KR20210089442A - Quantum-dot - Google Patents

Abstract

The present application relates to a quantum dot, a quantum dot solution including the same, a method for manufacturing a quantum dot, and a quantum dot light emitting device including the same. Provided is a quantum dot with improved optical stability and luminescence properties. The quantum dot includes nanoparticles and a passivation film.

Description

Quantum dots {QUANTUM-DOT}

The present application relates to a quantum dot, a quantum dot solution including the same, a method for manufacturing the quantum dot, and a quantum dot light emitting device including the same.

Quantum dots (hereinafter, may be referred to as "QDs") have high color purity, luminous efficiency, and wide color reproducibility, and can easily adjust the energy band gap according to their size, It is attracting attention as a next-generation light emitting diode technology.

Efforts have been made to apply these quantum dots to the field of optoelectronics such as light emitting devices, batteries, and sensors, and when quantum dots are used in the field of optoelectronics, quantum dots with high light emitting characteristics and optical stability are required.

Conventionally, when synthesizing quantum dots, an organic ligand having a long hydrocarbon chain was used as a surface treatment to control the reaction and maintain dispersibility. Although the nanoparticles whose surface is substituted by the organic ligand are maintained in dispersibility in an organic solvent by steric stabilization, the organic ligand itself acts as an insulation layer, which is a factor that degrades the performance of a device such as a light emitting diode. In order to solve this problem, research to facilitate charge transport between nanoparticles by replacing the organic ligand with an inorganic ligand is being conducted. However, in this case, there is a problem in that a defect is formed on the surface during the process of substituting the inorganic ligand, so that luminous efficiency is sharply decreased.

The present application relates to a quantum dot, and provides a quantum dot having improved optical stability and light emitting properties.

This application relates to quantum dots. The quantum dots may include nanoparticles, an inorganic ligand substituted on the surface of the nanoparticles, and a passivation film formed on the surface of the nanoparticles. The present application provides a quantum dot having excellent optical stability and light emitting characteristics, and minimizing a decrease in luminous efficiency by using the quantum dot.

In the present application, nanoparticles may include a semiconductor material. In the present specification, nanoparticles may refer to single-material semiconductors or compound semiconductors composed of particles having a size ranging from 1 nanometer or more to several tens of nanometers. The nanoparticles of the present specification may have a core-shell structure, and each of the core and the shell may consist of one or more layers. For example, it may have a core-shell-shell structure.

The semiconductor material constituting the nanoparticles of the present application may include, for example, a group II-VI semiconductor compound, a group III-V semiconductor compound, a group IV-VI semiconductor compound, a group IV element or compound, or a combination thereof. Group II-VI semiconductor compounds include, for example, binary compounds of CdS, CdSe, CdTe, ZnS, ZnSe, ZnTe, ZnO, HgS, HgSe, HgTe, or combinations thereof; CdSeS, CdSeTe, CdSTe, ZnSeS, ZnSeTe, ZnSTe, HgSeS, HgSeTe, HgSTe, CdZnS, CdZnSe, CdZnTe, CdHgS, CdHgSe, CdHgTe, HgZnS, HgZnSe or a combination thereof; CdHgZnTe, CdZnSeS, CdZnSeTe, CdZnSTe, CdHgSeS, CdHgSeTe, CdHgSTe, HgZnSeS, HgZnSeTe, HgZnSTe, or a combination thereof. The group III-V semiconductor compound includes, for example, a binary compound of GaN, GaP, GaAs, GaSb, AlN, AlP, AlAs, AlSb, InN, InP, InAs, InSb, or a combination thereof; ternary compounds of GaNP, GaNAs, GaNSb, GaPAs, GaPSb, AlNP, AlNAs, AlNSb, AlPAs, AlPSb, InNP, InNAs, InNSb, InPAs, InPSb, GaAlNP, or combinations thereof; GaAlNAs, GaAlNSb, GaAlPAs, GaAlPSb, GaInNP, GaInNAs, GaInNSb, GaInPAs, GaInPSb, InAlNP, InAlNAs, InAlNSb, InAlPAs, InAlPSb, or a quaternary compound of a combination thereof. The group IV-VI semiconductor compound may be, for example, a binary compound of SnS, SnSe, SnTe, PbS, PbSe, PbTe, or a combination thereof; a ternary compound of SnSeS, SnSeTe, SnSTe, PbSeS, PbSeTe, PbSTe, SnPbS, SnPbSe, SnPbTe, or a combination thereof; It may be a quaternary compound of SnPbSSe, SnPbSeTe, SnPbSTe, or a combination thereof. The group IV element or compound may be, for example, Si, Ge, SiC, SiGe, or a combination thereof. The nanoparticles may have a core-shell structure. In this case, each of the core and the shell may be formed of a single layer or two or more layers.

The nanoparticles of the present application may have an average particle diameter in the range of 1 to 100 nm according to the D50 particle size analysis. The lower limit of the particle size may be, for example, 5 nm, 8 nm, 10 nm, 15 nm, 20 nm, or 30 nm or more, and the upper limit is, for example, 95 nm, 90 nm, 85 nm, 80 nm, or 75 nm. nm or less. The present application may provide quantum dots with desired physical properties within the above particle size range.

The quantum dots of the present application may be those in which inorganic ligands are substituted on the surface of the nanoparticles. The inorganic ligand may include, for example, S, Se, Te, O, P or As.

In one example, the quantum dots according to the present application can obtain nanoparticles in which the inorganic ligand is substituted on the surface by exchanging the organic ligand of the nanoparticles surface-treated first with the inorganic ligand. The exchange of ligands may be accomplished through phase transfer of quantum dots between a solution in which quantum dots having organic ligands exist and a solution in which inorganic ligand compounds are present. Alternatively, the exchange of ligands may be performed in a common solvent in which quantum dots having organic ligands and an excess of inorganic ligand compounds are present.

First, the nanoparticles of the present application may be dispersed in a colloidal form in an organic solution, and an organic ligand may be coordinated to the surface of the nanoparticles. That is, the nanoparticles may be surrounded by an organic ligand. The organic ligand is, for example, TOP (trioctylphosphine), TOPO (trioctylphosphine oxide), oleic acid, oleylamine, octylamine, trioctylamine, hexadecylamine ( hexadecylamine), octanethiol, dodecanethiol, hexylphosphonic acid (HPA), tetradecylphosphonic acid (TDPA), octylphosphinic acid (OPA), ethanol, or mixtures thereof. it's not going to be The solvent of the organic solution may include, for example, cyclohexane, hexane, chloroform, toluene, octane, chlorobenzene, or a mixture thereof, but is not limited thereto. Meanwhile, the solvent may be the same compound as the organic ligand.

Substitution of the organic ligand may be performed by a method known in the art. For example, in the present application, a solvent in which an inorganic ligand precursor exemplified by _{(NH 4} ) _{2 S is dispersed in a solvent in which the nanoparticles are dispersed may be stirred.} The solvent may be, for example, n-methylformamide (NMF). The solvent in which the nanoparticles are dispersed and the solvent in which the inorganic ligand precursor is dispersed may be immiscible, and thus the two solvents may form two layers. In the present application, the inorganic ligand may be substituted on the surface of the nanoparticles by stirring the two solvents, and in this case, the nanoparticles substituted with the inorganic ligand may be initially moved toward the solvent in which the inorganic ligand precursor is dispersed. Thereafter, the present application can obtain nanoparticles whose surface is substituted with the inorganic ligand.

In an embodiment of the present application, the passivation layer may include a semiconductor material. The semiconductor material may be the same as or different from the semiconductor material described above. The passivation film according to the present application may be formed, for example, after the inorganic ligand is substituted on the surface of the nanoparticles. Conventionally, when synthesizing quantum dots, an organic ligand having a long hydrocarbon chain was used as a surface treatment to control the reaction and maintain dispersibility. The nanoparticles whose surface is substituted by the organic ligand are maintained in dispersibility in an organic solvent by steric stabilization, but the organic ligand itself acts as an insulation layer, which is a factor that degrades the performance of devices such as light emitting diodes. In order to solve this problem, research to facilitate charge transport between nanoparticles by replacing the organic ligand with an inorganic ligand is being conducted. However, in this case, there is a problem in that a defect is formed on the surface during the process of substituting the inorganic ligand, resulting in a sharp decrease in luminous efficiency. According to the present application, by forming a passivation film on the inorganic ligand-substituted nanoparticles, the defect is compensated, thereby improving luminous efficiency and providing quantum dots with excellent optical stability.

In one example, the passivation layer may have a thickness in the range of 0.1 to 5 nm. The upper limit of the thickness range may be, for example, 4 nm, 3 nm, 2 nm, 1.5 nm, 1.3 nm, 1.0 nm or 0.8 nm, and the lower limit is, for example, 0.15 nm, 0.2 nm, 0.23 nm or 0.25 nm or larger. The present application may provide a quantum dot having improved optical stability and light emitting properties within the thickness range. The passivation film is formed on the surface of the nanoparticles after the inorganic ligand substitution, but may be formed directly on the nanoparticles, that is, on the nanoparticle core or the nanoparticle core-shell.

The present application also relates to a quantum dot solution. The quantum dot solution may include the aforementioned quantum dots. In one example, the quantum dot solution may include the aforementioned quantum dots and a solvent. The solvent may include, for example, ethanolamine, dimethyl sulfoxide (DMSO), dimethylformamide (DMF), formamide, or n-methylformamide (NMF), but is not limited thereto.

The present application also relates to a method of manufacturing quantum dots. The manufacturing method may include, for example, forming a passivation film on the surface of the inorganic ligand-substituted nanoparticles. In the manufacturing method of the present application, first, the inorganic ligand is substituted on the nanoparticles, and then the passivation layer may be formed. By the above manufacturing method, the present application can compensate for the defects on the surface of the nanoparticles that occur when the inorganic ligand is substituted through the passivation film. The forming of the passivation film may be performed, for example, by UV treatment or heat treatment, but is not limited thereto.

In one example, in order to first form the nanoparticles, the manufacturing method of the present application may use a zinc source that can be used as a precursor of the first component to form a core. The zinc source may be zinc oleate, zinc hexanoate, zinc octanoate, zinc laurate, zinc palmitate, zinc stearate, zinc dithiocarbamate, or a mixture thereof.

Also, for example, the core-forming second component precursor is a group 16 element material such as S powder, selenium powder, Te powder, or Po powder, or a material thereof. may include.

With respect to the core-containing solution, the type of solvent included in the solution is not particularly limited. In one example, the core-containing solution may include 1-octadecene, 1-hexadecene, 1-eicosene, eicosane, octadecane, hexadecane, tetradecane, squalene, squalane, or dioctyl ether. .

A method for preparing the core-containing solution as described above is also not particularly limited. Taking the case in which the two-component core described above includes zinc (Zn) as an example, a mixture (M0) including a zinc source, which is the first component precursor for core formation, and a solvent is prepared, and a vacuum is maintained at a temperature of 100° C. or higher. to (the first step of forming a core); heating the mixture (M0) until it reaches a temperature of about 250° C. or higher after forming an inert atmosphere (the second step of forming a core); and preparing a mixture (M2) by injecting a solution (M1) in which the core-forming second component precursor is dispersed in a solvent into the mixture (M0) heated in an inert atmosphere (the third step of forming the core); This can be manufactured.

In one example, in relation to the first step of forming the core, specific types of the zinc source and the solvent may be the same as described above. In addition, in relation to the first step of forming the core, the upper limit of the temperature at which the mixture is maintained in a vacuum state may be, for example, 200° C. or less or 150° C. or less. The time for which the vacuum is maintained at the temperature in the above range is not particularly limited, but may be, for example, several minutes to several tens of minutes, specifically, about 5 minutes to 60 minutes.

In one example, in relation to the second step of forming the core, the inert atmosphere may be formed by injecting an inert gas such as _{nitrogen (N 2 ) or argon (Ar).} In addition, the upper limit of the temperature at which the mixture M0 is heated may be, for example, 400 °C or less or 300 °C or less.

In one example, in relation to the third step of forming the core, specific types of the core forming second component precursor and the solvent injected into the mixture M0 may be the same as described above.

In one example, the method for preparing the core-containing solution may further include a fourth step of forming the core. Specifically, the fourth step of forming the core may be performed by injecting the mixture (M2) into a complex made by heating and then dissolving the precursor of the second component for forming the core in a solvent. In this case, the content of the core-forming second component precursor may be greater than the content of the core-forming second component precursor used in the third step of forming the core.

The nanoparticles of the present application may additionally form a shell after the core is formed, but this is optional and is not necessarily limited to the following method.

In one example, the shell-forming first component precursor may include a zinc compound. In this case, the zinc compound may be of the same type as the zinc source described above.

For example, the shell-forming first component precursor comprises zinc oleate, zinc hexanoate, zinc octanoate, zinc laurate, zinc palmitate, zinc stearate, zinc dithiocarbamate, or mixtures thereof. It may be a zinc compound.

Although not particularly limited, the shell-forming first component precursor may be the same as or different from the core-forming first component precursor.

In one example, the shell-forming second component precursor included in the first solution is 16 such as S powder, selenium powder, Te powder, or Po powder. It may be a group element material or one containing the same. In this case, the shell-forming second component precursor may be selected to be different from the core-forming second component precursor.

In addition to the above, the preparation method of the present application may add a ligand solvent. The ligand can improve the compatibility of nanoparticles including the core, and has an effect on increasing the quantum yield of the nanostructures or improving the luminescent properties.

The kind of ligand is not particularly limited. In one example, the ligand may be selected from a fatty acid ligand, a phosphine ligand, and an amine ligand, which is an organic ligand.

Although not particularly limited, the fatty acid ligand may be, for example, lauric acid, caproic acid, myristic acid, palmitic acid, stearic acid, oleic acid, or a mixture thereof. In addition, as the phosphine ligand, trioctylphosphine oxide, trioctylphosphine, diphenylphosphine, triphenylphosphine oxide, tributylphosphine oxide, or mixtures thereof may be used. And, as the amine ligand, dodecylamine, oleylamine, hexadecylamine, dioctylamine, octadecylamine, or a mixture thereof may be used.

The present application may also substitute an inorganic ligand for the organic ligand. Substitution of the inorganic ligand can be performed by a known method. For example, in the present application, a solvent in which an inorganic ligand precursor exemplified by _{(NH 4} ) _{2 S is dispersed in a solvent in which the nanoparticles are dispersed may be stirred.} The solvent may be, for example, n-methylformamide (NMF). The solvent in which the nanoparticles are dispersed and the solvent in which the inorganic ligand precursor is dispersed may be immiscible with each other, and thus the two solvents may form two layers. In the present application, the inorganic ligand may be substituted on the surface of the nanoparticles by stirring the two solvents, and in this case, the nanoparticles substituted with the inorganic ligand may be initially moved toward the solvent in which the inorganic ligand precursor is dispersed. Thereafter, the present application can obtain nanoparticles whose surface is substituted with the inorganic ligand.

In addition, the manufacturing method of the present application may further include forming a passivation film. Formation of the passivation film may be performed by UV treatment or heat treatment, as described above. First, in the manufacturing method, as a precursor composition for forming a passivation film, UV treatment or heat treatment may be performed after the above-described precursor composition is added to the quantum dots. In one example, the precursor composition may be zinc acetate dihydrate, and further (NH ₄ ) ₂ S may be added to form a passivation film of ZnS, but is not limited thereto. That is, the manufacturing method may form a passivation film through the precursor composition described above through a known method so as to form a desired passivation film composition.

The present application also relates to a quantum dot light emitting device including quantum dots. The quantum dot light emitting device may include a pair of electrodes and a light emitting layer including quantum dots. The quantum dots may be the aforementioned quantum dots.

For example, the quantum dot light emitting device of the present application includes an anode; a negative electrode facing the positive electrode; and a light emitting layer positioned between the anode and the cathode. The light emitting layer may include quantum dots. In addition, in one example, the quantum dot light emitting device is a hole transport layer located between the anode and the light emitting layer; and an electron transport layer positioned between the light emitting layer and the cathode.

In the above, the hole transport layer includes a hole transport material. In the above, the electron transport layer includes an electron transport material. The hole transport layer may transport holes to the light emitting layer. The electron transport layer may transfer electrons to the emission layer. The light emitting layer may emit light formed by a combination of holes and electrons transmitted from each of the hole transport layer and the electron transport layer.

The present application provides a quantum dot with improved optical stability and light emitting properties.

1 and 2 are diagrams showing PL intensity measurement results of quantum dots according to Examples and Comparative Examples of the present application.

Hereinafter, the present application will be specifically described through Examples and Comparative Examples, but the scope of the present application is not limited to the following Examples.

Example 1

(1) Formation of nanoparticles

0.2 mmol of zinc oleate (Zn(oleate) ₂ ) and 10 mL of 1-octadecene were mixed in a reactor equipped with a syringe, a cooler, and a thermometer, and a vacuum was created at 130° C. for 20 minutes. . Then, nitrogen was injected into the reactor to create an inert atmosphere and then heated until reaching 300°C. A solution in which Se powder was dispersed in 1-octadecene (1-octadecene) at 15.8 mg/1 mL was prepared, and this was injected into the prepared reaction solution to proceed with the reaction. After 1 hour, the reaction was terminated and cooled to room temperature, and toluene and ethanol were added to the reaction mixture to precipitate the reaction, followed by purification. The final reactant was redispersed in 5 mL of hexane to prepare a nanoparticle solution.

(2) inorganic ligand exchange

After preparing a solution in which 100 μL of (NH ₄ ) ₂ S was added to 5 mL of N-methylformamide, the solution was added to the nanoparticle solution. After stirring the solution for 30 minutes, the supernatant was removed. After purification by adding iso-propanol to the reaction solution, it was re-dispersed in 10 mL of N-methylformamide ^{to prepare nanoparticles in which S 2-} inorganic ligands were surface-treated on the surface of ZnSe nanoparticles.

(3) Formation of passivation film

50 mg of zinc acetate dihydrate and 50 μL of (NH ₄ ) ₂ S were added to the surface-treated nanoparticles. By UV treatment for 1 hour using a UV lamp, ZnS was again formed as a passivation film on the surface of the ZnSe nanoparticles surface-treated with ^{the S 2-inorganic ligand prepared in (2) above.}

Example 2

In Example 1 through step (2), S ^2- inorganic ligand surface-treated nanoparticles on the surface of ZnSe nanoparticles were prepared. Thereafter, 50 mg of zinc acetate dihydrate and 50 μL of (NH ₄ ) ₂ S were added to the surface-treated nanoparticles. By performing heat treatment at 175° C. for 1 hour using a heating oven, ZnS was again formed as a passivation film on the surface of the ZnSe nanoparticles surface-treated with ^{the S 2-inorganic ligand prepared in (2) above.}

Example 3

(1) Formation of nanoparticles

1.2 mmol of zinc oleate (Zn(oleate) ₂ ) and 20 ml of 1-octadecene were mixed in a reactor equipped with a syringe, a cooler, and a thermometer, and a vacuum was created at 130° C. for 20 minutes. . Then, nitrogen was injected into the reactor to create an inert atmosphere and then heated until reaching 300°C. A solution in which Se powder was dispersed in 1-octadecene (1-octadecene) at 6.32 mg/1 mL was prepared, and this was injected into the prepared reaction solution to proceed with the reaction.

After the reaction was terminated after 1 hour, the Se powder was dispersed in tri-n-octylphosphine at 25.3 mg/1 mL to further prepare a solution, which was then injected into the reaction solution again. .

After completing the reaction after 1 hour, the Sulfur powder was dispersed in tri-n-octylphosphine at 25.6 mg/1 mL to additionally prepare a solution, which was again injected into the reaction solution. .

After the reaction was terminated after 2 hours, the mixture was cooled to room temperature, and toluene and ethanol were added to the reaction mixture to precipitate and then purified. The final reactant was redispersed in 5 mL of hexane to prepare a nanoparticle solution.

(2) inorganic ligand exchange

After preparing a solution in which 100 μL of (NH ₄ ) ₂ S was added to 5 mL of N-methylformamide, the solution was added to the nanoparticle solution. After stirring the solution for 30 minutes, the supernatant was removed. After purification by adding iso-propanol to the reaction solution and re-dispersion in 10 mL of N-methylformamide, S ^2- inorganic ligand surface-treated nanoparticles on the surface of ZnSe (core)/ZnS (shell) nanoparticles were prepared did.

(3) Formation of passivation film

100 mg of zinc acetate dihydrate and 80 mg of sodium sulfate were added to the surface-treated nanoparticles. By performing heat treatment at 175° C. for 5 hours using a heating oven, the surface of the ZnSe (core)/ZnS (shell) nanoparticles on ^{which the S 2-inorganic ligand prepared up to (2) was surface-treated was again passivated.} ZnS was formed as a film.

Comparative Example 1

(1) Formation of nanoparticles

0.2 mmol of zinc oleate (Zn(oleate) ₂ ) and 10 mL of 1-octadecene were mixed in a reactor equipped with a syringe, a cooler, and a thermometer, and a vacuum was created at 130° C. for 20 minutes. . Then, nitrogen was injected into the reactor to create an inert atmosphere and then heated until reaching 300°C. A solution in which Se powder was dispersed in 1-octadecene (1-octadecene) at 15.8 mg/1 mL was prepared, and this was injected into the prepared reaction solution to proceed with the reaction. After 1 hour, the reaction was terminated and cooled to room temperature, and toluene and ethanol were added to the reaction mixture to precipitate the reaction, followed by purification. The final reactant was redispersed in 5 mL of hexane to prepare a nanoparticle solution.

(2) inorganic ligand exchange

After preparing a solution in which 100 μL of (NH ₄ ) ₂ S was added to 5 mL of N-methylformamide, the solution was added to the nanoparticle solution. After stirring the solution for 30 minutes, the supernatant was removed. After purification by adding iso-propanol to the reaction solution, it was re-dispersed in 10 mL of N-methylformamide ^{to prepare nanoparticles in which S 2-} inorganic ligands were surface-treated on the surface of ZnSe nanoparticles.

Comparative Example 2

(1) Formation of nanoparticles

1.2 mmol of zinc oleate (Zn(oleate) ₂ ) and 20 ml of 1-octadecene were mixed in a reactor equipped with a syringe, a cooler, and a thermometer, and a vacuum was created at 130° C. for 20 minutes. . Then, nitrogen was injected into the reactor to create an inert atmosphere and then heated until reaching 300°C. A solution in which Se powder was dispersed in 1-octadecene (1-octadecene) at 6.32 mg/1 mL was prepared, and this was injected into the prepared reaction solution to proceed with the reaction.

After the reaction was terminated after 1 hour, the Se powder was dispersed in tri-n-octylphosphine at 25.3 mg/1 mL to further prepare a solution, which was then injected into the reaction solution again. .

After completing the reaction after 1 hour, the Sulfur powder was dispersed in tri-n-octylphosphine at 25.6 mg/1 mL to additionally prepare a solution, which was again injected into the reaction solution. .

After the reaction was terminated after 2 hours, the mixture was cooled to room temperature, and toluene and ethanol were added to the reaction mixture to precipitate and then purified. The final reactant was redispersed in 5 mL of hexane to prepare a nanoparticle solution.

(2) inorganic ligand exchange

After preparing a solution in which 100 μL of (NH ₄ ) ₂ S was added to 5 mL of N-methylformamide, the solution was added to the nanoparticle solution. After stirring the solution for 30 minutes, the supernatant was removed. After purification by adding iso-propanol to the reaction solution and re-dispersion in 10 mL of N-methylformamide, S ^2- inorganic ligand surface-treated nanoparticles on the surface of ZnSe (core)/ZnS (shell) nanoparticles were prepared did.

Experimental Example 1 - PL intensity

A sample was prepared by mixing 50 μL of the quantum dot solution (10 mg/mL) prepared in Examples and Comparative Examples with 3 mL of a hexane solvent. Using a photoluminescence spectrometer (SINCO, FS-2) equipment, the emission wavelength was measured according to the equipment manual, and the relative size (intensity, a.u.) of the center of the emission wavelength is shown as in FIGS. 1 and 2 . At this time, the emission wavelength was measured after setting the excitation wavelength to about 350 nm (Excitation wave) and the PML Voltage to 550V. On the other hand, the emission wavelength is a value measured at room temperature (about 25 ℃).

Claims (14)

Quantum dots comprising nanoparticles, an inorganic ligand substituted on the surface of the nanoparticles, and a passivation film formed on the surface of the nanoparticles. The quantum dot of claim 1 , wherein the nanoparticles comprise a semiconductor material. The quantum dot according to claim 1, wherein the nanoparticles are a group II-VI semiconductor compound, a group III-V semiconductor compound, a group IV-VI semiconductor compound, a group IV element or compound, or a combination thereof. The quantum dot according to claim 1, wherein the nanoparticles have a core-shell structure or a core-shell-shell structure. The quantum dot according to claim 1, wherein the nanoparticles have an average particle diameter in the range of 1 to 100 nm according to D50 particle size analysis. The quantum dot of claim 1 , wherein the inorganic ligand comprises S, Se, Te, O, P or As. The quantum dot of claim 1 , wherein the passivation film comprises a semiconductor material. The quantum dot according to claim 1, wherein the passivation film is formed after the inorganic ligand is substituted on the surface of the nanoparticles. The quantum dot according to claim 1, wherein the passivation film has a thickness in the range of 0.1 to 5 nm. A quantum dot solution comprising the quantum dot according to claim 1 and a solvent. The quantum dot solution of claim 10, wherein the solvent includes ethanolamine, dimethyl sulfoxide (DMSO), dimethylformamide (DMF), formamide, or n-methylformamide (NMF). A method for producing quantum dots, comprising the step of forming a passivation film on the surface of the inorganic ligand substituted nanoparticles. The method of claim 12 , wherein the forming of the passivation film is performed by UV treatment or heat treatment. A quantum dot light emitting device having a light emitting layer comprising a pair of electrodes and the quantum dots according to claim 1 .

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