Quantum dot and manufacturing method thereof

Abstract

The invention aims to provide the Cd-free chalcopyrite quantum dot which is narrow in fluorescence half-peak width and high in fluorescence quantum yield. The quantum dot according to the present invention is a quantum dot formed from an AgInxGa1-xSySe1-y system or a ZnAgInxGa1-xSySe1-y system (0 < = x < 1, 0 < = y < = 1), and is characterized by exhibiting fluorescence characteristics of a fluorescence half-peak width of 45 nm or less and a fluorescence quantum yield of 35% or more from a green wavelength domain to a red wavelength domain.

Description

[0001] This application is a divisional application of the PCT national phase entry application with an international filing date of July 31, 2020, a date of entry into the Chinese national phase of December 29, 2020, a national application number of 202080003773.9, and an invention title of "Quantum Dots and Method for Manufacturing the Same". Technical Field

[0002] The present invention relates to a cadmium-free quantum dot and a method for manufacturing the same. Background Art

[0003] Quantum dots are inorganic nanoparticles composed of several thousand to several tens of thousands of atoms and having a particle diameter of about several nm to more than ten nm. Since quantum dots emit fluorescence and their size is in the nanometer range, they are called fluorescent nanoparticles. Since their components are derived from semiconductor materials, they are called semiconductor nanoparticles, or since their structure has a specific crystal structure, they are called nanocrystals.

[0004] Quantum dots are composed of metal atoms with a positive charge and non-metal or semi-metal atoms with a negative charge, and the metal atoms and semi-metal atoms are bonded by an ionic bond or a covalent bond. The ionic nature of the bond depends on the combination of the properties of the metal atom and the semi-metal atom.

[0005] As quantum dots, the emission wavelength can be variously changed according to the particle diameter and its components. As parameters representing the performance of quantum dots, fluorescence quantum yield (Quantum Yield: QY) and full width at half maximum of fluorescence (Full Width at Half Maximum: FWHM) can be cited.

[0006] As one of the properties of quantum dots, photoluminescence can be cited. Quantum dots can absorb wavelengths in a specific wavelength region and convert them into wavelengths in a specific region to emit light. In addition, the absorption wavelength and the emission wavelength can be controlled by the structure, components, and size of the quantum dots, and by utilizing this feature, they can be used for various purposes respectively.

[0007] For example, when using quantum dots as a wavelength conversion material in the visible light region, as one of its characteristics, it can be cited that the range of colors that can be presented is wide, that is, high color gamut. In achieving high color gamut with a wavelength conversion component using such quantum dots in the visible light region, important optical properties are fluorescence quantum yield and full width at half maximum of fluorescence.

[0008] The highly efficient quantum dots that have been used all along mainly contain cadmium (Cd). The Cd-containing quantum dots have the following advantages, namely, high fluorescence quantum yield and narrow fluorescence half-width. On the other hand, due to the toxicity of Cd, each country has regulations on its use, which has been the main obstacle to its practical application.

[0009] In contrast, the development of many Cd-free quantum dots is being explored. For example, the following patent documents describe AIS or AIGS-based quantum dots containing Ag, In, S, or Ag, In, Ga, S, or Ag, In, Se, or Ag, In, Ga, Se, or AISe or AIGSe-based quantum dots.

[0010] Prior Art Documents

[0011] Patent Documents

[0012] Patent Document 1: Japanese Patent Application Laid-Open No. 2017-025201

[0013] Patent Document 2: Japanese Patent Application Laid-Open No. 2018-039971

[0014] Patent Document 3: Japanese Patent Application Laid-Open No. 2018-044142

[0015] Patent Document 4: Japanese Patent Application Laid-Open No. 2018-141141

[0016] Patent Document 5: WO2018 / 159699

[0017] Non-Patent Documents

[0018] Non-Patent Document 1: NPG Asia Materials volume 10, 2018, pp713-726. Non-Patent Document 2: ACS Publications 2018, 10, 49, 41844-41855

[0019] Non-Patent Document 3: ACS Publications Nano Mater. 2020, 3, 3275-3287

[0020] Non-Patent Document 4: The Journal of Physical Chemistry Letters; Ligand-Induced Luminescence Transformation in AgInS2 Nanoparticles: From Defect Emission to Band-Edge Emission Summary of the Invention

[0021] Problems to be Solved by the Invention

[0022] Although the research and development of Cd-free chalcopyrite-based quantum dots are in progress as described above, from the viewpoints of full width at half maximum (FWHM) of fluorescence and fluorescence quantum yield, the quantum dots have not reached the performance required to replace Cd-based quantum dots.

[0023] The present invention has been completed in view of the above points, and an object thereof is to provide a Cd-free chalcopyrite-based quantum dot having a narrow FWHM of fluorescence and a high fluorescence quantum yield.

[0024] In addition, another object of the present invention is to provide a method for manufacturing a quantum dot capable of mass-producing the above-described quantum dot.

[0025] Solutions to the Problems

[0026] The quantum dot of the present invention is characterized in that it is composed of AgIn x Ga 1-x S y Se 1-y system or ZnAgIn x Ga 1-x S y Se 1-y system (0 ≤ x < 1, 0 ≤ y ≤ 1), and exhibits fluorescence characteristics with a FWHM of fluorescence of 45 nm or less and a fluorescence quantum yield of 35% or more in the green wavelength region to the red wavelength region.

[0027] The method for manufacturing a quantum dot of the present invention is characterized in that it is formed from AgIn x Ga 1-x S y Se 1-y system, or ZnAgIn x Ga 1-x S y Se 1-y system (0 ≤ x < 1, 0 ≤ y ≤ 1), and synthesizes a quantum dot exhibiting fluorescence characteristics with a FWHM of fluorescence of 45 nm or less and a fluorescence quantum yield of 35% or more in the green wavelength region to the red wavelength region.

[0028] Advantages of the Invention

[0029] According to the quantum dot of the present invention, quantum dots having the same composition, particle shape, and size can be synthesized. Therefore, the FWHM of fluorescence can be narrowed and the fluorescence quantum yield can be increased.

[0030] In addition, according to the quantum dot of the present invention, quantum dots having a target emission wavelength can be synthesized according to the use.

[0031] In addition, the quantum dots according to the present invention can synthesize quantum dots with a narrow full width at half maximum (FWHM) at a luminescence wavelength corresponding to the purpose, and thus can achieve an improvement in a high color gamut when used as a wavelength conversion material.

[0032] In addition, according to the method for manufacturing quantum dots of the present invention, quantum dots with a narrow fluorescence FWHM and without Cd can be synthesized by a mass-producible method. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 It is a schematic diagram of the quantum dots in the embodiment of the present invention.

[0034] Figure 2 It is a schematic diagram of an LED device using the quantum dots of the embodiment of the present invention.

[0035] Figure 3 It is a longitudinal sectional view of a display device using the LED device in the embodiment of the present invention.

[0036] Figure 4 It is the fluorescence (Photoluminescence: PL) spectrum of AgInGaS in Example 1.

[0037] Figure 5 It is the PL spectrum of AgInGaS in Example 2.

[0038] Figure 6 It is the PL spectrum of AgInGaS in Example 3.

[0039] Figure 7 It is the PL spectrum of AgInGaS in Example 4.

[0040] Figure 8 It is the PL spectrum of AgInGaS in Example 5.

[0041] Figure 9 It is the PL spectrum of AgInGaS in Example 6.

[0042] Figure 10 It is the PL spectrum of AgInGaS in Example 7.

[0043] Figure 11 It is the PL spectrum of AgInGaS in Example 11.

[0044] Figure 12 It is the PL spectrum of AgInGaS in Example 12.

[0045] Figure 13 It is the PL spectrum of AgInGaS in Example 13.

[0046] Figure 14PL spectrum of ZnAgInGaS in Example 14.

[0047] Figure 15 PL spectrum of ZnAgGaSeS in Example 15.

[0048] Figure 16 PL spectrum of ZnAgGaSeS in Example 17.

[0049] Figure 17 PL spectrum of ZnAgGaSeS in Example 18.

[0050] Figure 18 PL spectrum of ZnAgInGaSeS in Example 19.

[0051] Figure 19 PL spectrum of ZnAgGaSeS in Example 20.

[0052] Figure 20 PL spectrum of ZnAgInGaS in Comparative Example 1.

[0053] Figure 21 Scanning Electron Microscopy (SEM) photograph of AgInGaS in Example 7.

[0054] Figure 22 Photograph of the analysis result of TEM-EDX in Example 15.

[0055] Figure 23 For Figure 22 Partial schematic diagram. Detailed implementation mode

[0056] A detailed description of an embodiment of the present invention (hereinafter simply referred to as "embodiment") is given below. In addition, the present invention is not limited to the following embodiments and can be implemented with various changes within the scope of its gist. In addition, the expression "~" in this specification means including its lower limit value and upper limit value.

[0057] Figure 1 Schematic diagram of the quantum dots in this embodiment. Figure 1 The quantum dot 5 shown in A is a Cd-free nanocrystal.

[0058] In this embodiment, the quantum dot 5 is composed of Ag In x Ga 1-x S y Se 1-y system or ZnAgIn x Ga 1-x S ySe 1-y Quantum dots formed by the system (0 ≤ x < 1, 0 ≤ y ≤ 1). The quantum dots 5 in this embodiment are preferably nanocrystals containing at least silver (Ag), gallium (Ga), sulfur (S), or silver (Ag), gallium (Ga), selenium (Se), and not containing cadmium (Cd). In addition, the quantum dots 5 contain Ag, Ga, S, or Ag, Ga, Se, and may also contain indium (In) or zinc (Zn).

[0059] Here, "nanocrystal" refers to nanoparticles with a particle size of about several nm to several tens of nm. In this embodiment, a plurality of quantum dots 5 with substantially uniform particle sizes can be generated.

[0060] The ratio of Ag to Ga contained in the quantum dots 5 is preferably in the range of Ag / Ga = 0.05 or more and 10 or less. In addition, the ratio Ag / Ga is more preferably in the range of 0.05 or more and 5 or less, and even more preferably in the range of 0.1 or more and 3 or less.

[0061] The ratio of Zn to Ga that can be contained in the quantum dots 5 is preferably in the range of Zn / Ga = 0.1 or more and 10 or less. The ratio Zn / Ga is more preferably in the range of 0.1 or more and 5 or less. By controlling this ratio, the emission wavelength can be adjusted.

[0062] In this embodiment, the fluorescence wavelength can be adjusted in the green wavelength region to the red wavelength region. In particular, in this embodiment, the fluorescence wavelength can be appropriately adjusted in the range of 400 nm or more and 700 nm or less. In this embodiment, the fluorescence wavelength can also be adjusted in the range of 500 nm or more and 650 nm or less.

[0063] As Figure 1 shown in A, preferably, a plurality of organic ligands (Ligand) 11 are coordinated on the surface of the quantum dots 5. Thereby, the aggregation of the quantum dots 5 with each other can be suppressed, and thus the optical properties as the object can be found. The ligands that can be used in the reaction are not particularly limited, and for example, the following ligands can be listed as representative ligands.

[0064] (1) Aliphatic primary amine series

[0065] Oleylamine: C 18 H 35 NH2, Stearyl (octadecyl) amine: C 18 H 37 NH2, Dodecyl (lauryl) amine: C 12 H 25 NH2, Decylamine: C 10 H 21 NH2, Octylamine: C8H 17 NH2

[0066] (2) Fatty acid series

[0067] Oleic acid: C 17 H 33 COOH, Stearic acid: C 17 H 35 COOH, Palmitic acid: C 15 H 31 COOH, Myristic acid: C 13 H 27 COOH, Lauric acid: C 11 H 23 COOH, Capric acid: C9H 19 COOH, Caprylic acid: C7H 15 COOH

[0068] (3) Thiol series

[0069] Octadecanethiol: C 18 H 37 SH, Hexadecanethiol: C 16 H 33 SH, Tetradecanethiol: C 14 H 29 SH, Dodecanethiol: C 12 H 25 SH, Decanethiol: C 10 H 21 SH, Octanethiol: C8H 17 SH

[0070] (4) Phosphine series

[0071] Trioctylphosphine: (C8H 17 )3P, Triphenylphosphine: (C6H5)3P, Tributylphosphine: (C4H9)3P

[0072] (5) Phosphine oxide series

[0073] Trioctylphosphine oxide: (C8H 17 )3P=O, Triphenylphosphine oxide: (C6H5)3P=O, Tributylphosphine oxide: (C4H9)3P=O

[0074] The characteristic part of the quantum dot 5 of the present embodiment will be described. The quantum dot 5 of the present embodiment has a fluorescence characteristic of showing a fluorescence half-peak width of 45 nm or less and a fluorescence quantum yield of 35% or more in the green wavelength region to the red wavelength region.

[0075] Herein, the "full width at half maximum of fluorescence" refers to the full width at half maximum (Full Width at Half Maximum) of the fluorescence wavelength at half the intensity of the peak of the fluorescence intensity in the fluorescence spectrum. In addition, the full width at half maximum of fluorescence is preferably 35 nm or less. Further, the full width at half maximum of fluorescence is more preferably 30 nm or less. Further, the full width at half maximum of fluorescence is more preferably 25 nm or less. In this way, the full width at half maximum of fluorescence can be narrowed, and thus an improvement in high color gamut can be achieved.

[0076] The fluorescence quantum yield of the quantum dots 5 of the present embodiment is more preferably 40% or more, further preferably 60% or more, still further preferably 70% or more, and most preferably 80% or more. In this way, in the present embodiment, the fluorescence quantum yield of the quantum dots can be improved.

[0077] In this way, in the present embodiment, the fluorescence half peak width in the green wavelength region to the red wavelength region of the AgIn x Ga 1-x S y Se 1-y system or ZnAgIn x Ga 1-x S y Se 1-y system (0 ≤ x < 1, 0 ≤ y ≤ 1) of quantum dots can be narrowed and the fluorescence quantum yield can be improved.

[0078] In the present embodiment, the fluorescence wavelength can be freely controlled to be around 400 nm or more and 700 nm or less. The quantum dots 5 in the present embodiment are solid solutions based on Ag, Ga, In, Zn as cation raw materials and Se, S as anion raw materials. In the present embodiment, by appropriately adjusting the particle size and composition of the quantum dots 5, the fluorescence wavelength can be controlled from blue to green to red. Therefore, for blue light emission, the fluorescence wavelength is preferably 400 nm or more and 480 nm or less, more preferably 410 nm or more and 470 nm or less, and further preferably 420 nm or more and 460 nm or less. For green light emission, it is preferably 500 nm or more and 560 nm or less, more preferably 510 nm or more and 550 nm or less, and further preferably 520 nm or more and 540 nm or less. In addition, for red light emission, it is preferably 600 nm or more and 660 nm or less, more preferably 610 nm or more and 650 nm or less, and further preferably 620 nm or more and 640 nm or less.

[0079] In addition, in the present embodiment, as described above, the fluorescence wavelength can be controlled to be 400 nm or more and 700 nm or less, and as a wavelength conversion material in the visible light region, green or red light emission is preferred.

[0080] Here, chalcopyrite is generally a material that emits defective light with a full width at half maximum (FWHM) of fluorescence of 45 to 80 nm. In contrast, for the quantum dot 5 of the present embodiment, the FWHM of fluorescence is narrow, and in addition, the fluorescence quantum yield is high, and the fluorescence lifetime is very short compared to defective light emission. Based on such characteristics, it can be speculated that the quantum dot 5 of the present embodiment emits light at the band edge.

[0081] In particular, the quantum dot 5 of the present embodiment can be synthesized, that is, a quantum dot 5 having an FWHM of fluorescence of 30 μm or less, a fluorescence quantum yield of 80% or more, and a fluorescence wavelength in the range of 510 nm or more and 650 nm or less. In this way, characteristics of narrow FWHM of fluorescence and high fluorescence quantum yield can be achieved not only at green fluorescence wavelengths (near 510 to 540 nm) but also at red fluorescence wavelengths (near 610 to 650 nm).

[0082] Figure 1 The quantum dot 5 shown in Fig. B has a core-shell structure having a core 5a and a shell 5b covering the surface of the core 5a. Preferably, as shown in Figure 1 Fig. B, a plurality of organic ligands 11 are coordinated on the surface of the quantum dot 5. In addition, Figure 1 For the quantum dot 5 shown in Fig. B, the FWHM of fluorescence is 45 nm or less, and the fluorescence quantum yield is 35% or more.

[0083] Figure 1 The core 5a of the quantum dot 5 shown in Fig. B is Figure 1 the nanocrystal shown in Fig. A. Therefore, the core 5a is preferably formed of a nanocrystal containing Ag, Ga, S, or Ag, Ga, Se and not containing Cd. The shell 5b does not contain cadmium (Cd) in the same manner as the core 5a. As the shell 5b, there is no particular requirement for the material, and examples thereof include indium sulfide, gallium sulfide, aluminum sulfide, zinc sulfide, indium selenide, gallium selenide, aluminum selenide, and zinc selenide. At this time, as the Ga source, gallium chloride, gallium bromide, and gallium iodide are preferred.

[0084] In addition, the shell 5b may be in a solid-solubilized state on the surface of the core 5a. In Figure 1 Fig. B, the boundary between the core 5a and the shell 5b is indicated by a dotted line, which means that the boundary between the core 5a and the shell 5b can be confirmed by analysis or cannot be confirmed, and either is acceptable. For the above-listed ZnAgIn x Ga 1-x S y Se 1-y series (0 ≤ x < 1, 0 ≤ y ≤ 1) of quantum dots, even if the core-shell structure cannot be confirmed, the form in which the core 5a is covered by the shell 5b can be speculated by the inclusion of Zn.

[0085] Figure 1 The quantum dot 5 shown in Fig. B is also the same as Figure 1Similarly, the fluorescence wavelength is freely controlled to be around 400 nm or more and 700 nm or less, or around 500 nm or more and 650 nm or less.

[0086] In addition, in this embodiment, the core formed only of AgGaS, AgGaSe, AgGaInS, or AgGaInSe also emits fluorescence, so the shell coverage is not necessary. However, by adopting a core-shell structure, it is expected that the fluorescence quantum yield will be further improved while the full width at half maximum of the fluorescence is maintained in a narrow state. In addition, regarding In, fluorescence can be observed whether or not In is contained. For example, the quantum dots with green fluorescence have good luminescence characteristics by containing In, but even if In is not contained, although the full width at half maximum of the fluorescence tends to increase slightly, they still emit light. Specifically, the luminescence of AgGaS can be confirmed.

[0087] In addition, generally when Zn is used, due to different valence states (Zn is divalent, Ag is monovalent, Ga or In is trivalent), defect luminescence occurs and the full width at half maximum of the fluorescence tends to expand. However, in this embodiment, as shown in the following experiments, even if Zn is added later, the fluorescence quantum yield can be increased while the full width at half maximum of the fluorescence is maintained in a narrow state, that is, the luminescence characteristics can be improved by using Zn.

[0088] Next, the manufacturing method of the quantum dots 5 of this embodiment will be described.

[0089] The manufacturing method of the quantum dots of this embodiment is characterized in that it is formed of an AgIn x Ga 1-x S y Se 1-y system or a ZnAgIn x Ga 1-x S y Se 1-y system (0 ≤ x < 1, 0 ≤ y ≤ 1), and in the green wavelength region to the red wavelength region, quantum dots are synthesized that exhibit fluorescence characteristics with a full width at half maximum of the fluorescence of 45 nm or less and a fluorescence quantum yield of 35% or more.

[0090] First, in this embodiment, an organic silver compound, an organic gallium compound, sulfur or selenium, or an organic silver compound, an organic indium compound, an organic gallium compound, sulfur or selenium are heated and synthesized in a one-pot manner.

[0091] At this time, the reaction temperature is set in the range of 100 °C or more and 320 °C or less to synthesize AgGaS, AgGaSe, AgGaInS, or AgGaInSe. In addition, the reaction temperature is preferably 280 °C or lower, which is a lower temperature.

[0092] In addition, in the present embodiment, an organic silver compound or an inorganic silver compound is used as the raw material of Ag. There is no particular limitation. For example, silver acetate: AgOAc, silver nitrate: AgNO3 can be used. As the halide, silver chloride: AgCl, silver bromide: AgBr, silver iodide: AgI can be used. As the carbamate, silver diethyldithiocarbamate: Ag(SC(=S)N(C2H5)2), silver dimethyldithiocarbamate: Ag(SC(=S)N(CH3)2), etc. can be used.

[0093] In addition, in the present embodiment, the above Ag raw material can be directly added to the reaction solution, but a solution in which the above Ag raw material is dissolved in an organic solvent to a certain concentration can also be used as the Ag raw material solution.

[0094] In addition, in the present embodiment, an organic indium compound or an inorganic indium compound is used as the raw material of In. There is no particular limitation. For example, indium acetate: In(OAc)3, indium nitrate: InNO3, indium acetylacetonate: In(acac)3 can be used. As the halide, indium chloride: InCl3, indium bromide: InBr3, indium iodide: InI3 can be used. As the carbamate, indium diethyldithiocarbamate: In[(SC(=S)N(C2H5)2]3, indium dimethyldithiocarbamate: In[(SC(=S)N(CH3)2)]3, etc. can be used.

[0095] In addition, in the present embodiment, an organic gallium compound or an inorganic gallium compound is used as the raw material of Ga. There is no particular limitation. For example, gallium acetate: Ga(OAc)3, gallium nitrate: GaNO3, gallium acetylacetonate: Ga(acac)3 can be used. As the halide, gallium chloride: GaCl3, gallium bromide: GaBr3, gallium iodide: Ga2I3 can be used. As the carbamate, gallium diethyldithiocarbamate: Ga[(SC(=S)N(C2H5)2]3, etc. can be used.

[0096] In addition, in the present embodiment, the In raw material or the Ga raw material can be directly added to the reaction solution, but it can also be used as the In raw material solution or the Ga raw material solution after the In raw material or the Ga raw material is first dissolved in an organic solvent to a certain concentration.

[0097] In addition, in the present embodiment, an organic sulfur compound such as thiol can be used as the raw material of S. For example, octadecanethiol: C 18 H 37 SH, hexadecanethiol: C 16 H 33 SH, tetradecanethiol: C 14 H 29 SH, dodecanethiol: C12 H 25 SH, decanethiol: C 10 H 21 SH, octanethiol: C8H 17 SH, etc.

[0098] Especially when synthesizing AgGaS or AgInGaS, the type of sulfur raw material greatly contributes to the fluorescence characteristics. In this embodiment, it is preferable to use an S-ODE raw material in which sulfur is dissolved in octadecene: ODE, a disulfide-based or thiuram-based S raw material, and an S-OLAm / DDT in which S is dissolved in oleylamine and dodecanethiol. Among them, the S-ODE raw material can obtain a fluorescence full width at half maximum of 40 nm or less and a fluorescence quantum yield of 40% or more, but better characteristics can be obtained by using disulfide. For example, diphenyl disulfide, dibenzyl disulfide, isopropyl xanthogen disulfide, 4,4'-dithiomorpholine. In addition, better fluorescence characteristics can be obtained by using thiuram-based raw materials. For example, thiuram disulfide, bis(pentamethylene)thiuram tetrasulfide, tetraethylthiuram disulfide, tetramethylthiuram disulfide, etc. Additionally, the S raw material can also be a raw material having a structure in which multiple sulfurs are connected (-S-)n or a structure having sulfur attached to nitrogen (N-S-), carbon (C-S-), etc.

[0099] In addition, in this embodiment, as a raw material for Se, an organoselenium compound (organochalcogen compound) can be used as a raw material. For example, trioctylphosphine selenite in which selenium is dissolved in trioctylphosphine: (C8H 17 )3P=Se, or tributylphosphine selenite in which selenium is dissolved in tributylphosphine: (C4H9)3P=Se, or a solution in which selenium is dissolved in a long-chain hydrocarbon such as octadecene, i.e., a high-boiling solvent.

[0100] When synthesizing AgGaSe or AgInGaSe, the type of selenium raw material greatly contributes to the fluorescence characteristics. In particular, a solution (Se-OLAm / DDT) formed by dissolving Se in a mixture of oleylamine and dodecanethiol exhibits good luminescence characteristics. In ordinary chalcopyrite-based quantum dots, two types of luminescence, namely a PL spectrum considered to be band-edge luminescence and a PL spectrum considered to be defect luminescence, can be confirmed at the initial stage of luminescence. As the ratio of their luminescence intensities, in most cases, the band-edge luminescence / defect luminescence is 10 or less. Then, as the reaction further proceeds, the intensity of the defect luminescence gradually decreases, and accordingly, the intensity of the band-edge luminescence also increases. However, as in this embodiment, when using Se-DDT / OLAm as the Se source, it is a single peak from the initial stage of luminescence, the band-edge luminescence / defect luminescence is 10 or more, and the peak considered to be defect luminescence can hardly be confirmed. In addition, the fluorescence lifetime reaches 1 / e and is as short as 20 ns or less. At the initial stage of luminescence, only the peak that is not defect luminescence can be confirmed.

[0101] In addition, in this embodiment, an organozinc compound and an inorganic zinc compound are used as the raw material of Zn. The organozinc compound and the inorganic zinc compound are raw materials that are stable even in air and are easy to handle. The structures of the organozinc compound and the inorganic zinc compound are not particularly limited. For example, the following organozinc compounds and inorganic zinc compounds can be used. As acetates, zinc acetate: Zn(OAc)2 and zinc nitrate: Zn(NO3)2 can be used. As fatty acid salts, zinc stearate: Zn(OC(=O)C 17 H 35 )2, zinc oleate: Zn(OC(=O)C 17 H 33 )2, zinc palmitate: Zn(OC(=O)C 15 H 31 )2, zinc myristate: Zn(OC(=O)C 13 H 27 )2, zinc laurate: Zn(OC(=O)C 11 H 23 )2, zinc acetylacetonate: Zn(acac)2 can be used. As halides, zinc chloride: ZnCl2, zinc bromide: ZnBr2, zinc iodide: ZnI2 can be used. As zinc carbamates, zinc diethyldithiocarbamate: Zn(SC(=S)N(C2H5)2)2, zinc dimethyldithiocarbamate: Zn(SC(=S)N(CH3)2)2, zinc dibutyldithiocarbamate: Zn(SC(=S)N(C4H9)2)2, etc. can be used.

[0102] In addition, in this embodiment, the precursor can be obtained in a one-pot manner without separation and purification.

[0103] In addition, in the present embodiment, even without performing various treatments such as washing, separation and purification, coating treatment, ligand exchange, etc. on the synthesized quantum dots, fluorescence characteristics can still be found.

[0104] However, as Figure 1 shown in B, by covering the core 5a formed of nanocrystals with the shell 5b, the fluorescence quantum yield can be further increased.

[0105] In addition, after having a core-shell structure, purification with a specific solvent can further increase the fluorescence quantum yield. For example, trioctylphosphine (TOP), etc.

[0106] In addition, in the present embodiment, by centrifuging the synthesized reaction solution, quantum dots with more excellent luminescence characteristics can be obtained.

[0107] In addition, in the present embodiment, by mixing toluene, methanol, ethanol, acetone, etc. into the synthesized reaction solution to centrifuge and remove the condensates, quantum dots with more excellent luminescence characteristics can be obtained.

[0108] The manufacturing method of the quantum dots of the present embodiment is preferably that after forming the initial reaction particles, a predetermined element is added later for synthesis. At this time, In is not contained in the initial stage of the reaction. Specifically, among the particles formed in the initial stage of the reaction, AgGaS or AgGaSe without In has the best luminescence characteristics.

[0109] Generally, In is contained from the initial stage of the reaction and the In / Ga ratio is adjusted, etc. The purpose of the quantum dots of the present embodiment is to suppress the dispersion of components and perform synthesis with as few components as possible. Therefore, it is preferred that In is not contained in the initial reaction. As a result, it can be inferred that luminescence characteristics with a narrow fluorescence half-width at half maximum can be obtained.

[0110] In addition, the quantum dots with green fluorescence are preferably quantum dots that finally contain In and may contain In during the reaction process. However, it is not necessary to contain In in the quantum dots with green fluorescence. For example, luminescence is confirmed for AgGaS without In although the fluorescence half-width at half maximum slightly expands.

[0111] In addition, in the present embodiment, when Zn is contained in the quantum dots, attention should be paid to the following aspects when adding Zn. First, Zn is not added in the initial reaction but added in the final process. This is because when Zn is contained inside the particles, it is possible that defect luminescence is dominant or only defect luminescence can be confirmed. Therefore, Zn is added in the final process to make the reaction occur on the particle surface. The second is to add Zn at a low temperature. This low temperature refers to about 150 - 200 °C. When the temperature at the time of adding Zn is high, Zn will react into the particles, so defect luminescence is likely to occur. Therefore, it is preferred to perform the reaction only on the particle surface at a low temperature to stop the reaction on the particle surface.

[0112] In addition, when synthesizing AgGaSe in this embodiment, the Se raw material is preferably Se-OLAm / DDT. Thereby, defect luminescence can be effectively suppressed.

[0113] In addition, when synthesizing AgGaS, a thiuram-based substance, especially tetraethylthiuram disulfide, rather than a substance that dissolves ordinary sulfur powder, can obtain good luminescence characteristics, so it is preferred.

[0114] In addition, the centrifugation process is a process of separating large particles from small particles. In the process of centrifuging by adding toluene and ethanol, even if the particle sizes are the same, the aggregation state can be changed according to different surface ligands of the quantum dots by controlling the ratio of toluene and ethanol. At this time, it can be controlled at a ratio of quantum dots:toluene:ethanol = 1:0.5 - 2:0.5 - 2. In addition, methanol can be used instead of ethanol. As a result, quantum dots with a high fluorescence quantum yield and quantum dots with a low fluorescence quantum yield can be separated. Then, TOP is added to the separated quantum dots, thereby further improving the fluorescence quantum yield.

[0115] As described above, according to the method for manufacturing quantum dots of this embodiment, quantum dots with a narrow fluorescence half-width, a high fluorescence quantum yield, and no Cd can be synthesized by a mass-producible method.

[0116] Figure 1 The use of the quantum dots shown in FIG. 5 is not particularly limited, and several specific examples are listed below.

[0117] Figure 2 It is a schematic diagram of an LED device using the quantum dots of this embodiment. The LED device 1 of this embodiment is configured as Figure 2 shown, and is configured to have: a storage container 2 having a bottom surface 2a and a side wall 2b surrounding the periphery of the bottom surface 2a, an LED core chip (light-emitting element) 3 disposed on the bottom surface 2a of the storage container 2, and a fluorescent layer 4 filled in the storage container 2 and sealing the upper surface side of the LED core chip 3. Here, the upper surface side refers to the direction in which the light emitted from the LED core chip 3 is emitted from the storage container 2, and represents the opposite direction of the bottom surface 2a with respect to the LED core chip 3.

[0118] The LED core chip 3 is disposed on a substrate wiring board (not shown), and the substrate wiring board may also constitute the bottom portion of the storage container 2. As the substrate, for example, a structure in which a wiring pattern is formed on a base material such as glass epoxy resin can be mentioned.

[0119] The LED core chip 3 is a semiconductor element that emits light when a voltage is applied in the clockwise direction, and has a basic structure in which a P-type semiconductor layer and an N-type semiconductor layer are PN-junctioned.

[0120] As Figure 2 shown, the fluorescent layer 4 is formed of a resin 6 in which a plurality of quantum dots 5 are dispersed.

[0121] In addition, the resin composition in which the quantum dots 5 of the present embodiment are dispersed may also contain the quantum dots 5 and other fluorescent substances different from the quantum dots 5. As the fluorescent substances, there are Theron series, KSF (K2SiF6:Mn 4+ ) red phosphors, etc., but there is no particular limitation on the material.

[0122] The resin 6 constituting the fluorescent layer 4 is not particularly limited, and polypropylene (PP), polystyrene (PS), acrylic resin, methacrylate resin, MS resin, polyvinyl chloride (PVC), polycarbonate (PC), polyethylene terephthalate (PET), polyethylene naphthalate (PEN), polymethylpentene, liquid crystal polymer, epoxy resin, silicone resin, or a mixture thereof, etc. can be used.

[0123] The LED device using the quantum dots of the present embodiment can be applied to a display device. Figure 3 FIG. Figure 2 is a longitudinal sectional view of a display device using the LED device shown. As Figure 3 shown, the display device 50 is configured to have a plurality of LED devices 20 and a display unit 54 such as a liquid crystal display opposed to each LED device 20. Each LED device 20 is disposed on the back side of the display unit 54. Each LED device 20 has the same structure as the LED device 1 shown in Figure 2 which seals the LED chip with a resin in which a plurality of quantum dots 5 are diffused.

[0124] As Figure 3 shown, the plurality of LED devices 20 are supported by a support 52. Each LED device 20 is arranged at a predetermined interval. Each LED device 20 and the support 52 constitute a backlight 55 opposed to the display unit 54. The support 52 is in a sheet shape, plate shape, or container shape, etc., and there is no particular limitation on the shape and material. As Figure 3 shown, a light diffusion plate 53 or the like may be interposed between the backlight 55 and the display unit 54.

[0125] By applying the quantum dots 5 with a narrow fluorescence half-width in this embodiment to Figure 2 the LED device shown in Figure 3 the display device shown in etc., the light-emitting characteristics of the device can be effectively improved.

[0126] In addition, the resin composition in which the quantum dots 5 of this embodiment are dispersed in a resin can be formed into a sheet shape or a film shape. Such a sheet or film can be assembled into, for example, a backlight device.

[0127]

Example

[0128] The effects of the present invention will be described below through examples and comparative examples of the present invention. In addition, the present invention is not limited by any of the following examples.

[0129] <Raw materials>

[0130] In the experiment, the following raw materials were used when synthesizing quantum dots of the AgIn x Ga 1-x S y Se 1-y system or ZnAgIn x Ga 1-x S y Se 1-y system (0≤X<1, 0≤Y≤1).

[0131] (Solvent)

[0132] Octadecene: manufactured by Aldrich Corporation

[0133] Oleylamine: manufactured by Kao Corporation

[0134] 1-Dodecanethiol: manufactured by Kao Corporation

[0135] Oleic acid: LUNAC O-V manufactured by Kao Corporation

[0136] Trioctylphosphine: manufactured by Kitakyo Chemical Co., Ltd.

[0137] (Silver raw material)

[0138] Silver acetate: manufactured by Aldrich Corporation

[0139] (Indium raw material)

[0140] Indium acetate: manufactured by Shinsei Chemical Industry Co., Ltd.

[0141] Indium diethyldithiocarbamate: a synthetic raw material prepared by the inventor

[0142] (Gallium raw material)

[0143] Gallium chloride: manufactured by Shinsei Chemical Industry Co., Ltd.

[0144] Gallium acetylacetonate: manufactured by Tokyo Chemical Industry Co., Ltd.

[0145] (sulfur raw material)

[0146] Sulfur: manufactured by KISHIDA CHEMICAL CO., LTD.

[0147] Tetraethylthiuram disulfide: manufactured by Sanshin Chemical Industry Co., Ltd.

[0148] Bis(pentamethylene)thiuram tetrasulfide: manufactured by Sanshin Chemical Industry Co., Ltd.

[0149] Isopropylxanthogen disulfide: manufactured by Sanshin Chemical Industry Co., Ltd.

[0150] Tetramethylthiuram disulfide: manufactured by Sanshin Chemical Industry Co., Ltd.

[0151] <Measuring instrument>

[0152] Fluorescence spectrometer: F-2700 manufactured by JASCO Corporation

[0153] UV-Visible spectrophotometer: V-770 manufactured by Hitachi, Ltd.

[0154] Quantum yield measuring device: QE-1100 manufactured by Otsuka Electronics Co., Ltd.

[0155] Scanning electron microscope (SEM): SU9000 manufactured by Hitachi, Ltd.

[0156] [Example 1]

[0157] Put 1.5 ml of a 0.2 M solution obtained by dissolving silver acetate: Ag(OAc) in oleylamine: OLAm, 165 mg of gallium acetylacetonate: Ga(acac)3, 28.5 mL of oleylamine: OLAm, and 1.5 ml of dodecanethiol: DDT into a 300 mL reaction vessel. Moreover, while stirring under an inert gas (N2) atmosphere, heat to dissolve the raw materials.

[0158] Dissolve the solution at 120 °C for 5 minutes, and on this basis, add 1.5 ml of a 0.4 M solution obtained by dissolving tetraethylthiuram disulfide (TETDS) in oleylamine: OLAm. Then, raise the temperature from 120 °C to 200 °C, stir for a total of 20 minutes. Then, cool the obtained reaction solution to room temperature.

[0159] Add 125.7 mg of indium diethyldithiocarbamate: In[SC(=S)N(C2H5)2]3, a carbamate, to the obtained reaction solution, and then stir and heat at 270 °C for 10 minutes.

[0160] Then, 9 ml of a 0.1 M solution obtained by dissolving gallium chloride: GaCl3 and myristic acid: MA in an equimolar ratio of Ga:MA = 1:3 in octadecene: ODE, and 4.5 ml of a 0.2 M solution obtained by dissolving sulfur: S in octadecene: ODE were mixed to form a 13.5 ml solution, which was dropped onto a solution stirred and heated at 270 °C over 50 minutes. After the dropping was completed, the mixture was stirred and heated for 70 minutes, and the resulting reaction solution was cooled to room temperature.

[0161] The resulting reaction solution was measured using a fluorescence spectrometer. As a result, optical properties with a fluorescence wavelength of 539 nm, a fluorescence full width at half maximum of 35 nm, and a fluorescence quantum yield of 49% were obtained.

[0162] Then, the QD dispersion solution obtained by repeating the operation of washing twice with toluene and ethanol and redispersing with TOP was measured using a fluorescence spectrometer. As a result, optical properties as shown Figure 4 with a fluorescence wavelength of 539 nm, a fluorescence full width at half maximum of 35.4 nm, and a quantum yield of 75% were obtained.

[0163] [Example 2]

[0164] 0.5 ml of a 0.2 M solution obtained by dissolving silver acetate: Ag(OAc) in oleylamine: OLAm, 55 mg of gallium acetylacetonate: Ga(acac)3, 9.5 mL of oleylamine: OLAm, and 0.5 ml of dodecanethiol: DDT were added to a 100 mL reaction vessel. Moreover, while stirring under an inert gas (N2) atmosphere, the mixture was heated to dissolve the raw materials.

[0165] The solution was dissolved at 120 °C for 5 minutes, and on this basis, 0.5 ml of a 0.4 M solution obtained by dissolving bis(pentamethylene)thiuram tetrasulfide (DPTT) in oleylamine: OLAm was added. Then, the temperature was raised from 120 °C to 200 °C over a total of 20 minutes while stirring. Then, the resulting reaction solution was cooled to room temperature.

[0166] 41.9 mg of indium diethyldithiocarbamate: In[SC(=S)N(C2H5)2]3 as a carbamate was added to the resulting reaction solution, and the mixture was further stirred and heated at 270 °C for 10 minutes.

[0167] Then, 3 ml of a 0.1 M solution obtained by dissolving gallium chloride: GaCl3 and myristic acid: MA in an equimolar ratio of Ga:MA = 1:3 in octadecene: ODE, and 1.5 ml of a 0.2 M solution obtained by dissolving sulfur: S in octadecene: ODE were mixed to form a 4.5 ml solution, which was dropped onto a solution stirred and heated at 270 °C over 50 minutes. After the dropping was completed, the mixture was stirred and heated for 70 minutes, and the resulting reaction solution was cooled to room temperature.

[0168] The resulting reaction solution was measured using a fluorescence spectrometer. As a result, optical properties with a fluorescence wavelength of 526 nm, a fluorescence half-width at half-maximum of 35.5 nm, and a quantum yield of 34% were obtained.

[0169] Then, a QD dispersion solution obtained by repeating the operation of washing twice with toluene and ethanol and redispersing with TOP was measured using a fluorescence spectrometer. As a result, optical properties as shown Figure 5 with a fluorescence wavelength of 526.5 nm, a fluorescence half-width at half-maximum of 34.8 nm, and a quantum yield of 54% were obtained.

[0170] [Example 3]

[0171] 0.5 ml of a 0.2 M solution obtained by dissolving silver acetate: Ag(OAc) in oleylamine: OLAm, 55 mg of gallium acetylacetonate: Ga(acac)3, 9.5 mL of oleylamine: OLAm, and 0.5 ml of dodecanethiol: DDT were added to a 100 mL reaction vessel. Moreover, while stirring under an inert gas (N2) atmosphere, the mixture was heated to dissolve the raw materials.

[0172] The solution was dissolved at 120 °C for 5 minutes, and on this basis, 0.5 ml of a 0.4 M solution obtained by dissolving 4,4'-dithiobis(morpholine) (DTDM) in oleylamine: OLAm was added. Then, the temperature was raised from 120 °C to 200 °C over a total of 20 minutes with stirring. Then, the resulting reaction solution was cooled to room temperature.

[0173] 41.9 mg of indium diethyldithiocarbamate: In[SC(=S)N(C2H5)2]3 as a carbamate was added to the resulting reaction solution, and the mixture was further stirred and heated at 270 °C for 10 minutes.

[0174] Then, 3 ml of a 0.1 M solution obtained by dissolving gallium chloride: GaCl3 and myristic acid: MA in an equimolar ratio of Ga:MA = 1:3 in octadecene: ODE, and 1.5 ml of a 0.2 M solution obtained by dissolving sulfur: S in octadecene: ODE were mixed to form a 4.5 ml solution, which was dropped onto a solution stirred and heated at 270 °C over 50 minutes. After the dropping was completed, the solution was stirred and heated for 70 minutes, and the resulting reaction solution was cooled to room temperature.

[0175] The resulting reaction solution was measured using a fluorescence spectrometer. As a result, optical properties with a fluorescence wavelength of 526 nm, a fluorescence half-width at half-maximum of 37.5 nm, and a quantum yield of 41% were obtained.

[0176] Then, a QD dispersion solution obtained by repeating the operation of washing twice with toluene and ethanol and redispersing with TOP was measured using a fluorescence spectrometer. As a result, optical properties as shown Figure 6 with a fluorescence wavelength of 527.5 nm, a fluorescence half-width at half-maximum of 36.9 nm, and a quantum yield of 56% were obtained.

[0177] [Example 4]

[0178] 0.5 ml of a 0.2 M solution obtained by dissolving silver acetate: Ag(OAc) in oleylamine: OLAm, 55 mg of gallium acetylacetonate: Ga(acac)3, 9.5 mL of oleylamine: OLAm, and 0.5 ml of dodecanethiol: DDT were added to a 100 mL reaction vessel. Moreover, while stirring under an inert gas (N2) atmosphere, the mixture was heated to dissolve the raw materials.

[0179] The solution was dissolved at 120 °C for 5 minutes. On this basis, 0.5 ml of a 0.4 M solution obtained by dissolving isopropylxanthogen disulfide in oleylamine: OLAm was added. Then, the temperature was raised from 120 °C to 200 °C over a total of 20 minutes while stirring. Then, the resulting reaction solution was cooled to room temperature.

[0180] 41.9 mg of indium diethyldithiocarbamate: In[SC(=S)N(C2H5)2]3, which is a carbamate, was added to the resulting reaction solution, and the mixture was further stirred and heated at 270 °C for 10 minutes.

[0181] Then, 3 ml of a 0.1 M solution obtained by dissolving gallium chloride: GaCl3 and myristic acid: MA in an equimolar ratio of Ga:MA = 1:3 in octadecene: ODE, and 1.5 ml of a 0.2 M solution obtained by dissolving sulfur: S in octadecene: ODE were mixed to form a 4.5 ml solution, which was dropped onto a solution stirred and heated at 270 °C over 50 minutes. After the dropping was completed, the mixture was stirred and heated for 70 minutes, and the resulting reaction solution was cooled to room temperature.

[0182] The resulting reaction solution was measured using a fluorescence spectrometer. As a result, optical properties with a fluorescence wavelength of 530 nm, a fluorescence full width at half maximum of 37 nm, and a quantum yield of 40% were obtained.

[0183] Then, a QD dispersion solution obtained by repeating the operation of washing twice with toluene and ethanol and redispersing with TOP was measured using a fluorescence spectrometer. As a result, optical properties as shown Figure 7 with a fluorescence wavelength of 532 nm, a fluorescence full width at half maximum of 36.9 nm, and a quantum yield of 65% were obtained.

[0184] [Example 5]

[0185] To a 100 mL reaction vessel, 0.5 ml of a 0.2 M solution obtained by dissolving silver acetate: Ag(OAc) in oleylamine: OLAm, 55 mg of gallium acetylacetonate: Ga(acac)3, 9.5 mL of oleylamine: OLAm, and 0.5 ml of dodecanethiol: DDT were added. Moreover, the raw materials were dissolved by heating while stirring in an inert gas (N2) atmosphere.

[0186] The solution was dissolved at 120 °C for 5 minutes, and on this basis, 0.5 ml of a 0.4 M solution obtained by dissolving tetramethylthiuram disulfide (TMTDS) in oleylamine: OLAm was added. Then, the temperature was raised from 120 °C to 200 °C over a total of 20 minutes while stirring. Then, the resulting reaction solution was cooled to room temperature.

[0187] 41.9 mg of indium diethyldithiocarbamate: In[SC(=S)N(C2H5)2]3 as a carbamate was added to the resulting reaction solution, and the mixture was further stirred and heated at 270 °C for 10 minutes.

[0188] Then, 3 ml of a 0.1 M solution obtained by dissolving gallium chloride: GaCl3 and myristic acid: MA in an equimolar ratio of Ga:MA = 1:3 in octadecene: ODE, and 1.5 ml of a 0.2 M solution obtained by dissolving sulfur: S in octadecene: ODE were mixed to form a 4.5 ml solution, which was dropped onto a solution stirred and heated at 270 °C over 50 minutes. After the dropping was completed, the solution was stirred and heated for 70 minutes, and the resulting reaction solution was cooled to room temperature.

[0189] The resulting reaction solution was measured using a fluorescence spectrometer. As a result, optical properties with a fluorescence wavelength of 542 nm, a fluorescence full width at half maximum of 36.5 nm, and a quantum yield of 54% were obtained.

[0190] Then, a QD dispersion solution obtained by repeating the operation of washing twice with toluene and ethanol and redispersing with TOP was measured using a fluorescence spectrometer. As a result, optical properties as shown Figure 8 were obtained, with a fluorescence wavelength of 542 nm, a fluorescence full width at half maximum of 36.5 nm, and a quantum yield of 71%.

[0191] [Example 6]

[0192] To a 100 mL reaction vessel, 0.5 ml of a 0.2 M solution obtained by dissolving silver acetate: Ag(OAc) in oleylamine: OLAm, 55 mg of gallium acetylacetonate: Ga(acac)3, 9.5 mL of oleylamine: OLAm, and 0.5 ml of dodecanethiol: DDT were added. Moreover, while stirring under an inert gas (N2) atmosphere, the mixture was heated to dissolve the raw materials.

[0193] The solution was dissolved at 120 °C for 5 minutes, and on this basis, 0.5 ml of a 0.4 M solution obtained by dissolving tetraethylthiuram disulfide (TETDS) in oleylamine: OLAm was added. Then, the temperature was raised from 120 °C to 200 °C over a total of 20 minutes while stirring. Then, the resulting reaction solution was cooled to room temperature.

[0194] To the resulting reaction solution, 41.9 mg of indium diethyldithiocarbamate: In[SC(=S)N(C2H5)2]3 as a carbamate was added, and the mixture was further stirred and heated at 270 °C for 10 minutes.

[0195] Then, 3 ml of a 0.1 M solution obtained by dissolving gallium chloride: GaCl3 and oleic acid: OLAc in an oleic acid: OLAc molar ratio of Ga:MA = 1:3 in octadecene: ODE, and 1.5 ml of a 0.2 M solution obtained by dissolving sulfur: S in octadecene: ODE were mixed to form a 4.5 ml solution, which was dropped onto a solution stirred and heated at 270 °C over 50 minutes. After the dropping was completed, stirring and heating were carried out for 70 minutes, and the resulting reaction solution was cooled to room temperature.

[0196] The resulting reaction solution was measured using a fluorescence spectrometer. As a result, optical properties with a fluorescence wavelength of 546 nm, a fluorescence half-width of 29.3 nm, and a quantum yield of 39% were obtained.

[0197] Then, a QD dispersion solution obtained by repeating the operation of washing twice with toluene and ethanol and redispersing with TOP was measured using a fluorescence spectrometer. As a result, optical properties as shown Figure 9 with a fluorescence wavelength of 548.5 nm, a fluorescence half-width of 30.5 nm, and a quantum yield of 59% were obtained.

[0198] [Example 7]

[0199] To a 100 mL reaction vessel, 0.5 ml of a 0.2 M solution obtained by dissolving silver acetate: Ag(OAc) in oleylamine: OLAm, 55 mg of gallium acetylacetonate: Ga(acac)3, 9.5 mL of oleylamine: OLAm, and 0.5 ml of dodecanethiol: DDT were added. Moreover, while stirring in an inert gas (N2) atmosphere, heating was carried out to dissolve the raw materials.

[0200] The solution was dissolved at 120 °C for 5 minutes, and on this basis, 0.5 ml of a 0.4 M solution obtained by dissolving tetraethylthiuram disulfide in oleylamine: OLAm was added. Then, the temperature was raised from 120 °C to 200 °C over a total of 20 minutes, and stirring was carried out. Then, the resulting reaction solution was cooled to room temperature.

[0201] To the resulting reaction solution, 0.75 ml of a 0.2 M solution obtained by dissolving indium acetate: In(OAc)3, 21.8 mg, and sulfur: S in octadecene: ODE were added, and stirring and heating were carried out at 270 °C for 10 minutes.

[0202] Then, 3 ml of a 0.1 M solution obtained by dissolving gallium chloride: GaCl3 and myristic acid: MA in an equimolar ratio of Ga:MA = 1:3 in octadecene: ODE, and 1.5 ml of a 0.2 M solution obtained by dissolving sulfur: S in octadecene: ODE were mixed to form a 4.5 ml solution, which was dropped onto a solution stirred and heated at 270 °C over 50 minutes. After the dropping was completed, the mixture was stirred and heated for 70 minutes, and the resulting reaction solution was cooled to room temperature.

[0203] The resulting reaction solution was measured using a fluorescence spectrometer. As a result, optical properties with a fluorescence wavelength of 546 nm, a fluorescence half-width at half-maximum of 36.5 nm, and a quantum yield of 55% were obtained.

[0204] Then, a QD dispersion solution obtained by repeating the operation of washing twice with toluene and ethanol and redispersing with TOP was measured using a fluorescence spectrometer. As a result, optical properties as shown Figure 10 with a fluorescence wavelength of 546.5 nm, a fluorescence half-width at half-maximum of 36.2 nm, and a quantum yield of 81% were obtained.

[0205] [Example 8]

[0206] To a 100 mL reaction vessel, 0.5 ml of a 0.2 M solution obtained by dissolving silver acetate: Ag(OAc) in oleylamine: OLAm, 55 mg of gallium acetylacetonate: Ga(acac)3, 9.5 mL of oleylamine: OLAm, and 0.5 ml of dodecanethiol: DDT were added. Moreover, while stirring under an inert gas (N2) atmosphere, the mixture was heated to dissolve the raw materials.

[0207] The solution was dissolved at 120 °C for 5 minutes, and on this basis, 1 ml of a 0.2 M solution (S-ODE) obtained by dissolving sulfur: S in octadecene: ODE was added. Then, the temperature was raised from 120 °C to 200 °C over a total of 20 minutes while stirring. Then, the resulting reaction solution was cooled to room temperature.

[0208] To the resulting reaction solution, 21.8 mg of indium acetate: In(OAc)3 and 2.25 ml of 0.2 M S-ODE were added, and the mixture was further stirred and heated at 270 °C for 10 minutes.

[0209] Then, 3 ml of a 0.1 M solution obtained by dissolving gallium chloride: GaCl3 and myristic acid: MA in an equimolar ratio of Ga:MA = 1:3 in octadecene: ODE, and 1.5 ml of a 0.2 M solution obtained by dissolving sulfur: S in octadecene: ODE were mixed to form a 4.5-ml solution, which was dropped onto a solution stirred and heated at 270 °C over 50 minutes. After the dropping was completed, the solution was stirred and heated for 70 minutes, and the resulting reaction solution was cooled to room temperature.

[0210] The resulting reaction solution was measured using a fluorescence spectrometer. As a result, optical properties with a fluorescence wavelength of 523 nm, a fluorescence full width at half maximum of 36.5 nm, and a quantum yield of 25% were obtained.

[0211] Then, the QD dispersion solution obtained by repeating the operation of washing twice with toluene and ethanol and redispersing with TOP was measured using a fluorescence spectrometer. As a result, optical properties with a fluorescence wavelength of 522 nm, a fluorescence full width at half maximum of 38 nm, and a quantum yield of 46% were obtained.

[0212] [Example 9]

[0213] 0.5 ml of a 0.2 M solution obtained by dissolving silver acetate: Ag(OAc) in oleylamine: OLAm, 55 mg of gallium acetylacetonate: Ga(acac)3, 9.5 mL of oleylamine: OLAm, and 0.5 ml of dodecanethiol: DDT were added to a 100-mL reaction vessel. Moreover, the raw materials were dissolved by heating while stirring in an inert gas (N2) atmosphere.

[0214] The solution was dissolved at 120 °C for 5 minutes, and on this basis, 1 ml of a 0.2 M solution (S-ODE) obtained by dissolving sulfur: S in octadecene: ODE was added. Then, the temperature was raised from 120 °C to 200 °C over a total of 20 minutes while stirring. Then, the resulting reaction solution was cooled to room temperature.

[0215] 41.9 mg of indium diethyldithiocarbamate: In[SC(=S)N(C2H5)2]3 as a carbamate was added to the resulting reaction solution, and the mixture was further stirred and heated at 270 °C for 10 minutes.

[0216] Then, 3 ml of a 0.1 M solution obtained by dissolving gallium chloride: GaCl3 and myristic acid: MA in an equimolar ratio of Ga:MA = 1:3 in octadecene: ODE, and 1.5 ml of a 0.2 M solution obtained by dissolving sulfur: S in octadecene: ODE were mixed to form a 4.5-ml solution, which was dropped onto a solution stirred and heated at 270 °C over 50 minutes. After the dropping was completed, the solution was stirred and heated for 70 minutes, and the resulting reaction solution was cooled to room temperature.

[0217] The obtained reaction solution was measured with a fluorescence spectrometer. As a result, optical properties with a fluorescence wavelength of 534 nm, a fluorescence half-width of 36 nm, and a quantum yield of 33% were obtained.

[0218] Then, the QD dispersion solution obtained by repeating the operation of washing twice with toluene and ethanol and redispersing with TOP was measured with a fluorescence spectrometer. As a result, optical properties with a fluorescence wavelength of 534 nm, a fluorescence half-width of 40 nm, and a quantum yield of 45% were obtained.

[0219] [Example 10]

[0220] 0.5 ml of a 0.2 M solution obtained by dissolving silver acetate: Ag(OAc) in oleylamine: OLAm, 73.4 mg of gallium acetylacetonate: Ga(acac)3, 9.5 mL of oleylamine: OLAm, and 0.3 ml of dodecanethiol: DDT were added to a 100 mL reaction vessel. Moreover, while stirring under an inert gas (N2) atmosphere, heating was performed to dissolve the raw materials.

[0221] The solution was dissolved at 120 °C for 5 minutes, and on this basis, 0.5 ml of a 0.4 M solution obtained by dissolving tetraethylthiuram disulfide (TETDS) in oleylamine: OLAm was added. Then, the temperature was raised from 120 °C to 200 °C, and stirring was performed for a total of 20 minutes. Then, the obtained reaction solution was cooled to room temperature.

[0222] 0.375 ml of a 0.2 M solution obtained by dissolving indium acetate: In(OAc)3 in oleylamine: OLAm and oleic acid: OLAc, and 1.225 ml of a 0.2 M solution obtained by dissolving sulfur: S in octadecene: ODE were added to the obtained reaction solution, and stirring and heating were performed at 270 °C for 10 minutes.

[0223] Then, 3 ml of a 0.1 M solution obtained by dissolving gallium chloride: GaCl3 and oleic acid: OLAc in a molar ratio of Ga:OLAc = 1:1.5 in octadecene: ODE and 1.5 ml of a 0.2 M solution obtained by dissolving sulfur: S in octadecene: ODE were mixed to obtain 4.5 ml of a solution, which was dropped onto the solution stirred and heated at 270 °C over 50 minutes. After the dropping was completed, stirring and heating were performed for 70 minutes, and the obtained reaction solution was cooled to room temperature.

[0224] Then, add 3 ml of TOP and heat it at 200 °C for 10 minutes. Cool the obtained reaction solution to room temperature. Then, measure the QD dispersion solution washed with toluene and ethanol and redispersed with toluene using a fluorescence spectrometer. As a result, optical properties with a fluorescence wavelength of 536.5 nm, a fluorescence full width at half maximum of 29.4 nm, and a quantum yield of 71% can be obtained.

[0225] [Example 11]

[0226] Add 0.5 ml of a 0.2 M solution obtained by dissolving silver acetate: Ag(OAc) in oleylamine: OLAm, 91.8 mg of gallium acetylacetonate: Ga(acac)3, 9.5 mL of oleylamine: OLAm, and 0.5 ml of dodecanethiol: DDT to a 100 mL reaction vessel. Moreover, heat while stirring under an inert gas (N2) atmosphere to dissolve the raw materials.

[0227] Dissolve this solution at 200 °C for 5 minutes. On this basis, add 1 ml of a 0.4 M solution obtained by dissolving tetraethylthiuram disulfide (TETDS) in oleylamine: OLAm, stir and heat for 40 minutes. Moreover, cool the obtained reaction solution to room temperature.

[0228] Add 0.375 ml of a 0.2 M solution obtained by dissolving indium acetate: In(OAc)3 in oleylamine: OLAm and oleic acid: OLAc, and 0.375 ml of a 0.2 M solution obtained by dissolving sulfur: S in octadecene: ODE to the obtained reaction solution, and then stir and heat at 270 °C for 10 minutes.

[0229] Wash the obtained reaction solution with 3 ml of toluene and 30 ml of ethanol and redisperse it with 10 ml of OLAm.

[0230] Then, a solution prepared by mixing 3 ml of a 0.1 M solution obtained by dissolving gallium chloride: GaCl3 and oleic acid: OLAc in octadecene: ODE such that the molar ratio of Ga:OLAc is 1:1.5 and 1.5 ml of a 0.2 M solution obtained by dissolving sulfur: S in octadecene: ODE, a total of 4.5 ml, is dropped onto the solution stirred and heated at 270 °C over 50 minutes. After the dropping is completed, stir and heat for 70 minutes, and cool the obtained reaction solution to room temperature.

[0231] Then, add 3 ml of TOP and heat it at 200 °C for 10 minutes. Cool the obtained reaction solution to room temperature. Then, measure the QD dispersion solution washed with toluene and ethanol and redispersed with TOP using a fluorescence spectrometer. As a result, as Figure 11Optical properties with a fluorescence wavelength of 530.5 nm, a fluorescence half-width of 38 nm, and a quantum yield of 86% as shown.

[0232] [Example 12]

[0233] Add 0.5 ml of a 0.2 M solution obtained by dissolving silver acetate: Ag(OAc) in oleylamine: OLAm, 55 mg of gallium acetylacetonate: Ga(acac)3, 9.5 mL of oleylamine: OLAm, and 0.5 ml of dodecanethiol: DDT into a 100 mL reaction vessel. Moreover, while stirring under an inert gas (N2) atmosphere, heat to dissolve the raw materials.

[0234] Dissolve this solution at 200 °C for 5 minutes, and on this basis, add 0.5 ml of a 0.4 M solution obtained by dissolving tetraethylthiuram disulfide (TETDS) in oleylamine: OLAm. Then, stir and heat at 200 °C for 40 minutes. Then, cool the obtained reaction solution to room temperature.

[0235] Add 0.375 ml of a 0.2 M solution obtained by dissolving indium acetate: In(OAc)3 in octadecene: ODE and oleic acid: OLAc, and 1.125 ml of a 0.2 M solution obtained by dissolving sulfur: S in octadecene: ODE into the obtained reaction solution, and then stir and heat at 300 °C for 10 minutes.

[0236] Then, a solution prepared by mixing 3 ml of a 0.1 M solution obtained by dissolving gallium chloride: GaCl3 and oleic acid: OLAc in a molar ratio of Ga:OLAc = 1:3 in octadecene: ODE, 1.5 ml of a 0.2 M solution obtained by dissolving sulfur: S in octadecene: ODE, and 0.141 mL of oleylamine: OLAm is dropped onto the solution stirred and heated at 300 °C over 50 minutes. After the dropping is completed, stir and heat for 20 minutes, and cool the obtained reaction solution to room temperature.

[0237] Then, add 1.5 m of a 0.2 M solution obtained by dissolving sulfur: S in octadecene: ODE, stir and heat at 200 °C for 30 minutes, and cool the obtained reaction solution to room temperature.

[0238] Then, centrifuge the reaction solution at 5500 rpm for 3 minutes using a centrifuge to recover the supernatant. Add 3 ml of TOP to the recovered supernatant, heat at 200 °C for 10 minutes, and cool the obtained reaction solution to room temperature.

[0239] Then, 1 ml of toluene and 1.5 ml of ethanol were added to 1 ml of the reaction solution, and centrifugation was performed. 2 ml of ethanol was added to the supernatant, and centrifugation was performed at 5500 rpm for 3 minutes (washing and separation). The QD dispersion solution was redispersed with toluene and measured using a fluorescence spectrometer. In addition, washing and separation refers to a process of separating by controlling the aggregation state affected by the ligand difference coordinated to the quantum dots according to the ratio of toluene and ethanol. After centrifugation and washing and separation, only the quantum dots coordinated with ligands can be recovered evenly, and thus good luminescence characteristics (high quantum yield) can be obtained. As a result, optical characteristics such as Figure 12 a fluorescence wavelength of 537.5 nm, a fluorescence half-width at half maximum of 25 nm, and a quantum yield of 63% as shown can be obtained.

[0240] [Example 13]

[0241] 0.5 ml of a 0.2 M solution obtained by dissolving silver acetate: Ag(OAc) in oleylamine: OLAm, 73.4 mg of gallium acetylacetonate: Ga(acac)3, 9.5 mL of oleylamine: OLAm, and 0.5 ml of dodecanethiol: DDT were added to a 100 mL reaction vessel. Moreover, while stirring under an inert gas (N2) atmosphere, heating was performed to dissolve the raw materials.

[0242] The solution was dissolved at 200 °C for 5 minutes, and on this basis, 0.5 ml of a 0.4 M solution obtained by dissolving tetraethylthiuram disulfide (TETDS) in oleylamine: OLAm was added. Then, stirring and heating were performed at 200 °C for 40 minutes. Then, the obtained reaction solution was cooled to room temperature.

[0243] 0.6 ml of a 0.2 M solution obtained by dissolving indium acetate: In(OAc)3 in octadecene: ODE and oleic acid: OLAc and 1.8 ml of a 0.2 M solution obtained by dissolving sulfur: S in octadecene: ODE were added to the obtained reaction solution, and stirring and heating were performed at 290 °C for 10 minutes.

[0244] Then, a solution prepared by mixing 3.6 ml of a 0.1 M solution obtained by dissolving gallium chloride: GaCl3 and oleic acid: OLAc in a molar ratio of Ga:OLAc = 1:3 in octadecene: ODE, 1.8 ml of a 0.2 M solution obtained by dissolving sulfur: S in octadecene: ODE, and 2.7 mL of oleylamine: OLAm was dropped onto the solution stirred and heated at 290 °C over 80 minutes. After the dropping was completed, stirring and heating were performed for 10 minutes, and the obtained reaction solution was cooled to room temperature.

[0245] Then, the reaction solution was centrifuged at 5500 rpm for 3 minutes using a centrifuge, and the supernatant was recovered. 3 ml of TOP was added to the recovered supernatant, and the mixture was heated at 180 °C for 10 minutes. The obtained reaction solution was cooled to room temperature.

[0246] Then, 1 ml of toluene and 1.5 ml of ethanol were added to 1 ml of the reaction solution for centrifugation. 2 ml of ethanol was added to the supernatant, and centrifugation was performed at 5500 rpm for 3 minutes. The QD dispersion solution redispersed with toluene was measured using a fluorescence spectrophotometer. As a result, optical properties with a fluorescence wavelength of 531.0 nm, a fluorescence half-width at half maximum of 29.3 nm, and a quantum yield of 85% were obtained as Figure 13 shown.

[0247] [Example 14]

[0248] 0.5 ml of a 0.2 M solution obtained by dissolving silver acetate: Ag(OAc) in oleylamine: OLAm, 73.4 mg of gallium acetylacetonate: Ga(acac)3, 9.5 mL of oleylamine: OLAm, and 0.5 ml of dodecanethiol: DDT were added to a 100 mL reaction vessel. Moreover, while stirring under an inert gas (N2) atmosphere, heating was performed to dissolve the raw materials.

[0249] The solution was dissolved at 200 °C for 5 minutes, and on this basis, 0.5 ml of a 0.4 M solution obtained by dissolving tetraethylthiuram disulfide (TETDS) in oleylamine: OLAm was added. Then, stirring and heating were performed at 200 °C for 40 minutes. Then, the obtained reaction solution was cooled to room temperature.

[0250] 0.5 ml of a 0.2 M solution obtained by dissolving indium acetate: In(OAc)3 in octadecene: ODE and oleic acid: OLAc and 1.5 ml of a 0.2 M solution obtained by dissolving sulfur: S in octadecene: ODE were added to the obtained reaction solution, and stirring and heating were performed at 290 °C for 10 minutes.

[0251] Then, 3 ml of a 0.1 M solution obtained by dissolving gallium chloride: GaCl3 and oleic acid: OLAc in oleylamine: OLAm such that the molar ratio of Ga:OLAc = 1:3, 0.5 ml of a 0.4 M solution obtained by dissolving tetraethylthiuram disulfide (TETDS) in oleylamine: OLAm, and 3 ml of oleylamine: OLAm were dropped onto the solution stirred and heated at 290 °C over 80 minutes. Stirring and heating were performed for 10 minutes after the dropping was completed, and the obtained reaction solution was cooled to room temperature.

[0252] Then, the reaction solution was centrifuged at 5500 rpm for 3 minutes using a centrifuge, and the supernatant was recovered. 3 ml of TOP was added to the recovered supernatant, and the mixture was heated at 180 °C for 10 minutes. The resulting reaction solution was cooled to room temperature.

[0253] To 1 ml of the resulting reaction solution, 1 ml of toluene and 1.5 ml of ethanol were added, and the mixture was centrifuged at 5500 rpm for 3 minutes. Then, 2 ml of ethanol was added to the supernatant, and the mixture was centrifuged at 5500 rpm for 3 minutes. The resulting QD dispersion solution redispersed with toluene was measured using a fluorescence spectrophotometer. As a result, optical properties with a fluorescence wavelength of 529.5 nm, a fluorescence half-peak width of 30.8 nm, and a quantum yield of 71% were obtained.

[0254] Then, the resulting reaction solution was heated at 200 °C for 5 minutes. On this basis, 0.075 ml of a 0.8 M solution in which zinc acetate: Zn(OAc)2 was dissolved in oleic acid: OLAc and trioctylphosphine: TOP, 0.6 ml of a 0.2 M solution in which sulfur: S was dissolved in trioctylphosphine: TOP, and 1.325 ml of oleylamine: OLAm were mixed to form 2 ml of a solution. The solution was dropped onto a solution stirred and heated at 200 °C over 120 minutes, and the resulting reaction solution was cooled to room temperature.

[0255] To 1 ml of the resulting reaction solution, 1 ml of toluene and 1.6 ml of ethanol were added, and the mixture was centrifuged at 5500 rpm for 3 minutes. Then, 2 ml of ethanol was added to the supernatant, and the mixture was centrifuged at 5500 rpm for 3 minutes. The resulting QD dispersion solution redispersed with toluene was measured using a fluorescence spectrophotometer. As a result, Figure 14 optical properties as shown with a fluorescence wavelength of 528 nm, a fluorescence half-peak width of 31 nm, and a quantum yield of 84% were obtained.

[0256] [Example 15]

[0257] To a 100 mL reaction vessel, 0.5 ml of a 0.2 M solution in which silver acetate: Ag(OAc) was dissolved in oleylamine: OLAm, 55.5 mg of gallium acetylacetonate: Ga(acac)3, 20 mL of oleylamine: OLAm, and 3 ml of dodecanethiol: DDT were added. Moreover, while stirring under an inert gas (N2) atmosphere, the mixture was heated to dissolve the raw materials.

[0258] Dissolve the solution at 150 °C for 5 minutes. On this basis, add 0.36 ml of a 0.7 M solution obtained by dissolving selenium: Se in oleylamine: OLAm and dodecanethiol: DDT. Then stir for 10 minutes. After cooling the obtained reaction solution to room temperature, heat it while stirring at 320 °C for 20 minutes. Then cool it to room temperature.

[0259] Centrifuge the obtained reaction solution at 5500 rpm for 3 minutes to precipitate the quantum dots. Redisperse the precipitated quantum dots with toluene. After adding methanol and ethanol, centrifuge at 5500 rpm for 3 minutes to precipitate the QD again. Then, add 9.5 ml of OLAm to the precipitated QD for redispersion.

[0260] Then, a solution of 3.64 ml is formed by mixing 3 ml of a 0.1 M solution obtained by dissolving gallium chloride: GaCl3 and oleic acid: OLAc in oleylamine: OLAm at a molar ratio of Ga:OLAc = 1:1.5 and 0.64 ml of a 0.7 M solution obtained by dissolving selenium: Se in oleylamine: OLAm and dodecanethiol: DDT. Drop this solution onto the solution that is stirred and heated at 290 °C over 20 minutes. After the dropping is completed, stir and heat for 100 minutes, and cool the obtained reaction solution to room temperature. In addition, as a result of measuring the solution obtained at this time with a fluorescence spectrometer, optical properties with a fluorescence wavelength of 639 nm and a fluorescence half-width at half maximum of 28.5 nm can be obtained.

[0261] Then, add 8 ml of TOP and heat at 200 °C for 5 minutes. On this basis, a solution of 2 ml is formed by mixing 1 ml of an 0.8 M solution obtained by dissolving zinc acetate: Zn(OAc)2 in oleic acid: OLAc and trioctylphosphine: TOP and 1 ml of an 0.8 M solution obtained by dissolving sulfur: S in oleylamine: OLAm and dodecanethiol: DDT. Drop this solution onto the solution that is stirred and heated at 200 °C over 20 minutes. After the dropping is completed, stir and heat for 130 minutes, and cool the obtained reaction solution to room temperature.

[0262] Add 2 ml of trioctylphosphine: TOP to 2 ml of the obtained reaction solution. Perform centrifugation to remove the precipitate. Measure the obtained solution with a fluorescence spectrometer. As a result, Figure 15 optical properties with a fluorescence wavelength of 642 nm, a fluorescence half-width at half maximum of 33 nm, and a quantum yield of 76% can be obtained as shown.

[0263] [Example 16]

[0264] Add 0.5 ml of a 0.2 M solution obtained by dissolving silver acetate: Ag(OAc) in oleylamine: OLAm, 55.5 mg of gallium acetylacetonate: Ga(acac)3, 20 mL of oleylamine: OLAm, and 3 ml of dodecanethiol: DDT into a 100 mL reaction vessel. Moreover, while stirring under an inert gas (N2) atmosphere, heat to dissolve the raw materials.

[0265] Dissolve the solution at 150 °C for 5 minutes. On this basis, add 0.36 ml of a 0.7 M solution obtained by dissolving selenium: Se in oleylamine: OLAm and dodecanethiol: DDT. Then stir for 10 minutes. After cooling the obtained reaction solution to room temperature, heat while stirring at 320 °C for 20 minutes. Then cool to room temperature.

[0266] Centrifuge the obtained reaction solution at 5500 rpm for 3 minutes to precipitate the quantum dots. Redisperse the precipitated quantum dots with toluene. After adding methanol and ethanol, centrifuge at 5500 rpm for 3 minutes to precipitate the QD again. Then, add 9.5 ml of OLAm to the precipitated QD for redispersion.

[0267] Then, dissolve gallium chloride: GaCl3 and oleic acid: OLAc in oleylamine: OLAm to obtain a 0.1 M solution with a molar ratio of Ga:OLAc = 1:1.5, 3 ml of this solution, and 0.64 ml of a 0.7 M solution obtained by dissolving selenium: Se in oleylamine: OLAm and dodecanethiol: DDT. Mix these two solutions to get 3.64 ml of the solution, and drip it onto the solution that is being stirred and heated at 290 °C over 30 minutes. After the dripping is completed, stir and heat for 90 minutes, and then cool the obtained reaction solution to room temperature.

[0268] Then, add 8 ml of TOP and heat at 150 °C for 5 minutes. On this basis, add 0.34 ml of a 0.7 M solution obtained by dissolving selenium: Se in oleylamine: OLAm and dodecanethiol: DDT, and heat at 150 °C for 40 minutes. On this basis, add 0.17 ml of a 0.7 M solution obtained by dissolving selenium: Se in oleylamine: OLAm and dodecanethiol: DDT, and 0.15 ml of an 0.8 M solution obtained by dissolving sulfur: S in oleylamine: OLAm and dodecanethiol: DDT, and heat at 150 °C for 40 minutes. Then cool to room temperature.

[0269] Add 0.4 ml of trioctylphosphine: TOP to 2 ml of the obtained reaction solution. Then perform centrifugation to remove the precipitate. Measure the obtained solution with a fluorescence spectrometer. As a result, optical properties with a fluorescence wavelength of 639 nm, a fluorescence full width at half maximum of 30.5 nm, and a quantum yield of 56% can be obtained.

[0270] [Example 17]

[0271] Add 0.5 ml of a 0.2 M solution obtained by dissolving silver acetate: Ag(OAc) in oleylamine: OLAm, 55.5 mg of gallium acetylacetonate: Ga(acac)3, 20 mL of oleylamine: OLAm, and 3 ml of dodecanethiol: DDT into a 100 mL reaction vessel. Moreover, while stirring under an inert gas (N2) atmosphere, heat to dissolve the raw materials.

[0272] Dissolve this solution at 150 °C for 5 minutes. On this basis, add 0.36 ml of a 0.7 M solution obtained by dissolving selenium: Se in oleylamine: OLAm and dodecanethiol: DDT. Then stir for 10 minutes. After cooling the obtained reaction solution to room temperature, heat while stirring at 320 °C for 20 minutes. Then cool to room temperature.

[0273] Centrifuge the obtained reaction solution at 5500 rpm for 3 minutes to precipitate the quantum dots. Redisperse the precipitated quantum dots with toluene. After adding methanol and ethanol, centrifuge at 5500 rpm for 3 minutes to precipitate the QD again. Then, add 9.5 ml of OLAm to the precipitated QD for redispersion.

[0274] Then, a solution of 3 ml of a 0.1 M solution obtained by dissolving gallium chloride: GaCl3 and oleic acid: OLAc in oleylamine: OLAm such that the molar ratio is Ga:OLAc = 1:1.5 and 0.64 ml of a 0.7 M solution obtained by dissolving selenium: Se in oleylamine: OLAm and dodecanethiol: DDT are mixed to form a 3.64 ml solution, and it is dripped dropwise onto the solution that is being stirred and heated at 290 °C over 30 minutes. After the dripping is completed, stir and heat for 90 minutes, and cool the obtained reaction solution to room temperature.

[0275] Then, add 8 ml of TOP and heat it at 150 °C for 5 minutes. On this basis, add 0.34 ml of a 0.7 M solution obtained by dissolving selenium: Se in oleylamine: OLAm and dodecanethiol: DDT. After heating at 150 °C for 20 minutes, add 0.3 ml of a 0.8 M solution obtained by dissolving zinc acetate: Zn(OAc)2 in oleic acid: OLAc and trioctylphosphine: TOP, and heat at 150 °C for 20 minutes. On this basis, add 0.17 ml of a 0.7 M solution obtained by dissolving selenium: Se in oleylamine: OLAm and dodecanethiol: DDT, 0.15 ml of a 0.8 M solution obtained by dissolving sulfur: S in oleylamine: OLAm and dodecanethiol: DDT. After heating at 150 °C for 20 minutes, add 0.3 ml of a 0.8 M solution obtained by dissolving zinc acetate: Zn(OAc)2 in oleic acid: OLAc and trioctylphosphine: TOP, and heat at 150 °C for 20 minutes. Then cool to room temperature.

[0276] Add 0.4 ml of trioctylphosphine: TOP to 2 ml of the obtained reaction solution. Then perform centrifugation to remove the precipitate. Measure the obtained solution with a fluorescence spectrometer. As a result, optical properties with a fluorescence wavelength of 633 nm, a fluorescence full width at half maximum of 27 nm, and a quantum yield of 81% can be obtained as Figure 16 shown.

[0277] [Example 18]

[0278] Add 0.5 ml of a 0.2 M solution obtained by dissolving silver acetate: AgOAc in oleylamine: OLAm, 55.5 mg of gallium acetylacetonate: Ga(acac)3, 20 mL of oleylamine: OLAm, and 3 ml of dodecanethiol: DDT to a 100 mL reaction vessel. Moreover, heat while stirring under an inert gas (N2) atmosphere to dissolve the raw materials.

[0279] Dissolve the solution at 150 °C for 5 minutes. On this basis, add 0.36 ml of a 0.7 M solution obtained by dissolving selenium: Se in oleylamine: OLAm and dodecanethiol: DDT. Then stir for 10 minutes. After cooling the obtained reaction solution to room temperature, heat while stirring at 320 °C for 20 minutes. Then cool to room temperature.

[0280] Treat the obtained reaction solution with a centrifuge to precipitate the quantum dots. Redisperse the precipitated quantum dots with toluene, and wash with methanol and ethanol. Then, add 9.5 ml of OLAm for redispersion.

[0281] After that, 3 ml of a 0.1 M solution obtained by dissolving gallium chloride: GaCl3 and oleic acid: OLAc in an oleylamine: OLAm such that the molar ratio of Ga:OLAc is 1:1.5, and 0.64 ml of a 0.7 M solution obtained by dissolving selenium: Se in oleylamine: OLAm and dodecanethiol: DDT are mixed to form a 3.64 ml solution, which is dropped onto a solution stirred and heated at 290 °C over 20 minutes. After the dropping is completed, stirring and heating are carried out for 100 minutes, and the obtained reaction solution is cooled to room temperature.

[0282] Then, 8 ml of TOP is added and heated at 150 °C for 5 minutes. On this basis, 0.34 ml of a 0.7 M solution obtained by dissolving selenium: Se in oleylamine: OLAm and dodecanethiol: DDT is added and heated at 150 °C for 20 minutes. Then, 0.6 ml of a 0.4 M solution obtained by dissolving zinc acetate: Zn(OAc)2 in oleic acid: OLAc and oleylamine: OLAm is added and heated at 150 °C for 20 minutes. On this basis, 0.17 ml of a 0.7 M solution obtained by dissolving selenium: Se in oleylamine: OLAm and dodecanethiol: DDT, and 0.15 ml of an 0.8 M solution obtained by dissolving sulfur: S in oleylamine: OLAm and dodecanethiol: DDT are added and heated at 150 °C for 20 minutes. Then, 0.6 ml of a 0.4 M solution obtained by dissolving zinc acetate: Zn(OAc)2 in oleic acid: OLAc and oleylamine: OLAm is added and heated at 150 °C for 20 minutes. Then it is cooled to room temperature.

[0283] 0.4 ml of trioctylphosphine: TOP is added to 2 ml of the obtained reaction solution. Then centrifugation is carried out to remove the precipitate. The obtained solution is measured with a fluorescence spectrometer. As a result, optical properties as shown in Figure 17 are obtained, with a fluorescence wavelength of 630.5 nm, a fluorescence half-width at half maximum of 24.5 nm, and a quantum yield of 70%.

[0284] [Example 19]

[0285] 0.5 ml of a 0.2 M solution obtained by dissolving silver acetate: Ag(OAc) in oleylamine: OLAm, 53.3 mg of gallium acetylacetonate: Ga(acac)3, 0.25 ml of a 0.02 M solution obtained by dissolving indium acetylacetonate: In(acac)3 in oleylamine: OLAm and oleic acid: OLAc, 9.5 mL of oleylamine: OLAm, and 2.5 ml of dodecanethiol: DDT are added to a 100 mL reaction vessel. Moreover, while stirring under an inert gas (N2) atmosphere, heating is carried out to dissolve the raw materials.

[0286] Dissolve the solution at 150 °C for 5 minutes. On this basis, add 0.36 ml of a 0.7 M solution obtained by dissolving selenium: Se in oleylamine: OLAm and dodecanethiol: DDT. Then stir for 10 minutes. After cooling the obtained reaction solution to room temperature, heat it while stirring at 320 °C for 60 minutes. Then cool it to room temperature.

[0287] Treat the obtained reaction solution with a centrifuge to precipitate the quantum dots. Redisperse the precipitated quantum dots with toluene and wash them with methanol and ethanol. Then, add 9.5 ml of OLAm for redispersion.

[0288] Then, dissolve gallium chloride: GaCl3 and oleic acid: OLAc in oleylamine: OLAm to obtain a 0.1 M solution of 3 ml in a molar ratio of Ga: OLAc = 1:1.5, and a solution of 3.57 ml obtained by mixing 0.57 ml of a 0.8 M solution obtained by dissolving sulfur: S in oleylamine: OLAm and dodecanethiol: DDT. Drop this solution onto the solution that is stirred and heated at 260 °C over 30 minutes. After the dropping is completed, stir and heat for 150 minutes, and cool the obtained reaction solution to room temperature.

[0289] Then, add 0.15 ml of a 0.8 M solution obtained by dissolving zinc acetate: Zn(OAc)2 in oleic acid: OLAc and trioctylphosphine: TOP, and 0.15 ml of a 0.8 M solution obtained by dissolving sulfur: S in oleylamine: OLAm and dodecanethiol: DDT, and heat at 150 °C for 20 minutes. Then, add 3 ml of trioctylphosphine: TOP and heat at 150 °C for 10 minutes. Add 0.15 ml of a 0.8 M solution obtained by dissolving zinc acetate: Zn(OAc)2 in oleic acid: OLAc and trioctylphosphine: TOP, and 0.15 ml of a 0.8 M solution obtained by dissolving sulfur: S in oleylamine: OLAm and dodecanethiol: DDT, and heat at 150 °C for 20 minutes.

[0290] Add 0.4 ml of trioctylphosphine: TOP to 2 ml of the obtained reaction solution. Then perform centrifugation to remove the precipitate. Measure the obtained solution with a fluorescence spectrometer. As a result, optical properties with a fluorescence wavelength of 631 nm, a fluorescence half-width at half-maximum of 25 nm, and a quantum yield of 67% can be obtained. Figure 18 as shown,

[0291] [Example 20]

[0292] Add 0.5 ml of a 0.2 M solution obtained by dissolving silver acetate: Ag(OAc) in oleylamine: OLAm, 55.5 mg of gallium acetylacetonate: Ga(acac)3, 20 mL of oleylamine: OLAm, and 3 ml of dodecanethiol: DDT into a 100 mL reaction vessel. Moreover, while stirring under an inert gas (N2) atmosphere, heat to dissolve the raw materials.

[0293] Dissolve this solution at 150 °C for 5 minutes, and on this basis, add 0.36 ml of a 0.7 M solution obtained by dissolving selenium: Se in oleylamine: OLAm and dodecanethiol: DDT. Then stir for 10 minutes. After cooling the obtained reaction solution to room temperature, heat while stirring at 320 °C for 20 minutes. Then cool to room temperature.

[0294] Treat the obtained reaction solution with a centrifuge to precipitate the quantum dots. Redisperse the precipitated quantum dots with toluene, and wash with methanol and ethanol. Then, add 9.5 ml of OLAm for redispersion.

[0295] Then, a solution prepared by mixing 3 ml of a 0.1 M solution obtained by dissolving gallium chloride: GaCl3 and oleic acid: OLAc in a molar ratio of Ga:OLAc = 1:1.5 in oleylamine: OLAm and 3.5 ml of a solution obtained by dissolving sulfur: S in oleylamine: OLAm and dodecanethiol: DDT is added dropwise over 10 minutes to a solution that is stirred and heated at 290 °C. After the addition is complete, stir and heat for 110 minutes, and cool the obtained reaction solution to room temperature.

[0296] Then, add 8 ml of TOP and heat at 150 °C for 5 minutes. On this basis, add 0.34 ml of a 0.7 M solution obtained by dissolving selenium: Se in oleylamine: OLAm and dodecanethiol: DDT, and heat at 150 °C for 20 minutes. Then, add 0.3 ml of a 0.8 M solution obtained by dissolving zinc acetate: Zn(OAc)2 in oleic acid: OLAc and trioctylphosphine: TOP, and heat at 150 °C for 20 minutes. On this basis, add 0.17 ml of a 0.7 M solution obtained by dissolving selenium: Se in oleylamine: OLAm and dodecanethiol: DDT and 0.15 ml of a 0.8 M solution obtained by dissolving sulfur: S in oleylamine: OLAm and dodecanethiol: DDT, and heat at 150 °C for 20 minutes. Then, add 0.3 ml of a 0.8 M solution obtained by dissolving zinc acetate: Zn(OAc)2 in oleic acid: OLAc and trioctylphosphine: TOP, and heat at 150 °C for 20 minutes. Then cool to room temperature.

[0297] To 2 ml of the obtained reaction solution, 0.4 ml of trioctylphosphine: TOP was added. Then, centrifugation was performed to remove the precipitate. The obtained solution was measured with a fluorescence spectrometer. As a result, optical properties with a fluorescence wavelength of 633 nm, a fluorescence half-width at half maximum of 23.9 nm, and a quantum yield of 75% were obtained. Figure 19 Optical properties as shown with a fluorescence wavelength of 633 nm, a fluorescence half-width at half maximum of 23.9 nm, and a quantum yield of 75%.

[0298] [Comparative Example 1]

[0299] To a 100 mL reaction vessel, 0.5 ml of a 0.2 M solution obtained by dissolving silver acetate: Ag(OAc) in oleylamine: OLAm, 29 mg of indium acetate: In(OAc)3, 9.5 mL of oleylamine: OLAm, and 0.5 ml of dodecanethiol: DDT were added. Moreover, while stirring under an inert gas (N2) atmosphere, heating was performed to dissolve the raw materials.

[0300] The solution was dissolved at 120 °C for 5 minutes, and on this basis, 1 ml of a 0.2 M solution (S-ODE) obtained by dissolving sulfur: S in octadecene: ODE was added. Then, the temperature was raised from 120 °C to 200 °C and stirring and heating were performed for a total of 20 minutes. The obtained reaction solution was cooled to room temperature.

[0301] To the obtained reaction solution, 27.9 mg of indium diethyldithiocarbamate: In[SC(=S)N(C2H5)2]3 as a carbamate was added, and stirring and heating were performed at 260 °C for 10 minutes.

[0302] Then, 2 ml of a 0.1 M solution obtained by dissolving gallium chloride: GaCl3 and myristic acid: MA in a molar ratio of Ga:MA = 1:3 in octadecene: ODE and 3.5 ml of a solution obtained by mixing 1.5 ml of a 0.2 M solution obtained by dissolving sulfur: S in octadecene: ODE were mixed, and the mixture was dropped onto the solution that was being stirred and heated at 260 °C over 50 minutes. After the dropping was completed, stirring and heating were performed for 70 minutes, and the obtained reaction solution was cooled to room temperature.

[0303] The obtained reaction solution was measured with a fluorescence spectrometer. As a result, optical properties as shown with a fluorescence wavelength of about 641 nm and a fluorescence half-width at half maximum of about 33.8 nm were obtained. In addition, the fluorescence quantum yield was a low value at an undetectable level. Figure 20 Optical properties as shown with a fluorescence wavelength of about 641 nm and a fluorescence half-width at half maximum of about 33.8 nm. In addition, the fluorescence quantum yield was a low value at an undetectable level.

[0304] As shown in Table 1 below, the initial particle components, post-added elements, fluorescence wavelength, fluorescence half-width at half maximum, and fluorescence quantum yield (PLQY) in each example were summarized. In addition, Table 2 summarized the main differences based on Example 1 (green QD) and 15 (red QD).

[0305]

Table 1

[0306]

[0307]

Table 2

[0308]

[0309] As shown in Table 1, in Examples 1 to 18 and 20, the initial particle components do not contain In, and good characteristics can be obtained. On the other hand, in Comparative Example 1, the initial particle components contain In, and in particular, the fluorescence quantum yield is a low value that cannot be observed.

[0310] The "post-added element" includes the components of the shell covering the surface of the core. However, as a result of TEM-EDX analysis, a clear core-shell structure cannot be confirmed, and all the added raw materials are mixed-crystallized. In addition, as described above, the particles that can be synthesized by reacting at the initial stage do not contain In, and thus good characteristics can be obtained. Therefore, the "initial particle components" and the "post-added elements" are described separately.

[0311] In addition, Example 16 does not contain Zn, Example 17 contains Zn, and compared with Example 16, Example 17 can obtain good characteristic results.

[0312] As shown in Table 1, it can be seen that in the examples, the full width at half maximum of fluorescence is all below 45 nm, preferably below 30 nm. In addition, the fluorescence quantum yield is above 35%, preferably above 70%.

[0313] In addition, as shown in Table 1, it can be seen that the fluorescence wavelength can be adjusted in the range of 400 nm to 700 nm. Quantum dots that emit green light can be synthesized through Examples 1 to 14, and quantum dots that emit red light can be synthesized through Examples 15 to 20.

[0314] In contrast, the AIS-based quantum dots described in the patent literature have a full width at half maximum of fluorescence of 45 nm or more or a fluorescence quantum yield of 35% or less in the green wavelength region to the red wavelength region, and it is impossible to obtain the AgIn with a narrow full width at half maximum of fluorescence and a high fluorescence quantum yield as in this example x Ga 1-x S y Se 1-y system, or ZnAgIn x Ga 1-x S y Se 1-y system (0 ≤ x < 1, 0 ≤ y ≤ 1) quantum dots.

[0315] In addition, a dispersion solution of the AgInGaS particles of Example 7 was measured using a scanning electron microscope (SEM). Figure 21 The measurement result is for a scanning electron microscope (SEM).

[0316] As Figure 21 shown, it can be seen that a large number of quantum dots with substantially uniform particle diameters can be produced.

[0317] In addition, the results (observation images) of analyzing the quantum dots of Example 15 by TEM-EDX are shown in Figure 22 . Figure 23 It is Figure 22 a partial schematic view of the observation image shown. As Figure 22 , Figure 23 shown, it can be seen that the more Zn is detected, the darker the detected color is, and Zn mainly exists on the surface of the quantum dots.

[0318] Industrial availability

[0319] According to the present invention, for example, quantum dots that exhibit high-brightness green fluorescence or red fluorescence can be stably obtained. Moreover, by applying the quantum dots of the present invention to LEDs, backlight devices, display devices, etc., excellent light-emitting characteristics can be obtained in each device.

[0320] This application is based on Japanese Patent Application No. 2019-153204 filed on August 23, 2019. The entire content thereof is incorporated herein.

Claims

1. A method for manufacturing quantum dots, characterized in that Zn, Ag, Ga, and S are used as essential elements, and In and Se are used as optional elements, meeting the following conditions, that is, In x Ga 1-x , where 0 ≤ x < 1 S y Se 1-y , where 0 ≤ y ≤ 1, a core-shell structure that exhibits a fluorescence full-width at half-maximum of 35 nm or less and a fluorescence quantum yield of 70% or more in the green wavelength region to the red wavelength region is adopted, the quantum dots with a core-shell structure are synthesized in a range where the ratio of Ag to Ga is Ag / Ga = 0.05 or more and 10 or less, and the ratio of Zn to Ga is Zn / Ga = 0.1 or more and 10 or less, after forming the reaction initial particles AgGaS or AgGaSe, a predetermined element is added later for synthesis, and In is not contained in the initial stage of the reaction, as the S source, it includes thiuram, disulfide, S-ODE obtained by dissolving S in octadecene, or S-OLAm / DDT obtained by dissolving S in oleylamine and dodecanethiol, the quantum dots are a core-shell structure including a core of nanocrystals containing at least Ag, Ga, S, or Ag, Ga, Se and a shell covering the surface of the core.

2. The method for manufacturing quantum dots according to claim 1, characterized in that as the Se source, S-OLAm / DDT obtained by dissolving Se in oleylamine and dodecanethiol is used.

3. The method for manufacturing quantum dots according to claim 1, characterized in that as the Ga source, gallium acetylacetonate (Ga(acac)3) or gallium chloride (GaCl3) is used.

4. The method for manufacturing quantum dots according to claim 1, characterized in that dispersion treatment is performed on the reaction solution obtained by adding TOP or TOP to the mixed Ag source, Ga source, and S source or Ag source, Ga source, and Se source.

5. The method for manufacturing quantum dots according to claim 1, characterized in that the reaction solution synthesized by mixing the Ag source, Ga source, and S source or Ag source, Ga source, and Se source is centrifuged.

6. The method for manufacturing quantum dots according to claim 5, characterized in that toluene, methanol, ethanol, or acetone is added to the reaction solution synthesized by mixing the Ag source, Ga source, and S source or Ag source, Ga source, and Se source, and then centrifuged.

7. A quantum dot, characterized in that Zn, Ag, Ga, and S are used as essential elements, and In and Se are used as optional elements, meeting the following conditions, that is, In x Ga 1-x , where 0 ≤ x < 1, S y Se 1-y , where 0 ≤ y ≤ 1, in the range of Ag / Ga = 0.05 or more and 10 or less, in the range of Zn / Ga = 0.1 or more and 10 or less, it exhibits fluorescence characteristics with a fluorescence full-width at half-maximum of 35 nm or less and a fluorescence quantum yield of 70% or more in the green wavelength region to the red wavelength region, the quantum dot is a core-shell structure and emits light at the band edge, the quantum dot is a core-shell structure including a core of nanocrystals containing at least Ag, Ga, S, or Ag, Ga, Se and a shell covering the surface of the core.

8. The quantum dot according to claim 7, characterized in that the fluorescence wavelength is in the range of 400 nm or more and 700 nm or less.

9. The quantum dot according to claim 7, characterized in that The full width at half maximum of the fluorescence is below 30 nm, the fluorescence quantum yield is above 80%, and the fluorescence wavelength ranges from 510 nm to 650 nm.

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