Method for manufacturing quantum dots

Abstract

To provide a silver bismuth chalcogenide quantum dot in which uniformization of particle diameter can be attained and a production method of the silver bismuth chalcogenide quantum dot which is simple, has high safety, and uses a raw material easy to handle.SOLUTION: A quantum dot is a nanocrystal represented by AgBiE2 (E is at least one of tellurium, selenium, or sulfur) containing silver, bismuth, and chalcogen. The quantum dot has an average particle diameter of 1 nm or more and 15 nm or less.SELECTED DRAWING: None

Description

[Technical field]

[0001] The present invention relates to an indirect transition quantum dot, a quantum dot ensemble, and a method for producing the same. [Background technology]

[0002] Quantum dots are nanoparticles composed of hundreds to thousands of atoms and having a particle size of several nm to several tens of nm. Quantum dots are also called fluorescent nanoparticles, semiconductor nanoparticles, or nanocrystals.

[0003] The emission wavelength of quantum dots can be varied by changing the particle size and composition of the nanoparticles. The performance of quantum dots can be expressed by the fluorescence quantum yield (QY), fluorescence full width at half maximum (FWHM), absorption wavelength, and fluorescence wavelength.

[0004] The following patents and non-patent documents contain information on AgBiS 2 Solar cells using quantum dots are described. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] JP 2017-28267 A [Non-patent literature]

[0006] [Non-Patent Document 1] ACS Applied Nano Materials,2020, 3, 5, pp 4014 Cubic AgBiS2 Colloidal Nanocrystals for SolarCells [Non-Patent Document 2] Nature Photonics, 2016, 10, pp521 Solution-processed solar cells based on environmentally friendly AgBiS2nanocrystals [Non-Patent Document 3] J. Mater. Chem. C, 2018, 6, pp 731 Enhanced optoelectronic performancein AgBiS2 nanocrystals obtained via an improved amine-based synthesis route Summary of the Invention [Problem to be solved by the invention]

[0007] However, research and development of silver bismuth chalcogenide quantum dots in line with practical application has not been reported. For example, in the synthesis of silver bismuth chalcogenide quantum dots described in the above Non-Patent Documents 1 to 3 and Patent Document 1, S(TMS) 2 (hexamethyldisilazane), which easily reacts with moisture in the air and produces toxic H 2 It is a reagent that releases S.

[0008] Given the above-mentioned background, there is a strong demand for the synthesis of silver bismuth chalcogenide quantum dots by a mass-producible method using simple and easy-to-handle raw materials, and for the elucidation of the physical properties of silver bismuth chalcogenide quantum dots synthesized by such a method.

[0009] The present invention has been made in view of the above-mentioned points, and has an object to provide silver bismuth chalcogenide quantum dots and quantum dot assemblies that can achieve a uniform particle size.

[0010] Another object of the present invention is to provide a method for producing silver bismuth chalcogenide quantum dots that is simple, highly safe, and uses raw materials that are easy to handle. [Means for solving the problem]

[0015] The method for producing quantum dots in the present invention comprises the steps of: Dodecanethiol is heated to 100°C or higher and 150°C or lower to dissolve, and the solution is Chalcogenide raw material (chalcogenide is at least one of tellurium, selenium, or sulfur) Add and continue reacting at the same temperature. AgBiE 2 (E is at least one of tellurium, selenium, and sulfur).

[0017] In the present invention, the silver raw material, the bismuth raw material, and Dodecanethiol is preferably added to a high boiling point solvent having a boiling point of 150° C. or more, reacted at a predetermined reaction temperature, and then the chalcogenide raw material is added and the reaction is continued at the same temperature. Effect of the Invention

[0019] According to the quantum dots of the present invention, the particle size distribution in STEM can be narrowed, and silver bismuth chalcogenide quantum dots with a uniform particle size can be synthesized.

[0020] Furthermore, according to the quantum dot production method of the present invention, it is possible to mass-produce silver bismuth chalcogenide quantum dots directly, simply, and safely, using an easy-to-handle reactant without going through an intermediate or the like. [Brief description of the drawings]

[0021] [Figure 1A] FIG. 2 is a schematic diagram of a quantum dot according to an embodiment of the present invention. [Figure 1B] FIG. 2 is a schematic diagram of a quantum dot according to an embodiment of the present invention. [Diagram 2] 1 is an absorption spectrum of AgBiS2 in Example 1. [Diagram 3] 1 is a TauC plot of AgBiS2 in Example 1. [Figure 4]FIG. 2 is a scanning transmission electron microscope (STEM) photograph and a particle size analysis diagram of AgBiS2 in Example 1. [Diagram 5] FIG. 2 is a differential thermal analysis diagram of AgBiS2 in Example 1. [Figure 6] 1 is an X-ray diffraction (XRD) spectrum of AgBiS2 in Example 1. [Figure 7] 1 is an absorption spectrum of AgBiS2 in Example 2. [Figure 8] 1 is a TauC plot of AgBiS2 in Example 2. [Figure 9] FIG. 1 is a scanning transmission electron microscope (STEM) photograph and a particle size analysis diagram of AgBiS2 in Example 2. [Figure 10] FIG. 1 is a differential thermal analysis diagram of AgBiS2 in Example 2. [Figure 11] 1 is an X-ray diffraction (XRD) spectrum of AgBiS2 in Example 2. [Figure 12] 1 is an absorption spectrum of AgBiS2 in Example 3. [Figure 13] 1 is a TauC plot of AgBiS2 in Example 3. [Figure 14] FIG. 1 shows a scanning transmission electron microscope (STEM) photograph and a particle size analysis diagram of AgBiS2 in Example 3. [Figure 15] FIG. 1 is a differential thermal analysis diagram of AgBiS2 in Example 3. [Figure 16] 1 is an X-ray diffraction (XRD) spectrum of AgBiS2 in Example 3. [Figure 17] 1 is an absorption spectrum of AgBiS2 in Example 4. [Figure 18] 1 is a TauC plot of AgBiS2 in Example 4. [Figure 19] FIG. 1 is a scanning transmission electron microscope (STEM) photograph and a particle size analysis diagram of AgBiS2 in Example 4. [Figure 20] FIG. 1 is a differential thermal analysis diagram of AgBiS2 in Example 4. [Figure 21] 1 is an X-ray diffraction (XRD) spectrum of AgBiS2 in Example 4. [Figure 22] 1 is an absorption spectrum of AgBiS2 in Example 5. [Diagram 23] 1 is a TauC plot of AgBiS2 in Example 5. [Figure 24] FIG. 1 shows a scanning transmission electron microscope (STEM) photograph and a particle size analysis diagram of AgBiS2 in Example 5. [Diagram 25] FIG. 13 is a differential thermal analysis diagram of AgBiS2 in Example 5. [Figure 26] 1 is an X-ray diffraction (XRD) spectrum of AgBiS2 in Example 5. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0022] In recent years, near-infrared luminescent quantum dots that do not contain toxic heavy metals such as Cd and Pb, which are subject to regulated regulations, have been attracting attention. 2 (E is at least one of tellurium, selenium, or sulfur) Focusing on ternary quantum dots, they have gently synthesized silver bismuth chalcogenide quantum dots directly and safely under atmospheric conditions using easy-to-handle reactants without going through intermediates, and have elucidated their physical properties.

[0023] An embodiment of the present invention (hereinafter, abbreviated as "embodiment") will be described in detail below. Note that the present invention is not limited to the following embodiment, and can be practiced in various modifications within the scope of the gist of the present invention.

[0024] 1A and 1B are schematic diagrams of quantum dots according to the present embodiment. The quantum dots 1 shown in Fig. 1A and 1B are nanocrystals directly synthesized using an easy-to-handle reactant without using an intermediate.

[0025] In this embodiment, the quantum dot 1 is AgBiE containing silver (Ag), bismuth (Bi), and chalcogen. 2 (E is at least one of tellurium (Te), selenium (Se) and sulfur (S)). This compound has an indirect transition and emits very weak light.

[0026] Here, "nanocrystal" refers to nanoparticles having a particle size of about 1 nm to several tens of nm. In this embodiment, a large number of quantum dots can be produced with a uniform particle size. "Uniform" refers to a state in which 2 / 3 or more of the total particles are contained within ±20% of the average particle size. In this manner, in this embodiment, fine, uniform, and high-quality quantum dots can be mass-produced. In this embodiment, the particle size of the quantum dots can be adjusted in the range of 1 nm to 15 nm. It is preferably 2 nm to 10 nm, more preferably 3 nm to 7 nm, and even more preferably 4 nm to 5 nm.

[0027] Ag, Bi, and chalcogen are the main components of the quantum dots, and other elements may be included. However, when producing quantum dots, it is preferable to satisfy the following conditions: the reactant is easy to handle, no intermediate is used, and the quantum dots can be synthesized by reacting the raw materials in a high boiling point solvent at a temperature of about 100°C to about 150°C after sequential addition of the raw materials.

[0028] By using such a synthesis method, quantum dots can be mass-produced stably without increasing the production cost, restricting the handling of reactants, and complicating the production process.

[0029] In this embodiment, as described later, a reaction system for synthesizing quantum dots is such that raw materials, that is, Ag raw material, Bi raw material, and ligand are added in order to a high boiling point solvent, and finally, a chalcogenide raw material is added, and then the reaction is carried out at about 100° C. to about 150° C. By manufacturing quantum dots based on such a direct and simple synthesis reaction, the particle diameter of the quantum dots can be made uniform, and specifically, 2 / 3 or more of the particles of the entire quantum dots can be contained within ±20% of the average particle diameter.

[0030] As shown in Fig. 1A, it is preferable that a large number of organic ligands 2 are coordinated to the surface of the quantum dot 1. This makes it possible to suppress the aggregation of the quantum dots 1, and to develop the desired optical properties. There is no particular limitation on the ligands that can be used in the reaction, but the following ligands are representative examples.

[0031] (1) Aliphatic primary amines Oleylamine: C 18 H 35 NH 2 , Stearyl (octadecyl)amine: C 18 H 37 NH 2 , dodecyl(lauryl)amine: C 12 H 25 NH 2 , Decylamine: C 10 H 21 NH 2 , Octylamine: C 8 H 17 NH 2

[0032] (2)Fatty acid Oleic acid: C 17 H 33 COOH, stearic acid: C 17 H 35 COOH, Palmitic acid: C15 H 31 COOH, myristic acid: C 13 H 27 COOH, lauric acid: C 11 H 23 COOH, decanoic acid: C 9 H 19 COOH, octanoic acid: C 7 H 15 COOH

[0033] (3) Thiols Octadecanethiol: C 18 H 37 SH, hexanedecanethiol: C 16 H 33 SH, tetradecanethiol: C 14 H 29 SH, dodecanethiol: C 12 H 25 SH, Decanethiol: C 10 H 21 SH, Octanethiol: C 8 H 17 SH (4) Phosphine Trioctylphosphine: (C 8 H 17 ) 3 P, triphenylphosphine: (C 6 H 5 ) 3 P, Tributylphosphine: (C 4 H 9 ) 3 P

[0034] (5) Phosphine oxides Trioctylphosphine oxide: (C 8 H 17 ) 3 P=O, triphenylphosphine oxide: (C 6 H 5 ) 3 P=O, tributylphosphine oxide: (C 4 H 9 ) 3 P=O

[0035] In this embodiment, as shown in Fig. 1B, the quantum dot 1 may have a core-shell structure having a core 1a and a shell 1b covering the surface of the core 1a. As shown in Fig. 1B, it is preferable that a large number of organic ligands 2 are coordinated to the surface of the quantum dot 1.

[0036] Core 1a shown in Figure 1B is AgBiE 2 Like the core 1a, the shell 1b does not contain regulated heavy metals such as Cd, Hg, and Pb, or substances derived from highly reactive reactants such as silicon compounds.

[0037] The shell 1b may be in a state of being solid-solubilized on the surface of the core 1a. However, in this embodiment, an optical band gap of 0.90 to 1.10 eV can be obtained in the TauC plot using only the core 1a without using the shell 1b, that is, the quantum dot 1 having only the core in FIG. 1A.

[0038] Next, a method for producing quantum dots according to the present embodiment will be described. In the present embodiment, AgBiE is produced from a silver raw material, a bismuth raw material, and a chalcogenide raw material (chalcogenide is at least one of tellurium, selenium, and sulfur). 2 (E is at least one of tellurium, selenium, and sulfur) is synthesized.

[0039] In this embodiment, AgBiE 2 The Ag raw material is not particularly limited, but for example, the following organic silver reagents or inorganic silver reagents can be used. That is, as an acetate, silver acetate (I): Ag(OAc), as a fatty acid salt, silver stearate: Ag(OC(=O)C 17 H 35 ), Silver Oleate: Ag(OC(=O)C 17 H 33 ), Silver myristate: Ag(OC(=O)C 13 H 27 ), Silver dodecanoate: Ag(OC(=O)C 11 H 23), silver acetylacetonate: Ag(acac), and monovalent compounds can be used as halides, such as silver chloride(I): AgCl, silver bromide(I): AgBr, and silver iodide(I): AgI.

[0040] In this embodiment, AgBiE 2 The Bi raw material is not particularly limited, but for example, the following organic bismuth reagents or inorganic bismuth reagents can be used. That is, as a fatty acid salt, bismuth oxide acetate (III): BiO(OC(=O)CH 3 ), Bismuth(III) acetate: Bi(OC(=O)CH 3 ) 3 , bismuth(III) 2-ethylhexanoate: Bi(OC(=O)C 21 H 45 ) 3 , Bismuth(III) neodecanoate: Bi(OC(=O)C 27 H 57 ) 3 , Bismuth(III) subgallate: Bi(C 7 O 6 H 5 ), trivalent compounds can be used as halides, such as bismuth fluoride (III): BiF 3 , Bismuth(III) chloride: BiCl 3 , Bismuth(III) bromide: BiBr 3 , as inorganic salt, bismuth nitrate pentahydrate(III): Bi(NO 3 ) 3 5H 2 O, Bismuth(III) oxycarbonate: (BiO) 2 CO 3 , bismuth(III) oxide: Bi 2 O 3 etc. can be used.

[0041] In this embodiment, as the tellurium (Te), an organic tellurium compound (organic chalcogen compound) or an inorganic tellurium compound is used as a raw material either in solid form or dissolved in a high boiling point solvent. Although there is no particular limitation on the structure of the compound, for example, trioctylphosphine telluride (C 8 H 17 ) 3 P = Te, tributylphosphine telluride obtained by dissolving tellurium in tributylphosphine: (C 4 H 9 ) 3 P=Te, or a solution of tellurium dissolved at high temperature in a high boiling point solvent, such as a long chain hydrocarbon, such as octadecene, can be used.

[0042] In the present embodiment, when selenium (Se) is dissolved in a solid solution, an organic selenium compound (organic chalcogen compound) or an inorganic selenium compound is used as a raw material either in solid form or dissolved in a high boiling point solvent. Although the structure is not particularly limited, for example, trioctylphosphine selenide: (C 8 H 17 ) 3 P=Se, tributylphosphine selenide obtained by dissolving selenium in tributylphosphine: (C 4 H 9 ) 3 P=Se, or a solution of selenium dissolved at high temperature in a high boiling point solvent, such as a long chain hydrocarbon, such as octadecene, can be used.

[0043] In the present embodiment, when sulfur (S) is dissolved in a solid solution, an organic sulfur compound (organic chalcogen compound) or an inorganic sulfur compound is used as a raw material either in solid form or dissolved in a high boiling point solvent. Although there are no particular limitations on the structure, for example, trioctylphosphine sulfide:(C 8 H 17 ) 3 P=S, or tributylphosphine sulfide, in which sulfur is dissolved in tributylphosphine: (C4 H 9 ) 3 P=S, or a solution of sulfur dissolved at high temperature in a high boiling point solvent, such as a long chain hydrocarbon, such as octadecene, can be used.

[0044] In this embodiment, an organic bismuth compound or an inorganic bismuth compound is added to a high boiling point solvent and dissolved. As the solvent, octadecene can be used as a saturated or unsaturated hydrocarbon having a high boiling point of 150° C. or more. In addition, dodecylbenzene:C is an aromatic high boiling point solvent. 6 H 5 (CH 2 ) 11 CH 3 As a high boiling point ester solvent, butyl butyrate: C 4 H 9 COOC 4 H 9 , benzyl butyrate: C 6 H 5 CH 2 COOC 4 H 9 It is also possible to use an aliphatic thiol-based, aliphatic amine-based, or fatty acid-based compound or an aliphatic phosphorus-based compound as the solvent.

[0045] At this time, the reaction temperature is set in the range of 100° C. to 200° C. to dissolve the silver compound. The reaction temperature is preferably lower, 100° C. to 175° C., and more preferably lower, 100° C. to 150° C.

[0046] In addition, in this embodiment, there is no particular limitation on the reaction conditions, but in order to obtain quantum dots with a uniform particle size, the reaction is carried out at a low temperature of about 100°C to a high temperature of about 140°C. 2 , AgBiSe 2 , and AgBiS 2For this reason, it is preferable to dissolve one or two types of raw materials in a high-boiling point solvent heated to about 100°C, add the other raw materials to the solution in sequence, and then continue the reaction at the same temperature to synthesize quantum dots.

[0047] In addition, in this embodiment, AgBiE having a uniform particle size 2 In order to obtain the above, in the reaction of the precursors, that is, the silver raw material, the bismuth raw material, and the chalcogen raw material, it is preferable to add 1 to 200 equivalents of thiol relative to Te, Se, or S, more preferably 5 to 1000 equivalents, and even more preferably 50 to 10000 equivalents. In particular, the thiol is not limited, but for example, octadecanethiol:C 18 H 37 SH, hexanedecanethiol: C 16 H 33 SH, tetradecanethiol: C 14 H 29 SH, dodecanethiol: C 12 H 25 SH, decanethiol: C 10 H 21 SH, Octanethiol: C 8 H 17 SH, etc. can be used.

[0048] In addition, in this embodiment, when each raw material is added and reacted, a compound is required that has an auxiliary role of liberating the precursor metal into the reaction solution by coordination or chelating.

[0049] Compounds having the above-mentioned role include ligands capable of forming a complex with silver. For example, phosphorus-based ligands, amine-based ligands, thiol-based ligands, and carboxylic acid-based ligands are preferred, and among these, thiol-based ligands are particularly preferred due to their high efficiency.

[0050] This allows the reaction between Ag, Bi, and chalcogen to proceed appropriately, producing AgBiE, which is based on Ag, Bi, and chalcogen, has an optical band gap of 0.90 to 1.10 eV, and has a uniform particle size.2 Quantum dots can be produced.

[0051] In the method for producing quantum dots of the present embodiment, it is preferable to include a step of dissolving one or two of the above-mentioned silver raw material, bismuth raw material, chalcogenide raw material, and ligand raw material in the high-boiling point solvent heated to 100°C to 150°C, a step of subsequently adding other raw materials, and a step of subsequently synthesizing quantum dots at approximately the same reaction temperature after all the raw materials have been added.

[0052] This makes it possible to safely and quickly mass-produce silver bismuth chalcogenide having a uniform particle size directly using an easy-to-handle reactant without going through an intermediate or the like. EXAMPLES

[0053] The effects of the present invention will be described below with reference to examples and comparative examples, but the present invention is not limited to the following examples.

[0054] <Raw materials> In the present invention, a silver chalcogenide compound (AgBiE) having a uniform particle size is prepared. 2 The following raw materials were used to synthesize the quantum dots: (solvent) Octadecene: manufactured by Aldrich Co., Ltd., manufactured by Idemitsu Kosan Co., Ltd. (Chalcogen raw material) Sulfur powder (99.0% or more): Kishida Chemical Co., Ltd. (Bismuth raw material) Bismuth oxide acetate: Kishida Chemical Co., Ltd. Bismuth nitrate pentahydrate: Fujifilm Wako Pure Chemical Corporation Bismuth oxide: Mitsuwa Chemical Co., Ltd. (Silver raw material) Silver acetate: Kishida Chemical Co., Ltd. (ligand) Trioctylphosphine: manufactured by Hokko Chemical Co., Ltd. Dodecanethiol: Arkema <Measuring equipment> UV-Visible spectrophotometer: Hitachi V-770 X-ray diffraction device (XRD): Bruker D2 PHASER Scanning transmission electron microscope (STEM): Hitachi SU9000 Differential thermobalance (TG-DTA): Rigaku Thermo Plus EVO2

[0055] [Example 1] In a 300 mL reaction vessel, add 200.2 mg of silver acetate (Ag(OAc)), 30.0 mL of dodecanethiol (DDT), and bismuth nitrate pentahydrate (Bi(NO 3 ) 3 5H 2 582.2 mg of O was added. Then, inert gas (N 2 ) atmosphere, the mixture was heated at 145°C for 5 minutes with stirring to dissolve the raw materials.

[0056] To this solution, 13.0 mL of 0.20 M octadecene sulfide (S-ODE) was added and heated with stirring at the same temperature for an additional 10 minutes.

[0057] The reaction solution was cooled to room temperature, toluene and ethanol were added to generate a precipitate, and the precipitate was collected by centrifugation. Hexane was then added to the precipitate to disperse it, resulting in AgBiS. 2 A particle dispersion solution was prepared.

[0058] The obtained dispersion solution was measured with a UV-Vis spectrometer. As a result, the UV-Vis near-infrared absorption spectrum shown in Figure 2 was obtained. In addition, the quantum dots obtained by this synthesis were found to have an optical band gap of 0.90 eV, as shown in the analysis result of the TauC plot in Figure 3. In addition, the average particle size of the quantum dots was about 4.43 nm, as shown in Figure 4, and it was found that more than two-thirds of the total number of particles were within ±20% of the average particle size. In addition, analysis by differential thermogravimetry (TG) revealed that about 15% of the ligands were coordinated to the entire quantum dots, as shown in Figure 5. In addition, the AgBiS shown in Figure 62 From the peak values ​​and peak patterns of the XRD spectrum of the particles, AgBiS 2 It was demonstrated that a solid solution was formed.

[0059] [Example 2] In a 300 mL reaction vessel, add 200.2 mg of silver acetate (Ag(OAc)), 30.0 mL of dodecanethiol (DDT), and bismuth nitrate pentahydrate (Bi(NO 3 ) 3 5H 2 582.2 mg of O was added. Then, inert gas (N 2 ) atmosphere, the mixture was heated at 145°C for 5 minutes with stirring to dissolve the raw materials.

[0060] To this solution, 13.0 mL of 0.20 M octadecene sulfide (S-ODE) was added and heated with stirring at the same temperature for an additional 20 minutes.

[0061] The reaction solution was cooled to room temperature, toluene and ethanol were added to generate a precipitate, and the precipitate was collected by centrifugation. Hexane was then added to the precipitate to disperse it, resulting in AgBiS. 2 A particle dispersion solution was prepared.

[0062] The obtained dispersion solution was measured with a UV-Vis spectrometer. As a result, the UV-Vis near-infrared absorption spectrum shown in Figure 7 was obtained. In addition, the quantum dots obtained by this synthesis were found to have an optical band gap of 1.075 eV, as shown in the analysis result of the TauC plot in Figure 8. In addition, the average particle size of the quantum dots was about 4.53 nm, as shown in Figure 9, and it was found that more than two-thirds of the total number of particles were within ±20% of the average particle size. In addition, analysis by a differential thermobalance revealed that about 18% of the ligands were coordinated with respect to the total mass of the quantum dots, as shown in Figure 10.

[0063] In addition, the AgBiS shown in Figure 11 2 From the peak values ​​and peak patterns of the XRD spectrum of the particles, AgBiS 2It was demonstrated that a solid solution was formed.

[0064] [Example 3] In a 300 mL reaction vessel, add 200.2 mg of silver acetate (Ag(OAc)), 30.0 mL of dodecanethiol (DDT), and bismuth oxide acetate (BiO(OC(=O)CH 3 ) 340.8 mg was added. Then, inert gas (N 2 ) atmosphere, the mixture was heated at 140°C for 5 minutes with stirring to dissolve the raw materials.

[0065] To this solution, 19.5 mL of 0.20 M octadecene sulfide (S-ODE) was added and heated with stirring at the same temperature for an additional 15 minutes.

[0066] The reaction solution was cooled to room temperature, toluene and ethanol were added to generate a precipitate, and the precipitate was collected by centrifugation. Hexane was then added to the precipitate to disperse it, resulting in AgBiS. 2 A particle dispersion solution was prepared.

[0067] The obtained dispersion solution was measured with a UV-Vis spectrometer. As a result, the UV-Vis near-infrared absorption spectrum shown in FIG. 12 was obtained. In addition, the quantum dots obtained by this synthesis were found to have an optical band gap of 1.065 eV, as shown in the analysis result of the TauC plot in FIG. 13. In addition, the average particle size of the quantum dots was about 4.23 nm, as shown in FIG. 14, and it was found that more than 2 / 3 of the total number of particles were within ±20% of the average particle size. In addition, analysis by a differential thermobalance revealed that about 18% of the ligands were coordinated with respect to the mass of the entire quantum dots, as shown in FIG. 15.

[0068] In addition, the AgBiS shown in Figure 16 2 From the peak values ​​and peak patterns of the XRD spectrum of the particles, AgBiS 2 It was demonstrated that a solid solution was formed.

[0069] [Example 4] In a 300 mL reaction vessel, add 200.2 mg of silver acetate (Ag(OAc)), 30.0 mL of dodecanethiol (DDT), and bismuth oxide acetate (BiO(OC(=O)CH 3 ) 340.8 mg was added. Then, inert gas (N 2 ) atmosphere, the mixture was heated at 100°C for 5 minutes with stirring to dissolve the raw materials.

[0070] To this solution, 13.0 mL of 0.20 M octadecene sulfide (S-ODE) was added and heated with stirring at the same temperature for an additional 15 minutes.

[0071] The reaction solution was cooled to room temperature, toluene and ethanol were added to generate a precipitate, and the precipitate was collected by centrifugation. Hexane was then added to the precipitate to disperse it, resulting in AgBiS. 2 A particle dispersion solution was prepared.

[0072] The obtained dispersion solution was measured with a UV-Vis spectrometer. As a result, the UV-Vis near-infrared absorption spectrum shown in FIG. 17 was obtained. In addition, the quantum dots obtained by this synthesis were found to have an optical band gap of 1.10 eV, as shown in the analysis result of the TauC plot in FIG. 18. In addition, the average particle size of the quantum dots was about 4.82 nm, as shown in FIG. 19, and it was found that more than 2 / 3 of the total number of particles were within ±20% of the average particle size. In addition, analysis by a differential thermobalance revealed that about 19% of the ligands were coordinated with respect to the mass of the entire quantum dots, as shown in FIG. 20.

[0073] In addition, the AgBiS shown in FIG. 2 From the peak values ​​and peak patterns of the XRD spectrum of the particles, AgBiS 2 It was demonstrated that a solid solution was formed.

[0074] [Example 5] In a 300 mL reaction vessel, add 200.2 mg of silver acetate (Ag(OAc)), 30.0 mL of dodecanethiol (DDT), and bismuth nitrate pentahydrate (Bi(NO 3 ) 35H 2 582.2 mg of O was added. Then, inert gas (N 2 ) atmosphere, the mixture was heated at 100°C for 5 minutes with stirring to dissolve the raw materials.

[0075] To this solution, 13.0 mL of 0.20 M octadecene sulfide (S-ODE) was added and heated with stirring at the same temperature for an additional 15 minutes.

[0076] The reaction solution was cooled to room temperature, toluene and ethanol were added to generate a precipitate, and the precipitate was collected by centrifugation. Hexane was then added to the precipitate to disperse it, resulting in AgBiS. 2 A particle dispersion solution was prepared.

[0077] The obtained dispersion solution was measured with a UV-Vis spectrometer. As a result, the UV-Vis near-infrared absorption spectrum shown in FIG. 22 was obtained. In addition, the quantum dots obtained by this synthesis were found to have an optical band gap of 1.10 eV, as shown in the analysis result of the TauC plot in FIG. 23. In addition, the average particle size of the quantum dots was about 4.52 nm, as shown in FIG. 24, and it was found that more than 2 / 3 of the total number of particles were within ±20% of the average particle size. In addition, analysis by a differential thermobalance revealed that about 22% of the ligands were coordinated with respect to the mass of the entire quantum dots, as shown in FIG. 25.

[0078] In addition, the AgBiS shown in FIG. 2 From the peak values ​​and peak patterns of the XRD spectrum of the particles, AgBiS 2 It was demonstrated that a solid solution was formed.

[0079] [Comparative Example 1] In a 300 mL reaction vessel, add 200.2 mg of silver acetate (Ag(OAc)), 30.0 mL of octadecene (ODE), and bismuth nitrate pentahydrate (Bi(NO 3 ) 3 5H 2 582.2 mg of O was added. Then, inert gas (N 2) atmosphere, and the mixture was heated at 150° C. for 5 minutes with stirring.

[0080] To this solution, 13.0 mL of 0.20 M octadecene sulfide (S-ODE) was added and heated with stirring at the same temperature for an additional 15 minutes.

[0081] The resulting reaction solution (AgBiS 2 The reaction solution did not change color, and XRD confirmed that the raw materials remained intact in the resulting solution.

[0082] [Comparative Example 2] In a 300 mL reaction vessel, add 200.2 mg of silver acetate (Ag(OAc)), 30.0 mL of dodecanethiol (DDT), and bismuth nitrate pentahydrate (Bi(NO 3 ) 3 5H 2 582.2 mg of O was added. Then, inert gas (N 2 ) atmosphere, the mixture was heated at 250° C. for 5 minutes with stirring to dissolve the raw materials.

[0083] To this solution, 13.0 mL of 0.20 M octadecene sulfide (S-ODE) was added and heated with stirring at the same temperature for an additional 15 minutes.

[0084] The resulting reaction solution (AgBiS 2 The reaction solution was changed to a black suspension, and no reflection peaks were observed by XRD from the resulting solution.

[0085] In Comparative Example 1, the ligand dodecanethiol was not present in the system, and in Comparative Example 2, the reaction temperature was as high as 250° C., so AgBiE 2 It was found that it was not possible to synthesize quantum dots based on this system properly.

[0086] As described above, according to Examples 1 to 5, AgBiE 2 It was found that quantum dots based on this system can be synthesized. [Industrial Applicability]

[0087] According to the present invention, AgBiS having a uniform particle size and an optical band gap of 0.90 to 1.10 eV is obtained. 2 The quantum dots can be synthesized by a method that uses an easy-to-handle reactant and allows direct mass production without intermediates, etc. By applying the quantum dots of the present invention to a light absorbing device, etc., it is possible to obtain excellent solar cell performance in the device. [Explanation of symbols]

[0088] 1: Quantum dots 1a: Core 1b: Shell 2 :Organic ligand

Claims

1. Heat and dissolve silver raw material, bismuth raw material, and dodecanethiol at 140 °C or higher and 150 °C or lower. Add a chalcogenide raw material (chalcogenide refers to at least one of tellurium, selenium, or sulfur) to the dissolved solution, and continue to react at the same temperature to obtain AgBiE ２ (E is at least one of tellurium, selenium, or sulfur), characterized by synthesizing quantum dots represented as such. A method for manufacturing quantum dots.

2. The method for producing quantum dots according to claim 1, characterized in that the silver raw material, the bismuth raw material, and dodecanethiol are sequentially added to a high-boiling solvent having a boiling point of 150°C or higher, reacted at a predetermined reaction temperature, and after adding the chalcogenide raw material, the reaction is continued at the same temperature.

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