a temperature of 250 to 300 ° C for 5 minutes, an anion precursor solution of a shell component was added, After 30 minutes of reaction, quenching is carried out at room temperature to prepare a quantum dot having a four-component core / shell structure.

Then, the reaction solution was mixed with methanol and chloroform in a volume ratio of 5: 1: 5, and centrifuged at 6000 rpm for 20 minutes to obtain a quantum dot.

≪ Example 2 >

The quantum dots obtained in Example 1 were dispersed in toluene at 1 wt%, and 5 mM zinc acetate dehydrate was dissolved in methanol. Then, the quantum dot solution and the zinc acetate dihydrate solution were mixed in a 35: 5 volume ratio To prepare a solution.

A solution in which 3 mM of potassium hydroxide (KOH) was dissolved in the above solution and methanol was mixed at a volume ratio of 4: 1 and reacted in an inert gas atmosphere at 60 ° C for 1 hour to prepare a zinc oxide-capped quantum dot.

Subsequently, the reaction solution was mixed with hexane and isopropyl alcohol in a volume ratio of 1: 1: 5 and centrifuged at 6000 rpm for 20 minutes to obtain a purified quantum dots.

3A, the quantum dots synthesized according to Example 1 have a size of 4 nm to 7 nm. Referring to FIG. 3B, in Example 2, a metal oxide (zinc oxide) having a size of 6 nm to 11 nm is capped It can be seen that quantum dots are formed.

≪ Example 3 >

The quantum dots obtained in Example 1 and Example 2 were dispersed in monomers, respectively, followed by mixing with oligomers at a volume ratio of 15:85. A PET scattering film was coated to a thickness of 100 μm, and a metal and mercury lamp The sheet was cured, and PL intensities were measured in an oven at 90 ° C over time to evaluate the optical characteristics by thermal factors. PL Intensity was measured using Ocean View products.

Referring to FIG. 4, a sheet using a metal oxide-capped quantum dot 210 according to Example 3 of the present invention is compared with a sheet using a general organic ligand quantum dot 220. Even after 40 hours have elapsed, Is maintained at 80% or more, so that the life span and high reliability can be confirmed.

While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it will be understood by those skilled in the art that various changes and modifications may be made without departing from the spirit and scope of the invention as defined by the appended claims. Anyone with it will know easily.

110: Four-component core of a quantum dot
120: shell of the quantum dot
130: Outermost shell of oxide nanoparticles
210: metal oxide-capped quantum dot
220: Quantum dots combined with organic ligands

Claims (8)

(a) reacting a precursor solution selected from Groups 11 to 17 at a temperature of 280 to 320 ° C to form a four-component core and a shell structure formed on the surface of the core; And
(b) mixing the quantum dot nanoparticles of the four-component core / shell with a solution in which the metal or semiconductor oxide is dissolved in step (a), and reacting the mixed solution with the hydroxide solution at a temperature of 50 ° C to 80 ° C, Or an outermost shell of a semiconductor oxide. ≪ Desc / Clms Page number 20 > The method according to claim 1,
In the step (a)
(a-1) synthesizing a cation precursor by mixing two or more elements selected from group 11 to group 14 elements with an unsaturated fatty acid and adding an ethylenic hydrocarbon organic solvent thereto;
(a-2) synthesizing an anion precursor by selectively mixing at least two elements selected from Group 14 to Group 17 in a solvent selected from the group consisting of alkylphosphine series, alkylphosphine series and trialkylphosphine series;
(a-3) at least one element selected from the two or more elements selected in the step (a-2) is selected and mixed in any one solvent selected from the group consisting of an alkylphosphine series, an alkyloxphosphine series and a trialkylphosphine series, Thereby synthesizing an anion precursor of the shell component; And
(a-4) mixing the cation precursor synthesized in the step (a-1) and the anion precursor synthesized in the step (a-2) in a predetermined volume ratio, and mixing the shell component synthesized in the step Adding an anion precursor; / RTI > of the four-component core / shell / oxide outermost shell structure. The method according to claim 1,
In the step (b)
(b-1) dispersing the quantum dots of the four-component core / shell formed in the step (a) in a hydrophobic solvent;
(b-2) dissolving a metal or semiconductor oxide precursor in a polar solvent to form a precursor solution;
(b-3) mixing the quantum dot solution formed in the step (b-1) and the precursor solution formed in the step (b-2) at a predetermined volume ratio; And
(b-4) mixing the solution mixed in the step (b-3) with the hydroxide solution in a predetermined volume ratio and reacting to cap the metal or semiconductor oxide into the outermost shell; / RTI > of the four-component core / shell / oxide outermost shell structure. The method according to claim 1,
The metal oxide or semiconductor oxide, zinc oxide (ZnOx), vanadium oxide (V ₂ Ox), nickel oxide (NiO), tin oxide (SnO _2), indium oxide (In ₂ O _3), molybdenum oxide (MoO ₃₎ , A _ternary oxide (WO ₃ ), a titanium oxide (TiO ₂ ), an alumina (Al ₂ O ₃ ), a silica (SiO ₂ ) Method for fabricating quantum dots of shell structure. 5. A process for the preparation of a compound according to any one of claims 1 to 4,
Four component cores;
A shell formed on a surface of the core; And
And an outermost shell of a metal oxide or a semiconductor oxide formed on the surface of the shell. A photocatalyst comprising a quantum dot of structure 5. A photoconversion device comprising quantum dots of structure 5. An electroluminescent device comprising the quantum dot of Structure 5.

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