KR102184320B1 - Quantum dot and method for preparing the same - Google Patents

Abstract

The present invention relates to a quantum dot and to a production method thereof. More specifically, the emission spectrum is adjusted by controlling the size of quantum dots produced by controlling the carbon length of aliphatic carboxylic acid used as a raw material during the production of the quantum dots. In addition, when a quantum dot of a uniform size is produced, it is possible to manage the quantum dot to maintain a certain level of quality, and the stability of quantum dot particles can be maximized by adjusting the ratio of S and Se contained in a shell.

Description

Quantum dot and its manufacturing method {QUANTUM DOT AND METHOD FOR PREPARING THE SAME}

The present invention relates to a quantum dot and a method of manufacturing the same.

Quantun Dot (QD) is a semi-conducting nano-sized particle of several nano-sized size with quantum confinement effect, and exhibits excellent optical and electrical properties that general semiconducting materials do not have in a bulk state. . Quantum dots can emit light when stimulated with energy such as light, and the color of the emitted light varies depending on the size of the particles. In the case of using such quantum dots, since it is possible to implement a large-area high-resolution display with good color purity, excellent color reproducibility, and good video characteristics, many studies on quantum dots are being conducted.

As a quantum dot light emitting material, a group II-VI compound semiconductor having high quantum efficiency and excellent stability is mainly used, and in particular, a quantum dot material having a core-shell structure is widely used.

However, since such a core-shell structured quantum dot cannot adjust the particle size, it is difficult to control the characteristics of the quantum dot whose emission spectrum varies depending on the particle size, and accordingly, it is difficult to manage to maintain a certain level of quality. have.

Korean Patent Publication No. 2015-0034755

Accordingly, the present inventors have conducted various studies to solve the above problems, and as a result, prepared a compound for a quantum dot ligand formed by a ligand exchange reaction between indium acetate and an aliphatic carboxylic acid having a controlled carbon length, and for the quantum dot ligand The emission spectrum can be adjusted by controlling the size of the quantum dot particles prepared using the compound, or the quality of the quantum dot particles can be uniformly controlled by preparing quantum dot particles of a certain size, and the ratio of S and Se of the shell Accordingly, it was confirmed that the stability of the quantum dot particles can be maximized.

Accordingly, an object of the present invention is to provide a compound for a quantum dot ligand with a controlled carbon length and a method for preparing the same.

Another object of the present invention is to provide a quantum dot with improved stability due to the composition of a shell and a method for producing the same, which is prepared using the compound for quantum dot ligand.

In order to achieve the above object, the present invention relates to a quantum dot having a core-shell structure, wherein the quantum dot is a particle having an average diameter of 2.0 to 7.0 nm, and the peak of Equation 1 is calculated as the UV absorption wavelength of the quantum dot particle core. Gives quantum dots with a -to-Valley (P) value of 0.70 or less:

[Equation 1]

Peak-to-Valley (P) = A/B

In the above equation, A is the absorption amount of the first inflection point of the UV absorption wavelength of the quantum dot particle, B is the absorption amount of the second inflection point of the UV absorption wavelength of the quantum dot particle, and the first and second inflection points are respectively based on the x-axis direction. It means the first and second inflection points.

The present invention also includes the steps of forming a first precursor for forming a core by reacting a ligand exchange reaction between indium acetate represented by the following Formula 1 and an aliphatic carboxylic acid represented by the following Formula 2; Preparing a core of quantum dot particles by reacting the first precursor for forming the core with a compound represented by the following formula (3); And heating the core by adding the core to the precursor solution for forming a shell.

[Formula 1]

[Formula 2]

In Formula 2, n is a real number of 9 to 16,

[Formula 3]

In Formula 3, n is an integer of 0 to 3, and R ₁ to R ₃ are each independently hydrogen, methyl, ethyl, n-propyl, iso-propyl, n-butyl, t-butyl, iso-butyl, phenyl, It is a phenyl containing a C ₁ to C ₂₀ alkyl group.

The present invention also provides a light emitting device or an optical device including the quantum dot.

The quantum dot according to the present invention can adjust the size of the produced quantum dot by adjusting the carbon length of the aliphatic carboxylic acid among the raw materials used in the production of the quantum dot, thereby producing a quantum dot having a specific emission wavelength according to the size of the quantum dot can do.

In addition, among the quantum dots, the quality of the core can be improved by controlling the number of carbon atoms of the ligand when forming the quantum dot core, and the improvement in the quality of the core can be confirmed that the Peak-to Valley (P) value is 0.70 or less.

In addition, it is possible to provide quantum dot particles with improved stability by controlling the ratio of S and Se contained in the shell of the quantum dot having a core-shell structure.

In addition, according to the method of manufacturing a quantum dot according to the present invention, it is possible to manufacture a quantum dot having a certain size, so that the quality of the quantum dot can be constantly managed.

1 is a graph showing the result of evaluating the quantum yield by storage date of the quantum dots prepared in Example 1.
2 is a graph showing the results of evaluating the quantum yield by storage date of the quantum dots prepared in Comparative Example 5.
3A to 3D are graphs showing the wavelength range of the absorption spectrum required to calculate the Peak to Valley (P) value, and are graphs showing absorption spectrum wavelengths of the quantum dot cores of Examples 1 and 6 and Comparative Examples 1 and 2, respectively. .

Hereinafter, the present invention will be described in more detail.

Quantum dots

The present invention relates to a quantum dot, and is manufactured in the form of particles having a predetermined diameter, relates to a quantum dot exhibiting a different maximum emission wavelength according to the diameter.

The quantum dots of the present invention may have a core-shell structure and may be particles having an average diameter of 2.0 to 7.0 nm. If the average diameter of the quantum dots is less than 2.0 nm, the emission wavelength of the quantum dots decreases, making it unsuitable for application to optical films for display purposes.If it exceeds 7.0 nm, the wavelength becomes excessively large, making it suitable to be applied to optical films for display purposes. I can't.

Specifically, the quantum dots may be classified into particle-shaped quantum dots having an average diameter of 2.0 nm or more and less than 5.0 nm and particle-shaped quantum dots having an average diameter of 5.0 to 7.0 nm, depending on their physical properties.

In the present invention, the quantum dot is a particle having an average diameter of 2.0 nm or more and less than 5.0 nm, the average diameter of the core of the quantum dot is 1.5 to 1.6 nm, the emission wavelength of the quantum dot is 520 to 540 nm, and The absorption wavelength of the core may be 430 to 480 nm.

When the quantum dots are in the form of particles having an average diameter of 2.0 nm or more and less than 5.0 nm, the quantum dots have a maximum emission characteristic in a green wavelength range of 520 to 540 nm, and thus, it may be advantageous to manufacture a green quantum dot.

In addition, in the present invention, the quantum dots are particles having an average diameter of 5.0 to 5.3 nm, the average diameter of the core of the quantum dots is 2.0 to 3.0 nm, the maximum emission wavelength of the quantum dots is 605 to 640 nm, the quantum dots The maximum absorption wavelength of the core of may be 540 to 570 nm.

When the quantum dots are in the form of particles having an average diameter of 5.0 to 5.3 nm, the quantum dots have a maximum emission characteristic in a red wavelength range of 605 to 640 nm, and thus, it may be advantageous for a method of making a reddish quantum dot.

In addition, the quantum dot may have a Peak-to-Valley (P) value of 0.70 or less in Equation 1, calculated as a UV absorption wavelength of the core.

[Equation 1]

Peak-to-Valley (P) = A/B

In the above equation, A is the absorption amount of the first inflection point of the UV absorption wavelength of the quantum dot particle, and B is the absorption amount of the second inflection point of the UV absorption wavelength of the quantum dot particle. In this case, the first and second inflection points refer to the first and second inflection points in the UV absorption wavelength, respectively, based on the x-axis direction.

In general, the Peak-to-Valley (P) value is an evaluation method for checking whether the core is well manufactured, and if the maximum absorption peak is large, it can be determined that the quality of the core is good.

In addition, the maximum absorption peak is proportional to the concentration of the solution for forming the core during the manufacture of the core, but since the concentration of the core cannot be measured constantly, it is difficult to determine the quality of the quantum dot core. Accordingly, in the present invention, the concept of Peak-to-valley(P) derived by Equation 1 is introduced, and a quantum dot whose value is defined as 0.70 or less is provided.

When the concentration of the core is high, not only the absorption amount of the maximum absorption peak but also the absorption amount of the primary inflection point increases at the same time. The low P value, that is, the A/B value, means that the absorption wavelength (A) of the first inflection point is low, and the maximum absorption wavelength (B) of the second inflection point is high. In addition, when a quantum dot core having a high P value is used, it means that the particle emission capacity of the quantum dot core is low and the particle size distribution is wide, so that the quantum yield and half width of the quantum dot particle having a core-shell structure are finally lowered. Problems arise.

Therefore, in the quantum dot having a core-shell structure according to the present invention, the Peak-to-Valley (P) is defined as 0.70 or less, thereby solving the above-described problems.

In the quantum dot of the present invention, the core may include a III-V group compound.

The group III-V compound is GaN, GaP, GaAs, GaSb, AlN, AlP, AlAs, AlSb, InN, InP, InAs, InSb, or a mixture thereof; GaNP, GaNAs, GaNSb, GaPAs, GaPSb, AlNP, AlNAs, AlNSb, AlPAs, AlPSb, InNP, InNAs, InNSb, InZnP, InPAs, InPSb or mixtures thereof; And GaAlNAs, GaAlNSb, GaAlPAs, GaAlPSb, GaInNP, GaInNAs, GaInNSb, GaInPAs, GaInPSb, GaAlNP, InAlNP, InAlNAs, InAlNSb, InAlPAs, or mixtures thereof; may include one or more selected from the group consisting of.

Alternatively, the core may be a compound containing In, Zn and P elements, and preferably, the core may contain InP and/or InZnP.

In the quantum dots of the present invention, the shell may include one or more selected from the group consisting of Al, Si, Ti, Mg, Zn, Se, and S.

Alternatively, the shell may include YS _x Se _{1 -x} (wherein Y is Al, Si, Ti, Mg, or Zn, and x is a real number of 0.50≦x<1.00).

In addition, the shell may be formed in the form of a layer on the surface of the core, and the thickness may be 2 to 10 nm, preferably 3 to 8 nm. At this time, the molar ratio of S and Se in the shell may be 1:0.01 to 1, preferably 1:0.05 to 0.5, more preferably 1:0.08 to 0.3. When the shell is formed in such a thickness range, it serves as a protective layer for the core, thereby improving the stability of the quantum dots and improving the luminous efficiency of the quantum dots.

In the present invention, the quantum dot having the core-shell structure is a quantum dot having a quantum yield (QY) of 75% or more, and a half width of 45 nm or less, which exhibits a light emission characteristic, and the initial quantum yield is 100%. The quantum yield after work may be 80% or more.

Quantum dots having such a quantum yield and half width can be widely applied to light emitting devices or optical devices.

The light emitting device or optical device may be a display, a sensor, a photodetector, a solar cell, a hybrid composite, or a bio labeling, but is not limited thereto.

Quantum dot Manufacturing method

The present invention also relates to a method of manufacturing a quantum dot, wherein the manufacturing method of the quantum dot comprises a ligand exchange reaction between indium acetate represented by the following formula (1) and an aliphatic carboxylic acid represented by the following formula (2) to obtain a first precursor for forming a core. Forming; Preparing a core of quantum dot particles by reacting the first precursor for forming the core with the compound represented by Formula 3; After heating by adding the core of the prepared quantum dot particles to a precursor solution for forming a shell, quantum dot particles may be prepared. In this case, when manufacturing the core, the step of mixing the second precursor for forming the core formed by ligand exchange reaction of zinc acetate and oleic acid to the first precursor for forming the core may be further included.

[Formula 1]

[Formula 2]

In Formula 2, n is a real number of 9 to 16, preferably n is an integer of 9 to 16, more preferably n is an integer of 10 to 15.

[Chemical Formula 3]

In Formula 3, n is an integer of 0 to 3, and R ₁ to R ₃ are each independently hydrogen, methyl, ethyl, n-propyl, iso-propyl, n-butyl, t-butyl, iso-butyl, phenyl, It is a phenyl containing a C ₁ to C ₂₀ alkyl group.

Hereinafter, in each step, a method of manufacturing a quantum dot according to the present invention will be described in more detail.

The indium acetate represented by Formula 1 and the aliphatic carboxylic acid represented by Formula 2 may be subjected to a ligand exchange reaction to form a precursor for forming a core (hereinafter, referred to as a first precursor for forming a core).

In the reaction of the indium acetate of Formula 1 and the aliphatic carboxylic acid of Formula 2, the molar ratio may be 1:1 to 3. If the molar ratio of the aliphatic carboxylic acid of Chemical Formula 2 to the indium acetate of Chemical Formula 1 is less than 1, indium acetate may remain and be included as an impurity, and if it exceeds 3, the aliphatic carboxylic acid remains and included as an impurity. There may be.

At this time, by controlling the carbon length of the aliphatic carboxylic acid represented by Formula 2, the diameter of the quantum dot and the diameter of the core included in the quantum dot can be controlled.

For example, if n is a real number of 9 to 12.5 in Formula 2, the quantum dots produced are particles having an average diameter of 2.0 or more and less than 5.0 nm, and the average diameter of the core of the quantum dots is 1.5 to 1.6 nm, and the quantum dots The emission wavelength of may be 520 to 540 nm, and the absorption wavelength of the core of the quantum dot may be 430 to 480 nm.

When n is an integer of 10 to 12 in Formula 2, the aliphatic carboxylic acid represented by Formula 2 may be selected from lauric acid, tridecanoic acid, and myristic acid.

In addition, if n in Formula 2 is a real number of more than 12.5 and less than 16, the produced quantum dots are particles having an average diameter of 5.0 to 5.3 nm, and the average diameter of the core of the quantum dots is 2.0 to 3.0 nm, and the maximum of the quantum dots The emission wavelength may be 605 to 640 nm, and the maximum absorption wavelength of the core of the quantum dot may be 540 to 570 nm.

When n is an integer of 13 to 15 in Formula 2, the aliphatic carboxylic acid represented by Formula 2 may be selected from pentadecylic acid, palmitic acid, and heptadecylic acid.

In addition, a second precursor for forming a core as described below may be further mixed with the first precursor for forming a core.

In this case, the reaction ratio of the first precursor for forming the core and the second precursor for forming the core may be 1 mol: 0.9 to 1.3 mol.

The second precursor for forming the core may be formed by dissolving zinc acetate and oleic acid in a non-coordinating solvent, followed by a ligand exchange reaction.

In this case, the molar ratio of the zinc acetate and the oleic acid may be 1: 1 to 3. If the weight ratio of the oleic acid to the zinc acetate is less than 1, zinc acetate may remain and be included as an impurity, and if it exceeds 3, oleic acid may remain and be included as an impurity.

The non-coordinating solvent is a solvent in which coordination bonding is impossible, and is not particularly limited as long as it is a solvent that does not affect the reaction during the production of quantum dots. For example, the non-coordinating solvent may include at least one selected from an alkyl-based solvent, an aromatic solvent, and an ether-based solvent. Specifically, the non-coordinating solvent may be 1-octadecene, dodecene, tetradecane, octyl ether, phenyl ether, or the like.

In addition, the core of the quantum dot particles may be prepared by reacting the first precursor and the second precursor for forming the core with the compound represented by Formula 3 above. It is characterized in that the Peak-to-Valley (P) value of the following Equation 1 calculated as the UV absorption wavelength of the core of the prepared quantum dot particle is 0.70 or less.

[Equation 1]

Peak-to-Valley (P) = A/B

In the above equation, A is the absorption amount of the first inflection point of the UV absorption wavelength of the quantum dot particle, and B is the absorption amount of the second inflection point of the UV absorption wavelength of the quantum dot particle.

In addition, the core-forming precursor may be dissolved in a solvent and then heated to form a shell.

The heating temperature may be 200 to 300 °C, preferably 210 to 290 °C, more preferably 220 to 280 °C. If the heating temperature is less than 200°C, the core may not be formed, and if the heating temperature is more than 300°C, the absorption wavelength of the core may be higher or lower than necessary.

A core manufactured using only the compound represented by Formula 3 and the first precursor for forming the core may be an InP-based core, and a second core formed in the compound represented by Formula 3 and the first precursor for forming the core The core prepared by mixing the precursor may be an InZnP-based core.

Thereafter, in order to form a shell on the core, the core may be added to and reacted with a precursor solution for forming a shell, thereby producing quantum dot particles having a shell formed on the core.

Specifically, the core may be added to the shell-forming precursor solution, mixed, and then heated to prepare quantum dot particles. In this case, the heating temperature may be 80 to 200° C., and when heated at the heating temperature, quantum dot particles may be manufactured without deteriorating the physical properties of the mixed materials.

The precursor solution for shell formation may form a precursor solution for shell formation by dissolving zinc oleic acid salt in a trivalent amine solvent represented by Formula 4 below.

[Formula 4]

In Formula 4, m is an integer of 6 to 9.

The zinc oleic acid salt may be prepared by mixing and heating zinc acetate and oleic acid in a non-coordination solvent.

In this case, the zinc acetate and oleic acid may have a molar ratio of 1:1 to 3. If the weight ratio of the oleic acid to the zinc acetate is less than 1, zinc acetate may remain and be included as an impurity, and if it exceeds 3, oleic acid may remain and be included as an impurity.

The non-coordinating solvent is a solvent in which coordination bonding is impossible, and is not particularly limited as long as it is a solvent that does not affect the reaction during the production of quantum dots. For example, the non-coordinating solvent may include at least one selected from an alkyl-based solvent, an aromatic solvent, and an ether-based solvent. Specifically, the non-coordinating solvent may be 1-octadecene, dodecene, tetradecane, octyl ether, phenyl ether, or the like.

In order to form the precursor solution for forming the shell, at least one selected from sulfur and selenium may be further dissolved in a solvent.

The shell formed by the above method includes YS _x Se _{1 -x} (wherein Y is Al, Si, Ti, Mg or Zn, and x is a real number of 0.50≦x<1.00), and the specific composition of the shell is described above. As shown.

In the present invention, the aliphatic carboxylic acid, characterized in that the n value in Formula 2 is 10 to 12, may be selected from the group of lauric acid, tridecanoic acid, and myristic acid as a saturated fatty acid.

In addition, the aliphatic carboxylic acid characterized in that the n-value of Formula 2 is 13 to 15 may be selected from the group of pentadecylic acid, pamicic acid, and heptadecylic acid as a saturated fatty acid.

According to the method of manufacturing a quantum dot according to a preferred embodiment of the present invention, a core is formed by a ligand exchange reaction of an aliphatic carboxylic acid in which n is 10 to 12 of the indium acetate represented by the following Formula 1 and the compound represented by the following Formula 2 Forming a solvent first precursor;

[Formula 1]

[Formula 2]

Forming a second precursor for forming a core formed by ligand exchange reaction between zinc acetate and oleic acid; And

The core of the quantum dot particles may be prepared by reacting the first precursor and the second precursor for forming the core with the compound represented by Formula 3-1:

[Formula 3-1]

.

.

The peak-to-valley (P) value of Equation 1, calculated as the UV absorption wavelength of the core of the produced quantum dot particle, may be 0.65 or less, and the maximum absorption wavelength of the core of the quantum dot is 440 to 470 nm. The quantum dot particle may have an InZnP structure.

[Equation 1]

Peak-to-Valley (P) = A/B

A: Absorption amount of the first inflection point of the UV absorption wavelength of quantum dot nanoparticles

B: absorption of the secondary inflection point of the UV absorption wavelength of quantum dot nanoparticles (maximum absorption)

In addition, the quantum dot includes a shell having a ZnSSe structure formed on the surface of the core, and has a maximum emission at a green wavelength of the InZnPZnSSe structure of the core/shell structure in which the molar ratio of S:Se in the shell is 1:1 to 99:1. As a quantum dot, characterized in that, the diameter of the quantum dot particle is 2.0 to 4.0 nm, the maximum emission wavelength may have a core/shell structure of 525 to 540 nm.

In addition, according to the method of manufacturing a quantum dot according to another preferred embodiment of the present invention, a ligand exchange reaction of an aliphatic carboxylic acid in which n is 13 to 15 of the indium acetate represented by the following Formula 1 and the compound represented by the following Formula 2 To form a precursor for forming a core;

[Formula 1]

[Formula 2]

The core of the quantum dot particles may be prepared by reacting the first precursor and the second precursor for forming the core with the compound represented by Formula 3-1:

[Formula 3-1]

The peak-to-valley (P) value of the following equation (1) calculated as the UV absorption wavelength of the core of the produced quantum dot particle is 0.70 or less, and the maximum absorption wavelength of the core of the quantum dot is 560 to 590 nm. It may be the core of the quantum dot particles of the InP structure, characterized in that:

[Equation 1]

Peak-to-Valley (P) = A/B

A: Absorption amount of the first inflection point of the UV absorption wavelength of quantum dot nanoparticles

B: absorption of the secondary inflection point of the UV absorption wavelength of quantum dot nanoparticles (maximum absorption)

In addition, the quantum dot includes a shell of ZnSSe structure formed on the surface of the core, and has a maximum emission at a red wavelength of the InPZnSSe structure of the core/shell structure in which the molar ratio of S:Se in the shell is 1:1 to 99:1. As a quantum dot, characterized in that, the diameter of the quantum dot particle is 5.0 to 7.0 nm, the maximum emission wavelength may be a core / shell structure quantum dot particle of 610 to 630 nm.

Quantum dots manufactured by the method as described above are applied to an optical film, for example, a quantum dot film, and can be widely used in a display field.

Hereinafter, preferred embodiments are presented to aid the understanding of the present invention, but the following examples are only illustrative of the present invention, and it is obvious to those skilled in the art that various changes and modifications are possible within the scope and spirit of the present invention. It is natural that changes and modifications fall within the scope of the appended claims.

Example One

(1-1) InP core formation

A solution was prepared by dissolving 0.2 mmol of indium acetate and 0.6 mmol of lauric acid (n=10 in Formula 2) in 10 mL of 1-octadecene. After stirring the solution while removing volatile components at 110°C and 100 mTorr for 30 minutes, maintain the temperature of 270°C in a nitrogen atmosphere until the solution becomes transparent to proceed with a ligand exchange reaction. A first precursor was formed.

The first precursor for forming the core was mixed with a tris(trimethylsilyl) phosphine solvent, stirred, and rapidly injected into the flask in front heated to 270°C in a nitrogen atmosphere. After reacting for 1 hour, the reaction was terminated by rapidly cooling. Thereafter, when the temperature of the flask reached 100° C., 10 mL of toluene was injected and transferred to a 50 mL centrifuge tube. After 10 mL of ethanol was added, purification was repeated twice using a precipitation and redispersion method, and dispersion in 13 g of toluene to prepare a particle dispersion of InP core.

(1-2) ZnS _x Se _{1 -x} (0.50≤x<1.00, x is a real number) Shell formation

Zinc acetate 5.5044 g (30 mmol), oleic acid 16.944 g (60 mmol), and 1-octadecene 30 mL were added. The flask was stirred and a mixture containing the first compound dispersed by 1-octadecene made through a process of removing volatile components at 140°C and 100 mTorr for 30 minutes at the same time as stirring was stored under an inert gas at 100°C. Into a 100 mL three-necked flask, 0.9612g (30mmol) of sulfur and 15 mL of trioctylphosphine were added and heated to 80°C while stirring under a nitrogen atmosphere to prepare a second compound in which sulfur is bound to trioctylphosphine. In a 100 mL three-necked flask, 2.3691 g (30 mmol) of selenium and 15 mL of trioctylphosphine were added and heated to 80° C. while stirring under a nitrogen atmosphere to prepare a third compound in which selenium was bound to trioctylphosphine. Prepare 2.5 mL of a toluene dispersion of the InP core prepared in Preparation Example 1, and add 1-octadecene (15 mL) and a mixture (2.4 mL) containing the first compound prepared above into a three-necked flask and stirred at 110° C., Volatile components were removed for 30 minutes under 200 mTorr. Then, the second compound (0.3 mL) and the third compound (0.3 mL) prepared above were added under an inert gas atmosphere and heated to 270°C. After reacting for 1 hour, it was cooled and InP/ZnS _{0 . 5} Se ₀ to _0.5 were prepared QDs.

Example 2

(2-1) InZnP core formation

A solution was prepared by dissolving 0.2 mmol of indium acetate and 0.6 mmol of lauric acid (n=10 in Formula 2) in 10 mL of 1-octadecene. After stirring the solution while removing volatile components at 110°C and 100 mTorr for 30 minutes, maintain the temperature of 270°C in a nitrogen atmosphere until the solution becomes transparent to proceed with a ligand exchange reaction. A first precursor was formed.

To form a second precursor for forming a core, 0.2 mmol of zinc acetate and 0.6 mmol of oleic acid were dissolved in 10 mL of 1-octadecene to prepare a solution. While stirring the solution, the volatile component is removed at 140° C. and 100 mTorr for 30 minutes, and then the ligand exchange reaction is performed by maintaining the temperature at 270° C. in a nitrogen atmosphere until the solution becomes transparent.

The first precursor and the second precursor for forming the core were mixed in a tris(trimethylsilyl) phosphine solvent at a molar ratio of 1:1, stirred, and rapidly injected into the flask in front heated to 270°C in a nitrogen atmosphere. After reacting for 1 hour, the reaction was terminated by rapidly cooling. Thereafter, when the temperature of the flask reached 100° C., 10 mL of toluene was injected and transferred to a 50 mL centrifuge tube. After 10 mL of ethanol was added, purification was repeated twice using a precipitation and redispersion method, and dispersion of particles of InZnP core was prepared by dispersing in 13 g of toluene.

(2-2) ZnS _x Se _{1 -x} (0.50≤x<1.00, x is a real number) Shell formation

Zinc acetate 5.5044 g (30 mmol), oleic acid 16.944 g (60 mmol), and 1-octadecene 30 mL were added. The flask was stirred and a mixture containing the first compound dispersed by 1-octadecene made through a process of removing volatile components at 140°C and 100 mTorr for 30 minutes at the same time as stirring was stored under an inert gas at 100°C. Into a 100 mL three-necked flask, 0.9612g (30mmol) of sulfur and 15 mL of trioctylphosphine were added and heated to 80°C while stirring under a nitrogen atmosphere to prepare a second compound in which sulfur is bound to trioctylphosphine. In a 100 mL three-necked flask, 2.3691 g (30 mmol) of selenium and 15 mL of trioctylphosphine were added and heated to 80° C. while stirring under a nitrogen atmosphere to prepare a third compound in which selenium was bound to trioctylphosphine. Prepare 2.5 mL of the toluene dispersion of the InP core prepared in Example 1, add 1-octadecene (15 mL) and a mixture (2.4 mL) containing the first compound prepared above into a three-necked flask together with stirring and at 110° C., Volatile components were removed under 200 mTorr for 30 minutes. Then, the second compound (0.3 mL) and the third compound (0.3 mL) prepared above were added under an inert gas atmosphere and heated to 270°C. After reacting for 1 hour, it was cooled and InZnP/ZnS _{0 . 5} Se ₀ to _0.5 were prepared QDs.

Example 3

When forming the first precursor for core formation, pentadecylic acid (n=13 in Formula 2) is used instead of lauric acid (n=10 in Formula 2), and when ZnS _x Se _{1 -x} shell is formed, S: Se in the shell Quantum dots were prepared in the same manner as in Example 1, except that the molar ratio of is 1:1 (x=0.5) instead of the molar ratio of 4:1 (x=0.75).

Example 4

ZnS _x Se _{1 -x When the} shell is formed, a quantum dot in the same manner as in Example 1, except that the molar ratio of S: Se in the shell is not 1:1 (x=0.5), but 9:1 (x=0.9). Was prepared.

Example 5

When forming the first precursor for forming the core, pentadecylic acid (n=13 in Chemical Formula 2) was used instead of lauric acid (n=10 in Chemical Formula 2), and when ZnS _x Se _{1 -x} shell was formed, S in the shell: Quantum dots were manufactured in the same manner as in Example 1, except that the molar ratio of Se was not 1:1 (x=0.5), but 99:1 (x=0.99).

Example 6

When forming the first precursor for forming the core, pentadecylic acid (n=13 in Chemical Formula 2) was used instead of lauric acid (n=10 in Chemical Formula 2), and when ZnS _x Se _{1 -x} shell was formed, S in the shell: Quantum dots were prepared in the same manner as in Example 2, except that the molar ratio of Se was 1:1 (x=0.5) instead of 3:2 (x=0.67).

Example 7

ZnS _x Se _{1 -x When} forming the shell, the same method as in Example 2, except that the molar ratio of S:Se in the shell is 1:1 (x=0.5) instead of 9:1 (x=0.90). To prepare a quantum dot.

Example 8

When forming the first precursor for forming the core, pentadecylic acid (n=13 in Chemical Formula 2) was used instead of lauric acid (n=10 in Chemical Formula 2), and when ZnS _x Se _{1 -x} shell was formed, S in the shell: Quantum dots were manufactured in the same manner as in Example 2, except that the molar ratio of Se was 1:1 (x=0.5) instead of 99:1 (x=0.99).

Comparative example 1 to 3

In Comparative Example 1, when forming the first precursor for forming the core, capric acid (n=8 in Formula 2) instead of lauric acid (n=10 in Formula 2), and Comparative Example 2 was Arachidic acid (Formula 2). Quantum dots were manufactured in the same manner as in Example 1, except that n=18) in 2) was used respectively.

In Comparative Example 3, a quantum dot was prepared in the same manner as in Example 1, except that the molar ratio of S: Se in the shell was 1:1 (x=0.5) instead of 2:3 (x=0.4).

Comparative example 4 to 5

Comparative Example 4 is the same method as in Example 2, except that capric acid (n=8 in Chemical Formula 2) was used instead of lauric acid (n=10 in Chemical Formula 2) when forming the first precursor for forming the core. To prepare a quantum dot.

In Comparative Example 5, a quantum dot was manufactured in the same manner as in Example 2, except that the molar ratio of S: Se in the shell was 1:1 (x=0.5), but the molar ratio was 1:4 (x=0.25).

Experimental example : Quantum dot Property evaluation

For the quantum dots each prepared in Examples 1 to 8 and Comparative Examples 1 to 5, physical properties were measured in the following manner, and the results are shown in Table 1.

(1) luminous wavelength

The PL (Photoluminescence) spectrum of the quantum dot was measured using a Cary Eclipse fluorescence spectrophotometer (λexc = 400 nm).

(2) absorption wavelength

The absorbance spectrum of the core of the quantum dot was measured using a Cary 5000 UV-vis-NIR (Agilent Technologies) spectrophotometer.

(3) Half width (FWHD)

Using OTSUKA's QE-2100, the half-value ratio was confirmed by using the absorption and photoluminescence spectra of the quantum dot particles dispersed in toluene.

(4) diameter

Using a projection electron microscope (TEM), the quantum dot particles and the core diameters of the quantum dots were measured.

(5) Peak-to-Valley

It was calculated by measuring the UV absorption wavelength of the quantum dot particle core using Equation 1 below.

[Equation 1]

Peak-to-Valley (P) = A/B

In the above equation, A is the absorption amount of the first inflection point of the UV absorption wavelength of the quantum dot particle, and B is the absorption amount of the second inflection point of the UV absorption wavelength of the quantum dot particle.

(6) S: Se ratio

The x value was determined by the molar ratio of S and Se when forming the ZnS _x Se _{1 -x} shell.

(7) Quantum Yield (QY)

Williams et al. “Relative fluorescence quantum yields using a computer luminescence spectrometer” 1983, Analyst 108:1067. Based on the following [Equation 2], with reference to the literature of, the relative quantum yield of the quantum dot was calculated using a fruorecein dye (a reference value for a green emission dot at an excitation wavelength of 440 nm).

[Equation 2]

The dot in the subscript refers to a quantum dot solution dispersed in toluene, and st refers to a fluorescein dye dispersed in toluene.

QY: quantum yield, I: area of emission peak, A: absorbance at excitation wavelength,

RI: refractive index in solvent

The quantum yield was measured after dispersion of the solvent and measured after 1 day, 2 days, 5 days, and 10 days, and the table shows the initial (QY _0d ) and 10 days (QY _10d ,% of the initial quantum yield) quantum yield. At this time, the time point measured after dispersion of the solvent may also be referred to as a “storage date”.

Quantum dot particles Quantum dot core Quantum dot particles Quantum dot core Peak-to-Valley Shell of quantum dots Half width
(nm) Initial quantum yield (QY _0d , %) Quantum yield after 10 days
(QY _10d .%)
Maximum emission wavelength
(nm) Absorption wavelength
(nm) diameter
(nm) diameter
(nm) (P) value S/Se
Ratio(x) Example 1 524 430 2.0 1.5 0.62 1:1
(0.50) 38 80 65(81.3) Example 2 530 433 2.1 1.6 0.59 1:1(0.50) 35 79 66(83.5) Example 3 605 566 5.1 2.0 0.65 4:1 (0.80) 39 75 70(93.3) Example 4 520 431 2.1 1.6 0.58 9:1 (0.90) 37 79 74(93.7) Example 5 610 570 5.2 2.1 0.63 99:1 (0.99) 40 81 76(93.8) Example 6 612 566 5.3 2.1 0.56 3:2 (0.67) 35 80 73(91.3) Example 8 612 565 5.3 2.0 0.58 99:1 (0.99) 35 80 76(95.0) Comparative Example 1 511 422 1.8 1.3 0.75 1:1(0.50) 48 67 53(79.1) Comparative Example 2 648 586 7.0 3.2 0.78 1:1(0.50) 47 65 43(66.2) Comparative Example 3 512 410 1.9 1.5 0.60 2:3 (0.40) 40 74 40(54.1) Comparative Example 4 503 415 1.9 1.3 0.71 1:1(0.50) 41 73 52(71.2) Comparative Example 5 525 422 1.6 1.3 0.61 1:4 (0.25) 39 79 29(36.7)

As a result, as shown in Table 1, the quantum dots of Examples 1 to 2 (in the case where n is an aliphatic carboxylic acid of 10 in Chemical Formula 2, and the core is InP and InZnP, respectively) show the maximum emission wavelength in the green wavelength range. , It can be seen that the quantum dots of Example 3 (in the case of an aliphatic carboxylic acid in which n is 13 in Formula 2) exhibits the maximum emission wavelength in the red wavelength range.

The initial quantum yield of Examples 1 to 8 is 75% or more, and after 10 days, the quantum yield is 80% or more of the initial quantum yield, and it can be confirmed that stability by the cell is secured.

On the other hand, the quantum dots of Comparative Examples 1 and 2 (in the case of an aliphatic carboxylic acid in which n is 8 and 18 in Chemical Formula 2) has a maximum emission wavelength that is not sufficiently within the green wavelength range or appears in the red wavelength range. In addition, the quantum dots of Comparative Example 3 (when the S: Se ratio of the shell is 2:3) did not have a maximum emission wavelength sufficiently within the green wavelength range, and the quantum yield after 10 days was significantly lower than the initial quantum yield, and stability was not secured. Can be confirmed.

In addition, the quantum dots of Comparative Example 4 (in the case of an aliphatic carboxylic acid having n = 8 in Formula 2) did not have a maximum emission wavelength sufficiently within the green wavelength range, and Comparative Example 5 (when the S: Se ratio of the shell is 1:4) It can be seen that the maximum emission wavelength of the quantum dot did not sufficiently reach the green wavelength range, and the quantum yield after 10 days was significantly lower than the initial quantum yield, and stability was not secured.

If the average diameter of the quantum dots is less than 2.0 nm, the wavelength becomes small and is not suitable for application to an optical film for display purposes, and if it exceeds 7.0 nm, the wavelength becomes excessively large and may not be suitable for application to an optical film for display purposes. have. In addition, when the molar ratio of the shell is out of 1:0.01~1, the size of the quantum dot particles is not sufficiently large, so that the maximum emission wavelength does not sufficiently fall within the green wavelength range, or after 10 days, the quantum yield decreases compared to the initial stage, indicating that stability is poor. Able to know.

The initial quantum yield of Comparative Examples 1 to 5 was 65% to 81%, and after 10 days, the quantum yield did not reach a value of 70% or more of the initial quantum yield.

In addition, the half width of the quantum dots shows values of 45 nm or less in all quantum dots, except that values of 48 nm and 47 nm are shown in Comparative Examples 1 and 2.

1 and 2 are graphs showing the results of evaluating the quantum yield according to the storage date of the quantum dots prepared in Example 1 and Comparative Example 5, respectively, and FIGS. 3A to 3D are respectively in Examples 1 and 6 and Comparative Examples 1 and 2 Photographs showing the absorption wavelength area of each manufactured quantum dot.

1 and 2, the decrease in quantum yield over time varies according to the ratio of S: Se constituting the shell, and Example 1 is a decrease in quantum yield over time compared to Comparative Example 5. It can be seen that this is minimized.

Also, referring to FIGS. 3A to 3D, it can be seen that the maximum absorption wavelength λmax varies according to the length of carbon.

In the above, although the present invention has been described by limited embodiments and drawings, the present invention is not limited thereto, and the technical idea of the present invention and the following description by those of ordinary skill in the art to which the present invention pertains. It goes without saying that various modifications and variations are possible within the equivalent range of the claims to be made.

Claims (16)

In the quantum dot having a core-shell structure,
The quantum dots are particles with an average diameter of 2.0 to 5.3 nm,
The shell of the quantum dot includes YS _x Se _{1 -x} (wherein Y is Al, Si, Ti, Mg or Zn, and x is a real number of 0.80≦x<1.00),
The molar ratio of S: Se in the shell is 1: 0.01 to 0.25,
The quantum yield of the quantum dots is 75% or more,
Quantum dots having a Peak-to-Valley (P) value of 0.70 or less in Equation 1, calculated as the UV absorption wavelength of the quantum dot particle core:
[Equation 1]
Peak-to-Valley (P) = A/B
In the above equation, A is the absorption amount of the first inflection point of the UV absorption wavelength of the quantum dot particle, B is the absorption amount of the second inflection point of the UV absorption wavelength of the quantum dot particle, and the first and second inflection points are respectively based on the x-axis direction. It means the first and second inflection points. The method of claim 1,
The quantum dots are particles having an average diameter of 2.0 nm or more and less than 5.0 nm,
The average diameter of the core of the quantum dot is 1.5 to 1.6 nm,
The maximum emission wavelength of the quantum dot is 520 to 540 nm,
The maximum absorption wavelength of the core of the quantum dot is 430 to 480 nm, quantum dot. The method of claim 1,
The quantum dots are particles having an average diameter of 5.0 to 5.3 nm,
The average diameter of the core of the quantum dot is 2.0 to 3.0 nm,
The maximum emission wavelength of the quantum dot is 605 to 640 nm,
The maximum absorption wavelength of the core of the quantum dot is 540 to 570 nm, quantum dot. The method of claim 1,
The core comprises a III-V compound,
The group III-V compound may include GaN, GaP, GaAs, GaSb, AlN, AlP, AlAs, AlSb, InN, InP, InAs, InSb, or a mixture thereof; GaNP, GaNAs, GaNSb, GaPAs, GaPSb, AlNP, AlNAs, AlNSb, AlPAs, AlPSb, InNP, InZnP, InNAs, InNSb, InPAs, InPSb, or mixtures thereof; And GaAlNAs, GaAlNSb, GaAlPAs, GaAlPSb, GaInNP, GaInNAs, GaInNSb, GaInPAs, GaInPSb, GaAlNP, InAlNP, InAlNAs, InAlNSb, InAlPAs, or mixtures thereof; that contains at least one selected from the group consisting of, quantum dots. The method of claim 1,
The quantum dot core is InP or InZnP, quantum dots. The method of claim 1,
The quantum dot is InP/ZnS _x Se _1-x or InZnP/ZnS _x Se _1-x (however, x is a real number of 0.80≤x<1.00), a quantum dot Forming a first precursor for forming a core by performing a ligand exchange reaction between indium acetate represented by the following Formula 1 and an aliphatic carboxylic acid represented by the following Formula 2;
Preparing a core of quantum dot particles by reacting the first precursor for forming the core with the compound represented by Formula 3; And
Including, the step of heating by adding the core to a precursor solution for forming a shell; the quantum dot manufacturing method of claim 1.
[Formula 1]

[Formula 2]

In Formula 2, n is a real number of 9 to 16,
[Chemical Formula 3]

In Formula 3, n is an integer of 0 to 3, and R ₁ to R ₃ are each independently hydrogen, methyl, ethyl, n-propyl, iso-propyl, n-butyl, t-butyl, iso-butyl, phenyl, It is a phenyl containing a C1 to C20 alkyl group. The method of claim 7,
A method for producing a quantum dot, further mixing a second precursor for forming a core formed by ligand exchange reaction of zinc acetate and oleic acid to the first precursor for forming the core. The method of claim 8,
The reaction ratio of the first precursor for forming the core and the second precursor for forming the core is 1 mol: 0.9 to 1.3 mol, a method of manufacturing a quantum dot. The method of claim 7,
N in Formula 2 is a real number of 9 to 12.5,
The average diameter of the quantum dots is 2.0 nm or more and less than 5.0 nm,
The average diameter of the quantum dot core is 1.5 to 1.6 nm,
The maximum emission wavelength of the quantum dot is 520 to 540 nm,
The maximum absorption wavelength of the quantum dot core is 430 to 480 nm, the method of manufacturing a quantum dot. The method of claim 10,
N in Formula 2 is an integer of 10 to 12,
The aliphatic carboxylic acid represented by Chemical Formula 2 is lauric acid, tridecanoic acid, or myristic acid. The method of claim 7,
N in Formula 2 is a real number of greater than 12.5 and less than or equal to 16,
The average diameter of the quantum dot particles is 5.0 to 5.3 nm,
The average diameter of the quantum dot core is 2.0 nm to 3.0 nm,
The maximum emission wavelength of the quantum dot is 605 to 640 nm,
The maximum absorption wavelength of the core of the quantum dot is 540 to 570 nm, the method of manufacturing a quantum dot. The method of claim 12,
N in Formula 2 is an integer of 13 to 15,
The aliphatic carboxylic acid represented by Formula 2 is pentadecylic acid, palmitic acid, or heptadecylic acid, a method for producing a quantum dot. The method of claim 7,
The precursor solution for forming a shell is prepared by dissolving a zinc oleic acid salt in a solvent. An optical device comprising the quantum dot of any one of claims 1 to 6. The method of claim 15,
The optical device is a display, a sensor, a photodetector, a solar cell, a hybrid composite, or a bio-labeling device.

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