JP2023033157A - Method of manufacturing quantum dot - Google Patents

Abstract

To provide an InP-based quantum dot having excellent half-value full width (FWHM) of an emission spectrum and symmetry.SOLUTION: Disclosed is a method of manufacturing a quantum dot having a core shell structure composed of an InP-based quantum dot obtained by reacting at least phosphorus source and indium source in its core and a coating compound other than an InP-based compound in its shell, wherein the reaction in coating the core with the coating compound is conducted in a solvent involving a plural kinds of amine derivatives. Preferably, the coating compound is one obtained by reacting with at least zinc source.SELECTED DRAWING: None

Description

The present invention relates to a method for producing quantum dots, and more particularly to a method for producing core-shell quantum dots having an InP-based quantum dot in the core and a non-InP-based coating compound in the shell.

In recent years, quantum dots have been developed as light-emitting materials. As typical quantum dots, development of cadmium-based quantum dots such as CdSe, CdTe, and CdS is underway because of their excellent light-emitting properties. However, due to the high toxicity and environmental load of cadmium, the development of cadmium-free quantum dots is expected.

One example of cadmium-free quantum dots is InP (indium phosphide)-based quantum dots. Compared to Cd-based quantum dots, InP-based quantum dots are inferior to Cd-based quantum dots in terms of quantum yield and full width at half maximum (hereinafter also referred to as FWHM) of the emission peak. Proposed. For example, Patent Document 1 discloses forming a Zn-based shell by mixing oleylamine and zinc acetate with an InP quantum dot serving as a core. Patent Document 2 discloses mixing InP quantum dots with zinc chloride and oleylamine, and then adding a Se source and an S source to form a Se/S based shell. In addition, Non-Patent Document 1 describes that zinc chloride and 1-dodecanethiol were used to form a ZnS shell on an InP quantum dot core.

U.S. Patent Application Publication No. 2020/0362241 Chinese Patent Application Publication No. 108641720

Halide-Amine Co-Passivated Indium Phosphide Colloidal Quantum Dots in Tetrahedral Shape, Angewandte Chemie, International Edition (2016), 55, 3714-3718

However, although the InP-based quantum dots obtained by the above-described conventional manufacturing method exhibit excellent properties in terms of FWHM and quantum yield, in order to achieve performance equivalent to that of Cd-based quantum dots, further improvement of FWHM and There was a need to improve the symmetry of the emission spectrum. Regarding the symmetry of the emission spectrum, the more bilaterally symmetrical the spectral shapes on the short wavelength side and the long wavelength side with respect to the emission peak wavelength, the more the color purity of the emitted light is improved. In order to improve the symmetry of the emission spectrum, a spectrum (tail) with a gentle slope appearing on the short wavelength side and the long wavelength side farther from the emission peak wavelength, or an inflection point appearing in the emission peak. It was necessary to suppress the generation of the spectrum (shoulder).

It is believed that the tails are caused by defects present on the surface of the core InP-based quantum dots. In addition, the cause of shoulder formation is that the ligand used for surface treatment strongly binds to a specific crystal plane of the quantum dot and inhibits shell formation, resulting in rapid and uniform shell formation. It is thought that this is caused by variations in quantum dot size.

The present inventors have made intensive studies to solve the above problems, and found that defects present on the surface of the core InP-based quantum dots can be eliminated by forming shells in a solvent containing multiple types of amine derivatives. The inventors have found that the FWHM and symmetry of the emission spectrum can be improved at the same time because of the effective blockage, and have completed the present invention.

That is, the present invention is a method for producing a core-shell structure quantum dot having an InP-based quantum dot obtained by the reaction of at least a phosphorus source and an indium source in the core and a coating compound other than the InP-based coating compound in the shell. There is
Provided is a method for producing quantum dots, wherein the reaction for coating the core with the coating compound is carried out in a solvent containing a plurality of types of amine derivatives.

According to the present invention, it is possible to provide a method for producing quantum dots with excellent FWHM and symmetry of the emission spectrum, and to obtain high-quality quantum dots with high color purity due to excellent FWHM and symmetry of the emission spectrum. can.

4 is an emission spectrum of the quantum dot dispersion liquid obtained in Example 1. FIG. 4 is an emission spectrum of the quantum dot dispersion liquid obtained in Example 2. FIG. 4 is an emission spectrum of the quantum dot dispersion liquid obtained in Example 3. FIG. 4 is an emission spectrum of the quantum dot dispersion liquid obtained in Example 4. FIG. 4 is an emission spectrum of the quantum dot dispersion liquid obtained in Example 5. FIG. 4 is an emission spectrum of the quantum dot dispersion liquid obtained in Comparative Example 1. FIG. 4 is an emission spectrum of the quantum dot dispersion liquid obtained in Comparative Example 2. FIG. 4 is an emission spectrum of the quantum dot dispersion liquid obtained in Comparative Example 3. FIG. 4 is an emission spectrum of the quantum dot dispersion liquid obtained in Comparative Example 4. FIG.

The present invention uses an InP-based quantum dot obtained by the reaction of at least a phosphorus source and an indium source as a core, and the core is coated with a coating compound other than an InP-based coating compound to produce a core-shell structure quantum dot having a shell layer. The method for producing quantum dots, wherein the reaction for coating the core with the coating compound is carried out in a solvent containing a plurality of types of amine derivatives. Preferred embodiments of the method for producing quantum dots of the present invention are described below.

(Phosphorus source)
As the phosphorus source used in the production of the InP-based quantum dots that serve as the core of the quantum dots in the present invention, various sources can be used according to the chemical synthesis method to be employed, such as silylphosphine compounds and aminophosphine compounds. phosphine derivatives, phosphine gas, and the like. A silylphosphine compound represented by the following general formula (1) is preferable from the viewpoints of easy acquisition of quantum dots, availability, and control of the particle size distribution of the obtained quantum dots. The silylphosphine compound used as the phosphorus source is tertiary, that is, a compound in which three silyl groups are bonded to the phosphorus atom.

（Ｒはそれぞれ独立に、炭素原子数１以上５以下のアルキル基又は炭素原子数６以上１０以下のアリール基である。）

(R is each independently an alkyl group having 1 to 5 carbon atoms or an aryl group having 6 to 10 carbon atoms.)

The alkyl group having 1 to 5 carbon atoms represented by R in the general formula (1) is preferably a linear or branched alkyl group, specifically a methyl group or an ethyl group. , n-propyl group, iso-propyl group, n-butyl group, sec-butyl group, tert-butyl group, iso-butyl group, n-amyl group, iso-amyl group, tert-amyl group and the like.

The aryl group having 6 to 10 carbon atoms represented by R in the general formula (1) includes a phenyl group, a tolyl group, an ethylphenyl group, a propylphenyl group, an iso-propylphenyl group, a butylphenyl group, sec-butylphenyl group, tert-butylphenyl group, iso-butylphenyl group, methylethylphenyl group, trimethylphenyl group and the like.

These alkyl groups and aryl groups may have one or more substituents, and examples of substituents for the alkyl groups include a hydroxy group, a halogen atom, a cyano group, an amino group, and the like. Examples of substituents include an alkyl group having 1 to 5 carbon atoms, an alkoxy group having 1 to 5 carbon atoms, a hydroxy group, a halogen atom, a cyano group, an amino group, and the like. When the aryl group is substituted with an alkyl group or an alkoxy group, the number of carbon atoms in the alkyl group or alkoxy group is included in the number of carbon atoms in the aryl group.

Plural Rs in the general formula (1) may be the same or different. Also, the three silyl groups (--SiR ₃ ) present in the general formula (1) may be the same or different. In the silylphosphine compound represented by the general formula (1), R is an alkyl group having 1 to 4 carbon atoms or a phenyl group unsubstituted or substituted with an alkyl group having 1 to 4 carbon atoms. is preferable as the phosphorus source during the synthesis reaction from the viewpoint of being excellent in reactivity with other molecules such as an indium source, and trimethylsilyl group is particularly preferable.

(indium source)
As the indium source used in the production of the InP quantum dots, various sources can be used according to the employed chemical synthesis method. Organic indium carboxylates are suitable from the viewpoints of the ease of obtaining quantum dots, the ease of availability, and the control of the particle size distribution of the obtained quantum dots. For example, indium acetate, indium formate, indium propionate, indium butyrate, indium valerate, indium caproate, indium enanthate, indium caprylate, indium pelargonate, indium caprate, indium laurate, indium myristate, indium palmitate. , saturated aliphatic indium carboxylates such as indium margarate, indium stearate, indium oleate, and indium 2-ethylhexanoate; and unsaturated aliphatic indium carboxylates such as indium oleate and indium linoleate. can be done. In particular, from the viewpoint of availability and particle size distribution control, it is preferable to use at least one selected from the group consisting of indium acetate, indium laurate, indium myristate, indium palmitate, indium stearate, and indium oleate. Indium salts of higher carboxylic acids having 12 to 18 carbon atoms are particularly preferred.

(Reaction of phosphorus source and indium source)
Examples of chemical synthesis methods for the InP quantum dots include a sol-gel method (colloid method), a hot soap method, a reverse micelle method, a solvothermal method, a molecular precursor method, a hydrothermal synthesis method, and a flux method. In the present invention, a phosphorus source and an indium source are mixed and reacted at a temperature of 20° C. or higher and 150° C. or lower to obtain an InP quantum dot precursor, and then reacted at a temperature of 200° C. or higher and 350° C. or lower. It is preferable to obtain InP-based quantum dots.

(Method for producing InP quantum dot precursor)
The InP quantum dot precursor is a finely divided cluster of InP quantum dots, which are nanoparticles having a particle size of several nanometers to several tens of nanometers obtained by the reaction of a phosphorus source and an indium source, and is excellently stable in a solvent. It consists of a specific number of constituent atoms, for example, from several to several hundred atoms. InP quantum dot precursors may be magic size clusters with tens to hundreds of atoms, or may be smaller. As described above, since the InP quantum dot precursor can exhibit excellent stability in a solvent, there is an advantage that it is easy to obtain quantum dots with a narrow particle size distribution by using the InP quantum dot precursor. In the present invention, InP in the InP quantum dot precursor means containing In and P, and does not require that In and P have a molar ratio of 1:1. Although the InP quantum dot precursor usually consists of In and P, even if a ligand derived from the raw material phosphorus source or indium source is bound to the In or P atom located in the outermost shell, good. Examples of such ligands include organic carboxylic acid residues when the indium source is an indium salt of an organic carboxylic acid, and alkylphosphine used as an additive.

From the viewpoint of successfully obtaining an InP quantum dot precursor, the mixing molar ratio of the phosphorus source and the indium source during the reaction is preferably P:In of 1:0.5 or more and 10 or less, and 1:1 or more and 5 or less. is more preferable.

The reaction between the phosphorus source and the indium source is preferably carried out in an organic solvent from the viewpoint of reactivity and stability. Examples of organic solvents include non-polar solvents such as phosphorus sources and indium sources from the viewpoint of stability, and aliphatic hydrocarbons, unsaturated aliphatic hydrocarbons, aromatic hydrocarbons, tri- Solvents such as alkylphosphine and trialkylphosphine oxide are preferred. Aliphatic hydrocarbons include n-hexane, n-heptane, n-octane, n-nonane, n-decane, n-dodecane, n-hexadecane and n-octadecane. Unsaturated aliphatic hydrocarbons include 1-undecene, 1-dodecene, 1-tetradecene, 1-hexadecene, 1-octadecene and the like. Aromatic hydrocarbons include benzene, toluene, xylene, styrene, and the like. Trialkylphosphine includes triethylphosphine, tributylphosphine, tridecylphosphine, trihexylphosphine, trioctylphosphine, tridodecylphosphine and the like. Trialkylphosphine oxides include triethylphosphine oxide, tributylphosphine oxide, tridecylphosphine oxide, trihexylphosphine oxide, trioctylphosphine oxide, tridodecylphosphine oxide and the like.

It is preferable to dehydrate the solvent before use from the viewpoint of preventing the decomposition of the phosphorus source and the indium source and the resulting generation of impurities. The water content in the solvent is preferably 20 ppm or less on a mass basis. It is also preferable to deaerate the solvent to remove oxygen before use. Degassing can be carried out by any method such as depressurizing the inside of the reactor or replacing it with an inert atmosphere.

The respective concentrations of the phosphorus source and the indium source in the reaction solution in which the phosphorus source and the indium source are mixed are, for example, the concentration of the phosphorus source based on the phosphorus atom and the concentration of the indium source based on the indium atom with respect to 100 g of the reaction solution, respectively. From the viewpoint of reactivity and stability, it is preferably in the range of 0.1 mmol or more and 10 mmol or less, and more preferably in the range of 0.1 mmol or more and 3 mmol or more.

As a method for mixing the phosphorus source and the indium source, the phosphorus source and the indium source are each dissolved in an organic solvent, and the solution obtained by dissolving the phosphorus source in the organic solvent and the solution obtained by dissolving the indium source in the organic solvent are mixed. is preferable in terms of easy production of InP quantum dot precursors. The solvent for dissolving the phosphorus source and the solvent for dissolving the indium source may be the same or different.

In this case, the concentration of the phosphorus source based on phosphorus atoms in the solution in which the phosphorus source is dissolved in the organic solvent is preferably in the range of 20 mmol/L or more and 2000 mmol/L or less in terms of reactivity and stability, and is preferably 80 mmol/L. It is more preferably in the range of L or more and 750 mmol or less. In terms of reactivity and stability, the indium atom-based concentration in a solution in which an indium source is dissolved in an organic solvent is preferably in the range of 0.1 mmol/L or more and 20 mmol/L or less, and is preferably 0.2 mmol/L. More preferably, it is in the range of not less than 10 mmol/L and not more than 10 mmol/L.

It is preferable to add an additive that can serve as a ligand to the reaction solution containing the phosphorus source and the indium source in terms of improving the quality of the resulting InP quantum dot precursor and InP-based quantum dots. The present inventors believe that the quality of InP quantum dot precursors and InP-based quantum dots is affected by the fact that additives that can serve as ligands coordinate to In or change the polarity of the reaction field. there is Such additives include phosphine derivatives, amine derivatives, phosphonic acid and the like.

The phosphine derivative is preferably a primary to tertiary alkyl phosphine, and preferably includes a linear alkyl phosphine having 2 to 18 carbon atoms in the molecule. The alkyl groups in the molecule may be the same or different. Examples of straight-chain alkylphosphine having an alkyl group of 2 to 18 carbon atoms include monoethylphosphine, monobutylphosphine, monodecylphosphine, monohexylphosphine, monooctylphosphine, monododecylphosphine, monohexadecylphosphine, diethylphosphine, dibutylphosphine, didecylphosphine, dihexylphosphine, dioctylphosphine, didodecylphosphine, dihexadecylphosphine, triethylphosphine, tributylphosphine, tridecylphosphine, trihexylphosphine, trioctylphosphine, tridodecyl Phosphine, trihexadecylphosphine. Among them, from the viewpoint of improving the quality of the resulting InP quantum dot precursor and InP-based quantum dots, those in which the number of carbon atoms in the alkyl group in the molecule is 4 or more and 12 or less are particularly preferable, and trialkylphosphines are preferable. Trioctylphosphine is most preferred.

The amine derivative is preferably a primary to tertiary alkylamine, a linear or branched alkylamine in which the alkyl group in the molecule has 2 to 18 carbon atoms, and Aromatic alkylamines of 6 to 12 are preferred. The alkyl groups in the molecule may be the same or different. Specific examples of straight-chain alkylamines having 2 to 18 carbon atoms in the alkyl group include monoethylamine, monobutylamine, monodecylamine, monohexylamine, monooctylamine, monododecylamine, monohexa Decylamine, diethylamine, dibutylamine, didecylamine, dihexylamine, dioctylamine, didodecylamine, dihexadecylamine, triethylamine, tributylamine, tridecylamine, trihexylamine, trioctylamine, tridodecylamine, trihexadecylamine is mentioned. Examples of branched chain alkylamines in which the alkyl group has 2 to 18 carbon atoms include isopropylamine, isobutylamine, 1-methylbutylamine, 1-ethylpropylamine, 2-ethylbutylamine, 2-ethylhexylamine, and di-isopropylamine. , di-isobutylamine, di-1-methylbutylamine, di-1-ethylpropylamine, di-2-ethylbutylamine, di-2-ethylhexylamine, tri-isopropylamine, tri-isobutylamine, tri-1-methyl Butylamine, tri-1-ethylpropylamine, tri-2-ethylbutylamine. Specific examples of aromatic alkylamines having alkyl groups of 6 to 12 carbon atoms include aniline, diphenylamine, triphenylamine, monobenzylamine, dibenzylamine, tribenzylamine, naphthylamine, dinaphthylamine, and trinaphthylamine. is mentioned. Further, the phosphonic acid is preferably a monoalkylphosphonic acid having a linear alkyl group with 2 to 18 carbon atoms in the molecule.

The addition amount of the additive that can be a ligand in the reaction solution containing the phosphorus source and the indium source is 0.2 mol or more with respect to 1 mol of In. By adding the additive that can be a ligand, This is preferable in terms of enhancing the quality improvement effect of the InP quantum dot precursor and InP-based quantum dots. The amount of additive that can be a ligand to be added is preferably 20 mol or less with respect to 1 mol of In in terms of quality improvement effect. From these points, it is more preferable that the amount of the additive that can be a ligand to be added is 0.5 mol or more and 15 mol or less per 1 mol of In.

The timing of adding the additive that can serve as a ligand to the reaction solution may be achieved by mixing the additive that can serve as a ligand with the indium source to form a mixed solution, and then mixing this mixed solution with the phosphorus source. The additive capable of serving as a ligand may be mixed with the phosphorus source to form a mixed solution, and this mixed solution may be mixed with the indium source, or the additive capable of serving as a ligand may be mixed with the mixed solution of the phosphorus source and the indium source. may

A solution obtained by dissolving a phosphorus source in an organic solvent and a solution obtained by dissolving an indium source in an organic solvent may be preliminarily heated to a preferable reaction temperature described below or to a temperature lower or higher than that before mixing, After mixing, the mixture may be heated to the preferred reaction temperature described below. The preliminary heating temperature is preferably within ±10°C of the reaction temperature and 20°C or higher from the viewpoint of reactivity and stability, and is within ±5°C of the reaction temperature and 30°C or higher. Temperature is more preferred.

From the viewpoint of reactivity and stability, the reaction temperature between the phosphorus source and the indium source is preferably 20° C. or higher and 150° C. or lower, more preferably 40° C. or higher and 120° C. or lower. From the viewpoint of reactivity and stability, the reaction time at the reaction temperature is preferably 0.5 minutes or more and 180 minutes or less, more preferably 1 minute or more and 80 minutes or less.
Through the above steps, a reaction solution containing an InP quantum dot precursor is obtained.

The formation of the InP quantum dot precursor in the reaction solution can be confirmed by measuring the ultraviolet-visible light absorption spectrum (UV-VIS spectrum), for example. When an InP quantum dot precursor is formed in the reaction solution in which the In source and the P source are reacted, a peak or shoulder is observed in the range of 300 nm or more and 460 nm or less in the UV-VIS spectrum. A shoulder does not have a sharp point shape as clearly as a peak, but clearly has an inflection point. When a shoulder is observed, it is preferable to have one or two or more inflection points in the range of 300 nm or more and 460 nm or less, particularly 310 nm or more and 420 nm or less. The UV-VIS spectrum is preferably measured at 0°C or higher and 40°C or lower. The sample solution is prepared by diluting the reaction solution with a solvent such as hexane. The amount of In and the amount of P in the sample liquid at the time of measurement are preferably in the range of 0.01 mmol or more and 1 mmol or less, and 0.02 mmol or more and 0.3 mmol or less per 100 g of the sample liquid for phosphorus atoms and indium atoms. is more preferably in the range of Examples of the solvent for the reaction solution include those described later as solvents that can be suitably used for the reaction with the indium source and the phosphorus source. As will be described later, when InP quantum dots are grown by heating an InP quantum dot precursor in a solvent to 200° C. or higher and 350° C. or lower, the UV-VIS spectrum of the reaction solution usually peaks in the range of 450 nm or higher and 550 nm or lower. is observed, but no peak is observed in the range of 450 nm or more and 550 nm or less in the reaction solution before heating.

In addition, the formation of the InP quantum dot precursor in the reaction solution can also be confirmed by, for example, yellow-green to yellow color of the reaction solution instead of the UV-VIS spectrum. This color may be confirmed by visual observation. For example, a reaction solution containing InP magic-size clusters is yellow, and a reaction solution containing a precursor made of In and P and having fewer atoms than the magic-size clusters is generally yellow-green.

(Method for producing InP-based quantum dots)
InP-based quantum dots refer to semiconductor nanoparticles containing at least In and P and having a quantum confinement effect. Quantum confinement effect is that when the size of a material is about the Bohr radius, the electrons in the material cannot move freely, and in such a state, the electron energy cannot be arbitrary and can only take a specific value. . The particle size of quantum dots (semiconductor nanoparticles) is generally in the range of several nanometers to several tens of nanometers. However, those corresponding to quantum dot precursors among those corresponding to the above description of quantum dots are not included in the category of quantum dots in the present invention.

The reaction solution containing the InP quantum dot precursor is preferably at a temperature of 20° C. or higher and 150° C. or lower, more preferably 40° C. or higher and 120° C. or lower at the time after the reaction is completed. or cooled to room temperature can be used.

InP-based quantum dots can be obtained by heating the reaction solution containing the InP quantum dot precursor as it is or by mixing it with a heated solvent. When the reaction solution containing the InP quantum dot precursor is heated as it is, it is preferably 200° C. or higher and 350° C. or lower, more preferably 240° C. or higher and 330° C. or lower from the viewpoint of particle size control. InP-based quantum dots can be obtained. The heating rate during heating is preferably 1° C./min or more and 50° C./min or less from the viewpoint of time efficiency and particle size control, and more preferably 2° C./min or more and 40° C./min or less. From the viewpoint of particle size control, the heating time at the temperature is preferably 0.5 minutes or more and 180 minutes or less, more preferably 1 minute or more and 60 minutes or less.

When mixing the reaction solution containing the InP quantum dot precursor with a heated solvent, when obtaining InP-based quantum dots by a so-called hot injection method, from the viewpoint of particle size control, preferably 200 ° C. or higher and 350 ° C. or lower, and further InP-based quantum dots can be obtained by rapidly adding a reaction solution containing an InP quantum dot precursor to an organic solvent that has been heated preferably to a temperature of 240° C. or higher and 330° C. or lower. As the organic solvent, the same organic solvent as used in the reaction between the phosphorus source and the indium source can be used. The reaction solution containing the InP quantum dot precursor and the organic solvent are mixed at a temperature of 200° C. or higher and 350° C. or lower, further 240° C. or higher and 330° C. or lower, for 10 minutes or less, further 0.1 minutes or more. Holding for 8 minutes or less is preferable from the viewpoint of particle size control.

The stability of InP quantum dot precursors in solvents is thermodynamic and InP quantum dot precursors have the property of being sensitive to heating. For example, an InP quantum dot precursor in a solvent can grow into InP quantum dots when heated to a temperature preferably between 200°C and 350°C, more preferably between 240°C and 330°C. This can be confirmed from the fact that when the reaction solution after heating is subjected to UV-VIS spectrum measurement, a peak shift to the longer wavelength side is observed. For example, when the InP quantum dot precursor in the solvent is heated to preferably 200 ° C. or higher and 350 ° C. or lower, more preferably 240 ° C. or higher and 330 ° C. or lower without adding other elements constituting the quantum dots other than In and P. , a peak is observed in the range of 420 nm to 590 nm in the UV-VIS spectrum. InP in the InP quantum dot means containing In and P, and the molar ratio of In and P need not be 1:1. The UV-VIS spectrum of the liquid containing the InP quantum dots obtained by heating the InP quantum dot precursor to preferably 200° C. or higher and 350° C. or lower, more preferably 240° C. or higher and 330° C. or lower shows the desired color. Although it depends on the InP quantum dot precursor for the purpose, it is preferable that the absorption peak with the highest peak height is observed in the range of 420 nm or more and 600 nm or less in the range of 300 nm or more and 800 nm or less.

In addition, the formation of InP quantum dots in the reaction solution can also be confirmed, for example, by the fact that the reaction solution turns yellow to red. This color may be confirmed by visual observation.

The description of the UV-VIS spectrum of the reaction solution after heating the above InP quantum dot precursor and the color of the reaction solution typically show that no other element constituting the quantum dots other than In and P is added. refers to the case of heating to However, as described above, the present invention does not exclude the case where such a compound is added to the InP quantum dot precursor and heated.
In the present invention, quantum dots that do not contain constituent elements other than In and P and quantum dots that contain constituent elements other than In and P are collectively referred to as "InP-based quantum dots."

Since the obtained InP-based quantum dots contain by-products and unreacted impurities in the reaction solution, purification treatment may be performed before the surface treatment described below. In this purification treatment, an organic solvent such as ethanol, methanol, 2-propanol, acetone, or acetonitrile is added to a reaction solution containing InP-based quantum dots to precipitate the InP-based quantum dots. It can be performed by separating the separated InP-based quantum dots into quantum dots and dispersing the separated InP-based quantum dots in an organic solvent such as toluene or hexane. Separation of the solution containing impurities from the InP-based quantum dots can be performed by operations such as centrifugation, decantation, and suction filtration.

The InP-based quantum dot produced by the production method of the present invention is a quantum dot made of a composite compound having an element M other than phosphorus and indium in addition to In and P (also referred to as a composite quantum dot of In, P and M). may be The element M is at least one selected from the group consisting of Be, Mg, Ca, Mn, Cu, Zn, Cd, B, Al, Ga, N, As, Sb and Bi. is preferable from the viewpoint of Typical examples of InP-based quantum dots containing element M include InGaP, InZnP, InAlP, InGaAlP, InNP, InAsP, InPSb, and InPBi. In order to obtain InP-based quantum dots containing the element M, a liquid containing a compound containing the element M may be added to the reaction liquid when heating the liquid containing the InP quantum dot precursor. A liquid containing the InP quantum dot precursor may be added to the reaction liquid when heating the liquid containing the compound. A compound containing element M means, when element M is Be, Mg, Ca, Mn, Cu, Zn, Cd, B, Al and Ga, a chloride, bromide, iodide form of element M, a carbon atom It is in the form of a higher carboxylate having a number of 12 or more and 18 or less, and when it is in the form of a higher carboxylate, it may be the same as or different from the carboxylic acid of the indium carboxylate used in the reaction. When the element M is N, As, Sb or Bi, a compound in which three silyl groups or amino groups are bonded to the element M can be preferably used.

The InP-based quantum dots in the present invention may be surface-treated with a surface treatment agent or the like for the purpose of increasing the quantum yield. By surface-treating the surface of the InP-based quantum dots, defects and the like on the surfaces of the InP-based quantum dots can be protected, and the quantum yield can be improved. In addition, the FWHM and symmetry of the emission spectrum of the obtained quantum dots can be improved by performing shell formation, which will be described later, following this surface treatment. Suitable surface treatment agents include metal-containing compounds such as metal carboxylates, metal carbamates, metal halides, metal thiocarboxylates, metal acetylacetonate salts and hydrates thereof; alkanoyl halide compounds; Halogen-containing compounds such as quaternary ammonium compound halides, quaternary phosphonium compound halides, halogenated aryl compounds and halogenated tertiary hydrocarbon compounds, carboxylic acids, carbamic acids, thiocarboxylic acids, phosphonic acids and sulfonic acids and organic acids such as Among these, metal carboxylates, metal carbamates, and metal halides are preferable from the viewpoint of further improving the quantum yield.

The metal carboxylate has a straight-chain, branched-chain or cyclic alkyl group containing a saturated or unsaturated bond and having 1 to 24 carbon atoms which may be unsubstituted or substituted with a halogen atom or the like. may have multiple carboxylic acids in the molecule. The metals of the metal carboxylates include Li, Na, K, Rb, Cs, Be, Mg, Ca, Sr, Ba, Sc, Y, Ti, Zr, V, Nb, Cr, Mo, Mn, Fe , Co, Ni, Cu, Ag, Zn, Cd, Hg, B, Al, Ga, In, Tl, Ge, Sn, Pb, Sb, Bi, La, Ce, Sm, and the like. Among these, the metal of the metal carboxylate is preferably Zn, Cd, Al and Ga, more preferably Zn, from the viewpoint of better protection against defects on the InP-based quantum dot surface. Such metal carboxylates include zinc acetate, zinc trifluoroacetate, zinc myristate, zinc oleate and zinc benzoate.

Among the metals described above, Zn, Cd, Al and Ga are preferred as the metal carbamate, and Zn is more preferred, from the viewpoint of better protection against defects on the InP-based quantum dot surface. Specific examples include zinc dimethyldithiocarbamate, zinc diethyldithiocarbamate, zinc dibutyldithiocarbamate and zinc N-ethyl-N-phenyldithiocarbamate.

Among the metals described above, the metal halide is preferably Zn, Cd, Al or Ga, more preferably Zn, from the viewpoint of better protection against defects on the surface of the InP-based quantum dots. Specific examples include zinc fluoride, zinc chloride, zinc bromide, zinc iodide and the like.

As a method of surface-treating the InP-based quantum dots, for example, a surface-treating agent can be added to the reaction solution containing the InP-based quantum dots. The temperature at which the surface treatment agent is added to the reaction solution containing the InP-based quantum dots is preferably 0° C. or higher and 350° C. or lower, more preferably 20° C. or higher and 250° C. or lower, from the viewpoint of particle size control and quantum yield improvement. The treatment time is preferably 1 minute or more and 600 minutes or less, more preferably 5 minutes or more and 240 minutes or less. In addition, although the amount of the surface treatment agent added depends on the type of the surface treatment agent, it is preferably 0.001 g/L or more and 1000 g/L or less, and 0.1 g/L, with respect to the reaction solution containing the InP-based quantum dots. It is more preferable to be 500 g/L or more.

Examples of the method of adding the surface treating agent include a method of directly adding the surface treating agent to the reaction solution, and a method of adding the surface treating agent dissolved or dispersed in a solvent to the reaction solution. When adding the surface treatment agent dissolved or dispersed in the solvent to the reaction solution, the solvent includes acetonitrile, propionitrile, isovaleronitrile, benzonitrile, acetone, methyl ethyl ketone, methyl isobutyl ketone, acetylacetone, Acetophenone, dimethylsulfoxide, dimethylformamide, dimethylacetamide, methanol, ethanol, isopropanol, cyclohexanol, phenol, methyl acetate, ethyl acetate, isopropyl acetate, phenyl acetate, tetrahydrofuran, 2-methyltetrahydrofuran, tetrahydropyran, diethyl ether, t-butyl methyl ether, cyclohexyl methyl ether, anisole, diphenyl ether, hexane, cyclohexane, benzene, toluene, 1-decene, 1-octadecene, triethylamine, tri-n-octylamine, oleylamine, dioctylamine, dibenzylamine, di-2-ethylhexylamine and water etc. can be used.

(Production of quantum dots with core-shell structure)
A quantum dot obtained by the production method of the present invention has a core-shell structure in which the InP-based quantum dot is used as a core and the core is covered with a coating compound. By growing a second inorganic material (shell layer) on the surface of the core, which has a wider bandgap than the core, defects on the surface of the core are protected, and non-radioactive deactivation due to recombination of charges is prevented. Suppressed, quantum yield and stability can be improved. Suitable coating compounds include ZnS, ZnSe, ZnSeS, ZnTe, ZnSeTe, ZnTeS, ZnO, ZnOS, ZnSeO, ZnTeO, GaP, GaN. In the present invention, the coating compound is preferably obtained by reaction with at least a zinc source.

In the case of producing a quantum dot having a core-shell structure in which an InP-based quantum dot is used as a core and covered with a coating compound, from the viewpoint of improving the FWHM and symmetry of the emission spectrum, the InP-based quantum dot that becomes the core is used. It is preferable to perform surface treatment of dots and shell formation continuously. As the surface treatment agent used in this surface treatment, the same one as the surface treatment agent for the InP-based quantum dots can be used. In addition, performing the surface treatment and the shell formation continuously means that the surface of the InP-based quantum dot as the core is simultaneously present in the reaction solution with the InP-based quantum dot as the core, the surface treatment agent and the raw material of the coating compound. After the treatment is carried out at a predetermined temperature, the reaction solution is subsequently heated to form a shell with the coating compound.

In the case of producing quantum dots with a core-shell structure in which InP-based quantum dots are used as cores and are coated with a coating compound, the method for forming the coating includes a reaction solution containing surface-treated InP-based quantum dots, and a coating compound. Alternatively, a reaction solution containing InP-based quantum dots, a coating compound raw material, and a surface treatment agent are mixed and reacted at a temperature of 200° C. or higher and 350° C. or lower. Alternatively, a part of the coating compound raw material (for example, a metal source such as Zn, etc.) is heated to the same temperature, and added and mixed with the reaction solution containing the InP-based quantum dots before the addition of the other coating compound raw material. After heating to 20° C. or more and 350° C. or less, further 20° C. or more and 330° C. or less, the remaining coating compound raw materials may be added and reacted. The timing of mixing the metal source such as Zn with the reaction solution containing the InP-based quantum dots is not limited to before the addition of other coating compound raw materials, and may be after the addition.

As a coating compound raw material, it is preferable to use a halide or an organic carboxylate thereof as a source of a metal such as Zn. Examples of metal halides include zinc fluoride, zinc chloride, zinc bromide, and zinc iodide as zinc sources. As the metal organic carboxylate, a long-chain fatty acid salt having 12 or more and 18 or less carbon atoms is particularly preferable in terms of particle size control, particle size distribution control, and quantum yield improvement. Among these metal sources, metal halides are preferable, zinc fluoride, zinc chloride, zinc bromide or zinc iodide are more preferable, and zinc chloride is more preferable, from the viewpoint of excellent affinity with the amine derivative described later. It is particularly preferred to have The purpose of the present invention is to obtain quantum dots with excellent FWHM and symmetry of the emission spectrum. Since the solubility of the metal halide increases, the effect of protecting defects existing on the surface of the InP-based quantum dot, which is the core, increases, and the slope appears on the short wavelength side and the long wavelength side further away from the emission peak wavelength. The inventors believe that the generation of spectrum (tail) can be suppressed.

Further, as the sulfur source, linear or branched long-chain alkanethiols having 8 to 18 carbon atoms such as dodecanethiol, and trialkylphosphine sulfides having 4 to 12 carbon atoms such as trioctylphosphine sulfide. Compounds are preferred. Preferred examples of the selenium source include trialkylphosphine selenide compounds having 4 to 12 carbon atoms such as trioctylphosphine selenide. The tellurium source is preferably a trialkylphosphine telluride compound having 4 to 12 carbon atoms such as trioctylphosphine telluride.

In the method for producing quantum dots of the present invention, the reaction between the InP-based quantum dots and the raw material of the coating compound, or the reaction between the InP-based quantum dots, the raw material of the coating compound, and the surface treatment agent is carried out in a solvent containing a plurality of types of amine derivatives. do it inside A mixture of plural kinds of amine derivatives can also be used as a solvent. The reaction solution for carrying out the reaction is prepared by mixing the coating compound raw material and the solvent, or mixing the coating compound raw material, the surface treatment agent and the solvent, and then mixing the InP-based quantum dots. preferably. By performing such a treatment, a uniform reaction field is provided during shell formation, and core-shell quantum dots with a uniform size can be obtained. The present inventors believe that it is possible to suppress the occurrence of

Examples of the amine derivatives include caprylamine, laurylamine, stearylamine, oleylamine, monoethylamine, monobutylamine, monodecylamine, monohexylamine, monooctylamine, monododecylamine, monohexadecylamine, benzylamine, diethylamine, di Butylamine, didecylamine, dihexylamine, dioctylamine, didodecylamine, dihexadecylamine, dibenzylamine, di-2-ethylhexylamine, triethylamine, tributylamine, tridecylamine, trihexylamine, trioctylamine, tridodecylamine , trihexadecylamine, tribenzylamine, and the like, and by using at least two or more of these amine derivatives in combination, the obtained quantum dots have excellent symmetry of the emission spectrum. From the viewpoint of preventing the short wavelength side shoulder and the long wavelength side tail of the emission spectrum, it is preferable to use a combination of a primary amine derivative and a secondary or tertiary amine derivative. In particular, it is a combination of one or more selected from oleylamine, monooctylamine, and monohexadecylamine and one or more selected from dioctylamine, trioctylamine, di-2-ethylhexylamine, and dibenzylamine. More preferably, it is a combination of oleylamine and dioctylamine, dibenzylamine, or di-2-ethylhexylamine.

The amount of the amine derivative used depends on the types of the coating compound raw material and the amine derivative used, but the weight ratio of the coating compound raw material: amine derivative is preferably 1:0.5 or more and 1:100 or less. It is more preferably 1 or more and 1:10 or less.

For example, when a metal such as zinc is used as the coating compound, the amount of the coating compound raw material used is preferably 0.5 mol or more and 100 mol or less, and 4 mol or more and 50 mol or less, relative to 1 mol of indium in the reaction solution containing the InP-based quantum dots. more preferred. As the sulfur source and the selenium source, it is preferable to use an amount corresponding to the above metal amount.

The amount of the surface treatment agent used depends on the type of the surface treatment agent, but is preferably 0.001 g/L or more and 1000 g/L or less, and 0.1 g/L or more and 500 g with respect to the reaction liquid containing the InP quantum dots. /L or less is more preferable.

In the present invention, for the purpose of increasing the quantum yield, the surface of the core-shell type quantum dots may be treated with a surface treatment agent or the like in the same manner as the surface treatment of the InP-based quantum dots. By surface-treating the surface of the core-shell type quantum dots, defects and the like on the surface of the shell layer are protected, and the quantum yield can be improved. Suitable surface treatment agents include metal-containing compounds such as metal carboxylates, metal carbamates, metal thiocarboxylates, metal halides, metal acetylacetonate salts and hydrates thereof; alkanoyl halide compounds; Halogen-containing compounds such as halides of quaternary ammonium compounds, halides of quaternary phosphonium compounds, halogenated aryl compounds, and halogenated tertiary hydrocarbon compounds. Among these, metal carboxylates or metal carbamates are preferable from the viewpoint of further improving the quantum yield.

The metal carboxylate has a straight-chain, branched-chain or cyclic alkyl group containing a saturated or unsaturated bond and having 1 to 24 carbon atoms which may be unsubstituted or substituted with a halogen atom or the like. may have multiple carboxylic acids in the molecule. The metals of the metal carboxylates include Li, Na, K, Rb, Cs, Be, Mg, Ca, Sr, Ba, Sc, Y, Ti, Zr, V, Nb, Cr, Mo, Mn, Fe , Co, Ni, Cu, Ag, Zn, Cd, Hg, B, Al, Ga, In, Tl, Ge, Sn, Pb, Sb, Bi, La, Ce and Sm. Among these, the metal of the metal carboxylate is preferably Zn, Cd, Al and Ga, more preferably Zn, from the viewpoint of better protection against defects on the core-shell type quantum dot surface. Such metal carboxylates include zinc acetate, zinc trifluoroacetate, zinc myristate, zinc oleate and zinc benzoate.

Among the metals described above, the metal carbamate is preferably Zn, Cd, Al or Ga, more preferably Zn, from the viewpoint of better protection against defects on the surface of the core-shell type quantum dots. Specific examples include zinc dimethyldithiocarbamate, zinc diethyldithiocarbamate, zinc dibutyldithiocarbamate and zinc N-ethyl-N-phenyldithiocarbamate.

As a method of surface-treating the shell layer, for example, a surface-treating agent can be added to a reaction solution containing core-shell quantum dots. The temperature at which the surface treatment agent is added to the reaction liquid containing core-shell quantum dots is preferably 0° C. or higher and 350° C. or lower, more preferably 20° C. or higher and 300° C. or lower, from the viewpoint of particle size control and quantum yield improvement. and the treatment time is preferably 1 minute or more and 600 minutes or less, more preferably 5 minutes or more and 240 minutes or less. In addition, although the amount of the surface treatment agent added depends on the type of the surface treatment agent, it is preferably 0.01 g / L or more and 1000 g / L or less, and 0.1 g / L or more and 100 g/L or less is more preferable.

Examples of the method of adding the surface treating agent include a method of directly adding the surface treating agent to the reaction solution, and a method of adding the surface treating agent dissolved or dispersed in a solvent to the reaction solution. When adding the surface treatment agent dissolved or dispersed in the solvent to the reaction solution, the solvent includes acetonitrile, propionitrile, isovaleronitrile, benzonitrile, acetone, methyl ethyl ketone, methyl isobutyl ketone, acetylacetone, Acetophenone, dimethylsulfoxide, dimethylformamide, dimethylacetamide, methanol, ethanol, isopropanol, cyclohexanol, phenol, methyl acetate, ethyl acetate, isopropyl acetate, phenyl acetate, tetrahydrofuran, tetrahydropyran, diethyl ether, t-butyl methyl ether, cyclohexylmethyl Ether, anisole, diphenyl ether, hexane, cyclohexane, benzene, toluene, 1-decene, 1-octadecene, triethylamine, tri-n-octylamine, water and the like can be used.

Since the obtained core-shell quantum dots contain by-products and unreacted impurities in the reaction solution, they may be purified. In this purification treatment, an organic solvent such as ethanol, methanol, 2-propanol, acetone, or acetonitrile is added to a reaction solution containing core-shell quantum dots to precipitate the core-shell quantum dots, and a solution containing impurities and a core-shell type It can be carried out by separating the quantum dots and dispersing the separated core-shell quantum dots in an organic solvent such as toluene or hexane. The solution containing impurities and the core-shell quantum dots can be separated by operations such as centrifugation, decantation, and suction filtration.

The quantum dots of the present invention obtained by the above method are of high quality with excellent emission spectrum symmetry, and can be used for single-electron transistors, security inks, quantum teleportation, lasers, solar cells, quantum computers, biomarkers. , light-emitting diodes, backlights for displays, color filters, and the like.

EXAMPLES The present invention will be described in more detail below with reference to Examples, but the present invention is not limited to these. The properties in the examples were measured by the following methods.
(1) Emission spectrum, maximum fluorescence wavelength, full width at half maximum (FWHM) and quantum yield (PLQY)
The resulting octane dispersion of quantum dots was measured with an absolute PL quantum yield measuring device (Quantaurus-QY, manufactured by Hamamatsu Photonics Co., Ltd.) under the measurement conditions of an excitation wavelength of 400 nm and a measurement wavelength of 200 to 1100 nm.

[Production Example 1] Synthesis of InP Quantum Dot Precursor 1.275 g of indium myristate was added to 1.578 g of 1-octadecene, and the mixture was heated to 120° C. under reduced pressure with stirring for 1.5 hours to deaerate. After degassing, the pressure was returned to atmospheric pressure with nitrogen gas and cooled to 60° C. to obtain a 1-octadecene solution of indium myristate.
2.505 g of trioctylphosphine containing 10% by mass of tris(trimethylsilyl)phosphine was added to the resulting 1-octadecene solution of indium myristate at 60° C. under a nitrogen atmosphere, and the mixture was maintained for 20 minutes. It was naturally cooled to 20°C. As a result, a yellow liquid containing the InP quantum dot precursor was obtained.

[Production Example 2] Synthesis of InZnP Quantum Dots 0.0832 g of zinc myristate was added to 31.56 g of 1-octadecene, and the mixture was heated to 120° C. under reduced pressure while stirring for 1.5 hours to deaerate. After degassing, the pressure was returned to atmospheric pressure with nitrogen gas, and the temperature was raised to 300° C. to obtain a 1-octadecene solution of zinc myristate.
5.4 g of the liquid containing the InP quantum dot precursor obtained in Production Example 1 was added to the resulting 1-octadecene solution of zinc myristate at 300°C under a nitrogen atmosphere, and the temperature was adjusted to 270°C. , and held for 2 minutes to obtain a brown liquid containing InZnP quantum dots.

[Example 1]
0.1885 g of zinc oleate, 0.102 g of zinc chloride, 0.112 g of trioctylphosphine selenide, 0.332 g of trioctylphosphine, 0.813 g of oleylamine and 0.799 g of dioctylamine were mixed in a 10 mL reactor, and It was heated to 120° C. with stirring and degassed for 30 minutes. After degassing, the pressure was returned to atmospheric pressure with nitrogen gas, and the temperature was raised to 180°C under a nitrogen atmosphere. After holding for 1 minute, the temperature was further raised to 300° C. and held for 60 minutes to obtain an oleylamine/dioctylamine dispersion of InZnP/ZnSe quantum dots having InZnP in the core and ZnSe in the shell. After cooling the obtained dispersion to 240° C., 0.423 g of dodecanethiol was injected and held for 90 minutes to obtain multishell quantum dots having InZnP in the core and ZnSe and ZnS stacked in the shell. An oleylamine/dioctylamine dispersion was obtained.
After cooling the resulting dispersion to room temperature, 15 g of acetone was added and stirred, and InZnP/ZnSe/ZnS quantum dots were collected as precipitates by centrifugation. The recovered InZnP/ZnSe/ZnS quantum dots were suspended in 0.866 g of toluene to obtain a toluene dispersion of InZnP/ZnSe/ZnS quantum dots. Further, 15 g of acetone was added to this dispersion and stirred, and InZnP/ZnSe/ZnS quantum dots were collected as precipitates by centrifugation. The recovered InZnP/ZnSe/ZnS quantum dots were suspended in 0.7 g of octane to obtain an octane dispersion of purified InZnP/ZnSe/ZnS quantum dots. Table 1 shows the results of measuring the luminescence properties of the obtained dispersion. FIG. 1 shows the result of measuring the emission spectrum of the obtained dispersion.

[Example 2]
0.1885 g of zinc oleate, 0.102 g of zinc chloride, 0.112 g of trioctylphosphine selenide, 0.332 g of trioctylphosphine, 0.813 g of oleylamine and 1.025 g of dibenzylamine were mixed in a 10 mL reaction vessel and , while stirring, was heated to 120° C. and degassed for 30 minutes. After degassing, the pressure was returned to atmospheric pressure with nitrogen gas, and the temperature was raised to 180°C under a nitrogen atmosphere. After holding for 1 minute, the temperature was further raised to 300° C. and held for 60 minutes to obtain an oleylamine/dibenzylamine dispersion of InZnP/ZnSe quantum dots having InZnP in the core and ZnSe in the shell. After cooling the obtained dispersion to 240° C., 0.423 g of dodecanethiol was injected and held for 90 minutes to obtain multishell quantum dots having InZnP in the core and ZnSe and ZnS stacked in the shell. An oleylamine/dibenzylamine dispersion was obtained.
After cooling the resulting dispersion to room temperature, 15 g of acetone was added and stirred, and InZnP/ZnSe/ZnS quantum dots were collected as precipitates by centrifugation. The recovered InZnP/ZnSe/ZnS quantum dots were suspended in 0.866 g of toluene to obtain a toluene dispersion of InZnP/ZnSe/ZnS quantum dots. Further, 15 g of acetone was added to this dispersion and stirred, and InZnP/ZnSe/ZnS quantum dots were collected as precipitates by centrifugation. The recovered InZnP/ZnSe/ZnS quantum dots were suspended in 0.7 g of octane to obtain an octane dispersion of purified InZnP/ZnSe/ZnS quantum dots. Table 1 shows the results of measuring the luminescence properties of the obtained dispersion. FIG. 2 shows the result of measuring the emission spectrum of the obtained dispersion.

[Example 3]
0.1885 g of zinc oleate, 0.102 g of zinc chloride, 0.112 g of trioctylphosphine selenide, 0.332 g of trioctylphosphine, 0.813 g of oleylamine and 0.805 g of di-2-ethylhexylamine were mixed in a 10 mL reaction vessel. , and degassed for 30 minutes by heating to 120° C. under reduced pressure and stirring. After degassing, the pressure was returned to atmospheric pressure with nitrogen gas, and the temperature was raised to 180°C under a nitrogen atmosphere. After holding for 1 minute, the temperature was further raised to 300° C. and held for 60 minutes to obtain an oleylamine/di-2-ethylhexylamine dispersion of InZnP/ZnSe quantum dots having InZnP in the core and ZnSe in the shell. After cooling the obtained dispersion to 240° C., 0.423 g of dodecanethiol was injected and held for 90 minutes to obtain multishell quantum dots having InZnP in the core and ZnSe and ZnS stacked in the shell. An oleylamine/di-2-ethylhexylamine dispersion was obtained.
After cooling the resulting dispersion to room temperature, 15 g of acetone was added and stirred, and InZnP/ZnSe/ZnS quantum dots were collected as precipitates by centrifugation. The recovered InZnP/ZnSe/ZnS quantum dots were suspended in 0.866 g of toluene to obtain a toluene dispersion of InZnP/ZnSe/ZnS quantum dots. Further, 15 g of acetone was added to this dispersion and stirred, and InZnP/ZnSe/ZnS quantum dots were collected as precipitates by centrifugation. The recovered InZnP/ZnSe/ZnS quantum dots were suspended in 0.7 g of octane to obtain an octane dispersion of purified InZnP/ZnSe/ZnS quantum dots. Table 1 shows the results of measuring the luminescence properties of the obtained dispersion. FIG. 3 shows the result of measuring the emission spectrum of the obtained dispersion.

[Example 4]
0.1885 g of zinc oleate, 0.102 g of zinc chloride, 0.112 g of trioctylphosphine selenide, 0.332 g of trioctylphosphine, 1.304 g of oleylamine and 0.410 g of dibenzylamine were mixed in a 10 mL reaction vessel and , while stirring, was heated to 120° C. and degassed for 30 minutes. After degassing, the pressure was returned to atmospheric pressure with nitrogen gas, and the temperature was raised to 180°C under a nitrogen atmosphere. After holding for 1 minute, the temperature was further raised to 300° C. and held for 60 minutes to obtain an oleylamine/dibenzylamine dispersion of InZnP/ZnSe quantum dots having InZnP in the core and ZnSe in the shell. After cooling the obtained dispersion to 240° C., 0.423 g of dodecanethiol was injected and held for 90 minutes to obtain multishell quantum dots having InZnP in the core and ZnSe and ZnS stacked in the shell. An oleylamine/dibenzylamine dispersion was obtained.
After cooling the resulting dispersion to room temperature, 15 g of acetone was added and stirred, and InZnP/ZnSe/ZnS quantum dots were collected as precipitates by centrifugation. The recovered InZnP/ZnSe/ZnS quantum dots were suspended in 0.866 g of toluene to obtain a toluene dispersion of InZnP/ZnSe/ZnS quantum dots. Further, 15 g of acetone was added to this dispersion and stirred, and InZnP/ZnSe/ZnS quantum dots were collected as precipitates by centrifugation. The recovered InZnP/ZnSe/ZnS quantum dots were suspended in 0.7 g of octane to obtain an octane dispersion of purified InZnP/ZnSe/ZnS quantum dots. Table 1 shows the results of measuring the luminescence properties of the obtained dispersion. FIG. 4 shows the result of measuring the emission spectrum of the obtained dispersion.

[Example 5]
0.1885 g of zinc oleate, 0.102 g of zinc chloride, 0.112 g of trioctylphosphine selenide, 0.332 g of trioctylphosphine, 0.650 g of oleylamine, 0.820 g of dibenzylamine and 0.316 g of 1-octadecene were reacted in 10 mL. The mixture was mixed in a vessel and heated to 120° C. under reduced pressure with stirring for 30 minutes to degas. After degassing, the pressure was returned to atmospheric pressure with nitrogen gas, and the temperature was raised to 180°C under a nitrogen atmosphere. After holding for 1 minute, the temperature was further raised to 300° C. and held for 60 minutes to obtain an oleylamine/dibenzylamine/1-octadecene dispersion of InZnP/ZnSe quantum dots having InZnP in the core and ZnSe in the shell. After cooling the obtained dispersion to 240° C., 0.423 g of dodecanethiol was injected and held for 90 minutes to obtain multishell quantum dots having InZnP in the core and ZnSe and ZnS stacked in the shell. An oleylamine/dibenzylamine/1-octadecene dispersion was obtained.
After cooling the resulting dispersion to room temperature, 15 g of acetone was added and stirred, and InZnP/ZnSe/ZnS quantum dots were collected as precipitates by centrifugation. The recovered InZnP/ZnSe/ZnS quantum dots were suspended in 0.866 g of toluene to obtain a toluene dispersion of InZnP/ZnSe/ZnS quantum dots. Further, 15 g of acetone was added to this dispersion and stirred, and InZnP/ZnSe/ZnS quantum dots were collected as precipitates by centrifugation. The recovered InZnP/ZnSe/ZnS quantum dots were suspended in 0.7 g of octane to obtain an octane dispersion of purified InZnP/ZnSe/ZnS quantum dots. Table 1 shows the results of measuring the luminescence properties of the obtained dispersion. FIG. 5 shows the result of measuring the emission spectrum of the obtained dispersion.

[Comparative Example 1]
0.1885 g of zinc oleate, 0.102 g of zinc chloride, 0.112 g of trioctylphosphine selenide, 0.332 g of trioctylphosphine and 1.578 g of 1-octadecene were mixed in a 10 mL reaction vessel, and under reduced pressure, 120 ℃ and degassed for 30 minutes. After degassing, the pressure was returned to atmospheric pressure with nitrogen gas, and the temperature was raised to 180°C under a nitrogen atmosphere. After holding, the temperature was further raised to 300° C. and held for 60 minutes to obtain a 1-octadecene dispersion of InZnP/ZnSe quantum dots having InZnP in the core and ZnSe in the shell. After cooling the obtained dispersion to 240° C., 0.423 g of dodecanethiol was injected and held for 90 minutes to obtain multishell quantum dots having InZnP in the core and ZnSe and ZnS stacked in the shell. A 1-octadecene dispersion was obtained.
After cooling the resulting dispersion to room temperature, 15 g of acetone was added and stirred, and the InZnP/ZnSeS quantum dots were recovered as a precipitate by centrifugation. The recovered InZnP/ZnSe/ZnS quantum dots were suspended in 0.866 g of toluene to obtain a toluene dispersion of InZnP/ZnSe/ZnS quantum dots. Further, 15 g of acetone was added to this dispersion and stirred, and InZnP/ZnSe/ZnS quantum dots were collected as precipitates by centrifugation. The recovered InZnP/ZnSe/ZnS quantum dots were suspended in 0.7 g of octane to obtain an octane dispersion of purified InZnP/ZnSe/ZnS quantum dots. Table 1 shows the results of measuring the luminescence properties of the obtained dispersion. FIG. 6 shows the result of measuring the emission spectrum of the obtained dispersion.

[Comparative Example 2]
0.1885 g of zinc oleate, 0.102 g of zinc chloride, 0.112 g of trioctylphosphine selenide, 0.332 g of trioctylphosphine and 1.626 g of oleylamine were mixed in a 10 mL reactor and heated to 120° C. under reduced pressure with stirring. Heat and degas for 30 minutes. After degassing, the pressure was returned to atmospheric pressure with nitrogen gas, and the temperature was raised to 180°C under a nitrogen atmosphere. After holding, the temperature was further raised to 300° C. and held for 60 minutes to obtain an oleylamine dispersion of InZnP/ZnSe quantum dots having InZnP in the core and ZnSe in the shell. After cooling the obtained dispersion to 240° C., 0.423 g of dodecanethiol was injected and held for 90 minutes to obtain multishell quantum dots having InZnP in the core and ZnSe and ZnS stacked in the shell. An oleylamine dispersion was obtained.
After cooling the resulting dispersion to room temperature, 15 g of acetone was added and stirred, and InZnP/ZnSe/ZnS quantum dots were collected as precipitates by centrifugation. The recovered InZnP/ZnSe/ZnS quantum dots were suspended in 0.866 g of toluene to obtain a toluene dispersion of InZnP/ZnSe/ZnS quantum dots. Further, 15 g of acetone was added to this dispersion and stirred, and InZnP/ZnSe/ZnS quantum dots were collected as precipitates by centrifugation. The recovered InZnP/ZnSe/ZnS quantum dots were suspended in 0.7 g of octane to obtain an octane dispersion of purified InZnP/ZnSe/ZnS quantum dots. Table 1 shows the results of measuring the luminescence properties of the obtained dispersion. FIG. 7 shows the result of measuring the emission spectrum of the obtained dispersion.

[Comparative Example 3]
0.1885 g of zinc oleate, 0.102 g of zinc chloride, 0.112 g of trioctylphosphine selenide, 0.332 g of trioctylphosphine and 1.599 g of dioctylamine were mixed in a 10 mL reactor and heated to 120° C. under reduced pressure while stirring. and degassed for 30 minutes. After degassing, the pressure was returned to atmospheric pressure with nitrogen gas, and the temperature was raised to 180°C under a nitrogen atmosphere. After holding, the temperature was further raised to 300° C. and held for 60 minutes to obtain a dioctylamine dispersion of InZnP/ZnSe quantum dots having InZnP in the core and ZnSe in the shell. After cooling the obtained dispersion to 240° C., 0.423 g of dodecanethiol was injected and held for 90 minutes to obtain multishell quantum dots having InZnP in the core and ZnSe and ZnS stacked in the shell. A dioctylamine dispersion was obtained.
After cooling the resulting dispersion to room temperature, 15 g of acetone was added and stirred, and InZnP/ZnSe/ZnS quantum dots were collected as precipitates by centrifugation. The recovered InZnP/ZnSe/ZnS quantum dots were suspended in 0.866 g of toluene to obtain a toluene dispersion of InZnP/ZnSe/ZnS quantum dots. Further, 15 g of acetone was added to this dispersion and stirred, and InZnP/ZnSe/ZnS quantum dots were collected as precipitates by centrifugation. The recovered InZnP/ZnSe/ZnS quantum dots were suspended in 0.7 g of octane to obtain an octane dispersion of purified InZnP/ZnSe/ZnS quantum dots. Table 1 shows the results of measuring the luminescence properties of the obtained dispersion. FIG. 8 shows the result of measuring the emission spectrum of the obtained dispersion.

[Comparative Example 4]
0.1885 g of zinc oleate, 0.102 g of zinc chloride, 0.112 g of trioctylphosphine selenide, 0.332 g of trioctylphosphine and 1.618 g of trioctylamine were mixed in a 10 mL reaction vessel, and under reduced pressure, 120 ℃ and degassed for 30 minutes. After degassing, the pressure was returned to atmospheric pressure with nitrogen gas, and the temperature was raised to 180°C under a nitrogen atmosphere. After holding, the temperature was further raised to 300° C. and held for 60 minutes to obtain a trioctylamine dispersion of InZnP/ZnSe quantum dots having InZnP in the core and ZnSe in the shell. After cooling the obtained dispersion to 240° C., 0.423 g of dodecanethiol was injected and held for 90 minutes to obtain multishell quantum dots having InZnP in the core and ZnSe and ZnS stacked in the shell. A trioctylamine dispersion was obtained.
After cooling the resulting dispersion to room temperature, 15 g of acetone was added and stirred, and the InZnP/ZnSeS quantum dots were recovered as a precipitate by centrifugation. The recovered InZnP/ZnSe/ZnS quantum dots were suspended in 0.866 g of toluene to obtain a toluene dispersion of InZnP/ZnSe/ZnS quantum dots. Further, 15 g of acetone was added to this dispersion and stirred, and InZnP/ZnSe/ZnS quantum dots were collected as precipitates by centrifugation. The recovered InZnP/ZnSe/ZnS quantum dots were suspended in 0.7 g of octane to obtain an octane dispersion of purified InZnP/ZnSe/ZnS quantum dots. Table 1 shows the results of measuring the luminescence properties of the obtained dispersion. FIG. 9 shows the result of measuring the emission spectrum of the obtained dispersion.

From the results in Table 1, it can be seen that although the FWHM values of Example 1 and Comparative Example 2 are equivalent, Example 1 is superior to Comparative Example 2 in PLQY value. Although the PLQY values of Example 1 and Comparative Example 1 are the same, it can be seen that Example 1 is superior to Comparative Example 1 in that the FWHM value is narrower. It can be seen that Comparative Example 3 is inferior to Example 1 in both FWHM value and PLQY value. 1 to 9 that the emission spectra of Examples 1 to 5 have less tails and shoulders than the emission spectra of Comparative Examples 1 to 4, and are superior in symmetry.

Claims (10)

A method for producing a core-shell structure quantum dot having an InP-based quantum dot obtained by the reaction of at least a phosphorus source and an indium source in the core and a coating compound other than the InP-based coating compound in the shell, comprising:
A method for producing quantum dots, wherein the reaction for coating the core with the coating compound is carried out in a solvent containing a plurality of types of amine derivatives. The amine derivative is caprylamine, laurylamine, stearylamine, oleylamine, monoethylamine, monobutylamine, monodecylamine, monohexylamine, monooctylamine, monododecylamine, monohexadecylamine, benzylamine, diethylamine, dibutylamine , didecylamine, dihexylamine, dioctylamine, didodecylamine, dihexadecylamine, dibenzylamine, di-2-ethylhexylamine, triethylamine, tributylamine, tridecylamine, trihexylamine, trioctylamine, tridodecylamine, 2. The method for producing quantum dots according to claim 1, wherein at least two selected from the group consisting of trihexadecylamine and tribenzylamine. 3. The method for producing quantum dots according to claim 1, wherein the reaction is carried out in a solvent further containing a metal halide compound. 4. The method for producing quantum dots according to claim 3, wherein the metal halide is at least one selected from the group consisting of zinc fluoride, zinc chloride, zinc bromide and zinc iodide. 3. The method for producing quantum dots according to claim 1, wherein the coating compound is obtained by reaction with at least a zinc source. 3. The method for producing quantum dots according to claim 1, wherein the coating compound is ZnS, ZnSe, ZnSeS, ZnTe, ZnSeTe, ZnTeS, ZnO, ZnOS, ZnSeO or ZnTeO. 3. The method for producing quantum dots according to claim 2, wherein the phosphorus source is a silylphosphine compound represented by the following general formula (1).

(R is each independently an alkyl group having 1 to 5 carbon atoms or an aryl group having 6 to 10 carbon atoms.) The production of quantum dots according to claim 1 or 2, wherein the indium source is at least one selected from the group consisting of indium acetate, indium laurate, indium myristate, indium palmitate, indium stearate and indium oleate. Method. The InP-based quantum dots are obtained by heating an InP quantum dot precursor obtained by reacting a phosphorus source and an indium source at a temperature of 20° C. or higher and 150° C. or lower to a temperature of 200° C. or higher and 350° C. or lower. The method for producing a quantum dot according to claim 1 or 2, which is a product. An InP quantum dot precursor and an elemental source M other than a phosphorus source and an indium source (M consists of Be, Mg, Ca, Mn, Cu, Zn, Cd, B, Al, Ga, N, As, Sb and Bi 3. The method for producing a quantum dot according to claim 1 or 2, wherein the core is an InP-based quantum dot obtained by heating at a temperature of 200° C. or higher and 350° C. or lower together with a compound containing at least one selected from the group.

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