KR101278257B1 - Quantum dots and method for manufacturing the same - Google Patents

Abstract

The quantum dot according to the present invention includes a core made of InP, a first shell layer surrounding the core, and a second shell layer surrounding the first shell layer, and the band gap of the second cell layer is smaller than the band gap of the first shell layer.

Description

QUANTUM DOTS AND METHOD FOR MANUFACTURING THE SAME

TECHNICAL FIELD The present invention relates to a quantum dot and a method for manufacturing the same, and more particularly, to a quantum dot having a multilayer structure and a method for manufacturing the same.

Nanocrystals are nanoscale crystals made up of hundreds to thousands of atoms. This small size of the material has a large surface area per unit volume, causing most atoms to exist on the surface and exhibit quantum confinement effects, resulting in unique electrical, magnetic, optical, and chemical properties that differ from the intrinsic properties of the material itself. , Mechanical properties.

Therefore, by controlling the physical size of these nanocrystals it is possible to control a variety of properties.

US Patent No. 6,322.901 discloses a semiconductor nanocrystal material having a core-shell structure with increased luminous efficiency, and US Patent No. 6,207,229 discloses a method for producing a semiconductor nanocrystal material having such a core-shell structure. Doing. The core-shell structured compound semiconductor nanocrystals are described to exhibit improved luminous efficiency while maintaining the emission wavelength of the core almost as the passivation effect and quantum limiting effect of reducing defect sites on the core surface.

However, the present invention has a problem of environmental pollution by forming a quantum dot mainly made of a material based on cadmium (Cd).

In order to replace cadmium, a method of synthesizing quantum dots with elements of group III-V has been studied.

However, quantum dots using elements of group III-V do not exhibit the same level of electrical and optical characteristics as quantum dots based on cadmium.

Accordingly, the present invention provides a method for synthesizing quantum dots on the same level as quantum dots based on InP and based on cadmium.

In order to achieve the above object, the quantum dot according to the present invention includes a core made of InP, a first shell layer surrounding the core, and a second shell layer surrounding the first shell layer, and a band gap of the second cell layer is defined by the first shell layer. Smaller than the bandgap.

The first shell layer may be made of ZnS, and the second shell layer may be made of ZnSe.

The diameter of the core is 3.5nm, the diameter of the quantum dot may be 4.5nm or more.

In accordance with another aspect of the present invention, there is provided a method of preparing a quantum dot, by mixing a first indium solution and a first phosphorus solution to prepare a solution including InP nanocrystals, and injecting a ZnS precursor solution into a solution. Forming a nanocrystal having a first shell layer surrounding the nanocrystal, and injecting a ZnSe precursor solution into the solution to form a nanocrystal having a second shell layer surrounding the first shell layer.

The ZnS precursor solution may be formed by mixing 1-octanethiol with any one of zinc oleate, zinc myristate, and zinc stearate.

The ZnSe precursor solution may be prepared by mixing selenium with one of zinc oleate, zinc myristate, and zinc stearate, and trioctylphosphine or octadicene.

The step of preparing the solution is a method of producing a quantum dot proceeds at a temperature of 150 ℃ or less than 350 ℃.

The forming of the nanocrystals having the first shell layer may proceed at a temperature of 200 ° C. or more and less than 350 ° C., and the forming of the nano crystals having the second shell layer may be performed at a temperature of 200 ° C. or more and less than 350 ° C.

After preparing the solution, the method may further include adding a second indium solution to the solution, and adding a second phosphorus solution to the solution.

The first indium solution or the second indium solution is prepared by dissolving indium acetate and myristic acid in 1-octadecene, and the first or second phosphorus solution is tris (trimethylsilyl) phosphine and 1-octylamine. It can be prepared by mixing.

When the shell layer formed at the outermost shell is formed to have a smaller band gap than the shell layer adjacent to the core as in the present invention, there is no change in wavelength, thereby providing a quantum dot having excellent light stability and chemical stability.

In addition, since quantum dots are formed based on InP, the problem of environmental pollution due to cadmium may be reduced.

1 is a schematic cross-sectional view for describing a quantum dot according to an embodiment of the present invention.
2 is a graph showing the potential energy value according to the distance from the center of the quantum dot.
3 is a graph showing a light emission spectrum corresponding to light and a photograph of visible light of a quantum dot according to the present invention.
4 is a graph measuring the intensity of photoluminescence (hereinafter referred to as PL) of InP / ZnS / ZnSe quantum dots according to the present invention and InP / ZnS quantum dots according to the prior art.
5 is a PL intensity and color table of a white LED including a YAG phosphor and multilayer quantum dots.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. The present invention may be embodied in many different forms and is not limited to the embodiments described herein.

In order to clearly illustrate the present invention, parts not related to the description are omitted, and the same or similar components are denoted by the same reference numerals throughout the specification.

Hereinafter, a quantum dot manufacturing apparatus will be described in detail with reference to the accompanying drawings.

1 is a schematic cross-sectional view for explaining a quantum dot according to an embodiment of the present invention, Figure 2 is a graph showing the potential energy value according to the distance from the center of the quantum dot, Figure 3 is a quantum dot according to the present invention It is a graph showing the photograph of the visible light and the emission spectrum corresponding to the light.

Referring to FIG. 1, a quantum dot according to an embodiment of the present invention includes a core 10 made of InP, a core surrounding the core, a first shell layer 20 made of ZnS, and a first shell layer 10 made of ZnSe. The second shell layer 30 is included.

Referring to the potential energy graph according to the distance of FIG. 2, the band gap of the second shell layer of the quantum dot has a smaller value than the band gap of the first shell layer.

As such, when the band gap of the second shell layer of the quantum dots is formed to be smaller than the band gap of the first shell layer, there is no change in the emission wavelength even if the shell layer increases. Accordingly, since the defects of the quantum dots can be removed due to the increase in the shell layer, the quantum dots exhibiting excellent light emission characteristics can be obtained without changing the emission wavelength.

Quantum dots are nano-sized crystals that are spherical, tetrahedral, cylindrical, rod-shaped, triangular, disc, tripod, tetrapod, cube, box, star, The tube may be selected from the group consisting of, but is not limited thereto.

The core may have a diameter of approximately 3.5 nm, the core / first shell layer may have a diameter of approximately 4 nm, and the core / first shell layer / second shell layer may have a diameter of 4.5 nm or more.

Quantum dots can optionally be surface coordinated by organic material. The organic layer may be formed by the solvent used in the nanocrystal growth process for forming the multilayer shell.

The quantum dots according to the embodiment of the present invention can be obtained from blue to red by varying the method of forming the quantum dots as shown in FIG. This will be described in more detail in the following production method.

Since various colors can be obtained, it can be applied to the manufacture of solar cells and LEDs.

4 is a graph measuring the intensity of photoluminescence (hereinafter referred to as PL) of InP / ZnS / ZnSe quantum dots according to the present invention and InP / ZnS quantum dots according to the prior art. The intensity of PL was measured here for 6 days under 254 nm UV light.

Referring to FIG. 4, it can be seen that the PL intensity of the InP / ZnS / ZnSe quantum dots according to the present invention decreases more slowly than the PL intensity of the InP / ZnS quantum dots. The PL intensity of the InP / ZnS / ZnSe quantum dots according to the present invention was reduced by 19% for 4 days. There was a 14% decrease in the first two days and a 5% decrease in the remaining four days.

However, the PL intensity of InP / ZnS quantum dots decreased sharply to 27% of the initial PL intensity after 6 days.

As the light intensity gradually decreases as described above, it can be applied to lighting and the like, and by using the quantum dots of the present invention, it is possible to manufacture lighting having light stability.

On the other hand, the quantum dot according to the present invention can obtain a variety of light from blue to green to red, it is possible to form a white LED.

Specifically, a white LED was obtained by using a yellow phosphor (YAG) and a multi-layered quantum dot on a blue LED. In this case, the silicone resin may include a resin: YAG phosphor: multilayer quantum dots may be mixed in a ratio of 0.5g: 0.015g: 0.02g.

The white LED shows the PL intensity and color palette as in FIG.

5 is a PL intensity and color table of a white LED including a YAG phosphor and multilayer quantum dots, and Table 1 is a table analyzing characteristics of a white LED according to an embodiment of the present invention.

Referring to FIG. 5, when a white LED is formed according to an embodiment of the present invention, an increased CRI average value (Color rendering index average) can be obtained.

The conventional CRI value was about 70. However, according to the present invention, as shown in Table 1, it can be seen that the increase is about 80.

[Table 1]

The method of forming a quantum dot according to an embodiment of the present invention will now be described by taking concrete experiments as an example.

Experimental Example 1-InP / ZnS / ZnSe with 515 nm Emitting

First, to prepare an InP core, 0.0230 g of indium acetate and 0.0703 g of myristric acid are dissolved in 6 ml of 1-octadecene (ODE) to prepare an indium solution. In this case, the vacuum may be maintained up to 110 ° C. and thereafter, at a temperature of 150 ° C. or higher and less than 350 ° C. in a nitrogen (N ₂ ) gas atmosphere. Preferably it may be more than 180 ℃ 325 ℃ and in one embodiment of the present invention was maintained at 188 ℃.

A solution containing InP nanocrystals was formed by rapidly injecting 0.029 ml of tris (trimethylsilyl) phosphine and 0.3 ml of 1-octylamine into the indium solution.

Next, in order to form the first shell layer made of ZnS on the InP core, 2.8 ml of zinc oleate and 0.14 ml of 1-octanethiol were injected into the InP nanocrystal solution to form the core / first shell layer. InP / ZnS nanocrystal solution of the structure was synthesized. At this time, the InP solution can maintain 200 ℃ or less than 350 ℃, preferably InP / ZnS nanocrystals were synthesized while maintaining the 300 ℃ and cooled to 200 ℃ after 40 minutes.

Zinc oate was formed by dissolving 0.2201 g of ginacetate and 0.68 g of oleic acid in 12 ml of trioctylamine while maintaining it at 200 ° C. in a nitrogen atmosphere.

In addition to the zinc acetate, organic acids such as zinc miristate zinc stearate and the like may be used.

Next, in order to form a second shell layer made of ZnSe on the InP / ZnS nanocrystals, 2.8 ml of cinkoleate and 0.14 ml of TOPSe are injected into the InP / ZnS nanocrystal solution to have a core / first shell layer / second shell layer structure. InP / ZnS / ZnSe nanocrystal solution is synthesized. At this time, InP / ZnS / ZnSe has a light emission wavelength of 515 nm.

At this time, the InP / ZnS nanocrystal solution can maintain 200 ℃ or less than 350 ℃, preferably cooled to room temperature after 40 minutes while maintaining 300 ℃.

Here TOPSe is prepared by mixing 2 mol selenium (Se) in 1L trioctylphosphine (trioctylphosphine).

At this time, selenium may be used by dissolving in octadecene or by using a thiol compound.

The synthesized InP / ZnS / ZnSe nanocrystal solution was washed with a washing solution, centrifuged and the filtered nanocrystals were redispersed in hexane. Washing solution is a mixed solution containing acetone (aceton), chloroform (butaneol), butanol (methanol).

Experimental Example 2-InP / ZnS / ZnSe with luminescence of 541 nm

To prepare the InP core, 0.0230 g of indium acetate and 0.0703 g of myristic acid were dissolved in 6 ml of 1-octadecene to prepare an indium solution. At this time, the vacuum was maintained up to 110 ° C and then 230 ° C in a nitrogen (N ₂ ) gas atmosphere.

Rapidly inject 0.029 ml of tris (trimethylsilyl) phosphine and 0.3 ml of 1-octylamine into the indium solution to form a solution containing InP nanocrystals.

Next, in order to form a first shell layer made of ZnS on the InP core, 2.8 ml of zinc oxide and 0.14 ml of 1-octanethiol were injected into the InP nanocrystal solution to include InP / ZnS nanocrystals having a core / first shell layer structure. Synthesize the solution. At this time, the InP solution synthesized InP / ZnS nanocrystals while maintaining 300 ° C, and cooled to 200 ° C after 40 minutes.

Next, in order to form a second shell layer made of ZnSe on the InP / ZnS nanocrystals, 2.8 ml of cinkoleate and 0.14 ml of TOPSe are injected into the InP / ZnS nanocrystal solution to have a core / first shell layer / second shell layer structure. InP / ZnS / ZnSe nanocrystal solution is synthesized. At this time, InP / ZnS / ZnSe has a light emission wavelength of 541 nm.

Thereafter, the InP / ZnS nanocrystal solution was heated to 300 ° C. and cooled to room temperature after 40 minutes.

The synthesized InP / ZnS / ZnSe nanocrystal solution was washed with a washing solution, centrifuged and the filtered nanocrystals were redispersed in hexane.

Experimental Example 3-Innm / ZnS / ZnSe of 556 nm Emitting

To prepare the InP core, 0.0460 g of indium acetate and 0.1406 g of myristic acid were dissolved in 6 ml of 1-octadecene to prepare an indium solution. At this time, the vacuum was maintained up to 110 ° C and then 230 ° C in a nitrogen (N ₂ ) gas atmosphere.

Rapidly inject 0.029 ml of tris (trimethylsilyl) phosphine and 0.3 ml of 1-octylamine into the indium solution to form a solution containing InP nanocrystals.

At this time, the indium solution was heated to 270 ° C and cooled to 170 ° C after 30 minutes.

Next, in order to form a first shell layer made of ZnS on the InP core, 5.6 ml of ginkoleate is injected into the InP nanocrystal solution. At this time, the InP nanocrystal solution was maintained at 230 ℃ for 20 minutes.

Thereafter, 0.28 ml of 1-octanethiol solution was injected into the InP nanocrystal solution to synthesize a solution containing InP / ZnS nanocrystals having a core / first shell layer structure.

At this time, the InP nanocrystal solution was heated to 300 ° C., and cooled to 170 ° C. after 20 minutes.

In order to form a second shell layer of ZnSe on the InP / ZnS nanocrystals, 5.6 ml of jinlkoleate was injected into the InP / ZnS nanocrystals solution and heated to 230 ° C. for 20 minutes.

0.28 ml of TOPSe was injected into the InP / ZnS nanocrystal solution to synthesize a solution including InP / ZnS / ZnSe nanocrystals having a core / first shell layer / second shell layer structure. At this time, InP / ZnS / ZnSe has a light emission wavelength of 556 nm.

Thereafter, the InP / ZnS nanocrystal solution was cooled to 70 ° C. after 20 minutes and cooled to room temperature after 40 minutes.

The synthesized InP / ZnS / ZnSe nanocrystal solution was washed with a washing solution, centrifuged and the filtered nanocrystals were redispersed in hexane.

Experimental Example 4-583nm InP / ZnS / ZnSe

To prepare the InP core, 0.0230 g of indium acetate and 0.0703 g of myristic acid were dissolved in 6 ml of 1-octadecene to prepare an indium solution. At this time, the vacuum was maintained up to 110 ° C and thereafter maintained at 200 ° C in a nitrogen (N ₂ ) gas atmosphere.

A solution containing InP nanocrystals was prepared by rapidly injecting 0.029 ml of tris (trimethylsilyl) phosphine and 0.3 ml of 1-octylamine into the indium solution. At this time, it was heated to 300 ℃ for 15 minutes.

Next, in order to form a first shell layer made of ZnS on the InP core, 2.8 ml of ginkoleate was injected into the InP solution and heated to 300 ° C. for 20 minutes.

0.14ml of 1-octanethiol was injected into the InP solution to synthesize a solution containing InP / ZnS nanocrystals having a core / first shell layer structure.

In order to form a second shell layer made of ZnSe on the InP / ZnS nanocrystals, 2.8 ml of ginkoleate was injected into the InP / ZnS nanocrystals solution and heated at 300 ° C. for 20 minutes.

Further, 0.28 ml of TOPSe was further injected to synthesize a solution including InP / ZnS / ZnSe nanocrystals having a core / first shell layer / second shell layer structure, and cooled to room temperature after 20 minutes.

At this time, InP / ZnS / ZnSe has a light emission wavelength of 583 nm.

The synthesized InP / ZnS / ZnSe nanocrystal solution was washed with a washing solution, centrifuged and the filtered nanocrystals were redispersed in hexane.

Experimental Example 5- InP / ZnS / ZnSe with luminescence of 608 nm

To prepare the InP core, 0.0230 g indium acetate and 0.0703 g myritic acid were dissolved in 6 ml of 1-octadecene to prepare an indium solution. At this time, the vacuum was maintained up to 110 ° C and thereafter maintained at 200 ° C in a nitrogen (N ₂ ) gas atmosphere.

A solution containing InP nanocrystals was prepared by rapidly injecting 0.029 ml of tris (trimethylsilyl) phosphine and 0.3 ml of 1-octylamine into the indium solution. At this time, the InP solution was heated to 300 ℃, and cooled to room temperature after 20 minutes.

Thereafter, an indium (In) solution and a phosphorus (P) solution were further injected into the InP solution, heated to 300 ° C., and then cooled to room temperature after 20 minutes.

At this time, the indium (In) solution was dissolved 0.0115g indium acetate and 0.352g mystic acid in 3ml 1-octadecene, phosphorus (P) 0.015ml tris (trimethylsilyl) phosphine and 0.3ml 1-octylamine Prepared by mixing in 1 ml of 1-octadecene.

Adding an indium solution and a phosphorus solution can increase the size of the InP core.

Next, in order to form a first shell layer made of ZnS on the InP core, 4.2 ml of ginkoleate and 0.1 ml of 1-octanethiol were injected into the InP solution to include a solution containing InP / ZnS nanocrystals having a core / first shell layer structure. Synthesize At this time, the InP solution was cooled to room temperature after 20 minutes while maintaining 300 ℃.

Next, in order to form a second shell layer made of ZnSe on the InP / ZnS nanocrystals, 4.2 ml of cinkoleate and 0.1 ml of TOPSe were injected into the InP / ZnS nanocrystal solution to form InP / of the core / first shell layer / second shell layer structure. A solution containing ZnS / ZnSe nanocrystals was synthesized and cooled to room temperature after 20 minutes after heating to 300 ° C. At this time, InP / ZnS / ZnSe has a light emission wavelength of 608 nm.

The synthesized InP / ZnS / ZnSe nanocrystal solution was washed with a washing solution, centrifuged and the filtered nanocrystals were redispersed in hexane.

Experimental Example 6-629nm InP / ZnS / ZnSe

To prepare the InP core, 0.0230 g of indium acetate and 0.0703 g of myristic acid were dissolved in 6 ml of 1-octadecene to prepare an indium solution. At this time, the vacuum was maintained up to 110 ° C and thereafter maintained at 200 ° C in a nitrogen (N ₂ ) gas atmosphere.

InP nanocrystal solution was prepared by rapidly injecting 0.029 ml of tris (trimethylsilyl) phosphine and 0.3 ml of 1-octylamine into the indium solution. At this time, the indium solution was heated to 300 ° C. and cooled to 200 ° C. after 20 minutes.

Thereafter, an indium solution was further injected into the InP solution, and heated to 300 ° C. The indium solution was prepared by dissolving 0.0115 g indium acetate and 0.352 g mystic acid in 3 ml 1-octadecene.

After 20 minutes the InP solution with the added indium solution was cooled to 230 ° C., and further phosphorus solution was injected and heated to 300 ° C.

The phosphorus solution was prepared by mixing 0.015 ml Tris (trimethylsilyl) phosphine and 0.3 ml 1-octylamine in 1 ml 1-octadecene.

After 20 minutes, the InP solution with added indium and phosphorus was cooled to 230 ° C.

Next, in order to form a first shell layer made of ZnS on the InP core, 4.2 ml of cinkoleate and 0.1 ml of 1-octanethiol were injected into an InP solution to form an InP / ZnS nano having a core / first shell layer / second shell layer structure. Synthesize a solution containing crystals. At this time, the InP solution was cooled to 230 ° C. after 20 minutes while maintaining 300 ° C.

Next, in order to form a second shell layer made of ZnSe on the InP / ZnS nanocrystals, InP having a core / first shell layer / second shell layer structure by injecting 4.2 ml of cinkoleate and 0.1 ml of TOPSe into the InP / ZnS nanocrystal solution. A solution containing / ZnS / ZnSe nanocrystals was synthesized, heated to 300 ° C., and cooled to room temperature after 20 minutes.

At this time, InP / ZnS / ZnSe has a light emission wavelength of 629 nm.

The synthesized InP / ZnS / ZnSe nanocrystal solution was washed with a washing solution, centrifuged and the filtered nanocrystals were redispersed in hexane.

Although the preferred embodiments of the present invention have been described in detail above, the scope of the present invention is not limited thereto, and various modifications and improvements of those skilled in the art using the basic concepts of the present invention defined in the following claims are also provided. It belongs to the scope of right.

10: InP Core
20: first shell layer
30: second shell layer

Claims (10)

delete delete delete Mixing a first indium solution and a first phosphorus solution to prepare a first solution including InP nanocrystals,
Preparing a second solution by injecting a ZnS precursor solution into the first solution to form nanocrystals having a first shell layer surrounding the InP nanocrystals,
Preparing a third solution by injecting a ZnSe precursor solution into the second solution to form nanocrystals having a second shell layer surrounding the first shell layer;
Lt; / RTI >
The ZnS precursor solution
A method for producing a quantum dot, which is prepared by mixing any one of cinkoleate, cink myristate and cink stearate with 1-octanethiol. delete 5. The method of claim 4,
The ZnSe precursor solution
A method for producing a quantum dot produced by mixing selenium with any one of zinc oleate, zinc myristate, and zinc stearate, and trioctylphosphine or octadicene. 5. The method of claim 4,
Preparing the first solution
The quantum dot manufacturing method which advances at the temperature of 150 degreeC or more and less than 350 degreeC. In claim 7,
Forming the nanocrystals having the first shell layer proceeds at a temperature of more than 200 ℃ 350 ℃,
Forming the nanocrystals having the second shell layer is a quantum dot manufacturing method proceeds at a temperature of 200 ℃ or less than 350 ℃. 5. The method of claim 4,
After the step of preparing the first solution,
Adding a second indium solution to the first solution,
Adding a second phosphorus solution to the first solution
Quantum dot manufacturing method further comprising. The method of claim 9,
The first indium solution or the second indium solution is prepared by dissolving indium acetate and myristic acid in 1-octadecene,
The first phosphorus solution or the second phosphorus solution is prepared by mixing tris (trimethylsilyl) phosphine and 1-octylamine.

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