KR20180060923A - Luminescent composition, quantum dot and method for producing the same - Google Patents

Abstract

Provided is a luminescent composition including a nanostructure, especially a quantum dot with high luminosity. A nanostructure has quantum yield with high luminosity and emits light at a particular wavelength and has a narrow size distribution in certain embodiments. In addition, a method of manufacturing the nanostructure with high luminosity is provided, wherein the method includes a shell-alloy synthesis technology of a nanostructure core using indium.

Description

FIELD OF THE INVENTION [0001] The present invention relates to a luminescent composition, a quantum dot,

The present invention relates to nanostructures. More particularly, the present invention relates to a luminescent composition comprising a nanostructure comprising an InP core and at least one shell layer, and to a highly emissive quantum dot having a high light emission quantum yield and emitting light at a specific wavelength and having a narrow size distribution . The present invention also relates to a method for producing such quantum dots.

Semiconductor nanostructures can be incorporated into a variety of electrical and optical devices. Such nanostructures of electrical and optical properties vary depending on, for example, their composition, shape, and size. For example, size-tunable semiconductor nanoparticles are of interest in applications including, for example, light emitting diodes (LEDs). Highly luminous nanostructures are particularly preferred for such applications.

Quantum dots with CdSe cores have been produced that exhibit high quantum yields. However, the inherent toxicity of cadmium limits the application of these cadmium-based nanoparticles. InP-based nanostructures have similar emission ranges and are therefore an ideal substitute for CdSe-based materials.

For example, the synthesis of InP-based nanostructures is described, for example, in: Xie et al. (2007) "Colloidal InP nanocrystals as efficient emitters covering blue to near-infrared" J. Am. Chem. Soc. 129: 15432-15433, Micic et al. (2000) "Core-shell quantum dots of lattice-matched ZnCdSe2 shells on InP cores: Experiment and theory" J. Phys. Chem. B 104: 12149-12156, Liu et al. (2008) "Coreduction of colloidal synthesis of III-V nanocrystals: The case of InP" Angew. Chem. Int. Ed. 47: 3540-3542, Li et al. (2008) "Economic synthesis of high quality InP nanocrystals using calcium phosphide as the phosphorus precursor" Chem. Mater. 20: 2621-2623, Battaglia and Peng (2002) "Formation of high quality InP and InAs nanocrystals in a noncoordinating solvent" Nano Lett. 2: 1027-1030, Kim et al. (2012) "Highly luminescent InP / GaP / ZnS nanocrystals and their application to white light-emitting diodes" J. Am. However, InP-based nanostructures having high light emission quantum yields and emitting light at specific wavelengths in certain embodiments and having narrow size distributions are difficult to synthesize.

Thus, there is a need for a simple and economical method of producing highly-emitting nanostructures, particularly highly-emitting InP-based nanostructures.

A problem to be solved by the present invention is to provide a luminescent composition comprising a nanostructure comprising an InP core and one or more shell layers and a method of producing a highly light emitting quantum dot, in particular a highly luminescent InP-based quantum dot.

One embodiment of the present invention relates to a nanostructure; And a ligand that binds to the surface of the nanostructure, wherein the ligand is an organic amine.

Another embodiment of the present invention is directed to a method for preparing a nanostructured core comprising the steps of: providing a zinc precursor and an indium precursor and reacting the indium precursor with a further phosphorus precursor in the presence of an organic amine ligand to provide a nanostructured core; And a second step of providing at least one of Se and S and reacting at least one of Se and S in the presence of a phosphine ligand to provide a shell, wherein said phosphine is an alkyl or aryl group having from 4 to 8 carbon atoms A trialkylphosphine or a triarylphosphine.

Another embodiment of the present invention is a nanostructured quantum dot, wherein the quantum dot has a light emission quantum yield of 70% or more, an emission maximum of 550 to 650 nm and a full width at half maximum of an emission spectrum of 60 nm or less, ZnSe _1-x S _x / ZnS core / shell (where 0.72? _X? 0.92).

According to the present invention there is provided a luminescent composition comprising a nanostructure comprising an InP core and one or more shell layers, wherein the luminescent composition has a high light emission quantum yield and in certain embodiments, There is an effect of providing a simple and economical method of manufacturing light emitting quantum dots, particularly highly luminescent InP-based quantum dots.

It is possible to form the core at the same wavelength as the existing synthesis method, at the same time, to form the shell thicker, and to form the core large, thereby reducing crystal defects occurring at the interface between the core and the cell, For reference, if the diameter of the core is large, the Se and S ratio of the anion precursor is easy, and it is easy to suppress the interface defect by forming the alloy layer of the ZnSeS layer at the interface. Therefore, the InP / ZnSeS / Not only a multi-layered shell structure is possible but also a multi-layered shell quantum dot, so that chemical stability and optical stability can be improved.

1 is a transmission electron microscope photograph of a quantum dot, (a) showing the case of Example 1 according to the present invention, and (b) showing the case of Comparative Example 1 according to the prior art, respectively.
FIG. 2 is a graph comparing the wavelengths of the quantum dots prepared in Examples 1 to 3 and Comparative Example 1. FIG.

Various embodiments of the present invention will now be described in more detail. The singular formulas used in the present invention include plural objects unless expressly indicated otherwise. Thus, for example, "nanostructures" include a plurality of such nanostructures.

The term drug as used in the present invention represents a value that may vary from +/- 10% or optionally +/- 5% of the value described, +/- 1% in some embodiments. For example, about 100 nm includes those having a size of 90 nm to 110 nm.

The term nanostructure is a structure having a feature dimension or one or more regions with dimensions less than about 500 nm, for example less than 200 nm, less than 100 nm, less than 50 nm, or even less than 20 nm, less than 10 nm. Typically, regions or characterization dimensions will exist along the smallest axis of the structure. Examples of such structures include nanowires, nanorods, nanotubes, bifurcated nanostructures, nanotetrapodes, tripods, bipods, nanocrystals, nanodots, quantum dots, nanoparticles, and the like. The nanostructure may be, for example, substantially crystalline, substantially monocrystalline, polycrystalline, amorphous, or a combination thereof. In one embodiment, each of the three dimensions of the nanostructure has dimensions less than about 500 nm, such as less than 200 nm, less than 100 nm, less than 50 nm, or even less than 20 nm, less than 10 nm.

The term heterostructure used with reference to a nanostructure refers to a nanostructure that is characterized by two or more different and / or distinguishable material types. Typically, one region of the nanostructure comprises a first material type, while a second region of the nanostructure comprises a second material type. In certain embodiments, the nanostructure comprises a core of a first material and one or more shells of a second (or third) material, wherein the different material types are, for example, the center of the nanocrystal or the arm of the bifurcated nanowire The long axis, and the long axis of the nanowire. Where the shell can completely cover the adjacent material considered as a shell or against the nanostructure considered as the heterostructure.

The diameter of the nanostructure used in the present invention refers to the diameter that is normal to the first axis of the nanostructure in cross section, where the first axis is the most divergent in the longitudinal direction with respect to the second and third axes. The second axis and the third axis are two axes having substantially the same length. The first axis need not be the longest axis of the nanostructure, and for example, for a disk-shaped nanostructure, the cross-section is a normal of a section that is substantially circular about the short longitudinal axis of the disk. The cross section is not circular, and the diameter is the average of the major and minor axes of the fragment. For elongated or high aspect ratio nanostructures (e.g., nanowires), the diameter is measured from one plane perpendicular to the longest axis of the nanowire.

The term quantum dot refers to a nanocrystal representing a quantum constraint or excitation constraint. The quantum dots may be substantially homogeneous in material properties, or may be heterogeneous in certain embodiments, including for example a core and one or more shells. The optical properties of the quantum dots can be influenced by their particle size, chemical composition and / or surface composition and can be determined by optical testing available in the art.

A "fatty acid" is a monocarboxylic acid having an aliphatic tail (saturated or unsaturated but containing only carbon and hydrogen atoms).

In a nanostructured synthetic reaction, a precursor is a chemical material (e.g., a compound or element) that reacts with another precursor, thereby imparting one or more atoms to the nanostructure produced by the reaction.

A ligand is a molecule that interacts with one or more surfaces of the nanostructure or another molecule that interacts with the surface of the nanostructure (e.g., covalent bond, ionic bond, weak or strong action through van der Waals).

The quantum yield of light emission is, for example, the proportion of protons emitted as a group of nanostructures or as protons absorbed by the nanostructures. As is known in the art, quantum yield is typically measured by a comparative method using well-characterized standard samples with known quantum yield values.

Methods for the synthesis of various nanostructured colloids are known in the art. Such methods include techniques for controlling nanostructure growth, for example, to control the size and / or shape distribution of the resulting nanostructures.

In typical colloidal synthesis, semiconductor nanostructures are prepared by rapid injection of a precursor that undergoes hydrolysis to a hot solution (e. G., A high temperature solvent and / or a surfactant). The precursors may be injected simultaneously or sequentially. The precursor reacts rapidly to form nuclei. Nanostructure growth occurs through the addition of monomers to the nucleus, typically at growth temperatures below the implantation / nucleation temperature.

Surfactant molecules interact with the surface of the nanostructures. At the growth temperature, the surfactant molecules rapidly absorb or dehydrate from the nanostructured surface, thereby inhibiting aggregation of the growing nanostructures while allowing for the addition and / or removal of atoms from the nanostructures. Generally, surfactants that are weakly coordinated to nanostructured surfaces allow rapid growth of nanostructures, while those that bind more strongly to nanostructured surfaces produce slower nanostructure growth. Surfactants also interact with one (or more) precursors to slow nanostructure growth.

Nanostructured growth in the presence of a sole surfactant typically produces a spherical nanostructure. However, the use of more than two surfactant mixtures can be used to control the growth such that, for example, the two (or more) surfactants are adsorbed differently on different crystallographic aspects of the growing nanostructures I will.

A number of parameters affecting the growth of the nanostructures are known and can be manipulated independently or in combination to produce for controlling the size and / or shape distribution of the nanostructures. These include, for example, temperature (nucleation and / or growth), precursor composition, time-dependent precursor concentration, ratio of precursor to one another, surfactant composition, number of surfactants, and ratio of surfactant And / or the ratio of surfactant (s) to the precursor.

The present invention overcomes the aforementioned difficulties (e. G., Low quantum yield) by providing shell-free synthesis techniques of indium-containing nanostructures or InP nanostructures. A method and composition for enhancing the quantum yield of a core / shell nanostructure in which shell growth is generated are disclosed. A step-growth method of layered ZnSe1-xSx / ZnS shells is also described. Compositions related to the method of the present invention are also characterized in that they include highly light emitting nanostructures with narrow size distribution and high quantum yield.

ZnSeS has less lattice mismatch with InP than ZnS. Thus, providing an intermediate layer of thin ZnSeS on the InP core increases the quantum yield. The application of the ZnS outer layer increases the quantum yield and also enhances the stability of the nanostructure. The synthesis of layered ZnSeS / ZnS shells provides greater control over the thickness of the resulting layer.

The light emitting composition according to one embodiment of the present invention may include nanostructures; And a ligand that binds to the surface of the nanostructure, wherein the ligand is an organic amine.

Wherein the nanostructures are selected from the group consisting of InP, ZnSe1-xSx (where 0 < = x < = 1) (e.g., x = 0, x = 1, 0 &lt; x &lt; 1, 0.72 x 0.92, 0.76 x 0. & 0.82? X? 0.92).

In addition, it may include ZnSeTe, MnSe, MgSe, InAs, InN, and the like. The nanostructure optionally comprises at least one shell.

The organic amine may be at least one selected from primary amines including laurylamine, stearylamine, octylamine, cetylamine, tetradecylamine, dodecylamine, hexadecylamine and oleylamine.

A quantum dot whose emission wavelength range is controlled according to the change of the content of the organic amine can be obtained. In particular, as the content of the organic amine is increased, the precursor is strongly bonded with the ionized precursor, so that nucleation of the quantum dots is retarded, nuclei of the quantum dots are formed less and the nuclei remain with fewer nuclei remain. And the emission peak moves toward the longer wavelength side.

According to one embodiment of the present invention, the content of the appropriate organic amine ligand may be 1 to 50 times, preferably 10 to 30 times, in terms of the molar ratio with respect to the Group 3 precursor. If the content of the organic amine ligand is less than the above range, the quantum dots may precipitate due to insufficient organic amine content or may not be effectively bound with the group III precursor, and the reaction may be unevenly formed. The nucleus of water may be formed and it may be difficult to control the wavelength. That is, by adjusting the content of organic amine, wavelength and size can be controlled. In addition, the wavelength and size can be controlled by appropriately selecting the kind of organic amine. For example, when quantum dots are synthesized using the same amount of organic amine ligand and then phosphine ligand and long chain fatty acid ligand are used, the quantum dots of short wavelength can be synthesized by increasing the content of the injected fatty acid. To maximize the quantum yield of the nanostructures, the organic amine is comprised of from 30 mole% to 70 mole%, from 40 mole% to less than 70 mole% of the total ligand (e.g., organic amine + phosphine + long chain fatty acid) .

And a phosphine ligand bonded to the surface of the nanostructure. The phosphine may be trialkylphosphine or triarylphosphine having an alkyl group or an aryl group having 4 to 8 carbon atoms, and specific examples thereof include Trioctylphosphine, triphenylphosphine or tributylphosphine. To maximize the quantum yield of the nanostructure, the phosphine is preferably present in the composition in an amount of less than 30 mole%, more preferably from 5 mole% to 25 mole% of the total ligand (e.g., organic amine + phosphine + long chain fatty acid) %, And 5 mol% to 15 mol%.

A long chain fatty acid ligand bound to the surface of the nanostructure, wherein the long chain fatty acid can be, for example, a material comprising at least 12 carbon atoms, less than 30 carbon atoms, less than 20 carbon atoms . Specific examples thereof include lauric acid, myristic acid, palmitic acid, stearic acid or oleic acid. In order to maximize the quantum yield of the nanostructure, the long chain fatty acid is preferably less than 50 mole%, more preferably from 10 mole% to less than 50 mole% of the total ligand (e.g., organic amine + phosphine + long chain fatty acid) Mol%, and more than 25 mol% to less than 50 mol%.

The nanostructures may be InP / ZnSe _1-x S _x / ZnS core / shell quantum dots.

For example, 0? X? 1.

As a specific example, 0.72? X? 0.92.

As a preferable example, 0.76? X? 0.92 may be generated. If the lower limit value is lowered, the quantum efficiency is decreased. If the upper limit value is exceeded, the half value width may be widened.

As a most preferred example, 0.82? X? 0.92 may be used.

For example, the nanostructure may be a luminescent composition in a form embedded in a matrix.

According to another embodiment of the present invention, there is provided a method of manufacturing a quantum dot comprising: providing a zinc precursor and an indium precursor; reacting the indium precursor and a further phosphorus precursor in the presence of an organic amine ligand to provide a nanostructured core; And a second step of providing at least one of Se and S and reacting at least one of Se and S in the presence of a phosphine ligand to provide a shell.

For reference, the synthesis of cores and shells at different stages also provides the ability to use different solvents and ligand systems in greater flexibility, e.g. core and shell synthesis. Thus, multistage synthesis techniques can facilitate fabrication of nanostructures with narrow size distributions (i.e., small FWHM) and high quantum yields. Accordingly, one aspect of the present invention provides a method of forming a shell comprising two or more layers, wherein one or more precursors are provided and reacted to form a first layer, and then (typically, The precursor for the formation of the at least one second layer is provided and reacted.

The indium precursor may be at least one selected from the group consisting of indium chloride, indium bromide, indium iodide, indium oxide, indium nitrate, indium sulfate, indium carboxylate and precursor compounds based on the precursors have. Preferably, it may be at least one selected from the group consisting of indium chloride, indium bromide, and indium iodide.

The zinc precursor may be, for example, zinc iodide, zinc bromide, zinc chloride, zinc fluoride, dimethyl zinc, diethyl zinc, zinc acetate, zinc acetylacetonate, zinc carbonate, zinc cyanide, zinc nitrate, zinc oxide , Zinc peroxide, zinc perchlorate, and zinc sulfate.

The zinc precursor is added for the purpose of suppressing the half width increase. The zinc precursor can be used in a sufficient amount to form a sufficient thickness of the shell, for example, 5 to 13 times the molar ratio with respect to the indium precursor. These excess Group 12 element precursors form core-shell quantum dots with shell thicknesses of the general size, but also allow the additional shells to grow such that shells of several nm thicker than conventional quantum dots are formed at the same wavelength. If the amount of the zinc precursor is less than the above range, the wavelength of the quantum dot may not be controlled, and undesired synthesis by-products such as In ₂ S ₃ may be synthesized above the above range.

The phosphorus precursor may be, for example, an alkyl-based phosphine compound. Specific examples thereof include tris (tri-alkylsilylphosphine (ex-P (TMS) ₃ ), trisdialkylsilylphosphine and tris p (DMA) ₃ ). Wherein a dialkylaminophosphine compound such as trisdialkylaminophosphine (e.g., tris (dimethylamino) phosphine p (DMA) ₃ or tris (diethylamino) phosphine) Is less expensive and less toxic than a trialkylsilylphosphine compound such as, for example, (tris (trimethylsilyl) phosphine P (TMS) ₃ ), so that the reactivity of the trialkylaminophosphine compound is preferably trialkylsilyl It is preferable to select an organic amine ligand in consideration of this, since it is relatively lower than a phosphine compound.

The mixed solution of the organic amine ligand can be deaerated at 100 to 250 ° C for 2 hours or less while stirring to remove internal moisture and oxygen. Then, after cooling from room temperature to 50 DEG C, it is converted into an inert atmosphere of nitrogen or argon, and then the aforementioned phosphine ligand can be injected. The temperature at which the phosphine ligand is introduced may be 150 to 300 ° C. If the temperature is lower than the temperature-raising temperature range, the nuclei of the quantum dots may not be formed or the crystallinity of the quantum dots may be lowered to deteriorate the optical properties of the quantum dots. If the temperature is exceeded, Lt; / RTI &gt;

A specific example of the first step is that a mixed solution of an indium precursor (for example, InCl ₃ ), a zinc precursor (for example, ZnCl ₂ ) and an organic amine ligand (for example, oleylamine) The mixture was stirred while being degassed for 60 minutes to remove water and oxygen therein, and then cooled to 40 DEG C and rapidly injected with phosphorus precursor (for example, tris (dimethylamino) phosphine P (DMA) ₃ ) under nitrogen or argon atmosphere and normal pressure And the temperature is raised to 185 DEG C, and the temperature raising temperature is maintained for 10 minutes to 60 minutes. The injection method is performed at a high speed using, for example, a syringe. As used herein, "rapid injection" means injecting the compound within 0.1 seconds to 5 seconds, preferably 0.5 seconds to 2 seconds. For example, it is preferable to inject at a rate of 5 ml / sec to 20 ml / sec in view of uniformity of the composition ratio of the core and particle size. At the time of injection, the ends of the syringe needles take the form of one or more porous holes, so that the materials can be added finely and uniformly, for example, in the form of a mist.

In the second step, the precursors for forming the shell can be selected to use two different species, and the shell for capping the core can be selected to have a larger bandgap. For example, the first precursor to form a shell may be a selenium-trioctylphosphine (Se-TOP) or a selenium-tributyl (selenium-tributylstannane) in which selenium (Se) is dissolved in phosphines including trialkylphosphine or triarylphosphine Phosphine (S-TBP), and the second precursor is sulfur-trioctylphosphine (S-TOP) or sulfur-sulfur trioxide in which sulfur (S) is dissolved in phosphine including trialkylphosphine or triarylphosphine, Tributylphosphine (S-TBP), wherein the second precursor is in an amount sufficient to synthesize core-shell quantum dots in the form of ally, for example in the range of 1 to 13 times molar basis, relative to the first precursor . If the amount of the second precursor is less than the above range, the wavelength of the quantum dot may not be controlled, and undesired synthesis by-products such as In ₂ S ₃ may be synthesized above the above range.

The selenium precursor is preferably controlled to have a molar ratio of 1: 6 to 2.5: 1 with respect to the indium precursor. From the viewpoint of quantum efficiency, the sulfur precursor is controlled to have a molar ratio of 1/6 to 2.5 times the precursor In terms of quantum efficiency. The reason is that if the amount of selenium precursor is excessively high relative to the indium precursor, the ratio of anion at the surface of the quantum dot increases, and when the ratio of anions increases, the phosphine ligand does not stick to the surface of the quantum dot, When the ratio of anions to the surface of the quantum dots increases, dangling bonds are increased, so that the wavelength shifts to a long wavelength due to a multistate band gap or the quantum efficiency can be lowered.

Quantum dots having an emission wavelength range controlled according to the change of the phosphine ligand content can be obtained. Particularly, as the ligand content increases, the precursor is strongly bonded with the ionized precursor, so that nucleation of the quantum dots is retarded or nuclei of the quantum dots are formed less and the nuclei formed with fewer nuclei remain. As a result, the size of the final quantum dots increases The luminescence peak moves toward the longer wavelength side.

According to one embodiment of the present invention, the content of the appropriate phosphine ligand may be 1 to 50 times, preferably 10 to 30 times, in molar ratio with respect to selenium. If the content of the phosphine ligand is less than the range, the quantum dots may precipitate due to the insufficient ligand content or may not be effectively bound to selenium to form heterogeneous reaction. If the content exceeds the range, nucleation of the quantum dots may not occur, So that it is difficult to control the wavelength. That is, by controlling the content of phosphine ligand, wavelength and size can be controlled.

For example, when a quantum dot is synthesized using the same amount of ligand, a long-chain fatty acid ligand is used to synthesize quantum dots of a long wavelength, and when an organic amine ligand is used , And quantum dots of short wavelength can be synthesized.

S phase and TOP-S (S) are prepared by heating the phosphine ligand in a nitrogen or argon atmosphere and an atmospheric pressure at 50 ° C for 10 minutes to 60 minutes in the second step, for example, selenium powder (Se) And then mixing them, or obtaining TOP-S-Se.

The shell comprises, by way of example, three or more layers, or four or more layers; The maximum layer may be five layers, providing at least one of Se and S and reacting at least one of Se and S in the presence of a phosphine ligand to provide a shell is to provide a first set of Se and S And reacting a precursor in the presence of a phosphine ligand and then providing a second set of one or more zinc precursors and reacting the precursor in the presence of a long chain fatty acid ligand to produce a first layer of shell, , Or may be repeated three or more times or four or more times to form the first layer of the shell.

Wherein providing the first set of Se and S and reacting the precursor in the presence of a phosphine ligand is as described in the second step above.

Subsequent to providing the second set of one or more zinc precursors and reacting the precursors in the presence of the long chain fatty acid ligands to produce the first layer of the shell, first a mixture of zinc precursor, long chain fatty acid ligand and organic solvent is provided do. This is to provide a raw material for growing an additional shell through reaction with excess selenium and sulfur remaining after the reaction in the second step even after core-shell quantum dot formation in the form of a core.

Examples of the zinc precursor may be independently selected from the types disclosed as the zinc precursors used in forming the cores of the first stage described above. The zinc precursor at the current stage and the first precursor at the first stage may be the same or different from each other and may be selected so that the shell that encapsulates the core at the time of forming the core and shell may have a larger bandgap. As a specific example, zinc chloride may be selected in the first step, and zinc acetate may be selected at this stage.

The long chain fatty acid ligands can be injected for uniform dispersion of the zinc precursor. The long chain fatty acid may be one containing at least 12 carbon atoms, for example.

The organic solvent is used for mixing precursors. The organic solvent is selected from the group consisting of 1-octadecene, 1-nonadecene, cis-2-methyl-7-octadecene, 2-methyl-7-octadecene, 1-heptadecene, 1-hexadecene, 1-pentadecene, 1-tetradecene, May be selected from 1-tridecene, 1-undecene, 1-dodecene, 1-decene, or combinations thereof, Or more.

The mixture may be carried out at an elevated temperature of 200 to 350 ° C. If the temperature is lower than the temperature-raising temperature range, the nucleation of the quantum dots may not be performed or the crystallinity of the quantum dots may be lowered to deteriorate the optical properties of the quantum dots. When the temperature is raised above the temperature range, the quantum dots may clump together, .

Specific reaction conditions include a mixed solution of a zinc precursor (for example, Zn (Ac)), a long chain fatty acid ligand (for example, oleic acid (OA)) and an organic solvent (for example, 1-octadecene Atmosphere and atmospheric pressure at 270 DEG C for 10 minutes to 60 minutes to make the mixture transparent and maintain the temperature elevation condition continuously. Thus forming a uniform precursor solution.

As a concrete example, in regard to shell formation of four layers, the mixture of the second step is injected into the mixture of the first step and reacted. The mixture of the second step is injected into the mixture of the first step under the above-mentioned elevated temperature condition, and it is preferable that the injection method is drip injection different from that described in the first step. Considering that the temperature of the precursor is much lower than the solution in the reactor, it may have an influence upon the rapid injection. For example, it can be injected at a rate of about 0.1 ml / sec.

In the case of the production according to this method, the shell of the quantum dots obtained has a higher proportion of the selenium precursor and a higher proportion of the sulfur precursor toward the core side. The reaction time is about 1 minute to 25 minutes, and the reaction temperature can be about 180 to 280 ° C.

 Further, by repeating the second step and the third step four times, it is possible to form the layer structure having different concentration grades by overlapping, and as a result, the deterioration (photo-oxidation) by light, the oxidation by oxygen flow in the air, It is possible to effectively reduce the decrease in the quantum efficiency due to thermal degradation. The reaction time of the second step in the repetition is about 1 minute to 25 minutes, and the reaction temperature can be increased in the stepwise range from 180 to 280 ° C. The reaction time of the third step in the repetition is about 1 minute to 25 minutes, and the reaction temperature can be increased in steps of 180 to 280 ° C.

Particularly, when the reaction temperature reaches 280 ° C. during the second and third steps, the second and third steps are repeatedly carried out while maintaining the upper limit value of 280 ° C. without increasing the temperature. To further form a shell. This is because, as shown in the reference example to be described later, when the composition is heated to a temperature higher than 280 deg. C, the half width may increase, and when the temperature is lowered, the quantum efficiency may be lowered due to limited shell coating.

For example, in the case of repeating 4 times, the mixture of the second step is injected, the temperature is raised to 200 ° C., the reaction is carried out for 20 minutes, the mixture of the third step is injected and maintained at 220 ° C. for 50 minutes, . Then, the mixture of the second step is injected, the temperature is raised to 240 ° C., the reaction is carried out for 20 minutes, the mixture of the third step is injected, and the mixture is maintained at 260 ° C. for 50 minutes to form a second shell. Then, the mixture of the second step is injected, and the mixture is heated to 270 ° C., reacted for 10 minutes, injected with the mixture of the third step, heated to 280 ° C. and held for 10 minutes to form a third shell. Then, the mixture of the second step is injected with maintaining the temperature at 280 ° C., the reaction is carried out for 5 minutes, the mixture of the third step is injected, and the mixture is maintained for 5 minutes to form the fourth shell.

Considering that the fourth shell is synthesized while being heated to a temperature higher than 280 ° C., the half-width is increased and the total diameter of the quantum dots is increased by increasing the thickness of the shell. As a result, And the fourth shell is formed while maintaining the temperature at a temperature not exceeding the temperature of the fourth shell.

It can then be cooled for stabilization of the product. The cooling conditions are suitably in the range of 200 to 220 캜 for the first and second reaction conditions of the second and third steps, but are not limited thereto.

The thickness of the shell layer can be conveniently controlled by controlling the amount of precursor provided. For a given layer, the one or more precursors are optionally provided in an amount when the growth reaction is substantially complete, and the layer is of a predetermined thickness. When more than one different precursor is provided, the amount of each precursor can be limited or one of the precursors can be provided while limiting the amount over which the others are provided in excess. The appropriate amount of precursor for various preparation to the desired shell thickness can be easily calculated. For example, the InP core can be dispersed in solution after synthesis and purification thereof, and its concentration can be calculated by UV / Vis spectroscopy using Beer-Lambert law. The extinction coefficient can be obtained from bulk InP. The size of the InP core can be measured, for example, by physical modeling based on excitation maxima and quantum confinement of the UV / Vis absorption spectrum. Knowing the particle size, the molar amount, and the desired production thickness of the shell material, the amount of precursor can be calculated using the bulk determination parameters (i. E., A single layer thickness of the shell material).

In one example, the first set of shells described above is a ZnSe1-xSx monolayer thickness of 1.0 nm to 3.0 nm, the core can be covered by a small island of ZnSe1-xSx, or 50% of the cationic moiety and 50 of the anionic moiety % Can be occupied by the shell material. Similarly, providing a second set of one or more precursors and reacting the precursors to produce the second layer of shells comprises providing the one or more precursors in an amount substantially the reaction is complete, The two layers are a single layer ZnS thickness of about 0.3 nm to about 1.0 nm, for example a single layer ZnS thickness of about 0.5 nm or a single layer thickness of about 0.8 nm to 1.0 nm.

And then adding an alkylthiol compound to the reaction product. The alkylthiol compound is added dropwise to react with the unreacted zinc precursor in the first or fourth step to form the outermost ZnS shell. Specific examples of the alkylthiol compound include hexane thiol, octane thiol, decane thiol, dodecane thiol, hexadecane thiol, and mercaptopropyl silane. At this time, if necessary, the mixture of the third step may be injected.

In this manner, a shell surrounding the core is formed in four or more layers, or three to five layers, and then reacted with a fresh zinc precursor and unreacted S in the presence of a C ₆ -C ₁₈ thiol compound to form a shell And then manufacturing the outermost layer. The zinc precursor may be at least one selected from the zinc precursor of the first stage and the fresh zinc precursor.

The C ₆ -C ₁₈ thiol compound may be, for example, 1-dodecanethiol, tert-dodecyl mercaptan or 1-octanethiol.

For example, a ZnS shell layer may be additionally formed to a thickness of 1 to 2 nm outside the core-shell quantum dot grain of the alloy structure. The injection of the raw material is performed by a high-speed injection method, and may be performed at a speed of, for example, 5 ml / sec to 200 ml / sec. The reaction time is about 5 minutes to 60 minutes, and the reaction temperature can be about 200 to 350 ° C.

The reaction is then purified to obtain a powder. When the reaction is completed, the reaction mixture is allowed to stand at room temperature and then purified. The refining process can be performed, for example, by refining the powder three or more times with a large amount of acetone, and then the powder can be stored and used by being dispersed in a solvent such as chloroform, toluene or hexane.

According to the above method, a shell other than a core can be synthesized in the form of a rod. More specifically, since the lattice mismatch between InP and ZnSe is smaller than that of InP and ZnS, a shell is formed in a multi-layer structure rather than a single layer. In order to reduce the lattice mismatch between the shells and the InP / ZnSeS / ZnS type Alloy shell using a concentration gradient other than a simple InP / ZnSe / ZnS multilayer structure, And the like.

The nanostructured quantum dot according to another embodiment of the present invention has a light emission quantum yield of 70% or more, an emission maximum of 550 to 650 nm and a full width at half maximum of the emission spectrum of 60 nm or less, wherein the nanostructure is InP / ZnSe _{1 - x} S _x / ZnS core / shell where 0.72? _X? 0.92.

The nanostructured quantum dots, for example InP / ZnSe1-xSx / ZnS quantum dots, may optionally have high light emitting quantum yields, such as greater than 65%, greater than 70%, greater than 75%, greater than 80%, greater than 85%, or even greater than 90 % &Lt; / RTI &gt; yield. The emission spectrum of the nanostructure can essentially represent the spectrum of any desired moiety. For example, the emission spectrum may have an emission maximum of 450 nm to 750 nm, for example, 500 nm to 650 nm, 500 nm to 560 nm, or 550 nm to 650 nm. The luminescence spectrum may reflect a narrow size distribution of the nanostructures with a full width at half maximum of 60 nm or less, for example, 50 nm or less, 45 nm or less, or even 40 nm or less or 35 nm or less

The resulting nanostructures may optionally be embedded in an organic polymer, a silicon-containing polymer, an inorganic, glassy and / or other matrix, or may be used in the manufacture of nanostructured phosphors, for example as a matrix.

The nanostructure may have an average diameter of less than 10.0 nm, more preferably 5.0 nm or more to less than 10 nm, 5.0 nm to 8.5 nm or 5.0 nm to 8.0 nm, and the InP core may have an average diameter of 1.0 nm to 4.0 nm, Wherein the ZnSe _{1 - x} S _x shell has a single layer thickness of about 1.0 nm to 3.0 nm and the ZnS shell is a quantum dot having a single layer thickness of 0.3 nm to 1.0 nm, (Such as having a high light emission quantum yield as described above and emitting light at a specific wavelength and having a narrow size distribution in a specific embodiment), and it is also possible to increase the particle size (or to form a thick shell) Can provide optical and chemical stability together.

In addition, the stability of the quantum dots according to the present invention is also excellent and, if necessary, various application products can be produced through various surface treatments.

While the present invention will be described by way of examples, the technical spirit of the present invention is not limited by the following examples.

[Example]

InP / ZnSe _{1 - x} S _x (x = 0.87 in the range of 0.82? _X ? 0.92, 4 layer structure) / ZnS, and quantum dots were synthesized by the following method.

Example 1

As a step S1, while stirring InCl ₃ 3mmol and ZnCl ₂ 18mmol, Oleylamine 42ml to which sealing solution for 30 minutes at 120 ℃ degassing (degassing) after mixing a 250ml three-necked flask to remove moisture and oxygen flow inside, and nitrogen (N ₂ ) Atmosphere. The solution was then heated to 180 ° C and 1.8 ml of tris (dimethylamino) phosphine (P (DMA) ₃ , 97%) was rapidly injected using a syringe and the reaction was maintained for 4 minutes (mixture I).

In Step S2, 1.0 mmol of Se and 1.0 mmol of S were dissolved in 1.5 ml of trioctylphosphine (TOP) to prepare a solution (Mixture II-a). In addition, 1.0 mmol of Se and 5.0 mmol of S were dissolved in 3.0 ml of TOP to prepare a solution (mixture II-b). In the same manner, 0.5 mmol of Se and 5.5 mmol of S were dissolved in 3.0 ml of TOP to prepare a solution (mixture II-c), and 5.0 mmol of S was dissolved in 2.5 ml of TOP to prepare a solution II-d).

Step S3 was prepared by mixing 10 mmol of zinc acetate, 20 mmol of oleic acid (OA) and 3.5 ml of 1-octadecene (ODE) and dissolving at 270 ° C for 15 minutes (Mixture III).

In Step S4, the mixture II-a was injected into the InP core quantum dots of the mixture I, and the temperature was raised to 200 ° C, followed by reaction for 20 minutes.

Then, in step S5, the mixture III was injected, and the mixture was maintained at 220 DEG C for 50 minutes to form a first shell.

The steps S4 and S5 were then repeated three more times in a similar manner. That is, the mixture II-b was injected, and the mixture was heated to 240 ° C., reacted for 20 minutes, and the mixture III was injected and maintained at 260 ° C. for 50 minutes to form a second shell. Next, the mixture II-c was injected, and the mixture was reacted at 270 ° C. for 10 minutes. Then, the mixture III was injected and maintained at 280 ° C. for 10 minutes to form a third shell. Finally, while holding the temperature at 280 ° C, the mixture II-d was injected and reacted for 5 minutes. After the mixture III was injected, the mixture was held for 5 minutes to form a fourth shell and cooled to 200 ° C.

In addition, 20 mmol of 1-dodecane thiol (DDT) was added and reacted for 20 minutes to react with the unreacted Group 12 precursor in step S1 or S4 to form the outermost ZnS shell, and the mixture III was injected The ZnS shell was formed by holding for 50 minutes and then cooled to room temperature.

Finally, in step S6, the synthesized InP / ZnSeS / ZnS quantum dots are dispersed in hexane, the by-products are removed using a centrifugal separator, acetone is added to precipitate, and the dispersion is finally dispersed in hexane. The quantum dots synthesized in this way were synthesized with an average particle diameter of 8.0 nm (total diameter) in the visible light wavelength region, a wavelength of 610 nm, a half width of 50 nm and a quantum efficiency of 78%. Results The core diameter of the InP / ZnSe _{1 - x} S _x / ZnS core / shell quantum dots was 3.0 nm, and the thickness of the shell layer was 2.5 nm.

The measurement was carried out using a QE-2000 (OTSUKA) instrument at an excitation wavelength of 450 nm and a measurement range of 480 nm to 800 nm under the measurement conditions. For the PL analysis, FP-8300 (JASCO) (JEOL) equipment was used.

Example  2

Synthesis was carried out by the same procedure as in Example 1 except that oleic acid (OA) in Step S3 of Example 1 was replaced with myristic acid (mols) of the same mole number (20 mmol). As a result, InP / ZnSe _{1 - x} S The total diameter of the _x / ZnS core / shell quantum dots was 7.0 nm, the core diameter was 3.0 nm, and the thickness of the shell layer was 2.0 nm.

The quantum dots showed an average particle diameter of 7.0 nm in the visible light wavelength region, a wavelength of 612 nm, a half width of 51 nm and a quantum efficiency of 73%.

Example 3

Synthesis was carried out by the same procedure as in Example 1, except that the oleic acid (OA) in Step S3 of Example 1 was replaced with the same molar amount (20 mmol) of palmitic acid. As a result, the results showed that InP / ZnSe _{1 - x} S The total diameter of the _x / ZnS core / shell quantum dots was 7.0 nm, the core diameter was 3.0 nm, and the thickness of the shell layer was 2.0 nm.

The quantum dots showed an average particle diameter of 7.0 nm in a visible light wavelength region, a wavelength of 614 nm, a half width of 52 nm and a quantum efficiency of 75%.

Example 4

Synthesis was carried out by the same procedure as in Example 1, except that P (DMA) ₃ in step S1 of Example 1 was replaced with P (TMS) ₃ in the same amount. As a result, the result showed that InP / ZnSe _{1 -x} The total diameter of the S _x / ZnS core / shell quantum dots was 5.0 nm, the core diameter was 1.0 nm, and the thickness of the shell layer was 2.0 nm.

The quantum dots showed an average particle diameter of 5.0 nm in the visible light wavelength region, a wavelength of 551 nm, a half width of 60 nm and a quantum efficiency of 81%.

Comparative Example 1

In step S3 of Example 1, 10 mmol of zinc acetate, 20 mmol of oleic acid (OA) and 3.5 ml of 1-octadecene (ODE) were mixed with 10 mmol of zinc stearate and 25 ml of 1-octa ZnSe _{1- x} S _x / ZnS core / shell quantum dots of 6.0 nm in total diameter, and the core of the ZnSe _{1- x} S _x / ZnS core / shell quantum dots was 6.0 nm in diameter. And the thickness of the shell layer was 1.5 nm.

The quantum dots had an average particle diameter of 6.0 nm in the visible light wavelength region, a wavelength of 600 nm and a half width of 55 nm, but showed a quantum efficiency of 62%.

FIG. 2 shows a graph of the wavelengths measured in Examples 1 to 3 and Comparative Example 1. As shown in FIG. 2, it was confirmed that the wavelengths of Examples 1 to 3 were in the range of 600 to 650 nm, while those of Comparative Example 1 were not.

Reference example

The mixture II-d was injected and the temperature was raised to 300 ° C, followed by a reaction for 5 minutes. After the mixture III was injected, ZnSe _1-x S _x / ZnS core / shell Quantum dots of the InP / ZnSe _1-x S _x / ZnS core / shell quantum dots were obtained as a result of the same procedure as in Example 1 except that the temperature was raised to 320 ° C., Diameter: 10.0 nm, core diameter: 3.0 nm, and shell layer thickness: 3.5 nm.

The quantum dots showed a wavelength of 605 nm and a quantum efficiency of 81%, but had an average particle diameter of 10.0 nm and a half width of 68 nm in the visible light wavelength region.

The invention being thus described, it is intended that the present invention be ascertained and understood, and that those skilled in the art will be able to make various modifications thereto, without departing from the scope of the present invention.

Claims (15)

Nanostructure; And a ligand that binds to the surface of the nanostructure,
Wherein the ligand is an organic amine. The method according to claim 1,
Wherein the organic amine is at least one selected from the group consisting of laurylamine, stearylamine, octylamine, cetylamine, tetradecylamine, dodecylamine, hexadecylamine and oleylamine. The method according to claim 1,
Wherein the phosphine is a trialkylphosphine or triarylphosphine having an alkyl group or an aryl group having 4 to 8 carbon atoms, wherein the phosphine ligand is bonded to the surface of the nanostructure. The method according to claim 1 or 3,
Wherein the composition further comprises a long chain fatty acid ligand bound to the surface of the nanostructure, wherein the long chain fatty acid comprises at least 12 carbon atoms. 5. The method of claim 4,
Wherein the long chain fatty acid is lauric acid, myristic acid, palmitic acid, stearic acid or oleic acid. The method according to claim 1,
Wherein the nanostructure is an InP / ZnSe _{1 - x} S _x / ZnS core / shell quantum dot wherein 0? _X? 1. The method according to claim 6,
0.72? X? 0.92. The method according to claim 1,
Wherein the nanostructure is embedded in a matrix. Providing a zinc precursor and an indium precursor and reacting the indium precursor with a further phosphorus precursor in the presence of an organic amine ligand to provide a nanostructured core; And
Providing a shell by providing at least one of Se and S and reacting at least one of Se and S in the presence of a phosphine ligand to provide a shell,
Wherein the phosphine is trialkylphosphine or triarylphosphine having an alkyl group or aryl group having 4 to 8 carbon atoms. 10. The method of claim 9,
The shell comprising three or more layers; Wherein providing at least one of Se and S and reacting at least one of Se and S in the presence of a phosphine ligand to provide a shell comprises providing a first set of Se and S and providing a precursor And then reacting the precursor in the presence of a long chain fatty acid ligand to produce a first layer of the shell, and then repeating at least three times to form the first layer of the shell Is formed in three or more layers. 11. The method of claim 10,
Wherein the zinc precursor is selected from the group consisting of zinc iodide, zinc bromide, zinc chloride, zinc fluoride, dimethyl zinc, diethyl zinc, zinc acetate, zinc acetylacetonate, zinc carbonate, zinc cyanide, zinc nitrate, zinc oxide, Wherein the long chain fatty acid comprises at least 12 carbon atoms, wherein the long chain fatty acid comprises at least 12 carbon atoms. 10. The method of claim 9,
Further comprising the step of reacting a fresh zinc precursor with an unreacted S in the presence of a C ₆ -C ₁₈ thiol compound to prepare an outermost layer of the shell, wherein the zinc precursor is reacted with the zinc precursor of the first step Wherein the zinc precursor is selected from fresh zinc precursors. 10. The method of claim 9,
Wherein the organic amine ligand is at least one selected from the group consisting of laurylamine, stearylamine, octylamine, cetylamine, tetradecylamine, dodecylamine, hexadecylamine and oleylamine. Wherein the quantum dot has a light emission quantum yield of 70% or more, an emission maximum of 550 to 650 nm and a full width at half maximum of an emission spectrum of 60 nm or less, wherein the nanostructure is InP / ZnSe _{1 - x} S _x / ZnS core / shell (where 0.72? _x? 0.92). 15. The method of claim 14,
Wherein the nanostructure has an average diameter of less than 10.0 nm, the InP core has an average diameter of 1.0 nm to 4.0 nm,
Wherein the ZnSe _{1 - x} S _x shell has a single layer thickness of 1.0 nm to 3.0 nm and the ZnS shell has a single layer thickness of 0.3 nm to 1.0 nm.

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